Sternexplosion am Anfang der Welt

Stern explodiert zu Schwarzem Loch, nur 600 Millionen Jahre nach dem Urknall! Beobachtet am 23.4. als Gammablitz und dann im IR - Licht. Pressemitteilung der ESO in Englisch und der dpa in Deutsch.

ESO 17/09 - Science Release

28 April 2009 

The Most Distant Object Yet Discovered in the Universe

ESO's Very Large Telescope has shown that a faint gamma-ray burst detected last Thursday is the signature of the explosion of the earliest, most distant known object in the Universe (a redshift of 8.2). The explosion apparently took place more than 13 billion years ago, only about 600 million years after the Big Bang.

Gamma-ray bursts (GRBs) are powerful flashes of energetic gamma-rays lasting from less than a second to several minutes. They release a tremendous amount of energy in this short time making them the most powerful events in the Universe. They are thought to be mostly associated with the explosion of stars that collapse into black holes.

The gamma-ray burst GRB 090423 was detected by the NASA/STFC/ASI Swift satellite during the morning (CEST) of Thursday 23 April 2009. The 10 second burst was located in the constellation of Leo (the Lion). It was soon being followed by a whole range of telescopes on the ground, including the 2.2-metre ESO/MPG telescope at La Silla and ESO’s Very Large Telescope (VLT) at Paranal, both in Chile.

VLT infrared observations, made 17 hours after the burst detection, allowed astronomers to establish the distance to the explosion. “We find that the light coming from the explosion has been stretched, or redshifted, considerably by the expansion of the Universe”, says Nial Tanvir, the leader of the team who made the VLT observations. “With a redshift of 8.2 this is the most remote gamma-ray burst ever detected, and also the most distant object ever discovered — by some way.”

Because light moves at a finite speed, looking farther into the Universe means looking back in time. The explosion occurred when the Universe was about 600 million years old, less than 5 percent of its current age. It is believed that the very first stars only formed when the Universe was between 200 and 400 million years old.

“This discovery proves the importance of gamma-ray bursts in probing the most distant parts of the Universe”, says Tanvir. “We can now be confident that even more remote bursts will be found in the future, which will open a window to studying the very first stars and the ultimate end of the Dark Age of the Universe.”

The previous record holder for the most distant GRB — first detected by Swift last year and then also studied with the VLT — had a redshift of 6.7 [1]. The blast, designated GRB 080913, arose from a star exploding about 200 million years after GRB090423. The previous most distant object known in the Universe confirmed spectroscopically is a galaxy with a redshift of 6.96 [2].

 

More information

The ISAAC observations at the VLT were done on behalf of an international collaboration by N. Tanvir (U. Leicester, UK), A. Levan (U. Warwick, UK), K. Wiersema (U. Leicester, UK), J. Fynbo and J. Hjorth (Dark Cosmology Centre, Copenhagen, Denmark), and P. Jakobsson (Reykjavik, Iceland).

The GROND observations with the 2.2-metre ESO/MPG telescope at La Silla were made by F. Olivares, T. Krühler, J. Greiner and R. Filgas (Max Planck Institute for Extraterrestrial Physics, Garching, Germany).

Gamma-ray bursts are discovered by telescopes in space. After releasing their intense burst of high-energy radiation, they become detectable for a short while in the optical and in the near-infrared. This ‘afterglow’ fades very rapidly, making detailed analysis possible for only a few hours after the gamma-ray detection. This analysis is important in particular in order to determine the GRB's distance and, hence, intrinsic brightness.

Gamma-ray bursts are the universe's most luminous explosions. Most occur when massive stars run out of nuclear fuel. As their cores collapse into a black hole or neutron star, gas jets — driven by processes not fully understood — punch through the star and blast into space. There, they strike gas previously shed by the star and heat it, which generates short-lived afterglows in many wavelengths.

Notes

[1] See http://www.nasa.gov/mission_pages/swift/bursts/farthest_grb.html
[2] See https://www.naoj.org/Pressrelease/2006/09/13/index.html

ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in the Atacama Desert region of Chile: La Silla, Paranal and Chajnantor. 

Sternenforscher entdecken fernstes Objekt im All


Garching (dpa) - Sternenforscher haben das bislang fernste Objekt im All erspäht. Am 23. April 2009 wurde ein schwacher Gammastrahlenblitz beobachtet, wie die Europäische Südsternwarte (ESO) am 28. April in Garching bei München bekanntgab. Das sei eine Spur der Explosion des frühesten und am weitesten entfernten Objekts im Weltall, das je beobachtet worden sei. Die Explosion habe sich in mehr als 13 Milliarden Lichtjahren Entfernung ereignet und gerade einmal 600 Millionen Jahre nach dem Urknall. Mit dem NASA-Satelliten «Swift» wurde die zehnsekündige Erscheinung im Sternbild Löwen entdeckt. Zahlreiche Astronomen verfolgten laut ESO das kosmische Spektakel von irdisch stationierten Teleskopen aus.

Die ESO selbst beobachtete die Explosion unter anderem mit ihrem Very Large Telescope (VLT) auf dem Cerro Paranal in Chile. Rund 17 Stunden später haben die Astronomen anhand der Infrarot-Aufnahmen des VLT die Entfernung der Explosion zur Erde berechnen können. Sie hätten herausgefunden, dass das Licht der Explosion erheblich von der Ausdehnung des Weltalls gestreckt worden sei, sagte Nial Tanvir, der Chef des Teams, das die Beobachtungen gemacht hatte.

Da sich das Licht mit einer endlichen Geschwindigkeit bewege, sei ein Blick in die Tiefen des Universums stets auch ein Blick zurück in die Vergangenheit. «Wir können sicher sein, dass künftig noch abgelegenere Explosionen entdeckt werden, die ein Fenster zum Studium der ersten Sterne und dem Ende des Dunklen Zeitalters des Universums öffnen», sagte Tanvir weiter. Als Dunkles Zeitalter bezeichnen Kosmologen die Ära vor dem Aufleuchten der ersten Sterne im jungen Universum.

Gammastrahlenblitze wie der beobachtete seien starke Explosionen, die von wenigen Sekunden bis zu einigen Minuten andauern können. Sie setzen laut ESO in dieser kurzen Zeit eine enorme Energie frei, so dass sie als energiereichste Erscheinungen im All eingestuft werden. Deshalb würden sie mit der Explosion von Sternen in Verbindung gebracht, die dann zu Schwarzen Löchern kollabieren. Das zuvor fernste bekannte Objekt im Weltall - ebenfalls ein explodierter Stern - ist den Angaben nach 200 Millionen Lichtjahre näher als das nun entdeckte.


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