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Posts Tagged ‘Moon

LROC Explores Aristarchus Crater

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http://youtu.be/yb10Cpx27w0

Space probe gets up close to lunar crater that is two miles deep and so huge it can be seen from Earth with the naked eye

  • Orbiter flies past just 16.2 miles up
  • Images of crater twice as deep as Grand Canyon
  • Shows layers of minerals like strip mines on Earth

Nasa's Lunar Reconnaissance Orbiter flew over the moon at just 16.2 miles up to capture shots of the huge Aristarchus crater on the moon - a feature so massive it's visible to the naked eye, created when a huge comet or asteroid slammed into a plateau on the surface

Nasa's Lunar Reconnaissance Orbiter flew over at just 16 miles up, just over twice the height that jets fly on Earth - twice as low as the orbiter normally flies. The cliffs of Aristarchus are more than two miles high - twice as deep as the Grand Canyon

The ledges forming the wall of the crater, which look a lot like those of a strip mine, are blocks of surface rocks that slumped into the crater during the late stages of its formation

This Hubble colour composite focuses on the Aristarchus impact crater, and uses colour information across the ultraviolet and infrared to accentuate differences between minerals

Pyroclastic beads (volcanic glasses formed during fire-fountain style eruptions similar to those of Stromboli or the Hawaiian Islands) that blanket the area around the crater have slid down parts of the walls in dark streaks and clumps

Read more: www.dailymail.co.uk

Written by physicsgg

January 3, 2012 at 11:16 am

Moon, Saturn and Spica

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The Moon and two bright companions line up across the southeast before dawn tomorrow. The closer of the Moon’s companions is Spica, the leading light of the constellation Virgo. It’s to the left or lower left of the Moon. The other is the planet Saturn, which is to the left of Spica.

Saturn is the brighter of the two, and it’s growing a little brighter night by night. By the middle of April, it’ll shine about twice as brightly as Spica.

The reason for the change in Saturn’s brightness is the changing distance between Saturn and Earth.

Right now, we’re separated by close to 950 million miles. But Earth follows a much smaller, faster orbit around the Sun, so we’re quickly catching up to Saturn. We’ll pass it in mid-April, when we’ll be about 130 million miles closer. At that range, Saturn will shine half again as bright as it is now.

Of course, the distance between Earth and Spica changes by that much, too. But the star is about 250 light-years away. At such a great range, the difference of a hundred million miles or so is insignificant. So Spica’s light holds steady all year long. And when Saturn is at its farthest from Earth, Spica outshines it.

Even as we move past Saturn, though, it’ll remain quite close to Spica in our sky. In fact, they will remain quite close until late next year, when Saturn will finally begin to pull away from its bright stellar companion. stardate.org

Le matin du 20 décembre, cherchez le croissant de Lune. Il vous permettra de trouver deux astres remarquables : l’étoile Spica et la planète Saturne. Ces deux astres sont de luminosité comparable mais ils sont en réalité très différents…
See a relevent video here

Written by physicsgg

December 19, 2011 at 5:20 pm

Posted in ASTRONOMY

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Santa and the moon

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Peter Barthel
Happy end-of-the-year evening and night events provide good opportunities to explain the phases of the moon. The need for such moon phase education is once again demonstrated, through an investigation of illustrations on Santa Claus and Christmas gift wrap and in children’s books, in two countries which have been important in shaping the image of Santa Claus and his predecessor Sinterklaas: The Netherlands and the USA. The moon on Halloween illustrations is also considered. The lack of knowledge concerning the physical origin of the moon phases, or lack of interest in understanding, is found to be widespread in The Netherlands but is also clearly present in the USA, and is quite possibly global. Definitely incomplete, but surely representative lists compiling both scientifically correct and scientifically incorrect gift wrap and children’s books are also presented….

Read more: http://arxiv.org/pdf

Written by physicsgg

November 28, 2011 at 5:26 pm

Posted in ASTRONOMY

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Mystery of the Lunar Ionosphere

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Lunar researchers have been struggling with the mystery for years, and they may have finally found a solution.
But first, what is an ionosphere?
Every terrestrial planet with an atmosphere has one. High above the planet’s rocky surface where the atmosphere meets the vacuum of space, ultraviolet rays from the sun break apart atoms of air. This creates a layer of ionized gas–an “ionosphere.”
Here on Earth, the ionosphere has a big impact on communications and navigation. For instance, it reflects radio waves, allowing shortwave radio operators to bounce transmissions over the horizon for long-range communications. The ionosphere also bends and scatters signals from GPS satellites, sometimes causing your GPS tracker to mis-read your position.


http://youtu.be/_zSrP4MacFE

The first convincing evidence for an ionosphere around the Moon came in the 1970s from the Soviet probes Luna 19 and 22. Circling the Moon at close range, the orbiters sensed a layer of charged material extending a few tens of km above the lunar surface containing as many as 1000 electrons per cubic centimeter—a thousand times more than any theory could explain. Radio astronomers also found hints of the lunar ionosphere when distant radio sources passed behind the Moon’s limb.
The idea of an “airless Moon” having an ionosphere didn’t make much sense, but the evidence seemed compelling.
As a matter of fact, the Moon isn’t quite as airless as most people think. Small amounts of gas created by radioactive decay seep out of the lunar interior; meteoroids and the solar wind also blast atoms off the Moon’s surface. The resulting shroud of gas is so thin, however, that many researchers refuse to call it an atmosphere, preferring instead the term “exosphere.” The density of the lunar exosphere is about a hundred million billion times less than that of air on Earth—not enough to support an ionosphere as dense as the ones the Luna probes sensed.
For 40 years, the Moon’s ionosphere remained a mystery until Tim Stubbs of the Goddard Space Flight Center published a possible solution earlier this year. The answer, he proposes, is moondust.
Stubbs–a 30-something scientist who wasn’t even born when the Moon’s ionosphere was discovered—read the accounts of Apollo 15 astronauts who reported seeing a strange glow over the Moon’s horizon. Many researchers believe the astronauts were seeing moondust. The Moon is an extremely dusty place, naturally surrounded by a swarm of dust grains–think PigPen in Charlie Brown. When these floating grains catch the light of the rising or setting sun, they create a glow along the horizon.
Stubbs and colleagues realized that floating dust could provide the answer. UV rays from the sun hit the grains and ionize them. According to their calculations, this process produces enough charge (positive grains surrounded by negative electrons) to create the observed ionosphere.
An ionosphere made of dust instead of gas is new to planetary science. No one knows how it will behave at different times of night and day or at different phases of the solar cycle, or how it might affect future radio communications and navigation on the Moon. NASA’s ARTEMIS probes (orbiting the Moon now) and the LADEE spacecraft (scheduled to launch in 2013 specifically for the purpose of studying the lunar exosphere) may yet reveal its habits.
Read more: http://science.nasa.gov

Written by physicsgg

November 15, 2011 at 6:35 pm

Posted in ASTRONOMY, ASTROPHYSICS, SPACE

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Aliens don’t need a moon like ours

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Adds stability, but only a little (Image: SPL)

by David Shiga
TALK about being over the moon. It seems planets don’t need a big satellite like Earth’s in order to support life, increasing the number on which life could exist.

In 1993, Jacques Laskar of the Paris Observatory in France and colleagues showed that the moon helps stabilise the tilt of Earth’s rotation axis against perturbations by Jupiter’s gravity. The researchers calculated that without the moon, Jupiter’s influence would make the current tilt of some 23 degrees wander chaotically between 0 and 85 degrees. That could cause huge climate swings, making it hard for life to survive, especially large, land-based organisms like us.

The result was taken by many to imply that complex life is rare in the universe, since Earth’s large moon is thought to have coalesced from the debris of a freak collision between a Mars-sized planet and Earth. Less than 10 per cent of Earth-sized planets are expected to experience such a trauma, making large moons a rarity.

But a study now suggests moonless planets have been dismissed unfairly. “There could be a lot more habitable worlds out there,” says Jack Lissauer of NASA’s Ames Research Center in Moffett Field, California, who led the research.

The 1993 study showed that the Earth would tilt wildly without the moon because two of its motions would end up in sync, allowing Jupiter to have an outsize influence. The Earth orbits the sun on an elliptical path, and the long axis of this path shifts position over time. The Earth also wobbles like a spinning top as it rotates. Without the moon’s gravitational tugs, the rate of this wobbling would be slower, matching up in just the right way with the drifting of its elliptical orbit to magnify Jupiter’s effects on Earth’s spin axis, leading to big changes in tilt.

However, Laskar’s study did not determine how fast these changes in tilt would occur. “The astrobiology community has taken it to mean there will be these really wild variations, and we wanted to test that,” says Lissauer. He and his colleagues simulated a moonless Earth over 4 billion years, about the age of the Earth today. They found that our planet’s tilt varied between only 10 and 50 degrees, a much smaller range than implied by the earlier study. There were also long stretches of up to 500 million years when the tilt was particularly stable, keeping between 17 and 32 degrees (Icarus, DOI: 10.1016/j.icarus.2011.10.013).

Much larger changes might still occur on timescales longer than 4 billion years, the team admits. But in that case they might be irrelevant for life anyway, they say, because sun-like stars burn out after 10 billion years.

Large moons are not required for a stable tilt and climate, agrees Darren Williams of Pennsylvania State University in Erie. In some circumstances, he adds, large moons can even be detrimental, depending on the arrangement of planets in a given system. “Every system is going to be different.”

Jason Barnes of the University of Idaho in Moscow, who co-authored the latest study, is now leading simulations to look at how planet tilts behave in a wider variety of circumstances, including planets arranged in different ways to our solar system.
Read more: http://www.newscientist.com

Written by physicsgg

November 13, 2011 at 5:01 pm

Posted in ASTRONOMY, ASTROPHYSICS

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Moon’s shadow creates a wake

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A total solar eclipse

During a total solar eclipse the Moon comes directly between the Sun and the Earth, casting a dark shadow that moves across land and sea. Now, researchers in Taiwan and Japan have shown that this shadow creates a pocket of high-pressure air that cuts through the atmosphere much like a boat through water – leaving a discernible wake. As well as confirming a 40-year-old prediction, the discovery could have implications for how nuclear tests are monitored.
Along with plunging a region into darkness, an eclipse also causes a sudden cooling of the atmosphere. The effect this has on atmospheric pressure is complicated and not properly understood. Some places cool faster than others, creating regions where the pressure increases and regions where it decreases.
Jianlin Liu of the National Central University in Taiwan and colleagues have used Global Positioning System (GPS) technology to confirm a 40-year-old prediction that “shadow boats” are created in the atmosphere during an eclipse. These are thought to be pockets of high-pressure air directly under the Moon’s shadow that push their way through low-pressure air much like a boat pushing through water…. Read the rest of this entry »

Written by physicsgg

October 12, 2011 at 8:13 pm

Posted in meteorology

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Apollo 11 descends to the Google Moon

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This is pretty neat: an Apollo enthusiast who goes by the handle GoneToPlaid has created a video comparing the Apollo 11 footage of its descent to the Moon with images from Google Moon:

http://youtu.be/G9Nh5qWzqMY

That’s very cool. You can see the same features in the Apollo 11 film footage and in the newer view from Google Moon, which uses images from NASA’s Lunar Reconnaissance Orbiter as well as Japan’s Kaguya mission. The lighting was different so sometimes it makes features hard to spot in both — direct sunlight changes shadows, and also creates a spotlight effect which can hide craters and such — but you can see how well everything lines up. GoneToPlaid provides a link to the KMZ files you can use for Google Moon to check this out for yourself as well.

This won’t convince people who think NASA faked the landings, of course, nor do I really care. What I do care about is how this brings home what the astronauts did all those decades ago. Going to the Moon washard; it’s another world, with all the dangers and unknowns and difficult terrains that made it necessary to explore it before we went, and to do so once again in preparation for going back. Hopefully sometime soon.
http://blogs.discovermagazine.com

Written by physicsgg

September 28, 2011 at 7:15 pm

Posted in SPACE

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How common are earth-moon planetary systems?

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This illustration shows a potential satellite-forming impact on a proto-planet. Credit: Michael Elser, University of Zurich

Sebastian Elser, Prof. Ben Moore and Dr. Joachim Stadel of the University of Zurich, Switzerland, in cooperation with Ryuji Morishima of NASA’s Jet Propulsion Laboratory, tried to estimate how common Earth-Moon planetary systems are. They have found that 1 in 12 Earth-like planets probably hosts a Moon-like satellite. Since the Moon might have played an important role in the history of life on Earth, this estimate is important concerning the search for habitable planets….. Read the rest of this entry »

Written by physicsgg

September 19, 2011 at 11:00 am

Posted in ASTRONOMY, ASTROPHYSICS

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