NASA finds 'Mighty Mouse' pulsar brighter than 10 million suns

[Buster's Uncle]

NASA finds 'Mighty Mouse' pulsar brighter than 10 million suns
The discovery of a new unusually bright dead star leads astronomers to question assumptions about a type of cosmic radiation -- and pulsars themselves.
CNET
by  Michael Franco @writermfranco /October 8, 2014 4:13 PM PDT



The pink spot in this shot of the Cigar Galaxy shows ultraluminous X-rays (ULXs) believed to come from the largest pulsar ever recorded.  NASA/JPL-Caltech/SAO/NOAO



Using their space-based Nuclear Spectroscopic Telescope Array, or NuSTAR, NASA has just discovered a pulsar radiating with energy equivalent to about 10 million of our suns -- which makes it, they say, the brightest pulsar ever recorded. It was discovered in the galaxy Messier 82, which is also known as the "Cigar Galaxy" and is located about 12 million light years from Earth.

"You might think of this pulsar as the 'Mighty Mouse' of stellar remnants," said Fiona Harrison in a statement. "It has all the power of a black hole, but with much less mass." Harrison is the NuSTAR principal investigator at the California Institute of Technology in Pasadena, California.

When a super massive star is in its death throes, its core gets so dense that it explodes under the pressure, forming a brilliant supernova. Some of the old star's material blasts off into space while part of it condenses back around its core. The gravity in that core is so intense that it forces electrons and protons together to form neutrons, creating a type of dead star called (for obvious reasons) a neutron star.

Some neutron stars begin spinning very fast, sending out regular pulses of energy from their poles. These are called -- you guessed it -- pulsars.

Pulsars are similar to black holes in that they both possess tremendous gravitational fields -- although pulsars are weaker, contain much less mass and they emit light instead of gobbling it up. The newly discovered pulsar, however, is as strong as a black hole despite its smaller size. It is pulsing at the rate of 1.37 seconds.

This NASA video illustrates what a pulsar might look like:

Beacons of X-ray Light

 

The discovery is causing astronomers to rethink the source of something known as ultraluminous X-ray sources -- or super-bright x-rays. Prior to this discovery, they believed all ULXs came from black holes -- especially from medium-sized black holes, which were just observed for the first time in August in the same galaxy as the new pulsar, according to Space.com.

But, while they were observing a supernova, the scientists accidentally discovered bright ULX pulses coming from Messier 82. Because black holes don't pulse, they've concluded that the ULXs must be coming from the pulsar.

"In the news recently, we have seen that another source of unusually bright X-rays in the M82 galaxy seems to be a medium-sized black hole," said astronomer Jeanette Gladstone of the University of Alberta, Canada. "Now, we find that the second source of bright X-rays in M82 isn't a black hole at all. This is going to challenge theorists and pave the way for a new understanding of the diversity of these fascinating objects." Gladstone wasn't related to the research, which has just been published in the October 9 edition of the journal Nature.

Astronomers are puzzled as to why what should be a small, dead star is throwing off such a tremendous amount of light and plan to use a trio of telescopes to investigate further including NASA's NuSTAR, Swift and Chandra spacecraft.

"Having a diverse array of telescopes in space means that they can help each other out," said Paul Hertz, director of NASA's astrophysics division in Washington. "When one telescope makes a discovery, others with complementary capabilities can be called in to investigate it at different wavelengths."


http://www.cnet.com/news/nasa-finds-mighty-mouse-pulsar-brighter-than-10-million-suns/#ftag=YHF65cbda0

[Buster's Uncle]

Shockingly Bright Dead Star with a Pulse Is an X-ray Powerhouse
SPACE.com
By Nola Taylor Redd, SPACE.com Contributor  8 hours ago



The galaxy M82 hosts two ultra-bright objects known as ultraluminous X-ray sources, or ULXs. One of them, M82 X-2 (or X42.3+59) is powered by a pulsar rather than a black hole, as previously suggested. The discovery was announced on Oct. 8, 2014



A compact dead star known as a pulsar is the source for one of two superbright X-ray signals from a distant galaxy, a surprising find that could mean that pulsars lie at the heart of other such known sources, scientists say.

The pulsar is the brightest of its kind ever seen, and is more than 10 million times brighter than the sun, researchers said.The discovery may even have possible implications for astronomers' understanding of how galaxies form, they added.

Scientists had long thought that black holes were the only sources for ULXs. As black holes consume nearby material, they emit powerful X-rays thought to be responsible for the extremely bright ULX objects. The the newly identified pulsar,

"Until now, nobody paid too much attention to neutron stars — pulsars — in ULXs," lead author of the new study, Matteo Bachetti, of the Université de Toulouse in France, told Space.com by email. "From now on, people will be looking for more pulsations in these objects that might identify them as pulsars, and so neutron stars. I bet some other ULXs will be identified as pulsars in the following years."


A pulsing heart

Bachetti and his team used NASA's NuSTAR telescope to examine M82 X-2, one of two ULXs located in the cigar-shaped galaxy M82, a which is located approximately 12 million light-years from Earth. The object, they discovered, is a dense neutron star that pulses as it spins, giving it its "pulsar" name.

"If it were as close as the sun, we would be fried before even being born," Bachetti said.



The core of galaxy Messier 82 (M82) contains two ultraluminous X-ray sources (or ULXs), X-1 and X-2.


While studying the ULX, the researchers noticed a strange pulsation every 1.37 seconds that appeared several days after the start of their observations. Such pulsations do not occur around black holes, but do happen around pulsars.

These pulsing stars sweep beams of light, much like a lighthouse beam, that can be detected by astronomers on Earth. They are a type of neutron star, objects that occur when a supernova explodes, leaving behind a dense star. As pulsars gobble material from nearby stars or other objects, they give off light, including the X-rays observed by Bachetti’s team.

In the past, pulsars have been discarded as an option for all but the weakest ULXs. The reason: They simply shouldn't be able to consume material fast enough to reach the brightness, or luminosity, demonstrated by ULXs. M82 X-2 shines 100 times brighter than models anticipate for such a system.

"This is going to be a problem challenging theorists when they read this result," Jeanette Gladstone, of the University of Alberta in Canada, told Space.com by email. Gladstone, who was not part of the research, studies accreting compact objects, with a focus on ULXs. She authored a News & Views article that appeared alongside the research in the journal Nature online today (Oct. .

Because the pulsar is consuming material faster than theories thought possible, the find may have a profound effect on scientists' understanding of accretion physics.



Galaxy Messier 82 (M82) appears in two different views. NASA's Hubble Space Telescope shows the galaxy in visible light (left) and NASA's Chandra X-ray Observatory shows an X-ray view (right).


The "rare object team"

Like neutron stars, black holes are born at the end of a star's lifetime. As a star blows off material in a violent supernova, a black hole may be left behind. This massive object is so gravitationally strong that not even light can escape its grip, which is why scientists have to study black holes indirectly, by how they interact with their environments.

In a binary system, black holes, like neutron stars, can accrete material from their companions, radiating energy in the form of X-rays. Some black holes are star size, while others are extremely massive; such supermassive black holes lie at the center of galaxies, including the heart of the Milky Way.

The black holes thought to be responsible for powering ULXs lie somewhere between the two in size; these intermediate black holes weigh hundreds to thousands of times the mass of the sun. Such black holes have proven elusive to astronomers. However, separate research has begun to cast doubt on the hypothesis that these objects power ULXs, as oddly behaving stellar-mass black holes come under closer scrutiny as potential sources of ULX emissions.

Black holes have been targeted as the most likely sources because of their extremely densely packed masses. The more massive an object, the more rapidly it feeds off of its companion. The speed of such "feeding" associated with ULXs had suggested that a black-hole-size mass was necessary. In comparison, a pulsar is only about 1.4 times as massive as the sun, though such a star is packed into a ball with a city-sized diameter.



A unique, powerful pulsar (pink) sits at the center of the galaxy Messier 82 as shown in this new multi-wavelength image. NASA's NuSTAR mission made the using its high-energy X-ray vision. Image released Oct. 8, 2014.


"Neutron stars were mostly discarded for all but the weakest sources of the sample, because the 'speed of the meal' should have been too high for such a small object," Bachetti said.

The revelation that a pulsar powers M82 X-2 may drive astronomers to take a closer look at previously identified ULXs.

"We need to look more carefully at the population of ULXs," Gladstone said. "We may find other exciting sources that will also push the limits of our understanding."

The team used NASA's Chandra X-ray Observatory to study the source, and NuSTAR to capture the pulsar signature from the compact star.

"NuSTAR is just perfect for the job," Bachetti said.

Unlike most telescopes, NuSTAR can measure the oscillations and pulsations that categorize M82 X-2 as a pulsar. Furthermore, the pulsations are stronger at the X-ray energies where NuSTAR is more sensitive than any other satellite, he said.

Such pulsations may prove to be tricky to identify in other sources, as M82 X-2 apparently endured periods of low or no pulsation. However, examining already-identified sources may well turn up more pulsars that were previously classified as black holes.

So is M82 X-2 a common occurrence, or is it a rare source?

"I would root for the 'rare object' team," Bachetti said.

Identifying a pulsar at the heart of a ULX is important to more than just the study of these extremely bright objects.

"Knowing that you can have accretion at these incredible rates has implications on the models of the evolution of black holes and galaxies," Bachetti said. "For these models, the maximum rate at which compact objects accrete and grow is an important parameter to understand how the universe has evolved."


http://news.yahoo.com/shockingly-bright-dead-star-pulse-x-ray-powerhouse-174928186.html