Even if spiders make you nervous, don't worry about this tarantula. It's not a big spider, it's a big nebula that looks a bit like a spider in some photographs. It's also so far away that even its light takes about 170,000 years to get to us. Stars are born there, stars die there, and it's one of the most spectacular nebulae in the galactic neighborhood.
1. A nebula is a giant cloud of gas and dust in the spaces between the stars.
Nebulae have the material to make new stars, and many of them are stellar nurseries. There are also nebulae made from the outer layers of massive stars that ended their lives in an enormous explosion called a supernovae. This kind of nebula is called a supernova remnant. The Tarantula contains regions of both of these types of nebula.
2. The Tarantula Nebula isn't in our Galaxy the Milky Way – it's in a nearby galaxy called the Large Magellanic Cloud (LMC).
The LMC is a dwarf galaxy that can easily be seen in the southern hemisphere in the constellation Dorado (the Mahi Mahi fish).
3. Although it's 170,000 light years away, the Tarantula Nebula is so bright that you can see it without a telescope. At first, people thought it was a star.
An early 17th-century star atlas showed it as a star. Later the nebula was even listed in star atlases as 30 Doradus, which is a star number. Telescopes finally showed that the object was a nebula, not a star, but it's still often called 30 Doradus. In the large telescopes of the early 20th century, the nebula reminded some astronomers of a big spider. That's how it got its nickname.
4. The Tarantula Nebula is much bigger than the Orion Nebula, but it's over a hundred times farther away.
Let's compare the Tarantula to one of the brightest and best known nebulae in our Galaxy, the Orion Nebula. That is nearly 25 light years across and 1350 light years away, and you can see it without a telescope in the constellation Orion. It's a faint fuzzy patch in the center of Orion's “sword”. The Tarantula Nebula is over 600 light years across, but it's also 170,000 light years away. Try to imagine the Tarantula Nebula in the Orion Nebula's place. If you went outside to look at the night sky, it would be bright enough for you to see your shadow. It probably wouldn't make astronomers happy to have so much light.
5. The Tarantula has been a very active starbirth region for several million years.
How can a cloud of gas and dust be bright enough to see from so far away? The answer is “stars”. There are star clusters of different ages in the Tarantula. A star cluster is a group of stars that formed together in the same part of a giant nebula and stayed together because of their gravitational pull on each other. Half of the Tarantula's light comes from R136, the central part of one star cluster.
6. R136 contains half a million or more fairly young stars.
Not only does R136 have a lot of stars, it also has some amazingly big ones. There are at least nine stars that are over a hundred times more massive than the Sun. One of these stars R136a1 is over 250 times more massive than the Sun. Since the Sun contains 99.9% of the mass of the whole Solar System, R136a1 has easily enough material in it to make 250 Solar Systems.
7. The biggest stars are also the hottest. A gigantic star burns brightly, but has a short life that ends in a supernova explosion.
A supernova is a massive explosion that gives out as much light and energy as a whole galaxy of stars. It creates a shock wave that can start off new star formation in a nebula. Heavy elements like copper, gold and titanium are made in a supernova, so they are added to the nebula and recycled into the new stars. The stars of R136 are still too young to have ended in supernovae, but the Tarantula has seen many supernovae in the past.
8. Hodge 301 is a star cluster older than R136, and about 150 light years away from it.
Astronomers have studied Hodge 301 and estimate that at least forty supernovae have happened there. They also think that these supernovae may have set off the star formation in R136.
9. The first supernova for nearly four hundred years to be visible without a telescope was in the Tarantula Nebula.
The first supernova of 1987 (SN 1987A) was also the first one since 1604 to be visible without binoculars or telescope. Unfortunately for those living in the northern hemisphere, it was a southern hemisphere event. It was certainly a big event for astronomers who were at last able to study a nearby supernova with modern telescopes and other detectors. In fact, thirty years later they're still observing the remnant.
10. The Tarantula Nebula has several known superbubbles.
A superbubble is a very large cavity blasted out of nebulae by supernovae. They're hundreds of light years across. Our Solar System formed in the middle of an an ancient superbubble.