A stunning new telescope image has revealed the growing tail of the interstellar comet 3I/ATLAS. The luminous limb is starting to take shape as the icy interloper zooms ever closer to the sun on its one-way trip through the solar system.
3I/ATLAS is a roughly 7-mile-wide (11 kilometers) comet that was first spotted in early July and is zooming toward us from beyond the asteroid belt between Jupiter and Mars. Scientists quickly realized that the superfast object did not originate within our cosmic neighborhood. Instead, it was likely ejected from a distant star within the Milky Way and is now passing by us as it flies through the galaxy. It is unclear exactly where the comet originated, but initial findings hint that it is likely much older than the solar system.
On Aug. 27, astronomers at the Gemini South telescope in the Chilean Andes captured a detailed new photo of 3I/ATLAS, revealing the first clear look at the comet's tail. This plume of ice and dust is blown away from the comet by the solar wind, the stream of charged particles emanating from the sun. The tail is only starting to appear now, as the comet's frozen shell, or nucleus, soaks up more solar radiation, causing it to expel more particles from its icy surface. The tail will continue to grow as the comet gets closer to the sun in the coming months and will eventually become several times wider than the comet itself.
The new photo also shows a fuzzy cloud of ice and dust surrounding the comet. This cloud, known as a coma, will continue to swell as the comet is further heated by the sun. This will allow the comet to reflect more light that causes it to appear brighter in the night sky, although it will not become visible to the naked eye.
These classic cometary features are further proof that 3I/ATLAS is a natural object and not an extraterrestrial probe, which has been controversially proposed by some scientists with little to no supporting evidence.
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3I/ATLAS is the third — and likely the largest — interstellar object ever discovered. It follows the past sightings of the mysterious object 'Oumuamua in 2017, which was also misidentified as a potential alien spacecraft, and Comet Borisov in 2019, which also grew a stunning tail.
The current extrasolar entity is shooting toward the sun at more than 130,000 mph (210,000 km/h) and will make a close approach to Mars next month, allowing Mars-orbiting spacecraft to get a better look at the comet and its tail, Live Science's sister site Space.com recently reported.
3I/ATLAS will reach perihelion, its closest point to the sun, on Oct. 29. But it will be on the opposite side of our home star as Earth, meaning we will lose sight of it during this time and may miss out on seeing its tail at its peak size. The comet will reach its minimum distance to Earth in December, when it will come within 170 million miles (275 million km) of our planet — around 700 times farther than Earth is from the moon — before beginning its long journey back out of the solar system.
Astronomers are racing to study the object as much as possible over the next year or so, to learn more about where it came from and how different star systems form and evolve. Recent observations from the James Webb Space Telescope hint that 3I/ATLAS has unusually high levels of water and carbon dioxide compared with other known comets. Additional photos of the comet, including a detailed shot from the Hubble Space Telescope and a colorful image from the Gemini North telescope in Hawaii, have also shed light on its composition.
Each new shot of the comet also acts as a permanent reminder of this rare cosmic encounter.
"As 3I/ATLAS speeds back into the depths of interstellar space, this [new] image is both a scientific milestone and a source of wonder," Karen Meech, an astronomer at the University of Hawaii and part of the Gemini observatories team, said in a statement. "It reminds us that our solar system is just one part of a vast and dynamic galaxy — and that even the most fleeting visitors can leave a lasting impact."
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