Hybrid solar eclipse: The rarest solar eclipse is a combination of a total and annular eclipse (sometimes known as an A-T eclipse) and is produced when the moon's shadow moves across Earth. These begin as one type of eclipse and transition to another. ...
Total solar eclipseshappen when the Moon completely covers the Sun, and it can only take place when the Moon is nearperigee, the point of the Moon's orbit closest to Earth. You can only see a total solar eclipse if you're in the path where the Moon casts its darkest shadow, theumbra...
smium comes in seven stable isotopes, and among them osmium-184 is the rarest at 0.02%. That times the element’s 1.8 parts per billion equals about a half part per trillion. But as mentioned above, osmium’s not the nicest stuff to deal with. For a far more serviceable candidate we ...
This is among the rarest of astronomical events. In fact, between the years 2000 BC and 4000 AD there are only 81 Venusian "transits," as astronomers call them. Only five times have humans recorded the passage of Venus in front of the Sun (in 1639, 1761, 1769, 1874 and 1882), althou...