Here Comes the Sun… and Moon!

Happy equinox, Earthlings! March 20 marks the spring equinox, one of two seasonal markers in Earth’s year-long orbit when the Sun appears to shine directly over the equator, and daytime and nighttime are nearly equal lengths–12 hours–everywhere on the planet.

During the equinoxes, both hemispheres receive equal amounts of daylight. (Image not to scale.)
During the equinoxes, both hemispheres receive equal amounts of daylight. (Image not to scale.) (NASA/GSFC/Genna Duberstein)

It’s the start of astronomical spring in the Northern Hemisphere, meaning more sunlight and longer days. From here until the beginning of fall, daytime will be longer than nighttime as the Sun travels a longer, higher arc across the sky each day, reaching a peak at the start of summer. It’s just the opposite in the Southern Hemisphere, where March 20 marks the fall equinox.

What’s more? The first full Moon of spring will rise tonight, lighting the skies on the equinox. Usually, a full Moon arrives a few days to weeks before or after the equinox. It’s close, but not a perfect match. Tonight’s full Moon, however, reaches maximum illumination less than four hours after the equinox. There hasn’t been a comparable coincidence since the spring equinox in 2000.

When the Moon, on its orbit around Earth, reaches the point farthest from the Sun, we see a full Moon.
When the Moon, on its orbit around Earth, reaches the point farthest from the Sun, we see a full Moon. (NASA/GSFC/Genna Duberstein)

And because the Moon is near perigee, it qualifies as a supermoon–the third and final of 2019. It’s not a big supermoon, so you won’t really be able to see the difference between this full Moon and any other one with your eyes. But keep an keep an eye on the Moon as it rises and creeps above the eastern skyline. A low-hanging Moon can appear strangely inflated. This is the Moon illusion at work.

Super or seemingly not, it’s a rare celestial coincidence to usher in springtime.

Ask an Astronomer: What’s a Supermoon?

“The second supermoon of 2019 happened Feb. 19. The third of 2019 will happen March 19. But what’s a supermoon? We asked NASA astronomer Mitzi Adams what’s really going on here. Here’s her answer!”

Like the orbits of all bodies in the solar system, the Moon’s orbit around Earth is not circular, it has an oval or elliptical shape, with Earth slightly offset from the center. As a result, there are two distance extremes of each orbit: closest approach, known as perigee, and the farthest, or apogee. When the Moon is at closest approach and within a day or so of being full, it is called a supermoon because the Moon will be at its brightest and largest.

For the supermoon on Feb.19, the Moon will be full only six hours after it reaches the perigee distance of its orbit, making it the brightest and largest full Moon of the year. A supermoon also occurred in January with a slightly more distant perigee, a mere 362 miles (583 kilometers) farther away, but 14 hours after the full Moon. However, January’s supermoon included a total lunar eclipse seen in all of North and South America. The third and last supermoon of the year will happen March 19, when the perigee distance will be reached a day and five hours before the full Moon (see the table below for details).

Date Perigee Distance Time Before or After Full Moon
Jan. 21 222,043 miles (357,344 km) 15 hours after
Feb. 19 221,681 miles (356,761 km) 6 hours before
March 19 223,308 miles (359,380 km) 1 day, 5 hours before
A total lunar eclipse accompanied the first in a trilogy of supermoons in 2019.
A total lunar eclipse accompanied the first in a trilogy of supermoons in 2019. Credit: NASA/MSFC/Joe Matus

To watch tonight’s supermoon, or any full Moon, simply look for the Moon to rise in the east as the Sun sets in the west. The Moon will look extremely large when it rises and sets. This “Moon illusion” happens when the Moon is close to the horizon and there are objects within our line of sight such as trees or buildings. Because these relatively close objects are in front of the Moon, our brain is tricked into thinking the Moon is much closer to the objects that are in our line of sight. At Moon rise or set, it only appears larger than when it is directly overhead because there are no nearby objects with which to compare it. You can check this. When the Moon rises, hold a coin at arm’s length so that the coin covers the Moon. Repeat this throughout the evening and you will see that the Moon’s size does not change.

As it rises on Feb. 19, the Moon will be in the constellation of Leo. However, since the Moon is so bright, you may have trouble seeing the bright star Regulus, which is at the end of the “backwards question mark” that makes Leo easy to spot.

Regulus
Credit: Stellarium

Looking more or less directly overhead, you could see the famous constellation Orion the Hunter with bright stars Betelgeuse, a reddish star, and Rigel, a bluish star. With a telescope or binoculars, you might be able to pick out the Orion nebula just below the belt stars of Orion, Alnitak, Alnilam, and Mintaka.

Great Nebula in Orion
Credit: Stellarium

To the west of Orion you should be able to spot reddish Mars.

Mars
Credit: Stellarium

As we observe this supermoon, keep in mind that 2019 marks the 50th anniversary of a great technological feat ­­– humans travelled to the Moon, walked on its surface and returned safely to Earth. Twelve people walked on the Moon. Neil Armstrong and Buzz Aldrin were the first two, but let us not forget the other ten: Alan Bean, Charles “Pete” Conrad, Edgar D. Mitchell, Alan Shepard, Dave Scott, James Irwin, John Young, Charles Duke, Eugene “Gene” Cernan and Harrison Schmitt. These men, along with the command module pilots Michael Collins, Dick Gordon, Stu Roosa, Al Worden, Ken Mattingly, Ron Evans and the multitudes of support staff back on Earth, fulfilled a dream of exploring our nearest neighbor in space. As NASA and its commercial and international partners plan to return the Moon over the next decade with a long-term continued presence, the list of Moon walkers will surely include women, as well.

A good resource for more information on supermoons may be found here: https://solarsystem.nasa.gov/moons/earths-moon/what-is-a-supermoon/.

Constellation screenshots are from Stellarium, a planetarium software package that is accompanied by a GNU General Public License

Mitzi Adams is a solar scientist in the Heliophysics and Planetary Science Branch at NASA’s Marshall Space Flight Center.

International Observe the Moon Night

Did you know there is a night set aside each year to observe Earth’s closest celestial neighbor, the Moon? International Observe the Moon Night has been held annually since 2010 and is a worldwide celebration of the Moon and lunar science. Each year, the celebration is held in September or October when the Moon is in the first quarter because it is visible in the afternoon and early evening hours when most events are held.International Observe the Moon Night 2018 graphic

If you live in or near Huntsville, Alabama, you can join our local celebration Saturday, Oct. 20, from 5:30-8:30 p.m. CDT at the U.S. Space & Rocket Center’s Davidson Center. The event is hosted by NASA’s Marshall Space Flight Center’s Planetary Missions Program. Members of the public are encouraged to attend and it is free. The event will include lunar and solar system exploration exhibits and a variety of hands-on activities for children and adults. Don’t live in Huntsville? No worries! There are events held worldwide and you can find a list of them here.

Full moon.As you are gearing up for your own International Observe the Moon Night celebration, check out these fun facts about the Moon.

  • The Moon is Earth’s satellite and orbits the Earth at a distance of about 384,000 km or 239,000 miles.
  • The Moon makes a complete orbit around the Earth in 27 Earth days. The Moon keeps the same side or face, towards the Earth during its orbit.
  • More than 100 spacecraft have been launched to explore the Moon. It is the only celestial body beyond Earth visited by human beings.
  • Astronauts brought back a total of 842 pounds of lunar rocks and soil to Earth.
  • The 50th anniversary of the Apollo 11 landing on the Moon will be next summer on July 20, 1969. Neil Armstrong was the first human to set foot on the Moon, followed by Buzz Aldrin.

Astronaut Edwin E. Aldrin Jr., lunar module pilot of the first lunar landing mission, poses for a photograph beside the deployed United States flag during an Apollo 11 extravehicular activity (EVA) on the lunar surface. Can’t get to an event this weekend? You can still go outside no matter where you live and look at our incredible neighbor. For a list of Moon phases and other cool Moon facts, check out the NASA Science Earth’s Moon page.

Total Lunar Eclipse

By Mitzi Adams, NASA Marshall solar scientist

Last August, citizens and visitors to the United States of America had a rare opportunity to see a total solar eclipse, because the path of totality ranged from Oregon to South Carolina, essentially bisecting the country. But alas, the total lunar eclipse happening on Friday, July 27, will totally miss the United States. Being able to observe the Moon totally immersed in Earth’s shadow depends mostly on whether it is dark at the time the eclipse happens, so about half the Earth would be in the right place to see the eclipse, weather permitting of course. This time, residents of Europe, Africa, Asia, Australia, and parts of South America will be so lucky. In contrast, totality for a solar eclipse is very narrow and only a very small portion of Earth is in the shadow of the Moon. For the August 2017 eclipse, only those within an approximately 100 km (63 miles) wide path saw the Sun totally eclipsed.

So what happens when there is a lunar eclipse? Unlike the solar variety, Earth blocks the Sun for a lunar eclipse. For the lunar eclipse to happen, the Moon’s phase must be “full”, which means that the orbiting Moon is opposite the Sun, with Earth in between. When the Sun sets in the west, the Moon rises in the east — and this event happens once a “moonth” (or month). But a lunar eclipse does not happen every month. Why is that?

The Moon is seen here during the January 2018 lunar eclipse, setting in the western horizon, not yet in totality.
The Moon is seen here during the January 2018 lunar eclipse, setting in the western horizon, not yet in totality.
Image credit: NASA/Alphonse Sterling

Well, now we get into more tricky territory. Let’s try a thought experiment. Draw a line between the centers of the Sun, Earth, and Moon. This line is part of a plane that describes how Earth orbits the Sun, called the plane of the ecliptic. The Moon orbits Earth, only its orbit is tilted with respect to the plane of the ecliptic, sometimes the Moon is above the plane, sometimes it is below the plane. Only when the Moon’s orbit lines up with the ecliptic plane do we have a chance for an eclipse. If the phase of the Moon is “full” when this happens, we have a lunar eclipse. If the phase of the Moon is “new,” we have a solar eclipse. Sometimes the orbital planes do not line up exactly, in those cases, we would have partial eclipses.

Fred Espenak, click here for more info on Lunar Eclipse Geometry.

The July 27 eclipse is somewhat special because the length of totality will be the longest of this century at one hour, 43 minutes. Why? Several reasons. The Moon will be at apogee, or at the farthest distance from Earth (406,000 km or 252,000 mi) possible for our Moon. Objects in orbit around Earth move slower the farther away they are, which means it will take longer for the Moon to traverse the width of Earth’s shadow. In addition, the Moon will be almost exactly on that line that connects Sun, Earth, Moon, also increasing the length of time the Moon will spend in the umbral (darkest) part of Earth’s shadow. Finally, Earth reached its greatest distance from the Sun (aphelion) quite recently (July 6), meaning that Earth’s shadow on July 27 will be close to the largest it can be, adding even more distance (and time) to the Moon’s shadowy traverse.

This image is of the full Moon before the January 2018 lunar eclipse.
This image is of the full Moon before the January 2018 lunar eclipse.
Image credit: NASA Marshall/Alphonse Sterling

The partial phase of the eclipse will begin at 18:24 UT, with totality beginning at 19:30 UT (see the NASA time zone page for help with conversion to your local time and official U.S. time). Totality will be over at 21:13 UT and the partial phase ends at 22:19 UT. Viewing a lunar eclipse does not require a telescope or even special glasses; however, while waiting for totality to begin, which is marked by a reddish-brown color to the Moon, a telescope could be used to view two planets that are in the evening sky. Mars will be visible, and should be pretty bright since there is currently a dust storm covering the entire planet. So the telescope will not see any surface detail here, but the redness of the planet will contrast well with the reddish hue of a totally eclipsed Moon. Saturn will be visible to the west of Mars — and even binoculars will resolve the rings, but a telescope could provide more detail. For all observers, find the full Moon in the night sky, Mars will be close to and below (south of) the Moon, a bright reddish “star-like” object. For detailed information about this eclipse, click here.

When the Earth, Moon and Sun Align

By Kevin Matyi

On Aug. 21, 2017, a total solar eclipse will cross the full continental United States along a narrow, 70-mile-wide path from Oregon to South Carolina.

The last total eclipse in the U.S. was in 1979. And the last total solar eclipse that crossed the entire continental U.S. happened in 1918. But why? Why has it been 99 years, and why have the intervening partial and even total eclipses caught only parts of the country?

In short, celestial geometry is complicated but predictable. Much like many other aspects of the cosmos, it is cyclic.


Need a minute to catch up? Go ahead. We’ll wait.  Credit: NASA

Eclipse cycles arise from a natural harmony between three motions of the moon’s orbit. We call them “months” due to their repetitive nature.

The synodic month governs the moon’s phases. It’s measured by the time it takes to go from one new moon to the next, which takes about 29 ½ days. In that time, the moon rotates once around its own axis and goes around Earth once.

From the perspective of a solar eclipse, the new moon phase is important. It’s the point in the moon’s orbit when it passes between Earth and the sun. A total solar eclipse can only happen at a new moon, and only when the other types of movement line up as well.

When the moon, on its orbit around Earth, reaches the point closest to the sun we can’t see the moon reflecting sunlight, so it appears dark. This is the new moon.
Credit: NASA/Genna Duberstein

New moons happen once a month, but we don’t see eclipses every month because the moon’s orbit is tipped by about five degrees from Earth’s orbit around the sun. On most months, the new moon casts its shadow either above or below Earth, making a solar eclipse a rare treat.

The moon’s tilted orbit meets the sun-Earth plane at two points called nodes. A draconic month is the time it takes the moon to return to the same node. The moon’s orbital nodes drift over time, which is why a single location on Earth’s surface might wait hundreds of years between total eclipses.


As the moon orbits Earth, it also wobbles up and down, making total eclipses rarer than they otherwise would be.  Credit: NASA

The moon’s path around Earth is not a perfect circle, which means the distance between us and the moon changes all the time. When the moon is closest to Earth in its orbit we call it perigee, and apogee when it’s farthest. This change in distance gives rise to the anomalistic month, the time from perigee to perigee.

The farther away the moon is from Earth, the smaller it appears. When the moon blocks all of the sun’s light, a total eclipse occurs, but when the moon is farther away — making it appear smaller from our vantage point on Earth — it blocks most, but not all of the sun. This is called an annular eclipse, which leaves a ring of the sun’s light still visible from around the moon. This alignment usually occurs every year or two, but is only visible from a small area on Earth.

When moon is too small to cover the entire sun’s disk, a ring or “annulus” of bright sunlight surrounds the moon.
Credit: NASA/Cruikshank

A total solar eclipse requires the alignment of all three cycles — the synodic, anomalistic, and draconic months. This happens every 18 years 11 days and 8 hours, a period known as a saros.

One saros period after an eclipse, the sun, moon and Earth return to approximately the same relative geometry, a near straight line, and a nearly identical eclipse will occur. The moon will have the same phase and be at the same node and the same distance from Earth. Earth will be nearly the same distance from the sun, and tilted to it in nearly the same orientation.

The extra eight hours is the reason why successive eclipses in the same saros cycle happen over different parts of Earth. Earth rotates an extra third of the way around its axis. Each total solar eclipse track looks similar to the previous one, but it’s shifted 120 degrees westward.

Earth turning on its axis impacts where total solar eclipses occur.
Credit: Espenak & Meeus

During this year’s total solar eclipse, anyone within the path of totality will be able to see one of nature’s most awe-inspiring sights. This path, where the moon will completely cover the sun and the sun’s tenuous atmosphere — the corona — can be seen, will stretch from Salem, Oregon to Charleston, South Carolina. Observers outside this path will still see a partial solar eclipse where the moon covers part of the sun’s disk. A total solar eclipse presents the rare opportunity to observe the corona and chromosphere, and eclipse observations are important for understanding why sun’s atmosphere is 1 million degrees hotter than its surface.

For more information on the eclipse, where to view it and how to view it safely (wear eye protection!), visit https://eclipse2017.nasa.gov/sun.

Make sure to wear eye protection when you go out to look at the eclipse!
Credit: NASA/Bill Ingalls

 

NASA’s Marshall Center Celebrates International Observe the Moon Night

On Saturday, Oct. 8, from 5:30 to 9 p.m. the public and media are invited to attend the 6th annual International Observe the Moon Night celebration, hosted by NASA’s Marshall Space Flight Center at the Davidson Center for Space Exploration at the U.S. Space & Rocket Center, both in Huntsville, Alabama.

The free event will include moon-related and solar system exhibits and hands-on activities for children and adults. Activities will include an out-of-this-world photo booth, airbrush tattoo station, and a meet and greet with Janet Ivey from “Janet’s Planet” on PBS. Live music will be provided by DJ Shell. Several large amateur telescopes will be set up to view the moon, stars, and other visible planets. Visitors can also take a virtual 3-D trip to the moon with the astronomy van, offering a magnified, command-module-like view of the lunar surface. The family movie, “Home,” will begin at dusk.

A panel discussion titled: “Planets, Moons & Meteorites Oh My!” will begin at 7:15 p.m. in the National Geographic Theater and will feature Marshall speakers Mitzi Adams, solar physicist; Dr. Barbara Cohen, planetary sceintist; Dr. Bill Cooke, manager of the Meteoroid Environments Office; and Dr. Renee Weber, planetary scientist.

The U.S. Space & Rocket Center is the official visitor center for NASA’s Marshall Space Flight Center.

For more information on NASA’s Marshall Space Flight Center, visit https://www.nasa.gov/centers/marshall/home/index.html.

For more information on the U.S. Space & Rocket Center, visit http://rocketcenter.com.

Full Moon Photographed From Apollo 11 Spacecraft
Full Moon Photographed From Apollo 11 Spacecraft

 

NASA Marshall Team Observing and Taking Questions about Upcoming Lunar Eclipse

In the Americas on Sunday night, Sept. 27, we will be treated to a lunar eclipse with its beautiful orange and red colors, a prelude to the fall color of leaves in Earth’s Northern Hemisphere. This eclipse will straddle midnight on Sept. 27, depending on where you live. If observing close to the Greenwich Meridian in the U.K., the eclipse begins just after midnight, in the morning of Sept. 28 at 00:11 Universal Time (UT). But Sept. 28, 00:11 UT, translates to Sept. 27, 8:11 p.m. EDT and 7:11 p.m. CDT.

All of the Americas are well placed to see this eclipse. The table below lists eclipse timing details. If you have questions about this eclipse, you will have an opportunity to ask experts at NASA’s Marshall Space Flight Center in Huntsville, Alabama!

About Lunar Eclipses

Throughout human culture, lunar eclipses have been viewed with awe and sometimes fear. Today we know that a total lunar eclipse happens when the full moon passes through the darkest part of Earth’s shadow, the umbra. Near the beginning and ending of an eclipse, the moon moves through a less dark portion of the shadow, called the penumbra, which is hardly visible. The partial phase begins (ends) when the moon enters (leaves) the umbra. When the moon has completely passed into Earth’s shadow, the eclipse is in its total phase.

The length of the eclipse is dependent on the position of the moon along an Earth-sun line. The longest eclipses occur when the moon is directly in line with Earth and sun. The shortest eclipses are when the moon is either above or below that line. The moon does not make its own light; it only reflects the light it receives from the sun. During a lunar eclipse, the moon appears less and less bright as sunlight is blocked by Earth. As totality approaches, more and more of the sunlight reaching the moon does so indirectly; it is refracted around the “edges”of Earth, through our atmosphere.

Because the light is going through the Earth’s atmosphere, almost all colors except red are “filtered” out and the eclipsed moon appears reddish or dark brown. The filtering is done by particulates in the atmosphere; when there have been a lot of fires and/or volcanic eruptions, lunar eclipses will be darker and redder. This eerie but harmless effect has earned the tongue-in-cheek nickname “blood moon.”

Supermoon – No, not SuperMan, SuperMoon

The moon orbits Earth in an ellipse that is almost circular (as is the orbit of most planets around the sun), but because the orbit is elliptical, sometimes the moon is closest to Earth (perigee) and sometimes farthest from Earth (apogee). The position of the moon for the Sept. 27/28 eclipse is very close to perigee, so it will appear a bit larger in the sky than a month from now.

You could measure this, with simple items from around the house. Try using a coin (or button or marble) at arm’s length to block the full moon, do this at a particular time, then try it again for the next several months at full moon, at the same time. If the coin (or other item) covers the moon on Sept. 27 (2015), it will more than cover the moon at later times, proving that the moon is smaller and thus farther away. Also, because the moon is at perigee (close approach to Earth) a supermoon will cause slightly larger tidal effects.

How to View and Ask Questions

NASA’s Marshall Space Flight Center will offer a live Ustream view of the lunar eclipse on the Sept. 27, the night of the event, via the Marshall Center Ustream feed. The live feed is an alternative for observers caught with bad weather or light-polluted night skies.

Mitzi Adams, a solar physicist at Marshall, will talk about what viewers are seeing on screen and answering questions from Twitter. To ask a question, use the hashtag: “AskNASA.”

eclipse

Ask an Astronomer About the Shortest Lunar Eclipse of the Century on April 4

On Saturday morning, April 4, 2015 not long before sunrise, the bright full moon over North America should turn a lovely shade of celestial red during a total lunar eclipse. Join NASA astronomer Mitzi Adams as she takes questions via Twitter @NASA_Marshall. For Twitter questions, use the hashtag #eclipse2015. The question and answer via Twitter will begin at 6 a.m. EDT and continue through the end of the eclipse (approximately 8:00 a.m. EDT on April 4).

The lunar eclipse will be visible from all parts of the United States.  Eastern North America and western South America can see beginning stages of the partial umbral eclipse low in the west before sunrise April 4, whereas middle Asia (India, western China, mid-Asian Russia) can view the ending stages of the partial umbral eclipse low in the east after sunset April 4. Greenland, Iceland, Europe, Africa and the Middle East won’t see this eclipse at all. A world map of eclipse visibility is available here. The total eclipse will last only five minutes. You can find more information  here.

This image shows the Dec. 20, 2012 total lunar eclipse, as seen from Sagamihara, Japan.
This image shows the Dec. 20, 2012 total lunar eclipse, as seen from Sagamihara, Japan.

NASA Book Available For Visually Impaired To Learn About Moon

NASA has released a new book for visually impaired people to experience the wonders of the moon. Called “Getting a Feel for Lunar Craters,” the 17-page book features Braille and tactile diagrams of the lunar surface, craters and peaks.

The book was created and funded by NASA’s Lunar Science Institute, or NLSI, at Moffett Field, Calif. The author is David Hurd, a space science professor at Edinboro University of Pennsylvania in Edinboro,PA.

“This book is one giant step for humankind, making lunar science,” NLSI Director Yvonne Pendleton said. “NASA is committed to the development of resources to bring lunar science into the world of those who cannot see.”

To obtain a free copy of “Getting a Feel for Lunar Craters,” visit: http://lunarscience.nasa.gov/tactile

 NLSI is a virtual organization that enables collaborative, interdisciplinary research in support of NASA lunar science programs.The institute uses technology to bring scientists together around the world and comprises competitively selected U.S. teams and several international partners. NASA’s Science Mission Directorate and the Exploration Systems Mission Directorate in Washington fund NLSI, which is managed by NASA’s Ames Research Center at Moffett Field, Calif. For more information about the NLSI, visit: http://lunarscience.nasa.gov

Biggest Full Moon in 20 Years!

Stargazers are in for a big treat this weekend!

On Mar. 19 the full moon will brighten the night sky as the biggest full moon seen in almost two decades.  The moon will be at perigee, its closest point to Earth — only 221,565 miles (356,575 km) away.


The moon’s orbit around Earth is not circular — it’s elliptical.  One part of the orbit,
the perigee, is closer to the Earth than the other, the apogee. The image is NOT to
scale — the eccentricity of the moon’s orbit has been exaggerated.

The last time the full moon coincided with an extreme perigee was Mar. 8, 1993 when it was a distance of 221,536 miles (356,528 km) from the Earth.

This Saturday night, the moon will appear 14 percent bigger and 30 percent brighter in the sky than lesser full moons — when the moon is farthest from the Earth. But to the casual observer, it may difficult to tell the difference.

For the best viewing — and dependent upon clear skies, of course– look when the moon is near the horizon at sunset. The orbital geometry combined with the moon’s location near the horizon, put in scale next to buildings and trees, will combine to produce an awesome sight.


Full moon over space shuttle Endeavour in 2008.

If you take some great images of this weekend’s full moon, we’d love to feature them on the Marshall Space Flight Center Facebook page! http://www.facebook.com/nasa.marshall#!/nasamarshallcenter