Interstellar comet 3I/ATLAS is once again visible from Earth after zooming in behind the sun, new images reveal.
Qicheng Zhang, a postdoctoral researcher at the observatory, later discovered that the comet was visible even with small telescopes, and posted an example on his comet blog on Sunday (Nov. 2). Chang said standard amateur telescopes should start picking up the comet across most of the Northern Hemisphere.
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“All we need is clear skies and a very low eastern horizon,” Zhang told Live Science on Friday. “It doesn’t look that impressive. It’s just a stain, but it’s going to get more noticeable over the next few days.”
Scientists have learned a lot about comet 3I/ATLAS since the comet was discovered in July. The comet, the only third interstellar object ever recorded, appears to be zooming through the solar system at speeds exceeding 130,000 miles per hour (210,000 kilometers per hour) in an unusually flat and straight orbit.
The comet flew around the sun on Thursday (October 29), reaching its closest point to the star, known as perihelion, and briefly disappearing from Earth’s view. The comet came within 1.4 astronomical units, or 130 million miles (210 million kilometers), of the Sun. But researchers and amateur astronomers used data from space telescopes to continue following the comet’s path even after it was hidden by the Sun.
On October 28, Zhang and his colleagues posted research results on the preprint server arXiv suggesting that comet 3I/ATLAS brightened rapidly prior to perihelion, making it noticeably bluer than the Sun. This is consistent with outgassing contributing to a significant portion of the visible brightness near perihelion. Zhang noted that the comet may still be brightening, but more data is needed to determine whether this is the case.
The Lowell Discovery Telescope is likely one of the largest telescopes that can point close enough to the horizon to observe Comet 3I/ATLAS just after perihelion, Chan said. From our vantage point, the comet is moving northward away from the northeastern horizon. Zhang pointed out that there is a window where you can observe the comet at dusk in the morning. At this time, the comet is just above the horizon, but the sun is still far enough below that the sky is not too bright.
Because time is a precious resource for large telescopes, Zhang is using a small telescope (with a 6-inch lens) to experiment and learn what conditions can be expected beyond the Lowell Discovery Telescope’s planned window. He was able to take a new image of the comet when it was about 16 degrees from the Sun (5 degrees above the horizon).
Zhang pointed out that radio observations have been made throughout the perihelion region of Comet 3I/ATLAS, and that someone else may have made post-perihelion optical observations before him, but no one else has seen them.
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We are entering an important period for 3I/ATLAS observations. As the comet approaches the star, it heats up, causing the ice on its surface to sublimate and turn into gas. This means researchers should be able to learn more about the composition of comets as they fly away from our star.
Although there is feverish speculation in the media that 3I/ATLAS is an alien spacecraft, most astronomers are convinced that this interstellar visitor is an ordinary comet from an unknown star system in the Milky Way. Comet 3I/ATLAS may be the oldest comet ever observed, with some studies suggesting it is about 3 billion years older than our solar system.
Some preliminary studies suggest that long-term exposure to cosmic radiation has deformed the interstellar travelers, giving them thick, irradiated crusts that no longer resemble their home systems. If so, it would be even more difficult for scientists to decipher the origin of comets. In any case, we can expect a flurry of new comet studies in the coming months as comet 3I/ATLAS reappears in the night sky.
“The comet is rising rapidly from the sun,” Zhang said. “I think within a week it will be about 25 or 30 degrees away from the sun. By then, a number of large telescopes around the world will also be able to start tracking the sun.”
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