I'm surprised this isn't getting more coverage. At the same time, I wouldn't really put much faith in it. The evidence that this is from another star system is based purely on simulations of the solar system formation, and given the problems of getting planets to form in the right places I wouldn't particularly trust results with regards to an individual asteroid.
The latest discovery marks the first time an asteroid that appears to be a permanent member of our solar system has been revealed as having its origins in another star system. ‘Oumuamua, an asteroid spotted hurtling through our solar system earlier this year, was only on a fleeting visit.
Known as asteroid 2015 BZ509, the permanent visitor is about 3km across and was first spotted in late 2014 by the Pan-Starrs project at the Haleakala Observatory in Hawaii. Experts quickly realised the asteroid travelled around the sun in the opposite direction to the planets – a retrograde orbit.
Writing in the Monthly Notices of the Royal Astronomical Society, Namouni and co-author Dr Helena Morais from São Paulo State University in Brazil describe how they developed a new computer model that allowed them to produce a million possibilities for the asteroid’s orbit, each with tiny differences, and trace their evolution.
To the team’s surprise, the results reveal that the asteroid’s orbit appears most likely to have remained very similar and linked to Jupiter for 4.5bn years – in other words, since the end of planet formation. “That was completely unexpected,” said Namouni.
The discovery provides vital clues as to the asteroid’s origins. “It couldn’t be debris of the solar system because at 4.5bn years, all objects, planets, asteroids, comets in the solar system are going around the solar system in the same direction,” he said, adding that the model suggests the most likely explanation is that the asteroid was captured by Jupiter as it hurtled through the solar system from interstellar space. “It means it is an alien to the solar system,” he said.
[But this is not evidence that the asteroid has been stable for that long, it's just a simulation showing that this scenario is compatible with observations. We have no way of knowing how long this asteroid has actually been in its present orbit.]
https://www.theguardian.com/science/2018/may/21/retrograde-asteroid-is-interstellar-immigrant-scientists-say?CMP=share_btn_gp
This may or may not be true in any number of possibly overlapping multiverses.
ReplyDeleteSo the reason this one didn't depart Sol's sphere of influence with the same velocity it arrived with is because it interacted with Jupiter?
ReplyDeleteI assume so. Why it can't just be an asteroid that's scattered off something else into a strange orbit, I don't know.
ReplyDeleteYeah. Extraordinary claims need extraordinary evidence.
ReplyDeleteIndeed. Extraordinary evidence often warrants extraordinary claims, though, but I have no feel for what's weirder : a backwards-moving asteroid from our own Solar System or one from outside it that's remained in a stable orbit for billions of years.
ReplyDeleteI thought the article said they estimated it had been in our system for about 10,000 years. I skimmed it, tho.
ReplyDeleteI think the 10,000 years reference is only in relation to other retrograde asteroids, but not this one :
ReplyDelete... while previous studies suggested retrograde centaurs stay gravitationally “tied” to planets for 10,000 years at most, recent work had suggested this asteroid’s orbit had been linked to Jupiter for far longer... To the team’s surprise, the results reveal that the asteroid’s orbit appears most likely to have remained very similar and linked to Jupiter for 4.5bn years – in other words, since the end of planet formation.