Pretty In Pink

The European Southern Observatory recently released this gorgeous photo of the spiral galaxy NGC 300 located in the southern constellation of Sculptor. Pink clouds of glowing hydrogen gas mark sites of new star formation within the galaxy's spiral arms. NGC 300 is 6 million light years away and similar to our own Milky Way in appearance - if we could get outside and look back! More info. Credit: ESO

Hydrogen is one of the more colorful gases in the universe once you zap it with a little ultraviolet light. It’s the most abundant element in the universe and found throughout the galaxy in the form of stars and vast congregations of interstellar gas called molecular clouds. It’s within these clouds that hydrogen, helium, silicate dust and other elements and molecules condense through gravity to form fresh star clusters and glowing gas clouds like the Orion Nebula. UV light from the newly formed stars excites the otherwise colorless hydrogen gas, causing it to glow a luscious pink. These lovely pink clouds litter our galaxy and many others including the pictured NGC 300. They mark the sites of stellar nurseries busy with star birth.

The Lagoon Nebula in Sagittarius is a star-forming region in our own galaxy similar to one of the pink patches in NGC 300. The nebula is some 5000 light years from Earth and about 100 light years across. Credit: Hunter Wilson

It’s a sad truth that hydrogen’s pink doesn’t come across very well to the naked eye. Yes, there are a few nebulas that show the color in larger telescopes – Orion’s a good example – but our eyes are not very sensitive to hydrogen’s deep red. CCD sensors in digital cameras as well as film are much better at recording it. That’s why when you see a photo of a flaming pink nebula, you’ll need to adjust your expectations if you plan on seeing it in your telescope.

Even if we can’t fully appreciate hydrogen’s colorful personality, we can still use it as a marker of exciting goings-on in the galaxy. The beacon of hydrogen shoots forth when a giant star explodes as a supernova and sends a shock wave into the surrounding interstellar gas compressed it and setting it aglow. There are close pairs of stars where matter from the companion is transferred to the other, accumulates on the surface and then ignites in a rage of nuclear fusion called a nova. Hydrogen leaves its calling card again as a spike of pink light expanding outward from the detonation. Bright novae often appear pink through a moderate-sized telescope.

You can find the Lagoon Nebula fairly easily with binoculars in Sagittarius as soon as the sky gets dark. Face due south and look about two outstretched fists above the horizon to trace the outline of the Teapot of Sagittarius. One binocular field due west (right) of the top of the pot, the nebula will appear as a misty patch dotted with stars. Although I've shown it in "hydrogen" pink, it will look white to your eye. Created with Stellarium

The next few nights will be the last for a while to see the International Space Station in the evening sky. After a series of daytime-only passes for the region, it will reappear after a few weeks in the dawn sky. Tomorrow we’ll learn how to track a fainter but just as interesting satellite,  the new X-37B space plane.

All times are CDT and good for Duluth, Minn. and region. For times for your town, click on either the Heaven’s Above or Spaceweather tracker links in the column at right.

* Tonight starting at 7:49 p.m. in twilight. Brilliant appearance
beginning in the northwestern sky and passing nearly overhead. Second
short-lived pass low in the southwestern sky at 9:25 p.m.
* Saturday Sept. 11 at 8:15 p.m. Fine, bright pass across the southern sky
* Sunday Sept. 12 at 8:43 p.m. Low pass in the southwest
* Monday Sept. 13 at 7:34 p.m. Bright pass across the south
* Tuesday Sept. 14 at 8:02 p.m. Low pass in the southwest.