By James Pero For Dailymail.com
Published: 23:06 BST, 1 April 2019 | Updated: 23:08 BST, 1 April 2019
Dark matter is the most mysterious and prolific substance known to humans, accounting for a major portion of all matter in the universe.
That is, except for in two outlier subjects recently identified by researchers who say a dark matter-less galaxy found last year now officially has a companion.
The findings, published by Yale researchers, build upon research made public last year that for the first time showed evidence of a galaxy devoid of most, if not all, of the dark matter characterized in every other known galaxy across the universe.
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A previously discovered dark matter-less galaxy caused a wave throughout the astronomical community after being announced last year.
The team published the latest findings in The Astrophysical Journal Letters.
'We thought that every galaxy had dark matter and that dark matter is how a galaxy begins,' said Pieter van Dokkum of Yale University in a statement regarding the discovery last year.
'This invisible, mysterious substance is the most dominant aspect of any galaxy. So finding a galaxy without it is unexpected.
'It challenges the standard ideas of how we think galaxies work, and it shows that dark matter is real: it has its own separate existence apart from other components of galaxies...'
Similar to the first galaxy, a newly discovered dark matter-less twin, dubbed DF4, is also what researchers call an 'ultra-diffuse' galaxy, meaning they contain about 100 to 1000 times fewer stars than our own galaxy.
'The fact that we're seeing something that's just completely new is what's so fascinating,' said Professor of Astronomy at Harvard University, Shany Danieli, who first spotted the galaxy about two years ago.
'No one knew that such galaxies existed, and the best thing in the world for an astronomy student is to discover an object, whether it's a planet, a star, or a galaxy, that no one