THE SOUTHWORTH PLANETARIUM
70 Falmouth Street Portland, Maine 04103
(207) 780-4249 usm.maine.edu/planet
43.6667° N 70.2667° W Founded January 1970
70 Falmouth Street Portland, Maine 04103
(207) 780-4249 usm.maine.edu/planet
43.6667° N 70.2667° W Founded January 1970
2022-2023: LXIV
Sunrise: 6:18 a.m.
Sunset: 5:29 p.m.
Civil twilight begins: 5:49 a.m.
Civil twilight ends: 5:58 p.m.
Sun's host constellation: Aquarius
Moon phase: Waxing gibbous (74% illuminated)
Moonrise: 11:35 a.m.
Moonset: 4:07 p.m.
Julian date: 2460005.29
"Behind every beautiful thing there is some kind of pain."
-Bob Dylan
THE DAILY ASTRONOMER
Wednesday, March 1, 2023
March 2023 Night Sky Calendar: Stars on Parade
Whew!
We're back! Hastily disinterred. Yanked away from Calypso's enveloping embrace. Propelled back up from the tenebrous depths of the Hadopelagic zone. Unwrapped, unfolded, smoothed out, steam cleaned, corners iron....yes, yes, yes. we're back and we just couldn't be happier to see you. Barring any unforeseen circumstance, the DA should not go into a protracted hiatus again..apart, of course, from those we regularly schedule, anyway. Thanks to the BWA for holding down the fortress in our absence.
Now, let's just get on with it.
THOSE BRIGHT WESTERN 'STARS!'
are not stars at all, but you might have realized that fact already. Those brilliantly bright and beguilingly beautiful orbs are none other than Jupiter and Venus! The latter always outshines all other celestial objects apart from the Sun and moon. The former is quite often the second brightest planet. Presently, Venus is approximately six times brighter than Jupiter, so one should experience no difficulty distinguishing between them. It's a delight to the eyes when Zeus and Aphrodite flit about and co-mingle. These worlds will come within 0.5 degrees of each other tonight.
FOLLOW THE LION
That our remote forebears relied at least in part on the constellations to keep track of the seasons is hardly surprising. Even in our modern era of grandfather clocks and graduated time candles, the constellations still emerge in the eastern pre-dawn and vanish into the western dusk with pleasingly perfect regularity. For instance, we can keep our admiring eyes fixed firmly on Leo the Lion over the next few months. In early March, this nasty Nemean menace starts its eastern sky ascent after sunset and remains visible throughout the night. However, as we trudge glacially through spring and then sprint madly through early summer, Leo will draw inexorably toward the setting Sun. By early August, Leo's luxuriant mane and heart star Regulus will dissolve into the dusk. By mid August, the Sun will move into the Leo the Lion constellation rendering it temporarily invisible. From now until early August, an observer can use Leo the Lion to follow our seasonal transition from biting cold to gnawing cool to lightly chilled to curiously warm to fleetingly hot.
ORION'S RULE
Venture outside just as darkness descends and you'll observe Orion moving along the meridian, the imaginary arc connecting north and south. This lusty, violence-prone bane to all creatures great and small remains prominent in our evening night sky. As Orion is arguably the most famous of all constellations by virtue of his array of bright stars and uncanny resemblance to an enormous human, many observers understandably want to know his location throughout the year. Fortunately, because of the regularity of the annual constellation motions caused by Earth's orbital motion around the Sun, Orion tracking is a rather straight-forward matter provided that one knows Orion's Rule, or the 'Two Hour Rule.' First, remember that all stars which are not circumpolar rise four minutes earlier each day as a consequence of Earth's changing position relative to the Sun. This difference amounts to about half an hour a week or two hours each month. On February 1, Orion is due south at 8:00 p.m. Using the Orion Rule, we can therefore conclude that Orion will be due south at 6:00 p.m. on March 1st and at 10:00 p.m. on January 1st. Oh, heavens, we're so full of pep and ginger at present, let's just go through the whole year:
Orion will be due south at
- 10:00 p.m. on Jan 1
- 8:00 p.m. on Feb 1
- 6:00 p.m. on Mar 1
- 4:00 p.m. on Apr 1
- 2:00 p.m. on May 1
- 12:00 p.m. on June 1
- 10:00 a.m. on July 1
- 8:00 a.m. on Aug 1
- 6:00 a.m. on Sept 1
- 4:00 a.m. on Oct 1
- 2:00 a.m. on Nov 1
- 12:00 a.m. on Dec 1
Orion's belt, consisting of the stars Mintaka, Alnilam, and Alnitak, is aligned just south of the celestial equator and so remains in the sky for approximately 12 hours each day. Bearing this fact in mind, we know that Orion's belt rises six hours before it is due south and sets six hours after it's due south. On February 1st, then, Orion's belt rises around 2:00 p.m. and sets around 2:00 a.m. So, one will find Orion ascending in the eastern sky between the times of first darkness and 8:00 p.m. on February 1st and then will watch this broad-chested behemoth of a bunny-basher descending through the west until 2:00 a.m. Orion's two shoulder stars Betelgeuse and Bellatrix, both of which are a bit less than ten degrees north of the celestial equator, remain above the horizon for about 12.5 hours. The knee stars, Rigel and Saiph, are at about the same angular distance south of the celestial equator and so remain above the horizon for 11.5 hours.
Finally, we realize that Orion vanishes into the dusk in mid-May only to return to the eastern pre-dawn sky in early August. Within this time frame, Orion is not visible. Otherwise, one can use the Orion Rule to seek out this celestial hunter at any other time of year.
Tomorrow, the actual calendar.
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