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The partially eclipsed moon is seen next to the Washington monument in 2010. (Image courtesy NASA/Bill Ingalls)

The first lunar eclipse in almost two and a half years occurs on the morning of May 26. Unfortunately, we’ll only see a partial eclipse as the moon sets in the west before totality begins.

A lunar eclipse happens when the moon enters Earth’s shadow. It’s a pretty common misconception to believe that the phases of the moon are caused by the shadow of the Earth. That is not the case.

Observe the position of the sun relative to the moon the next time you see a lunar crescent and you’ll notice that the sunlit portion of the moon is facing the sun, and the shadowed region is opposite the sun.

The same side of the moon always faces Earth. As the relative positions of sun and moon change, so does the lunar phase. When the sun and moon are on opposite sides of the Earth, we see a full moon.

Eclipses can only happen at new moon (for solar eclipses) or full moon (for lunar eclipses). Eclipses happen regularly, but not every month because the moon’s orbit is tipped about five degrees to Earth’s orbital plane.

The eclipse on May 26 is special as the moon will be near perigee, its closest point to Earth in its orbit. When the moon is at perigee when it is full, we call it a “supermoon.” We also name full moons every month, and Mays full moon is typically called the “flower moon.”

When the moon enters the deepest part of the Earth’s shadow, called the umbra, it appears reddish in hue. This redness is caused by light filtering through the edges of Earth’s atmosphere.

Think about how the sky appears red at sunrise or sunset. The moon in eclipse is reflecting all the sunrises and sunsets of the Earth at once. We often refer to this phenomenon as a “blood moon.”

Put all of these names together and you get a “super flower blood moon.”

The eclipse begins at 4:47 a.m. when the moon enters the outer region of Earth’s shadow, known as the penumbra and ends, for us, when the moon sets at about 6:25 a.m. The eclipse will continue until about 9:50 a.m. If you want to see the entire eclipse, there are plenty of livestreams to choose from.

The Morning Sky

The planetary lineup continues in the morning sky with Pluto, Saturn, Jupiter, Neptune and Uranus all rising before the sun. Only Saturn and Jupiter are visible without optical aid, with Jupiter appearing twice as large and 15 times brighter than Saturn. Vega, the star that sets the standard for the stellar magnitude scale, is directly overhead two hours before sunrise.

The Evening Sky

Mercury appears above brighter Venus low in the west just after sunset. Higher in the western sky as the sun sets is Mars, which added to its all-robot population last week with the landing of the Chinese rover “Zhurong.” The star Antares, whose name means “rival of Mars”, rises in the east around 9:30 p.m. and appears brighter than the red planet.

Dan Price is a NASA/JPL Solar System Ambassador and informal educator. He leads the Night Sky Tours at Josephine Sculpture Park. He has travelled over 45 billion kilometers in orbit around the sun. Have a question about astronomy or space science? Send an email to dan@starpointestudio.com and it might be featured in a future column.

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