Just a very quick post, this time from NASA who have released a few images, including a movie, of the Moon transiting the Sun, which were captured as the cameras aboard STEREO-B were being calibrated.
"What an extraordinary view," says Lika Guhathakurta, STEREO Program Scientist at NASA headquarters. The fantastically-colored star is our own sun as STEREO sees it in four wavelengths of extreme ultraviolet light. The black disk is the Moon. "We caught a lunar transit of the sun," she explains.
The purpose of the experiment was to measure the 'dark current' of STEREO-B's CCD detectors. The idea is familiar to amateur astronomers: Point your telescope at something black and see how much 'dark current' trickles out of the CCD. Later, when real astrophotography is taking place, the dark current is subtracted to improve the image.
STEREO-B is one of a pair of spacecraft tasked with imaging the Sun, and is 1 million miles 'back' from STEREO-A, the 'advanced' positioned craft, which allows for offset images to be captured, which are then later combined to produce 3-dimensional images of such events as solar storms.
Of particular interest are coronal mass ejections (CMEs), billion ton clouds of electrified gas hurled into space by explosions on the sun. "STEREO's ability to see these clouds in 3-dimensions will revolutionize our understanding of CMEs and improve our ability to predict when they will hit Earth," she says.
The STEREO mission is still in its early stages. The two spacecraft were launched in Oct. 2006 and reached their stations on either side of Earth in January 2007. Now it's time for check-out and calibration. The first 3D views of solar storms are expected in April.
So hopefully, we'll be back in a month or two hence, gazing at suitably wondrous images of our shining parent star.
In the meantime, it's definitely worth paying the STEREO website a visit, as well as bookmarking it for return visits