Tag Archives: Ecliptic

Aries (The ram)

Constellation AriesAries is the zodiacal constellation named after the ram.  In ancient times, this constellation represented the golden fleece that was stolen by Jason and the Argonauts. It is one of the 48 constellations cataloged by 2nd century astronomer Ptolemy that remain among the 88 modern constellations. It is located on the ecliptic between Pisces and Taurus, and just south of Triangulum. It is highest in the sky at darkness and can be best seen in December.  Its brightest star is Hamal (Alpha Arietis), and most of this constellation’s stars can be picked out in most light polluted urban skies, but the constellation bears little resemblance to a ram.
http://en.wikipedia.org/wiki/Aries_(constellation)

IAU Aries chart, IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg), June 4, 2011.
IAU Aries chart, IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg), June 4, 2011.

© James R. Johnson, 2014
jim@jrjohnson.net

Cetus (A sea monster in Greek mythology)

CetusCetus, the Greek mythological sea monster, is a large southern constellation on the celestial equator, and one of the 48 constellations cataloged by 2nd century astronomer Ptolemy. It is accompanied by other water constellations – Pisces, Aquarius and Eridanus. Its head is nestled among three zodiacal constellations: Taurus, Aries and Pisces. Its body is south (below) Pisces, and is flanked by Aquarius and Eridanus. Cetus’ close proximity to the ecliptic means that the Moon, planets and asteroids occasionally pass through this constellation. Cetus is placed highest in the sky at nightfall in December.

Cetus is home to one Messier object, M77, a striking face-on spiral galaxy. Among Cetus’ stars is an unusual variable star, the disappearing  one, or Mira (Omicron Ceti). This star’s high variability from 3rd magnitude to 10th magnitude means that it disappears from view when it dips below 5th or 6th magnitude. Cetus’ brightest star Menkar (Alpha Ceti) marks the sea monster’s nose.
http://en.wikipedia.org/wiki/Cetus

IAU Cetus chart, Sky & Telescope magazine (Roger Sinnott and Rick Fienberg), June 5, 2011.
IAU Cetus chart, Sky & Telescope magazine (Roger Sinnott and Rick Fienberg), June 5, 2011.

© James R. Johnson, 2014.
jim@jrjohnson.net

Pisces (The fishes)

Constellation PiscesThis zodiacal constellation is a rather dim grouping of stars that are strung out low across the southern sky, just below the Great Square of Pegasus. Pisces is one of the 48 constellations cataloged by the 2nd century astronomer Ptolemy that remain among the 88 modern constellations. It is highest in the sky and best observed at nightfall in December. The intersection of the ecliptic and the celestial equator lie within this constellation. There are two such intersections that mark the two equinoxes. At the intersection in Pisces, the Sun is moving from south to north, so this is the point of the Vernal (spring) Equinox. This constellation is home to just one Messier object, M74.
http://en.wikipedia.org/wiki/Pisces_(constellation)

IAU Pisces chart, IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg), June 5, 2011

© James R. Johnson, 2014
jim@jrjohnson.net

Aquarius (The water bearer)

Constellation AquariusAquarius, the water bearer, is a rather dim and nondescript zodiacal constellation. This southern constellation was cataloged by 2nd century astronomer Ptolemy. It is located in a region known to  the ancients as “the sea” because several water constellations, to include Capricornus (the sea goat), Piscis Austrinis (the fish), Pisces (the fishes), and Cetus (the sea monster) are gathered there. It is situated on the ecliptic between Capricornus and Pisces, and is just south of the Great Square of Pegasus. Aquarius reaches its highest nightfall ascension in November. Three globular star clusters, M2, M72 and M73 are the only Messier objects found in this constellation. The Eta Aquariids is the strongest meteor shower radiating from Aquarius, peaking at about 35 meteors per hour between May 5th and 6th.
http://en.wikipedia.org/wiki/Aquarius_(constellation)

IAU Aquarius chart, Sky & Telescope magazine (Roger Sinnott and Rick Fienberg), January 27, 1997.
IAU Aquarius chart, Sky & Telescope magazine (Roger Sinnott and Rick Fienberg), January 27, 1997.

© James R. Johnson, 2014.
jim@jrjohnson.net

Capricornus (The sea goat)

Constellation CapricornusCapricornus, the sea goat, is a zodiacal constellation and one of the 48 constellations cataloged by Ptolemy in the 2nd century. It is located on the ecliptic between Sagittarius and Aquarius, and is south of the Summer Triangle and the Great square of Pegasus.  Capricornus reaches its highest nightfall ascension in October. Its alpha star, Deneb Algedi (Delta Capricorni), is just brighter than magnitude 3, and can be seen under most reasonable conditions. The remainder of the constellation is rather dim and difficult to see in light-polluted urban skies. The globular star cluster, M30, is the only Messier object in this constellation.
http://en.wikipedia.org/wiki/Capricornus

IAU Capricornus chart, Sky & Telescope magazine (Roger Sinnott and Rick Fienberg), June 4, 2011.
IAU Capricornus chart, Sky & Telescope magazine (Roger Sinnott and Rick Fienberg), June 4, 2011.

© James R. Johnson, 2014.
jim@jrjohnson.net

Sagittarius (The archer)

Constellation SagittariusSagittarius, the archer, is a zodiacal constellation that is rather easily found because of its distinctive teapot asterism. It is one of the 48 constellations cataloged by the 2nd century astronomer Ptolemy. It is located on the ecliptic between Scorpius and Capricornus. It can also be found by starting at Altair (a Summer Triangle star) and tracing southward along Aquila’s long axis. As is situated on southern most point of the ecliptic, this constellation hangs low in the southern sky, reaching its highest nightfall ascension in August. The Sun’s arrival at the southernmost point of the ecliptic around December 21st marks Winter Solstice and the first day of Winter.

This constellation has the distinction of presenting the foreground stars in the direction of the dense center of the Milky Way galaxy, which is rich in Messier objects. As such, it is worth taking the time to scan this constellation with binoculars or a small telescope. Several well-known nebula can be found in Sagittarius to include the Lagoon Nebula (M8), the Horseshoe Nebula, the Omega Nebula (M17), the Trifid Nebula (M20), and the Small Sagittarius Star Cloud (M24). Other Messier objects include M18, M22, M23, M25, M28, M54, M55, M69, M70 and M75.
http://en.wikipedia.org/wiki/Sagittarius_(constellation)

IAU Sagittarius chart, Sky & Telescope magazine, June 5, 2011.
IAU Sagittarius chart, Sky & Telescope magazine (Roger Sinnott and Rick Fienberg), June 5, 2011.

© James R. Johnson, 2014.
jim@jrjohnson.net

Scorpius (The scorpion)

Constellation ScorpiusScorpius is perhaps the most beautiful of the zodiacal constellations. This southern constellation is located on the ecliptic between Libra and Sagittarius and is situated south of Ophiuchus. Antares (Alpha Scorpii), the reddish 1st magnitude star might first catch the observers attention. Then look for the remainder of the constellation which includes a distinct head, long slender body, curling tail, and stinger of a scorpion. Even though Sagittarius is on the lowest point of the ecliptic, Scorpius is the southernmost of the zodiacal constellations, which tends to leave the tail hanging below the treeline for us northern latitude observers. Southbound travelers in July, which is when Scorpius reaches its highest nightfall ascension, should make it a point to observe this very pretty constellation.

Scorpius’ location on the Milky way makes it home for many deep sky objects, such as the Butterfly Cluster (M6) and the Ptolemy Cluster (M7). Other objects cataloged by Charles Messier include globular clusters M4 and M80.
http://en.wikipedia.org/wiki/Scorpius

IAU Scorpius chart, IAU and Sky & Telescope magazine, 5 June 2011.
IAU Scorpius chart, IAU and Sky & Telescope magazine (Roger Sinnott and Rick Fienberg), 5 June 2011.

© James R. Johnson, 2014
jim@jrjohnson.net

Libra (The scales)

Constellation LibraLibra, the scales, is a small zodiacal constellation of  rather dim stars that was cataloged by 2nd century astronomer Ptolemy. It is located on the ecliptic between Virgo and Scorpius, and is to the south of Ophiuchus. This southern constellation, which never rises very far above the horizon, reaches its highest nightfall ascension in June. Its brightest star, Zubenelgenubi, is just brighter then 3rd magnitude, which can be a challenge to see in some light-polluted urban skies.
http://en.wikipedia.org/wiki/Libra_(constellation)

IAU Libra chart, Sky & Telescope magazine (Roger Sinnott and Rick Fienberg), June 5, 2011.
IAU Libra chart, Sky & Telescope magazine (Roger Sinnott and Rick Fienberg), June 5, 2011.

© James R. Johnson, 2014.
jim@jrjohnson.net

Leo (The lion)

Constellation LeoLeo, the lion, is a distinctive zodiacal constellation that was cataloged by 2nd century astronomer Ptolemy. It is located on the ecliptic between Cancer and Virgo, and can be found below the bowl of the Big Dipper with both constellations arriving at their highest nightfall ascension in April.  Leo closely resembles a crouching lion with its rather distinct backward question mark, or sickle asterism. This constellation features the bright star Regulus (Alpha Leonis) at the back of the lion’s head.

The most famous deep sky object in Leo is The Leo Triplet is a close grouping of the galaxies M65, M66 (displayed) and NGC3628 that can be seen together in a single telescopic field of view. For those observing with telescopes, there are several other galaxies cataloged by Charles Messier are located in Leo, to include M65, M66, M95, M96 and M105. Leo is also home to the famous Leonids meteor shower that occurs during November, peaking at about 10 meteors per hour on November 14th and 15th.
http://en.wikipedia.org/wiki/Leo_(constellation)

IAU Leo chart, IAU and Sky & Telescope magazine (Roger Sinnott and Rick Fienberg, June 5, 2011.
IAU Leo chart, IAU and Sky & Telescope magazine (Roger Sinnott and Rick Fienberg), June 5, 2011.

© James R. Johnson, 2014.
jim@jrjohnson.net

The Moon’s Planetary Conjunctions During May 2014

When two Solar System objects arrive at their closest approach to one another as viewed from Earth, they are said to be in conjunction. This month I will examine the Moon’s close approaches to all five of the visible planets that were known to the ancients. As both the Moon and the planets are in constant motion, the actual conjunction is represented by an instant in time. Because of their slow apparent motion, the close approaches (visits?) can be observed for many hours before or after a conjunction.

As previously mentioned, the planets and the Moon never wander far from the ecliptic. One implication of this fact is that as the Moon completes its 28-day orbit around the Earth, it will be in conjunction with each of the planets once. This month, the young (thin) crescent Moon will first visit Jupiter near the western horizon in Gemini on May 3rd (closest) and 4th. Try to observe on both evenings and note that the Moon has moved eastward. Also note Jupiter’s position among Gemini’s stars, perhaps by making a sketch of Gemini that indicates Jupiter’s position. This sketch will come in handy near the end of the month.

Next up is a very interesting series of close encounters with three bright and colorful objects (Mars, Spica and Saturn) in the east at dusk on May 10th through the 14th. There are lots of things to observe over the course of these five evenings. First, the waxing gibbous Moon will grow larger each evening until it reaches full Moon on May 14th. Next, note that its location is a little farther east each evening. These two phenomena are the result of the Moon moving along its orbital path around the Earth, which changes its angle relative to the Sun. Also note that the point at which the Moon became full last month was closer to Mars (read about the lunar eclipse in April’s Scope Out), and this month the full Moon occurs closer to Saturn. This eastward slide of the full Moon from one month to the next happens because of the Earth moving along its orbital path around the Sun. And finally, note the distinct colors of the three objects: Mars is red, Spica is blue, and Saturn is yellow. The Moon will be near Mars on May 10th, and between Mars and Spica on May 11th. It will be between Spica and Saturn, but closer to Spica on the 12th, and closer to Saturn on the 13th. And finally it will be on the eastward side of Saturn on May 14th, the last evening of this string of encounters.

Another rewarding and challenging opportunity to observe the Moon arrives near month’s end as it transitions from a thin waning crescent in the eastern sky at morning, to a thin waxing crescent in the evening sky in the evening. First, observe the Moon as a thin waning crescent on the eastern horizon during its close encounter with Venus just before sunrise in the pre-dawn hours of May 25th. A careful observer might see an even thinner crescent very low on the horizon and closer to the sunrise point the next morning. After this, the Moon cannot be seen because it is lost in the Sun’s glare as it approaches new Moon (conjunction with the Sun) on May 28th. A young Moon (thin waxing crescent) emerges from the Sun’s glare on May 30th, and can be seen very low on the western horizon near Mercury. On the next evening, it will appear a little higher above the horizon, and it will once again visit Jupiter. Check the sketch that you made at the beginning of the Month. Has Jupiter moved among the stars since its last visit with the Moon on May 3rd and 4th?