What's in the sky tonight?
September 28, 2013
-This is the time of year when, in mid-evening, W-shaped Cassiopeia stands on end halfway up the northeastern sky. And whenever that happens, the dim Little Dipper extends straight leftward from Polaris due north.
-On Sept. 25th, China's experimental Tiangong-1 space station passed directly in front of the sun over Arizona. Mike Weasner held his iPhone 5s up to the eyepiece of a solar-filtered 8" telescope and captured this picture of the spit-second transit.
"The Tiangong-1 space station is about 10 meters by 3 meters in size and was 510.4 kilometers from my observatory at the time of the transit," says Weasner. "The angular diameter of the station was only 4.4 arcsec. Yes, that's small!"
Weasner used CalSky to predict the moment of transit. "I began slo-mo video recording with the iOS 7 Camera app on the iPhone 5s at 095015 MST and continued it for one minute to ensure that I captured the space station," he says. "The Tiangong-1 was successfully imaged on several frames as it crossed the sun's disk."
Most readers are familiar with the 450-ton International Space Station. Fewer may be aware of China's 8.5-ton Tiangong-1 (Heavenly Palace-1). It was launched in Sept. 2011 to establish a foothold in Earth orbit for China's fledgling space program. Since then taikonauts (Chinese astronauts) have visited the Tiangong-1 to practice rendevous and docking procedures and to train for living in space. According to some reports, the Tiangong-1 will be de-orbited in late 2013 to make way for more advanced experimental stations, Tiangong-2 and Tiangong-3 in the years ahead. Ultimately, China hopes to place an Mir-class station in orbit by 2020.
Astro Picture of the Day:
September 28, 2013
Source:
From a geostationary orbit 36,000 kilometers above the equator, Russian meteorological satellite Elektro-L takes high-resolution images our fair planet every 30 minutes. But only twice a year, during an Equinox, can it capture an image like this one, showing an entire hemisphere bathed in sunlight. At an Equinox, the Earth's axis of rotation is not tilted toward or away from the Sun, so the solar illumination can extend to both the planet's poles. Of course, this Elektro-L picture was recorded on September 22nd, at the northern hemisphere's autumnal equinox. For a moment on that date, the Sun was behind the geostationary satellite and a telltale glint of reflected sunlight is seen crossing the equator, at the location on the planet with satellite and sun directly overhead. This gif is shown below.