Revealed! Dark side of the universe

Space scientists have got their first decent glimpse of the dark side of the universe in a major scientific breakthrough revealed today. The Hubble space telescope photographed a ghostly ring revealing the presence of the elusive and invisible dark matter that astronomers have been hunting for decades.

Hubble image of the ghostly ringIt was produced during an enormous head-on collison between two vast clusters of galaxies five billion light years away from Earth in the constellation of Pisces.

An international team of astronomers pointed Hubble at the celestial crash site, labelled ZwCl0024+1652. The orbiting observatory took a stunning image of the colliding galaxies, using Hubble’s Advanced Camera for Surveys which unfortunately stopped working in January. Since then, astronomers analysing the image traced out the ghostly blue ring, which is 2.6 million light-years wide.

They say it is like the ripple from a stone thrown into a pond – but at first they thought it was a blemish in Hubble’s photo. James Jee, of Johns Hopkins University, Baltimore, said: “I was annoyed when I saw the ring because I thought it was an artifact. I couldn’t believe my result. But the more I tried to remove the ring, the more it showed up. It took more than a year to convince myself that the ring was real.”

He added: “This is the first time we have detected dark matter as having a unique structure that is different from the gas and galaxies in the cluster.”

Dark matter is usually completely invisible because it does not emit light or reflect it. But the ring revealed itself by distorting around it the light from clusters of galaxies lying much further away. This is another form of gravitational lensing that Hubble has recorded in previous images of galactic clusters.

Astronomers reported indirect evidence of the existence of dark matter last year by studying another cluster of galaxies using Hubble and other telescopes and also by observing dwarf galaxies from the European Southern Observatory in Chile. And Hubble has even mapped out how it may be spread in the universe.

Previously astronomers knew dark matter must exist because galaxies could be seen to be much “heavier” and have a more powerful gravitational pull than was possible for the total contents of stars and other visible objects inside them.

It is a vital component of the cosmos. Astronomers estimate that 22 per cent of the universe is made up of dark matter and that stars and other visible material forms only four per cent!

They are still searching for another constituent, the invisible, so-called dark energy that astonishingly is predicted to make up around three-quarters of the universe. The Hubble discovery will be reported next month in the Astrophysical Journal.

Photo: Nasa, ESA, M.J. Jee and H. Ford (Johns Hopkins University)

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Paul Sutherland

Paul Sutherland

I have been a professional journalist for nearly 40 years. I write regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy. I have also authored three books on astronomy and contributed to others.
Paul Sutherland

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Paul Sutherland

I have been a professional journalist for nearly 40 years. I write regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy. I have also authored three books on astronomy and contributed to others.

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