Space

The solar system’s newest visitor, 3I/ATLAS, may be 3 billion years older than the sun and its planets.

First discovered on July 1, 3I/ATLAS is a rare interstellar object — only the third ever spotted. Since then, astronomers have been racing to uncover its origins. A new calculation predicts that 3I/ATLAS originated from a part of the Milky Way called the thick disk. If so, there’s a two-thirds chance that it’s a comet over 7 billion years old. That would make it the oldest comet known, researchers reported July 11 at the Royal Astronomical Society’s National Astronomy Meeting 2025 in Durham, England. More

For only the third time in history, astronomers have detected a new interstellar visitor — an object from another star — blitzing into our solar system.

First named A11pl3Z and now designated as 3I/ATLAS , the comet was spotted by a survey telescope in Chile on July 1 and confirmed by the International Astronomical Union’s Minor Planet Center the same day. To piece together its trajectory, astronomers dug through older sky surveys and found its position as early as mid-June. More

Bad news, earthlings. Computer simulations of the solar system’s future reveal a new risk facing us all: The gravitational tug of a passing star could either cause another planet to smack into Earth or else fling our planet into the sun or far away from it, where any inhabitants would freeze.

Blame Mercury. Astronomers have long known that the innermost planet’s orbit, which is fairly oval-shaped, can become even more elliptical due to gravitational jiggles from Jupiter. Passing stars exacerbate this danger, Nathan Kaib, an astronomer at the Planetary Science Institute who is based in Iowa, and Sean Raymond, an astronomer at the University of Bordeaux in France, report in work submitted to arXiv.org May 7. More

On some Martian nights, a subtle, green glow hangs low in the sky, wreathing the horizon in every direction.

A visible Martian aurora has finally been observed for the first time, researchers report May 14 in Science Advances. The observation, made March 18, 2024, by the Perseverance rover, is also the first of an aurora from the surface of a planet that isn’t Earth. Moreover, it suggests future astronauts may witness ethereal Martian auroras with their own eyes. “It would be a dull or dim green glow to astronauts’ eyes,” says Roger Wiens, a planetary scientist at Purdue University in Lafayette, Ind.

Auroras can appear when charged particles from space interact with a planet’s atmosphere. They’ve already been spotted on Mercury, Jupiter and every other non-Earth planet in our solar system, but only from orbit. And in Mars’ sky, scientists had only been able to detect auroral wavelengths of light invisible to the naked eye, using instruments. So it wasn’t clear how Martian auroras would appear to future, landed astronauts.

On March 18, 2024, instruments aboard the Perseverance rover captured an image of a Martian aurora. Though relatively faint, the aurora’s green hues (left) can be made out by comparing the image with one of the typical inky Martian night (right). Due to the phenomenon’s subtle nature, the rover’s instruments were pointed at a low angle over the horizon to peer through a thick layer of the atmosphere. E.W. Knutsen et al/Science Advances 2025

Compared to many Earthly aurora photos, the new image from Mars is fuzzy. There are a couple reasons for that. First, Perseverance’s cameras perform less well at night, Wiens says. “The instruments aren’t tremendously more sensitive than human eyes,” he says.

And second, Mars doesn’t have a global magnetic field that concentrates auroras near its poles like Earth does. Instead, its crust is magnetized in patches. That means auroras can appear all over the planet, but they’re relatively dim. More

After 35 years, the Hubble Space Telescope is still churning out hits. In just the last year or so, scientists have used the school bus–sized observatory to confirm the first lone black hole, reveal new space rocks created by a NASA asteroid-impact mission and pinpoint the origin of a particularly intense, mysterious burst of radio waves.

These findings are a testament to the fact that there’s still plenty of science for the telescope to do. And there are some observations that simply can’t be done with any other telescope, including Hubble’s younger sibling, the James Webb Space Telescope. More

The carbon that once warmed Mars’ atmosphere has been locked in its rusty rocks for millennia. 

That’s the story revealed by a hidden cache of carbon-bearing minerals unearthed by NASA’s Curiosity rover along its route up a Martian mountain. The finding is the first evidence of a carbon cycle on the Red Planet, but also suggests that Mars lost its life-friendly climate because that carbon cycle was slow, researchers report in the April 18 Science. More

The James Webb Space Telescope has caught a distant galaxy blowing an unexpected bubble in the gas around it, just 330 million years after the Big Bang.

The galaxy, dubbed JADES-GS-z13-1, marks the earliest sign yet spotted of the era of cosmic reionization, a transformative period in the universe’s history when the first stars and galaxies began to reshape their environment, astronomers report in the March 27 Nature.

“It definitely puts a pin in the map of the first point where [reionization] very likely has already started,” says astrophysicist Joris Witstok at the University of Copenhagen. “No one had predicted that it would be this early” in the universe’s history. More

The nearest single star to the sun, Barnard’s star, has a brood of planets all its own. The red dwarf star, about six light-years from Earth, hosts four close-in planets each about two to three times the mass of Mars, astronomers report in the March 20 Astrophysical Journal Letters.

“Barnard’s star has a long history of claimed detections, but none of them could be confirmed for a long time,” says astronomer Ritvik Basant of the University of Chicago. “It’s pretty exciting to know what’s orbiting the nearest stars.” More