The photosphere (visible surface) of the Sun has an average diameter 863,704 miles(1.39 million kilometers), which is equal to a little over 109 earths placed side by side. The parts of the Sun above the photosphere are referred to collectively as the solar atmosphere. They comprise five principal zones: the temperature minimum, the chromosphere, the transition region, the corona, and the heliosphere. The heliosphere, which may be considered the tenuous outer atmosphere of the Sun, extends outward past the orbit of Pluto to the heliopause, where it forms a sharp shock front boundary with the interstellar medium. In December 2004, the Voyager 1 probe passed through a shock front that is thought to be part of the heliopause.

The core of the Sun, estimated at 1/10th the diameter of the photosphere is at a temperature of close to 13.6 million K (24.5 Million F / 13.6 million C). The surface of the photosphere of the Sun is approximately 5,500 K (9,400 F / 5,200 C). The coolest layer of the Sun is a temperature minimum region about 500 km above the photosphere, with a temperature of about 4,000 K (6,700 F / 3,700 C). This part of the Sun is cool enough to support simple molecules such as carbon monoxide and water, which can be detected by their absorption spectra. Above the temperature minimum layer is a thin layer about 2,000 km thick, called the chromosphere. The temperature in the chromosphere increases gradually with altitude, ranging up to around 100,000 K (179,000 F / 99,000 C) near the top. Above the chromosphere is a transition region in which the temperature rises rapidly from around 100,000 K to coronal temperatures closer to one million K. The temperature of the corona is several million kelvin.

The Hubble Telescope has provided evidence that there are about one hundred and seventy five billion galaxies in the observable universe. Despite the prominence of large elliptical and spiral galaxies, most galaxies in the universe appear to be dwarf galaxies. Typical galaxies range from dwarfs with as few as ten million stars up to giants with one trillion stars, all orbiting a common center of mass. The Milky Way contains about two hundred billion stars. Observational data suggests that supermassive black holes may exist at the center of many, if not all, galaxies. The Milky Way galaxy, home of Earth and the solar system, appears to harbor at least one such object within its nucleus.

Contrary to popular belief, the Great Wall of China is not the only man made object on earth that is visible from space; in fact, the Great Wall is barely discernable, and only under perfect conditions. Low earth orbit(160-350 miles up) is the altitude that the space shuttle orbits at. At this "low" level of orbit, many man made objects are viewable to the naked eye, including airports, bridges, dams, and highways. The Wall is only 30 feet wide, and is of a similar color to its surroundings. The myth that "the Great Wall is the only man-made object visible from the moon" started in 1938 when the book "Second Book of Marvels, the Orient" was published, stating that "Astronomers say that the Great Wall is the only man-made thing on our planet visible to the human eye from the moon." Something that is almost invisible at 180 miles certainly isn't visible at 237,000 miles.

A meteoroid is particle floating in outer space that has a size ranging between a grain of sand and large boulder 10-50 meters across. Once a meteoroid enters the earth's atmosphere and becomes visible, it is considered a meteor. Most meteors burn up before they reach the ground. The remains of a meteor that impacts the earth, if it is not vaporized by the impact, is called a meteorite. Anything larger than a meteoroid is considered an asteroid.