What's Up in the Night Sky

November 2017 - Vol. 21, No. 11

This Month's Night Sky - NOTE: The next paragraph describes the sky as it appears at 10 pm EST (11 pm EDT) near mid- month. The sky also looks this way at 11 pm EST (midnight EDT) during the beginning of the month and at 9 pm EST (10 pm EDT) by month's end.

If you are blest with a dark observing site, the Orion arm of the Milky Way (the galaxy we inhabit) arches overhead from horizon to horizon. Embedded are the stars of constellations Cassiopeia, denoted by its familiar "W" or Sigma asterism, and Perseus. The Summer Triangle finally disappears in the W. Although there are no bright stars due S., red Aldebaran and the tiny dipper asterism of the Pleiades’s, a famous open star cluster (Taurus), as well as yellow Capella (Auriga) glow in the SE. Later follows the twins, Castor and Pollux (Gemini), and the hour-glass asterism of constellation Orion with fuzzy M42 (Great Orion Nebula) just below its three "belt" stars, which heralds the coming of winter.

MERCURY is well placed this month, in conjunction with Saturn on the 28th. VENUS still shines in the morning sky but closes in on the Sun, a mere 10 deg. away by month's end. MARS in the morning sky in the constellation Virgo gains some height as it pulls away from the Sun. JUPITER emerges in the morning twilight sky moving into the constellation Libra on the 15th. SATURN disappears from the evening sky, moving into the constellation of Sagittarius where it will remain for the next few years. URANUS is well placed in Pisces this month. NEPTUNE sets at mid-night this month, occulted by the moon on the 22nd if you happen to live in Antarctica.

Review how to determine Angular Measurement.

Calendar of Events

NOTE: For those observers not in the ET zone, convert the calendar times to your zone's time by subtracting one hour for CT, two for MT and three for PT. Don't forget to adjust for Daylight Savings Time when necessary by subtracting one hour from your planisphere's time. Dawn and dusk times must also be corrected. See your local newspaper, TV news, or cable TV's Weather Channel for sunrise and sunset times or check with the U.S. Naval observatory. Unfortunately some of these events may occur during daylight hours in your area.

DATE	EVENT
04	This month's full moon is also called the Beaver Moon, that is the full moon closest the time to set beaver traps before the swamps froze, to ensure a supply of warm winter furs according to the Farmer's Almanac.
05	S. Taurid meteor peak. The Taurid meteor shower generates about 7 meteors per hour for both north and south streams. Meteors originating from these areas may be observed from mid-September to early December. Daylight Savings Time ends and Standard Time begins in the U.S. states that observe this practice.
06	Aldebaran 0.8 deg S. of the Moon occultation from most of North America, north Europe, and NW Asia. Moon at perigee.
11	Regulus .4 deg S. of Moon, occultation from Central America as well as SW North America, Japan, and Eastern Asia.
12	N. Taurid meteor peak Mercury 2 deg N. of Antares.
13	Venus .3 deg N. of Jupiter.
15	Mars 3 deg S. of Moon.
16	Vesta 4 deg N. of Moon, occultation from East Brazil and SW Africa. Jupiter 4 deg S. of Moon.
17	Venus 4 deg S. of Moon. Leonid meteor shower produces up to 20 meteors per hour. This year the moon will be close to new and the sky will be inky black from dark sky sites. It will be best to look after midnight and the shower should be at its best before morning twilight.
18	Venus 2 deg S. of Moon.
20	Mercury 7 deg S. of Moon
21	Saturn 3 deg S. of Moon. Moon at apogee.
24	Mercury greatest elongation E.
27	Neptune 1.2 deg N. of Moon, occultation from Antarctica.
29	Mercury 3 deg S. of Saturn.

Lunar Almanac for November 2017

Phases of the Moon	Phase and Date(s)	Best viewed before local midnight
	New 18	Deep Space Objects
	1st. Qtr 26	Planets & Moon
	Full 04	Moon
	Last Qtr 10	Deep Space & Planets

Topic of the month: Vesta

Asteroids are small, rocky objects that orbit the sun. These small objects are believed to be material left over from the formation of the solar system. One of the largest asteroids is Vesta, named after the Roman virgin goddess of home and hearth. The asteroid was noted this month in the daily almanac as it will be occulted from some locations on Earth on November 16. This is the first occultation in a series of 4, occuring for the next few months. Unfortunately, the occultations will be visible in far southern locations.

Today, Vesta is considered a minor planet. It was discovered on March 29, 1807 by Heinrich Olbers and became the fourth known asteroid referred to as 4 Vesta. It is the brightest asteroid and also the easiest to observe. The largest asteroid and the first detected by observers on Earth is known as Ceres. This body is large enough that it was pulled it into its spherical shape by its own gravity. Ceres is classified today as dwarf planet, as is Pluto.

Asteroids are believe to orbit the Sun in a area of the solar system called the asteroid belt, a ring of widely spaced objects orbiting around the Sun. The main asteroid belt orbits between Mars and Jupiter, about 2.3 to 3.3 A.U. from the Sun. It is composed mostly of small bodies made up of rocky and metallic minerals. They range in size from hundreds of kilometers in diameter to microscopic dust particles. Asteroids are classed in groups and families based on their orbital characteristics. Some have "moons", smaller asteroids orbiting larger asteroids.

As members of the solar system, the orbit of these small bodies can be affected by planets due to gravitation. The planet Jupiter being a principle player. But as Asteroids drift into the inner solar system Mars, Earth, Venus and even Mercury can change an asteroid's orbit. Asteroids that have been attracted by Earth and cross its orbit are called "Near Earth Objects". Some asteroids are monitored because they come close to Earth, these are called "Potentional Hazardous Objects" or "PHAs". Find out more about these objects on Astra's Near Earth Asteroids page.

Asteroid Vesta mosaic from Dawn Mission space probe Vesta is 530 km in diameter and the second most massive object in the belt. It makes up about 9% of the total mass of the asteroid belt. Luckily this massive object is far enough away from our planet that the Earth is safe. Vesta and Ceres were explored by the Dawn space craft. The Dawn mission studied Vesta from July 2011 to September 2012. The image posted here was created by integrating many images from the Dawn probe. The Dawn space probe has been orbitting Ceres since March of 2015. In October of 2017, NASA was given permssion to extend the Dawn Mission. The space probe may end its days in orbit around the asteroid long after communications with the probe are not possible.

The asteroid Vesta is almost a dwarf planet, it is nearly spherical and the materials making it have differentiated into crust, mantle, and core similar to Earth. Key features on the asteroid are 3 overlapping craters Minucia (21.5 km), Calpurnia (50 km) and Marcia (58 km). Seen in the upper left section of the image, these three craters are affectionatley know as the "Snowman." Vesta has a bulge around its equator, but its southern pole has been blasted by a collision with another object. The huge impact basin is 500 km in diameter. Its central peak rises 15 km above the mean surface, almost as high as Olympus Mons. Occuring about a billion years ago, Vesta lost some 1% of its mass due to the impact. Fragments spewing out from this event have traveled all the way to earth. They have been identified as HED (Howardite-Eucrite-Diogenite) meteorites.

The magnitude of Vesta is variable, the best opposition tops out at 5.4 but a good opposition would be 6.2 or 6.3, just beyond the limit for naked eye observers. A telescope is required to detect the asteroid.

--See You Under the Stars!
Astra for Astra's Almanac