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News This false-colour image of the Lagoon Nebula (M8) in Sagittarius in the southern Milky Way shows starbirth in a cloud of gas and dust. Red indicates hydrogen, green shows ionized sulphur and blue picks out infrared radiation. Argentinean astronomers Julia Arias (Universidad de La Serena) and Rodolfo Barbá (Universidad de La Serena and ICATE-CONICET) used the Gemini Multi-Object Spectrograph to explore the relationship between newborn stars and Herbig–Haro (HH) objects. Most of the newborn stars are in the tips of thick dusty clouds which look like bright-rimmed pillars. Abundant fast-moving gas from the HH objects ploughs into the surrounding nebula, producing bright shock fronts. They found a dozen of these HH objects in the image, between a few thousand astronomical units across and 1.4 parsecs. http://www.gemini.edu/node/11631 Super-heavy superearth Predictions about the orbit of an exoplanet came good when observations pinned down the properties of 55 Cancri e, to show it was both hotter, denser and closer to its star than had been thought. This planet was discovered by the radial velocity method, which uses regular wobbles in the position of a star to indicate an orbiting planet. In this case, gaps in the data introduced systematic errors into the estimate of its orbital period at 2.8 days. Harvard graduate student Rebekah Dawson (Harvard-Smithsonian Center for Astrophysics) worked with Daniel Fabrycky (now at the University of California, Santa Cruz) and found that 55 Cancri e was much closer to its star, orbiting in less than 18 hours – and that the chances of seeing a transit were good. Jaymie Matthews (University of British Columbia) led an international team that scheduled observations with Canada’s MOST (Microvariability & Oscillations of STars) satellite. They found transits every 17 hours and 41 minutes, just as Dawson and Fabrycky predicted. And the new data show that 55 Cancri e is only 60% larger in diameter than Earth but eight times as massive, making it the densest solid planet known, almost as dense as lead. Its close orbit around its star means that it is extremely hot, about 3000 K. It is also the closest transiting planet known. http://www.cfa.harvard.edu/news/2011/ pr201112.html http://www.science.ubc.ca/news/539 3.6 Preparing for asteroid 2005 YU55 at close quarters The usual way to get a close-up of an asteroid is to fly a spacecraft there and have a look. But this is never going to be a routine means of studying the smaller members of the solar system, and space missions don’t exactly come cheap. So when an asteroid heads close to Earth, the obvious thing to do is to take a close look. That is what will happen in November this year, when asteroid 2005 YU55, a lump of rock some 400 m across, will make a close approach to Earth, 325 000 km away at its closest. Instruments on Earth now could get radar images of the asteroid at resolutions comparable to the best fly-by images. “Using the Goldstone radar operating with the software and hardware upgrades, the resulting images of YU55 could come in with resolution as fine as 4 m per pixel,” said Jet Propulsion Laboratory radar astronomer Lance Benner. “We’re talking about getting down to the kind of surface detail you dream of when you have a spacecraft fly by one of these targets.” Radar images are especially valuable because they give astronomers data that can be used to produce a 3D model of the body, as well as indicating by the quality of the reflections how rough or smooth the surface is. In April 2010, Mike Nolan and colleagues at the Arecibo Observatory in Puerto Rico generated some ghostly images of YU55 when the asteroid was about 2.3 million km (1.5 million miles) from Earth. The best resolution of those images was 7.5 m per pixel. Banner hopes to do a lot better this year: “The asteroid will be seven times closer. We’re expecting some very detailed radar images.” http://deepspace.jpl.nasa.gov/dsn Gravity probe shows Einstein got it right again Gravity Probe B, the NASA mission to carry out the most sensitive test yet of general relativity, has concluded that Einstein was right. The team measured the predicted distortion of spacetime around Earth from the mass of the planet, and demonstrated that the rotation of the Earth does indeed twist spacetime, causing frame dragging. Gravity Probe B was launched in 2004 to orbit Earth for 16 months carrying sensitive gyroscopes aligned with a distant guide star. In free fall, the gyroscope should continue to point at the reference star, unless spacetime is distorted in the way that general relativity predicts. The probe measured the misalignment of the gyroscope spin axis and the reference star, to a startling precision of 0.0005 arcsec, the equivalent of measuring the thickness of a sheet of paper edge-on from 160 km away. “We measured a geodetic precession of 6.600±0.017 arcsec and a frame dragging effect of 0.039±0.007 arcsec,” said Francis Everitt of Stanford University, principal investigator of Gravity Probe B. These measurements represent accuracies of 0.28% and 19% respectively. The results confirm Einstein’s predictions about spacetime around the Earth and may in future come to be seen as a classic experiment, albeit one requiring considerable new technology. Gravity Probe B required considerable technological development, becasue the effects that the researchers were hoping to see were beyond measurement at the time the project began. The gyroscopes, for example, use rotating balls of fused quartz coated with niobium, less than 4 cm across, that vary from a perfect sphere by less than 40 atomic layers. They feature in the Guinness World Records as the most perfect spheres manufactured; only neutron stars are considered more perfect spheres. This is one of NASA’s longest running projects, with initial funding coming in 1963, although the idea was first proposed in 1959 – a career-long project for Everitt and colleagues. Technology developed for this mission was used in the Cosmic Background Explorer mission, among others, and is used in commercial applications such as the GPS system that allows planes to land unaided. More than 100 postgraduate and 350 undergraduate students have worked on the project, including the astronaut Sally Ride and 2001 Nobel Prize Laureate Eric Cornell. http://www.nasa.gov/mission_pages/gpb http://einstein.stanford.edu A&G • June 2011 • Vol. 52