７ Solar System【What is the Universe？】Dialogue with the Universe
・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.
・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.