A Low Density Black Hole

By Anupum Pant

Imagine you have two equal sized balls of clay. You mix both of them together to get a bigger ball of clay. Now as simple math dictates, the mass of this new ball will be twice the mass that you had in each ball initially. However, the radius of this new ball is clearly only slightly more than the initial ball. Had you wanted to make a ball with the radius twice as much as the initial ball, you would have needed to club 8 of the small balls.

Black holes do not work that way. The event horizon, a kind of one-way membrane from which not even light can escape is like a boundary for the black hole. Let’s say this defines the size of a black hole.

The funny thing about the size of a black hole is that if you double the mass of a black hole, the size doubles. The physics of it is complex, unlike anything of a clay ball. So, just believe me when I say that doubling the mass doubles the radius.

When such things happen, there are weird results. That means, if you keep adding mass to a black hole, and at some point it reaches a really massive mass, say as much as Billion times that of our sun – That’s not unheard of, it happens. If you get your calculations right, you’ll find that in a black hole like that one, the density will be really low. A black hole of that size would span from the center of the sun to the orbit of Neptune. And the density of it would be around 1/1000 of a gram per cc. That, if you did not know, is also the density of air. That’s how low density black holes can be. Probably even lower, if they are bigger…

A very very big sphere of a radius 2.7 billion miles filled with air would be a black hole. Hard to believe, but it’s true.

via [BadAstronomy]

The Messier Catalogue

By Anupum Pant

This might be a prevalent piece of information but like so many other very common things I do not know about, the Messier catalogue, I found, was just one of them. Ignore this if you know what it is…

I realized not knowing about the Messier catalogue, when a friend of mine asked me what the M with a number beside it signify in his Google sky app. We some how collectively chose to blindly predict that this was the way stars are named, with no knowledge whatsoever on the fact why only M was used.


Boy, we were wrong! Of course, M was used because of the “Messier catalogue”.  But it wasn’t for stars.

Charles Messier was a French astronomer who had a decided on a mission for his life. He was to search and find as many comets he could, in his lifetime. He went on to find 15 of them – quite extraordinary for a single man to have done that.

While doing this search for comets Messier, to keep the comets separate from other cloudy objects he discovered, he started keeping a journal of non-comet objects. This came to be known as the Messier catalogue of deep sky objects.

As time progressed, objects were added one by one to the list. Their names on this catalogue start with the letter M – denoting “Messier  objects” (not stars, but nebulae, star clusters and galaxies.). There are a total of 110 objects in this catalogue and is a nice thing for amateur astronomers to do the Messier marathon. This involves watching all of the objects at night spotting the sun rises.

The last object, M110 was added by Kenneth Glyn Jones in the year 1967.

All of these objects have other names too. One other name is the one that comes from the New General Catalogue (NGC). And hence the names are like NGC 1952 for M1.

More information about each one of the 110 objects can be found here [Link]


Trekking on Mars

By Anupum Pant

Now just like Google let’s you move around with you having a bird-eyes view of the whole world, NASA has released an interactive map of the surface of Mars. This map lets you see the red-planet in 2D or 3D and you can zoom around to explore areas in a better detail.