Irradiated Comet 3I/ATLAS glows green and hides its tail in new image
A new image of the comet 3I/ATLAS revealed that the interstellar visitor glows green and hides its tail, but that doesn’t mean there’s anything wrong.
Comets develop an atmosphere, or comabecause they fly close to the sun. This cloud of gas and dust grows larger and brighter as the sun heats the comet’s ice and other materials, which sublimate into gas that astronomers can observe. In this case, the atmosphere is brighter when viewed with a green filter, as with most comets that fly near our star.
Zhang used a filter to detect diatomic carbon (C2) particles that glow green. He noted that there are a set of large molecules in the comet that contain carbon and hydrogen (hydrocarbons). And when the comet approaches the sun, ultraviolet (UV) light breaks these molecules apart.
“It’s kind of the same reason that if we stay in the sun too long without sunscreen, we get sunburned,” Zhang told Live Science. “UV rays destroy our DNA [in our skin cells]which is a similar type of molecule in that it is large and contains carbon. »
When this happens on a comet, some molecule fragments are made of two carbon atoms stuck together, or diatomic carbon, which are easy for astronomers to detect.
The comet doesn’t appear to have a dust tail in the image, but it’s still there. Zhang noted that if you look closely at the image, you can see that it is a little brighter on the left side of the comet than on the right. This slight asymmetrical glow occurs because we are seeing the tail mostly head-on, and it is just behind the comet, curving slightly to the left. In other words, the comet’s apparent lack of tail is nothing to get excited about.
Comet 3I/ATLAS became a celestial celebrity since its discovery in July. Much of this buzz comes from speculation that the comet could be an alien spaceshipeven though most astronomers are convinced that the interstellar visitor is a comet from a unknown star system in the Milky Way.
However, to describe 3I/ATLAS as just an ordinary comet would be an injustice to this rare interloper in the solar system. The comet is only the third interstellar visitor ever recorded and could be the the oldest comet ever seena study suggesting it is about 3 billion years older than the solar system.
Comet 3I/ATLAS only recently became visible from Earth again after briefly disappearing behind the sun, reaching its closest point to our star, known as perihelion, on October 29. This post-perihelion phase opens a critical window for astronomers hoping to learn more about the comet’s gases and composition, because comets tend to be most active at perihelion.
Preliminary research suggests that prolonged exposure to space radiation gave comet 3I/ATLAS a thick irradiated crust that no longer resembles its original star system. If confirmed, this crust could mean scientists will have a harder time deciphering the origins of 3I/ATLAS, as it will be shedding irradiated material rather than virgin material from its original star system.
Zhang has already used the Lowell Discovery telescope to obtain a first post-perihelion optical glimpse of 3I/ATLAS from Earth on Halloween (October 31). As with its first sighting, the new sighting was made at morning twilight. From our perspective, the comet is moving north, away from the northeast horizon. Currently, it is possible to observe the comet early in the morning, when it rises above the horizon.
Zhang took several images of the comet with different filters. The image of diatomic carbon, which he first published on his Comet blog Wednesday, roughly described what the comet might look like if humans were able to see it with the naked eye.
On October 28, Zhang and his colleague published a study on the preprint server. arXiv which suggested that comet 3I/ATLAS had undergone rapid lightening before perihelion and was significantly bluer than the sun. The green in the new image doesn’t mean the comet changed color after perihelion – it might. changed color before.
Zhang noted that in astronomical terms, bluer or redder generally refers to longer (red) or shorter (blue) wavelengths of light, with the new observation corresponding to the latter. The comet is much brighter when viewed with bluer filters than with redder filters, although the bluer filters are more of a mixture of green and blue, and are not really sensitive to pure blue.
“It’s the bluest filter we have that’s the brightest,” Zhang said.
The Lowell Discovery Telescope was likely one of the largest telescopes capable of pointing close enough to the horizon to see Comet 3I/ATLAS immediately after perihelion, according to Zhang. However, he noted that the comet is now high enough above the horizon for a number of large telescopes to make observations – small personal telescopes with a 6-inch (15-centimeter) objective lens can also spot it.
Expect a host of interesting discoveries about the comet in the coming months.
