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February 22, 2016

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Strange galaxy found to have huge tail of gas

Feb. 22, 2016
Courtesy of the International Centre 
for Radio Astronomy Research
and World Science staff

As­tro­no­mers say dis­cov­ered what they de­scribe as a spec­tac­u­lar tail of gas com­ing from a near­by spi­ral gal­axy. The plume con­sists hy­dro­gen gas—the ma­te­ri­al new stars are made of—and is five times long­er than the gal­axy it­self.

It took a super-sensitive cam­era to no­tice it, sci­en­tists said, with some pre­dict­ing that this gal­axy might be just the first of many to turn out to have such a fea­ture.

The larger, foreground gal­axy is NGC 4569 of the Vir­go clus­ter. The red fil­a­ments at the right of the gal­axy show the hy­dro­gen gas that has been re­moved. The tail rep­re­sents about 95 per cent of the gas res­er­voir the gal­axy needs to feed the for­ma­tion of new stars, sci­en­tists say. (Cred­it: CFHT/Coelum)


Re­search­ers no­ticed long ago that the gal­axy, known as NGC 4569, con­tained less gas than ex­pected, ex­plained as­t­ro­phys­i­cist and re­search team mem­ber Lu­ca Cor­tese. But they could­n’t see where it had gone. 

“Now, with these ob­serva­t­ions, we’ve seen a huge amount of gas that cre­ates a stream trail­ing be­hind the gal­axy for the first time.”

The amount of ma­te­ri­al in the stream matches the amount “miss­ing” from the gal­axy, based on its mass, said Cor­tese, who is with the In­terna­t­ional Cen­tre for Ra­di­o As­tron­o­my Re­search based in Perth, West­ern Aus­tral­ia.

The find­ing, by a team of sci­en­tists led by Al­es­san­dro Boselli at the Lab­o­ra­toire d’As­tro phy­sique de Mar­seille in France, is pub­lished in the jour­nal As­tron­o­my & As­t­ro­phys­ics.

The tail is mea­sured at more than 300,000 light years wide. A light-year is the dis­tance light trav­els in a year.

NGC 4569 sits in the Vir­go clus­ter, a group of ga­lax­ies 55 mil­lion light years from our own Milky Way. The gal­axy moves through that clus­ter at about 1,200 km (a­bout 700 miles) a sec­ond, and that move­ment is what’s caus­ing the gas to be stripped from the gal­axy, Cor­tese said.

“Big clus­ters of ga­lax­ies trap a lot of hot gas,” he ex­plained. “So when a gal­axy en­ters the clus­ter it feels the pres­sure of all the gas, like when you feel the wind on your face, and that pres­sure is able to strip mat­ter away from the gal­axy.”

The dis­cov­ery was made when the re­search team used what they de­scribed as a super-sensitive cam­era on the Can­a­da France Ha­waii Tel­e­scope to ob­serve NGC 4569 for long­er than ev­er be­fore.

Cor­tese said it could be the first of many ga­lax­ies found to have long tails of gas ex­tend­ing from them. “It’s pret­ty ex­cit­ing be­cause this was just a pi­lot and we only tar­geted the bright­est spir­al gal­axy in the Vir­go clus­ter,” he said. “We were amazed by what we got… this is really prom­is­ing be­cause it means it’s very likely we’ll find si­m­i­lar fea­tures in many oth­er gal­axy clus­ters.”


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Astronomers have discovered a spectacular tail of gas more than 300,000 light years across coming from a nearby galaxy. The plume consists hydrogen gas—the material new stars are made of—and is five times longer than the galaxy itself. It took a super-sensitive camera to notice it, scientists said, with some predicting that this galaxy might be just the first of many to turn out to have such a feature. Researchers noticed long ago that the galaxy, known as NGC 4569, contained less gas than expected, explained astrophysicist and research team member Luca Cortese. But they couldn’t see where it had gone. “Now, with these observations, we’ve seen a huge amount of gas that creates a stream trailing behind the galaxy for the first time.” The amount of material in the stream matches the amount “missing” from the galaxy, based on its mass, said Cortese, who is with the International Centre for Radio Astronomy Research based in Perth, Western Australia. The finding, by a team of scientists led by Alessandro Boselli at the Laboratoire d’Astrophysique de Marseille in France, is published in the journal Astronomy & Astrophysics. NGC 4569 sits in the Virgo cluster, a group of galaxies 55 million light years from our own Milky Way. The galaxy moves through that cluster at about 1,200 km (about 700 miles) a second, and that movement is what’s causing the gas to be stripped from the galaxy, Cortese said. “Big clusters of galaxies trap a lot of hot gas,” he explained. “So when a galaxy enters the cluster it feels the pressure of all the gas, like when you feel the wind on your face, and that pressure is able to strip matter away from the galaxy.” The discovery was made when the research team used what they described as a super-sensitive camera on the Canada France Hawaii Telescope to observe NGC 4569 for longer than ever before. Cortese said it could be the first of many galaxies found to have long tails of gas extending from them. “It’s pretty exciting because this was just a pilot and we only targeted the brightest spiral galaxy in the Virgo cluster,” he said. “We were amazed by what we got… this is really promising because it means it’s very likely we’ll find similar features in many other galaxy clusters.”