BUL­LETIN

The com­pound could be an im­por­tant part of planet for­ma­tion

Sky at Night Magazine - - CONTENTS -

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

The grav­i­ta­tional wave is thought to have been spawned by a kilo­nova, the ex­plo­sive col­li­sion of a pair of neu­tron stars

The or­gana­halo­gen methyl chlo­ride (in­set) was de­tected around the in­fant stars of IRAS 16293-2422, within the Rho Ophi­uchi cloud com­plex

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