It’s already turning out to be an exciting year in astronomy – at the 223rd meeting of the American Astronomical Society, news has broken of the discovery of 20 stars whose velocities and trajectories challenge existing models. Most stars in our galaxy
move orbit such that they appear arranged spirally along the same approximate path relative to its center. But some do not.
At least a few stars, however, are headed somewhere else entirely, and in a big hurry. They’re known as hypervelocity stars, and they’re going so fast that they’re on their way out of the Milky Way altogether. While the astronomers think they have an explanation for the 18 hypervelocity stars discovered since 2005, a new group of 20, just announced at a meeting of the American Astronomical Society outside of Washington, DC, seems to make no sense at all.
Astronomers already understand quite a bit about hypervelocity stars and modeling their acceleration (Universe Today). What makes this new group of stars exciting is that they do not appear to have originated from our own galaxy’s core, as in the case with the rest discovered since 2005.
According to Vanderbilt University’s press release:
“The original hypervelocity stars are large blue stars and appear to have originated from the galactic center. Our new stars are relatively small – about the size of the sun – and the surprising part is that none of them appear to come from the galactic core.”
While some press releases have been performing the usual mystery mongering, with cries of “astronomers baffled,” this discovery is exciting because it will add to our understanding of stellar orbits.
This also isn’t the final word. More verification is needed.
Holly-Bockelmann notes that additional observations are needed to truly nail down the velocities of the stars in the team’s sample. The effort requires the use of two ways of measuring the velocity, one of which can introduce significant errors in the estimates if too few observations are used.
Yet even if only one of the 20 turns out to be a hypervelocity star, “that’s still a pretty big discovery,” she says, noting that it would raise interesting questions about how these cooler, lower-mass hypervelocity stars initially got the boot.