Comet ATLAS: What Happened to Its Tail Now That It's No Longer Tailing Anything?

Comet ATLAS or also known as C/2019 Y4 ATLAS was first discovered in December 2019 by space agencies' radars. By May 2020, the comet starts to be visible in the naked eye as it grew brighter.

But in April 2020, Hubble Space Telescope captured the disintegration of what would have been the brightest comet since 1997. The disintegration of Comet ATLAS revealed a glow from its pieces when it was still 91 million miles from Earth, with each bit of pieces as big as a house and resembles the headlight of a submarine in the deep sea.

Now, NASA and ESA's Solar Orbiter just flew near the remnants of comet ATLAS to see what happens to a comet's tail when it is no longer tailing anything.

Comet ATLAS Disintegration

The Hubble Space Telescope provided the sharpest views of the breakup of comet ATLAS in April 2020. The space telescope identified about 30 fragments on April 20 and 25 more fragments on April 23.

According to NASA, the fragments were all enveloped in a sunlight-swept tail of cometary dust that changed dramatically in a span of two days, so much that they had a hard time identifying them. Perhaps it is due to the flashing lights of the fragments or because different fragments appear at different times.

The image captured by Hubble shows that comet fragmentation is quite common. It might be a dominant mechanism among the solid, icy nuclei of comets when they die. However, astronomers are still uncertain about the cause of the fragmentation as it happens quickly and unpredictably. Nonetheless, the images by the Hubble offer new clues to the collapse of the comet.

The space telescope was able to distinguish fragments that are as big as a house, which could mean that the entire nucleus could have been as big as two football fields.

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Solar Orbiter Checks on Comet ATLAS Fragments

While the disintegration of C/2019 Y4 ATLAS was a disappointment, its tail still has stuck around. So, NASA and ESA's Solar Orbiter checked on what was left of the comet, Gizmodo reported.

Comets have ionic dust tails that streaks away from the nucleus. The Solar Orbiter's magnetometer measures the local magnetic fields of the tail to see how it interacted with the magnetic field carried through the Solar System by the solar wind.

The team of scientists found that the interplanetary magnetic field bends around the comet, while the central tail of the comet has a weaker magnetic field. In a press release by the Royal Astronomical Society, scientists said that the combination of the magnetic field and ions of the comet's melting nucleus produced the comet's ionic tail.

"This is quite a unique event, and an exciting opportunity for us to study the makeup and structure of comet tails in unprecedented detail," solar physicist Lorenzo Matteini of Imperial College London and lead researcher said in the same press release. "Hopefully with the Parker Solar Probe and Solar Orbiter now orbiting the Sun closer than ever before, these events may become much more common in future!"