What is CosWatch?
There’s so much to see in the night sky! You may have seen Brian Cox on TV describing the “wonders of the universe”, or Carl Sagan talking about the “awesome machinery of nature”, and they’re absolutely right. But while huge rockets and observatories can help, space isn’t just for people with expensive equipment. You can see amazing things from millions of miles away from your very own back garden. Each week, I’m going to talk about one of these incredible objects, and how you can find them.
This lovely shot from Universe Today shows Orion’s Belt clearly – the three blue stars in a diagonal line in the middle.What is Orion’s Belt?
Orion’s Belt, sometimes titled “The Three Kings” or “The Three Sisters”. refers to three stars in the constellation of Orion. Constellations are shapes in the night sky, that ancient people compared to mythogical figures or pictures of stories. Constellations are specific to whiever planet you’re on, and don’t refer to an actual “thing” in space; the stars in Orion are millions of miles apart, and not “aligned”.
This drawing by Johaan Bayer demonstrates how Ancient Greeks interpreted their view of the stars, and this image from EarthSky.org shows how we see it today..What is in Orion’s Belt?
Again, describing something as being “in” Orion is a bit misleading, as Orion only looks like a flat shape from our planet; as this video shows, it’s actually a complex 3D shape with something like 1000 light-years between the different “dots” of light. [youtube https://www.youtube.com/watch?v=lD-5ZOipE48&w=560&h=315] What I can do, however, is describe the different stars and objects that make up the “belt” of the constellation you can see.
I’ve labelled this image from the Hubble space telescope to help you identify the different stars.1. Alnitak
Alnitak is actually a triple star system, three stars that orbit around each other. The three stars are blue super giants, far larger than the Sun.
A size comparison between one of the Alnitak stars and our Sun. The Sun is millions of times larger than the Earth – Alnitak is almost frighteningly colossal!2. Alnilam
Alnilam is also a blue supergiant. Within the next million or so years, this star may explode as a supernova!
3. Mintaka
Like Alnitak, Mintaka is another system of three stars. Once again we have some blue supergiants; because these perform nuclear fusion more powerfully than the Sun, they “die” more quickly and become beautiful nebulae or supernova.
It’s a bit like that bit in Star Wars where there are two Suns. In this case, rather than orange and red star, the Mintaka system is made up of three blue supergiants, which are extremely hot and far bigger than the sun.4. Orion nebula
The last part of Orion’s Belt to talk about is perhaps the most exciting. Just below Orion’s Belt is the Orion Nebula. A nebula is the gaseous remains of a star that has stopped necular fusion; the ghost of a star is a fun way to imagine it. In the Orion Nebula, there is a “Stellar Nursery”, where protostars (new, baby stars) are forming – about 750 of them. What’s more, many of them have “protoplanetary disks”, huge circles of dust and gas where planets like ours may be created. To put it another way, the Orion Nebula is pregnant with hundreds of new Solar Systems.
The video below shows what it might look like to travel through this beautiful nebula – though it’s travelling much faster than we think is physically possible.
[youtube https://www.youtube.com/watch?v=xCFg5udYbAg&w=560&h=315]How can I see Orion’s Belt?
Orion’s Belt can be seen fairly easily if you look in the South West sky during the evening (or North West in the Southern Hemisphere). View with the naked eye for the bigger picture, or with a telescope to examine individual stars; unfortunately, they are simply too far away to see anything like planets or moons. Trying to see Orion’s nebula is more complex. Nebulae are, as a rule, difficult or even impossible to see with the naked eye. For that reason, if you have a telescope, try aiming that at the Orion nebula. Once you’ve located it, increase magnification to get a better view, and try different filters to make it more vibrant.
The Orion Nebula as seen by Marian McGaffney.In conclusion:
- Orion’s Belt consists of three stars in the Orion Constellation; a constellation is a shape made of stars viewed from Earth.
- The three stars – Alnitak, Alnilam, and Mintaka – are blue supergiants.
- Two of those supergiants are triple systems, with three stars orbiting each other. Thus, the three stars of Orion’s Belt are actually seven stars!
- Just below the belt is the Orion Nebula, with hundreds of new Solar Systems being formed inside it.
- Orion’s Belt is easily visible on clear nights in the South-East.
- Seeing the Orion Nebula usually requires a telescope.
