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Journal of the Amateur Astrono mers Association of New York Nove mber 2010 Volume 58 Number 11, ISSN 0146-7662

EYEPIECE
Voltages in each antenna are transferred into a big grid, with sa mpling done ever y 20 nanoseconds. High-speed digital electronics performs fast transfor mations on sampled data. The prototype of this inexpensive scope was tested in West Forks, Maine, in dark skies near Canada. Tegmark needs to raise $100,000 to scale up to the next stage. Within a few years, he hopes to build the Omniscope, a square-kilometer array. While a typical scope has spherical aberration and a small field of view, the Omniscope would collect data from horizon to horizon and would be omni-chromatic and omni-directional. The Omniscope would be far cheaper to build than a similarly-sized single-dish radio telescope or a standard interferometer. A large number of antennas are needed to capture the very faint signal of neutral hydrogen left over from the early universe. This neutral hydrogen can be seen everywher e if the frequency knob on the scope is turned far enough. When space expands by a factor of 10, 21-cm. radio wa ves become 210 cm long. Tegmark wants to make a 3D map of the universe using redshifted survey data to be obtained from the Omniscope. Data from the early universe could further constrain Omega, the cosmological parameter defining the curvature of space. Tegmark's earlier research using SDSS data, in conjunction with other scientists, measured the spatial curvature as equal to 1.003 plus or minus 0.010. "This number Omega in cosmology measures whether space goes on for ever or curves back on itself. " "Since we've tested this thing out and it really works, I know we ca n do it because all we have to do is build and buy mor e copies of exactly the same stuff which alrea dy Tegmark continued on page 12

Scientists Will Look Even Further Back in Time, AAA Told
By Lynn Darsh
Although we know more about the early universe than ever, the best is yet to come, Dr. Max Tegmark, professor of physics at MIT, told the AAA October 1. Inaugurating the club's 2010-11 lecture series at the AMNH with a talk on "The History of the Universe in One Hour," Tegmark cited recent results such as precision measurements of the cosmic micr owave background by the Wilkinson Microwave Anisotropy Probe (WMAP) and thr ee-dimensional galaxy maps from the Sloan Digital Sky Survey (SDSS), which has mapped mor e than 100 million galaxies over a large part of the celestial spher e. Precision data have ma de cosmologists believable, Tegmark observed. The combination of advances in space technology to capture data in differ ent wavelengths from above Earth's atmospher e, in detector technology to improve sensitivity by 100 or even 1,000 times, and in computer technology to ma nipulate this large amount of infor mation, has produced a revolution. Tegmark's research plans include looking much farther back in time, earlier tha n SDSS (which he has worked with), at the epoch before galaxies had for med. He spoke just after returning from successfully testing the prototype of a Fast Fourier Transfor m Telescope (FFTT), designed in collaboration with Matias Zaldarriaga, professor of astronomy and physics at the Institute for Advanced Study in Princeton. The FFTT is a type of interfer ometer functioning as a digital telescope. It uses inexpensive modular TV antennas to search for redshifted 21 cm. radio waves given off by neutral hydrogen in the early universe. These modular, inexpensive antennas are arranged in a square grid.


What's Up
By Tony Hoffman The Sky for November 2010
November's Meteors. Two meteor showers grace our skies this month. The Leonids peak November 17. Prime time for observing begins after the waxing gibbous Moon sets around 3 p.m. It's expected to be a typical (non-stor m) year for the shower. Observers at dark-sky sites can see about 20 Leonids an hour radiating from the backwards question mark that represents the lion's head. The Leonids are debris from Comet 55P/Tempel-Tuttle. Earlier in the month, a lesser -known meteor shower, the Taurids, holds swa y. This shower, really two r elated showers, is associated with Comet Encke. The Taurids show some activity late September to early December, and show an extended peak. The shower should be at its best on moonless nights early in the month, when between five and 15 slow-moving meteors, including a relatively high percentage of fireballs, can be expected. Planets Everywhere. Five planets are on view this month. Jupiter lies to the southeast at nightfall benea th the Circlet of Pisces, and is visible most of the night. The planet fades slightly, from mag -2.8 to -2.6, as it slowly pulls away from Earth after its closest opposition in 50 years. Two other planets grace the evening twilight. Mercury and Mars can be seen together low in the southwest November 20, when they lie less than 2 degr ees apart. Their apparent motion takes them in opposite dir ections. Mars is lost in solar glare by month's end, while Mercury climbs into easy visibility above the twilight. Saturn climbs out of the pr eda wn glare. Its rings are much wider open than when we last saw it a few months ago. Saturn lies in Virgo, between stars Theta and Gamma Vir ginis. Venus emer ges from solar glare into the mor ning sky, below Spica, the brightest star in Virgo. Venus is unmistakable, blazing at mag -4.4, brighter than any object nor mally visible except the Sun and Moon. November November Earth, 1:25 November November
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November November November November November November November November November November Earth, 1:56

7 Moon lies near Mars in evening twilight. 9 Mars is closest to Antares. 13 First-quarter Moon at 11:39 a.m. 15 Mercury lies 2 degr ees from Antares. 16 Moon lies near Jupiter. 17 Leonid meteor shower pea ks. 20 Mars and Mercury lie 1.7 degr ees apart. 21 Full Moon at 12:27 p.m. 28 Last-quarter Moon at 3:36 p.m. 30 Moon is at perigee, 229,553 miles from p.m.

Jupiter Rules the Evening Sky
By Joseph A. Fedrick
In September, the Earth passed closer to Jupiter that it has in ma ny years. Jupiter loomed big and bright in the evening sky during September and October. It was the only bright planet visible in the late evening sky. Venus was visible near the southwest horizon in la te August and early S eptember, but by October was too near the horizon to be seen from my location after sunset. Mars was also too near the horizon and hidden in the solar glare this fall. Saturn also was lost in solar glare. Mercury ma de a brief morning appearance in September but then slid back into the solar glare, heading for a solar conjunction and then a poor autumn evening apparition. Jupiter was close enough in September so I could see, with only my 60mm r efractor at 100x, Europa's shadow transiting the Jovian disk. Europa is the smallest Galilean satellite to cast a shadow r egularly on the Jovian disk. The South Equatorial Belt was still a very faint bluegray during S eptember and October, while the North Equatorial Belt was a dark orange-brown. The Great Red Spot still maintained a relatively deep dark salmon redpink a nd was visible even with my 60mm r efractor at 100x. The spot stood out not only because of its deeper red color, but because the S outh Equatorial Belt that partially envelops it was still faded to near invisibility. Use of my reveal much through the blurry at the six-inch Newtonian r mor e detail because turbulent autumn air higher resolution of Fedrick eflector at 150x didn't fair -to-poor viewing caused Jupiter to be the six-inch scope. I continued on page 12

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Liftoff of Shuttle Discovery, 4:40 p.m. Moon is at perigee, 226,298 miles from m. Moon lies near Saturn in morning sky. New Moon at 12:52 a.m.


A Message from AAA President Richard Rosenberg
Hello members: Ther e's a chill in the air. Our lecture series has begun. Starfest was terrific. It must be membership -r enewal time! The good news is we're continuing to grow, approaching 400 members. The ba d news: Donations to the club are down, probably because of the recession. Our dues remain $25 a year, but it won't stay that way without your help. Bring friends to our events. They ma y develop an interest and join. If you have Internet access, please receive Eyepiece by e-mail. Almost 100 members have done so, but more than 200 haven't. The cost of printing and mailing Eyepiece is significa nt. The online version has links to related websites. Post our flyer on the lectures at your office or a nearby school or library. If you don't have a flyer, let me know. Although fall mea ns a tinue obser ving sessions, Rego Park in Queens. In total eclipse of the Moon hiatus of some outdoor activities, Floyd Bennett Field, Fort Greene and Great Kills will conand we'll probably meet occasionally at the High Line in Manhattan, Pier 1 in Brooklyn a nd December we'll be at Belvedere Castle in Central Park and a location yet to be chosen for the the mor ning of December 21.

Our indoor events, including the lectur e series and the seminar, will continue. Thanks to NYU, we have pizza and soda at the seminar on the second Thursday of the month. Another sign of the season: We've order ed copies of the "Obser ver's Handbook 2011" for $19.95 each. If you'r e interested in this fine combination of refer ence material and infor mation on next year's sky events, contact me. Rich Rosenberg, president@aaa.org, (718) 522-5014

AAA's December Lecturer to Discuss Phoenix Mission to Mars
Dr. Suzanne M. M. Young, chemistry instructor at the University of New Hampshire, will addr ess the AAA Friday, December 3 on "Top 10 Discoveries of the Phoenix Mission to Mars and the Implications for Biohabitability." The fr ee public lecture begins at 6:15 p. m. in the Kaufma nn Theater of the AMNH. "The [2007-09] mission had a goal of sampling to deter mine whether this environment may have been habitable for life at some time," Young notes. "The presence of water ice in the regolith was confir med. Salts offer evidence for the presence in the past of liquid water. An evaluation of habitability is a requir ement for sending any mission to search for life. The major discoveries of the mission will be discussed in evaluation of those requirements for life." Young did research for the mission for several years. She helped design instruments and develop experimental procedures, and was science plan integrator at mission control during the operation, both primary and extended. Other AAA lectures : January 7, Robert Nemiroff, Michiga n Technological University, "Best Astronomy Pictures of the Day, 2010." February 4, Neil Weiner, NYU, "Illuminating Dark Matter." March 4, Andrea Dupree, Harvard-S mithsonia n Center for Astrophysics, "Searching for Extrasolar Planets with Kepler." April 1, Greg Matloff, New York City College of Technology, "Regr eening the Earth Using Space Resources." May 6, David J. Thompson, NAS A, "Exploring the Extr eme Universe with the F er mi Gamma-ray Space Telescope. " Dupree's talk will be the annual John Marshall Memorial Lectur e, which honors a past president and executive director of the AAA. Marshall died in 1997.
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Panelists Delve into Factors that Make the Earth Unique
By Maya Kushner
There's usually one Isaac Asimov Memor ial panel a year, but in honor of The Rose Center's 10th anniversary, a special Asimov pa nel held the stage March 10 to discuss "Is Earth Unique?" Speakers wer e selected for their diverse expertise in geology, biology, chemistry and physics, and the wa y they've applied these fields to addr ess the existence a nd future of Earth. Moderator and Hayden Planetarium dir ector Dr. Neil DeGrasse Tyson began by speaking about the discovery of Gliese 581g, believed to be the planet with the greatest likelihood of having conditions suitable for liquid water at its surface found to date within the habitable zone of its star. He stressed the importance liquid water has to the origin of life as we know it. Don Br ownlee, professor of anatomy at the University of Washington, said "the Earth is undoubtedly rare" due to its liquid nature. Although liquid metha ne exists on Titan, "one would feel less at home on Titan than on Mars." So there are other qualities necessary for life, said Brownlee, who studies origins of the solar system. Paul G. Falkowski, professor of geological and marine sciences at Rutgers University, discussed the importance of volcanoes and the role they play in maintaining our atmospher e. Plate tectonics is important in this cycle since the crust gets reheated and comes out through volcanoes, perpetuating the nitrogen/oxygen cycle. Tyson noted that life itself has a tendency to "infuse" our atmospher e with nitrogen and oxygen. Life as elemental as bacteria exists in gr eater quantity in our lower colon than all the people who have ever been bor n. Chris Mckay, a.k.a. "Mr. Mars" of the NASA Ames Research Science Center, discussed life on other planets. If findings show an "independent origin of life"--i. e., a "second Genesis"--that would help show life is a natural feature of the universe, he said. Fred Adams, professor of Michigan, an expert on t for mation and the dyna mics planet for mation, said stars
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to for m solar systems. An estimated 20%-50% of stars have planets. Tyson noted there may be other ways to sustain life that we haven't thought of. Two factors brought up by the panel wer e self-replication of the species and its metabolism. Mckay said Darwinia n replication and mutation repr esent life. Minik Rosing, professor of geology at the University of Copenhagen, who wor ks on Earth's early history and the influence of life on Earth's evolution, suggested looking back to the Earth/Moon system mor e tha n 3.8 billion years ago, wher e complex organisms ha d a chance to flourish. Panelists generally agreed that geology and plate tectonics are big factors in keeping the Earth active, as are volcanoes producing the carbon in our atmospher e without which the Earth would freeze (as is the case with Mars, which lost its atmospher e). Mass is yet another factor which creates a set of physical properties for a planet, and influences its evolution. Distance from the host star is another variable. And Rosing noted the ocean floor is continually hydrated thr ough our ocea ns, which lubricates the ma ntle and influences plate tectonics. Adams mentioned the difficulty in cr eating a controlled-fusion r eaction, which nature does readily in stars and galaxies. Another factor to look at is the importance of Earth's ma gnetic field in protecting and sustaining life. Although Earth during its evolution temporarily lost its magnetic field, those times don't line up with ma ss extinctions. This suggests the ma gnetic field ma y not be as important as originally thought. In fact, it was suggested that without one, cosmic-radiation particles would cause mor e frequent mutations, and might move the presence and continuation of life along quicker.

Contacting the AAA
General club matters: president@aaa.org. Membership business, such as dues and change of addr ess: members@aaa.org. Eyepiece: editor@aaa.org. Lectures: lectures@aaa.org. Classes: classes@aaa.org. Seminar: seminar@aaa.org. Observing: president@aaa.org. Please visit us on the web at www.aaa.org.

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physics at the University radiative signature of star circumstellar disks during ve to have the right mass


AMNH's Astronomy SciCafe: The Next 50 Years in Space
By Greg Matloff
If you've never attended a Science CafИ, you've missed a treat. These fun events demonstrate ther e is a NYC audience for innovative science. On October 6, AMNH astrophysics curator Dr. Micha el Shara entranced a crowd at the Gottesman Hall of The Planet Earth at the museum with an infor mal discussion of huma nity's space future. Shara began his interactive talk by describing his research on stellar explosions and collisions, his work at the Rose Center designing shows and exhibits, and his previous work with the Hubble Space Telescope r esearch tea m. He briefly reviewed huma nity's space effort during the last 50 years. During this time, weapons have been converted to space vehicles, and humans have flown in space and visited the Moon. The main astrono mical result of the Apollo program was greater understanding of lunar and solar -system origins. Although the post-Apollo era has spurred international cooperation, the U. S. may have lost its nerve in space, Shara stated. China may now lead the wa y. Another great U. S. accomplishment, he noted, is the Hubble Space Telescope. With this instrument--which will be deorbited in 5-7 years--we've seen solar systems in for mation and plumbed the depths of extra -galactic space. Humans ha ve demonstrated their role in space during Hubble servicing missions. We're now gearing up for Hubble's replacement. The James Webb Space Telescope (JWST) will have about 10 times the Hubble's light-gather ing power. The JWST won't be in low-Earth orbit like the Hubble but will sit at a gravitationally stable Lagrange Point about 1 million miles distant. Unlike the Hubble, the JWST won't experience day/night therma l variations and will ther efore be a superior infrared (IR) instrument. Equipped with sunscreens, IR detectors will likely r equir e no liquidnitrogen coolant. Very distant galaxies and star clusters, and other highly redshifted objects, should be observable. Shara expects huma ns will visit the JWST and other telescopes in trans-lunar space even though such telescopes are designed to be non-r epairable. Regarding an eventual r eturn to the Moon, Shara believes commer cia l-government-internationa l collaborations might cut costs. But he expects that China will visit the Moon befor e our astronauts return there. Building a lunar observatory is one goal for explorers. One concept is an IR telescope of kilometer dimension in a lunar crater. Construction of such a huge device could be accomplished using a slowly rotating turntable sprayed with an ionic liquid. Such material should rema in liquid at low temperatures and be highly reflective. Although such a lunar telescope wouldn't be affected by atmospher e, lunar dust is an issue. Electrostatic fields could clear dust from the mirror surface. Using such a conceptual device, Manhattan-sized features could be resolved on planets 20-30 light-years distant. Although huma ns might ultimately mine the Moon for water in polar craters, Helium-3 might be a mor e lucrative lunar export. Present at low concentrations in lunar regolith and very rare on Earth, this isotope could be exported to Earth using a lunar space elevator and fused with deuterium to end the energy crisis. Unlike terrestrial space-elevator proposals, low lunar gravity allows application of stainless steel, and space debris is no problem. Lunar mining could concentrate on the lunar far side to conser ve the Moon's visual appearance. Main obstacles to human deep-space flight include cosmic radiation, psychologica l effects and bone degr adation caused by extended periods of weightlessness. Although weightlessness ca n be alleviated in a spinning spacecraft, the best solution to all these factors is improved in-space propulsion to reduce travel time. Eventually, crews could visit the Martian moons Deimos and Phobos. One of these small bodies could be maneuver ed into Mars-stationary orbit and used to anchor a Mars space elevator. According to Shara, such a device might enable colonization and terraforming of Mars. More distantly, humans might explore the ice-shrouded ocea ns of Europa, and the Kuiper Belt. Beyond that, they ma y colonize planets circling "nearby" stars. Shara suspects we are the galaxy's first spacefaring civilization.
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A Boffo Birthday for the Hayden is Rated a 10 -10-10
By Katherine Avakian
As twilight falls, the large spher e in the Hayden Planetarium, seemingly suspended in space, glows in a soft blue light, beckoning the viewer to come and explor e the infor mation the planetarium holds about the universe. Last month, the planetarium celebrated its 10th anniversary with a series of events, and on October 10, it buzzed with activity all day for visitors of all ages. Director Dr. Neil deGrasse Tyson welcomed visitors and noted it's also the 75th anniversary of the original Hayden. A little later, a birthday cake was enjoyed by all as the Chromatics sang "Happy Birthday" (a nd other favorites thr oughout the after noon). The audience viewed a short video of the entir e known universe mapped through astronomical observations. Tyson noted the video would show "empty areas not mapped yet because we don't know ever ything, not even the r eflectivity of the ocea n." The audience also viewed the three top videos out of numer ous submissions in a contest aimed at showing "how science has affected your life." The winner featured a sophisticated treatment of the Large Hadron Collider, which Tyson deemed "not only of entertainment value but of educational value." A question-and-answer session with Tyson is always dramatic, and this one was no exception. It quickly became obvious that children aren't afraid to challenge him. Tyson relishes this and the ensuing back-and-forth ener gizes both. Eight-year-old Sebastian brought up the subject that won't die: Pluto's status. Tyson gave sever al reasons why he believes Pluto to be a Kuiper Belt object, such as: It consists mostly of ice, as do other bodies in the outer solar system, and ther e are six moons in the solar system larger than Pluto, including our Moon. Sebastian was won over. Someone asked what happened to the old Zeiss Mark VI, which pr esented sky shows in the old Hayden; the much mor e sophisticated and technologically advanced Zeiss Mark IX now operates in the Space Theater. Tyson said Zeiss Mark VI was given to another planetarium "in a kind of planetarium organ-donor program." Ther e wer e ongoing activities throughout the day. A
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table was crowded with childr en for ming planets and other hea venly bodies out of clay. Saturn was a favorite, due to its rings, and it appeared in a variety of versions and colors. Childr en at another table folded shiny paper into space rockets. It was also fun to try out weight scales. One-year-old Madeline ma naged to get on the one for the Sun and found she would weigh a hefty 450 pounds ther e. Stepping on the nearby scale for a neutron star instantly zoomed one's pounds into the trillions. The Big Bang Theater's new presentation is a brief and spectacular journey to the Big Bang and back. Narrated by Liam Neeson, it travels to the ver y beginning, wher e in a nanosecond, the universe gr ew from an entity "smaller than an atom to astronomical size. " The digital pr esentation moves through the universe's dark period to the Cosmic Micr owave Background, the afterglow of the Big Bang, when the universe beca me transparent. As it returns to the present, the program dir ects the viewer to the already-fabled circular Cosmic Pathway, a 13-billion-year timeline of the universe. Each foot covers 45 million years. Although the long pathwa y seems spare of detail, its last tiny interval never fails to stun. In the space of only a few centimeters, it notes the first appearance of the hominid fa mily 4.5 million years ago, the appearance of homo sapiens ("anatomically modern huma ns") 100,000 years ago and, in the width of a strand of hair, the record of human art and creativity within the last 30,000 years. Earlier, Tyson said, "Exhibits that are bigger than you are, you remember forever." The Willa mette Meteorite ma kes one think how the fragment of a shattered planet made its fier y entry to Earth, wher e "over ma ny centuries rainwater interacted with its iron sulfide deposits, producing sulfuric acid" and burning large round cavities, creating a wonderfully tactile object. The r eplica of the Mars rovers makes one wonder what's happened to these intrepid travelers since they landed in 2004. Spirit is west of Home P late, wher e it's gone to sleep to try to recharge its batteries since falling silent in March. Opportunity has just cover ed another 100 meters (328 feet) in its trek to Endea vor Crater.


Review: Twin Voyagers Continue Our Quest for Discovery
By John Delaney
At first glance, one would assume that "Voyager: Seeking Newer Worlds in the Third Great Age of Discover y" by Stephen J. Pyne (Viking Penguin, $29.95) focuses exclusively on the most famous pair of NAS A space probes to traverse the solar system and beyond. In fact, the book offers much more. It uses the journeys of Voyagers 1 and 2 as a lens to scrutinize the essence of exploration itself, from the first forays of Europea n seagoing explorers to the a mbitious expeditions of the Space Age. The vehicles of discovery have cha nged, Pyne notes, but the social drivers, motivations and huma n nature itself rema in the sa me. The twin voyager spacecraft form the central narrative of the book. Only the 18th Century journeys of Captain Cook can claim so ma ny first encounters and discoveries, including new moons, ring systems, magnetospher es, even weather phenomena. The book contains a detailed saga of the Voya ger story, beginning within the sa me Cold War context that launched Sputnik, Explor er and Apollo. During this period, NASA researchers calculating potential gravity-assisted trajectories around the planets spied a golden opportunity: a rare alignment of the solar system occurring only once ever y 176 years. The two Voyager probes were launched in summer 1977. Like earlier chroniclers of Voya ger, Pyne enumerates its ma ny firsts. But rather than dwell largely on aspects of the mission, technology and discover ies, he compares and contrasts Voya ger explorations and other robotic planetary missions with earlier themes of discovery. In the era of Columbus, Cortez a nd Magellan, journeys into the unknown wer e driven by commer ce and conquest. In Pyne's second age of discover y, the quest becomes scientific, and the explor ers are often naturalists such as Charles Darwin and Alexander von Humboldt. The third age involves machines, those ma nned by astronauts and submariners, or remotely controlled robots in the depths of the ocea ns and space. One signature discover y of the Voya ger spacecraft --the volcanoes of Io--becomes one of the more successful themes of the book. Pyne points out that volcanoes loom large in the minds and travelogs of explorers dating to the first age. Many islands wer e volca nic. Von Humboldt's travels represented the beginning of the science of plant geography. The discovery of active volcanoes on Io lent the Voya ger mission a narrative device both exotic and traditional. Similarly, the discovery of nitrogen geysers on Neptune's moon Triton seems to connect different periods with a common thread. And the gravitational corridors of the Third Age echo the currents and winds of the first and second ages. Unlike previous eras of discover y, the Voyagers wer e unma nned space probes traveling through an abiotic medium. They encounter ed no other societies and sailed "serenely on autopilot, unworried, and unafflicted by lethargy and ennui." But in a sense, Pyne notes, much of Voyager's planning was geared for a public audience. While stunning ima ges of Jupiter, Saturn, Uranus and Neptune are clearly Voyager's most salient legacy, ma ny scientists were originally opposed to including camer as. Fortunately, cameras were included and photos were indispensable for geological and meteorological comparisons with earthly phenomena. Voya ger 1's ima ge of Earth from outside the solar system was a highlight. In spite of Voyagers' lack of a huma n crew, the craft are the crowning achievement of planetary exploration. Never again will so many worlds, and their staggering diversity of features and weather, be experienced by researchers for the first time. Voyager 2 was successfully redir ected to Uranus and Neptune, providing data on planets unlikely to receive additional visits anytime soon. And the spacecraft press on, gathering infor mation on the "soft geography" within the solar system's heliosheath, wher e solar and interstellar winds meet. For all its renown as an exemplar of successful technology and collaborative, government-supported science, the Voya ger program contains at its core the root of all journeys, according to Pyne, nothing less than a mecha nical manifestation of the huma n quest in keeping with literary traditions that include the Odyssey and other epics. One major differ ence: For Voyager, there's no return, but its images and data have profoundly increased our knowledge of the outer planets and for ever cha nged perceptions of the solar system.
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Briefs: Earth-size Planet is Found in Star's Habitable Zone
An Earth-size planet has been spotted orbiting a nearby star at a distance that would ma kes it not too hot and not too cold--comfortable enough for life to exist. If confir med, Gliese 581g would be the first Earth-like world found in a star's habitable zone, a region wher e a planet's temperature could sustain liquid water on its surface. Astronomers are optimistic about prospects for finding life there. Gliese 581g is one of two worlds discover ed orbiting red dwarf Gliese 581, upping that nearby star's planets to six. The other newfound planet, Gliese 581f, is outside the habitable zone. The star is 20 light-years away in Libra. Gliese 581g is an estimated 0.15 AUs from its star, close enough to be able to orbit in just under 37 days. Gliese 581 pla nets orbit in nearly circular paths. Gliese 581g has an estimated mass three to four times Earth's. From the mass and estimated size, the world is probably a rocky planet with enough gravity to hold onto an atmospher e. The planet is tidally locked to its star, so that one side basks in perpetual daylight while the other remains in darkness. This locked configuration helps stabilize the planet's surface climate. Any emer ging life for ms would have a wide range of stable climates to choose from and to evolve around, depending on their longitude. Average surface temperature may range from 24 below to 10 degr ees. New measurements of Kitt Peak National Observatory night-sky brightness show that, despite metro Tucson's rapid growth, sky brightness has remained constant for 20 years. This suggests strengthened lighting or dinances by Tucson and Pima Cou