- spring begins on March 20th
- summer begins on June 20th
- autumn begins on September 22nd
- winter begins on on December 21st
TUESDAY, MARCH 2: MOON AT PERIGEE
The moon travels along an elliptical orbit that is slightly elongated. (An elliptical orbit that is not elongated is called a circle.) During each orbit, the moon reaches a point of least distance (perigee) and a point of greatest distance apogee). Today, the moon reaches the perigee of this particular orbit. At the precise perigee moment, the moon will be 365,423 kilometers from Earth.
The above image shows the moon's orbit as a highly elongated ellipse. Here, one can readily observe that the perigee point is much closer to Earth than the point of apogee.
The second image shows the moon's orbit (solid curve) relative to a perfect circle (dotted curve). One can see that the moon's orbit only deviates slightly from a circle. The moon's orbital eccentricity is 0.0549. Were its eccentricity zero, the orbital path would be circular.
WEDNESDAY, MARCH 3: FINDING LEO THE LION
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Leo the Lion becomes a prominent early evening constellation in late winter. One can find Leo ascending in the eastern sky just after dark. The Lion's 16-degree high "sickle" represents the lion's head and mane. The southern sickle, star, Regulus, represents the lion's heart. One can find Leo by looking "under" the Big Dipper's bowl, which will rise into the northeastern sky early this evening. We'll observe Leo rising progressively earlier each night through the spring and into summer. The lion is part of the zodiac, meaning that the Sun appears to move through it each year. The Sun passes through Leo from mid August to mid September.
THURSDAY, MARCH 4: MARS NEAR THE PLEIADES
Tonight one will see Mars "close" to the Pleiades Star Cluster, a misty globule of faint light poised on Taurus' shoulder. Their apparent proximity to one another is illusory. While Mars will be approximately 140 million miles from Earth tonight, the Pleiades' distance from us equals 441 light years. To put this difference in perspective, if Mars were just one foot from us, the Pleiades would be 4,066 miles away.
FRIDAY, MARCH 5: MERCURY 0.3 DEGREES N OF JUPITER (BRONZE EVENT!)
The smallest planet -save Pluto- and the largest planet appear less than a degree apart in the pre-dawn eastern sky this morning! Both bodies will rise just before 5:15 a.m., approximately half an hour before the onset of civil twilight. One will experience little difficulty distinguishing between them as Jupiter (magnitude -1.8) will be slightly more than six times brighter than Mercury. Jupiter appears much brighter despite its considerably greater distance. Whereas Mercury will be 86.4 million miles from Earth today, more than half a billion miles separates us from Jupiter. We ascribe Jupiter's brightness to both its size (860 times larger than Mercury in terms of surface area) and albedo, the ratio of reflected-to-received solar radiation. While Mercury reflects only 14% of all incidental sunlight back into space, Jupiter reflects about 53 percent. Although Jupiter is much farther away, it still shines much brighter in our sky.
FRIDAY, MARCH 5: LAST QUARTER MOON
SATURDAY, MARCH 6: MERCURY AT GREATEST WESTERN ELONGATION
-When at greatest western elongation, an inferior planet will appear in the eastern pre-dawn sky.
-When at greatest eastern elongation, an inferior planet will appear in the western early-evening sky.
One will find Mercury in the eastern sky this morning. The first planet will rise at 5:10 a.m.
TUESDAY, MARCH 9: BRIGHT INTERNATIONAL SPACE STATION FLY-OVER
Watch the International Space Station traversing the sky before sunrise. The ISS rises at 5:12:34 a.m. (at which time it will be passing directly over Lake Superior). The station attains its maximum altitude of 69 degrees at 5:15:43 a.m. At this time, it will also attain its maximum brightness of magnitude -3.8, making just about as bright as Venus. The ISS will set in the southeastern sky at 5:21:08 a.m. During this fly-over, the ISS will appear to move between the Big Dipper and Leo the Lion; as well as across Bootes, along the northern tip of Ophiuchus and just south of Aquila, the southernmost of the "Summer Triangle" constellations.
WEDNESDAY, MARCH 10: MOON, JUPITER AND SATURN WITHIN A CIRCLE 5.3 DEGREES IN DIAMETER (SILVER EVENT!!)
What better reason to awaken early today than to see the waning crescent moon (8% illuminated) "close" to the gas giants Jupiter and Saturn. The best time to observe these three worlds is after 5:15 a.m. One will be easily able to distinguish between Jupiter and Saturn as the former will be ten times brighter than the latter.
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