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Tuesday, May 31, 2011

 

The Sky This Week - Thursday June 2 to Thursday June 9

The First Quarter Moon is Thursday June 9. Venus, Mercury, Mars and Jupiter form a line in the morning sky. Mercury leaves the morning sky. Saturn is very close to gamma Virginis.

Morning sky looking north-east as seen from Adelaide at 6:30 am local time on Sunday June 5 showing Jupiter, with Mars, Venus and Mercury lined up below. Mercury is just rising at this time. Similar views will be seen elsewhere at the equivalent local time. Click to embiggen.

The First Quarter Moon is Thursday June 9.

This week sees the bright planets strung out in a line, with Venus and Mercury heading towards the horizon.

Jupiter is prominent in the early morning sky above the threesome of Mars, Venus and Mercury. Mars is just above Venus, but is not very spectacular. Bright white Venus is coming closer to the horizon, but is still readily seen in the early morning sky. Venus is "gibbous" phase, and is nearly "full".

Mercury is still visible in the eastern twilight below Venus, but draws away from Venus during the week, becoming progressively more difficult to observe as it heads towards the horizon. Mercury is lost to view by the end of the week.

Evening sky on Saturday June looking north as seen from Adelaide at 9:00 pm local time in South Australia showing Saturn near Spica and very close to Porrima (gamma Virginis). Similar views will be seen elsewhere at the equivalent local time.

Inset, the telescopic view of Saturn on the 4th , you will need a fairly large telescope to see any moon other than Titan. Click to embiggen.

Saturn is rising before sunset, and is is readily visible as the bright yellowish object not far from the bright star Spica. It is high enough for telescopic observation in the early evening. This week Saturn comes very close to the star Porrima (gamma Virginis), being just a quarter of a finger-width from Saturn. They already look beautiful, paired close together.

The big storm on Saturn is now so large that it is visible in even small telescopes.

Even in small telescopes you can see Saturn's rings and it's moon Titan. Despite opposition, when Saturn was at its biggest, being well past, Saturn will be big and beautiful for many weeks to come.

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.

The asteroid Vesta is becoming brighter and is now readily visible in binoculars (magnitude 6.5), near iota Capricorni, making it very easy to find. It moves significantly night to night, so will be easy to follow. A chart showing Vesta's location is here.

Printable PDF maps of the Eastern sky at 10 pm ADST, Western sky at 10 pm ADST. 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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Monday, May 30, 2011

 

Aurora in Tasmania

Shortly after I went to bed on Saturday night, the automated aurora alert went off briefly (sorry tassie Subscribers to Aurora alert), with no prior warning of flares or such. It turns out there was a nice auroral display, some pictures are here at spaceweather, and here at the Hobart Mercury.

New Zealand also got to see some.

Maybe next time I will be awake when auroa happen.

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Carnival of Space #199 is here.

Carnival of Space #199 is now up at Weird Warp. There's space planes, a new look at the Roswel Incident, more multiplanet extrasolar solar systems, the nature of dark energy, WISE's Galaxy discoveries and much, much more. Head on over for a read.

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Saturday, May 28, 2011

 

Planet Dance Morning of May 29-31

Morning sky looking north-east as seen from Adelaide at 6:30 am local time on Sunday May 29 showing the Crescent Moon near Jupiter, with Mars, Venus and Mercury lined up below. Similar views will be seen elsewhere at the equivalent local time. Click to embiggen.

Don't forget the next installment of the Planet dance runs from this Sunday morning (29 May) to the morning of Tuesday May 31.

On Sunday the 29th, the crescent Moon forms a line with Jupiter and the rest of the bright planets, then on the 30th Mars, the crescent Moon and Jupiter from a triangle in the sky. Finally on the 31st the thin crescent Moon is not far from Venus.

You may need a clear level horizon to see Mercury at its best, and the 31st's Venus Moon conjunction is a bit low, but it is worth the effort of getting up. You will get the best views between an hour and 40 minutes before local sunrise. Check for satellite passes at Heavens Above.

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Wednesday, May 25, 2011

 

The Sky This Week - Thursday May 26 to Thursday June 2

Venus, Mercury, Mars and Jupiter form a line in the morning sky, and are visited by the thin crescent Moon later in the week. Saturn is close to gamma Virginis.

Morning sky looking north-east as seen from Adelaide at 6:30 am local time on Sunday May 29 showing the Crescent Moon near Jupiter, with Mars, Venus and Mercury lined up below. Similar views will be seen elsewhere at the equivalent local time. Click to embiggen.

The New Moon is Thursday June 2.

This week sees the bright planets strung out in a line as the final act in the "Planet Dance". The crescent Moon joins them at the end of the week.

Jupiter is prominent in the early morning sky above the threesome of Mars, Venus and Mercury. On the morning of Sunday the 29th, the crescent Moon forms a line with Jupiter and the rest of the bright planets.

Mars is just above Venus, but is not very spectacular. On the 30th Mars, the crescent Moon and Jupiter from a triangle in the sky.

Bright white Venus is readily seen in the early morning sky, although it is comeing closer to the horizon. Venus is "gibbous" phase, and is nearly "full". On the 31st, the thin crescent Moon is not far from Venus.

Mercury is is still visible in the eastern twilight not far below Venus, but draws away from Venus as the week wears on. Mercury becomes progressively more difficult to observe as it heads towards the horizon.

You can see a videocast of the entire months planet dance here.

Evening sky on Saturday May 28 looking north as seen from Adelaide at 9:00 pm local time in South Australia showing Saturn near Spica and very close to Porrima (gamma Virginis). Similar views will be seen elsewhere at the equivalent local time.

Inset, the telescopic view of Saturn on the 21st , you will need a fairly large telescope to see any moon other than Titan. Click to embiggen.

Saturn is rising before sunset, and is is readily visible as the bright yellowish object not far from the bright star Spica. It is high enough for telescopic observation in the early evening.

The big storm on Saturn is now so large that it is visible in even small telescopes.

Even in small telescopes you can see Saturn's rings and it's moon Titan. Saturn was at opposition on April 4th, when Saturn was at its biggest and brightest. Despite opposition being past, Saturn will be big and beautiful for many weeks to come.

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.

The asteroid Vesta is quite faint (magnitude 7), so you need binoculars to see it and may need to watch over a number of nights to make sure you are seeing it. Currently Vesta is in Capricornius, not near anything interesting, although it passes a couple of bright stars. Vesta is brightening and will be (just) visible to the unaided eye in a few months time. A chart showing Vesta's location is here.

Printable PDF maps of the Eastern sky at 10 pm ADST, Western sky at 10 pm ADST. 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, May 24, 2011

 

Carnival of Space #198 (Southern Hemisphere Edition)

Welcome to the 198th Carnival of Space, this time hosted in the Southern Hemisphere. We have lots of good stories for you this week.

Primates in Cans:
(10 points if you can name the SF author that inspired this title)

Over at the Next Big Future, putting primates in cans is considered, deeply. Robert Zubrin proposes using three Spacex Falcon Heavy launches to send two people to Mars by 2016. And TNBF follows up with Zubrin provides more explanation of his Space Falcon Heavy Mars Plan.

Vintage Space reminds us that Wednesday May 25 marks the 50th anniversary of Kennedy's pledge to send American astronauts to the moon and return them safely to Earth.

The Spacewriter exults over the successful launch of Endeavour on Monday, May 16th.

At the Universe Today, DARPA Wants Your Ideas for a 100-Year Starship


The Inner Solar System:

Astroswanny checks in on Comet Elenin and captures a 1500s color image with Asteroid (1793) Zoya and (7503) 1996 VJ38 travelling in the opposite direction on the plate. Speaking of Elenin, I try and dispell some misconceptions about the brightness of comets.

The Dawn spacecraft has taken its first photograph of asteroid Vesta. Dawn is due to rendezvous with Vesta on July 15, part of a journey that will take the spacecraft to Ceres in 2015.

Discovery News suggests that sometimes, Earth just needs to take one for the team. But how can we mitigate the worst an asteroid impact can inflict?

Cheap Astronomy presents a podcast exploring the logic of suggesting that tidally locked objects spin on their axis.

Weirs warp blogs about how planetary scientists use the look of planets and moons to find out information about their past. New maps of the moon have been put together that reveal the slopes and roughness of the moon’s surface.

Armagh Planetarium's latest night sky guide looks at the stars of the northern hemisphere's late spring.

How many discoveries of the century have you made this year, Chandra?

Deep Space:

Starry Critters explores the nebular glow of the newly released Hubble image of Messier 8 as well as a zoom of a HiRISE image.

We are all in the Gutter ponders: What is a white hole? Could it explain the mysterious gamma-burst objects we see? How does Fred fit into this? This post attempts to provide the answers.

Weird Warp reports that a massive search for alien life on 86 exoplanets has just started. The search will use a large radio telescope in West Virginia to listen for signs of life. These 86 planets have been picked from a list of 1235 planets which have been identified by NASA’s Kepler space telescope.

Wandering Planets:

A big theme this week has been the discovery of wandering planets in the vasty deep. The Next Big Future reports on the discovery of 10 wandering planets and the estimates there could be around 400 billion in the Milky Way. The Meridian Journal also comments of the rogue planets, as does the Urban Astronomer.

But Centauri Dreams is skeptical, pointing to the possibility that the ten candidate planets revealed by gravitational microlensing might have host stars after all. And do we really understand planet formation well enough to rule out something other than planetary ejection as the cause for rogue planets?

Other Astrostuff:

Vega00 releases chapter #21 of Introduction to Cosmology, in which is explained a way to determine the age of the Universe.

The Next Big Future reports that NASA confirms that they are conducting experiments to confirm the Widom Larsen theory of cold fusion.

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Friday, May 20, 2011

 

What makes a bright comet? The case of Elenin and Cassini at Saturn

Elenin "near" Saturn in 2009, click to embiggen.

When an astronomer says a comet is “bright”, it means that the comet will be brighter than magnitude 12. At this magnitude, the comet will be visible to the eye in moderate aperture amateur telescopes, rather than requiring substantial exposure times with film of CCD cameras. To the ordinary person on the Clapham Omnibus, this is still extremely faint; people with good eyesight under ideal dark sky conditions can see objects as dim as magnitude 6.6, over 100 times brighter than a magnitude 12 object.

Cassini in orbit around Saturn with the location of Elenin shown, Elenin is too dim to be seen, click to embiggen

Not surprisingly, the astronomical use of “bright comet” can cause considerable confusion, especially as most people don’t have a good feel for the brightness of objects in the sky. Comet C/2010 X1 Elenein is a “bright” comet; although it is currently around magnitude 14, it will reach a magnitude of somewhere between 6 (just visible to the unaided eye) and 4 (about as bright as epsilon Crucis, the 5th and dimmest star in the Southern Cross) at its brightest.

Why the variation? The brightness of an object like an asteroid depends on how big it is, how far it is from the Sun and us, and how shiny it is. Calculating the brightness of an asteroid at closest approach is fairly straightforward, even if we are a bit uncertain about how shiny and big it is.

Gustavo Muller's image of Elenin on August 8, 2011, from the Aerith gallery.

Unlike asteroids, we are not seeing the surface of the comet per se (except when it is very, very far from the Sun), but light reflected from the tenuous haze of dust and gas that boils off the “dirty snowball/icy dirtball” that is a comet. The coma of a comet can extend many thousands of kilometres from the surface.

The Great Comet was around 30km in diameter and had a coma nearly as big as the Sun, comet Halley is 6x15 km and had a coma 100,000 km wide when it last approached Earth, C/2010 X1 Elenin is roughly 3-4 Km and has a coma around 50,000 km wide. The coma is a pretty good vacuum by Earth standards, but there is enough dust and fluorescing gas in this thin haze to make the comet glow brighter than the mere iceball would.

How bright the comet is depends an exactly how active it is (ie how much dust and gas it produces and the size of the coma), which depends on a complex set of properties (if there are lots of rifts in the organic/silicate crust that coats the comet surface to blast out dust and gas, for example). We don’t have an exact handle on exactly what makes a comet bright, and there is substantial discussion on the comet lists about the best way to estimate the development of cometary brightness.

Light curve of comet Elenin, from Aerith, click to embiggen.

However we have a number of good rules of thumb. Comets that have just dropped in from the Oort cloud, like Elenin, are intrinsically dim. That is they tend produce much more gas than reflective dust and usually do not put on much of a show.

Again, there have been exceptions, comet 2006 P1 McNaught was initially expected to be very bright, around magnitude 2, but ended up around an astounding magnitude -1 when we could first see it again after it passed behind the Sun (although it’s brightness dropped rapidly after that). Still by following the light curve of a comet we can get a good idea of its brightness. The light curve of Elenin is still developing, but it looks on track to be somewhere between just visible to the unaided eye to being dimly visible.

People also confuse the concept of “bright” in terms of a comet and “big”. And example is here:
Elenin passed fairly close to Saturn in Mid-Late 2009. Cassini was in the area, taking pictures of Saturn and it's moons. It had just wrapped up its scheduled mission when project planners extended it.
[snip images]
So a big comet was nearby, and Cassini never saw it? This means either:
A) NASA saw Elenin with Cassini in 2009 (or earlier) and decided not to tell us
B) NASA did NOT see Elenin in 2009 because it's not really a bright comet after all
C) NASA did NOT see Elenin in 2009 due to chance or incompetence.

Rings of Saturn as seen from Cassini. See the Stars? No, they are all washed out in the image (click to embiggen)

Now there is a couple of issues here, “fairly close” was a large chunk of 1 AU away, what looks “close” on a JPL animation is still an enormous distance way (see the image at the top of the post). And again, the mistaken concept of “bright”. At the time (2009) Elenin was still fairly dim, around magnitude 22, just a tiny bare lump of ice with only the faintest traces of a coma around it, far from the illumination of the Sun.

You can use the JPL horizons program to find out how bright it would seem from Cassini. Turns out it’s around magnitude 22 as well (the comet was closer, but as seen from Saturn and Cassini it would only be partially illuminated).


Spica as imaged by the Cassini cameras (click to embiggen)

Now have a look at the typical image from Cassini (see above), can you see the background stars? No, Cassini is photographing relatively bright objects, and the typical exposures are too short for all but the brightest stars, let alone a dim comet.

Occasionally the spacecraft does do a long exposure image of the stars, for navigation purposes. The image to the left is just such an image centered on Spica, (alpha Virginis). The dimmest star in this image is magnitude 9, well above the brightness of Elenin. Even if a navigation image has been taken which had been pointing in Elenins direction (in general Cassini wasn’t pointing anywhere near Elenin), it couldn’t have picked the comet up.

NASA’s failure to pick up Elenin is not due to incompetence, bright comets are not bright for their entire journey around the Sun, but typically brighten substantially only during the closest approaches to the Sun, in principle Cassini could not have picked the comet up. Elenin won’t be spectacular, but at the very least will look nice through binoculars under a dark sky.

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Carnival of Space #197 is here.

Carnival of Space #197 is now up at Steve's Astro Corner (well, yeah it's been up a while but things hav ebeen busy here). There's Living in Black Holes, Lost Mars Landers and much, much more. Head on over for a read.

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Wednesday, May 18, 2011

 

The Sky This Week - Thursday May 19 to Thursday May 26

The Last Quarter Moon is Wednesday May 25. Venus, Mercury, Mars and Jupiter are still visible close together in the early morning and form some nice patterns with each other. On May 24th Mars, Venus and Mercury are close. Saturn is close to gamma Virginis.

Morning sky looking east as seen from Adelaide at 6:30 am local time on Tuesday May 24 showing Venus near Mars and Mercury with Jupiter above . Similar views will be seen elsewhere at the equivalent local time. Click to embiggen.

The Last Quarter Moon is Wednesday May 25.

This week sees the bright planets have still more close encounters with each other as part of a "Planet Dance".

Bright white Venus is readily seen in the early morning sky. Venus is "gibbous" phase, and is nearly "full". Near Venus are Mercury, Jupiter and Mars .

Mercury is readily visible in the eastern twilight not far below Venus. This week Mercury will still be prominent in the morning sky but will soon be lost to siht thereafter. On the 24th Venus and Mars are at their closest, with Mercury nearby. Jupiter heads higher in the sky above the threesome of Mercury, Mars and Venus.

You can see a videocast of the entire months planet dance here.

Evening sky on Saturday May 21 looking north as seen from Adelaide at 9:00 pm local time in South Australia showing Saturn near Spica and very close to Porrima (gamma Virginis). Similar views will be seen elsewhere at the equivalent local time.

Inset, the telescopic view of Saturn on the 21st , you will need a fairly large telescope to see any moon other than Titan. Click to embiggen.

Saturn is rising before sunset, and is is readily visible as the bright yellowish object not far from the bright star Spica. It is high enough for telescopic observation in the early evening.

The big storm on Saturn is now so large that it is visible in even small telescopes.

Even in small telescopes you can see Saturn's rings and it's moon Titan. Saturn was at opposition on April 4th, when Saturn was at its biggest and brightest. Despite opposition being past, Saturn will be big and beautiful for many weeks to come.

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.

The asteroid Vesta is quite faint (magnitude 7), so you need binoculars to see it and may need to watch over a number of nights to make sure you are seeing it. Currently Vesta is in Capricornius, not near anything interesting, although it passes a couple of bright stars. Vesta is brightening and will be (just) visible to the unaided eye in a few months time. A chart showing Vesta's location is here.

Printable PDF maps of the Eastern sky at 10 pm ADST, Western sky at 10 pm ADST. 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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See Endeavour and the ISS tonight (maybe)

The International Space Station as seen looking north-west at 7:14 pm from Adelaide on the 18th of May.

The space shuttle Endeavour is on its way to the ISS for the last time. Tonight (Wednesday 18 May), Australians have a chance to see the two of them flying together in our skies.

Except the view will be rubbish, both the ISS and the shuttle rise only a short way above the horizon before they disappear into the Earths' shadow. They may be entirely blocked from view if you have a cluttered horizon.

Your view is highly location dependent, so visit Heavens Above for the exact circumstances for your location.

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Thursday, May 12, 2011

 

Morning Line-up, Thursday May 12, 2011

Venus and Jupiter gleam through the clouds on the morning of Thursday may 12 as seen from Adelaide (click to embiggen).

So for the past few days its been raining here. Really pelting down, with no hope of seeing stars or planets. This moring looked just the same, but there were a few fleeting moments when a hole in the cloud came over and I could see Venus, Jupiter and Mercury. In this shot I captured Venus and Jupiter as the cloud rolled over them.

Hope you folks had better luck.

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Wednesday, May 11, 2011

 

The Sky This Week - Thursday May 12 to Thursday May 19

The Full Moon is Tuesday May 17. Venus, Mercury, Mars and Jupiter are visible close together in the early morning and form some nice patterns with each other. On May 12th Venus and Jupiter are close with Mercury nearby. On May 17th there is a particularly interesting pattern of planets.

Morning sky looking east as seen from Adelaide at 6:00 am local time on Thursday May 17 showing Venus near Jupiter and Mercury with Mars below. Similar views will be seen elsewhere at the equivalent local time. Click to embiggen.

The Full Moon is Tuesday May 17.

This week sees the bright planets have still more close encounters with each other as part of a "Planet Dance".

Bright white Venus is readily seen in the early morning sky. Venus is "gibbous" phase, and is nearly "full". Near Venus are Mercury, Jupiter and Mars .

Mercury is readily visible in the eastern twilight not far below Venus. This and the next week remain the best time to see Mercury in the morning this year. On the 12th Venus and Jupiter are at their closest, with Mercury nearby. Jupiter heads higher in the sky while Mercury and Venus remain close for some time. Mars is faint below the three. On the 17th the four planets make an interesting pattern in the sky.

You can see a videocast of the entire months planet dance here.

Evening sky on Saturday May 14 looking north as seen from Adelaide at 9:00 pm local time in South Australia showing Saturn near Spica. Similar views will be seen elsewhere at the equivalent local time.

Inset,the telescopic view of Saturn on the 7th , you will need a fairly large telescope to see any moon other than Titan. Click to embiggen.

Saturn is rising before sunset, and is
is readily visible as the bright yellowish object not far from the bright star Spica. It is high enough for telescopic observation in the early evening.

The big storm on Saturn is now so large that it is visible in even small telescopes.

Even in small telescopes you can see Saturn's rings and it's moon Titan. Saturn was at opposition on April 4th, when Saturn was at its biggest and brightest. Despite opposition being past, Saturn will be big and beautiful for many weeks to come.

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.

The asteroid Vesta is quite faint (magnitude 7), so you need binoculars to see it and may need to watch over a number of nights to make sure you are seeing it. Currently Vesta is in Capricornius, not near anything interesting, although it passes a couple of bright stars. Vesta is brightening and will be (just) visible to the unaided eye in a few months time. A chart showing Vesta's location is here.

Printable PDF maps of the Eastern sky at 10 pm ADST, Western sky at 10 pm ADST. 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, May 10, 2011

 

Carnival of Space #196 is here.

Carnival of Space #196 is now up at Vintage Space. There's Black Holes and Big Bangs, the size of the universe, how Earth twists space, the low-down on astrology and much much more, grab an aerostat and hop on over.

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Monday, May 09, 2011

 

Morning Line-up, Monday May 9, 2011

Jupiter climbs towards Venus and Mercury in the morning sky as seen from Adelaide around 6:10 am. Mars glimmers faintly below. Click to embiggen.

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Sunday, May 08, 2011

 

Mother's Day 2011

Mother's Day 2011

Middle Son decided to cook the Bettdeckererscnappender Weisle breakfast. He chose a Star Wars theme. There was Double Sun toast (a piece of toast with two eggs cooked in star shaped holes), Princess Leia cinnamon scrolls and Hoth Chocolate.

MiddleOnes cooking skills are certainly coming on (although I had to help him cutting up the cinnamon scrolls). After a relaxing breakfast the BEW got Mother's Bay presents including chocolate (SmallestOnes idea) and a nectar bird feeder (again MiddleOnes idea). We made up some artificial nectar then hung it in the Lilly-Pilly tree, hoping to attract lorikeets.

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Morning Line-up, Sunday May 8, 2011

Venus, Mercury, Jupiter and Mars in the eastern dawn sky over Adelaide, around 6:00 am. Mars is just above the cloud band.

When I went to bed (after watching Pirates of the Caribbean with EldestOne, my job was to be his pillow), the sky was covered in cloud. Nonetheless I still set my alarm for 3;30, just in case the cloud cleared and there were eta Aquariids to be seen.

Well, I slept straight through the alarm and woke at 10 to 6. The Messenger of the Gods glowed near the Goddess of Love in a sky streaked with clouds. I went down to the beach to get some shots of the line-up, then wended my way back to prepare for Mothers Day breakfast with MiddleOne cooking.

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Saturday, May 07, 2011

 

The ISS shoots the Line-up May 10, 2011

The ISS close to the planetary Line-up, as seen from Adelaide at 6:05 am local time on Tuesday May 10.

On morning of the 10th of May, the ISS passes close to the line-up of Venus, Mercury, Jupiter and Mars as seen from south-eastern Australia. From Sydney, the ISS best pass is on the following day, the 11th. Head over to Heavens Above and see what is visible from your location and the exact time (there is about a 10 minute window, so you need to be watching close to the right time for your location).

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Friday, May 06, 2011

 

596 Scheila - Asteroid Collision not Cometary Outburst?

Image Credit: Steve Larson of the University of Arizona's Catalina Sky Survey (CSS), December 11, 2010, Catalina 0.68-meter Schmidt telescope.

Back in December 2010 the Catalina Sky Survey picked up a remarkable comet-like outburst from the asteroid 596 Schelia. Multiple observers soon confirmed this outburst, including several members of the Global-rent-a-scope community.

If you want to see some good images of the comet-like coma around 596 Scheila, here is Martin Moberly's image taken on G-11, J-F Soulier's images, W-T Hsu's images, and Joseph Brimacombe has some amazing animations here and here, as well as some great images (my own images were pretty ordinary).

Scheila is a 113 Km diameter rock, one of 4 "T" class asteroids, which have a number of comet like features and are related to "D" class asteroids, which may be captured Kuiper belt objects. Scheila joined a growing list of asteroids like 3200 Phaethon which have shown comet-like characteristics. The question hotly debated at the time as whether this was a true outburst of buried cometary material, or the results of an impact. The asymmetric plumes of material were puzzling, and not entirely consistent with a cometary outburst.

Image Credit: NASA/Hubble.

A recent publication (PDF here) may resolve this debate. Shortly after the outburst was announced, the spacecraft SWIFT used its Ultraviolet/Optical Telescope (UVOT) to capture multiple images and, most importantly, a spectrum of the asteroid.

A cometary outburst sends a mass of dust, gas and water vapor into space. Ultraviolet sunlight then breaks up the water into hydroxyl and hydrogen. Other gases are also transformed into compounds with a characteristic UV-spectra. But none of the emissions most commonly identified in comets, such as hydroxyl or cyanogen, show up in the UVOT spectrum.

The combination of dust distribution and spectra strongly suggests that what we saw was the result of an asteroid collision, rather than a cometary outburst. This is pretty amazing, the chance that we would see the aftermath of an asteroidal collision before the dust settled, so to speak, is pretty slim. Two months after the first observation the dust tail had dissipated.

The press release says:
"The Hubble data are most simply explained by the impact, at 11,000 mph, of a previously unknown asteroid about 100 feet in diameter," said Hubble team leader David Jewitt at the University of California in Los Angeles. Hubble did not see any discrete collision fragments, unlike its 2009 observations of P/2010 A2, the first identified asteroid collision.
Amateurs played an important role in monitoring Scheila, for example the time sequence of J-F Soulier's images show the evolution of the coma. The SWIFT spectra result was anticipated by this spectrum at John Menke's site, which looks like a lot of dust, as well as susequent amateur and professional spectra (as detailed at J-F Soulier's site ). Given that the Global -rent-a-scope community played a role in confirming and monitoring the activity of 596 Schelia, these results should be of great interest to them. What would have been nice would have been a way to collate all the amateur images and spectroscopic results to systematically follow the evolution of the outburst.

Centauri dreams has a good discussion of the paper, and NASA has produced a really great video that explains the findings.

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Mothers Day Morning Sky Spectacular (May 8th, 2011)

In Australia Mothers Day Falls on Sunday May the 8th. This year this coincides with the peak of the Eta Aquarid meteor shower and the conjunction of Mercy and Venus in the morning sky. What says "I love you Mum" more than getting her up at 3:30 am to watch meteors flash across the sky and bright planets rise?

Morning sky looking east as seen from Adelaide at 6:00 am local time on Sunday May 8 showing Venus near Mercury with Jupiter and Mars. Similar views will be seen elsewhere at the equivalent local time. Click to embiggen.

If you have been following the planet dance (see here, here and here) in the morning you will have been watching Venus and Mercury close in on each other.

This cumulates this Sunday with Venus and Mercury at their closest (although they remain close for a couple of weeks thereafter) forming a beautiful sky pattern. The symbolism of the Planet named for the goddess of love being near the planet named for the messenger of the Gods would seem to be appropriate for Mothers Day.

You don't need anything special to see this line-up, just wander out somewhere between 5:45 and 6:15 and look east, and planets will be there in all their glory. Of course, if you get up earlier you can see the Eta Aquairid Meteor shower as well.

Eastern horizon around 4 am local time on May 8. The red cross shows the location of the apparent origin of the Eta Aquariid meteors (the radiant). Click to embiggen.

On the mornings of Saturday May 7 and Monday May 8 the Eta Aquariid meteor shower peaks. You can see meteors before or after this time but the numbers will be less (see the meteor flux estimator below).

People in the suburbs should see a meteor around once every 6 minutes, and in the country about once every 3 minutes, from between 4 am to 5 am.

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. A hot Thermos 0f something to drink (or maybe some Mothers Day chocolates) 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). At least in Adelaide, we get a nice Iridium flare during the meteor peak.

The sky will also be particularly beautiful, with the Milky Way stretching over the sky and constellation of Scorpius gracing the north-western sky. As well the conjunction of Venus and Mercury rising in the east with Jupiter and Mars below it.


Use the NASA meteor shower flux estimator for an estimate of what the shower will be like from your location. You need to choose 31 Eta Aquariids and remember to set the date to 6-7 or 7-8 May 2011. You can follow the progress of the shower ath the IMO live Aquariid site.

Cloud cover predictions can be found at SkippySky.

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Thursday, May 05, 2011

 

Morning Line-up, Thursday May 5, 2011

View east from Adelaide at 6:10 am this morning, click to embiggen to see Mars (just above the roof under Jupiter). Planet ored is Venus, Mercury, Jupiter and Mars.

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Wednesday, May 04, 2011

 

Have a Try of the Virtual Sky

My Blog Brother Stuart has produced a wonderful piece of code, the Virtual Sky that allows you to embed a live view of the sky in your web/blog pages with no additional widget or apps installed. It is customisable, scrollable and all things good (try running your mouse over the embedded bit in this page). The instruction on the introduction page look scary, but the customisation form makes setting them up a snap. The window below shows the sky pretty much as I see it from my back yard (without the houses and trees of course).

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Morning Line-up, Wednesday May 4, 2011

The line-up seen Wednesday morning, 6:00 am. A meteor flashed overhead as I watched.

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Tuesday, May 03, 2011

 

Want to see a Star with a Transiting Exoplanet?

55 Canceri is a dim, unprepossessing star in the constellation of Cancer. It's a double star, whose claim to fame is that the yellow, Sun-like star of the double is host to a solar system of at least 5 planets, one of the few stars with extensive planetary systems so far discovered.

It's fame has now increased as transits of the innermost planet, 55 Cnc e, has been observed. This makes 55 Cnc the closest system with a transiting exoplanet, and also the only transiting system whose star is visible to the unaided eye (well providing you live in the country with dark skies).

If you head out tonight (well, tomorrow night. as 55 Cnc has set now as seen from Australia), around 8 pm and look north east, You will easily see the twins, Castor and Pollux. Just above and to the right is a very dim star, just above that is a dimmer star (suburban dwellers will need binoculars to see it) which is 55 Cnc.

The planetary system was originally discovered by the radial velocity method, which fixes some parameters of the system.
)
The 55 Cnc system (excluding the outermost planet), 55 Cnc e is marked by the red cross near the sun.

When the inner planet ,55 Cnc e, transits were observed, the radius of the exoplanet could be determined more precisely. It turns out to be a mere 1.6 times that of Earth, placing it as one of the smallest "Super Earths" yet discovered. With a mass of nearly 9 times that of Earth, it must be a rocky world, almost as dense as lead.

The orbit was also revised, it turns out the planet screams around it's sun in a year that lasts 18 hours. It's surface temprature, depending on whether it has an atmosphere or not, can range between 2100 and 2900 degrees C.

As always, I've created a Celestia file for 55 Cnc e. Celestia already has a file with the 55 Cnc system in it. If you wish, you can comment out the old 55 Cnc e data in exoplanets.ssc or replace the data with the following.
==================55Cnce.ssc===================================
"e" "HD 75732" # Rho1 Cnc A
{
Texture "venuslike.*"
NightTexture "venuslikenight.*"

Mass 8.57 # M.sin(i) = 8.57 earths
Radius 10396.14

InfoURL "http://arxiv.org/PS_cache/arxiv/pdf/1104/1104.5230v1.pdf"

EllipticalOrbit {
Period 0.002016503
SemiMajorAxis 0.01573
Eccentricity 0.07
# Inclination 90.0 # inclination is differnt from rest of system as measured with radial velocity
ArgOfPericenter 107
MeanAnomaly 181
}

# likely to be in captured synchronous rotation
}

AltSurface "limit of knowledge" "HD 75732/e"
{
Texture "extrasolar-lok.*"
}
=============================================================

The original paper is here, more commentary at Universe Today and Centauri Dreams.

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Morning Line-up, Tuesday May 3, 2011

Venus, Mercury, Jupiter and Mars at 6:10 am as seen in Adelaide, 3 May, 2011 (click to embiggen)

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The Sky This Week - Thursday May 5 to Thursday May 12

The First Quarter Moon is Wednesday May 11. Venus, Mercury, Mars and Jupiter are visible lined up in the early morning and have some close encounters with each other. On May 8th Venus is close to Mercury and on May 12th Venus and Jupiter are close. The eta Aquariid meteor shower can be seen on the mornings of the 7th and 8th.

Morning sky looking east as seen from Adelaide at 6:00 am local time on Sunday May 8 showing Venus near Mercury with Jupiter and Mars. Similar views will be seen elsewhere at the equivalent local time. Click to embiggen.

The First Quarter Moon is Wednesday May 11.

This week sees the bright planets have close encounters with each other as part of a "Planet Dance".

Bright white Venus is readily seen in the early morning sky in Pisces. Venus is "gibbous" phase, and is nearly "full". Below Venus are Mercury, Jupiter and Mars .

Mercury is readily visible in the eastern twilight not far below Venus. This and the next two weeks are the best time to see Mercury in the morning this year. As the week progresses Mercury draws closer to Venus and is at its closest on May 8th (Mothers day in Australia). The pair remain close for some time. Mars and Jupiter are below the pair, with Jupiter heading towards Venus over the week. Jupiter and Venus are at their closest on May the 12th.

You can see a videocast of the entire months planet dance here.

Evening sky on Saturday May 7 looking north as seen from Adelaide at 9:00 pm local time in South Australia showing Saturn near Spica. Similar views will be seen elsewhere at the equivalent local time.

Inset,the telescopic view of Saturn on the 7th , you will need a fairly large telescope to see any moon other than Titan. Click to embiggen.

Saturn is rising before sunset, and is
is readily visible as the bright yellowish object not far from the bright star Spica. It is high enough for telescopic observation in the early evening.

The big storm on Saturn is now so large that it is visible in even small telescopes.

Even in small telescopes you can see Saturn's rings and it's moon Titan. Saturn was at opposition on April 4th, when Saturn was at its biggest and brightest. Despite opposition being past, Saturn will be big and beautiful for many weeks to come.

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.

Eastern horizon around 4 am local time on May 8. The red cross shows the location of the apparent origin of the Eta Aquariid meteors (the radiant). Click to embiggen.

On the mornings of Saturday May 7 and Monday May 8 the Eta Aquariid meteor shower peaks. You can see meteors before or after this time but the numbers will be less (see the meteor flux estimator below).

At the peak, people in the suburbs should see a meteor around once every 6 minutes, and in the country about once every 3 minutes, from between 4 am to 5 am on May 7 and 8. Don't forget to let your eyes adjust to the darkness for some minutes to get the best sensitivity for meteor watching.

Use the NASA meteor shower flux estimator for an estimate of what the shower will be like from your location. You need to choose 31 Eta Aquariids and remember to set the date to 6-7 or 7-8 May 2011. You can follow the progress of the shower ath the IMO live Aquariid site.

The asteroid Vesta is quite faint (magnitude 7.3), so you need binoculars to see it and may need to watch over a number of nights to make sure you are seeing it. Currently Vesta is in Capricornius, not near anything interesting, although it passes a couple of bright stars. Vesta is brightening and will be (just) visible to the unaided eye in a few months time. A chart showing Vesta's location is here.

Printable PDF maps of the Eastern sky at 10 pm ADST, Western sky at 10 pm ADST. 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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Monday, May 02, 2011

 

Morning Line-Up, 2 May 2011

Venus, Mercury, Jupiter and Mars glow in the early morning skies of Monday, May 2 (click to embiggen, Mars may be a bit hard to see otherwise, it's a bit below Jupiter between Jupiter and the tree).

The Line-up with added crescent Moon was completely rained out here, but this morning there was a break in the clouds so I could get this lovely view. Keep your eyes peeled for more celestial wonders over the coming weeks.

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Sunday, May 01, 2011

 

Videocast - The Dance of The Planets in May 2011

I've done my first Videocast of this months (May 2011) morning dance of the planets. The link is here, or you can watch the video below. The sound and images don't synchronize so well, as I had to do the sound recording on a different computer from the one the proto-video was on (don't ask). I may re-record it.

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