Saturday, November 04, 2017
Comet 96P/Machholz zooms past the sun
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| Single image of comet 96P Machholz from the SOHO LASCO C3 instrument on 27 October 2017. Click on any image to embiggen | Composte series of images as the comet swung around the sun fro 26-28 October. The gap is where some images were not taken | Animation of the same series. |
Comet 96P/Machholz came to perihelion on October 27, unfortunately, it was too close to the sun for us Earth-bound observers, but fortunately a bevy of sun-observing spacecraft watched intently as it passed by. It was picked up by the Solar and Heliospheric Observatory (SOHO) and the Solar TErrestrial RElations Observatory Ahead (STEREO-A) spacecraft.
Two of these fragments had been seen in the 2012 passage of the comet, the third was new.
You can read about the background to the comet, other observations and its fragmentation in far more detail at the excellent skyhunt blog (go now, you won't be disappointed, I'll wait).
I won't try and duplicate Trygve Prestgard's excellent work,I will just presnt my images from the STEREO spacecraft where I hunted for the fragments. Despite high resolution COR2A images, I found no fragments.
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| Comet 99P Macholz in the STEREO COR2 Imager on 26 October | Animation of 26 October images, note tail movement |
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| Single image of STEREO COR2A from 28 October, 2017 | Animation of 28 October images |
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| Comet 96P Machholz in the STEREO H1A imager on 23 October (right down the bottom left) click to emggen | Animation of the comets brief sojourn in the H1A imager field of view |
Labels: comet, comet 96P Machholz stereo astronomy, Soho, Stereo astronomy
Thursday, August 04, 2016
A Kreutz Comet Meets its Doom
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| Kreutz comet in SOHO LASCO C3 imager on 3 August at its brightest | Kreutz comet in SOHO C2 imager on 4 August. | Kreutz comet in STEREO COR2 imager on 4 August. |
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| Animation of Kreutz comet in SOHO LASCO C3 imager on 4 August. | Animation of Kreutz comet in SOHO C2 imager on 4 August. | Animation of Kreutz comet in STEREO COR2 imager on 4 August. |
On 31 July a small Kreutz comet entered the field of view of the SOHO C3 imager, Kreutz comets are sungrazing comets thought to be the remnants of a large comet which broke up several centuries ago. The comet rapidly brightened, causing Karl Battrams to suggest this is the brightest Kreutz for 21 years.
The comet came to perihelion on August 4 at around 05 UT, at around 1 solar diameter from the Sun. The even was captured by the SOHO C3 and C2 instruments and the STEREO COR2 and COR1 instruments.In the animations above you can see the comet going behind the occultation disks hiding the sun in all these instruments...and not coming out. The comet was vaporized by the intense heat of the sun.
Labels: comet, Kreutz, Soho, Stereo Satellite, sungrazer
Wednesday, December 04, 2013
A Bit of a Comet ISON Wrap-up.
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| 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.
Labels: C/2012 S1 ISON, Soho, Stereo Satellite
Saturday, November 30, 2013
Comet C/2012 S1 ISON Keeps On Keeping On (29 November UT)
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| 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.
Labels: C/2012 S1 ISON, comet lovejoy, Soho
Friday, November 29, 2013
Comet C/2012 S1 ISON stays on track (29 November UT)
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| 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.
Labels: C/2012 S1 ISON, Soho
Comet ISON, It's Not Dead Yet! (it may go for a little walk)
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| 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!".
Labels: C/2012 S1 ISON, Soho, Stereo Satellite
Is Comet C/2012 ISON channelling comet Lovejoy? (post perihelion, 28 November 2013)
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| 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.
Labels: C/2012 S1 ISON, Soho, Stereo Satellite
Thursday, November 28, 2013
Comet C/2012 S1 ISON Brightens More, Prospectes for Perihelion (28 November 2013)
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| 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.
Labels: C/2006 P1 McNaught, C/2012 S1 ISON, comet lovejoy, Soho
Is Comet C/2012 S1 ISON on Track?
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| 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.
Labels: C/2012 S1 ISON, Soho
Comet C/2012 S1 ISON Brightens, comparison with Lovejoy (28 November 2013)
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| 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.
Labels: C/2012 S1 ISON, comet lovejoy, comets, Soho
How Bright is ISON? Comparing Comet ISON to Lovejoy
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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?
Labels: C/2012 S1 ISON, comet lovejoy, Soho, Stereo Satellite
Wednesday, November 27, 2013
Comet ISON Reaches Perihelion Tomorrow (28 November 2013)
At this time it is a mere degree (that's one fingerwith) form the Sun (see here for diagrams). If you are not an experienced solar observer DO NOT look for it in daylight, your eyes can be severely damaged by exposure to the Suns glare.
However, a bevy of spacecraft will be observing, and you can watch from the safety of your computer screens.
These times are taken from Karl Battams info sheet.
November 28, 0400UT: Enters STEREO/SECCHI COR-2A (15:00 AEDST)
November 28, 1300UT: Enters SOHO/LASCO C2 (24:00 AEDST)
November 28, use links above for everything except the SDO.
~1600 - 2300UT: Transits STEREO/SECCHI COR-1B (10:00 29th AEDST)
~1700 - 2200UT: Transits STEREO/SECCHI COR-1A (15:00 AEDST)
~1720 - 1920UT: Transits SOHO/SUMER (15:00 AEDST)
~1810 – 2010UT: Transits STEREO/SECCHI EUVI-B (15:00 AEDST)
~1820UT +/- ?? hr: Transits SDO/AIA! (15:00 AEDST)
Post-Perihelion: November 28 2300UT: Exits SOHO/LASCO C2 (10:00 29th AEDST)
November 29 1400UT: Exits STEREO/SECCHI COR-2A (01:00 30th AEDST)
November 29 2000UT: Exits STEREO/SECCHI COR-2B (07:00 30th AEDST)
November 30 2300UT: Exits SOHO/LASCO C3 (10:00 31st AEDST)
November 31 0000UT: Enters STEREO/SECCHI HI-1A (to Dec 7) (11:00 AEDST)
There is always some lag in transmission from the spacecraft to Earth, so you won't actually be watching live, but it will be pretty close.
Labels: C/2012 S1 ISON, Soho, Stereo Satellite
Comet C/2012 S1 ISON meets a Coronal Mass Ejection (or does It?) 27 November 2013
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| Comet C/2012 S1 ISON in the field of view of the STEREO COR2B imager (lower left). Jupiter is the bright dot center left. Animation of 30 STEREO images. Click to embiggen. | Comet C/2012 S1 ISON in the field of view of the SOHOLASCO C3 imager (lower left). Animation of 30 SOHO images. Click to embiggen. |
Comet ISON may not have reached unaided eye visibility, but it is certainly putting on a show in the bevy of spacecraft observing it. Today ISON entered the field of view of the STEREO COR2B imager and the SOHO LASCO C3 imager. We only have the low resolution images from the STEREO COR2B imager at the moment, but it appears to have caught a dramatic moment.
When a Coronal Mass Ejection blasts out of the Sun and slams into the comet, causing great disruption to the tail.
As you can see, at the time the time (around 4:40 UT) when the CME apparently slams into the comet in COR2B, it is nowhere near the comet in LASCO C3.
If you look at the image to the left, this is the NASA Goddard solar wind/CME model, you may need to click on it and embiggen to see in detail, but the CME blasts out bottom right and misses ISON (top right) by a great distance.
The apparent CME impact is just a line of sight effect.
As ISON makes its final plumet into the Sun tomorrow, it may encounter, or appear to encounter, other CME's. Interpreting these will require a good understanding of where the CME actually is, and avoid confounding by line of sight effects.
Labels: C/2012 S1 ISON, Soho, Solar flare, Stereo Satellite
Tuesday, August 20, 2013
A Sundiving Keutz Sungrazer Evaporates (and doesn't cause a Coronal Mass Ejection)
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| Sungrazing comet in SOHO LASCO C2 imagery from 21:38 UT 19 August to 02:24 20 August. I have stacked and overlaid the individual images in ImageJ to show the path of the comet (the bright dot coming in from the right hand side that fades and smears out). The bands are the coronal mass ejection. Click to embiggen. | Animation of the same images of the comet. Yopu can see the comet burn away as it approaches the occulting disk (the white circle shows where the surface of the Sun is). If you look carefully you can see the remnants of the tail being blown away in the last few images. (click to embiggen also) |
The Sundiving Kreutz comet I wrote about yesterday entered the SOHO LASCO C3 camera field today, and disintegrated. In the C2 imagry you can see the bright comet eneter the camera view then fade away as it approaches the SUn and evaporates, you can even see the remamants of the tail being blown back by the solar wind.
Some claims have circulated saying that the comet hit the Sun and caused to coronal mass ejection you see. This caim is nased on the C3 images, where it is a bit hard to see the comet as it approaches the occulting disk when the CME blows. In the C3 images it is clear the CME blasts out when the comet is more than two solar diameters from the Sun (also, the CME blasted out from the far side of the Sun, away from the approaching comet).
Labels: comet, Soho, sun grazer
Monday, August 19, 2013
A bright SOHO comet does a Sundive
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| Bright sungrazer comet in SOHO Lasco C3 images on 18 August 2013. Inset shows expanded image of comet. Click to embiggen. Image Credit SOHO/NASA | GIF animation of latest 20 images of comet as it heads for the Sun, it will get brighter over the next day or so before disintegrating. |
A small Kreutz group comet has entered the field of view of the SOHO spacecraft. Karl Battams reports that it's around 30-50 meters wide and may reach magnitude 2 or more before being vaporised by the Sun in the next day or so. Sadly, it will be too close to the Sun to be visible from Earth when it reaches these magnitudes.
Thursday, April 11, 2013
Venus Meets Mars in SOHO, April 7 2013
The large dot is Venus, the smaller bright dot just above is Mars. The horizontal lines are image artefacts.
Image credits NASA/SOHO.
In the animation below there are some nice, small coronal Mass ejections as well as the encounter itself. 21 frames from the 3rd to the 10th (average 2.5 frames per day) were assembled in ImageJ and animated.
Thursday, April 04, 2013
A Sundiving Comet Meets its End (27-03-13)
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| Sundiving Kreutz comet captured in the STEREO COR2A instrument at 04:54 UT (click to embiggen) | Same comet captured in the SOHO Lasco C2 instrument at 05:00 UT |
While all eyes are on the spectacle of comet C/2011 L4 PanSTARRS (and rightly so), there is a lot of other cometary action out there. The STEREO and SOHO spacecraft recently caught a bright Kreutz comet on its final plunge into the Sun.
The comet evaporates before it reaches the occulting disks of the respective spacecraft imagers. The comet approaches from diffent quadrants of the imagers because of the spacecraft's different orbits. In the SOHO images the bright object bottom right is Venus, the long bright horizontal spike is an imaging artefact. Venus is not Visible from STEREO COR2A.
Animation of the comet in STEREO COR2A. Images stacked, cropped and animated using ImageJ.
Animation of the comet in SOHO Lasco C2. Images processed as above.
Labels: comet, Soho, Stereo astronomy, Stereo comet astronomy, Stereo Satellite
Sunday, January 13, 2013
News Flash! Jupiters Orbit Tilited with Respect to the Ecliptic, The Pole Hasn't Shifted
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These contentions are supported by a variety of telescope and SOHO imager artefacts, and a poor understanding of what planets look like through a telescope.
A prime example is here. Now Dave Greg has dealt extensively with the telescope appearance imager artefact side of things (see here, here and here).
But there is one area where I feel the need for a bit more comment. The video says it will show you shocking evidence that Jupiter has moved from the ecliptic. The images above are a series of images from SOHO, where the position of Jupiter in the SOHO imager has changed. In the images above I've shown the same SOHO images as are in the video, and Jupiters position is different with respect to the central occulting disk. The fourth image is an overlya of the previous three to show the changes clearly.
"Why Hasn't Astronomy Pointed out Disturbed Orbits?" asks the video after the SOHO images.Because the orbits aren't disturbed. Jupiter is exactly where we expect it to be, because Jupiter's orbit is not exactly on the plane of the ecliptic, but at an angle to it.
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Jupiter's orbit is inclined to the plane of the ecliptci by one degree. This may not sound much, but it is twice the apparent diameter of the Sun (and Moon), thus in its orbit, Jupiter can move (from earth's perspective), substantially above and below the ecliptic. The black and white charts above (click to embiggen for a better view) shows the predicted position of Jupiter at the same dates as in the SOHO images as seem from Earth.
As with the SOHO images, the fourth image is an overlay of the previous three to show the changes clearly. The central black line is the plane of the ecliptic and the big circle the Sun. Jupiter is labelled. Note that in the SOHO images the occulting disk is bigger than the Sun, so in image one in the SOHO series the occulting disk touches Mercury,
They are almost identical to that of SOHO, but aren't exactly the same as SOHO is in a halo orbit around Lagrange point 1, and has a slightly different point of view to that of Earth. Nonetheless, the charts show that the amount of movement we see in the SOHO images is what we expect of Jupiter's orbit.
Note that the software I am using is from 2005, using a 1989 model of the planets orbits, which has not been updated. Thus the agreement between the plotted positions and the observed positions is not due to post facto orbit tweaking.
Planetary orbits have not been disturbed, the planets positions are exactly where we expect them to be. It is hard to tell if the posters of these claims, like the poster of the video we have been discussion, are merely deeply clueless about astronomy, or are deliberately trying to wind people up.
In the meantime, the next tie someone posts a video or claim that the planets orbits are disturbed, ask yourself "how would hundreds of thousands of amateur astronomers not notice this?" and contavt your local planetarium if you are worried.
Labels: Jupiter, Pseudoscience, Satellite, Soho
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