ESO Instrument Finds Closest Black Hole to Earth

PR Image eso2007a

Artist’s impression of the triple system with the closest black hole

PR Image eso2007b

Location of the HR 6819 in the constellation of Telescopium

PR Image eso2007c

Wide-field view of the region of the sky where HR 6819 is located

---

Videos

PR Video eso2007a

ESOcast 220 Light: Closest Black Hole to Earth Found

PR Video eso2007b

Artist’s animation of the triple system with the closest black hole

PR Video eso2007c

Zooming into HR 6819

---

 Invisible object has two companion stars visible to the naked eye

A team of astronomers from the European Southern Observatory (ESO) and other institutes has discovered a black hole lying just 1000 light-years from Earth. The black hole is closer to our Solar System than any other found to date and forms part of a triple system that can be seen with the naked eye. The team found evidence for the invisible object by tracking its two companion stars using the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. They say this system could just be the tip of the iceberg, as many more similar black holes could be found in the future.

"We were totally surprised when we realised that this is the first stellar system with a black hole that can be seen with the unaided eye,” says Petr Hadrava, Emeritus Scientist at the Academy of Sciences of the Czech Republic in Prague and co-author of the research. Located in the constellation of Telescopium, the system is so close to us that its stars can be viewed from the southern hemisphere on a dark, clear night without binoculars or a telescope. “This system contains the nearest black hole to Earth that we know of,” says ESO scientist Thomas Rivinius, who led the study published today in Astronomy & Astrophysics.

The team originally observed the system, called HR 6819, as part of a study of double-star systems. However, as they analysed their observations, they were stunned when they revealed a third, previously undiscovered body in HR 6819: a black hole. The observations with the FEROS spectrograph on the MPG/ESO 2.2-metre telescope at La Silla showed that one of the two visible stars orbits an unseen object every 40 days, while the second star is at a large distance from this inner pair.

Dietrich Baade, Emeritus Astronomer at ESO in Garching and co-author of the study, says: “The observations needed to determine the period of 40 days had to be spread over several months. This was only possible thanks to ESO’s pioneering service-observing scheme under which observations are made by ESO staff on behalf of the scientists needing them.”

The hidden black hole in HR 6819 is one of the very first stellar-mass black holes found that do not interact violently with their environment and, therefore, appear truly black. But the team could spot its presence and calculate its mass by studying the orbit of the star in the inner pair. “An invisible object with a mass at least 4 times that of the Sun can only be a black hole,” concludes Rivinius, who is based in Chile.

Astronomers have spotted only a couple of dozen black holes in our galaxy to date, nearly all of which strongly interact with their environment and make their presence known by releasing powerful X-rays in this interaction. But scientists estimate that, over the Milky Way’s lifetime, many more stars collapsed into black holes as they ended their lives. The discovery of a silent, invisible black hole in HR 6819 provides clues about where the many hidden black holes in the Milky Way might be. “There must be hundreds of millions of black holes out there, but we know about only very few. Knowing what to look for should put us in a better position to find them,” says Rivinius. Baade adds that finding a black hole in a triple system so close by indicates that we are seeing just “the tip of an exciting iceberg.”

Already, astronomers believe their discovery could shine some light on a second system. “We realised that another system, called LB-1, may also be such a triple, though we'd need more observations to say for sure,” says Marianne Heida, a postdoctoral fellow at ESO and co-author of the paper. "LB-1 is a bit further away from Earth but still pretty close in astronomical terms, so that means that probably many more of these systems exist. By finding and studying them we can learn a lot about the formation and evolution of those rare stars that begin their lives with more than about 8 times the mass of the Sun and end them in a supernova explosion that leaves behind a black hole."

The discoveries of these triple systems with an inner pair and a distant star could also provide clues about the violent cosmic mergers that release gravitational waves powerful enough to be detected on Earth. Some astronomers believe that the mergers can happen in systems with a similar configuration to HR 6819 or LB-1, but where the inner pair is made up of two black holes or of a black hole and a neutron star. The distant outer object can gravitationally impact the inner pair in such a way that it triggers a merger and the release of gravitational waves. Although HR 6819 and LB-1 have only one black hole and no neutron stars, these systems could help scientists understand how stellar collisions can happen in triple star systems.

---

More information

This research was presented in the paper “A naked-eye triple system with a nonaccreting black hole in the inner binary”, published today in Astronomy & Astrophysics (doi: 10.1051/0004-6361/202038020).

The team is composed of Th. Rivinius (European Southern Observatory, Santiago, Chile), D. Baade (European Southern Observatory, Garching, Germany [ESO Germany]), P. Hadrava (Astronomical Institute, Academy of Science of the Czech Republic, Prague, Czech Republic), M. Heida (ESO Germany), and R. Klement (The CHARA Array of Georgia State University, Mount Wilson Observatory, Mount Wilson, USA).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It has 16 Member States: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile and with Australia as a Strategic Partner. 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 and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.

---

Links

• Research paper
• Photos of the MPG/ESO 2.2-metre telescope
• Photos of ESO’s La Silla Observatory

---

Contacts

Dietrich Baade
European Southern Observatory
Garching bei München, Germany
Tel: +49-89-6096295
Email: dbaade@eso.org

Petr Hadrava
Academy of Sciences of the Czech Republic
Prague, Czech Republic
Email: petr.hadrava@asu.cas.cz

Marianne Heida
European Southern Observatory
Garching bei München, Germany
Tel: +49-157-37744840
Email: mheida@eso.org

Thomas Rivinius
European Southern Observatory
Santiago, Chile
Tel: +56 9 8288 4950
Email: triviniu@eso.org

Bárbara Ferreira
ESO Public Information Officer
Garching bei München, Germany
Cell: +49 151 241 664 00
Email: pio@eso.org

Source: ESO/News

---

R B1259-63: Pulsar Punches Hole In Stellar Disk

PSR B1259-63/LS 2883
Credit: X-ray: NASA/CXC/PSU/G.Pavlov et al; 
Illustration: NASA/CXC/M.Weiss

JPEG (848.8 kb) - Large JPEG (477.3 kb) - Tiff (74.4 MB) - More Images

A Tour of Circinus X-1

This trio of images contains evidence from NASA's Chandra X-ray Observatory that a clump of stellar material has been jettisoned away from a double star system at incredibly high speeds. This system, known as PSR B1259-63/LS 2883 – or B1259 for short – is comprised of two objects in orbit around one another. The first is a star about 30 times as massive as the Sun that has a disk of material swirling around it. The other is a pulsar, an ultra-dense neutron star left behind when an even more massive star underwent a supernova explosion.

Researchers think that the pulsar knocked out the chunk of debris, which spans over a hundred times the size of the Solar System, when it collided with the disk around the massive star while traveling in its elliptical orbit lasting 41 months. (An artist's illustration shows the pulsar just after having collided with the disk.) Astronomers came to this conclusion after analyzing three separate Chandra observations taken between December 2011 and February 2014, as labeled in the three images. The bright source in the center of these images is the binary system, while the smaller point-like source to the lower right seen in the second two observations is the clump that has been dislodged.

The Chandra observations also suggest that the clump is not only moving quickly but may, in fact, be picking up speed. The average of the three observations shows the clump is moving about 7% the speed of light, but the data suggest it may have accelerated to 15% the speed of light between the second and third observations. This acceleration could be due to intense winds flowing off of the pulsar's surface at nearly the speed of light, which are caused by its rapid rotation and strong magnetic fields.

The X-ray emission observed by Chandra is likely produced by a shock wave created as the pulsar's wind rams into the clump of material. The ram pressure generated by this interaction could also accelerate the clump. Chandra will continue monitoring B1259 and its moving clump with observations scheduled for later this year and in 2016.

These results appeared in the June 20, 2015 issue of The Astrophysical Journal and are available online. The authors of this paper are George Pavlov (Penn State University), Jeremy Hare (George Washington University), Oleg Kargaltsev (George Washington University), Blagory Rangelov (George Washington University), and Martin Durant (University of Florida). 

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

 

Fast Facts for PSR B1259-63:

Scale: Image is about 40 arcsec across (1.3 light years)
Category: Neutron Stars/X-ray Binaries
Coordinates (J2000): RA 13 02 47.60 | Dec -63 50 08.70
Constellation: Centaurus
Observation Date: 4 pointings: 12/17/2011, 05/19/2013, 02/08 and 02/09/2014
Observation Time: 1 day 46 min (42 hours 46 min)
Obs. ID: 14205, 14206, 16563, 16583
Instrument: ACIS
References: Pavlov, G et al, 2015, ApJ, 806, 192; arXiv:1505.07155
Color Code: X-ray: Blue
Distance Estimate: About 7,500 light years

Source: NASA’s Chandra X-ray Observatory

Planets with Double Suns are Common

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

Vampire Star Reveals its Secrets

PR Image eso1148a
The unusual double star SS Leporis

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

PR Image eso1148c

Wide field view of the unusual double star SS Leporis

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

PR Video eso1148b

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

Pulsating Star Mystery Solved

PR Image eso1046a
Artist’s impression of the remarkable double star OGLE-LMC-CEP0227

PR Image eso1046b

Wide-field view of part of the Large Magellanic Cloud
and the remarkable double star OGLE-LMC-CEP0227

By discovering the first double star where a pulsating Cepheid variable and another star pass in front of one another, an international team of astronomers has solved a decades-old mystery. The rare alignment of the orbits of the two stars in the double star system has allowed a measurement of the Cepheid mass with unprecedented accuracy. Up to now astronomers had two incompatible theoretical predictions of Cepheid masses. The new result shows that the prediction from stellar pulsation theory is spot on, while the prediction from stellar evolution theory is at odds with the new observations.

The new results, from a team led by Grzegorz Pietrzyński (Universidad de Concepción, Chile, Obserwatorium Astronomiczne Uniwersytetu Warszawskiego, Poland), appear in the 25 November 2010 edition of the journal Nature.

Grzegorz Pietrzyński introduces this remarkable result: “By using the HARPS instrument on the 3.6-metre telescope at ESO’s La Silla Observatory in Chile, along with other telescopes, we have measured the mass of a Cepheid with an accuracy far greater than any earlier estimates. This new result allows us to immediately see which of the two competing theories predicting the masses of Cepheids is correct.”

Classical Cepheid Variables, usually called just Cepheids, are unstable stars that are larger and much brighter than the Sun [1]. They expand and contract in a regular way, taking anything from a few days to months to complete the cycle. The time taken to brighten and grow fainter again is longer for stars that are more luminous and shorter for the dimmer ones. This remarkably precise relationship makes the study of Cepheids one of the most effective ways to measure the distances to nearby galaxies and from there to map out the scale of the whole Universe [2].

Unfortunately, despite their importance, Cepheids are not fully understood. Predictions of their masses derived from the theory of pulsating stars are 20–30% less than predictions from the theory of the evolution of stars. This embarrassing discrepancy has been known since the 1960s.

To resolve this mystery, astronomers needed to find a double star containing a Cepheid where the orbit happened to be seen edge-on from Earth. In these cases, known as eclipsing binaries, the brightness of the two stars dims as one component passes in front of the other, and again when it passes behind the other star. In such pairs astronomers can determine the masses of the stars to high accuracy [3]. Unfortunately neither Cepheids nor eclipsing binaries are common, so the chance of finding such an unusual pair seemed very low. None are known in the Milky Way.

Wolfgang Gieren, another member of the team, takes up the story: “Very recently we actually found the double star system we had hoped for among the stars of the Large Magellanic Cloud. It contains a Cepheid variable star pulsating every 3.8 days. The other star is slightly bigger and cooler, and the two stars orbit each other in 310 days. The true binary nature of the object was immediately confirmed when we observed it with the HARPS spectrograph on La Silla.”

The observers carefully measured the brightness variations of this rare object, known as OGLE-LMC-CEP0227 [4], as the two stars orbited and passed in front of one another. They also used HARPS and other spectrographs to measure the motions of the stars towards and away from the Earth — both the orbital motion of both stars and the in-and-out motion of the surface of the Cepheid as it swelled and contracted.

This very complete and detailed data allowed the observers to determine the orbital motion, sizes and masses of the two stars with very high accuracy — far surpassing what had been done before for a Cepheid. The mass of the Cepheid is now known to about 1% and agrees exactly with predictions from the theory of stellar pulsation. However, the larger mass predicted by stellar evolution theory was shown to be significantly in error.

The much-improved mass estimate is only one outcome of this work, and the team hopes to find other examples of these remarkably useful pairs of stars to exploit the method further. They also believe that from such binary systems they will eventually be able to pin down the distance to the Large Magellanic Cloud to 1%, which would mean an extremely important improvement of the cosmic distance scale.

Notes

[1] The first Cepheid variables were spotted in the 18th century and the brightest ones can easily be seen to vary from night to night with the unaided eye. They take their name from the star Delta Cephei in the constellation of Cepheus (the King), which was first seen to vary by John Goodricke in England in 1784. Remarkably, Goodricke was also the first to explain the light variations of another kind of variable star, eclipsing binaries. In this case two stars are in orbit around each other and pass in front of each other for part of their orbits and so the total brightness of the pair drops. The very rare object studied by the current team is both a Cepheid and an eclipsing binary. Classical Cepheids are massive stars, distinct from similar pulsating stars of lower mass that do not share the same evolutionary history.

[2] The period luminosity relation for Cepheids, discovered by Henrietta Leavitt in 1908, was used by Edwin Hubble to make the first estimates of the distance to what we now know to be galaxies. More recently Cepheids have been observed with the Hubble Space Telescope and with the ESO VLT on Paranal to make highly accurate distance estimates to many nearby galaxies.

[3] In particular, astronomers can determine the masses of the stars to high accuracy if both stars happen to have a similar brightness and therefore the spectral lines belonging to each of the two stars can be seen in the observed spectrum of the two stars together, as is the case for this object. This allows the accurate measurement of the motions of both stars towards and away from Earth as they orbit, using the Doppler effect.

[4] The name OGLE-LMC-CEP0227 arises because the star was first discovered to be a variable during the OGLE search for gravitational microlensing. More details about OGLE are available at: http://ogle.astrouw.edu.pl/.

More information

This research was presented in a paper to appear in the journal Nature on 25 November 2010.

The team is composed of G. Pietrzyński (Universidad de Concepción, Chile, Obserwatorium Astronomiczne Uniwersytetu Warszawskiego, Poland), I. B. Thompson (Carnegie Observatories, USA), W. Gieren (Universidad de Concepción, Chile), D. Graczyk (Universidad de Concepción, Chile), G. Bono (INAF-Osservatorio Astronomico di Roma, Universita’ di Roma, Italy), A. Udalski (Obserwatorium Astronomiczne Uniwersytetu Warszawskiego, Poland), I. Soszyński (Obserwatorium Astronomiczne Uniwersytetu Warszawskiego, Poland), D. Minniti (Pontificia Universidad Católica de Chile) and B. Pilecki (Universidad de Concepción, Chile, Obserwatorium Astronomiczne Uniwersytetu Warszawskiego, Poland).

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 14 countries: Austria, Belgium, 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 VISTA, the world’s largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links

Research letter to Nature link

Contacts

Grzegorz Pietrzyński
Universidad de Concepción
Chile
Tel: +56 41 220 7268
Cell: +56 9 6245 4545
Email: pietrzyn@astrouw.edu.pl

Wolfgang Gieren
Universidad de Concepción
Chile
Tel: +56 41 220 3103
Cell: +56 9 8242 8925
Email: wgieren@astro-udec.cl

Richard Hook
ESO, La Silla, Paranal, E-ELT and Survey Telescopes Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org

Pulverized Planet Dust Might Lie Around Double Stars

This artist's concept illustrates an imminent planetary collision around a pair of double stars. NASA's Spitzer Space Telescope found evidence that such collisions could be common around a certain type of tight double, or binary, star system, referred to as RS Canum Venaticorums or RS CVns for short. The stars are similar to the sun in age and mass, but they orbit tightly around each other. With time, they are thought to get closer and closer, until their gravitational influences change, throwing the orbits of planetary bodies circling around them out of whack and leading to collisions. Spitzer's infrared vision spotted dusty evidence for such collisions around three tight star pairs.Credit: NASA/JPL-Caltech. High Resolution Image (jpg)

This artist's concept illustrates a tight pair of stars and a surrounding disk of dust -- most likely the shattered remains of planetary smashups. Using NASA's Spitzer Space Telescope, the scientists found dusty evidence for such collisions around three sets of stellar twins (a class of stars called RS Canum Venaticorums or RS CVns for short). The stars, which are similar to our sun in mass and age, orbit very closely around each other. They are separated by just one-fiftieth of the Earth-sun distance. As time goes by, the stars get closer and closer, and this causes the gravitational harmony in the systems to go out of whack. Comets and any planets orbiting around the stars could jostle about and collide. Credit: NASA/JPL-Caltech. High Resolution Image (jpg)

Cambridge, MA - Tight double-star systems might not be the best places for life to spring up, according to a new study using data from NASA's Spitzer Space Telescope. The infrared observatory spotted a surprisingly large amount of dust around three mature, close-orbiting star pairs. Where did the dust come from? Astronomers say it might be the aftermath of tremendous planetary collisions.

"This is real-life science fiction," said Jeremy Drake of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass. "Our data tell us that planets in these systems might not be so lucky -- collisions could be common. It's theoretically possible that habitable planets could exist around these types of stars, so if there happened to be any life there, it could be doomed."

Drake is the principal investigator of the research, published in the Aug. 19 issue of the Astrophysical Journal Letters.

The particular class of binary, or double, stars in the study are about as snug as stars get. Named RS Canum Venaticorums, or RS CVns for short, they are separated by only about two million miles (3.2 million kilometers), or one-fiftieth the distance between Earth and our sun. The stellar pairs orbit around each other every few days, with one face on each star perpetually locked and pointed toward the other.

The close-knit stars are similar to the sun in size and are probably about a billion to a few billion years old. But these stars spin much faster, and, as a result, have powerful magnetic fields and giant, dark spots. The magnetic activity drives strong stellar winds -- gale-force versions of the solar wind -- that slow the stars down, pulling the twirling duos closer over time. And this is where the planetary chaos might begin.

As the stars cozy up to each other, their gravitational influences change, and this could cause disturbances to planetary bodies orbiting around both stars. Comets and any planets that might exist in the systems would start jostling about and banging into each other, sometimes in powerful collisions. This includes planets that could theoretically be circling in the double stars' habitable zone -- a region where temperatures would allow liquid water to exist. Though no habitable planets have been discovered around any stars beyond our sun at this point in time, tight double-star systems are known to host planets; for example, one system not in the study, called HW Vir, has two gas-giant planets.

"These kinds of systems paint a picture of the late stages in the lives of planetary systems," said Marc Kuchner, a co-author from NASA Goddard Space Flight Center in Greenbelt, Md. "And it's a future that's messy and violent."

Spitzer spotted the infrared glow of hot dusty disks, about the temperature of molten lava, around three such tight binary systems. One of the systems was originally flagged as having a suspicious excess of infrared light in 1983 by the Infrared Astronomical Satellite. In addition, researchers using Spitzer recently found a warm disk of debris around another star that turned out to be a tight binary system.

The team says that dust normally would have dissipated and blown away from the stars by this mature stage in their lives. They conclude that something -- most likely planetary collisions -- must therefore be kicking up the fresh dust. In addition, because dusty disks now have been found around four, older binary systems, the scientists know that the observations are not a fluke. Something chaotic is very likely going on.

If any life forms did exist in these star systems, and they could look up at the sky, they would have quite a view. Marco Matranga, first author of the paper, from the Harvard-Smithsonian Center for Astrophysics and now a visiting astronomer at the Palermo Astronomical Observatory in Sicily, said, "The skies there would have two huge suns, like the ones above the planet Tatooine in 'Star Wars.'"

Other authors include V.L. Kashyap of the Harvard-Smithsonian Center for Astrophysics; and Massimo Marengo of Iowa State University, Ames.

The Spitzer observations were made before it ran out of its liquid coolant in May 2009, officially beginning its warm mission.

This press release is being issued jointly with the Jet Propulsion Laboratory, Pasadena, Calif.

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, also in Pasadena. Caltech manages JPL for NASA.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

Whitney Clavin
Jet Propulsion Laboratory
818-354-4673
whitney.clavin@jpl.nasa.gov