aads

Smoke-covered California, from space

Image via satellite of smoke along the entire U.S. West coast.

As of yesterday, more than 650 fires were blazing in California after unprecedented lightning strikes, storms, and a heatwave that has set new records in the state. Find out more and get updates here. This image is from Monday, from NASA’s Terra satellite; it shows a smoke-covered California. Read more from NASA.



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Image via satellite of smoke along the entire U.S. West coast.

As of yesterday, more than 650 fires were blazing in California after unprecedented lightning strikes, storms, and a heatwave that has set new records in the state. Find out more and get updates here. This image is from Monday, from NASA’s Terra satellite; it shows a smoke-covered California. Read more from NASA.



from EarthSky https://ift.tt/3jm64QF

Are there more rogue planets than stars in our galaxy?

Bluish planet with dark bands and stars in background.

Artist’s concept of rogue planet CFBDSIR J214947.2-040308.9. Researchers now think there could be more such nomadic planets than stars in our galaxy. Image via ESO/ L. Calçada/ P. Delorme/ Nick Risinger (skysurvey.org)/ R. Saito/ VVV Consortium.

There are some 100 to 400 billion stars in our Milky Way galaxy. Scientists now say there may be as many, or more, exoplanets or planets orbiting those distant stars. That’s incredible to ponder, but now consider this. Researchers at Ohio State University just announced a new study suggesting there may be more free-floating rogue planets – planets not orbiting any star – than stars in the Milky Way. Wow!

The theoretical, but fascinating, peer-reviewed conclusions were published in The Astronomical Journal on August 21, 2020.

What more, these scientists say, an upcoming NASA mission, the Nancy Grace Roman Space Telescope, should be able to find hundreds or more of these rogue planets. Astronomer Samson Johnson at Ohio State – lead author of the study – commented:

This gives us a window into these worlds that we would otherwise not have. Imagine our little rocky planet just floating freely in space; that’s what this mission will help us find.

As our view of the universe has expanded, we’ve realized that our solar system may be unusual. Roman will help us learn more about how we fit in the cosmic scheme of things by studying rogue planets.

Dark planet with galaxy in the background.

Illustration of a rogue planet floating through space between the stars. Image via NASA/ JPL-Caltech/ R. Hurt (Caltech-IPAC).

These rogue worlds are called free-floating planetary-mass objects (FFPs) and have masses similar to planets that orbit stars. Scientists don’t yet know how they came to be cosmic wanderers, untethered to any stars, but it’s possible that they were once part of regular solar systems, and somehow broke free of their stars’ gravity. Roman should be able to provide more clues, and provide a better idea of how many are out there. According to Scott Gaudi at Ohio State and a co-author of the paper:

The universe could be teeming with rogue planets and we wouldn’t even know it. We would never find out without undertaking a thorough, space-based microlensing survey like Roman is going to do.

If scientists can start to build a census of the numbers of FFPs, that itself would help them figure out how they formed. Do they form around stars just like other planets and then get ejected from those planetary systems? Or do they form from gas and dust independently of stars? It’s also thought that the ejection of planets from their home planetary systems might be more common in denser star clusters, since more frequent encounters between stars in dense clusters will make the planetary systems unstable.

Grid with small moving sphere and graph on black background.

Animation depicting how gravitational microlensing can reveal rogue planets. When an unseen rogue planet passes in front of a more distant star from our vantage point, light from the star bends as it passes through the warped space-time around the planet. The planet acts as a cosmic magnifying glass, amplifying the brightness of the background star. Image via NASA.

Roman will test various theories and models to see which ones come closest to explain these enigmatic worlds.

It is expected that Roman will be 10 times more sensitive in detecting these objects than previous searches. Roman will focus on searching for FFPs between our sun and the center of the galaxy. That search will span about 24,000 light-years in total. Johnson said:

There have been several rogue planets discovered, but to actually get a complete picture, our best bet is something like Roman. This is a totally new frontier.

According to the new paper, it is expected that Roman should find at least 250 FFPs, even ones as small as Mars.

Spacecraft in front of bright star cluster.

Artist’s rendering of NASA’s upcoming Nancy Grace Roman Space Telescope. Image via NASA/ Ohio State News.

Last year, another study estimated that there could be 50 billion such nomad planets in our galaxy. About a dozen or so confirmed rogue planets have been found so far, and two of those were announced last year: OGLE-2012-BLG-1323 and OGLE-2017-BLG-0560. The first is estimated to have a mass between Earth and Neptune, while the other has a mass between Jupiter and a brown dwarf star.

Exoplanets orbiting stars can be difficult to detect, and rogue exoplanets even more so. How will Roman find them? It will use a technique called gravitational lensing, which relies on the gravity of stars and planets to bend and magnify the light coming from stars that pass behind them, from the telescope’s viewpoint. This technique can find exoplanets thousands of light-years from Earth, and is based on Albert Einstein’s theory of General Relativity. According to co-author Matthew Penny at Louisiana State University in Baton Rouge:

The microlensing signal from a rogue planet only lasts between a few hours and a couple of days and then is gone forever. This makes them difficult to observe from Earth, even with multiple telescopes. Roman is a game-changer for rogue planet searches.

Of course, another question is whether any rogue planets could support life. Johnson said it is probably unlikely since they have no stars for heat and energy:

They would probably be extremely cold, because they have no star.

Smiling man in dark shirt with building behind him.

Samson Johnson at The Ohio State University, lead author of the new study. Image via Ohio State News.

Discovering how rogue planets came to be will help astronomers figure out what makes them so unique and also better understand how regular planetary systems form. Johnson said:

If we find a lot of low-mass rogue planets, we’ll know that as stars form planets, they’re probably ejecting a bunch of other stuff out into the galaxy. This helps us get a handle on the formation pathway of planets in general.

Rogue planets are enigmatic objects, essentially planets as we know them but with no stars to call home. And there may be many more of them than ever thought possible.

Bottom line: New research shows that there could be more rogue, free-floating planets than stars in our galaxy.

Source: Predictions of the Nancy Grace Roman Space Telescope Galactic Exoplanet Survey. II. Free-floating Planet Detection Rates*

Via Ohio State News

Via NASA

An upcoming NASA mission, the Nancy Grace Roman Space Telescope, should be able to find hundreds or more of them.



from EarthSky https://ift.tt/2FPGe8X
Bluish planet with dark bands and stars in background.

Artist’s concept of rogue planet CFBDSIR J214947.2-040308.9. Researchers now think there could be more such nomadic planets than stars in our galaxy. Image via ESO/ L. Calçada/ P. Delorme/ Nick Risinger (skysurvey.org)/ R. Saito/ VVV Consortium.

There are some 100 to 400 billion stars in our Milky Way galaxy. Scientists now say there may be as many, or more, exoplanets or planets orbiting those distant stars. That’s incredible to ponder, but now consider this. Researchers at Ohio State University just announced a new study suggesting there may be more free-floating rogue planets – planets not orbiting any star – than stars in the Milky Way. Wow!

The theoretical, but fascinating, peer-reviewed conclusions were published in The Astronomical Journal on August 21, 2020.

What more, these scientists say, an upcoming NASA mission, the Nancy Grace Roman Space Telescope, should be able to find hundreds or more of these rogue planets. Astronomer Samson Johnson at Ohio State – lead author of the study – commented:

This gives us a window into these worlds that we would otherwise not have. Imagine our little rocky planet just floating freely in space; that’s what this mission will help us find.

As our view of the universe has expanded, we’ve realized that our solar system may be unusual. Roman will help us learn more about how we fit in the cosmic scheme of things by studying rogue planets.

Dark planet with galaxy in the background.

Illustration of a rogue planet floating through space between the stars. Image via NASA/ JPL-Caltech/ R. Hurt (Caltech-IPAC).

These rogue worlds are called free-floating planetary-mass objects (FFPs) and have masses similar to planets that orbit stars. Scientists don’t yet know how they came to be cosmic wanderers, untethered to any stars, but it’s possible that they were once part of regular solar systems, and somehow broke free of their stars’ gravity. Roman should be able to provide more clues, and provide a better idea of how many are out there. According to Scott Gaudi at Ohio State and a co-author of the paper:

The universe could be teeming with rogue planets and we wouldn’t even know it. We would never find out without undertaking a thorough, space-based microlensing survey like Roman is going to do.

If scientists can start to build a census of the numbers of FFPs, that itself would help them figure out how they formed. Do they form around stars just like other planets and then get ejected from those planetary systems? Or do they form from gas and dust independently of stars? It’s also thought that the ejection of planets from their home planetary systems might be more common in denser star clusters, since more frequent encounters between stars in dense clusters will make the planetary systems unstable.

Grid with small moving sphere and graph on black background.

Animation depicting how gravitational microlensing can reveal rogue planets. When an unseen rogue planet passes in front of a more distant star from our vantage point, light from the star bends as it passes through the warped space-time around the planet. The planet acts as a cosmic magnifying glass, amplifying the brightness of the background star. Image via NASA.

Roman will test various theories and models to see which ones come closest to explain these enigmatic worlds.

It is expected that Roman will be 10 times more sensitive in detecting these objects than previous searches. Roman will focus on searching for FFPs between our sun and the center of the galaxy. That search will span about 24,000 light-years in total. Johnson said:

There have been several rogue planets discovered, but to actually get a complete picture, our best bet is something like Roman. This is a totally new frontier.

According to the new paper, it is expected that Roman should find at least 250 FFPs, even ones as small as Mars.

Spacecraft in front of bright star cluster.

Artist’s rendering of NASA’s upcoming Nancy Grace Roman Space Telescope. Image via NASA/ Ohio State News.

Last year, another study estimated that there could be 50 billion such nomad planets in our galaxy. About a dozen or so confirmed rogue planets have been found so far, and two of those were announced last year: OGLE-2012-BLG-1323 and OGLE-2017-BLG-0560. The first is estimated to have a mass between Earth and Neptune, while the other has a mass between Jupiter and a brown dwarf star.

Exoplanets orbiting stars can be difficult to detect, and rogue exoplanets even more so. How will Roman find them? It will use a technique called gravitational lensing, which relies on the gravity of stars and planets to bend and magnify the light coming from stars that pass behind them, from the telescope’s viewpoint. This technique can find exoplanets thousands of light-years from Earth, and is based on Albert Einstein’s theory of General Relativity. According to co-author Matthew Penny at Louisiana State University in Baton Rouge:

The microlensing signal from a rogue planet only lasts between a few hours and a couple of days and then is gone forever. This makes them difficult to observe from Earth, even with multiple telescopes. Roman is a game-changer for rogue planet searches.

Of course, another question is whether any rogue planets could support life. Johnson said it is probably unlikely since they have no stars for heat and energy:

They would probably be extremely cold, because they have no star.

Smiling man in dark shirt with building behind him.

Samson Johnson at The Ohio State University, lead author of the new study. Image via Ohio State News.

Discovering how rogue planets came to be will help astronomers figure out what makes them so unique and also better understand how regular planetary systems form. Johnson said:

If we find a lot of low-mass rogue planets, we’ll know that as stars form planets, they’re probably ejecting a bunch of other stuff out into the galaxy. This helps us get a handle on the formation pathway of planets in general.

Rogue planets are enigmatic objects, essentially planets as we know them but with no stars to call home. And there may be many more of them than ever thought possible.

Bottom line: New research shows that there could be more rogue, free-floating planets than stars in our galaxy.

Source: Predictions of the Nancy Grace Roman Space Telescope Galactic Exoplanet Survey. II. Free-floating Planet Detection Rates*

Via Ohio State News

Via NASA

An upcoming NASA mission, the Nancy Grace Roman Space Telescope, should be able to find hundreds or more of them.



from EarthSky https://ift.tt/2FPGe8X

5 myths about lightning debunked

Huge bolt of lighting in a purple sky over a baseball diamond.

Image via NOAA

This article was originally published by NOAA on August 19, 2020.

Although lighting can happen at any time of the year, lightning strikes most often during summer months. So far this year, there have been 26 people reported to have been struck by lightning; 12 of those people died.

It might be cool to look at from a safe distance, but lightning kills more than 20 people each year in the United States and injures hundreds more — with some survivors suffering lifelong neurological damage. One thing that is for certain: No place outside is safe during a thunderstorm.

As of August 18, 2020, 12 lightning fatalities have occurred this year. Image via NOAA National Weather Service

What else should you know about this electrical wonder of nature? We debunk 5 popular myths with science-backed facts about this dangerous and often misunderstood phenomenon.

Myth #1: A tree can act as sufficient shelter during a thunderstorm.

Fact: No. Standing underneath or near a tree is the second most dangerous place to be during a thunderstorm; the most dangerous is being outside in an open space. An enclosed building with wiring and plumbing is the safest place to be during a storm. Remember: Trees, sheds, picnic shelters, tents or covered porches will not protect you from lightning.

Myth #2: Lightning victims carry an electrical charge. If you touch them, you can be electrocuted.

Fact: Not true. The human body does not store electricity. If you are able to, you should give a lightning victim first aid and/or immediately call 911. This is the most chilling of lightning myths because it could be the difference between life and death.

NOAA’s GOES-East (GOES-16) satellite watched 10 hours of lightning in Florida on August 18, 2020, shown in this 3-second time-lapse video.The area spanning Tampa Bay to Titusville, Florida (a.k.a. Lightning Alley) receives the most yearly lightning in the U.S. Image via NOAA

Myth #3: If you are trapped outside during a thunderstorm, crouching down will reduce your risk of being struck by lightning.

Fact: No. Crouching down will not make you any safer. If you are stuck outside during a storm, keep moving toward a safe shelter.

Image via NOAA/ NWS)

Myth #4: Lightning never strikes in one place twice.

Fact: Actually, lightning can, and often does, strike the same place repeatedly — especially if it’s a tall and isolated object. For example, the Empire State Building is hit about 25 times per year.

Here’s more from the National Weather Service:

Myth #5: Lightning cannot strike in an area if it is not raining and skies are clear.

Fact: Not true. Do not wait until a thunderstorm is immediately overhead and for rain to begin to act. If you can hear thunder, lightning is close enough to pose an immediate threat, even if the sky above you is blue. If thunder roars, seek shelter immediately.

Bottom line: NOAA debunks five popular myths about lightning.



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Huge bolt of lighting in a purple sky over a baseball diamond.

Image via NOAA

This article was originally published by NOAA on August 19, 2020.

Although lighting can happen at any time of the year, lightning strikes most often during summer months. So far this year, there have been 26 people reported to have been struck by lightning; 12 of those people died.

It might be cool to look at from a safe distance, but lightning kills more than 20 people each year in the United States and injures hundreds more — with some survivors suffering lifelong neurological damage. One thing that is for certain: No place outside is safe during a thunderstorm.

As of August 18, 2020, 12 lightning fatalities have occurred this year. Image via NOAA National Weather Service

What else should you know about this electrical wonder of nature? We debunk 5 popular myths with science-backed facts about this dangerous and often misunderstood phenomenon.

Myth #1: A tree can act as sufficient shelter during a thunderstorm.

Fact: No. Standing underneath or near a tree is the second most dangerous place to be during a thunderstorm; the most dangerous is being outside in an open space. An enclosed building with wiring and plumbing is the safest place to be during a storm. Remember: Trees, sheds, picnic shelters, tents or covered porches will not protect you from lightning.

Myth #2: Lightning victims carry an electrical charge. If you touch them, you can be electrocuted.

Fact: Not true. The human body does not store electricity. If you are able to, you should give a lightning victim first aid and/or immediately call 911. This is the most chilling of lightning myths because it could be the difference between life and death.

NOAA’s GOES-East (GOES-16) satellite watched 10 hours of lightning in Florida on August 18, 2020, shown in this 3-second time-lapse video.The area spanning Tampa Bay to Titusville, Florida (a.k.a. Lightning Alley) receives the most yearly lightning in the U.S. Image via NOAA

Myth #3: If you are trapped outside during a thunderstorm, crouching down will reduce your risk of being struck by lightning.

Fact: No. Crouching down will not make you any safer. If you are stuck outside during a storm, keep moving toward a safe shelter.

Image via NOAA/ NWS)

Myth #4: Lightning never strikes in one place twice.

Fact: Actually, lightning can, and often does, strike the same place repeatedly — especially if it’s a tall and isolated object. For example, the Empire State Building is hit about 25 times per year.

Here’s more from the National Weather Service:

Myth #5: Lightning cannot strike in an area if it is not raining and skies are clear.

Fact: Not true. Do not wait until a thunderstorm is immediately overhead and for rain to begin to act. If you can hear thunder, lightning is close enough to pose an immediate threat, even if the sky above you is blue. If thunder roars, seek shelter immediately.

Bottom line: NOAA debunks five popular myths about lightning.



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Ophiuchus is part of the zodiac, too

Tonight – August 26, 2020 – the moon is passing in front of the faint zodiacal constellation Ophiuchus the Serpent Bearer. The above sky chart shows only the southern part of Ophiuchus. We show this constellation in his entirety later on in this post.

From Northern Hemisphere latitudes, you’ll see the Serpent Bearer in the south to southwest on August and September evenings. From the Southern Hemisphere, Ophiuchus is closer to overhead. The bright red star Antares – brightest light in the constellation Scorpius the Scorpion – is also nearby.

Poor Ophiuchus. Nobody ever claims him as a birth sign, despite the fact that the ecliptic runs across him, too, just as it does the 12 better-known constellations of the zodiac. But the sun, moon and planets do regularly move within this constellation’s boundaries. The sun moves in front of Ophiuchus from about November 30 to December 18 each year.

The zodiac – or “pathway of animals” – represents a rather narrow band of of sky astride the ecliptic, which is the plane of Earth’s orbit projected onto the sphere of stars. The signs of the zodiac are familiar to all who read online astrology advice. There are 12 familiar signs of the zodiac: Aries, Taurus, Gemini, Cancer and so on. But … no Ophiuchus.

Read more: Sun in zodiac constellations, 2020

Read more: Sun’s entry into zodiac signs, 2020

Antique colored etching of bald, bearded old man in ancient Greek garb holding a long snake.

Ophiuchus holding the serpent, Serpens, as depicted in Urania’s Mirror, a set of constellation cards published in London c. 1825. Image via Wikipedia.

On sky maps, Ophiuchus the Serpent Bearer is depicted as holding Serpens the Serpent, which is considered a separate constellation. According to ancient Greek star lore, Ophiuchus is Asclepius, Greek god of medicine and doctors. Asclepius is said to have concocted a healing potion from the venom of Serpens the Serpent, mixing it with a Gorgon’s blood and an unknown herb. This potion gave humans access to immortality, until the god of the underworld, Pluto, appealed to the king of the gods, Zeus, to reconsider the ramifications of the death of death.

Even today, the Staff of Asclepius – symbol of the World Health Organization and other medical organizations – pays tribute to the constellation Ophiuchus the Serpent Bearer.

black on white star chart of Ophiuchus with ecliptic line.

View larger. | Ophiuchus the Serpent Bearer.

How can you find this constellation? First of all, you need a dark sky. With the moon waxing now, you won’t have a moonless evening until the end of the first week of September 2020. We show the southernmost portion of Ophiuchus on the chart at top, and the constellation in full on the sky chart below. To see Ophiuchus, stand outside under your light-free sky until your eyes are fully adjusted to the dark. Ophiuchus is faint. But you’ll easily recognize the constellation Scorpius nearby. From our Northern Hemisphere locations, Ophiuchus looms above Scorpius. He’s a mighty figure that your eyes will pick out, if you’re looking for him.

The official boundary lines for all 88 constellations were drawn up by the International Astronomical Union in the 1930s. The photo below of the constellation Ophiuchus labels Ophiuchus’ brightest star, Rasalhague, and Scorpius’ brightest star, Antares. Rasalhague marks the head of Ophiuchus but is nowhere as bright as Antares, the star that depicts the Scorpion’s beating heart.

Constellation drawn on star field with stars Antares and Rasalhague marked.

Photo: Till Credner, AlltheSky.com.

Bottom line: Poor Ophiuchus. Astrologers don’t typically mention him, because he’s a constellation – not a sign – of the zodiac. However, the sun moves in front of this constellation’s stars from about November 30 to December 18, every year. Find Ophiuchus’ location in the sky tonight, and then when the moon moves away from this section of sky, try to envision the Serpent Holder in a dark sky!

Born late November to middle December? Here’s your constellation

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Tonight – August 26, 2020 – the moon is passing in front of the faint zodiacal constellation Ophiuchus the Serpent Bearer. The above sky chart shows only the southern part of Ophiuchus. We show this constellation in his entirety later on in this post.

From Northern Hemisphere latitudes, you’ll see the Serpent Bearer in the south to southwest on August and September evenings. From the Southern Hemisphere, Ophiuchus is closer to overhead. The bright red star Antares – brightest light in the constellation Scorpius the Scorpion – is also nearby.

Poor Ophiuchus. Nobody ever claims him as a birth sign, despite the fact that the ecliptic runs across him, too, just as it does the 12 better-known constellations of the zodiac. But the sun, moon and planets do regularly move within this constellation’s boundaries. The sun moves in front of Ophiuchus from about November 30 to December 18 each year.

The zodiac – or “pathway of animals” – represents a rather narrow band of of sky astride the ecliptic, which is the plane of Earth’s orbit projected onto the sphere of stars. The signs of the zodiac are familiar to all who read online astrology advice. There are 12 familiar signs of the zodiac: Aries, Taurus, Gemini, Cancer and so on. But … no Ophiuchus.

Read more: Sun in zodiac constellations, 2020

Read more: Sun’s entry into zodiac signs, 2020

Antique colored etching of bald, bearded old man in ancient Greek garb holding a long snake.

Ophiuchus holding the serpent, Serpens, as depicted in Urania’s Mirror, a set of constellation cards published in London c. 1825. Image via Wikipedia.

On sky maps, Ophiuchus the Serpent Bearer is depicted as holding Serpens the Serpent, which is considered a separate constellation. According to ancient Greek star lore, Ophiuchus is Asclepius, Greek god of medicine and doctors. Asclepius is said to have concocted a healing potion from the venom of Serpens the Serpent, mixing it with a Gorgon’s blood and an unknown herb. This potion gave humans access to immortality, until the god of the underworld, Pluto, appealed to the king of the gods, Zeus, to reconsider the ramifications of the death of death.

Even today, the Staff of Asclepius – symbol of the World Health Organization and other medical organizations – pays tribute to the constellation Ophiuchus the Serpent Bearer.

black on white star chart of Ophiuchus with ecliptic line.

View larger. | Ophiuchus the Serpent Bearer.

How can you find this constellation? First of all, you need a dark sky. With the moon waxing now, you won’t have a moonless evening until the end of the first week of September 2020. We show the southernmost portion of Ophiuchus on the chart at top, and the constellation in full on the sky chart below. To see Ophiuchus, stand outside under your light-free sky until your eyes are fully adjusted to the dark. Ophiuchus is faint. But you’ll easily recognize the constellation Scorpius nearby. From our Northern Hemisphere locations, Ophiuchus looms above Scorpius. He’s a mighty figure that your eyes will pick out, if you’re looking for him.

The official boundary lines for all 88 constellations were drawn up by the International Astronomical Union in the 1930s. The photo below of the constellation Ophiuchus labels Ophiuchus’ brightest star, Rasalhague, and Scorpius’ brightest star, Antares. Rasalhague marks the head of Ophiuchus but is nowhere as bright as Antares, the star that depicts the Scorpion’s beating heart.

Constellation drawn on star field with stars Antares and Rasalhague marked.

Photo: Till Credner, AlltheSky.com.

Bottom line: Poor Ophiuchus. Astrologers don’t typically mention him, because he’s a constellation – not a sign – of the zodiac. However, the sun moves in front of this constellation’s stars from about November 30 to December 18, every year. Find Ophiuchus’ location in the sky tonight, and then when the moon moves away from this section of sky, try to envision the Serpent Holder in a dark sky!

Born late November to middle December? Here’s your constellation

Enjoying EarthSky so far? Sign up for our free daily newsletter today!



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Quarter moon or a half moon?

The moon with the left half invisible and the right half illuminated.

July 27, 2020, first quarter moon via EarthSky friend Chili Dcpa. Thanks, Chili!

People sometimes look up and say:

Is that a ‘half’ moon in the sky?

Astronomically, the answer to that question is always no. There’s no half-moon phase, at least not in any official way. Invariably, when referring to a half moon, observers are looking at a quarter moon. You see a moon that looks half-illuminated, like half a pie. It might be first or last quarter moon, but – to astronomers – never a half moon. Why is that?

Let’s talk for a minute about the names for the various moon phases. A new moon is most nearly between the Earth and sun for any given lunar orbit. At such a time, the the moon is considered by astronomers to have entered a new orbital cycle, called a lunation.

Full moon signifies that the full visible surface of the moon – its day side – is fully turned toward Earth.

First quarter moon means we see half of the moon’s day side (a quarter of the whole moon), and the moon is one quarter of the way through the current orbital cycle.

Third or last quarter moon means we see a quarter of the moon’s day side, and the moon is three-quarters of the way through the cycle, as measured from one new moon to the next.

Just realize this. Astronomers recognize four primary moon phases (new, first quarter, full, last quarter) and four interstitial phases (waxing crescent, waxing gibbous, waning gibbous waning crescent). Notice … no half moon.

A moon that appears half-illuminated.

EarthSky friend Steve Pauken caught the 1st quarter moon on July 27, 2020, too, from Bisbee, Arizona. Thank you, Steve! See how the terminator line – or line between light and dark on the moon – is straight, dividing the illuminated from the shadowed side of the moon.

People frequently speak of half moons. There are geographical locations (e.g., Half Moon Bay in California), as well as restaurants, resorts and various other attractions and businesses with this moniker.

And so you see that the process of naming things in astronomy isn’t always logical, except perhaps in a very narrow sense. You may think that heavy metal refers to gold or lead, or your favorite band. But, in astronomy, a metal is means any element – even some that normally are gases on Earth – that’s anything other than the two lightest elements, hydrogen and helium. Oxygen and carbon, for example, are metals in the language of astronomers. Seriously.

Or consider the ad hoc definition of a dwarf planet adopted by the International Astronomical Union, and used to dump Pluto, unceremoniously, from full planethood. Astronomers are scientists, and, like all scientists, they use a jargon all their own.

In a couple of senses, though, every time you view the moon, you’re observing a half moon. First, just half the moon always faces us. You can’t see the back side since it’s always turned away from us.

Second, whether you can see it all or not, one half of the entire moon is always illuminated by the sun. In other words, the moon has a dayside, just as Earth does. We see this illuminated half of the moon – the entire dayside of the moon – only at full moon.

By the way, there are some other moon phases that are less well known. The moon is named for its shape, which can be a waxing crescent (growing) or waning crescent (diminishing). And we also have gibbous moons, indicating a shape that is unequally curved outward on both sides, but not full. Gibbous moons also wax and wane depending on its time in the cycle.

Half-lit Earth from north, and half-lit moon with divisions between dark and light sides lined up.

Click here to see animation. As seen from the north side of the moon’s orbital plane, the Earth rotates counterclockwise on its rotational axis, and the moon revolves counterclockwise around Earth. The terminators of the Earth and moon align at first and last quarter moons, and only the near half of the moon’s day side is visible from Earth.

Learn much more about the various phases of the moon at EarthSky’s article Four keys to understanding moon phases.

Bottom line: You might consider it just a play on words or an oddity of language, but, in the astronomy vocabulary, there are no half moons.



from EarthSky https://ift.tt/3lr0v5g
The moon with the left half invisible and the right half illuminated.

July 27, 2020, first quarter moon via EarthSky friend Chili Dcpa. Thanks, Chili!

People sometimes look up and say:

Is that a ‘half’ moon in the sky?

Astronomically, the answer to that question is always no. There’s no half-moon phase, at least not in any official way. Invariably, when referring to a half moon, observers are looking at a quarter moon. You see a moon that looks half-illuminated, like half a pie. It might be first or last quarter moon, but – to astronomers – never a half moon. Why is that?

Let’s talk for a minute about the names for the various moon phases. A new moon is most nearly between the Earth and sun for any given lunar orbit. At such a time, the the moon is considered by astronomers to have entered a new orbital cycle, called a lunation.

Full moon signifies that the full visible surface of the moon – its day side – is fully turned toward Earth.

First quarter moon means we see half of the moon’s day side (a quarter of the whole moon), and the moon is one quarter of the way through the current orbital cycle.

Third or last quarter moon means we see a quarter of the moon’s day side, and the moon is three-quarters of the way through the cycle, as measured from one new moon to the next.

Just realize this. Astronomers recognize four primary moon phases (new, first quarter, full, last quarter) and four interstitial phases (waxing crescent, waxing gibbous, waning gibbous waning crescent). Notice … no half moon.

A moon that appears half-illuminated.

EarthSky friend Steve Pauken caught the 1st quarter moon on July 27, 2020, too, from Bisbee, Arizona. Thank you, Steve! See how the terminator line – or line between light and dark on the moon – is straight, dividing the illuminated from the shadowed side of the moon.

People frequently speak of half moons. There are geographical locations (e.g., Half Moon Bay in California), as well as restaurants, resorts and various other attractions and businesses with this moniker.

And so you see that the process of naming things in astronomy isn’t always logical, except perhaps in a very narrow sense. You may think that heavy metal refers to gold or lead, or your favorite band. But, in astronomy, a metal is means any element – even some that normally are gases on Earth – that’s anything other than the two lightest elements, hydrogen and helium. Oxygen and carbon, for example, are metals in the language of astronomers. Seriously.

Or consider the ad hoc definition of a dwarf planet adopted by the International Astronomical Union, and used to dump Pluto, unceremoniously, from full planethood. Astronomers are scientists, and, like all scientists, they use a jargon all their own.

In a couple of senses, though, every time you view the moon, you’re observing a half moon. First, just half the moon always faces us. You can’t see the back side since it’s always turned away from us.

Second, whether you can see it all or not, one half of the entire moon is always illuminated by the sun. In other words, the moon has a dayside, just as Earth does. We see this illuminated half of the moon – the entire dayside of the moon – only at full moon.

By the way, there are some other moon phases that are less well known. The moon is named for its shape, which can be a waxing crescent (growing) or waning crescent (diminishing). And we also have gibbous moons, indicating a shape that is unequally curved outward on both sides, but not full. Gibbous moons also wax and wane depending on its time in the cycle.

Half-lit Earth from north, and half-lit moon with divisions between dark and light sides lined up.

Click here to see animation. As seen from the north side of the moon’s orbital plane, the Earth rotates counterclockwise on its rotational axis, and the moon revolves counterclockwise around Earth. The terminators of the Earth and moon align at first and last quarter moons, and only the near half of the moon’s day side is visible from Earth.

Learn much more about the various phases of the moon at EarthSky’s article Four keys to understanding moon phases.

Bottom line: You might consider it just a play on words or an oddity of language, but, in the astronomy vocabulary, there are no half moons.



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Hurricane Hanna shrinks Gulf of Mexico dead zone

Track of Hurricane Hanna as it crossed over the Gulf of Mexico. Hanna made landfall on July 25, 2020, in Texas as a category 1 hurricane. This image was created by FleurDeOdile with WikiProject Tropical cyclones/Tracks by using NASA imagery and data from NOAA’s National Hurricane Center.

Thanks to Hurricane Hannah, the Gulf of Mexico’s dead zone was much smaller this summer than usual. Researchers say the July storm stirred up the area of low-oxygen water.

Hurricanes are largely thankless affairs with damaging winds and heavy rains that can cause extensive flooding along coastal regions. But for some marine life in the Gulf of Mexico, a hurricane may just mean they get a bit of a reprieve from the dead zone, an area of stagnant, low-oxygen water that forms every summer off the coast.

Scientists have been tracking the Gulf of Mexico dead zone since 1985. This large area of low-oxygen water develops every summer in response to nutrient inputs from the Mississippi River. These nutrients along with warm water and sunlight stimulate the growth of algae, which eventually die-off and are decomposed by bacteria. During the process, the bacteria use up most of the dissolved oxygen in the water, and this creates conditions inhospitable to marine life. The dead zone eventually disappears when cooler weather arrives in the fall.

To help maintain a healthy coastal region and robust fisheries in the Gulf of Mexico, efforts are underway to reduce nutrient runoff into the Mississippi River basin from agricultural lands and other sources. Tracking of the annual size of the dead zone is an important way to monitor the effectiveness of these conservation efforts. Over the past five years, the size of the dead zone has averaged 5,408 square miles (14,007 square kilometers), which is similar to the area of Puerto Rico. This average size is nearly 3 times the goal of the Mississippi River/Gulf of Mexico Hypoxia Task Force, which aims to reduce the running five-year average size of the dead zone to no more than 1,930 square miles (approximately 5,000 square kilometers).

This year’s dead zone measured only 2,116 square miles (5,480 square kilometers), which is much smaller than the typical size. Overall, the dead zone in 2020 ranked as the third smallest in the 34-year historical record. According to the scientists responsible for monitoring the dead zone, Hurricane Hanna passed through the area just prior to the measurements and stirred up the waters, which greatly reduced the size of the dead zone. Because nutrient runoff into the Mississippi River basin remains high, the small size of the dead zone in 2020 can be attributed to the weather and not substantial reductions in nutrient loading to the Gulf.

Changes in the size of the Gulf of Mexico dead zone over the 34-year monitoring period. Image via LUMCON/NOAA.

Nancy Rabalais, a Louisiana State University professor and chief scientist for the Gulf of Mexico dead zone monitoring efforts, commented on the new findings in a statement. She said:

The passage of Tropical Storm/Hurricane Hanna across the central Gulf generated 5- to 6- and occasional 8-foot waves along the inner shelf, and mixed the water column down to about 15 to 20 meters. The consistent winds from the south generated downwelling favorable conditions, and the remaining low oxygen was further offshore, in deeper water than normally. Vertically uniform temperature, salinity and dissolved oxygen data across the broad area mapped is not the norm for a July shelf-wide hypoxia cruise.

Hurricane Hanna was the first such storm of the 2020 hurricane season in the Atlantic basin. It became a tropical storm on July 24 within the Gulf of Mexico and intensified into a hurricane on July 25. The hurricane made landfall in Texas later that day as a category 1 hurricane. This year is expected to be a very active hurricane season. Two more tropical storms are already threatening the coastal areas along the Gulf of Mexico as of mid-August.

In addition to the high winds and waves at the beginning of the research cruise, the crew also faced unique challenges stemming from the COVID-19 pandemic. In particular, advanced SARS-CoV-2 tests were conducted on crew members prior to boarding the vessel and there was a reduced crew size this year.

Jill Tupitza, a graduate student at Louisiana State University, collects water samples from the Gulf of Mexico onboard the R/V Pelican. Image via LUMCON.

Steven Thur, director of NOAA’s National Centers for Coastal Ocean Science, said:

The data collected from this annual, long-term research program is critical to our understanding of a wide range of Gulf issues including hypoxia. Not only is measuring the size of the Gulf of Mexico dead zone vital to informing the best strategy to reduce its size, but also to reduce its impacts on the sustainability and productivity of our coastal resources and economy.

Bottom line: The annual size of the Gulf of Mexico dead zone was much smaller than usual in 2020 because the area of low-oxygen water was stirred up by Hurricane Hanna.



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Track of Hurricane Hanna as it crossed over the Gulf of Mexico. Hanna made landfall on July 25, 2020, in Texas as a category 1 hurricane. This image was created by FleurDeOdile with WikiProject Tropical cyclones/Tracks by using NASA imagery and data from NOAA’s National Hurricane Center.

Thanks to Hurricane Hannah, the Gulf of Mexico’s dead zone was much smaller this summer than usual. Researchers say the July storm stirred up the area of low-oxygen water.

Hurricanes are largely thankless affairs with damaging winds and heavy rains that can cause extensive flooding along coastal regions. But for some marine life in the Gulf of Mexico, a hurricane may just mean they get a bit of a reprieve from the dead zone, an area of stagnant, low-oxygen water that forms every summer off the coast.

Scientists have been tracking the Gulf of Mexico dead zone since 1985. This large area of low-oxygen water develops every summer in response to nutrient inputs from the Mississippi River. These nutrients along with warm water and sunlight stimulate the growth of algae, which eventually die-off and are decomposed by bacteria. During the process, the bacteria use up most of the dissolved oxygen in the water, and this creates conditions inhospitable to marine life. The dead zone eventually disappears when cooler weather arrives in the fall.

To help maintain a healthy coastal region and robust fisheries in the Gulf of Mexico, efforts are underway to reduce nutrient runoff into the Mississippi River basin from agricultural lands and other sources. Tracking of the annual size of the dead zone is an important way to monitor the effectiveness of these conservation efforts. Over the past five years, the size of the dead zone has averaged 5,408 square miles (14,007 square kilometers), which is similar to the area of Puerto Rico. This average size is nearly 3 times the goal of the Mississippi River/Gulf of Mexico Hypoxia Task Force, which aims to reduce the running five-year average size of the dead zone to no more than 1,930 square miles (approximately 5,000 square kilometers).

This year’s dead zone measured only 2,116 square miles (5,480 square kilometers), which is much smaller than the typical size. Overall, the dead zone in 2020 ranked as the third smallest in the 34-year historical record. According to the scientists responsible for monitoring the dead zone, Hurricane Hanna passed through the area just prior to the measurements and stirred up the waters, which greatly reduced the size of the dead zone. Because nutrient runoff into the Mississippi River basin remains high, the small size of the dead zone in 2020 can be attributed to the weather and not substantial reductions in nutrient loading to the Gulf.

Changes in the size of the Gulf of Mexico dead zone over the 34-year monitoring period. Image via LUMCON/NOAA.

Nancy Rabalais, a Louisiana State University professor and chief scientist for the Gulf of Mexico dead zone monitoring efforts, commented on the new findings in a statement. She said:

The passage of Tropical Storm/Hurricane Hanna across the central Gulf generated 5- to 6- and occasional 8-foot waves along the inner shelf, and mixed the water column down to about 15 to 20 meters. The consistent winds from the south generated downwelling favorable conditions, and the remaining low oxygen was further offshore, in deeper water than normally. Vertically uniform temperature, salinity and dissolved oxygen data across the broad area mapped is not the norm for a July shelf-wide hypoxia cruise.

Hurricane Hanna was the first such storm of the 2020 hurricane season in the Atlantic basin. It became a tropical storm on July 24 within the Gulf of Mexico and intensified into a hurricane on July 25. The hurricane made landfall in Texas later that day as a category 1 hurricane. This year is expected to be a very active hurricane season. Two more tropical storms are already threatening the coastal areas along the Gulf of Mexico as of mid-August.

In addition to the high winds and waves at the beginning of the research cruise, the crew also faced unique challenges stemming from the COVID-19 pandemic. In particular, advanced SARS-CoV-2 tests were conducted on crew members prior to boarding the vessel and there was a reduced crew size this year.

Jill Tupitza, a graduate student at Louisiana State University, collects water samples from the Gulf of Mexico onboard the R/V Pelican. Image via LUMCON.

Steven Thur, director of NOAA’s National Centers for Coastal Ocean Science, said:

The data collected from this annual, long-term research program is critical to our understanding of a wide range of Gulf issues including hypoxia. Not only is measuring the size of the Gulf of Mexico dead zone vital to informing the best strategy to reduce its size, but also to reduce its impacts on the sustainability and productivity of our coastal resources and economy.

Bottom line: The annual size of the Gulf of Mexico dead zone was much smaller than usual in 2020 because the area of low-oxygen water was stirred up by Hurricane Hanna.



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Moon and Scorpius on August 25 and 26

As darkness falls on August 25, 2020, the moon will be at or near its half-illuminated first quarter phase, and close to the star Antares on the sky’s dome. The next night – August 26 – the moon will be farther from Antares, and closer to the graceful curved tail of Scorpius the Scorpion, the constellation in which Antares is the brightest star.

Of course, the moon and these stars are not truly close together in space on these nights. The moon, our closest celestial neighbor, resides at a average distance of 238,885 miles or 384,400 km; yet the sun, our nearest star, lodges some 400 times farther from Earth than our moon.

Meanwhile, Antares is estimated to be 600 light-years away from us. A light-year is about 63,000 times greater than one astronomical unit (sun-Earth distance). So Antares is somewhere around 38 million times the sun’s distance from Earth (600 x 63,000 = 37,800,000 astronomical units).

Antares, the brightest star in the constellation Scorpius the Scorpion, represents the Scorpion’s beating heart. This red gem of a star is truly enormous, with a radius in excess of 3 astronomical units (AU). If by some bit of magic Antares were suddenly substituted for our sun, the surface of the star would extend well past the orbit of Mars!

Antares’ ruddy complexion reveals that this star has a low surface temperature. However, Antares’ great size makes up for its low surface temperature to shine at 1st-magnitude brightness in Earth’s sky. That’s in spite of the fact that Antares lies nearly 600 light-years away.

In the visible spectrum, this red supergiant star has the luminosity of about 10,000 suns. But if we could include invisible infrared radiation, Antares might have as much as 60,000 times the sun’s luminosity.

If Antares replaced the sun in our solar system, its circumference would extend beyond the orbit of the fourth planet, Mars. Here, Antares is shown in contrast to another star, Arcturus, and our sun. Image via Wikimedia Commons.

Bottom line: The moon sweeps close to red supergiant star Antares on August 25, 2020. The next night, August 26, the moon is closer to the graceful curved tail of Scorpius the Scorpion, the constellation in which Antares is the brightest star.



from EarthSky https://ift.tt/3gm44pu

As darkness falls on August 25, 2020, the moon will be at or near its half-illuminated first quarter phase, and close to the star Antares on the sky’s dome. The next night – August 26 – the moon will be farther from Antares, and closer to the graceful curved tail of Scorpius the Scorpion, the constellation in which Antares is the brightest star.

Of course, the moon and these stars are not truly close together in space on these nights. The moon, our closest celestial neighbor, resides at a average distance of 238,885 miles or 384,400 km; yet the sun, our nearest star, lodges some 400 times farther from Earth than our moon.

Meanwhile, Antares is estimated to be 600 light-years away from us. A light-year is about 63,000 times greater than one astronomical unit (sun-Earth distance). So Antares is somewhere around 38 million times the sun’s distance from Earth (600 x 63,000 = 37,800,000 astronomical units).

Antares, the brightest star in the constellation Scorpius the Scorpion, represents the Scorpion’s beating heart. This red gem of a star is truly enormous, with a radius in excess of 3 astronomical units (AU). If by some bit of magic Antares were suddenly substituted for our sun, the surface of the star would extend well past the orbit of Mars!

Antares’ ruddy complexion reveals that this star has a low surface temperature. However, Antares’ great size makes up for its low surface temperature to shine at 1st-magnitude brightness in Earth’s sky. That’s in spite of the fact that Antares lies nearly 600 light-years away.

In the visible spectrum, this red supergiant star has the luminosity of about 10,000 suns. But if we could include invisible infrared radiation, Antares might have as much as 60,000 times the sun’s luminosity.

If Antares replaced the sun in our solar system, its circumference would extend beyond the orbit of the fourth planet, Mars. Here, Antares is shown in contrast to another star, Arcturus, and our sun. Image via Wikimedia Commons.

Bottom line: The moon sweeps close to red supergiant star Antares on August 25, 2020. The next night, August 26, the moon is closer to the graceful curved tail of Scorpius the Scorpion, the constellation in which Antares is the brightest star.



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