Rot und lange tot
Diese rötliche Gaswolke trägt den Namen Abell 24 und befindet sich im Sternbild Canis Minor (Kleiner Hund). Man bezeichnet solche Gaswolken als planetarische Nebel. Sie entstehen, wenn ein Stern stirbt und seine äußeren Schichten dabei ins All schleudert. Die Bezeichnung ist eigentlich irreführend, denn planetarische Nebel haben nichts mit Planeten zu tun. Sie wurde einstmals von Wilhelm Herschel geprägt, der auch den Planeten Uranus entdeckte. Zu einer Zeit, als die Auflösungskraft der Teleskope noch nicht so groß war, schienen diese nebelhaften Objekte ganz ähnlich wie riesige Planeten auszusehen; daher der Name.
Ein Stern wie die Sonne verbringt die meiste Zeit seines Lebens damit, in seinem Kern Wasserstoff zu Helium umzuwandeln. Im hohen Alter geht ihm dann der Treibstoff aus und er gerät aus dem Gleichgewicht; er kann der nach innen gerichteten Kraft der Gravitation nicht länger widerstehen und beginnt zu kollabieren. Die Kerntemperatur steigt dramatisch an, während gleichzeitig die äußeren kühleren Schichten expandieren, was den Stern dann zu einem Roten Riesen aufbläht. Wenn die Sonne irgendwann einmal ihre Transformation zu einem Roten Riesen beginnt, wird sie sich so weit ausdehnen, dass sie sogar die inneren Planeten umhüllt, vielleicht bis zur die Erde, und sich zum 250-Fachen ihres jetzigen Durchmessers aufblähen! Starke Sternwinde werden dann die äußeren gasförmigen Schichten des Sterns hinwegtragen und zu einer Hülle aus Gas werden lassen, die weit ins Weltall hinaus reicht. Durch das Ablösen der Atmosphäre des Roten Riesen wird dann sein heißer Kern freigelegt, der mit seiner intensiven ultravioletten Strahlung das umgebende Gas ionisieren wird. Das Bild zeigt das schwache Glühen des Gases eines solchen stellaren Schwanengesangs, den hellen Überrest eines längst gestorbenen Sterns.
Das Bild wurde mit dem FORS (FOcal Reducer and Spectrograph) am VLT im Rahmen des ESO Cosmic Gems Programms aufgenommen, einer Initiative zur Erstellung von Bildern wissenschaftlich interessanter und optisch attraktiver Objekte mittels der ESO-Teleskope zum Zwecke der Lehre und Öffentlichkeitsarbeit. Das Programm nutzt Teleskopzeit, die für wissenschaftliche Beobachtungen nicht geeignet wäre. Die gesammelten Bilddaten können jedoch für wissenschaftliche Zwecke genutzt werden und stehen den Astronomen über das ESO-Wissenschaftsarchiv zur Verfügung.
Bildnachweis:ESO
Über das Bild
ID: | potw1927a |
Sprache: | de-at |
Typ: | Beobachtung |
Veröffentlichungsdatum: | 8. Juli 2019 06:00 |
Größe: | 1729 x 1757 px |
Über das Objekt
Name: | Abell 24 |
Typ: | Milky Way : Nebula : Type : Planetary |
Constellation: | Canis Minor |
Bildschirm-Hintergrundbilder
Koordinaten
Position (RA): | 7 51 37.69 |
Position (Dec): | 3° 0' 25.84" |
Field of view: | 7.26 x 7.38 arcminutes |
Orientierung: | Die Nordrichtung liegt -0.0° links zur Vertikale |
Farben & Filter
Spektralbereich | Wellenlänge | Teleskop |
---|---|---|
Optisch b | 440 nm | Very Large Telescope FORS2 |
Optisch V | 557 nm | Very Large Telescope FORS2 |
Optisch R | 655 nm | Very Large Telescope FORS2 |
Optisch H-alpha | 656 nm | Very Large Telescope FORS2 |
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