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Mr Sam Morrell



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I'm a fourth year postgraduate research student in the astrophysics group here at Exeter. I completed my MPhys in Physics with Astrophysics at Exeter in 2015. My work during this project involved the study of interstellar dust grains and their effect on observations of diffuse and dense regions of the galaxy. Through this study, we were able to develop an empirical extinction law that was properly able to characterise previously anomalous extinction laws, such as that of Cep OB3b.

My current research involves understanding the fundamental properties of low-mass stars. Despite the fact that these stars the key ingredients to the modern slew of exoplanet discovery and characterisation missions, they are still remarkably poorly understood. Using cutting edge observations from the second data release of the Gaia mission, and photometry from a multiwavelength collection of wide area surveys, we are working on trying to understand what we do and don't understand about the physics that drives them.

Of particular interest to me is understanding the  apparent radius inflation in this class of star when compared directly to a model of equal luminosity. This discrepancy is commonly noted in M dwarf stars at all stages of evolution, but there still remain some important open questions:

  • How large is the radius discrepancy between these stars and the models?
  • Is the effect in some way linked to convective inhibition, driven by stellar magnetic fields?
  • Can the effect be described entirely by star spots and photospheric opacities?
  • What is the underlying physics driving this divergence from models?
  • What is the true effect of this discrepancy on star- and planet-formation timescales?

We are currently working on publications in this area and they will be shared here when they are available.


  • Member of the Institute of Physics (MInstP)
  • Fellow of the Royal Astronomical Society (FRAS)
  • Associate Fellow of the Higher Education Academy (AFHEA)