Latest Large-scale structure of the cosmos Stories

Located half a billion light-years from Earth, ESO 306-17, is a large, bright elliptical galaxy in the southern sky of a type known as a fossil group. Astronomers use this term to emphasize the isolated nature of these galaxies. However, are they like fossils "” the last remnants of a once active community "” or is it more sinister than that? Did ESO 306-17 gobble up its next-door neighbors?Gravity brings galaxies together and bigger ones swallow smaller ones. There is evidence that our...

One of the pleasures of perusing ancient maps is locating regions so poorly explored that mapmakers warned of dragons and sea monsters. Now, astronomers using NASA's Fermi Gamma-ray Space Telescope find themselves in the same situation as cartographers of old. A new study of the ever-present fog of gamma rays from sources outside our galaxy shows that less than a third of the emission arises from what astronomers once considered the most likely suspects -- black-hole-powered jets from active...

Using entire galaxies as lenses to look at other galaxies, researchers have a newly precise way to measure the size and age of the universe and how rapidly it is expanding, on par with other techniques. The measurement determines a value for the Hubble constant, which indicates the size of the universe, and confirms the age of the universe as 13.75 billion years old, within 170 million years. The results also confirm the strength of dark energy, responsible for accelerating the expansion of...

Today ESO has released a dramatic new image of NGC 346, the brightest star-forming region in our neighboring galaxy, the Small Magellanic Cloud, 210 000 light-years away towards the constellation of Tucana (the Toucan). The light, wind and heat given off by massive stars have dispersed the glowing gas within and around this star cluster, forming a surrounding wispy nebular structure that looks like a cobweb. NGC 346, like other beautiful astronomical scenes, is a work in progress, and changes...

Around a quarter of the globular star clusters in our Milky Way galaxy are invaders from other galaxies, according to a team of scientists from Swinburne University of Technology in Australia. In a paper accepted for publication in Monthly Notices of the Royal Astronomical Society, Swinburne astronomer Professor Duncan Forbes has shown that many of our galaxy's globular star clusters are actually foreigners - having been born elsewhere and then migrated to our Milky Way. "It turns out that...

Imagine finding a living dinosaur in your backyard. Astronomers have found the astronomical equivalent of prehistoric life in our intergalactic backyard: a group of small, ancient galaxies that has waited 10 billion years to come together. These "late bloomers" are on their way to building a large elliptical galaxy.Such encounters between dwarf galaxies are normally seen billions of light-years away and therefore occurred billions of years ago. But these galaxies, members of Hickson...

Two spectacular tails of X-ray emission have been seen trailing behind a galaxy using the Chandra X-ray Observatory. A composite image of the galaxy cluster Abell 3627 shows X-rays from Chandra in blue, optical emission in yellow and emission from hydrogen light -- known to astronomers as "H-alpha" -- in red. The optical and H-alpha data were obtained with the Southern Astrophysical Research (SOAR) Telescope in Chile.At the front of the tail is the galaxy ESO 137-001. The brighter...

Observations of faint and distant galaxy groups made with the European Space Agency's XMM-Newton observatory have been used to probe the evolution of dark matter. The results of the study are reported in the January 20 issue of The Astrophysical Journal.Dark matter is a mysterious, invisible constituent of the Universe which only reveals itself through its gravitational influence. Understanding its nature is one of the key open questions in modern cosmology. In one of the approaches used to...

Weak gravitational lensing is a uniquely promising way to learn how much dark matter there is in the Universe and how its distribution has evolved since the distant past. New work by a team led by a cosmologist from the U.S. Department of Energy's Lawrence Berkeley National Laboratory has made major progress in extending the use of gravitational lensing to the study of much older and smaller structures than was previously possible.Until recently, weak lensing had been limited to calculating...

For more than two decades, the cold dark matter theory has been used by cosmologists to explain how the smooth universe born in the big bang more than 13 billion years ago evolved into the filamentary, galaxy-rich cosmic web that we see today.There's been just one problem: the theory suggested most galaxies should have far more stars and dark matter at their cores than they actually do. The problem is most pronounced for dwarf galaxies, the most common galaxies in our own celestial...