・The solar system is considered to be located about 25,000 〜28,000 light years away from the center of the Milky Way(100,000 light years in diameter).
• There are 200 billion stars in the Milky Way galaxy.
• The solar system is orbiting in the galaxy at a speed of 220km / s, for about one orbiting of the galaxy about 226 million years.
・Revolution speed of the Earth is 30km per second.
・The brightness of the sun was only about 70% of the current in 4.6 billion years ago when the solar system was born, that has been increasing the brightness gradually thereafter.
・The sun continues to increase the brightness at a rate of 1% in about 100 million years now.