Wednesday, December 12, 2012
Monday, December 10, 2012
Sunday, December 09, 2012
Thursday, November 15, 2012
Tuesday, November 13, 2012
The Earth
The Earth is certainly the most familiar planet, though it has only been a few hundred years since we fully realized it was a planet. We begin our study of objects in the Solar System with the Earth because it is interesting in its own right, and it provides a test of many observing techniques that we wish to use for other objects in the Solar System. |
The Earth is, at least by human standards, a beautiful planet, as the following images indicate.
Wednesday, November 07, 2012
Image Planet Venus
Planet Venus
Venus in true - color. The surface is obscured by a thick blanket of clouds.
The surface of Venus
Saturday, November 03, 2012
10 Things You Should Know About Mercury
1. Mercury is the closest planet to the Sun
Mercury
speeds around the Sun in a wildly elliptical (non-circular) orbit that
takes it as close as 47 million km and as far as 70 million km from the
Sun. The planet completes a trip around the Sun every 88 days, speeding
through space at nearly 50 km per second, faster than any other planet.
2. Mercury's existence has been known of since before the third century BC
The Greeks gave it two names, Apollo for when it appeared as a morning star and Hermes when it came as an evening star.
3. Mercury's surface very much resembles Earth's Moon
Mercury
is scarred by thousands of impact craters resulting from collisions
with meteors. While there are areas of smooth terrain, there are also
cliffs, some soaring up to a mile high, formed by ancient impacts.
4. Mercury has a large iron core which is most likely at least partially molten
Mercury's
interior is made of a large iron core with a radius of 1,800 to 1,900
km, nearly 75 percent of the planet's diameter and nearly the size of
Earth's Moon. Mercury's outer shell, comparable to Earth's outer shell
(called the mantle) is only 500 to 600 km thick.
5. Mercury actually has a very thin atmosphere
6. Mercury is a planet of extremes
Temperature
variations swing from 90 K to 700 K. It's hotter on Venus, but with
less fluctuations. Mercuryalso has a very eccentric orbit; at perihelion
it is only 46 million km from the Sun but at aphelion it is 70 million.
7. Mercury has no known moons or satellites
While Mercury may resemble our own moon in many ways, it has no moon of its own.8. Until 1965, scientists thought that the same side always faced the Sun
In 1965, astronomers discovered that Mercury completes three rotations for every two orbits around the Sun. If you wanted to stay up for a Mercury day, you'd have to stay up for 176 Earth days.9. The Caloris Basin is about 1,300 km in diameter
One of the largest features on Mercury, it was the result of an asteroid impact on the planet's surface early in the solar system's history. Over the next 1/2-billion years, Mercury actually shrank in radius from 2 to 4 km as the planet cooled from its formation. The outer crust, called the lithosphere, was compressed and grew strong enough to prevent the planet's magma from reaching the surface, effectively ending the planet's period of geologic activity.10. Mercury is the least explored of our solar system's inner planets.
Only one spacecraft has ever visited Mercury: Mariner 10 in 1974-75. Mariner 10's discovery that Mercury has a very weak magnetic field, similar to but weaker than Earth's, was a major surprise. NASA is planning a new mission to Mercury called Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER), which will orbit Mercury toward the end of this decade. MESSENGER will investigate key science questions using a set of miniaturized instruments.Information Mercury
Named after the Roman god of commerce, travel and thievery, Mercury is the closest planet to the Sun and the eighth largest. Mercury's existence has been known of since before the third century BC. The Greeks gave it two names, Apollo for when it appeared as a morning star and Hermes when it came as an evening star.
Mercury has a large iron core which is most likely at least partially molten. The silicate outer shell is only 500 to 600 km thick. It actually has a very thin atmosphere made up of atoms blasted off its surface by the solar wind. Due to the heat of the planet, these atoms quickly escape into space. Thus unlike the Earth and Venus which have stable atmospheres, Mercury's atmosphere is constantly being replenished.Mercury is a planet of extremes. Temperature variations swing from 90 K to 700 K. It's hotter on Venus, but with less fluctuations. Mercury also has a very eccentric orbit; at perihelion it is only 46 million km from the Sun but at aphelion it is 70 million.
Mercury has no known moons or satellites.
Mercury orbits
closest to the Sun of all the planets, and is the smallest. Mercury's
diameter is 4,879 km (3,032 mi), and its volume and mass are about
one-eighteenth that of Earth. Discover more information about Mercury,
including pictures.
Mercury is so close to the Sun, it is hard to directly observe from
Earth, except during twilight. Mercury makes an appearance indirectly,
however 13 times each century, Earth observers can watch Mercury pass
across the face of the Sun, an event called a transit. These rare
transits fall within several days of May 8 and November 10. The first
two transits of Mercury in the 21st century oc…
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