The Night Sky This Month: March 2018

Earthshine
Image Credit: Earthshine by Abhijit Juvekar

Northern hemisphere observers will no doubt be overjoyed by the fact that the Vernal Equinox (spring equinox) occurs on March 20, which heralds the advent of spring in the northern hemisphere, the current severe weather notwithstanding. Moreover, the first half of March also offers some excellent opportunities to view the zodiacal light in the west just after astronomical twilight has faded, which is the result of the Sun illuminating the ring of dust that surrounds planet Earth.

Moon

March offers some great opportunities to view earthshine from the 10th to the 16th, when sunlight that is reflected off Earth illuminates the dark hemisphere of the waxing crescent Moon, and again from the 18th to the 23rd, when reflected sunlight will illuminate the dark hemisphere of the waning crescent Moon. March also brings a second or so-called blue Moon on the 31st of the month.

Phases

Full Moon: 2nd
Last Quarter: 9th
New Moon: 17th
First Quarter: 24th
2nd Full Moon: 31st

Planets

Mercury reaches is maximum eastern elongation from the Sun on the 15th, when it will be separated from the Sun by 18 degrees. Although the little planet sets about two hours after the Sun, the best time to view it is about one hour after sunset; look for Mercury in the west on the 4th, when Venus will be about 1 degree below Mercury. Venus and Mercury will again form a relatively close pairing on the 19th, when Venus will be about 4 degrees below Mercury. On both occasions, Venus will be the (much) brighter of the two planets.

Venus starts the month setting just more than an hour after the Sun, but sets progressively later until by month’s end, it will set about 2 hours after sunset. Bear in mind that Venus will always be close to the Sun during much of the month, so be sure to look for it only after the Sun has set.

Mars is now a predawn object, and will rise before 03H00 GMT throughout March. Mars will then grow progressively brighter as Earth catches up to it, and by mid-month the Red Planet is expected to shine at magnitude +0.58, which is about as bright as the star Betelgeuse in Orion. Look for Mars in the constellation Sagittarius, about 8 degrees above the south-eastern horizon from around 04H00. Be sure to look for Saturn, also in Sagittarius, about 9 degrees to the left of Mars.

Jupiter is now in the constellation Libra, where it is the brightest predawn object in the sky, apart from the Moon if it is present. Jupiter will rise at around midnight throughout the month, and it will culminate, or reach its highest elevation in the south at about 20 degrees above the horizon. On the morning of the 7th, the gibbous waning Moon will be about 4 degrees above Jupiter.

Saturn is now a predawn object, rising as it does about four hours before sunrise in the constellation Sagittarius. Throughout the month, Mars will be approaching Saturn, and the two planets will form a close pairing at about 03H00 GMT on the 2nd of April, albeit at an altitude of only about 5 degrees above the south-eastern horizon. Although Saturn remains low on the horizon, its ring system is still tilted towards our line of sight, and will remain so throughout the rest of 2018.

Uranus is still in the constellation Pisces, and although the planet sets about four hours after the Sun at the beginning of the month, its period of visibility will decrease rapidly as it sets progressively earlier as the month wears on. Nonetheless, on the evening of the 29th, observers with small telescopes might be able to observe Venus shining at magnitude -3.75, and approach magnitude +5.91 Uranus to within about 1 degree. Note that Uranus will be towards the lower right of Venus on this occasion.

Neptune will reach a position of conjunction with the Sun on the 4th, and will therefore not be visible during March.

Meteor Showers

Although there are no major meteor showers during March, about ten minor showers will be active at various times. March meteor showers include the Rho Leonids, Pi Virginids, Leonids-Ursids, xi Herculids, and the Eta Virginids, among others. However, all of the March meteor showers are expected to deliver fewer than 3-5 meteors per hour during their peaks, and some may not deliver any meteors at all. In short, March is not a good time for meteor watching.

Deep-Sky Objects

Some prominent constellations at this time of year include Crater, Hydra, the western half of Virgo, Leo, and the circumpolar constellation Ursa Major, which is now almost directly overhead. All of these constellations offer many spectacular deep-sky objects (DSOs), three of which are located in Hydra, and briefly discussed below.

Messier 48 (M48, NGC 2548)

Located in the constellation Hydra, M48 is an open cluster that is estimated to be about 300 million years old. Being relatively bright at magnitude 5.5, it is an easy target for binoculars and small telescopes. Under dark skies and with good seeing conditions, M48 is also visible without any optical aid.

Southern Pinwheel Galaxy (M83, NGC 5236)

Also located in Hydra, M83 is a barred spiral galaxy that bears a strong resemblance to the Pinwheel Galaxy (M101) in Ursa Major, hence its name, the Southern Pinwheel Galaxy. Being located only about 14.7 million light years away, the Southern Pinwheel Galaxy is one of the closest and brightest discovered to date, which makes it an easy target for binoculars and small telescopes. Note that although this galaxy bears a Messier designation, it was discovered by Nicolas Louis de Lacaille on February 23, 1752 while observing from the Cape of Good Hope. Messier merely added the galaxy to his catalogue in 1781.

Ghost of Jupiter (NGC 3242, Caldwell 59)

Located only about 1,400 light years away in the constellation Hydra, this magnitude 8.60 planetary nebula is an easy target for large binoculars and small telescopes. This nebula is also known as Jupiter’s Ghost, and less often as the Eye Nebula. It was discovered by William Hershel in February 1785, and it was included in John Hershel’s General Catalogue after he (John Hershel) had also observed the nebula from the Cape of Good Hope 1864.

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