It looks like a distant ring with three glittering gems, but the latest image from the Webb Space Telescope (JWST) is actually a view of a distant quasar lensed from a nearby elliptical galaxy. The telescope’s Mid-Infrared Instrument (MIRI) tracked the faint apparition while studying dark matter and its distribution in the universe.
We can see this eerie vision thanks to the gravitational lensing of a quasar. Such a lens creates one of nature’s great natural telescopes. It uses the gravitational effect of matter to warp space. All matter does this, but larger conglomerates do more. For example, a galaxy cluster and its aggregated stars, planets, gas clouds, black holes—and dark matter—distort space quite a bit. So does an individual galaxy.
When this happens, the path of light from more distant objects around (or through) the lens is also distorted. The lens magnifies the view of those distant objects between us and the mass of the lens. So, thanks to gravitational lensing, astronomers often get interesting views of objects that are otherwise too faint or distant for detailed study.
A lensed view of a distant quasar
The distant quasar RX J1131-1231, which JWST photographed for this view, lies about six billion light-years from Earth. Astronomers know that there is a supermassive black hole at the heart of the galaxy. It emits high-energy X-rays that have been captured by the Chandra X-ray Observatory and the XMM-Newton orbiting telescope. This eerie looking object has also been viewed by the Hubble Space Telescope.
These X-rays tell astronomers that something very energetic is happening in the galaxy – which is why it’s often called a quasar. The X-ray emission is produced by the superheated accretion disk and eventually bounces off the inner edge of the disk. Astronomers can pick up the spectrum of this reflected X-ray emission – but they must account for the fact that it is affected by the black hole’s strong gravity. The larger the spectrum change, the closer the inner edge of the disk lies to the black hole. In this case, the emissions come from a region that lies only three times the radius of the event horizon. This suggests that the black hole is spinning very, very fast – half the speed of light.
JWST’s mid-infrared observations of the lenticular quasar allow astronomers to probe the region around its heart. They should be able to find out details about the distribution of matter in the region, which should help them understand the distribution of dark matter there.
Mapping the history of the Black Hole
The central supermassive black hole at the heart of the quasar RX J1131-1231 has its own story. These X-ray emissions from its accretion disk provide clues to how fast this black hole grew over time and how it formed. There are several main theories about the growth of black holes. We know that stellar masses come from the death of supermassive stars. They explode like supernovae. What’s left collapses to form a black hole.
However, the supermassive ones in the hearts of galaxies probably form in one of two ways. They could come from the accumulation of material over long periods of time during collisions and mergers between galaxies. If this happens, the accreting black hole collects material in a stable disk. If it has a steady diet of new material from the disk, it should lead to a rapidly spinning black hole. On the other hand, if a black hole grows due to many small accretion episodes, its food would come from random directions and its rotation rate would be slower.
So what’s the story of the bright, supermassive monster at the heart of RX J1131-1231? All observations so far show a rapidly rotating black hole. This means that it probably grew through mergers and collisions. Further observations of its high-energy activity should help astronomers probe deeper into space and observe objects in earlier and earlier epochs of cosmic time. JWST’s contribution helps them use gravitational lensing to detect these things. At the same time, they will get to map the distribution of dark matter, which helps the universe create those natural scales.
For more information
Webb admires the Bejeweled ring
Distant Quasar RX J1131
RX J1131-1231: Chandra and XMM-Newton provide direct measurements of distant black hole rotation