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Category Archives: 13. The death of stars: recycling

Adapted from AIP Advances press release, March 18, 2014:

A powerful, new computer model provides fresh insight into the turbulent death throes of supernovae (see Section 13.2, p. 337).

Credit. W. D. Arnett, C. Meakin and M. Viallet/AIP Advances

The new model, developed by W. David Arnett (U. of Arizona) and colleagues, is the first to represent the start of a supernova collapse in three dimensions. It shows how the turbulent mixing of elements inside stars causes them to expand, contract, and spit out matter before they finally detonate. Arnett’s new model better matches what we observe in supernova remnants, with ejections of star material mixing with the material expelled during its final explosion.

The article, ‘Chaos and turbulent nucleosynthesis prior to a supernova explosion’ by David Arnett, Casey Meakin and Maxime Viallet is published in the journal AIP Advances.

Links: full AIP press release; the research article.

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A bright supernova discovered only six weeks ago in a nearby galaxy is provoking new questions about the exploding stars that scientists use as their main yardstick for measuring the Universe. (See this earlier post about SN 2014J.)

SN2014J-350

Credit: W. Zheng and A. Filippenko (UC Berkeley)

When The Cosmos author Alex Filippenko’s research team at UC Berkeley looked for the supernova in data collected by the Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory, they discovered that the robotic telescope had actually taken a photo of it 37 hours after it appeared, unnoticed, on January 14.

Combining this observation with another chance observation by a Japanese amateur astronomer, Filippenko’s team was able to calculate that SN 2014J had unusual characteristics – it brightened faster than expected for a Type Ia supernova and, even more intriguing, it exhibited the same unexpected, rapid brightening as another supernova that KAIT discovered and imaged last year (SN 2013dy).

Alex Filippenko reports: “Now, two of the three most recent and best-observed Type Ia supernovae are weird, giving us new clues to how stars explode. This may be teaching us something general about Type Ia supernovae that theorists need to understand. Maybe what we think of as ‘normal’ behavior for these supernovae is actually unusual, and this weird behavior is the new normal.”

A paper describing the SN 2014J observations was posted online this week by The Astrophysical Journal Letters and will appear in the March 1 print issue.

Links: UC Berkeley press release (including further background on Type Ia supernovae); the research paper in ApJL.

An exceptionally close supernova (a stellar explosion, see Section 13.2, p. 337) discovered on January 21, 2014, has become the focus of observatories around the globe, as well as a suite of orbiting spacecraft. The blast, designated SN 2014J, occurred in the bright galaxy M82 and lies about 12 million light-years away. This makes it the nearest optical supernova in two decades and potentially the closest type Ia supernova to occur during the life of currently operating space missions.

Credit and copyright: Adam Block, Mt. Lemmon SkyCenter, U. Arizona.

SN 2014J was first spotted as an unfamiliar source in the otherwise familiar galaxy by teaching fellow Steve Fossey and astronomy workshop students Ben Cooke, Tom Wright, Matthew Wilde, and Guy Pollack at the University College London Observatory on the evening of January 21.

To capitalize on this unusual event, astronomers have planned observations with the NASA/ESA Hubble Space Telescope and NASA’s Chandra X-ray Observatory, Nuclear Spectroscopic Telescope Array (NuSTAR), Fermi Gamma-ray Space Telescope, and Swift missions.

Links: Further information from the NASA press release; hi-res image from APOD January 24, 2014.

A massive telescope buried in the Antarctic ice has detected 28 record-breaking, extremely high-energy neutrinos – elementary particles that likely originate far beyond our Solar System. (See Sections 12.7c and 13.2g)

The achievement, which comes nearly 25 years after the pioneering idea of detecting neutrinos in ice, provides the first solid evidence for astrophysical neutrinos from cosmic accelerators and has been hailed as the dawn of a new age of astronomy. The team of researchers that detected the neutrinos with the IceCube Neutrino Observatory in Antarctica published a paper describing the detections on November 22, 2013, in the journal Science.

Credit: IceCube Collaboration

The neutrinos had energies greater than 1,000,000,000,000,000 electron volts, or 1 peta-electron volt (PeV). Two of these neutrinos had energies many thousands of times higher than the highest-energy neutrino that any man-made particle accelerator has ever produced. (1 joule of energy = 6.2419 × 1018 eV.)

While not telling scientists what the cosmic accelerators are or where they’re located, the IceCube results do provide scientists with a compass that can help guide them to the answers. Unlike other cosmic particles, neutrinos are electrically neutral and nearly massless, so that they travel through space in a straight line from their point of origin, passing through virtually everything in their path without being deflected by interstellar masses and magnetic fields.

Credit: Jamie Yang, IceCube Collaboration

The IceCube observatory consists of over 5,000 basketball-sized light detectors called Digital Optical Modules (DOMs). These are suspended along 86 strings that are embedded in a cubic kilometer of clear ice starting 1.5 kilometers beneath the Antarctic surface. Out of the trillions of neutrinos that pass through the ice each day, a couple of hundred will collide with oxygen nuclei, yielding the blue light of Cherenkov radiation that IceCube’s DOMs detect.

Links: LBNL press release; U. Wisconsin press release (with image gallery); Penn State press release (with movie).

One of the most famous objects in the sky, the Cassiopeia A supernova remnant (see Figure 13-18c) – Cas A, for short – has been rendered for display like never before, thanks to NASA’s Chandra X-ray Observatory and a new project from the Smithsonian Institution. A new three-dimensional viewer allows users to interact with many one-of-a-kind objects from the Smithsonian as part of a large-scale effort to digitize many of the Institutions objects and artifacts.

Scientists have combined data from Chandra, NASA’s Spitzer Space Telescope, and ground-based facilities to construct a unique 3D model of the 300-year old remains of a stellar explosion that blew a massive star apart, sending the stellar debris rushing into space at millions of miles per hour. The collaboration with this new Smithsonian 3D project allows the astronomical data collected on Cas A to be featured and highlighted in an open-access program.

casa_525

Credit: NASA/CSC/SAO

To coincide with Cas A being featured in this new 3D effort, a specially-processed version of Chandra’s data of this supernova remnant has been released. This new image shows with better clarity the appearance of Cas A in different energy bands, which will aid astronomers in their efforts to reconstruct details of the supernova process such as the size of the star, its chemical makeup, and the explosion mechanism. The color scheme used in this image is the following: low-energy X-rays are red, medium-energy ones are green, and the highest-energy X-rays detected by Chandra are colored blue.

Cas A is the only astronomical object to be featured in the new Smithsonian 3D project. This and other objects in the collection – which include the Wright brothers plane, a 1600-year-old stone Buddha, a gunboat from the Revolutionary War, and fossil whales from Chile – were showcased in the Smithsonian X 3D event on November 13th and 14th at the Smithsonian in Washington, DC.

Links: Smithsonian X 3D beta tour; Chandra X-ray Center press release; NASA press release; YouTube movie of a fly-through.

A strange stellar pair nearly 7,000 light-years from Earth has provided physicists with a unique cosmic laboratory for studying the nature of gravity. The extremely strong gravity of a massive neutron star in orbit with a companion white dwarf star puts competing theories of gravity to a test more stringent than any available before. Once again, Albert Einstein’s General Theory of Relativity, published in 1915, comes out on top.

A newly-discovered pulsar — a spinning neutron star with twice the mass of the Sun — and its white-dwarf companion, orbiting each other once every two and a half hours, has put gravitational theories to the most extreme test yet. Observations of the system, dubbed PSR J0348+0432, produced results consistent with the predictions of General Relativity.

In such a system, the orbits decay and gravitational waves are emitted, carrying energy from the system. By very precisely measuring the time of arrival of the pulsar’s radio pulses over a long period of time, astronomers can determine the rate of decay and the amount of gravitational radiation emitted. The large mass of the neutron star in PSR J0348+0432, the closeness of its orbit with its companion, and the fact that the companion white dwarf is compact but not another neutron star, all make the system an unprecedented opportunity for testing alternative theories of gravity.

Einstein’s predictions were found to hold up quite well, despite the extreme nature of the system. which is good news for researchers hoping to make the first direct detection of gravitational waves.

Credit: Antoniadis, et al.

 

The original NRAO press release may be viewed here.