Starry insights

By studying supernovae, scientists are determining the mass of the Universe

Published: Sunday 30 November 1997

 Observatories placed inside t (Credit: Science Photo Library)new observatories have been placed inside the Earth to study the properties of neutrinos -- one of the most weakly interacted particles -- produced when a sun explodes going supernova. The project called Observatory for Multiflavor Neutrinos from Supernovae ( omnis ) is a collaboration of four institutions from the us and the uk. The experiment consists of setting up two observatories in salt deposits near New Mexico and in Boulby Salt Mine, uk .

When nuclear fusion in a star takes place, reactants of the fusion such as hydrogen, carbon and nitrogen are totally utilised. Nuclear fusion is a phenomenon of two nuclei combining together to form a new nucleus. During the process, the star gradually loses its energy and stops emitting light. The temperature on the outermost layer of the star cools down and due to contraction, supernovae explosion takes place. The star ejects most of its mass in form of expanding cloud of debris that soon becomes a nebula.

At the brightest phase of explosion, the expanding cloud radiates as much energy in a day as the Sun has done in last three million years. Such explosions occur once in every 50 years within a large galaxy. One of the results of such an explosion is the burst of neutrinos that are released from the core ( Science , Vol 277, No 5329).

The neutrino burst coming from a supernovae, lasts for nearly 10 seconds of which 60 per cent are in first two seconds.

Most existing observatories for neutrinos such as the Super Kamiokande in Japan use enormous quantities of water to detect the neutrinos. After interacting with water, the neutrinos emit light that is based on a phenomenon known as 'Cerenkov effect'. These observatories are most sensitive to only one kind of neutrinos called 'electron neutrino'.

But omnis will detect all three kinds of neutrinos, thereby throwing light on whether neutrinos have mass. The researchers say that high energy neutrinos from the supernovae will enter the mine and a tiny fraction of them will interact with atomic nuclei in walls of the mine. Some of the neutrinos will also hit slabs of lead and iron that will line the walls. Neutrons released from these interactions will strike scintillation detectors placed in tunnels and be detected.

If the funding for omnis is confirmed, it would be a cheap and sensitive method to analyse supernovae neutrino pulse whenever it strikes the Earth next time. Information gathered about the neutrino pulse would enable the researchers to determine what happens when a star collapses during a supernovae explosion.

omnis 's ability to pick up other two kinds of neutrinos -- the muon and the tau particle -- will lead to ascertain the neutrino's mass. Once the mass is known, the researchers may calculate the mass present in the Universe. These findings may help them to know whether the Universe is open or closed.

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