A whiz constitute US 708 has been spot leaving our galaxy at 4.3 million kilometre an hour ( 2.7 million miles per hour ) , the fastest exit speed ever observed . US 708 ’s rush has been attributed to a supernova go off nearby , shedding light on how one such type of supernova occurs .
star move fast enough to escape a galaxy ’s soberness have been note often enough to be named hypervelocity stars ( HVSs ) . Last year , an entire cluster was found to have beenexpelled by the supergiant galaxy M87 . However , US 708 is distinctive both for the speeding at which it is move and for being the only HVS known that is a succinct He star .
Now , these unexampled measurements published inSciencecast doubtfulness on the previously favored possibility for the origins of HVSs .
“ concord to the widely accepted theory for the speedup of hypervelocity ace , a close double star is interrupt by the supermassive black hole ( SMBH ) in the center of our Galaxy , and one part is ejected as a HVS , ” the writer observe . They concord this theory fit well with many HVSs , most of whichare youngmain sequence stars .
However , US 708 does n’t fit so well . It is believed star topology require very closelipped fellow stars to evolve into the red-hot subdwarf form of US 708 . Although it is theoretically potential for such a close binary program to have an encounter with more massive target that send one of the star off at great focal ratio while leave the other behind , it is very improbable .
On the other hand , the alternative hypothesis to explain HVSs — where the speedup is a product of the shockwave from a nearby supernova — match very well with a lost binary comrade . If the supernova in enquiry was Type Ia , which is thought to occur in close binary systems where gun arestripped from a donor star onto a white nanus , the slice come together very well .
By valuate US 708 ’s movement and tracing its path back , Dr. Stephan Geier of the European Southern Observatory and co - author calculated that it belike cut across the galactic disk around 14 million years ago and almost certainly did not do from the center of the galax . They suggest that it was once couple with a carbon - oxygen ashen dwarf slightly more monumental than the sun .
Credit : Geier et al . Simulations of where US 708 may have cross the astronomical plane . Black dot is the astronomic center , wizard is the sun , trigon is the US 708 ’s current attitude .
The two star are thought to have had an orbital point of around 10 moment , which is amazing to non - astronomers , but logical with the Helium star / white dwarf binary SDSS J065133 + 284423 ’s geological period of 12 moment . Such a close association with a larger star would cause a hot subdwarf to spin very fast . Geier ’s team measured US 708 ’s twisting at an impressive 115km / s , much faster than similar star that never had companions , but a quarter of the speed their modeling predicted . The difference may be explained through the transfer of angulate impulse to the former fellow traveler star before the explosion .
The author take down that disgraceful hole slingshots stay the more potential explanation for most HVSs , but declare oneself US 708 could tell us a lot about Ia supernovae .
