Solar Eclipses
A solar eclipse happens when the moon blocks our view of the sun. This happens when the Moon is exactly between the Sun and the Earth.
How can something four hundred times smaller than the Sun block out its rays?
- By a coincidence, the Moon is four hundred times closer to Earth than the Sun. so it appears to fit right over the Sun, like a glove.
The longest solar eclipses occur when
the Earth is at aphelion
(farthest from the Sun, making the solar disc smaller) and the Moon is at perigee (closest
to the Earth, making the Moons apparent diameter larger).
- The Moon's shadow actually has two parts:
- The Moon's faint outer shadow.
- Partial solar eclipses are visible from within the penumbral shadow.
- The Moon's dark inner shadow.
- Total solar eclipses are visible from within the umbral shadow.
1. Penumbra
2. Umbra
STAGES IN A TOTAL SOLAR ECLIPSE
BAILY'S
BEADS:
Baily's beads (often spelled Bailey's beads) are bead-like bursts of light that appear about 15 seconds before and after totality during a solar eclipse. Baily's beads are caused by light shining through valleys on the edge of the moon. They were named for the British astronomer Francis Baily (1774-1844), one of the founders of the Royal Astronomical Society.
DIAMOND RING:
The "Diamond Ring" is a large burst of light that appears a few seconds before and after totality.
TOTALITY:
Totality is the short part of an eclipse when the moon entirely blocks the Sun. Totality usually lasts for just a few minutes (no more than 8 minutes in any one location on Earth). Only 8 solar total eclipses will be visible from the continental U.S. during the 21st century.
Baily's beads (often spelled Bailey's beads) are bead-like bursts of light that appear about 15 seconds before and after totality during a solar eclipse. Baily's beads are caused by light shining through valleys on the edge of the moon. They were named for the British astronomer Francis Baily (1774-1844), one of the founders of the Royal Astronomical Society.
DIAMOND RING:
The "Diamond Ring" is a large burst of light that appears a few seconds before and after totality.
TOTALITY:
Totality is the short part of an eclipse when the moon entirely blocks the Sun. Totality usually lasts for just a few minutes (no more than 8 minutes in any one location on Earth). Only 8 solar total eclipses will be visible from the continental U.S. during the 21st century.
What
We Can See During Totality
During a total solar eclipse some parts of the Sun that we normally can't see become visible, including the corona (the outermost layer of the sun's atmosphere). The corona is mostly X-ray emissions (which we can't see), but light from the photosphere is scattered by the loose electrons in the corona's plasma and we can see this. Normally, the intensely bright light of the photosphere (the visible disk of the Sun) dominates the corona and we don't see the corona. During an eclipse, the moon blocks the photosphere, and we can see the faint, scattered light of the corona (this part of the corona is called the K-Corona).
- The Moon blocks out the entire sun, except for a faint halo of light called a corona
In the few minutes of totality, we can see the coronal streamers, polar plumes, and prominences.
Types
of Solar Eclipses
- Partial Solar Eclipse - A partial solar eclipse is when
the Moon only covers part of the solar disc.
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- Total Solar Eclipse - A total solar eclipse is when
the Moon appears to cover the entire solar disc. Total solar eclipses are
only visible from a very small area on Earth, a narrow track that moves
across the Earth's surface (as the Earth rotates). The partial phase of a
total eclipse lasts about an hour. In any one place, totality (when the
solar disc is entirely covered) lasts no more than 8 minutes. During
totality, the sky is dark enough to see stars in the sky.
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- Annular Eclipse - During an annular eclipse, the sun looks like an "annulus" or ring. The ring is visible when the Moon does not entirely cover the disk of the Sun during a solar eclipse. This type of eclipse happens when the Sun is at perihelion (closest to the Earth, making the solar disc appear larger) and the Moon is at apogee (farthest from the Earth, making it look smaller).
- The Moon cannot block out the Sun totally because it is at a far point in its orbit. The result is an annulus, or ring, that's brighter than a corona.
