Once more with the Summer Triangle

Let's go look one more time at our friends in the Summer Triangle for another discussion. You can find the three stars of the triangle about half-way up the eastern sky about an hour after sunset any clear night this week.

All three stars appear to be about the same brightness except for the top one, Vega. It appears to be a little brighter than the other two. It's brighter because it is closer, right?

Well, not necessarily. Vega is the brightest of the three shining at about zero magnitude which makes it the fifth brightest star in the sky.

In size, Vega is two-and-a-half times larger than our million-mile wide sun and is about 25 light-years distant.

Next in brightness is Altair located down and right of Vega in the constellation Aquila, the Eagle. Its magnitude is a little dimmer at .75. Remember, the lower the number, the brighter the star.

Altair is 17 light-years away and is a little smaller at 1 and one-third the size of our sun.

The whopper of them all is Deneb, the tail star in Cygnus, the Swan. It is the left-most of the triangle stars. Cygnus is also called the Northern Cross for its obvious shape.

Now, for the size, Deneb is 116 times the size of our sun. Well, why isn't it brighter? Well, now comes the second of our brightness qualifiers.

Deneb is located about 1,500 light-years away. Remember, one light-year is about 6 trillion miles. That is the number six with 12 zeros behind it.

So, having said all that, what do we say next? Just remember, the size of a star is not the only contributing factor to its brightness as we see it, distance must also be considered.

Sky Watch: Third quarter moon, July 23. We have a lot going on this week, and some of it is in the morning sky, and there is one event I am getting up for.

The smallest of the planets, Mercury, is at its greatest distance from the sun tonight. Look in the west about a half-hour to 45-minutes after sunset for the little dot of light that is Mercury. It will be just a little below and right of Regulus, the brightest stat in Leo, the Lion. Binoculars will help.

As the week progresses Mercury will drop closer to the horizon and be gone from our evening sky by a week from today.

Saturn is still a good object for telescopic observation. It is located in Virgo, the Maiden just right of bright Spica. It too will be gone by the end of August. The ring plane is still opening making a grand sight.

On Saturday, July 23, a third-quarter moon will be hanging just above and right of bright Jupiter. The next night it will be to the left.

Now, here is the exciting part. Monday morning, July 25, set your alarm clocks to be up and outside by 4:45 a.m. and look east for a slender crescent moon. Use your binoculars and you will find the Pleiades star cluster to the right in the same field of view.

Reset your alarm clock for the same time Wednesday morning, July 27, and look east again to find the slender moon resting right between the horns of Taurus, the Bull.

But, that is not all, the really exciting part is, in the same binocular field of view is the red planet Mars to the moon's lower left and to the lower right you might be able to see the first item on Mr. Messier's list of things that are not comets, M1, the Crab Nebula.

M1 is the leftovers from a super nova explosion of a star that was recorded by the Chinese and Arab astronomers in 1054. It was so bright it could be seen in daylight and in the night sky for several months.

That is something worth getting up for.

Next Week: The return of the Mars hoax and more astronomical blathering.