X-ray Nova Reveals a New Black Hole in Our Galaxy

  • Released Friday, October 5th, 2012
  • Updated Wednesday, May 3rd, 2023 at 1:52PM
  • ID: 11108

On Sept. 16, NASA's Swift satellite detected a rising tide of high-energy X-rays from a source toward the center of our Milky Way galaxy. The outburst, produced by a rare X-ray nova, announced the presence of a previously unknown stellar-mass black hole.

An X-ray nova is a short-lived X-ray source that appears suddenly, reaches its emission peak in a few days and then fades out over a period of months. The outburst arises when a torrent of stored gas suddenly rushes toward one of the most compact objects known, either a neutron star or a black hole.

Named Swift J1745-26 after the coordinates of its sky position, the nova is located a few degrees from the center of our galaxy toward the constellation Sagittarius. While astronomers do not know its precise distance, they think the object resides about 20,000 to 30,000 light-years away in the galaxy's inner region. The pattern of X-rays from the nova signals that the central object is a black hole.

Ground-based observatories detected infrared and radio emissions, but thick clouds of obscuring dust have prevented astronomers from catching Swift J1745-26 in visible light.

The black hole must be a member of a low-mass X-ray binary (LMXB) system, which includes a normal, sun-like star. A stream of gas flows from the normal star and enters into a storage disk around the black hole. In most LMXBs, the gas in the disk spirals inward, heats up as it heads toward the black hole, and produces a steady stream of X-rays.

But under certain conditions, stable flow within the disk depends on the rate of matter flowing into it from the companion star. At certain rates, the disk fails to maintain a steady internal flow and instead flips between two dramatically different conditions — a cooler, less ionized state where gas simply collects in the outer portion of the disk like water behind a dam, and a hotter, more ionized state that sends a tidal wave of gas surging toward the center.

This phenomenon, called the thermal-viscous limit cycle, helps astronomers explain transient outbursts across a wide range of systems, from protoplanetary disks around young stars, to dwarf novae - where the central object is a white dwarf star - and even bright emission from supermassive black holes in the hearts of distant galaxies.

Short narrated video.

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Sequence of high resolution stills of Swift J1745-26 from September 13 to September 26, 2012.

Credit: NASA/Goddard Space Flight Center/S. Immler and H. Krimm

Swift J1745-26 with labels and scale of moon as it would appear in the field of view from Earth. This image is from September 18, 2012 when the source peaked in hard X-rays.Credit: NASA/Goddard Space Flight Center/S. Immler and H. Krimm

Swift J1745-26 with labels and scale of moon as it would appear in the field of view from Earth. This image is from September 18, 2012 when the source peaked in hard X-rays.

Credit: NASA/Goddard Space Flight Center/S. Immler and H. Krimm

Swift J1745-26. This image is from September 18, 2012 when the source peaked in hard X-rays. No LabelsCredit: NASA/Goddard Space Flight Center/S. Immler and H. Krimm

Swift J1745-26. This image is from September 18, 2012 when the source peaked in hard X-rays. No Labels

Credit: NASA/Goddard Space Flight Center/S. Immler and H. Krimm

For More Information

See http://www.nasa.gov/mission_pages/swift/bursts/new-black-hole.html

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NASA/Goddard Space Flight Center. However, individual images should be credited as indicated above.

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  • Flaring Black Hole (ID: 2012103)
    Thursday, October 4, 2012 at 4:00AM
    Produced by - Robert Crippen

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