Wednesday, June 27, 2007

Rethinking black holes

A research team concludes it is impossible to lose something inside a black hole.
Provided by Case Western Reserve Univ.

When material in the accretion disk spirals toward the black hole, gas and dust collide. Friction heats this material, making it shine brightly. The powerful jets associated with black holes originate from just outside a black hole's event horizon. These jets align themselves with the black hole's magnetic field, perpendicular to the accretion disk.

June 25, 2007
"Nothing there," Case Western Reserve University physicists concluded about black holes after spending a year working to calculate black hole formation. The research may solve the information-loss paradox that has perplexed physicists for the past 40 years."It's complicated and very complex," said Case physicists Tanmay Vachaspati, Dejan Stojkovic, and Lawrence Krauss, referring to the overall problem and their particular approach to solving it.The physicists set out to discover just what happens once something enters and collapses into a black hole. In current thinking, once this happens, all information is lost. Yet, the researchers thought, if all information is lost, then laws of quantum physics are defied."If you define the black hole as some place where you can lose objects, then there is no such thing, because the black hole evaporates before anything is seen to fall in," Vachaspati said.The team argues that information would remain forever on the event horizon — the black hole's point of no return. The masses on the edge of the incipient black hole appear to be collapsing, but never actually fall inside the event horizon.Researchers began by collapsing nonsingular matter to see if an event horizon formed, signaling the creation of a black hole.They found while mass shrank in size, the matter never collapsed inside an event horizon. Evidence of pre-Hawking radiation — a non-thermal radiation that allows information to be recovered from the collapsing mass — may be the explanation for this."Non-thermal radiation can carry information in it unlike thermal radiation. This means that an outside observer watching some object collapse receives non-thermal radiation back and may be able to reconstruct all the information in the initial object, and so the information never gets lost," the team said.According to the researchers, if new black holes form, information formed in the initial state would disappear in the black hole after a burst of thermal radiation.Using Schrodinger formalism, the researchers suggest that information about energy emitted from radiation is long-evaporated before an event horizon forms."An outside observer will never lose an object down a black hole," Stojkovic said. "If you are sitting outside and throwing something into the black hole, it will never pass over, but will stay outside the event horizon, even if one considers the effects of quantum mechanics. In fact, since in quantum mechanics the observer plays an important role in measurement, the question of formation of an event horizon is much more subtle to consider."The Case team's findings could be the beginning of a new era in black hole research. "From an external viewer's point it takes an infinite amount of time to form an event horizon, and the clock for the objects falling into the black hole appears to slow down to zero," said Krauss, director of Case's Center for Education and Research in Cosmology."This is one of the factors that led us to rethink this problem, and we hope our proposal at the very least will stimulate a broader reconsideration of these issues," Krauss added.If black holes exist in the universe, the astrophysicists speculate, they were formed only at the beginning of time.

Tuesday, June 26, 2007

"Cosmic Horseshoe"

A team led by Vasily Belokurov at the University of Cambridge in England has found the largest optical Einstein ring known. The astronomers say the object, which they dub the Cosmic Horseshoe, provides a unique laboratory for studying what the universe was like at one-fifth its present age. An Einstein ring is a kind of cosmic mirage. Gravity from a foreground galaxy distorts light from a background galaxy into an arc. If the alignment between the background galaxy and the foreground "lensing" galaxy is precise enough, the distant galaxy's light becomes warped into a complete ring. "Most Einstein rings were discovered in radio," Belokurov tells Astronomy. "There were close to none in optical, until recently." Last year, astronomers used spectra from the Sloan Digital Sky Survey to select imaging targets for the Hubble Space Telescope's Advanced Camera for Surveys. The search netted eight of the roughly dozen optical rings known. The SDSS survey can resolve a lensed ring into the multiple discrete images that compose it. Belokurov and his colleagues searched for multiple blue, faint companions around Luminous Red Galaxies (LRGs) in the SDSS catalog. Out came the Cosmic Horseshoe. "I didn't name it," Belokurov laughs, "but I like it."The ring measures 10.2" across — more than 5 times the size of previously-known optical rings. With an arc of 300-plus degrees, it's also one of the most complete. "The image of the source is very bright and highly magnified because the lens is so massive," Belokurov adds. The team followed up with images from the Isaac Newton Telescope on the Canary Islands and obtained the object's spectrum with the 6-meter BTA Telescope at the Special Astrophysical Observatory in Russia. The ring's spectrum shows its light comes from a star-forming galaxy at a redshift of 2.379, or when the universe was 2.8 billion years old. "This epoch is very important and rather active," Belokurov explains. "The galaxies are put together and most of the heavy elements are produced at this time. Black holes are most actively accreting, and the number of luminous quasars peaks." Only now are astronomers beginning to gather information on objects at this redshift. "With this huge magnifying glass, we'll be able to study one in great detail," he says.The lensing galaxy itself is an interesting object: It's a member of a rare population of LRGs. "These are the largest and most massive galaxies in the universe, and they're also believed to host massive black holes," Belokurov says. The ring encloses some 6 trillion Suns, which makes the Cosmic Horseshoe's lens one of the most massive LRGs detected. "We don't really know the mass of the whole galaxy," the astronomer adds, "but it can be 10 times more." The lens lies at redshift 0.444, so astronomers see the galaxy as it was when the universe was 9 billion years old.Astronomers believe galaxy halos harbor lots of dark matter — material that doesn't produce light and interacts with it only through gravity. At the lensing galaxy's distance, the ring spans nearly 200,000 light-years, so the new find also gives astronomers an opportunity to measure the distribution of dark matter in the lens' halo.

Thursday, March 8, 2007

Saturn radio waves - collected

ALMA, now under construction at an elevation of 16,500 feet in the Atacama Desert of northern Chile, will provide astronomers with the world's most advanced tool for exploring the universe at millimeter and submillimeter wavelengths.

March 8, 2007
The Atacama Large Millimeter/Submillimeter Array (ALMA), an international telescope project, reached a major milestone on March 2, when two ALMA prototype antennae were first linked together as an integrated system to observe an astronomical object.
Faint radio waves emitted by the planet Saturn were collected by the two ALMA antennae, then processed by new, state-of-the-art electronics to turn the two antennae into a single, high-resolution telescope system, called an interferometer.

The successful Saturn observation began at 7:13 p.m., U.S. Mountain Time Friday (0213 UTC Saturday). The planet's radio emissions at a frequency of 104 GigaHertz (GHz) were tracked by the ALMA system for more than an hour.

Friday, February 23, 2007

A new Star in our Universe?

On the heels of 1651-32 V1280 Scorpii (a.k.a. Nova Scorpii 2007), the "new star" discovered earlier this month in the constellation Scorpius, observers in Japan think they may have found another. The reputed nova is reportedly shining in the range of magnitude 9.2 or 9.3, which makes it visible with binoculars.On February 21, the American Association of Variable Star Observers (AAVSO) Special Notice #34 reported that Yuji Nakamura — one of the observers who found Nova Scorpii 2007 — and Hideo Nishimura independently discovered the possible second nova.

A nova, or "new star," recently discovered this month in Scorpius has brightened so much in recent weeks that it is now visible to the naked eye. Officially christened Nova Scorpii 2007, the nova is a star whose brightness has suddenly and dramatically increased.

Nova Scorpii 2007 brightened steadily from February 8 to 16, when it peaked at approximately magnitude 4. The magnitudes in this graph are daily averages based on data observers reported to the American Association of Variable Star Observers. Astronomy: Roen Kelly [larger image]
The nova was discovered independently by two Japanese observers, Yugi Nakamura and Yukio Sakurai. On February 7, the American Association of Variable Star Observers (
AAVSO) reported the nova's approximate brightness as magnitude 8.3. It peaked in brightness February 16 at about magnitude 4, according to the average brightness calculated from raw data posted by the AAVSO. On February 20, the AAVSO posted fresh observations showing that Nova Scorpii 2007 had dimmed to approximately magnitude 4.7.

To find the new star, locate Scorpius in the morning sky and use the finder chart here to locate Antares, Scorpius' brightest star. Then look down and a bit to the left to locate Nova Scorpii 2007. The nova is about the same brightness as the dim star in Orion's head. It will be easily visible with binoculars.

Thursday, February 22, 2007

Europa's potential for life

Jupiter with Europa & Callisto
There are four large, moons of Jupiter that in their character and behavior are more like planets than Earth's moon: Io, Europa, Ganymede and Callisto. The last three are icy.
Io's volcanic hyperactivity is well known, but there are mysteries about the temperature of its magmas and its spectacular mountains and what they might reveal about the satellite's interior processes. As for the exterior moon Callisto, how did it acquire an ocean yet not be deeply differentiated? Ganymede's liquid iron core is still generating a magnetic field. This was not predicted beforehand, and thus has much to teach planetary scientists on how magnetic fields are generated in the solar system.
Then, there is Europa.
"Of the four Galilean moons, Europa is the one that has the best chance to reveal the most about the origin of life, which is the biggest unanswered scientific question we have, bar none," he said. "With its massive body of liquid water, multiple energy sources proposed and different ways to provide carbon and other biogenic elements, the central question must be Europa's potential for life. What greater question can you ask of a planet?"
McKinnon reviewed each of the moons and their unanswered questions in his invited talk, "O Sister, Where Art Thou? The Galilean Satellites After Galileo," presented at the Fall 2006 meeting of the American Geophysical Union held Dec. 10-15, 2006, in San Francisco. All but Ganymede, a young male, are named after female Greek mythological characters. Thus, McKinnon refers to Ganymede as an honorary sister.
"Europa has been recently geologically active, but because Galileo's main antenna did not unfurl, we did not take enough images to catch any active geysering, such as seen on Saturn's itsy bitsy icy moon, Enceladus," McKinnon said. "Europa's surface appears very young and there are lots of interesting ice tectonics, and surface eruptions with weird colors and spectral signatures whose compositional implications everyone just loves to argue about."
'Capped' ocean
All the accumulated evidence points to an ocean under a global shell of ice, an ocean lying no more than 10 to 20 kilometers below Europa's airless surface, McKinnon said.
"That sounds really deep to a person with a pick ax, or even a drilling rig, but in geologic terms it's really pretty close," he said. "It's basically a capped ocean. "
The existence of the ocean is related to the great amount of heat coming up from Europa's interior.
"If you look at the surface and how deformed it is, you can tell the ice shell is relatively thin and really has been active in recent geological time, indeed is probably active today," McKinnon said.
Europa has a few, but not many, impact craters, also indicating its relative youth.
Europa's ocean begs to be studied, McKinnon said, as do the strikingly colored surface materials that Galileo images captured.
"To go into orbit around Europa with high-resolution cameras, spectral imagers and sophisticated, ice-penetrating radars of the sort mapping Mars right now, would allow us to really characterize that ocean and give us clues about the biogenic potential of the surface materials, "McKinnon said. "We'd see to the bottom of the ice shell, I predict. It would be a fantastic proof of concept."
A mission to Europa is feasible, McKinnon said. It would take about 10 years if started today (six of those years being spent in reaching the satellite). And it would be expensive, "about two billion dollars, give or take," he added.
"It would also have to compete for funds with NASA's plans to establish a Moon base," he said. "The Europeans are interested as well, so maybe we could cooperate and share the cost."
NASA has committees exploring a number of options, McKinnon said, and they include returning to Europa or Titan after the conclusion of the Cassini mission or perhaps returning to the little active moon around Saturn, Enceladus.
"It's a tiny moon, but it has an active plume that, because of that moon's very low gravity, extends well out into space, so you can just fly right through it," McKinnon said. "That's a nifty way to go sampling."
Of course, Europa is a much bigger target to explore.
"It has 40 times the surface area of Enceladus — there's a lot more there there," he concluded.
Cosmology is the study of the overall structure of the universe. Just what is the Universe? It is everything that exists. However, from Earth we cannot observe everything in the Universe. Some things are dark (brown dwarf stars, planets, and Dark Matter) and we cannot see them. Additionally, there are parts of the universe whose light has not yet reached us in this part of the Universe. And because light travels at a set speed we actually look back in time when we look into the cosmos.
Astronomers observe some interesting structure in the Current Universe. That structure can tell us much about the History of the Universe. It can also tell us what we can expect for the Future of the Universe and beyond...
A computer simulation depicting a large chunk of our universe