Skywatch

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    Episode 32: Was Mars Wet?

    Some scientists believe gullies running along the inner edges of some Martian craters were carved by liquid water, but new findings suggest they might instead be the result of landslides triggered by wind and meteor impacts. Researchers recently noticed similar gullies on a crater of Earth's Moon, where no water exists. The Moon gullies were likely caused by dry flows of dust and sand.

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    Episode 31: Galactic Twins

    Our Milky Way galaxy and one of our closest galactic neighbors, the Andromeda galaxy, appear to have had similar beginnings, and even evolved in similar ways over the first billion years of their lives. Astronomers found evidence of this when they recently used Hawaii's Keck Telescope to survey stars in Andromeda's halo, the fainter corona of stars and gas that extends well beyond the brighter visible familiar in photos.

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    Episode 30: Stardust Lives?

    We may not have seen the end of the Stardust mission. The mission, whose probe scooped up samples of comet material before returning to Earth in January 2006, still has a mothership in space. Analysis of the samples offers enticing clues about the formation of comets and our solar system. Researchers are considering whether the Stardust mothership, now in hibernation, could be used to take pictures of Comet Tempel 1 - specifically, the part blown open in July 2006 by another comet mission, Deep Impact. Lots of ideas are submitted to NASA for creating new missions and reusing old ones. The agency convenes a panel to fairly review all these ideas and see which ones are affordable.

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    Episode 29: Crystal Clouds in Galaxy Centers

    When galaxies merge, gemstone-like crystals form in the entangled hearts. Galaxy collisions trigger huge amounts of star formation. Some of the stars are extremely massive and burn through their fuel quickly, eventually exploding as supernovae. The supernovae spew out silicate material. The dust and crystals envelope the nuclei of the galaxies for a short time before the crystals are destroyed by radiation. Scientists using the Spitzer Space Telescope observed 77 galaxies in the process of merging. These galaxies are distributed across the sky and located at a variety of distances, from 240 million light years to 5.9 billion light years away. Twenty-one of the galaxies showed these crystal cocoons around their centers.

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    Episode 28: Planets Orbiting Backwards?

    Usually planets orbiting a star all orbit in the same direction. But a newly discovered system may have planets orbiting both ways. The new system isn't a true solar system yet, but has two disks of material rotating in opposite directions around a central star. The disk provides the material that will eventually form into planets. This is the first time anything like this has been seen in a forming solar system. It means that the process of forming planets from disks is more complex than previously expected.

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    Episode 27: Top Ten Stars to find ET's

    In our search for life on other worlds, where do we look among the billions of stars in our own Milky Way galaxy? Scientists can listen for radio transmissions from nearby stars where intelligent civilizations might be, or they can try to recognize planets similar to ours in habitable zones around nearby stars. Either method is tricky and depends on choosing the right targets out of the thousands of stars that lie relatively close to our own solar system. Recently, astronomer Margaret Turnbull identified the top 10 stars that may harbor habitable zones where life - either primitive or advanced - might exist. Earth-based telescopes may be able to examine five of the stars, while the other five would be good targets for a future "planet finder" mission.

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    Episode 26: Not Just an Empty Suit

    More than 8,000 objects orbit the Earth, so the competition is pretty fierce for the weirdest thing out there. That said, SuitSat has to take top honors. On Feb. 3, astronauts at the International Space Station threw overboard an empty Russian space suit equipped with batteries, a radio transmitter and internal sensors. SuitSat transmitted its condition as it floated through space. Students and ham radio operators listened in on the transmissions until its batteries wore out.

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    Episode 25: Asteroid's Destruction Caused Dust Storm

    Deep in the Indian and Atlantic Oceans lies evidence of a massive cosmic dust storm over 8 million years ago. Scientists found helium-3, an element rarely found on Earth, in a layer of ocean sediment dating to that time period. The dust storm, the biggest of the past 80 million years, was likely caused by an asteroid that broke apart in space. As the Earth traveled its orbit around the Sun, it eventually scooped up tons of the material.

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    Episode 24: Stardust

    Scientists now have samples of comet dust. On Jan. 15, 2006, the Stardust capsule successfully returned to Earth. Stardust was an ambitious mission to use a satellite to robotically intercept a comet and collect its material for analysis. Stardust encountered Comet Wild 2 in January 2004. The satellite then flew back to Earth and dropped the capsule with the samples. The capsule deployed a parachute and safely streaked through the atmosphere to the Utah desert. Scientists are busy analyzing the comet dust from the samples collected. Since comets contain material from the outer reaches of the solar system, scientists hope that the analysis will help us better understand the formation of the solar system.

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    Episode 23: Polaris' Third Star

    The North Star, that friendly, constant guide to sailors and travelers, is actually the North Stars. Scientists have known for some time that Polaris, though it looks like a single bright light from our perspective, is really a star system. The latest images from the Hubble Space Telescope show for the first time a third star, long hidden in the glare of the other two stars in the system. Polaris is a supergiant star more than 2,000 times brighter than Sun. Its distance from Earth makes Polaris only a medium-bright star in our sky - not the brightest by a long shot. Fifty other stars are brighter. The newly photographed companion star is a little more massive than Sun, as well as a little brighter, and a little hotter.

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    Episode 22: Black Holes Grow

    Scientists are finding evidence that the black holes in the centers of galaxies grow over time as galaxies collide and merge with one another. Data from the Hubble Ultra Deep Field, an image that shows galaxies from an early period in the universe, can be compared with computer simulations to uncover clues that point toward black holes in young galaxies. Black holes seem to grow by pulling in stars, gas and dust from surrounding regions of the galaxy. Simulations show the centers of the young galaxies fluctuate in brightness. The fluctuations suggest that black holes may be gobbling stars and dust that spiral near the centers of the host galaxies. More of this material becomes available when the galaxies merge.

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    Episode 21: Buffy the Kuiper Belt Object

    A new mystery is afoot in our solar system. Scientists at the Canada-France-Hawaii Telescope on Hawaii's Mauna Kea have discovered an object, about a fifth to half the size of Pluto, traveling in an orbit tilted about 47 degrees to most of the other objects in the solar system. The strange orbit is confounding astronomers. In addition to the tilt, the orbit is close to circular - odd in a solar system with mostly elliptical orbits. Scientists have tentatively named the object 2004 XR190, but nicknamed it "Buffy," after the TV show "Buffy the Vampire Slayer." Kuiper Belt objects like Buffy can acquire strange orbits by interacting with other objects - but those common explanations don't seem to apply in this case. Buffy's distance and strangely shaped orbit help rule out a close encounter with the usual suspect, Neptune. Likewise, a passing star would have given its orbit a different shape.

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    Episode 20: New Rings Around Uranus

    Scientists have discovered additional rings around the planet Uranus. Uranus has been known to have a ring system since 1977, but recent Hubble observations show that its ring system is much bigger than thought. The newly discovered rings are very diffuse and twice the diameter of the planet's previously known rings. In addition to this "secondary" ring system, more satellites, or moons, were discovered orbiting Uranus. These satellites are near the rings, giving rise to speculation that dust from the moons could be the basis for the distant rings.

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    Episode 19: Measuring a White Dwarf

    The mass of Earth's nearest white dwarf has finally been measured. White dwarf stars are the collapsed remains of low- to medium-mass stars that have burned out. For over 140 years, astronomers have known that Sirius, the brightest star in the northern sky, is actually a pair of stars: a bright blue-white star and a dim white dwarf. Unfortunately, Sirius A, the brighter of the two, overwhelms the light of Sirius B, the white dwarf. Using the Hubble Space Telescope, astronomers have been able to separate the light of the two stars. They measured Sirius B's mass by studying the effect its strong gravity has on the light it emits. Measuring the mass of white dwarfs is critical to understanding how stars like our Sun evolve.

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    Episode 18: Mars Rovers Mark Second Anniversary

    Mars rovers Spirit and Opportunity are celebrating two years of exploring Mars. These golf cart-sized vehicles were only expected to last 3 months, so they have long outlasted their warranties. Spirit landed on Mars on Jan. 3, 2004, and Opportunity on Jan. 24, 2004. Together, the rovers have traveled a total of seven miles - not very impressive until you consider average temperatures well below zero and 100-mph dust devils blowing across the landscape. The rovers accomplished their main mission - to uncover geologic evidence that water once flowed on Mars. They continue to explore the rocky alien terrain.

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    Episode 17: SOHO 10-Year Anniversary

    It's difficult to study our closest star, the Sun. Its brilliance blinds as well as illuminates. Fortunately, for the past decade, we've had Solar and Heliospheric Observatory, or SOHO, monitoring the Sun on a daily basis. SOHO, which celebrated its 10th anniversary in December, studies the Sun's internal structure and far-reaching outer atmosphere, and the stream of gases called the solar wind. Its observations help us better understand the interactions between the Sun and the Earth's environment. SOHO is a joint project of the European Space Agency and NASA. It was built in Europe with instruments provided by European and American scientists.

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    Episode 16: Dinner in Space

    Preparing a holiday dinner is complicated enough at home. Imagine what it must be like to throw a feast in space. Luckily, times have changed and meals have come a long way from the first applesauce tubes that John Glenn dined on. Holiday meals now consist of favorites - turkey and cranberry sauce and lots of goodies that appeal to astronauts' sweet tooths. Technology has lead to new packaging and better methods for reconstituting food, making dining in space more appealing and fun.

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    Episode 15: How to Set Up a Moon Base

    You're off to visit the Moon! It's a long trip, but pack light - the cost of carrying supplies from Earth is extremely expensive. You'll need to find and manufacture much of what you need on the Moon. Fortunately, the Hubble Space Telescope recently confirmed that some of the right materials exist there. It was the first time scientists used Hubble to plan for human space exploration. Hubble observed the Apollo 15 and Apollo 17 landing sites, where astronauts found oxygen-bearing minerals in the 1970s. Hubble also viewed areas that astronauts have never visited - the young Aristarchus impact crater and the adjacent Schroter's Valley. Hubble's ability to see ultraviolet light helped find lunar materials rich in oxygen. Hubble mapped variations in reflections of ultraviolet light off the lunar surface to search for specific minerals. Early measurements of the Hubble observations pinpoint locations of ilmenite at the Apollo 17 landing site. Ilmenite, a titanium material, is potentially a key resource because it contains easily extracted oxygen, which can be used for breathing and rocket fuel.

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    Episode 14: Andromeda's Black Hole

    Scientists believe that gigantic black holes exist in the centers of most galaxies, but only two had actually been confirmed. Now we can bring that number to three. Our neighbor galaxy, Andromeda, was long thought to harbor a black hole at its center. Its core gives off X-rays, the likely product of a disk of gas spiraling into a black hole. But the core also emits a mysterious blue light, a fact known for some time but never really understood. Scientists using the Hubble Space Telescope Imaging Spectrograph solved the puzzle. The blue glow comes from a flat disk of more than 200 young, hot stars very close to the galaxy's core. All these stars so close to the core is evidence that Andromeda, also known as M31, harbors a black hole twice as large as originally thought. It would contain 140 times the amount of material in our Sun.

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    Episode 13: Pluto's New Moons

    What is Pluto? Currently Pluto is embroiled in a controversy over whether it should be called a planet or a Kuiper Belt object. The Kuiper Belt is a group of icy bodies beyond the orbit of Neptune.

    Pluto's potential new moons
    Pluto's potential new moons
    Recently, scientists discovered two additional moons orbiting Pluto, fueling support for its classification as a planet. Pluto was thought to have only one moon, Charon, which orbits 12,024 miles (19,351 km) from Pluto. The two newly discovered moons are much further away. One orbits 30,000 miles (48,000 km) from Pluto; the other 40,000 miles (64,000 km). Scientists are working to confirm the discovery. And the debate continues over whether Pluto is a planet or a Kuiper Belt object that happens to have three other objects in orbit around it.