The July Night Sky

Get your sunglasses on, and break out the sun tan lotion! July is here and we’re glad to see it. Summer is fully upon us and many of us will be on our summer holidays this month. The month of July was named after Julius Caesar by the Roman senate, as this was the month of his birth. In the old calendar, before it was renamed, this month was known as Quintilis, and it was actually the fifth month not the seventh! Now that we know a little bit more about the origins of the month, let’s get down to the business of star gazing and what will actually be in our night sky.

At the Armagh Observatory and Planetarium, we want to give you the best chances to see as many wonderful things as you can in the night sky while you are on your holidays. Throughout this article not only will we cover things in the northern hemisphere, we will also cover some things in the southern hemisphere, just so that you’re fully prepared. As you will be well aware the northern and southern hemispheres have different sets of constellations and so during the summer months different constellations will be visible in different areas.

There will be a full moon on the 9^th of July. As any seasoned star gazer will know, this can cause a few problems when trying to view deep sky objects. With a full moon comes a flood of moon light in the sky. This moon light is able to overwhelm the dim light of more distant objects, so only the brightest objects will be visible. Take this chance however to observe our wonderful, natural satellite. This particular full moon was known in certain Native American tribes as the “Full Buck Moon”.  The reason for this name was due to the male deer who started to grow their new antlers at this time of the year. The Moon is covered in craters, some of which can be seen quite clearly with a simple pair of binoculars. One crater to look out for in particular is the Copernicus crater.

Copernicus crater up close and personal. Image Credit: NASA.

This crater is named after the famous astronomer Nicolaus Copernicus who was born in 1473 in Poland. Copernicus is one of the most famous astronomers who ever lived.  He was the person who first suggested that the Earth was not the centre of the solar system, it was in fact the Sun. This was not a popular notion at the time, but to us nowadays it seems like a ridiculous notion that the Sun wouldn’t be at the centre of the solar system. Copernicus crater is 93 kilometres in diameter and is 4 kilometres deep. The crater rays spread as far as 800 kilometres across the surrounding mare (large, dark, basaltic plains), overlying rays from the craters Aristarchus and Kepler.

The Copernicus crater has been highlighted in red. The Moon has many craters, over 300,000 on the side that we see alone. Image Credit: NASA.

There will be a new moon on the 23^rd July, so this will be the best time to do some stargazing as there will be no moonlight flooding the sky. One pattern to spot in the night sky is the Summer Triangle. This pattern is known as an asterism, which is a shape that can be found inside another constellation. The triangle comprises of three very bright stars that all have a link with three different constellations. One star is known as Altair and it marks the bottom point of the triangle. It is found in the constellation of Aquila the Eagle. Also known as Alpha Aquilae, it is the brightest star in this constellation and the twelfth brightest overall in the night sky. Altair is an A-type main sequence star with an apparent visual magnitude of 0.77.

The Summer triangle, the first three stars you will see in the nights sky. Image Credit: Heather Taylor, Stellarium.

Deneb is the second star in the triangle, and it marks the tail of the constellation Cygnus the swan. Cygnus appears in the Almagest, published by Ptolmey in the 2^nd Century. The story of Cygnus is linked to Zeus, the king of the Greek Gods, and the Spartan Queen Leda. It is said that Zeus disguised himself as a swan and was able to seduce the queen. The queen gave birth to two sets of twins, one set fathered by Zeus and the other by her husband. The immortal twins were Pollux and Helen, and the mortal twins were Castor and Clytemnestra. Castor and Pollux are actually represented in the constellation of Gemini, which is mainly seen in the winter night sky.

The final star in the triangle is Vega, and it belongs to the constellation of Lyra. In modern times this constellation is represented by a lyre, which is a musical instrument with strings. The constellation itself is meant to represent the Greek musician and poet Orpheus, who met an untimely end. Orpheus was the son of the Thracian King Oeagrus (however some other sources state that he was the son of the God Apollo) and the muse Calliope. When he was young, Apollo gave Orpheus a golden lyre and taught him to play it, and his mother taught him to write verses.  Orpheus is famous for many things including his travels with Jason and the Argonauts, and his attempts to save his wife Eurydice from the underworld. These inspired songs of their own, namely the classical piece “Orphée aux enfers,” which translates to “Orpheus in the Underworld”.  This was composed by Jacques Offenbach and first performed in 1858.

Roman mosaic depicting Orpheus, wearing a Phrygian cap and surrounded by the beasts charmed by the music of his lyre. Image Credit: Wikipedia.

The story goes that Eurydice was walking in the forest with some Nymphs one day and was pursued by a stranger. As she ran away from the stranger she was bitten by a snake and then died. Orpheus was distraught and started to play on his lyre a song that moved things living or not in the world; both humans and gods were deeply touched by his sorrow and grief. Orpheus was encouraged by the gods to go into the underworld to ask Hades for the return of his beloved. Orpheus was able to get into the underworld, calm the three headed beast Cerberus with his music, and finally convince Hades to release his wife. Hades agreed to release Eurydice however as Orpheus left the underworld, he was not allowed to look back to see if Eurydice was following him. He felt that he was patient enough to do this and so agreed to this condition. Eurydice did follow him, however it was in the form of a shadow. Now let me put this to you. If you knew that you would get the love of your life back from the dead, would you have turned around to look? Would you have trusted Hades, the Lord of the Underworld, to keep his word? Well guess what Orpheus does? That’s right. HE LOOKS BACK! Eurydice is flung back into the underworld and Orpheus is left without his wife. Naturally his grief is so strong he calls for death to take him. The writing’s are not clear but he either got ripped apart by vicious beasts, or Zeus killed him with a bolt of lightning (which happens quite a lot in Greek Mythology).

Back to the star; Vega is also known as Alpha Lyrae and is the fifth brightest star in the night sky and the second brightest star in the northern celestial hemisphere. Vega is actually relatively close to us. It is 25 light years away, so the light that we see today left Vega 25 years ago when Super Mario Kart was released for Super Nintendo, Wayne’s World premiered in cinema’s and Euro Disney opened in Paris. Nothing like looking up what things turn 25 this year to make you feel old!

On 23^rd July the planet Saturn will be visible in the night sky, and with there being no Moon visible in the sky, this is the perfect time to get your binoculars and telescopes out to have a good old peek at it. It will be located in the south at around 11:00pm. Saturn is the second biggest planet in our solar system and has 62 moons altogether.  It is famed for its beautiful rings, but we’re not overly sure how Saturn got those rings. A popular theory is that a small ice moon got torn apart by Saturn’s gravity, and that the rings are made up of its remnants. Other theories believe that these are remnants of comets, asteroids and moons, basically debris leftover over in the formation of the Solar System.

The ringed planet, Saturn visible on the 23rd of July. Image Credit: NASA.

If you’re in the mood for something special, then on 27^th-30^th July there will be a meteor shower known as the Delta Aquariids. The shower will actually start on roughly the 12^th July, but it will have its peak between the 27^th-30^th of the month. Astronomers are unsure of the origin of the meteor shower but believe it comes from the comet known as 96P Machholz. It is a short period, sun grazing comet that was discovered in May 1986. It will come to its next perihelion on 27^th October 2017. This is an excellent meteor shower to view if you are on your holidays. Astronomers say that this particular shower tends to favour the Southern hemisphere, but mid-northern latitudes will see plenty of meteors.

The planet Mercury will also be at its greatest eastern elongation on 30^th July. In astronomy, a planet’s elongation is the angular separation between the Sun and the planet, with Earth as the reference point. It will be 27.2 degrees from the Sun, making this the best time to actually view Mercury as it will be at its highest point above the horizon. Be wary though it is hard to view Mercury, make sure you don’t point your binoculars or telescope directly at the Sun!

So that concludes the night sky for July. There is a lot to see, and tune in again next month when we show you what can be seen in the night sky in August.

Article written by: Heather Taylor, Education Support Officer

Heather Taylor, Education Support Officer