We present in this contribution a review of recent results of parameters of massive OB stars in the Milky Way, the Magellanic Clouds and nearby spirals. The review is timely because of the strong lowering of the temperature scale of Galactic OB stars produced by the new model atmospheres, including sphericity, blanketing and mass-loss, that are

We report the first reliable measurement of the nebular [OI] 5577AA emission line in the Orion nebula. The use of diagnostic diagrams using the nebular [OI] and [NI] lines and the comparison with available photoionization models, indicate that the bulk of the nebular emission of the neutral ionic species in the Orion nebula is produced in regions

Measuring vector magnetic fields in the solar atmosphere using the profiles of the Stokes parameters of polarized spectral lines split by the Zeeman effect is known as Stokes Inversion. This inverse problem is usually solved by least-squares fitting of the Stokes profiles. However least-squares inversion is too slow for the new generation of solar

Whilst astronomy as a science is historically founded on observations at optical wavelengths, studying the Universe in other bands has yielded remarkable discoveries, from pulsars in the radio, signatures of the Big Bang at submm wavelengths, through to high energy emission from accreting, gravitationally-compact objects and the discovery of gamma

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We propose to use the flux variability of lensed quasar images induced by gravitational microlensing to measure the transverse peculiar velocity of lens galaxies over a wide range of redshift. Microlensing variability is caused by the motions of the observer, the lens galaxy (including the motion of the stars within the galaxy), and the source