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TOPIC: Extrasolar Planets
Blobrana


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HD 209458b
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Water has been detected for the first time in the atmosphere of a planet outside our Solar System.
The planet, known as HD 209458b, is a Jupiter-like gas giant located 150 light-years from Earth in the constellation Pegasus.

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Blobrana


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RE: Extrasolar Planets
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Title: Five Intermediate-Period Planets from the N2K Sample
Authors: Debra A. Fischer, Geoffrey W. Marcy, R. Paul Butler, Bun'ei Sato, Steven S. Vogt, Sarah Robinson, Gregory Laughlin, Gregory W. Henry, Shigeru Ida, Eri Toyota, Masashi Omiya, Peter Driscoll, Genya Takeda, Jason T. Wright, John A. Johnson

We report the detection of five jovian mass planets orbiting high metallicity stars. Four of these stars were first observed as part of the N2K program and exhibited low RMS velocity scatter after three consecutive observations. However, follow-up observations over the last three years now reveal the presence of longer period planets with orbital periods ranging from 21 days to a few years. HD 11506 is a G0V star with a planet of \msini = 4.85 \mjup in a 3.5 year orbit. HD 17156 is a G0V star with a 3.08 \mjup planet in an eccentric (e = 0.67) 21.2 day orbit. HD 125612 is a G3V star with a planet of \msini = 3.2 \mjup in a 1.37 year orbit. HD 170469 is a G5IV star with a planet of \msini = 0.68 \mjup in a 3 year orbit. HD 231701 is an F8V star with planet of 1.03 \mjup in a 143 day orbit. All of the stars have supersolar metallicity. Three of the five stars were observed photometrically but showed no evidence of brightness variability. A transit search conducted for HD 17156 was negative but covered only 25% of the search space and so is not conclusive.

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Blobrana


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Posts: 131433
Date:
HD 209458b
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Water has been found in the atmosphere of the gas giant planet HD 209458b.
Water has been detected in the atmosphere of an alien world for the first time, a new analysis of Hubble Space Telescope data suggests. Water was widely believed to exist on the planet, but previous observations with other telescopes had failed to find it.
The planet, called HD 209458b, is about 70% as massive as Jupiter and is scorched by the heat of its parent star, which it orbits 9 times as close as Mercury does to the Sun.
Because it is one of a small number of extrasolar planets observed to pass directly in front of and behind their parent stars as seen from Earth, astronomers have been able to glean a lot of information such as its size and mass about the distant world.

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Blobrana


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Posts: 131433
Date:
HD70573
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Title: Evidence for a planetary companion around a nearby young star
Authors: J. Setiawan (1), P. Weise (1), Th. Henning (1), R. Launhardt (1), A. Müller (1), J. Rodmann (2) ((1) Max Planck Institute for Astronomy, Heidelberg, Germany, (2) European Space Agency / ESTEC, Noordwijk, The Netherlands)

We report evidence for a planetary companion around the nearby young star HD 70573. The star is a G type dwarf located at a distance of 46 pc with age estimation between 20 and 300 Myrs. We carried out spectroscopic observations of this star with FEROS at the 2.2 m MPG/ESO telescope at La Silla. Our spectroscopic analysis yields a spectral type of G1-1.5V and an age of about 100 Myrs. Variations in stellar radial velocity of HD 70573 have been monitored since December 2003 until January 2007. The velocity accuracy of FEROS within this period is about 10 m/s. HD 70573 shows a radial velocity variation with a period of 852 ±12 days and a semi-amplitude of 149 ±6 m/s. The period of this variation is significantly longer than its rotational period, which is 3.3 days. Based on the analysis of the Ca II K emission line, Halpha and Teff variation as stellar activity indicators as well as the lack of a correlation between the bisector velocity span and the radial velocity, we can exclude the rotational modulation and non-radial pulsations as the source of the long-period radial velocity variation. Thus, the presence of a low-mass companion around the star provides the best explanation for the observed radial velocity variation. Assuming a primary mass m1=1.0 ±0.1 Msun for the host star, we calculated a minimum mass of the companion m2sini of 6.1 Mjup, which lies in the planetary mass regime, and an orbital semi-major axis of 1.76 AU. The orbit of the planet has an eccentricity of e=0.4. The planet discovery around the young star HD 70573 gives an important input for the study of debris disks around young stars and their relation to the presence of planets.

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Blobrana


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Nearby Stars project
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When Richard Gray looks at the stars, he sees more than just interesting bits of light in the night sky.
Gray, a professor in the Department of Physics and Astronomy at Appalachian State University, is part of an 11-member team looking for new planets. They have determined that planets may exist around twin or binary stars.

We used to think that planets could only be found around single stars. This is an interesting discovery because up until now, people have been skeptical about the possibility of planets with double stars. This project has shown is that it is possible for planets to exist around binary stars as well as single stars - Richard Gray.

Gray was invited to participate in the project because of his NASA-funded Nearby Stars project. Since 2000, Gray and a team of researchers have been collecting data on 3,600 nearby stars that may harbour planets.

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Blobrana


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Dual suns
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The dual suns that rise and set over Luke Skywalker's homeworld in the film Star Wars may be more than just fantasy, according to data from Nasa.In a classic scene from the 1977 movie, the hero gazes into the distance as two yellow suns set on the horizon.

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Blobrana


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Posts: 131433
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RE: Extrasolar Planets
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Two teams of astronomers have announced the discovery of four gas-giant planets around other stars, bringing the total number of know extrasolar planets to 204.
Among the new planets, one is roughly the same mass as Neptune, putting it in a relatively new class of lower-mass planets that recently have been detected. The planet orbits the star HD 219828, located 264 light-years away in the constellation Pegasus.
The planet is located at 0.052 AU from its star, closer than Mercury is to the sun, and it completes an orbit in just under four Earth days. It is the 11th Neptune-mass planet to be found orbiting a sun-like star.
A separate European team has announced the discovery of three new gas-giant planets, ranging in size from slightly larger than Jupiter to more than three times Jupiter's mass. These planets are located around the stars HD 100777, 172 light-years away; HD 190647, 176 light-years away; and HD 221287, 172 light-years away.
All of the new planets were discovered using the High Accuracy Radial velocity Planet Searcher (HARPS), part of the European Southern Observatory in La Silla, Chile. The HARPS instrument is a high-resolution spectrograph that detects planets indirectly, using the radial velocity method, which measures the back-and-forth wobble of a star induced by the gravitational tug of its planetary companion. The majority of extrasolar planets discovered so far have been detected using this method.

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Blobrana


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Posts: 131433
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Title: Discovery of a planet around the K giant star 4 UMa
Authors: M.P. Doellinger, A. P. Hatzes, L. Pasquini, E. W. Guenther, M. Hartmann, L. Girardi, M. Esposito

Context: For the past 3 years we have been monitoring a sample of 62 K giant stars using precise stellar radial velocity measurements taken at the Thueringer Landessternwarte Tautenburg.
Aims: To search for sub-stellar companions to giant stars and to understand the nature of the diverse radial velocity variations exhibited by K giant stars.
Methods: We present precise stellar radial velocity measurements of the K1III giant star 4 UMa (HD 73108). These were obtained using the coude echelle spectrograph of 2-m Alfred Jensch Telescope. The wavelength reference for the radial velocity measurements was provided by an iodine absorption cell.
Results: Our measurements reveal that the radial velocity of 4 UMa exhibits a periodic variation of 269.3 days with a semiamplitude K = 216.8 m/s. A Keplerian orbit with an eccentricity, e = 0.43 0.02 is the most reasonable explanation for the radial velocity variations. The orbit yields a mass function, f(m) = (2.05 0.24) x 10^(- 7) M_sun. From our high resolution spectra we calculate a metallicity of -0.25 0.05 and derive a stellar mass of 1.23 M_sun 0.15 for the host star.
Conclusions: The K giant star 4 UMa hosts a substellar companion with minimum mass m sin i = 7.1 1.6 M_Jupiter.

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Blobrana


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Title: Planets Formed in Habitable Zones of M Dwarf Stars Probably are Deficient in Volatiles
Authors: Jack J. Lissauer

Dynamical considerations, presented herein via analytic scalings and numerical experiments, imply that Earth-mass planets accreting in regions that become habitable zones of M dwarf stars form within several million years. Temperatures in these regions during planetary accretion are higher than those encountered by the material that formed the Earth. Collision velocities during and after the prime accretionary epoch are larger than for Earth. These factors suggest that planets orbiting low mass main sequence stars are likely to be either too distant (and thus too cold) for carbon/water based life on their surfaces or have abundances of the required volatiles that are substantially less than on Earth.

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Blobrana


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Posts: 131433
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To date, there are more than 200 catalogued extrasolar planets (exoplanets) orbiting other stars in our Milky Way Galaxy. We are very fortunate to live in a time when technology has caught up with theory, and the process of mapping other solar systems has begun.

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