Space and astronomy news
Here’s a fun trip through the galaxy, put together by PhD student Tom Hands at the University of Leicester: In the above video, you can fly to of all the known exoplanets (around single stars only), ordered roughly by semi-major axis of largest orbit. Hands said the video is designed to give the viewer an overview of the current distribution of exoplanets.
Hands used data from the Open Exoplanet Catalogue.
So, how big is that space rock?
Sometimes when I see data on sizes and distances in relation to stuff out in space, it’s hard to get a frame of reference, since those two categories tend to lean towards the super-big. But now, I’ve got a little help. Space enthusiast and software engineer Ciro Villa has brought some of these references closer to home with these fun graphics that provide accurate size ratios and proportions of objects in space compared to places on Earth.
Villa calls these graphics “hovering celestial objects” and while all of these scenarios are impossible in real life, he’s placed large asteroids and moons next to Earthly locations to provide a good frame of reference for dimensions. Please note that most of these objects have absolutely no chance of colliding with Earth as they are not anywhere near our neighborhood and are not expected to visit it either.
“My representations are is purely for illustrative purposes,” Villa said. “I have maintained the size ratios and proportions as accurately as possible just to demonstrate the dimensions. This is mostly a ‘fun’ exercise.”
For example, I regularly drive through the St. Louis, Missouri metro area, so I have a sense of how big it is. Above, Villa places Asteroid 243 Ida — which has an average diameter of 31.4 km (19.5 miles) — to hover right above St. Louis. 31 km is about the distance from East St. Louis, Illinois to Creve Coeur, Missouri, which are the generally accepted eastern and western borders of the St. Louis metro area. I could probably drive across Ida in about 30 minutes — if it’s not rush hour, that is!
To create these graphics, Villa uses Google Maps, NASA data and Gimp image editing software. Again, these graphics are for fun, but I really find them useful!
And Villa provided a caveat: “Please note that I am not a professional graphic artist, so I’m sure people are going to find plenty of imperfections in these depictions,” he said. “The important point I am trying to convey is mainly the size dimensions comparing with a known area of Earth.”
Here are more:
Here are a bigger pair of objects in comparison to an area of Eastern Texas and Western Arkansas. 90482 Orcus is a trans-Neptunian Kuiper belt object that is about 800 kilometers in diameter. Orcus has a fairly large moon orbiting it named Vanth, which is about 300 km in diameter.
This asteroid might pay Earth a close visit, but not for a couple of million years. Eros is the second largest NEO (Near Earth Object), with a diameter of approximately 34 kilometers, and here Villa imagines Eros centered over the VAB (Vehicle Assembly Building) at Cape Canaveral, covering the Cape area from approximately the southern end of the Canaveral National Seashore to the Pine Island Conservation area, with the VAB in about the middle, as the crow (or sandhill crane) flies.
While Eros is technically an NEO, it made one of its closest passes of Earth in 2012 of 16.6 million miles (26.7 million km) and won’t pass that close again until 2056. A look ahead with orbital mechanics suggests that Eros may move to an Earth-crossing orbit in about two million years, given the right perturbations by gravitational interactions.
And to show the scale of several moons in our Solar System, Villa made these comparisons:
“Deimos is about 15 kilometers across, so I have measured a portion of the city of Paris, France of about 5 Kilometers and properly scaled Deimos,” Villa said. “For added dramatics, I have purposely shown enough of Deimos hovering to show about 5 kilometers of Paris, to show some of the landmarks (notice the Eiffel tower). Had I decided to show all of Deimos, the scale would have been too large to recognize any of the landmarks of Paris.”
Continuing these imaginary montages, here is one of our favorite moons, Enceladus, with an approximate diameter of about 500 kilometers, seen drifting over Southern England. That’s about the same distance from Plymouth to Leigh-on-the-Sea in the UK.
This last one is a bit personal for Villa, since he lives in Florida. Here, Saturn’s moon Phoebe hangs over Central Florida. “Phoebe shares an approximate diameter of 200 kilometers with the central portion of the state,” Villa said, “and I wanted to ‘play’ with my imagination a bit!”
Thanks to Ciro Villa for sharing his “hovering celestial objects” with Universe Today. Check out his informative and entertaining G+ feed here.
Last month astronomers provided evidence that the universe underwent a brief but stupendous expansion at the very beginning of time. It was a landmark discovery. And while the media worldwide gleamed with fantastical headlines, I’m left overwhelmed with the feeling that it didn’t quite get the spotlight it deserves.
The day of the announcement was ablaze with excitement. When I first started to cover the news, I told my mother I was writing on something that was bigger than the Higgs boson. That was the best way I could explain the significance of this monumental discovery to someone with very little physics knowledge in a text message.
But inflation didn’t get the same hype as the Higgs. Why?
Scientific results are mostly tangible. The Higgs boson was created in a 27-kilometer ring of superconducting magnets designed to boost the energy of particles — marking the world’s largest and most powerful particle accelerator. There’s something about this experiment that we can wrap our minds around, even when the particle itself remains elusive. The $10 billion effort has 6,000 researchers working hard to control the system.
But we can’t control the universe. We can’t ask two galaxies to collide; We can’t speed up stellar evolution; And we can’t pull a nearby star a little closer to take a peek at its circling exoplanet. Instead we stand on our cosmic platform and wait for the light from various happenings to reach us. Once it does, we dig through that light — collecting photons in different filters or spreading them across a spectrum of wavelengths — reaping every last bit of knowledge possible.
Astronomical research is complex and abstract. But it’s what we love about it.
The vast cosmic arena — with its unimaginable vistas of time and space — is laid out in the small specks of light on the celestial sphere. By collecting this light we have placed ourselves within the cosmos. We know the universe began with the Big Bang nearly 13.8 billion years ago. We know that dark matter binds massive galaxy clusters together and that dark energy is causing the universe to accelerate rapidly. It’s truly phenomenal that so much can be learned from the study of light.
Still, there’s a fundamental difference between observing the direct light emitted from distant stars and galaxies and observing a slight polarization pattern on the cosmic microwave background — the radiation released 380,000 years after the Big Bang when photons were able to travel freely across the cosmos.
The result threw open a new window on the birth of the universe. To be more precise, it let us peer back at the moment that took place a mere trillionth of a trillionth of a trillionth of a second after the Big Bang. But it takes so many steps (potentially as many steps as seconds from then until now) to grasp this hazy and mind-boggling concept. It will stretch your ideas of space and time to their limits.
Not only does this result succeed in showing the universe in its infancy, explaining the origin of cosmic structure and providing evidence for the last untested prediction of Albert Einstein’s General Theory of Relativity (gravity comes in discrete packets like light), but it makes an even wilder prediction.
The model likely produces not just one universe, but rather an ensemble of universes: an endless series of big bangs that continue to pop up eternally. Our universe may just be one bubble out of a vast cosmic ocean of others.
Astronomy is moving further toward the abstract. Both in how we collect data and the scientific results we carefully and slowly unearth from that data.
I find this awe-inspiring. But while astronomers are finding ingenious and creative methods to further understand the phenomenal universe in which we live, science journalists and educators are going to have to follow suit. We need to act not as translators but as guides who map scientific knowledge, finding paths through vast amounts of abstract information and analyzing key points along the way. Only then will inflation trump the Higgs and the abstract become tangible.
But honestly I’m still ruminating on this question so all additional thoughts are welcome.
Spring is a time of treasures in eggs — think about the Easter weekend that just passed, for example, or the number of chicks hatching in farms across the world. That’s also true of “near-space” exploration. A project called PongSats has sent thousands of tiny experiments into space, and is ready to send up another batch this coming September.
The concept is simple for the students participating — slice open a ball, put something inside you want to test at high experiments, then repackage it and decorate it for the big trip up. The balloons will soar to about 19 miles (30 kilometers), which is well below the Karman Line of 62 miles or 100 kilometers that marks the edge of space. Don’t discount that, however — you will still see black skies and the curvature of the Earth from that altitude.
Anyway, about the PongSats. A Kickstarter campaign (closing in five days) is asking for money to shoot these balls into the atmosphere, for science. While it’s aimed at young students, anybody can get an experiment on that balloon, the founder says.
“My favorite is the marshmallow. You put a marshmallow inside the ping pong ball. At 100,000 feet the marshmallow puffs up completely filling the ball. Then it freeze dries. The student gets to hold in her hand the direct results of traveling [to] the top of the atmosphere,” wrote John Powell, the founder of the project.
PongSat has already been through one successful Kickstarter round, when in 2012 the concept received $12,466 — a 138% increase over its $9,000 goal. That money was slated to send 1,000 student experiments into space. To date, the company has sent over 14,000 experiments aloft with only three losses — a 0.02% failure rate.
“However, the risk for a complete vehicle loss does exist,” Powell acknowledged, but said that after 164 flights, they “have gotten pretty good at it.” Any PongSats lost in flight will be flown again, no questions asked.
Powell’s project is part of a larger trend of sending items high in the sky — sometime for scientific purposes, and sometimes for other reasons. A Lego man and teddy bears are among those that made the journey.
This 2012 project was called “Lego Man In Space” (although of course, balloons fly high in the atmosphere and well below the Karman Line at 62 miles or 100 kilometers above the surface.) Two teenagers from Toronto, Canada — Mathew Ho and Asad Muhammad — launched the weather balloon from a local field and captured some stunning video and pictures along the way.
“Upon launch we were very relieved. But we had a lot of anxiety on launch day because there were high winds when we were going up after all the hard work,” said Ho in a studio interview at the time on Canadian news channel CTV.
“We were also scared because now we would have to retrieve it back after it came down,” Asad said.
“We had no idea it would capture photos like that and would be so good,” said Ho. “We were blown away when we saw them back home.”
It’s a teddy bear party in the sky! A group of English 11-13-year-olds designed the spacesuits on these stuffed animals, which were sent aloft to 30,085 meters (101,066 feet) in 2008. While at first glance the purpose looks esoteric, the goal was to test which spacesuit materials best insulated against the -53 degrees Celsius (-63 Fahrenheit) temperatures the teddies endured.
Student-run Cambridge University Spaceflight helmed the project along with a science club and community college.
“We want to offer young people the opportunity to get involved in the space industry whilst still at school and show that real-life science is something that is open to everybody,” stated Iain Waugh, then chief aeronautical engineer of CU Spaceflight.
“High altitude balloon flights are a fantastic way of encouraging interest in science. They are easy to understand, and produce amazing results,” added Daniel Strange, treasurer of CU Spaceflight.
Sometimes the aim is more artistic, such as this German project that created a beautiful video showing the views from more than 100,000 feet (30,480 meters). You can see in the video above the careful preparations that go into launch, plus some of the side benefits — such as getting to make funny voices using helium! But it was the engineering challenges that attracted these students, they wrote Universe Today in 2011.
“Our challenge was to survive ambient air pressures as low as 1/100th of an atmosphere, temperatures as low as -60°C and finally to locate and recover the camera,” Tobias Lohf wrote . “We had a HD-Cam, GPS tracker and a heating pad on board, and all the construction had a total weight of about 1kg.”
The students emphasized that it doesn’t take a big budget or a lot of engineering to get that high. “All you need need is a camera, weather balloon and duct tape,” they said.
Book review by David Freiberg: Universe Today Book Reviewer
Most of us get up in the morning, shower, eat breakfast and sleepily make our way to work. Whether we work in an office, outdoors, with the public or in any number of exciting Earth-based careers, our daily commute can hardly compare to that of a moon astronaut! In Earthrise: My Adventures As An Apollo 14 Astronaut, Edgar Mitchell shares his personal story of how he came to share a career with a scarce 11 other people in history.
This new book tells the story Mitchell’s life; he started out as a farm boy from a small town in New Mexico who grew up in a normal family and lived a normal life but he worked hard enough and got lucky enough to go to the Moon. He wasn’t born into it, and he wasn’t so supremely gifted that he aced everything he tried in his life. He had the willpower to work through years of training, and he had the courage to get into a gigantic rocket that would launch him a quarter of a million miles through space, even though the last people who had tried to go to the Moon were lucky to get back alive.
And, being a real person doing an extraordinary thing, he came back changed by the experience.
Despite the trials and tribulations of training, of flying there, of a close call with a malfunctioning “abort” button, and of the moonwalk itself, Edgar details how the ride home was the most life-changing part of the entire journey. As he saw the Earth shining in front of him, he described a sensation he called metanoia that was to shape the rest of his life. He’d explored as much of outer space as current technology would allow: now he wanted to do the opposite and explore the mind. Though he’d always been interested in topics like ESP (he even conducted his own ESP experiment with a few doctors on Earth during the mission), it was easy to see how it changed his perspective on everything. And, from his descriptions, he’s not the only Apollo astronaut to have a different perspective on life after the mission: they were real people, after all, and if you went to the Moon, you’d probably be changed as well.
That’s where “Earthrise” really shines: you get the idea that you too could do the same thing if you were willing to work for it. This book is strongly recommended for all children who are interested in space; as Edgar Mitchell was inspired by stories of Roswell and of Buck Rogers when he was young, perhaps a child who reads this very book will someday fly around the Moon and watch the Earth come up.
About the authors: Dr. Edgar Mitchell was a pilot in the historic 1971 Apollo 14 mission and the sixth man to ever walk on the Moon. He is the author of “Paradigm Shift,” “The Space Less Traveled,” and “The Way of the Explorer,” and recipient of the Presidential Medal of Freedom, the NASA Distinguished Service Medal, three NASA Group Achievement Awards and was nominated for the Nobel Peace Prize in 2005. He is the founder of the renowned Institute of Noetic Sciences and lives in Lake Worth, Florida. Ellen Mahoney has worked for Walt Disney Imagineering and produced radio features for the BBC Science in Action show. She is an instructor of journalism at Metro State University of Denver and lives in Boulder, Colorado. Dr. Brian Cox is a professor of particle physics at the University of Manchester School of Physics and Astronomy, Manchester, England. He presents space and science programs on BBC radio and television, including “Wonders of the Universe.”
Universe Today and Chicago Review Press are pleased to be able to offer three free copies of “Earthrise: My Adventures as An Apollo 14 Astronaut” to our readers. This contest is open to US and Canadian residents only. In order to be entered into the giveaway drawing, just put your email address into the box at the bottom of this post (where it says “Enter the Giveaway”) before Wednesday, April 30, 2014. If this is the first time you’re registering for a giveaway, you’ll receive a confirmation email immediately where you’ll need to click a link to be entered into the drawing. For those who have registered previously, you’ll receive an email later where you can enter this drawing.
If you are not lucky enough to win one of our three free copies, or if you don’t want to wait, you can purchase the book from Amazon.com.
Saturn is well known for being a gas giant, and for its impressive ring system. But would it surprise you to know that this planet also has the second-most moons in the Solar System, second only to Jupiter? Yes, Saturn has at least 150 moons and moonlets in total, though only 62 have confirmed orbits and only 53 have been given official names.
Most of these moons are small, icy bodies that are little more than parts of its impressive ring system. In fact, 34 of the moons that have been named are less than 10 km in diameter while another 14 are 10 to 50 km in diameter. However, some of its inner and outer moons are among the largest and most dramatic in the Solar System, measuring between 250 and 5000 km in diameter and housing some of the greatest mysteries in the Solar System.
Saturn’s moons have such a variety of environments between them that you’d be forgiven for wanting to spend an entire mission just looking at its satellites. From the orange and hazy Titan to the icy plumes emanating from Enceladus, studying Saturn’s system gives us plenty of things to think about. Not only that, the moon discoveries keep on coming. As of April 2014, there are 62 known satellites of Saturn (excluding its spectacular rings, of course). Fifty-three of those worlds are named.
Prior to the invention of telescopic photography, eight of Saturn’s moons were observed using simple telescopes. The first to be discovered was Titan, Saturn’s largest moon, which was observed by Christiaan Huygens in 1655 using a telescope of his own design. Between 1671 and 1684, Giovanni Domenico Cassini discovered the moons of Tethys, Dione, Rhea, and Iapetus – which he collectively named the “Sider Lodoicea” (Latin for “Louisian Stars”, after King Louis XIV of France).
n 1789, William Herschel discovered Mimas and Enceladus, while father-and-son astronomers W.C Bond and G.P. Bond discovered Hyperion in 1848 – which was independently discovered by William Lassell that same year. By the end of the 19th century, the invention of long-exposure photographic plates allowed for the discovery of more moons – the first of which Phoebe, observed in 1899 by W.H. Pickering.
In 1966, the tenth satellite of Saturn was discovered by French astronomer Audouin Dollfus, which was later named Janus. A few years later, it was realized that his observations could only be explained if another satellite had been present with an orbit similar to that of Janus. This eleventh moon was later named Epimetheus, which shares the same orbit as Janus and is the only known co-orbital in the Solar System.
By 1980, three additional moons were discovered and later confirmed by the Voyager probes. They were the trojan moons (see below) of Helene (which orbits Dione) as well as Telesto and Calypso (which orbit Tethys).
The study of the outer planets has since been revolutionized by the use of unmanned space probes. This began with the arrival of the Voyager spacecraft to the Cronian system in 1980-81, which resulted in the discovery of three additional moons – Atlas, Prometheus, and Pandora – bringing the total to 17. By 1990, archived images also revealed the existence of Pan.
This was followed by the Cassini-Huygens mission, which arrived at Saturn in the summer of 2004. Initially, Cassini discovered three small inner moons, including Methone and Pallene between Mimas and Enceladus, as well as the second Lagrangian moon of Dione – Polydeuces. In November of 2004, Cassini scientists announced that several more moons must be orbiting within Saturn’s rings. From this data, multiple moonlets and the moons of Daphnis and Anthe have been confirmed.
The study of Saturn’s moons has also been aided by the introduction of digital charge-coupled devices, which replaced photographic plates by the end of the 20th century. Because of this, ground-based telescopes have begun to discover several new irregular moons around Saturn. In 2000, three medium-sized telescopes found thirteen new moons with eccentric orbits that were of considerable distance from the planet.
In 2005, astronomers using the Mauna Kea Observatory announced the discovery of twelve more small outer moons. In 2006, astronomers using Japan’s Subaru Telescope at Mauna Kea reported the discovery of nine more irregular moons. In April of 2007, Tarqeq (S/2007 S 1) was announced, and in May of that same year, S/2007 S 2 and S/2007 S 3 were reported.
The modern names of Saturn’s moons were suggested by John Herschel (William Herschel’s son) in 1847. In keeping with the nomenclature of the other planets, he proposed they be named after mythological figures associated with the Roman god of agriculture and harvest – Saturn, the equivalent of the Greek Cronus. In particular, the seven known satellites were named after Titans, Titanesses and Giants – the brothers and sisters of Cronus.
In 1848, Lassell proposed that the eighth satellite of Saturn be named Hyperion after another Titan. When in the 20th century, the names of Titans were exhausted, the moons were named after different characters of the Greco-Roman mythology, or giants from other mythologies. All the irregular moons (except Phoebe) are named after Inuit and Gallic gods and Norse ice giants.
Saturn’s moons are grouped based on their size, orbits, and proximity to Saturn. The innermost moons and regular moons all have small orbital inclinations and eccentricities and prograde orbits. Meanwhile, the irregular moons in the outermost regions have orbital radii of millions of kilometers, orbital periods lasting several years, and move in retrograde orbits.
Saturn’s Inner Large Moons, which orbit within the E Ring (see below), include the larger satellites Mimas, Enceladus, Tethys, and Dione. These moons are all composed primarily of water ice and are believed to be differentiated into a rocky core and an icy mantle and crust. With a diameter of 396 km and a mass of 0.4×1020 kg, Mimas is the smallest and least massive of these moons. It is ovoid in shape and orbits Saturn at a distance of 185,539 km with an orbital period of 0.9 days.
Some people jokingly call Mimas the “Death Star” moon because of the crater on its surface that resembles the machine from the Star Wars universe. The 140 km (88 mi) Herschel Crater is about a third the diameter of the moon itself and could have created fractures (chasmata) on the moon’s opposing side. There are in fact craters throughout the moon’s small surface, making it among the most pockmarked in the Solar System.
Enceladus, meanwhile, has a diameter of 504 km, a mass of 1.1×1020 kg, and is spherical in shape. It orbits Saturn at a distance of 237,948 km and takes 1.4 days to complete a single orbit. Though it is one of the smaller spherical moons, it is the only Cronian moon that is endogenously active – and one of the smallest known bodies in the Solar System that is geologically active. This results in features like the famous “tiger stripes” – a series of continuous, ridged, slightly curved, and roughly parallel faults within the moon’s southern polar latitudes.
Large geysers have also been observed in the southern polar region that periodically releases plumes of water ice, gas, and dust which replenish Saturn’s E ring. These jets are one of several indications that Enceladus has liquid water beneath its icy crust, where geothermal processes release enough heat to maintain a warm water ocean closer to its core.
The moon has at least five different kinds of terrain, a “young” geological surface of less than 100 million years. With a geometrical albedo of more than 140%, which is due to it being composed largely of water ice, Enceladus is one of the brightest known objects in the Solar System.
At 1066 km in diameter, Tethys is the second-largest of Saturn’s inner moons and the 16th-largest moon in the Solar System. The majority of its surface is made up of heavily cratered and hilly terrain and a smaller and smoother plains region. Its most prominent features are the large impact crater of Odysseus, which measures 400 km in diameter, and a vast canyon system named Ithaca Chasma – which is concentric with Odysseus and measures 100 km wide, 3 to 5 km deep, and 2,000 km long.
With a diameter and mass of 1,123 km and 11×1020 kg, Dione is the largest inner moon of Saturn. The majority of Dione’s surface is heavily cratered old terrain, with craters that measure up to 250 km in diameter. However, the moon is also covered with an extensive network of troughs and lineaments which indicate that in the past it had global tectonic activity.
It’s covered in canyons, crackings, craters, and is coated from dust in the E-ring that originally came from Enceladus. The location of this dust has led astronomers to theorize that the moon was spun about 180 degrees from its original disposition in the past, perhaps due to a large impact.
The Large Outer Moons, which orbit outside of the Saturn’s E Ring, are similar in composition to the Inner Moons – i.e. composed primarily of water ice, and rock. Of these, Rhea is the second-largest – measuring 1,527 km in diameter and 23×1020 kg in mass – and the ninth-largest moon in the Solar System. With an orbital radius of 527,108 km, it is the fifth-most distant of the larger moons and takes 4.5 days to complete an orbit.
Like other Cronian satellites, Rhea has a rather heavily cratered surface and a few large fractures on its trailing hemisphere. Rhea also has two very large impact basins on its anti-Saturnian hemisphere – the Tirawa crater (similar to Odysseus on Tethys) and the Inktomi crater – which measure about 400 and 50 km across, respectively.
Rhea has at least two major sections, the first being bright craters with craters larger than 40 km (25 miles), and a second section with smaller craters. The difference in these features is believed to be evidence of a major resurfacing event at some time in Rhea’s past.
At 5150 km in diameter and 1,350×1020 kg in mass, Titan is Saturn’s largest moon and comprises more than 96% of the mass in orbit around the planet. Titan is also the only large moon to have its own atmosphere, which is cold, dense, and composed primarily of nitrogen with a small fraction of methane. Scientists have also noted the presence of polycyclic aromatic hydrocarbons in the upper atmosphere, as well as methane ice crystals.
The surface of Titan, which is difficult to observe due to persistent atmospheric haze, shows only a few impact craters, evidence of cryovolcanoes, and longitudinal dune fields that were apparently shaped by tidal winds. Titan is also the only body in the Solar System besides Earth with bodies of liquid on its surface, in the form of methane–ethane lakes in Titan’s north and south polar regions.
Titan is also distinguished for being the only Cronian moon that has ever had a probe land on it. This was the Huygens lander, which was carried to the hazy world by the Cassini spacecraft. Titan’s “Earth-like processes” and thick atmosphere are among the things that make this world stand out to scientists, which include its ethane and methane rains from the atmosphere and flows on the surface.
With an orbital distance of 1,221,870 km, it is the second-farthest large moon from Saturn and completes a single orbit every 16 days. Like Europa and Ganymede, it is believed that Titan has a subsurface ocean made of water mixed with ammonia, which can erupt to the surface of the moon and lead to cryovolcanism.
Hyperion is Titan’s immediate neighbor. At an average diameter of about 270 km, it is smaller and lighter than Mimas. It is also irregularly shaped and quite odd in composition. Essentially, the moon is an ovoid, tan-colored body with an extremely porous surface (which resembles a sponge). The surface of Hyperion is covered with numerous impact craters, most of which are 2 to 10 km in diameter. It also has a highly unpredictable rotation, with no well-defined poles or equator.
At 1,470 km in diameter and 18×1020 kg in mass, Iapetus is the third-largest of Saturn’s large moons. And at a distance of 3,560,820 km from Saturn, it is the most distant of the large moons and takes 79 days to complete a single orbit. Due to its unusual color and composition – its leading hemisphere is dark and black whereas its trailing hemisphere is much brighter – it is often called the “yin and yang” of Saturn’s moons.
Beyond these larger moons are Saturn’s Irregular Moons. These satellites are small, have large radii, are inclined, have mostly retrograde orbits, and are believed to have been acquired by Saturn’s gravity. These moons are made up of three basic groups – the Inuit Group, the Gallic Group, and the Norse Group.
The Inuit Group consists of five irregular moons that are all named from Inuit mythology – Ijiraq, Kiviuq, Paaliaq, Siarnaq, and Tarqeq. All have prograde orbits that range from 11.1 to 17.9 million km, and from 7 to 40 km in diameter. They are all similar in appearance (reddish in hue) and have orbital inclinations of between 45 and 50°.
The Gallic group consists of four prograde outer moons that are named after characters in Gallic mythology – Albiorix, Bebhionn, Erriapus, and Tarvos. Here too, the moons are similar in appearance and have orbits that range from 16 to 19 million km. Their inclinations are in the 35°-40° range, their eccentricities around 0.53, and they range in size from 6 to 32 km.
Last, there is the Norse group, which consists of 29 retrograde outer moons that take their names from Norse mythology. These satellites range in size from 6 to 18 km, their distances from 12 and 24 million km, their inclinations between 136° and 175°, and their eccentricities between 0.13 and 0.77. This group is also sometimes referred to as the Phoebe group, due to the presence of a single larger moon in the group – which measures 240 km in diameter. The second-largest, Ymir, measures 18 km across.
Within the Inner and Outer Large Moons, there are also those belonging to the Alkyonide group. These moons – Methone, Anthe, and Pallene – are named after the Alkyonides of Greek mythology, are located between the orbits of Mimas and Enceladus, and are among the smallest moons around Saturn. Some of the larger moons even have moons of their own, which are known as Trojan moons. For instance, Tethys has two trojans – Telesto and Calypso, while Dione has Helene and Polydeuces.
It is thought that Saturn’s moon of Titan, its mid-sized moons and rings developed in a way that is closer to the Galilean moons of Jupiter. In short, this would mean that the regular moons formed from a circumplanetary disc, a ring of accreting gas, and solid debris similar to a protoplanetary disc. Meanwhile, the outer, irregular moons are believed to have been objects that were captured by Saturn’s gravity and remained in distant orbits.
However, there are some variations to this theory. In one alternative scenario, two Titan-sized moons were formed from an accretion disc around Saturn; the second one eventually broke up to produce the rings and inner mid-sized moons. In another, two large moons fused together to form Titan, and the collision scattered icy debris that formed to create the mid-sized moons.
However, the mechanics of how the moon formed remains a mystery for the time being. With additional missions mounted to study the atmospheres, compositions, and surfaces of these moons, we may begin to understand where they truly came from.
Much like Jupiter, and all the other gas giants, Saturn’s system of satellites is extensive as it is impressive. In addition to the larger moons that are believed to have formed from a massive debris field that once orbited it, it also has countless smaller satellites that were captured by its gravitational field over the course of billions of years. One can only imagine how many more remain to be found orbiting the ringed giant.
We have many great articles on Saturn and its moons here at Universe Today. For example, here’s How Many Moons Does Saturn Have? and Is Saturn Making a New Moon?
Here’s an article about the discovery of Saturn’s 60th moon, and another article about how Saturn’s moons could be creating new rings.
Want more information about Saturn’s moons? Check out NASA’s Cassini information on the moons of Saturn, and more from NASA’s Solar System Exploration site.
We have recorded two episodes of Astronomy Cast just about Saturn. The first is Episode 59: Saturn, and the second is Episode 61: Saturn’s Moons.
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Planet lovers can rejoice: one of the finest jewels of the solar system in returning to the evening night sky.
The planet Saturn reaches opposition next month on May 10th. This means that as the Sun sets to the west, Saturn will rise “opposite” to it in the east, remaining well positioned for observation in the early evening hours throughout the summer season. In fact, we’ll have four of the five naked eye planets above the horizon at once for our evening viewing pleasure in the month of May, as Jupiter also rides high to the west at sunset, Mars just passed opposition last month and Mercury reaches greatest eastern elongation on May 25th. Venus is the solitary holdout, spending a majority of 2014 in the dawn sky.
Saturn will shine at magnitude +0.3 this month and its disk spans an apparent 19,” or 44” if you take into account the apparent width of its rings. The rings are currently tipped open 22 degrees with respect to our line of sight. The ring opening is widening, and will reach a maximum of over 25 degrees in 2017 before the trend reverses. Anyone who remembers observing Saturn back in 2009 will recall that its rings were edge on to our view. This widening of Saturn’s rings also lends itself to a curious effect: although we’re in a cycle of oppositions that are getting farther away — Saturn is 12.5 million kilometres or 0.083 Astronomical Units (A.U.s) more distant in 2014 than it was during opposition last year as it’s headed towards aphelion in 2018 — its widening rings are actually making it appear a bit brighter.
This year’s opposition will find Saturn in the astronomical constellation of Libra, where it’ll spend most of 2014. Oppositions of the ringed planet are set to continue to “head south” until 2018, and won’t occur north of the celestial equator again until 2026. I remember when oppositions of Saturn returned to the constellation Virgo a few years back — where I had first looked at it with my 60mm Jason refractor as a teenager — and realizing that I had now been into observational astronomy for roughly one “Saturnian year.”
The ancients had little knowledge of how unique Saturn was. The faintest and slowest moving of the classical planets, even Galileo knew that something was up when he turned his first primitive telescope towards it. His sketches depict Saturn as something similar to a double handled coffee cup, a testament to how poor his view really was. It wouldn’t be until Christiaan Huygens in 1655 that the true nature of Saturn’s rings was deduced as a flat and separate feature from the disk.
At opposition, the disk of the planet casts a shadow straight back from our point of view. This vantage slowly changes as the planet moves towards eastern quadrature on August 9th and we get a glimpse slightly off to one side of the planet. After opposition, the shadow of the disk can again be seen casting back onto the rings.
Another interesting phenomenon to watch out for near opposition is known as the Seeliger effect. Also sometimes referred to as the “opposition surge,” this sudden brightening of the disk and rings is a subtle effect, as the globe of Saturn and all of those tiny little ice crystals reach 100% illumination. This effect can be noted to the naked eye on successive nights around opposition, and will get more prominent towards 2017. Coherent-backscattering of light has also been proposed as a possible explanation of this phenomenon. Perhaps a video sequence capturing this effect is in order for skilled astro-imagers in 2014.
Through a small telescope, the first feature that becomes apparent is Saturn’s glorious system of rings. Crank up the magnification, and you’ll note a dark groove in the ring system. This is the Cassini Division, first described by Giovanni Cassini in 1675.
Here’s a challenge we came across some years back: can you see the disk of Saturn through the Cassini Division? Right around opposition is a good time to attempt this unusual feat of visual athletics.
Saturn’s large moon Titan is an easy catch at magnitude +8 in a small telescope. Titan is the second largest moon in the solar system. Place it in a direct orbit about the Sun, and it would be considered a planet, no problem. 7 of Saturn’s 62 known moons are within reach of a small telescope. In addition to Titan, they are, with quoted magnitudes: Mimas (+13), Enceladus (+12), Tethys (+10), Rhea (+10), Dione (+11) and Iapetus. Iapetus is of special interest, as it brightens from +11.9 to magnitude +10.2 as it traces out its 79 day orbit. We always knew there was something unique about this moon, and NASA’s Cassini mission revealed the world to have two distinctly different hemispheres with vastly different albedos during its close 2007 flyby.
Also, be sure to check out Saturn on the night of May 14th — just 4 nights after opposition — as the Full Moon sits less than a degree south of the ringed planet. Can you see both in the same telescopic field of view? Can you nab Saturn next to the rising daytime Moon low to the horizon just before local sunset? The Moon will actually occult (pass in front of) Saturn for viewers based in Australia and New Zealand on the 14th. This is only one of 11 occultations — nearly one for each lunation — of Saturn by the Moon in 2014. Unfortunately, the best one for North America occurs in the daytime on August 31st, though it too may be observable telescopically.
Finally, this evening apparition of the planet runs through northern hemisphere summer and fall until Saturn reaches solar conjunction on November 18th. So get those homemade planetcams out, send those pics in to Universe Today, and be sure to join in to the Virtual Star Party every Sunday Night… Saturn is sure to be featured!
UPDATE, 11:42 a.m. EDT: Rick Mastracchio and Steve Swanson finished their spacewalk in just 1 hour and 36 minutes, nearly an hour faster than what NASA budgeted for. Early tests show the replacement computer is working well, providing backup once again for the robotics, solar arrays and other systems on station.
Can two astronauts fix a broken computer quickly on the International Space Station, preventing possible problems with the solar arrays and robotics? Watch live (above) to find out.
The NASA spacewalk involving Rick Mastracchio and Steve Swanson is scheduled to start today (April 23) at 9:20 a.m. EDT (1:20 p.m. UTC), with coverage starting around 8:30 a.m. EDT (12:30 p.m. UTC). The spacewalk is scheduled to last 2.5 hours. Bear in mind that the times could change as circumstances arise.
The computer, also called a multiplexer/demultiplexer (MDM), failed for unknown reasons a couple of weeks ago. While the primary computer is working perfectly and the crew is in no danger, things get more risky if the primary computer also breaks. That’s why NASA worked to get the spacewalkers outside as quickly as possible. You can see a full briefing of the rationale here.
As a note, all non-urgent spacewalks have been suspended because NASA is still working on addressing the recommendations given after a life-threatening water leak took place in a NASA spacesuit last summer. Urgent spacewalks can still go ahead because the agency has implemented safety measures such as snorkels and helmet absorption pads in case of another leak.
That said, in the months since NASA has traced the problem to contamination in a filter in the fan pump separator. After replacing the separator, the leaky spacesuit was used during two contingency spacewalks in December with no water problems at all.
In our Solar System, astronomers often divide the planets into two groups — the inner planets and the outer planets. The inner planets are closer to the Sun and are smaller and rockier. The outer planets are further away, larger and made up mostly of gas.
The inner planets (in order of distance from the sun, closest to furthest) are Mercury, Venus, Earth and Mars. After an asteroid belt comes the outer planets, Jupiter, Saturn, Uranus and Neptune. The interesting thing is, in some other planetary systems discovered, the gas giants are actually quite close to the sun.
This makes predicting how our Solar System formed an interesting exercise for astronomers. Conventional wisdom is that the young Sun blew the gases into the outer fringes of the Solar System and that is why there are such large gas giants there. However, some extrasolar systems have “hot Jupiters” that orbit close to their Sun.
The four inner planets are called terrestrial planets because their surfaces are solid (and, as the name implies, somewhat similar to Earth — although the term can be misleading because each of the four has vastly different environments). They’re made up mostly of heavy metals such as iron and nickel, and have either no moons or few moons. Below are brief descriptions of each of these planets based on this information from NASA.
Mercury: Mercury is the smallest planet in our Solar System and also the closest. It rotates slowly (59 Earth days) relative to the time it takes to rotate around the sun (88 days). The planet has no moons, but has a tenuous atmosphere (exosphere) containing oxygen, sodium, hydrogen, helium and potassium. The NASA MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft is currently orbiting the planet.
Venus: Venus was once considered a twin planet to Earth, until astronomers discovered its surface is at a lead-melting temperature of 900 degrees Fahrenheit (480 degrees Celsius). The planet is also a slow rotator, with a 243-day long Venusian day and an orbit around the sun at 225 days. Its atmosphere is thick and contains carbon dioxide and nitrogen. The planet has no rings or moons and is currently being visited by the European Space Agency’s Venus Express spacecraft.
Earth: Earth is the only planet with life as we know it, but astronomers have found some nearly Earth-sized planets outside of our solar system in what could be habitable regions of their respective stars. It contains an atmosphere of nitrogen and oxygen, and has one moon and no rings. Many spacecraft circle our planet to provide telecommunications, weather information and other services.
Mars: Mars is a planet under intense study because it shows signs of liquid water flowing on its surface in the ancient past. Today, however, its atmosphere is a wispy mix of carbon dioxide, nitrogen and argon. It has two tiny moons (Phobos and Deimos) and no rings. A Mars day is slightly longer than 24 Earth hours and it takes the planet about 687 Earth days to circle the Sun. There’s a small fleet of orbiters and rovers at Mars right now, including the large NASA Curiosity rover that landed in 2012.
The outer planets (sometimes called Jovian planets or gas giants) are huge planets swaddled in gas. They all have rings and all of plenty of moons each. Despite their size, only two of them are visible without telescopes: Jupiter and Saturn. Uranus and Neptune were the first planets discovered since antiquity, and showed astronomers the solar system was bigger than previously thought. Below are brief descriptions of each of these planets based on this information from NASA.
Jupiter: Jupiter is the largest planet in our Solar System and spins very rapidly (10 Earth hours) relative to its orbit of the sun (12 Earth years). Its thick atmosphere is mostly made up of hydrogen and helium, perhaps surrounding a terrestrial core that is about Earth’s size. The planet has dozens of moons, some faint rings and a Great Red Spot — a raging storm happening for the past 400 years at least (since we were able to view it through telescopes). NASA’s Juno spacecraft is en route and will visit there in 2016.
Saturn: Saturn is best known for its prominent ring system — seven known rings with well-defined divisions and gaps between them. How the rings got there is one subject under investigation. It also has dozens of moons. Its atmosphere is mostly hydrogen and helium, and it also rotates quickly (10.7 Earth hours) relative to its time to circle the Sun (29 Earth years). Saturn is currently being visited by the Cassini spacecraft, which will fly closer to the planet’s rings in the coming years.
Uranus: Uranus was first discovered by William Herschel in 1781. The planet’s day takes about 17 Earth hours and one orbit around the Sun takes 84 Earth years. Its mass contains water, methane, ammonia, hydrogen and helium surrounding a rocky core. It has dozens of moons and a faint ring system. There are no spacecraft slated to visit Uranus right now; the last visitor was Voyager 2 in 1986.
Neptune: Neptune is a distant planet that contains water, ammmonia, methane, hydrogen and helium and a possible Earth-sized core. It has more than a dozen moons and six rings. The only spacecraft to ever visit it was NASA’s Voyager 2 in 1989.
To learn more about the planets and missions, check out these links:
Solar System Exploration: Planets (NASA)
NASA Photojournal (NASA)
Missions (NASA)
Space Science (European Space Agency)
USGS Astrogeology (U.S. Geological Survey)
The Solar System And Its Planets (European Space Agency)
“The fact that none of these asteroid impacts shown in the video was detected in advance is proof that the only thing preventing a catastrophe from a ‘city-killer’ sized asteroid is blind luck.”
– Ed Lu, B612 Foundation CEO and former NASA astronaut
When we think of recent large asteroid impacts on Earth, only a handful may come to mind. In particular, one is the forest-flattening 1908 Tunguska explosion over Siberia (which may have been the result of a comet) and another is the February 2013 meteor that exploded over Chelyabinsk, shattering windows with its air blast. Both occurred in Russia, the largest country on Earth, and had human witnesses — in the case of the latter many witnesses thanks to today’s ubiquitous dashboard cameras.
While it’s true that those two observed events took place 105 years apart, there have been many, many more large-scale asteroid impacts around the world that people have not witnessed, if only due to their remote locations… impact events that, if they or ones like them ever occurred above a city or populated area, could result in destruction of property, injuries to people, or worse.
(And I’m only referring to the ones we’ve found out about over the past 13 years.)
A new video released by the B612 Foundation shows a visualization of data collected by a global nuclear weapons test network. It reveals 26 explosive events recorded from 2000 to 2013 that were not the result of nuclear detonations — these were impacts by asteroids, ranging from one to 600 kilotons in energy output.
Update: a list of the 26 aforementioned impacts and their energy outputs is below:
8/25/2000 (1-9 kilotons) North Pacific Ocean
4/23/2001 (1-9 kilotons) North Pacific Ocean
3/9/2002 (1-9 kilotons) North Pacific Ocean
6/6/2002 (20+ kilotons) Mediterranean Sea
11/10/2002 (1-9 kilotons) North Pacific Ocean
9/3/2004 (20+ kilotons) Southern Ocean
10/7/2004 (10-20 kilotons) Indian Ocean
10/26/2005 (1-9 kilotons) South Pacific Ocean
11/9/2005 (1-9 kilotons) New South Wales, Australia
2/6/2006 (1-9 kilotons) South Atlantic Ocean
5/21/2006 (1-9 kilotons) South Atlantic Ocean
8/9/2006 (1-9 kilotons) Indian Ocean
9/2/2006 (1-9 kilotons) Indian Ocean
10/2/2006 (1-9 kilotons) Arabian Sea
12/9/2006 (10-20 kilotons) Egypt
9/22/2007 (1-9 kilotons) Indian Ocean
12/26/2007 (1-9 kilotons) South Pacific Ocean
10/7/2008 (1-9 kilotons) Sudan
10/8/2009 (20+ kilotons) South Sulawesi, Indonesia
9/3/2010 (10-20 kilotons) South Pacific Ocean
12/25/2010 (1-9 kilotons) Tasman Sea
4/22/2012 (1-9 kilotons) California, USA
2/15/2013, (20+ kilotons) Chelyabinsk Oblast, Russia
4/21/2013 (1-9 kilotons) Santiago del Estero, Argentina
4/30/2013 (10-20 kilotons) North Atlantic Ocean
(Source: B612 Foundation)
To include the traditonally macabre comparison, the bomb used to destroy Hiroshima at the end of World War II was about 15 kilotons; the Nagasaki bomb was 20.
This evening former NASA astronauts Ed Lu, Tom Jones, and Apollo 8 astronaut Bill Anders will present this video to the public at a live Q&A event at the Museum of Flight in Seattle, Washington.
CEO and co-founder of the B612 Foundation, Ed Lu is working to increase awareness of asteroids and near-Earth objects with the ultimate goal of building and launching Sentinel, an infrared observatory that will search for and identify as-yet unknown objects with orbits that intersect Earth’s. The event, titled “Saving the Earth by Keeping Big Asteroids Away,” will be held at 6 p.m. PDT. It is free to the public and the visualization above is now available online on the B612 Foundation website. A press event will also be taking place at 11:30 a.m. PDT, and will be streamed live here.
Currently there is no comprehensive dynamic map of our inner solar system showing the positions and trajectories of these asteroids that might threaten Earth. The citizens of Earth are essentially flying around the Solar System with eyes closed. Asteroids have struck Earth before, and they will again – unless we do something about it.
– B612 Foundation
Want to support the Sentinel mission? Donate online here.
Added 4/24: The April 22 press conference at the Museum of Flight can be watched in its entirety below:
Technical note: While B612 and Ed Lu are presenting a new visualization on April 22, the data behind it are not entirely new. Previous surveys on NEA populations have determined within reasonable parameters the number of objects and likelihood of future impacts of varying sizes using data from WISE and ground-based observatories… see a series of slides by Alan Harris of JPL/Caltech here. (ht Amy Mainzer)
Also, if you have questions on the asteroid visualization, there are some FAQs on the B612 site here.