Posted on by Matt Williams

What is the Biggest Planet in the Solar System?

Jupiter and Io
Io and Jupiter as seen by New Horizons during its 2008 flyby. (Credit: NASA/Johns Hopkins University APL/SWRI).

Ever since the invention of the telescope four hundred years ago, astronomers have been fascinated by the gas giant of Jupiter. Between it’s constant, swirling clouds, its many, many moons, and its Giant Red Spot, there are many things about this planet that are both delightful and fascinating.

But perhaps the most impressive feature about Jupiter is its sheer size. In terms of mass, volume, and surface area, Jupiter is the biggest planet in our Solar System by a wide margin. But just what makes Jupiter so massive, and what else do we know about it?

Size and Mass:

Jupiter’s mass, volume, surface area and mean circumference are 1.8981 x 1027 kg, 1.43128 x 1015 km3, 6.1419 x 1010 km2, and 4.39264 x 105 km respectively. To put that in perspective, Jupiter diameter is roughly 11 times that of Earth, and 2.5 the mass of all the other planets in the Solar System combined.

But, being a gas giant, Jupiter has a relatively low density – 1.326 g/cm3 – which is less than one quarter of Earth’s. This means that while Jupiter’s volume is equivalent to about 1,321 Earths, it is only 318 times as massive. The low density is one way scientists are able to determine that it is made mostly of gases, though the debate still rages on what exists at its core (see below).

Composition:

Jupiter is composed primarily of gaseous and liquid matter. It is the largest of the gas giants, and like them, is divided between a gaseous outer atmosphere and an interior that is made up of denser materials. Its upper atmosphere is composed of about 88–92% hydrogen and 8–12% helium by percent volume of gas molecules, and approx. 75% hydrogen and 24% helium by mass, with the remaining one percent consisting of other elements.

This cut-away illustrates a model of the interior of Jupiter, with a rocky core overlaid by a deep layer of liquid metallic hydrogen. Credit: Kelvinsong/Wikimedia Commons
This cut-away illustrates a model of the interior of Jupiter, with a rocky core overlaid by a deep layer of liquid metallic hydrogen. Credit: Kelvinsong/Wikimedia Commons

The atmosphere contains trace amounts of methane, water vapor, ammonia, and silicon-based compounds as well as trace amounts of benzene and other hydrocarbons. There are also traces of carbon, ethane, hydrogen sulfide, neon, oxygen, phosphine, and sulfur. Crystals of frozen ammonia have also been observed in the outermost layer of the atmosphere.

The interior contains denser materials, such that the distribution is roughly 71% hydrogen, 24% helium and 5% other elements by mass. It is believed that Jupiter’s core is a dense mix of elements – a surrounding layer of liquid metallic hydrogen with some helium, and an outer layer predominantly of molecular hydrogen. The core has also been described as rocky, but this remains unknown as well.

In 1997, the existence of the core was suggested by gravitational measurements, indicating a mass of from 12 to 45 times the Earth’s mass, or roughly 4%–14% of the total mass of Jupiter. The presence of a core is also supported by models of planetary formation that indicate how a rocky or icy core would have been necessary at some point in the planet’s history in order to collect its bulk of hydrogen and helium from the protosolar nebula.

However, it is possible that this core has since shrunk due to convection currents of hot, liquid, metallic hydrogen mixing with the molten core. This core may even be absent now, but a detailed analysis is needed before this can be confirmed. The Juno mission, which launched in August 2011, is expected to provide some insight into these questions, and thereby make progress on the problem of the core.

The temperature and pressure inside Jupiter increase steadily toward the core. At the “surface”, the pressure and temperature are believed to be 10 bars and 340 K (67 °C, 152 °F). At the “phase transition” region, where hydrogen becomes metallic, it is believed the temperature is 10,000 K (9,700 °C; 17,500 °F) and the pressure is 200 GPa. The temperature at the core boundary is estimated to be 36,000 K (35,700 °C; 64,300 °F) and the interior pressure at roughly 3,000–4,500 GPa.

Moons:

The Jovian system currently includes 67 known moons. The four largest are known as the Galilean Moons, which are named after their discoverer, Galileo Galilei. They include: Io, the most volcanically active body in our Solar System; Europa, which is suspected of having a massive subsurface ocean; Ganymede, the largest moon in our Solar System; and Callisto, which is also thought to have a subsurface ocean and features some of the oldest surface material in the Solar System.

Then there’s the Inner Group (or Amalthea group), which is made up of four small moons that have diameters of less than 200 km, orbit at radii less than 200,000 km, and have orbital inclinations of less than half a degree. This groups includes the moons of Metis, Adrastea, Amalthea, and Thebe. Along with a number of as-yet-unseen inner moonlets, these moons replenish and maintain Jupiter’s faint ring system.

Jupiter also has an array of Irregular Satellites, which are substantially smaller and have more distant and eccentric orbits than the others. These moons are broken down into families that have similarities in orbit and composition, and are believed to be largely the result of collisions from large objects that were captured by Jupiter’s gravity.

Illustration of Jupiter and the Galilean satellites. Credit: NASA
Illustration of Jupiter and the Galilean satellites. Credit: NASA

Interesting Facts:

Much like Earth, Jupiter experiences auroras near its northern and southern poles. But on Jupiter, the auroral activity is much more intense and rarely ever stops. The intense radiation, Jupiter’s magnetic field, and the abundance of material from Io’s volcanoes that react with Jupiter’s ionosphere creates a light show that is truly spectacular.

Jupiter also has a violent atmosphere. Winds in the clouds can reach speeds of up to 620 kph (385 mph). Storms form within hours and can become thousands of km in diameter overnight. One storm, the Great Red Spot, has been raging since at least the late 1600s. The storm has been shrinking and expanding throughout its history; but in 2012, it was suggested that the Giant Red Spot might eventually disappear.

The discovery of exoplanets has revealed that planets can get even bigger than Jupiter. In fact, the number of “Super Jupiters” observed by the Kepler space probe (as well as ground-based telescopes) in the past few years has been staggering. In fact, as of 2015, more than 300 such planets have been identified.

Notable examples include PSR B1620-26 b (Methuselah), which was the first super-Jupiter to be observed (in 2003). At 12.7 billion years of age, it is also the third oldest known planet in the universe. There’s also HD 80606 b (Niobe), which has the most eccentric orbit of any known planet, and 2M1207b (Lerna), which orbits the brown dwarf Fomalhaut b (Illion).

Scientist theorize that a gas gain could get 15 times the size of Jupiter before it began deuterium fusion, making it a brown dwarf star. Good thing too, since the last thing the Solar System needs if for Jupiter to go nova!

Jupiter was appropriately named by the ancient Romans, who chose to name after the king of the Gods (Jupiter, or Jove). The more we have come to know and understand about this most-massive of Solar planets, the more deserving of this name it appears.

If you’re wondering, here’s how big planets can get with a lot of mass, and here’s what is the biggest star in the Universe. And here’s the 2nd largest planet in the Solar System.

Here’s another article about the which is the largest planet in the Solar System, and here’s what’s the smallest planet in the Solar System.

We have recorded a whole series of podcasts about the Solar System at Astronomy Cast. Check them out here.

Sources:

Posted on by Matt Williams

How Many Moons Does Uranus Have?

Uranus and Moons
Uranus and its system of Moons. Credit: NASA/JPL

In the outer Solar System, there are many worlds that are so large and impressive to behold that they will probably take your breath away. Not only are these gas/ice giants magnificent to look at, they are also staggering in size, have their own system a rings, and many, many moons. Typically, when one speaks of gas (and/or ice) giants and their moons, one tends to think about Jupiter (which has the most, at 67 and counting!).

But have you ever wondered how many moons Uranus has? Like all of the giant planets, it’s got rather a lot! In fact, astronomers can now account for 27 moons that are described as “Uranian”. Just like the other gas and ice giants, these moons are motley bunch that tell us much about the history of the Solar System. And, just like Jupiter and Saturn, the process of discovering these moons has been long and involved on multiple astronomers.

Continue reading “How Many Moons Does Uranus Have?”

Posted on by Matt Williams

Uranus’s Moon Oberon

Oberon, as imaged by the Voyager 2 probe during its flyby on Jan. 24, 1986. Credit: NASA

In 1610, Galileo’s observed four satellites orbiting the distant gas giant of Jupiter. This discovery would ignite a revolution in astronomy, and encouraged further examinations of the outer Solar System to see what other mysteries it held. In the centuries that followed, astronomers not only discovered that other gas giants had similar systems of moons, but that these systems were rather extensive.

For example, Uranus has a system of 27 confirmed satellites. Of these, Oberon is the outermost satellite, as well as the second largest and second most-massive. Named in honor of a mythical king of fairies, it is also the ninth most massive moon in the Solar System.

Discovery and Naming:

Discovered in 1787 by Sir William Herschel, Oberon was one of two major satellites discovered in a single day (the other being Uranus’ moon of Titania). At the time, he reported observing four other moons; however, the Royal Astronomical Society would later determine that these were spurious. It would be almost five decades after the moons were discovered that an astronomer other than Herschel observed them.

Initially, Oberon was referred to as “the second satellite of Uranus”, and in 1848, was given the designation Uranus II by William Lassell. In 1851, Lassell discovered Uranus’ other two moons – later named Ariel and Miranda – and began numbering them based on their distance from the planet . Oberon was thus given the designation of Uranus IV.

Size comparison between the Earth, the Moon, and Saturn's moon of Oberon. Credit: Tom.Reding/Public Domain
Size comparison between the Earth, the Moon, and Uranus’ moon of Oberon. Credit: Tom.Reding/Public Domain

By 1852, Herschel’s son John suggested naming the moon’s his father observed Oberon and Titania, at the request of Lassell himself. All of these names were taken from the works of William Shakespeare and Alexander Pope, with the name Oberon being derived from the King of the Fairies in A Midsummer Night’s Dream.

Size, Mass and Orbit:

With a diameter of approx. 1,523 kilometers, a surface area of 7,285,000 km², and a mass of 3.014 ± 0.075 x 10²¹ kilograms, Oberon is the second largest, and second most massive of Uranus’ moons. It is also the ninth most massive moon in the solar system.

At a distance of 584,000 km from Uranus, it is the farthest of the five major moons from Uranus. However, this distance is subject to change, as Oberon has a small orbital eccentricity and inclination relative to Uranus’ equator. It has an orbital period of about 13.5 days, coincident with its rotational period. This means that Oberon is a tidally-locked, synchronous satellite with one face always pointing toward the planet.

Since (like all of Uranus’ moons) Oberon orbits the planet around its equatorial plane, and Uranus orbits the Sun almost on its side, the moon experiences a rather extreme seasonal cycle. Essentially, both the northern and southern poles spend a period of 42 years in complete darkness or complete sunlight – with the sun rising close to the zenith over one of the poles at each solstice.

Voyager 2:

So far, the only close-up images of Oberon have been provided by the Voyager 2 probe, which photographed the moon during its flyby of Uranus in January 1986.  The images cover about 40% of the surface, but only 25% of the surface was imaged with a resolution that allows geological mapping.

In addition, the time of the flyby coincided with the southern hemisphere’s summer solstice, when nearly the entire northern hemisphere was in darkness. This prevented the northern hemisphere from being studied in any detail. No other spacecraft has visited the Uranian system before or since, and no missions to the planet are currently being planned.

Composition:

Oberon’s density is higher than the typical density of Uranus’ satellites, at 1.63 g/cm³. This would indicate that the moon consists of roughly equal proportions of water ice and a dense non-ice component. The latter could be made of rock and carbonaceous material including heavy organic compounds.

Spectroscopic observations have confirmed the presence of crystalline water ice in the surface of the moon. It is believed that Oberon, much like the other Uranian moons, consists of an icy mantle surrounding a rocky core. If this is true, then the radius of the core (480 km) would be equal to approx. 63% of the radius of the moon, and its mass would be around 54% of the moon’s mass.

A computer-projected false-color image of Oberon. The white region has not yet been photographed by a spacecraft. The large crater with the dark floor (right of center) is Hamlet; the crater Othello is to its lower left, and the 'canyon' Mommur Chasma is at upper left. Credit: USGS Astrogeology Research Program
False-color image of Oberon, showing the Hamlet and Othello craters (right of center and lower left) and the Mommur Chasma (upper left). Credit: USGS Astrogeology Research Program

Currently, the full composition of the icy mantle is unknown. However, it it were to contain enough ammonia or other antifreeze compounds, the moon may possess a liquid ocean layer at the core–mantle boundary. The thickness of this ocean, if it exists, would be up to 40 km and its temperature would be around 180 K.

It is unlikely that at these temperatures, such an ocean could support life. But assuming that hydrothermal vents exist in the interior, it is possible life could exist in small patches near the core. However, the internal structure of Oberon depends heavily on its thermal history, which is poorly known at present.

Interesting Facts:

Oberon is the second-darkest large moon of Uranus (after Umbriel), with a surface that appears to be generally red in color – except where fresh impact deposits have left neutral or slightly blue colors. In fact, Oberon is the reddest moon amongst its peers, with a trailing hemisphere that is significantly redder than its leading hemisphere.

The reddening of the surfaces is often a result of space weathering caused by bombardment of the surface by charged particles and micrometeorites over many millions of years. However, the color asymmetry of Oberon is more likely caused by accretion of a reddish material spiraling in from outer parts of the Uranian system.

Oberon’s surface is the most heavily cratered of all the Uranian moons, which would indicate that Oberon has the most ancient surface among them. Consistent with the planet’s name, these surface features are named after characters in Shakespearean plays. The largest known crater, Hamlet, measures 206 kilometers in diameter, while the Macbeth, Romeo, and Othello craters measure 203, 159, and 114 km respectively.

Uranus and its five major moons
Uranus and its five major moons. Credit: space.com

Other prominent surface features are what is known as chasmata – steep-sided depressions that are comparable to rift valleys or escarpments here on Earth. The largest known chasmata on Oberon is the Mommur Chasma, which measures 537 km in diameter and takes its name from the enchanted forest in French folklore that was ruled by Oberon.

As you can plainly see, there is much that remains unknown about this satellite. Much like its peers, how they came to be, and what secrets may lurk beneath their surfaces, is still open to speculation. One can only hope that future generations will choose to mount another Voyager-like expedition to the Outer Solar System for the sake of studying the Uranian satellites.

We have written many interesting articles on the moons of Uranus here at Universe Today. Here’s How Many Moons Does Uranus Have? and Interesting Facts About Uranus.

For more information, check out NASA’s Solar System Exploration page on Oberon and Nine Planet’s page on Oberon.

Astronomy Cast also has a good episode on the subject. Here’s Episode 62: Uranus.

Sources:

Posted on by Matt Williams

Mir: Russia’s Space Station

The Mir space station hangs above the Earth in 1995 (photo by Atlantis STS-71, NASA)

The Mir Space Station was Russia’s greatest space station, and the first modular space station to be assembled in orbit. Commissioned in 1986, the name can be translated from Russian as “peace”, “world”, and even “village” – alluding to the spirit of international cooperation that led to its creation. Owned and operated by the Soviet Union, it became the property of the Russian Federal Space Agency (Roscosmos) after 1991.

The space station was intended to advocate world peace and hosted international scientists and NASA astronauts. In this respect, Mir was very much the curtain-raiser for the International Space Station, which succeeded it as the largest satellite in Earth’s orbit after 2001.

Origin:

During the 1960s and 70s, when the United States was largely focused on Apollo and the Space Shuttle program, Russia began to focus on developing expertise in long-duration spaceflight, and felt that a larger space station would allow for more research in that area. Authorized in February 1976 by a government decree, the station was originally intended to be an improved model of the Salyut space stations.

The original plan called for a core module that would be equipped with a total of four docking ports, but eventual grew to include several ports for crewed Soyuz spacecraft and Progress cargo spaceships. By August 1978, the plan had grown to the final configuration of one aft port and five ports in a spherical compartment at the forward end of the station.

The Mir Space Station and Earth limb observed from the Orbiter Endeavour during NASA's STS-89 mission in 1998. Credit: NASA
The Mir Space Station and Earth limb observed from the Orbiter Endeavour during NASA’s STS-89 mission in 1998. Credit: NASA

Two would be located at either end of the station (as with the Salyut stations) with an additional two on either side of a docking sphere at the front of the station to enable further modules to expand the station’s capabilities.  These docking ports would each accommodate 20-tonne space station modules based on the TKS spacecraft – a previous generation of space craft used to bring cosmonauts and supplies to the Salyut space stations.

Work began on the station in 1979, and drawings were released in 1982 and 83. By early 1984, work had ground to a halt as virtually all of Russia’s space resources were being put into the Buran program – a Soviet and later Russian reusable spacecraft project. Funding resumed in early 1984 when the Central Committee became determined to orbit Mir by early 1986, just in time for the 27th Communist Party Congress.

Deployment:

On February 19th, 1986, the assembly process began with the launching of Mir’s core module on a Proton-K rocket into orbit. Between 1987 and 1996, four of the six modules were launched and added to the station – Kvant-2 in 1989, Kristall in 1990, Spektr in 1995 and Priroda in 1996. In these cases, the modules were sent into orbit aboard a Proton-K, chased the station automatically, and then used their robot Lyappa arms to mate with the core.

Soviet/Russian space station Mir, after completion in 1996. The date shown for each module is its year of launch. Docked to the station are a Soyuz TM manned spacecraft and an unmanned Progress resupply ferry. Credit: Encyclopedia Britannica
Soviet/Russian space station Mir, after completion in 1996. The date shown for each module is its year of launch. Credit: Encyclopedia Britannica

Kvant-1, having no engines of its own, was delivered by a TKS spacecraft in 1987, while the docking module was brought to the station aboard Space Shuttle Atlantis (STS-74) in 1995. Various other external components, including three truss structures, several experiments and other unpressurized elements, were also mounted to the exterior of the station over the course of its history.

The station’s assembly marked the beginning of the third generation of space station design, being the first to consist of more than one primary spacecraft. First generation stations such as Salyut 1 and Skylab had monolithic designs, consisting of one module with no resupply capability, while second generation stations (Salyut 6 and Salyut 7) comprised a monolithic station with two ports to allow resupply cargo spacecraft (like Progress).

The capability of Mir to be expanded with add-on modules meant that each could be designed with a specific purpose in mind, thus eliminating the need to install all the station’s equipment in one module. After construction was finished, Mir had a collection of facilities. At 13.1 meters (43 feet) long, the “core” module of the station was the main area where the cosmonauts and astronauts did their work. It also housed the main computer and vital space station parts, such as communications.

In addition to solar arrays and a docking port, the station had several facilities for orbital science. These included, but were not limited to, the two Kvant modules (where astronomy and other scientific research was conducted), the Kristall module (which had a facility for microgravity manufacturing) and Spektr (focused on Earth work).

A view of the Russian space station Mir on 3 July 1993 as seen from Soyuz TM-17. Credit: spacefacts.de
A view of the Russian space station Mir on 3 July 1993 as seen from Soyuz TM-17. Credit: spacefacts.de

Missions:

During its 15-year spaceflight, Mir was visited by a total of 28 long-duration, or “principal”, crews. Expeditions varied in length, but generally lasted around six months. Principal expedition crews consisted of two to three crew members, who often launched as part of one expedition but returned with another.

As part of the Soviet Union’s manned spaceflight program effort to maintain a long-term research outpost in space, operated by the new Russian Federal Space Agency after 1991, the vast majority of the station’s crew were Russian. However, through international collaborations, the station was made accessible to astronauts from North America, several European nations and Japan.

Collaborative programs included the Intercosmos, Euromir and Shuttle-Mir programs. Intercosmos, which ran from 1978-1988, involved astronauts from other Warsaw Pact Nations, other socialist nations – like Afghanistan, Cuba, Mongolia, and Vietnam – and pro-Soviet non-aligned nations such as India, Syria, and even France.

Euromir, which began in the 1990s, was a collaborative effort between the Russian Federal Space Agency and the European Space Agency (ESA) to bring European astronauts to the space station. With help provided by the NASA Space Shuttle program, the goal was to recruit and train European astronauts for the then-planned International Space Station.

Meanwhile, the Shuttle–Mir Program was a collaborative space program between Russia and the United States, and involved American Space Shuttles visiting the space station, Russian cosmonauts flying on the shuttle, and an American astronaut flying aboard a Soyuz spacecraft to engage in long-duration expeditions aboard Mir.

A view of the US Space Shuttle Atlantis and the Russian Space Station Mir during STS-71 as seen by the crew of Mir EO-19 in Soyuz TM-21. Credit: NASA
A view of the US Space Shuttle Atlantis and the Russian Space Station Mir during STS-71 as seen by the crew of Mir EO-19 in Soyuz TM-21. Credit: NASA

By the time of the station’s deorbit, it had been visited by 104 different people from twelve different nations, making it the most visited spacecraft in history (a record later surpassed by the International Space Station).

Decommissioning:

When it was launched in 1986, Mir was only supposed to have a life span of about five years, but it proved to have a greater longevity than anyone expected. Unfortunately, a series of technical and structural problems eventually caught up with the station; and in November 2000, the Russian government announced that it would decommission the space station.

This began on Jan. 24th, 2001, when a Russian Progress cargo ship rendezvoused with the station carrying twice its normal amount of fuel. The extra fuel was intended to fire the Progress’ thrusters once it had docked with Mir and push the station into a controlled descent through the Earth’s atmosphere.

The Russian government purchased insurance just in case the space station hit any populated area when it crashed to Earth. Luckily, the station ended up crashing into the South Pacific Ocean, landing about 2,897 kilometers from New Zealand. In 2001, former RKA General Director Yuri Koptev estimated that the cost of the Mir program to be $4.2 billion (including development, assembly and orbital operation).

Legacy:

The Mir Space Station endured for 15 years in orbit, three times its planned lifetime. It hosted scores of crew members and international visitors, raised the first crop of wheat to be grown from seed to seed in outer space, and served as a symbol of Russia’s past glories and it’s potential as a future leader in space exploration.

Jerry Linenger dons a mask during his mission on Mir in 1997. Credit: NASA
Jerry Linenger dons a mask during his mission on Mir in 1997. Credit: NASA

In addition, the station was a source of controversy over the years, due to the many accidents and hazards it endured. The most famous of these took place on February 24, 1997 during mission STS-81. On this occasion, which saw the Space Shuttle Atlantis delivering crew, supplies, and conducting a series of tests, the worst fire aboard an orbiting spacecraft broke out.

This caused failures in various on-board systems, a near collision with a Progress resupply cargo ship during a long-distance manual docking system test, and a total loss of station electrical power. The power failure also caused a loss of attitude control, which led to an uncontrolled “tumble” through space. Luckily, the crew managed to suppress the fire and regain control before long.

Another major incident took place on June 25th, when a Progress resupply ship collided with solar arrays on the Spektr module, creating a hole which caused the station to lose pressure. This was the first orbital depressurization in the history of spaceflight to take place. Luckily, no astronauts were lost while serving aboard the station.

Mir is also famous for hosting long-duration missions during its early years in space. Topping the list was Russian cosmonaut Valeri Polyakov, who spent nearly 438 days aboard Mir and landed on March 22, 1995. The station itself orbited the Earth more than 86,000 times during its lifespan, and was also the largest orbiting object in the Solar System.

But most importantly of all, Mir served as the stage for the first large-scale, technical partnership between Russia and the United States after a half-century of mutual antagonism. Without it, there would be no ISS today, and numerous joint-research efforts between NASA, the ESA, Russia, and other federal space agencies, would not have been possible.

We have written many interesting articles about space stations here at Universe Today. Here’s What is the International Space Station?, Fire! How the Mir Incident Changed Space Station History, The Mir Space Station: An Unlikely Place for a Beautiful Art Exhibit, and Mir’s Fiery Re-entry, March 23, 2001.

For more information, check out the Mir Space Station and Shuttle-Mir.

And Astronomy Cast has a wonderful episode on Mir, titled Episode 297: Space Stations, Part 2: Mir

Source:

Posted on by Matt Williams

What Is The Kuiper Belt?

Hubble Finds Smallest Kuiper Belt Object
Hubble Finds Smallest Kuiper Belt Object. Credit: NASA

Dr. Mike Brown is a professor of planetary astronomy at Caltech. He’s best known as the man who killed Pluto, thanks to his team’s discovery of Eris and other Kuiper Belt Objects. We asked him to help us explain this unusual region of our solar system.

Soon after Pluto was discovered by Clyde Tombaugh on February 18th, 1930, astronomers began to theorize that Pluto was not alone in the outer Solar System. In time, they began to postulate the existence of other objects in the region, which they would discover by 1992. In short, the existence of the Kuiper Belt – a large debris field at the edge of the Solar System – was theorized before it was ever discovered.

Definition:

The Kuiper Belt (also known as the Edgeworth–Kuiper belt) is a region of the Solar System that exists beyond the eight major planets, extending from the orbit of Neptune (at 30 AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, in that it contains many small bodies, all remnants from the Solar System’s formation.

But unlike the Asteroid Belt, it is much larger – 20 times as wide and 20 to 200 times as massive. As Mike Brown explains:

The Kuiper Belt is a collection of bodies outside the orbit of Neptune that, if nothing else had happened, if Neptune hadn’t formed or if things had gone a little bit better, maybe they could have gotten together themselves and formed the next planet out beyond Neptune. But instead, in the history of the solar system, when Neptune formed it led to these objects not being able to get together, so it’s just this belt of material out beyond Neptune.

Discovery and Naming:

Shortly after Tombaugh’s discovery of Pluto, astronomers began to ponder the existence of a Trans-Neptunian population of objects in the outer Solar System. The first to suggest this was Freckrick C. Leonard, who began suggesting the existence of “ultra-Neptunian bodies” beyond Pluto that had simply not been discovered yet.

That same year, astronomer Armin O. Leuschner suggested that Pluto “may be one of many long-period planetary objects yet to be discovered.” In 1943, in the Journal of the British Astronomical Association, Kenneth Edgeworth further expounded on the subject. According to Edgeworth, the material within the primordial solar nebula beyond Neptune was too widely spaced to condense into planets, and so rather condensed into a myriad of smaller bodies.

In 1951, in an article for the journal Astrophysics, that Dutch astronomer Gerard Kuiper speculated on a similar disc having formed early in the Solar System’s evolution. Occasionally one of these objects would wander into the inner Solar System and become a comet. The idea of this “Kuiper Belt” made sense to astronomers. Not only did it help to explain why there were no large planets further out in the Solar System, it also conveniently wrapped up the mystery of where comets came from.

In 1980, in the Monthly Notices of the Royal Astronomical Society, Uruguayan astronomer Julio Fernández speculated that a comet belt that lay between 35 and 50 AU would be required to account for the observed number of comets.

Following up on Fernández’s work, in 1988 a Canadian team of astronomers (team of Martin Duncan, Tom Quinn and Scott Tremaine) ran a number of computer simulations and determined that the Oort cloud could not account for all short-period comets. With a “belt”, as Fernández described it, added to the formulations, the simulations matched observations.

The bodies in the Kuiper Belt. Credit: Don Dixon
The bodies in the Kuiper Belt. Credit: Don Dixon

In 1987, astronomer David Jewitt (then at MIT) and then-graduate student Jane Luu began using the telescopes at the Kitt Peak National Observatory in Arizona and the Cerro Tololo Inter-American Observatory in Chile to search the outer Solar System. In 1988, Jewitt moved to the Institute of Astronomy at the University of Hawaii, and Luu later joined him to work at the University’s Mauna Kea observatory.

After five years of searching, on August 30th, 1992, Jewitt and Luu announced the “Discovery of the candidate Kuiper belt object” (15760) 1992 QB1. Six months later, they discovered a second object in the region, (181708) 1993 FW. Many, many more would follow…

In their 1988 paper, Tremaine and his colleagues referred to the hypothetical region beyond Neptune as the “Kuiper Belt”, apparently due to the fact that Fernández used the words “Kuiper” and “comet belt” in the opening sentence of his paper. While this has remained the official name, astronomers sometimes use the alternative name Edgeworth-Kuiper belt to credit Edgeworth for his earlier theoretical work.

However, some astronomers have gone so far as to claim that neither of these names are correct. For example, Brian G. Marsden – a British astronomer and the longtime director of the Minor Planet Center (MPC) at the Harvard-Smithsonian Center for Astrophysics – claimed that “Neither Edgeworth nor Kuiper wrote about anything remotely like what we are now seeing, but Fred Whipple (the American astronomer who came up with the “dirty snowball” comet hypothesis) did”.

The layout of the solar system, including the Oort Cloud, on a logarithmic scale. Credit: NASA
The layout of the solar system, including the Kuiper Belt and the Oort Cloud, on a logarithmic scale. Credit: NASA

Furthermore, David Jewitt commented that, “If anything … Fernández most nearly deserves the credit for predicting the Kuiper Belt.” Because of the controversy associated with its name, the term trans-Neptunian object (TNO) is recommended for objects in the belt by several scientific groups. However, this is considered insufficient by others, since this can mean any object beyond the orbit of Neptune, and not just objects in the Kuiper Belt.

Composition:

There have been more than a thousand objects discovered in the Kuiper Belt, and it’s theorized that there are as many as 100,000 objects larger than 100 km in diameter. Given to their small size and extreme distance from Earth, the chemical makeup of KBOs is very difficult to determine.

However, spectrographic studies conducted of the region since its discovery have generally indicated that its members are primarily composed of ices: a mixture of light hydrocarbons (such as methane), ammonia, and water ice – a composition they share with comets. Initial studies also confirmed a broad range of colors among KBOs, ranging from neutral grey to deep red.

This suggests that their surfaces are composed of a wide range of compounds, from dirty ices to hydrocarbons. In 1996, Robert H. Brown et al. obtained spectroscopic data on the KBO 1993 SC, revealing its surface composition to be markedly similar to that of Pluto, as well as Neptune’s moon Triton, possessing large amounts of methane ice.

8 largest Kuiper Belt Objects
Artist’s comparison of the eight largest Kuiper Belt Objects. Credit: Lexicon/NASA Images

Water ice has been detected in several KBOs, including 1996 TO66, 38628 Huya and 20000 Varuna. In 2004, Mike Brown et al. determined the existence of crystalline water ice and ammonia hydrate on one of the largest known KBOs, 50000 Quaoar. Both of these substances would have been destroyed over the age of the Solar System, suggesting that Quaoar had been recently resurfaced, either by internal tectonic activity or by meteorite impacts.

Keeping Pluto company out in the Kuiper belt, are many other objects worthy of mention. Quaoar, Makemake, Haumea, Orcus and Eris are all large icy bodies in the Belt. Several of them even have moons of their own. These are all tremendously far away, and yet, very much within reach.

Exploration:

On January 19th, 2006, NASA launched the New Horizons space probe for the sake of studying Pluto, its moons and one or two other Kuiper Belt objects. As of January 15th, 2015, the spacecraft began its approach to the dwarf planet, and is expected to make a flyby by July 14th, 2015. When it reaches the area, astronomers are expecting several interesting photographs of the Kuiper Belt as well.

Even more exciting is the fact that surveys of other solar systems indicate that our Solar System isn’t unique. Since 2006, there have been other “Kuiper Belts” (i.e. icy debris belts) discovered around nine other star systems. These appear to fall into two categories: wide belts, with radii of over 50 AU, and narrow belts (like our own Kuiper Belt) with radii of between 20 and 30 AU and relatively sharp boundaries.

According to infrared surveys, an estimated 15-20% of solar-type stars are believed to have massive Kuiper-Belt-like structures. Most of these appear to be fairly young, but two star systems – HD 139664 and HD 53143, which were observed by the Hubble Space Telescope in 2006 – are estimated to be 300 million years old.

Vast and unexplored, the Kuiper Belt is the source of many comets, and is believed to be the point of origin for all periodic or short-period comet (i.e. ones with an orbit lasting 200 years or less). The most famous of these is Halley’s Comet, which has been active for the past 16,000–200,000 years.

Future of the Kuiper Belt:

When he initially speculated about the existence of a belt of objects beyond Neptune, Kuiper indicated that such a belt probably did not exist anymore. Of course, subsequent discoveries have proven this to be wrong. But one thing that Kuiper was definitely right about was the idea that these Trans-Neptunian Objects won’t last forever. As Mike Brown explains:

We call it a belt, but it’s a very wide belt. It’s something like 45 degrees in extent across the sky – this big swath of material that’s just been churned and churned by Neptune. And these days, instead of making a bigger and bigger body, they’re just colliding and slowly grinding down into dust. If we come back in another hundred million years, there’ll be no Kuiper Belt left.

Given the potential for discovery, and what up-close examination could teach us about the early history of our Solar System, many scientists and astronomers look forward to the day when we can examine the Kuiper Belt in more detail. Here’s hoping that the New Horizons mission is just the beginning of future decades of research into this mysterious region!

We have many interesting articles here at Universe Today on the subject on the Outer Solar System and Trans-Neptunion Objects (TNOs).

And be sure to check out this article on the planet Eris, the latest dwarf planet and the largest TNO to be discovered.

And astronomers are expecting to discover two more large planets in our Solar System.

Universe Today also has a full-length interview with Mike Brown from Caltech.

Posted on by Matt Williams

Edwin “Buzz” Aldrin – The Second Man on the Moon

Astronaut Edwin E. Aldrin, Jr. Credit: NASA

Astronaut, engineer, author, and actor, Edwin “Buzz” Aldrin is what you might call a living legend. As the Lunar Module Pilot aboard the Apollo 11 mission, and second man to walk on the Moon, he is exceeded only by Neil Armstrong when it comes to the most famous astronauts that have ever lived.

And much like all astronauts who left an indelible mark on history, the path that brought Aldrin to the Moon began early in his life. And since achieving the dream of countless generations, he has gone on to inspire others to make similar leaps, advocating space exploration, and a mission to Mars.

Early Life:
Born Edwin Eugene Aldrin on January 20th, 1930, in Montclair, New Jersey to a military family, Aldrin picked up his famous nickname from the younger of his two elder sisters. Unable to pronounce brother, he let her call him “buzzer”, which was eventually shortened to “Buzz”. During his childhood, Aldrin was also a boy scout, earning the rank of Tenderfoot Scout.

After graduating from high school, Aldrin wanted to follow in his father’s footsteps. As such, he turned down a scholarship to the Massachusetts Institute of Technology (MIT) and instead enrolled in the United States Military Academy at West Point, New York. He would later enroll at MIT to complete his studies, but not before going off to war.

Military Career:
Upon graduating in 1951 from West Point with a Bachelors of Science in Mechanical Engineering, Aldrin was commissioned as a 2nd Lieutenant in the United States Air Force. During the Korean War, he served as a jet fighter pilot, flying 66 combat missions in F-86 Sabres and shooting down two MiG-15 aircraft.

After the war, he was assigned as an aerial gunnery instructor at Nellis Air Force Base in Nevada before becoming a flight commander at Bitburg Air Base in West Germany, where he flew F-100 Super Sabres with the 22nd Fighter Squadron.

F-86 Sabre Pilot Lieutenant Buzz Aldrin of 16th FS, 51st FW, Korea, 1953. Credit: openroadmedia.kinja.com
Buzz Aldrin in the cockpit of an F-86 Sabre while serving as part of the 16th FS, 51st FW, in Korea, 1953. Credit: openroadmedia.kinja.com

After completing his military service, Aldrin returned to MIT to receive his Doctor of Science degree in Aeronautics. In 1963, he was assigned to the Gemini Target Office of the Air Force Space Systems Division in Los Angeles, and began to pursue a career in space exploration. Initially, his application was rejected since he had never been a test pilot. However, that prerequisite was lifted when Aldrin re-applied, and he was accepted into the third group of astronauts in October of 1963.

Gemini Program:
Aldrin was initially selected to participate in the Gemini program, and after the deaths of the original Gemini 9 prime crew (Elliot See and Charles Bassett) Aldrin and Jim Lovell were promoted to backup crew for the mission. The main objective of the revised mission (Gemini 9A) was to rendezvous and dock with a target vehicle.

When this failed, Aldrin improvised an effective exercise for the craft to rendezvous with a co-ordinate in space. On his next mission – Gemini 12, which took place in 1966 – Aldrin served as the pilot and set a record for extra-vehicular activity (EVA), demonstrating that astronauts could work outside spacecraft.

Photograph of Major Edwin E. Aldrins helmet taken during the Gemini XII mission during orbit no. 14 on November 12,1966. Credit: NASA
Photograph of Major Edwin E. Aldrins helmet taken during the Gemini XII mission during orbit no. 14 on November 12,1966. Credit: NASA

Apollo 11:
As the Lunar Module Pilot of the Apollo 11 mission, Aldrin became the second astronaut to walk on the Moon on July 21st, 1969. Aldrin’s first words on the Moon were “Beautiful view. Magnificent desolation.” As a Presbyterian, Aldrin decided to hold a religious ceremony on the Moon, and became the first man to do so.

Using a home communion kit given to him, he reciting words used by his pastor at Webster Presbyterian Church (Rev. Dean Woodruff). The ceremony was not communicated back to Earth and was a private affair. However, after landing on the Moon, Aldrin radioed Earth and said:

I’d like to take this opportunity to ask every person listening in, whoever and wherever they may be, to pause for a moment and contemplate the events of the past few hours, and to give thanks in his or her own way.

In later years, Aldrin expressed some regret, thinking that a Christian service may not have been in keeping with the spirit of going to the Moon for all of humanity. However, for him personally, it was a significant event and in keeping with his personal faith.

According to different NASA accounts, it had originally been proposed that Aldrin be the first to step onto the Moon’s surface. But due to the physical positioning of the astronauts inside the compact lunar landing module, it was easier for the commander, Neil Armstrong, to be the first to exit the spacecraft.

Buzz Aldrin on the Moon
The iconic photo of Buzz Aldrin walking on surface the Moon as part of the Apollo 11 mission. Credit: NASA

Retirement:
After leaving NASA in 1971, Aldrin was assigned as the Commandant of the U.S. Air Force Test Pilot School at Edwards Air Force Base, California. In March 1972, Aldrin retired from active duty after 21 years of service, due to personal issues stemming from clinical depression and alcoholism. Afterward, he sought treatment for these problems, and his life improved considerably.

Following his retirement, Aldrin remained active in promoting space. He created a nonprofit organization named ShareSpace which supports space education, has written several books, and even released a CD with Snoop Dogg and other rappers in order to promote space. He has been very vocal regarding his belief that NASA should be moving ahead with a manned mission to Mars.

Since retiring from NASA, he has also had an impressive career in television and film, appearing on multiple episodes of hit TV shows, TV movies, documentaries, and as a contestant on Dancing with the Stars. He has also done extensive voice-over work for animated shows, movies, and the video game Mass Effect 3.

Like Neil Armstrong, Buzz Aldrin has received numerous medals and awards for his service – including the Presidential Medal of Freedom, the Air Force Distinguished Service Medal, three Air Medals, the NASA Distinguished Service Medal, the NASA Exceptional Service Medal, two NASA Space Flight Medals, and the Harmon International Trophy. He has also received honorary degrees from six colleges and universities.

Aldrin has been married three times and has three children and one grandson.

Universe Today has articles on Buzz Aldrin and Buzz Aldrin raps with Snoop Dogg.

For more information, try Buzz Aldrin and Snoop Dogg and biography of Buzz Aldrin.

Astronomy Cast has episodes on the Moon.

Source: NASA

Posted on by Matt Williams

Neil Armstrong: The First Man to Walk on the Moon

armstrong on the Moon
Neil Armstrong on the Moon in 1969. Credit: NASA

Neil Armstrong is considered one of the greatest heroes of the space age, earning renown within the United States and the world over for being the first person to land a spacecraft on the Moon and the first person to set foot on the Lunar surface. But what is the story behind the man? As with all heroes and inspiration figures, the road that led to his famous declaration “One small step for [a] man,” began early on in his life.

Early Life:
Neil was born on August 5, 1930, in Auglaize County near Wapakoneta, Ohio to Stephen Koenig Armstrong and Viola Louise Engel. His father worked as an auditor for the Ohio government, which meant that the family moved around quite a lot during Neil’s formative years. In fact, the Armstrong’s lived in a total of 20 towns for the first few years of Neil’s life.

From an early age, Neil demonstrated a deep passion for flying. When he was just two-years-old, his father took him to the Cleveland Air Races. On July 20, 1936, when he was five, he experienced his first airplane flight in Warren, Ohio, where he and his father took a ride in a Ford Trimotor airplane (also known as the “Tin Goose”).

The Experimental Aircraft Association is bringing a 1929 Ford Tri-Motor to the Purdue Airport on Wednesday (Sept 5). Purdue students, faculty and staff will be able to ride in the plane, which served as one of the worldÕs first airliners. (Photo provided by the Experimental Aircraft Association)
The 1929 Ford Tri-Motor, which Armstrong flew in with his father on July 20th, 1936, on display at Purdue Airport. Credit: Experimental Aircraft Association

As a child, Armstrong was also active in the Boy Scouts and obtained the rank of Eagle Scout. As a teenager, he began taking flying lessons and worked at the local airport and at other odd jobs in order to pay for it. At the age of 16, before he even had his driver’s license, Neil earned his pilot’s license and began down the path that would eventually take him into space.

At the age of 17, Armstrong went off to study aeronautical engineering. Although he had been accepted to the Massachusetts Institute of Technology, he decided instead to go to Purdue University in West Lafayette, Indiana, in order to be closer to home. His college tuition was paid for under the Holloway Plan, where applicants committed to two years of study, followed by three years of service in the U.S. Navy, before completed the final two years of their degree program.

Military Pilot:
In January of 1949, at the age of 18, Armstrong was called-up for military service and went off to the Naval Air Station in Pensacola, Florida, to begin his flight training. This lasted almost 18 months, during which time he qualified for carrier landing aboard the USS Cabot and USS Wright. On August 16th, 1950, two weeks after his 20th birthday, Armstrong was informed by letter that he was a fully qualified Naval Aviator.

Two F9F-2 Panthers over Korea, with Armstrong piloting S-116 (left). Credit: U.S. Navy National Museum of Naval Aviation
Two F9F-2 Panthers over Korea, with Armstrong piloting S-116 (left). Credit: U.S. Navy National Museum of Naval Aviation

In June 1951, the carrier he had been assigned to – the USS Essex – set sail for Korea, where his unit (VF-51, an all-jet squadron) would act as a ground-attack squadron. In the course of the war, he flew 78 missions and accumulated approximately 121 hours of combat experience. His plane was shot down once, but Armstrong managed to eject and was rescued without incident or serious injury.

For his service to his country, he received several commendations, including the Air Medal for his first 20 combat missions, a Gold Star for the next 20, and the Korean Service Medal and Engagement Star. Armstrong left the Navy at age 22 on August 23rd, 1952, and became a Lieutenant, Junior Grade, in the U.S. Naval Reserve. He remained in the reserve for eight years, then resigned his commission on October 21st, 1960.

After his service in Korea, Armstrong returned to his studies at Purdue. In 1955, he was awarded a Bachelor of Science degree in Aeronautical Engineering, and a Master of Science degree in Aerospace Engineering from the University of Southern California in 1970. Armstrong would also be awarded honorary doctorates by several universities later on in life.

Armstrong, 30, and X-15 1 after a research flight in 1960. Credit: NASA
Armstrong, at the age of 30, pictured in front of X-15 #1 after a research flight in 1960. Credit: NASA

It was also during his time at Purdue that Armstrong met Janet Elizabeth Shearon, the woman he would go on to marry. After graduating, the two moved to Cleveland, Ohio, where Armstrong was working at the National Advisory Committee for Aeronautics’ (NACA) Lewis Flight Propulsion Laboratory as a research test pilot. The two married on January 28th, 1956, at the Congregational Church in Wilmette, Illinois.

After 18-months, the Armstrongs moved to Edwards Air Force Base in California where he began working for the NACA’s High-Speed Flight Station. While there, he flew multiple experimental aircraft, including the Bell X-1B, the T-33 Shooting Star, the Lockheed F-104, and the North American X-15. He also met legendary test pilot Chuck Yeager, and was involved in several incidents that went down in Andrew’s AFB folklore.

Gemini Program:
In September of 1962, Armstrong joined the NASA Astronaut Corps as part of what the press dubbed “the New Nine” – a group of nine astronauts that were selected for the Gemini and Apollo programs. These programs, which were the successor to the Mercury Program – which sought to place an astronaut in orbit (popularized by the movie The Right Stuff) – were designed with the intent of conducting long-term space flights and a manned mission to the Moon.

The Agena Target Vehicle as seen from Gemini 8 during rendezvous. Credit: NASA
The Agena Target Vehicle as seen from Gemini 8 during rendezvous. Credit: NASA

Neil’s first mission to space would take place four years later, on March 16th, 1966, aboard a Titan II spacecraft, with Neil acting as Command Pilot and fellow astronaut David Scott as Pilot. Known as Gemini 8, this mission was the most complex mission to date, involving a rendezvous and docking with an unmanned Agena target vehicle, and some extra-vehicular activity (EVA) being performed.

The docking procedure was a success, but due to mechanical failure, the mission had to be cut short. On September 12th, 1966, Armstrong served as the Capsule Communicator (CAPCOM) for the Gemini 11 mission, remaining in communication with astronauts Pete Conrad and Dick Gordon as they conducted spacecraft rendezvous and EVA operations.

On April 5th, 1967, just three and half months after the Apollo 1 fire took place, Deke Slayton – one of the Mercury Seven astronauts and NASA’s first Chief of the Astronaut Office – brought Armstrong and many other veterans of project Gemini together and told that they would be flying the first Lunar missions.

Apollo 11 Crew Photo. Credit: NASA
Apollo 11 Crew Photo, showing Neil Armstrong (left), Buzz Aldrin (right), and Michael Collins (middle). Credit: NASA

Over the next six months, Armstrong and the other astronauts began training for a possible trip to the Moon, and Neil was named backup commander for the Apollo 8 mission. On December 23rd, 1968, as Apollo 8 orbited the Moon, Slayton informed Armstrong that he would be commander for the Apollo 11 mission, joined by Buzz Aldrin as lunar module pilot and Michael Collins as command module pilot.

Apollo 11:
On July 16th, 1969, the historic mission blasted off from the Kennedy Space Center in Florida at 13:32:00 UTC (9:32:00 a.m. EDT local time). Thousands of people crowded the highways and beaches near the launch site to watch the Saturn V rocket ascend into the sky. Millions more watched from home, and President Richard M. Nixon viewed the proceedings from the Oval Office at the White House.

The rocket entered the Earth’s orbit some twelve minutes later. After one and a half orbits, the S-IVB third-stage engine pushed the spacecraft onto its trajectory toward the Moon. After 30 minutes, the command/service module pair separated from this last remaining Saturn V stage, docked with the Lunar Module, and the combined spacecraft headed for the Moon.

The Apollo 11 Command and Service Modules (CSM) are photographed from the Lunar Module (LM) in lunar orbit during the Apollo 11 lunar landing mission. Credit: NASA
The Apollo 11 Command and Service Modules (CSM) are photographed from the Lunar Module (LM) in lunar orbit during the Apollo 11 lunar landing mission. Credit: NASA

On July 19th at 17:21:50 UTC, Apollo 11 passed behind the Moon and fired its service propulsion engine to enter lunar orbit. On July 20th, the Lunar Module Eagle separated from the Command Module Columbia, and the crew commenced their Lunar descent. When Armstrong looked outside, he saw that the computer’s landing target was in a boulder-strewn area which he judged to be unsafe. As such, he took over manual control of the LM, and the craft landed at 20:17:40 UTC with only 25 seconds of fuel left.

Armstrong then radioed to Mission Control and announced their arrival by saying: “Houston, Tranquility Base here. The Eagle has landed.” Once the crew had gone through their checklist and depressurized the cabin, the Eagles’ hatch was opened and Armstrong began walking down the ladder to the Lunar surface first.

When he reached the bottom of the ladder, Armstrong said: “I’m going to step off the LEM now” (referring to the Lunar Excursion Module). He then turned and set his left boot on the surface of the Moon at 2:56 UTC July 21st, 1969, and spoke the famous words “That’s one small step for [a] man, one giant leap for mankind.”

About 20 minutes after the first step, Aldrin joined Armstrong on the surface and became the second human to set foot on the Moon. The duo then began their tasks of unveiling a plaque commemorating their flight, setting up the Early Apollo Scientific Experiment Package, and planting the flag of the United States. The crew then returned to the LM and blasted off, commencing their return trip to Earth.

A teensy-tiny Neil Armstrong is visible in the helmet of Buzz Aldrin during the Apollo 11 landing in July 1969. Credit: NASA
Neil Armstrong is visible in the helmet of Buzz Aldrin during the Apollo 11 landing in July 1969. Credit: NASA

Upon returning to Earth, the Apollo 11 crew went on a 45-day tour around the world called the “Giant Leap” tour. Armstrong also traveled to the Soviet Union to talk at the 13th annual conference of the International Committee on Space Research. While there, he met Valentina Tereshkova (the first female astronaut to go into space), Premier Alexei Kosygin, and was given a tour of the Yuri Gagarin Cosmonaut Training Center.

Shortly after the Apollo 11 mission, Armstrong announced that he did not intend to fly in space again; and in 1971, resigned from NASA. He then settled into a life of teaching, accepting a position in the Department of Aerospace Engineering at the University of Cincinnati. After eight years, he resigned. He also spent much of this time acting as a corporate spokesperson and serving on the board of directors of several companies.

Retirement and Death:
During his post-Apollo years, Armstrong also served on two spaceflight accident investigations. The first took place in 1970, where he served as part of the panel that investigated the Apollo 13 mission, presented a detailed chronology of the mission and made recommendations. In 1986, President Reagan appointed him as vice-chairman of the Rogers Commission to investigate the Space-shuttle Challenger disaster of that year.

Members of the U.S. Navy ceremonial guard hold an American flag over the ashes of Apollo 11 astronaut Neil Armstrong during a burial at sea service on board the USS Philippine Sea (CG-58), on Friday, September 14, 2012, in the Atlantic Ocean. Credit: NASA
Neil Armstrong was buried at sea on Sept. 14th, 2012. The ceremony took place on board the USS Philippine Sea (CG-58) in the Atlantic Ocean. Credit: NASA

In 2012, Armstrong underwent vascular bypass surgery to relieve blocked coronary arteries. Although he was reportedly recovering well, he died on August 25th, in Cincinnati, Ohio. In a ceremony that was held aboard the USS Philippine Sea (an American missile cruiser) Armstrong was buried with honors in a ceremony where a U.S. Navy ceremonial guard draped an American flag over his ashes before commended them to the sea.

For his years of service, Armstrong has received numerous medals including the Presidential Medal of Freedom, the Congressional Space Medal of Honor, the Congressional Gold Medal, the Robert J. Collier Trophy, and the Sylvanus Thayer Award.

Neil Armstrong has had over a dozen elementary, middle and high schools named in his honor, and many streets, buildings, schools, and other places around the world have been named in honor of Armstrong and/or the Apollo 11 mission. The lunar crater Armstrong, which sits approx. 50 km (31 miles) from the Apollo 11 landing site, and asteroid 6469 Armstrong are named in his honor.

Armstrong was also inducted into the Aerospace Walk of Honor, the National Aviation Hall of Fame, and the United States Astronaut Hall of Fame. Armstrong and his Apollo 11 crewmates were the 1999 recipients of the Langley Gold Medal from the Smithsonian Institution. His alma mater, Purdue University, also named a new engineering hall after him, which was completed in 2007.

Universe Today has articles on Neil Armstrong and first man on the Moon.

For more information, check out Neil Armstrong and NASA’s Human Spaceflight.

Astronomy Cast has an episode on the Moon.

Sources:
NASA: Who is Neil Armstrong
NASA: Biography of Neil Armstrong

Posted on by Matt Williams

Who Was The First Man To Go Into Space?

Yuri Gagarin, posing for a photo op before the Vostok 1 mission on April 12th, 1961 Credit:

Picture if you will two titanic powers struggling to see who will be the first to conquer space. Between them, they have the best scientists in the world, many of whom they “borrowed” from Germany after the Second World War. They are sparing no expense, and that includes the cost in lives, in order to be the first to get a human being into space.

Sound scary? Well, if you were an American astronaut or a Soviet cosmonaut in the 1960’s, it sure would be! But for men like Yuri Gagarin, the first man to go into man in space (and also the first man to orbit the Earth) the rewards would last a lifetime.

Early Life:

Like most heroes of the space age, Gagarin’s story began in his infancy. Born to Alexey Ivanovich Gagarin and Anna Timofeyevna Gagarina in the village of Klushino, Russia (Smolensky Oblast) on March 9th, 1934, Yuri Alekseyevich Gagarin began his life on a collective farm and witnessed some terrible things in his early years.

In 1941, the village was occupied by the Nazis, and the Gagarin family was forced to relocate to a mud hut on their property as a German officer took possession of their house. His two older siblings were deported to Poland for slave labor in 1943, and did not return until after the war in 1945.

Gagarin pictured in a Yak-18 trainer plane. Credit: rian.ru
Gagarin pictured in a Yak-18 plane, while training to become a pilot with the Soviet Air Force. Credit: rian.ru

Another version of Gagarin’s biography suggests that the family relocated east of the Urals ahead of the Nazi advance, and returned to the region after the war. In either case, by 1946, the family moved to the nearby town of Gzhatsk, where Gagarin continued his secondary education.

At the age of 16, Gagarin entered into an apprenticeship as a foundryman at the Lyubertsy Steel Plant near Moscow, and also enrolled at a local “young workers” school for seventh grade evening classes. After graduating in 1951, he was selected for further training at the Saratov Industrial Technical School.

While there, Gagarin volunteered for weekend training as a Soviet air cadet at a local flying club, where he learned to fly biplanes and the Yak-18 trainer. He graduated from technical school in 1955, and was drafted into the Soviet Army.

Pilot:

In 1957, he was sent to the First Chkalov Air Force Pilot’s School in Orenburg, where he trained on Mig-15 jet fighters. While there, he met Valentina Ivanovna Goryacheva, a medical technician graduate of the Orenburg Medical School. The two were married on 7 November 1957, the same day Gagarin graduated from Orenburg.

launched into orbit on the Vostok 3KA-3 spacecraft (Vostok 1). Credit: space.com
Gagarin pictured inside the cockpit of the Vostok 3KA-3 spacecraft (Vostok 1) before being launched into orbit. Credit: Getty Images

By 1960, Gagarin had earned the rank of Senior Lieutenant and had come to the attention of the Soviet space program. After a rigorous selection process, he became one of 20 pilots selected to become a cosmonaut, and was further selected to be part of an elite training group known as the Sochi Six – from which the first cosmonauts of the Vostok program would be chosen.

Vostok Program:

Out of the twenty selected, Gagarin and fellow cosmonaut Gherman Titov were selected to be the first cosmonauts to go into space. This was due to a combination of factors, including their performance during training sessions, their height (since space was limited in the small Vostok cockpit), and by an anonymous vote by the members of the program.

Gagarin’s historic flight took place on April 12th, 1961, roughly one month before NASA was able to put a manned spacecraft of their own into space. His spaceship, the Vostok 1, weighing approximately 4700 kg (over 10,000 pounds), was quite primitive by modern standards. For starters, the craft wasn’t even piloted by Gagarin himself, mainly because the Russians had not yet tested the effects of weightlessness on any humans (only dogs!).

The actual flying was done by crews on the ground. It also had no maneuvering capabilities and consisted of a re-entry craft and service module. The cosmonaut was not even allowed to land in the re-entry craft because it was deemed too dangerous, and had to instead leave the craft and parachute to the ground.

Here the re-entry capsule of the Vostok 3KA-3 (also known as Vostok 1) spacecraft (Vostok 1) is seen with charring and its parachute on the ground after landing south west of Engels, in the Saratov region of southern Russia. Credit: space.com
The re-entry capsule of the Vostok 3KA-3 (Vostok 1) is seen with charring and its parachute on the ground after landing south west of Engels, in southern Russia. Credit: space.com

Gagarin’s flight began with his takeoff at the Baikonur Cosmodrome and ended with him parachuting safely to the ground in Kazakhstan one hour and forty-eight minutes later. During the flight, he was said to have been humming “The Motherland Hears, the Motherland Knows”, a patriotic song composed by Russian composer Dmitri Shostakovich.

According to western sources at the time, Gagarin was also rumored to have said “I don’t see any God up here” during his flight. However, the transcripts contradict this story, which appears to have been a reference to a remark Khrushchev had made after the flight and was falsely attributed to Gagarin. What he is known to have said during the flight was: “The Earth is blue… How wonderful. It is amazing.”

Retirement and Death:

Gagarin gained worldwide fame and recognition after the flight, touring Italy, Germany, the United Kingdom, Canada and Japan before returning home to Star City to continue his work with the Russian space program. He was no longer allowed into active service given his celebrity status, the government fearing that they might lose their poster boy in an accident.

Soviet cosmonaut Yuri Gagarin, the first man to fly in space, as seen in 1968 before his death in a jet crash. Credit: RSC Energia
Soviet cosmonaut Yuri Gagarin, the first man to fly in space, as seen in 1968 before his death in a jet crash. Credit: RSC Energia

This would prove to be an ironic decision, considering that seven years later, he died in an accident during a training flight. This occurred on March 27th, 1968, when Gagarin’s plane crashed and he and his instructor were killed. For many years, the circumstances surrounding the accident remained shrouded in mystery, and were the subject of much speculation and rumor.

In 2013, the truth about his death was finally revealed when the report detailing the incident was declassified. In an article that appeared on Russia Today, former cosmonaut Aleksey Leonov shared the details of the report, which indicated that the crash was the result of an unauthorized Su-15 fighter flying too close to Gagarin’s MiG, thus disrupting its flight and sending it into a spin.

Legacy:

In Russia, and around the world, Gagarin has gone down in history as one of the greatest astronauts/cosmonauts of all time and one of the biggest contributors to human space flight. For his accomplishments, he has been immortalized by numerous countries, and in countless ways.

The statue of Yuri Gagarin, the first human to fly in space, looms over the town square in Karaganda, Kazakhstan March 9 as officials prepared to commemorate him on his 80th birthday. Credit: NASA
The statue of Yuri Gagarin, the first human to fly in space, looms over the town square in Karaganda, Kazakhstan March 9 as officials prepared to commemorate him on his 80th birthday. Credit: NASA

In addition to commemorative coins, a hockey cup named in his honor and several commemorative stamps, he was given the title of “Hero of the Soviet Union” – a privilege reserved only for a select few. Numerous statues have also been erected in his honor, such as the one that towers over the town square in Karaganda, Kazakhstan (shown above).

Since 1962, April 12th has been celebrated in the USSR, and later in Russia and other post-Soviet states, as the Cosmonautics Day, in honor of his historic flight. In 2011, it was declared the International Day of Human Space Flight by the United Nations. Since 2001, Yuri’s Night, an international celebration, is held every April 12th to commemorate milestones in space exploration.

The Cosmonaut Training Center in Star City was renamed the Yuri Gagarin Cosmonaut Training Center in 1969, which was visited by Neil Armstrong during his tour of the Soviet Union.

The launch pad at Baikonur Cosmodrome from which Sputnik 1 and Vostok 1 were launched is now known as Gagarin’s Start. The village of Klushino where he was born was also renamed Gagarin in 1968 after his death, and his family’s house was converted into a museum.

Yuri Gagarin, the first man in space, during his visit to France in 1963. Credit: Ria Novosti
Yuri Gagarin, the first man in space, during his visit to France in 1963. Credit: Ria Novosti

But perhaps the most notable thing about Gagarin, for which he is remembered most fondly, is his smile. As Sergei Korolev – one of the masterminds behind the early Soviet space program – once said, Gagarin possessed a smile “that lit up the darkness of the cold war”.

We have written many articles about Yuri Gagarin for Universe Today. Here’s Yuri Gagarin and Vostok 1, on the 50th Anniversary of Human Spaceflight. And here’s Who was the First Woman to go into Space?, Alan Shepard: Complicated, Conflicted and the Consummate Astronaut, Sally Ride, First American Woman in Space, Passes Away, and Who was the First Dog to go into Space?

If you’d like more info on the Yuri Gagarin, check out the History of Human Spaceflight, and here’s a link to Yuri Gagarin, The First Man in Space.

We’ve also recorded an entire episode of Astronomy Cast all about Space Capsules. Listen here, Episode 124: Space Capsules, Part 1: Vostok, Mercury and Gemini.

Sources:

Posted on by Matt Williams

What is Halley’s Comet?

The Mawangdui silk, showing the shapes of comet tails and the different disasters associated with them, compiled in around 300 BC. Credit: NASA/JPL.

Halley’s Comet, also known as 1P/Halley, is the most well known comet in the Solar System. As a periodic (or short-term comet) it has orbital period that is less than 200 years, and has therefore been observed more than once by people here on Earth over the centuries.

It’s appearance in the skies above Earth has been noted since ancient times, and was associated with both bad and good omens by many cultures. But in truth, its behavior is no different than any short-term visitor that swings by from time to time. And its visits have become entirely predictable!

Discovery:
Halley’s Comet has been observed and recorded by astronomers since at least 240 BCE, with clear references to the comet being made by Chinese, Babylonian, and medieval European chroniclers. However, these records did not recognize that the comet was the same object reappearing over time. It was not until 1705 that English astronomer Edmond Halley, who used Newton’s Three Laws of Motion to determine that it was periodic.

Until the Renaissance, astronomers’ believed that comets – consistent with Aristotle’s views – were merely disturbances in the Earth’s atmosphere. This idea was disproved in 1577 by Tycho Brahe, who used parallax measurements to show that comets must lie beyond the Moon. However, for another century, astronomers would continue to believe that comets traveled in a straight line through the Solar System rather than orbiting the Sun.

In 1687, in his Philosophiæ Naturalis Principia Mathematica, Isaac Newton theorized that comets could travel in an orbit of some sort. Unfortunately, he was unable to develop a coherent model for explaining this at the time. As such, it was Edmond Halley – Newton’s friend and editor –  who showed how Newton’s theories on motion and gravity could be applied to comets.

In his 1705 publication, Synopsis of the Astronomy of Comets, Halley calculated the effect that Jupiter and Saturn’s gravitational fields would have on the path of comets. Using these calculations and recorded observations made of comets, he was able to determine that a comet observed in 1682 followed the same path as a comet observed in 1607.

Pairing this with another observation made in 1531, he concluded that these observations were all of the same comet, and predicted that it would return in another 76 years. His prediction proved to be correct, as it was seen on Christmas Day, 1758, by a German farmer and amateur astronomer named Johann Georg Palitzsch.

His predictions not only constituted the first successful test of Newtonian physics, it was also the first time that an object besides the planets was shown to be orbiting the Sun. Unfortunately for Halley, he did not live to see the comet’s return (having died in 1742). But thanks to French astronomer Nicolas Louis de Lacaille, the comet was named in Halley’s honor in 1759.

The illustration shows a view of Augsburg, Germany with the comets of 1680, 1682, and 1683 in the sky. Click on image for larger view. Image credit: NASA/JPL
The illustration shows a view of Augsburg, Germany with the comets of 1680, 1682 (Halley’s Comet), and 1683 in the sky. Credit: NASA/JPL

Origin and Orbit:
Like all comets that take less than about 200 years to orbit the Sun, Halley’s Comet is believed to have originated from the Kuiper Belt. Periodically, some of these blocks of rock and ice – which are essentially leftover matter from the formation of the Solar System some 4.6 billion years ago – are pulled deeper into the Solar System and becomes active comets.

In 2008, another point of origin for the Halley-type comets had been proposed when a trans-Neptunian object with a retrograde orbit similar to Halley’s was discovered. Known as 2008 KV42, this comet’s orbit takes it from just outside the orbit of Uranus to twice the distance of Pluto. This suggests that Halley ‘s Comet could in fact be member of a new population of small Solar System bodies that is unrelated to the Kuiper Belt.

Halley is classified as a periodic or short-period comet, one with an orbit lasting 200 years or less. This contrasts with long-period comets, whose orbits last for thousands of years and which originate from the Oort Cloud – the sphere of cometary bodies that is 20,000 – 50,000 AU from the Sun at its inner edge. Other comets that resemble Halley’s orbit, with periods of between 20 to 200 years, are called Halley-type comets. To date, only 54 have been observed, compared with nearly 400 identified Jupiter-family comets.

Artists' impression of the Kuiper belt and Oort cloud, showing both the origin and path of Halley's Comet. Image credit: NASA/JPL.
Artists’ impression of the Kuiper belt and Oort cloud, showing both the origin and path of Halley’s Comet. Credit: NASA/JPL

Halley’s orbital period over the last 3 centuries has been between 75–76 years, although it has varied between 74–79 years since 240 BC. Its orbit around the Sun is highly elliptical. It has a perihelion (i.e. the point where it is nearest the Sun) of just 0.6 AU, which places it between the orbits of Mercury and Venus. Meanwhile, it’s aphelion – the farthest distance from the Sun – is 35 AU, the same distance as Pluto.

Unusual for an object in the Solar System, Halley’s orbit is retrograde – which means that it orbits the Sun in the opposite direction to the planets (or clockwise from above the Sun’s north pole). Due to the retrograde orbit, it has one of the highest velocities relative to the Earth of any object in the Solar System.

The orbits of the Halley-type comets suggest that they were originally long-period comets whose orbits were perturbed by the gravity of the gas giants and directed into the inner Solar System. If Halley was once a long-period comet, it is likely to have originated in the Oort Cloud. However, Halley is believed to have been a short-term comet for the past 16,000–200,000 years.

Because its orbit comes close to Earth’s in two places, Halley is the parent body of two meteor showers: the Eta Aquariids in early May, and the Orionids in late October. Observations conducted around the time of Halley’s appearance in 1986, however, suggest that the Eta Aquarid meteor shower might not originate from Halley’s Comet, although it might be perturbed by it.

Photo of Haley's Comet crossing the Milky Way, taken by the Kuiper Airborne Observatory in New Zealand on April 8th/9th, 1986. Credit: NASA
Photo of Haley’s Comet crossing the Milky Way, taken by the Kuiper Airborne Observatory in New Zealand on April 8th/9th, 1986. Credit: NASA

Structure and Composition:
As Halley approaches the Sun, it expels jets of sublimating gas from its surface, which knock it very slightly off its orbital path. This process causes the comet to form a bright tail of ionized gas (ion tail), and a faint one made up of dust particles. The ion tail is also known as a coma (a small atmosphere) which spans up to 100,000 km across and consists of violatiles such as water, methane, ammonia and carbon dioxide.

Despite the vast size of its coma, Halley’s nucleus is relatively small – barely 15 kilometers long, 8 kilometers wide and roughly 8 kilometers thick. Its mass is also relatively low (an estimated 2.2 × 1014 kg, or 242.5 billion tons) and its average density is about 0.6 g/cm3, indicating that it is made of a large number of small pieces held loosely together.

Spacecraft observations have shown that the gases ejected from the nucleus were 80% water vapor, 17% carbon monoxide and 3–4% carbon dioxide, with traces of hydrocarbons (although more-recent sources give a value of 10% for carbon monoxide and also include traces of methane and ammonia).

The dust particles have been found to be primarily a mixture of carbon–hydrogen–oxygen–nitrogen (CHON) compounds – which are common in the outer Solar System – and silicates, like those found in terrestrial rocks. At one time, it was thought that Halley could have delivered water to Earth in the distant past – based on the ratio of deuterium to hydrogen found in the comet’s water that showed it to be chemically similar to the Earth’s oceans. However, subsequent observations have indicated that this is unlikely.

This view of comet Halley's nucleus was obtained by the Halley Multicolour Camera (HMC) on board the Giotto spacecraft, as it passed within 600 km of the comet nucleus on March 13, 1986. Credit: ESA
The nuclear of Halley’s Comet, obtained by the Halley Multicolour Camera (HMC) on board the Giotto spacecraft during its flyby on March 13, 1986. Credit: ESA

The ESA’s Giotto (1985-1992) and Russia’s Vega missions (1986) gave planetary scientists their first view of Halley’s surface and structure. The images could only capture roughly 25% of the comet’s surface, but nevertheless revealed an extremely varied topography – with hills, mountains, ridges, depressions, and at least one crater.

Role in Myths and Superstitions:
As already noted, Halley’s Comet has a long and rich history when it comes to being observed by humans. Including its most recent visits, Halley’s Comet has been visible from Earth on 30 separate occasions. The earliest record of which were the Shih Chi and Wen Hsien Thung Khao chronicles, written in China ca. 240 BCE.

While it is believed that Babylonian scribes recorded the appearance of Halley’s Comet when it returned in 164 and 87 BCE, it’s most famous appearance occurred shortly before the 1066 invasion of England by William the Conqueror. Whereas King Harold of England saw the comet as a bad omen, William and his forces interpreted it as a sign of their impending victory (at least according to legend).

Throughout the Middle Ages, the appearances of comets in the night sky were seen as heralds of bad news, indicating that either a person of royal standing had died, or that dark days lay ahead. This is perhaps owing to what was seen as the erratic and unpredictable behavior of comets, when compared to the Sun, the Moon and the stars.

The Bayeux Tapestry, showing the appearance of Halley's Comet in the sky prior to William the Conqueror's invasion of England. Credit: Wikipedia Commons/Myrabella
The Bayeux Tapestry, showing the appearance of Halley’s Comet in the sky in 1066. Credit: Wikipedia Commons/Myrabella

With the development of modern astronomy, this view of comets has been largely dispelled. However, there are many who still hold to the “doom and gloom” view of Halley’s Comet, believing that it will strike the Earth at some point and trigger an Extinction Level Event, the likes of which has not been seen since the Dinosaurs.

Disappearance:
Halley’s overall lifespan is difficult to predict, and opinions do vary. In 1989, Russian astronomers Boris Chirikov and Vitaly Vecheslavov performed an analysis of 46 apparitions of Halley’s Comet taken from historical records and computer simulations. Their study showed that the comet’s dynamics were chaotic and unpredictable over long timescales, and indicated that its lifetime could be as long as 10 million years.

In 2002, David C. Jewitt conducted a study that indicated that Halley will likely evaporate, or split in two, within the next few tens of thousands of years. Alternately, Jewitt predicted that it could survive long enough to be ejected from the Solar System entirely within a few hundred thousand years.

Meanwhile, observations conducted by D.W. Hughes et al. suggests that Halley’s nucleus has been reduced in mass by 80–90% over the last 2000–3000 revolutions (i.e. 150,000 – 230,000 years). By their estimations, it would not be surprising at all if the comet evaporated entirely within the next 300 revolutions or so (approx. 25,000 years).

The last time Halley’s Comet was seen was in 1986, which means it will not reappear until 2061. As always, some are choosing to prepare for the worst – believing its next pass will signal the end of life as we know it – while others are contemplating if they will live long enough to witness it.

Universe Today has articles on famous comets and distant Halley’s Comet.

For more information, take a look at Comet Halley and Halley’s Comet.

Astronomy Cast has an episode on comets.

Sources: Wikipedia, NASA

Posted on by Matt Williams

What are the Galilean Moons?

Illustration of Jupiter and the Galilean satellites. Credit: NASA

It’s no accident that Jupiter shares its name with the king of the gods. In addition to being the largest planet in our Solar System – with two and a half times the mass of all the other planets combined – it is also home to some of the largest moons of any Solar planet. Jupiter’s largest moons are known as the Galileans, all of which were discovered by Galileo Galilei and named in his honor.

They include Io, Europa, Ganymede, and Callisto, and are the Solar System’s fourth, sixth, first and third largest satellites, respectively. Together, they contain almost 99.999% of the total mass in orbit around Jupiter, and range from being 400,000 and 2,000,000 km from the planet. Outside of the Sun and eight planets, they are also among the most massive objects in the Solar System, with radii larger than any of the dwarf planets.

Continue reading “What are the Galilean Moons?”