Its “strange” orbit had been intriguing astronomers for 133 years since its discovery, but is there a chance that the Martian moon Phobos is a product of an alien civilization?
By: Ringo Bones
Anyone in the know will readily admit that there is something strange with the Martian moon called Phobos. Inexplicably, everything strange about the planet Mars was discovered in 1877. From the “discovery” of straight, geometrically patterned channels – or canali – by the Italian astronomer named Giovanni Schiaparelli to the two tiny satellites – called Phobos and Deimos - discovered by the American astronomer named Asaph Hall. The first generation of robotic spacecraft launched to explore Mars during the 1960s has since proved that Sciaparelli’s “canals” as nothing more than an optical illusion, but the “mystery” behind the Marian moons managed to “survive” space-probe scrutiny.
The small size and proximity of Deimos and Phobos to their parent planet make them unique in the Solar System. Both are too small to gain enough hydrostatic equilibrium to acquire a spherical shape. Deimos is about 7.5 miles in diameter and orbits about 15,000 miles from the surface of Mars. Phobos, 13.7 miles in diameter, orbits much closer at 5,800 miles and has enough “intriguing” characteristics – including recently discovered ones – that had acquired the interest of generations of astronomers over the years.
The most remarkable thing about Phobos, according to some observations, is that its period of revolution appears to be decreasing slowly but perceptibly. The only plausible explanation is that the slight drag of the Martian atmosphere is taking energy from it, thus making it move closer to Mars and follow a shorter and faster orbit. The Martian atmosphere is so thin than a satellite the size of Phobos affected this way must have extremely low density. If these observations are correct, then Phobos must be lighter than any known solid substance.
The Russian astronomer Iosif S. Shklovsky has supplied a novel answer to this puzzle. He believes that Phobos is hollow and artificial and the work of highly civilized Martians of hundreds of millions of years ago. According to Shklovsky, when the Martians discovered that they would soon became extinct, they constructed one or two extraordinarily spacious satellites to serve as libraries and museums as a way to preserve their culture for future explorers as a testament to the glorious history and achievements of their doomed civilization - a sort of mother-of-all-time-capsules.
Few scientists – Shklovsky included – actually count on finding any such rather “convenient” repositories of ancient learning, and discovering any sort of intelligent, civilized life flourishing is considered extremely unlikely. But future prospective explorers of Mars will certainly look for archaeological evidence of long dead civilizations. Maybe Iosif S. Shklovsky had a big beef with what is now called the Fermi Paradox – the inexplicable lack of even the most basic archaeological remains proving the existence of extraterrestrial biological beings as smart as – or smarter – than the human race.
Our current knowledge suggests that the beginning of life on a planet and its evolution toward higher forms has no fixed timetable. Life may have started early on Mars and evolved faster, reaching climax hundreds of millions of years ago. Even if nothing nearly as spectacular is found on Mars – even recent ones like the monkey-like humanoid face on Mars later turned out to be nothing more than an optical illusion – the exploration of the “red planet” will be an event unmatched in all of humanity’s history.
So will Phobos be the Fermi Paradox buster every believer in extraterrestrial life is waiting for? Maybe too soon to tell, but more recent images of Phobos taken by the Mars Reconnaissance Orbiter did show a blue patch near the rim of a deep crater on an otherwise reddish surface. A contrast that’s rarely seen on a body supposedly a captured asteroid turned into a moon. Some astronomers say the blue is recently exposed terrain that hasn’t yet weathered to red; others think it is a wholly different material poking out from the interior. Russia already has plans to send a lander to Phobos to gather samples – and perhaps clues to this Martian moon mystery. Maybe Iosif S. Shklovsky was right all along.
Thursday, September 16, 2010
Wednesday, July 28, 2010
Can the Phases of the Moon Affect Precipitation?
Often dismissed as an old superstition, but does the changing phases of the Moon affect when it would rain or snow?
By: Ringo Bones
I don’t know how many heard of it, but I first heard this supposedly old superstition back in 1989 that goes: Wet weather follows the new Moon and the full Moon. Dry weather follows the first quarter Moon and the last quarter Moon. Strangely enough, a correlation was indeed found out at that time using U.S. Weather Bureau precipitation records showing that there is indeed a better than average chance of rain or snow in the week after a full Moon and the week after new Moon. While the driest periods tend to occur the week after the first quarter Moon and the week after the last quarter Moon. Unfortunately at the time, no clear-cut explanation was provided behind the phenomena after the study was published showing a correlation between occurrence of precipitation and the phases of the Moon. Will a renewed study ever shed light on the validity of this old superstition?
My hypothesis on the matter is that probably during the week after the full Moon and the week after the new Moon, the gravitational effects between the Earth and the Moon during these periods probably allowed higher than average amounts of meteoric and cometary dust to fall into our atmosphere. These comet and meteorite sourced material probably acted as nuclei via the Bergeron-Findeisen Theory of Rain / Precipitation thus causing rainfall and snowfall frequency to increase a week after the full Moon and the new Moon. But is this explanation really satisfactory?
Swedish meteorologist Tor Bergeron first proposed the nuclei theory of precipitation around the mid-1930s, which was later elaborated by German physicist Walter Findeisen and is now widely accepted as the Bergeron-Findeisen Theory Rain. This theory was later applied as the working principle behind cloud seeding. Artificial seeding of rain clouds to induce precipitation during times of drought was developed in 1946 by General Electric’s Vincent J. Schaefer and Irving Langmuir. They used both silver iodide and dry ice as cloud seeding material.
Silver iodide, whose crystalline structure is similar to that of natural ice and therefore provides hospitable nuclei on which ice crystals readily form. Solid carbon dioxide or dry ice – another good cloud seeding agent - is so cold that it causes water vapor to solidify into enormous numbers of tiny ice crystals. In either case, precipitation should follow, according to the Bergeron-Findeisen Theory. Pellets of dry ice are usually sown into a cloud from airplanes while silver iodide is released as smoke, sometimes from an airplane, sometimes from the ground. Meteoric and cometary dust could act as a cloud seeding nuclei, increasing chances of rain or snow – depending on the season – during the week after full Moon and the week after new Moon.
By: Ringo Bones
I don’t know how many heard of it, but I first heard this supposedly old superstition back in 1989 that goes: Wet weather follows the new Moon and the full Moon. Dry weather follows the first quarter Moon and the last quarter Moon. Strangely enough, a correlation was indeed found out at that time using U.S. Weather Bureau precipitation records showing that there is indeed a better than average chance of rain or snow in the week after a full Moon and the week after new Moon. While the driest periods tend to occur the week after the first quarter Moon and the week after the last quarter Moon. Unfortunately at the time, no clear-cut explanation was provided behind the phenomena after the study was published showing a correlation between occurrence of precipitation and the phases of the Moon. Will a renewed study ever shed light on the validity of this old superstition?
My hypothesis on the matter is that probably during the week after the full Moon and the week after the new Moon, the gravitational effects between the Earth and the Moon during these periods probably allowed higher than average amounts of meteoric and cometary dust to fall into our atmosphere. These comet and meteorite sourced material probably acted as nuclei via the Bergeron-Findeisen Theory of Rain / Precipitation thus causing rainfall and snowfall frequency to increase a week after the full Moon and the new Moon. But is this explanation really satisfactory?
Swedish meteorologist Tor Bergeron first proposed the nuclei theory of precipitation around the mid-1930s, which was later elaborated by German physicist Walter Findeisen and is now widely accepted as the Bergeron-Findeisen Theory Rain. This theory was later applied as the working principle behind cloud seeding. Artificial seeding of rain clouds to induce precipitation during times of drought was developed in 1946 by General Electric’s Vincent J. Schaefer and Irving Langmuir. They used both silver iodide and dry ice as cloud seeding material.
Silver iodide, whose crystalline structure is similar to that of natural ice and therefore provides hospitable nuclei on which ice crystals readily form. Solid carbon dioxide or dry ice – another good cloud seeding agent - is so cold that it causes water vapor to solidify into enormous numbers of tiny ice crystals. In either case, precipitation should follow, according to the Bergeron-Findeisen Theory. Pellets of dry ice are usually sown into a cloud from airplanes while silver iodide is released as smoke, sometimes from an airplane, sometimes from the ground. Meteoric and cometary dust could act as a cloud seeding nuclei, increasing chances of rain or snow – depending on the season – during the week after full Moon and the week after new Moon.
Monday, July 19, 2010
Johannes Hevelius: Father of Selenology?
Given the existing technology at the time, did Johannes Hevelius (1611-1687) able to know more about the Moon in comparison to his astronomy contemporaries?
By: Ringo Bones
Some astronomers think that we only managed to know more about the Moon than Johannes Hevelius did when we had the ability to send robotic spacecraft and manned exploration of the Moon, but is there some truth to this? Even though it was Galileo who first documented the Moon’s topography as seen from his first telescope back in 1610. It was Johannes Hevelius, a notable Polish astronomer born in January 28, 1611 that from his crowded rooftop in Danzig laden with his custom built telescopes – where he gained the fame as the pioneer of Lunar topography a few years later. Hevelius also studied distant celestial objects, but learned little because of dust and other disturbances in the atmosphere over Poland despite using an aerial telescope of his own design that’s 150 feet (46-meter) long – equal to the height of a modern 12-story building.
In collaboration with his wife Elizabeth, they charted the Lunar landscape then published their descriptions in Selenographia back in 1647. During his extensive studies of the Moon, Hevelius got curious of the fact that 59% of the Moon’s surface visible from Earth. During his time, the period between new Moons was already measured with a fair degree of accuracy. And the fact that the same face is always turned toward the Earth with only minor wobbling – the extra 9% of the Moon’s surface seen from Earth – was noted although not explained. The modern explanation is in part that the Moon is not a perfectly symmetrical spheroid. The Moon has a massive bulge, which the Earth’s gravitation attracts like a plumb bob, thus keeping the same hemisphere towards the Earth. With such detailed observations of the Moon, Johannes Hevelus’ contribution to modern selenology was indeed indispensable.
During his lifetime, Johannes Hevelius was also credited for discovering four comets and was noted for his suggestion that the comets revolved around the Sun in a parabola. And his observations on comets were published in Prodromus Commeticus in 1665 and Cometographia in 1688. Hevelius also listed 1,564 stars and in 1661 became the second person on Earth to witness the transit of Mercury – i.e. the planet Mercury moving across the face of the Sun as seen from Earth. Coincidentally, he passed away during his birthday on 1687.
By: Ringo Bones
Some astronomers think that we only managed to know more about the Moon than Johannes Hevelius did when we had the ability to send robotic spacecraft and manned exploration of the Moon, but is there some truth to this? Even though it was Galileo who first documented the Moon’s topography as seen from his first telescope back in 1610. It was Johannes Hevelius, a notable Polish astronomer born in January 28, 1611 that from his crowded rooftop in Danzig laden with his custom built telescopes – where he gained the fame as the pioneer of Lunar topography a few years later. Hevelius also studied distant celestial objects, but learned little because of dust and other disturbances in the atmosphere over Poland despite using an aerial telescope of his own design that’s 150 feet (46-meter) long – equal to the height of a modern 12-story building.
In collaboration with his wife Elizabeth, they charted the Lunar landscape then published their descriptions in Selenographia back in 1647. During his extensive studies of the Moon, Hevelius got curious of the fact that 59% of the Moon’s surface visible from Earth. During his time, the period between new Moons was already measured with a fair degree of accuracy. And the fact that the same face is always turned toward the Earth with only minor wobbling – the extra 9% of the Moon’s surface seen from Earth – was noted although not explained. The modern explanation is in part that the Moon is not a perfectly symmetrical spheroid. The Moon has a massive bulge, which the Earth’s gravitation attracts like a plumb bob, thus keeping the same hemisphere towards the Earth. With such detailed observations of the Moon, Johannes Hevelus’ contribution to modern selenology was indeed indispensable.
During his lifetime, Johannes Hevelius was also credited for discovering four comets and was noted for his suggestion that the comets revolved around the Sun in a parabola. And his observations on comets were published in Prodromus Commeticus in 1665 and Cometographia in 1688. Hevelius also listed 1,564 stars and in 1661 became the second person on Earth to witness the transit of Mercury – i.e. the planet Mercury moving across the face of the Sun as seen from Earth. Coincidentally, he passed away during his birthday on 1687.
Tuesday, March 30, 2010
Aperture Synthesis: Making Radio Telescopes “See”?
Developed by Sir Martin Ryle back in 1952, can aperture synthesis be used to make radio telescopes finally “see” celestial objects when before it can only “hear” them?
By: Ringo Bones
When the Rayleigh Criterion is taken into account, radio telescopes seem to “hear” rather than actually “see” the celestial objects of interest they are aimed at due to the much longer wavelengths of the radio spectrum in comparison to the optical / visible light part of the electromagnetic spectrum. This is the reason why RADAR or radio wave-based imagery of the universe has always been inferior in resolution terms in comparison to optical astronomy. The most obvious solution is to make ever-larger radio telescope dish antennas so that their resolution capabilities would equal that of optical telescopes, but that presents its own problems. Even the 1,000-foot diameter RADAR dish in Arecibo, Puerto Rico - in imaging terms - still cannot match the detail resolution of the human eye, and making ever bigger dishes presents its own problems.
Since radio astronomy began, astronomers had been constructing ever-larger dish antennas in an attempt to detect radio emissions from objects millions of light years away from Earth where the optical portion of the electromagnetic spectrum – i.e. visible light – cannot be picked up by optical telescopes. Radio astronomers knew, however, that to “see” into more distant objects would require the construction of antennas several miles wide. And it had taken awhile for radio astronomy to rival that of its optical sibling in resolution terms.
Ever since Albert A. Michelson used his interferometer in optical astronomy to bypass the inherent Rayleigh Criterion limitations of reflecting telescope with finite-sized mirrors, radio astronomers have adopted this technique in radio astronomy. The simplest kind of radio interferometer is based on the Michelson interferometer – which consists of two small reflectors. Radio waves arriving at an angle to the baseline of the reflectors reach each other slightly before the other, producing a multi-lobed antenna pattern similar to the fringe pattern in optical interferometers. The farther apart the reflectors, the narrower the width of the lobes – or beams – of the antenna’s radiation pattern, thus greatly increasing the radio telescope’s resolution.
A very example of this type of radio telescope is the California Institute of Technology twin-element interferometer, which consists of two 90-foot steel-mesh parabolic antennas. The antennas are mounted on special vehicles that move along special railroad tracks that can be separated by up to 1,600 feet in either east-west or north-south direction. With a beam-width or acceptance angle as narrow as 0.03 degrees, the telescope is used to record the 960-MHz radio noise in our Milky Way galaxy.
Another type of radio interferometer consists two linear arrays at right angles to each other that electronically compares the fan-shaped beams of the two arrays that result in a single pencil beam being produced that can accurately pinpoint radio sources. Developed in the early 1950s by the Australian radio astronomers W. N. Christiansen and B. Y. Mills. Each array may consist of many dipole antennas (Mills cross), parabolic antennas (Christiansen cross), or a parabolic cylinder.
The Mills cross near Sydney Australia was completed in 1952 and has legs 1,500 feet in length. Later upgraded to a version in 1957 with 3,500-foot legs, and a 1.6-kilometer version. The cross antenna at Stanford University consists of 16 steerable 10-foot parabolic reflectors in a row 375 feet long bisected by a similar row at right angles to it. This antenna is roughly equivalent to a single paraboloidal antenna 375 feet in diameter. Other cross radio telescopes include the Soviet Union’s 0.62-mile (1-kilometer) cross consisting of two parabolic cylinders, while a similar instrument is also found in the University of Bologna in Italy.
Radio interferometer resolution further improved when British astronomer Sir Martin Ryle developed a more effective method called aperture synthesis. He discovered that if he periodically varied the distances between a number of small radio telescopes, they would yield the resolving power of a single mammoth-sized radio telescope. Aperture synthesis was developed over two decades starting in 1952. This technique revolutionized radio astronomy by allowing radio astronomers to achieve an accuracy and resolution rivaling that of optical science. Together with Antony Hewish, Ryle won the Nobel Prize in physics in 1974. The first ever given to astronomers since it began in 1901. In fact, the long time-exposure of Ryle’s telescopes allow “viewing” with a definition so sharp that in the words of the Nobel selection committee: “it corresponds to an observer on Earth being able to see details of a postage stamp on the Moon.”
Years later, aperture synthesis even influenced the development of the US Navy’s Synthetic Aperture RADAR technology that allows their ship and plane based radar systems to achieve the same capabilities to that of the Distant Early Warning (DEW) Line base in Thule, Greenland. Many pundits claim that Synthetic Aperture RADAR is the main technology that made Operation Desert Storm a success in 1991.
By: Ringo Bones
When the Rayleigh Criterion is taken into account, radio telescopes seem to “hear” rather than actually “see” the celestial objects of interest they are aimed at due to the much longer wavelengths of the radio spectrum in comparison to the optical / visible light part of the electromagnetic spectrum. This is the reason why RADAR or radio wave-based imagery of the universe has always been inferior in resolution terms in comparison to optical astronomy. The most obvious solution is to make ever-larger radio telescope dish antennas so that their resolution capabilities would equal that of optical telescopes, but that presents its own problems. Even the 1,000-foot diameter RADAR dish in Arecibo, Puerto Rico - in imaging terms - still cannot match the detail resolution of the human eye, and making ever bigger dishes presents its own problems.
Since radio astronomy began, astronomers had been constructing ever-larger dish antennas in an attempt to detect radio emissions from objects millions of light years away from Earth where the optical portion of the electromagnetic spectrum – i.e. visible light – cannot be picked up by optical telescopes. Radio astronomers knew, however, that to “see” into more distant objects would require the construction of antennas several miles wide. And it had taken awhile for radio astronomy to rival that of its optical sibling in resolution terms.
Ever since Albert A. Michelson used his interferometer in optical astronomy to bypass the inherent Rayleigh Criterion limitations of reflecting telescope with finite-sized mirrors, radio astronomers have adopted this technique in radio astronomy. The simplest kind of radio interferometer is based on the Michelson interferometer – which consists of two small reflectors. Radio waves arriving at an angle to the baseline of the reflectors reach each other slightly before the other, producing a multi-lobed antenna pattern similar to the fringe pattern in optical interferometers. The farther apart the reflectors, the narrower the width of the lobes – or beams – of the antenna’s radiation pattern, thus greatly increasing the radio telescope’s resolution.
A very example of this type of radio telescope is the California Institute of Technology twin-element interferometer, which consists of two 90-foot steel-mesh parabolic antennas. The antennas are mounted on special vehicles that move along special railroad tracks that can be separated by up to 1,600 feet in either east-west or north-south direction. With a beam-width or acceptance angle as narrow as 0.03 degrees, the telescope is used to record the 960-MHz radio noise in our Milky Way galaxy.
Another type of radio interferometer consists two linear arrays at right angles to each other that electronically compares the fan-shaped beams of the two arrays that result in a single pencil beam being produced that can accurately pinpoint radio sources. Developed in the early 1950s by the Australian radio astronomers W. N. Christiansen and B. Y. Mills. Each array may consist of many dipole antennas (Mills cross), parabolic antennas (Christiansen cross), or a parabolic cylinder.
The Mills cross near Sydney Australia was completed in 1952 and has legs 1,500 feet in length. Later upgraded to a version in 1957 with 3,500-foot legs, and a 1.6-kilometer version. The cross antenna at Stanford University consists of 16 steerable 10-foot parabolic reflectors in a row 375 feet long bisected by a similar row at right angles to it. This antenna is roughly equivalent to a single paraboloidal antenna 375 feet in diameter. Other cross radio telescopes include the Soviet Union’s 0.62-mile (1-kilometer) cross consisting of two parabolic cylinders, while a similar instrument is also found in the University of Bologna in Italy.
Radio interferometer resolution further improved when British astronomer Sir Martin Ryle developed a more effective method called aperture synthesis. He discovered that if he periodically varied the distances between a number of small radio telescopes, they would yield the resolving power of a single mammoth-sized radio telescope. Aperture synthesis was developed over two decades starting in 1952. This technique revolutionized radio astronomy by allowing radio astronomers to achieve an accuracy and resolution rivaling that of optical science. Together with Antony Hewish, Ryle won the Nobel Prize in physics in 1974. The first ever given to astronomers since it began in 1901. In fact, the long time-exposure of Ryle’s telescopes allow “viewing” with a definition so sharp that in the words of the Nobel selection committee: “it corresponds to an observer on Earth being able to see details of a postage stamp on the Moon.”
Years later, aperture synthesis even influenced the development of the US Navy’s Synthetic Aperture RADAR technology that allows their ship and plane based radar systems to achieve the same capabilities to that of the Distant Early Warning (DEW) Line base in Thule, Greenland. Many pundits claim that Synthetic Aperture RADAR is the main technology that made Operation Desert Storm a success in 1991.
Thursday, February 25, 2010
Those Other Moons of Jupiter
After being periodically surveyed by robotic spacecraft in recent years, did those astronomers that discovered the other moons of Jupiter years before got the accolades that they truly deserve?
By: Ringo Bones
I tend to have a rather rigid definition on the difference between space exploration and astronomy because to me, sending space probes to distant celestial bodies – in my point of view – is space exploration. While peering though an astronomical telescope via the eyepiece or via a high-resolution computer grade monitor in front of me is what I define as true astronomy. The Voyager and Galileo spacecraft flybys of Jupiter and the planet’s retinue of satellites may have gathered data previously unknown to late 19th and early 20th Century astronomers. But the astronomers themselves who discovered those excruciatingly tiny non-Galilean satellites decades before those robotic spacecraft flybys seem to have been largely forgotten in this day and age.
Before the Pioneer X and Voyagers I and II flybys, there are only 12 moons of Jupiter that can be seen from Earth using existing astronomical telescope technology prior to the 1960s. Set side-by-side to the relatively large four Galilean satellites: Io at 2,000 miles, Europa at 1,800 miles, Ganymede at 3,120 miles, and Callisto at 2,800 miles, the other moons of Jupiter look like grains of sands in comparison. With diameters that range from as large as 70 miles to as small as 10 to 12 miles, discovering these Jovian moons without resorting to optical interferometry is probably next to impossible.
The first one of these non-Galilean satellites to be discovered was discovered by an American astronomer named Edward Emerson Barnard of Barnard’s Star fame in 1892 and was called / designated as V. This tiny Jovian moon at just 70 miles in diameter in unique in many ways. V orbits just 110,000 miles from Jupiter allowing Jupiter’s strong gravitation to make the tiny moon hurtle through space at 1,000 miles a minute – 26 times faster than the Earth’s moon.
On average, Jupiter is 629 million kilometers from Earth, which makes Barnard’s discovery of V somewhat of a remarkable feat in astronomy back in 1892 because astronomical telescopes having at least a 4-meter diameter mirror is the minimum needed to see V from Earth due to the Rayleigh Criterion limitations. The smallest celestial object that a 4-meter mirrored astronomical reflecting telescope when the Rayleigh Criterion is taken into account is around 103.5 kilometers – a little under 70 miles - in diameter from 629 million kilometers away using the visible spectrum centered around 550 nanometers. And most important of all, use of optical interferometry in astronomy to bypass the inherent Rayleigh Criterion limitations of existing reflecting telescopes in 1892 was still several years away. Probably a few years after 1910 when Albert A. Michelson used an optical interferometer of his own design to accurately measure the diameters of those newly-discovered tiny satellites or moons of Jupiter.
Even the discovery of the next non-Galilean satellite designated as VI (diameter 50 miles) in 1904 and VII (diameter 20 miles) in 1905 by American astronomer Charles Dillon Perrine is also miraculous given that optical interferometry for astronomical use is still years away. Even back in 1908, when English astronomer Philbert Jaques Mellote discovered Jupiter’s moon designated as VIII with a diameter of 10 miles without an aid of optical interferometry is nothing short of a miracle.
In 1914, an American astronomer named Seth Barnes Nicholson discovered one of the last few moons of Jupiter whose diameter averages between 10 to 12 miles designated as IX, probably with the aid of Albert A. Michelson’s newfangled optical interferometer. Not only will Nicholson discover the last of the tiny moons of Jupiter that can be seen from Earth before the Pioneer X and Voyager spacecraft flybys, he also made remarkable theories that almost accurately predicted the actual climate of the planet Venus. Together with fellow astronomer Charles St. John, their hot and dry Venus climate hypothesis that they proposed back in 1922 was proven to be closer to reality. Compare that to the one proposed in 1918 by Swedish chemist Svante August Arrhenius – who also discovered the mechanism behind the greenhouse effect – depicted planet Venus as covered by hot steamy tropical swamps.
In 1938, Nicholson discovered another two of Jupiter’s very tiny non-Galilean satellites. Designated at the time as X and XI, X because Nicholson declined suggesting names for the new Jovian moons that he discovered orbits in a region 7,400,000 miles away from Jupiter while XI orbits in a region almost 15 million miles away from Jupiter. X is part of the other 4 of Jupiter’s outermost satellites that orbit in a retrograde direction. Two of these outer satellites even have “open” orbits that are never repeated from one circuit to the next. Probably due to the Sun’s much stronger gravitational influence in comparison to Jupiter’s at this distance.
The last of Jupiter’s satellites / moons that can be seen by Earth-based telescopes have to await discovery until 1951 when XII – now known as Ananke – was yet again discovered by Seth B. Nicholson. XII or Ananke was a difficult find not only because of the Jovian moon’s small size – 10 miles – but also because it shines no brighter than the light of a burning candle seen from 3,000 miles away at night. This is primarily due to the Jovian moon’s extremely low visual albedo or reflectivity, not to mention the Jovian moon’s relatively small size of 10 miles in diameter. Sadly, these amazing astronomers, especially Seth Barnes Nicholson, are largely forgotten given their amazing feats in the science of astronomy.
By: Ringo Bones
I tend to have a rather rigid definition on the difference between space exploration and astronomy because to me, sending space probes to distant celestial bodies – in my point of view – is space exploration. While peering though an astronomical telescope via the eyepiece or via a high-resolution computer grade monitor in front of me is what I define as true astronomy. The Voyager and Galileo spacecraft flybys of Jupiter and the planet’s retinue of satellites may have gathered data previously unknown to late 19th and early 20th Century astronomers. But the astronomers themselves who discovered those excruciatingly tiny non-Galilean satellites decades before those robotic spacecraft flybys seem to have been largely forgotten in this day and age.
Before the Pioneer X and Voyagers I and II flybys, there are only 12 moons of Jupiter that can be seen from Earth using existing astronomical telescope technology prior to the 1960s. Set side-by-side to the relatively large four Galilean satellites: Io at 2,000 miles, Europa at 1,800 miles, Ganymede at 3,120 miles, and Callisto at 2,800 miles, the other moons of Jupiter look like grains of sands in comparison. With diameters that range from as large as 70 miles to as small as 10 to 12 miles, discovering these Jovian moons without resorting to optical interferometry is probably next to impossible.
The first one of these non-Galilean satellites to be discovered was discovered by an American astronomer named Edward Emerson Barnard of Barnard’s Star fame in 1892 and was called / designated as V. This tiny Jovian moon at just 70 miles in diameter in unique in many ways. V orbits just 110,000 miles from Jupiter allowing Jupiter’s strong gravitation to make the tiny moon hurtle through space at 1,000 miles a minute – 26 times faster than the Earth’s moon.
On average, Jupiter is 629 million kilometers from Earth, which makes Barnard’s discovery of V somewhat of a remarkable feat in astronomy back in 1892 because astronomical telescopes having at least a 4-meter diameter mirror is the minimum needed to see V from Earth due to the Rayleigh Criterion limitations. The smallest celestial object that a 4-meter mirrored astronomical reflecting telescope when the Rayleigh Criterion is taken into account is around 103.5 kilometers – a little under 70 miles - in diameter from 629 million kilometers away using the visible spectrum centered around 550 nanometers. And most important of all, use of optical interferometry in astronomy to bypass the inherent Rayleigh Criterion limitations of existing reflecting telescopes in 1892 was still several years away. Probably a few years after 1910 when Albert A. Michelson used an optical interferometer of his own design to accurately measure the diameters of those newly-discovered tiny satellites or moons of Jupiter.
Even the discovery of the next non-Galilean satellite designated as VI (diameter 50 miles) in 1904 and VII (diameter 20 miles) in 1905 by American astronomer Charles Dillon Perrine is also miraculous given that optical interferometry for astronomical use is still years away. Even back in 1908, when English astronomer Philbert Jaques Mellote discovered Jupiter’s moon designated as VIII with a diameter of 10 miles without an aid of optical interferometry is nothing short of a miracle.
In 1914, an American astronomer named Seth Barnes Nicholson discovered one of the last few moons of Jupiter whose diameter averages between 10 to 12 miles designated as IX, probably with the aid of Albert A. Michelson’s newfangled optical interferometer. Not only will Nicholson discover the last of the tiny moons of Jupiter that can be seen from Earth before the Pioneer X and Voyager spacecraft flybys, he also made remarkable theories that almost accurately predicted the actual climate of the planet Venus. Together with fellow astronomer Charles St. John, their hot and dry Venus climate hypothesis that they proposed back in 1922 was proven to be closer to reality. Compare that to the one proposed in 1918 by Swedish chemist Svante August Arrhenius – who also discovered the mechanism behind the greenhouse effect – depicted planet Venus as covered by hot steamy tropical swamps.
In 1938, Nicholson discovered another two of Jupiter’s very tiny non-Galilean satellites. Designated at the time as X and XI, X because Nicholson declined suggesting names for the new Jovian moons that he discovered orbits in a region 7,400,000 miles away from Jupiter while XI orbits in a region almost 15 million miles away from Jupiter. X is part of the other 4 of Jupiter’s outermost satellites that orbit in a retrograde direction. Two of these outer satellites even have “open” orbits that are never repeated from one circuit to the next. Probably due to the Sun’s much stronger gravitational influence in comparison to Jupiter’s at this distance.
The last of Jupiter’s satellites / moons that can be seen by Earth-based telescopes have to await discovery until 1951 when XII – now known as Ananke – was yet again discovered by Seth B. Nicholson. XII or Ananke was a difficult find not only because of the Jovian moon’s small size – 10 miles – but also because it shines no brighter than the light of a burning candle seen from 3,000 miles away at night. This is primarily due to the Jovian moon’s extremely low visual albedo or reflectivity, not to mention the Jovian moon’s relatively small size of 10 miles in diameter. Sadly, these amazing astronomers, especially Seth Barnes Nicholson, are largely forgotten given their amazing feats in the science of astronomy.
Monday, February 22, 2010
Optical Interferometry: A Way Around the Rayleigh Criterion?
Invented by Albert A. Michelson during the 1870s, can optical interferometry be used effectively in circumventing the Rayleigh Criterion limitations of a typical reflecting telescope?
By: Ringo Bones
Albert A. Michelson was more famous for his work with Edward W. Morley in which they won the 1907 Nobel Prize in physics for proving that the mythical medium called the ether wind doesn’t exist, thus paving the way for Einstein’s theory of special relativity. Michelson invented the interferometer primarily as a way of accurately measuring the speed of light back in the 1870s. Albert A. Michelson also managed to earn the fame of being the first one to utilize optical interferometry as a very important astronomical instrument until 1920. It is this time when Michelson became the first ever person to measure a diameter of a star using an optical interferometer of his own design. He determined that Alpha Orion to be 260 million miles in diameter. A few years before, Michelson was also the first person to determine the diameter of Jupiter’s satellites. But how does optical interferometry works?
Optical interferometry depends on the light splitting and summing properties of an interferometer. An interferometer is an instrument that utilizes light interference phenomena for precise determinations of wavelength, fine structure of spectral lines, refractive indices of a given medium and very fine linear displacement of distant objects. By bringing together beams of starlight captured by two or more widely separated telescopes, a typical optical interferometer can achieve the equivalent resolving power of a single instrument equipped with a main mirror as large as the distance between the ganged telescopes.
When the starlight beams are combined, the light waves interfere with one another. Where the peak of one light wave meets the peak of another, they reinforce each other. When the peak of one light wave meets the through of another, they cancel out. An electronic detector or a video digital-to-analog-converter (video DAC) records the resulting pattern of dark and light areas – or interference fringes – which can then be analyzed by computer via digital signal processing to extract detailed information about the object being observed. If at least three telescopes are used, the fringes can be rendered into images hundreds of times crisper than even those obtained by the orbiting Hubble Space Telescope – at a much reduced expense, thus bypassing the Rayleigh Criterion limitations of constructing an ever bigger mirror of a typical astronomical telescope. Given its ability to improve reflecting telescope performance beyond their Rayleigh Criterion limitations, why is it that most astronomers are still mistrustful over optical interferometry?
There had been famous and amazing stargazing feats achieved by optical interferometry since the 1970s. In 1974, Kitt Peak National Observatory astronomers managed to penetrate the Earth’s atmospheric haze for the first time by discerning the features in the atmosphere of a star named Betelgeuse with the computer aided technique called speckle interferometry, while the Mark III Optical Interferometer on Mount Wilson Observatory in California had been in operation since 1986. Astronomers tend to be a conservative bunch and a lot of them consider optical interferometry to be “black magic” because even though they can measure the outlines of celestial objects millions – even billions - of miles away, optical interferometers cannot make true images of these objects.
If you remember the movie version of Tom Clancy’s Patriot Games when Langley analysts got a hard copy of a photo taken by a KH-11 reconnaissance satellite showing the cleavage of the female underwriters of the Ulster Liberation Army standing in the middle of the Libyan Desert. You’ll notice that it is monochromatic – i.e. black and white – yet managed to show features that according to Rayleigh Criterion on the KH-11 reconnaissance satellite’s mirror specifications cannot supposedly resolve that make it appear like a distinct black and white image of a woman’s cleavage seen from 160 miles up. That’s the power of optical interferometry put to use were the video signals are probably processed using the reconnaissance satellite’s built-in 10-bit video DAC that’s probably not more advanced than one’s found in a circa 1998 DVD player.
Image quality-wise, the resulting image is so “abstract” and “clinical” that free-spirited American under-aged teens who are frequent skinny-dippers have no fear having compromising photos taken by computer nerds who know how to re-task the US National Security Agency’s reconnaissance satellites - Largely because its image quality is far inferior in comparison to those photos taken by a typical paparazzi operating in the 90210 area code. Probably due to the fact that optical interferometry – a technique probably utilized by the KH-11 reconnaissance satellite to be able to read Soviet-era Pravda headlines and car license plates from 160 miles up - cannot make true images.
By: Ringo Bones
Albert A. Michelson was more famous for his work with Edward W. Morley in which they won the 1907 Nobel Prize in physics for proving that the mythical medium called the ether wind doesn’t exist, thus paving the way for Einstein’s theory of special relativity. Michelson invented the interferometer primarily as a way of accurately measuring the speed of light back in the 1870s. Albert A. Michelson also managed to earn the fame of being the first one to utilize optical interferometry as a very important astronomical instrument until 1920. It is this time when Michelson became the first ever person to measure a diameter of a star using an optical interferometer of his own design. He determined that Alpha Orion to be 260 million miles in diameter. A few years before, Michelson was also the first person to determine the diameter of Jupiter’s satellites. But how does optical interferometry works?
Optical interferometry depends on the light splitting and summing properties of an interferometer. An interferometer is an instrument that utilizes light interference phenomena for precise determinations of wavelength, fine structure of spectral lines, refractive indices of a given medium and very fine linear displacement of distant objects. By bringing together beams of starlight captured by two or more widely separated telescopes, a typical optical interferometer can achieve the equivalent resolving power of a single instrument equipped with a main mirror as large as the distance between the ganged telescopes.
When the starlight beams are combined, the light waves interfere with one another. Where the peak of one light wave meets the peak of another, they reinforce each other. When the peak of one light wave meets the through of another, they cancel out. An electronic detector or a video digital-to-analog-converter (video DAC) records the resulting pattern of dark and light areas – or interference fringes – which can then be analyzed by computer via digital signal processing to extract detailed information about the object being observed. If at least three telescopes are used, the fringes can be rendered into images hundreds of times crisper than even those obtained by the orbiting Hubble Space Telescope – at a much reduced expense, thus bypassing the Rayleigh Criterion limitations of constructing an ever bigger mirror of a typical astronomical telescope. Given its ability to improve reflecting telescope performance beyond their Rayleigh Criterion limitations, why is it that most astronomers are still mistrustful over optical interferometry?
There had been famous and amazing stargazing feats achieved by optical interferometry since the 1970s. In 1974, Kitt Peak National Observatory astronomers managed to penetrate the Earth’s atmospheric haze for the first time by discerning the features in the atmosphere of a star named Betelgeuse with the computer aided technique called speckle interferometry, while the Mark III Optical Interferometer on Mount Wilson Observatory in California had been in operation since 1986. Astronomers tend to be a conservative bunch and a lot of them consider optical interferometry to be “black magic” because even though they can measure the outlines of celestial objects millions – even billions - of miles away, optical interferometers cannot make true images of these objects.
If you remember the movie version of Tom Clancy’s Patriot Games when Langley analysts got a hard copy of a photo taken by a KH-11 reconnaissance satellite showing the cleavage of the female underwriters of the Ulster Liberation Army standing in the middle of the Libyan Desert. You’ll notice that it is monochromatic – i.e. black and white – yet managed to show features that according to Rayleigh Criterion on the KH-11 reconnaissance satellite’s mirror specifications cannot supposedly resolve that make it appear like a distinct black and white image of a woman’s cleavage seen from 160 miles up. That’s the power of optical interferometry put to use were the video signals are probably processed using the reconnaissance satellite’s built-in 10-bit video DAC that’s probably not more advanced than one’s found in a circa 1998 DVD player.
Image quality-wise, the resulting image is so “abstract” and “clinical” that free-spirited American under-aged teens who are frequent skinny-dippers have no fear having compromising photos taken by computer nerds who know how to re-task the US National Security Agency’s reconnaissance satellites - Largely because its image quality is far inferior in comparison to those photos taken by a typical paparazzi operating in the 90210 area code. Probably due to the fact that optical interferometry – a technique probably utilized by the KH-11 reconnaissance satellite to be able to read Soviet-era Pravda headlines and car license plates from 160 miles up - cannot make true images.
Thursday, February 11, 2010
The Rayleigh Criterion: The Bane of Mirrored Telescopes?
Named after a 19th Century English physicist, is the Rayleigh Criterion the true arbiter over press hype of the true capabilities of large mirrored telescopes and reconnaissance satellites?
By: Ringo Bones
I could have titled this blog entry as; “Is the KH-Series of American Reconnaissance Satellites’ Capability of Seeing Soviet-era Pravda headlines from 160 kilometers up Somewhat Overly Optimistic?” but that would only answer a part of a little understood concept of optics. And if the “hype” over the runaway success of adaptive optics were to be believed, would this imply that the best astronomical telescopes could soon be found here on Earth as opposed to orbital space? Though that too is only part of the story, but the point of this discussion is about how an oft-ignored, yet vital aspect, of advanced telescope design. Whether using a Hubble Space Telescope-sized 2.4-meter primary mirror or a 10-meter primary mirrored Earth-based astronomical telescope is ultimately diffraction limited. This means that the resolution of a large reflecting telescope – whether those on the KH-series reconnaissance satellites, the Hubble Space Telescope, or those very large astronomical telescopes found on top of Mauna Kea or in the Chilean desert – is limited by diffraction.
The first person to study the diffraction limitation problem of reflecting or mirrored astronomical – or other large - telescopes was a 19th Century English physicist / gentleman-scientist named John William Strutt, but he’s better known to the rest of the world as the 3rd Baron Rayleigh or Lord Rayleigh. Also more famous for his 1904 Nobel prize for Physics for the discovery of the element argon – which he isolated in cooperation with Sir William Ramsay – than his work / investigations in optics that lead to the criterion named after him. The Rayleigh Criterion defines the resolution capabilities of a reflecting telescope where two points are just resolved when their angular separation is equal to an angle designated as theta at which the first diffraction minimum occurs. As given in the equation theta = 1.22 multiplied by the wavelength of light of interest divided by the mirror diameter of the telescope. The number 1.22 is a constant derived by Lord Rayleigh when he used differential equations in tackling this problem. The angle theta can also be designated as dividing the linear separation of the characters of interest – like the headline of a Soviet-era Pravda newspaper at around an inch or 2.5 cm – with the orbital altitude of the reconnaissance satellite – often at 160 kilometers up.
If anyone – besides me – is really curious if a KH-11 like reconnaissance satellite is really capable of seeing clearly a Pravda newspaper headline from 160 kilometers from the Earth’s surface. One can use the Rayleigh Criterion to test to test whether the KH series of reconnaissance satellite’s capabilities are nothing more than cold War era media hype. Let’s just assume that the KH-11 reconnaissance satellite has a main mirror similar in size to that of the Hubble Space Telescope at 2.4 meters since the two are almost of similar dimensions. Assuming that it works in the visible light spectrum at 550 nanometers (smack down in the middle or the green portion of the visible light spectrum) as the wavelength of interest.
So to get the resolution limit of your typical reconnaissance satellite, just multiply 1.22 with the orbital altitude of the reconnaissance satellite – usually around 160 kilometers or 160,000 meters. Multiply this number with the quotient that resulted when the wavelength of interest – 550 nanometers (550 times 10 to the negative 9 meters) – is divided by the reconnaissance satellite’s main mirror diameter of 2.4 meters. The resulting figure is 4.47 centimeters, which makes the reflecting telescope of your typical reconnaissance satellite really have a hard time seeing a Pravda newspaper headline – even license plates – from 160 kilometers up. The letters and numbers may be 4.47 centimeters tall but if they are spaced closer than 4.47 centimeters, the resulting image will be a blur if taken from 160 kilometers up. Shifting to the longer infrared wavelengths worsen the resolution when looking at “small” objects, while the shorter ultraviolet wavelengths could face problems of increasing atmospheric opacity from going through more than 100 kilometers of air.
There might be truth to the rumors of the gripes of “civilian” optical technicians working on the Hubble Space Telescopes main mirror during the Reagan Administration being denied access to the mirror testing equipment primarily used to test the main mirrors on the KH-11 series of reconnaissance satellites. Citing national security concerns back when America was still engaged in a Cold War with the Soviet Union. Sadly, this resulted in the Hubble Space Telescope’s technicians not knowing that the telescope’s main mirror is ground a few millionths of an inch too much while still on the ground in the NASA clean room. Worse still, the astronomical community only knew of the Hubble’s misshapen mirror only after it has been launched 350 kilometers into orbital space when they tested it, hence the then famous press headline of the Hubble Space Telescope being a 1.2 billion dollar blunder.
Maybe, the end of the Cold War proved to be a blessing in disguise to the Hubble Space Telescope because there are rumors too that the potato chip-shaped “corrective lenses” that are retrofitted to the Hubble back in 1993 were borrowed from the KH series of reconnaissance satellites. Maybe this specially shaped lenses are the “magic wand” that allowed the NSA reconnaissance satellites to beat around the Rayleigh Criterion / diffraction limitations of space-based reflecting telescopes. Regardless whether they are used to look up and out into space or look down on Earth’s surface in search of WMDs.
By: Ringo Bones
I could have titled this blog entry as; “Is the KH-Series of American Reconnaissance Satellites’ Capability of Seeing Soviet-era Pravda headlines from 160 kilometers up Somewhat Overly Optimistic?” but that would only answer a part of a little understood concept of optics. And if the “hype” over the runaway success of adaptive optics were to be believed, would this imply that the best astronomical telescopes could soon be found here on Earth as opposed to orbital space? Though that too is only part of the story, but the point of this discussion is about how an oft-ignored, yet vital aspect, of advanced telescope design. Whether using a Hubble Space Telescope-sized 2.4-meter primary mirror or a 10-meter primary mirrored Earth-based astronomical telescope is ultimately diffraction limited. This means that the resolution of a large reflecting telescope – whether those on the KH-series reconnaissance satellites, the Hubble Space Telescope, or those very large astronomical telescopes found on top of Mauna Kea or in the Chilean desert – is limited by diffraction.
The first person to study the diffraction limitation problem of reflecting or mirrored astronomical – or other large - telescopes was a 19th Century English physicist / gentleman-scientist named John William Strutt, but he’s better known to the rest of the world as the 3rd Baron Rayleigh or Lord Rayleigh. Also more famous for his 1904 Nobel prize for Physics for the discovery of the element argon – which he isolated in cooperation with Sir William Ramsay – than his work / investigations in optics that lead to the criterion named after him. The Rayleigh Criterion defines the resolution capabilities of a reflecting telescope where two points are just resolved when their angular separation is equal to an angle designated as theta at which the first diffraction minimum occurs. As given in the equation theta = 1.22 multiplied by the wavelength of light of interest divided by the mirror diameter of the telescope. The number 1.22 is a constant derived by Lord Rayleigh when he used differential equations in tackling this problem. The angle theta can also be designated as dividing the linear separation of the characters of interest – like the headline of a Soviet-era Pravda newspaper at around an inch or 2.5 cm – with the orbital altitude of the reconnaissance satellite – often at 160 kilometers up.
If anyone – besides me – is really curious if a KH-11 like reconnaissance satellite is really capable of seeing clearly a Pravda newspaper headline from 160 kilometers from the Earth’s surface. One can use the Rayleigh Criterion to test to test whether the KH series of reconnaissance satellite’s capabilities are nothing more than cold War era media hype. Let’s just assume that the KH-11 reconnaissance satellite has a main mirror similar in size to that of the Hubble Space Telescope at 2.4 meters since the two are almost of similar dimensions. Assuming that it works in the visible light spectrum at 550 nanometers (smack down in the middle or the green portion of the visible light spectrum) as the wavelength of interest.
So to get the resolution limit of your typical reconnaissance satellite, just multiply 1.22 with the orbital altitude of the reconnaissance satellite – usually around 160 kilometers or 160,000 meters. Multiply this number with the quotient that resulted when the wavelength of interest – 550 nanometers (550 times 10 to the negative 9 meters) – is divided by the reconnaissance satellite’s main mirror diameter of 2.4 meters. The resulting figure is 4.47 centimeters, which makes the reflecting telescope of your typical reconnaissance satellite really have a hard time seeing a Pravda newspaper headline – even license plates – from 160 kilometers up. The letters and numbers may be 4.47 centimeters tall but if they are spaced closer than 4.47 centimeters, the resulting image will be a blur if taken from 160 kilometers up. Shifting to the longer infrared wavelengths worsen the resolution when looking at “small” objects, while the shorter ultraviolet wavelengths could face problems of increasing atmospheric opacity from going through more than 100 kilometers of air.
There might be truth to the rumors of the gripes of “civilian” optical technicians working on the Hubble Space Telescopes main mirror during the Reagan Administration being denied access to the mirror testing equipment primarily used to test the main mirrors on the KH-11 series of reconnaissance satellites. Citing national security concerns back when America was still engaged in a Cold War with the Soviet Union. Sadly, this resulted in the Hubble Space Telescope’s technicians not knowing that the telescope’s main mirror is ground a few millionths of an inch too much while still on the ground in the NASA clean room. Worse still, the astronomical community only knew of the Hubble’s misshapen mirror only after it has been launched 350 kilometers into orbital space when they tested it, hence the then famous press headline of the Hubble Space Telescope being a 1.2 billion dollar blunder.
Maybe, the end of the Cold War proved to be a blessing in disguise to the Hubble Space Telescope because there are rumors too that the potato chip-shaped “corrective lenses” that are retrofitted to the Hubble back in 1993 were borrowed from the KH series of reconnaissance satellites. Maybe this specially shaped lenses are the “magic wand” that allowed the NSA reconnaissance satellites to beat around the Rayleigh Criterion / diffraction limitations of space-based reflecting telescopes. Regardless whether they are used to look up and out into space or look down on Earth’s surface in search of WMDs.
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