CG 4
{{for|the American military glider of World War II|Waco CG-4}}{{for|the bok globule located in the Carina Nebula|Finger of God Globule}}
{{Short description|Star-forming region in the Puppis constellation}}
{{Infobox nebula
|name = CG 4
|image = CG 4 by ESO.jpg
|caption = Image of CG 4 taken by the European Southern Observatory's Very Large Telescope.
|type = Bok globule
|epoch = J2000
|ra = {{RA|07|34|09.0}}{{cite simbad |title=[DB2002b] G259.43-12.72 |accessdate=November 14, 2016}}
|dist_ly = 1,300
|dist_pc = 400
|constellation = Puppis
|dimensions = {{convert|1.5|xx|8|ly|pc|abbr=on}}
|names = {{nowrap|BHR 21}}, {{nowrap|DCld 259.4-12.7}}, {{nowrap|FEST 2-30}}, {{nowrap|Sandqvist 103}}
}}
CG 4, commonly referred to as God's Hand,{{cite news |url=http://www.sci-news.com/astronomy/science-gods-hand-cometary-globule-cg4-02441.html |title=God's Hand: Astronomers Capture Cometary Globule CG4 |work=Sci-News |date=January 28, 2015 |accessdate=January 31, 2015}} is a star-forming region located in the Puppis constellation, about {{convert|1300|ly|pc}} from Earth.{{cite web |url=https://www.noao.edu/image_gallery/html/im1000.html |title=Cometary Globule CG4 |publisher=National Optical Astronomy Observatory |accessdate=January 31, 2015 |archive-date=February 1, 2015 |archive-url=https://web.archive.org/web/20150201221444/http://www.noao.edu/image_gallery/html/im1000.html |url-status=dead }} It is one of several objects referred to as "cometary globules", because its shape is similar to that of a comet. It has a dense head formed of gas and dust, which is around {{convert|1.5|ly|pc|abbr=on}} in diameter, and an elongated faint tail around {{convert|8|ly|pc|abbr=on}} in length.
{{nowrap|CG 4}}, and the nearby cometary globules, generally point away from the Vela Supernova Remnant, located at the center of the Gum Nebula.{{cite news |url=http://www.seeker.com/staring-into-the-maw-of-a-mysterious-cosmic-globule-1769469476.html |title=Staring into the Maw of a Mysterious Cosmic Globule |work=Seeker |date=January 28, 2015 |accessdate=January 31, 2015}}
Discovery
In 1976, photographs from the UK Schmidt Telescope—operated by the Australian Astronomical Observatory—showed several objects resembling comets, located in the Gum Nebula, an emission nebula of the constellation. Due to their particular shape, these objects came to be known as cometary globules. Each globule has a dense, dark, ruptured head and a very long tail, with the latter pointing away from the Vela Supernova Remnant. As a part of the ESO Cosmic Gems program, the European Southern Observatory released an image of {{nowrap|CG 4}} in January 2015 showing the head of the nebula.{{cite web |url=http://www.eso.org/public/news/eso1503/ |title=The Mouth of the Beast: VLT images cometary globule CG4 |publisher=European Southern Observatory |date=January 28, 2015 |accessdate=January 31, 2015}}
Structure
The head of cometary globule {{nowrap|CG 4}} resembles a comet with a dusty cavernous mouth, as photographed by the European Southern Observatory's Very Large Telescope in 2015.{{cite web |url=https://www.noao.edu/outreach/press/pr06/pr0607.html#images |title=Image of Cometary Globule Marks 1,000 Online at NOAO |publisher=National Optical Astronomy Observatory |date=March 8, 2006 |accessdate=January 31, 2015 |archive-date=March 3, 2016 |archive-url=https://web.archive.org/web/20160303211621/http://www.noao.edu/outreach/press/pr06/pr0607.html#images |url-status=dead }} Composed of relatively dense, dark matter, it is an opaque structure that is being illuminated by the glow of a nearby star.{{cite news |url=https://www.cnet.com/news/mysterious-nebula-revealed-in-new-image-mouth-of-the-beast/ |title=Mysterious nebula revealed in new image: 'Mouth of the Beast' |work=CNET |first=Michelle |last=Starr |date=January 28, 2015 |accessdate=January 31, 2015}} An obscure red glow limbing the globule is possibly caused by emission from ionized hydrogen. The mouth of the globule appears to be ready to consume the edge-on spiral galaxy {{nowrap|ESO 257-19}}. In reality, the galaxy is over a hundred million light-years further away from the globule.