Star Swallowed by Galactic Black Hole

In summary, Dr. Joshua Bloom, an associate professor of astronomy at UC Berkeley, describes a rare event in which a dormant black hole captured a star that came too close and was ripped apart. The point of no return for a star varies with its mass and radius, with more massive stars needing to pass closer to the black hole to be disrupted. This event was detected because the material ejected from the star was pointed towards Earth, but other similar events may go undetected if they are not pointed in our direction. However, the interaction of a jet with matter away from the black hole can also indicate the presence of a dormant black hole.
  • #1
RJ Emery
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In an article in the NY Times http://www.nytimes.com/2011/06/21/science/space/21obhole.html" , it was written:

“This is a singular event in the history of mankind,” Dr. Joshua Bloom, an associate professor of astronomy at UC Berkeley, said. “This black hole was otherwise sitting dormant, a star got too close, its gas got ripped apart and in doing so some of it got spit up.”

My question is about objects getting too close to black holes. Does the point of no return vary with the mass of the object? Do more massive objects get caught in the death grip of a black hole further than a smaller object?
 
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  • #2
RJ Emery said:
In an article in the NY Times http://www.nytimes.com/2011/06/21/science/space/21obhole.html" , it was written:

“This is a singular event in the history of mankind,” Dr. Joshua Bloom, an associate professor of astronomy at UC Berkeley, said. “This black hole was otherwise sitting dormant, a star got too close, its gas got ripped apart and in doing so some of it got spit up.”

My question is about objects getting too close to black holes. Does the point of no return vary with the mass of the object? Do more massive objects get caught in the death grip of a black hole further than a smaller object?

Here is the paper behind this new story:

http://arxiv.org/abs/1104.3257
also as Report in Science: http://www.sciencemag.org/content/early/2011/06/15/science.1207150

Right at the beginning of the paper they describe a disruption radius. If the star passes closer than this to the black hole, it will be disrupted and swallowed. They give the formula:

R (MBH / M)^1/3

R = radius of star
MBH = mass of black hole (assumed > a million time M)
M = mass of star.

So yes, it depends on both mass and radius of star. However, a more massive star apparently needs to pass closer to be disrupted and absorbed.

For concreteness, for a star like the sun, and black hole of 10^7 solar masses, the disruption radius is 5 times the event horizon radius.
 
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  • #3
I have another question:

In the NY Times article, Bloom describes part of the swallowed star as having been "spit up." I presume this material spike fortuitously was pointed in the direction of earth, at which point the emission could be detected.

If other stars were swallowed by this same black hole with a resulting spike pointed away from earth, then we would have no way of detecting such an event.

Thus, while a (galactic) black hole may appear quiescent, it may be anything but. To detect an event, it really depends 1) if a spike occurred from a swallowed star and 2) if it was pointed in our direction.

Is the above reasoning correct?
 
  • #4
Actually, with a trivial rearrangement, the formula for disruption radius is inversely proportional to the cube root of the density of the passing star. Thus, within the parameters and validity scope of this approximation, the more 'compact' a body, the closer it has to come to be disrupted.
 
  • #5
RJ Emery said:
I have another question:

In the NY Times article, Bloom describes part of the swallowed star as having been "spit up." I presume this material spike fortuitously was pointed in the direction of earth, at which point the emission could be detected.

If other stars were swallowed by this same black hole with a resulting spike pointed away from earth, then we would have no way of detecting such an event.

Thus, while a (galactic) black hole may appear quiescent, it may be anything but. To detect an event, it really depends 1) if a spike occurred from a swallowed star and 2) if it was pointed in our direction.

Is the above reasoning correct?

Actually, the described event is seen off axis of the jet (year long interaction of jet with matter away from the massive black hole). Events seen closer to on axis are brighter, with short peak luminosity.

An active galaxy nucleus has high background luminosity from regular infall events, flashing very bright when a jet is oriented our way. Thus, a dormant black hole (that has cleared nearby material a long time ago) that sporadically captures a star is quite distinguishable - and very rare. Correction: Dormant black holes are not rare; infall of a star into one is rare - otherwise they wouldn't be dormant.
 
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FAQ: Star Swallowed by Galactic Black Hole

What is a "Star Swallowed by Galactic Black Hole"?

A "Star Swallowed by Galactic Black Hole" refers to a phenomenon in which a star, due to its close proximity to a supermassive black hole at the center of a galaxy, gets pulled into the black hole and disappears from view.

How does a star get swallowed by a galactic black hole?

A star can get swallowed by a galactic black hole when it comes within the event horizon of the black hole, which is the point of no return where the gravitational pull is too strong for anything, even light, to escape. The star then gets stretched and torn apart by the immense gravitational forces before being pulled into the black hole.

What happens to the star once it is swallowed by a galactic black hole?

Once the star is swallowed by the galactic black hole, it becomes part of the black hole's mass and adds to its overall size. The intense gravity of the black hole also causes the star's material to heat up and emit high-energy radiation, making it detectable to telescopes and other instruments.

What are the implications of a star being swallowed by a galactic black hole?

The swallowing of a star by a galactic black hole can have significant implications for the dynamics of the galaxy. The addition of mass to the black hole can affect the orbits of other stars and objects in the galaxy, and the high-energy radiation emitted during the process can also impact the surrounding environment.

Is it common for stars to be swallowed by galactic black holes?

While it is not uncommon for stars to be pulled into the vicinity of galactic black holes, the actual act of being swallowed is relatively rare. This is because most stars in a galaxy are located far enough away from the black hole to not be affected by its gravitational pull. However, in densely packed regions of galaxies, such as the galactic center, the chances of a star being swallowed by a black hole increase.

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