http://www.cfa.harvard.edu//sao/su/ SAO Weekly Updates en-us http://www.cfa.harvard.edu/sao/su/2008/su200840.html October 03, 2008: An "exoplanet" is an extra-solar planet, that is, a planet orbiting a star other than our own sun. Of the roughly 307 currently known extrasolar planets, about thirty of them transit their star (that is, their orbits take them in front of their star as seen from earth). http://www.cfa.harvard.edu/sao/su/2008/su200839.html September 26, 2008: Stars form as gravitational forces coalesce the gas and dust in interstellar clouds until the material forms clumps dense enough to become stars. But how this happens, and whether or not the processes are the same for all stars remains very uncertain. http://www.cfa.harvard.edu/sao/su/2008/su200838.html September 19, 2008: About ten years ago, astronomers using new submillimeter wavelength facilities discovered the existence of a new class of very distant galaxies. http://www.cfa.harvard.edu/sao/su/2008/su200837.html September 12, 2008: Black holes are by far the "simplest" objects in the universe because they can be completely characterized by just three numbers: their mass, electric charge, and spin. http://www.cfa.harvard.edu/sao/su/2008/su200836.html September 05, 2008: In 1967, an X-ray sounding rocket discovered a fantastically bright source of X-ray emission coming from the direction of the constellation of Cygnus. http://www.cfa.harvard.edu/sao/su/2008/su200835.html August 27, 2008: Perhaps the most astonishing and revolutionary discovery in cosmology was Edwin Hubble's observation that galaxies are moving away from us. http://www.cfa.harvard.edu/sao/su/2008/su200834.html August 20, 2008: New stars are continually forming in clouds of gas and dust in our galaxy. Astronomers at the CfA and elsewhere who watch these births have a very good (though not perfect) understanding of how and why they happen. http://www.cfa.harvard.edu/sao/su/2008/su200833.html August 13, 2008: There is now overwhelming evidence that the center of our Milky Way galaxy contains a giant black hole with a mass of about four million suns. http://www.cfa.harvard.edu/sao/su/2008/su200832.html August 06, 2008: As modern telescopes peer more and more deeply into the universe, they are seeing older and older galaxies. http://www.cfa.harvard.edu/sao/su/2008/su200831.html July 30, 2008: Solar flares, prominences, and so-called coronal mass ejections are three different manifestations of stored magnetic energy near the sun's surface being released in sudden eruptions. http://www.cfa.harvard.edu/sao/su/2008/su200830.html July 23, 2008: Radio galaxies are cosmic beacons, with the brightest ones beaming nearly a trillion solar-luminosities of radiation into space at radio wavelengths. http://www.cfa.harvard.edu/sao/su/2008/su200829.html July 16, 2008: Mars, Jupiter, and all the other planets and asteroids in the night sky that are visible to us can be seen because they reflect sunlight. http://www.cfa.harvard.edu/sao/su/2008/su200828.html July 09, 2008: Near Earth Objects (NEOs) are small solar system bodies that are infamous because their orbits take them near earth's orbit; sometimes they pass dangerously close to the earth or even collide with it. http://www.cfa.harvard.edu/sao/su/2008/su200827.html July 02, 2008: Polaris, the North Star, is not only renowned as a reliable beacon for early navigators. http://www.cfa.harvard.edu/sao/su/2008/su200826.html June 25, 2008: The sun's photosphere is hot, about 6000 kelvin, and so the sun emits about 70% of its light in the visible portion of the electromagnetic spectrum, and about one-quarter in the infrared.