As of 2010, the closest known black hole to Earth is V4641 Sgr. According to Tega Jessa of Universe Today, V4641 Sgr is located in the Sagittarius arm of the Milky Way galaxy and was first discovered in 1999. This black hole is 1600 light years from Earth.Know More
Black holes are the last stage in a star's life cycle, forming when a star collapses under the weight of its own gravity, explains Jessa. They are discovered using radio telescopes, which detect radioactive emissions from matter that falls into them.
Based on Einstein's theory of general relativity, objects can fall or be pulled into a black hole, but they can never reappear. Because black holes are basically invisible, scientists rely on the observation of matter surrounding the possible location of a black hole.Learn more about Stellar Astronomy
Far from being a galaxy, Orion is the name of a nebula approximately 1,500 light-years from Earth. In the Earth's night sky, the nebula is just visible as part of the "belt" of the constellation of Orion.Full Answer >
The majority of stars are much larger than the Earth. Even the Sun, which is a relatively average star, is many times the size of the Earth. The largest star is 1,800 times as large as the Sun.Full Answer >
The brightest star visible from Earth is Sirius, located in the Canis Major constellation. There are many very bright stars in the night sky that are visible from Earth, and as the moon makes its orbit it does pass near or in front of several of these.Full Answer >
The solar constant is calculated by multiplying the sun's surface irradiance by the square of the radius of the sun over the average distance between the Earth and the sun. Irradiance is sometimes referred to as flux and is a measurement of electromagnetic energy from the sun.Full Answer >