July 14, 2024
1 Solar System Way, Planet Earth, USA
Discovery

Webb observes one of the best gravitationally lensed quasars ever discovered

It looks like a distant ring with three sparkling jewels, but the latest image from the JWST Webb Space Telescope is actually a view of a distant quasar reflected by a nearby elliptical galaxy. The telescope's Mid-Infrared Instrument (MIRI) observed the faint apparition during a study of dark matter and its distribution in the universe.

We can see this ghostly sight thanks to the quasar's gravitational lensing effect. This lensing effect creates one of nature's great natural telescopes. It uses the gravitational effect of matter to warp space. All matter does this, but larger conglomerations of it do it more. So, for example, a galaxy cluster and its collection of stars, planets, gas clouds, black holes, and dark matter warp space quite a bit. The same is true for an individual galaxy.

When this happens, the path of light from more distant objects around (or through) the lens is also warped. The lens magnifies the view of those distant objects between us and the lensing mass. Thus, thanks to the gravitational lensing effect, astronomers often obtain fascinating views of objects that would otherwise be too faint or far away for detailed study.

A lensed view of a distant quasar

The distant quasar RX J1131-1231 that JWST imaged for this picture is located about six billion light-years from Earth. Astronomers know there is a supermassive black hole at the heart of the galaxy. It emits high-energy X-rays, which were detected by the Chandra X-ray Observatory and the orbiting XMM-Newton telescope. The Hubble Space Telescope has also spotted this eerie-looking object.

This image shows the quasar RX J1131-1231 as imaged by NASA's Chandra X-ray Observatory and the Hubble Space Telescope. Credit: X-ray: NASA/CXC/Univ of Michigan/RCReis et al; Optics: NASA/STScI
This image shows the quasar RX J1131-1231 as imaged by NASA's Chandra X-ray Observatory and the Hubble Space Telescope. The JWST image is in the infrared. Credit: X-ray: NASA/CXC/Univ of Michigan/RCReis et al; Optics: NASA/STScI

Those X-rays tell astronomers that something very energetic is happening in the galaxy, which is why it is also often called a quasar. The X-ray emissions 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 emission, but they have to account for the fact that it is affected by the strong gravitational pull of the black hole. The greater the shift 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 just 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 lensed quasar allows astronomers to explore the region surrounding its core. 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. Those X-ray emissions from its accretion disk provide clues about how quickly that black hole grew over time and how it formed. There are a couple of leading theories about the growth of black holes. We know that stellar-mass ones come from the deaths of supermassive stars. They explode as supernovae. What's left collapses, and that creates the black hole.

However, the supermassive ones at the hearts of galaxies probably form in one of two ways. They could come from the accretion of material over a long period of time during collisions and mergers between galaxies. If that happens, a growing black hole gathers 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 due to many small accretion episodes, its diet would come from random directions and its spin rate would be slower.

So what's the story of the bright supermassive monster at the heart of RX J1131-1231? All observations to date show a rapidly spinning black hole, meaning it likely grew through mergers and collisions. Further observations of its high-energy activity should help astronomers probe deeper into the Universe and see objects from ever older epochs of cosmic time. JWST's contribution helps them use gravitational lenses to spot these things. At the same time, they can map the distribution of dark matter that helps the Universe create those natural magnifying glasses.

For more information

Webb admires the jeweled ring
Distant quasar RX J1131
RX J1131-1231: Chandra and XMM-Newton provide a direct measurement of the spin of a distant black hole

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