Pictures in the sky, stories in the stars!

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Torbay Astronomical Society - Credit: Torbay Astronomical Society

Stargazing with Torbay Astronomical Society's John Stapleton:

Most people, when looking up at the night sky, find it difficult to see the constellations for what they are supposed to be.

Even the familiar zodiacal constellations do not really look like their namesakes: Gemini does not look like two brothers, Aries does not look like a ram, Virgo does not look much like a maiden, and so on, although Leo could be a lion and, Taurus could, at least, be the face and horns of a bull.

The constellations come to us as visual reminders of characters used in oral tradition storytelling.

Story tellers of old would use the stars as memory aids to tell stories at different times of the year and, much like modern film directors, each individual storyteller would add their own twists and embellishments.

When astronomers first mapped these patterns, they settled on 48 constellations. This was done by the Ancient Greeks around 100 AD so the constellations with mythical names and stories such as Orion, Hercules, Perseus and Andromeda are all original.

When astronomers travelled to the southern hemisphere in the 18th century new constellations were added commemorating new discoveries and inventions such as Volans (the flying fish) and Fornax Chemica (the chemical furnace).

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The invention of the telescope also allowed astronomers to see fainter stars that were not technically included in any constellation, so they were able to invent their own constellations and include them on their own star maps, so we had small, very faint groups such as Felis (the cat), Tarandus (the reindeer) and Noctua (the owl).

Needless to say, things became quite confusing.

A body was set up to decide on a definitive map.

This body became the International Astronomical Union and they settled on a total of 88 constellations in both hemispheres.

All stars, no matter how faint, lie within the designated boundaries of one constellation or another.

All the other constellations became defunct and were removed from future star charts.

This means that no-one can now create a new constellation or name a star as all stars are already designated within a known pattern.

The IAU still controls the naming of new astronomical bodies so the name of a recently discovered dwarf planet, for instance, would be suggested by the discoverer following guidelines set by the IAU and ratified by that body before it could be used.

In the northern sky, entire mythological stories are represented. Perseus and Andromeda, her vain mother, Cassiopeia and the flying horse Pegasus are all represented, while in the opposite side of the sky Cetus, the sea monster constantly chases Andromeda across the heavens.

So the constellations should be seen as symbols rather than depictions of the animals and characters they are said to represent. 

Despite the IAU, other patterns are used by astronomers simply because it makes finding one’s way around the sky easier and more practical.

However, these are informal patterns, originally passed on by word of mouth between observers, and they are called asterisms.

Well known asterisms include The Plough (which is only the seven brightest of over 200 stars that form the Great Bear), The Sickle or back-to-front Question Mark that forms the head of Leo the Lion, the three stars that form Orion’s Belt and the W of Cassiopeia (again only the brightest few stars).

There are many others in common use among astronomers.

One worth mentioning because it will soon dominate the Summer sky is The Summer Triangle, a single asterism even though each star is actually in a different constellation.

This pattern, formed by the three brightest stars first visible on summer evenings, became useful as a navigation aid for aircraft on night missions during World War Two as the long axis of the Triangle always points to the southern horizon.

It was named by an air force navigator and amateur astronomer called Patrick Moore.

Asterisms often do look more like the objects they are named for as they are supposed to be easily recognisable to any observer.

How many of those mentioned in this article can you find for yourself when you next go stargazing? 

Star chart for June

Star chart for June - Credit: Torbay Astronomical Society

The star chart 

The sky will look like the chart on June 5 at 9pm and again on June 21 at 8pm. And four minutes earlier on each successive night e.g. 8.56 on June 6. 

To use the chart, hold it above your head while facing south so that you can look directly from the chart to the sky. 

Skynotes 

Please note all times given in this article are in GMT so remember to add an hour to get the time in BST. 

Sun: The Sun is never very far below the horizon at night throughout June and into July, so it never gets astronomically dark and this is not the best time for observation of faint objects. On June 10 , a partial eclipse of the Sun will occur and be visible from Torbay. Never look directly at the Sun with an optical instrument! Rather, observe the Sun with specialised equipment or use a single lens of binoculars (with the other lens covered with the cap) to project an image onto a piece of white card.  The eclipse occurs between 9am and 11.15am with the maximum at 10.06am. 

Mercury and Venus: Both of these inner planets are closer to the Sun than the Earth so are never very far from the Sun (especially Mercury). Mercury and Venus are both technically visible on June 30 although neither is very far above the horizon. On June 11, Mercury will be at Inferior Conjunction (directly between the Earth and the Sun). When it reappears at the end of the month it will be visible in the E-NE sky about 40 minutes before sunrise and against the background constellation of Taurus.  Venus is also best seen at the end of the month in a W-NW direction against the background of Cancer.  

Mars: The red planet is still visible but is getting fainter as it moves away from the Earth.  It may be seen against the background constellation of Gemini, this month although is difficult to find in the evening twilight. On Mars, there are now two active rovers, with the Chinese 'Zhurong' joining the American 'Curiosity' on the surface of the red planet. 

Jupiter: Rises in the east nearly two hours after midnight on June 1 and just before midnight by the end of the month when it reaches its maximum altitude just before dawn. 

Saturn: The ringed planet can also be found rising in the east over an hour after midnight on June 1 and shortly after 11pm by June 30 when it also reaches its maximum altitude. The giant planets will be better seen against a dark sky later in the year. 

Uranus and Neptune: These planets are not visible this month. 

Meteor Shower: There are no major meteor showers this month, but you could still see stray (sporadic) meteors. 

Comet: Comet 7P Pons/Winnecke, is also visible in the pre-dawn sky, approximately halfway between Jupiter and Saturn at the beginning of the month. 

The Last Quarter Moon occurs on June 2 with New Moon on June 10. First Quarter follows on June 18 with Full Moon on June 26.

Data supplied by Simon Harding, observations secretary at Torbay Astronomical Society  

Diary dates 

The next meeting of the Torbay Astronomical Society, complying with the current Covid regulations will be online via Zoom. Visitors and prospective members especially welcome. For details contact the secretary TAS on astrosecretary@gmail.com