Moon Archives

July 13, 2013December 23, 2015 by Ken Kremer

Sierra Nevada Dream Chaser Gets Wings and Tail, Starts Ground Testing

Sierra Nevada Corporation’s Dream Chaser successfully rolls through two tow tests at NASA’s Dryden Flight Research Center in California in preparation for future flight testing later this year.
Watch way cool Dream Chaser assembly video below![/caption]

Sierra Nevada Corporation’s winged Dream Chaser engineering test article is moving forward with a series of ground tests at NASA’s Dryden Flight Research Center in California that will soon lead to dramatic aerial flight tests throughout 2013.

Pathfinding tow tests on Dryden’s concrete runway aim to validate the performance of the vehicles’ nose skid, brakes, tires and other systems to prove that it can safely land an astronaut crew after surviving the searing re-entry from Earth orbit.

The Dream Chaser is one of the three types of private sector ‘space taxis’ being developed with NASA seed money to restore America’s capability to blast humans to Earth orbit from American soil – a capability which was totally lost following the forced shutdown of NASA’s Space Shuttle program in 2011.

Dream Chaser commercial crew vehicle built by Sierra Nevada Corp docks at ISS

For the initial ground tests, the engineering test article was pulled by a tow truck at 10 and 20 MPH. Later this month tow speeds will be ramped up to 40 to 60 MPH.

Final assembly of the Dream Chaser test vehicle was completed at Dryden with installation of the wings and tail, following shipment from SNC’s Space Systems headquarters in Louisville, Colo.

Watch this exciting minute-long, time-lapse video showing attachment of the wings and tail:

In the next phase later this year, Sierra Nevada will conduct airborne captive carry tests using an Erickson Skycrane helicopter.

Atmospheric drop tests of the engineering test article in an autonomous free flight mode for Approach and Landing Tests (ALT) will follow to check the aerodynamic handling.

The engineering test article is a full sized vehicle.

Dream Chaser is a reusable mini shuttle that launches from the Florida Space Coast atop a United Launch Alliance Atlas V rocket and lands on the shuttle landing facility (SLF) runway at the Kennedy Space Center, like the Space Shuttle.

“It’s not outfitted for orbital flight. It is outfitted for atmospheric flight tests,” said Marc Sirangelo, Sierra Nevada Corp. vice president and SNC Space Systems chairman, to Universe Today.

“The best analogy is it’s very similar to what NASA did in the shuttle program with the Enterprise, creating a vehicle that would allow it to do significant flights whose design then would filter into the final vehicle for orbital flight,” Sirangelo told me.

NASA’s Dryden Flight Research Center welcomes SNC’s Dream Chaser shrink wrapped engineering test article for a flight test program in collaboration with NASA’s Commercial Crew Program this summer. Winds and tail were soon joined and ground testing has now begun. Credit: NASA/Tom Tschida Read more: http://www.universetoday.com/102020/sierra-nevada-dream-chaser-gets-wings-and-tail-starts-ground-testing/#ixzz2Yw1peNRJ — NASA’s Dryden Flight Research Center welcomes SNC’s Dream Chaser shrink wrapped engineering test article for a flight test program in collaboration with NASA’s Commercial Crew Program this summer. Winds and tail were soon joined and ground testing has now begun. Credit: NASA/Tom Tschida

Sierra Nevada Corp, along with Boeing and SpaceX are working with NASA in a public-private partnership using a combination of NASA seed money and company funds.

Each company was awarded contracts under NASA’s Commercial Crew Integrated Capability Initiative, or CCiCap, program, the third in a series of contracts aimed at kick starting the development of the private sector ‘space taxis’ to fly US and partner astronauts to and from low Earth orbit (LEO) and the International Space Station (ISS).

“We are the emotional successors to the shuttle,” says Sirangelo. “Our target was to repatriate that industry back to the United States, and that’s what we’re doing.”

The combined value of NASA’s Phase 1 CCiCap contracts is about $1.1 Billion and runs through March 2014.

Phase 2 contract awards will eventually lead to actual flight units after a down selection to one or more of the companies.

Everything depends on NASA’s approved budget, which seems headed for steep cuts in excess of a billion dollars if the Republican dominated US House has its way.

Dream Chaser awaits launch atop Atlas V rocket

The Commercial Crew program’s goal is to ensure the nation has safe, reliable and affordable crew transportation systems to space.

“Unique public-private partnerships like the one between NASA and Sierra Nevada Corporation are creating an industry capable of building the next generation of rockets and spacecraft that will carry U.S. astronauts to the scientific proving ground of low-Earth orbit,” said William Gerstenmaier, NASA’s associate administrator for human exploration and operations in Washington, in a statement.

“NASA centers around the country paved the way for 50 years of American human spaceflight, and they’re actively working with our partners to test innovative commercial space systems that will continue to ensure American leadership in exploration and discovery.”

All three commercial vehicles – the Boeing CST-100; SpaceX Dragon and Sierra Nevada Dream Chaser – are designed to carry a crew of up to 7 astronauts and remain docked at the ISS for more than 6 months.

The first orbital flight test of the Dream Chaser is not expected before 2016 and could be further delayed if NASA’s commercial crew budget is again slashed by the Congress – as was done the past few years.

In the meantime, US astronauts are totally dependent on Russia’s Soyuz capsule for rides to the ISS. NASA must pay Russia upwards of $70 million per seat until the space taxis are ready for liftoff – perhaps in 2017.

“We have got to get Commercial Crew funded, or we’re going to be paying the Russians forever,” said NASA Administrator Charles Bolden at Dryden. “Without Commercial Crew, we probably won’t have exploration.”

Concurrently, NASA is developing the Orion Crew capsule for missions to the Moon, Asteroids and beyond to Mars and other destinations in our Solar System -details here.

Ken Kremer

Scale models of NASA’s Commercial Crew program vehicles and launchers; Boeing CST-100, Sierra Nevada Dream Chaser, SpaceX Dragon. Credit: Ken Kremer/kenkremer.com — Scale models of NASA’s Commercial Crew program vehicles and launchers; Boeing CST-100, Sierra Nevada Dream Chaser, SpaceX Dragon.
Credit: Ken Kremer/kenkremer.com

Sierra Nevada Corp.'s Dream Chaser spacecraft landing on a traditional runway. Dream Chaser is being developed in collaboration with NASA's Commercial Crew Program during the Commercial Crew Integrated Capability initiative (CCiCAP). Credit: Sierra Nevada Corp. — Sierra Nevada Corp.’s Dream Chaser spacecraft landing on a traditional runway. Dream Chaser is being developed in collaboration with NASA’s Commercial Crew Program during the Commercial Crew Integrated Capability initiative (CCiCAP). Credit: Sierra Nevada Corp.

July 9, 2013December 23, 2015 by Ken Kremer

NASA Alters 1st Orion/SLS Flight – Bold Upgrade to Deep Space Asteroid Harbinger Planned

NASA Orion spacecraft blasts off atop 1st Space Launch System rocket in 2017 - attached to European provided service module – on an enhanced m mission to Deep Space where an asteroid could be relocated as early as 2021. Credit: NASA

NASA Orion spacecraft blasts off atop 1st Space Launch System rocket in 2017 – attached to European provided service module – on an ambitious mission to explore Deep Space some 40,000 miles beyond the Moon, where an asteroid could be relocated as early as 2021. Credit: NASA
Story updated with further details[/caption]

NASA managers have announced a bold new plan to significantly alter and upgrade the goals and complexity of the 1st mission of the integrated Orion/Space Launch System (SLS) human exploration architecture – planned for blastoff in late 2017.

The ambitious first flight, called Exploration Mission 1 (EM-1), would be targeted to send an unpiloted Orion spacecraft to a point more than 40,000 miles (70,000 kilometers) beyond the Moon as a forerunner supporting NASA’s new Asteroid Redirect Initiative – recently approved by the Obama Administration.

The EM-1 flight will now serve as an elaborate harbinger to NASA’s likewise enhanced EM-2 mission, which would dispatch a crew of astronauts for up close investigation of a small Near Earth Asteroid relocated to the Moon’s vicinity.

Orion crew module separates from Space Launch System (SLS) upper stage. Credit: NASA

Until recently NASA’s plan had been to launch the first crewed Orion atop the 2nd SLS rocket in 2021 to a high orbit around the moon on the EM-2 mission, said NASA Associate Administrator Lori Garver in an prior interview with me at the Kennedy Space Center.

Concept of NASA spacecraft with Asteroid capture mechanism deployed to redirect a small space rock to a stable lunar orbit for later study by astronauts aboard Orion crew capsule. Credit: NASA.

The enhanced EM-1 flight would involve launching an unmanned Orion, fully integrated with the Block 1 SLS to a Deep Retrograde Orbit (DRO) near the moon, a stable orbit in the Earth-moon system where an asteroid could be moved to as early as 2021.

Orion’s mission duration would be nearly tripled to 25 days from the original 10 days.

“The EM-1 mission with include approximately nine days outbound, three to six days in deep retrograde orbit and nine days back,” Brandi Dean, NASA Johnson Space Center spokeswoman told Universe Today exclusively.

The proposed much more technologically difficult EM-1 mission would allow for an exceptionally more vigorous work out and evaluation of the design of all flight systems for both Orion and SLS before risking a flight with humans aboard.

A slew of additional thruster firings would exercise the engines to change orbital parameters outbound, around the moon and inbound for reentry.

The current Deep Retrograde Orbit (DRO) plan includes several thruster firings from the Orion service module, including a powered lunar flyby, an insertion at DRO, an extraction maneuver from the DRO and a powered flyby on return to Earth.

Orion would be outfitted with sensors to collect a wide variety of measurements to evaluate its operation in the harsh space environment.

“EM-1 will have a compliment of both operational flight instrumentation and development flight instrumentation. This instrumentation suite gives us the ability to measure many attributes of system functionality and performance, including thermal, stress, displacement, acceleration, pressure and radiation,” Dean told me.

The EM-1 flight has many years of planning and development ahead and further revisions prior to the 2017 liftoff are likely.

“Final flight test objectives and the exact set of instrumentation required to meet those objectives is currently under development,” Dean explained.

Orion is NASA’s next generation manned space vehicle following the retirement of NASA’s trio of Space Shuttles in 2011.

The SLS launcher will be the most powerful and capable rocket ever built by humans – exceeding the liftoff thrust of the Apollo era Moon landing booster, the mighty Saturn V.

“We sent Apollo around the moon before we landed on it and tested the space shuttle’s landing performance before it ever returned from space.” said Dan Dumbacher, NASA’s deputy associate administrator for exploration systems development, in a statement.

“We’ve always planned for EM-1 to serve as the first test of SLS and Orion together and as a critical step in preparing for crewed flights. This change still gives us that opportunity and also gives us a chance to test operations planning ahead of our mission to a relocated asteroid.”

Both Orion and SLS are under active and accelerating development by NASA and its industrial partners.

The 1st Orion capsule is slated to blast off on the unpiloted EFT-1 test flight in September 2014 atop a Delta IV Heavy rocket on a two orbit test flight to an altitude of 3,600 miles above Earth’s surface.

Technicians work on mockups of the Orion crew capsule, Service Module and 6 ton Launch Abort System (LAS) to simulate critical assembly techniques inside the Vehicle Assembly Building (VAB) at NASA’s Kennedy Space Center (KSC) in Florida for the EFT-1 mission due to liftoff in September 2014. Credit: Ken Kremer/kenkremer.com

It will then reenter Earth’s atmosphere at speeds of about 20,000 MPH (11 km/sec) and endure temperatures of 4,000 degrees Fahrenheit in a critical test designed to evaluate the performance of Orion’s heatshield and numerous spacecraft systems.

Orion EFT-1 is already under construction at the Kennedy Space Center (KSC) by prime contractor Lockheed Martin – read my earlier story here.

Integration and stacking tests with Orion’s emergency Launch Abort System are also in progress at KSC – details here.

NASA says the SLS is also in the midst of a extensive review process called the Preliminary Design Review (PDR) to ensure that all launch vehicle components and systems will achieve the specified performance targets and be completed in time to meet the 2017 launch date. The PDR will be completed later this summer.

NASA’s goal with Orion/SLS is to send humans to the Moon and other Deep Space destinations like Asteroids and Mars for the first time in over forty years since the final manned lunar landing by Apollo 17 back in 1972.

NASA Headquarters will make a final decision on upgrading the EM-1 mission after extensive technical reviews this summer.

Ken Kremer

Schematic of Orion components. Credit: NASA

July 8, 2013December 23, 2015 by Nancy Atkinson

Incredible Astrophoto: The Youngest Possible New Moon by Thierry Legault

This image shows the tiny lunar crescent at the precise moment of the New Moon, in full daylight at 7h14min UTC on July 8 2013. Credit and copyright: Thierry Legault.

It’s always striking to see a tiny sliver of the New Moon. But you’ve probably never seen a sliver this tiny or a Moon this “new” before. This brand new image by astrophotographer extraordinaire Thierry Legault was taken this morning and is the youngest possible lunar crescent, with the “age” of the Moon at this instant being exactly zero — at the precise moment of the New Moon. The image was taken in full daylight at 07:14 UTC on July 8, 2013.

Normally it is just about impossible (and dangerous) to see this, as when the Moon is this “new,” the Moon is between the Earth and the Sun and it is so close to the Sun in our sky that it can’t be seen because of the Sun’s glare. Plus, the New Moon appears as an extremely thin crescent which is barely brighter than the blue sky. But Thierry has designed a special sunshade to prevent sunlight from entering the telescope (see it below).

Thierry says the irregularities and discontinuities seen in the edge of the crescent are caused by the relief at the edge of the lunar disk; i.e. mountains and craters on the Moon. Very cool!

The “New Moon” is defined as the instant when the Moon is at the same ecliptic longitude as the Sun. When we refer to the “age” of the Moon, it is the number of hours (or days) since New Moon.

From Thierry’s shooting site in Elancourt, France (a suburb of Paris), the angular separation between the Moon and the Sun was only 4.4° (nine solar diameters).

“At this very small separation, the crescent is extremely thin (a few arc seconds at maximum) and, above all, it is drowned in the solar glare, the blue sky being about 400 times brighter than the crescent itself in infrared (and probably more than 1000 times in visible light),” Thierry writes on his website. “In order to reduce the glare, the images have been taken in close infrared and a pierced screen, placed just in front of the telescope, prevents the sunlight from entering directly in the telescope.”

Thierry Legault with his special telescope filter for blocking the Sun's rays. Image courtesy Thierry Legault. — Thierry Legault with his special telescope filter for blocking the Sun’s rays. Image courtesy Thierry Legault.

Thierry cautions anyone trying to see this with the naked eye. Basically, don’t try it.

“The very thin crescent of the New Moon cannot be observed visually whatever the instrument (naked eye, binoculars, telescope, etc),” he said. “Moreover, pointing a celestial object that close to the Sun is dangerous for the observer and his equipment if it is not performed under the control of an experienced astronomer and with the proper equipment.”

See more information at Thierry’s website. He also took another image of the New Moon at the exact moment back in 2010.

If you want to keep track of what the Moon will look like each night (or day!), Universe Today has a great app for that, our Phases of the Moon app, available for iOS or Android.

July 6, 2013December 23, 2015 by Jason Major

New Desktop Image Alert: The Moon Over Earth

If you’re like me, you don’t change your computer’s desktop background nearly often enough… especially not considering all the fantastic space images that get released on an almost daily basis. But this picture, shared a couple of weeks ago by NASA’s Marshall Space Flight Center on their Flickr stream, really should inspire you to fix that. (I know it did for me!)

Captured by an Expedition 28 crew member aboard the International Space Station, this beautiful image shows a crescent-lit Moon seen through the upper layers of Earth’s atmosphere.

As it circles the globe, the ISS travels an equivalent distance to the Moon and back in about a day, making an excellent platform for viewing the Earth and its atmosphere. This photo shows the limb of Earth near the bottom transitioning into the orange-colored troposphere, the lowest and most dense portion of the Earth’s atmosphere. The troposphere ends abruptly at the tropopause, which appears in the image as the sharp boundary between the orange- and blue- colored atmosphere. Silvery-blue noctilucent clouds extend far above the Earth’s troposphere.

Expedition 28 began on May 23, 2011, with a crew consisting of Andrey Borisenko, Ron Garan, Alexander Samokutyaev, Sergei Volkov, Mike Fossum, and Satoshi Furukawa.

Image credit: NASA (Source)

July 4, 2013March 16, 2017 by Fraser Cain

How Many Moons Does Earth Have?

Look up into the night sky and count the moons. You can see only one moon, “the” Moon. But does the Earth have any other moons? Around the Solar System, multiple moons are the rule. Jupiter has 67 natural satellites, even Mars has two asteroid-like moons.

Could Earth have more than one?

Officially, the answer is no. The Earth has a single moon.

Today.

It’s possible Earth had more than one moon in the past, millions or even billions of years ago. Strange terrain on the far side of the Moon could be explained by a second moon crashing into it, depositing a layer of material tens of kilometers deep.

Moons could come and go over the billions of years of the Earth’s history.

For example, Mars has two Moons, but not for long. Phobos, the larger moon, is spiraling inward and expected to crash into the planet within the next 10 million years. And so, in the future, Mars will only have a single Moon, Deimos.

It’s also possible that the Earth might capture a Moon in the future. Neptune’s largest moon, Triton, orbits in the opposite direction from the rest of the moons around the planet. This suggests that Triton was actually a captured Kuiper Belt Object which strayed too close to the planet.

In fact, we did capture a 5-metre asteroid called 2006 RH120. It orbited the Earth four times during 2006/2007 before getting ejected again.

So we can assume events like this have happened in the past.

Additionally, we might have more moons, but they haven’t been discovered yet because they’re just too small. Researchers have calculated that there could be meter-sized asteroids in orbit around the Earth, remaining in orbit for hundreds of years before gravitational interactions push them out again.

And there are other objects that interact with Earth’s orbit in strange ways. Scientists don’t consider them moons, but they do stick around in our neighbourhood:

Asteroid 3753 Cruithne is in an orbital resonance with the Earth. It has a highly eccentric orbit, but takes exactly one year to orbit the Sun. From our perspective, it follows a slow, horse-shoe shaped path across the sky. Since the discovery of Cruithne in 1986, several other resonant near-Earth objects have been discovered.

There’s 2010 TK7, the Earth’s only known Trojan asteroid. It leads the Earth in the exact same orbit around the Sun, in a gravitationally stable point in space.

So, the answer… Earth only has a single Moon. Today. We might have had more moons in the past, and we might capture more in the future, but for right now… enjoy the one we’ve got.

Want to learn more? Here are some articles on Universe Today we’ve written about this topic:
What are some objects known as Earth’s other moons?
Did Earth have more than one moon in the past?
Does Earth have many tiny moons?

You might also enjoy this episode of Astronomy Cast: Where did the Moon come from?

July 3, 2013December 23, 2015 by Elizabeth Howell

Moon Dust Could ‘Engulf’ Lunar Rovers — Especially During Sunrise and Sunset

Apollo 17 Mission — An Apollo 17 astronaut digs in the lunar regolith to study the mechanical behavior of moon dust. Credit: NASA

That video above is perhaps the ultimate off-roading adventure: taking a rover out for a spin on the moon. Look past the cool factor for a minute, though, and observe the dust falling down around that astronaut.

The crew aboard Apollo 16 (as well as other Apollo missions) had a lot of problems with regolith. It got into everything. It was so abrasive that it wore away some equipment in days. It smelled funny and probably wasn’t all that good to breathe in, either. Many have said that when we return to the moon, dust must be dealt with for long-term survival.

Things could get worse at sunrise and sunset. One new study (not peer-reviewed yet) finds a “serious risk” that rovers “could be engulfed in dust.” That’s because lunar dust appears to have electrostatic properties that, somehow, is triggered by changes in sunlight. (NASA is already doing some serious investigation into this matter using its orbiting missions.)

What the researchers did, in conjunction with ONERA (The French Center of Aerospace Research) was conduct simulations for two types of lunar regions — the terminator (the day/night boundary) and an area experiencing full sunlight.

“Dust particles were introduced into the simulation over a period of time, when both the surface and the rover were in electrical equilibrium,” the Royal Astronomical Society stated.

“In both the test cases, dust particles travel upwards above the height of the rover, but results suggest that they move in different directions. On the day side, the particles are pushed outwards and on the terminator the dust travels upwards and inwards above the rover, regrouping in the vacuum above it. The terminator simulation began with a region void of dust which was later filled by lunar dust particles.”

The bottom line? A lunar rover could accumulate a significant amount of dust on the moon, especially if it’s sitting at or near the terminator. This could be addressed by using dome-shaped rovers that would see the dust fall off, added lead author Farideh Honary, a physicist at the University of Lancaster, in a statement.

The work was presented at the RAS National Astronomy Meeting today (July 3). A paper has been submitted to the Journal for Geophysical Research, so more details should be forthcoming if and when it is published.

Credit: Royal Astronomical Society

July 2, 2013December 23, 2015 by Shannon Hall

The Hunt for Exomoons Begins!

An artist's conception of a potentially-habitable exomoon. Credit: NASA

The latest exciting undertaking in exoplanet research is the search for exomoons. A team led by Dr. David Kipping at the Harvard-Smithsonian Center for Astrophysics has jumped at this challenge. After having theoretically proven that detecting an Earth-sized exomoon is possible, the team carried out the first detailed search for an exomoon.

Are you leaning forward on the edge of your seat awaiting the results? Well here you go: the data show no evidence of a moon. That’s simply the luck of the draw. We didn’t discover an exoplanet on our first try either. I believe that this non-detection shows that we’re on the verge of our next greatest discovery.

The reasons for searching for exomoons are abundant. “Exomoons may be frequent, habitable abodes for life and so far we know next to nothing about the underlying frequency of such objects in the cosmos,” Dr. Kipping told Universe Today. “They also play an important role in the habitability of those planets which they orbit, for example the Moon is thought to stabilize the axial tilt of the Earth and so too the climate.”

The project titled “The Hunt of Exomoons with Kepler,” more commonly known as HEK, was formed with these reasons in mind. As such, the HEK project will search for exomoons that are likely to be habitable.

The first target is Kepler-22b – the first transiting exoplanet to have been detected in the habitable zone of its host star. At 2.4 Earth radii, it is too large to be considered an Earth-analog, but it could easily have an Earth-sized moon

There are currently two methods in which we may detect exomoons.

1.) Dynamic effects – the exomoon tugs the planet, which causes deviations in the times and durations of the host planet’s transits. This is similar to the radial velocity technique for detecting exoplanets.

2.) Transit effects – the exomoon may transit the star immediately before or just after the planet does. This will cause an added dip in the observed light. See this video for a great demonstration. This is similar to the light curve technique for detecting exoplanets.

The team modeled the initial transit light curves of Kepler-22b. They then injected an Earth-sized moon into the system in order to analyze the effects. While this caused clear variations in the light curve, such variations had to be above the level of noise.

As such, they also injected noise in the light curves, which mirrors that of the Kepler data. In the end, the variations in a star’s light curve due to the presence of an exomoon are much higher than the noise. The team is able to recover the correct answer with extremely high confidence.

Here Kipping et al. presents injected moon fits. As an example, the upper left-hand figure shows an exoplanet transit, with a moon transiting as well. Here the moon transits first, causing the light to be blocked, then the planet follows, causing more of the light to be blocked. Source: Kipping et al. 2013

The real data does not show deviations like the previous figure does. This non-detection implies that there is no moon with a mass greater than 0.54 times the mass of the Earth. While there is no Earth-analog in this system, there may be a smaller undetectable moon.

I asked Dr. Kipping about our chances of success in other systems. His answer: “That depends upon nature herself!” We have no idea how regularly nature produces moons in other solar systems. “There is nothing more exciting than working on a project where the answer is wholly unknown.”

But remember: two decades ago we were unsure if nature regularly produced planets. We have since observed them in abundance. I have to believe that with 168 moons in our solar system alone, we’re likely to find them in other systems. We’re on the verge of the next greatest discovery. So stay tuned because I promise I’ll be writing about it when it happens.

Source: Kipping et al. 2013

June 29, 2013March 16, 2017 by Fraser Cain

What is the Distance to the Moon?

The short answer is, the average distance to the Moon is 384,403 km (238,857 miles). But before you go thinking that this is the final answer, you need to consider a few things. For starters, note the use of the word “average”. This refers to the fact that the Moon orbits around the Earth in an elliptical pattern, which means that at certain times, it will be father away; while at others, it will be closer.

Hence, the number 384,403 km, is an average distance that astronomers call the semi-major axis. At its closest point (known as perigee) the Moon is only 363,104 km (225,622 miles) away. And at its most distant point (called apogee) the Moon gets to a distance of 406,696 km (252,088 miles).

This means that distance from the Earth to the Moon can vary by 43,592 km. That’s a pretty big difference, and it can make the Moon appear dramatically different in size depending on where it is in its orbit. For instance, the size of the Moon can vary by more than 15% from when it’s at its closest to when it’s at the most distant point.

It can also have a dramatic effect on how bright the moon appears when it is in its Full phase. As one might expect, the brightest full Moons occur when the Moon is at the closest, which are typically 30% brighter than when it’s fathest away. When it’s a Full Moon, and it’s a close Moon, it’s known as a Supermoon; which is also known by it technical name – perigee-syzygy.

To get an idea of what this all looks like, check out the animation above that was released by the Goddard Space Flight Center Scientific Visualization Studio in 2011. The animation shows the geocentric phase, libration, position angle of the axis, and apparent diameter of the Moon throughout the year, at hourly intervals.

At this point, a good question to ask would be: how do we know how far away the Moon is? Well, that depends on when we’re talking. In the days of ancient Greece, astronomers relied on simple geometry, the diameter of the Earth – which they had already calculated to be the equivalent of 12,875 km (or 8000 miles) – and the measurements of shadows to make the first (relatively) accurate estimates.

Having observed and recorded how shadows work over a long period of history, the ancient Greeks had determined that when an object is placed in front of the Sun, the length of a shadow this generates will always be 108 times the diameter of the object itself. So a ball measuring 2.5 cm (1 inch) across and placed on a stick between the Sun and the ground will create a triangular shadow that extends for 270 cm (108 inches).

This reasoning was then applied to the phenomena of Lunar and Solar Eclipses.

In the former, they found that the Moon was imperfectly blocked by the shadow of the Earth, and that the shadow was roughly 2.5 times the width of the Moon. In the latter, they noted that the Moon was of sufficient size and distance to block out the Sun. What’s more, the shadow it would create terminated at Earth, and would end in the same angle that the shadow of the Earth does – making them different-sized versions of the same triangle.

Using the calculations on the diameter of the Earth, the Greeks reasoned that the larger triangle would measure one Earth diameter at its base (12,875 km/8000 miles) and be 1,390,000 km (864,000 miles) long. The other triangle would be the equivalent of 2.5 Moon diameters wide and, since the triangles are proportionate, 2.5 Moon orbits tall.

Adding the two triangles together would yield the equivalent of 3.5 Moon orbits, which would create the largest triangle and gave the (again, relatively) accurate measurement of the distance between the Earth and the Moon. In other words, the distance is 1.39 million km (864,000 miles) divided by 3.5, which works out to around 397,500 km (247,000 miles). Not exactly bang on, but not bad for ancient peoples!

Lunar Laser Ranging Experiment. NASA — *Lunar Laser Ranging Experiment from the Apollo 11 mission. Credit: NASA*

Today, millimeter-precision measurements of the lunar distance are made by measuring the time it takes for light to travel between LIDAR stations here on the Earth and retroreflectors placed on the Moon. This process is known as the Lunar Laser Ranging experiment, a process that was made possible thanks to the efforts of the Apollo missions.

When astronauts visited the Moon more than forty years ago, they left a series of retroreflecting mirrors on the lunar surface. When scientists here on Earth shoot a laser at the Moon, the light from the laser is reflected right back at them from one of these devices. For every 100 quadrillion photons shot at the Moon, only a handful come back, but that’s enough to get an accurate appraisal.

Since light is moving at almost 300,000 kilometers (186,411 miles) per second, it takes a little more than a second to make the journey. And then it takes another second or so to return. By calculating the exact amount of time it takes for light to make the journey, astronomers are able to know exactly how far the Moon is at any time, down to millimeter accuracy.

From this technique, astronomers have also discovered that the Moon is slowly drifting away from us, at a glacial rate of 3.8 cm (1.5 inches) a year. Millions of years in the future, the Moon will appear smaller in the sky than it does today. And within a billion years or so, the Moon will be visually smaller than the Sun and we will no longer experience total solar eclipses.

We’ve written many articles about the Moon for Universe Today. Here’s an article about how LCROSS discovered buckets of water on the Moon, and here’s an article about how long it takes to get to the Moon.

If you’d like more info on the Moon, check out NASA’s Solar System Exploration Guide on the Moon, and here’s a link to NASA’s Lunar and Planetary Science page.

We have recorded several episodes of Astronomy Cast about the Moon. Here’s a good one, Episode 113: The Moon, Part 1.

June 27, 2013December 23, 2015 by Nancy Atkinson

Astrophoto: Houston Super Moonrise

37 separate images showing the movement of the Moon as it rises behind the buildings in downtown Houston, Texas on June 22, 2013. Credit and copyright: Sergio Garcia Rill/SGR Photo.

While we recently posted a huge batch of images from the recent “Super Moon,” this new image from Sergio Garcia Rill in Houston is something special. It’s a composite photo of the Moonrise on June 22nd, and is a mosaic made from 37 separate images that show the Moon rising over the course of three hours, with the buildings of downtown Houston in the foreground.

“I stayed in place for over three hours,” Sergio explained on Flickr. “The hardest part was selecting which shots showed a sequential movement of the Moon, since I was altering shutter speeds between shots to compensate for changing light conditions.”

The full Moon of June 2013 was at perigee — or at its closest point in its orbit to Earth, and appeared up to 14% bigger and 30% brighter than other full Moons of 2013.

Want to get your astrophoto featured on Universe Today? Join our Flickr group or send us your images by email (this means you’re giving us permission to post them). Please explain what’s in the picture, when you took it, the equipment you used, etc.

June 24, 2013December 23, 2015 by Nancy Atkinson

‘Super Moon’ Images from Around the World, June 2013

The perigee 'Super Moon' of June 23, 2013 (21:43 PHT) over Marikina City, Philippines compared to the apogee Moon of November, 2012. Credit and copyright: Raven Yu.

The full Moon of June 23, 2013 was the largest Moon of the year. This so-called “Super Moon” was at perigee — or at its closest point in its orbit to Earth, and was 14% bigger and 30% brighter than other full Moons of 2013.

But, if you looked up at the Moon last night and didn’t know about this, you may not have noticed! Some claims circulating on the internet tended to exaggerate how large the Moon would actually appear. However, that doesn’t mean the Moon wasn’t photogenic last night! The Moon is always a great target for photography or just gazing with your own eyes, and these images from Universe Today readers attest to the beauty of our closest companion in the night sky.

This lead image from Raven Yu from the Philippines shows the difference in size between last night’s perigee Moon and the apogee Moon (when it was farthest from Earth during its orbit) last November.

If you want to find out more about the science of the perigee Super Moon, read our detailed article here.

See more beautiful images, below!

Three different views of the Moon over Italy during the night of June 23, 2013 helps debunk the optical illusion of the Moon looking bigger when it's low on the horizon. Credit and copyright: Giuseppe Petricca. — Three different views of the Moon over Italy during the night of June 23, 2013 helps debunk the optical illusion of the Moon looking bigger when it’s low on the horizon. Credit and copyright: Giuseppe Petricca.

Three different pictures of the Moon from June 23, shared by Guiseppe Petricca from Italy, detailing not only the perigee Super Moon, but the ‘Moon Illusion” — of how the Moon looks bigger when it is close to the horizon.

“The middle one is the Moon at culmination in the local sky and the other two are taken as low as possible my local horizon permitted,” Guiseppe said via email. “Doing this, I managed to obtain two results: the first one is observing the different colours that due to the Rayleigh Scattering, ‘paint’ our satellite, when it’s low on its elevation. The second one is that, keeping a fixed magnification (24x – 110mm) one can easily debunk the optical illusion of the ‘bigger moon when it’s low on the horizon’. Since, if you observe carefully, the lower two ‘Moons’ are smaller than the higher one. However, the total personal experience is surely wonderful!! And the ‘horizon illusion’ makes you really think that the Moon is way bigger that the reality.”

The Supermoon rising on June 23rd, 22:40 pm above the forest canopy top in Puerto Rico. This is a 6 panel mosaic. Credit and copyright: Efrain Morales, Jaicoa Observatory.

The Super Moon on June 23, 2013 as seen over Malta. Credit and copyright: Leonard E. Mercer.

The perigee 'Super Moon' of June 23, 2013 as seen over Sesimbra, Portugal and the church Nossa Senhora do Castelo. Credit and copyright: Miguel Claro. — The perigee ‘Super Moon’ of June 23, 2013 as seen over Sesimbra, Portugal and the church Nossa Senhora do Castelo. Credit and copyright: Miguel Claro.

Miguel Claro captured this beautiful image of the huge full Moon rising above a Moorish castle in Sesimbra, Portugal. “The church Nossa Senhora do Castelo stands on the spot where king Sancho I built a Romanesque chapel in the early 13th century,” Miguel said via email. “This image was captured 2 km away from the subject.” Miguel used a Canon 50D – ISO640; 1/80 sec. + ED80 APO refractor Astro Professional 560mm at f/7 taken on 23/06/2013 at 21h22.

The perigee Super Moon of June 23, 2013 as seen over São Paulo, Brazil. Time: 01:40 UTC, using a Maksutov Cassegrain Vixen 110 mm - F = 1035 mm - F/9.4 - Plano Focal - Nikon D3100 - 1/80 - ISO 200. Credit and copyright: Ednilson Oliveira. — The perigee Super Moon of June 23, 2013 as seen over São Paulo, Brazil. Time: 01:40 UTC, using a Maksutov Cassegrain Vixen 110 mm – F = 1035 mm – F/9.4 – Plano Focal – Nikon D3100 – 1/80 – ISO 200. Credit and copyright: Ednilson Oliveira.

An early image of the perigee Super Moon -- the Moon setting the morning of June 23, 2013 just after 5 a.m. EDT over Toronto, Canada. ‘As I understand it perigee occurred between 7:11 - 7:13 a.m. EDT, so this was my ‘launch window’ to 'Shoot the Perigee Moon'. The atmosphere was thick with haze which dimmed the Moon substantially and allowed the surface maria to be photographed.’ Credit and copyright: Rick Ellis. — An early image of the perigee Super Moon — the Moon setting the morning of June 23, 2013 just after 5 a.m. EDT over Toronto, Canada. ‘As I understand it perigee occurred between 7:11 – 7:13 a.m. EDT, so this was my ‘launch window’ to ‘Shoot the Perigee Moon’. The atmosphere was thick with haze which dimmed the Moon substantially and allowed the surface maria to be photographed.’ Credit and copyright: Rick Ellis.

The perigee Super Moon rising over the floodwaters of the Bow River during a record flood that inundated many parts of southern Alberta around rivers, including here on the Siksika First Nations reserve. Credit and copyright: Alan Dyer/Astronomy Calgary/Amazing Sky Photography.

A 3-photo HDR image of the supermoon rising over downtown Tucson, Arizona. During the longer exposure the Moon gave out its own flare due to its intensity. Credit and copyright: Sean Parker/Sean Parker Photography.

The full perigee Moon rising on June 23, 2013. Credit and copyright: Sculptor Lil on Flickr.

Full Moon Rising Over Northwest Georgia on June 22nd, 2013. Credit and copyright: Stephen Rahn.

The perigee Super Moon on June 23, 2013, taken with a Skywatcher ED80 Refractor and a Canon 600D at prime focus. Best 20 of 40 images stacked in Registax 6. False colour removed as the Moon appeared dull red as it was so low in sky. Credit and copyright: James Lennie.

The view of June 23rd 2013 Supermoon from Trinidad and Tobago, West Indies (Caribbean). Credit and copyright: Apple Lilly. (This image is the right size to fit a Facebook cover image, the photographer says).

You can see more great images of this perigee Super Moon — and lots more great astrophotography at our Flickr group page.