What's Up in the Night Sky

February 2017 - Vol. 21, No. 2

This Month's Night Sky - NOTE: The next paragraph describes the sky as it appears at 10 pm EST (11 pm EDT) near mid- month. The sky also looks this way at 11 pm EST (midnight EDT) during the beginning of the month and at 9 pm EST (10 pm EDT) by month's end.

The "Winter Triangle" asterism shines high overhead. It appears as an inverted triangle formed by three bright stars: Sirius (Canis Major) below, reddish Betelgeuse (Orion) upper right, and Procyon (Canis Minor). Betelgeuse is also the upper left member of my favorite asterism, hour-glass shaped Orion. If you have a clear sky, look for a hazy patch of light below Orion's middle "belt" star. That is M42, the Great Orion Nebula, the site of intense star formation. (At least it was some 1,600 years ago since it took that long for the light to reach you!) Other bright stars of interest are Rigel, the bottom left star in Orion, Aldebaran (Taurus) in the SW, Castor and Pollux (the Gemini twins) high above the winter triangle and orangish Arcturus (Bootes)right on the E horizon. The "Big Dipper" of Ursa Major stands majestically high in the N.

MERCURY is well placed for the evening twilight sky until late in the month, favoring the southern hemisphere. VENUS rides high in the evening sky reaching greatest brilliance on the 17th, it should be around mag -4.8 around this time. MARS in the constellation of Pisces sets in the early evening. This month the red planet enjoys several conjunctions.It comes within 5 deg of Venus early in the month, 1 deg of the Moon on the 1st and enjoys a close conjunction with Uranus on the 27th. JUPITER rises in the constellation of Virgo, just northwest of the 1st magnitude standard star Spica (1.0 mag) and dominates the morning sky. The giant planet will reach aphelion, its farthest distance from the Sun on the 17th. SATURN rises in the early morning sky; the ringed planet will be joined by a waning moon on the 20th. URANUS sets in the evening sky. The outer planet NEPTUNE will disappear in the evening twilight this month.

Review how to determine Angular Measurement.

Calendar of Events

NOTE: For those observers not in the ET zone, convert the calendar times to your zone's time by subtracting one hour for CT, two for MT and three for PT. Don't forget to adjust for Daylight Savings Time when necessary by subtracting one hour from your planisphere's time. Dawn and dusk times must also be corrected. See your local newspaper, TV news, or cable TV's Weather Channel for sunrise and sunset times or check with the U.S. Naval observatory. Unfortunately some of these events may occur during daylight hours in your area.

DATE	EVENT
01	Mars 2 deg N. of Moon
03	Ceres .4 deg S. of the Moon, occultation observable from eastern Siberia, Alaska, Canada, and Greenland. The minor planet is 7.4 magnitude so optical aid will be required to observe this event. Binoculars may serve unless accurate timings are desired.
05	Aldebaran 0.2 deg S. of the Moon occultation from Central America, northern South America, northern Africa, southern Europe, and western Middle East.
06	Moon at perigee. Jupiter stationary, use the 1st mag star Spica to track the motion of the giant planet as it begins retrograde motion.
11	Penumbral Lunar eclipse, the entire eclipse is visible Europe, Africa, western Asia, eastern N. and S. America. As this is a deep penumbral eclipse, it may be possible to see some of the effect from 00:00 UT to 1:30 UT, when more than 75% of the lunar surface is obscured by the Earth's atmosphere. The effect is subtle and may not be observable to everyone. Regulus .8 deg N. of Moon, occultation from Australia and New Zealand.
13	Look W from a dark location, at about an hour after sunset, to view zodiacal light. ("Zodiacal light" is a vertical band of white light believed to be sunlight reflected from meteoriods found in the plane of the ecliptic, the apparent "path" of the Sun, Moon and Planets as they travel across our sky.) It will appear to be a very large, but very dim, pyramid of of white light, "leaning" to the left. This effect may be visible for the next two weeks on dark nights.
15	Jupiter 3 deg S. of Moon.
17	Jupiter at aphelion. On this apsis, the giant planet is the farthest away from the Sun that cam be in its 11.86 year orbit, a distance of 816 million km (507 million miles). Venus greatest extant illuminated. Our sister planet is at crescent phase as our two planets move closer to each other.
18	Moon at apogee.
20	Saturn 4 deg. S. of Moon.
26	Annular Solar eclipse visible from South America, Pacific, and parts of Africa. This eclipse is part of the same eclipse season as the lunar eclipse earlier this month. The annular eclipse occurs at 14:54 UT and lasts only 44 seconds. This is a partial eclipse for locations outside the center line, check for your local conditions.
27	Mars .6 deg. N. of Uranus.

Lunar Almanac for February 2017

Phases of the Moon	Phase and Date(s)	Best viewed before local midnight
	New 26	Deep Space Objects
	1st. Qtr 04	Planets & Moon
	Full 11	Moon
	Last Qtr 18	Deep Space & Planets

Topic of the month: Cancer the Crab

The constellation of Cancer (the crab) finder chart

The constellation of Cancer is associated with a crab. None of the stars in this constellation are brighter than 3.7 magnitude, making it hard to observe under city lights. It is located squarely on the ecliptic and it is also the faintest ecliptic constellation. About 2000 years ago it was quite important to astronomers because it was the constellation where the Sun was located at Summer Solstice, For this reason, the constellation lent its name to the Tropic of Cancer, one of the five major circles of latitude on the planet. This is the northernmost location that the Sun can pass overhead at noon, about 23 degrees above the equator.

The alpha star of this constellation is also named Acubens or "claw." Beta Cancri, known as Al Tarf is the brightest star in this constellation. Delta Cancri, called Asellus Australis is a yellow giant star shining at mag 3.9. It is the second brightest star of the Crab constellation. Perhaps the most interesting star of the constellation is Tegmen, or Zeta Cancri a fine multiple star system. The system is composed of two binary stars, Zeta-1 Cancri and Zeta-2 Cancri. Zeta -1 is a pair of yellow dwarf stars. Zeta -2 contains two yellow type G stars and a 10th magnitude red dwarf star. The system’s its proximity to the ecliptic means that it can be occulted by the moon and (rarely) by planets.

The brightest jewel of this constellation is the open star cluster M-44, commonly called the Beehive cluster or Praesepe. Praesepe comes from Latin where it originally meant manger or alternately, hive. So whether you call it a beehive, a manger, M-44, or NGC 2632 most observers will know what object you are referring to: a bright cluster of about 40 members located in the constellation of Cancer. Recent studies have identified about 870 stars as proper members of this cluster but a backyard observer will never identify this many stars in the Beehive cluster. A naked eye observer will see a misty patch of stars in the center of the constellation, with the star Epsilon Cancri of the constellation being a member (mag ~8). The distance to this cluster is not exactly known, but 580 light years is a typical value that is given. This may be because of the great number of stars that are actual members of the cluster.

Another popular cluster, M-67 is also located in the constellation of Cancer. This galactic cluster is considered to have 500 or more members with about 100 visible in a large amateur telescope. The age of the cluster has been measured at about 4 billion years, it is the oldest open star cluster in the Messier catalog. In 2014, three extra-solar planets were discovered in the cluster using the 3.6m telescope at the La Silla Observatory in Chile.

--See You Under the Stars!
Astra for Astra's Almanac

The star chart above was generated by Stellarium, a free open source planetarium program. The above image was created by Dawn Jenkins, using Stellarium and a graphic editing program to format the image for this web page. Editing was done for educational purposes only. Stellarium offers much more to amateur astronomers and is being used in planetariums and to guide telescopes in the field. Simple charts like the one above can be used on the internet for non-profit, illustration purposes. Proper credit is due of course! Thank you to the makers of this fine program from Astra's Star Gate.