AST 1002: Study Guide Figure 9b.

AST 1002: "Study Guide" Figure 9b

[Sections Taught by Prof. H.L. Cohen]
Site Map • Prof. Cohen • Department of Astronomy • University of Florida

Last updated January 15, 2003

Home
Page Course
Information Study
Guide Chaisson
Textbook Other
Resources Alachua
Astron. Club Undergrad.
AstroPhy. Soc.

Examples Figures Other Outlines PowerPt Tables

Fig. 9b Fig. 13b Fig. 23 Fig. 24 Fig. 25 Fig.26a Fig.26b Fig. 27 Fig. 28 Fig. 29 Fig. 30

Figure 9b. Stellar Parallaxes: Some Results

Early Parallaxes

First successful parallax: Almost simultaneously:	61 Cygni Vega (Alpha Lyrae) Alpha Centauri	(F. Bessel, 1838) (F. Struve) (T. Henderson)	p = 0.29" (3.4 pc or 11 ly) p = 0.13" (7.7 pc or 25 ly) p = 0.75" (1.3 pc or 4 ly) (largest known)
Click here to see Alpha Centauri distance scaled onto map of Florida! (This picture was shown in class.)

A Few Parallax Stats (most parallaxes very small):

The 20 first magnitude stars
p = 0.25" ( 1/4") or larger
p = 0.10" (1/10") or larger
p = 0.05" (1/20") or larger

(i.e., d = 4 pc = 12 ly)
(i.e., d = 10 pc = 30 ly)

  0.005" to 0.76" (for Alpha Centauri)—notice large range
  about 25 stars (only 3 bright looking: Sirius, Alpha Cen, Procyon)
  about 300 stars
  about 1000 stars

Accuracy of Parallaxes (see figure below):

Prior to 1990 (10,000 stars measured): As of 1996: (Hipparcos Satellite)	"Reliable" (p over 0.05") "Reliable" (p over 0.005")	1,000 stars 126,000 stars	(d within 20 pc or 60 ly) (d within 200 pc or 600 ly)
(Seems like many but note that there are about one million stars visible in binoculars!)

The Naked Eye Stars
- The figure below (shown in class) displays the distance range for most naked eye stars (some examples shown)
- Note that most naked eye stars lie within about 1,000 pc (3,000 ly)!
  (Many are within 250 pc or 750 ly)
The Solar Neighborhood
- We live in a huge "galaxy" of stars, The Milky Way Galaxy (often called "The Galaxy")
- We don't know what the Milky Way Galaxy looks like because we live inside it!
- We think it may resemble a galaxy like M74, a large flattened, spiral galaxy in the constellation of Pisces
- Click here to see the location of the Sun assuming our galaxy is like M74. (This picture was shown in class.)
- Click here to see a schematic diagram of our Milky Way Galaxy showing the "solar neighborhood."
  (This picture was shown in class.)

Recommended web browser to view this site is Netscape Navigator 4.0 (or above) with video display supporting at least 256 colors.
High color (16 bit) or true color (24 bit) display is preferred.

For comments and suggestions contact Howard L. Cohen at cohen@astro.ufl.edu
About this site (department disclaimer and recommended web browser)
© Copyright 1999-2003 Howard L. Cohen