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Post Info TOPIC: Upsilon Andromedae b
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Upsilon Andromedae
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Title: The 3-dimensional architecture of the Upsilon Andromedae planetary system
Author: Russell Deitrick, Rory Barnes, Barbara McArthur, Thomas R. Quinn, Rodrigo Luger, Adrienne Antonsen, G. Fritz Benedict

The Upsilon Andromedae system is the first exoplanetary system to have the relative inclination of two planets' orbital planes directly measured, and therefore offers our first window into the 3-dimensional configurations of planetary systems. We present, for the first time, full 3-dimensional, dynamically stable configurations for the 3 planets of the system consistent with all observational constraints. While the outer 2 planets, c and d, are inclined by about 30 degrees, the inner planet's orbital plane has not been detected. We use N-body simulations to search for stable 3-planet configurations that are consistent with the combined radial velocity and astrometric solution. We find that only 10 trials out of 1000 are robustly stable on 100 Myr timescales, or about 8 billion orbits of planet b. Planet b's orbit must lie near the invariable plane of planets c and d, but can be either prograde or retrograde. These solutions predict b's mass is in the range 2 - 9 MJup and has an inclination angle from the sky plane of less than 25 degrees. Combined with brightness variations in the combined star/planet light curve ("phase curve"), our results imply that planet b's radius is about 1.8 RJup, relatively large for a planet of its age. However, the eccentricity of b in several of our stable solutions reaches values greater than 0.1, generating upwards of 1019watts in the interior of the planet via tidal dissipation, possibly inflating the radius to an amount consistent with phase curve observations.

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Title: Upsilon Andromedae b in polarized light: New constraints on the planet size, density and albedo
Authors: S.V. Berdyugina, A.V. Berdyugin, V. Piirola

Polarimetry is a novel tool to detect and characterise exoplanets and their atmospheres. Polarised scattered light from the non-transiting hot Jupiter \upsilon~And~b is measured to further constrain its orbit, mass, density, and geometrical albedo. We obtained polarimetric measurements in the UBV bands over the orbital period and deduce an average peak-to-peak amplitude of (49 ±5) x 10^{-6} in both Stokes q and u. From our data we evaluate the orbit inclination i=111° ±11°, longitude of the ascending node \Omega=236° ±12° (or equivalently 56°), the effective size of the scattering atmosphere in the optical blue of 1.36 ±0.20\,R_J. These combined with spectroscopic measurements result in the planet mass 0.74 ±0.07\,M_J, mean density 0.36 ±0.08\,g\,cm^{-3}, and surface gravity ~10^3\,cm\,s^{-2}, which favour a close similarity of \upsilon~And~b to other inflated hot Jupiters. We also significantly improved the periastron epoch T_p= JD 2,450,032.451, interior conjunction epoch T_t= JD 2,450,034.668, and periastron longitude \omega=279° ±14°. The latter indicates that the apsidal resonance known for planets c and d includes also planet b.
Obtained limits on the wavelength dependent geometrical albedo (average 0.35) indicate its similarity to Neptune with peak reflectivity in the blue. Combining all available measurements at various passbands, we construct a unified wavelength dependent albedo of an average hot Jupiter. It appears to be largely shaped by Rayleigh scattering in the blue and atomic and molecular absorption in the optical and near infrared. Our findings demonstrate the power of polarimetry for studying non-transiting exoplanets.

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Blobrana


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Astronomers Find Weird, Warm Spot on an Exoplanet

The gas-giant planet, named upsilon Andromedae b, orbits tightly around its star, with one face perpetually boiling under the star's heat. It belongs to a class of planets termed hot Jupiters, so called for their scorching temperatures and large, gaseous constitutions.
One might think the hottest part of these planets would be directly under the sun-facing side, but previous observations have shown that their hot spots may be shifted slightly away from this point. Astronomers thought that fierce winds might be pushing hot, gaseous material around.
But the new finding may throw this theory into question. Using Spitzer, an infrared observatory, astronomers found that upsilon Andromedae b's hot spot is offset by a whopping 80 degrees. Basically, the hot spot is over to the side of the planet instead of directly under the glare of the sun.
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Title: A New 24 micron Phase Curve for upsilon Andromedae b
Authors: Ian J. Crossfield, Brad M. S. Hansen, Joseph Harrington, James Y-K. Cho, Drake Deming, Kristen Menou, Sara Seager

We report the detection of 24 micron variations from the planet-hosting upsilon Andromedae system consistent with the orbital periodicity of the system's innermost planet, upsilon And b. We find a peak-to-valley phase curve amplitude of 0.00130 times the mean system flux. Using a simple model with two hemispheres of constant surface brightness and assuming a planetary radius of 1.3 Jupiter radii gives a planetary temperature contrast of >900 K and an orbital inclination of >28 degrees. We further report the largest phase offset yet observed for an extrasolar planet: the flux maximum occurs ~80 degrees before phase 0.5. Such a large phase offset is difficult to reconcile with most current atmospheric circulation models. We improve on earlier observations of this system in several important ways: (1) observations of a flux calibrator star demonstrate the MIPS detector is stable to 10^-4 on long timescales, (2) we note that the background light varies systematically due to spacecraft operations, precluding use of this background as a flux calibrator (stellar flux measured above the background is not similarly affected), and (3) we calibrate for flux variability correlated with motion of the star on the MIPS detector. A reanalysis of our earlier observations of this system is consistent with our new result.

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Perturbed Planets Outside of the Plane

The discovery of a planetary system "out of whack," where the orbits of two planets are at a steep angle to each other, was reported by a team of astronomers led by Barbara McArthur of The University of Texas at Austin McDonald Observatory.
This surprising finding will affect theories of how multi-planet systems evolve and shows that some violent events can happen to disrupt planets orbits after a planetary system forms, say researchers. This information is valuable for astrobiologists studying how planetary systems capable of supporting habitable planets form and evolve.
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Out of Whack Planetary System Offers Clues to a Disturbed Past

For just over a decade, astronomers have known that three Jupiter-type planets orbit the yellow-white star Upsilon Andromedae. But to their surprise it's now been discovered that not all planets orbit this star in the same plane, as the major planets in our solar system orbit the Sun. The orbits of two of the planets are inclined by 30 degrees with respect to each other. Such a strange orientation has never before been seen in any other planetary system. This surprising finding will impact theories of how planetary systems form and evolve, say researchers. It suggests that some violent events can happen to disrupt planets' orbits after a planetary system forms. The discovery was made by joint observations with the Hubble Space Telescope, the giant Hobby-Eberly Telescope, and other ground-based telescopes.
These findings were presented in a press conference today at the 216th meeting of the American Astronomical Society in Miami.
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Blobrana


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Upsilon Andromedae Ab
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Upsilon Andromedae b, occasionally referred to as Upsilon Andromedae Ab (to distinguish it from the red dwarf star  Upsilon Andromedae B), is an extrasolar planet approximately 44 light-years  away from Earth in the constellation  of Andromeda (the Chained Maiden). The planet was discovered orbiting the Solar twin star, Upsilon Andromedae, approximately every five days. Discovered in June 1996 by Geoffrey Marcy and R. Paul Butler, it was one of the first hot Jupiters to be discovered. Upsilon Andromedae b is the innermost known planet in its planetary system.
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Blobrana


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The discovery of a planetary system "out of whack," where the orbits of two planets are at a steep angle to each other, was reported today (May 24) by a team of astronomers led by Barbara McArthur of The University of Texas at Austin McDonald Observatory.
This surprising finding will affect theories of how multi-planet systems evolve and shows that some violent events can happen to disrupt planets' orbits after a planetary system forms, say researchers.
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Blobrana


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The top graph consists of infrared data from NASA's Spitzer Space Telescope. It tells astronomers that a distant planet, called Upsilon Andromedae b, always has a giant hot spot on the side that faces the star, while the other side is cold and dark. The artist's concepts above the graph illustrate how the planet might look throughout its orbit if viewed up close with infrared eyes.

Upsilon Andromedae b
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Credit: NASA/JPL-Caltech/B. Hansen (UCLA)

Position (2000): RA: 01 36 47.84 Dec: +41 24 19.7
Distance: 40 light-years
Constellation: Andromeda

Spitzer was able to determine the difference in temperature between the two sides of this planet by measuring the planet's infrared light, or heat, at five points during its 4.6-day-long trip around its star. The temperature rose and fell depending on which face, the sunlit or dark, was pointed toward Spitzer's cameras. Those temperature oscillations are traced by the wavy orange curve. They indicate that Upsilon Andromedae b has an extreme range of temperatures across its surface, about 1,400 degrees Celsius. This means that hot gas moving across the bright side of the planet cools off by the time it reaches the dark side.

The bottom graph and artist's concepts represent what astronomers might have seen if the planet had bands of different temperatures girdling it, like Jupiter. Some astronomers had speculated that "hot-Jupiter" planets like Upsilon Andromedae b, which circle very closely around their stars, might resemble Jupiter in this way. If Upsilon Andromedae b had been like this, there would have been no difference between the average temperatures of the sunlit and dark sides to detect, and Spitzer's data would have appeared as a flat line.

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NASA's Spitzer Space Telescope has made the first measurements of the day and night temperatures of a planet outside our solar system. The infrared observatory revealed that the Jupiter-like gas giant planet circling very close to its sun is always as hot as fire on one side, and potentially as cold as ice on the other.

"This planet has a giant hot spot in the hemisphere that faces the star. The temperature difference between the day and night sides tells about how energy flows in the planet's atmosphere. Essentially, we're studying weather on an exotic planet" - Dr. Joe Harrington of the University of Central Florida, Orlando, lead author of a paper appearing online today in Science.

The finding represents the first time any kind of variation has been seen across the surface of an extrasolar planet, a planet beyond our solar system. Previous measurements of extrasolar planets described only global traits like size and mass.

"This is a spectacular result. When we designed Spitzer years ago, we did not anticipate that it would be revolutionizing extrasolar-planet science" - Dr. Michael Werner, project scientist for Spitzer at NASA's Jet Propulsion Laboratory, Pasadena, California.

The researchers used Spitzer to determine the temperature variation in the atmosphere of a nearby planet called Upsilon Andromedae b. This "hot-Jupiter" planet is a gas giant similar to Jupiter, but it orbits very close to its scorching star, circling the star once every 4.6 days.
Scientists believe the planet is tidally locked to its star. This means it is rotating slowly enough that the same side always faces the star, just as the same side of Earth's tidally locked moon always faces toward us, hiding its "dark side." However, since this planet is made of gas, its outer atmosphere could be circulating much faster than its interior.
According to the astronomers, the observed temperature difference between the two sides of Upsilon Andromedae b is extreme -- about 1,400 degrees Celsius (2,550 degrees Fahrenheit). Such a large temperature difference indicates the planet's atmosphere absorbs and reradiates sunlight so fast that gas circling around it cools off quickly. This is unlike Jupiter, which is even-temperatured all the way around.

"If you were moving across the planet from the night side to day side, the temperature jump would be equivalent to leaping into a volcano" - Dr. Brad Hansen, project's principal investigator, University of California, Los Angeles.

Spitzer used its heat-seeking infrared eyes to periodically stare at the Upsilon Andromedae planetary system over approximately five days. It found the system's infrared light, or heat, dimmed and brightened in time with Upsilon Andromedae b's orbit. This change in heat is the result of the planet showing its different faces to Spitzer as it travelled around the star. When the planet's sunlit side was in Earth's view, Spitzer detected more heat from the system; when its dark side was facing us, it picked up less heat. The planet does not cross behind or in front of its star, but is always in Earth's line of sight.
Upsilon Andromedae b was discovered in 1996 around the star Upsilon Andromedae, which is 40 light-years away and visible to the naked eye at night in the constellation Andromeda. Upsilon Andromedae is circled by two other known planets located farther out than Upsilon Andromedae b.
Harrington and Hansen are presenting their results today at the 38th meeting of the Division for Planetary Sciences of the American Astronomical Society in Pasadena, California.
Harrington and three co-authors on this Science paper used Spitzer last year to directly detect light from an extrasolar gas-giant planet as it ducked behind its star and reappeared. That technique and the current method described above take advantage of the fact that planets stand out better relative to their stars when viewed in infrared light.

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