Mercury (planet)
 Mercury |
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| Orbital characteristics[1] Epoch J2000 |
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| Aphelion | 69,816,900 km 0.466 697 AU |
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| Perihelion | 46,001,200 km 0.307 499 AU |
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| Semi-major axis | 57,909,100 km 0.387 098 AU |
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| Eccentricity | 0.205 630[2] | |||||||||
| Orbital period | 87.969 1 d (0.240 846 a) |
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| Synodic period | 115.88 d[2] | |||||||||
| Average orbital speed | 47.87 km/s[2] | |||||||||
| Mean anomaly | 174.796° | |||||||||
| Inclination | 7.005° to Ecliptic 3.38° to Sun’s equator 6.34° to Invariable plane[3] |
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| Longitude of ascending node | 48.331° | |||||||||
| Argument of perihelion | 29.124° | |||||||||
| Satellites | None | |||||||||
| Physical characteristics | ||||||||||
| Mean radius | 2,439.7 ± 1.0 km[4][5] 0.3829 Earths |
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| Flattening | < 0.0006[5] | |||||||||
| Surface area | 7.48×107 km² 0.147 Earths[4] |
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| Volume | 6.083×1010 km³ 0.054 Earths[4] |
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| Mass | 3.3022×1023 kg 0.055 Earths[4] |
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| Mean density | 5.427 g/cm³[4] | |||||||||
| Equatorial surface gravity | 3.7 m/s² 0.38 g[4] |
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| Escape velocity | 4.25 km/s[4] | |||||||||
| Sidereal rotation period | 58.646 day 1407.5 h[4] |
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| Rotation velocity at equator | 10.892 km/h (3.026 m/s) | |||||||||
| Axial tilt | 2.11′ ± 0.1′[6] | |||||||||
| Right ascension of North pole | 18 h 44 min 2 s 281.01°[2] |
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| Declination of North pole | 61.45°[2] | |||||||||
| Albedo | 0.119 (bond) |
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| Surface temperature: 0°N, 0°W 85°N, 0°W |
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| Apparent magnitude | up to −1.9[2] | |||||||||
| Angular size | 4.5" – 13"[2] | |||||||||
| Adjectives | Mercurian, Mercurial[7] | |||||||||
| Atmosphere | ||||||||||
| Surface pressure | trace | |||||||||
| Composition | 42% Molecular oxygen 29.0% sodium 22.0% hydrogen 6.0% helium 0.5% potassium Trace amounts of argon, nitrogen, carbon dioxide, water vapor, xenon, krypton, & neon[2] |
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Mercury is the smallest planet in the Solar System.[8] It is the closest planet to the sun.[9] It makes one trip around the Sun once every 87.969 days.[2][10] Mercury is bright when it is able to be seen from Earth, ranging from −2.0 to 5.5 in apparent magnitude, but is not easily seen as it is usually too close to the Sun. Since Mercury is normally lost in the glare of the Sun, unless there is a solar eclipse, Mercury can only be seen in the morning or evening twilight.[11]
Compared to what is known about the other planets in the Solar System, little is known about Mercury; telescopes on the Earth show only a small, bright crescent. The first of two spacecraft to visit the planet was Mariner 10,[12] which mapped only about 45% of the planet’s surface from 1974 to 1975. The second is the MESSENGER spacecraft, which mapped another 30% during its trip to Mercury on January 14, 2008. MESSENGER made one more pass by Mercury in 2009, and is now orbiting the planet to complete the mapping.
Mercury looks a lot like our Moon: it has many craters with areas of smooth plains, no moons around it and no atmosphere. Mercury does have what is known as an exosphere.[9] However, unlike the moon, it has a large iron core, which gives off a magnetic field about 1% as strong as that of the Earth.[13] It is a very dense planet due to the large size of its core. Surface temperatures can be anywhere from about 90 to 700 K (−183 °C to 427 °C, −297 °F to 801 °F),[14] with the subsolar point being the hottest and the bottoms of craters near the poles being the coldest.
Known sightings of Mercury date back to at least the first millennium BC. Before the 4th century BC, Greek astronomers thought that Mercury was two different objects: one able to be seen only at sunrise, which they called Apollo; the other that was only able to be seen at sunset, which they called Hermes.[15] The English name for the planet is from the Romans, who named it after the Roman god Mercury, which they thought to be the same as the Greek god Hermes. The symbol for Mercury is based on Hermes' staff.[16]
Even though Mercury is the closest planet to the Sun, it is not the warmest. This is because it has no atmosphere, so any heat that the Sun gives to it quickly escapes into space.[17]
Contents |
[change] Inside Mercury
Mercury is one of four inner planets in the Solar System, and has a rocky body like the Earth. It is the smallest planet in the Solar System, with a radius of 2,439.7 km.[2] Mercury is even smaller, though it has a greater mass, than the largest moons in our Solar System. Mercury is made of about 70% metallic and 30% silicate material.[18] Mercury's density is the second highest in the Solar System at 5.427 g/cm³, only a little bit less than Earth’s.[2]
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[change] Other websites
[change] References
- ↑ Yeomans, Donald K. (April 7, 2008). "HORIZONS System". NASA JPL. http://ssd.jpl.nasa.gov/?horizons. Retrieved 2008-04-07.
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 "Mercury Fact Sheet". NASA Goddard Space Flight Center. November 30, 2007. http://nssdc.gsfc.nasa.gov/planetary/factsheet/mercuryfact.html. Retrieved 2008-05-28.
- ↑ "The MeanPlane (Invariable plane) of the Solar System passing through the barycenter". 2009-04-03. http://home.comcast.net/~kpheider/MeanPlane.gif. Retrieved 2009-04-03. (produced with Solex 10 written by Aldo Vitagliano; see also Invariable plane)
- ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 Munsell, Kirk; Smith, Harman; Harvey, Samantha (May 28, 2009). "Mercury: Facts & Figures". Solar System Exploration. NASA. http://solarsystem.nasa.gov/planets/profile.cfm?Object=Mercury&Display=Facts. Retrieved 2008-04-07.
- ↑ 5.0 5.1 Seidelmann, P. Kenneth; Archinal, B. A.; A’hearn, M. F.; et al. (2007). "Report of the IAU/IAGWorking Group on cartographic coordinates and rotational elements: 2006". Celestial Mechanics and Dynamical Astronomy 90: 155–180. doi:10.1007/s10569-007-9072-y. http://adsabs.harvard.edu/doi/10.1007/s10569-007-9072-y. Retrieved 2007-08-28.
- ↑ Margot, L.J.; Peale, S. J.; Jurgens, R. F.; Slade, M. A.; Holin, I. V. (2007). "Large Longitude Libration of Mercury Reveals a Molten Core". Science 316: 710–714. doi:10.1126/science.1140514. PMID 17478713. http://adsabs.harvard.edu/abs/2007Sci...316..710M.
- ↑ "mercurial". Merriam-Webster Online. http://www.merriam-webster.com/dictionary/mercurial. Retrieved 2008-06-12.
- ↑ Pluto was once thought to be the smallest, but, as of 2008, Pluto is now known as a dwarf planet.
- ↑ 9.0 9.1 Murchie, Scott L.; Vervack Jr., Ronald J.; Anderson, Brian J. (March 2011), "Space Science: Journey to the Innermost Planet", Scientific American (New York) 304 (3): 26-31
- ↑ [1]
- ↑ How it Works Book of Space. Imagine Publishing. 2010. p. 36-37. ISBN 9781906078829.
- ↑ [2]
- ↑ "Mercury magnetic field". C. T. Russell & J. G. Luhmann. http://www-spc.igpp.ucla.edu/personnel/russell/papers/merc_mag/. Retrieved 2007-03-16.
- ↑ "Background Science". European Space Agency. http://sci.esa.int/science-e/www/category/index.cfm?fcategoryid=4586. Retrieved 2008-05-23.
- ↑ Dunne, J. A. and Burgess, E. (1978). "Chapter One". The Voyage of Mariner 10 — Mission to Venus and Mercury. NASA History Office. http://history.nasa.gov/SP-424/ch1.htm.
- ↑ Duncan, John Charles (1946). Astronomy: A Textbook. Harper & Brothers. pp. 125. "The symbol for Mercury represents the Caduceus, a wand with two serpents twined around it, which was carried by the messenger of the gods."
- ↑ "CBBC Newsround". British Broadcasting Corporation. http://www.bbc.co.uk/newsround/14143062. Retrieved February 04, 2012.
- ↑ Strom, Strom, Robert G.; Sprague, Ann L. (2003). Exploring Mercury: The Iron Planet. p. 52. ISBN 1852337311.
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The Solar System |
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|---|---|---|---|---|---|---|---|
 |
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| Sun • Heliosphere |
Planets ☾ = moon(s) ∅ = rings |
Mercury | Venus | Earth ☾ | Mars ☾ | ||
| Jupiter ☾ ∅ | Saturn ☾ ∅ | Uranus ☾ ∅ | Neptune ☾ ∅ | ||||
| Dwarf planets | Ceres | Pluto ☾ | Haumea ☾ | Makemake | |||
| Eris ☾ | |||||||
| Small Solar System bodies |
Asteroids (minor planets) |
Groups and families: Vulcanoids · Near-Earth asteroids · Asteroid belt Jupiter Trojans · Centaurs · Neptune Trojans · Asteroid moons · Meteoroids · Pallas · Juno · Vesta · Hygiea · |
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| See also the list of asteroids. | |||||||
| Trans- Neptunians |
Kuiper belt – Plutinos: Orcus · Ixion – Cubewanos: Varuna · Quaoar · Huya |
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| Scattered disc: Sedna | |||||||
| Comets | Periodic comets and non-periodic comets Damocloids · Oort cloud |
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| See also the list of solar system objects | |||||||
