As the nights grow shorter the bright winter constellations edge their way towards the west but there is still time to do some serious sky gazing. 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!
Leo is dominant in the southern sky during April and does bare some semblance of the creature after which it is named. Gemini, due to its relatively high position in the sky remains visible with the bright stars, Castor and Pollux, representing the heads of the twins. In Greek mythology Castor and Pollux were the sons of Queen Leda of Sparta. Pollux was said to have been fathered by the god Zeus and was immortal, while Castor’s father was Leda’s husband, King Tyndareus, and he was a mortal. The Twins joined the crew of the Argo and went in search of the Golden Fleece, in one of the great epics of Ancient Greek mythology. When observing Gemini, one of its two main stars, Castor is a multi-star system, the two brightest of which can be seen through a small telescope. Although Castor is named Alpha Geminorum, it is not the brightest star in Gemini, which is Pollux, Beta Geminorum, the constellations other main star. One of the years richest meteor showers, the Geminids radiate from a point near Castor around 13th December each year when up to 100 meteors an hour can be observed. Unlike most meteor showers, this one does not originate from a comet but an asteroid, Phaeton. Cancer is one of the feintest zodiacal constellations and lies between Leo and Gemini. It represents the Crab that attacked Hercules as he fought the multi-headed monster Hydra. The brightest star, Alpha Cancri which lies 188 light-years from Earth, is named Acubens from the Arabic for claw.
Cygnus and the brighter areas of the Milky Way start to become more visible, running parallel to the horizon, from a north-east to westerly direction, followed by Cephus, Cassiopeia, Perseus and Auriga. Cygnus is sometimes called the northern cross because of its distinctive shape. Cygnus has the Milky Way’s hazy band running through it, dividing it into two streams by a dark lane of dust and gas called the Cygnus Rift. Cygnus is an ancient Greek constellation representing a Swan. Myths tell how the god Zeus turned himself into a swan to pursue the beautiful Queen Leda of Sparta and the constellation commemorates his disguise. Deneb the brightest star in Cygnus lies in the swan’s tail, while the birds neck extends along the Milky Way to the star Albireo, a binary star that makes its beak. Lesser stars suggest the swan’s outstretched wings.
Meteor shower, the Lyrids, peaks on Aril 21-22. The hourly rate is usually around 18 meteors per hour, with some leaving persistent trains. The parent body of the non-periodic comet C/1861 G1 (Thatcher). Another shower will arrive between 18 – May 27, Aquariid meteor shower which comes to maximum early May.
Mars continues dimming over the month. It will spend much of its time in the constellation of Taurus before entering Gemini on 24th April. Jupiter can be seen rising in the morning twilight within constellation Capricornus. Saturn is also to be seen in the morning twilight within Capricornus. Earth the full Moon on 27th April occurs only 12 hours before perigee, raising the possibility of extreme tides on Earth.
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 – 02.00 low in the southeast shortly after Moonrise, Antares (Alpha Scorpii) sits 4.5 degrees from the Moon.
4th – Moon Last Quarter
4th – Asteroid 9 Metis reaches opposition in Virgo. This is really a small telescope item and can be seen drifting westwards below Delta Virginis but may be visible with binoculars as it peaks to +9.5 tonight. 9 Metis is an “S type, siliceous, asteroid measuring 222 x 195 x 140 km.
6th – 08.29 Saturn 4.0 degrees North of the Moon
7th – 07.17 Jupiter 5.5 degrees North of the Moon
12th – New Moon
13th-29th – Lyrid meteor shower
14th – Moon at apogee (406,119km)
15th – 19.30-20.00 Moon 12% lit sits between Hyades and Pleiades clusters over the west-northwest horizon.
20th – Moon First Quarter
21st-22nd – Lyrid shower maximum
26th – Mars sits 1.6 degrees north of open cluster M35. M35 or Messier 35, is a relatively close open cluster of around 420 stars in the constellation of Gemini. It is 3,870 light years away and has a radius of 11 light years.