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Fireworks and Celebrations
There are times when we look into the night sky and see bright trails of light, lasting just a few seconds. These are caused by the burning up, due to friction, of small particles that orbit the Sun in the wake of comets and are swept up by the Earth’s atmosphere as it intersects that orbit. August sees the brightest and often, most spectacular, of the annual meteor showers; the Perseids – so called because they appear to radiate from a point in the constellation of Perseus. The maximum of activity takes place on the night of 11th/12th when up to 60 meteors an hour may be seen. This figure is standardized by assuming the radiant point will be directly overhead so that meteors travelling in all directions can be seen. However in actuality the radiant is relatively low in the North-Eastern sky until the early hours, and this is the best time for observation, although it is worth looking out from the moment it gets dark, after 22.30.
Observing meteors could not be simpler. The only necessary bit of equipment is a garden recliner or deck chair so that you can lay back and look at the sky about 40 degrees above the horizon comfortably. If you want to make a record, simply count the number of meteors you see. You can also note the direction of travel, the duration, which will typically be seconds, and anything unusual such as colour, faint trails, or sound. This shower is known for producing occasional, bright fireballs. A fireball is defined as a meteor bright enough to cast a shadow.
A word about nomenclature. When these particles are in space orbiting the Sun, they are known as meteoroids. When they are seen burning up in the Earth’s atmosphere they are known as meteors and when fragments of a larger meteor strike the ground they are called meteorites.
The Torbay Astronomical Society is fast approaching the start of its 70th Anniversary Season in which we have managed to engage some of the best speakers available including Professor Chris Lintott of BBC Sky at Night fame and Professor David Southwood who has been the Head of Science Missions at the European Space Agency and President of the Royal Astronomical Society, both of whom are Torquay born boys.
Sky Notes
Please note all times given in this article are in BST so remember to add an hour to get the time in BST which started on Sunday 30th March.
Sky Schedule
Please note all times given in this article are in GMT so remember to add an hour to get the time in BST which started on Sunday 30th March.
Sun: Astronomical darkness increases to 6 hours by the end of the month, so fainter objects are again becoming observable.
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 rises in the early hours of the morning reaching a peak altitude of 15 degrees (the distance between your index finger and little finger at arms’ length) above the horizon on 22nd. Venus is also a morning object low in the sky, making it difficult to observe clearly. Although the planet is bright, it reaches maximum altitude of 27 degrees at Sunrise on 14th. Venus can be found against the background stars of Gemini.
Mars: The red planet lies in the constellation of Virgo, visible in the evening sky. However Mars sets ay about 9.30 so it will not be dark enough for good views of the planet.
Jupiter: The largest planet rises in the East a little before Venus and against the background stars of Gemini. The coloured bands and zones on the surface of the planet can be distinguished with small telescopes as can the Great Red Spot, a colossal hurricane, greater in diameter than the planet Earth. The Galilean moons can be seen with a good pair of binoculars or a small (bird-spotting) telescope. DSLR images of the planet will also pick up the moons.
Saturn: The ringed planet can be found against the stars of Pisces, rising in the East around 20:30 and then visible for the rest of the night, albeit rather fainter than either Jupiter or Venus.. The rings are beginning to open out, from our point of view and are consequently becoming brighter and easier to see. Saturn’s largest moon, Titan, can also be seen with a good pair of binoculars or a small telescope.
Uranus and Neptune: Uranus rises at about 22.30 and is seen against the background stars of Taurus. At magnitude 5.8 it is visible in binoculars. Look for a tiny greenish disc compared to the pinpoints which are the stars. This disc should be relatively easy to find as it lies very close to, and just beneath the Pleiades star cluster in Taurus. Neptune is seen against the background stars of Pisces (below the asterism known as the Square of Pegasus). At magnitude 7.7 it will require large binoculars or a small telescope to find it. Neptune displays a smaller and truly blue disc compared to that of Uranus.
Meteor Shower: The Perseid meteor shower peaks on 11th-12th this month. This is the best shower of the year with up to 60 meteors an hour including some very bright ones. (See main article).
Moon: The First Quarter Moon occurs on August 1st with Full Moon on August 9th. Last Quarter follows on 16th with New Moon on August 23rd. The next cycle then begins with First Quarter on 31st.
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