Our place in the Galaxy
(courtesy Mexborough & Swinton AS)
Where we are in the galaxy
The Galactic centre is some 26,000 light years away from the Sol system, in the direction of the constellation Sagittarius. The centre comprises of a super massive black hole, and it is also estimated that there are upwards of a ten million stars within a few parsecs of this central black hole. This quantity of stars is believed to have formed within the last million years or so from a massive in fall of gas and dust being swept up by the central black hole. This black hole is estimated of having a mass in excess of 4 billion solar masses!
The Orion arm is a minor spiral arm of our galaxy which contains the Sun and solar system, it is a branch of the Perseus Arm and is thought to be 10,000 light years in length. Within the arm, the Solar System is close to its inner rim, in a relative cavity in the arm's Interstellar Medium known as the Local Bubble.
The local Bubble is a cavity in the interstellar medium. It is at least 300 light years across and is defined by its neutral-hydrogen density which is approximately one tenth of the average for the Milky Way.
The exceptionally sparse matter, namely gas, of the Local Bubble is the result of supernovae that exploded within the past ten to twenty million years and remains in an excited state, emitting in the X-ray band. It has been suggested that multiple supernovae in the Pleiades moving group are likely responsible.
The Solar System has been travelling through the region currently occupied by the Local Bubble for the last five to ten million years.
