Sand and Stars

A Quasar and a Stromatolite

Quasar 3C 273. Image credit ESA/Hubble/NASA

4 June 2021

The ancient and brilliant quasar 3C 273 resides in Virgo some 2.4 billion light-years away. Like many other quasars, it looks like just another dim star, but looks are deceiving! Albeit appearing as nothing more than a slightly bluish 12.9 mag “star”, 3C 273’s pinprick of light is pure energy radiating from the intensely powerful centre of a distant, active galaxy, powered by a supermassive black hole feeding on gas.

Some quasars have been observed to fire off super-fast jets into the surrounding space. In this amazing Hubble Space Telescope image, 3C 273 can be seen to have fired off just such a jet – that cloudy streak measures some 200,000 light-years in length.

Observing a quasar requires a dark and steady sky and an excellent star chart – it is not easy identifying exactly which small dim star is the quasar.

My stromatolite

Seeing the quasar with my 16″ Dobs was an extraordinary observing experience. Not just because seeing a quasar is extraordinary but also because a little while ago I was rock-hounding in a rock-filled region of the Kalahari, just north of Upington, and I found the most extraordinary fossil… a 2.4 billion year old stromatolite. Stromatolites are the layered colonial structures formed by cyanobacteria – blue-green algae. (Interestingly, stromatolites continue to form in certain areas of the world, but they grow in greatest abundance in Shark Bay in western Australia.)

It is no exaggeration to say that we owe our existence to cyanobacteria! When the light left the quasar 2.4 billion years ago, what paleontologists call the ‘Great Oxygenation Event’, was transforming life and environments on Earth. 

As we all know, our atmosphere is made up of roughly 21 percent of oxygen, yet itwas absent from our atmosphere for close to half its lifespan. Primitive microbes (and their ‘extremophile’ descendants today) lived anaerobically, thriving in the absence of oxygen and relying on sulfate for their energy needs.  

Living cyanobacteria (blue-green algae) in a pond

Then mysteriously, a microbe cyanobacteria somehow evolved the remarkable ability to perform photosynthesis – i.e. they could generate energy from sunlight. They possessed the machinery to use sunshine, water and carbon dioxide to produce carbohydrates. But more significantly (especially from our personal perspective) the by-product of photosynthesis happened to be oxygen and the oxygen was released steadily until the very composition of the atmosphere changed.

The Great Oxidation Event was an epochal moment in the evolutionary timeline. Not only did the planet experience what paleontologists believe was its first mass extinction event when the oxygen, acting as a poison, wiped out much of the anaerobic life, but it also gave rise to aerobic metabolism and the evolution of multicellularity… and here we are.

Copyright © Susan Young 2019