Several times each week, I receive e-mails and phone calls from “StarGazing” readers who have a question or an interest in some things that deal with the stars or other stellar objects.
I thought other readers may also have questions but haven’ asked them yet. If anyone has a question I can try to answer please e-mail me at email@example.com. I’ll be more than anxious to hear from you.
Here we go with the questions:
Q. Why does the Full Moon look so large when it is rising and much smaller when it is high in the sky?
A. This is an optical illusion that confuses a lot of people. Actually our brain is playing tricks on us. When we look toward the horizon we see trees and hills and houses and many other objects spread over the landscape in addition to the moon. Having these objects in our line of sight, gives us something to relate size to. A way to get away from this illusion is to look at the rising moon through a cardboard tube. It will suddenly look smaller and just as it does when overhead because with the tube you’ve cut off your view of the objects on the landscape that caused the illusion in the first place.
Q. Why do stars twinkle?
A. Stars twinkle because the light we see coming from the stars travels through the atmospheric layers surrounding Earth and there is turbulence in those layers caused by differing temperatures. This turbulence is called scintillation. To simulate stars twinkling, try this experiment. You’ll need:
- A 2-quart glass bowl
- A small mirror that fits in the bottom of the bowl
- A flashlight
Fill the bowl about three-fourths full with water and then lay the mirror in the bottom of the bowl of water. Turn on the flashlight and darken the room. Holding the flashlight at an angle about 6 inches above the bowl, move the flashlight as needed so that the light is reflected from the mirror hits a nearby wall.
There is little or no motion of the light reflecting from the mirror in still water. The reflected light passing through the moving water shimmers on the wall.
The reflected light waves are refracted or bent as they leave the water. Different depths of water cause the refracted light to strike the wall in different places.
Q. How Far Away Is the Nearest Star?
A. The nearest star to the Earth is our own Sun. Speed of light travels at 186,000 miles per second. If we could travel to our Sun in a space ship going 60,000 miles per hour, it would take us 125 days to get there. To the next nearest star, Proxima Centauri, if we could travel as fast as the speed of light, we’d spend 4 and one-half years getting there. Again, traveling at 60,000 miles per hour it would take us 88,000 years to reach it.
Q. Do Stars Have Color?
A. All stars in the sky have some color associated with them. The human eye does not have the visual acuity at night to see the various colors of the dimmer stars and for that reason the majority of stars appear white. But there are some stars, such as Betelgeuse or Antares, that have reddish colors easy to see with the naked eye.
The temperature of the star determines its color. The redder the star the older the star is, the whiter the star the younger it is. Blue-white stars are the youngest and the hottest of them all.