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What is the transit of Venus?
A rare astronomical event that happens when Venus travels across the face of the sun and appears as a small black dot on its surface.
When does it happen?
Transits occur in pairs eight years apart. There are two in December that repeat every 121.5 years, and two in June that repeat every 105.5 years.
The last transit of Venus of the 21st century occurs on Tuesday and Wednesday (5 and 6 June 2012) depending on where you are viewing from. The transit starts at 11.04pm BST (6.04pm ET) on Tuesday, when it will be visible from the US. The final hour of the transit will be visible from the UK just before 5am BST on Wednesday (12am ET US), clear skies permitting. The transit will not happen again until December 2117.
How long does the transit last?
Venus takes nearly seven hours to cross the face of the sun, but the event is divided into four "contacts" that mark different phases of the transit. Venus makes first contact when it encroaches onto the disc of the sun. Twenty minutes later, on second contact, the planet will be fully silhouetted. On third contact, at 5.37am BST (12.37am ET), Venus will begin to leave the sun, and the transit will be over on fourth contact at 5.55am BST (12.55am ET).
Where can I see it?
The whole transit is visible from Alaska, parts of northern Canada, and from New Zealand, much of Australia, Asia and Russia. In the US, the transit will be in progress as the sun sets on 5 June. In East Africa, Europe and Scandinavia, the transit will be under way as the sun rises on 6 June. Much of South America and western Africa will not see the event.
How can I watch it safely?
Never look directly at the sun, it will damage your eyes. You can use eclipse viewing glasses that carry a CE mark and are not damaged or worn, but only for a few minutes at a time. Venus is large enough to see with the naked eye and will appear as a spot about 1/32 the width of the sun. It is not safe to look at the sun through regular sunglasses. For a better view, use a small telescope or a pair of binoculars to project an image of the sun onto a screen. Never look at the sun directly through either binoculars or a telescope.
Can I watch online?
Nasa will broadcast a live webcast of the transit from the Mauna Kea Observatories in Hawaii.
What will it look like?
Venus will cross the northern part of the sun and appear as a black spot about 1/32 as wide as the solar disc. At the start and end of the transit, the black disc of the planet will seem to stretch onto the edge of the sun. This is the black drop effect, which made it so hard for 18th century astronomers to time accurately the transit. It is caused by the telescope blurring the image, and the drop in the sun's brightness close to its edge.
What have scientists used the transit for?
In the 18th century astronomers set out to far-flung corners of the globe to time the transit of Venus. Combined, their results gave them the first accurate measurement of the distance between the Earth and the sun, a figure they calculated to be between 93 million and 97 million miles (172-180 million kilometres). Today, the accepted distance is 93 million miles. The result allowed astronomers to calculate the size of the solar system.
What do scientists hope to learn this time?
More precise measurements of the transit, particularly from telescopes in space, will hone astronomers' skills for spotting planets beyond our own solar system as they pass in front of their own stars. David Ehrenreich, an astronomer in Grenoble, France, has been granted time on the Hubble space telescope to watch the transit of Venus as if viewed from the moon. To do this, he will use Hubble to watch for the exquisitely fine fall in the brightness of sunlight reflected off the moon as Venus passes in front of the sun.
Why is Venus called Earth's sister planet?
Venus has always been considered a sister planet to Earth. At 12,000km across, the planet is nearly as large and has 80% of Earth's mass. Earth is the third rock from the sun, and Venus is the second, orbiting around 40 million kilometres (25 million miles) from our planet. Venus circles the sun faster than Earth, clocking up a year in 224.7 Earth days. But the rotation of the planet is so slow, a day on Venus lasts 342 Earth days – longer than a Venutian year.
Useful resources on the web: | 0.824385 | 3.378726 |
The idea of exploring and colonizing Mars has never been more alive than it is today. Within the next two decades, there are multiple plans to send crewed missions to the Red Planet, and even some highly ambitious plans to begin building a permanent settlement there. Despite the enthusiasm, there are many significant challenges that need to be addressed before any such endeavors can be attempted.
These challenges – which include the effects of low-gravity on the human body, radiation, and the psychological toll of being away from Earth – become all the more pronounced when dealing with permanent bases. To address this, civil engineer Marco Peroni offers a proposal for a modular Martian base (and a spacecraft to deliver it) that would allow for the colonization of Mars while protecting its inhabitants with artificial radiation shielding.
Last week, ESA’s Schiaparelli lander smashed onto the surface of Mars. Apparently its descent thrusters shut off early, and instead of gently landing on the surface, it hit hard, going 300 km/h, creating a 15-meter crater on the surface of Mars.
Fortunately, the orbiter part of ExoMars mission made it safely to Mars, and will now start gathering data about the presence of methane in the Martian atmosphere. If everything goes well, this might give us compelling evidence there’s active life on Mars, right now.
It’s a shame that the lander portion of the mission crashed on the surface of Mars, but it’s certainly not surprising. In fact, so many spacecraft have gone to the galactic graveyard trying to reach Mars that normally rational scientists turn downright superstitious about the place. They call it the Mars Curse, or the Great Galactic Ghoul.
Mars eats spacecraft for breakfast. It’s not picky. It’ll eat orbiters, landers, even gentle and harmless flybys. Sometimes it kills them before they’ve even left Earth orbit.
At the time I’m writing this article in late October, 2016, Earthlings have sent a total of 55 robotic missions to Mars. Did you realize we’ve tried to hurl that much computing metal towards the Red Planet? 11 flybys, 23 orbiters, 15 landers and 6 rovers.
How’s our average? Terrible. Of all these spacecraft, only 53% have arrived safe and sound at Mars, to carry out their scientific mission. Half of all missions have failed.
Let me give you a bunch of examples.
In the early 1960s, the Soviets tried to capture the space exploration high ground to send missions to Mars. They started with the Mars 1M probes. They tried launching two of them in 1960, but neither even made it to space. Another in 1962 was destroyed too.
They got close with Mars 1 in 1962, but it failed before it reached the planet, and Mars 2MV didn’t even leave the Earth’s orbit.
Five failures, one after the other, that must have been heartbreaking. Then the Americans took a crack at it with Mariner 3, but it didn’t get into the right trajectory to reach Mars.
Finally, in 1964 the first attempt to reach Mars was successful with Mariner 4. We got a handful of blurry images from a brief flyby.
For the next decade, both the Soviets and Americans threw all kinds of hapless robots on a collision course with Mars, both orbiters and landers. There were a few successes, like Mariner 6 and 7, and Mariner 9 which went into orbit for the first time in 1971. But mostly, it was failure. The Soviets suffered 10 missions that either partially or fully failed. There were a couple of orbiters that made it safely to the Red Planet, but their lander payloads were destroyed. That sounds familiar.
Now, don’t feel too bad about the Soviets. While they were struggling to get to Mars, they were having wild success with their Venera program, orbiting and eventually landing on the surface of Venus. They even sent a few pictures back.
Finally, the Americans saw their greatest success in Mars exploration: the Viking Missions. Viking 1 and Viking 2 both consisted of an orbiter/lander combination, and both spacecraft were a complete success.
Was the Mars Curse over? Not even a little bit. During the 1990s, the Russians lost a mission, the Japanese lost a mission, and the Americans lost 3, including the Mars Observer, Mars Climate Orbiter and the Mars Polar Lander.
There were some great successes, though, like the Mars Global Surveyor and the Mars Pathfinder. You know, the one with the Sojourner Rover that’s going to save Mark Watney?
The 2000s have been good. Every single American mission has been successful, including Spirit and Opportunity, Curiosity, the Mars Reconnaissance Orbiter, and others.
But the Mars Curse just won’t leave the Europeans alone. It consumed the Russian Fobos-Grunt mission, the Beagle 2 Lander, and now, poor Schiaparelli. Of the 20 missions to Mars sent by European countries, only 4 have had partial successes, with their orbiters surviving, while their landers or rovers were smashed.
Is there something to this curse? Is there a Galactic Ghoul at Mars waiting to consume any spacecraft that dare to venture in its direction?
Flying to Mars is tricky business, and it starts with just getting off Earth. The escape velocity you need to get into low-Earth orbit is about 7.8 km/s. But if you want to go straight to Mars, you need to be going 11.3 km/s. Which means you might want a bigger rocket, more fuel, going faster, with more stages. It’s a more complicated and dangerous affair.
Your spacecraft needs to spend many months in interplanetary space, exposed to the solar winds and cosmic radiation.
Arriving at Mars is harder too. The atmosphere is very thin for aerobraking. If you’re looking to go into orbit, you need to get the trajectory exactly right or crash onto the planet or skip off and out into deep space.
And if you’re actually trying to land on Mars, it’s incredibly difficult. The atmosphere isn’t thin enough to use heatshields and parachutes like you can on Earth. And it’s too thick to let you just land with retro-rockets like they did on the Moon.
Landers need a combination of retro-rockets, parachutes, aerobraking and even airbags to make the landing. If any one of these systems fails, the spacecraft is destroyed, just like Schiaparelli.
If I was in charge of planning a human mission to Mars, I would never forget that half of all spacecraft ever sent to the Red Planet failed. The Galactic Ghoul has never tasted human flesh before. Let’s put off that first meal for as long as we can. | 0.868391 | 3.152871 |
A meridian is the half of an imaginary great circle on the Earth's surface, terminated by the North Pole and the South Pole, connecting points of equal longitude, as measured in angular degrees east or west of the Prime Meridian. The position of a point along the meridian is given by that longitude and its latitude, measured in angular degrees north or south of the Equator; each meridian is perpendicular to all circles of longitude. Each is the same length, being half of a great circle on the Earth's surface and therefore measuring 20,003.93 km. The first prime meridian was set by Eratosthenes in 200 BCE; this prime meridian was used to provide measurement of the earth, but had many problems because of the lack of latitude measurement. Many years around the 19th century there was still concerns of the prime meridian; the idea of having one prime meridian came from William Parker Snow, because he realized the confusion of having multiple prime meridian locations. Many of these geographical locations were traced back to the ancient Greeks, others were created by several nations.
Multiple locations for the geographical meridian meant that there was inconsistency, because each country had their own guidelines for where the prime meridian was located. The term meridian comes from the Latin meridies, meaning "midday"; the Sun crosses the celestial meridian at the same time. The same Latin stem gives rise to the terms a.m. and p.m. used to disambiguate hours of the day when utilizing the 12-hour clock. Because of a growing international economy, there was a demand for a set international prime meridian to make it easier for worldwide traveling which would, in turn, enhance international trading across countries; as a result, a Conference was held in 1884, in Washington, D. C. Twenty-six countries were present at the International Meridian Conference to vote on an international prime meridian; the outcome was as follows: there would only be a single meridian, the meridian was to cross and pass at Greenwich, there would be two longitude direction up to 180°, there will be a universal day, the day begins at the mean midnight of the initial meridian.
Toward the ending of the 12th century there were two main locations that were acknowledged as the geographic location of the meridian and Britain. These two locations conflicted and a settlement was reached only after there was an International Meridian Conference held, in which Greenwich was recognized as the 0° location; the meridian through Greenwich, called the Prime Meridian, was set at zero degrees of longitude, while other meridians were defined by the angle at the center of the earth between where it and the prime meridian cross the equator. As there are 360 degrees in a circle, the meridian on the opposite side of the earth from Greenwich, the antimeridian, forms the other half of a circle with the one through Greenwich, is at 180° longitude near the International Date Line; the meridians from West of Greenwich to the antimeridian define the Western Hemisphere and the meridians from East of Greenwich to the antimeridian define the Eastern Hemisphere. Most maps show the lines of longitude.
The position of the prime meridian has changed a few times throughout history due to the transit observatory being built next door to the previous one. Such changes had no significant practical effect; the average error in the determination of longitude was much larger than the change in position. The adoption of World Geodetic System 84" as the positioning system has moved the geodetic prime meridian 102.478 metres east of its last astronomic position. The position of the current geodetic prime meridian is not identified at all by any kind of sign or marking in Greenwich, but can be located using a GPS receiver, it was in the best interests of the nations to agree to one standard meridian to benefit their fast growing economy and production. The disorganized system they had before was not sufficient for their increasing mobility; the coach services in England had erratic timing before the GWT. U. S. and Canada were improving their railroad system and needed a standard time as well. With a standard meridian, stage coach and trains were able to be more efficient.
The argument of which meridian is more scientific was set aside in order to find the most convenient for practical reasons. They were able to agree that the universal day was going to be the mean solar day, they agreed that the days would begin at midnight and the universal day would not impact the use of local time. A report was submitted to the "Transactions of the Royal Society of Canada," dated 10 May 1894; the magnetic meridian is an equivalent imaginary line connecting the magnetic south and north poles and can be taken as the horizontal component of magnetic force lines along the surface of the earth. Therefore, a compass needle will be parallel to the magnetic meridian. However, a compass needle will not be steady in the magnetic meridian, because of the longitude from east to west being complete geodesic. Th
The 2012 Campeonato Internacional de Verano known as 2012 Copa Bimbo for sponsoring purposes, is the fourth edition of the Campeonato Internacional de Verano, an exhibition international club football competition that featured two clubs from Uruguay, one from Peru and one from Chile. It is played in Montevideo, Uruguay at the Estadio Centenario from 13 to 15 January 2012. Man of the match: Emiliano Albín Assistant referees: Carlos Pastorino Raúl Hartwig Fourth official: Gustavo Siegler 2 goals Emiliano Albín Santiago Silva David Llanos 1 goal Héber Arriola Sebastián Cristóforo Joaquín Boghossián Luis Perea Álvaro Recoba Matías Vecino Nicolás Canales
The Barbary pirates, sometimes called Barbary corsairs or Ottoman corsairs, were Ottoman and Berber pirates and privateers who operated from North Africa, based in the ports of Salé, Algiers and Tripoli. This area was known in Europe as the Barbary Coast, a term derived from the name of its ethnically Berber inhabitants, their predation extended throughout the Mediterranean, south along West Africa's Atlantic seaboard and into the North Atlantic as far north as Iceland, but they operated in the western Mediterranean. In addition to seizing merchant ships, they engaged in Razzias, raids on European coastal towns and villages in Italy, France and Portugal, but in the British Isles, the Netherlands, Iceland; the main purpose of their attacks was slaves for the Ottoman slave trade as well as the general Arab slavery market in North Africa and the Middle East. Slaves in Barbary could be black, brown or white, Protestant, Jewish or Muslim. While such raids had occurred since soon after the Muslim conquest of Iberia in the 8th century, the terms "Barbary pirates" and "Barbary corsairs" are applied to the raiders active from the 16th century onwards, when the frequency and range of the slavers' attacks increased.
In that period Algiers and Tripoli came under the sovereignty of the Ottoman Empire, either as directly administered provinces or as autonomous dependencies known as the Barbary States. Similar raids were undertaken from other ports in Morocco. Barbary corsairs captured thousands of merchant ships and raided coastal towns; as a result, residents abandoned their former villages of long stretches of coast in Spain and Italy. Between 100,000 and 250,000 Iberians were enslaved by these raids; the raids were such a problem coastal settlements were undertaken until the 19th century. Between 1580 and 1680 corsairs were said to have captured about 850,000 people as slaves and from 1530 to 1780 as many as 1,250,000 people were enslaved. However, these numbers have been questioned by the historian David Earle; some of these corsairs were European converts such as John Ward and Zymen Danseker. Hayreddin Barbarossa and Oruç Reis, Turkish Barbarossa Brothers, who took control of Algiers on behalf of the Ottomans in the early 16th century, were notorious corsairs.
The European pirates brought advanced sailing and shipbuilding techniques to the Barbary Coast around 1600, which enabled the corsairs to extend their activities into the Atlantic Ocean. The effects of the Barbary raids peaked in the early to mid-17th century. Long after Europeans had abandoned oar-driven vessels in favor of sailing ships carrying tons of powerful cannon, many Barbary warships were galleys carrying a hundred or more fighting men armed with cutlasses and small arms; the Barbary navies were not battle fleets. When they sighted a European frigate, they fled; the scope of corsair activity began to diminish in the latter part of the 17th century, as the more powerful European navies started to compel the Barbary States to make peace and cease attacking their shipping. However, the ships and coasts of Christian states without such effective protection continued to suffer until the early 19th century. Following the Napoleonic Wars and the Congress of Vienna in 1814–15, European powers agreed upon the need to suppress the Barbary corsairs and the threat was subdued.
Occasional incidents occurred, including two Barbary wars between the United States and the Barbary States, until terminated by the French conquest of Algeria in 1830. In 1198 the problem of Berber piracy and slave-taking was so great that the Trinitarians, a religious order, were founded to collect ransoms and to exchange themselves as ransom for those captured and pressed into slavery in North Africa. In the 14th century Tunisian corsairs became enough of a threat to provoke a Franco-Genoese attack on Mahdia in 1390 known as the "Barbary Crusade". Morisco exiles of the Reconquista and Maghreb pirates added to the numbers, but it was not until the expansion of the Ottoman Empire and the arrival of the privateer and admiral Kemal Reis in 1487 that the Barbary corsairs became a true menace to shipping from European Christian nations. During the American Revolution the pirates attacked American merchant vessels in the Mediterranean. But, on December 20, 1777, Sultan Mohammed III of Morocco issued a declaration recognizing America as an independent country, that American merchant ships could enjoy safe passage into the Mediterranean and along the coast.
The relations were formalized with the Moroccan-American Treaty of Friendship signed in 1786, which stands as the U. S.'s oldest non-broken friendship treaty with a foreign power. As late as 1798, an islet near Sardinia was attacked by the Tunisians, more than 900 inhabitants were taken away as slaves. From 1659, these African cities, although nominally part of the Ottoman Empire, were in fact military republics that chose their own rulers and lived by war booty captured from the Spanish and Portuguese. There are several cases of Sephardic Jews, including Sinan Reis and Samuel Pallache, who upon fleeing Iberia turned to attacking the Spanish Empire's shipping under the Ottoman flag, a profitable strategy of revenge for the Inquisition's religious persecution. During the first period, the beylerbeys were admirals of the sultan, commanding great fleets and conducting war operations for political ends, they were slave-hunters and their methods were ferocious. After 1587, the sole object of their successors became plunder, on sea.
The maritime operations were conducted by the captains, or reises, who formed a class or a corporation. Cruisers were commanded by the reises. Ten percent of | 0.808872 | 3.527634 |
Taurus is one of the constellations of the zodiac, which means it is crossed by the plane of the ecliptic. Taurus is a prominent constellation in the northern hemisphere's winter sky, it is one of the oldest constellations, dating back to at least the Early Bronze Age when it marked the location of the Sun during the spring equinox. Its importance to the agricultural calendar influenced various bull figures in the mythologies of Ancient Sumer, Assyria, Egypt and Rome. A number of features exist. Taurus hosts two of the nearest open clusters to Earth, the Pleiades and the Hyades, both of which are visible to the naked eye. At first magnitude, the red giant Aldebaran is the brightest star in the constellation. In the northwest part of Taurus is the supernova remnant Messier 1, more known as the Crab Nebula. One of the closest regions of active star formation, the Taurus-Auriga complex, crosses into the northern part of the constellation; the variable star T Tauri is the prototype of a class of pre-main-sequence stars.
Taurus is a large and prominent constellation in the northern hemisphere's winter sky, between Aries to the west and Gemini to the east. In late November-early December, Taurus is visible the entire night. By late March, it is setting at sunset and disappears behind the Sun's glare from May to July; this constellation forms part of the zodiac and hence is intersected by the ecliptic. This circle across the celestial sphere forms the apparent path of the Sun as the Earth completes its annual orbit; as the orbital plane of the Moon and the planets lie near the ecliptic, they can be found in the constellation Taurus during some part of each year. The galactic plane of the Milky Way intersects the northeast corner of the constellation and the galactic anticenter is located near the border between Taurus and Auriga. Taurus is the only constellation crossed by all three of the galactic equator, celestial equator, ecliptic. A ring-like galactic structure known as Gould's Belt passes through the constellation.
The recommended three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is "Tau". The official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of 26 segments. In the equatorial coordinate system, the right ascension coordinates of these borders lie between 03h 23.4m and 05h 53.3m, while the declination coordinates are between 31.10° and −1.35°. Because a small part of the constellation lies to the south of the celestial equator, this can not be a circumpolar constellation at any latitude. During November, the Taurid meteor shower appears to radiate from the general direction of this constellation; the Beta Taurid meteor shower occurs during the months of June and July in the daytime, is observed using radio techniques. Between 18 and 29 October, the Southern Taurids are active. However, between November 1 and 10, the two streams equalize; the brightest member of this constellation is Aldebaran, an orange-hued, spectral class K5 III giant star.
Its name derives from الدبران al-dabarān, Arabic for "the follower" from the fact that it follows the Pleiades during the nightly motion of the celestial sphere across the sky. Forming the profile of a Bull's face is a V or K-shaped asterism of stars; this outline is created by prominent members of the Hyades, the nearest distinct open star cluster after the Ursa Major Moving Group. In this profile, Aldebaran forms the bull's bloodshot eye, described as "glaring menacingly at the hunter Orion", a constellation that lies just to the southwest; the Hyades span about 5° of the sky, so that they can only be viewed in their entirety with binoculars or the unaided eye. It includes Theta Tauri, with a separation of 5.6 arcminutes. In the northeastern quadrant of the Taurus constellation lie the Pleiades, one of the best known open clusters visible to the naked eye; the seven most prominent stars in this cluster are at least visual magnitude six, so the cluster is named the "Seven Sisters". However, many more stars are visible with a modest telescope.
Astronomers estimate that the cluster has 500-1,000 stars, all of which are around 100 million years old. However, they vary in type; the Pleiades themselves are represented by bright stars. The cluster is estimated to dissipate in another 250 million years; the Pleiades cluster is classified as a Shapley class c and Trumpler class I 3 r n cluster, indicating that it is irregularly shaped and loose, though concentrated at its center and detached from the star-field. In the northern part of the constellation to the northwest of the Pleiades lies the Crystal Ball Nebula, known by its catalogue designation of NGC 1514; this planetary nebula is of historical interest following its discovery by German-born English astronomer William Herschel in 1790. Prior to that time, astronomers had assumed that nebulae were unresolved groups of stars. However, Herschel could resolve a star at the center of the nebula, surrounded by a nebulous cloud of some type. In 1864, English astronomer William Huggins used the spectrum of this nebula to deduce that the nebula is a luminous gas, rather than stars.
To the west, the two horns of the bull are formed by Zeta Tauri.
Nils Hønsvald was a Norwegian newspaper editor and politician for the Labour Party. He was one of the leading figures in Norwegian politics from 1945 to 1969, he served as President of the Nordic Council in 1958 and 1963. Hønsvald was born in Vestfold County, Norway, he was editor of Østfold Arbeiderblad in Sarpsborg, regional newspaper for the Norwegian Labour Party, discontinued in 1929 and editor of Sarpsborg Arbeiderblad, a local newspaper published in Sarpsborg. He participated in the Left Communist Youth League's military strike action of 1924, he was sentenced to 120 days of prison. He was present at the congress of 24 April 1927 when the Left Communist Youth League was merged with the Socialist Youth League to found the Workers' Youth League. During the occupation of Norway by Nazi Germany, he was arrested in March 1941, he was incarcerated at Møllergata 19 before being transferred to Åneby concentration camp and Grini concentration camp in May. He was released on 12 June 1941. In December 1944 he was arrested again, was transferred from Fredrikstad to Grini, where he remained until the war's end.
Hønsvald was Minister of Supplies and Reconstruction, minister without ministry in 1950. Hønsvald was President of the President of the Odelsting. Nils Hønsvalds gate in Sarpsborg was named in his honor. Photograph of Nils Hønsvald
The appendicular skeleton is the portion of the skeleton of vertebrates consisting of the bones that support the appendages. The appendicular skeleton includes the skeletal elements within the limbs, as well as supporting shoulder girdle pectoral and pelvic girdle; the word appendicular is the adjective of the noun appendage, which itself means a part, joined to something larger. Of the 206 bones in the human skeleton, the appendicular skeleton comprises 126. Functionally it is involved in locomotion of the axial skeleton and manipulation of objects in the environment; the appendicular skeleton forms during development from cartilage, by the process of endochondral ossification. The appendicular skeleton is divided into six major regions: Shoulder girdles - Left and right clavicle and scapula. Arms and forearms - Left and right humerus and radius. Hands - Left and right carpals, proximal phalanges, intermediate phalanges and distal phalanges. Pelvis - Left and right hip bone. Thighs and legs - Left and right femur, patella and fibula.
Feet and ankles - Left and right tarsals, proximal phalanges, intermediate phalanges and distal phalanges. It is important to realize that through anatomical variation it is common for the skeleton to have many accessory bones; the appendicular skeleton of 126 bones and the axial skeleton of 80 bones together form the complete skeleton of 206 bones in the human body. Unlike the axial skeleton, the appendicular skeleton is unfused; this allows for a much greater range of motion. Axial skeleton pectoral girdle pelvic girdle Legs Bones | 0.803521 | 3.722268 |
Astronomers are expected to reveal the first close-up images of a monster black hole during a global event later.
Eight radio telescopes around the world have been pointed at two of the cosmic behemoths, one at the heart of our galaxy, the Milky Way, and another nearly 54 million light years away.
Now, after two years of acquiring and processing the data, the international team of scientists at the Event Horizon Telescope (EHT) programme is set to present their ‘groundbreaking’ first results.
Media have been told to gather for press conferences in Brussels, Washington, Santiago, Shanghai, Taipei, Tokyo, and Lyngby in Denmark that are due to begin at around 2pm BST.
Black holes are regions where matter has been crushed by gravity to an infinitely small space where the normal laws of physics no longer apply.
While nothing can escape the gravitational vortex of a black hole – not even light – gas and radiation rage in a swirling eddy around the brink of the abyss. It is this point-of-no-return precipice, called the Event Horizon, that astronomers have tried to observe for the first time.
The EHT project was launched in April 2017.
Sagittarius A (SgrA), the supermassive black hole at the centre of the Milky Way, is some 26,000 light years away. Images of SgrA are likely to show a lopsided ring of brightness due to gravity bending light closer to the black hole more strongly than light further away. The project may help scientists struggling to marry together two apparently incompatible pillars of physics, Einstein’s theory of general relativity and quantum mechanics.
The first relates to laws of nature on cosmic scales, while the second governs the weird world of subatomic particles where it is possible to be in two places at once.
Physicist and black hole expert Lia Medeiros, from the University of Arizona, US, told ScienceNews magazine: ‘If general relativity buckles at a black hole’s boundary, it may point the way forward for theorists.’
The EHT’s other target, M87, is notable for shooting out a fast jet of charged subatomic particles that stretches for some 5,000 light years.
The new observations are expected to provide clues about M87’s magnetic field, which may be linked to the jet mechanism. | 0.878694 | 3.580467 |
Mouse over the image and scroll to zoom in and out, or use the blue buttons that appear in the lower right corner of the image.
Several million young stars are vying for attention in this NASA Hubble Space Telescope image of a nearby region of star birth known as 30 Doradus. Located about 170,000 light-years away in the heart of the Tarantula Nebula, 30 Doradus is part of the Large Magellanic Cloud, a small, satellite galaxy of our own Milky Way galaxy.
30 Doradus is the brightest star-forming region visible in a neighboring galaxy and home to the most massive stars ever seen. No known star-forming region that is inside our Milky Way is as large or as prolific as 30 Doradus. It churns out stars at a furious pace over millions of years. The region's sparkling centerpiece is a giant, young star cluster called NGC 2070, only 2 million to 3 million years old.
The image reveals the stages of star birth, from young stars a few thousand years old and still wrapped in cocoons of dark gas, to behemoths that die young in supernova explosions. It also shows star clusters of various ages, from about 2 million to 25 million years old.
30 Doradus is also near enough to Earth for its contents and structures to be studied in detail. Astronomers using Hubble can resolve individual stars, which provide important information about the stars' birth and evolution. Because of this, 30 Doradus is a "Rosetta Stone" for understanding regions of intense star formation.
This image was released to celebrate Hubble's 22nd anniversary. Learn more at HubbleSite's NewsCenter.
NASA, ESA, D. Lennon and E. Sabbi (ESA/STScI), J. Anderson, S. E. de Mink, R. van der Marel, T. Sohn, and N. Walborn (STScI), N. Bastian (Excellence Cluster, Munich), L. Bedin (INAF, Padua), E. Bressert (ESO), P. Crowther (University of Sheffield), A. de Koter (University of Amsterdam), C. Evans (UKATC/STFC, Edinburgh), A. Herrero (IAC, Tenerife), N. Langer (AifA, Bonn), I. Platais (JHU), and H. Sana (University of Amsterdam) | 0.871936 | 3.191411 |
NASA has narrowed its choices for a new billion-dollar robotic space mission: A nuclear-powered quadcopter to explore the hazy landscape of Saturn’s largest moon Titan, or a probe to scoop up a piece of a comet and return it to Earth.
The space agency announced its selections Wednesday, picking two concepts from 12 proposals submitted by scientists earlier this year in a competition to win government funding to build and launch a mission by the end of 2025.
The teams behind the Dragonfly mission to Titan and the CAESAR mission to comet 67P/Churyumov-Gerasimenko will receive $4 million from NASA over the next year to refine their plans and designs, setting the stage for NASA to decide in July 2019 which mission will go forward to launch.
The winner will become the fourth mission in NASA’s New Frontiers program, a series of science-driven solar system probes cost-capped at about $1 billion that has so far produced the New Horizons mission to Pluto, the Juno orbiter at Jupiter, and the OSIRIS-REx spacecraft on the way to snag a sample of an asteroid and bring it back to Earth.
The Dragonfly mission would reach Titan in 2034, descend through its thick atmosphere and deploy a rotorcraft to make multiple hops across the moon’s alien surface over a two-year mission, surveying dune fields and rivers and lakes of liquid methane and ethane in search of the building blocks of life.
“Titan is a unique ocean world,” said Elizabeth Turtle, principal investigator for the Dragonfly mission at the Johns Hopkins University Applied Physics Laboratory. “It has a dense atmosphere, with very complex hydrocarbons produced in the atmosphere and littering the surface.
Most of what scientists know about Titan came from NASA’s Cassini spacecraft and a European Space Agency probe named Huygens, which made the first landing on Saturn’s largest moon in 2005.
Cassini made 127 flybys of Titan in its 13-year tour of Saturn before its mission ended in September, unveiling the moon’s surface for the first time to see oceans with rugged shorelines, streams and sand dunes. NASA’s Voyager probes could not see through Titan’s hazy veneer when they flew by Saturn in 1980 and 1981.
“It has lakes and seas of liquid methane and ethane, and rivers that flow across the surface, and what we’re excited to continue with this mission concept is to build upon the Cassini-Huygens exploration of Titan with Dragonfly, which is a rotorcraft lander,” Turtle said Wednesday.
“Unique about Titan is that it’s got a liquid cycle very much like Earth’s water cycle, but it’s with methane,” said Peter Bedini, Dragonfly project manager at the Applied Physics Laboratory in Laurel, Maryland, where the craft would be designed and built.
But many questions about Titan remain unanswered. It’s the solar system’s only moon with a dense atmosphere — made primarily of nitrogen and methane — but Titan’s orange haze hides its surface from conventional cameras.
Cassini peered through the atmosphere with an imaging radar to reveal huge land masses, oceans and other surface features.
But Cassini and Huygens “left us with a lot of fundamental unknowns,” Turtle said. “We don’t know the basic composition of the solid surface on Titan. We have some information from spectral characteristics from orbit. We have some information from the Huygens probe, but neither (Cassini nor Huygens) was designed or able to do detailed measurements of the kind of rich organic chemistry that we know is occurring there. So Dragonfly is designed to go back to build on what we’ve learned from Cassini-Huygens and answer the fundamental unknowns that remain about Titan.”
The Dragonfly drone would carry cameras, drills, seismic and weather sensors, and spectrometers to examine the composition of Titan’s rocks and soil, collecting four basic types of measurements. A plutonium power source, known as a Multi-Mission Radioisotope Thermoelectric Generator, or MMRTG, would charge the craft’s batteries to power the instruments, eight electrically-driven rotors and a high-gain antenna to beam data directly to Earth.
Dragonfly’s mobility is a key advantage, officials said, allowing it to travel tens to hundreds of kilometers across Titan, Turtle said.
“In this way, we can evaluate how far pre-biotic chemistry has progressed in an environment that we know had the ingredients for life — for water-based life, or potentially even hydrocarbon-based life,” she said.
“When you first hear the high concept of Dragonfly, it might seem a little ambitious, or maybe even a little audacious,” Bedini said in a presentation earlier this year.
A flying drone would allow scientists to explore a wider range on Titan, first touching down in a relatively flat region before departing to more interesting — and hazardous — locations to land and conduct observations for weeks at a time, then moving on again.
“We could take a lander and we could plop it down on Titan, and we could take these four measurements at one place, and we would significantly increase our understanding of Titan and … bodies like it and other ocean worlds,” Bedini said. “However, we can multiply the value of this mission if we add aerial mobility because now we can look at this very diverse surface that is Titan. It’s got a variety of geologic settings. Instead of just measuring in one place, we can go to many places and increase the science return substantially.”
And unlike a rover on the surface, an instrumented drone would not be stopped or delayed by obstacles like rocks and steep slopes.
Titan’s thick atmosphere makes getting down to the ground tricky, but once there, flying a drone should be feasible.
“It turns out that the easiest place in the solar system to fly a quadcopter is on Titan,” Bedini said. “That’s because Titan’s got an atmosphere more than four times as dense as Earth, and the gravity is only one-seventh that of Earth.”
The other New Frontiers finalist — the Comet Astrobiology Exploration Sample Return mission, or CAESAR — would embark on a round-trip journey to comet 67P/Churyumov-Gerasimenko, revisiting the same comet explored by the European Space Agency’s Rosetta mission from 2014 through 2016.
The CAESAR mission concept is led by Steve Squyres, a professor of astronomy at Cornell University and lead scientist for NASA’s Spirit and Opportunity rovers on Mars.
After launching in the mid-2020s, CAESAR would depart toward comet 67P powered by solar-electric thrusters and armed with an extendable collector to capture at least 100 grams, or 3.5 ounces, of material from its icy nucleus.
Built by Orbital ATK, the spacecraft would bring the specimens back to Earth for scientists to analyze in ground-based labs. While NASA’s Stardust mission brought back dust grains from the coma of a comet in 2006, samples from a comet’s nucleus have never been returned from space.
“Comets are among the most scientifically important objects in the solar system, but they’re also among the most poorly understood,” Squyres said Wednesday.
“They’re the most primitive building blocks of planets,” he said. “They contain materials that date from the very earliest moments of solar system formation, and even before. Comets were a source of water for the Earth’s oceans, and critically, they were a source of organic molecules that contributed to the origin of life.”
CAESAR would approach comet 67P for touch-and-go maneuvers to retrieve two types of samples: volatile and non-volatile material.
Frozen volatile compounds, like water ice, are heated when comets get close to the sun, spewing jets of dust and gas dozens of miles into space.
“What makes comets really special, what distinguishes them from every other primitive body out there, is what we call their volatile components,” Squyres said. “The ices, the volatile organic compounds, just aren’t present in any other kind of planetary body.”
The two types of samples would be separated into different chambers inside a re-entry capsule that would return to a parachute-assisted landing in Utah in November 2038.
“Patience is a virtue in this business,” Squyres said.
The return canister would be provided by the Japan Aerospace Exploration Agency, based on the design employed on Japan’s Hayabusa asteroid sample return mission, which landed in 2010.
“Of course, the end date of the flight is really just the beginning of the mission,” Squyres said. “That’s the beginning of the mission science, when those samples come back, and the science will extend for decades.”
Squyres said going back to comet 67P/Churyumov-Gerasimenko will give mission planners an idea of what to expect at the destination ahead of time.
“By going to that comet, there’s an enormous amount of risk reduction that takes place because we’re going to an object that we’ve already got good maps of,” Squyres said.
“The reason that we’re going to Churyumov-Gerasimenko is that it provides us with an enormous amount of information about how to conduct our mission,” he said. “Churyumov-Gerasimenko has been mapped in detail by the Rosetta mission, so we are able to design our mission, our spacecraft, specifically for the conditions that we know to exist there.”
Squyres said he will step down as lead scientist on the Opportunity rover mission, which still operates on Mars nearly 14 years after its arrival, if NASA picks CAESAR for development and launch.
Thomas Zurbuchen, head of NASA’s science mission directorate, told reporters Wednesday he selected Dragon and CAESAR based on their scientific and technical merits.
“I selected these mission concepts based on their outstanding and visionary science, as well as the endorsement of our rigorous selection process that looks at both scientific and technical viability,” Zurbuchen said.
The 12 proposals submitted to NASA in April focused on six themes outlined by the National Academy of Sciences:
- Comet Surface Sample Return
- Lunar South Pole-Aitken Basin Sample Return
- Ocean Worlds (Titan and/or Enceladus)
- Saturn Probe
- Trojan Tour and Rendezvous
- Venus In Situ Explorer
The winning mission selected in 2019 will have a cost cap of $850 million, a figure that does not include the cost of a launcher or operations, which will likely drive the project’s total budget above $1 billion.
NASA is expected to pick a launch vehicle for the next New Frontiers mission in the early 2020s.
The space agency will fund further technological research on two other proposals that did not make Wednesday’s cut.
A team that proposed sending a robotic mission named ELSAH to search for biosignatures at Saturn’s moon Enceladus will receive additional NASA funding develop ways to achieve stringent contamination controls for life detection. Scientists who worked on the VICI proposal — a twin-lander mission to Venus — will also get support in advancing technologies that can withstand the extreme pressures and temperatures at the planet’s surface.
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Follow Stephen Clark on Twitter: @StephenClark1. | 0.884391 | 3.097356 |
NASA has selected a mission to dispatch six CubeSats, each the size of a toaster oven, to an orbit more than 20,000 miles from Earth to study massive particle ejections from the sun.
The Sun Radio Interferometer Space Experiment, or SunRISE, mission will launch no later than July 1, 2023, after its selection by NASA as a mission of opportunity under the agency’s Explorers program.
SunRISE will consist of six CubeSats flying as close as 6 miles (10 kilometers) from each other. The nanosatellites will together act as a giant radio telescope, detecting low-frequency emissions from solar activity and downlinking the measurements through NASA’s Deep Space Network.
Data gathered by the SunRISE CubeSats will tell scientists about the source of coronal mass ejections, which launch huge bubbles of gas and magnetic fields from the sun. Employing a constellation of small satellites will allow researchers to localize the eruptions.
Coronal mass ejections accelerate energetic particles throughout the solar system, and the particles can spawn geomagnetic storms when they reach Earth. Such storms can impact radio communications, satellite navigation, electrical grids and satellite and human spaceflight operations.
“We are so pleased to add a new mission to our fleet of spacecraft that help us better understand the sun, as well as how our star influences the space environment between planets,” said Nicky Fox, director of NASA’s heliophysics division. “The more we know about how the sun erupts with space weather events, the more we can mitigate their effects on spacecraft and astronauts.”
Scientists want to better understand the processes at the sun that accelerate solar energetic particles during coronal mass ejections.
The six SunRISE CubeSats will detect radio emissions simultaneously from slightly different locations in space. The radio signals that are the focus of the SunRISE mission are blocked by Earth’s atmosphere, so scientists must send up satellites to study them.
The SunRISE mission will create 3D maps to pinpoint the locations of powerful solar eruptions, while tracking how the particle clouds and magnetic field lines evolve as they depart the sun. According to NASA, the data will help determine what initiates and accelerates the giant jets of radiation.
The principal investigator for the SunRISE mission is Justin Kasper at the University of Michigan in Ann Arbor. The mission will be managed at NASA’s Jet Propulsion Laboratory in Pasadena, California.
NASA says the SunRISE mission will cost $62.6 million to design, build and launch.
Each of the SunRISE nanosatellites is a six-unit, or 6U, CubeSat. They will launch together on a geostationary satellite built by Maxar Technologies equipped with a Payload Orbital Delivery System, or PODS, rideshare accommodation.
The Maxar-built satellite will deploy the SunRISE satellites into an orbit just above geostationary altitude — a so-called GEO graveyard orbit — more than 22,000 miles above Earth, Kasper said in an email to Spaceflight Now.
Kasper said Maxar and NASA have not identified the satellite that SunRISE will ride into orbit. That will come in about one year, he said.
The SunRISE satellites will be built at the Space Dynamics Laboratory at Utah State University, and the radio detectors will be provided by JPL, according to Kasper.
SunRISE was selected in 2017 for an 11-month mission concept study as one of two missions of opportunity under NASA’s Explorers program. In February 2019, NASA approved an extended formulation study for an additional year to further mature technologies and plans for the SunRISE mission.
The other mission of opportunity selected for study in 2017 was the Atmospheric Waves Experiment, or AWE, mission. NASA decided last year to proceed with development of the $42 million AWE mission, which will mount an instrument outside the International Space Station to investigate the link between weather patterns in Earth’s atmosphere and space weather.
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Follow Stephen Clark on Twitter: @StephenClark1. | 0.83257 | 3.4154 |
French scientists have experimentally optimized the operation of the first wall-less Hall thruster prototype, a novel electric rocket engine design suitable for long-duration, deep space missions
Washington, D.C., Oct.27, 2015 – Hall thrusters are advanced electric rocket engines primarily used for station-keeping and attitude control of geosynchronous communication satellites and space probes. Recently, the launch of two satellites based on an all-electric bus has marked the debut of a new era – one in which Hall thrusters could be used not just to adjust orbits, but to power the voyage as well. Consuming 100 million times less propellant or fuels than conventional chemical rockets, a Hall thruster is an attractive candidate for exploring Mars, asteroids and the edge of the solar system. By saving fuel the thruster could leave room for spacecraft and send a large amount of cargo in support of space missions. However, the current lifespan of Hall thrusters, which is around 10,000 operation hours, is too short for most space explorations, which require at least 50,000 operation hours.
To prolong the lifespan of Hall thrusters, a team of researchers from the French National Center for Scientific Research have experimentally optimized the operation of a novel, wall-less thruster prototype developed a year ago by the same team. The preliminary performance results were satisfactory, the team said, and pave the way toward developing a high-efficiency wall-less Hall thruster suitable for long-duration, deep space missions. The researchers present their work in a paper published this week in the journal Applied Physics Letters, from AIP Publishing.
Hall thrusters are electric rocket engines using a super high speed (on the order of 45,000 mph) stream of plasma to push spacecraft forward. Their operating principle relies on the creation of a low-pressure quasi-neutral plasma discharge in a crossed magnetic and electric field configuration. The propellant gas, typically xenon, is ionized by electrons trapped in the magnetic field.
In the conventional Hall thruster configuration, the magnetized discharge is confined to an annular dielectric cavity with the anode at one end, where the gas is injected, and an external cathode injecting electrons. Ionization of the propellant gas occurs inside the cavity, with ions accelerated by the electric field that stretches from the interior to the exterior of the cavity.
"The major drawback of Hall thrusters is that the discharge channel wall materials largely determine the discharge properties, and consequently, the performance level and the operational time,” said Julien Vaudolon, the primary researcher in the Electric Propulsion team led by Professor Stéphane Mazouffre in the ICARE-CNRS Laboratory, France.
Vaudolon explained that the wall materials play a role in the plasma properties mainly through secondary electron emission, a phenomenon where high-energy ions hit the channel wall surface and induce the emission of secondary electrons. Additionally, the erosion of the discharge cavity walls due to bombardment of high-energy ions shortens the thruster’s lifetime.
“Thus, an effective approach to avoid the interaction between the plasma and the discharge channel wall is to move the ionization and acceleration regions outside the cavity, which is an unconventional design named a Wall-Less Hall Thruster,” Vaudolon said.
Last year, the team developed a small-scale, wall-less thruster prototype based on a classical Hall thruster. At first the researchers simply moved the anode to the channel exhaust plane. However, this first wall-less thruster turned out to be a low-performance device, as the magnetic field lines are perpendicular to the thruster axis, which cross the anode placed at the channel exhaust plane.
“Magnetic fields are used to trap hot electrons injected from the external cathode and prevent them from reaching the anode,” Vaudolon said. “Basically an electron travels along the magnetic field line. If the magnetic field lines cross the anode, a large portion of hot electrons will be collected at the anode and won’t take part in the ionization of the xenon atoms, resulting in high discharge current, low ionization degree, and consequently, low performance level.”
To optimize the wall-less prototype and make the magnetic lines avoid the anode surface, the team rotated the magnetic barrier by 90 degrees, so that it injected the magnetic field lines parallel with the axial direction. The anode was still placed at the channel exhaust plane, but its shape is curved to avoid any interaction with the magnetic field lines.
Based on the PPS-Flex, a 1.5 kilowatts class thruster designed by the GREM3 Team at LAPLACE Laboratory, France and capable of modifying the magnetic field topology over a broad range of configurations, the team has validated their optimization strategies by modifying several parts and parameters of the thruster. The measurement of some operation parameters such as the thrust level, anode efficiency and far-field ion properties displayed a satisfactory performance level. However, Vaudolon said, some further optimization is still needed for the thruster’s efficient operation at high power.
“The wall-less thruster allows scientists to observe regions of the plasma previously hidden behind the channel walls. Now the plasma region can be observed and diagnosed using probes and/or laser diagnostic tools,” Vaudolon said. He also pointed out that the access to key regions of the plasma facilitates a thorough investigation of plasma instability and small-scale turbulence for a better understanding of the discharge physics and anomalous electron transport.
“Despite decades of research, the physics of Hall thrusters is still far from being understood, and the device characterization methods still rely on trials and testing, leading to expensive efforts,” Vaudolon said. “The major difficulty in developing predictive simulations lies in modeling the interaction between plasma and wall. The wall-less design would be an effective solution, potentially making future predictive simulations feasible and reliable.”
After the lessons learned from the testing of the PPS-Flex version, the team’s next step is to design a dedicated wall-less Hall thruster and fully exploit the possibilities offered by a wall-less architecture.
For More Information:
Jason Socrates Bardi
jbardi [at] aip.org
Applied Physics Letters
Applied Physics Letters features concise, rapid reports on significant new findings in applied physics. The journal covers new experimental and theoretical research on applications of physics phenomena related to all branches of science, engineering, and modern technology. | 0.811185 | 3.006925 |
Despite being much larger than Earth with a radiation environment, an exoplanet called K2-18b had detected water vapor signatures detected for the first time in the atmosphere of a planet beyond our solar system that resides in a habitable zone. NASA’s Hubble Space Telescope found water vapor in the atmosphere of K2-18b, an exoplanet orbiting a small red dwarf star about 110 light-years away in the constellation Leo. Once confirmed, this will be the first and only exoplanet known to have both water in its atmosphere as well as temperatures that could sustain liquid water on a rocky surface. Read more for a video and additional information.
Unfortunately, K2-18b may be more hostile to life as we know it than Earth due to the high level of activity of its red dwarf star exposing the planet to more high-energy radiation. It also has a mass eight times greater than Earth’s, which means its surface gravity would be significantly higher than on our own planet.
“K2-18b is one of hundreds of ‘super-Earths’ — exoplanets with masses between those of Earth and Neptune — found by Kepler. NASA’s TESS mission is expected to detect hundreds more super-Earths in the coming years. The next generation of space telescopes, including the James Webb Space Telescope, will be able to characterize exoplanet atmospheres in more detail,” said NASA in a press release. | 0.874231 | 3.40251 |
Joining the search for the sources of gravitational waves
BlackGEM is a wide-field array of optical telescopes to be located at ESO’s La Silla Observatory in Chile’s Atacama desert. It will initially comprise 3 telescopes, each 0.65 metre in diameter, and the aim is to eventually expand the array to 15 telescopes. The telescopes can look at different parts of the sky, or work together as a single 3.6-metre telescope. The array is largely robotic and remotely controlled from Radboud University. It was jointly developed by Radboud University, the Netherlands Research School for Astronomy (NOVA), and the KU Leuven.
BlackGEM’s scientific goals are to detect and characterise optical counterparts to gravitational wave detections. To enable this, it will conduct an all-sky survey of the southern sky, perform a bi-weekly scan of the southern sky, and characterise intra-night transients, new stars that appear or disappear within a single night.
Events that produce detectable gravitational waves are expected to occur within approximately 650 million light-years of Earth. Many will therefore be located in or near resolved galaxies and will be faint. It is essential for BlackGEM to have high spatial resolution in order to resolve and accurately locate these sources against the background of the night-sky, making La Silla — with its excellent weather and thin atmosphere — an ideal observing site.
Science with BlackGEM
BlackGEM is joining the search for some of the most powerful and dramatic events in the Universe: merging neutron stars and black holes. Such exotic events cause ripples in the fabric of spacetime known as gravitational waves, and BlackGEM will work in conjunction with the new generation of gravitational wave detectors such as LIGO and Virgo to follow up these events in visible light. BlackGEM will pinpoint the sources responsible for gravitational waves so that bigger telescopes — such as ESO’s Very Large Telescope (VLT) — can carry out detailed follow-up observations, providing astronomers with insight into some of the most extreme events in the cosmos.
The BlackGEM array can also function as a highly capable survey telescope and a portion of its time will be spent surveying the southern skies (30 000 square degrees in six optical filters). Detailed surveys provide astronomers with statistical information about objects in the sky, enabling, for example, studies of galactic evolution from the early Universe to today. During this survey, BlackGEM will also study fast (less than one day) transient sources. Transients are astronomical events that only last for a certain amount of time; usually these are deep sky events such as supernovae, gamma-ray bursts, transits, and tidal disruption events.
More about BlackGEM
- Read more about this telescope on the BlackGEM website. | 0.857193 | 4.051591 |
The first in a cycle of challenging occultations of the bright star Spica for northern hemisphere observers begins this coming Monday on August 12th.
Watching a bright star or planet wink out on the dark limb of the Moon can be an amazing event to witness. It’s an abrupt “now you see it, now you don’t” event in a universe which often seems to move at an otherwise glacial pace. And if the event grazes the limb of the Moon, an observer may see a series of winks as the starlight streams through the lunar valleys.
An occultation occurs when one object passes in front of another as seen from the observer’s vantage point. The term has its hoary roots back in a time when astronomy was intertwined with its pseudoscience ancestor of astrology. Even today, I still get funny looks from non-astronomy friends when I use the term occultation, as if it just confirms their suspicions of the arcane arts that astronomers really practice in secret.
But back to reality-based science. At an apparent magnitude of +1.1, Spica is the 3rd brightest star that the Moon can occult along its five degree path above and below the plane of the ecliptic. It’s also one of only four stars brighter than +1.4 magnitude on the Moon’s path. The others are Antares (magnitude +1.0), Regulus (magnitude +1.4), and Aldebaran (magnitude +0.8). All of these are bright enough to be visible on the lunar limb through binoculars or a telescope in the daytime if conditions are favorable.
It’s interesting to note that this situation also changes over time due to the precession of the equinoxes. For example, the bright star Pollux was last occulted by the Moon in 117 BC, but cannot be covered by the Moon in our current epoch.
Spica is currently in the midst of a cycle of 21 occultations by our Moon. This cycle started in July 25th, 2012 and will end in January 2014.
Spica is a B1 III-IV type star 10 times the mass of the Sun. At 260 light years distant, Spica is one of the closest candidates to the Earth along with Betelgeuse to go supernova. Now, THAT would make for an interesting occultation! Both are safely out of the ~100 light year distant “kill zone”.
What follows are the circumstances for the next four occultations of Spica by the Moon. The times are given for closest geocentric conjunction of the two objects. Actual times of disappearance and reappearance will vary depending on the observer’s location. Links are provided for each event which include more info.
First up is the August 12th occultation of Spica, which favors Central Asia and the Asian Far East. This will occur late in the afternoon sky around 09:00 UT and prior to sunset. The waxing crescent Moon will be six days past New phase. North American observers will see the Moon paired five degrees from Spica with Saturn to the upper left on the evening of August 12th.
Next is the September 8th daytime occultation of Spica for Europe, the Middle East and northern Africa around ~15UT. This will be a challenge, as the Moon will be a waxing crescent at only 3 days past New. Observers in the Middle East will have the best shot at this event, as the occultation occurs at dusk and before moonset. Note that the Moon also occults Venus six hours later for Argentina and Chile.
After taking a break in October (the occultation of October 5 occurs only 23 hours after New and is unobservable), the Moon again occults Spica on November 2nd for observers across Europe & Central Asia. This will be a difficult one, as the Moon will be only 20 hours from New and a hybrid solar eclipse that will cross the Atlantic and central Africa. It may be possible to lock on to the Moon and track it up into the daylight, just be sure to physically block the rising Sun behind a building or hill!
Finally, the Moon will occult Spica for North American observers on November 29th centered on 17:03 UT. This will place the event low in the nighttime sky for Alaskan observers. It’ll be a bit more of a challenge for Canadian and U.S. observers in the lower 48, as the Moon & Spica will be sandwiched between the Sun and the western horizon in the mid-day sky. As an added treat, comet C/2012 S1 ISON will reach perihelion on November 28th, just 20 hours prior and will be reaching peak brilliance very near the Sun.
And as an added bonus, the Moon will be occulting the +2.8 star Alpha Librae (Zubenelgenubi) on August 13th for central South America.
All of these events are challenges, to be sure. Viewers worldwide will still catch a close night time pairing of the Moon and Spica on each pass. We’ve watched the daytime Moon occult Aldebaran with binoculars while stationed in Alaska back in the late 1990’s, and can attest that such a feat of visual athletics is indeed possible.
And speaking of which, the next bright star due for a series of occultations by the Moon is Aldebaran starting in 2015. After 2014, Spica won’t be occulted by the Moon again until 2024.
But wait, there’s more- the total eclipse of the Moon occurring on April 15th 2014 occurs just 1.5 degrees from Spica, favoring North America. This is the next good lunar eclipse for North American observers, and one of the best “Moon-star-eclipse” conjunctions for this century. Hey, at least it’ll give U.S. observers something besides Tax Day to look forward to in mid-April. More to come in 2014! | 0.872603 | 3.721497 |
Fall will soon be at our doorstep. But before the leaves change colors and the smell of pumpkin fills our coffee shops, the Pleiades star cluster will mark the new season with its earlier presence in the night sky.
The delicate grouping of blue stars has been a prominent sight since antiquity. But in recent years, the cluster has also been the subject of an intense debate, marking a controversy that has troubled astronomers for more than a decade.
Now, a new measurement argues that the distance to the Pleiades star cluster measured by ESA’s Hipparcos satellite is decidedly wrong and that previous measurements from ground-based telescopes had it right all along.
The Pleiades star cluster is a perfect laboratory to study stellar evolution. Born from the same cloud of gas, all stars exhibit nearly identical ages and compositions, but vary in their mass. Accurate models, however, depend greatly on distance. So it’s critical that astronomers know the cluster’s distance precisely.
A well pinned down distance is also a perfect stepping stone in the cosmic distance ladder. In other words, accurate distances to the Pleiades will help produce accurate distances to the farthest galaxies.
But accurately measuring the vast distances in space is tricky. A star’s trigonometric parallax — its tiny apparent shift against background stars caused by our moving vantage point — tells its distance more truly than any other method.
Originally the consensus was that the Pleiades are about 435 light-years from Earth. However, ESA’s Hipparcos satellite, launched in 1989 to precisely measure the positions and distances of thousands of stars using parallax, produced a distance measurement of only about 392 light-years, with an error of less than 1%.
“That may not seem like a huge difference, but, in order to fit the physical characteristics of the Pleiades stars, it challenged our general understanding of how stars form and evolve,” said lead author Carl Melis, of the University of California, San Diego, in a press release. “To fit the Hipparcos distance measurement, some astronomers even suggested that some type of new and unknown physics had to be at work in such young stars.”
If the cluster really was 10% closer than everyone had thought, then the stars must be intrinsically dimmer than stellar models suggested. A debate ensued as to whether the spacecraft or the models were at fault.
To solve the discrepancy, Melis and his colleagues used a new technique known as very-long-baseline radio interferometry. By linking distant telescopes together, astronomers generate a virtual telescope, with a data-gathering surface as large as the distances between the telescopes.
The network included the Very Long Baseline Array (a system of 10 radio telescopes ranging from Hawaii to the Virgin Islands), the Green Bank Telescope in West Virginia, the William E. Gordon Telescope at the Arecibo Observatory in Puerto Rico, and the Effelsberg Radio Telescope in Germany.
“Using these telescopes working together, we had the equivalent of a telescope the size of the Earth,” said Amy Miouduszewski, of the National Radio Astronomy Observatory (NRAO). “That gave us the ability to make extremely accurate position measurements — the equivalent of measuring the thickness of a quarter in Los Angeles as seen from New York.”
After a year and a half of observations, the team determined a distance of 444.0 light-years to within 1% — matching the results from previous ground-based observations and not the Hipparcos satellite.
“The question now is what happened to Hipparcos?” Melis said.
The spacecraft measured the position of roughly 120,000 nearby stars and — in principle — calculated distances that were far more precise than possible with ground-based telescopes. If this result holds up, astronomers will grapple with why the Hipparcos observations misjudged the distances so badly.
ESA’s long-awaited Gaia observatory, which launched on Dec. 19, 2013, will use similar technology to measure the distances of about one billion stars. Although it’s now ready to begin its science mission, the mission team will have to take special care, utilizing the work of ground-based radio telescopes in order to ensure their measurements are accurate.
The findings have been published in the Aug. 29 issue of Science and is available online. | 0.858063 | 3.993653 |
Basically there were atoms of CHOMPS chemical elements floating in space.
After the bigbang explodes came together and from there the first live cell was created, then it evolved
Contemporary biology, in particular biochemistry, has made it clear that living organisms are made up of a variety of chemical elements. Among them there is a small group that are majority in quantity, these are: carbon (C), hydrogen (H), oxygen (O) and nitrogen (N), or briefly and as a mnemonic rule: CHON. In addition, there are other elements in much smaller quantities that are also essential for living organisms and that make possible the amazing phenomenon that we call "life". Among them we can mention, using their chemical symbols: Na, K, Ca, Mn, Mg, S, P, Si, Cr, Fe, Cu, Zn, F, Cl, I, Mo and others.
It should be clarified that the majority are found as ions and not as elements, since in many cases the latter are very reactive. For example, elements of the alkali metal family, such as Na and K, are explosive in contact with water. Obviously, it is not in this chemical way how they intervene in cellular biochemistry, but as ions (or cations, to give them their more specific name) Na + and K +. The same can be said of some elements that give rise to ions of opposite sign (anions), such as fluorine (F). This is the most reactive element of all, it is an extremely irritating gas and its inhalation represents a danger. The F - ion, called fluoride, has lost that reactivity, is soluble in water and is fundamental for cell physiology, mainly for use in teeth and bones.
Now let's go to another branch of science: cosmogony, which is the branch of astronomy that studies the evolutionary behavior of the universe and the origin of its characteristic features. According to this science the universe had a beginning, which is located 13 ± 2 billion years ago. That is, there is uncertainty about the precise time, but there is a very high probability that it has happened in the time interval between 11 and 15 billion years ago, with the highest probability occurring in the vicinity of 13 billion years.
The theory that best explains this event is known as the "Big Bang" (or Big Bang in English). It also states that within 4 minutes of our vertiginous expansion universe, its chemical composition was 76% hydrogen (H, with atomic number one), 24% helium (He, with atomic number two) and insignificant amounts of lithium (Li, with atomic number three). The atomic number indicates how many protons the nucleus of the atoms of each element has.
Figure 1. Timeline for the history of Universe life
There was no other element. Only the first two, if any three, positions of the table of the periodic classification of the elements had been occupied. With this raw material the chemistry was, evidently, quite limited. There was not enough variety (diverse chemical elements) to constitute systems as complex as life.
Where did the C, the N, the O, the Cu, the Zn and so many other elements with an atomic number greater than three arise and which, as we have already seen, are indispensable constituents of a living system? The cosmogony clearly answers this question, based on nuclear physics, as we shall see below.
Nuclear physics and cosmogony
The explanation offered by the cosmogony about the origin of the other elements involves the stars, which according to their mass were producing in the course of their evolution (or life) the different elements heavier than the H and the He.
The star conditions are such that they favor the realization of the different nuclear reactions that are forming the other elements of the table of the periodic classification that we know today.
Due to its very high temperature (for example, in the surface of our Sun the temperature is between 4 700 and 6 000 K and in its center to 20 million K) each star is a huge plasma sphere. Plasma is the state of matter that is characterized by having atomic nuclei devoid of all their peripheral electrons and shaking at high speeds, just like electrons.
Under these conditions it is possible that the nuclei collide with each other even though there are repulsive forces between them (because they all have a positive charge). At lower temperatures, with less thermal agitation, nuclear reactions are not possible. The nuclei would be accompanied by their electrons and simply would not touch each other, they would be diverted by the repulsive forces between charges of the same sign (negative, of their respective peripheral electrons). However, at high temperatures the nuclei do touch, collide and fuse together, like two droplets of water that collide and form a larger droplet. These are the nuclear fusion reactions that give rise to the process of nucleosynthesis, that is, to the synthesis of new nuclei, of new elements (heavier).
For a star like our Sun, by nucleosynthesis and starting from the mixture of H and He, could reach the formation of carbon and oxygen. Stars of greater mass are required to generate other heavier elements during their evolution. And still others (different) are synthesized in the final stages of life of these stars more massive than the Sun, during explosive processes of unimaginable violence.
The material produced by nucleosynthesis in the stars reaches to be dispersed by the space, in particular the one that is derived from those stars that are massive with an explosive and furious death.
In short, the mixture of H and He of the initial universe has been changing slowly thanks to the formation of stars of mass similar or greater to that of our Sun. At present the chemical composition of the universe is 75% hydrogen, 23 % helium and 2% of all other chemical elements. Slowly, the space of the universe has been subtly enriched by those elements heavier than the H and the He, in particular of C, O and N, and also of others that are essential for the development of life.
This material enriched in elements heavier than H and He will be dispersed and, under the appropriate conditions, a solar nebula can be formed, a protosol ignited by the nuclear reactions between the H and the He and forge a sun. Perhaps, planets are also formed to constitute a planetary star system, perhaps with characteristics similar to ours. But this history of the formation of the Planetary Solar System and the Earth must be told, in more detail, in another issue of Teacher's Mail.
Stellar physics and the emergence of life
In the preceding paragraphs, I have implicitly classified the stars according to their mass into two classes: those with a mass similar to the Sun, and those with a greater mass. There can not be stars much smaller than the Sun; if the mass of the latter had been lower by only 9%, the temperatures required to initiate nuclear fusion reactions would not have been reached, there would be no sun and we would not be here to tell.
It happens that according to the magnitude of its mass will be the duration of a star or, to put it another way, "the duration of its life" (since a star arises, burns or uses its fuel in nuclear fusion reactions, this one sooner or later it ends, and therefore, without more fuel, the star dies or dies).
All stars start their combustion with the primal mixture of H and He. Massive stars consume their fuel much faster than stars with sun-like mass. In fact, they consume it a thousand times faster. This makes a big difference. Indeed, thanks to the massive stars it was possible to synthesize elements of greater atomic number. This at the same time introduces a much broader variability in chemistry, which surely makes the emergence of life more feasible. However, although appropriate to produce diverse elements, the massive stars have a life too short to serve as a luminous and energetic source to possible planets that surround them and that could be the cradle of life.
On the other hand, the smallest stars, like our Sun, only produce light elements such as carbon and oxygen, and perhaps in that way the emergence of life would be less feasible or perhaps impossible because sufficient complexity and variety would not be achieved. chemical functions. However, because of their long life, these lower mass stars can be a reliable source of light and energy for a sufficiently long time to planets that could present the necessary conditions for the emergence of life. Our Sun is in the middle of its life (its total duration will be approximately 10 billion years).
To put it simply, there is a kind of complementation of functions, for the purposes of the origin of life in the universe, between both types of stars.
Fig. 2 Re presentation is the chemistry of different events in the history of the Universe. Assuming a total age of 13 million years. (If we suppose an age of 15 million years, the prcentajes would fit respectively to 11.16%, 37.4% and 70%).
In our Planetary Solar System, we, on Earth, have been able to verify the existence of a great variety of elements, we have identified them and built a periodic classification table. Now we know that these elements, of which the Earth and all its inhabitants are made, were created in previous generations of stars, from their remains or ashes. The solar nebula that gave rise to the Planetary Solar System must already contain those heavier elements, vestiges of stars that shone before our Sun.
After having flown over cosmogony, nuclear physics and biochemistry we can make at least one inference that has to do with the title of this article.
The emergence of life in the universe could not be an early event in its history. The appropriate chemical elements had to be had, which arose after a long succession of events. It was to be expected first that the first stars were formed, perhaps a billion years after the Great Explosion. Then, they burned in nuclear fusion reactions. Massive stars take about 10 million years to consume. At least one generation of these stars had to burn to begin to disperse new elements to the interstellar vacuum. Then, a planetary star system enriched in the new elements and that contained a small star like our Sun, to be able to provide a contribution of luminous energy sufficiently prolonged and constant (the Sun began to ignite in nuclear fusion reactions 4.6 billion years ago). Life arises on Earth (as prokaryotic unicellular life) at 730 million years after the emergence of our Planetary Solar System, and only 4.6 billion years later, life adopts, among many other forms of life, the human form.
Taking into account these numbers, assuming a duration of the universe of 13,000 million years and considering a history similar in duration to that of the Earth, a unicellular life could have arisen somewhere in the universe at about 1 740 million years (1 000 + 10 + 730 million years) from the Big Bang. Put another way, after a time equal to 13.4% of the current universe age.
The emergence of intelligent life like ours (thus qualified by us) would have taken much longer: 5 610 million years (1 000 + 10 + 4.6 billion years). That is, it could have appeared after a time equal to 43% of the current age of the universe, not before, not earlier.
Considering this, the flowering of our humanity has been late, very late in the history of the universe. We exist at the tip of time, at the tip of the current age of the universe. There has been plenty of time (57% of the current age) for intelligent life to blossom in other corners of it. In fact, just when our Planetary Solar System was being formed, there could already be outbreaks of intelligent life in the universe (Figure 2).
Another aspect that deeply impresses me when I evoke this scenario is the unimaginable violence and the enormous temperatures through which each and every one of the elements that constitute me, that constitute us, had to pass; to be finally thrown that matter into the cold and black void of interstellar space ... waiting for a new beginning.
This is a really good question.
It is speculated on but it is extremely difficult to come up with a proven theory on exactly how that happened. What has been known since the 1950's is that conditions on early Earth are capable of producing all the amino acids needed as raw material for DNA and other molecules essential in cells. That was proven in the Miller-Urey experiment in 1952.
There exist two types of cells. Eukaryotes have differentiated organelles and a separate nucleus containing the DNA of the cell. Prokaryotes are much simpler and they have everything mixed up in one cytoplasm separated by the cell membrate from the environment. The first are thought to be prokaryotes. It is conveivable that the currently existing prokaryotes evolved from simpler ones. The crucial step is the formation of the cellular membrane and the ability to self-copy.
We may never have the capacity to demonstrate without question how life initially advanced. However, of the numerous clarifications proposed, one emerges – the possibility that life developed in aqueous vents profound under the ocean. Not in the superhot dark smokers, but rather more serene undertakings known as soluble aqueous vents.
This hypothesis can clarify life's most interesting component, and there is developing proof to help it.
Prior this year, for example, lab tests affirmed that conditions in a portion of the various pores inside the vents can prompt high centralizations of huge atoms. This makes the vents a perfect setting for the "RNA world" generally thought to have gone before the primary cells.
In the event that life evolved in antacid aqueous vents, it may have happened something like this:
Dilute permeated into recently shaped shake under the ocean bottom, where it responded with minerals, for example, olivine, creating a warm soluble liquid wealthy in hydrogen, sulfides and different synthetics – a procedure called serpentinisation.
This hot liquid sprang up at soluble aqueous vents like those at the Lost City, a vent framework found close to the Mid-Atlantic Ridge in 2000.
Dissimilar to the present oceans, the early sea was acidic and wealthy in broken down iron. While upwelling aqueous liquids responded with this primordial seawater, they delivered carbonate rocks loaded with modest pores and a "froth" of iron-sulfur bubbles.
Inside the iron-sulfur bubbles, hydrogen responded with carbon dioxide, framing basic natural atoms, for example, methane, formate and acetic acid derivation. A portion of these responses were catalyzed by the iron-sulfur minerals. Comparative iron-sulfur impetuses are as yet found at the core of numerous proteins today.
The electrochemical angle between the antacid vent liquid and the acidic seawater prompts the unconstrained development of acetyl phosphate and pyrophospate, which act simply like adenosine triphosphate or ATP, the concoction that forces living cells.
These particles drove the development of amino acids – the building squares of proteins – and nucleotides, the building hinders for RNA and DNA.
Warm streams and dissemination inside the vent pores concentrated bigger particles like nucleotides, driving the development of RNA and DNA – and giving a perfect setting to their advancement into the universe of DNA and proteins. Development got going, with sets of particles equipped for delivering a greater amount of themselves beginning to command.
Greasy particles covered the iron-sulfur foam and immediately shaped cell-like air pockets. A portion of these air pockets would have encased self-duplicating sets of atoms – the main natural cells. The soonest protocells may have been slippery substances, however, regularly dissolving and improving as they coursed inside the vents.
The development of a compound called pyrophosphatase, which catalyzes the generation of pyrophosphate, permitted the protocells to separate more vitality from the inclination between the antacid vent liquid and the acidic sea. This old catalyst is as yet found in numerous microscopic organisms and archaea, the initial two branches on the tree of life.
Some protocells began utilizing ATP and additionally acetyl phosphate and pyrophosphate. The generation of ATP utilizing vitality from the electrochemical slope is idealized with the advancement of the catalyst ATP synthase, found inside all life today.
Protocells facilitate from the principle vent pivot, where the regular electrochemical slope is weaker, begun to produce their own inclination by drawing protons over their films, utilizing the vitality discharged when carbon dioxide responds with hydrogen.
This response yields just a little measure of vitality, insufficient to make ATP. By rehashing the response and putting away the vitality as an electrochemical inclination, be that as it may, protocells "set aside" enough vitality for ATP generation.
When protocells could produce their very own electrochemical angle, they were not any more fixing to the vents. Cells left the vents on two separate events, with one mass migration offering ascend to microscopic organisms and the other to archaea. | 0.823856 | 3.455907 |
Astronomers love to remind us that there’s no up or down in space. Look out into the depths of the universe and you’ll see galaxies floating edge-on, face-on and at every angle in between. Look at planets circling stars within the Milky Way, and their orbits might be oriented in any direction at all.
But for one class of celestial objects this seems to be untrue: planetary nebulae, the gorgeous clouds of gas puffed by stars in their last, gasping moments of life, seem to be mysteriously aligned with the plane of the Milky Way—something that Bryan Rees, an astronomer at the University of Manchester in England, and lead author of a paper in an upcoming issue of Monthly Notices of the Royal Astronomical Society calls “quite unexpected.”
That’s putting it mildly. Most planetary nebulae are roughly spherical; they’re not visibly “aligned” with anything. One especially spectacular subclass, however, is more hourglass-shaped, and when Rees and his colleague Albert Zijlstra examined this particular kind, the long dimensions of the clouds pointed more or less in the same direction. “They’re not exactly aligned,” he says, “but they’re not random.”
The question is, why? To answer that, you’d have to know how the hourglass shape forms in the first place, and astronomers still aren’t certain about that. The gas clouds are created when a star in its death throes bloats out to many times its original size, then shrinks back to form a white dwarf, leaving its outer layers to expand. Usually, these layers maintain the star’s original, spherical shape as they grow, leading the observers who first spotted them in the 1700’s to describe them as planet-shaped.
One way to turn a sphere into an hourglass is to put a belt around it, and that’s a leading theory: a belt of dust leftover from the raw material that originally condensed into the star restricts expansion in that direction while leaving the star’s top and bottom halves free to move outward. Another is to surround the star with a magnetic field that shapes the expanding cloud—and such a field could be generated if the original star were part of a double-star system. The orbit of the second star, still intact after its partner expanded and contracted, could set up magnetic field lines that would sculpt the burgeoning cloud into its characteristic hourglass shape.
Neither of these explains why the hourglasses all point in the same direction, though. But Rees and Zijlstra have an idea. The interstellar cloud of gas and dust out of which stars form in the first place spreads out into a disk shape and then condenses, with the newly formed star toward the center of a platter of leftover dust swirling around it. That dust often forms planets. If the collapse happens in the presence of a strong magnetic field, the collapsing disk could be forced to align with that field.
Since the nebulae Rees and Zijlstra looked at in this study are located toward the dense core of the Milky Way, there might well have been strong magnetic fields present when the original stars formed. Double stars and single stars with belts of dust might thus have been lined up with the plane of the Milky Way right from birth—an effect that wouldn’t happen further out from the core of the galaxy, where Earth is located.
This is by no means a definitive explanation yet, says Rees, but it’s at least a plausible one, which theorists will now chew over in detail. Whether it’s true or not doesn’t detract from the ghostly beauty of the nebulae, of course, and it also doesn’t detract from Rees’s own remarkable story. He did this work as part of his Ph.D. thesis, but unlike most Ph.D. students, he had a first career, as a telephone engineer. When he took early retirement from his job a few years ago, he says, “I didn’t want my brain to ossify so I thought I’d have a look at some astrophysics.” It seems to have turned out rather well. | 0.914977 | 4.029894 |
Newswise — A mountaintop observatory about four hours east of Mexico City, built and operated by an international team of scientists, has captured the first wide-angle view of gamma rays emanating from two rapidly spinning stars. The High-Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory offers perspective on the very high energy light streaming from our stellar neighbors and casts serious doubt on one possible origin for a mysterious excess of anti-matter particles near Earth.
In 2008, a space-borne detector measured an unexpectedly high number of positrons—the anti-matter cousins of electrons—in orbit. Ever since, scientists have debated the cause of the anomaly, split over two competing theories of its origin. Some suggested a simple explanation: The extra particles might be coming from nearby collapsed stars called pulsars, which spin around several times a second and throw off electrons, positrons and other matter with violent force. Others speculated that the extra positrons have an exotic origin, perhaps coming from as-yet undetected processes involving dark matter—the invisible but pervasive substance seen so far only through its gravitational pull.
“This new measurement is tantalizing because it strongly disfavors the idea that these extra positrons are coming to Earth from two nearby pulsars, at least when you assume a relatively simple model for their propagation,” says Jordan Goodman, professor of physics at the University of Maryland and the lead investigator and US spokesperson for the HAWC collaboration. “Our measurement doesn’t decide the question in favor of dark matter, but any new theory that attempts to explain the excess using pulsars will need to match the new data.”
Using this new data from the HAWC observatory, researchers made the first detailed measurements of two pulsars previously identified as possible sources of the excess. By catching and counting particles of light streaming from these nearby stellar engines, the HAWC collaboration showed that the two pulsars are unlikely to be the origin of the positron excess. Despite being the right age and the right distance from Earth, the pulsars are surrounded by an extended murky cloud from which positrons can’t escape in great numbers, according to results published this week in Science (DOI: 10.1126/science.aan4880).
Petra Huentemeyer, associate professor physics at Michigan Technological University and founding member of the HAWC collaboration, started working with her former PhD student, Hao Zhou, on the related analysis of HAWC data while he was a postdoc at Michigan Tech in 2016.
“Our analysis does not support previous claims that the two nearby pulsars are responsible for the excess of positrons detected by two space-born telescopes, the Italian-lead PAMELA project and the AMS-02 detector of NASA,” she says.
Some researchers posit that the positrons are produced in dark matter interactions.
“There are all kinds of efforts all over the globe to detect dark matter directly,” she says. “Dark matter is difficult to detect. Dark matter is elusive. We don’t see it. The reason we think it exists is because if you take what we know about gravitation and then look at the velocity of stars traveling around the center of disk galaxies, they are not traveling at the speeds we expect from visible matter. There must be dark, non-light emitting mass somewhere that causes this from what we understand about gravitation.”
While the results in the Science paper do not affirm the detection of dark matter, they do confirm that positron excess is not explained by a pulsar nebula throwing off the particles.
Looking for Answers
The HAWC Observatory sits at an elevation of 13,500 feet, flanking the Sierra Negra volcano inside Pico de Orizaba National Park in the Mexican state of Puebla. More than 300 massive water tanks sit waiting at the site for cascades of particles initiated by high-energy packets of light called gamma rays—many of which have more than a million times the energy of a dental X-ray.
When these gamma rays smash into the upper atmosphere, they blast apart atoms in the air, producing a shower of particles that moves at nearly the speed of light toward the ground. When this shower reaches HAWC’s tanks, it produces coordinated flashes of blue light in the water, allowing researchers to reconstruct the energy and cosmic origin of the gamma ray that kicked off the cascade.
This measurement wouldn’t have been possible without HAWC’s wide view. It continuously scans about one-third of the sky overhead, which provided researchers with a broad view of the space around the pulsars.
“Thanks to its wide field of view, HAWC provides unique measurements on the very-high-energy gamma-ray profiles caused by the particle diffusion around nearby pulsars, which allows us to determine how fast the particles diffuse more directly than previous measurements,” says Hao Zhou, now a scientist at the Los Alamos National Laboratory in New Mexico and Michigan Tech alumnus.
Zhou, one of the paper’s corresponding authors, is responsible for developing the particle diffusion model and calculating the gamma-ray emission morphology around the two pulsars in HAWC data. He fit this model to the data to constrain the physical parameter about these sources, which describes how fast a particle diffuses away from its source.
As with an ordinary camera, collecting lots of light allows HAWC to build sharp images of individual gamma-ray sources. The highest energy gamma rays originate in the graveyards of big stars, such as the spinning pulsar remnants of supernovae. But that light doesn’t come from the stars themselves. Instead, it's created when the spinning pulsar accelerates particles to extremely high energies, causing them to smash into lower-energy photons left over from the early universe.
The size of this stellar debris field, measured by the patch of sky that glows bright in gamma rays, tells researchers how quickly matter moves relative to a local astrophysical engine—in this case, the nearby pulsars. This, in turn, enables researchers to estimate how quickly positrons are moving and how many positrons could have reached Earth from a given source. Using the most complete catalog of HAWC data to date, scientists have determined that the nearby pulsar Geminga and its unnamed sister are not sources of the positron excess. Even though the two pulsars are old enough and close enough to account for the excess, matter isn’t drifting away from the pulsars fast enough to have reached the Earth.
Even with the energy's source becoming clearer, Zhou says there are still questions left unanswered.
“There are still questions left before we can draw more concrete conclusions on the origin of positron excess,” he says. “How does the morphology depend on energy? Are there more pulsars like these two in the sky that we have not detected? With more data and dedicated analysis, we will work on answering these questions.” | 0.889824 | 3.989411 |
Since it was first proposed in the 1960s to account for all the “missing mass” in the Universe, scientists have been trying to find evidence of dark matter. This mysterious, invisible mass theoretically accounts for 26.8% of the baryonic matter (aka. visible matter) out there. And yet, despite almost fifty years of ongoing research and exploration, scientists have not found any direct evidence of this missing mass.
However, according to two new research papers that were recently published in the journal Physical Review Letters, we may have gotten our first glimpse of dark matter thanks to an experiment aboard the International Space Station. Known as the Alpha Magnetic Spectrometer (AMS-02), this a state-of-the-art particle physics detector has been recording cosmic rays since 2011 – which some theorize are produced by the annihilation of dark matter particles.
Like its predecessor (the AMS), the AMS-02 is the result of collaborative work and testing by an international team composed of 56 institutes from 16 countries. With sponsorship from the US Department of Energy (DOE) and overseen by the Johnson Space Center’s AMS Project Office, the AMS-02 was delivered to the ISS aboard the Space Shuttle Endeavour on May 16th, 2011.
Ostensibly, the AMS-02 is designed to monitor cosmic rays to see how much in the way of antiprotons are falling to Earth. But for the sake of their research, the two science teams also been consulted the data it has been collecting to test theories about dark matter. To break it down, the WIMPs theory of dark matter states that it is made up of Weakly-Interacted Massive Particles (WIMPS), protons and antiprotons are the result of WIMPs colliding.
By monitoring the number of antiprotons that interact with the AMS-02, two science teams (who were working independently of each other) hoped to infer whether or not any of the antiprotons being detected could be caused by WIMP collisions. The difficulty in this, however, is knowing what would constitute an indication, as cosmic rays have many sources and the properties of WIMPs are not entirely defined.
To do this, the two teams developed mathematical models to predict the cosmic ray background, and thus isolate the number of antiprotons that AMS-02 would detect. They further incorporated fine-tuned estimates of the expected mass of the WIMPs, until it fit with the AMS-02 data. One team, led by Alessandro Cuoco, was made up of researchers from the Institute for Theoretical Particle Physics and Cosmology.
Using computer simulations, Cuoco and his colleagues examined the AMS-02 data based on two scenarios – one which accounted for dark matter and one which did not. As they indicate in their study, they not only concluded that the presence of antiprotons created by WIMP collisions better fit the data, but they were also able to constrain the mass of dark matter to about 80 GeV (about 85 times the mass of a single proton or antiproton).
As they state in their paper:
“[T]he very accurate recent measurement of the CR antiproton flux by the AMS-02 experiment allows [us] to achieve unprecedented sensitivity to possible DM signals, a factor ~4 stronger than the limits from gamma-ray observations of dwarf galaxies. Further, we find an intriguing indication for a DM signal in the antiproton flux, compatible with the DM interpretation of the Galactic center gamma-ray excess.”
The other team was made up of researchers from the Chinese Academy of Sciences, Nanjing University, the University of Science and Technology of China, and the National Center for Theoretical Sciences. Led by Ming-Yang Cui of Nanjing University, this team made estimates of the background parameters for cosmic rays by using prior data from previous boron-to-carbon ratio and proton measurements.
These measurements, which determine the rate at which boron decays into carbon, can be used to guage the distance that boron molecules travel through space. In this case, they were combined with proton measurements to determine background levels for cosmic rays. They incorporated this data into a Bayesian Analysis framework (i.e. a statistical model used to determine probabilities) to see how many antiprotons could be attributed to WIMP collisions.
The results, as they state it in their paper were quite favorable and produced similar mass estimates to the study led by Cuoco’s team. “Compared with the astrophysical background only hypothesis, we find that a dark matter signal is favored,” they write. “The rest mass of the dark matter particles is ?20 – 80 GeV.”
What’s more, both scientific teams obtained similar estimates when it came to cross-section measurements of dark matter – i.e. the likelihood of collisions happening based on how densely dark matter is distributed. For example, Cuoco’s team obtained a cross-section estimate of 3 x 10-26 per cm³ while Cui’s team obtained an estimate that ranged from 0.2 – 5 × 10-26 per cm³.
The fact that two scientific teams, which were operating independently of each other, came to very similar conclusions based on the same data is highly encouraging. While it is not definitive proof of dark matter, it is certainly a step in the right direction. At best, it shows that we are getting closer to creating a detailed picture of what dark matter looks like.
And in the meantime, both teams acknowledge that further work is necessary. Cuoco and his team also suggest what further steps should be taken. “Confirmation of the signal will require a more accurate study of the systematic uncertainties,” they write, “i.e., the antiproton production cross-section, and the modeling of the effect of solar modulation.”
While scientists have attempted to find evidence of dark matter by monitoring cosmic rays in the past, the AMS-02 stands apart because of its extreme sensitivity. As of May 8th, the spectrometer has conducted measurements on 100 billion particles. As of the penning of this article, that number has increased to over 100,523,550,000! | 0.809168 | 4.113633 |
Callippus of Cyzicus
Cyzicus, Asia Minor (now Turkey)
BiographyThe dates given for the birth and death of Callippus of Cyzicus are guesses but he is known to have been working with Aristotle in Athens starting in 330 BC.
We know that Callippus was a student in the School of Eudoxus. We also know that he made his astronomical observations on the shores of the Hellespont, which can be deduced from the observations themselves. Simplicius writes in his commentary on De caelo by Aristotle (see for example ):-
Callippus of Cyzicus, having studied with Polemarchus, Eudoxus's pupil, following him to Athens dwelt with Aristotle, correcting and completing, with Aristotle's help, the discoveries of Eudoxus.Callippus made accurate determinations of the lengths of the seasons and constructed a 76 year cycle comprising 940 months to harmonise the solar and lunar years which was adopted in 330 BC and used by all later astronomers. This calendar of Callippus is examined in detail by van der Waerden in . Ptolemy gave us an accurate date for the beginning of this cycle in 330 BC in the Almagest Ⓣ saying that year 50 of the first cycle coincided with the 44th year following the death of Alexander.
The Callippic period is based on the Metonic period devised by Meton (born about 460 BC). Meton's observations were made in Athens in 432 BC but he gave a length for the year which was of a day too long. The relation between Callippus's period and that of Meton are explained in as follows:-
Callippus of Cyzicus (c. 370-300 BC) was perhaps the foremost astronomer of his day. He formed what has been called the Callippic period, essentially a cycle of four Metonic periods. It was more accurate than the original Metonic cycle and made use of the fact that 365.25 days is a more precise value for the tropical year than 365 days. The Callippic period consisted of 4 × 235, or 940 lunar months, but its distribution of hollow and full months was different from Meton's. Instead of having totals of 440 hollow and 500 full months, Callippus adopted 441 hollow and 499 full, thus reducing the length of four Metonic cycles by one day. The total days involved therefore became (441 × 29) + (499 × 30), or 27,759 and 27,759 ÷ (19 × 4) gives 365.25 days exactly. Thus the Callippic cycle fitted 940 lunar months precisely to 76 tropical years of 365.25 days.Callippus introduced a system of 34 spheres to explain the motions of the heavenly bodies. The Sun, Moon, Mercury, Venus and Mars each had five spheres while Jupiter and Saturn had four and the stars had one. This addition of six spheres over the system proposed by Eudoxus increased the accuracy of the theory while preserving the belief that the heavenly bodies had to possess motion based on the circle since that was the 'perfect' path. Heath writes :-
Callipus tried to make the system of concentric spheres suit the phenomena more exactly by adding other spheres; he left the number of spheres at four in the case of Jupiter and Saturn, but added one each to the other planets and two each in the case of the sun and the moon ... . This would substitute for the hippopede [see the Eudoxus article] a still more complicated elongated figure ...Other contributions of Callippus to mathematical astronomy included his observation of the inequality in the lengths of the seasons. He accounted for this in his model by making the velocity of the Sun vary through the year and this was achieved with the two extra spheres described above.
The Callippic period contributed to the accuracy of later astronomical theories. Kieffer writes in :-
Although the system of concentric spheres gave way to epicycles and eccentrics, Callippus's period became the standard for correlating observations accurately over many centuries, and thus contributed to the accuracy of later astronomical theories.
- J S Kieffer, Biography in Dictionary of Scientific Biography (New York 1970-1990). See THIS LINK.
- Calendar, Encyclopaedia Britannica.
- T L Heath, Aristarchus of Samos (Oxford, 1913).
- T L Heath, A History of Greek Mathematics (2 Vols.) (Oxford, 1921).
- O Neugebauer, A history of ancient mathematical astronomy (New York, 1975).
- B L van der Waerden, Greek astronomical calendars. II. Callippos and his calendar, Arch. Hist. Exact Sci. 29 (2) (1984), 115-124.
Additional Resources (show)
Other pages about Callippus:
Other websites about Callippus:
Honours awarded to Callippus
Written by J J O'Connor and E F Robertson
Last Update April 1999
Last Update April 1999 | 0.811443 | 3.692704 |
Written speculation about life beyond the confines of Earth dates back thousands of years, to the time of the Greek philosophers Epicurus and Democritus. Unrecorded curiosity about this question undoubtedly goes back much further still. Remarkably, today’s generation seems about to get an answer from the study of exoplanets — planets orbiting other stars than the Sun. The early results are upending many assumptions from that long history.
Two months ago, our research team at the University of Cambridge and the University of Liège in Belgium reported that a nearby star, called TRAPPIST-1A, is orbited by seven planets similar in size and mass to Earth. All seven planets are temperate, meaning that under the right atmospheric and geologic conditions, they could sustain liquid water. Three of the planets show particular potential for habitability, receiving about as much energy from their star as the Earth receives from the Sun.
Our discovery received ecstatic and gratifying news coverage around the world. In many ways, though, the TRAPPIST-1 system is an odd place to look for life. The central star is just 1/12th the mass of the Sun and scarcely bigger than the planet Jupiter. It gives off just 0.05 per cent as much light as the Sun. TRAPPIST-1A belongs to a class that we call ultra-cool dwarfs, the very smallest stars that exist.
Searching for habitable planets around ultra-cool dwarfs has long been considered a waste of time. Even as astronomers found that exoplanetary systems are generally different from the solar system, old attitudes lingered. The Earth and Sun appear so normal and hospitable to our eyes that we get blinded by their attributes. Major programs are therefore directed at finding an Earth twin: a planet the mass and size of our own, orbiting a star just like the Sun, at the same Earth-Sun distance. The detection of such a world remains decades away.
In the effort to answer the question ‘Is there life elsewhere?’ the focus on Earth twins is perceived as a safe path, since we can expect that similar conditions will lead to similar results (at least part of the time). However, we argue that this is far too conservative a goal, considering the huge number and diversity of available planets. That is part of the message of TRAPPIST-1. Research should be about finding what we don’t already know. Identifying a life-bearing Earth twin would be a resounding scientific success, but it would teach little about the overall emergence of biology in the Universe.
Our ambition is wider. Instead, we seek an answer to ‘How frequently is life found elsewhere?’ This simple change of words means that we should also be investigating planetary systems unlike the solar system. It would be disappointing and surprising if Earth were the only template for habitability in the Universe. Sun-like stars represent just 15 per cent of all stars in the Milky Way. More than half of those, in turn, exist in binary star systems that have also been disregarded as being too different from the conditions present in the solar system. The search for Earth twins therefore covers a nearly insignificant fraction of all the outcomes in nature.
Once we reset the goal to measuring the total frequency of biology, ultra-cool dwarfs become an obvious target. Half the stars in the Milky Way have masses less than one-quarter of the Sun’s. Our preliminary results suggest that rocky worlds are common orbiting low-mass stars, including ultra-cool dwarf systems, possibly more so than in orbit around Sun-like stars. Ultra-cool dwarfs also open a much easier route to detecting and studying temperate, Earth-like planets.
The scientific advantages of ultra-cool dwarfs come from their stellar properties, from how we identify exoplanets, and from how we expect to investigate their atmospheres. The TRAPPIST-1 planets were found as they passed in front of their star, events known as transits. When the planet transits, it casts a shadow whose depth tells us how much of the stellar surface is being hidden by the planet; the bigger the planet, the deeper the shadow. Because ultra-cool dwarfs are so small, the transit of an Earth-sized planet in front of TRAPPIST-1A is approximately 80 times as prominent as an equivalent transit against a much larger, Sun-like star.
During a transit, any gases in the planet’s atmosphere change the appearance of starlight streaming through. Around ultra-cool dwarfs, the atmospheric signature is boosted by about a factor of 80. The atmospheric composition of the TRAPPIST-1 planets will be detectable using current and upcoming facilities, such as the James Webb Space Telescope launching in 2018, unlike the decades of technological development needed to study an Earth twin. Extracting a reliable atmospheric signal requires observing dozens of transits. Here, too, systems such as TRAPPIST-1 have huge advantages. Around tiny ultra-cool dwarfs, transits of temperate planets happen once every few days to every couple of weeks, instead of once a year for a planet exactly like Earth.
Astronomers, including ourselves, have already begun investigating the compositions of giant planets around other stars, detecting molecules such as water, carbon monoxide, methane, and hydrogen cyanide. With the discovery of the TRAPPIST-1 system, we can extend those explorations to Earth-sized planets. Our first efforts will be to characterize the greenhouse gas content of atmosphere, and assess whether the surface conditions are conducive for liquid water. Then we will seek out signs of biologically produced gases, analogous to ways that living organisms have transformed the composition of Earth’s atmosphere.
Claiming a discovery of life will be hard. We cannot rely on the detection of a single gas but instead will need to detect several, and will need to measure their relative abundances. In addition, we will have to be extremely wary of false positives. For instance, repeated stellar flares could build up oxygen in an atmosphere without the presence of life. The richness of the TRAPPIST-1 system is an important asset, because we can compare its planets to one another. All seven planets originated from the same nebular chemistry; they share a similar history of receiving flares and meteoritic impacts. Weeding out false positives will be much easier here than in planetary systems containing only one or two temperate, potentially Earth-like worlds.
More important, TRAPPIST-1 is not a one-off discovery. Ultra-cool dwarf stars are so common that there could be numerous other similar systems close to us in the galaxy. The TRAPPIST (Transiting Planets and Planetesimals Small Telescopes) facility we used to find the TRAPPIST-1 planets was just the prototype of a more ambitious planet survey called SPECULOOS (Search for habitable Planets Eclipsing Ultra-Cool Stars), which has already begun operations. We expect to find many more Earth-sized, rocky planets around dwarf stars within the next five years. With this sample in hand, we will explore the many climates of such worlds. The solar system contains two: Venus and Earth. How many different types of environments will we discover?
Using SPECULOOS, we will also begin to address the many objections scientists have raised about the habitability of planets around ultra-cool dwarfs. One argument is that such planets will be tidally locked, meaning that they have permanent day and night sides. Planets orbiting in close proximity around small stars could excite each other’s orbits, leading to major instabilities. Ultra-cool dwarf stars frequently flare up, emitting ultraviolet and X-rays that might vaporise a planet’s oceans into space.
Far from holding us back, those arguments motivated us. Now we can assess the actual conditions, and explore counter-arguments that Earth-sized planets around stars such as TRAPPIST-1A might in fact be hospitable to life. Oceans and thick atmospheres could mitigate the temperature contrast between day and night sides. Tidal interaction between close-orbiting planets might provide energy for biology. Some models suggest that planets forming around ultra-cool dwarfs start out with much more water than Earth has. Ultraviolet radiation could help to produce biologically relevant compounds… We are optimistic.
No matter what we find by studying planets orbiting ultra-cool dwarfs, we cannot lose. We can only learn. If we manage to identify the presence of life on a planet similar to those in the TRAPPIST-1 system, then we can start measuring how frequently biology emerges in the universe. We could have the first clues of extraterrestrial biology in a decade! If we find that none of those worlds is habitable, or that they are habitable but barren, we would learn that life is rare and precious. It will vindicate the Earth-twin approach without delaying it.
In either case, we will define the context of our existence: as one among many, or as an isolated outlier. Both possibilities are humbling. Both are thrilling.
This article was originally published at Aeon and has been republished under Creative Commons. | 0.891266 | 3.874311 |
About This Chapter
MTEL Physics: Laws of Gravitation - Chapter Summary
Use our lessons to help you prepare for questions on the laws of gravitation, weight, mass and the motion of planets when you take the MTEL Physics exam. Reviewing these topics with our videos and quizzes will enable you to tackle test questions on the following:
- The law of universal gravitation and its importance
- Centripetal force and its formula
- Gravitational attraction of extended bodies
- The formula for gravitational potential energy
- Newton's laws pertaining to weight, mass and gravity
- Kepler's laws of planetary motion
- Periods and speeds of elliptical orbits
- Eccentricity and the orbits of planets
Our lessons are designed and taught by instructors who are professionals in the field and who know what you'll need to be ready for the exam. You can count on them to provide useful information on the laws of gravitation.
1. The Law of Universal Gravitation: Definition, Importance & Examples
Gravity is what pulls us toward Earth, but it's also what pulls Earth toward us. This is explained by the law of universal gravitation, which describes how all objects in the universe have this important force between them.
2. Centripetal Force: Definition, Formula & Examples
When an object is traveling in a circular path, centripetal force is what keeps it fixed in that path. Learn more about this force, how it is calculated and examples of its occurrence. A quiz is provided to test your learning.
3. Gravitational Attraction of Extended Bodies
After watching this lesson, you will be able to explain what an extended body is, understand the derivation for the force of gravity between a point charge and a long, thin bar and solve problems using the result of that derivation.
4. Gravitational Potential Energy: Definition, Formula & Examples
In this lesson, you will learn what gravitational potential is, the equation we use to calculate it, and how to use that equation. We'll look at some real-life examples so you can see how it works. A short quiz will follow.
5. Newton's Laws and Weight, Mass & Gravity
Did you know that mass and weight are not the same? This lesson describes the difference between the two as well as the effect of gravity on weight. Examples are used to teach you how to calculate weight based on mass and acceleration of gravity.
6. Kepler's Three Laws of Planetary Motion
Find out about the interesting life and major contributions of Johannes Kepler. This lesson will also teach you how to find out how long it takes a planet to revolve around the sun!
7. Elliptical Orbits: Periods & Speeds
After watching this lesson, you will be able to explain what an elliptical orbit is and calculate the period and speed of an object in an elliptical orbit, if given enough information. A short quiz will follow.
8. Eccentricity & Orbits of Planets
After watching this lesson, you should be able to explain what eccentricity is and calculate the eccentricity of an orbit given relevant distance measurements. A short quiz will follow.
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Other chapters within the MTEL Physics (11): Practice & Study Guide course
- MTEL Physics: Scientific Research Overview
- MTEL Physics: Interpreting & Analyzing Scientific Data
- MTEL Physics: Physics Lab Safety
- MTEL Physics: Historical & Contemporary Relationships in Science
- MTEL Physics: Force & the Laws of Motion
- MTEL Physics: Rotational Motion, Collisions & Conservation
- MTEL Physics: Fluid Mechanics
- MTEL Physics: Work & Energy
- MTEL Physics: Linear & Angular Momentum
- MTEL Physics: Principles of Thermodynamics
- MTEL Physics: Electrostatics
- MTEL Physics: Circuits
- MTEL Physics: Electromagnetism
- MTEL Physics: Oscillations & Wave Motion
- MTEL Physics: Sound Waves & Principles of Acoustics
- MTEL Physics: Electromagnetic Waves
- MTEL Physics: Light, Mirrors & Lenses
- MTEL Physics: Atomic Nature of Matter & Relativity
- MTEL Physics: Quantum Theory
- MTEL Physics: Radioactive Decay & Nuclear Reactions
- MTEL Physics Flashcards | 0.871949 | 3.024946 |
At first sight, Dark Matter and the Dinosaurs looks like a title thought up by the marketing department. “Hmm, what interests the public? Dark matter is trendy. And who doesn’t love a dinosaur, right?” To be fair, physicist Lisa Randall does make a tenuous connection between a new dark matter theory and the comet that is thought to have caused the extinction of the dinosaurs, but that is by no means the most interesting aspect of this book.
Much of the content takes us on a solid, if surprise-free, tour of the history of the Universe, zooming in to see how far the Solar System reached in its present form, and exploring the nature of comets, meteors, and asteroids. But where Randall really triumphs is with her coverage of extraterrestrial impacts on the Earth. The detective story that led to the identification of the Chicxulub crater as the site of the dinosaur-killing meteoroid strike is extremely engaging.
Better still, the chapters on dark matter go far beyond most other popular books on the subject. Randall paints a truly fascinating picture of the possibility that dark matter is as rich and varied as normal matter, perhaps forming dark matter suns that pour out dark light, or are even orbited by dark planets hosting dark life.
Where the book could do better is in hitting the right level of detail. Randall dismisses modified Newtonian dynamics (MOND)–the alternative to dark matter based on a tweak to Newton’s laws–with an example of a star cluster unsupported by the modified theory. Yet she continues to support dark matter, despite listing four or five examples where it fails to match observation, and it’s never made entirely clear why dark matter is given the benefit of the doubt but MOND isn’t. Elsewhere, it seems as if the book hasn’t been adequately edited–it isn’t unusual for Randall to take a page to say something that only required a couple of lines.
The climax of Dark Matter and the Dinosaurs is the discovery that a possible regular cycle of comet strikes–for which the evidence, it should be pointed out, is rather thin–combined with an unsubstantiated dark matter theory just might explain the extinction of the dinosaurs. But to consider this the highlight misses the point. This book is not about the destination, but the journey. And that is often delightful.
This review is by Brian Clegg for BBC Focus magazine on page 106. | 0.856187 | 3.402685 |
NASA is adding a new antenna for communicating with the agency’s farthest-flung robotic spacecraft. Part of the Deep Space Network (DSN), the 112-foot-wide (34-meter-wide) antenna dish represents a future in which more missions will require advanced technology such as lasers capable of transmitting vast amounts of data from astronauts on the Martian surface. As part of its Artemis program, NASA will send the first woman and next man to the Moon by 2024, applying lessons learned there to send astronauts to Mars.
Strengthening the Network
Using massive antenna dishes, NASA talks to more than 30 deep space missions on any given day including many international missions. As more missions have launched and with more in the works, NASA is looking to strengthen the network. When completed in 2½ years, the new dish will be christened Deep Space Station-23 (DSS-23), bringing the DSN’s number of operational antennas to 13.
“Since the 1960s, when the world first watched live pictures of humans in space and on the Moon — to revealing imagery and scientific data from the surface of Mars and vast, distant galaxies — the Deep Space Network has connected humankind with our solar system and beyond,” said Badri Younes, NASA’s deputy associate administrator for Space Communications and Navigation (SCaN), which oversees NASA’s networks. “This new antenna, the fifth of six currently planned, is another example of NASA’s determination to enable science and space exploration through the use of the latest technology.”
Managed by NASA’s Jet Propulsion Laboratory in Pasadena, CA, the world’s largest and busiest deep space network is clustered in three locations — Goldstone, CA; Madrid, Spain; and Canberra, Australia — positioned approximately 120 degrees apart around the globe to enable continual contact with spacecraft as the Earth rotates. (Visit here to see which DSN dishes are sending up commands or receiving data at any given time.)
The first addition to Goldstone since 2003, the new dish is being built at the complex’s Apollo site, so named because its DSS-16 antenna supported NASA’s human missions to the Moon. Similar antennas have been built in recent years in Canberra, while two are under construction in Madrid.
“The DSN is Earth’s one phone line to our two Voyager spacecraft — both in interstellar space — all our Mars missions, and the New Horizons spacecraft that is now far past Pluto,” said JPL Deputy Director Larry James. “The more we explore, the more antennas we need to talk to all our missions.”
Critical Laser Communications
While DSS-23 will function as a radio antenna, it will also be equipped with mirrors and a special receiver for lasers beamed from distant spacecraft. This technology is critical for sending astronauts to places like Mars. Humans there will need to communicate with Earth more than NASA’s robotic explorers do and a Mars base, with its life support systems and equipment, would buzz with data that needs to be monitored.
“Lasers can increase your data rate from Mars by about 10 times what you get from radio,” said Suzanne Dodd, director of the Interplanetary Network, the organization that manages the DSN. “Our hope is that providing a platform for optical communications will encourage other space explorers to experiment with lasers on future missions.”
While clouds can disrupt lasers, Goldstone’s clear desert skies make it an ideal location to serve as a laser receiver about 60% of the time. A demonstration of DSS-23’s capabilities is around the corner: When NASA launches an orbiter called Psyche to a metallic asteroid in a few years, it will carry an experimental laser communications terminal developed by JPL. Called the Deep Space Optical Communications project, this equipment will send data and images to an observatory at Southern California’s Palomar Mountain.
For more information, visit here . | 0.863273 | 3.029215 |
September 16, 2019 report
Researchers study young stellar objects population in NGC 6822
Using NASA's Spitzer spacecraft, astronomers have conducted a comprehensive study of massive young stellar objects (YSOs) in the metal-poor galaxy NGC 6822. The research, detailed in a paper published September 9 on the arXiv pre-print repository, resulted in identifying hundreds of new YSOs in this galaxy.
YSOs are stars in early stage of evolution, in particular, protostars and pre-main sequence stars. They are usually observed embedded in dense molecular clumps, environments containing plenty of molecular gas and interstellar dust.
Located some 1,600 light years away from the Earth, NGC 6822 is an isolated, gas-rich and metal-poor barred irregular galaxy. Taking into account the galaxy's proximity, its isolation and low metallicity, it seems to be an ideal target for studying resolved stellar populations.
However, although many studies of star-forming regions in NGC 6822 have been conducted, its massive young stellar population has been more difficult to characterize on a global scale. Hence, NGC 6822 lacks global surveys of its YSOs and studies of how these objects relate to the galaxy's gas and dust distributions.
A team of astronomers led by Olivia Jones of the Royal Observatory in Edinburgh, U.K., has now investigated massive YSOs in NGC 6822. Their research is based on data collected by Spitzer's two instruments: the Infrared Array Camera (IRAC) and the Multiband Imaging Photometer for Spitzer (MIPS).
"We present a comprehensive study of massive young stellar objects (YSOs) in the metal-poor galaxy NGC 6822 using IRAC and MIPS data obtained from the Spitzer Space Telescope," the researchers wrote in the paper.
The study found over 500 new YSO candidates in seven massive star-formation regions of NGC 6822. 90 YSO candidates, which comprise the highest number in this galaxy, were detected in the newly discovered Spitzer I region of active star formation.
According to the paper, most of the newfound candidates are massive protostars with an accreting envelope in the initial stages of formation. About 25 percent of YSOs from the sample have an average mass greater than 15 solar masses. However, the researchers noted that the mass estimates still have large uncertainties, and further studies are required to gather more detailed information.
The study also calculated the global star-formation rate for NGC 6822. This value turns to be about 0.04 solar masses per year, which is consistent with previous observations of this galaxy, however, it is higher than star-formation rate estimates based on integrated ultraviolet fluxes.
In concluding remarks, the astronomers emphasized the importance of their research into NGC 6822 and the YSO population within it. "This is the first catalogue of young embedded stars in the process of formation identified in the galaxy," the scientists wrote in the paper.
They added that future observations of NGC 6822 using NASA's James Webb Space Telescope (JWST) could reveal the presence of more YSO candidates at all stages of evolution.
© 2019 Science X Network | 0.850976 | 3.857753 |
If NASA says it is a magnetic universe then how is the universe magnetized?
The bold title by the University of Chicago is Astrophysicists settle century-old cosmic debate on magnetism of planets and stars. The research paper does not quite take that tone, suggesting it is a viable mechanic.
Laser experiments verify ‘turbulent dynamo’ theory of how cosmic magnetic fields are created ... to demonstrate for the first time in the laboratory the existence of turbulent dynamo, an astrophysical process that has long been theorized to explain the present-day magnetization of the Universe.
Advanced monoenergetic proton radiography, developed by MIT to probe the evolution and structure of fields and plasma flows in high-energy-density-plasma experiments, was used for measuring the spatial structure and temporal evolution of spontaneous magnetic fields which grew, due to plasma turbulence, from an initial value ~ 50 kG to ~ 500 kG. These field measurements, led by MIT senior research scientist Dr. Chikang Li, provided critical experimental evidence of the 10-fold turbulent amplification of the fields. Though the mechanism of field amplification is widely believed to be pervasive in generating strong cosmic magnetic fields, these experimental results are the first laboratory demonstration that many-fold field amplification can result from such plasma turbulence.
Measuring the magnetized universe | Massachusetts Institute of Technology
What, in total, monstrous energetic processes create the magnetization of stars, solar systems, plasma Universe? Gravity? Plasma turbulent dynamos?
Are plasmas responsible for space magnetism?
"We now know for sure that turbulent dynamo exists, and that it's one of the mechanisms that can actually explain magnetization of the universe," said Petros Tzeferacos, research assistant professor of astronomy and astrophysics and associate director of the Flash Center. "This is something that we hoped we knew, but now we do."
The universe is highly magnetic, with everything from stars to planets to galaxies producing their own magnetic fields. Astrophysicists have long puzzled over these surprisingly strong and long-lived fields, with theories and simulations seeking a mechanism that explains their generation. The image shows the magnetic field of the Whirlpool Galaxy, M51.
Using one of the world's most powerful laser facilities, a team led by University of Chicago scientists experimentally confirmed one of the most popular theories for cosmic magnetic field generation: the turbulent dynamo. By creating a hot turbulent plasma the size of a penny, that lasts a few billionths of a second, the researchers recorded how the turbulent motions can amplify a weak magnetic field to the strengths of those observed in our sun, distant stars, and galaxies.
Confirming decades of numerical simulations, the experiment revealed that turbulent plasma could dramatically boost a weak magnetic field up to the magnitude observed by astronomers in stars and galaxies.
Our Magnetic Universe | Daily Galaxy
When one or more of the outer (valence) electrons are stripped away from an atom we say the atom has become 'ionized'. It then exhibits a net positive electrical charge, and is called a 'positive ion'. On the other hand, if an extra electron is added onto a neutral atom, the combination then carries a net negative charge and is referred to as a 'negative ion'. The electrical forces between dissimilar ions are orders of magnitude stronger than any mechanical force such as that produced by gravity.
An electrical plasma is a cloud of ions and electrons that, under the excitation of applied electrical and magnetic fields, can sometimes light up and behave in some unusual ways. The most familiar examples of electrical plasmas are the neon sign, lightning, and the electric arc welding machine. The ionosphere of Earth is an example of a plasma that does not emit visible light. Plasma permeates the space that contains our solar system. The cloud of particles that constitutes the solar 'wind' is a plasma. Our entire Milky Way galaxy consists mainly of plasma. In fact 99% of the entire universe is plasma!
Plasma - The Fundamental State of Matter | electric cosmos
A turbulent dynamo of astrophysicists settled science debate on cosmic magnetism
3-D radiation magneto-hydrodynamic FLASH simulation of the experiment, performed on the Mira supercomputer at Argonne National Laboratory. The values demonstrate strong amplification of the seed magnetic fields by turbulent dynamo.
Measuring the magnetized universe | MIT
Magnetic fields are ubiquitous in the Universe. The energy density of these fields is typically comparable to the energy density of the fluid motions of the plasma in which they are embedded, making magnetic fields essential players in the dynamics of the luminous matter. The standard theoretical model for the origin of these strong magnetic fields is through the amplification of tiny seed fields via turbulent dynamo to the level consistent with current observations.
However, experimental demonstration of the turbulent dynamo mechanism has remained elusive, since it requires plasma conditions that are extremely hard to re-create in terrestrial laboratories. Here we demonstrate, using laser-produced colliding plasma flows, that turbulence is indeed capable of rapidly amplifying seed fields to near equipartition with the turbulent fluid motions. These results support the notion that turbulent dynamo is a viable mechanism responsible for the observed present-day magnetization.
Laboratory evidence of dynamo amplification of magnetic fields in a turbulent plasma | 0.810851 | 4.019642 |
Imagine a spacecraft small enough to fit in your hand. Now imagine that it costs $30 in materials and can be built from off-the-shelf parts available at your local technology store. It may sound incredible, but such a spacecraft already exists. It’s called the Sprite, and it was designed and built by Mason A. Peck, Mechanical and Aerospace Engineering, and his lab—the Space Systems Design Studio.
The Sprite is the size of a Wheat Thin cracker and weighs about 4 grams. Within that tiny package, Peck and his team have packed a propulsion system, sensors, communications system, memory, and processing system, all using over-the-counter available technology. “Sprite is meant to be a general-purpose space-exploration platform in the same way a laptop is a platform,” Peck says. “You can use it for anything.”
What Sprites Can Do in Space
While a single Sprite can’t compete with something like the Hubble Space Telescope, which has a huge aperture for optics, a swarm of many Sprites can take distributed measurements across large distances and over time. For instance, a swarm could be sent to investigate the sun’s corona, the bursts of plasma that can destroy communications satellites and Earth-based power grids. “We can send a million Sprites for the same mass as a traditional spacecraft,” says Peck, “and they can measure things like plasma density and potential magnetic field at a million different locations. When that information comes back to earth, we can stitch it together in a very new model of those physics.”
Sprites could be used to explore asteroids as well. Asteroids have just enough gravity for something as small as a Sprite to stick, Peck explains. “Once they’re in close contact, the Sprites could take pictures of the surface so we could get a precise idea of the color—the spectrum—of the asteroid. From that we can tell the asteroid’s chemical constituents, whether there’s water, platinum, or other metals of interest for mining.” And once the Sprites were on the asteroid, their transmitters would allow us to track its orbit, should humans ever want to mine it—or in case there’s a risk it might collide with Earth.
Citizen Space Science
As part of his commitment to citizen space, Peck's lab purposefully designed the Sprite so it could be built with off-the-shelf technology. “Every one of us has the opportunity to do science, to do engineering,” Peck says. “Every aspect of Sprite technology we have fully shared in a public forum online called GitHub. Anyone can download the info and make their own Sprite. We’re doing our part to democratize space exploration.”
“People forget that innovation doesn’t always demand complexity. The very basic, fundamental ideas we have are game changing because they’re so simple, and yet no one saw them before.”
Peck also relied on individual citizens to crowdfund the first attempt to launch Sprites in space. He and his lab designed a 3U CubeSat, a carrier spacecraft about the size of a loaf of bread, called KickSat, and filled it with 100 Sprites. The money raised through KickStarter funded KickSat’s launch in 2014. KickSat was designed to open and release the Sprites once it reached orbit, but as a consequence of last-minute change in the launch rules, the Sprites were never released. Peck didn’t give up, however. He and his lab hope to fulfill their promise to their citizen funders by launching KickSat2 in the fall of 2016 with a new batch of 128 Sprites.
Who Funds What? Traditional Questions versus Open-ended Questions
Much of Peck’s research is funded by government agencies, such as the National Aeronautics and Space Administration (NASA), the Defense Advanced Research Projects Agency (DARPA), and the United States Air Force, or by prime contractors in the aerospace industry like Northrup Grumman and Lockheed Martin. He also partners with small, aerospace companies based in and around Ithaca, New York, such as Cayuga Astronautics and the new startup, Ursa Space Systems Inc., founded by Adam Maher (MEng ’07), one of Peck’s former students.
These types of funders were not interested in supporting KickSat, however, which is why Peck turned to crowdfunding for this particular project. “Often government agencies and traditional funders don’t ask open-ended questions like, ‘What is a new technology that can change the world?’” Peck says. “Instead, they start by asking the questions they know there are answers to. They’ve got finite time and resources, and need to make sure the money they spend is consistent with their priorities. But Cornell gives us the freedom to pursue ideas that no one is yet asking for because no one knows these things can exist, and when we have that kind of freedom, we can make a lot of progress.”
While KickSat is what Peck calls “blue sky research,” he also does plenty of research supported by traditional funders such as NASA. Currently the government agency is sponsoring the Space Systems Design Studio’s research in On-orbit Autonomous Assembly with Nanosatellites (OAAN)—two 3U CubeSats that will dock with each other in orbit. “OAAN demonstrates how to construct objects in space,” Peck explains. “We’re basically making space Lego.” NASA’s typical docking technique requires hundreds of people and millions of dollars of technology. Peck’s space Lego approach, on the other hand, concentrates on the basics—simple components like springs and magnets.
“There’s fundamental research involved in this project—algorithms and physics,” says Peck. “But we’re also designing technology. We’re making progress in systems research, looking at the big-picture architecture and asking, ‘How can we change our design approach to accommodate other solutions?’ One way we’re doing that is by using the guts of a satellite phone as our communications system.”
From Science Fiction to Aerospace Engineering
Peck’s love of creativity and outer space was born from childhood, growing up as the son of science fiction writer Richard Peck. “I was surrounded by my dad’s library of thousands of science fiction books,” he says. “I grew up reading them, and I took them seriously. I always wanted to be an aerospace engineer, but I didn’t know that’s what it was called. I originally got a degree in English because that’s what my dad had done, and I thought that was a way to be creative. But then I discovered engineering was where I could contribute to unsolved problems, where there was room for innovation and unfettered thinking.” Peck elaborated on some of his most innovative ideas in a talk he gave at TEDx SchechterWestchester in 2014.
Unfettered thinking is helping Peck and his lab create a wide range of aerospace engineering firsts, including a revolutionary propulsion system that uses water for fuel. They have been working on the design since 2011, but when NASA issued the CubeQuest Challenge in 2014, asking engineers to design the first CubeSat to orbit the moon, Peck saw a chance to demonstrate his lab’s propulsion system in space. It uses an off-the-shelf toy electrolyzer to separate the oxygen from the hydrogen in the water and turns it into a gaseous mixture that is combustible. If Peck and his team’s design passes muster, their CubeSat will launch along with other contenders in 2017-18.
“We’re trying not to be sophisticated,” Peck says with satisfaction. “We’re going back to basics, and it’s down in the mud with the basics that there’s lots of room for innovation. People forget that innovation doesn’t always demand complexity. The very basic, fundamental ideas we have are game changing because they’re so simple, and yet no one saw them before.” | 0.85293 | 3.320638 |
This is a false color image of a mosaic of Mercury.
Click on image for full size
Courtesy of NASA.
Observations of Mercury from Earth
Before the Mariner 10 mission of Mercury, it was very difficult to
see any markings on the surface of the planet from Earth. This image
shows a view of Mercury obtained from a telescope on Earth. The first
attempts to find out the day length of the planet found an 88 earth-day
rotation period, equal to the orbital period, or year length. It was only in the
1960s, when a radar technique allowed the rotation rate to be
determined, we found that Mercury spins on its axis every 59
Earth days. But the length of a day on Mercury is about three times
this. To find out why, click the link below.
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Compared to the 40m diameter ELT, which will likely be used for 100 years and more, the JWST will fail 10 years after launch due to lack of fuel. If he can no longer stay on point L2 Lagrange, it will be difficult to target the stars and we will lose contact with him. Another disadvantage of telescopes put into orbit, a breakdown on these space facilities forces the sending of a team of astronauts on site, raising the cost of such infrastructure at great prices. In short, the JWST is not profitable and we can thank the American senators who agreed to sign the bill.
The future of terrestrial observatories remains assured and all the more knowing that they take advantage of state-of-the-art techniques (very high-resolution CCD, ultrathin mirror, adaptive optics, cooled mirror, bearings on oil bath, VLTI, etc.). Their lower cost than space telescopes also makes it possible to multiply their number, the only way to continuously follow certain planetary and extragalactic phenomena.
But in the future, space projects are nonetheless indispensable and will be even more ambitious. Thus, NASA in collaboration with BOEING envisages nothing less than to build in the space of the hypertelescopes of 150 km of diameter!
According to Antoine Labeyrie, such a telescope would consist of 150 mirrors of 3 m in diameter each operating in interferometry. LISE, Hyper-OVLA or Lopez’s Redundant Linear Array would be able to discern details of 10 km on the surface of a planet the size of the Earth at 10 light-years or to observe the surface of nearby stars with a resolution of 50 meters! It leaves dreamer.
Observe, listen to or analyze the stars throughout the electromagnetic spectrum does not satisfy the curiosity of researchers. The approach of the scientific community can not stop once the practitioners (astrophysicists, radio astronomers, etc.) have closed the door of their observatory. Theorists (mathematicians, physicists, cosmologists, etc.) need to know the results obtained during these observation programs to corroborate, refine or even refute their theories and possibly predict new facts that practitioners will try to observe.
The role of any scientist is to try to understand by reproducing on a small scale what he has observed. It started with the prism that reproduced the colors of the rainbow and the spectrum of stars and continues today with particle accelerators trying to discover the missing particles in the quantum taxonomic classification and the supercomputers that try to simulate the properties of celestial objects and the Universe.
Let’s see how astronomers exploit computer science to better understand the nature and properties of the stars. This is the subject of the last chapter. | 0.878327 | 3.407372 |
Massive Space Telescope Will Look for ‘Another Earth’
It’s taken 1000 people and 20 years, but the James Webb Space Telescope (JWST) is nearing completion. Once it’s done, NASA will attach the $8 billion project to a rocket and shoot it into space, where the telescope will begin its search for Earth-like exoplanets. This weekend, the Discovery Channel will premiere TELESCOPE, a behind-the-scenes documentary on the project.
Matt Mountain is president of the Association of Universities for Research in Astronomy (AURA) and former director of the Space Telescope Science Institute. As a manager, he’s acutely aware of the risks. There is a chance, after all, that the telescope could fail to deploy, or that it will be damaged in the launch. Mountain tells mental_floss that if the JWST fails, “it will be a disaster.”
But he remains optimistic. “In all science, there’s always risk,” Mountain says. “We’re doing something nobody has ever done before. We’re building the largest space telescope anybody’s ever built. We’re going to send it out a million miles and we’re going to deploy it. We just hope that we’ve done enough testing and checking here back on Earth that that won’t happen.”
The JWST has a number of scientific objectives. Astronomers know that the universe began with the so-called Big Bang, and that an explosion eventually became millions of galaxies. What happened in between—what astronomers call the Dark Ages—remains unseen. The JWST will use its powerful imaging capabilities to search for evidence of this missing period of cosmic history.
Just as amazing, Mountain says, is the JWST’s potential to discover Earth-like exoplanets—planets that are not too big or too small, too hot or too cold: “Now, we’ve got to be very lucky, because we don’t know where all these planets are yet, but if it’s about the size of the Earth, and it’s in the goldilocks zone, it can hold liquid water. And liquid water is the prerequisite for life. And then we’ll know where to look for life in another planetary zone. That would be damn cool.”
Speaking in the documentary, astronomer and planetary scientist Sara Seagar agreed: “Another Earth is undoubtedly out there.”
As a telescope expert and enthusiast, Mountain is also excited about the documentary. “The telescope has been one of the most transformative instruments in human history,” he says. “Before telescopes, the Earth was thought to be the center of our universe. Then we discovered that, no, it was the Sun, because of Galileo. And then with telescopes we discovered that those funny things we saw in the sky were not just nebulae—they were other galaxies. Every time people had theories, whether it be from Plato and Aristotle, Ptolemy, or even Einstein, telescopes have revealed a universe that people hadn’t expected.”
Like the Hubble, observations made by the James Webb Space Telescope will be accessible to everyone via images uploaded to the Internet. “That’s why telescopes have been so powerful,” Mountain says. “Everybody can come on this journey.”
The James Webb Space Telescope is scheduled to launch in 2018. TELESCOPE will air Saturday at 9 p.m. EST on the Discovery Channel and Sunday at 9 p.m. EST on the Science Channel. | 0.833987 | 3.142689 |
Fundamental questions remain unanswered in understanding galactic-scale star formation, despite many decades of investigation and progress. These include: how do stars cluster in galaxies, and how do these structures evolve in time? Do we actually have "clustered" and "diffused" modes of star formation? When structures remain bound (star clusters), how do their populations evolve? How are they related to the galactic-scale star formation? Is the stellar Initial Mass Function universal? How are popular star formation rate indicators affected by the recent star formation history of a galaxy? How are these effects impacting our understanding of the scaling laws of star formation with the gas reservoir? The answers to these questions inform our theories for the evolution of galaxies through cosmic times. Many of these questions are being addressed by recent projects that combine UV and high-angular resolution with the Hubble Space Telescope, and which I will describe together with the results they have obtained so far. | 0.90719 | 3.628378 |
Dubbed 55 Cancri e, the rocky world is only twice the size of Earth but has eight times its mass—classifying it as a "super Earth," a new study says. First detected crossing in front of its parent star in 2011, the close-in planet orbits its star in only 18 hours. As a result, surface temperatures reach an uninhabitable 3,900 degrees Fahrenheit (2,150 degrees Celsius)—which, along with carbon, make perfect conditions for creating diamonds.
NASA's Spitzer Space Telescope collected data on the planet's orbital distance and mass, and resulting computer models created a picture of 55 Cancri e's chemical makeup.
"Science fiction has dreamed of diamond planets for many years, so it's amazing that we finally have evidence of its existence in the real universe," said study leader Nikku Madhusudhan, a postdoctoral researcher at Yale University.
"It's the first time we know of such an exotic planet that we think was born mostly of carbon—which really makes this a fundamental game-changer in our understanding of what's possible in planetary chemistry."
At only 40 light-years away, in the northern constellation Cancer, the gemlike planet sits relatively near Earth. In dark skies, 55 Cancri e's host star is clearly visible to the naked eye. (See gem pictures.)
Diamond Planet Has Odd Chemistry
The new models fit with previous studies that showed 55 Cancri e's parent star was abundant in carbon—much more so than our sun.
"If we make the assumption that the star and its surrounding planets are all born from the same primordial disk of material, then it makes sense that the entire planetary system would be carbon rich," said Madhusudhan, whose study will appear in an upcoming issue of the journal Astrophysical Journal Letters.
Princeton astronomer David Spergel believes the diamond-planet find probably represents the first discovery of a whole new class of planets whose chemistry has never been encountered. (Related: "'Diamond Planets' Hint at Dazzling Promise of Other Worlds.")
"Unlike our solar system, which is dominated by oxygen and silicates, this planetary system is filled with carbon," said Spergel, who was not involved in the new study.
"While it's still unknown exactly what implication this will have on our understanding of evolution of planetary systems," he said, "there's no doubt it is an important step towards understanding the full diversity of planets." | 0.906787 | 3.908121 |
The site is led and funded by NASA and developed by the Zooniverse, a collaboration of scientists, software developers and educators who collectively develop and manage the Internet's largest, most popular and most successful citizen science projects.
WISE, located in Earth orbit and designed to survey the entire sky in infrared light, completed two scans between 2010 and 2011. It took detailed measurements of more than 745 million objects, representing the most comprehensive survey of the sky at mid-infrared wavelengths currently available. Astronomers have used computers to search this haystack of data for planet-forming environments and narrowed the field to about a half-million sources that shine brightly in the infrared, indicating they may be "needles": dust-rich circumstellar disks that are absorbing their star's light and reradiating it as heat.
Planets form and grow within these disks. But galaxies, interstellar dust clouds, and asteroids also glow in the infrared, which stymies automated efforts to identify planetary habitats.
Disk Detective incorporates images from WISE and other sky surveys in the form of brief animations the website calls flip books. Volunteers view a flip book and then classify the object based on simple criteria, such as whether the image is round or includes multiple objects. By collecting this information, astronomers will be able to assess which sources should be explored in greater detail.
The project aims to find two types of developing planetary environments. The first, known as young stellar object disks, typically are less than 5 million years old, contain large quantities of gas, and are often found in or near young star clusters. For comparison, our own solar system is 4.6 billion years old.
The other type of habitat is called a debris disk. These systems tend to be older than 5 million years, possess little or no gas, and contain belts of rocky or icy debris that resemble the asteroid and Kuiper belts found in our own solar system. Vega and Fomalhaut, two of the brightest stars in the sky, host debris disks.
Through Disk Detective, volunteers will help the astronomical community discover new planetary nurseries that will become future targets for NASA's Hubble Space Telescope and its successor, the James Webb Space Telescope. | 0.937072 | 3.518508 |
By Yusuke Hagihara
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Extra info for Celestial mechanics. Vol. 5, Part 2. Topology of the three-body problem.
7) IXo - IX1 + IX2 = 3 - K we compare the connectivity tc* of the covering surface S* with the connectivity ;c of S and obtain 3 - tc* = s(3 - ;c) - b, ( 6) where b is the number of equivalent simple branch points of the covering surface. But since S* and S are each images of S we have tc* = ;c = tc, and (6) reduces to (s - 1)(3 - tc) - b = 0. ( 7) Consequently, if " exceeds 3 then the transformation must be one-toone and if " = 3 the covering surface S* can have no branch point. SURFACE TRANSFORMATIONS If A is an s-to-one transformation of an oriented surface S into itself, then r = ± s is defined as the index of the transformation where the plus or minus is taken according as the transformation preserves or reverses the orientation.
Because of the continuity in the variation of rot AA 1 so long as the curve does not acquire any multiple point the stated formula continues to be true or false in this second process of variation. In the first plane the arc P 0P 1 crosses the strip a ;;;;; r ;;;;; b while P 1Q 1 lies outside of it. Hence P 0P 1 can be deformed on the strip into a rectilinear segment P 0P 1 • Moreover the arc P 1Q0Q1 crosses the strip b ;;;;; r ;;;;; c, and can be continuously deformed into the broken line P 1Q0Q1 without changing the position of P 1 , Q0 or Q1 • Hence we obtain by legitimate modification a broken line P 0P 1Q0Q1 , where these points are arranged in the order of increasing r-coordinates, while P 1 has a larger 8-coordinate than P 0 , and Q1 has a smaller 8-coordinate than Q0 • In this normal position the validity of the expression f3 - IX for rot AA, is evident.
Proof: Suppose that the transformation T has no invariant point. Let (r, | 0.875798 | 3.309592 |
Observations taken by NASA's Galileo spacecraft five months apart reveal a new dark spot the size of Arizona on Jupiter's moon Io, indicating that dramatic volcanic activity occurred during that time.
"This is the largest surface change on Io observed by Galileo during its entire two-year tour of the Jovian system," said Galileo imaging team member Dr. Alfred McEwen, a research scientist at the University of Arizona in Tucson.
The visible change took place during the five months between Galileo's seventh and tenth orbits of Jupiter. The change is manifested as a dark spot about 249 miles in diameter, surrounding a volcanic center named Pillan Patera, which is named after the South American god of thunder, fire and volcanoes. Dark features at the center of the deposits may be new lava flows.
These changes appear in images taken by the Solid State Imaging system aboard Galileo, with marked differences between the pictures taken on April 4, 1997 and September 19, 1997. In June of 1997 an active plume was observed over Pillan by Galileo and the Hubble Space Telescope with a height of 75 miles, and both Galileo and ground-based astronomers observed an intense hot spot.
"Most of the volcanic plume deposits on Io show up as white, yellow or red due to sulfur compounds. However, this new deposit is gray, which tells us it has a different composition, possibly richer in silicates than the other regions," McEwen explained. "While scientists knew that silicate volcanism existed on Io from high temperatures, this may provide clues as to the composition of the silicates, which in turn tells us about Io's evolution."
"Io is probably primarily composed of silicates, which is the type of volcanic rock found on Earth, " McEwen added, "but the extreme volcanism of Io may have led to the creation of silicate compositions that are unusual on Earth."
The Io images showing the changes in Pillan Patera also reveal alterations in the plume deposit of Pele, the large red oval southwest of Pillan, which may indicate that both plumes were active at the same time and interacted with one another. A dark region southwest of Pele, which appears similar to the Pillan deposits, has been present since the Voyager flybys in 1979.
Io is the most volcanically active body in the Solar System. Scientists hope to learn more about the fiery satellite when Galileo continues its studies over the next two years, during a mission extension known as the Galileo Europa Mission. The extended mission will include eight additional encounters of Europa, four of Callisto, and two close Io flybys in late 1999, depending on spacecraft health. Galileo will pass very close to Pillan Patera in the first of the two Io flybys, so high- resolution images can be acquired over a small portion of this area.
Galileo was launched in 1989 and entered orbit around Jupiter on Dec. 7, 1995. The final satellite encounter of its two-year primary mission will occur on Thursday, Nov. 6, 1997 at 3:32 p.m. EST, when the spacecraft swoops over Europa at an altitude of 1,269 miles.
"The Galileo Orbiter is performing flawlessly and all 11 of its sophisticated science instruments and the radio science investigations are still providing excellent data," said Galileo Project Manager Bill O'Neil of NASA's Jet Propulsion Laboratory (JPL), Pasadena, CA. "A great bounty of Jupiter system science has been obtained and the continuing study of these data will surely add many important discoveries. While not all of the original objectives could be met due to the antenna failure, I believe that the overall science return from Galileo will easily exceed what was envisioned at project inception 20 years ago, because our team of scientists and engineers has done such a superb job of capturing the most important observations."
The Galileo mission is managed by JPL for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology, Pasadena, CA.
Images of Io and other data received from Galileo are posted on the Galileo home page on the World Wide Web at URL: | 0.842539 | 4.023527 |
On Monday, the NASA Mars InSight lander survived the "seven minutes of terror" during entry, descent and landing to safely arrive on Mars and took up permanent residence on the Red Planet. Unlike the rovers already on the Martian surface, InSight will stay put during its planned two-year mission.
What will the stationary craft do until November 24, 2020?
InSight has already been busy. Since landing, it has taken two photos and sent them back as postcards to Earth, showing off its new home. These initial images are grainy because the dust shields haven't been removed from the camera lenses yet.
And late Monday, mission scientists were able to confirm that the spacecraft's twin 7-foot-wide solar arrays have unfurled. With the fins folded out, InSight is about the size of a big 1960s convertible, NASA said.
"We are solar-powered, so getting the arrays out and operating is a big deal," said InSight project manager Tom Hoffman at NASA's Jet Propulsion Laboratory. "With the arrays providing the energy, we need to start the cool science operations. We are well on our way to thoroughly investigate what's inside of Mars for the very first time."
The solar arrays are key to helping InSight function. Although Mars receives less sunlight than Earth, InSight doesn't need much power to conduct its science experiments. On clear days, the panels will provide InSight with between 600 and 700 watts -- enough to power the blender on your kitchen counter, NASA said. During more dusty conditions, as Mars is known to have, the panels can still pull in between 200 and 300 watts.
Within the next few days, InSight's 5.9-foot-long robotic arm will unfold and take photos of the ground surrounding the lander. This will help mission scientists determine where its will place instruments.
This whole unpacking process as InSight settles into its new home will take about two to three months as the instruments begin functioning and sending back data.
The suite of geophysical instruments will take measurements of Mars' internal activity like seismology and the wobble as the sun and its moons tug on the planet.
These instruments include the Seismic Experiment for Interior Structures to investigate what causes the seismic waves on Mars, the Heat Flow and Physical Properties Package to burrow beneath the surface and determine heat flowing out of the planet and the Rotation and Interior Structure Experiment to use radios to study the planet's core.
InSight will be able to measure quakes that happen anywhere on the planet. And it's capable of hammering a probe into the surface.
This is why the information InSight sends back about its landing site is crucial. Creating a 3D model of the surface will help engineers understand where to place instruments and hammer in the probe, called the Mars mole HP3 by those who built it.
"An ideal location for our Mars mole would be one that is as sandy as possible and does not contain any rocks," HP3 operations manager Christian Krause said.
Tilman Spohn, principal investigator of the HP3 experiment, said, "our plan is to use these measurements to determine the temperature of Mars' interior and to characterize the current geological activity beneath its crust. In addition, we want to find out how the interior of Mars developed, whether it still possesses a hot molten core and what makes Earth so special by comparison."
The first science data isn't expected until March, but InSight will be sharing snapshots of Mars along the way. And InSight's magnetometer and weather sensors are taking readings of the landing site, Elysium Planitia -- "the biggest parking lot on Mars." It's along the Martian equator, bright and warm enough to power the lander's solar array year-round.
The information InSight will gather about Mars applies to more than just the Red Planet. It will expand the understanding of rocky planets in general.
"This has important implications beyond just these two neighbors [Mars and Earth], as we are currently discovering thousands of exoplanets around other stars, some of which may be quite similar to Earth or Mars in terms of size, location and composition," said Jack Singal, a physics professor at the University of Richmond and a former NASA astrophysics researcher.
What about MarCO?
The two suitcase-size spacecraft that followed InSight, MarCO, are the first cube satellites to fly into deep space. MarCO shared data about InSight when it entered the Martian atmosphere for the landing.
They were nicknamed EVE and WALL-E, for the robots from the 2008 Pixar film. And their mission is over. The MarCO team will collect data from each satellite to determine how much fuel they have left and a deeper look at how they performed.
"WALL-E and EVE performed just as we expected them to," MarCO chief engineer Andy Klesh at JPL said. "They were an excellent test of how CubeSats can serve as 'tag-alongs' on future missions, giving engineers up-to-the-minute feedback during a landing."
The cube satellites bid farewell to InSight after it landed. MarCO-B took an image of Mars from 4,700 miles away during its flyby at 3:10 p.m. ET after helping establish communications with mission control.
"WALL-E sent some great postcards from Mars!" said Cody Colley of JPL, MarCO's mission manager. "It's been exciting to see the view from almost 1,000 miles (1,600 kilometers) above the surface."
There are no science instruments on MarCO. But during the flyby, MarCO-A transmitted signals through the edge of the Martian atmosphere. That atmosphere causes interference to change the signal when it's received on Earth, a way for scientists to detect how much atmosphere is present and even its composition.
"CubeSats have incredible potential to carry cameras and science instruments out to deep space," said John Baker, JPL's program manager for small spacecraft. "They'll never replace the more capable spacecraft NASA is best known for developing. But they're low-cost ride-alongs that can allow us to explore in new ways."
And for the team that worked on MarCO, the success of the mission is just the beginning.
"MarCO is mostly made up of early-career engineers and, for many, MarCO is their first experience out of college on a NASA mission," said Joel Krajewski of JPL, MarCO's project manager. "We are proud of their accomplishment. It's given them valuable experience on every facet of building, testing and operating a spacecraft in deep space." | 0.843739 | 3.149114 |
In 2021, NASA will launch its Lucy mission to explore Jupiter's Trojan asteroids for the first time. Billions of years old, these asteroids serve as a time capsule for the earliest days of the solar system. Getting there will require some of the fanciest flying in the space agency's history and NASA has just started publicly discussing how Lucy will navigate its way through some of the oldest asteroids in the solar system.
The challenge with planning a mission like Lucy is that solar system is constantly moving. Normally, scientists can plan out a clear-cut route with a large planetary body, like Mars or Earth's moon. But with the Trojan asteroids, which are comprised of two separate clouds, the spacecraft will have to navigate through multiple gravitational forces. Each of these gravitational forces will be moving in their own direction and will be threatening to take Lucy with them.
"There are two ways to navigate a mission like Lucy,” says Jacob Englander, the optimization technical lead for the Lucy mission, in a press statement. “You can either burn an enormous amount of propellant and zig-zag your way around trying to find more targets, or you can look for an opportunity where they just all happen to line up perfectly.”
As Lucy moves through the solar system, the majority of its course corrections will use what are known as gravity assists. Gravity assists have a long history of helping NASA satellites get the job done. They're a favorite when navigating through interplanetary travel. Most famously, they were used to allow Voyager 2 to visit Jupiter, Saturn, Uranus and Neptune.
When a planetary body, or Lucy's case an asteroid, is much larger than the craft itself, the body shows no reaction to the craft's approach. This will allow for Lucy's energy to be conserved on its approach. As Lucy falls into an asteroid's gravity well, it will speed up and gain kinetic energy as it loses potential energy, similar to a ball rolling down the hill. It will navigate a turn and will expend that extra kinetic energy move in a new direction
But approaching these asteroids will be tricky. It will require what's known as optical navigation—perhaps the most long-distance form of remote flying ever attempted. Using a communication link and images from Lucy's onboard cameras, the team on Earth will learn the craft's location, direction and velocity. From there the team, which will include the private Arizonan space company KinetX, will design trajectory correction maneuvers.
“The maneuvers to correct Lucy’s trajectory are all going to be really critical because the spacecraft must encounter the Trojan at the intersection of the spacecraft and Trojan orbital planes,”says navigation technical lead Dale Stanbridge, who works at KinetX. “Changing the spacecraft orbital plane requires a lot of energy, so the maneuvers need to be executed at the optimal time to reach to next body while minimizing the fuel cost.”
These maneuvers will vary greatly. “The first maneuver is tiny,” Stanbridge says. “But the second one is at 898 meters per second." That's a little over 2,000 MPH.
After the tricky flying Lucy will be rewarded with clear skies, so to speak. Its mission will complete in 2033 with nothing ahead. “We’re just going to leave it out there,” Englander said. “We did an analysis to see if it passively hits anything, and looking far into the future, it doesn’t.”
After helping humanity better understand the origins of the solar system, it will be a much-deserved retirement. | 0.911336 | 3.815033 |
Scientists at the Columbia University have conducted a study, which uncovered new evidence of the possibility of an imminent collision between two black holes, HNGN reports. According to the study, details of which have been published in Nature magazine, two black holes, both located in the constellation of Virgo, are on the path to collide with each other.
Both the black holes are estimated to be a staggering three-and-a-half-billion light years away from our solar system. And, no, do not expect the collision to happen any time soon — it would take at least 100,000 more years for that to happen. However, 100,000 years is a relatively short time span when you compare it with the age of the universe — estimated to be a tad over 13-billion-years-old.
As for the collision, scientists say this giant collision between the black holes will send ripples across the galaxy in which they are located, and could possibly destroy it.
Zoltan Haiman, a senior author who was a part of the team that discovered that the two black holes are on a collision course, says as follows.
“Some people think these systems are always going to be hung up at large separations. Our study is important because it shows that, yes, black holes can reach very small distances from each other.”
The fact that these two black holes are on a collision course was discovered last winter by a team of astronomers from Caltech, the New York Times reports. The latest study only adds credence to the discovery that was made last year. According to scientists, the evidence of the collision came from the flickering that was observed from the galaxy’s nucleus, a quasar by the name PG 1303-102. This flickering was, according to them, caused by the effects of the tremendous gravitation that the pair of black holes exerted on the nucleus. Just to give you an idea, the mass of both the galaxies combined would be more than the mass of a billion suns. And our sun is quite a large object, with considerable mass.
While it would be impossible for any of us to witness this incident, it could be possible that our future generations might be able to do it. The collision would release a massive burst of energy, from which we would be able to unravel a lot of mysteries of the universe that continue to perplex us.
Haiman adds the following.
“Watching this process reach its culmination can tell us whether black holes and galaxies grow at the same rate, and ultimately test a fundamental property of space-time: its ability to carry vibrations called gravitational waves, produced in the last, most violent, stage of the merger.”
[Photo by NASA / ESAvia / Getty Images] | 0.845468 | 3.80023 |
The European Space Agency’s Rosetta spacecraft was the first to orbit a comet when it circled Comet 67P/Churyumov-Gerasimenko from 2014 to 2016. Rosetta’s up-close look at 67P has given scientists an unprecedented chance to understand what these small, icy worlds are like.
Now, a team of researchers has unlocked another one of the comet’s secrets. As the comet zooms around the sun, clouds of gas and dust billow and settle, surrounding the comet in a haze of shifting colors visible to telescopes.
Different parts of the comet tend to reflect different colors of light depending on where the comet is in its orbit, and the researchers have figured out that seasonal cycles of dust and ice on the comet are causing these color changes.
The researchers presented their findings in a paper published Wednesday in Nature.
A Comet's Changing Colors
The team of researchers, led by Gianrico Filacchione of the National Institute for Astrophysics (INAF) in Italy, analyzed observations of Comet 67P from Rosetta’s VIRTIS instrument. VIRTIS measured the light the comet reflected in various colors, letting scientists puzzle out what chemical compounds are inside.
The researchers looked at more than a year of data from VIRTIS and found that the wavelengths, or colors, of light the comet reflected changed as the comet got closer to and then farther from the sun.
As the comet approached its closest point to the sun, the atmosphere, or coma, of the comet got redder while the nucleus of the comet appeared bluer. Then, when the comet was moving farther away from the sun in its orbit, the coma got bluer while the nucleus got redder.
Cycles of Ice and Dust
With careful analysis and computer simulations, the researchers deduced that the color changes all came down to dust and ice. Water-ice tends to reflect bluer light, while dust grains made of carbon and organic compounds reflect more reddish light.
As the comet approached the sun in its orbit, the sun’s rays heated the comet and lifted lots of dust grains off of the comet’s surface and into the coma. This made the coma appear redder, while removing dust from the nucleus revealed more ice on its surface, making the nucleus look bluer.
The process flipped when the comet was in the part of its orbit that took it farther from the sun: Dust settled back onto the nucleus, making the nucleus look redder. And the particles lifted off the nucleus in this part of the orbit tended to be richer in water-ice, making the coma look bluer.
Capturing these simultaneous changes in both the coma and nucleus of Comet 67P would not have been possible with observations from Earth, Filacchione wrote in an email. But by sending a spacecraft to the vantage point of the comet's orbit, scientists have gained a clearer picture than ever before of this icy world. | 0.817869 | 4.030895 |
The Earth will evaporate when the sun dies
the Sun is going to run out of fuel in about 7-8 billion years. What will happen to the planets then, especially to Earth? Research suggests, if tidal forces are taken into account, then the Earth is likely to evaporate when the Sun treads towards its death ( Icarus , Vol 151, p130).
The Sun belongs to a class of stars called the main sequence stars. Thermonuclear fusion reactions in their core convert hydrogen atoms into helium atoms and in the process releases a lot of energy. This energy holds up the Sun against its own gravitational force. In the absence of any energy generation, the material in the Sun would collapse into the core. This very energy also provides us with our life force on Earth.
And though the sun is massive, it holds a limited volume of hydrogen. At some point of time all the hydrogen is bound to be converted into helium. At this point, the Sun will enter the 'red giant phase' when the helium in the core will undergo thermonuclear reaction to produce energy and other heavier elements. The Sun will become huge and probably engulf planets as distant as the Venus' orbital radius. Towards the end of the red giant phase, the helium in the core will ignite and emit a huge flash. After a couple of hundred million years, the Sun would run out of nuclear fuel to ignite and then begin its compression. It will, depending on its mass and size, settle down to a dense cold object that could be a white dwarf or a neutron star. The fate of our solar system will then hinge on how the Sun will move from a main sequence star to a red giant.
Some calculations suggest that the red giant would be big enough to cover the orbit of Earth while others feel that it will only engulf Venus. The calculations are horrendously difficult to perform because of all the various variables that need to be taken into account.
K Rybicki, researcher at the Polish Academy of Sciences, Warsaw and C Denis, researcher at the University of Lige, Belgium have calculated the future of our own planet taking into account tidal forces. As the Sun becomes huge and its envelope of hot gases reaches out to the Earth's orbit, the planets will experience tidal forces. These forces will change the orbits significantly because of the huge mass and distances involved. For instance, if there were no tidal forces, calculations suggest that Venus (and all the other planets beyond that) would move away from the red giant. If the tidal forces are taken into consideration, then Venus will spiral into the Sun.
As for the Earth, it will probably stay out of the Sun's envelope but may get trapped in one of the heat pulses that come after a star has finished its red giant phase. If it gets trapped, then the earth will be sucked into the Sun and eventually evaporate. On the other hand, if these pulses did not last for too long, Earth may, like the outer planets, continue in its orbit around the much cooler and denser Sun. In any case, life as we know it would have long become extinct, either because of too much heat or ultimately because of too little heat and energy!
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|GENERAL INFORMATION ON NEPTUNE|
Neptune cannot be seen using the eyes alone. Neptune was the first planet whose existence was predicted mathematically (the planet Uranus's orbit was perturbed by an unknown object which turned our to be another gas giant, Neptune).
Neptune is about 30,775 miles (49,528 km) in diameter. This is 3.88 times the diameter of the Earth. If Neptune were hollow, it could hold almost 60 Earths.
Neptune is the fourth largest planet in our Solar System (after Jupiter, Saturn, and Uranus).
MASS AND GRAVITY
Neptune's mass is about 1.02 x 1026 kg. This is over 17 times the mass of the Earth, but the gravity on Neptune is only 1.19 times of the gravity on Earth. This is because it is such a large planet (and the gravitational force a planet exerts upon an object at the planet's surface is proportional to its mass and to the inverse of its radius squared).
A 100-pound person would weigh 119 pounds on Neptune.
LENGTH OF A DAY AND YEAR ON NEPTUNE
Each day on Neptune takes 19.1 Earth hours. A year on Neptune takes 164.8 Earth years; it takes almost 165 Earth years for Neptune to orbit the sun once.
Since Neptune was discovered in 1846; since then it completed about a single revolution around the sun.
NEPTUNE'S ORBIT AND DISTANCE FROM THE SUN
Neptune is about 30 times farther from the sun than the Earth is; it averages 30.06 A.U. from the sun. Occasionally, Neptune's orbit is actually outside that of Pluto; this is because of Pluto's highly eccentric (non-circular) orbit. During this time (20 years out of every 248 Earth years), Neptune is actually the farthest planet from the Sun (and not Pluto). From January 21, 1979 until February 11, 1999, Pluto was inside the orbit of Neptune. Now and until September 2226, Pluto is outside the orbit of Neptune.
At aphelion (the point in Neptune's orbit farthest from the sun) Neptune is 4,546,000,000 km from the sun, at perihelion (the point in Neptune's orbit closest from the sun) Neptune is 4,456,000,000 km from the sun.
Neptune's rotational axis is tilted 30 degrees to the plane of its orbit around the Sun (this is few degrees more than the Earth). This gives Neptune seasons. Each season lasts 40 years; the poles are in constant darkness or sunlight for 40 years at a time.
The mean temperature is 48 K.
DISCOVERY OF NEPTUNE
Neptune's existence was predicted in 1846, after calculations showed perturbations in the orbit of Uranus. The calculations were done independently by both J.C. Adams and Le Verrier. Neptune was then observed by J.G. Galle and d'Arrest on September 23, 1846.
Neptune was visited by NASA's Voyager 2 in August, 1989. Before this visit, virtually nothing was known about Neptune.
This is the symbol of the planet Neptune.
Find It!, a quiz on Neptune.
Neptune Cloze Printout: A fill-in-the-blanks activity on the planet Neptune. Answers
An interactive puzzle about Neptune
How to write a report on a planet - plus a rubric.
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From atmospheric changes, to timelapse imagery from Google Earth...our planetary presence is hard to miss.
This past week has seen the concentration of carbon dioxide (CO2) in Earth's atmosphere reach a level of 400 parts-per-million, a value the planet hasn't seen since several million years ago. To put this into some kind of context let's take a look at the variation in CO2 over the past half century or so - via the classic 'Keeling Curve'.
There are two basic features of this plot. First is that it wiggles up and down on an annual basis. That's because the Earth has seasons and oceans and landmasses with living organisms that absorb and generate CO2. Plants, for example, tend to absorb CO2 in summers when they're growing, and can release CO2 in winters when they're rotting or dormant. The planet is also lopsided in the sense that there is more 'habitable' continental land mass in the north than in the south - otherwise the net contribution to CO2 variation between northern summer and southern winter, or vice versa, would cancel out.
The second feature of this plot is that CO2 concentration is increasing with time. Why? Well, it's simple, it's because of us. This is seen most starkly if we take a look at a rather longer timeline - made using ice-core measurements of atmospheric CO2 (since our ancestors weren't monitoring the atmosphere for us). It begins going uphill just around 1760 - the start of the Industrial Revolution.
You can begin to see just how steep the rate of change has become since the mid 20th century if we go even further back and look at the past 800,000 years.
See that little spike at the right hand side up to 400 ppm? That's us, today. Although CO2 concentrations have been far from stable over the past 800,00 years, they take a sharp upward turn right in line with the rise of industrialized human civilization.
Now of course the ice core data are not perfect, there could potentially be some other spikes in there that get washed out in the measurements, but we would probably spot anything like our present fast rise.
How far back do we need to look to hit similar CO2 levels to today's? It's not quite clear, but it might be around 3 to 4 million years. A study by Bartoli, Honisch, and Zeebe in 2011 measured boron isotopes in the mineral shells formed by types of plankton, and suggests this was the case.
Looking further back, across more of the immense history of the planet, and we see that CO2 wanders all over the place. For example, here are some estimates showing both measurements and computer models (timeline flipped from previous plots).
There's a lot of uncertainty, but it's clear that even our present 400 ppm CO2 concentration is small compared to what it has been tens to hundreds of millions of years in the past. Amounts that were five to twenty times higher than today seem more like the norm.
But humans, and the world we find around us, didn't exist back then. These were periods where the Earth, our lovely home planet, would have felt about as alien as some of the exoplanets we're now discovering in the surrounding universe. The environmental chemistry, the fauna (not always any flora), and the climate may have never before been a match for what it has been the past million years or so.
Like it or not, the historically low trough in the CO2 concentration of yesterday is a defining characteristic of the window of opportunity where our peculiar ape-related ancestors managed to get a foothold. The fascinating but rather terrifying thing is that we've now gone global, and we've learned how to extract vast amounts of energy from our environment, driven by an extraordinary ability to innovate and survive. By doing so we've altered that window, significantly changing the chemical composition of the atmosphere. And although I'm not going to discuss it in detail here, simple physics tells us what's going to happen next. You cannot deny basic thermodynamics.
This is merely one change our presence has brought to the planet. There are many others. In fact you can now be a first-hand witness to the visible alterations going on around the globe through the magic of Google Earth. Terabytes of imaging data from 1984 to the present have been stitched together to allow a timelapse view of just about any part of the world. Go check it out here.
Even in this day and age of planetary awareness it's pretty amazing to see just how infested a place it is. Here's an example, Las Vegas, 1984 to 2012.
Once you're done with looking at other examples, try entering your own search...it's quite educational.
Is it all doom and gloom? Yes and no. Clearly we're testing the limits, we have a good chance of pushing our planet (if we haven't done so already) to a place it hasn't been to for millions of years - the kind of place that we might not like. The kind of place that might kill us. But we're also amazingly clever, or else we wouldn't know that we're doing this. So what's going to happen?
I wish I knew. But as a scientist, and an optimist, I can't help but notice that if we're serious about looking for life beyond the Earth and if we're serious about looking for complex, technological life, it's this kind of filthy disregard for planetary equilibrium that we should be sniffing for. We might have to wait a while if we find suitable candidate worlds to aim our telescopes at, but it's conceivable we might catch some other life-form making precisely the same mistakes we are.
Through early morning fog I see
Visions of the things to be
The pains that are withheld for me
I realize and I can see
That suicide is painless
It brings on many changes
And I can take or leave it if I please
(Johnny Mandel and Michael Altman, 'Suicide Is Painless'/M.A.S.H. theme) | 0.830689 | 3.147537 |
The Hill sphere or Roche sphere of an astronomical body is the region in which it dominates the attraction of satellites. The outer shell of that region constitutes a zero-velocity surface. To be retained by a planet, a moon must have an orbit that lies within the planet's Hill sphere. That moon would, in turn, have a Hill sphere of its own. Any object within that distance would tend to become a satellite of the moon, rather than of the planet itself. One simple view of the extent of the Solar System is the Hill sphere of the Sun with respect to local stars and the galactic nucleus.
In more precise terms, the Hill sphere approximates the gravitational sphere of influence of a smaller body in the face of perturbations from a more massive body. It was defined by the American astronomer George William Hill, based on the work of the French astronomer Édouard Roche. For this reason, it is also known as the "Roche sphere" (not to be confused with the Roche limit or Roche Lobe).
In the example to the right, Earth's Hill sphere extends between the Lagrangian points L1 and L2, which lie along the line of centers of the two bodies (the Earth and the Sun). The region of influence of the second body is shortest in that direction, and so it acts as the limiting factor for the size of the Hill sphere. Beyond that distance, a third object in orbit around the second (e.g. the Moon) would spend at least part of its orbit outside the Hill sphere, and would be progressively perturbed by the tidal forces of the central body (e.g. the Sun), eventually ending up orbiting the latter.
Formula and examplesEdit
If the mass of the smaller body (e.g. the Earth) is , and it orbits a heavier body (e.g. the Sun) of mass with a semi-major axis and an eccentricity of , then the radius of the Hill sphere of the smaller body, calculated at the pericenter, is approximately
When eccentricity is negligible (the most favourable case for orbital stability), this becomes
In the Earth-Sun example, the Earth (5.97×1024 kg) orbits the Sun (1.99×1030 kg) at a distance of 149.6 million km, or one astronomical unit (AU). The Hill sphere for Earth thus extends out to about 1.5 million km (0.01 AU). The Moon's orbit, at a distance of 0.384 million km from Earth, is comfortably within the gravitational sphere of influence of Earth and it is therefore not at risk of being pulled into an independent orbit around the Sun. All stable satellites of the Earth (those within the Earth's Hill sphere) must have an orbital period shorter than seven months.
The previous (eccentricity-ignoring) formula can be re-stated as follows:
This expresses the relation in terms of the volume of the Hill sphere compared with the volume of the second body's orbit around the first; specifically, the ratio of the masses is three times the ratio of the volume of these two spheres.
The expression for the Hill radius can be found by equating gravitational and centrifugal forces acting on a test particle (of mass much smaller than ) orbiting the secondary body. Assume that the distance between masses and is , and that the test particle is orbiting at a distance from the secondary. When the test particle is on the line connecting the primary and the secondary body, the force balance requires that
where is the gravitational constant and is the (Keplerian) angular velocity of the secondary about the primary (assuming that ). The above equation can also be written as
which, through a binomial expansion to leading order in , becomes
Hence, the relation stated above
If the orbit of the secondary about the primary is elliptical, the Hill radius is maximum at the apocenter, where is largest, and minimum at the pericenter of the orbit. Therefore, for purposes of stability of test particles (for example, of small satellites), the Hill radius at the pericenter distance needs to be considered. To leading order in , the Hill radius above also represents the distance of the Lagrangian point L1 from the secondary.
A quick way of estimating the radius of the Hill sphere comes from replacing mass with density in the above equation:
where and are the average densities of the primary and secondary bodies, and and are their radii. The second approximation is justified by the fact that, for most cases in the Solar System, happens to be close to one. (The Earth–Moon system is the largest exception, and this approximation is within 20% for most of Saturn's satellites.) This is also convenient, because many planetary astronomers work in and remember distances in units of planetary radii.
True region of stabilityEdit
The Hill sphere is only an approximation, and other forces (such as radiation pressure or the Yarkovsky effect) can eventually perturb an object out of the sphere. This third object should also be of small enough mass that it introduces no additional complications through its own gravity. Detailed numerical calculations show that orbits at or just within the Hill sphere are not stable in the long term; it appears that stable satellite orbits exist only inside 1/2 to 1/3 of the Hill radius. The region of stability for retrograde orbits at a large distance from the primary is larger than the region for prograde orbits at a large distance from the primary. This was thought to explain the preponderance of retrograde moons around Jupiter; however, Saturn has a more even mix of retrograde/prograde moons so the reasons are more complicated.
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An astronaut could not have orbited the Space Shuttle (with mass of 104 tonnes), where the orbit was 300 km above the Earth, because its Hill sphere at that altitude was only 120 cm in radius, much smaller than the shuttle itself. A sphere of this size and mass would be denser than lead. In fact, in any low Earth orbit, a spherical body must be more dense than lead in order to fit inside its own Hill sphere, or else it will be incapable of supporting an orbit. A spherical geostationary satellite, however, would only need to be more than 6% of the density of water to support satellites of its own.
Within the Solar System, the planet with the largest Hill radius is Neptune, with 116 million km, or 0.775 au; its great distance from the Sun amply compensates for its small mass relative to Jupiter (whose own Hill radius measures 53 million km). An asteroid from the asteroid belt will have a Hill sphere that can reach 220,000 km (for 1 Ceres), diminishing rapidly with decreasing mass. The Hill sphere of 66391 Moshup, a Mercury-crossing asteroid that has a moon (named Squannit), measures 22 km in radius.
A typical extrasolar "hot Jupiter", HD 209458 b, has a Hill sphere radius of 593,000 km, about eight times its physical radius of approx 71,000 km. Even the smallest close-in extrasolar planet, CoRoT-7b, still has a Hill sphere radius (61,000 km), six times its physical radius (approx 10,000 km). Therefore, these planets could have small moons close in, although not within their respective Roche limits.
The following logarithmic plot shows the Hill radius (in km) of some bodies of the Solar System:
- Chebotarev, G. A. (March 1965). "On the Dynamical Limits of the Solar System". Soviet Astronomy. 8: 787. Bibcode:1965SvA.....8..787C.
- D.P. Hamilton & J.A. Burns (1992). "Orbital stability zones about asteroids. II - The destabilizing effects of eccentric orbits and of solar radiation". Icarus. 96 (1): 43–64. Bibcode:1992Icar...96...43H. doi:10.1016/0019-1035(92)90005-R.
- Astakhov, Sergey A.; Burbanks, Andrew D.; Wiggins, Stephen & Farrelly, David (2003). "Chaos-assisted capture of irregular moons". Nature. 423 (6937): 264–267. Bibcode:2003Natur.423..264A. doi:10.1038/nature01622. PMID 12748635.
- HD 209458 b
- CoRoT-7 b | 0.903577 | 4.050556 |
This FLAMINGOS-2 near-infrared image details part of the magnificent Swan Nebula (M17), where ultraviolet radiation streaming from young hot stars sculpts a dense region of dust and gas into myriad fanciful forms. M17 lies some 5,200 light-years distant in the constellation Sagittarius and is one of the most massive and luminous star-forming region's in our Galaxy. It is also one of the most studied. Field of view: 5.5 x 4.0 arcmin. Credit: Gemini Observatory/AURA
Full Resolution TIF (4MB) | Full Resolution JPG (2MB) | Med Resolution JPG (280KB)
NGC 6300 is an intriguing barred spiral galaxy in the constellation of Ara. This near-infrared image with FLAMINGOS-2 shows the galaxy’s complex arm structure forming a spectacular ring of star formation. The galaxy’s bar also has a strong vein of dust that almost obscures its bright active nucleus –– whose prodigious energy is the result of matter accreting onto a black hole with an estimated mass of 280,000 Suns. Field of view: 3.1 x 2.9 arcmin. Credit: Gemini Observatory/AURA
Full Resolution TIF (2.3MB) | Full Resolution JPG (1.2MB) | Med Resolution JPG (153KB)
In this near-infrared image, FLAMINGOS-2 peered deep into the heart of spiral galaxy NGC 253, which lies about 11.5 million light-years nearby in the constellation of Sculptor. The new instrument captured an intricate whirlpool of dust spiraling in to a diffuse nuclear region, where violent star formation may be occurring around a supermassive black hole. The instrument also imaged a dusting of star forming sites in its spiral arms. Field of view: 4.8 x 4.1 arcmin. Credit: Gemini Observatory/AURA
Full Resolution TIF (4MB) | Full Resolution JPG (2MB) | Med Resolution JPG (141KB)
Spiral galaxy NGC 7582 is the brightest member of the Grus Quartet of galaxies, some 60 million light-years distant traveling together through space. In this near-infrared image, FLAMINGOS-2 resolved its high quantity of dust that line NGC 7582’s arms as well as regions rich in star formation. Field of view: 2.5 x 1.7 arcmin. Credit: Gemini Observatory/AURA
Full Resolution TIF (836KB) | Med Resolution JPG (425KB)
Gemini Observatory Press Release/Image Release
For release on August 8, 2013
- Percy Gomez
Gemini Observatory, La Serena, Chile
Phone (Desk): 56-51-2-205696
- Peter Michaud
Gemini Observatory, Hilo, Hawai‘i
Office: +1 (808) 974-2510
Cell: +1 (808) 936-6643
- Antonieta Garcia
Gemini Observatory, La Serena, Chile
Phone (Desk): 56-51-2-205628
Gemini Observatory’s latest instrument, a powerful infrared camera and spectrograph at Gemini South, reveals its potential in a series of striking on-sky commissioning images released today.
Gemini Observatory’s latest tool for astronomers, a second-generation infrared instrument called FLAMINGOS-2, has “traveled a long road” to begin science observations for the Gemini scientific community. Recent images taken by FLAMINGOS-2 during its last commissioning phase dramatically illustrate that the instrument was worth the wait for astronomers around the world who are anxious to begin using it.
“It’s already one of our most requested instruments at the Gemini telescopes,” remarks Nancy Levenson, Gemini’s Deputy Director and Head of Science. “We see a long and productive life ahead for FLAMINGOS-2 once astronomers really start using it later this year.”
“It has not been an easy journey,” says Percy Gomez Gemini’s FLAMINGOS-2 Instrument Scientist, “but thanks to the dedicated work of Gemini engineers and scientists very soon astronomers will be able to use a reliable and robust instrument.” After significant redesign and rebuilds for optimal performance on the Gemini South telescope, FLAMINGOS-2 has proven that it will provide astronomers with a powerful mix of capabilities. These include extreme sensitivity to infrared (heat) radiation from the universe, high-resolution wide-field imaging, and a combination of spectroscopic capabilities that will allow cutting-edge research in topics spanning from the exploration of our Solar System, to the most distant and energetic explosions in our universe.
While work still remains on some of its spectroscopic features, as well as refining imaging at the edge of its large field of view, Gemini’s team of engineers and scientists has mitigated its most severe risk – potential damage to a large collimator lens that catastrophically cracked during a planned final commissioning in early 2012 (it was later replaced). The thermal environment surrounding this lens – located where the temperature changes periodically for routine switching of masks for multi-object spectroscopy - creates special challenges. It was these temperature changes that initially caused the crack, but a year later procedures and design modifications are now in place to significantly reduce risks to the lens’s integrity and functionality.
“The Gemini team has done a remarkable job in optimizing this instrument for Gemini and it will soon be everything, and more, that we had envisioned years ago when the project began,” says Steve Eikenberry, who led the team who built FLAMINGOS-2 at the University of Florida. “Like a lot of scientists, I’m anxious to use FLAMINGOS-2 to collect data – specifically, I want to look toward the center of our Galaxy and study binary black holes as well as the mass evolution of the super-massive black hole that lurks at the heart of our Galaxy.” Eikenberry and collaborators are eager to make the most of FLAMINGOS-2’s power as soon as the instrument’s multi-object spectroscopy capability is fully functional. “With most of the challenges behind us, now the fun begins!” Eikenberry said.
Kevin Stevenson of the University of Chicago already has plans to use FLAMINGOS-2 later this year to study the intriguing exoplanet WASP-18b. This well-known exoplanet is being strongly heated by its ultra-nearby host star and according to Stevenson, “It's even hotter than some of the coolest, low-mass stars known.” Stevenson and his team hope to determine the abundances of water vapor and methane when the planet is eclipsed by its host star. “Our plan is to compare the system's light immediately before and during an eclipse to measure the contribution from the planet. When we do this over several parts of the infrared part of the light spectrum, we can piece together the planet's spectrum and learn about its temperature and composition.”
The quality and usefulness of FLAMINGOS-2 for these and future projects is reflected in the images released today. They cover a wide range of targets which are representative of the types of science in which FLAMINGOS-2 is expected to excel. In addition, the instrument may later accept an adaptive optics (AO) feed for extremely high-resolution imaging from GeMS (Gemini Multi-conjugate adaptive optics System).
It is expected that most of these systems, including multi-object spectroscopy, will be fully integrated in 2014 with imaging and long-slit spectroscopy available now. The next round of observations with FLAMINGOS-2 are slated to begin on September 1st.
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A podcast about Gemini Observatory and its role in the Era of Multi-Messenger Astronomy. Featuring news related to multi-messenger astronomy (MMA), time-domain astronomy (TDA), our visiting instrument program, and more through interviews with astronomers, engineers, and staff both here at Gemini (North and South) and abroad. | 0.877662 | 3.769712 |
Saturn-Day and Moon-Day Arrive
Last Saturday, we looked at news about Saturn and its rings. This Saturday we look at news about Saturn’s moons.
The planet Saturn just surpassed Jupiter in number of moons. Twenty more moons were discovered in Cassini data, Science Daily says, bringing the total to 82, compared to Jupiter’s 79. NASA is calling on the public to help give them names. But actually, Saturn has so many moons, they could never be counted. Within the rings are “propeller” moons that, while not obvious, leave evidence of their existence in propeller-shaped wakes consisting of disturbed ring particles. And actually, every ring particle is a moon orbiting Saturn, some as large as houses, some mere specks of dust. Here we concentrate on two of the most noteworthy moons of Saturn: Titan and Enceladus.
Lakes on Saturn’s moon Titan are explosion craters, new models suggest (Science Daily). Some of the small polar lakes on Titan have steep rims hundreds of feet high. A new model that might account for them considers them craters where frozen nitrogen exploded upward, contributing to Titan’s nitrogen-rich atmosphere. In order to keep Titan billions of years old when they know the atmosphere cannot be sustained that long, some planetary scientists like Jonathan Lunine (whose prediction of a global ethane ocean was falsified by Cassini) are now envisioning “cycles” —
Over the last half-billion or billion years on Titan, methane in its atmosphere has acted as a greenhouse gas, keeping the moon relatively warm — although still cold by Earth standards. Scientists have long believed that the moon has gone through epochs of cooling and warming, as methane is depleted by solar-driven chemistry and then resupplied.
This, however, amounts to special pleading, and could not work. By now (if the current atmosphere were at most 10 million to 100 million years old, as they believe), there would have been 45 to 450 cycles of methane depletion and resupply over the assumed age of the solar system. We know, however, that the methane is subject to the solar wind 20% of Titan’s orbit. Nothing is going to resupply it. And the ethane should have formed that global ocean over billions of years, as Lunine had predicted; it would be going nowhere, so where is it?
Cassini explores ring-like formations around Titan’s lakes (European Space Agency, via Phys.org). Cassini found “around 650 lakes and seas in the polar regions of Titan—300 of which are at least partially filled with a liquid mix of methane and ethane.” Some of the lakes have steep-walled rims, as noted above, and some have broken rims. But others “are surrounded by ramparts: ring-shaped mounds that extend for tens of km from a lake’s shoreline” that completely enclose the liquid. How did these form? So far they cannot tell if the ramparts are “old” or “young.” They may have to wait for the next mission, named Dragonfly, to look from ground level instead of from orbit.
‘Bathtub rings’ around Titan’s lakes might be made of alien crystals (Science Daily). Cue the Twilight Zone music: the rims of Titan’s lakes “might be encrusted with strange, unearthly minerals, according to new research being presented here.” Once again, though, confirmation of these features, which resemble rings of precipitated salt around salty lakes on Earth, will await more data from the next mission. They might consist of butane, acetylene and benzene, which are known to precipitate in Titan’s atmosphere. These alien crystals, though, appear to form snowflakes with ethane molecules captured inside.
Flying on Saturn’s moon Titan: what we could discover with NASA’s new Dragonfly mission (The Conversation). Think of what scientists could see with a drone flying around Titan above the surface, instead of from orbit. That’s the plan for a follow-up visit to Titan. The mission is named Dragonfly. To promote it, Christian Schroeder (U of Stirling) has learned his propaganda well. Insert the L-word life to trigger public drooling.
Flying on other worlds is the next leap in the exploration of our solar system. The Mars Helicopter will piggyback on the NASA Mars 2020 rover mission to demonstrate the technology. But this is only the start. The real prize will be the Dragonfly mission in 2026, sending a drone to Saturn’s largest moon, Titan – as just announced by NASA.
For a craft to become airborne, it needs air or, more generally, an atmosphere. Only a handful of objects in our solar system fit that bill. Titan boasts an atmosphere thicker than Earth’s, which has shrouded this world in mystery for a long time. Studies have shown Titan may be able to host primitive lifeforms and is the ideal place to study how life may have arisen on our own planet.
SMU’s ‘Titans in a Jar’ could answer key questions ahead of NASA’s space exploration (Southern Methodist University). This university long ago went from “Methodist” in the tradition of John Wesley to “Methodological Naturalist” in the atheist sense. As such, its research department will spend its $195,000 NASA grant looking for evidence of a naturalistic origin of life.
Before the rotorcraft lands on Titan, chemists from SMU will be recreating the conditions on Titan in multiple glass cylinders — each the size of a needle top — so they can learn about what kind of chemical structures could form on Titan’s surface. The knowledge on these structures can ultimately help assess the possibility of life on Titan — whether in the past, present or future.
Saturn’s Icy Moon Enceladus Is Likely the ‘Perfect Age’ to Harbor Life (Live Science). Astrobiological fervor about Titan is only exceeded by the fervor of looking for life on Enceladus. As we saw last week, the evolutionary moyboys that control planetary science these days need to keep these moons old in order for life to have time to emerge by chance (as if time helps). They realize that just a few tens or hundreds of millions of years is far too short for that. One way they keep them old is just to declare them old, hoping nobody will notice that it’s an evolution-based assumption, not a measurable fact.
Below the ice-covered surface of Saturn’s moon Enceladus hides a vast ocean.
This sprawling ocean is likely 1 billion years old, which means it’s the perfect age to harbor life, said Marc Neveu, a research scientist at NASA Goddard Space Flight Center last Monday (June 24) during a talk at the 2019 Astrobiology Science Conference.
In order to appear sciency, the chief wizard Neveu ran some computer simulations with contrived parameters to make Enceladus look just old enough for the time he thinks would be needed for the miracle of life to happen, if you had carbon, hydrogen, oxygen and nitrogen available (Enceladus has lots of water ice, but very little of anything else). Yet Neveu has to admit that it’s rather surprising Enceladus would have an ocean left after all this time.
One of Cassini’s major discoveries was that Enceladus had an ocean filled with hydrothermal vents. “It’s very surprising to see an ocean today,” Neveu told Live Science after the talk. “It’s a very tiny moon and, in general, you expect tiny things to not be very active [but rather] like a dead block of rock and ice.”
Neveu needs the moon to be the right age. So he imagines it, guided by evolutionary magic.
If the ocean is too young – for example, only a couple of million years old – there probably wouldn’t have been enough time to mix those ingredients together to create life, he said. What’s more, that’s not enough time for little sparks of life to spread enough for us Earthlings to detect them.
On the other hand, if the ocean is too old, it’s as if the planet’s “battery” is running out of juice; the chemical reactions needed to sustain life might stop, Neveu said.
In this world, the elements that needed to dissolve would have dissolved, all the minerals needed to form would have formed, he said. The moon would’ve then reached an equilibrium, meaning that the reactions to sustain life wouldn’t take place.
That means Enceladus’ ocean may be the perfect age to harbor life.
How he got to that non-sequitur isn’t clear. In the meantime, his computer simulations continue running.
Organic Compounds Found in Plumes of Saturn’s Icy Moon Enceladus (Space.com). Ready to supply some building blocks of life for the astrobiologists, this article triumphantly announces “organic molecules” in the plumes of Enceladus, but doesn’t say what they are. (Note: many deadly poisons are “organic molecules”). It only teases readers that “Similar compounds on Earth take part in the chemical reactions that form amino acids, which are the organic compounds that combine to form proteins and are essential to life as we know it.” Were any of these things found? No.
Saturn’s moon Enceladus is having a snowball fight with other moons (New Scientist). Now here’s a finding that should put the moyboys into clinical depression. The geysers of Enceladus are spray-painting other moons white with icy snow. The amount of snow is not trivial, either:
Alice Le Gall at the University of Paris-Saclay in France and her colleagues analysed these radar observations and found that three of the moons, Mimas, Enceladus and Tethys, seem to be twice as bright as we previously thought. They presented their work this week at at a joint meeting of the European Planetary Science Congress and the Division for Planetary Sciences in Geneva, Switzerland.
That can be partly explained by Enceladus: it has huge geysers that spew water from its subsurface ocean into space, which then freezes and snows down on the nearby moons and Enceladus’ surface. Le Gall and her colleagues calculated that this layer of ice and snow should be at least a few tens of centimetres thick.
“Now we know that the snow is actually accumulating, it’s not just a thin veneer but a much thicker layer of water ice,” Le Gall says.
Could that go on for billions of years? Enceladus, remember, also builds a huge E-ring around Saturn, but this tiny moon is only about the diameter of Washington State. Neveu in the previous article said that this small moon should be like a dead block of rock and ice after all this time. As usual, the scientists completely ignore the age implications of this discovery. Spray cans give out after a while of continuous spraying.
Why are the planetary scientists ignoring this? They will never admit defeat. Charlie & Charlie* are too important in their pantheon to disgrace. | 0.892992 | 3.518834 |
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Named after the Roman god of agriculture, its astronomical symbol (♄) represents the god's sickle. Saturn is a gas giant with an average radius about nine times that of Earth. While only one-eighth the average density of Earth, with its larger volume Saturn is just over 95 times more massive. Saturn has a prominent ring system that consists of nine continuous main rings and three discontinuous arcs, composed mostly of ice particles with a smaller amount of rocky debris and dust. Sixty-two known moons orbit the planet; fifty-three are officially named.
- Quotes are arranged alphabetically by author
A - F
- Adorned with thousands of beautiful ringlets, Saturn is unique among the planets. All four gas giant planets have rings -- made of chunks of ice and rock -- but none are as spectacular or as complicated as Saturn's. Like the other gas giants, Saturn is mostly a massive ball of hydrogen and helium. Ten important facts related to Saturn are: If the sun were as tall as a typical front door, the Earth would be the size of a nickel and Saturn would be about as big as a basketball; Saturn orbits our sun, a star. Saturn is the sixth planet from the sun at a distance of about 1.4 billion km (886 million miles) or 9.5 AU; One day on Saturn takes 10.7 hours (the time it takes for Saturn to rotate or spin once); Saturn makes a complete orbit around the sun (a year in Saturnian time) in 29 Earth years; Saturn is a gas-giant planet and does not have a solid surface; Saturn's atmosphere is made up mostly of hydrogen (H2) and helium (He); Saturn has 53 known moons with an additional 9 moons awaiting confirmation of their discovery; Saturn has the most spectacular ring system of all our solar system's planets. It is made up of seven rings with several gaps and divisions between them; Five missions have been sent to Saturn; Since 2004, Cassini|Cassini has been exploring Saturn, its moons and rings; Saturn cannot support life as we know it. However, some of Saturn's moons have conditions that might support life; When Galileo Galilei looked at Saturn through a telescope in the 1600s, he noticed strange objects on each side of the planet and drew in his notes a triple-bodied planet system and then later a planet with arms or handles. The handles turned out to be the rings of Saturn.
- Discovered by the ancients, Saturn has an orbit size around the sun of 1,426,666,422 km (886,489,415 miles); is 9.537 times the size of the earth; its perihelion (closest) is : 1,349,823,615 km (838,741,509 miles) is 9.176x Earth; Aphelion (farthest) is 1,503,509,229 km (934,237,322 miles), 9.885 x Earth; Sidereal Orbit Period (Length of Year) is 29.447498 Earth years (10,755.70 Earth days), 29.447 x Earth; Orbit Circumference is 8,957,504,604 km (5,565,935,315 miles), 9.530 x Earth; its Average Orbit Velocity is 34,701 km/h (21,562 mph, is 0.324 times of earth’s orbit velocity; orbit eccentricity is 0.05386179 which is 3.223 x Earth; its Orbit Inclination is 2.49 degrees; Equatorial Inclination to Orbit is 26.7 degrees; it has a mean radius of 58,232 km (36,183.7 miles), 9.1402 x Earth; has an Equatorial Circumference of 365,882.4 km (227,348.8 miles), 9.1402 x Earth; its volume is 8.2713 x 1014 km3, 763.594 x Earth; it has a Mass of, 95.161 x Earth; its Density is 0.687 g/cm3, 0.125 x Earth; its surface area measures 4.2612 x 1010 km2 which is 83.543 x Earth; it has a Surface Gravity 10.4* m/s2 (34.3 ft/s2 )_( 100 pounds on Earth, you would weigh about 107 pounds on Saturn); has an Escape Velocity Of 129,924 km/h (80,731 mph), Escape velocity of Earth is 25,030 mph; Sidereal Rotation Period (Length of Day) is 0.444 Earth days (10.656 hours}, 0.445 x Earth; its Effective Temperature is 178 °C (288 °F) and scientific notation is 95 K; its Atmospheric Constituents are Hydrogen (H2), Helium (He) while Earth's atmosphere consists mostly of N2 and O2.
- Each planet takes a certain amount of time to travel thru all 12 signs and return to its original position in any given chart. The Moon takes only a month. The Sun takes a year. … Mercury and Venus stay close to the Sun, so their cycles through all signs are close to the Sun’s. Mars takes longer about two years...Jupiter takes about 12 months to complete a full cycle thru all 12 signs. Saturn takes 28-30 years to complete a full cycle. Because Saturn is a symbol of the wisdom which grows with age, its cycle is particularly important in reflecting our development. Every seven years, Saturn completes a a quarter of the cycle, and we move into a new stage of awareness.
- Marc Allen in: Astrology for the New Age: An Intuitive Approach. New World Library, 18 December 2011, p. 64
- The astrologers and historians write that the ascendant as of Oxford is Capricornus, whose lord is Saturn, a religious planet, and patron of religious men.
- I came into the world under the sign of Saturn -- the star of the slowest revolution, the planet of detours and delays.
- We must believe then, that as from hence we see Saturn and Jupiter; if we were in either of the two, we should discover a great many Worlds which we perceive not; and that the de Bergerac]] in: Cyrano de Bergerac, Archibald Lovell, Curtis Hidden Page A Voyage to the Moon, Doubleday and McClure Company, 1899, p. 32
- The star [Tycho's supernova] was at first like Venus and Jupiter, giving pleasing effects; but as it then became like Mars, there will next come a period of wars, seditions, captivity and death of princes, and destruction of cities, together with dryness and fiery meteors in the air,pestilence, and venomous snakes. Lastly, the star became like Saturn, and there will finally come a time of want, death, imprisonment and all sorts of sad things.
- Burden not the back of Aries, Leo, or Taurus, with thy faults, nor make Saturn, Mars, or Venus, guilty of thy Follies. Think not to fasten thy imperfections on the Stars, and so despairingly conceive thy self under a fatality of being evil.
- You think that a wall as solid as the earth separates civilization from barbarism. I tell you the division is a thread, a sheet of glass. A touch here, a push there, and you bring back the reign of Saturn.
- In the night sky Saturn is easily visible to the unaided eye as a non-twinkling point of light. When viewed through even a small telescope, the planet, encircled by its magnificent rings, is arguably the most sublime object in the solar system. Saturn is designated by the symbol ♄ .... Saturn’s name comes from the Roman god of agriculture, who is equated with the Greek deity Kronos, one of the Titan and the father of Zeus (the Roman god Jupiter). As the farthest of the planets known to ancient observers, Saturn also was noted to be the slowest-moving ...Italy:Italian astronomer Galileo in 1610 was the first to observe Saturn with a telescope. Although he saw a strangeness in Saturn’s appearance, the low resolution of his instrument did not allow him to discern the true nature of the planet’s rings....Saturn’s structure and evolutionary history, however, differ significantly from those of its larger counterpart. Like the other giant, or Jovian planets—Jupiter, Uranus, and Neptune Saturn has extensive systems of moons (natural satellites) and rings, which may provide clues to its origin and evolution as well as to those of the Solar System|solar system. Saturn’s moon Titan is distinguished from all other moons in the Solar System by the presence of a significant atmosphere, one that is denser than that of any of the terrestrial planets except Venus.
- Bonnie Buratti in: Saturn, Encyclopedia Britannica, December 2014
- The greatest advances in knowledge of Saturn, as well as of most of the other planets, have come from deep-space probes. Four spacecraft have visited the Saturnian system: Pioneer 11 in 1979, [[w:Four spacecraft have visited the Saturnian system: Pioneer 11 in 1979, Voyagers 1] and 2 in the two years following, and, after almost a quarter-century, , which arrived in 2004. The first three missions were short-term flybys, but Cassini -Huuygens|Cassini-Huygens went into orbit around Saturn for years of investigations, while its Huygens probe parachuted through the atmosphere of Titan and reached its surface, becoming the first spacecraft to land on a moon other than Earth’s..
- Bonnie Buratti in "Saturn"
- I wol yow telle, as was me taught also,
The foure spirites and the bodies sevene,
By ordre, as ofte I herde my lord hem nevene.
The firste spirit quiksilver called is,
The seconde orpyment, the thridde, ywis,
Sal armonyak, and the firthe brimstoon.
The bodys sevene eek, lo! hem heer anoon:
Sol gold is, and Luna silver we threpe,
Mars iren, Mercurie quyksilver we clepe,
Saturnus leed, and Jupiter is tyn,
And Venus coper, by my fader kyn!
- Saturn Return would be caused by the planet Saturn returning to its original birth position in the sky, thus energetically influencing the individual’s multi energy dimensional system.
- Barbara Hand Clow in: Liquid Light of Sex: Kundalini, Astrology, and the Key Life Transitions, Inner Traditions / Bear & Co, Sep 1, 2001, p. 8
- The universe is globe-shaped, either because that is the most perfect shape of all, needing no joint, an integral whole; or because that is the most capacious of shapes, which is most fitting because it is to contain and preserve all...The first and highest of all is the sphere of the fixed stars, which contains itself and all things, and is therefore motionless. It is the location of the universe, to which the motion and position of all the remaining stars is referred. For though some consider that it also changes in some respect, we shall assign another cause for its appearing to do so in our deduction of the Earth's motion. There follows Saturn, the first of the wandering stars, which completes its circuit in thirty years. After it comes Jupiter which moves in a twelve-year long revolution. Next is Mars, which goes round biennially. An annual revolution holds the fourth place, in which as we have said is contained the Earth along with the lunar sphere which is like an epicycle. In fifth place Venus returns every nine months. Lastly, Mercury holds the sixth place, making a circuit in the space of eighty days. In the middle of all is the seat of the Sun. For who in this most beautiful of temples would put this lamp in any other or better place than the one from which it can illuminate everything at the same time? Aptly indeed is he named by some the lantern of the universe, by others the mind, by others the ruler. Trismegistus called him the visible God, Sophocles' Electra, the watcher over all things. Thus indeed the Sun as if seated on a royal throne governs his household of Stars as they circle around him. Earth also is by no means cheated of the Moon's attendance, but as Aristotle says in his book On Animals the Moon has the closest affinity with the Earth. Meanwhile the Earth conceives from the Sun, and is made pregnant with annual offspring. We find, then, in this arrangement the marvellous symmetry of the universe, and a sure linking together in harmony of the motion and size of the spheres, such as could be perceived in no other way. For here one may understand, by attentive observation, why Jupiter appears to have a larger progression and retrogression than Saturn, and smaller than Mars, and again why Venus has larger ones than Mercury; why such a doubling back appears more frequently in Saturn than in Jupiter, and still more rarely in Mars and Venus than in Mercury; and furthermore why Saturn, Jupiter and Mars are nearer to the Earth when in opposition than in the region of their occultation by the Sun and re-appearance. Indeed Mars in particular at the time when it is visible throughout the night seems to equal Jupiter in size, though marked out by its reddish colour; yet it is scarcely distinguishable among stars of the second magnitude, though recognized by those who track it with careful attention.
- We find then in this arrangement an admirable harmony of the world, and a dependable, harmonious interconnexion of the motion and the size of the paths, such as otherwise cannot be discovered. For here the penetrating observer can note why the forward and the retrograde movement of Jupiter appears greater than that of Saturn, and smaller than that of Mars, and again greater with Venus than with Mercury; and why such retrogression appears oftener with Saturn than with Jupiter, less often with Mars and Venus than with Mercury. Moreover, why Saturn, Jupiter, and Mars, when they rise in the evening, appear greater than when they disappear and reappear [with the sun]...And all this results from the same cause, namely the motion of the earth.
- Nicolaus Copernicus quoted in: Edwin Arthur Burtt The Metaphysical Foundations of Modern Physical Science: A Historical and Critical Essay, Routledge, Jun 23, 2014, p. 45
- There's something strange going on below the surface of Saturn's )|Death Star-looking moon Mimas. Mimas' rotation and its orbit around Saturn make the moon look like it's rocking and back forth and oscillating similar to the way a pendulum swings. The rocking motion is called Llibration, and it's commonly observed in moons that are influenced by the gravity from neighboring planets. However, using images of the moon captured by the Cassini spacecraft, Radwan Tajeddine, a research associate at Cornell University, discovered that the satellite's libration was much more exaggerated in one spot than predicted.
- Kelly Dickerson in: Saturn's 'Death Star' moon Mimas is weird inside, Fox News, October 17, 2014
- The Solar System consists of eight "planets" Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. A new distinct class of objects called "dwarf planets" exist. "Planets" and "dwarf planets" are two distinct classes of objects. The first members of the "dwarf planet" category are Ceres, Pluto and 2003 UB313 (temporary name).
- The word planet comes from the Greek for “wanderer,” because the planets' positions change relative to those of the stars. The eight (formerly nine) recognized planets that orbit the Sun are, in order of increasing distance, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The first four are called terrestrial planets and the next four giant, or Jovian, planets.
- Saturn seems to have impre\ssed the seal of melancholy on me from the beginning.
- Marsilio Ficino in: Juliana Schiesari The Gendering of Melancholia: Feminism, Psychoanalysis, and the Symbolics of Loss in Renaissance Literature, Cornell University Press, 1992, p. 114
G - L
- I had rather be Mercury, the smallest among seven [planets], revolving round the sun, than the first among five [moons] revolving round Saturn.
- Johann Wolfgang von Goethe in: Rev. James Wood Dictionary of Quotations from Ancient and Modern, English and Foreign Sources:, Warne, 1893, p. 166
- I was, I remember, I still remember when the first time I pointed the telescope at the sky and I saw Saturn with the rings. It was a beautiful image. And that really made my mind to become a scientist. And that was the first step in order to become an astronaut, of course.
- Galileo claimed to have seen mountains on the Moon, to have proved the Milky Way was made up of tiny stars, and to have seen four small bodies orbiting Jupiter. These last, with an eye to getting a position in Florence, he quickly named 'the Mediciean Stars. But when all was finished, no one besides my brother could get a glimpse of Jupiter or Saturn, for the great length of the tube would not allow it to be kept in a straight line. This difficulty, however, was soon removed by substituting tin tubes.
- There is not perhaps another object in the heavens that presents us with such a variety of extraordinary phenomena as the planet Saturn: a magnificent globe, encompassed by a stupendous double ring: attended by seven satellites: ornamented with equatorial belts: compressed at the poles: turning upon its axis: mutually eclipsing its ring and satellites, and eclipsed by them: the most distant of the rings also turning upon its axis, and the same taking place with the farthest of the satellites: all the parts of the system of Saturn occasionally reflecting light to each other: the rings and moons illuminating the nights of the Saturnian: the globe and satellites enlightening the dark parts of the rings: and the planet and rings throwing back the sun's beams upon the moons, when they are deprived of them at the time of their conjunctions.
- Sir William Herschel (1805) in: Knowledge...: A Monthly Record of Science, Volume 5, Wyman and sons, 1884, p. 203
- August 28, 1780, having brought the telescope to the parallel of Saturn, I discovered a sixth satellite of that planet; and 'l also saw the spots upon Saturn better than I had ever seen them before; so that I may date the finishing of the forty~feet telescope from that time.
- William Herschel in: John TIMBS Stories of Inventors and Discoverers in Science and the Useful Arts … With illustrations, 1860, p. 164
- I shall explain a System of the World differing in many particulars from any yet known, answering in all things to the common Rules of Mechanical Motions: This depends upon three Suppositions. First, That all Cœlestial Bodies whatsoever, have an attraction or gravitating power towards their own Centers, whereby they attract not only their own parts, and keep them from flying from them, as we may observe the Earth to do, but that they do also attract all the other Cœlestial bodies that are within the sphere of their activity; and consequently that not only the Sun and Moon have an influence upon the body and motion the Earth, and the Earth upon them, but that Mercury also Venus, Mars, Saturn and Jupiter by their attractive powers, have a considerable influence upon its motion in the same manner the corresponding attractive power of the Earth hath a considerable influence upon every one of their motions also. The second supposition is this, That all bodies whatsoever that are put into a direct and simple motion, will continue to move forward in a straight line, till they are by some other effectual powers deflected and bent into a Motion, describing a Circle, Ellipse, or some other more compounded Curve Line. The third supposition is: That these attractive powers are so much the more powerful in operating, by how much the nearer the body wrought upon is to their own Centers. Now what these several degrees are I have not yet experimentally verified; but it is a notion, which if fully prosecuted as it ought to be, will mightily assist the Astronomer to reduce all the Cœlestial Motions to a certain rule, which I doubt will never be done true without it. He that understands the nature of the Circular Pendulum and Circular Motion, will easily understand the whole ground of this Principle, and will know where to find direction in Nature for the true stating thereof. This I only hint at present to such as have ability and opportunity of prosecuting this Inquiry, and are not wanting of Industry for observing and calculating, wishing heartily such may be found, having myself many other things in hand which I would first complete and therefore cannot so well attend it. But this I durst promise the Undertaker, that he will find all the Great Motions of the World to be influenced by this Principle, and that the true understanding thereof will be the true perfection of Astronomy.
- Robert Hook in: Jean Baptiste Biot Life of Sir Isaac Newton [tr. by sir H.C. Elphinstone, 1829, p. 16
- The Pythagorean harmony of the spheres lives on to this day. In his Natural History (circa AD77), the Roman scientist and noble man Pliny the Elder considered formed by the earth and Moon to be a tone; Moon to Mercury a semi-tone; Mercury to Venus, a semi-tone; Venus to the Sun, a minor third; Sun to Mars, a tone, Mars to Jupiter, a semi-tone; Jupiter to Saturn, a semi-tone; and Saturn to the fixed stars, a minor third. The 'Pythagorean Scale' created from this musical arrangement is still recognised. And Pliny's report reveals not only a heavenly musical scale, but also a Cosmic architecture that was to have a profound influence on the history of astrobiology. The story goes that only the master, Pythagoras, was graced with the gift of actually hearing this harmony of the spheres.
- Christian Huygens in: Mark Brake Alien Life Imagined: Communicating the Science and Culture of Astrobiology, Cambridge University Press, 8 November 2012, p. 8
- To the ancient eye, without the use of spyglass, only seven of these ‘wanderers’ or ‘planets’ as they were known, could be seen among the thousands of lights that bejewelled the firmament. The 'Wanderers' were different. True, like the fixed stars, the Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn all seemed to revolve once a day around the Earth. But the Plants also had a peculiar motion.
- Christian Huygens in: “Alien Life Imagined: Communicating the Science and Culture of Astrobiology”, p. 9
- ...cosmos was complete. Its out limit was the stellar sphere. Just inside was Saturn, since it was the planet that took longest to move around the Zodiac. Next came Jupiter and Mars, set in order of decreasing orbital period, the time taken to make one complete orbit about the central Earth. Innermost was the Moon, since the lunar orbit placed it closest to us. The remaining three planets of Sun, Venus and Mercury, posed a problem. All three vagabond stars made their seeming journey about the Earth, in the same common time of one year.
- Christian Huygens in: “Alien Life Imagined: Communicating the Science and Culture of Astrobiology”, p. 11
- The term ‘superior planet’ was used by those bodies (Mars, Jupiter, and Saturn) that lay behind the Sun’s orbit. The system gave no idea of the sheer size of the orbits, and no account of inconsistencies of the planets in their apparent motion. But these mathematical features were to develop later.
- Christian Huygens in: “Alien Life Imagined: Communicating the Science and Culture of Astrobiology”, p. 11
- Attendants of Jupiter and Saturn are of the same nature with our Moon, as going round them, and being carry'd with them round the Sun just as the Moon is with the Earth. Their Likeness reaches to other things too,...Therefore whatsoever we can with reason affirm or fancy of our Moon must be supposed with very little alteration to belong to the Guards of Jupiter and Saturn, as having no reason to be at all inferior to that.
- Christian Huygens in: “Alien Life Imagined: Communicating the Science and Culture of Astrobiology”, p. 112
- If the Moon is not inhabited, as observations suggest based on the absence of water and an atmosphere, this says little about life on other worlds, save for those of similar rank, i.e., other moons. Which means that other planets, especially those superior and majestic worlds, such as Saturn and Jupiter, should be equal in all ways to the Earth, intelligent inhabitants included.
- Christian Huygens in: “Alien Life Imagined: Communicating the Science and Culture of Astrobiology”, p. 112
- Featured in his Celestial Scenery (1837), Dick discusses the cosmos, as seen from Mars, Jupiter, the planetoids, and beyond. Using a method similar to that of Huygens, Dick takes the topic further still, allotting populations to all the planetary bodies of the solar system, and even for the rings of Saturn, a rather arresting idea.
- Christian Huygens in: “Alien Life Imagined: Communicating the Science and Culture of Astrobiology”, p. 146
- Rather under-represented in moons, petite in mass and magnitude, Earth does not fare well in comparison with gas giants Jupiter and Saturn, and especially the Sun. Rejecting the idea the giant planets are poorly placed, Flammarion even so admits atmospheres of other plants are ‘essentially different’, from those on Earth, as there is no evidence extant to show they are ‘of a chemical composition analogous to our planet.
- Christian Huygens in: “Alien Life Imagined: Communicating the Science and Culture of Astrobiology”, p. 193
- I can't say they are exactly of the same nature with our Water; but that they should be liquid their use requires, as their beauty does that they be clear. For this Water of ours, in Jupiter or Saturn, would be frozen up instantly by reason of the vast distance of the Sun.
- Christiaan Huygens in: Mark Brake Alien Life Imagined: Communicating the Science and Culture of Astrobiology, Cambridge University Press, 8 November 2012, p. 111
- But it is a very remarkable circumstance, that an acquaintance with the seven days of the week, so familiar from remote antiquity to the people who originally spoke Sanskrit language, though unknown to the Greeks and Romans, should have been preserved among the Germans. It is true, indeed, that among them the days received their names from their principal deities, and not merely from the planets, which, in Hindu mythology, are considered only as celestial beings of an inferior description. There seems, also, to be no doubt that Germans selected the names of the same planets to designate the days of the week, which have been immemorially used for the same purpose by the Hindus; and that, in both Germany and India, their consecutive order was the day of the Sun, the Moon, Mars, Mercury, Jupiter, Venus and Saturn.
- Vans Kennedy in: Researches Into the Nature and Affinity of Ancient and Hindu Mythology by Vans Kennedy, Longman, Rees, Orme, Brown and Green, 1831, p. 396-97
- Each planet, according to its dimension, has a certain length of planetary life, the youth and age of which include the following eras :- a Sun like state; a state like that of Jupiter or Saturn, but when much heat but little light is evolved; a condition like that of our earth; and lastly, the stage through which our Moon is passing, which may be regarded as planetary decrepitude.
- The orbit of the earth is a circle; round the spheres to which this circle belongs describe a dodecahedron; the spheres including this will give the orbit of Mars. Round Mars describe a tetrahedron; the circle including this will be orbit of Jupiter. Describe a cube round Jupiter’s orbit; the circle including this will be Saturn. Now, inscribe in the earth’s orbit an icosahedron, the circle inscribed in it will be the orbit of Venus: inscribe an octahedron in the orbit of Venus: the circle inscribed in it will be Mercury’s orbit. This is the reason of number of planets.
- When the movement of the comets is considered and we reflect on the laws of gravity, it will be readily perceived that their approach to Earth might there cause the most woeful events, bring back the deluge, or make it perish in a deluge of fire, shatter it into small dust, or at least turn it from its orbit, drive away its Moon, or, still worse, the Earth itself outside the orbit of Saturn, and inflict upon us a winter several centuries long, which neither men nor animals would be able to bear. The tails even of comets would not be unimportant phenomena, if in taking their departure left them in whole or part in our atmosphere.
M - R
- Wide are the meadows of night
And daisies are shining there,
Tossing their lovely dews, Lustrous and fair;
And through these sweet fields go,
Wanderers amid the stars — Venus, Mercury, Uranus, Neptune, Saturn, Jupiter, Mars.
- I have been battering away at Saturn, returning to the charge every now and then. I have effected several breaches in the solid ring, and now I am splash into the fluid one, amid a clash of symbols truly astounding. When I reappear it will be in the dusky ring, which is something like the state of the air supposing the siege of Sebastopol conducted from a forest of guns 100 miles one way, and 30,000 miles the other, and the shot never to stop, but go spinning away round a circle, radius 170,000 miles.
- Science is the part of NASA that's actually conducting interesting and scientifically important missions. Spacecraft sent to Mars, Saturn, Mercury, the Moon, comets, and asteroids have been making incredible discoveries, with more to come from recent launches to Jupiter, the Moon, and Mars. The country needs more of these robotic space exploration missions, not less.
- Below Saturn is the well known group, the Sickle, part of the constellation of Leo. The elevation of the plane of Saturn's rings above the earth is increasing slightly at present, being now 15°, so that the rings are coming into better position for observation. The outer major axis of the rings is a little over 45 inches.
- The Obsevatory in: The Sidereal Messenger: A Monthly Review of Astronomy, Volume 8 , The Obsevatory, 1889, p. 81
- It’s amazing to me that not only can we put a probe around Saturn and get images of its moons, but our math and physics are so freaking accurate we can say, "Hey, you know what? On this date at this time if we turn Cassini that way we’ll see a moon over 2 million kilometers away pass in front of another one nearly 3 million kilometers away.
- The Spirits survey the heavens and the earth and all the harmonious motions of the universe. They see the heavenly bodies set in revolving whorls, which, whorl within whorl, combine to form the Spinning-whorl on the Spindle of Necessity; and the Goddess holds the spindle on her knee, and spins the thread which the Fates wind, unwind and cut. The heavenly bodies, or the spheres or whorls in which they lie, are arranged one within another in the following order:
1. The Fixed Stars.
7. The Sun.
8. The Moon.
This order is as good as any other that can be framed under a geocentric hypothesis
- As the whorls differ from one another in respect of “ breadth of rim”, the first and outermost whorl is that which has its circular rim the broadest, and the sixth whorl comes next to it in regard to breadth of rim; and, proceeding in order of breadth, the fourth whorl comes third, and the eighth fourth, and the seventh fifth, and the fifth sixth, and the third seventh, and the second eighth.' Thus we have now a new classification of the heavenly bodies, in the following sequence:
1. The Fixed Stars.
4. The Moon.
5. The Sun.
- Plato in: The Classical Review, Volume 24 Plato’s Theory of Planets, Editors of the Observatory, 1904, p. 137
- The scientific theory I like best is that the rings of Saturn are composed entirely of lost airline luggage.
S - Z
- The White Spot on Saturn's Ring, recently announced by Terby of Belgium, was observed at this Observatory [Warner Observatory, Rochester] on the evening of March 14th both by Professor Brooks and myself. In consequence, however, of its faintness, and of the bright moonlight in which it was viewed, it was a difficult object; but as we both saw in the same position and of the same size and shape, there could be no doubt in the mind of either of us that we had seen the “spot” which appeared as a narrow band extending across both outer rings, its western boundary being in contact with the black notch termed as shadow of the ball on the ring.
- Lewis Swift in The Obsevatory in: “The Sidereal Messenger: A Monthly Review of Astronomy, Volume 8”, p. 189
- It is marvelous indeed to watch on television the rings of Saturn close; and to speculate on what we may yet find at galaxy's edge. But in the process, we have lost the human element; not to mention the high hope of those quaint days when flight would create one world. Instead of one world, we have star wars, and a future in which dumb dented human toys will drift mindlessly about the cosmos long after our small planet's dead.
Packing my bags -- going away
To a place where the air is clean
There's no sense to sit and watch people die
We don't fight our wars the way you do
We put back all the things we use
There's no sense to keep on doing such crimes
Going back to Saturn where the rings all glow
Rainbow, moonbeams and orange snow
People live to be two hundred and five
Going back to Saturn where the people smile
Don't need cars cause we've learned to fly
Just to live to us is our natural high. | 0.901967 | 3.451885 |
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Winter is the coldest season of the year in polar and temperate zones (winter does not occur in most of the tropical zone). It occurs after autumn and before spring in each year. Winter is caused by the axis of the Earth in that hemisphere being oriented away from the Sun. Different cultures define different dates as the start of winter, and some use a definition based on weather. When it is winter in the Northern Hemisphere, it is summer in the Southern Hemisphere, and vice versa. In many regions, winter is associated with snow and freezing temperatures. The moment of winter solstice is when the Sun's elevation with respect to the North or South Pole is at its most negative value (that is, the Sun is at its farthest below the horizon as measured from the pole). The day on which this occurs has the shortest day and the longest night, with day length increasing and night length decreasing as the season progresses after the solstice. The earliest sunset and latest sunrise dates outside the polar regions differ from the date of the winter solstice, however, and these depend on latitude, due to the variation in the solar day throughout the year caused by the Earth's elliptical orbit (see earliest and latest sunrise and sunset).
The English word winter comes from the Proto-Germanic noun *wintru-, whose origin is unclear. Several proposals exist, a commonly mentioned one connecting it to the Proto-Indo-European root *wed- 'water' or a nasal infix variant *wend-.
The tilt of the Earth's axis relative to its orbital plane plays a large role in the formation of weather. The Earth is tilted at an angle of 23.44° to the plane of its orbit, causing different latitudes to directly face the Sun as the Earth moves through its orbit. This variation brings about seasons. When it is winter in the Northern Hemisphere, the Southern Hemisphere faces the Sun more directly and thus experiences warmer temperatures than the Northern Hemisphere. Conversely, winter in the Southern Hemisphere occurs when the Northern Hemisphere is tilted more toward the Sun. From the perspective of an observer on the Earth, the winter Sun has a lower maximum altitude in the sky than the summer Sun.
During winter in either hemisphere, the lower altitude of the Sun causes the sunlight to hit the Earth at an oblique angle. Thus a lower amount of solar radiation strikes the Earth per unit of surface area. Furthermore, the light must travel a longer distance through the atmosphere, allowing the atmosphere to dissipate more heat. Compared with these effects, the effect of the changes in the distance of the Earth from the Sun (due to the Earth's elliptical orbit) is negligible.
The manifestation of the meteorological winter (freezing temperatures) in the northerly snow–prone latitudes is highly variable depending on elevation, position versus marine winds and the amount of precipitation. For instance, within Canada (a country of cold winters), Winnipeg on the Great Plains, a long way from the ocean, has a January high of −11.3 °C (11.7 °F) and a low of −21.4 °C (−6.5 °F). In comparison, Vancouver on the west coast with a marine influence from moderating Pacific winds has a January low of 1.4 °C (34.5 °F) with days well above freezing at 6.9 °C (44.4 °F). Both places are at 49°N latitude, and in the same western half of the continent. A similar but less extreme effect is found in Europe: in spite of their northerly latitude, the British Isles have not a single non-mountain weather station with a below-freezing mean January temperature.
Meteorological reckoning is the method of measuring the winter season used by meteorologists based on "sensible weather patterns" for record keeping purposes, −40 °C (−40 °F) due to air with slightly higher moisture from above mixing with colder, surface-based air. They are made of simple hexagonal ice crystals. The Swedish meteorological institute (SMHI) defines winter as when the daily mean temperatures are below 0 °C (32 °F) for five consecutive days. According to the SMHI, winter in Scandinavia is more pronounced when Atlantic low-pressure systems take more southerly and northerly routes, leaving the path open for high-pressure systems to come in and cold temperatures to occur. As a result, the coldest January on record in Stockholm, in 1987, was also the sunniest.so the start of meteorological winter varies with latitude. Winter is often defined by meteorologists to be the three calendar months with the lowest average temperatures. This corresponds to the months of December, January and February in the Northern Hemisphere, and June, July and August in the Southern Hemisphere. The coldest average temperatures of the season are typically experienced in January or February in the Northern Hemisphere and in June, July or August in the Southern Hemisphere. Nighttime predominates in the winter season, and in some regions winter has the highest rate of precipitation as well as prolonged dampness because of permanent snow cover or high precipitation rates coupled with low temperatures, precluding evaporation. Blizzards often develop and cause many transportation delays. Diamond dust, also known as ice needles or ice crystals, forms at temperatures approaching
Accumulations of snow and ice are commonly associated with winter in the Northern Hemisphere, due to the large land masses there. In the Southern Hemisphere, the more maritime climate and the relative lack of land south of 40°S makes the winters milder; thus, snow and ice are less common in inhabited regions of the Southern Hemisphere. In this region, snow occurs every year in elevated regions such as the Andes, the Great Dividing Range in Australia, and the mountains of New Zealand, and also occurs in the southerly Patagonia region of South Argentina. Snow occurs year-round in Antarctica.
In the Northern Hemisphere, some authorities define the period of winter based on astronomical fixed points (i.e. based solely on the position of the Earth in its orbit around the Sun), regardless of weather conditions. In one version of this definition, winter begins at the winter solstice and ends at the March equinox.These dates are somewhat later than those used to define the beginning and end of the meteorological winter – usually considered to span the entirety of December, January, and February in the Northern Hemisphere and June, July, and August in the Southern.
Astronomically, the winter solstice, being the day of the year which has fewest hours of daylight, ought to be in the middle of the season,but seasonal lag means that the coldest period normally follows the solstice by a few weeks. In some cultures, the season is regarded as beginning at the solstice and ending on the following equinox – in the Northern Hemisphere, depending on the year, this corresponds to the period between 20, 21 or 22 December and 19, 20 or 21 March.
In the United Kingdom, meteorologists consider winter to be the three coldest months of December, January and February.In Scandinavia, winter in one tradition begins on 14 October and ends on the last day of February. In Russia, calendar winter is widely regarded to start on 1 December and end on 28 February. In many countries in the Southern Hemisphere, including Australia, New Zealand and South Africa, winter begins on 1 June and ends on 31 August. In Celtic nations such as Ireland (using the Irish calendar) and in Scandinavia, the winter solstice is traditionally considered as midwinter, with the winter season beginning 1 November, on All Hallows, or Samhain. Winter ends and spring begins on Imbolc, or Candlemas, which is 1 or 2 February. This system of seasons is based on the length of days exclusively. (The three-month period of the shortest days and weakest solar radiation occurs during November, December and January in the Northern Hemisphere and May, June and July in the Southern Hemisphere.)
Also, many mainland European countries tended to recognize Martinmas or St. Martin's Day (11 November), as the first calendar day of winter.The day falls at the midpoint between the old Julian equinox and solstice dates. Also, Valentine's Day (14 February) is recognized by some countries as heralding the first rites of spring, such as flowers blooming.
In Chinese astronomy and other East Asian calendars, winter is taken to commence on or around 7 November, with the Jiéqì (known as 立冬 lì dōng – literally, "establishment of winter").
The three-month period associated with the coldest average temperatures typically begins somewhere in late November or early December in the Northern Hemisphere and lasts through late February or early March. This "thermological winter" is earlier than the solstice delimited definition, but later than the daylight (Celtic) definition. Depending on seasonal lag, this period will vary between climatic regions.
Cultural influences such as Christmas creep may have led to the winter season being perceived as beginning earlier in recent years, although high latitude countries like Canada are usually well into their real winters before the December solstice.
Since by almost all definitions valid for the Northern Hemisphere, winter spans 31 December and 1 January, the season is split across years, just like summer in the Southern Hemisphere. Each calendar year includes parts of two winters. This causes ambiguity in associating a winter with a particular year, e.g. "Winter 2018". Solutions for this problem include naming both years, e.g. "Winter 18/19", or settling on the year the season starts in or on the year most of its days belong to, which is the later year for most definitions.
Ecological reckoning of winter differs from calendar-based by avoiding the use of fixed dates. It is one of six seasons recognized by most ecologists who customarily use the term hibernal for this period of the year (the other ecological seasons being prevernal, vernal, estival, serotinal, and autumnal).The hibernal season coincides with the main period of biological dormancy each year whose dates vary according to local and regional climates in temperate zones of the Earth. The appearance of flowering plants like the crocus can mark the change from ecological winter to the prevernal season as early as late January in mild temperate climates.
To survive the harshness of winter, many animals have developed different behavioral and morphological adaptations for overwintering:
Some annual plants never survive the winter. Other annual plants require winter cold to complete their life cycle; this is known as vernalization. As for perennials, many small ones profit from the insulating effects of snow by being buried in it. Larger plants, particularly deciduous trees, usually let their upper part go dormant, but their roots are still protected by the snow layer. Few plants bloom in the winter, one exception being the flowering plum, which flowers in time for Chinese New Year. The process by which plants become acclimated to cold weather is called hardening.
Humans are sensitive to cold, see hypothermia. Snowblindness, norovirus, seasonal depression. Slipping on black ice and falling icicles are other health concerns associated with cold and snowy weather. In the Northern Hemisphere, it is not unusual for homeless people to die from hypothermia in the winter.
One of the most common diseases associated with winter is influenza.
In Persian culture, the winter solstice is called Yaldā (meaning: birth) and it has been celebrated for thousands of years. It is referred to as the eve of the birth of Mithra, who symbolised light, goodness and strength on earth.
In Greek mythology, Hades kidnapped Persephone to be his wife. Zeus ordered Hades to return her to Demeter, the goddess of the Earth and her mother. However, Hades tricked Persephone into eating the food of the dead, so Zeus decreed that Persephone would spend six months with Demeter and six months with Hades. During the time her daughter is with Hades, Demeter became depressed and caused winter.
In Welsh mythology, Gwyn ap Nudd abducted a maiden named Creiddylad. On May Day, her lover, Gwythr ap Greidawl, fought Gwyn to win her back. The battle between them represented the contest between summer and winter.
The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's North Pole.
The subarctic climate is a climate characterised by long, usually very cold winters, and short, cool to mild summers. It is found on large landmasses, away from the moderating effects of an ocean, generally at latitudes from 50° to 70°N poleward of the humid continental climates. Subarctic or boreal climates are the source regions for the cold air that affects temperate latitudes to the south in winter. These climates represent Köppen climate classification Dfc, Dwc, Dsc, Dfd, Dwd and Dsd.
The year 1816 is known as the Year Without a Summer because of severe climate abnormalities that caused average global temperatures to decrease by 0.4–0.7 °C (0.72–1.26 °F). Summer temperatures in Europe were the coldest on record between the years of 1766–2000. This resulted in major food shortages across the Northern Hemisphere.
Spring, also known as springtime, is one of the four temperate seasons, succeeding winter and preceding summer. There are various technical definitions of spring, but local usage of the term varies according to local climate, cultures and customs. When it is spring in the Northern Hemisphere, it is autumn in the Southern Hemisphere and vice versa. At the spring equinox, days and nights are approximately twelve hours long, with daytime length increasing and nighttime length decreasing as the season progresses.
Örebro is a city with 124,027 inhabitants, the seat of Örebro Municipality and the capital of Örebro County in Sweden. It is the sixth largest city in Sweden and one of the largest inland hubs of the country. It is located near the lake of Hjälmaren, although a few kilometres inland along the small river Svartån.
The Ice Saints are St. Mamertus, St. Pancras, and St. Servatius. They are so named because their feast days fall on the days of May 11, May 12, and May 13 respectively, known as "the blackthorn winter" in Austrian, Belgian, Croatian, Czech, Dutch, French, German, Hungarian, North-Italian, Polish, Slovak, Slovene and Swiss folklore.
A cold wave is a weather phenomenon that is distinguished by a cooling of the air. Specifically, as used by the U.S. National Weather Service, a cold wave is a rapid fall in temperature within a 24-hour period requiring substantially increased protection to agriculture, industry, commerce, and social activities. The precise criterion for a cold wave is determined by the rate at which the temperature falls, and the minimum to which it falls. This minimum temperature is dependent on the geographical region and time of year.
The winter of 1962–63, known as the Big Freeze of 1963, was one of the coldest winters on record in the United Kingdom. Temperatures plummeted and lakes and rivers began to freeze over.
The winter solstice, hiemal solstice or hibernal solstice, also known as midwinter, occurs when one of the Earth's poles has its maximum tilt away from the Sun. It happens twice yearly, once in each hemisphere. For that hemisphere, the winter solstice is the day with the shortest period of daylight and longest night of the year, when the Sun is at its lowest daily maximum elevation in the sky. At the pole, there is continuous darkness or twilight around the winter solstice. Its opposite is the summer solstice.
The five main latitude regions of the Earth's surface comprise geographical zones, divided by the major circles of latitude. The differences between them relate to climate. They are as follows:
The winter of 1894–95 was severe for the British Isles with a CET of 1.27 °C or 34.3 °F. Many climatologists have come to view this winter as the end of the Little Ice Age and the culmination of a decade of harsh winters in Britain. Whereas the average CET for the ten winters from 1885–86 to 1894–95 was 2.87 °C or 37.2 °F, no winter with a CET under 3.0 °C or 37.4 °F followed for twenty-two years and no month as cold as February or January 1895 until 1940. In contrast, between 1659 and 1894 no spell with every winter CET above 3.0 °C or 37.4 °F had lasted longer than twelve winters.
The summer solstice or estival solstice, also known as midsummer, occurs when one of the Earth's poles has its maximum tilt toward the Sun. It happens twice yearly, once in each hemisphere. For that hemisphere, the summer solstice is when the Sun reaches its highest position in the sky and is the day with the longest period of daylight. Within the Arctic circle or Antarctic circle, there is continuous daylight around the summer solstice. On the summer solstice, Earth's maximum axial tilt toward the Sun is 23.44°. Likewise, the Sun's declination from the celestial equator is 23.44°.
The climate of the Arctic is characterized by long, cold winters and short, cool summers. There is a large amount of variability in climate across the Arctic, but all regions experience extremes of solar radiation in both summer and winter. Some parts of the Arctic are covered by ice year-round, and nearly all parts of the Arctic experience long periods with some form of ice on the surface.
The December solstice, is the solstice that occurs each December – typically on Dec 21, and can vary ± 1 day according to the Gregorian calendar. In the Northern Hemisphere, the December solstice is the winter solstice, whilst in the Southern Hemisphere it is the summer solstice. It is also known as the southern solstice.
A season is a division of the year marked by changes in weather, ecology, and the amount of daylight. On Earth, seasons are the result of Earth's orbit around the Sun and Earth's axial tilt relative to the ecliptic plane. In temperate and polar regions, the seasons are marked by changes in the intensity of sunlight that reaches the Earth's surface, variations of which may cause animals to undergo hibernation or to migrate, and plants to be dormant. Various cultures define the number and nature of seasons based on regional variations.
An ice cap climate is a polar climate where no mean monthly temperature exceeds 0 °C (32 °F). The climate covers areas in or near the high latitudes to polar regions, such as Antarctica and Greenland, that have vast deserts of snow and ice. In the coldest months, most ice cap climates have mean temperatures between -30 and -55 °C. Ice cap climates are normally covered by a permanent layer of ice and have no vegetation. There is limited animal life in most ice cap climates, usually found near the oceanic margins. Although ice cap climates are inhospitable to human life, there are some small research stations scattered in Antarctica and interior Greenland.
The 2014–15 North American winter refers to winter in North America as it occurred across the continent from late 2014 through early 2015. While both the meteorological and astronomical definitions of winter involve the onset of winter occurring in December, many places in North America experienced their first wintry weather during mid November. A period of below-average temperatures affected much of the contiguous United States, and several records were broken. An early trace of snowfall was recorded in Arkansas. There were greater accumulations of snow across parts of Oklahoma as well. A quasi-permanent phenomenon referred to as the polar vortex may have been partly responsible for the cold weather. Temperatures in much of the United States dropped 15 to 35 °F below average by November 19 following a southward "dip" of the polar vortex into the eastern two-thirds of the country. The effects of this dip were widespread, bringing about temperatures as low as 28 °F (−2 °C) in Pensacola, Florida. Following a significant snowstorm there, Buffalo, New York received several feet of snow from November 17–21. During the 2014–15 winter season, Boston broke its all-time official seasonal 107.6-inch (2.73-meter) snowfall record from the winter of 1995–96, with a total snowfall record of 108.6 inches (2.76 m) as of March 15, 2015.
Sweden had a very unusual start and finish to the year 2010, with two consecutive winter cold waves occurring in a single calendar year. Since both events were notable, both are covered in this article.
The 2017–18 North American winter refers to winter in North America as it occurred across the continent from late 2017 through early 2018. Similar to the previous winter, a La Niña was expected to influence the winter weather across North America. Winter weather patterns were very active, erratic, and protracted, especially near the end of the season. Significant events included rare snowfall in the South, a strong cold wave that affected the United States during the early weeks of January, and a series of strong nor'easters that affected the Northeastern U.S during the month of March. In addition, flooding also took place during the month of February in the Central United States. Finally the winter came to a conclusion with a powerful storm system that caused a tornado outbreak and flooding in mid-April. The most intense event, however, was an extremely powerful cyclonic blizzard that impacted the northeastern United States in the first week of 2018.
The 2018–19 European winter occurred from late 2018 to early 2019. Notable events included the early snows in Spain and intense flooding in Italy, in cities such as Venice, the intense snow storms which affected central Europe in January, the snow storms in Greece over the New Year period, as well as the end of February. As well as severe winter weather, there was also exceptional warmth across western Europe in the last week of February. Parts of France had their warmest February day on record, with temperatures up to 28.1 °C (82.6 °F) at Eus on the 27th. Many places in the United Kingdom also broke temperature records, including the national record in Kew Gardens, at 21.2 °C (70.2 °F) on the 26th. Unlike previous winters, a developing El Niño was expected to influence weather patterns across Europe, although the affect is not fully known.
On St. Martin's day (11 November) winter begins, summer takes its end, harvest is completed. ...This text is one of many that preserves vestiges of the ancient Indo-European system of two seasons, winter and summer. | 0.867934 | 3.549397 |
Hubble delivers first insight into atmospheres of potentially habitable planets orbiting TRAPPIST-1 [heic1802]
5 February 2018An international team of astronomers has used the NASA/ESA Hubble Space Telescope to look for atmospheres around four Earth-sized planets orbiting within or near TRAPPIST-1's habitable zone. The new results further support the terrestrial and potentially habitable nature of three of the studied planets. The results are published in Nature Astronomy.
|Seven planets orbiting the ultracool dwarf star TRAPPIST-1. Credit: NASA|
Seven Earth-sized planets orbit the ultracool dwarf star TRAPPIST-1, 40 light-years away from the Earth . This makes TRAPPIST-1 the planetary system with the largest number of Earth-sized planets discovered so far. These planets are also relatively temperate, making them a tantalizing place to search for signs of life beyond our Solar System. Now, an international team of astronomers has presented a study in which they used the NASA/ESA Hubble Space Telescope to screen four planets in the system – TRAPPIST-1d, e, f and g – to study their atmospheres .
Three of the planets orbit within the system's habitable zone, the region at a distance from the star where liquid water – the key to life as we know it – could exist on the surface of a planet. The fourth planet orbits in a borderline region at the inner edge of the habitable zone. The data obtained rule out a cloud-free hydrogen-rich atmosphere for three of the planets – but for the fourth planet, TRAPPIST-1g, such an atmosphere could not be excluded .
Lead author Julien de Wit, from the Massachusetts Institute of Technology, USA, describes the positive implications of these measurements: "The presence of puffy, hydrogen-dominated atmospheres would have indicated that these planets are more likely gaseous worlds like Neptune. The lack of hydrogen in their atmospheres further supports theories about the planets being terrestrial in nature. This discovery is an important step towards determining if the planets might harbour liquid water on their surfaces, which could enable them to support living organisms."
The observations were made while the planets were in transit in front of TRAPPIST-1. In this configuration a small section of the star's light passes through the atmosphere of the exoplanet and interacts with the atoms and molecules in it. This leaves a weak fingerprint of the atmosphere in the spectrum of the star.
While the results rule out one type of atmosphere, many alternative atmospheric scenarios are still consistent with the data gathered by de Wit and his team. The exoplanets may possess a range of atmospheres, just like the terrestrial planets in our Solar System .
"Our results demonstrate Hubble's ability to study the atmospheres of Earth-sized planets. But the telescope is really working at the limit of what it can do," adds co-author Hannah Wakeford from the Space Telescope Science Institute, illustrating both the power and limitation of Hubble.
These latest findings complement the analysis of ultraviolet observations made with Hubble in 2017 (heic1713) and help us understand more about whether life might be possible in the TRAPPIST-1 system.
By ruling out the presence of a large abundance of hydrogen in the planets' atmospheres, Hubble is helping to pave the way for the NASA/ESA/CSA James Webb Space Telescope.
"Spectroscopic observations of the TRAPPIST-1 planets with the next generation of telescopes – including the James Webb Space Telescope – will allow us to probe deeper into their atmospheres," concludes Michael Gillon, from the University of Líege, Belgium. "This will allow us to search for heavier gases such as carbon, methane, water, and oxygen, which could offer biosignatures for life."
The planets were discovered using the ground-based TRAPPIST-South at ESO's La Silla Observatory in Chile; TRAPPIST-North in Morocco; the orbiting NASA Spitzer Space Telescope; ESO's HAWK-I instrument on the Very Large Telescope at the Paranal Observatory in Chile; the 3.8-metre UKIRT in Hawaii; the 2-metre Liverpool and 4-metre William Herschel telescopes on La Palma in the Canary Islands; and the 1-metre SAAO telescope in South Africa.
An atmosphere largely dominated by hydrogen, if cloud-free, should yield prominent spectroscopic signatures in the near infrared. However, the spectra for TRAPPIST-1d, -e, and -f do not show significant features.
This includes atmospheres dominated by water vapor, nitrogen, carbon dioxide or tenuous atmospheres composed of a variety of chemical species.
The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
The team is composed of Julien de Wit (Massachusetts Institute of Technology, USA), Hannah R. Wakeford (NASA Goddard Space Flight Center, USA), Nikole K. Lewis (Space Telescope Science Institute, USA), Laetitia Delrez (Cavendish Laboratory, University of Cambridge, UK), Michael Gillon (Université de Liège, Belgium), Brice-Olivier Demory (Cavendish Laboratory, University of Cambridge, UK; University of Bern, Switzerland), Emeline Bolmont (Astrophysics Division of CEA de Saclay, France), Vincent Bourrier (Observatoire de l'Université de Genève, Switzerland), Adam J. Burgasser (University of California San Diego, USA), Emmanuel Jehin (Université de Liège, Belgium), Jeremy Leconte (Université Bordeaux, France; CNRS, France), Susan M. Lederer (NASA Johnson Space Center, USA ), Frank Selsis (Université Bordeaux, France; CNRS, France), Vlada Stamenkovic (Jet Propulsion Laboratory, USA; California Institute of Technology, USA), and Amaury H. M. J. Triaud (University of Cambridge, UK)
Julien de Wit
Massachusetts Institute of Technology
Tel: +1 617 258 0209
Space Telescope Science Institute
Université de Liège
Tel: +32 4 3669743
ESA/Hubble Public Information Officer
Garching bei München, Germany
Tel: +49 8932006376 | 0.821137 | 3.879679 |
Tides are the rise and fall of sea levels.
The combined effects of the gravitational forces exerted by the Moon and the Sun, and the rotation of the Earth causes tides to fluctuate.
Tide tables can be used for any given locale to find the predicted times and amplitude (or “tidal range”). Many factors influence such predictions. These include the alignment of the Sun and Moon, the phase and amplitude of the tide (pattern of tides in the deep ocean), the amphidromic systems of the oceans, and the shape of the coastline. Wind and atmospheric pressure play a part in their actual time and height, too. This is why tide charts are but an educated prediction. Many shorelines experience semi-diurnal tides—two nearly equal high and low tides each day. Hilton Head and the rest of the Sea Islands tides are semi-diurnal. Other locations have a diurnal tide—one high and low tide each day. A “mixed tide”—two uneven magnitude tides a day—is a third regular category.
The semi-diurnal range (the difference in height between high and low waters over about half a day) varies in a two-week cycle.
Approximately twice a month, around new moon and full moon when the Sun, Moon, and Earth form a line the tidal force due to the Sun reinforces that due to the Moon. The tide’s range is then at its maximum; this is called the spring tide. It is not named after the season, but, like that word, derives from the meaning “jump, burst forth, rise”, as in a natural spring.
When the Moon is at first quarter or third quarter, the Sun and Moon, 90° separate the two. When viewed from the Earth, and the solar tidal force partially cancels the Moon’s tidal force. At these points in the lunar cycle, the tide’s range is at its minimum; this is called the neap tide. Neap is an Anglo-Saxon word meaning “without the power.”
Spring tides result in high waters that are higher than average, low waters that are lower than average, ‘slack water’ time that is shorter than average, and stronger tidal currents than average. Neaps result in less extreme tidal conditions. There is about a seven-day interval between springs and neaps.
Tides vary on timescales ranging from hours to years due to a number of factors, which determine the lunitidal interval.
To make accurate records, tide gauges at fixed stations measure water level over time. Gauges ignore variations caused by waves with periods shorter than minutes.
While tides are usually the largest source of sea-level fluctuations, sea levels are also subject to forces. Wind and barometric pressure changes from the weather affect those levels. This results in storm surges, especially in shallow seas and near coasts. Storm surges often accompany hurricanes. | 0.843575 | 3.837338 |
Astronomers are constantly uncovering the "most distant," "most massive" or "most energetic" objects in our universe, but today, researchers have announced the discovery of a truly monstrous structure consisting of a ring of galaxies around 5 billion light-years across.
The galactic ring, which was revealed by 9 gamma-ray bursts (GRBs), is located 7 billion light-years away and spans an area of the sky more than 70 times the diameter of a full moon.
GRBs are thought to be detonated when a massive star reaches the end of its life. As the star implodes after running out of fuel, a black hole is formed and vast quantities of energy are blasted in collimated beams. Should Earth be aligned with these beams, an incredibly luminous signal can be observed and these beacons can be used to precisely gauge the distance to the GRB and the location of the galaxy that hosts it.
The GRBs are all cataloged in the Gamma Ray Burst Online Index, which precisely records each GRB distance and location, like pins on a cosmic map.
Astronomers believe these GRBs (and therefore the galaxies they inhabit) are somehow associated as all 9 are located at a similar distance from Earth. According to its discoverers, there's a 1-in-20,000 probability of the GRBs being in this distribution by chance — in other words, they are very likely associated with the same structure, a structure that, according to cosmological models, should not exist.
"If the ring represents a real spatial structure, then it has to be seen nearly face-on because of the small variations of GRB distances around the object's center," said Lajos Balazs, of Konkoly Observatory in Budapest, Hungary, and lead author of a paper published in the journal Monthly Notices of the Royal Astronomical Society. "The ring could though instead be a projection of a sphere, where the GRBs all occurred within a 250 million year period, a short timescale compared with the age of the universe."
But what could possibly be creating a sphere an unprescedented 5 billion light-years across?
According to most cosmological models, the universe should have a roughly uniform distribution of matter over the largest scales. This is known as the "Cosmological Principal" and observations by NASA's Wilkinson Microwave Anisotropy Probe (WMAP) and Europe's Planck space telescope, which both studied the distribution of the universe's ancient cosmic microwave background (CMB) radiation, seem to agree. However, other results have recently challenged this idea hinting that structures as large as 1.2 billion light-years may exist. But a growing list of discoveries in the cosmic abyss seem to contradict even the 1.2 billion light-year "limit."
The GRB ring is 5 times larger than the 1.2 billion light-year limit; a pretty huge anomaly by anyone's standard. And this latest discovery isn't even the biggest. In 2013, another distribution of GRBs revealed a 10 billion light-year structure. Other large structures also defy this theoretical limit.
So what could be causing this particular ring of GRBs? One idea focuses around the large-scale structure of the universe where clusters of galaxies amass together in a web-like structure, thought to be clumped around concentrations of dark matter. The "holes" in this web are referred to as voids — regions of the cosmos that are conspicuously near-empty of any matter. The largest voids are called, unsurprisingly, "super-voids."
But this new structure dwarfs all known super-voids.
"If we are right, this structure contradicts the current models of the universe. It was a huge surprise to find something this big — and we still don't quite understand how it came to exist at all," added Balazs.
So is the Cosmological Principal flawed? It's certainly looking that way.
Source: Royal Astronomical Society
This article was provided by Discovery News. | 0.839887 | 4.08188 |
Homeless planets discovered in deep space
Interstellar wanderers Scientists using theories first developed by Albert Einstein believe they've found a huge population of planets that don't orbit stars.
The discovery by scientists including Dr Takahiro Sumi from Osaka University in Japan, supports previous suggestions that free floating planets between three and 15 times the mass of Jupiter may exist in young star forming regions of interstellar space.
The new research, reported in the journal Nature, also suggests there could be twice as many of these free floating planets as there are stars.
Since the first discovery in 1995, more than 500 planets have been detected beyond our solar system, most by the so-called "wobble method" which looks for tiny movements in a star caused by the gravitational pull of an orbiting planet.
However, 12 extraterrestrial planets have been detected by a different process called gravitational micro-lensing. First theorised by physicist Albert Einstein in 1915, it involves the mass of a foreground object acting as a lens to bend and magnify light from a more distant background source.
Sumi and colleagues examined two years of gravitational micro-lensing survey observations of the galactic bulge of the Milky Way.
By determining the duration of each gravitational micro-lensing event, they were able to estimate the mass of the foreground object causing it.
After ruling out failed stars called brown dwarfs and stellar remnants including white dwarfs, neutron stars and stellar black holes, Sumi and colleagues believe they detected ten Jupiter-mass objects that don't appear to be orbiting a star.
Galaxy full of planets
Based on the frequency of the occurrence of these objects, they believe there are nearly twice as many free floating planets as there are stars.
Sumi and colleagues believe these planets would have formed in proto-planetary disks of molecular gas and dust around new stars similar to the one our solar system formed in.
But they think these free floating planets were then flung out of their systems or pushed in to very distant orbits.
Dr Simon O'Toole from the Australian Astronomical Observatory says it's an intriguing result, but needs more data to back it up.
"We're only speaking about 10 objects, only one of which has enough data to rule out a host star, or at least rule out a star within ten astronomical units of the planet", says O'Toole.
An astronomical unit is the distance between the Earth and the Sun.
"Ten astronomical units isn't that far out, Saturn's only just under that, both Uranus and Neptune are much further out and Pluto (even though it's no longer a planet) is about 30, while the Kuiper belt is 50," he says.
"You can't just use one result to infer that none of these objects are bound to host stars".
According to O'Toole the paper's support of the theory that planets migrate during their lifetime is most likely correct.
"Good examples are Neptune and Uranus, which may have formed much further in, possibly between the orbits of Jupiter and Saturn, and later moved out to their current positions.
"They may even have swapped places, all due to various gravitational interactions." | 0.894896 | 3.908233 |
Earth’s carbon points to planetary smashup
Research by Rice University Earth scientists suggests that virtually all of Earth’s life-giving carbon could have come from a collision about 4.4 billion years ago between Earth and an embryonic planet similar to Mercury.
In a new study this week in Nature Geoscience, Rice petrologist Rajdeep Dasgupta and colleagues offer a new answer to a long-debated geological question: How did carbon-based life develop on Earth, given that most of the planet’s carbon should have either boiled away in the planet’s earliest days or become locked in Earth’s core?
“The challenge is to explain the origin of the volatile elements like carbon that remain outside the core in the mantle portion of our planet,” said Dasgupta, who co-authored the study with lead author and Rice postdoctoral researcher Yuan Li, Rice research scientist Kyusei Tsuno and Woods Hole Oceanographic Institute colleagues Brian Monteleone and Nobumichi Shimizu.
Dasgupta’s lab specializes in recreating the high-pressure and high-temperature conditions that exist deep inside Earth and other rocky planets. His team squeezes rocks in hydraulic presses that can simulate conditions about 250 miles below Earth’s surface or at the core-mantle boundary of smaller planets like Mercury.
“Even before this paper, we had published several studies that showed that even if carbon did not vaporize into space when the planet was largely molten, it would end up in the metallic core of our planet, because the iron-rich alloys there have a strong affinity for carbon,” Dasgupta said.
Earth’s core, which is mostly iron, makes up about one-third of the planet’s mass. Earth’s silicate mantle accounts for the other two-thirds and extends more than 1,500 miles below Earth’s surface. Earth’s crust and atmosphere are so thin that they account for less than 1 percent of the planet’s mass. The mantle, atmosphere and crust constantly exchange elements, including the volatile elements needed for life.
If Earth’s initial allotment of carbon boiled away into space or got stuck in the core, where did the carbon in the mantle and biosphere come from?
“One popular idea has been that volatile elements like carbon, sulfur, nitrogen and hydrogen were added after Earth’s core finished forming,” said Li, who is now a staff scientist at Guangzhou Institute of Geochemistry, Chinese Academy of Sciences. “Any of those elements that fell to Earth in meteorites and comets more than about 100 million years after the solar system formed could have avoided the intense heat of the magma ocean that covered Earth up to that point.
“The problem with that idea is that while it can account for the abundance of many of these elements, there are no known meteorites that would produce the ratio of volatile elements in the silicate portion of our planet,” Li said.
In late 2013, Dasgupta’s team began thinking about unconventional ways to address the issue of volatiles and core composition, and they decided to conduct experiments to gauge how sulfur or silicon might alter the affinity of iron for carbon. The idea didn’t come from Earth studies, but from some of Earth’s planetary neighbors.
“We thought we definitely needed to break away from the conventional core composition of just iron and nickel and carbon,” Dasgupta recalled. “So we began exploring very sulfur-rich and silicon-rich alloys, in part because the core of Mars is thought to be sulfur-rich and the core of Mercury is thought to be relatively silicon-rich.
“It was a compositional spectrum that seemed relevant, if not for our own planet, then definitely in the scheme of all the terrestrial planetary bodies that we have in our solar system,” he said.
The experiments revealed that carbon could be excluded from the core — and relegated to the silicate mantle — if the iron alloys in the core were rich in either silicon or sulfur.
“The key data revealed how the partitioning of carbon between the metallic and silicate portions of terrestrial planets varies as a function of the variables like temperature, pressure and sulfur or silicon content,” Li said.
The team mapped out the relative concentrations of carbon that would arise under various levels of sulfur and silicon enrichment, and the researchers compared those concentrations to the known volatiles in Earth’s silicate mantle.
“One scenario that explains the carbon-to-sulfur ratio and carbon abundance is that an embryonic planet like Mercury, which had already formed a silicon-rich core, collided with and was absorbed by Earth,” Dasgupta said. “Because it’s a massive body, the dynamics could work in a way that the core of that planet would go directly to the core of our planet, and the carbon-rich mantle would mix with Earth’s mantle.
“In this paper, we focused on carbon and sulfur,” he said. “Much more work will need to be done to reconcile all of the volatile elements, but at least in terms of the carbon-sulfur abundances and the carbon-sulfur ratio, we find this scenario could explain Earth’s present carbon and sulfur budgets.” | 0.838355 | 3.295853 |
For the first time, astronomers may have seen direct evidence of a planet forming around a young star.
A spiral disk of gas and dust surrounding the star AB Aurigae contains a small S-shaped twist near the spiral’s center, infrared telescope images show.
That twist “is the precise spot where a new planet must be forming,” says astrophysicist Emmanuel Di Folco of the University of Bordeaux in France.
Previously, astronomers have seen gaps (SN: 11/6/14) and large-scale spirals (SN: 6/14/18) that are thought to be created by unseen planets in disks of gas and dust around young stars. Theories of how planets coalesce and gather material from these disks predict that planets’ motions would further twist the gas around them like swirling skirts, pinpointing a planet’s location (SN: 5/11/18).
Now, Di Folco and colleagues have used infrared observations from the Atacama Large Millimeter/submillimeter Array and the Very Large Telescope, both in Chile, to find a spiral and zero in on one such S-shaped twist around AB Aurigae. The team describes its findings in the May Astronomy & Astrophysics.
“It was amazing,” Di Folco says. “It was exactly as we were expecting from the theoretical predictions of planet formation.”
The star, about 520 light-years away in the constellation Auriga, is just 4 million years old, about one one-thousandths of the age of the sun. “It’s really a baby,” Di Folco says.
The potential planet’s exact mass is not known, but it probably would have to be a gas giant like Jupiter rather than a rocky planet like Earth to make such big waves in the disk. And it might not be alone — there’s a hint of another planet near the disk’s outer edge. | 0.836824 | 3.81602 |
Jan. 31, 2019: A Japanese research group has identified a giant streak structure among the clouds covering Venus based on observation from the spacecraft Akatsuki.
The team also revealed the origins of this structure using large-scale climate simulations. The group was led by Project Assistant Professor Hiroki Kashimura (Kobe University, Graduate School of Science) and these findings were published on January 9 in Nature Communications.
Second planet from the Sun and our closest planetary neighbor, Venus is similar in structure and size to Earth, but it is now a very different world. Venus spins slowly in the opposite direction most planets do. Its thick atmosphere traps heat in a runaway greenhouse effect, making it the hottest planet in our solar system—with surface temperatures hot enough to melt lead. Glimpses below the clouds reveal volcanoes and deformed mountains. Explore Venus ›
If the sun were as tall as a typical front door, the Earth and Venus would each be about the size of a nickel.
Venus orbits our Sun, a star. Venus is the second closest planet to the sun at a distance of about 67 million miles (108 million km).
A Day Longer Than a Year
One day on Venus lasts 243 Earth days because Venus spins backwards, with its sun rising in the west and setting in the east.
Chasing Clouds on Venus
Venus' solid surface is a volcanic landscape covered with extensive plains featuring high volcanic mountains and vast ridged plateaus.
Moonless and Ringless
Venus has no moons and no rings.
The planet’s surface temperature is about 900 degrees Fahrenheit (465 degrees Celsius)—hot enough to melt lead.
Water on Venus
Many scientists believe water once existed on the surface. Future Venus explorers will search for evidence of an ancient ocean.
More than 40 spacecraft have explored Venus. The ‘90s Magellan mission mapped the planet's surface and Akatsuki is currently orbiting Venus.
Life on Venus
Venus’ extreme temperatures and acidic clouds make it an unlikely place for life as we know it.
Super Rotating Atmosphere
While the surface rotates slowly, the winds blow at hurricane force, sending clouds completely around the planet every five days.
Venus - 3-D Perspective View of Sapas Mons
Did You Know?
The Soviet Union’s Venera 13 survived the intense heat and crushing pressure of Venus’ surface for more than two hours. Engineers from several nations are currently studying methods to extend the life of robotic spacecraft in the extreme environment.
Named after the goddess of love and beauty, Venus has become nearly synonymous with "woman" in popular culture, as referenced by the famous relationship guide Men are from Mars, Women are from Venus. As a solar system locale, Venus was a popular destination for early 20th century science fiction writers; before we knew about what lay beneath Venus' mysterious cloud cover, writers could speculate about a more hospitable planet and its possible inhabitants.
More recently, Venus has been a backdrop for video games such as Transhuman Space, Battlezone and Destiny. And in the Disney animated film The Princess and the Frog, Ray the firefly falls in love with Venus, "the evening star," as he has mistaken it for another firefly. | 0.853693 | 3.731919 |
An illustration of the helium atom, depicting the nucleus (pink) and the electron cloud distribution (black). The nucleus (upper right) in helium-4 is in reality spherically symmetric and closely resembles the electron cloud, although for more complicated nuclei this is not always the case. The black bar is one angstrom ( or ).
|Smallest recognized division of a chemical element|
|Electric charge||zero (neutral), or ion charge|
|Diameter range||62 pm (He) to 520 pm (Cs) (data page)|
|Components||Electrons and a compact nucleus of protons and neutrons|
An atom is the smallest constituent unit of ordinary matter that constitutes a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Atoms are extremely small; typical sizes are around 100 picometers (, a ten-millionth of a millimeter, or 1/254,000,000 of an inch). They are so small that accurately predicting their behavior using classical physics - as if they were billiard balls, for example - is not possible. This is due to quantum effects. Current atomic models now use quantum principles to better explain and predict this behavior.
Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Protons and neutrons are called nucleons. More than 99.94% of an atom's mass is in the nucleus. The protons have a positive electric charge whereas the electrons have a negative electric charge. The neutrons have no electric charge. If the number of protons and electrons are equal, then the atom is electrically neutral. If an atom has more or fewer electrons than protons, then it has an overall negative or positive charge, respectively. These atoms are called ions.
The electrons of an atom are attracted to the protons in an atomic nucleus by the electromagnetic force. The protons and neutrons in the nucleus are attracted to each other by the nuclear force. This force is usually stronger than the electromagnetic force that repels the positively charged protons from one another. Under certain circumstances, the repelling electromagnetic force becomes stronger than the nuclear force. In this case, the nucleus shatters and leaves behind different elements. This is a kind of nuclear decay. All electrons, nucleons, and nuclei alike are subatomic particles. The behavior of electrons in atoms is closer to a wave than a particle.
The number of protons in the nucleus, called the atomic number, defines to which chemical element the atom belongs. For example, each copper atom contains 29 protons. The number of neutrons defines the isotope of the element. Atoms can attach to one or more other atoms by chemical bonds to form chemical compounds such as molecules or crystals. The ability of atoms to associate and dissociate is responsible for most of the physical changes observed in nature. Chemistry is the discipline that studies these changes.
The idea that matter is made up of discrete units is a very old idea, appearing in many ancient cultures such as Greece and India. The word atomos, meaning "uncuttable", was coined by the ancient Greek philosophers Leucippus and his pupil Democritus (5th century BC). However, these ancient ideas were based on metaphysical reasoning rather than empirical evidence.
In the early 1800s, John Dalton used the concept of atoms to explain why chemical elements seemed to combine in ratios of small whole numbers (the law of multiple proportions). For instance, there are two types of tin oxide: one is 88.1% tin and 11.9% oxygen, and the other is 78.7% tin and 21.3% oxygen. This means that 100g of tin will combine either with 13.5g or 27g of oxygen. 13.5 and 27 form a ratio of 1:2, a ratio of small whole numbers. Similarly, there are two common types of iron oxide: 112g of iron can combine with either 32g or 48g of oxygen, which gives a ratio of 2:3. This recurring pattern suggested that elements react in multiples of discrete units, which Dalton concluded were atoms. In the case of tin oxides, for every one tin atom, there are either one or two oxygen atoms (SnO and SnO2). In the case of iron oxides, for every two iron atoms, there are either two or three oxygen atoms (FeO and Fe2O3).
Dalton also believed atomic theory could explain why some gases dissolve in water better than other gases. For example, he observed that water absorbs carbon dioxide far better than it absorbs nitrogen. Dalton hypothesized this was due to the differences in the mass and configuation of the particles. Indeed, carbon dioxide molecules (CO2) are heavier and larger than nitrogen molecules (N2).
In 1827, botanist Robert Brown used a microscope to look at dust grains floating in water and discovered that they moved about erratically, a phenomenon that became known as "Brownian motion". This was thought to be caused by water molecules knocking the grains about. In 1905, Albert Einstein proved the reality of these molecules and their motions by producing the first statistical physics analysis of Brownian motion. French physicist Jean Perrin used Einstein's work to experimentally determine the mass and dimensions of atoms, thereby conclusively verifying Dalton's atomic theory.
In 1897, J.J. Thomson discovered that cathode rays are not electromagnetic waves but made of particles that are 1,800 times lighter than hydrogen (the lightest atom). Therefore, they were not atoms, but a new particle, the first subatomic particle to be discovered, which he originally called corpuscles but were later named electrons, after particles postulated by George Johnstone Stoney in 1874. Thomson also showed they were identical to particles given off by photoelectric and radioactive materials. It was quickly recognized that they are the particles that carry electric currents in metal wires, and carry the negative electric charge within atoms. Thus Thomson overturned the belief that atoms are the indivisible, fundamental particles of matter.
In 1909, Hans Geiger and Ernest Marsden, working under the direction of Ernest Rutherford, bombarded metal foil with alpha particles to observe how they scattered. They expected all the alpha particles to pass straight through with little deflection, because Thomson's model said that the charges in the atom are so diffuse that their electric fields could not affect the alpha particles much. However, Geiger and Marsden spotted alpha particles being deflected by angles greater than 90°, which was supposed to be impossible according to Thomson's model. To explain this, Rutherford proposed that the positive charge of the atom is concentrated in a tiny nucleus at the center of the atom.
While experimenting with the products of radioactive decay, in 1913 radiochemist Frederick Soddy discovered that there appeared to be more than one type of atom at each position on the periodic table. The term isotope was coined by Margaret Todd as a suitable name for different atoms that belong to the same element. J.J. Thomson created a technique for isotope separation through his work on ionized gases, which subsequently led to the discovery of stable isotopes.
In 1913 the physicist Niels Bohr proposed a model in which the electrons of an atom were assumed to orbit the nucleus but could only do so in a finite set of orbits, and could jump between these orbits only in discrete changes of energy corresponding to absorption or radiation of a photon. This quantization was used to explain why the electrons' orbits are stable (given that normally, charges in acceleration, including circular motion, lose kinetic energy which is emitted as electromagnetic radiation, see synchrotron radiation) and why elements absorb and emit electromagnetic radiation in discrete spectra.
Later in the same year Henry Moseley provided additional experimental evidence in favor of Niels Bohr's theory. These results refined Ernest Rutherford's and Antonius Van den Broek's model, which proposed that the atom contains in its nucleus a number of positive nuclear charges that is equal to its (atomic) number in the periodic table. Until these experiments, atomic number was not known to be a physical and experimental quantity. That it is equal to the atomic nuclear charge remains the accepted atomic model today.
Chemical bonds between atoms were now explained, by Gilbert Newton Lewis in 1916, as the interactions between their constituent electrons. As the chemical properties of the elements were known to largely repeat themselves according to the periodic law, in 1919 the American chemist Irving Langmuir suggested that this could be explained if the electrons in an atom were connected or clustered in some manner. Groups of electrons were thought to occupy a set of electron shells about the nucleus.
The Stern-Gerlach experiment of 1922 provided further evidence of the quantum nature of atomic properties. When a beam of silver atoms was passed through a specially shaped magnetic field, the beam was split in a way correlated with the direction of an atom's angular momentum, or spin. As this spin direction is initially random, the beam would be expected to deflect in a random direction. Instead, the beam was split into two directional components, corresponding to the atomic spin being oriented up or down with respect to the magnetic field.
In 1925 Werner Heisenberg published the first consistent mathematical formulation of quantum mechanics (Matrix Mechanics). One year earlier, in 1924, Louis de Broglie had proposed that all particles behave to an extent like waves and, in 1926, Erwin Schrödinger used this idea to develop a mathematical model of the atom (Wave Mechanics) that described the electrons as three-dimensional waveforms rather than point particles.
A consequence of using waveforms to describe particles is that it is mathematically impossible to obtain precise values for both the position and momentum of a particle at a given point in time; this became known as the uncertainty principle, formulated by Werner Heisenberg in 1927. In this concept, for a given accuracy in measuring a position one could only obtain a range of probable values for momentum, and vice versa. This model was able to explain observations of atomic behavior that previous models could not, such as certain structural and spectral patterns of atoms larger than hydrogen. Thus, the planetary model of the atom was discarded in favor of one that described atomic orbital zones around the nucleus where a given electron is most likely to be observed.
The development of the mass spectrometer allowed the mass of atoms to be measured with increased accuracy. The device uses a magnet to bend the trajectory of a beam of ions, and the amount of deflection is determined by the ratio of an atom's mass to its charge. The chemist Francis William Aston used this instrument to show that isotopes had different masses. The atomic mass of these isotopes varied by integer amounts, called the whole number rule. The explanation for these different isotopes awaited the discovery of the neutron, an uncharged particle with a mass similar to the proton, by the physicist James Chadwick in 1932. Isotopes were then explained as elements with the same number of protons, but different numbers of neutrons within the nucleus.
In 1938, the German chemist Otto Hahn, a student of Rutherford, directed neutrons onto uranium atoms expecting to get transuranium elements. Instead, his chemical experiments showed barium as a product. A year later, Lise Meitner and her nephew Otto Frisch verified that Hahn's result were the first experimental nuclear fission. In 1944, Hahn received the Nobel prize in chemistry. Despite Hahn's efforts, the contributions of Meitner and Frisch were not recognized.
In the 1950s, the development of improved particle accelerators and particle detectors allowed scientists to study the impacts of atoms moving at high energies. Neutrons and protons were found to be hadrons, or composites of smaller particles called quarks. The standard model of particle physics was developed that so far has successfully explained the properties of the nucleus in terms of these sub-atomic particles and the forces that govern their interactions.
Though the word atom originally denoted a particle that cannot be cut into smaller particles, in modern scientific usage the atom is composed of various subatomic particles. The constituent particles of an atom are the electron, the proton and the neutron; all three are fermions. However, the hydrogen-1 atom has no neutrons and the hydron ion has no electrons.
The electron is by far the least massive of these particles at , with a negative electrical charge and a size that is too small to be measured using available techniques. It was the lightest particle with a positive rest mass measured, until the discovery of neutrino mass. Under ordinary conditions, electrons are bound to the positively charged nucleus by the attraction created from opposite electric charges. If an atom has more or fewer electrons than its atomic number, then it becomes respectively negatively or positively charged as a whole; a charged atom is called an ion. Electrons have been known since the late 19th century, mostly thanks to J.J. Thomson; see history of subatomic physics for details.
Protons have a positive charge and a mass 1,836 times that of the electron, at . The number of protons in an atom is called its atomic number. Ernest Rutherford (1919) observed that nitrogen under alpha-particle bombardment ejects what appeared to be hydrogen nuclei. By 1920 he had accepted that the hydrogen nucleus is a distinct particle within the atom and named it proton.
Neutrons have no electrical charge and have a free mass of 1,839 times the mass of the electron, or . Neutrons are the heaviest of the three constituent particles, but their mass can be reduced by the nuclear binding energy. Neutrons and protons (collectively known as nucleons) have comparable dimensions--on the order of --although the 'surface' of these particles is not sharply defined. The neutron was discovered in 1932 by the English physicist James Chadwick.
In the Standard Model of physics, electrons are truly elementary particles with no internal structure. However, both protons and neutrons are composite particles composed of elementary particles called quarks. There are two types of quarks in atoms, each having a fractional electric charge. Protons are composed of two up quarks (each with charge +) and one down quark (with a charge of -). Neutrons consist of one up quark and two down quarks. This distinction accounts for the difference in mass and charge between the two particles.
The quarks are held together by the strong interaction (or strong force), which is mediated by gluons. The protons and neutrons, in turn, are held to each other in the nucleus by the nuclear force, which is a residuum of the strong force that has somewhat different range-properties (see the article on the nuclear force for more). The gluon is a member of the family of gauge bosons, which are elementary particles that mediate physical forces.
All the bound protons and neutrons in an atom make up a tiny atomic nucleus, and are collectively called nucleons. The radius of a nucleus is approximately equal to 1.07 fm, where A is the total number of nucleons. This is much smaller than the radius of the atom, which is on the order of 105 fm. The nucleons are bound together by a short-ranged attractive potential called the residual strong force. At distances smaller than 2.5 fm this force is much more powerful than the electrostatic force that causes positively charged protons to repel each other.
Atoms of the same element have the same number of protons, called the atomic number. Within a single element, the number of neutrons may vary, determining the isotope of that element. The total number of protons and neutrons determine the nuclide. The number of neutrons relative to the protons determines the stability of the nucleus, with certain isotopes undergoing radioactive decay.
The proton, the electron, and the neutron are classified as fermions. Fermions obey the Pauli exclusion principle which prohibits identical fermions, such as multiple protons, from occupying the same quantum state at the same time. Thus, every proton in the nucleus must occupy a quantum state different from all other protons, and the same applies to all neutrons of the nucleus and to all electrons of the electron cloud.
A nucleus that has a different number of protons than neutrons can potentially drop to a lower energy state through a radioactive decay that causes the number of protons and neutrons to more closely match. As a result, atoms with matching numbers of protons and neutrons are more stable against decay. However, with increasing atomic number, the mutual repulsion of the protons requires an increasing proportion of neutrons to maintain the stability of the nucleus, which slightly modifies this trend of equal numbers of protons to neutrons.
The number of protons and neutrons in the atomic nucleus can be modified, although this can require very high energies because of the strong force. Nuclear fusion occurs when multiple atomic particles join to form a heavier nucleus, such as through the energetic collision of two nuclei. For example, at the core of the Sun protons require energies of 3-10 keV to overcome their mutual repulsion--the coulomb barrier--and fuse together into a single nucleus.Nuclear fission is the opposite process, causing a nucleus to split into two smaller nuclei--usually through radioactive decay. The nucleus can also be modified through bombardment by high energy subatomic particles or photons. If this modifies the number of protons in a nucleus, the atom changes to a different chemical element.
If the mass of the nucleus following a fusion reaction is less than the sum of the masses of the separate particles, then the difference between these two values can be emitted as a type of usable energy (such as a gamma ray, or the kinetic energy of a beta particle), as described by Albert Einstein's mass-energy equivalence formula, , where is the mass loss and is the speed of light. This deficit is part of the binding energy of the new nucleus, and it is the non-recoverable loss of the energy that causes the fused particles to remain together in a state that requires this energy to separate.
The fusion of two nuclei that create larger nuclei with lower atomic numbers than iron and nickel--a total nucleon number of about 60--is usually an exothermic process that releases more energy than is required to bring them together. It is this energy-releasing process that makes nuclear fusion in stars a self-sustaining reaction. For heavier nuclei, the binding energy per nucleon in the nucleus begins to decrease. That means fusion processes producing nuclei that have atomic numbers higher than about 26, and atomic masses higher than about 60, is an endothermic process. These more massive nuclei can not undergo an energy-producing fusion reaction that can sustain the hydrostatic equilibrium of a star.
The electrons in an atom are attracted to the protons in the nucleus by the electromagnetic force. This force binds the electrons inside an electrostatic potential well surrounding the smaller nucleus, which means that an external source of energy is needed for the electron to escape. The closer an electron is to the nucleus, the greater the attractive force. Hence electrons bound near the center of the potential well require more energy to escape than those at greater separations.
Electrons, like other particles, have properties of both a particle and a wave. The electron cloud is a region inside the potential well where each electron forms a type of three-dimensional standing wave--a wave form that does not move relative to the nucleus. This behavior is defined by an atomic orbital, a mathematical function that characterises the probability that an electron appears to be at a particular location when its position is measured. Only a discrete (or quantized) set of these orbitals exist around the nucleus, as other possible wave patterns rapidly decay into a more stable form. Orbitals can have one or more ring or node structures, and differ from each other in size, shape and orientation.
Each atomic orbital corresponds to a particular energy level of the electron. The electron can change its state to a higher energy level by absorbing a photon with sufficient energy to boost it into the new quantum state. Likewise, through spontaneous emission, an electron in a higher energy state can drop to a lower energy state while radiating the excess energy as a photon. These characteristic energy values, defined by the differences in the energies of the quantum states, are responsible for atomic spectral lines.
The amount of energy needed to remove or add an electron--the electron binding energy--is far less than the binding energy of nucleons. For example, it requires only 13.6 eV to strip a ground-state electron from a hydrogen atom, compared to 2.23 million eV for splitting a deuterium nucleus. Atoms are electrically neutral if they have an equal number of protons and electrons. Atoms that have either a deficit or a surplus of electrons are called ions. Electrons that are farthest from the nucleus may be transferred to other nearby atoms or shared between atoms. By this mechanism, atoms are able to bond into molecules and other types of chemical compounds like ionic and covalent network crystals.
By definition, any two atoms with an identical number of protons in their nuclei belong to the same chemical element. Atoms with equal numbers of protons but a different number of neutrons are different isotopes of the same element. For example, all hydrogen atoms admit exactly one proton, but isotopes exist with no neutrons (hydrogen-1, by far the most common form, also called protium), one neutron (deuterium), two neutrons (tritium) and more than two neutrons. The known elements form a set of atomic numbers, from the single proton element hydrogen up to the 118-proton element oganesson. All known isotopes of elements with atomic numbers greater than 82 are radioactive, although the radioactivity of element 83 (bismuth) is so slight as to be practically negligible.
About 339 nuclides occur naturally on Earth, of which 252 (about 74%) have not been observed to decay, and are referred to as "stable isotopes". However, only 90 of these nuclides are stable to all decay, even in theory. Another 162 (bringing the total to 252) have not been observed to decay, even though in theory it is energetically possible. These are also formally classified as "stable". An additional 34 radioactive nuclides have half-lives longer than 100 million years, and are long-lived enough to be present from the birth of the solar system. This collection of 286 nuclides are known as primordial nuclides. Finally, an additional 53 short-lived nuclides are known to occur naturally, as daughter products of primordial nuclide decay (such as radium from uranium), or else as products of natural energetic processes on Earth, such as cosmic ray bombardment (for example, carbon-14).[note 1]
For 80 of the chemical elements, at least one stable isotope exists. As a rule, there is only a handful of stable isotopes for each of these elements, the average being 3.2 stable isotopes per element. Twenty-six elements have only a single stable isotope, while the largest number of stable isotopes observed for any element is ten, for the element tin. Elements 43, 61, and all elements numbered 83 or higher have no stable isotopes.[page needed]
Stability of isotopes is affected by the ratio of protons to neutrons, and also by the presence of certain "magic numbers" of neutrons or protons that represent closed and filled quantum shells. These quantum shells correspond to a set of energy levels within the shell model of the nucleus; filled shells, such as the filled shell of 50 protons for tin, confers unusual stability on the nuclide. Of the 252 known stable nuclides, only four have both an odd number of protons and odd number of neutrons: hydrogen-2 (deuterium), lithium-6, boron-10 and nitrogen-14. Also, only four naturally occurring, radioactive odd-odd nuclides have a half-life over a billion years: potassium-40, vanadium-50, lanthanum-138 and tantalum-180m. Most odd-odd nuclei are highly unstable with respect to beta decay, because the decay products are even-even, and are therefore more strongly bound, due to nuclear pairing effects.[page needed]
The large majority of an atom's mass comes from the protons and neutrons that make it up. The total number of these particles (called "nucleons") in a given atom is called the mass number. It is a positive integer and dimensionless (instead of having dimension of mass), because it expresses a count. An example of use of a mass number is "carbon-12," which has 12 nucleons (six protons and six neutrons).
The actual mass of an atom at rest is often expressed in daltons (Da), also called the unified atomic mass unit (u). This unit is defined as a twelfth of the mass of a free neutral atom of carbon-12, which is approximately .Hydrogen-1 (the lightest isotope of hydrogen which is also the nuclide with the lowest mass) has an atomic weight of 1.007825 Da. The value of this number is called the atomic mass. A given atom has an atomic mass approximately equal (within 1%) to its mass number times the atomic mass unit (for example the mass of a nitrogen-14 is roughly 14 Da). However, this number will not be exactly an integer except in the case of carbon-12 (see below). The heaviest stable atom is lead-208, with a mass of .
As even the most massive atoms are far too light to work with directly, chemists instead use the unit of moles. One mole of atoms of any element always has the same number of atoms (about ). This number was chosen so that if an element has an atomic mass of 1 u, a mole of atoms of that element has a mass close to one gram. Because of the definition of the unified atomic mass unit, each carbon-12 atom has an atomic mass of exactly 12 Da, and so a mole of carbon-12 atoms weighs exactly 0.012 kg.
Atoms lack a well-defined outer boundary, so their dimensions are usually described in terms of an atomic radius. This is a measure of the distance out to which the electron cloud extends from the nucleus. However, this assumes the atom to exhibit a spherical shape, which is only obeyed for atoms in vacuum or free space. Atomic radii may be derived from the distances between two nuclei when the two atoms are joined in a chemical bond. The radius varies with the location of an atom on the atomic chart, the type of chemical bond, the number of neighboring atoms (coordination number) and a quantum mechanical property known as spin. On the periodic table of the elements, atom size tends to increase when moving down columns, but decrease when moving across rows (left to right). Consequently, the smallest atom is helium with a radius of 32 pm, while one of the largest is caesium at 225 pm.
When subjected to external forces, like electrical fields, the shape of an atom may deviate from spherical symmetry. The deformation depends on the field magnitude and the orbital type of outer shell electrons, as shown by group-theoretical considerations. Aspherical deviations might be elicited for instance in crystals, where large crystal-electrical fields may occur at low-symmetry lattice sites. Significant ellipsoidal deformations have been shown to occur for sulfur ions and chalcogen ions in pyrite-type compounds.
Atomic dimensions are thousands of times smaller than the wavelengths of light (400-700 nm) so they cannot be viewed using an optical microscope. However, individual atoms can be observed using a scanning tunneling microscope. To visualize the minuteness of the atom, consider that a typical human hair is about 1 million carbon atoms in width. A single drop of water contains about 2 sextillion atoms of oxygen, and twice the number of hydrogen atoms. A single carat diamond with a mass of contains about 10 sextillion (1022) atoms of carbon.[note 2] If an apple were magnified to the size of the Earth, then the atoms in the apple would be approximately the size of the original apple.
Every element has one or more isotopes that have unstable nuclei that are subject to radioactive decay, causing the nucleus to emit particles or electromagnetic radiation. Radioactivity can occur when the radius of a nucleus is large compared with the radius of the strong force, which only acts over distances on the order of 1 fm.
Other more rare types of radioactive decay include ejection of neutrons or protons or clusters of nucleons from a nucleus, or more than one beta particle. An analog of gamma emission which allows excited nuclei to lose energy in a different way, is internal conversion--a process that produces high-speed electrons that are not beta rays, followed by production of high-energy photons that are not gamma rays. A few large nuclei explode into two or more charged fragments of varying masses plus several neutrons, in a decay called spontaneous nuclear fission.
Each radioactive isotope has a characteristic decay time period--the half-life--that is determined by the amount of time needed for half of a sample to decay. This is an exponential decay process that steadily decreases the proportion of the remaining isotope by 50% every half-life. Hence after two half-lives have passed only 25% of the isotope is present, and so forth.
Elementary particles possess an intrinsic quantum mechanical property known as spin. This is analogous to the angular momentum of an object that is spinning around its center of mass, although strictly speaking these particles are believed to be point-like and cannot be said to be rotating. Spin is measured in units of the reduced Planck constant (?), with electrons, protons and neutrons all having spin ½ ?, or "spin-½". In an atom, electrons in motion around the nucleus possess orbital angular momentum in addition to their spin, while the nucleus itself possesses angular momentum due to its nuclear spin.
The magnetic field produced by an atom--its magnetic moment--is determined by these various forms of angular momentum, just as a rotating charged object classically produces a magnetic field. However, the most dominant contribution comes from electron spin. Due to the nature of electrons to obey the Pauli exclusion principle, in which no two electrons may be found in the same quantum state, bound electrons pair up with each other, with one member of each pair in a spin up state and the other in the opposite, spin down state. Thus these spins cancel each other out, reducing the total magnetic dipole moment to zero in some atoms with even number of electrons.
In ferromagnetic elements such as iron, cobalt and nickel, an odd number of electrons leads to an unpaired electron and a net overall magnetic moment. The orbitals of neighboring atoms overlap and a lower energy state is achieved when the spins of unpaired electrons are aligned with each other, a spontaneous process known as an exchange interaction. When the magnetic moments of ferromagnetic atoms are lined up, the material can produce a measurable macroscopic field. Paramagnetic materials have atoms with magnetic moments that line up in random directions when no magnetic field is present, but the magnetic moments of the individual atoms line up in the presence of a field.
The nucleus of an atom will have no spin when it has even numbers of both neutrons and protons, but for other cases of odd numbers, the nucleus may have a spin. Normally nuclei with spin are aligned in random directions because of thermal equilibrium. However, for certain elements (such as xenon-129) it is possible to polarize a significant proportion of the nuclear spin states so that they are aligned in the same direction--a condition called hyperpolarization. This has important applications in magnetic resonance imaging.
The potential energy of an electron in an atom is negative, its dependence of its position reaches the minimum (the most absolute value) inside the nucleus, and vanishes when the distance from the nucleus goes to infinity, roughly in an inverse proportion to the distance. In the quantum-mechanical model, a bound electron can only occupy a set of states centered on the nucleus, and each state corresponds to a specific energy level; see time-independent Schrödinger equation for theoretical explanation. An energy level can be measured by the amount of energy needed to unbind the electron from the atom, and is usually given in units of electronvolts (eV). The lowest energy state of a bound electron is called the ground state, i.e. stationary state, while an electron transition to a higher level results in an excited state. The electron's energy raises when n increases because the (average) distance to the nucleus increases. Dependence of the energy on ℓ is caused not by electrostatic potential of the nucleus, but by interaction between electrons.
For an electron to transition between two different states, e.g. ground state to first excited state, it must absorb or emit a photon at an energy matching the difference in the potential energy of those levels, according to the Niels Bohr model, what can be precisely calculated by the Schrödinger equation. Electrons jump between orbitals in a particle-like fashion. For example, if a single photon strikes the electrons, only a single electron changes states in response to the photon; see Electron properties.
The energy of an emitted photon is proportional to its frequency, so these specific energy levels appear as distinct bands in the electromagnetic spectrum. Each element has a characteristic spectrum that can depend on the nuclear charge, subshells filled by electrons, the electromagnetic interactions between the electrons and other factors.
When a continuous spectrum of energy is passed through a gas or plasma, some of the photons are absorbed by atoms, causing electrons to change their energy level. Those excited electrons that remain bound to their atom spontaneously emit this energy as a photon, traveling in a random direction, and so drop back to lower energy levels. Thus the atoms behave like a filter that forms a series of dark absorption bands in the energy output. (An observer viewing the atoms from a view that does not include the continuous spectrum in the background, instead sees a series of emission lines from the photons emitted by the atoms.) Spectroscopic measurements of the strength and width of atomic spectral lines allow the composition and physical properties of a substance to be determined.
Close examination of the spectral lines reveals that some display a fine structure splitting. This occurs because of spin-orbit coupling, which is an interaction between the spin and motion of the outermost electron. When an atom is in an external magnetic field, spectral lines become split into three or more components; a phenomenon called the Zeeman effect. This is caused by the interaction of the magnetic field with the magnetic moment of the atom and its electrons. Some atoms can have multiple electron configurations with the same energy level, which thus appear as a single spectral line. The interaction of the magnetic field with the atom shifts these electron configurations to slightly different energy levels, resulting in multiple spectral lines. The presence of an external electric field can cause a comparable splitting and shifting of spectral lines by modifying the electron energy levels, a phenomenon called the Stark effect.
If a bound electron is in an excited state, an interacting photon with the proper energy can cause stimulated emission of a photon with a matching energy level. For this to occur, the electron must drop to a lower energy state that has an energy difference matching the energy of the interacting photon. The emitted photon and the interacting photon then move off in parallel and with matching phases. That is, the wave patterns of the two photons are synchronized. This physical property is used to make lasers, which can emit a coherent beam of light energy in a narrow frequency band.
Valency is the combining power of an element. It is equal to number of hydrogen atoms that atom can combine or displace in forming compounds. The outermost electron shell of an atom in its uncombined state is known as the valence shell, and the electrons in that shell are called valence electrons. The number of valence electrons determines the bonding behavior with other atoms. Atoms tend to chemically react with each other in a manner that fills (or empties) their outer valence shells. For example, a transfer of a single electron between atoms is a useful approximation for bonds that form between atoms with one-electron more than a filled shell, and others that are one-electron short of a full shell, such as occurs in the compound sodium chloride and other chemical ionic salts. However, many elements display multiple valences, or tendencies to share differing numbers of electrons in different compounds. Thus, chemical bonding between these elements takes many forms of electron-sharing that are more than simple electron transfers. Examples include the element carbon and the organic compounds.
The chemical elements are often displayed in a periodic table that is laid out to display recurring chemical properties, and elements with the same number of valence electrons form a group that is aligned in the same column of the table. (The horizontal rows correspond to the filling of a quantum shell of electrons.) The elements at the far right of the table have their outer shell completely filled with electrons, which results in chemically inert elements known as the noble gases.
Quantities of atoms are found in different states of matter that depend on the physical conditions, such as temperature and pressure. By varying the conditions, materials can transition between solids, liquids, gases and plasmas. Within a state, a material can also exist in different allotropes. An example of this is solid carbon, which can exist as graphite or diamond. Gaseous allotropes exist as well, such as dioxygen and ozone.
At temperatures close to absolute zero, atoms can form a Bose-Einstein condensate, at which point quantum mechanical effects, which are normally only observed at the atomic scale, become apparent on a macroscopic scale. This super-cooled collection of atoms then behaves as a single super atom, which may allow fundamental checks of quantum mechanical behavior.
The scanning tunneling microscope is a device for viewing surfaces at the atomic level. It uses the quantum tunneling phenomenon, which allows particles to pass through a barrier that would normally be insurmountable. Electrons tunnel through the vacuum between two planar metal electrodes, on each of which is an adsorbed atom, providing a tunneling-current density that can be measured. Scanning one atom (taken as the tip) as it moves past the other (the sample) permits plotting of tip displacement versus lateral separation for a constant current. The calculation shows the extent to which scanning-tunneling-microscope images of an individual atom are visible. It confirms that for low bias, the microscope images the space-averaged dimensions of the electron orbitals across closely packed energy levels--the Fermi level local density of states.
An atom can be ionized by removing one of its electrons. The electric charge causes the trajectory of an atom to bend when it passes through a magnetic field. The radius by which the trajectory of a moving ion is turned by the magnetic field is determined by the mass of the atom. The mass spectrometer uses this principle to measure the mass-to-charge ratio of ions. If a sample contains multiple isotopes, the mass spectrometer can determine the proportion of each isotope in the sample by measuring the intensity of the different beams of ions. Techniques to vaporize atoms include inductively coupled plasma atomic emission spectroscopy and inductively coupled plasma mass spectrometry, both of which use a plasma to vaporize samples for analysis.
A more area-selective method is electron energy loss spectroscopy, which measures the energy loss of an electron beam within a transmission electron microscope when it interacts with a portion of a sample. The atom-probe tomograph has sub-nanometer resolution in 3-D and can chemically identify individual atoms using time-of-flight mass spectrometry.
Spectra of excited states can be used to analyze the atomic composition of distant stars. Specific light wavelengths contained in the observed light from stars can be separated out and related to the quantized transitions in free gas atoms. These colors can be replicated using a gas-discharge lamp containing the same element.Helium was discovered in this way in the spectrum of the Sun 23 years before it was found on Earth.
Baryonic matter forms about 4% of the total energy density of the observable Universe, with an average density of about 0.25 particles/m3 (mostly protons and electrons). Within a galaxy such as the Milky Way, particles have a much higher concentration, with the density of matter in the interstellar medium (ISM) ranging from 105 to 109 atoms/m3. The Sun is believed to be inside the Local Bubble, so the density in the solar neighborhood is only about 103 atoms/m3. Stars form from dense clouds in the ISM, and the evolutionary processes of stars result in the steady enrichment of the ISM with elements more massive than hydrogen and helium.
Up to 95% of the Milky Way's baryonic matter are concentrated inside stars, where conditions are unfavorable for atomic matter. The total baryonic mass is about 10% of the mass of the galaxy; the remainder of the mass is an unknown dark matter. High temperature inside stars makes most "atoms" fully ionized, that is, separates all electrons from the nuclei. In stellar remnants--with exception of their surface layers--an immense pressure make electron shells impossible.
Electrons are thought to exist in the Universe since early stages of the Big Bang. Atomic nuclei forms in nucleosynthesis reactions. In about three minutes Big Bang nucleosynthesis produced most of the helium, lithium, and deuterium in the Universe, and perhaps some of the beryllium and boron.
Ubiquitousness and stability of atoms relies on their binding energy, which means that an atom has a lower energy than an unbound system of the nucleus and electrons. Where the temperature is much higher than ionization potential, the matter exists in the form of plasma--a gas of positively charged ions (possibly, bare nuclei) and electrons. When the temperature drops below the ionization potential, atoms become statistically favorable. Atoms (complete with bound electrons) became to dominate over charged particles 380,000 years after the Big Bang--an epoch called recombination, when the expanding Universe cooled enough to allow electrons to become attached to nuclei.
Since the Big Bang, which produced no carbon or heavier elements, atomic nuclei have been combined in stars through the process of nuclear fusion to produce more of the element helium, and (via the triple alpha process) the sequence of elements from carbon up to iron; see stellar nucleosynthesis for details.
Isotopes such as lithium-6, as well as some beryllium and boron are generated in space through cosmic ray spallation. This occurs when a high-energy proton strikes an atomic nucleus, causing large numbers of nucleons to be ejected.
Elements heavier than iron were produced in supernovae and colliding neutron stars through the r-process, and in AGB stars through the s-process, both of which involve the capture of neutrons by atomic nuclei. Elements such as lead formed largely through the radioactive decay of heavier elements.
Most of the atoms that make up the Earth and its inhabitants were present in their current form in the nebula that collapsed out of a molecular cloud to form the Solar System. The rest are the result of radioactive decay, and their relative proportion can be used to determine the age of the Earth through radiometric dating. Most of the helium in the crust of the Earth (about 99% of the helium from gas wells, as shown by its lower abundance of helium-3) is a product of alpha decay.
There are a few trace atoms on Earth that were not present at the beginning (i.e., not "primordial"), nor are results of radioactive decay. Carbon-14 is continuously generated by cosmic rays in the atmosphere. Some atoms on Earth have been artificially generated either deliberately or as by-products of nuclear reactors or explosions. Of the transuranic elements--those with atomic numbers greater than 92--only plutonium and neptunium occur naturally on Earth. Transuranic elements have radioactive lifetimes shorter than the current age of the Earth and thus identifiable quantities of these elements have long since decayed, with the exception of traces of plutonium-244 possibly deposited by cosmic dust. Natural deposits of plutonium and neptunium are produced by neutron capture in uranium ore.
The Earth contains approximately atoms. Although small numbers of independent atoms of noble gases exist, such as argon, neon, and helium, 99% of the atmosphere is bound in the form of molecules, including carbon dioxide and diatomic oxygen and nitrogen. At the surface of the Earth, an overwhelming majority of atoms combine to form various compounds, including water, salt, silicates and oxides. Atoms can also combine to create materials that do not consist of discrete molecules, including crystals and liquid or solid metals. This atomic matter forms networked arrangements that lack the particular type of small-scale interrupted order associated with molecular matter.
All nuclides with atomic numbers higher than 82 (lead) are known to be radioactive. No nuclide with an atomic number exceeding 92 (uranium) exists on Earth as a primordial nuclide, and heavier elements generally have shorter half-lives. Nevertheless, an "island of stability" encompassing relatively long-lived isotopes of superheavy elements with atomic numbers 110-114 might exist. Predictions for the half-live of the most stable nuclide on the island range from a few minutes to millions of years. In any case, superheavy elements (with Z > 104) would not exist due to increasing Coulomb repulsion (which results in spontaneous fission with increasingly short half-lives) in the absence of any stabilizing effects.
Each particle of matter has a corresponding antimatter particle with the opposite electrical charge. Thus, the positron is a positively charged antielectron and the antiproton is a negatively charged equivalent of a proton. When a matter and corresponding antimatter particle meet, they annihilate each other. Because of this, along with an imbalance between the number of matter and antimatter particles, the latter are rare in the universe. The first causes of this imbalance are not yet fully understood, although theories of baryogenesis may offer an explanation. As a result, no antimatter atoms have been discovered in nature. However, in 1996 the antimatter counterpart of the hydrogen atom (antihydrogen) was synthesized at the CERN laboratory in Geneva.
Other exotic atoms have been created by replacing one of the protons, neutrons or electrons with other particles that have the same charge. For example, an electron can be replaced by a more massive muon, forming a muonic atom. These types of atoms can be used to test the fundamental predictions of physics.
There are 2,000,000,000,000,000,000,000 (that's 2 sextillion) atoms of oxygen in one drop of water--and twice as many atoms of hydrogen. | 0.871033 | 3.885594 |
New measurements from an experiment held at the top of an extinct volcano in Mexico have confirmed that there is a new limit on whether light is able to go faster than the known speed of light.
Observations of record-breaking gamma rays from a distant galaxy confirmed the robustness of a piece of Einstein's theory of relativity: the Lorentz Invariance. No matter where you are or how fast you're moving, the laws of physics hold.
The findings were published in Physical Review Letters.
The speed of light
Einstein's Lorentz Invariance predicts that the speed of light is constant everywhere in the universe. The new measurements taken from the High-Altitude Water Cherenkov (HAWC) Observatory in Puebla, Mexico, detected gamma rays from far-away galactic sources, and physicists were able to confirm, to the highest energies yet explored, that these laws of physics are true, no matter where you are or how fast you're moving.
"How relativity behaves at very high energies has real consequences for the world around us," said Pat Harding, an astrophysicist in the Neutron Science and Technology group at Los Alamos National Laboratory and a member of the HAWC scientific collaboration.
"Most quantum gravity models say the behavior of relativity will break down at very high energies. Our observation of such high-energy photons at all raises the energy scale where relativity holds by more than a factor of a hundred."
The physicists were looking for a deviation from the well-established theory of Lorentz Invariance because this law suggests that it may not hold at the highest of energies. If Lorentz Invariance were not to hold true, a number of phenomena would become possibilities. For instance, gamma rays may travel at speeds faster or slower than the speed of light.
The HAWC Gamma Ray Observatory had noticed a number of astrophysical sources that produce photons higher than 100 TeV (or one trillion times the energy of visible light). As HAWC is able to detect these gamma rays it extends the range that the Lorentz Invariance holds by a factor of 100 times.
"Detections of even higher-energy gamma rays from astronomical distances will allow more stringent checks on relativity. As HAWC continues to take more data in the coming years and incorporate Los Alamos-led improvements to the detector and analysis techniques at the highest energies, we will be able to study this physics even further," said Harding. | 0.819333 | 3.992131 |
Using two NASA X-ray satellites, astronomers have discovered what drives the “heartbeats” seen in the light from an unusual black hole system. These results give new insight into the ways that black holes can regulate their intake and severely…
University of California, Berkeley, astronomers may have found the missing link between gas-filled, star-forming galaxies and older, gas-depleted galaxies typically characterized as “red and dead.”
In a poster to be presented this week at t…
A mammoth sky survey led by University of Florida astronomers has uncovered seven planet-forming disks in clusters of young stars, doubling the number of such disks discovered and expanding the territory that might yield new planets.
Astronomers have discovered three of the oldest, most distant quasars yet found — quasars close to the Big Bang that began the universe. Xiaohui Fan of the University of Arizona’s Steward Observatory in Tucson, Ariz., will present the results at the American Astronomical Society’s meeting in Seattle. Fan, leader of the team that discovered the objects, explained that these distant quasars — compact but luminous objects thought to be powered by super-massive black holes — reach back to a time when the universe was just 800 million years old. The highest redshift quasar is roughly 13 billion light years away and was discovered recently in the constellation Ursa Major.
Giant jets of subatomic particles moving at nearly the speed of light have been found coming from thousands of galaxies across the Universe, but always from elliptical galaxies or galaxies in the process of merging — until now. Using the combined power of the Hubble Space Telescope, the Very Large Array (VLA) and the 8-meter Gemini-South Telescope, astronomers have discovered a huge jet coming from a spiral galaxy similar to our own Milky Way.
A new type of star has been discovered lurking as a low mass component in a very compact binary star system. Astronomers announced today at the American Astronomical Society Meeting in Seattle, Wash., that they have confirmed the existence of a new variety of stellar end-product. This previously unknown type of star has some properties similar to brown dwarf stars and may help astronomers understand some of the recently discovered extra-solar planets in close proximity to their suns.
The discovery of a faint trail of stars in the nearby Andromeda galaxy offers new evidence that large spiral galaxies have grown by gobbling up smaller satellite galaxies. Andromeda (also known as M31) is the nearest large galaxy to our own Milky Way and is very similar to it in appearance. Studying Andromeda gives astronomers an external perspective on a galaxy much like our own–it’s like looking at a bigger sibling of our galaxy. | 0.884061 | 3.83376 |
An Amazing Spectacle is ComingCredit: Javrsmith
Comet Nevski-Novichonok is on its way. This visitor from the depths of space is going to be spectacular. Throughout history, many comets have been stunning but few have been spectacular. Nevski-Novichonok is destined to be one of the best of all time. Discovered in September, 2012, it was researched and found to be on a very close trajectory to the sun. In fact, it will seem to come close enough to graze the solar atmosphere. This factor is what will make this comet very bright in the sky. It will likely even be visible in the daytime.
There is always a degree of uncertainty when evaluating the maximum brightness of a comet. They are often discovered when they are extremely far away when they appear to be insignificant, dim objects. By comparing two photographs, astronomers realize that some objects have moved compared to those that remain fixed in place. The identified object may be a comet, an asteroid or even a piece of space debris near the Earth. By calculating the path in space for the object, a precise determination of the object can be made. For some, the path is calculated which show it to be on an orbit of the sun, which defines it as a comet. These items are quite rare.
After a comet is identified, based on its orbit, the determination of the eventual brightness is attempted. Several factors affect the brightness value. Chief among these is the eventual proximity to the sun. The closest approach of the comet to the sun is called its "perihelion". Generally, the closer to the sun, the brighter the comet will be. Comet Nevski-Novichonok will have a perihelion of about 1 million miles. This is extremely close. The perihelion of Halley's Comet was 54 million miles. In 1986, that comet orbited the sun and was not very bright for Earthbound observers. In 1997, Comet Hale-Bopp passed the sun with over 84 million miles of separation. That comet was very much brighter and was a great object to observe for months. Considering that Comet Nevski-Novichonok is so very much closer to the sun at its perihelion, predictions are that the brightness of the 2013 will be extremely bright.
Other factors that influence comet brightness are the composition of the object and the size. Larger ones made predominantly of ice and dust are apt to be brighter. That is because they give off more of their material as they are warmed by the sun as they near perihelion. More rocky objects simply warm up without having as much material expelled. The ice and dust of a comet creates the distinctive tail, or coma, which is often visible from Earth. Each particle in the tail is illuminated by sunlight. More material in the tail provides more particles that can be lit. Comet tails can be millions of miles long, much of which is often visible from Earth.
Comet Nevski-Novichonok is likely to put on a show which might never be equalled. The comet passes within 0.012 astronomical units of the center of the sun. An "au" is almost 93 million miles and the sun's diameter is very large, so the comet will be about 680,000 miles above the surface of the sun. As mentioned, this close separation will cause the warm of the sun to heat up the ice and dust of the comet. The solar wind which emanates from the sun will buffet the comet and carry off particles. The solar wind will be very strong, and the comet well heated, as Comet Nevski-Novichonok nears perihelion. The particles will for a tail, or coma, beyond the comet. How long the tail will be is really anyone's guess. Many such tails are millions of miles long.
It is when this great comet nears the sun that things become interesting. How big will the comet's tail be? How illuminated will the particles be? Will the comet even survive the close approach. Other comets are called "sun grazers" because they pass even closer to the sun. Many of those don't survive the encounter. Perhaps Comet Nevski-Novichonok is large enough to escape unscathed. There is also the effect of Jupiter on the planet. As the object passes the giant planet, gravity is affected. This can affect the subsequent orbits of the comet. Currently, this 2013 comet takes perhaps a million years to orbit the sun. Jupiter may cause the orbit length, (or period), to increase or decrease. Jupiter may also deflect the orbit. This is an unlikely possibility but it has happened before. Comet Shoemaker-Levy 9 was so affected and it soon crashed into the giant planet. Comet Nevski-Novichonok is not likely to collide with a planet but its orbit may not be exactly stable after the 2013 close approach.
Luckily for those in the Northern Hemisphere, Comet Nevski-Novichonok will be high in the sky during the latter part of 2013. This is in marked contrast to Halley's Comet in 1986 which was very low for northern observers. Comet Hale-Bopp in 1996-97 was better positioned for northerners as well. Since it is never too early to prepare, those people in the Northern Hemisphere should acquaint themselves with the night sky in the fall and winter of 2012. Find out where north is for your location. Locate the North Star. This star is situated almost directly above the North Pole. As such, it makes a great locating point in the night sky. Stand outside at night where you have a clear view to the north. Look up at an angle which corresponds to your current latitude. For the people in the USA, that will be between 25 and 49 degrees, 21.3 in Hawaii and 51-70 in Alaska. While the comet passes this start on January 8, 2014, it will be a better view in mid to late 2013 starting about when the comet passes through the Leo constellation. Look for a backwards question mark in the sky made up of about 7 stars. Find that and you'll be ready to view Comet Nevski-Novichonok. | 0.800869 | 3.797278 |
Using several thousand images of Saturn's moons produced by the Cassini probe (NASA/ESA), an international team led by an astronomer from the Observatoire de Paris in the Institute of Celestial Mechanics and Calculation of Ephemerides ( Observatoire de Paris / CNRS / UPMC / Université Lille 1), in collaboration with CEA researchers, has succeeded in bringing to light small fluctuations in the gravitational field of the planet. These extremely fine results are the outcome of a series of works carried out by the same team on the Saturn ecosystem and should allow to better understand the internal structure of Saturn. These results are in press in the International Journal Icarus and are the subject of an video.
For more information : see the French version
The birth spin of a neutron star is a key parameter to better understand the nature of its progenitor as well as the dynamical processes at play during the collapse of a massive star. However, the distribution of initial pulsar spins is poorly known. A study led by R. Kazeroni from SAP/CEA and his collaborators, using numerical simulations, emphasized the efficiency of a hydrodynamic instability named “SASI” to impart a rotational velocity to the neutron star. Surprisingly, the simulations show that, in some cases, the direction of rotation of the compact object is opposite to the perturbation which triggers the rotation. These results are published in the journal Monthly Notices of the Royal Astronomical Society. | 0.844321 | 3.454086 |
Over the weekend, a pair of robots, each about the size of a frying pan, tumbled out of a spacecraft and landed on the surface of another world.
The robots are part of a Japanese mission to visit an asteroid, collect some of its rocky material, and then return it to Earth. In late 2014, Japan launched the Hayabusa2 spacecraft bound for Ryugu, a small asteroid that measures slightly more than half a mile and orbits near Earth. The spacecraft caught up with Ryugu in June after a three-year chase. Then, last week, it cozied up to the asteroid, coming within several hundred feet of its rocky surface, and dropped the two bots.
Their successful deployment is a very impressive achievement. It’s not easy to land something on such a fast-moving, faraway object; a similar attempt on a comet in 2014 ended with a robot becoming permanently wedged in a dark crevice. But perhaps the most striking part of the maneuver is in the photographs of the landing.
The two Japanese robots have captured Ryugu in incredible detail. The images reveal a richly textured surface, with rocks of all sizes jutting out into the darkness of space:
From this vantage point, Ryugu doesn’t look like a hazy space rock floating hundreds of millions of miles away. It looks comfortingly familiar, like a rocky outcrop you might stumble across while hiking on Earth.
The images are unlike the majority of previous observations of asteroids. For many decades, other spacecraft and telescopes have shown asteroids as tiny specks of light, or fuzzy blots, or hazy lumps of smooth rock. My personal favorite description of one picture, from 1989, reads: “The slightly elongated smudge in this image is the asteroid.”
Telescope technology has vastly improved in the more than 200 years since asteroids were first discovered, but today, only the most powerful telescopes can resolve distinct features on the surface of the objects. The best way to photograph an asteroid is to visit, or at least fly past.
In 1991, the Galileo spacecraft buzzed past the asteroid Gaspra on its way to Jupiter. NASA engineers used data from the spacecraft to stitch together an image of the asteroid, which The New York Times described as “the first close-up photograph ever made of a rocky asteroid hurtling through the solar system.” This was the photo:
Galileo was about 10,000 miles from the asteroid when its camera pointed toward Gaspra. The Times referred to the composite photo as “a sharp portrait” of an asteroid, and, indeed, it was at the time.
The Hayabusa2 mission will produce many more close-up images in the coming weeks, thanks to the two robots. JAXA, the Japanese space agency, calls them rovers, but that’s a bit of a misnomer. The robots don’t have any wheels, which wouldn’t be efficient in Ryugu’s low-gravity environment. Instead, the bots are designed to push themselves around, and will quite literally bounce around the surface.
As the mission provides us with more close-up views of Ryugu, it will also deliver an unprecedented look at the solar system’s ancient past. Scientists believe that asteroids like Ryugu are remnants of the system’s creation about 4.5 billion years ago. The rocks have remained mostly unchanged since then, which means they still contain the materials—a mix of rock, minerals, and organic compounds—that coalesced to form the planets.
The Hayabusa2 spacecraft will soon attempt to excavate some of that history. The probe will fire a projectile at Ryugu to create a crater and expose long-buried material, and then dip its instruments inside to collect some samples before heading back to Earth. Like the two robots, Hayabusa2 has cameras on board. Our views of an asteroid are bound to become sharper still.
We want to hear what you think about this article. Submit a letter to the editor or write to [email protected]. | 0.828485 | 3.664588 |
Editor’s Note: An earlier version of this story stated that it has not been possible to capture images of the entire sunlit side of Earth since Apollo 17 astronauts captured the iconic Blue Marble photograph in 1972. In fact, other satellites—including Galileo, the Lunar Reconnaissance Orbiter, and geostationary weather satellites including GOES—have captured full-disc views of Earth since then.
The journey has been a long one for the Deep Space Climate Observatory (DSCOVR). Once known as Triana, the satellite was conceived in 1998 to provide continuous views of Earth, to monitor the solar wind, and to measure fluctuations in Earth’s albedo. The mission was put on hold in 2001, and the partly-built satellite ended up in storage for several years with an uncertain future. In 2008, the National Oceanic and Atmospheric Administration (NOAA), NASA, and the U.S. Air Force decided to refurbish and update the spacecraft for launch.
On February 11, 2015, DSCOVR was finally lofted into space by a SpaceX Falcon 9 rocket. After journey of about 1.6 million kilometers (1 million miles) to the L1 Lagrange Point, the satellite and its Earth Polychromatic Imaging Camera (EPIC) has returned its first view of the entire sunlit side of Earth. At L1—four times farther than the orbit of the Moon—the gravitational pull of the Sun and Earth cancel out, providing a stable orbit and a continuous view of Earth. The image above was made by combining information from EPIC’s red, green, and blue bands. (Bands are narrow regions of the electromagnetic spectrum to which a remote sensing instrument responds. When EPIC collects data, it takes a series of 10 images at different bands—from ultraviolet to near infrared.)
This first public image shows the effects of sunlight scattered by air molecules, giving the disk a characteristic bluish tint. The EPIC team is developing data processing techniques that will emphasize land features and remove this atmospheric effect. Once the instrument begins regular data acquisition, new images will be available every day, 12 to 36 hours after they are acquired by EPIC. These images will be posted to a dedicated web page by autumn 2015. Data from EPIC will be used to measure ozone and aerosol levels in Earth’s atmosphere, as well as cloud height, vegetation properties, and the ultraviolet reflectivity of Earth. NASA will use this data for a number of Earth science applications, including dust and volcanic ash maps of the entire planet.
“This first DSCOVR image of our planet demonstrates the unique and important benefits of Earth observation from space,” said NASA Administrator Charles Bolden. “As a former astronaut who’s been privileged to view the Earth from orbit, I want everyone to be able to see and appreciate our planet as an integrated, interacting system.”
- Scientific American (2015, February 6) Al Gore Weighs in on a Long-Delayed Earth Observatory Launch. Accessed July 20, 2015.
- The Atlantic (2015, February 10) 7 Truly Amazing Reasons to Care About NASA’s New Satellite. Accessed July 20, 2015.
- The Planetary Society (2015, July 20) DSCOVR mission releases first EPIC global view of Earth, more to come in September. Accessed July 20, 2015.
- The White House (2015, July 20) A New Blue Marble. Accessed July 20, 2015.
Image courtesy of the DSCOVR EPIC team. Caption by Rob Gutro and Adam Voiland. | 0.857226 | 3.337449 |
It has long been hypothesized that comets are one of the main carriers of DNA/RNA and complex molecules of life inside the Solar System.
Surely 67P/Rosetta offers an important opportunity that ESA must seize – and on THIS mission! NOT on a new mission sometime in the future.
When Chandra Wickramasinghe attended early design meetings on Rosetta as a principal investigator, it was well known that he brought the view that “life detection” experiments should be carried on each of the two parts of the spacecraft.
But in those days, just 13 years ago, the field of astrobiology was of limited respectability to the astronomers, geologists, chemists and physicists who dominated the focus of the early team.
Since the 2013 consciousness change with the Kepler Mission breakthrough discoveries and announcements, current probabilities calculate that every star in the galaxy most likely has at least one exoplanet and perhaps a large number have an exoplanet in their “Goldilocks zone”.
This was strong evidence for the “life is a cosmic phenomenon” philosophy of Hoyle and Wickramasinghe. NASA astrobiologist Dr. Chris McKay, is often heard confirming his adoption of this theory.
So have the local Panspermia processes already seeded most of the inner Solar System with desiccated viruses, bacteria and algae?
I believe so.
As for “contamination by humans”, we know over 500 different species of bacteria can be found in a healthy human mouth, with at least ten times that many viruses. An experiment with a probiotic yoghurt counted the number of bacteria exchanged in a 10 second “intimate” kiss – and found a whopping 80 million passed from tongue to tongue.
If that surprises you, did you know every whale on the planet excretes 1013 viruses per day in their feces.
No wonder the Space Station is considered contaminated. MARS itself has likely already been contaminated, even without humans taking our biome with us there on manned landings.
Dr. Chris McKay talks about asteroid collisions causing the ejection of microbes from a given planet with the possible transfer of life planet to planet, comet to planet. McKay is guiding us to learn that “the theory of Panspermia” is the best current guess for NASA’s short and long term planning.
This is the reason that “Seeking the Signs of Life” is “Difficult”, because not only are viruses very small and hard to remotely detect and classify, but even the larger particles such as bacteria and algae (diatoms) have similar (if not quite as challenging) difficulties.
At the Astrobiology conference in Sri Lanka last week, I talked with Professor Milton Wainwright, the biologist from Sheffield University in the UK. I was struck by his reaction when I pointed out new lens-free microscope technology which offers real-time bio-imaging (from a small and light device) which could allow much easier detection of viruses.
“Our tests in the stratosphere have been focused on larger particles typically algae (aka plankton; diatoms). The benefit of our focusing on these larger-sized particles has been that they are much less likely to have been lifted from the surface of Earth. Plus the particles we are finding are spectacularly interesting”, Professor Milton Wainwright .
But comets as carriers? Many of us will recall reading that Sir Arthur C. Clark was most impressed with the Hoyle-Wickramasinghe Model but cautioned us that we would have to wait for the return of the short-period comet, Halley, in 2061, to confirm the theory.
Little did Clark know how quickly humans would be able to dance around the solar system jumping from one comet to another, taking samples and transmitting the results back to our control centres on Earth!
Chandra left the Rosetta team in frustration, around 2002, saddened that his advice seemed to have been ignored. But it now seems that many quietly heeded his input and raised their game. So we actually have a very sophisticated set of “seeds of life” detection instruments on Rosetta and Philae.
We do NOT have an instrument that actually detects a “moving” microbe. At least this is not overtly stated (MIDAS is very close). But the experiments on Philae and Rosetta together detect almost everything else you might wish to seek.
Chandra has been particularly intrigued with the MIDAS experiment which is operating at the virus–size level. It might not be able to deliver conclusive proof of microbes on this voyage, but this technology augurs well for the next comet visit.
Long Period Comets
My own particular request is for us to visit a long-period comet –similar to ISON 2 years ago. Unlike 67P, which orbits over just 8 years and in the plane of the Galaxy, the long-period comets have orbits of over 100,000 years and might well come in from adjacent stars. They also come in at a steep angle to the plane of the Galaxy.
The Solar System is at an angle to the plane of the galactic disk. This is almost certainly because the Solar system is not from the Milky Way. Rather it is now believed to be part of the Sagittarius Galaxy passing through the Milky Way. I believe the long period comets, if they come in from an adjacent star, or even from the Oort Cloud, can come in at any angle to the ecliptic – ie to the plane of the solar system. Whereas short period comets are always IN the plane of the solar system.
Typically the bulk of the long period comets, have been moving in the plane of the Milky Way (at the constant angle to the solar system). So they usually come in at a steep angle.
I believe it is highly likely we will confirm life in the short period comets – as Hoyle and Wickramasinghe predicted. But finding life in a long-period comet would be even more significant, as this would be life not just from another star system but even from another galaxy – the Milky Way.
According to Wickramasinghe’s predictions, the whole Galaxy is a homogenized life pool, so it would be an exciting experiment to seek and discover life in a long-period comet, and to compare any of its RNA/DNA with our known Solar System RNA/DNA. Although we might predict differences in the life-form roots from the two separate galaxies, the inter-galactic contamination has been going on for a very long time, so it is unlikely there is any major differences between life in the two galaxies.
I have recently learned much about the iBOL Project (International Barcode of Life – DNA classification project) and believe this will become very important. I will cover this in my next “Letter from Canada”.
At AbReCon 2015
Astrobiology Research Conference
University of Peradeniya, Sri Lanka
21-23 August 2015 | 0.911335 | 3.317952 |
NASA scientists have announced that they have contacted Pioneer 10, the plucky small spacecraft launched 29 years ago, ending speculation that its signal had finally fallen silent.
In a test of communication technologies for future interstellar missions, scientists operating a radio telescope antenna in Madrid, Spain established contact with the small spacecraft on Saturday, April 28, 2001 at 10:27 a.m. PDT (GMT 17:27:30). It was the first time the spacecraft had been heard since August of 2000.
"Pioneer 10 lives on," declared Pioneer 10 Project Manager Dr. Larry Lasher of NASA Ames Research Center, Moffett Field, CA. "The fact that we can still stay connected with the spacecraft is fantastic. We are overjoyed," Lasher added.
"We have been listening for the Pioneer 10 signal in a one-way downlink non-coherent transmission mode since last summer with no success," Lasher said. "We therefore concluded that in order for Pioneer 10 to talk to us, we need to talk to it." A signal was sent to the spacecraft, which locked onto it and returned a signal to the Madrid facility.
Pioneer 10 lives on. The fact that we can still stay connected with the spacecraft is fantastic. We are overjoyed.
Now orbiting 7 billion miles from Earth, well outside the solar system, Pioneer 10 was launched on March 2, 1972. Pioneer 10 was the first spacecraft to pass through the asteroid belt and the first to obtain close-up images of Jupiter. During the passage by Jupiter, Pioneer 10 also charted Jupiter's intense radiation belts, located the planet's magnetic field, and discovered that Jupiter is predominantly a liquid planet.
Following its encounter with Jupiter, Pioneer 10 explored the outer regions of the solar system, studying energetic particles from the sun, and cosmic rays entering our portion of the Milky Way. In 1983, it became the first man-made object to leave the solar system when it passed the orbit of distant Pluto. The spacecraft continued to make valuable scientific investigations in the outer regions of our solar system until its mission ended on March 31, 1997. When the mission formally ended, Pioneer 10 was at a distance of 6.28 billion miles (10.10 billion km) from Earth.
At that distance, it took over 9 hours 43 minutes for the radio signal (traveling at the speed of light) to reach Earth.
Pioneer 10 carries the now-famous gold plaque with an image of a man and a woman and goodwill information about Earth.
Pioneer 10 is currently 7.29 billion miles from Earth, traveling at 27,830 miles per hour, relative to the sun. At that distance, the signals take 21 hours 45 minutes to make the round trip between Earth and the spacecraft. Pioneer 10's weak signal continues to be tracked by the Deep Space Network as it heads toward the constellation Taurus, where it will pass the nearest star in about 2 million years. | 0.87831 | 3.040387 |
Life on the International Space Station is luxurious. Its living accommodation is spacious, with two bathrooms, two toilets and a gym. There’s also Wi-Fi, DVDs, musical instruments, even fresh fruit on a good day. Some occupants even have enough leisure time to film themselves performing David Bowie tunes.
The first US space station was rather more basic. Forty years ago this month, Skylab took off aboard a Saturn V rocket from the Kennedy Space Centre in Florida. It was a bridging mission by NASA, intended to fill the gap between the Apollo moon landings and the Space Shuttle yet to come. With only one window, drinking water that made the astronauts fart, bland food, and an on-board excrement store (for scientific purposes), it was like a garden shed to the ISS’s Taj Mahal. But, garden shed or not, Skylab was home to nine astronauts in 1973 and 1974.
Back in 1973, nobody was even sure that humans could live and work in space for an extended period. By the end of that year, the station crews had racked up more hours in space than all the world’s previous missions put together, and NASA had learned a lot about how weightlessness affected human physiology.
Being in orbit, Skylab was constantly in free fall around Earth, circling at more than 25,000 kilometres an hour. The astronauts found they soon got used to the feeling, though, reporting that, bar the initial motion sickness, life was pretty normal. It was harder to adjust when coming back to terra firma. After months in space, the body’s muscles waste and so the astronauts had difficulty walking.
The most frequent problem for returning astronauts was that they had picked up bad habits. In zero gravity there was no problem if they just let go of an object – it would float off. When they returned to Earth, such an attitude resulted in a few breakages.
Skylab’s crews collected their own excretions for good reason: they brought them back to Earth so doctors could study how bodily processes change in space. Among other things, they found that peristalsis – the movement of food through the digestive tract – slowed, although not to a degree hazardous to health.
Perhaps the quirkiest thing we learned is that under weightless conditions, astronauts don’t get dizzy when spun around. A seat, looking much like a dentist’s chair, on board Skylab was used to spin astronauts at speed while their reactions were monitored, leading to the discovery that the inner ear needs gravity to register dizziness.
Skylab also served as the greatest solar observatory of its time, a microgravity lab, and an Earth and environment-observing facility. Yet despite all the sophistication of the labs, some of the more childish experiments proved to be the most repeated. Letting a blob of water float around the station until it struck another astronaut in the face proved to be inordinately popular. But such lessons guided future space station design, including both the Russian Mir station and the ISS. Skylab revealed the most useful places to put footholds and handles, the benefits of using Velcro in space, and the need for padded areas to avoid harm from astronauts or their instruments banging into surfaces. It also pioneered the use of zero-gravity showers, vital when you are cooped up with other humans.
These insights were hard won. The mission was fraught with trouble from the start, when Skylab’s meteoroid shield was accidentally deployed just after launch. It ripped away, damaging the onboard workshop’s solar array. Solutions had to be found before astronauts could visit the station and, once aboard, the first crew spent much of the time on DIY fixes, including deploying a makeshift parasol to reduce solar heating. A leak in one of the engines even had the second crew on the verge of an emergency rescue until they thought up another ad hoc fix at the eleventh hour.
NASA had intended crews to continue to use Skylab after the launch of the shuttle programme, after which it was to be boosted into a higher orbit. This never came to pass, in part because intense solar activity made the atmosphere more dense where Skylab was in orbit, causing the orbit to degrade. Skylab eventually met an undignified end, burning up over the Indian Ocean and Australia in July 1979. But the trail the world’s first space station blazed is what made the ISS possible today.
Skylab toilets, kitchens, food stations, labs, along with everyday objects such as scissors, games and toilet paper are all on show at the National Air and Space Museum in Washington DC, which has an unflown backup of Skylab’s orbital workshop
More on these topics: | 0.843108 | 3.358773 |
youtsumi*hiroshima-u.ac.jp (Please change * into @)
A research group led by Hiroshima University has revealed a picture of the increasing fraction of massive star-forming galaxies in the distant universe. Massive star-forming galaxies in the distant universe, about 5 billion years ago, trace large structure in the universe. In the nearby universe, about 3 billion years ago, massive star-forming galaxies are not apparent. This change in the way star-forming galaxies trace the matter distribution in two different kinds of maps is consistent with the picture of galaxy evolution established by other independent studies.
Galaxies in the universe trace patterns on very large scales; there are large empty regions and dense regions where the galaxies are. This distribution is called the cosmic web. The most massive concentrations of galaxies are clusters. The formation of the cosmic web is governed by the action of gravity on the invisible mysterious "dark matter". The normal baryonic material we can see falls into the dark matter halos and forms stars. The action of gravity over the fourteen billion year history of the universe makes the halos cluster together. The location of clusters in this enormous cosmic web tests our understanding of the way structure forms in the universe.
Increasingly deeper and more extensive observations with telescopes like Subaru provide a clearer and clearer picture of the way galaxies evolve within the cosmic web. Of course, we cannot see the dark matter directly. We can use the galaxies we see to trace the dark matter. We can also use the way the gravity of clusters of galaxies distort more distant background galaxies, weak gravitational lensing, as another tracer.
The Hiroshima group combined these two tracers, galaxies and their weak lensing signal to map the changing role of massive star-forming galaxies as the universe evolves.
Weak lensing is powerful technique for mapping the changing contribution of star-forming galaxies as tracers of the cosmic web. A massive cluster of galaxies distorts the shapes of background galaxies behind of the cluster. The cluster acts as a gravitational lens and the phenomenon is called "weak lensing". The distortions of the background galaxies provide a 2D image of the foreground dark matter distribution that acts as a huge lens. The excellent imaging of the Subaru telescope covering large regions of the sky are exactly the data needed to construct the weak lensing maps.
Dr. Yousuke Utsumi, a member of Hyper Suprime-Cam builders and a project assistant professor at Hiroshima University, conducted a 1 hour observation with Hyper Suprime-Cam of a 4deg2 patch of sky at Cancer. Figure 1 shows a close-up view of a cluster of galaxies with the weak lensing map. The highest peaks in the maps correspond the foreground massive clusters of galaxies.
To map the 3D distribution of the foreground galaxies spectrographs on large telescopes like the 6.5-meter MMT disperse the light with a grating. The expansion of the universe shifts the light to the red and by measuring this shift we measure the distances to the galaxies. Using spectroscopy places the galaxies in the cosmic web. The observations locate star-forming galaxies and those that are no longer forming stars.
Collaborators led by Dr. Margaret Geller (Harvard-Smithsonian Center for Astrophysics) conducted spectroscopic measurements for galaxies. The Hectospec instrument on the MMT enables measurements of redshifts for 250 galaxies at a time. The survey contains measurements for 12,000 galaxies.
The MMT redshift survey provides the map for the way all types of galaxies might contribute to the weak lensing map. Because the MMT survey provides distances to the galaxies, slices of the map at different distances corresponding to different epochs in the history of the universe can also be made and compared with the lensing map.
The MMT survey provides a predicted map of the cosmic web based on the 3D positions of galaxies. We can compare this map with the weak lensing map to discover the similarities. Figure 2 shows that both the highest peak and the largest empty regions are similar in the two maps. In other words the matter distribution traced by the foreground galaxies and the distribution traced by the Subaru weak lensing map are similar; we have two complementary views of the cosmic web in this patch of the universe.
If we slice up the 3D map in different redshift or time slices, we can examine the way the correspondence between these maps and the weak lensing map changes for different slices (Figure 3). Remarkably, the distribution of star-forming galaxies around a cluster of galaxies in the more distant universe (5 billion years ago) corresponds much more closely with the weak lensing map than a slice of the more nearby universe (3 billion years ago). In other words, the contribution of star-forming galaxies to the cosmic web becomes prominent in a distant universe. These maps are the first demonstration of this effect in the weak lensing signal (Figure 4)
We provide a new window on galaxy evolution by comparing the 3D galaxy distribution mapped with a redshift survey including star-forming galaxies to a weak lensing map based on Subaru imaging. Dr. Utsumi says "It turns out that the contribution of star-forming galaxies as tracers of the mass distribution in the distant universe is not negligible. The HSC weak lensing map should contain signals from more distant galaxies in the 8 billion year old universe. Deeper redshift surveys combined with similar weak lensing maps should reveal an even greater contribution of star-forming galaxies as tracers of the matter distribution in this higher redshift range. Using the next generation spectrograph for the Subaru telescope, Prime Focus Spectrograph (PFS), we hope to extend our maps to the interesting era."
This research is published in the Astrophysical Journal in its December 14, 2016 on-line version and December 20, 2016 in the printed version, Volume 833, Number 2. The title of the paper is "A weak lensing view of the downsizing of star-forming galaxies" by Y. Utsumi et al., which is also available in preprint from arXiv:1606.07439v2. This work is supported by a JSPS Grant-in-Aid for Young Scientists (B) (JP26800103) and a MEXT Grant-in-Aid for Scientific Research on Innovative Areas (JP24103003).
Figure 1. A close-up view of a cluster of galaxies observed with HSC (i-band as Red) and the Kitt-Peak Mayall 4-m telescope (R-band as Green, V band as Blue).
Figure 2. The weak lensing map (left) and the map revealed by galaxy distribution (right).
Figure 3. The distribution of galaxies in the 3D redshift survey. Red points represent quiescent galaxies and blue points are star-forming galaxies. The size of a point reflects the mass of the galaxy. Boxes in the cone are 3 and 5 billion light years from us (left bottom). The maps next to the boxes show the mass distribution constructed from the redshift survey.
Figure 4. Close-ups of the weak lensing map and the predicted maps from the redshift survey for quiescent galaxies and star-forming galaxies. The upper panels are a picture of the region 3 billion years ago and lower panels show the picture 5 billion years ago. Three billion years ago, it is hard to see any similarity between the predicted map for star-forming galaxies and the weak lensing map, but there is much greater similarity in the maps 5 billion years ago.
Authors: Yousuke Utsumi, Margaret J. Geller, Ian P. Dell'Antonio, Yukiko Kamata, Satoshi Kawanomoto, Michitaro Koike, Yutaka Komiyama, Shintaro Koshida, Sogo Mineo, Satoshi Miyazaki, Jyunya Sakurai, Philip J. Tait, Tsuyoshi Terai, Daigo Tomono, Tomonori Usuda, Yoshihiko Yamada, Harus J. Zahid
Title: A weak lensing view of the downsizing of star-forming galaxies
Journal: The Astrophysical Journal, Volume 833, Number 2 (December, 2016)
Assistant Professor (Special Appointment)
Hiroshima Astrophysical Science Center | 0.853466 | 4.122812 |
Top 10 universe factsUniverse quiz
What are the most luminous objects in the universe?
Quasars. A quasar is an extremely energetic source of radiation powered by accretion disc around galaxy's central supermassive black hole. Quasars were much more common in the early universe, as all known quasars are extremely distant.
What is the source of the most powerful release of energy in the universe, second in scale only to the Big Bang?
Gamma-ray bursts are the brightest in the universe, even brighter than the glare of quasars, second only to the brightness and power of the Big Bang. It is believed that arise during disruption of stars by black holes.
What was the object that collided with Earth, according to the giant-impact hypothesis?
A planet. According to the giant impact hypothesis Earth once collided with a planet of Mars size usually referred to as Theia, a titaness of Greek mythology, mother of Selene - Moon goddess, which is to reflect the believe the collision was an origin of the Moon.
What was the most beautiful comet of the second half of the twentieth century, with two tails visible to the naked eye?
Comet Hale-Bopp. Hale–Bopp was discovered on July 23, 1995 separately by Alan Hale and Thomas Bopp prior to it becoming naked-eye visible on Earth. Comet Hale-Boppit was visible to the naked eye for a record 18 months, twice as long as the previous record holder, the Great Comet of 1811. Accordingly, Hale–Bopp was dubbed the Great Comet of 1997.
What properties do sunspots have?
Lower temperature and strong magnetic field. Sunspots are temporary phenomena on the Sun's photosphere that appear as spots darker than the surrounding areas. They are regions of reduced surface temperature caused by concentrations of magnetic field flux that inhibit convection.
Which of the constellations is the largest?
Hydra is the largest of the 88 modern constellations, measuring 1303 square degrees. Also one of the longest at over 100 degrees, It has a long history, having been included among the 48 constellations listed by the 2nd century astronomer Ptolemy. It is commonly represented as a water snake.
The celestial sphere is divided into ...
88 constellations. The current list of 88 constellations recognized by the International Astronomical Union since 1922 is based on the 48 listed by Ptolemy in his Almagest in the 2nd century, with early modern modifications and additions In 1930, the boundaries between the 88 constellations were devised by Eugène Delporte along vertical and horizontal lines of right ascension and declination.
Which of the following cosmic structures is the largest?
Galaxy filaments are the largest known structures in the universe. They group galaxy superclusters, which in turn are formed by cluster composed of galaxies. Hercules–Corona Borealis Great Wall is considered the largest known structure of Universe. It is estimated to span 10 billions light years.
What are the Perseids meteor showers associated with?
Comet Swift–Tuttle. In 1866, after the perihelion passage of Swift-Tuttle in 1862, the Italian astronomer Giovanni Virginio Schiaparelli discovered the link between meteor showers and comets. His findings put new light on a subject, and changed the approach of astronomers to comets. | 0.873036 | 3.512909 |
Instruments & Techniques for Space Weather Measurements
Scientists use a broad array of techniques and instruments to make the measurements needed for space weather investigations.
Telescopic observations via spacecraft and ground-based observatories provide us with spectacular images of the Sun and the solar atmosphere. These observations are not confined to visible light, but range across the electromagnetic spectrum from radio wave and infrared (IR) images to ultraviolet (UV) and X-ray views. A technique called helioseismology allows us to probe the Sun's interior by watching pressure waves ripple across the photosphere. Coronagraphs create artificial eclipses which give us great views of the Sun's atmosphere. Spectroscopy allows us to study the elemental composition of the Sun and provides information about temperature and magnetic field strength.
The Sun emits various types of electromagnetic radiation and subatomic particles. Some types generate secondary cascades of particles when they crash into the gases in Earth's atmosphere. Radiation sensors, plasma wave detectors, and similar instruments on spacecraft and the ground measure the flux of protons, electrons, ions, neutrinos, and other types of radiation.
Optical techniques, broadly defined to include IR and UV "light", also aid studies of near-Earth "geospace". Images and spectroscopic studies help us understand the auroras, while extreme UV images from satellites reveal the structure of Earth's plasmasphere.
Techniques and instruments employing radio waves help us probe the electrically charged layers of Earth's atmosphere collectively referred to as the ionosphere. Radars and antenna arrays called riometers allow us to determine which radio waves pass through, get absorbed by, and bounce off specific layers of the ionosphere.
Magnetometers detect the orientation and measure the strength of magnetic fields. A network of ground-based magnetometers tracks Earth's magnetic field. Magnetometers aboard orbiting satellites monitor magnetic fields in near-Earth space; magnetometers on interplanetary spacecraft measure fields in deep space. | 0.815622 | 3.576482 |
We can advance the frontiers of physics by observations of the extremes. Fast radio transients, with timescales typically less than a second, are likely associated with the extremes of energy, magnetic field strength, gravity and density. These sources provide a unique laboratory with which to probe physical regimes well beyond those achievable in any terrestrial experiment. Located at extragalactic distances, they can be used as probes of the content of the intergalactic medium (IGM) and the nature of the missing baryons. Moreover, if they can be shown to be standard candles, then they will be useful additional components of the distance ladder reaching out to redshifts up to 2 and perhaps beyond. We are only just scratching the surface in terms of our understanding of the fast radio transient sky, and so we are also exploring the unknown.
Detecting fast radio transients is extremely challenging; their sporadic nature requires either vast amounts of observing time and/or wider fields of view to catch them. The known sources already span a range of durations from nanoseconds, e.g. giant pulses from the Crab pulsar, to seconds, e.g the Galactic centre transient GCRT J1745-3009. Likewise the luminosity spans 20 orders of magnitude, from Jupiter emission to fast radio bursts (FRBs); however, the majority of the intervening parameter space is unexplored. Other known and proposed sources include: ultra-high-energy particles, annihilating black holes, merging neutron stars, supernovae and gamma-ray bursts, flare stars, planets (solar and extra-solar), neutron stars (intermittent pulsars/magnetars/RRATs), extra-terrestrial intelligence and things that have not yet even been thought of!
We can summarise the goals of MeerTRAP as being:
Goal 1: The bursting sky
Goal 2: The periodic sky
Discover radio pulsars over an unprecedented range of parameter space by covering: variability on timescales from days to years, luminosity, spectral index, binarity, and multiple systems. This will give us the most comprehensive view yet of the radio emitting neutron star population with the implications this has for star formation history, binary evolution, and neutron star merger rates. It will reveal individual systems that can be used to test gravitational theories, probe the equation of state of ultra-dense matter, and enable the direct detection of nano-hertz gravitational waves. | 0.849186 | 4.046336 |
There are just three moons in our solar system that measure more than 5,000km across. Of these, Jupiter’s moons Ganymede and Callisto are airless and have ancient heavily cratered surfaces. But Saturn’s largest moon, Titan, abounds in landscapes that are eerily Earth-like – and it may even harbour life.
But we have had a rather limited view of what’s lurking beneath the thick atmosphere of this mysterious world. A new study, published in Nature Astronomy, however, unveils the first geomorphologic map to cover the whole of Titan. This is important because it shows how Titan’s various kinds of terrain relate to each other.
Despite the fact that Titan’s “bedrock” is ice, its surface is so cold (-180°C) that the ice is sufficiently strong and rigid to behave just like rock on Earth. Furthermore, Titan is the only moon with a dense atmosphere, having a surface pressure that is one and a half times that of Earth’s.
In common with Earth, by far the most abundant atmospheric gas on Titan is nitrogen. The moon’s second most abundant gas is methane, which makes Titan Earth-like in a different but very remarkable way. The gaseous methane can condense to form clouds from which droplets of liquid methane can fall like rain. Methane rainfall erodes the surface, carves out channels, and drains into depressions to form methane seas and lakes. Evaporation back into the atmosphere completes the cycle, so Titan has a methane cycle to match Earth’s water cycle.
Despite two Titan flybys by NASA’s Voyager probes in 1980 and 1981, we knew little about the moon’s surface until the Cassini spacecraft arrived to orbit Saturn between 2005 and 2017. This is because sunlight causes the molecules of methane high in Titan’s atmosphere to link into larger molecules, making a high-altitude smog that the Voyager cameras could not see through.
But Cassini was equipped to cope with this, carrying an imaging radar system and near-infrared and thermal infrared cameras that could detect radiation reflected or emitted from the ground in specific wavelengths that the smog does little to obstruct. Cassini also sent a lander called Huygens down to the surface by parachute, giving us unimpeded visual views from below the clouds – albeit of only a small area.
The most detailed images to inform the new geological map come from the radar. These cover slightly less than half the globe so, to achieve global coverage, other Cassini data had to be used to fill in the gaps.
Six major units are on the global map, depicted at a scale of 1:20 million. Plains make up 65% of the globe, these are smooth and dark, possibly because of smog-derived sooty particles on the ground. In a belt hugging the equator, the plains are overlaid by extensive fields of dunes (17% of the globe by area), sculpted by winds that blow from west to east.
These dunes are not sand grains made of quartz as they would be on Earth, nor grains of water ice, but particles made from organic molecules that presumably originated from the atmosphere in the same way as the dark colouring of the plains (derived from smog).
Exposed icy bedrock is apparent in places where neither plains nor dunes have covered it. This is divided into a “hummocky” unit (14% of the globe) characterised by hilly and mountainous ground. There are some branching valleys here (including some seen by the Huygens lander), but such valleys are more extensively developed in a unit named “labyrinth” (1.5% of the globe), which is perhaps ice mixed with organic material that has been more strongly cut by methane rivers.
Impact craters occupy just 0.4% of the globe, and there are only 23 that are more than 20km in diameter. Their scarcity attests to Titan’s active geology – erosion of high ground, burial under sediments, and possibly erasure by volcanism (spewing out ice instead of molten rock).
Titan’s polar regions contain over 650 lakes or seas covering 1.5% of the total surface area. Some are currently dry, but many are filled by liquid methane. Parts of the shoreline of the second largest lake, named Ligeia Mare, which is 400km across and up to 170 metres deep, have an odd shape suggesting that either the lake level has risen, or that parts of the land surface have sunk due to tectonic forces. Elsewhere, and on other lakes, there are shoreline features suggestive of wave action and river deltas.
If Titan is home to any microbial life, this is much more likely to be in Titan’s water ocean deep in its interior, rather than at the surface. But understanding the distribution of landscapes documented in the global map is a vital step towards understanding the environments and history of this amazing world. | 0.86108 | 3.949737 |
Our place in the universe
Seeking Answers to the Big Questions
Finding answers to questions about our origins, using those answers to further understand this big, beautiful planet, its past, present and future; that's the business we are in. Tracking the data, sharing that knowledge, and helping others to also explore our place in the universe is what makes any academic pursuit worthwhile.
Exploring our Origins
Feathered dinosaurs, meteorite discoveries, cosmic rays, the atmosphere and other phenomena. Partnering with other institutes, universities and governments help make the journey of discovery possible.
SULPHUR MOUNTAIN COSMIC RAY RESEARCH STATION ESTABLISHED
The first meteorological station on Sulphur Mountain was built in 1902 and consisted of a twelve-foot square stone hut. For the next 30 years, Mr. Norman Sanson climbed the peak every week or fortnight to replace the recorder charts; in winter the journey could take up to 9 hours on snowshoes.
The Cosmic Ray Station was built in the winter of 1956-57 as part of Canada’s contribution to the International Geophysical Year (1957-58). Cosmic rays intensify at the geomagnetic pole and are easier to track at higher elevations; the monitor on Sulphur Mountain was among the most sensitive in the world.
The Cosmic Ray Station became operable in late spring 1957 after the hauling and installation of five tons of equipment at the site. Dr. Brian Wilson of the National Research Council was appointed Office-in-Charge; his initial research trip was extended by a week at the station after he came down with the chicken pox.
The Station was part of a world-wide network of cosmic ray monitors; the data received and recorded was invaluable in the furthering of our understanding of space. Research at Sulphur Mountain included measuring cosmic ray intensity variations and interactions, properties of extensive air showers, solar flares and the study of auroral emissions. In an era before long-term space probes were viable, the study of cosmic rays was our window to interplanetary space.
The Cosmic Ray Station was closed and the building was dismantled in 1981. The university initiated proceedings to officially recognize the Station’s valuable contributions to international science; a National Historic Site plaque was placed on Sulphur Mountain in 1984.
SPUTNIK I LAUNCHED
The Space Race begins and an emphasis on science education.
RESEARCH ROCKET LAUNCHED
Dr. Baxter, Dr. Will, Dennis Green, Charles Hansen and William Jones of the Physics Department, complete a successful probe in the third series of X-ray research rocket fringes from Resolute Bay, NWT. Their Black Bryant III rocket is sent 100 miles (160 km) into the upper atmosphere.
UNPRECEDENTED ARCHAELOGICAL FIND
Bison butchering site with 7,000-year-old bones and tools is dug up by construction workers. Archaeology Department faculty and students describe it as the first good archaeological find in Calgary.
APOLLO 11 MOON LANDING
Dr. Gordon W. Hodgson, Exobiologist (study of extraterrestrial life) awaits samples of the moon gathered on Apollo 15 mission. Hodgson becomes a principal investigator of Apollo moon samples.
AURORAL IMAGES CAPTURED
UCalgary helps capture the first global auroral images from space.
ASTROPHYSICAL OBSERVATORY OPENS
Originally called the University of Calgary Astrophysical Observatory, the facility is later renamed the Rothney Astrophysical Observatory after Alexander Rothney (Sandy) Cross, who donated the land for the observatory. His father was A.E. Cross, one of the Big Four ranchers who backed the 1912 Calgary Stampede
SPACE SCIENCE RESEARCH GROUP ESTABLISHED
Later named the Institute for Space Imaging Science in the '90s.
COSMIC RAY STATION CLOSES AS RESEARCH BECOMES OBSOLETE
The National Research Council established a Cosmic Ray Laboratory on Sulphur Mountain—one of three in Canada. The research into cosmic rays has matured and become obsolete and the Sulphur Mountain lab was closed, however the data gathered over the 32 years in operation is invaluable to this day.
Cairn erected by Surveying Engineering to commemorate the 1987 Canadian Engineering Centennial. It is the most precisely measured place in Canada at LSD 14 30-24-1 W5, 115.4 m above sea level, 6,366,344 metres from the centre of the earth, 384,400 kilometres from the moon and 149,600,000 kilometres from the sun.
HUB OF EXPLORATION
Institute for Space Research established. UCalgary named headquarters of Canadian Network for Space Research.
RESEARCH ABOARD SPACE SHUTTLE COLUMBIA MISSION
NASA space shuttle Columbia blasts off carrying a UCalgary science experiment to determine how much energy astronauts use when they are in space. Mechanical engineering grad, Laura Lucier, and 2004 Distinguished Alumni award recipient, worked at NASA’s Johnson Space Centre as flight controller during the Discovery mission.
CHANCELLOR ROBERT THIRSK IN SPACE
His first trip into space was aboard Columbia on which Thirsk and six crewmates performed 43 experiments related to life and materials sciences.
MARTIAN PROBE SENT INTO SPACE
The design of an atmospheric probe, called a Thermo-Plasma Analyzer (TPA), led by physics and astronomy professors Greg Garbe and Andrew Yau, was successfully launched on the Japanese spacecraft Planet-B. The probe remained in orbit for three years to survey Mars.
ARABIAN DESERT SURRENDERS QUEEN OF SHEBA'S SECRETS
3,000-year-old temple opens a new door to Arabia's ancient civilizations
Researchers from the University of Calgary are participating in an American Foundation for the Study of Man project to unlock the secrets of a 3,000-year-old temple in Yemen. Archaeologists believe the temple could prove as significant a discovery as the ruins of Pompeii, the pyramids of Giza, or the Acropolis of Athens.
The Mahram Bilqis - pronounced Mah-ram Bill-kees (or Temple of the Moon God) lies buried under the sands of the southern Arabian Desert in northern Yemen and is believed to have been used throughout the reign of the legendary Queen of Sheba. According to University of Calgary archaeology professor Dr. Bill Glanzman, the project's field director, the sanctuary was a sacred site for pilgrims throughout Arabia from about 1200 B.C. to 550 A.D.
Eight limestone pillars remain standing at the front of the temple, half-buried by the desert sands. Behind the site's peristyle hall, a wall of heavy limestone blocks (around 3.5 metres thick), covered in ancient inscriptions, surround the sanctuary. While the top six metres of the wall are exposed, sub-surface surveys of the area indicate the temple's foundations still lie 9–10 metres below the sands. Glanzman estimates it will take another 2–3 years before the excavation of the walls is completed.
Despite the team using state-of-the-art equipment, the excavation and documentation of the site remains a slow process, with the work frequently being hampered by sand storms and blistering heat.
While excavating, researchers have discovered large quantities of animal bones at the site, suggesting the sanctuary was used for animal sacrifices. Samples of these bones have been brought back to the UCalgary for DNA analysis and for comparison with the skeletons of modern species.
Once the site has been excavated, Glanzman says the team plans to restore and reconstruct sections of the temple to show visitors how they believe it looked during its last period of use in the 6th Century.
"The ancient builders of this temple used extremely advanced engineering techniques," says Glanzman. "To reconstruct it, we first have to understand how the original stone masons carved the blocks and then teach the Yemeni masons these skills. We're hoping to rejuvenate crafts and masonry skills that have lain dormant for more than 1,400 years."
Plans have been discussed to retain part of the sanctuary as it was found, giving archaeologists of the future—who will have different methods and more advanced technology—opportunity to work on the site in its original condition.
"In many respects, the Queen of Sheba's kingdom was the cradle of the Arab civilization and the Mahram Bilqis was at the very heart of this kingdom," he says. "This temple may well be considered the eighth wonder of the world."
Archaeologist Brian Kooyman, geologist and paleontologist Len Hills and their research team discover 13,000-year-old tracks of wooly mammoths, camels, horses, bison and caribou in St. Mary’s Reservoir in southern Alberta.
GOING TO GREAT HEIGHTS TO HONOUR ASTRONAUT
Canadian Space Agency astronaut and UCalgary alumnus Robert Thirsk has become the first Canadian to receive an Honorary Doctor of Laws via live downlink from the International Space Station.
GPS TECHNOLOGY HELPS CANADIAN ALPINE SKI TEAM
A little GPS system called STEALTH, developed at the Schulich School of Engineering, has helped the country’s best ski racers perfect their technique and route down a course.
NOW SHOWING: CANADA'S NORTHERN LIGHTS
AuroraMAX online observatory begins streaming Canada’s northern lights live over the Internet every night. AuroraMAX is a collaboration between the Canadian Space Agency, UCalgary, City of Yellowknife and Astronomy North.
WORLD'S BIGGEST RADIO TELESCOPE
Physics professor Russ Taylor appointed to represent Canada in project that will create the world’s biggest radio telescope
Physics professor Russ Taylor is set to play a leading role in a mega-science project that will create the world’s biggest radio telescope, the Square Kilometre Array. Taylor has been appointed to represent Canada on the international SKA Board, the decision-making body for the project, alongside a National Research Council of Canada representative.
"Becoming a member of the international SKA organization means that Canadian researchers and industries can participate in the planning and design of the Square Kilometre Array, and in its eventual construction,” says Taylor, physics professor in the Faculty of Science, chair of the Canadian SKA consortium board and director of the Institute for Space Imaging Science.
As a partner, Canada along with Australia, China, Italy, the United Kingdom, the Netherlands, New Zealand and South Africa will determine the location of the SKA—either Southern Africa or Australia-New Zealand.
"The international partners in SKA are extremely pleased that Canada has now formally joined the project. Our Canadian colleagues bring a history of technical and scientific strengths to the partnership and we very much look forward to working with them to make SKA a reality,” says John Womersley, chair of the International SKA Organization Board.
The university and NRC have for several years been involved in research and development for the SKA. Researchers from the Schulich School of Engineering are working on the design for the receivers that will pick up signals from deep space. Radio astronomers and computer scientists in science faculty are developing information systems for a global network to manage the vast amount of data what will be produced.
Instead of gathering and focusing visible light like optical telescopes, radio telescopes operate in the radio-frequency portion of the electromagnetic spectrum and typically use large, dish-shaped antennas, “seeing” a universe that is invisible to our eyes.
The SKA will be made of thousands of receptors linked together across an area the size of a continent. The total collecting area will be about one square kilometre. The first astronomical observations are expected toward the end of this decade.
The university, through the Institute for Space Imaging Science, will hold a workshop April 27 to develop international linkages and the national collaborations among Canadian industry, government and university research for Canadian participation in the pre-construction phase of the SKA.
COL. CHRIS HADFIELD VISITS CAMPUS
UCalgary hosts astronaut Hadfield for his first public presentation since leaving the International Space Station. Hadfield shared his breath-taking photos and remarkable accounts of his time in space.
FUNDING RECEIVED TO STUDY SPACE STORMS
Christopher Cully, Faculty of Science, will lead a team from UCalgary, University of Washington and Dartmouth College to develop a novel in-flight experiment that will clarify the dynamics of the harsh radiation environment satellites travel through and why the high-energy particles that make up that radiation rain collide with the upper atmosphere.
SPACE FLIGHT BONE LOSS STUDY
Radiologist Dr. Steven Boyd, will lead one of four experiments conducted by Canadian universities. His project, dubbed “TBone" to reflect the ‘three-dimensional bone’ techniques used, will investigate the effects of weightlessness on the human body. | 0.89526 | 3.06101 |
You can now build your very own Earth 2.0! A new website allows users to create an Earth-like planet with a wide selection of options in an effort to demonstrate how many of the new exoplanets lauded as "Earth-like" may not resemble our planet at all. The researchers behind this website hope to clear up some of the confusion about what the phrase "Earth-like" really means.
"It is very tempting to think that an Earth-sized planet is like our habitable Earth," Kana Ishimaru, a graduate student at the University of Arizona, told Space.com in an email. "But changing only one property of the planet can affect the environment significantly."
Ishimaru lead the development of the website "Earth-like" and the Twitterbot of the same name while she was an undergraduate student at the University of Tokyo. Within the website, users can manipulate factors including the land-fraction and volcanism of the planet and where it lies within the habitable zone, the distance from a star where liquid water can remain on the surface. These small shifts can dramatically affect the environments on the surface of a planet.
Between the thousands of exoplanets revealed by NASA's Kepler Space Telescope and the bounty expected by the Transiting Exoplanet Survey Satellite (TESS), along with worlds clarified with other instruments, many planets whose size and mass are similar to Earth have been publicly heralded as "Earth-like."
But a variety of factors could mean that those worlds are as different from Earth as Venus, a solar system world often heralded as Earth's twin that is at times hot enough to melt lead. Ishimaru's advisor, Elizabeth Tasker, worried that these planets were too-often viewed as true Earth twins, identical to our own world in their ability to allow life to evolve, when in fact they are likely to be dramatically different. With this in mind, she set off to build a website where anyone could probe how small changes in planetary conditions could change its habitability.
"Given we currently know the radius or mass [or both] for most of the Earth-sized exoplanets we've discovered, their surfaces could be wildly different from our own home world," Tasker said in an email to Space.com.
The journey of our generation
Planetary scientists have a wealth of models that they can tweak to demonstrate the effect of several different conditions on a planet all at once. By adjusting a variety of inputs, researchers can get a better handle on what kind of conditions are most likely to prevail on far-away planets. But most of these models are very computationally intensive, beyond what a regular space fan can run on their home computers. And they are rarely user friendly, Tasker added.
Instead, she turned her eyes toward a few key elements of planetary conditions that impact the carbon cycle, which moves carbon from Earth's atmosphere to its rocks and back again. Carbon helps to regulate the planet's temperature and makes life as we know it possible.
On Earth, most carbon is stored in rocks and sediments, the ocean and the atmosphere. A gentle rain can kick off the carbon cycle, as atmospheric carbon combines with water that falls to the surface. The resulting acid dissolves rock through chemical weathering to release a variety of ions. These ions are carried to the ocean, where calcium and carbon ions combine to form calcium carbonate. Ocean organisms can also produce calcium carbonate in their shells, which cement together and turn into rock after they die. Plate tectonics can bury one layer of carbon-rich rock beneath another, causing it to melt under extreme heat and pressure and releasing carbon dioxide. Erupting volcanoes carry the carbon gas to the surface and back into the atmosphere, where the cycle starts over again.
By allowing users to fiddle with a world's landmass and volcanism, this website can create dramatic changes in the resulting planets. Additionally, by moving your planet on this website closer to or farther from its star, you can change how much heat hits and heats the world.
"This model makes it really exciting to think about what kind of surface conditions exoplanets can have," Ishimaru said.
In addition to a website, the project also includes a Twitterbot @EarthLikeWorld. Users can interact with the bot by tweeting the land-fraction of a world, its volcanism, and its habitable zone location and it returns a realistic-looking image of a world that meets those qualifications, though it's not likely to be identical to an exoplanet with the same characteristics.
According to Tasker, the hardest part of the website was keeping the code light enough to run on a website. That became most challenging when they added the option to render an image of the supposed planet. The visual image reveals the land and water percentages as a grey color to indicate volcanic mountainous regions and snowy land to demonstrate the surface temperatures. Originally, the images in the website were pixelated, but colleague Nicholas Guttenberg created a neural network that created a realistic-looking landscape based on images from Google-Earth. The images looked "so cool" that Tasker decided to add them to the website as well, Tasker said.
To keep the website from getting bogged down, the initial calculations run separately from the images. The inputs take only a few seconds. Images can be more challenging and can take 10 seconds or longer.
Already the researchers themselves have learned a great deal from the website.
"The biggest surprise I had was how good our carbon cycle is!" Tasker said. She went on to say that the carbon cycle controls the temperature reasonably well as land is increasingly exposed. "While geological cycles are too slow to save us from global warming, they really pull their weight to make the Earth habitable," she said.
In the future, the website might go beyond the most Earth-like models to consider broader changes in the planets, perhaps including other chemical elements or planet sizes. But Tasker worries that such changes might make the site too bulky, increasing runtimes.
"This is the journey of our generation," Tasker said. "In less than 30 years, we've gone from only knowing the planets of our solar system to discovering thousands of other worlds."
Upcoming instruments such as the James Webb Space Telescope and the Extremely Large Telescope will provide even more detail of exoplanets as they allow scientists to probe the atmosphere of these planets and gain a better understanding of their surface conditions.
"It's an incredible journey and one that may change the entire way humans perceive their place in the universe," Tasker said. "I don't understand why anyone would want to deprive someone of traveling that path through meaningless hype."
- The 6 Most Earth-like Alien Planets
- Exoplanet Kepler-452b: Closest Earth Twin in Pictures
- Sweet Super-Puffs: These 2 Exoplanets Have the Density of Cotton Candy
All About Space magazine takes you on an awe-inspiring journey through our solar system and beyond, from the amazing technology and spacecraft that enables humanity to venture into orbit, to the complexities of space science.View Deal | 0.92618 | 3.219431 |
The solar system is a grouping of eight planets and many other objects that are bound together by gravity. At the center of our solar system is a star, the Sun. Our solar system is one of billions in the universe, but is unique in the fact it is the only one we know of that contains life. Each planet has different characteristics that make it uninhabitable for humans, except, of course, Earth.
Our solar system formed 4.6 billion years ago, and at the center of it is the Sun, which is an average-sized star about halfway through its life cycle. It is a near-perfect sphere of plasma that emits radiation due to nuclear fusion reactions taking place. Nearly three-quarters of the Sun’s mass is its main nuclear fuel, hydrogen. The Sun is essential for life on Earth because it provides heat and light energy for green plants to photosynthesize. The Sun accounts for over 99% of the mass in the solar system.
Humans haven’t always been sure about the structure of our universe. Until Galileo Galilei, people thought the structure of our universe was different. Aristotle put forward the idea that the Earth was at the center of our universe, and this proposal is known as the geocentric model. People believed this because the apparent motion of the Moon, the Sun and other celestial bodies seemed to be going around the Earth. Using the newly invented telescope, Galileo observed four objects orbiting around the planet Jupiter and came to the conclusion that the Earth was NOT at the center of the universe. For millennia, we assumed our planet was at the center of everything, which gave Earth a huge amount of importance in the eyes of humans. It turns out our planet is very small and insignificant; one of many, many trillions in the universe.
Scientists have spent a lot of time and resources finding out more about the different planets that make up our solar system. Early exploration was done using telescopes, like William Herschel discovering the planet Uranus in 1781. Telescopes only allow us to understand the other planets with limited detail. It wasn’t until space flight had been refined that we were able to find out detailed information about the other planets of our solar system. Scientists sent man-made spacecraft to orbit and even landed on other planets.
There are eight planets in our solar system. In order from closest to the Sun to furthest away they are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. An easy way to remember the order of the planets is using the mnemonic: My very easy method just speeds up naming.
Note: Pluto was downgraded from a planet to a dwarf planet in 2006 by the International Astronomical Union.
Orbital Period: 88 Earth Days
Length of a Day: 4,222 Earth Hours
Diameter: 4,879 km
Distance from the Sun: 57,900,000 km
Strength of Gravity: 3.7 N/kg
Number of Moons: 0
Mercury is the closest planet to the Sun. The planet is named after the Roman god of commerce, who was known for being very swift. Mercury does not have an atmosphere so it doesn’t retain the heat from the Sun. Temperatures can range from 430 °C (800 °F) during the day and -180 °C (-290 °F) during the night. The first spacecraft to visit mercury was Mariner 10. When it visited, it managed to take pictures of about 45% of Mercury’s surface. The surface of Mercury looks similar to our moon, with lots of large craters from objects impacting the planet.
Orbital Period: 225 Earth Days
Length of a Day: 2,802 Earth Hours
Diameter: 12,104 km
Distance from the Sun: 108,000,000 km
Strength of Gravity: 8.9 N/kg
Number of Moons: 0
Venus is the second planet from the Sun. It is similar in size to the Earth and it also has a similar composition. Like our planet, Venus has a hot iron core surrounded by a mantle. The planet also has a dense atmosphere of gases composed mainly carbon dioxide; these gases can retain a lot of the Sun’s heat, making it the hottest planet in our solar system with an average temperature of 464 °C (867 °F). Venus, named after the Roman goddess of love, has the least elliptical orbit out of all the planets. After our own moon, it is the brightest object in the night sky. Missions to Venus can be difficult due to the extreme temperatures found on the planet’s surface. There have been several unmanned missions to Venus. In 1970, the Soviet Union landed Venera 7, making it the first spacecraft to land on another planet. Between 1990 and 1994, the Magellan mission orbited the planet and managed to image 98% of the planet's surface.
Orbital Period: 365.25 Earth Days (1 Earth Year)
Length of a Day: 24 Hours (1 Earth Day)
Diameter: 12,756 km
Distance from the Sun: 149,600,000 km
Strength of Gravity: 9.8 N/kg
Number of Moons: 1
Our home! Earth is the only planet in the universe we know has life. If other planets have life, we have yet to find it. Earth is the third planet from the Sun and the fifth largest planet.
Orbital Period: 687 Earth Days
Length of a Day: 24.7 Earth Hours
Diameter: 6,792 km
Distance from the Sun: 227,900,000 km
Strength of Gravity: 3.7 N/kg
Number of Moons: 2
Mars is also known as the Red Planet due to the color of its surface. Mars was named after the Roman god of war because people thought the planet was the color of blood. After six US and Soviet attempts, the first successful flyby of Mars was in 1961, when the Mariner 4 spacecraft managed to send back some black and white images to Earth. These images were the first images of another planet taken from space. More recently, NASA managed to successfully land the Curiosity rover to look at the composition of its rocks and atmosphere. Scientists are interested in the possibility of liquid water on Mars and the implications this could have for Martian life. Mars is about half the size of Earth and like our planet, it experiences seasons due to a tilt in its axis. The Martian atmosphere is mainly carbon dioxide (96%) with some argon and nitrogen. Temperatures on the Martian surface vary from lows of -143 °C (-225 °F) at the polar caps and 35 °C (95 °F) on the equator during the summer.
While not a planet, the asteroid belt sits between the orbits of Mars and Jupiter. It is made up of fragments of rock and dust. The largest object in the asteroid belt is Ceres, a dwarf planet, which makes up roughly one third of the total mass of the asteroid belt. The belt is not very densely populated, so spacecraft can easily pass through.
Orbital Period: 4,331 Earth Days
Length of a Day: 9.9 Earth Hours
Diameter: 142,984 km
Distance from the Sun: 778,600,000 km
Strength of Gravity: 23.1 N/kg
Number of Moons: 67
Jupiter is the largest planet in our solar system and also has the largest number of moons. It is the fifth planet from the Sun and the first gas giant. It is known for its stripes and swirls on the surface which are caused by the movement of gases in the Jovian atmosphere. Jupiter only has a small 3° tilt, so it doesn’t really experience seasons as Earth and Mars do. The composition of Jupiter is similar to that of the Sun, made up of mainly hydrogen and helium. In 1610, Galileo made observations of four of Jupiter’s moons, which led to disproving the heliocentric model of the solar system. One of the moons that Galileo observed was Ganymede, the largest moon in the solar system.
Orbital Period: 10,747 Earth Days
Length of a Day: 10.7 Earth Hours
Diameter: 120,536 km
Distance from the Sun: 1,443,500,000 km
Strength of Gravity: 9 N/kg
Number of Moons: 62
Saturn is most famous for its rings made of ice and rocks. Other planets, like Jupiter, also have rings, but none are as impressive as Saturn's. Saturn is another planet that is known as a gas giant due to its size and composition. It is made up of mostly hydrogen and helium. Saturn is the only planet in our solar system that is less dense than water. This means it would float on an ocean (if we could find one big enough)! It is named after the Roman god of agriculture and wealth. Saturn has the solar system’s second largest moon, Titan. Titan is slightly larger than the planet Mercury.
Orbital Period: 30,589 Earth Days
Length of a Day: 17.2 Earth Hours
Diameter: 49,528 km
Distance from the Sun: 2,872,500,000 km
Strength of Gravity: 8.7 N/kg
Number of Moons: 27
Uranus is not only composed of hydrogen and helium, but also ammonia, water, and methane. Its blue color comes from methane in the upper atmosphere that absorbs red light from the Sun, but reflects back the blue light. Uranus has been observed and incorrectly recorded many times as a star or comet. It was first correctly identified as a planet by William Herschel in 1781. Herschel originally wanted to call the planet Georgium Sidus, after the British Monarch King George III, but he wasn’t successful. The planet is named after the Greek god of the sky. It wasn’t until the planet was observed in 1977 that scientists found that Uranus, like Saturn, is surrounded by rings. Uranus is unique in the solar system as its axis is 97° off the vertical, meaning Uranus spins on its side. The first flyby of Uranus was in 1986 when Voyager 2 flew 81,500 km away from the planet.
Orbital Period: 59,800 Earth Days
Length of a Day: 16.1 Earth Hours
Diameter: 49,528 km
Distance from the Sun: 4,495,100,000 km
Strength of Gravity: 11.0 N/kg
Number of Moons: 14
Neptune is invisible to the naked eye and can only be viewed using a telescope. It was first discovered at the Berlin Observatory in 1846 after a mathematical prediction, making Neptune the only planet not to be discovered empirically. It has a composition similar to that of Uranus. The planet is named after the Roman god of the sea. The outer parts of Neptune’s atmosphere are extremely cold, -235 °C (-391°F), because of its distance from the Sun. After the Voyager 2 spacecraft visited Uranus, it then flew past Neptune, passing the poles 4,800 km away. Its images confirmed the existence of the rings of Neptune.
This pricing structure is only available to academic institutions. Storyboard That accepts purchase orders. | 0.893679 | 3.43 |
Cosmic rays — high-energy particles that move through space at the speed of light — are intensifying as the Sun enters a ‘solar minimum’, which could be a hazard to astronauts and produce more storms.
The reason that rays are intensifying is because of the lack of sunspots — dark spots that appear on the Sun’s surface caused by magnetic fields which illuminate earth with X-ray and ultraviolet radiation.
A solar minimum, which is a “regular part of the sunspot cycle,” according to Dean Pesnell of Nasa’s Goddard Space Flight Center, means that the Sun's magnetic field is weak. This results in extra cosmic rays entering the solar system.
Neutron counts from the University of Oulu’s Sodankyla Geophysical Observatory show that cosmic rays reaching Earth in 2020 are near a “Space Age peak” wrote Dr. Tony Phillips on his website.
“So far this year, the sun has been blank 76 per cent of the time, a rate surpassed only once before in the Space Age. Last year, 2019, the sun was blank 77 per cent of the time. Two consecutive years of record-setting spotlessness adds up to a very deep Solar Minimum” Phillips also wrote, while suggesting that “excess cosmic rays...affect the electro-chemistry of Earth”s upper atmosphere and may help trigger lightning.”
Some have speculated that the lowered output from the sun could result in a “Little Ice Age”, similar to the one that occurred between the 14th and 19th century and happened concurrently with mountain glacier expansion in the European Alps, New Zealand, and Alaska among other locations, and lower temperatures across the northern hemisphere.
However, even that has been contended, with research suggesting that “multiple factors, particularly volcanic activity, were crucial for causing the cooler temperatures” and that “a reduction in total solar irradiance likely contributed at a level comparable to changing land use.” The Independent
India is seventh among worst-hit nations by COVID-19
Army, police launch joint cordon-and-search operation (CASO)...
It will control all ITBP formations in the western theatre
Ludhiana reports 6 cases, Bathinda 3 | 0.829449 | 3.462252 |
The Electric Winds of Jupiter
By Andrew Hall
Jupiter is our largest neighbor and generates the largest electromagnetic field in the Solar System except for the Sun. It has a thick, turbulent atmosphere with swirling storms producing winds of supersonic speed, and lightning arcs that dwarf the puny sparks we have on Earth. Thus immediately, we see attributes of electrical processes like the processes we are exploring in Earth’s primordial past.
Nothing exemplifies the electrical nature of Jupiter more than its bands of counter-flowing winds and the giant swirl known as The Great Red Spot.
Electric winds occur when an electric field potential exists that motivates ionic species in the air to move. Positive ionic species are drawn in one direction, and negative ions and free electrons are drawn in the opposite direction, as dictated by the polarity of the electric field. The ions may be only a small percentage of the bulk mass of air, but electrically they form a current — moving charge — that will drag neutral molecules with it.
These opposing motions produce uni-polar winds. A positive wind from one direction and a negative wind from the other attracted to or pushed away from the “electrodes” in the circuit.
If the wind occurs in the atmosphere surrounding a planet, the winds will circumnavigate the globe in alternating bands in a direction transverse to the magnetic polarity of the planet. This is the effect on display in Jupiter’s atmosphere as well as other planets in our Solar system with strong electric fields.
The “electrodes” are nodal regions where current flows through the planet’s atmospheric sheath and crust. That is why they appear at certain latitudes. Uni-polar winds mix in whirlwinds at these “electrodes.” The mixing of ions results in a plasma, where, with much condensation, violent arcing, and swirling, they electrically adhere to form molecular bonds and precipitate. This is what is known as a storm.
The primary electrodes in a planetary circuit are around the magnetic poles, and the evidence of the electric field strength is in the glow-mode currents called aurora.
Another type of “electrode” is an accumulation of charge density from a volcanic eruption, where discharges internal to the crust expel huge volumes of charged pyroclastic dust into the atmosphere and spread hot magma across the land.
Another “electrode” is produced where the planet’s electromagnetic field produces regions of high flux from cosmic rays, driven by stellar winds or perhaps some other motivating force. Charged particles spiral down magnetic lines of flux and charge the crustal surface, creating electrode spots.
In every case, discharge follows the geometry of a plasmoid Earth, where the “Blue Marble” we live on is just a bubble, or drop of matter encapsulated in an electric circuit. The plasmoid circuit is what matters — what controls everything — and it flows through the atmosphere and crust to create the capacitance that motivates weather, earthquakes, and volcanoes.
Uni-polar winds are drawn to the electrode spots like water flows to an open drain. Only a solid crustal surface provides no hole to sink into. The winds are constrained by the vacuum of space above and the solid crust (or ocean) below. They circulate in induced vortex currents to mix in a plasma storm, recombining charged species into neutral matter that rains to the surface.
Storms are evidence of currents induced by capacitance in the layers of atmosphere and crust of the planet. It does not matter if it is Earth, Jupiter, or an exo-planet yet to be discovered. A planet with an active electromagnetic field will form a spherical layer of capacitance in its atmosphere and crust through which loops of magnetic flux will induce ring currents to flow transversely through the layers.
A ring current is the simplest form of circuit. In Nature, where there are no insulated wires to guide current flow, ring currents form naturally. Unlike a Birkeland current in space, where current flows from one body to another along the electric field between them, a ring current simply circulates on itself.
Ring currents rule the universe — not gravity. It’s because magnetic fields are closed fields — they form closed loops between poles, and magnetic flux induces current to flow along these loops — the induced current follows to form ring currents. Nature can’t stop itself forming ring currents. They exist at the atomic level, the molecular level, the planetary level, the stellar level, and the galactic level of our cosmos.
Because Earth’s ring currents have no end, they are infinitely long conductors that induce current from the Solar Wind. Because they are infinitely long, there is no limit to the current they can induce. The currents form a winding, that, like a transformer inside the Earth, raises potential in the circuit. The result is an internal electric field in opposition to the ambient electric field of the Solar System.
Earth’s crust and atmosphere is the ‘almost’ neutral boundary — the dielectric plates between the internal and external fields that seek a charge balance.
Any change in the external electric field causes a response internally, because the internal electric field acts like a mirror, reflecting a feedback response. The mirroring effect is caused by capacitance because if charge builds on one plate of a capacitor, the other plate responds by building an equal and opposite charge. So change takes place both internally and externally, and the neutral balance between — where we live — is disrupted, until the internal and external fields come back to equilibrium.
Of course, there is never an equilibrium. Because Earth is a sphere, each capacitor plate of the sphere has a bigger area, as a function of radius, so there can never be two layers with equal charge density across equal areas. Layers of earth and atmosphere are always building charge and discharging. It is physically impossible not to.
This is the wisdom of the ancients, which today we confuse with mysticism: “As above, so below” has a simple, classical scientific meaning. It refers to the capacitance in Earth’s circuit and the feedback (or reflection) inside the Earth caused by whatever is going on in the Solar System.
To see this in action, one need only look at the extremely intense current loops that form on the Sun. These are called coronal loops and are produced by the same kind of capacitance in the circuitry that causes weather on Jupiter and Earth. The difference isn’t in the circuitry, the difference is the plasma state the atmospheres are in. The Sun is almost completely ionized, whereas Earth and Jupiter have partial plasma atmospheres. The ionized atmosphere of the sun produces ray-gun like currents, whereas partial plasma atmospheres like Earth and Jupiter produce more diffuse hydrodynamic currents we see as wind and clouds.
The rings are currents of excess charge the solar circuit is shedding. As in the Sun, the interior Earth layers have less area, so as charge accumulates by induction, it develops greater charge density in the ground and must shed current outward through the atmosphere.
In a storm on Earth, the ambient electric field reverses, from a 200 kV “clear weather” current flowing outward, to a 500 MV current aimed at the ground. The Earth beneath a storm becomes positive to a negative sky, as accumulated charge finds a path to discharge.
Ring currents also produce a magnetic field inside them that is stronger than the magnetic field outside. The geometry of a ring causes magnetic flux to disperse in a greater area outside of the ring than inside. Therefore, there is a stronger magnetic flux inside the loop that induces a secondary current flow, perpendicular to the coronal loop. Current flows through the atmosphere and crust both in the vertical columns of the loops and horizontally in current induced by the loops. These currents travel through layers of atmosphere and Earth’s crust.
Another property of ring currents is very strange and counter-intuitive. When we look at a ring current generated in a looped wire with a battery — generating, say, one amp, any two points in the loop will measure a current of one amp. But if we generate the same amount of current in the wire by induction, by passing a magnet through the ring, the current at any two points may be different, even though the sum of all current in the wire still adds to one amp. The induced current may be different where the wire’s contact with the magnetic field is weaker, but elsewhere in the ring the magnetic field will be diametrically stronger and generate current that makes up the difference.
The result is that current density may form in one part of the ring and not in another, or one part of the ring may even flow backwards — a current of opposite polarity. Coronal loops on the Sun display this. NASA imagery shows plasma bolides shooting through rings at varying speeds and sometimes reversing direction.
On Earth, current rings formed by the geomagnetic field also display this inductive behavior, developing a severe storm at one leg while doing nothing at the other. It also allows direct current inputs from induction to become alternating currents, as currents in a ring will oscillate as charge stores and discharges in the capacitance of the system.
Weather forms where currents pass through the atmosphere and crust. A whirlpool of mixing plasma forms storms where current draws-up channels of air and positively charge ions.
Coronal loops generate winds as ionic matter follows electric fields, dragging bulk air mass with it. Ultimately, the winds form jet-streams that must thread in three dimensions through the inflow/outflow, updraft/downdraft regions formed by coronal loops, like rope wound into a knot.
If you look at the last image of an electromagnetic wave in a double layer, you can see, first, how a double layer of charge — a capacitor — will produce waves of electromagnetic peak and trough, like a rogue wave on the ocean.
If one also includes spherical geometry, as in the capacitance of planetary circuits, then it becomes simple deduction that the geometry results in higher charge concentration inside Earth than outside and will produce these kinds of waves. It cannot “physics-wise” be otherwise. So waves like this form naturally, consistently, and unavoidably. And that results in ring currents — coronal loops, magnetic field lines inducing current — call it what you like. It’s electric.
In Part 3 we’ll see how ring currents produce storms on Jupiter and Earth and how they progress in fractal elements from a common thunderstorm to The Great Red Spot on Jupiter.
Additional Resources by Andrew Hall:
Andrew Hall is a natural philosopher, engineer, and writer. A graduate of the University of Arizona’s Aerospace and Mechanical Engineering College, he spent thirty years in the energy industry. He has designed, consulted, managed and directed the construction and operation of over two and a half gigawatts of power generation and transmission, including solar, gasification, and natural gas power systems. From his home in Arizona, he explores the mountains, canyons, volcanoes, and deserts of the American Southwest to understand and rewrite an interpretation of Earth’s form in its proper electrical context. Andrew was a speaker at the EU2016 and EU2017 conferences. He can be reached at [email protected] or thedailyplasma.blog
Disclosure: The proposed theories are the sole ideas of the author, as a result of observation, experience in shock and hydrodynamic effects, and deductive reasoning. The author makes no claims that this method is the only way mountains or other geological features are created.
The ideas expressed in Thunderblogs do not necessarily express the views of T-Bolts Group Inc or The Thunderbolts ProjectTM. | 0.846436 | 4.060069 |
CURA : Accueil
The most ancient layer of astronomical data
in the Babylonian Astrolabe dated to 5,500 BC
by Rumen Kolev
The following is a press release by Placidus Research Center on occasion of the forthcoming
publication of the research of Rumen Kolev, Astronomical Dating of the Babylonian Astrolabe in
the Proceedings of the Melammu VI Symposium of the Assyrian and the Babylonian Intellectual
Heritage Project Sep. 1st-3rd, 2008, Sofia, Bulgaria. The publication is expected in early 2010.
You may follow updated information on the official website of the Melammu Project.
Astronomical data from 5,500 BC was found in a babylonian astronomical text known
as the Babylonian Astrolabe. If confirmed, this may substantially change our understanding
of history, astronomy and prehistory.
The discovery gives vision for a comparatevely advanced astronomy in prehistoric
Mesopotamia and may give the possibility to gain direct insight into its spiritual world.
The 5,500 BC layer of astro info was found in a number of texts |1| from which the Astrolabe,
known also as the Calendar of the Creation, is the most important.
In the Akkadian Creation epic, Enuma Elish, the Astrolabe is described as the calendar
set in motion by Marduk himself when creating the Universe. The present discovery strongly
suggests that the whole Astrolabe has been conceived around 5,500 BC.
The Astrolabe is a map of the sky. It comes in circular and in list form |2|.
It shows which 3 stars/constellations rise heliacally (first appearance in morning after conjunction
with the Sun) every month over the 3 sectors of the eastern horizon called paths.
The position of a star on the sky (over the eastern horizon) is revealed by its path.
Extremely important is to note that there is another group of texts, headed by the famous
MUL.APIN which assign different paths to half of the stars in the Astrolabe. This turned out to be a
crucial evidence in the analysis because it allowed us to correlate another section of the precessional
path-changes of the stars to another text !
On the technical side of the matter, the celestial paths and the path-positions of the stars can be
computed, more or less exactly, astronomically. This gives us the possibility to analyse mathematically
and date any text that assigns paths to stars as the Astrolabe, Mul Apin and so on.
In the last hundred years, some scholars in Babylonian astronomy repeatedly expressed the view
that the stars in the Astrolabe are not in their correct celestial paths (Kugler, Schaumberger, van der
Waerden). Their big error was that they made computations only for the period 2,000 BC - 1,000 BC...
This is not so surprising when we take in account that these researchers worked before the computers
and had to make thousands of tedious computations with spherical trigonometry.
One of the amazing things in the story is that the Babylonian Astrolabe has laid around for more
than 100 years (30 of which are well in the computer age) and no-one ever tried to do a most simple
check ... check for the time-frame when the text made astronomical sense ...
|1|: The tablets date from the Kassite (HS 1897), Middle Assyrian (VAT 9416) and Late Babylonian period (LBAT 1499,
BM 82923). These texts are from 2 groups: in one group are the Astrolabe texts (VAT 9416, LBAT 1499, BM 82923)
spanning 1100 BC to 100 BC and in the other group are the 30-stars List texts (HS 1897) from around 1400 BC.
|2|: The first piece of the riddle came when the pioneer assyriologist George Smith found a small piece with
the names of 4 stars in 1874. Rassam, Pinches and Zimmern later found more parts and better preserved copies.
The oldest and best preserved list Astrolabe was examined by Ernst Weidner in 1913 and published almost in a
complete translation in German in 1915. It is known since as astrolabe B (from Berlin) which belonged
to the Assyrian king Tiglatpileser ( 1114 BC -1075 BC). The tablet is in the Berlin museum.
It all started one July evening in 2005 when I, still in Seattle, in the library of the University of
Washington stumbled per chance on an article about the Astrolabe by the famous mathematician and
history of science scholar van der Waerden (JNES 8, 1949).
After thouroughly examining his work, I decided to check manually if the Pleiades have ever
been in their correct astrolabe path. I was using a simple Planetarium program (my own computer
program Babylonia 1)
On the picture: piece of a circular Astrolabe from the New-Assyrian
Empire in the British Museum. Photo: courtesy of Florentina Geller.
What I did was to check with the program the path position of the Pleiades in a full precessional
cycle, starting from 1,000 BC and moving back in time with a step of 500 years.
I worked with both theories of the paths- the azimuthal of Pingree-Reiner and the declinational of
Kopff. The result was confusing. The Pleiades turned out to be in their correct southern path of Ea
only in the period 12,000 BC - 4,800 BC !
Then I repeated the same procedure on 8 bright stars with certain identifications.
The result was more than shocking. The time frame when all 8 bright stars were in their
Astrolabe paths turned out to be between 9,500 BC and 5,200 BC !
A most astonishing thing was to see on the graphs computed with the program how, when
moving forward in time, the stars change their declination and path until we come to one moment
in-around 3,600 BC when already 6 of the 8 bright stars have moved out of their Astrolabe-paths
and moved in into their Mul Apin paths !
No-one would have expected such a result. Even a writer of fantasy books !
Staggered, I left the research for several months. Then I was back.
In order to expand my analysis I spent several months feverishly writing a special computer
program that would allow me to check all kinds of different situations: different star-identifications,
different path theories, different latitudes of observation, different sets of stars analyzed and different
extinctions of the atmosphere...
Then I set to examine the model of the Astrolabe changing all described variables and watching
how this would change the time-period of the best fit ...
All results were pointing to the same time period: 5,500 BC +-500.
The model was robust and statistically significant. This was something impossible, yet happenning !
The famous Astrolabe B found by Ernst Weidner in the Berlin Museum.
photo: courtesy of Florentina Geller.
But how can we explain the fact that the majority of the stars from the Babylonian Astrolabe are
in their correct paths in-around 5,500 BC ? We have several options:
- I. The result is by chance;
- II. Someone who knew about the precession in-around 1500 BC or before, made-up the Astrolabe with
- positions of the stars as in 5,500 BC.;
- III. The path positions of the stars in the Astrolabe have been observed and determined around 5,500 BC.
12 months and 3 stars heliacally appearing in each month, was conceived around 5,500 BC.
- IV. Not only the path positions of the stars in the Astrolabe but also the complete Astrolabe, as a calendar with
I. The probability of the first hypothesis happenning can be calculated and I do it in my paper. It is one
in several millions.
II. The second possibility (the conspirational theory) has been aired as a conjecture by some scholars
in the discussion after the lecture and in private. I do not consider this a serious option.
The fact that very strongly goes against the conspirational theory is that there are several different
layers of astronomical data in the astrolabes.
There are 2, 3 and eventually even 4 layers coming from in-between 5,500 BC and 700 BC !
This means that new data has been added several times in the course of long transmission.
These layers of astronomical data are like the layers in a sea-floor sediment. They come from different
eras. The astronomical equivalent of a stratigraphical analysis of the astrolabe texts is attempted in the
forthcoming article and a more detailed research of the layers is being done in the moment (Nov. 2009)
III. The third hypothesis is true several millions to one and I have strong arguments to claim that :
IV. not only the path-positions of the stars in the Astrolabe are coming from 5,500 BC, but the complete Astrolabe!
Because the babylonian celestial paths depend on and are a function of the way of division of the
The Sun must spend equal time in the northern and the southern paths and double that in the central
path of the horizon (going trough the two equinoctia). This requires a division of the seasonal year in a number
of time intervals divisible by 4 id est: 4, 8, 12, 16....
We should remember also that Mul.Apin and Enuma Elish describe division of the year in 12 and that
the number of months in the lunar year is 12 or 13.
All these considerations, I believe, give considerable weight to the theory that the Astrolabe was conceived
in 5,500 BC.
The Astrolabe dated to 5,500 BC, without doubt, may open up for us a New World- the world of a
prehistoric civilization with astronomical knowledge on comparatively high level...
If we now jump in mythology, the 5,500 BC point in time can easily refer to the prediluvial prophet of Star
Knowledge and Divination En Meduranki. The Astrolabe then must come from the First Age- 5,500 BC- the time
of foundation of the civilizations of Sumer (the first temple in Eridu) and Vincha (the first settlements and cities
along Danube) that coincides with advanced agriculture using irrigation and humid and warm climate- the very
onset of what later probably came to be considered as the Golden Age: 5,500 BC to 3,600 BC.
Have we captured with the magic of mathematics what was until now only a myth ?!
Rumen Kolev: The most ancient layer of astronomical data in the Babylonian Astrolabe dated to 5,500 BC
All rights reserved © 2009 Rumen Kolev
Centre Universitaire de Recherche en Astrologie
Web site Designer & Editor: Patrice Guinard
© 1999-2009 Dr. Patrice Guinard | 0.816099 | 3.335911 |
Rosetta is destined to make a controlled impact into the Ma’at region of Comet 67P/Churyumov–Gerasimenko on 30 September 2016, targeting a point within a 700 x 500 m ellipse (a very approximate outline is marked on the image).
The target area is home to several active pits measuring over 100 m across and 60 m deep, from which a number of the comet’s dust jets originate. Some of the pit walls also exhibit intriguing metre-sized lumpy structures called ‘goosebumps’, which could be the signatures of early cometesimals that agglomerated to create the comet in the early phases of Solar System formation.
Rosetta’s final descent may afford detailed close-up views of these features.
The full size inset image can be found in the Archive Image Browser. | 0.810775 | 3.07702 |
"The results are vital to our general understanding of planetary upper atmospheres."
A spacecraft that died in 2017 is still providing insights about Saturn, the planet it studied up close for 13 years.
NASA's Cassini spacecraft helped scientists to discover why Saturn's upper atmosphere is so hot, which puzzled planetary scientists for decades since the planet is too far from the sun to receive our star's heat. But, using old data from Cassini, scientists are closer to solving this mystery.
This new work, which was conducted by NASA and the European Space Agency and led by Zarah Brown, a graduate student at the University of Arizona's Lunar and Planetary Laboratory, suggests that it's auroras that are heating up Saturn's atmosphere. These auroras are triggered by the constant stream of charged particles from the solar wind, which interacts with charged particles that flow from Saturn's moons and creates electric currents.
This insight not only helps scientists understand what is going on at Saturn, but perhaps also at gas giant planets in general. Jupiter, Neptune and Uranus all have strangely hot upper atmospheres as well. There are also numerous exoplanet gas giants far outside of our solar system that may exhibit similar behavior.
"The results are vital to our general understanding of planetary upper atmospheres, and are an important part of Cassini's legacy," study co-author Tommi Koskinen, a member of Cassini's Ultraviolet Imaging Spectrograph instrument team, said in a statement from NASA's Jet Propulsion Laboratory.
Researchers previously used Cassini data to build a map of the temperature and density of Saturn's upper atmosphere, which was not well known before the spacecraft arrived at the planet in 2004. In this study, this map helped scientists to study how electric currents from Saturn's auroras heats the planet's upper atmosphere, generating the solar wind. The solar wind, in turn, distributes energy from the poles (where the auroras are located) towards the equator. That energy then heats the equator to twice the temperatures than could be generated from the sun's heat.
It's common for archival data from spacecraft like Cassini to continue providing new insights long after the craft are no longer operational. This particular dataset came from Cassini's final few months at Saturn when it did 22 very close orbits of the gas giant before deliberately hurling itself into the planet on Sept. 15, 2017 (to prevent possible Earthly contamination of Saturn's icy moons, which could host microbial life.)
For six weeks, Cassini examined bright stars in the constellations Orion and Canis Major, watching as the stars rose and set behind Saturn. By observing the shifting starlight, scientists were able to learn more about the density of Saturn's atmosphere. Since density decreases with altitude, the rate of decrease is dependent on temperature, allowing scientists to estimate temperatures in Saturn's upper atmosphere.
Cassini's observations showed the temperatures peaking around the auroras, in turn providing evidence that it is electric currents are what Saturn's upper atmosphere so hot. Wind speeds on Saturn were also determined using density and temperature measurements. | 0.861422 | 4.013598 |
Astronomers working to find alien life have found new evidence to suggest a distant solar system could be strikingly similar to our own.
Stargazers at the Search for Extraterrestrial Life Institute (SETI) used the brand new Gemini Planet Imager to closely examine a star which is 100 million light years away in the constellation of Eridanus.
Using this super sensitive new telescope, scientists discovered a huge gas giant which looks a lot like Jupiter - and suggested it could even be home to a planet similar to Earth.
The star had already been examined four times by more primitive instruments, which totally missed the massive planet in orbit around it.
Eric Nielsen, postdoctoral fellow at the SETI Institute, told Mirror Online his team were delighted to have spotted the planet.
"The reason we say this star system looks similar to ours is because we see so many which look nothing like our own," he told us.
Scientists often discover planetary systems with planets which resemble those in our solar system, but which are the wrong size or too close or far away from their parent star.
Earth itself exists in a region referred to as the Goldilocks zone, which is just close enough to the sun to give the planet enough heat and light, but far away enough that we are spared the ravages of its radiation and the scorching heat which would boil the oceans off the planet.
"This gas planet is the first which looks quite similar to our own and is only twice the size of Jupiter," Nielsen continued.
"However, our observations would miss planets smaller or closer into the star.
"We could quite easily have a planet with an Earth-like mass which simply cannot be seen using current technology."
The star has the unprepossessing name 51 Eri B and is relatively young, having formed 40 million years after the demise of the dinosaurs.
Yet because it boasts a massive Jupiter-like gas giant just like our own solar system, it is a fascinating system for scientists to study.
"This is indeed a planet like our own Jupiter. We have found its first distant and younger cousin,” said Franck Marchis, senior planetary astronomer at the SETI Institute.
Last month, NASA announced the discovery of a distant planet which could potentially hold life. | 0.898467 | 3.158297 |
Using a CSIRO radio telescope, astronomers have caught an enormous cloud of cosmic gas and dust in the process of collapsing in on itself. They hope the discovery could help establish how massive stars form.
Dr Peter Barnes from the University of Florida says astronomers have a good grasp of how stars such as our sun form from clouds of gas and dust. But for heavier stars – ten times the mass of the sun or more – they are still largely in the dark, despite years of work.
“Astronomers are still debating the physical processes that can generate these big stars,” says Barnes.
“Massive stars are rare, making up only a few per cent of all stars, and they will only form in significant numbers when really massive clouds of gas collapse, creating hundreds of stars of different masses. Smaller gas clouds are not likely to make big stars.”
Most regions in space where massive stars are forming are well over 1,000 light-years away, making them hard to spot.
But using CSIRO’s ‘Mopra’ radio telescope – a 22m dish near Coonabarabran, New South Wales – the team discovered a massive cloud made mostly of hydrogen gas and dust, three or more light-years across, that is collapsing in on itself and will probably form a huge cluster of stars.
Dr Stuart Ryder of the Anglo-Australian Observatory said the discovery was made during a survey of more than 200 gas clouds. Called BYF73, it’s about 8,000 light years away, in the constellation of Carina in the Southern sky.
“With clouds like this we can test theories of massive star cluster formation in great detail,” says Ryder.
Evidence for ‘infalling’ gas came from the radio telescope’s detection of two kinds of molecules in the cloud – HCO+ and H13CO+. The spectral lines from the HCO+ molecules in particular showed the gas had a velocity and temperature pattern that indicated collapse.
The research team calculates that the gas is falling in at the rate of about three per cent of the Sun’s mass every year – one of the highest rates known.
Follow-up infrared observations made with the 3.9-m Anglo-Australian Telescope showed signs of massive young stars that have already formed right at the centre of the gas clump, and new stars forming.
Star-formation in the cloud also showed up in archival data from the Spitzer and MSX spacecraft, which observe in the mid-infrared. | 0.850635 | 3.880839 |
In the last two days we’ve looked at a discussion of a possible SETI observable, a ‘shielding swarm’ that an advanced civilization might deploy in the event of a nearby supernova. As with Richard Carrigan’s pioneering searches for Dyson swarms in the infrared, this kind of SETI makes fundamentally different assumptions than the SETI we’ve grown familiar with, where the hope is to snag a beacon-like signal at radio or optical wavelengths. So-called ‘Dysonian SETI’ assumes no intent to communicate. It is about observing a civilization’s artifacts.
Both radio/optical SETI and this Dysonian effort are worth pursuing, because we have no idea what the terms of any discovery of an extraterrestrial culture will be. The hope of receiving a deliberate signal carries the enthralling possibility that somewhere there is an Encyclopedia Galactica that we may one day gain access to, or at the least that there is a civilization that wants to talk to us. A Dysonian detection would tell us that civilizations can survive their youth to become builders on a colossal scale, pushing up toward Kardashev levels II and III.
Keeping both SETI tracks engaged is good science. It’s encouraging on the radio front to see that the Parkes radio telescope in Australia has now joined the Green Bank Telescope (West Virginia) and the Automated Planet Finder (Lick Observatory) in SETI observations funded by Breakthrough Listen. A key component of the Breakthrough Initiatives effort (which includes Breakthrough Starshot), Breakthrough Listen has just announced the activation of its SETI project at Parkes with observations of the newly discovered planet around Proxima Centauri.
About this study, several points. First, Parkes marks a welcome expansion of the northern hemisphere efforts. Situated about 20 kilometers north of the town of Parkes in New South Wales, the telescope can observe those parts of the sky that are not visible to its northern counterparts, making it a major component in any comprehensive SETI effort.
Image: The Parkes radio telescope in New South Wales. Credit: CSIRO.
As to Proxima Centauri, we now have an Earth-sized planet orbiting in what appears to be its habitable zone, meaning that temperatures could allow liquid water to exist on its surface. The discovery of Proxima b has enlivened the interstellar community as we examine ways to learn more about it, including the Breakthrough Starshot flyby probe studies. But I think we can agree that the chances of finding a civilization on any particular planet are low.
So says Andrew Siemion, director of the Berkeley SETI Research Center and leader of the Breakthrough Listen science program. And he adds:
“…once we knew there was a planet right next door, we had to ask the question, and it was a fitting first observation for Parkes. To find a civilisation just 4.2 light years away would change everything.”
It was in the same spirit that a number of SETI instruments have been turned to Boyajian’s Star (KIC 8462852), whose unusual light curves have drawn a great deal of attention because we have so far been unable to explain them. In both cases, we have a high-interest target, in the Proxima system because of its sheer proximity to Earth and in the Boyajian’s Star system because one explanation for those light curves is intelligent engineering.
So I am all for examining Proxima Centauri even though I think the real action there will be in one day analyzing its atmosphere for signs of biosignatures. 14 days of commissioning and test observations at Parkes led up to the first observation of Proxima on November 8 (local time). The broader strategy is to continue the SETI effort at radio wavelengths across a wide range of targets, as listed in this Breakthrough Initiatives news release.
- All 43 stars (at south declinations) within 5 parsecs, at 1-15 GHz. Sensitive to the levels of radio transmission at which signals ‘leak’ from Earth-based radar transmitters (with available receivers).
- 1000 stars (south) of all spectral-types (OBAFGKM) within 50 parsecs (1-4 GHz).
- One Million Nearby Stars (south). In 2016-2017, first 5,000 stars; 1 minute exposure (1-4 GHz).
- Galactic plane and Center (1-4 GHz).
- Centers of 100 nearby galaxies (south declinations): spirals, ellipticals, dwarfs, irregulars (1-4 GHz).
- Exotic sources will include white dwarfs, neutron stars, black holes, and other anomalous natural sources (1-4 GHz).
Bear in mind as these efforts proceed that Breakthrough Listen will also be coordinating searches with the FAST (Five hundred meter Aperture Spherical Telescope) in southwest China, exchanging observing plans, search methods and data. Thus we move toward a global SETI effort that can quickly share promising signals for analysis. Data from Parkes and the other Breakthrough Listen telescopes will be made available to the public online. | 0.85546 | 3.556709 |
Under Earth’s protective magnetic field, we don’t usually need to worry too much about the health effects of cosmic radiation – although it’s something that’s known to impact astronauts in space, and even passengers travelling in airplanes.
But the same can’t be said for our technological systems – fierce solar storms can wreak havoc on Earth’s communication networks, and new research shows that even ordinary levels of cosmic radiation can have a disruptive effect on our personal devices.
“This is a really big problem, but it is mostly invisible to the public,” says electrical engineer Bharat Bhuva from Vanderbilt University. To see just how big the problem is, Bhuva and his team took 16-nanometre computer chips – the kind used in many of today’s consumer PCs – and exposed them to a neutron beam, in an attempt to replicate what happens when cosmic radiation penetrates our atmosphere.
When cosmic rays collide with Earth’s magnetic field, they create cascades of secondary particles – including energetic neutrons, muons, and pions.
Millions of these particles strike our bodies every second, and while they aren’t thought to have any effect on our health, they can interfere with the operation of microelectronic circuitry. When these particles interact with integrated circuits, they can actually alter or ‘flip’ individual bits of data stored in memory – a phenomenon that’s called a single-event upset (SEU).
Most of the time, such an event probably wouldn’t create much of a problem. An app running on your smartphone or PC might glitch somehow, making a miscalculation, but it’s probably not something you’ll notice for more than a moment. But in some cases, SEUs could have drastic and potentially far-reaching consequences. In 2003, a ‘bit flip’ in a Belgian electronic voting machine gave one candidate in the election an extra 4,096 votes, before the mistake was caught. Even more worrying – the avionics system of a Qantas passenger jet malfunctioned due to a suspected SEU in 2008, forcing the aircraft into an abrupt dive that injured about a third of the passengers on board. (1)
A particle costing a life.
A life being born from a particle.
Universe ridiculing life.
Universe praising life.
But could life be unimportant?
Could life be important?
What if there was another answer?
An answer which negated both questions?
Seek the meaning of life and death in irony.
It is not the words or conscious thought the ones who will guide you.
It is the music. During an Aeschylus tragedy… | 0.800628 | 3.443526 |
For the first time, astronomers have measured light emitted from extrasolar planets around sun-like stars using ground-based telescopes. The observations were obtained simultaneously and independently by two separate teams for two different planets. Incredibly, they were also able to determine properties of the exoplanets’ atmospheres as well. Measuring the light emitted from a planet at different wavelengths reveals the planet’s spectrum, which can be used to determine the planet’s day-side temperature. In addition, this spectrum can reveal many physical processes in the planet’s atmosphere, such as the presence of molecules like water, carbon monoxide and methane, and the redistribution of heat around the planet. “This first direct detection of light emitted by another planet, using existing telescopes on the ground, is a major milestone in the study of planets beyond our own Solar System,” said Professor Gary Davis, Director of the United Kingdom Infrared Telescope (UKIRT). “This is a very exciting scientific discovery.”
The measurements of the first planet, TrES-3b, were conducted by a team of Astronomers from the University of Leiden, using the William Herschel Telescope (WHT) on La Palma (Canary Islands, Spain) and the United Kingdom Infrared Telescope on Mauna Kea in Hawai`i. TrES-3b is in a very tight orbit around its host star, TrES-3, transiting the stellar disk once per 31 hours. For comparison, Mercury orbits the sun once every 88 days. TrES-3b is just a little larger than Jupiter, yet orbits around its parent star much closer than Mercury does, making it a “hot jupiter.”
UKIRT observations caught the planet transiting in front of the star, from which the size of the planet has been worked out extremely precisely. The WHT observations also show the moment the planet moves behind the star, and allow the strength of the planet light to be measured. Astronomers have been trying to observe this effect from the ground for many years, and this is the first success.
Ernst de Mooij, leader of the research team, said, “While a few such observations have been conducted previously from space, they involved measurements at long wavelengths, where the contrast in brightness between the planet and the star is much higher. These are not only the first ground-based observations of this kind, they are also the first to be conducted in the near-infrared, at wavelengths of 2 micron for this planet, where it emits most of its radiation.”
The researchers determined the temperature of TrES-3b to be a slightly over 2000 Kelvin. “Since we know how much energy it should receive by the type of its host star, this gives us insights into the thermal structure of the planet’s atmosphere,” added Dr. Ignas Snellen, “which is consistent with the prediction that this planet should have a so-called ‘inversion layer.’ It is absolutely amazing that we can now really probe the properties of such a distant world”.
An atmospheric inversion layer is a layer of air where the normal change of temperature with altitude reverses. Current theory says that there are two types of “hot jupiters,” one with an inversion layer, and one without. One theory is that the presence of an inversion layer would depend on the amount of light the planet receives from its star. If the inversion layer could be confirmed, for example by measurements at other wavelengths, these observations would fit in perfectly with this theory.
A second team has made a ground-based detection of a different extrasolar planet, OGLE-TR-56b,using the Southern Observatory’s Very Large Telescope. This planet is about 5,000 light-years away, located towards the center of the galaxy. The planet is quite hot; its atmosphere is more than 4,400 degrees Fahrenheit (2,400 degrees Celsius). This is one of the hottest extrasolar planets detected.
The researchers say both landmark observations will open up a new window for studying exoplanets and their atmospheres using ground-based telescopes, and show great promise for using future extremely large telescopes which will have much higher sensitivity than the telescopes used today.
Source: Joint Astronomy Center | 0.870894 | 4.062614 |
The 2019 Physics Nobel Prize was announced this week, awarded to James Peebles for work in cosmology and to Michel Mayor and Didier Queloz for the first observation of an exoplanet.
Peebles introduced quantitative methods to cosmology. He figured out how to use the Cosmic Microwave Background (light left over from the Big Bang) to understand how matter is distributed in our universe, including the presence of still-mysterious dark matter and dark energy. Mayor and Queloz were the first team to observe a planet outside of our solar system (an “exoplanet”), in 1995. By careful measurement of the spectrum of light coming from a star they were able to find a slight wobble, caused by a Jupiter-esque planet in orbit around it. Their discovery opened the floodgates of observation. Astronomers found many more planets than expected, showing that, far from a rare occurrence, exoplanets are quite common.
It’s a bit strange that this Nobel was awarded to two very different types of research. This isn’t the first time the prize was divided between two different discoveries, but all of the cases I can remember involve discoveries in closely related topics. This one didn’t, and I’m curious about the Nobel committee’s logic. It might have been that neither discovery “merited a Nobel” on its own, but I don’t think we’re supposed to think of shared Nobels as “lesser” than non-shared ones. It would make sense if the Nobel committee thought they had a lot of important results to “get through” and grouped them together to get through them faster, but if anything I have the impression it’s the opposite: that at least in physics, it’s getting harder and harder to find genuinely important discoveries that haven’t been acknowledged. Overall, this seems like a very weird pairing, and the Nobel committee’s citation “for contributions to our understanding of the evolution of the universe and Earth’s place in the cosmos” is a pretty loose justification. | 0.86981 | 3.510592 |
Hubble spies edge-on beauty
(Phys.org) -- Visible in the constellation of Andromeda, NGC 891 is located approximately 30 million light-years away from Earth. The NASA/ESA Hubble Space Telescope turned its powerful wide field Advanced Camera for Surveys towards this spiral galaxy and took this close-up of its northern half. The galaxy's central bulge is just out of the image on the bottom left.
The galaxy, spanning some 100,000 light-years, is seen exactly edge-on, and reveals its thick plane of dust and interstellar gas. While initially thought to look like our own Milky Way if seen from the side, more detailed surveys revealed the existence of filaments of dust and gas escaping the plane of the galaxy into the halo over hundreds of light-years. They can be clearly seen here against the bright background of the galaxy halo, expanding into space from the disk of the galaxy.
Astronomers believe these filaments to be the result of the ejection of material due to supernovae or intense stellar formation activity. By lighting up when they are born, or exploding when they die, stars cause powerful winds that can blow dust and gas over hundreds of light-years in space.
A few foreground stars from the Milky Way shine brightly in the image, while distant elliptical galaxies can be seen in the lower right of the image.
NGC 891 is part of a small group of galaxies bound together by gravity.
A version of this image was entered into the Hubbles Hidden Treasures Image Processing Competition by contestant Nick Rose. Hidden Treasures is an initiative to invite astronomy enthusiasts to search the Hubble archive for stunning images that have never been seen by the general public. | 0.853885 | 3.16648 |
This blog was written for EGU’s blog, the original post can be found on Geolog.
NASA scientists have revealed surprising new information about Jupiter’s magnetic field from data gathered by their space probe, Juno.
Unlike earth’s magnetic field, which is symmetrical in the North and South Poles, Jupiter’s magnetic field has startlingly different magnetic signatures at the two poles.
The Juno probe flew 2.8 billion kilometres between its launch from earth and insertion into orbit around Jupiter. Image: NASA/JPL-Caltech
The information has been collected as part of the Juno program, NASA’s latest mission to unravel the mysteries of the biggest planet in our solar system. The solar-powered spacecraft is made of three 8.5 metre-long solar panels angled around a central body. The probe (pictured above) cartwheels through space, travelling at speeds up to 250,000 kilometres per hour.
Measurements taken by a magnetometer mounted on the spacecraft have allowed a stunning new insight into the planet’s gigantic magnetic field. They reveal the field lines’ pathways vary greatly from the traditional ‘bar magnet’ magnetic field produced by earth.
The Earth’s magnetic field is generated by the movement of fluid in its inner core called a dynamo. The dynamo produces a positive radiomagnetic field that comes out of one hemisphere and a symmetrical negative field that goes into the other.
The interior of Jupiter on the other hand, is quite different from Earth’s. The planet is made up almost entirely of hydrogen gas, meaning the whole planet is essentially a ball of moving fluid. The result is a totally unique magnetic picture. While the south pole has a negative magnetic field similar to Earth’s, the northern hemisphere is bizarrely irregular, comprised of a series of positive magnetic anomalies that look nothing like any magnetic field seen before.
“The northern hemisphere has a lot of positive flux in the northern mid latitude. It’s also the site of a lot of anomalies,” explains Juno Deputy Principal Investigator, Jack Connerney, who spoke at a press conference at the EGU General Assembly in April. “There is an extraordinary hemisphere asymmetry to the magnetic field [which] was totally unexpected.”
NASA have produced a video that illustrates the unusual magnetism, with the red spots indicating a positive magnetic field and the blue a negative field:
Before its launch in 2016, Juno was programmed to conduct 34 elliptical ‘science’ orbits, passing 4,200 kilometres above Jupiter’s atmosphere at its closest point. When all the orbits are complete, the spacecraft will undertake a final deorbit phase before impacting into Jupiter in February 2020.
So far Juno has achieved eleven science orbits, and the team analysing the data hope to learn more as it completes more passes. “In the remaining orbits we will get a finer resolution of the magnetic field, which will help us understand the dynamo and how deep the magnetic field forms” explains Scott Bolton, Principal Investigator of the mission.
The researchers’ next steps are to examine the probe’s data after its 16th and 34th passes meaning it will be a few more months before they are able to learn more of Jupiter’s mysterious magnetosphere. | 0.832783 | 3.624795 |
Describe a practical way to determine in which constellation the Sun is found at any time of the year.
What is a constellation as astronomers define it today? What does it mean when an astronomer says, “I saw a comet in Orion last night”?
Draw a picture that explains why Venus goes through phases the way the Moon does, according to the heliocentric cosmology. Does Jupiter also go through phases as seen from Earth? Why?
Show with a simple diagram how the lower parts of a ship disappear first as it sails away from you on a spherical Earth. Use the same diagram to show why lookouts on old sailing ships could see farther from the masthead than from the deck. Would there be any advantage to posting lookouts on the mast if Earth were flat? (Note that these nautical arguments for a spherical Earth were quite familiar to Columbus and other mariners of his time.)
Parallaxes of stars were not observed by ancient astronomers. How can this fact be reconciled with the heliocentric hypothesis?
Why do you think so many people still believe in astrology and spend money on it? What psychological needs does such a belief system satisfy?
Consider three cosmological perspectives—the geocentric perspective, the heliocentric perspective, and the modern perspective—in which the Sun is a minor star on the outskirts of one galaxy among billions. Discuss some of the cultural and philosophical implications of each point of view.
The north celestial pole appears at an altitude above the horizon that is equal to the observer’s latitude. Identify Polaris, the North Star, which lies very close to the north celestial pole. Measure its altitude. (This can be done with a protractor. Alternatively, your fist, extended at arm’s length, spans a distance approximately equal to 10°.) Compare this estimate with your latitude. (Note that this experiment cannot be performed easily in the Southern Hemisphere because Polaris itself is not visible in the south and no bright star is located near the south celestial pole.)
What were two arguments or lines of evidence in support of the geocentric model?
Although the Copernican system was largely correct to place the Sun at the center of all planetary motion, the model still gave inaccurate predictions for planetary positions. Explain the flaw in the Copernican model that hindered its accuracy.
During a retrograde loop of Mars, would you expect Mars to be brighter than usual in the sky, about average in brightness, or fainter than usual in the sky? Explain.
The Great Pyramid of Giza was constructed nearly 5000 years ago. Within the pyramid, archaeologists discovered a shaft leading from the central chamber out of the pyramid, oriented for favorable viewing of the bright star Thuban at that time. Thinking about Earth’s precession, explain why Thuban might have been an important star to the ancient Egyptians.
Explain why more stars are circumpolar for observers at higher latitudes.
What is the altitude of the north celestial pole in the sky from your latitude? If you do not know your latitude, look it up. If you are in the Southern Hemisphere, answer this question for the south celestial pole, since the north celestial pole is not visible from your location.
If you were to drive to some city south of your current location, how would the altitude of the celestial pole in the sky change?
Hipparchus could have warned us that the dates associated with each of the natal astrology sun signs would eventually be wrong. Explain why.
Explain three lines of evidence that argue against the validity of astrology.
What did Galileo discover about the planet Jupiter that cast doubt on exclusive geocentrism?
What did Galileo discover about Venus that cast doubt on geocentrism? | 0.849951 | 3.751598 |
Todd J. Barber, Cassini lead propulsion engineer
(RPWS) instrument, but Cassini is just one of about 35 different spacecraft that he has worked over five decades.
Don has a very colorful and interesting background, one that would take up far too much of my column to elucidate. I learned of his roots from a wonderful article in “The Iowan”, and I invite interested readers of this column to check out Dr. Gurnett’s early history there. Suffice it to say, he arrived at the University of Iowa in September, 1957, watched Sputnik launch a month later, and sought (and obtained) his first job from Dr. James Van Allen himself ( Van Allan discovered Earth’s radiation belts, which now bear his name) just after the Explorer 1 launch in early 1958. Talk about a pioneer!
Before we delve into a myriad of wonderful RPWS science results, for the engineering aficionados in the audience, I will mention the RPWS is basically comprised of a Langmuir probe, a magnetic search coil, an electric field sensor, and a set of radio receivers that can be connected to these antennas. I’ll stop short of invoking Maxwell’s equations, but essentially the Langmuir probe measures electron temperature and density, the magnetic search coil measures magnetic fields, and the electric field sensor analyzes electric fields via three deployable 10-meter-long (33-foot-long) antennas. The instrument assemblies together use an average of only about 7 watts of power and weigh only about 6.8 kilograms (15 pounds). That’s a lot of scientific capability from a small and lightweight instrument!
One of Dr. Gurnett’s principal interests is finding new ways to represent the often difficult-to-comprehend science data returned by fields and particles instruments such as RPWS. Since this instrument primarily looks at a variety of waves within plasma (a rareified, charged cloud of gas), an excellent tool for doing this is to use sound waves, scaled to audible frequencies if necessary. Dr. Gurnett suggested this article have a link to his “Sounds of Space” website (http://www-pw.physics.uiowa.edu/space-audio/) from the university. For trepidatious readers, this might offer a user-friendly entry to the arcane world of fields and particles science. Just as interestingly, a composer named Terry Riley has written a piece of music entitled “Sun Rings” which uses actual data from Don’s earlier instruments! This is also available on the “Sounds of Space” website.
There are two broad types of wave phenomena picked up by RPWS at Saturn—whistlers and Saturn kilometric radiation (SKR). Whistlers are caused by lightning and were discovered at Saturn by Cassini. At Jupiter, in fact, Jovian lightning was discovered BY finding whistlers! These waves are actually a few hundred hertz to a few kilohertz in frequency—right in the “juicy range” of human hearing and Earthly music! When rendered in audio, they sound like a whistle of decreasing frequency (pitch) vs. time, and this is because high-frequency waves arrive first as lower-frequency waves slowed down by electron interaction. This slowdown can be quite dramatic, up to a factor of 100 or so! Incidentally, RPWS can also detect Saturnian lightning directly via high-frequency radio emissions from Saturn, just as AM radio receivers on Earth make pretty good lightning indicators (if making us a bit jumpy in the process). In addition, in radiation belts around Saturn akin to Earth’s van Allen radiation belts, electrons in the plasma can sometimes emit these high-frequency waves spontaneously, which are then called a “chorus” (from a British term for birds singing in the morning, sometimes called a “dawn chorus”). At Saturn’s equinox in 2009, lightning origination switched from Saturn’s southern hemisphere to the northern hemisphere, yet another dynamic change at the ringed planet around equinox. For decades, Don has used instruments like RPWS to tease out the mysteries of lightning on other planets, which sounds pretty cool to me.
As interesting as whistlers are, some of the most profound science results from Cassini have come from the study of Saturn kilometric radiation (SKR) by RPWS. Discovered by Voyager, SKR emanates from electrons in Saturn’s auroral zones at frequencies of a few hundred kilohertz. One of the most basic concepts for a planet is the length of its day—the time for it to rotate once about its own spin axis. For gas giants like Saturn, it is difficult to determine the true rotation rate of the deep interior, but SKR may offer the best glimpse into this value. Using SKR measurements from Voyager, the Saturn day was determined to be 10 hours, 39 minutes, 24 seconds (plus or minus 7 seconds), which has remarkably small uncertainties. Textbooks were printed, surely, with this value, only to be rendered obsolete in 1997 when the Ulysses spacecraft measured SKR and found the length of Saturn’s day had changed by about 1 percent, or six minutes. Some doubted this could be correct, given this unexpectedly large change in a highly certain parameter. The Ulysses data were based on weak signals (barely above noise levels), but Cassini verified the Ulysses data were correct during its approach to Saturn and at Saturn orbit insertion . However, that’s when things really got complicated!
During Cassini’s prime and Equinox Missions, Dr. Gurnett continued to uncover one perplexing find after another. It turned out the SKR period was different for the northern vs. southern auroral zones, with the former being lower. It is now recognized (from interdisciplinary science work) that the SKR period does not equal the true rotation period (due to probable slippage of the magnetic field versus the true core rotation), but that doesn’t explain why the two periods switched places after equinox! Dr. Gurnett suggests zonal winds at high altitudes (in the ionosphere) may be causing the north/south differences, but there is no way to measure this at the moment, so he’ll have to rely on modeling to confirm his hypothesis. Don plans to continue his role in the Solstice Mission by investigating how SKR changes as the sun shifts north with respect to Saturn.
Other methods have emerged to measure Saturn’s rotation rate as well, including a model based on how oblate (“squashed”) Saturn is due to rotation. Thankfully, others have determined a rotation rate slightly faster than the inferred RPWS rate, which is good because it implies some slippage of the magnetic field rotation vs. the true rotation. If the oblateness modeling had derived a slower rotation than Dr. Gurnett’s value, that would imply that Saturn’s magnetosphere is driving Saturn’s rotation (rather than vice versa), which is rather hard to fathom.
Recent Cassini and Hubble Space Telescope data suggest magnetic field, aurora wobble, and SKR frequencies at least agree with each other within each hemisphere, but plenty of puzzles remain. What is the true length of Saturn’s day? Why are the SKR periods different in each hemisphere and why do they change with Saturn’s seasons? How can Saturn’s magnetic field even affect the radio emission, since the rotation and magnetic field axes are aligned to within less than 0.1 degree? I’m relieved to hear Dr. Gurnett is having a good time on Cassini and has no intentions of retiring anytime soon. I think we may need another 50 years of your time to untangle all of the mysteries Saturn keeps throwing at us! Thank you for your time, Dr. Gurnett, and I wish you and the entire RPWS team many more triumphs throughout the solar system. | 0.838617 | 3.045096 |
Contrary to recent reports, NASA’s Cassini spacecraft is not experiencing unexplained deviations in its orbit around Saturn, according to mission managers and orbit determination experts at NASA’s Jet Propulsion Laboratory in Pasadena, California.
Several recent news stories have reported that a mysterious anomaly in Cassini’s orbit could potentially be explained by the gravitational tug of a theorised massive new planet in our Solar System, lurking far beyond the orbit of Neptune. While the proposed planet’s existence may eventually be confirmed by other means, mission navigators have observed no unexplained deviations in the spacecraft’s orbit since its arrival there in 2004.
“An undiscovered planet outside the orbit of Neptune, 10 times the mass of Earth, would affect the orbit of Saturn, not Cassini,” says William Folkner, a planetary scientist at JPL. Folkner develops planetary orbit information used for NASA’s high-precision spacecraft navigation. “This could produce a signature in the measurements of Cassini while in orbit about Saturn if the planet was close enough to the Sun. But we do not see any unexplained signature above the level of the measurement noise in Cassini data taken from 2004 to 2016.”
Recent research predicts that, if data tracking Cassini’s position were available out to the year 2020, they might be used to reveal a “most probable” location for the new planet in its long orbit around the Sun. However, Cassini’s mission is planned to end in late 2017, when the spacecraft – too low on fuel to continue on a longer mission – will plunge into Saturn’s atmosphere.
“Although we’d love it if Cassini could help detect a new planet in the Solar System, we do not see any perturbations in our orbit that we cannot explain with our current models,” says Earl Maize, Cassini project manager at JPL. | 0.839522 | 3.515281 |
In less than one week’s time, NASA’s $1.1 Billion Juno probe will blast off on the most powerful Atlas V rocket ever built and embark on a five year cruise to Jupiter where it will seek to elucidate the mysteries of the birth and evolution of our solar system’s largest planet and how that knowledge applies to the remaining planets.
The stage was set for Juno’s liftoff on August 5 at 11:34 a.m. after the solar-powered spacecraft was mated atop the Atlas V rocket at Space Launch Complex 41 at Cape Canaveral and firmly bolted in place at 10:42 a.m. EDT on July 27.
“We’re about to start our journey to Jupiter to unlock the secrets of the early solar system,” said Scott Bolton, the mission’s principal investigator from the Southwest Research Institute in San Antonio. “After eight years of development, the spacecraft is ready for its important mission.”
The launch window for Juno extends from Aug. 5 through Aug. 26. The launch time on Aug. 5 opens at 11:34 a.m. EDT and closes at 12:43 p.m. EDT. Juno is the second mission in NASA’s New Frontiers program.
JUNO’s three giant solar panels will unfurl about five minutes after payload separation following the launch, said Jan Chodas, Juno’s project manager at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif.
The probe will cartwheel through space during its five year trek to Jupiter.
Upon arrival in July 2016, JUNO will fire its braking rockets and go into polar orbit and circle Jupiter 33 times over about one year. The goal is to find out more about the planet’s origins, interior structure and atmosphere, observe the aurora, map the intense magnetic field and investigate the existence of a solid planetary core.
“Juno will become the first polar orbiting spacecraft at Jupiter. Not only are we over the poles, but we’re getting closer to Jupiter in our orbit than any other spacecraft has gone,” Bolton elaborated at a briefing for reporters at the Kennedy Space Center. “We’re only 5,000 kilometers above the cloud tops and so we’re skimming right over those cloud tops and we’re actually dipping down beneath the radiation belts, which is a very important thing for us. Because those radiation belts at Jupiter are the most hazardous region in the entire solar system other than going right to the sun itself.”
“Jupiter probably formed first. It’s the largest of all the planets and in fact it’s got more material in it than all the rest of the solar system combined. If I took everything in the solar system except the sun, it could all fit inside Jupiter. So we want to know the recipe.”
Watch for my continuing updates and on-site launch coverage of Juno, only the 2nd probe from Earth to ever orbit Jupiter. Galileo was the first. | 0.856412 | 3.114529 |
Alpha Centauri is the nearest star system to the Sun, located at a distance of only 4.37 light years or 1.34 parsecs from Earth. It is the brightest star in Centaurus constellation and the third brightest star in sky.
Alpha Centauri is only slightly brighter than Arcturus in Boötes constellation and Vega in Lyra. The star is also known as Rigil Kent, Rigil Kentaurus, or Toliman.
Alpha Centauri is a binary star system consisting of Alpha Centauri A and Alpha Centauri B. It is sometimes referred to as Alpha Centauri AB (α Cen AB).
The components Alpha Centauri A and B form a visual binary star, which means that they appear as a single star to the naked eye and cannot be resolved without binoculars or a telescope. They are, however, very easily resolved in binoculars and small telescopes.
The system may have a third component, Alpha Centauri C (Proxima Centauri), which is believed to be associated with the binary system, but is located an an angular separation of 2.2° to the south-west of Alpha Centauri AB, at a distance much greater than that between components A and B. The distance is about four times the angular diameter of the full Moon and roughly half the distance from Alpha to Beta Centauri.
If it were visible to the naked eye, Proxima Centauri would appear as a separate star, not as part of the Alpha Centauri system. There is still no direct evidence that Proxima has an elliptical orbit, which is typical of binary star systems.
The estimated age of the Alpha Centauri system is between 4.5 and 7 billion years, which makes the stars slightly older than the Sun.
The name Rigil Kent, or Rigil Kentaurus, is the romanization of the Arabic Rijl Qanṭūris, derived from the phrase Rijl al-Qanṭūris, meaning “the foot of the Centaur.” The star marks the foot of the centaur represented by Centaurus constellation.
Alpha Centauri’s other proper name, Toliman, may come from the Arabic al-Ẓulmān, which means “the ostriches.”
Alpha Centauri is circumpolar south of latitude 29°S, which means that it never sets below the horizon for observers in those latitudes.
It is one of the Southern Pointers, stars that point the way to the Southern Cross and help observers distinguish it from the False Cross, a faint asterism also found in the southern sky. The line from Alpha to Beta Centauri, also known as Hadar or Agena, points directly to Crux constellation.
The Alpha Centauri system lies too far south to be seen from mid-northern latitudes. It can be seen near the southern horizon in the northern summer in latitudes between 29°N and the equator.
Alpha Centauri lies at a distance of 4.37 light years from Earth. This translates into 277,600 astronomical units, or 41.5 trillion kilometres, or 25.8 trillion miles. The two unmanned probes, Voyager 1 and Voyager 2, launched in 1977, are not headed toward the system, but if they were, it would take them tens of thousands of years to get there. To reach the system within a human lifetime, one would need to travel at one-tenth of the speed of light.
The Scottish astronomer Thomas James Henderson was the first to calculate the distance to Alpha Centauri using the parallax method between April 1832 and May 1833 from the Royal Observatory at the Cape of Good Hope. He did not publish his findings until 1839 because he thought the results were too large to be accurate. Once Friedrich Wilhelm Bessel released his findings for the star 61 Cygni, also using the parallax method, in 1838, Henderson decided to publish his own. Technically, Alpha Centauri was the first star to have its parallax measured, but since it was not recognized first, it is generally considered as the second, after 61 Cygni in Cygnus constellation.
Henderson also realized that the components of the Alpha Centauri system displayed a significantly high proper motion. The system’s motion was later discovered to be about 6.1 arcminutes each century, or 61.3 arcminutes each millennium. This means that Alpha Centauri moves about 1.02° across the sky every 1,000 years. 6.1 arcminutes is roughly a fifth of the diameter of the full Moon, and 61.3 arcminutes is about twice the Moon’s diameter.
Based on the system’s proper motions and radial velocities, it will keep becoming brighter and pass to the north of Crux constellation before moving to the northwest. By the year 29,700, Alpha Centauri will be at a distance of 3.26 light years and reach a maximum visual magnitude of -0.86, close to the current magnitude of Canopus. However, even at its closest approach , the star’s apparent magnitude will not surpass that of the brightest star in the sky, Sirius. Sirius will also brighten over the next 60,000 years and continue to be the brightest star for about 210,000 years.
After it has made its closest approach to the solar system, Alpha Centauri will gradually move away, until it reaches a final vanishing point in about 100,000 years.
The Alpha Centauri system may contain at least one planet, discovered in the orbit of Alpha Centauri B. The planet, if confirmed, will be the closest known exoplanet to Earth.
The star system has been the target for searches for decades because of its proximity to Earth, but previous studies have been unsuccessful in finding a planet orbiting any of the stars. The first planet was discovered on 16 October 2012 by researchers at the Observatory of Geneva and the Centre for Astrophysics of the University of Porto. They used the radial velocity technique. It took three years of observations to make an analysis. The planet is not in the habitable zone, as it orbits too close to the star, at only 0.04 astronomical units.
Designated Alpha Centauri Bb, the planet has a mass at least 13 percent more than Earth’s and a surface temperature of 1,500 K (1,200°C), which makes it too hot to support life. For comparison, the hottest planet in the solar system, Venus, has a surface temperature of only 735 K (462°C). Alpha Centauri Bb orbits the star with a period of 3.2357 days at a distance of 6 million kilometres, which is only about 4 percent of the distance between the Earth and the Sun.
It is possible that there are other planets orbiting Alpha Centauri A and B, but the searches have so far failed to find any gas giants or brown dwarfs.
For a planet to be in the habitable zone of Alpha Centauri A, it would need to orbit the star at a distance of around 1.25 astronomical units, which is roughly halfway between the distances of Earth’s and Mars’ orbits around the Sun. At this distance, an Earth-like planet would have a similar temperature and conditions for liquid water to exist.
The habitable zone for Alpha Centauri B would be a little bit closer to the star, at roughly 0.7 astronomical units, or 100 million kilometres, which is about the same distance as that between the Sun and Venus.
ALPHA CENTAURI A
Alpha Centauri A has 110 percent of the Sun’s mass and 151.9 percent of its luminosity. It is a main sequence star similar to the Sun, with a radius about 23 percent larger. It belongs to the spectral class G2 V.
The star has a projected rotational velocity of 2.7 and a rotational period of about 22 days, which makes it a slightly faster spinner than the Sun, which takes 24.47 days to complete a rotation.
Alpha Centauri A is the fourth individual brightest star in the night sky, with an apparent magnitude of -0.01, only slightly fainter than Arcturus (-0.04), the brightest star in Boötes constellation. The star has an absolute magnitude of 4.38.
ALPHA CENTAURI B
Alpha Centauri B has 90 percent of the Sun’s mass and 44.5 percent of its luminosity. It is a main sequence star with the stellar classification K1 V, which makes it more orange in colour than Alpha Centauri A, which is yellowish. The star has a radius about 14 percent smaller than the Sun.
Alpha Centauri B has a projected rotational velocity of 1.1 and an estimated rotational period of 41 days. Even though it is not as luminous as Alpha Centauri A, the star emits more energy in X-ray. If it could be seen as a star separate from Alpha Centauri A, star B would be the 21st individual brightest star in the sky, with an apparent magnitude of 1.33. It has an absolute magnitude of 5.71.
PROXIMA CENTAURI (ALPHA CENTAURI C)
Alpha Centauri C, better known as Proxima Centauri, is the nearest known individual star to the Sun, at a distance of 4.24 light years.
It is likely gravitationally bound to Alpha Centauri AB and lies at a distance of 0.24 light years, or 0.06 parsecs (13,000 astronomical units), or 2.2 trillion kilometres from the main pair. Unlike Alpha Centauri AB, Proxima Centauri is too faint to be seen with the naked eye.
Proxima Centauri belongs to the stellar class M5 Ve or VIe, which means that it is red in colour and either a small main sequence star (V) or a subdwarf (VI) with emission lines.
The star has a mass of about 0.123 solar masses. It is classified as a flare star, and its brightness can sometimes suddenly increase to magnitude 11.0 or 11.09. The star has an absolute magnitude of 15.53.
If Proxima Centauri is gravitationally bound to the Alpha Centauri system, it orbits the binary pair with a period between 100,000 and 500,000 years.
Alpha Centauri A and Alpha Centauri B orbit a common centre every 79.91 years. The distance between the stars varies from 35.6 astronomical units (5.3 billion kilometres) to 11.2 astronomical units (1.67 billion kilometres). The distances are roughly equivalent to those between the Sun and Pluto and between the Sun and Saturn. The angular separation between Alpha Centauri A and Alpha Centauri B varies from 2 to 22 arcseconds. The total mass of the binary star system is about 2 solar masses.
Alpha Centauri was brought to the attention of Europeans by the English explorer Robert Hues in his Tractatus de Globis (1592), along with two other bright southern stars, Canopus in Carina and Achernar in Eridanus.
Hues wrote, “Now, therefore, there are but three Stars of the first magnitude that I could perceive in all those parts which are never seene here in England. The first of these is that bright Star in the sterne of Argo which they call Canobus. The second is in the end of Eridanus. The third is in the right foote of the Centaure.”
The Chinese know Alpha Centauri as the Second Star of the Southern Gate, referring to the Southern Gate asterism that it forms with Epsilon Centauri.
Australian aboriginal Boorong people in northwestern Victoria call Alpha and Beta Centauri Bermbermgle. The stars represent two brothers who heroically killed the Emu, represented by the Coalsack Nebula, a famous dark nebula located in Crux constellation.
Since Alpha Centauri can only be seen from the southern latitudes, there are no Greek or Roman myths associated with it, and it lacks historical and metaphorical significance in northern cultures. However, because of its proximity to us, the Alpha Centauri system is a huge part of popular culture, with numerous references in the works of science fiction, from novels including Arthur C. Clarke’s The Songs of Distant Earth, Isaac Asimov’s Foundation and Earth, William Gibson’s Neuromancer, and Philip K. Dick’s Clans of the Alphane Moon to episodes of Star Trek and Babylon 5, to films like Lost in Space, Impostor, Avatar, Transformers, and Guardians of the Galaxy. The system is also referenced in a number of games like Civilization, Frontier: Elite II and Frontier: First Encounters, Alien Legacy, Terra Nova: Strike Force Centauri, Colony Wars, Earth & Beyond, Kill Zone, Mass Effect 2, and Sid Meier’s Alpha Centauri.
The first astronomer to recognize Alpha Centauri as a binary star system was the Jesuit priest Jean Richaud in Puducherry in India. His discovery of the star’s binary nature happened by accident, while he was observing a passing comet. At the time, the only other binary star known was Acrux, the brightest star in the constellation Crux.
The South African astronomer William Stephen Finsen calculated Alpha Centauri’s estimated orbit by 1926.
The nearest known star system to Alpha Centauri is Luhman 16 in Vela constellation, lying at a distance of 3.6 light years.
A hypothetical observer in the Alpha Centauri system would see the sky as very similar to ours, except that the brightest star in Centaurus constellation would be missing. The Sun would appear as a magnitude 0.5 star in the direction of the constellation Cassiopeia, near the star Epsilon Cassiopeiae. Cassiopeia’s \/\/ shape would look like a /\/\/. Sirius would be much closer to Betelgeuse in Orion constellation, appearing less than a degree away, but it would be the brightest star in the sky when observed from Alpha Centauri, too.
Distance: 4.366 light years (1.339 parsecs)
Orbital period: 79.91 years
Designations: Alpha Centauri, Rigil Kentaurus, Rigil Kent, Toliman, Bungula, FK5 538, CP(D)−60°5483, GC 19728, CCDM J14396-6050
Alpha Centauri A: Alpha-1 Centauri, GJ 559, HR 5459, HD 128620, GCTP 3309.00, LHS 50, SAO 252838,HIP 71683
Alpha Centauri B: Alpha-2 Centauri, GJ 559 B, HR 5460, HD 128621,LHS 51, HIP 71681
Alpha Centauri A
Coordinates: 14h 39m 36.4951s (right ascension), -60°50’02.308” (declination)
Visual magnitude: -0.01
Absolute magnitude: 4.38
Spectral class: G2 V
Mass: 1.100 solar masses
Radius: 1.227 solar radii
Luminosity: 1.519 solar luminosities
Temperature: 5,790 K
Age: 6 Gyr
Alpha Centauri B
Coordinates: 14h 39m 35.0803s (right ascension), -60°50’13.761” (declination)
Visual magnitude: +1.33
Absolute magnitude: 5.71
Spectral class: K1 V
Mass: 0.907 solar masses
Radius: 0.865 solar radii
Luminosity: 0.500 solar luminosities
Temperature: 5,260 K | 0.902394 | 3.963784 |
Have you always wanted to explore space and find strange new alien worlds? Are you too lazy to leave your comfortable chair and the warm, reassuring glow of your computer screen? Google has some good news for you armchair star-ship captains out there. The machine-learning code responsible for the discovery of two exoplanets back in December has been released to the public, so you can now join the ongoing search for exoplanets and help uncover the strange secrets of our universe.
In a blog post published Thursday, March 8, senior Google software engineer Chris Shallue detailed the machine-learning code and how it can be used to help search for alien planets. To detect planets outside our solar system using tools like the Kepler space telescope, astronomers look at the light and other cosmic radiation that hits the telescope’s photometer. When there’s a conspicuous dip in an otherwise stable amount of light being detected by the telescope, there’s a chance that a planet, star, or something else may be responsible for blocking out some the light. There’s a chance, too, that it might just be instrumental noise. Once an anomaly in the signal is noticed, an algorithm makes a calculation as to the probability of an exoplanet’s existence. It’s not confirmed, however, until an astronomer manually looks through the data and can make an informed decision about what is causing the anomaly.
Because of the immense amount of data being analyzed, astronomers had to develop a way to avoid being overwhelmed by false positives caused by instrumental noise. A signal-to-noise cutoff ratio is applied to the data and any signals below the cutoff point are deemed too likely to be noise to warrant further review. While necessary, such a practice means there may be a number of actual exoplanets who’s signal was below the cutoff ratio, most likely smaller Earth-sized planets, the planets most likely to harbor alien life. That’s where Google’s code comes in.
Google’s code looks through the rejected Kepler signals and, like the terrifying piece of artificial intelligence it is, learns more ways to separate signal noise and actual anomalies. To test this, Google put its code to work on the data from 670 stars observed by the Kepler telescope and rejected by the automated analysis. From that formerly rejected data, Google identified two more exoplanets, Kepler-90 i and Kepler-80 g.
There is much more rejected Kepler data to sort through and Google has released its code to the public in hopes that open-sourcing it can help improve it. There is another space telescope being launched next month, too: the Transiting Exoplanet Survey Satellite (TESS) will launch on April 16, 2018 for a two year mission to observe potential exoplanets. This mission also uses the transiting method of detection, and Google’s code will likely be instrumental in distinguishing noise from potential alien worlds.
You can find the download for the code, and instructions on how to use it, on GitHub. If the thought of a machine-learning code on your computer makes you uneasy, you can also help sort data with your eyes, the old fashioned way. | 0.882765 | 3.124928 |
Europe’s flagship telescopes will be “moderately affected” by the new satellite mega-constellations now being launched, according to a new study.
Having thousands more bright objects in the sky will create inconvenience and extra cost, but the idea that astronomy faces some kind of a “cliff edge” is not correct, says Olivier Hainaut.
He’s calculated how observing time might be limited by having 26,000 additional spacecraft in orbit.
And it’s manageable, he believes.
Dr Hainaut works for the European Southern Observatory (ESO) organisation which operates world-class facilities in Chile’s Atacama Desert, including the VLT (Very Large Telescope) and the forthcoming Extremely Large Telescope (ELT).
Neither is likely to be deeply troubled by the wave of new broadband satellites being launched by companies such as SpaceX of California and London-based OneWeb.
“We will lose some telescope time due to the satellites crossing the field of view. For us, for ESO telescopes, this is something that we can mitigate by scheduling, and by ‘closing the shutter’ when they pass overhead,” Dr Hainaut told BBC News.
“It has a cost, of course; we would need to develop the software to compute the positions of the satellites, etc. That’s not horribly complicated, but it will need to be done.”
His study, co-authored with Andrew Williams, has been accepted for publication in the journal Astronomy & Astrophysics.
It was prompted by the furore that followed the initial launches last year of 60-at-a-time “Starlink” satellites from SpaceX.
The internet platforms shocked many with their brightness; astronomers complained of streaks in their telescope images. And with thousands more spacecraft in the planning, scientists feared the full roll-out of large constellations might seriously compromise their observations of the cosmos.
The ESO study attempts to make a calm forecast of the likely impacts. It necessarily follows some assumptions about the networks’ scale and distribution, and the reflectivity of individual spacecraft. But for arguments’ sake, it imagines there will be 18 orbiting constellations comprising 26,000 satellites.
For this scenario, the research reveals there would be about 1,600 illuminated spacecraft in view (above the horizon) of a mid-latitude observatory like the VLT or the ELT. The vast majority of these spacecraft, however, would be low in the sky; and above 30 degrees — that portion of the sky where most observations occur — there would be only about 250 satellites at any given time.
Up to about 100 satellites could potentially be bright enough to be visible with the naked eye during twilight hours, about 10 of which would be higher than 30 degrees of elevation.
All these numbers fall off sharply as more of the sky moves into the shadow of the Earth in the middle of the night.
Short exposures on ESO’s narrow-field observatories like the VLT and ELT should cope in this scenario.
“For a 100-second exposure time at twilight, we would lose 0.3% of the exposures. So, that means for every 1,000 exposures we take, three of them would be ruined by a satellite. And that number goes down as the Sun goes down,” Dr Hainaut explained.
But there are facilities, he concedes, that will be greatly affected. These are the ones dedicated to long exposures on wide fields of view.
The example citied is the upcoming NSF Vera C Rubin Observatory (formerly called the Large Synoptic Survey Telescope).
This will be attempting to draw a map of the entire sky every three days. Its wide field of view and remarkable sensitivity to anything that’s moving in sight of its detectors will make Vera Rubin especially vulnerable to interference.
If no mitigating strategy is introduced for this telescope, up to 40% of its imagery at twilight hours could be unusable.
For ESO, its greatest concern centres on the Vista telescope. This is a wide-field observatory that was paid for by the UK when it joined the organisation in 2002.
It’s about to be fitted with a new fibre-optic spectroscopic camera, able to capture the detailed colours of 2,400 objects simultaneously, over an area on the sky equivalent to 20 full Moons.
In the worst case, up to 30 fibres could be affected by a satellite trailing across the sky.
“Once you crunch the numbers, the numbers are not as bad as what some people feared,” Dr Hainaut told BBC News. “People said ‘oh no, there’ll be 40,000 bright satellites in the sky? No, there won’t be, simply because most of these satellites will be below the horizon, and then most of the others will be in the shadow of the Earth. That’s the first bit of good news.
“The second bit of good news is that the space industry, and specifically Space X and OneWeb are talking to us. They are really listening.”
The two companies have promised to work with the astronomical community to limit the interference as much as possible.
Hainaut and Williams’ study only concerned itself with optical/infrared telescopes. Radio telescopes will face a separate challenge of interference if the mega-constellation internet satellites transmit outside their designated wavelength bands.
And Dr Hainaut goes out of his way to stress the limitations imposed on the study by the assumptions made.
For example, today no-one really knows how many satellites will be launched. It could be less than 26,000; it could be substantially more. Problems will certainly scale if there are more.
And no-one knows just how bright the different designs of spacecraft will be. For this paper, each object is treated as a representative sphere.
and follow me on Twitter: @BBCAmos | 0.843695 | 3.483292 |
Are we alone in the Galaxy? Is there life in other planets? Have other species evolved to technological societies comparable to ours? Or maybe the right question is, How near are we from detecting signals of alien life?
In 2013 I met Lisa Kaltenegger at The Falling Walls event, in Berlin. She is an astronomer working now at Cornell University, looking for signatures of life in exoplanets (planets outside our solar system). She is quite convinced that we are very near to detecting them.
But last week, an article was published pointing to a star, KIC 8462852, whose light shows weird changes in luminosity. Astronomers can't explain it and, of course, some raise the question, Why not? to the possibility that the behavior is due to an alien technology.
Changes in luminosity is a well known effect in stars, some of them are called variable stars. It can be produced by the star's internal dynamics, spots in its surface, by the transit of one or various planets in front of the star, hiding a small portion of the star. This last effect is used to detect planets around stars, but it lowers, at much, about 1% of its total luminosity. Another method to detect exoplanets is by tracking the gravitational effect of the planet in its star (a small but detectable bouncing effect). For this star those reductions arrive up to an inexplicable 20%. Astronomers have checked all the known physics on luminosity variability in stars, and haven't been able to explain the observations of KIC 8462852. They have also accounted for different errors in their instruments, as well as for the effect of interstellar dust, but haven't found an acceptable explanation.
Are those irregular, unpredictable and inexplicable decreases in luminosity due to a technological structure being built near the star to get its energy to feed an alien society in a nearby planet? If that was the case we would be facing a much more advanced civilization, one that can use and control the energy of its star for its needs. This idea is not new, in fact it can be found in science fiction stories. Fred Hoyle, British astronomer that coined the term "Big Bang" Theory, wrote a novel, The Black Cloud, on something similar. Some scientists say that a civilization that can control its star energy is a type II civilization. If it can control its planet energy it is a type I civilization, and if it can control its galaxy energy it is a type III civilization. We are somewhere around type 0.8 civilization.
But this is not the kind of alien life that Dr. Kaltenegger is expecting to find in the next decades. What she and many other astronomers are studying are signals from the atmosphere of planets. The light that travels through the planet's atmosphere, is absorbed and re-emitted. This changes its properties (frequency distribution, for instance) and can give hints to astronomers about the atmosphere's content. Depending on the content, we can know it can have been produced without the help of organic life (bacteria, plants, ...).
A similar announcement took place in the 1960s, when astronomers detected a very precise periodic signal coming from a star. It was originally coined LGM, after Little Green Men. But that happened to be the discovery of a new type of stars, a pulsar or pulsating star, a star of very high density and magnetic field, that ejects powerful X rays in an specific axes. As the star is rotating and that X ray doesn't need to be in the same axes as the axes of rotation of the star, when the ray points to the Earth we detect is as a pulse, that is repeated every time the star rotates. The speed of rotation can be very high, several times per second.
If KIC 8462852 is the home of a technological alien society or new physics to understand we will know in the near future. In any case, astronomy doesn't stop being surprising and fascinating.
Physicist, working in quantum optics and nonlinear dynamics in optical systems. Loves to communicate science. | 0.901476 | 3.245626 |
Resource: NASA/Johns Hopkins College Utilized Physics Laboratory/Southwest Study Institute/Alex Parker
Pluto’s atmosphere is really hard to notice from Earth. It can only be analyzed when Pluto
passes in entrance of a distant star, permitting astronomers to see the outcome the
atmosphere has on starlight. When this transpired in 2016, it confirmed that Pluto’s atmosphere was developing, a trend that astronomers experienced observed due to the fact 1988, when they noticed it for the very first time.
Now all that has modified– Pluto’s atmosphere appears to have collapsed. The most
modern occultation in July very last year was observed by Ko Arimatsu at Kyoto College in Japan and colleagues. They say the atmospheric force seems to have dropped by in excess of 20 for each cent due to the fact 2016.
To start with some track record. Astronomers have very long recognized that Pluto’s atmosphere expands as it strategies the Sunlight and contracts as it recedes. When the Sunlight heats its icy surface, it sublimates, releasing nitrogen, methane and carbon dioxide into the atmosphere. When it moves absent, the atmosphere is considered to freeze and drop out of the sky in what need to be a single of the most stunning ice storms in the Photo voltaic Procedure.
Pluto achieved its point of closest approach to the Sunlight in 1989 and has due to the fact been going absent. But its atmosphere has ongoing to enhance to a level that is about 1/a hundred,000th of Earth’s.
Astronomers assume they know why thanks to the illustrations or photos despatched back by the New
Horizons spacecraft which flew past Pluto in 2015. These illustrations or photos unveiled an
unexpectedly elaborate surface with extensively varying hues. A mysterious reddish
cap at the north pole turned out to be colored by natural and organic molecules. And a
significant white, ice-coated basin named Sputnik Planitia stretched throughout
a significant portion of a single hemisphere.
Planetary geologists assume Sputnik Planitia performs an essential part in
regulating Pluto’s atmosphere. That is mainly because, when it faces the Sunlight, it releases
gas into the atmosphere. Simulations suggest that this is why Pluto’s atmosphere
has ongoing to grow, even as it has begun to go absent from the Sunlight.
The simulations are complex by Sputnik Planitia’s color which
decides the amount of light it absorbs and this in switch is influenced by ice
formation in techniques that are really hard to predict.
Nevertheless, these exact simulations suggest that due to the fact 2015, Sputnik
Planitia must have begun to cool, creating the atmosphere to condense into
ice. Arimatsu and co say that’s in all probability what’s at the rear of their new observation.
There is a challenge, even so. The models suggest that Pluto’s atmosphere should
to have shrunk by much less than 1 for each cent due to the fact 2016, not the 20 for each cent observed
by the Japanese group. So there may possibly be some other factor at operate that is
accelerating Pluto’s atmospheric collapse.
The outcome need to also be dealt with with warning. The outcome of Pluto’s atmosphere
on distant starlight is compact and really hard to notice with the 60cm reflecting
telescope that the group utilised. They say the many sources of error in their measurement
make it only marginally substantial.
Superior observations from much larger telescopes are desperately wanted. But this is
not likely to occur any time quickly. As nicely as going absent from the Sunlight, Pluto is
going out of the galactic plane, earning stellar occultations substantially rarer and
with much less shiny stars.
That means the possibilities to make far better observations in long run will be number of and
significantly concerning. The group conclude with a plea for astronomers to notice Pluto
with bigger, extra delicate telescopes, preferably these with diameters
calculated in meters.
Right until then, Pluto’s vanishing atmosphere will keep on being a thing of a secret.
Ref: arxiv.org/stomach muscles/2005.09189 : Proof For a Quick Decrease of Pluto’s Atmospheric Strain Unveiled by a Stellar Occultation In 2019 | 0.911448 | 3.782322 |
A lot of planets have homes — warm, loving stars that nurture and care for them and make sure they have everything they need. But sometimes, a planet finds itself homeless, moving around the universe aimlessness and carelessly. These free floaters just haven’t found a place to call home.
That was thought to be the case with 2MASS J2126, a gaseous nomad planet about 104 light-years from our own sun. While not common, free floating planets do exist. Astronomers, equipped with better instruments and more experience in how to find and identify strange objects in the universe, are in a better position these days to distinguish whether these lonesome celestial bodies are really planets, or just failed “brown dwarf” stars that couldn’t ignite.
In the same neighborhood, there was TYC 9486-927-1 — a young star thought to be on its own as well. No one really made any connections between 2MASS J2126 and TYC 9486-927-1. Why would they? The two are more than 6 billion miles from one another. That’s 7,000 times the distance between Earth and the sun. If the two were indeed pursuing an orbital relationship, it would take 2MASS J2126 nearly a million years to complete a single orbit around TYC 9486-927-1.
Well when it comes to space, time is relative. It turns out 2MASS J2126 has indeed found its host star in TYC 9486-927-1. It’s also the widest planetary system ever found, according to researchers at the University of Hertfordshire, who detail their findings in a new paper published today in Monthly Notices of the Royal Astronomical Society.
“Nobody had made the link between the objects before,” said lead author Niall Deacon in a press release. “The planet is not quite as lonely as we first thought, but it’s certainly in a very long-distance relationship.”
The astronomers determined the link by measuring the orbital strength of the two lovebirds through the element lithium, which is very abundant in young stars and much rarer in older ones. The host star TYC 9486-927-1 looks to contain an amount of lithium characteristic of stars between 10 million and 45 million years old.
Knowing the age of the star allowed astronomers to determine the mass of 2MASS J2126 — which is estimated to be somewhere between 11.6 and 15 times the mass of Jupiter. It’s a hefty planet, but still too small to be a star. And it’s moving together with TYC 9486-927-1.
A lot of questions remain about how such a star system forms and survives. This kind of orbit is basically stretched out to its limit. The sheer distance also means the likelihood that 2MASS J2126 could be habitable is close to nil. (Sorry.)
In any case, further study of this planet and star certainly makes it clear that we should take a closer look at other planets we’re calling free floaters — and how easy it might be for one of those little buggers to find a star system they can call home. | 0.854675 | 3.830249 |
Rosetta has imaged the smallest grains of Comet 67P/Churyumov-Gerasimenko’s dust yet, with its Micro-Imaging Dust Analysis System, MIDAS.
MIDAS works by collecting and then physically scanning grains with an Atomic Force Microscope. This uses a very fine tip, a bit like an old-fashioned record player needle, that is scanned over a particle. The deflection of the needle and therefore the height of the sample are measured to build up a 3D picture. This enables scientists to determine the structure of the particle, and thus gain insight into how it might have formed.
The new results, published in the journal Nature, provide evidence that dust particles continue to be aggregates below the size range already reported by the COSIMA instrument. That is, even at the very small scales of a few tens of micrometres down to a few hundred nanometres, the dust grains analysed by MIDAS appear to be made up of numerous smaller grains.
“To understand how comets are formed, we need to understand the structure of the smallest grains and how they are built,” says Mark Bentley of the Space Research Institute at the Austrian Academy of Science in Graz, Austria, principal investigator of MIDAS and lead author of the paper. “What we see with MIDAS is that everything is made of smaller and smaller aggregates; it’s similar to what the COSIMA instrument sees but continued down to even smaller scales.”
MIDAS detected both small, tightly packed ‘compact’ grains and larger more porous, loosely arranged ‘fluffy’ grains. The comet grains also appear to be elongated, several times longer in one direction than the others, in agreement with observations of dust in the interstellar medium.
Examples of the different types, which were collected by MIDAS from mid-November 2014 to February 2015, are shown in the figures accompanying this post.
One particularly large, porous grain captured from Comet 67P/C-G has similar properties to a type of so-called ‘interplanetary dust grain’ (IDP) thought to have grown into porous aggregates of smaller spheroidal particles during the early phases of Solar System formation.
These new results from MIDAS further strengthen the link between IDPs and cometary dust. The observed “aggregate of aggregates” structure of the particles gives hints to their formation mechanism, and how such particles could form a weakly bound layer at the surface of the comet nucleus.
“Aggregate dust particles at comet 67P/Churyumov-Gerasimenko” by M.S. Bentley et al is published in Nature.
See our 2014 blog post “Introducing MIDAS” for background on the instrument.
All images, credit: ESA/Rosetta/IWF for the MIDAS team IWF/ESA/LATMOS/Universiteit Leiden/Universität Wien | 0.812365 | 4.050192 |
Water is crucial to life as we know it, so it’s one of the key things astronomers look out for on exoplanets. And now, water vapor has been detected in the atmosphere of a potentially habitable exoplanet for the first time.
Water vapor has turned up on planets outside our solar system before, but none of those were anything close to liveable. These worlds include broiling hot versions of our own Jupiter, Saturn and Neptune, and steamy Super-Earths that are more water than rock.
But this new discovery of atmospheric water vapor is more promising. The planet in question is known as K2-18b, and orbits a red dwarf star some 110 light-years away in the constellation of Leo. It’s rocky and Earth-like, measuring 2.25 times wider and eight times more massive than our home planet. | 0.829041 | 3.193084 |
By sticking microbes to the outside of the International Space Station, Japanese researchers aim to test the “panspermia” theory that comets and asteroids can spread life between planets.
The Japanese experiment is called Tanpopo, Japanese for “dandelion”, after the plant’s fluffy seeds, which travel long distances on the wind. The Tanpopo experiment should begin in 2011 after the bugs arrive at the Space Station.
As well as exposing microbes to space, the experiment will capture tiny meteors using a superlight material called aerogel and return them to Earth for analysis. Scientists will examine any minerals and organic compounds, and look for any microbes inside.
“The experiment will tell us whether there are microbes at the Space Station’s height,” says the project’s lead scientist, Akihiko Yamagishi from Tokyo University of Pharmacy and Life Sciences, Japan.
Champions of the panspermia theory believe that microbes can hitch hike around the solar system on comets or asteroids, defying the hostile temperatures and high radiation levels of space.
A delivery of ready-made life could explain why life on Earth arose so quickly after our planet formed around 4.5 billion years ago.
Although panspermia is not proven, there’s some evidence that hardy microbes can survive in space for long periods. The Tanpopo mission will thoroughly test this by applying microbes to metal plates placed outside the International Space Station for periods of between 1 and 5 years.
Some of the Tanpopo bugs will be surrounded by the type of clay minerals found on comets, which might offer them some protection. Others will be on their own when exposed to the void of space around 350 km above earth.
The bacteria on the mission will include Deinococcus radiodurans, one of the toughest bugs of all. “These microbes are known to be resistant to many extreme conditions, such as ultraviolet and gamma radiation, dryness and vacuums,” says team member Kensei Kobayashi from Yokohama National University, Japan, who outlined the project today at the 2008 Astrobiology Science Conference in Santa Clara, California, US.
The team also plans to capture small meteors inside the aerogel, an extremely low-density, transparent solid nicknamed “frozen smoke”. They have already tested this in the lab, showing that their aerogels can trap tiny particles moving at 14,000 kilometres per hour, the typical speed at which they’ll hit the space station.
Astronauts will have to make spacewalks to retrieve the aerogels and metal plates at the end of their exposure periods, and the equipment will return to Earth in a Russian Soyuz spacecraft. Scientists will then assess how well the microbes have survived on the metal plates, and analyse any captured micrometeors.
That will involve identifying the chemical make-up of micrometeors and finding out if they contain any microbes. Any found could well have been blown up from the Earth’s surface. In balloon and aircraft experiments, Kobayashi and his colleagues have already discovered microorganisms at altitudes of up to 35 kilometres. Finding them in a low Earth orbit would boost the plausibility of the panspermia theory, they say.
There is also a faint possibility that the aerogel will capture alien bugs. “But the possibility is very low,” Kobayashi told New Scientist, adding that if micrometeors at that altitude contained alien microbes we would probably know about it already.
“If there are extraterrestrial microbes at the Space Station’s height, they must have already reached the Earth’s surface, because tens of thousands of tonnes of micrometeoroids reach Earth’s surface every year,” he says.
Astrobiology – Learn more in our out-of-this-world special report.
More on these topics: | 0.816814 | 3.77867 |
ASTROSAT is India’s first dedicated multi wavelength space observatory. This scientific satellite mission endeavours for a more detailed understanding of our universe. One of the unique features of ASTROSAT mission is that enables the simultaneous multi-wavelength observations of various astronomical objects with a single satellite.
ASTROSAT observes universe in the optical, Ultraviolet, low and high energy X-ray regions of the electromagnetic spectrum, whereas most other scientific satellites are capable of observing a narrow range of wavelength band. Multi-wavelength observations of ASTROSAT can be further extended with co-ordinated observations using other spacecraft and ground based observations. All major astronomy Institutions and some Universities in India are participating in these observations.
ASTROSAT with a lift-off mass of about 1513 kg was launched into a 650 km orbit inclined at an angle of 6 deg to the equator by PSLV-C30. After injection into Orbit, the two solar panels of ASTROSAT were automatically deployed in quick succession. The spacecraft control centre at Mission Operations Complex (MOX) of ISRO Telemetry, Tracking and Command Network (ISTRAC) at Bangalore manages the satellite during its mission life.
The science data gathered by five payloads of ASTROSAT are telemetered to the ground station at MOX. The data is then processed, archived and distributed by Indian Space Science Data Centre (ISSDC) located at Byalalu, near Bangalore.
The scientific objectives of ASTROSAT mission are:
- To understand high energy processes in binary star systems containing neutron stars and black holes
- Estimate magnetic fields of neutron stars
- Study star birth regions and high energy processes in star systems lying beyond our galaxy
- Detect new briefly bright X-ray sources in the sky
- Perform a limited deep field survey of the Universe in the Ultraviolet region
Payloads of ASTROSAT :
Five payloads of ASTROSAT are chosen to facilitate a deeper insight into the various astrophysical processes occurring in the various types of astronomical objects constituting our universe. These payloads rely on the visible, Ultraviolet and X-rays coming from distant celestial sources.
- The Ultraviolet Imaging Telescope (UVIT), capable of observing the sky in the Visible, Near Ultraviolet and Far Ultraviolet regions of the electromagnetic spectrum
- Large Area X-ray Proportional Counter (LAXPC), is designed for study the variations in the emission of X-rays from sources like X-ray binaries, Active Galactic Nuclei and other cosmic sources.
- Soft X-ray Telescope (SXT) is designed for studying how the X-ray spectrum of 0.3-8 keV range coming from distant celestial bodies varies with time.
- Cadmium Zinc Telluride Imager (CZTI), functioning in the X-ray region, extends the capability of the satellite to sense X-rays of high energy in 10-100 keV range.
- Scanning Sky Monitor(SSM), is intended to scan the sky for long term monitoring of bright X-ray sources in binary stars, and for the detection and location of sources that become bright in X-rays for a short duration of time. | 0.883336 | 3.958556 |
HONOLULU — For the second time, a collision between two neutron stars in another galaxy has rattled a gravitational-wave detector on Earth. But this duo is being much more coy than the first.
In 2017, astronomers announced with much fanfare that they had detected ripples in spacetime, from the merging of two neutron stars, the ultradense remains of massive stars (SN: 10/16/17). Observatories around the world and in space witnessed a simultaneous flash of radiant energy, light from all across the electromagnetic spectrum.
Now, gravitational waves from a second neutron star smashup have been detected. But unlike the first detection, researchers were not able to pinpoint the collision’s location on the sky and did not see an accompanying burst of light. Katerina Chatziioannou, an astrophysicist at the Flatiron Institute in New York City, presented the results January 5 at meeting of the American Astronomical Society.
The event was picked up on April 25, 2019, during the third observing run of the LIGO and Virgo gravitational-wave observatories. However, only one of LIGO’s two detectors registered the collision — the one in Livingston, La. The Advanced Laser Interferometer Gravitational-Wave Observatory facility in Hanford, Wash., was offline at the time — and the event was too weak for the Virgo observatory, which is in Italy, to detect.
Nevertheless, the team deduced that the most likely source of the gravitational waves was a collision between a pair of neutron stars with a combined mass 3.4 times as great as the sun. The smashup occurred between 290 million and 720 million light-years away, Chatziioannou said.
While the lack of an electromagnetic counterpart is disappointing, it’s not too surprising. “We do not expect a detectable counterpart from most mergers,” says Avi Loeb, an astrophysicist at Harvard University who is not part of the LIGO-Virgo collaboration. The light from a neutron star collision, he says, comes from jets of gas that spew out from the crash. Those jets are so narrow, that a fortuitous alignment is needed to see the light from Earth.
However, it is possible that there was a flash, but astronomers missed it. With a gravitational wave detection at only one facility, researchers weren’t able to narrow down where on the sky to look. “It was very poorly localized, to about one quarter of the entire sky,” says Edo Berger, a Harvard astrophysicist who participated in one search for visible light from the collision. “No electromagnetic search could have covered the entire region of interest…. The bottom line is that we can’t actually state that this event had no [electromagnetic] counterpart.”
Even if a telescope had been pointed in the right direction, there still might have been no light. The relatively high combined mass of the neutron stars means the final product likely collapsed immediately into a black hole, Chatziioannou says. If that’s the case, then little material would have escaped to be seen. | 0.800357 | 3.946493 |
The Serbian astrophysicist Milutin Milankovitch is best known for developing one of the most significant theories relating Earth motions and. Milankovitch cycles are insufficient to explain the full range of Quaternary climate change, which also requires greenhouse gas and albedo. What are Milankovitch Cycles? Natural global warming, and cooling, is considered to be initiated by Milankovitch cycles. These orbital and axial variations.
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You can also talk about it in connection to a runaway greenhouse, or perhaps even smaller-scale phenomena like abrupt climate change, but there’s coclos as to whether this is an artifact of simpler models for many processes relevant to the real world.
The combined albedo should lock the globe into a glacial. Ciclls don’t need to think inside just this solar system though. Starting at the bottom of a glacial. Milankovitch Cycles Where are we currently in the natural Milankovitch cycle?
This elliptical shape changes from less elliptical nearly a perfect circle to more elliptical and back, and is due to the gravitational fields of neighboring planets particularly the large ones — Jupiter and Saturn. Eccentricity varies primarily due to the gravitational pull of Jupiter and Saturn. Join the Party and let’s do our best to ‘Make a Meaningful Difference’. One would think that since the changes in eccentricity occur slowly, that the temperature would follow at a similar pace.
You need to be logged in to post a comment. For instance, while we know changes in the orbit pace ice ages, the precise way the three Milankovitch variations conspire to regulate the timing of glacial-interglacial cycles is not well known. Explaining theyr recurrence period of ice ages is difficult because although theyr cycle dominates the ice-volume record, it is small in the insolation spectrum.
I know this article works on TSI basically because of the orbital changes. An exceptionally long interglacial ahead? After 1 million years ago, this switched to the ,year cycle matching eccentricity. Facts Related Climate Images.
Increasing insolation there decreases temperature?
As ice sheets retreat they leave bare ccilos. Earth presently moves through the invariable plane around January 9 and July 9. What Causes Milankovitch Cycles?
This is a very small effect though, amounting to less than 0. Modern Forcing Natural vs. Then Milankovitch starts to tip things the other way. This page was last edited on 28 Decemberat However, these effects are not uniform everywhere on the Earth’s surface.
The Earth is actually not perfectly round so the gravitational pull tugs the axis over time creating the wobble cycle. This means we get less solar energy on an annual basis, and tends to cool the Earth. As you see, the difference between maximum and minimum global insolation during the lastyears is only about 0. When the Earth’s axis is aligned such that aphelion and perihelion occur near the equinoxes, axial tilt will not be aligned with or against eccentricity.
Most certainly these continually altering amounts of mliankovitch solar energy around the globe result in prominent changes in the Earth’s climate and glacial regimes. Because the Earth will be faster when closer to the sun? Winter, for instance, will be in a different section of the orbit.
Earth sciences portal Geology portal Paleontology portal. Therefore, he deduced a 41,year period for ice ages.
A Causality Problem for Milankovitch”. This would explain kilankovitch observations of its surface compared to evidence of different conditions in its past, such as the extent of its polar caps. This is known as solar forcing an example of radiative forcing.
The transition problem refers to the need to explain what changed 1 million years ago. Canon of Insolation and the Ice Age Problem.
Ciclos de Milankovitch e glaciações by Jana Rangel on Prezi
So compare these patterns to the glacial cycles. Natural Cycle Departure The natural cycle is range bound and well understood, largely constrained by the Milankovitch cycles. Aphelion is the opposite, when the Earth spends more time during the year away from the sun, or in the case of the tilt and wobble cycles when the northern hemisphere land mass facing the sun is further from the sun, causing cooling.
Today, the Northern Hemisphere winter occurs near Perihelion, and NH summer occurs when the Earth is farthest from the sun. Now there’s a technical term for you. This shows that Milankovitch theory fits the data extremely well, over the past million years, provided that we consider derivatives. What causes this are the natural cycles that influence earth climate — the Milankovitch Cycles? However, less tilt also increases the difference in radiation receipts between the equatorial and polar regions.
This surely makes for a nice complicated cycle over 1 glacial period.
Retrieved from ” https: Global warming and climate change. Since the beginning of the industrial age, humankind has caused such a dramatic departure from the natural cycle, that it is hard to imagine anyone thinking that we are still in the natural cycle. | 0.850981 | 3.302187 |
ESA shortlists landing sites for ExoMars rover
Four potential landing sites have been shortlisted for the 2018 ExoMars mission. ExoMars is a joint venture between the ESA and the Russian Federal Space Agency Roscosmos, with the ultimate goal of scouring the Red Planet for any signs of life, past or present. The mission will consist of multiple spacecraft in addition to two rovers. The ExoMars rover will be one of the final assets to launch, with an expected arrival date on Mars estimated at January 2019.
The ESA is currently in the process of testing new and innovative approaches for safely deploying the rover onto the surface of the Red Planet. ESA and its partner Airbus are striving to make the testing conditions as realistic as possible, going so far as to create a 30 x 13 m (98 x 42 ft) "Mars yard," representing the closest approximation to the Martian surface available here on Earth.
The process of selecting a suitable landing site began late last year, with a call for the scientific community to propose candidate landing zones with the greatest chance of yielding clues to the existence of life on Mars. Eight of these proposals were considered by a Landing Site Selection Working Group in April, with a successive ESA-appointed panel officially selecting four locations for further analysis.
"The present-day surface of Mars is a hostile place for living organisms," states Jorge Vago, project scientist for the ExoMars mission. "Primitive life may have gained a foothold when the climate was warmer and wetter, between 3.5 billion and 4 billion years ago."
All four sites are located close to the equator, with each representing a potential treasure trove of scientific discovery. The candidate sites are named Aram Dorsum, Hypanis Vallis, Mawrth Vallis and Oxia Planum. As the mission's primary goal is to seek out clues to life on the Red Planet, each of the suggested mission areas sit in or around locations that are believed to be the site of substantial water activity in ancient times, as they represent the ideal place for life to gain a foothold.
Aram Dorsum sits in a channel littered with what appear to be sedimentary rocks. It is believed that the area may contain well-preserved biosignatures, as all signs point towards the area experiencing sustained water activity in the planet's past. Similarly, Hypanis Vallis is situated in what is believed to be an ancient river delta. Deploying the rover at this location would allow scientists to analyze materials deposited at the site roughly 3.45 billion years ago.
Finally two of the selected sites, Mawrth Vallis and Oxia Planum, are located near one of the largest exposures of rock present on the Red Planet. The site is of particular scientific curiosity, as it has only been exposed to the harsh climate of Mars relatively recently – "recently" in cosmological terms meaning over the last few hundred million years. Therefore the high levels of radiation, as well as the oxidizing elements present in the Martian atmosphere, have not altered the nature of potential samples, allowing scientists a glimpse at a relatively well-preserved piece of the ancient Martian landscape.
Moving closer to the 2018 launch date, the team will attempt to ascertain which of the four shortlisted sites have the best balance in terms of scientific output versus the risks of a potential landing. Therefore, the next step in the process will involve a detailed risk assessment on each site, considering factors such as surface composition, atmospheric qualities and entry profile. A final decision on the landing site is slated to be made sometime in 2017 | 0.849681 | 3.115925 |
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