Dec 16, 2015 08:03 PM
Gaps in the Grammar of the Universe?
http://bigthink.com/errors-we-live-by/ga...e-universe
EXCERPT: Does our grasp of the grammar of the universe have gaps? Is our chosen language in tune with key patterns? [...] The issue isn’t the math. It’s presuming that physics-like math is the one true way (the only properly precise language). Mathematics itself needs different languages in its different domains....
Star Wars' Worlds Exoplanet Scientists Can't Help But Love
http://www.space.com/31377-star-wars-pla...picks.html
EXCERPT: [...] Last week, close to 350 exoplanet scientists gathered in Hawaii for the American Astronomical Society's Extreme Solar Systems III conference. Space.com took the opportunity to ask 20 of these folks about their favorite "Star Wars" worlds. [...] The scientists we polled were almost evenly split among three worlds from the "Star Wars" original trilogy: Hoth (from "Star Wars: Episode V - The Empire Strikes Back,"), Tatooine (from "Star Wars: Episode IV - A New Hope,"), and the moon of the planet Endor (from "Star Wars: Episode VI - Return of the Jedi."). Some of the scientists chose a particular planet because it reminded them of a place on Earth; others picked their favorite world based on how it related to the topic they study; and still others chose a fictional world that they hope will resemble a real one that may be discovered in the future....
ALMA reveals planetary construction sites
http://www.eurekalert.org/pub_releases/2...121415.php
Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found the clearest indications yet that planets with masses several times that of Jupiter have recently formed in the discs of gas and dust around four young stars. Measurements of the gas around the stars also provide additional clues about the properties of those planets.
Planets are found around nearly every star, but astronomers still do not fully understand how -- and under what conditions -- they form. To answer such questions, they study the rotating discs of gas and dust present around young stars from which planets are built. But these discs are small and far from Earth, and the power of ALMA was needed for them to reveal their secrets.
A special class of discs, called transitional discs, have a surprising absence of dust in their centres, in the region around the star. Two main ideas have been put forward to explain these mysterious gaps. Firstly, the strong stellar winds and intense radiation could have blown away or destroyed the encircling material [1]. Alternatively, massive young planets in the process of formation could have cleared the material as they orbit the star [2].
The unparalleled sensitivity and image sharpness of ALMA have now allowed the team of astronomers, led by Nienke van der Marel from the Leiden Observatory in the Netherlands to map the distribution of gas and dust in four of these transitional discs better than ever before [3]. This in turn has allowed them to choose between the two options as the cause of the gaps for the first time.
The new images show that there are significant amounts of gas within the dust gaps [4]. But to the team's surprise, the gas also possessed a gap, up to three times smaller than that of the dust.
This could only be explained by the scenario in which newly formed massive planets have cleared the gas as they travelled around their orbits, but trapped the dust particles further out [5].
"Previous observations already hinted at the presence of gas inside the dust gaps," explains Nienke van der Marel. "But as ALMA can image the material in the entire disc in much greater detail than other facilities, we could rule out the alternative scenario. The deep gap points clearly to the presence of planets with several times the mass of Jupiter, creating these caverns as they sweep through the disc."
Remarkably, these observations were conducted utilising just one tenth of the current resolving power of ALMA, as they were performed whilst half of the array was still under construction on the Chajnantor Plateau in northern Chile.
Further studies are now needed to determine whether more transitional discs also point towards this planet-clearing scenario, although ALMA's observations have, in the meantime, provided astronomers with a valuable new insight into the complex process of planetary formation.
"All the transitional discs studied so far that have large dust cavities also have gas cavities. So, with ALMA, we can now find out where and when giant planets are being born in these discs, and compare these results with planet formation models," says Ewine van Dishoeck, also of Leiden University and the Max Planck Institute for Extraterrestrial Physics in Garching [6]. "Direct planetary detection is just within reach of current instruments, and the next generation telescopes currently under construction, such as the European Extremely Large Telescope, will be able to go much further. ALMA is pointing out where they will need to look."
- - - - - -
Notes
[1] This process, which clears the dust and gas from the inside out, is known as photoevaporation.
[2] Such planets are difficult to observe directly -- eso1310 and previous studies at millimetre wavelengths eso1325 have failed to achieve a sharp view of their inner, planet-forming zones where these different explanations could be put to the test. Other studies eso0827 could not measure the bulk of the gas in these discs.
[3] The four targets of these investigations were SR 21 , HD 135344B (also known as SAO 206462), DoAr 44 and Oph IRS 48.
[4] The gas present in transitional discs consists primarily of hydrogen, and is traced through observations of the carbon monoxide -- or CO -- molecule.
[5] The process of dust trapping is explained in an earlier release -- eso1325.
[6] Other examples include the HD 142527 -- eso1301 and here -- http://almaobservatory.org/en/press-room...ary-system and J1604-2130 transitional discs.
Gamma rays from distant galaxy tell story of an escape
http://www.eurekalert.org/pub_releases/2...121515.php
RELEASE: A flare of very high-energy gamma rays emitted from a galaxy halfway across the universe has put new bounds on the amount of background light in the universe and given astrophysicists clues to how and where such gamma rays are produced.
The galaxy, known as PKS 1441+25, is a rare type of galaxy called a blazar, a tremendously bright beacon powered by a supermassive black hole at the heart of the galaxy. Blazars are intrinsically unsteady light sources and can sometimes emit flares ten to a hundred times brighter than their baseline emissions. A flare from PKS 1441+25 was detected in April 2015 and observed by a range of telescopes sensitive to different wavelengths, including the Very Energetic Radiation Imaging Telescope Array System (VERITAS) in Arizona.
"With VERITAS, we detected gamma rays from this unusual object at the highest energies observed on Earth," said Jonathan Biteau, who led the analysis of the data as a postdoctoral researcher at UC Santa Cruz.
Such very high-energy gamma rays were unexpected, he said, because they faced a good chance of being annihilated at some point during the 7.6 billion years they spent traveling toward Earth. When high-energy gamma rays collide with lower-energy photons, they annihilate and create an electron-positron pair. To reach telescopes on Earth, the gamma rays from PKS 1441+25 had to avoid a tight net of photons surrounding the vicinity of the black hole, as well as a looser net of photons, the extragalactic background light (EBL), that fills the universe.
The EBL is a faint glow that pervades the space between galaxies, consisting of photons from all the stars and galaxies that have existed. It is hard to measure because there are so many bright sources of light nearby. Astronomers have used cosmological models to estimate the EBL, galaxy counts to set lower limits, and gamma rays from blazars (as well as direct observations of dark patches of sky) to set upper limits. The farther gamma rays have to travel the more likely they are to encounter photons of the EBL and annihilate, so the detection of a source 7.6 billion light-years away was surprising.
"With PKS 1441+25, we can now place tight constraints on this loose net of photons," said Biteau. "This is clearly the opening of a new era where we can compare source-by-source measurements and start to probe the cosmic evolution of the extragalactic background light."
Biteau, now an associate professor at Institut de Physique Nucléaire d'Orsay in France, and UC Santa Cruz graduate student Caitlin Johnson are corresponding authors of a paper on the findings to be published in Astrophysical Journal Letters and currently available online. Johnson analyzed data from the Fermi Gamma-ray Space Telescope which complemented the data from VERITAS.
"Combining the Fermi data with the VERITAS data enabled us to make the constraints on the EBL much tighter," she said. "The window is slowly narrowing."
But what about the tight net of photons around the tremendously bright blazar? That helps locate the region where the gamma rays were emitted, said coauthor David Williams, adjunct professor of physics at UC Santa Cruz. "If the gamma rays were produced close to the black hole, the radiation fields there are strong enough to absorb them. So the fact that the gamma rays are getting out of the galaxy at all indicates they were produced farther away from the black hole," Williams said.
The black hole is surrounded by a glowing disk of hot gas and dust swirling in toward the center. Some of this infalling matter, instead of being swallowed by the black hole, gets channeled into two powerful jets emitted from the poles of the spinning black hole, perpendicular to the accretion disk. One of these jets is pointing in our direction, "like a flashlight shining in our eyes," Johnson said.
Physicists are still debating the exact mechanism behind gamma-ray emissions from the jets, but PKS 1441+25 provides important clues, Biteau said. "With observations across the entire electromagnetic spectrum, we have now realized that the location of the gamma-ray emissions for this source has to be at least a tenth of a light year away from the black hole. Otherwise, none of the gamma rays would escape," he said.
The researchers estimated that the emission region is probably at a distance of about five light years from the black hole, much further than expected. According to a leading scenario for the gamma-ray emissions, high energy electrons are accelerated to near the speed of light in the jet, interact with photons, and transfer their energy, boosting the photons to gamma-ray energies.
"These observations constitute a fantastic step forward in our understanding of blazars as cosmic accelerators and as light beacons for gamma ray cosmology," Biteau said.
http://bigthink.com/errors-we-live-by/ga...e-universe
EXCERPT: Does our grasp of the grammar of the universe have gaps? Is our chosen language in tune with key patterns? [...] The issue isn’t the math. It’s presuming that physics-like math is the one true way (the only properly precise language). Mathematics itself needs different languages in its different domains....
Star Wars' Worlds Exoplanet Scientists Can't Help But Love
http://www.space.com/31377-star-wars-pla...picks.html
EXCERPT: [...] Last week, close to 350 exoplanet scientists gathered in Hawaii for the American Astronomical Society's Extreme Solar Systems III conference. Space.com took the opportunity to ask 20 of these folks about their favorite "Star Wars" worlds. [...] The scientists we polled were almost evenly split among three worlds from the "Star Wars" original trilogy: Hoth (from "Star Wars: Episode V - The Empire Strikes Back,"), Tatooine (from "Star Wars: Episode IV - A New Hope,"), and the moon of the planet Endor (from "Star Wars: Episode VI - Return of the Jedi."). Some of the scientists chose a particular planet because it reminded them of a place on Earth; others picked their favorite world based on how it related to the topic they study; and still others chose a fictional world that they hope will resemble a real one that may be discovered in the future....
ALMA reveals planetary construction sites
http://www.eurekalert.org/pub_releases/2...121415.php
Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found the clearest indications yet that planets with masses several times that of Jupiter have recently formed in the discs of gas and dust around four young stars. Measurements of the gas around the stars also provide additional clues about the properties of those planets.
Planets are found around nearly every star, but astronomers still do not fully understand how -- and under what conditions -- they form. To answer such questions, they study the rotating discs of gas and dust present around young stars from which planets are built. But these discs are small and far from Earth, and the power of ALMA was needed for them to reveal their secrets.
A special class of discs, called transitional discs, have a surprising absence of dust in their centres, in the region around the star. Two main ideas have been put forward to explain these mysterious gaps. Firstly, the strong stellar winds and intense radiation could have blown away or destroyed the encircling material [1]. Alternatively, massive young planets in the process of formation could have cleared the material as they orbit the star [2].
The unparalleled sensitivity and image sharpness of ALMA have now allowed the team of astronomers, led by Nienke van der Marel from the Leiden Observatory in the Netherlands to map the distribution of gas and dust in four of these transitional discs better than ever before [3]. This in turn has allowed them to choose between the two options as the cause of the gaps for the first time.
The new images show that there are significant amounts of gas within the dust gaps [4]. But to the team's surprise, the gas also possessed a gap, up to three times smaller than that of the dust.
This could only be explained by the scenario in which newly formed massive planets have cleared the gas as they travelled around their orbits, but trapped the dust particles further out [5].
"Previous observations already hinted at the presence of gas inside the dust gaps," explains Nienke van der Marel. "But as ALMA can image the material in the entire disc in much greater detail than other facilities, we could rule out the alternative scenario. The deep gap points clearly to the presence of planets with several times the mass of Jupiter, creating these caverns as they sweep through the disc."
Remarkably, these observations were conducted utilising just one tenth of the current resolving power of ALMA, as they were performed whilst half of the array was still under construction on the Chajnantor Plateau in northern Chile.
Further studies are now needed to determine whether more transitional discs also point towards this planet-clearing scenario, although ALMA's observations have, in the meantime, provided astronomers with a valuable new insight into the complex process of planetary formation.
"All the transitional discs studied so far that have large dust cavities also have gas cavities. So, with ALMA, we can now find out where and when giant planets are being born in these discs, and compare these results with planet formation models," says Ewine van Dishoeck, also of Leiden University and the Max Planck Institute for Extraterrestrial Physics in Garching [6]. "Direct planetary detection is just within reach of current instruments, and the next generation telescopes currently under construction, such as the European Extremely Large Telescope, will be able to go much further. ALMA is pointing out where they will need to look."
- - - - - -
Notes
[1] This process, which clears the dust and gas from the inside out, is known as photoevaporation.
[2] Such planets are difficult to observe directly -- eso1310 and previous studies at millimetre wavelengths eso1325 have failed to achieve a sharp view of their inner, planet-forming zones where these different explanations could be put to the test. Other studies eso0827 could not measure the bulk of the gas in these discs.
[3] The four targets of these investigations were SR 21 , HD 135344B (also known as SAO 206462), DoAr 44 and Oph IRS 48.
[4] The gas present in transitional discs consists primarily of hydrogen, and is traced through observations of the carbon monoxide -- or CO -- molecule.
[5] The process of dust trapping is explained in an earlier release -- eso1325.
[6] Other examples include the HD 142527 -- eso1301 and here -- http://almaobservatory.org/en/press-room...ary-system and J1604-2130 transitional discs.
Gamma rays from distant galaxy tell story of an escape
http://www.eurekalert.org/pub_releases/2...121515.php
RELEASE: A flare of very high-energy gamma rays emitted from a galaxy halfway across the universe has put new bounds on the amount of background light in the universe and given astrophysicists clues to how and where such gamma rays are produced.
The galaxy, known as PKS 1441+25, is a rare type of galaxy called a blazar, a tremendously bright beacon powered by a supermassive black hole at the heart of the galaxy. Blazars are intrinsically unsteady light sources and can sometimes emit flares ten to a hundred times brighter than their baseline emissions. A flare from PKS 1441+25 was detected in April 2015 and observed by a range of telescopes sensitive to different wavelengths, including the Very Energetic Radiation Imaging Telescope Array System (VERITAS) in Arizona.
"With VERITAS, we detected gamma rays from this unusual object at the highest energies observed on Earth," said Jonathan Biteau, who led the analysis of the data as a postdoctoral researcher at UC Santa Cruz.
Such very high-energy gamma rays were unexpected, he said, because they faced a good chance of being annihilated at some point during the 7.6 billion years they spent traveling toward Earth. When high-energy gamma rays collide with lower-energy photons, they annihilate and create an electron-positron pair. To reach telescopes on Earth, the gamma rays from PKS 1441+25 had to avoid a tight net of photons surrounding the vicinity of the black hole, as well as a looser net of photons, the extragalactic background light (EBL), that fills the universe.
The EBL is a faint glow that pervades the space between galaxies, consisting of photons from all the stars and galaxies that have existed. It is hard to measure because there are so many bright sources of light nearby. Astronomers have used cosmological models to estimate the EBL, galaxy counts to set lower limits, and gamma rays from blazars (as well as direct observations of dark patches of sky) to set upper limits. The farther gamma rays have to travel the more likely they are to encounter photons of the EBL and annihilate, so the detection of a source 7.6 billion light-years away was surprising.
"With PKS 1441+25, we can now place tight constraints on this loose net of photons," said Biteau. "This is clearly the opening of a new era where we can compare source-by-source measurements and start to probe the cosmic evolution of the extragalactic background light."
Biteau, now an associate professor at Institut de Physique Nucléaire d'Orsay in France, and UC Santa Cruz graduate student Caitlin Johnson are corresponding authors of a paper on the findings to be published in Astrophysical Journal Letters and currently available online. Johnson analyzed data from the Fermi Gamma-ray Space Telescope which complemented the data from VERITAS.
"Combining the Fermi data with the VERITAS data enabled us to make the constraints on the EBL much tighter," she said. "The window is slowly narrowing."
But what about the tight net of photons around the tremendously bright blazar? That helps locate the region where the gamma rays were emitted, said coauthor David Williams, adjunct professor of physics at UC Santa Cruz. "If the gamma rays were produced close to the black hole, the radiation fields there are strong enough to absorb them. So the fact that the gamma rays are getting out of the galaxy at all indicates they were produced farther away from the black hole," Williams said.
The black hole is surrounded by a glowing disk of hot gas and dust swirling in toward the center. Some of this infalling matter, instead of being swallowed by the black hole, gets channeled into two powerful jets emitted from the poles of the spinning black hole, perpendicular to the accretion disk. One of these jets is pointing in our direction, "like a flashlight shining in our eyes," Johnson said.
Physicists are still debating the exact mechanism behind gamma-ray emissions from the jets, but PKS 1441+25 provides important clues, Biteau said. "With observations across the entire electromagnetic spectrum, we have now realized that the location of the gamma-ray emissions for this source has to be at least a tenth of a light year away from the black hole. Otherwise, none of the gamma rays would escape," he said.
The researchers estimated that the emission region is probably at a distance of about five light years from the black hole, much further than expected. According to a leading scenario for the gamma-ray emissions, high energy electrons are accelerated to near the speed of light in the jet, interact with photons, and transfer their energy, boosting the photons to gamma-ray energies.
"These observations constitute a fantastic step forward in our understanding of blazars as cosmic accelerators and as light beacons for gamma ray cosmology," Biteau said.