A lunar eclipse
On Feb. 20 there will be a total eclipse of the moon. It should be a good one and will be the last total we will see for another three years.
So, what causes an eclipse? As the moon orbits the Earth, it passes between the Earth and the sun, blocking out the sun’s light and producing an eclipse of the sun. Later in its orbit, the moon goes behind the Earth and passes through the Earth’s shadow, producing an eclipse of the moon. A solar (sun) eclipse occurs at new moon phase and the lunar (moon) eclipse occurs at full moon.
So why is there not a solar and lunar eclipse every month, which is 29.5 days? The answer is that the moon’s orbit is inclined 5 degrees to the Earth’s orbit. This means that most of the time the moon rides above or below the sun and Earth’s shadow, but sometimes it rides through some or all of the sun and passes through the Earth’s shadow and we see an eclipse.
The lunar eclipse on Feb. 20 will begin at 8:34 p.m., when the moon starts to enter the darker shadow of the Earth. From this point on, the Moon will appear to get smaller as the Earth’s shadow moves across the Moon’s surface. During the eclipse you can see that the Earth’s shadow on the Moon is curved. The curvature of the Earth’s shadow was the first proof that the Earth was not flat. The next stage in the eclipse is just before the shadow completely covers the moon, then its surface will take on a yellowish-orange or reddish-orange color due to the Earth’s atmosphere bending light from its edges and sending it in the Earth’s shadow down to an almost dark moon. Whether the color is yellow or red depends upon on how deep the moon rides through the shadow and how dirty the Earth’s atmosphere is at the time. If there has been a volcanic eruption, the moon may be deep red in color. For this eclipse the color is expected to be yellow with some orange.
Total eclipse will begin at 10 p.m. and totality will last until 10:52 p.m. After this, the moon will uncover a little at a time until 12:09 a.m., when we will once again see a full moon. So if you have to get early to go to work, you can watch the first half and know that the second half is just the first have reversed.
I will be observing and photographing the eclipse with my Oxford students, but I can’t get too excited because Mother Nature can put on some great celestial shows sometimes, but sometimes she also hides then with clouds.
Until next time, clear and dark skies.