Tag: supernovae

New data suggests that the crash of two white dwarf stars caused the nearest supernovae in 25 years

11:03 am

New data has found that the crash of two white dwarf stars not only caused the nearest supernova in 25 years, but appear to be the prime cause for these types of supernovae.

The data also says that there are no white dwarf primary systems in the Milky Way that are candidates to go supernova in this way. Thus, we can all sleep easy tonight!

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The most distant supernova discovered so far.

10:43 am

The most distant supernova discovered so far.

SN Primo is the farthest Type Ia supernova whose distance has been confirmed through spectroscopic observations. The supernova was discovered as part of a three-year Hubble program to survey faraway Type Ia supernovae, enabling searches for this special class of stellar explosion at greater distances than previously possible. The remote supernovae will help astronomers determine whether the exploding stars remain dependable distance markers across vast distances of space in an epoch when the cosmos was only one-third its current age of 13.7 billion years.

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The supernova of a generation

12:00 pm

The supernova of a generation.

There will be a slew of stories about this in the next few days. The important takeaways are as follows:

  • After almost a half century, astronomers have finally proven the theory that type Ia supernovae come from the explosion of a white dwarf star, overloaded with material sucked from its binary companion.
  • The prediction that the companion would be a red giant star, however, has turned out to be wrong. At the same time, astronomers still do not know what kind of star it was in this particular case.
  • With this new knowledge astronomers will have a better chance of identifying type Ia supernovae, before they go boom.
  • Finally, type Ia supernovae are used to measure the expansion rate of the universe, and thus were the key to discovering dark energy. By better understanding how these supernovae occur, cosmologists will be better able to constrain what they know about dark energy.
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The first observations of a star, just prior to going supernova

1:30 pm

Astronomers have for the first time observed the changes that took place in a binary star system in the years before one star in the system erupted as a supernova.

In the first survey of its kind, the researchers have been scanning 25 nearby galaxies for stars that brighten and dim in unusual ways, in order to catch a few that are about to meet their end. In the three years since the study began, this particular unnamed binary system in the Whirlpool Galaxy was the first among the stars they’ve cataloged to produce a supernova.

The astronomers were trying to find out if there are patterns of brightening or dimming that herald the end of a star’s life. Instead, they saw one star in this binary system dim noticeably before the other one exploded in a supernova during the summer of 2011.

Key quote: “Our underlying goal is to look for any kind of signature behavior that will enable us to identify stars before they explode,”

The supernova in question, 2011dh, was the closest supernova in decades, occurring in June 2011 in the Whirlpool Galaxy (M51). See my previous posts here and here.

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Astronomers have found a dozen supernovae taking place closer to the Big Bang than ever detected.

10:18 pm

Astronomers have found a dozen supernovae taking place only a few billion years after the Big Bang.

[The results suggest that these types of supernovae] were exploding about five times more frequently 10 billion years ago than they are today. These supernovas are a major source of iron in the universe, the main component of the Earth’s core and an essential ingredient of the blood in our bodies.

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The 2011 Nobel Prize for Physics has been awarded

8:54 am

The 2011 Nobel Prize for Physics has been awarded to the astronomers who discovered dark energy.

Saul Perlmutter from the Lawrence Berkeley National Laboratory and University of California, Berkeley, has been awarded half of this year’s prize for his work on the Supernova Cosmology Project, with the other half awarded to Brian P. Schmidt from the Australian National University and Adam G. Riess from the Johns Hopkins University and Space Telescope Science Institute, Baltimore, for their work on the High-z Supernova Search Team.

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A Yellow Supergiant Progenitor of a Massive Star Supernova in M51

3:31 pm

The uncertainty of science: Astronomers have determined that the star that went supernova in the Whirlpool Galaxy (M51) in June — making it the nearest supernova in 25 years — was a yellow supergiant star, not an aging red supergiant as predicted by theory. From the preprint paper:

Despite the canonical prediction that Type II supernovae arise from red supergiants, there is mounting evidence that some stars explode as yellow supergiants. A handful of Type II supernovae have been observed to arise from yellow supergiants: supernovae 1993J, 2008cn, and 2009kr. The locations of the progenitors on the Hertzsprung-Russell diagram shows clearly that these stars are not located on the predicted end points for single star stellar evolution tracks. In addition, despite arising from supposedly similar yellow supergiant progenitors, these supernovae display a wide range of properties.

The Hertzsprung-Russell diagram is a graph mapping the color of stars against their luminosity. Because color and brightness change as the star evolves over time, the graph is used by astronomers to track the birth, growth, and death of stars. That these yellow supergiants don’t appear to be at “the predicted end points for single star evolution” on the diagram is a serious problem for the theorists who have tried to explain what causes this particular type of supernova.

Which also means astronomers are still unable to tell us what stars in the sky are most likely to go supernova in the future.

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The closest supernovae in almost 25 years

7:56 pm

Astronomers have spotted the closest supernovae in almost 25 years, only 21 million light years away.

The supernova, dubbed PTF 11kly, occurred in the Pinwheel Galaxy, located in the “Big Dipper,” otherwise known as the Ursa Major constellation. It was discovered by the Palomar Transient Factory (PTF) survey, which is designed to observe and uncover astronomical events as they happen. “We caught this supernova very soon after explosion. PTF 11kly is getting brighter by the minute. It’s already 20 times brighter than it was yesterday,” said Peter Nugent, the senior scientist at Berkeley Lab who first spotted the supernova. Nugent is also an adjunct professor of astronomy at UC Berkeley. “Observing PTF 11kly unfold should be a wild ride. It is an instant cosmic classic.”

Astronomers expect the supernova to continue to brighten over the next two weeks, when it should be visible to anyone using binoculars.

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The progenitor of the May supernova in M51 identified

10:08 am

supernova 2011dh before it exploded

The progenitor star that produced the May supernovae in the Whirlpool Galaxy (also known as M51) has been identified, and it isn’t what scientists predicted.

In a preprint paper published today on the Los Alamos astro-ph website, astronomers describe the star that exploded as a yellow supergiant, not a red supergiant or Wolf-Rayet star, as predicted by the theory explaining this particular type of supernova. Moreover, though theory also favors the star being a member of a binary system, the progenitor of 2011dh appears to be a lone star, not even a member of a cluster.
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A press conference of my very own

3:57 pm

This week the Space Telescope Science Institute in Baltimore, Maryland was holding a conference on the future research possibilities of the James Webb Space Telescope, and ended the conference with a writer’s workshop/press conference today.

Not surprisingly, there was not a lot of press interest. The Webb telescope is way behind schedule and over budget, and is not scheduled for launch until 2018. For most of the press, a press conference now on what Webb might someday do is really nothing more than a NASA sales pitch. Most reporters, including myself, don’t find these kinds of press conferences of much worth.

However, after thinking about it a bit, I decided to go, with the hope that I might be able to find out some more details about the state of the telescope’s construction.

To my astonishment, I discovered how little press interest there was, as it turned out I was the only journalist there! When the presentations ended, the whole workshop became an exercise in answering Bob Zimmerman’s questions about Webb and astronomy. I felt a bit embarrassed about this, but then decided the only stupid question is the one you don’t ask, and forged ahead. Moreover, the situation probably was far more embarrassing for the press people at the Institute then it was for me.
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very big stars

11:20 am

Using the Very Large Telescope in Chile, astronomers have identifed a number of stars with masses thought to range from 150 to as much as 300 times the mass of our Sun. Fun quote from the press release:

Within [star cluster] R136, only four stars weighed more than 150 solar masses at birth, yet they account for nearly half of the wind and radiation power of the entire cluster, comprising approximately 100 000 stars in total.

Stars this gigantic are believed to end their life in an explosion so intense it destroys the star entirely, leaving nothing behind but an expanding debris cloud, from which other stars and planets (and even life) can form.

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