logo
7 Big Mysteries about Interstellar Object 3I/ATLAS

7 Big Mysteries about Interstellar Object 3I/ATLAS

Earlier this month astronomers were thrilled to discover only the third known interstellar object ever seen in our solar system. Now dubbed 3I/ATLAS, the suspected comet has just zoomed past the orbit of Jupiter, traveling so fast that it's bound to slip through our sun's gravitational grip. The high speed and hyperbolic trajectory of 3I/ATLAS means it must have come from another star and was cast adrift in the Milky Way by some unknown process before it eventually, by chance, briefly swooped by our sun. It will reach about the orbit of Mars before it boomerangs back toward interstellar space, never to be seen again, at the end of this year.
That's why astronomers have been racing to study 3I/ATLAS since July 1, when Larry Denneau of the University of Hawaii first spied it using a telescope in Chile that's part of the globe-spanning Asteroid Terrestrial-Impact Last Alert System (ATLAS). Soon more powerful observatories, including the James Webb Space Telescope (JWST) and Hubble Space Telescope, will scrutinize the object—which, thanks to its alien, interstellar provenance may be the oldest comet anyone has ever seen.
'I didn't get any sleep for like 35 hours,' says Bryce Bolin of Eureka Scientific in California, who rushed to release a preprint paper and arrange additional observations following 3I/ATLAS's discovery. 'It ruined my weekend.'
On supporting science journalism
If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.
Stefanie Milam of NASA's Goddard Space Flight Center is part of a group that had reserved time on JWST to observe an interstellar object—if the researchers were fortunate enough for one to be discovered. But the group's luck was tested when it couldn't reach the lead of its program—Martin Cordiner, also at Goddard—to kick the observations into action. 'He was hiking in Maine when the object was discovered, and we could not reach him—he was completely off the grid,' Milam says. 'When he finally got back, his phone just blew up. I said, 'You're never allowed to go on vacation again!''
So why exactly are astronomers so eager to observe this object, and what do they hope to learn?
Where did 3I/ATLAS come from?
The first major question to answer about 3I/ATLAS is its origin. Tracing it back to an individual star is likely impossible, given the mixing of myriad stars in their orbits around our galaxy across billions of years. But we might be able to work out roughly the region it came from.
One team of astronomers has already begun doing just that, using the high velocity of the object with respect to our sun—60 kilometers (37 miles) a second—to argue that it might have come from the vicinity of our galaxy's thick disk. This is a puffy torus of older stars moving at high velocities above and below the main flat plane of the Milky Way—which is where our sun serenely orbits.
A thick-disk origin might mean that 3I/ATLAS is extremely ancient, more than eight billion years old. 'It's from a star that's potentially not even there anymore,' says Michele Bannister of the University of Canterbury in New Zealand, a co-author on the work.
Aster Taylor of the University of Michigan performed a different age analysis based on the trajectory of 3I/ATLAS and suggests the object is 11 billion to three billion years old. 'We get similar answers,' Taylor says. Such estimates might soon be revised if subsequent observations can show just how much space weathering the object has endured during its interstellar sojourn.
How big is it?
Currently, 3I/ATLAS is inside the orbit of Jupiter and approaching the orbit of Mars, which it will cross in October, passing about 0.2 astronomical unit (one fifth the Earth-sun distance) from the Red Planet.
Although early observations have led astronomers to categorize 3I/ATLAS as a comet, at the moment, it's not behaving exactly like one. The object doesn't display a large tail or enveloping coma of cast-off gas, only a hint of dust—but that is expected to change soon. As it traverses the asteroid belt between Mars and Jupiter and basks in the sun's radiance, its surface should warm enough to sublimate ice, venting sufficient material to form a large coma and perhaps a prominent tail.
A substantial coma would be like a curtain drawn over astronomers' eyes, obscuring their view of the object and complicating efforts to gauge its dimensions. Before that happens, a team led by David Jewitt at the University of California, Los Angeles, is hoping to pin down its size with Hubble in August. (Other telescopes might be able to determine the size of 3I/ATLAS, too.)
Initial estimates suggested 3I/ATLAS might be up 20 kilometers (12 miles) across—very big for a comet—but most astronomers now think it is much smaller. 'It's probably somewhere in the range of one or two kilometers,' says John Noonan at Auburn University in Alabama. That would be somewhat comparable in size to our first two interstellar visitors: 1I/ʻOumuamua, which was discovered in 2017 and was up to about 400 meters (0.25 mile) long, and 2I/Borisov, which was found in 2019 and was about one kilometer (0.6 mile) wide.
If 3I/ATLAS turns out to be much bigger, 10 kilometers (six miles) or more, this would pose problems for preexisting estimates of many big interstellar objects reside in the galaxy. 'It's statistically extremely unlikely we should ever see something that size,' Noonan says. 'Theorists don't like that. But as an observer, I would love to see a really weird, big object.'
How fast is it spinning?
As well as its size, one of the key properties astronomers want to know about 3I/ATLAS is its rotation rate—something they might discern by watching the object's changing brightness as it spins. The spin of 3I/ATLAS could carry clues as to how the object was ejected from its home star in the first place.
'Certain ways of kicking these objects out tend to make them spin up,' Taylor says. A close pass of a gas giant planet, for instance, could easily set the object twirling while hurling it away from its home star. Conversely, a slow rotation period would suggest the object experienced a more gentle ejection.
'You could do this when stars die,' Taylor says. 'They lose a lot of mass, and so the gravitational force on objects at the outer edge of their system goes away. Those objects become unbound and just flow out into the galaxy.'
The rotation period can also tell us more about the shape of 3I/ATLAS—a steady rotation suggests a fairly spherical form, whereas a fluctuating rotation speed might suggest a 'wonky shape,' Taylor says, like that of 'Oumuamua, which was estimated to be cigar- or pancake-shaped.
What is 3I/ATLAS made of?
If 3I/ATLAS really is an ancient cometary castaway that has been drifting through the galaxy for eons, it might be full of ice that has never been heated by a star. If so, then as it gets closer, the object might suddenly erupt into activity. While that could be bad news for measuring its size, it would aid efforts to determine 3I/ATLAS's chemical composition.
JWST and Hubble would be best suited for the task of picking apart the different species of molecules that might erupt from 3I/ATLAS. Unfortunately, however, in October, when the object will be at its warmest, closest point to our star (called perihelion), Earth will be on the other side of the sun. This will make observations from our planet almost impossible.
In November, post-perihelion, Noonan will use Hubble to study 3I/ATLAS and its emissions, looking for signs of substances such as hydroxide and hydrogen that can help clarify its composition.
If the object is several billion years old, as predicted, then it might be rich in water because of the suspected formation environment around older stars. 'You would expect a lot of hydrogen coming from these water-rich irradiated objects, if this is really as old as [thought],' Noonan says.
Milam and her colleagues, meanwhile, will use JWST in August and December to observe 3I/ATLAS before and after perihelion. Thanks to its keen infrared vision, JWST is better suited for teasing out the presence of molecules such as water, carbon monoxide, carbon dioxide and ammonia.
'We can really home in and see what this thing looks like,' she says. 'Borisov had a pretty boring chemistry, but it wasn't like any object in our solar system—there was hardly any water at all but a lot of carbon monoxide and hydrogen cyanide. With JWST, we're hoping to see a lot of carbon dioxide [on 3I/ATLAS], maybe even water, if it's as pristine as people are projecting.'
Although the overall view from Earth degrades as the object approaches perihelion, some telescopes will be less visually impaired. Those operated by the Lowell Observatory in Arizona, for instance, are primed to observe 3I/ATLAS at dawn and dusk, when the sun is below the horizon. This will allow for studies even when the object will be close to our star from our planet-bound perspective. 'The Lowell Discovery Telescope is really well suited to observations close to the horizon,' says Nick Moskowitz, an astronomer at Lowell Observatory. 'We will be able to track it closer in to perihelion than other facilities.'
An unlikely additional capability will be at Mars, where spacecraft such as NASA's Mars Atmosphere and Volatile Evolution (MAVEN) orbiter may be able to see 3I/ATLAS as it passes about 30 million kilometers (19 million miles) from the planet. 'It'll be pretty large and apparent in the sky,' Noonan says, providing the object kicks into activity as hoped. 'They'll be able to see the coma,' giving us an insight into 3I/ATLAS's activity near the sun that would otherwise be impossible to see from Earth.
Will it survive?
A big unknown about 3I/ATLAS is whether it will actually survive its close encounter with our sun. While 'Oumuamua did so, Comet Borisov was not so fortunate, with the object appearing to split and break apart on its way out of our solar system.
The same fate could befall 3I/ATLAS. 'Borisov fragmented, which is pretty usual for comets,' Bannister says. All eyes will be on our latest visitor to see if the same thing happens again.
An additional quirk of 3I/ATLAS's survivability is the impact of solar wind, which may snip away any cometary tail as it is ejected. By chance, the object is entering our solar system at quite a shallow angle, much flatter than that of most comets, which means it will experience stronger solar headwinds.
Sarah Watson of the University of Reading in England and her colleagues are using this quirk to study how the solar wind traverses into the outer solar system. 'We can potentially calculate the speed of the solar wind,' she says, by noticing the impact of the solar wind on the purported comet's tail, if one materializes.
Could we reach it?
No spacecraft will be able to reach 3I/ATLAS. It is moving too fast and is too far from Earth for us to consider launching something in time.
Yet an upcoming European Space Agency (ESA) mission called Comet Interceptor, set to launch in 2029, might attempt to visit another interstellar object, if we find one within its reach. The spacecraft will be positioned past the moon's orbit away from the sun and, if a suitable target is found, will be commanded to fire its engines and try and intercept the incoming alien object.
If no suitable interstellar object is found, Comet Interceptor will instead be sent to one of several intriguing comets of our solar system. 'It is possible we could get an interstellar object, but we have to be really lucky,' says Colin Snodgrass, an astronomer at the University of Edinburgh, who is deputy lead on the mission.
How many are there?
One of our biggest outstanding questions about interstellar objects concerns their unknown abundance. The object 3I/ATLAS is our third interstellar visitor in eight years—a real but weak hint of how many are out there, waiting to be found.
Predictions estimate there are trillions upon trillions of interstellar objects drifting around our galaxy, and perhaps one in our solar system at any given time—but they're typically just so faint that they're unlikely to be found by most telescopes. This is expected to change when a new telescope called the Vera C. Rubin Observatory begins a 10-year survey of the sky later this year.
Rubin is expected to see somewhere between six and 51 interstellar objects in its 10-year survey. Seeing such a population will tell us 'how unique, or varied, planetesimal formation is across different parts of the galaxy,' Bannister says, referring to kilometer-scale objects thought to coalesce around newborn stars that become the feedstock for planets—and, when kicked to a system's hinterlands, become a reservoir of comets.
One puzzling question is why we haven't seen much smaller interstellar objects, Moskowitz says. If smaller objects are more plentiful than larger objects, as scientists expect, then we should have seen some small interstellar objects entering our atmosphere, appearing as meteors streaking across Earth's skies at speeds and trajectories that clearly convey their interstellar origins.
Detections of such objects have been claimed, but the evidence behind them has failed to convince most experts. The apparent absence of small interstellar interlopers 'is telling us something, but we don't know what that is yet,' Moskowitz says. 'I think that's going to be one of the major questions: Why are we seeing these big cometlike things coming through the solar system, but we're not seeing things that are smaller? It may have to do with the survivability of stuff out there in the galaxy, but we need more data.'
Orange background

Try Our AI Features

Explore what Daily8 AI can do for you:

Comments

No comments yet...

Related Articles

Start your week smart: NASA's future, Starvation in Gaza, Stabbing incident, Extreme heat risk, Swimming showdown
Start your week smart: NASA's future, Starvation in Gaza, Stabbing incident, Extreme heat risk, Swimming showdown

CNN

timean hour ago

  • CNN

Start your week smart: NASA's future, Starvation in Gaza, Stabbing incident, Extreme heat risk, Swimming showdown

If you've been suffering through the high temperatures that have scorched much of the country this summer, you know the toll it can take on your body, leaving you dizzy, dehydrated and, in some severe cases, at risk of death. But there's another lesser-known impact of extreme heat — and it might surprise you. Here's what else you need to know to start your week smart. 🔦 Few US government agencies have navigated as much turmoil in recent months as NASA. With the impending loss of thousands of jobs looming, this week saw the release of a scathing letter from nearly 300 current and former NASA employees and the abrupt resignation of the director of the Goddard Space Flight Center. Scientists and agency workers criticized budget cuts, grant cancellations and a 'culture of organizational silence.' They also raised concerns about suggested changes to a system of safety checks and balances. President Donald Trump appointed US Secretary of Transportation Sean Duffy as interim NASA administrator to replace Janet Petro, a longtime agency employee. That came after the nomination of tech billionaire Jared Isaacman to lead NASA was rescinded. Some scientists are criticizing the agency as the Trump administration tries to dismantle the NASA Goddard Institute for Space Studies, one of the country's top climate labs. Employees are working remotely after their New York City office was shut down. Back in March, NASA astronauts Suni Williams and Butch Wilmore returned to Earth after gaining international attention as their short trip to space stretched into a saga lasting more than nine months. It's an example of how quickly things can go sideways. Meanwhile, leaks have plagued the International Space Station. 📸 In photos: Astronaut Don Pettit captures unique views of the cosmos. Take a look. Blue Origin took a star-studded all-female crew — including singer Katy Perry and journalist Gayle King — to the 'edge of space' and back. The mission had its critics, but is this the future of spaceflight? Israel says it will open aid corridors as fury grows over starvation in Gaza A 'random' stabbing at a Michigan Walmart left 11 injured, officials say. Here's what we know so far Alabama toddler dies in hot car while in state custody GET '5 THINGS' IN YOUR INBOX If your day doesn't start until you're up to speed on the latest headlines, then let us introduce you to your new favorite morning fix. Sign up here for the '5 Things' newsletter. Looking for a way to beat the summer heat? July 28 is National Water Park Day, so grab your swimsuits and hit the water slide or tube down a lazy river! The International Monetary Fund will release its July 2025 World Economic Outlook Update. This publication provides analyses and projections of the global economy. In an update in April, the IMF said forecasts for global growth had been revised markedly down compared with its January update, reflecting effective tariff rates at levels not seen in a century. The Federal Reserve is set to conclude its fifth interest rate meeting since President Donald Trump returned to office in January, with policymakers expected to hold rates steady once again. The decision is likely to draw sharp criticism from Trump, who has repeatedly clashed with Fed Chair Jerome Powell over the bank's refusal to cut rates. Tension between the two was evident last week during a tour of the Fed's $2.5 billion headquarters renovation, a project the Trump administration has used to intensify pressure on Powell. 📹 Watch this awkward exchange between Powell and the president. The National Transportation Safety Board will begin a three-day public hearing to investigate the January 29 mid-air collision between a regional jet and an Army helicopter over the Potomac River near Washington, DC, that killed 67 people. President Trump's so-called reciprocal tariffs are set to go into effect on August 1 after a 90-day delay, impacting multiple countries, including Mexico, Canada and the European Union. If Trump's proposed duties of 30% do kick in, Americans could wind up paying more for everything from produce to medical equipment, electronics and alcohol. It's also the day we get the monthly jobs report for July. In this episode of the 'One Thing' podcast, CNN's David Rind speaks to science journalist Jane C. Hu about why Republicans are increasingly open to the purported healing properties of psychedelics. Listen here. Prev Next 📸 Check out more images curated by the CNN Photo team. The Tour de France, which began on July 5, wraps up today in Paris. After more than 2,000 miles of racing, riders will make their way down the Champs-Élysées to the finish line. (TK look for a London write) The World Aquatics Championships kick off today in Singapore, and all eyes will be on the high-stakes showdown between swimming legend Katie Ledecky and Canadian phenom Summer McIntosh. Ledecky, 28, boasts nine Olympic golds and 21 world titles, while 18-year-old McIntosh arrives with four Olympic medals and three world records set just last month. 📹 Hear how Ledecky is preparing to face her fiercest challenger yet. And the World Dog Surfing Championships are Saturday at Linda Mar Beach in Pacifica, California. What began as the short-lived TV comedy series 'Police Squad!' in the early 1980s got a second life as 'The Naked Gun' series of movies starring Leslie Nielsen and George Kennedy. Now, more than 30 years after 1994's 'The Naked Gun 33 1/3: The Final Insult,' a reboot starring Liam Neeson and Pamela Anderson arrives on the big screen this Friday. Will it be riddled with moronic jokes, toilet humor and sight gags, just like its predecessors? Let's hope so! 🧠 Take CNN's weekly news quiz to see how much you remember from the week that was! So far, 5.4% of fellow quiz fans have gotten eight or more questions right. How will you fare? Heavy metal icon and reality TV star Ozzy Osbourne passed away last week at the age of 76. Rest in peace, Prince of Darkness. (Click here to view) Today's edition of 5 Things Sunday was edited and produced by CNN's Tricia Escobedo.

Scientists may have solved a chemistry mystery about Jupiter's ocean moon Europa
Scientists may have solved a chemistry mystery about Jupiter's ocean moon Europa

Yahoo

time2 hours ago

  • Yahoo

Scientists may have solved a chemistry mystery about Jupiter's ocean moon Europa

When you buy through links on our articles, Future and its syndication partners may earn a commission. A long-standing mystery about the presence of hydrogen peroxide (H2O2) on Jupiter's icy ocean moon Europa may be closer to being solved. Hydrogen peroxide forms as a byproduct when energetic particles break apart water molecules, leading to the recombination of OH radicals — highly reactive molecules with unpaired electrons. H2O2 was first observed on Europa by the Galileo Near Infrared Mapping Spectrometer, a scientific instrument aboard NASA's Galileo Jupiter orbiter that was designed to study the composition and surface features of the gas giant's moons and atmosphere using infrared light. Later, the James Webb Space Telescope (JWST) noticed elevated levels of hydrogen peroxide in unexpected areas on the Jovian satellite. Lab studies predicted that higher concentrations of hydrogen peroxide would be found in Europa's colder polar regions — but JWST observations showed the opposite, detecting higher levels in the moon's warmer equatorial regions. These areas, known as chaos terrains, are marked by broken blocks of surface ice that appear to have shifted, drifted and refrozen. "Europa's peroxide distribution does not follow the temperature dependence predicted for pure water ice," wrote the team in their paper. Lab studies consistently show that colder ice has more H2O2, while warmer ice has less. In a new study, scientists report that they have noticed higher levels of carbon dioxide (CO2) in the chaos terrains alongside elevated levels of H2O2. This is probably the result of CO2 escaping Europa's subsurface ocean through cracks in the ice, the researchers say. The team therefore wondered if the presence of CO2 might be changing the ice's chemistry. "Could the presence of CO2 drive the enhanced peroxide production in Europa's chaos regions, signaling a surface composition more conducive to the formation of this radiolytic oxidant?" they wrote in their paper. "Supporting this hypothesis are preliminary experiments on irradiated H2O-CO2 ice mixtures that show increased H2O2 yields compared to pure water ice." To find a definitive answer, they "simulated the surface environment of Europa inside a vacuum chamber by depositing water ice mixed with CO2," Bereket Mamo, a graduate student at The University of Texas at San Antonio and a contractor with the Southwest Research Institute, said in a statement. "We then irradiated this ice mixture with energetic electrons to see how the peroxide production changed." The experiment confirmed what the team had suspected: Even small amounts of CO2 in water ice can greatly boost hydrogen peroxide production at temperatures similar to those on Europa's surface, helping to explain the unexpected JWST observations. This occurs because CO2 molecules behave as "molecular scavengers," grabbing hold of any stray electrons produced when radiation hits the water ice. By capturing these electrons, the CO2 helps protect hydrogen peroxide from being broken apart by further impacts or reactions. Related Stories: — Europa: A guide to Jupiter's icy ocean moon — 'Chaos' reigns beneath the ice of Jupiter moon Europa, James Webb Space Telescope reveals — Europa Clipper: A complete guide to NASA's astrobiology mission "Synthesis of oxidants like hydrogen peroxide on Europa's surface is important from an astrobiological point of view," said study co-author Richard Cartwright, from the Johns Hopkins University Applied Physics Laboratory. "In fact, an entire NASA mission, the Europa Clipper, is en route to the Jovian system right now to explore the icy moon and help us understand Europa's habitability. "Our experiments provide clues to better understand JWST Europa observations and serve as a prelude to upcoming close-range investigations by Europa Clipper and ESA's [the European Space Agency] JUICE spacecraft," Cartwright added. The new study was published in the Planetary Science Journal on Monday (July 21). Solve the daily Crossword

Scientists figure out the flaw behind stuck rovers using free software
Scientists figure out the flaw behind stuck rovers using free software

Digital Trends

time4 hours ago

  • Digital Trends

Scientists figure out the flaw behind stuck rovers using free software

Space operations are extremely sophisticated and expensive undertakings. There are so many things that can go wrong, especially when it comes to on-ground missions on extra-terrestrial bodies such as the Moon and nearby planets, conducted through remotely-operated robots and vehicles. An event as minor as a rover getting stuck can dramatically impact the mission objective or even abandonment. In 2005, the wheels of NASA's Mars Exploration Rover Opportunity were stuck in sand, and it took six weeks of inch-by-inch maneuvering by experts at the agency's Jet Propulsion Laboratory to free it. Just a few weeks ago, the Perseverance rover also struggled with a stuck drill bit, but the situation was fortunately resolved. But not every story has a happy ending. In 2009, the Spirit rover found itself on a slope in a rather peculiar situation, and could never be recovered. With the Martian winter further complicating the rescue efforts, the Spirit mission was officially abandoned two years later. Such accidents could soon become a thing of the past. A major breakthrough Engineers at the University of Wisconsin–Madison have spotted a flaw in the testing protocols of these rovers on Earth, which often gives an overly optimistic view of their exploration capabilities. Rovers are often tested in desert-like areas, which simulate the dry conditions on the Moon and Mars, accounting for the reduced gravity on these bodies. Recommended Videos But as per the research team at UW-Madison, the tests often ignore the impact of gravity exerted on the sand particles, which means the simulation tests are not nearly as accurate (read: realistic) as they should be. 'An important element in preparing for these missions is an accurate understanding of how a rover will traverse extraterrestrial surfaces in low gravity to prevent it from getting stuck in soft terrain or rocky areas,' the team explains. Notably, it's the same team that is working on simulation modeling for NASA's VIPER rover. The Volatiles Investigating Polar Exploration Rover, or VIPER, mission was supposed to look for water and other useful resources on the harsher side of the Moon, but the project was terminated in 2024. The team relied on an open-source simulation software called Chrono to discover the discrepancy in the Earth-based rover testing protocols. It's the same software that is also used for estimating the off-roading capabilities of US Army vehicles. The team has detailed its findings in a paper published in the Journal of Field Robotics. The road to safer rover missions The team at UW-Madison, however, continued its work on rover tech for space missions. Elaborating on the phenomenon, the team notes that Earth's gravity creates a stronger pull on the sand particles than what the same particles would feel on the Moon, or Mars. Additionally, the sand on Earth is said to be more rigid, while the top surface on the Moon is softer, which means it will shift more dramatically under the rover's wheels, and as a result, reduces the traction. Interestingly, the software that enabled the aforementioned discovery, is used across diverse industries. Aside from educational institutions, some of its more notable users include the U.S. Army Ground Vehicle Systems Center, NASA's Jet Propulsion Lab, the U.S. Army Engineer Research and Development Center, and the National Renewable Energy Lab. It was also used by the experts at the Politecnico di Milano in Italy for the Mascot lander for its asteroid Ryugu mission. In addition to vehicle simulations and advanced robots, Project Chrono has even been deployed for 'miniaturized mechanisms for watches.'

DOWNLOAD THE APP

Get Started Now: Download the App

Ready to dive into a world of global content with local flavor? Download Daily8 app today from your preferred app store and start exploring.
app-storeplay-store