Coma Cluster

In one of the few examples of good naming in astronomy, this process is called ram pressure stripping.

In a new paper published in The Astrophysical Journal, a team led by William Kramer looked at one particularly striking example of this process, Galaxy D100 in the Coma Cluster.

As this galaxy has fallen into the cluster, dust and gas were systematically stripped, working from the outside of the galaxy, and that stripped-out material was left trailing behind the galaxy like a tail.

This kind of galaxy with trailing material is called a jellyfish galaxy.

and who was, for many years, quietly kept at arm's length by the astronomical establishment.

But he had eyes and he had mathematics, and in 1933 he turned both to a rich swarm of galaxies known as the Coma Cluster.

The Coma Cluster lies in the direction of the constellation Coma Berenice , about 320 million light-years from us.

It is a great gathering, perhaps a thousand or more galaxies, moving about one another in a slow gravitational dance, bound together by the mutual pull of their combined mass.

Zwicky measured their velocities.

They did not agree quietly or by a small margin in a way that might have been explained by a measurement error or a minor correction.

They disagreed by a factor of hundreds.

The galaxies of the Coma Cluster were moving much too fast to be held together by the gravity of their visible matter alone.

It is fossilised before it arrives.

Push further to the Coma Cluster and the absurdity deepens.

Coma is one of the densest and most well-studied galaxy clusters in the observable universe, containing over 1,000 major galaxies dominated by two supergiant ellipticals at its core.

The cluster is bound together by dark matter so massive that the visible galaxies account for less than 5% of its total gravitational budget.

Every animal that has ever lived on Earth fits inside that waiting period.

Push further.

The Coma Cluster, a dense knot of galaxies bound together by dark matter and superheated intracluster gas, lies roughly 320 million light years from Earth.

At light speed, the journey requires 320 million years.

At 90% of light speed, the journey would take 60 million years as measured from Earth and roughly 26 million years on board.

The Coma Cluster, a rich concentration of galaxies, lies 320 million light years distant.

The trip would consume over 350 million years.

a duration stretching back to the early Carboniferous period on Earth, an era when shallow seas covered much of the continents and the earliest four-limbed creatures were still adapting to life beyond the water's edge.

A message sent to the Virgo Cluster would take 54 million years to arrive.

By the time a reply could return, 108 million years would have elapsed.

A message to the Coma Cluster would take over 600 million years for a round trip.

These are not communication timescales.

The Virgo Cluster, the nearest major cluster to our local group, contains over 1,300 galaxies and lies roughly 54 million light-years away.

Larger clusters, like the Coma Cluster, contain thousands of galaxies and span tens of millions of light years.

At the centre of nearly every large galaxy cluster sits a special type of galaxy.

Astronomers call these Brightest Cluster Galaxies, or BCGs.

The visible galaxies move too fast to be held together by their own gravity alone.

This was one of the earliest lines of evidence for dark matter's existence, identified by the astronomer Fritz Zwicky in the 1930s when he noticed that galaxies in the Coma Cluster were moving so rapidly that the cluster should have flown apart long ago unless it contained far more mass than its visible matter could provide.

The second most massive component is hot gas, the intracluster medium, and this is the component that will become most important for our story.

The intracluster medium is a vast atmosphere of ionized hydrogen and helium, heated to temperatures of tens of millions of degrees, sometimes exceeding 100 million degrees in the most massive clusters.

A massive galaxy cluster can have a total mass exceeding 1 quadrillion solar masses, or 10 to the 15th power solar masses.

That is more than a million billion times the mass of our Sun.

The Coma Cluster, one of the best studied examples, contains over a thousand large galaxies and sits at the centre of the Coma Supercluster, roughly 320 million light years from Earth.

Galaxy clusters are the most massive gravitationally bound structures in the universe.