Although we ’ve known our galaxy is spiral - shaped for almost a century and a half , our idea of what it looks like as a whole often changes thanks to new discovery made possible by advances in experimental techniques .
It was consider for some prison term that the Milky Wayconsisted of four arms , pack with clouds of junk , gas and stars , which give forth outwards in an elegant twist from a cardinal area . But back in 2008 , Spitzer datum suggested that our Galax urceolata actually only has two arms , extending from a large central bar . Now , it seems that our portrait of the Milky Way has changed once again with the find of a new section of a spiral arm . And , invitingly , it could be an annexe of a distant weapon reveal a yoke of geezerhood ago , which would imply that one of the arms may wrap around our total galaxy .
This mighty arm , Scutum - Centaurus , air current outwardin a replication - clockwise direction from one end of the Milky Way ’s bar , snuff it between us and the astronomical nitty-gritty , and extends all the way to the other side of the galaxy . In 2011 , two astronomer from the Harvard - Smithsonian Center for Astrophysics , Thomas Dame and Patrick Thaddeus , spotted an extension of this arm , which placed it outside of our solar system . But now , newfangled datafrom the Purple Mountain Observatory , China , could suggest that the incredible arm is even longer than that .
For the study , uranologist Yan Sun and confrere used radio telescope information to look for interstellar gasoline clouds that mark helical branch . Rather than looking for the most common ingredient , hydrogen , which is hard to detect , they hunted radio undulation emitted by the 2d most abundant speck in interstellar space — carbon monoxide gas .
The researchers centre on clouds located between 46,000 and 67,000 scant - years from the galactic center ; for some context of use , our sun is around 27,000 light - years out . As described inThe Astrophysical Journal Letters , the scientists found a sum of 72 clouds , include 42 that were previously nameless , which line up along a 30,000 - scant - class - foresighted spiraling limb section . But that ’s not the most interesting part . If it turns out to be an extension service of the aloof segment describe back in 2011 , Scutum - Centaurus may actually make a full 360oturn around the Milky Way . regard something like that has never been observed in nearby spiral galaxies , it would be pretty unbelievable if the proposal holds up .
representative of the Milky Way , prove the possible extension of Scutum - Centaurus . Credit : Yan Sun / The Astrophysical Journal Letters / NASA / JPL - Caltech / SSC
“ It ’s rare,”said Dame . “ I reckon that you would have to look through dozens of face - on spiral coltsfoot images to find out out where you could win over yourself you could dog one limb 360 degrees round . ”
While the aspect is certainly exciting , there is still the possible action that this limb is not in reality part of Scutum - Centaurus at all , but instead a newly discovered lonely section . There exists a problematic40,000 - promiscuous - year - long gapbetween the start of the new weapon and the tail of the 2011 annexe . However , it should n’t take long for scientists to work out whether the weapon system do indeed join up , as they can startlooking for the beingness of molecular cloudswithin this region . If the segment do indeed get in touch , then we shack in one truly magnificent and unusual beetleweed .
[ ViaUniverse Today , Smithsonian , io9andThe Astrophysical Journal Letters ]
