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Our science editor celebrates the Hubble Space Telescope's 25th Anniversary

The Crab Nebula

Image credit ESO (European Southern Observatory)



Friday 24th April 2015 marked the 25th anniversary of the launch of the Hubble Space Telescope (HST), Sarah Barnett celebrates its amazing contribution to science…


In 1990, Hubble was launched from the Kennedy Space Center in Florida, on board the Discovery space shuttle. It suffered some teething trouble – the primary mirror had a flaw, it had been ground flat 2.2 microns (about a 50th the width of a human hair) too much; as a result, its images were no better than if the telescope had been on the Earth’s surface. However, this problem was overcome when astronauts installed new instruments and upgraded existing ones in 1993. Hubble could now reach its full potential. With no interference from light, air pollution and atmosphere, Hubble really opened our eyes to the universe, by being able to see so much more, much more clearly.


Hubble uses mirrors to gather light from the far reaches of the universe, which is then focused on the cameras and numerous instruments. These can capture light at many different wavelengths so we can ‘see’ and study a huge range of astronomical objects and data.


Thanks to Hubble, we not only have a stunning gallery of photos of the universe in all its splendour but scientists have really expanded their knowledge in the fields of astronomy and cosmology. Observations have revealed numerous extra-solar planets in our galaxy, in our quest for finding a chance of alien life out there. Plus we’ve learnt more about how planets form from nebulae.


We have peered further back into the depths of space than ever before and learnt more about the early universe, calculated to be 13.8 billion years old. Looking far away also means looking backwards in time, and Hubble can view details of galaxies when they were much closer to the Big Bang, at a much higher resolution than earth-bound telescopes. This means that we now have a much better idea of the processes by which galaxies formed.


We have also discovered the mysteries of dark matter and dark energy and their prominence throughout the universe. It may sound like science fiction, but around 85 per cent of the universe’s mass is thought to be made up of dark matter, while most of actual ‘space’ is thought to be made up of dark energy, which drives the expansion of the universe. Dark matter is invisible and deduced by its gravitational effects. It does not emit or reflect light and passes through matter without friction. It’s the glue that holds galaxies together. It was thought until now (see story below) to only interact with gravity.


Click on the link to see some of the stunning photos taken by Hubble.



Is dark matter playing with itself in the cosmic playground?


Galaxy cluster Abell 3827

Credit: ESO/R. Massey


Only last month, astronomers observed what they thought were the first potential signs of dark matter interacting with a force other than gravity. An international team of scientists, led by researchers at Durham University, made the discovery using the Hubble Space Telescope, through which they viewed the simultaneous collision of four distant galaxies at the centre of a galaxy cluster 1.3 billion light years away from Earth. They observed dark matter slowing down after interacting with other dark matter, so it was effectively interacting with itself.


Such a shift in alignment is predicted during collisions if dark matter interacts, even very slightly, with forces other than gravity. Computer simulations show that the extra friction from the collision would make the dark matter slow down, and eventually lag behind.


Scientists believe that all galaxies exist inside clumps of dark matter. In the latest study, the researchers were able to 'see' the dark matter clump because of the distorting/bending effect its mass has on the light from background galaxies - a phenomenon called 'gravitational lensing'. Using the Hubble Space Telescope the team was able to see this effect in detail and interpret it.


Lead author Dr Richard Massey, a Royal Society Research Fellow in Durham University’s Institute for Computational Cosmology says: "We used to think that dark matter sits around, minding its own business. But if it slowed down during this collision, this could be the first dynamical evidence that dark matter notices the world around it. Dark matter may not be completely 'dark' after all."


Dr Massey believes this measurement of offset dark matter is a concrete example of Hubble's value. “My colleagues first spotted that something funny was happening using a telescope atop a mountain in Chile,” he told Impolite Science. “However, the image was blurred, and they didn't have enough resolution to figure out what was happening. We got together to take images on HST, and – literally - everything became clear.


“Hubble has been absolutely vital for our studies. We can't see dark matter directly - we have to look at its effect on light rays from galaxies (much further) behind the dark matter. These incredibly distant galaxies are half-way across the Universe. They are tiny and faint. We simply can't see far enough from the ground, through the swirling, turbulent soup that is the Earth's atmosphere. The light is bounced around, and the image is blurred out. That's why stars twinkle - it may be romantic, but it screws up astronomy!”


In March, Dr Massey and colleagues published observations showing that dark matter interacted very little during 72 collisions between galaxy clusters (each containing up to 1,000 galaxies). However, the more recent study concentrated on just four galaxies, believed to be colliding at a much slower pace, possibly allowing a small frictional force to build up over time. More investigations will be needed into other potential effects that could produce a lag between the dark matter and the galaxy it hosts. Similar observations of more galaxies and computer simulations of galaxy collisions are under way to confirm the interpretation.


Dr Massey certainly hopes to be employing Hubble as he furthers his research on dark matter, “But everyone wants to use Hubble, so there's fierce competition for its time,” he points out. It’s also important to take into account that Hubble has a tiny field of view – “It is like a camera with a super-long zoom lens, so it can miss the big picture,” he adds.


In order to see more of that big picture, Dr Massey and his team – in collaboration with University of Toronto and NASA’s Jet Propulsion Lab – are building a new telescope on a balloon. “This gets above 99 per cent of the atmosphere, but for 1 per cent the cost of a satellite, which means we can build our own,” says Dr Massey, “And we're fitting it with a wide-angle lens.”
The Balloon Imaging Telescope (BIT) will have its first test flight from Canada this September.


Story sources


This article includes information based on a Durham University press release.


R. Massey et al., "The behaviour of dark matter associated with 4 bright cluster galaxies in the 10kpc core of Abell 3827", Monthly Notices of the Royal Astronomical Society, vol. 449, pp. 3393-3406, 2015, published by Oxford University Press.


The research was funded by the Royal Society, the Science and Technology Facilities Council and the Leverhulme Trust.

Sarah Barnett

About the Writer

Sarah is Impolite Conversation's science editor.


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