Tuesday, October 27, 2015

Researchers Shed New Light on Black Holes

A supermassive black hole is depicted in this artist's concept, surrounded by a swirling disk of material falling onto it. Credits: NASA/JPL-Caltech

Patience and observation have paid off for Saint Mary’s University researchers with a discovery that just may hold one of the keys to the Universe. For Dr. Luigi Gallo, a professor in the Department of Astronomy and Physics, the excitement began in 2014 when the NASA Explorer mission Swift detected a large flare of light coming from Markarian 335 (Mrk 335), a supermassive black hole located 324 million light-years away in a distant galaxy.

As principal investigator for the study at Saint Mary's University in Halifax (Canada), Dr. Gallo asked the Nuclear Spectroscopic Telescope Array (NuSTAR) team to interrupt its regular program of observation to monitor the event --- a protocol used for important discoveries --- and eight days later, NuSTAR set its X-ray eyes on Mrk 335 in time to witness the final half of a giant eruption of X-ray light. The data were analyzed by a team of Dr. Gallo’s that included postdoctoral fellow Dr. Dan Wilkins and graduate student Kirsten Bonson.

“We realized that we were seeing the ejection of the black hole's surrounding corona,” explains Dr. Wilkins. “It gathered inward at first before launching up like a rocket.”

Wilkins details the event as lead author in a paper to be released this week in the Monthly Notices of the Royal Astronomical Society. The hope, he says, is that the dramatic flare of light from Markarian 335 will help us understand how supermassive black holes power some of the brightest objects in the Universe.

This diagram shows how a shifting feature, called a corona, can create a flare of X-rays around a black hole. The corona (feature represented in purplish colors) gathers inward (left), becoming brighter, before shooting away from the black hole (middle and right). Astronomers don't know why the coronas shift, but they have learned that this process leads to a brightening of X-ray light that can be observed by telescopes. Credits: NASA/JPL-Caltech
This diagram shows how a shifting feature, called a corona, can create a flare of X-rays around a black hole. The corona (feature represented in purplish colors) gathers inward (left), becoming brighter, before shooting away from the black hole (middle and right). Astronomers don't know why the coronas shift, but they have learned that this process leads to a brightening of X-ray light that can be observed by telescopes. Credits: NASA/JPL-Caltech

“This is the first time we have been able to link an X-ray flare to a shifting corona,” says Dr. Gallo. “Looking at what changed during this event may be a clue to unlocking the secrets of the corona and even explaining why black holes flare.”

Studying the night skies may seem a solitary pursuit, but both Gallo and Wilkins are quick to attribute their discovery to teamwork. “We couldn’t do what we do without the people who work on the telescopes and our international colleagues who make these observations possible,” says Gallo. “Collaborations are an important part of scientific discovery.”

"The nature of the energetic source of X-rays we call the corona is mysterious, but now with the ability to see dramatic changes like this we are getting clues about its size and structure," said Fiona Harrison, the principal investigator of NuSTAR at the California Institute of Technology in Pasadena, who was not affiliated with the study.

NuSTAR is a Small Explorer mission led by Caltech and managed by NASA's Jet Propulsion Laboratory in Pasadena, California, for NASA's Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp., Dulles, Virginia. NuSTAR's mission operations center is at UC Berkeley, and the official data archive is at NASA's High Energy Astrophysics Science Archive Research Center. ASI provides the mission's ground station and a mirror archive. JPL is managed by Caltech for NASA.

Credit: smu.caNASA

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