ALMAs Loch im Universum
Die Ereignisse rund um den Urknall waren so drastisch, dass davon ein dauerhafter Abdruck in der Struktur des Kosmos erhalten geblieben ist. Wir können diese Narben noch heute ausmachen, indem wir das älteste Licht im Universum beobachten. Es entstand vor fast 14 Milliarden Jahren und ist heute als schwache Mikrowellenstrahlung zu erkennen. Diese wird als kosmischer Mikrowellenhintergrund (abgekürzt: CMB, für englisch: cosmic microwave background) bezeichnet und füllt inzwischen den gesamten Kosmos mit Photonen aus, die sich unserer Beobachtung erschließen.
Der CMB kann genutzt werden, um den Kosmos mittels eines Effektes zu erkunden, den man als Sunjajew-Seldowitsch-Effekt bezeichnet und der erstmals vor über 30 Jahren beobachtet wurde. Die Photonen des CMB erreichen uns hier auf der Erde, nachdem sie einen langen Weg durch den Weltraum zurückgelegt haben. Auf dieser Reise haben sie möglicherweise Galaxienhaufen passiert, die hochenergetische Elektronen enthalten. Diese Elektronen verpassen einigen der Photonen einen kleinen Energieschub, wodurch sie zu einer kürzeren Wellenlänge verschoben werden. Dadurch wird das Spektrum des CMB zu kleineren Wellenlängen hin verformt, wenn auch nur geringfügig. Diesen Effekt mit unseren Teleskopen zu beobachten ist zwar schwierig, aber bedeutsam – er kann uns dabei helfen, einige der fundamentalen Eigenschaften des Universums zu verstehen, wie zum Beispiel den Ort und die Verteilung von Galaxienhaufen.
Das Bild zeigt die erste Messung des thermalen Sunjajew-Seldowitsch-Effektes mit dem Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. Dabei hat man Daten der 7- und 12-Meter-Antennen von ALMA zusammengefasst, um damit ein möglichst scharfes Bild zu erzeugen. Das Untersuchungsobjekt war dabei einer der massereichsten bekannten Galaxienhaufen, RX J1347.5–1145, der sich hier als dunkles „Loch“ im Bild bemerkbar macht. Die Farben entsprechen hier Helligkeitsstufen – oder anders gesagt, der Anzahl der aufgefangenen Elektronen im untersuchten Wellenlängenbereich. Rote, orange und gelbe Stellen sind besonders hell, blaugrüne und grüne mittelhell und blaue und violette dunkel. Die Energieverteilung der CMB-Photonen weist eine Verschiebung auf und erscheint wie ein Temperaturabfall in der von ALMA beobachteten Wellenlänge. Daher sehen wir auf dem Bild einen dunklen Fleck (blau und violette Farbtöne) an der Stelle, an dem sich der Galaxienhaufen befindet.
Herkunftsnachweis:ALMA (ESO/NAOJ/NRAO)/T. Kitayama (Toho University, Japan)/ESA/Hubble & NASA
Über das Bild
| ID: | potw1708a |
| Sprache: | de |
| Typ: | Beobachtung |
| Veröffentlichungsdatum: | 20. Februar 2017 06:00 |
| Größe: | 3816 x 3559 px |
Über das Objekt
| Typ: | Early Universe : Cosmology |
| Constellation: | Virgo |
Bildschirm-Hintergrundbilder
Koordinaten
| Position (RA): | 13 47 30.65 |
| Position (Dec): | -11° 45' 18.95" |
| Field of view: | 1.91 x 1.78 arcminutes |
| Orientierung: | Die Nordrichtung liegt 130.7° rechts zur Vertikale |
Farben & Filter
| Spektralbereich | Wellenlänge | Teleskop |
|---|---|---|
| Millimeter 92 GHz | 3.258613 mm | Atacama Large Millimeter/submillimeter Array Band 3 |
| Optisch g | 475 nm | Hubble Space Telescope ACS |
| Optisch B | 435 nm | Hubble Space Telescope ACS |
| Optisch V | 606 nm | Hubble Space Telescope ACS |
| Optisch r | 625 nm | Hubble Space Telescope ACS |
| Optisch i | 775 nm | Hubble Space Telescope ACS |
| Optisch z | 850 nm | Hubble Space Telescope ACS |
| Infrarot J | 1.1 μm | Hubble Space Telescope WFC3 |
| Infrarot H short | 1.6 μm | Hubble Space Telescope WFC3 |
| Optisch I | 814 nm | Hubble Space Telescope ACS |
| Infrarot J | 1.1 μm | Hubble Space Telescope WFC3 |
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