Stellar behemoth self-destructs in a Type IIb supernova

A star in a distant galaxy explodes as a supernova: while observing a galaxy known as UGC 9379 (left; image from the Sloan Digital Sky Survey; SDSS) located about 360 million light years away from Earth, the team discovered a new source of bright blue light (right, marked with an arrow; image from the 60-inch robotic telescope at Palomar Observatory). 

This very hot, young supernova marked the explosive death of a massive star in that distant galaxy. 

A detailed study of the spectrum (the distribution of colors composing the light from the supernova) using a technique called "flash spectroscopy" revealed the signature of a wind blown by the aging star just prior to its terminal explosion, and allowed scientists to determine what elements were abundant on the surface of the dying star as it was about to explode as a supernova, providing important information about how massive stars evolve just prior to their death, and the origin of crucial elements such as carbon, nitrogen and oxygen. 

Credit: Avishay Gal-Yam, Weizmann Institute of Science

Our Sun may seem pretty impressive: 330,000 times as massive as Earth, it accounts for 99.86 percent of the Solar System's total mass; it generates about 400 trillion trillion watts of power per second; and it has a surface temperature of about 10,000 degrees Celsius. Yet for a star, it's a lightweight.

The real cosmic behemoths are Wolf-Rayet stars, which are more than 20 times as massive as the Sun and at least five times as hot.

Because these stars are relatively rare and often obscured, scientists don't know much about how they form, live and die.

But this is changing, thanks to an innovative sky survey called the intermediate Palomar Transient Factory (iPTF), which uses resources at the National Energy Research Scientific Computing Center (NERSC) and Energy Sciences Network (ESnet), both located at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), to expose fleeting cosmic events such as supernovae.

For the first time ever, scientists have direct confirmation that a Wolf-Rayet star, sitting 360 million light years away in the Bootes constellation, died in a violent explosion known as a Type IIb supernova.

Using the iPTF pipeline, researchers at Israel's Weizmann Institute of Science led by Avishay Gal-Yam caught supernova SN 2013cu within hours of its explosion.

They then triggered ground- and space-based telescopes to observe the event approximately 5.7 hours and 15 hours after it self-destructed.

These observations are providing valuable insights into the life and death of the progenitor Wolf-Rayet.

"Newly developed observational capabilities now enable us to study exploding stars in ways we could only dream of before."

"We are moving towards real-time studies of supernovae," says Gal-Yam, an astrophysicist in the Weizmann Institute's Department of Particle Physics and Astrophysics.

He is also the lead author of a recently published Nature paper on this finding.

"This is the smoking gun. For the first time, we can directly point to an observation and say that this type of Wolf-Rayet star leads to this kind of Type IIb supernova," says Peter Nugent, who heads Berkeley Lab's Computational Cosmology Center (C3) and leads the Berkeley contingent of the iPTF collaboration.

"When I identified the first example of a Type IIb supernova in 1987, I dreamed that someday we would have direct evidence of what kind of star exploded."

"It's refreshing that we can now say that Wolf-Rayet stars are responsible, at least in some cases," says Alex Filippenko, Professor of Astronomy at UC Berkeley. Both Filippenko and Nugent are also co-authors on the Nature paper.

More information: Paper: dx.doi.org/10.1038/nature13304

Hubble extends stellar tape measure 10 times farther into space

By applying a technique called spatial scanning to an age-old method for gauging distances called astronomical parallax, scientists now can use NASA’s Hubble Space Telescope to make precision distance measurements 10 times farther into our galaxy than previously possible. 

Credit: NASA /ESA, A.Feild /STScI

Using NASA’s Hubble Space Telescope, astronomers now can precisely measure the distance of stars up to 10,000 light-years away—10 times farther than previously possible.

Astronomers have developed yet another novel way to use the 24-year-old space telescope by employing a technique called spatial scanning, which dramatically improves Hubble's accuracy for making angular measurements.

The technique, when applied to the age-old method for gauging distances called astronomical parallax, extends Hubble's tape measure 10 times farther into space.

"This new capability is expected to yield new insight into the nature of dark energy, a mysterious component of space that is pushing the universe apart at an ever-faster rate," said Noble laureate Adam Riess of the Space Telescope Science Institute (STScI) in Baltimore, Md.

Parallax, a trigonometric technique, is the most reliable method for making astronomical distance measurements, and a practice long employed by land surveyors here on Earth.

The diameter of Earth's orbit is the base of a triangle and the star is the apex where the triangle's sides meet.

The lengths of the sides are calculated by accurately measuring the three angles of the resulting triangle.

Astronomical Parallax works reliably well for stars within a few hundred light-years of Earth.

For example, measurements of the distance to Alpha Centauri, the star system closest to our sun, vary only by one arc second.

This variance in distance is equal to the apparent width of a dime seen from two miles away.

This illustration shows how the precision stellar distance measurements from NASA’s Hubble Space Telescope have been extended 10 times farther into our Milky Way galaxy than possible previously. 

This greatly extends the volume of space accessible to refining the cosmic yardstick needed for measuring the size of the universe. 

This most solid type of measurement is based on trigonometric Parallax, which is commonly used by surveyors. 

Because the stars are vastly farther away than a surveyor's sightline, Hubble must measure extremely small angles on the sky. 

Credit: NASA, ESA, and A. Feild (STScI)

Stars farther out have much smaller angles of apparent back-and-forth motion that are extremely difficult to measure.

Astronomers have pushed to extend the parallax yardstick ever deeper into our galaxy by measuring smaller angles more accurately.

This new long-range precision was proven when scientists successfully used Hubble to measure the distance of a special class of bright stars called Cepheid variables, approximately 7,500 light-years away in the northern constellation Auriga.

The technique worked so well, they are now using Hubble to measure the distances of other far-flung Cepheids.

Such measurements will be used to provide firmer footing for the so-called cosmic "distance ladder."

This ladder's "bottom rung" is built on measurements to Cepheid variables stars that, because of their known brightness, have been used for more than a century to gauge the size of the observable universe.

They are the first step in calibrating far more distant extra-galactic milepost markers such as Type Ia supernovae.

Riess and the Johns Hopkins University in Baltimore, Md., in collaboration with Stefano Casertano of STScI, developed a technique to use Hubble to make measurements as small as five-billionths of a degree.

To make a distance measurement, two exposures of the target Cepheid star were taken six months apart, when Earth was on opposite sides of the sun.

A very subtle shift in the star's position was measured to an accuracy of 1/1,000 the width of a single image pixel in Hubble's Wide Field Camera 3, which has 16.8 megapixels total.

A third exposure was taken after another six months to allow for the team to subtract the effects of the subtle space motion of stars, with additional exposures used to remove other sources of error.

GBT NRAO: Pulsar in stellar triple system makes unique gravitational laboratory

The pulsar (L) is orbited by a hot white dwarf star (C) both of which are orbited by a cooler, distant white dwarf (R)

Credit: NRAO

Astronomers using the National Science Foundation's Green Bank Telescope (GBT) have discovered a unique stellar system of two white dwarf stars and a superdense neutron star, all packed within a space smaller than Earth's orbit around the Sun.

The results appear in Nature journal and will be presented at the 223rd American Astronomical Society meeting.

The closeness of the stars, combined with their nature, has allowed the scientists to make the best measurements yet of the complex gravitational interactions in such a system.

In addition, detailed studies of this system may provide a key clue for resolving one of the principal outstanding problems of fundamental physics—the true nature of gravity.

"This triple system gives us a natural cosmic laboratory far better than anything found before for learning exactly how such three-body systems work and potentially for detecting problems with General Relativity that physicists expect to see under extreme conditions," said Scott Ransom of the National Radio Astronomy Observatory (NRAO).

West Virginia University graduate student Jason Boyles (now at Western Kentucky University) originally uncovered the pulsar as part of a large-scale search for pulsars with the GBT.

Pulsars are neutron stars that emit lighthouse-like beams of radio waves that rapidly sweep through space as the object spins on its axis.

GALEX satellite

One of the search's discoveries was a pulsar some 4200 light-years from Earth, spinning nearly 366 times per second.

Such rapidly-spinning pulsars are called millisecond pulsars, and can be used by astronomers as precision tools for studying a variety of phenomena, including searches for the elusive gravitational waves.

Subsequent observations showed that the pulsar is in a close orbit with a white dwarf star, and that pair is in orbit with another, more-distant white dwarf.

WIYN NRAO Telescope

"This is the first millisecond pulsar found in such a system, and we immediately recognized that it provides us a tremendous opportunity to study the effects and nature of gravity," Ransom said.

The scientists began an intensive observational program using the GBT, the Arecibo radio telescope in Puerto Rico, and the Westerbork Synthesis Radio Telescope in the Netherlands.

They also studied the system using data from the Sloan Digital Sky Survey, the GALEX satellite, the WIYN telescope on Kitt Peak, Arizona, and the Spitzer Space Telescope.

"The gravitational perturbations imposed on each member of this system by the others are incredibly pure and strong," Ransom said.

"The millisecond pulsar serves as an extremely powerful tool for measuring those perturbations incredibly well," he added.

More information: Nature DOI: 10.1038/nature12917

Hubble captures a stellar "sneeze"

Credit: ESA/Hubble & NASA, Acknowledgement: Gilles Chapdelaine

Look at the bright star in the middle of this image.

It appears as if it just sneezed. This sight will only last for a few thousand years—a blink of an eye in the young star's life.

If you could carry on watching for a few years you would realize it's not just one sneeze, but a sneezing fit.

This young star is firing off rapid releases of super-hot, super-fast gas, like multiple sneezes, before it finally exhausts itself.

These bursts of gas have shaped the turbulent surroundings, creating structures known as Herbig-Haro objects.

These objects are formed from the star's energetic "sneezes." Launched due to magnetic fields around the forming star, these energetic releases can contain as much mass as our home planet, and cannon into nearby clouds of gas at hundreds of kilometers/miles per second.

Shock waves form, such as the U-shape below this star. Unlike most other astronomical phenomena, as the waves crash outwards, they can be seen moving across human timescales of years.

Soon, this star will stop sneezing, and mature to become a star like our sun.

This region is actually home to several interesting objects. The star at the center of the frame is a variable star named V633 Cassiopeiae, with Herbig-Haro objects HH 161 and HH 164 forming parts of the horseshoe-shaped loop emanating from it.

The slightly shrouded star just to the left is known as V376 Cassiopeiae, another variable star that has succumbed to its neighbour's infectious sneezing fits; this star is also sneezing, creating yet another Herbig-Haro object—HH 162.

Both stars are very young and are still surrounded by dusty material left over from their formation, which spans the gap between the two.

Super-Massive Black Hole Simulator - Video

When massive suns run out of fuel and collapse a stellar black hole forms. It has the power to crush objects the size of the Sun into a 75 mile wide object. 

Astronomers are studying how these black holes produce their highest-energy light. 

Credit: NASA / GSFC

NASA Chandra Finds Fastest Wind From Stellar-Mass Black Hole

This artist's impression shows a binary system containing a stellar-mass black hole called IGR J17091-3624, or IGR J17091 for short.

The strong gravity of the black hole, on the left, is pulling gas away from a companion star on the right.

This gas forms a disk of hot gas around the black hole, and the wind is driven off this disk.

New observations with NASA's Chandra X-ray Observatory clocked the fastest wind ever seen blowing off a disk around this stellar-mass black hole.

Stellar-mass black holes are born when extremely massive stars collapse and typically weigh between five and 10 times the mass of the Sun.

The record-breaking wind is moving about twenty million miles per hour, or about three percent the speed of light.

This is nearly ten times faster than had ever been seen from a stellar-mass black hole, and matches some of the fastest winds generated by supermassive black holes, objects millions or billions of times more massive.

Another unanticipated finding is that the wind, which comes from a disk of gas surrounding the black hole, may be carrying away much more material than the black hole is capturing.

The high speed for the wind was estimated from a spectrum made by Chandra in 2011. A spectrum shows how intense the X-rays are at different energies.

Ions emit and absorb distinct features in spectra, which allow scientists to monitor them and their behavior.

A Chandra spectrum of iron ions made two months earlier showed no evidence of the high-speed wind, meaning the wind likely turns on and off over time.

Image Credit: NASA/CXC/M.Weiss

NASA Sky Survey - Cygnus X-1: A Stellar Mass Black Hole

On the left, an optical image from the Digitized Sky Survey shows Cygnus X-1, outlined in a red box.

Cygnus X-1 is located near large active regions of star formation in the Milky Way, as seen in this image that spans some 700 light years across.

An artist's illustration on the right depicts what astronomers think is happening within the Cygnus X-1 system. Cygnus X-1 is a so-called stellar-mass black hole, a class of black holes that comes from the collapse of a massive star.

The black hole pulls material from a massive, blue companion star toward it. This material forms a disk (shown in red and orange) that rotates around the black hole before falling into it or being redirected away from the black hole in the form of powerful jets.

A trio of papers with data from radio, optical and X-ray telescopes, including NASA's Chandra X-ray Observatory, has revealed new details about the birth of this famous black hole that took place millions of years ago.

Using X-ray data from Chandra, the Rossi X-ray Timing Explorer, and the Advanced Satellite for Cosmology and Astrophysics, scientists were able to determine the spin of Cygnus X-1 with unprecedented accuracy, showing that the black hole is spinning at very close to its maximum rate.

Its event horizon -- the point of no return for material falling towards a black hole -- is spinning around more than 800 times a second.

Using optical observations of the companion star and its motion around its unseen companion, the team also made the most precise determination ever for the mass of Cygnus X-1, of 14.8 times the mass of the Sun.

It was likely to have been almost this massive at birth, because of lack of time for it to grow appreciably.

The researchers also announced that they have made the most accurate distance estimate yet of Cygnus X-1 using the National Radio Observatory's Very Long Baseline Array (VLBA).

The new distance is about 6,070 light years from Earth. This accurate distance was a crucial ingredient for making the precise mass and spin determinations.

Credits: X-ray: NASA/CXC; Optical: Digitized Sky Survey

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WISE Captures a Cosmic Rose - NASA Jet Propulsion Laboratory

WISE Captures a Cosmic Rose - NASA Jet Propulsion Laboratory

A new infrared image from NASA's Wide-field Infrared Survey Explorer, or WISE, shows a cosmic rosebud blossoming with new stars.

The stars, called the Berkeley 59 cluster, are the blue dots to the right of the image center. They are ripening out of the dust cloud from which they formed, and at just a few million years old, are young on stellar time scales.

The rosebud-like red glow surrounding the hot, young stars is warm dust heated by the stars. Green "leafy" nebulosity enfolds the cluster, showing the edges of the dense, dusty cloud. This green material is from heated polycyclic aromatic hydrocarbons, molecules that can be found on Earth in barbecue pits, exhaust pipes and other places where combustion has occurred.

Red sources within the green nebula indicate a second generation of stars forming at the surface of the natal cloud, possibly as a consequence of heating and compression from the younger stars.

A supernova remnant associated with this region, called NGC 7822, indicates that a massive star has already exploded, blowing the cloud open in a "champagne flow" and leaving behind this floral remnant. Blue dots sprinkled throughout are foreground stars in our Milky Way galaxy.