Monday, December 10, 2007

Physical sciences news, 12/3/07-12/9/07

Active galaxies
Jets of high-energy particles are produced by a variety of astronomical objects. The largest example of this phenomenon has been discovered in the active galaxy CGCG 049-033.

Intergalactic particle beam is longest yet found

Galaxies in the early universe
The earliest stars in the universe consisted entirely of primordial hydrogen and helium, since heavier elements were formed almost entirely by the demise of these first stars in supernova events. Planets (which are generally considered a necessity for the development of life in any form similar to what we know) require elements heavier than hydrogen and helium. New simulations suggest that the earliest stars, having masses of perhaps 100 Suns, may have formed earlier than previously supposed, meaning that planets (and life) could also have formed earlier.

Earliest galaxies had building blocks of life

Dark matter stars
Many observations indicate that dark matter in the universe is about 5 times as plentiful (by mass) as "ordinary" baryonic matter. Consequently, the first compact objects to form in the universe may have consisted mostly of dark matter. Although ordinary matter would have been mixed in, the dark matter could have prevented, for a time, ordinary matter from collapsing to a density sufficient to form stars powered by thermonuclear reactions.

‘Dark stars’ may have populated early universe
Drowning in Dark Matter?
Universe's first stars may have been dark
First Stars Were Huge and Dark
Dark matter in newborn universe doused earliest stars

Dark matter in galaxies
Computer simulations of the early universe, until now, have predicted larger amounts of dark matter in the central parts of galaxies than is actually observed. Refined simulations that take into account the supernova explosions of the first generation of stars now indicate that gravitational effects of the supernovae could have driven much of the original dark matter out of the central regions of galaxies.

Galaxies Are Born Of Violence Between Dark Matter and Interstellar Gas
Invisible Matter Loses Cosmic Battle

Gas giant planets
Most extrasolar planets that have been detected so far are gas giants located very close to the central star – because this is the configuration most likely to be detected by current technology. Some of these planets are so close to their star that it has been difficult to understand how they have escaped being completely evaporated by the heat. New simulations indicate that positively charged hydrogen ions containing three protons are capable of radiating away enough heat to allow gas giant planets in close proximity to their stars.

Planets can survive extreme roasting by their stars
How to Destroy a Giant Planet

Cosmic textures
Phase transitions, such as occur in the freezing of ice and other solids, should also have occurred very early around the hypothesized time of inflation in big bang models of the universe. Such transitions may have led to inhomogeneities called "topological defects", which in principle could lead to observable inhomogeneities in the cosmic microwave background. Theoretical calculations now indicate that particular types of defects called "textures" may account for puzzling features actually observed in the microwave background.

Possible Cosmic Defect, Remnant From Big Bang, Discovered
A Texture in the Sky?
A Cosmic Microwave Background Feature Consistent with a Cosmic Texture

White dwarfs in globular clusters
Astronomers have been surprised to find that white dwarf stars are unexpectedly scarce in the central regions of some globular clusters. It is hypothesized that the explanation for this may lie in asymmetrical flows of gas out of stars in their red giant phase, just before the star collapses to a white dwarf.

Sun-like stars get a kick out of death
Dead Stars Propelled Like Rockets

The solar corona
Observations that have been deduced from data collected by the Japanese Hinode mission may have solved a long-standing mystery of why the Sun's corona is so hot – several million degrees K – even though the solar surface is only about 6000° K. The cause appears to be strong magnetic turbulence in the corona, called "Alfvén waves".

Mission illuminates solar mysteries
Roiling magnetic waves explain solar enigma
Unlocking the riddle of Sun's heat
Results from Hinode: Sunrise on Coronal Heating
Are There Alfvén Waves in the Solar Atmosphere?

Slushball Earth
It now appears possible that the Earth's oceans never entirely froze solid, as hypothesized in the "snowball Earth" scenario. Carbon dioxide dissolved in the oceans, coming from carbonate minerals on the ocean floor, may be responsible for a milder freeze that produced only a "slushball".

Did Carbon Save Earth From a Deep Freeze?
'Snowball Earth' was more a slushball

Interruption of the Gulf Stream
About 8200 years ago a huge (100,000 km3, seven times the volume of the present Great Lakes combined) North American glacial lake known as Lake Agassiz had swelled so large that it burst out and mostly flooded into the Atlantic Ocean. There is now evidence that all this cold, dense fresh water was sufficient to disrupt the flow of the Gulf Stream and cause a temporary but severe cooling of the climate.

Ancient flood brought Gulf Stream to a halt
Epic Flood Triggered Ancient "Big Chill," Study Says

Scientists have generated, modulated and electrically detected a pure spin current in silicon. This could be a key step in the development of silicon-based "spintronic" devices, which might be used to make denser information-processing devices than can be implemented using present technology based on currenjts of electric charge.

Scientists generate, modulate, and electrically detect pure spin currents in silicon


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