For an overview of astronomy by the great Carl Sagan, this video from the original Cosmos series might be a good starting point. (It's a bit dated, but so are many classics.)

Inventory of the Universe

Our Cosmic Address

Useful astronomical distance scales

Example

Light Time
Approximate Distance

~Earth-Moon

1.2 seconds
384,000 km

~Sun-Mercury

3 minutes
54,000,000 km

Sun to Earth (1 AU)

8.3 minutes
149,600,000 km

~1.5 x Sun-Jupiter Distance

1 hour
6.7 AU

Sun-Pluto distance

5 hours
40 AU

Voyager-1 (April, 2001)

11 hours
80 AU

Light-year

1 year
63,000 AU

Proxima Centauri

4 years
253,000 AU
Betelgeuse

470 years

30 million AU

Most naked-eye stars
Several thousand years
~100 million AU

Size of Milky Way

100,000 years
6 billion AU
Andromeda Galaxy

2.2 million years

140 billion AU

 

Speed and distance

  • A jet moves about 1 million times slower than light; a rocket moves about 27 thousand times slower.
  • At rocket speed, it would take about 100,000 years for us to travel to the nearest star (Proxima Centauri).

 

Destination
Jet
(600 mi/hr=0.9
μc)
Rocket
(25,000 mi/hr=37
μc)
Sunbeam
(186,000 mi/sec)
Moon
16.5 days
9.4 hr
1.2 sec
Sun
17 years 8 months
4 months
8.3 min
Mercury
10 years 10 months
3 months
5 min
Venus
5 years 5 months
1.5 months
2.5 min
Mars
8 years 10 months
2.5 months
4 min
Jupiter
74 years 3 months
1 year 9 months
35 min
Saturn
150 years 5 months
3 years 7 months
1 hr 11 min
Uranus
318 years 6 months
7 years 7 months
2 hr 30 min
Pluto
690 years 1 month
16 years 5 months
5 hr 25 min
Alpha Centauri
4.8 million years
114,155.2 years
4.2 years
Sirius
9.6 million years
228,310.4 years
8.4 years
Center of Milky Way
30 million years
800,000 years
38,000 years
Andromeda Galaxy
2 trillion years
50 billion years
2.2 million years

Measuring distance

Several techniques have been developed to measure cosmic distance, and different techniques must be used on different scales. This is the brief version. For more details, visit this wikipedia article.

method not effective beyond this distance
radar ranging 1 AU
stellar parallax 1000 light-years
spectroscopic parallax 50,000 light-years
variable stars 100 million light-years

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