We have both good and bad news coming in from the astronomy community. The good news is that the Hubble Space Telescope managed to capture some once-in-a-decade images of a fragmenting comet. The bad news is that the very same comet was expected to put on an extraordinary, luminous show for skywatchers in May—something that almost certainly will not happen now.
Like exploding aerial fireworks shells, comet ATLAS is breaking apart into more than 30 pieces, each roughly the size of a house. Hubble captured detailed images of the breakup last week: https://t.co/PYcgDD64hA pic.twitter.com/hV2n2OrVnY— Hubble (@NASAHubble) April 28, 2020
Gizmodo picked up on the good-slash-bad news, which was recently announced by NASA (among others). According to NASA’s post, Hubble identified 30 fragments of the comet (dubbed C/2019 Y4 or Comet ATLAS) on April 20, then 25 fragments on April 23. Comet ATLAS was first spotted in December of last year by the Asteroid Terrestrial-impact Last Alert System (or ATLAS), a robotic astronomical survey and early warning system developed and operated by the University of Hawaii’s Institute for Astronomy.
“This [comet breakup] is really exciting—both because such events are super cool to watch and because they do not happen very often,” said Quanzhi Ye of the University of Maryland, College Park. Ye is the leader of one of the two Hubble teams that captured the breakup. Ye added that “Most comets that fragment are too dim to see,” and that “Events at such scale only happen once or twice a decade.”
Comet ATLAS’s fragments on April 20 and April 23. NASA, ESA, D. Jewitt
Ye and the other researchers involved in studying the breakup of Comet ATLAS say that this instance is evidence that comet fragmentation is likely common. The researchers note that fragmentation may even be the most prevalent method by which the solid nuclei of comets “die.” (Recall that a comet’s nucleus is its solid, central part made up of frozen gases, dust, and rock.)
Although the cause of Comet ATLAS’ breakup is not confirmed as of now, some astronomy outlets (e.g. Sky & Telescope) have said that accelerating spin is a likely catalyst for nuclear breakups in comets in general. This accelerating spin would—probably—be the result of jets of gas blasting from the surface of a given comet’s nucleus. That gas would be catalyzed by the Sun’s heating of the comet as it approaches perihelion (the point at which an orbiting body is closest to the Sun).
UCLA professor David Jewitt, the leader of the other Hubble team to capture the breakup of Comet ATLAS, said in a UCLA News report that “Suddenly, [Comet ATLAS] been thrust into the hot zone near the sun and the stress of the new environment is causing it to disintegrate.” Jewitt added that “It is quite special to get a look with Hubble at this dying comet.”
Prior to the confirmed breakup of Comet ATLAS, skywatchers were hoping to be able to see it with the naked eye in May. NASA, unfortunately, now says that “If any of it survives, the comet will make its closest approach to Earth on May 23 at a distance of about 72 million miles….” Essentially, that means it may not be visible at all.
What do you think about these images of Comet ATLAS breaking up? Do you think we’ll still be able to see any fragments of it in May during its closest approach to Earth? Let us know your thoughts in the comments!
Feature image: NASA, ESA, D. Jewitt