July night sky, looking south before sunrise

July 2007 night sky

—CHARLIE CHRISTMANN

MORNING STARS

This month’s edition of the Night Sky is for the early risers. I’m talking about 4:00 a.m.! So, get out your binoculars and enjoy the sights.

We’ll start this tour with the constellation Capricorni and its beta star named Dabih. This star is actually a triple star system. The main pair, separated by over three minutes of arc, is dominated by third magnitude “Dabih Major.” Its companion is referred to as “Dabih Minor,” a sixth magnitude star. The third partner in this system is a blue star that orbits very close to Dabih Major every nine days. Through your binoculars, you may see another star in the field of view which may orbit with the other three. This forth star is unusual because it contains high concentrations of the heavy metals mercury, gold, and platinum in its atmosphere. There is speculation that there may be even more stars in this complex. Dabih could well take up an astronomer’s entire career.

Equuleus, the little horse, is the smallest constellation visible from the northern hemisphere. Its delta star is a binary located about sixty light-years away. There are two sun-like stars that circle each other every 5.7 years. They are separated by a distance just short of that between our sun and Jupiter. Combined, the two shine at almost fifth magnitude. They are unusual because it is rare to find stars similar to the sun visible to the unaided eye. Here are two in orbit about each other—a double sun. Science fiction writers seem intrigued by what life would be like on a planet orbiting a double star. Studies show that a planet could orbit either of the two, or be in a distant orbit about the pair. A planet with a stable orbit taking just under half a year to orbit would likely see two sunrises and sunsets every day for part its year. But, when the second sun moved into the “night” sky, night as we know it would be impossible. A planet could also be in a stable thirty-seven-year orbit around the stellar pair’s orbital center. Though icy cold, an astronaut on such a distant planet would see a pair of suns going through their own orbit, making quite the sight as they first pass close to each other and then stretch to up to fifteen degrees apart, each looking like a brilliant star.

Finally, who could miss the bright four? Looking in the east, you will find Aldebaran, the eye of Taurus. In the northeast is bright Capella in Auriga. Vega, in Lyra, can be found in the west-northwest and Altair, in Aquila, is in the west-southwest, both about forty-five degrees above the horizon.

So there you go. If you are not a morning person, it may be worthwhile making an exception to find this month’s stars.

THE PLANETS AND THE MOON

• Mercury can be found before sunrise in the eastern sky in the second half of July. It will be at its highest point in the sky on the 20th.

• Venus is still the brightest thing, except for the Moon, in the evening sky. Look west; you can’t miss it. On the 16th, look in the west-northwest about forty-five minutes after sunset. There you will find, in a line, Venus on the left, the two-day-old crescent Moon in the center, and Saturn on the right. The star Regulus will be floating above and between Venus and the Moon. Dim Saturn may be hard to spot without binoculars.

• Mars is found in the morning eastern sky rising about 2:00 a.m. An hour before sunrise on the 9th, look for Mars five degrees below the crescent Moon.

• Jupiter is the bright “star” in the east after sunset. On July 25, an hour after sunset, look south. There will be Jupiter, nine degrees to the upper left of the waxing gibbous Moon. The star Antares will be to the right of the Moon.

• Saturn is in the west at sunset hanging out near Venus. On July 1, about ninety minutes after sunset, look for Venus and Saturn separated by about one degree.

• Want a challenge? Five hours after sunrise on the 17th, try looking at the Moon through binoculars. Look closely and you can find Venus less than four degrees to the upper right of the Moon.

• The Earth will reach aphelion, the farthest distance from the Sun in its orbit at noon MDT on the 6th. The sun will be 94.5 million miles away.

• The Moon will be new on the 14th and full on the 29th.

• Look for scattered lights flashing in the sky. Some may even emit showers of sparks on the 4th. Happy Independence Day.

If you have a question or comment for Charlie, you may email him at k5cec@yahoo.com.