Tag Archives: Arcturus

Virgo (The virgin)

Constellation VirgoVirgo, the virgin, is one of the zodiacal constellations,  is one of the 48 constellations cataloged by 2nd century astronomer Ptolemy, and is the 2nd largest constellation in the sky. It can be found at is highest point in the sky at nightfall in March. Virgo is located on the ecliptic, flanked by Leo and Libra. It can also be found by following the arc of the Big Dipper’s handle through Arcturus in Bootes to Spica (Alpha Virginis), Virgo’s brightest star. Some of Virgo’s remaining stars can be difficult to see in light-polluted urban skies because this is not a particularly bright constellation. Within Virgo is one of the two points where the ecliptic intersects the celestial equator.  The moment of the Sun’s southward crossing of the celestial equator as it moves along the ecliptic is the Autumnal Equinox, which marks the first day of Fall.

The Virgo Cluster is a very large scale object spanning about eight degrees and containing 1,300 or more individual galaxies. The cluster is centered in Virgo, and extends northward into Coma Berenices. The member galaxies that were cataloged by Charles Messier are M49, M58, M59, M60, M61, M84, M86, M87, M89, and M90. Many other galaxies in this cluster have NGC designations. The Sombrero Galaxy, M104, is a very unusual galaxy in Virgo that is not a member of the Virgo Cluster.
http://en.wikipedia.org/wiki/Virgo_(constellation)

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

© James R. Johnson, 2014.

Boötes (The herdsman or plowman)

BootesBoötes is a bright and distinct northern constellation that is one of the 48 constellations cataloged by 2nd century astronomer Ptolemy. It can be found by looking south of Draco, lying between Hercules and Ursa Major. It is also found by following the curve of the Big Dipper’s handle southward and away from the bowl to the bright star Arcturus. Sometimes the phrase “arc to Arcturus” is used to describe this approach to locating it. Boötes reaches its highest nightfall ascension in June. Arcturus is the fourth brightest star in the night sky, and Boötes is home to many other bright stars, including eight above the fourth magnitude and an additional 21 above the fifth magnitude, making a total of 29 stars easily visible to the naked eye.

There are no Messier objects located in Boötes, but several NGC galaxies can be found with a telescope. The radiant of the Quadrantids meteor shower, which displays about 100 meteors per hour when it peaks over January 3rd and 4th, is located between Bootes’ head and the end of Ursa Major’s tail.
http://en.wikipedia.org/wiki/Bootes_(constellation)

IAU Bootes chart, IAU and Sky  Telescope magazine (Roger Sinnott and Rick fienberg), June 4, 2011.

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

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

Ursa Major (The great bear)

Ursa MajorUrsa Major is a circumpolar constellation that was cataloged by 2nd century astronomer Ptolemy. The Big Dipper asterism is perhaps the most easily identifiable aspect of this constellation. As a circumpolar constellation at 40 degrees north latitude, it can be seen at any time on any clear night from a location with an unobstructed view of the northern horizon. In April, however, Ursa Major reaches its highest ascension at nightfall.

All seven stars comprising the Big Dipper were named by the ancients. The Big Dipper’s handle is the bear’s tail and the bowl is the bear’s hindquarter. Upon closer examination and in a darker sky, all of the constellations stars add to the dipper to form a distinct and complete bear. The two Big Dipper bowl stars opposite the handle are the pointer stars that guide the eye to Polaris, or the north star. Following the arc of the tail away from the bowl, a method sometimes referred to as “arc to Arcturus,” leads the observer to the star Arcturus in the constellation Bootes.  Starting at the end of the tail and moving around through the bottom of the dipper’s bowl, the are: Alkaid (Eta Ursae Majoris), Mizar (Zeta Ursae Majoris) and its naked eye binary companion star Alcor,  Alioth (Epsilon Ursae Majoris), Megrez (Delta Ursae Majoris), Phecda (Gamma Ursae Majoris), Merak (Beta Ursae Majoris), and Dubhe (Alpha Ursae Majoris) . Impress your friends by committing these stars’ names to memory and pointing them out on a late Spring evening when the dipper is high in the northern sky.

Ursa Major contains several Messier objects. A famous pair is M81, a nearly face-on spiral galaxy, and M82, a nearly edge-on galaxy, that gravitationally  interact with one another and can be see within a single field of view of a modest telescope. M101, 108 and 109 are three other Messier galaxies, and M97, a planetary nebula are also found in Ursa Major. One rather odd Messier object is M40, which is the only double star in the Messier catalog.
http://en.wikipedia.org/wiki/Ursa_Major_(constellation)

IAU Ursa Major chart, IAU and Sky & Telescope magazine (Roger Sinnott and Fick Fienberg), June 5, 2011.
IAU Ursa Major chart, IAU and Sky & Telescope magazine (Roger Sinnott and Fick Fienberg), June 5, 2011.

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