The Universe Through X-ray Eyes
Celebrating 20 years of the XMM-Newton X-ray telescope.
Twenty years ago this month, on 10 December 1999, Europe’s largest ever space telescope blasted off into space.
At a length of 10 metres, with solar panels that stretch 16 metres across, and weight of 3.8 tonnes, XMM-Newton has been a workhorse for high-energy astrophysics for an astonishing two decades. Only the Hubble Space Telescope and the Chandra X-ray telescope have lasted longer as an astronomy mission.
XMM-Newton orbits above the Earth, capturing the elusive and energetic X-rays from the universe that are blocked by our atmosphere. X-rays stream from the most violent, exotic objects in the universe, such as black holes, massive clusters of galaxies, and gamma-ray bursts. But X-rays also come from objects much closer to home, such as the aurora on the poles of Jupiter and stars such as our Sun.
XMM-Newton has revealed the X-ray universe to us in all its glory and phenomenal power, and in this blog, we celebrate its 20th birthday by focusing on some of its most exotic research – the nature of the black hole.
Mysterious Black Holes
XMM-Newton has particularly excelled at studying black holes and the extreme environments that around them.
Black holes are extremely dense, exotic objects that have so much gravity that nothing has enough energy to escape, not even light, if it passes too close. This makes black holes impossible to see directly; they are by definition invisible.
However, the area around a black hole can be incredibly energetic – a giant whirlpool of gas and dust that is falling inwards towards the black hole. This is known as an accretion disc and the gases can be so hot that they glow in X-rays.
So X-ray telescopes like XMM-Newton are perfect for spying on active black holes. Astronomers are particularly interested in supermassive black holes that dwell in the centres of almost all galaxies. Supermassive black holes are millions or even billions of times more massive than our Sun. We think these cosmic beasts play a big role in shaping the growth of the galaxy, but we don’t know exactly how.
One of the biggest discoveries of XMM-Newton was back in 2013 when it detected X-rays from iron atoms as they swirled around the supermassive black hole in the centre of a distant galaxy called NGC 1365. By carefully measuring the signals from these X-rays, scientists were able to measure how fast the black hole was rotating, and thus how it was twisting the fabric of space-time around it.
This spin of a black hole helps us know the history of the galaxy and whether it has formed alone or merged with other galaxies along the way.
More recently, in September 2019, XMM-Newton detected mysterious flashes of X-ray light from the central black hole in another galaxy, called GSN 069. Every nine hours, the X-rays from this galaxy would suddenly flare up to become a hundred times brighter. It’s thought that these flares are perhaps from a smaller black hole circling the more massive one, or perhaps from matter in the accretion disc swirling around.
The role of black holes on their host galaxies is still unclear, and the next decade for XMM-Newton, and other X-ray telescopes to come, is bound to be an exciting one.
From the scientists
Of course these black hole discoveries are just a small fraction of the work that XMM-Newton has made possible.
It’s estimated that thousands and thousands of science papers have been published thanks to XMM-Newton’s view of the X-ray universe.
As a fitting tribute to its legacy, we especially love this NASA video below which captures just how much XMM-Newton has meant to the careers of so many scientists.
Made in Leicester
Here in Leicester, we’re particularly attached to XMM-Newton.
Back in the 1990s the University of Leicester’s speciality in X-ray astronomy was put to the test as they were tasked with designing the CCD camera, called EPIC, for XMM-Newton. EPIC is one of just three scientific instruments on the telescope, and it’s responsible for capturing weak X-ray light from the universe on an extremely rapid scale – down to a thousandth of a second!
This CCD chip uses the same technology that’s ubiquitous in smartphone cameras today, and converts X-ray photons into electric signals in order to build up an image.
Amazingly, XMM-Newton is still going strong. It’s estimated that the most limiting factor to the mission is the fuel, which will run out around 2031. Scientists will review the mission in 2020, but in the meantime, ESA has just confirmed funding for a new X-ray telescope, Athena, planned to launch in the early 2030s
To find out more about the amazing discoveries of XMM-Newton, check out these links below:
About the author: Dr Tamela Maciel is the Space Communications Manager for the National Space Centre.