Download Mountain Skies March 21 2016

PISGAH
ASTRONOMICAL
RESEARCH
INSTITUTE
Text by Dr. Bob Hayward
Astronomer/Educator
Graphics by TheSky
Bisque Software
Mountain Skies
March 21, 2016
MARS AND SATURN FORM A TRIANGLE WITH THE RIVAL OF MARS IN THE SCORPION
The stars: While the bright stars of winter continue to dominate the southern sky in the early
evening, turn around and look to the north, specifically the northeast. Here, low in the sky we find the
familiar pattern of the Big Dipper. It’s still not late enough in the year to see it high in the north, but we
can see it rising, standing on its handle with the bowl opening to the left. Watch the dipper over the
next several weeks as it gets higher and higher in the northeast until, with the coming of spring, it will lie
high in the north. Realize, of course, that the Big Dipper is not an official constellation as defined by the
International Astronomical Union. Astronomers would call it an asterism. This familiar pattern of stars
was known to the ancient Greeks as the hindquarters and long tail of the Great Bear, Ursa Major.
Now use the two stars in the end of the bowl of the Big Dipper to find the most famous star in
the sky. Draw a line between the two stars in the bowl and trace it to the left about five times the
distance between the two stars and you will come to a fairly bright (but not the brightest) star. This is
Polaris, the North Star. The North Star is the end of the tail of the Little or Lesser Bear, Ursa Minor. To
our way of thinking it is also the end of the handle of the asterism we call the Little Dipper. Once you
have found the North Star, look down to the right to locate two moderately bright stars. These are the
so-called “Guardians” which mark the end of the bowl of the Little Dipper. The other stars of the Little
Dipper, stretching between the Guardians and the North Star, are much fainter; you must have a very
clear, dark night to spot them and, thus, trace out the entire Little Dipper.
The planets: The change to Daylight Saving Time has caused everything influenced by the
rotation of the earth to happen an hour later on our clocks. Not only is the sun setting later but also the
risings and settings of the stars, the moon and the planets are affected. For example on Sunday
morning, March 13 Mars rose at 12:03 a.m. EST, an hour before we changed the clocks an hour
ahead. Then, on Monday, March 14, Mars rose at 1:03 a.m. EDT. Tomorrow morning, the red planet
rises at 12:41 a.m. EDT. So, we see that, while Mars was delayed an hour because of the time
change, it is rising earlier each night and by late May it will be up at sunset.
Already up at sunset is the giant planet Jupiter. Under the tail of Leo the lion it is the brightest
object in the evening skies other than our nearly full moon. Speaking of which, tonight Jupiter will lie
just to the left of that moon. You can’t miss the two; look about halfway up in the east after the sky
darkens. This would be a great evening to notice the relative motion of these two objects. The moon
moves about its own diameter every hour while Jupiter, since it takes almost twelve years to circle
around the sky, doesn’t move noticeably in such a short time. So, watch these two for a couple of
hours and you will see the moon passing by the planet Jupiter. Of course, realize that Jupiter is much
more distant than our moon. So this apparent close encounter is nothing of the sort; there is no near
collision.
Saturn is following Mars up tonight; the ringed planet is rising about 1:32 a.m. EDT tomorrow
morning or less than an hour after Mars. These two planets are forming a nice triangle with Antares,
the heart of the scorpion.
Note the brightness and
colors of both Mars and
Antares.
They are very
similar; in fact, the name
Antares is translated “rival
of Mars” since it can easily
be mistaken for the planet
named after the god of war,
an insult no ancient Greek
would want to be guilty of.
In the predawn sky the queen of the sky, Venus, is much lower than even a week ago. These
are really our last few days to spot it before it moves into the evening skies to become our “Evening
Star” in late June. Mercury is currently too close to the sun to be seen since it passes through inferior
conjunction behind the sun on Wednesday.
Celestial Calendar:
March 23, 8:01 a.m. EDT – Full Moon
March 31, 11:17 a.m. EDT – Last 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
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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.