You’ve Never Seen the Phases of the Moon from This Perspective: The Far Side

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Sometimes, it seems to be a cosmic misfortune that we only get to view the universe from a singular vantage point.

Take the example of our single natural satellite. As the Moon waxes and wanes through its cycle of phases,  we see the familiar face of the lunar nearside. This holds true from the day we’re born until the day we die. The Romans and Paleolithic man saw that same face, and until less than a century ago, it was anyone’s guess as to just what was on the other side.

Enter the Space Age and the possibility to finally get a peek at the universe from different perspective via our robotic ambassadors. This week, the folks over at NASA’s Scientific Visualization Studio released a unique video simulation that utilized data from NASA’s Lunar Reconnaissance Orbiter to give us a view unseen from Earth. This perspective shows just what the phases of the Moon would look like from the vantage point of the lunar farside:

You can see the Moon going through the synodic 29.5 day period a familiar phases, albeit with an unfamiliar face. Note that the Sun zips by, as the lunar farside wanes towards New. And in the background, the Earth can be seen, presenting an identical phase and tracing out a lazy figure eight as it appears and disappears behind the lunar limb.

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The lunar nearside: A familiar view. Credit: Stephen Rahn.

What’s with the lunar-planetary game of peek-a-boo? Well, the point of view for the video assumes that your looking at down at the lunar farside from a stationary point above the Moon. Note that the disk of the Moon stays fixed in place. The Moon actually ‘rocks’ or nods back and forth and side-to-side in motions referred to as libration and nutation, and you’re seeing these expressed via the motion of the Earth in the video.  This assures that we actually get a peek over the lunar limb and see a foreshadowed extra bit of the lunar farside, with grand 59% of the lunar surface visible from the Earth. Such is the wacky motion of our Moon, which gave early astronomers an excellent crash course in celestial mechanics 101.

Now, to dispel some commonly overheard lunar myths:

Myth #1: The moon doesn’t rotate. Yes, it’s tidally locked from our perspective, meaning that it keeps one face turned Earthward. But it does turn on its axis in lockstep as it does so once every 27.3 days, known as a sidereal month.

Myth #2:  The Farside vs. the Darkside. (Cue Pink Floyd) We do in fact see the dark or nighttime side of the Moon just as much as the daytime side. Despite popular culture, the farside is only synonymous with the darkside of the Moon during Full phase.

Humanity got its first glimpse of the lunar farside in 1959, when the Soviet Union’s Luna 3 spacecraft looked back as it flew past the Moon and beamed us the first blurry image. The Russians got there first, which is why the lunar farside now possesses names for features such as the “Mare Moscoviense”.

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Our evolving view of the lunar farside over 60 years… Credit: NASA/LRO.

Think we’ve explored the Moon? Thus far, no mission – crewed or otherwise – has landed on the lunar farside. The Apollo missions were restricted to nearside landing sites at low latitudes with direct line of sight communication with the Earth. The same goes for the lunar poles: the Moon is still a place begging for further exploration.

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China’s Chang’e 5 T1 pathfinder mission looks back at the Earth and the lunar farside. Credit: Xinhua/SASTIND.

Why go to the lunar farside? Well, it would be a great place to do some radio astronomy, as you have the bulk of the Moon behind you to shield your sensitive searches from the now radio noisy Earth. Sure, the dilemmas of living on the lunar farside might forever outweigh the benefits, and abrasive lunar dust will definitely be a challenge to lunar living… perhaps an orbiting radio astronomy observatory in a Lissajous orbit at the L2 point would be a better bet?

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An artist’s conception of LRO in lunar orbit. Credit: NASA/LRO.

And exploration of the Moon continues. Earlier this week, the LRO team released a finding suggesting that surface hydrogen may be more abundant on the poleward facing slopes of craters that litter the lunar south pole region. Locating caches of lunar ice in permanently shadowed craters will be key to a ‘living off of the land’ approach for future lunar colonists… and then there’s the idea to harvest helium-3 for nuclear fusion (remember the movie Moon?) that’s still science fiction… for now.

Perhaps the Moonbase Alpha of Space: 1999 never came to pass… but there’s always 2029!

SpaceX Prepares for Crucial Crew Dragon Capsule Pad Abort Test

SpaceX Dragon V2 pad abort test flight vehicle. Credit: SpaceX

SpaceX is preparing for the first of two critical abort tests for the firm’s next generation human rated Dragon V2 capsule as soon as March.

The purpose of the pair of abort tests is to demonstrate a crew escape capability to save the astronauts’ lives in case of a rocket failure, starting from the launch pad and going all the way to orbit.

The SpaceX Dragon V2 and Boeing CST-100 vehicles were selected by NASA last fall for further funding under the auspices of the agency’s Commercial Crew Program (CCP) as the world’s privately developed spaceships to ferry astronauts back and forth to the International Space Station (ISS).

Both SpaceX and Boeing plan to launch the first manned test flights to the ISS with their respective transports in 2017.

During the Sept. 16, 2014, news briefing at the Kennedy Space Center, NASA Administrator Charles Bolden announced that contracts worth a total of $6.8 Billion were awarded to SpaceX to build the manned Dragon V2 and to Boeing to build the manned CST-100.

The first abort test involving the pad abort test is currently slated to take place soon from the company’s launch pad on Cape Canaveral Air Force Station in Florida, according to Gwynne Shotwell, president of SpaceX.

“First up is a pad abort in about a month,” said Shotwell during a media briefing last week at NASA’s Johnson Space Center in Houston, Texas.

SpaceX engineers have been building the pad abort test vehicle for the unmanned test for more than a year at their headquarters in Hawthorne, California.

Dragon V2 builds on and significantly upgrades the technology for the initial cargo version of the Dragon which has successfully flown five operational resupply missions to the ISS.

“It took us quite a while to get there, but there’s a lot of great technology and innovations in that pad abort vehicle,” noted Shotwell.

First look at the SpaceX Crew Dragon’s pad abort vehicle set for flight test in March 2014.  Credit: SpaceX.
First look at the SpaceX Crew Dragon’s pad abort vehicle set for flight test in March 2014. Credit: SpaceX.

The pad abort demonstration will test the ability of a set of eight SuperDraco engines built into the side walls of the crew Dragon to pull the vehicle away from the launch pad in a simulated emergency.

The SuperDraco engines are located in four jet packs around the base. Each engine can produce up to 120,000 pounds of axial thrust to carry astronauts to safety, according to a SpaceX description.

Here is a SpaceX video of SuperDraco’s being hot fire tested in Texas:

Video caption: Full functionality of Crew Dragon’s SuperDraco jetpacks demonstrated with hotfire test in McGregor, TX. Credit: SpaceX

For the purpose of this test, the crew Dragon will sit on top of a facsimile of the unpressurized trunk portion of the Dragon. It will not be loaded on top of a Falcon 9 rocket for the pad abort test.

The second abort test involves a high altitude abort test launching atop a SpaceX Falcon 9 rocket from Vandenberg Air Force Base in California.

“An in-flight abort test [follows] later this year,” said Shotwell.

“The Integrated launch abort system is critically important to us. We think it gives incredible safety features for a full abort all the way through ascent.”

“It does also allow us the ultimate goal of fully propulsive landing.”

Both tests were originally scheduled for 2014 as part of the firm’s prior CCiCAP development phase contract with NASA, SpaceX CEO Elon Musk told me in late 2013.

“Assuming all goes well, we expect to conduct [up to] two Dragon abort tests next year in 2014,” Musk explained.

Last year, NASA granted SpaceX an extension into 2015 for both tests under SpaceX’s CCiCAP milestones.

SpaceX founder and CEO Elon Musk briefs reporters, including Universe Today, in Cocoa Beach, FL, during prior SpaceX Falcon 9 rocket blastoff from Cape Canaveral, FL. Credit: Ken Kremer/kenkremer.com
SpaceX founder and CEO Elon Musk briefs reporters, including Universe Today, in Cocoa Beach, FL, during a prior SpaceX Falcon 9 rocket blastoff from Cape Canaveral, FL. Credit: Ken Kremer/kenkremer.com

The SpaceX Dragon V2 will launch atop a human rated Falcon 9 v1.1 rocket from Space Launch Complex 40 at Cape Canaveral.

“We understand the incredible responsibility we’ve been given to carry crew. We should fly over 50 Falcon 9’s before crewed flight,” said Shotwell.

To accomplish the first manned test flight to the ISS by 2017, the US Congress must agree to fully fund the commercial crew program.

“To do this we need for Congress to approve full funding for the Commercial Crew Program,” Bolden said at last week’s JSC media briefing.

Severe budget cuts by Congress forced NASA into a two year delay in the first commercial crew flights to the ISS from 2015 to 2017 – and also forced NASA to pay hundreds of millions of more dollars to the Russians for crews seats aboard their Soyuz instead of employing American aerospace workers.

Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.

Ken Kremer

Boeing and SpaceX are building private spaceships to resume launching US astronauts from US soil to the International Space Station in 2017. Credit: NASA
Boeing and SpaceX are building private spaceships to resume launching US astronauts from US soil to the International Space Station in 2017. Credit: NASA

An Even Closer View of Ceres Shows Multiple White Spots Now

One several images NASA's Dawn spacecraft took on approach to Ceres on Feb. 4, 2015 at a distance of about 90,000 miles (145,000 kilometers) from the dwarf planet. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

NASA’s Dawn spacecraft has acquired its latest and closest-yet snapshot of the mysterious dwarf planet world Ceres. These latest images, taken on Feb. 4, from a distance of about 90,000 miles (145,000 km) clearly show craters – including a couple with central peaks –  and a clearer though still ambiguous view of that wild white spot that has so many of us scratching our heads as to its nature.

Get ready to scratch some more. The mystery spot has plenty of company.

Take a look at some still images I grabbed from the video which NASA made available today. In several of the photos, the white spot clearly looks like a depression, possibly an impact site. In others, it appears more like a rise or mountaintop. But perhaps the most amazing thing is that there appear to be not one but many white dabs and splashes on Ceres’ 590-mile-wide globe. I’ve toned the images to bring out more details:

Here the spot appears more like a depression. Frost? Ice? Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Here the spot appears more like a depression. Frost? Ice? Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Here the white spot is at the asteroid's left limb. You can also see additional smaller spots that remind me of rayed lunar craters. Credit:
Here the white spot is at the asteroid’s left limb. You can also see lots of additional smaller spots that remind me of rayed lunar craters. Of course, they may be something else entirely.  Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Look down along the lower limb to spot a crater with a cool central peak. Credit:
Look down along the lower limb to spot a crater with a cool central peak. Note also how many white spots are now visible on Ceres. The mystery spot is a little right of center in this view. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Our mystery white spot is further right of center. Is it a rise or a hole? Credit:
Our mystery white spot is further right of center. Is it a rise or a hole?Are the streaks rays for fresh material from an impact the way the lunar crater Tycho appears from Earth?  Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Yet another view of the mystery spot. Credit:
Yet another view of the mystery spot. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

 

Animation made from images taken by Dawn on Feb. 4. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Animation made from images taken by Dawn on Feb. 4. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Now let’s take a look at an additional NASA animation of Ceres made using processed images. As the spot first rounds the limb it looks like a depression. But just before it disappears around the backside a pointed peak seems to appear. Intriguing, isn’t it?

What Is A Wolf-Rayet Star?

M1-67 is the youngest wind-nebula around a Wolf-Rayet star, called WR124, in our Galaxy. Credit: ESO

Wolf-Rayet stars represent a final burst of activity before a huge star begins to die. These stars, which are at least 20 times more massive than the Sun, “live fast and die hard”, according to NASA.

Their endstate is more famous; it’s when they explode as supernova and seed the universe with cosmic elements that they get the most attention. But looking at how the star gets to that explosive stage is also important.

When you look at a star like the Sun, what you are seeing is a delicate equilibrium of the star’s gravity pulling stuff in, and nuclear fusion inside pushing pressure out. When the forces are about equal, you get a stable mass of fusing elements. For planets like ours lucky enough to live near a stable star, this period can go on for billions upon billions of years.

Being near a massive star is like playing with fire, however. They grow up quickly and thus die earlier in their lives than the Sun. And in the case of a Wolf-Rayet star, it’s run out of lighter elements to fuse inside its core. The Sun is happily churning hydrogen into helium, but Wolf-Rayets are ploughing through elements such as oxygen to try to keep equilibrium.

The core of a red or blue supergiant moments before exploding as a supernova looks like an onion with multiple elements "burning" through the fusion process to create the heat to stay the force of gravity. Fusion stops at iron. With no energy pouring from the central core to keep the other elements cooking, the star collapses and the rebounding shock wave tears it apart. Credit: Wikimedia
The core of a red or blue supergiant moments before exploding as a supernova looks like an onion with multiple elements “burning” through the fusion process to create the heat to stay the force of gravity. Fusion stops at iron. With no energy pouring from the central core to keep the other elements cooking, the star collapses and the rebounding shock wave tears it apart. Credit: Wikimedia

Because these elements have more atoms per unit, this creates more energy — specifically, heat and radiation, NASA says. The star begins to blow out winds reaching 2.2 million to 5.4 million miles per hour (3.6 million to 9 million kilometers per hour). Over time, the winds strip away the outer layers of the Wolf-Rayet. This eliminates much of its mass, while at the same time freeing its elements to be used elsewhere in the Universe.

Eventually, the star runs out of elements to fuse (the process can go no further than iron). When the fusion stops, the pressure inside the star ceases and there’s nothing to stop gravity from pushing in. Big stars explode as supernova. Bigger ones see their gravity warped so much that not even light can escape, creating a black hole.

We still have a lot to learn about stellar evolution, but a few studies over the years have provided insights. In 2004, for example, NASA issued reassuring news saying these stars don’t “die alone.” Most of them have a stellar companion, according to Hubble Space Telescope observations.

A composite image with Chandra data (purple) showing a "point-like source" beside the remains of a supernova, suggesting a companion star may have survived the explosion. Hydrogen is shown in optical light (yellow and cyan) from the Magellanic Cloud Emission Line Survey and there is also optical data available from the Digitized Sky Survey (white). Credit: X-ray: NASA/CXC/SAO/F.Seward et al; Optical: NOAO/CTIO/MCELS, DSS
A composite image with Chandra data (purple) showing a “point-like source” beside the remains of a supernova, suggesting a companion star may have survived the explosion. Hydrogen is shown in optical light (yellow and cyan) from the Magellanic Cloud Emission Line Survey and there is also optical data available from the Digitized Sky Survey (white). Credit: X-ray: NASA/CXC/SAO/F.Seward et al; Optical: NOAO/CTIO/MCELS, DSS

While at first glance this appears as just a simple observation, cosmologists said that it could help us figure out how these stars get so big and bright. For example: Maybe the bigger star (the one that turns into a Wolf-Rayet) feeds off its companion over time, gathering mass until it becomes stupendously big. With more fuel, the big stars burn out faster. Other things the smaller star could influence could be the bigger star’s rotation or orbit.

Here’s a few other facts about Wolf-Rayets, courtesy of astronomer David Darling:

  • Their names come from two French astronomers, Charles Wolf and Georges Rayet, who discovered the first known star of this kind in 1867.
  • Wolf-Rayets come in two flavours: WN (emission lines of helium and nitrogen) and WC (carbon, oxygen and hydrogen).
  • Stars like our Sun evolve into more massive red giants as they run out of hydrogen to burn in the core. When these stars begin to shed their outer layers, they behave somewhat similarly to Wolf-Rayets. So they’re called “Wolf-Rayet type stars”, although they’re not exactly the same thing.

We have written many articles about stars here on Universe Today. Here’s an article about a binary pair of Wolf-Rayet stars, and the good news that WR 104 won’t kill us all. We have recorded several episodes of Astronomy Cast about stars. Here are two that you might find helpful: Episode 12: Where Do Baby Stars Come From, and Episode 13: Where Do Stars Go When they Die?

Rosetta to Snuggle Up to Comet 67P for Closest Encounter Yet

Rosetta will dance close to 67P on Valentine's Day coming to within 3.7 miles of the comet. Credit: Bob King

Who doesn’t like to snuggle up with their Valentine on Valentine’s Day? Rosetta will practically whisper sweet nothings into 67P’s ear on February 14 when it swings just 3.7 miles (6 km) above its surface, its closest encounter yet.

Rosetta had been orbiting the comet at a distance of some  16 miles (26 km) but beginning yesterday, mission controllers used the spacecraft’s thrusters to change its orbit in preparation for the close flyby.  First, Rosetta will move out to a distance of roughly 87 miles (140 km) from the comet this Saturday before swooping in for the close encounter at 6:41 a.m. CST on Feb. 14. Closest approach happens over the comet’s larger lobe, above the Imhotep region.

The relative position of Rosetta with Comet 67P/Churyumov–Gerasimenko at the moment of closest approach this Valentine's Day when the spacecraft will pass just 3.7 miles (6 km) above the comet’s large lobe. Credit: ESA/C.Carreau
The relative position of Rosetta with Comet 67P/Churyumov–Gerasimenko at the moment of closest approach this Valentine’s Day when the spacecraft will pass just 3.7 miles (6 km) above the comet’s large lobe. Credit: ESA/C.Carreau with additions by the author

The close encounter will provide opportunities for Rosetta’s science instruments to photograph 67P’s surface at high resolution across a range of wavelengths as well as get a close sniff of what’s inside its innermost coma or developing atmosphere. Scientists will also be looking closely at the outflowing gas and dust to see how it evolves during transport from the comet’s interior to the coma and tail.

As Rosetta swoops by its view of the comet will continuously change. Instruments will collect data on how 67P’s dust grains reflect light across a variety of orbital perspectives – from shadowless lighting with the Sun at the orbiter’s back to slanted lighting angles –  to learn more about its properties.

The Imhotep region of comet 67P features a large, relatively smooth region. Rosetta will make high resolutions of Imhotep during its close flyby. Credit: ESA/Rosetta/Navcam
The Imhotep region of comet 67P features a large, relatively smooth region and a smattering of large boulders. Rosetta will make high resolutions of Imhotep during its close flyby. Credit: ESA/Rosetta/Navcam

“After this close flyby, a new phase will begin, when Rosetta will execute sets of flybys past the comet at a range of distances, between about 15 km (9 miles) and 100 km (62 miles),” said Sylvain Lodiot, ESA’s spacecraft operations manager.

During some of the close flybys, Rosetta trajectory will be almost in step with the comet’s rotation, allowing the instruments to monitor a single point on the surface in great detail as it passes by.


Helpful animation of how ESA mission controllers are changing Rosetta’s orbit to ready the probe for the Valentine’s Day flyby.

Perihelion, when the comet arcs closest to the Sun at a distance of 115.6 million miles (186 million km), occurs on August 13. Activity should be reaching its peak around that time. Beginning one month before, the Rosetta team will identify and closely examine one of the comet’s jets in wickedly rich detail.

“We hope to target one of these regions for a fly-through, to really get a taste of the outflow of the comet,” said Matt Taylor, ESA’s Rosetta project scientist.

Yum, yum. Can’t wait for that restaurant review!

A Night-Sky Timelapse You Don’t Want to Miss

Still image from the timelapse, "Illusion of Lights: A Journey into the Unseen." Credit and copyright: Brad Goldpaint Photography.

It’s an old story: a couple leave their jobs, sell everything, and live in motorhome to capture footage and imagery of the night sky.

Wait… what?

This unique story is exactly what Brad and Marci Goldpaint did. They left their jobs and traveled throughout the western US in an RV to begin educating the public about the damaging effects of light pollution. They wanted to help reconnect people with the simple beauty of the night sky and have been teaching photography workshops and gathering footage for a new timelapse called “Illusion of Lights: A Journey into the Unseen.”

With breathtaking scenes and soaring music, this video “introduces you to the concept of movement and time that visually explores our night skies,” says Brad on Vimeo.

We’ve featured images and timelapses from Brad before, and he shared how the sudden loss of his mother caused him to reassess his goals and priorities. Since 2009 he’s been working on outdoor photography and has now dedicated his work to sharing images of the night sky with others.

For this timelapse, Brad said he “spent countless nights traversing in the dark, carrying heavy camera equipment, and braving the dark unseen.” He dealt with lightning storms, dangerous winds, and up-close encounters with bears and other wildlife. Sometimes, after spending days hiking to a remote location and with optimistic weather reports, Mother Nature showed up and ruined his opportunity to get the shot.

A few highlights: at about 2:00 there is an exploding meteor with a persistent train that is stunning. You’ll also see strange lights on Mount Rainier. Brad explained these lights are from people climbing the mountian at night in hopes of reaching the summit by sunrise the following day. The white lights you see are from their headlamps. “Can you imagine climbing up a mountain in the middle of the night?” he asks?

Another still from "Illusions of Light." Credit and copyright: Brad Goldpaint Photography.
Another still from “Illusions of Light.” Credit and copyright: Brad Goldpaint Photography.

For more about this film see their website.

Illusion of Lights: A Journey into the Unseen from Goldpaint Photography on Vimeo.

What is Gravitational Lensing?

Hubble Frontier Fields observing programme, which is using the magnifying power of enormous galaxy clusters to peer deep into the distant Universe. Credit: NASA.

Gravity’s a funny thing. Not only does it tug away at you, me, planets, moons and stars, but it can even bend light itself. And once you’re bending light, well, you’ve got yourself a telescope.

Everyone here is familiar with the practical applications of gravity. If not just from exposure to Loony Tunes, with an abundance of scenes with an anthropomorphized coyote being hurled at the ground from gravitational acceleration, giant rocks plummeting to a spot inevitably marked with an X, previously occupied by a member of the “accelerati incredibilus” family and soon to be a big squish mark containing the bodily remains of the previously mentioned Wile E. Coyote.

Despite having a very limited understanding of it, Gravity is a pretty amazing force, not just for decimating a infinitely resurrecting coyote, but for keeping our feet on the ground and our planet in just the right spot around our Sun. The force due to gravity has got a whole bag of tricks, and reaches across Universal distances. But one of its best tricks is how it acts like a lens, magnifying distant objects for astronomy.

Continue reading “What is Gravitational Lensing?”

Which Planets Have Rings?

Which Planets Have Rings?
This colorized image taken by the Cassini orbiter, shows Saturn's A and F rings, the small moon Epimetheus and Titan, the planet's largest moon. Credit: NASA/JPL/Space Science Institute

Planetary rings are an interesting phenomena. The mere mention of these two words tends to conjure up images of Saturn, with its large and colorful system of rings that form an orbiting disk. But in fact, several other planets in our Solar System have rings. It’s just that, unlike Saturn, their systems are less visible, and perhaps less beautiful to behold.

Thanks to exploration efforts mounted in the past few decades, which have seen space probes dispatched to the outer Solar System, we have come to understand that all the gas giants – Jupiter, Saturn, Uranus and Neptune – all have their own ring systems. And that’s not all! In fact, ring systems may be more common than previously thought…

Jupiter’s Rings:

In was not until 1979 that the rings of Jupiter were discovered when the Voyager 1 space probe conducted a flyby of the planet. They were also thoroughly investigated in the 1990s by the Galileo orbiter. Because it is composed mainly of dust, the ring system is faint and can only be observed by the most powerful telescopes, or up-close by orbital spacecraft. However, during the past twenty-three years, it has been observed from Earth numerous times, as well as by the Hubble Space Telescope.

A schema of Jupiter's ring system showing the four main components. For simplicity, Metis and Adrastea are depicted as sharing their orbit. Credit: NASA/JPL/Cornell University
A schema of Jupiter’s ring system showing the four main components. Credit: NASA/JPL/Cornell University

The ring system has four main components: a thick inner torus of particles known as the “halo ring”; a relatively bright, but extremely thin “main ring”; and two wide, thick, and faint outer “gossamer rings”. These outer rings are composed of material from the moons Amalthea and Thebe and are named after these moons (i.e. the “Amalthea Ring” and “Thebe Ring”).

The main and halo rings consist of dust ejected from the moons Metis, Adrastea, and other unobserved parent bodies as the result of high-velocity impacts. Scientists believe that a ring could even exist around the moon of Himalia’s orbit, which could have been created when another small moon crashed into it and caused material to be ejected from the surface.

Saturn’s Rings:

The rings of Saturn, meanwhile, have been known for centuries. Although Galileo Galilei became the first person to observe the rings of Saturn in 1610, he did not have a powerful enough telescope to discern their true nature. It was not until 1655 that Christiaan Huygens, the Dutch mathematician and scientist, became the first person to describe them as a disk surrounding the planet.

Subsequent observations, which included spectroscopic studies by the late 19th century, confirmed that they are composed of smaller rings, each one made up of tiny particles orbiting Saturn. These particles range in size from micrometers to meters that form clumps orbiting the planet, and which are composed almost entirely of water ice contaminated with dust and chemicals.

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/Gordan Ugarkovic

In total, Saturn has a system of 12 rings with 2 divisions. It has the most extensive ring system of any planet in our solar system. The rings have numerous gaps where particle density drops sharply. In some cases, this due to Saturn’s Moons being embedded within them, which causes destabilizing orbital resonances to occur.

However, within the Titan Ringlet and the G Ring, orbital resonance with Saturn’s moons has a stabilizing influence. Well beyond the main rings is the Phoebe ring, which is tilted at an angle of 27 degrees to the other rings and, like Phoebe, orbits in retrograde fashion.

Uranus’ Rings:

The rings of Uranus are thought to be relatively young, at not more than 600 million years old. They are believed to have originated from the collisional fragmentation of a number of moons that once existed around the planet. After colliding, the moons probably broke up into numerous particles, which survived as narrow and optically dense rings only in strictly confined zones of maximum stability.

Uranus has 13 rings that have been observed so far. They are all very faint, the majority being opaque and only a few kilometers wide. The ring system consists mostly of large bodies 0.2 to 20 m in diameter. A few rings are optically thin and are made of small dust particles which makes them difficult to observe using Earth-based telescopes.

The labeled ring arcs of Neptune as seen in newly processed data. The image spans 26 exposures combined into a equivalent 95 minute exposure, and the ring trace and an image of the occulted planet Neptune is added for reference. (Credit: M. Showalter/SETI Institute).
The labeled ring arcs of Neptune as seen in newly processed data. Credit: M. Showalter/SETI Institute

Neptune’s Rings:

The rings of Neptune were not discovered until 1989 until the Voyager 2 space probe conducted a flyby of the planet. Six rings have been observed in the system, which are best described as faint and tenuous. The rings are very dark, and are likely composed by organic compounds processed by radiation, similar to that found in the rings of Uranus. Much like Uranus, and Saturn, four of Neptune’s moons orbit within the ring system.

Other Bodies:

Back in 2008, it was suggested that the magnetic effects around the Saturnian moon of Rhea may indicate that it has its own ring system. However, a subsequent study indicated that observations obtained the Cassini mission suggested that some other mechanism was responsible for the magnetic effects.

Years before the the New Horizons probe visited the system, astronomers speculated that Pluto might also have a ring system. However, after conducting its historic flyby of the system in July of 2015, the New Horizons probe did not find any evidence of a ring system. While the dwarf planet had many satellites aside from its largest (Charon), debris from around the planet has not coalesced into rings, as was theorized.

Artist's impression of the New Horizons spacecraft in orbit around Pluto (Charon is seen in the background). Credit: NASA/JPL
Artist’s impression of the New Horizons spacecraft in orbit around Pluto (Charon is seen in the background). Credit: NASA/JPL

The minor planet of Chariklo – an asteroid that orbits the Sun between Saturn and Uranus – also has two rings that orbit it. These are perhaps due to a collision that caused a chain of debris to form in orbit around it. The announcement of these rings was made on March 26th of 2014, and was based on observations made during a stellar occultation on June 3rd, 2013.

This was followed by findings made in 2015 that indicated that 2006 Chiron – another major Centaur – could have a ring of its own. This led to further speculation that there might be many minor planets in our Solar System that have a system of rings.

In short, four planets in our Solar System have intricate ring systems, as well as the minor planet Chariklo, and perhaps even many other smaller objects. In this sense, ring systems appear to be a lot more common in our Solar System than previously thought.

We have written many articles about planets with rings for Universe Today. Here’s an article about the composition of Saturn’s rings, and here’s an article about the planets with rings.

If you’d like more info on the planets, check out NASA’s Solar System exploration page, and here’s a link to NASA’s Solar System Simulator.

We’ve also recorded a series of episodes of Astronomy Cast about every planet in the Solar System. Start here, Episode 49: Mercury.

The Moment We’ve been Waiting For: First New Images of Pluto from New Horizons

Pluto and Charon, the largest of Pluto's five known moons, seen Jan. 25 and 27, 2015, through the telescopic Long-Range Reconnaissance Imager (LORRI) on NASA's New Horizons spacecraft. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.

Here we go! New Horizons is now on approach and today – on the anniversary of Pluto discoverer Clyde Tombaugh’s birth – the spacecraft has sent back its first new images of the Pluto system. The images aren’t Earth-shattering (Pluto-shattering?) but they do represent the mission is closing in on its target, and will allow the New Horizons engineers to precisely aim the spacecraft as it continues its approach.

The photos were taken with the telescopic Long-Range Reconnaissance Imager (LORRI) on January 25 and 27, 2015.

“Pluto is finally becoming more than just a pinpoint of light,” said Hal Weaver, New Horizons project scientist. “LORRI has now resolved Pluto, and the dwarf planet will continue to grow larger and larger in the images as New Horizons spacecraft hurtles toward its targets. The new LORRI images also demonstrate that the camera’s performance is unchanged since it was launched more than nine years ago.”

A comparison of images of Pluto and its large moon Charon, taken in July 2014 and January 2015. Between takes, New Horizons had more than halved its distance to Pluto, from about 264 million miles (425 million kilometers) to 126 million miles (203 million kilometers). Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.
A comparison of images of Pluto and its large moon Charon, taken in July 2014 and January 2015. Between takes, New Horizons had more than halved its distance to Pluto, from about 264 million miles (425 million kilometers) to 126 million miles (203 million kilometers). Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.

New Horizons was about 203 million kilometers (126 million miles) away from Pluto when it began taking images. Pluto appears as a pixelated smudge, and New Horizons is only close enough so that just Pluto and its largest moon, Charon are visible. In this current view from LORRI, Pluto is about 2 pixels and Charon is 1, compared to 1 pixel and 0.5 pixels last July. The images were magnified four times to make Pluto and Charon more visible.

NASA says that over the next few months, LORRI will take hundreds of pictures of Pluto, against a starry backdrop, to refine the team’s estimates of New Horizons’ distance to Pluto. As in these first images, the Pluto system will resemble little more than bright dots in the camera’s view until late spring. However, mission navigators can still use such images to design course-correcting engine maneuvers to direct the spacecraft for a more precise approach. The first such maneuver based on these optical navigation images, or OpNavs, is scheduled for March 10.

The image of Pluto and its moon Charon, taken by NASA’s New Horizons spacecraft, was magnified four times to make the objects more visible. Over the next several months, the apparent sizes of Pluto and Charon, as well as the separation between them, will continue to expand in the images. Image Credit:  NASA/JHU APL/SwRI
The image of Pluto and its moon Charon, taken by NASA’s New Horizons spacecraft, was magnified four times to make the objects more visible. Over the next several months, the apparent sizes of Pluto and Charon, as well as the separation between them, will continue to expand in the images.
Image Credit:
NASA/JHU APL/SwRI

Closest approach for the spacecraft will be on July 14.

These first images represent a milestone.

“These images of Pluto, clearly brighter and closer than those New Horizons took last July from twice as far away, represent our first steps at turning the pinpoint of light Clyde saw in the telescopes at Lowell Observatory 85 years ago, into a planet before the eyes of the world this summer,” said Alan Stern, New Horizons principal investigator. “This is our birthday tribute to Professor Tombaugh and the Tombaugh family, in honor of his discovery and life achievements — which truly became a harbinger of 21st century planetary astronomy.”

During its flyby, New Horizons will be characterizing the global geology and topography of Pluto and Charon, mapping their surface compositions and temperatures, examining Pluto’s atmospheric composition and structure, studying Pluto’s smaller moons, and searching for new moons and rings.

Sources: NASA, JHUAPL

The World’s Rockets to Scale

A graphics of all rockets that have flown, shown to scale. Credit: Tyler Skrabek

Inspired by a book and poster from 1995, titled “Rockets of the World,” graphic artist Tyler Skrabek has provided a new and updated “clean” look for his latest work.

“The ‘Rockets of the World’ poster emulates a 1960 style of drawing,” he said, “employing a consistent pallet across all rockets allowing for a distraction-free look at the size and power of the world’s greatest machines.”

Skrabek told Universe Today that he’s been working on this poster for 3 months, but he’s had the idea of creating it since 2012.

It is available in various sizes on etsy here.

“The ‘Rockets of the World’ poster is something I put a lot of work into,” he said, “as it’s been my sole project for the last 3 months. Three years ago I was just interested in rockets and wanted to see how the most popular rockets stacked up against each other. But when I looked online to see if I could find a chart, all that existed were height comparisons using technical drawings with 3D renderings of newer rockets squished in. There just weren’t any posters that I could find that used consistent 3D full color renderings and that’s what I set out to create.”

He wanted an uncluttered look for his poster, and therefore used a set of rules to eliminate some rockets: The Rocket had to have more than 3 successful flights and each rocket had to be unique – no later versions from the same rocket family, such as the Soyuz.

Also, rocket wannabes didn’t make the cut … not yet anyway.

“Just to keep things tidy I choose not to include rockets that haven’t flown yet on the off-chance they don’t actually make it off the ground,” Tyler said on reddit. “But rest assured there will be a version that includes the Falcon 9 Heavy as soon as it does.”

A few months ago he created the “Rockets of Human Spaceflight” poster and posted it on reddit. He took suggestions from fellow redditors to create the final version, below. He used that poster as the impetus to continue the Rockets of the World poster.

Rockets of Human Spaceflight. Credit and copyright: Tyler Skrabek.
Rockets of Human Spaceflight. Credit and copyright: Tyler Skrabek.

You can see the original “Rockets of the World” illustration from physics professor Peter Alway’s 1995 book “Rockets of the World” here.

Tyler said he’s always been passionate about space, spaceflight and human exploration in space.

“I find it fascinating that we as a society have the power to take a person, put that person inside a metal box on top of a cylinder filled with explosives and explore space,” he says on his website. “As an active member in space circles, I realized there was a lack of infographics that did a reasonable job of portraying comparisons between the various types of spacecraft while being visually appealing. I decided to research and develop a series of infographics to better explain this to the everyday person.”

You can see more of his work on his website here, including his great space infographics here.

On reddit he said, “I hope you like these posters and can help me come up with even more exciting projects!”