Digital Universe Guide - Hayden Planetarium

3.2. MILKY WAY ATLAS TUTORIAL 47
Notice that these intrinsically bright stars lie mostly along the band of the Milky Way. Also, some of
the brighter stars in the sky are missing, including Sirius, the brightest star in the sky.
Dim Stars Far Outnumber Bright Stars in the Galaxy Now let’s look at the intrinsically dim stars
using the
see faint
command. Here we show those stars with 0 < MV < 10, and you may notice that most of the stars in
the sky fall into this category. There are many more intrinsically dim stars in the Galaxy than bright stars.
Next let’s explore stellar distances and see how well astronomers have determined the positions of
the stars.
Tutorial: Stellar Distances
Goals: Explore the nearby stars and investigate their parallax values and uncertainties.
Before starting, turn on: stars, mwVis
You will be using: thresh command
In this tutorial, you will learn about stellar distances and parallax. Let’s begin at Earth looking toward
Orion (press the Home Button if necessary).
Seeing Only the Nearest Stars First tell Partiview that you want to see only those stars within
25 light-years of the Sun (make sure stars is the active data group). Do this by using the thresh
command on the data variable distly:
thresh distly 0 25
This removes all stars outside this range (their labels remain, though, an oversight in Partiview).
Partiview reports that there are 103 stars in this range.
Let’s see how this looks from outside the solar neighborhood. Pull away from the Sun to see all of
these stars. Turn off the constellations and the visible Milky Way (mwVis). You may need to brighten the
stars with the Slum Slider. You can see that Sirius, Procyon, and Altair dominate the scene.
Let’s expand our scope and increase the limit to 100 light-years using