What’s up in the sky this October?

Article written by: Heather Alexander

October is here! It is one of our favourite months as there is so much more to see in the sky and the nights are getting deliciously darker. One thing to remember when you are stargazing is to wrap up warm when you venture outside. The nights are getting much colder, and with some of the best stargazing occurring in the early hours of the morning, we don’t want anyone catching a chill. Thermals and a thermos filled with hot chocolate or coffee will do the trick. Also don’t forget that we will be starting our Star Tracker evenings in the coming months! Check our website for more details and how to book. www.armaghplanet.com

 

If you love meteor showers, then this month is the perfect month for you. There are two main meteor showers and the first occurs at the beginning of the month, so you don’t have long to wait. The Draconids meteor shower will have its peak on the 8th October, and this year it will be particularly brilliant as there will be no moon in the sky to hinder your viewing.

The radiant point of the Draconids meteor shower 2018. Image Credit: Heather Alexander/Stellarium/Armagh Observatory and Planetarium

The Draconids are the result of the Earth passing through dust grains leftover by the comet 21P Giacobini-Zinner. This comet was first discovered in 1900 at the Nice Observatory. It was discovered by Michael Giacobini in December 1900 and was then unknowingly observed by Ernst Zinner six and a half years later. Comet 21P Giacobini-Zinner is a relatively small comet of around 1.24 miles (2km) in diameter. 2018 is a big year for this comet as it passed within 0.39AU of the Earth. The Draconids are usually a pretty underwhelming meteor shower, but with this recent close encounter and the zero-moon light in the sky, hopefully we will get to see more amazing shooting stars.

 

The second meteor shower this month is the Orionids. This shower tends to have more meteors than the Draconids, at 20 meteors per hour rather than 10. Also, these meteors come from the dust grains leftover by the most famous comet of all time, Halley’s comet. Halley’s comet has been known to humans since the ancient times, but it was Edmond Halley who first successfully predicted the comet’s orbital period of 76 years. Sadly, Halley was not alive when the comet made its next appearance, but they named it after him regardless. The Orionids will hit their peak on the evening of the 21st October and the early morning of the 22nd October.

Orionids meteor shower radiant point 2018. Image Credit: Heather  Alexander/Stellarium/Armagh Observatory and Planetarium

When observing the Orionids this year keep in mind that the Moon will be full in the sky and so will be creating a lot of light pollution. However the Orionids tend to be brighter than the Draconids and so while it will hinder some of the fainter meteors, you will be able to observe the bright Orionids.

 

On 9th October there will be a new Moon in the sky and so with the lack of moon light we will have a plethora of objects to observe in the night sky. Here is what we would recommend:

Pegasus

The autumn time is the best time to observe the constellation of Pegasus the winged horse. The main body of this constellation is made up of four very bright stars that form the shape of a square. This square is known, very creatively, as the Great Square of Pegasus.

The Great Square of Pegasus makes the belly of the much larger constellation of Pegasus the winged horse from Greek mythology. Located in the South at this time of the year, the best time to go out to view him is later in the evening. Image credit: Heather Alexander/Stellarium/Armagh Observatory and Planetarium.

Stating that the Great Square of Pegasus is made up of four bright stars, is inaccurate. It is made up of three bright stars and the fourth actually belongs to the constellation of Andromeda. The three stars that belong to Pegasus are called Markab, Scheat and Algenib.

Markab, also known as Alpha Pegasi and is the third brightest star in the constellation of Pegasus. Its name literally translates in the “the saddle of the horse.” Markab is an A-type subgiant star. A subgiant is a star that is brighter than a main sequence star (of the same spectral class) but not as bright as a proper giant star.

Scheat, also known as Beta Pegasi, is the second brightest star in the constellation of Pegasus. Its name translates into “the upper arm” and it is located roughly 196 light-years away from our Sun. It is an M-type star and has a relatively cool surface. It is around 95 times larger than the Sun and has a total luminosity of 1500 times that of the Sun.

Algenib, also known as Gamma Pegasi, and the final star in the Great Square of Pegasus that belongs to the constellation of the same name. It is the fourth brightest star in the constellation and its distance has been calculated at roughly 390 light-years from the Sun. It is a large star and is almost nine times the mass of the Sun. It is a B-type star and is also classed as a subgiant.

The final star in the square is called Alpheratz and as previously mentioned it now belongs to the constellation Andromeda. It is known as Alpha Andromedae. Up until the year 1923, this star did belong to the constellation of Pegasus, however the International Astronomical Union changed this and recategorized the star so that it now belonged to Andromeda. This is strange as the word Alpheratz translates into the “the navel of the mare,” or more simply, “the horse’s bellybutton.” This is strange when you think that Andromeda is a Princess, and she now has a horse’s bellybutton for a head!

Speaking of Andromeda, the Andromeda Galaxy will be visible in October as well, right through the Autumn time. The large galaxy is one of our neighbours and is visible to the naked eye. Check back in our November Night Sky blog and get tips on how to find this amazing galaxy.

 

Aries

In Greek Mythology Aries the Ram was said to have a fleece made of gold rather than a fleece made of wool. Image credit: Heather Alexander/Stellarium/Armagh Observatory and Planetarium.

To find the constellation of Aries, all you have to do is take the end two stars of the Great Square of Pegasus, Alpheratz and Algenib, and imagine drawing a triangle out from these stars until your reach the point star. This star is known as Hamal and belongs to Aries the Ram.

Aries is a sign of the zodiac and is found in-between Pieces and Taurus. It is one of the original 48 constellations described by Ptolemy in the 2nd Century and is an average sized constellation, sitting at 39th in the overall size ranking. It is a relatively dim constellation altogether, but once you know how to find the star Hamal, it relatively easy to spot in the night sky.

Hamal is also known as Alpha Arietis and is the brightest star in the constellation and is amongst the brightest stars in the night sky. Hamal translates into the “head of the ram,” and it is roughly 65.8 light-years away from the Earth. It is classed as a K-type star, which means that it is slightly cooler than the Sun. In 2011, a report was given about the potential presence of an exoplanet orbiting around this star. The mass of this object is said to be 1.8 times the mass of Jupiter.

 

Mars

Facing south on the 9th October you will be able to see our neighbouring planet Mars. Mars has been a prominent feature in the night sky for a couple of months now, and it will be visible for some time to come.

The Red Planet, named after the Roman God of War: Credit: NASA

Mars has been visible in the night sky since ancient times. The Egyptians were the first to notice that the stars seem “fixed” and that the sun moves relative to the stars. They also noticed five bright objects in the sky (Mercury, Mars, Venus, Jupiter, and Saturn) that seemed to move in a similar manner. They called Mars Har Decher or the Red One.

Mars also has two moons, called Phobos and Deimos. Mars is named after the Roman God of War and Phobos and Deimos are named after the Romans Gods of Pain and Terror. Phobos is the God of Fear and Deimos is the God of Terror. The existence of the moons of Mars had been speculated from the time Galileo discovered the moons of Jupiter. It wasn’t until 1877 that they were discovered. Asaph Hall was the first to discover Deimos on 12th August 1877 and Phobos was discovered by the US Naval Observatory on 18th August 1877.

 

Here in Armagh there will be plenty of opportunity to view the International Space Station (ISS) in the night sky. The website we always recommend using is www.heavens-above.com. It can give you sightings of the ISS, Iridium Flares and much more, all you have to do is input your location. From 1st October to 7th October, the ISS will be visible most evenings. Below is a table from Heavens Above showing you when and where you will be able to see the ISS passing over head.

On 2nd October there will be an Iridium Flare visible in the South East at around 8:11pm. The sun is due to set on the 2nd October at roughly 7:01pm, so the sky might be dark enough in your area to view it. Below is another table showing how when and where to view this Iridium Flare.