EMBRYONIC solar systems are thriving in a surprisingly dangerous part of the Galaxy. Dozens of these baby planetary systems, called proplyds, have been spotted in the turbulent Carina Nebula, 7000 light years from Earth. It is only the second nursery of proplyds to be found, giving astronomers a new opportunity to study the earliest stages of planetary system formation.
Proplyds look a little like comets, with a tail, a head and sometimes a dark nucleus (see Graphic). But some are more than a trillion kilometres across, many times bigger than our Solar System. Each proplyd is thought to be a cloud of gas that has collapsed and begun to form a star at its centre, with a disc of gas and dust around it that could later condense into planets.
Proplyds were first spotted in the Orion Nebula. Now, using data from the Blanco telescope in Chile, Nathan Smith of the University of Colorado in Boulder and his team have discovered that the Carina Nebula is also home to dozens of proplyds, and possibly many more.
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That’s surprising, because the Carina Nebula does not seem like a particularly nurturing environment. It is packed with tremendously powerful stars, including the monstrous Eta Carinae, one of the brightest stars in the Galaxy. These stars pump out so much radiation that astronomers expected any proplyds to be blown away altogether.
That means proplyds may be more robust than we thought. That would make planets very common, and implies that the Carina Nebula could be the nearest thing to Earth’s own nursery.
On the other hand, the proplyds seen so far in the Carina Nebula may be special. They are huge compared with those in Orion, and the stars forming inside them are larger than our Sun. So it may be that only big proplyds can survive the ultraviolet onslaught from the bullies of the Carina Nebula, making planets rarer and suggesting that our own Solar System couldn’t have been born in such a place.
So was our Solar System the child of a large and fractious family like Carina, or a quieter one like Orion far from the hurly-burly? To decide between these two points of view, Smith and his colleagues plan to look in more detail at the Carina Nebula to search for smaller proplyds holding Sun-like stars.
