If you find yourself in the great outdoors any evening during April and it’s a cloudless night, turning your eyes towards the heavens could be an unusually interesting way for you to spend a few minutes.
If we look at star charts we can see the night sky divided up into degrees with grid lines. A simple method for locating celestial objects and measuring distances across the heavens for a stargazer of any age is to stretch your arm out in front of your face towards your chosen area of sky. Either the palm or back of your hand should be slightly visible as it continues the sloping angle of your arm away from your face. If your information tells you that a celestial object lies approximately 5 degrees away from another marker, turn your palm inwards with your first three fingers together pointing towards the sky and your little finger pulled in. The breadth you can see across the tips of these 3 fingers will give you an approximation of 5 degrees on the night sky’s celestial sphere. So to commence your free celestial star show position yourself in the direction where the Sun rises in the morning (East). Heels together, but with your right foot now at a right angle to your left to point to south, adjust your stance so you are facing ESE.
We are looking for the planet Saturn. Low in the sky and around 5 degrees up from the 0-degree horizon, your 3-finger ‘handy’ guide should help you identify what looks like a bright yellow star standing more or less alone. To confirm that it is Saturn you have found, look for a slightly brighter and more blue-white star higher up and diagonally to the right of Saturn. This more south-easterly object is the star Spica. As it’s the second largest planet in our Solar System and more than 9 times the diameter of Earth, why not get hold of a small telescope and feast your eyes on those spectacular icy rings? Stretching to a total diameter of about 270 000km into space and although only around 10 metres thick in places these, these rings which are made predominantly of water ice actually serve as Saturn’s very own cosmic spotlight. Although unable to provide any light in and of themselves this surrounding sheet of multiple icy bodies enhance the brightness of the creamish gas giant by reflecting light from the Sun onto its belly.
Above you and still spectacularly holding its own while in very close proximity to the brightest nocturnal celestial object, the Moon, this planetary king of the gods will reveal its four largest moons to those who trouble to dig out a good pair of binoculars or a small telescope. To see these ‘Galilean moons’ in the west you will need to turn to face in the opposite direction from our starting point. Having located the constellation of Orion low on the horizon with the three diamond-like stars of his belt, look across to the right to see the bright orangey star Aldebaran that makes up the left eye of the bull. In your mind above this join up the two diagonal lines of stars that form Taurus’ horns and between them and almost directly above Aldebaran, the bright object you shall see will be the planet Jupiter. Collectively named after the famous astronomer who discovered them in 1610, Jupiter’s largest natural satellites perhaps represent some of the most impressive and most readily accessible extensions of the near celestial objects in our Solar System for the avid sky watcher.
For those keen for further planetary observation Venus should become visible once again from Saturday 20th of April, first appearing in the NW at dusk. Until then, the famous bright light reflected off the thick clouds of Earth’s sister planet is being drowned out by the dominant radiance of our nearest star as Venus completes its orbit behind the Sun. From your current westerly view where the Sun sets in the evening, turn 90 degrees to your left and look up, directly above you. At the zenith or highest point above you in the sky should be the seven bright stars that make up the saucepan-shaped ‘Big Dipper’. Forming only the tail and hindquarters of the great bear, Ursa Major, you will need to join up the other seven stars at the front and the other four prominent ones curving down and forwards beneath to complete the head and big paws of this most famous of constellations.
Although making Ursa easy to spot in the heavens, the animal experts among us may recognise that bears do not usually have long tails like a fox or a dog, instead theirs are much shorter and stubby. However as the Greeks apparently had an answer for everything, Ursa’s majestic tail was stretched when the gods came to his rescue and swung him high up in the sky by it to keep him safe from the hunter’s bow. While facing south allow your eyes to drop below the bear’s front legs until they are resting on one of the brightest stars to be seen from the Northern hemisphere at this time of year. If you observe closely and connect it with an arc of stars above it you will see that it forms the bright dot beneath some back-to-front celestial question mark. For those familiar with your signs of the Zodiac however you will instead recognise this as the head and mane of Leo the lion.
The bright star or grammatical ‘dot’ is called Regulus and is the brightest star within this well-known constellation. Marking the lion’s chest and top of his forelegs it lies in fact about 77.5 light years from Earth. With an estimated diameter of 3.2 times that of the Sun its luminosity is also thought to be 150 times brighter. If however we could somehow travel this enormous distance within a single lifetime scientists believe that we would be greeted with the sight of not one, but four stars working together to produce this naked-eye single star image from Earth. Regulus or Alpha Leonis (its official title as the brightest star of its constellation group) is in fact a fine example of something astrophysicists refer to as a ‘multiple star system’, a group of stars bound together and orbiting each other as a result of mutual gravitational attraction.Composed of stars Regulus A, B, and C, binary star Regulus A and its suspected white dwarf orbiting star take only 40 days to orbit their shared centre of mass.
According to the Greek myth, the Nemean lion, Leo, was the first beast to be killed as one of the twelve challenges or ‘labours’ assigned to Hercules by king Eurystheus. Hercules’ triumph over the lion however could only be proven by the bringing of the lion’s skin before the king. In what transpired to be a far greater ordeal than just the slaying of any big cat, Hercules initially engaged the lion unaware that the fearsome creature before him possessed not only great strength but the power of immortality. During battle Hercules’s discovery that no arrow could pierce the lion’s tough hide compelled the great hero to wrestle the creature and ultimately end the struggle by choking it with his bare hands.
Also worth looking out for this month are: a partial eclipse of the Moon on the 25th, and the Lyrid meteor shower on the 22nd. Best observed between moonset and dawn, these meteors should be bright and may even leave trails as they nose-dive through our atmosphere near the constellation Lyra’s star Vega, in the northeast. With 10-20 per hour predicted, but with surges sometimes raising that figure to anywhere up
to 100 shooting stars within an hour, the Lyrids should not disappoint even our naked-eye April stargazers, (provided of course there is no spoiling cloud cover!) If you have a small telescope you can point it northwest to see a collection of stars held together by gravity in an ‘open cluster’ formation. With Orion positioned near the skyline and Taurus to his right, follow up the bull’s right horn. The star marking the tip of his horn along with the brighter star Capella, again diagonally up and to the right of it, form the somewhat tombstone-shaped pattern, Auriga. M36 is the middle cluster of the three Messier objects contained within.
Once again looking southeast, where we might imagine the tip of Leo’s tail stretching out behind him, we have the pick of at least four galaxies in this patch of sky to go looking for. Revealing themselves through amateur optical aids as fuzzy elliptical smudges, it is still mind-boggling to think that each of these other ‘star cities’ in space, M84, M87, M86, and M64 contain billions of stars. With the first three located in the upper half of the star pattern Virgo and just about level with Leo’s hind legs, M64, a bright spiral, sometimes called the ‘Black Eye’ galaxy should be easy to find, centre of an imaginary line running east from the lion’s back to the brilliant golden star Arcturus in the constellation of Bootes. With a downward arc of cosmic dust blocking the starlight and giving the centre region of the galaxy its ‘black eye’ appearance, along with the theory that the two systems of stars rotating in different directions at 3000 light years and 40 000 light years out from centre point to a previous merger between two galaxies, make this a very interesting deep space object to track down.
So as you look forward to the sights of the April night sky, happy hunting and enjoy the celestial star show put on just for you!
(Article by Nick Parke, Education Support Officer)