Elephant's Trunk Nebula

{{Short description|Nebula in the constellation Cepheus}}

{{for|similarly the named type of formation in other nebulae|Elephant trunk (astronomy)}}

{{More citations needed|date=May 2024}}

{{Infobox nebula

|name = Elephant's Trunk Nebula

|image = File:Elephant's Trunk Nebula, IC 1396A.png

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|type = emission

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|dist_ly = 2,400

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|constellation = Cepheus

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The Elephant's Trunk Nebula (IC 1396A) is a concentration of interstellar gas and dust within the much larger ionized gas region IC 1396 located in the constellation Cepheus about 2,400 light years away from Earth.{{cite journal| last = Matthews| first = HI| title = High resolution radio observations of bright rims in IC 1396| journal = Astronomy and Astrophysics| year = 1979| volume = 75| pages = 345–50| bibcode = 1979A&A....75..345M}} The nebula is a dark, dense globule that gets its name from its appearance at visible light wavelengths, where there is a dark patch with a bright, sinuous rim. The bright rim is the surface of the dense cloud that is being illuminated and ionized by a very bright, massive multiple star (HD 206267) that is just to the east of the Elephant's Trunk Nebula . The entire IC 1396 region is ionized by the massive star, except for dense globules that can protect themselves from the star's harsh ultraviolet rays.{{cn|date=June 2022}}

File:Elephant's Trunk nebula.jpg

The Elephant's Trunk Nebula is now thought to be a site of star formation, containing several very young (less than 100,000 yr) stars that were discovered in infrared images in 2003. Two older (but still young, a couple of million years, by the standards of stars, which live for billions of years) stars are present in a small, circular cavity in the head of the globule. Winds from these young stars may have emptied the cavity.{{cn|date=June 2022}}

The combined action of the light from the massive star ionizing and compressing the rim of the cloud, and the wind from the young stars shifting gas from the center outward lead to very high compression in the Elephant's Trunk Nebula. This pressure has triggered the current generation of protostars.{{cite journal| last = Barentsen| first = G| title = T Tauri candidates and accretion rates using IPHAS: method and application to IC1396| journal = Monthly Notices of the Royal Astronomical Society| year = 2011| bibcode = 2011MNRAS.415..103B

| doi=10.1111/j.1365-2966.2011.18674.x| arxiv=1103.1646| volume=415| issue = 1| pages=103–32| doi-access = free| s2cid = 27173042}}{{cite journal|last1=Getman|first1 = KV |last2=Feigelson |first2= ED |last3=Sicilia-Aguilar|first3=A |last4=Broos|first4=PS|last5=Kuhn|first5=MA |last6=Garmire |first6=GP| title = The Elephant Trunk Nebula and the Trumpler 37 cluster: contribution of triggered star formation to the total population of an H II region| journal = Monthly Notices of the Royal Astronomical Society| year = 2012| volume= 426| issue=4| pages= 2917–43| bibcode = 2012MNRAS.426.2917G| doi=10.1111/j.1365-2966.2012.21879.x|doi-access = free | arxiv= 1208.1471| s2cid = 49528100}}