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Mercury is farthest from the sunset February 19

Two charts showing the positions of the planets in the western sky shortly after sunset. In the first, a starred dot, Venus, lies just above a wavy line, the horizon. A dot, Mercury, is directly above the starred dot, and another dot, Saturn, is much higher. On the second chart, the starred dot, Venus, rises slightly higher, and a dot, Mercury, first rises higher, then drops. Another dot, Saturn, slowly descends towards the wavy line of the horizon. — **Mercury** isn’t as blazingly bright as **Venus**, but you can catch it in the western twilight now. It’ll climb away from Venus until February 19, then begin dropping back toward the sunset horizon. **Saturn** is also nearby. It’s slowly creeping closer to Venus, Mercury and the western horizon as the month goes by. Chart via EarthSky.

February 2026 is a great (though brief) opportunity to see the most elusive planet, Mercury. As our sun’s innermost planet, Mercury always lies near the sun in our sky. This small, speedy planet is now in the west after sunset. It’ll reach its greatest elongation, its greatest apparent distance from the sun in our sky on February 19, 2026. Just don’t mistake Mercury for the blazing planet Venus – or for much-fainter Saturn – which are also in the west in evening twilight.

Mercury after sunset in February 2026

Where to look: Look west, in the sunset direction – shortly after sunset – for Mercury. Venus is up there, too, blazing away at -3.9 magnitude. So the very bright one is Venus. From mid- to late February, Mercury is above Venus in the evening twilight sky. And Saturn is higher up still. The ecliptic – or path of the sun, moon and planets in our sky – is nearly perpendicular to the western horizon after sunset in spring. So, for the Northern Hemisphere, this is Mercury’s best evening apparition of 2026. Watch for the moon near Mercury on the evening of February 18.
Greatest elongation: Mercury is farthest from the sun on our sky’s dome at 18 UTC (1 p.m. CST) on February 19, 2026. At that time, Mercury will be 18 degrees from the sun in our sky. See a comparison of elongations, below.
Brightness: Mercury emerged in the evening sky early in February. Since then, it’s been shining at around -1.0 magnitude. At greatest elongation it’ll be farther from the sunset glare, shining around 0 magnitude and therefore brighter than most stars! In the evenings after greatest elongation, the innermost planet will rapidly fade. It’ll be moving between Earth and the sun, with its illuminated side becoming less and less visible. It’ll disappear early next month and will reach inferior conjunction – when it passes between Earth and the sun – at 11 UTC on March 7.
Through a telescope: Mercury will appear about 48% illuminated at greatest elongation. It’ll measure 7.18 arcseconds across.
Constellation: Mercury will lie in front of the constellation Pisces the Fish at this elongation. Doubtless, the stars in this constellation will be lost in the twilight.
Note: As the innermost planet, Mercury is tied to the sun in our sky. As a result, it never ventures very far above the horizon after sunset. So as soon as the sun disappears below your horizon, your clock starts ticking. Will you see the glowing point of light that is Mercury before it drops below the horizon, following the setting sun?

For precise sun and Mercury rising times at your location:

timeanddate.com (worldwide)
Stellarium (online planetarium)

Mercury events in 2026

Note: Times are in UTC

Jan 21, 2026: Superior conjunction (passes behind sun from Earth)
Feb 19, 2026: Greatest elongation (evening)
Mar 7, 2026: Inferior conjunction (races between Earth and sun)
Apr 3, 2026: Greatest elongation (morning)
May 14, 2026: Superior conjunction (passes behind sun from Earth)
Jun 15, 2026: Greatest elongation (evening)
Jul 13, 2026: Inferior conjunction (races between Earth and sun)
Aug 2, 2026: Greatest elongation (morning)
Aug 27, 2026: Superior conjunction (passes behind sun from Earth)
Oct 12, 2026: Greatest elongation (evening)
Nov 4, 2026: Inferior conjunction (races between Earth and sun)
Nov 21, 2026: Greatest elongation (morning)

Diagram: Earth and Mercury orbits with sun in middle and lines of sight from Earth to Mercury and sun. — At greatest elongation, Mercury is to one side of the sun and is at its greatest distance from the sun on our sky’s dome. Mercury reaches greatest eastern (evening) elongation from the sun at 18 UTC on February 19, 2026. That’s 1 p.m. CST. It’s then 18 degrees from the sun in the evening sky. This will be the best evening apparition of Mercury for the Northern Hemisphere in 2026. Chart via EarthSky.

Heliocentric view of Mercury February 2026

Circle with sun at center, planets around, and zodiac names on outer edge. — Heliocentric view of solar system, February 2026. Chart via Guy Ottewell’s 2026 Astronomical Calendar. Used with permission. Plus Guy Ottewell explains heliocentric charts here.

A comparison of elongations

In February 2026, Mercury stretches out 18 degrees from the sun in our sky. In fact, the farthest from the sun that Mercury can ever appear on the sky’s dome is about 28 degrees. And the least distance is around 18 degrees.

Mercury (and Venus) elongations are better or worse depending on the time of the year they occur. So in 2026, the Northern Hemisphere will have the best evening apparition in February. And the Southern Hemisphere will have its best evening elongation of Mercury in June.

In the autumn for either hemisphere, the ecliptic – or path of the sun, moon and planets – makes a narrow angle to the horizon in the evening. But it makes a steep slant, nearly perpendicular, in the morning. So, in autumn from either hemisphere, morning elongations of Mercury are best. That’s when Mercury appears higher above the horizon and farther from the glow of the sun. However, evening elongations in autumn are harder to see.

In the spring for either hemisphere, the situation reverses. The ecliptic and horizon meet at a sharper angle on spring evenings and a narrower angle on spring mornings. So, in springtime for either hemisphere, evening elongations of Mercury are best. Meanwhile, morning elongations in springtime are harder to see.

Chart with row of steep, alternating light blue and gray arcs, each with a date and height in degrees. — Mercury elongations compared. Here, gray areas represent evening apparitions (eastward elongation). Blue areas represent morning apparitions (westward elongation). The top figures are the maximum elongations, reached at the top dates shown beneath. Curves show the altitude of the planet above the horizon at sunrise or sunset, for latitude 40 degrees north (thick line) and 35 degrees south (thin line). Likewise, maxima are reached at the parenthesized dates below (40 degrees north in bold). Chart via Guy Ottewell’s 2026 Astronomical Calendar. Used with permission.

More Mercury evening elongation comparisons for 2026

Sky chart with arc-shaped dotted planet paths, and sky objects labeled. — Mercury’s greatest evening elongations in 2026 from the Northern Hemisphere as viewed through a powerful telescope. The planet images are at the 1st, 11th, and 21st of each month. Dots show the actual positions of the planet for every day. Chart via Guy Ottewell’s 2026 Astronomical Calendar. Used with permission.

Bottom line: The sun’s innermost planet, Mercury, will be 18 degrees from the sunset when it reaches its greatest elongation at 18 UTC on February 19. Also, this is the best evening apparition of Mercury in 2026 for the Northern Hemisphere.

Submit your photos to EarthSky here.

Read about greatest elongations, superior and inferior conjunctions: Definitions for stargazers

The post Mercury is farthest from the sunset February 19 first appeared on EarthSky.

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Mercury after sunset in February 2026

For precise sun and Mercury rising times at your location:

timeanddate.com (worldwide)
Stellarium (online planetarium)

Mercury events in 2026

Note: Times are in UTC

Heliocentric view of Mercury February 2026

A comparison of elongations

More Mercury evening elongation comparisons for 2026

Submit your photos to EarthSky here.

Read about greatest elongations, superior and inferior conjunctions: Definitions for stargazers

The post Mercury is farthest from the sunset February 19 first appeared on EarthSky.

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Pale Blue Dot 36 years later: Earth in a sunbeam

Pale blue dot: Bluish space, with streaks of sunlight crossing it, and with a single dot - Earth - within one of the sunbeams. — View larger. | In this image from Voyager 1 – acquired on February 14, 1990, from a distance slightly past the orbit of Saturn – planet Earth appears as a pale blue dot within the sunbeam, just right of center. As you can see, the blue glow of Earth occupies less than a single pixel so it’s not fully resolved. Image via NASA.

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February 14, 1990: the Pale Blue Dot

The Voyager 1 spacecraft, out near Saturn, took this iconic image of Earth 36 years ago. It turned out to be one of the most memorable images ever taken from space. Astronomer Carl Sagan wrote in his 1994 book Pale Blue Dot:

Look again at that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every ‘superstar,’ every ‘supreme leader,’ every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.

An updated look at the Pale Blue Dot

NASA said on February 12, 2020, that it updated the Pale Blue Dot image, using modern image-processing software and techniques. NASA explained:

… the Voyager project planned to shut off the Voyager 1 spacecraft’s imaging cameras to conserve power because the probe – along with its sibling Voyager 2 – would not fly close enough to any other objects to take pictures. Before the shutdown, the mission commanded the probe to take a series of 60 images designed to produce what they termed the Family Portrait of the Solar System. Executed on Valentine’s Day 1990, this sequence returned images for making color views of six of the solar system’s planets and also imaged the sun in monochrome.

Carl Sagan named the image

The popular name of this view comes from the title of the 1994 book by Voyager imaging scientist Carl Sagan. He originated the idea of using Voyager’s cameras to image the distant Earth and played a critical role in getting the family portrait taken.

The direction of the sun is toward the bottom of the view (where the image is brightest). Rays of sunlight scattered within the camera optics stretch across the scene. By coincidence, one of those light rays intersects dramatically with Earth.

From Voyager 1’s vantage point – a distance of approximately 3.8 billion miles (6 billion km) – Earth appears separated from the sun by only a few degrees. The close proximity of the inner planets to the sun was a key factor as to why engineers couldn’t take these images earlier in the mission. At that time, our star was still close and bright enough to damage the cameras with its blinding glare.

Scientists combined green, blue and violet spectral filters from the Voyager 1 Narrow-Angle Camera for this composite. Voyager took these photos at 4:48 UTC on February 14, 1990. That was just 34 minutes before Voyager 1 powered off its cameras forever.

Our family portrait

Diagram of plantary orbits with squares overlying them showing locations of Voyager's individual photos. — View larger. | The *Family Portrait of the Solar System*. Voyager 1 acquired this series of 60 images on February 14, 1990. Image via NASA.

Diagram of solar system planetary orbits with spacecraft in foreground. — View larger. | This simulated view from NASA’s Eyes on the Solar System app shows Voyager 1’s perspective when it took its final series of images. This *Family Portrait of the Solar System* includes the Pale Blue Dot image. Image via NASA.

Bottom line: February 14, 2026, is the 36th anniversary of the Voyager 1 image of Earth. Voyager was near Saturn when it took this image, which is now known as the Pale Blue Dot.

Via NASA

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February 14, 1990: the Pale Blue Dot

Look again at that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every ‘superstar,’ every ‘supreme leader,’ every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.

An updated look at the Pale Blue Dot

NASA said on February 12, 2020, that it updated the Pale Blue Dot image, using modern image-processing software and techniques. NASA explained:

… the Voyager project planned to shut off the Voyager 1 spacecraft’s imaging cameras to conserve power because the probe – along with its sibling Voyager 2 – would not fly close enough to any other objects to take pictures. Before the shutdown, the mission commanded the probe to take a series of 60 images designed to produce what they termed the Family Portrait of the Solar System. Executed on Valentine’s Day 1990, this sequence returned images for making color views of six of the solar system’s planets and also imaged the sun in monochrome.

Carl Sagan named the image

Our family portrait

Bottom line: February 14, 2026, is the 36th anniversary of the Voyager 1 image of Earth. Voyager was near Saturn when it took this image, which is now known as the Pale Blue Dot.

Via NASA

The post Pale Blue Dot 36 years later: Earth in a sunbeam first appeared on EarthSky.

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Star dims for 9 months, likely due to giant ringed object

Star dims: Distant small red orb and a bright oval with a ring around it in the foreground. — Artist’s impression of a star dimming due to its light being blocked by a giant ringed planet or possibly a brown dwarf. In this illustration, a super-Jupiter with massive rings in the foreground forms an opaque “saucer” through which some light from the star ASASSN-24fw shines. Scientists also discovered a neighboring red dwarf star during their research. Image via S. Shah et al./ Royal Astronomical Society (CC BY 4.0).

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A star called ASASSN-24fw dimmed by 97% for more than nine months. It was one of the longest stellar dimming events ever recorded. But why did it get so dim for so long?
Astronomers think an unseen brown dwarf or super-Jupiter with a huge ring system passed in front of the star, blocking its light.
The researchers expect the star to dim again in about 42 or 43 years. At that time, astronomers can carry out further analysis to find out more about this fascinating system.

The Royal Astronomical Society published this original story on February 12, 2026. Edits by EarthSky.

Star dims for 9 months, likely due to giant ringed planet

One of the longest stellar dimming events ever observed was likely caused by the gigantic saucer-like rings of either an unseen “super-Jupiter” or a brown dwarf blocking its host star’s light. That’s according to astronomers at the Royal Astronomical Society, who described the new research on the fading star on February 12. 2026. The star, named ASASSN-24fw, sits 3,200 light-years from Earth and is about twice as big as our sun. For decades, astronomers had observed the star as stable, but at the end of 2024 it faded dramatically.

It then remained this way for more than nine months, far longer than is normal for an event like this. The unusual length of the dimming sparked confusion among researchers and prompted speculation as to what could have caused such an “extremely rare” phenomenon.

Now, in a new study published February 12, 2026, in the peer-reviewed Monthly Notices of the Royal Astronomical Society, a team of international researchers propose a solution of the riddle of this mysterious star in the Monoceros constellation.

They think it was most likely a brown dwarf (an object between the size of a star and Jupiter) with Saturn-like rings that caused ASASSN-24fw to dim by about 97%. This ring system is so enormous it extends out about 0.17 astronomical units (AU), comparable to half the distance between our sun and Mercury.

Brown dwarf or super-Jupiter

The two most likely objects responsible for blocking the star’s light are a brown dwarf or super-Jupiter.

Brown dwarfs are mysterious objects. They’re too big to be a planet but also too small to be a star. They lack the mass to keep fusing atoms and blossom into fully fledged suns.

The other option, the researchers said, is a super-Jupiter. These are massive gas giant exoplanets that exceed the mass of Jupiter and bridge the gap between brown dwarfs and planets.

Their findings offer a glimpse into complex planetary-scale structures beyond our solar system. And they pave a new way to study how planets and their rings may form and evolve around other stars.

Unlike typical eclipses, which usually last days or weeks, this dimming continued for nearly 200 days, making it one of the longest ever observed.

Lead author Sarang Shah, a post-doctoral researcher at the Inter-University Centre for Astronomy and Astrophysics (IUCAA), in Pune, India, said:

Various models made by our group show that the most likely explanation for the dimming is a brown dwarf – an object heavier than a planet but lighter than a star – surrounded by a vast and dense ring system. It is orbiting the star at a farther distance with the ring.

Long-lasting dimming events like this are exceptionally uncommon as they require very perfect lineups. The dimming began gradually because the outer parts of the rings are thin, and only became obvious when the denser regions passed in front of the star.

A bright orb at center with a disk around it, a separate, thin disk at lower right and a red dot at lower left. — Artist’s impression of ASASSN-24fw after the eclipse is over. Now we can see the star shining unobstructed. And it also has a debris disk, possibly the remnants from a planetary collision. The unseen object with its huge rings is at lower right. A companion red dwarf star is at lower left. Image via S. Shah et al./ Royal Astronomical Society (CC BY 4.0).

Large ring system

Analysis of photometric and spectroscopic studies of the event suggests that the companion object has a mass of more than three times that of Jupiter.

The analysis also shows that ASASSN-24fw itself has a circumstellar environment (possibly remnants from past or ongoing planetary collisions) very near to it, which is unusual for a star of this age (likely more than 1 billion years).

Co-author Jonathan Marshall, an independent post-doctoral researcher affiliated with Academia Sinica, Taiwan, has expertise is in circumstellar material and debris discs. Marshall said:

Large ring systems are expected around massive objects, but they are very difficult to observe directly to determine their characteristics. This rare event allows us to study such a complex system in remarkable detail. In fact, while studying this dimming, we also serendipitously discovered that ASASSN-24fw also has a red dwarf star in its vicinity.

The team of researchers now want to measure the temperature, evolutionary status, chemical composition and age of the star that dimmed. They then hope to obtain more data from the European Southern Observatory’s Very Large Telescope in Chile and the James Webb Space Telescope to better understand the evolution of such systems and relate them to planetary formation theories.

The researchers expect the star to dim again in about 42 or 43 years’ time. At that time, astronomers can carry out further analysis to find out more about this fascinating system.

Bottom line: Astronomers watched a star dim to less than 97% of its brightness for nine months. They believe a giant ringed object blocked the light from our view.

Source: The nature of ASASSN-24fw’s occultation: modelling the event as dimming by optically thick rings around a sub-stellar companion

Via Royal Astronomical Society

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A star called ASASSN-24fw dimmed by 97% for more than nine months. It was one of the longest stellar dimming events ever recorded. But why did it get so dim for so long?
Astronomers think an unseen brown dwarf or super-Jupiter with a huge ring system passed in front of the star, blocking its light.
The researchers expect the star to dim again in about 42 or 43 years. At that time, astronomers can carry out further analysis to find out more about this fascinating system.

The Royal Astronomical Society published this original story on February 12, 2026. Edits by EarthSky.

Star dims for 9 months, likely due to giant ringed planet

Brown dwarf or super-Jupiter

The two most likely objects responsible for blocking the star’s light are a brown dwarf or super-Jupiter.

Brown dwarfs are mysterious objects. They’re too big to be a planet but also too small to be a star. They lack the mass to keep fusing atoms and blossom into fully fledged suns.

The other option, the researchers said, is a super-Jupiter. These are massive gas giant exoplanets that exceed the mass of Jupiter and bridge the gap between brown dwarfs and planets.

Their findings offer a glimpse into complex planetary-scale structures beyond our solar system. And they pave a new way to study how planets and their rings may form and evolve around other stars.

Unlike typical eclipses, which usually last days or weeks, this dimming continued for nearly 200 days, making it one of the longest ever observed.

Lead author Sarang Shah, a post-doctoral researcher at the Inter-University Centre for Astronomy and Astrophysics (IUCAA), in Pune, India, said:

Various models made by our group show that the most likely explanation for the dimming is a brown dwarf – an object heavier than a planet but lighter than a star – surrounded by a vast and dense ring system. It is orbiting the star at a farther distance with the ring.

Long-lasting dimming events like this are exceptionally uncommon as they require very perfect lineups. The dimming began gradually because the outer parts of the rings are thin, and only became obvious when the denser regions passed in front of the star.

Large ring system

Analysis of photometric and spectroscopic studies of the event suggests that the companion object has a mass of more than three times that of Jupiter.

Co-author Jonathan Marshall, an independent post-doctoral researcher affiliated with Academia Sinica, Taiwan, has expertise is in circumstellar material and debris discs. Marshall said:

Large ring systems are expected around massive objects, but they are very difficult to observe directly to determine their characteristics. This rare event allows us to study such a complex system in remarkable detail. In fact, while studying this dimming, we also serendipitously discovered that ASASSN-24fw also has a red dwarf star in its vicinity.

The researchers expect the star to dim again in about 42 or 43 years’ time. At that time, astronomers can carry out further analysis to find out more about this fascinating system.

Bottom line: Astronomers watched a star dim to less than 97% of its brightness for nine months. They believe a giant ringed object blocked the light from our view.

Source: The nature of ASASSN-24fw’s occultation: modelling the event as dimming by optically thick rings around a sub-stellar companion

Via Royal Astronomical Society

The post Star dims for 9 months, likely due to giant ringed object first appeared on EarthSky.

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New clues to how giant galaxies formed in the early universe

Watch a video explaining how giant galaxies in the early universe might have formed. Video via Max Planck Institute for Radio Astronomy.

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New clues to how giant galaxies formed in the early universe

For decades, astronomers have puzzled over the galaxies they see in the early universe. They’ve spotted massive galaxies just a few billion years after the Big Bang that consist of old stars and are depleted of the gas needed to form new stars. How are galaxies so close to the beginning of the universe already so evolved? On February 10, 2026, astronomers at the Max Planck Institute in Germany said they found evidence a giant elliptical galaxy may form through the rapid collapse of a young galaxy cluster.

The astronomers focused their study on a protocluster – or a massive collection of young galaxies in the early universe – named SPT2349-56. This protocluster existed just 1.4 billion years after the Big Bang, or when the universe was 10% of its current age.

Lead author Nikolaus Sulzenauer, of the Max Planck Institute for Radio Astronomy at the University of Bonn, said:

In a universe where larger galaxies grow hierarchically through gravitational interactions and mergers of smaller building blocks, some giant ellipticals must have formed completely differently than previously thought. Instead of slowly assembling mass throughout 14 billion years, a massive elliptical galaxy might swiftly emerge in just a few hundred million years. It can form through the collapse and coalescence of a major primordial structure, in the time it takes the sun to orbit around the Milky Way’s center once. We find that the structures with the very highest densities must have decoupled first from the universe’s expansion at only 10% of the current cosmic age, and then rapidly assembled entire protoclusters.

The researchers published their peer-reviewed paper in The Astrophysical Journal on February 10, 2026.

Spotlighting a distant protocluster

The researchers used the radio telescopes ALMA and Atacama Pathfinder Experiment in Chile to analyze the cold gas and dust at the center of the protocluster. They chose the protocluster SPT2349-56 – which lies in the direction of the Southern Hemisphere constellation Phoenix – because it’s one of the earliest clusters of massive galaxies that we’ve seen. Co-author Axel Weiss of the Max Planck Institute said:

SPT2349-56 holds the record for the most vigorous stellar factory.

Co-author Ryley Hill from the University of British Columbia in Canada added:

In the center, we found four tightly-interacting galaxies forging one star every 40 minutes.

In comparison, our own Milky Way forms just three to four stars in a year.

A cluster of many galaxies with orange streaks swirling away. — Artist’s impression of the protocluster SPT2349-56. These interacting galaxies are different shapes and sizes. Tidal forces are heating the gas (orange) and tearing it apart. We see SPT2349-56 as it looked only 1.4 billion years after the Big Bang, when the universe was 10% of its current age. Image via N.Sulzenauer/ Max Planck Institute for Radio Astronomy.

A cascading merger

The astronomers found that the core cluster of galaxies spun out brightly glowing gas that led them to more colliding galaxies. Their computer simulations showed them that this whole structure of 40-plus galaxies will eventually merge into one mega elliptical galaxy.

Sulzenauer explained:

Importantly, this galaxy quartet launches coherent giant tidal arms at 300 kilometers per second [671,081 mph], stretching over an area much larger than the Milky Way. They glow intensely at submillimeter wavelengths, their brightness boosted 10-fold by shockwaves exciting ionized carbon atoms. This bright emission allowed us to precisely measure the motion of gas in this gravitationally ejected spiral, resembling beads on a string encircling the protocluster core.

To our surprise, clumps of tidal debris link to a chain of 20 additional colliding galaxies in the outer parts of the collapsing structure. This hints at a common origin. For the first time, we are witnessing the onset of a cascading merging transformation. Most of the 40 gas-rich galaxies in this core will be destroyed and will eventually transform into a giant elliptical galaxy within less than 300 million years – a mere blink of an eye.

Giant galaxies: Chart showing blobs of coloring, brighter at their centers with stars marking the middles and lines encircling some clumps. — This radio image of the protocluster SPT2349-56 tracks ionized carbon emitted at a wavelength of 158 micrometers. The centers of galaxies are marked with stars, while orange highlights the tidal arms around the inner region. These tidally ejected, galaxy-scale gas clumps are 10 times brighter than astronomers expected. Note the Milky Way for scale at lower right. Image via N. Sulzenauer/ Max Planck Institute for Radio Astronomy.

Case closed on giant galaxies in the early universe?

While the new research provides insight into tidal forces of galaxies and the possibility of creating a huge elliptical out of dozens of smaller galaxies, there’s still much to learn. Co-author Scott Chapman of Dalhousie University said:

While our findings offer exciting new insights into rapid elliptical galaxy assembly, the various interactions between the merger shocks, gas heating from the growth of supermassive black holes, and their effect on the fuel for star formation, remain big mysteries. It might be too early to claim a full understanding of the ‘early childhood’ of giant ellipticals, but we have come a long way in linking tidal debris in protoclusters to the formation process of massive galaxies located in today’s galaxy clusters.

Bottom line: Astronomers used radio data to study the creation of giant galaxies in the early universe. They found some 40 galaxies are tied together and will likely transform into one huge elliptical.

Source: Bright [C II] 158 Micrometer Streamers as a Beacon for Giant Galaxy Formation in SPT2349-56 at z = 4.3

Via Max Planck Institute

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Watch a video explaining how giant galaxies in the early universe might have formed. Video via Max Planck Institute for Radio Astronomy.

EarthSky’s 2026 lunar calendar is available now. Get yours today! Makes a great gift.

New clues to how giant galaxies formed in the early universe

Lead author Nikolaus Sulzenauer, of the Max Planck Institute for Radio Astronomy at the University of Bonn, said:

In a universe where larger galaxies grow hierarchically through gravitational interactions and mergers of smaller building blocks, some giant ellipticals must have formed completely differently than previously thought. Instead of slowly assembling mass throughout 14 billion years, a massive elliptical galaxy might swiftly emerge in just a few hundred million years. It can form through the collapse and coalescence of a major primordial structure, in the time it takes the sun to orbit around the Milky Way’s center once. We find that the structures with the very highest densities must have decoupled first from the universe’s expansion at only 10% of the current cosmic age, and then rapidly assembled entire protoclusters.

The researchers published their peer-reviewed paper in The Astrophysical Journal on February 10, 2026.

Spotlighting a distant protocluster

SPT2349-56 holds the record for the most vigorous stellar factory.

Co-author Ryley Hill from the University of British Columbia in Canada added:

In the center, we found four tightly-interacting galaxies forging one star every 40 minutes.

In comparison, our own Milky Way forms just three to four stars in a year.

A cascading merger

Sulzenauer explained:

Importantly, this galaxy quartet launches coherent giant tidal arms at 300 kilometers per second [671,081 mph], stretching over an area much larger than the Milky Way. They glow intensely at submillimeter wavelengths, their brightness boosted 10-fold by shockwaves exciting ionized carbon atoms. This bright emission allowed us to precisely measure the motion of gas in this gravitationally ejected spiral, resembling beads on a string encircling the protocluster core.

To our surprise, clumps of tidal debris link to a chain of 20 additional colliding galaxies in the outer parts of the collapsing structure. This hints at a common origin. For the first time, we are witnessing the onset of a cascading merging transformation. Most of the 40 gas-rich galaxies in this core will be destroyed and will eventually transform into a giant elliptical galaxy within less than 300 million years – a mere blink of an eye.

Case closed on giant galaxies in the early universe?

While our findings offer exciting new insights into rapid elliptical galaxy assembly, the various interactions between the merger shocks, gas heating from the growth of supermassive black holes, and their effect on the fuel for star formation, remain big mysteries. It might be too early to claim a full understanding of the ‘early childhood’ of giant ellipticals, but we have come a long way in linking tidal debris in protoclusters to the formation process of massive galaxies located in today’s galaxy clusters.

Source: Bright [C II] 158 Micrometer Streamers as a Beacon for Giant Galaxy Formation in SPT2349-56 at z = 4.3

Via Max Planck Institute

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Great Backyard Bird Count begins February 13

EarthSky’s 2026 lunar calendar is available now. Get yours today! Makes a great gift.

Great Backyard Bird Count

The 29th annual Great Backyard Bird Count is set to take place February 13-16, 2026. During this popular community science event, people from all over the world head outdoors to count birds. Scientists use the data to track the health of bird populations.

Watching birds can be a pleasant activity to engage in, and participating in the bird count is free and easy. You just have to commit to counting birds for as little as 15 minutes (or as long as you wish) on one or more days of the four-day event, and report your sightings online at the event’s website. Anyone can take part in the Great Backyard Bird Count, from beginning bird watchers to experts, and you can do the count from your backyard or anywhere in the world. It’s a great way to burn off some of those of extra calories from eating chocolate on Valentine’s Day. Learn more about how to participate here.

A small bird, gray back and white front, with black smudge around eyes, sitting on a bare twig. — A dark-eyed junco seen in Cambridge, Ontario, Canada. Image via Ryan Hodnett/ Wikimedia.

About the Great Backyard Bird Count

The Great Backyard Bird Count is a joint project of the Cornell Lab of Ornithology, National Audubon Society and Birds Canada, and support is provided in part by founding sponsor Wild Birds Unlimited. Chad Wilsey, chief scientist at the National Audubon Society, commented on the value of this event for both birds and people:

By participating in the Great Backyard Bird Count, community scientists contribute data that we use to protect birds and the places they need, today and tomorrow. In return, studies tell us that pausing to observe birds, their sounds and movements and improve human health. Participating in the Great Backyard Bird Count is a win-win for birds and people.

Bright red bird perches on a patio table in someone's yard. — View at EarthSky Community Photos. | Mark Wralstad of Virginia Beach, Virginia, captured this image on January 20, 2025, and wrote: “My Feathersnap bird feeder has captured some great bird shots since I installed it this month but this is one of the brightest visitors I have captured so far! This male Northern Cardinal has become a regular guest.” Thank you, Mark!

How to participate

If you would like to join the 2026 Great Backyard Bird Count, please follow these three easy steps.

1. Familiarize yourself with the event website at the link here.

2. Spend some time counting birds on the weekend of the event at the location of your choice, such as your backyard or a local park. The minimum amount of time required is 15 minutes, but you can count for longer if you wish. During your count, simply record the start and end time, location and number and types of birds that you see. You can perform counts in multiple locations too. Just be sure to submit separate checklists for each location.

And, not to worry if you can’t identify the birds you see at first. Just take good notes about their prominent features such as their size, shape, color and unusual markings, or you can try to snap a closeup picture. Then, you can use a bird guide to look them up later. All About Birds and What Bird are two good online bird identification guides that are free and easy to use.

Additionally, the free Merlin Bird ID app can be downloaded to your smartphone and used offline. Merlin will ask you five simple questions about the bird you are trying to identify and suggest matches for you. Plus, you can even upload a picture to Merlin and let the app try to identify it.

3. The last step involves sending your data to the event’s website. This step usually only takes a few minutes to complete. While you’re visiting the website, check out the live map that displays dots in the various locations where people have submitted a checklist. It’s fun to watch the data pour in from all over the world.

There’s a photo contest too

As an added bonus, there is a photo contest for those who want to submit pictures of the birds that they see during the event. You can even submit photos of yourself bird watching. If you do shoot some good photos, please share them with us at EarthSky Community Photos. We love birding photos!

Most red bird with dark feathers on a tree branch. — View at EarthSky Community Photos. | Lynzie Flynn of Fountain Valley, California, submitted this image on December 22, 2024, and wrote: “This is an adult male Vermilion Flycatcher. It was flying from tree to tree and posing for me. It’s such a colorful bird and one of the few colorful birds we see in my area. They are always a treat to see and photograph.” Thank you. Lynzie! Find out more about the Great Backyard Bird Count below.

2025 bird count

During the 2025 count, more than 217 countries and regions reported approximately 8,078 species out of the estimated 10,000 bird species that live on Earth today. Wow!

Use the hashtag #GBBC to follow Great Backyard Bird Count conversations on social media.

The first annual Great Backyard Bird Count was held in 1998, and the event has continued to grow year after year. Hopefully, 2026 will be another record breaker.

Small bird with yellow on top of its head on a partly-eaten yellow apple. — View at EarthSky Community Photos. | Stephanie Becker in the San Francisco Bay Area, California, gets a gold star for capturing this photo of a sparrow. She wrote: “In looking forward to the Great Backyard Bird Count, I’ve been observing birds in our backyard. This one is a golden-crowned sparrow enjoying a Golden Delicious apple.” Thanks, Stephanie!

Bottom line: The annual Great Backyard Bird Count runs from February 13-16, 2026. This popular community science project helps scientists keep track of the health of bird populations. Participating is free and easy, so why not give it a try?

Great Backyard Bird Count

About the Great Backyard Bird Count

By participating in the Great Backyard Bird Count, community scientists contribute data that we use to protect birds and the places they need, today and tomorrow. In return, studies tell us that pausing to observe birds, their sounds and movements and improve human health. Participating in the Great Backyard Bird Count is a win-win for birds and people.

How to participate

If you would like to join the 2026 Great Backyard Bird Count, please follow these three easy steps.

1. Familiarize yourself with the event website at the link here.

There’s a photo contest too

2025 bird count

During the 2025 count, more than 217 countries and regions reported approximately 8,078 species out of the estimated 10,000 bird species that live on Earth today. Wow!

Use the hashtag #GBBC to follow Great Backyard Bird Count conversations on social media.

The first annual Great Backyard Bird Count was held in 1998, and the event has continued to grow year after year. Hopefully, 2026 will be another record breaker.

2026 has 3 Friday the 13ths. What are the odds?

Point of highlighter pen drawing a bright pink circle around Friday 13 on a calendar. — 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 (CC BY-SA 3.0).

EarthSky’s 2026 lunar calendar is available now. Get yours today! Makes a great gift.

February 13, 2026, is a Friday, ushering in Act I of this year’s epic Friday the 13th trilogy. Plus, we’ll also have a Friday the 13th in March and November. To start things off, we’ll have 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.

Sepia-tinted photo of a portly man, seated, holding a cane, dressed in a suit. — 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. Public domain.

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):

2009, 2015, 2026, 2037, 2043, 2054, 2065, 2071, 2082, 2093 and 2099

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):

2409, 2415, 2426, 2437, 2443, 2454, 2465, 2471, 2482, 2493 and 2499

Calendar for 2026

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):

2009, 2037, 2065, 2093
2015, 2043, 2071, 2099
2026, 2054, 2082

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:

2105, 2111, 2122, 2133, 2139, 2150, 2161, 2167, 2178, 2189 and 2195.

However, within the 22nd century (2101-2200), these Friday the 13th years also repeat in cycles of 28 years.

2105, 2133, 2161, 2189
2111, 2139, 2167, 2195
2122, 2150, 2178

The cycle is perturbed again in the 23rd century (2201-2300):

2201, 2229, 2257, 2285
2207, 2235, 2263, 2291
2218, 2246, 2274

And again in the 24th century (2301-2400):

2303, 2331, 2359, 2387
2314, 2342, 2370, 2398
2325, 2353, 2381

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 comes 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 the 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 happens 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:

2015 + 372 = 2387

2015 + 400 = 2415

The 372-year period is known as the Gregoriana eclipse cycle, which we elaborate about in our post: How often does a solar eclipse happen on the March equinox?.

Can three Friday the 13ths occur in a leap year?

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).

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EarthSky’s 2026 lunar calendar is available now. Get yours today! Makes a great gift.

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.

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.

In modern times, the slasher-movie franchise Friday the 13th has helped keep friggatriskaidekaphobia alive.

In 2026, blame Thursday

The February-March-November Friday the 13th trilogy repeats …

A grand total of eleven February-March-November Friday the 13th years takes place in the 21st century (2001-2100):

2009, 2015, 2026, 2037, 2043, 2054, 2065, 2071, 2082, 2093 and 2099

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):

2409, 2415, 2426, 2437, 2443, 2454, 2465, 2471, 2482, 2493 and 2499

Calendar for 2026

The rhyme and reason of the Friday the 13th cycle

2009, 2037, 2065, 2093
2015, 2043, 2071, 2099
2026, 2054, 2082

2105, 2111, 2122, 2133, 2139, 2150, 2161, 2167, 2178, 2189 and 2195.

However, within the 22nd century (2101-2200), these Friday the 13th years also repeat in cycles of 28 years.

2105, 2133, 2161, 2189
2111, 2139, 2167, 2195
2122, 2150, 2178

The cycle is perturbed again in the 23rd century (2201-2300):

2201, 2229, 2257, 2285
2207, 2235, 2263, 2291
2218, 2246, 2274

And again in the 24th century (2301-2400):

2303, 2331, 2359, 2387
2314, 2342, 2370, 2398
2325, 2353, 2381

Friday-the-13th-year repetitions within 28-year cycle

2009, 2015, 2026, 2037

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 happens 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:

2015 + 372 = 2387

2015 + 400 = 2415

The 372-year period is known as the Gregoriana eclipse cycle, which we elaborate about in our post: How often does a solar eclipse happen on the March equinox?.

Can three Friday the 13ths occur in a leap year?

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Tatooine exoplanets are oddly rare, and we finally know why

Tatooine exoplanets: A small, dark planet between the viewer and a pair of stars, one large and one small. — Artist’s concept of a planet – the black dot – orbiting a pair of stars in a binary star system. A new study says Einstein’s general theory of relativity can explain why these Tatooine exoplanets seem to be rarer than 1st thought. Image via NASA/ Goddard Space Flight Center.

Tatooine planets are exoplanets that orbit two stars instead of just one. The name comes from the fictional arid desert world in “Star Wars.”
These planets seem to be rarer than first thought, although they do exist.
Einstein’s general theory of relativity – specifically the gravitational effects of the two stars – is to blame for their rarity, according to a new study.

EarthSky’s 2026 lunar calendar shows every day’s moon phase. Get yours today!

Tatooine exoplanets are rare

In “Star Wars,” the planet Tatooine was remarkable because it orbited a pair of stars, not just one. And astronomers have found real examples of Tatooine worlds, called circumbinary planets. But they seem to be rare. Why? On January 30, 2026, scientists said Einstein’s general theory of relativity is to blame. Over time, the orbits of the two stars around each other shrink. As a consequence, the planet’s orbit becomes wildly elongated. Ultimately, the planet will either be consumed by one of the stars or get ejected from the system entirely.

The theory of general relativity basically says the observed gravitational effect between masses – such as a pair of binary stars – results from their warping of spacetime. It interprets gravity as a warping of the fabric of spacetime by a mass, similar to how a person on a trampoline warps the surface and makes other objects on the trampoline fall inward toward the person.

Astrophysicists at the University of California, Berkeley and the American University of Beirut in Lebanon published their peer-reviewed findings in The Astrophysical Journal Letters on December 8, 2025.

University of California, Berkeley: Why Are Tatooine Planets Rare? Blame General Relativity. news.berkeley.edu/2026/01/30/w…

— AAS Press Office (@press.aas.org) 2026-02-02T16:14:05.036Z

A dearth of binary star exoplanets

Astronomers had found massive exoplanets – like Jupiter and Saturn in our solar system – around 10% of single, sunlike stars. These were in the datasets from the Kepler and TESS space telescopes, about 300 planets overall. They had expected to find similar numbers orbiting binary stars also. However, they only found 47 candidate planets and 14 confirmed planets. Lead author Mohammad Farhat, a Miller Postdoctoral Fellow at UC Berkeley, said:

You have a scarcity of circumbinary planets in general and you have an absolute desert around binaries with orbital periods of seven days or less. The overwhelming majority of eclipsing binaries are tight binaries and are precisely the systems around which we most expect to find transiting circumbinary planets.

6 diagrams showing the various orbits of planets around binary stars. Explanatory text is below each one. — View larger. | This diagram shows the step-by-step explanation for why planets that orbit binary stars eventually enter an unstable orbit and disappear from the system. Image via Mohammad Farhat/ UC Berkeley.

The instability zone

Binary star systems have an instability zone. This is a region where no planet can survive for long, and it ties in with the theory of relativity. The gravitational interactions of a planet and both stars can be chaotic. As a result, the planet will either be consumed or shredded by one of the stars, or it will be expelled from the system altogether. Indeed, 12 of the 14 confirmed planets orbiting close binary stars orbit just beyond the edge of this instability zone. This is why they are still safe. As Farhat explained:

Planets form from the bottom up, by sticking small-scale planetesimals together. But forming a planet at the edge of the instability zone would be like trying to stick snowflakes together in a hurricane.

General theory of relativity is to blame

The researchers found general relativity had a significant effect on planets orbiting binary stars. They calculated that eight out of 10 such planets would be disrupted in their orbits. And 75% of those would end up being destroyed. Why does this happen?

In binary star systems, the stars usually have similar, but not identical, masses. They orbit each other in elongated, egg-shaped orbits. If there is a planet orbiting both stars, the gravity from the stars will cause the planet’s orbit to precess, similar to how the axis of a spinning top wobbles. Precession is the slow gyration of the rotation axis of a spinning body around another line intersecting it.

The orbit of the planet Mercury also experiences precession. In fact, it’s slightly higher than predicted by the earlier theory of gravity by Isaac Newton. The additional precession is explained by the general theory of relativity.

Bearded man standing with messenger bag with the strap over his chest. Trees and a domed building are behind him. — Mohammad Farhat, a Miller Postdoctoral Fellow at University of California, Berkeley, is the lead author of the new study about Tatooine planets orbiting binary stars and Einstein’s general theory of relativity. Image via University of California, Berkeley.

2 possible fates of Tatooine exoplanets

The orbits of the two binary stars also undergo precession, due mostly to general relativity. The distance between the two stars gradually shrinks over time. As the precession rate of the stars increases, the precession rate of the planet slows down. Eventually, the two precession rates will match and become in resonance. As a result, the planet’s orbit becomes even more elongated. As Farhat explained, there are then two possible outcomes for the planet, neither of which are good:

Two things can happen: Either the planet gets very, very close to the binary, suffering tidal disruption or being engulfed by one of the stars, or its orbit gets significantly perturbed by the binary to be eventually ejected from the system. In both cases, you get rid of the planet.

Co-author Jihad Touma, a physics professor at the American University of Beirut, added:

A planet caught in resonance finds its orbit deformed to higher and higher eccentricities, precessing faster and faster while staying in tune with the orbit of the binary, which is shrinking. And on the route, it encounters that instability zone around binaries, where three-body effects kick into place and gravitationally clear out the zone.

2 bright suns setting amid yellow and orange sunset clouds. — View larger. | Artist’s concept of an alien sunset from a planet with 2 suns. Image via NASA/ JPL-Caltech/ University of Arizona.

Opposite effects of general relativity

Curiously, general relativity could stabilize some planetary systems, like Mercury, yet destabilize others, as Touma noted:

Interestingly enough, nearly a century following Einstein’s calculations, computer simulations showed how relativistic effects may have saved Mercury from chaotic diffusion out of the solar system. Here we see related effects at work disrupting planetary systems. General relativity is stabilizing systems in some ways and disturbing them in other ways.

Bottom line: Tatooine exoplanets – planets orbiting two stars – are less common than scientists first thought. A new study says Einstein’s general theory of relativity is to blame for their rarity.

Source: Capture into Apsidal Resonance and the Decimation of Planets around Inspiraling Binaries

Via University of California, Berkeley

The post Tatooine exoplanets are oddly rare, and we finally know why first appeared on EarthSky.

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Tatooine planets are exoplanets that orbit two stars instead of just one. The name comes from the fictional arid desert world in “Star Wars.”
These planets seem to be rarer than first thought, although they do exist.
Einstein’s general theory of relativity – specifically the gravitational effects of the two stars – is to blame for their rarity, according to a new study.

EarthSky’s 2026 lunar calendar shows every day’s moon phase. Get yours today!

Tatooine exoplanets are rare

University of California, Berkeley: Why Are Tatooine Planets Rare? Blame General Relativity. news.berkeley.edu/2026/01/30/w…

— AAS Press Office (@press.aas.org) 2026-02-02T16:14:05.036Z

A dearth of binary star exoplanets

You have a scarcity of circumbinary planets in general and you have an absolute desert around binaries with orbital periods of seven days or less. The overwhelming majority of eclipsing binaries are tight binaries and are precisely the systems around which we most expect to find transiting circumbinary planets.

The instability zone

Planets form from the bottom up, by sticking small-scale planetesimals together. But forming a planet at the edge of the instability zone would be like trying to stick snowflakes together in a hurricane.

General theory of relativity is to blame

2 possible fates of Tatooine exoplanets

Two things can happen: Either the planet gets very, very close to the binary, suffering tidal disruption or being engulfed by one of the stars, or its orbit gets significantly perturbed by the binary to be eventually ejected from the system. In both cases, you get rid of the planet.

Co-author Jihad Touma, a physics professor at the American University of Beirut, added:

A planet caught in resonance finds its orbit deformed to higher and higher eccentricities, precessing faster and faster while staying in tune with the orbit of the binary, which is shrinking. And on the route, it encounters that instability zone around binaries, where three-body effects kick into place and gravitationally clear out the zone.

Opposite effects of general relativity

Curiously, general relativity could stabilize some planetary systems, like Mercury, yet destabilize others, as Touma noted:

Interestingly enough, nearly a century following Einstein’s calculations, computer simulations showed how relativistic effects may have saved Mercury from chaotic diffusion out of the solar system. Here we see related effects at work disrupting planetary systems. General relativity is stabilizing systems in some ways and disturbing them in other ways.

Source: Capture into Apsidal Resonance and the Decimation of Planets around Inspiraling Binaries

Via University of California, Berkeley

The post Tatooine exoplanets are oddly rare, and we finally know why first appeared on EarthSky.

from EarthSky https://ift.tt/HSJ0RzY

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Mercury is farthest from the sunset February 19

Mercury after sunset in February 2026

For precise sun and Mercury rising times at your location:

Mercury events in 2026

Heliocentric view of Mercury February 2026

A comparison of elongations

More Mercury evening elongation comparisons for 2026

Mercury after sunset in February 2026

For precise sun and Mercury rising times at your location:

Mercury events in 2026

Heliocentric view of Mercury February 2026

A comparison of elongations

More Mercury evening elongation comparisons for 2026

Pale Blue Dot 36 years later: Earth in a sunbeam

February 14, 1990: the Pale Blue Dot

An updated look at the Pale Blue Dot

Carl Sagan named the image

Our family portrait

February 14, 1990: the Pale Blue Dot

An updated look at the Pale Blue Dot

Carl Sagan named the image

Our family portrait

Star dims for 9 months, likely due to giant ringed object

Star dims for 9 months, likely due to giant ringed planet

Brown dwarf or super-Jupiter

Large ring system

Star dims for 9 months, likely due to giant ringed planet

Brown dwarf or super-Jupiter

Large ring system

New clues to how giant galaxies formed in the early universe

New clues to how giant galaxies formed in the early universe

Spotlighting a distant protocluster

A cascading merger

Case closed on giant galaxies in the early universe?

New clues to how giant galaxies formed in the early universe

Spotlighting a distant protocluster

A cascading merger

Case closed on giant galaxies in the early universe?

Great Backyard Bird Count begins February 13

Great Backyard Bird Count

About the Great Backyard Bird Count

How to participate

There’s a photo contest too

2025 bird count

Great Backyard Bird Count

About the Great Backyard Bird Count

How to participate

There’s a photo contest too

2025 bird count

2026 has 3 Friday the 13ths. What are the odds?

Scary coincidence or super unlucky?

In 2026, blame Thursday

The February-March-November Friday the 13th trilogy repeats …

The rhyme and reason of the Friday the 13th cycle

Friday-the-13th-year repetitions within 28-year cycle

Can three Friday the 13ths occur in a leap year?

Scary coincidence or super unlucky?

In 2026, blame Thursday

The February-March-November Friday the 13th trilogy repeats …

The rhyme and reason of the Friday the 13th cycle

Friday-the-13th-year repetitions within 28-year cycle

Can three Friday the 13ths occur in a leap year?

Tatooine exoplanets are oddly rare, and we finally know why

Tatooine exoplanets are rare

A dearth of binary star exoplanets

The instability zone

General theory of relativity is to blame

2 possible fates of Tatooine exoplanets

Opposite effects of general relativity

Tatooine exoplanets are rare

A dearth of binary star exoplanets

The instability zone

General theory of relativity is to blame

2 possible fates of Tatooine exoplanets

Opposite effects of general relativity

adds 2