Ancient Solar System
Astronomers announced this week the age of an ancient star system, some 117 light years from Earth. Kepler 444 and its five planets are around 11.2 billion years old, making it among the first generation of stars in the Milky Way. Our own sun and solar system are less than half as old, having formed about 4.6 billion years ago.
The age of the star was determined through asteroseismology. Basically, as a star ages, it converts its hydrogen into helium, and the composition of its core changes. The change in composition changes the speed at which sound waves moves through the stellar body. The speed of sound inside a star affects the star’s brightness. Therefore, by observing minute changes in Kepler 444’s brightness with NASA’s Kepler space telescope, scientists were able to determine the star’s age. Got that?
Each of Kepler 444’s planets is Earth-size or smaller, making them likely to be rocky, terrestrial worlds, but they also orbit extremely close to their parent star. Even though Kepler 444 isn’t as large or as bright as the Sun, the planets would still be sizzling hot and well outside the star’s habitable zone.
However, “This tells us that these kinds of planets formed very early in the history of the galaxy. If some fraction formed in the habitable zones around their host stars, then you have environments where life may develop, and it could have been there for a very long time,” said Bill Chaplin, professor of astrophysics at the University of Birmingham.
Until recently, it was not known if terrestrial planets could form so early in the history of the Universe. Since the Universe started with almost nothing but hydrogen and helium, requiring generations of stars to fuse anything heavier, some astronomers thought the first stars would not have had adequate time to create heavier elements necessary for terrestrial planets.
Astronomers are now eager to discover other ancient planetary systems to help pinpoint when the era of planetary formation in the Universe began. -Elise Ricard
Super Saturn’s spectacular rings
Within our solar system few planets are as immediately recognizable as Saturn, and what makes it so recognizable? Its hazy color? Its hexagonal polar features? No—its rings!
We have so inextricably tied our ideas of Saturn to the thin but highly visible rings around it that without them, the planet might seem a featureless orange-yellow ball. We even forget the rings of Jupiter, Uranus, and Neptune sometimes, since they pale in comparison. But if Saturn’s rings make it the “jewel of the Solar System,” astronomers have just found a veritable Hope Diamond.
J1407 is a large exoplanet with rings that potentially dwarf Saturn’s. While the extrasolar world is quite big (nearly as large as a small brown dwarf), the ring structure observed around it is 200 times the width of Saturn’s rings, or about 180,000,000 kilometers (112,000,000 miles) across!
An easy way to think about these daunting scales is to imagine placing J1407 at the center of our solar system, where the Sun is. From that location, the planet’s colossal rings would reach beyond the orbit of Mercury and nearly to that of Venus!
This discovery might herald other interesting news. Saturn’s rings are shepherded into place and slowly sculpted by moons within and around them, and there is some early evidence that suggests that J1407 might have some moons playing a similar role. If that is the case, then for the first time ever, scientists have found not just a planet orbiting a distant star, but also evidence of a moon orbiting a planet orbiting a distant star! -Josh Roberts
The Big Asteroid with a Little Moon
Passing about 745,000 miles from Earth on January 26, asteroid 2004 BL86 was big enough to be seen in small telescopes as it cruised through the night sky. About a thousand feet across, the Near Earth Object was observed by amateur astronomers worldwide who knew exactly where and when to look and photographed it as it passed M-44, the “Beehive” star cluster.
Never closer to Earth than three times the distance to the Moon, the asteroid never posed a threat to Earth and continued safely into the night.
However, the passing rock didn’t come without its surprises. Although seen as a pinpoint in amateur telescopes, the asteroid’s spherical shape was revealed by radar images taken from NASA’s Deep Space Network facility at Goldstone, California. Some of the images, with a resolution of four meters per pixel, were assembled into a stunning animation that also revealed surface features and, unexpectedly, a small moon measuring about 200 feet across.
This is not the first time a moon has been found orbiting an asteroid, but this discovery shows how little we still know about the minor members of the solar system, with recent observations from current spacecraft missions to Ceres and Vesta (two of the largest objects in the asteroid belt, and we’ll tell you more about Vesta below) showing their surfaces in greater detail than ever before, plus new conclusions being drawn from the Rosetta mission about the source of Earth’s water.
In an effort to educate the public more about asteroids, world-renowned scientists, astronauts, Nobel laureates, artists, and other visionaries are in the process of organizing Asteroid Day on June 30, the 107th anniversary of an asteroid encounter that didn’t miss Earth—the largest asteroid impact on our planet in modern times—the 1908 impact in Tunguska, Siberia. -Bing Quock
Water on Vesta?
While much of the attention in the asteroid belt is turned towards Ceres in anticipations of NASA’s Dawn mission’s March 6th arrival, scientist are still poring over discoveries from the spacecraft’s previous target, Vesta. Last week, researchers with the Jet Propulsion Laboratory (JPL) released images of what appear to be gullies and fan-shaped deposits in eight impact craters on Vesta. They suggest that this is evidence that flowing, liquid water once existed on the surface of the large asteroid.
But wait! Vesta has no atmosphere, extremely low pressure, and a freezing cold surface. Any water on the surface should sublimate away. (With no atmosphere to support water in a liquid state, ice would transition directly to vapor, or sublimate. When liquid transitions from liquid to gas, we say that it evaporates—a far more familiar process here on Earth.)
However, they are not suggesting that Vesta once hosted vast rivers of pure water that carved the gullies. Rather, according to Jennifer Scully, postgraduate researcher at UC Los Angeles, “We’re suggesting a process similar to debris flows, where a small amount of water mobilizes the sandy and rocky particles into a flow.” She then explained that laboratory experiments suggest the debris would slow the water’s evaporation rate enough to allow the gullies to form. And the formations do bear a striking resemblance to similar debris flows found on Earth and Mars.
But that still requires at least a little liquid water. Where might it have come from? Scientists are still debating the source of the initial water, although the team argues that Vesta may have pre-existing sub-surface ice. The impact shock from an encounter with another asteroid or comet would heat pre-existing ice into liquid water. Water lasted just long enough in this form to flow down the edge of the crater, mobilize sand and rock to create the gullies, and then freeze or—in the absence of a substantial atmosphere—boil away.
Although too small to be considered a planet, the second most massive asteroid (or third-largest in size, or the densest, take your pick) is turning out to be far more complex, even more planet-like, than we could have imagined. -Elise Ricard
Images: Kepler 444, Tiago Campante/Peter Devine; J1407, Ron Miller; Vesta, NASA/JPL-Caltech/UCLA/MPS/DLR/IDA; Asteroid 2004 BL86, NASA/JPL-Caltech