Invading black holes cause ‘cosmic flashes’

Washington, September 19 (ANI): Mathematicians at the University of Leeds, UK, have determined that cosmic flashes, known as gamma ray bursts, are produced by jets of plasma that originate from invading black holes.

Gamma ray bursts are beams of high-energy radiation that are similar to the radiation emitted by explosions of nuclear weapons.

The orthodox model for this cosmic jet engine involves plasma being heated by neutrinos in a disk of matter that forms around a black hole, which is created when a star collapses.

But, mathematicians at the University of Leeds, have come up with a different explanation: the jets come directly from black holes, which can dive into nearby massive stars and devour them.

Their theory is based on recent observations by the Swift satellite, which indicates that the central jet engine operates for up to 10,000 seconds – much longer than the neutrino model can explain.

Mathematicians believe that this is evidence for an electromagnetic origin of the jets, that is, that the jets come directly from a rotating black hole, and that it is the magnetic stresses caused by the rotation that focus and accelerate the jet’s flow.

For the mechanism to operate, the collapsing star has to be rotating extremely rapidly.

This increases the duration of the star’s collapse as the gravity is opposed by strong centrifugal forces.

One particularly peculiar way of creating the right conditions involves not a collapsing star, but a star invaded by its black hole companion in a binary system.

The black hole acts like a parasite, diving into the normal star, spinning it with gravitational forces on its way to the star’s centre, and finally eating it from the inside.

“The neutrino model cannot explain very long gamma ray bursts and the Swift observations, as the rate at which the black hole swallows the star becomes rather low quite quickly, rendering the neutrino mechanism inefficient, but the magnetic mechanism can,” said Professor Komissarov from the School of Mathematics at the University of Leeds.

“Our knowledge of the amount of the matter that collects around the black hole and the rotation speed of the star allow us to calculate how long these long flashes will be – and the results correlate very well with observations from satellites,” he added. (ANI)

NASA’s Swift satellite makes best-ever ultraviolet portrait of Andromeda galaxy

Washington, September 17 (ANI): NASA’s Swift satellite has acquired the highest-resolution view of a neighboring spiral galaxy ever attained in the ultraviolet.

The galaxy, known as M31 in the constellation Andromeda, is the largest and closest spiral galaxy to our own.

“Swift reveals about 20,000 ultraviolet sources in M31, especially hot, young stars and dense star clusters,” said Stefan Immler, a research scientist on the Swift team at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

“Of particular importance is that we have covered the galaxy in three ultraviolet filters. That will let us study M31′s star-formation processes in much greater detail than previously possible,” he added.

M31, also known as the Andromeda Galaxy, is more than 220,000 light-years across and lies 2.5 million light-years away.

On a clear, dark night, the galaxy is faintly visible as a misty patch to the naked eye.

Between May 25 and July 26, 2008, Swift’s Ultraviolet/Optical Telescope (UVOT) acquired 330 images of M31 at wavelengths of 192.8, 224.6, and 260 nanometers.

The images represent a total exposure time of 24 hours.

The task of assembling the resulting 85 gigabytes of images fell to Erin Grand, an undergraduate student at the University of Maryland at College Park who worked with Immler as an intern this summer.

“After ten weeks of processing that immense amount of data, I’m extremely proud of this new view of M31,” she said.

Several features are immediately apparent in the new mosaic.

The first is the striking difference between the galaxy’s central bulge and its spiral arms.

“The bulge is smoother and redder because it’s full of older and cooler stars,” Immler explained. “Very few new stars form here because most of the materials needed to make them have been depleted,” he added.

Dense clusters of hot, young, blue stars sparkle beyond the central bulge.

M31′s disk and spiral arms contain most of the gas and dust needed to produce new generations of stars.

Star clusters are especially plentiful in an enormous ring about 150,000 light-years across.

“Swift is surveying nearby galaxies like M31 so astronomers can better understand star- formation conditions and relate them to conditions in the distant galaxies where we see gamma-ray bursts occurring,” said Neil Gehrels, the mission’s principal investigator at NASA Goddard. (ANI)

Astronomers spot most distant object in the Universe

London, April 28 (ANI): Astronomers have spotted the most distant object yet confirmed in the universe, which is a self-destructing star that exploded 13.1 billion light years from Earth.

According to a report in New Scientist, it detonated just 640 million years after the big bang, around the end of the cosmic “dark ages”, when the first stars and galaxies were lighting up space.

The object is a gamma-ray burst (GRB) – the brightest type of stellar explosion.

GRBs occur when massive, spinning stars collapse to form black holes and spew out jets of gas at nearly the speed of light.

These jets send gamma rays our way, along with “afterglows” at other wavelengths, which are produced when the jet heats up surrounding gas.

The burst, dubbed GRB 090423 for the date of its discovery on April 23, was originally spotted by NASA’s Swift satellite at 0755 GMT.

Within an hour, astronomers began training ground-based telescopes on the same patch of sky to study the burst’s infrared afterglow.

Some of the first observations were made on Mauna Kea in Hawaii with the United Kingdom Infrared Telescope and the Gemini North telescope.

Other telescopes later measured the spectrum of the afterglow, revealing that the burst detonated about 13.1 billion light years from Earth.

“It’s the most distance gamma-ray burst, but it’s also the most distant object in the universe overall,” said Edo Berger of the Harvard-Smithsonian Center for Astrophysics, a member of the team that observed the afterglow with Gemini North.

This burst lies at a redshift of 8.2, more distant than the previous GRB record holder, which lay at a redshift of 6.7.

Other astronomers have claimed to find galaxies at even greater distances – at redshifts of 10 and 9, but those findings are still ambiguous, according to Joshua Bloom of the University of California, Berkeley, who observed the afterglow using the Gemini South telescope in Chile.

Until now, the record holder for the farthest galaxy had a spectroscopically confirmed redshift of 6.96.

The burst’s immense distance makes the now-dead star the earliest object to be discovered from an era called ‘reionisation’, which occurred within the first billion years after the big bang.

At that time, an obscuring fog of neutral hydrogen atoms was being burned off by radiation from the first stars and galaxies, and possibly also from the annihilation of dark matter particles.

“For astronomy, this is a watershed event,” Bloom told New Scientist. “This is the beginning of the study of the universe as it was before most of the structure that we know about today came into being,” he added. (ANI)

NASA satellite records early stage of gamma-ray burst

Washington, March 3 (ANI): A team of astronomers, using a telescope aboard the NASA Swift satellite, have captured information from the early stages of a gamma-ray burst, the most violent and luminous explosions occurring in the Universe since the Big Bang.

By using Swift’s Ultraviolet/Optical Telescope (UVOT), the astronomers were able to obtain an ultraviolet spectrum of a GRB just 251 seconds after its onset, the earliest ever captured.

The gamma-ray burst observed on this occasion originated in a galaxy 8 billion light years from Earth

Further use of the instrument in this way will allow them to calculate the distance and brightness of GRBs within a few hundred seconds of their initial outburst, and gather new information about the causes of bursts and the galaxies they originate from.

It is currently thought that some GRBs are caused by immense explosions following the collapse of the core of a rapidly rotating, high-mass star into a black hole, but there are still many mysteries surrounding them.

“The UVOT’s wavelength range, coupled with the fact that Swift is a space observatory with a speedy response rate, unconstrained by time of day or weather, has allowed us to collect this early ultraviolet spectrum,” said Martin Still from the Mullard Space Science Laboratory (MSSL) at University College London (UCL).

Paul Kuin, also from MSSL, who works on the calibration of the UVOT instrument, explained that, “By looking at these earlier moments of gamma-ray bursts, we will not only be able to better calculate things such as the luminosity and distance of a burst, but to find out more about the galaxies that play host to them and the impact these explosions have on their environments.”

“Once this new technique is applied to much brighter bursts, we’ll have a wealth of new data,” he added.

According to Massimiliano De Pasquale, a GRB scientist of the UVOT team from MSSL, “The UVOT instrument is particularly suited to study bursts with an average to high redshift – a part of the ultraviolet spectrum that is difficult for even the very big ground-based telescopes to study.”

“Using UVOT with Swift, we can now find redshifts for bursts that were difficult to capture in the past and find out more about their distant host galaxies, about ten billion light years away,” he added.

“The new spectrum has not only allowed us to determine the distance of the gamma-ray burst’s host galaxy but has revealed the density of its hydrogen clouds. Learning more about these far-away galaxies helps us to understand how they formed during the early universe,” said Kuin. (ANI)

Treat your eyes to a ‘green’ comet on February 24!

London, Feb 21 (ANI): Avid skygazers are all set to get a cosmic treat in the form of a ‘green’ comet, which is fast approaching Earth, and would be visible to the naked eye on February 24.

Comet Lulin will streak by the earth within 38 million miles – 160 times farther than the moon -and is expected to be visible to the naked eye.

Discovered only a year ago, the comet gains its green colour from poisonous cyanogen and diatomic carbon gases in its atmosphere.

This will be the comet’s first visit to the Earth’s inner solar system – and will enable the team from the University of Leicester to gain valuable insights into the comet.

Scientists are using NASA’s Swift satellite to monitor Comet Lulin as it closes on Earth. The spacecraft has recorded simultaneous ultraviolet and X-ray images of a comet.

“Swift is the ideal spacecraft with which to observe this comet,” said Jenny Carter, a scientist working with Dr Andrew Read at the University of Leicester, UK.

“We alerted the Swift team that the comet might be visible, and they quickly responded to take images using both the X-ray (XRT) and Ultraviolet/Optical Telescopes (UVOT) on-board,” said Dr Read.

According to Dr Julian Osborne, leader of the Swift project at Leicester, “The wonderful ease of scheduling of Swift and its joint UV and X-ray capability make Swift the observatory of choice for observations like these.”

“It is important to carry out these observations as they give us clues about the origin of comets and the solar system,” Carter added.

Comet Lulin, which is formally known as C/2007 N3, was discovered last year by astronomers at Taiwan’s Lulin Observatory.

On January 28, Swift trained its Ultraviolet/Optical Telescope and X-Ray Telescope on Comet Lulin.

“The comet is quite active,” said team member Dennis Bodewits, a NASA Postdoctoral Fellow at the Goddard Space Flight Center in Greenbelt, Maryland, USA.

“The UVOT data show that Lulin was shedding nearly 800 gallons of water each second,” he added.

“We are looking forward to future observations of Comet Lulin, when we hope to get better X-ray data to help us determine its makeup,” said Carter.

“They will allow us to build up a more complete 3-D picture of the comet during its flight through the solar system,” he added. (ANI)