Back to the main page

Archives Of Astronomy Blog

Subscribe To Astronomy Blog RSS Feed  RSS content feed What is RSS feed?


January 13, 2006, 6:42 PM CT

Search for Magic Dust

Search for Magic Dust The Swedish rocket, upon which MAGIC flew
You have probably seen shooting stars, or meteors, in the night sky, but have you ever wondered what happens to the meteoric material after it burns? Researchers in the Naval Research Laboratory's Space Science Division (SSD) are attempting to find out by directly sampling the smoke products thought to be produced by meteors as they burn. The project is called MAGIC: Mesospheric Aerosol: Genesis, Interaction and Composition.

Current theory suggests that up to 44 tons of small, grain-sized meteors burn or "ablate" in the upper atmosphere each day. It is thought that the products of this ablation process are even smaller, nanometer-sized, smoke particles (1/1000th the size of beach sand grains), which form a layer in the atmospheric region known as the mesosphere (50-90 km altitude). In turn these smoke particles are believed to be responsible for the nucleation of the mysterious and beautiful summertime phenomenon known as noctilucent clouds. These smoke particles may also be transported to lower altitudes in the atmosphere, such as the stratosphere (15-50 km altitude) where they may play a role in seeding polar stratospheric clouds, believed to be implicated in polar ozone depletion. Given the potential significance of these particles, it is surprising that they have never actually been detected. Indeed, the acronym for the NRL experiment, MAGIC, is a play on the comment of one scientist who termed these particles "magic dust".........

Posted by: Brooke      Permalink


January 13, 2006, 6:34 PM CT

Opening A New Window On The Universe

Opening A New Window On The Universe
Recent technological advances are about to open one of the most poorly explored areas of astronomy, providing researchers with critical new insights about objects such as galaxy clusters, pulsars, and supernova explosions and perhaps about extrasolar planets and the first stars and black holes ever to have formed in the Universe, according to astronomers at the Naval Research Laboratory in Washington, DC. The researchers are planning a next-generation, long wavelength radio telescope that will remove certain technical obstacles to provide unique information about celestial objects.

"With our new telescope, the Long Wavelength Array (LWA), we will be opening an entirely new window on the Universe," said Dr. Namir Kassim, a radio astronomer in NRL's Remote Sensing Division, in a presentation to the 205th meeting of the American Astronomical Society in San Diego, CA. The plans will be carried out by a collaboration of astronomers at NRL, the University of New Mexico (UNM), the Applied Research Laboratories of the University of Texas at Austin (ARL:UT), and the Los Alamos National Laboratory (LANL).

Ironically, the wavelengths for which the LWA is being designed to work, between 15 and 3.75 meters (or 20 and 80 Megahertz [MHz]) are the wavelengths at which the first radio astronomy observations occurred. Karl Jansky made the discovery of radio emission from celestial objects in 1932 at the wavelength of 15 meters (or frequency of 20 MHz). Long wavelength radio astronomy in the 1950s and 1960s produced landmark discoveries responsible for much of modern astrophysics, such as quasars and pulsars.........

Posted by: Brooke      Permalink


January 10, 2006, 11:43 PM CT

Spitzer Captures Our Galaxy's Bustling Center

Spitzer Captures Our Galaxy's Bustling Center
A new infrared mosaic from NASA's Spitzer Space Telescope offers a stunning view of the stellar hustle and bustle that takes place at our Milky Way galaxy's center. The picture shows throngs of mostly old stars, on the order of hundreds of thousands, amid fantastically detailed clouds of glowing dust lit up by younger, massive stars.

"With Spitzer, we can peer right into the heart of our own galaxy and see breathtaking detail," said Dr. Susan Stolovy of the Spitzer Science Center at the California Institute of Technology in Pasadena. "This picture is crammed with fascinating features that we have just begun to explore."

The image is available online at http://www.spitzer.caltech.edu/spitzer.

The Milky Way's core is indeed a very busy place. Stars are packed together like subway riders as they race around the supermassive black hole that lies at the center. Our sun is located 26,000 light-years away in a more peaceful, spacious neighborhood, out in the galactic suburbs. It circles the galaxy about every 225 million years, which amounts to 20 trips over the course of its 4.5-billion-year lifetime. In contrast, stars at the galactic center complete one lap in only a few million years or less.

"One question we hope to address is how stars can form so efficiently in a place like the galactic center," said Stolovy. "Stars there are still able to form in an environment with uncommonly strong magnetic fields and tidal shear forces."........

Posted by: Brooke      Permalink


January 7, 2006, 6:32 PM CT

Black hole in search of a home

Black hole in search of a home
A team of European astronomers has used two of the most powerful astronomical facilities available, the NASA/ESA Hubble Space Telescope and the ESO Very Large Telescope (VLT) at Cerro Paranal, to confidently claim the discovery of a bright quasar without a massive host galaxy. Quasars are powerful and typically very distant source of prodigious amounts of radiation. They are commonly associated with galaxies containing an active central black hole.

The team conducted a detailed study of 20 relatively nearby quasars. For 19 of them, they found, as expected, that these super massive black holes are surrounded by a host galaxy. But when they studied the bright quasar HE0450-2958, located some 5 billion light-years away, they could not find evidence for a host galaxy. This, the astronomers suggest, may indicate a rare case of a collision between a seemingly normal spiral galaxy and an exotic object harbouring a very massive black hole.

With masses up to hundreds of millions that of the Sun, super massive black holes are commonly found in the centres of the most massive galaxies, including our own Milky Way. These black holes sometimes dramatically manifest themselves by devouring matter that they gravitationally swallow from their surroundings. The best fed of these shine as quasars (the name quasar is a contraction of quasi-stellar object, as they had initially been confused with stars).........

Posted by: Brooke      Permalink


January 2, 2006, 10:47 PM CT

Laser To Take Clearest Images Of The Center Of The Milky Way

Laser To Take Clearest Images Of The Center Of The Milky Way
UCLA astronomers and colleagues have taken the first clear picture of the center of our Milky Way galaxy, including the area surrounding the supermassive black hole, using a new laser virtual star at the W.M. Keck observatory in Hawaii.

"Everything is much clearer now," said Andrea Ghez, UCLA professor of physics and astronomy, who headed the research team. "We used a laser to improve the telescope's vision - a spectacular breakthrough that will help us understand the black hole's environment and physics. It's like getting Lasik surgery for the eyes, and will revolutionize what we can do in astronomy".

Astronomers are used to working with images that are blurred by the Earth's atmosphere. However, a laser virtual star, launched from the Keck telescope, can be used to correct the atmosphere's distortions and clear up the picture. This new technology, called Laser Guide Star adaptive optics, will lead to important advances for the study of planets in our solar system and outside of our solar system, as well as galaxies, black holes, and how the universe formed and evolved, Ghez said.

"We have worked for years on techniques for 'beating the distortions in the atmosphere' and producing high-resolution images," she said. "We are pleased to report the first Laser Guide Star adaptive optics observations of the center of our galaxy".........

Posted by: Brooke      Permalink


December 31, 2005, 8:32 PM CT

Galaxy Collisions And The Universe

Galaxy Collisions And The Universe
More than half of the largest galaxies in the nearby universe have collided and merged with another galaxy in the past two billion years, according to a Yale astronomer in a study using hundreds of images from two of the deepest sky surveys ever conducted.

The idea of large galaxies being assembled primarily by mergers rather than evolving by themselves in isolation has grown to dominate cosmological thinking. However, a troubling inconsistency within this general theory has been that the most massive galaxies appear to be the oldest, leaving minimal time since the Big Bang for the mergers to have occurred.

"Our study found these common massive galaxies do form by mergers. It is just that the mergers happen quickly, and the features that reveal the mergers are very faint and therefore difficult to detect," said Pieter van Dokkum, assistant professor of astronomy at Yale University, and sole author of the paper appearing in the December 2005 issue of the Astronomical Journal.

The paper uses two recent deep surveys done with the National Science Foundation's 4-meter telescopes at Kitt Peak National Observatory and Cerro Tololo Inter-American Observatory, known as the NOAO Deep Wide-Field Survey and the Multiwavelength Survey by Yale/Chile. Together, these surveys covered an area of the sky 50 times larger than the size of the full Moon and more than 5,000 times larger than the famous Hubble Deep Field........

Posted by: Brooke      Permalink


December 31, 2005, 8:16 PM CT

Did Our Sun Capture Alien Worlds?

Did Our Sun Capture Alien Worlds?
Computer simulations show a close encounter with a passing star about 4 billion years ago may have given our solar system its abrupt edge and put small, alien worlds into distant orbits around our sun.

The study, which used a supercomputer at NASA's Jet Propulsion Laboratory in Pasadena, Calif., was published in the Dec. 2 issue of the journal Nature by physicist Ben Bromley of the University of Utah and astronomer Scott Kenyon of the Smithsonian Astrophysical Observatory in Cambridge, Mass.

Bromley and Kenyon simulated what would have happened if our sun and another star in our Milky Way galaxy had passed a relatively close 14 billion to 19 billion miles from each other a few hundred million years after our solar system formed. At that time, our solar system was a swirling "planetary disk" of gas, dust and rocks, with planets newly formed from the smaller materials.

Imagine the encounter of two young solar systems by envisioning two circular saw blades brushing past each other while spinning rapidly. When they make contact, their outer edges are buzzed off by the other saw. But in the case of planetary disks, colliding rocks at the edges of the solar systems are pulverized into pebbles, causing particles to be flung in all directions.

"Any objects way out in the planetary disk would be stirred up greatly," says Bromley, an associate professor of physics at the University of Utah.........

Posted by: Brooke      Permalink


December 31, 2005, 2:24 PM CT

Hubble To 'weigh' Dog Star's Companion

Hubble To 'weigh' Dog Star's Companion
White dwarfs are important to theories of both stellar and cosmological evolution. New results published in the Monthly Notices of the Royal Astronomical Society provide for the first time an accurate measurement of the weight of the nearest white dwarf, Sirius B, companion of the brightest star in the sky. It turns out that Sirius's companion, despite being smaller than the Earth, has a mass that is 98% that of our own Sun.

For astronomers, it's always been a source of frustration that the nearest white-dwarf star is buried in the glow of the brightest star in the nighttime sky. This burned-out stellar remnant is a faint companion of the brilliant blue-white Dog Star, Sirius, located in the winter constellation Canis Major.

Now, an international team of astronomers has used the keen eye of the NASA/ESA Hubble Space Telescope to isolate the light from the white dwarf, called Sirius B. The new results allow them to measure precisely the white dwarf's mass based on how its intense gravitational field alters the wavelengths of light emitted by the star.

"Studying Sirius B has challenged astronomers for more than 140 years," said Martin Barstow of the University of Leicester, U.K., who is the leader of the observing team. "Only with Hubble have we at last been able to obtain the observations we need, uncontaminated by the light from Sirius, in order to measure its change in wavelengths".........

Posted by: Brooke      Permalink


December 31, 2005, 2:21 PM CT

Most detailed image of the Crab Nebula

Most detailed image of the Crab Nebula
A new Hubble image - among the largest ever produced with the Earth-orbiting observatory - gives the most detailed view so far of the entire Crab Nebula. The Crab is arguably the single most interesting object, as well as one of the most studied, in all of astronomy. The image is the largest ever taken with Hubble's WFPC2 workhorse camera.

The Crab Nebula is one of the most intricately structured and highly dynamical objects ever observed. The new Hubble image of the Crab was assembled from 24 individual exposures taken with the NASA/ESA Hubble Space Telescope's Wide Field and Planetary Camera 2 (WPFC2) and is the highest resolution image of the entire Crab Nebula ever made.

The Crab Nebula is a six-light-year-wide expanding remnant of a star's supernova explosion. Japanese and Chinese astronomers witnessed this violent event nearly 1,000 years ago in 1054.

The filaments are the tattered remains of the star and consist mostly of hydrogen. The rapidly spinning neutron star embedded in the centre of the nebula, only barely visible in this Hubble image, is the dynamo powering the nebula's eerie interior bluish glow. The blue light comes from electrons whirling at nearly the speed of light around magnetic field lines from the neutron star. The neutron star, like a lighthouse, ejects twin beams of radiation that appear to pulse 30 times a second due to the neutron star's rotation. A neutron star is the crushed ultra-dense core of the exploded star.........

Posted by: Brooke      Permalink


December 31, 2005, 2:18 PM CT

Young stars sculpt gas with powerful outflows

Young stars sculpt gas with powerful outflows
This Hubble Space Telescope view shows one of the most dynamic and intricately detailed star-forming regions in space, located 210,000 light-years away in the Small Magellanic Cloud (SMC), a satellite galaxy of our Milky Way. At the centre of the region is a brilliant star cluster called NGC 346. A dramatic structure of arched, ragged filaments with a distinct ridge surrounds the cluster.

A torrent of radiation from the hot stars in the cluster NGC 346, at the centre of this Hubble image, eats into denser areas around it, creating a fantasy sculpture of dust and gas. The dark, intricately beaded edge of the ridge, seen in silhouette, is especially dramatic. It contains several small dust globules that point back towards the central cluster, like windsocks caught in a gale.

Energetic outflows and radiation from hot young stars are eroding the dense outer portions of the star-forming region, formally known as N66, exposing new stellar nurseries. The diffuse fringes of the nebula prevent the energetic outflows from streaming directly away from the cluster, leaving instead a trail of filaments marking the swirling path of the outflows.

The NGC 346 cluster is resolved into at least three sub-clusters and collectively contains dozens of hot, blue, high-mass stars, more than half of the known high-mass stars in the entire SMC galaxy. A myriad of smaller, compact clusters is also visible throughout the region.........

Posted by: Brooke      Permalink


Older Blog Entries   1   2   3   4   5   6   7   8   9   10   11   12