Dwarf satellites orbit galaxy in bizarre ‘ordered fashion’

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Scientists have discovered a group of satellites orbiting a distant galaxy in a ‘coordinated dance’.

Centaurus A, a massive elliptical galaxy 13 million light-years from Earth, is orbited by a narrow, synchronised disk of smaller, dwarf galaxies, researchers found.

It is the first time such an arrangement has been seen outside of the dwarf clusters that orbit the Milky Way and its neighbouring galaxy Andromeda. 

The discovery uproots standard models of the universe that assume the existence of dark matter, potentially revealing that the enigmatic substance does not exist.

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Scientists have discovered a group of satellites orbiting a distant galaxy in a ‘coordinated dance’. Centaurus A (pictured), a massive elliptical galaxy 13 million light-years from Earth, is orbited by a narrows disk of smaller, dwarf galaxies

The dwarf satellites analysed by the team orbit Centaurus A in a flat, disk-like plane, much like the planets of the solar system orbit the sun. 

The researchers, from the University of California, Irvine, and University of Basel, Switzerland, say leading models of space suggest this phenomenon should be an extremely rare occurrence.

Study coauthor and University of California researcher Dr Marcel Pawlowski told MailOnline: ‘According to cosmological simulations of the formation and evolution of galaxies in the universe, this behaviour is completely unexpected.

‘Our cosmological models rather predict that satellite galaxies are approximately randomly distributed around their host galaxies, and move in all kinds of directions. 

‘On average, we should find an arrangement similar to that around Centaurus A in one out of 200 to 1,000 galaxies only.’

The researchers analysed 16 satellite galaxies around Centaurus A.

They found that the satellite galaxies are not only arranged in a single plane, but the plane also rotates coherently: Satellite galaxies on one side of Centaurus A are approaching, while those on the other side are receding.

Study coauthor and University of Basel researcher Dr Oliver Muller told MailOnline that from Earth, we see the plane of these galaxies from the side, meaning they move ‘like the horses on a carousel if you stand in front of it.’

Of the 16 satellite galaxies for which scientists have data, 14 followed this organised movement.

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.

It cannot be seen directly with telescopes, but 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)

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.’

Dark matter is thought to be the gravitational ‘glue’ that holds the galaxies together.

Just five per cent the observable universe consists of known material such as atoms and subatomic particles.

Yet the probability of such a scenario, based on models of the universe that rely on the existence of dark matter, is less than 1 per cent based on simulations. 

Dark matter is a hypothetical substance said to make up roughly 27 per cent of the universe, but has never been directly observed by scientists.

Models of the universe that rely on the existence of dark matter suggest that smaller systems of stars should be more or less randomly scattered around their anchoring galaxies, and should move in all directions.

he dwarf satellites analysed by the team (black spots) orbit Centaurus A in a flat, disk-like plane (outlined in grey), much like the planets of the solar system orbit the sun

This image shows the relative spin of each satellite galaxy around Centaurus A (green spot)

The dwarf satellites analysed by the team (black spots in left image) orbit Centaurus A in a flat, disk-like plane (outlined in grey), much like the planets of the solar system orbit the sun. The right image shows the relative spin of each satellite galaxy around Centaurus A (green spot)

Study coauthor and University of Basel researcher Dr Oliver Muller told MailOnline: ‘We would expect to find the dwarfs randomly distributed around their host, and with different motions, like bees around a beehive.’

Yet Centaurus A is the third documented example, behind the Milky Way and Andromeda, not to follow this supposedly rare pattern. 

‘This means that we are missing something,’ Dr Pawlowski said.

‘Either the simulations lack some important ingredient, or the underlying model is wrong. This research may be seen as support for looking into alternative models.’





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