It looks like a distant ring with three glittering jewels, but the latest image from the Webb Space Telescope (JWST) is actually the view of a distant quasar surrounded by a nearby elliptical galaxy. The telescope’s Mid-Infrared Instrument (MIRI) spotted the faint apparition during a study of dark matter and its distribution in the universe.
This spooky vision is brought to us by the quasar’s gravitational lensing. Such lensing creates one of nature’s largest natural telescopes. It uses the gravitational effect of matter to warp space. All matter does this, but larger conglomerates do it even more. So, for example, a cluster of galaxies and its combined stars, planets, gas clouds, black holes—and dark matter—warp space quite a bit. So does an individual galaxy.
When that 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 lens mass. So, thanks to gravitational lensing, astronomers often get intriguing views of objects that are otherwise too faint or too distant to study in detail.
A lens view of a distant quasar
The distant quasar RX J1131-1231 that JWST imaged for this view lies about six billion light-years away. Astronomers know that a supermassive black hole lies at the heart of the galaxy. It is emitting high-energy X-rays, which have been detected by the Chandra X-ray Observatory and the XMM-Newton orbiting telescope. The Hubble Space Telescope has also observed this eerie-looking object.
Those X-rays tell astronomers that something very energetic is happening in the galaxy, which is why it is often called a quasar. The X-rays are produced by a superheated accretion disk and eventually bounce off the inner edge of the disk. Astronomers can take a spectrum of that reflected X-ray, but they have to take into account that it is being affected by the strong gravity of the black hole. The larger the change in the spectrum, the closer the inner edge of the disk is to the black hole. In this case, the emissions are coming from a region that is only three times the radius of the event horizon. That suggests that the black hole is spinning very, very fast, at half the speed of light.
JWST’s mid-infrared observation of the lens quasar will allow astronomers to probe the region around its heart. They should be able to tease out details of 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 quasar RX J1131-1231 has its own story to tell. That X-ray emission from its accretion disk gives clues to how quickly that black hole grew over time and how it formed. There are a few main theories about how black holes grow. We know that stellar-mass black holes come from the deaths of supermassive stars. They explode as supernovae. What’s left over collapses, creating the black hole.
The supermassive ones at the heart of galaxies, however, probably form in one of two ways. They can form by the accumulation of material over long periods of time during collisions and mergers between galaxies. When that happens, a growing black hole collects material into a stable disk. If it has a steady diet of new material from the disk, that should result in a rapidly spinning black hole. On the other hand, if the black hole grows through many small accretion episodes, its diet 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 spinning black hole. That means it likely grew through mergers and collisions. Further observations of its high-energy activity should help astronomers as they delve deeper into the universe and see objects at increasingly earlier epochs of cosmic time. JWST’s contribution will help them use gravitational lensing to spot these things. At the same time, they can map out the distribution of dark matter that helps the universe create those natural magnifying glasses.
For more information
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Distant Quasar RX J1131
RX J1131-1231: Chandra & XMM-Newton Provide Direct Measurement of Spin of Distant Black Holes