16 Jahre lang haben deutsche Astronomen mit den Infrorot Teleskopen der Europäischen Südsternwarte ESO in Chile 28 Sterne im Zentrum der Galaxis beobachtet, die um das supermassive Schwarze Loch kreisen. Im sichtbaren Licht sind diese Sterne nicht sichtbar, weil ihre Strahlung vom Satub stark abgeschwächt wird.

Die Auflösung der Bilder liegt bei 0,3 Millibogensekunden, das ist nur mit der speziellen adaptiven Optik, die das Verzerren der Bilder durch die Luft ausgleicht (blurring), möglich geworden.

Durch diese Beobachtungen ist die Existenz des 4 Millionen Sonnemassen schweren Schwarzen Loches endgültig gesichert.

Der Stern S2 ist in der Beobachtungszeit mehr als einmal um das Schwarze Loch gelaufen, er kommt bis auf wenige Lichtstunden an das Schwarze Loch heran.

Noch ist nicht verstanden, wie die Sterne in dieser Nähe zum Schwarzen Loch entstanden sind, zukünftige Messungen werden aber nicht nur dieses Rätsel lösen, sondern auch die Allgemeine Relativitätstheorie in der Nähe solcher großen Massen testen.

Interessant ist noch, dass 95% der Masse, die die Sterne in ihreren Bahnen hält, vom Schwarzen Loch stammen. Es bleibt wenig Raum für Dunkle Materie.

Es folgen die ESO Pressemeldung in Englisch und ein Link zu mehreren Filmen.

Bilder, Filme und Animationen findet man hierHier klicken!

ESO 46/08 - Science Release

10 December 2008
For immediate release

Unprecedented 16-Year Long Study Tracks Stars Orbiting Milky Way Black Hole

In a 16-year long study, using several of ESO's flagship telescopes, a team of German astronomers has produced the most detailed view ever of the surroundings of the monster lurking at our Galaxy's heart — a supermassive black hole. The research has unravelled the hidden secrets of this tumultuous region by mapping the orbits of almost 30 stars, a five-fold increase over previous studies. One of the stars has now completed a full orbit around the black hole.

By watching the motions of 28 stars orbiting the Milky Way's most central region with admirable patience and amazing precision, astronomers have been able to study the supermassive black hole lurking there. It is known as "Sagittarius A*" (pronounced "Sagittarius A star"). The new research marks the first time that the orbits of so many of these central stars have been calculated precisely and reveals information about the enigmatic formation of these stars — and about the black hole to which they are bound.

"The centre of the Galaxy is a unique laboratory where we can study the fundamental processes of strong gravity, stellar dynamics and star formation that are of great relevance to all other galactic nuclei, with a level of detail that will never be possible beyond our Galaxy," explains Reinhard Genzel, leader of the team from the Max-Planck-Institute for Extraterrestrial Physics in Garching near Munich.

The interstellar dust that fills the Galaxy blocks our direct view of the Milky Way's central region in visible light. So astronomers used infrared wavelengths that can penetrate the dust to probe the region. While this is a technological challenge, it is well worth the effort. "The Galactic Centre harbours the closest supermassive black hole known. Hence, it is the best place to study black holes in detail," argues the study's first author, Stefan Gillessen.

The team used the central stars as "test particles" by watching how they move around Sagittarius A*. Just as leaves caught in a wintry gust reveal a complex web of air currents, so does tracking the central stars show the nexus of forces at work at the Galactic Centre. These observations can then be used to infer important properties of the black hole itself, such as its mass and distance. The new study also showed that at least 95% of the mass sensed by the stars has to be in the black hole. There is thus little room left for other dark matter.

"Undoubtedly the most spectacular aspect of our long term study is that it has delivered what is now considered to be the best empirical evidence that supermassive black holes do really exist. The stellar orbits in the Galactic Centre show that the central mass concentration of four million solar masses must be a black hole, beyond any reasonable doubt," says Genzel. The observations also allow astronomers to pinpoint our distance to the centre of the Galaxy with great precision, which is now measured to be 27 000 light-years.

To build this unparalleled picture of the Milky Way's heart and calculate the orbits of the individual stars the team had to study the stars there for many years. These latest groundbreaking results therefore represent 16 years of dedicated work, which started with observations made in 1992 with the SHARP camera attached to ESO's 3.5-metre New Technology Telescope located at the La Silla observatory in Chile. More observations have subsequently been made since 2002 using two instruments mounted on ESO's 8.2 m Very Large Telescope (VLT). A total of roughly 50 nights of observing time with ESO telescopes, over the 16 years, has been used to complete this incredible set of observations.

The new work improved the accuracy by which the astronomers can measure the positions of the stars by a factor of six compared to previous studies. The final precision is 300 microarcseconds, equivalent at seeing a one euro coin from a distance of roughly 10 000 km.

For the first time the number of known stellar orbits is now large enough to look for common properties among them. "The stars in the innermost region are in random orbits, like a swarm of bees," says Gillessen. "However, further out, six of the 28 stars orbit the black hole in a disc. In this respect the new study has also confirmed explicitly earlier work in which the disc had been found, but only in a statistical sense. Ordered motion outside the central light-month, randomly oriented orbits inside – that's how the dynamics of the young stars in the Galactic Centre are best described."

One particular star, known as S2, orbits the Milky Way's centre so fast that it completed one full revolution within the 16-year period of the study. Observing one complete orbit of S2 has been a crucial contribution to the high accuracy reached and to understanding this region. Yet the mystery still remains as to how these young stars came to be in the orbits they are observed to be in today. They are much too young to have migrated far, but it seems even more improbable that they formed in their current orbits where the tidal forces of the black hole act. Excitingly, future observations are already being planned to test several theoretical models that try to solve this riddle.

"ESO still has much to look forward to," says Genzel. "For future studies in the immediate vicinity of the black hole, we need higher angular resolution than is presently possible." According to Frank Eisenhauer, principal investigator of the next generation instrument GRAVITY, ESO will soon be able to obtain that much needed resolution. "The next major advance will be to combine the light from the four 8.2-metre VLT unit telescopes – a technique known as interferometry. This will improve the accuracy of the observations by a factor 10 to 100 over what is currently possible. This combination has the potential to directly test Einstein's general relativity in the presently unexplored region close to a black hole."

 

Max-Planck-Gesellchaft:

Im Herzen der Milchstraße lauert ein supermassives Schwarzes Loch. In einer 16 Jahre langen Beobachtungskampagne haben Astronomen nun das bisher detailreichste Bild dieser turbulenten Region gezeichnet. Die Forscher konnten die Umlaufbahnen von 28 Sternen verfolgen - fünf Mal mehr als in vorhergehenden Untersuchungen. Seit Beginn der Messungen im Jahr 1992 hat einer der Sterne jetzt sogar das Schwarze Loch einmal vollständig umrundet. (The Astrophysical Journal)

"Das Zentrum der Galaxis ist ein einzigartiges Labor, in dem wir grundlegende Gesetze der Schwerkraft, der Sternendynamik und Sternbildung studieren können. Diese Prozesse sind für alle anderen galaktischen Kerne von zentraler Bedeutung, aber nur im galaktischen Zentrum erreicht man den notwendigen Detaillierungsgrad", sagt Reinhard Genzel, der das Team am Max-Planck-Institut für extraterrestrische Physik in Garching bei München leitet.

Der interstellare Staub, der die Galaxis füllt, behindert im sichtbaren Licht die direkte Sicht auf das Zentrum. Daher benutzten die Astronomen für ihre Untersuchung dieser Himmelsregion Wellenlängen im Infraroten, die den Staub durchdringen. Das bedeutete eine große technische Herausforderung, doch der Aufwand lohnte sich: "Das galaktische Zentrum beherbergt das nächstliegende uns bekannte superschwere Schwarze Loch, auch Sagittarius A* genannt. Daher ist das der beste Ort überhaupt, wenn man diese Klasse von Objekten untersuchen möchte", meint Stefan Gillessen, Erstautor der Studie.

Die zentralen Sterne der Galaxis dienten als "Testteilchen", denn die Forscher beobachteten genau, auf welche Weise sie sich um Sagittarius A* bewegten. Ähnlich wie Laub, das von einem Windstoß hinweggefegt wird, ein komplexes Netzwerk aus Luftströmen enthüllt, spiegelten auch die Umläufe der Sterne deutlich die Kräfte wider, die im galaktischen Zentrum wirken.

Diese Beobachtungen wurden dann benutzt, um wichtige Eigenschaften des Schwarzen Lochs abzuleiten, etwa seine Masse und Entfernung. Die neue Untersuchung zeigt auch, dass mindestens 95 Prozent der Masse, die auf die Sterne einwirkt, sich im Schwarzen Loch befinden muss. Es bleibt daher wenig Raum für andere dunkle Materie.

"Unsere Langzeitstudie hat den bisher besten empirischen Beweis erbracht, dass supermassive Schwarze Löcher wirklich existieren. Die Sternorbits im galaktischen Zentrum zeigen zweifelsfrei, dass die zentrale Massenkonzentration von vier Millionen Sonnenmassen ein Schwarzes Loch sein muss", sagt Genzel. Die Beobachtungen erlaubten es den Astronomen auch, die Entfernung der Erde vom Zentrum der Galaxis mit hoher Genauigkeit zu bestimmen: Sie beträgt demnach 27.000 Lichtjahre.

Um das beispiellos detaillierte Bild vom Herzen der Milchstraße erstellen und die Umlaufbahnen der einzelnen Sterne berechnen zu können, musste das Team die Sterne über viele Jahre hinweg beobachten. Vor 16 Jahren wurden mit der SHARP-Kamera am New Technology Telescope der Europäischen Südsternwarte die ersten Daten gewonnen und seit 2002 weitere Folgebeobachtungen mit zwei Instrumenten am Very Large Telescope (VLT) gemacht.

Insgesamt rund 50 Nächte Beobachtungszeit mussten investiert werden, bis die Wissenschaftler zu ihren spektakulären Ergebnissen kamen. Die langfristige Vision des deutschen Forscherteams um Reinhard Genzel wurde im Juni dieses Jahres mit dem hoch angesehenen Shaw-Preis ausgezeichnet.

Durch die neue Studie lassen sich nun die Positionen der Sterne mit sechsfach höherer Präzision vermessen als zuvor. Dabei erreichten die Forscher eine Genauigkeit von 300 Mikrobogensekunden: Unter diesem winzigen Winkel erscheint eine Ein-Euro-Münze aus einer Entfernung von rund 10.000 Kilometern.

Zum ersten Mal ist jetzt die Anzahl bekannter Sternorbits groß genug, um sie auf gemeinsame Eigenschaften hin zu untersuchen. "Die Bahnen der Sterne in der innersten Region sind völlig regellos. Dort geht es zu wie in einem Bienenschwarm", sagt Stefan Gillessen. Jedoch umkreisen weiter draußen sechs der 28 Sterne das Schwarze Loch in einer Scheibe. In dieser Hinsicht hat die neue Studie auch frühere Arbeiten bestätigt, in denen die Scheibe gefunden worden war. "Geordnete Bewegung außerhalb des ersten Lichtmonats, zufällig orientierte Bahnen innerhalb davon - so lässt sich die Dynamik der jungen Sterne im galaktischen Zentrum am besten beschreiben", sagt Gillessen.

Ein bestimmter Stern, bekannt als S2, umkreist das Zentrum der Milchstraße so schnell, dass er innerhalb der 16-Jahres-Dauer der Studie seine Bahn einmal vollständig durchlaufen hat. Die Beobachtung eines kompletten Umlaufs von S2 trug entscheidend zur Messgenauigkeit und damit zum Verständnis dieser Region bei. Ein Rätsel bleibt jedoch, wie diese jungen Sterne in die beobachteten Umlaufbahnen gelangten. Sie sind viel zu jung, um von weit her gekommen zu sein, aber es erscheint noch unwahrscheinlicher, dass sie in ihren jetzigen Bahnen entstanden, wo die Gezeitenkräfte des Schwarzen Loches wirken. Zukünftige Beobachtungen sollen theoretische Erklärungsmodelle testen.

"Für Untersuchungen in der unmittelbaren Umgebung des Schwarzen Lochs benötigen wir eine höhere Winkelauflösung als zurzeit möglich", sagt Genzel. Laut Frank Eisenhauer, Projektleiter des Nahinfrarot-Instrumentes GRAVITY, soll die Europäische Südsternwarte jedoch bald in der Lage sein, diese benötigte Auflösung zu erreichen. "Der nächste große Schritt wird sein, das Licht von den vier 8,2-Meter-Teleskopen des VLT zu kombinieren." Das werde die Genauigkeit der Beobachtungen im Vergleich zum heute Möglichen um einen Faktor zwischen 10 und 100 steigern. Eisenhauer: "Diese Kombination besitzt das Potenzial, Einsteins Allgemeine Relativitätstheorie in der gegenwärtig noch unerforschten Region nahe an einem Schwarzen Loch zu überprüfen."

Quelle: Max-Planck-Gesellschaft 

 

Im Sternbild Centaurus steht eine Sternenkugel, die man früher zu den Kugelsternhaufen gezählt hat.

Entfernung: 17 000 Lj

Helligkeit: 3m,7 (d.h. leicht mit bloßem Auge zu sehen)

Bedeckt am Himmel eine Vollmondfläche

Gigantisch ist der Anblick in einem Fernglas oder Fernrohr.

Mit dem 2,2 -Meter-Teleskop der Europäischen Südsternwarte ESO in Chile wurde jetzt eine neue Aufnahme mit dem Wide Field Imager erstellt, die 10 Millionen Einzelsterne bis in das Zentrum hinein zeigt.

Vieles spricht dafür dass kein Kugelstenrhaufen vorliegt, sondern das Zentrum einer kleinen Galaxie, die mit unserer Galaxis verschmolzen ist. Lediglich der Zentralbereich hat sich noch nicht aufgelöst.

- Die schnelle Bewegung der zentrumsnahen Sterne lässt sich nur durch ein Schwarzes Loch mit 40000 Sonnenmassen erklären. Solche großen Schwarzen Löcher stehen nur in den Zentren von Galaxien und nicht in denen von Kugelsternhaufen.

- In einem Kugelsternhaufen sind alle Sterne vor langer Zeit zu gleicher Zeit entstanden, sie sind also alt und gleich alt! In Omega Cenaturi lassen sich aber durch die Sternspektren Sterne verschiedener Generationen nachweisen. Dies merkt man an dem unterschiedlichen Gehalt schwerer Elemente.

Das obige Bild kann durch Anklicken vergrößert werden!

Ein Bild mit der vollen Auflösung kann man unter:  http://www.eso.org/public/outreach/press-rel/pr-2008/phot-44-08.html herunterladen (72 Mb!)

 

ESO- Presseerklärung:

2 December 2008
For Immediate Release

Omega Centauri — the glittering giant of the southern skies

Omega Centauri is one of the finest jewels of the southern hemisphere night sky, as ESO's latest stunning image beautifully illustrates. Containing millions of stars, this globular cluster is located roughly 17 000 light-years from Earth in the constellation of Centaurus.

 
The Glittering Giant

Sparkling away at magnitude 3.7 and appearing nearly as large as the full moon on the southern night sky, Omega Centauri is visible with the unaided eye from a clear, dark observing site. Even through a modest amateur telescope, the cluster is revealed as an incredible, densely packed sphere of glittering stars. But astronomers need to use the full power of professional telescopes to uncover the amazing secrets of this beautiful globular cluster.

This new image is based on data collected with the Wide Field Imager (WFI), mounted on the 2.2-metre diameter Max-Planck/ESO telescope, located at ESO's La Silla observatory, high up in the arid mountains of the southern Atacama Desert in Chile. Omega Centauri is about 150 light-years across and is the most massive of all the Milky Way's globular clusters. It is thought to contain some ten million stars!

Omega Centauri has been observed throughout history. Both the great astronomer Ptolemy and later Johann Bayer catalogued the cluster as a star. It was not until much later, in the early 19th century, that an Englishman, the astronomer John Frederick William Herschel (son of the discoverer of Uranus), realised that Omega Centauri was in fact a globular cluster. Globular clusters are some of the oldest groupings of stars to be found in the halos that surround galaxies like our own Milky Way. Omega Centauri itself is thought to be around 12 billion years old.

Recent research into this intriguing celestial giant suggests that there is a medium sized black hole sitting at its centre. Observations made with the Hubble Space Telescope (see heic0809 ) and the Gemini Observatory showed that stars at the cluster's centre were moving around at an unusual rate — the cause, astronomers concluded, was the gravitational effect of a massive black hole with a mass of roughly 40 000 times that of the Sun.

The presence of this black hole is just one of the reasons why some astronomers suspect Omega Centauri to be an imposter. Some believe that it is in fact the heart of a dwarf galaxy that was largely destroyed in an encounter with the Milky Way. Other evidence (see ESO 07/05 andheic0708) points to the several generations of stars present in the cluster — something unexpected in a typical globular cluster, which is thought to contain only stars formed at one time. Whatever the truth, this dazzling celestial object provides professional and amateur astronomers alike with an incredible view on clear dark nights.

Insgesamt 55 Stunden lang ist ein kleines Gebiet am Himmel am Übergang zum UV Licht fototgrafiert worden. Eine Unzahl von Galaxien (bitte das Nachrichtenbild anklicken, abspeichern und dann mit einem eigenen Bildprogramm hineinzoomen) ist bis zu Entfernungen  von 11 Mrd. Lj zu sehen.

Die Pressemeldung der ESO:

A Pool of Distant Galaxies – the deepest ultraviolet image of the Universe yet

Anyone who has wondered what it might be like to dive into a pool of millions of distant galaxies of different shapes and colours, will enjoy the latest image released by ESO. Obtained in part with the Very Large Telescope, the image is the deepest ground-based U-band image of the Universe ever obtained. It contains more than 27 million pixels and is the result of 55 hours of observations with the VIMOS instrument.

 
A Pool of Distant Galaxies

This uniquely beautiful patchwork image, with its myriad of brightly coloured galaxies, shows the Chandra Deep Field South (CDF-S), arguably the most observed and best studied region in the entire sky. The CDF-S is one of the two regions selected as part of the Great Observatories Origins Deep Survey (GOODS), an effort of the worldwide astronomical community that unites the deepest observations from ground- and space-based facilities at all wavelengths from X-ray to radio. Its primary purpose is to provide astronomers with the most sensitive census of the distant Universe to assist in their study of the formation and evolution of galaxies.

The new image released by ESO combines data obtained with the VIMOS instrument in the U- and R-bands, as well as data obtained in the B-band with the Wide-Field Imager (WFI) attached to the 2.2 m MPG/ESO telescope at La Silla, in the framework of the GABODS survey.

The newly released U-band image – the result of 40 hours of staring at the same region of the sky and just made ready by the GOODS team – is the deepest image ever taken from the ground in this wavelength domain. At these depths, the sky is almost completely covered by galaxies, each one, like our own galaxy, the Milky Way, home of hundreds of billions of stars.

Galaxies were detected that are a billion times fainter than the unaided eye can see and over a range of colours not directly observable by the eye. This deep image has been essential to the discovery of a large number of new galaxies that are so far away that they are seen as they were when the Universe was only 2 billion years old.

In this sea of galaxies – or island universes as they are sometimes called – only a very few stars belonging to the Milky Way are seen. One of them is so close that it moves very fast on the sky. This "high proper motion star" is visible to the left of the second brightest star in the image. 

Notes

Because the Universe looks the same in all directions, the number, types and distribution of galaxies is the same everywhere. Consequently, very deep observations of the Universe can be performed in any direction. A series of fields were selected where no foreground object could affect the deep space observations (such as a bright star in our galaxy, or the dust from our Solar System). These fields have been observed using a number of telescopes and satellites, so as to collect information at all possible wavelengths, and characterise the full spectrum of the objects in the field. The data acquired from these deep fields are normally made public to the whole community of astronomers, constituting the basis for large collaborations.

Observations in the U-band, that is, at the boundary between visible light and ultraviolet are challenging: the Earth's atmosphere becomes more and more opaque out towards the ultraviolet, a useful property that protects people's skin, but limiting to ground-based telescopes. At shorter wavelengths, observations can only be done from space, using, for example, the Hubble Space Telescope. On the ground, only the very best sites, such as ESO's Paranal Observatory in the Atacama Desert, can perform useful observations in the U-band. Even with the best atmospheric conditions, instruments are at their limit at these wavelengths: the glass of normal lenses transmits less UV light, and detectors are less sensitive, so only instruments designed for UV observations, such as VIMOS on ESO's Very Large Telescope, can get enough light.

The Chandra Deep Field South, observed in the U-, B-, and R-bands with ESO's VIMOS and WFI instruments. The U-band VIMOS observations were made over a period of 40 hours and constitute the deepest image ever taken from the ground in the U-band. The image covers a region of 14.1 x 21.6 arcmin on the sky and shows galaxies that are 1 billion times fainter than can be seen by the unaided eye. The VIMOS R-band image was assembled by the ESO/GOODS team from archival data, while the WFI B-band image was produced by the GABODS team. 

Die ESO (Europäische Südsternwarte)  berichtet über die Herstellung des aktuellen Fotots eines Exoplaneten, die auf deutsch kommentiert sind:

Beta Pictoris planet finally imaged?

A team of French astronomers using ESO's Very Large Telescope have discovered an object located very close to the star Beta Pictoris, and which apparently lies inside its disc. With a projected distance from the star of only 8 times the Earth-Sun distance, this object is most likely the giant planet suspected from the peculiar shape of the disc and the previously observed infall of comets onto the star. It would then be the first image of a planet that is as close to its host star as Saturn is to the Sun.

 
Der Planet steht etwa so weit wie Saturn von seiner Sonne entfernt.
Um Beta Pictoris wurde schon 1984 die Staubscheibe entdeckt. Inzwischen kennt man ihre Verbiegung und hat in den Stern fallende Kometen entdeckt. Viele Beobachtungen deuteten auf einen Planeten hin.
Dieser konnte jetzt (sehr wahrscheinlich) fotografiert werden, nach dem es gelungen ist, die Infrarot-Strahlung der Staubscheibe abzuziehen. Übrig blieb ein Lichtpunkt, der an der richtigen Stelle zu sehen ist und sehr wahrscheinlich weder Vorder- noch Hintergrundstern ist.
Beta Pictoris ist 12 Millionen Jahre alt und 70 Lichtjahre von uns entfernt.
 

The hot star Beta Pictoris is one of the best-known examples of stars surrounded by a dusty 'debris' disc. Debris discs are composed of dust resulting from collisions among larger bodies like planetary embryos or asteroids. They are a bigger version of the zodiacal dust in our Solar System. Its disc was the first to be imaged — as early as 1984 — and remains the best-studied system. Earlier observations showed a warp of the disc, a secondary inclined disc and infalling comets onto the star. "These are indirect, but tell-tale signs that strongly suggest the presence of a massive planet lying between 5 and 10 times the mean Earth-Sun distance from its host star," says team leader Anne-Marie Lagrange. "However, probing the very inner region of the disc, so close to the glowing star, is a most challenging task."

In 2003, the French team used the NAOS-CONICA instrument (or NACO [1]), mounted on one of the 8.2 m Unit Telescopes of ESO's Very Large Telescope (VLT), to benefit from both the high image quality provided by the Adaptive Optics system at infrared wavelengths and the good dynamics offered by the detector, in order to study the immediate surroundings of Beta Pictoris.

Recently, a member of the team re-analysed the data in a different way to seek the trace of a companion to the star. Infrared wavelengths are indeed very well suited for such searches. "For this, the real challenge is to identify and subtract as accurately as possible the bright stellar halo,"explains Lagrange. "We were able to achieve this after a precise and drastic selection of the best images recorded during our observations."

The strategy proved very rewarding, as the astronomers were able to discern a feeble, point-like glow well inside the star's halo. To eliminate the possibility that this was an artefact and not a real object, a battery of tests was conducted and several members of the team, using three different methods, did the analysis independently, always with the same success. Moreover, the companion was also discovered in other data sets, further strengthening the team's conclusion: the companion is real.

"Our observations point to the presence of a giant planet, about 8 times as massive as Jupiter and with a projected distance from its star of about 8 times the Earth-Sun distance, which is about the distance of Saturn in our Solar System [2]," says Lagrange.

"We cannot yet rule out definitively, however, that the candidate companion could be a foreground or background object," cautions co-worker Gael Chauvin. "To eliminate this very small possibility, we will need to make new observations that confirm the nature of the discovery."

The team also dug into the archives of the Hubble Space Telescope but couldn't see anything, "while most possible foreground or background objects would have been detected", remarks another team member, David Ehrenreich.

The fact that the candidate companion lies in the plane of the disc also strongly implies that it is bound to the star and its proto-planetary disc.

"Moreover, the candidate companion has exactly the mass and distance from its host star needed to explain all the disc's properties. This is clearly another nail in the coffin of the false alarm hypothesis," adds Lagrange.

When confirmed, this candidate companion will be the closest planet from its star ever imaged. In particular, it will be located well inside the orbits of the outer planets of the Solar System. Several other planetary candidates have indeed been imaged, but they are all located further away from their host star: if located in the Solar System, they would lie close or beyond the orbit of the farthest planet, Neptune. The formation processes of these distant planets are likely to be quite different from those in our Solar System and in Beta Pictoris.

"Direct imaging of extrasolar planets is necessary to test the various models of formation and evolution of planetary systems. But such observations are only beginning. Limited today to giant planets around young stars, they will in the future extend to the detection of cooler and older planets, with the forthcoming instruments on the VLT and on the next generation of optical telescopes," concludes team member Daniel Rouan.

Only 12 million years old, the 'baby star' Beta Pictoris is located about 70 light-years away towards the constellation Pictor (the Painter). 

Notes

[1] NACO is one of the instruments on ESO's VLT that make use of Adaptive Optics (AO). Such systems work by means of a computer-controlled deformable mirror that counteracts the image distortion induced by atmospheric turbulence (see e.g. ESO Press Release 25/01).

[2] The astronomers can only see the projected separation between the star and the planet (that is, the separation projected on the plane of the sky). 

More Information

"A probable giant planet imaged in the β Pictoris disk. VLT/NACO Deep L-band imaging", by A.-M. Lagrange et al., 2008, Letter to the Editor of Astronomy and Astrophysics, in press. (a PDF file can be downloaded here
The team is composed of A.-M. Lagrange, G. Chauvin, D. Ehrenreich

 

 

Zum Foto:

This composite image represents the close environment of Beta Pictoris as seen in near infrared light. This very faint environment is revealed after a very careful subtraction of the much brighter stellar halo. The outer part of the image shows the reflected light on the dust disc, as observed in 1996 with the ADONIS instrument on ESO's 3.6 m telescope; the inner part is the innermost part of the system, as seen at 3.6 microns with NACO on the Very Large Telescope. The newly detected source is more than 1000 times fainter than Beta Pictoris, aligned with the disc, at a projected distance of 8 times the Earth-Sun distance. This corresponds to 0.44 arcsecond on the sky, or the angle sustained by a one Euro coin seen at a distance of about 10 kilometres. Because the planet is still very young, it is still very hot, with a temperature around 1200 degrees Celsius. Both parts of the image were obtained on ESO telescopes equipped with adaptive optics. 
Credit: ESO/A.-M. Lagrange et al.

Gamma-Bursts sind die stärksten Explosionen im Kosmos. In einer Sekunde setzen sie soviel Energie frei wie die Sonne in ihrer ganzen Existenz. Im Sternbild Bootes wurde im März 2008 ein solcher Gamma-Burst beobachtet, dessen optisches Nachleuchten in einer Entfernung von 7,5 Milliarden Lichtjahren mit bloßem Auge sichtbar war (5,7 mag).

Vermutlich ist ein Schwarzes Loch entstanden, aus dessen Akkretionsscheibe ein Jet herausgeschleudert kam, der zufälligerweis exakt auf die Erde ausgerichtet war.

13.9.2008: Nicht so hell, aber dafür weiter weg:

Am 13.9. wurde ein Gammjaburst beobachtet, der sechs Minuten später auch optisch utnersucht werden konnte. Dafurch konnte die Rotverschiebung und somit die Entfernung vermessen werden. Es kam der Rekordwert von z = 6,8 für Gammabursts heraus, d.h. diese Explosion fand 825 Millionen Jahre nach dem Urknall statt, "kurz" nachdem sich die ersten Sterne und Galaxien gebildet haben!

Ausführlicher BildberichtHier klicken!

 

ESO - Pressemeldung:

The Double Firing Burst

Brightest gamma-ray burst provides wealth of information on how stars explode

Astronomers from around the world combined data from ground- and space-based telescopes to paint a detailed portrait of the brightest explosion ever seen. The observations reveal that the jets of the gamma-ray burst called GRB 080319B were aimed almost directly at the Earth.

GRB 080319B was so intense that, despite happening halfway across the Universe, it could have been seen briefly with the unaided eye (ESO 08/08). In a paper to appear in the 11 September issue of Nature, Judith Racusin of Penn State University, Pennsylvania (USA), and a team of 92 co-authors report observations across the electromagnetic spectrum that began 30 minutes before the explosion and followed it for months afterwards.

"We conclude that the burst's extraordinary brightness arose from a jet that shot material almost directly towards Earth at almost the speed of light - the difference is only 1 part in 20 000," says Guido Chincarini, a member of the team.

Gamma-ray bursts are the Universe's most luminous explosions. Most occur when massive stars run out of fuel. As a star collapses, it creates a black hole or neutron star that, through processes not fully understood, drives powerful gas jets outward. As the jets shoot into space, they strike gas previously shed by the star and heat it, thereby generating bright afterglows.

The team believes the jet directed toward Earth contained an ultra-fast component just 0.4 degrees across (this is slightly smaller than the apparent size of the Full Moon). This jet is contained within another slightly less energetic jet about 20 times wider.

The broad component is more typical of other bursts. "Perhaps every gamma-ray burst has a narrow jet, but astronomers miss it most of the time," says team member Stefano Covino. "We happened to view this monster down the barrel of the very narrow and energetic jet, and the chance for this nearly head-on alignment to occur is only about once a decade," added his colleague Cristiano Guidorzi.

GRB 080319B was detected by the NASA/STFC/ASI Swift satellite towards the constellation of Boötes, the "Herdsman". A host of ground-based telescopes reacted promptly to study this new object in the sky, including ESO's Very Large Telescope, which was the first to provide the distance of the object, 7.5 billion light-years. The visible light from the burst was detected by a handful of wide-field cameras worldwide that are mounted on telescopes constantly monitoring a large fraction of the sky. One of these was the TORTORA camera mounted on the 0.6-m REM telescope at ESO's La Silla Observatory (ESO 26/07).

TORTORA's rapid imaging provides the most detailed look yet at the visible light associated with the initial blast of a gamma-ray burst. "We've been waiting a long time for this one," says TORTORA senior scientist Grigory Beskin of Russia's Special Astrophysical Observatory. The data collected simultaneously by TORTORA and the Swift satellite allowed astronomers to explain the properties of this burst.