Posts tagged space
If Earth Had a Ring Like Saturn
Our planet is lucky enough to have a large moon orbiting not too far away, which makes for very pretty moonlit nights. But for spectacular skies it might almost be worth trading in our moon for a ring like Saturn’s.
In fact, the earth did once have a ring - as part of the formation of our moon, ironically enough. When the planet Thea crashed into the earth, a titanic amount of material was blown into space. This went into orbit around the earth, forming a ring until it all eventually coalesced into our present-day satellite. This only happened because the material was orbiting outside of earth’s Roche limit.
In 1848, the French mathematician Edouard Roche calculated that if a large satellite were to approach too closely to a planet, it would be torn apart by the planet’s gravitational forces. This happens because the gravitational attraction of a planet on a moon is not equal. The planet pulls more on the side of the moon closest to it and less on the side further away. If the moon gets too close, this unequal pull can become great enough to tear the moon apart. Every planet has what is called a Roche limit.
Some astronomers believe that Saturn’s rings are material that was unable to form into a moon because it lies within the planet’s Roche limit. The gravitational pull of Saturn prevents particles from clumping together to form a moon. Another idea popular among scientists suggests that during the time when Saturn was first forming, it had one or more moons just outside its Roche limit. The bigger a planet is, the more gravity it has. And the more gravity it has, the bigger its Roche limit is. So as Saturn grew larger, its Roche limit grew, too. The limit soon moved past the inner moons and these moons soon broke apart. The remnants of the destroyed moons eventually formed the magnificent rings we see today. There may still be large pieces of these ancient moons within the rings. They would be much smaller than their ancestors but a thousand times larger than a typical ring particle. Another theory suggests that a few hundred million years ago - at a time when the early ancestors of the dinosaurs were roaming Earth - Saturn may have had no rings at all. The rings formed when one or more small moons wandered too close to Saturn. When they got within the Roche limit, Saturn’s gravity ripped them apart. After millions of years of bumping against one another, the pieces of moon were ground into the tiny particles that form the rings today.
If we had rings in the same proportion to our planet that Saturn’s are to it, it is pretty easy to figure out what they would like like from different places on the earth. From the equator the rings would be passing directly overhead. Since you’d be looking in the same plane as the rings, all you would see is a bright line arching from horizon to horizon. Here is what the rings might look like from Quito, Ecuador:
If we travel just a little further north to Guatemala, the rings begin to spread across the sky. The earthlight illuminating the dark side of the moon is many times brighter than we are accustomed to, due to the increased sunlight being reflected from the rings.
From Washington, DC (at 38° latitude), the rings begin to sink below the horizon, though they would still be an awe-inspiring sight as they dominate the sky both day and night.
At the Arctic Circle, the rings barely reach above the horizon. Seen here from Nome, Alaska, the brilliant rings illuminate the barren landscape scarcely more than a full moon would. Unlike the sun or moon, however, the rings neither rise nor set… they are always visible, day or night, always in exactly the same place.
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blua:
What the city is missing: Thierry Cohen photographs cityscapes and then photographs deserts at night, combing the two to show us what our cities would look like with the lights off. The stars are not enhanced, they are actual photos from relative latitudes that would expose the same starry sky view if it weren’t for light pollution. Click on each photo to see which city it is.
Light pollution and pollution in general
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NASA Probe Gets Close Views of Large Saturn Hurricane
NASA’s Cassini spacecraft has provided scientists the first close-up, visible-light views of a behemoth hurricane swirling around Saturn’s north pole.
In high-resolution pictures and video, scientists see the hurricane’s eye is about 1,250 miles (2,000 kilometers) wide, 20 times larger than the average hurricane eye on Earth. Thin, bright clouds at the outer edge of the hurricane are traveling 330 mph(150 meters per second). The hurricane swirls inside a large, mysterious, six-sided weather pattern known as the hexagon.
“We did a double take when we saw this vortex because it looks so much like a hurricane on Earth,” said Andrew Ingersoll, a Cassini imaging team member at the California Institute of Technology in Pasadena. “But there it is at Saturn, on a much larger scale, and it is somehow getting by on the small amounts of water vapor in Saturn’s hydrogen atmosphere.”
Scientists will be studying the hurricane to gain insight into hurricanes on Earth, which feed off warm ocean water. Although there is no body of water close to these clouds high in Saturn’s atmosphere, learning how these Saturnian storms use water vapor could tell scientists more about how terrestrial hurricanes are generated and sustained.
Both a terrestrial hurricane and Saturn’s north polar vortex have a central eye with no clouds or very low clouds. Other similar features include high clouds forming an eye wall, other high clouds spiraling around the eye, and a counter-clockwise spin in the northern hemisphere.
A major difference between the hurricanes is that the one on Saturn is much bigger than its counterparts on Earth and spins surprisingly fast. At Saturn, the wind in the eye wall blows more than four times faster than hurricane-force winds on Earth. Unlike terrestrial hurricanes, which tend to move, the Saturnian hurricane is locked onto the planet’s north pole. On Earth, hurricanes tend to drift northward because of the forces acting on the fast swirls of wind as the planet rotates. The one on Saturn does not drift and is already as far north as it can be.
“The polar hurricane has nowhere else to go, and that’s likely why it’s stuck at the pole,” said Kunio Sayanagi, a Cassini imaging team associate at Hampton University in Hampton, Va.
Scientists believe the massive storm has been churning for years. When Cassini arrived in the Saturn system in 2004, Saturn’s north pole was dark because the planet was in the middle of its north polar winter. During that time, the Cassini spacecraft’s composite infrared spectrometer and visual and infrared mapping spectrometer detected a great vortex, but a visible-light view had to wait for the passing of the equinox in August 2009. Only then did sunlight begin flooding Saturn’s northern hemisphere. The view required a change in the angle of Cassini’s orbits around Saturn so the spacecraft could see the poles.
“Such a stunning and mesmerizing view of the hurricane-like storm at the north pole is only possible because Cassini is on a sportier course, with orbits tilted to loop the spacecraft above and below Saturn’s equatorial plane,” said Scott Edgington, Cassini deputy project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “You cannot see the polar regions very well from an equatorial orbit. Observing the planet from different vantage points reveals more about the cloud layers that cover the entirety of the planet.”
Cassini changes its orbital inclination for such an observing campaign only once every few years. Because the spacecraft uses flybys of Saturn’s moon Titan to change the angle of its orbit, the inclined trajectories require attentive oversight from navigators. The path requires careful planning years in advance and sticking very precisely to the planned itinerary to ensure enough propellant is available for the spacecraft to reach future planned orbits and encounters.
Image credit: NASA/JPL-Caltech/SSI
Space boner.
(Source: spaceplasma)
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Hubble Space Telescope launched 23 years ago today.
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Footprints and tire tracks left behind by astronauts on the moon will stay there forever as there is no wind to blow them away.
Credit: NASA
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Dr. Neil deGrasse Tyson on the defunding of NASA.
HNGGGGG THIS
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What’s six miles wide and can end civilization in an instant? An asteroid. But astronomer and former Hubble worker Phil Plait has a solution. In a humorous and optimistic talk at TEDxBoulder, Plait discusses the death of the dinosaurs, detecting asteroids, preventing impact, and the asteroid Apophis. Apophis is the size of three and a half football fields and will fly close to the Earth in 2036. Don’t worry, it won’t impact Earth. Plait thinks this is a blessing and an opportunity to study asteroids. First, research and technology development need funding.
You’re not a dinosaur. You have a space program and can vote. Use your voice to write to Congress and tell them you want NASA’s budget doubled.
View Phil Plait’s How to defend Earth from asteroids TEDxBoulder talk
Check out Phil Plait’s blog, Bad Astronomy
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How much would you pay to live forever? The late science fiction author Ray Bradbury believed that by reinvesting in space travel humanity had a chance to live forever. Bradbury dreamed of us building a base on the moon, going to Mars, and moving further out into the universe. NASA could turn dreams that seem like science fiction into reality with increased funding.
NASA has repeatedly shown that an investment in space is also an investment in the future——the future of the United States, the world, and the long-term survival of humanity. In a 2010 interview Bradbury said, “So our future is investing, right now, in space travel, and money should be given to NASA sometime next year to build the rockets to go back to the moon.” Let’s invest in our future by investing in NASA.
Tell Congress that you support doubling funding for NASA
Learn about NASA’s future missions
Listen to the rest of the 2010 Comic Con interview with Ray Bradbury
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“…and we invented the Industrial Revolution along the way. Investing in science is vital to our future.” - Brian Cox
With painful budget cuts facing the entire spectrum of public spending, it’s more important than ever to keep in mind just how much economic benefit a little investment in science can have. Midwest Research Institute studies found that every federal dollar spent on NASA returned 7 into the economy. A study by the Space Division of Rockwell International also found that NASA’s space shuttle program had an employment multiplier of 2.8—for every man-year of employment directly created by the Shuttle program, 2.8 man-years of total employment was generated.
NASA has shown time and again that an investment in space is also an investment in the future and in America as a whole. Not only does NASA research benefit the country economically, it inspires us to dream and drives generations into STEM fields like nothing else.
Read the findings of the MRI study and other ways NASA aids the economy here: http://goo.gl/ao51M
Watch Dr. Brian Cox’s TED Talk, “Why We Need The Explorers”, here: http://goo.gl/vjC2#Penny4NASA #NASA #BrianCox #SpaceExploration
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From Wired Science Space Photo of the Day, solar flare on December 31, 2012.
Mostly posted for @warrenellis.
Goddamn, that’s impressive.
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We’re ready. Are you?
Tell Congress its time to establish a permanent presence off-world at penny4NASA.org/take-action/
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At top, the Soyuz that we flew here and will fly home in May. Below, the Progress that undocked and burnt up.
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