As has been reported previously, there is something weird going on around a star which is a little over 1,400 light-years away. Astronomers are still baffled as to just what that is, and theories have ranged from a huge mass of comets to alien megastructures. Indeed, comets had become the leading explanation offered for the star’s odd behaviour, although that was really just the best of a bunch of ideas which all had flaws in them. Now, new research shows that the comet explanation is even less likely to be the answer, although the actual explanation is still as elusive as ever. Needless to say, this has resulted in a lot of discussion and debate in the past few months.
To say that 2015 has been a great year for planetary exploration would be an understatement, with fantastic new discoveries from around the Solar System. From our first ever close-up look at Pluto and its moons, to more evidence for ancient lakes and rivers on Mars (and current briny streams) to weird bright spots and mountains on Ceres, to the continuing study of Saturn and its moons, notably Enceladus, to spectacular close-up views of a comet, it has indeed been quite a year.
Comet 67P/Churyumov–Gerasimenko, or 67P, has been the focus of intense study by the Rosetta spacecraft since 2014. One of the key mysteries scientists have been trying to figure out is how the comet became the odd “rubber duck” shape that it is, with its two distinct lobes. Now they think they have the answer: Comet 67P was formed by the collision of two other, separate comets which fused together to form its distinctive shape.
Since August 2014, the Rosetta spacecraft has been orbiting Comet 67P/Churyumov-Gerasimenko, providing an unprecedented look at an active comet as it moves closer to the Sun in its orbit. As expected, the level of activity increased the closer the comet was to the Sun, with jets of water vapour, gas, and dust becoming bigger and more prominent. The comet reached perihelion, the closest point to the Sun on its orbit, on Aug. 13, 2015. For the first time ever, a spacecraft is observing this activity close-up, as it happens. But now, scientists have been noticing other dramatic and rapid changes on the comet’s surface as well, which haven’t been explained yet.
The impact of comet Shoemaker-Levy 9 into Jupiter in 1994 was a spectacular event for astronomers. The scars in Jupiter’s atmosphere lasted for weeks afterward; while those have long since faded, there are still other features of the impact visible even now, it was announced last Tuesday.
New evidence from the Spitzer Space Telescope suggests that there is a “storm” of comets surrounding a nearby star, Eta Corvi, which is about 60 light-years from Earth. It is thought to be similar to the “Late Heavy Bombardment” in our own solar system several billion years ago, when comets rained down on the planets and are believed to have brought water and organics to the early Earth. The same thing may be happening now at Eta Corvi, if there are any planets there.
“We believe we have direct evidence for an ongoing Late Heavy Bombardment in the nearby star system Eta Corvi, occurring about the same time as in our solar system,” said Carey Lisse, senior research scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., and lead author of a paper detailing the findings. “We think the Eta Corvi system should be studied in detail to learn more about the rain of impacting comets and other objects that may have started life on our own planet,” Lisse said.
The makeup of this comet cloud closely resembles comets in our solar system, and suggest that a giant comet may have been obliterated, perhaps when it collided with a planet. Water ice, organics and rock have all been identified in the comet cloud. There is also an even larger, colder ring of dust farther out from Eta Corvi, which resembles the Kuiper Belt of comets and other debris in our solar system, left over from the solar system’s formation.
All of these similarities reinforce the idea that the way in which our solar system formed is much like how other older ones formed in the past, and younger ones are still forming today, as a common process in the universe.
This article was first published on Examiner.com.
As a follow-on to the previous post, which newly proposed mission for NASA’s Discovery program would you like to see happen? Only one will be selected next year, to launch in 2016…