A quasar tripled by a gravitational lens

The quasar cataloged as RX J1131-1231, or simply RX J1131 (Image ESA/Webb, NASA & CSA, A. Nierenberg)
The quasar cataloged as RX J1131-1231, or simply RX J1131 (Image ESA/Webb, NASA & CSA, A. Nierenberg)

A new image captured by the James Webb Space Telescope depicts the quasar cataloged as RX J1131-1231, or simply RX J1131. About six billion light-years away from Earth, it’s visible in three different copies, recognizable in the upper part of the bright ring in the center of the image, due to a gravitational lensing effect generated by a galaxy between it and Earth. In particular, MIRI (Mid-Infrared Instrument) was used to observe RX J1131 with different mid-infrared filters as part of an observation program that studies dark matter.

Quasars are the brightest objects in the universe thanks to the supermassive black holes that power them by heating the materials around them to the point of generating powerful electromagnetic emissions. This allows us to see them even at distances of billions of light-years but sometimes, those emissions reach a galaxy which, with its mass, acts like a magnifying glass allowing the Earth’s astronomers to see them better. The image that arrives on Earth can be distorted in various ways but in some cases, it can be multiplied instead. In the case of RX J1131, the image is tripled thanks to the lens generated by the elliptical galaxy visible as a blue dot in the center of the ring.

Seeing a quasar in detail and in various bands of the electromagnetic spectrum allows to study its characteristics. For example, RX J1131 was already studied in the past in the infrared with the Hubble Space Telescope but also in X-rays with the Chandra Observatory. This is important to understand how the supermassive black hole that powers the quasar grew.

A black hole that grows mainly through galaxy collisions and mergers should accumulate materials in a stable disk and should swallow materials at a steady rate with the consequence that its spin should be fast. Instead, a black hole growing through many small episodes of accretion would accumulate materials from random directions. The supermassive black hole that powers the quasar RX J1131 spins at a speed that is more than half the speed of light, suggesting it grew through mergers.

The new observations conducted with the James Webb Space Telescope will allow to obtain greater details and more precise calculations of the characteristics of the quasar RX J1131. The details may also be important for dark matter studies to test various models on a smaller scale than ever. Dark matter is believed to be responsible for a large part of the gravitational effects exerted by galaxies, therefore a gravitational lens such as the one that triples the image of the quasar RX J1131 can also represent an interesting target for this type of cosmological research.

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