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Wednesday, November 19, 2014

 

The Sky This Week - Thursday November 20 to Thursday November 27

The New Moon is Saturday November 22.   Mars is easily visible in the early evening and is visited by the crescent Moon on the 26th.  Jupiter is prominent in the morning sky. Comet C/2102 K1 PanSTARRS is visible in binoculars in the early evening.

The New Moon is Saturday November 22.

Evening sky on Wednesday November 26 looking west as seen from Adelaide at 21:00 (9:00 pm) ACDST in South Australia.  The Moon is close to Jupiter. Similar views will be seen elsewhere at the equivalent local time (click to embiggen).



Venus is comes out the glare of the Sun by the end of the week, but will be very difficult to see low on the western horizon in the twilight.

 Mars  is easily seen in the western evening sky, setting around 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 western horizon in the early evening.

Mars is still in the constellation of  Sagittarius, but is heading for Capricornius.

Morning sky on Saturday November 22 looking north-east as seen from Adelaide at 5:00 am ACDST.  Jupiter is above the north-east horizon. (click to embiggen).

Saturn is lost in the twilight.
  
Mercury  is in the morning sky, but is too low for easy visibility.

 Jupiter  rises higher in the morning twilight, and now is easy to see above the horizon before twilight. Jupiter is the brightest object above the north-eastern horizon. It is now not far from the bright star Regulus in the sickle of Leo (this forms the head of the constellation of the  Lion).
Evening sky on Saturday November 22 looking south  as seen from Adelaide at 21:00 (9:00 pm) ACDST in South Australia. Comet C/2012 K1 PanSTARRS neaer Achernar.  Similar views will be seen elsewhere at the equivalent local time (click to embiggen).

Comet C/2012 K1 PanSTARRS is now visible in the evening sky from around 8 pm. With the Moon gone from the evening sky, under reasonably dark sky conditions it should be visible in 10x50 binoculars as a fuzzy dot.

At magnitude 7.7 you will need to let your eyes adapt to darkness to see the comet clearly. It doesn't have any spectacular encounters, but will look nice amongst the stars. While the comet is fading, and becoming more difficult to see in binoculars, it remains very easily visible n small telescopes. 

More detailed charts and a printable binocular map  are here.

 There are lots of interesting things in the sky to view with a telescope. Especially with Mars prominent in the early evening 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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Saturday, November 15, 2014

 

SmallestOne turns a prime number old

In case you're wondering why I have not been posting on the historic Philae landing on comet 67P, I have been involved in SmallestOne's birthday party. SmallestOne is a prime number old, the sum of the two digits of his age is an even number and a prime number too. There was swimming, trampolining, table tennis and lots of screaming. We will return to astronomy tomorrow

Thursday, November 13, 2014

 

Philae Made It! We have Landed ona a Comet!

The landing as seen by XKCD.

After all the waiting and agonising, the Philae lander separated cleanly form Rosetta and made a slow, 7 hour journey to comet 67P.

And landed. Story here


Wednesday, November 12, 2014

 

The Towering Cliffs of Comet 67P/Churyumov–Gerasimenko

Agilkia, the Philae landing site, looks pretty okay in this image (image credit ESA). Click to embiggenBut with a different lighting angle you can see it (indicated by box) is perched near a pretty worrying cliff. (image credit ESA). Click to embiggen

Lighting angle can  make a huge difference to how a place looks. With the lighting above, Philae's landing environs look relatively smooth, with some scalloping. With the light at a different angle, the "scalloping" is revealed as terrifying cliffs.

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Comet 67P/Churyumov–Gerasimenko in Celestia

Comet 67P//Churyumov–Gerasimenko and the Rosetta orbiter rendered in Celestia.

As usual, I have been trying to make a Celestia file for comet 67P.

And failing miserably. I tried to convert the ESA public shape model to celestia 3Ds format and failed miserably. So I ended up using Jack Selden's Rosetta files, with a surface map taken from this thread on the Celestia. The Celestia comet looks nothing like the rubber duck shape of 67P, but until some kind person points me to a pubic Celestia shape model that is what I am stuck with.

I utterly failed to make any of the XYZ orbital files work for me, so I just copied the orbit of Dactyl around Ida. Yes, that's cheating, but after days of frustration I wanted something that works. If you want a stunning Celestia simulation, go here.


As usual, copy the code below and save as it as a text file 67P.ssc in the Celestia extras folder.
==========================67P.ssc=======================================
# Taken from Jack Seldens 67P ssc file
# Created By Ian Shazell, Spacecraft Analyst for Rosetta
# On Behalf of the European space Agency, www.esa.int
# Comet 67P Churyumov-Gerasimenko, Celestia SSC file. www.shatters.net/celestia
#
#
"Churyumov-Gerasimenko" "Sol"
{
    Class "comet"
    Mesh "asteroid.cms"
        Texture "67p720x361.png" # texture from the Celestia forum from
    Radius 1.98                             # http://forum.celestialmatters.org/viewtopic.php?f=4&t=690
    EllipticalOrbit
    {
        Period                   6.4451441700205338809034907597536
        PericenterDistance       1.2431213
        SemiMajorAxis          3.4632382 
        Eccentricity            0.6410523343769
        Inclination            7.04073996
        AscendingNode          50.150595169
        ArgOfPericenter        12.77512076
                MeanAnomaly            -71.72623185
        Epoch                   2456778.5
    }
        Albedo            0.2
}

"Rosetta" "Sol/Churyumov-Gerasimenko"
{
        Class "spacecraft"
        Mesh "rosetta.3ds" # rosetta model http://homepage.eircom.net/~jackcelestia/files/rosetta.zip
        Radius 0.005

        EllipticalOrbit
        {
    Epoch         2449228.2028  # Using orbit of Dactyl around Ida
    Period             0.96534 #
    SemiMajorAxis     25.0     # Why? I can't make anything else work
    Eccentricity       0.13    #
    LongOfPericenter 310       #
    AscendingNode     90       #
                                   #
    Inclination        8       #
        }

        Albedo 0.5
}
======================end 67P.ssc==========================

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BREAKING NEWS! Philae Lives! (Philae heads towards comet 67P)

UPDATE 21:57 ACDST: Telemetry received shows flywheel working and Landing gear deployed. Everything appears to be working.

XKCD's wonderful cartoon of Philae leaving Rosetta and heading for comet 67P, the cartoon updates so every time you visit there will be a different image of the journey.

Philae has separated from Rosetta and is heading towards the comet.

Until the lander and Rosetta are lined up properly we won't have any telemetry, the first telemetry should be at 12:00 UT (that's 11 pm AEDST).

 BREAKING NEWS! Telemetry acquired from  and  !! WOOT!

The ony problem has been the nitrogen thruster that was supposed to hold the lander down as the harpoons and ice screws deployed has apparently failed. Unless the surface is rally solid, this should not be a problem. Everything else seems to be working fine.

The lander is heading towards Comet 67P/Churyumov-Gerasimenko at a leisurely 2 Km per hour, it should arrive at the landing site in around 5 hours at 3:00 am AEDST (16:02 UT).

the Livestream is here http://new.livestream.com/ESA/cometlanding


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Tomorrow we Land on a Comet

Small bodies landed (or about to be landed on) by spacecraft. Asteroid Itokawa size 540m x 270m x 210m (image Credit JAXA)Comet 67P size 4.1×4.5 Km (image credit ESA) Asteroid Eros size 34.4×11.2×11.2 Km (image credit JPL/NASA)

Tomorrow (Wednesday) at 04:03:20 UT, if all has gone well, the Philae lander will separate from the Rosetta spacecraft and begin its descent to Comet 67P/Churyumov-Gerasimenko, by 16:02:20 UT Philae will have either landed on the comet, or crashed, or bounced off and gone spinning into space  (for Australians, that is 3 pm Wednesday and 3 am Thursday). Either way this represents a remarkable achievement.

Humans have done some extraordinary things in space, we have landed a laser wielding, atomic powered robot on Mars with a sky crane, parachuted a probe into the freezing methane clouds of Titan, sent a probe ballooning in the searing hell  that is Venus's atmosphere, but nothing compares to this.

Mars, Venus and Titan are all challenges on their own, but compared to comets they are staid. They orbit predictably, they rotate predictably, gravity is predictably down  and we had a reasonably good idea of what their surfaces are like (well Titan was a gamble, the probe could have landed in one of the methane seas).

But comets are a different kettle of fish, while their orbits are more or less predicable (given that outgassing can push them off course), they tumble rather than rotate and they vent gas and small particles that can .. inconvenience .. a spacecraft in a rather terminal way.

Comet 67P is even more of a nightmare, instead of a sort of battered potato shape most people expected, it is like a rubber duck from the dungeon dimensions. Flat plains are interspersed with boulder fields, craters and towering cliffs. The concepts of up and down on this weirdly spinning object are more like an Escher drawing than our traditional concept of a planet or asteroid.


Asteroid Itokawa from 4.1 Km (image Credit JAXA)Agilkia, landing site of Philae from around 10 Km (image credit ESA). Even the safe site is a lot more bramatic than the two asteroid we have visited.Eros surface from around 10 Km (image credit JPL/NASA)

While we have sent spacecraft scooting past comets before, even fired a copper slug into one, but we have never attempted to land on one. We have sort of landed on two asteroids. Itokawa, where the Hayabusa probe sort of bumped into it (and bounced off again with a precious dust sample)  rather than landed per se, and Eros, where the Shoemaker orbiter  wasn't actually designed to land but was rather crashed slowly on it. Itokawa is around 10 times smaller than 67P, and Eros 10 times larger, both giving entirely different challenges.


In contrast, Philae is designed to soft land and stay on the comet for months, taking measurements as the comet heats up. The descent will be slow, and it should touch down relatively softly, given the complicated calculations required to land the craft of the around 1 Km square patch of level surface Philae is aiming for, nestled in between  boulders and scarps (and a rather dramatic cliff).

67P is a 60's science fiction cover art image of a comet. (Image credit ESA)

Unlike Itokawa and Eros, which had rather plain surfaces (even if scattered with alarming boulders), 67 P is a nightmare of chaos. Missing the landing site will be catastrophic.

If it succeeds in making it to the landing spot safely, Philae has a harpoon (a SPACE HARPOON!) to help anchor it to the surface as well as the equivalent of crampons on the lander feet.

The Agilkia site seems to be faily level, and covered with what looks like snow, but this is probably unconsolidated dust. What it is on top of nobody knows. While the comet has the overall density, and possibly the structural strength, of a snowbank, exactly how the material that makes up the comet, (rock, dust, ices, organic gunge) is organised is unclear.

Will there be a  layer of rock cemented with ice, a layer of mostly ice, a messy honeycomb of rock and ice fragments with lots of space between? Will the dust layer be too deep and fragile for Philae to hold on to? Will the lander plummet into the surface like a rock thrown at a snowbank?

These are all questions that will be answered on the day. So until then we have to take a deep breath and wait. You can make a model of Rosetta while you wait.

You can watch the comet landing livestream here http://new.livestream.com/ESA/cometlanding
It will remain live until 19:00 UT (6 am Australian time).

In the meantime, you can watch this video of amateur images of  67P. http://vimeo.com/111177163


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Tuesday, November 11, 2014

 

The Sky This Week - Thursday November 13 to Thursday November 20

The Last Quarter Moon is Saturday November 15.  Southern and Western Australia will see the Last Quarter Moon occult the bright star Subra on the morning of the 15th, with Jupiter close by. Mars is easily visible in the early evening.  Jupiter is prominent in the morning sky. Comet C/2102 K1 PanSTARRS is visible in binoculars in the early evening. Leonid meteor shower on the morning of the 18th.

The Last Quarter Moon is Saturday November 15. The Moon is at apogee, its furthest from the Earth, at this time.
 

Evening sky on Saturday November 15 looking west as seen from Adelaide at 21:00 (9:00 pm) ACDST in South Australia.  Similar views will be seen elsewhere at the equivalent local time (click to embiggen).

Mars  is easily seen in the western evening sky, setting around 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 western horizon in the early evening.

Mars is still in the constellation of  Sagittarius. At the beginning of the week Mars is close to the classic globular cluster M22. This will look rather nice in binoculars. As the week goes on Mars travels into less rich stellar fields, but is still nice in binoculars.

Saturn is lost in the twilight.

Morning sky on Saturday November 15 looking north-east as seen from Adelaide at 5:00 am ACDST.  Jupiter is above the north-east horizon. (click to embiggen).
  
Mercury  is in the morning sky, but is too low for easy visibility.

Venus is lost in the glare of the Sun.

 Jupiter  rises higher in the morning twilight, and now is easy to see above the horizon before twilight. Jupiter is the brightest object above the north-eastern horizon. It is now not far from the bright star Regulus in the sickle of Leo (this forms the head of the constellation of the  Lion). On November 15 the Last Quarter Moon is near Jupiter.

At this time the Moon occults the star Subra. Subra (Omicron Leo) is a brightish white star visible to the unaided eye (magnitude 3.5). The occultation will be seen from Western Australia and Central Australia.

From Perth the star disappears behind the bright limb of the Moon at 2:48 AWST, and reappears from the dark limb at 3:31 AWST. From Hobart the star disappears behind the bright limb of the Moon at 3:54 ACST, and reappears from the dark limb at 5:29 ACST (in twilight). From Adelaide the star disappears behind the bright limb at 5:58 ACDST, this is quite deep in the twilight and so will be a bit tricky to see.

With the Moon at Last Quarter, this event is really best seen with binoculars or a small telescope (especially for the reappearance of the star in the twilight in Darwin and Adelaide). If you have a tripod or other stand for your binoculars, it will be much easier to observe. Set up about half an hour before the occultation to watch the star disappear (so you are not mucking around with equipment at the last moment).

Evening sky on Saturday November 15 looking south  as seen from Adelaide at 21:00 (9:00 pm) ACDST in South Australia. Comet C/2012 K1 PanSTARRS is above Canopus.  Similar views will be seen elsewhere at the equivalent local time (click to embiggen).

Comet C/2012 K1 PanSTARRS is now visible in the evening sky from around 8 pm. With the Moon gone from the evening sky, under reasonably dark sky conditions it should be visible in 10x50 binoculars as a fuzzy dot.

At magnitude 7.5 you will need to let your eyes adapt to darkness to see the comet clearly. It doesn't have any spectacular encounters, but will look nice amongst the stars. On the 15th it is within binocular distance of the faint (magnitude 8.3) globular cluster NGC 1261. While the comet is fading, and becoming more difficult to see in binoculars, it remains very easily visible n small telescopes. 

More detailed charts and a printable binocular map  are here.




Morning sky looking north-east as seen from Adelaide at 5:00 am local daylight saving time on Tuesday November 18 showing Jupiter near Regulus and the Moon nearby, with the Leonid Meteor shower radiant indicated with a starburst. Similar views will be seen elsewhere at the equivalent local time. Click to embiggen.

On the morning of Tuesday November 18 the Leonid Meteor shower peaks (from the point of view of Australians, that's 17 November UT), with the best time being between 3-4 am.

While the Leonids radiant is reasonably far from the crescent  Moon, this is a bad Leonid year. Very few meteors will be visible (maybe one per hour). You can use the Meteor Flux Estimator to get a prediction for your location. Use the 13 Leonids option and don't forget to set the year to 2014.

 There are lots of interesting things in the sky to view with a telescope. Especially with Mars prominent in the early evening 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, November 04, 2014

 

The Sky This Week - Thursday November 6 to Thursday November 13

The Full Moon is Friday November 7.  Saturn is lost in the twilight. Mars is in the star clouds of Sagittarius and is close to the globular cluster M22 on the 6th.  Jupiter is prominent in the morning sky. Comet C/212 K1 PanSTARRS is visible in binoculars before midnight.

The Full Moon is Friday November 7.
 
Evening sky on Thursday November 6 looking west as seen from Adelaide at 21:00 (9:00 pm) ACDST in South Australia. The inset shows the approximate binocular view of Mars and M22 at this time. Similar views will be seen elsewhere at the equivalent local time (click to embiggen).

Mars  is easily seen in the western evening sky, setting around 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 western horizon in the early evening.

Mars is in the constellation of  Sagittarius and is close to the globular cluster M22 on the 6th. This will look rather nice in binoculars.

Saturn is lost in the twilight.

Morning sky on Sunday November 9 looking north-east as seen from Adelaide at 5:00 am ACDST.  Jupiter is above the north-east horizon. (click to embiggen).
  
Mercury  is in the morning sky, but is too low for easy visibility.

Venus is lost in the glare of the Sun.

 Jupiter  rises higher in the morning twilight, and now is easy to see above the horizon before twilight. Jupiter is the brightest object above the north-eastern horizon. It is now not far from the bright star Regulus in the sickle of Leo (this forms the head of the constellation of the  Lion).


Evening sky on Saturday November 8 looking south  as seen from Adelaide at 21:00 (9:00 pm) ACDST in South Australia. Comet C/2012 K1 PanSTARRS is above Canopus.  Similar views will be seen elsewhere at the equivalent local time (click to embiggen).

Comet C/2012 K1 PanSTARRS is now visible in the evening sky from around 9 pm. While  should be easily visible in 10x50 binoculars as a fuzzy dot, until the end of the week the waxing and Full Moon will make the comet very difficult to see.

At magnitude 7 you will need to let your eyes adapt to darkness to see the comet clearly. It doesn't have any spectacular encounters, but will look nice amongst the stars. On the 8th it is very close to the star alpha Doradus. Towards the end of the week the waning Moon rises later, and the early evening will be a good time to see the comet. .

More detailed charts and a printable binocular map  are here.

There are lots of interesting things in the sky to view with a telescope. Especially with Mars prominent in the early evening 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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Catch a Series of Bright International Space Station Passes (4-9 November 2014)

All sky chart showing local  times from Heavens Above for Tuesday November 4 for Adelaide.  All sky chart showing local times from Heavens Above for Tuesday November 4 for Melbourne.
The ISS passes above Mars, as seen from Adelaide on the evening of Tuesday November 4 at 21:13 ACDST. Simulated in Stellarium (the ISS will actually be a bright dot), click to embiggen.The ISS passes near the Southern Cross, as seen from Melbourne on the evening of Tuesday November 4 at 21:44 AEDST. Simulated in Stellarium (the ISS will actually be a bright dot), click to embiggen.

Starting tonight there are a series of bright evening passes of the International Space Station lasting for 5 days. For many places in Southern Australia this series has the ISS gliding either above or under Mars, depending on where you are, on Tuesday November 4. On the 5th there is a bright pass in the twilight close to the bright star Fomalhaut.

Some of the passes are very short although bright as the ISS enters Earth's shadow, but it is interesting to see the ISS wink out abruptly.

When and what you will see is VERY location dependent, so you need to use either Heavens Above or CalSky to get site specific predictions for your location (I'm using Melbourne and Adelaide and Perth as examples).
  
Start looking several minutes before the pass is going to start to get yourself oriented and your eyes dark adapted. Be patient, on the night there may be slight differences in the time of the ISS appearing due to orbit changes not picked up by the predictions. The ISS will be moving reasonably fast when it passes near Mars, so viewers should be alert as the ISS comes up from the horizon very quickly.

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Saturday, November 01, 2014

 

Southern Skywatch November, 2014 edition is now out!

Western horizon as seen from Adelaide on 26 November at 9:00 pm ACDST . Click to embiggen.

The November edition of Southern Skywatch is now up.  This month has a little bit of  planetary action an occultation and a comet.
 
Jupiter rises higher in the morning twilight and is near the Moon on the 15th. There is a nice occultation visible from Central and Western Australia at this time.

Mars is obvious in the western evening sky.  Mars is close to the globular clusters M28 and M22 early in the month (3rd and 6th respectively).

Saturn is lost in the twilight

Venus is lost in the twilight.

Mercury returns to the morning sky but is very difficult to see.

Comet C/2012 K1 graces our skies this month.

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