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More to the North Star Than Meets the Eye

Posted by ScuttleMonkey on Mon Jan 09, 2006 01:35 PM
from the polaris-trifecta dept.
Space News
__roo writes "By stretching the capabilities of NASA's Hubble Space Telescope to the limit, astronomers have photographed the close companion of Polaris for the first time. This sequence of images shows that the North Star, Polaris is really a triple star system. 'The star we observed is so close to Polaris that we needed every available bit of Hubble's resolution to see it'" said astronomer Nancy Evans of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts."
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  • Just Beyond The Capabilities of My 125 ETX (Score:3, Insightful)

    by ackthpt (218170) * on Monday January 09 2006, @01:36PM (#14429274) Homepage Journal
    Cool as beans, but still won't save dear old Hubble, will it? The one thing Hubble can't find, no matter how much straining of limits is the willingness of NASA to save the faithful servant. With recent budget cuts for Katrina and the on-going war, don't hold your breath for a reprieve.

    they should nickname the mini star, Cooper

    Got an ETX for Christmas? You should know this site. [weasner.com]

    • Re:Just Beyond The Capabilities of My 125 ETX (Score:4, Informative)

      by artitumis (934987) on Monday January 09 2006, @01:43PM (#14429350) Homepage

      The Hubble already has a repalcement in the works. It is called The James Webb Space Telescope and is scheduled to go up in 2013. More about the JWST [nasa.gov]

      • Re:Just Beyond The Capabilities of My 125 ETX (Score:5, Informative)

        by Rolan (20257) * on Monday January 09 2006, @02:17PM (#14429652) Homepage Journal
        Yes, someone always posts this when the death of the hubble is brought up, but what they never do is pay attention that the JWST can't see all that Hubble sees. They're built to look at different parts of the spectrum (yes, there is overlap), so one will never actually replace the capabilites of the other. They would however complement eachother's abilities.
    • Actually, I'm not sure that there's anything in this observation that Hubble is needed for. AO is limited in the ultraviolet, but this observation could have been made in the visisble spectrum, I would expect. As such, any of the more recent large telescopes with AO should have been able to make this observation. It just so happens that it was done with Hubble instead.

      For those not aware, AO is "Addaptive Optics". This is how you use ground-based scopes, but compensate for the atmosphere. It usually involves deforming a physical mirror, though I think there are some AO systems that work purely digitally. I'm not sure. IANAA.

      AO was perfected after Hubble went up, and many ground-based scopes have gotten imaging that's just as detailed (more so in some cases) as Hubble is capable of. I have an astronomer friend who was fond of showing off some photos that he had from AO scopes off of relatively old, retrofitted systems that he claimed were better imaging that Hubble had been able to get from the same objects.
    • Cool as beans, but still won't save dear old Hubble, will it? The one thing Hubble can't find, no matter how much straining of limits is the willingness of NASA to save the faithful servant. With recent budget cuts for Katrina and the on-going war, don't hold your breath for a reprieve.

      Or, better yet, we could scrap hubble and use the money we saved to build a telescope twice as powerful for half as much, including giving it a properly ground mirror this time.

  • Not Informative (Score:5, Funny)

    by saskboy (600063) on Monday January 09 2006, @01:39PM (#14429306) Homepage Journal
    "sequence of images shows that the North Star, Polaris is really a triple star system."

    Damit! OK, so which star do I point my sextant at then if I'm trying to find my latitude? Modern science complicates things so much!

    [Yes this is a joke, for those who don't get astronomy humour.]
    • Call me a luddite but I still use an astrolabe....
          • Certainly not every Christian looks to superstition to "prove" their faith. But I don't even have to go to creationism to prove my point (which is too easy a target anyway), I only have to go to the current news... Pat Robertson's comments about Ariel Sharon's stroke being divine retribution.

            I think for fun, I'll keep a lookout for someone making this point.

  • Looks like the Bard screwed that up... (Score:3, Funny)

    by Gandalf_the_Beardy (894476) on Monday January 09 2006, @01:40PM (#14429320)
    "I am as constant as the Northern Star." Always though Caesar was a little unstable and went round and round in circles....
  • Another day, another star. Yet this one is important because it is the companion of Polaris? When do we get to see the edge of the universe cafe?

    • Re:More. (Score:3, Informative)

      by hattig (47930)
      As the FA points out: "it is the nearest Cepheid variable star. Cepheids' brightness variations are used to measure the distances of galaxies and the expansion rate of the universe"

      So quite useful in astronomy.

    • Re:More. (Score:2, Informative)

      by Anonymous Coward
      Actually I think what you actually meant was the "Restaurant at the End of the Universe". And the name refers to the temporal aspect, not locality.
    • When do we get to see the edge of the universe cafe?

      When Starbucks agrees to the contract negotiations.
  • My God, it's full of stars!
  • According to google calculator:

                      2 000 000 000 miles = 21.5155818 Astronomical Units

    which puts it just inside the closest approach of Saturn, but well outside Jupiter's orbit.

  • ummm... (Score:4, Insightful)

    by heatdeath (217147) on Monday January 09 2006, @01:45PM (#14429359)
    Am I the only one who doesn't think that that's very clearly a triple star from the pictures? =P The title of the article made it look like the light we see from it is actually from three really close together stars...but it seems like we're only seem polaris A, since the smaller ones are so tiny.

  • ASCII Picture Mirror (Score:5, Funny)

    by big_groo (237634) <groovis.gmail@com> on Monday January 09 2006, @01:48PM (#14429383) Homepage
    Polaris ---> O
    Polaris Ab---->.

    Polaris A --------->o
  • Is it just me, or does that picture make it look like Polaris just has some version of an interstellar zit? Maybe it's a boil...

  • Second star inside Neptune's orbit (Score:5, Informative)

    by RobertB-DC (622190) * on Monday January 09 2006, @01:49PM (#14429398) Homepage Journal
    From the article: "The companion proved to be less than two-tenths of an arcsecond from Polaris... At the system's distance of 430 light-years, that translates into a separation of about 2 billion miles."

    I did a little googling, and found that Neptune's orbit is just over 2 billion miles from the Sun. So for reference, Hubble has directly imaged two distant objects that could fit inside our own solar system.

    I think they could have gotten more "Oomph!" from their press release if they'd mentioned this fact. Also, they may have wanted to measure the distance in a standard publicity unit, such as roundtrip NY-LA distances ("A little over 350,000 round-trips from New York to Los Angeles").
  • It's just drifting south over Siberia.

  • Some perspective... (Score:2, Informative)

    by Anonymous Coward
    TFA states that the close companion orbits at about 2 billion miles, or about 21.5 AU from the parent. That is a bit more than the orbit of Uranus (19.5 AU) in our own system. They had to stretch the Hubble to its limit to see something as bright as a STAR that was far enough away from the parent to fit most of our entire solar system inside. 490 light years is a long way away.

  • Gah.... (Score:3, Funny)

    by Anonymous Coward on Monday January 09 2006, @01:57PM (#14429472)
    That's space for ya, nothing for millions of miles, and all of sudden, three stars at once.
  • Triple star systems degrade by kicking out one of the stars so the remaining two stars can settle into a stable binary system.

    Likely the small nearly hidden star is similar to Jupiter.

    • Re:I doubt this a a triple star system (Score:5, Informative)

      by hcg50a (690062) on Monday January 09 2006, @02:16PM (#14429641) Journal
      Your first comment is true in the general 3-body problem, but certain cases are actually stable over a long period of time. Namely, when two of the bodies are in a very tight orbit which is not significantly perturbed by the 3rd body.

      So, the system approximates a stable two body system.

      Another similar case is 4 stars, where there are two close pairs in orbit around each other. This idea can be extrapolated to any number of stars as long as each pair is not significantly perturbed by its non-pair neighbors.

    • Re:I doubt this a a triple star system (Score:5, Interesting)

      by coyote-san (38515) on Monday January 09 2006, @02:23PM (#14429705)
      Where did you get this? There are many reasonably stable three-plus body systems. ("reasonably stable" meaning that they'll last the lifetime of the stars, but could still be disrupted by passing stars, etc.)

      The classic example is a close binary with a distant third. The distant star essentially sees the binaries as a point. The binaries see the gravitational attraction of the third star as essentially flat (since the tidal forces drop off as 1/r^3). This doesn't mean non-zero, it just means that the attraction of the "near" star won't be higher than the attraction of the "far" star. IIRC that's why the moon is slowly pulling away from the earth -- the sun is slowly pulling the earth and the moon apart.

      Another example is a pair of close binaries. Again each binary is overwhelmingly dominated by its pair, with the gravitational attraction of the other pair as essentially flat.

  • Odd phrasing (Score:3, Interesting)

    by Kelson (129150) * on Monday January 09 2006, @02:03PM (#14429520) Homepage Journal
    "With Hubble, we've pulled the North Star's companion out of the shadows and into the spotlight."

    Of course, stars are easier to see surrounded by shadow than in the glare of a spotlight. Shouldn't this say, "We've pulled the North Star's companion out of the spotlight and into the shadows?"
  • No wonder I never got my orienteering merit badge!
  • The North Star: Robots In Disguise

  • no wonder I've been getting lost! (Score:3, Funny)

    by peter303 (12292) on Monday January 09 2006, @02:51PM (#14429966)
    I've been following Polaris #3 instead of Polaris #1.

  • Why this is significant (Score:4, Informative)

    by radtea (464814) on Monday January 09 2006, @05:03PM (#14431200)

    Cepheid variable stars are one of the most basic "standard candles" on which our measurement of interstellar distances depends. Polaris is one of the closest Cepheids.

    Cepheid periods depend on luminosity, but the period-luminosity relation is still semi-empirical. Knowing the mass of Polaris (which you can get from measuring the orbital elements of the companion star) pins down one of the important variables in the theoretical model of Cepheids, and so helps firm up one of the basic measuring instruments we use to determine the scale of the universe.

    In the past, there have been significant changes in our beliefs about the scale of the universe due to problems with interpretation of variable star data--the discovery that some presumed Cepheids were actually RR Lyrae variables changed things by about a factor of two, IIRC.

    Things are a lot better than that now, but it is still good to see that people are working to ensure our view of the universe is as consistent and accurate as possible.

  • We're missing the real news here (Score:5, Funny)

    by Jay L (74152) <jay+slash.jay@fm> on Monday January 09 2006, @08:10PM (#14432392) Homepage
    astronomers have photographed the close companion of Polaris

    Waitaminute. Polaris is GAY?

    • Re:some questions (Score:5, Informative)

      by hattig (47930) on Monday January 09 2006, @01:53PM (#14429449) Journal
      It's a triple star system if they're all rotating around a common centre of gravity, even if PolarisB seems to be quite an outsider (although on the scale they're showing it is probably still at a distance similar to a Kuiper belt object (rough guess) whilst this Ab star is at Saturn distance from A.

      I suppose it is possible that Ab is behind A and thus appears further away, but I'm sure they've done their maths and checked it over a lot before releasing the PR.

    • Re:some questions (Score:4, Informative)

      by hcg50a (690062) on Monday January 09 2006, @02:08PM (#14429567) Journal
      There are three stars (Polaris A, Polaris B, and Polaris Ab) in orbit around each other (in various ways). That's why it's called a triple star.

      A and B are indeed very far from each other. I don't know how long the period is, but it is probably on the order of hundreds or thousands of years. The center of mass of that orbit may be well outside of Polaris A.

      A and Ab are in a very close orbit, with a period of around 30 years. The center of mass of that orbit may be well inside of Polaris A.

      You can say Polaris B sucks, but that won't affect it, or the triple star system at all. Polaris B is easily visible in small amateur telescopes. It makes Polaris a very pretty star to look at.
        • I think it is probably possible, though I suspect it will be difficult. Most reports I've seen it's an easy split in a 6" to 10" scope.

          One guy has reported an easy split at 27x and 96x in an 80mm scope.

          With 70mm aperture, I think the key will be high magnification. I would try at least 100x.

          If this is a finder scope or binocular with limited power (ie., fixed at 10x or 8x), I doubt you will be able to split it.

    • Re:Hubble (Score:4, Interesting)

      by amliebsch (724858) on Monday January 09 2006, @02:27PM (#14429744) Journal
      And what will really blow your mind is the knowledge that right at this moment, those stars are probably no longer in that configuration, if they even all still exist.

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