Archive for category SOHO
You may have heard of Comet ISON, a comet discovered last year that is currently approaching the Sun. It is expected to be visible in the SOHO-LASCO C2 and C3: from SOHO’s viewpoint the comet enters from the lower right early on November 27 and exits towards the top near the end of November 30 this year.
It will also be visible from the COR1 and COR2 instruments on board both STEREO spacecraft. The SOHO Hotshot webpage for Comet ISON has many more links to more details on the path of the comet as seen from SOHO and STEREO. At the moment it looks like this, as seen by the Hubble Space Telescope. It might be a spectacular sight from Earth. The appearance of comets from Earth is hard to predict because how it looks when it gets closer to the Sun depends on the details of its composition. We’ll have to wait and see!
We are currently experiencing some technical difficulties with our main Helioviewer server. While we work on fixing it, we have moved all helioviewer.org services over to our backup server. All normal helioviewer.org services should be operating nominally. Please contact us if you notice anything amiss with helioviewer.org. JHelioviewer services are currently not operational, but we hope to have these up and running as soon as possible. Near real-time AIA and HMI images should be available as usual; streams of images from SOHO, STEREO and PROBA2 should be back to near real-time within 24 hours.
We apologize for the interruption to Helioviewer services, and we thank you for your patience.
YouTube and Helioviewer.org user otraLoly shared this short video of the return of Comet 96P/Machholz to the LASCO-C3 field of view. Thanks for sharing your video! More images of the comet will be available soon on Helioviewer.org.
Comet 96P/Machholz has an orbital period of about 5.2 years, which means it has been seen before in LASCO observations. Here is an example image from 2007
and five years before that in 2002,
The dates for the entry of Comet 96P/Machholz were obtained from the transit page of the LASCO instrument. It is projected to be visible in the LASCO C3 field of view from July 12 – 17, and it may also be visible in the images from the STEREO A/B coronagraphs.
SDO AIA and HMI images are currently lagging behing real time by about 18 – 22 hours. This is due to some necessary hardware upgrades in the processing pipeline that have interrupted the flow of images. The availability of LASCO, EIT, COR1, COR2, EUVI and SWAP images is unaffected by these hardware upgrades. We expect that the lag in SDO AIA and HMI images compared to real time will be caught up in the next few hours. We apologize for the interruption in availability of near real time AIA and HMI images.
A new version of JHelioviewer is available for download. What’s new? This update release contains improved movie export functionality, an updated LASCO C2 coronagraph mask, the new SDO Cutout Service plug-in plus various bug fixes.
The new movie export menu makes it easier to set the exact scaling of the area you are interested in, and the processing itself is now performed on the graphics card using OpenGL:
The SDO Cutout Service plug-in allows you to request science-quality image data from the SDO/AIA and HMI instruments for the region of interest and time range selected in JHelioviewer:
Recent images from the LASCO, EIT, COR1/2 instruments are now available again. We will be filling in the missing images over the coming days. We apologize for the interruption in providing these images.
The most recent LASCO, EIT, COR1/2 and EUVI images are currently unavailable to Helioviewer Project browse clients. This is because the computer that converts the science data to JPEG 2000 images experienced a mechanical failure on Friday January 13th. We will replace the failed machine, and make an announcement via the blog concerning the resumption of the availability of images from LASCO, EIT, COR1/2 and EUVI. We are apologize for any inconvenience this may cause. Finally, images from AIA and HMI should be unaffected.
Comet Lovejoy will be passing close to the Sun in the next couple of days. SDO will be taking special observations of the comet beginning 22:59 UT on 2011/12/15 (5.59pm 2011/12/15, Eastern Time), and lasting for a couple of hours. The comet will pass behind the solar limb at around 00:07 UT 2011/12/16 (7:07pm 2011/12/15, Eastern Time). There is a chance the comet will survive its encounter with the Sun.
SDO/AIA will take special observations to view the comet; AIA will change its pointing and point slightly away from the center of the Sun in order to try to get more observations of the comet as it gets close to the disk of the Sun.
Why are these observations being taken? Well, we are looking for something like we saw on 2011/07/05 this year. On that day a comet fell in to the Sun. These kinds of comets have been seen before in LASCO-C3 and LASCO-C2 images. What was new about this observation was that for the first time the comet was seen against the disk of the Sun. The video below gives a description of what was seen.
SDO/AIA detects different wavelengths of light. So in order for us to see it, the comet must have been emitting at those different wavelengths, and the comet must have disintegrated in to a big enough cloud of ionized gas for us to see it. So the big scientific question about seeing this comet against the disk of the Sun is explaining both how it came to be emitting at wavelengths that SDO/AIA could see, and figuring out how it could have disintegrated. This is an active area of research, with presentations on this subject given last week at the American Geophysical Union‘s Fall Meeting, and a paper set to appear in Science.
We hope you enjoy tracking Comet Lovejoy as it gets closer to the Sun. Please let us know if you have any further questions about the Helioviewer Project and Comet Lovejoy.
Helioviewer user otraLoly was first to share this rather spectacular looking event in SDO AIA data yesterday:
As the event progresses, you can clearly see that the material is spiraling around as it slowly moves away from the Sun’s surface. It may be associated with an ejection seen in LASCO C2, although the data here is as yet incomplete. Other users have also shred movies of the same event: here is one shared by danielchangck:
and another movie shared by papavalium:
If you find something interesting, please let us know by either emailing us at firstname.lastname@example.org, or by sharing it on helioviewer.org via YouTube.
YouTube and Helioviewer.org user galaxy387 posted the video below showing a comet falling towards the Sun.
LASCO (Large Angle Spectrometric COronagraph) on board the SOHO spacecraft has seen very many comets since it started observing in 1996. SOHO has reported over 2000 comets, almost all of them found by members of the public. Thanks to the many amateur observers that hunt for comets in SOHO data, SOHO has seen many more comets than any other mission (there was another bright comet observed on May 10-11, 2011. A lot of these comets come from the Kreutz sungrazer family of comets. There is an active community of comet hunters, so if you think you’ve discovered one – and it is certainly possible that you may have – please check the latest reports over there. Thanks for sharing, galaxy387!
We are pleased to announce that the most recent, high quality STEREO images are now available on helioviewer.org.
First off, there are two spacecraft, called STEREO-A and STEREO-B. Both spacecraft orbit the Sun at roughly 1 AU (astronomical unit), or about as far away from Sun as the Earth is. However, STEREO-A is moving ahead of the Earth in its orbit, and STEREO-B is drifting behind the Earth in its orbit. This means that each STEREO spacecraft sees different parts of the Sun, parts that we can’t see from Earth. STEREO-B sees features on the Sun that we eventually see in SDO and SOHO, and STEREO-A allows us to see the continuing evolution of features that we did see in SDO and SOHO.
This plot shows where each spacecraft is now:
As you can see, they are quite far away from the Earth. This puts some operational constraints on each spacecraft that means we get high-quality images two days after they were taken. These are the data we are making available today; images from June 1st 2011, up to the most recently available data will be available initially. We ask for your patience, as we are uploading these images right now. Over the course of the next few weeks we will be making images from earlier in the mission available so that you can explore the Sun from many different angles over the past 4 1/2 years.
The benefit of seeing the Sun from many different angles is apparent when you look at the following three videos of the prominence eruption of June 7, 2011. The first one consists of images from SDO-AIA and SOHO-LASCO
We hope you enjoy these new images! As ever, please let us know if you spot any problems.
These videos show some of the larger scale effects of flares on the Sun. In the video, you can see two big eruptions approximately 10 and 17 seconds into the video, from the active region in the lower left.
But look more closely – can you see a wave of coming out of each of these explosions? They are faint, and can be difficult to see, but they are there. These are examples of EIT waves, so called because they were first seen in the SOHO-EIT instrument. These waves are thought to be examples of magnetohydrodynamic waves that propagate in the corona. They are truly large waves; for comparison, the radius of the Earth is about 1/100th that of the Sun. By studying these waves we can learn more about the structure and properties of the solar corona. There is also some evidence that these waves have ‘knock-on’ effects on other parts of the Sun, perhaps causing other events at parts distant from the original explosion. Look at the video – what do you think?
This image caught our attention for the unusual streaks in the LASCO-C3 field of view:
What causes the streaks? Well, it turns out this has been seen before – check out this similar example and and an explanation of what they are.
Some of you may have noticed that recent LASCO C2 images are upside down. You can notice this quite easily, as the streamer belts in LASCO C2 do not line up with the streamer belts in LASCO C3. This is due to an error in the way we write out LASCO C2 images. We are diagnosing the problem and will rewrite the affected images shortly. This in itself will be delayed due to the fact that the machine which writes out new LASCO C2 and C3 images will be offline for a couple of days. We apologize for the interruption to our service in the delivery of good quality new and recent LASCO images. Older LASCO images are unaffected, as are HMI and AIA images.
The latest JHelioviewer update adds support for SDO/HMI data and features a new contrast filter, as well as an improved plugin to access the Heliophysics Event Knowledgebase (HEK).