Hubble eyes disks that may form planets.New images suggest that disks of dust and gas -- the raw material for making planets -- surround at least half the stars in the nearby Orion nebula Orion Nebula, bright diffuse nebula in the constellation Orion; also known as the Great Nebula of Orion and cataloged as M42 or NGC 1976. It is located near the middle of the "sword" hanging from Orion's "belt" of stars. . If the disks in this crowded stellar nursery A stellar nursery is a massive cosmic dust cloud in which microscopic particles may slowly aggregate due to gravitational attraction and eventually give rise to protostars and subsequently planetary systems, with one or more stars and planets. survive long enough, the material they contain could condense con·dense v. con·densed, con·dens·ing, con·dens·es v.tr. 1. To reduce the volume or compass of. 2. To make more concise; abridge or shorten. 3. Physics a. into planet-size bodies within a few million years, says C. Robert O'Dell of Rice University in Houston. O'Dell, who worked with Zheng Wen of the University of Kentucky The University of Kentucky, also referred to as UK, is a public, co-educational university located in Lexington, Kentucky. in Lexington, bases his conclusion on images taken with the repaired Hubble Space Telescope's new wide-field and planetary camera. In its survey of 110 Orion stars, most with a mass equal to or less than that of the sun, the instrument revealed that dusty disks surround 56 of them. The new observations aren't the first evidence of protoplanetary disks. Ground-based and satellite observations of several starbirth regions in the Milky Way Milky Way, the galaxy of which the sun and solar system are a part, seen as a broad band of light arching across the night sky from horizon to horizon; if not blocked by the horizon, it would be seen as a circle around the entire sky. have detected excess infrared radiation from young, low-mass stars -- an indication that infrared-emitting dust, possibly in the shape of a disk, surrounds these newborns (SN: 10/3/92, p.214). And even before Hubble's repair, the telescope had imaged dusty rings -- possible planet-spawning disks -- around 15 stars in Orion This is the list of notable stars in the constellation Orion, sorted by decreasing brightness. Name Designation Location Magnitude Dist. (ly) Sp. class Notes B F HD HIP RA Dec vis. abs. Rigel β 19 34085 24436 05h 14m 32. (SN: 12/19&26/92, p.421). But the new images constitute "strong proof that protoplanetary disks [exist and] are a common product of star formation," O'Dell asserts. The images reveal that the disks are indeed pancake-shaped, rather than spherical, as some astronomers had maintained. The observations also enabled O'Dell and Wen to measure the variation in brightness across the disks, which are set aglow by the light f rom hot, background stars. This, in turn, enabled the researchers to estimate the mass in the disks' outer rims. They conclude that the rims contain at least enough material to make three planets the size of Earth. One of the Hubble pictures shows an oval disk, silhouetted against background light, with a width equal to 7.5 times the diameter of the solar system solar system, the sun and the surrounding planets, natural satellites, dwarf planets, asteroids, meteoroids, and comets that are bound by its gravity. The sun is by far the most massive part of the solar system, containing almost 99.9% of the system's total mass. . O'Dell presented the images last week at a press conference in Washington, D.C. The camera recorded the pictures in late December, just weeks after astronauts installed it during Hubble's repair mission. |
|
||||||||||||||||||||
Printer friendly
Cite/link
Email
Feedback
Reader Opinion