Wonders of the April Night Sky

The month of April is fantastic month for stargazing and for astronomy in general with numerous dates to mark in your calendar.  From Earth Day celebrated on 22 April, in aid of creating awareness of Earth’s environment and encourage conservation efforts, to International Astronomy Day on 28 April which is to help create better understanding of the wonders of our Universe. The skies in the midst of April alone make it a particularly special month with the heavens being much darker due to a waning Moon. This will make the ancient and special Lyrid meteor shower much more visible this year, weather permitting of course. We also get a front row seat to the beauty of Saturn visiting the bright star of Spica as well as some other yearly visitors that make the April and spring night skies so magical.

First of all let’s take a look at the show stealer this month, Saturn!

Image of Saturn

Sometimes “Wow!” is the only thing to say. Saturn (with an auroral display) and its rings seen by the Hubble Space Telescope (image credit: NASA, ESA, J. Clarke (Boston University), and Z. Levay (STScI))

 

As you may know, Saturn is the second largest planet in the solar system with a beautiful majestic ring system that is made of particles of dust, ice and rocks. This is the perfect time of the year to view Saturn as it is gliding across the sky alongside the brightest star in the constellation of Virgo, Spica. April 15th is the best time to see Saturn as it is at opposition so it is closest to earth and fully illuminated by the sun. If you find you’re having trouble locating these two beauties this clever rhyme alongside one of the most well-known asterisms in the night sky can help:

“Follow the arc to Arcturus and drive a spike to Spica.”

To use this playful rhyme firstly find the Plough or as some call it, the Big Dipper, located in the tail area of the grand constellation of Ursa Major, the Great Bear in the south-east of the sky. Once you have located the Plough draw an imaginary line connecting the handle, and follow through with this curve until you arrive at a bright orange star, Arcturus. Then as the rhyme states, drive an imaginary spike though the sky until you arrive at Spica and you should find your eyes resting on these two bright sky wanderers. Spica is very bright with an apparent magnitude of 1 and an absolute magnitude of -3.55. It is the 15th brightest star in the night sky and it is over 12,000 times brighter than our day-time Star, the Sun, but no need to panic and run for the sun block, it is 262 light years away from us!

image of spike to spica

Making the Spike to Spica. (Image credit: Kerry Scullion/Armagh Planetarium)

 

Despite this impressively bright star Virgo is a relatively dim constellation that represents the goddess of corn and agriculture and is the second largest in the night sky, only the constellation of Hydra the Water snake is larger. But thanks to its size and location in the night sky, this proud Goddess has many stellar accolades.  Virgo has dozens of visible galaxies that can be found throughout her region of the sky but thousands lying further in the background, but a telescope would be needed to attempt to view these beautiful star ‘cities’. At the northern border of Virgo and running in to the constellation of Coma Berenices is the Virgo Supercluster, which is a huge mass of some of the brightest galaxies that can be seen using even a small telescope. Virgo also has more exoplanets found in this area of the sky than any other constellation in the Zodiac with 26 being found so far, and exoplanets is the term used for planets found outside our solar system. Unfortunately an ordinary telescope will not let you glimpse these other worlds but you can look up at Virgo knowing these wonders exist within her.

image of Bootes

Bootes, Canes Venetici and Coma Berenices as seen in the early 1800s. Note the lost constellation of Quadrans Muralis. (Image: © Ian Ridpath)

 

There are many large constellations dominating the sky at this time of the year, and to the left and up from Virgo we have the famous herdsman Boötes which is the 13th largest pattern in the night sky. Boötes is very special as it home to the very useful star Arcturus, which also happens to be the brightest star in the constellation. Arcturus is the third brightest star in the night sky and is a Greek word meaning “Guardian of the Bear.” In classical mythology Boötes was said to be Arcas, the son of Zeus and the Arcadian princess Callisto. Years later when Hera found out of her husband Zeus’ infidelity she turned Callisto into a bear. Many years later when Arcas was grown he came across Callisto in the woods and unknowingly hunted his mother through them. Callisto ran to a temple for protection as blood could not be spilled within it and Zeus, to avoid tragedy, placed them into the sky. Today we can see this sad story continue with Arcas as Boötes the Herdsman chasing his mother Callisto, Ursa Major the Great Bear around the North Pole.

To the right of Bootes is his very own set of hunting dogs called the Canes Venatici, Latin for ‘Hunting Dogs.’ It is not a very bright constellation with virtually no noticeably bright stars. The brightest Star is that of Cor Caroli meaning ‘Heart of Charles.’ It is believed to be named after King Charles I, the deposed king of Britain. Legend had it said that when Oliver Cromwell died in 1658 and Charles’ son King Charles II took to the throne, this star got brighter. A small telescope will reveal Cor Caroli is actually a double star and many who believe in happy endings think of this as father and son reunited in the skies. It is also referred to as a True Binary star which means that these two stars revolve around the same centre of mass although it takes nearly 8000 years for this father and son star to complete one orbit!

Every year sees multiple impressive displays of meteor showers but this time last year the Ancient April “shooting stars” called the Lyrids were obscured by a bright moon light glow but the New Moon in April will guarantee the perfect dark sky to watch this natural wonder.  The Lyrids fall from the comet Thatcher as the Earth passes through her tail. Activity from the Lyrids meteor shower can be captured from 16April to 25 April but the height of activity and the perfect time to set up camp is the late night of  21st to the early morning of the 22nd. The Lyrids can offer a display of 10 to 20 per hour or have a surge of activity of up to 100 per hour. The darkest hours of the night and early morning are the optimal times to watch for these falling beauties, specifically the final few hours of darkness before dawn. And the constellation they radiate from is that of Lyra the Harp, a small pattern with some very interesting stars, which on 21 – 22 of April you can see rise around 11pm from the north east and continue to rise high into the sky towards the south east during the darkest hours of the night sky.

image of Lyrid Radiant

How to find the Lyrid radiant. (Image credit: Kerry Scullion/Armagh Planetarium)

 

The brightest star in the pattern of Lyra is a fairly famous one, the “Falling Eagle” Vega.  It is the 5th brightest star in the sky and has a very interesting past and distant future. Once upon a time, in fact in 12000 BC Vega had the prestigious position of being the Pole Star and will again take up this role in roughly 10,000 – 12,000 years! This bright and beautiful ‘Starlet’, only 25 light years away, also has the honour of being the first star outside of our solar system to have its photograph taken, definitely an ideal star to begin a stellar modelling career. The absolute magnitude scale is actually based on this show stealing star and it has an absolute magnitude of zero. So whilst waiting for the appearance of the Lyrids meteor shower you could distract yourself observing this magnificent star specimen.

There are many objects to see in the sky at this time of the year, some very famous patterns that many people may need no introduction to including the majestic Leo the Lion, who is quite easily found as the pattern does look quite like a lion! If you have difficulties spotting this proud beast in the sky search for a backwards question mark which forms the head of Leo and then see if you can spot a sphinx like shape following around it. Leo, like Virgo, has many galaxies to be found within him. As we travel above Leo in the sky we arrive at one of the oldest and biggest constellations, Ursa Major the Great Bear. Ursa Major is the third largest constellation, only Virgo and Hydra are bigger and it is one of the most well-known patterns with its dominant presence. As mentioned before it is home to the very famous asterism, the Plough or the Big Dipper.  The Plough is very special to us as it contains the Pointer Stars, Merak and Dubhe, which lead us to the ever standing still North Star or Polaris, so as long as you can spot the Big Dipper, you should be able to direct yourself well around the night sky.

For all those moon gazers this month there are some interesting occurrences that you might want to watch out for. As stated earlier we will have quite dark skies towards the middle to the end of the month due to a mystical new moon but the start of the month promises to be a treat. If you watch the Moon’s progress in the sky on the 3rd of April you will find the Moon below the constellation of Leo, quite close to the ‘Rusty Red Planet’ Mars. This can easily be seen with the naked eye with Mars looking very bright and slightly orange in colour. To make it easy to fine, at roughly 11pm GMT towards the South, the Moon, Mars and the brightest star Regulus in the pattern of Leo, make up the shape of a triangle; Mars will be the slightly orange of the 3.  A few days later, on the 7th of April you will see a waxing gibbous moon, a day after the full moon on the 6th of April, flying below and to the left of the sky wanders of April, Spica and Saturn. The Moon’s journey this month definitely will not disappoint.

There are many dates to add to the astronomical calendar this April and if you are new to watching the skies you couldn’t have picked a more entertaining month to start getting your eyes filled with galaxies, planets, stars, constellations and a hopefully a very active ancient meteor shower. The month of April should not disappoint so keep those fingers crossed that the skies stay clear!

(Article by Kerry Scullion, Education Support Officer)