Astronomy Picture of the Day
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2003 October 19 
Posted on 10/18/2003 10:56:54 PM PDT by petuniasevan
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2003 October 19
Explanation: Is there a monster in IC 1396? Known to some as the Elephant's Trunk Nebula, parts of gas and dust clouds of this star formation region may appear to take on foreboding forms, some nearly human. The only real monster here, however, is a bright young star too far from Earth to hurt us. Energetic light from this star is eating away the dust of the dark cometary globule near the top of the above image. Jets and winds of particles emitted from this star are also pushing away ambient gas and dust. Nearly 3,000 light-years distant, the relatively faint IC 1396 complex covers a much larger region on the sky than shown here, with an apparent width of more than 10 full moons.
Here is the brighter center of the nebula complex. It actually is even bigger than the photo shows.
IC 1396
Emission Nebulae
Constellation: Cepheus RA: 21h 39' Dec: +57 30'
The brightest star in the frame, at top, is mu Cephei. It is a red supergiant star with a diameter larger than the orbit of Saturn, some 2536 times the diameter of the Sun. It is one of the largest stars we know of.
It is very red colored with a B-V magnitude of 2.5. Also called Herschel's Garnet Star, and Erakis, mu Cephi is a variable star that varies in magnitude from 3.4 to 5.1 over a period of approximately 730 days. It's absolute visual magnitude is -6.7, 38,000 times brighter than the Sun.
Mu Cephei is located about 1500 light years from the Earth. ---petunia's note - the error in determining distance for this star is large. Parallax is no good at this star's distance, and it is not a true Cepheid variable; thus the distance given varies greatly according to source. Starry Night Pro software's source says 5436 ly for this star. Another source says 2700 ly.
Below is a chart showing IC 1396. The little "µ" within the nebula's outline is Mu Cephei.
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