Astronomers know comets disintegrate during their long, meandering journey through our solar system. We usually see a comet’s life end as they swing way too close to the sun. These are known as sungrazers. But comets can begin to break up much further away from the sun. Earlier this year, NASA’s Hubble Space Telescope captured a series of images showing the immediate aftermath of a portion of a comet breaking off.
We just learned about Comet 332P/Ikeya-Murakami in 2010, but it is no stranger to our neck of the woods. The comet is estimated to be about 4.5 billion years old.
On January 26th, Hubble captured this series of images over a three-day period:
We can see about 25 separate pieces in the animation above. Each one measures 65 feet to 200 feet wide with the entire collection stretching for 3,000 miles. And they are spreading out at a few miles per hour.
What makes the observations above special is that astronomers can see how the pieces change from day to day. “And that has allowed us to make the best measurements ever obtained on such an object,” says lead researcher David Jewitt from the University of California at Los Angeles.
So, what do the Hubble observations tell us besides the number and size of the pieces? We can see individual pieces brighten and then dim. Especially, on the right side. Those pieces are rotating into sunlight and then back out. Plus, astronomers estimate that all the building-size pieces make up about 4% of the parent comet. You can see it shining brightly to the left of its fragments.
As for the main chunk of comet? Astronomers estimate it completes a rotation every two to four hours. If you were parked on the surface, you would see the sun rise and set every hour or two. Comet 332P is also much smaller than originally thought. Observations based on the Hubble images point to the comet measuring about 1,600 feet across, or about five football fields. Maybe not that big for astronomers, but five football fields stretched out is pretty damn big.
Now, that we know more about Comet 332P – what caused it to lose 4% of itself? It was still 150 million miles away from the sun when a chunk broke off.
While it didn’t experience the dramatic flare outs sungrazing comets see, Comet 332P still feels the effects of the sun that far out. Jewitt and his colleagues suggest sunlight heated up the comet, which caused jets of gas and dust to erupt from its surface. Remember Deep Impact?
Kind of like that. In Comet 332P’s, it’s so small that the jets of gas act more like thrusters and makes the comet spin faster. As it spins faster, chunks of the comet loosen and drift into space.
The research team believes the fragmentation continues on the ejected pieces. “Our analysis shows that the smaller fragments are not as abundant as one might expect based on the number of bigger chunks,” said Jewitt.
Jewitt went on to talk about how the idea around comets dying is changing. “In the past, astronomers thought that comets die when they are warmed by sunlight, causing their ices to simply vaporize away,” Jewitt said. “Either nothing would be left over or there would be a dead hulk of material where an active comet used to be. But it’s starting to look like fragmentation may be more important. In Comet 332P we may be seeing a comet fragmenting itself into oblivion.”
How much longer does Comet 332P have? For much of its 4.5 billion year life, the comet enjoyed it undisturbed in Kuiper Belt. But the gravitational tug from Neptune pulled it into the inner solar system. And sealed its fate. The research team thinks Comet 332P has enough mass to handle another 25 similar fragmentations. If one fragmentation event happens every trip around the sun, Comet 332P will be history in 150 years. Way to go Neptune.