Most Massive Star in the Universe - Deep Sky Videos

So far on DeepSkyVideos we've focused very much on the Messier catalogue. But we do occasionally go off-piste, and that's what we're doing today. I want to talk to you about the Tarantula Nebula. Now this nebula is huge. And that's probably shown by the fact you can take pictures like this, even though this nebula is in a whole other galaxy. And the Tarantula Nebula contains some of the heaviest stars we've ever found. And let's put that in some perspective here. The Sun is 300,000 times heavier than the Earth. And yet this star in the Tarantula Nebula is 300 times heavier than the Sun. So for all intents and purposes, this star is 100 million times heavier than our Earth. And as luck would have it, one of the world experts on the topic is DeepSkyVideos' very own Paul Crowther. Well, today I'm going to talk about the Tarantula Nebula. It's got a lot of similarities to the Messier objects in the sense that it's a nebula. And therefore it's a diffuse collection, basically, of, in this case of stars and gas that's being illuminated by those stars. And there is a connection with the Messier catalogue in the sense of most original Messier objects were observed in the Northern Hemisphere. But this was supplemented by ones observed by other people in the Southern Hemisphere. And the Tarantula Nebula is a Southern Hemisphere object which is not a Messier object, but it was actually included as an appendix to the final Messier catalogue. So as Messier observed in the Northern Hemisphere, he can observe things within a certain range of latitude, effectively. But what he can't see are things down here, because the Earth's in the way. And so people, to actually observe a Southern sky, have to travel to the Southern Hemisphere. So there was another Frenchman, Delacalle, who was in France, but actually wanted to observe Southern stars and Southern nebulae. And so he actually went off in 1751 via Buenos Aires down to the Cape of Good Hope and spent nearly two years putting together a catalogue of stars and a catalogue of 42 nebulae. And one of these nebulae was the Tarantula Nebula. There are two well-known satellite galaxies which are kind of orbiting the Milky Way. There's a large magellanic cloud and a small magellanic cloud. And the Tarantula Nebula is in the largest of those two galaxies. In the Northern Hemisphere, the Orion Nebula is kind of the nearest big star-forming region. It's about, on the sky, about the same size as the Tarantula Nebula. So it appears about as big on the sky. It's about the same size as, say, the full Moon or the Sun. But it's 100 times closer, which means the Tarantula is 100 times bigger. Not only is it 100 times bigger, but it's probably 1,000 times brighter. So imagine if we were as close to the Tarantula Nebula as we are to the Orion Nebula, it would kind of subtend this much of the sky and it would be so bright it would cast shadows. This is an image of the entire large magellanic cloud. And this pinky region here is the Tarantula Nebula. It's humongous. It really is. It's maybe 1,000 light-years across. And so whereas the Orion Nebula has a few thousand stars in it, this has got millions of stars in it, including several hundred thousand newborn stars. Because the Tarantula is the biggest star factory in our nearby universe, we can study the massive stars in that region in much greater detail than we can in anything much further away. And so in the same way that the four stars of the Trapezium power the nebula of the Orion Nebula, there's the central stars in the central cluster in the Tarantula, which kind of more or less power that huge nebula. So this is now a zoomed-in view of the central region of the Tarantula Nebula. And you can kind of make out this central cluster, which is kind of, I would say, something like half of the entire UV photons that power that nebula are being created within stars within this one cluster. And this is tiny. This cluster is only a few light-years across. Whereas the most massive star in the Orion has a mass of maybe 30 times the mass of the Sun, the most massive stars in here may have masses up to 300 times the mass of the Sun. And so this is an image of that central cluster. And if we now put a different contrast in there to look at the bright things in this central region, there's A1, which is the most massive star anywhere in the local universe, and right next to it, A2, which is the second most massive star, we think, in the local universe. When you say local universe, how local is local? Well, certainly local group, which means basically the Milky Way and its satellite galaxies, and Andromeda and its satellite galaxies. So this is kind of a central few million light-years. So right now, when I zoom in there on that thing that says A1, I'm looking at pretty much the brightest star in this part of the universe. Is that like your Mount Everest? Yeah. And in fact, just Easter, I got my first Hubble observations of that object. Hubble is the only thing that we can use to observe these things in the sort of detail we need to to really piece together their properties. From the ground, we can observe in the optical and observe in the infrared. We can't observe in the ultraviolet because, good for life on Earth, the atmosphere gets in the way and it blocks out the ultraviolet radiation. But the ultraviolet radiation is kind of close to where the hot stars peak in their energy. Where are these images? Well, it's spectroscopy. So it's not as pretty as this. It's basically, it's where I'm dispersing the light so that actually I'm getting the kind of signature of these stars. Its continuum is kind of doing this. And then these are fingerprints of individual elements. This line here is a line of highly ionised nitrogen. This one's a line of ionised carbon. And this kind of shape profile is what we call a P-Cygni profile. And it's kind of a signature of a dense outflow. The wind from this really massive star is flying out at about 3,000 kilometres per second. So that's about 1% of the speed of light. The next generation Hubble isn't going to be able to do this kind of thing. It's going to be optimised in the infrared. So Hubble's really our last hope to be able to look at these things in individual stars in this exquisite resolution in the ultraviolet. I think if it wasn't for having something like the tarantula up close and personal, then when we're actually looking at these more fuzzy things far away, we would be struggling to kind of get to grips with what they are. There's nothing, anything like it really, as extreme as this, that we can look at the individual stars in this huge sun nursery. I mean, that's why it's been used as a Rosetta Stone for these kind of big, big factories of star formation.