Visiting the Helix
One of the often-asked questions astronomers get is “What will happen when the Sun dies?” It’s an obvious concern, since whatever happens to the Sun will affect Earth, but it’s not an immediate concern. The death of the Sun isn’t going to happen for another few billion years yet, so we don’t have to worry about facing it grow larger during its red giant stage and then shrink down to become a tiny ghost of its former brilliance. Many, many generations of humans will live and die on our planet before future astronomers will start to detect the first instabilities that indicate the Sun’s upcoming demise.
There are stars like the Sun out there in space that have already gone through the death process, and so astronomers study them to understand what our star will look like when it finally gets down to the serious business of stardeath. One of the objects they have studied quite a bit is called the Helix Nebula.
ESO’s VISTA telescope, at the Paranal Observatory in Chile, has captured a striking new image of the Helix Nebula. This picture, taken in infrared light, reveals strands of cold nebular gas that are invisible in images taken in visible light, as well as bringing to light a rich background of stars and galaxies.
The Helix was created as a Sun-like star reached the final stages of its life. It began to lose its outer layers of gas, which you can see in the image above as they expand into space. What’s left of the star appears as a tiny blue dot at the center of shell of material surrounding it. That ring spreads out over an area about four light-years across (almost the distance between the Sun and the nearest star in the Alpha Centauri system. This infrared view shows the extent of the gas cloud.
The nebula is made up of of dust, ionized material and molecular gas. it’s all being heated up by ultraviolet light streaming out from the central star (which is very hot). Notice the details in the cloud—there are clumpy, comet-shaped objects called cometary knots. They aren’t really comets, but they look similar to comets with their tails blowing out in the solar wind. In this case, the knots are strands of molecular hydrogen being shaped by the flow of high-energy radiation streaming out from the dying star. Even though they look small, each is about the size of our solar system.
This, in a nutshell (or a gas shell) is about how our Sun will look billions of years from now. Perhaps our descendants will watch it all unfold from a planet around neighboring star, and take similar pictures with their orbiting space telescopes.
Want to know more about this image. Check out the European Southern Observatory site for more details and an array of downloadable images.