Our Solar System resides roughly 27,000 light-years away from the Galactic Center, on the inner edge of one of the spiral-shaped concentrations of gas and dust particles called the Orion Arm.
It would be like trying to take a picture of your own house from the inside.
This means that any of the beautiful pictures you’ve ever seen of a spiral galaxy that is supposedly the Milky Way is either a picture of another spiral galaxy, or the rendering of a talented artist.
Most larger galaxies have a supermassive black hole (SMBH) at the center, and the Milky Way is no exception.
The center of our galaxy is called Sagittarius A*, a massive source of radio waves that is believed to be a black hole that measures 22,5 million kilometers (14 million miles) across – about the size of Mercury’s orbit. All of the mass trying to get into the black hole – called the accretion disk – forms a disk that has 4.6 million times the mass of our Sun and would fit inside the orbit of the Earth.
That means that all of the “luminous matter” – i.e.
that which we can see with the naked eye or a telescopes – makes up less than 10% of the mass of the Milky Way.The Milky Way has between 100-400 billion stars; but when you look up into the night sky, the most you can see from any one point on the globe is about 2,500.This number is not fixed, however, because the Milky Way is constantly losing stars through supernovae, and producing new ones all the time (about seven per year).Hence, the rest of that mass must be made up of an elusive, invisible mass – aka.“dark matter” – or matter that only interacts gravitationally with “normal matter”.The tugging creates a sort of oscillating frequency that pulls on the galaxy’s hydrogen gas, of which the Milky Way has lots of (for more information, check out How the Milky Way got its Warp).Scientists believe that 90% of our galaxy’s mass consists of dark matter, which gives it a mysterious halo.The Milky Way Galaxy is an immense and very interesting place.Not only does it measure some 120,000–180,000 light-years in diameter, it is home to planet Earth, the birthplace of humanity.Our galaxy is roughly 100,000 light years across, and we can only see about 6,000 light years into the disk in the visible spectrum.Still, when light pollution is not significant, the dusty ring of the Milky Way can be discerned in the night sky.