Galaxies linked by quasar-making nebula six times bigger than the Milky Way

Billions of light years away, quasars are the brightest objects in the universe. So bright, in fact, that we'd never gotten a good look at what makes them tick...until scientists discovered a gargantuan nebula linking galaxies and fueling one quasar.

A subclass of galaxies contain an incredibly active galactic nucleus, thought to contain a central black hole millions of times the mass of our Sun. This huge amount of activity makes these galaxies what's known as quasi-stellar radio source, or quasars for short. The quasar is basically the result of the massive accretion disc of debris, which can be anywhere from ten to ten-thousand times the size of the black hole itself. The unbelievably strong gravitational forces in the accretion disc make the debris become super hot, emitting massive amounts of energy, which creates what we see as the quasar.

There are two types of quasars, both defined in terms of the thick, opaque ring that forms around them. If this ring is positioned relative to our vantage point such that it looks like a circle and we can clearly see the quasar inside, then it's a Type I quasar. If the ring is positioned such that it blocks our view of the bright quasar inside and hides all the radiation, that's a Type II quasar. Not surprisingly, Type I quasars have attracted far more attention than Type II quasars, although a group of astronomers led by Montserrat Villar Martin of Spain's Instituto de Astrofisica de Andalucía-CSIC are looking to change that.

Using Chile's Very Large Telescope - you really have to appreciate the thought that goes into naming telescopes - and the Gran Telescopio Canarias on Spain's Canary Islands, Villar Martin and his team zeroed in on SDSS J0123+00, a Type II quasar. Although far harder to detect than their brighter brethren, Type II quasars are potentially far more useful to astronomers in understanding the broader cosmic environment around the quasars. This is because the surround rings dims the otherwise overwhelmingly bright radiation, allowing the astronomers to get a better look at what surrounds the quasar.

What they discovered is nothing short of awe-inspiring. They discovered a faint nebula of ionized gas surrounding the entire galaxy. This nebula is about six times the size of our own galaxy at roughly 590,000 light years long. The nebula acts as a cosmic bridge between SDSS J0123+00 and its neighboring galaxy, strengthening the hypothesis that quasars are in part the result of intense interactions between galaxies. Here's a visual approximation of the vast nebula of ionized gas connected to galaxy SDSS J0123+00 and its quasar:

Villar-Martin says this provides strong support for the idea that the accretion discs that form quasars are indeed the debris from these galactic interactions, with the nebula a key link in the exchange of cosmic material. Indeed, the nebula is itself most likely composed of the detritus of these interactions.

[Monthly Notices of the Royal Astronomical Society]