Difference between revisions of "Mercury"
(The ancient Greeks & Romans saw Mercury without benefit of telescopes) |
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:''For information about the NASA project, see [[Project Mercury]].'' | :''For information about the NASA project, see [[Project Mercury]].'' | ||
| − | [[Mercury]] is the smallest planet in the [[Solar System]], and it is the closest to the [[Sun]]. It orbits the [[Sun]] in 88 (Earth) days. It rotates on its axis every 58.6 days,<ref>"The theory that Mercury is in [[synchronous rotation]] with its orbital motion was shattered in 1965. Astronomers Gordon Pettengill and Rolf Dyce used a radio telescope to make radar observations of Mercury’s spin rate. They found that Mercury’s rotation period is only 58.6 Earth days, not the 88 days accepted for nearly a century." [http://btc.montana.edu/messenger/elusive_planet/modern_times.htm]</ref> which is 3 rotations for every two orbits (called "3:2 resonance"). It can be seen from [[Earth]] only at sunrise and sunset. It is named for the Roman messenger god who was known as [[Hermes]] in Greek. | + | [[Mercury]] is the smallest planet in the [[Solar System]], and it is the closest to the [[Sun]]. It orbits the [[Sun]] in 88 (Earth) days. It rotates on its axis every 58.6 days,<ref>"The theory that Mercury is in [[synchronous rotation]] with its orbital motion was shattered in 1965. Astronomers Gordon Pettengill and Rolf Dyce used a radio telescope to make radar observations of Mercury’s spin rate. They found that Mercury’s rotation period is only 58.6 Earth days, not the 88 days accepted for nearly a century." [http://btc.montana.edu/messenger/elusive_planet/modern_times.htm]</ref> which is 3 rotations for every two orbits (called "3:2 resonance"). It can be seen from [[Earth]] only at sunrise and sunset.<ref>[http://www.space.com/spacewatch/mercury_view_030404.html Seeing Mercury at sunset], April 2003</ref> |
| + | It is named for the Roman messenger god who was known as [[Hermes]] in Greek. | ||
{{quotebox|Mercury has a very elliptical orbit. At its farthest distance from the Sun, it is nearly 50% farther than at its nearest distance to the Sun. <ref> [http://astroprofspage.com/archives/139 ] </ref> }} | {{quotebox|Mercury has a very elliptical orbit. At its farthest distance from the Sun, it is nearly 50% farther than at its nearest distance to the Sun. <ref> [http://astroprofspage.com/archives/139 ] </ref> }} | ||
Revision as of 12:27, April 17, 2008
| Mercury | |
|---|---|
 Reprocessed Mariner 10 data was used to produce this image of Mercury. The smooth band is an area of which no images were taken. | |
| Name of discoverer | Known to ancients |
| Name origin | Roman messenger god and prince of thieves |
| Orbital characteristics | |
| Primary | Sun |
| Order from primary | 1 |
| Perihelion | 46,000,000 km (0.307 AU) |
| Aphelion | 70,000,000 km (0.468 AU) |
| Semi-major axis | 57,909,175 km (0.387 AU) |
| Titius-Bode prediction | 0.4 AU |
| Orbital eccentricity | 0.20563069 |
| Sidereal year | 87.96934 da (0.241 a) |
| Synodic year | 115.8776 da (0.317 a) |
| Avg. orbital speed | 47.36 km/s |
| Inclination | 7.00487° to the ecliptic |
| Rotational characteristics | |
| Sidereal day | 58.6462 da |
| Solar day | 175.93868 da |
| Axial tilt | 0° |
| Physical characteristics | |
| Mass | 3.30 * 1023 kg (5.522% earth) |
| Density | 5427 kg/m³ |
| Mean radius | 2439.7 km |
| Surface gravity | 2.78 m/s² (0.283 g) |
| Escape speed | 4.25 km/s |
| Surface area | 75,000,000 km² (14.704% earth) |
| Minimum temperature | 90 K |
| Mean temperature | 452 K |
| Maximum temperature | 700 K |
| Number of moons | None known |
| Composition | Iron, Silicate |
| Color | Reddish |
- This article is about the planet Mercury. For information about the chemical element, Mercury see Mercury (element).
- For information about the NASA project, see Project Mercury.
Mercury is the smallest planet in the Solar System, and it is the closest to the Sun. It orbits the Sun in 88 (Earth) days. It rotates on its axis every 58.6 days,[1] which is 3 rotations for every two orbits (called "3:2 resonance"). It can be seen from Earth only at sunrise and sunset.[2] It is named for the Roman messenger god who was known as Hermes in Greek.
Mercury has a very elliptical orbit. At its farthest distance from the Sun, it is nearly 50% farther than at its nearest distance to the Sun. [3]
Orbital oddities
It was the study of this planet's orbit that Albert Einstein used to help confirm the theory of General Relativity.[4][5]
Mercury has more or less no atmosphere, and many craters. [6] It has no known moons.
Magnetic Field
A curiosity of the planet is its magnetic field, which is about 1% that of Earth's. Scientists were perplexed to discover its existence, speculating that planet's outer core consisted of liquid iron. However, because it is relatively small and hot, such an outer core would long ago have expired. That Mercury is so intensely cratered would also suggest that Mercury should long ago have given up its magnetic field because of its extreme apparent age.
Thus, according to current scientific understandings, the existence of Mercury's magnetic field presents a serious theoretical problem for uniformitarian models of the creation of the Solar System.[Who says?]
Gallery
Mariner 10's first image of Mercury acquired on March 24, 1974
MESSENGER's first flyby of Mercury showing previously unseen surface, January 14, 2008
Notes
- ↑ "The theory that Mercury is in synchronous rotation with its orbital motion was shattered in 1965. Astronomers Gordon Pettengill and Rolf Dyce used a radio telescope to make radar observations of Mercury’s spin rate. They found that Mercury’s rotation period is only 58.6 Earth days, not the 88 days accepted for nearly a century." [1]
- ↑ Seeing Mercury at sunset, April 2003
- ↑ [2]
- ↑ Testing general relativity European Space Agency Accessed July 16 2007
- ↑ Albert Einstein Fizički odsjek Accessed July 16 2007
- ↑ John Gribbin, Companion to the Cosmos (Little, Brown & Company, 1996)
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