This Month’s Sky – March 2015


What’s Up in the Sky
AAA Observers’ Guide
By Tony Faddoul

 

March’s Evening Planets: Mars will be visible for about an hour after sunset in Pisces the Fish. Venus will be visible for about 3 hours after sunset moving from toward Taurus the Bull. Uranus will also be in Pisces for about one hour after sunset in the first half of the month. Bright Jupiter is found in Cancer the Crab all night.

March’s Evening Stars: The Winter Triangle will be up in March until 11:00 PM with Sirius, the brightest star viewed from Earth, in Canis Major the Great Dog; Betelgeuse in Orion the Hunter; and Procyon in Canis Minor the Small Dog. Spot Capella in Auriga the Charioteer, Aldeberan in Taurus the Bull, Arcturus in Bootes the Herdsman, and bright Castor and Pollux in Gemini the Twins. Also find the stars of constellations Cassiopeia, Perseus, Cepheus, Draco, Virgo, Leo, Cancer, Corona Borealis, and the two Dippers during the month.

March’s Morning Planets: Jupiter will linger in Cancer the Crab until dawn. Saturn be up in Scorpius the Scorpion after midnight and will stay until sunrise. Mercury is between Capricornus the Seagoat and Aquarius the Water Bearer during the first half of March for about an hour before sunrise. Later in the month, Neptune will be in Aquarius shortly before sunrise. Dwarf planet Pluto will be in Sagittarius the Archer a couple of hours before sunrise.

March’s Morning Stars: Spot the Summer Triangle around 3:00 AM, rising earlier every night, formed by Vega in Lyra the Harp, Deneb in Cygnus the Swan, and Altair in Aquila the Eagle. Look for reddish Antares in Scorpius the Scorpion, Arcturus in Bootes the Herdsman, and Spica in Virgo the Virgin, along with the stars of constellations Leo, Lyra, Hercules, Libra, Corona Borealis, Cassiopeia, Cepheus, Draco, and the two Dippers.

March “Skylights”

Mar 3 Jupiter is 5° north of the Moon (morning)
Mar 5 Full Moon at 1:05 PM EST (smallest of 2015)
Moon at apogee (252,515 miles from Earth)
Mar 8 Daylight Saving Time begins ETS
Mar 13 Last Quarter Moon at 1:45 PM
Mar 19 Moon at perigee (222,190 miles from Earth)
Mar 20 New Moon at 5:35 AM
Vernal Equinox at 6:45 PM
Total Solar Eclipse (not visible in the US)
Mar 21 Mars is 1° north of the Moon (at sunset)
Saturn is 2° south of the Moon (morning)
Mar 22 Moon pairs with Venus after sunset
Mar 27 First Quarter Moon at 3:45 AM

Times given in EDT, unless noted.

Pluto and the Dwarf Planets
In 2006, the International Astronomical Union (IAU) changed Pluto’s classification to a dwarf planet, defined as: “a celestial body that (a) is in orbit around the Sun, (b) has suffi-cient mass for its self-gravity…so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neigh-bourhood around its orbit, and (d) is not a satellite.” Dwarf plan-ets are tiny, dim, and often in far-flung orbits, making them tough to find. Scientists estimate that dozens remain undiscov-ered. Here are the five most recognized.

dwarf_orbit

Pluto was discovered by Clyde Tombaugh in 1930 and named for the Roman god of the under-world (Hades, in Ancient Greece). The 1,455 mile-wide body has an extremely elliptical orbit in a different plane than the eight planets of our Solar System. It orbits the Sun at an average distance of 39.3 au, taking 248 Earth years to complete a lap. Its five moons are named for elements of underworld mythology: Charon, Nix, Hydra, Kerberos, and Styx. The largest, Charon, is nearly equal in size to Pluto, forming a double system. NASA’s New Hori-zons spacecraft is scheduled to reach Pluto in July 2015. It was still the ninth planet when the mission launched in early 2006.

Ceres is the smallest of the dwarf planets at 590 miles wide, but the largest object in the Asteroid Belt between Mars and Jupiter. Discovered in 1801, it was named for the Roman grain goddess (Demeter, to the Greeks). It is nearest at only 2.8 au from the Sun and completes one orbit in 4.6 Earth years. It is thought to be an icy protoplanet, the only one not found in the Kuiper Belt. NASA’s Dawn mission will arrive at Ceres this month for our first study of a dwarf planet.

 

Haumea, discovered in 2003, has an elongated shape with a rocky interior, covered by a thin, icy crust. It is named for the Hawaiian goddess of fertility, and its moons are named for her daughters Hi‘iaka and Namaka. Haumea is about as wide as Pluto at 1,200 miles, but it is 1/3 as massive. Haumea averages 43.2 au in its 283 Earth-year orbit. It completes one full rotation in less than four hours, making it one of the fastest-spinning bod-ies in the Solar System.

Makemake, a plutoid (orbiting beyond Neptune), was discovered ten years ago and is named after the fertility god of the native people of Easter Island. Its surface is thought to be composed of frozen methane, ethane, and nitrogen. It is about 3/4 as big as Pluto and at 45.7 au from the Sun, it completes one orbit every 310 Earth years.
Eris, a plutoid, was found in January 2005 and briefly considered our tenth planet. It was demoted by the IAU with Pluto. It is named for the Greek goddess of chaos and has one known moon named for her daughter, Dysnomia, the god-dess of lawlessness. Eris is similar in size to Pluto but about 25% more massive. It has a highly elliptical orbit at an average distance of 67.8 au, which takes 557 Earth years to complete.

Sources: IAU; Encyclopedia Britannica; nasa.govspace.com.