Wed, Oct 18, 2017 page1

• Taiwan contributes to discovery of ‘kilonova’

  • By Lin Chia-nan / Staff reporter
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  The discovery of gravitational waves on Aug. 17 resulted from a merger of two neutron stars, a National Central University (NCU) researcher said yesterday while discussing the results of joint research by Taiwanese scientists and the US-based Global Relay of Observatories Watching Transients Happen (GROWTH).

  The discovery of gravitational waves with light, named GW170817, was made by the US-based Laser Interferometer Gravitational Wave Observatory (LIGO) and the Europe-based Virgo detector, which started a race among scientists to find the source.

  The next day, a team led by Ryan Foley at Las Campanas Observatory in Chile identified the gravitational waves’ source in the NGC 4993 galaxy about 130 million light years away.

  

  Members of the Global Relay of Observatories Watching Transients Happen team at National Central University’s Institute of Astronomy work in their laboratory in Taoyuan in an undated photograph.

  Photo courtesy of National Central University

  Taiwanese researchers made contributions by studying the formation of the galaxy as part of the GROWTH team of scientists from Taiwan, the US, Japan, Germany, the UK, Sweden, Israel and India.

  They agreed that the new gravitational waves are different from the four previous discoveries —GW150914, GW151226, GW170104 and GW170814, NCU Institute of Astronomy researcher Yu Po-chieh (俞伯傑) told a news conference in Taipei yesterday.

  The nature of the gravitational waves indicate that they did not result from a merger of black holes or a clash between a black hole and a neutron star, but a merger of neutron stars, Yu said.

  

  An undated image shows galaxy NGC 4993 in the constellation Hydra, marked with the position of gravitational-wave event GW170817 emitted by a kilonova resulting from the merger of two neutron stars.

  Photo courtesy of National Central University

  “Researchers worldwide arrived at the same conclusion,” he said. “This is the first time that humankind has found that some gravitational waves can emit light.”

  Their findings were documented in a paper titled Illuminating Gravitational Waves: A Concordant Picture of Photons from a Neutron Star Merger, which has been published in the journal Science.

  Studying the collision of neutron stars can help scientists explore the origin of gold and other heavier elements in the cosmos, Yu said.

  As the merger of neutron stars produced a “kilonova” brighter than any other previously discovered stars, scientists around the world are watching it for any changes, he said.

  NCU’s Lulin Observatory (鹿林) on the boundary of Chiayi and Nantou counties is one of the 18 observatories in the GROWTH program that is engaging in round-the-clock observation of the cosmic event.

  Given that its telescope has a 1m resolution similar to one in a Chilean observatory, Lulin Observatory could have been the first to identify the source had the weather permitted, NCU associate professor Jao Chao-tsung (饒兆聰) said.

  The discovery of the optical counterpart of the gravitational waves should be accredited to the this year’s Nobel Prize in Physics laureates — Rainer Weiss, Barry Barish and Kip Thorne — who made contributions to the LIGO detector and observation of gravitational waves, Yu said.
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