Tuesday, December 10, 2013
Venus over the Harbour
Saturday, December 07, 2013
Southern Skywatch December, 2013 edition is now out!
The December edition of Southern Skywatch is now up.
There's a bit of planetary action this month with Venus, Jupiter and Mars meeting the Moon.
Mars climbs higher to the morning sky and is near the crescent Moon on the 26th. Jupiter climbs higher still and is also near the Moon on the19th.
Mercury is lost in the twilight.
Saturn returns to the morning sky and is close to the Moon on the 29th.
The Geminid meteor shower is best on the morning of the 14th, and some decent meteors should be seen.
Labels: southern skywatch
Venus and the Moon, 6 December 2013
Venus and the Moon were close last night, and it was an excellent opportunity to see Venus in the daylight, which I did, easily.
Nova Centauri 2013 (7 December 2013)
Exposure time was 30 seconds, and it is still overexposed. I'll try again tomorrow. No useful nearby reference starts (come back T12 all is forgiven) to estimate the magnitude, looks like it has maxed out at around magnitude 3.6-3.7 from recent reports.
One day the clouds here will lift and I can see it with my own eyes.
Wednesday, December 04, 2013
A Bit of a Comet ISON Wrap-up.
|Comet C/2012 S1 ISON (indicated) has survived its passage around the Sun. It is much faded, and is probably no more than a pile of rubble gently dissipating into space. image from 30 Nov 2013||Animation of 20 images from 30 November to 1 December 2013 showing ISONs progressive fading|
Being off at a conference and away from my astronomy software I have not been able to blog ISONs going saga. After initially recovering from its beating as it passed perihelion, it has continued to fade as it passed from the LASCO C3 imager to the STEREO H1A imager.
While still visible in H1A up until the time it passed out of the H1A field of view, it is very much faded, and it is uncertain if the remnants will be visible in amateur instruments when it gets high enough in dark sky several days from now.
I've done a quick image and animation of the high resolution H1A images available now, this give a more realistic view than the medium resolution highly enhanced images that have been available until now.
ALERT! Bright (Mag 5!) Nova in Centaurus
|Location of Nova Centaurus 2013 as seen looking north from Adelaide at 3:00 am ACDST 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.||Black and White map suitable for printing at a scale useful for binoculars, view from the Southern hemisphere, click to embiggen. The circle is the approximate field of view of 10x 50 binoculars. A high definition PDF map that is better for printing is here.|
UPDATE! the nova has now been reported to be as bright as magnitude 3.8! This makes it the brightest nova in years, and beats Nova Delpinis earlier this year.
Via John Goodrick and Carl Gruber, a magnitude 5 nova has been discovered in Centaurus http://www.cbat.eps.harvard.edu/unconf/followups/J13544700-5909080.html
This nova has now been independently confirmed and is currently around magnitude 5.0. It has been imaged by many amateurs. An example image is here.
Location R.A. = 13 54 47.00, Decl.= -59 09 08.0 (J2000 coordinates)
It is bright enough to be seen with the unaided eye under dark sky conditions but most people will need binoculars to see it clearly. PDF map here. Unfortunately it is best seen in the early morning when the pointers are at their highest.
|Stellarium simulation of the view through binoculars (actually this is equivalent to a few binocular fields stitched together for ease of explanation). The square is the location of the nova. The guide star HIP 66849 is indicated. Click to embiggen.|
At magnitude 5 (or so) the nova is readily visible if you know where to look, but is a bit nondescript. It's best to hunt it with a printout of this binocular location map in your hand (use a torch with red cellophane over the end to not destroy you night vision, wait at least 5 minutes before searching so your eyes accommodate to the dark). However, this description may help you find it in binoculars as well.
This description will work for between 2-4 am, local time. Facing south, the southern cross is seen clearly to the south east (see top map above). Just below the cross, the two brightest stars above the horizon are beta (the top blue-white star, also known as Hadar) and alpha (the bottom orange star, aslo known as Rigel Kentaurus) Centauri.
Above and to the left of beta Centuari by about 3 finger widths is the dim star HIP 66849. at magnitude 5.37 it is the brightest star aside from the nova that is near beta Centauri. The nova is almost directly between these two and currently just a trace brighter than HIP 66849.
Aim your binoculars at beta Centauri. Through the binoculars you will see two brightish stars off two the left. The one in the middle is the nova (again, consult the maps for guidance, it may need several back and forth for you to be sure you have seen it).
The Sky This Week - Thursday December 5 to Thursday December 12
The First Quarter Moon is Tuesday December 10.
Evening sky looking west as seen from Adelaide at 21:00 pm ACDST on Thursday December 5. Venus is quite high in the evening sky above the Teapot asterism of Sagittarius. The inset shows the telescopic view of Venus. Similar views will be seen elsewhere at the equivalent local times. Click to embiggen.
Venus continues to fall back in the evening twilight. However, it can easily be seen shortly after sunset (indeed, with a little effort you can see it before sunset) until late in the evening.
The brightest (spectacularly so) object above the western horizon it is still visible up to three hours or more after sunset (depending on how flat your western horizon is) when the sky is fully dark. Venus is beginning to sink to the horizon, but will be spectacular for many weeks hence.
Venus is in the Constellation of Sagittarius. It is a distinct crescent moon shape in even small telescopes. This week Venus is above the "Teapot" asterism of Sagittarius and is not far from the crescent Moon on December 5 and 6
Morning sky on Tuesday December 10 looking north as seen from Adelaide at 2:00 am ACDST in South Australia. The inset shows the view of Jupiter through a telescope at this time. Io and its shadow is transiting Jupiter at this time, Similar views will be seen elsewhere at the equivalent local time (click to embiggen).
Jupiter is in the constellation Gemini. Mars is is in the constellation of Virgo. Saturn and Mercury are in Libra.
Mars rises still higher in the morning twilight, and is visible well before twilight.
Jupiter is now well above the northern horizon near the bright stars Castor and Pollux, the twins of Gemini. It is quite easy to see in the morning sky well into the twilight. Jupiter's Moons are now readily visible in binoculars. There are some good Moon events on the10th at around 2 am local daylight saving time. Jupiter rises around 10:00 pm local daylight saving time, but is still best for telescopes in the early morning.
Morning sky on Sunday December 8 looking east as seen from Adelaide at 5:00 am ACDST in South Australia. Mars is high above the horizon, Saturn is low above the horizon. Both are roughly equidistant from the bright star SPica/ Similar views will be seen elsewhere at the equivalent local time (click to embiggen).
Saturn is visible low in the eastern horizon before dawn. It will be difficult to see unless you have a flat, level horizon.
Mercury is lost in the twilight.
Location of Nova Centaurus 2013 as seen looking north from Adelaide at 3:00 am ACDST 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.
A new nova has been reported near beta Centauri. It is currently bright enough (magnitude 5) to be seen faintly with the unaided eye, and very easily in binoculars. Unfortunately, you have to wait until early morning for the nova to be heigh enough for a good look.
More detailed spotters charts and instructions are here.
There are lots of interesting things in the sky to view with a telescope. Especially with Venus 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 AEDST, Western sky at 10 pmAEDST. For further details and more information on what's up in the sky, see Southern Skywatch.
Labels: weekly sky
Monday, December 02, 2013
They do better Loos here
Saturday, November 30, 2013
Venus over Chinatown
Comet C/2012 S1 ISON Keeps On Keeping On (29 November UT)
|Comet C/2012 S1 ISON seen in the SOHO LASCO C3 instrument from 12:30 UT 29 November.It is 0.107AU from the Sun by the end.||C/2011 W3 Lovejoy in SOHO C3 (16 December 2011 UT). Lovejoy is 0.08 AU from the Sun here. Image credit NASA/SOHO|
Comet ISON keeps on going, despite several news reports suggesting its demise, the comet still looks more or less comet like over 24 hours from perihelion (for views of what it looked like then see here, and its subsequent return here and here). For comparison I show the other great survivor, comet C/2011 W3 Lovejoy.
Lovejoy was brighter, and continued to brighten developing a spectacular tail before its ultimate demise. ISON is fading slowly, although what is probably the synchronic tail is developing nicely.
It is still too early to write ISON off yet, but it is also still too early to determine if we can see it in the skies in the next few days.
A nice ABC article immediately post perihelion, which quotes me, is here.
Friday, November 29, 2013
Comet C/2012 S1 ISON stays on track (29 November UT)
|Comet C/2012 S1 ISON seen in the SOHO LASCO C3 instrument at 06:18 UT 29 November. Stars indicated for comparison with chart. Click to embiggen||Chart of the predicted position of ISON at 06:18 UT 29 November.Click to embiggen|
In the wake of the dramatic breakup and revival of comet ISON as it rounded the Sun, once again there has been speculation that it is significantly off track.
Here I show one of the latest SOHO images together with the predicted position of ISON at the same time, using old orbit parameters. ISON is exactly where it should be, between Chi Ophiuchus and the dim star TYC-6210-254-1. Measuring their positions I find the present position of ISON is within 6" of teh predicted poition, well within the measurement error from the images.
Pre-perihelion track positions diagram and predictions are here.
Note the broad fan shape of comet ISON at the moment, comet ISON seems to be reviving, a bit. But it is still not clear what we are seeing is a pile of gravel with attitude, or a substantial chunk of comet remnant. Karl Battams and the STEREO team think it likely that there is a substantial chunk of material, Terry Lovejoy and Jacub Cerny think it likely there is not.
All I can say is keep on watching, even if it is just gravel with attitude, it is still beautiful and we can still learn a lot.
Comet ISON, It's Not Dead Yet! (it may go for a little walk)
|Latest 12 images from the SOHO LASCO C3instrument animated. Comet ISON breaks up, but some comet-looking material comes out the other side. You can see the remnants of the old tail on the other side of the Sun.||Latest 30 low resolution beacon images from the STEREO COR2B instrument animated. As for LASCO C3 you can see a big bright blob of material coming out.|
C/2012 S1 ISON continues to amaze. After fizzing out, it seems to have turned on again. Whether this is just a bunch of gravel fizzing out or a fragment of nucleus turning on again, as happened with comet Lovejoy is not clear. Because of the orientation of the comet and it's orbit in COR2B it looks like it is spinning, but this is just a line of sight effect. However, looking carefully at the image it may be that we are seeing the beginning of new tail production. Only time will tell, so we need to keep on watching.
Monty Python: "I'm not dead yet!".
Is Comet C/2012 ISON channelling comet Lovejoy? (post perihelion, 28 November 2013)
|Latest 30 images from the SOHO LASCO C2 instrument animated. Comet ISON breaks up, but some material comes out the other side.||Latest 30 low resolution beacon images from the STEREO COR2A instrument animated. The Big blob is Venus. As for LASCO C2 you can see the breakup, but something continues on.|
C/2012 S1 ISON reached perihelion. And then broke up, and then something continues on. It might be just gravel and dust, or there might be a chunk big enough to be comet like. This is not unlike what happened to comet Lovejoy. Only time will tell if there is a chunk big enough to turn on again.
Insert favourite Monty Python or Princess Bride Quote here.
Thursday, November 28, 2013
Comet C/2012 S1 ISON Brightens More, Prospectes for Perihelion (28 November 2013)
|Latest 30 images from the SOHO LASCO C3 instrument animated. Comet ISON skims past delta Scorpii.||Latest 30 low resolution beacon images from the STEREO COR2A instrument animated. The Big blob is Venus.|
We are just over 7 hours away from comet C/2012 S1 ISON reaching perihelion. What an amazing trip it has been, with the comet defying all expectations, stops and starts in brightness increase, dramatic outbursts and fades.
Now on the last leg of its long journey, which began around a million years ago in the Oort cloud at the edge of the solar system, in a few short hours it will skim around a solar diameter from the surface of the sun, being exposed to almost unimaginable heart wich will vaporize the very dust on its surface.
Will it survive is the question on everyone's lips? How bright will it get?
Currently it is outperforming C/2011 W3 Lovejoy, latest brightness estimates put it at around magnitude -3 (a bit dimmer than Venus ), quite a bit above Lovejoy at the same time, and ISON has a more complex tail. The twin tails you see in the LASCO C3 instrument are a broad dust tail and a synchronic dust streamer. No ion tail can be seen in the LASCO C3 image at the moment (info from the latest CBET via Jakub Cerny).
So, what happenes next? Will it disintegrate? For typical Kreutz sungrazer comets with radii under 100 meters, they tend to disintegrate at 10 solar radii from the Sun. ISON is much larger than 100 meteres (somewhere between 1 Km and 2.4 Km in radius), but the 10 Solar radii checkpoint is at around 12:00 UT in a half an hour from now as I type. If it passes this check point, then there is a good chance it will get to perihelion. After that, it's all still up in the air. Karl Battams of the STEREO mission is enthusiastic but cautious. Jakub Cerny has a detailed post here were he expects it not to survive.
How bright will it get? Jakub Cerny reports J. N. Marcus as saying it will not get too much brighter, as the heat from the Sun begins to vaporise the dust grains.
If it survives perihelion, it's grazing approach to the Sun, what happens then? Will it be like Lovejoy and disintegrate a few days later, leaving us with a pale and impressive tail? Perhaps the best analogs will be two sungrazers of around 1 Km radius, the great Southern Comet of 1880 and C/1970 K1, which survived and were reasonably bright with decently long tails for a short time.
So if ISON survies we might expect it to not be as bright as C/2006 P1 McNaught, but brighter than Lovejoy.
The best we can say is "don't count your comets before they are hatched". As the excitement mounts you can watch the comet in various spacecraft instruments (links here) . No matter what happens, this is the first sungrazing comet from the Oort cloud, so the show will be well worth watching.
So happy comet watching folks.
Is Comet C/2012 S1 ISON on Track?
|Comet C/2012 S1 ISON seen in the SOHO LASCO C3 instrument at 05:06 UT 28 November. Stars indicated for comparison with chart.||Chart of the predicted position of ISON at 05:06 UT 28 November|
There has been some rumination on the interwebs that comet ISON is off course. Here I show one of the latest SOHO images with the predicted position of ISON, using an old orbit. ISON is exactly where it should be; right next to delta Scorpii.
Comet C/2012 S1 ISON Brightens, comparison with Lovejoy (28 November 2013)
|Comet C/2012 S1 ISON in the SOHO Lasco C3 imager at 00:30 UT 28 November 2013||Comet C/2011 w3 Lovejoy in the SOHO Lasco C3 imager at 09:30 UT 15 December 2011||Overlay of the two images|
Comet ISON continues to brighten, its head is now brighter than comet Lovejoy at a similar distance from the Sun in the STEREO imager (ISON was at 0.084 AU from the Sun in this image, Lovejoy was closer at 0.079 AU). ISON's tail is a bit wimpier though.
What does this all mean for ISON's chances of survival? Who knows, we just have to keep watching.
How Bright is ISON? Comparing Comet ISON to Lovejoy
How bright is comet C/2012 S1 ISON now? It's pretty hard to tell with the images we have, as we don't really have high resolution images with good comparison stars at the moment. So I've compared ISON as it looks now to C/2011 W3 Lovejoy as it looked when it just entered the SOHO LASCO C3 imager and STEREO COR2B imager.
Both comets look roughly the same in the SOHO images, but Lovejoy looks brighter in the COR2B images. Unfortunately I don't know where Lovejoy was with respect to COr2B, so I don't know if this is due to the comet being closer to the camera.ISON looks around the same brightness as
Still, overall it is looking similar to Lovejoy at the moment, perhaps it will perform like Lovejoy?