Lyceum B - Astronomy - Week 20 - Mercury
- Apr 7, 2022
- 3 min read
The four planets closet to the Sun (the inner planets - Mercury, Venus, Earth and Mars) are called the terrestrial planets. “Terra” coming from the Latin word “terra” which means earth, because these four planets are solid and have a rock based surface, which breaks down into an earthy substance.
The planet closet to the Sun is Mercury. Mercury is the second smallest planet in the Solar System (Pluto is the smallest).
Because Mercury is so close to the Sun and so small, it travels around the Sun at a very fast pace - 1 orbit every 88 days. But it rotates on its axis at a very, very slow pace so that a day on Mercury lasts longer than its year.
From How the Universe Works:
During the 19th century, astronomers discovered that the oval orbit of Mercury is gradually swinging around in space. This perplexed astronomers until 1915, when Albert Einstein devised a new theory of gravity called the General Theory of Relativity. Einstein’s theory predicted this motion for a planet so close to the Sun’s strong gravity. Mercury helped prove that Einstein’s theory was correct.
Mercury does not have any air. Because it doesn’t have an atmosphere, it gets much hotter in the daytime (up to 840°F) than any place on Earth and it gets colder in the night time (as ow as -275°F) than any place on Earth. Our atmosphere protects us from the harmful rays of the Sun so it acts as a buffer to Earth heating up too much. It also traps in the heat from the Sun, so that when our side of the Earth is facing away from the heat of the Sun, our atmosphere retains enough warmth to hold us over until the Sun once again warms up our atmosphere.
The surface of Mercury is totally covered in craters and wrinkles from getting bombarded with space debris, like meteorites and rocks.
Mercury has a large core made of iron, which generates a magnetic field.
The unmanned space probe Mariner 10 visited Mercury in 1974 and 1975 and sent back pictures, but it only covered about 45% of the surface.
Fromsolarsystem.nasa.gov
NASA’s MESSENGER spacecraft orbited Mercury for more than four years. Among its accomplishments, the mission determined Mercury’s surface composition, revealed its geological history, discovered details about its internal magnetic field, and verified its polar deposits are dominantly water-ice. The mission ended when MESSENGER slammed into Mercury’s surface.
Aug. 3, 2004 - Launch
Mar. 11, 2011 - MESSENGER finally entered orbit around Mercury nearly seven years after launch
Apr. 30, 2015 - MESSENGER plunged into Mercury at the end of its mission.
Pictured below is a diagram of Mercury’s interior (Figure below). Mercury is one of the densest planets. Scientists think that the interior contains a large core made mostly of melted iron. The inner core may be solid. Mercury’s core takes up about 85% of the planet’s radius.
From Ducksters.com:
Interesting Facts about the Planet Mercury. Mercury has a huge crater called the Caloris Basin. The impact that caused this crater was so huge that it formed hills on the other side of the planet! The element mercury was named after the planet. Alchemists once thought they could make gold from Mercury. The planet is named after the Roman god Mercury. Mercury was the messenger to the gods and the god of travelers and merchants. Mercury orbits the Sun faster than any other planets. Early Greek astronomers thought it was two planets. They called the one they saw at sunrise Apollo and the one they saw at sunset Hermes. It has the most eccentric (least round) orbit of all the planets.
-----------------------------------------
Videos
Professor Dave Explains:
History of Astronomy Part 1: The Celestial Sphere and Early Observations - 11:38 min
Crash Course Astronomy #10 - The Sun - 12:03 min
Comments