Kategorie: Kosmologie

The infrared surveyor AKARI, a Japan Aerospace Exploration Agency (JAXA) mission with ESA participation, is nearing the completion of its first scan of the entire sky. During this phase of the mission, it has supplied the largest wavelength coverage of the Large Magellanic Cloud to date, and provided fascinating new images of this galaxy. The Large Magellanic Cloud is a neighbouring galaxy to the Milky Way, the galaxy to which our Solar System belongs. It is located extremely close by astronomical standards, at a distance of 160.000 light years, and it contains about 10 thousand million stars, about one tenth of our Galaxy’s stellar population.
Images

An apparent discrepancy in the Big Bang theory of the universe’s evolution has been reconciled by astrophysicists examining the movement of gases in stars. Professor John Lattanzio from Monash’s School of Mathematical Sciences and Director of the Centre for Stellar and Planetary Astrophysics said the confusion surrounding the Big Bang revolved around the amount of the gas Helium 3 in the universe. „The Big Bang theory predicts a certain amount of Helium 3 in the universe“, Professor Lattanzio said. „The trouble is, low mass stars (about one to two times the size of our sun) also make Helium 3 as a side product of burning the hydrogen in their cores.“ It’s been thought that when the star becomes a giant it mixes the Helium 3 to its surface and, near the end of its life, spews the Helium 3 into space just before it becomes a planetary nebula. But there are inconsistencies with the amount of Helium 3 predicted to be in the universe and the amount that’s actually there; there’s much less than expected. Some scientists have theorised that the rapid rotation of low mass stars destroys the Helium 3 they produce. But computer models that have included this rotation, while showing some destruction of Helium 3, have not been able to reconcile the Big Bang theory. Professor Lattanzio, in collaboration with Dr. Peter Eggleton and Dr. David Dearborn from the Lawrence Livermore National Laboratories in the US, ran 3D computer models of a red giant’s life on some of the world’s fastest computers to investigate whether there was some sort of gaseous mixing occurring in stars that destroyed Helium 3. Their findings have been published in the new issue of the international journal „Science“. Near the end of a star’s life there is a „core flash“ and it was at around this time that the computer models revealed a small instability in the movement of the gases in the star. „When we looked at this in 3D we found this hydrodynamic instability caused mixing and destroyed the Helium 3 so that none was released into space,“ Professor Lattanzio said. „This apparent problem with the Big Bang has been solved – the Helium 3 in the universe comes from the Big Bang and low mass stars, although they produce Helium 3, they do not release any into the universe because they destroy it.“
Scientists crack open stellar evolution

Deep Mixing of He-3: Reconciling Big Bang and Stellar Nucleosynthesis

Mit Hilfe der europäischen H.E.S.S.-Teleskope in Namibia entdeckten Forscher hochenergetische Gammastrahlung, die aus dem Zentrum der riesigen Radiogalaxie M87 kommt. Wegen der beobachteten Schwankungen der Strahlung kommt als Ursprung eigentlich nur ein Ort in Frage: ein Schwarzes Loch im Zentrum der Galaxie.

Gamma-Strahlung vom Rand eines supermassiven schwarzen Lochs entdeckt

A new photograph from the Spitzer Space Telescope shows how supernova remnant Cassiopeia A evolved over time. The original star contained 15 to 20 times the mass of our Sun, and was made up of concentric shells of elements. The lightest elements, like hydrogen, were in the outermost shell, while the heaviest elements sunk to the centre. The shells of the exploded material match up quite well with the original layers in the star before it detonated as a supernova.

Press release

New images taken with Hubble’s Advanced Camera for Surveys (ACS) in November 2005 and September 2006 show the evolution of the light echo around the star V838 in the constellation of Monoceros.
Hubble’s Latest Views of Light Echo from Star V838 Monocerotis

Astronomers have discovered two of the most distant galaxies ever seen, when the Universe was only 700 million years old. The galaxies were first discovered as part of the Hubble Space Telescope’s Deep Field Survey, which looked into the distant Universe. Astronomers then did follow-on observations with the Spitzer Space Telescope to confirm their distance and age. The galaxies are between 50-300 million years old, and have only 1% of the mass of our own Milky Way.

Astronomers weigh 200-million-year-old baby galaxies

In 1054 A.D., Chinese astronomers recorded the temporary brightening of a star in the constellation Taurus. Nearly 1000 years later, we look into the same region and see the exploded remnants of a dead star: the Crab Nebula. A new composite photograph of the Crab Nebula was made by merging images from Hubble, the Chandra X-Ray Observatory, and the Spitzer Space Telescope. It shows only a hail of high-energy particles and expanding debris cloud that once was a massive star.
https://chandra.harvard.edu/photo/2006/crab/

Zooming in on a nearby young star called HD 141569A, astronomers using the Subaru telescope on Mauna Kea, Hawaii, discovered a hole in a disk of gas and dust encircling the star. The existence of this large gap, which is about the size of the orbit of Saturn, supports the theory that this young star ended its infancy abruptly by ionizing and pushing away the gas in the disk from which it was born.
https://www.subarutelescope.org/Pressrelease/2006/10/23/index.html

Astronomers using NASA’s Spitzer Space Telescope have recently identified two quasars, or supermassive black holes, that may be on the verge of a colossal cosmic „belch“.
https://www.spitzer.caltech.edu/news/feature06-34-belching-black-holes

Imagine trying to understand how a football game works based on just a few fuzzy snapshots of the game in play. Astronomers have faced this challenge when it comes to understanding the dynamics of the beehive swarm of stars in the globular star clusters that orbit our Milky Way Galaxy. Now, NASA’s Hubble Space Telescope has provided astronomers with the best observational evidence to date that globular clusters sort out stars according to their mass, governed by a gravitational billiard ball game between stars.
https://hubblesite.org/contents/news-releases/2006/news-2006-33.html