The dust tail on Asteroid P/2010 A2 (LINEAR) has grown to over 1 million kilometers long. Image taken with the new One Degree Imager (ODI), a wide field optical camera at the WIYN telescope on Kitt Peak.
A strange comet-like object discovered in 2010 ended up being an asteroid that had been the victim of a head-on collision from another space rock. The object created a bit of buzz because of its mysterious X-shaped debris pattern and long, trailing streamers of dust. Named P/2010 A2 (LINEAR), the object is located in the asteroid belt between Mars and Jupiter, and has been the focus of much study, including images taken by the Hubble Space Telescope and many ground-based observatories. But over time, the asteroid’s long dust tail has grown to be so long that the entire object can’t fit into the field of view of most observatories.
“Here, we are watching the death of an asteroid,” said Jayadev Rajagopal, a scientist at the WIYN (Wisconsin Indiana at Yale NOAO) Telescope, speaking today at the American Astronomical Society meeting in Indianapolis, Indiana. “We know of dozens of asteroids this has happened to in the past, but this is the only one showing us the event as it is happening.”
A graphic showing the orbit of Asteroid P/2010 A2. Credit: WIYN telescope.
Using the new wide-field camera at the WIYN 3.5 meter telescope, Rajagopal and his team have found that the peculiar asteroid P/2010 A2’s tail is much longer than was previously supposed. The tail is about a million kilometers long, roughly three times the distance from the Earth to the Moon. The new One Degree Imager (ODI) can currently image an area of the sky about the size of the full moon: a future upgrade will increase the size of the field to about four times as large.
“Three and a half years after the initial disruption, and almost a full orbit around the Sun, the tail is still visible and growing,” said Rajagopal. “One of the reasons it is so long is that radiation pressure and gravity are stretching out the tail. It will progressively grow and sweep out into the ecliptic.”
He added that imaging the full extent of the tail will help pin down the total mass in the dust tail, as well as helping to determine the size of dust particles.
Hubble Views of Comet-like Asteroid P/2010 A2. Credit: NASA, ESA, and D. Jewitt (UCLA)
Asteroid collisions are thought to be a commonplace occurrence, and are responsible for kicking up dust in our Solar System and probably other planetary systems, too. Just how much dust is produced, and how frequent the collisions happen is still a hazy topic. But the observations of P/2010 A2 are helping astronomers to better model this phenomenon. By figuring out how much dust is produced by the process of ‘collisional grinding,’ astronomers can better model the dusty debris disks of other planetary systems, as well as our own.
“This object is giving us insight into the interplay between asteroids and debris disks,” Rajagopal said. “How much dust do objects like this contribute to our zodiacal dust disk to keep it replenished? This dust must be constantly replenished because it is constantly being destroyed by radiation. The very unusual tail of this active asteroid will help us pin down the mass of the tail, and in a broader context, help us understand how asteroids brought organics and other materials into the inner planets.”
Rajagopal also said this the tail of Asteroid P/2010 A2 is a meteor stream in the making. “It will eventually sweep into the Earth’s orbit and give us a meteorite stream, sending some meteorites our way, maybe a million years from now.”
When we look at the night sky, filled with stars, it’s hard to resist counting. Just with the unaided eye, in dark skies, you can see a few thousand.
How many stars are there in the entire Universe? Before we get to that massive number, let’s consider what you can count with the tools available to you.
Perfect vision in dark skies allows us to see stars down to about magnitude 6. But to really make an accurate census of the total number of stars, you’d need to travel to both the Northern and Southern Hemispheres, since only part of the sky is visible from each portion of the Earth. Furthermore, you’d need to make your count over several months, since a portion of the sky is obscured by the Sun. If you had perfect eyesight and traveled to completely dark skies in both the Northern and Southern Hemispheres, and there was no Moon, you might be able to get to count up almost 9,000 stars.
With a good pair of binoculars, that number jumps to about 200,000, since you can observe stars down to magnitude 9. A small telescope, capable of resolving magnitude 13 stars will let you count up to 15 million stars. Large observatories could resolve billions of stars.
But how many stars are out there? How many stars are there in the Milky Way?
Milky Way. Image credit: NASA
According to astronomers, our Milky Way is an average-sized barred spiral galaxy measuring up to 120,000 light-years across. Our Sun is located about 27,000 light-years from the galactic core in the Orion arm. Astronomers estimate that the Milky Way contains up to 400 billion stars of various sizes and brightness.
A few are supergiants, like Betelgeuse or Rigel. Many more are average-sized stars like our Sun. The vast majority of stars in the Milky Way are red dwarf stars; dim, low mass, with a fraction of the brightness of our Sun.
As we peer through our telescopes, we can see fuzzy patches in the sky which astronomers now know are other galaxies like our Milky Way. These massive structures can contain more or less stars than our own Milky Way.
Elliptical galaxy ESO 325-G004. ESO
There are spiral galaxies out there with more than a trillion stars, and giant elliptical galaxies with 100 trillion stars.
And there are tiny dwarf galaxies with a fraction of our number of stars.
So how many galaxies are there?
According to astronomers, there are probably more than 170 billion galaxies in the observable Universe, stretching out into a region of space 13.8 billion light-years away from us in all directions.
And so, if you multiply the number of stars in our galaxy by the number of galaxies in the Universe, you get approximately 1024 stars. That’s a 1 followed by twenty-four zeros.
That’s a septillion stars.
But there could be more than that.
It’s been calculated that the observable Universe is a bubble of space 47 billion years in all directions.
It defines the amount of the Universe that we can see, because that’s how long light has taken to reach us since the Big Bang.
This is a minimum value, the Universe could be much bigger – it’s just that we can’t ever detect those stars because they’re outside the observable Universe. It’s even possible that the Universe is infinite, stretching on forever, with an infinite amount of stars. So add a couple more zeros. Maybe an infinite number of zeroes.
The sun's newly classified neighborhood -- the Local Arm, as shown in this picture -- is more prominent than previously supposed. Credit: Robert Hurt, IPAC; Bill Saxton, NRAO/AUI/NSF
Some cultures used to say the Earth was the center of the Universe. But in a series of “great demotions,” as astronomer Carl Sagan put it in his book Pale Blue Dot, we found out that we are quite far from the center of anything. The Sun holds the prominent center position in the center of the Solar System, but our star is just average-sized, located in a pedestrian starry suburb — a smaller galactic arm, far from the center of the Milky Way Galaxy.
But perhaps our suburb isn’t as quiet or lowly as we thought. A new model examining the Milky Way’s structure says our “Local Arm” of stars is more prominent than we believed.
“We’ve found there is not a lot of difference between our Local Arm and the other prominent arms of the Milky Way, which is in contrast what astronomers thought before,” said researcher Alberto Sanna, of the Max-Planck Institute for Radio Astronomy, speaking today at the American Astronomical Society’s annual meeting in Indianapolis, Indiana.
Sanna said that one of the main questions in astronomy is how the Milky Way would appear to an observer outside our galaxy.
If you imagine the Milky Way as a rippled cookie, our star is in a neighborhood in between two big ripples (the Sagittarius Arm and the Perseus Arm). Before, we thought the Local Arm (or Orion Arm) was just a small spur between the arms. New research using trigonometric parallax measurements, however, suggests the Local Arm could be a “significant branch” of one of those two arms.
In a few words, our stellar neighborhood is a bigger and brighter one than we thought it was.
Colorado Milky Way. Credit: Michael Underwood
As part of the BeSSeL Survey (Bar and Spiral Structure Legacy Survey) using the Very Long Baseline Array (VLBA), astronomers are able to make more precise measurements of cosmic distances. The VLBA uses a network of 10 telescopes that work together to figure out how far away stars and other objects are.
It’s hard to figure out the distance from the Earth to other stars. Generally, astronomers use a technique called parallax, which measures how much a star moves when we look at it from the Earth.
VLBA telescope locations, courtesy of NRAO/AUI
When our planet is at opposite sites of its orbit — in spring and fall, for example — the apparent location of stellar objects changes slightly.
The more precisely we can measure this change, the better a sense we have of a star’s distance.
The VLBA undertook a search for spots in our galaxy where water and methanol molecules (also known as masers) enhance radio waves — similar to how lasers strengthen light waves. Masers are like stellar lighthouses for radio telescopes, the National Radio Astronomy Observatory stated.
Trigonometric Parallax method determines distance to star or other object by measuring its slight shift in apparent position as seen from opposite ends of Earth’s orbit. CREDIT: Bill Saxton, NRAO/AUI/NSF
Between 2008 and 2012, the VLBA tracked the distances to (and movements of) several masers to higher precision than previously, leading to the new findings.
Will the findings help ease our “inferiority complex” after all those great demotions?
“I would say yes, that’s a nice conclusion to say we are more important,” Sanna told Universe Today. “But more importantly, we are now mapping the Milky Way and discovering how the Milky Might appear to an outside observer. We now know the Local Arm arm is something that an observer from afar would definitely notice!”
An orbital sunset puts Earth in a unique light, as seen from the International Space Station. Credit: NASA, via astronaut Karen Nyberg.
This is just a gorgeous shot of our home planet from the International Space Station, shared by astronaut Karen Nyberg via Twitter. While many pictures of Earth from space show a bright view of our planet, this view of the world plunging into darkness provides a unique, not-often-seen view. If a picture can be this beautiful, imagine what must look like in person.
Nyberg is sharing her experiences via Twitter and also — I believe she is the first astronaut sharing on Pinterest. She describes herself as “Aspiring quilter, crafter, artist” (perfect for the Pinterest crowd) in addition to being an astronaut by day, and said she hopes to do some crafting in space if she has any spare time. Nyberg has a special board for “Hair in Space” (which includes both bald pates and gravity defying hair,) hoping to inspire the younger generation of women to get interested in space exploration. “When girls see pictures of ponytails, don’t you think it stirs something inside them that says, that could be ME up there!” Nyberg writes.
The aurora borealis over Crater Lake National Park taken on June 1, 2013. This image also includes the flyover of the International Space Station (ISS). Credit and copyright: Brad Goldpaint.
An unexpected arrival of a surprisingly strong (6 KP) geomagnetic storm from the Sun provided an amazing weekend for astrophotographers. Stargazers from both hemispheres were treated with seeing the aurora. We already posted the images from Mike Hollingshead seeing the aurora and red sprite lightning in Iowa, but here are some more great views, including this gorgeous shot of the aurora over Crater Lake in Oregon, from astrophotographer Brad Goldpaint, with the added intrigue of the International Space Station flying over at 2:35 am, local time. He’s also provided an amazing video, too, below.
“I drove to Crater Lake National Park last night to photograph the Milky Way rising above the rim,” Goldpaint said via email to Universe Today. “I’ve waited months for the roads to open and spring storms to pass, so I could spend a solitude night with the stars. Near 11pm, I was staring upward towards a clear night sky when suddenly, without much warning, an unmistakable faint glow of the aurora borealis began erupting in front of me. I quickly packed up my gear, hiked down to my truck, and sped to a north facing location. With adrenaline pumping, I raced to the edge of the caldera, set up a time-lapse sequence, and watched northern lights dance until sunrise. The moon rose around 2am and blanketed the surrounding landscape with a faint glow, adding depth and texture to the shot.”
A green aurora even colors the waters in this image from May 31, 2013, taken near Leith, Ontario, Canada. Credit and copyright: Adam Wipp.Aurora seen on May 31, 2013 near Leith, Ontario, Canada. Credit and copyright: Adam Wipp.
This video from Loic Le Guilly shows the aurora australis (southern lights) and the glow of the Milky Way in the skies over Tasmania he saw at Signal Station, near Hobart, Tasmania:
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.
The blue areas show locations on the Moon's south pole where water ice is likely to exist (NASA/GSFC)
The Moon might seem like a poor place to hunt for water, but in fact there’s a decent amount of the stuff dispersed throughout the lunar soil — and even more of it existing as ice deposits in the dark recesses of polar craters. While the LCROSS mission crashed a rocket stage into one of these craters in October 2009 and confirmed evidence of water in the resulting plume of debris, there haven’t been any definitive maps made of water deposits across a large area on the Moon — until now.
Over the course of several years, NASA’s Lunar Reconnaissance Orbiter scanned the Moon’s south pole using its Lunar Exploration Neutron Detector (LEND) to measure how much hydrogen is trapped within the lunar soil. Areas exhibiting suppressed neutron activity — shown above in blue — indicate where hydrogen atoms are concentrated most, strongly suggesting the presence of water molecules… aka H2O.
The incredibly-sensitive LEND instrument measures the flux of neutrons from the Moon, which are produced by the continuous cosmic ray bombardment of the lunar surface. Even a fraction of hydrogen as small as 100 ppm can make a measurable change in neutron distribution from the surface of worlds with negligible atmospheres, and the hydrogen content can be related to the presence of water.
No other neutron instrument with LEND’s imaging capability has ever been flown in space.
Watch the video below for more details as to how LRO and LEND obtained these results:
“While previous lunar missions have observed indications of hydrogen at the Moon’s south pole, the LEND measurements for the first time pinpoint where hydrogen, and thus water, is likely to exist.”
What’s so important about finding water on the Moon? Well besides helping answer the question of where water on Earth and within the inner Solar System originated, it could also be used by future lunar exploration missions to produce fuel for rockets, drinking water, and breathable air. Read more here.
Red sprite lightning appears in the sky with an aurora, as well as a distant thunderstorm, near Denison, Iowa on May 31, 2013. Credit and copyright: Mike Hollingshead, extremeinstability.com
“Holy crap, this is the rarest scene I’ve ever captured and likely ever will,” said photographer Mike Hollingshead. “I was standing there just watching when bam, big red sprites ‘squirting’ up into the air in the aurora.”
Mike said was hoping to see the aurora the night of May 31, 2013, and felt lucky when he saw a faint yellow glow begin to rise in the skies. At the same time, a thunderstorm could be seen off on the horizon and almost before he could even ponder the possibility of seeing something unusual, sprites started appearing.
This is an extremely rare event to be captured on film; in fact an image appearing just a few days ago on Astronomy Picture of the Day (APOD) on May 22 showed red sprite lighting with an aurora, and the APOD team said the image was a “candidate for the first color image ever recorded of a sprite and aurora together.”
“Sprites were first imaged in 1989 accidentally and first color photograph in 1994,” wrote Mike on his Extreme Instability website. “Recent. But with auroras, evidently it is possible the very first time was a couple freaking weeks before this one of mine. It’s that crazy rare.”
Sprites are huge electrical discharges that occur high above thunderstorm clouds. They are rare, but at least one has been captured on film from the International Space Station. They are triggered by the discharges of positive lightning between an underlying thundercloud and the ground. They often occur in clusters within the altitude range 50–90 km above the Earth’s surface.
Aurora captured on May 31, 2013, seen from near Denison, Iowa. Credit and copyright: Mike Hollingshead.
Stunning! Thanks to Mike Hollingshead for sharing his amazing photos, and congratulations on capturing such a rare event!
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.
Planet HD95086 b is shown at lower left in this picture. Astronomers blocked out the light of the star (center) to image the exoplanet. The blue circle represents the equivalent orbit of Neptune in this star system. Credit: ESO/J. Rameau
We’ve found hundreds of planets outside the solar system, but taking a picture of one is still something quite special. The light of the parent star tends to greatly overwhelm the faint light of the alien planet. (So usually we learn about planets by tracking the effects each planet has on its star, like dimming light when it passes in front or making the star slightly wobble.)
This picture (above) shows HD95086 b, which astronomers believe is one of only about a dozen exoplanets ever imaged. It’s 300 light-years from Earth. The planet candidate is about four to five times the mass of Jupiter and orbiting a very young star that is probably only 10 million to 17 million years old. That’s a baby compared to our own solar system, estimated at 4.5 billion years old.
We still have a lot to learn about this object (and the observations from the Very Large Telescope will need to be confirmed independently), but so far astronomers say they figure that planet formed in the gas and dust surrounding star HD 95086. But the planet is actually very far away from the star now, about twice the distance as the Sun-Neptune orbital span in our own solar system.
The Very Large Telescope (VLT) at ESO’s Cerro Paranal observing site. Credit: European Southern Observatory
“Its current location raises questions about its formation process,” stated team member Anne-Marie Lagrange, who is with the Grenoble Institute of Planetology and Astrophysics in France.
“It either grew by assembling the rocks that form the solid core and then slowly accumulated gas from the environment to form the heavy atmosphere, or started forming from a gaseous clump that arose from gravitational instabilities in the disc.
“Interactions between the planet and the disc itself,” she added, “or with other planets may have also moved the planet from where it was born.”
Astronomers estimate the planet candidate has a surface temperature of 1,292 degrees Fahrenheit (700 degrees Celsius), which could allow water vapor or methane to stick around in the atmosphere. It will take more VLT observations to figure this out, though.
The results from this study will be published in Astrophysical Journal Letters. The paper is also available on prepublishing site Arxiv.
NASA astronauts exploring Mars on future missions starting perhaps in the 2030’s will require protection from long term exposure to the cancer causing space radiation environment. Credit: NASA.
New measurements of the energetic space radiation environment present in interplanetary space taken by NASA’s Curiosity rover confirm what has long been suspected – that lengthy years long voyages by astronauts to deep space destinations like Mars will expose the crews to high levels of radiation that – left unchecked – would be harmful to their health and increase their chances of developing fatal cancers.
Although the data confirm what scientists had suspected, it’s equally important to state that the space radiation data are not ‘show stoppers” for human deep space voyages to the Red Planet and other destinations because there are a multitude of counter measures- like increased shielding and more powerful propulsion – that NASA and the world’s space agencies can and must implement to reduce and mitigate the dangerous health effects of radiation on human travelers.
The new radiation data was released at a NASA media briefing on May 30 and published in the journal Science on May 31.
Indeed the new measurements collected by Curiosity’s Radiation Assessment Detector (RAD) instrument during her 253-day, 560-million- kilometer journey enroute to the Red Planet in 2011 and 2012 will provide important insights to allow NASA to start designing systems for safely conducting future human missions to Mars.
“NASA wants to send astronauts to Mars in the 2030’s,” Chris Moore, NASA’s deputy director of Advanced Exploration Systems NASA HQ, said to reporters at the media briefing.
“The Human Spaceflight and Planetary Science Divisions at NASA are working together to get the data needed for human astronauts. RAD is perfect to collect the data for that,” said Moore.
The RAD data indicate that astronauts would be exposed to radiation levels that would exceed the career limit levels set by NASA during a more than year long voyage to Mars and back using current propulsion systems, said Eddie Semones, spaceflight radiation health officer at the Johnson Space Center.
This graph compares the radiation dose equivalent for several types of experiences, including a calculation for a trip from Earth to Mars based on measurements made by the Radiation Assessment Detector (RAD) instrument shielded inside NASA’s Mars Science Laboratory spacecraft during the flight from Earth to Mars in 2011 and 2012. The data show that during a typical 6 month cruise to Mars the astronaut crews would be exposed to more than 3 times the typical 6 month exposure of astronauts aboard the ISS. The scale is logarithmic; each labeled value is 10 times greater than the next lowest one. The “dose equivalent” units are millisieverts. Credit: NASA/JPL-Caltech/SwRI
NASA’s Humans to Mars planning follows initiatives outlined by President Obama.
“As this nation strives to reach an asteroid and Mars in our lifetimes, we’re working to solve every puzzle nature poses to keep astronauts safe so they can explore the unknown and return home,” said William Gerstenmaier, NASA’s associate administrator for human exploration and operations in Washington, in a statement.
The International Space Station already in low Earth orbit and the Orion crew capsule under development will serve as very useful platforms to conduct real life experiments on resolving the health risks posed by long term exposure to space radiation.
“We learn more about the human body’s ability to adapt to space every day aboard the International Space Station, said Gerstenmaier. “As we build the Orion spacecraft and Space Launch System rocket to carry and shelter us in deep space, we’ll continue to make the advances we need in life sciences to reduce risks for our explorers. Curiosity’s RAD instrument is giving us critical data we need so that we humans, like the rover, can dare mighty things to reach the Red Planet.”
RAD was the first instrument to collect radiation measurements during the cruise phase to the Red Planet. It is mounted on the top deck of the Curiosity rover.
“Although RAD’s objective is to characterize the radiation environment on the surface of Mars, it’s also good for the cruise phase,” Don Hassler, RAD Principal Investigator at the Southwest Research Institute (SWRI) told reporters.
“Since Orion and MSL are similar sized RAD is ideal for collecting the data.”
Mars Cruise Vehicles. This graphic shows a comparison of NASA’s Mars Science Laboratory (MSL) cruise capsule and NASA’s Orion spacecraft, which is being built now at NASA’s Johnson Space Center and will one day send astronauts to Mars. The rover Curiosity is tucked inside of the Mars Science Laboratory cruise vehicle like human beings would be tucked inside Orion. MSL are Orion are similar in size. Credit: NASA/JPL-Caltech/JSC
Hassler explained that RAD measures two types of radiation that pose health risks to astronauts. First, the steady stream of low dose galactic cosmic rays (GCRs), and second the short-term and unpredictable exposures to solar energetic particles (SEPs) arising from solar flares and coronal mass ejections (CME’s).
Radiation exposure is known to increase a person’s risk of suffering fatal cancer.
Exposure is measured in units of Sievert (Sv) or milliSievert (one one-thousandth Sv). Being exposed to a dose of 1 Sievert (Sv) over time results in a five percent increased risk of developing cancer.
NASA’s current regulations limit the potential for increased cancer risk to 3 percent for astronauts currently working on the ISS in low-Earth orbit.
RAD determined that the Curiosity rover was exposed to an average of 1.8 milliSieverts per day during the 8.5 month cruise to Mars, due mostly to Galactic Cosmic Rays, said Cary Zeitlin, SWRI Principal Scientist for MSL,at the briefing. “Solar particles only accounted for about 3 to 5 percent of that.”
During a typical 6 month cruise to Mars the astronaut crews would be exposed to 330 millisieverts. That is more than 3 times the typical 6 month exposure of astronauts aboard the ISS which amounts to about 100 millisieverts. See graphic above.
“The 360 day interplanetary round trip exposure would be 660 millisieverts based on chemical propulsion methods,” Zeitlin told Universe Today. “A 500 day mission would increase that to 900 millisieverts.”
By comparison, the average annual exposure for a typical person in the US from all radiation sources is less than 10 millisieverts.
The Earth’s magnetic field provides partial radiation shielding for the ISS astronauts living in low-Earth orbit.
“In terms of accumulated dose, it’s like getting a whole-body CT scan once every five or six days,” says Zeitlin.
And that round trip dose of 660 millisieverts doesn’t even include the astronauts surface stay on Mars – which would significantly raise the total exposure count. But luckily for the crew the surface radiation is less.
“The radiation environment on the surface of Mars is about half that in deep space since its modified by the atmosphere,” Hassler told Universe Today. “We will publish the surface data in a few months.”
NASA will need to decide whether to reassess the acceptable career limits for astronauts exposure to radiation from galactic cosmic rays and solar particle events during long duration deep space journeys.
Panoramic view of Yellowknife Bay basin back dropped by Mount Sharp shows the location of the first two drill sites – John Klein & Cumberland – targeted by NASA’s Curiosity Mars rover and the RAD radiation detector which took the first deep space measurements of harmful space radiation during the cruise phase to Mars in 2011 and 2012 . Curiosity accomplished historic 1st drilling into Martian rock at John Klein outcrop on Feb 8, 2013 (Sol 182) near where the robotic arm is touching the surface. This week the rover scooted about 9 feet to the right to Cumberland (right of center) for 2nd drill campaign on May 19, 2013 (Sol 279). Credit: NASA/JPL-Caltech/Ken Kremer – kenkremer.com/Marco Di Lorenzo
And don’t forget to “Send Your Name to Mars” aboard NASA’s MAVEN orbiter- details here. Deadline: July 1, 2013
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Learn more about Conjunctions, Mars, Curiosity, Opportunity, MAVEN, LADEE and NASA missions at Ken’s upcoming lecture presentations
June 4: “Send your Name to Mars on MAVEN” and “CIBER Astro Sat, LADEE Lunar & Antares Rocket Launches from Virginia”; Rodeway Inn, Chincoteague, VA, 8:30 PM
Sources of Ionizing Radiation in Interplanetary Space. The Radiation Assessment Detector (RAD) on NASA’s Curiosity Mars rover monitors high-energy atomic and subatomic particles coming from the sun, distant supernovae and other sources. The two types of radiation are known as Galactic Cosmic Rays and Solar Energetic Particles. RAD measured the flux of this energetic-particle radiation while shielded inside the Mars Science Laboratory spacecraft on the flight delivering Curiosity from Earth to Mars, and continues to monitor the flux on the surface of Mars. Credit: NASA/JPL-Caltech/SwRI
A ladder-like structure in Saturn's F ring seen by Cassini on Feb. 13, 2013 (NASA/JPL-Caltech/SSI)
Saturn’s F ring is certainly a curious structure. Orbiting the giant planet 82,000 kilometers above its equatorial cloud tops, the F ring is a ropy, twisted belt of bright ice particles anywhere from 30-500 km wide. It can appear as a solid band or a series of braided cords surrounded by a misty haze, and often exhibits clumps and streamers created by the gravitational influence of embedded moonlets or passing shepherd moons.
In the picture above, acquired by the Cassini spacecraft on Feb. 13, 2013 and released on May 27, we see a section of the F ring separated into long ropes and spanned by connecting bands of bright material — the “ladder” structure suggested in the title.
Scientists believe that interactions between the F ring and the moons Prometheus and Pandora cause the dynamic structure of the F ring. (Watch an animation of the F ring and shepherd moons here.)
Made of particles of water ice finer than cigarette smoke, the F ring orbits Saturn beyond the outer edge of the A ring across the expanse of the 2,600-km-wide Roche Division. In these images, Saturn and the main ring systems are off frame to the left.
Detail of ladder structure in the F ring
This view looks toward the unilluminated side of the rings from about 32 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft’s narrow-angle camera (NAC).
The view was obtained at a distance of approximately 426,000 miles (686,000 kilometers) from Saturn and at a phase angle of 162 degrees. Image scale is 2 miles (4 kilometers) per pixel.
