Are you ready for July? The big ticket space event of the year is coming right up, as NASA’s New Horizons spacecraft is set to make its historic flyby targeting a pass 12,500 kilometres (7,750 miles) from the surface of Pluto at 11:50 UT on July 14th. Already, Pluto and its moons are growing sharper by the day, as New Horizons closes in on Pluto at over 14 kilometres per second.
And the good news is, this flyby of the distant world occurs just eight days after Pluto reaches opposition for 2015, marking a prime season to track down the distant world with a telescope.
Pluto and its large moon Charon are snapping into focus as we reach the two week out mark. Discovered in 1930 by astronomer Clyde Tombaugh while working at the Lowell observatory in Flagstaff Arizona, these far off worlds are about to become real places in the public imagination. It’s going to be an exciting—if tense—few weeks, as new details and features are seen on these brave new worlds, all calling out for names. Are there undiscovered moons? Does Pluto host a ring system? What is the history of Pluto?
A wide field view of Sagittarius and Pluto with inset (see chart above) Image credit: Starry Night education software
Hunting for Pluto with a backyard telescope is difficult, though not impossible. We suggest an aperture of 10-inches or greater, though the tiny world has been reliably spotted using a 6-inch reflector. Pluto reaches opposition on July 6th at 10:00 UT/6:00 AM EDT, marking a period when it will rise opposite to the setting Sun and transit highest near local midnight. Pluto spends all of 2015 in the constellation Sagittarius. This presents two difficulties: 1). We’re currently looking at Pluto against the very star-rich backdrop towards the center of the Milky Way Galaxy, and 2). Its southerly declination means that it won’t really ‘clear the weeds’ much for northern hemisphere observers.
But don’t despair. With a good finder chart and patience, you too can cross Pluto off of your life list. In fact, the month of July sees Pluto thread its way between the 27’ wide +4th magnitude pair Xi Sagittarii, making a great guidepost to spot the 14th magnitude world.
Don’t own a telescope? You can still wave in the general direction of New Horizons and Pluto on the evening of July 1st, using the nearby Full Moon as a guide:
Pluto near the Full Moon on the night of July 1st. Image credit: Stellarium
Pluto orbits the Sun once every 248 years, and reaches opposition every 367 days. A testament to this slow motion is the fact that Mr. Tombaugh first spied Pluto south of the star Delta Gemini, and it has only moved as far as Sagittarius in the intervening 85 years. Pluto also passed perihelion in 1989, when it was about half a magnitude brighter than it currently is now. Pluto’s distance from the Sun varies from 30 AU to 49 AU, and Pluto will reach aphelion just under a century from now on 2114.
Pluto versus Charon at greatest elongation. Image credit: Starry Night Education software
Up for a challenge? Hunting down Pluto’s elusive moon Charon is an ultimate feat of astronomical athletics. Amazingly, this has actually been done before, as reported here in 2008 on Universe Today.
Pluto… and Charon! Image credit: Antonello Medugno and Daniele Gasparri
Charon reaches greatest elongation 0.8” from Pluto once every three days. Shining at +16th magnitude, Charon is a faint catch, though not impossible. We’re already seeing supporting evidence from early New Horizons images that these two worlds stand in stark contrast, with dark Charon covered in relatively low albedo dirty water-ice and while brighter Pluto is coated with reflective methane snow.
Greatest elongation times and dates for Charon through the month of July 2015. Credit: Ed Kotapish
The current forward-looking view from New Horizons of Pluto is amazing to consider. As of July 1st, the spacecraft is 0.11 AU (17 million kilometres) from Pluto and closing, and the world appears as a +1.7 magnitude object about 30 arc seconds across. The views of Pluto are courtesy of New Horizons’ LORRI (Long Range Reconnaissance Imager), which in many ways is very similar to a familiar backyard 8-inch Schmidt-Cassegrain telescope. It’s interesting to note that the views we’re currently getting very closely resemble amateur views of Mars near opposition, though we suspect that will change radically in about a week.
And it will take months for all of the New Horizons data to make its way back to Earth. The real nail-biter will be the 20 hour period of close rendezvous on July 14th, a period in which the spacecraft will have to acquire Pluto and Charon, do its swift ballet act, and carry out key observations—all on its own before phoning home. This will very likely be the only mission to Pluto in our lifetimes, as New Horizons will head out to rendezvous with several Kuiper Belt Objects in the 2020 time frame before joining the Voyager I & II and Pioneer 10 & 11 spacecraft in an orbit around the Milky Way Galaxy.
Pluto (marked) from the morning of June 25th, 2015. Image credit and copyright: Jim Hendrickson
Just think, in less than a few weeks time, science writers will (at last!) have a wealth of Plutonian imagery to choose from courtesy of New Horizons, and not just a few blurry pics and artist’s conceptions that we’ve recycled for decades… let us know of your tales of tribulation and triumph as you attempt to hunt down Pluto this summer!
Pluto with its enigmatic "crater" photographed on June 27. The apparent row of three depressions near the bottom of the globe are most likely artifacts from processing. Credit:
You’re probably as eager as I am for new images of Pluto and Ceres as both New Horizons and Dawn push ever closer to their respective little worlds. Recent photos, of which there are only a few, reveal some wild new features including what appears to a large crater on Pluto.
The latest photo of Pluto (lower left) and its largest moon Charon taken on June 29. A large possible crater-like feature is visible at lower right. Charon shows intriguing dark markings. Pluto’s diameter is 1,471 miles (700 miles smaller than Earth’s Moon); Charon is 750 miles across. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
In the end, this apparent large impact might only be a contrast effect or worse, an artifact of over-processing, but there’s no denying its strong resemblance to foreshortened, shadow-filled craters seen on the Moon and other moons. It’s also encouraging that an earlier photo from June 27 shows the same feature. But the “crater” is just so … big! Its size seems disproportionate to the Pluto’s globe and recalls Saturn’s 246-mile-wide moon Mimas with its 81-mile-wide crater Herschel.
Pluto (right) and Charon, showing an unusual dark north polar cap or “anti-cap” in a photo taken by New Horizons’ long-range camera on June 19, 2015. The two were about 20 million miles away at the time. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Astronomers speculate the impact that gouged out Herschel came perilously close to shattering the moon to pieces. If it does turn out to be an crater, Pluto’s surface opposite the impact will likely show many fractures. Not to be outdone, the dwarf planet’s largest moon, Charon, is starting to show a personality of its own with a prominent dark north polar cap.
Since polar caps are normally bright, icy features, some have referred to this one as an “anti-polar cap”. Speaking of ice, the bright rim around Pluto in the photo above may be nitrogen frost condensing out of Pluto’s scant atmosphere as it slowly recedes from the Sun. Think how cold it must have to get for nitrogen to freeze out. How about -346° F (-210° C)! For new images of the Pluto system, be sure to check the New Horizons LORRI gallery page.
Dawn took this photo of an intriguing pyramidal mountain (top center) on Ceres on June 14 from an altitude of 2,700 miles. It rises 3 miles above a relatively smooth surface. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Closer to home, new photos of Ceres show a peculiar, pyramid-shaped mountain towering 3 miles (5 km) high from a relatively smooth region between two large craters. Mountains poking from crater floors aren’t unusual. They’re tossed up after the crust later rebounds after a large impact. What makes this one unusual is the lack of an associated crater. Moreover, the mountain’s pale hue could indicate it’s younger than the surrounding landscape. As far as we can tell, it’s the only tall mountain on the face of the dwarf planet.
Another more overhead view of the mountain (right of center) taken by NASA’s Dawn probe on June 6. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDACropped version of the photo above. Notice the striations on the mountainside possibly from landslides. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
The Dawn team also photographed that cluster of white spots again, this time with a very shot exposure in to eke out more details. What do you think? If you’re as interested in asteroids as I am, Italian astrophysicist Gianluca Masi, a frequent photo contributor to Universe Today, will host a special live Asteroid Day event today starting at 6 p.m. CDT (23:00 UT). Masi will review near-Earth asteroids, explain discovery techniques and observe several in real time.
The Dawn team greatly underexposed Ceres in order to tease out more details from the white spot cluster in this image made on June 15 from 2,700 miles altitude. I’ve lightened the limb of Ceres to provide context. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDADawn photographed the large crater at left along with an interesting chain of craters and possible fault or collapse structures. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Bootprint in the lunar regolith left behing by the Apollo 11 crew. Credit: NASA
On July 20th, 1969, history was made when men walked on the Moon for the very first time. The result of almost a decade’s worth of preparation, billions of dollars of investment, strenuous technical development and endless training, the Moon Landing was the high point of the Space Age and the single greatest accomplishment ever made.
Because they were the first men to walk on the Moon, Neil Armstrong and Edwin “Buzz” Aldrin are forever written in history. And since that time, only ten men have had the honor of following in their footsteps. But with plans to return to the Moon, a new generation of lunar explorers is sure to be coming soon. So just who were these twelve men who walked on the Moon?
Prelude to the Moon Landing:
Before the historic Apollo 11 mission and Moon Landing took place, NASA conducted two manned missions to test the Apollo spacecraft and the Saturn V rockets that would be responsible for bringing astronauts to the lunar surface. The Apollo 8 mission – which took place on Dec. 21st, 1968 – would be the first time a spacecraft left Earth orbit, orbited the Moon, and then returned safely to Earth.
During the mission, the three-astronaut crew – Commander Frank Borman, Command Module Pilot James Lovell, and Lunar Module Pilot William Anders – spent three days flying to the Moon, then completed 10 circumlunar orbits in the course of 20 hours before returning to Earth on Dec. 27th.
During one of their lunar orbits, the crew made a Christmas Eve television broadcast where they read the first 10 verses from the Book of Genesis. At the time, the broadcast was the most watched TV program in history, and the crew was named Time magazine’s “Men of the Year” for 1968 upon their return.
On May 18th, 1969, in what was described as a “dress rehearsal” for a lunar landing, the Apollo 10 mission blasted off. This involved testing all the components and procedures that would be used for the sake of the Moon Landing.
The crew – which consisted of Thomas P. Stafford as Commander, John W. Young as the Command Module Pilot, and Eugene A. Cernan as the Lunar Module Pilot – flew to the Moon and passed within 15.6 km (8.4 nautical miles) of the lunar surface before returning home.
Apollo 11:
On July 16th, 1969, at 13:32:00 UTC (9:32:00 a.m. EDT local time) the historic Apollo 11 mission took off from the Kennedy Space Center in Florida. The crew consisted of Neil Armstrong as the Commander, Michael Collins as the Command Module Pilot), and Edwin “Buzz” Aldrin as the Lunar Module Pilot.
Neil Armstrong and Buzz Aldrin plant the US flag on the Lunar Surface during the first human moonwalk in history on July 20, 1969. Credit: NASA
On July 19th at 17:21:50 UTC, Apollo 11 passed behind the Moon and fired its service propulsion engine to enter lunar orbit. On the following day, the Lunar Module Eagle separated from the Command Module Columbia, and Armstrong and Aldrin commenced their Lunar descent.
Taking manual control of the Lunar Module, Armstrong brought them down to a landing spot in the Sea of Tranquility, and then announced their arrival by saying: “Houston, Tranquility Base here. The Eagle has landed.” After conducting post-landing checks and depressurizing the cabin, Armstrong and Aldrin began descending the ladder to the lunar surface.
When he reached the bottom of the ladder, Armstrong said: “I’m going to step off the LEM now” (Lunar Excursion Module). He then turned and set his left boot on the surface of the Moon at 2:56 UTC July 21st, 1969, and spoke the famous words “That’s one small step for [a] man, one giant leap for mankind.”
About 20 minutes after the first step, Aldrin joined Armstrong on the surface, and the two men began conducting the planned surface operations. In so doing, they became the first and second humans to set foot on the Moon.
Apollo 12:
Four months later, on November 14th, 1969, the Apollo 12 mission took off from the Kennedy Space Center. Crewed by Commander Charles “Pete” Conrad, Lunar Module Pilot Alan L. Bean and Command Module Pilot Richard F. Gordon, this mission would be the second time astronauts would walk on the Moon.
Ten days later, the Lunar Module touched down without incident on the southeastern portion of the Ocean of Storms. When Conrad and Bean reached the lunar surface, Bean’s first words were: “Whoopie! Man, that may have been a small one step for Neil, but that’s a long one for me.” In the course of conducting a Extra-Vehicular Activities (EVAs), the two astronauts became the third and fourth men to walk on the Moon.
The crew also brought the first color television camera to film the mission, but transmission was lost after Bean accidentally destroyed the camera by pointing it at the Sun. On one of the two EVAs, the crew visited the Surveyor3 unmanned probe, which had landed in the Ocean of Storms on April 20th, 1967. The mission ended on November 24th with a successful splashdown.
Pete Conrad descends from the Lunar Module (LM). Credit: NASA
Apollo 14:
TheApollo 13 mission was intended to be the third lunar landing; but unfortunately, the explosion of the oxygen tank aboard the Service Module forced the crew to abort the landing. Using the Lunar Module as a “lifeboat”, the crew executed a single loop around the Moon before safely making it back to Earth.
As a result, Apollo 14 would be the third manned mission to the lunar surface, crewed by veteran Alan Shepard (as Commander), Stuart Roosa as Command Module Pilot, and Edgar Mitchell as Lunar Module Pilot. The mission launched on January 31st, 1971 and Shepard and Mitchell made their lunar landing on February 5th in the Fra Mauro formation, which had originally been targeted for the Apollo 13 mission.
During two lunar EVAs, Shepard and Mitchell became the fifth and sixth men to walk on the Moon. They also collected 42 kilograms (93 lb) of Moon rocks and conducted several surface experiments – which including seismic studies. During the 33 hours they spent on the Moon (9½ hours of which were dedicated to EVAs), Shepard famously hit two golf balls on the lunar surface with a makeshift club he had brought from Earth.
Shepard poses next to the American flag on the Moon during Apollo 14. Credit: NASA
Apollo 15:
The seventh and eight men to walk on the Moon were David R. Scott, and James B. Irwin – the Commander and Lunar Module Pilot of the Apollo 15 mission. This mission began on July 26th, 1971, and landed near Hadley rille – in an area of the Mare Imbrium called Palus Putredinus (Marsh of Decay) – on August 7th.
The mission was the first time a crew explored the lunar surface using a Lunar Vehicular Rover (LVR), which allowed them to travel farther and faster from the Lunar Module (LM) than was ever before possible. In the course of conducting multiple EVAs, the crew collected 77 kilograms (170 lb) of lunar surface material.
While in orbit, the crew also deployed a sub-satellite, and used it and the Scientific Instrument Module (SIM) to study the lunar surface with a panoramic camera, a gamma-ray spectrometer, a mapping camera, a laser altimeter, and a mass spectrometer. At the time, NASA hailed the mission as “the most successful manned flight ever achieved.”
Image from Apollo 15, taken by Commander David Scott at the end of EVA-1. Credit: NASA
Apollo 16:
It was during the Apollo 16 mission – the penultimate manned lunar mission – that the ninth and tenth men were to walk on the Moon. After launching from the Kennedy Space Center on April 16th, 1972, the mission arrived on the lunar surface by April 21st. Over the course of three days, Commander John Young and Lunar Module Pilot Charles Duke conducted three EVAs, totaling 20 hours and 14 minutes on the lunar surface.
The mission was also the second occasion where an LVR was used, and Young and Duke collected 95.8 kilograms (211 lb) of lunar samples for return to Earth, while Command Module Pilot Ken Mattingly orbited in the Command/Service Module (CSM) above to perform observations.
Apollo 16’s landing spot in the highlands was chosen to allow the astronauts to gather geologically older lunar material than the samples obtained in the first four landings. Because of this, samples from the Descartes Cayley Formations disproved a hypothesis that the formations were volcanic in origin. The Apollo 16 crew also released a subsatellite from the Service Module before breaking orbit and returning to Earth, making splashdown by April 27th.
John W. Young standing next to the LM Orion during the Apollo 16 mission, April 21, 1972. Credit: NASA
Apollo 17:
The last of the Apollo missions, and the final time astronauts would set foot on the moon, began at 12:33 am Eastern Standard Time (EST) on December 7th, 1972. The mission was crewed by Eugene Cernan, Ronald Evans, and Harrison Schmitt – in the roles of Commander, Command Module Pilot and Lunar Module Pilot, respectively.
After reaching the lunar surface, Cernan and Schmitt conducted EVAs and became the eleventh and twelve men to walk on the lunar surface. The mission also broke several records set by previous flights, which included the longest manned lunar landing flight, the longest total lunar surface extravehicular activities, the largest lunar sample return, and the longest time in lunar orbit.
While Evans remained in lunar orbit above in the Command/Service Module (CSM), Cernan and Schmitt spent just over three days on the lunar surface in the Taurus–Littrow valley, conducting three periods of extra-vehicular activity with an LRV, collecting lunar samples and deploying scientific instruments. Cernan, After an approximately 12 day mission, Evans, and Schmitt returned to Earth.
Astronaut Eugene A. Cernan, commander of the Apollo 17 mission, using a Lunar Roving Vehicle (LRV) for an EVA on December 11th 1972. Credit: NASA
Apollo 17 remains the most recent manned Moon mission and also the last time humans have traveled beyond low Earth orbit. Until such time as astronauts begin to go to the Moon again (or manned missions are made to Mars) these twelve men – Neil Armstrong, Edwin “Buzz” Aldrin, Charles “Pete” Conrad, Alan L. Bean, Alan Shepard, Edgar Mitchell, David R. Scott, James B. Irwin, John Young, Charles Duke, Eugene Cernan, and Harrison Schmitt – will remain the only human beings to ever walk on a celestial body other than Earth.
Venus and Jupiter at dusk over Australia's Outback on June 27, 2015. Credit: Joseph Brimacombe
The year’s finest conjunction is upon us. Chances are you’ve been watching Venus and Jupiter at dusk for some time.
Like two lovers in a long courtship, they’ve been slowly approaching one another for the past several months and will finally reach their minimum separation of just over 1/4° (half a Full Moon diameter) Tuesday evening June 30.
The view facing west-northwest about 50 minutes after sunset on June 30 when Venus and Jupiter will be at their closest. If bad weather moves in, they’ll be nearly as close tonight (June 29) and July 1. Two celestial bodies are said to be in conjunction when they have the same right ascension or “longitude”and line up one atop the other. Source: Stellarium
Most of us thrill to see a single bright planet let alone the two brightest so close together. That’s what makes this a very special conjunction. Conjunctions are actually fairly common with a dozen or more planet-to-planet events a year and 7 or 8 Moon-planet match-ups a month. It’s easy to see why.
From our perspective in the relatively flat plane of the Solar System we watch the planets cycle around the Sun projected against the backdrop of the zodiac constellations. They – and the Moon – follow the ecliptic and occasionally pass one another in the sky to make for wonderful conjunctions. Credit: Bob King
All eight planets travel the same celestial highway around the sky called the ecliptic but at different rates depending upon their distance from the Sun. Distant Saturn and Neptune travel more slowly than closer-in planets like Mercury and Mars. Over time, we see them lap one another in the sky, pairing up for a week or so and inspiring the gaze of those lucky enough to look up. After these brief trysts, the worlds part ways and move on to future engagements.
Venus and Jupiter above St. Peter’s Dome in Rome on Sunday June 28, 2015. Details: Canon 7D Mark II DSLR, with a 17-55-f/2.8 lens at 24mm f/4 and exposure time was 1/40″. Credit: Gianluca Masi
In many conjunctions, the planets or the Moon and planet are relatively far apart. They may catch the eye but aren’t exactly jaw-dropping events. The most striking conjunctions involve close pairings of the brightest planets. Occasionally, the Moon joins the fray, intensifying the beauty of the scene even more.
As Venus orbits interior to Earth’s orbit, its apparent distance from the Sun (and phase) changes. Since June 6, the planet’s separation from the Sun in the sky has been shrinking and will reach a minimum on August 15, when the planet is directly between the Sun and Earth. Credit: Bob King
While moving planets are behind many conjunctions, they often don’t do it alone. Earth’s orbital motion around the Sun helps move things along. This week’s event is a perfect example. Venus is currently moving away from Jupiter in the sky but not quickly enough to avoid the encounter. Each night, its apparent distance from the Sun decreases by small increments and the planet loses altitude. Meanwhile, Jupiter’s moving away from Venus, traveling east toward Regulus as it orbits around the Sun.
So how can they possibly get together? Earth to the rescue! Every day, our planet travels some 1.6 million miles in our orbit, completing 584 million miles in one year. We see this movement reflected in the rising and setting times of the stars and planets.
View of Earth’s orbit seen from above the northern hemisphere. As our planet moves to the left or counterclockwise around the Sun, the background constellations appear to drift to the right or westward. This causes constellations and planets in the western sky to gradually drop lower every night, while those in the east rise higher. Credit: Bob King
Every night, the stars rise four minutes earlier than the night before. Over days and weeks, the minutes accumulate into hours. When stars rise earlier in the east, those in the west set earlier. In time, all stars and planets drift westward due to Earth’s revolution around the Sun.
It’s this seasonal drift that “pushes” Jupiter westward to eventually overtake a reluctant Venus. Despite appearances, in this particular conjunction, both planets are really fleeing one another!
Johannes Kepler’s depiction of the conjunction of Mercury (left), Jupiter and Saturn shortly before Christmas in the year 1603. He believed a similar conjunction or series of conjunctions – the Christmas Star – may have heralded the birth of Christ.
We’re attuned to unusual planetary groupings just as our ancestors were. While they might have seen a planetary alignment as a portent of kingly succession or ill fortune in battle, we’re free to appreciate them for their sheer beauty. Not to say that some might still read a message or experience a personal revelation at the sight. There’s something in us that sees special meaning in celestial alignments. We’re good at sensing change in our environment, so we sit up and take notice when unusual sky events occur like eclipses, bright comets and close pairings of the Moon and planets.
Venus and Jupiter over the next few nights facing west at dusk. Times and separations shown for central North America at 10 p.m. CDT. 30 minutes of arc or 30′ equals one Full Moon diameter. Source: Stellarium
You can watch the Jupiter-Venus conjunction several different ways. Naked eye of course is easiest. Just face west starting about an hour after sunset and drink it in. My mom, who’s almost 90, will be watching from her front step. Binoculars will add extra brilliance to the sight and perhaps show several moons of Jupiter.
The view through a small telescope of Jupiter (top) and Venus on June 30 around 9:30 p.m. CDT. Jupiter’s moons are G = Ganymede, E = Europa, I = Io and C = Callisto. Source: Stellarium
If you have a telescope, I encourage you to point it at the planetary doublet. Even a small scope will let you see Jupiter’s two dark, horizontal stripes — the North and South Equatorial Belts — and several moons. Venus will appear as a pure white, thick crescent 32 arc seconds across virtually identical in apparent size to Jupiter. To tame Venus’ glare, start observing early when the sky is still flush with pale blue twilight. I think the best part will be seeing both planets in the same field of view even at moderate magnification — a rare sight!
To capture an image of these shiny baubles try using your cellphone. For many, that’s the only camera we have. First, find a pretty scene to frame the pair. Hold your phone rock-solid steady against a post or building and click away starting about an hour after sundown when the two planets have good contrast with the sky, but with light still about. If your pictures appear too dark or light, manually adjust the exposure. Here’s a youtube video on how to do it with an iPhone.
Jupiter and Venus at dusk on June 26. This is a 6-second exposure at f/2.8 and ISO 80 taken with a basic point-and-shoot digital camera. I braced the camera on top of a mailbox and stuck my phone underneath to prop up the lens. Credit: Bob King
Point-and-shoot camera owners should place their camera on a tripod, adjust the ISO or sensitivity to 100, open the aperture or f/stop to its widest setting (f/2.8 or f/4), autofocus on the planets and expose from 5-10 seconds in mid-twilight or about 1 hour to 90 minutes after sunset. The low ISO is necessary to keep the images from turning grainy. High-end digital SLR cameras have no such limitations and can be used at ISO 1600 or higher. As always, review the back screen to make sure you’re exposing properly.
I’m not a harmonic convergence kind of guy, but I believe this week’s grand conjunction, visible from so many places on Earth, will stir a few souls and help us appreciate this life that much more.
Portrait of Galileo Galilei by Giusto Sustermans (1636). Credit: nmm.ac.uk
Galileo is considered one of the greatest astronomers of all time. His discovery of Jupiter’s major moons (Io, Europa, Ganymede and Callisto) revolutionized astronomy and helped speed the acceptance of the Copernican Model of the universe. However, Galileo is also known for the numerous scientific inventions he made during his lifetime.
These included his famous telescope, but also a series of devices that would have a profound impact on surveying, the use of artillery, the development of clocks, and meteorology. Galileo created many of these in order to earn extra money to support his family. But ultimately, they would help cement his reputation as the man who challenged centuries worth of previously-held notions and revolutionized the sciences.
Hydrostatic Balance:
Inspired by the story of Archimedes’ and his “Eureka” moment, Galileo began looking into how jewelers weighed precious metals in air, and then by displacement, to determine their specific gravity. In 1586, at the age of 22, he theorized of a better method, which he described in a treatise entitled La Bilancetta (or “The Little Balance”).
In this tract, he described an accurate balance for weighing things in air and water, in which the part of the arm on which the counter weight was hung was wrapped with metal wire. The amount by which the counterweight had to be moved when weighing in water could then be determined very accurately by counting the number of turns of the wire. In so doing, the proportion of metals like gold to silver in the object could be read off directly.
Galileo’s “La Billancetta”, in which he describes a new method of measuring the specific gravity of precious metals. Credit: Museo Galileo
Galileo’s Pump:
In 1592, Galileo was appointed professor of mathematics at the University of Padua and made frequent trips to the Arsenal – the inner harbor where Venetian ships were fitted out. The Arsenal had been a place of practical invention and innovation for centuries, and Galileo used the opportunity to study mechanical devices in detail.
In 1593, he was consulted on the placement of oars in galleys and submitted a report in which he treated the oar as a lever and correctly made the water the fulcrum. A year later the Venetian Senate awarded him a patent for a device for raising water that relied on a single horse for operation. This became the basis of modern pumps.
To some, Galileo’s Pump was a merely an improvement on the Archimedes Screw, which was first developed in the third century BCE and patented in the Venetian Republic in 1567. However, there is apparent evidence connecting Galileo’s invention to Archimedes earlier and less sophisticated design.
Pendulum Clock:
During the 16th century, Aristotelian physics was still the predominant way of explaining the behavior of bodies near the Earth. For example, it was believed that heavy bodies sought their natural place or rest – i.e at the center of things. As a result, no means existed to explain the behavior of pendulums, where a heavy body suspended from a rope would swing back and forth and not seek rest in the middle.
Spring driven pendulum clock, designed by Huygens, built by instrument maker Salomon Coster (1657),[96] and copy of the Horologium Oscillatorium,[97] Museum Boerhaave, Leiden.
Already, Galileo had conducted experiments that demonstrated that heavier bodies did not fall faster than lighter ones – another belief consistent with Aristotelian theory. In addition, he also demonstrated that objects thrown into the air travel in parabolic arcs. Based on this and his fascination with the back and forth motion of a suspended weight, he began to research pendulums in 1588.
In 1602, he explained his observations in a letter to a friend, in which he described the principle of isochronism. According to Galileo, this principle asserted that the time it takes for the pendulum to swing is not linked to the arc of the pendulum, but rather the pendulum’s length. Comparing two pendulum’s of similar length, Galileo demonstrated that they would swing at the same speed, despite being pulled at different lengths.
According to Vincenzo Vivian, one of Galileo’s contemporaries, it was in 1641 while under house arrest that Galileo created a design for a pendulum clock. Unfortunately, being blind at the time, he was unable to complete it before his death in 1642. As a result, Christiaan Huygens’ publication of Horologrium Oscillatoriumin 1657 is recognized as the first recorded proposal for a pendulum clock.
The Sector:
The cannon, which was first introduced to Europe in 1325, had become a mainstay of war by Galileo’s time. Having become more sophisticated and mobile, gunners needed instrumentation to help them coordinate and calculate their fire. As such, between 1595 and 1598, Galileo devised and improved a geometric and military compass for use by gunners and surveyors.
The Sector, a military/geometric compass designed by Galileo Galilei. Credit: chsi.harvard.edu
Existing gunner’s compasses relied on two arms at right angles and a circular scale with a plumb line to determine elevations. Meanwhile, mathematical compasses, or dividers, developed during this time were designed with various useful scales on their legs. Galileo combined the uses of both instruments, designing a compass or sector that had many useful scales engraved on its legs that could be used for a variety of purposes.
In addition to offering a new and safer way for gunners to elevate their cannons accurately, it also offered a quicker way of computing the amount of gunpowder needed based on the size and material of the cannonball. As a geometric instrument, it enabled the construction of any regular polygon, computation of the area of any polygon or circular sector, and a variety of other calculations.
Galileo’s Thermometer:
During the late 16th century, there existed no practical means for scientists to measure heat and temperature. Attempts to rectify this within the Venetian intelligentsia resulted in the thermoscope, an instrument that built on the idea of the expansion of air due to the presence of heat.
In ca. 1593, Galileo constructed his own version of a thermoscope that relied on the expansion and contraction of air in a bulb to move water in an attached tube. Over time, he and his colleagues worked to develop a numerical scale that would measure the heat based on the expansion of the water inside the tube.
Galileo Galilei’s telescope with his handwritten note specifying the magnifying power of the lens, at an exhibition at The Franklin Institute in Philadelphia. Credit: AP Photo/Matt Rourke
And while it would take another century before scientists – such as Daniel G. Fahrenheit and Anders Celsius – began developing universal temperature scales that could be used in such instrument, Galileo’s thermoscope was a major breakthrough. In addition to being able to measure heat in air, it also provided quantitative meteorological information for the first time ever.
Galileo’s Telescope:
While Galileo did not invent the telescope, he greatly improved upon them. Over the course of many months during 1609, he unveiled multiple telescope designs that would collectively come to be known as Galilean Telescopes. The first, which he constructed between June and July of 1609, was a three-powered spyglass, which he replaced by August with an eight-powered instrument that he presented to the Venetian Senate.
By the following October or November, he managed to improve upon this with the creation a twenty-powered telescope – the very telescope that he used to observe the Moon, discover the four satellites of Jupiter (thereafter known as the Galilean Moons), discern the phases of Venus, and resolve nebular patches into stars.
These discoveries helped Galileo to advance the Copernican Model, which essentially stated that the Sun (and not the Earth) was the center of the universe (aka. heliocentrism). He would go on to refine his designs further, eventually creating a telescope that could magnify objects by a factor of 30.
Though these telescopes were humble by modern standards, they were a vast improvement over the models that existed during Galileo’s time. The fact that he managed to construct them all himself is yet another reason why they are considered his most impressive inventions.
Because of the instruments he created and the discoveries they helped make, Galileo is rightly recognized as one of the most important figures of the Scientific Revolution. His many theoretical contributions to the fields of mathematics, engineering and physics also challenged Aristotelian theories that had been accepted for centuries.
In short, he was one of just a few people who – through their tireless pursuit of scientific truth – forever changed our understanding of the universe and the fundamental laws that govern it.
The symbols of the eight planets, and Pluto, Credit: insightastrology.net
In our long history of staring up at the stars, human beings have assigned various qualities, names, and symbols for all the objects they have found there. Determined to find patterns in the heavens that might shed light on life here on Earth, many of these designations also ascribed (and were based on) the observable behavior of the celestial bodies.
When it came to assigning signs to the planets, astrologists and astronomers – which were entwined disciplines in the past -made sure that these particular symbols were linked to the planets’ names or their history in some way.
Mercury:
This planet is named after the Roman god who was himself the messenger of the gods, noted for his speed and swiftness. The name was assigned to this body largely because it is the planet closest to the Sun, and which therefore has the fastest rotational period. Hence, the symbol is meant to represent Mercury’s helmet and caduceus – a herald’s staff with snakes and wings intertwined.
Mercury, as imaged by the MESSENGER spacecraft, which was named after the messenger of the gods because it has the fastest orbit around the Sun. Image Credit: NASA/JHU/Carnegie Institution.
Venus:
Venus’ symbol has more than one meaning. Not only is it the sign for “female”, but it also represents the goddess Venus’ hand mirror. This representation of femininity makes sense considering Venus was the goddess of love and beauty in the Roman Pantheon. The symbol is also the chemical sign for copper; since copper was used to make mirrors in ancient times.
Earth:
Earth’s sign also has a variety of meanings, although it does not refer to a mythological god. The most popular view is that the circle with a cross in the middle represents the four main compass points. It has also been interpreted as the Globus Cruciger, an old Christian symbol for Christ’s reign on Earth.
This symbol is not just limited to Christianity though, and has been used in various culture around the world. These include, but are not limited to, Norse mythology (where it appears as the Solar or Odin’s Cross), Native American cultures (where it typically represented the four spirits of direction and the four sacred elements), the Celtic Cross, the Greek Cross, and the Egyptian Ankh.
In fact, perhaps owing to the simplicity of the design, cross-shaped incisions have made appearances as petroglyphs in European cult caves dating all the way back to the beginning of the Upper Paleolithic, and throughout prehistory to the Iron Age.
Mars, as photographed with the Mars Global Surveyor, is identified with the Roman god of war. Credit: NASA
Mars:
Mars is named after the Roman god of war, owing perhaps to the planet’s reddish hue, which gives it the color of blood. For this reason, the symbol associated with Mars represents the god of wars’ shield and spear. Additionally, it is the same sign as the one used to represent “male”, and hence is associated with self-assertion, aggression, sexuality, energy, strength, ambition and impulsiveness.
Jupiter:
Jupiter’s sign, which looks like an ornate, oddly shaped “four,” also stands for a number of symbols. It has been said to represent an eagle, which was the Jovian god’s bird. Additionally, the symbol can stand for a “Z,” which is the first letter of Zeus – who was Jupiter’s Greek counterpart.
The line through the symbol is consistent with this, since it would indicate that it was an abbreviation for Zeus’ name. And last, but not least, there is the addition of the swirled line which is believed to represent a lighting bolt – which just happens to Jupiter’s (and Zeus’) weapon of choice.
Saturn:
Like Jupiter, Saturn resembles another recognizable character – this time, it’s an “h.” However, this symbol is actually supposed to represent Saturn’s scythe or sickle, because Saturn is named after the Roman god of agriculture (after the Greek god Cronus, leader of the Titans, who was also depicted as holding a scythe).
Jupiter, the largest planet in the Solar System, is appropriately named after the Roman father of the gods. Credit: NASA/ESA/A. Simon (Goddard Space Flight Center)
Uranus:
The sign for Uranus is a combination of two other signs – Mars’ sign and the symbol of the Sun – because the planet is connected to these two in mythology. Uranus represented heaven in Roman mythology, and this ancient civilization believed that the Sun’s light and Mars’ power ruled the heavens.
Neptune:
Neptune’s sign is linked to the sea god Neptune, who the planet was named after. Appropriately, the symbol represents this planet is in the shape of the sea god’s trident.
Pluto:
Although Pluto was demoted to a dwarf planet in 2006, it still retains its old symbol. Pluto’s sign is a combination of a “P” and a “L,” which are the first two letters in Pluto as well as the initials of Percival Lowell, the astronomer who discovered the planet.
A full Moon flyby, as seen from Paris, France. Credit and copyright: Sebastien Lebrigand.
Moon:
The Moon is represented by a crescent shape, which is a clear allusion to how the Moon appears in the night sky more often than not. Since the Moon is also tied to people’s perceptions, moods, and emotional make-up, the symbol has also come to represents the mind’s receptivity.
Sun:
And then there’s the Sun, which is represented by a circle with a dot in the middle. In the case of the Sun, this symbol represents the divine spirit (circle) surrounding the seed of potential, which is a direct association with ancient Sun worship and the central role the Sun gods played in their respective ancient pantheons.
A picture of Earth taken by Apollo 11 astronauts. Credit: NASA
With the end of World War II, the Allies and the Soviet Bloc found themselves locked in a state of anatgonism. As they poured over the remains of the Nazi war machine, they discovered incredible advances in rocketry and aerospace engineering, and began scrambling to procure all they could.
For many of the many decades that followed, this state would continue as both sides struggled to make advancements in the field of space exploration ahead of the other. This was what is popularly known as the “Space Age”, an era that was born of the advent of nuclear power, advances in rocketry, and the desire to be the first to put men into space and on the Moon.
11 March 2011: The wave from a tsunami crashes over a street in Miyako City, Japan Credit: REUTERS/Mainichi Shimbun
For people living in oceanfront communities, the prospect of a tsunami is a frightening one. Much like earthquakes, volcanoes, hurricanes and tornadoes, tsunamis are one of the most destructive natural forces on the planet. And much like these other phenomena, they require the right conditions to happen and are more common in some areas of the world than others.
Knowing how and when a tsunami will strike has therefore a subject of great interest for scientists over the ages. But for anyone who has lived in certain parts of the world where “tsunami zones” are common – namely Japan and the South Pacific – it is a matter of survival.
Definition: Numerous terms are used in the English language to describe large waves created by the displacement of water, with varying degrees of accuracy. The term tsunami, for example, is literally translated from Japanese to mean “harbor wave”. There are only a few other languages that have an equivalent native word, though similar meanings can be found in Indonesia, Sri Lanka, and the Indian Subcontinent.
The term tidal wave has also been used, which is derived from the most common appearance of a tsunami – an extraordinarily high tidal bore. However, in recent years, the term “tidal wave” has fallen out of favor with the scientific community because tsunami actually have nothing to do with tides, which are produced by the gravitational pull of the moon and sun rather than the displacement of water.
Tsunamis initiate when an earthquake causes the seabed to rupture, which leads to a rapid decrease in sea surface height directly above it. Credit: howitworksdaily.com
The term seismic sea wave also is used to refer to the phenomenon, due to the fact that the waves most often are generated by seismic activity such as earthquakes. However, like “tsunami,” “seismic sea wave” is not a completely accurate term, as forces other than earthquakes – including underwater landslides, volcanic eruptions, underwater explosions, land or ice slumping into the ocean, meteorite impacts, or even sudden changes in weather – can generate such waves by displacing water.
Causes: The principal cause of a tsunami is the displacement of a substantial volume of water or perturbation of the sea. This is usually the result of earthquakes, landslides, volcanic eruptions, glacier calvings, or more rarely by meteorites and nuclear tests. The waves formed in this way are then sustained by gravity.
Tectonic earthquakes trigger tsunamis when the sea floor abruptly deforms and vertically displaces the water above. More specifically, a tsunami can be generated when thrust faults associated with convergent or destructive plate boundaries move abruptly and displace water.
Tsunamis have a small amplitude (wave height) offshore, and a very long wavelength (often hundreds of kilometers long), and only grow in height when they reach shallower water. Once there, the wavelength shortens as the wave encounters resistance, thus increasing the amplitude increases and causing the wave to rears up in a massive tidal bore.
In the 1950s, it was discovered that tsunamis larger than what had previously been believed possible could be caused by giant submarine landslides. These rapidly displace large water volumes, as energy transfers to the water at a rate faster than the water can absorb. Their existence was confirmed in 1958, when a giant landslide in Lituya Bay, Alaska, caused the highest wave ever recorded (524 meters/1700 feet).
A village near the coast of Sumatra that was devastated by the Tsunami that struck South-East Asia in 2004. Credit: US Navy/Public Domain
In general, landslides generate displacements mainly in the shallower parts of the coastline, such as in closed bays and lakes. But an open oceanic landslide large enough to cause a tsunami across an ocean has not yet happened since the advent of modern seismology, and only rarely in human history.
Meteorological phenomena, such tropical cyclones, can generate a storm surge that will cause sea levels to rise, often in coastal regions. These are what is known as meteotsunamis, which are tsunamis triggered by sudden changes in weather. When such tsunamis reach shore, they rear up in shallows and surge laterally, just like earthquake-generated tsunamis.
Tsunamis can also be triggered by external factors, such as meteors or human intervention. For instance, when a meteor of significant strikes a region of the ocean, the resulting impact is enough to displace high volumes of water, thus triggering a tsunami. There has also been much speculation since World War II of how a nuclear detonations have trigger a tsunami, but all attempts at research (especially in the Pacific) have yielded poor results.
Characteristics and Effects: Tsunamis can travel at well over 800 kilometers per hour (500 mph), but as they approach the coast, wave shoaling compresses the wave and its speed decreases to below 80 kilometers per hour (50 mph). A tsunami in the deep ocean has a much larger wavelength of up to 200 kilometers (120 mi), but diminishes to less than 20 kilometers (12 mi) when it reaches shallow water.
When the tsunami’s wave peak reaches the shore, the resulting temporary rise in sea level is termed run up. Run up is measured in metres above a reference sea level. A large tsunami may feature multiple waves arriving over a period of hours, with significant time between the wave crests.
Tsunamis cause damage by two mechanisms. First, there is the smashing force of a wall of water traveling at high speed, while the second is the destructive power of a large volume of water draining off the land and carrying a large amount of debris with it.
It is often difficult for people to recognize a tsunami in the open ocean because the waves are much smaller further out at sea than they are close to shore. As with earthquakes, several attempts have been made to set up scales of tsunami intensity or magnitude to allow comparison between different events.
Ships try to extinguish a blaze at oil refinery tanks in Ichihara, Chiba Prefecture, after the tsunami that struck in March, 2011. Credit: EPA
The first scales used routinely to measure the intensity of tsunami were the Sieberg-Ambraseys scale, used in the Mediterranean Sea and the Imamura-Iida intensity scale, used in the Pacific Ocean. This latter scale was modified by Soloviev to become the Soloviev-Imamura tsunami intensity scale, which is used in the global tsunami catalogs compiled by the NGDC/NOAA and the Novosibirsk Tsunami Laboratory as the main parameter for the size of the tsunami.
In 2013, following the intensively studied tsunamis in 2004 and 2011, a new 12 point scale was proposed, known as the Integrated Tsunami Intensity Scale (ITIS-2012). This scale was intended to match as closely as possible to the modified ESI2007 and EMS earthquake intensity scales.
Tsunamis throughout History: Japan and the Pacific Ocean may have the longest recorded history of tsunamis, but they are an often underestimated hazard in the Mediterranean Sea region and Europe in general. In his History of the Peloponnesian War (426 BCE), Greek historian Thucydides offered what could be considered the first recorded speculation about the causes of tsunamis – where he argued that earthquakes at sea were the reason for them.
An aerial view of tsunami damage in Tohoku. Credit: US Navy
After the tsunami of 365 CE devastated Alexandria, Roman historian Ammianus Marcellinus described the typical sequence of a tsunami. His descriptions included an earthquake and the sudden retreat of the sea, followed by a gigantic wave.
More modern examples include the 1755 Lisbon earthquake and tsunami (which was caused by activity in the Azores–Gibraltar Transform Fault); the 1783 Calabrian earthquakes, which caused several ten thousand deaths; and the 1908 Messina earthquake and tsunami – which caused 123,000 deaths in Sicily and Calabria and is considered one of the most deadly natural disasters in modern European history.
But by far, the 2004 Indian Ocean earthquake and tsunami was the most devastating of its kind in modern times, killing around 230,000 people and laying waste to communities throughout Indonesia, Thailand, and Southern Asia.
In 2010, an earthquake triggered a tsunami which devastated several coastal towns in south-central Chile, damaged the port at Talcahuano and caused 4334 confirmed fatalities. The earthquake also generated a blackout that affected 93 percent of the Chilean population.
In 2011, an earthquake off the Pacific coast of Tohoku led to a tsunami that struck Japan and led to 5,891 deaths, 6,152 injuries, and 2,584 people to be declared missing across twenty prefectures. The tsunami also caused meltdowns at three reactors in the Fukushima Daiichi Nuclear Power Plant complex.
Tsunamis are a force of nature, without a doubt. And knowing when, where, and how severely they will strike is intrinsic to ensuring that we can limit the damage they do cause.
Universe Today has articles on about tsunamis and causes of tsunamis.
Io and Jupiter as seen by New Horizons during its 2008 flyby. (Credit: NASA/Johns Hopkins University APL/SWRI).
Ever since the invention of the telescope four hundred years ago, astronomers have been fascinated by the gas giant of Jupiter. Between it’s constant, swirling clouds, its many, many moons, and its Giant Red Spot, there are many things about this planet that are both delightful and fascinating.
But perhaps the most impressive feature about Jupiter is its sheer size. In terms of mass, volume, and surface area, Jupiter is the biggest planet in our Solar System by a wide margin. But just what makes Jupiter so massive, and what else do we know about it?
Size and Mass:
Jupiter’s mass, volume, surface area and mean circumference are 1.8981 x 1027 kg, 1.43128 x 1015 km3, 6.1419 x 1010 km2, and 4.39264 x 105 km respectively. To put that in perspective, Jupiter diameter is roughly 11 times that of Earth, and 2.5 the mass of all the other planets in the Solar System combined.
But, being a gas giant, Jupiter has a relatively low density – 1.326 g/cm3 – which is less than one quarter of Earth’s. This means that while Jupiter’s volume is equivalent to about 1,321 Earths, it is only 318 times as massive. The low density is one way scientists are able to determine that it is made mostly of gases, though the debate still rages on what exists at its core (see below).
Composition:
Jupiter is composed primarily of gaseous and liquid matter. It is the largest of the gas giants, and like them, is divided between a gaseous outer atmosphere and an interior that is made up of denser materials. Its upper atmosphere is composed of about 88–92% hydrogen and 8–12% helium by percent volume of gas molecules, and approx. 75% hydrogen and 24% helium by mass, with the remaining one percent consisting of other elements.
This cut-away illustrates a model of the interior of Jupiter, with a rocky core overlaid by a deep layer of liquid metallic hydrogen. Credit: Kelvinsong/Wikimedia Commons
The atmosphere contains trace amounts of methane, water vapor, ammonia, and silicon-based compounds as well as trace amounts of benzene and other hydrocarbons. There are also traces of carbon, ethane, hydrogen sulfide, neon, oxygen, phosphine, and sulfur. Crystals of frozen ammonia have also been observed in the outermost layer of the atmosphere.
The interior contains denser materials, such that the distribution is roughly 71% hydrogen, 24% helium and 5% other elements by mass. It is believed that Jupiter’s core is a dense mix of elements – a surrounding layer of liquid metallic hydrogen with some helium, and an outer layer predominantly of molecular hydrogen. The core has also been described as rocky, but this remains unknown as well.
In 1997, the existence of the core was suggested by gravitational measurements, indicating a mass of from 12 to 45 times the Earth’s mass, or roughly 4%–14% of the total mass of Jupiter. The presence of a core is also supported by models of planetary formation that indicate how a rocky or icy core would have been necessary at some point in the planet’s history in order to collect its bulk of hydrogen and helium from the protosolar nebula.
However, it is possible that this core has since shrunk due to convection currents of hot, liquid, metallic hydrogen mixing with the molten core. This core may even be absent now, but a detailed analysis is needed before this can be confirmed. The Juno mission, which launched in August 2011, is expected to provide some insight into these questions, and thereby make progress on the problem of the core.
The temperature and pressure inside Jupiter increase steadily toward the core. At the “surface”, the pressure and temperature are believed to be 10 bars and 340 K (67 °C, 152 °F). At the “phase transition” region, where hydrogen becomes metallic, it is believed the temperature is 10,000 K (9,700 °C; 17,500 °F) and the pressure is 200 GPa. The temperature at the core boundary is estimated to be 36,000 K (35,700 °C; 64,300 °F) and the interior pressure at roughly 3,000–4,500 GPa.
Moons:
The Jovian system currently includes 67 known moons. The four largest are known as the Galilean Moons, which are named after their discoverer, Galileo Galilei. They include: Io, the most volcanically active body in our Solar System; Europa, which is suspected of having a massive subsurface ocean; Ganymede, the largest moon in our Solar System; and Callisto, which is also thought to have a subsurface ocean and features some of the oldest surface material in the Solar System.
Then there’s the Inner Group (or Amalthea group), which is made up of four small moons that have diameters of less than 200 km, orbit at radii less than 200,000 km, and have orbital inclinations of less than half a degree. This groups includes the moons of Metis, Adrastea, Amalthea, and Thebe. Along with a number of as-yet-unseen inner moonlets, these moons replenish and maintain Jupiter’s faint ring system.
Jupiter also has an array of Irregular Satellites, which are substantially smaller and have more distant and eccentric orbits than the others. These moons are broken down into families that have similarities in orbit and composition, and are believed to be largely the result of collisions from large objects that were captured by Jupiter’s gravity.
Illustration of Jupiter and the Galilean satellites. Credit: NASA
Interesting Facts:
Much like Earth, Jupiter experiences auroras near its northern and southern poles. But on Jupiter, the auroral activity is much more intense and rarely ever stops. The intense radiation, Jupiter’s magnetic field, and the abundance of material from Io’s volcanoes that react with Jupiter’s ionosphere creates a light show that is truly spectacular.
Jupiter also has a violent atmosphere. Winds in the clouds can reach speeds of up to 620 kph (385 mph). Storms form within hours and can become thousands of km in diameter overnight. One storm, the Great Red Spot, has been raging since at least the late 1600s. The storm has been shrinking and expanding throughout its history; but in 2012, it was suggested that the Giant Red Spot might eventually disappear.
The discovery of exoplanets has revealed that planets can get even bigger than Jupiter. In fact, the number of “Super Jupiters” observed by the Kepler space probe (as well as ground-based telescopes) in the past few years has been staggering. In fact, as of 2015, more than 300 such planets have been identified.
Notable examples include PSR B1620-26 b (Methuselah), which was the first super-Jupiter to be observed (in 2003). At 12.7 billion years of age, it is also the third oldest known planet in the universe. There’s also HD 80606 b (Niobe), which has the most eccentric orbit of any known planet, and 2M1207b (Lerna), which orbits the brown dwarf Fomalhaut b (Illion).
Scientist theorize that a gas gain could get 15 times the size of Jupiter before it began deuterium fusion, making it a brown dwarf star. Good thing too, since the last thing the Solar System needs if for Jupiter to go nova!
Jupiter was appropriately named by the ancient Romans, who chose to name after the king of the Gods (Jupiter, or Jove). The more we have come to know and understand about this most-massive of Solar planets, the more deserving of this name it appears.
Out with the old... changing out the historic coundown clock at the Kennedy Space Center, perhaps an easier 'time change' than the insertion of the leap second. Image credit: NASA/Frankie Martin
The month of June 2015 is just a tad longer than usual… but not for the reason you’ve been told.
Chances are, you’ll soon be hearing that we’re tacking on an extra second to the very end of June 30th, though the reason why is a bit more complex than the explanation you’ll be hearing.
It’s an error that comes around and is repeated about every 500 days or so, as we add a leap second to June 30th or December 31st.
‘The rotation of the Earth is slowing down,’ your local weather newscaster/website/anonymous person on Twitter will say. ‘This is why we need to add in an extra second every few years, to keep our accounting for time in sync.’
The observed variation of the Earth’s rotation in milliseconds since the adoption of the leap second. Image credit: The United States Naval Observatory
Now, I know what you’re thinking.
Doesn’t adding a second once every 18-24 months or so add up to an awful lot? Are we really slowing down to the tune of (calculator apps out) over 11 minutes per millennium? What’s going on here?
Here’s what your weatherman won’t tell you.
The story of the second and the insertion of the modern day leap second is a curious case of modern astronomical history.
Universe Today recently covered the quirks of the Earth’s rotation on this past weekend’s June solstice. We are indeed slowing down, to the tune of an average of 2.3 milliseconds (thousands of a second) of a day per century in the current epoch, mostly due to the tidal braking action of the Moon. The advent of anthropogenic global warming will also incur variations in the Earth’s rotation rate as well.
Historically, the second was defined as 1/86,400th (60 seconds x 60 minutes x 24 hours) of a mean solar day. We’ve actually been on an astronomical standard of time of one sort or another for thousands of years, though it’s only been over the last two centuries that we’ve really needed—or could even reliably measure—time to an accuracy of less than a second. These early observations were made by astronomers using transit instruments as they watched stars ‘cross the wire’ in an eyepiece using nothing more sophisticated than a Mark-1 eyeball.
A transit instrument on display at the Quito Observatory in Quito, Ecuador. Image credit: David Dickinson
The whole affair was addressed in 1956 by the International Committee for Weights and Measures, which defined what was known as the ephemeris, or astronomical second as a fraction—1/31,556,925.9747th to be precise—of the tropical year set at noon on January 1st 1900.
Simon Newcomb. Image in the Public Domain
Now, this decision relied on measurements contained in Simon Newcomb’s 1895 book Tables of the Sun to describe the motion of the Earth. Extrapolating back, a day was exactly 86,400 modern seconds long… in 1820.
In the intervening 195 years, the modern day is now about an extra 1/500th (86,400.002) of an SI second long. In turn, the SI second was defined in 1967 as:
The duration of 9,192,631,770 periods of radiation corresponding to the transition between two hyperfine levels of the ground state of the Cesium-133 atom.
An atomic clock at the Federal Office of Metrology in Bern, Switzerland. Image credit: Wikimedia Commons/Public Domain
Now, physicists love to have an SI definition that isn’t reliant on an artifact. In fact, the pesky holdout known as the kilogram is the last of the seven SI base units that is based on an object and not a constant that anyone can measure in a lab worldwide. Simply locking a second at 1/86,400th of a mean solar day would mean that the second itself was slowly lengthening, creating its own can of worms…
So the leap second came to be, as a compromise between UT1 (Astronomical observed time) and UTC (Coordinated Universal Time), which defines a day as being comprised of 86,400 SI seconds. These days, the United States Naval Observatory utilizes observations which include quasars, GPS satellites and laser ranging experiments left on the Moon by Apollo astronauts to measure UT1.
The difference between Universal and Terrestrial Time is often referred to as Delta T.
An 1853 Universal Dial Plate depicting time worldwide before the adoption of Universal Time. Image credit: Wikimedia Commons/Public Domain image
The first leap second was inserted on June 30th 1972, and 25 leap seconds have been introduced up until the extra June 30th second next week.
But the Earth’s rotation isn’t actually slowing down a second every time we add one… this is the point most folks get wrong. Think of it this way: the modern Gregorian calendar inserts a leap day every four years to keep it in sync with the mean tropical year… but the length of the year itself doesn’t increase by a day every four years. Those fractions of a second per day just keep adding up until the difference between UT1 and UTC mounts towards one second, and the good folks at the International Earth Rotation Service decide something must be done.
And don’t fear the leap second, though we’ve already seen many ‘Y2K redux’ cries already cropping up around the web. We do this every 18-24 months or so, and Skynet hasn’t become self-aware… or at least, not yet.
Of course, programmers hate the leap second, and much like the patchwork of daylight saving time and time zone rules, it causes a colossal headache to assure all of those exceptions and rules are accounted for. Consider, for example, how many transactions (emails, tweets, etc) fly around the globe every second. Many services such as Google instead apply what’s known as a ‘leap smear,’ which slices the leap second out into tinier micro-second sized bites.
With the current system in place, leap seconds will become ever more frequent as the Earth’s rotation continues to slow. There have been calls over the years to even do away with the astronomical standard for measuring time entirely, and go exclusively to the SI second and UTC. This would also create a curious situation of not only, say, throwing off local sunset and sunrise times, but users of GOTO telescope pointing systems would probably note errors within a few decades or so.
This coming November, The World Radiocommunication Conference being held in Geneva, Switzerland is looking to address the issue, though we suspect that, for now at least, the future of the leap second is secure… perhaps, if we did indeed go off the astronomical time standard for the first time in the history of modern human civilization, a leap hour might have to be instituted somewhere around oh say, 2600 AD.
What do you, the reader think? Should it be ‘down with the leap second,’ or should we keep our clocks in lock step with the cosmos?
![Spring driven pendulum clock, designed by Huygens, built by instrument maker Salomon Coster (1657),[96] and copy of the Horologium Oscillatorium,[97] Museum Boerhaave, Leiden](https://www.universetoday.com/wp-content/uploads/2008/11/Christiaan_Huygens_Clock_and_Horologii_Oscillatorii.jpg)
