On Not-Spiraling Out of Control

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.

Unknown Force Kicks Stars Out of Milky Way. Really.

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.

Speeding stars pose puzzle to scientists: What got them moving?

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.


  9 comments for “On Not-Spiraling Out of Control

  1. January 11, 2014 at 2:43 PM

    2014 looks to be an exciting year for science in general, not just astronomy/astrophysics. So many scientific “certainties & immovable laws” seem to have been burst in 2013, & looking forward to the remaking & new explanations for stellar phenomena. I also look forward to the damn skies in northern France being clearer of bloody clouds to see the stellar fireworks. Was great watching the night sky without light pollution & so many clouds, when visited sis in law to be in the Morbihan, in the south of Bretagne, in ass end of nowhere in countryside. Lying on my back with a cool beer watching meteor showers, shooting stars & the constellations revolving around us was spectacular. Roll on another year of new scientific discovery.

    • Frederick
      January 11, 2014 at 3:03 PM

      I used to lived in countryside, i was raised there, rural Quebec, We could just walk in the field behind the house ( with the telescope) to escape the powerful automatic light that blast white light all over the long driveway, But we also could just pull the break shift, me and my brother, sitting beside the car with music, beer and magic smoke lol. Now i lived in a city, i like it, but i missed the sky ( although it is a small city not Montreal ( our paris in you case) so not to bad :-) ) ah que de souvenir!

  2. Lagaya1
    January 11, 2014 at 4:24 PM

    Doesn’t it make more sense that a star passing through our galaxy’s core originated elsewhere; rather than as a part of our galaxy, suddenly taking off in a wayward direction?

    I’m not educated in astronomy, so forgive me if ignorant about this. Just seems that the laws of physics would better support a motion through as opposed to a deviation within.

    • January 12, 2014 at 3:24 AM

      Just a guess, but travel between galaxies takes a long time. Even coming from the Magellanic Clouds, (slightly less than 50 kiloparsecs ≈163,000 light-years. sez Wiki) a star would age significantly. The stars observed are too young to have traveled that far. (“The stars travel at over 1.5 million kilometers per hour” quote from an article.) One light year = just under 9.5 trillion kilometres.

      • Lagaya1
        January 12, 2014 at 12:59 PM

        Oh, thanks! The more I thought about it, the more I realized that the stars went “rogue” from SOME galaxy, whether near or far. With that in mind, near makes more sense. Your explanation about the ages of the stars seems to confirm that. I am a bit embarrassed by my lack of knowledge in this area, and appreciate the info!

  3. Brian
    January 11, 2014 at 5:26 PM

    *sigh* I am gonna get smacked for this, but- what if the ‘stars’ are actually faster than light craft? I read somewhere that a faster than light craft, while hurtling along, would look just like a sun, flying off somewhere.

    • Blargh
      January 11, 2014 at 8:14 PM

      @ Brian
      If you have a link to a paper, I’d like to read it!
      But my immediate response is: sure, that might be… iff they radiate the black-body radiation of an equivalent star, they don’t move any faster than stars in the galaxy, and they don’t ever accelerate (i.e. they’re hurtling through space on inertia alone).

      But here’s the thing: we know that black-body radiation exists. We know stars exist, and what powers them. That allows us to predict a spectrum. Furthermore, parallax allows us to measure their distance and velocity.
      And so far, we have not seen a star with a radiation signature to suggest anything other than “huge hot black-body”, and we have not seen a single astronomical object accelerate of its own accord.
      From there, it’s all Occam’s razor…

  4. Randy Griffin
    January 12, 2014 at 8:58 AM

    The phrase “Most stars in our galaxy move spirally” bothers me. Orbits are ellipses, not spirals. While stars make up the visually appealing arms in spiral galaxies, each star is still in an elliptical orbit about the galaxy’s center of mass.

    • January 13, 2014 at 7:41 PM

      That’s a good point, Randy. Should have been more careful with the language there; you don’t pay close enough attention to the verbal imagery you’re using, and it’ll spiral away from you. ;-)

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