The interstellar comet 3I/ATLAS It is the third body coming from outside the Solar system recorded, which is why it has garnered enormous attention since it was discovered in July. Last week it reached its perihelionits closest approach to Sunbut passing, from Earth’s perspective, behind him. After placing the October 29 just 1.4 astronomical units –210 million kilometers– of the Sun, has once again been visible from the Earth and an astronomer has published the first new images of 3I/ATLAS.
The image was captured on October 31 with the Lowell Observatory Discovery Telescopein Arizona. Qicheng Zhanga postdoctoral researcher at the observatory, also discovered that 3I/ATLAS, which travels to 210,000 km/h and follow a path unusually flat and straightis already visible not only for large telescopes like Discovery, but also for standard telescopes such as those used by amateurs.
How to observe 3I/ATLAS with a standard telescope
‘All you need is a clear sky and a very low eastern horizon. It won’t look very impressive, just a stain, but it will be a stain increasingly visible in the coming days‘, the astronomer told Live Science.
The discovery, which will interest amateur astronomers around the world, came by chance. The operating time of large telescopes is a valuable resource, so Zhang also uses a small telescope with a 6-inch lens to anticipate conditions ahead of their scheduled shifts on Discovery.
Zhang points out that there are a window of opportunity to observe it during the morning twilightwhen the comet is just above the horizon but the Sun is still low enough that the sky is not too bright. At the time of capturing the new image with Discovery, the comet was about 16 degrees from the Sun (5 degrees above the horizon).
Zhang has also published an image of 3I/ATLAS on his Cometary blog captured with his own telescope. According to the astronomer, standard amateur telescopes should now begin to detect it in much of the northern hemisphere.
‘The comet is rising rapidly from the Sun. I think in a week it will be about 25 or 30 degrees from the Sunat which point there will be a large number of other important telescopes around the world that will also be able to begin to follow it,’ he explained to the media.
Why does 3I/ATLAS get brighter as it gets closer to the Sun?
On October 28, Zhang and his colleague Karl Battams published a study suggesting that comet 3I/ATLAS experienced a rapid increase in brightness before perihelion and was noticeably bluer than the Sun -showed proportionally more light at short (blue) wavelengths-, which coincides with increased gas emissions contributing to visible glow. Zhang noted that the comet could continue to brighten, although more data is needed to confirm this.
This is related to the phenomenon of sublimation. Comets heat up as they approach stars, causing the ice on their surface to sublimate –change state– and turns into gas, which has a double effect. On the one hand, the gas drags dust that makes it grow the comma -the diffuse cloud of gas and dust that surrounds the core- and the tailwhich are always much larger than the comet’s nucleus. On the other hand, As there is more gas and dust, there is more surface area that reflects and emits light and, therefore, more apparent brightness. Some gases emit light in specific lines (through fluorescence, photoionization, etc.), often in the blue/green.
These phenomena will allow researchers to learn more about the comet’s composition as it moves away from our star. One study has suggested that 3I/ATLAS could be the oldest comet ever observed, 3 billion years older than the solar system.
Other research indicates that prolonged exposure to space radiation from 3I/ATLAS has transformed the cometgiving it a thick irradiated crust that no longer resembles its system of origin. If so, scientists will have a harder time deciphering its origins. In any case, expect a flurry of new studies on 3I/ATLAS in the coming weeks and months as the comet approaches Earth. It will reach its closest point next December 19.