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.

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.

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.

Marshall Scientists to Take Questions via Twitter About the Partial Solar Eclipse

On Thursday, October 23, 2014, from 5:00pm – 6:00pm CDT, Marshall scientists Mitzi Adams, Sabrina Savage and Alphonse Sterling will be taking questions about the partial solar eclipse on the NASA Marshall Twitter account: http://twitter.com/NASA_Marshall, using the hashtag #askNASA.

At approximately 4:54 p.m. CDT, the eclipse will begin, with maximum eclipse occurring at 5:54 p.m. The partial eclipse will end at 6:49 p.m. CDT, which is after 6:02 pm sunset in Huntsville.

The magnitude of this eclipse, that is the fraction of the Sun’s diameter covered by the moon, will be 44%.  The obscuration, or the fraction of the Sun’s area occulted by the moon, will be 32%.The Sun will be in the constellation Virgo, with Saturn low on the horizon after sunset, and Mars will be farther to the east.

A live Ustream feed of the partial solar eclipse will be available here.

Local Viewing Opportunity

Von Braun Astronomical Society (VBAS) is partnering with the U.S. Space & Rocket Center® on Thursday, October 23, 2014, from 5 p.m. until sundown, for the observance of the partial solar eclipse. Join astronomers in the Davidson Center for Space Exploration parking lot to discuss the phenomenon and observe the solar eclipse through the telescopes. There will be visible-light viewing telescopes to see any sunspots, and special telescopes with hydrogen-light viewing in order to see the prominences at the edge of the sun.

The telescopes are equipped with filters for safe viewing of the sun.  Never look at the Sun directly!  Attempting to look directly at the sun without such special filters is harmful to the eyes.
This event is free and open to the public.

 

Stay ‘Up All Night’ to Watch the Lunar Eclipse!

Spring is here and ready to capture the world’s attention with a total lunar eclipse. The eclipse will begin early on the morning of April 15 at approximately 2 a.m. EDT. If you have questions about the eclipse, this will be your chance!

NASA will host two events for NASA moon experts to answer your questions. On Monday, April 14 from 2-3 p.m. EDT, NASA planetary scientist Renee Weber will take your questions via a Reddit AMA (Ask Me Anything). The Reddit page will be live on April 14 at approximately 1:45 p.m. EDT. 

NASA astronomer Mitzi Adams and astrophysicist Alphonse Sterling will also answer questions in a live web chat, beginning on April 15 at 1 a.m. EDT and continuing through the end of the eclipse (approximately 5 a.m. EDT).  The chat module will go live on this page at approximately 12:45 a.m. EDT.

nasa_lunar1

Lunar Eclipse, Sprinkled With Fireballs


The 2010 solstice lunar eclipse is one for the books, but check out these images from two cameras in the Canadian all-sky meteor camera network.These cameras are similar to the ones used for observation at NASA’s Marshall Space Flight Center: all-sky, black-and-white, and detecting bright meteors, or fireballs. Below are two stacked images of the eclipse:


Stacked image of the eclipse using images taken every five minutes from McMaster University
between 6:32 and 9:32 UT.


A similarly stacked image, combining pictures every five minutes between 5:27-9:37;
it was taken from Orangeville, ON, Canada.

Just as a reminder, the eclipse event timings in UT were:

  • Partial begins: 6:33
  • Total begins: 7:41
  • Mid eclipse: 8:17
  • Total ends: 8:53
  • Partial ends: 10:01

 
So both cameras captured the full moon as it normally appears, then imaged it as it was eclipsed through the partial and total phases. Unfortunately, bad weather rolled in before the eclipse ended!

The Canadian cameras also detected meteors during the eclipse. Here are a few good ones:

The following two images were also taken from McMaster and Orangeville at about 7:38 UT, just before the total eclipse began, but after the partial eclipse had started. These pictures show an image of a meteor fairly close to the moon in the field of view.




The following three images were recorded from Elginfield, ON, Canada, McMaster, and Orangeville, respectively, at about 9:00 UT, just after the total eclipse phase ended, but before the partial eclipse ended. This meteor ablated by a height of 83 kilometers, or 52 miles.



Images courtesy of the Meteor Physics Group at the University of Western Ontario in London, ON, Canada
Text courtesy of  Danielle Moser, NASA’s Marshall Space Flight Center, Meteoroid Environment Office

Cloudy Skies? You Can Still Watch the Lunar Eclipse!

Cloudy skies over much of the U.S. might make for challenging viewing tonight for the solstice lunar eclipse.


This screenshot shows a view of the skies over Marshall Space Flight Center in
Huntsville, Ala., at approximately 6:45 p.m. on Dec. 20. (See Current View)

To help work around the mercurial weather, here’s a list of web sites that are offering live web views. Many of these are located in parts of the country where the weather is clear – and you can still check out the Marshall Space Flight Center Web cam. We’ve had some breaks in the clouds, and we’re hoping for the best as the eclipse time draws closer. Check back on this page throughout the evening for added links. Happy viewing!

List of links – please check individual sites for their viewing times and instructions:

› SpaceVidCast Lunar Eclipse Coverage→
› WPBT2/Miami Science Museum→
› Lunar Eclipse by Coaster Storm’s Weather Center→
› South Florida Amateur Astronomers Association & The Fox Observatory→
› Columbus State University→
› Rothney Astrophysical Observatory→
› Night Skies Network, Jack Huerkamp→
› Astronomers Without Borders Camera Network→
› Lunar Eclipse from Santiago, Chile→

Note: All of the links above are to external sites controlled by organizations other than NASA.

Tonight is the Solstice Lunar Eclipse!

The first total lunar eclipse in two years will grace the sky the night of Monday, Dec. 20, and we want you to be there. Sure, it’s a school night, but with winter solstice and a new year upon us, what better time to gather your family and friends to see the moon in a new light?

At NASA, we’re pretty excited for this year’s lunar eclipse, so we’re offering a number of features and activities for astronomy buffs and moon-gazers alike. To learn about the science behind eclipses, visit NASA’s Eclipse page, where Mr. Eclipse provides information about viewing the eclipse from all over the United States.

Want to know more about the lunar eclipse? Lunar experts from NASA’s Marshall Space Flight Center will be hosting two live Web chats to discuss the eclipse. On Monday, Dec. 20 from 3-4 p.m. EST, Dr. Rob Suggs will answer your questions. Later on Dec. 20, make plans to stay “Up All Night” with astronomer Mitzi Adams at she answers your questions from midnight to 5:00 a.m. EST.

Starting now, you can subscribe to NASA JPL’s “I’m There: Lunar Eclipse” text campaign to connect with others in your area by texting us your viewing location and comments on the night of the eclipse. To sign up, text IMTHERE to 67463 and we’ll send you a reminder to go out and watch on Dec. 20 (message and data rates may apply).

Want to share or flip through photos of the eclipsed moon? Join NASA JPL’s lunar eclipse Flickr group and connect with other professional and amateur photographers as they capture the moon’s path through the Earth’s shadow. We’ll choose one lucky photographer to have his or her work featured as official JPL wallpaper at http://www.jpl.nasa.gov/wallpaper.

If you don’t want to brave the December chill, or if your weather doesn’t cooperate for lunar viewing, we have you covered! A live video feed of the lunar eclipse will be streamed online on Dec. 20. The camera is mounted at NASA’s Marshall Space Flight Center in Huntsville, Ala.

On Dec. 20 and 21, join the conversation on Twitter by including #eclipse and @NASAJPL in your lunar eclipse tweets, and you may even see them show up among our live comment stream on NASA JPL’s “I’m There: Lunar Eclipse” program.