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ASTRONOMY CLUB TONIGHT: 2011 Nobel Prize in Physics, The Accelerating Universe October 12, 2011

Posted by jcconwell in Astronomy, Cosmology, General Relativity, supernova.
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Physics-Nobel-Prize Medal

Physics-Nobel-Prize Medal

Tonight at 8:00PM, October 12, 2011 in Room 2153 Physical Science Building

Dr James Conwell will be giving a talk on this years Nobel Prize in Physics: The Accelerating Universe and “Dark Energy”

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2011 NOBEL PRIZE IN PHYSICS October 4, 2011

Posted by jcconwell in Astronomers, Cosmology, supernova, white dwarf.
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The Royal Swedish Academy of Sciences said American Saul Perlmutter would share the 10 million kronor ($1.5 million) award with U.S.-Australian Brian Schmidt and U.S. scientist Adam Riess. Working in two separate research teams during the 1990s – Perlmutter in one and Schmidt and Riess in the other – the scientists raced to map the change in the  universe’s expansion over time. They were measuring the change in  Hubble’s Constant,  by analyzing a particular type of supernovas, Type Ia, or exploding stars.

SN 1994D in NGC 4526. in lower left

Type Ia supernovas are thought to be caused by a white dwarf star exceeding its maximum mass, the Chandrasekar limit, of about 1.4 Solar masses, collapsing and detonating into a supernova. Since this collapse occurs at the same mass limit , it’s though all Type Ia supernova are equally bright.

They found that the light emitted by more than 50 distant Ia supernovas was weaker than expected, a sign that the universe was expanding at an accelerating rate, the academy said.

“For almost a century the universe has been known to be expanding as a consequence of the Big Bang about 14 billion years ago,” the citation said. “However the discovery that this expansion is accelerating is astounding. If the expansion will continue to speed up the universe will end in ice.”

Perlmutter, 52, heads the Supernova Cosmology Project at the Lawrence Berkeley National Laboratory and University of California, Berkeley.

Schmidt, 44, is the head of the High-z Supernova Search Team at the Australian National University in Weston Creek, Australia.

Riess, 41, is an astronomy professor at Johns Hopkins University and Space Telescope Science Institute in Baltimore, Maryland.

Schmidt said he was just sitting down to have dinner with his family in Canberra, Australia, when the phone call came.

“I was somewhat suspicious when the Swedish voice came on,” Schmidt told The Associated Press. “My knees sort of went weak and I had to walk around and sort my senses out.”

The academy said the three researchers were stunned by their own discoveries – they had expected to find that the expansion of the universe was slowing down. But both teams reached the opposite conclusion: faraway galaxies were racing away from each other at an ever-increasing speed.

The discovery was “the biggest shakeup in physics, in my opinion, in the last 30 years,” said Phillip Schewe, a physicist and spokesman at the Joint Quantum Institute, which is operated by the University of Maryland and the federal government.

AstroAlert: Type Ia supernova in M101! August 25, 2011

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(FROM the Bad Astronomy BLOG)  Attention all astronomers! There is a new Type Ia supernova that has been seen in the nearby spiral galaxy M101, and it’s very young — currently only about a day old! This is very exciting news; getting as much data on this event as possible is critical.

Most likely professional astronomers are already aware of the supernova, since observations have already been taken by Swift (no X-rays have yet been seen, but it’s early yet) and Hubble observations have been scheduled. Still, I would urge amateur astronomers to take careful observations of the galaxy.

M 101 (From Astronomy Picture of the Day)

We’ll be out at the observatory tonight getting some pictures and spectra.

For more info see the articles on BAD ASTRONOMY and PHYSORG

White Dwarf Star System Exceeds Chandrasakar’s Mass Limit!? March 15, 2010

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Type 1a Supernova

Richard Scalzo of Yale, as part of called the Nearby Supernova Factory, a collaboration of American and French physicists, has measured the mass of the white dwarf star that resulted in one of these rare supernovae, called SN 2007if, and found it exceeded the Chandrasekhar limit.

It is thought that white dwarfs could not exceed what is known as the Chandrasekhar limit, a critical mass of about 1.4 times that of the Sun, before exploding in a type Ia supernova. This assumption is crucial in measuring distances to supernovae, and using them as standard candles

Using observations from telescopes in Chile, Hawaii and California, the team was able to measure the mass of the central star, the shell and the envelope individually, providing the first conclusive evidence that the star system itself did indeed surpass the Chandrasekhar limit. They found that the star itself appears to have had a mass of 2.1 times the mass of the Sun (plus or minus 10 percent), putting it well above the limit.

More information: Paper: http://arxiv.org/abs/1003.2217

Provided by Yale University

Type Ia supernova TALK at 4:00 TODAY March 9, 2010

Posted by jcconwell in Observatory, supernova.
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Room 2153 Physical Science Building

And as a sweetener we will have coffee and cookies at 3:45.  Some come for the cookies at 3:45 then we get to blow up some stars at 4:00! What more could you want!

How about a working dome!

EIU Observatory

The slit opening to the dome is working again. We just had to alleviate some of the tension on the steel cables, and now we can open the slit (and close it). My thanks to Tyler Linder for help in getting the cables straightened out and things working.

A Type Ia Supernova Lifetime: From Simmers to Explosions March 7, 2010

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Vampire mechanism for Type Ia supernova

Vampire mechanism for Type Ia supernova

A Talk  Chris Richardson

(Dept of Astrophysics, Michigan State University)

Tuesday March 9th, at 4:00PM, Room 2153

Physical Science Building

Type Ia Supernovae are seen at the far reaches of the Universe due to thermonuclear incineration of white dwarves. Their uniform light curves serve as valuable assets in determining cosmological parameters, however, the underlying mechanisms are far from understood. Exploring the lifetimes and models of SNe Ia provide valuable insight to these mechanisms.

Rare Outburst of the Recurrent Nova U Scorpii Begins January 28, 2010

Posted by jcconwell in Nova, stars, supernova, white dwarf.
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Artists rendition of the recurrent nova RS Oph Credit: David Hardy/PPARC

(From Universe Today): Today, two amateur astronomers from Florida detected a rare outburst of the recurrent nova U Scorpii, which set in motion satellite observations by the Hubble Space Telescope, Swift and Spitzer. The last outburst of U Scorpii occurred in February of 1999. Observers around the planet will now be observing this remarkable system intensely for the next few months trying to unlock the mysteries of white dwarfs, interacting binaries, accretion and the progenitors of Type IA supernovae.

One of the remarkable things about this outburst is it was predicted in advance by Dr. Bradley Schaefer, Louisiana State University, so observers of the American Association of Variable Star Observers (AAVSO) have been closely monitoring the star since last February, waiting to detect the first signs of an eruption. This morning, AAVSO observers, Barbara Harris and Shawn Dvorak sent in notification of the outburst, sending astronomers scrambling to get ‘target of opportunity observations’ from satellites and continuous coverage from ground-based observatories. Time is a critical element, since U Sco is known to reach maximum light and start to fade again in one day.

Extreme Universe: New Class of Supernovae: SN 2007bi December 2, 2009

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First confirmed pair instability supernova

Berkeley, CA – An extraordinarily bright, extraordinarily long-lasting supernova named SN 2007bi, snagged in a search by a robotic telescope, turns out to be the first example of the kind of stars that first populated the Universe. The superbright supernova occurred in a nearby dwarf galaxy, a kind of galaxy that’s common but has been little studied until now, and the unusual supernova could be the first of many such events soon to be discovered.

from SN factory team

The analysis indicated that the supernova’s precursor star could only have been a giant weighing at least 200 times the mass of our Sun and initially containing few elements besides hydrogen and helium – a star like the very first stars in the early Universe.

“Because the core alone was some 100 solar masses, the long-hypothesized phenomenon called pair instability must have occurred,” says astrophysicist Peter Nugent. A member of the SNfactory, Nugent is the co-leader of the Computational Cosmology Center (C3), a collaboration between Berkeley Lab’s Physics Division and Computational Research Division (CRD), where Nugent is a staff scientist. “In the extreme heat of the star’s interior, energetic gamma rays created pairs of electrons and positrons, which bled off the pressure that sustained the core against collapse.”

“SN 2007bi was the explosion of an exceedingly massive star,” says Alex Filippenko, a professor in the Astronomy Department at UC Berkeley whose team helped obtain, analyze, and interpret the data. “But instead of turning into a black hole like many other heavyweight stars, its core went through a nuclear runaway that blew it to shreds. This type of behavior was predicted several decades ago by theorists, but never convincingly observed until now.”

SN 2007bi is the first confirmed observation of a pair-instability supernova. The researchers describe their results in the 3 December 2009 issue of Nature.

3D Supernova Simulation! September 27, 2009

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What’s a simulation? It’s a computer model, usually of a complicated system, that can’t be solved using pencil and paper. You tell the computer what the physical laws are, usually in the form of differential equations, and let the computer try to solve them.  They are also used in design and prototypes of airplanes, buildings and complicated systems. Simulations are also used in cases where doing lab measurement might not be possible, think nuclear detonations, and their big brother, type Ia Supernova.

Type Ia supernova are thought to be caused by a white dwarf stealing mass from a companion star. If it exceeds Chandrasakar’s limit of 1.4 Solar Masses, it will start to compress and detonate. They have found a new importance in astronomy as standard candles to measure distance. It is thought that since they detonate at the same mass they will have the same brightness. They’ve been used to measure Hubble’s constant in the distance past and are the foundation for the existence of the accelerated universe and the existence of dark energy.  BUT  it not KNOWN if all behave the same. Maybe small variations of  chemical abundance or rotation change the energy given off by the supernova. That’s were the simulations are important.

3D simulations take a big computer. The computational requirements can go up like the 4th power of the grid size (how finely divided do chop up a linear dimension in the star). So up until this point most simulations have been 2D or 1D. When simulations went from 1D to 2D new physics appeared. Asymmetric explosions and other effects not seen in simpler simulations. It is expected that going to 3D we’ll be able to see new effects. If you are interested in Computational Physics, Eastern has a an option in its physics major. Contact either me ( Dr. Conwell) or Dr. Zou for more information.

“WHEN STARS ATTACK” September 16, 2009

Posted by jcconwell in IYA 2009, supernova.
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THURSDAY, Sept 17 in the Phipps Lecture Hall at 7:00 P.M

Crab Supernova.

Crab Supernova.

“When Stars Attack! In Search of Near-Earth Supernova Explosions,” a presentation by a University of Illinois faculty member, will continue Eastern Illinois University’s yearlong celebration of the International Year of Astronomy.

Brian Fields, associate professor of astronomy and physics at the U of I, is to speak at 7 p.m. Thursday, Sept. 17, in the EIU Physical Science Building’s Phipps Lecture Hall. The event is free and open to the public.

In a supernova, a massive star is destroyed in an extremely powerful explosion, leaving behind a neutron star or a black hole. A shock wave carries the star’s ashes — newly created heavy elements — through space, stirring interstellar gas and, at times, spurring the formation of new stars. Fields will discuss how recent evidence suggests that radioactive iron atoms found deep in the Earth’s ocean are debris from a star exploding near Earth about 3 million years ago.

In addition to giving scientists a clue of what powers supernovae, the findings suggest that the explosion’s proximity to Earth might have had major results on the planet, Fields wrote. “An explosion so close to Earth was probably a ‘near-miss,’ which emitted intense and possibly harmful radiation,” Fields wrote on his Web site. “The resulting environmental damage may even have led to extinction of species which were the most vulnerable to this radiation.”

Fields’ presentation will be the first event of the fall semester in EIU’s yearlong celebration of the International Year of Astronomy. IYA is a worldwide commemoration of many historic astronomical achievements, including the 400th anniversary of Galileo’s first look through a telescope and the 40th anniversary of man’s first steps on the moon.

EIU’s IYA events are sponsored by the EIU College of Sciences and the EIU Department of Physics.