Archivi tag: Exoplanets

Second Kepler Science Conference

This conference will highlight the full range of scientific results emerging from more than three years of Kepler observations, as well as what to expect from continued observations.

Topics to be covered include:

  • Exoplanet Statistics, False Positives, and Completeness Corrections
  • Earth Analogues and Super-Earths
  • Multiple Planets and Multiple Star Systems
  • Planet Formation and Migration Theories
  • Habitable Zone
  • Characterizing Transiting Planets
  • Stellar Activity, Rotation, Ages, Metallicity
  • Eclipsing and Interacting Binaries
  • Future Exoplanet Telescopes and Instrumentation
  • Asteroseismology
  • Galactic and Extragalactic Astrophysics
Pubblicità

Exoplanets and Brown Dwarfs: Mind the Gap!

The University of Hertfordshire is delighted to be hosting Exoplanets and Brown Dwarfs: Mind the Gap. This year represents a milestone of sorts as the 18th anniversary of the first discoveries of both planets around Sun-like stars and brown dwarfs. The last 18 years have seen the study of these fascinating objects flourish into diverse and exciting astronomical fields. However, as these scientific siblings reach adulthood, there is a danger of missed opportunities as they drift apart. The aim of this meeting is to bring the exoplanet and brown dwarf communities together to explore common science questions, share exciting results, and foster collaboration to overcome shared challenges.

Hunting for water on exoplanets

Grazie ad una serie di osservazioni mediante il Very Large Telescope (VLT) dell’ESO, un gruppo di astronomi sono stati in grado di rivelare alcune tracce della presenza di molecole di acqua nell’atmosfera di un esopianeta. La scoperta dà credito ad una nuova tecnica che permetterà agli astronomi di cercare l’acqua in maniera efficiente su centinaia di mondi alieni senza far uso di telescopi spaziali.

Since the early 1990s scientists have found almost 1000 planets in orbit around other stars. These so-called exoplanets are mostly much larger than the Earth and many are much closer to their stars than we are to the Sun, leading them to be described as ‘hot Jupiters’. In the new work the team studied the exoplanet HD 189733b, a world that orbits its star every 2.2 days and is heated to a temperature of over 1500 degrees Celsius.

Astronomers usually find exoplanets by measuring the gravitational influence of the planet on the star, which acts to pull the star around in a very small orbit, at velocities of a few kilometres per hour.

This movement causes a small shift in the lines of the stellar spectrum (known as the Doppler shift), which move back and forth with the wobble of the star. The Leiden University-led team have flipped the technique on its head by measuring the gravitational influence of the star on the planet, which is much larger, hurling the planet around its orbit at some 400,000 km per hour. They measured this by tracing the Doppler shift of the water lines in the exoplanet’s spectrum as it orbited the star. Despite the much larger velocity of the planet, it is nearly a thousand times fainter than the star, which makes detecting it very difficult. The team were able to detect the spectral line of water in the exoplanet atmosphere by using the CRyogenic high-resolution InfraRed Echelle Spectrograph (CRIRES) instrument mounted on the VLT. Using the same technique, scientists were recently able to find the simple molecule carbon monoxide (CO) in the atmosphere of the same planet, but this is the first time it has been used to identify a more complex molecule like water (H2O). The detection means that the door is now open for a much more detailed census of the chemical make-up of many other exoplanet atmospheres, including molecules such as methane (CH4) and carbon dioxide (CO2), which are key ingredients for unravelling a planet’s formation history. It also paves the way for future observations with the coming generation of large telescopes like the European Extremely Large Telescope (E-ELT) that will begin operations from its site in Chile in 2020.

These instruments will be able to use the technique to hunt for potential signs of life, such as oxygen, in the atmospheres of planets similar to the Earth.

Jayne Birkby, who led the team, said, “We knew our technique worked for simple molecules at shorter wavelengths, but in order to hunt for water, we had to go to longer wavelengths where the Earth’s atmosphere really starts to obstruct the signals we are looking for, so we weren’t sure we would find anything. Of course we were delighted when we saw the signal jump out at us. It means we can do much more with this technique. In the next decade our work will help astronomers refine their search for Earth-like planets, and even life, in orbit around other stars. It’s incredibly exciting to think that in my lifetime we will reach a day when we can point up to a star and say with confidence that it has a world just like our own”.

RAS: Novel technique boosts hunt for water on planets around other stars

arXiv: Detection of water absorption in the dayside atmosphere of HD 189733 b using ground-based high-resolution spectroscopy at 3.2 microns

New type of pulsating star

Un gruppo internazionale di astronomi hanno osservato i resti di una collisione stellare trovando che la luminosità della stella varia in modo insolito. L’analisi delle curve di luce sta fornendo agli astronomi preziosi indizi che permettono di comprendere cosa accade quando due stelle collidono.

Stars like our Sun expand and cool to become red giant stars when the hydrogen that fuels the nuclear fusion in their cores starts to run out. Many stars are born in binary systems so an expanding red giant star will sometimes collide with an orbiting companion star. As much as 90% of the red giant star’s mass can be stripped off in a stellar collision, but the details of this process are not well understood. Only a few stars that have recently emerged from a stellar collision are known, so it has been difficult to study the connection between stellar collisions and the various exotic stellar systems they produce. When an eclipsing binary system containing one such star turned up as a by-product of a search for extrasolar planets, Pierre Maxted and his colleagues decided to use the high-speed camera ULTRACAM to study the eclipses of the star in detail.

These new high-speed brightness measurements show that the remnant of the stripped red giant is a new type of pulsating star.

Many stars, including our own Sun, vary in brightness because of pulsations caused by sound waves bouncing around inside the star. For both the Sun and the new variable star, each pulsation cycle takes about 5 minutes. These pulsations can be used to study the properties of a star below its visible surface. Computer models produced by the discovery team show that the sound waves probe all the way to the centre of the new pulsating star. Further observations of this star are now planned to work out how long it will be before the star starts to cool and fade to produce a stellar corpse (“white dwarf’”) of abnormally low mass. Pierre Maxted from Keele University, who led the study, said  “We have been able to find out a lot about these stars, such as how much they weigh, because they are in a binary system. This will really help us to interpret the pulsation signal and so figure out how these stars survived the collision and what will become of them over the next few billion years”.

See animation here.

Keele University: Survivor of stellar collision is new type of pulsating star
Nature: Multi-periodic pulsations of a stripped red-giant star in an eclipsing binary system
arXiv: Discovery of a stripped red giant core in a bright eclipsing binary star

EChO Open Science Workshop

EChO2013 is an open workshop about the EChO (Exoplanet Characterisation Observatory) M3 mission candidate to be held at ESA-ESTEC in Noordwijk (the Netherlands) on July 1-3, 2013. EChO is a mission dedicated to the observation of atmospheres of planets around nearby stars. These planets will span a range of masses, from gas giants to super-Earths, stellar companions and temperatures, from hot to habitable. EChO will investigate their composition and chemical/physical properties through repeated, simultaneous, multi-wavelength spectroscopic observations. This international workshop will provide an overview of the EChO mission and an opportunity for discussion and feedback in advance of the ESA Cosmic Vision review process. The ESA study and science teams will present the science case, mission objectives and concept, with invited talks by Industry and the Instrument Consortium on the mission and instrument designs respectively. Contributions from the Community covering all aspects of EChO, including science, targets, data processing and instrument design/critical technologies are welcomed. Time will be set aside for dedicated poster sessions and discussion.

From Exoplanets to Distant Galaxies

The first international conference on the science of SPICA (Space Infrared Telescope for Cosmology and Astrophysics) mission will be held on 18-21 June, 2013. The conference is open to interested scientists from around the world. The primary aims of the conference are to introduce the scientific capabilities of the SPICA mission to the international community, and to foster interactions in the IR community on how to optimally utilise this new facility to further explore the physical processes in formation and evolution of planets, stars and galaxies.

Topics covered:

  • Galaxies formation and evolution as revealed in the infrared
  • The cycling of matter between stars, galaxies and the intergalactic medium
  • Planet formation and detection/Characterization of exoplanets

222° Meeting of the American Astronomical Society

One of the largest astronomy meetings of the year will open to the public for the first time in its history. More than 500 astronomers, journalists and guests will bring their cosmic know-how to Indianapolis next week for the 222nd meeting of the American Astronomical Society (AAS). The conference begins on Sunday (June 2) and runs through June 6 at the Indiana Convention Center; it is the second of two meetings held annually by the AAS. New findings about alien worlds, mysterious dark matter and the Milky Way will be discussed, and this year anyone can take part in the cosmic action. Several presentations on Monday and Tuesday will be geared toward amateurs that decide to pay the fee and attend. The presentations include information about the Hubble Space Telescope, nearby exoplanets, Pluto, and the formation of galaxies in the early universe. In addition to those talks, the society will also hold two free public events during the convention. Throughout the course of the conference, scientists will take part in town hall-style meetings about NASA, the National Science Foundation and other agencies. The latest findings from the badly damaged planet hunting Kepler Space Telescope will be presented as well. Twitter users can follow the conference using the hashtag #AAS222.

44° Annual Division on Dynamical Astronomy Meeting

The 2013 Meeting of the Division on Dynamical Astronomy will be held from 5 – 9 May 2013 in Paraty, Brazil. The annual DDA Meeting brings together top researchers in astronomy, astrophysics, planetary science, and astrodynamics for in-depth and stimulating discussions and talks on all aspects of dynamics in the space sciences. The DDA meeting features invited talks on a range of topics, contributed talks (with no parallel sessions), and posters that can be displayed throughout the entire meeting.

Kepler, SOPHIE & HARPS-N detect two new exoplanets

An international team of astronomers, including Alexandre Santerne of the EXOEarths team at CAUP, has identified and characterized two new exoplanets thanks to combined observations from the Kepler space telescope plus the SOPHIE and HARPS-N spectrographs. These planets, named KOI-200b and KOI-889b, are among the first detected with the new high-accuracy spectrograph HARPS-N, the northern hemisphere counterpart of the most prolific exoplanet hunter, HARPS (ESO). CAUP researcher Alexandre Santerne commented: “The SOPHIE spectrograph was already playing an important role in the characterization of Kepler planets by unveiling the true nature of the candidates and measuring the mass of giant planets. With the new HARPS-N spectrograph, with an even better accuracy, we expect to characterize much smaller exoplanets, hopefully down to the size of the Earth“.

The new planets have about the size of Jupiter but eccentric orbits with periods of less than 10 days. These new results help to further understand the evolution of orbits of these planets located very close to their star, known as “hot Jupiters.” There are currently more than 850 known exoplanets, but as seen from the Earth, only some of them are oriented in a way that they are passing in front of their star every orbital period. These periodic transits of the planet in front of its star produce a small dip in its brightness. These micro eclipses allow astronomers to know the diameter of the planet and some details about its atmosphere. The Kepler space mission (NASA) has identified more than 2,000 stars that have a great chance of hosting transiting planets. However, most of them need complementary ground-based observations to establish their nature and to complete their characterization. The team participated in these ground-based observations since 2010, using the SOPHIE instrument, which has already participated in the detection and characterization of more than fifteen Kepler planets, through the radial velocity method. Their observing program is now completed by new observations with the more accurate HARPS-N spectrograph. KOI-200b is slightly bigger than Jupiter and slightly less massive. With a low density, this gaseous planet is orbiting around its star in less than one week. The planet KOI-889b is of the size of Jupiter but is ten times more massive. This very-massive planet is orbiting around its star in slightly less than 9 days. These two planets have eccentric orbits: during their orbit, their distance to their star is varying. This produces large variation in their equilibrium temperature of several hundred of degrees in a few days. KOI-889b, which is among the most massive planets discovered so far, is also among the most eccentric transiting planets. It could have been formed by a different mechanism than less massive planets. Santerne added: “Even if there are just hot and giant planets as we already know hundreds of them, these two planets are orbiting on a highly eccentric orbit, which is relatively rare for such short-period planets. I prefer to see these two new planets as two other bricks in the wall of our knowledge about planetary systems: bigger is the wall, better we understand planetary formation and evolution“.

arXiv: KOI-200b and KOI-889b: two transiting exoplanets detected and characterized with Kepler, SOPHIE and HARPS-N

Kepler’s exoworlds as targets for SETI

NASA’s Kepler mission has discovered a new planetary system that is home to five small planets around a slightly smaller star than our Sun (post). Two of them are super-Earth planets, most likely made of rock or ice mixed with rock, which are located in the habitable zone of their host star. This discovery is providing a target for the SETI search, since if life has thrived on these worlds and reached a point where civilization has developed complex technology, it may be detectable.

When the NASA Kepler mission was launched on March 9, 2007, the Delta II rocket was carrying the hope of a large community of scientists who dedicate their work to studying extra-solar planets, planets in orbit around other stars. The Kepler mission’s main scientific objective is exploration of the structure and diversity of planetary systems. It accomplishes this goal by staring almost constantly at a large field composed of about 150,000 stars to detect small dips in brightness due to the transits of a planet. Kepler has already been a successful NASA mission with the discovery of 2,740 planet candidates with estimated sizes from Mercury to larger than Jupiter. A fifth of these planet candidates are also called “super-Earths”, a new class of planets, without analog in our solar system, with a radius between 1.25 to 2 times the radius of our planet. The Kepler team has announced the discovery of a multiple planet system, composed of 5 Earth-sized and super-Earth planets orbiting a K-type star. The detection of these planets was indirect since Kepler astronomers observed the attenuation of the host star’s brightness due to the passage of a planet in the line of sight, and not the planets themselves. The authenticity of this multiple planet system was confirmed by a statistical analysis based on previous detections of multiple planets by Kepler. “By estimating the rate of false-positives due the remote possibility of additional planet-hosting stars in the photometric aperture we have strong confidence that we have discovered two genuine transiting super-Earth planets in the habitable zone  of their host star.  Such calculations are only possible because of the thousands of additional transiting extrasolar planets that Kepler has discovered” said Jason Rowe, Research Scientist at the Carl Sagan Center of the SETI Institute and co-author of the work. The outermost planet, named Kepler-62f (radius about 1.4 times Earth’s radius and a period of 267 Earth days) is located in the habitable zone of the star, a region around the star where a rocky planet with an atmosphere similar to Earth could host liquid water on its surface. The team expanded the definition of the habitable zone by taking into account the evolution of the brightness of the host star. Their calculations suggest that Kepler-62e (radius about 1.6 times Earth’s radius and a period of 122 Earth days) was also in the habitable zone so that liquid water could have existed on its surface, too. Similar to Venus and Mars that are believed to have lost their surface water 1 billion years and 3.8 billion years ago respectively, before our sun was more luminous, the host star’s habitable zone was broader in the past. The Kepler team’s calculations suggest that Kepler-62e (radius about 1.6 times Earth’s radius and a period of 122 Earth days) is also in the habitable zone so that liquid water could exist on its surface, too. “These discoveries move us farther down the road to discovering planets similar to Earth. While we don’t know if Kepler-62e and f are rocky or whether they have liquid water pooling on their surfaces, their existence shows that the incidence of small worlds in the habitable zone of sun-like stars is high. Thus we can look forward to the discovery and detailed characterization of Earth’s cousins in the years and decades to come by future missions and telescopes”, said Jon Jenkins Senior Scientist at the Carl Sagan Center of the SETI Institute and also co-author of the work. Both Goldilocks planets’ masses remain unknown since they are too small to produce detectable gravitational effects on the host star and between themselves. However, considering a lower upper limit for their mass and the age of the star, estimated to be 7 billion years, the team suggests that both planets are solid and either made of a dry rocky material, like Earth, or a large body of water surrounding a core of iron and rock (a water world). Kepler discoveries are an amazing opportunity to focus the search for technosignatures conducted at the Center for SETI Research led by Gerry Harp. Kepler provides the detection of exoworlds that could host water on their surfaces and potentially life. Unfortunately, the planets of the Kepler-62 system are too distant (850 light-years from Earth) to be fully characterized, and no direct measurement of their atmospheric composition is possible with current technologies. “Since December of 2011, the SonATA program to search for extraterrestrial intelligence with the Allen Telescope Array has been focusing on the Kepler exoplanet candidates and especially those planets expected to be within the “Habitable Zone” of their stars. Our surveys improve on previous, generally narrowband SETI by covering the radio frequency range where Earth’s atmosphere is most transparent, including many frequencies never before observed. We expect to complete a meaningful survey of these stars in less than 1 year — be sure to check back soon“, says Gerry Harp, Director of the Center for SETI Research.

SETI: Has Kepler Found Ideal SETI-target Planets?
See also: Kepler’s Tally of Planets