This month we can enjoy more daylight as we approach the spring equinox and the start of British Summertime, however there are still some great night skies to be enjoyed. Vernon from the Callander and West Perthshire U3A Astronomy group shares what to look out for this month.
It is always helpful to have a star chart to follow when navigating and observing the heavens. A free star chart which also contains lots of additional observational notes is published monthly by Skymaps. Simply go to skymaps.com and scroll down to ‘Download the latest issue’. From here you will can download the northern hemisphere version and save it. This is then best printed double sided to an A4 sheet. It is worth noting that planets do not appear on skymaps. In this note of astronomical events I have only included items that can be seen either with the naked eye or with a pair of binoculars.
Should you venture outside you will need a torch. Use a red light head torch if you have one, or put red plastic over a torch to illuminate the skymap and preserve your night vision which improves greatly over time. Wrap up warm and with a little perseverance, about 20 minutes, you will feast your eyes on the universe that you live within. Enjoy and indulge!
During March, the centre of the Sun’s disc appears to cross the celestial equator heading south to north. This instant occurs at 09.37 (Universal Time) on March 20th marking the Northern Hemisphere’s spring or vernal equinox. It is often said that day and night are equal at the equinoxes, but this is an approximation. Other factors adjust the length of day and night for different latitudes and the actual dates when day and night are of equal length occur a few days off of the equinox. These days are known as equiluxes.
The winter constellations of Gemini and Orion are starting to drift to the west to be replaced by more subtle constellations of Leo, Virgo and Coma Berenices. Leo can be found by looking due south and identifying the bright star Regulus, (can be easily found on 25th at 7pm when it is next to the Moon). Leo is the home of a regular November treat, the Leonid meteors when Earth moves through a stream of particles left by the comet Tempel-Tuttle. The meteors radiate from the sickle, or head, of the Lion. Rates are typically low but on occasion storms do occur such as in 1833 when shooting stars were said to have fallen from the sky “like snowflakes”. Virgo is the largest constellation in the Zodiac and also the second largest in the entire sky. It has several identities in Ancient Greek mythology. In one story she represented Demeter, the corn goddess and was depicted holding an ear of grain marked by the constellations brightest star, Spica. Usually though she was equated with Dike, the goddess of justice and the adjoining constellation of Libra was visualised as her scales of justice. The constellation is shaped like a sloping letter Y, with Spica at the base. In the bowl of the Y is the Virgo Cluster some 55 million lightyears away. At the heart of the Virgo Cluster lies the giant elliptical galaxy M87 one of the most massive local galaxies with a mass of almost 3 trillion Suns. Coma Berenices is named after Ancient Egyptian Queen, Berenices II. It is easily found between Leo and Bootes. This constellation was considered to be part of Leo until 1536 when it was shown as a separate entity by German cartographer Caper Vopel. The constellation has no significant bright stars, but it is of considerable interest to astronomers because of its deep sky galaxies and clusters, which include the lenticular and Black Eye galaxies.
Looking directly overhead
Observing from the South finds Ursa Major overhead right side up and facing to the right with the Pointers Dubhe and Merak directly overhead giving directions to the north star, Polaris. Ursa Major is the 3rd largest constellation in the sky and has been imagined as a bear by widely separated civilisations since ancient times. Homer mentions it in book XVIII of the Iliad referring to “the Bear which men also call the Wain”. Its seven brightest stars form the body and tail of the bear, while feinter outlying stars mark the head and limbs. Forming a triangle with the tail stars of Alkaid and Mizar is a favourite deep sky object, the Pinwheel Galaxy M101, which can be seen with binoculars and lies some 27 million light years from Earth.
Looking due north in the first half of the month finds Cephus lying across the edge of the Milky Way with the distinctive W shape of Cassiopeia to its west. Cephus is shaped like a building with a pointed roof. The constellation represents a king in Ancient Greek mythology who was supposedly the King of Ethiopia, a mythical country on the eastern Mediterranean, not the African country we know today. He was the husband of Cassiopeia, who lies next to him in the sky and the father of Andromeda. There are many stars at the base of Cephus with one that stands out because of its deep red colour. This is Mu Cephei, also known as the Garnet Star. It is a pulsating star which varies from 3.4 to 5.1 and back every 2 years, and also a red supergiant 2400 times the diameter of our Sun. If placed in our solar system it would extend beyond the orbit of Saturn. Betelgeuse in Orion is also a red supergiant, but it is only 500 times our Sun. Cassiopeia lies within the band of the Milky Way with its five main stars forming a zig-zag pattern that resembles the letter W, making this constellation easier to recognise than some others in the northern sky. Cassiopeia was a vain queen of Greek mythology, the wife of King Cephus. As a punishment for her vanity, the sea god Poseidon sent a monster to ravage her countries coastline. To rid themselves of the monster, Cassiopeia and Cephus chained their daughter Andromeda to a rock as a sacrifice. Fortunately, she was rescued from the monster’s jaws by the hero Perseus. All the characters of this myth are close by. Using your chart try and identify where they are. The two main stars of Cassiopeia are Shedir, an Orange giant and Caph, a white giant. Somewhat confusingly these two stars make up the shoulders of Cassiopeia and it is only when you realise the constellation is upside down does the constellations shape begin to make sense.
Mercury is not visible in the morning twilight this month.
Venus is also not visible to us this month.
Earth reaches an equinox on 20th March when the Sun crosses the celestial equator marking Spring.
Mars an evening dimming planet that can be found in the constellation of Taurus until shortly after midnight.
Jupiter can be seen rising in the early morning within constellation Capricornus.
Saturn is an early morning object also in Capricornus. At +0.8 only Jupiter and the Moon are brighter.
Uranus is in the constellation of Aries and sets shortly after the Sun o the twilight.
Neptune is in conjunction with the Sun and not visible this month.
Minor Planets Vesta, discovered by Heinrich Olbers 29 March 1807, is one of the largest asteroids with a diameter of 525km (326 miles) and an orbital period of 3.63 years. This is the second most massive object in the asteroid belt and holds the distinction of being the brightest minor planet. Vesta can be found tracking over the course of the month in the constellation of Leo just south of Denebola and Zosma.
Position of Vesta in Leo, 15th March at 20.20hrs using the Stellarium App.
Nights of particular interest
Some of the objects described below are expressed in degrees from the Moon. This is far less complicated to measure than you might think. To measure 10 degrees, hold your hand up towards the sky at arm’s length and turn your hand up so that it obscures part of your view. The width of your hand is 10 degrees and holding just one finger is two degrees.
2nd Moon at perigee (365,423km)
4th 18.08 Minor planet Vesta at opposition, mag 6.0
5th 06.10-06.20 Mercury, very low in East-Southeast
6th Moon last quarter
9th 22.57 Saturn 3.7degrees North of Moon
13th New Moon
19th 22.00 Moon passes between Aldebaran and Mars
20th 09.37 Vernal equinox, Sun crosses celestial equator
21st Moon first quarter
22nd 19.00 Moon passes Castor and Pollux high in the Southeast
25th 19.00 Moon passes between Regulus and Algieba in Leo
26th Venus reaches superior conjunction lining up with the Sun on the far side of its orbit from Earth. After today the planet will slowly return to the evening sky
28th Full Moon occurs close to lunar perigee making it appear slightly brighter and larger than an average Full Moon
28th European Daylight Saving Time begins (UK Summer Time)
30th Moon at perigee (360,309km)