Jeff Ragan’s Reviews > The Star Guide: Learn How To Read the Night Sky Star by Star > Status Update

"Only Ceres, Pallas, Vesta and a few other asteroids are roughly spherical in shape. The others are irregular-shaped lumps, looking rather like huge potatoes. From the way they reflect light, asteroids appear to be of three main kinds. Some are made up mainly of rock, some mainly of metal and others a mixture of the two" (154).

"The four terrestrial (Earth-like) planets have only three moons between them, compared with more than 130 for the four gas, giant planets" (150).

"Mars has an atmosphere like Earth, though it is very much thinner, with only about one-hundredth the pressure of Earth's atmosphere, and the main gas present is carbon dioxide" (144).

"...all lunar rocks...[are] volcanic" (134).

"Maria cover the best part of the near side of the Moon, but are strangely absent on the far side. Largest by far is the sprawling Oceanus Procellarum, the Ocean of Storms. It merges in the north with the largest circular mare, Mare Imbrium, the Sea of Showers" (126).

"Compared with Earth, the Moon is a small body. Its diameter is only 2,160 miles (3,476 km), or about a quarter the size of Earth. This is actually extraordinarily large for a satellite in relation to the size of its parent planet. This is why astronomers sometimes consider Earth-Moon to be a double planetary system" (122).

"...the Sun...lies on average about 93 million miles (150 million km) away from Earth, a distance known as the astronomical unit (AU). As stars go, it is relatively small, with a diameter of about 865,000 miles (1,390,000 km). It gives off a yellowish light. Astronomers classify it as a yellow dwarf" (118).

"Aldebaran, Alpha (a) Tauri, is easy to find because it is in line with the three stars that make up Orion's Belt - and the Pleiades lies farther away along the same line" (114).

"The Andromeda Galaxy, M31, is one of the foremost objects in the whole night sky. It is a spiral galaxy, like our own in structure, but much bigger. With a diameter of around 150,000 light years, it measures half as big again as our own Galaxy and could contain as many as 400 billion stars. It is the largest galaxy by far in our local galaxy cluster...of about 30 galaxies" (108).