This is the Dudley Observatory’s Skywatch Line for Monday and Tuesday March 8th, and 9th, written by Joe Slomka.
The Sun sets at 5:54 PM; night falls at 7:28. Dawn breaks at 4:43 AM and ends with sunrise at 6:17.
Monday’s Moon already rose and set by sunset. Tuesday’s 29-day-old Moon rises in Capricornus at 4:38 AM and sets at 1:52 PM, 15% illuminated. Wednesday’s Moon rises at 5:18 AM and appears 8% lit.
Monday’s night sky displays a glittering array for the beginner.
Three bright stars dazzle: Sirius (the Dog Star), Betelgeuse and Rigel in Orion, Aldebaran and Mars in Taurus. Mars continues to shrink and dim; it is now 6 arc-seconds in size and 1st magnitude in brightness. Mars sets shortly after Midnight. However, the main attraction is the asteroid Vesta. Vesta travels in the Main Belt, between Mars and Jupiter. It rises at 4:56 PM, is highest at 12:04 AM and sets at 7:12 AM.
Like planets and comets, asteroids have defined orbits about the Sun. Comets are ice and rock mixes, while asteroids are mostly rock. There are several types of asteroid. Some orbit between Jupiter and Mars, others accompany planets, and then there are interlopers from the far reaches of the solar system.
Vesta is the fourth dwarf planet to be discovered. It orbits the Sun every 3.6 years, and is past opposition, which occurred on March 4th. Like the first three asteroids, Vesta was temporarily named a planet, until astronomers realized its small size; it’s about 330 miles in diameter. Vesta is the brightest asteroid. It can be seen with binoculars from a dark, rural site. The Dawn spacecraft discovered layers of rock and metal. It also found that liquid water once flowed and that frozen water may lurk underground. Vesta was victim of an ancient collision; some pieces may have traveled to Earth as meteorites, which have a chemistry similar to Vesta’s.
Vesta currently inhabits the body of Leo, the Lion. Since it is currently in Opposition to the Sun and up all night, this is prime time to study this brightest of asteroids. It is located a bit above the 3rd magnitude star Theta Leonis (Chort), which forms the Lion’s hip. Monday at 7 PM, it shines about 21° above the Eastern horizon. Astronomy magazines and websites have finder charts for beginners.
The pre-sunrise southeastern sky contains similar treasures. The thin Moon rises in Sagittarius about 8° high. Capricornus exhibits 3 bright planets. Saturn rises first at 4:45 AM and glows with 0.7 magnitude. Jupiter follows 9° behind Saturn by rising at 5:08 AM and blazing with minus 2nd magnitude. Mercury brings up the rear by rising at 5:19 AM, shining with 0.52 magnitude and trailing Jupiter by 3°