Beyond Our Solar System

Our sun is one of at least 100 billion stars in the Milky Way, a spiral galaxy about 100,000 light years across. The stars are arranged in a pinwheel pattern with four major arms, and we live about two-thirds of the way up one of them. Many if not most of the stars host their own families of planets. More than a thousand of these extrasolar (or exoplanets) have been discovered and thousands more are awaiting confirmation. Continue reading

Hypothetical ‘Planet X

Caltech researchers have found evidence suggesting there may be a “Planet X” deep in the solar system. This hypothetical Neptune-sized planet orbits our sun in a highly elongated orbit far beyond Pluto. The object, which the researchers have nicknamed “Planet Nine,” could have a mass about 10 times that of Earth and orbit about 20 times farther from the sun on average than Neptune. It may take between 10,000 and 20,000 Earth years to make one full orbit around the sun.  Continue reading


In the distant past, people were both awed and alarmed by comets, perceiving them as long-haired stars that appeared in the sky unannounced and unpredictably. Chinese astronomers kept extensive records for centuries, including illustrations of characteristic types of comet tails, times of cometary appearances and disappearances, and celestial positions. These historic comet annals have proven to be a valuable resource for later astronomers. Continue reading