Tag: comets

NASA Finally Weighs In on the Origin of 3I/ATLAS

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After the prolonged shutdown of the US government, NASA has finally started its nonessential work back up. It’s starting off with a bang: The agency called a press conference to show its hitherto reserved images of the interstellar object 3I/ATLAS. NASA scientists also confirmed that 3I/ATLAS is in fact a comet, contrary to the speculations about alien technology flooding the internet.

During the broadcast, a panel of scientists showed the results of observations obtained by different NASA missions across various points in the journey 3I/ATLAS has taken. Each provided insights in the infrared, visible, ultraviolet, and gamma-ray spectrums, providing a better understanding of the true nature of 3I/ATLAS.

Among the most relevant data are images captured by the Mars Reconnaissance Orbiter and MAVEN satellites, as well as those from the Psyche and Lucy space probes, and even from the SOHO solar probe. The scientists clarified that all the data will be publicly available for anyone to investigate.

3I/ATLAS Images Shared by NASA

The shape of 3I/ATLAS as seen by the SOHO solar probe.

Lowell Observatory/Qicheng Zhang/NASA

SOHO: Image From the Sun-Monitoring Probe

This orange-toned photo comes from NASA. The SOHO probe that monitors the sun managed to capture 3I/ATLAS between October 15 and 26. In the words of the agency, this image was a surprise. They did not expect that the object could be seen from so far away, 358 million kilometers.

3I/ATLAS as seen from the Mars Reconnaissance Orbiter.

NASA

MRO: One of the Best Close-Ups of 3I/ATLAS

One of the most anticipated photos of the comet is the one obtained by the Mars Reconnaissance Orbiter satellite in October, when 3I/ATLAS approached at “only” 29 million kilometers. NASA finally shared it. The image shows the frozen body surrounded by a cloud of characteristic dust ejected as the comet approached the sun.

NASA’s STEREO (Solar Terrestrial Relations Observatory) observed interstellar comet 3I/ATLAS from September 11 to October 25.

NASA/Observatorio Lowell/Qicheng Zhang

STEREO: The Photo Confirming the Shape of 3I/ATLAS

The STEREO observatory analyzes the behavior of the sun. To get at least one coherent image of the comet, scientists had to stack several images taken at different exposures. In the end, the interstellar object was revealed as a bright orb against a noisy background.

Image of the water signature of 3I/ATLAS taken by the MAVEN satellite.

NASA

MAVEN: A Glimpse of Comet Hydrogen

MAVEN is a Mars orbiter. Its lens captured this ultraviolet spectrum image of 3I/ATLAS before it reached its closest approach to the Red Planet. It shows hydrogen emitted from different sources. The portion on the left belongs to the comet’s signature.

This movie shows PUNCH observations of comet 3I/ATLAS from September 28 to October 10, 2025,

NASA/Instituto de Investigación del Suroeste

PUNCH: Another Solar Glimpse

PUNCH is a polarimeter that monitors the sun’s corona and its heliosphere. However, its lenses made it possible to visualize the comet’s tail for weeks from October to September. In this animation, each frame represents a daily snapshot, while the streaks in the background are produced by the movement of the stars.

On December 19, 2025, the comet will reach its closest point to Earth. It will pass at a completely safe distance: about 267 million kilometers away. To put that in perspective, it’s equivalent to almost 700 times the distance between the Earth and the moon, and 1.8 times the separation between our planet and the sun. This flyby will have no effect on the Earth.

Both NASA and other space agencies are expected to initiate additional observing campaigns to capture better photographs and relevant information about the third confirmed interstellar object in history.

This story originally appeared in WIRED en Español and has been translated from Spanish.

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Jorge Garay

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November 19, 2025
You Need to See This Bright New Comet Shine in the Night Sky This Month Before It Disappears for 1,000 Years

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This year is a boom time for comets. Not only did we have the interstellar object 3I/ATLAS gracing our skies (and Mars’) earlier this year, but now we have another brand new comet to look out for.

Expected to be at its brightest on October 21, this month you might have the chance to spot the comet Lemmon (C/2025 A6) blazing across the night sky—no telescope or binoculars required.

Lemmon was first discovered in January this year by the Mount Lemmon Survey in Arizona. As amateur astronomers may be aware, several comets will pass the detection range of binoculars or telescopes in any given year. But it’s rare that a comet will shine bright enough to be spotted with the naked eye. October 21 also happens to be a date of the new moon, meaning the sky will be otherwise dark and primed for the comet to zip by.

“This comet is developing very nicely and it is already an impressive object, well-placed for observation in the morning sky,” Nick James of the British Astronomical Association told Spaceweather.com. “It is definitely worth getting up for!”

The anatomy of a comet

Comets, simply put, are “cosmic snowballs,” orbs of icy material that orbit the Sun. Predicting their appearance and trajectory is no easy task, but Lemmon’s unusually bright, active tail has allowed both professional and casual observers to characterize its likely path through the solar system.

At its closest approach to Earth, Lemmon will be about 56 million miles (90 million kilometers) away. Lemmon’s current orbital period is approximately 1,350 years, which will be reduced to about 1,150 years after passing by the Sun’s gravitational field in November. That is, if you miss the comet this year, you’ll have to wait until at least 3175 to see it again.

How to spot Lemmon

As of now, Lemmon is visible only in the morning, although the comet’s trajectory will progressively allow observers to spot it in the evenings. Last month, it passed by the Gemini constellation, traveling through the skies until it entered Ursa Major earlier this month.

Again, comet luminosity can be touch-and-go, so it may well grow dimmer than expected. But astronomers are reasonably confident about their current predictions. “

So far, the comet has performed very well and there is no reason not to believe that it will continue to delight Northern Hemisphere observers for a few more weeks,” according to Space.com.

“I think we can now be reasonably confident that this will be a very nice evening object when it is at its brightest around New Moon in late October,” James said.

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Gayoung Lee

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October 13, 2025
Two Newly Discovered Comets Will Streak Across the Skies This Month. Here’s How to See Them

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Skywatchers, rejoice. This month, not one but two comets are set to soar into our night skies for your viewing pleasure.

The two comets, C/2025 R2 (SWAN) and C/2025 A6 (Lemmon), were both discovered in 2025. The celestial visitors are gearing up for a close flyby of Earth in October, becoming more visible as they approach our planet. SWAN will be closest to Earth on October 19, while Lemmon is set for its own close approach on October 21. Both icy comets may even be visible to the naked eye around that time.

Cosmic pair

Astronomers spotted Lemmon in January using the Mt. Lemmon SkyCenter observatory in Arizona’s Santa Catalina Mountains. The comet was speeding toward the inner solar system at speeds up to 130,000 miles per hour (209,000 kilometers per hour).

Later in September, amateur astronomer Vladimir Bezugly discovered comet SWAN in images from the SWAN instrument on NASA’s SOHO satellite. The comet became significantly brighter as it emerged from the Sun’s direction.

At its closest approach, SWAN will be at a distance of approximately 24 million miles (39 million kilometers) from our planet, or about a quarter of the distance between the Sun and Earth. SWAN is now at a brightness magnitude of around 5.9, according to EarthSky. The unexpectedly bright comet is currently in the southern skies, but it is slowly moving north, according to NASA.

Following SWAN’s closest approach, comet Lemmon will be right behind. The comet will be about half the distance between the Sun and Earth before rounding the Sun on November 8. From there, it will begin its next journey around the star. Lemmon will continue to brighten as it approaches the Sun, but it will likely stay visible, and possibly become even brighter, around October 31 to November 1, according to EarthSky.

How to see SWAN and Lemmon

SWAN is best viewed in the Southern Hemisphere. The comet crossed into the Libra constellation on September 28, and will make its way across Scorpius on October 10. Around October 9-10, it will appear near Beta Librae, the brightest star in the Libra constellation, EarthSky reports.

It may, however, be a bit tricky to spot because its position in the skies will be close to the setting Sun. Sky watchers hoping to catch a glimpse of SWAN need up toward the west after sunset.

Conditions are more favorable for Lemmon. The comet is best viewed in the Northern Hemisphere, where it will be positioned near the Big Dipper for most of October. Sky watchers should look to the eastern skies just before sunrise to spot the comet.

By mid-October, the comet may be easier to view. On October 16, Lemmon will pass near Cor Caroli, a binary star system in the northern constellation of Canes Venatici, according to EarthSky. Around that time, the comet could be visible to the naked eye.

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Passant Rabie

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October 5, 2025
This Visiting Interstellar Comet Just Keeps Getting Weirder

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Ever since interstellar comet 3I/ATLAS whizzed into our cosmic neighborhood in July, astronomers have been racing to uncover its characteristics. Now that the powerful James Webb Space Telescope has taken a good look at this icy interloper, it seems to be weirder than anyone imagined.

A preprint submitted to the Astrophysical Journal Letters for peer review on Monday, August 25, describes the first results from JWST’s survey of 3I/ATLAS.

A team of astronomers observed the comet with the telescope’s Near-Infrared Spectroscopic (NIRSpec) instrument to measure the composition of its coma—the cloud of gas and dust that surrounds its nucleus—and determine what drives its activity. Their surprising findings bring 3I/ATLAS’s origin into clearer focus, helping astronomers retrace the comet’s long journey to our solar system.

3I/ATLAS, detected by the ATLAS (Asteroid Terrestrial-impact Last Alert System) survey telescope on July 1, is only the third interstellar object ever discovered. These celestial bodies hail from star systems beyond our own. Studying them offers a glimpse of the conditions and processes that shaped these distant systems. Over the past two months, researchers have already uncovered unprecedented details about this latest cosmic visitor.

JWST spies unusual characteristics

Now, JWST has revealed even more of 3I/ATLAS’s distinctive features. Most comets have comas dominated by water, but this one is chock-full of carbon dioxide, according to the study. In fact, the researchers found that its ratio of carbon dioxide to water is among the highest ever observed in any comet. This may indicate that 3I/ATLAS has a nucleus that’s intrinsically rich in carbon dioxide, suggesting it formed in an environment with higher levels of radiation than our solar system.

Alternatively, the carbon dioxide-dominated coma may indicate that 3I/ATLAS formed near the CO2 ice line within the protoplanetary disk that surrounded its parent star, according to the researchers. This is the distance from a young star where the temperature drops low enough for carbon dioxide gas to freeze into ice. What’s more, the lack of water in the coma points to unusual surface properties—or perhaps an insulating crust—that may prevent heat from penetrating the comet’s icy core.

A comet unlike any other

These new findings suggest the comet formed under conditions far different from those in our corner of the galaxy, adding to a growing list of traits that make it unlike any seen before. Prior to this JWST survey, astronomers found evidence to suggest 3I/ATLAS is the oldest interstellar comet ever discovered—potentially older than our solar system. This, coupled with its trajectory, suggests it originated from a relatively old, low-metallicity star system in the Milky Way’s “thick disk”—the part of the galaxy that contains 10% of its total stellar mass.

Astronomers have put forth a wealth of astonishing new information about 3I/ATLAS since its discovery, but this is only the beginning. Experts expect this comet to remain observable through mid-2026, providing ample research opportunities. The more information scientists gather on this interstellar object, the closer they’ll get to unraveling the secrets of its origin.

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Ellyn Lapointe

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August 27, 2025
How to View the ‘Comet of the Century’ C/2023 A3

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This story originally appeared on WIRED en Español and has been translated from Spanish.

C/2023 A3, also known as Tsuchinshan–ATLAS and considered “the comet of the century,” will appear in all its splendor in our sky during September and October 2024. Due to its characteristics, astronomers believe it will be exceptionally bright, similar to Halley’s comet in 1986 or NEOWISE in 2020.

Comets like C/2023 A3 are balls of frozen gases, rocks, and dust that orbit the sun. They are often spectacular because of two physical phenomena that occur during their journey.

The first is the tail, which stretches out from the nucleus of the comet as it gets closer to the star that it’s orbiting. Solar radiation from the star—in our case the sun—vaporizes some of the comet’s frozen material, blowing gas and dust away from the nucleus that then reflects the star’s light. As a comet gets closer to its star, it’s tail grows in size because of the increase in solar radiation.

The second phenomena is the comet’s coma. This is an envelope of sublimated ice that forms a kind of atmosphere around the nucleus as it approaches its star, again because of solar radiation. This also enhances the comet’s brightness.

What Is the Best Day to See the Comet?

C/2023 A3 will shine in the northern hemisphere sky from September 27 and will remain visible until the last week of October. During this period, the comet will reach its minimum distance from the sun, before beginning its journey back out of the solar system.

According to the specialized blog Cometography, the day when C/2023 A3 will shine the brightest will be October 2. The comet’s tail will be long and spectacular at this point due to its proximity to the sun.

Tsuchinshan–ATLAS will be positioned between the orbits of Mercury and Venus when it is most visible, but will be closer to Earth than those two planets.

Cometografía

At What Time Will the Comet Be Visible?

Because of its proximity to the sun, the comet will behave similarly to Mercury and Venus: It will be seen near the horizon, in the path of the sun, and just before sunrise. An appropriate window to admire it will be between 5 am and 7 am from September 27 onwards. The timing and position will be similar across the northern hemisphere.

As October progresses, the comet will elevate its position in relation to the horizon and at the same time lose brightness. Since Tsuchinshan–ATLAS is a long-orbiting body and comes from the Oort cloud, beyond the edge of the solar system, it will not appear again in our skies for tens of thousands of years.

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Jorge Garay

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September 13, 2024