Spring has truly sprung. Welcome to the month of April, and doesn’t time fly when you’re having fun. We can hardly believe that it is April already, and we’ve had so much fun stargazing at the Planetarium so far this year. April is certainly not the cruellest month for us! What delights will the night sky hold for us this month we wonder?
First and foremost we’re starting to see different constellations in the night sky, and we would encourage you to have a look out for them. The constellations of the winter night sky are heading out of the sky again, leaving us with some brilliant stars to look at. A great night to do some stargazing would be 7th April, as there is a New Moon that night, so the sky will not be flooded with moon light, and so you may stand a chance of seeing some brilliant stars.
Hail Hydra! The first constellation you’ll want to look out for is the biggest constellation of them all, Hydra the water snake. All in all the constellation of Hydra measures at 1303 square degrees. It was originally part of the 48 constellations listed by Ptolemy in the 2nd Century. As I said last month, surprisingly, Hydra only contains one reasonably bright star and it is called Alphard, or Alpha Hydrae for you Bayer designation fans out there. Alphard means “solitary one,” in Arabic and is also known as the “backbone of the serpent.” Tycho Brahe, the famous Danish astronomer and bon vivant par excellence, also called this star Cor Hydræ, meaning the “heart of the snake.” Either way, they both sound pretty awesome. Alphard is an orange giant star about 50 times as wide as our Sun with an apparent magnitude of 2.0 at roughly 177 light years away from the Earth.
The constellation of Hydra has a couple of different stories woven into it. One of these stories associates the constellation with the monster Hydra, with its many heads. “Cut off one head and two more shall take its place”…sorry I went all Captain America there. Back to ancient mythology. Hercules was tasked in his twelve labours to kill the monstrous Hydra, and in order to do this he burned out the roots of the heads as he severed them, meaning none could grow back.
The other story that this constellation is linked to is maybe not as commonly known as the story of Hercules. It actually involves another couple of constellations in the sky, Corvus (the Crow) and Crater (the Cup). In ancient Greek mythology, the sun god Apollo, wanted a cup of water. He sent Corvus the crow with the cup (Crater) to collect the water. On his journey, Corvus got distracted by a fig tree with unripe fruit. Corvus decided to wait for the fruit to ripen and then took some for himself. He then quickly collected some water, brought it back to Apollo and offered the excuse that Hydra the Water Serpent had hindered him in his journey of collecting water. Apollo was not fooled by this excuse. He punished Corvus by turning his silver-white plumage to black, and changing his beautiful bird song into a screeching caw. He also placed Corvus and Crater into the sky, resting them on the back of Hydra the Water Snake. Hydra was to keep Corvus away from the cup so that he could never quench his thirst. The constellations of Corvus and Crater lie side by side between Hydra and Virgo.
The constellation of Virgo the Maiden is also now visible in the night sky and it well-known as a sign of the zodiac. Virgo is the second largest constellation in the sky, and looks a little bit like a sun lounger. Virgo can be easily located through its brightest star Spica. Spica is the fifteenth brightest star in the night sky, and is actually a spectroscopic binary and rotating ellipsoidal variable, a system whose two main stars are so close together their mutual gravitational interaction has made them egg-shaped rather than spherical. The best way to find Spica is to follow the handle of the Plough (also known as the Big Dipper), and arc to Arcturus, the brightest star in the constellation Boötes. Once you reach Arcturus, you travel down in a straight line to Spica, you “spike” to Spica. In Latin, Spica means “ear of wheat,” and represents the grains that Virgo is always drawn holding.
Now I know what you’re thinking. Did you just say Arcturus? And Boötes? What are they? I want to hear more about them. Boötes the Herdsman is another constellation that you can see at this time of the year and as mentioned it can be used to help you find the constellation of Virgo. However, kite-shaped Boötes itself is a brilliant and easy to find constellation. It was another one of the 48 constellations mentioned by Ptolemy in Roman times, and contains Arcturus, the fourth brightest star in the night sky. Arcturus is a red giant star that is in its latter stages of life. Arcturus is fascinating for another reason, this star is fast. Arcturus is moving at a staggering 120 km per second towards the constellation of Virgo. It’s interesting to think that Arcturus is almost as bright as it will ever be to us here on the Earth, as it is as nearly as close to us as it will ever come. Arcturus is destined to speed off into the void of space, and as it does this it will become ever fainter to human beings.
Moving along into the month we will see Mercury at its greatest eastern elongation on 18th April. This will be a great time if you would like to try and view Mercury in the night sky, as it will be at its highest point above the horizon in the evening sky. To find it, simply look towards the western sky just after sunset. Don’t forget that next month we will have a very exciting transit of Mercury. Set your alarms for 9th May.
If you’re a fan of the Moon, like we are here at the Planetarium, you will be able to see the Moon in its full glory on 22nd April. As always, this moon has a specific name that was given to it by different cultures. To Native Americans, this is known as the Full Pink Moon and it heralded the appearance of the moss pink, or wild ground phlox, one of the first spring flowers. It is also known as the Sprouting Grass Moon, the Egg Moon, and the Fish Moon.
The end of the month holds something that we haven’t really had much of this year, a meteor shower! Everyone loves a meteor shower and on the 22nd and 23rd April you will be able to see the Lyrids Meteor Shower. This shower starts roughly around 16th April and continues on to the 25th April, but will peak on the night of the 22nd and morning of the 23rd April. The only problem we will have this year in seeing the meteors, is that the moon will be full in the sky and its light will hinder the view of some of the fainter meteors. The Lyrids meteor shower is an average meteor shower that can produce up to 20 meteors per hour. To get this particular meteor shower, the Earth crosses the orbital path of Comet Thatcher (C/1861 G1). Sadly there are no photographs of this comet due to its orbit of roughly 415 years around the Sun. Comet Thatcher last visited the inner Solar System in 1861, before the photographic process became widespread. It’s not expected to return until the year 2276.
(Article by Heather Taylor, Education Support Officer)
Paul Evans · April 12, 2016 at 15:49
Very nice writeup on the April Sky Heather, I enjoy the inclusion of the mythical as well as the purely scientific aspect to what we can see.
Looking forward to that Mercury Transit in May!