Astronomy

The Night Sky

WITH THIS MONTH’S SHINING OCTOBER NIGHT SKY WHEN WE CAN WELCOME BACK LONGER AND COOLER EVENINGS FOR OBSERVING

By Claire Wardlaw

Claire Wardlaw, originally from Edinburgh, lives in the Charente with her husband. Since their move nearly 6 years ago, Claire has become passionate about astronomy

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We can look forward to another beautiful Meteor shower - The Orionids - which will of course seem to emanate from the slowly returning constellation of Orion: one of my favourites. We can follow the vast clouds of the Milky Way as they traverse the skies overhead, passing through (looking from east to west) the constellations of: Auriga, Perseus, Cassiopeia and Cygnus. As you face south, and looking just below the clouds and dusty lanes of the Milky Way, the main constellations and features to observe will be: ▪ Orion will be rising in the east, later in the night and towards the end of the month ▪ Taurus (The Bull): towards the east with its very prominent orange star Aldebaran, also known as the 'Eye of the Bull'. ▪ The Pleiades open star cluster is a little higher and west of Taurus and is a stunning sight through binoculars ▪ The Andromeda Galaxy, M31 will be visible on a clear night to the naked eye as a bright smudge of light (also beautiful through binoculars) ▪ Pegasus will be well placed to the south where you can find the 'Great Square of Pegasus'

The Moon and Planets

The Full Moon will be on the 20th this month and the New Moon is on the 6th. Some of the best nights to observe detailed features on the Moon will be during its many different crescent phases. If you have binoculars then it is possible to search along the 'Terminator' where the lit and shaded areas of the Moon meet. Some of the best dates for seeing details on the surface of the Moon will be from the 1st to the 4th, before New Moon and from the 9th to the 16th. These dates will show the Moon in various crescent phases when light contrasts make for much better views. A thin crescent Moon can be seen very close to the stars Algieba and Regulus (in Leo) in the eastern morning twilight of the 3rd. The planet Venus will be close to Antares for a few days low in the south west after sunset with a waxing crescent Moon passing just above them. On the evening of the 14th the Moon, Jupiter and Saturn will form a triangle towards the south east. On the 15th the Moon will be even closer to Jupiter. The two bright colourful stars of Gemini - Castor and Pollux - will form a line with a waning gibbous Moon on the evening of the 27th. Look out for them just north of east after midnight. It may be possible to spot the planet Mercury during the second part of the month. It will be very low, rising in the east just ahead of the Sun. Be sure not to observe for too long as the planet is lost in the Sun's glare.

Shining a light on Astronomy Jargon: The Zenith Object of the Month; Globular Clusters

The Zenith, which you will often see marked with an X on a sky chart, is simply the point of the sky which is directly above an observer. This is therefore the point of the sky which has an altitude of 90 degrees.

Meteor showers in October

The Orionids annual meteor shower returns this month, from the 5th to the 30th. The peak (when meteor activity is likely to be at its highest) will be on the 21st this year. These meteors are associated with Halley's Comet (Comet 1P/ Halley). During the Orionids the Earth will be passing near the dust trail left by the orbiting Halley's Comet. Each tiny particle which hits our atmosphere results in a Meteor which we can observe with the naked eye. These Meteors will be fast and often leave persistent trains which can be wonderful imaging opportunities. We may be able to observe around 25 per hour although the bright Full Moon on the 20th will be somewhat in the way. If you are planning an evening of Meteor spotting a date when the Moon is less bright would be better. Allow your eyes to become adjusted to the dark. Lie back on a 'meteor lounger' or on the ground where you have a wide open view of the sky. The Meteors' radiant will be in the constellation of Orion. There is a fainter shower - 'The Southern Taurids' - which may have its peak on the 10th when the Moon is in a crescent phase. This faint shower has produced bright fireballs in past years. This shower is active from September through to November and has only around 5 meteors per hour. There are many different things to be seen in our beautiful dark skies here in France. Globular Clusters can be stunning targets to view with the aid of binoculars or telescopes. These objects, of which there are around 150 in our own Milky Way, are formed by very old stars (over 10 billion

These objects, of which there are around 150 in years old) bound tightly together. The first Globular our own Milky Way, are Cluster to be formed by very old stars discovered was (over 10 billion years old) M22. It was bound tightly together observed by the amateur astronomer J Abraham Ihle in 1665. M13, which is also known as 'The Hercules' or 'Great Globular' (see next page for images) is found in the Constellation of Hercules. I have viewed and imaged this spectacular object many times as it is such an amazing sight.

Observing/ Imaging Challenge for October

As mentioned earlier, the Orion Meteor shower can have bright meteors with persistent trains. Some objects however, are best viewed with optical aids. These will be easy to spot or image on a night

The Night Sky

The Globular cluster M13

Like shiny flakes sparkling in a snow globe, over 100,000 stars whirl within the globular cluster M13, one of the brightest star clusters visible from the Northern Hemisphere. Located 25,000 light-years from Earth with an apparent magnitude of 5.8, this glittering metropolis of stars in the constellation Hercules can be spotted with a pair of binoculars. Near the core of this cluster, the density of the stellar population is about a hundred times greater than the density in the neighborhood of our sun. These stars are so crowded that they can, at times, run into each other and even form a new star. The resulting “blue stragglers” appear to be younger than the other stars in their immediate vicinity and are of great scientific interest to astronomers.

Image (left): Messier 13 (The Hercules Cluster) Credits: NASA, ESA, and the Hubble Heritage Team (STScI/AURA); Acknowledgment: C. Bailyn (Yale University), W. Lewin (Massachusetts Institute of Technology), A. Sarajedini (University of Florida), and W. van Altena (Yale University) Source: www.nasa.gov