Slim and beautiful: Galaxies too good to be true

 作者:熊虬划     |      日期:2019-03-14 01:04:03
By Vanessa Thomas and Richard Webb Pristine spiral galaxies are some of the most stunning sights in the night sky – so perfect that they have cosmologists scratching their heads THEY are the pin-ups of the cosmos – elegant, luminous spiral swirls that whisper to us the word “galaxy”. It’s how we think our Milky Way would appear if we could look down on it from above. Other captivating examples are not far away: our nearest large galactic neighbour, Andromeda, for instance, or the evocatively named Pinwheel galaxy. Easy as these spiral beauties are on the eye, for cosmologists they are becoming something of a headache. As we survey the spiral galaxies around us more closely, nagging doubts are creeping in that some of the largest, most luminous examples in fact look rather too perfect. What’s more, many of them seem to be in entirely the wrong place. There could still be a simple explanation, in some unanticipated twist in the tale of how these galaxies formed. But as the evidence stacks up it is beginning to look like our favoured theory of the cosmos is due for a makeover – and with it our conception of the unseen “dark matter” that controls it. In a cosmos like ours that consists largely of very little, galaxies are a not-so-minor detail that demands explanation. Any working theory of the universe’s development must unravel how these huge agglomerations of matter formed from the featureless, homogeneous universe created in the big bang some 13.7 billion years ago. Over time a convincing story has evolved,