We tell you all you need to know about halos in our YouTube video here. Don’t forget to subscribe!
What causes halos?
Have you ever looked up and spotted a large ring of light around the sun or moon? Scientists refer to these as 22-degree halos. They got that name because the radius of the circle is always approximately 22 degrees.
There’s an old weather saying: ring around the moon means rain soon. There’s truth to this saying, because high cirrus clouds often come before a storm. Notice in these photos that the sky looks fairly clear. After all, you can see the sun or moon. And yet halos are a sign of high, thin cirrus clouds drifting 20,000 feet (6 km) or more above our heads.
These clouds contain millions of tiny ice crystals. The halos you see are caused by both refraction, or splitting of light, and also by reflection, or glints of light from these ice crystals. The crystals must be oriented and positioned just so with respect to your eye, for the halo to appear.
That’s why, like rainbows, halos around the sun – or moon – are personal. Everyone sees their own unique halo, made by the ice crystals from their point of view. So they are different from the ice crystals making the halo of a person standing next to you.
View at EarthSky Community Photos. | Roberto Ortu captured this moon halo on February 2, 2026, in Italy and wrote: “A moon halo has an apparent radius of 22 degrees and forms around the moon due to refraction by hexagonal-shaped ice crystals that are present in Earth’s atmosphere.” Thank you, Roberto! Notice that – unlike solar halos, which can be colorful – lunar halos are mostly colorless.
A word of caution for photographers
Take care when photographing solar halos. Pointing a camera directly at the unobscured sun can damage it. Never look directly at the sun, even when it is less bright through clouds or fog.
Are halos more common at high latitudes?
We asked Les Cowley of the website Atmospheric Optics if halos around the sun and moon are more frequently seen at high latitudes and less commonly seen closer to the equator. He said:
That’s a good question that is not easy to answer accurately because no halo frequency statistics are collected except in one or two mid-latitude European countries.
We need to distinguish between (a) halos formed by low level diamond dust during very cold weather and (b) halos formed by ice crystals in high cirrus cloud.
Obviously (a) halos only occur in polar regions or countries with very cold winters (Canada for example is not high latitude).
(b) Halos can occur anywhere on the planet during winter or summer. Their frequency depends on the frequency of cirrus coverage and whether it has had a history such that it contains halo forming crystals. The latter is hard to predict. For example, there are major differences in halo frequencies and types of halos across even 200 miles [300 km] in the U.K.
Halos are made by both refraction and reflection ice crystals, such as these, in this photo by Walt Tate. Image via Walt Tate/ Atmospheric Optics. Used with permission.
If you see a halo, notice this!
Because moonlight isn’t very bright, lunar halos are mostly colorless. However, you might notice red on the inside and blue on the outside of the halo. These colors are more noticeable in halos around the sun. If you do see a halo around the moon or sun, notice that the inner edge is sharp, while the outer edge is more diffuse. Also, notice that the sky surrounding the halo is darker than the rest of the sky.
Halo photos from EarthSky’s Community
View at EarthSky Community Photos. | Samit Saha captured this image on January 30, 2026, and wrote: “A bright lunar halo surrounds the moon on a bone-chilling winter night in India. The circular ring formed as moonlight passed through countless hexagonal ice crystals suspended in high, thin cirrostratus clouds, creating the classic 22-degree halo. Snow-covered hills beneath the sky emphasize the clarity and depth of the winter atmosphere. The wide-field view reveals several familiar constellations – Orion, Taurus, Gemini, and the Pleiades – along with the bright planet Jupiter, all sharing the frame with the glowing halo. Such halos often signal approaching weather changes, yet for a brief moment, the sky offered a rare balance of atmospheric optics and celestial geometry, captured in a single exposure.” Thank you, Samit!View at EarthSky Community Photos. | Bonnie Swan captured this image in Wisconsin on January 21, 2026, and wrote: “While driving east early in the morning, the halo and sun dogs around the rising sun continued to be very bright, when I found a vantage point to get the whole image, I had to pull over to capture it!” Thank you, Bonnie!View at EarthSky Community Photos. | Dario Giannobile captured this in Manhattan on December 12, 2025, and wrote: “In a handheld shot of the Statue of Liberty taken from the ferry connecting Ellis Island to Manhattan, with seagulls crossing the sky, a series of rare optical phenomena framed the Statue’s crown. These are complex interactions of light with small ice crystals suspended in the air. This rare atmospheric condition created an extraordinary scene: a perfect solar halo, accompanied by parhelia (so-called “false suns”), a parhelic arc and a superior tangent arc.” Thank you, Dario!
More halo photos from our friends
Everyone sees his or her own halo. That’s because – for every individual – a solar or lunar halo is made of light reflecting and refracting from different ice crystals in high, thin cirrus clouds. Image via Vincenzo Mirabella/ NASA. Used with permission.View at EarthSky Community Photos. | Amrinderjit Singh captured this photo from India on December 12, 2025, and wrote: “At 2200 meters high in the mountains, the sky offered its beauty by displaying a halo around the sun and I was right there to capture this beautiful landscape.” Thank you, Amrinderjit!View at EarthSky Community Photos. | Teresa Raines captured this image from Arizona on January 4, 2026, and wrote: “Lunar halo, with Orion in the bottom right corner, Jupiter next to moon peeking through top palm tree frond.” Thank you, Teresa!Eliot Herman wrote on May 5, 2018: “This shows the change that occurred over 7 minutes as a lunar halo emerged. It then persisted for about 40 minutes and disappeared with increasing clouds. Although it appears the halo is forming from an odd shape, what is actually illuminated is the edge of the clouds just before the halo formed as the clouds drifted in front of the moon. But it does have a nice illusion of an odd-shaped halo then becoming round.” Used with permission.
Bottom line: High, thin cirrus clouds drifting high above your head create the halos you see around the sun or moon. The halos are from tiny ice crystals in Earth’s atmosphere. They do it by refracting and reflecting the light. Lunar halos are signs that storms are nearby.
We tell you all you need to know about halos in our YouTube video here. Don’t forget to subscribe!
What causes halos?
Have you ever looked up and spotted a large ring of light around the sun or moon? Scientists refer to these as 22-degree halos. They got that name because the radius of the circle is always approximately 22 degrees.
There’s an old weather saying: ring around the moon means rain soon. There’s truth to this saying, because high cirrus clouds often come before a storm. Notice in these photos that the sky looks fairly clear. After all, you can see the sun or moon. And yet halos are a sign of high, thin cirrus clouds drifting 20,000 feet (6 km) or more above our heads.
These clouds contain millions of tiny ice crystals. The halos you see are caused by both refraction, or splitting of light, and also by reflection, or glints of light from these ice crystals. The crystals must be oriented and positioned just so with respect to your eye, for the halo to appear.
That’s why, like rainbows, halos around the sun – or moon – are personal. Everyone sees their own unique halo, made by the ice crystals from their point of view. So they are different from the ice crystals making the halo of a person standing next to you.
View at EarthSky Community Photos. | Roberto Ortu captured this moon halo on February 2, 2026, in Italy and wrote: “A moon halo has an apparent radius of 22 degrees and forms around the moon due to refraction by hexagonal-shaped ice crystals that are present in Earth’s atmosphere.” Thank you, Roberto! Notice that – unlike solar halos, which can be colorful – lunar halos are mostly colorless.
A word of caution for photographers
Take care when photographing solar halos. Pointing a camera directly at the unobscured sun can damage it. Never look directly at the sun, even when it is less bright through clouds or fog.
Are halos more common at high latitudes?
We asked Les Cowley of the website Atmospheric Optics if halos around the sun and moon are more frequently seen at high latitudes and less commonly seen closer to the equator. He said:
That’s a good question that is not easy to answer accurately because no halo frequency statistics are collected except in one or two mid-latitude European countries.
We need to distinguish between (a) halos formed by low level diamond dust during very cold weather and (b) halos formed by ice crystals in high cirrus cloud.
Obviously (a) halos only occur in polar regions or countries with very cold winters (Canada for example is not high latitude).
(b) Halos can occur anywhere on the planet during winter or summer. Their frequency depends on the frequency of cirrus coverage and whether it has had a history such that it contains halo forming crystals. The latter is hard to predict. For example, there are major differences in halo frequencies and types of halos across even 200 miles [300 km] in the U.K.
Halos are made by both refraction and reflection ice crystals, such as these, in this photo by Walt Tate. Image via Walt Tate/ Atmospheric Optics. Used with permission.
If you see a halo, notice this!
Because moonlight isn’t very bright, lunar halos are mostly colorless. However, you might notice red on the inside and blue on the outside of the halo. These colors are more noticeable in halos around the sun. If you do see a halo around the moon or sun, notice that the inner edge is sharp, while the outer edge is more diffuse. Also, notice that the sky surrounding the halo is darker than the rest of the sky.
Halo photos from EarthSky’s Community
View at EarthSky Community Photos. | Samit Saha captured this image on January 30, 2026, and wrote: “A bright lunar halo surrounds the moon on a bone-chilling winter night in India. The circular ring formed as moonlight passed through countless hexagonal ice crystals suspended in high, thin cirrostratus clouds, creating the classic 22-degree halo. Snow-covered hills beneath the sky emphasize the clarity and depth of the winter atmosphere. The wide-field view reveals several familiar constellations – Orion, Taurus, Gemini, and the Pleiades – along with the bright planet Jupiter, all sharing the frame with the glowing halo. Such halos often signal approaching weather changes, yet for a brief moment, the sky offered a rare balance of atmospheric optics and celestial geometry, captured in a single exposure.” Thank you, Samit!View at EarthSky Community Photos. | Bonnie Swan captured this image in Wisconsin on January 21, 2026, and wrote: “While driving east early in the morning, the halo and sun dogs around the rising sun continued to be very bright, when I found a vantage point to get the whole image, I had to pull over to capture it!” Thank you, Bonnie!View at EarthSky Community Photos. | Dario Giannobile captured this in Manhattan on December 12, 2025, and wrote: “In a handheld shot of the Statue of Liberty taken from the ferry connecting Ellis Island to Manhattan, with seagulls crossing the sky, a series of rare optical phenomena framed the Statue’s crown. These are complex interactions of light with small ice crystals suspended in the air. This rare atmospheric condition created an extraordinary scene: a perfect solar halo, accompanied by parhelia (so-called “false suns”), a parhelic arc and a superior tangent arc.” Thank you, Dario!
More halo photos from our friends
Everyone sees his or her own halo. That’s because – for every individual – a solar or lunar halo is made of light reflecting and refracting from different ice crystals in high, thin cirrus clouds. Image via Vincenzo Mirabella/ NASA. Used with permission.View at EarthSky Community Photos. | Amrinderjit Singh captured this photo from India on December 12, 2025, and wrote: “At 2200 meters high in the mountains, the sky offered its beauty by displaying a halo around the sun and I was right there to capture this beautiful landscape.” Thank you, Amrinderjit!View at EarthSky Community Photos. | Teresa Raines captured this image from Arizona on January 4, 2026, and wrote: “Lunar halo, with Orion in the bottom right corner, Jupiter next to moon peeking through top palm tree frond.” Thank you, Teresa!Eliot Herman wrote on May 5, 2018: “This shows the change that occurred over 7 minutes as a lunar halo emerged. It then persisted for about 40 minutes and disappeared with increasing clouds. Although it appears the halo is forming from an odd shape, what is actually illuminated is the edge of the clouds just before the halo formed as the clouds drifted in front of the moon. But it does have a nice illusion of an odd-shaped halo then becoming round.” Used with permission.
Bottom line: High, thin cirrus clouds drifting high above your head create the halos you see around the sun or moon. The halos are from tiny ice crystals in Earth’s atmosphere. They do it by refracting and reflecting the light. Lunar halos are signs that storms are nearby.
The March equinox is coming up fast. It’ll come at 14:46 UTC (9:46 a.m. CDT) on March 20, 2026. And here’s a little-known equinox phenomenon: the sun sets faster around the time of an equinox. The fastest sunrises happen at or near the equinoxes, too. On the other hand, the slowest sunsets (and sunrises) happen around the solstices. It’s true whether you live in Earth’s Northern or Southern Hemisphere.
By the way, when we say sunset here, we’re talking about the actual number of minutes it takes for the body of the sun to sink below the western horizon.
So why does it happen? Why does the body of the sun fall below the horizon so quickly at equinox-time? It’s because, at every equinox, the sun rises due east and sets due west. That means – on the day of an equinox – the setting sun hits the horizon at its steepest possible angle.
The equinox is an event that takes place in Earth’s orbit around the sun. Image via National Weather Service/ weather.gov.
Year’s slowest sunsets and sunrises
Meanwhile, at a solstice, the sun is setting farthest north or farthest south of due west. And, the farther the sun sets from due west along the horizon, the shallower the angle of the setting sun. So that means a longer duration for sunset at the solstices.
Also, the sunset duration varies by latitude. Farther north or south on the Earth’s globe, the duration of sunset lasts longer. So, closer to the equator, the duration is shorter. But let’s just consider one latitude, 40 degrees north, the latitude of Denver or Philadelphia in the United States; parts of Spain; and Beijing, China.
At that latitude, on the day of equinox, the sun sets in about 2 3/4 minutes.
On the other hand, the solstice sun sets in roughly 3 1/4 minutes at 40 degrees latitude.
Sunset images from the EarthSky community
View at EarthSky Community Photos. | Teresa Molinaro captured this image on August 28, 2024, in Italy. Teresa wrote: “A very intense dawn occurred on the morning of late September; and in the seaside village everything was silent.” Thank you, Teresa!View at EarthSky Community Photos. | Peter Lowenstein captured these images and wrote: “Equinox sunsets before and after equinox sunrise on 23 September. The instant of the Southern Hemisphere spring equinox in 2023 was at 6.50 UTC on 23 September. This means it was possible to record two equinox sunsets one on the 22nd a few hours before and another a few hours after the equinox sunrise on the 23rd. These are shown in the accompanying composite of three 9 video frame montages.” Thank you, Peter!
Bottom line: The fastest sunsets and sunrises of the year are happening now, around the time of the September equinox.
The March equinox is coming up fast. It’ll come at 14:46 UTC (9:46 a.m. CDT) on March 20, 2026. And here’s a little-known equinox phenomenon: the sun sets faster around the time of an equinox. The fastest sunrises happen at or near the equinoxes, too. On the other hand, the slowest sunsets (and sunrises) happen around the solstices. It’s true whether you live in Earth’s Northern or Southern Hemisphere.
By the way, when we say sunset here, we’re talking about the actual number of minutes it takes for the body of the sun to sink below the western horizon.
So why does it happen? Why does the body of the sun fall below the horizon so quickly at equinox-time? It’s because, at every equinox, the sun rises due east and sets due west. That means – on the day of an equinox – the setting sun hits the horizon at its steepest possible angle.
The equinox is an event that takes place in Earth’s orbit around the sun. Image via National Weather Service/ weather.gov.
Year’s slowest sunsets and sunrises
Meanwhile, at a solstice, the sun is setting farthest north or farthest south of due west. And, the farther the sun sets from due west along the horizon, the shallower the angle of the setting sun. So that means a longer duration for sunset at the solstices.
Also, the sunset duration varies by latitude. Farther north or south on the Earth’s globe, the duration of sunset lasts longer. So, closer to the equator, the duration is shorter. But let’s just consider one latitude, 40 degrees north, the latitude of Denver or Philadelphia in the United States; parts of Spain; and Beijing, China.
At that latitude, on the day of equinox, the sun sets in about 2 3/4 minutes.
On the other hand, the solstice sun sets in roughly 3 1/4 minutes at 40 degrees latitude.
Sunset images from the EarthSky community
View at EarthSky Community Photos. | Teresa Molinaro captured this image on August 28, 2024, in Italy. Teresa wrote: “A very intense dawn occurred on the morning of late September; and in the seaside village everything was silent.” Thank you, Teresa!View at EarthSky Community Photos. | Peter Lowenstein captured these images and wrote: “Equinox sunsets before and after equinox sunrise on 23 September. The instant of the Southern Hemisphere spring equinox in 2023 was at 6.50 UTC on 23 September. This means it was possible to record two equinox sunsets one on the 22nd a few hours before and another a few hours after the equinox sunrise on the 23rd. These are shown in the accompanying composite of three 9 video frame montages.” Thank you, Peter!
Bottom line: The fastest sunsets and sunrises of the year are happening now, around the time of the September equinox.
The March equinox has arrived! Here’s all you need to know about it.
What is it? The March equinox – aka the vernal equinox – marks the sun’s crossing above Earth’s equator, moving from south to north. Earth’s tilt on its axis is what causes this northward shift of the sun’s path across our sky at this time of year. Earth’s tilt is now bringing spring and summer to the Northern Hemisphere. At the same time, the March equinox marks the beginning of autumn – and a shift toward winter – in the Southern Hemisphere. When is it? The sun crosses the celestial equator – a line directly above Earth’s equator – at 14:46 UTC on March 20, 2026 (9:46 a.m. CDT).
No matter where you are on Earth, the equinox brings us a number of seasonal effects, noticeable to nature lovers around the globe.
Equal day and night on the equinox?
At the equinox, Earth’s two hemispheres are receiving the sun’s rays equally. Night and day are often said to be equal in length. In fact, the word equinox comes from the Latin aequus (equal) and nox (night). For our ancestors, whose timekeeping was less precise than ours, day and night likely did seem equal. But today we know it’s not exactly so.
The fastest sunsets and sunrises of the year happen at the equinoxes. We’re talking here about the length of time it takes for the whole sun to sink below the horizon.
Here’s another equinox phenomenon. You might hear that the sun rises due east and sets due west at the equinox. Is that true? Yes it is. In fact, it’s the case no matter where you live on Earth, with the exception of the North and South Poles. At the equinoxes, the sun appears overhead at noon as seen from Earth’s equator, as the illustration below shows. This illustration shows the sun’s location on the celestial equator, every hour, on the day of the equinox.
No matter where you are on Earth – except at the Earth’s North and South Poles – you have a due east and due west point on your horizon. That point marks the intersection of your horizon with the celestial equator: the imaginary line above the true equator of the Earth.
The sun is on the celestial equator, and the celestial equator intersects all of our horizons at points due east and due west. Voila! The sun rises due east and sets due west.
The day arc of the sun, every hour, at the equinox, as seen on the (imaginary) celestial sphere surrounding Earth. At the equinox, the sun is directly above Earth’s equator. Image via Tau’olunga/ Wikimedia Commons (CC BY-SA 2.5).
More March equinox effects
And there are also plenty more effects in play around the time of the March equinox that all of us can notice. In the Northern Hemisphere, the March equinox brings earlier sunrises, later sunsets and sprouting plants.
Meanwhile, you’ll find the opposite season – later sunrises, earlier sunsets, chillier winds, dry and falling leaves – south of the equator.
The equinoxes and solstices are caused by Earth’s tilt on its axis and ceaseless motion in orbit. You can think of an equinox as happening on the imaginary dome of our sky, or as an event that happens in Earth’s orbit around the sun.
The Earth-centered view
If you think of it from an Earth-centered perspective, you can think of the celestial equator as a great circle dividing Earth’s sky into its Northern and Southern Hemispheres. The celestial equator is an imaginary line wrapping the sky directly above Earth’s equator. At the equinox, the sun crosses the celestial equator to enter the sky’s Northern Hemisphere.
The day arc of the equinox sun as seen from Earth’s equator. Also showing are twilight suns (in red) down to -18 degrees altitude. Note that the sun is at its highest point at noon. And see that the tree’s shadow at noon is cast straight down. That is – as seen from the equator on the day of an equinox – a tree stands in the center of its own shadow. Image via Tau’olunga/ Wikimedia Commons (CC BY-SA 2.5).
The Earth-in-space view
If you think of it from an Earth-in-space perspective, you have to think of Earth in orbit around the sun. And we all know Earth doesn’t orbit upright but is instead tilted on its axis by 23 1/2 degrees. So Earth’s Northern and Southern Hemispheres trade places in receiving the sun’s light and warmth most directly. We have an equinox twice a year – spring and fall – when the tilt of the Earth’s axis and Earth’s orbit around the sun combine in such a way that the axis is inclined neither away from nor toward the sun.
Here are satellite views of Earth on the solstices and equinoxes, via NASA Earth Observatory.
Things change fast around the equinoxes
Since Earth never stops moving around the sun, the position of the sunrise and sunset – and the days of approximately equal sunlight and night – will change quickly.
The video below was the Astronomy Picture of the Day for March 19, 2014. APOD explained:
At an equinox, the Earth’s terminator – the dividing line between day and night – becomes vertical and connects the North and South Poles. The time-lapse video [above] demonstrates this by displaying an entire year on planet Earth in 12 seconds. From geosynchronous orbit, the Meteosat satellite recorded these infrared images of the Earth every day at the same local time. The video started at the September 2010 equinox with the terminator line being vertical.
As the Earth revolved around the sun, the terminator was seen to tilt in a way that provides less daily sunlight to the Northern Hemisphere, causing winter in the north. As the year progressed, the March 2011 equinox arrived halfway through the video, followed by the terminator tilting the other way, causing winter in the Southern Hemisphere and summer in the north. The captured year ends again with the September equinox, concluding another of billions of trips the Earth has taken – and will take – around the sun.
The equinox is an event that takes place in Earth’s orbit around the sun. Image via National Weather Service/ weather.gov.
Where are signs of the March equinox in nature?
Everywhere! Forget about the weather for a moment, and think only about daylight. In terms of daylight, the knowledge that spring is here – and summer is coming – permeates all of nature on the northern half of Earth’s globe.
Notice the arc of the sun across the sky each day. You’ll find that it’s shifting toward the north. Responding to the change in daylight, birds and butterflies are migrating back northward, too, along with the path of the sun.
The longer days do bring with them warmer weather. People are leaving their winter coats at home. Trees are budding, and plants are beginning a new cycle of growth. In many places, spring flowers are beginning to bloom.
Meanwhile, in the Southern Hemisphere, the days are getting shorter and nights longer. A chill is in the air. Fall is here, and winter is coming!
Bottom line: Happy equinox! The 2026 March equinox falls March 20 at 14:46 UTC. All you need to know about the March equinox here.
The March equinox has arrived! Here’s all you need to know about it.
What is it? The March equinox – aka the vernal equinox – marks the sun’s crossing above Earth’s equator, moving from south to north. Earth’s tilt on its axis is what causes this northward shift of the sun’s path across our sky at this time of year. Earth’s tilt is now bringing spring and summer to the Northern Hemisphere. At the same time, the March equinox marks the beginning of autumn – and a shift toward winter – in the Southern Hemisphere. When is it? The sun crosses the celestial equator – a line directly above Earth’s equator – at 14:46 UTC on March 20, 2026 (9:46 a.m. CDT).
No matter where you are on Earth, the equinox brings us a number of seasonal effects, noticeable to nature lovers around the globe.
Equal day and night on the equinox?
At the equinox, Earth’s two hemispheres are receiving the sun’s rays equally. Night and day are often said to be equal in length. In fact, the word equinox comes from the Latin aequus (equal) and nox (night). For our ancestors, whose timekeeping was less precise than ours, day and night likely did seem equal. But today we know it’s not exactly so.
The fastest sunsets and sunrises of the year happen at the equinoxes. We’re talking here about the length of time it takes for the whole sun to sink below the horizon.
Here’s another equinox phenomenon. You might hear that the sun rises due east and sets due west at the equinox. Is that true? Yes it is. In fact, it’s the case no matter where you live on Earth, with the exception of the North and South Poles. At the equinoxes, the sun appears overhead at noon as seen from Earth’s equator, as the illustration below shows. This illustration shows the sun’s location on the celestial equator, every hour, on the day of the equinox.
No matter where you are on Earth – except at the Earth’s North and South Poles – you have a due east and due west point on your horizon. That point marks the intersection of your horizon with the celestial equator: the imaginary line above the true equator of the Earth.
The sun is on the celestial equator, and the celestial equator intersects all of our horizons at points due east and due west. Voila! The sun rises due east and sets due west.
The day arc of the sun, every hour, at the equinox, as seen on the (imaginary) celestial sphere surrounding Earth. At the equinox, the sun is directly above Earth’s equator. Image via Tau’olunga/ Wikimedia Commons (CC BY-SA 2.5).
More March equinox effects
And there are also plenty more effects in play around the time of the March equinox that all of us can notice. In the Northern Hemisphere, the March equinox brings earlier sunrises, later sunsets and sprouting plants.
Meanwhile, you’ll find the opposite season – later sunrises, earlier sunsets, chillier winds, dry and falling leaves – south of the equator.
The equinoxes and solstices are caused by Earth’s tilt on its axis and ceaseless motion in orbit. You can think of an equinox as happening on the imaginary dome of our sky, or as an event that happens in Earth’s orbit around the sun.
The Earth-centered view
If you think of it from an Earth-centered perspective, you can think of the celestial equator as a great circle dividing Earth’s sky into its Northern and Southern Hemispheres. The celestial equator is an imaginary line wrapping the sky directly above Earth’s equator. At the equinox, the sun crosses the celestial equator to enter the sky’s Northern Hemisphere.
The day arc of the equinox sun as seen from Earth’s equator. Also showing are twilight suns (in red) down to -18 degrees altitude. Note that the sun is at its highest point at noon. And see that the tree’s shadow at noon is cast straight down. That is – as seen from the equator on the day of an equinox – a tree stands in the center of its own shadow. Image via Tau’olunga/ Wikimedia Commons (CC BY-SA 2.5).
The Earth-in-space view
If you think of it from an Earth-in-space perspective, you have to think of Earth in orbit around the sun. And we all know Earth doesn’t orbit upright but is instead tilted on its axis by 23 1/2 degrees. So Earth’s Northern and Southern Hemispheres trade places in receiving the sun’s light and warmth most directly. We have an equinox twice a year – spring and fall – when the tilt of the Earth’s axis and Earth’s orbit around the sun combine in such a way that the axis is inclined neither away from nor toward the sun.
Here are satellite views of Earth on the solstices and equinoxes, via NASA Earth Observatory.
Things change fast around the equinoxes
Since Earth never stops moving around the sun, the position of the sunrise and sunset – and the days of approximately equal sunlight and night – will change quickly.
The video below was the Astronomy Picture of the Day for March 19, 2014. APOD explained:
At an equinox, the Earth’s terminator – the dividing line between day and night – becomes vertical and connects the North and South Poles. The time-lapse video [above] demonstrates this by displaying an entire year on planet Earth in 12 seconds. From geosynchronous orbit, the Meteosat satellite recorded these infrared images of the Earth every day at the same local time. The video started at the September 2010 equinox with the terminator line being vertical.
As the Earth revolved around the sun, the terminator was seen to tilt in a way that provides less daily sunlight to the Northern Hemisphere, causing winter in the north. As the year progressed, the March 2011 equinox arrived halfway through the video, followed by the terminator tilting the other way, causing winter in the Southern Hemisphere and summer in the north. The captured year ends again with the September equinox, concluding another of billions of trips the Earth has taken – and will take – around the sun.
The equinox is an event that takes place in Earth’s orbit around the sun. Image via National Weather Service/ weather.gov.
Where are signs of the March equinox in nature?
Everywhere! Forget about the weather for a moment, and think only about daylight. In terms of daylight, the knowledge that spring is here – and summer is coming – permeates all of nature on the northern half of Earth’s globe.
Notice the arc of the sun across the sky each day. You’ll find that it’s shifting toward the north. Responding to the change in daylight, birds and butterflies are migrating back northward, too, along with the path of the sun.
The longer days do bring with them warmer weather. People are leaving their winter coats at home. Trees are budding, and plants are beginning a new cycle of growth. In many places, spring flowers are beginning to bloom.
Meanwhile, in the Southern Hemisphere, the days are getting shorter and nights longer. A chill is in the air. Fall is here, and winter is coming!
Bottom line: Happy equinox! The 2026 March equinox falls March 20 at 14:46 UTC. All you need to know about the March equinox here.
We know what pie is, but what is pi? It’s the number that results from dividing the circumference of any circle by its diameter. Although pi is an infinite number, it’s usually rounded off to 3.14. Hence, Pi Day on March 14! Image via Delft University of Technology/ Wikimedia Commons.
Have you heard of Pi Day? It happens every year on March 14. The numbers 3-1-4 are the first three digits of the famous mathematical constant pi, which, in case you’re wondering, is the ratio of the circumference of a circle to its diameter.
No matter how large or small the circle, that ratio always works out to 3.14. That’s the magic of mathematics.
Plus, pi is a never-ending number. You often see it written as 3.14, but in fact it’s approximately equal to 3.14159 … and so on, into infinity. That sense of infinity is in part what makes pi – and Pi Day – so much fun.
So here’s a quick guide to Pi Day, which is celebrated by science aficionados all over the world. It is a unique combination of fun and education, and anyone can participate.
What is pi? It’s the number that results from dividing the circumference of any circle by its diameter. Although pi is an infinite number, it’s usually rounded off to 3.14. Hence, Pi Day on March 14! Image via NASA/ JPL-Caltech.
People compete in memorizing it. Rajveer Meena has the record for memorizing the most decimal places of pi at 70,000.
It’s used as stress tests for computers. Computing pi is a kind of “digital cardiogram” for computers.
A Givenchy men’s cologne is named pi. So you can smell like pi, too, if you are the intellectual and visionary kind.
Pi by other names. Pi is also known as Archimedes’ constant or Ludolph’s number.
Heroes sometimes use pi. For example, Spock foils an evil computer in Wolf in the Fold (the 14th episode of the second season of the American sci-fi TV series “Star Trek”), by preoccupying it forever by having it calculate pi’s value.
Happy Pi Day! Pi is a mathematical constant. It equals 3.14159 … and so on, into infinity. So for short, we refer to pi as 3.14. Image via NASA/ JPL-Caltech.
History of Pi Day
Physicist Larry Shaw founded Pi Day in 1988, as part of his great work at the ground-breaking science museum Exploratorium in San Francisco. During the first festivities, both staff and the public marched around one of the circular spaces in the museum while eating fruit pies.
In the United States, the U.S. House of Representatives officially recognized Pi Day as an annual event – National Pi Day – on March 12, 2009.
Today, many people and institutions celebrate, including students, teachers, parents, museums, science centers and planetariums.
At the NASA site you can find many resources, including a Pi Day Challenge, along with lessons and downloads. The challenge allows the public to solve some of the same problems NASA scientists and engineers do using pi.
Take part in the NASA Pi Day Challenge and find a list of handy resources below. Image via NASA/ JPL.
More NASA resources
Here are more resources and ways you can celebrate, including:
By the way, did you know that there’s even a pi planet? It is an exoplanet known as K2-315b, whose orbital period matches the value of pi. That is, this planet orbits its star every 3.14 Earth days.
It is, in fact, almost the same size as Earth, with a radius 95% that of our own planet. That’s also about the same size as Venus, and like our nearby sister world, it’s a blisteringly hot place, with temperatures up to 350 degrees Fahrenheit (177 degrees C). It orbits a red dwarf (or M-type dwarf) star that’s cooler than our sun and only about 1/5 as large, called EPIC 249631677, which is 186 light-years from Earth.
There is even a “pi planet.” This is an artist’s concept of K2-315b, which has an orbital period of 3.14 Earth days, the same value as pi. Image via NASA Ames/ JPL-Caltech/ T. Pyle/ Christine Daniloff/ MIT (CC BY-NC-ND 4.0).
Bottom line: March 14 is Pi Day, an annual mathematical event for science lovers. Here’s how to celebrate and take part in the NASA Pi Day Challenge!
We know what pie is, but what is pi? It’s the number that results from dividing the circumference of any circle by its diameter. Although pi is an infinite number, it’s usually rounded off to 3.14. Hence, Pi Day on March 14! Image via Delft University of Technology/ Wikimedia Commons.
Have you heard of Pi Day? It happens every year on March 14. The numbers 3-1-4 are the first three digits of the famous mathematical constant pi, which, in case you’re wondering, is the ratio of the circumference of a circle to its diameter.
No matter how large or small the circle, that ratio always works out to 3.14. That’s the magic of mathematics.
Plus, pi is a never-ending number. You often see it written as 3.14, but in fact it’s approximately equal to 3.14159 … and so on, into infinity. That sense of infinity is in part what makes pi – and Pi Day – so much fun.
So here’s a quick guide to Pi Day, which is celebrated by science aficionados all over the world. It is a unique combination of fun and education, and anyone can participate.
What is pi? It’s the number that results from dividing the circumference of any circle by its diameter. Although pi is an infinite number, it’s usually rounded off to 3.14. Hence, Pi Day on March 14! Image via NASA/ JPL-Caltech.
People compete in memorizing it. Rajveer Meena has the record for memorizing the most decimal places of pi at 70,000.
It’s used as stress tests for computers. Computing pi is a kind of “digital cardiogram” for computers.
A Givenchy men’s cologne is named pi. So you can smell like pi, too, if you are the intellectual and visionary kind.
Pi by other names. Pi is also known as Archimedes’ constant or Ludolph’s number.
Heroes sometimes use pi. For example, Spock foils an evil computer in Wolf in the Fold (the 14th episode of the second season of the American sci-fi TV series “Star Trek”), by preoccupying it forever by having it calculate pi’s value.
Happy Pi Day! Pi is a mathematical constant. It equals 3.14159 … and so on, into infinity. So for short, we refer to pi as 3.14. Image via NASA/ JPL-Caltech.
History of Pi Day
Physicist Larry Shaw founded Pi Day in 1988, as part of his great work at the ground-breaking science museum Exploratorium in San Francisco. During the first festivities, both staff and the public marched around one of the circular spaces in the museum while eating fruit pies.
In the United States, the U.S. House of Representatives officially recognized Pi Day as an annual event – National Pi Day – on March 12, 2009.
Today, many people and institutions celebrate, including students, teachers, parents, museums, science centers and planetariums.
At the NASA site you can find many resources, including a Pi Day Challenge, along with lessons and downloads. The challenge allows the public to solve some of the same problems NASA scientists and engineers do using pi.
Take part in the NASA Pi Day Challenge and find a list of handy resources below. Image via NASA/ JPL.
More NASA resources
Here are more resources and ways you can celebrate, including:
By the way, did you know that there’s even a pi planet? It is an exoplanet known as K2-315b, whose orbital period matches the value of pi. That is, this planet orbits its star every 3.14 Earth days.
It is, in fact, almost the same size as Earth, with a radius 95% that of our own planet. That’s also about the same size as Venus, and like our nearby sister world, it’s a blisteringly hot place, with temperatures up to 350 degrees Fahrenheit (177 degrees C). It orbits a red dwarf (or M-type dwarf) star that’s cooler than our sun and only about 1/5 as large, called EPIC 249631677, which is 186 light-years from Earth.
There is even a “pi planet.” This is an artist’s concept of K2-315b, which has an orbital period of 3.14 Earth days, the same value as pi. Image via NASA Ames/ JPL-Caltech/ T. Pyle/ Christine Daniloff/ MIT (CC BY-NC-ND 4.0).
Bottom line: March 14 is Pi Day, an annual mathematical event for science lovers. Here’s how to celebrate and take part in the NASA Pi Day Challenge!
A new study suggests our sun might be a migrant from a more central region of our home galaxy, the Milky Way. It suggests our sun joined a migration of other stars, which moved outward from the inner part of the galaxy some 4 to 6 billion years ago. Image via NAOJ/ EurekaAlert.
Astronomers suggest the sun might have migrated from near the central bar-shaped nucleus of our Milky Way galaxy.
Scientists studied 6,594 solar “twin” stars, using Gaia data. Many share the sun’s age (about 4–6 billion years) and appear to have migrated outward from the galaxy’s inner regions together.
The sun eventually took up residence in a quieter part of the galaxy, where planets (and life) could develop with fewer threats.
Astronomers have long thought our sun was born closer to the center of our Milky Way galaxy than it is today.
The stumbling block to that idea has been the Milky Way’s huge central bar, which is essentially a massive gravitational engine. The galaxy’s central bar creates its own high-pressure, high-energy environment, where stars are being born and dying, and where energetic events like supernovas happen frequently. So it’s not a nice, quiet part of the galaxy for the founding and evolution of life.
Previous studies had shown the gravitational pull of this bar served as a barrier for escaping stars. But now a new study from Tokyo Metropolitan University – and reported by EurekAlert on March 12, 2026 – suggests that, as the central bar was forming somewhere between 4 and 6 billion years ago, it triggered both star formation and a wave of outward migration for stars … maybe including our sun.
How do we know?
Assistant professors Daisuke Taniguchi at Tokyo Metropolitan University and Takuji Tsujimoto at the National Astronomical Observatory of Japan led the new studies. They looked at stars that are similar to our sun – a G-type star – in terms of temperature, composition and surface gravity. Altogether, the survey included 6,594 of these virtual twins to our sun. That was out of the overall observations of 2 billion stars.
The data came from the European Space Agency’s amazing Gaia spacecraft. Gaia did what’s called astrometry. In other words, it obtained precise measurements of the positions of stars, over and over again. In this way, it revealed the movement of stars in our galaxy for more than a decade. The data showed there was a mass movement of stars, out of the turbulent inner galactic regions to more serene pastures.
Out here, farther from our galaxy’s core and its central bar, our sun now resides in a quieter part of the galaxy. And this could have big implications for why life could arise on Earth, and possibly on planets around similar stars in our neighborhood.
The researchers published two new papers in the peer-reviewed journal Astronomy and Astrophysics on March 12, 2026.
Our current place in the Milky Way
The sun and solar system lie about 25,000 light-years from the center of the Milky Way. And the central bar in the Milky Way extends some 10,000 to 15,000 light-years from its center. The 4.6-billion-year-old sun is in the Orion-Cygnus Arm, or Orion Spur, a minor spiral arm of the Milky Way galaxy.
The new study suggests our sun began its life in the galaxy at more than 10,000 light-years nearer to the galactic center than we are today. That would have put us close to the central bar.
But the central bar has a gravitational effect that scientists call a corotation barrier. Basically, its pull of gravity makes it hard for stars to travel far away from the bar. Enter the new study. It suggests the bar wasn’t fully formed until after the sun – and thousands of similar stars – made their escape.
A graphic of the Milky Way showing our solar system’s current location in our galaxy. Note our distance from the central bar. Image via Universität Wien.
Migrating to a safer neighborhood
The scientists who conducted the new study looked at a notable concentration of stars that are around 4 to 6 billion years old, similar in age to our sun. And they all currently inhabit a region of the galaxy that’s about the same distance from the center as we are.
The scientists concluded that the age and locations of these stars are evidence of a stellar migration. They said these stars and our sun were able to escape the gravity of the still-forming bar region. The stars made a mass exodus from a region that was, coincidentally, hostile to the formation of life.
Afterward, our sun and its planets – along with thousands of similar sibling stars – came to live in a quieter galactic neighborhood. It’s a region of the Milky Way where life was able to – at least once – evolve in relative peace.
By the way, researchers using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile recently took a stunning new, detailed image of a molecular cloud feature in the heart of the Milky Way.
They captured the huge image in millimeter radio wavelengths. It revealed new details of a chaotic gaseous region with massive stars that orbits the supermassive black hole in our galaxy’s center. See it here, or watch the video below.
Bottom line: A new study suggests the sun might be a migrant that was born in the inner galaxy and journeyed outward. Researchers believe it made that crossing in the company of many other stars similar to our sun.
A new study suggests our sun might be a migrant from a more central region of our home galaxy, the Milky Way. It suggests our sun joined a migration of other stars, which moved outward from the inner part of the galaxy some 4 to 6 billion years ago. Image via NAOJ/ EurekaAlert.
Astronomers suggest the sun might have migrated from near the central bar-shaped nucleus of our Milky Way galaxy.
Scientists studied 6,594 solar “twin” stars, using Gaia data. Many share the sun’s age (about 4–6 billion years) and appear to have migrated outward from the galaxy’s inner regions together.
The sun eventually took up residence in a quieter part of the galaxy, where planets (and life) could develop with fewer threats.
Astronomers have long thought our sun was born closer to the center of our Milky Way galaxy than it is today.
The stumbling block to that idea has been the Milky Way’s huge central bar, which is essentially a massive gravitational engine. The galaxy’s central bar creates its own high-pressure, high-energy environment, where stars are being born and dying, and where energetic events like supernovas happen frequently. So it’s not a nice, quiet part of the galaxy for the founding and evolution of life.
Previous studies had shown the gravitational pull of this bar served as a barrier for escaping stars. But now a new study from Tokyo Metropolitan University – and reported by EurekAlert on March 12, 2026 – suggests that, as the central bar was forming somewhere between 4 and 6 billion years ago, it triggered both star formation and a wave of outward migration for stars … maybe including our sun.
How do we know?
Assistant professors Daisuke Taniguchi at Tokyo Metropolitan University and Takuji Tsujimoto at the National Astronomical Observatory of Japan led the new studies. They looked at stars that are similar to our sun – a G-type star – in terms of temperature, composition and surface gravity. Altogether, the survey included 6,594 of these virtual twins to our sun. That was out of the overall observations of 2 billion stars.
The data came from the European Space Agency’s amazing Gaia spacecraft. Gaia did what’s called astrometry. In other words, it obtained precise measurements of the positions of stars, over and over again. In this way, it revealed the movement of stars in our galaxy for more than a decade. The data showed there was a mass movement of stars, out of the turbulent inner galactic regions to more serene pastures.
Out here, farther from our galaxy’s core and its central bar, our sun now resides in a quieter part of the galaxy. And this could have big implications for why life could arise on Earth, and possibly on planets around similar stars in our neighborhood.
The researchers published two new papers in the peer-reviewed journal Astronomy and Astrophysics on March 12, 2026.
Our current place in the Milky Way
The sun and solar system lie about 25,000 light-years from the center of the Milky Way. And the central bar in the Milky Way extends some 10,000 to 15,000 light-years from its center. The 4.6-billion-year-old sun is in the Orion-Cygnus Arm, or Orion Spur, a minor spiral arm of the Milky Way galaxy.
The new study suggests our sun began its life in the galaxy at more than 10,000 light-years nearer to the galactic center than we are today. That would have put us close to the central bar.
But the central bar has a gravitational effect that scientists call a corotation barrier. Basically, its pull of gravity makes it hard for stars to travel far away from the bar. Enter the new study. It suggests the bar wasn’t fully formed until after the sun – and thousands of similar stars – made their escape.
A graphic of the Milky Way showing our solar system’s current location in our galaxy. Note our distance from the central bar. Image via Universität Wien.
Migrating to a safer neighborhood
The scientists who conducted the new study looked at a notable concentration of stars that are around 4 to 6 billion years old, similar in age to our sun. And they all currently inhabit a region of the galaxy that’s about the same distance from the center as we are.
The scientists concluded that the age and locations of these stars are evidence of a stellar migration. They said these stars and our sun were able to escape the gravity of the still-forming bar region. The stars made a mass exodus from a region that was, coincidentally, hostile to the formation of life.
Afterward, our sun and its planets – along with thousands of similar sibling stars – came to live in a quieter galactic neighborhood. It’s a region of the Milky Way where life was able to – at least once – evolve in relative peace.
By the way, researchers using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile recently took a stunning new, detailed image of a molecular cloud feature in the heart of the Milky Way.
They captured the huge image in millimeter radio wavelengths. It revealed new details of a chaotic gaseous region with massive stars that orbits the supermassive black hole in our galaxy’s center. See it here, or watch the video below.
Bottom line: A new study suggests the sun might be a migrant that was born in the inner galaxy and journeyed outward. Researchers believe it made that crossing in the company of many other stars similar to our sun.
After 150 years, giant tortoises are back on Floreana! Watch as 158 tortoises take their first steps into the wild, guided by cutting-edge NASA data. Video via EarthSky.
NASA helps giant tortoises return to a Galápagos island
For the first time in more than 150 years, giant tortoises are roaming the wild again on Floreana Island in the Galápagos. On February 20, 2026, conservation teams from the Galápagos National Park Directorate and the Galápagos Conservancy released 158 tortoises at two sites. They chose those sites using NASA satellite data, identifying areas where the animals could easily find food, water and nesting locations.
Keith Gaddis, manager of NASA Earth Action’s Biological Diversity and Ecological Forecasting program, said:
This is exactly the kind of project where NASA Earth observations make a difference. We’re helping partners answer a practical question: where will these animals have the best chance to survive, not just today, but decades from now?
Giant tortoises: A history lost and found
Giant tortoises disappeared from Floreana in the mid-1800s. The Floreana giant tortoise went extinct due to a few reasons. First, sailors arrived and hunted the animals for their meat. The tortoises could be stored alive on ships for up to six months, providing fresh food in other locations. But sailors also introduced predators, such as pigs and rats, which preyed on tortoise eggs and hatchlings.
So, without the tortoises, the island began to change. Historically, giant tortoises helped shape the landscape. They grazed on vegetation, opening pathways through dense plant growth and carrying seeds.
The path to reintroduction began decades later. In 2000, James Gibbs, Vice President of Science and Conservation at the Galápagos Conservancy, and other researchers discovered unusual tortoises on Wolf Volcano in northern Isabela Island. They did not resemble any known living species.
About 10 years later, scientists compared DNA from these animals with genetic material from bones of extinct Floreana tortoises from caves and museums. The analysis confirmed some of the Wolf Volcano tortoises carried Floreana ancestry. These tortoises were a sort of hybrid. It seems as if the sailors, in moving the tortoises on their ships, at one point dropped some off on Isabela Island more than a century ago.
Scientists then used these hybrid tortoises to establish a breeding program. And it has produced hundreds of offspring that are now ready to return to Floreana.
From extinction to revival: Hybrid tortoises with Floreana ancestry are paving the way for the giant tortoise’s return to its historic island home. Image via David Liberio/ Galápagos Conservancy. Used with permission.
Matching tortoises with the right habitat
Releasing tortoises into the wild is not as simple as opening a gate. Young tortoises raised in captivity must learn to find food, water and nesting sites. Gibbs said:
They don’t know where food is; they don’t know where water is; they don’t know where to nest. If you can place them where conditions are already right, you give them a much better chance.
Floreana’s terrain adds another layer of challenge. Some hills and mountains capture clouds and support cool, moist forests. Meanwhile, lower areas remain dry most of the year. Because tortoises need both food and nesting areas, they naturally migrate between these contrasting habitats. Thanks to NASA satellite data, researchers can identify the best release sites.
This Landsat 8 image of Floreana Island from October 6, 2020, shows dry coastal lowlands surrounding greener, higher-elevation vegetation toward the island’s center. Image via Wanmei Liang/ NASA Earth Observatory.
Using NASA data to guide release of giant tortoises
NASA satellite data play a key role in understanding these movement patterns. Observations track vegetation, rainfall, moisture and land-surface temperatures across the islands. Thus, the data highlight the areas most suitable for tortoises.
The project’s team, including professor Giorgos Mountrakis at the State University of New York College, created a decision tool. It combines satellite measurements with millions of field observations of tortoise locations. The tool maps habitat suitability today and predicts conditions decades into the future. This is crucial for an animal that can live over a century. Giorgos Mountrakis said:
This isn’t a one-year project. We’re looking at where tortoises will succeed 20, 40 years from now.
The scientists used various satellites in the project. They include Landsat and European Sentinel, which monitors vegetation, the Global Precipitation Measurement mission, which provides rainfall information, and Terra, which measures land-surface temperature. Also, teams used high-resolution commercial satellite imagery from NASA’s Commercial Smallsat Data Acquisition Program. All these data allowed them to evaluate potential release sites before conducting field surveys.
Christian Sevilla, director of ecosystems at the Galápagos National Park Directorate, said:
Habitat suitability models and environmental mapping are essential tools. They allow us to integrate climate, topography and vegetation data to make evidence-based decisions. We move from intuition to precision.
This map shows modeled giant tortoise habitat suitability across the Galápagos under current environmental conditions. Colors from dark to light indicate increasing likelihood of suitable food, moisture and nesting habitat availability. Image via Wanmei Liang/ NASA Earth Observatory.
Restoring Floreana’s ecosystem
The tortoise release is part of the broader Floreana Ecological Restoration Project. This project focuses on removing invasive species such as rats and feral cats that threaten eggs and hatchlings. Eventually, the plan is that 12 native animal species will return, with giant tortoises serving as a keystone species to help rebuild ecological processes.
Over the past six decades, the Galápagos National Park Directorate has raised and released more than 10,000 tortoises across the archipelago. It’s one of the largest rewilding efforts ever attempted.
Each island presents unique challenges because of differences in vegetation, moisture and terrain. Combining long-term field observations with NASA data helps scientists anticipate how tortoises will interact with these environments. Plus, they can assess habitat changes forecast for decades ahead.
If successful, Floreana could once again support a thriving tortoise population. It could restore the interactions between animals, plants and landscapes that have shaped the island for thousands of years. Sevilla said:
For those of us who live and work in Galápagos, this release is deeply meaningful. It demonstrates that large-scale ecological restoration is possible and that, with science and long-term commitment, we can recover an essential part of the archipelago’s natural heritage.
Carrying hope on their backs: Conservation teams transport young giant tortoises to carefully chosen release sites, giving Floreana Island’s ecosystem a second chance after more than a century. Image via David Liberio/ Galápagos Conservancy. Used with permission.
Bottom line: Giant tortoises return to Floreana Island in the Galápagos. NASA satellites are guiding their release and helping revive the island’s wild ecosystem.
After 150 years, giant tortoises are back on Floreana! Watch as 158 tortoises take their first steps into the wild, guided by cutting-edge NASA data. Video via EarthSky.
NASA helps giant tortoises return to a Galápagos island
For the first time in more than 150 years, giant tortoises are roaming the wild again on Floreana Island in the Galápagos. On February 20, 2026, conservation teams from the Galápagos National Park Directorate and the Galápagos Conservancy released 158 tortoises at two sites. They chose those sites using NASA satellite data, identifying areas where the animals could easily find food, water and nesting locations.
Keith Gaddis, manager of NASA Earth Action’s Biological Diversity and Ecological Forecasting program, said:
This is exactly the kind of project where NASA Earth observations make a difference. We’re helping partners answer a practical question: where will these animals have the best chance to survive, not just today, but decades from now?
Giant tortoises: A history lost and found
Giant tortoises disappeared from Floreana in the mid-1800s. The Floreana giant tortoise went extinct due to a few reasons. First, sailors arrived and hunted the animals for their meat. The tortoises could be stored alive on ships for up to six months, providing fresh food in other locations. But sailors also introduced predators, such as pigs and rats, which preyed on tortoise eggs and hatchlings.
So, without the tortoises, the island began to change. Historically, giant tortoises helped shape the landscape. They grazed on vegetation, opening pathways through dense plant growth and carrying seeds.
The path to reintroduction began decades later. In 2000, James Gibbs, Vice President of Science and Conservation at the Galápagos Conservancy, and other researchers discovered unusual tortoises on Wolf Volcano in northern Isabela Island. They did not resemble any known living species.
About 10 years later, scientists compared DNA from these animals with genetic material from bones of extinct Floreana tortoises from caves and museums. The analysis confirmed some of the Wolf Volcano tortoises carried Floreana ancestry. These tortoises were a sort of hybrid. It seems as if the sailors, in moving the tortoises on their ships, at one point dropped some off on Isabela Island more than a century ago.
Scientists then used these hybrid tortoises to establish a breeding program. And it has produced hundreds of offspring that are now ready to return to Floreana.
From extinction to revival: Hybrid tortoises with Floreana ancestry are paving the way for the giant tortoise’s return to its historic island home. Image via David Liberio/ Galápagos Conservancy. Used with permission.
Matching tortoises with the right habitat
Releasing tortoises into the wild is not as simple as opening a gate. Young tortoises raised in captivity must learn to find food, water and nesting sites. Gibbs said:
They don’t know where food is; they don’t know where water is; they don’t know where to nest. If you can place them where conditions are already right, you give them a much better chance.
Floreana’s terrain adds another layer of challenge. Some hills and mountains capture clouds and support cool, moist forests. Meanwhile, lower areas remain dry most of the year. Because tortoises need both food and nesting areas, they naturally migrate between these contrasting habitats. Thanks to NASA satellite data, researchers can identify the best release sites.
This Landsat 8 image of Floreana Island from October 6, 2020, shows dry coastal lowlands surrounding greener, higher-elevation vegetation toward the island’s center. Image via Wanmei Liang/ NASA Earth Observatory.
Using NASA data to guide release of giant tortoises
NASA satellite data play a key role in understanding these movement patterns. Observations track vegetation, rainfall, moisture and land-surface temperatures across the islands. Thus, the data highlight the areas most suitable for tortoises.
The project’s team, including professor Giorgos Mountrakis at the State University of New York College, created a decision tool. It combines satellite measurements with millions of field observations of tortoise locations. The tool maps habitat suitability today and predicts conditions decades into the future. This is crucial for an animal that can live over a century. Giorgos Mountrakis said:
This isn’t a one-year project. We’re looking at where tortoises will succeed 20, 40 years from now.
The scientists used various satellites in the project. They include Landsat and European Sentinel, which monitors vegetation, the Global Precipitation Measurement mission, which provides rainfall information, and Terra, which measures land-surface temperature. Also, teams used high-resolution commercial satellite imagery from NASA’s Commercial Smallsat Data Acquisition Program. All these data allowed them to evaluate potential release sites before conducting field surveys.
Christian Sevilla, director of ecosystems at the Galápagos National Park Directorate, said:
Habitat suitability models and environmental mapping are essential tools. They allow us to integrate climate, topography and vegetation data to make evidence-based decisions. We move from intuition to precision.
This map shows modeled giant tortoise habitat suitability across the Galápagos under current environmental conditions. Colors from dark to light indicate increasing likelihood of suitable food, moisture and nesting habitat availability. Image via Wanmei Liang/ NASA Earth Observatory.
Restoring Floreana’s ecosystem
The tortoise release is part of the broader Floreana Ecological Restoration Project. This project focuses on removing invasive species such as rats and feral cats that threaten eggs and hatchlings. Eventually, the plan is that 12 native animal species will return, with giant tortoises serving as a keystone species to help rebuild ecological processes.
Over the past six decades, the Galápagos National Park Directorate has raised and released more than 10,000 tortoises across the archipelago. It’s one of the largest rewilding efforts ever attempted.
Each island presents unique challenges because of differences in vegetation, moisture and terrain. Combining long-term field observations with NASA data helps scientists anticipate how tortoises will interact with these environments. Plus, they can assess habitat changes forecast for decades ahead.
If successful, Floreana could once again support a thriving tortoise population. It could restore the interactions between animals, plants and landscapes that have shaped the island for thousands of years. Sevilla said:
For those of us who live and work in Galápagos, this release is deeply meaningful. It demonstrates that large-scale ecological restoration is possible and that, with science and long-term commitment, we can recover an essential part of the archipelago’s natural heritage.
Carrying hope on their backs: Conservation teams transport young giant tortoises to carefully chosen release sites, giving Floreana Island’s ecosystem a second chance after more than a century. Image via David Liberio/ Galápagos Conservancy. Used with permission.
Bottom line: Giant tortoises return to Floreana Island in the Galápagos. NASA satellites are guiding their release and helping revive the island’s wild ecosystem.
In 2026, there are 3 Friday the 13ths. They are in February, March and November. Do you believe Friday the 13th is a bad day? An unlucky day? See below to explore the myths and the legacy behind Friday the 13th. Image via Wikimedia Commons.
March 13, 2026, is a Friday, and it’s Act 2 of this year’s epic Friday the 13th trilogy. Plus, we’ll also have another Friday the 13th in November. We started off this year’s trilogy with a Friday the 13th in February, exactly 4 weeks before Friday, March 13, 2026!
Not that we at EarthSky suffer from friggatriskaidekaphobia – an irrational fear of Friday the 13th – but, gosh darn, it’s Friday the 13th three times over in 2026. What’s more, last year’s lone Friday the 13th on June 13, 2025, occurred exactly 39 weeks (3 x 13 weeks) before the Friday the 13th in March 2026. And next year’s lone Friday the 13th on August 13, 2027, will happen exactly 39 weeks (3 x 13 weeks) after the Friday the 13th in November 2026. Follow the links below to learn more about why some people fear this day and about 2015’s three Friday the 13ths.
Gioachino Rossini, a 19th century Italian composer. Folklorists say there’s no written evidence that Friday the 13th was considered unlucky before the 19th century. The earliest known documented reference in English appears to be in Henry Sutherland Edwards’ 1869 biography of Rossini. Image via Wikimedia Commons.
Scary coincidence or super unlucky?
It’s neither a scary coincidence or super unlucky. It’s just a quirk of our calendar, as you’ll see if you keep reading.
The fact is that, according to folklorists, there’s no written evidence that Friday the 13th was considered unlucky before the 19th century. The earliest known documented reference in English appears to be in Henry Sutherland Edwards’ 1869 biography of Gioachino Rossini. His portrait is above. He doesn’t look scary.
And indeed, Friday has always gotten a bad rap. In the Middle Ages, people would not marry – or set out on a journey – on a Friday.
There are also some links between Christianity and an ill association with either Fridays or the number 13. Jesus was said to be crucified on a Friday. Seating 13 people at a table was seen as bad luck because Judas Iscariot, the disciple who betrayed Jesus, is said to have been the 13th guest at the Last Supper. Meanwhile, our word for Friday comes from Frigga, an ancient Scandinavian fertility and love goddess. Christians called Frigga a witch and Friday the witches’ Sabbath.
In modern times, the slasher-movie franchise Friday the 13th has helped keep friggatriskaidekaphobia alive.
The Friday the 13th slasher-movie franchise helped keep this day maintain its notoriety. Image via Wikimedia Commons.
In 2026, blame Thursday
In 2026, you can blame Thursday because the year started on a Thursday. Whenever a common year of 365 days starts on a Thursday, it’s inevitable that the months of February, March and November will start on a Sunday. And any month starting on a Sunday always has a Friday the 13th.
Of course, February has exactly four weeks in a non-leap year. So, for that reason, the days of the week have to match up with the same dates in both February and March during any common year. And in any year, the days of the week always fall on the same dates in both March and November. In short, because the year 2026 started on a Thursday, that means February, March and November all have to start on a Sunday and all must have a Friday the 13th.
The February-March-November Friday the 13th trilogy repeats …
How often does the February-March-November Friday the 13th trilogy repeat? More often than you might imagine! The last February-March-November Friday the 13th year happened 11 years ago, in 2015, for the second time in the 21st century (2001-2100). It will next happen eleven years from now, in 2037. After that, the following February-March-November Friday the 13th year will happen six years after 2037, in the year 2043.
A grand total of eleven February-March-November Friday the 13th years takes place in the 21st century (2001-2100):
And because the Gregorian calendar has a 400-year cycle, we also know the February-March-November Friday the 13th years will repeat exactly 400 years later in the 25th century (2401-2500):
Calendar for the year 2026. There are 3 Friday the 13ths. They are in February, March and November. Calendar via EarthSky.
The rhyme and reason of the Friday the 13th cycle
Is there any rhyme and reason to the Friday the 13th cycle? Yes, it does make sense. Within the 21st century (2001-2100), note that the February-March-November Friday the 13th years repeat in 28-year cycles (going crosswise):
Because the Gregorian calendar suppresses the leap year in 2100, the cycle is perturbed, meaning that all eleven February-March-November Friday the 13th years in the 22nd century (2101-2200) come four years earlier than in the 21st century:
Friday-the-13th-year repetitions within 28-year cycle
Some of you, who might not yet be dazed by calendar numerology, may wonder if some formula governs how a given Friday the 13th year repeats within the 28-year cycle. The answer is a definite yes. Keep in mind that this particular February-March-November Friday the 13th year can only happen in a common year of 365 days, and when January 1 falls on a Thursday.
Therefore, if this threefold Friday the 13th year comes one year after a leap year, the days again match up with the dates in 6, 17 and 28 years afterward. For example, take the year 2009, which came one year after a leap year:
2009, 2015, 2026, 2037
However, if this triple Friday the 13th year falls two years after a leap year, the days and dates realign in 11, 17 and 28 years. Take this year, 2026, which takes place two years after a leap year:
2026, 2037, 2043, 2054
Finally, if this trio of Friday the 13ths happens three years after a leap year, the days recur with the same dates in 11, 22 and 28 years. The year 2015 happened three years after a leap year:
2015, 2026, 2037, 2043
It appears as though cycles of 372 and 400 years prevail over the long course of centuries. Take the year 2015, for instance:
What about three Friday the 13ths in a leap year? Yes, a leap year can harbor three Friday the 13ths (January 13 – April 13 – July 13) if the leap year starts on a Sunday, which last happened in 2012. However, given that this particular Friday the 13th year happens in a leap year, and a leap year only, it recurs only in periods of 28 years. So the last January-April-July Friday the 13th year happened in 1984, and will next happen in 2040.
If a common year starts on a Thursday, there are three Friday the 13ths; and if a leap year begins on a Sunday, there are three Friday the 13ths. So these are the two scenarios whereby three Friday the 13ths can occur in single calendar year.
Bottom line: From what we have been able to gather, the 400-year cycle displayed by Gregorian calendar features 59 years with three Friday the 13ths, consisting of 44 common years (February – March – November Friday the 13ths) and 15 leap years (January – April – July Friday the 13ths).
In 2026, there are 3 Friday the 13ths. They are in February, March and November. Do you believe Friday the 13th is a bad day? An unlucky day? See below to explore the myths and the legacy behind Friday the 13th. Image via Wikimedia Commons.
March 13, 2026, is a Friday, and it’s Act 2 of this year’s epic Friday the 13th trilogy. Plus, we’ll also have another Friday the 13th in November. We started off this year’s trilogy with a Friday the 13th in February, exactly 4 weeks before Friday, March 13, 2026!
Not that we at EarthSky suffer from friggatriskaidekaphobia – an irrational fear of Friday the 13th – but, gosh darn, it’s Friday the 13th three times over in 2026. What’s more, last year’s lone Friday the 13th on June 13, 2025, occurred exactly 39 weeks (3 x 13 weeks) before the Friday the 13th in March 2026. And next year’s lone Friday the 13th on August 13, 2027, will happen exactly 39 weeks (3 x 13 weeks) after the Friday the 13th in November 2026. Follow the links below to learn more about why some people fear this day and about 2015’s three Friday the 13ths.
Gioachino Rossini, a 19th century Italian composer. Folklorists say there’s no written evidence that Friday the 13th was considered unlucky before the 19th century. The earliest known documented reference in English appears to be in Henry Sutherland Edwards’ 1869 biography of Rossini. Image via Wikimedia Commons.
Scary coincidence or super unlucky?
It’s neither a scary coincidence or super unlucky. It’s just a quirk of our calendar, as you’ll see if you keep reading.
The fact is that, according to folklorists, there’s no written evidence that Friday the 13th was considered unlucky before the 19th century. The earliest known documented reference in English appears to be in Henry Sutherland Edwards’ 1869 biography of Gioachino Rossini. His portrait is above. He doesn’t look scary.
And indeed, Friday has always gotten a bad rap. In the Middle Ages, people would not marry – or set out on a journey – on a Friday.
There are also some links between Christianity and an ill association with either Fridays or the number 13. Jesus was said to be crucified on a Friday. Seating 13 people at a table was seen as bad luck because Judas Iscariot, the disciple who betrayed Jesus, is said to have been the 13th guest at the Last Supper. Meanwhile, our word for Friday comes from Frigga, an ancient Scandinavian fertility and love goddess. Christians called Frigga a witch and Friday the witches’ Sabbath.
In modern times, the slasher-movie franchise Friday the 13th has helped keep friggatriskaidekaphobia alive.
The Friday the 13th slasher-movie franchise helped keep this day maintain its notoriety. Image via Wikimedia Commons.
In 2026, blame Thursday
In 2026, you can blame Thursday because the year started on a Thursday. Whenever a common year of 365 days starts on a Thursday, it’s inevitable that the months of February, March and November will start on a Sunday. And any month starting on a Sunday always has a Friday the 13th.
Of course, February has exactly four weeks in a non-leap year. So, for that reason, the days of the week have to match up with the same dates in both February and March during any common year. And in any year, the days of the week always fall on the same dates in both March and November. In short, because the year 2026 started on a Thursday, that means February, March and November all have to start on a Sunday and all must have a Friday the 13th.
The February-March-November Friday the 13th trilogy repeats …
How often does the February-March-November Friday the 13th trilogy repeat? More often than you might imagine! The last February-March-November Friday the 13th year happened 11 years ago, in 2015, for the second time in the 21st century (2001-2100). It will next happen eleven years from now, in 2037. After that, the following February-March-November Friday the 13th year will happen six years after 2037, in the year 2043.
A grand total of eleven February-March-November Friday the 13th years takes place in the 21st century (2001-2100):
And because the Gregorian calendar has a 400-year cycle, we also know the February-March-November Friday the 13th years will repeat exactly 400 years later in the 25th century (2401-2500):
Calendar for the year 2026. There are 3 Friday the 13ths. They are in February, March and November. Calendar via EarthSky.
The rhyme and reason of the Friday the 13th cycle
Is there any rhyme and reason to the Friday the 13th cycle? Yes, it does make sense. Within the 21st century (2001-2100), note that the February-March-November Friday the 13th years repeat in 28-year cycles (going crosswise):
Because the Gregorian calendar suppresses the leap year in 2100, the cycle is perturbed, meaning that all eleven February-March-November Friday the 13th years in the 22nd century (2101-2200) come four years earlier than in the 21st century:
Friday-the-13th-year repetitions within 28-year cycle
Some of you, who might not yet be dazed by calendar numerology, may wonder if some formula governs how a given Friday the 13th year repeats within the 28-year cycle. The answer is a definite yes. Keep in mind that this particular February-March-November Friday the 13th year can only happen in a common year of 365 days, and when January 1 falls on a Thursday.
Therefore, if this threefold Friday the 13th year comes one year after a leap year, the days again match up with the dates in 6, 17 and 28 years afterward. For example, take the year 2009, which came one year after a leap year:
2009, 2015, 2026, 2037
However, if this triple Friday the 13th year falls two years after a leap year, the days and dates realign in 11, 17 and 28 years. Take this year, 2026, which takes place two years after a leap year:
2026, 2037, 2043, 2054
Finally, if this trio of Friday the 13ths happens three years after a leap year, the days recur with the same dates in 11, 22 and 28 years. The year 2015 happened three years after a leap year:
2015, 2026, 2037, 2043
It appears as though cycles of 372 and 400 years prevail over the long course of centuries. Take the year 2015, for instance:
What about three Friday the 13ths in a leap year? Yes, a leap year can harbor three Friday the 13ths (January 13 – April 13 – July 13) if the leap year starts on a Sunday, which last happened in 2012. However, given that this particular Friday the 13th year happens in a leap year, and a leap year only, it recurs only in periods of 28 years. So the last January-April-July Friday the 13th year happened in 1984, and will next happen in 2040.
If a common year starts on a Thursday, there are three Friday the 13ths; and if a leap year begins on a Sunday, there are three Friday the 13ths. So these are the two scenarios whereby three Friday the 13ths can occur in single calendar year.
Bottom line: From what we have been able to gather, the 400-year cycle displayed by Gregorian calendar features 59 years with three Friday the 13ths, consisting of 44 common years (February – March – November Friday the 13ths) and 15 leap years (January – April – July Friday the 13ths).
