25 Neutrinos from Heavenly Sources
191
useful means. By the same token, we need more mammoth detectors to capture
the neutrinos. For instance, the 25 to 30 neutrino events from SN 1987A have
confirmed our broad understanding of how solar collapse takes place. But we
need to know more details about what causes the explosion in a supernova,
what is happening in neutron stars that form after the collapse, etc. They can be
accurately learned by studying the supernova neutrinos. By the same token, we
can also learn more about the properties of the neutrinos from such studies. For
example, their mass ordering can leave an imprint on the supernova neutrino
energy spectrum. They can also explore events like exploding stars, gamma-ray
bursts, and cataclysmic phenomena involving black holes and neutron stars.
The gravitational wave observatories LIGO and VIRGO have recently
observed gravity waves from a binary neutron star merger. To know the full
details of how this merger happened and its consequences, it will be important
to know as many other signals as possible from them. The neutrino signal is
one important signal since in the neutron star merger, there is likely to be a
lot of neutrino emission. This provides another reason why observing neutrino
signals from outer space is so important for our understanding of the universe.
25.2 Supernova Neutrinos
In 1987, several detectors had been set up mainly to search for proton decay.
They were the Kamiokande (pre-cursor to the Super-Kamiokande detector
that made the neutrino oscillation discovery) detector in Japan, the IMB
detector in the USA, and the Baksan detector in the mountains of Russia.
On February 24, 1987, a sudden brightening of a star, named Sanduleak, was
observed in the Large Magellanic Cloud. That was light from a supernova
explosion. What took place was a supernova that exploded 168,000 years
ago, and whose light just reached the Earth on Feb. 24, 1987. It is called
SN1987A. Within the same 24 h of light observation, the neutrino detectors
mentioned above saw several energetic neutrino events, all clustered within less
than 13 s. They were the neutrinos from the supernova explosion, which was
the end point of stellar evolution. For the first time, supernova neutrinos were
observed on Earth. Their energies were in the few MeV range and they could
be understood using the stellar collapse theories known. These few observed
events confirmed the broad picture of how supernova explosion generally takes
place. To know all the intricacies of a cataclysmic event like this, we need to
observe more such supernova neutrinos. There are now many more sensitive
water Cherenkov detectors set up around the world for detecting supernova
neutrinos, both from our own galaxy as well as galaxies outside the Milky Way.
191
useful means. By the same token, we need more mammoth detectors to capture
the neutrinos. For instance, the 25 to 30 neutrino events from SN 1987A have
confirmed our broad understanding of how solar collapse takes place. But we
need to know more details about what causes the explosion in a supernova,
what is happening in neutron stars that form after the collapse, etc. They can be
accurately learned by studying the supernova neutrinos. By the same token, we
can also learn more about the properties of the neutrinos from such studies. For
example, their mass ordering can leave an imprint on the supernova neutrino
energy spectrum. They can also explore events like exploding stars, gamma-ray
bursts, and cataclysmic phenomena involving black holes and neutron stars.
The gravitational wave observatories LIGO and VIRGO have recently
observed gravity waves from a binary neutron star merger. To know the full
details of how this merger happened and its consequences, it will be important
to know as many other signals as possible from them. The neutrino signal is
one important signal since in the neutron star merger, there is likely to be a
lot of neutrino emission. This provides another reason why observing neutrino
signals from outer space is so important for our understanding of the universe.
25.2 Supernova Neutrinos
In 1987, several detectors had been set up mainly to search for proton decay.
They were the Kamiokande (pre-cursor to the Super-Kamiokande detector
that made the neutrino oscillation discovery) detector in Japan, the IMB
detector in the USA, and the Baksan detector in the mountains of Russia.
On February 24, 1987, a sudden brightening of a star, named Sanduleak, was
observed in the Large Magellanic Cloud. That was light from a supernova
explosion. What took place was a supernova that exploded 168,000 years
ago, and whose light just reached the Earth on Feb. 24, 1987. It is called
SN1987A. Within the same 24 h of light observation, the neutrino detectors
mentioned above saw several energetic neutrino events, all clustered within less
than 13 s. They were the neutrinos from the supernova explosion, which was
the end point of stellar evolution. For the first time, supernova neutrinos were
observed on Earth. Their energies were in the few MeV range and they could
be understood using the stellar collapse theories known. These few observed
events confirmed the broad picture of how supernova explosion generally takes
place. To know all the intricacies of a cataclysmic event like this, we need to
observe more such supernova neutrinos. There are now many more sensitive
water Cherenkov detectors set up around the world for detecting supernova
neutrinos, both from our own galaxy as well as galaxies outside the Milky Way.