July night sky, looking south before sunrise
July 2007 night sky
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
• 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 firstname.lastname@example.org.