Known to some as the name of the weekly lottery in Spain, “El Gordo” is synonymous to astronomers as the most massive object known in space.
It has several hundred galaxies in it of 10 billion stars each plus ten times more matter in the form of dark matter, and is a prodigious producer of X-rays. Indeed it would not be safe for a galaxy to get too close to El Gordo.
Not only would such a unsuspecting object suffer from the high energy radiation, but in addition there is such a powerful gravity spread out over such a large area that it will stretch incoming objects like taffy.
Not to worry though - this object is about 6 billion lights years away, which equates to about half the age of the observable universe, so we are not going to encounter El Gordo anytime soon.
To be fair, it is not really a single object anyway, but rather a pair of two massive galaxy clusters undergoing a head-on collision at speeds of millions of miles per hour (yes, millions).
Interestingly, the dominant dark matter is relatively blind to the collision, and just continues straight on as if the other galaxy cluster was not even there. Meanwhile, the stars, gas and dust get stopped cold at the site of the collision.
It is akin in some ways to two great American football teams meeting on the field. In a reasonably successful play, the running backs race with the football (the dark matter), while the defensive and offensive lines suffer a big crunch at the line of scrimmage (the stars, gas and dust).
The discovery of this “separation” of the dark plus visible matter is enabling us to gain a better understanding of what this elusive dark matter material really is. This installment is based, in part, on a recent article on the El Gordo cluster in the January 18th issue of Astronomy Magazine.