ESO 42/09 - Pressemitteilung Wissenschaft

 

Exoplaneten lösen Rätsel der Sonnenchemie

Eine bahnbrechende Studie an hunderten von Sternen weist auf eine Vebindung zwischen dem “Lithiumrätsel” der Sonnenchemie – dem Umstand, dass unser Heimatstern unerwartet geringe Mengen des chemischen Elements Lithium enthält – und dem Vorhandensein von Planetensystemen um Sterne hin. Die Astronomen untersuchten ihre 500 Zielsterne, von denen 70 ein Planetensystem besitzen, mit dem HARPS-Spektrografen der ESO und fanden heraus, dass sonnenähnliche Sterne, die ein Planetensystem besitzen, das in ihnen enthaltene Lithium deutlich schneller in andere Elemente umwandeln als planetenlose Sterne. Die Studie wirft damit nicht nur neues Licht auf ein altes Rätsel der Sonnenchemie, sondern zeigt auch einen hocheffizienten Weg auf, um Sterne mit Planetensystemen ausfindig zu machen.

Fast  zehn Jahre lang haben wir uns bemüht, herauszufinden, wie sich Sterne, die ein Planetensystem besitzen, von ihren unfructhbaren Cousins unterscheiden”, sagt Garik Israelian, Erstautor der Studie, die in dieser Woche in der Zeitschrift Nature erscheint. “Jetzt haben wir herausgefunden, dass der Lithiumgehalt sonnenähnlicher Sterne davon abhängt, ob die Sterne von Planeten umkreist werden oder nicht.

Seit Jahrzehnten ist bekannt, dass die Sonne im Vergleich mit sonnenähnlichen Sternen nur geringe Mengen des leichten chemischen Elements Lithium enthält – doch eine Erklärung für diese Anomalie fehlte. Die Entdeckung, dass geringer Lithiumgehalt charakteristisch für Sterne ist, die ein Planetensystem haben, legt nahe, worin des Rätsels Lösung besteht: “Damit ist die Erklärung für dieses 60 Jahre alte Rätsel recht einfach”, so Israelian: “Der Sonne fehlt das Lithium, weil sie Planeten besitzt.”

Diesen Schluss ziehen die Forscher aus der Analyse von 500 Sternen, von denen 70 von Planeten umkreist werden. Die meisten der Sterne wurden über mehrere Jahre mit dem High Accuracy Radial Velocity Planet Searcher (wörtlich der “Planetensucher für hochpräzise Radialgeschwindigkeitsmessungen”) überwacht. Dieser Spektrograf, besser bekannt unter dem Akronym HARPS, ist eines der am 3,6-Meter-Teleskop der ESO installierten Instrumente, und der weltweit erfolgreichste Planetenjäger. “Dies ist die beste bislang verfügbare Stichprobe um  zu verstehen, was Sterne, die ein Planetensystem besitzen, auszeichnet”, so die Aussage von Koautor Michel Mayor.

Die Astronomen betrachteten insbesondere sonnenähnliche Sterne, die ein Viertel der Stichprobe ausmachen. Sie fanden, dass die Mehrheit der Sterne, die von Planeten umkreist werden, weniger als ein Prozent des Lithiumgehalts der meisten anderen Sterne aufwiesen. “Genau wie unsere Sonne waren auch diese Sterne sehr effizient, als es darum ging, das Lithium, das sie bei ihrer Entstehung enthielten, zu zerstören” sagt Nuno Santos, ein weiteres Mitglied der Forschergruppe. “Mit Hilfe dieser einzigartigen großen Stichprobe konnten wir zeigen, dass das Fehlen von Lithium nicht mit irgendeiner anderen Eigenschaft der betreffenden Sterne – etwa ihrem Alter – zusammenhängt.

Lithium hat einen sehr leichten Atomkern, der aus nur drei Protonen und vier Neutronen besteht. Die meisten chemischen Elemente leichter als Eisen werden im Inneren von Sternen erzeugt. Die leichten Atomkerne Lithium, Beryllium und Bor entstehen dort allerdings nicht in nennenswerten Mengen. Was wir im Kosmos an Lithium finden ist den heutigen Modellen zufolge kurz nach dem Urknall entstanden, also vor rund 13,7 Milliarden Jahren. Die meisten Sterne haben daher einen sehr ähnlichen Lithiumgehalt – es sei denn, beachtliche Mengen dieses Elements sind bei Prozessen im Sterninneren zerstört worden.

Die neuen Ergebnisse zeigen eine Methode auf, wie Astronomen effektiver als bisher nach Planetensystemen suchen können: Anhand des Lithiumgehalts eines Sterns lässt sich entscheiden, ob sich aufwändigere Beobachtungen überhaupt lohnen.

Nun, da der Zusammenhang zwischen der Anwesenheit von Planeten und besonders geringem Lithiumgehalt bekannt ist, gilt es, die physikalischen Mechanismen aufzuklären, die dahinterstecken. “Es gibt verschiedene Weisen, wie ein Planet die Bewegung von Materie im Inneren seines Heimatsterns stören, so die Verteilung der verschiedenen chemischen Elemente beeinflussen und möglicherweise die Zerstörung von Lithium herbeiführen kann. Nun sind die Theoretiker gefragt, welche der Möglichkeiten am wahrscheinlichsten ist,” schließt Mayor.

Hintergrundinformationen

Die zugehörige Fachveröffentlichung, G. Israelian et al., “Enhanced lithium depletion in Sun-like stars with orbiting planets”, erscheint am 12. November 2009 in Nature.

Die beteiligten Astronomen sind Garik Israelian, Elisa Delgado Mena, Carolina Domínguez Cerdeña und Rafael Rebolo (Instituto de Astrofisíca de Canarias, La Laguna, Teneriffa), Nuno Santos und Sergio Sousa (Centro de Astrofisica, Universidade de Porto, Portugal), Michel Mayor und Stéphane Udry (Observatorium Genf) und Sofia Randich (INAF, Osservatorio di Arcetri, Florenz).

Die Europäische Südsternwarte ESO (European Southern Observatory) ist die führende europäische Organisation für astronomische Forschung und das wissenschaftlich produktivste Observatorium der Welt. Getragen wird die Organisation durch ihre 14 Mitgliedsländer: Belgien, Dänemark, Deutschland, Finnland, Frankreich, Italien, die Niederlande, Österreich, Portugal, Spanien, Schweden, die Schweiz, die Tschechische Republik und das Vereinigte Königreich. Die ESO ermöglicht astronomische Spitzenforschung, indem sie leistungsfähige bodengebundene Teleskope entwirft, konstruiert und betreibt. Auch bei der Förderung internationaler Zusammenarbeit auf dem Gebiet der Astronomie spielt die Organisation eine maßgebliche Rolle. Die ESO betreibt drei weltweit einzigartige Beobachtungsstandorte in Nordchile: La Silla, Paranal und Chajnantor. Auf Paranal betreibt die ESO mit dem Very Large Telescope (VLT) das weltweit leistungsfähigste Observatorium für Beobachtungen im Bereich des sichtbaren Lichts. Die ESO ist der europäische Partner für den Aufbau des Antennenfelds ALMA, das größte astronomische Projekt überhaupt. Derzeit entwickelt die ESO das European Extremely Large Telescope (E-ELT) für Beobachtungen im Bereich des sichtbaren und Infrarotlichts, mit 42 Metern Spiegeldurchmesser ein Großteleskop der Extraklasse.

Die Übersetzungen von englischsprachigen ESO-Pressemitteilungen sind ein Service des ESO Science Outreach Network (ESON), eines internationalen Netzwerks für astronomische Öffentlichkeitsarbeit, in dem Wissenschaftler und Wissenschaftskommunikatoren aus allen ESO-Mitgliedsstaaten (und einigen weiteren Ländern) vertreten sind. Deutscher Knoten des Netzwerks ist das Haus der Astronomie am Max-Planck-Institut für Astronomie in Heidelberg.

Links

 

Englischer Originaltext:

Exoplanets Clue to Sun's Curious Chemistry

A ground-breaking census of 500 stars, 70 of which are known to host planets, has successfully linked the long-standing “lithium mystery” observed in the Sun to the presence of planetary systems. Using ESO’s successful HARPS spectrograph, a team of astronomers has found that Sun-like stars that host planets have destroyed their lithium much more efficiently than “planet-free” stars. This finding does not only shed light on the lack of lithium in our star, but also provides astronomers with a very efficient way of finding stars with planetary systems.

For almost 10 years we have tried to find out what distinguishes stars with planetary systems from their barren cousins,” says Garik Israelian, lead author of a paper appearing this week in the journal Nature. “We have now found that the amount of lithium in Sun-like stars depends on whether or not they have planets.

Low levels of this chemical element have been noticed for decades in the Sun, as compared to other solar-like stars, and astronomers have been unable to explain the anomaly. The discovery of a trend among planet-bearing stars provides a natural explanation to this long-standing mystery. “The explanation of this 60 year-long puzzle is for us rather simple,” adds Israelian. “The Sun lacks lithium because it has planets.”

This conclusion is based on the analysis of 500 stars, including 70 planet-hosting stars. Most of these stars were monitored for several years with ESO’s High Accuracy Radial Velocity Planet Searcher. This spectrograph, better known as HARPS, is attached to ESO's 3.6-metre telescope and is the world’s foremost exoplanet hunter. “This is the best possible sample available to date to understand what makes planet-bearing stars unique,” says co-author Michel Mayor.

The astronomers looked in particular at Sun-like stars, almost a quarter of the whole sample. They found that the majority of stars hosting planets possess less than 1% of the amount of lithium shown by most of the other stars. “Like our Sun, these stars have been very efficient at destroying the lithium they inherited at birth,” says team member Nuno Santos. “Using our unique, large sample, we can also prove that the reason for this lithium reduction is not related to any other property of the star, such as its age.”

Unlike most other elements lighter than iron, the light nuclei of lithium, beryllium and boron are not produced in significant amounts in stars. Instead, it is thought that lithium, composed of just three protons and four neutrons, was mainly produced just after the Big Bang, 13.7 billion years ago. Most stars will thus have the same amount of lithium, unless this element has been destroyed inside the star.

This result also provides the astronomers with a new, cost-effective way to search for planetary systems: by checking the amount of lithium present in a star astronomers can decide which stars are worthy of further significant observing efforts.

Now that a link between the presence of planets and curiously low levels of lithium has been established, the physical mechanism behind it has to be investigated. “There are several ways in which a planet can disturb the internal motions of matter in its host star, thereby rearrange the distribution of the various chemical elements and possibly cause the destruction of lithium. It is now up to the theoreticians to figure out which one is the most likely to happen,” concludes Mayor.

More Information

This research was presented in a paper that appears in the 12 November 2009 issue of Nature (Enhanced lithium depletion in Sun-like stars with orbiting planets, by G. Israelian et al.).

The team is composed of Garik Israelian, Elisa Delgado Mena, Carolina Domínguez Cerdeña, and Rafael Rebolo (Instituto de Astrofisíca de Canarias, La Laguna, Tenerife, Spain), Nuno Santos and Sergio Sousa (Centro de Astrofisica, Universidade de Porto, Portugal), Michel Mayor and Stéphane Udry (Observatoire de Genève, Switzerland), and Sofia Randich (INAF, Osservatorio di Arcetri, Firenze, Italy).

ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. 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 Chile: La Silla, Paranal

Struktur liegt 6,7 Mrd. jahre in der Vergangenheit

Vielleicht ausgehend von Zufallsschwankungen der Energie beim Urknall hat sich ein ksomisches Netzwerk aus Dunkler Materie entwickelt, längs dem sich schon 380000 Jahre nach dem Urknall normale Materie verdichtet hat (Bild 1).

Daraus ist das heute vorhandene kosmische Netz aus Dunkler Materie geworden (Bild 2,3).

Die Verteilung naher Galaxien spiegelt dies wieder (aktuelles Bild 4). Jetzt ist es gelungen eine solche Struktur in einer Entfernung von 6,7 Mrd. Lichtjahren zu finden (Bild 5, 6).

Hier ist der originale Pressetext der europäischen Südsternwarte:

03 November 2009
Shedding Light on the Cosmic Skeleton

Astronomers have tracked down a gigantic, previously unknown assembly of galaxies located almost seven billion light-years away from us. The discovery, made possible by combining two of the most powerful ground-based telescopes in the world, is the first observation of such a prominent galaxy structure in the distant Universe, providing further insight into the cosmic web and how it formed.

Matter is not distributed uniformly in the Universe,” says Masayuki Tanaka from ESO, who led the new study. “In our cosmic vicinity, stars form in galaxies and galaxies usually form groups and clusters of galaxies. The most widely accepted cosmological theories predict that matter also clumps on a larger scale in the so-called ‘cosmic web’, in which galaxies, embedded in filaments stretching between voids, create a gigantic wispy structure.

These filaments are millions of light years long and constitute the skeleton of the Universe: galaxies gather around them, and immense galaxy clusters form at their intersections, lurking like giant spiders waiting for more matter to digest. Scientists are struggling to determine how they swirl into existence. Although massive filamentary structures have been often observed at relatively small distances from us, solid proof of their existence in the more distant Universe has been lacking until now.

The team led by Tanaka discovered a large structure around a distant cluster of galaxies in images they obtained earlier. They have now used two major ground-based telescopes to study this structure in greater detail, measuring the distances from Earth of over 150 galaxies, and, hence, obtaining a three-dimensional view of the structure. The spectroscopic observations were performed using the VIMOS instrument on ESO’s Very Large Telescope and FOCAS on the Subaru Telescope, operated by the National Astronomical Observatory of Japan.

Thanks to these and other observations, the astronomers were able to make a real demographic study of this structure, and have identified several groups of galaxies surrounding the main galaxy cluster. They could distinguish tens of such clumps, each typically ten times as massive as our own Milky Way galaxy — and some as much as a thousand times more massive — while they estimate that the mass of the cluster amounts to at least ten thousand times the mass of the Milky Way. Some of the clumps are feeling the fatal gravitational pull of the cluster, and will eventually fall into it.

This is the first time that we have observed such a rich and prominent structure in the distant Universe,” says Tanaka. “We can now move from demography to sociology and study how the properties of galaxies depend on their environment, at a time when the Universe was only two thirds of its present age.

The filament is located about 6.7 billion light-years away from us and extends over at least 60 million light-years. The newly uncovered structure does probably extend further, beyond the field probed by the team, and hence future observations have already been planned to obtain a definite measure of its size.

More Information

This research was presented in a paper published as a letter in the Astronomy & Astrophysics Journal: The spectroscopically confirmed huge cosmic structure at z = 0.55, by Tanaka et al. 

The team is composed of Masayuki Tanaka (ESO), Alexis Finoguenov (Max-Planck-Institute for Extraterrestrial Physics, Garching, Germany and University of Maryland, Baltimore, USA), Tadayuki Kodama (National Astronomical Observatory of Japan, Tokyo, Japan), Yusei Koyama (Department of Astronomy, University of Tokyo, Japan), Ben Maughan (H.H. Wills Physics Laboratory, University of Bristol, UK) and Fumiaki Nakata (Subaru Telescope, National Astronomical Observatory of Japan).

ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. 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 Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links

Contact

Masayuki TanakaDichteverteilung im Urknallgas

 

 

 

 

 

 

 

 

 

Simulation des Netzwerkes aus Dunkler Materie

 

 

 

 

 

 

 

 

 

 

 

 

Simulation des kosmischen Netzes aus Dunkler Materie

 

 

 

 

 

 

 

 

 

 

 

 

Verteilung nahe Galaxien am Himmel

 

 

 

 

 

 

 

 

 

Galaxiennetzwerk

 

 

 

 

 

 

 

 

 

 

 

Galaxiennetzwerk 2

Zwei Teams haben mit dem ESO Very Large Telescope hochaufgelöste Bilder des Überriesen im Sternbild Orion aufgenommen.

Sie haben dabei sowohl mit adaptiver Optik gearbeitet (zum Ausgleich der störenden Luftunruhe) aber auch mit Interferometrie (zur Erhöhung der Auflösung).

Beteigeuze ist 1000 mal größer als unsere Sonne und trotz ihres astronomisch jungen Alters von ein paar Millionen Jahren schon am Ende ihres Lebens angekommen (je massereicher ein Stern ist, desto schneller entwickelt er sich und desto kürzer ist seine Lebenserwartung): Sie wird vermutlich innerhalb der nächsten 1000 Jahre als Supernova explodieren.

Die Forscher haben eine Gasfahne entdeckt, die von der Oberfläche ausgeht und sechsmal größer als dieser Überriesenstern ist. Das zeigt, dass Beteigeuze unsymmetrisch ihre Masse reduziert, bevor sie explodieren wird. Vermutlich gibt es riesige blubbernde Gasströmungen im Stern selbst, die zur Abstoßung dieser gewaltigen Gasfahne beitragen. Jedenfalls zeigen Untersuchungen gewaltige Auf- und Abwärtsbewegungen der Oberflächengase des Sternes.

Weitere Infos: http://www.eso.org/public/outreach/press-rel/pr-2009/pr-27-09.html

Hier eine künstlerische Darstellung:

Künstlerische Darstellung

 

Quelle: ESO Pressemitteilung 27/09

Die Entdeckung fremder Planeten boomt: Mit einem Schlag wurden 32 Exoplaneten gefunden.

Die Methode ist einfach: Mit hochauflösenden Spektrographen bestimmt man die durch umkreisende Planeten hervorgerufene Bewegung des Sternes an Hand der Verschiebung der Spektrallinien (Doppler-Effekt).

Frühere Nachrichten:

Erdähnlicher Planet entdeckt

Moleküle auf Exoplanet

Exoplanet fotografiert

 

Und nun der aktuelle  der Original Pressebericht der ESO vom 19.10.09:

VideoberichtHier Klicken!

32 New Exoplanets Found

Today, at an international ESO/CAUP exoplanet conference in Porto, the team who built the High Accuracy Radial Velocity Planet Searcher, better known as HARPS, the spectrograph for ESO's 3.6-metre telescope, reports on the incredible discovery of some 32 new exoplanets, cementing HARPS's position as the world’s foremost exoplanet hunter. This result also increases the number of known low-mass planets by an impressive 30%. Over the past five years HARPS has spotted more than 75 of the roughly 400 or so exoplanets now known.

"HARPS is a unique, extremely high precision instrument that is ideal for discovering alien worlds," says Stéphane Udry, who made the announcement. “We have now completed our initial five-year programme, which has succeeded well beyond our expectations.

The latest batch of exoplanets announced today comprises no less than 32 new discoveries. Including these new results, data from HARPS have led to the discovery of more than 75 exoplanets in 30 different planetary systems. In particular, thanks to its amazing precision, the search for small planets, those with a mass of a few times that of the Earth — known as super-Earths and Neptune-like planets — has been given a dramatic boost. HARPS has facilitated the discovery of 24 of the 28 planets known with masses below 20 Earth masses. As with the previously detected super-Earths, most of the new low-mass candidates reside in multi-planet systems, with up to five planets per system.

In 1999, ESO launched a call for opportunities to build a high resolution, extremely precise spectrograph for the ESO 3.6-metre telescope at La Silla, Chile. Michel Mayor, from the Geneva Observatory, led a consortium to build HARPS, which was installed in 2003 and was soon able to measure the back-and-forward motions of stars by detecting small changes in a star’s radial velocity — as small as 3.5 km/hour, a steady walking pace. Such a precision is crucial for the discovery of exoplanets and the radial velocity method, which detects small changes in the radial velocity of a star as it wobbles slightly under the gentle gravitational pull from an (unseen) exoplanet, has been most prolific method in the search for exoplanets.

In return for building the instrument, the HARPS consortium was granted 100 observing nights per year during a five-year period to carry out one of the most ambitious systematic searches for exoplanets so far implemented worldwide by repeatedly measuring the radial velocities of hundreds of stars that may harbour planetary systems.

The programme soon proved very successful. Using HARPS, Mayor’s team discovered — among others — in 2004, the first super-Earth (around µ Ara; ESO 22/04); in 2006, the trio of Neptunes around HD 69830 (ESO 18/06); in 2007, Gliese 581d, the first super Earth in the habitable zone of a small star (ESO 22/07); and in 2009, the lightest exoplanet so far detected around a normal star, Gliese 581e (ESO 15/09). More recently, they found a potentially lava-covered world, with density similar to that of the Earth’s (ESO 33/09).

 “These observations have given astronomers a great insight into the diversity of planetary systems and help us understand how they can form,” says team member Nuno Santos.

The HARPS consortium was very careful in their selection of targets, with several sub-programmes aimed at looking for planets around solar-like stars, low-mass dwarf stars, or stars with a lower metal content than the Sun. The number of exoplanets known around low-mass stars — so-called M dwarfs — has also dramatically increased, including a handful of super Earths and a few giant planets challenging planetary formation theory.

By targeting M dwarfs and harnessing the precision of HARPS we have been able to search for exoplanets in the mass and temperature regime of super-Earths, some even close to or inside the habitable zone around the star,” says co-author Xavier Bonfils.

The team found three candidate exoplanets around stars that are metal-deficient. Such stars are thought to be less favourable for the formation of planets, which form in the metal-rich disc around the young star. However, planets up to several Jupiter masses have been found orbiting metal-deficient stars, setting an important constraint for planet formation models.

Although the first phase of the observing programme is now officially concluded, the team will pursue their effort with two ESO Large Programmes looking for super-Earths around solar-type stars and M dwarfs and some new announcements are already foreseen in the coming months, based on the last five years of measurements. There is no doubt that HARPS will continue to lead the field of exoplanet discoveries, especially pushing towards the detection of Earth-type planets.

More Information

This discovery was announced today at the ESO/CAUP conference “Towards Other Earths: perspectives and limitations in the ELT era", taking place in Porto, Portugal, on 19–23 October 2009. This conference discusses the new generation of instruments and telescopes that is now being conceived and built by different teams around the world to allow the discovery of other Earths, especially for the European Extremely Large Telescope (E-ELT). The new planets are simultaneously presented by Michel Mayor at the international symposium “Heirs of Galileo: Frontiers of Astronomy” in Madrid, Spain.

This research was presented in a series of eight papers submitted — or soon to be submitted — to the Astronomy and Astrophysics journal.

The team is composed of

  • Geneva Observatory: M. Mayor, S. Udry, D. Queloz, F. Pepe, C. Lovis, D. Ségransan, X. Bonfils
  • LAOG Grenoble: X. Delfosse, T. Forveille, X. Bonfils, C. Perrier
  • CAUP Porto: N.C. Santos
  • ESO: G. Lo Curto, D. Naef
  • University of Bern: W. Benz, C. Mordasini
  • IAP Paris: F. Bouchy, G. Hébrard
  • LAM Marseille: C. Moutou
  • Service d’aéronomie, Paris: J.-L. Bertaux

ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. 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 Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links

Contacts

Stéphane Udry
Geneva University, Switzerland
Phone: +41 22 379 2467
E-mail: stephane.udry (at) unige.ch

Xavier Bonfils
Université Joseph Fourier - Grenoble 1 / CNRS,  
Laboratoire d'Astrophysique de Grenoble (LAOG), France
Phone : +33 47 65 14 215
E-mail: xavier.bonfils (at) obs.ujf-grenoble.fr

Nuno Santos
Centro de Astrofisica da Universidade do Porto, 
Portugal

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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