With no surprise, the first Google hit for 'Identification + Classification' is about Astronomy. http://www.mpia-hd.mpg.de/GAIA/
The GAIA project is aiming at identifying and classifying over 10^9 light sources, sorting them in stars, solar system objects, galaxies, quasars and the like. Astronomers have always led the way in classification and inventories. This is the next step ...
10^9 might seem quite a big number of stars, but actually it's just the beginning of the inventory. Our galaxy alone is home for a population of stars estimated to be about 100 times this figure, and the estimation of the number of galaxies in the observable universe is in the same range than the number of stars in the average galaxy. So the number of stars in the observable universe is something around (10^11)^2 = 10^22.
ReplyDeleteThat's big, but not *that* big. For example the total volume of water on Earth, a shallow layer of a few kilometers covering a small planet, is about 1.3*10^9 km3, otherwise said 1.3*10^24 cc, which means that there is roughly a half-cup (13 cl) of water on Earth for each star in the observable universe ...