BULLETIN
The compound could be an important part of planet formation
7KH ZDYH LV DOVR WKH UVW IURP FROOLGLQJ QHXWURQ VWDUV The first ever light from the source of a detected gravitational wave has been observed. The light, believed to have been created by two neutron stars crashing together, was picked up by the Laser Interferometry Gravitational-Wave Observatory (LIGO) on 17 August 2017, and located somewhere in a 30 square degree area of southern sky.
“We knew this wave was special as soon as it was announced,” says Stephen Smartt of Queen’s University Belfast, who led part of the follow up observations. “It lasted 60 seconds in the detectors, but the previous signals from black hole mergers lasted less than a second. Then two seconds after it finished we had a gamma-ray detection, which immediately alerted the LIGO team that this was something quite different.”
Earthbound and space-based telescopes began tracking down a visible counterpart to the event and soon saw a new source of light in a galaxy 130 million lightyears away, NGC 4993. “I’ve never seen anything like this before,” says Smartt. “It faded and turned red really quickly. This matched what some people thought we might see when it comes to what’s called a kilonova – the signature from a neutron star merger.”
The find is a new dawn for ‘multi-messenger astronomy’, which combines gravitational, electromagnetic and particle observations.
“The gravitational waves elucidate the strong gravity environment of the merger, invisible to telescopes,” says Gregg Hallinan of CalTech, who also conducted follow up observations. “The electromagnetic radiation tells us how the explosion evolves, forms the heavy elements, and then interacts with and enriches the surrounding interstellar medium. This complete story – both hearing [via gravitational waves] and seeing the violent universe – is the gift of multi-messenger astronomy.”
The organic chemical methyl chloride has been found in interstellar space for the first time. The discovery could help us understand how the ingredients of life came to Earth, but is a blow to exoplanet researchers hoping to use the chemical as a sign of life on other worlds.
Methyl chloride, also known as Freon-40, is an ‘organohalogen’ – a compound containing, carbon, hydrogen and one of the elements known as halogens, in this case chlorine. On Earth, the molecule is created by living organisms and industrial processes. Such chemicals, which are produced biologically but not geologically, could be used as biomarkers and help to find life remotely – if you find them in the atmosphere of an exoplanet, there could be living organisms creating them. Yet the discovery of Freon-40 in interstellar space suggests that the chemical can form without the intervention of biology.
The Atacama Large Millimeter/Submillimeter Array (ALMA) uncovered the chemical around an infant star, IRAS 16293-2422.
“Finding the organohalogen Freon-40 near these young, Sun-like stars was surprising,” says Edith Fayolle, a researcher with HarvardSmithsonian Centre for Astrophysics who led the study. “We simply didn’t predict its formation and were surprised to find it in such significant concentrations. It’s clear now that these molecules form readily in stellar nurseries, providing insights into the chemical evolution of planetary systems, including our own.”
The chemical was also found in the thin atmosphere of comet 67P/ChuryumovGerasimenko by the Rosetta orbiter. As comets are the leftovers of planetary formation, this suggests that Freon-40 is an integral part of the way planets grow.
“ALMA’s discovery of organohalogens in the interstellar medium also tells us something about the starting conditions for organic chemistry on planets,” says Karin Öberg, also from the Harvard-Smithsonian Centre for Astrophysics and co-author of the study. “Such chemistry is an important step toward the origins of life. Based on our discovery, organohalogens are likely to be a constituent of the so-called ‘primordial soup’, both on the young Earth and on nascent rocky exoplanets.”
Rather than being a sign of life, organohalogens could be a prerequisite to allowing it to evolve. www.eso.org