From Min. to Max. to Min. (February 17, 2006)
Hi-res TIF image (2.5M)
This week SOHO offers a sense of the kind of retrospective that ten years of solar observations from the same instrument can offer: a comparison of three EIT 304 Angstrom images (in extreme ultraviolet light) across ten years. The left-hand image is one of the earliest EIT images from SOHO, taken just months after its launch in late 1995 when the Sun was near its minimum level of activity. Overall, it is strikingly similar in the general level of solar activity observed (usually seen as whiter areas in these kinds of images) to the right-hand image taken just this week. Both are almost devoid of intense regions of magnetic activity. At solar minimum, they also give a much clearer view of the polar coronal holes, the darker regions at the bottom and, to a lesser extent, the top of the Sun. The central image from this same week in 2001 shows a very different Sun: one that is brighter, features several large regions of activity, and with a large prominence extending out on its right. This is the Sun near its period of maximum of activity in its 11-year cycle.
We can also glean from this comparison that SOHO's CCD imager for EIT has held up quite well in that the level of detail and lack of burn in are quite comparable. Kudos to the scientists and engineers who designed and built such a dependable instrument.
SOHO began its Weekly Pick some time after sending a weekly image or video clip to the American Museum of Natural History (Rose Center) in New York City. There, the SOHO Weekly Pick is displayed with some annotations on a large plasma display.
If your institution would also like to receive the same Weekly Pick from us for display (usually in Photoshop or QuickTime format), please send your inquiry to firstname.lastname@example.org.