The 19th century was an auspicious time for astronomers and planet hunters. In addition to the discovery of the Asteroid Belt that rests between Mars and Jupiter – as well as the many minor planets within – the outer solar planet of Uranus and its series of moons were also observed for the very first time.
Of these, Umbriel was certainly one of the most interesting finds. Aside from being Uranus’ third largest moon, it is also its darkest – a trait which contributed greatly to the selection of its name. And to this day, this large satellite of Uranus is shrouded in mystery…
Discovery and Naming:
Umbriel, along with its fellow moon Ariel, was discovered by English astronomer William Lassell on October 24th, 1851. Fellow English astronomer William Herschel, who had discovered Uranus’ moons of Titania and Oberon at the end of the 18th century, also claimed to have observed four additional moons around Uranus. However, his observations were not confirmed, leaving the confirmed discoveries of Ariel and Umbriel to Lassell, roughly half a century later.
Much like all of Uranus’ 27 moons, Umbriel was named after a character from Alexander Pope’s The Rape of the Lock, as well as plays by William Shakespeare. These names were suggested by John Herschel, the son of William Herschel, when he announced the discoveries of Titania and Oberon.
Size comparison of Earth, the Moon, and Umbriel. Credit: Tom Reding/Public Domain
In keeping with the moon’s dark appearance, the name Umbriel – which was the name of the ‘dusky melancholy sprite’ in the The Rape of the Lock and is derived from the Latin Umbra (which means “shadow”) – seemed most appropriate for this satellite.
Size, Mass and Orbit:
Ariel and Umbriel are nearly the same size, with diameters of 1,158 kilometers and 1,170 kilometers respectively. Based on spectrograph analyses and estimates of the moon’s mass and density, astronomers believe that the majority of the planet consists of water ice, with a dense non-ice component constituting around 40% of its mass.
This could mean that Umbriel consists of an icy outer shell that surrounds a rocky core, or one made out of carbonaceous materials. It also means that though Umbriel is the third largest moon of Uranus, it is only the fourth largest in terms of mass. Furthermore, its dark appearance is believed to be the result of the interactions of surface water ice with energetic particles from Uranus’ magnetosphere.
These energetic particles would cause methane deposits (trapped in the ice as clathrate hydrate) to decompose and other organic molecules to darken, leaving behind a dark, carbon-rich residue. The satellite’s dark color is also due to its very low bond albedo – which is basically the amount of electromagnetic radiation (i.e. light) that gets reflected back from the surface.
So far, spectrographic analyses have only confirmed the existence of water and carbon dioxide. So the existence of organic particles or methane deposits in the ice remains theoretical. However, their presence would explain the prevalence of CO² and why it is concentrated mainly on the trailing hemisphere.
Umbriel’s orbital period – i.e. the time it takes the moon to orbit Uranus – is approximately 4.1 days, which is coincident with its rotational period. This means that the moon is a synchronous and tidally-locked satellite, with one face always pointing towards Uranus. The satellite is at an average distance of 266,000 kilometers from its planet, which makes it the third farthest from Uranus, behind Miranda and Ariel.
Voyager 2:
So far, the only close-up images of Umbriel have been provided by the Voyager 2 probe, which photographed the moon during its flyby of Uranus in January of 1986. During this flyby, the closest distance between Voyager 2 and Umbriel was 325,000 km (202,000 mi).
The images cover about 40% of the surface, but only 20% was photographed with the quality required for geological mapping. At the time of the flyby, the southern hemisphere of Umbriel was pointed towards the Sun – so the northern, darkened hemisphere could not be studied. At present, no future missions are planned to study the moon in greater detail.
US Geological Survey map of Umbriel, showing its cratered surface and polygons. Credit: ISGS
Interesting Facts:
The surface of Umbriel has far more and larger craters than do Ariel and Titania, ranging in diameter from a few kilometers to several hundred. The largest known crater on the surface is Wokolo, which is 210 km in diameter. Wunda, a crater with a diameter of about 131 kilometers, is the most noticeable surface feature, due to the ring of bright material on its floor (which scientists think are from the impact).
Other craters include Fin, Peri, and Zlyden which, like all of Umbriel’s surface features, are named after dark sprites from different cultures’ mythology. The only satellite of Uranus to have more craters is Oberon, and the planet is believed to be geologically stable.
It is further believes that surface has probably been stable since the Late Heavy Bombardment. The only signs of ancient internal activity are canyons and dark polygons – dark patches with complex shapes measuring from tens to hundreds of kilometers across. The polygons were identified from precise photometry of Voyager 2′s images and are distributed more or less uniformly on the surface of Umbriel, trending northeast – southwest.
Because Uranus orbits the Sun almost on its side, it is subject to an extreme seasonal cycle. Both northern and southern poles spend 42 years in complete darkness, and another 42 years in continuous sunlight, with the Sun rising close to the zenith over one of the poles at each solstice.
The southern hemisphere of Umbriel displays heavy cratering in this Voyager 2 image, taken Jan. 24, 1986. The large impact crater of Wunda is visible at the top. Credit: NASA/JPL
Because they are in the planet’s equatorial plane, Uranus’ satellites also experience these changes. This means that Umbriel’s north and south poles spend 42 years in light and then 42 years in darkness before repeating the cycle. In fact, the Voyager 2 flyby coincided with the southern hemisphere’s 1986 summer solstice, when nearly the entire northern hemisphere was in darkness.
Interesting little moon isn’t it? Even though no missions are currently planned to observe it in the coming years, one can only hope that future satellites happen to sneak a peek at it on their way to some other destination in the outer Solar System.
This set of computer modeling illustrations of Pluto’s moon Nix shows how the orientation of the moon changes unpredictably as it orbits the “double planet” Pluto-Charon.
Credit: NASA/ESA/M. Showalter (SETI)/G. Bacon (STScI)
Simulation of Pluto’s moon Nix sped up so that one orbit takes 2 seconds instead of 25 days.
Wobbling and tumbling end-over-end like a badly thrown football, Pluto’s moons are in a state of orbital chaos, say scientists. Analysis of data from NASA’s Hubble Space Telescope shows that two of Pluto’s moons, Nix and Hydra, wobble unpredictably. If you lived on either, you’d never know when and in what direction the Sun would rise. One day it would pop up over your north horizon, the next over the western. Every sunset would be like a proverbial snowflake — not a single one the same.
Watch the video, and you’ll see what I mean. Not only does the moon totter, but the poles flip. If there was ever a solar system body to meet the criteria of end-of-the-world, doomsday crowd, Nix is it. The moons wobble because they’re embedded in the bizarro gravity field of the Pluto-Charon duo. Charon is officially the dwarf planet’s largest moon, but the two bodies act more like a double planet because Charon’s so huge.
OK, it’s only 750 miles (1,212 km) in diameter, but that’s half as big as Pluto. Imagine if our moon was twice as big as it is now, and you get the picture.
Charon is large compared to Pluto, so they orbit about their common center of gravity located in the space between the two bodies. Credit: Wikipedia
As the duo dances an orbital duet about their common center of gravity, their variable gravitational field sends the smaller moons tumbling erratically. The effect is enhanced even more by their irregular and elongated shapes. It’s likely Pluto’s other two moons, Kerberos and Styx, are in a similar situation.
Because their moment to moment motions are essentially unpredictable, scientists describe their behavior is chaotic. Saturn’s moon, Hyperion, also tumbles chaotically.
Pluto (upper right) and its largest moon Charon form a “double planet” as seen in this photo taken by NASA’s New Horizons probe which is set to make a close flyby of the Pluto system on July 14. Credit: NASA / NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute
The discovery was made by Mark Showalter of the SETI Institute and Doug Hamilton of the University of Maryland using the Hubble Space Telescope and published in today’s issue of the journal Nature. Showalter also found three of Pluto’s moons are presently locked together in resonance, meaning there’s a precise ratio for their orbital periods.
“If you were sitting on Nix, you would see that Styx orbits Pluto twice for every three orbits made by Hydra,” said Hamilton.
That’s not all. If you’ve ever grilled with charcoal, you’d have a good idea what Kerberos looks like. Dark as one those briquettes. The other moons are as bright as sand because they’re mostly made of ice. Astronomers had thought that material blasted off the moons by meteorite impacts should make them all the same basic tone, so what’s up with Kerberos? No one knows.
This illustration shows the scale and comparative brightness of Pluto’s small satellites. The surface craters are for illustration only and are not real. Credits: NASA/ESA/A. Feild (STScI)
Pluto’s moons are thought to have formed during a collision long ago between the dwarf planet and a similar-sized object. The smash-up created lots of smaller bodies that eventually took up orbits about the present-day Pluto. Outside of Charon, the biggest leftover, the other moons measure in the tens of miles across. The four little ones — Nix, Styx, Kerberos and Hydra — were discovered with the Hubble scope during surveys to better map the Pluto system before New Horizons arrives next month. No one would be surprised if even more itty-bitty moons are found as we draw ever closer to the dwarf planet.
Situated on the south shore of New Jersey’s Shark River lies 37 acres of land known as Camp Evans. On April 1, 2015, I was privileged to attend the dedication ceremony celebrating Camp Evans’ becoming one of only 2532 locations in the United States designated as a National Historic Landmark.
In 1912, Gugliemlo Marconi and his company, the American Marconi Company, constructed the Belmar Receiving Station which became part of the wireless girdle of the earth.
In 1917, the site was acquired as part of the Navy’s World War I “Trans-Atlantic Communication System.”
In 1941, the Army Signal Corps purchased the property to construct a top-secret research facility, and it was renamed Evans Signal Laboratory which later became Camp Evans Signal Laboratory.
Following a visit in late October, 1953, Senator Joseph McCarthy described Camp Evans as a “house of spies.” Following an investigation that spanned 1953-1954, not one single employee was prosecuted.
But perhaps Camp Evans’ most interesting – and surprising – place in history begins with a small, informal research project taking place on a parcel of land in the Camp’s northeast corner. The ramifications of this project would ultimately give birth the to Space Age, lead to the development of the US Space Program, and start the Cold War.
Following the end of WWII, American scientists at Camp Evans continued their investigation into whether the earth’s ionosphere could be penetrated using radio waves – a feat that had been studied prior to the end of the War but had long been believed impossible. Project Diana, led by Lt. Col. John H. DeWitt, Jr., aimed to prove that it could indeed be penetrated. A group of radar scientists awaiting their discharge from the Army modified a radar antenna – including significantly boosting its output power – and placed it in the northeast corner of Camp Evans.
Location of the Radar Antenna on the Northeast Corner of Camp Evans Circa 1946. [photo: InfoAge website]
On the morning of January 10, 1946, with the dish pointed at the rising moon, a series of radar signals was broadcast. Exactly 2.5 seconds after each signal’s broadcast, its corresponding echo was detected. This was significant because 2.5 seconds is precisely the time required for light to travel the round trip distance between the earth and the moon. Project Diana – and her scientists – had successfully demonstrated that the ionosphere was, in fact, penetrable, and communication beyond our planet was possible. And thus was born the Space Age – as well as the field of Radar Astronomy.
SCR-271 Bedspring RADAR Antenna Pointing at the Moon [photo: David Mofenson; InfoAge website]By mid-1958 the United States had launched the Television InfraRed Observation Satellite (TIROS) program designed to study the viability of using satellite imagery and observations as a means of studying the Earth and improving weather forecasting. As part of this effort, the original “Moonbounce” antenna was replaced with a 60-foot parabolic radio antenna dish which would serve as the project’s downlink Ground Communication Station.
60-Meter Parabolic Dish Being Constructed on Project Diana Site [photo: Frank Vosk; InfoAge website]On April 1, 1960, NASA successfully launched its TIROS I satellite and the “Silent Sentinel Radio Dish” at Camp Evans began receiving its data being sent down to earth.
TIROS I Satellite [photo: NASA; National Space Science Data Center]The resulting images were so astonishing and groundbreaking that the first photos received from TIROS I were immediately printed and flown to Washington where they were presented to President Eisenhower by NASA Administrator T. Keith Glennan.
President Eisenhower and NASA Administrator Glennan Viewing the First Satellite Images from TIROS I. [photo: wikimedia commons]The TIROS program would go on to be instrumental in meteorological applications not only because it provided the first accurate weather forecasts and hurricane tracking based on satellite information, but also because it began providing continuous coverage of the earth’s weather in 1962, and ultimately lead to the development of more sophisticated observational satellites. [1]
In addition to serving as the downlink Ground Communications Center for the TIROS I and TIROS II satellites, this same dish has also tracked:
Explorer 1, America’s first satellite, in January, 1958 (pre-dates the launch of TIROS I), and
Sadly, by the mid-1970s, the technology within the TIROS dish (officially named the TLM-18 Space Telemetry Antenna) had become obsolete, and it was retired. Camp Evans was decommissioned and closed in 1993 and its land was transferred to the National Park Service. But in 2012, Camp Evans was designated a National Historic Landmark, and thus began a new, revitalized era for this immensely significant site. In addition to the TIROS Dish and the InfoAge Science History Learning Center and Museum, Camp Evans is also home to:
The Military History Museum;
The Radio Technology Museum;
The National Broadcasters’ Hall of Fame.
The Apollo Guidance Computer, Just One of the Many Historical Exhibits on Display at the InfoAge Science History Learning Center and Museum at Historic Camp Evans [photo: Robert Raia Photography]
DISH RESTORATION
In 2001, InfoAge stepped in and began preserving and restoring the mechanical systems of the TIROS dish. In 2006, a donation from Harris Corporation allowed the dish to be completely repainted and preserved.
Norman Jarosik, Senior Research Physicist at Princeton University and Daniel Marlow, PhD. and Evans Crawford 1911 Professor of Physics at Princeton, as well as countless volunteers from the University, InfoAge, Wall Township (NJ), and the Ocean-Monmouth Amateur Radio Club, Inc. (OMARC) have provided the engineering/scientific knowledge and sweat-equity required to refurbish and update the inoperative radio dish. The original vacuum-tube technology has been replaced with smaller electronic counterparts. Rusty equipment has been replaced. Seized/inoperative motors have been reconditioned and rebuilt. And system-level software controls have been added. The TIROS dish has been transformed into a truly modern, state-of-the-art Radio Astronomy Satellite Dish and Control Center.
The TIROS Dish as it Appears Today [photo: Nancy J. Graziano]On January 19, 2015, scientists from Princeton University pointed the dish skyward toward the center of our galaxy and detected a clear peak at 1420.4 MHz, the well-known 21 cm emission line originating from the deepest recesses of the Milky Way – the dish was working!
The Control Console Today. [photo: Nancy J. Graziano]
FUTURE PLANS
After almost 15 years of restoration and nearly 40 years since it last listened to the sky, the TIROS dish is once again operational, is detecting radio signals from the universe, and is well on its way to be used for science education.
Work continues on renovating Building 9162, the original TIROS Control Building, to convert it into the InfoAge Visitor Center. Plans include a NASA-style control room with theater seating for 20-30 students, a full-scale model of the original TIROS I satellite, and other exhibits dedicated to the history of Project Diana, the TIROS program, and the scientific impact these projects have had on our daily lives.
Artist’s Conception: Visitor Center Floorplan [credit: InfoAge]Future activities being planned using the dish include a Moonbounce experiment, communicating with NOAA weather satellites, performing real-time satellite imaging, viewing the Milky Way in the radio spectrum, and tracking deep space pulsars.
If you are interested in visiting the InfoAge Science History Learning Center and Museum at Historic Camp Evans, they are open to the public on Wednesdays, Saturdays, and Sundays, from 1-5pm.
To learn more about Camp Evans, Project Diana, the TIROS Satellite project, and InfoAge, tune into this week’s Weekly Space Hangout. This week’s special guest is Stephen Fowler, the Creative Director at InfoAge. He will be chatting with Fraser about the history and plans for Camp Evans and the TIROS dish.
Still want to learn more? Click on any of the links provided in this article, or visit the following sites:
There have been many astronauts who have made tremendous contributions to our knowledge of space. But asking “who is the most famous?” is somewhat tricky. For one, its a bit subjective. And second, it can be hard to objectively measure just how important and individuals contributions really are. Surely, all astronauts are deserving of recognition and respect for their bravery and contributions to the pursuit of knowledge.
Nevertheless, in the course of human space exploration, some names do stand out more than others. And some have made such immense contributions that their names will live on long after we too have passed away. So without further ado, here are just a few of the most famous astronauts, along with a list of their accomplishments.
Yuri Gagarin:
As the first man to ever go into space, no list of famous astronauts would be complete without Yuri Gagarin. Born in the village of Klushino in the Smolensk Oblast on March 9th, 1934, Gagarin was drafted into the Soviet Air Force in 1955 and trained in the use of jet fighters. In 1960, he was selected alongside 19 other pilots to join the newly-formed Soviet Space Program.
Yuri Gagarin before a space flight aboard the Vostok 1 spacecraft, April 12th, 1961. Credit: RIA Novosti
Gagarin was further selected to become part of the Sochi Six, an elite group of cosmonauts who formed the backbone of the Vostok program. Due to his training, physical size (as the spacecraft were quite cramped), and favor amongst his peers, Gagarin was selected to be the first human cosmonaut (they had already sent dogs) to make the journey.
On April 12th, 1961, Gagarin was launched aboard the Vostok 1 spacecraft from the Baikonur Cosmodrome, and thus became the fist man to go into space. During reentry, Gagarin claimed to have whistled “The Motherland Hears, The Motherland Knows”, and reportedly said, “I don’t see any God up here” when he reached suborbital altitude (which was falsely attributed).
Afterwards, he toured the world and became a celebrity at home, commemorated with stamps, statues, and the renaming of his ancestral village to Gagarin. The 12th of April is also known as “Cosmonauts Day” in Russia and many former Soviet-states in his honor.
Gagarin died during a routine training exercise in March 27th, 1968. The details of his death were not released until June of 2013, when a declassified report indicated that Gagarin’s death was caused by the error of another pilot.
Alan B. Shepard Jr.:
In addition to being an astronaut and one of the Mercury Seven – the first seven pilots selected by NASA to go into space – Shepard was also the first American man to go into space. He was born November 18th, 1923 in Pebble, California and graduated from the United States Naval Academy with a Bachelor of Science degree. While in the Navy, Shepard became a fighter pilot and served aboard several aircraft carriers in the Mediterranean.
Alan Shepard prepares for his historic flight on May 5, 1961. Credit: NASA
In 1959, he was selected as one of 110 military test pilots to join NASA. As 0ne of the seven Mercury astronauts, Shepard was selected to be the first to go up on May 5th, 1961. Known as the Freedom 7mission, this flight placed him into a suborbital flight around Earth. Unfortunately, Alan was beaten into space by Soviet cosmonaut Yuri Gagarin by only a few weeks, and hence became the first American to go into space.
Shepard went on to lead other missions, including the Apollo 14mission – which was the third mission to land on the Moon. While on the lunar surface, he was photographed playing a round of golf and hit two balls across the surface. After leaving NASA, he became a successful businessman. He died of leukemia on July 21st, 1998, five weeks before the death of his wife of 53 years.
Valentina Tereshkova:
Another famous Russian cosmonaut, Tereshkova is also internationally renowned for being the first woman to go into space. Born in the village of Maslennikovo in central Russia on March 6th, 1937, Tereshkova became interested in parachuting from a young age and began training at the local aeroclub.
After Gagarin’s historic flight in 1961, the Soviets hopes to also be the first country to put a woman into space. On 16 February 1962, Valentina Tereshkova was selected to join the female cosmonaut corps, and was selected amongst hundreds to be one of five women who would go into space.
In addition to her expertise in parachuting (which was essential since Vostok pilots were to parachute from the capsule after reentry), her background as a “proletariat”, and the fact that her father was a war hero from the Russo-Finnish War, led to her being selected.
Soviet Cosmonaut Valentina Tereshkova photographed inside the Vostok-6 spacecraft on June 16, 1963. Credit: Roscosmos
Her mission, Vostok 6, took place on June 16th, 1963. During her flight, Tereshkova orbited Earth forty-eight times, kept a flight log and took photographs that would prove useful to atmospheric studies. Aside from some nausea (which she later claimed was the result of spoiled food!) she maintained herself for the full three days and parachuted down during re-entry, landing a bit hard and bruising her face.
After returning home, Tereshkova went on to become a cosmonaut engineer and spent the rest of her life in key political positions. She married fellow cosmonaut Andrian Nikolayev and had a daughter. After her flight, the women’s corps was dissolved. Vostok 6 was to be the last of the Vostok flights, and it would be nineteen years before another woman would go into space (see Sally Ride, below).
John Glenn Jr.:
Colonel Glenn, USMC (retired) was a Marine Corps fighter pilot and a test pilot before becoming an astronaut. Due to his experience, he was chosen by NASA to be part of the Mercury Seven in 1959. On February 20, 1962, Glenn flew the Friendship 7 mission, and thus became the first American astronaut to orbit the Earth and the fifth person to go into space.
John Glenn enters his Friendship 7 spacecraft on On Feb. 20, 1962. Credit: NASA
For his contributions to spaceflight, John Glenn earned the Space Congressional Medal of Honor. After an extensive career as an astronaut, Glenn retired from NASA on January 16th, 1964, to enter politics. He won his first bid to become a US Senator in 1974, representing Ohio for the Democratic Party, and was reelected numerous times before retiring in January of 1999.
With the death of Scott Carpenter on October 10, 2013, he became the last surviving member of the Mercury Seven. He was also the only astronaut to fly in both the Mercury and Space Shuttle programs – at age 77, he flew as a Payload Specialist on Discovery mission (STS-95). For his history of service, he was awarded the Presidential Medal of Freedom in 2012.
Neil Armstrong:
Neil Armstrong is arguably the most famous astronauts, and indeed one of the most famous people that has ever lived. As commander of the historic Apollo 11 mission, he will forever be remembered as the first man to ever walk on a body other than Earth. Born on August 5th, 1930, in Wapakoneta, Ohio, he graduated from Purdue University and served the National Advisory Committee for Aeronautics High-Speed Flight Station before becoming an astronaut.
Neil A. Armstrong inside the Lunar Module after EVA. Credit: NASA
In accordance with the Holloway Plan, Neil studied at Purdue for two years and then committed to three years of military service as a naval aviator before completing his degree. During this time, he trained in the use of jet aircraft and became a test pilot at Andrews Air Force base, meeting such personalities as Chuck Yeager.
In 1962, when NASA was looking to create a second group of astronauts (after the Mercury 7), Armstrong joined and became part of the Gemini program. He flew two missions, as the command pilot and back-up command pilot for Gemini 8 and Gemini 11 (both in 1966), before being offered a spot with the Apollo program.
On July 16th, 1969, Armstrong went into space aboard the Apollo 11 spacecraft, alongside “Buzz” Aldrin and Michael Collins. On the 20th, after the lunar module set down on the surface, he became the first person to walk on the Moon. As he stepped onto the lunar surface, Armstrong uttered the famous words, “That’s one small step for a man, one giant leap for mankind.”
After retiring from NASA in 1971, Armstrong completed his master’s degree in aerospace engineering, became a professor at the University of Cincinnati, and a private businessman.
On Augusts 25th, 2012, he died at the age of 82 after suffering complications from coronary artery bypass surgery. On September 14th, his cremated remains were scattered in the Atlantic Ocean during a burial-at-sea ceremony aboard the USS Philippine Sea.
For his accomplishments, Armstrong was awarded the Presidential Medal of Freedom, the Congressional Space Medal of Honor, and the Congressional Gold Medal in 2009.
James Lovell Jr.:
Lovell was born on March 25th, 1928 in Cleveland, Ohio. Like Shepard, he graduated from the US Naval Academy and served as a pilot before becoming one of the Mercury Seven. Over the course of his career, he flew several missions into space and served in multiple roles. The first was as the pilot of the Apollo 8 command module, which was the first spacecraft to enter lunar orbit.
He also served as backup commander during the Gemini 12 mission, which included a rendezvous with another manned spacecraft. However, he is most famous for his role as commander the Apollo 13 mission, which suffered a critical failure en route to the Moon but was brought back safely due to the efforts of her crew and the ground control team.
Lovell is a recipient of the Congressional Space Medal of Honor and the Presidential Medal of Freedom. He is one of only 24 people to have flown to the Moon, the first of only three people to fly to the Moon twice, and the only one to have flown there twice without making a landing. Lovell was also the first person to fly in space four times.
Original crew photo, (left to right) Jim Lovell, Thomas K. Mattingly, and Fred W. Haise. Credit: NASA
Dr. Sally Ride:
Sally Ride became renowned in the 1980s for being one of the first women to go into space. Though Russians had already sent up two female astronauts – Valentina Tereshkova (1963) and Svetlana Savitskaya (1982) – Ride was the first American female astronaut to make the journey. Born on May 26th, 1951, in La Jolla, California, Ride received her doctorate from Stanford University before joining NASA in 1978.
On June 18th, 1983, she became the first American female astronaut to go into space as part of the STS-7 mission that flew aboard the space shuttle Challenger. While in orbit, the five-person crew deployed two communications satellites and Ride became the first woman to use the robot arm (aka. Canadarm).
Her second space flight was in 1984, also on board the Challenger. In 1986, Ride was named to the Rogers Commission, which was charged with investigating the space shuttle Challenger disaster. In 2003, she would serve on the committee investigating the space shuttle Columbia disaster, and was the only person to serve on both.
Sally Ride communicates with ground controllers from the flight deck during STL-7 in 1983. Credit: U.S. National Archives and Records Administration
Ride retired from NASA in 1987 as a professor of physics and continued to teach until her death in 2012 from pancreatic cancer. For her service, she was given numerous awards, which included the National Space Society’s von Braun Award, two NASA Space Flight Medals, and was inducted into the National Women’s Hall of Fame and the Astronaut Hall of Fame.
Chris Hadfield:
Last, but certainly not least, there’s Chris Hadfield, the Canadian astronaut, pilot and engineer who became famous for his rendition of “Space Oddity” while serving as the commander of the International Space Station. Born on August 29th, 1959 in Sarnia, Ontario, Hadfield became interesting in flying at a young age and in becoming an astronaut when he watched the televised Apollo 11 landing at age nine.
After graduating from high school, Hadfield joined the Canadian Armed Forces and spent two years at Royal Roads Military College followed by two years at the Royal Military College, where he received a bachelor’s degree in mechanical engineering in 1982. He then became a fighter pilot with the Royal Canadian Air Force, flying missions for NORAD. He also flew as a test pilot out of Andrews Air Force Base as part of an officer exchange.
In 1992, Hadfield became part of the Canadian Space Agency and was assigned to NASA’s Johnson Space Center in Houston, as a technical and safety specialist for Shuttle Operations Development. He participated in two space missions – STS-74 and STS-100 in 1995 and 2001, respectively – as a Mission Specialist. These missions involved rendezvousing with Mir and the ISS.
Canadian astronaut Chris Hadfield performing his rendition of “Space Oddity”. Hadfield is the first Canadian to serve as commander of the ISS. Credit: CTV
On December 19th 2012, Hadfield launched in the Soyuz TMA-07M flight for a long duration stay on board the ISS as part of Expedition 35. He became the first Canadian to command the ISS when the crew of Expedition 34 departed in March 2013, and received significant media exposure due to his extensive use of social media to promote space exploration.
Forbes described Hadfield as “perhaps the most social media savvy astronaut ever to leave Earth”. His promotional activities included a collaboration with Ed Robertson of The Barenaked Ladies and the Wexford Gleeks, singing “Is Somebody Singing?“(I.S.S.) via Skype. The broadcast of this event was a major media sensation, as was his rendition of David Bowie’s “Space Oddity“, which he sung shortly before departing the station in May 2013.
For his service, Hadfield has received numerous honors, including the Order of Canada in 2014, the Vanier Award in 2001, NASA Exceptional Service Medal in 2002, the Queen’s Golden Jubilee Medal in 2002, and the Queen’s Diamond Jubilee Medal in 2012. He is also the only Canadian to have received both a military and civilian Meritorious Service Cross, the military medal in 2001 and the civilian one in 2013.
Getting closer... Venus, Jupiter, the Moon and an iridium flare on the night of May 26th, 2015. Image credit and copyright: Chris Lyons
Are you ready to hear an upswing in queries from friends/family and/or strangers on Twitter asking “what are those two bright stars in the evening sky?”
It’s time to arm yourself with knowledge against the well-meaning astronomical onslaught. The month of June sees the celestial action heat up come sundown, as the planet Jupiter closes in on Venus in the dusk sky. Both are already brilliant beacons at magnitudes -1.5 and -4 respectively, and it’s always great to catch a meeting of the two brightest planets in the sky.
Looking west on the evening of June 5th from latitude 30 degrees north… Image credit: Stellarium
Be sure to follow Venus and Jupiter through June, as they close in on each other at a rate of over ½ a degree—that’s more than the diameter of a Full Moon—per day.
…and looking west on the evening of June 20th…
Venus starts June at 20 degrees from Jupiter on the first week of the month, and closes to less than 10 degrees separation by mid-month before going on to a final closing of less than one degree on the last day of the June. Th climax comes on July 1st, when Venus and Jupiter sit just over 20’ apart—2/3rds the diameter of a Full Moon—on July 1st at 3:00 UT or 11:00 PM EDT (on June 30th). This translates to a closest approach on the evening of June 30th for North America.
… and finally, looking westward on the evening of July 1st.
Venus starts the first week of June forming a straight line equally spaced with the bright stars Castor and Pollux in the astronomical constellation Gemini. On June 12-13, Venus actually nicks the Beehive cluster M44 in the constellation Cancer, a fine sight through binoculars.
Jupiter and Venus will then be joined by the Moon on the evening of June 20th to form a skewed ‘smiley face’ emoticon pairing. Not only is the pairing of Venus and the crescent Moon represented on many national flags, But the evening of June 20th will also be a great time to try your hand at daytime planet spotting before sunset, using the nearby crescent Moon as a guide.
The daytime view of Venus, the Moon and Jupiter of the evening of June 20th. Image Credit: Stellarium
The Moon will actually occult Venus three times in 2015: On July 19th as seen from the South Pacific, on October 8th as seen from Australia and New Zealand, and finally, on December 7th as seen from North America in the daytime.
This conjunction of Venus and Jupiter occurs just across the border in the astronomical constellation of Leo. As Venus can always be found in the dawn or dusk sky, Jupiter must come to it, and conjunctions of the two planets occur roughly once every calendar year. A wider dawn pass of the two planets occurs this year on October 25th, and in 2019 Jupiter again meets up with Venus twice, once in January and once in November. The last close conjunction of Venus and Jupiter occurred on August 18th, 2014, and an extremely close (4’) conjunction of Venus and Jupiter is on tap for next year on August 27th. Check out our nifty list of conjunctions of Venus and Jupiter for the remainder of the decade from last year’s post.
The view through the telescope on the evenings June 30th and July 1st will be stunning, as it’ll be possible to fit a 34% illuminated 32” crescent Venus and a 32” Jupiter plus its four major moons all in the same low power field of view. Jupiter sits 6 astronomical units (AU) from Earth, and Venus is 0.5 AU away on July 1st.
Venus reaches solar conjunction this summer on August 15th, and Jupiter follows suit on August 26th. Both enter the field of view of the European Space Agency’s Solar Heliospheric Observatory (SOHO) LASCO C3 camera in mid-August, and are visible in the same for the remainder of the month before they pass into the dawn sky.
But beyond just inspiring inquires, close conjunctions of bright planets can actually raise political tensions as well. In 2012, Indian army sentries reported bright lights along India’s mountainous northern border with China. Thought to be reconnaissance spy drones, astronomers later identified the lights as Venus and Jupiter, seen on repeated evenings. We can see how they got there; back in the U.S. Air Force, we’ve seen Venus looking like a ‘mock F-16 fighter’ in the desert dusk sky as we recovered aircraft in Kuwait. Luckily, cooler heads prevailed during the India-China incident and no shots were exchanged, which could well have led to a wider conflict…
Remember: Scientific ignorance can be harmful, and astronomical knowledge of things in the sky can save lives!
The Nile River and Delta, viewed at night by the Expedition 25 crew on Oct. 28, 2010. Credit: NASA
There are many long rivers in the world, but which ones are the longest? Naturally, there is a disagreement over the answer to this question. While The Nile has traditionally been considered to be longest in the world, the Amazon has some pretty fierce defenders as well. The debate arises over the difficulty in determining the full extent of a river, and also because measurements differ according to who measured them.
Another source of disagreement is the role played by tributaries, with some scientists arguing for their inclusion while others leave them out. Luckily, when determining length, several major rivers stand out from the crowd. Here are a few, and the reasons for why they made the list:
Definition:
There are many factors in determining the precise length of a river. These include the source, the identification (or the definition) of the river’s mouth, and the scale of measurement when determining the river length between source and mouth. As a result, the length measurements of many rivers are only approximations.
A river’s “true source” is considered to be the source of whichever tributary is farthest from the mouth, but this tributary may or may not have the same name as the main stem river. Furthermore, it is sometimes hard to state exactly where a river begins – especially rivers that are formed by ephemeral streams, swamps, or changing lakes.
Nile Delta from space by the MODIS sensor on the Terra satellite. Credit: Jacques Descloitres/NASA/GSFC
The mouth of a river is hard to determine in cases where the river has a large estuary that gradually widens and opens into the ocean. Some rivers do not have a mouth, and instead dwindle to very low water volume and disappear underground. A river may also have multiple channels, or anabranches, and it may not be clear how to measure the length through a lake.
Seasonal and annual changes may alter rivers as well, not to mention cycles of erosion and flooding, dams, levees, and geological engineering. In addition, the length of meanders can change significantly over time when a new channel cuts across a narrow strip of land, bypassing a large river bend.
The Nile: The Nile River, located in Africa, is listed as being 6,853 kilometers (4,258 miles) long, and is hence commonly considered to be the longest river in the world. This river and its water resources are shared by eleven countries – Tanzania, Uganda, Rwanda, Burundi, Congo-Kinshasa, Kenya, Ethiopia, Eritrea, South Sudan, the Sudan and Egypt.
In ancient times, its existence was closely tied to the rise of civilization in the Near East, being the main source of irrigation and fresh water for multiple Egyptian dynasties. Today, it remains the primary water source for both Egypt and the Sudan.
Lake Victoria, as viewed by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra satellite. Credit: NASA/EO
The source of the Nile is traditionally considered to be Lake Victoria, but Victoria itself has feeder rivers of considerable size. It’s two main tributaries, are the White Nile and Blue Nile. The former is considered to be the headwaters and primary stream of the Nile itself, but the latter is the primary source of water and silt.
The Amazon: The Amazon River is the longest river in South America, and the largest river in the world in terms of water discharge. This river has a series of major river systems in Colombia, Ecuador and Peru. At roughly 6,437 km(4,000 mi) in length, it is also considered to be the second-longest river in the world.
However, Brazilian scientists claimed to have found the most distant source of the Amazon in the Andes. This source is apparently a glacial stream emanating from the peak of Nevado Mismi in the Peruvian Andes, roughly 700 km (430 mi) southeast of Lima. If this is correct, then the Amazon is in fact 6.800 kilometers (4,225 miles) long, making it the world’s longest.
Satellite image of a flooded section of the Amazon river. Credit: NASA
The Yangtze: The third longest river in the world is the Yangtze – or as it’s known in China, the Chang Jiang River. The Yangtze is 6,380 kilometers (3,964 miles) in length, making it the longest river in Asia. It originates from the glaciers of the Qinghai-Tibet Plateau in Qinghai province, flows eastward across southwest, central and eastern China, and then empties into the East China Sea at Shanghai.
The Yangtze River has played a large role in the history, culture and economy of China, and continues to do so to this day. In addition to running through multiple ecosystems in China, its existence was also pivotal to human settlement, the development of agriculture, and the rise of civilization in East Asia.
Today, the prosperous Yangtze River Delta generates as much as 20% of China’s Gross Domestic Product (GDP), and the Three Gorges Dam – located on the Yangtze River near the town of Sandouping – is the largest hydro-electric power station in the world. Because of the impact of human infrastructure, some sections of the river are now protected wildlife preserves.
The first turn of the Yangtze in Yunnan Province, where the river turns 180 degrees from south- to north-bound. Credit: peace-on-earth.org/Jialiang Gao
The Mississippi-Missouri-Jefferson: At 6,275 kilometers (3,902 miles) the Mississippi-Missouri-Jefferson River system is the fourth longest in the world and the longest river in the United States. Although each river separately would not be in the top five, these three rivers are grouped together into one because the Missouri River meets the Mississippi near the city of St. Louis, while the Missouri connects to the Jefferson river in Montana.
However, the main thrust of the Mississippi runs north-south, rising in northern Minnesota and meandering slowly southwards for 3,730 km (2,320 miles) before reaching the Mississippi River Delta at the Gulf of Mexico.
With its many tributaries, the Mississippi’s watershed drains all or parts of 31 U.S. states and 2 Canadian provinces between the Rocky and Appalachian Mountains. It also borders and/or passes through the states of Minnesota, Wisconsin, Iowa, Illinois, Missouri, Kentucky, Tennessee, Arkansas, Mississippi, and Louisiana.
The Mississippi River and its tributaries have a long history of significance to Native American cultures. Many nations lived along its river banks, most of which were hunters and gathers who used the river as a source of water and for transportation. But for some – such as the Mound builders – the river was key to the formation of prolific agricultural societies.
The Mississippi River Delta shown draining into the Gulf of Mexico from space. Credit: ESA
The arrival of Europeans in the 1500s changed the native way of life drastically as first explorers, then settlers, ventured into the basin in increasing numbers and colonized the area. Initially a barrier between New Spain, New France, and the Thirteen Colonies, it grew to become a major artery of transportation and western expansion for the United States by the 19th century.
The Yellow River:
Huang He, which is also known as the Yellow River because of the color of its silt, is the third longest river in Asia and the sixth longest river in the world. Located in China and measuring 5,464 kilometers (3,395 miles) in length, the river originates the Bayan Har Mountains in Qinghai province, western China. It then flows through nine provinces before emptying into the Bohai Sea near the city of Dongying in Shandong province.
The Yellow River is also known as “the cradle of Chinese civilization” because of the pivotal role it played in the development of Chinese culture. Much like the Yangtze, the presence of human settlements dates back to the Paleolithic Era, and the fertile flood basins contributed to the rise of agricultural communities which eventually integrated with the less-developed settlements along the southern Yangtze.
Before modern dams became an option, the Yellow River was extremely prone to flooding. In the roughly 2,540 years before 1946 CE, the Yellow River is believed to have flooded 1,593 times and shifted its course many times (sometimes severely). These floods include some of the deadliest natural disasters ever recorded, thus earning the river the nicknames “China’s Sorrow” and “Scourge of the Sons of Han.”
China’s Yellow River Delta, as seen from space in 2009. Credit: NASA/EO
The Congo-Chambeshi:
At 4,700 km (2,920 miles), the Congo River (aka. Zaire River) in Africa is the ninth longest river in the world. Interestingly enough, it is also its deepest – with measured depths exceeding 220 m (720 ft) – and the second largest river in the world in terms of discharge (after the Amazon).
Originating deep in the eastern region of the Democratic Republic of Congo (DRC, formerly Zaire), the Congo is fed by the Lualaba river, which is itself fed by the Luyua and Luapula rivers that are connected to Lake Mweru and Lake Bangwelo. The river then runs west and constitutes much of the border between the DRC and its eastern neighbor, the Republic of Congo.
The Congo river gets its name from the Kingdom of Kongo which was situated on the left banks of the river estuary. The kingdom is in turn named for its Bantu population, which were described in 17th century European records as Esikongo. The name Zaire is from a Portuguese adaptation of a Kikongo word nzere (“river”), a truncation of nzadi o nzere (“river swallowing rivers”).
The Congo River and rainforest, as acquired on Jan 14th, 2009 by the ESA’s Envisat satellite. Credit: ESA
The river was known as Zaire during the 16th and 17th centuries, but the word Congo has since replaced Zaire gradually in English usage. However, references to Zahir or Zaire, as the name used by the natives (i.e. derived from Portuguese usage), has remained common throughout this same period.
All the states that have existed in the region since attaining their independence from Belgium in 1960 – the DRC (which was named Zaire from 1971-1997) and the Republic of Congo – in turn derive their names from the river.
And those are just some of the longest rivers in the world! If you’re interested, Universe Today has many articles on rivers, such as what is the world’s widest river?
This chart of the position of a nova (marked in red) that appeared in the year 1670 recorded by the astronomer Hevelius and was published by the Royal Society in England in their journal Philosophical Transactions. Image credit: The Royal Society
It is a 17th century astronomical enigma that has persisted right up until modern times.
On June 20, 1670, a new star appeared in the evening sky that gave 17th century astronomers pause. Eventually peaking out at +3rd magnitude, the ruddy new star in the modern day constellation of Vulpecula the Fox was visible for almost two years before vanishing from sight.
The exact nature of Nova Vulpeculae 1670 has always remained a mystery. The event has often been described as a classic nova… but if it was indeed a garden variety recurrent nova in our own Milky Way galaxy, then why haven’t we seen further outbursts? And why did it stay so bright, for so long?
Now, recent findings from the European Southern Observatory announced in the journal Nature this past March reveal something even more profound: the Nova of 1670 may have actually been the result of a rare stellar collision.
The remnant of the nova of 1670 seen with modern instruments and created from a combination of visible-light images from the Gemini telescope (blue), a submillimetre map showing the dust from the SMA (yellow) and finally a map of the molecular emission from APEX and the SMA (red). Image credit: ESO/T. Kaminski
“For many years, this object was thought to be a nova,” said ESO researcher Tomasz Kaminski of the Max Planck Institute for Radio Astronomy in Bonn Germany in a recent press release. “But the more it was studied, the less it looked like an ordinary nova—or indeed any other kind of exploding star.”
A typical nova occurs when material being siphoned off a companion star onto a white dwarf star during a process known as accretion builds up to a point where a runaway fusion reaction occurs.
ESO researchers used an instrument known as the Atacama Pathfinder EXperiment telescope (APEX) based on the high Chajnantor plateau in Chile to probe the remnant nebula from the 1670 event at submillimeter wavelengths. They found that the mass and isotopic composition of the resulting nebula was very uncharacteristic of a standard nova event.
So what was it?
A best fit model for the 1670 event is a rare stellar merger, with two main sequence stars smashing together and exploding in a grand head on collision, leaving the resulting nebula we see today. This event also resulted in a newly recognized category of star known as a “red transient” or luminous red nova.
Universe Today caught up with Mr. Kaminski recently on the subject of red transients and the amazing find:
“In our galaxy we are quite confident that four other objects were observed in outburst owing to a stellar merger: V838 Mon (famous for its spectacular light echo, eruption 2002), V4332 Sgr (eruption 1994), V1309 Sco (observed as an eclipsing binary before its outburst in 2008), OGLE-2002-BLG-360 (recent, but most similar to CK Vul eruption, 2002).Red transients are bright enough to be observed in nearby galaxies. Among them are M31 RV (first recognized “red variable”, eruption 1989), M85 OT2006 (eruption 2006), NGC300 OT2008, etc. Very recently, a few months ago, another one went off in the Andromeda Galaxy. With the increasing number of sky surveys we surely will discover many more.”
Though astronomers such as Voituret Anthelme, Johannes Hevelius and Giovanni Cassini all noted the 1670 nova, the nebula and suspected progenitor star wasn’t successfully recovered until 1981. Often cited as the oldest and faintest observation of a nova, Hevelius referred to the 1670 apparition as ‘nova sub capite Cygni,’ or a new star located below the head of the Swan near the star Albireo the constellation of Cygnus. Astronomers of the day also noted the crimson color of the new star, also fitting with the modern red transient hypothesis of two main sequence stars merging.
This chart shows the small constellation of Vulpecula (The Fox), and the location of the exploding star Nova Vul 1670 (red circle). Image credit: ESO/IAU/Sky & Telescope
“We observed CK Vul with the hope to find some submillimeter emission, but were completely surprised by how intense the emission was and how abundant in molecules the gas surrounding CK Vul is,” Kaminski told Universe Today. “Also, we have ongoing observational programs to search for objects similar to CK Vul.”
Follow up observations of the region were also carried out by the Submillimeter Array (SMA) and the Effelsberg radio telescope in Germany. The Nova of 1670 occurred about 1,800 light years distant along the galactic plane in the Orion-Cygnus arm of our Milky Way galaxy, of which the Sun and our solar system is a member. We actually had a naked eye classical nova just last year in roughly the same direction, which was visible in the adjacent constellation of Delphinus the Dolphin.
Of course, these garden variety novae are in a distinctly different class of events from supernovae, the likes of which have not been seen in our galaxy with the unaided eye in modern times since Kepler’s supernova in 1604.
The Atacama Pathfinder Experiment (APEX) telescope on the hunt. Image credit: ESO/ Babak Tafreshi
How often do stars collide? While rogue collisions of passing stars are extremely rare—remember, space is mostly nothing—the odds go up for closely orbiting binary pairs. What would really be amazing is to witness a modern day nearby red transient in the act of formation, though for now, we’ll have to console ourselves with studying the aftermath of the 1670 event as the next best thing.
“Recent estimates give one (merger) event per 2 years in the Milky Way galaxy,” Kaminski told Universe Today. “But we currently know so little about violent merger events that this number is very uncertain.”
Previously cited as a recurrent nova, the story of the 1670 event is a wonderful example of how new methods, combined with old observations, can be utilized to solve some of the lingering mysteries of modern astronomy.
A full moon in October is known as a "Hunters Moon". Credit: David Haworth/stargazing.net
If you live in the northern hemisphere, than stargazing during the early autumn months can a bit tricky. During certain times in these seasons, the stars, planets and Milky Way will be obscured by the presence of some very beautiful full moons. But if you’re a fan of moongazing, then you’re in luck.
Because it is also around this time (the month of October) that people looking to the night sky will have the chance to see what is known as a Hunter’s Moon. A slight variation on a full moon, the Hunter’s Moon has long been regarded as a significant event in traditional folklore, and a subject of interest for astronomers.
Definition:
Also known as a sanguine or “blood” moon, the term “Hunters Moon” is used traditionally to refer to a full moon that appears during the month of October. It is preceded by the appearance of a “Harvest Moon”, which is the full moon closest to the autumnal equinox (which falls on the 22nd or 23rd of September).
The Hunter’s Moon typically appears in October, except once every four years when it doesn’t appear until November. The name dates back to the First Nations of North America. It is so-called because it was during the month of October, when the deers had fatted themselves over the course of the summer, that hunters tracked and killed prey by autumn moonlight, stockpiling food for the coming winter.
Full Moon Rising Over Northwest Georgia on June 22nd, 2013. Credit and copyright: Stephen Rahn.
Characteristics:
Although typically the Moon rises 50 minutes later each day, things are different for the Hunter’s Moon (as well as the Harvest Moon). Both of these moons usually rise 30 minutes later on each successive night, which means that sunset and moonrise are not far apart.
This means there is prolonged periods of light during this time of the the year, which is the reason why these moons have traditionally been used by hunters and farmers to finish their work.
This difference between the timing of the sunset and moonrise is due to its orbit, meaning that the angle the Moon makes with the horizon is narrower during this time of year. The Hunter’s Moon is generally not bigger or brighter than any of the other full moons. Thus, the only difference between it and other full moons is the that the time between sunset and moonrise is shorter.
History of Observation:
Because the approach of winter signaled the possibility of going hungry in pre-Industrial times, the Hunter’s Moon was generally accorded with special honor, historically serving as an important feast day in both northern Europe and among many Native American tribes.
Traditionally, Native American hunters used the full moon of October to stalk deer and to spot foxes at night as they prepared for the coming winter. Because the fields were traditionally reaped in late September or early October, hunters could easily see foxes and other animals that came out to glean from the fallen grains.
The Hunter’s Moon is accorded similar significance in Europe, where it was also seen as a prime time to hunt during the post-harvest, pre-winter period when conditions were optimal for spotting prey. However, the term did not enter into usage for Europeans until after they made contact with Indigenous Americans and began colonizing North America.
The first recorded mentions of a “Hunter’s Moon” began in the early 18th century. The entry in the Oxford English Dictionary for “Hunter’s Moon” cites a 1710 edition of The British Apollo, where the term is attributed to “the country people”. The names are now referred to regularly by American sources, where they are often popularly attributed to “the Native Americans”.
In India, the harvest festival of Sharad Purnima, which marks the end of the monsoon season, is celebrated on the full moon day of the lunar month of Ashvin (September-October). There is a traditional celebration of the moon during this time that is known as the “Kaumudi” celebration – which translated, means “moonlight”.
The harvest festival of Shrad Purnima is celebrated on the full moon day of the Hindu lunar month of Ashvin. Credit: dfwhindutemple.org
Interesting Facts:
Sometimes, the Harvest Moon is mistaken for the Hunter’s Moon because once every four years or so the Harvest Moon is in October instead of September. When that happens, the Hunter’s Moon is in November. Traditionally, each month’s full moon has been given a name, although these names differ according to the source.
Other full moons of interest include the Wolf Moon in January, the Strawberry Moon in June, the Sturgeon Moon in August, the Cold Moon in December, and the Pink Moon in April. All of the full moons have different characteristics due to the location of the ecliptic – i.e. the path of the Sun – at the time of each.
The Hunter’s Moon is also associated with feasting. In the Northern Hemisphere, some Native American tribes and some places in Western Europe held a feast day. This feast day, the Feast of the Hunter’s Moon, was not been held since the 1700’s. However, the Feast of the Hunters’ Moon is a yearly festival in Lafayette, Indiana, which has been held in late September or early October every year since 1968.
We have many interesting articles about the moon here at Universe Today. For example, here are some about the red moon and a rundown of what a full moon is all about.
Various meteorites from 2008 TC3.
Credit: P. Jenniskens, et. al. Click image for full description
Asteroids, meteors, and meteorites … It might be fair to say these rocks from space inspire both wonder and fear among us Earthlings. But knowing a bit more about each of them and how they differ may eliminate some potential misgivings. While all these rocks originate from space, they have different names depending their location — i.e. whether they are hurtling through space or hurtling through the atmosphere and impacting Earth’s surface.
In simplest terms here are the definitions:
Asteroid: a large rocky body in space, in orbit around the Sun.
Meteoroid: much smaller rocks or particles in orbit around the Sun.
Meteor: If a meteoroid enters the Earth’s atmosphere and vaporizes, it becomes a meteor, which is often called a shooting star.
Meteorite: If a small asteroid or large meteoroid survives its fiery passage through the Earth’s atmosphere and lands on Earth’s surface, it is then called a meteorite.
Another related term is bolide, which is a very bright meteor that often explodes in the atmosphere. This can also be called a fireball.
Let’s look at each in more detail:
Asteroids An artists impression of an asteroid belt. Credit: NASA
Asteroids are found mainly in the asteroid belt, between Mars and Jupiter. Sometimes their orbits get perturbed or altered and some asteroids end up coming closer to the Sun, and therefore closer to Earth. In addition to the asteroid belt, however, there have been recent discussions among astronomers about the potential existence of large number asteroids in the Kuiper Belt and Oort Cloud. You can read a paper about this concept here, and a good article discussing the topic here.
The asteroid Vesta as seen by the Dawn spacecraft. Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA
Asteroids are sometimes referred to as minor planets or planetoids, but in general, they are rocky bodies that do not have an atmosphere. However, a few have their own moons. Our Solar System contains millions of asteroids, many of which are thought to be the shattered remnants of planetesimals – bodies within the young Sun’s solar nebula that never grew large enough to become planets.
The size of what classifies as an asteroid is not extremely well defined, as an asteroid can range from a few meters wide – like a boulder — to objects that are hundreds of kilometers in diameter. The largest asteroid is asteroid Ceres at about 952 km (592 miles) in diameter, and Ceres is so large that it is also categorized as a dwarf planet.
Most asteroids are made of rock, but as we explore and learn more about them we know that some are composed of metal, mostly nickel and iron. According to NASA, a small portion of the asteroid population may be burned-out comets whose ices have evaporated away and been blown off into space. Recently, astronomers have discovered some asteroids that mimic comets in that gas and dust are emanating from them, and as we mentioned earlier, there appears to be a large number of bodies with asteroid-like compositions but comet-like orbits.
How Often Do Asteroids Hit Earth?
Meteor Crater near Winslow, Arizona. Image credit: NASA.
While we know that some asteroids pass very close to Earth’s orbit around the Sun, we’ve been lucky in the history of humanity that we haven’t had a large asteroid hit Earth in the past several thousand years. It wasn’t until satellite imagery of Earth became widely available that scientists were able to see evidence of past asteroid impacts.
One of the more famous impact craters on Earth is Meteor Crater in Arizona in the US, which was made by an impact about 50,000 years ago. But there are about 175 known impact around the world – a few are quite large, like Vredefort Crater in South Africa which has an estimated radius of 190 kilometers (118 miles), making it the world’s largest known impact structure on Earth. Another notable impact site is off the coast of the Yucatan Peninsula in Mexico, and is believed to be a record of the event that led to the extinction of the dinosaurs 65 million years ago. You can see images of some of the most impressive Earth impact craters here.
These days, asteroid impacts are less of a threat. NASA estimates that about once a year an automobile-sized asteroid enters Earth’s atmosphere, creates an impressive fireball and disintegrates before ever reaching the surface. Studies of Earth’s history indicate that about once every 5,000 years or so on average an object the size of a football field hits Earth and causes significant damage. Once every few million years on average an object large enough to cause regional or global disaster impacts Earth. You can find more information about the frequency of impacts in this article from NASA.
Meteors, Meteoroids and Bolides
A bright meteor from September 21, 1994. Credit: John Chumack.
Space debris smaller than an asteroid are called meteoroids. A meteoroid is a piece of interplanetary matter that is smaller than an asteroid and frequently are only millimeters in size. Most meteoroids that enter the Earth’s atmosphere are so small that they vaporize completely and never reach the planet’s surface. When they burn up during their descent, they create a beautiful trail of light known as a meteor, sometimes called a shooting star.
Mostly these are harmless, but larger meteors that explode in the atmosphere – sometimes called bolides — can create shockwaves, which can cause problems. In February 2013 a meteor that exploded over Chelyabinsk, Russia shattered windows with its air blast. This meteoroid or bolide was estimated to be 18 meters (59 feet) in diameter. In 1908, a rocky meteoroid less than 100 meters in diameter is believed to have entered the atmosphere over the Tunguska region of Siberia in 1908 and the resulting shockwave knocked down trees for hundreds of square kilometers
How often is Earth hit by meteroids?
Chelyabinsk fireball recorded by a dashcam from Kamensk-Uralsky north of Chelyabinsk where it was still dawn.
Because of the Chelyabinsk meteor in 2013, astronomers have acquired more information about the frequency of larger meteors that hit Earth, and there is now a growing consensus that the Earth gets hit by bigger space rocks more often than we previously thought. You can read more about that concept here.
This video from the B612 Foundation shows a visualization of the location of 26 space rocks that hit Earth between 2000 and 2013, each releasing energy equivalent to some of our most powerful nuclear weapons. The B612 foundation says that a Hiroshima-scale asteroid explosion happens in our atmosphere on average once a year, but many are not detected because they explode high in the atmosphere, or because most of the Earth’s surface is water and even a large percentage of land is fairly uninhabited by humans.
Estimates vary of how much cosmic dust and meteors enter Earth’s atmosphere each day, but range anywhere from 5 to 300 metric tons. Satellite observations suggest that 100-300 metric tons of cosmic dust enter the atmosphere each day. This figure comes from the rate of accumulation in polar ice cores and deep-sea sediments of rare elements linked to cosmic dust, such as iridium and osmium.
But other measurements – which includes meteor radar observations, laser observations and measurements by high altitude aircraft — indicate that the input could be as low as 5 metric ton per day. Read more about this here.
For a documented list of bolide events, you can check out this page from JPL.
Meteorite A stunning slice of the Glorieta pallasite meteorite cut thin enough to allow light to shine through its many olivine crystals. Credit: Mike Miller
If any part of a meteoroid survives the fall through the atmosphere and lands on Earth, it is called a meteorite. Although the vast majority of meteorites are very small, their size can range from about a fraction of a gram (the size of a pebble) to 100 kilograms (220 lbs) or more (the size of a huge, life-destroying boulder). Meteorites smaller than 2mm are classified as micrometeorites.
Meteorites have traditionally been divided into three broad categories, depending on their structure, chemical and isotopic composition and mineralogy. Stony meteorites are rocks, mainly composed of silicate minerals; iron meteorites that are largely composed of metallic iron-nickel; and, stony-iron meteorites that contain large amounts of both metallic and rocky material.
Meteorites have also been found on the Moon and Mars and conversely, scientists have traced the origination of the meteorites found here on Earth to four other bodies: the Moon, Mars, the asteroid 4 Vesta, and the comet Wild 2. Meteorites are the source of a great deal of the knowledge that we have have about the composition of other celestial bodies.
How Often Do Meteorites Hit Earth?
On Feb. 28, 2009, Peter Jenniskens (SETI/NASA), finds his first 2008TC3 meteorite after an 18-mile long journey. “It was an incredible feeling,” Jenniskens said. The African Nubian Desert meteorite of Oct 7, 2008 was the first asteroid whose impact with Earth was predicted while still in space approaching Earth. 2008TC3 and Chelyabinsk are part of the released data set. (Credit: NASA/SETI/P.Jenniskens)
According to the Planetary Science Institute, it is estimated that probably 500 meteorites reach the surface of the Earth each year, but less than 10 are recovered. This is because most fall into water (oceans, seas or lakes) or land in remote areas of the Earth that are not accessible, or are just not seen to fall.
In short, the difference between asteroids and meteors all comes down to a question of location. Asteroids are always found in space. Once it enters an atmosphere, it becomes a meteor, and then a meteorite after it hits the ground. Each are made of the same basic materials – minerals and rock – and each originated in space. The main difference is where they are when they are being observed.
A multi-ringed, oval shaped corona around the Sun on May 30, 2015 seen from northern Minnesota. The white spots are aspen seeds better known as "cotton fluff". Credit: Bob King
Don’t be surprised if you look up in the Sun’s direction and squint with itchy, watery eyes. You might be staring into billows of tree pollen wafting through your town. It’s certainly been happening where I live.
When conditions are right, billions of microscopic pollen grains consort to create small, oval-shaped rings around a bright Moon during the peak of the spring and early summer allergy season. With the Full Moon coming up this week, there’s no better time to watch for them.
Pollen grains from a variety of different common plants including sunflower, morning glory, prairie hollyhock and evening primrose magnified 500x and colorized. The green, bean-shaped grain at lower left is 0.05 mm across. Credit: Dartmouth Electron Microscope Facility
Because they’re often lost in the glare of the Sun or Moon, the key to finding one is to hide the solar or lunar disk behind a thick tree branch, roof or my favorite, the power pole. Look for a telltale oval glow, sometimes tinted with rainbow colors, right up next to the Moon or Sun’s edge. Common halos, those that form when light is refracted by ice crystals, span 44° compared to pollen coronas, which measure just a few degrees in diameter.
To see or photograph coronas, you need plenty of light. The Sun’s ideal, but so is the Moon around full. Fortunately, that happens on June 2, neatly fitting into the sneezing season. Last night, the same grains — most likely pine tree pollen — also stoked a lunar corona. Once my eyes were dark adapted and the Moon hidden by an arboreal occulting instrument (tree branch), it was easy to see.
A lunar pollen corona on May 30, 2015. The Moon was hidden by a utility pole. Like the solar version, this one was also oval and measured about 3.5° across. The shape is caused by elongated pollen grains fact that orient themselves as they drift in the wind. Credit: Bob King
One of things you’ll notice right away about these biological bullseyes is that they’re not circular. Pollen coronas are oval because the pollen particles are elongated rather than spherical like water droplets. When light from the moon or sun strikes pollen, the minute grains diffract the light into a series of closely-spaced colored rings. I’ve read that pine and birch produce the best coronas, but spruce, alder and and others will work, too.
And here’s another amazing thing about these coronas. You don’t need a transparent medium to produce them. No ice, no water. All that’s necessary are very small, similarly-shaped objects. Light waves are scattered directly off their surfaces; the waves interfere with one another to create a diffraction pattern of colored rings.
A lunar pollen corona photographed on June 22, 2008 displays “bumps” or extensions at approximately 90° angles around its periphery. Credit: Bob King
Pollen coronas tend to become more elongated when the Sun or Moon is closer to the horizon, so look be on the lookout during those times for more extreme shapes. For some reason I’ve yet to discover, pollen disks sometimes exhibit “bumps” or extensions at their tops, bottoms and sides.
So many of us suffer from allergies, perhaps the glowing presence of what’s causing all the inflammation will serve as partial compensation for our misery.
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