STELLAR CANNIBALISM: TRUE TALES FROM THE GALACTIC CENTER
A stellar mass black hole in our galactic center has been caught in the rare act of cannibalizing its own binary companion.
A weeks-long gamma ray burst has been detected by the European Space Agency
This highly-energetic burst is thought to have been produced by the accretion of an active sun-like star being gradually ripped apart by its black hole companion. The starÃ¢â¬â¢s cannibalized gas surrounds the black hole in what is known as an accretion disk. But periodically, instabilities in this surrounding accretion disk will cause the starÃ¢â¬â¢s gas to be gobbled up by the black hole, releasing a burst of gamma rays that can last for days or weeks. Integral
will devote a few more weeks to looking for more of the same.
Unlike the massive elliptical galaxy featured in the previous post, this "topsy- turvy" starburst galaxy seen in this image by the European Southern Observatory
's Very Large Telescope
in Chile is a comparative lone wolf, undergoing an unusually large amount of stellar formation. Starburst galaxies usually result from mergers with other galaxies in galaxy clusters.
At a distance of some 15 million light years in the minor southern constellation of Reticulum, NGC 1313 shows no evidence of such mergers and it has no nearby neighbors.
Not only is it oddly asymmetrical and riddled with starbursts; deeper x-ray imaging reveals that NGC 1313
has at least two black holes, estimated to be hundreds of times the mass of our own sun. Our own Milky Way has a supermassive black hole in its center, and our galaxy is also rife with smaller black holes produced from massive single stars. But NGC 1313's intermediate-mass black holes as identified in images of ultra-luminous x-ray sources (ULX), can't be easily dismissed with current theory. That's mainly because astrophysical theory doesn't readily explain how such intermediate-sized black holes could form from a single binary (or double) star system.
FUZZY PIC OF OLE SAINT NICK?
No, it's not a bleary-eyed shot of Santa after a night out at the North Pole. It's the unusual phenomenon of twin supernovae captured in this image made by NASA's Swift satellite. The host galaxy, NGC 1316 (or Fornax A), a massive elliptical galaxy located some 75 million light years away, is now the most prodigious producer of galactic supernovae yet known.
Why would such an elliptical galaxy produce at least four supernovae in a little over a quarter of a century? That's a tough one. But some astronomers think that at least part of the fireworks may have been stirred up by Fornax A's recent merger with a nearby galactic spiral. Could be, since the galaxy is located on the fringes of the Fornax galaxy cluster in the southern constellation of Fornax (the Furnace). Massive elliptical galaxies are believed to form from the merger of one or more spiral galaxies. The devil remains in the details.
Image: courtesy NASA/Swift/Stefan Immler
PERE NOEL TO HIT YULETIDE LAUNCH PAD AT RUSSIA'S BAIKONUR SPACE CENTER
The French space agency, CNES, is planning a late December launch for a space telescope that will finally place some hard parameters on the number of terrestrial mass planets circling other stars. COROT is an acronym for Convection, Rotation and Planetary Transits, in honor of the 19th century painter Jean-Baptiste Camille Corot. The French impressionist's own work may not conjure images of "Starry Night"s as does the famous painting by his better known Dutch counterpart Vincent van Gogh. But Corot's telescopic namesake will lead the way for future terrestrial planet-finding space telescopes by surveying as many as 60,000 stars for rocky planets like our own. Kepler, an ambitious NASA follow-on mission, may see launch as early as 2008. Astrobiologists looking for earth-like analogues will likely have an exciting holiday season.
Planetary scientists are still scratching their heads over why Venus is so radically different from our own planet. An obvious explanation lies in its enigmatic atmosphere. But posing the questions isn't the same as pondering the answers. The planet's South Pole has a mysterious double-eyed vortex fueled by super-hurricane force winds.
Above: A night-side false color image of Venus' South Pole and its tumultuous and thick climatic system as taken by a visible and infrared spectrometer aboard the European Space Agency's Venus Express
spacecraft. Venus Express
is celebrating the first anniversary of its launch.
ORION EYED BY HUBBLE & SPITZER
This false color image
is a spectacular
composite of real
images taken by
NASA's Hubble and
Spitzer Space Telescopes.
The image illustrates the chaos surrounding young stars in the Trapezium, a collection of massive stars in the Orion Nebula, in the middle of Orion's sword. Researchers believe they've detected a plethora of PAHs, Polycyclic Hydrocarbons, which are thought to be a key to the evolution of carbon-based life.
Image: NASA HST/SSC
VIOLENCE ROCKS A CLUSTER
For the first time, an international team of astronomers has found observational evidence of shock waves and radio-emitting rings rippling around a giant galaxy cluster some 600 million light years away.
Observations made with the VLA (Very Large Array) radio telescope in New Mexico and with the European Space Agency's XMM-Newton x-ray observatory have confirmed the presence of both giant radio-emitting rings and magnetic shock waves around the galaxy cluster Abell 3376.
As reported in a recent issue of the journal Science, x-ray observations of Abell 3376 suggests that these emissions must have originated after the violent collision of smaller sub-clusters within the larger main cluster. These collisions are so powerful that researchers estimate that the resulting energy would be enough to keep our own sun alive and kicking for another 20 sextillion years. That's a 2 trailed by 22 zeroes.
Particle physicists and cosmologists alike are still puzzled over the origin of Ultra High Energy Cosmic Rays. Often the purview of science fiction, in reality, cosmic rays are highly-energetic atomic particles kicked up to speeds approaching that of light. While it's certain that the cluster Abell 3376 must be responsible for at least some cosmic rays, whether it is generating these ultra high energy rays is still open to debate.
Ultra High Energy Cosmic Rays --- some 100 million times more energetic than such particles created in the largest accelerators here on earth; have been detected by ground-based astronomers. But only future highly sensitive cosmic ray observatories will be able to determine if this far-flung galaxy cluster is the source of such ultra high energy particles. The bonafide origin of Ultra High Energy Cosmic Rays remains one of cosmology's greatest conundrums.
The above x-ray image from XMM-Newton shows a bullet-like supersonic
shock of x-rays emanating from gas superheated by
Abell 3376's sub-cluster collisions.
Image credit: Joydeep Bagchi, IUCAA, ESA
NO WATER ON MOON?
Radar observations made by the giant Arecibo radio telescope show no indication of water ice at the lunar South Pole. Lunar colonization advocates had hoped that the region could have harbored at least a small amount of H2O. Some researchers won't be completely convinced of this until boots hit the lunar regolith once again.
Shackleton crater pictured in this close-up image taken by the European Space Agency's SMART-1 lunar probe lies almost dead center on the lunar South Pole.
For more info:
Image: courtesy ESA
2009 IS INTERNATIONAL YEAR OF ASTRONOMY
Dr. Ken Rumstay's SPIRAL CORNER
Winter 2006 officially began on December 21st at 7:23 pm EST in the U.S. I love to stargaze this time of year; it seems as though the winter evening sky has more than its share of bright stars. Image: courtesy Roger Smith/NOAO/AURA/NSF
Orion, the most prominent constellation in the sky is high in the southeast. Look for three fairly bright stars in a straight line; this is the belt of mighty Orion! Every primitive culture has imagined a human figure in this pattern of stars, and Orion is usually portrayed as a warrior or a hunter. I prefer the latter.
Surrounding the three stars of OrionÃ¢â¬â¢s belt is a large rectangle formed by four stars, two of them exceptionally bright. At the upper-left corner is Betelgeuse, an orange supergiant star located some 520 light years from Earth. Most of our star names are of Arabic origin, though some are Greek and others Latin, and the names usually have some meaning. Translated from the Arabic, Betelgeuse means Ã¢â¬Åarmpit of the giant,Ã¢â¬Â and in artistic renderings of Orion, this star is invariably located at the base of his right arm. Some things are better left untranslated!Betelgeuse (at left) is the tenth brightest star in the sky, while Rigel in OrionÃ¢â¬â¢s left leg, is number seven. These two stars make a remarkable contrast. Both are tens of thousands of times more luminous than our own Sun, but for somewhat different reasons.
RigelÃ¢â¬â¢s tremendous power output results largely from its high surface temperature; this blue-white star is twice as hot as our Sun, and about fifty times larger in diameter. Orange Betelgeuse is cooler than our Sun, but its huge size more than compensates for this. In fact, if Betelgeuse were transposed into the center of our solar system, this orange supergiant, with a diameter 700 times that of the Sun, would stretch more than halfway to Jupiter!
Orion contains numerous fainter stars, of course, and a chart will help you pick out his sword and shield. By picturing Orion as a hunter, we can construct a little tableau around him using the surrounding stars. A hunter has to have hunting dogs, right? And Orion has two. Below Orion and to his left lies the Ã¢â¬ÅDog StarÃ¢â¬Â Sirius, the very brightest star in our night sky. This star is not nearly as luminous as Betelgeuse or Rigel, but it is much closer to us, and lies only nine light years away. To visualize Canis Major (the greater dog), picture Sirius in its head. Below Sirius lies a triangle of three faint stars; remember, the dog is standing on his hind legs, but with one paw thrust towards OrionÃ¢â¬â¢s feet.Sirius (left) in images taken by the Chandra X-ray Observatory, clearly shows its white dwarf companion. A white dwarf is a hyperdense star of compacted atomic matter that manifests itself when certain normal hydrogen-burning stars exhaust their thermonuclear fuel.
The lesser dog, Canis Minor, requires a stretch of the imagination. Above and to the left of Sirius lies the bright star of Procyon. It is in fact the eighth brightest star, falling between Rigel and Betelgeuse. Like Sirius, its brightness stems from its proximity, only eleven light years away. Canis Minor is a long, skinny dog (a dachshund?) composed of just two stars: Procyon and Gomeisa.
Now, what prey is Orion hunting? Above Orion, and a bit to the right, is another bright orange star. Aldebaran, the eye of Taurus the Bull, ranks number thirteen in our list of brightest stars. Located 65 light years away, it is slightly hotter than Betelgeuse, but not nearly so large (Ã¢â¬ÅonlyÃ¢â¬Â 25 times the SunÃ¢â¬â¢s diameter!).
Aldebaran lies at one corner of a Ã¢â¬ÅVÃ¢â¬Â of faint stars; these form the Hyades, the star cluster closest to Earth. Above Aldebaran lies a more distant, but much more familiar cluster, the Pleiades. Look for a group of five or six faint stars, forming a tiny box with a handle about the size of the of the Full Moon. Many people mistake this for the Little Dipper, but that recognizable collection of stars is much larger, and is always found in the northern sky. In Arabic, Aldebaran means Ã¢â¬Åthe followerÃ¢â¬Â: for as the Earth turns Aldebaran follows the Pleiades as they move from east to west.
Finally, to the left of Procyon and slightly above it is the constellation Gemini, the twin brothers of ancient mythology watching the hunt. Look for two bright stars close together. The upper star is Castor; his twin Pollux lies just below.If you own a telescope or a pair of binoculars, there are two easily-observed objects to look for in the winter sky. The first is of course the Pleiades (at left) in Taurus.
Easily visible to the naked eye, a telescope reveals more than a hundred stars in this fine cluster. The second is the Great Nebula in Orion.
Below the central star of his belt (at about half the distance to Rigel) appears a tight grouping of faint stars; this is OrionÃ¢â¬â¢s sword. If you have sharp eyesight, you will notice that one of the stars looks slightly fuzzy. The telescope reveals the Trapezium, a tiny cluster of four bright stars, surrounded by the faint wispy material of the nebula itself. The stars in the Trapezium are among the hottest stars known! They emit prodigious amounts of ultraviolet light that causes the surrounding interstellar gas to light up like a neon sign. Nebulae such as these are stellar nurseries; thousands of newborn stars lie deep inside.
ItÃ¢â¬â¢s worth emphasizing that even a small telescope or binoculars will reveal thousands of deep-sky objects. And even more important than the size of your telescope is the darkness and clarity of your sky. If you are considering purchasing a telescope, you might want to resist the urge to purchase the biggest one you can afford, and simply drive out of town with a smaller, more portable instrument.
But if you already have a telescope, look for a bright yellow orb rising in the east after Gemini. ThatÃ¢â¬â¢s the planet Saturn, and its beautiful system of rings makes it one of the finest of astronomical sights!
Dr. Ken Rumstay's SPIRAL CORNER
A century ago, the Milky Way would have been familiar to all but the few who lived in the largest cities.
Most Americans of the era would have been able to point out at least a dozen constellations.
Today, a plethora of electronic diversions --- including the internet --- keep us indoors at night. For those who do venture outdoors, light pollution has washed the Milky Way out of most of our skies.
The end result is that few people today have the time or inclination to study the night sky. Yet stargazing is still loved by a hardy minority of millions!
To share in the fun, thereÃ¢â¬â¢s no need to spend thousands on fancy equipment; in fact, thereÃ¢â¬â¢s no need for equipment at all.
In my astronomy classes here at Valdosta State University, I always have my students observe the heavens for at least a week before hauling out the telescopes.
This column will provide tips on how to get the most out of your night sky. All thatÃ¢â¬â¢s required are two good eyes and a clear sky.
The first thing youÃ¢â¬â¢ll notice about the night sky is that itÃ¢â¬â¢s dark! That seems obvious. But as Heinrich Olbers pointed out in 1823, this actually tells us a lot about our universe.
Without much evidence to the contrary, 18th century astronomers and philosophers believed that the universe in which we live was infinite, and had always existed.
In other words, the universe had no boundaries in space or time but Olbers pointed out that if this were true, then the universe would contain an infinite number of stars, and in whatever direction we chanced to look, our line of sight would eventually intersect the surface of one of those stars.
If so, then the entire sky would glow as brightly as the surface of the sun! This is obviously not the case, and cosmologists have since validated the theory of the big bang in which the universe had a definite beginning, forming some 14 billion years ago.
Because of OlbersÃ¢â¬â¢ Paradox, youÃ¢â¬â¢ll notice how dark everything really seems once youÃ¢â¬â¢re outside under a night time sky. Gradually as your eyes adjust and begin to dilate, you will notice gradations in brightness until your eyes are able to discern darkness.
Astronomers refer to this process as Ã¢â¬Åbecoming dark adapted,Ã¢â¬Â which takes about five minutes for a typical adult.
Once youÃ¢â¬â¢ve learned the lessons of taking the time to allow your eyes to fully adjust to the night sky, then believe it or not, if youÃ¢â¬â¢re still not convinced that you can observe the cosmos without a piece of astronomical equipment, then the first thing to buy would be a small flashlight.
Buy one small enough to hold in your mouth. That may sound crazy or even unsanitary, but itÃ¢â¬â¢s a skill that you will find handy later on.
The lens of your new flashlight should be covered with some red translucent material. Since red light tends not to overpower human night vision like light from other parts of the spectrum, both amateur and professional astronomers use it to avoid killing themselves in the dark and to avoid diminishing their Ã¢â¬Ådark adaptedÃ¢â¬Â night vision.
Plastic report binders from office supply stores typically sell translucent red covers that can be fashioned at the end of oneÃ¢â¬â¢s flashlight. If thatÃ¢â¬â¢s too hard to track down, then red cellophane or even painted-on red nail polish applied to the flashlight lens can do the trick.
In some cases, the head of the flashlight can be disassembled to allow the filter to be placed against the inner surface of the lens. If not, simply secure it into place with double-sided adhesive tape.
If observing near your own house, turn off all your outside lights and if you can convince the neighbors to join you, have them do the same. Leave the house, and use your newly fashioned red light flashlight to make your way to a spot clear of obstructions from nearby trees or buildings.
Turn off your red light, wait five minutes or so, and look upwards. Towards the north, you should be able to see the Big Dipper, the most famous and most easily recognized set of stars within any of the constellations.
Depending on the date and the time of night, the Dig Dipper may be rightside-up, upside-down, or standing on its handle. But it is always in the northern sky. In November and December it is rightside-up. But at its lowest point; if you live in the southern United States, it may be obscured by trees or buildings.
Higher in the northern sky, you will see five stars, easily visible but not terribly bright, which form a shape not unlike the letter Ã¢â¬ÅM.Ã¢â¬Â ThatÃ¢â¬â¢s the constellation of Cassiopeia, the Queen of Ethiopia, seated on her throne.
Now turn towards the west. High in the sky are three bright stars which form the so-called Ã¢â¬ÅSummer Triangle.Ã¢â¬Â The Summer Triangle is not a constellation. Its three stars are each the brightest stars in three separate constellations.
The star at the top of the triangle is Deneb; hanging down from it (and tilted at a slight angle to the left) are stars which form the shape of a cross. This is the constellation of Cygnus the swan, although the pattern is also commonly known as the Northern Cross.
Below Deneb is a much brighter star called Vega. Vega belongs to the constellation of Lyra the harp; the other stars in Lyra form a parallelogram to the left and slightly above Vega itself. These stars are faint; you may have difficulty seeing them if your sky is not very dark.
To the left of Vega, is the bright star Altair. Altair belongs to the constellation Aquila, the eagle. But it in now way resembles an eagle! At least IÃ¢â¬â¢ve never seen an eagle in it.
Next time, weÃ¢â¬â¢ll look at some of the constellations rising in the east at this time of the year. There are many myths and legends immortalized in the night sky, and they are accessible to everyone!
Image: courtesy Roger Smith/NOAO/AURA/NSF
sor:hand;" src="/blog/uploaded_images/lunar photo1-774238.jpg" border="0" alt="">Whether waxing, waning or at its fullest, our moon affects everyone who gazes skyward. It's been a fixture of our imaginations since time immemorial.
But the question of just how it formed remains in dispute.
The first edition of Cosmic Cast explores the possibilities.
NASA Johnson Space Center
the Red Sox completed that arrangement
with Dr. Ken Rumstay
Valdosta State University