Thoughts
19
Earlier I have
mentioned how because of the human intellect we have to set up
standards (reference frames) to try to understand our world, society
or anything. This week I want to show some comparisons; reference
frames that will borrow from others. I am fat weighing 275 pounds.
Comparing my size to a new born of 7 pounds, I am large. Compare my
size to the size of the Earth and I am small. I seem to be getting
fatter and fatter but I do not believe I will be anything but small
if I am compared to the Earth.
I have found
illustrations that will show and tell the sizes of the planets and
the distances involved in the solar system.
How Distances are Measured in Astronomy
Dealing with the numbers involved with the distances to the stars or even with those found in the solar system can be hard going. Astronomers make their lives easier by using a number of rulers (units of distance) for the distances and although they have some strange names they can be very useful for comparing the distances to stars, other galaxies and even the planets in our solar system.AU (astronomical units)
One AU is the distance that the average distance that the Earth orbits the Sun at. The AUis most commonly used for the distances of objects with in our solar system. Pluto, the last planet in the solar system is found at an average distance of 39.47 au from the Sun. Sedna the new body nearly as large as a planet found beyond Pluto is never nearer to the Sun than 76AU and then goes to 880AU from the Sun in its giant elliptical orbit.Light Years
One of the most common rulers is the light year. The light year is is the distance that light travel in one year (365 1/4 days). It is most commonly used for the distances to stars and other galaxies.The nearest star is 4.2 light years away from our sun. We are 8.3 light minutes away form the Sun. the distance to the outer most planet Pluto is about 13 light hours.
Some other interesting distances in light years:
|
Object |
Distance in light years |
|
Nearest Star (Proxima Centuri) |
4.2 |
|
Sirius the dog star (the brightest star in the sky) |
8.6 |
|
centre of the galaxy |
approximately 30 000 |
|
Andromeda (one of our nearest neighbouring galaxies) |
approximately 2 million |
|
The stars of Orion. (Betelgeuse and Rigel) |
1400 light years |
Parsec (pc)
Astronomers
started measuring distances from the amount that a star moves as the
Earth goes from one side of the Sun to the other. Try moving your
head and you will see that the postion of everything around you
changes. One parsec is derived from the smallest angle measurement of
1/3,600th of a degree or an arc second that is the angle that a star
at this distance would appear to move in 6 months as the Earth
journeys around the Sun. A parsec is 3.2616 light years or
30,857,000,000,000 km.. Two parsecs is 6.5532 light years or twice
the distance, it is not a measure of change in angles of the stars.
Due to the massive distance in the universe astronomers often use
multiples of parsec commonly found are kiloparsec (kpc) a 1000
parsecs or a megaparsec (Mpc) 1,000,000 parsecs.
|
|
kilometres (km) |
Astronomical units (AU) |
Light Years (l.y.) |
Parsec (pc) |
|
kilometres (km) |
1 |
149.6 million |
9,460,000,000,000 |
30,857,000,000,000 |
|
Astronomical units (AU) |
0.0000000067 |
1 |
63,240 |
206,263 |
|
Light Years (l.y.) |
0.00000000000011 |
0.000016 |
1 |
3.2616 |
|
Parsec (pc) |
0.000000000000033 |
0.0000048 |
0.3066 |
1 |
*
Planet Radius Radius Object ideal ideal
(Jupiter=1) circumference diameter
Jupiter 68,700 km 1.000 basketball 73.5
cm 23.4 cm
Saturn 57,550 km 0.838 soccer ball 61.5
cm 19.6 cm
Uranus 25,050 km 0.365 softball 26.8 cm 8.52 cm
Neptune 24,700 km 0.360 softball 26.4
cm 8.40 cm
Earth 6,378 km 0.093 large marble 6.81
cm 2.17 cm
Moon 1,738 km 0.025 tiny bead 1.86 cm 5.91 mm
Venus 6,050 km 0.088 large marble 6.47
cm 2.06 cm
Mars 3,394 km 0.049 small marble 3.61
cm 1.15 cm
Mercury 2,440 km 0.036 small bead 2.60
cm 8.30 mm
Pluto 1,700 km 0.025 tiny bead 1.81 cm 5.78 mm
Charon 750 km 0.011 tiny bead 0.80 cm 2.55 mm
The chart is arranged in order of
decreasing size, with the only exception being the moon given right
after the Earth. **
The reason for all the data is preparing
for the next post. I hope you weren't too bored this time.
Pictures are from google and duckduckgo
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