The first day of summer is Tuesday. The actual moment of what astronomer’s call the Summer Solstice occurs at 1:16 p.m.

This the longest day of the year and the shortest night, and as I’ve complained several times before, you really have to stay up late for stargazing, which for people like me forced to get up very early in the morning for their jobs, stargazing becomes a weekend adventure.

Because the sun is at its maximum distance north of the celestial equator, the sun takes its longest path across the sky — rising in the northeast and setting in the northwest — and that means here in Butler a little more than 73 degrees above the southern horizon.

As soon as if finally gets dark enough, you can easily see what’s call the “Summer Triangle” in the eastern sky. It’s not one of the 65 to 70 official constellations we can see around here, but rather what astronomers dub an asterism — an easily seen pattern or picture in the stars that’s not one of the official constellations. Most asterisms are made up of bright stars of several constellations.

That’s certainly the case with the Summer Triangle. It’s so easy to see even if you’re stargazing from a lit up urban location. Just look for the three brightest stars you can see in the low eastern sky and that’s it. Each of those bright shiners is the brightest star in three respective summer constellations, and each of them is very special in its own way.

The brightest and highest of them is Vega, the brightest star in a small constellation called Lyra the Lyre, which is an old fashioned harp. Vega is a star that’s more than 25 light-years away with just one light-year equaling nearly six trillion miles. The light we see from Vega this week left that star when Ronald Reagan was president.

Vega’s also bigger and hotter than our sun. It’s about two million miles in diameter, more than three times the girth of the sun and 17,000 degrees Fahrenheit at its surface, 7,000 degrees hotter than our sun. In fact, you can tell Vega’s one of the hotter stars in the sky by the faint blue tinge it shines with.

The second brightest star in the Summer Triangle is Altair, on the lower right corner, fairly low in the eastern heavens. Altair is the brightest star in constellation Aquila the Eagle. Altair also is the closest star in the triangle, just more than 16 light-years away.

Now even with the best of backyard telescopes there’s nothing all that special you can see. However, astronomers know from spectroscopic analysis that Altair really has a spin to it, literally. It rotates on its axis every ten hours! It takes our sun nearly month to make a complete spin. In fact, Altair spins on its axis so fast that it’s believed to be a lot fatter at its equator than it is at its poles. Because of centrifugal force, it’s actually an ovalish star. It’s a star with a beer belly!

My favorite star in the Summer Triangle is the faintest member on the left hand corner. It’s Deneb, the brightest star in the constellation Cygnus the Swan, also known as the Northern Cross. It is one fanatically large and luminous star.

According to the latest data, this star at the tail of the heavenly swan is more than 1,500 light-years away. As well as we see this star you have to figure that it’s one humongous object. In fact, it may be more than 250 million miles in diameter and kicking out more than 39,000 times more light than our sun.

If you could magically pull Deneb in from its 1,500 light-year distance to the proximity of Vega, about 25 light-years away, about the only thing brighter in the sky would be the moon!

Deneb is virtually the biggest single thing you can see with the naked eye in our early summer skies!

Celestial Hugging

In the early morning low eastern skies about an hour before sunrise, the fairly bright planet Mars will be hanging just below the Pleiades Star Cluster. The Pleiades are easily seen with the naked eye and look like a tiny little dipper.

Mike Lynch is an amateur astronomer and professional broadcast meteorologist in Minneapolis and is author of the book, “Pennsylvania Starwatch.”