Showing posts with label double-star system. Show all posts
Showing posts with label double-star system. Show all posts

Planets with Double Suns are Common

Posted by carsimulator on Wednesday, January 11, 2012

This artist's conception shows Kepler-34b, a newfound gas-giant that orbits a double-star system. Its two suns are both yellow, G-type stars that swing around each other every 28 days. The planet circles them both in 289 days. The discovery of Kepler-34b and Kepler-35b shows that circumbinary planets are common in our Galaxy. Credit: David A. Aguilar (CfA). High Resolution Image (jpg) - Low Resolution Image (jpg)

Austin, TX - Astronomers using NASA's Kepler mission have discovered two new circumbinary planet systems - planets that orbit two stars, like Tatooine in the movie Star Wars. Their find, which brings the number of known circumbinary planets to three, shows that planets with two suns must be common, with many millions existing in our Galaxy.

"Once again, we're seeing science fact catching up with science fiction," said co-author Josh Carter of the Harvard-Smithsonian Center for Astrophysics.

The work was published online in the journal Nature and presented by lead author William Welsh (San Diego State University) at a press conference at a meeting of the American Astronomical Society.

The two new planets, named Kepler-34b and Kepler-35b, are both gaseous Saturn-size planets. Kepler-34b orbits its two Sun-like stars every 289 days, and the stars themselves orbit each other every 28 days. Kepler-35b revolves around a pair of smaller stars (80 and 89 percent of the Sun's mass) every 131 days, and the stars orbit one another every 21 days. Both systems reside in the constellation Cygnus the Swan, with Kepler-34 located 4,900 light-years from Earth and Kepler-35 at a distance of 5,400 light-years.

Circumbinary planets have two suns, not just one, and due to the orbital motion of the stars, the amount of energy the planet receives varies greatly. This changing energy flow could produce wildly varying climates.

"It would be like cycling through all four seasons many times per year, with huge temperature changes," explained Welsh. "The effects of these climate swings on the atmospheric dynamics, and ultimately on the evolution of life on habitable circumbinary planets, is a fascinating topic that we are just beginning to explore."

The Kepler team announced the first circumbinary planet, Kepler-16b, last September. Like Kepler-16b, these new planets also transit (eclipse) their host stars, which is how Kepler spotted them. When only Kepler-16b was known, many questions remained about the nature of circumbinary planets; most importantly, was it a fluke? With the discovery of these two new worlds, astronomers can now answer many of those questions as they begin to study an entirely new class of planets.

"It was once believed that the environment around a pair of stars would be too chaotic for a circumbinary planet to form, but now that we have confirmed three such planets, we know that it is possible, if not probable, that there are at least millions in the Galaxy," said Welsh.

"The search is on for more circumbinary planets," agreed Carter, "and we hope to use Kepler for years to come."

This release is being issued jointly with San Diego State University.

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.

For more information, contact:

David A. Aguilar
Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
617-495-7462
daguilar@cfa.harvard.edu

Christine Pulliam
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
617-495-7463
cpulliam@cfa.harvard.edu

Gina Jacobs, SDSU
619-594-4563
gina.jacobs@sdsu.edu

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Vampire Star Reveals its Secrets

Posted by carsimulator on Wednesday, December 7, 2011

PR Image eso1148a
The unusual double star SS Leporis

PR Image eso1148b
A unusual double star in the constellation of Lepus

Wide field view of the unusual double star SS Leporis

PR Video eso1148a
Zooming in on the unusual double star SS Leporis

The vampire double star SS Leporis

PR Video eso1148c
The vampire double star SS Leporis (unannotated)

Astronomers have obtained the best images ever of a star that has lost most of its material to a vampire companion. By combining the light captured by four telescopes at ESO’s Paranal Observatory they created a virtual telescope 130 metres across with vision 50 times sharper than the NASA/ESA Hubble Space Telescope. Surprisingly, the new results show that the transfer of mass from one star to the other in this double system is gentler than expected.

“We can now combine light from four VLT telescopes and create super-sharp images much more quickly than before,” says Nicolas Blind (IPAG, Grenoble, France), who is the lead author on the paper presenting the results, “The images are so sharp that we can not only watch the stars orbiting around each other, but also measure the size of the larger of the two stars.”

The astronomers observed [1] the unusual system SS Leporis in the constellation of Lepus (The Hare), which contains two stars that circle around each other in 260 days. The stars are separated by only a little more than the distance between the Sun and the Earth, while the largest and coolest of the two stars extends to one quarter of this distance — corresponding roughly to the orbit of Mercury. Because of this closeness, the hot companion has already cannibalised about half of the mass of the larger star.

“We knew that this double star was unusual, and that material was flowing from one star to the other,” says co-author Henri Boffin, from ESO. “What we found, however, is that the way in which the mass transfer most likely took place is completely different from previous models of the process. The ‘bite’ of the vampire star is very gentle but highly effective.”

The new observations are sharp enough to show that the giant star is smaller than previously thought, making it much more difficult to explain how the red giant lost matter to its companion. The astronomers now think that, rather than streaming from one star to the other, the matter must be expelled from the giant star as a stellar wind and captured by the hotter companion.

“These observations have demonstrated the new snapshot imaging capability of the Very Large Telescope Interferometer. They pave the way for many further fascinating studies of interacting double stars,” concludes co-author Jean-Philippe Berger.

Notes

[1] The images were created from observations made with the Very Large Telescope Interferometer (VLTI) at ESOʼs Paranal Observatory using the four 1.8-metre Auxiliary Telescopes to feed light into a new instrument called PIONIER (see ann11021).

PIONIER, developed at LAOG/IPAG in Grenoble, France, is a visiting instrument at the Paranal Observatory. PIONIER is funded by Université Joseph Fourier, IPAG, INSU-CNRS (ASHRA-PNPS-PNP) ANR 2G-VLTI and ANR Exozodi. IPAG is part of the Grenoble Observatory (OSUG).

The VLTI engineers had to control the distance traversed by the light from the widely separated telescopes with an accuracy of about one hundredth of the thickness of a strand of human hair. Once the light reached PIONIER, it was then channelled into the heart of the instrument: a remarkable optical circuit, smaller than a credit card, that finally brought the light waves from the different telescopes together in a very precise way so that they could interfere. The resulting resolving power of the telescope array has the sharpness not of the individual 1.8-metre Auxiliary Telescopes, but that of a much bigger “virtual telescope” about 130 metres across, limited only by how far apart the telescopes can be positioned.

The resolution of the NASA/ESA Hubble Space Telescope is approximately 50 milliarcseconds whereas the resolution attainable with the VLTI is about one milliarcsecond — corresponding to the apparent size of an astronaut on the surface of the Moon, seen from Earth.

More information

This research was presented in a paper, “An incisive look at the symbiotic star SS Leporis — Milli-arcsecond imaging with PIONIER/VLTI”, by N. Blind et al. in press in the journal Astronomy & Astrophysics.

The team is composed of Nicolas Blind (UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble, France [IPAG]), Henri Boffin (ESO, Chile), Jean-Philippe Berger (ESO, Chile), Jean-Baptiste Le Bouquin (IPAG, France), Antoine Mérand (ESO, Chile), Bernard Lazareff (IPAG, France), and Gérard Zins (IPAG, France).

ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 40-metre-class European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links
Research paper in Astronomy & Astrophysics

Contacts

Nicolas Blind
IPAG
Grenoble, France
Tel: +33 4 76 63 57 30
Email: nicolas.blind@obs.ujf-grenoble.fr

Jean-Baptiste Le Bouquin
IPAG
Grenoble, France
Tel: +33 4 76 63 58 93
Email: jean-baptiste.lebouquin@obs.ujf-grenoble.fr

Henri Boffin
ESO
Santiago, Chile
Tel: +56 2 463 3126
Email: hboffin@eso.org

Jean-Philippe Berger
ESO
Santiago, Chile
Tel: +56 2 463 3103
Email: jpberger@eso.org

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