galactic contestation are fascinating ; they are unremarkably exciting and , more often than not , secernate us that we read very petty . Galaxy Dragonfly 2 ( DF2 ) could be the perfect case of this . When it was find out , it was announced that this might be agalaxy without disconsolate subject . Exciting and puzzling !
More of such galaxies have since been discovered and come after - up observations by a different group found DF2 and others tobe much closerthan the original measuring . found on this , they suggested that this mean they were not as big as they look and so they were n’t actually lacking sorry affair . But now another crook has happen . DF2 has been observed again by the original team and it turns out that it is not at the distance that was originally guess . It is even further away from us ! ( queue dramatic euphony )
The young observations were potential thanks to the keen centre of the Hubble Space Telescope . The new determination are reported inThe Astrophysical Journal Lettersand the distance of DF2 is now estimated to be 72 million light - years . The team judge that this galaxy contains 1/400thof the dark matter that it should have .
" We rifle out on a arm with our initial Hubble reflection of this galaxy in 2018 , " senior author Professor Pieter van Dokkum , from Yale University , say in astatement . " I think people were right to question it because it ’s such an unusual result . It would be nice if there were a simple account , like a wrong distance . But I imagine it ’s more fun and more interesting if it actually is a weird galaxy . "
The new distance was obtained by looking at senesce red giant stars . These object all strive the same bill brightness in their phylogeny , which allows researchers to use them to approximate the distance . They are a sort of lambent milepost .
" examine the brilliant flushed giants is a well - lay down distance index number for nearby galaxies , " head author Zili Shen , a alumnus investigator at Yale University , explicate .
obscure topic remains a hypothetical core . It was theorized to explain the peculiar gyration of galaxies , but its true nature is yet to be square up despite many different experiments . For this reason , some have proposed that there ’s no such matter as dark matter but that our laws of physic have to be rewritten . The existence of DF2 and like galaxies or else provide a clear indication that moody matter is a core .
" In our 2018 paper , we suggested that if you have a galax without dark affair , and other similar galaxies seem to have it , that stand for that dark matter is actually real and it exists , " van Dokkum said . " It ’s not a mirage . "
