Leading-edge astronomy: Hunting down cosmic predators

ASTRO-H will peer down the throat of supermassive black holes that lurk at the heart of distant, young galaxies. Astronomers hope to get an unprecedented peek into the inner clockwork of the largest of these galactic predators that are billions of times more massive than our Sun.

ASTRO-H will also focus on unraveling the mysteries behind the remnants of star blasts known as supernovae. Astronomers believe that everything in the cosmos—even humans—was made from heavy elements forged in large part inside ancient supernovae. By using unmatched spectral resolution, combined with the ability to focus high-energy X-rays, ASTRO-H will make the most precise measurements ever obtained of the chemical ingredients that go into making these colossal cosmic explosions, and will probe the sites of particle acceleration to the highest energies.

According to the Canadian Principal Investigator for ASTRO-H mission, Dr. Luigi Gallo, this mission is a unique opportunity for Canada. ASTRO-H will mark the first time Canada is part of an X-ray astronomy mission that will explore the unseen Universe in unprecedented detail. Because of the CSA's contribution to ASTRO-H, "Canadian scientists get a chance to go to the front of the line in getting time to use this unique astronomical telescope," said Gallo, Professor of Astronomy at St. Mary's University, Halifax, Nova Scotia. "There is no doubt that we will be making big discoveries when it opens for business in three years' time."

Dr. Gallo will be making good use of his time on board ASTRO-H to study the ebb and flow in the X-rays belched out by the supermassive black holes. These fluctuations in the amount of X-rays are thought to be directly correlated to the amount of material being gobbled up by the black hole: any nearby stars, gas and dust clouds get swept up from the plane of the surrounding inner region of the galaxy. As matter is sucked in by the gravitational pull of the black hole, it gets torn apart and superheated, shooting radiation back out in space, which ASTRO-H will detect.

Astronomers believe early on in a galaxy's life, supermassive black holes sweep up most of the surrounding material in the galactic core. The black hole eventually quiets down as it runs out of cosmic things to eat; these voracious cosmic predators then calm down, allowing their host to become a normal galaxy (much like our own Milky Way).

ASTRO-H will be able to look at the very closest region around these giant black holes where the most intense X-ray radiations are being emitted. Not only will this give astronomers a clearer picture of how these cosmic predators evolve, but also how galaxies like our own came to be.

Dr. Samar Safi-Harb of the University of Manitoba will be investigating with ASTRO-H the high-energy phenomena associated with the supernova explosions of massive stars that form some of the most exotic compact objects in the Universe: neutron stars. These phenomena include particle acceleration of cosmic rays to extremely high energies, the formation of the heavy elements essential for life, and the physics of the extreme associated with neutron stars and their associated high-energy nebulae. Such studies will be enabled by ASTRO-H's combination of its broadband X-ray spectroscopic coverage, hard X-ray focusing capability, and the unprecedented spectral resolution offered by its X-ray micro-calorimeter.

Dr. Brian McNamara, Professor of Physics and Astronomy and University Research Chair in Astrophysics at the University of Waterloo, will use ASTRO-H to study powerful outbursts from massive black holes located at the centres of galaxy clusters. The energy released by matter falling onto supermassive black holes weighing more than one billion suns is equivalent to the mechanical energy of ten billion supernova explosions. This energy drives outflows of chemically enriched gas hundreds of thousands of light years into space. ASTRO-H will measure the mass and speed of the outflowing gas, allowing McNamara's team to determine the rate at which supermassive black holes are growing. The measurements will also help unravel the nature of the mysterious extragalactic "radio jets," which are streams of energetic particles flowing from the centres of galaxies at nearly the speed of light. ASTRO-H will advance our understanding of energetic feedback from supermassive black holes, an area in which Dr. McNamara is a recognized expert.

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Black hole enthusiasts, galaxy cluster aficionados, and X-ray astronomers have much to be excited about. On Friday, Feb. 12, the Japan Aerospace Exploration Agency (JAXA) will be launching their sixth satellite dedicated to X-ray astronomy, ASTRO-H, from the Tanegashima Space Center in Kagoshima, Japan. The observatory carries a state-of-the-art instrument and two telescope mirrors built at NASA's Goddard Space Flight Center in Greenbelt, Maryland. The launch is scheduled at 3:45 a.m. EST.

ASTRO-H is expected to provide breakthroughs in a wide variety of high-energy phenomena in the cosmos, ranging from the superheated material on the brink of falling into a black hole to the evolution of vast galaxy clusters. It is equipped with four advanced instruments covering a broad energy range, from low-energy, or "soft," X-rays around 300 electron volts (eV) to soft gamma rays up to 600,000 eV. For comparison, the energy of visible light spans about 2 to 3 eV.

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This illustration shows the locations and energy ranges of ASTRO-H science instruments and their associated telescopes. One keV equals 1,000 electron volts, which is hundreds of times the energy of visible light.

Credits: JAXA/NASA's Goddard Space Flight Center

Download additional images from NASA Goddard's Scientific Visualization Studio

"We see X-rays from sources throughout the universe, wherever the particles in matter reach sufficiently high energies," said Robert Petre, chief of Goddard's X-ray Astrophysics Laboratory and the U.S. project scientist for ASTRO-H. "These energies arise in a variety of settings, including stellar explosions, extreme magnetic fields, or strong gravity, and X-rays let us probe aspects of these phenomena that are inaccessible by instruments observing at other wavelengths."

ASTRO-H is capable of observing X-ray sources, like galaxy clusters and neutron stars, more than 10 times fainter than its predecessor, Suzaku, which operated from 2005 to 2015. To achieve this, ASTRO-H uses four co-aligned focusing X-ray telescopes and a suite of cutting-edge instruments that provide simultaneous coverage across the observatory's entire energy range.

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