The EGGs where stars are hatched

时间:2019-02-28 02:16:03166网络整理admin

By Vincent Kiernan EVER wanted to know where stars come from? The Hubble Space Telescope has provided one of the most spectacular images yet of stars being born. Each of the finger-like projections crowning the Eagle Nebula has a new star in its tip. The nebula used to be much bigger, but ultraviolet radiation from older stars, away to the upper right and not shown in this picture, has blown away most of the hydrogen that made up the cloud. The projections are not destroyed because they are sitting in the shadow of the embryonic stars, says Jeff Hester of Arizona State University in Tempe. The whitish haze surrounding the nebula is where hydrogen is being dispersed into interstellar space. The protrusions are each about the size of our Solar System, says Hester The Arizona astronomers call them evaporating gaseous gloules – or EGGs. By studying EGGs at various stages of formation it may be possible to piece together the process of stellar birth. The image of the nebula, which is 7000 light years away in the constellation of Serpens, may help explain why the cosmos has so few large stars, says Bruce Margon of the University of Washington, Seattle. Astronomers believe that stars form inside hydrogen clouds when the gas grows so dense at certain points that it collapses under its own gravity. Then more and more gas is pulled in until the matter becomes dense enough to trigger nuclear fusion, and the star begins to burn. Hubble’s latest image suggests that after one large star forms in a region of space, its powerful ultraviolet light might disperse the hydrogen cloud around it, and so limit the size of neighbouring stars forming from the gas. But our own Sun probably did not hatch from an EGG, Margon says. The fact that the planets exist is evidence that the early Solar System was not exposed to powerful ultraviolet radiation. If it had been,