THIS month has astronomical events to interest everyone. We can look forward to a Super Moon, two meteor showers and the chance to see the Andromeda Galaxy, the most distant object visible to the naked eye.
On October 17 the moon will be full, and it will be the Super Hunter’s Moon; the third supermoon of the year and the closest one to us. The Moon orbits the Earth not in a circle but in an egg-shaped orbit called an ellipse. This means that sometimes, like this month, the Moon will be closer to us than normal.
This month the Moon will only be 222,055 miles (357,363 kilometres) away. The average distance is 238,000 miles (383,064 kilometres). This moon is called the Hunter’s Moon because following the harvest people would go out hunting for meat to be stored over the winter.
On October evenings the autumn constellations are at their best. The Plough is now at its lowest in the north, although it is still reasonably high in the sky. Cassiopeia is now very high and not far from the overhead point. The two bright stars; Vega, which was overhead in summer and is part of the Summer Triangle, and Capella, which will be overhead in winter, are roughly the same height in the sky. Vega is in the north-west whilst Capella is in the north-east.
Ophiuchus is now becoming low in the west and is replaced by another faint group, Cetus, the Whale or Sea Monster. Perseus and Taurus, two splendid looking winter groups, are becoming far more conspicuous. The summer triangle of Altair, Deneb and Vega is still easy to see, as is the Milky Way which is directly overhead. The southern skies are now dominated by Pegasus.
On maps the square of Pegasus looks easy to find, but because the four stars are not the brightest in the sky they don’t stand out. However, once recognised, it is easy to find again. One way of finding Pegasus is to look below the ‘W’ of Cassiopeia.
The brightest star in the square is Alpheratz in the top left position. For a reason now forgotten, this star was transferred to the neighbouring constellation of Andromeda. Alpheratz is nearly the same brightness as the North Star, while the other three stars of the square are a little bit fainter.
In mythology, Pegasus was the flying horse ridden by the hero Perseus who, after killing the Medusa, returned to rescue the princess Andromeda who was chained to a rock waiting to be eaten by the Kraken or sea monster. Perseus still had the head of the Medusa with him, so he turned it towards the monster, turning it to stone. All these characters can be found in the sky, including the sea monster.
Andromeda’s main stars are arranged in an irregular line, running from the Square of Pegasus towards Perseus. However, the main interest in Andromeda is the Andromeda Galaxy, which is visible to the naked eye if you are away from city or town lights. To find the galaxy, take this route: Alpha (or Alpheratz) is the top left-hand star in the square of Pegasus; next to the left comes Delta, then Beta Andromeda.
Looking upwards you will see the two fainter stars Mu and Nu, and the Andromeda Galaxy is just to the right-hand side of Nu. The Andromeda Galaxy is the most distant you can see with the naked eye. It is about 2.5 million light years away.
Below the line of stars that forms Andromeda is a fairly bright star called Hamal, which is the brightest star in the constellation of Aries the Ram. There should be no problem finding Hamal as it is quite isolated. In mythology, Aries represents the ram whose golden fleece was sought by Jason and the Argonauts.
Aries used to be the first sign of the Zodiac. Around 2000 years ago, the point where the Sun passes the celestial equator from south to north in the sky was in Aries. This point is called the ‘vernal equinox’. However, because the Earth wobbles very slightly over a very long period of time, this point in space has moved into the neighbouring constellation of Pisces, the Fishes. Astronomers still call this place in Pisces ‘The First Point of Aries’.
Between Aries and Andromeda is a small but quite noticeable group of three stars. This is Triangulum, the Triangle, and it is one of the few constellations whose name describes what it actually looks like.
The area below the square of Pegasus is barren. Faint constellations such as Aquarius, Capricornus and Pisces are visible, but Fomalhaut, in the otherwise unremarkable constellation of Piscis Austrinus (The Southern Fish), is a good bright star. Use the two right hand stars of the square and draw a line down towards the horizon. Fomalhaut is the brightest star you can see in Piscis Austrinus.
Another of the large but faint groups in the autumn is Cetus the Whale. In mythology, Cetus was identified with the Kraken, but more recently it has become a harmless whale. Cetus is a difficult constellation to identify, but it has one star that is worth looking out for - the normally faint star Omicron Cetus.
The star is better known by its proper name of ‘Mira the Wonderful Star’, and it varies in brightness every 331 days, sometimes becoming so bright that it totally transforms the area. Mira is a red giant star and when it brightens it is very noticeably red in colour. It will remain at its brightest for many weeks. Sometimes when at its faintest it is hard to see, and a telescope will be needed to find it.
The Planets in October Now is a good time to look for the planets in the evening sky. If you look low to the south from 9.00pm onwards, you will see the planet Saturn. Mars and Jupiter create an equally spectacular sight in the southeast from 10.00pm onwards. Jupiter will be the brightest of the bright dots in the sky.
Although Mercury is still too close to the Sun to be seen, if you look to the southwest just after sunset at the end of the month you might spot the planet Venus, a very bright star-like object.
Meteor Showers There are two meteor showers visible this, month, one very reliable and the other less so. The Orionids are so named because the meteors all appear to come from the constellation of Orion the Hunter. The meteors, or shooting stars, are the trail of dust left behind by the famous comet Halley. The peak will be on the night of October 21 / 22 when around 20 meteors per hour might be seen.
The second meteor shower is the Draconids which will peak on the night of October 8/9. They appear to come from the constellation of Draco the Dragon. Harry Potter fans will recognise the name given to the character Draco Malfoy. The Draconids are associated with the comet Giacobini-Zinner. This meteor shower usually only produces a few meteors per hour, but there have been outbursts of meteor activity in 1926, 1933,1946,1952,1988 and 2011 so it is always worthwhile having a look for Draconid meteors.
Phases of the Moon for September New Moon 2, First Quarter 10, Full Moon 17, Last Quarter, 24 If it is dark enough around 9pm on October 14, the Moon will be just below Saturn, while on October 21 around midnight the Moon can be seen above Jupiter.
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