The interstellar comet 3I/ATLAS is heading out of the inner solar system and is set to make its closest approach to Earth this week. According to the European Space Agency (ESA), the comet will be at around 270 million kilometres from Earth on December 19, offering scientists a closer look at its puzzling characteristics. 3I/ATLAS was discovered by the NASA-funded ATLAS (Asteroid Terrestrial-impact Last Alert System) survey telescope in Rio Hurtado, Chile on July 1.
It soon became the third confirmed interstellar object to visit our solar system when astronomers calculated its extreme hyperbolic trajectory. Here’s all you need to know about this strange visitor.
Comet 3I/ATLAS and its mysteries
While NASA confirmed last month that 3I/ATLAS is indeed a comet and not a potential alien spacecraft (as suggested by Harvard scientist Avi Loeb), its characteristics are unusual. For one, it lacks a visible, millions of kilometres long tail in several pictures, which has led many to suspect that the comet may have an extraterrestrial origin. Besides, spectroscopic observations initially revealed that 3I/ATLAS had a higher nickel content than iron, unlike other comets, and a high nickel-to-cyanide ratio.
Dr. Cyrielle Opitom, astronomer at Scotland’s University of Edinburgh, who has published many papers on 3I/ATLAS based on observations of the European Southern Observatory’s (ESO) Very Large Telescope, explains in the video below that high nickel emission from the comet was “very surprising.”
Scientists determine the chemical makeup of a comet through spectroscopic data. Spectroscopy is the method of studying light that materials emit, absorb, transmit, or reflect. Light beams carry information (like a barcode) about the regions they’ve emerged from and areas they’ve travelled through. By analysing the ‘spectra’ or different wavelengths of light, spectroscopes can reveal what things are made of, how hot they are, how dense they are, and how fast they are moving in space.
Comet 3I/ATLAS has an icy nucleus few metres to a few kilometres wide, like all comets do, and has a cloud of gas and dust around the nucleus called the coma. Interestingly, spectroscopic measurements revealed that the comet’s composition changed as expected after it reached closest point to the Sun (perihelion) on October 29. Astrophysicist Suzanna Randall from the ESO says that its iron to nickel ratio is now similar to solar system comets.
Another ‘anomaly’ highlighted by Loeb, was the comet’s unusual brightness after perihelion. This bolstered the theory of 3I/ATLAS being an alien spaceship. Opitom said that this is usual for comets that either undergo an explosion in the nucleus or fragmentation.
An ‘anti-tail’ was also cited as an anomaly, as a result of material spewing in the direction of the Sun. Loeb published a blog on the anti-tail today, saying it has grown longer than the distance between Earth and the Moon. According to Opitom, anti-tail forms because the radiation pressure from the Sun may not be strong enough to push large materials behind the comet.
ALSO READ: ESA Drops Surprise Preview Of Comet 3I/ATLAS Images From JUICE Spacecraft
Why study comet 3I/ATLAS?
Comets like 3I/ATLAS, especially the interstellar ones, carry information about other star systems. ESA says that 3I/ATLAS might be billions of years old, possibly older than our solar system, and its analysis could reveal what environments it was formed in.
There are two other comets – 1I/Oumuamua and 2I/Borisov – that visited our solar system in 2017 and 2019, respectively but none are being studied as extensively as 3I/ATLAS. Notably, Loeb had posited that Oumuamua may also be an alien spacecraft, but it wasn’t.
Meanwhile, NASA and ESA along with other institutions are preparing to point there telescopes to get a better look at 3I/ATLAS. The former recently released pictures taken by numerous spacecraft and space telescopes.
ALSO READ: Interstellar Comet 3I/ATLAS Captured In Ghostly X-ray Image By ESA Telescope
