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Tuesday, May 21, 2013


The Sky This Week - Thursday May 23 to Thursday May 30

The Full Moon is Saturday May 25. Mercury returns to the evening sky. Venus, Jupiter and Mercury meet in the evening twilight. This will be the closest bright planet grouping until 2026. Saturn is high in the evening skies with the Moon close to Saturn on the 23rd. See an Emu in the sky.

Sky on Wednesday May 23 looking north-east as seen from Adelaide at 21:00 local time in South Australia. The left inset shows a telescopic view of Saturn at this time. Similar views will be seen elsewhere at the equivalent local time (click to embiggen).

The Full Moon is Saturday May 25.

Saturn is now easily visible above the eastern horizon before midnight in the constellation of Libra. Saturn climbs higher in the evening sky during the week, becoming easier to see. On Thursday the 23rd the Moon is close to Saturn.

Saturn, Arcturus and Aldebaran from a broad triangle above the eastern horizon.

Opposition (when Saturn is biggest and brightest as seen from Earth) was on April 28. However, Saturn will be a worthwhile evening target for telescopes of any size for several months. The sight of this ringed world is always amazing.

Mars is lost in the twilight.

Evening sky looking west as seen from Adelaide at 17:45 pm local time on Thursday May 23. Similar views will be seen elsewhere at the equivalent local times indicated here.  Click to embiggen.

There will be a beautiful meeting of  three bright planets  in the twilight this evening, the closest meeting of three bright planets until 2026.

Mercury  returns to the evening skies this week week, but is very low in the twilight. You will need a level, unobscured horizon to see it (see below).

Venus climbs higher in the evening twilight. It is still quite close to the horizon, and you need a clear, level horizon like the ocean to see it at its best. As the week progresses it climbs towards a meeting with Jupiter, making a fine sight in the twilight (see below).

Jupiter is visible low in the early evening and rapidly descends into the twilight, heading towards a rendezvous with Venus and Mercury this week. Jupiter is setting progressively earlier, by 6:40 pm local time, so the giant world is now not really possible to follow in a telescope (see below).

On Friday 24 May Venus and Mercury are closest. On 26 and 27 May (Sunday and Monday), these three bright planets will be inside a circle 3 degrees wide (that's three finger-widths wide). On the 27th, Mercury and Jupiter will be at their closest. On the 28th, Venus and Jupiter will be at their closest. On 31 May the planets from a straight line.

You don't need a telescope to see this fine display, just your eyes. For more charts and observing hints (and an animation) see my Planet Dance page.

The south-eastern horizon, around 9:00 pm local time in Australia. Can you see the Emu? Click to embiggen.

Now that the Moon is past full and the evening sky is dark it is a great time to find the constellation of the Emu. Now you are saying: ‘Emu – but there is no Emu!’ However, the Emu is one of the indigenous Australian constellations. And interestingly, it is a "dark" constellation, one that is made up entirely of dark dust lanes!

"Dark" constellations are unique to the Southern hemisphere. In South America they had the constellations of the Tinamou (and Emu relative) and two llamas making up the constellation the Indigenous Australians called the Emu*.

See the Emu now?

The Emu consists of the Coal Sack, the dark dust cloud that nestles in the crook of the Southern Cross (the head of the Emu), and a dark dust lane that stars near the Pointers (alpha and beta Centauri) and runs down to the curl of stars that forms the body of Scorpio. This is the neck and wings of the Emu. A second dark dust lane forms the lower body and legs.

Being made of dark dust lanes, it is almost impossible to see in any city. However, here in the suburbs, if I let my eyes adapt for several minutes I can make it out. And of course in the country it is almost immediately obvious. Once you spot it, you will wonder why you never saw the Emu before. The best time too look currently is about an hour and a half after sunset, when the Emu is nearly vertical and easier to recognise. Later, it stretches over the Southern sky more or less side on, so it is less impressive.

*There is more than one Emu, another Indigenous group identifies Orion as an Emu.

There are lots of interesting things in the sky to view with a telescope. Especially with Saturn so prominent in the sky.  If you don't have a telescope, now is a good time to visit one of your local astronomical societies open nights or the local planetariums. Especially during the school holidays.

Printable PDF maps of the Eastern sky at 10 pm AEST, Western sky at 10 pm AEST. For further details and more information on what's up in the sky, see Southern Skywatch.

Cloud cover predictions can be found at SkippySky.


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