Hun Kal (crater) explained
Hun Kal is a small (about 1.5 km in diameter) crater on Mercury that serves as the reference point for the planet's system of longitude. The longitude of Hun Kal's center is defined as being 20° W, thus establishing the planet's prime meridian.[1] The name "Hun Kal" means '20' in the language of the Maya.
Hun Kal was chosen as a reference point since the actual prime meridian was in shadow when Mariner 10 photographed the region, hiding any features near 0° longitude from view.
The prime meridian of Mercury is thermocentric, it runs through the point on the equator where the planet is hottest (due to the planet's rotation and orbit, the sun briefly retrogrades at noon at this point during perihelion, giving it more sun).[2] [3] [4]
The large crater in which Hun Kal lies is not named. To the northwest is Al-Jāhiz crater, and to the west is Lu Hsun crater.
Notes and References
- Web site: USGS Astrogeology: Rotation and pole position for the Sun and planets (IAU WGCCRE). 22 October 2009. https://web.archive.org/web/20111024101856/http://astrogeology.usgs.gov/Projects/WGCCRE/constants/iau2000_table1.html. 24 October 2011. dead.
- Davies, M. E., "Surface Coordinates and Cartography of Mercury," Journal of Geophysical Research, Vol. 80, No. 17, June 10, 1975.
- Archinal . Brent A. . 4 . A'Hearn . Michael F. . Bowell . Edward L. . Conrad . Albert R. . Consolmagno . Guy J. . Courtin . Régis . Fukushima . Toshio . Hestroffer . Daniel . Hilton . James L. . Krasinsky . George A. . Neumann . Gregory A. . Oberst . Jürgen . Seidelmann . P. Kenneth . Stooke . Philip J. . Tholen . David J. . Thomas . Peter C. . Williams . Iwan P. . Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2009 . Celestial Mechanics and Dynamical Astronomy . 109 . 2 . 2010 . 101–135 . 0923-2958 . 10.1007/s10569-010-9320-4 . 2011CeMDA.109..101A. 189842666 .
- Web site: USGS Astrogeology: Rotation and pole position for the Sun and planets (IAU WGCCRE) . October 22, 2009 . https://web.archive.org/web/20111024101856/http://astrogeology.usgs.gov/Projects/WGCCRE/constants/iau2000_table1.html . October 24, 2011 . dead.
