Download PISGAH Text by Dr. Bob Hayward ASTRONOMICAL Astronomer

PISGAH
ASTRONOMICAL
RESEARCH
INSTITUTE
Text by Dr. Bob Hayward
Astronomer/Educator
Starmap by TheSky
Software Bisque
Mountain Skies
January 18, 2016
CLASSICAL PLANETS LINE UP IN THESE MORNINGS
The planets: Now, we have all five of the classical planets visible to us in the predawn skies.
Mercury, which was in conjunction with the sun last Thursday is now rapidly rising higher each morning.
I would be exaggerating to say it is easily visible tomorrow morning but throughout the rest of January it
will get higher each morning in the dawn twilight such that it will be easily spotted. So, over the rest of
the month go out before dawn and look for a line of planets across the morning skies. As the sky
brightens we find the bright Jupiter high just a little bit west of south. A bit lower and to the east is the
planet Mars. While Mars is not anywhere as bright as Jupiter, it is easily recognizable by its red hue.
Down to the left of Mars is the planet Saturn with its distinct yellow hue. Saturn lies just to the east or
left of Antares the red heart of the scorpion. Be careful not to confuse Mars with Antares. Mars is
higher and it does not twinkle. (You’ve never heard of “Twinkle, twinkle, little planet” have you?)
Finally, below Saturn and Antares, in the twilight is the elusive planet Mercury in the eastern edge of
Sagittarius with its distinctive teapot asterism. Incidentally, way far behind Mercury is the planet Pluto.
Of course, Pluto is much, much too faint to be seen with the naked eye; a large telescope is needed for
that.
Why are the planets clustered in the morning skies these mornings? There is no particular
reason for that; the world will not end because of this apparent alignment of the planets. It is just a
coincidence in the timings and locations of each of these planets in its respective orbit.
The stars: Orion the hunter is rising higher in the eastern sky each evening. Locate his belt
marked by three bright stars in a row from east to west, Alnitak, Alnilam and Mintaka. Now, draw a line
through his belt and extend it upwards towards the west; you’ll come to a bright red star, Aldebaran, the
fierce eye of Taurus the bull. The face of the bull is made up a group of stars forming a noticeable
letter “V.” This is the famous Hyades star cluster. Although Aldebaran is the brightest star in the face
of the bull, it is not actually a member of the Hyades cluster. Instead, it is what astronomers call a
foreground star, one that lies in the same direction but which is closer to us. Realize that, while the
celestial sphere over our heads at first glance appears to be a two-dimensional surface, it is not.
Objects that appear to be close together in the sky often are at vastly different distances from us.
As if to emphasize this point, tomorrow evening we will be treated to a very interesting
occurrence in our nighttime sky. The planets and the moon move through the sky along paths that take
them in front of the zodiac constellations. Since Taurus is one of the classical zodiac constellations, it
is not unusual to find planets or the moon in front of the bull. Tomorrow night at about 9:20 p.m. EST
Aldebaran will disappear behind the eastern leading edge of the waxing gibbous moon. Astronomers
call this an occultation of Aldebaran by the moon. Since the moon in its orbit around the earth moves
roughly its own diameter in an hour, we should see Aldebaran reappear from behind the western edge
of the moon at around 10:20 p.m. Obviously, the moon, at about a quarter million miles from the earth,
is much closer than Aldebaran which lies about 67 light years away.
Since Orion is a fierce competitor in the bull, he holds up a shield made from the skin of a lion.
This can be found in a faint arc of stars between Orion and Taurus. On the shoulder of the bull is a
small cluster of stars that some people mistake for the Little Dipper. This is the Pleiades or the “Seven
Sisters.” In the tradition of the Native American Mono tribe, the Hyades were a group of mountain lion
hunters while the Pleiades were their wives. As the Earth rotates the hunters are eternally chasing their
wives across the nighttime sky.
Celestial Calendar:
January 19 - The Sun in its annual path around the sky passes from Sagittarius the archer into the
fainter constellation of Capricornus the sea-goat.
January 19, approx. 9:20-10:20 p.m. EST, Moon occults Aldebaran, the eye of Taurus the bull
January 23, 8:46 p.m. EST - Full Moon
January 31, 10:28 p.m. EST - Last Quarter Moon
February 8, 9:39 a.m. EST – New 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.