2017 Week 6: (February 5-11)

This week we will be treated to a penumbral lunar eclipse!  A lunar eclipse occurs when the Earth is between the Sun and the Moon and the plane of the Earth's shadow is in line with the Moon.  This causes the Moon to become darker as though some big object stepped between the Sun and the Moon.  A shadow has several parts associated with it.  The deep dark part of a shadow is known as the 'Umbra' and the lighter fuzzy part is known as the 'Penumbra'.  In Latin umbra means 'shadow' and penumbra means 'almost shadow'.

Penumbral Lunar Eclipse

In the case this week the penumbral part of the Earth's shadow will pass over the Moon.  Some astute observers may notice the Moon become a light red colour.  The red colour comes from the Earth's atmosphere scattering the blue part of the light spectrum away while leaving the red light to transmit through.  This is the same reason sunrises and sunsets appear to be an orange/red colour.  The Moon is red because the red light part of the spectrum from the Sun is transmitted and refracted through the Earth's atmosphere to the Moon.  It is almost like a lens that transmits only a certain frequency of light.

A penumbral eclipse is sometimes difficult to notice as only the outside of the Earth's shadow passes across the face of the Moon.  For more information see the article in Sky and Telescope below.

http://www.skyandtelescope.com/astronomy-news/feb-10th-penumbral-lunar-eclipse/

For observers in Calgary the eclipse will have already started when the Moon rises at 5:43pm and will continue until 7:53pm.  For the best view find a location where you can see the eastern horizon during the given times.  Other astronomical events for the week are listed below.

Date	Event
Feb 5	Aldebaran 0.2°S of Moon
Feb 6	Moon at Perigee
Feb 6	Jupiter Stationary
Feb 10	Penumbral Lunar Eclipse 3:34pm - 7:53pm
Feb 10	Full Moon
Feb 11	Regulus 0.8°N of Moon

It is interesting to note that Jupiter is stationary to the background stars and begins what is known as its retrograde motion on February 6.  Retrograde motion is caused by the Earth completing its orbit in a shorter amount of time compared to the outer planets.  A useful video on this phenomenon provided by the University of Nebraska-Lincoln is linked below.

Retrograde Motion

The forecast at the time of writing this calls for extreme cold and snow until Wednesday.  The weather starts to come back to seasonal conditions for Thursday and Friday, just in time for the lunar eclipse.  Stay warm this week and prepare for our first eclipse of the year.