Galaxy believed to be devoid of dark matter could prove the mysterious material does not exist
A galaxy believed to be devoid of dark matter could finally prove the mysterious material does not exist, a controversial new study claims.
Researchers in March claimed the galaxy NGC1052-DF2 was the first ever found to have no dark matter - but a new paper argues the original researchers were wrong.
Based on what they say are older readings of the celestial object, the latest paper suggests the galaxy believed to be devoid of matter is full of the mysterious material, much like any other galaxy.
Paradoxically, researchers say this finding could prove the material does not exist since it revives a leading alternative theory of the universe which claims dark matter is a nonentity.
Scientists behind the original March study have hit back at the new findings, arguing that the authors of the new paper took inaccurate readings.
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A galaxy believed to be devoid of dark matter could finally prove the mysterious material does not exist. Researchers in March claimed the galaxy NGC1052-DF2 (pictured) was the first ever found to have no dark matter - but a new paper argues they were wrong
Dark matter is so-called because it cannot be seen.
It is the mysterious and invisible skeleton of the universe that scientists speculate makes up about 27 per cent of the mass of the cosmos.
Astronomers use the substance to explain why there appears to be more mass in the universe than Einstein's theory of relativity had predicted.
Dark matter is supposed to be everywhere, so when researchers found a galaxy seemingly devoid of the substance in March, they were baffled.
Scientists studying NGC1052-DF2, 'DF2' for short, found almost all of its mass could be accounted for by visible stars, gas and dust - the expected 'invisible' mass consisting of dark matter was not there.
The finding promised to change our understanding of how galaxies form and quashed a leading alternative theory to dark matter.
Researchers in March identified 10 globular clusters, each containing a compact group of stars that orbit the galactic core (left). A closer look at one of these bright clusters is shown on right. A new paper claims the Yale team made inaccurate measurements
Now, a second paper published in the pre-print journal arXiv claims this galaxy acts as if it contains dark matter after all.
The March study made its finding by studying the movement of star clusters through DF2 - a thin, diffuse galaxy about 65 million light years from Earth.
Readings from the Dragonfly Telephoto Array telescope in New Mexico, which were published in Nature, appeared to show that the stars moved slower than physicists would predict had the galaxy contained dark matter.
But the new study, from researchers at the Instituto de Astrofisica de Canarias in Tenerife, claims these readings were inaccurate.
WHAT IS NGC 1015-DF2 AND DOES IT CONTAIN DARK MATTER? NGC1052-DF2, or 'DF2' for short, is 65 million light years away and one of a newly recognised family of 'ultra-diffuse' galaxies. They are thought of as 'ghostly' because they contain so few stars, making them very faint despite their large size. DF2 is about the same size as the Milky Way but contains 200 times fewer stars, as well as almost no dark matter. The weird object was first spotted by astronomers using the Dragonfly Telephoto Array, a special 48-lens telescope in New Mexico, US, designed to find ultra-diffuse galaxies. Follow-up observations revealed a number of unusual characteristics. Unlike typical spiral galaxies, DF2 had no dense central region, and lacked spiral arms or a disc. And unlike elliptical galaxies it had no central black hole. But the oddest thing about DF2 was revealed when astronomers estimated the galaxy's mass by measuring the speed at which clusters of stars were orbiting its centre. Slower velocity equated to greater mass. They found that almost all of DF2's mass could be accounted for by visible stars, gas and dust. The expected 'invisible' mass consisting of dark matter was not there. 'If there is any dark matter at all, it's very little,' said Prof van Dokkum. 'The stars in the galaxy can account for all of the mass, and there doesn't seem to be any room for dark matter.' Describing DF2 as 'astonishing', he said the galaxy was so sparse it was possible to see right through it.
They suggest the galaxy was first discovered in 1976 and had previously been referred to by three names: KKSG04, PGC3097693 and [KKS2000]04.
Researchers used the Dragonfly Telephoto Array telescope (pictured) in New Mexico to take readings of NGC1052-DF2
Using decades-worth of readings of these objects, the new paper says the Nature team measured DF2 to be much further away from Earth than is true.
The mass of galaxies is calculated by the objects' brightness and distance, and as a result of the Nature team's mismeasurement, DF2 is much less massive than thought.
This means the speed its star clusters were travelling were quite normal for the lightweight galaxy, researchers said, meaning DF2 does have dark matter.
However, Yale astrophysicist Professor Pieter van Dokkum, lead author of the March Nature paper, said the new arXiv analysis is mistaken.
'The key distance measurement comes from the Hubble Space Telescope data, and it looks like they misinterpreted it,' he told Live Science.
'The argument is a bit technical, but essentially, they mistook pixel variations for individual stars.
'If NGC1052-DF2 were as close as they claim, then the galaxy would be resolved into a sea of individual stars,' but it's not, he added.
WHAT IS DARK MATTER? Dark matter is a hypothetical substance said to make up roughly 27 per cent of the universe. The enigmatic material is invisible because it does not reflect light, and has never been directly observed by scientists. Astronomers know it to be out there because of its gravitational effects on known matter. The European Space Agency says: 'Shine a torch in a completely dark room, and you will see only what the torch illuminates. Dark matter is a hypothetical substance said to make up roughly 27 per cent of the universe. It is thought to be the gravitational 'glue' that holds the galaxies together (artist's impression) 'That does not mean that the room around you does not exist. 'Similarly we know dark matter exists but have never observed it directly.' The material is thought to be the gravitational 'glue' that holds the galaxies together. Just five per cent the observable universe consists of known matter such as atoms and subatomic particles.
Dr Ignacio Trujillo, lead author of the controversial new arXiv paper, said he and his colleagues stand by their estimates.
'Our paper not only uses a criteria for estimating the distance to the galaxy, but up to five different (and completely independent) methods, and all of them converge to the same number,' he said.
If Dr Trujillo and his team are correct, the new study could prove once and for all that dark matter does not exist.
A preeminent alternative theory to dark matter suggests that the universe's 'extra' mass is caused by gravity behaving slightly differently to Einstein's predictions.
There are many mysteries swirling about the nature of dark matter – but, one thing that remains widely accepted is that it is a fundamental component of galaxies - including the Milky Way (file photo) - making up far more of their substance than normal matter
Called 'Modified Newtonian Dynamics', the theory puts forward a number of tweaks to the fundamental laws of physics that eliminate the need for dark matter.
For these new rules to be real, they would have to be consistent throughout the universe, meaning DF2's strange star cluster dynamics outlined in March all-but spelled an end for the theory.
The Arxiv paper, which is yet to undergo peer review, bizarrely revives the theory by 'proving' DF2 features dark matter.