A solar eclipse is when the Moon lines up between Earth and the Sun such that the Moon either partially or completely blocks out the Sun.

Photo Credits: Fred Espenak (L) / Stephan Heinsius (R)


While the sun is the main focus of a solar eclipse, our moon plays the most crucial role in creating this unique event.

Solar Eclipse
Lunar Eclipse

This video tutorial explains what happens during a total solar eclipse and a partial eclipse and how often they both occur. It also explains how a solar eclipse differs from a lunar eclipse, and gives a helpful tip on how to remember the difference. In addition, the video examines how the two parts of the moon’s shadow, the umbra and penumbra, affect how we see an eclipse on the Earth, and illustrates the surprising true shape of the umbra. The video concludes by highlighting how data from NASA’s Lunar Reconnaissance Orbiter has helped us better map a solar eclipse’s path of totality. Visualizations included in this piece showcase the August 21, 2017 total solar eclipse happening in the United States.

This video explains how our moon creates a solar eclipse, why it’s such a rare event to see, and how data from NASA’s Lunar Reconnaissance Orbiter has enhanced our ability to map an eclipse’s path of totality.Credit: NASA, Music Provided By Killer Tracks: “Bring Me Up” – Kampe Wikstrom



  • A solar eclipse occurs when the moon passes between the Sun and the Earth, and the moon fully or partially blocks the Sun as viewed from a location on Earth.
  • The longest duration for a total solar eclipse is 7.5 minutes.
  • The shortest total solar eclipse in the 21st Century will be 1:06 on May 31, 2068, visible in New Zealand and Australia.
  • Eclipse shadows travel at 1,100 miles per hour at the equator and up to 5,000 miles per hour near the poles.
  • The maximum number of solar eclipses (partial, annular, or total) is 5 per year.
  • A total eclipse can only happen during a new moon.
  • The shortest total lunar eclipse in recorded history was in 1529 and lasted only 1 minute and 41 seconds.
  • Nearly identical eclipses (total, annual, or partial) occur after 18 years and 11 days, or every 6,585.32 days (Saros Cycle).
  • A total solar eclipse is not noticeable until the Sun is more than 90 percent covered by the Moon. At 99 percent coverage, daytime lighting resembles local twilight.
  • The width of the Moon’s shadow is at most 170 miles wide.
  • There are at least 2 solar eclipses per year somewhere on the Earth. However, since the Earth is mostly water, and weather (or a single cloud) can block your view, it is still a rare event—especially to see a total solar eclipse.
  • Total solar eclipses happen about once every year or two.
  • The Sun’s corona (“crown”) can ONLY be seen from the Earth’s surface during a total eclipse.
  • One can see the corona or atmosphere of the Sun safely with naked eyes only during a total solar eclipse.
  • Gemini 12 witnessed a total solar eclipse in 1966 and the International Space Station, in 2006.
  • The alignment of Sun, Venus, and Earth comes in pairs that are eight years apart but separated by over a century.
  • There will be 36 solar eclipses from 2001-2025, of which 15 will be total eclipses on some part of Earth’s surface – a little less than the average of one a year.
  • Transits and eclipses are rare celestial events but the Transit of Venus is the rarest.
  • A transit of Venus occurs when Venus passes directly between the Sun and the Earth.
  • The most recent pair was in June 2004 and June 2012.
  • The last transit of Venus pair before 2012 happened in December 1874 and December 1882.
  • After 2012, subsequent Transit of Venus pairs will be in December 2117 and December 2125.
  • Transits of Venus allow astronomers to calculate more accurately the distance of Venus from the Sun, and subsequently the distances of other planets.
  • The Hubble Space Telescope will be aimed at the moon to detect dips in brightness during the 2012 transit of Venus.
  • The Solar Dynamic Observatory captured the Sun and Venus during the 2012 transit in unprecedented detail.


Total Solar Eclipse
credit: NASA/GSFC/ Fred Espenak
lunar-eclipse-Johnson Space Center2
Image Credit: Stefan Seip
Credit: Stefan Seip
Lunar Eclipse
Credit: NASA KSC
This image is a composite photograph that shows the progression of the total solar eclipse over Madras, Oregon.

Annular Solar Eclipses

An annular eclipse happens when the moon is farthest from Earth.

Because the moon is farther away from Earth, it seems smaller and does not block the entire view of the sun.

Image Credit: Stefan Seip

Photo Credit: Stefan Seip

Partial Solar Eclipses

When the Sun is completely blocked out we called it a total solar eclipse, and often this is what people think of with an eclipse. But a partial eclipse can be just as exciting.

When the Moon comes just shy of completely blocking out the Sun a bright ring or annulus is visible.
This is a special kind of partial eclipse, an annular eclipse.


2017 Total Solar Eclipse - Partial View

This composite image of seven pictures shows the progression of a partial solar eclipse near from Ross Lake, Northern Cascades National Park, Washington on Monday, Aug. 21, 2017. The second to the last frame shows the International Space Station, with a crew of six onboard, in silhouette as it transits the Sun at roughly five miles per second. A total solar eclipse swept across a narrow portion of the contiguous United States from Lincoln Beach, Oregon to Charleston, South Carolina. A partial solar eclipse was visible across the entire North American continent along with parts of South America, Africa, and Europe. Photo Credit: (NASA/Bill Ingalls)


Lunar Eclipses

During a lunar eclipse, Earth gets in the way of the sun’s light hitting the moon. That means that during the night, a full moon fades away as Earth’s shadow covers it up.

The moon can also look reddish because Earth’s atmosphere absorbs the other colors while it bends some sunlight toward the moon. Sunlight bending through the atmosphere and absorbing other colors is also why sunsets are orange and red. During a total lunar eclipse, the moon is shining from all the sunrises and sunsets occurring on Earth!

NASA TV provided coverage of Super Blue Moon Lunar Eclipse on Jan. 31. The full moon was the third in a series of “supermoons,” when the Moon is closer to Earth in its orbit — known as perigee — and about 14 percent brighter than usual. It was also the second full moon of the month, commonly known as a “blue moon.” As the super blue moon passed through Earth’s shadow, viewers in some locations experienced a total lunar eclipse. While in Earth’s shadow, the moon also took on a reddish tint – which is sometimes referred to as a “blood moon.” Credit: NASA


Studying the Sun during total solar eclipses helps scientists understand the source and behavior of solar radiation that drives space weather near Earth, which can affect the health of astronauts in space and the durability of materials used to build spacecraft.

Similar data will be important in planning NASA’s return of astronauts to the Moon in 2024 and eventual crewed missions to Mars.

NASA - What can you see during a total solar eclipse?

Eclipses also set the stage for historic science.

NASA took advantage of the Aug. 21, 2017 eclipse by funding 11 ground-based scientific studies. As our scientists prepare their experiments for next week, we’re looking back to an historic 1860 total solar eclipse, which many think gave humanity our first glimpse of solar storms — called coronal mass ejections — 100 years before scientists first understood what they were.

Scientists observed these eruptions in the 1970s during the beginning of the modern satellite era, when satellites in space were able to capture thousands of images of solar activity that had never been seen before. But in hindsight, scientists realized their satellite images might not be the first record of these solar storms. Hand-drawn records of an 1860 total solar eclipse bore surprising resemblance to these groundbreaking satellite images.

CREDITS: NASA’s Goddard Space Flight Center • Music credits: ‘Electricity Wave’ by Jean-François Berger [SACEM] and ‘Solar Winds’ by Ben Niblett [PRS], Jon Cotton [PRS]


Click on an image below to view larger.

Eclipse Highlights


CREDIT: Exploratorium

Eclipse flyer by NASA


How can I view the eclipse safely?

The most important this to remember is that it is never safe to look directly at the uneclipsed or partially eclipsed sun without the proper safety glasses. The only time you can look at the sun without safety glasses is during the brief moments of totality. There is a lot of great information at NASA and the AAS (American Astronomical Society) about how to safely look directly at the sun as well as indirectly. For all these points and more check out:

NASA eye safety

You don’t necessarily need fancy equipment to watch one of the sky’s most awesome shows: a solar eclipse.

@DawnSunrise1 shows a smart & easy way to have a hands-free multiple pinhole camera setup! Brilliant!!

With just a few simple supplies, you can make a pinhole camera that allows you to view the event safely and easily.

Before you get started, remember: You should never look at the sun directly without equipment that’s specifically designed for solar viewing. Do not use standard binoculars or telescopes to watch the eclipse, as the light could severely damage your eyes. Sunglasses also do NOT count as protection when attempting to look directly at the sun.

Stay safe and still enjoy the sun’s stellar shows by creating your very own pinhole camera. It’s easy!

Eclipse projector

CREDIT: Music Credit: Chic to Chic by Piero Piccioni • Video credit: NASA’s Goddard Space Flight Center/SVS

Eclipse 2017 Pinhole Projector (and hydration for the hot sun!)
Eclipse 2017 Pinhole Projector (and hydration for the hot sun!)
Eclipse 2019 & 2020 Pinhole Projector
Eclipse 2019 & 2020 Pinhole Projector

CREDIT: Music credit: Apple of My Eye by Frederik Wiedmann • Video credit: NASA’s Goddard Space Flight Center/SVS

Eclipse mirror