Archive for category User Highlights

User hightlight: venus visible in LASCO C3


Helioviewer and YouTube user atomlibre1 shared a video of the planet Venus moving across the SOHO LASCO C3 coronagraph’s field-of-view.

At the very start of the video the bright planet is already well within C3’s view. Coronal streamers are visible as well as a coronal mass ejection or CME at the end of the video. Planets and comets are often observed by LASCO, which views as far out as 30 solar radii (a solar radius is almost 700,000 kilometers) in distance out from the sun over 2 million kilometers. The planet is so bright, too much for C3’s CCD, that lines extend out from either side giving almost a flying saucer shape. Venus and other planets are often mistaken for flying saucers.

A close-up view of Venus showing the extended nature of Venus in C3 was shared by user RAPTURE5770.

http://youtu.be/7WLlcL0dgGo

The time and direction of planets moving through C3’s view (called a transit) are well known and calculations of past and future transits can be found on the website devoted to comets observed by LASCO especially sungrazers. This particular transit of venus will be in C3’s field-of-view from July 18, 2011 until September 15, 2011. Thanks for sharing atomlibre1 and RAPTURE5770!

For more about the rare event of Venus transits of the sun seen from Earth check out TransitofVenus.org.

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User highlight: active region appearing on the Sun’s limb

YouTube and helioviewer.org user galaxy387 shared this movie of an active region appearing on the limb of the Sun.

It’s a great example of the complex evolution that an active can undergo in a relatively short amount of time. Studying the evolution of active region loops on the limb cuts right through the loops themselves so you don’t see any of the disk emission along your line of sight, and so removes a potential source of confusion.

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User highlight: comet in LASCO-C2

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!

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User highlight: contracting loops?

Helioviewer and YouTube user otraLoly spotted this interesting active region earlier on today.

Right at the very start you can see that loops on the southern side of the active region appear to contract (a CME and a prominence eruption are occuring). As the event progresses, you’ll notice that two dark areas appear in the coronal moss, outlined by some very bright, and small scale emission, which end up as loop footpoints to the subsequent loop brightening that occurs. This event is interesting for the detail it is possible to see in AIA, particularly in the brightening of the loop footpoints before the main bright loop occurs. Thanks to user otraLoly for sharing this video with users of helioviewer.org!

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User highlights: a cool loop arcade.

The event below was found and shared by helioviewer.org and YouTube user “LudzikLegoTechnics” – thanks for that! It’s a wonderful example of a cool loop arcade forming and evolving.

Cool loop arcade seen in SDO AIA 304.

What you’re looking at is a bunch of magnetic field lines, forming into loops of relatively cool plasma (50,000 K), at the limb of the Sun. For comparison, the surface of the Sun is around 4500-6000 K, and natural temperatures on the Earth’s surface are around 200 – 340 K.

There are quite a number of things going on here. Firstly, there are two active regions quite close by each other. Secondly, in the movie below (in AIA 171, which sees plasma at around 600,000 K):

Same loop system seen in SDO AIA 171.

you can see that some field lines appear to open up and a small faint eruption takes off. Finally, the loops form, with bright loop tops; it is likely that magnetic reconnection is taking place here. All in all, this is a very good example of just how complicated the activity on the Sun can be; with so much going on, there’s a lot to learn.

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