Astronomical Adventures

The Location of the Solar System in the Milky Way Galaxy

Did you ever wonder where in the galaxy we are? Our sun Sol is just one of more than a couple hundred billion stars that make up our home galaxy: the Milky Way. Our home lies within the disk of the Milky Way. It's the disk where most of the galaxy's gas and dust is located. As a result this is where most new stars are being born. Just as the Earth has an equator, so too does the galaxy and we are about 14 light years above what's called the equatorial symmetry plane. As to the thickness of the disk, most current estimates put it at around 1,000 light years thick. Obviously our solar system lies very close to the galaxy's equator.

Location of Solar System in Milky Way Galaxy Figure 1. Polar view of the Milky Way Galaxy showing the location of the Solar System.

As to our distance from the center of the galaxy, the best guess is that we are 26,000 to 28,000 light years from the center. The estimates vary due to uncertainty in the exact size of the galaxy and the time it takes the solar system to complete one orbit of our galaxy. The yellow circle in the picture shows the orbital path of our solar system as it travels around the center of the Milky Way. The red dot, located just above the 'r' in the 'arm' associated with the Orion Arm shows our current location on this path.

You're next question may well be 'how long does it take the solar system to complete one orbit of the galaxy?' We all know that it takes the Earth one year to orbit the Sun. The time it takes our solar system to complete one orbit of the galaxy is referred to as the galactic year. Values for the galactic year vary between 200 and 250 million Earth years. That the values differ by 50 million Earth years is due to uncertainty in the values we have for the speed with which the solar system moves relative to the galaxy's center and the estimates for the value of the radius of our orbit.


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