A laboratory scale-model of accretion column onto a highly magnetized dense star

15 June 2016

Scientists from a large international collaboration (Oxford, AWE, CEA, LULI, Observatoire de Paris, University of Michigan, University of York and STFC Rutherford Appleton Laboratory) have succeeded for the first time in generating a laboratory analogue of a strong shock that is generated when matter falls at very high speed on the surface of extremely dense stars called white dwarfs.

Understanding the physics of these astrophysical objects is crucial because they are considered as the possible progenitors of thermonuclear supernovae. These supernovae are used in cosmology to measure the acceleration of the universe expansion that is linked to dark energy. To perform this spectacular astrophysics experiment, the scientists made use of the powerful Orion Laser Facility at Aldermaston (UK) to evaporate a millimetre size target and produce a hot plasma flow for an extremely short duration (less than 100 nanoseconds).
Recent theoretical work has shown that, by using adapted scaling laws, this tiny size experiment can be scaled to its cosmic counterpart making it a valid replicate. Powerful lasers can therefore be used as microscopes to explore, during few nanoseconds, the high-energy radiation processes occurring in astrophysical objects from regions largely unresolved by the most powerful telescopes. The Orion experiment which is the first academic experiment on this facility, confirms that these accretion shocks, which could not be studied in laboratory a few years ago at exact scale, can now be produced commonly in laboratory.

These results are published in Nature Communications [1], with Joseph Cross (DPhil student under Prof Gianluca Gregori supervision) leading author.
They open a way to more complete astrophysical experimentations in the laboratory using the most powerful Megajoule lasers as the National Ignition Facility (NIF) or Laser MegaJoule (LMJ).

[1] “Laboratory analogue of a supersonic accretion column in a binary star system”, J. E. Cross et al., was published in Nature Communications 7, 11899 (2016) and can be viewed here