Hot Jupiter exoplanet has cloudy mornings and clear evenings

Artist’s concept of WASP-94A b, a hot Jupiter-type exoplanet about 700 light-years away. New observations by the James Webb Space Telescope show that sandy clouds fill the skies in the morning, but dissipate by the evening. Image via Hannah Robbins/ Johns Hopkins University/ EurekAlert! (CC BY).

• WASP-94A b is a hot Jupiter exoplanet about 700 light-years from Earth. Astronomers recently performed more observations of it with the James Webb Space Telescope.
• The planet has cloudy morning and clear evenings, Webb found. Clouds of sandy particles form in the mornings and the dissipate by the evening.
• The cloud-free evenings also allowed Webb to analyze the atmosphere itself more clearly, without clouds contaminating the data.

You deserve a daily dose of good news. For the latest in science and the night sky, click here to subscribe to our free daily newsletter.

Cloudy mornings on a hot Jupiter exoplanet

On a hot Jupiter-type exoplanet about 700 light-years away, sand clouds build up every morning, but then dissipate by nightfall. That’s the amazingly precise finding of a team of researchers at Johns Hopkins University, announced on May 21, 2026.

The planet – WASP-94A b – is tidally locked to its star. So it always keeps a single side facing its star, which is a little hotter, larger, and more luminous than our sun. No one has directly measured the rotation period of WASP-94A b. But its orbital period is about four Earth days. So it probably rotates once in that amount of time (much as our moon takes about a month to orbit Earth, while rotating once on its axis).

The clouds appear to form on the cooler nightside of WASP-94A b. They circulate toward this world’s dayside and ultimately evaporate in the intense heat. Why so intense? Because WASP-94A b is orbiting super-closely to its star, only about 5 million miles (8 million km) away. That’s in contrast to Earth at 93 million miles (150 million km), or the sun’s innermost planet, Mercury, which gets no closer than 29 million miles (47 million km) to our star.

And, by isolating the clouds in their analysis, the researchers said they could better determine the composition of the planet’s atmosphere.

This is one of just a handful of times that astronomers have detected cloud cycles on a hot Jupiter. The researchers made the observations with the James Webb Space Telescope.

They published the new peer-reviewed findings in the journal Science on May 21, 2026. There is also an earlier preprint version of the paper from last year available.

Observing the transit of WASP-94A b

The Webb telescope observed the planet as it transited – passed in front of – its star. The researchers took measurements as the planet started to transit, and as it finished the transit. At the leading edge, the atmosphere flows from the nightside to the dayside. This makes it the morning. But at the trailing edge, the atmosphere flows from the dayside to the nightside, making it evening.

The observations revealed that the morning atmosphere is filled with clouds made of magnesium silicate – aka talc – a common mineral found in rocks on Earth. The evening atmosphere, though, is clear and cloud-free.

Cloudy Mornings And Clear Evenings On Giant Extrasolar World WASP-94A bastrobiology.com/2025/05/clou… #astrobiology #exoplanet #atmosphere

— Astrobiology (@astrobiology.bsky.social) 2025-05-19T17:22:22.927Z

Now on @sciam.bsky.social: NASA's JWST just delivered a fascinating weather report for the distant exoplanet WASP-94A b, finding the gas-giant world has partly cloudy skies. By @krcallaway.bsky.social.https://ift.tt/Dc9PvoV…

— Lee Billings (@leebillings.bsky.social) 2026-05-21T18:21:32.933Z

What is causing this?

So, what is the reason for this interesting atmospheric phenomenon? Right now, the researchers have two main hypotheses:

First, powerful winds could be lifting clouds higher up on the cooler nightside of the planet. Then, the clouds plunge back down on the hotter dayside. This buries the clouds much deeper in the atmosphere where they remain hidden.

Or, another possibility is that this process is similar to when fog burns off on Earth. The clouds form on the cooler nightside of the planet. Then, they drift into the hotter dayside. Because it is so hot, the chemicals in the clouds boil away and the clouds vaporize.

As co-author and program principal investigator David Sing at Johns Hopkins University said:

It was a huge surprise. People have expected some differences, like it’s cooler in the morning than the evening; that’s something natural that we experience here on Earth. But what we saw was a real dichotomy between the weather on both sides of the planet, and huge differences in cloud coverage, and that changes our whole picture of the planet.

Sagnick Mukherjee at Arizona State University is the lead author of the new study about clouds on WASP-94A b. Image via GitHub.

Cloud-free evenings

The evenings being free of clouds gave the researchers an opportunity. They could study the atmosphere itself more clearly with Webb. The Hubble Space Telescope isn’t able to do this. Lead author Sagnick Mukherjee at Arizona State University explained:

With the Hubble telescope, when we used to do this type of observation, we got an average view of the whole planet with data from the clouds and the atmosphere squished together and indistinguishable. This approach with the JWST lets us localize our observations, which helped us see the cloud cycle.

And what did the observations show? That WASP-94A b is actually more like Jupiter than first thought. Earlier observations suggested that WASP-94A b had hundreds of times more oxygen and carbon than Jupiter. But now the newer, cleaner analysis shows that really only has five times more. That fits much better into current planetary formation models.

View larger. | Jupiter as captured by the Juno spacecraft in February 2019. The new study also shows that WASP-94A b is more like Jupiter than previously thought, with only 5 times more oxygen and carbon. Image via NASA/ JPL-Caltech/ SwRI/ MSSS/ Kevin M. Gill.

A clearer view of the atmosphere

The new observations are a big step in being able to study both clouds and the atmosphere on exoplanets. Sing said:

I’ve been looking at exoplanets for 20 years, and general cloudiness has been a thorn in our side. We’ve known for quite a while that clouds are pervasive on hot Jupiter planets, which is annoying because it’s like trying to look at the planet through a foggy window. Not only have we been able to clear the view, but we can finally pin down what the clouds are made out of and how they’re condensing and evaporating as they move around the planet.

Bottom line: New observations with the Webb space telescope of the hot Jupiter exoplanet WASP-94A b show that sandy clouds fill the morning skies, but dissipate by evening.

Source: Cloudy mornings and clear evenings on a gas giant exoplanet

Source (preprint): Cloudy mornings and clear evenings on a giant extrasolar world

Via Johns Hopkins University

Read more: Double hot Jupiters: How do these rare gigantic worlds form?

Read more: A hot Jupiter exoplanet’s dark side revealed

The post Hot Jupiter exoplanet has cloudy mornings and clear evenings first appeared on EarthSky.

from EarthSky https://ift.tt/SMxV5gd

Artist’s concept of WASP-94A b, a hot Jupiter-type exoplanet about 700 light-years away. New observations by the James Webb Space Telescope show that sandy clouds fill the skies in the morning, but dissipate by the evening. Image via Hannah Robbins/ Johns Hopkins University/ EurekAlert! (CC BY).

• WASP-94A b is a hot Jupiter exoplanet about 700 light-years from Earth. Astronomers recently performed more observations of it with the James Webb Space Telescope.
• The planet has cloudy morning and clear evenings, Webb found. Clouds of sandy particles form in the mornings and the dissipate by the evening.
• The cloud-free evenings also allowed Webb to analyze the atmosphere itself more clearly, without clouds contaminating the data.

You deserve a daily dose of good news. For the latest in science and the night sky, click here to subscribe to our free daily newsletter.

Cloudy mornings on a hot Jupiter exoplanet

On a hot Jupiter-type exoplanet about 700 light-years away, sand clouds build up every morning, but then dissipate by nightfall. That’s the amazingly precise finding of a team of researchers at Johns Hopkins University, announced on May 21, 2026.

The planet – WASP-94A b – is tidally locked to its star. So it always keeps a single side facing its star, which is a little hotter, larger, and more luminous than our sun. No one has directly measured the rotation period of WASP-94A b. But its orbital period is about four Earth days. So it probably rotates once in that amount of time (much as our moon takes about a month to orbit Earth, while rotating once on its axis).

The clouds appear to form on the cooler nightside of WASP-94A b. They circulate toward this world’s dayside and ultimately evaporate in the intense heat. Why so intense? Because WASP-94A b is orbiting super-closely to its star, only about 5 million miles (8 million km) away. That’s in contrast to Earth at 93 million miles (150 million km), or the sun’s innermost planet, Mercury, which gets no closer than 29 million miles (47 million km) to our star.

And, by isolating the clouds in their analysis, the researchers said they could better determine the composition of the planet’s atmosphere.

This is one of just a handful of times that astronomers have detected cloud cycles on a hot Jupiter. The researchers made the observations with the James Webb Space Telescope.

They published the new peer-reviewed findings in the journal Science on May 21, 2026. There is also an earlier preprint version of the paper from last year available.

Observing the transit of WASP-94A b

The Webb telescope observed the planet as it transited – passed in front of – its star. The researchers took measurements as the planet started to transit, and as it finished the transit. At the leading edge, the atmosphere flows from the nightside to the dayside. This makes it the morning. But at the trailing edge, the atmosphere flows from the dayside to the nightside, making it evening.

The observations revealed that the morning atmosphere is filled with clouds made of magnesium silicate – aka talc – a common mineral found in rocks on Earth. The evening atmosphere, though, is clear and cloud-free.

Cloudy Mornings And Clear Evenings On Giant Extrasolar World WASP-94A bastrobiology.com/2025/05/clou… #astrobiology #exoplanet #atmosphere

— Astrobiology (@astrobiology.bsky.social) 2025-05-19T17:22:22.927Z

Now on @sciam.bsky.social: NASA's JWST just delivered a fascinating weather report for the distant exoplanet WASP-94A b, finding the gas-giant world has partly cloudy skies. By @krcallaway.bsky.social.https://ift.tt/Dc9PvoV…

— Lee Billings (@leebillings.bsky.social) 2026-05-21T18:21:32.933Z

What is causing this?

So, what is the reason for this interesting atmospheric phenomenon? Right now, the researchers have two main hypotheses:

First, powerful winds could be lifting clouds higher up on the cooler nightside of the planet. Then, the clouds plunge back down on the hotter dayside. This buries the clouds much deeper in the atmosphere where they remain hidden.

Or, another possibility is that this process is similar to when fog burns off on Earth. The clouds form on the cooler nightside of the planet. Then, they drift into the hotter dayside. Because it is so hot, the chemicals in the clouds boil away and the clouds vaporize.

As co-author and program principal investigator David Sing at Johns Hopkins University said:

It was a huge surprise. People have expected some differences, like it’s cooler in the morning than the evening; that’s something natural that we experience here on Earth. But what we saw was a real dichotomy between the weather on both sides of the planet, and huge differences in cloud coverage, and that changes our whole picture of the planet.

Sagnick Mukherjee at Arizona State University is the lead author of the new study about clouds on WASP-94A b. Image via GitHub.

Cloud-free evenings

The evenings being free of clouds gave the researchers an opportunity. They could study the atmosphere itself more clearly with Webb. The Hubble Space Telescope isn’t able to do this. Lead author Sagnick Mukherjee at Arizona State University explained:

With the Hubble telescope, when we used to do this type of observation, we got an average view of the whole planet with data from the clouds and the atmosphere squished together and indistinguishable. This approach with the JWST lets us localize our observations, which helped us see the cloud cycle.

And what did the observations show? That WASP-94A b is actually more like Jupiter than first thought. Earlier observations suggested that WASP-94A b had hundreds of times more oxygen and carbon than Jupiter. But now the newer, cleaner analysis shows that really only has five times more. That fits much better into current planetary formation models.

View larger. | Jupiter as captured by the Juno spacecraft in February 2019. The new study also shows that WASP-94A b is more like Jupiter than previously thought, with only 5 times more oxygen and carbon. Image via NASA/ JPL-Caltech/ SwRI/ MSSS/ Kevin M. Gill.

A clearer view of the atmosphere

The new observations are a big step in being able to study both clouds and the atmosphere on exoplanets. Sing said:

I’ve been looking at exoplanets for 20 years, and general cloudiness has been a thorn in our side. We’ve known for quite a while that clouds are pervasive on hot Jupiter planets, which is annoying because it’s like trying to look at the planet through a foggy window. Not only have we been able to clear the view, but we can finally pin down what the clouds are made out of and how they’re condensing and evaporating as they move around the planet.

Bottom line: New observations with the Webb space telescope of the hot Jupiter exoplanet WASP-94A b show that sandy clouds fill the morning skies, but dissipate by evening.

Source: Cloudy mornings and clear evenings on a gas giant exoplanet

Source (preprint): Cloudy mornings and clear evenings on a giant extrasolar world

Via Johns Hopkins University

Read more: Double hot Jupiters: How do these rare gigantic worlds form?

Read more: A hot Jupiter exoplanet’s dark side revealed

The post Hot Jupiter exoplanet has cloudy mornings and clear evenings first appeared on EarthSky.

from EarthSky https://ift.tt/SMxV5gd

Meet Crux, the constellation of the Southern Cross

Crux is the constellation of the Southern Cross. And it lies deep in Southern Hemisphere skies. Image via EarthSky.

Your support = more stars, more science, more wonder. Donate to EarthSky and be part of something bigger.

If you’re in the Southern Hemisphere, Crux the Southern Cross is one of the easiest constellations you can identify. It’s also one of the most famous! And it’s a reliable marker to the south celestial pole, the point around which the entire southern sky turns.

Crux consists of four relatively bright stars, close to one another and suggestive of a cross. This constellation is circumpolar, staying above the horizon all year round for observers at and south of 34 degrees south latitude. So, for example:

• At Sydney, Australia, (~34° S), most or all of Crux is circumpolar.
• At Buenos Aires, Argentina, (~35° S), it’s comfortably circumpolar.
• At Cape Town, South Africa, (~34° S), same story.
• Farther north – say at the equator – Crux rises and sets seasonally.
• North of about 27 degrees north latitude, Crux never rises at all.

In many ways, Crux is almost the mirror opposite of northern circumpolar constellations like Ursa Major the Greater Bear, with its famous Big Dipper asterism. Like the Big Dipper for northern observers, the Southern Cross is the southern sky’s iconic “always there” pattern.

And for a short time each year it can be seen by those in the southern reaches of the Northern Hemisphere. Jump to that section.

How to see it from the Southern Hemisphere

Crux lies between the constellations Centaurus the Centaur and Musca the Fly. You can locate it simply by looking for four bright stars close together. The stars are less than 5 degrees apart. Five degrees is about the width of your three middle fingers held at arm’s length.

The compact size of Crux makes it the smallest of all the 88 constellations.

And Crux does resemble a cross. But it could also be considered kite-shaped.

Want an exact view from your location? Try Stellarium

Crux the Southern Cross lies in front of the Milky Way with Centaurus and Musca nearby. Image via Stellarium. Used with permission.

How to see it from the Northern Hemisphere

Seeing the Southern Cross from the Northern Hemisphere is a matter of your location + timing + atmosphere + horizon quality.

First, your location. Know what your latitude allows. Crux sits around -60 degrees declination, so:

• At the equator (0 degrees) it can rise to ~30° high. That’s easy to see if the sky is clear.
• At 26 degrees north latitude it barely scrapes the sky at about 4 degrees above the southern horizon.
• At ~27 degrees north latitude and northward it never rises above the horizon.

So at 26 degrees north latitude you are in the extreme edge zone. You can’t just look up and observe the Southern Cross. Instead, you must hunt for it at the most distorted layer of atmosphere above your southern horizon. And you must be hunting at the exact right time.

More Northern Hemisphere viewing tips

Consider the timing. May is a good time to find Crux in the evening sky from the Northern Hemisphere. It’s visible in other months, too, but not at such a convenient time. In March, you have to wait until about 1 a.m. your local time to catch the Southern Cross at its highest elevation. In December and January, you have to catch it before dawn.

No matter the hour or date, Crux climbs to its highest point – crosses your sky’s meridian – in the sky when it’s due south. It’s easy to visualize a cross within this pattern of stars, because the pattern stands upright over your southern horizon.

And speaking of your horizon … To see the Southern Cross from anywhere in the Northern Hemisphere, you’ll want a clear, unobstructed southern horizon. A dark sky will be best. Visit EarthSky’s Best Places to Stargaze.

Read more about seeing the Southern Cross from the Northern Hemisphere.

Want an exact view from your location? Try Stellarium

View at EarthSky Community Photos. | Prateek Pandey in Bhopal, India, caught the Southern Cross at its highest point around midnight (its midnight culmination) on March 6, 2021. In April and May, the Southern Cross reaches its highest point in the sky earlier in the evening. Thank you, Prateek!

Stars of Crux

The brightest star of the Southern Cross is Alpha Crucis, or Acrux. It’s the bottom star of the Cross and shines at magnitude 0.77 from a distance of 320 light-years. It’s also the 12th brightest star in the sky.

Moving in a clockwise circle around the Cross we come to the 2nd brightest star, Beta Crucis, sometimes called Becrux or Mimosa. Beta Crucis is magnitude 1.25 from a distance of 350 light-years.

Next, on the top of the Cross, is Gamma Crucis, or Gacrux. Gacrux shines at magnitude 1.59 at a distance of 88 light-years. Finally, on the right side of the cross, is Delta Crucis. It shines at magnitude 2.79 from a distance of 360 light-years.

The stars of Crux the Southern Cross. Image via/ IAU/ Sky and Telescope/ Wikimedia Commons.

Use the Southern Cross to find due south

Method #1. The south celestial pole is located halfway between Gacrux, the head of the Southern Cross, and the bright star Achernar. For a practical trick, place one hand at the Cross and the other at Achernar. Now bring them together in a clap! Your hands should meet right at the south celestial pole. Chart via EarthSky.

Method #2. Draw an imaginary line extending the long axis of the Southern Cross, and another one bisecting the 2 “Pointer Stars,” Alpha and Beta Centauri. The south celestial pole lies at the intersection between those 2 lines. Chart via EarthSky.

Method #3. To locate the south celestial pole, extend the long axis of the Southern Cross from the head of the cross through its foot, 4 times its own length. Chart via EarthSky.

The Jewel Box and other clusters in Crux

The Jewel Box is one of the most beautiful open clusters in the Southern Hemisphere. It lies just 1 degree from Beta Crucis. The Jewel Box, or NGC 4755, is bright at magnitude 4.2. Kappa Crucis, a magnitude 5.89 star, lies inside.

You can see the Jewel Box without optical aid. But a pair of binoculars or a telescope will bring more of the stars into focus.

Can you see color differences between these glittering gems?

NGC 4755, or the Jewel Box, from ESO’s La Silla Observatory. Image via ESO.

The Coalsack Nebula

The easiest dark nebula to see in the sky is the Coalsack Nebula, found in the southeastern corner of Crux. The Coalsack is a dark, cloudy patch of dust and gas that obscures an entire swath of the Milky Way’s stars that lies behind it.

Meet the Coalsack, a huge cloud of gas and dust in space. The dust in this and other dark nebulae absorb and scatter the light of background stars. This creates a region of the sky that looks starless, but it’s really a place where new stars are forming. May is one of the best months to see the Coalsack in the constellation Crux in the Southern Hemisphere. This image is from the Wide Field Imager on the MPG/ESO 2.2-meter telescope. Image via ESO.

Bottom line: Crux, the constellation of the Southern Cross, is a hallmark of southern skies and contains the open cluster known as the Jewel Box.

Read more: How to see the Southern Cross from the Northern Hemisphere

The post Meet Crux, the constellation of the Southern Cross first appeared on EarthSky.

from EarthSky https://ift.tt/XTkY6ey

Crux is the constellation of the Southern Cross. And it lies deep in Southern Hemisphere skies. Image via EarthSky.

Your support = more stars, more science, more wonder. Donate to EarthSky and be part of something bigger.

If you’re in the Southern Hemisphere, Crux the Southern Cross is one of the easiest constellations you can identify. It’s also one of the most famous! And it’s a reliable marker to the south celestial pole, the point around which the entire southern sky turns.

Crux consists of four relatively bright stars, close to one another and suggestive of a cross. This constellation is circumpolar, staying above the horizon all year round for observers at and south of 34 degrees south latitude. So, for example:

• At Sydney, Australia, (~34° S), most or all of Crux is circumpolar.
• At Buenos Aires, Argentina, (~35° S), it’s comfortably circumpolar.
• At Cape Town, South Africa, (~34° S), same story.
• Farther north – say at the equator – Crux rises and sets seasonally.
• North of about 27 degrees north latitude, Crux never rises at all.

In many ways, Crux is almost the mirror opposite of northern circumpolar constellations like Ursa Major the Greater Bear, with its famous Big Dipper asterism. Like the Big Dipper for northern observers, the Southern Cross is the southern sky’s iconic “always there” pattern.

And for a short time each year it can be seen by those in the southern reaches of the Northern Hemisphere. Jump to that section.

How to see it from the Southern Hemisphere

Crux lies between the constellations Centaurus the Centaur and Musca the Fly. You can locate it simply by looking for four bright stars close together. The stars are less than 5 degrees apart. Five degrees is about the width of your three middle fingers held at arm’s length.

The compact size of Crux makes it the smallest of all the 88 constellations.

And Crux does resemble a cross. But it could also be considered kite-shaped.

Want an exact view from your location? Try Stellarium

Crux the Southern Cross lies in front of the Milky Way with Centaurus and Musca nearby. Image via Stellarium. Used with permission.

How to see it from the Northern Hemisphere

Seeing the Southern Cross from the Northern Hemisphere is a matter of your location + timing + atmosphere + horizon quality.

First, your location. Know what your latitude allows. Crux sits around -60 degrees declination, so:

• At the equator (0 degrees) it can rise to ~30° high. That’s easy to see if the sky is clear.
• At 26 degrees north latitude it barely scrapes the sky at about 4 degrees above the southern horizon.
• At ~27 degrees north latitude and northward it never rises above the horizon.

So at 26 degrees north latitude you are in the extreme edge zone. You can’t just look up and observe the Southern Cross. Instead, you must hunt for it at the most distorted layer of atmosphere above your southern horizon. And you must be hunting at the exact right time.

More Northern Hemisphere viewing tips

Consider the timing. May is a good time to find Crux in the evening sky from the Northern Hemisphere. It’s visible in other months, too, but not at such a convenient time. In March, you have to wait until about 1 a.m. your local time to catch the Southern Cross at its highest elevation. In December and January, you have to catch it before dawn.

No matter the hour or date, Crux climbs to its highest point – crosses your sky’s meridian – in the sky when it’s due south. It’s easy to visualize a cross within this pattern of stars, because the pattern stands upright over your southern horizon.

And speaking of your horizon … To see the Southern Cross from anywhere in the Northern Hemisphere, you’ll want a clear, unobstructed southern horizon. A dark sky will be best. Visit EarthSky’s Best Places to Stargaze.

Read more about seeing the Southern Cross from the Northern Hemisphere.

Want an exact view from your location? Try Stellarium

View at EarthSky Community Photos. | Prateek Pandey in Bhopal, India, caught the Southern Cross at its highest point around midnight (its midnight culmination) on March 6, 2021. In April and May, the Southern Cross reaches its highest point in the sky earlier in the evening. Thank you, Prateek!

Stars of Crux

The brightest star of the Southern Cross is Alpha Crucis, or Acrux. It’s the bottom star of the Cross and shines at magnitude 0.77 from a distance of 320 light-years. It’s also the 12th brightest star in the sky.

Moving in a clockwise circle around the Cross we come to the 2nd brightest star, Beta Crucis, sometimes called Becrux or Mimosa. Beta Crucis is magnitude 1.25 from a distance of 350 light-years.

Next, on the top of the Cross, is Gamma Crucis, or Gacrux. Gacrux shines at magnitude 1.59 at a distance of 88 light-years. Finally, on the right side of the cross, is Delta Crucis. It shines at magnitude 2.79 from a distance of 360 light-years.

The stars of Crux the Southern Cross. Image via/ IAU/ Sky and Telescope/ Wikimedia Commons.

Use the Southern Cross to find due south

Method #1. The south celestial pole is located halfway between Gacrux, the head of the Southern Cross, and the bright star Achernar. For a practical trick, place one hand at the Cross and the other at Achernar. Now bring them together in a clap! Your hands should meet right at the south celestial pole. Chart via EarthSky.

Method #2. Draw an imaginary line extending the long axis of the Southern Cross, and another one bisecting the 2 “Pointer Stars,” Alpha and Beta Centauri. The south celestial pole lies at the intersection between those 2 lines. Chart via EarthSky.

Method #3. To locate the south celestial pole, extend the long axis of the Southern Cross from the head of the cross through its foot, 4 times its own length. Chart via EarthSky.

The Jewel Box and other clusters in Crux

The Jewel Box is one of the most beautiful open clusters in the Southern Hemisphere. It lies just 1 degree from Beta Crucis. The Jewel Box, or NGC 4755, is bright at magnitude 4.2. Kappa Crucis, a magnitude 5.89 star, lies inside.

You can see the Jewel Box without optical aid. But a pair of binoculars or a telescope will bring more of the stars into focus.

Can you see color differences between these glittering gems?

NGC 4755, or the Jewel Box, from ESO’s La Silla Observatory. Image via ESO.

The Coalsack Nebula

The easiest dark nebula to see in the sky is the Coalsack Nebula, found in the southeastern corner of Crux. The Coalsack is a dark, cloudy patch of dust and gas that obscures an entire swath of the Milky Way’s stars that lies behind it.

Meet the Coalsack, a huge cloud of gas and dust in space. The dust in this and other dark nebulae absorb and scatter the light of background stars. This creates a region of the sky that looks starless, but it’s really a place where new stars are forming. May is one of the best months to see the Coalsack in the constellation Crux in the Southern Hemisphere. This image is from the Wide Field Imager on the MPG/ESO 2.2-meter telescope. Image via ESO.

Bottom line: Crux, the constellation of the Southern Cross, is a hallmark of southern skies and contains the open cluster known as the Jewel Box.

Read more: How to see the Southern Cross from the Northern Hemisphere

The post Meet Crux, the constellation of the Southern Cross first appeared on EarthSky.

from EarthSky https://ift.tt/XTkY6ey

Joplin tornado: 15-year anniversary of a disaster

In this image from 10 days after the May 22, 2011, EF5 tornado that hit Joplin, Missouri, piles of rubble mark where people’s homes once stood. It’s now been 15 years since the Joplin tornado, which killed 158 people directly and 5 through a deadly fungus it stirred up. Image via Bob Webster/ Wikimedia Commons.

The 15-year anniversary of the deadly Joplin tornado

On May 22, 2011, an EF5 tornado with winds of more than 200 miles (322 km) per hour devastated Joplin, Missouri. It was the 7th-deadliest tornado in the U.S. and the deadliest tornado since 1947. As the tornado bulldozed a path nearly a mile wide through the city, it took the lives of 158 people and injured more than 1,000.

And, in the days that followed, five more people died due to a deadly soil-dwelling fungus the tornado stirred up.

The Joplin tornado flattened homes, schools and businesses. It caused catastrophic damage at a nine-story hospital, St. John’s Regional Medical Center, which would later have to be demolished. And it became the costliest tornado in U.S. history at the time, with damages approaching $3 billion.

The Joplin tornado damaged St. John’s Hospital beyond repair. Today, a new hospital stands by the interstate. Image via Interlati/ Wikimedia Commons.

A hesitancy to act

The tornado struck on a Sunday evening. A local high school had just finished graduation ceremonies, plus other people were out and about, wrapping up their weekends. Due to the high death toll, the National Weather Service (NWS) conducted a service assessment to try to understand why so many people died.

On the one hand, the NWS found that many of the homes that were in the path of the tornado were poorly constructed. In fact, fatalities occurred in 59 different homes. There were also 19 deaths at a nursing home, four at an ICU, 11 in churches and eight in a Home Depot.

But another finding by the NWS was that when the tornado sirens first went off, many people were initially complacent. Instead of reacting at the first warning, many people reported that they waited as they assessed the risk and looked for more confirmation.

For many, confirmation came in the form of black skies and a terrifying roar as the rain-wrapped tornado overtook them.

Netflix made an excellent documentary on the Joplin tornado called The Twister: Caught in the Storm.

After the tornado, the killer fungus

As the city came together to clean up and mourn the dead, a new lethal aspect of the tornado came to light. While treating the injured in the following days, doctors noticed some survivors were developing severe infections in their wounds.

The culprit turned out to be a rare and often lethal fungal infection. The fungal spores were mucormycetes. Normally, they live in soil and decaying plant matter. But the violent tornado scoured the ground, ripping off topsoil and throwing the dirt and debris into the air. For some people, this dirt became deeply embedded in their wounds.

A 2013 study found that 13 people were affected by the fungus, and five of them died. The fungus can cause flesh-eating infections. The study said:

The researchers discovered a significant link between fungal infection and the occurrence of penetrating wounds (especially multiple wounds) containing wood, soil, gravel, and other foreign bodies.

Joplin today

Today, much of the city of Joplin has been rebuilt. At the site of the former hospital a park now stands. And the new hospital, Mercy Hospital Joplin, stands alongside Interstate 44.

The six schools that were destroyed have now been rebuilt. While many homes replaced those that were turned to rubble, there are still some empty lots. Those lots, and the lack of mature trees, mean you can still see the path of the Joplin tornado on satellite even after 15 years.

This was the satellite view of Joplin, Missouri, in 2011 following the May 22 tornado. Image via NOAA.

This is the satellite view of Joplin, Missouri, today. You can still see a lighter brown strip where the tornado destroyed buildings and trees, changing the landscape. Image via Google Earth Pro.

Bottom line: It’s been 15 years since the Joplin tornado killed more than 150 people. What is the town of Joplin, Missouri, like today?

Read more: The Enhanced Fujita Scale rates the strength of a tornado

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In this image from 10 days after the May 22, 2011, EF5 tornado that hit Joplin, Missouri, piles of rubble mark where people’s homes once stood. It’s now been 15 years since the Joplin tornado, which killed 158 people directly and 5 through a deadly fungus it stirred up. Image via Bob Webster/ Wikimedia Commons.

The 15-year anniversary of the deadly Joplin tornado

On May 22, 2011, an EF5 tornado with winds of more than 200 miles (322 km) per hour devastated Joplin, Missouri. It was the 7th-deadliest tornado in the U.S. and the deadliest tornado since 1947. As the tornado bulldozed a path nearly a mile wide through the city, it took the lives of 158 people and injured more than 1,000.

And, in the days that followed, five more people died due to a deadly soil-dwelling fungus the tornado stirred up.

The Joplin tornado flattened homes, schools and businesses. It caused catastrophic damage at a nine-story hospital, St. John’s Regional Medical Center, which would later have to be demolished. And it became the costliest tornado in U.S. history at the time, with damages approaching $3 billion.

The Joplin tornado damaged St. John’s Hospital beyond repair. Today, a new hospital stands by the interstate. Image via Interlati/ Wikimedia Commons.

A hesitancy to act

The tornado struck on a Sunday evening. A local high school had just finished graduation ceremonies, plus other people were out and about, wrapping up their weekends. Due to the high death toll, the National Weather Service (NWS) conducted a service assessment to try to understand why so many people died.

On the one hand, the NWS found that many of the homes that were in the path of the tornado were poorly constructed. In fact, fatalities occurred in 59 different homes. There were also 19 deaths at a nursing home, four at an ICU, 11 in churches and eight in a Home Depot.

But another finding by the NWS was that when the tornado sirens first went off, many people were initially complacent. Instead of reacting at the first warning, many people reported that they waited as they assessed the risk and looked for more confirmation.

For many, confirmation came in the form of black skies and a terrifying roar as the rain-wrapped tornado overtook them.

Netflix made an excellent documentary on the Joplin tornado called The Twister: Caught in the Storm.

After the tornado, the killer fungus

As the city came together to clean up and mourn the dead, a new lethal aspect of the tornado came to light. While treating the injured in the following days, doctors noticed some survivors were developing severe infections in their wounds.

The culprit turned out to be a rare and often lethal fungal infection. The fungal spores were mucormycetes. Normally, they live in soil and decaying plant matter. But the violent tornado scoured the ground, ripping off topsoil and throwing the dirt and debris into the air. For some people, this dirt became deeply embedded in their wounds.

A 2013 study found that 13 people were affected by the fungus, and five of them died. The fungus can cause flesh-eating infections. The study said:

The researchers discovered a significant link between fungal infection and the occurrence of penetrating wounds (especially multiple wounds) containing wood, soil, gravel, and other foreign bodies.

Joplin today

Today, much of the city of Joplin has been rebuilt. At the site of the former hospital a park now stands. And the new hospital, Mercy Hospital Joplin, stands alongside Interstate 44.

The six schools that were destroyed have now been rebuilt. While many homes replaced those that were turned to rubble, there are still some empty lots. Those lots, and the lack of mature trees, mean you can still see the path of the Joplin tornado on satellite even after 15 years.

This was the satellite view of Joplin, Missouri, in 2011 following the May 22 tornado. Image via NOAA.

This is the satellite view of Joplin, Missouri, today. You can still see a lighter brown strip where the tornado destroyed buildings and trees, changing the landscape. Image via Google Earth Pro.

Bottom line: It’s been 15 years since the Joplin tornado killed more than 150 people. What is the town of Joplin, Missouri, like today?

Read more: The Enhanced Fujita Scale rates the strength of a tornado

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Meet Regulus, Leo the Lion’s Heart and brightest star

Leo the Lion’s brightest star is Regulus, aka the Lion’s Heart. Regulus marks the bright dot at the bottom of a backward question mark that forms Leo’s head and shoulders. This pattern is called the Sickle. An easily identifiable triangle depicts the Lion’s hindquarters and tail, with the star Denebola marking the tail of the Lion. Chart via EarthSky.

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Regulus is the brightest star in the constellation Leo the Lion. Also known as Alpha Leonis, it ranks 21st in the list of brightest stars in our sky.

It’s located near the ecliptic, or sun’s path across our sky. So both Earth’s Northern and Southern Hemispheres see Regulus equally well.

Regulus is part of a backward question mark star pattern, and it marks the dot at the bottom of the question mark. This pattern, known as the Sickle, makes up the head and forequarters of Leo the Lion.

You’ll recognize Regulus for its brightness and blue-white color. It looks like one star to the eye, but it’s really four stars (that we know of so far).

Regulus is located about 79 light-years from Earth.

A star chart showing the constellation Leo the Lion. On the right is a pattern that looks like a flipped question mark, the Sickle. This is the most recognizable pattern to look for when trying to locate Leo in the sky. Image via Torsten Bronger/ Wikimedia Commons.

Finding the Lion from the Northern Hemisphere

In the Northern Hemisphere, the star Regulus and its constellation Leo the Lion are harbingers of spring.

They crept higher in the sky with each passing day in March and April, as northern winter favorites – like Orion the Hunter – descended westward.

And now, in May, blue-white Regulus is brilliant in the eastern evening sky as soon as the sun goes down.

And a darker sky reveals the distinctive Sickle and the overall shape of the Lion.

From the Northern Hemisphere, Regulus is visible at some time of night throughout the year, except for about a month on either side of August 22. If you looked toward Regulus around that date, you’d see the sun.

In the Northern Hemisphere, Regulus is known as one of three bright stars making up the asterism of the Spring Triangle.

From the Southern Hemisphere, the Lion is upside down

Via Daniel Gaussen, Founder & Guide – Stargaze Mackenzie – New Zealand

From southern latitudes, the figure of the Lion – named long ago by stargazers on the northern part of Earth’s globe – appears upside down. Regulus traditionally marks Leo’s lower front paw. But Regulus appears as the highest of Leo’s stars from our southerly perspective.

And, from our latitudes on the south of Earth’s globe, the Sickle asterism appears as a mirrored upside-down question mark. This pattern is clearly recognizable for skywatchers tracing the inverted Lion across the northern sky.

As seen from either the Northern or Southern Hemisphere, Regulus more or less follows the sun and moon’s path across our sky. So those in the Northern Hemisphere face generally southward to see Regulus make its wide arc across the sky. But we in the Southern Hemisphere face generally northward to see it.

At a latitude of 35 degrees south, Regulus climbs to about 43 degrees above the northern horizon at its highest. It’s noticeably higher than other bright northern stars, such as Vega. In the Southern Hemisphere, Regulus is one of the easier northern stars to spot during the southern autumn and early winter evenings (May through August).

So, while Leo is a northern constellation, its most prominent marker – Regulus – remains a useful and reliable reference point from the Southern Hemisphere during the colder months.

Despite the constellation’s inverted appearance, the clarity of Regulus and the distinctive Sickle pattern make Leo surprisingly easy to identify once you know what to look for.

Planets and the moon pass near it

Regulus is the only 1st magnitude star to sit almost squarely on the ecliptic, or path of the sun, moon and planets across our sky.

So the moon sweeps past Regulus once a month when this star is visible. In some years, the moon occults – or passes in front of – Regulus as seen from Earth. We’re in a series of 20 lunar occultations of Regulus now, lasting from July 2025 to December 2026. During the December 2026 occultation, Mars and Jupiter will be nearby.

And bright planets also sometimes pass Regulus. Planets can even sometimes occult – or pass in front of – this star. The last planet to occult Regulus was Venus on July 7, 1959. Then on October 1, 2044, Venus will occult Regulus again.

Don’t miss a thing! Visit our monthly night sky guide.

A blue, egg-shaped star

Regulus is a multiple star system, consisting of at least four stars. The main star – Regulus A – is large and blue with a spectral type of B8 IVn. Its surface temperature averages about 12,460 kelvin (21,970 degrees F or 12,190 degrees C), which is much higher than our sun’s surface temperature. Regulus A is 3.8 times the mass of our sun, about 4 times as wide, and almost 300 times as bright.

Regulus A spins on its axis once every 16 hours. In contrast, our sun spins on its axis about once every 27 days. This fast rotation causes Regulus A to bulge at its equator, so it appears oblate, or egg-shaped. In fact, if Regulus rotated just a bit faster, it would fly apart!

And Regulus isn’t the only star with a fast spin. The stars Altair and Achernar are also fast spinners with flattened, oblate shapes.

Georgia State University’s Center for High Angular Resolution Astronomy (CHARA) created this computer-generated model of Regulus in 2005. Next to it there is a model of our sun for scale. The high rotation rate of Regulus creates pronounced equatorial bulging, such that its diameter across its equator (running nearly vertically in this image) is 1/3 longer than its north-south diameter. Image via Wenjin Huang/ Georgia State University/ NOIRlab.

We can see 3 of Regulus’ 4 stars

Look through a small telescope using at least 50x magnification, and you will see Regulus as two objects separated by 177 arcseconds. The brighter of the pair is Regulus A.

The fainter one is Regulus B, a cool “orange” dwarf star with a spectral classification of K2 V. The B star has a mass that is 80% of the sun’s, and it’s half as bright. It has a surface temperature of 4,885 kelvin (8,300 F or 4,600 C), and it shines at magnitude 8.1.

Regulus B has its own companion: Regulus C. At magnitude 13.5, it’s only visible with powerful telescopes. With just 1/3 the mass of the sun, Regulus C is a red dwarf star with a spectral classification of M4 V. Regulus B and C are gravitationally bound to each other, and together they’re called Regulus BC. The distances between B and C ranged from 4.0 to 2.5 arcseconds between 1867 and 1943. There are no recently available measurements.

The 4th star in the system has never been directly resolved via imaging. But its presence is revealed by spectroscopic analysis of Regulus A. Astronomers think it may be a closely orbiting white dwarf star.

You might have heard of a star called Regulus D. This doesn’t refer to the spectroscopic companion of Regulus A, but to a 12th-magnitude star that sits 212 arcseconds from Regulus. For decades, people believed it to be a companion of Regulus, but recent studies from the Gaia satellite show this to be a background star not related to the Regulus system.

A rex by any other name

The name Regulus is from the diminutive form of the Latin rex, meaning little king.

Ancient Arab stargazers called Regulus by the name Qalb al-Asad, which means Heart of the Lion. It also bears the nickname Cor Leonis, again meaning Lion’s Heart. Fittingly, King Richard I of England was also famously known as the Lionheart, or more commonly Coeur de Lion in French.

There is a great deal of mythology associated with Leo, perhaps the most common tale being that Leo was the Nemean Lion of the Hercules story. Some Peruvians also knew these stars as the Mountain Lion, whereas in China it was sometimes seen as a horse, and at other times as part of a dragon. Christians in the Middle Ages sometimes referred to it as one of Daniel’s lions.

The larger lion is the constellation Leo, with the star Regulus at its heart, as depicted on a set of constellation cards, Urania’s Mirror, published in London in 1825. Above it is the faint constellation Leo Minor. Image via Library of Congress/ Wikimedia Commons.

A galaxy photobombs Regulus

Situated 1/3 degree north of Regulus is the galaxy Leo I. You can see it as a faint patch of light in the photo below. Leo I is difficult to see due to its proximity to Regulus. Albert George Wilson found it on photographic plates taken as part of the National Geographic Society-Palomar Observatory Sky Survey in 1950. It would be another 40 years before anyone viewed it.

Leo I is a dwarf galaxy, and a member of our local group. Amateur astronomers can view it, but this requires dark skies and a large telescope.

Regulus as photographed using a telescope. The faint smudge above it is the dwarf galaxy Leo I. Image via Fred Espenak. Used with permission.

Bottom line: Regulus, the brightest star in the constellation Leo the Lion, is associated with the arrival of spring and is prominent in May skies. It looks like a single point of light, but is really four stars.

Summer Triangle star: Altair is variable and spins fast!

What is the Sickle in Leo?

The post Meet Regulus, Leo the Lion’s Heart and brightest star first appeared on EarthSky.

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Leo the Lion’s brightest star is Regulus, aka the Lion’s Heart. Regulus marks the bright dot at the bottom of a backward question mark that forms Leo’s head and shoulders. This pattern is called the Sickle. An easily identifiable triangle depicts the Lion’s hindquarters and tail, with the star Denebola marking the tail of the Lion. Chart via EarthSky.

Don’t miss the next unmissable night sky event. Sign up for our free newsletter for daily night sky updates, as well as the latest science news.

Regulus is the brightest star in the constellation Leo the Lion. Also known as Alpha Leonis, it ranks 21st in the list of brightest stars in our sky.

It’s located near the ecliptic, or sun’s path across our sky. So both Earth’s Northern and Southern Hemispheres see Regulus equally well.

Regulus is part of a backward question mark star pattern, and it marks the dot at the bottom of the question mark. This pattern, known as the Sickle, makes up the head and forequarters of Leo the Lion.

You’ll recognize Regulus for its brightness and blue-white color. It looks like one star to the eye, but it’s really four stars (that we know of so far).

Regulus is located about 79 light-years from Earth.

A star chart showing the constellation Leo the Lion. On the right is a pattern that looks like a flipped question mark, the Sickle. This is the most recognizable pattern to look for when trying to locate Leo in the sky. Image via Torsten Bronger/ Wikimedia Commons.

Finding the Lion from the Northern Hemisphere

In the Northern Hemisphere, the star Regulus and its constellation Leo the Lion are harbingers of spring.

They crept higher in the sky with each passing day in March and April, as northern winter favorites – like Orion the Hunter – descended westward.

And now, in May, blue-white Regulus is brilliant in the eastern evening sky as soon as the sun goes down.

And a darker sky reveals the distinctive Sickle and the overall shape of the Lion.

From the Northern Hemisphere, Regulus is visible at some time of night throughout the year, except for about a month on either side of August 22. If you looked toward Regulus around that date, you’d see the sun.

In the Northern Hemisphere, Regulus is known as one of three bright stars making up the asterism of the Spring Triangle.

From the Southern Hemisphere, the Lion is upside down

Via Daniel Gaussen, Founder & Guide – Stargaze Mackenzie – New Zealand

From southern latitudes, the figure of the Lion – named long ago by stargazers on the northern part of Earth’s globe – appears upside down. Regulus traditionally marks Leo’s lower front paw. But Regulus appears as the highest of Leo’s stars from our southerly perspective.

And, from our latitudes on the south of Earth’s globe, the Sickle asterism appears as a mirrored upside-down question mark. This pattern is clearly recognizable for skywatchers tracing the inverted Lion across the northern sky.

As seen from either the Northern or Southern Hemisphere, Regulus more or less follows the sun and moon’s path across our sky. So those in the Northern Hemisphere face generally southward to see Regulus make its wide arc across the sky. But we in the Southern Hemisphere face generally northward to see it.

At a latitude of 35 degrees south, Regulus climbs to about 43 degrees above the northern horizon at its highest. It’s noticeably higher than other bright northern stars, such as Vega. In the Southern Hemisphere, Regulus is one of the easier northern stars to spot during the southern autumn and early winter evenings (May through August).

So, while Leo is a northern constellation, its most prominent marker – Regulus – remains a useful and reliable reference point from the Southern Hemisphere during the colder months.

Despite the constellation’s inverted appearance, the clarity of Regulus and the distinctive Sickle pattern make Leo surprisingly easy to identify once you know what to look for.

Planets and the moon pass near it

Regulus is the only 1st magnitude star to sit almost squarely on the ecliptic, or path of the sun, moon and planets across our sky.

So the moon sweeps past Regulus once a month when this star is visible. In some years, the moon occults – or passes in front of – Regulus as seen from Earth. We’re in a series of 20 lunar occultations of Regulus now, lasting from July 2025 to December 2026. During the December 2026 occultation, Mars and Jupiter will be nearby.

And bright planets also sometimes pass Regulus. Planets can even sometimes occult – or pass in front of – this star. The last planet to occult Regulus was Venus on July 7, 1959. Then on October 1, 2044, Venus will occult Regulus again.

Don’t miss a thing! Visit our monthly night sky guide.

A blue, egg-shaped star

Regulus is a multiple star system, consisting of at least four stars. The main star – Regulus A – is large and blue with a spectral type of B8 IVn. Its surface temperature averages about 12,460 kelvin (21,970 degrees F or 12,190 degrees C), which is much higher than our sun’s surface temperature. Regulus A is 3.8 times the mass of our sun, about 4 times as wide, and almost 300 times as bright.

Regulus A spins on its axis once every 16 hours. In contrast, our sun spins on its axis about once every 27 days. This fast rotation causes Regulus A to bulge at its equator, so it appears oblate, or egg-shaped. In fact, if Regulus rotated just a bit faster, it would fly apart!

And Regulus isn’t the only star with a fast spin. The stars Altair and Achernar are also fast spinners with flattened, oblate shapes.

Georgia State University’s Center for High Angular Resolution Astronomy (CHARA) created this computer-generated model of Regulus in 2005. Next to it there is a model of our sun for scale. The high rotation rate of Regulus creates pronounced equatorial bulging, such that its diameter across its equator (running nearly vertically in this image) is 1/3 longer than its north-south diameter. Image via Wenjin Huang/ Georgia State University/ NOIRlab.

We can see 3 of Regulus’ 4 stars

Look through a small telescope using at least 50x magnification, and you will see Regulus as two objects separated by 177 arcseconds. The brighter of the pair is Regulus A.

The fainter one is Regulus B, a cool “orange” dwarf star with a spectral classification of K2 V. The B star has a mass that is 80% of the sun’s, and it’s half as bright. It has a surface temperature of 4,885 kelvin (8,300 F or 4,600 C), and it shines at magnitude 8.1.

Regulus B has its own companion: Regulus C. At magnitude 13.5, it’s only visible with powerful telescopes. With just 1/3 the mass of the sun, Regulus C is a red dwarf star with a spectral classification of M4 V. Regulus B and C are gravitationally bound to each other, and together they’re called Regulus BC. The distances between B and C ranged from 4.0 to 2.5 arcseconds between 1867 and 1943. There are no recently available measurements.

The 4th star in the system has never been directly resolved via imaging. But its presence is revealed by spectroscopic analysis of Regulus A. Astronomers think it may be a closely orbiting white dwarf star.

You might have heard of a star called Regulus D. This doesn’t refer to the spectroscopic companion of Regulus A, but to a 12th-magnitude star that sits 212 arcseconds from Regulus. For decades, people believed it to be a companion of Regulus, but recent studies from the Gaia satellite show this to be a background star not related to the Regulus system.

A rex by any other name

The name Regulus is from the diminutive form of the Latin rex, meaning little king.

Ancient Arab stargazers called Regulus by the name Qalb al-Asad, which means Heart of the Lion. It also bears the nickname Cor Leonis, again meaning Lion’s Heart. Fittingly, King Richard I of England was also famously known as the Lionheart, or more commonly Coeur de Lion in French.

There is a great deal of mythology associated with Leo, perhaps the most common tale being that Leo was the Nemean Lion of the Hercules story. Some Peruvians also knew these stars as the Mountain Lion, whereas in China it was sometimes seen as a horse, and at other times as part of a dragon. Christians in the Middle Ages sometimes referred to it as one of Daniel’s lions.

The larger lion is the constellation Leo, with the star Regulus at its heart, as depicted on a set of constellation cards, Urania’s Mirror, published in London in 1825. Above it is the faint constellation Leo Minor. Image via Library of Congress/ Wikimedia Commons.

A galaxy photobombs Regulus

Situated 1/3 degree north of Regulus is the galaxy Leo I. You can see it as a faint patch of light in the photo below. Leo I is difficult to see due to its proximity to Regulus. Albert George Wilson found it on photographic plates taken as part of the National Geographic Society-Palomar Observatory Sky Survey in 1950. It would be another 40 years before anyone viewed it.

Leo I is a dwarf galaxy, and a member of our local group. Amateur astronomers can view it, but this requires dark skies and a large telescope.

Regulus as photographed using a telescope. The faint smudge above it is the dwarf galaxy Leo I. Image via Fred Espenak. Used with permission.

Bottom line: Regulus, the brightest star in the constellation Leo the Lion, is associated with the arrival of spring and is prominent in May skies. It looks like a single point of light, but is really four stars.

Summer Triangle star: Altair is variable and spins fast!

What is the Sickle in Leo?

The post Meet Regulus, Leo the Lion’s Heart and brightest star first appeared on EarthSky.

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2026 name list for Atlantic hurricanes: Is yours among them?

This is the list of tropical cyclone names for the 2026 Atlantic hurricane season. Read about the names of hurricanes below.

Read: NOAA’s hurricane season forecast for 2026

Atlantic hurricane names for 2026

NOAA’s Climate Prediction Center has just released its hurricane season outlook for 2026. But what are the names for the 2026 Atlantic tropical cyclones and hurricanes?

See the complete list of 2026 tropical cyclone and hurricane names in the image above. If any of these storms become truly destructive in 2026, the World Meteorological Organization, which is in charge of the list, retires and replaces the name. For example, in 2024, the World Meteorological Organization retired the names Beryl, Helene and Milton. Helene, in particular, became the deadliest storm in the U.S. since Katrina in 2005.

The 2026 Atlantic hurricane season officially starts June 1 and extends through November 30.

If you live near the Atlantic basin, you can keep up-to-date with forecasts from the National Hurricane Center.

Learn more about how to prepare for hurricane season.

How do hurricanes get their names?

Meteorologists long ago learned that naming tropical storms and hurricanes helps people remember the storms, communicate about them more effectively, and consequently stay safer if and when a particular storm strikes a coast.

These experts assign names to tropical storms according to an approved list before the start of each hurricane season. The U.S. National Hurricane Center started this practice in the early 1950s. Now, the World Meteorological Organization (WMO) generates and maintains the list of hurricane names.

Here are the hurricane names for 2026

Atlantic hurricane names (season runs from June 1 to November 30) are: Arthur, Bertha, Cristobal, Dolly, Edouard, Fay, Gonzalo, Hanna, Isaias, Josephine, Kyle. Leah, Marco, Nana, Omar. Paulette, Rene, Sally, Teddy, Vicky and Wilfred.

Eastern North Pacific hurricane names (season runs from May 15 to November 30) are: Amanda, Boris, Cristina, Douglas, Elida, Fausto, Genevieve, Hernan, Iselle, Julio, Karina, Lowell, Marie, Norbert, Odalys, Polo, Rachel, Simon, Trudy, Vance, Winnie. Xavier, Yolanda and Zeke.

If you’re interested, you can view those names, and names for upcoming years, at the U.S. National Hurricane Center.

In 2022, Hurricane Ian devastated Florida’s Gulf Coast. It also brought flooding to central Florida, ripped roofs off on the Atlantic Coast and then menaced South Carolina. The name Ian will never again be used for a tropical cyclone or hurricane. Image via NOAA/ GOES.

The history of hurricane names

While people have been naming major storms for hundreds of years, most hurricanes originally had a designation using a system of latitude-longitude numbers. This was useful to meteorologists trying to track these storms. Unfortunately, this system confused people living on coasts seeking hurricane information.

In the early 1950s, the U.S. National Hurricane Center first developed a formal practice for storm naming for the Atlantic Ocean. At that time, storms got their names according to a phonetic alphabet (e.g., Able, Baker, Charlie) and the names used were the same for each hurricane season. In other words, the first hurricane of a season was always named “Able,” the second “Baker,” and so on.

In 1953, to avoid the repetitive use of names, the National Weather Service revised the system to give storms female names. By doing this, the National Weather Service was mimicking the habit of naval meteorologists, who named the storms after women, much as ships at sea traditionally had female names.

In 1978–1979, they revised the system again to include both female and male hurricane names.

See the complete history of naming hurricanes, including retired names, from NOAA.

When does a storm receive a name?

Tropical storms get a name when they display a rotating circulation pattern and wind speeds reach 39 miles per hour (63 kilometers per hour). A tropical storm develops into a hurricane when wind speeds go above 74 mph (119 km/h).

Experts have developed lists of hurricane names for many of the major ocean basins around the world. Today, there are six lists of hurricane names in use for Atlantic Ocean and Eastern North Pacific storms. These lists rotate, one each year. So that means the list of this year’s hurricane names for each basin will come up again six years from now.

However, there’s an exception to this practice. The World Meteorological Organization retires the names of extremely damaging hurricanes for legal, cultural sensitivity and historical reasons. For example, they retired the name Katrina in 2005 following the devastating impact that Hurricane Katrina had on New Orleans. In 2022, the World Meteorological Organization Hurricane Committee retired the names Fiona and Ian.

Hurricane Katrina on August 28, 2005. Image via NASA.

Bottom line: The forecasts for Atlantic hurricanes and tropical storms is out. And the hurricane names for 2026 are ready. What’ll happen next?

Read: NOAA’s hurricane season forecast for 2026

Read more: What is a hurricane storm surge?

The post 2026 name list for Atlantic hurricanes: Is yours among them? first appeared on EarthSky.

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This is the list of tropical cyclone names for the 2026 Atlantic hurricane season. Read about the names of hurricanes below.

Read: NOAA’s hurricane season forecast for 2026

Atlantic hurricane names for 2026

NOAA’s Climate Prediction Center has just released its hurricane season outlook for 2026. But what are the names for the 2026 Atlantic tropical cyclones and hurricanes?

See the complete list of 2026 tropical cyclone and hurricane names in the image above. If any of these storms become truly destructive in 2026, the World Meteorological Organization, which is in charge of the list, retires and replaces the name. For example, in 2024, the World Meteorological Organization retired the names Beryl, Helene and Milton. Helene, in particular, became the deadliest storm in the U.S. since Katrina in 2005.

The 2026 Atlantic hurricane season officially starts June 1 and extends through November 30.

If you live near the Atlantic basin, you can keep up-to-date with forecasts from the National Hurricane Center.

Learn more about how to prepare for hurricane season.

How do hurricanes get their names?

Meteorologists long ago learned that naming tropical storms and hurricanes helps people remember the storms, communicate about them more effectively, and consequently stay safer if and when a particular storm strikes a coast.

These experts assign names to tropical storms according to an approved list before the start of each hurricane season. The U.S. National Hurricane Center started this practice in the early 1950s. Now, the World Meteorological Organization (WMO) generates and maintains the list of hurricane names.

Here are the hurricane names for 2026

Atlantic hurricane names (season runs from June 1 to November 30) are: Arthur, Bertha, Cristobal, Dolly, Edouard, Fay, Gonzalo, Hanna, Isaias, Josephine, Kyle. Leah, Marco, Nana, Omar. Paulette, Rene, Sally, Teddy, Vicky and Wilfred.

Eastern North Pacific hurricane names (season runs from May 15 to November 30) are: Amanda, Boris, Cristina, Douglas, Elida, Fausto, Genevieve, Hernan, Iselle, Julio, Karina, Lowell, Marie, Norbert, Odalys, Polo, Rachel, Simon, Trudy, Vance, Winnie. Xavier, Yolanda and Zeke.

If you’re interested, you can view those names, and names for upcoming years, at the U.S. National Hurricane Center.

In 2022, Hurricane Ian devastated Florida’s Gulf Coast. It also brought flooding to central Florida, ripped roofs off on the Atlantic Coast and then menaced South Carolina. The name Ian will never again be used for a tropical cyclone or hurricane. Image via NOAA/ GOES.

The history of hurricane names

While people have been naming major storms for hundreds of years, most hurricanes originally had a designation using a system of latitude-longitude numbers. This was useful to meteorologists trying to track these storms. Unfortunately, this system confused people living on coasts seeking hurricane information.

In the early 1950s, the U.S. National Hurricane Center first developed a formal practice for storm naming for the Atlantic Ocean. At that time, storms got their names according to a phonetic alphabet (e.g., Able, Baker, Charlie) and the names used were the same for each hurricane season. In other words, the first hurricane of a season was always named “Able,” the second “Baker,” and so on.

In 1953, to avoid the repetitive use of names, the National Weather Service revised the system to give storms female names. By doing this, the National Weather Service was mimicking the habit of naval meteorologists, who named the storms after women, much as ships at sea traditionally had female names.

In 1978–1979, they revised the system again to include both female and male hurricane names.

See the complete history of naming hurricanes, including retired names, from NOAA.

When does a storm receive a name?

Tropical storms get a name when they display a rotating circulation pattern and wind speeds reach 39 miles per hour (63 kilometers per hour). A tropical storm develops into a hurricane when wind speeds go above 74 mph (119 km/h).

Experts have developed lists of hurricane names for many of the major ocean basins around the world. Today, there are six lists of hurricane names in use for Atlantic Ocean and Eastern North Pacific storms. These lists rotate, one each year. So that means the list of this year’s hurricane names for each basin will come up again six years from now.

However, there’s an exception to this practice. The World Meteorological Organization retires the names of extremely damaging hurricanes for legal, cultural sensitivity and historical reasons. For example, they retired the name Katrina in 2005 following the devastating impact that Hurricane Katrina had on New Orleans. In 2022, the World Meteorological Organization Hurricane Committee retired the names Fiona and Ian.

Hurricane Katrina on August 28, 2005. Image via NASA.

Bottom line: The forecasts for Atlantic hurricanes and tropical storms is out. And the hurricane names for 2026 are ready. What’ll happen next?

Read: NOAA’s hurricane season forecast for 2026

Read more: What is a hurricane storm surge?

The post 2026 name list for Atlantic hurricanes: Is yours among them? first appeared on EarthSky.

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Ice volcanoes on Ganymede? New promising candidates found

View larger. | Jupiter’s moon Ganymede is the largest moon in our solar system. Are there ice volcanoes on Ganymede? It’s possible, and now a new study has identified several good candidates. NASA’s Juno spacecraft captured this view of Ganymede on June 7, 2021. Image via NASA/ JPL-Caltech/ SwRI/ MSSS/ Kalleheikki Kannisto.

• Ganymede is Jupiter’s largest moon. It has a deep ocean beneath its outer icy surface. Does it also have ice volcanoes?
• A new international study has identified several good candidates on Ganymede’s frozen surface.
• These are depressions in the surface surrounded by flow-like formations, where water could have erupted to the surface from below.

You deserve a daily dose of good news. For the latest in science and the night sky, click here to subscribe to our free daily newsletter.

Possible ice volcanoes on Ganymede

Does Jupiter’s largest moon Ganymede have ice volcanoes? We don’t know for sure yet, but a new international study has identified some promising candidates.

Ganymede has a deep ocean hidden beneath its icy crust. That’s led scientists to speculate it could have ice volcanoes similar to the explosive geysers on Saturn’s ocean moon Enceladus. And on May 9, 2026, researchers said they have identified four primary locations where water and other volatile materials might have erupted to Ganymede’s surface.

Anezina Solomonidou at the Hellenic Space Center (HSC) in Greece led the new study. The study also includes researchers from France, Italy, Germany, the United States, the Czech Republic, ESA and NASA’s Jet Propulsion Laboratory.

The new peer-reviewed paper is accepted for publication in the Planetary Science Journal.

Musa Patera, a depression on Ganymede some 43 miles (69 km) across. Scientists think it could have been left by an erupting ice volcano. NASA’s Galileo spacecraft captured this view on May 7, 1997. Image via NASA/ JPL/ Wikipedia.

View larger. | Another view of Jupiter’s largest moon Ganymede, from the Juno flyby on June 7, 2021. Image via NASA/ JPL-Caltech/ SwRI/ MSSS; image processing by Kevin M. Gill.

Most promising locations for ice volcanoes

Ganymede has unusual depressions – called paterae – and flow-like structures on its surface. Could upwelling water have formed them?

It certainly seems possible, since Ganymede has a deep, dark ocean beneath its outer icy crust. But it depends on whether the water could get through the crust in cracks or by other means. Scientists estimate Ganymede’s crust to be about 90-95 miles (145-153 km) thick. And they estimate the ocean below to be 60 miles (96 km) deep.

Intriguingly, the flow-like structures would have been formed by flowing icy watery material. And the paterae depressions would have been the volcanic vents. It’s similar to regular volcanism, but involving icy fluids rather than molten rock.

View larger. | Saturn’s ocean moon Enceladus is famous for its geyser-like ice volcanoes. NASA’s Cassini spacecraft took this image on November 21, 2009. Does Ganymede have ice volcanoes too? Image via NASA/ JPL-Caltech/ Space Science Institute.

Implications for life

If there were – or perhaps still are – active ice volcanoes on Ganymede, that could provide clues about the conditions in the ocean below. And those conditions could determine whether Ganymede’s ocean might be habitable or not.

Solomonidou said:

Ganymede is one of the most fascinating worlds in the solar system. Understanding possible cryovolcanic activity can help us better understand how ocean worlds evolve and whether they may host conditions suitable for life.

Anezina Solomonidou at the Hellenic Space Center in Greece led the new study about ice volcanoes on Ganymede. Image via Hellenic Space Center.

Future observations by JUICE

The candidate ice volcanoes will be of great interest for the European Space Agency’s upcoming Jupiter Icy Moons Explorer (JUICE) mission. JUICE was launched in 2023 and will arrive at Jupiter in 2031. It will focus on exploring the largest moons of Jupiter: Ganymede, Callisto, Io and Europa. JUICE will use its MAJIS imaging spectrometer and the JANUS camera system to take a closer look at these potential ice volcanoes.

In 2023, scientists found that Ganymede is coated in salts and organics; and in 2021, they found water vapor in Ganymede’s thin atmosphere.

Also in 2021, NASA released new closeups of Ganymede from its Juno spacecraft. Juno obtained the images on June 7, 2021.

Bottom line: Are there ice volcanoes on Ganymede? A new international study reveals several good candidates on Jupiter’s large ocean moon.

Via Hellenic Space Center

Read more: Jupiter’s moon Ganymede is coated in salts and organics

Read more: Why do Jupiter’s large moons outnumber Saturn’s?

The post Ice volcanoes on Ganymede? New promising candidates found first appeared on EarthSky.

from EarthSky https://ift.tt/UCOoDVx

View larger. | Jupiter’s moon Ganymede is the largest moon in our solar system. Are there ice volcanoes on Ganymede? It’s possible, and now a new study has identified several good candidates. NASA’s Juno spacecraft captured this view of Ganymede on June 7, 2021. Image via NASA/ JPL-Caltech/ SwRI/ MSSS/ Kalleheikki Kannisto.

• Ganymede is Jupiter’s largest moon. It has a deep ocean beneath its outer icy surface. Does it also have ice volcanoes?
• A new international study has identified several good candidates on Ganymede’s frozen surface.
• These are depressions in the surface surrounded by flow-like formations, where water could have erupted to the surface from below.

You deserve a daily dose of good news. For the latest in science and the night sky, click here to subscribe to our free daily newsletter.

Possible ice volcanoes on Ganymede

Does Jupiter’s largest moon Ganymede have ice volcanoes? We don’t know for sure yet, but a new international study has identified some promising candidates.

Ganymede has a deep ocean hidden beneath its icy crust. That’s led scientists to speculate it could have ice volcanoes similar to the explosive geysers on Saturn’s ocean moon Enceladus. And on May 9, 2026, researchers said they have identified four primary locations where water and other volatile materials might have erupted to Ganymede’s surface.

Anezina Solomonidou at the Hellenic Space Center (HSC) in Greece led the new study. The study also includes researchers from France, Italy, Germany, the United States, the Czech Republic, ESA and NASA’s Jet Propulsion Laboratory.

The new peer-reviewed paper is accepted for publication in the Planetary Science Journal.

Musa Patera, a depression on Ganymede some 43 miles (69 km) across. Scientists think it could have been left by an erupting ice volcano. NASA’s Galileo spacecraft captured this view on May 7, 1997. Image via NASA/ JPL/ Wikipedia.

View larger. | Another view of Jupiter’s largest moon Ganymede, from the Juno flyby on June 7, 2021. Image via NASA/ JPL-Caltech/ SwRI/ MSSS; image processing by Kevin M. Gill.

Most promising locations for ice volcanoes

Ganymede has unusual depressions – called paterae – and flow-like structures on its surface. Could upwelling water have formed them?

It certainly seems possible, since Ganymede has a deep, dark ocean beneath its outer icy crust. But it depends on whether the water could get through the crust in cracks or by other means. Scientists estimate Ganymede’s crust to be about 90-95 miles (145-153 km) thick. And they estimate the ocean below to be 60 miles (96 km) deep.

Intriguingly, the flow-like structures would have been formed by flowing icy watery material. And the paterae depressions would have been the volcanic vents. It’s similar to regular volcanism, but involving icy fluids rather than molten rock.

View larger. | Saturn’s ocean moon Enceladus is famous for its geyser-like ice volcanoes. NASA’s Cassini spacecraft took this image on November 21, 2009. Does Ganymede have ice volcanoes too? Image via NASA/ JPL-Caltech/ Space Science Institute.

Implications for life

If there were – or perhaps still are – active ice volcanoes on Ganymede, that could provide clues about the conditions in the ocean below. And those conditions could determine whether Ganymede’s ocean might be habitable or not.

Solomonidou said:

Ganymede is one of the most fascinating worlds in the solar system. Understanding possible cryovolcanic activity can help us better understand how ocean worlds evolve and whether they may host conditions suitable for life.

Anezina Solomonidou at the Hellenic Space Center in Greece led the new study about ice volcanoes on Ganymede. Image via Hellenic Space Center.

Future observations by JUICE

The candidate ice volcanoes will be of great interest for the European Space Agency’s upcoming Jupiter Icy Moons Explorer (JUICE) mission. JUICE was launched in 2023 and will arrive at Jupiter in 2031. It will focus on exploring the largest moons of Jupiter: Ganymede, Callisto, Io and Europa. JUICE will use its MAJIS imaging spectrometer and the JANUS camera system to take a closer look at these potential ice volcanoes.

In 2023, scientists found that Ganymede is coated in salts and organics; and in 2021, they found water vapor in Ganymede’s thin atmosphere.

Also in 2021, NASA released new closeups of Ganymede from its Juno spacecraft. Juno obtained the images on June 7, 2021.

Bottom line: Are there ice volcanoes on Ganymede? A new international study reveals several good candidates on Jupiter’s large ocean moon.

Via Hellenic Space Center

Read more: Jupiter’s moon Ganymede is coated in salts and organics

Read more: Why do Jupiter’s large moons outnumber Saturn’s?

The post Ice volcanoes on Ganymede? New promising candidates found first appeared on EarthSky.

from EarthSky https://ift.tt/UCOoDVx

Cumulonimbus clouds bring thunderstorms: How to spot them

Terry O’Leary of Virginia Beach, Virginia, captured the classic anvil shape of cumulonimbus clouds – out the window of an airplane – in early summer 2003 over central Virginia. Image via NASA GLOBE Clouds.

Love wildlife and the natural world? Get the latest animal stories – as well as space and night sky updates – delivered to your inbox.

What are cumulonimbus clouds?

Cumulonimbus clouds are among the most awe-inspiring of cloud formations. They might start as low as 0.6 miles (1,000 meters) above Earth’s surface. And their tops can reach up to 7 miles (12,000 meters) or more. So they can tower for miles into the sky, bumping into Earth’s stratosphere. Cumulonimbus clouds are known to flatten out into an anvil shape on top. They’re sometimes called thunderheads, because they’re the engines behind thunderstorms, severe weather and even tornadoes.

If you see a cumulonimbus cloud bubbling upward into the sky, get ready to take cover!

The word cumulonimbus comes from the Latin cumulo meaning heap or pile and nimbus meaning cloud. They begin as puffy white cumulus clouds that can rapidly grow under the right conditions.

How do they form?

As with cumulus clouds, which are fair-weather clouds, a cumulonimbus cloud begins with the process of convection. That’s what happens when warm air rises, because it’s less dense than the cooler air around it. Convection tends to happen on warm days when Earth’s surface heats unevenly, for example, in the afternoon over land. As the warm, moist air rises, it cools and condenses, forming puffy cumulus clouds.

If the rising air continues to be warmer than its surroundings, it’ll keep growing. That’s when it’ll form larger and taller clouds. When the atmosphere is particularly unstable – meaning that temperature decreases rapidly with height – this upward motion becomes more vigorous. In this case, a cumulus cloud can quickly grow into a cumulonimbus cloud.

Inside a developing cumulonimbus cloud, there are both updrafts and downdrafts. The winds of the updrafts can reach speeds of more than 100 mph (161 kph). These updrafts carry water vapor high into the atmosphere, where it condenses into water droplets or ice crystals. This process releases latent heat, fueling further cloud growth. The top of the cloud eventually flattens out when it hits the tropopause, the divider between the lower troposphere (the bottom layer of the atmosphere, where we live) and the higher stratosphere.

Watch this time lapse of cumulus clouds growing into a towering cumulonimbus cloud with an anvil top.

When and where do you see cumulonimbus clouds?

Cumulonimbus clouds can form anywhere in the world. But they’re most common in regions where warm, moist air is prevalent. In the United States, for instance, you can frequently see these clouds in the spring and summer months. That’s especially true if you live in the U.S. Great Plains, Midwest and Southeast, where warm, humid air from the Gulf of Mexico interacts with cooler air masses. But you can also see these clouds nearly every summer afternoon in central Florida, thanks to sea breezes and lots of tropical moisture.

And indeed – although they can also occur at other times of the day or night – afternoon and early evening are the best times to look for cumulonimbus clouds. That’s when surface heating from the sun is at its peak.

What kind of weather do cumulonimbus clouds bring?

Cumulonimbus clouds are synonymous with severe weather. They are the primary cloud type responsible for thunderstorms.

Depending on their intensity and the conditions around them, cumulonimbus clouds can produce:

• Torrential rain: Localized downpours that can lead to flash flooding.
• Hail: Ice particles carried in updrafts and downdrafts, growing larger before falling to the ground.
• Strong winds: Often associated with downdrafts or microbursts, which can cause damage similar to weak tornadoes.
• Tornadoes: In the most severe storms, rotating updrafts can spawn tornadoes.
• Lightning: Electrical charges can trigger lightning within the cloud and also send bolts careening to the ground.

Due to all these hazards, airplanes fly around – and not through – cumulonimbus clouds.

In this video, you can see air traffic diverting around cumulonimbus clouds and then circling, waiting for the storms to clear the Atlanta airport before landing.

Stay safe

When you see a cumulonimbus cloud, think safety. The lightning from these clouds can strike miles away, far from where the cloud is producing rain. Hail can be dangerous for people and animals without shelter. Torrential rain can cause flash flooding, and strong winds and tornadoes can send objects flying.

Cumulonimbus clouds are awe-inspiring and formidable phenomena that remind us of nature’s raw power. Spotting a cumulonimbus cloud offers us a glimpse into the dynamic processes of the atmosphere. And it provides a warning of the powerful forces brewing above.

If you catch a great image of a cumulonimbus cloud, submit it to EarthSky’s community page.

View at EarthSky Community Photos. | Ross Stone captured this image in California on July 31, 2024. Ross wrote: “When I saw this gigantic cumulonimbus cloud I had to pull off to the side of the road and take out my camera. I absolutely love the summertime clouds.” Thank you, Ross!

Bottom line: Cumulonimbus clouds, sometimes called thunderheads, are towering formations that can bring severe storms such as hail, lightning, flooding and tornadoes.

Read more:

Cloud shapes are a useful tool for predicting weather

Media we love: The book A Cloud a Day

Bumpy flight? Here’s how clouds affect air travel

The post Cumulonimbus clouds bring thunderstorms: How to spot them first appeared on EarthSky.

from EarthSky https://ift.tt/yfUla1o

Terry O’Leary of Virginia Beach, Virginia, captured the classic anvil shape of cumulonimbus clouds – out the window of an airplane – in early summer 2003 over central Virginia. Image via NASA GLOBE Clouds.

Love wildlife and the natural world? Get the latest animal stories – as well as space and night sky updates – delivered to your inbox.

What are cumulonimbus clouds?

Cumulonimbus clouds are among the most awe-inspiring of cloud formations. They might start as low as 0.6 miles (1,000 meters) above Earth’s surface. And their tops can reach up to 7 miles (12,000 meters) or more. So they can tower for miles into the sky, bumping into Earth’s stratosphere. Cumulonimbus clouds are known to flatten out into an anvil shape on top. They’re sometimes called thunderheads, because they’re the engines behind thunderstorms, severe weather and even tornadoes.

If you see a cumulonimbus cloud bubbling upward into the sky, get ready to take cover!

The word cumulonimbus comes from the Latin cumulo meaning heap or pile and nimbus meaning cloud. They begin as puffy white cumulus clouds that can rapidly grow under the right conditions.

How do they form?

As with cumulus clouds, which are fair-weather clouds, a cumulonimbus cloud begins with the process of convection. That’s what happens when warm air rises, because it’s less dense than the cooler air around it. Convection tends to happen on warm days when Earth’s surface heats unevenly, for example, in the afternoon over land. As the warm, moist air rises, it cools and condenses, forming puffy cumulus clouds.

If the rising air continues to be warmer than its surroundings, it’ll keep growing. That’s when it’ll form larger and taller clouds. When the atmosphere is particularly unstable – meaning that temperature decreases rapidly with height – this upward motion becomes more vigorous. In this case, a cumulus cloud can quickly grow into a cumulonimbus cloud.

Inside a developing cumulonimbus cloud, there are both updrafts and downdrafts. The winds of the updrafts can reach speeds of more than 100 mph (161 kph). These updrafts carry water vapor high into the atmosphere, where it condenses into water droplets or ice crystals. This process releases latent heat, fueling further cloud growth. The top of the cloud eventually flattens out when it hits the tropopause, the divider between the lower troposphere (the bottom layer of the atmosphere, where we live) and the higher stratosphere.

Watch this time lapse of cumulus clouds growing into a towering cumulonimbus cloud with an anvil top.

When and where do you see cumulonimbus clouds?

Cumulonimbus clouds can form anywhere in the world. But they’re most common in regions where warm, moist air is prevalent. In the United States, for instance, you can frequently see these clouds in the spring and summer months. That’s especially true if you live in the U.S. Great Plains, Midwest and Southeast, where warm, humid air from the Gulf of Mexico interacts with cooler air masses. But you can also see these clouds nearly every summer afternoon in central Florida, thanks to sea breezes and lots of tropical moisture.

And indeed – although they can also occur at other times of the day or night – afternoon and early evening are the best times to look for cumulonimbus clouds. That’s when surface heating from the sun is at its peak.

What kind of weather do cumulonimbus clouds bring?

Cumulonimbus clouds are synonymous with severe weather. They are the primary cloud type responsible for thunderstorms.

Depending on their intensity and the conditions around them, cumulonimbus clouds can produce:

• Torrential rain: Localized downpours that can lead to flash flooding.
• Hail: Ice particles carried in updrafts and downdrafts, growing larger before falling to the ground.
• Strong winds: Often associated with downdrafts or microbursts, which can cause damage similar to weak tornadoes.
• Tornadoes: In the most severe storms, rotating updrafts can spawn tornadoes.
• Lightning: Electrical charges can trigger lightning within the cloud and also send bolts careening to the ground.

Due to all these hazards, airplanes fly around – and not through – cumulonimbus clouds.

In this video, you can see air traffic diverting around cumulonimbus clouds and then circling, waiting for the storms to clear the Atlanta airport before landing.

Stay safe

When you see a cumulonimbus cloud, think safety. The lightning from these clouds can strike miles away, far from where the cloud is producing rain. Hail can be dangerous for people and animals without shelter. Torrential rain can cause flash flooding, and strong winds and tornadoes can send objects flying.

Cumulonimbus clouds are awe-inspiring and formidable phenomena that remind us of nature’s raw power. Spotting a cumulonimbus cloud offers us a glimpse into the dynamic processes of the atmosphere. And it provides a warning of the powerful forces brewing above.

If you catch a great image of a cumulonimbus cloud, submit it to EarthSky’s community page.

View at EarthSky Community Photos. | Ross Stone captured this image in California on July 31, 2024. Ross wrote: “When I saw this gigantic cumulonimbus cloud I had to pull off to the side of the road and take out my camera. I absolutely love the summertime clouds.” Thank you, Ross!

Bottom line: Cumulonimbus clouds, sometimes called thunderheads, are towering formations that can bring severe storms such as hail, lightning, flooding and tornadoes.

Read more:

Cloud shapes are a useful tool for predicting weather

Media we love: The book A Cloud a Day

Bumpy flight? Here’s how clouds affect air travel

The post Cumulonimbus clouds bring thunderstorms: How to spot them first appeared on EarthSky.

from EarthSky https://ift.tt/yfUla1o