Astronomy Year 1 Notes
written by Wren Munro
My notes from Astronomy Year 1 to help anyone struggling with the class.
For any further questions, feel free to message me as I'm always happy to help
Last Updated
05/31/21
Chapters
12
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2,383
Mercury
Chapter 3
- Mercury is the closest planet to The Sun
- Is named after to Roman God of Thievery, Commerce and Travel.
- Mercury is so close to the sun that it is visible during both sunrises and sunsets.
- Originally, astronomers believed this to be two different planets, but Greek Astronomers found this to be false and that the two planets were really just different alignments of the same body.
Mercury in Depth
Mercury is a rocky planet, covered in large craters and pulverised dust. It has no atmosphere to moderate day/night changes in solar heating and therefore has wild temperature swings. These temperature can range from 90-700 Kelvin. Mercury is a geologically dead planet.
In 1974, The Mariner 10 approached within a mere 10,000km of the planets surface, sending back thousands of images that essentially revolutionised our knowledge of this planet. Thanks to another mission in 2008 we now have an even greater knowledge with higher quality images. These images have proven there is no sign of clouds, rivers, dust storms or any form of weather at all. Much of the surface is similar to that of Earth's moon.
The fact that Mercury has any magnetic field at all came as a big surprise, and it is 1/100th that of Earth's. Although small, it is strong enough to deflect solar wind and create a small magnetosphere around the planet
Without being able to use seismographs on the surface, we can infer that most of its interior must be dominated by a large, heavy, iron-rich core with a radius of around 1800 Kilometers. A less-dense lunar-like mantle lies above this core, to a depth of only around 500-600 kilometers. This means that only around 40% of the volume of Mercury (60% of its mass) is contained inside its iron core.
Spin Right Around
In the mid-19th century, an Italian astronomer named Giovanni Schiaparelli used a telescope to discern surface features on Mercury. And in doing so, he used those features to measure its rotation rate simply by watching the motion of a particular region around the planet. He concluded that Mercury always keeps one side facing the Sun, much as our Moon presents only one face to the Earth. The belief that Mercury rotates synchronously with its revolution about the Sun (i.e. once every 88 Earth days) persisted for almost half a century. However, in 1965, Muggle Astronomers making observations of Mercury from a radio telescope in Puerto Rico discovered that this long-held view was in error.
They found that the rotation period of Mercury is not 88 days, as had previously been thought, but only 59 days, exactly two-thirds of the planet’s orbital period. This means that the planet rotates three times when it has completed two orbits around the Sun.
