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Posts Tagged ‘stars’

Delta Cephei’s Hidden Companion


Bow shock around star Delta Cephei. Credit: NASA/JPL-Caltech/M

Bow shock around star Delta Cephei. Credit: NASA/JPL-Caltech/M

To measure distances in the universe, astronomers use cepheids, a family of variable stars whose luminosity varies with time. Their role as distance calibrators has brought them attention from researchers for more than a century. While it was thought that nearly everything was known about the prototype of cepheids, named Delta Cephei, a team of researchers at the University of Geneva (UNIGE), the Johns Hopkins University, and the European Space Agency (ESA), have now discovered that this star has a hidden companion. They have published an article about the discovery in The Astrophysical Journal.

Delta Cephei, prototype of the cepheids, which has given its name to all similar variable stars, was discovered 230 years ago by the English astronomer John Goodricke. Since the early 20th century, scientists have been interested in measuring cosmic distances using a relationship between these stars’ periods of pulsation and their luminosities (intrinsic brightness), discovered by the American Henrietta Leavitt. Today, researchers from the Astronomical Observatory of UNIGE, Johns Hopkins University and the ESA show that Delta Cephei is, in fact, a double star, made up of a cepheid-type variable star and a companion that had thus far escaped detection, probably because of its low luminosity. Yet, pairs of stars, called binaries, complicate the calibration of the period-luminosity relationship, and can bias the measurement of distances. This is a surprising discovery, since Delta Cephei is one of the most studied stars, of which scientists thought they knew almost everything.

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Strange Supernova Is “Missing Link” In Gamma-Ray Burst Connection


CREDIT: Bill Saxton, NRAO/AUI/NSF

CREDIT: Bill Saxton, NRAO/AUI/NSF

Astronomers using the National Science Foundation’s Very Large Array (VLA) have found a long-sought “missing link” between supernova explosions that generate gamma-ray bursts (GRBs) and those that don’t. The scientists found that a stellar explosion seen in 2012 has many characteristics expected of one that generates a powerful burst of gamma rays, yet no such burst occurred.

“This is a striking result that provides a key insight about the mechanism underlying these explosions,” said Sayan Chakraborti, of the Harvard-Smithsonian Center for Astrophysics (CfA). “This object fills in a gap between GRBs and other supernovae of this type, showing us that a wide range of activity is possible in such blasts,” he added.

The object, called Supernova 2012ap (SN 2012ap) is what astronomers term a core-collapse supernova. This type of blast occurs when the nuclear fusion reactions at the core of a very massive star no longer can provide the energy needed to hold up the core against the weight of the outer parts of the star. The core then collapses catastrophically into a superdense neutron star or a black hole. The rest of the star’s material is blasted into space in a supernova explosion.

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Astronomers Identify The Closest Known Flyby Of A Star To Our Solar System: A Dim Star That Passed Through The Oort Cloud 70,000 Years Ago

February 18, 2015 Leave a comment

Credit: Michael Osadciw/University of Rochester.

Credit: Michael Osadciw/University of Rochester.

A group of astronomers from the US, Europe, Chile and South Africa have determined that 70,000 years ago a recently discovered dim star is likely to have passed through the solar system’s distant cloud of comets, the Oort Cloud. No other star is known to have ever approached our solar system this close – five times closer than the current closest star, Proxima Centauri.

In a paper published in Astrophysical Journal Letters, lead author Eric Mamajek from the University of Rochester and his collaborators analyzed the velocity and trajectory of a low-mass star system nicknamed “Scholz’s star.”

The star’s trajectory suggests that 70,000 years ago it passed roughly 52,000 astronomical units away (or about 0.8 light years, which equals 8 trillion kilometers, or 5 trillion miles). This is astronomically close; our closest neighbor star Proxima Centauri is 4.2 light years distant. In fact, the astronomers explain in the paper that they are 98% certain that it went through what is known as the “outer Oort Cloud” – a region at the edge of the solar system filled with trillions of comets a mile or more across that are thought to give rise to long-period comets orbiting the Sun after their orbits are perturbed.

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NASA’s Airborne Observatory Begins 2015 Science Campaign

January 15, 2015 Leave a comment

Credit: NASA/USRA/Greg Perryman

Credit: NASA/USRA/Greg Perryman

The Stratospheric Observatory for Infrared Astronomy, or SOFIA, Program began its third season of science flights on Jan. 13, 2015. SOFIA is NASA’s next generation flying observatory and is fitted with a 2.5-meter (100-inch) diameter telescope that studies the universe at infrared wavelengths.

“Last night’s flight used the German Receiver for Astronomy at Terahertz Frequencies (GREAT) spectrometer to study the chemical composition and motions of gas in a star-forming region, a young star, and a supernova remnant,” said Pamela Marcum, NASA’s SOFIA project scientist. “Observing at infrared wavelengths enables us to see through interstellar dust to record the spectral signatures of molecules in these regions. From this we can study the abundances of molecules and their formation process.”

Water vapor in the Earth’s atmosphere absorbs infrared radiation, preventing a large section of the infrared spectrum from reaching ground-based observatories. SOFIA is a heavily modified Boeing 747 Special Performance jetliner that flies at altitudes between 39,000 to 45,000 feet (12 to 14 km), above more than 99 percent of Earth’s atmospheric water vapor giving astronomers the ability to study celestial objects at wavelengths that cannot be seen from ground-based observatories.

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The Gemini Planet Imager Produces Stunning Observations In Its First Year

January 8, 2015 Leave a comment

Image credit: Christian Marois (NRC Canada), Patrick Ingraham (Stanford University) and the GPI Team

Image credit: Christian Marois (NRC Canada), Patrick Ingraham (Stanford University) and the GPI Team

Stunning exoplanet images and spectra from the first year of science operations with the Gemini Planet Imager (GPI) were featured today in a press conference at the 225th meeting of the American Astronomical Society (AAS) in Seattle, Washington. The Gemini Planet Imager GPI is an advanced instrument designed to observe the environments close to bright stars to detect and study Jupiter-like exoplanets (planets around other stars) and see protostellar material (disk, rings) that might be lurking next to the star.

Marshall Perrin (Space Telescope Science Institute), one of the instrument’s team leaders, presented a pair of recent and promising results at the press conference. He revealed some of the most detailed images and spectra ever of the multiple planet system HR 8799. His presentation also included never-seen details in the dusty ring of the young star HR 4796A. “GPI’s advanced imaging capabilities have delivered exquisite images and data,” said Perrin. “These improved views are helping us piece together what’s going on around these stars, yet also posing many new questions.”

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A New, Public View Of The Sky

January 8, 2015 Leave a comment

Photo: Adam Block and Vic Eden/Mount Lemmon SkyCenter/UA

Photo: Adam Block and Vic Eden/Mount Lemmon SkyCenter/UA

For the first time, scientists and the public are beginning to see the large-scale structure of the universe, thanks to the Sloan Digital Sky Survey. UA scientists provide scientific expertise and crucial technology to the largest project ever undertaken to map the cosmos.

On Jan. 6, the Sloan Digital Sky Survey issued its latest public data release, the final release of the third epoch of the survey. Weighing in at more than 100 Terabytes, “Data Release 12” (DR12) contains measurements of the properties of nearly half a billion stars and galaxies, making it one of the largest and richest databases in the history of astronomy.

“The most astonishing feature of the SDSS is the breadth of ground-breaking research it enables,” said Daniel Eisenstein of the Harvard-Smithsonian Center for Astrophysics, the director of SDSS-III. Eisenstein started the survey during his tenure as a professor at the UA’s Steward Observatory, one of the survey’s partner institutions.

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‘Perfect Storm’ Quenching Star Formation Around A Supermassive Black Hole

December 17, 2014 Leave a comment

A combined Hubble Space Telescope / ALMA image of NGC 1266. Credit: NASA/ESA Hubble; ALMA (NRAO/ESO/NAOJ)

A combined Hubble Space Telescope / ALMA image of NGC 1266. Credit: NASA/ESA Hubble; ALMA (NRAO/ESO/NAOJ)

High-energy jets powered by supermassive black holes can blast away a galaxy’s star-forming fuel, resulting in so-called “red and dead” galaxies: those brimming with ancient red stars yet containing little or no hydrogen gas to create new ones.

Now astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have discovered that black holes don’t have to be nearly so powerful to shut down star formation. By observing the dust and gas at the center of NGC 1266, a nearby lenticular galaxy with a relatively modest central black hole, the astronomers have detected a “perfect storm” of turbulence that is squelching star formation in a region that would otherwise be an ideal star factory.

This turbulence is stirred up by jets from the galaxy’s central black hole slamming into an incredibly dense envelope of gas. This dense region, which may be the result of a recent merger with another smaller galaxy, blocks nearly 98 percent of material propelled by the jets from escaping the galactic center.

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