Nanda Rea receives the Zeldovich Medal
This prestigious award is given to young scientists who have demonstrated excellence and achievement in the field of research. Dr. Nanda Rea has won the Zeldovich Medal for her valuable contribution to the study of neutron stars, and in particular for the discovery that magnetars can have low magnetic fields”.
The Zeldovich medal will be awarded during a special meeting of COSPAR, which is being held in Moscow in August 2014 to mark the centenary of the birth of the famous Russian physicist, Yakov B. Zeldovich.
Dr. Rea’s research
A magnetar is a type of neutron star, the dense, compact core of a giant star which has collapsed and blasted away its outer layers in a supernova explosion. Only 15 to 20 km across, their material is so compressed that a teaspoonful would weigh about a billion tones. As their name suggests, they have some of the strongest magnetic fields in the Universe.
These magnetic monsters are characterised by sudden outbursts of highly energetic radiation, often in the form of X-ray flares and gamma ray outbursts. These outbursts are caused by changes in their super-strong magnetic fields, which are hundreds or thousands of times more intense than those of the more familiar type of neutron stars, also known as pulsars.
At the time when Dr. Rea started her PhD studies in 2002, magnetars were believed to be steady X-ray emitters powered only by their magnetic energy. Their magnetic fields were also thought to be dipolar – resembling fields produced by a bar magnet or planet Earth.
The most exciting – and unexpected – discovery was an object known as SGR 0418 +5729 (SGR 0418 for short), which had the lowest surface magnetic field ever found on a magnetar.
Dr. Rea’s team was able to make an accurate estimate of the strength of SGR 0418′s magnetic field by measuring tiny changes in its rotation speed during an X-ray outburst. “We found that it has a surface magnetic field similar to that of ordinary neutron stars or pulsars,” said Dr. Rea. “However, the star was producing flares and X-ray outbursts like other magnetars, leading us to theorise that its magnetic activity might be caused by a very strong, twisted magnetic field hidden beneath or close to its solid crust.
By modeling the evolution of the cooling of the neutron star and its crust, as well as the gradual decay of its magnetic field, the team estimated that SGR 0418 is about 550,000 years old – older than most other magnetars.
Since the breakthrough with SGR 0418, Dr. Rea has discovered two more magnetars which exhibit unusually low surface magnetism.
Dr. Rea continues to study magnetars in an effort to unravel more of the mysteries associated with these exotic objects. “Many things are still not understood about magnetars,” she said. “It is a very exciting field of study. Ideas are always changing and every year there are new discoveries.”
IEEC in the media
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