Mercury
| 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's core is made of molten metal, much like the Earth's, but with a thick layer of ferric oxide on the outside, resulting in its vivid and beautiful color. This layer is believed to have increased steadily over the past 6,000 years, resulting in the planet we now know today, but would originally have been very thin and easily cracked. It is only because of Mercury's extreme proximity to the sun, scientists believe, that it was not broken up by asteroids long ago. [3]
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. [4]
The precession of Mercury's eccentric orbit was detectable to 19th century astronomers.[5][6]
Mercury is one of the five brightest planets, and has been known since ancient times.
In the pre-Christian era, this planet actually had two names, as it was not realized it could alternately appear on one side of the Sun and then the other. Mercury was called Mercury when in the evening sky, but was known as Apollo when it appeared in the morning. It is said that Pythagoras, about the fifth century B.C., pointed out that they were one and the same.[2]
Orbital oddities
It was the study of this planet's orbit that Albert Einstein used to help confirm the General Theory of Relativity.[7][8] Specifically, Mercury's perihelion precesses by 5600 arc-seconds per century, which is 43 arc-seconds per century more than Newtonian physics alone would predict from the respective masses of Mercury, the Sun, and the other planets. Astronomers of the period hypthesized either an asteroid belt or another planet (which they named Vulcan) inside Mercury's orbit. Einstein's second-order correction to Mercury's orbit accounted exactly for the 43 arc-seconds of precession and obviated the need to look for any unseen asteroids or innermost planet.[9][5][6]
Mercury has more or less no atmosphere, and many craters. [10] 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.[11][12]
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]
- ↑ 2.0 2.1 Seeing Mercury at sunset, April 2003
- ↑ Fulbright, Jeannie. Exploring Creation with Astronomy. Apologia Educational Ministries, 2004.
- ↑ [2]
- ↑ 5.0 5.1 Wudka, Jose. "Precession of the perihelion of Mercury." September 24, 1998. Accessed April 17, 2008.
- ↑ 6.0 6.1 "Mercury: Mercury in tests of relativity." In "Mercury," Encyclopædia Britannica, 2008. Encyclopædia Britannica Online. 17 April 2008
- ↑ Testing general relativity European Space Agency Accessed July 16 2007
- ↑ Albert Einstein Fizički odsjek Accessed July 16 2007
- ↑ Hartnett, John. Starlight, Time, and the New Physics. Creation Book Publishers, 2007, pp. 34-36. ISBN 9780949906687.
- ↑ John Gribbin, Companion to the Cosmos (Little, Brown & Company, 1996)
- ↑ Psarris, Spike, Our Solar System: Evidence for Design, Seattle Creation Conference, 2006.
- ↑ Franco, Lucia M. "Lecture 10.1: Mercury." Astronomy 100 at Indiana University Northwest, Indiana University, 1996. Accessed April 17, 2008.
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