Ken Tapping, August 29, 2012
For some excellent pictures to illustrate this week’s subject, see the images of galaxies Messier 33 and Messier 51 on the website of the Canada France Hawaii Telescope (CFHT). These and the other images show the quality that is achievable from ground-based observatories, provided they are equipped with state-of-the-art optics and imaging. CFHT website.
Our Solar System, which is comprised of the Sun, planets — including ours — and a lot of other objects, is just one microscopic mote in a great spiral galaxy we call the Milky Way, which is home for billions of stars and planets. The images we are getting with telescopes like the CFHT give us a hint of the treasure trove of cosmic jewellery we live in. Unfortunately, from our position well inside, it is very hard to get a big picture of what our galaxy is like and what is going on in it. With projects like the Canadian Galactic Plane Survey we can see a lot of what is going on in our neighbourhood, which in Star Trek is referred to as the Alpha Quadrant, and somewhat beyond, but that is more or less all we can see.
The Milky Way has been established as a spiral galaxy like the billions we see in deep surveys such as the Hubble Deep Field. However, we can learn a lot by looking at similar galaxies in our galactic neighbourhood. Good examples are Messier 33 and Messier 51. M33 is close by, only about three million light years away. M51 is further away, about 23 million light years; a light year is how far light travels in a year, or more specifically, 9,460,730,472,580.82 km. The most distant galaxies we can see are billions of light years away. Both M33 and M51 have the great advantage that we see them pretty well face on. In both cases, we see a glowing nucleus, made of stars so closely spaced that we only see a glow from which there a number of spiral arms radiating; these arms contain billions of stars. Extending along these arms are dark lanes of gas and dust. This is the raw material from which new stars and planets are made. Scattered along these lanes are little glowing pink knots and blobs. They show up beautifully in the CFHT images. These glowing blobs are places where the dust and gas has given birth to a new star, or sometimes more than one. The strong ultraviolet light from these new stars make the remains of their birth clouds glow.
Luckily, even though these clouds are opaque to visible light, they are transparent to very short radio waves. The forming stars can be imaged by special radio telescopes such as the James Clerk Maxwell Telescope (the JCMT), which sits along with the CFHT and other telescopes on top of Mauna Kea, an extinct volcano in Hawaii.
The CFHT website also contains many images of things in our galaxy, such as star clusters, nebulae (clouds of glowing gas) and the remains of exploded stars. These images are lovely, and show once again what makes astronomy a unique science; what we observe is both scientifically fascinating and visually beautiful. They also show what we can achieve from the ground with modern optics and imaging techniques.
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