2006-09-19 09:59:21 · 6 answers · asked by entropy 3 in Science & Mathematics ➔ Astronomy & Space
If the sphere is 8 parsecs in DIAMETER, then there would be none ( other than our Sun ) since the closest star (Proxima Centauri) is 4.22 light years away, which is .22 light years outside of the sphere.
If the sphere has a RADIUS of 8 parsecs, then I'd refer to answer #3.
:)
2006-09-19 10:48:33 · answer #1 · answered by Anonymous · 1⤊ 2⤋
On statistics alone:
Nearest star is 4.3 lt yrs. Parsec is 3.12.
So, just let's say there are two stars (sun and Alpha Centauri) in every sphere that is 2 parsec wide.
An 8 parsec sphere (I assume you are talking 8 parsec diameter and not radius) is 4x4x4 times as voluminous as a 2 parsec sphere.
So, statisically, there should be about 128 stars in an 8 parsec sphere around the sun.
Allowing for error, probably anywhere from 60 to 200, which falls in line with the previous answers.
2006-09-19 10:48:20 · answer #2 · answered by nick s 6 · 1⤊ 0⤋
The stellar density is approximately 1 star per cubic parsec in this part of the galaxy (maybe it is 0.5; I don't recall exactly.) Many of these stars are too faint to be detected from Earth, even at distances of 4 parsecs, so you cannot rely upon high parallax star surveys and be sure you have caught them all (that is why you don't see any M9 and too few M8 stars in catalogues like the Gliese high parallax catalogue. A main sequence M9 star will have an absolute magnitude in the neighborhood of 15-16. At 4 pc distance this will be an apparent visual magnitude of 12. There is no complete parallax survey down to this magnitude!) A simple volume calculation times average stellar density is more reliable. The density number itself comes from the galactic mass to light ratio, an estimate of the mass of molecular and atomic gas in the galaxy and a stellar mass distribution function extrapolated to the lower masses.
I would estimate 180 stars +/- 50in a 4 parsec radius sphere in the solar neighborhood.
(to a prior answerer a parsec is ~ 3.27 times longer than a ly)
2006-09-19 15:12:05 · answer #3 · answered by Mr. Quark 5 · 0⤊ 0⤋
You're getting some really poor answers here. There are 188 stars within 8 parsecs of earth.
http://nstars.nau.edu/nau_nstars/multi_search_result.php
2006-09-19 10:30:36 · answer #4 · answered by Jack D 2 · 1⤊ 0⤋
There are 63 stars (including our sun) that are within 16.3 Light-years (5 parsecs)
2006-09-19 10:05:18 · answer #5 · answered by HungryHunter 3 · 1⤊ 1⤋
One. Our sun.
2006-09-19 10:05:08 · answer #6 · answered by Jonathon M 1 · 0⤊ 2⤋