Download PISGAH Text by Dr. Bob Hayward ASTRONOMICAL Astronomer

PISGAH
ASTRONOMICAL
RESEARCH
INSTITUTE
Text by Dr. Bob Hayward
Astronomer/Educator
Graphics by TheSky
Bisque Software
Mountain Skies
April 4, 2016
WINTER GIVES WAY TO SPRING IN THE EVENING SKIES
The stars: Early evening in April catches us betwixt and between the prominent constellations
of the receding winter skies and those of the quickly rising spring skies. In the former, the great hunter
Orion can still be seen in the west. But now, as the sky darkens, he is leaning over looking downward
as he follows the bull Taurus towards the horizon. The Gemini twins Castor and Pollux stand to the
north of their mentor as they follow him across the sky. Two bright stars mark their heads. Following
these folks as the sky turns are the two dogs. The Dog Star Sirius, the brightest star in the nighttime
sky, is in the southwest. Above Sirius is the lesser or little dog consisting of only two naked eye stars,
Procyon and the much dimmer Gomiesa.
Meanwhile, to the east we find the
springtime constellations becoming more
apparent. Leo the lion is standing high in
the east. The front or western portion of the
lion has traditionally been called the sickle
and can be found labeled as such on some
star charts.
It consists of an almost
complete circle of stars with the bright star
Regulus lying below it.
In more modern
times, we view this pattern as a coat hanger
or a backward question mark with Regulus
as the dot below the question mark. The
hindquarters and tail of the lion are found in
a triangle to the east of the sickle.
Between the twins and the lion is Cancer the crab, basically an open area without any bright
stars. In the middle of Cancer is a pretty cluster of stars popularly known as Praesepe or the “Beehive
Cluster” since, with a pair of binoculars or a small telescope, it looks like a swarm of celestial bees. To
the astronomer this cluster is known as M44 for Messier 44. Since the Beehive lies close to the zodiac,
it is often occulted, i.e., covered up, by the moon. The planets can pass through this swarm of bees as
well as they follow their own orbits in front of Praesepe.
The Planets: Normally, we mention Mercury just in passing since viewing this elusive planet
takes more than casual effort. But, this month Mercury is experiencing its most favorable evening
apparition of the year. What does that mean? It means that as Mercury orbits the sun, it swings
quickly back and forth from the predawn twilight to sunset, never very far from the rising or setting sun.
This month, because of the orientation of its orbit, Mercury is brighter than average and higher in the
evening sky after sunset than normal. Look for it low in the west-northwest as the sun sets. It will
remain in that general area until the last week of the month when it disappears into the sunset in
preparation for its long awaited transit in front of the sun on May 9.
The only other visible planet up in the evening sky can’t be missed and is no challenge
compared to Mercury. The planet Jupiter is well up in the southeast at sunset as moves into the south
as the evening progresses. For those who will be out late at night we are beginning to see a pretty
triangle of objects in the east about midnight. These are the planets Mars and Saturn and the bright
star Antares which marks the heart of the scorpion. The moon moves through this area of the sky on
its monthly orbit of the earth and, on the night of the 25th, will be right in the midst of this triangle.
Since it will be at waning gibbous phase, less than four days past full moon, its light will actually wash
out our view of the two planets and Antares. But, never fear, by the 26th the moon will have moved out
of the way. By the way, the Greeks called Mars by the name Ares. They noted that this bright star
marking the heart of Scorpius is almost the same brightness and color as the planet Ares (Mars). So,
they named the star Antares which when translated stands for “Rival of Mars.” You mistake Antares for
Mars/Ares at the risk of the wrath of the God of War.
Venus is extremely low in the morning twilight and basically lost in the light of the rising sun.
Celestial Calendar:
April 7, 7:24 a.m. EDT – New Moon
April 12 – The sun in its apparent annual path around the sky moves from the constellation
of Pisces the fish into Aries the ram.
April 13, 11:59 p.m. EDT – First Quarter Moon
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PARI is a public not-for-profit public foundation established in 1998. Located in the Pisgah National
Forest southwest of Asheville, NC, PARI offers educational programs at all levels, from K-12 through postgraduate research. For more information about PARI and its programs, visit www.pari.edu. Follow PARI on
Twitter at http://twitter.com/Astronomy_PARI. “Like” PARI on Facebook at
www.facebook.com/Pisgah.Astronomical.Research.Institute.
For further information or questions about this Mountain Skies column, contact Dr. Bob Hayward at
[email protected]. Graphics produced with TheSky Astronomical Software, Software Bisque.