Download Volume 36 Number 10 October 2010 Jeremiah Baker

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

Messier 87 wikipedia, lookup

Milky Way wikipedia, lookup

Transcript
FALL ASTRONOMY DAY
Saturday, October 16
PUBLIC OBSERVING
Prairie Park Nature Center
SUNDAY
October 24
8:00—9:30 PM
November 21
8:00—9:30 PM
December 12
8:00—9:30 PM
MONTHLY MEETING
Friday, Oct. 22, 2010
2001 Malott Hall
L.S.S.T
Dr. Barbara Anthony–Twarog
President:
Rick Heschmeyer
[email protected]
University Advisor:
Dr. Bruce Twarog
[email protected]
Webmaster:
Gary Webber
[email protected]
Observing Clubs
Doug Fay
[email protected]
Volume 36 Number 10
October 2010
Report from the Officers:
Our first meeting of the semester was well attended with a
presentation on the changing
face of the sun. Despite the
title, the change referred to the
revision in the current estimate
of the chemical composition of
the sun. Revised and improved
analysis of high resolution
spectra implies that the sun has
carbon, nitrogen, and oxygen
abundances that are 40% lower
than adopted 15 years ago.
These changes require significant revision in the interior
models of the sun and impact our estimates of abundances in other stars
and nebulae in the Milky Way. For our next meeting in October, we will have
(Continued on page 2)
A Stellar Welcome to a new member of the AAL
Jeremiah Baker
Jack Horkheimer: 1938—2010
INSIDE THIS ISSUE
Milky Way Sidelined
3
NASA Space Place
4
OCT. MEETING POSTER
5
HST: Supernova 1987A
6
HST: TNO’s
6
Spitzer: Dark Cocoons
7
WISE: Dark Heart of the King
8
Stellar Cannibalism
9
WISE (continued)
9
Cannibalism (continued)
10
Jack Horkheimer, a playwright turned amateur astronomer who inspired millions of people to look a little closer at the nighttime sky with his pioneering
planetarium shows and long-running public television show, "Jack Horkheimer: Star Gazer," died Aug. 20 in Miami of a respiratory ailment. He was
still writing and hosting the weekly five-minute segment at the time of his
death; prerecorded episodes scheduled to run through Sept. 5 are available
on his Web site. Using plain language, cheesy animation and a trippyspacey synthesized soundtrack, he deciphered constellations and explained
everything from solar eclipses to the winter solstice.
"Greetings, greetings, fellow stargazers," was his signature introduction, delivered each week with caffeinated eagerness. Often pictured perched on the
cartoon rings of Saturn, Mr. Horkheimer also recounted age-old myths about
the celestial realm. The constellation known as Lepus the hare, he reminded
viewers in a 1986 episode, has been seen in the West as a "heavenly rabbit,
huddled and cringing in fear in the grass beneath the feet of Orion the
Hunter." Or, according to Chinese tradition, it is a rest stop in the sky -- in
Mr. Horkheimer's terms, a "heavenly outhouse in the sweet bye and bye. If
(Continued on page 2)
1
(Continued from page 1)
a report on the Large Synoptic Survey Telescope (LSST). This 8m-class telescope is currently in the design and
construction phase, with the mirror purchased and a site selected at Cerro Pachon in Chile. The telescope has been
selected as the top priority for the astronomical community by the 2010 Decadal Survey (see pg. 4), which sets
funding/planning priorities for the community.
The public observing schedule for the semester is posted at left on page 1. Our first observing session was exceptional with beautifully dark, clear skies and modest temperatures. A respectable stream of high school students from
Kent McDonald’s class kept Bill Winkler, Dave Kolb (supplier of the photo on pg. 1), and Bill Wachspress actively
supplying sights and insight. Upcoming events include Fall Astronomy Day on Oct. 16 and our annual Webelo Scout
session planned for the November 5 meeting. It’s a little earlier than usual to avoid conflicts with the basketball
schedule. Both events require a lot of help, so please note these on your calendar and contact Rick
([email protected]) if you can contribute your time and scopes. See you in a couple of weeks.
(Continued from page 1)
you've never heard this stuff before," he told Astronomy magazine in
2006, "it blows your little blue booties off because it's fun, fun, fun."
Millions of people each week watched the show, which aired on PBS
and on the United States Information Agency's Worldnet. Mr. Horkheimer also organized stargazing parties and was a frequent commentator in the national media on comets, eclipses and other astronomical
events. He called himself a science dramatist, not an astronomer, and
was clear that his interest in outer space lay not so much in science as
in more sweeping existential questions.
"Stargazing is all about where you are in time and space. The reason
people get out their telescopes and attend star parties is because they
are trying to peer out over the horizon to find their place in the universe," he told the Miami Herald in a 1982 profile. "If I can help them find that, that's all that matters."
Mr. Horkheimer served for 35 years as the director of the Space Transit Planetarium at the Miami Science Museum.
He turned presentations there from academic lessons into whiz-bang shows that used music, metaphor and animation to explore the night sky and inspire curiosity about the heavens. Tinkering with lasers and state-of-the-art projectors, he created images of floating, three-dimensional planets and other special effects. Among his awardwinning presentations were "Child of the Universe," starring talk show host Sally Jessy Raphael as the voice of the
solar system. Mr. Horkheimer's early multimedia shows captured the imagination of young children and scienceaverse grown-ups alike, attracting wide audiences that helped make the planetarium a profit center for the Miami
Science Museum. Planetarium directors around the world began to imitate his style.
"He changed the way that people thought about the use of planetaria," said Gillian Thomas, the museum's president
and chief executive. "Jack was the first person to imagine it was an immersive experience that could take you beyond just what you see to look at the universe in a different way."
About the Astronomy Associates of Lawrence
The club is open to all people interested in sharing their love for astronomy. Monthly meetings are typically on the second Friday of each month and often feature guest speakers, presentations by club members, and a chance to exchange amateur astronomy tips. Approximately the last Sunday of each month we have an open house at the Prairie Park Nature Center. Periodic
star parties are scheduled as well. For more information, please contact the club officers:our president, Rick Heschmeyer at
[email protected], our webmaster, Gary Webber, at [email protected], or our faculty advisor, Prof. Bruce Twarog at
[email protected] Because of the flexibility of the schedule due to holidays and alternate events, it is always best to check the
Web site for the exact Fridays and Sundays when events are scheduled. The information about AAL can be found at
http://www.ku.edu/~aal.
Copies of the Celestial Mechanic can also be found on the web at
http://www.ku.edu/~aal/celestialmechanic
2
Milky Way Sidelined in Galactic Tug-of-War, Computer Simulation Shows
Science Daily
The Magellanic Stream is an arc of hydrogen gas spanning more than 100 degrees of the sky as it trails
behind the Milky Way's neighbor galaxies, the Large and Small Magellanic Clouds. Our home galaxy, the
Milky Way, has long been thought to be the dominant gravitational force in forming the Stream by pulling
gas from the Clouds.
A new computer simulation by Gurtina Besla (Harvard-Smithsonian Center for Astrophysics) and her colleagues now shows, however, that the Magellanic Stream resulted from a past close encounter between
these dwarf galaxies rather than effects of the Milky Way.
"The traditional models required the Magellanic Clouds to complete an orbit about the Milky Way in less
than 2 billion years in order for the Stream to form," says Besla. Other work by Besla and her colleagues,
and measurements from the Hubble Space Telescope by colleague Nitya Kallivaylil, rule out such an orbit,
however, suggesting the Magellanic Clouds are new arrivals and not long-time satellites of the Milky Way.
This creates a problem: How can the Stream have formed without a complete orbit about the Milky Way?
To address this, Besla and her team set up a simulation assuming the Clouds were a stable binary system
on their first passage about the Milky Way in order to show how the Stream could form without relying on a
close encounter with the Milky Way. The team postulated that the Magellanic Stream and Bridge are similar
to bridge and tail structures seen in other interacting galaxies and, importantly, formed before the Clouds
were captured by the Milky Way.
"While the Clouds didn't actually collide," says Besla, "they came close enough that the Large Cloud pulled
large amounts of hydrogen gas away from the Small Cloud. This tidal interaction gave rise to the Bridge we
see between the Clouds, as well as the Stream."
"We believe our model
illustrates that dwarf-dwarf
galaxy tidal interactions
are a powerful mechanism
to change the shape of
dwarf galaxies without the
need for repeated interactions with a massive host
galaxy like the Milky Way."
While the Milky Way may
not have drawn the
Stream material out of the
Clouds, the Milky Way's
gravity now shapes the
This plot shows the simulated gas distribution of the Magellanic System result- orbit of the Clouds and
thereby controls the aping from the tidal encounter between the Large Magellanic Cloud (LMC) and
Small Magellanic Cloud (SMC) as they orbit our home Milky Way Galaxy. The pearance of the tail. "We
entire sky is plotted in galactocentric coordinates of longitude and latitude. The can tell this from the lineof-sight velocities and spaMagellanic Stream is the pronounced tail of material that stretches 150 degrees across the southern sky. The solid line shows the calculated path of the tial location of the tail observed in the Stream toLMC and the dotted line is the path of the SMC. The color range from dark to
day," says team member
light shows the density (lower to higher) of the hydrogen gas making up the
Lars Hernquist of the CenMagellanic Stream and the Bridge that connects the two dwarf galaxies.
ter.
(Credit: Plot by G. Besla, Milky Way background image by Axel Mellinger
(used with permission))
3
The Hunt is On!
By Carolyn Brinkworth
The world of astronomy was given new direction on August 13, 2010, with the publication of the Astro2010 Decadal Survey. Astro2010 is the latest in a series of surveys produced every 10 years by the National Research Council (NRC) of the
National Academy of Sciences. This council is a team of senior astronomers who recommend priorities for the most important topics and missions for the next decade.
Up near the top of their list this decade is the search for Earth-like planets around other stars—called “extrasolar planets”
or “exoplanets” —which has become one of the hottest topics in astronomy.
The first planet to be found orbiting a star like our Sun was discovered in 1995. The planet, called “51 Peg b,” is a “Hot
Jupiter.” It is about 160 times the mass of Earth and orbits so close to its parent star that its gaseous “surface” is seared by
its blazing sun. With no solid surface, and temperatures of about 1000 degrees Celsius (1700 Fahrenheit), there was no
chance of finding life on this distant world. Since that discovery, astronomers have been on the hunt for smaller and more
Earth-like planets, and today we know of around 470 extrasolar planets, ranging from about 4 times to 8000 times the
mass of Earth.
This explosion in extrasolar planet discoveries is only set to get bigger, with a NASA mission called Kepler that was
launched last year. After staring at a single small patch of sky for 43 days, Kepler has detected the definite signatures of
seven new exoplanets, plus 706 “planetary candidates” that are unconfirmed and in need of further investigation. Kepler is
likely to revolutionize our understanding of Earth's place in the Universe.
We don't yet have the technology to search for life on exoplanets. However, the infrared Spitzer Space Telescope has
detected molecules that are the basic building blocks of life in two exoplanet atmospheres. Most extrasolar planets appear unsuitable for supporting life,
but at least two lie within the
“habitable zone” of their stars,
where conditions are theoretically
right for life to gain a foothold.
We are still a long way from detecting life on other worlds, but in
the last 20 years, the number of
known planets in our Universe
has gone from the 8 in our own
Solar System to almost 500. It's
clear to everyone, including the
Astro2010 decadal survey team,
that the hunt for exoplanets is only
just beginning, and the search for
life is finally underway in earnest.
Explore Spitzer’s latest findings at
http://www.spitzer.caltech.edu.
Kids can dream about finding
other Earths as they read “Lucy’s
Planet Hunt” at http://
spaceplace.nasa.gov/en/kids/
storybooks/#lucy.This article was
provided by the Jet Propulsion Laboratory, California Institute of TechArtist’s rendering of hot gas planet HD209458b. Both the Hubble and Spitzer Space
nology, under a contract with the
Telescopes have detected carbon dioxide, methane, and water vapor—in other words,
National Aeronautics and Space Adthe basic chemistry for life—in the atmosphere of this planet, although since it is a hot
ministration.
ball of gas, it would be unlikely to harbor life.
4
5
New Hubble Observations of Supernova 1987A Trace Shock Wave
HST PRESS RELEASE I
An international team of astronomers using the Hubble
Space Telescope reports a
significant brightening of the
emissions from Supernova
1987A. The results, which
appear in this week's Science
magazine, are consistent with
theoretical predictions about
how supernovae interact with
their immediate galactic environment.
The team observed the supernova remnant in optical, ultraviolet, and near-infrared light.
They studied the interaction
between the ejecta from the
stellar explosion and a glowing
6-trillion-mile-diameter ring of
gas encircling the supernova
remnant. The gas ring was
probably shed some 20,000
years before the supernova
exploded. Shock waves resulting from the impact of the
ejecta onto the ring have
brightened 30 to 40 pearl-like
"hot spots" in the ring. These
blobs likely will grow and merge together in the coming years to form a continuous, glowing circle.
"We are seeing the effect a supernova can have in the surrounding galaxy, including how the energy deposited by these
stellar explosions changes the dynamics and chemistry of the environment," said University of Colorado at Boulder Research Associate Kevin France of the Center for Astrophysics and Space Astronomy. "We can use these new data to
understand how supernova processes regulate the evolution of galaxies."
Discovered in 1987, Supernova 1987A is the closest exploding star to Earth to be detected since 1604 and it resides in
the nearby Large Magellanic Cloud, a dwarf galaxy adjacent to our own Milky Way Galaxy.
Hubble Harvests Distant Solar
System Objects
HST PRESS RELEASE II
This is an artist's concept of a craggy piece of
solar system debris that belongs to a class of bodies called trans-Neptunian objects (TNOs). Most
TNOs are small and faint, making them difficult to
spot. Generally, they are more than 100 million
times fainter than objects visible to the unaided
eye. The newfound TNOs range from 25 to 60
miles (40-100 km) across. In this illustration, the
distant Sun is reduced to a bright star at a distance of over 3 billion miles. Astronomers culling
the data archives of NASA's Hubble Space Telescope have added 14 new TNOs to the catalog.
Their search method promises to turn up hundreds more.
6
Shining Starlight on the Dark Cocoons of Star Birth
Spitzer Telescope Press Release
Astronomers have discovered a new, cosmic phenomenon, termed "coreshine," which is revealing new information
about how stars and planets come to be.
The scientists used data from NASA's Spitzer Space Telescope to measure infrared light deflecting off cores -- cold,
dark cocoons where young stars and planetary systems are blossoming. This coreshine effect, which occurs when
starlight from nearby stars bounces off the cores, reveals information about their age and consistency. In a new paper, to be published Friday, Sept. 24, in the journal Science, the team reports finding coreshine across dozens of
dark cores.
"Dark clouds in our Milky Way galaxy, far from Earth, are huge places where new stars are born. But they are shy
and hide themselves in a shroud of dust so that we cannot see what happens inside," said Laurent Pagani of the
Observatoire de Paris and the Centre National de la Recherche Scientifique, both in France. "We have found a new
way to peer into them. They are like ghosts because we see them but we also see through them."
Pagani and his team first observed one case of the coreshine phenomenon in 2009. They were surprised to see that
starlight was scattering off a dark core in the form of infrared light that Spitzer could see. They had thought the
grains of dust making up the core were too small to deflect the starlight; instead, they expected the sunlight would
travel straight through. Their finding told them that the dust grains were bigger than previously thought -- about 1
micron instead of 0.1 micron (a typical human hair is about 100 microns). That might not sound like a big difference,
but it can significantly change astronomers' models of star and planet formation. For one thing, the larger grain size
means that planets -- which form as dust circling young stars sticks together -- might take shape more quickly. In
other words, the tiny seeds for planet formation may be forming very early on, when a star is still in its preembryonic phase.
But this particular object observed in 2009 could have been a fluke. The researchers did not know if what they found
was true of other dark clouds -- until now. In the new study, they examine 110 dark cores, and find that about half of
them exhibit coreshine. The finding amounts to a new tool for not only studying the dust making up the dark cores,
but also for assessing their age. The more developed star-forming cores will have larger dust grains, so, using this
tool, astronomers can better map their ages across our Milky Way galaxy. Coreshine can also help in constructing
three-dimensional models of the cores -- the deflected starlight is scattered in a way that is dependent on the cloud
structures.
Said Pagani, "We're opening a new window on the realm of dark, star-forming cores."
7
The Dark Heart of the King
NASA’s Wide-field Infrared Survey Explorer, or WISE, captured this image of a hidden star-forming cloud complex
of dust and gas located in the constellation of Cepheus. Cepheus, father of Andromeda, was a mythological king in
the ancient Greek world. This image of dark nebulae lies near the heart of the king, as imagined by the ancient
Greeks.
The dust in these nebulae blocks visible light passing through it, and the cloud and its contents are mostly hidden
when viewed in visible light. What appears to the naked eye as the blackness of space is in fact a dark nebula.
WISE’s infrared vision both penetrates the dust to see stars within the cloud as well as detects the glow of the dust
that makes up the cloud.
Different parts of this nebula have a variety of names in astronomical catalogs. The central portion is known as
IRAS 22298+6505. IRAS stands for Infrared Astronomical Satellite, a predecessor to WISE and an international
satellite that mapped the sky in infrared light in the 1980s. Other portions of this cloud are called TGU H686 P2 and
(Continued on page 9)
8
(Continued from page 8)
LDN 1213. As with IRAS, the first letters of these objects refer to astronomical catalogs. TGU is an acronym for the Tokyo
Gakugei University catalog, while LDN stands for Lynds Dark Nebula catalog. The surveys that produced these catalogs
were often done with fields of view that were much smaller than WISE's. What looked like distinct nebulae in those surveys are revealed as a much larger cloud complex by WISE. This complex spans about 120 light-years across and is located about 2,500 light-years away at the edge of a spiral arm of the Milky Way Galaxy, called the Orion spur.
These types of clouds are the locations where stars are born. When a cloud of dust and gas becomes so dense that it can
block out light, it is ripe for parts of the cloud to collapse into newborn stars. The whole cloud doesn’t form stars all at one
time. Some parts of the cloud go first, and the winds and radiation from the biggest and hottest stars in that first generation will blow away parts of the cloud and compress other parts causing further star formation to occur. The bright blue
giant star, 26 Cephei, is an example. Seen in the upper central part of this image, 26 Cephei is surrounded by a bubble of
cool, red dust and dust-enshrouded younger stars that may owe their existence to their older sibling.
BP Psc: Chandra Finds Evidence for Stellar Cannibalism
The composite image on the left shows X-ray and optical data for BP Piscium (BP Psc), a more evolved version of our Sun about 1,000 light years from Earth. Chandra X-ray Observatory data are colored in purple,
and optical data from the 3-meter Shane telescope at Lick Observatory are shown in orange, green and blue.
BP Psc is surrounded by a dusty and gaseous disk and has a pair of jets several light years long blasting out
of the system. A close-up view is shown by the artist's impression on the right. For clarity a narrow jet is
shown, but the actual jet is probably much wider, extending across the inner regions of the disk. Because of
the dusty disk, the star's surface is obscured in optical and near-infrared light. Therefore, the Chandra observation is the first detection of this star in any wavelength.
(Continued on page 10)
9
(Continued from page 9)
The disk and the jets, seen distinctly in the optical data, provide evidence for a recent and catastrophic interaction in which BP Psc consumed a nearby star or giant planet. This happened when BP
Psc ran out of nuclear fuel and expanded into its "red giant" phase.
Jets and a disk are often characteristics of very young stars, so astronomers thought BP Psc might be
one as well. However, the new Chandra results argue against this interpretation, because the X-ray
source is fainter than expected for a young star. Another argument previously used against the possible youth of BP Psc was that it is not located near any star-forming cloud and there are no other
known young stars in its immediate vicinity. The Chandra image supports this absence of a cluster of
young stars, since multiwavelength studies show that most of the X-ray sources in the composite image are likely to be rapidly growing supermassive black holes in the centers of distant galaxies.
Celestial Mechanic October 2010
AAL
Astronomy Associates of
Lawrence
University of Kansas
Malott Hall
1251 Wescoe Hall Dr, Room 1082
Lawrence, KS 66045-7582
10