Rare White Dwarf Systems Do A Doubletake

For those of us who remain forever fascinated by astronomy, nothing could spark our imaginations more than a cosmic curiosity. In this case, the unusual object is a star cataloged as AM Canum Venaticorum (AM CVn) located in the constellation of Canes Venatici. What makes this dual star system of interest? Try the fact that the pair revolve completely around each other in a brief 18 minutes. What’s more, they are the stuff of which Einstein dreamed… creators of ripples in space-time known as gravitational waves.

Like other astronomical anomalies, AM CVn became the forerunner of a new class of stellar objects. It is a white dwarf, a sun-like star which has exhausted its fuel and collapsed to around the size of Earth. Yet it also has a white dwarf companion – a very compact orb which is delivering matter to its neighbor. AM Canum Venaticorum is not alone, however. There are similar systems where the stellar pairs complete their rotations in about an hour and even as rapidly as five minutes! Can you imagine the crackling amount of energy a system like this produces?!

Even though we have been aware of systems like AM CVn for almost five decades, no one is quite sure how they originate. Now, through the use of X-ray and optical observations, astronomers are taking a look at newly evolved double stars systems which one day might become a dueling duo dwarf. Heading their list are two binary systems, J0751 and J1741. These candidates were observed in the X-ray part of the electromagnetic spectrum by NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton telescope. In addition, observations at optical wavelengths were made using the McDonald Observatory’s 2.1-meter telescope in Texas, and the Mt. John Observatory 1.0-meter telescope in New Zealand.

dual_dwarf“The artist’s illustration depicts what these systems are like now and what may happen to them in the future. The top panel shows the current state of the binary that contains one white dwarf (on the right) with about one-fifth the mass of the Sun and another much heavier and more compact white dwarf about five or more times as massive (unlike Sun-like stars, heavier white dwarfs are smaller).” says the Chandra X-ray Observatory news release.

What’s happening here? As the pair of white dwarf stars whip around each other, they are releasing gravitational waves which constrict the orbit. In time, the heavier, diminutive dwarf will begin stripping material from its lighter, larger companion (as seen in the middle panel). This material consumption will continue for perhaps a 100 million years, or until the collected matter reaches a critical mass and releases a thermonuclear explosion.

Another scenario is the thermonuclear explosion could annihilate the larger white dwarf completely in what astronomers call a Type Ia supernova. An event like this is well-known and gives a measurement in standard candles for cosmic distance. However, chances are better the explosion will happen on the surface of the star – an event known as .Ia supernovae. While .Ia supernovae events have been recorded in other galaxies, J0751 and J1741 are the first binary stars which have the potential to erupt in .Ia supernovae.

“The optical observations were critical in identifying the two white dwarfs in these systems and ascertaining their masses. The X-ray observations were needed to rule out the possibility that J0751 and J1741 contained neutron stars.” says the Chandra team. “A neutron star – which would disqualify it from being a possible parent to an AM CVn system – would give off strong X-ray emission due to its magnetic field and rapid rotation. Neither Chandra nor XMM-Newton detected any X-rays from these systems.”

Are AM CVn systems riding the gravitational wave? While astronomers haven’t been able to detect them yet, these new observations are highly important because equipment to verify their presences is currently being developed. It won’t be long until we can see the wave and have a whole new way of looking at the Universe!

Original Story Source: Chandra Observatory News Release.

The 2013 Super and Mini Moon Together in One Photo

A composition of the nearest and farthest 2013 full moons, with the SuperMoon of June on the left and the MiniMoon of December on the right. Credit and copyright: Giuseppe Petricca.

Astrophotographer Giuseppe Petricca from Pisa, Tuscany, Italy managed to capture two of the very ‘special’ full Moons from 2013 and created a comparative mosaic. Here is both the 2013 “SuperMoon” in June – when the Moon is the closest to Earth in its orbit and visually largest – and the recent December 2013 “MiniMoon” — the most distant and visually smallest Full Moon of the year.

“I was amazed, to say the least, from the actual difference!” Petricca told Universe Today via email. “The motto ‘It’s not that evident until you, by yourself, get to notice it!’ applies perfectly to this situation.

While with naked eye, the full Moon seems about the same size every month, the difference in its visual size is clearly visible via pictures. Of course, the Moon itself doesn’t change size, it’s just how big or small it appears in the sky due to the eccentricities in its orbit around Earth.

The two pictures were both taken at the same focal length, with a simple non reflex camera, a Nikon P90, on tripod, with matching ISO speed and exposure, at ISO 100, f5.0, 1/200″. Both taken from Pisa, Tuscany, Italy.

You can read all about the recent “MiniMoon” here, and find out more about the mechanics of the “SuperMoon” here.

App Review: Earth or Not Earth

The folks at Cosmoquest have released a cool new citizen science app for Android! “Earth or Not Earth” allows players to test their knowledge of Earth, as well as learn more about the fascinating geology of the rocky worlds in our solar system. You can also challenge your friends on Facebook to beat your scores, thanks to the Facebook integration feature.

“Earth or Not Earth” was developed by Southern Illinois University graduate student and Cosmoquest developer Joseph Moore. Moore designed “Earth or Not Earth,” and included two additional game features: “Matching” and “Pick 2.” The images used in “Earth or Not Earth” are public domain, and are sourced primarily from NASA planetary science missions, with more images to be added to the app in the future.

The app does cost $1.99 USD, and the Proceeds from “Earth or Not Earth” help fund the programmers at Cosmoquest, as well as citizen science programs, educational programs, and future mobile apps.

"Earth or Not Earth" Main Menu - Click to embiggen
“Earth or Not Earth” main menu – Click to embiggen.
Image Credit: Cosmoquest
The user interface for “Earth or Not Earth” is pretty straightforward. After installing the app, the initial screen will prompt users to login with their Cosmoquest credentials (or create a new account). While some may see this as an annoyance, a Cosmoquest account allows access to many of the other citizen science projects Cosmoquest offers, such as Moon Mappers, Asteroid Mappers, and others.

After logging in, users are able to select one of several game-play options.

Players can start with the “Learn” section, which allows users to learn more about the rocky worlds in our solar system. Additionally, users can learn about geologic features such as craters, volcanism, fault lines, and even man-made surface alterations.

After learning about the processes that shape and alter rocky worlds in our solar system, users can test their knowledge with the “Earth or Not Earth”, “Matching”, or “Pick Two” mini-games.

Earth or Not Earth? Click to embiggen. Image Credit: Cosmoquest
Earth or Not Earth?
Click to embiggen.
Image Credit: Cosmoquest
“Earth or Not Earth” Displays images from various NASA planetary missions. The goal for the player is to determine if the image is of Earth, or Not. For those looking for a greater challenge, the “Matching” minigame provides an image that players must try to match to a rocky world, or a planetary geology process.

The most challenging mini-game in “Earth or Not Earth” is “Pick Two”, where players select two images that belong to the same world out of several shown on screen. With some images being in color, and others in black and white, players must rely on the knowledge gained from the “Learn” feature to make educated deductions about which images belong to which world.

Fans of planetary science will find “Earth or Not Earth” a challenging, yet entertaining and educational gaming experience. Gameplay is quick, and makes for a nice break between meetings, or something to pass the time while waiting to catch the bus.

“Earth or Not Earth” is available from the Google Play store at: https://play.google.com/store/apps/details?id=org.cosmoquest.earthnotearth If you’d like to learn more about how the app was developed, Cosmoquest has a blog post available at: http://cosmoquest.org/blog/2013/12/got-earth/

See the Apollo 8 “Earthrise” in a Whole New Way

Earthrise - Apollo 8
Earthrise - as seen from Apollo 8. Credit: NASA.

One of the most famous images from the history of spaceflight is the picture taken by the crew of Apollo 8 of the “Earthrise” — the first color picture of taken of Earth as it became visible as the spacecraft came from behind the farside of the Moon. The photo was taken 45 years ago on December 24, 1968. It’s been called one of the most influential environmental photographs ever taken, and is one of the most-published pictures ever. As the photographer of this photo, astronaut Bill Anders has said, “We came all this way to discover the Moon. And what we really did discover is Earth.”

The NASA Goddard Scientific Visualization Studio has now released a new video that is a re-creation of that first Earthrise. The video is based on detailed analysis of Apollo 8 photography, including vertical stereo photos that were being taken at the same time as the Earthrise photos, combined with recent topographic models from the Lunar Reconnaissance Orbiter.

“In the video,” space historian Andrew Chaikin — who narrates the new video — told Universe Today, “we see the Moon’s surface, generated from LRO data, exactly as it appeared to the astronauts through the different windows of the spacecraft. We also hear the astronauts’ voices as captured by the spacecraft’s onboard voice recorder, synchronized with the visual. The video reveals new details about this historic event and the resulting color photograph, which became an icon of the 20th century.”

Enjoy this wonderful new video, which explains how this historic image was taken. The visualization shows how Apollo 8 Commander Frank Borman and crew members Anders and James Lovell worked together to photograph the stunning scene as their spacecraft orbited the Moon in 1968. The video allows anyone to virtually ride with the astronauts and experience the awe they felt at the vista in front of them.

The “Earthrise” photo is the cover photo of TIME’s Great Images of the 20th Century, and is the central photo on the cover of LIFE’s 100 Photographs That Changed the World.

“Earthrise had a profound impact on our attitudes toward our home planet, quickly becoming an icon of the environmental movement,” said Ernie Wright, who lead the video project with the SVS.

You can read more details of how the video was put together in this NASA press release.

A computer-generated visualization of the Apollo 8 spacecraft in orbit around the moon, with Earth rising over the horizon. Image Credit:  Ernie Wright/NASA Goddard Scientific Visualization Studio
A computer-generated visualization of the Apollo 8 spacecraft in orbit around the moon, with Earth rising over the horizon.
Image Credit:
Ernie Wright/NASA Goddard Scientific Visualization Studio

This Hilarious Conversation With A Space Robot Makes Kirobo Seem Almost Human

The Kirobo talking robot on the ISS. Credit: Toyota.

Just how human-sounding is Kirobo, the first talking robot on the station? This amusing conversation, recorded on the International Space Station and broadcast on a Toyota YouTube channel, shows a pint-sized robot that not only responds to questions, but also gestures and moves around in a scary person-like way.

As Kirobo chats with Japanese astronaut Koichi Wakata — who is excellent at deadpan, by the way — the two discussed matters such as how the Earth looks from space, the Japanese robotic arm Kibo and — right at the end — the most important difference between Kirobo and his backup, Mirata.

We don’t want to spoil the joy of the conversation for you by repeating what Kirobo says, but let’s just say there’s something special about watching a Japanese space robot make a reference to the first landing on the moon, which was hailed as a huge technological achievement when it happened in 1969. 

The 13.4-inch (0.34 meter) Kirobo is sponsored by Toyota and the University of Tokyo and is supposed to be able to pick up on the facial expressions of crewmates. The robot will be working closely with Wakata during Expedition 38 and then Expedition 39, when Wakata assumes command of station.

One goal is to see how well humans and semi-autonomous robots can work together in space. To see Kirobo’s first words from station, check out our past story from September.

Book Review and Giveaway: Physics: An Illustrated History of the Foundations of Science


Book review by David L. Hamilton

Tom Jackson’s Physics: An Illustrated History of the Foundations of Science is an enjoyable read for anyone who is fascinated by the world in which we live and curious about how the world works. Reading and comprehension of the material does not require one to have a background in physics or science. Jackson takes 100 important events that occurred throughout different periods in our history and presents them in such a way that they can be understood and enjoyed by people of all ages and backgrounds. Each event covers about a page and each page has beautiful illustrations and diagrams of the various tools of the trade that the physicists used in each of the 100 breakthroughs.

The book is divided into five sections ranging from antiquity to modern physics. The first section, The Dawn of Science, covers the important figures that set the stage for scientific inquiry for the next several centuries, such as Thales, Democritus, and Aristotle.

The second section, The Scientific Revolution, introduces us to Newton and his Laws of Motionand Theories of Light, John Dalton and his investigations into the characteristics of gases, and Thomas Seebeck and his discovery of the thermoelectric effect.The third section of Jackson’s book examines the Doppler effect, Absolute Temperature, and the discovery of X-Rays, all extremely important discoveries that are still relevant in the various branches of science today, such as astronomy and medicine.

The fourth section brings the reader into the subatomic age where contributions from Titians such as Max Planck and his Constant, Albert Einstein and his Theory of Relativity, and Dane Niels Bohr who gave us Bohr’s Model of an atom.

The fifth and final section of the book covers modern physics. Jackson does a great job of explaining how Slipher, Hubble, and Georges Lemaitre used Einstein’s theory of relativity to show that our universe is not static and eternal but an expanding, changing and evolving universe that had a beginning. In this final section, the reader will also learn about Quarks, Neutrinos, Dark matter and energy, and the famous Higgs boson.

Another great feature about this book is that it includes a foldout timeline that puts the people and their discoveries into the larger contexts of World events so that the reader can see the big picture more easily.

Universe Today and Shelter Harbour Press is offering free copies to two lucky winners. In order to be entered into the giveaway drawing, just put your email address into the box at the bottom of this post (where it says “Enter the Giveaway”) before Thursday, December 26th, 2013. We’ll send you a confirmation email, so you’ll need to click that to be entered into the drawing.

David and his wife live in Conway, Arkansas. They are amateur astronomers that love spending nights stargazing and their days working in Higher Education. David graduated from the University of Arkansas at Little Rock with a Master of Education degree.

ESA’s Gaia Mission Launches to Map the Milky Way

Soyuz VS06, with Gaia space observatory, lifted off from Europe's Spaceport, French Guiana, on 19 December 2013. (ESA–S. Corvaja)

Early this morning, at 09:12 UTC, the cloudy pre-dawn sky above the coastal town of Kourou, French Guiana was brilliantly sliced by the fiery exhaust of a Soyuz VS06, which ferried ESA’s “billion-star surveyor” Gaia into space to begin its five-year mission to map the Milky Way.

Ten minutes after launch, after separation of the first three stages, the Fregat upper stage ignited, successfully delivering Gaia into a temporary parking orbit at an altitude of 175 km (108 miles). A second firing of the Fregat 11 minutes later took Gaia into its transfer orbit, followed by separation from the upper stage 42 minutes after liftoff. 46 minutes later Gaia’s sunshield was deployed, and the spacecraft is now cruising towards its target orbit around L2, a gravitationally-stable point in space located 1.5 million km (932,000 miles) away in the “shadow” of the Earth.

The launch itself was really quite beautiful, due in no small part to the large puffy clouds over the launch site. Watch the video below:

A global space astrometry mission, Gaia will make the largest, most precise three-dimensional map of our galaxy by surveying more than a billion stars over a five-year period.

“Gaia promises to build on the legacy of ESA’s first star-mapping mission, Hipparcos, launched in 1989, to reveal the history of the galaxy in which we live,” says Jean-Jacques Dordain, ESA’s Director General.

Soyuz VS06, with Gaia, lifted off from French Guiana, 19 December 2013. (ESA - S. Corvaja)
Soyuz VS06 with Gaia (ESA – S. Corvaja, 2013)

Repeatedly scanning the sky, Gaia will observe each of the billion stars an average of 70 times each over the five years. (That’s 40 million observations every day!) It will measure the position and key physical properties of each star, including its brightness, temperature and chemical composition.

By taking advantage of the slight change in perspective that occurs as Gaia orbits the Sun during a year, it will measure the stars’ distances and, by watching them patiently over the whole mission, their motions across the sky.

The motions of the stars can be put into “rewind” to learn more about where they came from and how the Milky Way was assembled over billions of years from the merging of smaller galaxies, and into “fast forward” to learn more about its ultimate fate.

“Gaia represents a dream of astronomers throughout history, right back to the pioneering observations of the ancient Greek astronomer Hipparchus, who catalogued the relative positions of around a thousand stars with only naked-eye observations and simple geometry. Over 2,000 years later, Gaia will not only produce an unrivaled stellar census, but along the way has the potential to uncover new asteroids, planets and dying stars.”

– Alvaro Giménez, ESA’s Director of Science and Robotic Exploration

Gaia will make an accurate map of the stars within the Milky Way from its location at L2 (ESA/ATG medialab; background: ESO/S. Brunier)
Gaia will make an accurate map of a billion stars within the Milky Way from its location at L2 (ESA/ATG medialab; background: ESO/S. Brunier)

Of the one billion stars Gaia will observe, 99% have never had their distances measured accurately. The mission will also study 500,000 distant quasars, search for exoplanets and brown dwarfs, and will conduct tests of Einstein’s General Theory of Relativity.

“Along with tens of thousands of other celestial and planetary objects,” said ESA’s Gaia project scientist Timo Prusti, “this vast treasure trove will give us a new view of our cosmic neighbourhood and its history, allowing us to explore the fundamental properties of our Solar System and the Milky Way, and our place in the wider Universe.”

Follow the status of Gaia on the mission blog here.

Source: ESA press release and Gaia fact sheet

Gaia's launch aboard an Arianespace-operated Soyuz on Dec. 19, 2013 from ESA's facility in French Guiana (ESA)
Gaia’s launch aboard an Arianespace-operated Soyuz on Dec. 19, 2013 from ESA’s facility in French Guiana (ESA)

Where Did Saturn’s Rings Come From?

Where Did Saturn's Rings Come From?

Dr. Kevin Grazier was a planetary scientist with the Cassini mission for over 15 years, studying Saturn and its icy rings. He was also the science advisor for Battlestar Galactica, Eureka and the movie Gravity.

Mike Brown is a professor of planetary astronomy at Caltech. He’s best known as the man who killed Pluto, thanks to his team’s discovery of Eris and other Kuiper Belt Objects.

We recently asked them about many things – here’s what they shared with us about the rings of Saturn.

Saturn’s majestic, iconic rings define the planet, but where did they come from?

Kevin Grazier: “Saturn’s rings, good question. And the answer is different depending on which ring we’re discussing.”

That’s Dr. Kevin Grazier, a planetary scientist who worked on NASA’s Cassini mission or over 15 years, studying Saturn’s rings extensively.

Mike Brown: “Saturn’s rings – the strange things about Saturn’s rings is that they shouldn’t be there, really, in the sense that they don’t last for very long. So, if they are just left over from when Saturn was formed, they’d be gone by now. They would slowly work their way into Saturn and burn up and be gone. And yet they’re there. So they are either relatively new or somehow continuously regenerated. ‘Continuously regenerated’ seems strange and ‘relatively new’ seems also kind of strange. Something broke up – a large moon broke up, or a comet broke up – something had to have happened relatively recently. And by relatively recently, that means hundreds of millions of years ago for someone like me.”

And that’s Mike Brown, professor of planetary geology at Caltech, who studies many of the icy objects in the Solar System.

Saturn and its rings, as seen from above the planet by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute. Assembled by Gordan Ugarkovic.
Saturn and its rings, as seen from above the planet by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute. Assembled by Gordan Ugarkovic.

Saturn’s rings start just 7,000 km above the surface of the planet, and extend out to an altitude of 80,000 km. But they’re gossamer thin, just 10 km across at some points.

We’ve known about Saturn’s rings since 1610, when Galileo was the first person to turn a telescope on them. The resolution was primitive, and he thought he saw “handles” attached to Saturn, or perhaps what were big moons on either side.

In 1659, using a better telescope, the Dutch astronomer Christiaan Huygens figured out that these “handles” were actually rings. And finally in the 1670s, the Italian astronomer Giovanni Cassini was able to resolve the rings in more detail, even observed the biggest gap in the rings.

The Cassini mission, named after Giovanni, has been with Saturn for almost a decade, allowing us to view the rings in incredible detail. Determining the origin and evolution of Saturn’s rings has been one of its objectives.

Saturn's rings. Credit: NASA/JPL/Space Science Institute.
Saturn’s rings. Credit: NASA/JPL/Space Science Institute.

So far, the argument continues:

Kevin Grazier: “There’s an age-old debate about whether the rings are old or new. And that goes back and forth – it’s been going back and forth for ages and it still goes back and forth. Are they old, or have they been there a long period of time? Are they new? I don’t know what to think, to be quite honest. I’m not being wishy-washy, I just don’t know what to think anymore.”

Evidence from NASA’s Voyager spacecraft indicated that the material in Saturn’s rings was young. Perhaps a comet shattered one of Saturn’s moons within the last few hundred million years, creating the rings we see today. If that was the case case, what incredible luck that we’re here to see the rings in their current form.

But when Cassini arrived, it showed evidence that Saturn’s rings are being refreshed, which could explain why they appear so young. Perhaps they are ancient after all.

Kevin Grazier: “If Saturn’s rings are old, a moon could have gotten too close to Saturn and been pulled apart by tidal stresses. There could have been a collision of moons. It could have been a pass by a nearby object, since in the early days of planetary formation, there were many objects zooming past Saturn. Saturn probably had a halo of material in it’s early days that was loosely bound to the moon.”

Enceladus, backdropped by Saturn's rings. Credit: NASA/JPL/ Space Science Institute.
Enceladus, backdropped by Saturn’s rings. Credit: NASA/JPL/ Space Science Institute.

There is one ring that we know for certain is being refreshed…

Kevin Grazier: “The E-Ring, certainly a new ring, because the E-Ring consists of roughly micron-sized ice particles. And micron-sized ice particles don’t last in space. They sputter and sublimate – they go away in very short time periods, and we knew that. And so when we went to Saturn with Cassini, we knew to look for a source of materiel because we knew that the individual components of the E-Ring don’t last, so it has to be replenished. So the E-Ring stands alone from the established system, and the E-Ring is absolutely new.”

In 2005, scientist discovered that Saturn’s E-Ring is being constantly replenished by the moon Enceladus. Cryovolcanoes spew water ice into space from a series of fissures at its south pole.

So where did Saturn’s rings come from? We don’t know. Are the new or old? We don’t know. It just another great mystery of the Solar System.

You can follow Kevin Grazier and Mike Brown at their Google+ pages!

Visions of Earth through the Yutu Rover’s Eyes

Earth eclipses the sun from Chang'e 3's location in the Sea of Rains on April 15, 2014. At the same time, we'll see a total lunar eclipse from the ground. Stellarium

Last night I used my telescope to eye-hike the volcanic plains of the Sea of Rains (Mare Imbrium) where the Yutu rover and lander sit beneath a blistering sun. With no atmosphere to speak of and days that last two weeks, noontime temperatures can hit 250 degrees Fahrenheit (122 C) . That’s hot enough that mission control at the Beijing Aerospace Command and Control Center has decided to draw the shades and give the rover a nap from science duties until December 23 when things cool down a bit.

While studying the subtle gray hues of the Imbrium lava flows I got to wondering what the sky might look like if I could don a spacesuit and visit the landing site “where the skies are not cloudy all day” (to quote a famous song). With no atmosphere to speak of, stargazing can be done both day and night on the moon though I suspect it’s better at night when there’s less glare from your surroundings. Night, defined as the time from sunset to sunrise (no twilights here), lasts about 14.5 Earth days. Days are equally long.

Lunar landscape photographed by the Chang'e 3 lander on Dec. 15, 2013. Credit: CCTV
Lunar landscape photographed by the Chang’e 3 lander on Dec. 15, 2013. Credit: CCTV

 

From Yutu’s point of view, it’s very nearly lunar noon today (Dec. 19) with the sun halfway up in the southern sky.  Looking at the map of the sky from the lander’s location, you’ll see a few familiar constellations and one very familiar planet – Earth!

Phases of the moon and Earth are complementary. When the moon is full, Earth's a crescent. This map shows the Earth in Capricornus on Dec. 20 as thin blue crescent. Stellarium
Phases of the moon and Earth are complementary. When the moon is full, Earth’s a crescent. This map shows the Earth in Capricornus on Dec. 20 as thin blue crescent. Stellarium

Today Earth appears as a very thin crescent a short distance to the left or east of the sun. Because the moon takes just as long to rotate on its axis as it does to revolve around the Earth, the same face of the moon always faces our planet. Because the two are in synchrony, astronomers call it synchronous rotation.

From the perspective of someone standing on the moon, Earth stands still in one spot of sky throughout the 29.5 day lunar day-night cycle. Well, not perfectly still. Because the moon’s orbit is inclined about 5 degrees to Earth’s orbit and its speed varies along its non-circular orbit, Earth describes a little circle in the lunar sky about 10 degrees in diameter every four weeks.

As the sun slowly moves off to the west, our blue planet remains nearly stationary from Yutu’s perspective and undergoes all the familiar phases we see the moon experience back here on Earth: an evening crescent to start followed by a first quarter Earth, Full Earth last quarter and finally, New Earth. I like the ring of that last one.

The lunar landscape at the rover's location is bathed in pale blue light on Dec. 31, 2013 during "Full Earth". Stellarium
The lunar landscape at the rover’s location is bathed in pale blue light on Dec. 31, 2013 during a Full Earth. Stellarium

Yutu and the lander will see the sun drift to the west while Earth moves east, rises higher in the lunar sky and putting on the pounds phase-wise. Today Earth’s glides across the border of Sagittarius into Capricornus. The next Full Earth happens on New Year’s Eve when the sun is directly opposite the Earth in the lunar sky.

Full Earth always happens around local midnight or about one week before sunrise during the long lunar day. On the moon the sun is up for about  two weeks and then disappears below the horizon for another two weeks before rising again.  At Full Earth time, the sun remains hidden around the lunar backside. When the nights are blackest, the bright ball of Earth spreads a welcome blue glow over the desolate landscape.

Earth covering the sun with a flash of the "diamond ring effect" just before total solar eclipse on April 15 and Oct. 8 next year. Stellarium
Simulated eclipse of the sun by the Earth just before totality on April 15 and Oct. 8 next year. On both dates, we’ll see a  total lunar eclipse from the ground.  Stellarium

Things really get interesting during lunar eclipses when the moon moves behind the Earth into the planet’s shadow. The next one’s on April 15, 2014. Here on the ground we’ll see the moon gradually munched into by Earth’s  shadow until totality, when sunlight from all the sunrises and sunsets around the rim of the planet are refracted by the atmosphere into the shadow, coloring the moon a coppery red.

Two pictures of the ring of sunset-sunrise fire around the Earth as it totally eclipsed the sun from the moon. Credit: NASA
Two pictures of the ring of sunset-sunrise fire around the Earth as it totally eclipsed the sun from the moon. Credit: NASA

Yutu will see just the opposite. Looking back toward the Earth from inside its shadow, the rover will witness a total eclipse of the sun by the Earth. If by some wonder the Chinese are able to photograph the event, we’ll see photos of the black ball of Earth rimmed in red fire from sunset and sunrise light refracted by our atmosphere. My interpretation using sky mapping software only hints at the wonder of the scene. Beijing Aerospace, if you’re reading this, please make it happen.


Earth eclipses the sun filmed by Japan’s Kaguya lunar orbiter. There are really two eclipses here – the Earth eclipsed by the limb of the moon at the video’s start followed by the solar eclipse.

On two other occasions, our robotic emissaries have photographed solar eclipses from Luna. NASA’s Surveyor 3 snapped a couple crude pictures of the April 24, 1967 eclipse from inside a crater in Mare Cognitium, the Sea that has Become Known. Japan’s orbiting Kaguya probe did the job much more eloquently on video during the February 9, 2009 penumbral lunar eclipse. In a penumbral eclipse (seen from Earth) the moon misses Earth’s dark inner shadow called the umbra, passing only through the outer penumbra, but because the Earth is three times larger than the sun (seen from the moon), it easily covered the sun completely in the complementary total solar eclipse.

And the best thing about watching eclipses from the moon? Guaranteed clear skies!