Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: lunar11 on 29/12/2012 14:02:10

Title: Can Solar eclipses occur during sunset or sunrise?
Post by: lunar11 on 29/12/2012 14:02:10

Can Solar eclipses happen during sunrise and sunset? If so, would the Sun and Moon still appear large (due to optical illusion)?

Title: Re: Can Solar eclipses occur during sunset or sunrise?
Post by: Phractality on 29/12/2012 18:55:25

The short answer is YES. Any solar eclipse that is classified as a total eclipse will have a total phase at locations all the way across the Earth from start to finish. It will start at a point where the sun is rising and finish at a point where the sun is setting.

In an annular eclipse, the Moon is too far away to produce a total eclipse anywhere on Earth.

In a hybrid eclipse, the Moon is close enough to produce a total eclipse around noon on the side of Earth nearest the Moon. Before and after the total phase, it will only produce an annular phase.

The partial phase of every eclipse occurs somewhere at sunrise and sunset. So I assume you mean the total phase of an eclipse, when some part of the Earth is in the Moon's umbra. When the Earth is too far from the moon, the umbra never reaches any part of the Earth.

In the long term, total eclipses are more common in December and January, because that is when the Earth and Moon are about 3% farther from the sun than in May and June. When the Moon is 3% closer to the sun, its umbra is about 12,000 km longer. That is very significant because it is nearly equal to the Earth's diameter.

The Moon's distance from Earth varies by nearly 12%, which is about four times the Earth's diameter, so that is even more significant. But the time of Moon's perigee and apogee (http://www.saao.ac.za/public-info/sun-moon-stars/moon-index/lunar-perigee-apogee-2004-2020/) varies from year to year because the orbit is precessing. There will be a solar eclipse on May 10, 2013. The Moon will be a apogee on May 13, so that will be an annular eclipse.

Title: Re: Can Solar eclipses occur during sunset or sunrise?
Post by: evan_au on 29/12/2012 21:58:20

The ground track of totality for the November 2012 Solar eclipse is shown here: http://eclipse.gsfc.nasa.gov/SEgoogle/SEgoogle2001/SE2012Nov13Tgoogle.html

The ground track starts in Australia's Northern Territory (where it was dawn, at left), and ends near the coast of Chile (where it was sunset, far right).