The Elephant’s Trunk Nebula is a dense region of dust and gas found within the considerably larger star forming region IC 1396 in Cepheus constellation. Designated IC 1396A, the elongated globule of dust and gas was named the Elephant’s Trunk because it resembles an elephant’s head and trunk at visible wavelengths, appearing as a dark patch with a bright winding rim. It is located at a distance of 2,400 light years from Earth.
The large and relatively faint emission nebula IC 1396 is more than 100 light years across. The star responsible for its glow is the blue multiple star system HD 206267. The Elephant’s Trunk itself stretches over a region of 20 light years. The dark globule is eroded by the radiation pressure from the central star that illuminates the nebula.
The Elephant’s Trunk Nebula is a region of star formation, with more than 250 young stars identified within and around it. Several of these stars are very young, less than 100,000 years old. There are two stars with an estimated age of a couple of million years, found in a small cavity in the head of the Elephant’s Trunk. The newly born protostars were formed as a result of the pressure created by the high compression caused by the radiation of the massive central star and the winds from the young stars within the nebula. The radiation and stellar winds of the central star are eroding some of the nebula’s dust and gas while also compressing some of the material into clumps from which new stars are formed.
Many of the newly formed stars are embedded in regions of thick dust and gas and cannot be seen in visible light. They can, however, be detected in infrared wavelengths, including the very young stars that have only begun to shine. The glowing circumstellar disks of material that surround these stars make the stars bright in infrared images. The disks are considerably thicker when the stars are still very young and they are very prominent in infrared light.
IC 1396 contains a number of globules similar to the Elephant’s Trunk, differing in size and shape. These appear as black silhouettes positioned against the nebula’s bright clouds of gas.
The brightest star visible in the region is Mu Cephei, also known as Herschel’s Garnet Star. The luminous red supergiant or hypergiant appears at the nebula’s edge and lies at a distance of 2,840 light years from Earth. It is one of the largest known stars, as well as one of the reddest stars in the sky. It has a radius 1,260 to 1,650 times that of the Sun. If it were placed within our solar system, it would reach between the orbits of Jupiter and Saturn.
The Elephant’s Trunk Nebula lies near several other notable deep sky objects. These include the Bubble Nebula (NGC 7538) in Cassiopeia, the Wizard Nebula (Sharpless 142) and the Fish Nebula (Sharpless 132) in Cepheus.
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