Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.aaa.org/EyepieceFiles/aaa/2016_01_January_Eyepiece.pdf Дата изменения: Fri Jan 8 03:51:20 2016 Дата индексирования: Sun Apr 10 03:42:32 2016 Кодировка: Поисковые слова: trees

NASA

2015 saw the first vegetable crop in space. Astronauts aboard the International Space Station sampled the "Outredgeous" red romaine lettuce, grown in microgravity.

Journal of the Amateur Astronomers Association of New York
January 2016 V
olume 65 Number 1; ISSN 0146-7662

An X-Ray Picture is Worth a Thousand Words
AAA LECTURE SERIES By Stanley Fertig On December 4, AAA's 2015-2016 Lecture Series at the American Museum of Natural History continued with a presentation by Bret Lehmer from the University of Arkansas called "T he S tory of Galax y Ev olution f rom an X -ray Perspective." Dr . Br ehmer specia lizes in X-Ray astronomy, and his talk covered the history, methodology, findings, and future of this very special way of seeing the universe. Except during a supernova, very little X-ray light is emitted by ordinary stars, no matter how massive they are. The visible light of our Sun is a million times brighter than its X-ray output. So, where should you look if you NASA/CXC want see invisible X-ray The Chandra X-ray Observatory light? There are two primary orbits 86,500 mi above Earth. and consistent sources of this radiation in the universe: X-ray binaries and Active Galactic Nuclei (AGN). Astronomers had no knowledge of these objects when they first began imaging X-rays in the 1950s. Earth's atmosphere is opaque to X-rays, so they can only be detected from space. Early X-ray astronomy relied on sounding rockets that took pictures during the brief moment when they reached their apogee. This was neither easy nor very successful. A breakthrough came in 1962, when advances in imaging technology produced a hundredfold increase in sensitivity. Astronomer Ricardo Giacconi launched a rocket that year that found bright X-rays coming from the constellation Scorpius ("SCO-X1"). The only understood sources of X -rays at the time were the Sun and the Moon. The discovery of an X ray source outside our Solar System won Giacconi the 2002 Nobel Prize in Physics. Follow-on flights revealed another set of X -rays localized at the Crab Nebula, which were less bright than SCO -X1. But what could have brighter X-rays than a supernova remnant? Scientists determined that SCO -X1 was 9,000 lightyears away, and its apparent brightness implied that its X -rays
X-ray Astronomy (cont'd on Page 4)

The Hidden Stars Behind Stellar Classification
THEATRE REVIEW By Jaclyn Avidon, Rori Baldari, and Amy Wagner If you haven't heard much about early female astronomers, it's not because there weren't any. They were hidden in the shadows, kept behind the scenes by their male counterparts. Last month's Ey epiece introduced a new play by Sean Michael Welch at the Kraine Theater in Manhattan called Insignificant, which tells the stor ies of the unsung fema le a stronomers at the Harvard College Observatory during the turn of the 20th century. AAA members received discount tickets, and we were lucky enough to see this production. Profiled in an episode of the new Cosmos TV series, they were dubbed the "Harvard Computers," or more derogatorily "Pickering's Harem." The all-female staff at the Observatory was hired beginning in 1896 by its director, Edward Charles Pickering for the arduous job of poring over photographic plates to classify stars based on spectral analysis. Essentially human computers, theirs was a tedious task that today we assign to machines. But a computer cannot look up at the night sky and appreciate the beauty of a star, ponder its mysteries, or make connections about its properties. These "computers" acquired a familiarity with the stars and amassed such a wealth of data through their observations, that they were able to put forth brilliant yet uncelebrated theories about the stars ­ and all Harvard University Library without the aid of a telescope. Astronomers Annie Jump They devoted their lives to obser- Cannon (left) and Henrietta Swan Leavitt in 1913. vation but were never permitted access to Harvard's telescopes, just one of many indignities they had to suffer. Despite the fact that several of the women held degrees in astronomy, telescopes were a privilege reserved only for "real" scientists, and therefore, just the men. The play opens in 1925 as Cecelia Payne, a brilliant, young PhD astronomy student ­ the first ever to graduate from Harvard/Radcliffe ­ discusses her doctoral thesis with the older, seasoned astronomer, Annie Jump Cannon. Payne
Theatre Review (cont'd on Page 4)

THIS MONTH: A A A L ect ur e on Jan 8; A A A W int er Par t y on Jan 12.


January 2016

WHAT'S UP IN THE SKY
AAA Observers' Guide
By Tony Faddoul

The First Meteors of 2016
The New Year brings a nighttime display of shooting stars with the Quadrantids Meteor Shower from Jan 1 -6. At its peak, typically 60 Quadrantids per hour can be seen, under perfect conditions and moonless, dark skies. However, the Moon will wash out some of the meteors this year, so only the brightest ones will be visible. There is a very narrow window for watching the Quadrantids. The best viewing this year will be at their peak for only about 6 hours from midnight on Jan 3-4 until dawn. Depending on your location and weather conditions, the number of shooting stars will vary between 25 and 40 per hour in the moonlit sky. The nights before and after the peak may also see a similar number of meteors. Where does it get its name? First seen in 1825, the Quadrantids Meteor Shower appeared to radiate from the constellation Quadrans Muralis. However, when the International Astronomical Union set the list of 88 modern constellations in 1922, Quadrans Muralis was excluded. For this reason, they are sometimes referred to as the BoЖtids, after the nearby modern constellation BoЖtes. The Quadrantids meteors are debris from asteroid 2003 EH1, burning up as they enter the Earth's atmosphere. 2003 EH1 may in fact be a broken off piece of a comet. It takes about 5.5 years to orbit the Sun. Who can see the Quadrantids? This meteor shower favors the skies of the northern hemisphere. Those who live further south will see fewer meteors. The southern hemisphere can only see about 10-15 meteors per hour at peak under dark skies. How can I view the meteor shower? The Quadrantids are fast meteors with blue trails. If you trace their paths backward, they seem to originate from the northern part of the sky below the Big Dipper. But, you don't need to know the constellations or to use a telescope or other visual aid to enjoy the meteor shower. These falling stars will streak everywhere across the sky, so it doesn't matter where you look. Try to find a dark spot as far away from light pollution as possible, and hope for clear skies. Just look up, and enjoy. Have a meteoric New Year!
Sources: timeanddate.com; Encyclopedia Britannica; International Astronomical Union. Follow veteran sky watcher Tony Faddoul each month, as he points our minds and our scopes toward the night sky.

January's Evening Planets: Neptune is in Aquarius
the Water Bearer until 9 PM, setting earlier every night until 7PM by the end of January. Uranus is in Pisces the Fish until 1 AM and setting earlier toward 11 PM through the month. Jupiter will be in Virgo the Virgin as of 10 PM, rising earlier every night until 8PM at the end of the month. Mercury is in Capricornus the Sea-goat for about one hour after sunset in the first half of January.

January's Evening Stars: The Winter Triangle will
dominate the night in January: Sirius, the brightest star viewed from Earth, is in Canis Major the Great Dog, Betelgeuse is in Orion the Hunter, and Procyon is in Canis Minor the Small Dog. Spot Rigel in Orion, Capella in Auriga the Charioteer, Aldeberan in Taurus the Bull, and bright Castor and Pollux in Gemini the Twins. Also find the stars of constellations Andromeda, Cassiopeia, Perseus, Cepheus, Draco, Aquarius, Taurus, Pisces, and Ursa Major and Ursa Minor (the Big and Little Dippers).

January's Morning Planets: Venus will be up between Scorpio the Scorpion and Sagittarius the Archer as of 4 AM and later until 5 AM by the end of the month. Mars will be moving between Virgo and Libra as of 1 AM, lingering until sunrise. Jupiter can be seen in Virgo until sunrise. Mercury is in Sagittarius the Archer around 5 AM for about one hour during the second half of January. Saturn will be in Scorpio the Scorpion as of 4 AM until sunrise.

January's Morning Stars: The Winter Triangle of
Sirius, Betelgeuse, and Procyon will be up until around 3 AM during January. Spot Capella in Auriga the Charioteer, Arcturus in BoЖtes the Herdsman, and Spica in Virgo, along with the stars of constellations Leo, Gemini, Hercules, Libra, Cancer, Orion, Corona Borealis, Cassiopeia, Cepheus, Draco, Perseus, Ursa Major, and Ursa Minor.

January "Skylights"
Jan 2 J J J J J an an an an an 4 9 14 16 21 Last Quarter Moon at 12:30 AM Moon at apogee (251,250 miles away) Quadrantid meteor shower peaks, pre-dawn New Moon at 8:30 PM Moon at perigee (229,670 miles away) First Quarter Moon at 6:25 PM Capella, Moon, Betelgeuse, and Sirius align at 1:00 AM Full Moon at 8:45 PM Moon at apogee (251,377 miles away) Last Quarter Moon at 10:28 PM
Times given in EST.

Jan 23 Jan 30 Jan 31

2


January 2016

Behold the Moon
FOCUS ON THE UNIVERSE By Stan Honda The Moon is a windfall for night sky photographers: it's relatively large and it's easy to predict where it will be in the sky. Even for amateurs with modest equipment, this celestial object offers endless variations. For New Yorkers, it's also readily visible in our light-polluted skies. Still, it's worthwhile to get a glimpse of Earth's natural satellite away from town. Last fall, I found myself at Shippensburg University in south-central Pennsylvania, giving talks about photojournalism, when the planets Jupiter, Venus and Mars approached each other in the pre -dawn sky. Shippensburg is a small town of about 5,500 surrounded by farmland, so I thought I would have a decent chance of capturing the planets away from the glare of big city lights. I woke up at 4 AM on Oct 27 to try to photograph the rising trio. Unfortunately, a thin layer of clouds had moved in overnight, all but obscuring the view of the planets to the east. I could only just make out Venus, the brightest of the three, which showed up only faintly in a few photos I took. Turning to the west, I was then confronted with the magnificent sight of the nearly full Moon surrounded by a giant halo. It was low above the horizon and seemed to hover over the tree line. A lunar halo forms when moonlight refracts through hexagonal ice crystals in the clouds, creating a ring with a radius of about 22 degrees. A variation in the refraction causes the inner part of the circle to be reddish in color and the outer part to be bluish. You don't need an extra-long telephoto lens to take an interesting picture of the phenomenon. The widest angle lens I had with me was a 14-24mm zoom. Setting it at 14mm, I was able to take in a great expanse of the sky and the two -lane road below it. Since it was the middle of the night, I was able to venture into the road and stand directly in the middle, without any fear of traffic. From that vantage point, the halo nestled into a dip in the trees, making a nice composition.

emphasize the halo, but the final image was still very close to what it looked like in person. Earlier in October, I had tried to photograph a crescent moon in a conjunction with the same trio of planets, again during pre-dawn hours. From the reservoir in Central Park, I looked toward the east side of Manhattan as the Moon and Venus rose from behind the buildings. While waiting for the other planets to appear, I shot the crescent moon very near the top of a Fifth Avenue apartment building. I used a 70-200mm zoom set at 200mm and cropped in close around the building and the Moon, focusing attention on the pair. As a result, the Moon became more prominent in the frame and look as if I had used a longer focal length lens.

Stan Honda

Fifth Avenue Moon: Sony a7S camera with a Nikon 70200mm f4 lens at 200mm, exposure of Ѕ sec., f4, ISO6400 at 4:28 AM.

Using an exposure of Ѕ second and lens opening of f4 at ISO 6400 on my Sony a7S camera, I captured some detail in the building, but the lit crescent was washed out. However, the unlit side of the Moon reflecting earthshine showed up nicely, although no detail on this "dark side" can be seen. Normally, you can count on a new or nearly new Moon photo to show off the seas and craters of the lunar surface that are undetectable when the Moon is brighter around full phase. But shooting details on a less luminous Moon and on a surrounding landscape or cityscape can be difficult ­ often you get one or the other. Luckily, crescent phases are very picturesque, so you don't need to show much detail on the orb to make it interesting. If you overexpose the Moon and permit earth shine, you still get a nice skyline -crescent Moon combo. Keeping the Moon very low on the horizon helps too, because atmospheric haze can cut the light down quite a bit. Another trick is to find an opportunity to shoot a moonrise or moonset right around sunset or sunrise, which will level out the exposure difference between the Moon and the foreground. The Sun helps illuminate the terrestrial objects, so you can concentrate on an accommodating lunar subject.

Explore more night sky photography at
Stan Honda

Lunar Halo: Nikon D800 camera with 14-24mm f2.8 lens at 14mm, exposure of 4 sec., f5.6, ISO 800 at 4:12 AM.

www.stanhonda.com.
Submit your photography questions to

stanhonda@gmail.com.

My camera was attached to a small tripod, and with many night sky photos, I chose a relatively shor sure at 4 seconds, with a lens opening of f5.6 and an 800. In processing the image, I increased the contrast

unlike t expoISO of a bit to 3

Stan Honda is a professional photographer. Formerly with Agence France-Presse, Stan covered the Space Shuttle program. In his "Focus on the Universe" column, he shares his night sky images and explores his passions for astronomy and photography.


January 2016 X-ray Astronomy (cont'd from Page 1)
NASA/CXC/Wesleyan Univ./R.Kilgard, et al NASA/STScI

Theatre Review (cont'd from page 1)

M51 and its companion galaxy imaged in visible light (left) and X-rays (right). Large white spots in optical are AGNs; point sources in X-ray are X-ray binaries.

emitted 1,000 times the total energy output of the Sun. Its temperature must be tens of millions of degrees, considerably hotter than the cores of most stars! SCO -X1 was eventually found to be an X-ray binary, where an energetic accretion disk around a neutron star was sucking material from a companion. In 1970, the first dedicated X-ray observatory, Uhuru, launched. It promptly discovered 300 cosmic X -ray sources, many of which were similar to SCO -X1. But others appeared to lie far outside the Milky Way, like Cygnus X-1 (first discovered by a rocket in 1964). Cygnus X-1 became the subject of a famous bet in 1975 between Stephen Hawking and Kip Thorne, who believed its source was a black hole. By 1990, enough evidence proved Cygnus X-1 was indeed a black hole, in binary with a blue supergiant. Hawking conceded, and Kip Thorne won (a subscription to Penthouse!). Scientists now know that AGNs, including quasars, are another cosmic X-ray source. Found at some galactic centers, they are excessively bright across the electromagnetic spectrum, the result of supermassive black holes accreting mass. In the decades after Uhuru, better and better X -ray satellites launched, culminating in the 1999 Chandra X-ray Observatory. Sill in operation, Chandra represents a 7000x increase in resolution from Giacconi's 1962 X-ray observing rocket. Lehmer's research focuses on X-ray binaries of neutron stars. They are distinguished by the mass of their companions, which either have higher mass (HMXBs) or lower mass (LMXBs) than the neutron star. Because a neutron star is the result of a supernova, it must have originally had more mass than its companion in order to explode. This HMXBs are very young pairs; otherwise, the higher mass companion would also have gone supernova too. HMXBs and LXMBs give off different X -ray signatures, and astronomers use them to study galaxy evolution. The universe's earliest galaxies had very massive stars and therefore, more HMXBs. But HMXBs don't last. After a billion years, they die out, and the LMXB population peaks before gradually declining. Young, starburst galaxies have more HMXBs, while galaxies with older stars have more LMXBs. The future of X-ray astronomy and Lehmer's work depends on a successor to Chandra that will have greater sensitivity and resolving power. The best candidate is ESA's Athena, but that isn't planned to launch until 2028; NASA's X-Ray Surveyor project is still on the drawing board. 4

has discovered that the Sun is largely made of hydrogen and helium. Astronomers at the time believed the Sun was predominantly iron, composed like the Earth. On the advice of astronomer Henry Norris Russell, Payne has decided to publish the paper with a disclaimer that would undercut her conclusion, calling it "improbable." As Cannon urges Payne to reconsider, voices from the past begin to call out to her. Through a series of flashbacks, Cannon, who classified more stars in her lifetime than anyone, shows Payne the early days of the "computers." Scenes of the past play as vignettes while Payne watches from the wings. Pickering, who had become dissatisfied with his male assistants, declares his maid could do a better job ­ and so she does. His servant, Williamina Fleming, was the first woman hired, and she was a quick study. Subsequently, he brought in astronomy graduates like Antonia Maury, Cannon, and Henrietta Swan Leavitt, real bargains, as he could get away with paying the women smaller wages. The characters often talk directly to Payne and the audience, and in another bit of meta -theatrics, a vaudevillian trio of male colleagues condescend to and berate the women for working outside the home, making jokes at their expense. During the play, we discover the personalities of the women, who spend day after day, year after year, peering through magnifying glasses and calling out star types. As they work, they bond, bicker, and inspire each other, while each develops Smithsonian Institution her own relationship with Astronomer Cecilia Payne-Gaposchkin the stars. Theories emerge became the first female professor at Harvard in 1956. and discoveries abound, but they concede that personal recognition should take a backseat to science. While Payne watches, she struggles to decide whether to take credit for her bold new theory. Meanwhile, Cannon regrets disappointments of the past, especially those for Leavitt, whose work surely deserved a Nobel Prize. Paid a pittance and never permitted a telescope, Leavitt discovered the relationship between Cepheid variable stars' period and luminosity, making them the standard candles for measuring distances to remote galaxies. Produced by Infinite Variety Productions, the play, directed by Colleen Britt, was specifically written for the company. Its mission is "dedicated to telling stories of w om en throughout history; stories of hope, friendship, and impact." All five of the pioneering women featured in this play made huge impacts on astronomy. You don't hear their names until you go deep into the field, but their discoveries still hold or are in use today. Their stellar classification schema are taught in high schools, though named for their male professors. Near the end of the play, Payne asks Cannon if she thinks girls will one day use their work in their astronomy study. "YES!" we wanted to scream out to the actresses onstage, to reassure their characters that their work will someday be considered anything but insignificant.


January 2016

Inquiring Alien Minds Want to Know
WHAT IF??? By Richard Brounstein Are we alone in the universe? Many of us hope the answer is "no." Despite the unlikely risk of an alien invasion, most of us would welcome the news that extra terrestrials do exist. Popular culture would suggest that we love the idea of advanced, space-faring societies with cool technology beyond our own capabilities ­ even if we don't all agree on whether they should visit Earth. We want to know they exist, but we don't want to find out the hard way. Humans are a very young species, and the advent of our civilization and industrialization was only recent. We're just waking up, so to speak. If there are other forms of intelligent life out there, it is unlikely that they would all be so underdeveloped. More likely, they would be hundreds, thousands, or perhaps millions of years more advanced in terms of technology. According to the Kardashev scale of energy usage, a Type 1 civilization utilizes and stores energy from its home star. As humans still rely mostly on fossil fuels, ours is considered to be more of a Type 0 civilization. Type 2 or Type 3 civilizations can harness enough energy for interstellar or intergalactic travel. We're a far cry from that.

SETI

The Allen Telescope Array at the SETI Institute in California.

In November, the SETI Institute, which is actively engaged in the search for extraterrestrial intelligence, announced it was focusing on the star system KIC 8462852. Known as Tabby's Star, it experiences aperiodic dimming of up to 20%, according to the Kepler Space Telescope. Transits of large planets dim a star's light by only 1%. With a planet ruled out as the cause, SETI searched for signals of a Type 2 civilization, which can control the energy output of a star. After searching for a month, no laser or radio signals were detected. The star's dimming may be the result of debris from a comet break-up, but an artificial source hasn't been ruled out. Even if SETI's search had proved that aliens exist, why wouldn't these intelligent lifeforms have contacted us or stopped by already? Would such an advanced civilization care about an infant species like us? "W e are arrogant to think that we are so interesting, extraterrestrial beings would travel thousands of light years just to visit us," sa ys r enowned physicist Michio Kaku. He believes there are intelligent lifeforms out there, and they likely know we're here, but they have no incentive to check us out: "...w e are lik e ants to them ... .W e have nothing to offer a civilization that advanced ." I respectfully disagree with Dr. Kaku. Imagine a future where humans become a technology superpower? An ad5

vanced, space-faring species no longer bound to Earth, we would first live and work in colonies around the Solar System. We would engineer great structures in space, leveraging materials found on moons, comets, and asteroids. Machines would do the work of building and maintaining human habitats, growing food, and manufacturing goods. Our greatest driver for building such a future is exploration. That impulse wouldn't stop. We would push ourselves to improve portable energy and artificial intelligence in order to send space probes to other systems. A probe on a journey tens or hundreds of light-years from Earth would be out of contact for many years. It would work autonomously, and the data it sends back would be analyzed over several generations of scientists. While extending our civilization outside the Solar System would occur on a very long time scale, our short human history would suggest that expansion is inevitable. So, would our own future advanced civilization be interested in some primitive intelligent species on a barely industrialized planet, if it came across one? What if it came across a bunch of them? It is true that finding an anthill on Earth doesn't make headlines, but discovering ants elsewhere in the universe would be front-page news. Spotting even a microbe on Mars would be the story of the century. Dr. Kaku argues that an advanced species that has come across plenty of "ants" in its time would find another one too boring to investigate, but myrmecologists would beg to differ. Ants are complex life forms with many variations. Even if thousands of discoveries made finding another primitive species ho-hum, we would still take a closer look. Each find would merit a science expedition. Each civilization would be poked, prodded, and put under a microscope for study. How do its societies operate? How do its members feed themselves, power their cities, move around their planet, communicate with one another, or engage in exploration? Our future selves would be as far ahead of them as we are ahead of our primate cousins today. We would absolutely be interested in studying them. Yes! An intelligent species that can communicate and create technology, no matter how crude, is worth studying. Studying an alien civilization would help us understand how life evolves and manifests throughout the universe, and would show us the possible evolutionary paths out there. How does ours compare? Yet, despite our interest in studying less technologically advanced species, we should not necessarily make contact. Star Trek's " P r ime Dir ective" should a pply: do not inter fer e with the development of a society. Announcing our existence would surely do that. Unfortunately, a look back at human history once again would suggest that we may not be able to resist doing so. Throughout time, when an advanced civilization has encountered one that is more primitive, exploitation, persecution, and land abuse have ensued. As long as greed and glory are the impetus for exploration, the outlook would be grim for the nascent species. Let us hope a truly advanced alien civilization that spots us here on Earth will have evolved beyond that. While I would really want to meet them, ask a million questions, and learn all I could, I almost hope they won't reveal themselves. They can look, but they shouldn't touch. So enjoy the show, you voyeuristic aliens!
Sources: seti.org; astronomynow.com; observer.com; wiki.


January 2016

The Dark Source of Dino Demise
AMNH FRONTIERS LECTURE By Bart Erbach Ham and Eggs. Hall and Oats. Dark matter and dinosaurs. If that last pairing strikes you as odd, then chances are you missed a fascinating talk at the Hayden Planetarium on December 7 that was part of the American Museum of Natural History's Frontiers L ecture Series. It wa s given by Ha r va r d astrophysicist and author Lisa Randall. Randall, who grew up in Queens, opened her talk by reminiscing about how her primary school only took one class trip a year, either to the zoo or to AMNH, where her favorite exhibits were the dinosaurs and the planetarium. Randall was introduced that evening by fellow New Yorker and Director of the Hayden Planetarium, Neil deGrasse Tyson, who noted that he also discovered the cosmos at the AMNH planetarium, because he could "only see eleven or twelve stars" in the Br onx neighbor hood wher e he grew up. Speaking under the Hayden's newly -installed seamless dome, Randall described a theory she presents in her new book, Dark Matter and the Dinosaurs: The Astounding Interconnectedness of the Universe. Randall's storytelling skills were on display as she took the audience on a whirlwind celestial tour, connecting invisible dark matter to the extinction of dinosaurs, and ultimately to the rise of humans on earth. "Dark m atter is a really conf using term ," said Randall. "W e call it dark m atter because w e don't k now w hat it is. It sounds exotic. But it's just matter that is made up of something that we're not made up of." The world we see during the day, the stars we see at night, the galaxies we explore with telescopes and satellites ­ this is all ordinary matter, the purview of particle physicists like Randall. However vast it seems, there is five times less of that visible stuff out there than the matter we can't see. First postulated by astronomers like Jan Oort in the 1930s, invisible dark matter is now believed to account for 85% of all matter in the universe. Even though we cannot see them, "billions of dark matter particles pass through you every second," Ra nda ll sa id. "A better nam e w ould be transparent m atter." While much about dark matter remains a mystery, scientists do know that dark matter exerts an enormous gravitational influence. "Dark matter is the scaffolding of the universe," and without it, the universe would not have been able to form galaxies, Randall explained. Randall said her research led to the idea that dark matter might collect in a disk within the plane of the Milky Way. Now she hypothesizes that there may be a connection between that dark matter disk and mass extinctions on Earth. The most famous mass extinction event on Earth oc6

curred about 66 million years ago when a mountain -sized asteroid crashed into the planet with the force of a billion atomic bombs. It obliterated the dinosaurs and three -fourths of all living beings. We can still see its point of impact today, a nearly 200-kilometer-wide crater off the coast of the Yucatan Peninsula. Randall began to wonder whether there was any pattern to the occurrence of such large impact events on Earth. She found evidence to suggest that more of them happened every 30 to 35 million years: "S o the question is w hy w ould this happen on a periodic basis?" Our Solar System orbits around the center of the Milky Way every 240 million years. But its path isn't entirely smooth. As it orbits, it moves up and down slightly through the plane of the galaxy. If a disk of dark matter resided in that plane, then the Solar System would pass through it about every 30 to 35 million years during the galactic orbit. Icy objects the outermost region of our Solar System known as the Oort Cloud (named for the very same Jan Oort), are so far out that they are only weakly bound by the Sun's gravity. Theoretically, they could be influenced by galactic dark matter if the Solar System passes through it. When this occurs, the enhanced gravitational pull of the dark matter could disturb these icy objects and trigger them to become long period comets that travel toward the inner Solar System. Randall believes that the sources of large species-ending impact events on Earth are comets ejected from the Oort Cloud at the fringe of our Solar System, set into motion by a dark matter disk in the galactic plane. If true, this would establish an astounding connection between dark matter and the dinosaurs and could win Randall a Nobel Prize. Is there any way to prove Randall's theory? ESA's Gaia satellite may hold the answer. Charting a three -dimensional map of our galaxy, it will complete a stellar census and measure positions and velocities of stars. It will also be able to determine the gravitational effect of dark matter on those stars. In this process, Gaia may reveal to us the composition of the Milky Way and the dark matter scaffolding that holds it up. We may know soon if Randall is right. Until then, we are left to wonder if it was dark matter we have to thank for our presence on Earth, killing off the dinosaurs to give us small mammals a chance to thrive. 20% off tickets for AAA Members with code 48714. Call 718-636-4100 or visit BAM.org/Encompass Opera.

At BAM Fisher


January 2016

Solar Sagas
SOHO Celebrates 20 Years in Space ESA and NASA's Solar and Heliospheric Observatory (SOHO) has illuminated our Sun for 20 years, revolutionizing heliophysics. "S OHO changed the popular v iew of the sun from a picture of a static unchanging object in the