Massive Black Hole Implicated in Stellar Destruction

Jan 04, 2010
Evidence from NASA's Chandra X-ray Observatory and the Magellan telescopes suggest a star has been torn apart by an intermediate-mass black hole in a globular cluster. In this image, X-rays from Chandra are shown in blue and are overlaid on an optical image from the Hubble Space Telescope. The Chandra observations show that this object is a so-called ultraluminous X-ray source (ULX). An unusual class of objects, ULXs emit more X-rays than stars, but less than quasars. Their exact nature has remained a mystery, but one suggestion is that some ULXs are black holes with masses between about a hundred and a thousands times that of the Sun. Credits: X-ray: NASA/CXC/UA/J. Irwin et al. Optical: NASA/STScI

(PhysOrg.com) -- New results from NASA's Chandra X-ray Observatory and the Magellan telescopes suggest that a dense stellar remnant has been ripped apart by a black hole a thousand times as massive as the Sun. If confirmed, this discovery would be a cosmic double play: it would be strong evidence for an intermediate mass black hole, which has been a hotly debated topic, and would mark the first time such a black hole has been caught tearing a star apart.

This scenario is based on Chandra observations, which revealed an unusually luminous source of X-rays in a dense cluster of old , and optical observations that showed a peculiar mix of elements associated with the X-ray emission. Taken together, a case can be made that the X-ray emission is produced by debris from a disrupted white dwarf star that is heated as it falls towards a . The optical emission comes from debris further out that is illuminated by these X-rays.

The intensity of the X-ray emission places the source in the "ultraluminous X-ray source" or ULX category, meaning that it is more luminous than any known stellar X-ray source, but less luminous than the bright X-ray sources () associated with supermassive in the nuclei of galaxies. The nature of ULXs is a mystery, but one suggestion is that some ULXs are black holes with masses between about a hundred and several thousand times that of the Sun, a range intermediate between stellar-mass black holes and supermassive black holes located in the nuclei of galaxies.

This ULX is in a globular cluster, a very old and crowded conglomeration of stars. Astronomers have suspected that globular clusters could contain intermediate-mass black holes, but conclusive evidence for this has been elusive.

"Astronomers have made cases for stars being torn apart by supermassive black holes in the centers of galaxies before, but this is the first good evidence for such an event in a globular cluster," said Jimmy Irwin of the University of Alabama who led the study.

Irwin and his colleagues obtained optical spectra of the object using the Magellan I and II telescopes in Las Campanas, Chile. These data reveal emission from gas rich in oxygen and nitrogen but no hydrogen, a rare set of signals from globular clusters. The physical conditions deduced from the spectra suggest that the gas is orbiting a black hole of at least 1,000 solar masses. The abundant amount of oxygen and absence of hydrogen indicate that the destroyed star was a white dwarf, the end phase of a solar-type star that has burned its hydrogen leaving a high concentration of oxygen. The nitrogen seen in the optical spectrum remains an enigma.

"We think these unusual signatures can be explained by a white dwarf that strayed too close to a black hole and was torn apart by the extreme tidal forces," said coauthor Joel Bregman of the University of Michigan.

Theoretical work suggests that the tidal disruption-induced X-ray emission could stay bright for more than a century, but it should fade with time. So far, the team has observed there has been a 35 percent in from 2000 to 2008.

The ULX in this study is located in NGC 1399, an elliptical galaxy about 65 million light years from Earth.

Irwin presented these results at the 215th meeting of the American Astronomical Society in Washington, DC. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

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User comments : 9

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omatumr
2.3 / 5 (3) Jan 04, 2010
Interesting story.

But I doubt that the stellar remnant was ripped apart by a black hole, although a massive neutron star may have caused this.

With kind regards,
Oliver K. Manuel
Oliver_k_Manuel
1 / 5 (1) Jan 04, 2010
So far, the team has observed there has been a 35 percent in X-ray emission from 2000 to 2008.

35 percent what
the sun is a plasma cannon controlling climate change
Birger
5 / 5 (4) Jan 05, 2010

But I doubt that the stellar remnant was ripped apart by a black hole, although a massive neutron star may have caused this.


Neutron stars cannot get more massive than 3 solar masses -any bigger and the escape velocity exceeds C, which is the definition of a black hole. The inferred mass of this object is ca. 1000 solar masses.
Phelankell
5 / 5 (1) Jan 05, 2010
Neutron stars cannot get more massive than 3 solar masses -any bigger and the escape velocity exceeds C, which is the definition of a black hole. The inferred mass of this object is ca. 1000 solar masses.


The upper limit mass of neutron stars is highly uncertain. 3 solar masses is our best guess supported by our limited understanding of gravity.
frajo
1 / 5 (1) Jan 05, 2010
The upper limit mass of neutron stars is highly uncertain.
Yes.
3 solar masses is our best guess supported by our limited understanding of gravity.
Yes. Should we apply a worse guess instead?
Phelankell
5 / 5 (1) Jan 05, 2010
No, but we shouldn't consider it an absolute with no evidence to that effect.
PinkElephant
not rated yet Jan 05, 2010
There may be some uncertainty, but there are two orders of magnitude between 3 and 1000.

It's pretty safe to conclude that by the time you get to 1000 solar masses, you no longer have a neutron, quark, or any other kind of star that can possibly be made of any matter whatsoever. When no interaction can occur without violating the cosmic speed limit, you have no matter. Case closed.
frajo
1 / 5 (1) Jan 06, 2010
Case closed.
As long as we can't observe and can't calculate what happens "inside".
My hope is that someday someone will find or invent a "tool" to peek inside, be it theoretical or observational.
Phelankell
1 / 5 (1) Jan 06, 2010
It's pretty safe to conclude that by the time you get to 1000 solar masses, you no longer have a neutron, quark, or any other kind of star that can possibly be made of any matter whatsoever.
Black holes are far larger and are made of matter.

When no interaction can occur without violating the cosmic speed limit, you have no matter. Case closed.
Completely incorrect in addition to being ridiculously irrelevant to what we're talking about.

The weight of a neutron star is loosely bounded at 3 solar masses because we think we have an understanding of the tipping points for gravitational interaction against energy pressure and dispersion rates. Keep in mind neutron stars were completely theoretical up until about 1962 or so when we started discovering them. If we're not 100% sure on how gravity works, we can't upper bound neutron stars. Our best guess is 3 solar masses because a single solar mass of degenerate neutron matter has a theoretical escape velocity of 1/3 C.