... January 4, 1997 . A Star Where Photons Orbit . ... Explanation : The above computer animated picture depicts how a very compact star would look to a nearby observer. ... From here one can either look down and see several duplicate images of the entire surface of the star, look up and see several duplicate images of the entire night sky, or look along the photon sphere and see the back of one's own head. Tomorrow's picture: Too Close to a Black Hole . ... About APOD > . ...

... Observers looking at an object that is moving away from them see light that has a longer wavelength than it had when it was emitted (a redshift), while observers looking at an approaching source see light that is shifted to shorter wavelength (a blueshift). ... By measuring the amount of the shift to the red, we can determine that the bright galaxy is moving away at 3,000 km/sec, which is 1 percent of the speed of light, because its lines are shifted in wavelength by 1 percent to the red. ... Part 2...

... Tonight's Sky . ... Sky this Month . ... Star Atlas . ... stars . ... The Sky This Week: April 1 - 10 . ... Observing springtime deep-sky objects with a large telescope . ... Why do some stars appear to flash a variety of different colors when you look at them through a telescope? ... So, Earthт??s atmosphere will bend some colors from especially bright stars more so than others, which makes the source look like itт??s flashing colors. Get instant access to subscriber content on Astronomy.com! ...

... 29a. Satellite looking up . 29c. Satellites probing around . ... The US Air Force furthermore sponsors polar satellites of the DMSP series, scanning the cloud cover of the polar region and also studying ions and electrons of the magnetosphere. ... The Canadian satellite Alouette in 1962 bounced radio signals off the top of the ionosphere, and UARS (Upper Atmosphere Research Satellite) has studied the Earth atmosphere. ... Next Satellite Class: #29c Those observing local conditions . ...

... August 30, 1999 . Looking Back on an Eclipsed Earth . ... Explanation: Here is what the Earth looks like during a solar eclipse. ... Only observers near the center of the dark circle see a total solar eclipse - others see a partial eclipse where only part of the Sun appears blocked by the Moon . This spectacular picture of the 1999 August 11 solar eclipse was one of the last ever taken from the Mir space station , as Mir is being decommissioned after more than ten years of productive use. ...

These include satellites which monitor the weather, such as the GOES series (one of which is shown on the right) of the US National Oceanic and Atmospheric Administration (NOAA). ... To this class also belong "spy satellites" which observe the ground from low circular orbits. ... The Canadian satellite Alouette in 1962 bounced radio signals off the top of the ionosphere, and UARS (Upper Atmosphere Research Satellite) is currently studying the Earth atmosphere. ...