Astronomer Qicheng Zhang reportedly took new images of Comet 3I/ATLAS after it slipped behind the Sun on October 29. The images reveal that the interstellar visitor “glows green and hides its tail”.
According to a Live Science report, Qicheng Zhang, a researcher at the Lowell Observatory in Arizona, used the observatory’s powerful Discovery Telescope to make fresh observations of the interstellar comet as it moved away from the Sun on Wednesday (Nov. 5).
The comet recently became visible again after orbiting the far side of our star.
Green glow
According to the report, the researcher used the filter to detect carbon diatomic (C2) particles, which glow green.
He noted that there are many 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 for the same reason that if we stay in the sun too long without sunscreen, we get sunburned,” Zhang told Live Science.
Qicheng Zhang used the Lowell Observatory to observe Comet 3I/ATLAS in all its green glory.
“UV rays destroy our DNA (in our skin cells), which is kind of a similar type of molecule in the sense that it’s big and contains carbon.”
When this happens on a comet, some parts of the molecules are two carbon atoms stuck together, or diatomic carbon, which astronomers easily detect.
It was previously reported that the comet “changed color” when it got close to the Sun. She turned bright blue instead of the usual red.
3I/ATLAS used to be bluer: What does the new green color mean?
On Oct. 28, Zhang and his colleague published a study on the arXiv preprint server that suggested Comet 3I/ATLAS underwent rapid brightening before perihelion (when it approached the Sun) and was distinctly bluer than the Sun.
The green in the new image does not mean the comet changed color after perihelion — it could have changed color earlier, the report added.
Zhang said that in astronomical terms, bluer or redder usually refers to longer (red) or shorter (blue) wavelengths of light, with the new observation consistent with the latter.
The comet is much brighter when viewed with bluer filters than with redder filters, although bluer filters are more of a mixture of green and blue and are not really as sensitive to pure blue.
Hidden Tail 3I/ATLAS
The comet’s dust tail appears to be missing in the image, but it’s still there, Live Science reported.
Zhang told the media that if we look closely at the image, we can see that the left side of the comet is slightly brighter than the right side.
This slightly asymmetric glow occurs because we see the tail essentially head-on, and it’s directly behind the comet, curving slightly to the left.
In other words, the apparent absence of a comet’s tail is nothing to get excited about.
What we know about comet 3I/ATLAS
Comet 3I/ATLAS was only recently visible from Earth again after it briefly disappeared behind the Sun and reached 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, since comets tend to be at their most active at perihelion.
This comet, which NASA says originates from regions outside our solar system, was discovered this past July. The comet is only the third interstellar visitor ever recorded and could be the oldest comet ever observed, with one study suggesting it is about 3 billion years older than the Solar System.
