Measuring Distances

Keep your distance!

Hello, do you know what? This should have been the first post that I should have written but I just found out now. Sorry about that. Hopefully you will be able to catch up.

Measuring Distances

When measuring stuff in Astronomy, the numbers are big, not up to hundred but up to millions, to there's other words used. So the Astronomical Units, for example, are used. 1 Astronomical unit is equal to 150 million km, which is the distance of Earth from the Sun.

But obviously there are other galaxies, so the distance beyond our solar system are given in light years. Where 1 light year is the distance light travel in one year.
•Light travels 300,000 km/s .

• One year has roughly 365.25 days and each day has 24 hours of 3600 seconds
So in one year, light travels
365.25 x 24 x 3600 x 300000 km = 9.46 x 10^12 km

Radar

Radar signals are used to measure a distance of an object in our solar system, so when a radar signal is sent it travels there and bounces off the surface of the planet and comes back to Earth.
Radio Waves travel in the speed of light, so distance = speed of light x time taken / 2.

Heliocentric parallax

Obviously beyond the solar system distance are more difficult to work out, so people use the Heliocentric parallax method.

More than me blowing my mind out trying to explain the Heliocentric parallax, you will better off and less confused looking at the pictures below:



•The position of a star is measured against more distant stars. Six months later the position is measured again, when the Earth is on the other side of its orbit.

You can measure the distance of a star using this equation:
d = 1 / p .

d is Distance, and p is the parallax angle of a arcsec.

Arcsec...yes..i know, Parallax angles are measured in arcseconds (arcsec) where one arcsec = 1 / 3600th of a degree.

•The heliocentric parallax angles of all stars are less than one arcsec because they are so far away.

•This method works out to a distance of 500 pc – beyond this the parallax angles are too small to measure accurately

That's all for today..
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Simplicity is the ultimate sophistication. Leonardo DA Vinci