What is the size of the Solar System?
What is the diameter of our solar system and how many times would our solar system fit between us and the nearest star?
Defining the size of the Solar System is a hard thing to do because it does not have a clear boundary. I will answer the question by calculating it two ways. First, using the orbit of Pluto as the boundary, and second using the orbit of the farthest comets we know.
1 - Orbit of Pluto To calculate this we will use the orbit of Pluto as the limit of the solar system. A problem is that the orbit of Pluto is not circular, it is rather an ellipse. All the planets orbit the Sun on ellipses. For most of the planets the ellipses are almost circles, but not for Pluto. This means that the distance from Pluto to the Sun varies quite a bit. In fact, at some time,s it is closer to the Sun than Neptune! So we will take the average distance between the Sun and Pluto as the radius of the Solar System (which is 5,913,520,000 km, or 39.5 AU, where AU stands for Astronomical Unit)
2 - Orbit of comets Beyond the orbit of Pluto, there are object that orbit the Sun. These are the comets. Two populations of comets have been identified: the Kuiper Belt and the Oort Cloud. The Oort Cloud has a larger radius, estimated at about 50,000 AU (or 7.5x10^12 km). As you can see, comets are found much farther from the Sun than any of the planets!
Now the nearest star to the Sun is Proxima Centauri which is located at a distance of 4.3 light years (one light year is the distance traveled by light in one year). Now, 1 light year is 63,270 AU, which means that the distance to the nearest star is 272,061 AU.
We took the radius of the solar system to be 39.5 AU, which means it has a diameter of 79 AU. This means you could put the Solar System about 3440 times between the Sun and the nearest star taking this definition.
If you include all the comets like we did in the second part, then the Solar System has a diameter of about 100,000 AU, which means it would fit 2.7 times between the Sun and the nearest star.
Get More 'Curious?' with Our New PODCAST:
- Podcast? Subscribe? Tell me about the Ask an Astronomer Podcast
- Subscribe to our Podcast | Listen to our current Episode
- Cool! But I can't now. Send me a quick reminder now for later.
How to ask a question:
If you have a follow-up question concerning the above subject, submit it here. If you have a question about another area of astronomy, find the topic you're interested in from the archive on our site menu, or go here for help.
This page has been accessed 86565 times since November 5, 2002.
Last modified: October 18, 2005 7:34:04 PM
Ask an Astronomer is hosted by the Astronomy Department at Cornell University and is produced with PHP and MySQL.
Warning: Your browser is misbehaving! This page might look ugly. (Details)