The Great Annihilator

I have no clue how I came across this, but I thought I’d write a detailed post about this super cool and rare object in space!

First thing’s First, Microquasars!

Artist’s impression of a microquasar. Credit: NASA

Microquasars are an extremely rare and rather specific type of object in space, that share some characteristics of a normal quasar. If you need a refresher on those, click here.

A microquasar is made up of a stellar mass black hole (sometimes neutron star) referred to as the accretor, and a comparatively small companion star called the donor. The black hole needs to be much more massive than the star so that it can violently strip the star’s material and create an accretion disk.

The accretion disk will become hot due to friction, and will start to have distinct x-ray emission and even radio-wave jets.

We can think of a microquasar as a quasar belonging to a galaxy containing exactly TWO stars. We’ve discovered under 20 of these in the universe so far.

How is it different to an X-ray Binary?


Microquasars are a subclass of X-ray Binary that have relativistic radio-wave jets, and their emission and accretion disk strongly resembles that of a quasar.

Other odd types of X-ray binaries include X-ray bursters (which have extreme changes in luminosity), and X-ray pulsars (pulsars that peak in the X-ray).

Artist’s impression of SS 433. Credit: DESY, Science Communication Lab

So Now for The Great Annihilator

The Great Annihilator is a black hole + low mass companion star microquasar near the centre of our own galaxy! It is exceedingly bright in the X-ray, and despite it being close to Sagittarius A* it is pretty much distinguishable in this part only of the electromagnetic spectrum!

The reason it’s called Great Annihilator is because astronomers at the time suspected a lot of matter-antimatter annihilation due to the large quantities of high energy photon pairs. This annihilation is most likely the source of the 5 ly radio jets, but this isn’t certain.

The Great Annihilator is estimated to be around 16’300 ly from us, which means it could be closer to us than Sagittarius A*, the supermassive black hole in the centre of our galaxy.

If you go on Aladin Lite and search up 1E 1740.7-2942 which is the proper name for Great Annihilator, you can see where it is in the night sky. Check the coordinates match up with the ones on SIMBAD. It’s nearly invisible because it’s so close to Sgr A*, but have a play around with the 2 X-ray catalogues. It’s so fun!

Here’s a screenshot from SPITZER, you can’t see it, but the image is wonderful nonetheless:

Honourable Mention

LS 5039 is a real crazy microquasar, and emits gamma rays! This one is made up of a black hole and an O type star (one of the largest and rarest stars, the black hole would have also been quite large too).

Search LS 5039 in Aladin, and you’ll see easily see it in the x-ray catalogues and in Gamma too. My favourite is Chandra by far!

That’s all this week. For now, I am trying to recover from surgery, which either means I’ll post more, or I won’t post. It depends on the pain.

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