September 9, 2013 - Blue Skies and Neon Signs

Blue Skies and Neon Signs The Trifid Nebula, located in the constellation Sagittarius, is a great example of two of the most common types of nebulae: emission and reflection. The red area, trisected by dust lanes that give the nebula its name, is an emission nebula, which glows because of the cluster of hot young stars at its core. Their intense ultraviolet light ionizes nearby hydrogen gas, which recombines and emits the red light characteristic of ionized hydrogen. A similar ionization process occurs in glowing neon signs. Further away from the star cluster, another cloud of dust and gas is too distant to be ionized by the radiation, but shines instead because the light of the nearby stars is reflected and scattered by the gas and dust in the nebula, similar to the way sunlight scattered by our atmosphere creates blue skies.

Image credit: R. Jay GaBany / www.Cosmotography.com

Weekly Calendar

September 9-15, 2013

Holidays - Sky Events - Space History

Monday 9

Saturn 2° north of Moon

1789: William Bond born
1892: E. E. Barnard discovers Amalthea
1975: Viking 2 launched
1982: Conestoga 1 launched
1994: STS-64 Discovery launched
2006: STS-115 Atlantis launched

Tuesday 10

1857: James Keeler born
1967: Surveyor 5 lands on Moon
1978: Venera 11 launched
2011: GRAIL spacecraft launched

Wednesday 11

1877: James Jeans born
1985: International Cometary Explorer satellite probes Comet Giacobini-Zinner (first comet flyby)
1997: Mars Global Surveyor arrives at Mars

Thursday 12

First Quarter Moon 1:08 PM ET

1959: Luna 2 launched
1966: Gemini XI launched
1970: Luna 16 launched
1991: STS-48 Discovery launched
1992: STS-47 Endeavour launched
1993: STS-51 Discovery launched