Movie of Chi Cygni pulsating over 408 days December 21, 2009Posted by jcconwell in stars.
Tags: Astronomy, stars
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At a distance of 550 light years away, Chi Cyni is a classic example of a red supergiant, and a variable star. It’s the last stage of a star that has exhausted it supply of Hydrogen in its core and has started to burn Helium. When its diameter is a minimum at 300 million miles, the star’s surface becomes splotchy with bright spots of hot plasma boil to its surface. Then, as it expands, Chi Cygni cools and dims, growing to a diameter of 480 million miles. The new images taken by the now closed IOTA (Infrared Optical Telescope Array) where arranged as a movie of the pulsating star, and shows that the pulsation is not only radial, but comes with inhomogeneities, for example, a giant hotspot that appeared when the star approaches minimum.
The IOTA, was a Michelson stellar interferometer located on Mt. Hopkins in southern Arizona. It operated with three 45 cm collectors that can be located at different stations on each arm of an L-shaped array (15 m X 35 m) and reaches a maximum baseline of 38 m. These IOTA pictures have 15 time the resolution of the Hubble space telescope.
Astronomers find a “Super Earth” with Atmosphere & Water December 17, 2009Posted by jcconwell in Astronomy, planets.
Tags: exoplanet, GJ1214b, planets
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The discovery is to be published today (December 17th) in the Journal Nature. A Super-Earth is a rocky planet between one and ten times the mass of the Earth. The planet was discovered orbiting the star, GJ1214, which is a nearby red dwarf about 40 light years from Earth. This type M star is about 1/5 the size of the Sun. The star is cool at 4,900 degrees F (3000 degrees K) compared to the Sun’s 10,000F (5700 degrees K) and has a luminosity only .003 as bright as the Sun.The planet, GJ1214b, is about 6.5 times as massive as the Earth.
The MEarth project spotted the planet using a 16″ telescope, The same size as at Eastern Observatory. However , it is not as simple as looking at a random star to see a planet.
The MEarth (pronounced “mirth”) Project is an array of eight identical 16-inch-diameter RC Optical Systems telescopes that monitor a pre-selected list of 2,000 red dwarf stars. Each telescope perches on a highly accurate Software Bisque Paramount and funnels light to an Apogee U42 charge-coupled device (CCD) chip, which many amateurs also use. The project looks for the signature dimming of a star caused by an orbiting planet eclipsing the star.
Credit: Dan Brocious, CfA
GJ1214b orbits its star once every 38 hours at a distance of only two million kilometres — 70 times closer to its star than the Earth is to the Sun. “Being so close to its host star, the planet must have a surface temperature of about 200 degrees Celsius, too hot for water to be liquid,” said Charbonneau.
However, computer models show that because of its larger diameter, compared to its mass, it may have an interior made of water ice. Because the planet is nearby, the Hubble space telescope has a good chance of directly observing the atmosphere of the planet and measure its composition.
Holiday Present for the Observatory December 15, 2009Posted by jcconwell in Observatory.
Tags: EIU, Observatory, spectra
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The end of the semester is here and the physics students are completing their projects for their third semester senior advanced lab. The third semester is an independent project (read: “give them enough rope to hang themselves”). This semester Alicia made a nice present for the observatory’s spectrometer. A Calibration source.
The spectrometer and camera are sort of dumb. When we take a picture of a star’s spectra the camera assigns a spectral line to a column of pixels on the camera, but it doesn’t know the wavelength corresponding to that column. What Alicia made is a combination Mercury-Neon lamp, that feeds the light through a fiber optic wire directly into the spectrometer. The Mercury for the blue end and Neon for the red end of the spectra. We then take a picture of the combination Hg-Ne spectra (whose wavelengths are known) and the computer uses those lines to assign the wavelengths to each column of pixels, thus calibrating it .
We ‘ll now be able to do this from the nice warm control room. No more trudging up to the telescope at 2:00AM, in below zero weather to shine a Hg lamp and take a calibration spectra!
Astronomy Club Tonight: Movie Night December 9, 2009Posted by jcconwell in Astronomy.
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Room 2153, at 8:00Pm, Physical Science Building! Bring money for Pizza, we are showing “Galaxy Quest”
IYA PODCAST: The Celestial Alignment of 2012 December 6, 2009Posted by jcconwell in Astronomy, IYA 2009, planets, Podcast.
Tags: 2012, EIU, International Year of Astronomy, IYA 2009, planets, Podcast, Venus
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is sponsored by the Department of Physics at
The Celestial Alignment of 2012….but not the one in the movies
An astronomical alignment in 2012 heralds the second coming (in the 21st century) of a significant global event. Share the enthusiasm of adventurous astronomers from the past as you witness the heavens in motion, the means by which we learned the size of our solar system—a transit of Venus.
Extreme Universe: New Class of Supernovae: SN 2007bi December 2, 2009Posted by jcconwell in Astronomy, Extreme Universe, supernova.
Tags: pair instability supernova, SN 2007bi, supernova
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First confirmed pair instability supernova
Berkeley, CA – An extraordinarily bright, extraordinarily long-lasting supernova named SN 2007bi, snagged in a search by a robotic telescope, turns out to be the first example of the kind of stars that first populated the Universe. The superbright supernova occurred in a nearby dwarf galaxy, a kind of galaxy that’s common but has been little studied until now, and the unusual supernova could be the first of many such events soon to be discovered.
The analysis indicated that the supernova’s precursor star could only have been a giant weighing at least 200 times the mass of our Sun and initially containing few elements besides hydrogen and helium – a star like the very first stars in the early Universe.
“Because the core alone was some 100 solar masses, the long-hypothesized phenomenon called pair instability must have occurred,” says astrophysicist Peter Nugent. A member of the SNfactory, Nugent is the co-leader of the Computational Cosmology Center (C3), a collaboration between Berkeley Lab’s Physics Division and Computational Research Division (CRD), where Nugent is a staff scientist. “In the extreme heat of the star’s interior, energetic gamma rays created pairs of electrons and positrons, which bled off the pressure that sustained the core against collapse.”
“SN 2007bi was the explosion of an exceedingly massive star,” says Alex Filippenko, a professor in the Astronomy Department at UC Berkeley whose team helped obtain, analyze, and interpret the data. “But instead of turning into a black hole like many other heavyweight stars, its core went through a nuclear runaway that blew it to shreds. This type of behavior was predicted several decades ago by theorists, but never convincingly observed until now.”
SN 2007bi is the first confirmed observation of a pair-instability supernova. The researchers describe their results in the 3 December 2009 issue of Nature.