Chinese satellite may shed new light on dark matter
Print Edition
SCIENTISTS have detected cosmic ray energy readings that could bring them closer to proving the existence of dark matter, a mysterious substance believed to comprise a quarter of our universe, a study said yesterday.
Likely made up of unknown sub-atomic material, dark matter is invisible to telescopes and can be perceived only through its gravitational pull on other objects in the universe.
China’s first astronomical satellite, launched two years ago, detected 1.5 million cosmic ray electrons and protons, the study said, and unprecedented measurements found curiously low-energy rays.
The team of researchers from China, Switzerland and Italy, who published their first results in the journal Nature, said the data may cast light on “the annihilation or decay of particle dark matter.”
“This new unseen phenomena can bring breakthroughs,” Bai Chunli, president of the Chinese Academy of Sciences, said at a briefing yesterday.
“After collecting more data, if we can identify it is dark matter for sure then that is very significant. And if not, it is even more significant because they would be fresh new particles that no one had predicted before,” Bai added, to applause from fellow scientists.
“We should remember this day in the history of human scientific development,” Bai said, “when Chinese scientists are no longer learners, successors and onlookers in major natural science discoveries, but, instead, they are gradually entering the center of the scientific stage.
“In the future, the CAS will continue to support Chinese scientists at the frontiers of basic science. We plan to develop and launch more science satellites to study fields such as gravitational waves, the origin of the universe, dark matter, solar activities and the global water cycle.”
The Dark Matter Particle Explorer (DAMPE) was launched from the Jiuquan Satellite Launch Center in the Gobi Desert in December 2015, after nearly 20 years in development.
Its designers say it is superior to its US counterpart, the AMS-02 (Alpha Magnetic Spectrometer) that NASA installed on the International Space Station in 2011.
“DAMPE has opened a new window for observing the high-energy universe, unveiling new physical phenomena beyond our current understanding,” said Chang Jin, chief scientist of DAMPE and vice director of CAS’s Purple Mountain Observatory.
Proving its existence
“Our cosmic ray detection range is 10 times that of AMS-02 and three times as accurate,” Chang said.
“Proving the existence of dark matter takes a lot of time. Now we have worked out the most precise spectrum, but we are not 100 percent sure that this can lead us to the location of dark matter.”
Precise measurement of cosmic rays, especially at the very high energy range, is important for scientists to look for traces of dark matter annihilation or decay, as well as to understand the universe’s most energetic astrophysical phenomena, such as pulsars, active galaxy nuclei and supernova explosions.
“Our data may inspire some new ideas in particle physics and astrophysics,” said Chang.
Dark matter, which cannot be seen or touched, passes right through us as if we don’t exist. The ghost-like material is one of the great mysteries of science.
Scientists calculate that normal matter, such as galaxies, stars, trees, rocks and atoms, accounts for only about 5 percent of the universe. About 26.8 percent of the universe is dark matter and 68.3 percent dark energy.
Exploration of dark matter will be revolutionary for physics and space science. Any discovery in this area could be as significant as the law of gravity, the theory of relativity or quantum mechanics.
Asked why exploring dark matter matters, Chang said: “It is not important to you, but it’s important to me, and it will be important to your offspring. When scientists established quantum mechanics in the early 1900s, nobody expected it would be useful in daily life. But now quantum mechanics is a pillar of modern physics and everything is related to it.
“I believe exploring dark matter will also bring breakthroughs in technological development. Only when we understand the nature of dark matter, can we find how it will change the future. But the development of fundamental physics will definitely boost science and technology,” Chang said.
DAMPE is expected to record a total of more than 10 billion cosmic ray events over its useful life of around three more years.
Currently, scientists mainly use three approaches to detect dark matter — underground direct detection, collider experiments and space indirect exploration. The space exploration approach is based on speculation that detectable particles such as electrons, positrons and photons can be created during the annihilation or decay of dark matter.
China invests hundreds of billions of dollars in scientific research each year, under a five-year plan for 2016 to 2020 to lift its technological research capabilities into the world’s top 15.
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