Our current cosmology says cold dark matter helped small galaxies form in the early universe. But recent data from the James Webb Space Telescope is challenging that idea. Astronomers, like Stacy McGaugh of Case Western Reserve University, think since our theories don’t match the observations, it might be time to rethink our story of how the universe formed in its extreme youth. According to the scientists, new research supports the MOND theory. We’ll sit down with McGaugh to talk about what his team discovered, what it means for cosmology and where we go from here at 12:15 p.m. CST (18:15 UTC) on Monday, November 18. Join us!
The standard model for how galaxies formed in the early universe predicted that the James Webb Space Telescope would see dim signals from small, primitive galaxies. But data are not confirming the popular hypothesis that invisible dark matter helped the earliest stars and galaxies clump together.
Instead, the oldest galaxies are large and bright, in agreement with an alternate theory of gravity – called MOND – according to new research from Case Western Reserve University published November 12, 2024, in The Astrophysical Journal. The results challenge astronomers’ understanding of the early universe. Case Western Reserve astrophysicist Stacy McGaugh, whose paper describes structure formation in the early universe, said:
What the theory of dark matter predicted is not what we see.
McGaugh, professor and director of astronomy at Case Western Reserve, said instead of dark matter, modified gravity might have played a role. He says a theory known as MOND, for Modified Newtonian Dynamics, predicted in 1998 that structure formation in the early universe would have happened very quickly, much faster than the theory of Cold Dark Matter, known as lambda-CDM, predicted.
The new Webb space telescope was designed to answer some of the biggest questions in the universe. For example, how and when did stars and galaxies form? Until it was launched in 2021, no telescope was able to see that deeply into the universe and that far back in time.
Lambda-CDM predicts that galaxies were formed by gradual accretion of matter from small to larger structures, due to the extra gravity provided by the mass of dark matter. McGaugh said:
Astronomers invented dark matter to explain how you get from a very smooth early universe to big galaxies with lots of empty space between them that we see today.
The small pieces assembled in larger and larger structures until galaxies formed. Webb should be able to see these small galaxy precursors as dim light. McGaugh said:
The expectation was that every big galaxy we see in the nearby universe would have started from these itty-bitty pieces.
Webb isn’t giving the expected answers
But even at higher and higher redshift – looking earlier and earlier into the evolution of the universe – the signals are larger and brighter than expected.
MOND predicted that the mass that becomes a galaxy assembled rapidly, and initially expands outward with the rest of the universe. The stronger force of gravity slows, then reverses, the expansion, and the material collapses on itself to form a galaxy. In this theory, there is no dark matter at all.
The large and bright structures seen by Webb very early in the universe were predicted by MOND over a quarter century ago, McGaugh said. He co-authored the paper with former Case Western Reserve postdoctoral researcher Federico Lelli, now at Arcetri Astrophysical Observatory in Italy (INAF), and former graduate student Jay Franck. The fourth co-author is James Schombert from the University of Oregon. McGaugh was moved to comment:
The bottom line is, ‘I told you so.’ I was raised to think that saying that was rude, but that’s the whole point of the scientific method: Make predictions and then check which come true.
He added that finding a theory compatible with both MOND and general relativity is still a great challenge.
Bottom line: There’s increasing evidence that astronomical theories don’t match the observations. Is it time to rethink our story of how our universe came to be?
Our current cosmology says cold dark matter helped small galaxies form in the early universe. But recent data from the James Webb Space Telescope is challenging that idea. Astronomers, like Stacy McGaugh of Case Western Reserve University, think since our theories don’t match the observations, it might be time to rethink our story of how the universe formed in its extreme youth. According to the scientists, new research supports the MOND theory. We’ll sit down with McGaugh to talk about what his team discovered, what it means for cosmology and where we go from here at 12:15 p.m. CST (18:15 UTC) on Monday, November 18. Join us!
The standard model for how galaxies formed in the early universe predicted that the James Webb Space Telescope would see dim signals from small, primitive galaxies. But data are not confirming the popular hypothesis that invisible dark matter helped the earliest stars and galaxies clump together.
Instead, the oldest galaxies are large and bright, in agreement with an alternate theory of gravity – called MOND – according to new research from Case Western Reserve University published November 12, 2024, in The Astrophysical Journal. The results challenge astronomers’ understanding of the early universe. Case Western Reserve astrophysicist Stacy McGaugh, whose paper describes structure formation in the early universe, said:
What the theory of dark matter predicted is not what we see.
McGaugh, professor and director of astronomy at Case Western Reserve, said instead of dark matter, modified gravity might have played a role. He says a theory known as MOND, for Modified Newtonian Dynamics, predicted in 1998 that structure formation in the early universe would have happened very quickly, much faster than the theory of Cold Dark Matter, known as lambda-CDM, predicted.
The new Webb space telescope was designed to answer some of the biggest questions in the universe. For example, how and when did stars and galaxies form? Until it was launched in 2021, no telescope was able to see that deeply into the universe and that far back in time.
Lambda-CDM predicts that galaxies were formed by gradual accretion of matter from small to larger structures, due to the extra gravity provided by the mass of dark matter. McGaugh said:
Astronomers invented dark matter to explain how you get from a very smooth early universe to big galaxies with lots of empty space between them that we see today.
The small pieces assembled in larger and larger structures until galaxies formed. Webb should be able to see these small galaxy precursors as dim light. McGaugh said:
The expectation was that every big galaxy we see in the nearby universe would have started from these itty-bitty pieces.
Webb isn’t giving the expected answers
But even at higher and higher redshift – looking earlier and earlier into the evolution of the universe – the signals are larger and brighter than expected.
MOND predicted that the mass that becomes a galaxy assembled rapidly, and initially expands outward with the rest of the universe. The stronger force of gravity slows, then reverses, the expansion, and the material collapses on itself to form a galaxy. In this theory, there is no dark matter at all.
The large and bright structures seen by Webb very early in the universe were predicted by MOND over a quarter century ago, McGaugh said. He co-authored the paper with former Case Western Reserve postdoctoral researcher Federico Lelli, now at Arcetri Astrophysical Observatory in Italy (INAF), and former graduate student Jay Franck. The fourth co-author is James Schombert from the University of Oregon. McGaugh was moved to comment:
The bottom line is, ‘I told you so.’ I was raised to think that saying that was rude, but that’s the whole point of the scientific method: Make predictions and then check which come true.
He added that finding a theory compatible with both MOND and general relativity is still a great challenge.
Bottom line: There’s increasing evidence that astronomical theories don’t match the observations. Is it time to rethink our story of how our universe came to be?
A view of Pikes Peak. Rocks here that are hundreds of millions of years old hold clues to Earth’s history and the missing link in the Snowball Earth theory. Image via Christine S. Siddoway/ The Conversation.
Snowball Earth is a theory that some 700 million years ago, all of Earth was covered in ice.
Most of the evidence for this comes from former coastlines, where sedimentary rocks show structures that could have been created only by glacial activity.
But new evidence in rocks on Pikes Peak that would have formed close to the equator within the heart of an ancient continent provides a missing link for the theory.
Around 700 million years ago, the Earth cooled so much that scientists believe massive ice sheets encased the entire planet like a giant snowball. This global deep freeze, known as Snowball Earth, endured for tens of millions of years.
Yet, miraculously, early life not only held on, but thrived. When the ice melted and the ground thawed, complex multicellular life emerged, eventually leading to lifeforms we recognize today.
The Snowball Earth hypothesis is largely based on evidence from sedimentary rocks exposed in areas that once were along coastlines and shallow seas, as well as climate modeling. Physical evidence that ice sheets covered the interior of continents in warm equatorial regions had eluded scientists … until now.
In new research published in the Proceedings of the National Academy of Sciences, our team of geologists describes the missing link. We found it in an unusual pebbly sandstone encapsulated within the granite that forms Colorado’s Pikes Peak.
Artist’s concept of Snowball Earth. Earth iced over during the Cryogenian Period, but life on the planet survived. Image via NASA.
Solving a Snowball Earth mystery on a mountain
Pikes Peak, originally named Tavá Kaa-vi by the Ute people, lends its ancestral name, Tava, to these notable rocks. They are composed of solidified sand injectites, which formed in a similar manner to a medical injection when sand-rich fluid was forced into underlying rock.
A possible explanation for what created these enigmatic sandstones is the immense pressure of an overlying Snowball Earth ice sheet forcing sediment mixed with meltwater into weakened rock below.
Dark red to purple bands of Tava sandstone cross through pink and white granite. The Tava is also cross-cut by silvery-gray veins of iron oxide. Image via Liam Courtney-Davies/ The Conversation.
An obstacle for testing this idea, however, has been the lack of an age for the rocks to reveal when the right geological circumstances existed for sand injection.
We found a way to solve that mystery, using veins of iron found alongside the Tava injectites, near Pikes Peak and elsewhere in Colorado.
Advancements in dating rocks
Iron minerals contain very low amounts of naturally occurring radioactive elements, including uranium, which slowly decays to the element lead at a known rate. Recent advancements in laser-based radiometric dating allowed us to measure the ratio of uranium to lead isotopes in the iron oxide mineral hematite. And this revealed how long ago the individual crystals formed.
The iron veins appear to have formed both before and after the sand was injected into the Colorado bedrock. We found veins of hematite and quartz that both cut through Tava dikes and were crosscut by Tava dikes. That allowed us to figure out an age bracket for the sand injectites, which must have formed between 690 million and 660 million years ago.
Here you can see a 5-meter-tall, almost vertical Tava dike in this section of Pikes Peak granite. Image via Liam Courtney-Davies/ The Conversation.
Linking Tava rocks to the Snowball Earth period
The time frame means these sandstones formed during the Cryogenian Period, from 720 million to 635 million years ago. The name is derived from “cold birth” in ancient Greek and is synonymous with climate upheaval and disruption of life on our planet … including Snowball Earth.
While the triggers for the extreme cold at that time are debated, prevailing theories involve changes in tectonic plate activity, including the release of particles into the atmosphere that reflected sunlight away from Earth. Eventually, a buildup of carbon dioxide from volcanic outgassing may have warmed the planet again.
University of Exeter professor Timothy Lenton explains why the Earth was able to freeze over.
The Tava found on Pikes Peak would have formed close to the equator within the heart of an ancient continent named Laurentia, which gradually over time and long tectonic cycles moved into its current northerly position in North America today.
Scientists have debated the origin of Tava rocks for more than 125 years. But the new technology allowed us to conclusively link them to the Cryogenian Snowball Earth period for the first time.
Here’s how it happened
Thus, the scenario we envision for how the sand injection happened looks something like this:
A giant ice sheet with areas of geothermal heating at its base produced meltwater, which mixed with quartz-rich sediment below. The weight of the ice sheet created immense pressures that forced this sandy fluid into bedrock that had already been weakened over millions of years. Similar to fracking for natural gas or oil today, the pressure cracked the rocks and pushed the sandy meltwater in, eventually creating the injectites we see today.
Clues to another geologic puzzle
Not only do the new findings further cement the global Snowball Earth hypothesis, but the presence of Tava injectites within weak, fractured rocks once overridden by ice sheets provides clues about other geologic phenomena.
Across the U.S. today we can see time gaps in the rock record created through erosion that are referred to as unconformities. Most famously, we can see these unconformities at the Grand Canyon, where in places over a billion years of time is missing. Unconformities occur when a sustained period of erosion removes and prevents newer layers of rock from forming, leaving an unconformable contact.
Unconformity in the Grand Canyon is evident here where horizontal layers of 500-million-year-old rock sit on top of a mass of 1.8-billion-year-old rocks. The unconformity, or ‘time gap,’ demonstrates that years of history are missing. Image via Mike Norton/ Wikipedia (CC BY-SA 4.0).
The results
Our results support that a Great Unconformity near Pikes Peak must have been formed prior to Cryogenian Snowball Earth. That’s at odds with hypotheses that attribute the formation of the Great Unconformity to large-scale erosion by Snowball Earth ice sheets themselves.
We hope the secrets of these elusive Cryogenian rocks in Colorado will lead to the discovery of further terrestrial records of Snowball Earth. Such findings can help develop a clearer picture of our planet during climate extremes and the processes that led to the habitable planet we live on today.
Bottom line: Rocks atop Pikes Peak in Colorado provide evidence for the Snowball Earth theory, which says the entire globe was once covered in a sheet of ice.
A view of Pikes Peak. Rocks here that are hundreds of millions of years old hold clues to Earth’s history and the missing link in the Snowball Earth theory. Image via Christine S. Siddoway/ The Conversation.
Snowball Earth is a theory that some 700 million years ago, all of Earth was covered in ice.
Most of the evidence for this comes from former coastlines, where sedimentary rocks show structures that could have been created only by glacial activity.
But new evidence in rocks on Pikes Peak that would have formed close to the equator within the heart of an ancient continent provides a missing link for the theory.
Around 700 million years ago, the Earth cooled so much that scientists believe massive ice sheets encased the entire planet like a giant snowball. This global deep freeze, known as Snowball Earth, endured for tens of millions of years.
Yet, miraculously, early life not only held on, but thrived. When the ice melted and the ground thawed, complex multicellular life emerged, eventually leading to lifeforms we recognize today.
The Snowball Earth hypothesis is largely based on evidence from sedimentary rocks exposed in areas that once were along coastlines and shallow seas, as well as climate modeling. Physical evidence that ice sheets covered the interior of continents in warm equatorial regions had eluded scientists … until now.
In new research published in the Proceedings of the National Academy of Sciences, our team of geologists describes the missing link. We found it in an unusual pebbly sandstone encapsulated within the granite that forms Colorado’s Pikes Peak.
Artist’s concept of Snowball Earth. Earth iced over during the Cryogenian Period, but life on the planet survived. Image via NASA.
Solving a Snowball Earth mystery on a mountain
Pikes Peak, originally named Tavá Kaa-vi by the Ute people, lends its ancestral name, Tava, to these notable rocks. They are composed of solidified sand injectites, which formed in a similar manner to a medical injection when sand-rich fluid was forced into underlying rock.
A possible explanation for what created these enigmatic sandstones is the immense pressure of an overlying Snowball Earth ice sheet forcing sediment mixed with meltwater into weakened rock below.
Dark red to purple bands of Tava sandstone cross through pink and white granite. The Tava is also cross-cut by silvery-gray veins of iron oxide. Image via Liam Courtney-Davies/ The Conversation.
An obstacle for testing this idea, however, has been the lack of an age for the rocks to reveal when the right geological circumstances existed for sand injection.
We found a way to solve that mystery, using veins of iron found alongside the Tava injectites, near Pikes Peak and elsewhere in Colorado.
Advancements in dating rocks
Iron minerals contain very low amounts of naturally occurring radioactive elements, including uranium, which slowly decays to the element lead at a known rate. Recent advancements in laser-based radiometric dating allowed us to measure the ratio of uranium to lead isotopes in the iron oxide mineral hematite. And this revealed how long ago the individual crystals formed.
The iron veins appear to have formed both before and after the sand was injected into the Colorado bedrock. We found veins of hematite and quartz that both cut through Tava dikes and were crosscut by Tava dikes. That allowed us to figure out an age bracket for the sand injectites, which must have formed between 690 million and 660 million years ago.
Here you can see a 5-meter-tall, almost vertical Tava dike in this section of Pikes Peak granite. Image via Liam Courtney-Davies/ The Conversation.
Linking Tava rocks to the Snowball Earth period
The time frame means these sandstones formed during the Cryogenian Period, from 720 million to 635 million years ago. The name is derived from “cold birth” in ancient Greek and is synonymous with climate upheaval and disruption of life on our planet … including Snowball Earth.
While the triggers for the extreme cold at that time are debated, prevailing theories involve changes in tectonic plate activity, including the release of particles into the atmosphere that reflected sunlight away from Earth. Eventually, a buildup of carbon dioxide from volcanic outgassing may have warmed the planet again.
University of Exeter professor Timothy Lenton explains why the Earth was able to freeze over.
The Tava found on Pikes Peak would have formed close to the equator within the heart of an ancient continent named Laurentia, which gradually over time and long tectonic cycles moved into its current northerly position in North America today.
Scientists have debated the origin of Tava rocks for more than 125 years. But the new technology allowed us to conclusively link them to the Cryogenian Snowball Earth period for the first time.
Here’s how it happened
Thus, the scenario we envision for how the sand injection happened looks something like this:
A giant ice sheet with areas of geothermal heating at its base produced meltwater, which mixed with quartz-rich sediment below. The weight of the ice sheet created immense pressures that forced this sandy fluid into bedrock that had already been weakened over millions of years. Similar to fracking for natural gas or oil today, the pressure cracked the rocks and pushed the sandy meltwater in, eventually creating the injectites we see today.
Clues to another geologic puzzle
Not only do the new findings further cement the global Snowball Earth hypothesis, but the presence of Tava injectites within weak, fractured rocks once overridden by ice sheets provides clues about other geologic phenomena.
Across the U.S. today we can see time gaps in the rock record created through erosion that are referred to as unconformities. Most famously, we can see these unconformities at the Grand Canyon, where in places over a billion years of time is missing. Unconformities occur when a sustained period of erosion removes and prevents newer layers of rock from forming, leaving an unconformable contact.
Unconformity in the Grand Canyon is evident here where horizontal layers of 500-million-year-old rock sit on top of a mass of 1.8-billion-year-old rocks. The unconformity, or ‘time gap,’ demonstrates that years of history are missing. Image via Mike Norton/ Wikipedia (CC BY-SA 4.0).
The results
Our results support that a Great Unconformity near Pikes Peak must have been formed prior to Cryogenian Snowball Earth. That’s at odds with hypotheses that attribute the formation of the Great Unconformity to large-scale erosion by Snowball Earth ice sheets themselves.
We hope the secrets of these elusive Cryogenian rocks in Colorado will lead to the discovery of further terrestrial records of Snowball Earth. Such findings can help develop a clearer picture of our planet during climate extremes and the processes that led to the habitable planet we live on today.
Bottom line: Rocks atop Pikes Peak in Colorado provide evidence for the Snowball Earth theory, which says the entire globe was once covered in a sheet of ice.
We sometimes get this question. The North Star for Earth is Polaris. Does our next-door neighbor planet, Mars, have the same North Star as Earth? If not, does Mars have a star located more or less above its north pole?
Let’s talk about what we mean by North Star. Every planet in our solar system spins on its axis. Earth’s spin is what defines the length of our day of approximately 24 hours. If you continue the imaginary line of a planet’s axis out into space – in a northern direction as measured from earthly north – it might point to a star that’s visible to the eye. Or it might not. We call such stars pole stars, or North Stars. On Earth, that northern pole star – less than a degree from the north celestial pole – is the beloved star Polaris. Scouts and hikers know you can use Polaris to find the direction north when compasses fail.
Meanwhile, Earth’s Southern Hemisphere doesn’t have a comparable South Star. The nearest visible star to the south celestial pole of Earth is about 9 degrees away.
Artist’s illustration of the relative tilts of the orbits of Earth and Mars, Earth doesn’t orbit exactly upright with respect to our orbit around the sun. Instead, Earth’s tilt is about 23 1/2 degrees. Meanwhile, Mars’ tilt is about 25 degrees. What’s more, the rotational axes of the Earth and Mars don’t tilt in the same direction, as in this illustration. For both reasons – different amount of tilt, and different direction of tilt – Mars doesn’t have the same North Star as Earth. Image via NASA.
A North Star for Mars?
So, does Mars have a North or South Star? The answer is … not in any satisfying way. There’s no bright North Star, and only a modestly-bright South Star, for Mars.
In the northern sky as seen from Mars, the best candidate for a North Star is located on Mars’ sky dome about 1/2 degree from Mars’ north celestial pole. That’s closer than Polaris is to Earth’s north celestial pole, but, while Polaris is relatively bright (50th brightest of all stars in the night sky), the star near Mars’ north celestial pole is faint.
In fact, this star is barely within the limit of visibility to the eye alone.
Mars’ north pole points to a spot in the sky that’s about midway between Deneb, the brightest star in the constellation Cygnus the Swan, and Alderamin, the brightest star in the constellation Cepheus the King. See a chart of the position of Mars’ north celestial pole between the constellations Cygnus and Cepheus.
The southern sky view from Mars
Meanwhile, in the southern sky as seen from Mars, Kappa Velorum is only about 3 degrees from the Martian south celestial pole. That’s not as close as Polaris is to Earth’s north celestial pole, plus this star is only modestly bright, not nearly as bright as Polaris.
Future Mars colonists aren’t going to have a bright North Star – like our Polaris – to guide them.
On the other hand, if you were standing outside at night on the surface of Mars, you’d see some other cool stuff!
Earth and moon, as seen from Mars by the Curiosity rover in 2014. From Mars, you’d see both the Earth and moon with the eye alone. Image via NASA/ Wikimedia Commons (public domain). Read more about this image.
Can you see the moon orbiting the Earth from Mars?
As seen from Mars, you could see Earth’s moon orbiting around Earth once each month. From Earth, we can’t see any other planets’ satellites with the unaided eye, but this amazing sight on Mars would be visible to the eye alone. Both the Earth and the moon would appear starlike.
In general, the Earth as seen from Mars would somewhat mimic our view of Venus as seen from Earth. By that we mean that – like Venus in relationship to Earth – Earth in relationship to Mars is an inner planet. It orbits closer to the sun than Mars. Thus Earth as seen from Mars would be a morning or evening “star” – just as Venus is as seen from our world.
And although both the Earth and moon would appear as stars to the unaided eye, observers on Mars with telescopes would sometimes see them as crescent worlds, just as we see Venus.
So … no North Star for Mars. But Martian stargazers wouldn’t lack for things to see!
This series of images shows the Martian moon Phobos as it crossed in front of the sun, as seen by NASA’s Curiosity Mars rover on Tuesday, March 26, 2019 (Sol 2359). Image via NASA/JPL-Caltech.
Bottom line: Does planet Mars have a North Star akin to Earth’s North Star Polaris? No, there is not a Mars North Star. But Martian stargazers wouldn’t lack for things to see!
We sometimes get this question. The North Star for Earth is Polaris. Does our next-door neighbor planet, Mars, have the same North Star as Earth? If not, does Mars have a star located more or less above its north pole?
Let’s talk about what we mean by North Star. Every planet in our solar system spins on its axis. Earth’s spin is what defines the length of our day of approximately 24 hours. If you continue the imaginary line of a planet’s axis out into space – in a northern direction as measured from earthly north – it might point to a star that’s visible to the eye. Or it might not. We call such stars pole stars, or North Stars. On Earth, that northern pole star – less than a degree from the north celestial pole – is the beloved star Polaris. Scouts and hikers know you can use Polaris to find the direction north when compasses fail.
Meanwhile, Earth’s Southern Hemisphere doesn’t have a comparable South Star. The nearest visible star to the south celestial pole of Earth is about 9 degrees away.
Artist’s illustration of the relative tilts of the orbits of Earth and Mars, Earth doesn’t orbit exactly upright with respect to our orbit around the sun. Instead, Earth’s tilt is about 23 1/2 degrees. Meanwhile, Mars’ tilt is about 25 degrees. What’s more, the rotational axes of the Earth and Mars don’t tilt in the same direction, as in this illustration. For both reasons – different amount of tilt, and different direction of tilt – Mars doesn’t have the same North Star as Earth. Image via NASA.
A North Star for Mars?
So, does Mars have a North or South Star? The answer is … not in any satisfying way. There’s no bright North Star, and only a modestly-bright South Star, for Mars.
In the northern sky as seen from Mars, the best candidate for a North Star is located on Mars’ sky dome about 1/2 degree from Mars’ north celestial pole. That’s closer than Polaris is to Earth’s north celestial pole, but, while Polaris is relatively bright (50th brightest of all stars in the night sky), the star near Mars’ north celestial pole is faint.
In fact, this star is barely within the limit of visibility to the eye alone.
Mars’ north pole points to a spot in the sky that’s about midway between Deneb, the brightest star in the constellation Cygnus the Swan, and Alderamin, the brightest star in the constellation Cepheus the King. See a chart of the position of Mars’ north celestial pole between the constellations Cygnus and Cepheus.
The southern sky view from Mars
Meanwhile, in the southern sky as seen from Mars, Kappa Velorum is only about 3 degrees from the Martian south celestial pole. That’s not as close as Polaris is to Earth’s north celestial pole, plus this star is only modestly bright, not nearly as bright as Polaris.
Future Mars colonists aren’t going to have a bright North Star – like our Polaris – to guide them.
On the other hand, if you were standing outside at night on the surface of Mars, you’d see some other cool stuff!
Earth and moon, as seen from Mars by the Curiosity rover in 2014. From Mars, you’d see both the Earth and moon with the eye alone. Image via NASA/ Wikimedia Commons (public domain). Read more about this image.
Can you see the moon orbiting the Earth from Mars?
As seen from Mars, you could see Earth’s moon orbiting around Earth once each month. From Earth, we can’t see any other planets’ satellites with the unaided eye, but this amazing sight on Mars would be visible to the eye alone. Both the Earth and the moon would appear starlike.
In general, the Earth as seen from Mars would somewhat mimic our view of Venus as seen from Earth. By that we mean that – like Venus in relationship to Earth – Earth in relationship to Mars is an inner planet. It orbits closer to the sun than Mars. Thus Earth as seen from Mars would be a morning or evening “star” – just as Venus is as seen from our world.
And although both the Earth and moon would appear as stars to the unaided eye, observers on Mars with telescopes would sometimes see them as crescent worlds, just as we see Venus.
So … no North Star for Mars. But Martian stargazers wouldn’t lack for things to see!
This series of images shows the Martian moon Phobos as it crossed in front of the sun, as seen by NASA’s Curiosity Mars rover on Tuesday, March 26, 2019 (Sol 2359). Image via NASA/JPL-Caltech.
Bottom line: Does planet Mars have a North Star akin to Earth’s North Star Polaris? No, there is not a Mars North Star. But Martian stargazers wouldn’t lack for things to see!
The 2024 Leonid meteor shower, seen in earth mode (above the earth’s surface, looking down). Chart via Guy Ottewell’s 2024 Astronomical Calendar. Used with permission.
In 2024, the famous Leonid meteor shower will compete with moonlight from a waning gibbous moon on the shower’s peak morning, November 18. You might also try watching on the morning of November 17.
Mid-November meteors … the Leonids
Predicted peak: The peak is predicted** for 5 UTC on November 18, 2024. When to watch: Watch late on the night of November 17 until dawn on November 18. The morning of November 17 might be worthwhile, too. Duration of shower: November 3 through December 2. Radiant: Rises around midnight, highest in the sky at dawn. Nearest moon phase: In 2024, the full moon falls at 21:29 UTC on November 15. So the bright waning gibbous moon will wash out some meteors in 2024. Here are some tips for watching the Leonids in moonlight. Expected meteors at peak, under ideal conditions: Under a dark sky with no moon, you might see 10 to 15 Leonid meteors per hour. Note: The famous Leonid meteor shower produced one of the greatest meteor storms in living memory. Rates were as high as thousands of meteors per minute during a 15-minute span on the morning of November 17, 1966. That night, Leonid meteors did, briefly, fall like rain. Some who witnessed it had a strong impression of Earth moving through space, fording the meteor stream. Leonid meteor storms sometimes recur in cycles of 33 to 34 years. But the Leonids around the turn of the century – while wonderful for many observers – did not match the shower of 1966. And, in most years, the Lion whimpers rather than roars.
From the late, great Don Machholz (1952-2022), who discovered 12 comets …
Periodic Comet Tempel-Tuttle, officially known as 55P/Temple-Tuttle, is responsible for the Leonid meteor shower. William Tempel of Marseille Observatory in France discovered this comet on the evening of December 19, 1865. He found the comet in the northern sky, located in a part of the sky under the North Star, near the star Beta Ursae Minoris.
Word of the comet discovery became known throughout Europe, but the news had not yet spread to the United States. Horace Tuttle of Harvard College Observatory picked up the comet 17 days later, on the evening of January 5, 1866. Because this was an independent discovery, Tuttle’s name was added to the comet. Based upon the measurements during this visit of the comet, scientists calculated an orbit of 33.17 years. Astronomers quickly realized that the meteor storms and showers which occurred in mid-November of each year were the result of this comet.
One would think that there would be great interest in recovering this comet as it came back to the earth’s vicinity in 1899. But there wasn’t much interest in seeing the comet, everyone wanted to see a meteor storm. So, observers missed the comet in 1899. Also missing was a great meteor shower that year.
Scientists expected the next return in 1932. The observatories, using photographic plates with narrow field-of-view telescopes, missed it then too. And again, a major meteor shower did not materialize.
The comet was recovered in 1965
The comet was finally recovered in 1965. The brightest the comet got that year was 16th magnitude, visible only in very large telescopes. A spectacular meteor storm followed in 1966. On the next return, in early 1998, the comet was bright enough that you could see it in binoculars. This pass produced additional impressive meteor showers in 1999-2001. 55P/Temple-Tuttle is due back in early 2031.
With so much anticipation with the 1998 return and the expected meteor storms, several astronomers calculated the exact time and intensity of the storm. And they were accurate. This was the first instance of correct predictions. It is done by analyzing filaments of material expelled from each trip of the comet through the inner solar system. Quite often, a filament left behind by the comet hundreds of years ago will intersect the earth and produce a fabulous shower.
The Leonids: a meteor shower that revolutionized meteor science.
Note: This article, Leonids 1901-2100, gives specific meteor predictions for each year for this shower from the year 2001 to 2100.
The radiant of the Leonids
Leonids stream from a single point in the sky – their radiant point – in the constellation Leo the Lion. Leo rises just before midnight in mid-November. Regulus, the brightest star in Leo the, dots a backwards question mark of stars known as the Sickle.The 2024 Leonid meteor shower, seen in sky mode (from the the Earth’s surface, looking up). On the morning of November 17, 2024, the radiant appears to originate inside the Sickle of Leo the Lion. Chart via Guy Ottewell’s 2024 Astronomical Calendar. Used with permission.
Which direction should I look to see the Leonid meteor shower?
Meteors in annual showers get their names from the point in the starry sky from which they appear to radiate. This shower’s name comes from the constellation Leo the Lion, because these meteors radiate outward from the vicinity of stars representing the Lion’s Mane.
If you trace the paths of Leonid meteors backward on the sky’s dome, they do seem to stream from near the star Algieba in the constellation Leo. The point in the sky from which they appear to radiate is the radiant point. This radiant point is an optical illusion. It’s like standing on railroad tracks and peering off into the distance to see the tracks converge. The illusion of the radiant point comes from the fact that the meteors – much like the railroad tracks – are moving on parallel paths.
In recent years, people have gotten the mistaken idea that you must know the whereabouts of a meteor shower’s radiant point in order to watch the meteor shower. You don’t need to. The meteors often don’t become visible until they are 30 degrees or so from their radiant point. They are streaking out from the radiant in all directions.
Thus, the Leonid meteors – like meteors in all annual showers – will appear in all parts of the sky.
Old woodcuts depicting the 1833 Leonid meteor storm known as “the night the stars fell.” Image via Wikimedia (public domain).
A history of meteor storms
Scientists don’t expect a Leonid meteor storm this year. Most astronomers say you need more than 1,000 meteors an hour to consider a shower a storm. That’s far from the 10 to 15 meteors per hour the Leonids deliver in average years.
The Leonid shower is famous for producing meteor storms, though. The parent comet, Tempel-Tuttle, completes a single orbit around the sun about once every 33 years. It releases fresh material every time it approaches the sun. Since the 19th century, skywatchers have looked for Leonid meteor storms about every 33 years, beginning with the meteor storm of 1833, which witnesses said produced more than 100,000 meteors an hour.
The next great Leonid storms were about 33 years later, in 1866 and 1867. In 1899, a meteor storm did not materialize. In fact, the anticipation of a great meteor storm was so high, and the results so disappointing, that many astronomers felt it was the worst blow ever suffered by astronomy in the eyes of the public.
Leonid meteors viewed from space in 1997. Image via NASA.
Some Leonid meteor storms last century
Not until 1966 did the next spectacular Leonid storm occur, this time over the Americas. In 1966, observers in the southwest United States reported seeing 40 to 50 meteors per second (that’s 2,400 to 3,000 meteors per minute) during a span of 15 minutes on the morning of November 17, 1966.
In 2001, another great Leonid meteor storm occurred (though not as great as 1966). Spaceweather.com reported:
The display began on Sunday morning, November 18, when Earth glided into a dust cloud shed by Comet Tempel-Tuttle in 1766. Thousands of meteors per hour rained over North America and Hawaii. Then, on Monday morning November 19 (local time in Asia), it happened again: Earth entered a second cometary debris cloud from Tempel-Tuttle. Thousands more Leonids then fell over East Asian countries and Australia.
The night the stars fell. Engraving by Adolf Vollmy (1889). Image via Wikimedia Commons (public domain).
The Leonid meteor shower of 1833
Adolf Vollmy produced the famous engraving above of the 1833 Leonid meteor shower for the Adventist book “Bible Readings for the Home Circle.” It’s based on a painting by Swiss artist Karl Jauslin, which, in turn, was based on a first-person account of the 1833 storm by a minister, Joseph Harvey Waggoner, who saw the 1833 shower on his way from Florida to New Orleans.
In that famous shower, hundreds of thousands of meteors per hour fell. It was the first recorded meteor storm of modern times.
Leonid meteors from the EarthSky Community
View larger to see the colors better. | Eliot Herman in Tucson, Arizona, shared this double Leonid meteor photo, captured 2 days before the peak of the shower in 2018. Eliot commented, “The Leonids are the greenest meteors I see.” And he has seen a lot of meteors!
Bottom line: In 2024, watch for Leonids after midnight until dawn on November 18. The radiant point rises around midnight and is highest in the sky at dawn. A waning gibbous moon will interfere with Leonid meteors this year.
**Predicted peak times and dates for meteor showers are from the American Meteor Society. Note that meteor shower peak times can vary.
The 2024 Leonid meteor shower, seen in earth mode (above the earth’s surface, looking down). Chart via Guy Ottewell’s 2024 Astronomical Calendar. Used with permission.
In 2024, the famous Leonid meteor shower will compete with moonlight from a waning gibbous moon on the shower’s peak morning, November 18. You might also try watching on the morning of November 17.
Mid-November meteors … the Leonids
Predicted peak: The peak is predicted** for 5 UTC on November 18, 2024. When to watch: Watch late on the night of November 17 until dawn on November 18. The morning of November 17 might be worthwhile, too. Duration of shower: November 3 through December 2. Radiant: Rises around midnight, highest in the sky at dawn. Nearest moon phase: In 2024, the full moon falls at 21:29 UTC on November 15. So the bright waning gibbous moon will wash out some meteors in 2024. Here are some tips for watching the Leonids in moonlight. Expected meteors at peak, under ideal conditions: Under a dark sky with no moon, you might see 10 to 15 Leonid meteors per hour. Note: The famous Leonid meteor shower produced one of the greatest meteor storms in living memory. Rates were as high as thousands of meteors per minute during a 15-minute span on the morning of November 17, 1966. That night, Leonid meteors did, briefly, fall like rain. Some who witnessed it had a strong impression of Earth moving through space, fording the meteor stream. Leonid meteor storms sometimes recur in cycles of 33 to 34 years. But the Leonids around the turn of the century – while wonderful for many observers – did not match the shower of 1966. And, in most years, the Lion whimpers rather than roars.
From the late, great Don Machholz (1952-2022), who discovered 12 comets …
Periodic Comet Tempel-Tuttle, officially known as 55P/Temple-Tuttle, is responsible for the Leonid meteor shower. William Tempel of Marseille Observatory in France discovered this comet on the evening of December 19, 1865. He found the comet in the northern sky, located in a part of the sky under the North Star, near the star Beta Ursae Minoris.
Word of the comet discovery became known throughout Europe, but the news had not yet spread to the United States. Horace Tuttle of Harvard College Observatory picked up the comet 17 days later, on the evening of January 5, 1866. Because this was an independent discovery, Tuttle’s name was added to the comet. Based upon the measurements during this visit of the comet, scientists calculated an orbit of 33.17 years. Astronomers quickly realized that the meteor storms and showers which occurred in mid-November of each year were the result of this comet.
One would think that there would be great interest in recovering this comet as it came back to the earth’s vicinity in 1899. But there wasn’t much interest in seeing the comet, everyone wanted to see a meteor storm. So, observers missed the comet in 1899. Also missing was a great meteor shower that year.
Scientists expected the next return in 1932. The observatories, using photographic plates with narrow field-of-view telescopes, missed it then too. And again, a major meteor shower did not materialize.
The comet was recovered in 1965
The comet was finally recovered in 1965. The brightest the comet got that year was 16th magnitude, visible only in very large telescopes. A spectacular meteor storm followed in 1966. On the next return, in early 1998, the comet was bright enough that you could see it in binoculars. This pass produced additional impressive meteor showers in 1999-2001. 55P/Temple-Tuttle is due back in early 2031.
With so much anticipation with the 1998 return and the expected meteor storms, several astronomers calculated the exact time and intensity of the storm. And they were accurate. This was the first instance of correct predictions. It is done by analyzing filaments of material expelled from each trip of the comet through the inner solar system. Quite often, a filament left behind by the comet hundreds of years ago will intersect the earth and produce a fabulous shower.
The Leonids: a meteor shower that revolutionized meteor science.
Note: This article, Leonids 1901-2100, gives specific meteor predictions for each year for this shower from the year 2001 to 2100.
The radiant of the Leonids
Leonids stream from a single point in the sky – their radiant point – in the constellation Leo the Lion. Leo rises just before midnight in mid-November. Regulus, the brightest star in Leo the, dots a backwards question mark of stars known as the Sickle.The 2024 Leonid meteor shower, seen in sky mode (from the the Earth’s surface, looking up). On the morning of November 17, 2024, the radiant appears to originate inside the Sickle of Leo the Lion. Chart via Guy Ottewell’s 2024 Astronomical Calendar. Used with permission.
Which direction should I look to see the Leonid meteor shower?
Meteors in annual showers get their names from the point in the starry sky from which they appear to radiate. This shower’s name comes from the constellation Leo the Lion, because these meteors radiate outward from the vicinity of stars representing the Lion’s Mane.
If you trace the paths of Leonid meteors backward on the sky’s dome, they do seem to stream from near the star Algieba in the constellation Leo. The point in the sky from which they appear to radiate is the radiant point. This radiant point is an optical illusion. It’s like standing on railroad tracks and peering off into the distance to see the tracks converge. The illusion of the radiant point comes from the fact that the meteors – much like the railroad tracks – are moving on parallel paths.
In recent years, people have gotten the mistaken idea that you must know the whereabouts of a meteor shower’s radiant point in order to watch the meteor shower. You don’t need to. The meteors often don’t become visible until they are 30 degrees or so from their radiant point. They are streaking out from the radiant in all directions.
Thus, the Leonid meteors – like meteors in all annual showers – will appear in all parts of the sky.
Old woodcuts depicting the 1833 Leonid meteor storm known as “the night the stars fell.” Image via Wikimedia (public domain).
A history of meteor storms
Scientists don’t expect a Leonid meteor storm this year. Most astronomers say you need more than 1,000 meteors an hour to consider a shower a storm. That’s far from the 10 to 15 meteors per hour the Leonids deliver in average years.
The Leonid shower is famous for producing meteor storms, though. The parent comet, Tempel-Tuttle, completes a single orbit around the sun about once every 33 years. It releases fresh material every time it approaches the sun. Since the 19th century, skywatchers have looked for Leonid meteor storms about every 33 years, beginning with the meteor storm of 1833, which witnesses said produced more than 100,000 meteors an hour.
The next great Leonid storms were about 33 years later, in 1866 and 1867. In 1899, a meteor storm did not materialize. In fact, the anticipation of a great meteor storm was so high, and the results so disappointing, that many astronomers felt it was the worst blow ever suffered by astronomy in the eyes of the public.
Leonid meteors viewed from space in 1997. Image via NASA.
Some Leonid meteor storms last century
Not until 1966 did the next spectacular Leonid storm occur, this time over the Americas. In 1966, observers in the southwest United States reported seeing 40 to 50 meteors per second (that’s 2,400 to 3,000 meteors per minute) during a span of 15 minutes on the morning of November 17, 1966.
In 2001, another great Leonid meteor storm occurred (though not as great as 1966). Spaceweather.com reported:
The display began on Sunday morning, November 18, when Earth glided into a dust cloud shed by Comet Tempel-Tuttle in 1766. Thousands of meteors per hour rained over North America and Hawaii. Then, on Monday morning November 19 (local time in Asia), it happened again: Earth entered a second cometary debris cloud from Tempel-Tuttle. Thousands more Leonids then fell over East Asian countries and Australia.
The night the stars fell. Engraving by Adolf Vollmy (1889). Image via Wikimedia Commons (public domain).
The Leonid meteor shower of 1833
Adolf Vollmy produced the famous engraving above of the 1833 Leonid meteor shower for the Adventist book “Bible Readings for the Home Circle.” It’s based on a painting by Swiss artist Karl Jauslin, which, in turn, was based on a first-person account of the 1833 storm by a minister, Joseph Harvey Waggoner, who saw the 1833 shower on his way from Florida to New Orleans.
In that famous shower, hundreds of thousands of meteors per hour fell. It was the first recorded meteor storm of modern times.
Leonid meteors from the EarthSky Community
View larger to see the colors better. | Eliot Herman in Tucson, Arizona, shared this double Leonid meteor photo, captured 2 days before the peak of the shower in 2018. Eliot commented, “The Leonids are the greenest meteors I see.” And he has seen a lot of meteors!
Bottom line: In 2024, watch for Leonids after midnight until dawn on November 18. The radiant point rises around midnight and is highest in the sky at dawn. A waning gibbous moon will interfere with Leonid meteors this year.
**Predicted peak times and dates for meteor showers are from the American Meteor Society. Note that meteor shower peak times can vary.
On November 16, 1974, the Arecibo Observatory beamed the 1st intentional signal to space. Image via Wikimedia Commons. Click here for an explanation of each part of the message.
1st intentional signal to space in 1974
On November 16, 1974, astronomers used the Arecibo telescope in Puerto Rico to beam out the most powerful broadcast ever deliberately sent to space. They said the goal was to contact alien life. And some applauded it, but others didn’t. On the plus side, it reminded people that Earth likely isn’t the only planet in the Milky Way where intelligent life has evolved. But others felt – if alien civilizations do exist out there – we shouldn’t call attention to ourselves.
The message was designed by Cornell astronomy professor Frank Drake with input from other scientists including Carl Sagan. So, the final result was a simple and elegant broadcast. Basically, it consisted of a pattern of binary numbers. This message contained information about the basic chemicals of life and the structure of DNA. Plus, it included Earth’s place in our solar system and even a stick figure of a human.
The Arecibo radio telescope in Puerto Rico broadcast the 1st intentional radio signal into space in 1974. Image via Wikimedia Commons.
Sending the Arecibo message
It took three minutes to send 1,679 bits of information, a snail’s pace compared to modern computer modems. And according to the SETI Institute:
The broadcast was particularly powerful because it used Arecibo’s megawatt transmitter attached to its 1,000 feet (305 meter) antenna. The latter concentrates the transmitter energy by beaming it into a very small patch of sky. The emission was equivalent to a 20 trillion-watt omnidirectional broadcast, and would be detectable by a SETI experiment just about anywhere in the galaxy, assuming a receiving antenna similar in size to Arecibo’s.
In fact, the 1974 signal went out in the direction of M13, a globular star cluster orbiting the center of our Milky Way galaxy. Basically, it was chosen because it’s a large collection of stars and was available in the sky at the time and place of the ceremony.
Also, globular star clusters are very far away. For instance, M13 is about 25,000 light-years from Earth.
And now, the 1974 signal is 50 light-years away from us.
By the way, the Arecibo radio telescope collapsed in 2020 when its 900-ton receiver platform came loose from its cables and fell onto the reflector dish more than 400 feet (120 meters) below.
Bottom line: Iconic Arecibo telescope is no longer operational, but its legacy lives on. Fifty years ago, on November 16, 1974, Arecibo sent our first intentional signal to space. What do you think? Should we be advertising our presence in space?
On November 16, 1974, the Arecibo Observatory beamed the 1st intentional signal to space. Image via Wikimedia Commons. Click here for an explanation of each part of the message.
1st intentional signal to space in 1974
On November 16, 1974, astronomers used the Arecibo telescope in Puerto Rico to beam out the most powerful broadcast ever deliberately sent to space. They said the goal was to contact alien life. And some applauded it, but others didn’t. On the plus side, it reminded people that Earth likely isn’t the only planet in the Milky Way where intelligent life has evolved. But others felt – if alien civilizations do exist out there – we shouldn’t call attention to ourselves.
The message was designed by Cornell astronomy professor Frank Drake with input from other scientists including Carl Sagan. So, the final result was a simple and elegant broadcast. Basically, it consisted of a pattern of binary numbers. This message contained information about the basic chemicals of life and the structure of DNA. Plus, it included Earth’s place in our solar system and even a stick figure of a human.
The Arecibo radio telescope in Puerto Rico broadcast the 1st intentional radio signal into space in 1974. Image via Wikimedia Commons.
Sending the Arecibo message
It took three minutes to send 1,679 bits of information, a snail’s pace compared to modern computer modems. And according to the SETI Institute:
The broadcast was particularly powerful because it used Arecibo’s megawatt transmitter attached to its 1,000 feet (305 meter) antenna. The latter concentrates the transmitter energy by beaming it into a very small patch of sky. The emission was equivalent to a 20 trillion-watt omnidirectional broadcast, and would be detectable by a SETI experiment just about anywhere in the galaxy, assuming a receiving antenna similar in size to Arecibo’s.
In fact, the 1974 signal went out in the direction of M13, a globular star cluster orbiting the center of our Milky Way galaxy. Basically, it was chosen because it’s a large collection of stars and was available in the sky at the time and place of the ceremony.
Also, globular star clusters are very far away. For instance, M13 is about 25,000 light-years from Earth.
And now, the 1974 signal is 50 light-years away from us.
By the way, the Arecibo radio telescope collapsed in 2020 when its 900-ton receiver platform came loose from its cables and fell onto the reflector dish more than 400 feet (120 meters) below.
Bottom line: Iconic Arecibo telescope is no longer operational, but its legacy lives on. Fifty years ago, on November 16, 1974, Arecibo sent our first intentional signal to space. What do you think? Should we be advertising our presence in space?
View at EarthSky Community Photos. | Roosevelt Silva captured this setting full moon over a misty rainforest in Brazil on May 26, 2021. Thank you, Roosevelt! Scientists recently discovered that some tropical mammals, like those in Brazilian tropical forests, avoid the moonlight.
Many mammals in tropical forests adjust their behavior based on moon phases, with some species becoming less active during the full moon.
Using wildlife cameras, researchers observed that about 30% of mammals in these habitats are less active when the moon is full, while 20% are drawn to the moonlight.
The study highlights concerns about how increasing artificial light and forest canopy loss may disrupt animal behavior and interactions in tropical ecosystems.
On a night like tonight – when there’s a full moon in the sky – the landscape is lit by bright moonlight. And you might think mammals living on the floor of tropical forests would welcome the moonlight. After all, it helps them see better. But scientists at the Norwegian University of Life Sciences studied the behavior of animals in the tropics under varying conditions of moonlight. They said on October 15, 2024, that – while some tropical mammals do appear more active under bright moonlight – an even larger percentage is less active when the moon is full.
The researchers published their findings in the peer-reviewedProceedings of the Royal Society B on October 16, 2024.
Nighttime lighting affects tropical mammals
Scientists don’t know a lot about how tropical mammals behave under different levels of moonlight. Their habitat – the floors of tropical forests under a thick canopy of leaves – are some of the darkest places on the planet at night.
So scientists used automatic wildlife cameras to observe how mammals behaved during the night under different phases of the moon. They found at least half of the mammal species altered their activity around the full moon. Some became less active, in an effort to be inconspicuous and avoid predators.
Imagine playing hide-and-seek in a dark room, and then somebody lights a candle. The light, even if it is weak, may make it easier for you to find your way around the room. But if you are the one hiding, you suddenly become a lot easier to detect.
Some tropical mammals, such as this paca, avoid the full moon and are less active when there is more moonlight. This image is from a wildlife camera. Image via Tropical Ecology Assessment and Monitoring Network/ Norwegian University of Life Sciences.
Studying wild mammals in the dark
The researchers studied 2.1 million wildlife camera images collected by the Tropical Ecology Assessment and Monitoring Network. The data came from 17 protected forests in Asia, Central America, South America and Africa.
Of the 86 tropical mammal species they observed, the scientists found 12 of them strongly avoided moonlight at night. Just three species were drawn to moonlight.
Bischof commented:
These were the species with the most pronounced reactions. However, half of all the species responded to lunar phases. Either by changing their nocturnal habits, altering their overall activity levels, or both.
Of the mammals that changed their behavior, the scientists discovered about 30% of them kept a low profile during the full moon. This was especially the case for nocturnal rodents. And about 20% of mammal species were drawn to the full moon.
A nine-banded armadillo captured on a wildlife camera in the Caxiuana National Forest, Brazil. These armadillos are not fans of the full moon and are less active when there is more moonlight. This image is from a wildlife camera. Image via Tropical Ecology Assessment and Monitoring Network/ Norwegian University of Life Sciences.
Why does this study matter?
Tropical forests hold a significant portion of Earth’s biological diversity. These wild places are being increasingly fragmented and cleared. Logging reduces the forest canopy, allowing more light through. Artificial light from streetlamps and buildings can also influence animal activity.
Bischof explained:
The key takeaway from our research is that light affects animal behavior. It raises further questions about how changes in illumination affect species activity.
The effect of increasing light on wild tropical mammals
About 30% of tropical mammal species avoid the full moon, in part by becoming less active. A degraded tropical forest that lets in more light does not bode well for these species and could upset a delicate ecological balance.
Bischof said:
If these results extend to artificial light, loss of dark nights could curtail the amount of time animals invest into foraging and other important activities.
There is a risk that we are fundamentally altering both species composition and species interactions in tropical forest communities through light conditions alone.
Bottom line: Scientists have found that half of all mammal species in tropical forests change their behavior based on phases of the moon. About 1/3 of them avoid the full moon.
View at EarthSky Community Photos. | Roosevelt Silva captured this setting full moon over a misty rainforest in Brazil on May 26, 2021. Thank you, Roosevelt! Scientists recently discovered that some tropical mammals, like those in Brazilian tropical forests, avoid the moonlight.
Many mammals in tropical forests adjust their behavior based on moon phases, with some species becoming less active during the full moon.
Using wildlife cameras, researchers observed that about 30% of mammals in these habitats are less active when the moon is full, while 20% are drawn to the moonlight.
The study highlights concerns about how increasing artificial light and forest canopy loss may disrupt animal behavior and interactions in tropical ecosystems.
On a night like tonight – when there’s a full moon in the sky – the landscape is lit by bright moonlight. And you might think mammals living on the floor of tropical forests would welcome the moonlight. After all, it helps them see better. But scientists at the Norwegian University of Life Sciences studied the behavior of animals in the tropics under varying conditions of moonlight. They said on October 15, 2024, that – while some tropical mammals do appear more active under bright moonlight – an even larger percentage is less active when the moon is full.
The researchers published their findings in the peer-reviewedProceedings of the Royal Society B on October 16, 2024.
Nighttime lighting affects tropical mammals
Scientists don’t know a lot about how tropical mammals behave under different levels of moonlight. Their habitat – the floors of tropical forests under a thick canopy of leaves – are some of the darkest places on the planet at night.
So scientists used automatic wildlife cameras to observe how mammals behaved during the night under different phases of the moon. They found at least half of the mammal species altered their activity around the full moon. Some became less active, in an effort to be inconspicuous and avoid predators.
Imagine playing hide-and-seek in a dark room, and then somebody lights a candle. The light, even if it is weak, may make it easier for you to find your way around the room. But if you are the one hiding, you suddenly become a lot easier to detect.
Some tropical mammals, such as this paca, avoid the full moon and are less active when there is more moonlight. This image is from a wildlife camera. Image via Tropical Ecology Assessment and Monitoring Network/ Norwegian University of Life Sciences.
Studying wild mammals in the dark
The researchers studied 2.1 million wildlife camera images collected by the Tropical Ecology Assessment and Monitoring Network. The data came from 17 protected forests in Asia, Central America, South America and Africa.
Of the 86 tropical mammal species they observed, the scientists found 12 of them strongly avoided moonlight at night. Just three species were drawn to moonlight.
Bischof commented:
These were the species with the most pronounced reactions. However, half of all the species responded to lunar phases. Either by changing their nocturnal habits, altering their overall activity levels, or both.
Of the mammals that changed their behavior, the scientists discovered about 30% of them kept a low profile during the full moon. This was especially the case for nocturnal rodents. And about 20% of mammal species were drawn to the full moon.
A nine-banded armadillo captured on a wildlife camera in the Caxiuana National Forest, Brazil. These armadillos are not fans of the full moon and are less active when there is more moonlight. This image is from a wildlife camera. Image via Tropical Ecology Assessment and Monitoring Network/ Norwegian University of Life Sciences.
Why does this study matter?
Tropical forests hold a significant portion of Earth’s biological diversity. These wild places are being increasingly fragmented and cleared. Logging reduces the forest canopy, allowing more light through. Artificial light from streetlamps and buildings can also influence animal activity.
Bischof explained:
The key takeaway from our research is that light affects animal behavior. It raises further questions about how changes in illumination affect species activity.
The effect of increasing light on wild tropical mammals
About 30% of tropical mammal species avoid the full moon, in part by becoming less active. A degraded tropical forest that lets in more light does not bode well for these species and could upset a delicate ecological balance.
Bischof said:
If these results extend to artificial light, loss of dark nights could curtail the amount of time animals invest into foraging and other important activities.
There is a risk that we are fundamentally altering both species composition and species interactions in tropical forest communities through light conditions alone.
Bottom line: Scientists have found that half of all mammal species in tropical forests change their behavior based on phases of the moon. About 1/3 of them avoid the full moon.
View at EarthSky Community Photos. | Nancy Ricigliano in Long Island, New York, captured this image on November 13, 2023, and wrote: “When I found out Uranus was at opposition I figured I would give it a try. I was able to capture it in an eyepiece but had a difficult time finding it with my camera. It took me about an hour but I finally found it and was thrilled to capture this planet that is the 7th planet from the sun. The ice giant is surrounded by 13 faint rings and 27 small moons as it rotates at a nearly 90-degree angle from the plane of its orbit.” Thank you! When is Uranus at opposition in 2024? See below.
Our planet Earth will swing between the sun and the 7th planet – Uranus – at 3 UTC on November 17, 2024. That means we’re now smack in the middle of the best time of year to see this outer planet. Have you ever spotted Uranus? Indeed, it’s theoretically possible to see with the eye alone. But, in practice, Uranus is tough to locate without optical aid. Still, it’s easier with Uranus opposite the sun. It’s rising in the east as the sun sets in the west, highest in the sky at midnight.
When and where to watch in 2024: Uranus is theoretically visible to the unaided eye – assuming you have good eyesight – and you are under a dark sky. The planet is easily visible in good binoculars or a telescope, however. By the time of its November 17 opposition, Uranus is rising in the east at sunset and is visible all night. It’ll remain in the evening sky through April of 2025. Opposition for Uranus will fall at 3 UTC on November 17, 2024. That’s 10 p.m. CDT on November 16. Brightness at opposition: The 7th planet shines most brightly for 2024, at magnitude +5.6. In fact, Uranus shines at this brightness from about mid-October to mid-December. So, it should be possible to glimpse Uranus with the unaided eye, if you have dark-sky conditions. Find printable finder charts for Uranus here. Distance from Earth: Uranus is at its least distance from Earth for 2024, 2.6 light-hours or 18.6 AU from Earth. Constellation at opposition: At this 2024 opposition, Uranus is in front of the constellation Taurus the Bull. Through a telescope: Uranus appears as a tiny, greenish disk 3.8 arcseconds across. In addition, look for up to four moons of Uranus as well. Note: William Herschel discovered Uranus in 1781. It was the first planet to be discovered in modern times, and the first to be discovered with a telescope. It expanded the known limits of our solar system. Herschel called the new planet “the Georgium Sidus” (the Georgian Planet) in honor of King George III of England. However, the other planets were named from classical mythology. So the German astronomer Johann Elert Bode later suggested Uranus, in order to bring Uranus into conformity with the other planets’ names. In mythology, Uranus is the ancient Greek deity of the heavens, the earliest supreme god. His mythological granddaughter, Urania, is the goddess of astronomy. The name Uranus for this planet didn’t come into common use, however, until 1850.
Quick facts about oppositions
Opposition marks the middle of the best time of year to see an outer planet.
Think of us on Earth, sweeping between the sun and Uranus in our smaller, faster orbit. Around the same time as Uranus reaches opposition, it is also making its closest approach to Earth.
Uranus is the 7th planet from our sun. A year on Uranus is 84.4 Earth-years long. So, because Uranus’s orbit around the sun is so gigantic, and because Earth whips around the sun so quickly in comparison, Uranus’s opposition date falls about four days later each year.
2023 Uranus opposition – November 13
2024 Uranus opposition – November 16
2025 Uranus opposition – November 21
2026 Uranus opposition – November 25
Uranus as seen by Voyager 2 on January 14, 1986. Image via NASA/ JPL-Caltech.
Our planet Earth swings between the sun and Uranus on November 17, 2024, placing us squarely in the middle of the best time of year to see this outer planet. Why? Because in November 2024, Uranus is opposite the sun in our sky. It rises in the east as the sun sets in the west. November 17, 2024, is when Uranus reaches its yearly opposition.
And because Uranus is opposite the sun in November 2024, it climbs highest for the night at midnight (midway between sunset and sunrise). So, Uranus stays out all night long. Also, around the time of opposition, Earth’s motion brings Uranus closest to Earth for 2024. The planet shines at its brightest in our sky. How bright is that? Not very bright.
The fact is, even at its brightest, Uranus is still quite faint. Indeed, it’s barely perceptible as a dim speck of light to the unaided eye, even under dark skies. At a magnitude +5.6, Uranus shines no more brilliantly than the sky’s faintest visible stars. Given a dark sky free of light pollution, you might see Uranus with the eye alone. But you’ll need to have a good finder chart to know right where to look for this distant world in the constellation Taurus.
Distance to Uranus
At its closest point to Earth, Uranus is still twice as far away from us as its next-door neighbor, Saturn. At opposition, Uranus will be just shy of 19 astronomical units AU away from Earth and 20 AU from the sun. (One astronomical unit equals the average distance of Earth from the sun). Visit Heavens-Above to find out the present distance of Uranus and the other solar system planets.
Other Uranus observing opportunities
While opposition is mathematically the best time to view Uranus due to its nearness and brightness, another great opportunity is when the dim planet is near a brighter, closer planet, or near the moon. For example, when Venus or Mars passes close to distant Uranus as seen from our point of view, we get an easy guidepost to point us to the gas giant. The moon will be near Uranus on November 15 and 16, 2024, with the planet Jupiter nearby. And later, the moon will visit Uranus again on December 13, 2024.
View at EarthSky Community Photos. | Jim Bruzek of Dayton, Maryland, captured this image on March 30, 2023, and wrote: “Venus and Uranus at dusk from Dayton, Maryland.” Thank you, Jim!
Bottom line: Uranus reaches opposition on November 16-17, 2024. At this time, it’s brightest for the year and visible to the eye under optimum observing conditions. Here’s how to see it.
View at EarthSky Community Photos. | Nancy Ricigliano in Long Island, New York, captured this image on November 13, 2023, and wrote: “When I found out Uranus was at opposition I figured I would give it a try. I was able to capture it in an eyepiece but had a difficult time finding it with my camera. It took me about an hour but I finally found it and was thrilled to capture this planet that is the 7th planet from the sun. The ice giant is surrounded by 13 faint rings and 27 small moons as it rotates at a nearly 90-degree angle from the plane of its orbit.” Thank you! When is Uranus at opposition in 2024? See below.
Our planet Earth will swing between the sun and the 7th planet – Uranus – at 3 UTC on November 17, 2024. That means we’re now smack in the middle of the best time of year to see this outer planet. Have you ever spotted Uranus? Indeed, it’s theoretically possible to see with the eye alone. But, in practice, Uranus is tough to locate without optical aid. Still, it’s easier with Uranus opposite the sun. It’s rising in the east as the sun sets in the west, highest in the sky at midnight.
When and where to watch in 2024: Uranus is theoretically visible to the unaided eye – assuming you have good eyesight – and you are under a dark sky. The planet is easily visible in good binoculars or a telescope, however. By the time of its November 17 opposition, Uranus is rising in the east at sunset and is visible all night. It’ll remain in the evening sky through April of 2025. Opposition for Uranus will fall at 3 UTC on November 17, 2024. That’s 10 p.m. CDT on November 16. Brightness at opposition: The 7th planet shines most brightly for 2024, at magnitude +5.6. In fact, Uranus shines at this brightness from about mid-October to mid-December. So, it should be possible to glimpse Uranus with the unaided eye, if you have dark-sky conditions. Find printable finder charts for Uranus here. Distance from Earth: Uranus is at its least distance from Earth for 2024, 2.6 light-hours or 18.6 AU from Earth. Constellation at opposition: At this 2024 opposition, Uranus is in front of the constellation Taurus the Bull. Through a telescope: Uranus appears as a tiny, greenish disk 3.8 arcseconds across. In addition, look for up to four moons of Uranus as well. Note: William Herschel discovered Uranus in 1781. It was the first planet to be discovered in modern times, and the first to be discovered with a telescope. It expanded the known limits of our solar system. Herschel called the new planet “the Georgium Sidus” (the Georgian Planet) in honor of King George III of England. However, the other planets were named from classical mythology. So the German astronomer Johann Elert Bode later suggested Uranus, in order to bring Uranus into conformity with the other planets’ names. In mythology, Uranus is the ancient Greek deity of the heavens, the earliest supreme god. His mythological granddaughter, Urania, is the goddess of astronomy. The name Uranus for this planet didn’t come into common use, however, until 1850.
Quick facts about oppositions
Opposition marks the middle of the best time of year to see an outer planet.
Think of us on Earth, sweeping between the sun and Uranus in our smaller, faster orbit. Around the same time as Uranus reaches opposition, it is also making its closest approach to Earth.
Uranus is the 7th planet from our sun. A year on Uranus is 84.4 Earth-years long. So, because Uranus’s orbit around the sun is so gigantic, and because Earth whips around the sun so quickly in comparison, Uranus’s opposition date falls about four days later each year.
2023 Uranus opposition – November 13
2024 Uranus opposition – November 16
2025 Uranus opposition – November 21
2026 Uranus opposition – November 25
Uranus as seen by Voyager 2 on January 14, 1986. Image via NASA/ JPL-Caltech.
Our planet Earth swings between the sun and Uranus on November 17, 2024, placing us squarely in the middle of the best time of year to see this outer planet. Why? Because in November 2024, Uranus is opposite the sun in our sky. It rises in the east as the sun sets in the west. November 17, 2024, is when Uranus reaches its yearly opposition.
And because Uranus is opposite the sun in November 2024, it climbs highest for the night at midnight (midway between sunset and sunrise). So, Uranus stays out all night long. Also, around the time of opposition, Earth’s motion brings Uranus closest to Earth for 2024. The planet shines at its brightest in our sky. How bright is that? Not very bright.
The fact is, even at its brightest, Uranus is still quite faint. Indeed, it’s barely perceptible as a dim speck of light to the unaided eye, even under dark skies. At a magnitude +5.6, Uranus shines no more brilliantly than the sky’s faintest visible stars. Given a dark sky free of light pollution, you might see Uranus with the eye alone. But you’ll need to have a good finder chart to know right where to look for this distant world in the constellation Taurus.
Distance to Uranus
At its closest point to Earth, Uranus is still twice as far away from us as its next-door neighbor, Saturn. At opposition, Uranus will be just shy of 19 astronomical units AU away from Earth and 20 AU from the sun. (One astronomical unit equals the average distance of Earth from the sun). Visit Heavens-Above to find out the present distance of Uranus and the other solar system planets.
Other Uranus observing opportunities
While opposition is mathematically the best time to view Uranus due to its nearness and brightness, another great opportunity is when the dim planet is near a brighter, closer planet, or near the moon. For example, when Venus or Mars passes close to distant Uranus as seen from our point of view, we get an easy guidepost to point us to the gas giant. The moon will be near Uranus on November 15 and 16, 2024, with the planet Jupiter nearby. And later, the moon will visit Uranus again on December 13, 2024.
View at EarthSky Community Photos. | Jim Bruzek of Dayton, Maryland, captured this image on March 30, 2023, and wrote: “Venus and Uranus at dusk from Dayton, Maryland.” Thank you, Jim!
Bottom line: Uranus reaches opposition on November 16-17, 2024. At this time, it’s brightest for the year and visible to the eye under optimum observing conditions. Here’s how to see it.
