A Beautiful Pinwheel of a Galaxy
Taking a break from all the heavy-duty science news for a minute, I want to share a beautiful recent image with you from the Hubble Space Telescope. What you see on our photo is a large part of a spiral shaped galaxy (or island) of stars, known by its catalog number M83. It is about 15 million light years away in the constellation of Hydra, the water snake.
M83 contains billions upon billions of stars and quite a bit of gas and dust -- the cosmic raw material from which new stars, new planets, and perhaps even new Facebook fans can form.
This remarkably detailed image emphasizes the pinkish-red regions that are glowing clusters (or groups) of young stars, seen on the edges of the galaxy's spiral arms. Actually, the young (adolescent) stars in these clusters glow so hot, they give off not just the light our eyes can see, but also energetic ultraviolet light. The left-over gas that still surrounds these new star groups (in a way, the womb that gave birth to them) then is set to glow. The excited gas -- mostly the cheapest, simplest element in the universe, hydrogen -- glows with a characteristic pinkish red.
Just look at all the pinkish glow! That is to say, see all the new stars that we can see having been born recently -- at least recently on the cosmic time scale, or somewhere between 1 to 10 million years ago. Like most of our cities in the spring and summer, there is still lots of construction going on in such galaxies.
This magnificent (but artificial color) image of the ringed planet Saturn was assembled and enhanced from 60 different pictures taken with the Cassini spacecraft. You are looking up at Saturn from a perspective below its rings, at a time when the Sun happened to be directly behind Saturn. Thus we are seeing the planets and the rings back-lit, something we can never see from Earth.
The image is constructed not merely with visible light pictures, but also with some in the infra-red (commonly called heat rays). So this is not what your eyes would see if you (like Cassini) were orbiting Saturn -- this is a view only our sophisticated instruments can make available. And the details have been enhanced to show you the complex structure of Saturn's rings (made up of billions of chunks of mostly water ice, all moving around the equator of Saturn in a traffic pattern so vast it puts the Los Angeles freeway system to shame.)
From one side to the other, Saturn's giant ring system spans 170,000 miles across. This means that if you were to take the ring system off Saturn and put it next to the Earth, it would almost fill the space between the Earth and the Moon.
Near the top of the picture, you see the round dark shadow that Saturn casts on its own rings. Below that shadow, the greenish glow is light reflected from the rings on to the cloudtops of Saturn.
The pictures that make up this fantastic mosaic were taken from a distance of about 500,000 miles from Saturn (quite close in astronomical terms.) Just look at all the structure you can see in the ring system, which consists of many, many ringlets.
What a beautiful holiday ornament this planet makes! Happy Holidays.
