Sunday, December 23, 2007

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

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
Red Planet Still Packs Surprises
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

Sunday, December 16, 2007

Physical sciences news, 12/10/07-12/16/07

Milky Way
Stars occupying regions above and below the disk of a spiral galaxy like the Milky Way are said to be in the galaxy's halo. In our own galaxy it turns out that there are two distinct halo regions, and they are rotating in opposite directions.

Milky Way's two stellar halos have opposing spins
Discovery shows Milky Way halo is split in two
Huge Newfound Part of Milky Way Rotates Backward

Extrasolar planets
Some other solar systems besides ours undoubtedly have rocky planets like Mercury which always show the same face to the host star. A computer simulation shows that there could be a narrow potentially habitable region between the light and dark sides of such a planet.

'Twilight zones' on scorched planets could support life

Gliese 581d
Gliese 581d is a rocky planet recently discovered in orbit around the red dwarf star Gliese 581. It has about 8 times the mass of Earth. Two teams have now done simulations of the atmosphere of Gliese 581d and concluded that an atmosphere could exist and have properties considered necessary for Earthlike life to develop.

Gliese 581: one planet might indeed be habitable
Gliese 581d: A Habitable World After All?
Is Gliese 581 Habitable?
More Evidence that Gliese 581 Has Planets in the Habitable Zone

Haze on HD 189733b
HD 189733b is a gas giant extrasolar planet of the yellow dwarf star HD 189733 A. Although previous observations had suggested the presence of water vapor in the atmosphere, the latest set observations using the Hubble Space Telescope did not find evidence of water, sodium, or potassium in the atmosphere. However, there was an indication that the atmosphere did contain a haze of dust particles of unknown composition about 1 micron in size.

Hazy red sunset on extrasolar planet
Dust in a Hot Jupiter's Atmosphere
First Sunset Outside Our Solar System Glimpsed
A Red Haze on Distant Exoplanet
HD 189733b: A 'Murky' Extrasolar Planet

Silica and the possibility of life on Mars
One of NASA's Mars rovers has found what appears to be a a deposit consisting largely of silica (SiO2) – very fine grained beach sand, essentially. On Earth such deposits are found only in certain hot springs or volcanic fumaroles. Here both such environments support a great deal of microbial life. If life ever existed on Mars, it would likewise probably have thrived in such an environment.

Clues to a Steamy Martian Past
Mars Rover Investigates Signs of Steamy Martian Past
Mars robot unearths microbe clue
Mars Rover Finding Suggests Once Habitable Environment
Mars rover finds signs of microbial life
Spirit's Big Discovery

Organic compounds on Martian meteorite ALH 84001
ALH 84001 is a meteorite whose composition indicates it crystallized from molten rock 4.5 billion years ago on Mars. Over 10 years ago a team of NASA scientists hypothesized that some very small (20-100 nm) structures in the meteorite might be traces of life, but the claim was quite controversial and is no longer widely accepted. However, a recent comparison of the meteorite with terrestrial rocks suggests that simple organic compounds found in ALH 84001 could have formed, as in their terrestrial counterparts, in a chemical process catalyzed by magnetite (Fe3O4).

Building blocks of life formed on Mars
Building Blocks of Life Formed on Early Mars?
Life's Building Blocks Found in Mars Rock
Allan Hills 84001 Analysis Confirms Building Blocks Of Life Also Formed On Mars
Building Blocks of Life Can Form on Cold, Rocky Planets — Anywhere

Saturn's rings
When Saturn's rings were first examined close-up by the Voyager missions in the 1970s, it was concluded that they had formed relatively recently (like 100 million years ago) when a moon of Saturn was destroyed in a collision with another moon or an asteroid. But the latest evidence from the Cassini mission indicates that Saturn may have had similar rings since the formation of the solar system 4.5 billion years ago. However, it appears that material in the rings is continually accreting into new moonlets, only to be destroyed again in later collisions.

Saturn's Rings May Be As Old As Solar System
Saturn's rings 'may live forever'
Saturn's Rings Older Than First Thought?
Saturn's Rings Could Be as Old as the Solar System
Saturn’s Rings More Ancient than First Thought
Saturn's Rings: Moon Remnants Or As Old As The Solar System?

Greenhouse gases
A new study indicates that human destruction of peat bogs may be responsible for emission of amounts of CO2 possibly 10% as much as all burning of fossil fuels. Another study proposes a new model, taking into account the role of nitrogen, of how carbon is recycled among plants, soils, and the atmosphere.

Peatland destruction is releasing vast amounts of CO2
New model revises estimates of terrestrial carbon dioxide uptake

Arctic ice
Some scientists who have studied the melting of Arctic ice now believe the ice could melt entirely in summer as soon as 2013, instead of 2040 as previously thought. Even this summer the melting has resulted in sea surface temperatures, in some places, 5° C above average – a level never before recorded. And this summer's melt of the Greenland ice sheet was 10% more than the previous record from 2005.

'The Arctic is screaming' — summer sea ice could be gone in five years
Arctic summers ice-free 'by 2013'
Without its insulating ice cap, Arctic surface waters warm to as much as 5 C above average
Greenland melt accelerating, according to CU-Boulder study

Near-record high temperatures
And overall, 2007 figures to be Earth's second-warmest year on record, while the past 10 years have been the warmest decade ever recorded.

2007 Brought Near-Record Heat
2007 data confirms warming trend
1998-2007 warmest decade, UN agency says at climate meet

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

Sunday, December 02, 2007

Trying some new things

As you may have noticed, new editions of Philosophia Naturalis have not been coming out on a very regular schedule of late.

There are two reasons for this. Firstly, we are getting few volunteers to host this carnival. Hosting is not really that difficult or time-consuming to do, and I could do it myself once a month (say).

But secondly, we are getting too few submissions of suitable blog posts on topics in the physical sciences to include in the carnival. This is a much more serious problem, since without such submissions, there is nothing to include in the carnival (duh). Again, the editor could go out and round up material, but that puts all the burden on one person.

However, I'm not going to give up easily. I have a few ideas of how to encourage more participation. To begin with, you will see another post today entitled "Physical sciences news". This is a list I've put together of what I consider to be the most interesting news in the physical sciences that's come out in (roughly) the past week.

The first post of this kind is heavily weighted towards astronomy and astrophysics. In my experience, this is simply where most of the "action" in the physical sciences is these days, so I would expect this weighting to continue. However, if you happen to know of important news in other areas, such as physics, chemistry, geosciences, or mathematics, by all means feel free to let me know about it. (You'll find the email address here.)

I'll try to do this every weekend. I see two purposes of this. First, it should be a useful resource for anyone interested in the physical sciences who wants to easily keep aware of "significant" news that a non-specialist can appreciate. This in turn will increase traffic here, leading to more blog traffic for you, if you host an edition of the carnival or have an article of yours included in the carnival.

The second purpose is to suggest topics for you to write about on your blog, which articles you can in turn submit to the carnival. As you can see from the news post, there's more than enough happening in just a single week to make up an entire carnival edition. You need not confine yourself to this news, of course. Or if it suggests a topic, you need not write only about the specific news development. You could, for instance, write a review-type article that treats the topic more generally, placing the news in a broader context.

I have other ideas that may be tried, but this seems to me like a good place to start. If enough people are motivated to write and submit articles inspired by something mentioned in the news, perhaps we can evolve this carnival into something more like a useful news service for the community of people who have a serious interest in the physical sciences.

Physical sciences news, 11/26/07-12/2/07

Climate change
To the surprise of practically nobody except climate change denialists, levels of CO2 in the atmosphere continued to increase in 2006 to new record levels. And Scientific American comes up with a nice suite of several articles (two listed here), which key off the recent report of the U.N. Intergovernmental Panel on Climate Change.

U.N.: Greenhouse Gases Hit High in 2006
Beyond the Worst Case Climate Change Scenario
10 Solutions for Climate Change

Some results are in from the European Space Agency's Venus Express mission, and they paint a picture of Venus as not such a great place for your next summer vacation. Much of the crappy climate is due to a CO2-induced greenhouse effect. Uh, oh.

How Earth's twin became so hellishly hot
NASA Scientist Confirms Light Show on Venus
Probe likens young Venus to Earth
Twin Planets Earth and Venus Were "Separated at Birth"
Signs of Lightning on Venus
Venus offers Earth climate clues
Did life once thrive on Evil Twin Venus?

The Milky Way and its neighborhood
Two things here about our galactic neighborhood. We might have another neighbor galaxy that has never actually been seen yet, even though it's almost as close and as large as the Andromeda galaxy. And there's a cluster of very young stars – only 100 light-years from our galactic center – that's moving way too fast.

Milky Way galaxy may have hidden twin
Dynamical Constraints on the Local Group from the CMB and 2MRS Dipoles
Star cluster's extreme speed puzzles astronomers
The proper motion of the Arches cluster with Keck Laser-Guide Star Adaptive Optics

Early galaxies
Astronomers using Europe's new Very Large Telescope, located in Chile, have observed 27 young "proto-galaxies" as they appeared about 2.5 billion years after the big bang. This provides evidence that larger galaxies like our own may have formed by the amalgamation of a number of such proto-galaxies.

Faint galaxies spotted in the early universe
Proto-galaxies tip cold dark matter
A Long, Hard Look at the Early Universe
Discovering Teenage Galaxies
Sighting of 'teenage' galaxies gives scientists
stellar return

New population of faint protogalaxies discovered
A Population of Faint Extended Line Emitters and the Host Galaxies of Optically Thick QSO Absorption Systems

Formation of planetary systems
Astronomers think they have found the two youngest solar systems ever detected, about 450 light-years from Earth. Elsewhere, one bright, massive young star in the Trapezium of the Orion Nebula is pumping out hot gas at a temperature of about 2 million degrees C, and this probably affects the formation of planetary systems around other nearby young stars.

Planet Formation is Child's Play
Of Young Stars and Ancient Planets
Huge Stars Seen as Source of Glowing Gas
Million-Degree Plasma Pervading the Extended Orion Nebula

Preon nuggets
Preons are hypothetical particles that have been proposed to make up quarks. Although there is as yet no experimental evidence for preons, if they ever existed in the universe soon after the big bang, a few preon clumps might still survive as objects a few centimeters in size but with as much mass as the Moon.

Nuggets of New Physics
The observational legacy of preon stars - probing new physics beyond the LHC

Large clumps of hydrogen and helium in the early universe may have condensed into star-like objects initially 1000 times as massive as the Sun. Although the core would collapse into a black hole, the resulting "quasistar" might be massive enough to avoid destruction, and continue to accrete matter, evolving into a supermassive black hole such as seems to exist in the center of most galaxies.

Biggest black holes may grow inside 'quasistars'
Quasistars: Accreting black holes inside massive envelopes

Saturday, December 01, 2007

Philosophia Naturalis #15 has been published

Sam Wise at Sorting Out Science has put together a great collection of posts. It's a wonderful look at a number of different viewpoints on a lot of recent news in the physical sciences. Thanks, Sam.