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Basic fragment of Jupiter's column, in limestone with a representation of Venus in the center, Juno and his peacock on the right, a statue of Apollo the archer running and a dog sitting. Fontaine-Valmont (from Hainaut). Musée d'Art et d'Histoire (Musée du Cinquantenaire, Brussels, Belgium). Made with ReMake and ReCap Pro from AutoDesk.
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File:Two columns with entablature from the courtyard-colonades, reconstruction with orginal basis and fragments of Egyptian Granite, from the Sanctuary of Jupiter Heliopolitanus at Baalbek, Pergamon Museum Berlin (8405358034).jpg
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Shoemaker-Levy 9 was discovered by Carolyn and Gene Shoemaker and David Levy in a photograph taken on Mar. 18, 1993 with the 0.4-meter Schmidt telescope at Mt. Palomar.
When the comet was discovered in 1993, it already had been torn into more than 20 pieces traveling around the planet in a two year orbit. Further observations revealed the comet (believed to be a single body at the time) had made a close approach to Jupiter in July 1992 and was torn apart by tidal forces resulting from planet's powerful gravity. The comet was thought to have been orbiting Jupiter for about a decade before its demise.
The disruption of a comet into multiple fragments was rare and observing a captured comet in orbit about Jupiter was even more unusual, but the biggest and rarest revelation was that the fragments were going to smash into Jupiter.
NASA had spacecraft in position to watch&mdashfor the first time in history&mdasha collision between two bodies in the solar system.
NASA's Galileo orbiter (then still en route to Jupiter) captured unprecedented direct views as the string of fragments labeled A through W smashed into Jupiter's cloud tops. The impacts started on 16 July 1994 and ended on 22 July 1994.
Many Earth-based observatories and orbiting spacecraft including Hubble Space Telescope, Ulysses and Voyager 2 also studied the impact and its aftermath.
The "freight train" of fragments smashed into Jupiter with the force of 300 million atomic bombs. The fragments created huge plumes that were 2,000 to 3,000 kilometers (1,200 to 1,900 miles) high, and heated the atmosphere to temperatures as hot as 30,000 to 40,000 degrees Celsius (53,000 to 71,000 degrees Fahrenheit). Shoemaker-Levy 9 left dark, ringed scars that were eventually erased by Jupiter's winds.
While the impact was dramatic, it was more than a show. It gave scientists an opportunity to gain new insights into Jupiter, Shoemaker-Levy 9 and cosmic collisions in general. Researchers were able to deduce the composition and structure of the comet. The collision also left dust floating on the top of Jupiter's clouds. By watching the dust spread across the planet, scientists were able to track high-altitude winds on Jupiter for the first time. And by comparing changes in the magnetosphere with changes in the atmosphere following the impact, scientists were able to study the relation-ship between them.
Scientists have calculated that the comet was originally about 1.5 to 2 kilometers (0.9 to 1.2 miles) wide. If a similar-sized object were to hit Earth, it would be devastating. The impact might send dust and debris into the sky, creating a haze that would cool the atmosphere and absorb sunlight, enveloping the entire planet in darkness. If the haze lasted long enough, plant life would die - along with the people and animals that depend on it to survive.
These kinds of collisions were more frequent in the early solar system. In fact, comet impacts were probably the main way that elements other than hydrogen and helium got to Jupiter.
Today, impacts of this size probably occur only every few centuries&mdashand pose a real threat.
How Shoemaker-Levy 9 Got Its Name
The comet was named for its discoverers. Comet Shoemaker-Levy 9 was the ninth short-periodic comet discovered by Eugene and Carolyn Shoemaker and David Levy.
Jupiter Just Got Hit by a Comet or Asteroid . Again (Video)
Take that, Jupiter! The largest planet in the solar system just got whacked by an asteroid or a comet, and some intrepid stargazers have captured the planet's latest collision on camera.
Amateur astronomer John McKeon was observing the king of planets by telescope from Swords, Ireland, on March 17 when he captured this stunning time-lapse video of something hitting Jupiter. McKeon was recording the transit of Jupiter's moons Io and Ganymede with an 11-inch Schmidt-Cassegrain telescope and his ASI120mm camera when something struck Jupiter, and he struck cosmic pay dirt.
"The original purpose of the imaging session was to get this time-lapse, with a happy coincidence of the impact in the second, last capture of the night," McKeon wrote in a YouTube video description.
While it's still too early to know exact details on the Jupiter crash, NASA asteroid expert Paul Chodas, who heads the agency's Center for Near-Earth Object Studies at the Jet Propulsion Laboratory in Pasadena, California, said there's greater chance that an asteroid, not comet, is the culprit.
"It's more likely to be an asteroid simply because there are more of them," Chodas told Space.com by phone.
It's not yet clear what hit Jupiter, but the impact was also captured by at least one other amateur astronomer &mdash Gerrit Kernbauer of Mödling, Austria &mdash according to Bad Astronomy's Phil Plait, who posted Kernbauer's YouTube video of the impact. According to Plait, the impact occurred at 00:18 GMT, or just after midnight, on March 17.
Kernbauer used a Skywatcher Newton 200/1000 Telescope to capture the Jupiter impact video, which you can see here:
"The seeing was not the best, so I hesitated to process the videos," he wrote in his video description. "Nevertheless, 10 days later I looked through the videos and I found this strange light spot that appeared for less than one second on the edge of the planetary disc. Thinking back to Shoemaker-Levy 9, my only explanation for this is an asteroid or comet that enters Jupiter's high atmosphere and burned up/explode very fast [sic]."
As Kernbauer says, this isn't the first time Jupiter has been walloped by a space rock or comet.
"From our point of view this simply serves to remind us that impacts in the solar system are real and Jupiter gets more than its fair share of impacts," said Chodas said. "It draws in a lot of asteroids and comets. We are seeing these impact flashes on Jupiter about once a year now, and that&rsquos I believe because of instrumentation."
Between July 16 and July 22 of 1994, fragments of the comet Shoemaker-Levy 9 slammed into Jupiter as astronomers and stargazers watched in awe through their telescopes on Earth. The impacts left great scars that were visible on the Jupiter for months through even a small telescope. [Comet Shoemaker-Levy 9's Epic Jupiter Crash in Pictures]
While astronomers watched comet Shoemaker-Levy 9's Jupiter crash from Earth, NASA's Galileo spacecraft &mdash which was en route Jupiter at the time &mdash captured stunning images of the collision. The Hubble Space Telescope recorded views of the impacts in different wavelengths, while NASA used its Deep Space Network to track radio disturbances in Jupiter's radiation belt.
Then it happened in again.
On July 19, 2009, Australian amateur astronomer Anthony Wesley noticed a dark spot near Jupiter's southern pole: the telltale bruise from an impact, likely from a rogue asteroid about 1,600 feet (500 meters) wide. It was roughly the size of the ill-fated Titanic cruise ship.
A year later, on June 3, 2010, it happened yet again. This impact was also spotted by Wesley in Australia, as well as by fellow Jupiter-watcher Christopher Go in the Philippines.
Later in 2010, on Aug. 20, the flash from another impact on Jupiter was spotted by amateur astronomer Masayuki Tachikawa in Japan. Then on Sept. 12, 2012, another flash and crash on Jupiter, this one first spotted by Dan Peterson of Racine, Wisconsin.
The photos from the recent Jupiter impacts show how the planet is under constant surveillance by some die-hard amateur astronomers. "Better and better instruments means Jupiter is being monitored, even by amateur astronomers, much more than it was in the past," Chodas said.
And the planet is about to get another visitor, this one from NASA.
On July 4 of this year, NASA's Juno spacecraft will arrive in orbit around Jupiter to pick up where the Galileo mission (which ended in 2003) left off. The $1.1 billion Juno mission launched in 2011 and is expected to spend at least a year mapping Jupiter in amazing detail.
If the thought of a sequestered disc makes you want to rush out and get some back surgery, it may first behoove you to know that conservative care, which generally consists of medication and physical therapy, may help you fully recover.
A small 2002 study found that non-surgical treatment for herniated discs, especially those that have sequestered, may be surprisingly successful.
Over 75% of the twenty-two participants in the study, regardless of what type of herniation they had, reported positive outcomes without the use of surgery. For most of the eleven patients with the sequestered type herniation, the migrated fragments disappeared altogether. And for the remaining study participants with the sequestered discs, MRIs revealed definite decreases in the free fragment sizes.
A 2017 meta-analysis published in the journal Pain Physician not only confirms the study's findings but also reports what they refer to as a well-known fact—that 66.66% of disc herniations spontaneously resorb. Resorption occurs when the body's tissues that come into contact with the free fragments secrete substances that chemically break down the disc pieces. The broken-down disc material is, over time, re-absorbed by the body.
While going the conservative route may help you avoid the stress and uncertainty of an invasive procedure, keep in mind that it may take much longer to get significant pain relief and symptom abatement.
If you have a sequestered disc, and you're thinking of going the conservative care route, you may be in luck. This is because the more progressed a herniation is, the more likely it is the disc will spontaneously resorb.
A study published in the February 2015 issue of Clinical Rehabilitation found that both the extrusion and sequestration herniation types have a higher probability of spontaneous resorption than do disc bulges and protrusions. The study also found that in comparison to bulging, protruding, extruding, prolapsed discs — in other words, all the other progressive phases of disc herniation — free fragments and sequestered disc have a higher probability of complete remission and resolve of the condition.
And finally, the standard surgery for a simple herniated disc may not work for your sequestered disc. Not only may locating the free fragment or fragments responsible for your symptoms be extra challenging for your surgeon, but at least two invasive procedures, percutaneous discectomy, and chemonucleolysis have been identified by experts as, at best, ineffective, but, worse, potentially harmful.
An article in the October 2016 issue of the Asian Spine Journal warns surgeons that while laser disc surgery is fine for an uncomplicated case of herniated discs, it's not recommended for sequestered discs. And if you an underlying back problem that makes your spine unstable, the authors say, laser surgery is, likely not a good choice of procedures, even for a simple herniation.
Babylonian astronomers computed position of Jupiter with geometric methods
Left: Cuneiform tablet with calculations involving a trapezoid. Right: A visualization of trapezoid procedure on the tablet: The distance travelled by Jupiter after 60 days, 10º45', is computed as the area of the trapezoid. The trapezoid is then divided into two smaller ones in order to find the time (tc) in which Jupiter covers half this distance. Credit: Mathieu Ossendrijver (HU)
Ancient Babylonians are now believed to have calculated the position of Jupiter using geometry. This is revealed by an analysis of three published and two unpublished cuneiform tablets from the British Museum by Prof. Mathieu Ossendrijver, historian of science of the Humboldt-Universität zu Berlin. The tablets date from the period between 350 and 50 BCE. Historians of science have thus far assumed that geometrical computations of the kind found on these tablets were first carried out in the 14th century. Moreover, it was assumed that Babylonian astronomers used only arithmetical methods.
"The new interpretation reveals that Babylonian astronomers also used geometrical methods", says Mathieu Ossendrijver. His results are published in the current issue of the journal Science.
On four of these tablets, the distance covered by Jupiter is computed as the area of a figure that represents how its velocity changes with time. None of the tablets contains drawings but, as Mathieu Ossendrijver explains, the texts describe the figure of which the area is computed as a trapezoid. Two of these so-called trapezoid texts had been known since 1955, but their meaning remained unclear, even after two further tablets with these operations were discovered in recent years.
One reason for this was the damaged state of the tablets, which were excavated unscientifically in Babylon, near its main temple Esagila, in the 19th century. Another reason was, that the calculations could not be connected to a particular planet. The new interpretation of the trapezoid texts was now prompted by a newly discovered, almost completely preserved fifth tablet. A colleague from Vienna who visited the Excellence Cluster TOPOI in 2014, the retired Professor of Assyriology Hermann Hunger, draw the attention of Mathieu Ossendrijver to this tablet. He presented him with an old photograph of the tablet that was made in the British Museum.
The new tablet does not mention a trapezoid figure, but it does contain a computation that is mathematically equivalent to the other ones. This computations can be uniquely assigned to the planet Jupiter. With this new insight the other, thus far incomprehensible tablets could also be deciphered.
In all five tablets, Jupiter's daily displacement and its total displacement along its orbit, both expressed in degrees, are described for the first 60 days after Jupiter becomes visible as a morning star. Mathieu Ossendrijver explains: "The crucial new insight provided by the new tablet without the geometrical figure is that Jupiter's velocity decreases linearly within the 60 days. Because of the linear decrease a trapezoidal figure emerges if one draws the velocity against time."
"It is this trapezoidal figure of which the area is computed on the other four tablets", says the historian of science. The area of this figure is explicitly declared to be the distance travelled by Jupiter after 60 days. Moreover, the time when Jupiter covers half this distance is also calculated, by dividing the trapezoid into two smaller ones of equal area.
European scholars used similar techniques
"These computations anticipate the use of similar techniques by European scholars, but they were carried out at least 14 centuries earlier", says Ossendrijver. The so-called Oxford calculators, a group of scholastic mathematicians, who worked at Merton College, Oxford, in the 14th century, are credited with the "Mertonian mean speed theorem". This theorem yields the distance travelled by a uniformly decelerating body, corresponding to the modern formula S=t•(u+v)/2, where u and v are the initial and final velocities.
In the same century Nicole Oresme, a bishop and scholastic philosopher in Paris, devised graphical methods that enabled him to prove this relation. He computed S as the area of a trapezoid of width t and heights u and v. The Babylonian trapezoid procedures can be viewed as a concrete examples of the same computation.
Babylonian trapezoid figures exist in an abstract mathematical space
Furthermore, it was hitherto assumed that the astronomers in Babylon used arithmetical methods but no geometrical ones, even though they were common in Babylonian mathematics since 1800 BCE. Ancient Greek astronomers from the time between 350 BCE and 150 CE are also known for their use of geometrical methods. However, the Babylonian trapezoid texts are distinct from the geometrical calculations of their Greek colleagues. The trapezoid figures do not describe configurations in a real space, but they come about by drawing the velocity of the planet against time. As opposed to the geometrical constructions of the Greek astronomers the Babylonian trapezoid figures exist in an abstract mathematical space, defined by time on the x-axis and velocity on the y-axis.
Fragment of Jupiter's Column - History
Jupiter, Giant of the Solar System.
Figure 1-1. Important to the ancient Babylonians, the brilliant planet Jupiter ruled the night sky and mapped out the Zodiacal constellations.
[ 1 ] IN ROMAN AND GREEK MYTHOLOGY the god Jupiter was accepted as the most powerful and capricious ruler of the heavens no wonder ancient astronomers gave the same name to the planet that year after year so brilliantly rules the night sky. After the Sun and the Moon, Jupiter is, indeed, the most spectacular object in the sky. Although Venus is at times brighter it cannot ride the midnight sky as does Jupiter.
Today's astronomers acknowledge Jupiter as being perhaps the most important planet of the Solar System. It is the largest and most massive. After the Sun-the star about which all bodies of the Solar System revolve -Jupiter contains two-thirds of the matter in the Solar System. Orbiting the Sun at an average distance of 779 million km (484 million mi.), Jupiter is some 5.2 times as far away as Earth.
Cuneiforms of the Babylonian epic Enuma Elish or Tablets of Creation refer to Jupiter in the Fifth Tablet as the marker of the signs of the Zodiac . . . "He (Marduk - the Creator) founded the station of Nibir (Jupiter) to determine their bounds. . ." To the Babylonians, Nibir was the special name for Jupiter when the planet appeared directly opposite to the Sun and thus shone high and brightly in the midnight sky over the fertile valley of the Euphrates. Since Jupiter travels around its orbit once in almost 12 years, the planet each year moves eastward to occupy the next constellation of the Zodiac. Also, as a result of the relative motions of Earth and Jupiter around the Sun, the faster moving Earth overtakes Jupiter and thereby causes the planet each year to trace out a third of the Zodiacal constellation, i.e., 10 degrees of arc, in a westward, or retrograde, direction relative to the stars (Figure 1-1).
Figure 1-2. Spacecraft have provided a new look at the Solar System. The best ground based photographs showed little if any detail compared with photographs of planets from space probes.
(a) Mercury (Pic du Midi Observatory). (b) Venus (Lick Observatory). (c) Moon, Tycho (Lick Observatory). (d) Mars (Catalina Observatory). (e) Jupiter (Catalina Observatory). (f) Saturn (Catalina Observatory). (g) Uranus (Catalina Observatory).
Planets of the Solar System consist of two types: small, dense, inner planets with solid surfaces-Mercury, Venus, Earth with its Moon, and Mars-and large, mainly gaseous, outer planets- Jupiter, Saturn, Uranus, and Neptune, with some satellites as big as the smaller inner planets. Pluto, the outermost known planet, cannot be observed well enough from Earth to be accurately classified, though it is believed to be more like the inner than the outer planets in size.
Between the orbits of Mars and Jupiter, like a transition zone dividing the inner from the outer Solar System, is a wide belt of asteroids, or minor planets, the largest of which, Ceres, is only 1022 km (635 mi.) in diameter. Most asteroids are smaller and many seem to be irregularly shaped.
The first decade of space exploration concentrated on the inner Solar System (Figure 1-2), but at the beginning of the second decade scientists and space technologists started to look at missions to the outer planets. The old fascination of mankind, brilliant Jupiter, became the target for the first mission beyond Mars.
Figure 1-2 (continued). Spacecraft have provided a new look at the Solar System. The best ground based photographs showed little if any detail compared with photographs of planets from space probes.
[Left to right, top to bottom] (h) Mercury (Mariner 10) (i) Venus (Mariner 10) (j) Moon, Tycho (Lunar Orbiter V) (k) Mars (Mariner 9) (l) Jupiter (Pioneer 10)
Figure 1-3. Jupiter is the dominant planet of the Solar System. The terrestrial planets, Mercury, Venus, Earth, and Mars are relatively small compared with the outer giants, Jupiter, Saturn, Uranus and Neptune.
[ 5 ] Dominant Position of Jupiter
Jupiter is an unusual planet by terrestrial standards, both in size and composition. Only slightly denser than water, Jupiter is 317.8 times more massive than Earth. Secondary only to the Sun itself, the giant planet dominates the Solar System (Figure 1-3). Its gravity affects the orbits of other planets and may have prevented the asteroids from coalescing into a planet. Many comets are pulled by Jupiter into distorted orbits, and some of the short period comets appear to have become controlled by Jupiter so that their orbits have their most distant points from the Sun about the distance of the orbit of the giant planet.
Although Jupiter is big (Figure 1-4), it is not big enough to have become a second sun, being too small for its own weight to raise its central temperature high enough for a nuclear reaction to be triggered in its core. However, had Jupiter been 60 to 100 times its present size, our Solar System might have become a binary star system, like so many other stellar systems and nighttime would have been infrequent on Earth. As it is, Jupiter emits several times more energy than it receives.
Figure 1-4. A whole series of Earths could be strung along the equator of Jupiter like beads.
. from the Sun, energy probably derived from continued cooling of the planet following its primordial gravitational collapse eons ago when the Solar System formed. A continuing gravitational collapse at a present rate of 1 millimeter per year could alternatively provide the observed heat output from Jupiter.
Early in the seventeenth century news spread across Europe of an astounding invention by a spectacle-maker, Hans Lippershey of Middelburgh, Holland. Using a convex and a concave lens at opposite ends of a tube, he made remote objects appear nearer. Two men acted on this news and separately constructed telescopes as the new invention was called. Looking at Jupiter they were astounded to discover that the bright planet possessed a system of satellites - an undreamed of condition in the Aristotelean world of Earth-centered philosophy holding sway at that time. In fact, some scientists of that day claimed the luminous objects were defects of the new instrument, not real objects.
Figure 1-5. Jupiter and its four Galilean satellites present a fine sight, even in good field glasses. Some sharp-eyed people claim they can see these satellites with their unaided eyes. The photograph at top of page shows a typical configuration right to left the satellites are: Europa, Ganymede, and Callisto. Io is obscured by the planet. (Catalina Observatory)
Figure 1-6. Each year as the Earth moves around its orbit, the times of eclipse of Jupiter's satellites become late. This is because light takes nearly 16 minutes longer to cross the orbit of the Earth. In 1675 the Danish astronomer Roemer determined the velocity of light from this effect.
The discovery of these satellites of Jupiter (Figure 1-5) is usually accredited to Galilei Galileo, who published the results of an observation made at Padua on January 7, 1610. Some historians claim, however, that it was Simon Marius of Ausbach, Germany, who first observed the Jovian satellites on December 29, 1609 but he did not publish his observation. These satellites were later given the names Io, Europa, Ganymede, and Callisto by Marius, but are often referred to as the Galilean satellites. Today the satellites are frequently identified by the Roman numerals I, II, III, and IV, respectively.
Figure 1-7. The large satellites of Jupiter rival the smaller planets in size. (a) The relative sizes of the satellites. (b) The relative distances from Jupiter.
One of the most important discoveries in physics was made by the Danish astronomer, Ole Roemer, by means of Jupiter's satellites. Astronomers had observed that the eclipses of Jovian satellites occur 16 minutes and 40 seconds late when Jupiter is on the far side of the Sun from the Earth. In 1675, while in Paris, Roemer explained that this delay results from the finite velocity of light. Light traveling across Earth's orbit, when Earth is farthest from Jupiter, takes 16 minutes and 40 seconds to cover the additional distance. He thereby measured the velocity of light as being about 300,000 km ( 186,000 mi.) per second (Figure 1-6).
The Galilean satellites of Jupiter are quite large bodies (Figure 1-7). Two of the satellites, Callisto and Ganymede, are about the size of the planet Mercury, while Io and Europa rival Earth's Moon. All four satellites are easily seen through a pair of field glasses, appearing as star-like objects nearly in a straight line on either side of the disc of the planet because their orbits are viewed almost edgewise from Earth. Some people with acute vision have been able to see the satellites with their unaided eyes-a good test for sharp vision. The best time to do this is when the sky is still faintly light following sunset, before the planet becomes too brilliant in a black sky.
A fifth satellite of Jupiter was not discovered until almost three centuries later - by E. E. Barnard in 1892. Today, Jupiter is known to have at least fourteen satellites-the other ten are much smaller bodies than the four Galilean satellites. The Jovian system thus resembles a miniature solar system, except that the outermost four satellites of Jupiter orbit oppositely to the others, whereas all the planets go around the Sun in the same direction.
Figure 1-8. When superior planets as seen from Earth are on the far side of the Sun they are said to be in superior conjunction (A). When opposite to the Sun in Earth's skies, they are then closest to Earth and said to be in opposition (B). Inferior planets can never be in opposition but instead attain inferior conjunction (C), i. e., are between Earth and Sun.
Solar Orbit of Jupiter and Appearance in Earth's Skies
Ancient astronomers, observing the motions of planets against the background of stars, called them wandering stars. The word "planet" is derived from the Greek word "wanderer." Today we know that all the planets, including the Earth, move around the Sun in approximately circular orbits. Because Jupiter orbits the Sun outside the orbit of the Earth, it is called a superior planet. As seen from Earth, all superior planets appear to move eastward close to the ecliptic-the apparent yearly path of the Sun relative to the stars, which is the projection of the plane of the Earth's orbit, the ecliptic plane, against the stars.
In their solar orbits, planets move completely around the celestial sphere. Since Jupiter takes 11.86 Earth years to orbit the Sun, it also takes this time to move around the star sphere. So, as viewed from Earth, Jupiter moves along the ecliptic year by year progressively entering each of the Zodiacal constellations, as noted by the ancient Babylonian writers of the Enuma Elish.
When a superior planet is directly opposite to the Sun in the sky it is in opposition (Figure 1-8). Earth is between the Sun and the planet which, at this time, shines its brightest in the southern sky at midnight in the northern hemisphere. The planet is closest to Earth, too. Jupiter comes into opposition every 13 months. Inferior planets Mercury and Venus cannot reach opposition because they are always within Earth's orbit. So they cannot appear in the midnight sky but remain relatively close to the Sun as seen from Earth.
Figure 1-9. Because of the relative motions of Earth and Jupiter on their orbits, the Earth sometimes catches up with Jupiter since it moves faster. Then, as seen from Earth, Jupiter appears to move backwards through the sky for several months. A typical loop motion of Jupiter, as shown, covers about one-third of a Zodiacal constellation and was used by the Babylonians to trace 10 degrees in the sky.
Conjunction occurs when a planet is on the part of its orbit directly behind the Sun, as seen from Earth, and is thus not visible in the night sky. The planet is then most distant from Earth. This is referred to as superior conjunction to differentiate from inferior conjunction when a planet, orbiting within the Earth's orbit (i.e., Venus and Mercury), is between the Earth and Sun and is closest to Earth in its orbit.
Because the orbit of a superior planet is outside the orbit of the Earth, and because the Earth moves fastest, there is a period each year around the date of opposition when a superior planet is being overtaken and appears to move backward - toward the west among the stars in what is termed retrograde motion (Figure 1-9).
Figure 1-10. Jupiter presents a magnificent colored globe in the best Earth-based photographs of the giant planet. The various belts and zones are dearly defined and the polar flattening is quite apparent. (Photo.- Catalina Observatory, University of Arizona)
Jupiter measures 133,516 km (82,967 mi.) from pole to pole, compared with Earth's 12,900 km (8,000 mi.). Rotating faster than any other planet in the Solar System, Jupiter turns completely on its axis once in 9 hours 55-1/2 minutes. But the equatorial regions rotate slightly faster than other regions: in 9 hours 50-1/2 minutes. This means that any point on Jupiter's equator moves at 35,400 km (22,000 mi.) per hour compared with 1,600 km (1,000 mi.) per hour for a point on the Earth's equator.
As a consequence of the rapid rotation, the equatorial regions of Jupiter bulge outward under centripetal force to make the equatorial diameter of the visible globe about 9,280 km (5,767 mi.) greater than the polar diameter. Consequently, Jupiter (Figure 1-10) is not a sphere but has an oblate shape, its polar diameter being 94.2 percent of its equatorial diameter. Earth is flattened at the poles but proportionately much less to only 99.66 percent.
Although Jupiter's volume is 1317 times that of Earth, its mass is only just under 318 times Earth's mass. Since Jupiter is much less dense than Earth, it being only one and one-third times as dense as water, it cannot be a solid sphere like the Earth but instead must consist mainly of gas and liquid with possibly a small solid core. At least three-quarters of Jupiter probably consists of the lightest gases, hydrogen and helium the same gases that are most common in the Sun and the stars. Jupiter is probably more like the Sun in basic composition than like the Earth.
The gases methane and ammonia have been detected in Jupiter's atmosphere and small.
Figure 1-11. The belts and zones of Jupiter are permanent enough to be given the names shown here.
. amounts of other gases such as ethane and acetylene. Other gases may be there but are difficult to detect in measurements made directly from Earth.
Seen through a telescope from Earth, Jupiter presents a magnificent sight, a striped banded disc of turbulent clouds with all the stripes parallel to the planet's equator. Large dusky gray regions cap each pole in an amorphous hood. Dark, brown or gray stripes are called belts lighter, yellow-white colored bands between the belts are called zones. All the colors are soft, muted, but quite definite. Many of the belts and zones are permanent enough features to be given names (Figure 1-11).
Over the years, colors on Jupiter are observed to change the zones vary from yellow to white, while the belts vary from gray to reddish brown. The bands fade and darken as well as change color. They may also widen or become narrow and move up and down in latitude, i.e., farther from or closer to the equator.
Some astronomers suggest that the cold tops of the Jovian clouds in the zones consist of ammonia crystals and vapor. Water clouds are also likely but probably form at a level too deep in the atmosphere to be identified from Earth.
A transparent atmosphere rises some 50 to 65 km (30 to 40 mi.) above the cloud tops.
Many smaller features add interesting details to the zones and bands - streaks, wisps, arches, loops, plumes, patches, lumps, spots, festoons. Some are probably knots of clouds. These small features sometimes change form rapidly in the course of days or even of hours. The scale of Jupiter is so vast that even these features are thousands of miles in extent.
The cloud features of Jupiter move around the.
Figure 1-12. On the South Tropical Zone of Jupiter is a Great Red Spot which has intrigued astronomers for centuries. Speculation about the spot ranged from a floating island to a swirling column of gas anchored to some prominent feature on a solid core. (Photo: Catalina Observatory)
. planet at different rates. For example, a great equatorial current sweeps around the planet at 360 km (225 mi.) per hour faster than regions on either side of it. It represents a 20 degree-wide girdle around the planet. In addition, some astronomers have interpreted observations as showing that the clouds move at different speeds at different altitudes.
In the southern hemisphere of Jupiter is an outstanding long oval feature known as the Great Red Spot (Figure 1-12). At present 24,000 km (15,000 mi.) long, it has at times extended almost 48,000 km (30,000 mi.). The spot has intrigued generations of astronomers since first observed and recorded centuries ago. In 1664, during the reign of Charles II, the astronomer Robert Hooke reported seeing a large red spot on Jupiter, which could have been the first observation of the Great Red Spot. This was, indeed, the first record of a scientific discovery from a government research contract. In 1665, Cassini referred to the marking as the "Eye of Jupiter." The spot appeared and vanished at least eight times between the years 1665 and 1708, and became a strikingly conspicuous red object in 1878. Early in 1883, the Great Red Spot faded to become almost invisible and then became distinct again, only to fade once more at the beginning of the present century.
The spot was likened to something floating in the atmosphere of Jupiter early astronomers suggested that it was a raft or an island, since over the centuries the spot drifted around the planet relative to the average movement of the clouds. Sometimes cloud currents have swept around it as though the spot itself were a vortex in the atmosphere. Some scientists postulated that the Great Red Spot represents a column of gas, the center of an enormous whirlpool-like mass of gas rising from deep in the planet to the top of the atmosphere and anchored in some way to the surface far below.
That the Great Red Spot is a hurricane-like structure a fantastic grouping of "thunderstorms" was suggested from recent astronomical investigations prior to the Pioneer mission to Jupiter. Photographs to detect methane revealed that the Great Red Spot is the highest cloud structure on Jupiter and thus implied that the marking might have some internal energy source to push it above the other cloud layers. This would be unlikely if it were a floating mass such as an island, but could be explained by its consisting of a large grouping of thunderstorms-rising air masses.
On Jupiter there are also white spots which are more short lived than the Great Red Spot. They seem to be atmospheric storms, too, and become quite bright for relatively short periods of time (Figure 1-13). These white spots also move relative to the nearby cloud systems.
Jupiter emits three different types of radio waves. These are not like the signals that carry programs on Earth radios but are more akin to the sferics (static or "noise") that interfere with a program when lightning flashes or electric motors are run nearby. The radio noise reaching Earth from Jupiter is greater than that from any other extraterrestrial source except the Sun. The three types are called thermal, decimetric, and decametric radiation.
Figure 1-13. Jupiter often exhibits temporary white spots which suddenly appear, become bright then fade away. This set of ultraviolet photographs from the International Planetary Patrol Program shows the spectacular early growth of a major disturbance in the South Equatorial Belt of Jupiter. North is at the top. The event started as a tiny spot barely detectable in ultraviolet light on June 18 and spread to a size comparable with the Red Spot in less than a week. It is identified (at an age of two days) by the arrow on the image of June 20, where it stands out very clearly. At that time the disturbance was not yet detectable in red photographs of comparable quality. The images in this particular set were obtained at the Mauna Kea Observatory and the Perth Observatory.
The thermal radiation is at wavelengths less than a few centimeters. Decimetric radio waves are from a few centimeters to tens of centimeters in length. Decametric refers to radio waves with wavelengths of tens of meters (Figure 1-14).
Thermal radio waves are produced by molecules moving about in the atmosphere of Jupiter. Decimetric radio waves are produced by electrons moving about - oscillating - above the atmosphere. Decametric radio waves are produced by electrical discharges, like lightning flashes, in the upper atmosphere of Jupiter.
Figure 1-14. Jupiter emits radio waves which have been recorded and measured by radio astronomers for several decades. They are of three main types: thermal, decimetric and decametric. Each has a different origin.
[ 14 ] Scientists observed that the decametric radio signals from Jupiter appeared to be linked in some mysterious way to the orbital motion of Jupiter's closest big satellite, Io. Bursts of electrical energy, somehow triggered by Io, are equivalent to billions of simultaneous lightning flashes on Earth.
Observations of the decimetric radio waves from Jupiter caused scientists to conclude that the planet possesses radiation belts similar to those of Earth in which charged particles are trapped and move under the influence of an intense magnetic field. From the intensity of the radiation it was also concluded that Jupiter's magnetic field must be many times stronger than Earth's field. Thus Jupiter and the Earth are the only two planets of the Solar System known to have strong magnetic fields.
The magnetic field of Jupiter traps protons (nuclei of hydrogen atoms) and electrons that flow through interplanetary space from the Sun and are referred to as the solar wind. These trapped, electrically charged particles move backward and forward across the equator of the planet, forming radiation belts.
The electrons, oscillating along the lines of force of the magnetic field, generate radio waves in a similar fashion to electrons caused to oscillate within the antenna of a radio transmitter.
Jupiter is internally quite different from the inner planets (Figure 1-15).
Astronomers generally agree to a basic internal structure of Jupiter, although they differ in detail and interpretation. The average temperature on the top of the cloud layer is very low by terrestrial standards, probably about 150 degrees Kelvin ( - 189° F). Below the cloud tops the temperature rises steadily. The topmost regions consist of supercold ammonia crystals, ammonia droplets, and ammonia vapor. As temperature rises with depth into the atmosphere, there may be ice crystals, water droplets, and water vapor present. Estimates of the total depth of the Jovian atmosphere vary enormously, from 9 5 to 5,800 km (60 to 3,600 mi.) before a "surface" would be reached. This "surface," however, may be a gradual transition from gaseous to liquid hydrogen rather than a sharp interface between gas and liquid or a solid surface. Modern theories suggest a very deep atmosphere at the bottom of which the pressure, exerted by the weight of all the gas above, is enormous, reaching millions of times Earth's 14 pounds per square inch sea level pressure.
Such great pressure could convert hydrogen into a special form in which it behaves like a metal: it readily conducts both heat and electricity as metals do. So beneath a sea of liquid hydrogen could be a shell of metallic hydrogen (probably liquid because of the high temperature) surrounding a small internal core consisting of rocky material and other metals somewhat the same as the composition of the inner planets, including the Earth. Jupiter's core has been estimated as ten times the mass of the Earth. However, the existence of such a rocky core is still widely debated among planetologists.
Near the center of Jupiter, the temperature might be tens of thousands of degrees and could account for Jupiter radiating into space 2.3 times as much energy as the planet receives from the Sun.
Planets of the Solar System probably formed four to five billion years ago when hosts of small rocky particles and clouds of gas were drawn together by their own gravity. It is believed that after the Sun itself condensed from a primordial nebula, planets of different sizes formed from different concentrations of matter present at various distances from the Sun. Electrical and magnetic forces in the gas clouds or gravitational collapse of the proto solar cloud probably thrust the condensing planets into orbits around the central Sun. Those planets that started to aggregate early scooped up more matter than those which started later and had less free material to collect. Mass distribution in the cloud probably had a lot to do with the resultant masses of the planets.
Figure 1-15. The interior of Jupiter is quite different from the interiors of terrestrial planets such as Earth and Moon.
[ 16 ] Scientific experiments made by space probes that photographed the inner planets and their satellites, coupled with geological evidence on Earth and radar probing to the surface of Venus, indicate that the terrestrial planets have been highly cratered, and this cratering presents evidence of the final stages of planetary accretion (Figure 1-16). On Earth, subsequent changes to the surface through internal heat, plate tectonics, and weathering obliterated nearly all evidence of impact cratering.
Much of the primordial gas was hydrogen the most common material in the universe which consists of a proton and an orbital electron. The Sun, for example, is nearly all hydrogen, as are the stars. Astronomers have also discovered vast clouds of hydrogen in the spaces between the stars.
While it is most probable that the Earth and the other inner planets were never able to attract much hydrogen, they may have possessed some hydrogen in their atmospheres for a relatively short time on the scale of planetary development. Hydrogen atmospheres of the inner planets could have been lost by massive eruptions on the Sun during its early development. Also, the closeness of the terrestrial type planets to the Sun, coupled with their.
Figure 1-17. Heat in an atmosphere drives rising masses of air which on Earth produce thunderstorms. As the air cools in the upper atmosphere it spreads sideways and rotation of the planet causes swirling motions. Internal heat on Jupiter may be producing huge groups of thunderstorms which appear as spots such as the Great Red Spot.
. relatively small gravities, allowed hydrogen to escape into space. But the cooler Jupiter, 565 million km (350 million mi.) beyond Mars, with additionally a much stronger gravity, holds hydrogen in tremendous quantities. So probably do the other large planets: Saturn, Uranus, and Neptune.
Knowledge about these complex atmospheres may help our understanding of Earth's more simple atmosphere. Already the study of dust storms in Mars' very thin, dry atmosphere, and the circulation patterns in Venus' very dense atmosphere, is helping meteorologists understand the dynamics of planetary atmospheres in general.
At some level in the deep atmosphere of Jupiter the temperature should equal that on Earth. At this level ammonia crystals could become liquid ammonia droplets. Water could condense too. Such droplets could rain from the clouds, sometimes frozen into snows of water and ammonia. But the drops and snowflakes could never fall to the surface as they do on Earth. Instead, at warm lower regions of the deep atmosphere, they would probably evaporate and rise back into the clouds.
Such a circulation pattern, somewhat analogous to those that build up violent thunderstorms and tornadoes in Earth's atmosphere (Figure 1-17), would probably give rise to endless violent turbulence in the Jovian atmosphere more violent by far than the thunderstorms of Earth. Accompanying electrical discharges would probably make Earth's lightning flashes mere sparks by comparison. Thus, vertical movements in the atmosphere of Jupiter may provide examples of the most violent storms imaginable. At the same time jet circulations in the [ 18 ] cloud bands and zones may be analogous to Earth's major atmospheric patterns such as the trade winds, tropical convergences and jet streams.
At first thought Jupiter might be considered an inhospitable planet on which life could not survive. This need not necessarily be so. Since there are probably liquid water droplets in an atmosphere of hydrogen, methane and ammonia, Jupiter may provide the same kind of primordial "soup" in which scientists currently believe that life originated on Earth.
Life has been described as an unexplained ability to organize inanimate matter into a living system that perceives, reacts to, and evolves to cope with changes to the physical environment that threaten to destroy its organization. In 1953, a mixture of hydrogen, methane, ammonia, and water vapor the kind of atmosphere Jupiter still retains today and many scientists believe Earth possessed soon after its formation was bombarded in a laboratory with electrical discharges. These were passed through the gas mixture to simulate the effects of bolts of lightning. The electrical energy bound together some of the simple gas molecules into more complex molecules of carbon, hydrogen, nitrogen, and oxygen of the type believed to be the building blocks for living systems (Figure 1-18).
Figure 1-18. By passing electrical sparks through mixtures of hydrogen, methane, ammonia, and water vapor, scientists produced colored amino acids, the building blocks of organic life. The experiment was first performed by Stanley Miller in 1953 and has now been repeated many times elsewhere. These photographs show an experiment at NASA-Ames Research Center's Chemical Evolution Branch. When methane or acetylene, both constituents of the Jovian atmosphere, is sparked in a chamber together with ammonia at the temperature of liquid nitrogen, reddish-brown polymeric material is synthesized. Such processes might be responsible for the colors of the Jovian atmosphere.
[ 19 ] At some point in Earth's history, postulated at about 3.5 billion years ago, something organized the complex carbon-based molecules of Earth's oceans and atmosphere into living systems which were then able to make copies of themselves to reproduce. It is theorized that from then on, by slight changes to subsequent copies, biological evolution produced all the living creatures of Earth, including Man.
The big question is: Has life evolved in the atmosphere of Jupiter? It is known that the temperature may be right at lower elevations in the Jovian atmosphere. It is known that the gas mixture may be suitable. It is known that electrical discharges probably take place. Jupiter could hold a key to the evolution of life, and this key may be found if unmanned probes are sent to the Jovian atmosphere later this century. Such probes are technologically possible today as a result of experience gained with the Pioneer flyby of Jupiter and probes to other planets.
The question of beginnings has always intrigued mankind. How did something appear from nothing and become the physical universe? Man is still far from having satisfactory answers even as to how the Solar System condensed from charged atoms, energetic molecules, and electromagnetic forces of some primeval nebula. How did the various planets evolve their unique differences? How did life originate and flourish on Earth, a planet so different from all the others?
It is not easy to find answers here on Earth since this planet can be studied only in its present stage of evolution, a single frame in the long motion picture of Earth's history as an astronomical body. The single picture does not provide enough information for scientists to be really sure about Earth's past let alone its future. However, other planets may pass through evolutionary history at different rates, and some, such as the Moon and Mercury.
Figure 1-19. Because the Earth's atmosphere selectively absorbs certain wavelengths of light, especially in the infrared and the ultraviolet regions of the spectrum, astronomers obtain only a partial view of planets from the Earth.
. have "fossilized" so that they preserve the ancient record of planetary evolution.
It is not possible to study planets in very great detail by use of telescopes on Earth all the planets are much too far away and, in addition, observations are limited by the screening and distorting effects of the Earth's atmosphere (Figure 1-19). Since planetary probes have been dispatched, astronomers have undoubtedly learned more about the planets during the last ten years than in all the previous centuries of observation from Earth.
Knowledge about these other planets is important to our understanding of our own planet, its.
Figure 1-20. The planet Saturn will be visited by Pioneer 11 in 1979 and later by a more advanced spacecraft, Mariner Jupiter-Saturn. (Photo.: Catalina Observatory, University of Arizona).
. past and its future. Such knowledge and understanding might be vital to the long-term survival of the human species if people are to adapt to inevitable natural and man-caused changes to the Earth's environment. Mankind might be able to predict long-term changes to the terrestrial environment and prepare for them.
In many respects, Jupiter provides a model of what is taking place in the universe at large. Many processes on Jupiter may be similar to those in stars before their nuclear reactions begin. And the great turmoil in Jupiter's processes, coupled with the high speed of planetary rotation, provides an extreme model for the study of jet streams and weather in quieter planetary atmospheres such as the Earth's.
The satellites of Jupiter represent a veritable Solar System in miniature, even to the densities of the satellites, like the planets, decreasing with distance from the central body. Thus, their formation may have paralleled the formation of the Solar System. Astronomers are questioning whether these satellites are Earth-like planetary bodies, or more like giant snowballs. The four outermost satellites, Andrastea, Pan, Poseidon, and Hades, move around Jupiter in a counter direction to most of the Jovian satellites. They could be captured asteroids. Examination of the surfaces of the Jovian satellites by space probes may reveal differences that will throw light upon their origin. So far only the four large Jovian satellites have been seen at close hand, as described later in this book.
The outer Solar System is relatively unknown to Man. Saturn (Figure 1-20), the next planet beyond Jupiter, never approaches closer than 1250 million km (780 million mi.) of Earth while Uranus, the next planet, is almost one billion miles farther away.
Saturn will not be reached by a spacecraft until Pioneer 11 flies by it in September 1979.
Figure 1-21. The gravity of Jupiter, coupled with the planet's orbital motion, can be used in a slingshot technique to speed spacecraft to the outer planets. But first NASA had to find out if the environment of Jupiter could be penetrated without causing the spacecraft to fail.
Yet these big planets of the Solar System are probably of great importance to developing a full understanding of the system's origin. Since they are so distant, they require that spacecraft travel very fast to reach them in reasonable times. Unfortunately, launch vehicles cannot boost spacecraft of practical size to the necessary high velocities. However, by using the gravitational field and orbital motion of Jupiter in a slingshot technique, spacecraft can be swung into more energetic paths to carry them relatively quickly to the outer planets (Figure 1 -21).
Jupiter thus provides a means to explore the outer Solar System. But there is a problem: Jupiter's strong magnetic field traps charged particles in radiation belts that extend out from the planet a greater distance than from Earth to Moon. Without exploring these radiation belts, scientists could not be sure the belts would not damage any spacecraft using Jupiter as a gravity slingshot to the outer planets. If the radiation belts proved to be a serious hazard, the exploration of the outer Solar System might have to wait until more energetic propulsion systems than chemical rockets could be developed, perhaps several decades hence.
Although scientists can tell from the radio waves emitted by the Jovian radiation belts approximately how many electrons are trapped in the belts' they have no way of knowing from Earth how many high energy protons are trapped there, and it is especially the protons that do the damage. The only way to find out is to send a spacecraft to Jupiter to penetrate the radiation belts and measure the protons on the spot and this has been done by the two Pioneers.
Such a mission to Jupiter poses many technical challenges. It extends Man's exploration of the Solar System to a new scale 800 million km (half a billion mi.) to Jupiter compared with only 65 million km (40 million mi.) to Mars. The vast.
Figure 1-22. A problem with visiting the outer planets is the long time needed for radio waves, traveling at 300,000 km (186,000 miles) per second, to travel between Earth and the spacecraft this time is 92 minutes for the round trip by radio from Earth to Jupiter and back.
. distance presents problems of communications not only the diminution of the radio signals, but also the time delay in information traveling to Earth from the spacecraft and the equal time delay for radio commands from Earth to reach the spacecraft (Figure 1-22). This delay makes it necessary for controllers on Earth to become skilled in flying the spacecraft 90 minutes out of step with the spacecraft itself at the distance of Jupiter. Everything has to be planned well in advance with no opportunity to react to and correct for any hazards caused by unknowns.
Figure 1-23. Converting solar power to electrical energy is not practical for small spacecraft at the distance of Jupiter where sunlight carries only one twenty-seventh the energy it does at Earth.
Additionally, because of the great distance traveled from the Sun itself, the sunlight at the distance of Jupiter has an intensity of only one twenty-seventh of that at Earth's distance from the Sun (Figure 1-23). The normal method of supplying electrical power in space by converting sunlight to electricity cannot be used. A spacecraft bound for Jupiter has to carry a nuclear energy source to generate electricity. Also the spacecraft must fly through space for several years before reaching its objective. So new levels of high reliability are mandatory. Moreover, the high velocities needed to reach Jupiter call for a lightweight spacecraft, thereby demanding lightweight design of the spacecraft and all its components and scientific instruments.
Finally, between Mars and Jupiter is the asteroid belt (Figure 1-24), which some theories suggested may be a 280-million-km (175-million-mi.) wide zone of abrasive dust that might seriously damage any spacecraft trying to cross it.
Figure 1-24. Between Mars and Jupiter lies the asteroid belt, which spacecraft must cross if they are to visit the outer solar system. The big question faced was how dangerous would this asteroid belt be to such spacecraft?
Such were the obstacles. But the opportunity to explore the outer Solar System beyond the orbit of Mars beckons strongly, challenging the ingenuity of space technologists. The National Aeronautics and Space Administration accepted the challenge in a double-pronged exploratory program: two spacecraft, Pioneers F and G, were planned to make the assault on Jupiter. Their mission was a journey into the unknown territory of space, truly a pioneer odyssey for an encounter with a giant to open the outer Solar System for mankind. Thus began to unfold early in 1970, the story of an incredible journey to the planet Jupiter and beyond a mission to the most spectacular object in the night skies of Earth, an object that has not only held the attention of mankind since time immemorial, but also offers a doorway to the outer Solar System.
Manhattan Project Shield Window Fragment (1195g)
A truly exceptional, one-of-a-kind artifact from WWII. This enormous fragment of the Manhattan Project Shield Window glass weighs 1,195g (2.63lbs)!
The Manhattan Project Shield window also appears in the Large and Touch versions of the Fourth Edition of the Mini Museum!
The Manhattan Project was the codename for the research and development effort which allowed the United States to rapidly develop a series of atomic breakthroughs during World War II, including the first industrial-scale plutonium production reactor and the first atomic bombs. This enormous project involved over one hundred thousand scientists, engineers, technicians, and construction workers at more than 30 sites across the United States, including well-known locations such as Oak Ridge, Los Alamos, Trinity, and Hanford.
This specimen is a FULL-size leaded glass shield window once installed in the T Plant (221-T) Plutonium Recovery Building, the first and largest of two production bismuth-phosphate chemical separations plants used to extract plutonium from fuel rods irradiated in the Hanford Site’s reactors.
During WWII, engineers at Hanford would look through this glass while extracting plutonium for both the Trinity test on July 16, 1945, and the "Fat Man" atomic bomb used over Nagasaki, Japan on August 9, 1945.
The window was sold during a government surplus auction in the late 1980s as part of the long (and continuing) decommissioning process. The yellow color of the glass is due to a high concentration of lead-oxide (up to 30% in this case), which blocks blue and near-UV spectral frequencies, and also gives the glass its protective qualities.
In addition, to this large fragment, there are a handful of smaller full windows and very large fragments of glass available. As you might suspect, they are very expensive and very heavy. These items are priced by weight and run between $10,000 to $3,400,000 (yes, that's three million).
If you are interested in obtaining one of these incredibly rare items, please contact us directly for details.
LEAD WARNING : The glass is not radioactive but it is comprised of lead-oxide. The glass should be handled with care and only while wearing gloves. Lead is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov .
About the Manhattan Project
For more details about the glass and the Manhattan Project please visit our long-form article "Nothing Would Ever Be the Same: Notes from the Mini Museum."
Above: Photo of the Nagasaki bombing taken by Hiromichi Matsuda (Source: Nagasaki Atomic Bomb Museum)
1623: The Great Conjunction of Jupiter and Saturn
The Great Conjunction of 1623 was a very close conjunction of Jupiter and Saturn. Since that time, many Jupiter – Saturn conjunctions have occurred .
What were the circumstances of that conjunction?
Was the 1623 conjunction observed? (Did anybody see it?)
2016, August 27: The Venus-Jupiter conjunction
The Venus-Jupiter conjunction of August 27, 2016 had nearly the same separation as the predicted separation of the Jupiter-Saturn Great Conjunction of December 21, 2020.
The Jupiter – Saturn conjunction of 1623 occurred in the wake of the invention of the telescope, so observing was in its infancy yet, the sky was full of planetary activity. A partial lunar eclipse (April 15, 1623) was visible throughout the Americas and in Central Europe, where the moon was setting as the eclipse reached its 90% magnitude. Venus passed Jupiter and Saturn in late June and Mercury passed the planetary pair less than two weeks later, when the planets were about 22° east of the sun. With the inner planets in the vicinity of the impending Great Conjunction and Mars reaching opposition (July 4, 1623), surely sky watchers were observing the planets’ locations to test and revise their planetary motion equations.
- Feature article on about the 2020 Great Conjunction on When the Curves Line Up
- Full-length semi-technical article about the Great Conjunction of 2020.
By the time of the Great Conjunction on July 16, 1623, the planetary pair was less than 13° east of the sun. By Civil Twilight, the pair was near the horizon at mid-latitudes. Without optical help, the conjunction likely went unobserved, even for those with recently minted telescopes. Even then, the observer needed some luck to find the conjunction.
In later years, two British publications stated that the 1623 conjunction was not observed. In 1886, the Monthly Notices of the Royal Astronomical Society state that the February 8, 1683, Jupiter – Saturn conjunction was the first observed “since the invention of the telescope” and that the 1623 passing went unobserved. The same statement was written in the Journal of the British Astronomical Association in 1897. Perhaps the conjunction was observed without optical aid and recorded from more southerly latitudes, when the planets were higher in the sky.
Did the two British publications make the statements out of parochialism, rather than from factual observations made around Europe regarding the first Great Conjunction observed with a telescope, or was this the first time that the conjunction fit into an eyepiece since the telescope’s invention? The February 24, 1643, conjunction was visible in the western sky during mid-twilight as well as the October 16, 1663, conjunction. At the second conjunction the planets were about 10° up in the southwest at one hour after sunset. However, at both conjunctions, the planets were nearly 1° apart. At the 1683 conjunction, the planets were close, about 0.2° apart, twice the separation of the upcoming event. While the two previous conjunctions were visible to the naked eye and individually in a telescopic eyepiece, the 1683 conjunction was the first observed with both planets simultaneously in an eyepiece. With a separation of 0.1°, the 1623 conjunction would have fit into telescopes eyepieces of that generation, but certainly those early telescopes were unwieldy to steer and hold steady, and the telescope operator needed some persistence during the days preceding the conjunction to follow the converging planets into bright twilight while they had sufficient altitude to observe them. So, while the British publications are accurate about viewing the planets simultaneously through a telescope, the two preceding conjunctions were visible to the unaided eye and individually through a telescope, and this does not speak to the issue as whether the 1623 conjunction when unobserved across all of humanity.
In recent times, Great Conjunctions occurred February 18, 1961 followed by a triple conjunction of the two planets in 1980-81 and the last occurred May 30, 2000, although this was difficult to observe.
Read the Great Conjunction of 2020 Article.
November 29, 2020 Update: Patrick Hartigan from Rice University has generated a list of Great Conjunctions spanning 3000 years. The dates may be off a day or two from the actual conjunction dates. His list includes the following close conjunctions:
- March, 1226, separation 2.1′, one-third the separation of 2020
- August, 1563, Separation 6.8′, slightly larger than 2020
- July,1623, separation 5.2′, slightly less than 2020, but not likely visible.
So how do we properly describe this? Closest since 1623? Yes, although not likely observed. Closest since 1563? Yes. This was easily visible in the morning sky. Closest observable since 1226? Yes, this was clearly visible as well.
A common pattern in React is for a component to return multiple elements. Fragments let you group a list of children without adding extra nodes to the DOM.
There is also a new short syntax for declaring them.
A common pattern is for a component to return a list of children. Take this example React snippet:
<Columns /> would need to return multiple <td> elements in order for the rendered HTML to be valid. If a parent div was used inside the render() of <Columns /> , then the resulting HTML will be invalid.
results in a <Table /> output of:
Fragments solve this problem.
which results in a correct <Table /> output of:
There is a new, shorter syntax you can use for declaring fragments. It looks like empty tags:
You can use <></> the same way you’d use any other element except that it doesn’t support keys or attributes.
Fragments declared with the explicit <React.Fragment> syntax may have keys. A use case for this is mapping a collection to an array of fragments — for example, to create a description list:
key is the only attribute that can be passed to Fragment . In the future, we may add support for additional attributes, such as event handlers.