INTERACTIVE CHELYABINSK QUIZOn 15 February 2013, a fireball blazed across the sky over the Ural Mountains in Russia. The asteroid broke up over the Chelyabinsk region, injuring inhabitants below and leaving destruction in its wake.
AN INTERACTIVE VIDEO OF THE CHELYABINSK EVENTRe-experience February 15, 2013. The day a meteor exploded over Russia
QUIZ: Are you a rock star?Play our fun asteroid Quiz!
Which asteroid was discovered to have its own satellite? – User submitted Question
The first asteroid to be discovered having its own satellite is the main belt asteroid Ida (average diameter of 31.5 km; average because it is elongated). The probe Galileo performed a fly-by of Ida in 1993 and during the fly-by, a small moon named Dactyl (about 1 km in diameter) was discovered, separated from Ida by 90 km. Thanks to the moon’s presence, the bulk density of Ida could be much better constrained.
Other binaries (even triples) were discovered either thanks to optical observations, or Hubble space telescope or radar observations. The big advantage of binaries is that the mass of the system can be estimated by what is called Kepler third law, something that cannot be done for a single asteroid for which the mass is unknown unless we visit it (short answer; there are other possible estimates, if radar observations can be performed).
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