At just barely tenth magnitude (9.54), Barnard's Star -- named after Yerkes Observatory's E. E. Barnard (1857-1923), who discovered it in 1916 -- is not close to being visible to the naked eye, even though at a distance of just 6.0 light years it is the second closest star to the Earth (considering the Alpha Centauri system, including Proxima, as a unit).
That is just what you would expect from a dim, low mass, class M (M4) dwarf. In northeastern Ophiuchus near the asterism known as "Poniatowski's Bull," the star's fame derives from a variety of properties, chief among them its speed record.
Barnard's has the world's greatest "proper motion," the angular annual movement across the line of sight against the distant stellar background, a whopping 10.4 seconds of arc per year.
While that may not seem like much, it amounts to an easily- seen quarter of a degree in a human lifetime, roughly the angular diameter of the full Moon.
This huge angular displacement derives from a truly high speed of 139 kilometers per second relative to the Sun, both toward us and to the north. Cool (3170 Kelvin, as befits an M star), this dim dwarf has a luminosity a mere 0.0035 times that of the Sun, most of it in the infrared, which shows it to have a diameter only 20 percent that of the Sun (found also from the angular diameter) and a mass a mere 17 percent solar.
Far from rare, the great majority of stars fall into the M dwarf category: they are just so faint, like Proxima Centauri, that none is visible to the naked eye. Nature seems to love the lesser. No one really knows why. Barnard's has a metal content only 10 percent that of the Sun. That coupled with its high velocity shows it to be a special, rather rare, kind of star called a "subdwarf" that more belongs to the metal-poor and ancient halo of our Galaxy (the Sun belonging to the disk). It is merely passing through our local neighborhood.
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#stars, #universe, #barnardstar, #space #astronomy, #animation
This new portrait of the bright star-forming region NGC 346, in which different wavelengths of light swirl together like watercolours, reveals new information about how stars form.
NGC 346 is located 210,000 light-years away in the Small Magellanic Cloud, a neighbouring dwarf galaxy of the Milky Way. The image is based on data from ESA XMM-Newton (X-rays; blue), ESO's New Technology Telescope (visible light; green), and NASA's Spitzer (infrared; red).
The infrared light shows cold dust, while the visible light denotes glowing gas, and the X-rays represent very hot gas. Ordinary stars appear as blue spots with white centres, while young stars enshrouded in dust appear as red spots with white centres.
► Image source and explanation>> http://www.eso.org/public/unitedkingdom/images/eso0834a/
ESO/ESA/ JPL-Caltech/NASA/ D. Gouliermis (MPIA) et al.
#Universe, #ESO, #ESA, #NASA, #NGC346, #dwarf_galaxy, #Small_Magellanic_Cloud #Astronomy #space
Earth is famous for its blue skies. It gets it blue skies through an effect known as Rayleigh scattering. Rayleigh scattering is a subtle effect, so it’s been difficult to observe beyond our solar system. But recently a team has observed Rayleigh scattering in the atmosphere of a planet about 100 light years away.
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