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Thursday, July 31, 2014

 

Southern Skywatch August, 2014 edition is now out!

The Moon looking north-west at 8:15 pm ACST in Adelaide on 4 August just before the Moon covers Saturn. Similar views will be seen elsewhere at the equivalent local time.

The August edition of Southern Skywatch is now up.  This month features an occultation of Saturn and a "supermoon".

There's still a bit of planetary action this month with Venus, Jupiter and Mars meeting the Moon. Mars and Saturn are also close.

Jupiter reappears in the morning twilight and comes very close to Venus on the 18th.

Mars is obvious in the western evening sky.  Mars is near Saturn on the 25th-27th.

Saturn is high in the north-western evening sky and is occulted by the Moon on the 4th.

Venus is close to the crescent Moon on the 24th, and close to Jupiter on the 18th.

Mercury enters the evening sky and is close to the Moon on the 27th.

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Wednesday, July 30, 2014

 

Carnival of Space #364 is Here!

Carnival of Space #364 is now up at Photos to Space. There are occultations, Rosetta's imminent arrival, Chandra's 15th anniversary and much more. There is also a contest for space memorabilia. Zip on over and check it out.

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The Sky This Week - Thursday July 31 to Thursday August 7

The First Quarter Moon is Monday August 4. Mars and Saturn are prominent in the evening sky. The Moon is close to Mars on August 3. Saturn is occulted by the Moon August 4 in the third of a series of rare occulations. Venus is prominent in the twilight.

The First Quarter Moon is Monday August 4. Saturn is occulted by the Moon August 4.  (scroll down for times)

Evening sky on Sunday August 3 looking north-west as seen from Adelaide at 22:00 (10:00 pm) ACST in South Australia. Mars and the Moon are close together (the Moon will be close to Saturn the following night, see below). Similar views will be seen elsewhere at the equivalent local time (click to embiggen). The insets show telescopic view of Saturn at this time,

Jupiter is lost in the twilight.

Mars  is easily seen in the north-western evening sky. It is highest in the sky around 17:30, setting after midnight. Mars was at opposition, when it is biggest and brightest, on the 9th of April, and is still  readily distinguishable as the bright red/orange object above the north-western horizon in the early evening. Mars is in the constellation of Virgo not far from the bright star Spica. Over the week it draws away from Spica heading towards Saturn.  The Moon is close to Mars on August 3.

Saturn is high in the evening sky, and was at opposition on June 11th. Saturn is visible most of the night. Saturn is high enough from around 8 pm for decent telescopic observation and sets around 1:30 am.  Saturn is in Libra near the head of the constellation of the Scorpion and forms a line with the two brightest stars of Libra. Saturn is occulted by the Moon August 4. (see below)

Morning sky on Sunday August 3 looking north-east as seen from Adelaide at 6:30 am ACST.  Venus forms a triangle with the bright red star Betelgeuse and the bright star Procyon. Similar views will be seen throughout Australia at equivalent local times. (click to embiggen).

Venus is in the morning sky, above the north-eastern horizon.  The brightest object in the morning sky, it is easy to see it the twilight.

Venus was at its furthest distance from the Sun on the 23rd of March, and is slowly sinking towards the horizon. Venus is a clear gibbous Moon shape in a telescope. Venus forms a triangle bright red star Betelgeuse and the bright star Procyon. During the week Venus comes closer to the horizon, although still readily visible in the twilight.

Mercury is lost in the twilight.

The Moon looking north-west at 8:15 pm ACST in Adelaide on 4 August just before the Moon covers Saturn. Similar views will be seen elsewhere at the equivalent local time.

On the evening of Monday 4 August Saturn is occulted by the Moon as seen from the most of Australia (and all of New Zealand).

The Moon is a very obvious signpost where look and Saturn will be the brightest object near the Moon. Start watching about half an hour before hand to get set up and familiar with the sky. The occultation is early enough so that kids can get involved. Why not have a star party in your back yard?

The occultation starts around 21:20 eastern time, 20:30 central time  and 18:15 Western time. For exact times from many cities and observing hints, see my Saturn Occultation site.
 

There are lots of interesting things in the sky to view with a telescope. Especially with Mars and Venus and 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.

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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Tuesday, July 29, 2014

 

Occultation of Saturn by the Moon 4 August, 2014

The Moon looking north-west at 8:15 pm ACST in Adelaide on 4 August just before the Moon covers Saturn. Similar views will be seen elsewhere at the equivalent local time. See table below for exact local times. Click to embiggen.Telescopic view of the occultation. Saturns' giant moon Titan is just about to go behind the Moon at 8:30 pm ACST. Simulated in Stellarium. Click to embiggen.

On the evening of Monday 4 August Saturn is occulted by the Moon as seen from the most of Australia (and all of New Zealand). This is the third and best of these rare occultations, it is under reasonable dark skies, with Saturn slipping behind the dark limb of the Last Quarter Moon. Saturn reappears while the Moon is still reasonably high.  See here  and here for images of the May 14 occulation.

The Moon is a very obvious signpost where look and Saturn will be the brightest object near the Moon. Start watching about half an hour before hand to get set up and familiar with the sky, earlier if you need to set up at telescope and get it aligned properly.

Although this event is easily seen with the unaided eye, it is best seen in a small telescope so you can see the ringed world in detail as it vanishes behind the Moon. Saturn's moon Titan will be occulted before Saturn, so you can see the Moon occult a moon.

The occultation occurs in the early evening with the Moon will be reasonably high above the north west horizon, a good time to show the kids this event. The Moon easily visible and a ready signpost to Saturn. It is advisable to set up and practise on the Moon a day or so before the event, so you are familiar with your telescope set-up.

Set up at least half an hour ahead of time so that you can be sure everything is working well and you can watch the entire event comfortably (trying to focus your telescope on Saturn moments before the occultation will cause a lot of unnecessary stress). Saturn will be clearly visible in a telescope or binoculars near the Moon.

This time the Moon is in its First Quarter phase, and it will be easier to see Saturn as the glare of the Moon will not be so intense. On the other hand picking up precisely when Saturn is about to reach the dark edge of the Moon will be harder.

Timings for major cities are shown below, nearby towns will have similar timing.

PlaceDisappears Dark Limb Reappears Bright Limb
Adelaide ACST20:3321:28
Brisbane AEST21:1922:27
Canberra AEST21:2222:07
Darwin ACST20:0521:19
Hobart AEST21:35 (graze of Titan)-
Melbourne AEST21:2421:52
Perth AWST18:1519:17
Sydney AEST21:2222:13

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Sunday, July 27, 2014

 

Who discovered the Southern Cross?

 A chart of the Southern Sky as seen from Adelaide at 10:00 pm this month, with the Karuna (pronounced Gah-Nah) names for the Southern Cross and the Coal Sack indicated (Click to embiggen).

I recently received an email asking me, amongst other things, who discovered the Southern Cross.

The question of who "discovered" Crux, the Southern Cross, is complex. The Southern Cross would have been familiar to the Ancient humans who lived in Africa, before they expanded out of Africa and in to the rest of the World. Some modern South African groups see the Southern Cross as part of a group of giraffes. 

By 40,000 years ago humans had colonised Australia, where the Southern Cross takes pride of place in the sky. The Karuna people of the Adelaide Pains, where I live now, saw the Southern Cross as the footprint of the Wedge Tailed Eagle, Wilto. The Boorong Peoples of the Western Victorian Plains, where my spouses family live, see the Southern Cross as a ring tailed possum. Other indigenous groups see it as part of a larger constellation of an eagle, or as a stingray.

I've made a cross-eyed stereo image of Crux, the Southern Cross. Stare at the picture and cross your eyes until the x of Crux aligns, and the stereo version will pop out at you (you can click on the image to embiggen and get a higher definition view).
 
By 12,000 years ago Humans had colonised South America, where the cross is also prominent, the descendants of the Incas see the Southern Cross as part of a constellation the represents a Llama. Up until 3000 years ago, the Southern Cross could be seen low in the sky from Ancient Greece. It formed part of the constellation of the Centaur.

But the tilt of the Earth's axis slowly changes due to precession. Over a thousand years ago the Southern Cross was lost from the northern skies as the Earth's tilt increased. It was first sighted by Europeans when Portuguese and Spanish explorers entered the Southern seas. Amerigo Vespucci mapped the stars of the constellation during his expedition to South America in 1501, depicting Crux as an almond! It then appeared as "Crux" on star charts from Petrus Plancius and Jodocus Hondius in 1598 and 1600.

The are 5 primary stars in Crux, in order of brightness Alpha Crucis (Acrux), Beta Crucis (Mimosa), Gamma Crucis (Gacrux), Delta Crucis and Epsilon Crucis. The four brightest form the obvious cross shape of the constellation.

Printable black and white chart of the Soutern Cross, suitable for binoculars (click to embiggen and print)

Alpha Crucis, the brightest star of the Southern Cross is the 12th brightest star in the sky. In a small telescope it is an easily resolvable double star. This blue-white giant star is 320 light years away from us.




 The Jewel Box is one of my favourite open clusters.

Beta Crucis is another blue-white giant star, 353 light years away from us, in a pair of binoculars or small telescope you can see the beautiful Jewel Box cluster (NGC 4775). Between Alpha and Beta Cruscis lies the edge of the dark nebula, the Coal Sack (Yurakawe to the Karuna people).

Gamma Crucis is a red giant, 88 light years away and  Delta Crucis is also a red giant, although 360 light years away.

Further reading:
http://www.abc.net.au/science/starhunt/tour/virtual/southern-cross/
http://www.atnf.csiro.au/people/rnorris/AboriginalAstronomy/literature/Curnow2006b.pdf
http://sa.apana.org.au/~paulc/loreaussie03.html
http://www.ianridpath.com/startales/crux.htm
http://www.universetoday.com/20563/crux/#ixzz38eR7fXxu

Friday, July 25, 2014

 

Southern Delta Aquariid Meteor Shower 29-31 July, 2014



Evening sky looking east from Adelaide at 10 pm local time in South Australia. The cross marks the radiant  (the point where the meteors appear to originate from) of the Southern Delta Aquariids. Similar views will be seen elsewhere at the equivalent local time (click to embiggen).

The Southern Delta-Aquarids meteor shower runs from from 12 July to 23rd August, peaking on Wednesday July the 30th. The number of meteors you will see depends on how high the radiant is above the horizon, and how dark your sky is. This shower is fairly faint, with the highest rate of around a meteor every 4 minutes (more detail below).

Evening sky looking east from Adelaide at 2 pm local time on July 30th in South Australia. The cross marks the radiant. Similar views will be seen elsewhere at the equivalent local time (click to embiggen).

At 10 pm, face east, and look 4 hand spans and two finger widths above the horizon. One finger width right is the 4th magnitude star delta Aquarii. The radiant is just above this star. This meteor shower should be visible from 10.00 pm until dawn. The best rates will be at 2 am in the morning of the 30th. The radiant will be due north then, and close to the Zenith. The ZHR  for Southern Delta Aquariids is 16 meteors per hour.

The figure ZHR is zenithal hourly rate. This is the number of meteors that a single observer would see per hour if the shower's "point of origin", or radiant, were at the zenith and the sky were dark enough for 6.5-magnitude stars to be visible to the naked eye.

In practise, you will never see this many meteors as the radiant will be some distance below the zenith. Also, unless you are out deep in the countryside, the darkness will be less than ideal. As well, moonlight will significantly reduce rates. How many are you likely to see in reality? I discuss this further down, lets talk about when to see them first.

People in the suburbs should see a meteor around once every 8 minutes, and in the country about once every 4 minutes at 2 am in the morning of the 30th.

When looking, be sure to let your eyes adjust for at least 5 minutes so your eyes can be properly adapted to the dark. Don't look directly at the radiant site, because the meteors will often start their "burn" some distance from it, but around a handspan up or to the side. Be patient, although you should see an average of a meteor every six to three minutes, a whole stretch of time can go by without a meteor, then a whole bunch turn up one after the other.

Make yourself comfortable, choose an observing site that has little to obstruct the eastern horizon, have a comfortable chair to sit in (a banana lounger is best), or blankets and pillows. Rug up against the cold.  A hot Thermos of something to drink and plenty of mosquito protection will complete your observing preparations. As well as meteors, keep an eye out for satellites (see Heavens Above for predictions from your site).


The sky will also be particularly beautiful, with the Milky Way stretching over the sky and constellation of Scorpius gracing the western sky.

Use the NASA  meteor shower flux estimator for an estimate of what the shower will be like from your location. You need to choose 5 Southern Delta Aquariids and remember to set the date to 29-30 July or 30-31 July 2014.

Cloud cover predictions can be found at SkippySky.

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Thursday, July 24, 2014

 

The Cresent Moon vists Venus and Mercury, Morning July 25-26, 2014

Morning sky on Friday July 25 looking north-east as seen from Adelaide at 6:30 am ACST. The crescent Moon is close to Venus. Mercury is close to the horizon. Similar views will be seen throughout Australia at equivalent local times. (click to embiggen).Morning sky on Saturday July 26 looking north-east as seen from Adelaide at 6:30 am ACST. VThe crescent Moon is close to Mercury . Similar views will be seen throughout Australia at equivalent local times. (click to embiggen).

On the morning of Friday July 25 and Saturday July 26 respectively, the crescent Moon is close to Venus and Mercury respectively, making for a nice morning view. Mercury is very close to the horizon, so you will need a clear , level horizon for a chance of catching Mercury and the Moon together on Saturday. Friday mornings Venus and Moon pairing will be much easier to see as they rise into the twilight.

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Tuesday, July 22, 2014

 

The Sky This Week - Thursday July 24 to Thursday July 31

The New Moon is Sunday July 27. Jupiter is lost in the twilight. Mars and Saturn are prominent in the evening sky. Venus is prominent in the morning sky. The crescent Moon is close to Venus on the 25th, and Mercury on the 26th. A brightish comet may be glimpsed under good conditions low in the morning skies. The Southern Delta Aquariid meteor shower is on the 30th.

The New Moon is Sunday July 27. The Moon is at apogee, when it is furthest from the Earth, on the 28th.


Evening sky on Saturday July 26 looking north-west as seen from Adelaide at 22:00 (10:00 pm) ACST in South Australia. Mars and Spica are close together. Similar views will be seen elsewhere at the equivalent local time (click to embiggen). The insets show telescopic views of Mars and Saturn at this time,

Jupiter is lost in the twilight.

Mars  is easily seen in the north-western evening sky. It is highest in the sky around 18:00, setting after midnight. Mars was at opposition, when it is biggest and brightest, on the 9th of April, and is still  readily distinguishable as the bright red/orange object above the north-western horizon in the early evening. Mars is in the constellation of Virgo not far from the bright star Spica. Over the week it draws away from Spica heading towards Saturn.

Saturn is high in the evening sky, and was at opposition on June 11th. Saturn is visible most of the night. Saturn is high enough from around 8 pm for decent telescopic observation and sets around 2:00 am.  Saturn is in Libra near the head of the constellation of the Scorpion and forms a line with the two brightest stars of Libra.


Morning sky on Friday July 25 looking north-east as seen from Adelaide at 6:30 am ACST.  Venus forms a triangle with the bright red stars Aldebaran and Betelgeuse. The crescent Moon is close to Venus. Mercury is close to the horizon. Similar views will be seen throughout Australia at equivalent local times. (click to embiggen).

Venus is in the morning sky, above the north-eastern horizon.  The brightest object in the morning sky, it is easy to see and although it is past maximum brightness, it will dominate the early morning sky for some time to come.

Venus was at its furthest distance from the Sun on the 23rd of March, and is slowly sinking towards the horizon. Venus is a clear gibbous Moon shape in a telescope. Venus forms a triangle with the bright red stars Aldebaran and Betelgeuse. During the week Venus comes closer to the horizon. On the 25th the crescent Moon is close to Venus.

Mercury is rapidly sinking into the twilight and is now low above the morning horizon. The Moon is close to Mercury on the 26th, but you will need a clear level horizon to be able to see them.

Comet C/2014 E2 Jacques is bright enough (magnitude 6) to potentially be seen in binoculars, but it is low to the horizon, and the rapidly brightening sky this week soon overwhelms it. Look to the left of the bright star Elnath (the tip of the horn of Taurus the Bull) with strong binoculars (at least 10x50's) for a fuzzy dot in the very early twilight.

Evening sky looking east from Adelaide at 10 pm local time in South Australia. The cross marks the radiant  (the point where the meteors appear to originate from) of the Southern Delta Aquariids. Similar views will be seen elsewhere at the equivalent local time (click to embiggen).

The Southern Delta-Aquarids meteor shower runs from from 12 July to 23rd August, peaking on Wednesday July the 30th. The number of meteors you will see depends on how high the radiant is above the horizon, and how dark your sky is. This shower is fairly faint, with the highest rate of around a meteor every 4 minutes.

At 10 pm, face east, and look 4 hand spans and two finger widths above the horizon. One finger width right is the 4th magnitude star delta Aquarii. The radiant is just above this star. This meteor shower should be visible from 10.00 pm until dawn. The best rates will be at 3 am in the morning of the 31st.

Use the NASA meteor shower flux estimator for an estimate of what the shower will be like from your location. You need to choose 5 Southern Delta Aquariids and remember to set the date to 29-30 July or 30-31 July 2014. More details here.

There are lots of interesting things in the sky to view with a telescope. Especially with Mars and Venus and 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.

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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