Posts tagged astronomy.
The Freakiest Places in the Solar System
1. WEIRDEST ROTATION
The Saturnian moon Hyperion is a lumpy thing, measuring about 255 x 163 x 137 miles in diameter along its three axes. Since moons of this size typically have enough gravity to pull them into a spherical shape, astronomers suggest that it may be a fragment of a larger moon that was shattered by an impact. The planet’s odd shape explains why the planet is, as Baker and Ratcliff put it, “a tumbling chaotic mess.” Most large moons are tidally locked, meaning that the same face of the moon always faces its planet. But Hyperion’s bizarre shape prevents such locking, because the gravitational torques from Saturn and the moon Titan tug at it unevenly.
Picture a canyon that stretches from San Francisco to Washington DC, and you’ll have an idea of the scope of Valles Marineris on Mars.
This enormous gorge was first spotted by the NASA spacecraft Mariner 9 in 1972, and the canyon was named in the spacecraft’s honor. It stretches 2,485 miles across the planet’s surface, and reaches depths of 6.2 miles (for comparison, our Grand Canyon plunges 1.1 miles down at its deepest point). Valles Marineris is thought to be a rift valley, formed by uplift when hot material from the Mars’s mantle bubbled up and stretched the planet’s crust.
The result: A rotation that’s impossible to predict. “The days are never the same,” the authors write. “Not only does the rotation rate (the length of day) vary erratically, but Hyperion’s north pole continually points to a different location in space.” Astronomers know the equation to predict the moon’s rotational motion, but small uncertainties in measurements of the moon’s initial location or velocity turn into large uncertainties over time. For Hyperion, the authors say, “it is completely impossible to predict the direction of its spin axis after about 300 days—it could be pointed anywhere!”
The Jovian moon Io is fascinating from a planetary science perspective—it’s the most volcanically active place in our solar system, and its surface is pockmarked with volcanic craters. But it wouldn’t be much fun to visit. Baker and Ratcliff write that “Jupiter’s moon Io smells like a jumbo rotten egg.” The stink is due to hydrogen sulfide on Io’s surface and in its upper atmosphere, and the moon owes its distinctive yellow and red coloration to sulfur compounds.
Volcanic eruptions are quite common on Io, and they constantly refresh the atmosphere’s supply of sulfur gas. The moon is highly active because it travels around Jupiter in a slightly elliptical orbit. As the moon repeatedly dances closer to and farther from the giant planet, Jupiter’s gravity produces tidal flexing in the moon’s interior that heats its mantle and causes violent explosions. In 2007 NASA’s New Horizons spacecraft flew by Io and observed a volcanic eruption with sulfur plumes that stretched 180 miles above the surface. The largest volcanic eruptions on Earth reach about 12 miles high.
This storm shows no inclination of blowing itself out. Jupiter’s Great Red Spot was first observed by the Italian astronomer Giovanni Cassini in 1665; while observations were sporadic in the 18th and early 19th centuries, many astronomers think the storm has been roaring for the 345 years since it was first seen. The immense storm is the size of three Earths, and the winds reach speeds topping 400 miles per hour.
How has it kept churning through the centuries? Baker and Ratcliff explain that its energy comes from Jupiter’s interior and smaller vortices. “Remarkably, Jupiter’s interior supplies 70 percent more energy to the cloud tops than the planet receives from the Sun,” they write. “Like a giant air compressor, gravitational contraction generates intense pressures and heat deep inside the planet. Powerful thunderstorms in Jupiter’s atmosphere channel much of this heat to the cloud tops.” Smaller storms are devoured by the Great Red Spot, which allows it to roar on.
Sun’s Twin Discovered — the Perfect SETI Target?
There are 10 billion stars in the Milky Way galaxy that are the same size as our sun. Therefore it should come as no surprise that astronomers have identified a clone to our sun lying only 200 light-years away.
Still, it is fascinating to imagine a yellow dwarf that is exactly the same mass, temperature and chemical composition as our nearest star. In a recent paper reporting on observations of the star — called HP 56948 — astronomer Jorge Melendez of the University of San Paulo, Brazil, calls it “the best solar twin known to date.”
The “Golden Record” would be an upgrade to Pioneer’s plaques. Mounted on Voyager 1 and Voyager 2, twin probes launched in 1977, the two copies of the record would serve as time capsules and transmit much more information about life on Earth should extraterrestrials find it.
Photo: J. Marshall - Tribaleye Images / Alamy
Serious blow to dark matter theories? New study finds mysterious lack of dark matter in Sun's neighborhood ›
“The most accurate study so far of the motions of stars in the Milky Way has found no evidence for dark matter in a large volume around the Sun. According to widely accepted theories, the solar neighbourhood was expected to be filled with dark matter, a mysterious invisible substance that can only be detected indirectly by the gravitational force it exerts. But a new study by a team of astronomers in Chile has found that these theories just do not fit the observational facts. This may mean that attempts to directly detect dark matter particles on Earth are unlikely to be successful.”
This gimballing rig was designed to test astronauts’ ability to right a tumbling aircraft. It’s formally called MASTIF or Multiple Axis Space Test Inertia Facility and it’s pictured operating in the Altitude Wind Tunnel at the (then) Lewis Research Center.
It was designed as part of the Mercury program.
Image description: NASA engineer Ernie Wright looks on as the first six mirror segments from the James Webb Space Telescope are prepped to begin final cryogenic testing at NASA’s Marshall Space Flight Center.
Photo by David Higginbotham, NASA
April 16, 2012: A prominence shoots off the left side of the sun in association with an M1 class flare that was not Earth-directed. [x]
Planetwide changes in Jupiter’s atmosphere during 24 rotations from October 31st to November 9th, 2000. Make sure to view it big.
Compiled from photographs by the Cassini Orbiter.
Venus Transit, 2004
The transit on June 8th, 2004 was the first in 122 years. The next one is coming up soon, but don’t miss it, otherwise you’re in for a long wait. Read about the next one, here.
(Credit; Radu Corlan, P.M. Heden, Elio Daniele, Aleksandra Jasar Miklavicic & Kapler Sabina, Aleksander Shulevski)
A tornado of plasma on the sun
So here is a real image taken by the Cassini probe last night. What you’re looking at are jets of water and ice spewing out of cracks on the surface of Saturn’s moon Enceladus.
These jets contain salty, icy particles as well as organic compounds. Cassini has been able to test the salinity of the vapour jets and has found the same salt content as in Earth’s oceans!
What is even more awesome is that there is a possibility that underneath its icy shell, Enceladus harbours life similar to that found in harsh conditions on Earth.
Read read read, its quite cool!