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More to the North Star Than Meets the Eye
__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."
they should nickname the mini star, Cooper
Got an ETX for Christmas? You should know this site.
A feeling of having made the same mistake before: Deja Foobar
"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.]
Saskboy's blog is good. 9 out of 10 dentists agree.
"I am as constant as the Northern Star." Always though Caesar was a little unstable and went round and round in circles....
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.
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.
I'm sorry. The number you have reached is imaginary. Please rotate your phone 90 degrees and try again.
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.
Polaris ---> O
Polaris Ab---->.
Polaris A --------->o
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").
Stressed? Me? Of course not. Stress is what a rubber band feels before it breaks, silly.
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.
That's space for ya, nothing for millions of miles, and all of sudden, three stars at once.
"We only have the binary stars that nature provided us"
Don't give up so easily. Make some more binary stars, instead of making excuses.
SHEESH, IDIOTS!
Exam 4/C again. Maybe I'll do better this time.
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.
HCG 50a = 2MASX J11170638+5455016
11h17m06.4s +54d55m02s
The North Star: Robots In Disguise
Old people fall. Young people spring. Rich people summer and winter.
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.
HCG 50a = 2MASX J11170638+5455016
11h17m06.4s +54d55m02s
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.
For every complex problem there is an answer that is clear, simple, and wrong. -- H L Mencken
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.
If you don't know where you are going, you will wind up somewhere else.
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.
Blasphemy is a human right. Blasphemophobia kills.
astronomers have photographed the close companion of Polaris
Waitaminute. Polaris is GAY?