Spirograph in the sky.Some 2,000 light-years from Earth, an elderly star has ejected its puffy outer layers to form a luminous, jewel-like ball of gas. Set aglow by ultraviolet radiation UV index predicts how long it would take a light-skinned American to get a sunburn if exposed, unprotected, to the noonday sun, given the geographical location and the local weather. It ranges from 1 (about 60 minutes before the skin will burn) to a high of 10 (about 10 minutes before the skin will burn). A small amount of sunlight is necessary for good health. pouring out from the core of the aging star, this gaseous gas·e·ous (g  s  - s, g nebula 1. a slight corneal opacity. 2. a preparation, particularly an oily preparation, for use in a nebulizer. neb·u·la (n  by--called IC 418--resembles a "spirograph spi  ro·graphic adj.spi·rog ", the pattern produced by the familiar drawing toy. The Hubble Space Telescope took pictures of the nebula last year, and NASA released the images on Sept. 7. ra·phy (spAstronomers more than a century ago dubbed such gaseous structures planetary nebulae because their disk like shape, as discerned in the telescopes of the day, reminded the researchers of planets. Over the next several thousand years, IC 418 will slowly disperse. The aging star then left behind--the remnant of a bloated bloat star called a red giant red giant, star that is relatively cool but very luminous because of its great size. All normal stars are expected to pass eventually through a red-giant phase as a consequence of stellar evolution. As a star uses up its hydrogen by converting it to helium, its central core contracts while the outer layers expand and cool; this process produces the low temperature and large size (from 10 to 1,500 times that of the sun) that characterize the red giant.--will collapse to become a white dwarf white dwarf, in astronomy, a type of star that is abnormally faint for its white-hot temperature (see mass-luminosity relation). Typically, a white dwarf star has the mass of the sun and the radius of the earth but does not emit enough light or other radiation to be easily detected. The existence of white dwarfs is intimately connected with stellar evolution. A white dwarf is the hot core of a star, left over after the star uses up its nuclear fuel and dies.. It will take billions of years to completely cool and fade. Our sun will meet the same fate, but not for about 5 billion years.
ed (bl t d) adj. |
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