Astrofysiikka
Astrofysiikka on monialainen tutkimussuuntaus. Sen painopisteitä Helsingin yliopistossa ovat tähtienvälinen aine ja tähtien synty, tähtien magneettinen aktiivisuus, galaksien synty ja kehitys sekä planeettakunnan tutkimus.
Tutkimusryhmät

The research concentrates on the properties of the interstellar medium and the process of star formation, both in the Milky Way and other galaxies. 

The topics include:

  • Physical and chemical properties of interstellar molecular clouds and the initial conditions for star formation by means of radio spectroscopy
  • Properties and composition of interstellar dust grains by observing continuum emission and polarisation from dust
  • Measurement and modelling of the Extragalactic Background Light (EBL) in the optical and infrared
  • Numerical radiative transfer modelling of spectral lines and dust emission and scattering in interstellar clouds
  • Numerical magnetohydrodynamical modelling of the physical properties of the molecular clouds

 

The main instruments currently used are:

  • ESO (European Southern Observatory)
    • Large optical telescopes (VLT etc.) and radio telescopes (APEX, ALMA) located in Chile.
      • Finland is a member of ESO since 2004
      • ESO/ESA synergy important for Finnish Astronomy
      • Participation in ALMA and ESO/VLT infrared projects building on previous experience with SEST, ISO, ODIN 
      • See also ESO press releases:
  • Planck
    • Cosmology satellite with an important contribution to Galactic studies (see ESA press release New Planck images trace cold dust and reveal large-scale structure in the Milky Way)
    • Coordinator status in a Scientific Working Group and a Technical Working Group
    • Analysis of interstellar medium and the properties of the interstellar dust, polarisatio measurements as a tracer of Galactic magnetic fields.
      • See here for more information in Finnish
  • Herschel

 

Personnel

  • Lauri Haikala, University researcher 
    • Physicum D319 
    • Infrared and radio observations, interstellar dark clouds and globules 
  • Jorma Harju, University researcher 
    • Physicum D312 
    • Interstellar chemistry, molecular lines, studies of pre-stellar cores
  • Mika Juvela, University lecturer 
    • Physicum D331a 
    • Modelling of interstellar medium, Herschel and Planck satellite projects
  • Kalevi Mattila, Professor (emeritus) 
    • Physicum A218
  • Oskari Miettinen, Postdoctoral researcher 
    • Radio observations, high-mass star formation
  • Veli-Matti Pelkonen, postdoctoral researcher (FINCA)
    • Planck studies of interstellar medium, infrared observations

The main topics of the research

  • Photometric, spectroscopic and spectropolarimetric observations of stars at various evolutionary stages, ranging from young main-sequence stars to RS CVn type systems. The main instrument used is the high-resolution echelle spectropolarimeter SOFIN, currently located at Nordica Optical Telescope, La Palma, Spain.
    • Unique spectroscopic time series, extending over 20 years, collected of various late-type stars, the last 8 years in the spectropolarimetric mode.
    • Doppler and Zeeman-Doppler imaging methods used to invert the observational data into surface maps of temperature and magnetic field.
    • Photometric data, with even longer time extent and better time sampling, obtained via international collaboration, and analysed with time series analysis methods developed within the group.

    • Numerical modelling of stellar convection and magnetic fields in local and global geometries, aiming at understanding the observed magnetic activity ranging from the Sun to our observational targets.

      • The main line of study is the excitation of dynamos in direct simulations of turbulence and convection in Cartesian and spherical geometries and the generation of differential rotation in the Sun and other stars.
      • The simulation results for differential rotation and dynamos are compared with observational data of stars in different evolutionary stages.
      • Mean-field models of differential rotation and dynamos using turbulent transport coefficients from closure models and/or direct simulations.
      • Development of numerical methods suitable for Graphics Processing Units (GPU) within the `Active Suns' research project.
      • The bulk of the computations are made at CSC - IT Center for Science in Espoo, Finland. The group uses roughly 5 million CPU hours yearly.
      • Projects related to the research have been awarded CSC Grand Challenge special allocations in 2008 (DYNAMO08, 1.66M CPU hours), and in 2012 (NEMPI, 2.1M CPU hours)(2), and by Distributed European Infrastructure for Supercomputing Applications (DEISA) in 2008 (CONVDYN, 0.9M CPU hours).

    The main topics of the research

    The research concentrates on understanding the formation and subsequent evolution of galaxies primarily using numerical methods. The main topics include:

    • Formation and evolution of disk and elliptical galaxies
    • The role of dark matter in galaxy formation
    • Formation and evolution of supermassive black holes
    • Modelling galactic stellar dynamics
    • Dynamics of the interstellar medium and star formation in external galaxies
    • Computational astrophysics -- numerical N-Body, SPH simulations
    • Observational studies of high-redshift and local galaxies

    Tutkimuksen aiheet

    Planeettakunnan tutkimuksen kohteita ovat asteroidit ja komeetat sekä regoliittien ja planeettojen kaasukehien pienhiukkaset.

    Tutkimusaiheita ovat muun muassa:

    • Valonsironta pienhiukkasista ja niistä koostuvista väliaineista
    • Säteilynkuljetus stokastisissa väliaineissa
    • Asteroidien radanmääritys ja fysikaaliset ominaisuudet
    • Röntgensäteilyn emissio, sironta ja absorptio planeettojen regoliiteistä
    • Paperin ja paperipigmenttien fysikaaliset ominaisuudet

    Käytössä olevat havainto- ja tutkimuslaitteistot

    • ESO/VLT: 
      • Polarimetrisia havaintoja Neptunuksen takaisista kohteista ja komeettojen ytimistä
    • ESA/SMART-1: 
      • Kuun fotometriaa AMIE-kameralla
    • ESA/Gaia: 
      • Asteroidien astro- ja fotometriaa (2013-)
    • ESA/BepiColombo MIXS/SIXS:
      • Merkuriuksen röntgenspektrometrinen kuvantaminen (2021-)
    • NEOSSat & MarcoPolo-R:
      • Maan lähelle tulevien asteroidien törmäysuhan määrittäminen
    • Sirontalaboratorio: 
      • Valonsironta- ja röntgenfluoresenssimittauksia pienhiukkasista koostuvista väliaineista
      • Meteoriittien spektroskopiaa