Sun-Earth-Moon relationship: First total lunar eclipse of 2011
Distance travelled ~ 424'512'000 km: day 165
One of the few significant things Earth and the Moon share is their relationship with the Sun. To an observer on Earth at least - as different portions of both the Earth and Moon's surfaces are illuminated, this signifies the movement of time and the root of our calendar, which is very important.
On 15th/16th June we will observe a unique point in the Sun-Earth-Moon annual relationship - a total lunar eclipse and the first for this year.
Image courtesy of Fred Espenak/NASA
It takes the Moon 27 1/3 days to orbit the Earth (lunar month 29 ½ days), going through the new Moon, first quarter, full Moon, last quarter and back to new Moon. A total lunar eclipse happens when there's a full Moon and the Moon passes through a part of the Earth's shadow, known as the umbra - an area not directly receiving the Sun's rays.
Although there is a full Moon every month, we don't get a total lunar eclipse each month because the Moon's orbit is not in the same plane as the Earth's around the Sun (the ecliptic). From the image below we can see that the Moon's orbit goes over and under the Earth's orbital plane around the Sun.
Image courtesy Wikimedia commons
The inclination of the Moon's orbit is around 5 degrees to the Earth's orbit, and passes through the ecliptic only twice a month at a pair of points called the ascending and descending nodes. This is where the Nodal Axis is aligned with, or pointing at, the Sun.
The period when the Earth completely blocks the Sun's rays from the Moon is when we experience a total lunar eclipse - known as totality. This moment repeats itself every 6 months.
For this week's eclipse the best placed observers to see it in it's entirety are those in East Africa, central Asia, Middle East and West Australia, lasting a total of 1 hour and 6 minutes. For Europe and South America we will miss the beginning of the show and places like west Australia will miss the end - check specific times for your location. North America completely misses the total lunar eclipse.
Penumbral Eclipse Begins: 17:24:34 UT
Partial Eclipse Begins: 18:22:56 UT
Total Eclipse Begins: 19:22:30 UT
Greatest Eclipse: 20:12:37 UT
Total Eclipse Ends: 21:02:42 UT
Partial Eclipse Ends: 22:02:15 UT
Penumbral Eclipse Ends: 23:00:45 UT
What can you expect to see? The shade of the Moon at eclipse is hard to predict because of the Earth's atmosphere. Although the Earth will block out the Sun during totality, the Sun's rays will still penetrate through the Earth, and mixed with the dust and cloud in the atmosphere the total lunar eclipse may take a variation of different shades. Volcanic ash can also affect the shade of the total lunar eclipse - turning it a darker shade of red. Ash from the recent eruption of the Puyehue volcano in Chile may have placed some sulphur dioxide into the stratosphere, according to atmospheric scientist Richard Keen of the University of Colorado.
If you plan on observing or photographing the total lunar eclipse of June 15th/16th and would like to share your comments and images with the 23 Degrees team for a possible story or image gallery do get in touch.
The next long lunar eclipse will be in 2018.