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Mystery diamond-shape “object” entering the field-of-view of the HI2 telescope on STEREO Behind around December 26, 2011. Credit: NASA
The STEREO (Solar TErrestrial RElations Observatory) is a two-year mission conducted by NASA. It employs nearly identical twin telescopes – one positioned ahead of Earth’s orbit and the other behind – designed to study the Sun’s activities spectroscopically. However, it can sometimes pick up some very unusual findings! On December 26, 2011, the STEREO Behind Observatory’s HI2 telescope captured an ambiguous triangle entering the field of view and moving from right to left just above the trapezoidal occulter as seen in the above movie. Just what is this “thing”?!
Before you get ready to call the men in black, know that there is a logical answer… and it comes into play on the opposite side of the STEREO image. Play the movie again and watch. (It’s a bit more obvious in this close-up view.) Just as the weird triangle begins its approach, you’ll notice the dazzling Venus enters the field of view of the HI2-B at the same time to the lower left. As you watch, you’ll see they keep exactly the same time – in opposite – across the detector image. This isn’t just a chance happening… it’s a naturally-occurring internal reflection caused by Venus’ brilliance in the telescope’s optics. It might be exciting for the moment, but it’s nothing that hasn’t happened in the past. Just check out these great STEREO Reflections of Earth, and all sorts of other cool images on the STEREO Image Artifacts pages.
What else can be seen? As you can tell from this photograph, Earth is also starring in the show, but doesn’t come in as striking as Venus. What’s more you can also see the tail of Comet Lovejoy streaking in from the left just above Venus towards the end of the movie.
Original Story Source: Triangular shaped object in STEREO data explained.