 This stunning photograph shows the Dumbell Nebula, M27, which is the remnant of a star which exploded as a nova more than 3000 years ago. This is the way we see it now ... but this nebula is about 1000 light years away, so this is actually how it looked a thousand years ago. (At that time, the explosion was several thousand years old). Here's what happened. An old star had finally used up all its fuel, and nuclear fusion could no longer continue. Without the outward pressure of radiation from its core to sustain it, the star collapsed on itself. As the relatively cooler outer layers of the star fell toward the hot core, a massive explosion occurred, spewing the layers of gas into interstellar space in an expanding cloud. This ever-expanding sphere of gas is what we see (the colours are not necessarily true ones; sometimes the colours are enhanced by astronomers to make the internal structure of the object clearer). Hidden in the center is the core of the star, stripped bare ... still hot and radiating x-rays. This stellar 'remnant' is called a white dwarf, and it is the usual last stage for many low-mass stars like our sun. M27 can be seen in the constellation Vulpecula with binoculars, as one of the brightest nebulas of its kind. |