Universe Flashcards
Light year comparison with mile
The 20th century astronomer Robert Burnham Jr. – author of Burnham’s Celestial Handbook – devised an ingenious way to portray the distance of one light-year. He did this by relating the light-year to the astronomical unit – the Earth-sun distance.
One astronomical unit equals about 150 million kilometers (93 million miles). Another way of looking at it: the astronomical unit is a bit more than 8 light-minutes in distance.
Quite by coincidence, the number of astronomical units in one light-year and the number of inches in one mile are virtually the same. For general reference, there are 63,000 astronomical units in one light-year, and 63,000 inches in one mile. This wonderful coincidence enables us to bring the light-year down to Earth. If we scale the astronomical unit – the Earth-sun distance – at one inch, then the light-year on this scale represents one mile.
Object distances in light-years
The closest star to Earth, other than the sun, is Alpha Centauri at some 4.4 light-years away. Scaling the Earth-sun distance (astronomical unit, AU) at one inch places this star at 4.4 miles (7 kilometers) distant.
Scaling the astronomical unit (93 million miles, 150 million kilometres, 8.3 light-minutes) at one inch, here are distances to various stars, star clusters and galaxies:
Alpha Centauri: 4 miles
Sirius: 9 miles
Vega: 25 miles
Fomalhaut: 25 miles
Arcturus: 37 miles
Antares: 600 miles
Pleiades open star cluster: 440 miles
Hercules globular star cluster (M13): 24,000 miles
Center of Milky Way galaxy: 27,000 miles
Great Andromeda galaxy (M31): 2,300,000 miles
Whirlpool galaxy (M51): 37,000,000 miles
Sombrero galaxy (M104): 65,000,000 miles
the edge of the observable universe is about 46.5 billion light years
Sun + Moon distances
The moon is about 1.3 light-seconds away, 240,000 miles.
The sun is 8 minutes and 18 seconds, 93 million miles, 150 million kilometres
Speed of light
Light is the fastest-moving stuff in the universe. It travels at an incredible 300,000 kilometers (186,000 miles) per second. That’s very fast. If you could travel at the speed of light, you would be able to circle the Earth’s equator about 7.5 times in just one second!
How many stars in our galaxy
200 billion - various estimates
How many galaxies in observable universe
1 trillion. 10 x power 12, 1 with 12 zeros 1,000,000,000,000
Most recent reports say a few hundred billion so less than trillion…?
How many stars within 10 light year sphere of our sun ?
12, most are dim dwarf stars
What is size of sun if AU (astronomical unit, 93 million mile) is 1 inch ?
Approx the size ofa poppy seed
Poppy seed is 0.02 inch, 20 thousands on an inch, so ratio of 1 to 50.
Actual answer is 1 to 93. Sun diameter is approx 1 million miles (864,576 miles). So closer to half a poppy seed .01 inch 10 thousands of an inch, guitar top E string
How many stars in observable universe ?
Kornreich used a very rough estimate of 10 trillion galaxies in the universe. Multiplying that by the Milky Way’s estimated 100 billion stars results in a large number indeed: 1,000,000,000,000,000,000,000,000 stars, or a “1” with 24 zeros after it.
