>>164843While the chemical ratios are unusual, perhaps this is to be expected from an object which may be a 10-billion-year-old time capsule from an earlier age of the universe. The main puzzle is how these metals ended up in the comet's coma.
“At the distances at which comets are observed, the temperature is far too low to vaporize silicate, sulfide, and metallic grains that contain nickel and iron atoms,” the team added.
“Therefore, the presence of nickel and iron atoms in cometary coma is extremely puzzling.”
The new paper reports the clear detection of nickel (Ni) and cyanide (CN), as reported by previous observations, and weak/no detection of the presence of iron (Fe).
In this work, the team was able to get a better spatial profile of the comet and its coma, mapping where the elements are originating.
"The Ni is more centrally concentrated than CN, with the majority of Ni flux coming from the innermost 2,000 km [1,243 miles] of 3I/ATLAS," the team explains.
"On the other hand, the radial profiles suggest that CN, though still concentrated near the nucleus, extends farther out into the coma."
The team suggests that nickel, which spreads out to around 594 kilometers (369 miles) and far less than cyanide at 841 kilometers (523 miles), may be released by an intermediate "parent" molecule which is quickly broken apart by solar radiation.
"Metals such as Ni may attach to PAHs to form Ni+PAH molecules (e.g., Ni-naphthalene Ni(C10H8) potentially).
These molecules are easily unbound by absorbing light and may produce centrally concentrated Ni, as observed in 3I/ATLAS," the team writes.
As well as this the team found other mysteries, including that the production rate of nickel relative to cyanide is "higher than 2I/Borisov and orders of magnitude above the solar system comet median.”
One particularly interesting aspect of the comet is that it has developed an "anti-tail" or "anti-solar tail", which is a tail pointed towards the Sun, backed up by the new paper.
Previously, sometimes-controversial Harvard astronomer Avi Loeb caused controversy (see) by suggesting in a paper with colleague Eric Keto, "This phenomenon, observed at a distance of 3.8 au from the Sun, is not common and possibly observed for the first time in 3I/ATLAS." However, before you suggest aliens like Loeb, it is not entirely unheard of.
There are two different types of anti-tail. One is actually an optical illusion, caused by the position of the comet and the Sun relative to Earth.
A second type – the one seen in 3I/ATLAS – happens when large grains are ejected from the comet, but do not get pushed away by the solar wind on the comet's Sun-facing side.
"While such a morphology is certainly unusual – given that dust tails are typically directed antisolar due to radiation pressure acting on dust grains – it is not without precedent among distant active bodies," a paper on the topic explains. "Notably, Farnham et al. (2021) reported a similar sunward enhancement in comet C/2014 UN271 (Bernardinelli–Bernstein), which they interpreted as the result of the slow ejection of relatively large dust particles predominantly from the sunlit hemisphere."
As always, more observations of these objects are needed to learn about them, and the environments they evolved in.
We will learn more by looking for more interstellar objects, something that will hopefully become easier when the Vera C. Rubin Telescope begins searching the skies.
When we do find more, we may even be able to catch up with them.
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