<Tr> <Td> A total solar eclipse occurs when the Moon completely covers the Sun's disk, as seen in this 1999 solar eclipse . Solar prominences can be seen along the limb (in red) as well as extensive coronal filaments . </Td> </Tr> <Tr> <Td> An annular solar eclipse (left) occurs when the Moon is too far away to completely cover the Sun's disk (May 20, 2012). During a partial solar eclipse (right), the Moon blocks only part of the Sun's disk (October 23, 2014). </Td> </Tr> <P> A solar eclipse (as seen from the planet Earth) is a type of eclipse that occurs when the Moon passes between the Sun and Earth, and when the Moon fully or partially blocks ("occults") the Sun . This can happen only at new moon when the Sun and the Moon are in conjunction as seen from Earth in an alignment referred to as syzygy . In a total eclipse, the disk of the Sun is fully obscured by the Moon . In partial and annular eclipses, only part of the Sun is obscured . </P> <P> If the Moon were in a perfectly circular orbit, a little closer to the Earth, and in the same orbital plane, there would be total solar eclipses every new moon . However, since the Moon's orbit is tilted at more than 5 degrees to the Earth's orbit around the Sun, its shadow usually misses Earth . The Moon's orbit must cross Earth's ecliptic plane in order for an eclipse (both solar as well as lunar) to occur . In addition, the Moon's actual orbit is elliptical, often taking it far enough away from Earth that its apparent size is not large enough to block the Sun entirely . The orbital planes cross each other at a line of nodes resulting in at least two, and up to five, solar eclipses occurring each year; no more than two of which can be total eclipses . However, total solar eclipses are rare at any particular location because totality exists only along a narrow path on the Earth's surface traced by the Moon's shadow or umbra . </P>

When moon completely covers sun what's it called