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Space NASA Science

The Spin of a Star Reveals Its Age 67

eldavojohn writes "Some soon-to-be-published research on gyrochronology has yielded a possible method for more accurately determining a star's age. While determining the age of stars in clusters has been done using the patterns of its color and brightness, singular stars are much more difficult. By comparing established age information from clusters and analyzing the spin of stars, the researchers have established a defined relationship between color (mass), spin and age giving them the beginning of a guide of 'stellar clocks.' This was accomplished after four painstaking years of collecting data from 71 single dwarf members of the open cluster NGC6811 and establishing a model using data from Kepler."
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The Spin of a Star Reveals Its Age

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  • by Anonymous Coward

    Given that astronomy, in its modern form, only goes back a few hundred years at most (and even then, most of the knowledge was obtained within the past century), how can these scientists feel secure measuring events that span billions of years?

    • by Aquina ( 1923974 )
      Thats a bit to much philosophic for my taste. Science has concepts involved. Just think what we achieved so far. Things can be proven -- or the opposite.
    • Well, that's the joy of science. You work using models you can't disprove, until they are disproved, then you work under new models.

    • by Anonymous Coward

      Because of lots of hard work, math, observations, and more math. The paper is available in the first link in the summary if you want to read it and come up with legitimate criticisms instead of going with navel-gazing one-liner.

      If the technique Meibom et al. have proposed continues to hold up under further observations -- and it looks like there has already been quite a lot of testing -- this will be an awesome tool for astronomers. The age of a star tells you quite a lot, both about the star and about othe

    • If you point a telescope into deeper space you can effectively look further back in time. Maybe not the same thing as watching a single star get older, but it's better than sitting around for 6 billion years and watching paint dry. Hell, you might even be able to measure rotational period accurately enough to verify a theory.
    • by Kjella ( 173770 ) on Tuesday May 24, 2011 @07:53PM (#36234206) Homepage

      If you took photos of billions of people - but only one per person - could you get a decent idea of how humans age? Same with stars there's roughly 10,000,000,000,000,000,000,000 of them and there's many in every phase of life even though we pretty much only see a snapshot of each one. Take supernovas for example, a very short and rare event we haven't seen since 1604 in the Milky Way even though it has 200-400 billion stars. And yet we find 2-500 of them each year because there's so insanely many galaxies to look at. We won't have observed one star birth to death, but we will have observed everything from baby stars to stars in death throes many, many times.

    • Their measurements are not based on tracking these events as they unfold, like measuring distance with a perambulator. Thus the amount of time modern astronomy has been around for is irrelevant. Devising theories based on inferences from data, using logical reasoning, and attempts at falsification is a widely used method in science.
      Shall i risk the obligatory comparison?
      If i had a car...
      How about: Evolutionary biology has only been around for 150 years, how can these scientists feel secure measuri
      • Evolutionary biology has only been around for 150 years, how can these scientists feel secure measuring events that span millions of years?

        While I don't know the AC who made this particular anti-science rant, I would imagine the typical response to this would be "Yes! See? Evolution is wrong!"

        The underlying issues is a lack of understanding and confidence in science. The only way I know of to deal with the lack of confidence is to work on the understanding.

      • So how many years does a science need to be around before you feel secure in its ability to measure events that span millions of years? 200 years? 500 years? 1000 years? 10,000 years?

    • by khallow ( 566160 )

      Given that astronomy, in its modern form, only goes back a few hundred years at most (and even then, most of the knowledge was obtained within the past century), how can these scientists feel secure measuring events that span billions of years?

      Light, for example, is the same, no matter what the age of the source or how long it took to get to Earth. They aren't measuring events that spanned billions of years, they're measuring things like light. The interpretation follows very sound observations.

    • Because they build a chain of reasoning based on what is actually enormously well-known, mundane physics. We have only known about radioactive decay for just about one hundred years, but at this point we completely understand the process, understand how and why it represents a possible consistent clock, can validate the clock by looking back in time as we look at the light of stars given off in the remote past, and use it routinely to date things like the Earth itself, the fossil record, and the age of th
    • Simple answer; By looking at numerous similar objects, each being at a different stage on its order-of-billion-years life, and by assuming the laws of physics are the same everywhere (and everywhen).
  • by PhxBlue ( 562201 ) on Tuesday May 24, 2011 @06:25PM (#36233394) Homepage Journal
    The thesis makes a lot of sense. If stars lose mass as they age (stellar winds), that's going to affect their spin. Of course, the tricky part is (a) doing the math and (b) proving it.
  • ...otherwise how do you know the relationship holds true outside of that one cluster. Perhaps there was something special about the conditions in which that cluster formed. These people aren't amateurs and probably have good reason to believe these relationships hold true elsewhere, but since we're talking science, credentials mean squat and it should be repeated.

    • From the paper, they were using it to determine what stars were cluster members and what stars were field stars (i.e. stars which just happened to be in that direction). It has already been tested as a classifier to determine cluster members versus non-members. Whether it holds up as an absolute measure is another question, but it already holds "outside that one cluster" to a useful error rate.
  • Does this mean famous people won't be able to lie about their age anymore?
  • I'm happy enough with the idea that a star's mass determines its initial angular momentum (or, more likely, vice versa.) While not obviously true, it is certainly plausible. But once its angular momentum is set, how can it slow down? Here are all the possibilities I can think of:
    * It expands (radius increases) and so it can spin slower for the same angular momentum. However, this would be very uninteresting - if we have luminosity and temperature, we already know the radius. Adding an extra measurement whic

    • by Michael Woodhams ( 112247 ) on Tuesday May 24, 2011 @08:11PM (#36234402) Journal

      OK, I've done some cursory research (abstracts and intros of a few papers.) I didn't find a review, however it seems that there has been quite a bit written about such angular momentum transfers, and the age-rotational period-mass relationship for stars. (So this result is a step in an already developed field, not a breakthrough.)
      There was mention of interactions with a magnetized solar wind (i.e. a combination of my points 3 and 4 above) and also something called the Tayler-Spruit dynamo, which I think is about angular momentum transport between the star's core and envelope. For a young star, you'd expect the core to rotate faster than the envelope (conservation of angular momentum during the contraction) but the sun rotates like a solid body - same rotation period for all depths (or as far as we can probe by helioseismology.) The Tayler-Spruit appears to be a possible explanation for how a middle aged star like the sun can rotate like a solid body.

  • but it made my head spin. I know that I: am getting old; am red in the face; and am my father's son. Is this what they were talking about ?

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