Astroblog

Comet C/2012 S1 ISON and asteroid 433 Eros captured on 25 September with iTelescope T4 at around 5:10 am local time in New Mexico, USA. The image is a stack of 10 x 60 second Luminance exposures. Images stacked then SUMMED using ImageJ, then contrast enhancement applied. click to embiggen	Animation made from all 10 images. Contrast enhanced to see the comet tail better.

Comet C/2012 S1 ISON was further from asteroid 433 Eros this morning (compare with last nights images) . The Moon being rather close there was strong interference with the images. My run with T5 with an R band filter was not any improvement, with strong twilight interference.

Labels: asteroids, C/2012 S1 ISON, iTelescope

The International Space Station passes over Venus and belwo the head of the Scorpion. 8 images stacked and SUMMED in ImageJ. Canon IXUS 400 ASA 5 second exposure. Click to embiggen	Images cropped and animated using ImageJ (click to embiggen)

So I got to see the ISS pass I wrote about earlier. I was beautiful, with the brightening ISS gliding above Venus and disappearing into Earth's shadow. The Cygnus cargo craft was supposed to be visible too, but neither I noire JupiterisBig managed to see it. Still, very nice show.

Labels: ISS, Venus

There is a series of bright passes of the International Space Station occurring now.  Tonight the ISS will pass above Venus in the early evening as seen from many parts of Australia.

For exact predictions for your location see Heavens Above. http://www.heavens-above.com/

Labels: ISS, Venus

Comet C/2012 S1 ISON and asteroid 433 Eros captured on 24 September with iTelescope T4 at around 5:20 am local time in New Mexico, USA. The image is a stack of 10 x 60 second Luminance exposures. Images stacked then SUMMED using ImageJ, then contrast enhancement applied.	Animation made from 9 of 10 images. Contrast enhanced to see the comet tail better.

Had a good night tonight. Comet C/2012 S1 ISON was very close to asteroid 433 Eros (line of sight only, they were around 0.6 AU from each other). Despite strong Moonlight I got some reasonable images I could do astrometery on. Later. Now just revel in the neat little animation showing Eros and ISON moving together in the sky. I have a run with T5 with an R band filter, lets see if that gets rid of the Moonlight interference.

Labels: asteroids, C/2012 S1 ISON, iTelescope

The Last Quarter Moon is Friday September 27. Mars and Jupiter are prominent in the early morning. The Moon is near Jupiter on the 28th and Mars on October 1st. Venus is easily visible in the western evening sky and above Saturn. Mercury rises higher in the evening sky leaving the bright star Spica behind. Comet C/2012 S1 ISON visible in telescopes.

 The Last Quarter Moon is Friday September 27. The Moon is at apogee on the 28th.


Evening sky looking west as seen from Adelaide at 19:00 pm local time on Saturday September 28. Venus is quite high in the evening sky above Saturn.  Mercury is above the bright star Spica. The inset shows the telescopic view of Venus at this time. Similar views will be seen elsewhere at the equivalent local times.  Click to embiggen.

Venus  climbs higher in the evening twilight. It can easily be seen 20 minutes after sunset (indeed, with a little effort you can see it before sunset). The brightest (spectacularly so) object above the western horizon it is visible up to two hours or more after sunset (depending on how flat your western horizon is).

Venus passes through Libra heading for Scorpius. It is a distinct gibbous shape in even small telescopes

Mercury  is now readily visible in the evening twilight. Mercury climbs higher in the evening sky this week heading leaving behind the bright star Spica.

Saturn is still easily visible above the western horizon in the early evening in the constellation of Virgo. Telescopic views of the ringed world are progressively harder as the planet gets lower in the sky and deeper in the twilight. Saturn sets around 8:30 pm local time.

Neptune is currently at opposition, and visible in strong binoculars. Location maps here which can be used in conjunction with the printable PDF maps below. My images with a little point and shoot camera here. 


Morning sky on Tuesday October 1 looking north-east as seen from Adelaide at 5:00 am local time in South Australia. Mars, Jupiter, and Procyon form a long triangle in the morning sky.

Jupiter is close to the star Wassat. The crescent Moon is close to Mars. Comet C/2012 S1 ISON is below Mars, and visible in high end amateur telescopes. The inset shows the view of Jupiter through a telescope at this time. Similar views will be seen elsewhere at the equivalent local time (click to embiggen).

Mars, Jupiter and the bright star Procyon start the week forming a triangle in the morning twilight.  Jupiter is in the constellation Gemini. Mars is passing through the constellation Cancer and enters The constellation of Leo.

Mars rises  a still higher in the morning twilight, and is visible before the sky pales substantially. The crescent Moon is close to Mars on October 1. Mars comes closer to the bright star Regulus.

Jupiter is now well above the north-eastern horizon, above and well to to the left of Mars. It is quite easy to see in the morning sky well into the twilight. During the week Jupiter rises higher and comes close to the moderately bright star Wassat. Jupiter's Moons are now readily visible in binoculars.


Comet C/2012 S1 ISON is expected to become very bright in late November Early December. Currently it is visible in modest amateur instruments such as  12" reflecting telescopes. While the comet will be around magnitude 10 at the beginning of October and around 8.6-9 mid October, it is never very high at Astronomical twilight (5 and 7 degrees above the horizon in most of Australia). The horizon murk means that that it will be mid October before the comet is visible in smaller telescopes such as 4" reflectors and late October for strong binoculars.

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

Labels: weekly sky

Comet C/2012 S1 ISON captured on 22 September with iTelescope T5 at around 5:40 am local time in New Mexico, USA.

It's a bit too twilight contaminated to be anything other than eye candy, but I hope to get some shots I can do actual astrometery on later this week.

Labels: C/2012 S1 ISON, iTelescope

Venus, Saturn, Spica and Mercury imaged on 22 September at 6:55 pm ACST using my Canon IXUS, 400 ASA 1 second exposure. Mercury is the dot just above the second lowest branch, Spica is just above Mercury. Venus is the obvious brightest object in the field and Saturn is below and to the right of Venus. Click to embiggen.	Closer up view of Venus, Saturn, Spica and Mercury imaged on 22 September using my Canon IXUS, 400 ASA 1.6 second exposure 2 x zoom. In the embiggened version it is easier to see alpha2 Librae, which Venus is heading towards. The bright line at the bottom is me  with a torch trying to illuminate the tree for artistic effect.. Click to embiggen.

Beautiful clear evening, finally got to see the planets in the evening twilight. The photographs do not do justice to the colours. Mercury is very easy to see now, and will be close to Spcia soon.

Labels: Conjunction, Mercury, Saturn, Venus

Comet C/2013 R1 Lovejoy imaged with iTelescope T9 at around 4:00 am AEST  21 September. the image is a stack of 10 x 60 second Luminance exposures. Images stacked then SUMMED using ImageJ, then contrast enhancement applied.	Animation made from all 10 images.

Finally got an image of Terry Lovejoys new comet, C/2013 R1. It's about magnitude 14 now, I didn't catch much of a tail, but with strong Moonlight interference this isn't a bad little image.

Labels: comet, iTelescope

Head on over to the Red Lime Shack to have your picture taken by someone who worked on Dr Who on the 80's. You get a free mug of coffee as part of the Mug Shot Project.

The Mug Shot project is part of the 5015 project, which is in turn part of the Port Festival's art program. The 5015 project is to get people to use analog photography to capture Port Adelaide and its environs (postcode 5015).

In the Mug Shot project you get to pose for "mug shots" with a coffee mug. People can use the mug in various creative ways. I was wearing my Dalek T-shirt, so I posed the mug next to the Dalek. This lead to the conversation with one of the photographers (Dianca) who had worked on Dr. Who (go Silurians!).

That is just the first part of the project. The next is to use coffee and vitamin C to develop the film, and coffee to make the prints. Yes, you read that right, they are using coffee to develop the film. You can see a video of the process here.

That is pretty amazing, as I use coffee often as an example in my teaching, I'm going to have to introduce my students to this (and give it a try myself). I'm really looking forward to the exhibition (which will take place in the Red Lime Shack 18-20 October).

I may even try to enter myself, using a drink can pinhole camera.

Labels: miscellaneous

By now most of you will have seen the breathless reports that claim alien life has been found in cometary debris collected by a high altitude balloon during the Perseid meteor shower. The facts however are far more mundane.

A fragment of diatom caught in the upper atmosphere by the sampling ballooon. Image Credit University of Sheffield.

You can see the actual research the news paper reports are based on  here. The summary in the conclusion of the paper is a bit less triumphal than the news reports

"To conclude we note that the results presented here provide unequivocal evidence that a diatom fragment has been found in the lower stratosphere."

Yes. That's the whole paper basically. "We found a diatom fragment, it's unlikely that diatom fragments can last that long in the high atmosphere, therefore it came from outer space"

Despite all the images of weird looking blobs in the newspapers they have one, count it, one, fragment of a diatom (a kind of algae with hard shells, they found a bit of the shell). No alien DNA, no other evidence except this one fragment (most of the pictures in the press reports aren't even of the actual diatom fragment, but random dust particles). The authors even admit it looks like a terrestrial diatom fragment.

The authors entire argument rests on it being unlikely that chunks of diatom can last in the stratosphere for a long time.

Cometary dust, almost certain to not contain diatoms.

Except it is not that unlikely. We know that diatoms are ubiquitous in atmospheric dusts, indeed the worlds largest source of atmospheric dust is diatomaceous earth, let alone marine and other surface water droplets. Contamination of forensic and other materials with extraneous diatoms is a perennial problem. So extreme caution is need when interpreting these sorts of results.

Diatomaceous dusts can travel long distances, from the Sahara to Great Britain, and diatom containing droplets can travel far and be wafted high up.

So high that Diatoms are thought to play important roles in forming nucleation centres for rain clouds. While the authors claim there is no known mechanism for getting big dust particles that high, the very ubiquity of diatomaceous dusts, their presence at high altitude in cloud formation, and the ability of cloud air currents to loft material high into the sky make it plausible that diatom fragments could be lofted high but turbulent air currents.

Another mechanism for getting diatoms high in the air is volcanic eruptions.  Despite authors claim that there were no volcanic eruptions before the balloon flight, the volcano Bata Tara in Indonesia has been exploding continuously since March, producing huge ash plumes).

Another issue relating to the contamination question is appropriate controls. While the authors had a good control for the ground based contamination of the sample cabinet, they did not do a control flight when there was no meteor shower, so we do not know if they would have picked up any diatom fragements in the absence of meteor dust.

Also, there is the question of WHY an algae that has evolved to live in marine or fresh water environments is on a comet in the first place, a frozen ball that spends most of its time far from the light of the sun is hardly the best place for things that photosynthesise in liquid water. Algae live in some very extreme environments, but spending your life frozen in a vacuum in the dark just doesn't make any sense algae wise.

The authors claims that comets have a "watery environment" is cause for head shaking, Comets are mixtures of ices (water, carbon dioxide, Carbon monoxide amongst others) which is normally frozen at the temperature below that of dry ice (frozen CO₂), when the ices heat up during the comets fleeting visit to the Sun they don't go liquid, but sublimate. Hardly the best environment for a marine or river organism.

The Journal of Cosmology has form for publishing articles on life from outer space with very weak evidence. You can see my discussion of a previous paper from a different group claiming bacterial fossils in a meteorite here http://pandasthumb.org/archives/2011/03/life-from-beyon.html

Comets may have bought the building blocks of life to a primitive Earth billions of years ago, but  modern diatoms living on current comets? No.

You can see the Bad Astronomers sceptical take here, and the Conversation commentary here. 

Labels: comet, origin of life, scepticism

Saturn-Earth "Alignment" on September the 18th, Venus is off the alignment axis. As this "alignment" doesn't actually pass through the Earth-Moon-Sun axis it actually decreases the tidal force, reducing the likelihood of Earthquakes. Click to embiggen.	Venus near Saturn. Apparently this is a close alignment.

As I write it is the waning hours of September 19. Why does this matter? Because the Barcarroler had predicted a 6.6 magnitude quake on the 18th.

The Barcarroler predicts earthquakes based on a combination of planetary alignments and astrology. I've written about alignments and earthquakes before (See here, here and here). Basically, while it is plausible that crustal tides might set off earthquakes lunar alignments have no significant effect. The tidal effects of distant planets, millions to billions of times weaker than the Moon, can have no effect.

None the less, this does not deter the Barcarroler. Over the past 12 months (2012, 2013 predictions) he has made 15 predictions for earthquakes of magnitude 7 or over, how has that panned out?

Predicted date	Predicted Magnitude	Quake Occurred
Aug 14, 2012	7.2	No
Oct 26, 2012	7.2	No
Nov 14, 2012	7.2	No
Dec 17-18, 2012	7.5	No
Dec 21-22, 2012	8.0	No
Jan 18-19	7.0	No
Jan 28-29	7.5	No
Mar 27-28	8.0	No
April 5-6	7.5 Black Sea region	7.0 Indonesia, April 6
April 28-29	7.8	No
May 10-11	7.5	No
May 25-26	7.7 Peru, NI New Zealand	Earthquakes on 24th, Tonga/Russia
June 19-20	8.3	No
July 20-30	7.5-7.8	No
Aug 25-26	7.8	No
Sept 18	6.6	No

Actual earthquake dates and magnitudes from Geosciences Australia. Of the 15 Earthquakes predicted in the 12 months since August 2012, one fell within the prediction interval (the magnitude was out as was the location, but we will accept this one) and one fell just outside the predicted time (and in completely different spots).

If we include the near miss this represents an 87% failure rate. If we look at the 18 earthquakes of M7+ that did occur, this represents an 89% failure rate. This is just slightly worse than what could have been achieved by guessing randomly (you would have expected to get 3 earthquakes right just from random guessing allowing +/- one day either side of the guessed range). So, we can conclude that the Barcarroler's prediction success is worse than just guessing.

Oh, and has a magnitude 6+ quake occurred? No, another Barcarroler's prediction failed. As there is a magnitude 6-6.9 quake every 2.7 days on average, missing this is pretty sad for his method, as if a 87% failure rate wasn't bad enough.

A good video on why the Barcarroler's alignments are not valid is here.  My extensive list of postings on astronomical phenomena and earthquakes is here.

Labels: Conjunction, earthquakes, Pseudoscience

Comet ISON, nowhere near Phobos.

You may have seen an article circulating through the internet in various venues. It claims that the Russian  Federal Space Agency ROSCOSMOS has reported that

Comet C/2012 S1 has made a number of “unexplained orbital adjustments” around the planet Mars seemingly to better align itself with the Red planets strange moon Phobos.

This is a hoax. Comet C/2012 S1 ISON is not orbiting Mars, it will reach Mars on October 1, where it will pass 20 Earth-Moon distances away from the Red Planet, and well away from Phobos. Also the 132 day "standstill" refers to its slow increase in brightness, not any change in orbit. The comet is not much dimmer than expected, and is not under intelligent control (this was another hoax purportedly from Russia that tuned up with comet Elenin)

The author of the article, Sorcha Faal, is a well known hoaxer.

Labels: C/2012 S1 ISON, Hoax, Mars

In the wake of the publication of my Comet ISON, a Guide for the Perplexed, I did a Skype Interview with  Dazza the Cameraman going over some of the points in my post, with animations and vigorous head waving and lots of umming and erring.

You can see it in all its glory here. Caution, it's nearly an hour long.

Labels: C/2012 S1 ISON, science communicators

Carnival of Space #319 is now up at Dear Astronomer. Go check it out!.

Labels: carnival of space

Venus, Saturn, Spica and Mercury imaged on 17 September using my Canon IXUS, 400 ASA 6 second exposure.Mercury is the faint dot just above the cloud, Spica is between Mercury and Venus (the obvious brightest object in the field) and Saturn is to the right of Venus. Click to embiggen.	Closer up view of Venus, Saturn and Mercury imaged on 17 September using my Canon IXUS, 400 ASA 6 second exposure 2 x zoom. Mercury is harder to see as the cloud started coming over it. Click to embiggen..

Finally got a decent clear night where I could image the trio of Mercury, Venus and Saturn (with the star Spica as well). Mercury is quite clear now in the twilight, and the grouping is very attractive.

Tomorrow night Venus and Saturn are at their closest (so of course it will be cloudy).

Labels: Mercury, Saturn, Venus

The Full Moon is Thursday September 19. Earth is at Equinox on the 23rd. Mars and Jupiter are prominent in the early morning. Venus is easily visible in the western evening sky and near Saturn. Mercury rises higher in the evening sky and is close to the bright star Spica on the 25th.

The Full Moon is Thursday September 19. Earth is at Equinox on the 23rd (for us in the Southern Hemisphere it's spring equinox).


Evening sky looking west as seen from Adelaide at 18:45 pm local time on Wednesday September 25. Venus is quite high in the evening sky above Saturn.  Mercury is next to the bright star Spica. The inset shows the telescopic view of Venus at this time. Similar views will be seen elsewhere at the equivalent local times.  Click to embiggen.

Venus  climbs higher in the evening twilight. It can easily be seen 20 minutes after sunset (indeed, with a little effort you can see it before sunset). The brightest (spectacularly so) object above the western horizon it is visible up to two hours or more after sunset (depending on how flat your western horizon is).

Venus leaves Saturn this week, heading towards Libra.

Mercury  is now readily visible in the evening twilight. Mercury climbs higher in the evening sky this week heading towards the bright star Spica. On the 25th they are at their closest.

Saturn is still easily visible above the western horizon in the early evening in the constellation of Virgo. Telescopic views of the ringed world are progressively harder as the planet gets lower in the sky and deeper in the twilight. Saturn sets around 9:00 pm local time.

Neptune is currently at opposition, and visible in strong binoculars. Location maps here which can be used in conjunction with the printable PDF maps below. My images with a little point and shoot camera here. 

Morning sky on Sunday September 22 looking north-east as seen from Adelaide at 5:00 am local time in South Australia. Mars, Jupiter, and Procyon form a long triangle in the morning sky. Similar views will be seen elsewhere at the equivalent local time (click to embiggen).

Mars, Jupiter and the bright star Procyon start the week forming a triangle in the morning twilight.  Jupiter is in the constellation Gemini. Mars is passing through the constellation Cancer.


Mars rises  a little higher in the morning twilight, and is reasonably visible before the sky pales substantially.

Jupiter is now well above the north-eastern horizon, above and to the left of Mars. It is quite easy to see in the morning sky well into the twilight. During the week Jupiter rises higher and heads towards to moderately bright star Wassat. Jupiter's Moons are now readily visible in binoculars.

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

Labels: weekly sky

The view of comet C/2012 S1 ISON and Earth from the Moon as simulated in Celestia on November 13, 2013. Click to embiggen.

I can't believe this, but it seems that I have not previously posted a  Celestia file for comet C/2012 S1 ISON. I remedy this oversight now.

Unfortunately, comet C/2012 S1 ISON has a hyperbolic orbit, and Celestia doesn't like those. The comet's orbit and name won't turn up when you turn on the comet attributes, or when you select the comet by clicking on it. As usual, copy the code below and save as it as a text file 2012S1.ssc in the Celestia extras folder.
======================2012S1.ssc=============================
"C2012S1:ISON" "Sol"
{
Class "comet" # Just copying the data for Halley
Mesh "halley.cmod"
Texture "asteroid.jpg"
Radius 5 # best guess at maximum semi-axis
MeshCenter [ -0.338 1.303 0.230 ]


# Data from latest JPL Horizons orbit as of 15 Sep 2013
# Comet has a hyperbolic orbit, so Celestia will not show an orbit track
#
EllipticalOrbit
{
Epoch 2456625.280420214468 #  2013-Nov-28.78042021 TT
Period 165849.9873 # (q/(e-1))^1.5 hyperbolic orbit
SemiMajorAxis -3018.632859      #Hyperbolic orbit
PericenterDistance   0.01249597828341519           
Eccentricity 1.000004139615141    
Inclination 61.91714591634256
AscendingNode 295.7273670259968
ArgOfPericenter 345.5153902820819
MeanAnomaly 0.0   
}

# Again, this data is copied straight from the ssc files for Halleys’ Comet
# chaotic rotation, imperfectly defined:
# this version from "The New Solar System", 4th Edition; Eds.
# JK Beatty, CC Petersen, A Chaikin
PrecessingRotation
{
Period 170 # 7.1 day axial rotation period
Inclination 66
PrecessionPeriod 3457004.12 # 3.7 day precession period
}

Albedo 0.8
}
=======================================================

Labels: C/2012 S1 ISON, celestia

Lost balloons sail over the City to Bay fun run. Not running this year, watching while waiting for EldestOne to finish his rehearsal.

My first, rubbish image of ISON.

Comet C/2012 S1 ISON has come out from behind the sun, and around the world amateur and professional telescopes alike are focusing on it, trying to follow the evolution of this visitor from the frigid depths of space. But faster than the information comes from these scopes comes misinformation, misunderstanding and outright hoaxes.

 For many of us this is Deja Vu. Virtually everything that is being said about ISON was said about comet C/2010 X1 Elenin.

But it is worth dispelling some of the misapprehension about ISON so people can enjoy the spectacle of the comet without fear.

So, I heard comet ISON has broken up.

No, it was found where it was predicted to be and it's brightness is pretty much as predicted.  The hoax images going around of comet ISON's "breakup" are from the breakup of comet 73P.

Will it hit the Earth? 

No, it comes nowhere near the Earth, the closest it comes is 0.4 AU from Earth. This is just under half the distance between the Earth and the Sun. Venus comes closer to us than the comet. To give you a feel of the distances involved, get a soccer ball, a pea and a sesame seed (or a grain of salt). Go to your back door, then place the pea there. That represents the Earth. Now walk towards your back fence with 10 full strides. Place the soccer ball there. That represents the Sun. Pace out 4 full strides at right angles to the soccer ball pea axis (you may need to go into your neighbours yard to do this) and place the sesame seed/grain of salt. That's the comet (and this exaggerates the size of the comet). See the illustrations below for more context.

Comet ISON in relation to Earth on 1 November, when it crosses Earth's orbit. Top view above, side view below. The comet is marked with a red cross. You will probably need to click on the image to embiggenit to see that the comet passes above, not through, Earths' orbit.	Comet ISON in relation to Earth on 26 December, when it is closest to Earth. Top view above, side view below. The comet is marked with a red cross. You will probably need to click to embiggen the image.	Comet ISON in relation to Earth on 14 January 2014, when it is crosses the point where comet ISON crossed Earths' orbit back on 1 November. Top view above, side view below. The comet is marked with a red cross. You will probably need to click to embiggen the image.

There is a video claiming that NASA has slowed down Earth in a simulation of the orbit so that Earth will miss the comet in the simulation. However, everything has been slowed down to show ISON at perihelion clearly. As you know from the explanation and images above, and this Celestia simulation (nothing to do with NASA) you can clearly see Earth is nowhere near the comet.

But surely the comets encounter with Mars and the Sun will alter its orbit! 

This is already accounted for in the orbital calculations. We have a very good understanding of gravity and the interactions of bodies with each other, and use these interactions to slingshot spacecraft very precisely into the depths of space. There is some uncertainty involved, we don't know the precise mass of ISON, and non-gravitational effects from the gas and dust blasting from the comet will alter the orbit slightly. However, from our experience with past sun grazing comets we can estimate the range of orbits we could have, and none of these come anywhere near Earth.

Again, go back to your sesame seed/grain of salt, move it 10 millimetres closer to the pea. That's the level of variation involved. When comet C/2011 W3 Lovejoy, a smaller comet than ISON, slingshoted around the Sun in 2011, it turned up pretty much bang where it was predicted to be.

What if the comet breaks up? 

Comet 73P after breaking up. Image Credit: NASA/Spitzer via Wikipedia Commons 

Hollywood script writers should be smacked along side the head with the thickest astronomy textbook you can find. They are responsible for the idea that comets (or asteroids) break up and shower chunks in every direction.

What will happen is that the chunks will carry on in the same orbit as the original comet. Just as Ikea-Seki did. It may be possible we will see a spectacular "chain of pearls" effect as seen with comets 73P and Shoemaker-Levi. But the chunks will come nowhere near us, just like the original comet. Even if it completely disintegrates, like C/2010 X1 Elenin or C/2011 W3 Lovejoy, the cloud of dust will continue on the same orbit just as it did for these comets. Again, it will come nowhere near us.

What about all the objects following ISON? 

There are no objects following ISON, people have been misinterpreting hot pixels on some animations. In most CCD camera chips, there are always a few pixels that are permanently on, these are the "hot" pixels.

What about the "UFO" image?

Combination of three separate Hubble images of ISON aligned on the background stars. Image credit NASA/Hubble.

That was a combination of three separate images taken when Hubble was tracking the stars. Not only does ISON move in regard to the background stars, Hubble is also orbiting the Earth, so it's view of ison while it is pointing towards the stars changes considerably with time. if you just combine these separate images so that all the stars are aligned, the comet will be seen in different places. See here for a more detailed explanation with images.

Will we go through the comet ISON's tail? 

No.

But the tail will be enormous! 

And nowhere near us. The comet crosses above Earths' orbit on November 1, at that time the comet and its tail will be 0.023 AU above Earths' orbit, that's 10 times the distance from Earth to the Moon. On our backyard model, the sesame seed will be the length of your foot away from the line that defines the Earth's orbit. But at this time Earth itself is over 12 full strides away from the comet and its tail. The tail always points away from the Sun so it can't come near Earth. Replace the sesame seed with a piece of string one stride long, that will give you a sense of the scale of the tail within the solar system (and it's relation to Earth)

Tails actually, there is the gas tail, which points directly away from the Sun, and the dust tail, which points away from the Sun but follows the comets orbit (so it looks curved to us). The particles in the dust tail follow the comet in its orbit, so two and a half months, when Earth reaches the point in its orbit where the comet crossed above it, all the dust and gasses will be long gone. Also remember that the tail will not be as big in November, the tails of comets only reach their fullest extension after perihelion, when the comet is closest to the Sun and the rapidly sublimating ices blast lots of dust and gas into space.

See this post on the tail of ISON and the animations in it. Also, scroll back up to the illustrations of the comets orbit.

So, no meteor shower then?

No. we might get some increase in noctilucent clouds, but not a meteor shower (NASA PR flacks should be whacked with an astronomy textbook for describing noctilucent clouds as a meteor shower).

But it would be really bad if we went through the tail wouldn't it? 
 
No. Remember that a comets tail is a fairly good vacuum, it's less of a vacuum than the interplanetary medium and solar wind, but still it's mostly nothing. People get upset at the idea there is cyanogen in the gases of the comets tail, but cyanogen only represent 0.5% of the gases, and 0.5% of what rates as a pretty good vacuum isn't dangerous.

We have been immersed in comets tails before, notably comet Halley, the Great Comet of 1861 and we were in the tail of the Great Comet of 1853 for two whole days. Nothing happened.

To give you a feel for how little material is in a comets tail, I' ll use the gas density (dust density is similar, but the gas density is more easily comparable. In one cubic centimetre of air in Earths' atmospher there at around 10²² air molecules, in the dense coma of a comet the average density is 10¹¹ molecules, just under a trillion times less, in the tail (depending on how far you go out, the further along the tail, the less gas there is) around 10² molecules, just short of a billion trillion times less.

So if you took a volume of comets tail equal to ten volumes of Earths' atmosphere, and dumped it in Earths' atmosphere, you would have much much less than a trillionth of the gas coming form the comet (and most of that is water). A similar proportionality holds for comet dust, so the answer to "how much dust or gas will we get from ISON's tail" is "almost unimaginably tiny, and well below the threshold that could possibly cause any harm"

What about Earthquakes?

No, just no. Just like comet C/2010 X1 Elenin (which didn't cause any earthquakes) Comet C/2012 ISON has less than a billionth of the tidal force of the Moon at closest approach (as well as a negligible magnetic field). If the Moon can't cause the poles to tip, cause massive tidal floods or earthquakes, C/2012 ISON won't (and the previous Comet of Doom Comet 2010 X1 Elenin didn't). We've been closer to other comets before with no ill effect. See this link for comprehensive discussion of solar system objects and Earthquakes.

Giant Solar Flares?

No. Comets don't cause solar flares.

What is the size of the comet? Some say it is bigger than Mars

Comet ISON as imaged by Hubble in May 2013, Image Credit NASA/Hubble

Independent measurements from the Spitzer telescope and the Hubble telescope put a maximum size of around 5 kilometres in diameter for comet ISON's nucleus, it is probably a bit smaller.

Some people are confusing the size of the coma, the thin envelope of dust and gas around the comet nucleus, with the enormously smaller chunk of dust and ice that is the nucleus. Remember that the coma, like the tail, is still a pretty good vacuum by Earth standards.

One commentator is claiming the nucleus is as big as Mars, but its is easy to see that it is not. Comet ISON is almost at the orbit of Mars. If you go out around 5 am this morning Mars is easy to see at magnitude 1.5, ISON is around magnitude 12 (just below Mars), many times fainter the threshold the unaided eye can see (magnitude 6).

Even if ISON was as dark as charcoal (like the Moon is) it should be an easy unaided eye object of around magnitude 2 if it was the same size as Mars (using this formula to work out how bright any given astronomical object is (http://space.wikia.com/wiki/Absolute_magnitude), see also here). For comparison, the 400 Km diameter asteroid Vesta is currently 3.3 AU from Earth in comparison to ISON's 2.7 AU, and it is magnitude 7.8, so ISON must be much, much smaller than Vesta.

Oh, Okay. So, brighter than the full Moon at Perihelion then?

No. When it was first seen some tentative predictions suggested it could get as bright as the full Moon. But it turns out that ISON is an Oort cloud comet on its first visit to the solar system, and these don't brighten as much as comets that have been around several times. Current predictions based on over 3000 observations by amateur and profession astronomers suggest it will probably get as bright as Venus, maybe a bit more, when it is closest to the Sun.

While that is bright enough to see in the daytime, the comet is so close to the Sun that only very seasoned observers have a chance to catch it. See this post on seeing comet ISON at its brightest.

So, a bit disappointing then.

No, provided that comet ISON does not break up before perihelion (when it is closest to the Sun), it will be a nice little comet, even with the most pessimistic of projections. We can only make tentative guesses about how long and bright the tail post perihelion will be, as it depends on details of ISON's composition we don't know yet (like the exact ratio of dust to gas).

It might sport a spectacular tail like C/2006 P1 McNaught, or a thin searchlight like C/2011 W3 Lovejoy. If it breaks up into chunks post perihelion it might become as spectacular as Ikea-Seki, if it falls apart completely it might be more like C/2011 W3 Lovejoy.

All we can do is watch and wait as it evolves.

So where can I get good information on comet ISON then?

Well, this blog for a start.

Comet ISON in Celestia
Seeing ISON at its brightest
No meteor showers from ISON

Then there is

Comet ISON news
Waiting for ISON (with good northern hemisphere spotters charts)
ISON Observers Page  and its blog.
ISON Atlas
Hubble ISON Blog
Comet ISON ephemeris
Comet ISON Factsheet

Keep watching the skies and happy observing!

Labels: C/2012 S1 ISON, science

Carnival of Space #318 is now up at Everyday Spacer. There's Lunar geology, auroras, inflatable space stations and much, much more. Float on over for a read.

Labels: carnival of space

The Full Moon is Thursday September 19. Mars and Jupiter are prominent in the early morning. Venus is easily visible in the western evening sky and is closing in on Saturn. The two are closest on the 18th.  Mercury rises higher in the evening sky.

The Full Moon is Thursday September 19. The Moon is at Perigee on the 16th.

Evening sky looking west as seen from Adelaide at 18:45 pm local time on Wednesday September 18. Venus is quite high in the evening sky next to Saturn.  Mercury is visible below Spica. Similar views will be seen elsewhere at the equivalent local times.  Click to embiggen.

Venus  climbs higher in the evening twilight. It can easily be seen 20 minutes after sunset. The brightest (spectacularly so) object above the western horizon it is visible up to two hours or more after sunset (depending on how flat your western horizon is).

Venus approaches the Saturn this week, leaving the bright star Spica behind. On the 18th, Venus is closest to  Saturn.

Mercury  climbs higher in the evening sky this week. it is now relative easy to see in the late twilight, below Spica.

Saturn is still easily visible above the western horizon in the early evening in the constellation of Virgo. Telescopic views of the ringed world are progressively harder as the planet gets lower in the sky. Saturn sets around 9:30 pm local time.

Neptune is currently at opposition, and visible in strong binoculars. Location maps here which can be used in conjunction with the printable PDF maps below. My images with a little point and shoot camera here. 

Morning sky on Sunday September 15 looking north-east as seen from Adelaide at 5:30 am local time in South Australia. Mars, Jupiter, and Procyon form a long triangle in the morning sky. Similar views will be seen elsewhere at the equivalent local time (click to embiggen).

Mars, Jupiter and the bright star Procyon start the week forming a triangle in the morning twilight.  Jupiter is in the constellation Gemini. Mars is passing through the constellation Cancer.


Mars rises  a little higher in the morning twilight, and is reasonably visible before the sky pales substantially.

Jupiter is now well above the north-eastern horizon, above and to the left of Mars. It is quite easy to see in the morning sky well into the twilight. During the week Jupiter rises higher and heads towards to moderately bright star Wassat.

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

Labels: weekly sky

Location of comet C/2013 R1 now. This Stellarium simulation is for 5:00 am as seen from Adelaide, but most of Australia will have similar views at the equivalent local time. At magnitude 14 you will need a decent telescope to see it. Click to embiggen.	Location of comet C/2013 R1 on the 9th of November. This Stellarium simulation is for 5:00 am as seen from Adelaide, but most of Australia will have similar views at the equivalent local time. At magnitude 9 you can see it with strong binoculars under dark skies or with a small telescope.

Terry Lovejoy has found his fourth comet. While not as amazing as C/2011 W3 Lovejoy, this is still a nice comet, predicted to get as bright as magnitude 8, or maybe a tad brighter.

Terry's new comet will make for interesting November skies with both  comet C/2012 S1 ISON and C/2013 R1. Unfortunately, from the Southern hemisphere both ISON and Lovejoy are not visible at their brightest, but with good binoculars or a small telescope the addition of Lovejoy to the morning ISON sky will be great.

Comet convoy as seen from Roswell, New Mexico on the 11th of November.

From the northern hemisphere the view will be even more interesting, with comets ISON, Lovejoy and 2P/Enke visible in what Stuart Atkinson calls the "comet convoy". We won't see 2P/Enke from Australia at the hight of the line-up, it will be belwo our horizon.

For printable black and white spotters maps suitable for telescope use (and links to the Minor Planet Ephemeris) see this post. 

Labels: comet, comets

C/2012 V2 Linear is brighter than expected (around magnitude 9). Imaged on the morning of 9 September with iTelescope T9, 5 x 120 second images stacked on the comet in ImageJ, then a MAX Z-project applied to the stack. a bit of contrast enhancement to bring out the tail.

A bit too close to twilight for good resolution, will try again later to try and improve the tail.

Labels: comet, imageJ, iTelescope

The almost line up of Jupiter, Mars and the crescent Moon on September 3, 2013. Taken with a Canon IXUS at 400 ASA. You will need to click to embiggen to see the dot that is Mars properly (just above the palm tree).	Close up of Mars and the crescent Moon on September 3, 2013. You still really need to embiggen this to see the dot that is Mars.  Taken with a Canon IXUS at 400 ASA.

As I was completely clouded out for both of the Venus-Moon massings, I though I'd post something from the recent past that I didn't get around to previously. This is from September 3, I was clouded out for the main Jupiter-Mars-Moon line-up, but I caught this the day after.

Badly light contaminated image of comet C/2012 S1 ISON taken with iTelescope T4, single 120 second image. This was right at nautical twilight. Next time I will image earlier and use shorter exposures. Click to embiggen

Labels: C/2012 S1 ISON, iTelescope

The ISS passes between Venus and the Moon, close to the bright star Spica, as seen from Adelaide on the evening of Sunday September 8 at 19:54 ADST. Simulated in Stellarium (the ISS will actually be a bright dot), click to embiggen.

Don't forget that this Sunday and Monday nights the ISS passes close to the pairing of Venus and the Moon for most of Australia. Details and charts in this post.

Labels: ISS, Moon, Venus

Venus and the crescent Moon on the 7th of September. Spica and Mercury are hidden behind clouds. Canon IXUS 400 ASA, 1 minute exposure. 6:30 pm ACST. Click to embiggen.	Close up of Venus, Spica and the crescent Moon (3x Zoom). You will need to embiggen the iage to see Spica clearly.

Venus, Spica and the crescent Moon put on a nice display this afternoon. Pity about the clouds, but there were enough glimpses of the trio to be worth it. Mercury remained hidden by the cloud. This is a taste r for tomorrow night when the Moon and Venus are closer.

Labels: Moon, Venus

Carnival of Space #317 is now up at the Urban Astronomer, there's the question of Asylum in space, why so few X-rays from our galactic black hole, monster protostars, starship design and a whole lot more. Rocket over and have a read. .

Labels: carnival of space

The First Quarter Moon is Friday September 13. Mars and Jupiter are prominent in the early morning. Venus is easily visible in the western evening sky and is closest to the bright star Spica on the 6th. The crescent Moon visits Venus on the 8th.  Saturn is  not far above Venus.  On the 9th the Moon is between Venus and Saturn. The ISS visits the grouping on the 8th and 9th. Mercury returns to the evening sky. Nova in Delphinus is visible in binoculars.

The First Quarter Moon is Friday September 13.


Evening sky looking west as seen from Adelaide at 19:54 pm local time on Sunday September 8. Venus is quite high in the evening sky next to the bright star Spica. Venus, Spica, and the crescent Moon form a triangle in the evening sky. The ISS is passing just under Spica at this time. Similar views (except for the ISS, see below) will be seen elsewhere at the equivalent local times.  Click to embiggen.

Venus  climbs higher in the evening twilight. It can easily be seen 20 minutes after sunset. The brightest (spectacularly so) object above the western horizon it is visible up to two hours or more after sunset (depending on how flat your western horizon is).

Venus climbs higher in the sky and approaches the bright star Spica. On the 6th, Venus is closest to Spica. On the 8th Venus, the bright star Spica, and the crescent Moon form a triangle in the evening sky. On the 9th the crescent Moon is between Venus and Saturn.


On the 8th and the 9th many places in Australia will see the International Space Station pass close to Venus. Details, links to prediction sites and viewing hints are here.


Evening sky looking west as seen from Adelaide at 18:30 pm local time on Friday September 6. Mercury and the crescent Moon are close together just above the horizon. Similar views will be seen elsewhere at the equivalent local times.  Click to embiggen.
  
Mercury  returns to the evening sky this week. On the 6th Mercury and the thin crescent Moon are close together. This will be hard to see unless you have a clear level horizon.



As the week passes Mercury becomes easier to see as it rapidly climbs into the twilight sky.

Saturn is still easily visible above the western horizon in the early evening in the constellation of Virgo. This is still a good time to view this planet in a small telescope, you can show the kids before they go to bed. Saturn sets around 10:00 pm local time.


The formation of Venus, Spica, Saturn and the crescent Moon on the 8th and the 9th will be beautiful to watch, on the 10th the waxing Moon forms a line with Saturn, Venus, Spica and Mercury (very low on the 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 a while. The sight of this ringed world is always amazing.

Neptune is currently at opposition, and visible in strong binoculars. Location maps here which can be used in conjunction with the printable PDF maps below. My images with a little point and shoot camera here. 

Morning sky on Sunday September 8 looking north-east as seen from Adelaide at 5:30 am local time in South Australia. Mars, Jupiter, and Procyon form a triangle in the morning sky. Similar views will be seen elsewhere at the equivalent local time (click to embiggen).

Mars, Jupiter and the bright star Procyon start the week forming a triangle in the morning twilight.  Jupiter is in the constellation Gemini. Mars is passing through the constellation Cancer.


Mars rises only a little higher in the morning twilight, but is now reasonably visible before the sky pales substantially. Between Sunday September 8 and Tuesday September 10 Mars passes close to the Beehive cluster. On the 9th Mars is actually in front of the cluster. This is best viewed with binoculars or a small telescope on low power. .

Jupiter is now well above the north-eastern horizon, above and to the left of Mars. It is quite easy to see in the morning sky well into the twilight. During the week Jupiter rises higher and continues to move away from Mars. On Sunday September 1 the crescent Moon is close to Jupiter.

Location of Nova Delphinus 2013 as seen looking north from Adelaide at 9:30 pm local time.The location is marked with a square. Similar views will be seen at the equivalent local time in other Southern Hemisphere locations. Click to embiggen.

Nova Delphinus is magnitude 7, fading slowly from its peak of 4.4. It is visible only in binoculars or a small telescope, but may have brighter mini-outbursts. A printable binocular map and telescopic coordinates are here. 

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

Labels: weekly sky