As we have noted in the preceding section, the Earth casts a shadow that the Moon can pass through. When this happens we say that a lunar eclipse occurs. Just as for solar eclipses, lunar eclipses can be partial or total, depending on whether the light of the Sun is partially or completely blocked from reaching the Moon. The following figure illustrates a total lunar eclipse with the Moon lying in the umbra of the Earth's shadow.
 |
| A Lunar Eclipse |
During a total lunar eclipse the Moon takes on a dark red color because it is being lighted slightly by sunlight passing through the Earth's atmosphere and this light has the blue component preferentially scattered out (this is also why the sky appears blue from the surface of the Earth), leaving faint reddish light to illuminate the Moon during the eclipse.
Stargazers across Australia awoke early on Thursday to catch a glimpse of a red lunar eclipse, but some were undoubtedly disappointed.
The event started about 3.25am (AEST) and finished at sunrise, said Professor Fred Watson, astronomer-in-charge at the Australian Astronomical Observatory.
It created a different show in states across Australia, with stargazers in NSW unlikely to have seen much amid dense cloud cover and rain.
Victorians were lucky with clear skies, while West Australian residents got the best view, with the spectacle fading into twilight.
The ash from a volcano in Chile had little impact, Prof Watson told AAP on Thursday.
The lunar show happens when the earth, sun and moon perfectly align, creating a deep shadow on the moon. Instead of plunging the moon into darkness it turns it a blood red.
"The reason why it goes red is the earth has a thin band of air around it, which scatters the sun's light and always this turns the moon a deep red," Prof Watson said.
The best view would have been from the moon itself.
"If you could watch the phenomena, you would see the earth moving across the sun and it creating a brilliant red rim around the earth."
The last lunar eclipse was on August 28, 2007, with the next one expected sometime in December, he said.
But although it is not a monthly experience on earth, across our solar system lunar eclipses are a regular occurrence.
"Saturn has 63 moons, many of which are quite large objects, so they go into eclipses very often," Prof Watson said.
"It's all part of the way the solar system works, and the constant dance of the planets."
No comments:
Post a Comment