Imagine the Universe!
Imagine Home  |   Ask an Astrophysicist  |  
Ask an Astrophysicist

The Question

(Submitted January 23, 1998)

Could you please give me an estimate of the amount of stars located within 100 light years from earth?

The Answer

As a function of distance, the Gliese star catalog lists the following number of stars. A parsec is 3.26 light years.

Distance Number Density

Distance from Sun in parsecsnumber of starsstars/cubic parsec
5630.120
10
3280.078
1510080.071
2021270.063
2534960.053

http://www.stellarium.com/nearstar/nearby.html

The fall-off in density is probably due to the fact that many stars are too faint to be cataloged at a distance more than 5 parsecs. (At still larger distances, the density of stars does vary as you move outside of the local spiral arm of our galaxy and into the less-populated regions above and below the disk.)

Using the 0.120 stars/cubic parsec number, and using a volume for a distance 100 light-years = 100/3.26 = 30.7 parsecs

Number = density * volume
	= 0.120 stars/cubic parsec  * 4/3 pi (30.7 parsecs)^3
	= 14,600 stars

Most of these stars are completely unknown.

David Palmer
for Ask an Astrophysicist

Previous question
Prev
Main topic
Main
Next question
Next

If words seem to be missing from the articles, please read this.

Imagine the Universe! is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center.

The Imagine Team
Project Leader: Dr. Barbara Mattson
Curator: J.D. Myers
Responsible NASA Official: Phil Newman
All material on this site has been created and updated between 1997-2014.
This page last updated: Thursday, 01-Dec-2005 13:58:39 EST