Thursday, May 24, 2007

The Brightest Supernova Ever

The brightest stellar explosion ever recorded may be a long-sought new type of supernova, according to observations by NASA's Chandra X-ray Observatory and ground-based optical telescopes. This discovery indicates that violent explosions of extremely massive stars were relatively common in the early universe, and that a similar explosion may be ready to go off in our own galaxy.

"This was a truly monstrous explosion, a hundred times more energetic than a typical supernova," said Nathan Smith of the University of California at Berkeley, who led a team of astronomers from California and the University of Texas in Austin. "That means the star that exploded might have been as massive as a star can get, about 150 times that of our sun. We've never seen that before."

Photo 1: An artist's illustration of supernova

Astronomers think many of the first stars in the Universe were this massive, and this new supernova may thus provide a rare glimpse of how those first generation stars died. It is unprecedented, however, to find such a massive star and witness its death. The discovery of the supernova, known as SN 2006gy, provides evidence that the death of such massive stars is fundamentally different from theoretical predictions.

"Of all exploding stars ever observed, this was the king," said Alex Filippenko, leader of the ground-based observations at the Lick Observatory at Mt. Hamilton, Calif., and the Keck Observatory in Mauna Kea, Hawaii. "We were astonished to see how bright it got, and how long it lasted."

The Chandra observation allowed the team to rule out the most likely alternative explanation for the supernova: that a white dwarf star with a mass only slightly higher than the sun exploded into a dense, hydrogen-rich environment. In that event, SN 2006gy should have been 1,000 times brighter in X-rays than what Chandra detected.

Photo 2: Optical (left) and X-ray (right) images of SN 2006gy. The dimmer source at lower-left is the nucleus of the host galaxy. The brighter source at upper-right is the stellar explosion. The supernova was as bright as the entire core of a galaxy!

"This provides strong evidence that SN 2006gy was, in fact, the death of an extremely massive star," said Dave Pooley of the University of California at Berkeley, who led the Chandra observations.

The star that produced SN 2006gy apparently expelled a large amount of mass prior to exploding. This large mass loss is similar to that seen from Eta Carinae, a massive star in our galaxy, raising suspicion that Eta Carinae may be poised to explode as a supernova. Although SN 2006gy is intrinsically the brightest supernova ever, it is in the galaxy NGC 1260, some 240 million light years away. However, Eta Carinae is only about 7,500 light years away in our own Milky Way galaxy.

"We don't know for sure if Eta Carinae will explode soon, but we had better keep a close eye on it just in case," said Mario Livio of the Space Telescope Science Institute in Baltimore, who was not involved in the research. "Eta Carinae's explosion could be the best star-show in the history of modern civilization."

Photo 3: eta Carinae--a supernova waiting to happen in our own galaxy? The giant star is highlighted by diffraction spikes in this astrophoto taken by Brad Moore.

Supernovas usually occur when massive stars exhaust their fuel and collapse under their own gravity. In the case of SN 2006gy, however, astronomers think that a very different effect may have triggered the explosion. Under some conditions, the core of a massive star produces so much gamma ray radiation that some of the energy from the radiation converts into particle and anti-particle pairs. The resulting drop in energy causes the star to collapse under its own huge gravity.

After this violent collapse, runaway thermonuclear reactions ensue and the star explodes, spewing the remains into space. The SN 2006gy data suggest that spectacular supernovas from the first stars that spew their remains - rather than completely collapsing to a black hole as theorized - may be more common than previously believed.

"In terms of the effect on the early universe, there's a huge difference between these two possibilities," said Smith. "One [sprinkles] the galaxy with large quantities of newly made elements and the other locks them up forever in a black hole."

Wednesday, May 23, 2007

Crater for moon settlement

Although ESA’s SMART-1 was smashed into the Moon in 2006, it had the opportunity to gather a tremendous amount of science. Its view of this crater in particular has given ESA scientists the feeling that they might be looking at the perfect spot for a future permanent base on the Moon.

Crater Plaskett sits very close to the Moon’s north pole. This means it’s bathed in eternal sunlight. This would provide plenty of solar energy for future explorers, and creates a predictable temperature - it’s only hot, not hot and cold. Nearby craters bathed in eternal darkness might contain large stores of water ice that could be used for air, fuel and drinking water.

moon crater, moon krater, moon setltement

Crater Plaskett might provide a good first step for exploration of the Solar System. It’s close enough that astronauts would still be able to see the Earth. Help could arrive within days, if necessary, and communications would be almost instantaneous. But it’s remote enough to help mission planners understand what would be involved for future, longer duration missions on the Moon, and eventually to Mars.

SMART-1 ended its mission on September 3, 2006, when it ran out of fuel and crashed into the lunar surface. Scientists will be studying its data and images for years.

Saturday, May 19, 2007

Young Stars Hatching in Orion

star, space, orion

The latest image released from the Spitzer Space Telescope shows infant stars “hatching” in the head of Orion. Astronomers think that a supernova 3 million years ago sent shockwaves through the region, collapsing clouds of gas and dust, and beginning a new generation of star formation.

The region imaged by Spitzer is called Barnard 30, located about 1,300 light-years from Earth in the constellation of Orion. More specifically, it’s located right beside the star considered to be Orion’s head, Lambda Orionis.

Since the region is shrouded in dark clouds of gas and dust that obscure visible light images, this was an ideal target for Spitzer, which can peer right through them in the infrared spectrum. The tints of orange-red glow are dust particles warmed by the newly forming stars. The reddish-pink dots are the young stars themselves, embedded in the clouds of gas and dust.

Sunday, April 29, 2007

From the Ashes of the First Stars

space image

Above, an artist's impression shows a primordial quasar as it might have been, surrounded by sheets of gas, dust, stars and early star clusters. Exacting observations of three distant quasars now indicate emission of very specific colors of the element iron. These Hubble Space Telescope observations, which bolster recent results from the WMAP mission, indicate that a whole complete cycle of stars was born, created this iron, and died within the first few hundred million years of the universe.

Image credit: NASA/ESA/ESO/Wolfram Freudling et al. (STECF)

Thursday, April 12, 2007

Big Jupiter's auroras

Big Jupiter's auroras

Image: X-ray auroras observed by the Chandra X-ray Observatory

Northern Lights in Alaska are big??? No way, Jupiter's auroras are much much bigger.
The purple ring traces Jupiter's X-ray auroras. Gladstone calls them "Northern Lights on steroids. They're hundreds of times more energetic than auroras on Earth."
The purple ring traces Jupiter's X-ray auroras. Gladstone calls them "Northern Lights on steroids. They're hundreds of times more energetic than auroras on Earth."
Back in 1979 Jupiter's auroras were discovered by Voyager 1 spacecraft. In the 1990s, ultraviolet cameras on the Hubble Space Telescope photographed raging lights thousands of times more intense than anything ever seen on Earth, while X-ray observatories saw auroral bands and curtains bigger than Earth itself.
Jupiter's hyper-auroras never stop. "We see them every time we look," says Gladstone. You don't see auroras in Alaska every time you look, yet on Jupiter the Northern Lights always seem to be "on." Gladstone explains the difference: On Earth, the most intense auroras are caused by solar storms. An explosion on the sun hurls a billion-ton cloud of gas in our direction, and a few days later, it hits. Charged particles rain down on the upper atmosphere, causing the air to glow red, green and purple. On Jupiter, however, the sun is not required. "Jupiter is able to generate its own lights," says Gladstone.
The process begins with Jupiter's spin: The giant planet turns on it axis once every 10 hours and drags its planetary magnetic field around with it. As any science hobbyist knows, spinning a magnet is a great way to generate a few volts—it's the basic principle of DC motors. Jupiter's spin produces 10 million volts around its poles.
The February 2007 dataset may hold important clues. "Chandra observed the auroras for 15 hours, and we weren't the only ones watching," he says. The Hubble Space Telescope, the FUSE satellite, XMM-Newton (a European X-ray observatory), the New Horizons spacecraft and many ground-based observatories were all taking data at the same time. The campaign was timed to coincide with New Horizons flyby of Jupiter—a slingshot maneuver designed to increase its velocity en route to Pluto.

"Jupiter's auroras have never been observed by so many telescopes at once," says Gladstone. "I'm really excited by these data, and the analysis is just beginning."

Wednesday, February 14, 2007

nebula NGC 2440 with Sun-like star

This image is taken by NASA/ESA Hubble Space Telescope! It shows the colorful "last hurrah" of a star like Sun. The star is ending its life. The star, called white dwarf, is the with dot in the center. The planetary nebula in this image is called NGC 2440. The white dwarf at the center of NGC 2440 is one of the hottest known, with a surface temperature of more than 200,000 degrees Celsius.

Credit: NASA, ESA, and K. Noll (STScI)

Wednesday, December 27, 2006

Did you know?

Some NASA facts

Four days after it was launched, the Deep Space 1 spacecraft was about 1,000,000 kilometers (about 600,000 miles) from Earth. To fly that far in a jet, you would have to fly for 6 weeks without stopping!


To communicate with distant spacecraft, NASA's Deep Space Network uses antenna with a diameter of up to 70 meters (230 feet). That is almost as big as a football field.


It's a small world. More than 1,000 Earths would fit into Jupiter's vast sphere.


Saturn's beautiful rings are not solid. They are made up of particles of ice, dust and rock -- some as tiny as grains of sand, some much larger than skyscrapers.

Tuesday, October 17, 2006

How the Really Big Stars Form

Astronomers think they’ve got a handle on how Sun-sized stars come together. But the formation of the largest stars - more than 10 times the mass of the Sun - still puzzle astronomers. New observations on a 20 solar mass star have revealed that these giant stars maintain a torus of material around themselves. They can continuously feed from this “doughnut” of material, while powerful jets of radiation pour from their poles. The material can continue gathering onto the star while avoiding this radiation, which would normally blast it back into space.
Astronomers using the National Science Foundation’s Very Large Array (VLA) radio telescope have discovered key evidence that may help them figure out how very massive stars can form.
“We think we know how stars like the Sun are formed, but there are major problems in determining how a star 10 times more massive than the Sun can accumulate that much mass. The new observations with the VLA have provided important clues to resolving that mystery,” said Maria Teresa Beltran, of the University of Barcelona in Spain.
Beltran and other astronomers from Italy and Hawaii studied a young, massive star called G24 A1 about 25,000 light-years from Earth. This object is about 20 times more massive than the Sun. The scientists reported their findings in the September 28 issue of the journal Nature.
Stars form when giant interstellar clouds of gas and dust collapse gravitationally, compacting the material into what becomes the star. While astronomers believe they understand this process reasonably well for smaller stars, the theoretical framework ran into a hitch with larger stars.
“When a star gets up to about eight times the mass of the Sun, it pours out enough light and other radiation to stop the further infall of material,” Beltran explained. “We know there are many stars bigger than that, so the question is, how do they get that much mass?”
One idea is that infalling matter forms a disk whirling around the star. With most of the radiation escaping without hitting the disk, material can continue to fall into the star from the disk. According to this model, some material will be flung outward along the rotation axis of the disk into powerful outflows.
“If this model is correct, there should be material falling inward, rushing outward and rotating around the star all at the same time,” Beltran said. “In fact, that’s exactly what we saw in G24 A1. It’s the first time all three types of motion have been seen in a single young massive star,” she added.
The scientists traced motions in gas around the young star by studying radio waves emitted by ammonia molecules at a frequency near 23 GHz. The Doppler shift in the frequency of the radio waves gave them the information on the motions of the gas. This technique allowed them to detect gas falling inward toward a large “doughnut,” or torus, surrounding the disk presumed to be orbiting the young star.
“Our detection of gas falling inward toward the star is an important milestone,” Beltran said. The infall of the gas is consistent with the idea of material accreting onto the star in a non-spherical manner, such as in a disk. This supports that idea, which is one of several proposed ways for massive stars to accumulate their great bulk. Others include collisions of smaller stars.
“Our findings suggest that the disk model is a plausible way to make stars up to 20 times the mass of the Sun. We’ll continue to study G24 A1 and other objects to improve our understanding,” Beltran said.
Beltran worked with Riccardo Cesaroni and Leonardo Testi of the Astrophysical Observatory of Arcetri of INAF in Firenze, Italy, Claudio Codella and Luca Olmi of the Institute of Radioastronomy of INAF in Firenze, Italy, and Ray Furuya of the Japanese Subaru Telescope in Hawaii.
The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Original Source: NRAO News Release

Wednesday, September 27, 2006

Solar System and white star

Our solar system comparing to big white star

Hubble photo

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Description: This one of the NASA Hubble Telescope photos...
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