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Exoplanets - Planets Beyond Our Solar System


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#1    Waspie_Dwarf

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Posted 05 April 2006 - 09:39 PM

NASA's Spitzer Finds Hints of Planet Birth Around Dead Star

The NASA press release is reproduced below:

NASA's Spitzer Space Telescope has uncovered new evidence that planets might rise up out of a dead star's ashes.

The infrared telescope surveyed the scene around a pulsar, the remnant of an exploded star, and found a surrounding disk made up of debris shot out during the star's death throes. The dusty rubble in this disk might ultimately stick together to form planets.

user posted image
Image above: This artist's concept depicts a type of dead star called a pulsar and the surrounding disk of rubble discovered by NASA's Spitzer Space Telescope. Image credit: NASA/JPL-Caltech
+ Related animation (6.5Mb): This artist's animation depicts the explosive death of a massive star, followed by the creation of a disk made up of the star's ashes.

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This is the first time scientists have detected planet-building materials around a star that died in a fiery blast.

"We're amazed that the planet-formation process seems to be so universal," said Dr. Deepto Chakrabarty of the Massachusetts Institute of Technology in Cambridge, principal investigator of the new research. "Pulsars emit a tremendous amount of high energy radiation, yet within this harsh environment we have a disk that looks a lot like those around young stars where planets are formed."

A paper on the Spitzer finding appears in the April 6 issue of Nature. Other authors of the paper are lead author Zhongxiang Wang and co-author David Kaplan, both of the Massachusetts Institute of Technology.

The finding also represents the missing piece in a puzzle that arose in 1992, when Dr. Aleksander Wolszczan of Pennsylvania State University found three planets circling a pulsar called PSR B1257+12. Those pulsar planets, two the size of Earth, were the first planets of any type ever discovered outside our solar system. Astronomers have since found indirect evidence the pulsar planets were born out of a dusty debris disk, but nobody had directly detected this kind of disk until now.

The pulsar observed by Spitzer, named 4U 0142+61, is 13,000 light-years away in the Cassiopeia constellation. It was once a large, bright star with a mass between 10 and 20 times that of our sun. The star probably survived for about 10 million years, until it collapsed under its own weight about 100,000 years ago and blasted apart in a supernova explosion.

Some of the debris, or "fallback," from that explosion eventually settled into a disk orbiting the shrunken remains of the star, or pulsar. Spitzer was able to spot the warm glow of the dusty disk with its heat-seeking infrared eyes. The disk orbits at a distance of about 1 million miles and probably contains about 10 Earth-masses of material.

Pulsars are a class of supernova remnants, called neutron stars, which are incredibly dense. They have masses about 1.4 times that of the sun squeezed into bodies only 10 miles wide. One teaspoon of a neutron star would weigh about 2 billion tons. Pulsar 4U 0142+61 is an X-ray pulsar, meaning that it spins and pulses with X-ray radiation.

Any planets around the stars that gave rise to pulsars would have been incinerated when the stars blew up. The pulsar disk discovered by Spitzer might represent the first step in the formation of a new, more exotic type of planetary system, similar to the one found by Wolszczan in 1992.

"I find it very exciting to see direct evidence that the debris around a pulsar is capable of forming itself into a disk. This might be the beginning of a second generation of planets," Wolszczan said.

Pulsar planets would be bathed in intense radiation and would be quite different from those in our solar system. "These planets must be among the least hospitable places in the galaxy for the formation of life," said Dr. Charles Beichman, an astronomer at NASA's Jet Propulsion Laboratory and the California Institute of Technology, both in Pasadena, Calif.

The Jet Propulsion Laboratory manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech. JPL is a division of Caltech. Spitzer's infrared array camera, which made the pulsar observations, was built by NASA's Goddard Space Flight Center, Greenbelt, Md. The instrument's principal investigator is Dr. Giovanni Fazio of the Harvard-Smithsonian Center for Astrophysics.

For more information about Spitzer, visit:

http://www.spitzer.caltech.edu/spitzer



Media contact:
Whitney Clavin
Jet Propulsion Laboratory, Pasadena, Calif.
(818) 354-4673

Erica Hupp/Grey Hautaluoma
Headquarters, Washington
(202) 358-1237/0668

2006-049


Source: NASA - Explore the Universe - Stars and Galaxies

Edited by Waspie_Dwarf, 05 April 2006 - 09:40 PM.

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#2    Waspie_Dwarf

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Posted 17 May 2006 - 11:27 PM

Trio of Neptunes and their Belt

The European Southern Observatory (ESO) press release pr-18-06 is reproduced below:

18 May 2006
Under embargo till 17 May 19:00 CET

Trio of Neptunes and their Belt

HARPS Instrument Finds Unusual Planetary System



Using the ultra-precise HARPS spectrograph on ESO's 3.6-m telescope at La Silla (Chile), a team of European astronomers have discovered that a nearby star is host to three Neptune-mass planets. The innermost planet is most probably rocky, while the outermost is the first known Neptune-mass planet to reside in the habitable zone. This unique system is likely further enriched by an asteroid belt.

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The HARPS measurement reveal the presence of three planets with masses between 10 and 18 Earth masses around HD 69830, a rather normal star slightly less massive than the Sun. The planets' mean distance are 0.08, 0.19, and 0.63 the mean distance between the Earth and the Sun. From previous observations, it seems that there exists also an asteroid belt, whose location is unknown. It could either lie between the two outermost planets, or farther from its parent star than 0.8 the mean Earth-Sun distance.

linked-image
This image is taken from a point of view inside the asteroid belt, which is assumed here to lie between the two outermost planets.

"For the first time, we have discovered a planetary system composed of several Neptune-mass planets", said Christophe Lovis, from the Geneva Observatory and lead-author of the paper presenting the results [1].

During more than two years, the astronomers carefully studied HD 69830, a rather inconspicuous nearby star slightly less massive than the Sun. Located 41 light-years away towards the constellation of Puppis (the Stern), it is, with a visual magnitude of 5.95, just visible with the unaided eye. The astronomers' precise radial-velocity measurements [2] allowed them to discover the presence of three tiny companions orbiting their parent star in 8.67, 31.6 and 197 days.

"Only ESO's HARPS instrument installed at the La Silla Observatory, Chile, made it possible to uncover these planets", said Michel Mayor, also from Geneva Observatory, and HARPS Principal Investigator. "Without any doubt, it is presently the world's most precise planet-hunting machine" [3].

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Measurements of the radial velocity of the star HD 69830 obtained by HARPS on the ESO 3.6m telescope at La Silla as a function of time, from November 2004 till February 2005 (a) and from mid-October 2005 till February 2006 (B). The two innermost planets are clearly revealed, while the presence of the third one becomes clear when removing the signal of the inner planets and binning the data points (one per observing run), as shown in ©. The lower parts of (a) and (B) show the residuals from the best fit indicated by the solid line.

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The HARPS radial velocity measurements of HD 69830 are folded with the orbital periods of the three discovered planets: 8.67, 31.6 and 197 days, respectively. In each case, the contribution of the two other planets has been subtracted. The solid line shows the best fit to the measurements, corresponding to minimum masses of 10.2, 11.8 and 18.1 Earth masses. Note that the full span of the vertical axis is only 13 m/s! Error bars indicate the accuracy of the measurements. The integration time was 4 minutes on average for the first 18 measurements (shown as open dots), and was increased to 15 minutes for the remaining points (full dots). The latter measurements are therefore of much higher quality.

The detected velocity variations are between 2 and 3 metres per second, corresponding to about 9 km/h! That's the speed of a person walking briskly. Such tiny signals could not have been distinguished from 'simple noise' by most of today's available spectrographs.

The newly found planets have minimum masses between 10 and 18 times the mass of the Earth. Extensive theoretical simulations favour an essentially rocky composition for the inner planet, and a rocky/gas structure for the middle one. The outer planet has probably accreted some ice during its formation, and is likely to be made of a rocky/icy core surrounded by a quite massive envelope. Further calculations have also shown that the system is in a dynamically stable configuration.

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Illustration of the possible formation process and present day structure of the planetary system around HD 68930. The three planets form from embryos originally located at larger distances (dashed ellipses) than the present ones (indicated by solid ellipses at 0.07, 0.18 and 0.63 the mean Earth-Sun distance). The embryos of the inner and middle planets start interior to the ice line, so that these two planets build up from rocky planetesimals and gas. The two planets consist of a central rocky core (in brown) and an envelope of gas (in gray). The embryo of the outermost planet starts beyond the ice line, and the planet accumulates a large amount of ice at the beginning of its formation. The planet finally consists of a central rocky core (brown), surrounded by a shell of water (ice or liquid - in blue), and a quite massive gas envelope (gray).  

The outer planet also appears to be located near the inner edge of the habitable zone, where liquid water can exist at the surface of rocky/icy bodies. Although this planet is probably not Earth-like due to its heavy mass, its discovery opens the way to exciting perspectives.

"This alone makes this system already exceptional", said Willy Benz, from Bern University, and co-author. "But the recent discovery by the Spitzer Space Telescope that the star most likely hosts an asteroid belt is adding the cherry to the cake."

With three roughly equal-mass planets, one being in the habitable zone, and an asteroid belt, this planetary system shares many properties with our own solar system.

"The planetary system around HD 69830 clearly represents a Rosetta stone in our understanding of how planets form", said Michel Mayor. "No doubt it will help us better understand the huge diversity we have observed since the first extra-solar planet was found 11 years ago."

Video footage and animations are available on this page.

Notes

[1]: These results appear in the 18 May issue of the research journal Nature ("Discovery of an extrasolar planetary system with three Neptune-Mass Planets", by C. Lovis et al.). The team is composed of Christophe Lovis, Michel Mayor, Francesco Pepe, Didier Queloz, and Stéphane Udry (Observatoire de l'Université de Genève, Switzerland), Nuno C. Santos (Observatoire de l'Université de Genève, Switzerland, Centro de Astronomia e Astrofisica da Universidade de Lisboa and Centro de Geofisica de Evora, Portugal), Yann Alibert, Willy Benz, Christoph Mordasini (Physikalisches Institut der Universität Bern, Switzerland), François Bouchy (Observatoire de Haute-Provence and IAP, France), Alexandre C. M. Correia (Universidade de Aveiro, Portugal), Jacques Laskar (IMCCE-CNRS, Paris, France), Jean-Loup Bertaux (Service d'Aéronomie du CNRS, France), and Jean-Pierre Sivan (Laboratoire d'Astrophysique de Marseille, France).

[2]: A planet in orbit around a star will manifest its presence by pulling the star in different directions, thereby changing by rather small amounts its measured velocity. Astronomers therefore measure with very high precision the velocity of a star to detect the signature of one or more planets.

[3]: The High Accuracy Radial velocity Planet Searcher (HARPS) at the ESO La Silla 3.6-m telescope is dedicated to the discovery of extrasolar planets. It is a fibre-fed high-resolution echelle spectrograph that has demonstrated a long-term precision of about 1 m/s.


Source: ESO Press Release pr-18-06

Edited by Waspie_Dwarf, 01 June 2007 - 12:46 PM.

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#3    TooFarGone

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Posted 18 May 2006 - 12:24 AM

Wow, thats pretty incredible....great artist depictions too.

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#4    Waspie_Dwarf

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Posted 18 May 2006 - 06:41 PM

Astronomers Use Innovative Technique to Find Extrasolar Planet

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Artist's Concept of Transiting Planet XO-1b
This artist's impression shows a dramatic close-up of the extrasolar planet XO-1b passing in front of a Sun-like star 600 light-years from Earth. The Jupiter-sized planet is in a tight four-day orbit around the star.

Credit: NASA, ESA and G. Bacon (STScI)

Image Type: Artwork
STScI-PRC2006-22a


An international team of professional and amateur astronomers, using simple off-the-shelf equipment to trawl the skies for planets outside our solar system, has hauled in its first "catch."

The astronomers discovered a Jupiter-sized planet orbiting a Sun-like star 600 light-years from Earth in the constellation Corona Borealis. The team, led by Peter McCullough of the Space Telescope Science Institute in Baltimore, Md., includes four amateur astronomers from North America and Europe.

Using modest telescopes to search for extrasolar planets allows for a productive collaboration between professional and amateur astronomers that could accelerate the planet quest.

"This discovery suggests that a fleet of modest telescopes and the help of amateur astronomers can search for transiting extrasolar planets many times faster than we are now," McCullough said. The finding has been accepted for publication in the Astrophysical Journal.

McCullough deployed a relatively inexpensive telescope made from commercial equipment to scan the skies for extrasolar planets. Called the XO telescope, it consists of two 200-millimeter telephoto camera lenses and looks like a pair of binoculars. The telescope is on the summit of the Haleakala volcano, in Hawaii.

"To replicate the XO prototype telescope would cost $60,000," McCullough explained. "We have spent far more than that on software, in particular on designing and operating the system and extracting this planet from the data."

McCullough's team found the planet, dubbed X0-1b, by noticing slight dips in the star's light output when the planet passed in front of the star, called a transit. The light from the star, called XO-1, dips by approximately 2 percent when the planet XO-1b passes in front of it. The observation also revealed that X0-1b is in a tight four-day orbit around its parent star.

Although astronomers have detected more than 180 extrasolar planets, X0-1b is only the tenth planet discovered using the transit method. It is the second planet found using telephoto lenses. The first, dubbed TrES-1, was reported in 2004. The transit method allows astronomers to determine a planet's mass and size. Astronomers use this information to deduce the planet's characteristics, such as its density.

The team confirmed the planet's existence by using the Harlan J. Smith Telescope and the Hobby-Eberly Telescope at the University of Texas's McDonald Observatory to measure the slight wobble induced by the planet on its parent star. This so-called radial-velocity method allowed the team to calculate a precise mass for the planet, which is slightly less than that of Jupiter (about 0.9 Jupiter masses). The planet also is much larger than its mass would suggest. "Of the planets that pass in front of their stars, XO-1b is the most similar to Jupiter yet known, and the star XO-1 is the most similar to the Sun," McCullough said, although he was quick to add, "but XO-1b is much, much closer to its star than Jupiter is to the Sun."

The astronomer's innovative technique of using relatively inexpensive telescopes to look for eclipsing planets favors finding planets orbiting close to their parent stars. The planet also must be large enough to produce a measurable dip in starlight.

The planet is the first discovered in McCullough's three-year search for transiting extrasolar planets. The planet quest is underwritten by a grant from NASA's Origins program.

McCullough's planet-finding technique involves nightly sweeps of the sky using the XO telescope in Hawaii to note the brightness of the stars it encounters. A computer software program sifts through many thousands of stars every two months looking for tiny dips in the stars' light, the signature of a possible planetary transit. The computer comes up with a few hundred possibilities. From those candidates, McCullough and his team select a few dozen promising leads. He passes these stars on to the four amateur astronomers to study the possible transits more carefully.

From September 2003 to September 2005, the XO telescope observed tens of thousands of bright stars. In that time, his team of amateur astronomers studied a few dozen promising candidate stars identified by McCullough and his team. The star X0-1 was pegged as a promising candidate in June 2005. The amateur astronomers observed it in June and July 2005, confirming that a planet-sized object was eclipsing the star. McCullough's team then turned to the McDonald Observatory in Texas to obtain the object's mass and verify it as a planet. He received the news of the telescope's observation at 12:06 a.m. Feb. 16, 2006, from Chris Johns-Krull, a friend and colleague at Rice University.

"It was a wonderful feeling because the team had worked for three years to find this one planet," McCullough explained. "The discovery represents a few bytes out of nearly a terabyte of data: It's like trying to distill gold out of seawater."

The discovery also has special familial significance for the astronomer. "My father's mentor was Harlan J. Smith, the man whose ambition and hard work produced the telescope that we used to acquire the verifying data."

McCullough believes the newly found planet is a perfect candidate for study by the Hubble and Spitzer space telescopes. Hubble can measure precisely the star's distance and the planet's size. Spitzer can actually see the infrared radiation from the planet. By timing the disappearance of the planet behind the star, Spitzer also can measure the "ellipticity," or "out-of-roundness," of the planet's orbit. If the orbit is elliptical, then the varying gravitational force would result in extra heating of the planet, expanding its atmosphere and perhaps explaining why the object's diameter seems especially large for a body of its calculated mass.

"By timing the planet's passages across the star, both amateur and professional astronomers might be lucky enough to detect the presence of another planet in the XO-1 system by its gravitational tugs on XO-1b," McCullough said. "It's even possible that such a planet could be similar to Earth."

Release Date: 1:00PM (EDT) May 18, 2006
Release Number: STScI-2006-22


Source: Hubblesite - Newsdesk

Edited by Waspie_Dwarf, 01 June 2007 - 12:40 PM.

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#5    Waspie_Dwarf

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Posted 01 June 2006 - 02:37 PM

Understanding "Hot Jupiters"

The Astronomy & Astrophysics press release is reproduced below:



Interiors of extrasolar planets: A first step

Released on May 30th, 2006

“A correlation between the heavy element content of transiting extrasolar planets and the metallicity of their parent stars”, by Guillot et al.

To be published in Astronomy & Astrophysics.

This press release is issued as a collaboration with the CNRS and Astronomy & Astrophysics.
--------------------------------------------------------------------------------

A team of European astronomers, led by T. Guillot (CNRS, Observatoire de la Côte d’Azur, France), will publish a new study of the physics of Pegasids (also known as hot Jupiters) in Astronomy & Astrophysics. They found that the amount of heavy elements in Pegasids is correlated to the metallicity of their parent stars. This is a first step in understanding the physical nature of the extrasolar planets.

Up to now, astronomers have discovered 188 extrasolar planets, among which 10 are known as “transiting planets”. These planets pass between their star and us at each orbit (Figure 1). Given the current technical limitations, the only transiting planets that can be detected are giant planets orbiting close to their parent star known as “hot Jupiters” or Pegasids. The ten transiting planets known thus far have masses between 110 and 430 Earth masses (for comparison, Jupiter, with 318 Earth masses, is the most massive planet in our Solar System).

user posted image
Fig. 1 - Animation of a typical Pegasid system, with both the star and planet drawn to scale. Here, the planet orbits the star in just 3.5 days. For comparison, the Earth orbits the Sun every single year, and Mercury, which has the shortest orbital period in the solar system, orbits the Sun every 88 days.

Although rare, transiting planets are the key to understanding planetary formation because they are the only ones for which both the mass and radius can be determined. In principle, the obtained mean density can constrain their global composition. However, translating a mean density into a global composition needs accurate models of the internal structure and evolution of planets. The situation is made difficult by our relatively poor knowledge of the behaviour of matter at high pressures (the pressure in the interiors of giant planets is more than a million times the atmospheric pressure on Earth). Of the nine transiting planets known up to April 2006, only the least massive one could have its global composition determined satisfactorily. It was shown to possess a massive core of heavy elements, about 70 times the mass of the Earth, with a 40 Earth-mass envelope of hydrogen and helium. Of the remaining eight planets, six were found to be mostly made up of hydrogen and helium, like Jupiter and Saturn, but their core mass could not be determined. The last two were found to be too large to be explained by simple models.

Considering them as an ensemble for the first time, and accounting for the anomalously large planets, Tristan Guillot and his team [1] found that the nine transiting planets have homogeneous properties, with a core mass ranging from 0 (no core, or a small one) up to 100 times the mass of the Earth, and a surrounding envelope of hydrogen and helium. Some of the Pegasids should therefore contain larger amounts of heavy elements than expected. When comparing the mass of heavy elements in the Pegasids to the metallicity of the parent stars, they also found a correlation to exist, with planets born around stars that are as metal-rich as our Sun and that have small cores, while planets orbiting stars that contain two to three times more metals have much larger cores, as shown in Figure 2. Their results will be published in Astronomy & Astrophysics.

Planet formation models have failed to predict the large amounts of heavy elements found this way in many planets, so these results imply that they need revising. The correlation between stellar and planetary composition has to be confirmed by further discoveries of transiting planets, but this work is a first step in studying the physical nature of extrasolar planets and their formation. It would explain why transiting planets are so hard to find, to start with. Because most Pegasids have relatively large cores, they are smaller than expected and more difficult to detect in transit in front of their stars. In any case, this is very promising for the CNES space mission COROT to be launched in October, which should discover and lead to characterization of tens of transiting planets, including smaller planets and planets orbiting too far from their star to be detected from the ground.

What of the tenth transiting planet? XO-1b was announced very recently (see NASA press release) and is also found to be an anomalously large planet orbiting a star of solar metallicity. Models imply that it has a very small core, so that this new discovery strengthens the proposed stellar-planetary metallicity correlation.


user posted image
Fig. 2 - Correlation between the amount of heavy elements in the transiting planets and the metallicity of their parent stars.


--------------------------------------------------------------------------------

[1] The team includes T. Guillot (France), N.C. Santos (Portugal), F. Pont (Switzerland), N. Iro (USA), C. Melo (Germany), I. Ribas (Spain).

--------------------------------------------------------------------------------

A correlation between the heavy element content of transiting extrasolar planets and the metallicity of their parent stars by T. Guillot, N.C. Santos, F. Pont, N. Iro, C. Melo, I. Ribas.
To be published in Astronomy & Astrophysics (DOI number: 10.1051/0004-6361:20065476)
Full article available in PDF format


Source: Astronomy & Astrophysics press release

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#6    Waspie_Dwarf

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Posted 05 June 2006 - 08:41 PM

Do 'Planemos' Have Progeny?

The European Southern Observatory (ESO) press release pr-19-06 is reproduced below:

6 June 2006
Under Embargo Until 17:30 CEST (11:30 A.M. EDT) Monday 5 June 2006

Do 'Planemos' Have Progeny?

Planetary-Mass Objects Found to be Surrounded by Discs



Two new studies, based on observations made with ESO's telescopes, show that objects only a few times more massive than Jupiter are born with discs of dust and gas, the raw material for planet making. This suggests that miniature versions of the solar system may circle objects that are some 100 times less massive than our Sun.

These findings are to be presented Monday, 5 June at the American Astronomical Society meeting in Calgary, Canada.

Since a few years, it is known that many young brown dwarfs, 'failed stars' that weigh less than 8 percent the mass of the Sun, are surrounded by a disc of material. This may indicate these objects form the same way as did our Sun.

The new findings reveal that the same appears to be true for their even punier cousins, sometimes called planetary mass objects or 'planemos'. These objects have masses similar to those of extra-solar planets, but they are not in orbit around stars - instead, they float freely through space.

"Our findings, combined with previous work, suggest similar infancies for our Sun and objects that are some hundred times less massive", says Valentin D. Ivanov (ESO), co-author of the first study.

user posted image
Optical spectra of the six planetary mass object candidates, along with those of comparison objects. The dotted lines mark the location of Hα while the dashed line corresponds to a telluric absorption feature.

"Now that we know of these planetary mass objects with their own little infant planetary systems, the definition of the word 'planet' has blurred even more," adds Ray Jayawardhana, from the University of Toronto (Canada) and lead author of the study. "In a way, the new discoveries are not too surprising - after all, Jupiter must have been born with its own disc, out of which its bigger moons formed."

Unlike Jupiter, however, these planemos are not circling stars. In their study, Jayawardhana and Ivanov used two of ESO's telescopes - Antu, the 8.2-metre Unit Telescope no. 1 of the Very Large Telescope, and the 3.5-metre New Technology Telescope - to obtain optical spectra of six candidates identified recently by researchers at the University of Texas at Austin. Two of the six turned out to have masses between five to 10 times that of Jupiter while two others are a tad heftier, at 10 to 15 times Jupiter's mass. All four of these objects are 'newborns', just a few million years old, and are located in star-forming regions about 450 light-years from Earth. The planemos show infrared emission from dusty discs that may evolve into miniature planetary systems over time.

In another study, Subhanjoy Mohanty (Harvard-Smithsonian Center for Astrophysics, CfA), Ray Jayawardhana (Univ. of Toronto), Nuria Huelamo (ESO) and Eric Mamajek (also at CfA) used the Very Large Telescope, this time with its adaptive optics system and infrared camera NACO, to obtain images and spectra of a planetary mass companion discovered at ESO two years ago around a young brown dwarf that is itself about 25 times the mass of Jupiter. This planetary mass companion is the first-ever exoplanet to have been imaged (see ESO 12/05).

user posted image
VLT NACO J-band image, showing the 2M1207Ab system: the planetary companion is visible near the lower left rim of the brown dwarf, at a separation of 769 mas. North is up, East is left.

The brown dwarf, dubbed 2M1207 for short and located 170 light-years from Earth, was known to be surrounded by a disc. Now, this team has found evidence for a disc around the eight-Jupiter-mass companion as well.

"The pair probably formed together, like a petite stellar binary", explains lead author Mohanty, "instead of the companion forming in the disc around the brown dwarf, like a star-planet system."

"Moreover", Jayawardhana adds, "it is quite likely that smaller planets or asteroids could now form in the disc around each one."


Source: ESO Press Release pr-19-06

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#7    Waspie_Dwarf

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Posted 05 June 2006 - 08:48 PM

Jupiter's "Big Brother" Has Moon-Forming Dust Disk

The Harvard-Smithsonian Center for Astrophysics press release is reproduced below:

Release No.: 06-16
For Release: For Release: 9:30 a.m. MDT (11:30 a.m. EDT) Monday, June 5, 2006

Jupiter's "Big Brother" Has Moon-Forming Dust Disk

Calgary, AB - Earth's Moon was created by an early collision with another large planetary body. It was a "chip off the old block." Mars captured its asteroidal moons as they passed by. But Jupiter made its own moons out of dust and gas remaining from its formation. Now, observations by astronomer Subhanjoy Mohanty of the Harvard-Smithsonian Center for Astrophysics (CfA) and his colleagues provide the first direct evidence for a dusty disk around a distant planet that in mass would be Jupiter's "big brother."

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Astronomers have discovered a dusty disk around the 8-Jupiter-mass object called 2M1207B, shown here in an artist's conception. That disk eventually may form one or more moons like those orbiting the giant planets of our solar system. As seen from Earth, 2M1207B lies in the constellation Centaurus, which is also home to the peculiar galaxy NGC 5128 shown in the upper left of this image. Credit: David A. Aguilar (CfA)

"It is quite possible that moons or moonlets could form out of this disk, just as they have around the giant planets in our own solar system," said Mohanty.

Mohanty presented the discovery today in a press conference at the 208th meeting of the American Astronomical Society. Other members of the team are Ray Jayawardhana (University of Toronto), Nuria Huélamo (ESO) and Eric Mamajek (CfA).

The team studied a planetary mass object known as 2MASS1207-3932B, which is located about 170 light-years from Earth in the direction of the constellation Centaurus. 2M1207B, as it is abbreviated, orbits a tiny brown dwarf star at a separation of about 40 astronomical units, or 3.7 billion miles - comparable to the size of Pluto's orbit. That separation is much larger than typical for binary brown dwarf systems. The wide separation may indicate that the duo formed in relative isolation, far from passing stars that could have pulled them apart.

"This system probably won't survive for long. It won't last 5 billion years like our solar system has," said Mamajek. "All it would take is for a more massive interloper star to come along and yank the planet away from the brown dwarf."

Observations by Mohanty's team showed that the brown dwarf has a mass of about 25 Jupiters and a temperature of 4100 degrees Fahrenheit (2600 K). Its companion 2M1207B weighs about 8 times Jupiter and has a temperature of 2400 degrees F (1600 K). Both objects are warm due to their young age of 5-10 million years, having retained the heat of formation.

Given those temperatures, the team then calculated the expected brightness of both objects. The brown dwarf matched predictions but its companion was about 8 times fainter than expected. After examining several potential causes, the team concluded that the only plausible explanation was the presence of an edge-on dusty disk that blocked most of the planet's light. The planet is seen only in light scattered from the disk.

Spectral analysis shows that 2M1207B is a gas giant like Jupiter with no solid surface. As a result, it would be a poor abode for life. Any moons that might form around it, however, could prove more hospitable.

The large mass of 2M1207B relative to the brown dwarf star poses a puzzle for planetary formation theories. Typical planets like those in our solar system are less than one-hundredth the size of the central star. In contrast, 2M1207B holds one-third as much mass as the brown dwarf.

"Mass ratios of that size are more typical for binary stars than for planetary systems," said Mohanty. "2M1207B probably formed like a star, together with the brown dwarf, rather than from core accretion like giant planets around other stars."

Mohanty and his colleagues plan to study the polarization of light from 2M1207B in order to investigate the inclination of its disk as well as the size of dust grains within the disk. Further studies await the next generation of large telescopes, such as the Giant Magellan Telescope and the Atacama Large Millimeter Array, which may be able to directly detect the disk around the planetary mass companion.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.


Source: CfA Press Release

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#8    Waspie_Dwarf

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Posted 24 July 2006 - 06:36 PM

Planet-Forming Disks Might Put the Brakes on Stars

Astronomers using NASA's Spitzer Space Telescope have found evidence that dusty disks of planet-forming material tug on and slow down the young, whirling stars they surround.

Young stars are full of energy, spinning around like tops in half a day or less. They would spin even faster, but something puts on the brakes. While scientists had theorized that planet-forming disks might be at least part of the answer, demonstrating this had been hard to do until now.

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Image above: This artist's concept shows a
dusty planet-forming disk in orbit around a
whirling young star.
Image credit: NASA/JPL-Caltech.
+ Larger view
+ Video: Spitzer's Spin on Stars (14Mb)


"We knew that something must be keeping the stars' speed in check," said Dr. Luisa Rebull of NASA's Spitzer Science Center, Pasadena, Calif. "Disks were the most logical answer, but we had to wait for Spitzer to see the disks."

Rebull, who has been working on the problem for nearly a decade, is lead author of a new paper in the July 20 issue of the Astrophysical Journal. The findings are part of a quest to understand the complex relationship between young stars and their burgeoning planetary systems.

Stars begin life as collapsing balls of gas that spin faster and faster as they shrink, like twirling ice skaters pulling in their arms. As the stars whip around, excess gas and dust flatten into surrounding pancake-like disks. The dust and gas in the disks are believed to eventually clump together to form planets.

Developing stars spin so fast that, left unchecked, they would never fully contract and become stars. Prior to the new study, astronomers had theorized that disks might be slowing the super speedy stars by yanking on their magnetic fields. When a star's fields pass through a disk, they are thought to get bogged down like a spoon in molasses. This locks a star's rotation to the slower-turning disk, so the shrinking star can't spin faster.

To prove this principle, Rebull and her team turned to Spitzer for help. Launched in August of 2003, the infrared observatory is an expert at finding the swirling disks around stars, because dust in the disks is heated by starlight and glows at infrared wavelengths.

The team used Spitzer to observe nearly 500 young stars in the Orion nebula. They divided the stars into slow spinners and fast spinners, and determined that the slow spinners are five times more likely to have disks than the fast ones.

"We can now say that disks play some kind of role in slowing down stars in at least one region, but there could be a host of other factors operating in tandem. And stars might behave differently in different environments," Rebull said.

Other factors that contribute to a star's winding down over longer periods of time include stellar winds and possibly full-grown planets.

If planet-forming disks slow down stars, does that mean stars with planets spin more slowly than stars without planets? Not necessarily, according to Rebull, who said slowly spinning stars might simply take more time than other stars to clear their disks and develop planets. Such late-blooming stars would, in effect, give their disks more time to put on the brakes and slow them down.

Ultimately, the question of how a star's rotation rate is related to its ability to support planets will fall to planet hunters. So far, all known planets in the universe circle stars that turn around lazily. Our sun is considered a slowpoke, currently plodding along at a rate of one revolution every 28 days. And, due to limits in technology, planet hunters have not been able to find any extrasolar planets around zippy stars.

"We'll have to use different tools for detecting planets around rapidly spinning stars, such as next-generation ground and space telescopes," said Dr. Steve Strom, an astronomer at the National Optical Astronomy Observatory, Tucson, Ariz.

Other members of Rebull's team include Drs. John Stauffer of the Spitzer Science Center; S. Thomas Megeath at the University of Toledo, Ohio; and Joseph Hora and Lee Hartmann of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass. Hartmann is also affiliated with the University of Michigan, Ann Arbor.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology. Caltech manages JPL for NASA.

For an animation depicting how disks slow stars and more information about Spitzer, visit www.spitzer.caltech.edu/spitzer.

Media contact: Whitney Clavin (818) 354-4673
Jet Propulsion Laboratory, Pasadena, Calif.

2006-094


Source: NASA - Exploring the Universe - Stars and Galaxies

"Space is big. Really big. You just won't believe how vastly, hugely, mind-boggingly big it is. I mean, you may think it's a long way down the street to the chemist, but that's just peanuts to space." - The Hitch-Hikers Guide to the Galaxy - Douglas Adams 1952 - 2001

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#9    Roj47

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Posted 25 July 2006 - 09:26 AM

I really do enjoy reading these links..... Many thanks.

My questions is however -

Is there any theory as to the effect that the speed of rotation of a star would have on surrounding planets?

i.e. What would the potential difference if any be to Earth between the Sun rotating every 28 days and twice daily.
I guess the other assumption would be that at twice dailt the Sun would be compact enough to actually be a star, but I go beyond my knowledge and understanding here.

regards

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#10    leadbelly

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Posted 25 July 2006 - 02:15 PM

Take this for what it is- a guess.

The Sun is a mid-life dwarf yellow star, with an onion-like interior. There are layers that move at different rates. Add to this, the electromagnetic field lines running north to south,
and things wind and unwind every eleven years. The field lines gradually wrap around the Sun latitudinaly, which leads to tension, which leads to flairs amd coronal mass discharges.
Those can have more of a detrimental effect on planets if they lack sufficient  magnetospheres.

For example, Mars would in its past have been a more deadly place to be during solar storm cycles, compared to Earth. Because Mars is smaller, retains less atmosphere, and has less magnetosphere due to it's less molten iron core, any theoretical primitive life would have been more irradiated, especially during solar storms.

Thus, as you speed up the Sun's rotation, you might shorten the time between storm cycles, making them a frequently occurring fact of life. For us, that could cause damage to satellites, and fry the electric transformers on Earth, if the storms were severe enough.


I also imagine that if the sun were to rotate at a very high rate of speed, for instance, once every two hours, it would probably start to break up.







#11    Roj47

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Posted 25 July 2006 - 02:22 PM

Thank you, and a very interesting idea.

Sun spots is something I can look up as are solar flares.

Kind regards

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#12    Bella-Angelique

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Posted 25 July 2006 - 02:30 PM

Perhaps 26 to 30 day stars are the ones most likely then to have earth sized planets worth exploring.

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#13    Waspie_Dwarf

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Posted 25 July 2006 - 02:31 PM

Stars can rotate at very rapid rates without breaking up. This is because they are not solid bodies. However it would become highly oblate, being very obviously flattened at the poles and bulging at the equator.

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#14    Roj47

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Posted 25 July 2006 - 02:32 PM

Quote


Perhaps 26 to 30 day stars are the ones most likely then to have earth sized planets worth exploring.


Now that would be a very very interesting theory to establish.

However is it not the planets forming that reduce the speed. If so...... would the question be -

Perhaps 26 to 30 day stars are the ones most likely to have planets witgh the ability to sustain life.

Edited by Roj47, 25 July 2006 - 02:35 PM.

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#15    leadbelly

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Posted 26 July 2006 - 12:42 AM

"If planet-forming disks slow down stars, does that mean stars with planets spin more slowly than stars without planets? Not necessarily, according to Rebull, who said slowly spinning stars might simply take more time than other stars to clear their disks and develop planets...

So far, all known planets in the universe circle stars that turn around lazily. Our sun is considered a slowpoke, currently plodding along at a rate of one revolution every 28 days. And, due to limits in technology, planet hunters have not been able to find any extrasolar planets around zippy stars..."

Evidently, it has been the case that when we employ the two common methods currently used to detect planets, the planets have been around "slowpoke" stars.  

And, sustaining life is a relative term. You could have a "zippy" star with harsh light, and a planet at sufficient orbital distance, to allow extremophiles, or at best bacteria in liquid conditions, to survive against heat, light, maybe meteors in a younger star system...

But, all things considered, conditions identicle to Earth, or our sun at least, could be the ideal scenario.





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