Archivi tag: asteroseismology

New Windows on Massive Stars

The important outputs of mass, momentum and energy of massive stars strongly modify their environment and make them key agents in the evolution of galaxies during the whole of cosmic history. Their high luminosities make them objects detectable at far distances in the Universe. Massive stars are thus important probes for studying star formation at high redshifts. As the progenitors of core collapse supernovae, of the long soft Gamma Ray Bursts, and of neutron stars and black holes, they are connected with the most intriguing objects in the Universe. Their physics is, however, not yet very well known and such basic understanding as the origin of the various massive star populations (Be-type stars, red and blue supergiants, Luminous Blue Variables, Wolf- Rayet stars) are still matters of debate, as well as the nature of the progenitors of the various types of core-collapse supernovae (type IIP, IIL, IIb, IIn, Ibc). Continua a leggere New Windows on Massive Stars

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

PLATO 2.0 Science Workshop

PLATO 2.0 is an ESA M3 candidate mission in the Cosmic Vision Programme and has been designed and optimized from the outset specifically to detect habitable zone rocky sized planets around bright solar type stars. Not only are these host stars suitable for planetary confirmation and follow-up studies, but they are ideal for asteroseismology studies whose impact has been proven from the CoRoT and Kepler missions. Thus PLATO 2.0 will produce catalogues of accurate parameters of terrestrial planets and planetary systems. It will be the first large-scale survey determining the ages of its detected planetary systems from their host stars. PLATO 2.0 data will be vital to test and develop planetary formation and evolution models and to address planetary science questions via its large numbers of accurate bulk planet parameters in systems of all kinds. As a result of the many hundred thousands of stars observed, PLATO 2.0 has furthermore a large complementary and legacy science program, from stellar to galactic science.

The PLATO 2.0 Science Workshop is open to the interested community. It will be held at ESA-ESTEC, Noordwijk, on 29-31 July, 2013. The workshop shall examine the impact that PLATO will make on all areas of exoplanet, stellar, and legacy science areas. The preliminary program addresses a range of topics, describing the mission and where PLATO 2.0 will make an impact, e.g.:

  • The PLATO 2.0 Mission
  • Exoplanet science in the next decade
  • Asteroseismology across the HR diagram
  • Composition and internal structure of planets
  • Planet formation and evolution
  • Indications for extended atmospheres around small planets
  • Star-planet interaction, stellar activity and planet detection
  • Legacy science

KASC-6: A new era of stellar astrophysics with Kepler

KASC-6, the 6th Kepler Asteroseismic Science Consortium Conference, will take place in Sydney, Australia, in June 2013. It will be the first KASC conference after all Kepler data became public in 2012 — marking a new era in science with Kepler. We therefore welcome everyone to attend KASC-6, both members and non-members of KASC, who are interested in the stellar astrophysics that we can investigate with Kepler data. The main themes of the conference will be Stellar structure and evolution using asteroseismology, Stellar activity and rotation, Binary stars, and connections to Extrasolar planets. This conference offers great opportunities to establish new collaborations in these scientific fields, which are currently experiencing dramatic progress driven by the vast amounts of exquisite photometric data from space missions like Kepler.

Discovered a new class of variable stars

Grazie ad una serie di osservazioni realizzate con il telescopio svizzero Eulero da 1,2m di La Silla in Cile, un gruppo di astronomi hanno identificato un nuovo tipo di stella che presenta delle pulsazioni. La scoperta si basa sull’individuazione di minuscole variazioni di luminosità di alcune stelle nell’ammasso. Inoltre, le osservazioni hanno rivelato alcune proprietà di queste stelle precedentemente sconosciute che sfidando gli attuali modelli sull’evoluzione stellare e pongono interessanti domande sull’orgine della variabilità.

The Swiss are justly famed for their craftsmanship when creating extremely precise pieces of technology. Now a Swiss team from the Geneva Observatory has achieved extraordinary precision using a comparatively small 1.2-metre telescope for an observing programme stretching over many years.

They have discovered a new class of variable stars by measuring minute variations in stellar brightness.

The new results are based on regular measurements of the brightness of more than three thousand stars in the open star cluster NGC 3766 over a period of seven years. They reveal how 36 of the cluster’s stars followed an unexpected pattern, they had tiny regular variations in their brightness at the level of 0.1% of the stars’ normal brightness. These variations had periods between about two and 20 hours. The stars are somewhat hotter and brighter than the Sun, but otherwise apparently unremarkable. The new class of variable stars is yet to be given a name. This level of precision in the measurements is twice as good as that achieved by comparable studies from other telescopes and sufficient to reveal these tiny variations for the first time. “We have reached this level of sensitivity thanks to the high quality of the observations, combined with a very careful analysis of the data”, says Nami Mowlavi leader of the research team, “but also because we have carried out an extensive observation programme that lasted for seven years. It probably wouldn’t have been possible to get so much observing time on a bigger telescope”. Many stars are known as variable or pulsating stars, because their apparent brightness changes over time. How the brightness of these stars changes depends in complex ways on the properties of their interiors. This phenomenon has allowed the development of a whole branch of astrophysics called asteroseismology, where astronomers can “listen” to these stellar vibrations, in order to probe the physical properties of the stars and get to know more about their inner workings. “The very existence of this new class of variable stars is a challenge to astrophysicists”, says Sophie Saesen another team member. “Current theoretical models predict that their light is not supposed to vary periodically at all, so our current efforts are focused on finding out more about the behaviour of this strange new type of star.

Although the cause of the variability remains unknown, there is a tantalising clue: some of the stars seem to be fast rotators.

They spin at speeds that are more than half of their critical velocity, which is the threshold where stars become unstable and throw off material into space. “In those conditions, the fast spin will have an important impact on their internal properties, but we are not able yet to adequately model their light variations”, explains Mowlavi. “We hope our discovery will encourage specialists to address the issue in the hope of understanding the origin of these mysterious variations.

ESO: New Kind of Variable Star Discovered

arXiv: Stellar variability in open clusters. I. A new class of variable stars in NGC 3766