Astronomers study 40 X-ray binaries comprised of black hole or neutron star feeding on material from companion star
Space news (February 05, 2016) – 2.5 million light-years away in Andromeda –
Astronomers using NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) to study 40 X-ray binaries in Andromeda Galaxy (M31). Astrophysicists study the critical role these energetic, intense sources of X-rays could have played in heating the intergalactic gasses in which the first galaxies were born. A study expected to help scientists view more distant galaxies and develop current and new theories on cosmic evolution.
“Andromeda is the only large spiral galaxy where we can see individual X-ray binaries and study them in detail in an environment like our own,” said Daniel Wik of NASA Goddard Space Flight Center in Greenbelt, Maryland, who presented the results at the 227th meeting of American Astronomical Society in Kissimmee, Florida. “We can then use this information to deduce what’s going on in more distant galaxies, which are harder to see.”
Andromeda and the Milky Way are fated to collide billions of years in the future, which will disrupt their spiral structures. Andromeda is slightly bigger than our home galaxy and is viewable from Earth by the naked human eye on dark, clear nights. The galaxy that results from their fated meeting in the dark of space will look nothing like the pair as we see them now. Watch this video on the Hubble site called “Clash of the Titans: Milky Way & Andromeda Collision“.
Astronomers are currently going over the data obtained through their use of NuSTAR to study the 40 X-ray binaries in Andromeda. Astrophysicists are identifying the fraction containing black holes as compared to neutron stars in order to better understand X-ray binaries as a whole.
“We have come to realize in the past few years that it is likely the lower-mass remnants of normal stellar evolution, the black holes, and neutron stars, may play a crucial role in heating of the intergalactic gas at very early times in the universe, around the cosmic dawn,” said Ann Hornschemeier of NASA Goddard, the principal investigator of the NuSTAR Andromeda studies.
She continued, “Observations of local populations of stellar-mass-sized black holes and neutron stars with NuSTAR allow us to figure out just how much power is coming out from these systems. The new research also reveals how Andromeda may differ from our Milky Way.“
Fiona Harrison, the principal investigator of the NuSTAR mission, added, “Studying the extreme stellar populations in Andromeda tells us about how its history of forming stars may be different than in our neighborhood.”
You can learn more about the mission of NASA’s NuSTARhere.
Discover the history and future plans of NASA here.
Space scientists have debated the nature and origin of high energy ultra-luminous x-ray sources for years
Space news (Oct. 28, 2014) –
Space scientists have been looking at celestial objects called ultraluminous x-ray sources (ULXs) for years in search of answers to the mystery surrounding their nature and origin. Celestial bodies radiating enormous amounts of high-energy x-rays, astronomers have been studying three nearby ULXs changing thoughts and present theory on these energetic characters.
Space scientists using the Chandra X-ray Observatory, Hubble Space Telescope, Swift Gamma-ray Burst Explorer and XMM-Newton Space Observatory have been studying two ULXs discovered in Andromeda galaxy (M31). The first is called CXOM31 and was discovered in 2009 using the Chandra X-ray Space Observatory. The second, XMMU, was discovered on Jan. 15, 2014 by the European Space Agency’s XMM-Newton spacecraft.
Space scientists believe both ULXs they observe in Andromeda are binary star systems with a black hole rapidly accreting (consuming) material from its neighbor at a rate near the theoretical Eddington limit (the maximum accretion rate of a black hole).
“There are four black hole binaries within our own galaxy that have been observed accreting at these extreme rates,” said Matthew Middleton, an astronomer at the Anton Pannekoek Astronomical Institute in Amsterdam. “Gas and dust in our own galaxy interfere with our ability to probe how matter flows into ULXs, so our best glimpse of these processes comes from sources located out of the plane of our galaxy, such as those in M31.”
“As gas spirals toward a black hole, it becomes compressed and heated, eventually reaching temperatures where it emits X-rays. As the rate of matter ingested by the black hole increases, so does the X-ray brightness of the gas. At some point, the X-ray emission becomes so intense that it pushes back on the inflowing gas, theoretically capping any further increase in the black hole’s accretion rate. Astronomers refer to this as the Eddington limit, after Sir Arthur Eddington, the British astrophysicist who first recognized a similar cutoff to the maximum luminosity of a star.”
“Black-hole binaries in our galaxy that show accretion at the Eddington limit also exhibit powerful radio-emitting jets that move near the speed of light,” Middleton said. “Although astronomers know little about the physical nature of these jets, detecting them at all would confirm that the ULX is accreting at the limit and identify it as a stellar mass black hole.”
Space scientists operating NASA’s Nuclear Array (NuSTAR) have also found the brightest ULX on record near the center of galaxy Messier 82 (M82) 12 million light-years away. Called M82 X-2, they believe this particular object is actually a dead pulsating star called a pulsar, rather than a binary star system with a black hole accreting material from its neighbor.
“Astronomers have found a pulsating, dead star beaming with the energy of about 10 million suns. This is the brightest pulsar – a dense stellar remnant left over from a supernova explosion – ever recorded. The discovery was made with NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR.”
“You might think of this pulsar as the ‘Mighty Mouse’ of stellar remnants,” said Fiona Harrison, the NuSTAR principal investigator at the California Institute of Technology in Pasadena, California. “It has all the power of a black hole, but with much less mass.”
This ULX being something other than a binary star system with an accreting black hole is surprising to astronomers. They’ll have to rethink present theories on the nature and origin of these mysterious celestial objects.
“The pulsar appears to be eating the equivalent of a black hole diet,” said Harrison. “This result will help us understand how black holes gorge and grow so quickly, which is an important event in the formation of galaxies and structures in the universe.”
“ULXs are generally thought to be black holes feeding off companion stars — a process called accretion. They also are suspected to be the long-sought-after “medium-sized” black holes – missing links between smaller, stellar-size black holes and the gargantuan ones that dominate the hearts of most galaxies. But research into the true nature of ULXs continues toward more definitive answers.”
“We took it for granted that the powerful ULXs must be massive black holes,” said lead study author Matteo Bachetti, of the University of Toulouse in France. “When we first saw the pulsations in the data, we thought they must be from another source.”
“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.”
Space scientists will now use NASA’s complete array of astronomical equipment and spacecraft to look at how this dead star is able to radiate x-rays so intensely. Plans are for NuSTAR, the Swift Gamma-ray Burst Explorer, and Chandra X-ray Space Observatory to have a look at the weird behavior of M82 X-2.
They’ll also start looking at other ULXs to see if they can find anymore that are pulsars, rather than a binary star system with an accreting black hole. This research could open a window of discovery on the true nature and origin of these energetic and enigmatic celestial objects.
Astronomers studying galaxies have discovered something unusual
Astronomy news (November 29, 2013) – Astronomers have found galaxies of different shapes and sizes during the human journey to the beginning of space and time, but the rectangular-shaped galaxy astronomers recently located 68 million light-years away in Eridanus the River doesn’t fit any current theory of what a galaxy should look like. Leda 074886 is one of about 250 galaxies in the cluster of galaxies around the massive galaxy NGC 1407, which lies about 70 million light-years from Earth in the constellation Eridanus.
Astronomers wonder about this rectangular shape
Astronomers detected LEDA 074886 in a wide-field image taken with the Japanese Subaru Telescope. After analysis astronomers detected a stellar disk inside the rectangular-galaxy, aligned edge-on to our line of sight in the Milky Way. This disk is rotating at speeds up to 33 km/second, but at this point they’re not sure it has a spiral structure characteristic of a galaxy.
Astronomers classify galaxies according to their overall shape, using three general categories; elliptical, disk-like, and irregular. The unusual shape of the galaxy designated LEDA 074886 doesn’t fit into any of these three categories. The question astronomers are asking is how did this galaxy come to have this unusual shape?
Could this rectangular shaped galaxy be the result of a galactic collision?
Is the unusual shape of this galaxy due to a collision with another galaxy, perhaps between two spiral galaxies? Astronomers models indicate this scenario could possibly result in the stars of each galaxy flinging outward to form a rectangular shape. Astronomers also detected a disk of bluish, relatively young stars near the center of this galaxy, which they believe could indicate a recent collision with another small galaxy. This discovery should help astronomers model the formation and evolution of galaxies better and perhaps get a picture of the fated collision between the Milky Way and Andromeda 4 billion years from now.