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Super-Earth Found, 18-Hour Year, 55 Cancri e 40 Light Years Away Says MIT Team
 
A group of astronomers led by an MIT professor has spotted an exoplanetary eclipse of a star only 40 light years away - right around the corner, astronomically speaking - revealing a "super-Earth."
The far-out planet, named 55 Cancri e, is twice as big as Earth and nearly nine times more massive.
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Stellar eclipse gives glimpse of exoplanet

A group of astronomers led by an MIT professor has spotted an exoplanetary eclipse of a star only 40 light years away - right around the corner, astronomically speaking - revealing a "super-Earth."
The far-out planet, named 55 Cancri e, is twice as big as Earth and nearly nine times more massive. It is most likely composed of rocky material, similar to Earth, supplemented with light elements such as water and hydrogen gas. Scientists estimate the planets surface is much hotter than ours: close to 2,700 degrees Celsius.
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Title: The 55 Cancri System: Fundamental Stellar Parameters, Habitable Zone Planet, and Super-Earth Diameter
Authors: K. von Braun (1), T. S. Boyajian (2,3), T. A. ten Brummelaar (6), G. T. van Belle (4), S. R. Kane (1), D. R. Ciardi (1), M. Lopez-Morales (5), H. A. McAlister (2), G. Schaefer (6), S. T. Ridgway (7), L. Sturmann (6), J. Sturmann (6), R. White (2), N. H. Turner (6), C. Farrington (6), P. J. Goldfinger (6) ((1) NExScI/Caltech, (2) Georgia State, (3) Hubble Fellow, (4) ESO, (5) CSIC-IEEC/CIW-DTM, (6) CHARA, (7) NOAO)

The bright star 55 Cancri is known to host five planets, including a transiting super-Earth. We use the CHARA Array to directly determine the following of 55 Cnc's stellar astrophysical parameters: R=0.943 ±0.010 solar radii, T_{EFF} = 5196 ±24 K. Planet 55 Cnc f (M \sin i = 0.155 M_{Jupiter}) spends the majority of the duration of its elliptical orbit in the circumstellar habitable zone (0.67--1.32 AU) where, with moderate greenhouse heating, it could harbour liquid water. Our determination of 55 Cancri's stellar radius allows for a model-independent calculation of the physical diameter of the transiting super-Earth 55 Cnc e (\simeq 2.1 R_{\earth}), which, depending on the assumed literature value of planetary mass, implies a bulk density of 0.76
ho_{\earth} or 1.07
ho_{\earth}.

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Blobrana


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Title: 55 Cancri: Stellar Astrophysical Parameters, a Planet in the Habitable Zone, and Implications for the Radius of a Transiting Super-Earth
Authors: Kaspar von Braun (1), Tabetha S. Boyajian (2,3), Theo A. ten Brummelaar (6), Gerard T. van Belle (4), Stephen R. Kane (1), David R. Ciardi (1), Mercedes Lopez-Morales (5,8), Harold A. McAlister (2), Gail Schaefer (6), Stephen T. Ridgway (7), Laszlo Sturmann (6), Judit Sturmann (6), Russel White (2), Nils H. Turner (6), Chris Farrington (6), P.J. Goldfinger (6) ((1) NASA Exoplanet Science Institute / Caltech, (2) Georgia State U., (3) Hubble Fellow, (4) ESO, (5) CSIC-IEEC, (6) CHARA, (7) NOAO, (8) Carnegie/DTM)

The bright star 55 Cancri is known to host five planets, including a transiting super-Earth. The interferometric study presented here yields directly determined values for 55 Cnc's stellar astrophyiscal parameters: R=0.943 ±0.010 solar radii, T_{EFF} = 5196 ±24 K. We use isochrone fitting to determine 55 Cnc's age to be 10.2 ±2.5 Gyr, implying a stellar mass of 0.905 ±0.015 solar masses. Our analysis of the location and extent of the system's habitable zone (0.67--1.32 AU) shows that planet f (M \sin i = 0.155 Jupiter masses) spends the majority of the duration of its elliptical orbit in the circumstellar habitable zone, where, with moderate greenhouse heating, it could harbour liquid water. Finally, our direct value for 55 Cancri's stellar radius allows for a model-independent calculation of the physical diameter of the transiting super-Earth 55 Cnc e (~ 2.05 ±0.15 Earth Radii), which, depending on the planetary mass assumed, implies a bulk density of 0.76
ho_{\earth} or 1.07
ho_{\earth}.

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Student's Prediction Points the Way to Hot, Dense Super-Earth

A planet that we thought we knew turns out to be rather different than first suspected. Our revised view comes from new data released today by an international team of astronomers. They made their observations of the planet "55 Cancri e" based on calculations by Harvard graduate student Rebekah Dawson (Harvard-Smithsonian Centre for Astrophysics), who worked with Daniel Fabrycky (now at the University of California, Santa Cruz) to predict when the planet crosses in front of its star as seen from Earth. Such transits give crucial information about a planet's size and orbit.
The team found that 55 Cancri e is 60 percent larger in diameter than Earth but eight times as massive. (A super-Earth has one to 10 times the mass of Earth.) It's the densest solid planet known, almost as dense as lead. Even better, the star it orbits is so close and bright that it's visible to the naked eye in the constellation Cancer the Crab. This makes it an excellent target for follow-up studies.
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Title: A Super-Earth Transiting a Naked-Eye Star
Authors: Joshua N. Winn, Jaymie M. Matthews, Rebekah I. Dawson, Daniel Fabrycky, Matthew J. Holman, Thomas Kallinger, Rainer Kuschnig, Dimitar Sasselov, Diana Dragomir, David B. Guenther, Anthony F.J. Moffat, Jason F. Rowe, Slavek Rucinski, Werner W. Weiss

We have detected transits of the innermost planet "e" orbiting 55 Cnc (V=6.0), based on two weeks of precise photometric monitoring with the MOST space telescope. The transits of 55 Cnc e occur with the period (0.74 d) and phase that had been predicted by Dawson & Fabrycky, and with the expected duration and depth for the crossing of a Sun-like star by a hot super-Earth. Assuming the star's mass and radius to be 0.96 ±0.10 Msun and 1.10 ±0.10 Rsun, the planet's mass, radius, and mean density are 8.57 ±0.64 Me, 1.63 ±0.16 Re, and 10.9 ±3.1 g/cm³. The high density suggests the planet has a rock-iron composition as opposed to hydrogen, water, or other light elements. This makes 55 Cnc e similar to the other transiting super-Earths in tight orbits around G stars (Kepler-10b and Corot-7b), and unlike the lower-density super-Earths that are less strongly irradiated (GJ 1214b and Kepler-11d,e,f). The host star of 55 Cnc e is far brighter than that of any other known transiting planet, which will facilitate further investigations.

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A team of American astronomers announced today (Tuesday, Nov. 6, 2007) the discovery of a record-breaking fifth planet around the nearby star 55 Cancri, making it the only star aside from the sun known to have five planets.
The discovery comes after 19 years of observations of 55 Cancri and represents a milestone for the California and Carnegie Planet Search team, which this year celebrates the 20th anniversary of its first attempts to find extrasolar planets by analysing the wobbles they cause in their host star.
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Position (2000):     RA = 08 52 37.60,      DEC = +28 20 02.6


Astronomers have announced the discovery of a fifth planet circling 55 Cancri, a star beyond our solar system. The star now holds the record for number of confirmed extrasolar planets orbiting in a planetary system.
55 Cancri is located 41 light-years away in the constellation Cancer and has nearly the same mass and age as our sun. It is easily visible with binoculars. Researchers discovered the fifth planet using the Doppler technique, in which a planet's gravitational tug is detected by the wobble it produces in the parent star. NASA and the National Science Foundation funded the research.
The newly discovered planet weighs about 45 times the mass of Earth and may be similar to Saturn in its composition and appearance. The planet is the fourth from 55 Cancri and completes one orbit every 260 days. Its location places the planet in the "habitable zone," a band around the star where the temperature would permit liquid water to pool on solid surfaces. The distance from its star is approximately 116.7 million kilometres, slightly closer than Earth to our sun, but it orbits a star that is slightly fainter.

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Blobrana


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Astronomers unveil portrait of "super-exotic super-Earth:" Densest known rocky planet

The planet, named 55 Cancri e, is 60 per cent larger in diameter than Earth but eight times as massive. Twice as dense as Earth - almost as dense as lead - it is the densest solid planet known, according to a team led by astronomers from the Massachusetts Institute of Technology (MIT), the University of British Columbia (UBC), the Harvard-Smithsonian Center for Astrophysics and the University of California at Santa Cruz (UCSC).
The research, based on observations from Canada's MOST (Microvariability & Oscillations of STars) space telescope, was released online today at arXiv.org and has been submitted for publication in The Astrophysical Journal Letters. MOST is a Canadian Space Agency mission.
Approximately 40 light years from Earth, 55 Cancri e orbits a star - called 55 Cancri A - so closely that its year is less than 18 hours long.
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55 Cancri
This wide-angle photograph of the night sky shows the location of 55 Cancri, a star where astronomers have found a record-breaking five planets.
Expand (713kb, 1247 x 859) | Image, no labels (807Kb, 1280 x 1230)

55 Cancri.kmz
Google Sky file


55 Cancri (1 Cnc)

Location
RA: 8h52m35.8s
DEC: +28°19m51.0s



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