On 10 February 2017, sky watchers will experience a confluence of three celestial events in the same night: a penumbral lunar eclipse, a “snow moon,” and a comet.

The lunar eclipse will be somewhat less spectacular than the image usually conjured up by that term:

This weekend’s event is what’s known as a penumbral lunar eclipse, a much more subtle counterpart to the dramatic total eclipse.

As the moon rises on Friday, it will pass through the outer edge of the Earth’s shadow, called the penumbra. During these type of eclipses, you will see a darkening of the moon from the bottom edge moving towards the top as the night progresses but not a total lunar blackout.

The eclipse will begin around 5:45 p.m. ET (4:45 p.m. CT) – shortly before moonrise – and end at around 9:50 p.m. ET (8:50 p.m. CT). The best viewing time will be around 7:45 p.m. ET (6:45 p.m. CT). You can see all the time information from NASA here.

A penumbral eclipse is less striking than a full or partial lunar eclipse, in which the moon turns blood red or appears to have had a “bite” taken out of it. Instead, in a penumbral eclipse, observers may notice only a darkening of the moon’s face:

In a total eclipse of the moon, the inner part of Earth’s shadow, called the umbra, falls on the moon’s face. At mid-eclipse, the entire moon is in shadow, which may appear blood red.

In a partial lunar eclipse, the umbra takes a bite out of only a fraction of the moon. The dark bite grows larger, and then recedes, never reaching the total phase.

In a penumbral lunar eclipse, only the more diffuse outer shadow of Earth falls on the moon’s face. This third kind of lunar eclipse is much more subtle, and much more difficult to observe, than either a total or partial eclipse of the moon. There is never a dark bite taken out of the moon, as in a partial eclipse. The eclipse never progresses to reach the dramatic minutes of totality. At best, at mid-eclipse, very observant people will notice a dark shading on the moon’s face. Others will look and notice nothing at all.

The full moon aspect of this trifecta isn’t really unusual at all, since lunar eclipses can only occur when the moon is full. News accounts having been playing up the fact that this full moon will be a “snow moon,” but that’s simply the traditional name given to the full moon that occurs every February in North America (due to its coincidence with snow and cold air temperatures).

If that’s not enough, a green-hued comet will also hurtle past Earth in the early morning hours of 11 February 2017. According to Sky & Telescope the comet, 45P/Honda-Mrkos-Pajdusakova, will zoom by the planet at 3 a.m. EST at a distance of 7.7 million miles:

While it won’t be coming in for a landing, 45P/H-M-P will miss the planet by just 7.7 million miles or about 32 times the Earth-Moon distance. Because of its proximity, we’ll see this frenetic fuzzball barrel across more than 2 hours of R.A. and nearly 20° of declination in the next five days.


Gore, Leada.   “Eclipse, Comet and Full ‘Snow’ Moon All Coming Friday Night.”
    AL.com.   8 February 2017.

Byrd, Deborah.   “What’s a Penumbral Eclipse of the Moon?
    EarthSky.   7 February 2017.

Sky & Telescope.   “Green Comet Makes Close Earth Flyby.”
    8 February 2017.