NASA JPL News: Teachable Moment: Watching This Month’s Total Lunar Eclipse

Animation showing a total lunar eclipse. Credit: NASA Goddard Media Studios



A full moon is always a good reason to go outside and turn your head toward the sky, but those who do so early on January 31 will be treated to the sight of a total lunar eclipse.  It’s the only total lunar eclipse visible from North America in 2018, so it’s a great opportunity for students to observe the Moon – and for teachers to make connections to in-class science content.

In the latest Teachable Moment from NASA/JPL Edu, education specialist Lyle Tavernier explains what causes a total lunar eclipse, what it tells us about Earth and how to see one in action on January 31. Teachers and parents can also explore a collection of lessons and activities to get students curious and excited about the Moon.

Read the article here.



2018, January 31: Chicago’s View of the Lunar Eclipse

Lunar Eclipse (image Credit: NASA)

A lunar eclipse occurs on the morning of January 31 during the second full moon of the month and the new year.  All the events of the lunar eclipse are visible from Asia, Australia, the Pacific Ocean Basin and western North America.

In the Chicago area, the moon sets in the western sky during the maximum phase.

Here are the events of the eclipse for Chicago area observers:

January 31, 4:51 a.m. CST — The moon is low in the western sky (altitude 23 degrees), just about two hours before it sets.  At this time, the moon enters the outer section of the lunar shadow — the penumbra.  For most observers not much change occurs in the moon’s brightness.

5:28 a.m. CST (Moon’s altitude, 16 degrees) — The moon appears lower in the western sky as the earth is rotating.  Morning twilight begins at this time.

5:48 a.m. CST (Moon’s altitude, 12 degrees) — The moon’s descent toward the horizon continues.  At this time the moon begins to move into the darker umbra and the partial eclipse begins.

6:01 a.m. CST (Moon’s altitude, 10 degrees) — The partial eclipse continues and the sky brightens.  Nautical twilight occurs at this time.  The sky is bright enough to distinguish the horizon — the line the separates the sky from the ground.

6:35 a.m. CST (Moon’s altitude, 4 degrees) — The moon’s descent continues as it is now only about 30 minutes before moonset.  Sometimes the moon and sun seem orange when they rise,  This is from the atmosphere erasing the yellow and blue light from  sunlight — atmospheric extinction. (This can also diminish the brightness of celestial objects.)  The moon appears orange during a lunar eclipse when red and orange light are bent through our atmosphere  While the moon is not in total eclipse, yet, the moon appears orange from the eclipse as well as the atmospheric extinction.  At this time Civil Twilight occurs; the sky is bright.  Street lights begin turning off.  It’s easy to distinguish details in terrestrial features.

6:51 a.m. CST (Moon’s altitude, 2 degrees) — The moon is very low in the western sky.  The moon is now completely inside the earth’s shadow — total eclipse.

7:04 a.m. CST — Sunrise

7:06 a.m. CST — Moonset

While all the stages of the eclipse are not visible from the Chicago area, the events leading up to the total eclipse are easily visible.

The articles that follow provide details about the planets visible without optical assistance (binoculars or telescope):


Size of #Supermoon

Can you tell the which image is 4% bigger than the other image -- difference between a typical full moon and a "supermoon?"

Can you tell the which image is 14% bigger than the other image — difference between a typical full moon and a “supermoon?”

One of my astro associates posted this image in another venue and asked whether we could tell the difference between the two images: “Which is 14% bigger than the other?” This is the difference between the size of a typical full moon and a #supermoon  (source)

Lunar Eclipse, September 27, 2015

(NASA Photo)

(NASA Photo)

On the night of September 27, the moon moves into the Earth’s shadow. Observers across the western hemisphere see a total lunar eclipse with the best part occurring from 9:11 p.m. through 10:23 p.m. No special equipment is necessary the eclipse.


The October 8, 2014 Total Lunar Eclipse.  The third eclipse in the current tetrad of total lunar eclipses.  See the text below.

Every planet and moon casts a two-leveled, round shadow into space. From the darker center of the shadow (umbra), the sun is completely blocked. From the outer shadow (penumbra), the sun is partly blocked. Because the moon shines from reflected sunlight, the moon loses its brightness when in passes into the umbra. Sunlight from the earth’s atmosphere gets bent into the shadow causing the moon to gently glow in a coppery color as in the image at the top of this posting.


Here are the events of the evening  (Times are for the Central Time zone, add or subtract time depending on your location)

Moon rise (Chicago): 6:34 p.m. (CDT) — The moon rises in the eastern sky.
Penumbral Eclipse:  7:11 p.m. (P1) — The moon begins moving into the outer shadow of Earth.  Casual observing will see not much difference between a full moon and this phase of the eclipse.
Partial Eclipse: 8:07 p.m. (U1) — The moon is within the lighter penumbral shadow and begins to move into the darker umbra.
Total Eclipse Begins: 9:11 p.m. (U2) — The moon is within the earth’s shadow and for the next 72 minutes the total eclipse occurs
Mid-Eclipse: 9:47 p.m. (Greatest) — The moon is midway through the shadow and midway through the eclipse.  This could be when the moon is at its darkest.
Total Eclipse Ends: 10:23 p.m. (U3) — The moon begins moving from the dark umbra.
Penumbral Eclipse: 11:27 p.m. (U4) — The moon is back into the penumbral shadow.  As earlier in the evening, not much difference is visible between the full moon and this part of the eclipse.
Eclipse Ends:  12:22 a.m. (September 28)
Moon set (Chicago): 7:16 a.m.

The moon and Mars were near each other during the lunar eclipse on April 15, 2014. Click the image to see the eclipsed moon, Spica, and Mars.

The moon and Mars were near each other during the lunar eclipse on April 15, 2014. Click the image to see the eclipsed moon, Spica, and Mars.

The 2016 Observers Handbook reports that this eclipse is the fourth consecutive total lunar eclipse in a series known as a tetrad.  This series of eclipse is rare.  The last tetrad occurred in 2003-2004.  The next tetrad series of consecutive total lunar eclipses is in 2032-2033.  There will be lunar eclipses during the intervening time, even total eclipses.  The tetrad is a series of four total eclipses with no other type in between.  Eight tetrads occur during the 21st century, according to the article.  Two of the images shown above are from this lunar eclipse tetrad.



Winter Solstice Lunar Eclipse

(NASA Photo)

A spectacular lunar eclipse is visible across the skies of North America, just hours before the winter solstice, on the night of December 20/21, 2010.

A lunar eclipse is visible when the moon, at the full phase, moves into the Earth’s shadow.  Occurring infrequently because the orbit is tilted slightly compared to the earth’s solar orbital path, the moon usually moves above or below the shadow when on the opposite side of Earth from the sun.

As the moon slowly plunges into the Earth’s shadow, it loses its reflected sunlight.  A total eclipse is not completely dark, but some red and orange sunlight is refracted into the shadow.  The moon then has a reddish orange glow.

Earth’s shadow has two zones:  The penumbra is the outer part of the shadow where the sunlight is not completely blocked.  The umbra is dark because it receives no direct sunlight.  During the nighttime we are inside the earth’s umbra.  No sunlight is visible.

Lunar eclipses are seen more often from any one location as they are visible from over half the earth, where the moon is above the horizon.  A lunar eclipse is not dangerous to view.  Binoculars or a telescope under low power, 15x to 40x present outstanding views of the eclipse.

Here are the events for the evening:

December 20, 2010  (The times that follow are accurate for any location in North American, except times for sunrise, sunset, moonrise, and moonset.  Observers in other time zones can adjust the eclipse times by adding or subtracting their time zone difference from Central Standard Time.)

  • 3:50 p.m. CST (Chicago) — The moon rises in the east-northeast sky.
  • 4:22 p.m. CST — Sunset.  Throughout the evening, the moon rises higher in the eastern sky.
  • 11:30 p.m. CST — The moon begins to move into the penumbra.  Not much darkening is noticed.

December 21, 2010

  • 12:32 a.m. CST — The moon moves into the darker central shadow, the umbra.  The partial phases of the eclipse begins.  As the eclipse progresses, more of the moon grows darker.  The moon appears high in the southern sky during this part of the eclipse.
  • 1:40 a.m. CST — The moon is completely immersed inside the umbral shadow and the best part of the eclipse begins.  For the next 73 minutes, the moon may be illuminated by a soft coppery color, like the image above.  Some sunlight streams through the earth’s atmosphere and is bent into the shadow by the air’s prismatic effects.  The brightness and depth of color will depend on the amount of dust suspended in the Earth’s atmosphere.  Volcanic ash suspended at high altitudes is one factor that can affect the colorful display.
  • 2:53 a.m. CST — The moon begins to exit the umbra and the total phase of the eclipse is finished. 
  • 4:01 a.m. CST — The moon is fully inside the penumbra continuing to exit into bright sunshine.
  • 5:04 a.m. CST — The eclipse is finished.
  • 7:14 a.m. CST — Sunrise
  • 7:31 a.m. CST — Moonset
  • 5:38 p.m. CST — Winter Solstice

The next lunar eclipse visible from North America occurs on June 4, 2012.  The start of the eclipse occurs June 4, 2012, although it completes after moonset.  The next total lunar eclipse visible from the Americas is on the night of April 14/15, 2014.

For more information about lunar eclipses and general sky watching, see the Waubonsie Valley High School Planetarium website.