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Astronomers have detected three new rocky bodies that share the same orbit as Neptune as it travels around the sun.
The finding brings the total number of the gas giant’s asteroid companions, or "Trojans," up to four.
The highly inclined orbit of one of them supports the hypothesis that the Neptune Trojans were captured from a much larger asteroid "cloud" that surrounds the planet, and that they are not the broken remains of some larger object, as some scientists have speculated.
The International Astronomical UnionI(IAU) is expected to propose wording to delineate planets from other small, round objects at its 12-day General Assembly meeting in Prague this August.
Depending on the outcome of a separate controversial procedural issue — whether IAU members should be allowed to vote on such things — astronomers might then have the chance to weigh in on the definition later in the same meeting.
If approved, the definition would then be announced in September.
The issue surfaced in the late 1990s, when astronomers began discovering Pluto-like objects in the distant reaches of our solar system.
All the newfound worlds—there are several known now—were until recently smaller than Pluto, but they are round and orbit the Sun, two characteristics that had for centuries been sufficient for the implicit definition of ‘planet.’ The hitch: These small objects are typically on wild, elongated orbits that stretch well above and below the main plane of the solar system where eight of the traditional planets travel. Pluto has a wild orbit, too, which is one reason many astronomers do not consider it a planet anymore.
So what to call them? Astronomers have been arguing about it in earnest since 1999.
The controversy came to a head with the July 2005 announcement of 2003 UB313, an object roughly the size of Pluto that orbits the Sun beyond Neptune. The object’s discoverer, Mike Brown of Caltech, has argued it should be called a planet.
But other astronomers say that if planethood is bestowed upon 2003 UB313, then several similar way-out bodies should gain the same status, and the number of planets in our solar system could ultimately climb into the thousands as search technology improves.
The first space probe sent to land on an asteroid and take samples delivered the goods, Japanese scientists reported in a journal article published Friday, saying the otter-shaped celestial body is the first found to be made of rubble.
While previously probed asteroids consisted of lumps of solid rock Itokawa appears to consist of loosely packed and porous rubble bound together by its own gravity.
Itokawa has few craters because signs of impact from space rocks are erased when the asteroid’s rubble shifts after the impacts.
Its surface has patches of rough, boulder-strewn terrain and ‘seas’ of uniformly sized, fine-gravel-like particles.
The Hayabusa probe was launched in May 2003, and during its visit to the asteroid, which was named after a Japanese scientist, it also orbited it and took photographs.
A huge slab of folded Earth that scientists think used to be part of the ocean floor has been detected near the planet’s core. The discovery supports the theory that Earth’s crust is constantly recycled deep into the planet as molten material from below simultaneously pushes up to refresh the surface.
The structure is about 125 miles deep and at least 125 miles wide and 370 miles in the north-south direction. The slab began its plunge toward the center of the Earth about 50 million years ago. It is denser than surrounding material, which is why it sinks. Its lower reaches are near the core, about 1,740 miles down. Yet it is still attached to the surface, much like a conveyor belt.
Earth is divided into three main layers: the core, mantle and crust. The crust, a thin surface layer, is divided into more than a dozen major plates. In the middle of the Pacific Ocean, plates spread apart and fresh material from the mantle wells up.
Along the west coast of North America, crust beneath the ocean dives under a continental plate, creating earthquakes and volcanoes. Geologists have long speculated that when crust is folded into the planet, it sinks to the bottom of the mantle, where it displaces the material down there and forces some of it up.
If the scientists have correctly interpreted their data, the folding slab is the first hard evidence that sinking crust drives the upwelling of material so deep inside the planet.
The slab was found by monitoring seismic waves—generated by earthquakes in South America—reflecting from deep inside the mantle and recorded in the United States.
The diving crust is made of essentially the same material as the lower mantle, the researchers said, but it is much cooler, by about 1,260 degrees Fahrenheit. The lower mantle is roughly 4,500 degrees.
The Swedish 1-m Solar Telescope (SST) on the island of La Palma, Spain, had first light with a stopped down 60 cm aperture on March 2, 2002. On May 21, the telescope was opened to full aperture and the adaptive optics system was switched on for the first time. SST has very small optical aberrations after compensation by the adaptive optics system, designed to counteract blurring caused by the atmosphere. This enables solar astronomers to see and photograph solar details of smaller size than previously possible.
The SST will address current and important questions concerning solar magnetic fields and the dynamics of the upper solar atmosphere and will also be used to improve our understanding of the formation of stellar spectra
It is run by the Institute for Solar Physics of the Royal Swedish Academy of Sciences
The SST is a vacuum telescope - meaning that it is evacuated internally to avoid disruption of the image from air inside. This is a particular problem with solar telescopes because of the heating from the large amounts of light collected being passed on to any air causing image degradation. As of 2005 it has produced the highest resolution images on the Sun of any telescope,.
Back when the solar system was young, Neptune might have nabbed its giant moon Triton from a pair of passing sister planets, a new study says.
Dual systems like Pluto and its large moon Charon are not uncommon among objects in the Kuiper Belt region, located beyond Neptune’s orbit, astronomers say. About 10 percent of the known objects in this region have partners.
Triton stands out among all the large moons in the solar system because it orbits Neptune in a direction opposite to the planet’s rotation, a so-called retrograde orbit.
While most scientists explained the moon’s odd orbit and inclination by some variation of a capture scenario — a collision between objects. The most troubling conundrum was accounting for the tremendous amount of speed Triton must have shed to leave itself vulnerable to Neptune’s gravitational embrace. The collision theory, for example, would have required an impact so powerful that Triton itself should have been destroyed.
Scientists also have suggested that Neptune once had an extended gaseous atmosphere, which could have gradually slowed Triton until it fell into orbit around Neptune.
Now, it seems that Triton was wandering through space locked in the gravitational embrace of a companion when the pair happened to pass by Neptune. The gravity of the giant planet extricated Triton from its partner, flinging one into deep space and keeping the other as a moon.
About 40 per cent larger than Pluto, Triton moves through its tilted orbit in the opposite direction to Neptune’s rotation. This is the hallmark of a captured body, rather than one formed in situ, but astronomers have never been able to work out how Neptune managed to capture Triton.
Their calculations show that as Triton and its partner drew close to Neptune, the giant planet’s gravity overwhelmed the attraction between the pair with little regard for the size difference between the companions or the precise distance of the encounter. In the resulting interaction, Triton effectively cast off its partner for the planet.
The partner object likely would have been buffeted by Neptune’s gravity, passed along to Uranus and then Saturn until it finally reached giant Jupiter and was booted out of the solar system altogether, Agnor said.
The researchers are now curious to see if other eccentric moons in the solar system have similar life stories.
Saturn’s moon Titan has huge regions covered with dunes, possibly made out of ice crystals, sand or some other unknown material, international space scientists reported on Thursday.
Images of Titan beamed back to Earth from the joint U.S.-European Cassini mission look very much like sand dunes in the Sahara desert, Namibia, Saudi Arabia and Australia, the researchers said. The latest radar images show the dunes are up to 500 feet (150 meters) high and hundreds of miles (kilometers) long. Dark patches on Titan, the largest of Saturn’s 47 moons, were at first thought to be seas — but now they appear to be largely made up of these dunes.
On Earth, sand dunes are created by wind and wind is a result of heat differences produced by sunlight that warms the planet unevenly. Scientists have long assumed Titan is too far from the Sun to have solar-driven surface winds powerful enough to cause sand dunes.
Titan’s flat surface is very cold, with a temperature of minus 180 degrees Celsius and scientists believe its thick atmosphere may occasionally rain methane.
Scientists have more recently learned that Saturn’s powerful gravity creates tidal effects in Titan’s thick atmosphere. This tidal force, almost 400 times greater than that of Earth’s moon tugging at our oceans, dominates near surface winds on Titan and sculpts dunes that are up to 330 feet high.
The existence of pristine dunes, piled over other geological features, shows that wind recently blew fine grains of some material around, the researchers wrote in their report, published in the journal Science. It could be sand, ice or something else, they added.
Jupiter is growing a new red spot and the Hubble Space Telescope is photographing the scene. Backyard astronomers have been following the action, too.
"Red Spot Jr." as it is being called, formed after three white oval-shaped storms—two of which were at least 90 years old—merged between 1998 and 2000.
similar merger took place centuries ago and formed the bigger and legendary Great Red Spot, a storm twice as big as Earth and almost 300 years old.
Close inspections of Red Spot Jr., in Hubble images released today, reveal that similar to the Great Red Spot, the more recently developed storm rises above the top of the main cloud deck on Jupiter.
Little is known about how storms form on the giant planet. They are often described as behaving similar to hurricanes on Earth. Some astronomers believe that the spots dredge up material deep below Jupiter’s clouds and lift it to where the Sun’s ultraviolet light chemically alters it to give it a red hue.
The latest images could provide evidence that Jupiter is in the midst of a global change that can modify temperatures by as much as 10 degrees Fahrenheit on different parts of the globe.
The global change cycle began when the last of the white oval-shaped storms formed south of the Great Red Spot in 1939. As the storms started to merge between 1998 and 2000, the mixing of heat began to slow down at that latitude and has continued slowing ever since.
The movement of heat from the equator to Jupiter’s south pole is expected to stop at 34 degrees southern latitude, where Red Spot Jr. is forming.
This will create a big wall and stop the mixing of heat and airflow, the thinking goes. As a result, areas around the equator become warmer, while the poles can start to cool down.
The rotation period of rocky worlds like Earth can be calculated through simple observations of the motions of a particular spot on the planet in relation to other celestial objects. This method doesn’t work, however, for the likes Jupiter and Saturn because the solid cores of these gas giants are completely obscured by thick clouds that make direct visual measurements impossible.
Instead, the typically stated rotation periods for these planets are those of their magnetic fields, which scientists believe are closely tied to the rotations of their solid interiors.
But measuring the rotation period of Saturn’s magnetic field is difficult because its rotational axis — the imaginary line around which the planet rotates — is nearly identical to the axis around which its magnetic field revolves.
In contrast, the magnetic and rotational axes of Jupiter are separated by a few degrees and scientists can use this difference to calculate its rotation period. It’s like measuring the spin rate of a CD that has a distinct label on it versus a blank one that doesn’t.
For Saturn, the accepted workaround had been to analyze distortions in radio signals emitted by the planet—the signals are thought to be linked to the planet’s magnetic field.
Analysis of Saturnian radio emissions by NASA’s Voyager spacecrafts during the 1980s revealed a rotation period of about 10 hours, 39 minutes and 22 seconds. But more recent radio data collected by the agency’s Cassini spacecraft in 2003 and 2004 got a different number: 10 hours, 45 minutes and 45 seconds.
This discrepancy has long puzzled scientists. One explanation is that Saturn’s rotation rate actually slowed down by about 6 minutes, but many scientists think this is highly unlikely.
Another possible explanation is that the radio emissions never reflected the planet’s rotation period at all, but something else.
In any case, using radio signals to measure Saturn’s rotation period is like relying on a substitute for a substitute: the radio signals were linked to magnetic fields that were in turn linked to the rotation of Saturn’s solid core.
The new method potentially cuts out one of these steps.
Using magnetic field data collected by Cassini over a period of 14 months beginning in summer 2004, Giampieri and his team teased out a signal that they think is probably linked to Saturn’s magnetic field rotation and thus to the planet’s true rotation period.
More studies will be needed to confirm the link between the magnetic field signal and Saturn’s rotation period.
A precise value of Saturn’s rotation period will help scientists accurately determine the speed of its atmospheric winds and the size of its solid core, which is believed to be composed of rock and ice.
NASA has decided to fly the space shuttle Discovery in July without making all potential modifications to its external fuel tank that might reduce damaging foam debris, a move that concerns some agency engineers, officials said today.
Engineers have removed two large sections of insulating foam from the tank and are still evaluating the effects of that action, they said. Work will continue on redesigning or removing all or some of 34 smaller, potentially hazardous foam wedges in the future, but they will fly "as is" on the upcoming flight, they said.
Reducing falling fuel tank debris has been a priority for NASA since the loss of the shuttle Columbia on Feb. 1, 2003. Foam insulation falling from the tank during the launching damaged Columbia’s heat shield, causing the destruction of the craft and the deaths of seven astronauts as the ship attempted to return through the atmosphere from a science mission.
When Discovery flew last July on the first mission since Columbia, a greatly reduced but hazardous amount of foam still fell from its redesigned tank during the launching. Afterward, engineers removed more than 37 pounds of foam that formed two air ramps, or deflectors, that protected pressurized fuel lines and a tray guiding cables down the side of the tank, places from which the biggest pieces of foam fell in the last mission.
NASA wants to fly the shuttle three times before the end of the year to get back on schedule for building the International Space Station before the shuttle fleet’s mandatory retirement in 2010. Officials hope to then fly four per year to finish the station with 16 flights, plus send a shuttle to repair the Hubble Space Telescope, before the deadline.
Mo'nonymous on New companion of Nep...
Mo'nonymous on New companion of Nep...
Mo'nonymous on New companion of Nep...
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