Does this cluster make my mass look fat?

Does this cluster make my mass look fat?

Does this cluster make my mass look fat?

Bad Astronomy
The entire universe in blog form
Feb. 3 2010 11:19 AM

Does this cluster make my mass look fat?

What's better than a gorgeously stunning image of a massive cluster surrounded by delicate, wispy nebulosity?

Well, nothing, really. Unless you can use it for SCIENCE!

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  


[Click to gigantisize.]

Purty, ain't it? That's NGC 3603, a very large star-forming region in our own Milky Way Galaxy, lying about 20,000 light years away. It can only be seen from the southern hemisphere, which is why the European Southern Observatory folks got this image using the ginormous Very Large Telescope, an 8-meter behemoth in Chile (and actually, Ginormous Telescope would be a cool name).

Not too long ago -- no more than a million years, give or take -- a lot of the stars forming the central cluster there were born. There are so many that they appear to overlap, but that's an illusion due to the blurring of the image from the Earth's atmosphere (and the nature of light itself only allows us to make star images so small).


Lost in that crowd is a star designated NGC 3603 A1, and it is the most massive star to ever have its mass directly measured. It's actually a binary star, two monsters locked in a gravitational dance, orbiting each other once every 3.77 days -- which right away tells you this is a special pair, possessing enough gravity to toss themselves around that rapidly.

Using simple laws of physics discovered by Kepler back in the 1600s, we can measure the masses of each star in the duo. The heftier of the two is a whopping 116 times the mass of the Sun -- which is close to the upper limit of what a star can get to without tearing itself apart. The more massive a star, the more luminous it is, and the surface can get so hot that any material there gets blown off... so that sets a lid on how big a star can get. Details vary depending on a lot of factors, but really 116 times the mass of the Sun is about as big as you'll ever get for a star in our galaxy.

The other star in the binary is no slouch, tipping the scales at 89 solar masses. If it were just sitting out there all by itself it would rate as a phenomenal star, too. But its partner still wins the prize.

And how do I know those stars were born no more than a million years ago? Because massive stars don't live long, and any beasts like these two live short lives indeed. It won't be long before they detonate as supernovae, lighting up with a violence and fury that will make each outshine the rest of the stars in our entire galaxy combined!

Not only that, but pretty much every star you see in that cluster is of the massive and luminous classes astronomers call O and B stars, bruisers with enough oomph to explode as supernovae. How many stars do you see in that cluster? Dozens? So think about that: each one of those will become a titanic supernova, wreaking havoc across dozens of light years, sending out blasts of light to outshine galaxies, and throwing out octillions of tons of gas.

Eventually that gas, laced with heavier elements created in the nuclear forge of the supernova blast wave itself, will slam into, merge with, and seed the surrounding gas in the nebula. Compressed beyond its ability to sustain itself, the gas will collapse and form more stars. Some of these may be massive ones which will again repeat the cycle, and some will have lower mass, be fainter, cooler. They may form planets from those heavy elements. It will be a rocky birth, given the environment, but the vagaries of orbital dynamics dictate that eventually those systems will leave the nebula and move out on their own in the Milky Way. And a billion years from now, two, four billion, who knows what creatures may roam the surfaces of any of those worlds.

And will they see more stellar factories dotting the galaxies starscape, and wonder what their own looked like, all those eons ago?