Beschreibung

NASA's new Spitzer Space Telescope has captured an image of an unusual comet that experiences frequent outbursts, which produce abrupt changes in brightness. Periodic comet Schwassmann-Wachmann I (P/SW-1) has a nearly circular orbit just outside that of Jupiter, with an orbital period of 14.9 years. It is thought that the outbursts arise from the build-up of internal gas pressure as the heat of the Sun slowly evaporates frozen carbon dioxide and carbon monoxide beneath the blackened crust of the comet nucleus. When the internal pressure exceeds the strength of the overlying crust, a rupture occurs, and a burst of gas and dust fragments is ejected into space at speeds of 450 miles per hour (200 meters per second).

This 24-micron image of P/SW-1 was obtained with Spitzer's multiband imaging photometer. The image shows thermal infrared emission from the dusty coma and tail of the comet. The nucleus of the comet is about 18 miles (30 kilometers) in diameter and is too small to be resolved by Spitzer. The micron-sized dust grains in the coma and tail stream out away from the Sun. The dust and gas comprising the comet's nucleus is part of the same primordial materials from which the Sun and planets were formed billions of years ago. The complex carbon-rich molecules they contain may have provided some of the raw materials from which life originated on Earth.

Schwassmann-Wachmann 1 is thought to be a member of a relatively new class of objects called "Centaurs," of which 45 objects are known. These are small icy bodies with orbits between those of Jupiter and Neptune. Astronomers believe that Centaurs are recent escapees from the Kuiper Belt, a zone of small bodies orbiting in a cloud at the distant reaches of the solar system.

Two asteroids, 1996 GM36 (left) and 5238 Naozane (right) were serendipitously captured in the comet image. Because they are closer to us than the comet and have faster orbital velocities, they appear to move relative to the comet and background stars, thereby producing a slight elongated appearance. The Spitzer data have allowed astronomers to use thermal measurements, which reduce the uncertainties of visible-light albedo (reflectivity) measurements, to determine their size. With radii of 1.4 and 3.0 kilometers, these are the smallest main-belt asteroids yet measured by infrared means.

Ursprüngliches Datei-Logbuch

Individual images

see http://gallery.spitzer.caltech.edu/Imagegallery/image.php?image_name=ssc2003-06j
High quality tif files also avaliable.

Lizenz

	Diese Datei ist gemeinfrei (public domain), da sie von der NASA erstellt worden ist. Die NASA-Urheberrechtsrichtlinie besagt, dass „NASA-Material nicht durch Urheberrecht geschützt ist, wenn es nicht anders angegeben ist“. (NASA-Urheberrechtsrichtlinie-Seite oder JPL Image Use Policy).
	Warnung: Die Verwendung von NASA-Logos, Wappen und Symbolen ist durch das US-Gesetz 14 CFR 1221 eingeschränkt. Die NASA-Homepage hostet viele Bilder der Sowjetischen bzw. Russischen Raumfahrtagentur sowie anderer nicht-amerikanischer Raumfahrtagenturen. Diese sind nicht gemeinfrei. Material des Hubble-Weltraumteleskops kann urheberrechtlich geschützt sein, wenn es nicht ausdrücklich vom STScI ist. [1] Jegliches Material des Solar and Heliospheric Observatory (SOHO) ist urheberrechtlich geschützt und benötigt eine gesonderte Genehmigung für kommerzielle, nicht-pädagogische Zwecke. [2] Bilder, die als Astronomie-Bild des Tages (APOD) veröffentlicht werden, sind unter Umständen urheberrechtlich geschützt. [3]