Solar and Lunar Eclipses

Solar and Lunar Eclipses

Solar and Lunar EclipsesEclipse:

The total or partial obscuring of one celestial body by another…

The obscuration can be either• One celestial body blocking

the view to the other:– Solar eclipse---Moon

blocking Earth’s view to the Sun…

• One celestial body is in the shadow of another:– Lunar eclipse---Moon is in

the shadow of the Earth…

Lunar eclipse image from http://www.mreclipse.com

What Causes an Eclipse?• The Earth and Moon cast shadows.

• When either passes through the other’s shadow, we have an eclipse.

• Because the Sun is an extended bright object, there are two different regions of the shadow:

– Penumbra is partially illuminated

– Umbra is completely dark

Solar Eclipse

• Solar Eclipse Animation

Solar Eclipses• When the Moon’s shadow covers part of the Earth• Only happens at New Moon• Three types: Annular, Partial, and Total

Total Solar EclipseWhat’s the difference between a total and ring (annular) eclipse?The distance between the Earth and the Sun.

You see the whole Sun outside of the shadow

You see the partial Sun if you are in the penumbra

You don’t see the Sun at all if you are in the umbra

Moon

Surface of the Earth

Sun

Solar eclipses

• Solar eclipses occur when the shadow of the Moon falls on the surface of Earth– Only people in the shadow

can see the eclipse.

• Solar eclipses can be partial, annular, or total.

• Solar eclipses can occur only at new moon.

Total Solar Eclipse• Observers in the “umbra” shadow see a total eclipse (safe to view the

Sun); can see the corona• Those in “penumbra” see a partial eclipse—not safe to look directly at

Sun• Only lasts a few minutes

Annular Solar Eclipse• When the Moon is too far to completely cover the Sun—the

umbra doesn’t reach the Earth• Sun appears as a donut around the Moon

South Pole

North Pole

Solar Eclipse Details

SunMoon

What is the phase of the moon?

New Moon!

Ring Eclipse (or Annular)• A Ring eclipse happens when the Moon does not

completely block the Sun, like partial eclipses…

You see the whole Sun if you are outside of the shadow

You see the partial Sun if you are in the penumbra

• The umbra is NOT completely dark!

• You see a ring if you are in here

Moon

Surface of the Earth

Sun

Solar Eclipses

The solar corona is revealed during a total solar eclipse

Why not a solar eclipse every month then?

Sun

Ecliptic

Moon

Moon’s Orbit

Earth5o

Moon's orbit is tilted about 5o with respect to the Earth's orbit (ecliptic), so the shadows usually miss!

Solar Eclipse ForecastSolar eclipses from 2004 to 2030

Knowing the orbit of the Earth and the Moon, we can now calculate the time and path of solar eclipses with great accuracy.

A Total Solar Eclipse from beginning to end

When the Earth’s shadow covers the Moon, we have a lunar eclipse

Lunar eclipses

• Lunar eclipses happens when the Moon passes through the shadow of the Earth– Everybody on the night side

of Earth can see the lunar eclipse.

• Lunar eclipses can be partial, penumbral, or total.

• Lunar eclipses can occur only at full moon.

A Lunar Eclipse

Moon

Sun EarthMoon’s

PathA lunar eclipse occurs when the Earth lies between the Sun and Moon, so that Earth's shadow darkens the Moon.

This image shows a complete transition during a lunar eclipse. Notice that the phase of the moon is “full.”

Earth’s Atmosphere

Sunlight

MoonEarth

The Blood Moon

The moon often does not totally disappear during a total lunar eclipse. Instead it can be seen as a very dark red color because of the refraction of sunlight through the Earth's atmosphere.

Three types of Lunar Eclipses

• Penumbral lunar eclipse—the Moon only passes through the penumbra of Earth’s shadow

• Partial lunar eclipse—part of the Moon passes through the umbra of Earth’s shadow

• Total lunar eclipse—the entire Moon passes through the umbra of Earth’s shadow

• Who on Earth will be able to see a lunar eclipse?

Anyone who can see the Moon (anyone who is on the nighttime side of the Earth during the eclipse)

Lunar Eclipse

• Lunar Eclipse Animation

How Often Does Eclipse Occur?• Do we have one solar and one lunar eclipse every six month,

when the nodes line-up with the Earth-Moon line?– NO! Because of the precession of the lunar orbit!

Nodes: the two points when the Moon crosses the ecliptic plane• Only when the

nodes are located right between the Earth-Sun line can solar eclipses occur.

Eclipses: Summary

• The parties involved: Sun, Moon, and Earth• Motion of the Moon around Earth: • Solar eclipse happens when the Moon is between the Earth

and the Sun.• The size and distance of the Moon need to be just right for us

to see total eclipse.– The changing distance between the Earth and the Moon explains the

occurrences of the total and ring solar eclipses. – The changing distance between the Earth and the Sun, and the Earth

and the Moon explains the difference in the duration of the solar eclipses.

• Lunar eclipse happens when Earth is between the Moon and the Sun.

• Interactive Eclipses

What type of an Eclipse?

Answer: Solar Eclipse

What type of an Eclipse?

Answer: Lunar Eclipse