May 29, 2009 | 1
Astronomers looking for planets encircling stars outside our solar system—known as extrasolar planets, or exoplanets—are claiming the first planetary detection from a technique known as astrometry, which tracks the location of stars in the sky with great precision.
Astrometric observations of a nearby star called VB 10 revealed a telltale motion in the star's position caused by the gravitational pull of its companion planet, dubbed VB 10b. VB 10 and its planet are an astronomical odd couple: the star is one of the least massive known, whereas the planet itself is some six times the mass of Jupiter. In contrast to the solar system, where the sun is some 10 times the diameter of the largest planet, VB 10 and VB 10b have roughly the same width.
May 22, 2009 | 7
New research may shed light on the stellar explosions used as cosmic mileposts.
Type Ia supernovae, known as "standard candles" in astronomy, have consistent properties that make them good markers of distance when peering at galaxies across the universe. In fact, studies of this kind of exploding star a decade ago produced one of the most significant scientific discoveries in recent history: that the universe is expanding at an accelerating rate, thanks to the influence of so-called dark energy.
In a paper set to be published in Astronomy & Astrophysics, members of a consortium known as the Nearby Supernova Factory present a new way to ascertain type Ia supernovae's relative distance quickly and accurately, thereby increasing their usefulness as markers. Whereas past approaches painstakingly tracked the light output from the explosion over time, the new method can be used to measure a supernova's luminosity, and hence distance, much more quickly, and with a level of accuracy the study's authors say surpasses the traditional approach.
May 7, 2009 | 3
In April we reported on the deep and ongoing lull in solar activity, noting that the predicted sunspot minimum, which comes about every 11 years or so, seemed to be longer and quieter than usual. (A sunspot is a dark patch on the sun that marks a region of elevated magnetic activity.)
At that time, 2009 was on pace to surpass 2008 in terms of sunspot-free days, as observed from Earth—and 2008 was already the second-quietest year of the past century. The solar cycle is no mere astronomical oddity: so-called space weather that originates from solar activity can have very tangible effects on Earth and its environs, disrupting power grids, upsetting satellite communications and causing pipelines to rust.
Apr 30, 2009 | 13
Black holes are thought to be common in the universe, with a supermassive gobbler lurking at the core of galaxies such as our own Milky Way. But might they also be found roaming outside the galactic centers?
A new study estimates that approximately 300 black holes may lurk throughout the Milky Way, remnants of the building blocks that came together billions of years ago to form the galaxy. What is more, those black holes may retain properties that would allow astronomers to identify them, providing an archaeological record of the galaxy's formation.
Ryan O'Leary, a graduate student at the Harvard-Smithsonian Center for Astrophysics (CfA), and CfA professor Avi Loeb conducted the research, set to be published in the Monthly Notices of the Royal Astronomical Society.
Apr 8, 2009 | 5
Mission controllers last night sent a command to the Kepler spacecraft, NASA's unprecedented planet hunter launched last month, to eject its dust cover, effectively opening the telescope to the heavens.
Kepler, now some two million miles (three million kilometers) from Earth, will trail our planet in an orbit around the sun, observing a patch of sky for three-plus years in search of possible companion planets around a group of 100,000 stars. The spacecraft bears the largest space-borne camera ever, a photometer composed of 42 charge-coupled devices (CCDs), to monitor those stars for periodic dips in stellar brightness that occur as orbiting planets block a portion of the stars' light from Kepler's view.
Apr 7, 2009 | 4
The sun's tumult waxes and wanes in a fairly predictable cycle, with sunspots, patches of intense magnetic activity on the solar surface, peaking in number every 11 or so years. We currently find ourselves in a solar minimum, a period of reduced solar activity, and a deep one at that. Last year was the second-quietest sunspot year of the past century, as the sun was blank on 72.7 percent of the days.
But this year is on pace to be even quieter—through the first three months of 2009 the sun was blank on 86.7 percent of the days. The continued lull in solar activity is mostly good, as the sun can wreak havoc on satellites and infrastructure during its more rambunctious stretches, as we've chronicled in the past.
Apr 3, 2009 | 1
Two teams of astronomers made headlines in November after announcing they had photographed planets orbiting regular stars other than our own sun. (Such bodies are known as extrasolar planets, or exoplanets.) One of those planets, Fomalhaut b, the companion to a star called Fomalhaut some 25 light-years away, was spotted by the Hubble Space Telescope; a star known as HR 8799, nearly 130 light-years distant, was found by ground-based observations to harbor a system of at least three planets.
Now reprocessed images taken by Hubble in October 1998 show that the space-based observatory had picked up the signal of the outermost of HR 8799's planets (white dot at lower right in image) 10 years prior to that announcement. Astronomer David Lafrenière, a postdoctoral fellow at the University of Toronto and a member of the team that found the planets around HR 8799 last year, led the archival work. In a statement, he credited an improved image-processing technique that he and colleagues developed for uncovering the hidden planet, saying it can now be used "to see planets that are one-tenth the brightness of what could be detected before with Hubble."
Mar 22, 2009 | 1
A supernova, or stellar explosion, some 200 million light-years away has been traced to its progenitor star, one of only a few times the source of a supernova has been identified based on pre- and post-supernova images.
Astrophysicist Avishay Gal-Yam of the Weizmann Institute of Science in Rehovot, Israel, and astronomer Douglas Leonard of San Diego State University used images from the Hubble Space Telescope to single out the star. In 1997 images, there was a bright light source near where the explosion, dubbed SN 2005gl, was detected in 2005.
In a previous paper Gal-Yam, Leonard and their colleagues had cited this evidence as indicative that the luminous, massive star begat the supernova. But without post-event images, it was not clear that the star had disappeared with the explosion or that the suspect light source had not been a cluster of stars to begin with. Thanks to 2007 Hubble images showing a void where the star (and subsequent supernova) had been, the researchers concluded that the solitary star indeed met its end in supernova SN 2005gl. They report their finding today in Nature.
Mar 4, 2009 | 27
Black holes, as frighteningly extreme as they may be, are relatively commonplace across the universe. Like most large galaxies, our own Milky Way packs a supermassive black hole at its core, a lurking monster some four million times as massive as the sun.
But our own neighborhood bully appears relatively tame next to a distant quasar, or bright galactic center, recently spotted by astronomers Todd Boroson and Tod Lauer of the National Optical Astronomy Observatory (NOAO) in Tucson, Ariz. The quasar, known as SDSS J153636.22+044127.0, appears to host a pair of black holes, bound together in a tight orbital relationship, circling each other every 100 or so years. The finding appears today in Nature.
Mar 3, 2009
Saturn's G ring, a faint band of material near the outer bounds of the planet's famed ring system, hosts a bright arc about 90,000 miles (150,000 kilometers) long. The arc, or partial ring, which stretches through about a sixth of the G ring's length, is believed to provide the rest of the ring with dust and ice, but its evolution has remained a mystery.
Recent images from the Cassini spacecraft (at left) point to a moonlet embedded in the G ring. The moonlet, the Cassini team speculates, might help to repopulate the arc, and then the ring as a whole, with material as it suffers collisions with meteoroids or other small bodies within the ring.
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