Sökning: "stars: planetary systems: formation"

Visar resultat 1 - 5 av 8 avhandlingar innehållade orden stars: planetary systems: formation.

1. 1. Turbulence-Assisted Planetary Growth : Hydrodynamical Simulations of Accretion Disks and Planet Formation

   Författare :Wladimir Lyra; Nikolai Piskunov; Thomas Henning; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; accretion; accretion disks; hydrodynamics; instabilities; methods: numerical; solar system: formation; planets and satellites: formation; magnetohydrodynamics MHD ; turbulence; diffusion; stars: planetary systems: formation; Astronomy and astrophysics; Astronomi och astrofysik;

   Sammanfattning : The current paradigm in planet formation theory is developed around a hierarquical growth of solid bodies, from interstellar dust grains to rocky planetary cores. A particularly difficult phase in the process is the growth from meter-size boulders to planetary embryos of the size of our Moon or Mars. LÄS MER

3. 2. Solar Type Stars as Calibrators : A Photometric and Spectroscopic Study on the Atmospheric Properties of Late-type Stars

   Författare :Anna Önehag; Ulrike Heiter; Andreas Korn; Bengt Gustafsson; Frank Grundahl; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; stars: atmospheres; stars: late-type; techniques: photometric; stars: abundances; techniques: spectroscopic; Astronomy; Astronomi;

   Sammanfattning : Detailed knowledge of solar-type stars is essential in the understanding of the evolutionary past, presence and future of the Sun as well as the formation of its planetary system. Moreover, solar-type stars are of key significance for the study of the evolution of the Galaxy. The ages of solar-type stars map the full galactic evolution. LÄS MER

4. 3. Formation and Early Evolution of Planetary Systems

   Författare :Daniel Carrera; Astronomi - Genomgår omorganisation; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; planet formation; planets and satellites: dynamical evolution and stability -- planets and satellites: gaseous planets -- planets and satellites: terrestrial planets; planets and satellites: terrestrial planets;

   Sammanfattning : Over the past 20 years we have discovered that exoplanets are common in the Galaxy, and are far more diverse than anyone expected. Half of all Sun-like stars are accompanied by at least one super-Earth (a planet with a size between Earth and Neptune), many planets have very high eccentricities indicative of a dynamical origin, and a small fraction of stars are accompanied by hot Jupiters, whose origin is poorly understood. LÄS MER

5. 4. The Effects of Encounters on Planetary Systems in Stellar Clusters

   Författare :Daniel Malmberg; Astronomi - Genomgår omorganisation; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

   Sammanfattning : Extrasolar planets are found to be on orbits very different from those of the planets in the solar system. Gas-giant planets have been found on orbits tighter than that of the planet Mercury, often with very high eccentricities. LÄS MER

7. 5. Debris disks from an astronomical and an astrobiological viewpoint

   Författare :Gianni Cataldi; Alexis Brandeker; Göran Olofsson; Eric Stempels; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; debris disks; planetary systems; exoplanets; astrobiology; circumstellar matter; biomarker; biosignature; extraterrestrial life; Astronomy; astronomi;

   Sammanfattning : In this licentiate thesis, I consider debris disks from an observational, astronomical viewpoint, but also discuss a potential astrobiological application. Debris disks are essentially disks of dust and rocks around main-sequence stars, analogue to the Kuiper- or the asteroid belt in our solar system. LÄS MER