Posted on by Fraser Cain

Mini Solar System Around a Brown Dwarf

Moons circle planets, and planets circle stars. Now, astronomers have learned that planets may also circle celestial bodies almost as small as planets.

NASA’s Spitzer Space Telescope has spotted a dusty disk of planet-building material around an extraordinarily low-mass brown dwarf, or “failed star.” The brown dwarf, called OTS 44, is only 15 times the mass of Jupiter. Previously, the smallest brown dwarf known to host a planet-forming disk was 25 to 30 times more massive than Jupiter.

The finding will ultimately help astronomers better understand how and where planets — including rocky ones resembling our own — form.

“There may be a host of miniature solar systems out there, in which planets orbit brown dwarfs,” said Dr. Kevin Luhman, lead author of the new study from the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass. “This leads to all sorts of new questions, like ‘Could life exist on such planets?’ or ‘What do you call a planet circling a planet-sized body? A moon or a planet?'”

Brown dwarfs are something of misfits in the astronomy world. These cool orbs of gas have been called both failed stars and super planets. Like planets, they lack the mass to ignite and produce starlight. Like stars, they are often found alone in space, with no parent body to orbit.

“In this case, we are seeing the ingredients for planets around a brown dwarf near the dividing line between planets and stars. This raises the tantalizing possibility of planet formation around objects that themselves have planetary masses,” said Dr. Giovanni Fazio, an astronomer at the Harvard Smithsonian Center for Astrophysics and a co-author of the new study.

The results were presented today at the Planet Formation and Detection meeting at the Aspen Center for Physics, Aspen, Colo., and will be published in the Feb. 10th issue of The Astrophysical Journal Letters.

Planet-forming, or protoplanetary, disks are the precursors to planets. Astronomers speculate that the disk circling OTS 44 has enough mass to make a small gas giant planet and a few Earth-sized, rocky ones. This begs the question: Could a habitable planet like Earth sustain life around a brown dwarf?

“If life did exist in this system, it would have to constantly adjust to the dwindling temperatures of a brown dwarf,” said Luhman. “For liquid water to be present, the planet would have to be much closer to the brown dwarf than Earth is to our Sun.”

“It’s exciting to speculate about the possibilities for life in such as system, of course at this point we are only beginning to understand the unusual circumstances under which planets arise,” he added.

Brown dwarfs are rare and difficult to study due to their dim light. Though astronomers recently reported what may be the first-ever image of a planet around a brown dwarf called 2M1207, not much is understood about the planet-formation process around these odd balls of gas. Less is understood about low-mass brown dwarfs, of which only a handful are known.

OTS 44 was first discovered about six months ago by Luhman and his colleagues using the Gemini Observatory in Chile. The object is located 500 light-years away in the Chamaeleon constellation. Later, the team used Spitzer’s highly sensitive infrared eyes to see the dim glow of OTS 44’s dusty disk. These observations took only 20 seconds. Longer searches with Spitzer could reveal disks around brown dwarfs below 10 Jupiter masses.

Other authors of this study include Dr. Paola D’Alessia of the Universidad Nacional Autonoma de Mexico; and Drs. Nuria Calvet, Lori Allen, Lee Hartmann, Thomas Megeath and Philip Myers of the Harvard-Smithsonian Center for Astrophysics.

NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington, D.C. Science operations are conducted at the Spitzer Science Center, Pasadena, Calif. JPL is a division of Caltech. The infrared array camera, which spotted the protoplanetary disk around OTS 44, was built by NASA Goddard Space Flight Center, Greenbelt, Md.; its development was led by Fazio.

Original Source: Spitzer News Release

Posted on by Fraser Cain

Smallest Extrasolar Planet Found

Penn State’s Alex Wolszczan, the discoverer in 1992 of the first planets ever found outside our solar system, now has discovered with Caltech’s Maciej Konacki the smallest planet yet detected,in that same far-away planetary system. Immersed in an extended cloud of ionized gas, the new planet orbits a rapidly spinning neutron star called a pulsar. The discovery, to be announced during a press conference at a meeting concerning planetary formation and detection in Aspen, Colorado, on 7 February, yields an astonishingly complete description of the pulsar planetary system and confirms that it is remarkably like a half-size version of our own solar system ? even though the star these planets orbit is quite different from our Sun.

“Despite the extreme conditions that must have existed at the time these planets were forming, Nature has managed to create a planetary system that looks like a scaled-down copy of our own inner solar system,” Wolszczan reports. The star at the center of this system is a pulsar named PSR B1257+12 ? the extremely dense and compact neutron star left over from a massive star that died in a violent explosion 1,500 light years away in the constellation Virgo.

Wolszczan and his colleagues earlier had discovered three terrestrial planets around the pulsar, with their orbits in an almost exact proportion to the spacings between Mercury, Venus, and Earth. The newly discovered fourth planet has an orbit approximately six times larger than that of the third planet in the system, which Konacki says is amazingly close to the average distance from our Sun to our solar system’s asteroid belt, located between the orbits of Mars and Jupiter.

“Because our observations practically rule out a possible presence of an even more distant, massive planet or planets around the pulsar, it is quite possible that the tiny fourth planet is the largest member of a cloud of interplanetary debris at the outer edge of the pulsar’s planetary system, a remnant of the original protoplanetary disk that created the three inner planets,” Wolszczan explains. The small planet, about one-fifth of the mass of Pluto, may occupy the same outer-boundary position in its planetary system as Pluto does in our solar system. “Surprisingly, the planetary system around this pulsar resembles our own solar system more than any extrasolar planetary system discovered around a Sun-like star,” Konacki says.

Fifteen years ago, before Wolszczan’s discovery of the first extrasolar planets, astronomers did not seriously entertain the idea that planets could survive around pulsars because they would have been blasted with the unimaginable force of the radiation and remnants of their exploding parent star. Since then, Wolszczan, Konacki, and colleagues have gradually been unraveling the mysteries of this system of pulsar planets, using the Arecibo radio telescope in Puerto Rico to collect and analyze pulsar-timing data. “We feel now, with this discovery, that the basic inventory of this planetary system has been completed,” Wolszczan says.

These discoveries have been possible because pulsars, especially those with the fastest spin, behave like very accurate clocks. “The stability of the repetition rate of the pulsar pulses compares favorably with the precision of the best atomic clocks constructed by humans,” Konacki explains. Measurements of the pulse arrival times, called pulsar timing, give astronomers an extremely precise method for studying the physics of pulsars and for detecting the phenomena that occur in a pulsar’s environment.

“A pulsar wobble due to orbiting planets manifests itself by variations in the pulse arrival times, just like a stellar wobble is detectable with the well-known Doppler effect so successfully used by optical astronomers to identify planets around nearby stars by the shifts of their spectral lines,” Wolszczan explains. “An important advantage of the fantastic stability of the pulsar clocks, which achieve precisions better than one millionth of a second, is that this method allows us to detect planets with masses all the way down to those of large asteroids.”

The very existence of the pulsar planets may represent convincing evidence that Earth-mass planets form just as easily as do the gas giants that are known to exist around more than 5 percent of the nearby Sun-like stars. However, Wolszczan says, “the message carried by the pulsar planets may equally well be that the formation of Earth-like planets requires special conditions, making such planets a rarity. For example, there is growing evidence that a nearby supernova explosion may have played an important role in our solar system’s formation.” Future space observatories, including the Kepler and the Space Interferometry Missions, and the Terrestrial Planet Finder, will play a decisive role in making a distinction between these fundamental alternatives.

Posted on by Fraser Cain

ESA Will Risk Deploying MARSIS

The European Space Agency has given the green light for the MARSIS radar on board its Mars Express spacecraft to be deployed during the first week of May. Assuming that this operation is successful, the radar will finally start the search for subsurface water reservoirs and studies of the Martian ionosphere.

ESA’s decision to deploy MARSIS follows eight months of intensive computer simulations and technical investigations on both sides of the Atlantic. These were to assess possible harmful boom configurations during deployment and to determine any effects on the spacecraft and its scientific instruments.

The three radar booms of MARSIS were initially to have been deployed in April 2004, towards the end of the Mars Express instrument commissioning phase. They consist of a pair of 20-metre hollow cylinders, each 2.5 centimetres in diameter, and a 7-metre boom. No satisfactory ground test of deployment in flight conditions was possible, so that verification of the booms’ performance had to rely on computer simulation. Just prior to their scheduled release, improved computer simulations carried out by the manufacturer, Astro Aerospace (California), revealed the possibility of a whiplash effect before they locked in their final outstretched positions, so that they might hit the spacecraft.

Following advice from NASA?s Jet Propulsion Laboratory (JPL), which contributed the boom system to the Italian-led MARSIS radar instrument, and the Mars Express science team, ESA put an immediate hold on deployment until a complete understanding of the dynamics was obtained. JPL led a comprehensive investigation, including simulations, theoretical studies and tests on representative booms, the latter to assess potential aging of the boom material. European experts, from ESA and the former spacecraft prime contractor, Astrium SAS, France, worked closely with JPL throughout the entire investigation. An independent engineering review board, composed of ESA and industry experts, met in January to evaluate the findings and advise on ?if and when? to proceed with deployment.

The ESA review board, at its final meeting on 25 January, recommended deployment of the MARSIS booms. The rationale for the decision was based on the results of the analyses, which showed the possible impact scenarios, the amount of energy involved, the nature of the materials, and the physical conditions in space. The board concluded that the risk of an impact on the spacecraft could not be ruled out, but that the impact energy would be low and the probability of a severe failure was very small.

One credible failure case is that an antenna boom could become blocked during deployment, either by itself or by the spacecraft. Although means are available to unblock a deployment, in the worst case MARSIS would have to be considered partially or completely lost. However, the analyses have shown that the Mars Express control systems would be able to cope with such a configuration and minimise the consequences for the other scientific instruments.

The ESA board recommended planning the deployment for the week beginning 2 May. However, should the remaining preparations proceed faster than planned, it might be feasible to start deployment during the week beginning 25 April. An early deployment is scientifically desirable, as the evolution of the Mars Express orbit will allow radar measurements of the most interesting scientific regions on Mars to start in May 2005.

If, as expected, the deployment is successful, MARSIS will probe the secrets of Mars?s subsurface at least until 30 November 2005, the nominal end date of Mars Express operations, and beyond if the mission is further extended.

Original Source: ESA News Release

Posted on by Fraser Cain

This Star is Leaving Our Galaxy

Using the MMT Observatory in Tucson, AZ, astronomers at the Harvard-Smithsonian Center for Astrophysics (CfA) are the first to report the discovery of a star leaving our galaxy, speeding along at over 1.5 million miles per hour. This incredible speed likely resulted from a close encounter with the Milky Way’s central black hole, which flung the star outward like a stone from a slingshot. So strong was the event that the speedy star eventually will be lost altogether, traveling alone in the blackness of intergalactic space.

“We have never before seen a star moving fast enough to completely escape the confines of our galaxy,” said co-discoverer Warren Brown (CfA). “We’re tempted to call it the outcast star because it was forcefully tossed from its home.”

The star, catalogued as SDSS J090745.0+24507, once had a companion star. However, a close pass by the supermassive black hole at the galaxy’s center trapped the companion into orbit while the speedster was violently flung out. Astronomer Jack Hills proposed this scenario in 1998, and the discovery of the first expelled star seems to confirm it.

“Only the powerful gravity of a very massive black hole could propel a star with enough force to exit our galaxy,” explained Brown.

While the star’s speed offers one clue to its origin, its path offers another. By measuring its line-of-sight velocity, it suggests that the star is moving almost directly away from the galactic center. “It’s like standing curbside watching a baseball fly out of the park,” said Brown.

Its composition and age provide additional proof of the star’s history. The fastest star contains many elements heavier than hydrogen and helium, which astronomers collectively call metals. “Because this is a metal-rich star, we believe that it recently came from a star-forming region like that in the galactic center,” said Brown. Less than 80 million years were needed for the star to reach its current location, which is consistent with its estimated age.

The star is traveling twice as fast as galactic escape velocity, meaning that the Milky Way’s gravity will not be able to hold onto it. Like a space probe launched from Earth, this star was launched from the galactic center onto a never-ending outward journey. It faces a lonely future as it leaves our galaxy, never to return.

Brown’s co-authors on the paper announcing this find are Margaret J. Geller, Scott J. Kenyon and Michael J. Kurtz (Smithsonian Astrophysical Observatory). This study will be published in an upcoming issue of The Astrophysical Journal.

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

What’s Up This Week – Feb 7 – 13, 2005

Monday, February 7 – Tonight let’s start with a wonderful binocular or low power richfield telescope object. Located just east of the Cassiopeia border into Camelopardalis is a beautiful chain of around 20 colorful stars that stretch over five moon widths across the sky. This delightful asterism of stellar jewels was made popular by amateur astronomer Lucian Kemble, and are known in his memory as “Kemble’s Cascade”. Although the stars are really not related to one another, they create an outstandingly picturesque image with the stars in a line and tiny open cluster NGC 1502 connected to the end.

Now that we’ve got a “line” let’s get out the scopes and go fishing in Pisces tonight! We’re heading for Gamma Arietis, and drawing a mental line between it and Eta. Approximately two-thirds of the way is the spectacular M74. This is a by-gosh spiral galaxy! Its “rolled” structure becomes immediately apparent in mid to large telescopes. The outstanding core area is intense and the arms twist away from it quite tightly. It sports several areas of bright clusters/nebulosity – and as it twists away into space, two lovely spiral arms reach right out and wrap themselves around it. Very similar the “Whirlpool” (M51), the “galactic stuff” wisps away at the edges where several bright stars play the field with it. This is one exceptionally pretty galaxy!

Tuesday, February 8 – Hey, hey, hey… It’s “Fat Tuesday”! Why not begin the day by scoring a binocular trophy? You’ll find that Mars is wonderfully positioned between the M20 and M8! Even the skies will be celebrating tonight as the Moon officially goes new at 12:12 UT. Since we will have dark skies for the next couple of days, let’s do some challenge studies!

Tonight we’ll be hunting that “wascally wabbit” Lepus. One of the finest pieces of work in this area is our previous study – globular cluster, M79. It is not the most brilliant of small globulars that I have seen, but at higher magnification in larger scopes the outer stars begin to resolve, making it quite pretty. Another faint fuzzy to be found in Lepus is spiral galaxy, NGC 1964. Again, not the most awe inspiring one I’ve ever traveled to, but with patience and steady sky, some brightenings around the outer edge of the central structure begin to show making it worth the hunt! Also take the time to re-visit R Leporis – Hind’s “Crimson Star”. It sits below Rigel and is a very deep red like Mu Cephii.

As the skies move westward, we head next to Canis Major. By locating Beta, this galaxy drop is fairly simple by continuing on a basic southern trajectory working the “fall line” one field of view at a time from west to east. Use mid-range magnification as you move between Beta and Theta, then power up as you locate each one. The NGC 2207 and IC 2163 is an interesting double spiral galaxy complex for large scopes. While the results are far from a Hubble picture, it is possible with aperture to make out two brightened galactic cores whose outer regions overlap making it a most curious region to explore and well worth the hunt! The NGC 2223 is next along the line, and is also a spiral galaxy. There is a subtle hint of a core region, but for the most part this galaxy is evenly distributed with just the faintest indications of spiral structure at the outer edges. Continuing south will find the NGC 2217 – a somewhat brighter spiral galaxy that appears under higher magnification to have a halo surrounding it. Now for a jump back to Sirius (but don’t look at it!) and drop south below the binocular target – M41. The last of the galaxy hunt in Canis Major is tiny spiral, NGC 2280. Set in a delightfully rich field of stars, this shy oval of galactic “stuff” reveals only the faintest hint of an arm during excellent seeing conditions.

Wednesday, February 9 – Today is not only the 5th Anniversary of the STARDUST Launch, but Chinese “New Year” as well! Let’s celebrate it and dark skies by heading into more new studies.

The challenge to the Cetus field is not so much finding these objects as it is having the correct sky to see them. Heading to Diphda, we’re ready to drop down for galaxy study number one: the NGC 247. A very definite spiral galaxy with an intense “stellar” nucleus! Sitting right up in the eyepiece as a delightful oval, the NGC 247 is has a very proper galaxy structure with a defined core area and a concentration that slowly disperses toward its boundaries with one well-defined dark dust lane helping to enhance a spiral arm. Most entertaining! Continuing “down” we move on to the NGC 253. Talk about bright! Very few galactic studies come in this magnitude (small scopes will pick it up very well, but it requires large aperture to study structure.) Very elongated and hazy, it reminds me sharply of the “Andromeda Galaxy”. The center is very concentrated and the spiral arms wrap their way around it beautifully! Dust lanes and bright hints of concentration are most evident. and its most endearing feature is that it seems to be set within a mini “Trapezium” of stars. A very worthy study…

Now, let’s hop off to Delta, shall we? I want to rock your world – because the M77 rocked mine! Once again, easily achieved in the small scope, M77 comes “alive” with aperture. This one has an incredible nucleus and very pronounced spiral arms – three big, fat ones! Underscored by dark dust lanes, the arms swirl away from the center in a galactic display that takes your breath away! The “mottling” inside the structure is not just a hint in this ovalish galaxy. I guarantee you won’t find this one “ho hum”!

Thursday, February 10 – Today is the 30th Anniversary Mars 4, Mars Flyby. Hard to believe that only three decades later we’re still up there studying! By the way, today also marks Muslim New Year. Let’s celebrate with study!

With the very slim crescent of the Moon setting very early tonight, I ask you… Are you ready to dig deeper into Cetus? Then grab that map and let’s go! Delta will be our starting point here and the “fall line” runs west to east on the north side. First up is galaxy NGC 1073, a very pretty little spiral with a very “stretched” appearing nucleus that seems to be “ringed” by its arms! Continuing along the same trajectory, we find the NGC 1055. Oh, yes… Edge-on! This soft streak of light is accompanied by a trio of stars. The galaxy itself is cut through by a dark dust lane, but what appears so unusual is the core is to one side! Now we’ve made it to the incredible M77, but let’s keep on the path and pick up the NGC 1087 – a nice, even-looking spiral galaxy with a bright nucleus and one curved arm. Ready to head for the beautiful variable Mira? Then let her be the guidestar, because halfway between there and Delta is the NGC 936 – a soft spiral galaxy with a “saturn” shaped nucleus.

Ya’ done good, kid…

Friday, February 11 – Once again, the Moon will set early tonight. Wanna’ go play with the “Pup”?

The Puppis Star Fields are an exceptional challenge. Starting in the area of the binocular easy M46 and M47, a great place to hunt out is NGC 2423 – a soft collection of stars that resembles a fishook. Dropping south of the M47, we head on to tiny planetary nebula – NGC 2440 – who appears as nothing more than a slightly elongated “soft star”. Continue southwest for open cluster, NGC 2421 – a small open cluster that reminds me of an exquisitely tiny Brocchi’s Cluster! Ready for some more? Go for the M93 next, because a move southeast will find the NGC 2482 – a pretty, looping open cluster. Time to start nudging the scope to the southeast this time, to capture NGC 2467 a gentle open cluster also accompanied by a faint nebula. Continue on the same trajectory for open cluster, NGC 2453 – a small “patch” of faint stars.

Saturday, February 12 – And just when you thought I couldn’t go any lower, I ask you to wait until the crescent Moon has dipped below the horizon and Puppis stands high in the sky!

When Puppis stands straight up on the southern horizon, a clear sky provides a “peek” into those much sought after open clusters that can’t be found at any other time. Tonight we are going to move from east to west, dropping the field south on each successive pass. Starting southwest of Rho, we find the NGC 2489. Faint, but well resolved, this cluster is a double handful of diamond dust. Now, bump the field, and let’s rock again! Next pass brings up NGC 2489 – a rich field of stars, that seems to concentrate. Return again and let’s capture NGC 2533 – a very faint field of stars that are basically the same magnitude. A move over brings us to NGC 2439 – who is much brighter and also has a much larger star in the field. Get “down” now for the NGC 2571 – a “looping” field of faint stars with a couple of brighter members. A bit lower this time captures the NGC 2567 – a delightful group of stars that remind me of a greek letter.

Astronomy rocks!

Sunday, February 13 – Today is the birthday of J.L.E. Dreyer, a Danish-born Irish astronomer who came into the world in 1852. At the age of 22, Dreyer became the Assistant to Lord Rosse at Birr where the giant six-foot Leviathan – the world’s largest telescope – was at his disposal. It was here that he began a comprehensive survey of star clusters, nebulae and galaxies. His most important contribution to astronomy was The New General Catalogue of Nebulae and Clusters of Stars (NGC) published in 1888. This catalogue remains to this very day the standard reference used by astronomers the world over. He listed a fantastic total of 7840 objects! He followed with two supplementary Index Catalogues in 1895 and 1908 which contained an additional 5386 (IC) objects. It is the order in which they appear in these catalogues that define their names. It is also fascinating to note that most astronomers (including myself) still also use a form of “shorthand” devised by Dreyer, known as “Dreyer Descriptions” to make our own notations more brief and standard to all who read them some 117 years later after first being penned!

If a man who managed to view, describe and catalog 13,226 objects over his career says in a notation – !!! – you better go look!

Despite the Moon tonight, let’s do some comet hunting. Look for the Magnificent Machholz just a bit northwest of Gamma Camelopardalis. Still bright and still an easy binocular target! If you’d like more of a challenge, try spotting 9th magnitude C/2003 K4 less than half a moon’s width away from large, faint planetary – NGC 1360 – in Fornax. If you’d rather just relax with a bit of Moon? Metius, Fabricus and Jannsen will be your reward…

Until next week, keep Practicing, stay Patient and be Persistent! The sky is the limit… Keep reaching for the stars!

Light speed… ~Tammy Plotner

Posted on by Fraser Cain

NASA 2006 Budget Released

The US White House released its 2006 budget today, which included $16.45 billion US for NASA. This is a 2.5% increase over the previous year, but it doesn’t include any funds to save the Hubble Space Telescope. Only $75 million have been set aside for Hubble, which would only be enough to have a robot steer the aging observatory into a safe trajectory when it needs to be destroyed. The budget sets aside $9.6 billion for science, aeronautics and exploration, and $6.7 billion for the space shuttle and International Space Station.

Posted on by Fraser Cain

Galaxies Might Exist Without Stars

Fitted with its new compound eye on the heavens, the National Science Foundation’s (NSF) Arecibo Observatory telescope, the world’s largest and most sensitive single-dish radio telescope, early tomorrow morning begins a years-long survey of distant galaxies, perhaps discovering elusive “dark galaxies” — galaxies that are devoid of stars.

Astronomers at Arecibo Observatory hope the new sky survey will result in a comprehensive census of galaxies out to a distance of 800 million light years from our galaxy, the Milky Way, in nearly one-sixth of the sky — or some 7,000 square degrees.

The search, conducted by an international team of students and scholars, is the first of a series of large-scale Arecibo surveys that will take advantage of a the telescope’s new instrument, installed last year, called ALFA (for Arecibo L-Band Feed Array). The device is essentially a seven-pixel camera with unprecedented sensitivity for making radio pictures of the sky, allowing astronomers to collect data about seven times faster than at present. The project has been dubbed ALFALFA, for Arecibo Legacy Fast Alfa Survey.

“Fast” does not refer to the time necessary to carry out the survey, which will require thousand hours of telescope time and a few years to complete, but rather to the observing technique, which consists in fast sweeps of broad swaths of sky.

The survey is supported by the National Astronomy and Ionosphere Center (NAIC) at Cornell University, Ithaca, N.Y., which manages the Arecibo Observatory for the NSF. In addition, support is being provided through research grants from the NSF and the Brinson Foundation to the project’s leader, Cornell professor of astronomy Riccardo Giovanelli, and to Martha Haynes, a Goldwin Smith Professor of Astronomy at Cornell.

Giovanelli explains that ALFA operates at radio frequencies near 1420 MegaHertz (MHz), a frequency range that includes a spectral line emitted by neutral atomic hydrogen, the most abundant element in the universe. ALFA detects this signature of hydrogen, which hopefully signals the presence of an undiscovered galaxy. Nearly every previous sky survey has been of optically, infrared- or X-ray-selected galaxies.

ALFALFA will be six times more sensitive — meaning that it will go much deeper in distance — than the only previous hydrogen wide-field survey carried out in Australia in the late 1990s. “What has made ALFALFA possible is the completion of the Gregorian upgrade to the Arecibo telescope in 1997, which allowed feed arrays to be placed in the telescope focal plane and expanded the instantaneous frequency coverage of the telescope,” he says.

Besides providing a comprehensive census of the gaseous content of the near universe, ALFALFA will explore galaxies in groups and clusters and investigate the efficiency by which galaxies convert gas into stars. What particularly intrigues astronomers is that ALFALFA could determine whether gas-rich systems of low mass that have not been able to convert their cosmic material into stars — the so-called dark galaxies — actually exist. Because these galaxies, being starless, are optically inert, it is hoped that they can be detected by their hydrogen signature.

The galaxy survey is feasible now because ALFA lets the telescope see seven spots — seven pixels — on the sky at once, greatly reducing the time needed to make all-sky surveys. The Australian-built detector, on the 305-meter (1,000-foot) diameter Arecibo radio telescope, provides the imaging speed and sensitivity that astronomers will need for their search.

Robert Brown, the NAIC’s director, said that a significant fraction of the Arecibo telescope time in the next few years will be devoted to extensive surveys with the ALFA array, such as ALFALFA. The new survey consortium consists of 38 scientists from 10 countries, including the United States, France, the United Kingdom, Italy, Spain, Israel, Argentina, Chile, Russia and the Ukraine.

Several of the members are graduate students who will base their Ph.D. theses on ALFALFA data. Among them are Cornell graduate students Brian Kent, Sabrina Stierwalt and Amelie Saintonge.

Says Giovanelli: “My one and only paper published in an engineering journal proposed the construction of a feed array at the upgraded Arecibo telescope to carry out hydrogen line surveys of the sky. It took 15 years of waiting, but I am finally going to do the experiment.”

Original Source: Cornell News Release

Posted on by Mark Mortimer

Book Review: Apollo 12 The NASA Mission Reports, Volume Two

The Apollo 12 mission landed the second set of crewmen onto the moon. After the success of Apollo 11, the attitude had swung a bit from ‘can we make it’ to ‘what’s the best we can do’. The lunar orbit insertion technique changed, the landing had a distinct target (i.e. near Surveyor 3), and expectations for exploration and assessment were more detailed and grander. If everything else remained the same, this might be considered a trivial advance. But space travel was still new and with the complex and tightly coupled systems involved, something always sprang up. Godwin, in his compilation, provides the official view of many of these occurrences.

The book is loosely divided into three sections. The first examines the expectations and the operations, the second examines the equipment and experiments, while the third looks at equipment anomalies. The expectations centre about the men’s activity on the surface, the geological examination, scientific experiments and their own mobility. Coarse maps and photographs show routes and setups for surface equipment. The operations description describes the descent in some detail, including charts of altitude, pitch, yaw and roll as a function of time. In fact, by continually using a time reference, Godwin provides an excellent metric to keep tabs of what’s happening..

Seeing as this is an official report, it is not surprising that the next section gives much more attention to the equipment and experiments rather than crew activities. Descriptions portray the purpose and composition of most of the experiments. Direct results are listed, such as identifying the number of rolls of film successfully taken. Charts show seismic output. Some of the equipment is profiled. The included pilot’s report gives the precise bureaucratic description of events from launch through to landing back on earth. A simple strip chart lists major events opposite ground elapsed time to permit quick review of activities. Suffice it to say that Apollo12’s mission objectives were almost all completed satisfactorily, that is, the equipment and experiments did what they needed to do.

One of the more interesting parts of this compilation is the review of the anomalies. Imagine sitting on more than 5 million pounds of propellent and then being struck twice by lightening as they were! No serious consequences ensued similarly with other less exciting anomalies. Filters backed up, valves stuck, electronics failed, just like the operation of any large piece of machinery. Perhaps what is more revealing is the small quantity of anomalies. To clarify each, the book provides a point by point description of the anomaly, the resolution and any subsequent action.

Upon reading this book, two powerful messages clearly jump out. The first is the overall complexity of the mission. With help being five days away at best, reliability was critical so care had to be taken and it is a wonder that things went as smoothly as they did. This may account for the pedantic nature of the operations and the dry tone of the reports in the book. The second message is that lessons were learned and actions taken; after all this was the 12th Apollo mission; the second that landed. However, where are these lessons now? Are they only in books like this and dusty government repositories? These unasked questions arise but no answers are present.

Fine as this book is, don’t forget its source, bureaucracy. Dry yes, but to liven your day just watch the included DVD. Astronauts rejoice on landing, sing while collecting geological samples and smile broadly while resting in quarantine. The live video pictures the launch from many angles, the lunar landing, many of the astronaut’s activities on the surface, the rendezvous and the recovery of the crew and capsule after splash down. This double sided disc gives many hours to recreate the mood and feeling of this great event.

What is missing from this book is any discussion, in particular where is the information on the importance of the mission and its objectives. Further, and more important, as most of the book focuses on the anomalies, the consequence of failure should have been added. Did the lightening strikes pose much of a danger? Did the mission ever come close to a hazardous situation and to what consequence? Taking the opportunity to add this perspective would have made this rich book more rewarding.

Von Braun’s vision of the lunar missions was as a stepping stone to bigger and better things. Robert Godwin’s compilation in ‘Apollo 12 The NASA Mission Reports, Volume Two‘ provides an excellently edited selection of the milestones that Apollo 12 achieved and the glitches that made its journey interesting. As a combination, the dry tone of the book and the lively feel of the included DVD make for an entertaining and informative reference for this lunar mission.

To get your own copy, visit Amazon.com.

Review by Mark Mortimer

Posted on by Fraser Cain

New Logo

You might have noticed, I’ve got a new logo for Universe Today – I figured it was time for a change. 🙂 A big thanks to Liam at neopod for the design. We’re actually working on redesigning the website itself, so if you have any suggestions, now’s the time. Just drop me an email at [email protected].

Fraser Cain
Publisher
Universe Today

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Posted on by Fraser Cain

Upper Limit on Star Mass

New research from the University of Michigan shows that there may be an upper limit to the mass of a star, somewhere around 120 to 200 times bigger than our sun.

The sun is the closest star to Earth and therefore looks very big to us, but compared to other stars in the Milky Way, it?s considered a low-mass star. Knowing that there may be a limit to a star?s mass answers a fundamental question, but raises a raft of other issues about what limits their mass, said Sally Oey, assistant professor of astronomy.

The study is the first to determine the stellar upper mass limit by examining a wide range of star clusters, said Oey (rhymes with chewy). In the paper, ?Statistical Confirmation of a Stellar Upper Mass Limit,? Oey and colleague C.J. Clarke, from the Institute of Astronomy at Cambridge, England, compared historical data on 12 OB associations, large aggregates of hundreds to several thousands of young stars.

The paper will appear in the Feb. 10 edition of the Astrophysical Journal Letters.

Other studies have suggested an upper mass limit of about the same size, but had looked at only one cluster. ?Ours has more statistical significance because we were able to use many clusters,? Oey said.

Oey and Clarke looked at star clusters in the Milky Way, our galaxy, and in the Magellanic Clouds, the brightest satellite galaxies, because they are close enough to enable seeing individual stars and making measurements, Oey said.

?If you looked at any of the clusters, you?ll see roughly the same ratio of big to little stars,? Oey said. Based on the size and number of stars, the probability of finding stars above a certain mass dropped significantly at 120-200 solar masses, Oey said.

The question of mass is an important one because it relates to basic star formation, Oey said. ?My African violets won?t grow any bigger now because their roots are totally taking up the maximum room in the pot,? she said. ?If I repotted them they would grow larger. Are the stars maxed out because the parent clouds are limiting them, or because, like a whale in the sea, there?s something else physical about stars themselves that limits the size?

?The question about why stars have the masses that they do is fundamental, and our lack of understanding shows that we really don?t know some basics of how stars form.?

The biggest stars put out huge amounts of energy by exploding when they die or by releasing ultraviolet radiation during the star?s normal life. That puts tremendous energy into the interstellar medium, which in turn leads to evolutionary activity like renewed star formation and the conversion of gas into stars.

?If you have more stars and energy in the interstellar medium it means more evolutionary activity,? Oey said. ?It stirs things up.?

Original Source: University of Michigan News Release