Monday, April 22, 2013
Comet C/2012 F6 Lemmon in STEREO, April 17-19 2013
While all eyes have been on C/2011 L4 PanSTARRS (and rightly so, while small it has been magnificent), comet C/2012 F6 Lemmon has been quietly chugging away in the background.
While C/2011 L4 PanSTARRS has had it's moment in the STEREO imagers, Lemmon has not, until yet.
On April 17 the comet began to enter the field of view of the H2A camera, and is crossing the bottom half of the camera quite nicely. It's a bit hard to see in the image above, where I have boosted the brightness a bit to bring out the tail, but the comet has quite a long and dynamic tail.
For the animation below I stacked 29 images from 17 April to 19 April in ImageJ, then inverted the image and tried to maximise the brightness and contrast to get the tail as visible as possible. The stack was then exported as an AVI. While not the best, if you look closely you can see some tail dynamics.
Labels: C/2012 F6, comet, Stereo comet astronomy, Stereo Satellite
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
Saturday, March 23, 2013
Comet PanSTARRS Does Not Dodge a Coronal Mass Ejection
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| Comet C/2011 L4 PanSTARRS on 15 March, 2013 as seen from the STEREO H1B imager showing the comet and a billowing Coronal Mass Ejection. It looks like the CME just misses the comet, but this is an illusion due to the spacecraft's perspective, the comet and CME are nowhere near each other. Click to Embiggen. | Location of the comet in respect to the Earth and the STEREO B spacecraft simulated in Celestia (click to embiggen). My STEREO orbit files are a little old, so it's position is not exact, but it's not very different from the real position. The CME of 15 March was Earth directed and I've indicated it on the chart. You can see it goes nowhere near the comet. |
There is a stunning video from the Sungrazer Comets group that shows comet C/2011 L4 PanSTARRS for the 9th to the 16th as it passes through the field of view of the SETREO B spacecraft's H1 imager. On the 15th, there was a large coronal mass ejection which produced lots of aurora here on Earth on the 17th and 18th. You can see the comet glide past the CME in stunning detail in the video (my less awesome effort is below).
Some commentators on the video around the web are saying the comet "dodged the CME" (in the sense that it just missed the comet). But that,s an illusion of perspective. The spacecraft is is almost behind the Sun from the Spacecrafts perspective looking back at Earth. The CME was Earth directed. fanning out to be sure but faning AWAY from the spacecraft. And the comet, which is above the plane of the Sun (not shown in the Celestia perspective) and over 90 degrees away from the CME Earth axis.
Occasionally someone will claim that comets cause CME's so it's useful to try and think about the geometry and timing of these events. In this case, the CME occurred 5 days after the closest approach to the Sun, and was directed away from the comet.
Labels: animation, celestia, comet, comets, Stereo astronomy, Stereo comet astronomy, Stereo Satellite
Sunday, March 17, 2013
Comet C/2011 PanSTARRS in STEREO, 13-14 March 2013
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Comet C/2011 L4 PanSTARRS from 18:29 UT on 13 March. A Coronal Mass Ejection is billowing out tworads the comet. The bright object to the upper right is Earth, the vertical spikes image artefacts. Click to embiggen. Image credit NASA/STEREO | An image from earlier in the sequences from the H1B imager I've used the difference method in ImageJ to enhance the dust features in the tail, the CME and the ion spikes. Thanks CometAl for the suggestion Click to embiggen |
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| C/2011 L4 PanSTARRS on the 14th. Click to embiggen. Getting the dust stream brightness balance is not easy. | A blast from the past, this is comet C/2006 P1 McNaught, the most impressive comet we've had in a long time, as seen in the H1B imager. It also had impressive dust steamers. |
Previous images are here and here.
Here's a YouTube Animation for the 13th.
And another for the 14th.
Labels: comet, Comet Al, comets, Stereo astronomy, Stereo comet astronomy, Stereo Satellite
Thursday, March 14, 2013
Comet C/2011 PanSTARRS in STEREO, 11 March 2013
Comet C/2011 L4 PanSTARRS from 23:29 UT on 11 March, high resolution images from the STEREO Behind H1 imager. The image has been inverted to make the faint tails clearer. Image stretched in ImageJ after background subtraction. Contrast enhanced to make details in the dust tail clear at the expense of the intensity of the ion tail. The long straight lines (and apparent holes in the comets tail) are imaging artefacts. Click to embiggen.
In this image you can see the detail in the main dust tail (Compare to yesterdays image here), as well there is the ion tail to the right, and what may be a large particle tail to the left. In order to bring out the detail in the main dust tail I've had to make the ion and other tail dimmer.
The broad conical fan of dust looks quite beautiful, If I get figure out a more clever way of bringing out the detail in the main dust tail while keeping the side tails, this will look really good.
Here's a YouTube Animation (the animated GIF was just too big). The colours have also been inverted.
Labels: comet, Stereo astronomy, Stereo comet astronomy, Stereo Satellite
Wednesday, March 13, 2013
Comet C/2011 PanSTARRS in STEREO, 9-10 March 2013
Comet C/2011 L4 PanSTARRS from 20:49 UT on 10 March, high resolution images from the STEREO Behind H1 imager. The image has been inverted to make the faint tails clearer. Image stretched in FITS liberator after background subtraction in ImageJ. Click to embiggen.
Finally downloaded the high resolution images. (Yes Daniel, I know Karl Battams did it better earlier). In this image you can see the complex tails of the comet. (Compare to the beacon images here and here, although Messier hunter did a good job cleaning them up here).
There are at least thee tails visible (see here for a more detailed processed image from the STEREO group that shows the tails more clearly).
There has been a lot of discussion on the STEREOHUNTERS group of what the tails consist of, the thin far right-hand tail that is pointing directly at the Sun might be something like iron (Fe) ions blasted off the surface of the comet, something similar was seen with comet McNaught. It may also be CO+ or H2O+ (or perhaps a combination). It's unlikely to be sodium ions due to the wavelength sensitivity of the H1 behind imager.
The dark, broad conical fan is the dust tail, and the shorter tail on the left with the fainter fan connecting to the broad fan may be large dust particles.
Here's a YouTube Animation (the animated GIF was just too big). The colours have also been inverted.
Labels: comet, Stereo astronomy, Stereo comet astronomy, Stereo Satellite
Tuesday, March 12, 2013
Update on Comet PanSTARRS in STEREO
Comet C/2011 L4 PanSTARRS captured in the low resolution beacon images for the STEREO Behind H1 imager.
Still waiting to download the high resolution images, but this expanded set of beacon images you can distinguish between the image artefact spike and the dust tail (the spike is the straightish line, the broad fan of the dust tail sweeps off to the right, compare to yesterdays set).
Also in the image is Mercury (up close to the Sun) and Earth (the bright dot centre right).
Here's another animated GIF. There is a better one at the STEREO site.
Labels: comet, Stereo astronomy, Stereo comet astronomy, Stereo Satellite
Monday, March 11, 2013
And Hello Comet PanSTARRS (In STEREO)
Comet C/2011 L4 PanSTARRS captured in the blow resolution beacon images for the STEREO Behinds H1 imager. With the comet only 0.8 AU from the STEREO imagers, and around magnitude 0 from the spacecraft, the comet and its tail is over exposed on the low resolution beacon images, making it look like a bright come at the bottom of the image.
In a few days I will be able to download the high resolution images, but it is likley to be over exposed on them too, as the CCD camera is designed to pick up the dim coraolal mass ejections and solar atmosphere.
Also in the image is Mercury (up close to the Sun) and Earth (the bright dot centre right).
Here's an animated GIF.
Labels: comet, Stereo comet astronomy, Stereo Satellite
Wednesday, August 31, 2011
Comet Elenin in STEREO H1B (August 25 and 26)
Elenin passes through the image field of view of the STEREO H1 Behind imager on August 25. Click to embiggen. Image processed from NASA/STEREO raw images using ImageJ. Inverted image, dark lines and weird loopy bits are imaging artifacts. |  Elenin passes through the image field of view of the STEREO H1 Behind imager on August 26. Click to embiggen. Image processed from NASA/STEREO raw images using ImageJ. Inverted image, dark lines and weird loopy bits are imaging artifacts. |
Once again, as with the previous posts I've zoomed and cropped these images of Comet Elenin from the STEREO H1B imager. There are asteroids on the 25 and 26th (although only one is obvious on the 26th). Here's the AVI animation of the August 25 images (1 Mb) and the AVI animation of the August 26 images (1 Mb).
I've plotted the intensity of comet Elenin images relative to a reference star (indicated on the image from the 26th) from the 18th to the 26th. I have the data from the 27th, but the comet passes over a bright star and I can't separate out the brightness of the comet from the star.
There is some dropped points on the 23rd when the imaging arefact of Mercury passed over the comet and reference star images. Again, click to embiggen.
As I've stated before, on calibrated images the comet has faded over 80% since the 19th, however, using this method of normalising (compared to how I did it on the calibrated images earlier) the drop is more like 70%.
Again, we have to factor in that it is further away from the H1B camera despite being closer to the Sun. I have not explicitly tried to calculate magnitudes, especially since Elenin is an extended source.
Anyway, important things to notice: The Coronal Mass Ejection that did all the fancy tail twirling hit between two flare-ups of the comet. The second peak (coming after the arrow showing where the peak CME hit, comes after the CME has washed over it (ie the big peak is not an artefact of the CME brightness adding to the comet, it genuinely gets brighter). The next peak is an aretfact form the comet crossing in from of a star, but the peak after that, although it crosses a star early, is probably also a flare.
After this, the intensity of the comet drops quite a bit; this corresponds to Michael Mattiazzo's August 22 UT image showing a big drop in intensity and Rob Kauffmans images showing the same drop on August 23 UT. After the 23rd there is another big drop that recovers slightly by the 26th.
Images from STEREO on the 27th (image right) don't show the same nucleus elongation that you see in Michaels images on the 27th, but with the STEREO images it's like looking through a pair of 7x30 binoculars compared to the telescopic images. I don't expect to see much until later images.
Labels: comet, Stereo comet astronomy, Stereo Satellite
Latest C/2010 X1 Elenin News
Rob McMaught reports that he can see only a smear and no central condensation using the E12 instrument, indicative that the comet is indeed disintegrating
The Sungrazing Comets site has a graphic showing the dimming of comet Elenin in STEREO-B , covering August 15-26, 2011 http://bit.ly/ouoRum
which is backed up by quicktime movie (warning 25MB file) from August 14th to August 26, 2011 http://bit.ly/mS4LY5
The Sungrazing Comets site has a graphic showing the dimming of comet Elenin in STEREO-B , covering August 15-26, 2011 http://bit.ly/ouoRum
which is backed up by quicktime movie (warning 25MB file) from August 14th to August 26, 2011 http://bit.ly/mS4LY5
Labels: comet, Stereo comet astronomy, Stereo Satellite
Monday, August 29, 2011
Comet Elenin in STEREO H1B (August 23 and 24)
Once again, as with this post and this post I've zoomed and cropped these images of Comet Elenin from the STEREO H1B imager in order to capture the tail of Elenin. It doesn't really work so well this time as the comet is fading rapidly. On calibrated images the comet has faded over 80% since the 19th, but we have to factor in that it is further away from the H1B camera despite being closer to the Sun. Mercury is in the field of view, and an asteroid on the 23rd (there is lots more on the larger images). Here's the AVI animation of the August 23 images (1 Mb) and the AVI animation of the August 24 images (1 Mb). |
Labels: comet, Stereo comet astronomy, Stereo Satellite
Saturday, August 27, 2011
Comet Elenin in STEREO H1B (August 21 and 22)
As with the previous post I've zoomed and cropped these images of Comet Elenin from the STEREO H1B imager in order to capture the tail of Elenin. Presenting the images this way makes the tail easier to see. On the 21st another solar flare passed over Elenin, but the effects weren't so dramatic this time. Elenin does seem to be fading more, but I need to calibrate the images to be sure. Mercury is now in the field of view, and an asteroid on the 21st (there is lots more on the larger images, an the 23rd has a couple more coming through). Here's the AVI animation of the August 21 images (1 Mb) and the AVI animation of the August 22 images (1 Mb). |
Labels: comet, Stereo comet astronomy, Stereo Satellite
Friday, August 26, 2011
Comet Elenin Fades
Elenin passes through the image field of view of the STEREO H1 Behind imager on August 19. Click to embiggen. Image processed from NASA/STEREO raw images using ImageJ. Inverted image, dark lines are imaging artifacts.
I wrote earlier that comet C/2010 X1 Elenin was hit by intense solar wind, and that its tail flared up. See the AVI animation of the August 19 images (1 Mb) for the tail dramatically flaring and twisting around. Also see Comet Al's animation of the August 19 event here.
Well, in the wake of that event the brightness of comet Elenin has dropped dramatically, by almost a magnitude (from magnitude 8.1 on the 19th to magnitude 8.9 on the 23rd, the last reported magnitude). You can see before and after images by Rob Kaufmann here showing the drop. Michael Mattiazzo also has images of comet Elenin before and after the flare with estimates of the comet magnitude here.
So what is happening? What is most likely going is that the bast of energetic solar wind particles has eroded exposed "ices" (water and carbon dioxide) creating the brief highly active tail (comet Elein has had a small but nice tail for some time). With these exposed ices gone, the generation of dust and gas drops off and the magnitude drops. UPDATE: Jakub Cerny thinks it is more likely due to depletion of particles in the inner coma, causing dimming that way. Also see Michael Mattiazzo's latest images here, showing what looks to be an elongated nucleus.
Elenin is a new comet, this is the first time it has dropped in to the inner solar system from the Oort Cloud. New comets generally are bright early than drop off quickly as their surface ices are depleted. Older comets tend to be brighter due to fissures and cracks penetrating more deeply into the comet allowing more volatiles to be accessed.
What does it mean for the future? Comets, despite the images of them that look like asteroids, and quite fragile, loose agglomerations of dust and ices smeared together. It has already been suggested that Elenein will not survive perihelion. This recent dimming of Elenin suggests it may be sufficiently fragile to evaporate as it passes close to the Sun, astronomers will be watching this small but cute comet as it plunges towards perihelion for more clues about the structure and dynamics of comets.
Labels: astrophotography, comet, Stereo comet astronomy, Stereo Satellite
Tuesday, August 23, 2011
Comet Elenin in STEREO H1B (August 19 and 20)
I've done something different here. I've zoomed and cropped these images of Comet Elenin from the STEREO H1B imager in order to capture the tail of Elenin. Presenting the images this way makes the tail easier to see. On the 19th a solar flare passed over Elenin and the tail flared as well and was twisted about. The weird white patches in the image of the 19th are artefacts of the background subtraction process I use. It looks better in animation. Here's the AVI animation of the August 19 images (1 Mb) and the AVI animation of the August 20 images (1 Mb). |
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Comet Al has a better animation of the August 19 event here.
Labels: comet, Stereo comet astronomy, Stereo Satellite
Thursday, August 18, 2011
Comet Elenin in STEREO H1B (August 15)
August 15 image of Comet Elenin in the STEREO H1B field of view, compare with the image of the 14th. I've cropped the image, so that Jupiter and Mercury are out of fame compared to the 14th
I've made a little AVI animation of it (1 Mb).
Labels: comet, Stereo comet astronomy, Stereo Satellite
Friday, March 19, 2010
Yet Another Comet Death Dive
Over at Spaceweather there are images of yet another comet that has come too close to the SUn and evaporated. CometAl has far better pictures though via the STEREO satellite, pop on over and have a look.
Labels: comets, Stereo comet astronomy, Stereo Satellite
Monday, January 05, 2009
Comet Al tells the tale of P/2008 X4 Christensen's recovery.
Comet Al has published his account of the recovery of comet P/2008 X4 Christensen. I have to make porridge for breakfast now!
Labels: comets, Stereo comet astronomy
Thursday, March 13, 2008
It's just like having your own cloud-free telescope
As you know, I regularly download images from the STEREO SECCHI imagers to search for comets. I haven't found any yet, but Comet Al has found one or two (or three). But you can see lots more than comets (and coronal mass ejections) in the STEREO images. Like lots of asteroids. As the H1 and H2 instruments only go down to about magnitude 14 at best, you are unlikely to discover any new asteroids though. Nova too, Comet Al caught this image of Nova Scorpii 2007 near comet McNaught in the H2 imager. And variable stars.
The animation above is of the minima of Algol that took place on the 7th of February. Now, this is no big deal for many people, but I have never seen a minima of Algol before (Algol is always too close to my horizon to reliably check it out), so catching it in the STEREO images was something special. Of course, Algol is old hat and well known, but the STEREO images could be used to monitor other less well characterised variables (or at least harder to follow in my scopes). Also, as these at FITS images, you can quantitate the intensity of the star and its drop in magnitude.
Could you use the SECCHI imagers to detect exoplanets? It's a possibility, the exoplanet bearing star has to be relatively bright, lie within the H1 or H2 field of view and have a fairly deep eclipse. WASP-2 and HD 209458 might scrape in under these conditions. HD46375 and HD46375 are within the field of view, fairly bright but have only shallow eclipses. HD2638 is relatively bright (magnitude 9.3), in the field of view of the H1 imager and has a fairly deep eclipse (about 1.2% of total brightness, not to dissimilar to TRES-1's 1.7% fall). Sadly, TRES-1, which has been observed by amateurs, is too far away from the H1 instruments to be imaged.
Still, there is so much out there that is caught in the STEREO imaging cameras, on rainy or cloudy nights it's like having your own personal telescope. Of course, STEREO is a research instrument, actually intended for studying the solar atmosphere, so for us astronomers everything else is gravy. So don't go crazy and download huge chunks of data, think about the researchers who don't need their bandwidth hogged by frenzied amateurs sucking down every last image. Remember, play nice, it's due to them that we get to play with such and awesome instrument for free.
Labels: asteroids, Stereo comet astronomy, variable star
Sunday, February 24, 2008
Congratulations cubed - Comet Al's third Secchi comet!
Comet Al has done it again, and again! Not content with finding a Kreutz family comet in the STEREO Secchi imager, he's found a second and a third!
The third one is a real cracker, as you can see in the animation above, it shoots through the field like a meteor! If the animation is a bit confusing at first, look at the illustration opposite. The comet heads bottom left to upper right, staring near the asteroid Pallas. The asteroid 2 Pallas, magnitude 10 at the time these Secchi images were taken (Feb 20th), is down the bottom. Both the animation and the JPG are assembled from aligning and stacking images from the STEREO Secchi H1A camera.And if that is not enough, they have just located a 4th one just above this one. Sheesh! I just can't keep up!
Labels: asteroids, comets, Stereo comet astronomy
Thursday, February 21, 2008
Congratulations Comet Al!
Congratulations Comet Al! He has discovered his first STEREO comet! In fact, this may be the first comet that has been discovered exclusively in the STEREO Secchi imagers, rather than via SOHO. The faint dot just above the arrow is the comet. It is one of the Kreutz family of sun grazer comets. You can see an animation of the comet here (warning 3Mb file). Off to the bottom left-hand side is also an asteroid, see if you can find it.Labels: comets, Stereo comet astronomy
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