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Astronomy news
Super-bright supernovae may
be powered by Magnetars
23 November 2013
New light has been shed on the rarest and brightest exploding stars ever
discovered in the universe.
New research proposes that the
brightest exploding stars, called super-luminous supernovae, are powered
by magnetars — small and incredibly dense neutron stars, with gigantic
magnetic fields, that spin hundreds of times a second.
Scientists at Queen's Astrophysics Research Centre observed two
super-luminous supernovae for more than a year. Contrary to existing
theories, which suggested that the brightest supernovae are caused by
super-massive stars exploding, their findings suggest that their origins
may be better explained by a type of explosion within the star's core
which creates a smaller but extremely dense and rapidly spinning
magnetic star.
Artist's illustration of a magnetar— a very dense,
rapidly spinning neutron
star with a gigantic magnetic field. (Credit:
ESO/L.Calçada)
Matt Nicholl, lead author of the study, said: "Supernovae are several
billions of times brighter than the Sun, and in fact are so bright that
amateur astronomers regularly search for new ones in nearby galaxies. It
has been known for decades that the heat and light from these supernovae
come from powerful blast-waves and radioactive material. But recently
some very unusual supernovae have been found, which are too bright to be
explained in this way. They are hundreds of times brighter than those
found over the last fifty years and the origin of their extreme
properties is quite mysterious.
"Some theoretical physicists
predicted these types of explosions came from the biggest stars in the
universe destroying themselves in a manner quite like a giant
thermonuclear bomb. But our data doesn't match up with this theory. In a
supernova explosion, the star's outer layers are violently ejected,
while its core collapses to form an extremely dense neutron star —
weighing as much as the Sun but only tens of kilometers across.
"We think that, in a small number of cases, the neutron star has a very
strong magnetic field, and spins incredibly quickly — about 300 times a
second. As it slows down, it could transmit the spin energy into the
supernova, via magnetism, making it much brighter than normal. The data
we have seems to match that prediction almost exactly."
Queen's
astronomers led an international team of scientists on the study, using
some of the world's most powerful telescopes. Much of the data was
collected using Pan-STARRS — the Panoramic Survey Telescope and Rapid
Response System. Based on Mount Haleakala in Hawaii, Pan-STARRS boasts
the world's largest digital camera, and can cover an area 40 times the
size of the full moon in one shot.
The study is one of the
projects funded by a €2.3million grant from the European Research
Council. The grant was awarded to Professor Stephen Smartt, Director of
Queen's Astrophysics Research Centre, in 2012 to lead an international
study to hunt for the Universe's earliest supernovae.
Professor Smartt said: "These are really special supernovae. Because
they are so bright, we can use them as torches in the very distant
Universe. Light travels through space at a fixed speed, as we look
further away, we see snapshots of the increasingly distant past. By
understanding the processes that result in these dazzling explosions, we
can probe the Universe as it was shortly after its birth. Our goal is to
find these supernovae in the early Universe, detecting some of the first
stars ever to form and watch them produce the first chemical elements
created in the Universe."
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