Posted on 01/09/2006 10:07:02 PM PST by neverdem
RELEASE: 06-004
By stretching the capabilities of NASA's Hubble Space Telescope to the limit, astronomers photographed the close companion to Polaris, known also as the North Star, for the first time.
"Hubble's exceptional pointing capabilities combined with the wonderful performance of its instruments allow scientists to see the universe in finer detail than ever before," said Michael Moore, NASA's Hubble program executive. "It is that clear vision that makes these types of images possible," he added.
The North Star is thought to be a steady, solitary point of light that guided sailors for ages, but there is more to this star than meets the eye. The North Star is actually a triple star system. While one companion is easily viewed with small telescopes, the other hugs Polaris so tightly that it has never been seen until now.
"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, Mass. The companion proved to be less than two-tenths of an arcsecond from Polaris. That is an incredibly tiny angle equivalent to the apparent diameter of a quarter located 19 miles away. At the system's distance of 430 light-years from Earth, that translates into a separation of about 2 billion miles.
"The brightness difference between the two stars made it even more difficult to resolve them," said astronomer Howard Bond of the Space Telescope Science Institute, Baltimore. Polaris is a super-giant more than two thousand times brighter than the sun, while its companion is a dwarf star. "With Hubble, we've pulled the North Star's companion out of the shadows and into the spotlight," he said.
"Our ultimate goal is to get the accurate mass for Polaris," Evans said. "To do that, the next milestone is to measure the motion of the companion in its orbit," she added. Astronomers want to determine the mass of Polaris, because 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. It is essential to understand their intrinsic physics makeup and evolution. Knowing their mass is the most important ingredient in this understanding.
The researchers plan to continue observing the Polaris system for several years. The movement of the small companion during its 30-year orbit around the primary should be detectable. The researchers presented their data today during the 207th meeting of the American Astronomical Society in Washington.
The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. The Space Telescope Science Institute in Baltimore conducts Hubble science operations. The Institute is operated for NASA by the Association of Universities for Research in Astronomy, Inc., Washington.
For images and additional information about this research on the Web, visit: http://hubblesite.org/news/2006/02
For information about NASA and agency programs on the Web, visit: http://www.nasa.gov/home
ping
The article states it's a triple star system, but then only discusses two stars. Additionally, if there is a 30 year orbit for the second star doesn't that make it a planet? I hve never heard of one star orbiting another.
Oh come on Tom Cruise and Katie holmes?
1. in any binary mas system, both masses orbit a common "center" of mass - from the outside, they appear to wobble and weave or orbit each other.
2. there is no difference in the mechanics of gravity between planets and stars. if one is far more massive than another, it becomes the primary (the mutual center of mass is substantially closer to the primary) and the smaller mass is considered a satellite of the primary
3. if you reread the article, you will note that it makes passing mention of the third star, states that its existence has long been known through use of small telescopes, and then devotes itself to discussing the newly discovered proximal dwarf star and its relation to Polaris Prime.
Most of the stars in our galaxy are part of binary/trinary/multiple star systems. It's very common to have two stars orbiting each other relatively closely, and have yet another star(s) orbiting the two of them at a much greater distance.
bookmark for later
And a few astronomy buffs will point out that the 'North Star' (it goes in circles to the observer over time, a REAL long time as Earth's axis changes in relation to the plane of the Galaxy) is never a true north beyond the Earth's rotation and given even that, you've got an axis nasty wobble that will give a cutesy mini ice age before the planet warms one proved damned degree.
wellll.. 10 times bigger.. give or take.. :-)
Our own system would have been one if Jupiter hadn't decided to remain a planet.
Thanks for posting the information about this interesting discovery.
An excellent example of a binary star system is the center star(s) in the handle of the Big Dipper. It's visible to the naked eye.
Until they detect orbital motion around each other, you can't necessarily tell if a particular pair of stars is an "Optical Double," which means that they are simply a line-of-sight double, or a "Physical Binary," which means that they're indeed orbiting each other.
Astronomers classify physical binary stars depending on how they are detected. Some (perhaps not all of these) are...
*Visual Binary - Close enough to resolve individually and detect orbital motion over time.
*Spectroscopic Binary - Orbital motion is revealed by periodic Doppler shifts of the spectral lines, but the individual stars can't be resolved.
*Eclipsing Binary - Usually an unresolved pair, but as they orbit each other one (or both) of the pair occults the other as they orbit. The presence of two stars can be deduced by a careful monitoring of the light curve they produce. Most eclipsing binaries are actually eclipsing-spectroscopic binaries, in which both Doppler shifts and occultations can be detected.
*Also there's a "Spectrum Binary" - which is a rare type where spectral lines show that there are two different temperatures of star, but no other movement is detected. Often these type "graduate" into one of the other more common types once motion can be deduced. Note that a spectrum binary can't necessarily be proven to be an optical double or a visual binary since line-oif-sight could also explain the phenomena.
The whole universe seems to work like a fine watch, amazing isn't it!
Absolutely! My favorite hobby is heading out to the Mojave on New Moon Saturday nights and hang out with my friends and our telescopes. The most beautiful cathedral I've ever known! :)
Totally cool.
Polaris BumP
Technically they all orbit around their common center of mass. But if one is much larger than the other, that's very near the center of the larger one.
Generally speaking, if it's glowing, it's a star, if not, and is only visible by reflected starlight, it's a planet. However there are so many different stellar systems, that's probably too simplistic to cover all configurations. For example, a new planet might glow from the heat of it's initial formation, fed by gravitational collapse. Maybe if you added that stars glow by nuclear fusion... but then that wouldn't include everything we consider a star.
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