New satellite to shed light on invisible dark matter

2015-12-17 11:06Xinhua Editor: Mo Hong'e
A Long March 2-D rocket carrying the Dark Matter Particle Explorer Satellite blasts off at the Jiuquan Satellite Launch Center in Jiuquan, northwest China's Gansu Province, Dec. 17, 2015.  (Photo: Xinhua/Jin Liwang)

China on Thursday sent into space the country's first space telescope in a fresh search for signals of dark matter, invisible material that scientists say makes up most of the universe's mass.

The Dark Matter Particle Explorer (DAMPE) Satellite, which has been given the moniker "Wukong" after the Monkey King from the Chinese classical fiction "Journey to the West," was launched at 8:12 a.m. Thursday on a Long March 2-D rocket from Jiuquan Satellite Launch Center.

It will enter a sun-synchronous orbit at a height of 500 kilometers to observe the direction, energy and electric charge of high-energy particles in space.

The satellite is designed to undertake a three-year space mission, but scientists hope it could last five.

They also hope the 1.9-tonne desk-sized satellite could help shine more light on the hypothetical mass during that short period.

Dark matter, which does not emit or reflect enough electromagnetic radiation to be observed directly, is one of the huge mysteries of modern science.

Theorized by scientists who could not understand missing mass and strangely bent light in faraway galaxies, dark matter has become widely accepted in the physics community even though its existence has never been concretely proven.

Scientists now believe that only around five percent of the total mass-energy of the known universe is made up of ordinary matter -- protons, neutrons, electrons -- whereas dark matter and dark energy make up the rest.

Exploration of dark matter could, therefore, give us a clearer idea about the past and future of galaxies and the universe, and will be revolutionary for the world of physics and space science, said Chang Jin, chief scientist on the project.


Hints of the true nature of dark matter have already emerged from some previous observations, including those conducted by the Alpha Magnetic Spectrometer onboard the International Space Station and by the Large Hadron Collider (LHC) at the CERN physics research center near Geneva, Switzerland.

China also runs an underground dark matter lab in the southwest province of Sichuan, some 2,400 meters under the earth's surface.

So far, scientists have developed three investigative methods -- a particle accelerator that "creates" dark matter particles; special targets underground to see the traces left by colliding dark matter particles; and the calculation of dark matter particles' annihilation or decay that are in space, which help calculate details and space distribution.

DAMPE will support research using the third method, scientists are hoping the findings will help clarify previous observation results and lift the "invisible cloak" of dark matter.

"This is like tracking down the 'son' of dark matter -- if you cannot find the father, you go to the son and you could learn about at least some properties of his father," said Chang.

Wukong will scan space in all directions in the first two years and focus on sections where dark matter is most likely to be observed afterward.

More than 100 scientists will study the data. Initial findings will be published in the second half of 2016.

Chang said Wukong has the widest observation spectrum and highest energy resolution of any dark-matter probe in the world.

The new satellite's observation spectrum is approximately nine times wider than the Alpha Magnetic Spectrometer onboard the International Space Station, while its energy resolution is at least three times higher than its international peers, according to Chang.

However, he cautioned, there is no guaranteed success in the mission.

"We have not entirely figured out the physical properties of dark matter, so no one is one hundred percent sure that the satellite can find it," Chang said.

"As long as Wukong keeps working, it will open a new window for our search," he said, adding that the satellite could also serve as a cosmic ray telescope and be used to study the origin, transportation and acceleration of cosmic rays.

Chang, who is also vice director of the Purple Mountain Observatory in Nanjing, said it is hard to predict when dark matter could eventually be found and how to utilize its discovery.

"Only when we understand the nature of dark matter, will we know how it will change the future," he said.


Thursday's launch, the 221st mission by the Long March rocket series, is a new step in China's multi-billion-dollar space endeavors, which have become a source of surging national pride and a marker of China's global stature and technical expertise.

The country sent its first astronaut into space in 2003, the third nation after Russia and the United States. to achieve manned space travel independently. In 2008, astronauts aboard Shenzhou-7 made China's first space walk. There are plans for a permanent space station, expected around 2022.

"China is already a major player in space. To seek further progress in the field, however, we have to launch more space science satellites," said Wu Ji, director of National Space Science Center under the Chinese Academy of Sciences (CAS).

China's first satellite was launched into space 45 years ago, and since a number of communication, remote sensing and navigation satellites have followed. Yet, it has very few satellites that are solely designed for scientific research.

Hopefully, this looks set to change.

According to Ai Changchun, Wukong chief engineer, Thursday's mission is the first large-scale space science project in the world led by Chinese scientists.

Wukong is first of four scientific satellites under a Chinese Academy of Sciences (CAS) space program.

The other three satellites -- one for quantum science experiments, another for microgravity research and space life science, and a hard X-ray telescope which will observe black holes, neutron stars and other phenomena -- will be launched next year.

Wu said development of the other three satellites is going well.

"Space science is an inseparable part of the innovation-driven development of China," said Wu.

Current investment in fundamental research only accounts for about five percent of overall research investment. Whereas in the United States and Germany, that figure is 40 percent and 28 percent.

"If you want to innovate, you must have knowledge of the sciences," Wu said.

"China [...] should not only be the user of space knowledge, we should also be the creator," he said.


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