Space and astronomy news
Wish you were at the A A S conference in Pasadena, California? You can watch the press conferences today live, via Dr. Pamela Gay and her minions at Astronomy Cast Live and UStream. Or just watch in the embedded player below. Here’s the schedule for Tuesday’s conferences:
9 a.m. PDT (12 noon EDT): Galaxy Discoveries
10:30 a.m. PDT (1:30 EDT): International Year of Astronomy 2009 Update from the AAS meeting.
12:40 pm PDT (3:40 EDT): Stars and Clusters
Astronomers have developed a new technique to accurately determine the ages of millisecond pulsars, the fastest-spinning stars in the universe. The standard method for estimating pulsar ages is known to yield unreliable results, especially for the fast-spinning millisecond pulsars, said Bülent Kiziltan, a graduate student in astronomy and astrophysics at University of California Sant a Cruz. “An accurate determination of pulsar ages is of fundamental importance, because it has ramifications for understanding the formation and evolution of pulsars, the physics of neutron stars, and other areas,” he said.
Continue reading “New Technique Reveals Ages of Millisecond Pulsars”
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Volcanoes have many ways to kill you, from hot lava, rocks blasted through the air, to poisonous gasses. But one of the most dangerous parts of a volcano are mud flows that can stream down their sides, following the path of river valleys. Volcano lahars have been the cause of many deaths in the last few centuries. With more people living close to or even on the flanks of steep volcanoes, even more deaths are certain.
Lahars are volcanic mudflows, and they don’t have to come directly from volcanic activity. They occur when huge amounts of volcanic ash, mixed with water flows down the side of a mountain. They can flow at speeds more than 100 km/hour, following the path of a river valley, but with the weight of concrete. Lahars are liquid when they’re flowing, and then harden almost solid when they stop. One cause of a volcano lahar is an eruption, when volcanic ash mixes with a volcano glacier, creating this muddy mixture. It’s also possible for a lahar to form when a lake or dam breaks, mixing water with ash already on the side of a volcano.
And they’ve caused terrible damage. The eruption of Nevado del Ruiz in Columbia in 1985 sent lahars down the mountainside, burying the city of Armero under 5 meters of mud and debris. A lahar coming off Mount Rainier in Washington sent a wall of mud 140 meters deep, covering a total area of 330 square kilometers – 300,000 people now live in the area covered by that lahar. In the recent eruption of Mount Pinatubo in 1991, 700 people were killed by the lahars that came down the mountain after the intense rainfall that followed the eruption.
The term lahar comes from the Indonesian word for “wave”.
We have written many article about volcanoes in Universe Today. Here’s an article about pyroclastic flows, and here’s an article Plinian eruptions which can cause pyroclastic flows.
Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.
We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.
Using a rare type of giant Cepheid variable stars as cosmic milemarkers, astronomers have found a way to measure distances to objects three times farther away in space than previously possible. Classical Cepheids are stars that pulse in brightness and have long been used as reference points for measuring distances in the nearby Universe. But astronomers have found a way to use “ultra long period” (ULP) Cepheid variables as beacons to measure distances up to 300 million light years and beyond.
Continue reading “Astronomers Find New Way to Measure Cosmic Distances”
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Using a new computer model, astronomers have determined that the black hole in the center of the M87 galaxy is at least twice as big as previously thought. Weighing in at 6.4 billion times the Sun’s mass, it is the most massive black hole yet measured, and this new model suggest that the accepted black hole masses in other large nearby galaxies may be off by similar amounts. This has consequences for theories of how galaxies form and grow, and might even solve a long-standing astronomical paradox.
Astronomers Karl Gebhardt from the University of Texas at Austin and Jens Thomas from the Max Planck Institute for Extraterrestrial Physics detailed their findings Monday at the American Astronomical Society conference in Pasadena, California.
To try to understand how galaxies form and grow, astronomers start with basic information about the galaxies today, such as what they are made of, how big they are and how much they weigh. Astronomers measure this last category, galaxy mass, by clocking the speed of stars orbiting within the galaxy.
Studies of the total mass are important, Thomas said, but “the crucial point is to determine whether the mass is in the black hole, the stars, or the dark halo. You have to run a sophisticated model to be able to discover which is which. The more components you have, the more complicated the model is.”
To model M87, Gebhardt and Thomas used one of the world’s most powerful supercomputers, the Lonestar system at The University of Texas at Austin’s Texas Advanced Computing Center. Lonestar is a Dell Linux cluster with 5,840 processing cores and can perform 62 trillion floating-point operations per second. (Today’s top-of-the-line laptop computer has two cores and can perform up to 10 billion floating-point operations per second.)
Gebhardt and Jens’ model of M87 was more complicated than previous models of the galaxy, because in addition to modeling its stars and black hole, it takes into account the galaxy’s “dark halo,” a spherical region surrounding a galaxy that extends beyond its main visible structure, containing the galaxy’s mysterious “dark matter.”
“In the past, we have always considered the dark halo to be significant, but we did not have the computing resources to explore it as well,” Gebhardt said. “We were only able to use stars and black holes before. Toss in the dark halo, it becomes too computationally expensive, you have to go to supercomputers.”
The Lonestar result was a mass for M87’s black hole several times what previous models have found. “We did not expect it at all,” Gebhardt said. He and Jens simply wanted to test their model on “the most important galaxy out there,” he said.
Extremely massive and conveniently nearby (in astronomical terms), M87 was one of the first galaxies suggested to harbor a central black hole nearly three decades ago. It also has an active jet shooting light out the galaxy’s core as matter swirls closer to the black hole, allowing astronomers to study the process by which black holes attract matter. All of these factors make M87 the “the anchor for supermassive black hole studies,” Gebhardt said.
These new results for M87, together with hints from other recent studies and his own recent telescope observations (publications in preparation), lead him to suspect that all black hole masses for the most massive galaxies are underestimated.
That conclusion “is important for how black holes relate to galaxies,” Thomas said. “If you change the mass of the black hole, you change how the black hole relates to the galaxy.” There is a tight relation between the galaxy and its black hole which had allowed researchers to probe the physics of how galaxies grow over cosmic time. Increasing the black hole masses in the most massive galaxies will cause this relation to be re-evaluated.
Higher masses for black holes in nearby galaxies also could solve a paradox concerning the masses of quasars — active black holes at the centers of extremely distant galaxies, seen at a much earlier cosmic epoch. Quasars shine brightly as the material spiraling in, giving off copious radiation before crossing the event horizon (the region beyond which nothing — not even light — can escape).
“There is a long-standing problem in that quasar black hole masses were very large — 10 billion solar masses,” Gebhardt said. “But in local galaxies, we never saw black holes that massive, not nearly. The suspicion was before that the quasar masses were wrong,” he said. But “if we increase the mass of M87 two or three times, the problem almost goes away.”
Today’s conclusions are model-based, but Gebhardt also has made new telescope observations of M87 and other galaxies using new powerful instruments on the Gemini North Telescope and the European Southern Observatory’s Very Large Telescope. He said these data, which will be submitted for publication soon, support the current model-based conclusions about black hole mass.
For future telescope observations of galactic dark haloes, Gebhardt notes that a relatively new instrument at The University of Texas at Austin’s McDonald Observatory is perfect. “If you need to study the halo to get the black hole mass, there’s no better instrument than VIRUS-P,” he said. The instrument is a spectrograph. It separates the light from astronomical objects into its component wavelengths, creating a signature that can be read to find out an object’s distance, speed, motion, temperature, and more.
VIRUS-P is good for halo studies because it can take spectra over a very large area of sky, allowing astronomers to reach the very low light levels at large distances from the galaxy center where the dark halo is dominant. It is a prototype, built to test technology going into the larger VIRUS spectrograph for the forthcoming Hobby-Eberly Telescope Dark Energy Experiment (HETDEX).
Sources: AAS, McDonald Observatory
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Thanks to the Swift satellite and several ground based optical telescopes, astronomers are learning more about so-called “dark” gamma-ray bursts, which are bright in gamma- and X-ray emissions but with little or no visible light. These dark bursts are also providing astronomers with insights on finding areas of star formation that are hidden by dust. “Our study provides compelling evidence that a large fraction of star formation in the universe is hidden by dust in galaxies that do not appear otherwise dusty,” said Joshua Bloom, associate professor of astronomy at UC Berkeley and senior author of the study, who presented his findings at the American Astronomical Society meeting in California.
Gamma-ray bursts are the universe’s biggest explosions, capable of producing so much light that ground-based telescopes easily detect it billions of light-years away. Yet, for more than a decade, astronomers have puzzled over the nature of so-called dark bursts, which produce gamma rays and X-rays but little or no visible light. They make up roughly half of the bursts detected by NASA’s Swift satellite since its 2004 launch.
The study finds that most occur in normal galaxies detectable by large, ground-based optical telescopes.
“One possible explanation for dark bursts was that they were occurring so far away their visible light was completely extinguished,” said Bloom. Thanks to the expansion of the universe and a thickening fog of hydrogen gas at increasing cosmic distances, astronomers see no visible light from objects more than about 12.9 billion light-years away. Another possibility: Dark bursts were exploding in galaxies with unusually thick amounts of interstellar dust, which absorbed a burst’s light but not its higher-energy radiation.
Using one of the world’s largest optical telescopes, the 10-meter Keck I in Hawaii, the team looked for unknown galaxies at the locations of 14 Swift-discovered dark bursts. “For eleven of these bursts, we found a faint, normal galaxy,” said Daniel Perley, the UC Berkeley graduate student who led the study. If these galaxies were located at extreme distances, not even the Keck telescope could see them.
Most gamma-ray bursts occur when massive stars run out of nuclear fuel. As their cores collapse into a black hole or neutron star, gas jets — driven by processes not fully understood — punch through the star and blast into space. There, they strike gas previously shed by the star and heat it, which generates short-lived afterglows in many wavelengths, including visible light.
The study shows that dark bursts must be similar, except for the dusty patches in their host galaxies that obscure most of the light in their afterglows.
The astronomers surveyed 14 bursts whose optical light was either much fainter than expected or completely absent. They found that almost every “dark” gamma-ray burst has a host galaxy that is able to be detected by large optical telescopes.
Star formation occurs in dense clouds that quickly fill with dust as the most massive stars rapidly age and explode, spewing newly created elements into the interstellar medium to seed new star formation. Therefore, astronomers presume that a large amount of star formation is occurring in dust-filled galaxies, although actually measuring how much dust this process has built up in the most distant galaxies has proved extremely challenging.
The stars thought to explode as gamma-ray bursts live fast and die young. Dark bursts may represent stars that never drifted far from the dusty clouds that formed them.
Gamma-ray bursts have been detected in infrared wavelengths as far out as 13.1 billion light-years. “If gamma-ray bursts were frequent 13 billion years ago — less than a billion years after the universe formed — we ought to be detecting large numbers of them,” explained team member S. Bradley Cenko, also at UC Berkeley. “We don’t, which indicates that the first stars formed at a less frenzied pace than some models suggested.”
The astronomers conclude that less than about 7 percent of dark bursts can be occurring at such distances, and they propose radio and microwave observations of the new galaxies to better understand how their dusty regions block light. A paper on the findings has been submitted to The Astronomical Journal.
Source: NASA, UC Berkeley, AAS
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A new method for measuring large astronomical distances is providing researchers with a cosmic yardstick to determine precisely how far away distant galaxies are. This could also offer a way to help determine how fast the Universe is expanding, as well as the nature of the mysterious Dark Energy that pervades the Universe. “We measured a direct, geometric distance to the galaxy, independent of the complications and assumptions inherent in other techniques. The measurement highlights a valuable method that can be used to determine the local expansion rate of the Universe, which is essential in our quest to find the nature of Dark Energy,” said James Braatz, of the National Radio Astronomy Observatory (NRAO), who spoke today at the American Astronomical Society’s meeting in Pasadena, California.
Braatz and his colleagues used the National Science Foundation’s Very Long Baseline Array (VLBA) and Robert C. Byrd Green Bank Telescope (GBT), and the Effelsberg Radio Telescope of the Max Planck Institute for Radioastronomy (MPIfR) in Germany to determine that a galaxy dubbed UGC 3789 is 160 million light-years from Earth. To do this, they precisely measured both the linear and angular size of a disk of material orbiting the galaxy’s central black hole. Water molecules in the disk act as masers to amplify, or strengthen, radio waves the way lasers amplify light waves.
The observation is a key element of a major effort to measure the expansion rate of the Universe, known as the Hubble Constant, with greatly improved precision. That effort, cosmologists say, is the best way to narrow down possible explanations for the nature of Dark Energy. “The new measurement is important because it demonstrates a one-step, geometric technique for measuring distances to galaxies far enough to infer the expansion rate of the Universe,” said Braatz.
Dark Energy was discovered in 1998 with the observation that the expansion of the Universe is accelerating. It constitutes 70 percent of the matter and energy in the Universe, but its nature remains unknown. Determining its nature is one of the most important problems in astrophysics.
“Measuring precise distances is one of the oldest problems in astronomy, and applying a relatively new radio-astronomy technique to this old problem is vital to solving one of the greatest challenges of 21st Century astrophysics,” said team member Mark Reid of the Harvard-Smithsonian Center for Astrophysics (CfA).
The work on UGC 3789 follows a landmark measurement done with the VLBA in 1999, in which the distance to the galaxy NGC 4258 — 23 million light-years — was directly measured by observing water masers in a disk of material orbiting its central black hole. That measurement allowed refinement of other, indirect distance-measuring techniques using variable stars as “standard candles.”
The measurement to UGC 3789 adds a new milepost seven times more distant than NGC 4258, which itself is too close to measure the Hubble Constant directly. The speed at which NGC 4258 is receding from the Milky Way can be influenced by local effects. “UGC 3789 is far enough that the speed at which it is moving away from the Milky Way is more indicative of the expansion of the Universe,” said team member Elizabeth Humphreys of the CfA.
Following the achievement with NGC 4258, astronomers used the highly-sensitive GBT to search for other galaxies with similar water-molecule masers in disks orbiting their central black holes. Once candidates were found, astronomers then used the VLBA and the GBT together with the Effelsberg telescope to make images of the disks and measure their detailed rotational structure, needed for the distance measurements. This effort requires multi-year observations of each galaxy. UGC 3789 is the first galaxy in the program to yield such a precise distance.
Team member Cheng-Yu Kuo of the University of Virginia presented an image of the maser disk in NGC 6323, a galaxy even more distant than UGC 3789. This is a step toward using this galaxy to provide another valuable cosmic milepost. “The very high sensitivity of the telescopes allows making such images of galaxies even beyond 300 million light years,” said Kuo.
Source: AAS
Were you tuned in to Galactic TV last week? If not, you missed an opportunity to visit with Messier object. Although the Moon was shining bright, mighty M7 could still cut through and send us a starry view! If you didn’t get a chance to see it – no worries. We did a video recording for you and saved it. Just step inside the library to watch….
(The following information is a direct quote from Wikipedia.)
OBJECT INFORMATION: M 7 – SCORPIUS
Messier 7 or M7, also designated NGC 6475 and sometimes known as known as the Ptolemy Cluster, is an open cluster of stars in the constellation of Scorpius.
The cluster is easily detectable with the naked eye, close to the “stinger” of Scorpius. It has been known since antiquity; it was first recorded by the 1st century astronomer Ptolemy, who described it as a nebula in 130 AD. Giovanni Batista Hodierna observed it before 1654 and counted 30 stars in it. Charles Messier catalogued the cluster in 1764 and subsequently included it in his list of comet-like objects as ‘M7’.
Telescopic observations of the cluster reveal about 80 stars within a field of view of 1.3° across. At the cluster’s estimated distance of 800-1000 light years this corresponds to an actual diameter of 18-25 light years. The age of the cluster is around 220 million years while the brightest star is of magnitude 5.6.
As always, you can visit the remote telescope by clicking on the IYA “LIVE Remote Cam” Logo to your right. We’ll be broadcasting whenever skies are clear and dark in Central Victoria! Enjoy…
Many thanks to all the contributors at Wikipedia for all that you do!
What would happen if the Moon wasn’t tidally locked to the Earth? What happens to all that mass and energy disappearing into a black hole? And how can we explain the space station’s crazy orbit?
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Quantum mechanics is the study of the very tiny; the nature of reality at the smallest scale. It’s a science that defies common sense, and delivers no helpful analogies. And yet it delivers the goods, making scientific predictions with incredible accuracy. Let’s look into the history of quantum theory, and then struggle to comprehend its connection to the Universe.
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Quantum Mechanics- Transcript and show notes.