Galaxies collide, Quasar burns

Quasars, or Quasi Stellar Objects, are distant but incredibly bright sources in the far off regions of the Universe. They are believed to be the result of massive amounts of gas and dust being pulled towards a supermassive black hole and forming an accretion disc around it. The violent swirl towards the black hole, with attendant friction and acceleration of matter, results in a massive release of energy as light. From our distant viewpoint, that light was initially seen as just a star like point of brightness, but one whose spectrum resembled no known star, and which failed to register sufficient motion relative to other objects over the course of the year to suggest it was a nearby thing.

Many years after the first quasars were spotted and we’ve seen loads and divided them up into two groups, imaginatively named 1 and 2. Type 1 quasars have the black holes face on, or nearly face on, shovelling vast amounts of radiation our way (Blazars are quasars that are either directly face on, or just incredibly energetic). Type 2 quasars are thought to be edge on, with the matter swirling towards the black hole blocking out part of the light emitted our way. On the one hand, these are very much dimmer and so more difficult to find. On the other, these are very much dimmer and so don’t outshine everything around them so much.

Astronomers using the OSIRIS instrument on the 10.4m Gran Canaria Telescope, GTC, and the European Southern Observatory’s Very Large Telescope, VLT, in Chile have examined a quasar known romantically as SDSS J0123+00. This quasar is a type 2, rather helpfully for all the preamble I just gave, and is dim enough for an image to be taken of the stuff around it. What has been found is a galaxy swelled to six times the size of the Milky Way. At one point, a stream of matter, known as a tidal bridge, reaches from the glowing active galaxy over a distance of 180 thousand parsecs and touches the outer rim of a neighbouring galaxy, suggesting a violent encounter has happened between the two, with the nascent quasar coming off worse.

I’d probably glow brightly in that case too…


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