Is a Dark-Matter Galaxy Orbiting the Milky Way?

People used to think that the heavens were a vast clockwork, with planets and moons moving in circular orbits like a vast timepiece. Recent advances have shown us that this stellar machinery is far vaster than they ever suspected - even our galaxy has satellites, mini-galaxies orbiting the Milky Way and some of them could be very interesting indeed.

We now know about two dozen of these satellite galaxies. One of the most recent is "Segue 1", uncovered by the Sloan Digital Sky Survey (SDSS), whose extremely low light-to-mass ratio makes it a particularly significant cosmic find. Despite having a mass of a million suns it is nowhere near as luminous as astronomers would expect, with only a couple of hundred stars visible. They think "How can so much matter be so dark?", then they go "Dark matter!" and at this point we like to believe their monocle flies out and they dash down the street shouting Eureka.

Of course, the actual physics of arriving at this conclusion is a tiny bit more complicated, but the result is the same: Marla Geha (Yale professor of astronomy) and colleagues believe that it's a galaxy composed mainly of dark matter. A handy thing to have around when you're trying to study the stuff or even prove that it exists.

The SDSS has made many such observations possible, picking out objects in the sky which have the bad manners not to twinkle twinkle bright enough, despite being little stars. These mini-galaxies and other previously unobservable objects offer a wealth of data on galaxy formation, evolution, and even the composition of the universe itself.

Posted by Luke McKinney

650 Million Year-Old Reef Discovered in Australia’s Outback

For original article, click here.

Scientists at the University of Melbourne have discovered the relics of a 650 million year-old reef in the Australian Outback. The reef is 10 times higher than the modern Great Barrier Reef and predates the evolution of animal life by at least 40 million years. It could also offer valuable information about climate change.

The reef is located in the Flinders Ranges of southeastern Australia (pictured here). When the reef was submerged, these mountains formed Australia’s eastern seaboard. Since then, tectonic and natural forces have combined to expose a section of the reef around 20 km (12.4 miles) wide. Despite its size and relative proximity to Melbourne, Australia’s second most populous city, the reef remained hidden to science until this week.

The discovery is of tremendous scientific value in understanding the origins of modern life. Little is known about life before around 542 million years ago–the end of the Precambrian age–since discoveries of fossils this old are rare. To put the reef’s age in perspective, it predates the first known fish by about 150 million years and the first mammals by about 450 million years. The reef itself, the only one of its age ever discovered, is not composed of coral like today’s reefs. Most of the reef is made of layers of non-living stromatolite accretion formed by previously unknown unicellular organisms.

Jonathan Giddings, one of the researchers studying the reef, says it could offer new insights into the formation of early animals.

“The organisms that build the majority of the reefs are previously undescribed and may help us to understand the evolution of early multicellular life,” said Giddings. “It could prove that life took more complex forms much earlier in history than we previously thought.”

The find could also hold information for climate scientists. The reef formed very gradually over a period of 5 million to 10 million years. During this same time span, the planet was relatively warm. Even in the absence of plant life on land, earth’s climate was what we might consider tropical. This warm spell came between two epochs of intense cold, when scientists believe ice existed even at the equator. The reef might therefore have recorded information about extreme climate variations, which would be valuable in today’s studies of climate change.

Researchers say that more information about the reef’s discovery will be made available later this week at the Selwyn Symposium at the University of Melbourne.