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SKY REPORTER: March 2011

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Saturn's night side

Night side of Saturn, imaged by the Cassini mission.

Credit: CICLOPS, JPL, ESA, NASA


On Tuesday March 1st the Sun is in the direction of stars in the constellation Aquarius.

In New York City that morning civil twilight begins at 6:03 a.m. followed by sunrise at 6:30. The following evening sunset is at 5:47 and civil twilight concludes at 6:14 p.m.

Sunrise is defined as the time when the top edge of the solar disk reaches the horizon. Sunset is when that edge is again at the horizon and descending. Civil twilight occurs at times before sunrise and after sunset when the center of the Sun’s disk is less than six degrees of arc from the horizon. That angle is about equal to the width of three fingers of your fist, seen with arm fully extended. During civil twilight in good weather it is usually possible to read outdoors without the help of artificial light.

In March average overnight temperatures recorded in Central Park by Belvedere Castle rise from 31 degrees Fahrenheit on the first, to 39 degrees on the 31st.

Jupiter is low in the west and sets at 7:59 p.m. at the beginning of this month. The big planet is then in the constellation Cetus, just inside the northwest corner of its border with Pisces. Sixth magnitude Uranus sets at 7:17 p.m. on the evening of March 1st.

At the start of this month Mercury and Mars are too close to the Sun’s direction for observation. Although Mars remains in this unfavorable zone throughout March, Mercury, in the evening sky, becomes increasingly separated from the Sun’s direction as weeks pass. During this time Jupiter moves progressively lower in the west sky, and by month’s end it’s lost in the glare of twilight.

Meanwhile Saturn becomes more conveniently placed for evening observations. It rises at 8:32 p.m. on March 1st. Always brilliant Venus remains prominent in the eastern pre-dawn sky all month.

If the sky is clear on a night in early March, you might like to participate in the project called Globe at Night designed to survey astronomical seeing conditions at reporting locations worldwide. Observations for this endeavor are underway from February 21st through March 6th.

New Moon is on Friday the fourth.

Springtime evenings can often offer good opportunities for locating Mercury, during years when the planet is near its greatest eastern elongation from the Sun during this season. It is especially true on nights when a crescent moon is in Mercury’s vicinity to serve as a marker. During spring evenings substantial angles the zodiac makes with the western horizon have potential for keeping Mercury in the sky for longer periods after sunset than at other times of the year. Corresponding good opportunities for seeing Mercury occur in the eastern predawn sky during autumn.

On the evening of Sunday March 6th at 7 p.m. a narrow crescent moon may be seen low in the western sky six degrees to the right of Jupiter and nine degrees above the horizon. This height is about the same angular span as the width of your fist seen at arm’s length.

On Thursday March 10th the waxing moon is just a few degrees from the Pleiades (PLEA-ah-deez) open star cluster in Taurus. Located at a distance of about 370 light years from the Solar System, this cluster of several hundred stars, of which six or seven may be individually visible to the unaided eye, is also identified as Messier 45.

The night of Saturday March 12th, the First Quarter moon is in the direction of the constellation Taurus, between stars Zeta Tauri and El Nath, objects that traditionally marked horn tips of the celestial Bull. This night the supernova remnant known as the Crab Nebula, and number one in Messier’s catalogue, is about halfway between the moon and Zeta, the more southerly of the two Taurus horn tip stars.

Crab Nebula

Messier 1 - The Crab Nebula.

Credit: NASA, ESA, J. Hester, A. Loll (ASU); Davide De Martin (Skyfactory)


First recorded observations of a brilliant supernova that produced the Crab Nebula were made in China on July 4, 1054. The object is located 6,300 light years from us and has a diameter of about 10 light years. In its heart is a neutron star that spins 30 times per second. Also known as a pulsar, the object contains about the same mass as the Sun but crushed into a volume just a few miles in diameter. Its apparent magnitude is a faint 8.4 and M1 has an apparent diameter in our sky about 1/8 that of the moon. Although a telescope and dark sky are required to observe the Crab Nebula, on this night the moon provides an indication of where M1 is located in our sky.

Daylight Time begins at two a.m. Sunday March 13th, with our clocks springing ahead by one hour.

By 7:30 p.m. at the end of civil twilight Monday March 14th Jupiter is ten degrees, about one fist length seen at arm’s length, above the western horizon. It’s also just two degrees of arc to the upper left of Mercury. Use the lure of bright Jupiter shining at magnitude -2 to guide your view toward Mercury, currently 2.5 times less vivid. The following evening at that time Jupiter may be seen slightly lower than Mercury. Binoculars provide considerable benefit when seeking a glimpse of elusive Mercury. However, you also need a clear view toward the western horizon, such as vistas from the eastern side of the Hudson.

On the evening of Wednesday the 16th at 7:30, Jupiter may be seen as having lost altitude while Mercury is slightly further from the horizon than it appeared in previous nights at that time. The two planets are juxtaposed with Jupiter at an horizon elevation of 8 degrees at 7:30 p.m., now appearing two degrees to the lower left of Mercury.

Full Moon is on Saturday the 19th, when the lunar disk is located within boundaries of the constellation Virgo. March’s Full Moon was referred to as the “Worm Moon” in Algonquian traditions. The general area between bright stars of the constellations Leo and Virgo is the direction toward the largest assembly of galaxies in the Milky Way’s region. The gigantic elliptical galaxy M87 is located 50 million light years from us at the center of the Virgo supercluster that includes several thousand member galaxies.

The next evening, March 20th, a waning but still brilliant gibbous moon moves further east in Virgo to a location about four degrees east of the star Spica (SPY-ca) and 10 degrees south of Saturn. Use your hand to shield the eyes from lunar glare to more easily spot first magnitude Spica and the sixth planet from the Sun, shining at magnitude 0.4. Spica is the brightest star in the constellation Virgo and is at a distance is about 260 light years from the Solar System.

Earth and Saturn are currently on the same side of the Sun. Earth is racing along in its solar orbit at 18 miles per second as it catches up to the more leisurely moving ringed behemoth which orbits nearly 10 times further from the Sun than Earth at just one-third Earth’s speed. On the night of the 20th Earth and Saturn are about 790 million miles apart.

Spring begins in the northern hemisphere at 7:21 p.m. Eastern Daylight Time March 20th. At that moment, the center of the Sun’s disk is directly above Earth’s equator at a mid-Pacific point, about 1,600 miles southwest of Hawaii and 550 miles east of tiny Howland Island. That was the erstwhile stopover point never reached on Amelia Earhart’s ill-fated around the world flight attempt in 1937.

During the late 18th century French astronomer Charles Messier sought fame by discovering comets. However, during this quest he often wasted time tracking fuzzy spots in the sky that resembled comets but lacked comets’ motion relative to background stars. Not wishing to repeat the diversions, Messier kept careful records of his celestial red herrings. During subsequent years, as astronomical technology developed, many objects on Messier’s list of bogus comets came to be understood as scientifically intriguing and often esthetically beautiful in their own right. In addition to providing gold mines of information for professional astronomers, many of the 110 objects eventually included on Messier’s list (including some discovered by his colleague Pierre Méchain) are now seen as prime targets for observers interested in seeking and personally viewing cosmic gems.

Messier objects are often referred to simply by their “M” catalogue numbers, some are also known by names such as The Great Nebula in Orion (M42), and the Andromeda galaxy (M31).

Although several Messier objects such as the Pleiades star cluster and Orion Nebula may be visible to unaided eyes in urban locales, many others can be sighted with the help of binoculars, especially if one is looking from dark sky locations far from artificial lights. All objects on the list may be seen over time, with varying degrees of difficulty, by knowledgeable sky watchers from dark sky sites using moderate sized telescopes.

Although Messier objects are present in our night sky over a progression of evenings throughout the year, late March provides the best opportunity for seeing all 110 objects on a single night. Attempting to do so is a feat known as a “Messier Marathon.” The distribution of these objects in our sky combines with the Sun’s position along the ecliptic to allow this annual window of opportunity. However the venture is a considerable challenge, even for experienced, well-equipped observers. In years when a New Moon occurs during late March, thereby reducing interference from the lunar glow, many intrepid observers in mid-northern latitudes stay at their telescopes through the night with Messier’s list in hand.

Unfortunately 2011 is not an optimal year for doing the Messier Marathon. During the last weeks of this month light from bright gibbous and crescent moons tend to overwhelm faint Messier objects. Although completing the full Messier Marathon is unlikely, the brighter catalogue members are certainly available this month for our viewing pleasure.

On Saturday March 26th the Moon is at its Last Quarter phase, located in the direction of the constellation Sagittarius, and it rises at 2:19 a.m. EDT. The Moon is then located near some of the sky’s basic references: the ecliptic, the summer solstice, the equator of the Milky Way, and the direction to a supermassive black hole located about 26,000 light years from us at the Galactic center.

March 31st, in the eastern sky at about 6:30 A.M., a thin waning crescent moon may be seen low in the east-southeast, five degrees to the upper left of brilliant Venus, shining at magnitude -4.0.

The daily duration of time the Sun is above the horizon increases during March by a total of one hour 21 minutes. On the last day of the month civil twilight begins at 6:14 a.m. with Sunrise arriving at 6:41. The Sun sets that evening at 7:19, followed 28 minutes later by the end of civil twilight. Our nearest star’s direction is then within boundaries of the constellation Pisces.

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