Posted on by Fraser Cain

How Much Did the Earth Move?

NASA scientists using data from the Indonesian earthquake calculated it affected Earth’s rotation, decreased the length of day, slightly changed the planet’s shape, and shifted the North Pole by centimeters. The earthquake that created the huge tsunami also changed the Earth’s rotation.

Dr. Richard Gross of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., and Dr. Benjamin Fong Chao, of NASA’s Goddard Space Flight Center, Greenbelt, Md., said all earthquakes have some affect on Earth’s rotation. It’s just they are usually barely noticeable.

“Any worldly event that involves the movement of mass affects the Earth’s rotation, from seasonal weather down to driving a car,” Chao said.

Gross and Chao have been routinely calculating earthquakes’ effects in changing the Earth’s rotation in both length-of- day as well as changes in Earth’s gravitational field. They also study changes in polar motion that is shifting the North Pole. The “mean North pole” was shifted by about 2.5 centimeters (1 inch) in the direction of 145 degrees East Longitude. This shift east is continuing a long-term seismic trend identified in previous studies.

They also found the earthquake decreased the length of day by 2.68 microseconds. Physically this is like a spinning skater drawing arms closer to the body resulting in a faster spin. The quake also affected the Earth’s shape. They found Earth’s oblateness (flattening on the top and bulging at the equator) decreased by a small amount. It decreased about one part in 10 billion, continuing the trend of earthquakes making Earth less oblate.

To make a comparison about the mass that was shifted as a result of the earthquake, and how it affected the Earth, Chao compares it to the great Three-Gorge reservoir of China. If filled, the gorge would hold 40 cubic kilometers (10 trillion gallons) of water. That shift of mass would increase the length of day by only 0.06 microseconds and make the Earth only very slightly more round in the middle and flat on the top. It would shift the pole position by about two centimeters (0.8 inch).

The researchers concluded the Sumatra earthquake caused a length of day change too small to detect, but it can be calculated. It also caused an oblateness change barely detectable, and a pole shift large enough to be possibly identified. They hope to detect the length of day signal and pole shift when Earth rotation data from ground based and space-borne position sensors are reviewed.

The researchers used data from the Harvard University Centroid Moment Tensor database that catalogs large earthquakes. The data is calculated in a set of formulas, and the results are reported and updated on a NASA Web site.

The massive earthquake off the west coast of Indonesia on December 26, 2004, registered a magnitude of nine on the new “moment” scale (modified Richter scale) that indicates the size of earthquakes. It was the fourth largest earthquake in one hundred years and largest since the 1964 Prince William Sound, Alaska earthquake.

The devastating mega thrust earthquake occurred as a result of the India and Burma plates coming together. It was caused by the release of stresses that developed as the India plate slid beneath the overriding Burma plate. The fault dislocation, or earthquake, consisted of a downward sliding of one plate relative to the overlying plate. The net effect was a slightly more compact Earth. The India plate began its descent into the mantle at the Sunda trench that lies west of the earthquake’s epicenter. For information and images on the Web, visit:

http://www.nasa.gov/vision/earth/lookingatearth/indonesia_quake.html .

For details on the Sumatra, Indonesia Earthquake, visit the USGS Internet site:

http://neic.usgs.gov/neis/bulletin/neic_slav_ts.html .

For information about NASA and agency programs Web, visit:

http://www.nasa.gov .

JPL is managed for NASA by the California Institute of Technology in Pasadena.

Original Source: NASA News Release

Posted on by Fraser Cain

Three Largest Stars Discovered

Image credit: Hubble
Astronomers are announcing today the identification of three red supergiants that have the largest diameters of any normal stars known, more than a billion miles across. The report is being presented by Ms. Emily Levesque, an undergraduate junior at MIT, who has been working with an international team of astronomers, including Philip Massey (Lowell Observatory, in Flagstaff, Arizona), Knut Olsen (Cerro Tololo Inter-American Observatory, in Chile), Bertrand Plez and Eric Josselin (Universite de Montpellier II, in France), and Andre Maeder and Georges Meynet (Geneva Observatory, in Switzerland). Nat White of Lowell Observatory also participated in the study. The findings are being presented today at the American Astronomical Society meeting in San Diego, California. The group studied a sample of 74 red supergiant stars in the Milky Way. This research is significant in finally reconciling theory and observation for these stars. Red supergiants, massive stars nearing the ends of their lifetimes, are extremely cool and luminous ? and very large.

The three biggest stars are KW Sagitarii (distance 9,800 light-years), V354 Cephei (distance 9,000 light-years), and KY Cygni (distance 5,200 light-years), all with radii about 1500 times that of the Sun, or about 7 astronomical units (AU). For comparison, the well-known red supergiant star Betelgeuse in the constellation Orion is known from other work to have a radius about 650 times that of the Sun, or about 3 AU. If one of these stars were placed in the sun’s location, its outer layers would extend to midway between the orbits of Jupiter (5.2 AU) and Saturn (9.5 AU) [see figure].

The previous record holder, Herschel’s “Garnet Star” (also known as “mu Cephei”) comes in a close fourth in size in the study. The only other star for which a very large size has been claimed is the binary star system VV Cephei, which consists of a red supergiant and a hot companion orbiting within a common gaseous envelope, in which the gravitational forces of the companion have distended the surface of the supergiant and the meaning of the size of the star is therefore fuzzy. None of the stars in the new study are believed to be binaries, and thus their properties tell us about the extreme sizes that normal stars reach.

The study used the National Science Foundation’s 2.1-meter (84-inch) telescope at Kitt Peak National Observatory, located outside of Tucson, Arizona, and the 1.5-m (60-inch) telescope at Cerro Tololo Inter-American Observatory, located outside of La Serena, Chile, in the foothills of the Andes. The new observations were combined with state-of-the-art computer models that contain improved data on the molecules that are found in the outer layers of these cool stars. The analysis yielded the most accurate temperatures yet found for this type of object. The temperatures of the coolest red supergiants are about 3450 Kelvins, or about 10 percent warmer than previously thought. Combined with modern estimates of the distances of these stars, the group was able to determine the stellar sizes as well.

“The significance of this study is that for the first time in many decades there is good agreement between the theory of how large and cool these stars should be, and how large and cool we actually observe them to be,” explained Dr. Philip Massey, Astronomer at Lowell Observatory, the project’s leader. “For the past two decades there has been a significant disagreement. The problem in this case turned out NOT to be the theory, but the ‘observations’ ? the conversion between the observed qualities (brightness and spectral type) and the deduced properties (temperature and luminosity and/or size) needed improvement.” The team’s new analysis provides a better means of converting between these properties.

“These stars are not the most massive known,” noted Levesque. “They are only 25 times the mass of the sun, while the most massive stars may have as much material as 150 suns. Nor are they the most luminous, as they are only about 300,000 times the luminosity of the sun, not the factor of 5 million or so attributed to the most luminous stars. They aren’t even the coldest stars known ? brown dwarfs have such low temperatures that they can’t even fuse hydrogen. But the combination of modestly high luminosities and relatively low temperatures DOES mean that they are the biggest stars known, in terms of their stellar diameters.”

The study has been submitted to the Astrophysical Journal for review and publication. Support was provided by a grant to Lowell Observatory by the National Science Foundation, which also provided support for Ms. Levesque’s participation in the project through the Research Experiences for Undergraduates program at Northern Arizona University.

Original Source: Lowell Observatory

Posted on by Fraser Cain

Hubble Could Be Seeing a Planet

Unique follow up observations carried out with NASA’s Hubble Space Telescope are providing important supporting evidence for the existence of a candidate planetary companion to a relatively bright young brown dwarf star located 225 light-years away in the southern constellation Hydra.

Astronomers at the European Southern Observatory’s Very Large Telescope (VLT) in Chile detected the planet candidate in April 2004 with infrared observations using adaptive optics to sharpen their view. The VLT astronomers spotted a faint companion object to the brown dwarf star 2MASSWJ 1207334-393254 (aka 2M1207). The object is a candidate planet because it is only one-seven-hundredth the brightness of the brown dwarf (at the longer-than-Hubble wavelengths observed with the VLT) and glimmers at barely 1800 degrees Fahrenheit, which is cooler than a light bulb filament.

Because an extrasolar planet has never been directly imaged before, this remarkable observation required Hubble’s unique abilities to do follow-up observations to test and validate if it is indeed a planet. Hubble’s Near Infrared Camera and Multi-Object Spectrometer (NICMOS) camera conducted complementary observations taken at shorter infrared wavelength observations unobtainable from the ground. This wavelength coverage is important because it is needed to characterize the object’s physical nature.

Very high precision measurements of the relative position between the dwarf and companion were obtained with NICMOS in August 2004. The Hubble images were compared to the earlier VLT observations to try and see if the two objects are really gravitationally bound and hence move across the sky together. Despite the four months between the VLT and NICMOS observations, astronomers say they can almost rule out the probability that the suspected planet is really a background object, because there was no noticeable change in its position relative to the dwarf.

If the two objects are indeed gravitationally bound together they are at least 5 billion miles apart, about 30 percent farther apart than Pluto is from the Sun. Given the mass of 2M1207, inferred from its spectrum, the companion object would take a sluggish 2,500 years to complete one orbit. Therefore, any relative motion seen between the two on much shorter time scales would reveal the candidate planet to be a background interloper and not a gravitationally bound planet.

“The NICMOS photometry supports the conjecture that the planet candidate is about five times the mass of Jupiter if it indeed orbits the brown dwarf,” says Glenn Schneider of the University of Arizona. “The NICMOS position measurements, relative to VLT’s, indicate the object is a true (and thus orbiting) companion at a 99 percent level of confidence — but further planned Hubble observations are required to eliminate the 1 percent chance that it is a coincidental background object which is not orbiting the dwarf.”

Schneider is presenting these latest Hubble observations today at the meeting of the American Astronomical Society in San Diego, Calif.

The candidate planet and dwarf are in the nearby TW Hydrae association of young stars that are estimated to be no older than 8 million years. The Hubble NICMOS observations found the object to be extremely red and relatively much brighter at longer wavelengths. The colors match theoretical expectations for an approximately 8 million-year-old object that is about five times as massive as Jupiter.

Further Hubble observations by the NICMOS team are planned in April 2005.

Original Source: Hubble News Release

Posted on by Fraser Cain

What’s Up This Week – Jan 10 – Jan 16, 2005

Monday, January 10 – On this day in 1946, the US Army Signal Corps set an “astronomy first” by successfully bouncing radar waves off the Moon. Earlier today, the New Moon made its closest approach Earth (perigee) for this year – its gravitation favouring higher than normal tides – but tonight we will celebrate its absence by taking a celestial journey to the Eridanus/Fornax studies.

Starting with Alpha Fornacis, we find a beautiful disparate double, a “white” star with its yellow/orange companion. But this is not about doubles tonight – it is about deep sky – and Alpha is merely a stepping stone. Our next hop is to Beta, the guide to the NGC 1049 to the southwest. Only large aperture may reach for this one. The NGC 1049 appears to me as a very soft, very faded globular cluster. It is like a “ghost” – seen, yet not seen – an ethereal hint of what lay on the outer reaches of our own galaxy. Next stop is north, and slightly to the east for a galaxy revealed in both small and large scopes – the NGC 1097. In a small scope (114 mm minimum) it shows averted as an upright bar of light that pulls at the tips. The large scope (12.5″ and larger) will reveal a barred-spiral. The NGC 1097 is truly beautiful. The central portion of the galaxy is evenly illuminated from end to end, but at each of those ends lay the spiral arms, twisting away opposite of each other into space.

Next hop is Omega – again a double star – but much closer in magnitude this time! They can be separated easily enough with scopes at a minimum of power, but let’s head back for Alpha. Go north and a bit west into the border of Eridanus in search of NGC 1232. Smaller scopes can only make out of soft circle of light, while large ones reveal a spiral galaxy. It is not an exceptional one, but it contains a very “stellar” nucleus and fades out evenly towards its frontiers. Aversion plus magnification can only add just the most wispy of hints of a single spiral arm. From there, head for Tau 4, and a target you will repeat again and again! The NGC 1300 is an “all scopes” kind of galaxy and one you can appreciate. Smaller (114 mm) and mid-sized (150 mm) scopes will show a very bright core and transient arms upon aversion that remind me of a cat’s eye marble. Larger scopes can hold it direct, allowing for study of perhaps the finest barred-spiral I have ever encountered. Its nucleus is a bright point of light set within its structure, the “bar” itself being rather ephemeral and almost nebula-like in appearance. Two very well defined arms wrap round it, with mottled indications suggesting giant clusters of stars in this faraway island universe! A most fascinating galaxy…

Now back to Tau 4, and a shift north and a bit east to return to the “River”. NGC 1332 is our next stop, an elliptical galaxy. Just a silver oval in the small scope, and not overly improved by aperture. With the additional light gathering ability, the NGC 1332 now contains a much brighter nucleus, and very even form. Let’s go south back down into “the Furnace” and breathe the scopes east to capture planetary nebula NGC 1360. Say hello to a ball of greenish light in a small scope and go for aperture. Now we’re talking! The planetary now stretches itself out and reveals a bright, almost distracting inner star. When you can peel your concentration away from it, averted vision reveals a certain vagueness – almost a transparency – inside one very kicking planetary! Just a touch southwest of here brings up yet another bright barred-spiral, the NGC 1398. Once again, we’re looking at easily distinguishable in most scopes, but what intrigues me is WHY does this area of the sky contain so many barred spirals?! What “string” resonates in the vast reaches of space that spawns this structure?!

As the radio plays music in the night keeping us company, shall I take you on a radio journey? Let’s go to Chi 1 ,2, 3 and drop southwest for the NGC 1316. Hey up! Just another elliptical, right? Wrong. The NGC 1316 is THE radio source for Fornax A. (i wonder if it does rock and roll? 😉 The little oval smear of light shows well averted in small scopes, but aperture brings up a bonus! Just a tiny bit north of “the Source” lies a companion known the NGC 1317! Let’s hop back to the Chi triangle, and go for yet another. A degree east will bring up the NGC 1365 – “lightning” frozen in the form of a barred-spiral galaxy. There are no “hints” in form here. This 11th magnitude galaxy shows well in mid-aperture, with aversion in small and will come alive in larger scopes. The central core is Z-shaped, very definite and bright. The central bar continues to hold up to direct vision, bracketed by two arms that differ. One tends to diffuse away a bit, but the other holds a very solid brightness.

Large scopes? Come with me, and be thankful that our feet are upon the ground. I am going to take you to a galaxy playground in this region – one degree northeast of NGC 1365. Using a mid-sized scope, in this new “field” you will see two ellipticals, the NGC 1399, and the NGC 1404. For experienced galaxy hunters, you know how to play this game. Look directly at those galaxies, yet “feel” the field with your eyes. Ah, you see it! Now let’s put the power of aperture to work and watch them dance! With a quality wide-field eyepiece in a 12.5″ telescope, the Fornax Galaxy cluster is stunning. How many do you see in one degree? Nine? When you touch the scope, how many in the relative field? Twelve? Fifteen? Yes, of course some of them we’ve already visited. The tightest portion of the cluster also has designations: NGC 1374, NGC 1379, NGC 1380, NGC 1381, NGC 1387, NGC 1399, NGC 1404, NGC 1386 and NGC 1389. They will be tiny and faint, but very beautiful. You can see now why we have taken so much time to study Eridanus. It shares its soul with Fornax.

And tonight it has shared with us…

Tuesday, January 11 – Over the next two days, be sure to set your alarm for approximately 45 minutes before local sunrise to witness Mercury and Venus slow dancing on the horizon! At approximately 0.3 degrees apart, this wonderful union will be quite low (about a half fist above the horizon), but SkyWatchers will appreciate watching as the pair seems to “trade places” in the morning sky. How long can you follow them from your location?

Tonight the tender crescent of the one-day old Moon will create a similar challenge as it makes its appearance at dusk on the western horizon. Thankfully it will have set long before skies get truly dark, giving deep sky hunters an additional night to continue studies!

Wednesday, January 12 – Tonight we will greet the “Old Moon In The New Moon’s Arms” as the two-day old Selene will make a brief appearance after sunset to the west. The origins of this romantic phrase are very apropos, for many shadowy details of the full Moon are softly visible thanks to reflected sunlight from our atmosphere known as “Earthshine”. For those viewing with either telescopes of binoculars tonight, take the time to study the emerging Mare Crisium. Crisium is a unique for it does not connect with other maria and is seen on the curved limb. Viewing an area like Crisium on a curvature makes its dimensions appear smaller than they truly are. In terms of true size, Mare Crisium has about the same area as the state of Washington, yet appears visually to be only about half that size!

For Southern Hemisphere viewers, Comet C/2003 K4 (LINEAR) will be a splendid target for binoculars and small telescopes at around magnitude 7.8. On the night of January 12, it will be very close to Lambda Pictor.

Thursday, January 13 – Today Saturn reaches opposition, (my how a year flies when you’re having fun! 😉 In astronomical terms, this means that Saturn and the Sun are on opposite sides of the sky. Opposition also means that not only is Saturn closer than normal, but it will be visible all night long. Take the time tonight to watch as the Sun sets and notice its departure to the southwest – Saturn will rise at precisely the same angle to the northeast!

Tonight, let’s wait for the Moon to get as far west as possible and set our sites about halfway between Theta Auriga and El Nath. Our study object will be open cluster, M37! Apparently discovered by Messier himself in 1764, this galactic cluster will appear almost nebula-like to binoculars and very small telescopes – but comes to perfect resolution with larger instruments.

At around 4700 light years away, and spanning a massive 25 light years, the M37 is often billed as the finest of the three Aurigan opens for bigger scopes. Offering beautiful resolvability, this one contains around 150 members down to magnitude 12, and has an estimated population in excess of 500. What makes it unique? As you view, you will note the presence of several “red giants”. For the most part, open clusters are usually comprised of stars that are all about the same “age”, but the brightest star in the M37 appears orange in color and not blue! So what exactly is going on in here? Apparently some of these big, bright stars have evolved much faster – consuming their fuel at an incredible rate. Other stars in this cluster are still quite young in the cosmological scale, yet they all left the “nursery” at the same time! In theory, this allows us to judge the relative age of open clusters. For example, M36 is around 30 million years old and the M38 about 40, but the presence of the “red giants” in the M37 puts its estimated age at 150 million years! Just awesome…

Friday, January 14 –
Happy New Year to those who follow the Julian calendar! Today begins the year 2758 AUC and tonight we will celebrate antiquity by studying two craters on the Moon named for mythological figures – Atlas and Hercules.

Easily identified on the terminator in the northern hemisphere, this pair of craters can be spotted in binoculars and offer a wealth of detail to the small telescope. The smaller one to the west is Atlas and the larger to the east is Hercules. Because they are near the terminator tonight, their differences in depth make for a fascinating contrast in illumination. Note Hercules’ bright west wall – it is so deep that the interior is literally hidden in shadow! Atlas, only under slightly higher “sunrise”, will show the majority of grey floor with a boundary of dark shadows on its east wall and a brilliant west crest. Sharp-eyed observers may note a “Y” shaped rimae in Atlas’ interior with a small central peak caught in its intersection. Wishing you steady skies!

Saturday, January 15 – Ready for another weekend treat? Then realize for the next two nights, the “Magnificent Machholz” will race closely past a previous study star – Algol!

As we remember, Algol is a fascinating variable and for most of us it will be at minima (magnitude 3.4) tonight. Using our binoculars, we will find the 4th magnitude Comet Machholz about 2 degrees to the lower right of the “Demon Star”. Although the Moon will hamper tracing the tail for most, try de-focusing and comparing magnitudes. The fun is about to begin! If skies permit, return again tomorrow to the Machholz/Algol pairing – Beta Persi has now jumped to a magnitude brighter and the comet has moved even closer and to its lower left!

Hey, now… Astronomy doesn’t get much more exciting than that!

Sunday, January 16 – Wake up! Early this morning will be the peak of Delta Cancrid meteor shower. Yes, it’s a pretty obscure one – no exciting parent comet or disintegrating asteroid to blame it on – but since the Moon will long be set, why not give it a go? The radiant will be just slightly west of the M44 “Beehive Cluster”, making a worthy trip with binoculars. The Delta Cancrids are not exactly prolific – with a rate of only about 4 per hour – but they are very fast!

Ad speaking of fast, Mercury is now below Venus and gradually pulling away. Our planetary “pair” are now separated by 0.7 of a degree this morning and will part by almost a full degree tomorrow morning. Only SkyWatchers with an open horizon to the east will be able to catch them, because they are barely 2 degrees above the horizon before dawn. Enjoy them one last time for they are about to disappear!

Is it back yet? Yes. The Moon will definitely figure prominently in the coming days, but don’t be discouraged. The first few days of this week will see it set in ample time to enjoy deep sky studies, search out bright objects and continue to enjoy the swift progress of Comet Machholz! I hope I have challenged veteran observers and inspired those “new to the game” to seek out the beauty of our Cosmos. Until next week? I thank you for your many kind comments! I might be clouded out, but your words are as welcome as a clear night. So ask for the Moon, my friends… But keep on reaching for the stars!

Light Speed… ~Tammy Plotner

Posted on by Fraser Cain

Spitzer Sees the Aftermath of a Planetary Collision

Astronomers say a dusty disc swirling around the nearby star Vega is bigger than earlier thought. It was probably caused by collisions of objects, perhaps as big as the planet Pluto, up to 2,000 kilometers (about 1,200 miles) in diameter.

NASA’s Spitzer Space Telescope has seen the dusty aftermath of this “run-in.” Astronomers think embryonic planets smashed together, shattered into pieces and repeatedly crashed into other fragments to create ever-finer debris. Vega’s light heats the debris, and Spitzer’s infrared telescope detects the radiation.

Vega, located 25 light-years away in the constellation Lyra, is the fifth brightest star in the night sky. It is 60 times brighter than our sun. Observations of Vega in 1984, with the Infrared Astronomical Satellite, provided the first evidence for dust particles around a typical star. Because of Vega’s proximity and because its pole faces Earth, it provides a great opportunity for detailed study of the dust cloud around it.

“Vega’s debris disc is another piece of evidence demonstrating the evolution of planetary systems is a pretty chaotic process,” said lead author of the study, Dr. Kate Su of the University of Arizona, Tucson, Ariz. The findings were presented today at the 205th meeting of the American Astronomical Society in San Diego.

Like a drop of ink spreading out in a glass of water, the particles in Vega’s dust cloud don’t stay close to the star long. “The dust we are seeing in the Spitzer images is being blown out by intense light from the star,” Su said. “We are witnessing the aftermath of a relatively recent collision, probably within the last million years,” she explained.

Scientists say this disc event is short-lived. The majority of the detected material is only a few microns in size, 100 times smaller than a grain of Earth sand. These tiny dust grains leave the system and dissipate into interstellar space on a time scale less than 1,000 years. “But there are so many tiny grains,” Su said. “They add up to a total mass equal to one third of the weight of our moon,” she said.

The mass of these short-lived grains implies a high dust-production rate. The Vega disc would have to have an improbably massive reservoir of planet-building material and collisions to maintain this amount of dust production throughout the star’s life (350 million years, 13 times younger than our sun). “We think a transient disc phenomenon is more likely,” Su said.

Su and her colleagues were struck by other characteristics of Vega’s debris disc, including its physical size. It has a radius of at least 815 astronomical units, roughly 20 times larger than our solar system. One astronomical unit is the distance from Earth to the sun, which is 150 million kilometers (93 million miles). A study of the disc’s surface brightness indicates the presence of an inner hole at a radius of 86 astronomical units (twice the distance between Pluto and the sun). Large embryonic planets at the edge of this inner hole may have collided to make the rest of the debris around Vega.

“Spitzer has obtained the first high spatial-resolution infrared images of Vega’s disc,” said Dr. Michael Werner, co-author and project scientist for Spitzer at NASA’s Jet Propulsion Laboratory (JPL), Pasadena, Calif. “Its sensitive infrared detectors have allowed us to see that Vega is surrounded by an enormous disc of debris,” he said.

JPL manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology (Caltech) in Pasadena. JPL is a division of Caltech. The multi-band imaging photometer for Spitzer, which made the new disc observations, was built by Ball Aerospace Corporation, Boulder, Colo.; the University of Arizona; and Boeing North American, Canoga Park, Calif.

Imagery and additional information about the Spitzer Space Telescope is available on the Internet, at:

http://www.spitzer.caltech.edu/Media

Original Source: NASA News Release

Posted on by Fraser Cain

Seeing Into the Heart of the Milky Way

The center of our galaxy is hidden behind a “brick wall” of obscuring dust so thick that not even the Hubble Space Telescope can penetrate it. Astronomers Silas Laycock and Josh Grindlay (Harvard-Smithsonian Center for Astrophysics) and colleagues have lifted that veil to reveal a beautiful vista swarming with stars. Moreover, their hunt for specific stars associated with X-ray-emitting sources has ruled out one of two options for the nature of these X-ray sources: most apparently are not associated with massive stars, which would have shown up as bright counterparts in their deep infrared images. This points to the X-ray sources being white dwarfs, not black holes or neutron stars, accreting matter from low-mass binary companion stars.

Their study is being presented today at a press conference at the 205th meeting of the American Astronomical Society in San Diego, Calif.

To peer into the galactic center, Laycock and Grindlay used the unique capabilities of the 6.5-meter-diameter Magellan Telescope in Chile. By gathering infrared light that more easily penetrates dust, the astronomers were able to detect thousands of stars that otherwise would have remained hidden. Their goal was to identify stars that orbit, and feed, X-ray-emitting white dwarfs, neutron stars or black holes – any of which could yield the faint X-ray sources discovered originally with NASA’s Chandra X-ray Observatory.

Chandra previously detected more than 2000 X-ray sources in the central 75 light-years of our galaxy. About four-fifths of the sources emitted mostly hard (high-energy) X-rays. The precise nature of those hard X-ray sources remained a mystery. Two possibilities were suggested by astronomers: 1) high-mass X-ray binary systems, containing a neutron star or black hole with a massive stellar companion; or, 2) cataclysmic variables, containing a highly magnetized white dwarf with a low-mass stellar companion. Determining the nature of the sources can teach us about the star formation history and dynamical evolution of the region near the galactic center.

“If we found that most of the hard X-ray sources were high-mass X-ray binaries, it would tell us that there had been a lot of recent star formation because massive stars don’t live long,” says Laycock. “Instead, we found that most of the X-ray sources are likely to be older systems associated with low-mass stars.”

That conclusion comes from a null result: that is, most of the counterparts to the X-ray sources must be fainter than the brightness expected if the X-ray sources had massive companions. Since massive stars are both rare and bright, an association with the X-ray sources would have been easy to spot. Smaller stars are more common and fainter, making it difficult to match them to a specific X-ray source. Analysis of the infrared images found only a chance number of matches between stars and the locations of X-ray sources. Many of those matches likely were due to the crowded field of view.

“The fact that we found no significant excess of bright infrared counterparts means that the galactic center Chandra sources are probably low-mass binaries. Since by far the most common low-mass binaries with X-ray luminosities, spectra, and variability similar to the galactic center Chandra sources are accreting magnetic white dwarfs, we conclude these are the most likely identification,” says Grindlay.

If the X-ray sources near the galactic center are accreting white dwarfs, the large numbers of compact low-mass binaries required could suggest that they formed in the very dense star cluster around the galactic center or that they have been “deposited” there by the destruction of globular clusters. Deeper infrared observations and spectra of the sources are needed to make actual identifications and constrain the masses of the accreting compact objects.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

Original Source: CfA News Release

Posted on by Fraser Cain

Iapetus Has a Seam

Images returned by NASA’s Cassini spacecraft cameras during a New Year’s Eve flyby of Saturn’s moon Iapetus (eye-APP-eh-tuss) show startling surface features that are fueling heated scientific discussions about their origin.

One of these features is a long narrow ridge that lies almost exactly on the equator of Iapetus, bisects its entire dark hemisphere and reaches 20 kilometers high (12 miles). It extends over 1,300 kilometers (808 miles) from side to side, along its midsection. No other moon in the solar system has such a striking geological feature. In places, the ridge is comprised of mountains. In height, they rival Olympus Mons on Mars, approximately three times the height of Mt. Everest, which is surprising for such a small body as Iapetus. Mars is nearly five times the size of Iapetus.

Images from the flyby are available at http://saturn.jpl.nasa.gov, http://www.nasa.gov/cassini and http://ciclops.org.

Iapetus is a two-toned moon. The leading hemisphere is as dark as a freshly-tarred street, and the white, trailing hemisphere resembles freshly-fallen snow.

The flyby images, which revealed a region of Iapetus never before seen, show feathery-looking black streaks at the boundary between dark and bright hemispheres that indicate dark material has fallen onto Iapetus. Opinions differ as to whether this dark material originated from within or outside Iapetus. The images also show craters near this boundary with bright walls facing towards the pole and dark walls facing towards the equator.

Cassini’s next close encounter with Iapetus will occur in September 2007. The resolution of images from that flyby should be 100 times better than the ones currently being analyzed. The hope is that the increased detail may shed light on Iapetus’ amazing features and the question of whether it has been volcanically active in the past.

With a diameter of about 1,400 kilometers (890 miles), Iapetus is Saturn’s third largest moon. It was discovered by Jean-Dominique Cassini in 1672. It was Cassini, for whom the Cassini-Huygens mission is named, who correctly deduced that one side of Iapetus was dark, while the other was white.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The European Space Agency built and manages the development of the Huygens probe and is in charge of the probe operations. The Italian Space Agency provided the high-gain antenna, much of the radio system and elements of several of Cassini’s science instruments. The imaging team is based at the Space Science Institute, Boulder, Colo.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Topography Mission Wraps Up With Australia

Culminating more than four years of processing data, NASA and the National Geospatial-Intelligence Agency have completed Earth’s most extensive global topographic map.

The data, extensive enough to fill the U.S. Library of Congress, were gathered during the Shuttle Radar Topography Mission, which flew in February 2000 on the Space Shuttle Endeavour.

The digital elevation maps encompass 80 percent of Earth’s landmass. They reveal for the first time large, detailed swaths of Earth’s topography previously obscured by persistent cloudiness. The data will benefit scientists, engineers, government agencies and the public with an ever-growing array of uses.

“This is among the most significant science missions the Shuttle has ever performed, and it’s probably the most significant mapping mission of any single type ever,” said Dr. Michael Kobrick, mission project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

The final data release covers Australia and New Zealand in unprecedented uniform detail. It also covers more than 1,000 islands comprising much of Polynesia and Melanesia in the South Pacific, as well as islands in the South Indian and Atlantic oceans.

“Many of these islands have never had their topography mapped,” Kobrick said. “Their low topography makes them vulnerable to tidal effects, storm surges and long-term sea level rise. Knowing exactly where rising waters will go is vital to mitigating the effects of future disasters such as the Indian Ocean tsunami.”

Data from the Shuttle Radar Topography Mission are being used for applications ranging from land use planning to “virtual” Earth exploration. “Future missions using similar technology could monitor changes in Earth’s topography over time, and even map the topography of other planets,” said Dr. John LaBrecque, manager of NASA’s Solid Earth and Natural Hazards Program, NASA Headquarters, Washington, D.C.

The mission’s radar system mapped Earth from 56 degrees south to 60 degrees north of the equator. The resolution of the publicly available data is three arc-seconds (1/1,200th of a degree of latitude and longitude, about 295 feet, at Earth’s equator). The mission is a collaboration among NASA, the National Geospatial- Intelligence Agency, and the German and Italian space agencies. The mission’s role in space history was honored with a display of the mission’s canister and mast antenna at the Smithsonian Institution’s Udvar-Hazy Center, Chantilly, Va.

To view a selection of new images from the Shuttle Radar Topography Mission’s latest data set on the Internet, visit http://photojournal.jpl.nasa.gov/mission/SRTM.

To view a new fly-over animation of New Zealand on the Internet, visit http://www2.jpl.nasa.gov/srtm/.

To learn more about this mission, visit http://www.jpl.nasa.gov/srtm . For an interactive multimedia geography quiz using data from the mission, visit http://www.jpl.nasa.gov/multimedia/srtm/.

For information about NASA and agency programs, visit: http://www.nasa.gov.

Original Source: NASA News Release

Posted on by Fraser Cain

New Shuttle Tank Arrives in Florida

NASA marked a major milestone for the Space Shuttle’s Return to Flight, as the redesigned External Tank rolled out today from the barge that carried it to the agency’s Kennedy Space Center (KSC), Fla.

The tank was taken to the Vehicle Assembly Building (VAB) for a final checkout. It will eventually be attached to the twin Solid Rocket Boosters and the Space Shuttle Discovery for its Return to Flight mission, STS-114.

“With the arrival of the External Tank, all of the elements of the Space Shuttle system are in place for Return to Flight,” said Michael Kostelnik, deputy associate administrator for International Space Station and Space Shuttle programs. “This improved tank will be the safest we’ve ever flown. The modifications we have made will ensure the Shuttle completes its long-term mission of assembling the International Space Station,” he said.

NASA and Lockheed Martin Corp. spent nearly two years modifying the 15-story, rust-colored tank to make it safer. Among dozens of changes is a redesigned forward bipod fitting to reduce the risk to the Shuttle from falling debris during ascent. Reducing the debris risk was a key recommendation of the Columbia Accident Investigation Board.

“Although we can never completely eliminate insulating foam coming off the External Tank, we have absolute confidence we have eliminated the type of debris that caused the loss of Columbia,” said Bill Parsons, Space Shuttle program manager. “This tank is safe to fly the Return to Flight mission.”

The External Tank arrived at KSC after a 900-mile journey at sea. It departed NASA’s Michoud Assembly Facility in New Orleans on Dec. 31. It was transported via Pegasus, NASA’s specially designed barge. The Solid Rocket Booster retrieval ship Liberty Star brought the barge to Port Canaveral yesterday. The barge was moved by tugs to the KSC Turn Basin, the tank off-loaded and transported to the Vehicle Assembly Building.

“The team here at KSC is tremendously excited to receive the final Shuttle element for the Return to Flight mission,” said Mike Wetmore, director of Shuttle processing at KSC. “We have an experienced team in place that will complete the final checkout and processing of the tank and prepare it for its final journey out to the launch pad before flight.”

In the VAB, the tank will be raised to a vertical position. It will be lifted high up in the transfer aisle into the “checkout cell,” where the tank’s mechanical, electrical and thermal protection systems are inspected. The tank will also undergo new processes resulting from its re-design, including inspection of the bipod heater and External Tank separation camera.

The tank will be prepared for “mating” to the Shuttle’s Solid Rocket Boosters. When preparations are complete, the tank will be lifted from the checkout cell, moved across the transfer aisle and into High Bay 1. It will be lowered and attached to the boosters, which are sitting on the Mobile Launch Platform.

The arrival of the External Tank, the largest element of the Space Shuttle system, follows other recent Return to Flight milestones, including the “stacking” of the Solid Rocket Boosters in the Vehicle Assembly Building and installation of the Space Shuttle Main Engines into Discovery. The External Tank is the only Shuttle component not recovered after launch and reused.

The Return to Flight mission is targeted for a launch window beginning in May. The seven-member Discovery crew will fly to the International Space Station primarily to test and evaluate new procedures for flight safety, Shuttle inspections and repair techniques.

The Space Shuttle Propulsion Office at NASA’s Marshall Space Flight Center, Huntsville, Ala., manages the tank project. Lockheed Martin Space Systems Co., New Orleans, is the primary contractor.

Video b-roll and sound bites of the tank shipment and arrival will be broadcast on NASA TV. Satellite coordinates and NASA TV schedules are available at: http://www.nasa.gov/ntv

For information on NASA’s Return to Flight efforts, including fact sheets and photos about the tank shipment, visit: http://www.nasa.gov/returntoflight

Original Source: NASA News Release

Posted on by Fraser Cain

10 Things to Do in 2005

Image credit: NASA
1.Begin the New Year by observing Saturn. Saturn will be at opposition (i.e. opposite the sun in the sky) on January 13th at 08:00 UTC. Saturn is in the constellation Gemini the Twins, about 6 degrees south east of the star Pollux.

2.Begin learning the names of 20 constellations. The inclination is to start with the brightest, most obvious ones. But sometimes it can be a fun challenge to find a less conspicuous one. Obviously this is a project that could last throughout the entire year. It is also a good chance to learn which constellations are visible during each season.

3.Learn the names of 20 bright stars. While many of us know the names of the constellations, the names of the stars are somewhat less well known. Knowing the star names is a good way to find and learn the constellations as well. Sometimes a constellation will have only one or two bright stars. These can act as guide posts to finding the entire constellation. As with learning the constellations, this is a project that can last all year.

4.Count the stars in the Pleiades, also known as the Seven Sisters. This little star cluster is west of the constellation Taurus the Bull. From a dark location you may see 5 or 6 stars. Then look at them with a pair of binoculars, what do you see?

5.Observe the moon for a month. Notice how much of its surface is illuminated from night to night. Kids can use a calendar and draw what shape the moon is each night (or even day!) Use binoculars or a telescope to observe the lunar features especially near the line that divides day from night (called the terminator).

6.In June look for Mercury and Venus in the evening sky between 0:300 and 04:00 UTC. The pair will be only 0.1 degrees apart. At that distance you will probably need binoculars to tell them apart. Venus will be the brightest object in the sky while Mercury will be much fainter. Saturn will be the bright object to the North West.

7.Observe a meteor shower. The famed Perseids is visible from July 17th to August 24th with the peak occurring before dawn on August 12th . Meteor showers get their names from the constellation they appear to radiate from, in this case Perseus the Hero. The best way to observe meteors is lying back on the ground or in a lawn chair. Kids can have fun counting how many they see in an hour.

8.On September 1st, about 03:00 UTC. Jupiter and Venus will be about 1 degree apart in the west just after sunset. No need to use binoculars to find this pair, but it might be fun to see them both through a telescope. Don’t forget to look for Jupiter’s 4 large moons: Ganymede, Callisto, Europa and Io.

9. Hunt for double stars. Many of the stars that we see in the sky have one or more companion stars. In many cases they are not visible to the naked eye. Here is a good opportunity to hone your binocular or telescope skills. Begin with the star Mizar in the constellation Ursa Major (the Big Dipper); it is the middle star in the Dipper’s handle.

10.Share the sky with your children or other young people. Kids love stories, and most never tire of hearing the same ones over and over again. Learn the myths and legends of your favorite constellations and tell them to your kids. Who knows, maybe your love for the sky will spark an interest in them that will last a lifetime.

This list should give even the most timid of beginners a starting point for their celestial quest. And don’t forget, there are lots of other enthusiasts out there, don’t be shy in contacting them and asking questions and sharing your experiences. Enjoy 2005, and clear skies to you all.

Written by Rod Kennedy.