Black holes in space remain a mystery. One of their many secrets is why they get "angry". China will soon launch a space telescope in a bid to find out.
The Hard X-ray Modulation Telescope (HXMT), developed by Chinese scientists, will observe the black holes and neutron stars.
"Black holes will be the focus of our observation since they are very interesting, and can generate various types of radiation, including X-rays and high energy cosmic rays, as well as strong jets," says Zhang Shuangnan, the lead scientist of HXMT and director of the Key Laboratory of Particle Astrophysics at the Chinese Academy of Sciences (CAS).
Scientists are curious about what the black holes are doing. So far about 20 black holes have been found in our galaxy. "We hope our telescope can discover more black holes. We also hope to better observe the black holes already discovered," says Zhang.
A black hole is a region of spacetime showing such strong gravitational effects that nothing - not even particles and electromagnetic radiation such as light - can escape from inside it.
There are two kinds of these "space monsters": black holes of stellar mass and supermassive black holes. Black holes of stellar mass are thought to form when massive stars collapse at the end of their lifecycle.
After a black hole forms, it can continue to grow by absorbing mass from its surroundings. Some scientists believe that by absorbing gas and other stars and merging with other black holes supermassive black holes of millions of solar masses may form. There is general consensus that supermassive black holes exist in the centers of most galaxies.
Black holes are key to understanding the origins of time and nature of space and the ultimate destiny of the universe, scientists say.
Despite its invisible interior, the presence of a black hole can be inferred through its interaction with other matter and with electromagnetic radiation.
Matter that falls into a black hole can form an external accretion disk heated by friction, forming some of the brightest objects in the universe.
The first black hole was discovered in 1972. Named Cygnus X-1, it is about 6,000 light-years from Earth and is a strong X-ray source.
"If a black hole does nothing, it cannot be found. But if matter falls into a black hole, it is accelerated and heated during the process, emitting X-rays. Scientists may get to understand the characteristics of black holes through the X-rays," Zhang says.
Some times a black hole is calm, but other times it's very "bad tempered." When a black hole gets "angry", it generates very strong X-rays or gamma ray bursts or jet-flows, Zhang says.
Other countries have sent about a dozen X-ray satellites into orbit, but most are suitable for observing only relatively calm black holes. However, HXMT is suitable for observing angry black holes and neutron stars, Zhang explains.
"We will scan the galaxy to track the 'tempers' of black holes. We are still not clear why some black holes suddenly get angry, since we haven't observed them for long enough," says Zhang. "We plan to make a thorough survey of the black holes and neutron stars in the galaxy."
Xiong Shaolin, a young scientist at the Institute of High Energy Physics of CAS, says the research will push forward the development of astronomy. "We hope to take X-ray photos of black holes in the future."
