Messier 72
Template:Short description Template:Infobox globular cluster Template:Sister project
Messier 72 (also known as M72 or NGC 6981) is a globular cluster in the south west of the very mildly southern constellation of Aquarius.
Observational history and guideEdit
M72 was discovered by astronomer Pierre Méchain in 1780.Template:Efn His countryman Charles Messier looked for it 36 days later, and included it in his catalog.<ref name=garfinckle1997/> Both opted for the then-dominant of the competing terms for such objects, considering it a faint nebula rather than a cluster. With a larger instrument, astronomer John Herschel called it a bright "cluster of stars of a round figure". Astronomer Harlow Shapley noted a similarity to Messier 4 and 12.<ref name=burnham1978/>
It is visible in a good night sky as a faint nebula in a telescope with a Template:Convert aperture. The surrounding field stars become visible from a Template:Convert-aperture device. One of Template:Convert will allow measurement of an angular diameter of 2.5 [[arcminutes|Template:Prime]]. At Template:Convert the core is clear: its 1.25 [[arcminutes|Template:Prime]] diameter, meaning a broad spread; and small parts scarcer in stars to the south and east.<ref name=luginbuhl_skiff1998/>
PropertiesEdit
Based upon a 2011 census of variable stars, the cluster is Template:Convert away from the Sun.<ref name=rmaa40_235/> It has an estimated combined mass of 168,000<ref name=apj742_1_51/> solar masses (Template:Solar mass) and is around 9.5 billion years old. The core region has a density of stars that is radiating 2.26 times solar luminosity (Template:Lo) per cubic parsec.<ref name=aaa481_3_701/> There are 43 identified variable stars in the cluster.<ref name=rmaa40_235/>
Image GalleryEdit
- A glittering cluster shines again (potw2516a).jpg
M72 imaged by the Hubble Space Telescope
See alsoEdit
References and footnotesEdit
Template:Reflist Template:Notelist
External linksEdit
- Messier 72, SEDS Messier pages
- Messier 72, Galactic Globular Clusters Database page
- Messier 72, LRGB CCD image based on two hours total exposure
- M-72 Information
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Template:Sky Template:Portal bar Template:Catalogs Template:Messier objects Template:Ngc70 Template:Aquarius (constellation)