Bob Raymond, age 12,of Lansing, Michigan, and to Hunt, age 12, of Waynesboro, Tennessee for their question:
How do they measure star distances?
Sometimes the bright stars seem to hang just above the tree tops but the nearest star to sun, we are told, is abou4G 27 million million miles away, No one knew for sure that the stars were so very far away until 1838 when the first star was measured for distance. Even without powerful instruments it is a hard job to measure the distance of a sear, all the millions of stars in the Milky Way only a few thousands have bean measured for distance,
The stars, of course, are scattered near and far with vast distances between them. Their fixed patterns do not seem to change, though we know that they are all pinwheeling around the Galaxy at fantastic speeds. Meantime one earth is orbiting the sun and wheeling with the Solar System. This heavenly hoedown makes it very difficult to pinpoint a distant star and to measure its distance from us.
All job is done with a giant triangle. The base of this triangle is 2,900,000 miles long and each side reaches to the star which is being measured. Where they meet the star the lines form an angle. Now when you know this angle and the triangle’s base inn, it is a simple matter to figure out the length of a side and the Length of one side of the heavenly triangle is the distance from the earth to the star.
Our little world is only about 24,000 miles around its middle. So how do we draw a base line more than 92 million miles 1ong? We wait for this world of ours to revolve around the sun. A telescope is used to photograph the star against its background of stars. Six months later the earth will have made half an orbit around the sun and will be about 1.35 million miles away from where we started. More pictures are taken of our star.
As the earth orbits, the stars shift their positions. A nearer star makes a tiny circle against the background of distant star. You see this happen on a small scale when you look at a house through the tree trunks. As you step this way or that, the trunks hide first one park and then another part of the house. The two sets of star pictures ate checked to see how our star has shifted against its background of more distant stars. This gives an angle called the parallax at the top of a giant triangle, The base line is the distance of the earth from the sun, and with these items the astronomer can figure the lane which runs from the sun to our star.
A square corner is a right angle of 0 degrees. Imagine the corner is at the center of a circle and the two sides t•aach to the rim of the circle. The distance, between them is 90 equal degrees. No star has a parallax of 90, ten or even five degrees. The nearest stars are so far away that the parallax is just a fraction of one degree,