Diagnosing a black hole flare

May 07, 2012
An optical-IR image showing a galaxy that suddenly brightened when the supermassive black hole at its center shredded and absorbed a star that wandered too close. Credit: NASA; Gezari, Rest, and Chornock

(Phys.org) -- Black holes can come in a wide range of masses. Some, with only about one solar mass, result from the supernova death of a massive star, while those at the center of galaxies (called supermassive black holes) have millions or even billions of solar masses. Supermassive black holes are relatively famous because they are responsible for the powerful jets and other dramatic phenomena seen in some galaxies. The center of our Milky Way galaxy contains a modest-sized supermassive black hole, with about four million solar masses, and (fortunately for us) it is inactive - it lacks the extreme phenomena seen elsewhere.

Black holes are so dense that nothing, not even light, can escape from their gravitational . Still, can be detected because matter that falls into them heats up, and emits bright radiation. A short-lived flare, for example, can result when a body (perhaps a cloud of gas or a star) wanders too close to a black hole and is eaten. Astronomers are particularly interested in measuring the way the brightness of the flare increases, versus its decline, because the shape of the rising emission holds clues to the actual infall process. Observing such events is difficult, though, because the flaring activity may only last for a few months -- by the time it is spotted in the sky the most diagnostic phases of flare activity may have passed. Moreover, flares from smaller supermassive black holes (like the one in the center of the Milly Way) may be correspondingly weaker.

Pan-STARRS (Panoramic Survey Telescope & Rapid Response System) is a telescope with a small mirror (1.8 meters) but a very large field of view, and large digital cameras (1.4 billion pixels) developed especially to look for transient events. It can observe the entire available sky several times a month. In May of 2010 it spotted what appeared to be a flare from a previously inactive, Milky-Way-sized in a galaxy about two billion light-years away. A team including CfA astronomers Ryan Chornock, Edo Berger, Peter Challis, Gautham Narayan, Ryan Foley, George Marion, Laura Chomiuk, Alicia Soderberg, Bob Kirshner, and Chris Stubbs, then led an aggressive follow-up campaign of observations to see what was going on.

The team reports on their discovery in this week's Nature. They began observing the flare about 40 days after it went off and about 40 days before it peaked, providing excellent data over most of the event. Detailed modeling of the light led the team to conclude that the black hole is less massive than previously thought, only about two million , and that the object it devoured was probably an evolved star (about 5 billion years old) whose mass was about 0.2 solar masses. These new results provide a particularly impressive, detailed view of what goes on in these exotic cosmic , and offer support for the overall model of these flaring events.

Explore further: Astronomers find 'cousin' planets around twin stars

Related Stories

Measuring galaxy black hole masses

May 27, 2011

(PhysOrg.com) -- Black holes, one of the most amazing and bizarre predictions of Einstein's theory of gravity, are irresistible sinks for matter and energy. They are so dense that not even light can escape ...

The Milky Way's supermassive black hole

Aug 08, 2011

Supermassive black holes - objects with masses of millions or even billions of suns - are found at the nuclei of galaxies. Our Milky Way galaxy, for example, has a massive black hole at its core, albeit one ...

Astronomers calculate mass of largest black hole yet

Jan 14, 2011

(PhysOrg.com) -- Weighing 6.6 billion solar masses, the black hole at the center of galaxy M87 is the most massive black hole for which a precise mass has been measured. Using the Frederick C. Gillett Gemini ...

Chandra finds nearest pair of supermassive black holes

Aug 31, 2011

(PhysOrg.com) -- Astronomers have used NASA's Chandra X-ray Observatory to discover the first pair of supermassive black holes in a spiral galaxy similar to the Milky Way. At a distance of 160 million light ...

Black hole jets

Jan 16, 2012

(PhysOrg.com) -- Black holes are irresistible sinks for matter and energy. They are so dense that not even light can escape from their gravitational clutches. Massive black holes (equal to millions or even ...

Scientists watch black hole feast on unlucky star

May 02, 2012

Scientists have witnessed the rare spectacle of a supermassive black hole devouring a star that had ventured too close -- an event that occurs about once in 10,000 years, they reported on Wednesday.

Recommended for you

How small can galaxies be?

Sep 29, 2014

Yesterday I talked about just how small a star can be, so today let's explore just how small a galaxy can be. Our Milky Way galaxy is about 100,000 light years across, and contains about 200 billion stars. Th ...

The coolest stars

Sep 29, 2014

One way that stars are categorized is by temperature. Since the temperature of a star can determine its visual color, this category scheme is known as spectral type. The main categories of spectral type are ...

Simulations reveal an unusual death for ancient stars

Sep 29, 2014

(Phys.org) —Certain primordial stars—those 55,000 and 56,000 times the mass of our Sun, or solar masses—may have died unusually. In death, these objects—among the Universe's first-generation of stars—would ...

User comments : 0