David Cohen, age 10, of E. Brunswick, New Jersey, for his question:

Which star is nearest to the earth?

The stars that sparkle in our skies at night are all separated by many billions of miles. Out in the vast ocean of space, a million million miles is such a short distance that it's hardly worth mentioning. Yet the star closest to our earth is less than 100 million miles away. This enormous nuclear power plant rises every morning in the eastern sky and sinks every evening below the western horizon. Naturally, of course, it is our glorious sun.

The sun was named ages before astronomers figured out that it is really a star, like those that twinkle in the sky when day is done. Our starry sun looks bigger and shines so bright because it is only about 93 million miles away from us. Actually at this time of year it is a million miles or so closer than it will be in July. No other star is anywhere near this close. Distance, even out in space, makes things look smaller. This is why the faraway stars look smaller and dimmer than our sun. They are there in the daytime sky    but its razzle dazzle brilliance outshines them.

North of the equator, we face Polaris and a vast dome of star studded outer space. The Southern Hemisphere faces a different view, strewn with other stars. One of the starry constellations is Centaurus, the Centaur. The brightest member of this group is Alpha Centauri. It looks like one star. But telescopes reveal that it is a pair of bright stars near a small red dwarf star. The triplets orbit around one another and belong together in one star system. As they orbit each other, sometimes the double Alpha Centauri is the closest star to our sun. But right now the red dwarf is closest. Its name is Proxima, meaning the near one.

We can measure the distance of the Centauri triplets in miles. The figure is almost 26 million million miles    26 plus 12 zeros. This is roughly 270,000 times farther than the earth's distance from our starry sun. The light year is a neater measuring unit, more suitable for the vast distances of outer space. The closest stars to our sun are 4.3 light years away. Alight year is the distance it takes a beam of light to travel in one earth year. So the light from Alpha Centaurs travels about four years arid four months before we see it shining there, south of the equator.

Light whips across space at about 186,000 miles per second    which is almost 670 million miles per hour. No spaceship can reach anywhere near this fantastic speed. But if it could, it could reach our starry sun in about eight minutes. Traveling non stop, it would take almost four and a half years to reach the second nearest star to the earth.