Handy Astronomical Facts

Useful for outreach volunteers or anyone teaching astronomy. All figures are approximate and designed with the NYC public in mind, in terms of analogies and units. Please add as many things as you like.

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Solar System

Saturn​1 ​2

• 30 year orbit, on average 900 million miles from the Sun
  
• 10 hour rotation
  
• about 10 times Earth's diameter
  
• you could pack about 500 Earths inside Saturn (hard to find the exact number--look up sphere packing and enter a world of pain)
  
• has at least 61 moons
  
• average density is below that of liquid water
  
• composed of 96% Hydrogen, 3% Helium
  
• upper atmosphere temperature is -290 deg F
  
• the rings span 175,000 miles, 3/4 the Earth-Moon distance
  
• the rings are made of water ice particles ranging size from microns to cars
  
• the rings were probably formed in the early Solar System from the remains of a destroyed moon
  
• the rings have a complex structure of gaps and subdivisions created by gravitational interaction with Saturn's moons and moonlets
  

Titan​1 ​2

• slight less than half the diameter of Earth, and slightly bigger than Mercury
  
• 16 day orbit around Saturn
  
• a dense atmosphere composed of 98% Nitrogen, with an orange smog made of organic compounds, that may partially resemble that of early Earth
  
• air pressure at the surface is 1.5 times that on Earth -- like being at the bottom of a swimming pool
  
• surface temperature is -290 F
  
• has Methane versions of rain, snow, seas, rivers, and lakes
  
• like on Earth, geological activity is driven by radioactive heat from the core
  
• has "cryovolcanoes" -- volcanoes that spew ammonia and water instead of magma
  

Stars

There are six trillion miles in a light year.

If the Earth's orbit around the Sun were shrunk down to the size of a quarter, a light year would extend about 10 short city blocks. In other words, a light year in this scale is 0.5 miles. Now you can make comparisons between the distances to the bright stars in our sky:

star		dist. (lyr)
Altair		17
Deneb		1400
Vega		25
Pollux		34
Castor		50
Capella		42
Aldebaran		65
Betelgeuse		600
Rigel		800
Sirius		9
Arcturus		37
Mizar		78
Polaris		430