Astronomers Watch as a Black Hole Eats a Rogue Planet

In Star Wars, the Millennium Falcon narrowly escaped being devoured by an exogorth (space slug) slumbering inside an asteroid crater. An unsuspecting rogue giant planet wasn’t as lucky. Astronomers using the Integral space observatory were able to watch as the planet was eaten by a black hole that had been inactive for decades. It woke up just in time to make a meal out of the unwary planet.

“The observation was completely unexpected, from a galaxy that has been quiet for at least 20–30 years,” says Marek Nikolajuk of the University of Bialystok, Poland, lead author of the paper in Astronomy & Astrophysics.

Nikolajuk and his team added that the event is a preview of a similar feeding event that is expected to take place with the black hole at the center of our own Milky Way Galaxy.

The discovery in galaxy NGC 4845, 47 million light-years away, was made by Integral, with follow-up observations from ESA’s XMM-Newton, NASA’s Swift and Japan’s MAXI X-ray monitor on the International Space Station.

Astronomers were using Integral to study a different galaxy when they noticed a bright X-ray flare coming from another location in the same wide field-of-view. Using XMM-Newton, the origin was confirmed as NGC 4845, a galaxy never before detected at high energies.

Along with Swift and MAXI, the emission was traced from its maximum in January 2011, when the galaxy brightened by a factor of a thousand, and then as it subsided over the course of the year.

By analyzing the characteristics of the flare, the astronomers could determine that the emission came from a halo of material around the galaxy’s central black hole as it tore apart and fed on an object of 14–30 Jupiter masses, and so the astronomers say the object was either a super-Jupiter or a brown dwarf.

This object appears to have been ‘wandering,’ which would fit the description of recent studies that have suggested that free-floating planetary-mass objects of this kind may occur in large numbers in galaxies, ejected from their parent solar systems by gravitational interactions.

The black hole in the center of NGC 4845 is estimated to have a mass of around 300,000 times that of our own Sun. The astronomers said it also appears to enjoy playing with its food: the way the emission brightened and decayed shows there was a delay of 2–3 months between the object being disrupted and the heating of the debris in the vicinity of the black hole.

“This is the first time where we have seen the disruption of a substellar object by a black hole,” said co-author Roland Walter of the Observatory of Geneva, Switzerland. “We estimate that only its external layers were eaten by the black hole, amounting to about 10% of the object’s total mass, and that a denser core has been left orbiting the black hole.”

The flaring event in NGC 4845 might be similar to what is expected to happen with the supermassive black hole at the center of our own Milky Way Galaxy, perhaps even this year, when an approaching Earth-mass gas cloud is expected to meet its demise.

Along with the object seen being eaten by the black hole in NGC 4845, these events will tell astronomers more about what happens to the demise of different types of objects as they encounter black holes of varying sizes.

“Estimates are that events like these may be detectable every few years in galaxies around us, and if we spot them, Integral, along with other high-energy space observatories, will be able to watch them play out just as it did with NGC 4845,” said Christoph Winkler, ESA’s Integral project scientist.

The team’s paper: Tidal disruption of a super-Jupiter in NGC 4845

Source: ESA

8 Replies to “Astronomers Watch as a Black Hole Eats a Rogue Planet”

  1. I find it interesting that some of the planet actually remained intact. Surely the immense gravitational forces and a comparatively small planet wouldn’t stand a hope?

  2. I love your site but please try to avoid zoomorphic language like “It woke up just in time to make a meal out of the unwary planet.” and “The astronomers said it also appears to enjoy playing with its food:…” It’s amusing but uninformative and inaccurate. Did it really wake up? Surely the wondering planet just started interacting with the black hole’s ever active gravitational field as it drifted closer?

    For people just learning about astronomy phrases like those that you’ve used could lead them down confusing dead ends.

  3. It appears this super-Jovian planet or brown dwarf passed by the BH on a highly elliptical orbit. The object got a severe haircut by passing close to the BH. If it is on this elliptical orbit it is destined to get a repeated treatment of this sort until it is reduced to nothing. I suppose this does not exclude the possibility the planet is on an elliptical orbit relative to the BH and this is a one time pass. The orbital dynamics is complicated, but if this object were not bound to the BH maybe this interaction robbed enough kinetic energy of this body to place it into a captured orbit.

    I have yet to search out the research paper, but I am presuming this is deduced to be a “planet” by the optical signature. A gas cloud would turn on an optical signature less rapidly I presume.

    The deduced mass of this BH puts it at the extreme limit of intermediate mass BHs. This BH may have then been formed in the early period of star and galaxy formation.


  4. Is this a late April Fool’s Day joke? You’re trying to tell us that a telescope could actually visualize a planetary disk in another galaxy 47 million light-years away? When we’re just barely imaging planets now in our own galactic neighborhood? I don’t think so.

    1. This is the price we now pay for living in a ‘Reality’ world – you know, Reality TV and contrived ‘adventure’ shows, passed off as real-time life. Regrettably serious numbers of our population are barely able to distinguish fact from fairy-tale. Could it be our glamorous editor also (temporally) slipped into na-na land? A forgivable lapse, surely?

      1. Yes, it’s understandable, especially given the rapid advancements in spotting planets. Perhaps people didn’t notice the distance given, 47 Mly. The farthest exoplanet distance I could find was 27 kly, 1,700 time closer.

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