Andrew Yee[_1_]
February 25th 07, 05:21 AM
ESO Education and Public Relations Dept.
----------------------------------------------------------------------------
Text with all links and the photos are available on the ESO Website at URL:
http://www.eso.org/outreach/press-rel/pr-2007/pr-08-07.html
----------------------------------------------------------------------------
Contacts
Roberto Gilmozzi, Bruno Leibundgut, Jason Spyromilio
ESO
Phone: +49 89 3200 6667, +49 89 3200 6295, +49 89 3200 6411
John Danziger
OAT-INAF, Trieste, Italy
Phone: +39 040 3199 223
Patrice Bouchet
Observatoire de Paris, France
Email: pbouchet (at) mesiog.obspm.fr
ESO Science Release 08/07
For Immediate Release: 24 February 2007
SN1987A's Twentieth Anniversary
Looking back at 20 Years of Observations of this Supernova with ESO
telescopes
The unique supernova SN 1987A has been a bonanza for astrophysicists. It
provided several observational 'firsts,' like the detection of neutrinos
from an exploding star, the observation of the progenitor star on archival
photographic plates, the signatures of a non-spherical explosion, the direct
observation of the radioactive elements produced during the blast,
observation of the formation of dust in the supernova, as well as the
detection of circumstellar and interstellar material.
Today, it is exactly twenty years since the explosion of Supernova 1987A in
the Large Magellanic Cloud was first observed, at a distance of 163,000
light-years. It was the first naked-eye supernova to be seen for 383 years.
Few events in modern astronomy have met with such an enthusiastic response
by the scientists and now, after 20 years, it continues to be an extremely
exciting object that is further studied by astronomers around the world, in
particular using ESO's telescopes.
When the first signs of Supernova 1987A, the first supernova of the year
1987, were noticed early on 24 February of that year, it was clear that this
would be an unusual event. It was discovered by naked-eye and on a panoramic
photographic plate taken with a 10-inch astrograph on Las Campanas in Chile
by Oscar Duhalde and Ian Shelton, respectively. A few hours earlier, still
on 23 February, two large underground detectors:- in Japan and the USA:- had
registered the passage of high-energy neutrinos.
Since SN 1987A exploded in the Large Magellanic Cloud (LMC), it was only
accessible to telescopes in the Southern Hemisphere, more particularly in
Australia, South Africa, and South America. In Chile, ESO's observatory at
La Silla with its armada of telescopes with sizes between 0.5 and 3.6-m,
played an important role.
Astronomers John Danziger and Patrice Bouchet, who were there at the time,
recall: "When astronomers at La Silla arrived for the ritual afternoon tea
at 4pm on the 24th February 1987 after the previous night's clear observing,
they were greeted by the news that a supernova had been detected in the LMC
the previous night. The tea-time ritual of groggy astronomers quietly
sipping their tea was transformed, to be succeeded by flurries of excited
but still to some extent uncoordinated planning. Nobody doubted for one
second that the sky would be clear and there would be excitement galore in
the days and nights ahead. And indeed there was!
A large observatory such as La Silla with its many telescopes can be
considered like a naval fleet consisting of many ships from torpedo boats to
cruisers and even aircraft carriers. La Silla had them all. All observers
were encouraged to plan for observing SN1987A by whatever means at their
disposal."
"Ironically, the supernova was too bright for the state-of-the-art 4m-class
telescopes and some of them had to be stopped down, e.g. by half-closed
telescope covers," says Jason Spyromilio (ESO). Some of the smaller
telescopes took their chance. The 61-cm Bochum telescope on La Silla was
used, on a nearly daily basis for more than a year, to measure optical
spectroscopy with photometric accuracy. Since the LMC is circumpolar for
most southern observatories, this also meant that there exists an
uninterrupted record of the photometry and spectroscopy; else part of the
peak phase, which lasted into May of 1987, would have been missed.
By July, the first conference on SN 1987A, organised by John Danziger, had
already taken place at ESO in Garching to be followed by several others
during that year and following years.
The optical light curve of SN 1987A was rather different from those of
previously observed core-collapse supernovae. The old models of spherical
explosions had to be revised. The spectroscopic evolution provided further
evidence for asymmetries in the explosion. The 'Bochum event' was a rapid
change in the line profile observed with the Bochum telescope on La Silla.
It is the signature of a radioactive blob rising from the inner ejecta to
the surface. "The picture emerging from the observations of the first
several weeks was certainly more complex than what had ever been assumed of
supernovae before," says Bruno Leibundgut (ESO).
The 1-m telescope at La Silla was also extensively used in daytime observing
the supernova in the near- and mid-infrared for more than one year after the
explosion. A clear excess emission developed in the near-infrared already 10
days after the explosion, the origin of which is still not fully understood.
It was most probably due to circumstellar material that was lighted up by
the explosion.
Dust condensation in the ejecta was discovered by spectroscopy about 500
days after the explosion. Macroscopic dust grains partially covered the
ejecta, and most probably still do. They might explain why no compact object
is seen at the location of the supernova.
In 1989, when the NTT came into operation, it imaged for the first time the
circumstellar ring around SN 1987A. And, about three years after the
explosion, NTT images revealed a circumstellar structure around SN 1987A
which resembled the triangular hat which Napoleon wore. Napoleon's hat gave
the first opportunity for a 3-dimensional view of SN 1987A.
"The existence of the ring presents an unsolved puzzle for SN 1987A," says
Roberto Gilmozzi (ESO). "Even though it is not clear how to construct such a
ring, it is likely that the star that exploded as SN 1987A had a companion."
When ESO's Very Large Telescope came into operation, the interest in the
supernova had not faded away. Far from it! Observations were done with the
VLT's many instruments, including FORS, UVES, ISAAC, and VISIR, to probe in
more detail the surroundings of the explosion. More recently, adaptive
optics instruments, which compensate for the blurring effect of the
atmosphere, and so can see as if they were in space, have also been used.
The NACO instrument has obtained amazing images of the rings, while SINFONI
has been used to study the changes in the rings' appearances and the
evolution of the spectral lines.
"SN 1987A was full of surprises and it remains unique amongst the known
supernovae," says Leibundgut. "Not only was it the closest supernova for
several centuries, it was also very peculiar, coming from a blue supergiant
progenitor, with a circumstellar environment unlike any other supernova
known. We will certainly continue to monitor its evolution for many years to
come."
One goal will be to find the possible compact object that should have
survived the dramatic explosion. But until now, this remnant has proved
elusive.
More Information
Two articles in the forthcoming issue of ESO's Messenger discuss SN 1987A:
* "SN1987A at La Silla: The early days", by Ivan John Danziger and Patrice
Bouchet.
* "Twenty Years of Supernova 1987A" by Claes Fransson, Roberto Gilmozzi, Per
Gringsson, Reinhard Hanuschik, Karina Kj, Bruno Leibundgut, and Jason
Spyromilio
National contacts for the media:
Belgium: Dr. Rodrigo Alvarez, +32-2-474 70 50
Finland: Ms. Tiina Raivo, +358 9 7748 8369
Denmark: Dr. Michael Linden-Vnle, +45-33-18 19 97
France: Dr. Daniel Kunth, +33-1-44 32 80 85
Germany: Dr. Jakob Staude, +49-6221-528229
Italy: Dr. Leopoldo Benacchio, +39-347-230 26 51
The Netherlands: Ms. Marieke Baan, +31-20-525 74 80
Portugal: Prof. Teresa Lago, +351-22-089 833
Sweden: Dr. Jesper Sollerman, +46-8-55 37 85 54
Switzerland: Dr. Martin Steinacher, +41-31-324 23 82
United Kingdom: Mr. Peter Barratt, +44-1793-44 20 25
----------------------------------------------------------------------------
ESO Press Information is available on Receive email notification
the WWW at about important news from
http://www.eso.org/outreach/press-rel/ ESO - subscribe to the
ESO-NEWS Mailing List.
----------------------------------------------------------------------------
Copyright ESO Education & Public Relations Department
Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany
----------------------------------------------------------------------------
----------------------------------------------------------------------------
Text with all links and the photos are available on the ESO Website at URL:
http://www.eso.org/outreach/press-rel/pr-2007/pr-08-07.html
----------------------------------------------------------------------------
Contacts
Roberto Gilmozzi, Bruno Leibundgut, Jason Spyromilio
ESO
Phone: +49 89 3200 6667, +49 89 3200 6295, +49 89 3200 6411
John Danziger
OAT-INAF, Trieste, Italy
Phone: +39 040 3199 223
Patrice Bouchet
Observatoire de Paris, France
Email: pbouchet (at) mesiog.obspm.fr
ESO Science Release 08/07
For Immediate Release: 24 February 2007
SN1987A's Twentieth Anniversary
Looking back at 20 Years of Observations of this Supernova with ESO
telescopes
The unique supernova SN 1987A has been a bonanza for astrophysicists. It
provided several observational 'firsts,' like the detection of neutrinos
from an exploding star, the observation of the progenitor star on archival
photographic plates, the signatures of a non-spherical explosion, the direct
observation of the radioactive elements produced during the blast,
observation of the formation of dust in the supernova, as well as the
detection of circumstellar and interstellar material.
Today, it is exactly twenty years since the explosion of Supernova 1987A in
the Large Magellanic Cloud was first observed, at a distance of 163,000
light-years. It was the first naked-eye supernova to be seen for 383 years.
Few events in modern astronomy have met with such an enthusiastic response
by the scientists and now, after 20 years, it continues to be an extremely
exciting object that is further studied by astronomers around the world, in
particular using ESO's telescopes.
When the first signs of Supernova 1987A, the first supernova of the year
1987, were noticed early on 24 February of that year, it was clear that this
would be an unusual event. It was discovered by naked-eye and on a panoramic
photographic plate taken with a 10-inch astrograph on Las Campanas in Chile
by Oscar Duhalde and Ian Shelton, respectively. A few hours earlier, still
on 23 February, two large underground detectors:- in Japan and the USA:- had
registered the passage of high-energy neutrinos.
Since SN 1987A exploded in the Large Magellanic Cloud (LMC), it was only
accessible to telescopes in the Southern Hemisphere, more particularly in
Australia, South Africa, and South America. In Chile, ESO's observatory at
La Silla with its armada of telescopes with sizes between 0.5 and 3.6-m,
played an important role.
Astronomers John Danziger and Patrice Bouchet, who were there at the time,
recall: "When astronomers at La Silla arrived for the ritual afternoon tea
at 4pm on the 24th February 1987 after the previous night's clear observing,
they were greeted by the news that a supernova had been detected in the LMC
the previous night. The tea-time ritual of groggy astronomers quietly
sipping their tea was transformed, to be succeeded by flurries of excited
but still to some extent uncoordinated planning. Nobody doubted for one
second that the sky would be clear and there would be excitement galore in
the days and nights ahead. And indeed there was!
A large observatory such as La Silla with its many telescopes can be
considered like a naval fleet consisting of many ships from torpedo boats to
cruisers and even aircraft carriers. La Silla had them all. All observers
were encouraged to plan for observing SN1987A by whatever means at their
disposal."
"Ironically, the supernova was too bright for the state-of-the-art 4m-class
telescopes and some of them had to be stopped down, e.g. by half-closed
telescope covers," says Jason Spyromilio (ESO). Some of the smaller
telescopes took their chance. The 61-cm Bochum telescope on La Silla was
used, on a nearly daily basis for more than a year, to measure optical
spectroscopy with photometric accuracy. Since the LMC is circumpolar for
most southern observatories, this also meant that there exists an
uninterrupted record of the photometry and spectroscopy; else part of the
peak phase, which lasted into May of 1987, would have been missed.
By July, the first conference on SN 1987A, organised by John Danziger, had
already taken place at ESO in Garching to be followed by several others
during that year and following years.
The optical light curve of SN 1987A was rather different from those of
previously observed core-collapse supernovae. The old models of spherical
explosions had to be revised. The spectroscopic evolution provided further
evidence for asymmetries in the explosion. The 'Bochum event' was a rapid
change in the line profile observed with the Bochum telescope on La Silla.
It is the signature of a radioactive blob rising from the inner ejecta to
the surface. "The picture emerging from the observations of the first
several weeks was certainly more complex than what had ever been assumed of
supernovae before," says Bruno Leibundgut (ESO).
The 1-m telescope at La Silla was also extensively used in daytime observing
the supernova in the near- and mid-infrared for more than one year after the
explosion. A clear excess emission developed in the near-infrared already 10
days after the explosion, the origin of which is still not fully understood.
It was most probably due to circumstellar material that was lighted up by
the explosion.
Dust condensation in the ejecta was discovered by spectroscopy about 500
days after the explosion. Macroscopic dust grains partially covered the
ejecta, and most probably still do. They might explain why no compact object
is seen at the location of the supernova.
In 1989, when the NTT came into operation, it imaged for the first time the
circumstellar ring around SN 1987A. And, about three years after the
explosion, NTT images revealed a circumstellar structure around SN 1987A
which resembled the triangular hat which Napoleon wore. Napoleon's hat gave
the first opportunity for a 3-dimensional view of SN 1987A.
"The existence of the ring presents an unsolved puzzle for SN 1987A," says
Roberto Gilmozzi (ESO). "Even though it is not clear how to construct such a
ring, it is likely that the star that exploded as SN 1987A had a companion."
When ESO's Very Large Telescope came into operation, the interest in the
supernova had not faded away. Far from it! Observations were done with the
VLT's many instruments, including FORS, UVES, ISAAC, and VISIR, to probe in
more detail the surroundings of the explosion. More recently, adaptive
optics instruments, which compensate for the blurring effect of the
atmosphere, and so can see as if they were in space, have also been used.
The NACO instrument has obtained amazing images of the rings, while SINFONI
has been used to study the changes in the rings' appearances and the
evolution of the spectral lines.
"SN 1987A was full of surprises and it remains unique amongst the known
supernovae," says Leibundgut. "Not only was it the closest supernova for
several centuries, it was also very peculiar, coming from a blue supergiant
progenitor, with a circumstellar environment unlike any other supernova
known. We will certainly continue to monitor its evolution for many years to
come."
One goal will be to find the possible compact object that should have
survived the dramatic explosion. But until now, this remnant has proved
elusive.
More Information
Two articles in the forthcoming issue of ESO's Messenger discuss SN 1987A:
* "SN1987A at La Silla: The early days", by Ivan John Danziger and Patrice
Bouchet.
* "Twenty Years of Supernova 1987A" by Claes Fransson, Roberto Gilmozzi, Per
Gringsson, Reinhard Hanuschik, Karina Kj, Bruno Leibundgut, and Jason
Spyromilio
National contacts for the media:
Belgium: Dr. Rodrigo Alvarez, +32-2-474 70 50
Finland: Ms. Tiina Raivo, +358 9 7748 8369
Denmark: Dr. Michael Linden-Vnle, +45-33-18 19 97
France: Dr. Daniel Kunth, +33-1-44 32 80 85
Germany: Dr. Jakob Staude, +49-6221-528229
Italy: Dr. Leopoldo Benacchio, +39-347-230 26 51
The Netherlands: Ms. Marieke Baan, +31-20-525 74 80
Portugal: Prof. Teresa Lago, +351-22-089 833
Sweden: Dr. Jesper Sollerman, +46-8-55 37 85 54
Switzerland: Dr. Martin Steinacher, +41-31-324 23 82
United Kingdom: Mr. Peter Barratt, +44-1793-44 20 25
----------------------------------------------------------------------------
ESO Press Information is available on Receive email notification
the WWW at about important news from
http://www.eso.org/outreach/press-rel/ ESO - subscribe to the
ESO-NEWS Mailing List.
----------------------------------------------------------------------------
Copyright ESO Education & Public Relations Department
Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany
----------------------------------------------------------------------------