Physical sciences news, 12/17/07-12/23/07

Gamma-ray bursts

There are several types of gamma-ray events that go under the name of "gamma-ray bursts", but the two main categories are "long" and "short" – referring to the duration of the burst. Long bursts have been generally attributed to very energetic supernovae that direct most of their energy into a narrow beam, which just happens to be visible from Earth. But most powerful supernovae are due to the collapse of a very large, young star – normally found only inside galaxies. So the detection of a long gamma-ray burst outside of any visible galaxy is rather a surprise. On the other hand, short gamma-ray bursts have been suspected to result from the merger of black holes and/or neurton stars. So another surprise is that the LIGO gravitational wave detector did not register any such event in connection with a recent short gamma-ray burst event.

• Intergalactic 'Shot In The Dark' Shocks Astronomers
• Cosmic explosion detonates in empty space
• A Gamma-Ray Burst Out of Nowhere
• Baffling Cosmic Explosion Comes Out of Nowhere
• Cosmic explosion is shot in the dark
• LIGO Sheds Light on Cosmic Event

Supernova remnants

It has generally been supposed that most elements heavier than hydrogen and helium that are not still locked up inside stars were formed in very massive stars that became supernovae and scattered most of their material into space. But actual traces of such "dust" in the vicinity of known supernova remnants have not been confirmed – until now.

• 10,000 Earths' Worth Of Fresh Dust Found Near Star Explosion
• Litterbugs of the Universe Busted
• Freshly Formed Dust in the Cassiopeia A Supernova Remnant as Revealed by the Spitzer Space Telescope

Very early star formation

Given that interstellar dust contained within galaxies is the result of supernovae explosions of previous generations of massive stars (see above), it is surprising that a galaxy seen as it was only 1.5 billions years after the big bang exhibits a very high rate of star formation (1000 times what now occurs in the Milky Way), and in a very dusty environment besides. But that's exactly what the galaxy GOODS 850-5 seems to show.

• New View of Distant Galaxy Reveals Furious Star Formation
• Galaxy Has 1,000 Times Our Rate of Star Formation
• GOODS 850-5 -- A z>4 Galaxy Discovered in the Submillimeter?

Cosmic inflation

Although the cosmic microwave background (CMB) represents an image of the universe at about 380,000 years after the big bang, some very subtle details of the variation in temperature of the CMB from point to point contain information about the very earliest instants of the universe. (Like time t=10^-35 sec, to be more precise.) It has been expected that a very careful analysis of the data will tell us something about the hypothesized phenomenon of cosmic inflation. The latest analysis claims to rule out the simplest model of inflation. However, it may be that the data obtained in the WMAP mission is insufficiently detailed for a satisfactory resolution of this issue, and we'll have to wait for a more sensitive measurement from the forthcoming Planck mission.

• No Dice for Slow Roll?
• Detection of primordial non-Gaussianity (fNL) in the WMAP 3-year data at above 99.5% confidence
• Detection of primordial non-Gaussianity (fNL) in the WMAP 3-year data at above 99.5% confidence

Mars

Data gathered from many years of surveillance of Mars by satellite missions and landers provides strong indications that Mars was warm and wet early in its history. Yet evidence of the most likely greenhouse gas, CO₂, that could have sustained a warm, wet environment has been conspicuously absent. The evidence now points to a different greenhouse gas, SO₂, instead. But early history aside, it now looks as though Mars could have an active (water ice) glacier at the present time.

• Sulfur dioxide may have helped maintain a warm early Mars
• Fire and Brimstone Helped Form Mars Oceans
• Possible solution to Mars enigma
• Maybe Sulfur Dioxide, Not Carbon Dioxide, Kept Mars Warm
• Greenhouse clue to water on Mars
• How Mars Could Have Been Warm And Wet But Limestone Free
• Red Planet Still Packs Surprises
• 'Active glacier found' on Mars
• Red Planet Appears to Host Active Glacier

Extrasolar planets

How much technology would be required to learn something about the surface conditions (e. g. continents, oceans, clouds) on extrasolar planets in our neighborhood? New calculations based on plausible strategies for observing such features suggest... not a whole lot more technology than we will soon have. So if there are any civilizations at least as advanced as our own on any of those planets, they probably already have a fair idea of what Earth is like.

• Alien astronomers could discern Earth's features
• To curious aliens, Earth would stand out as living planet
• MIT Asks: How Would Extraterrestrial Astronomers Study Earth?

Sea level rise

A rise in sea levels is one of the most troublesome effects expected from global warming over the next several hundred years, but it has been difficult to make a good estimate of how quickly this would happen. However, about 124,000 years ago the planet was on average about 2° C warmer than it is now – and what it may be in just 100 years. New research claims to show that sea levels then were rising at a rate of 1.5 meters per century – about twice the current "consensus" forecast for our own times.

• Study suggests future sea-level rises may be even higher than predicted
• Rising seas 'to beat predictions'
• Lessons From an Interglacial Past
• Fast-Rising Sea Levels: An Interview on Research in the Red Seas