Quasars are supermassive black holes at the centres of galaxies. We can see them because material is falling in, being superheated, and so become incredibly bright as a side-effect.

Although my image is just a few blurry pixels, what it represents is quite mind-blowing: a supermassive black hole, the light from which began its journey when the Universe was only around 1.3 billion years old, which is 10% of its current age. The quasar is also very faint, having a magnitude of 19.38.

To expand on this a little, the quasar has a redshift of z = 4.57. This means that the light captured in my image has been travelling for roughly 12.5 billion years. The Universe has been expanding during that entire journey, so the quasar is now about 26 billion light-years away (in today’s comoving distance). Comoving distance is a way astronomers measure how far apart objects are while considering the expansion of the Universe. As the light was crossing space, space itself was stretching, so the quasar has been carried further away the whole time. That’s why its present-day distance is much larger than the 12.5 billion light-years the light actually travelled. This stuff makes my head hurt!

I think it’s fair to say that J08570+1534 is the most distant object that I can see with my equipment from Bristol. (There are some quasars that are slightly further away, but they’re a lot fainter and would need hugely longer integration times, so I don’t really consider them realistic possibilities).