THE FIRST DIRECT IMAGE OF THE SURFACE OF A STAR
The first direct image of the surface of a star, other than our own sun, has been made with NASA's Hubble Space Telescope. Called Alpha Orionis, or Betelgeuse, it is a red supergiant star, and can be located in the constellation Orion. Betelgeuse is so huge that, if it replaced the Sun at the center of our solar system, its outer atmosphere would extend past the orbit of Jupiter!
 The surface of Betelgeuse had been indirectly photographed earlier, from the Earth, using interferometry, in which many brief exposures are added up to make a composite image, ... but the images were not as good as the ones from Hubble, which reveals a huge ultraviolet atmosphere, and a mysterious hot spot on the giant star's surface. The enormous bright spot, more than ten times the diameter of Earth's orbit, is at least 2,000 degrees hotter than the surface of the star. This is a brand new phenomenon that is at present unexplained. (Sunspots, familiarly seen on our own sun's surface, are actually cooler areas, and are reasonably well understood). Hubble's optical system can resolve the star even though its apparent size is 20,000 times smaller than the width of the full Moon -- roughly equivalent to being able to resolve a car's headlights at a distance of 10,000 km!
|
|