EAS BUSINESS…
June Meeting Recap
Julianne
Dalcanton spoke to us about her study of dwarf galaxies.
Next Meeting – Saturday June 24th At
Providence Pacific Clinic Hospital – Monte Cristo Room – 7:00 PM
The
Everett Astronomical Society's next meeting will be Saturday July 22nd,
at 7:00 PM, in the PROVIDENCE Monte Cristo Room at Providence Hospital
PACIFIC Clinic at 916 Pacific Avenue in Everett. The speaker will be Kevin
Krisciunas of the UW Astronomy department talking
about “Observations of Type 1A Supernovae, and what they can tell us”.
Scheduled Meeting Topics:
Jul 22 -
Kevin Krisciunas - UW
Aug 26 –
(speaker not confirmed)
Sep 30 –
John Armstrong UW - Mars climate modeling/astrobiology
Oct 28 –
Vandana Desai of UW?
Nov 18 –
Brad Snowder, WWU, Native American star lore
Dec 16 –
Holiday party
Member News
We are glad to introduce two new writers for the radio show
IT'S OVER YOUR HEAD.
Greg Donohue of the Everett Astronomical Society and Ted
Vosk of the Seattle club are currently sharing the duties of script writing and
reading the material into the microphones, with Jim Ehrmin of EAS operating the
recording equipment and reading some paragraphs.
The program is broadcast every Wednesday morning at
approximately 7:20 (exact time varies a bit) on KSER, FM 90.7. If you miss a broadcast, or would like to go
over the material again, you can find it on KSER's website, www.kser.org Go to Links, then choose IT'S OVER YOUR
HEAD. You can also get it on Greg
Donohue's website, www.galaxyguy.com
If you like the program, give the station a call and tell
them so. We recently asked the station
manager if he could put us on twice on Wednesdays. Maybe he will, if he knows people are interested. Sometimes we describe club activities, so
it's good publicity.
Financial Health
The club maintains a safe $1400+ balance. We try to keep
approximately a $500 balance to allow for contingencies.
Club Star Party Info
Dates for
this season’s club star parties:
Aug 5 Sept 2 Sept 30 Oct 7
The next star party on August 5th is scheduled to
be held at Brad Ashforth’s place near Lake Rosinger, at 2224 Dubuque, Snohomish.
Call Brad at (360) 862-0907, or email bashforth@foxinternet.net for directions, or contact Dave Mullen.
We try to hold
informal close-in star parties each month during the spring and summer months
on a weekend near the New moon at a member’s property or a local park. (call
Dave Mullen at (425) 347-3151 or club officers for info.) During the winter, phone tree is used to
arrange spur-of-the –moment events during clear weather spells when there are
significant celestial happenings.
Club Scopes’ Status
Scope Loan
Status Waiting
10-inch
Dobsonian On loan No wait list
8-inch Dobsonian On
Loan No wait
list
60 mm Refractor On
Loan No wait
list
Astro Calendar
July 2000
Jul 01 - Partial
Solar Eclipse, Visible From S. America, S. Pacific
Jul 01 - Asteroid 80
Sappho Occults TYC 5156 02199 (10.1 M.)
Jul 02 - Mercury
Passes 5 Degrees From Venus
Jul 03 - Asteroid 142
Polana Occults TYC 6847 00998 (9.7 Mag)
Jul 04 - Earth At
Aphelion (1.017 AU From Sun)
Jul 04 - Comet C/1999
K5 (LINEAR) Perihelion (3.255 AU)
Jul 04 - Asteroid 40
Harmonia At Opposition (9.3 Mag)
Jul 06 - Ast. 441
Bathilde Occults TYC 5735 02403 (9.7 Mag)
Jul 08 – EAS Star Party – at the Ward’s
Jul 12 - Venus At
Perihelion
Jul 12 - Asteroid 80
Sappho At Opposition (10.2 Magnitude)
Jul 16 - Lunar
Eclipse visible from central Pacific ocean.
Jul 17 - Asteroid 4
Vesta At Opposition (5.4 Magnitude)
Jul 22 - EAS Meeting 7:00 PM
– Providence Pacific Clinic
Jul 23 - Comet C/1999
S4 (LINEAR) Near-Earth Flyby (0.37 AU)
Jul 24 - P/1999 J5
(LINEAR) Closest Approach To Earth (3 AU)
Jul 26 - Comet C/1999
S4 (LINEAR) Perihelion (0.765 AU)
Jul 27-30 Table Mt. Regional Star Party (Ellensburg)
Jul 27 - Mercury at
Greatest Western Elongation (19 Degrees)
Jul 27 - Neptune At
Opposition
Jul 29 - South
Delta-Aquarids Meteor Shower Peak
Jul 29 - Moon Occults
Mercury
Jul 30 - Moon Occults
Mars
Jul 31 - Partial
Solar Eclipse (Visible from N. Asia & NW US)
Jul 31 - Asteroid 8
Flora At Opposition (8.6 Magnitude)
August 2000
Aug 01 - Moon Occults
Venus
Aug 01 - Alpha
Capricornids Meteor Shower Peak
Aug 05 - Asteroid 9
Metis At Opposition (9.5 Magnitude)
Aug 05 – EAS Star Party – at the Ashforth’s, Lake Roesinger
Aug 05 - Neil
Armstrong's 70th Birthday (1930)
Aug 06 - Southern
Iota Aquarids Meteor Shower Peak
Aug 06 - Asteroid 3
Juno Occults TAC -03 16114 (11.5 M. Star)
Aug 07 - Asteroid 372
Palma Occults HIP 11333 (7.4 M. Star)
Aug 09 - Mercury At
Perihelion
Aug 09 - Asteroid 3
Juno At Opposition (8.7 Magnitude)
Aug 09 – Ast. 88
Thisbe Occults GSC 0599 01001 (10.8 M Star)
Aug 10 - Mercury
Passes 0.1 Degrees From Mars
Aug 10 - Asteroid 140
Siwa At Opposition (10.5 Magnitude)
Aug 11 - Uranus At
Opposition
Aug 12 - Perseids
Meteor Shower Peak
Aug 12 - Comet C/1999
T2 LINEAR Closest To Earth (2.9AU)
Aug 12 - 40th
Anniversary (1960), Echo 1 Launch
Aug 13 - Moon Occults
Neptune
Aug 17 - Asteroid 135
Hertha At Opposition (9.6 Magnitude)
Aug 23 - Asteroid 393
Lampetia At Opposition (10.6 Magnitude)
Aug 25 - Northern
Iota Aquarids Meteor Shower Peak
Aug 26 - EAS Meeting 7:00 PM
– Providence Pacific Clinic
Aug 28 - Moon Occults
Mars
Aug 30 - Asteroid 3
Juno Occults GSC 5204 00253 (11.7 M Star)
Aug 31 - Asteroid 626
Notburga At Opposition (11.0 Magnitude)
Over The Airwaves
E.A.S.
members, Jim Ehrmin and Pat Lewis, with writing from Greg Donohue and Ted Vosk,
present the astronomy radio show, "It's Over Your Head", on radio
station KSER. The show is broadcast
every Wednesday morning at 7:20 AM to KSER FM 90.7. The six minute astronomy segment gives a weekly look of what's up
in the night sky over Snohomish County.
Pat would appreciate your
suggestions about subjects for scripts that you would find interesting. If you have information on a good subject,
send her a copy. If you think of a good
subject but don't have the information, call her; she may be able to research
it. Send to Pat Lewis, 5307 30th N.E.,
Seattle WA 98105, or call (206) 524-2006. If you are a listener of the program show your support by giving
the program director of KSER a call!
KPLU 88.5 FM National Public Radio has daily broadcasts of "Star
Date" by the McDonald Observatory of the University of Texas at Austin,
Monday through Friday at 8:58 A.M. and 5:58 P.M. Saturday and Sunday). The short 2 minute radio show deals with
current topics of interest in astronomy.
The
University of Washington TV broadcasts programs from NASA at 12:00 AM Monday
through Friday, 12:30 AM Saturday, and 1:30 AM Sunday on the Channel 27 cable
station.
EAS Library – Book & Video List
The EAS has a library of books, videotapes, and software
for members to borrow. We always value
any items you would like to donate to this library. You can contact Mike Eytcheson to borrow or donate any materials.
MEMBERSHIP BENEFITS & INFORMATION
Membership in the Everett Astronomical Society (EAS) will
give you access to all the material in the lending library. The library, which
is maintained by Mike Eytcheson, consists of several VCR tapes, over 40 books,
magazines, and software titles.
Membership includes invitations to all of the club meetings and star
parties, plus the monthly newsletter, The Stargazer. In addition you will be able subscribe to Sky
and Telescope for $29.95 that
is $7 off the normal subscription rate, contact the treasurer for more
information. When renewing your subscription to Sky
& Telescope you should send your S&T renewal form along with a
check made out to Everett Astronomical Society to the EAS address. The EAS treasurer will renew your Sky and Telescope subscription for
you. Astronomy magazine ($29) offers a similar opportunity to club
members once a year in September.
EAS is a member of the Astronomical League and you will
receive the Astronomical League's newsletter, The Reflector. Being a member also allows you the use of
the club's telescopes, an award winning 10 inch Dobsonian mount reflector,
built as a club project or the 60mm refractor.
Contact Dave Mullen (425-347-3151) to borrow a telescope. EAS dues are $25. Send your annual dues to
the Everett Astronomical Society,
P.O. Box 12746, Everett, WA 98206.
Funds obtained from membership dues allows the Society to publish the
newsletter, pay Astronomical League dues and maintain our library.
OBSERVER’S INFORMATION…
Lunar Facts
Jul 01 New
Moon
Jul
08 First Quarter Moon
Jul
16 Full Moon
Jul 24 Last
Quarter Moon
Jul 31 New
Moon – Partial eclipse visible here
Aug
07 First Quarter Moon
Aug
15 Full Moon
Aug 22 Last
Quarter Moon
Aug 29 New
Moon
Up In The Sky -- The Planets
MERCURY is moves from inferior conjunction with the sun on July 6th and then gradually becomes visible for both northern and southern hemisphere observers during the last half of the month, rising ahead of the sun over the eastern horizon.
VENUS and MARS are in the dawn twilight and not visible.
JUPITER and SATURN are beginning to emerge into the morning twilight about a degree apart in the ENE sky, about 30 minutes before sunrise. Jupiter is the brighter planet, to the upper left. By month's end both planets will be rising between 2-3 hours ahead of the sun and better placed above the horizon for observing from the southern hemisphere
URANUS and NEPTUNE
are
rising around 11 PM, transiting the meridian an hour or so before sunrise, and
are at magnitude 6 and 8 respectively.
PLUTO is in
Ophiuchus in the south in the evening transiting around 11 PM, but at mag. 14,
requires an 8 to 10-inch scope a dark sky, and a good
Constellation(s) of the Month
SAGITTA: (The Arrow). With a midnight
culmination date of July 16th, Sagitta (pronounced “suh-gee’-tah”) is
well-placed for summer viewing. It contains no asterisms, but the stars of the
constellation do trace out an arrow in the sky, situated approximately between
the constellations of Aquila and Cygnus, its point pointing roughly towards the
dolphin that is the constellation Delphinus.
Besides Aquila and Delphinus (it does not officially border Cygnus),
Sagitta also officially borders on the constellations of Vulpecula and Hercules.
Sagitta ranks 18th in overall brightness among the constellations, but 86th in
size; it takes up approximately 80 square degrees of the sky (0.194%). It contains no known meteor showers, but
does contain one Messier object: M-71.
Sagitta is completely visible from latitudes North of –69 degrees, and
completely invisible from latitudes South of –74 degrees. It has 8 stars greater than magnitude 5.5,
and its central point is at RA=19h37m, Dec.= +18.5 degrees. The solar conjunction date of Sagitta is January
15th.
Sagitta is one
of only two constellations whose abbreviation (Sge) contains a letter (‘e’) not
found in the name of the constellation (the other constellation with this minor
distinction is Hydrus). The famous legend
of Sagitta the Arrow commemorates the magic arrow of Hercules, which was used
to kill Jupiter’s pet eagle Aquila.
Aquila had been inflicting repeated attacks on the chained Prometheus
(who had stolen fire for use by earthly mortals without Jupiter’s permission).
Hercules sympathized with Prometheus and his rationale for stealing fire for
use by mortals, and thus wanted to protect Prometheus from the repeated
peckings and barrages of Aquila. He
used his magic arrow (Sagitta) to kill Aquila in order to spare Prometheus
these repeated attacks.
M-71
(NGC-6838) is a globular cluster with a total magnitude of 8.3, visible as a
very loose bright cluster of over 100 stars, 7’ across in a 12-inch
telescope. Most of the component stars
appear to be of 11th and 12th magnitude.
M-71 lies midway between the 4th magnitude stars of Gamma and Delta
Sagittae. Astronomers thought for many
years that rather than being a globular, M-71 was actually a very rich open
cluster; most astronomers now believe that it is indeed a globular, but an
unusually loose one, not as compact and without the strong central stellar
condensation typical of normal globular clusters. Other objects of interest within the constellation of Sagitta
include Harvard 20, an open cluster less than one degree SW of M-71, and three
planetary nebulae suitable for amateur telescopes: NGC-6879, IC-4997, and
NGC-6886. Sagitta also contains some
unusual stars, notably WZ-Sagittae, FG-Sagittae, and V-Sagittae. WZ-Sagittae is a recurring nova, which last
had an outburst in 1978; this resulted in its normal 15th magnitude brightening
to 7th magnitude; it is expected to have another outburst around the year
2010. FG Sagittae is an unusual
variable star, which progressively brightened (to about magnitude 9.5 from
13.7) for 75 years until the early 1970’s, and currently appears to be
surrounded by a slender nebulosity.
V-Sagittae is an erratic variable star which varies irregularly between
magnitudes 9.5 and 13.9 with overlapping periods of variability; this leads
astronomers to believe that it may have been a nova at one time, or may indeed
soon become one. Try to enjoy the
beautiful and very interesting wonders of Sagitta this summer star party
season.
Young
Astronomer’s Corner
Last month, the Young
Astronomer’s Corner finished an almost year-long series on the planets. Instead of starting a new series this month,
when most students are away from school and on summer vacation, this column
will not publish in July, but will return in August in time for the new school
year. Have a safe and happy summer,
and try to observe the night skies if you can during your summer. If you can go to an official Star Party this
summer with family or friends, such as the Table Mountain Star Party or Oregon
Star Party, you should. It is a
wonderful experience to look at the beautiful summer night skies, and to meet
lots of great people and perhaps make new friends. Have a safe, healthy, and happy summer, and school vacation. Take
care, and see you next month!!!
Astronomy and Telescope “Lingo”
ASTRONOMY LINGO: 61
CYGNI: A faint star in the
constellation of Cygnus and one of the nearest stars to the Sun. Because of its large proper motion (thought
to be the largest at the time), it was the first star to have its trigonometric
parallax measured (by F. Bessel in 1838).
61 Cygni is a visual-binary star system, and one of the components is
itself a binary. Disturbances
discovered in the motions of the visual-binary members have been explained as
resulting from the influence of one or more very large planets.
TELESCOPE LINGO:
RADIO
HELIOGRAPH: A telescope designed for
mapping the sun in radio wavelengths.
Astronomy Fun Facts
July Fun
Facts:
** About 500,000
craters on the Moon can be seen from the Earth with the world’s largest and
most powerful telescopes; this large amount does not include those craters on
the Moon’s far side, which cannot be seen from the Earth. It would take one person at least 400
continuous hours to count all the visible craters on the moon.
** Sunlight falling
on one square yard of land in Arizona for one year was worth $83.00 in
1980. If all the sunlight falling on an
Arizona one-acre home lot in all of 1980 were converted into electricity, it
would have been worth almost $403,000 dollars at the time!
** Sunlight exerts a
pressure on anything in its way, including the Earth; a square mile of
sunlight, if it could be placed in one’s hand, would weigh 3 pounds!!
**
One square inch of the Sun shines with an intensity of 300,000 candles. In order to manufacture enough candles to
equal the total brightness of the Sun, the amount of tallow needed would be 10
times larger than the mass of the Earth itself. If all those candles were placed on a birthday cake, the
circumference of the cake would be equal to the orbit of the Earth around the
Sun - almost 600 million miles!!! Make
a wish and blow out the candles indeed!!!!!
“MIRROR” IMAGES
“MIRROR” IMAGES”:
Because we live in the Northern Hemisphere, we often tend to focus (in both
observing and reading) on celestial objects in this hemisphere. The point of this column is to inform club
members about similar objects in the Southern Hemisphere (to the ones we are
already familiar with in the Northern Hemisphere). The general class of object
will first be defined, and then a representative object from each hemisphere
will be described. Note: “MIRROR” IMAGES” is strictly the name of the new
column, and is not intended to imply that there is optical mirror symmetry
between the two objects.
CLASS OF
OBJECT: SUPERGIANT: The largest
and most luminous class of star.
Supergiants lie above both the main sequence and the giant region of the
Hertzprung-Russell diagram. Supergiants
are classified in luminosity classes Ia (bright supergiants) and Ib
(supergiants), and ordinarily have absolute bolometric magnitudes (the
luminosity calculated over all wavelengths, instead of any one or several
particular wavelengths) of between –5 and –12.
These stars are very rare, since only the most immense stars become
supergiants. Their brightness is so
great however, that they can stand out in external galaxies. The absolute bolometric magnitude of cool
red supergiants has an upper limit of –9.7; as a result, the brightest
supergiants can also be used as indicators of distance. Supergiants have masses exceeding 50 solar
masses, and diameters 100 to 1000 times greater than that of the Sun;
supergiants are also 10 to 20 times hotter than the Sun, and 10,000 to one
million times brighter!!
REPRESENTATIVE
NORTHERN HEMISPHERE OBJECT: P Cygni:
This bluish white supergiant in Cygnus has surface temperatures of
approximately 25,000 degrees Celsius. P
Cygni is an unstable variable star about 2,000 parsecs away. It has randomly undergone outbursts, and
then faded, in recorded history; since 1700 however it has continually and
gradually brightened. It is also an
ultraviolet source; its UV brightness is decreasing as its visual brightness is
increasing however. There are many
known stars (P Cygni stars) with similar characteristics to the P Cygni prototype;
their spectra show numerous strong emission lines and sharp blueshifted
(resulting from a continuously ejected and expanding shell of low density
matter) absorption lines. P Cygni stars
are a subclass of luminous blue variables (LBVs), very massive stars known for
sporadic mass ejections, which are most likely due to fluctuations in their
stellar outer layer because of radiation pressure.
REPRESENTATIVE
SOUTHERN HEMISPHERE OBJECT: ANTARES: In the constellation of Scorpius, Antares
was one of the four Royal Stars of the ancient Persians (the others were
Aldebaran, Regulus, and Fomalhaut).
Antares is an M1 ruddy-colored supergiant (luminosity class Ia-b) of
magnitude 0.9. It is about 700 times
larger than the Sun, but is only about 15 times more massive than it because of
its low density: it is about 600 million miles across and approximately 160
parsecs away from Earth. Antares has a
surface temperature of only a few thousand degrees, but it is the brightest
star in Scorpius. Antares is also a visual
binary with a 5th magnitude greenish companion. ”.
Astronomical Notes --
On & Off the Net...
A
new study portrays the paths of asteroids in the inner solar system as a vast
Los Angeles-style traffic system crisscrossed with superhighways along which
are hurtling huge, rocky projectiles.
And in the middle of the highway network, on a possible collision path,
is the planet Earth. The study
estimates that an armada of asteroids, 900 strong, all a kilometer in diameter
or larger, present a potential hazard to life on Earth. Some pass within a few moon distances of
Earth every year. "Sometime in the future, one of these objects could
conceivably run into the Earth," warns astronomy researcher William
Bottke at Cornell University. "One
kilometer (about .6 of a mile) in size is thought to be a magic number,
because it has been estimated that these asteroids are capable of wreaking
global devastation if they hit the Earth."
Bottke
is lead researcher on a U.S.-French team that has discovered the spatial and
size distribution of a large group of asteroids called NEAs (for near-Earth
asteroids), a vast system of orbiting rocks in inner space, ranging in size
from mere specks to more than 64 kilometers (40 miles) in diameter. The astronomers believe the results of their
observational and computer-based study will better quantify the likelihood of
future catastrophic collisions with Earth.
The survey also is expected to help observational astronomers in
improving their search for hard-to-find asteroids that might pose a threat to
the planet.
The
team's report, "Understanding the Distribution of Near-Earth
Asteroids," appears in the latest edition (June 23) of the journal
Science. The authors, besides Cornell's Bottke, are astronomers with the
Spacewatch group at the University of Arizona's Lunar and Planetary Laboratory
and at the Observatoire de la Côte d'Azur in Nice, France.
Calculating
which, if any, of the 900 asteroids identified in the study could hit the Earth
is tricky, says Bottke. "The
problem is that fewer than half of these Earth-threatening asteroids have been
discovered so far. Of those we have found, we can accurately predict whether
they will strike the Earth over the next hundred years or so, but we can't
project out several thousands of years.
So it's possible some of these asteroids eventually will move onto an
Earth-collision trajectory. It's a
dangerous place out there."
The
new predictions for the distribution of NEAs in the inner solar system, say the
astronomers, imply that 40 percent of the kilometer-or-larger asteroids near
Earth already have been discovered. The
remaining 60 percent, however, might be more difficult to find, says Bottke.
"Most of these asteroids are too far from Earth to be easily detected
or are located in regions of the sky that are challenging for astronomers to
survey."
The
study's authors refer to their survey as a "NEA treasure map"
indicating in which orbits most NEAs spend their time. The researchers say the new estimate of the
number of large asteroids is about half of that predicted by similar types of
analyses reported in the past decade and is slightly larger than an estimate
published recently in the journal Nature.
For
many decades there has been good evidence that most of the small chunks of
rocky or iron material that slam into the Earth's atmosphere daily are chips
off old blocks of asteroids. Most of
the asteroids in the solar system revolve around the sun on independent orbits,
corralled between Mars and Jupiter in a formation known as the main belt. Occasionally, two of these asteroids -- some
of them hundreds of miles in diameter -- slam into each other at great speed,
causing chunks of all sizes to be blasted off the surfaces.
Most
of this material continues to orbit the sun in the main belt. But sometimes the
newly formed asteroids migrate to unstable regions of the asteroid belt known
as resonances, areas where the tiny gravitational kicks produced by nearby
planets such as Mars, Jupiter or Saturn can significantly change asteroid
orbits. In some cases, these changes are enough to swing asteroids into a
possible future collision path with the Earth.
To
find the location of these potentially threatening and hard-to-find
projectiles, the researchers used the results of the Spacewatch group's 10-year
search for asteroids in the solar system during which it has discovered about
100 NEAs. The problem is that this
tally is only a small fraction of the predicted number of NEAs. Using a statistical technique to compensate
for the big gaps, Spacewatch astronomers were able to calculate the total
number of NEAs but not their approximate location. To obtain the orbits of the undetected NEAs, Spacewatch
astronomers combined their NEA population estimates with theoretical models,
produced by the Cornell and Nice researchers, which show how asteroids in the
main belt are transported to the near-Earth environment.
University
of Arizona, Lunar and Planetary Observatory, Spacewatch Project: http://www.lpl.arizona.edu/spacewatch
Near-Earth Object Program,
Jet Propulsion Laboratory: http://neo.jpl.nasa.gov/, Asteroid and Comet Impact Hazards, NASA
Ames Space Science Division: http://impact.arc.nasa.gov/index.html
The
American Museum of Natural History and
the Confederated Tribes of the Grand Ronde Community of Oregon signed an
agreement that ensures access to the Willamette Meteorite, a world famous
scientific specimen at the Museum, by the Grand Ronde for religious, historical,
and cultural purposes while maintaining its continued presence at the Museum
for scientific and educational purposes. The agreement recognizes the Museum's
tradition of displaying and studying the Meteorite for almost a century, while
also enabling the Grand Ronde to re-establish its relationship with the
Meteorite with an annual ceremonial visit to the Meteorite. The agreement reflects mutual recognition of
and respect for the traditions of both the Tribe and the Museum. As part of the
agreement, the Tribe agrees to drop its claim for repatriation of the
Willamette Meteorite and not to contest the Museum's ownership of it. However,
the agreement also stipulates the Meteorite would be conveyed to the Tribe if
the Museum failed to publicly display it, except for temporary periods for
preservation, safety, construction and reasons beyond the reasonable control of
the Museum. Also in keeping with the agreement, the Museum will place a
description of the Meteorite's significance to the Clackamas in the Hall of the
Universe, alongside a description of the Meteorite's scientific importance.
Officiating
at the announcement and signing ceremony, which took place in the Museum's Rose
Center for Earth and Space and beside the 15 1/2-ton Willamette Meteorite, were
Ellen V. Futter, president of the American Museum of Natural History, and
Kathryn Harrison, chair of the Grand Ronde Tribal Council.
"I
can't begin to tell you how much this means to us," said Kathryn
Harrison, Grand Ronde Tribal Council chair. "Since the termination of
our tribe by the federal government in 1954, we have worked hard to gather our
people together to share our unique and important past. This agreement goes
even further because it looks towards our future. I consider it one of the
outstanding milestones we've reached for our tribal members."
The
largest meteorite ever found in the United States, the Willamette is believed
by scientists to be the iron core of a planet that was shattered in a stellar
collision billions of years ago. The Meteorite crashed into Earth's surface
thousands of years ago traveling at more than 40,000 miles per hour. The Museum
purchased the Willamette Meteorite in 1906 and since then the unique scientific
specimen has been on almost continuous display at the Museum and viewed by
millions of visitors from around the world. The Willamette Meteorite is the
centerpiece of the Cullman Hall of the Universe in the Museum's recently opened
Rose Center of Earth and Space.
Known
as "Tomanowos" to the Clackamas, who lived in the Willamette Valley
before the arrival of European settlers, the Meteorite is revered by the
Clackamas and their descendants. According to the tradition of the Clackamas,
Tomanowos has healed and empowered people in the Willamette Valley since the
beginning of time. The Clackamas believe that Tomanowos came to the valley as a
representative of the Sky People and that a union occurred between the sky,
earth, and water when it rested in the ground and collected rainwater in its
basins. The rainwater served as a powerful purifying, cleansing, and healing
source for the Clackamas and their neighbors. Tribal hunters, seeking power,
dipped their arrowheads in the water collected in the Meteorite's crevices.
These traditions and the spiritual link with Tomanowos are preserved today
through the ceremonies and songs of the descendants of the Clackamas. Beginning
in the 1850s, the Clackamas, along with more than 20 other tribes and bands
from western Oregon and northern California, were relocated to the Grand Ronde
Reservation in Oregon. Today, the Confederated Tribes of the Grand Ronde, a
federally recognized tribe, is the successor to the Clackamas Tribe.
Growing
out of discussions with the Grand Ronde, but separate from the agreement, the
Museum also proposes, in keeping with its mission of scientific and cultural
education, to establish an internship program for Native American young people.
Such a program, which the Museum anticipates developing in consultation with
the Grand Ronde and others, would facilitate an open and reciprocal exchange of
information and expertise between Native Americans and the Museum and would
have the following general purposes:
1.
to foster Native Americans' sharing a deeper understanding and appreciation of
their customs, traditions, and history with the Museum community and the
general public;
2.
to share with Native Americans information from Museum collections and research
about their history, and help to restore their ancestral traditions;
3.
to share Museum expertise in archaeology and anthropology to advance ongoing
study by Native Americans of their culture and traditions;
4.
to cultivate scientific knowledge and appreciation of the local environments of
Native American tribes; and
5.
to assist in the dissemination of learning on these and related matters between
and among Native Americans, museums, and the general public.
The
Museum's internship program is expected to have tribal members from the Grand
Ronde as its first participants.
Over
one million people from around the world have already visited the Rose Center
for Earth and Space, universally hailed as an architectural, scientific, and
educational triumph since it opened to the public on February 19, 2000. The
Rose Center comprises the Cullman Hall of the Universe, the Hayden Planetarium,
and the Gottesman Hall of Planet Earth. The American Museum of Natural History,
since its founding in 1869, has been one of the world's preeminent institutions
of scientific and cultural research and education.
The
Confederated Tribes of Grand Ronde was formed in 1856 when the federal
government forced member tribes to cede their ancestral lands in the valleys of
Western Oregon and relocate to a reservation in Oregon's Coast Range. Member
tribes included the Kalapuya, Molalla, Chasta, Umpqua, Rogue River and
Clackamas, as well as other smaller bands and tribes. Grand Ronde leaders are
committed to building self-sufficiency and turning things around for tribal
members and the Oregon communities in which they live. The Grand Ronde own and
operate Spirit Mountain Casino, the most successful casino in the Pacific
Northwest, and have developed other tribal enterprises in construction and
environmental management, real estate investment and inventory logistics
services.
The
Willamette Meteorite is a rare and important scientific specimen that is
preserved as part of the collections of the Museum's Department of Earth and
Planetary Sciences. It was found in the Willamette Valley of Oregon and
acquired by the Museum in 1906. In structure it is a metallic iron meteorite,
weighing over 15.5 tons, the largest meteorite ever found in the United States,
and the sixth largest meteorite in the world. Metallic iron meteorites are a
relatively rare kind of meteorite. They comprise a class of about 600 out of a
total of 25,000 meteorites so far found on the Earth's surface.
The
microscopic structure of the meteorite is unusually complicated and suggests a
unique set of events subsequent to its original formation, yet to be fully
analyzed. What we do know about formation of the Willamette Meteorite can be
best summarized in four stages.
Stage 1: Billions of years ago in the early history
of our solar system, a planet which orbited the Sun was shattered. Fragments of
this shattered planet likely included the Willamette Meteorite, which probably
represents the iron-nickel core of this planet. The original break-up of the
planet and cooling of the resulting fragments is evident in the microscopic
structure of the meteorite.
Stage 2: During its long sojourn in space, the
Willamette Meteorite sustained at least two subsequent shocks. These were
high-energy impacts likely due to collisions among planetary fragments, which
caused re-heating and re-crystallization observable in the micro-structure of
the meteorite. One of these shocks may have been responsible for knocking the
Willamette Meteorite into a collision course with the Earth.
Stage 3: Perhaps a billion years later, the
meteorite penetrated the Earth's atmosphere and collided with the Earth's
surface at supersonic speed. Unfortunately, we cannot directly see any remnants
of this impact stage because of long-term weathering of the meteorite after its
impact.
Stage
4: The final form of the Willamette Meteorite resulted from the long-term
exposure and weathering in the humid Northwest region. The large cavities on
the exposed flat side of the meteorite formed not in space but on Earth during
this weathering period. This occurred from interaction of rainwater with iron
sulfide deposits in the meteorite, producing weak sulfuric acid. The etching by
this acid, an extremely slow process, dissolved the metal and produced the
cavities that you see now. http://www.amnh.org/rose/meteorite.html
Thanks
to NASA's unmanned planetary exploration program, evidence of the existence of
past oceans on Mars has been accumulating for years, but no one had ever been
able to say what the overall chemical composition of those oceans might
actually have been like * until now.
A
recent analysis of the interior of a 1.2 billion-year-old Martian meteorite
known as the Nakhla Meteorite has shown the presence of water-soluble ions that
are thought to have been deposited in cracks by evaporating brine, according to
a study by Arizona State University Regents Professor of Chemistry and Geology
Carleton Moore, Douglas Sawyer of Scottsdale Community College, ASU graduate
student Michael McGehee and Julie Canepa of Los Alamos National Laboratory. The
finding, announced in the July issue of the journal Meteoritics and Planetary
Science, indicates that ancient Martian oceans had a chemical composition
similar in variety and concentration to Earth oceans.
"We
have concluded that we have extracted salts that were originally present in
Martian water," said Moore. "The salts we found mimic the
salts in Earth's ocean fairly closely." Moore, who is the director of the ASU Meteorite Center, decided
to examine the ion content of Martian meteorites in ASU's sizable meteorite
collection, when he noticed an oddity in chemical analyses done by Canepa, then
a graduate student at ASU, 15 years ago.
"She studied chlorine and sulfur in basalts from all over the
solar system, including the moon, the Earth, and the meteorites. At the time,
we didn't realize that some of the meteorite basalts came from Mars. Then one
day I realized that some of the meteorites were high in chlorine and some were
low in chlorine. When I checked on it, it turned out that all the high chlorine
meteorites were Martian meteorites and the low chlorine meteorites were all
asteroidal."
Then
the now-famous study of Martian meteorite ALH48001 helped Moore make a second
connection: "When the study of this meteorite revealed not just possible
evidence of life but also the presence of salts, I said to myself 'Aha! Perhaps
our meteorites' chlorine is the remains of salt that had gotten into the
meteorites.' If this was so, it would most likely be from salt water that had
leaked in through cracks in the Martian rock the meteorites came from." Moore chose the Nakhla meteorite to test,
since it had the highest chlorine content of all those in the survey. Nakhla is
named for El-Nakhla in northern Egypt, where it was found following a meteorite
shower in 1911. "We had a very
nice piece of the Nakhla meteorite, about the size of a golf ball so that there
was a clean, uncontaminated interior for us to study," Moore said.
Sawyer and McGehee prepared the meteorite and carefully drilled into its interior
so to get a convincingly uncontaminated sample.
Using
an ion chromatograph first on the sample and then on water to which the sample
was exposed later, Moore tested for chlorine in both. The results showed that a
high percentage of the element present was water soluble and therefore had
probably originated from a water solution -- from salt water. "Then we
tested for the other elements and we found the highest concentrations of
negative ions were chloride, sulfate, fluoride, and a little dissolved silica ,
and, in positive ions, sodium, magnesium and calcium," Moore
said. "The elements in highest
abundance were sodium and chloride -- like the salt water on Earth. In ocean
water, these are the predominant ionic elements. We are interpreting the elements
that we have extracted as having come from an early Martian ocean."
The
only significant difference Moore found between the ionic elements found in the
Martian rock and those found in Earth ocean water was the abundance of calcium,
which was significantly higher in the Nakhla meteorite than in sea water. Moore
points out, however, that the lower calcium concentration in seawater may be
due to the mineral being removed biologically by plants, corals and shellfish.
When the Nakhla meteorite left Mars 1.2 billion years ago, life on Earth had
not yet evolved to these higher forms (shells only appear in the fossil record
about 600 million years ago).
To
Moore, the finding is interesting because it implies not just a chemical
similarity between the planets that may improve the likelihood of finding life
on Mars, but also because it provides a window of sorts into the Earth's own
past. "There was apparently a uniformity between the planets. The
inference that the early Martian ocean was very similar to our current ocean
also implies that the early Earth's ocean may have been very similar to what it
is today. This is a clue to what it might have been."
http://clasdean.la.asu.edu/news/images/marsocean/
A
group of European astronomers have obtained the first detailed images of a
galaxy in which a gamma-ray burst has occurred. The image was taken with one of
the NASA/ESA Hubble Space Telescope's high-resolution cameras and reveals a
barred spiral galaxy with numerous star-forming regions. The gamma-ray burst
has been located in one such actively star- forming region. This is a very
important step forward in our understanding of gamma-ray bursts and their
immediate surroundings and offers possible clues to their progenitors.
The
images of the galaxy ESO 184-G82 are the most detailed images of a gamma-ray
burst galaxy ever obtained. They were taken with the Space Telescope Imaging
Spectrograph (STIS) onboard the NASA/ESA Hubble Space Telescope. The galaxy ESO 184-G82 was host to a
combined gamma-ray burst and supernova explosion seen first time in 25 April
1998. The galaxy is a barred spiral of type SBbc which is a loosely wound
spiral galaxy with a central bar. These galaxies are typically star-forming,
and this galaxy is no exception. In its spiral arms large clumps of
star-forming regions are visible.
These new Hubble observations reveal that the host galaxy is actively
star- forming and contains numerous clouds of hydrogen and regions teeming with
activity from newly born hot stars. The galaxy is a spiral with loosely wound
spiral arms and a large bar of gas and dust running through the center.
The
sharpness of the Hubble Space Telescope's vision has enabled astronomers to
discover that the gamma-ray burst and the supernova occurred in an active
region in one of the galaxy's spiral arms. Here an underlying hydrogen gas
complex is overlaid with several bright red giant stars. At the exact position
of the gamma-ray burst a very compact source of emission is seen. Most of this
emission is probably the last remnant of the fading light from the supernova
itself, but the scientists suspect that a faint underlying star cluster may
contribute as well.
The Hubble observations were
carried out June 12th. http://sci.esa.int/hubble/news/image.cfm?oid=21186&ooid=21205
Several
scientific spacecraft play starring roles in a remarkable new widescreen IMAX
movie entitled 'Solarmax', which received its world première at London's
Science Museum yesterday.
During
a spellbinding 40 minute showing, 'Solarmax' tells the story of humankind's
struggle to understand the Sun, taking audiences on an incredible voyage from
pre-history to the leading edge of today's contemporary solar science. Although it is impossible for us to pay a
visit to the enormous nuclear powerhouse we know as the Sun, film producer /
director John Weiley has provided the best possible substitute by allowing the
general public to see for the first time a star in full spate as it builds up
to its next peak of violent activity -- the solar maximum of the year
2000/2001.
One
of the most memorable sections of the movie includes spectacular satellite
images from ESA's Solar and Heliospheric Observatory (SOHO). These incredibly
detailed images from the battery of instruments on board SOHO reveal its bubbling,
turbulent surface, as well as enormous explosions and magnetic loops in the
tenuous, million degree atmosphere. By combining the images of the Sun's
surface through digital compositing, Weiley has created close-up, high
definition images that allow us to see the Sun as we have never seen it
before. "It was amazing to see
the SOHO images in IMAX format -- we almost felt the solar wind! "
said Professor Bonnet. "By collaborating in this wonderful movie, ESA
Science Program has found an innovative -- and effective! -- medium to share
with the world its passion for space."
Adding
suspense to the movie is a section covering last year's loss of communication
with SOHO and the successful struggle to reacquire its signal by specialists at
the spacecraft operations center.
Also
included in 'Solarmax' are animations and live footage of ESA's next generation
of scientific spacecraft -- the quartet of Cluster satellites that will study
the Sun-Earth interaction in unprecedented detail. Granted special access to
the thermal test chamber at IABG near Munich, Weiley was able to shoot the
Cluster spacecraft on one of the rare occasions when all four of them were
together prior to their shipment to Baikonur for launch.
"The
Science Museum is very excited to have the world première of this new film
which looks at the Sun and its importance in everybody's lives. The images from
ESA are spectacular and we believe the size and clarity they give will lead to
a whole new understanding of how the Sun works among the general public,"
said Alison Roden of the London Science Museum. The general theme of the film is the triumph of knowledge over
ignorance, light over darkness. This is exemplified by humankind's struggle to
understand the Sun and its relationship with the Earth, from the earliest times
to the present day. As well as drawing
upon material from ESA and NASA, Weiley has included 20 weeks of location
shooting, capturing on 70mm film many magnificent shots taken in numerous locations
around the globe.
These
include some of the most elusive and awesome solar phenomena: a shimmering
auroral display over the Sondrestrom radar facility in Greenland; a total
eclipse of the Sun over Aruba in the Caribbean; solstice alignments at ancient
observatories in South America; the winter solstice at neolithic temples in
Europe; a unique time-lapse shot of the midnight Sun circling in the sky over
Tromso, Norway; and Sun worshipping ceremonies and festivals. Apart from images of awesome natural and
cultural events, the film has an equally valuable educational aspect. Viewers
will gain insights into such questions as why the Moon has phases, and why we
experience seasons on Earth. Beyond
that, the audience will gain a basic understanding of the Sun's structure and
behavior, of the Earth's magnetosphere or magnetic shield, of the significance
of 'space weather' and of the urgent need to understand better our mother star
as we become more dependent on technologies that are increasingly vulnerable to
the caprices of solar behavior. 'Solarmax'
will also be opening in many other IMAX cinemas around the world in the coming
year.
Amateur
astronomers are discovering pieces of a giant comet that broke apart in
antiquity as the fragments zoom perilously close to the Sun. In October 1965 comet Ikeya-Seki swooped
past the Sun barely 450 thousand kilometers above our star's bubbling, fiery
surface. Gas and dust exploded away from the comet's core as fierce solar
radiation vaporized the icy nucleus. Most comets wouldn't survive passing as
close to the Sun as the Moon is to the Earth, but Ikeya-Seki literally came
through with flying colors. When the comet emerged from perihelion (closest
approach to the Sun) it was so bright that observers on the street with very
clear skies could see it during broad daylight if the Sun was hidden behind a
house or even an outstretched hand.
"In Japan (where observers spied the comet 1/2 degree from the
Sun) it was described as 10 times brighter than the Full Moon,"
recounted Brian Marsden of the Harvard Center for Astrophysics in the December
1965 issue of Sky & Telescope. "At Kitt Peak National Observatory
in Arizona, Stephen Maran observed the comet with binoculars from within the
shadow of a black disk erected to hide the Sun. '[It was] the most splendid
thing I have ever seen,' he noted."
Ikeya-Seki,
a.k.a. "The Great Comet of 1965", is a member of the family of comets
called Kreutz sungrazers (after the nineteenth-century German astronomer who
studied them in some detail). These ill-fated visitors to the inner solar
system have been seen to pass less than 50,000 km above the Sun's photosphere.
Most never make it past perihelion -- they are completely obliterated. But the
few that do, like Ikeya-Seki, can be very bright.
"There
are 2 or 3 really bright ones like Ikeya-Seki every century," says
Brian Marsden. "Most of these sungrazers are fragments from the breakup
of a giant comet at least 2000 years ago, perhaps the one that the Greek
astronomer Ephorus saw in 372 BC. Ephorus reported that the comet split in two.
This can be made to fit with my calculation that Ikeya-Seki and an even better
Kreutz sungrazer observed in 1882 split off from each other when their parent
revisited the Sun around AD 1100. Splits have occurred again and again,
producing the sungrazer family, all still coming from the same direction."
The
nucleus of Ikeya-Seki was probably some kilometers across. Tinier pieces of
Ephorus's comet streak past the Sun every day. Measuring perhaps only ten
meters in diameter, they brighten briefly as they approach the Sun and
disappear forever when they vaporize above the photosphere. Most of the faint
fragments must have escaped detection entirely.. Now, thanks to coronagraphs on board the orbiting ESA/NASA Solar
and Heliospheric Observatory (SOHO), amateur and professional astronomers can
easily monitor the sky around the Sun for the telltale streaks of faint
sungrazers. All that's needed is a computer and a connection to the
internet. "In late 1998 we put
SOHO's real-time coronagraph movies online so that anyone with an internet
connection could access the data" says Doug Biesecker, a solar
physicist at the Goddard Space Flight Center and SOHO's champion comet hunter
with 47 finds. "Over a three year period before that time we had found
58 comets near the Sun in SOHO images. Now the total is up to nearly 170.
Amateur astronomers watching coronagraph movies on the web are responsible for
nearly all of the new finds this year. They're keeping me very busy!"
The
pace of SOHO comet discoveries has accelerated to such an extent that during
the 45 minute interview with Biesecker, two new comets were found!
One
of the most successful amateur comet hunters is Michael Boschat. He's credited
(or shares credit) with a dozen discoveries since March 2000. "I use the C3 512 x 512 pixel
images," explains Boschat. "They appear on the SOHO site every
30 minutes and I download them as soon as they do. After I have four images I
begin to loop them using GIF animation software that can be found on the
Internet. I usually loop them at four frames per second looking for an object
that is moving towards the Sun in a steady manner. I also use a magnifying
glass to watch the possible comet move. After I feel it is a comet I put my
mouse arrow as near as possible to the object to get the X and Y coordinates
then send all that information off via email to Douglas Biesecker at Goddard."
All
of the comets identified in images from SOHO are called "comet SOHO"
followed by a number denoting the order of discovery. This differs from the
traditional convention of naming a comet after the person who finds it. The
most recent confirmed sungrazer, as of July 4, 2000, was comet SOHO-143. The
International Astronomical Union's official designation for SOHO-143 is C/1998
K15, because the actual images were obtained in 1998, with the K15 indicating
that this was the fifteenth comet (of any description) found during the second
half of May.
"It
started in the early 1980s with the SOLWIND mission, which also carried a coronagraph,"
explains Biesecker. "SOLWIND detected 6 sungrazers and they were all
named after the satellite. The tradition continued for the Solar Maximum
Mission (10 comets) and now for SOHO (143 confirmed comets and counting). It's
reasonable because all of the comet finds have to be confirmed by mission
scientists who are familiar with the hardware. Cosmic rays, noise in the
detectors and other factors can mimic comets and we have to carefully examine
each one. It's really a team effort."
"In
the early 1980s there were also the 'IRAS' comets, found by the Infrared
Astronomical Satellite," added Marsden. "Most of the comets
found nowadays from the ground--and far from the sun--are named 'LINEAR',
acronym for the Lincoln Near Earth Asteroid Research team, which scans the sky
intensely with a U.S. Air Force telescope." (One of these is about to
become a naked eye object in late July, 2000.)
Biesecker
says he hopes the recent spate of amateur discoveries will continue unabated.
SOHO's Top Comet Hunters updated July 2000
Comets Astronomer
47 D. Biesecker*
28 M. Oates
14 S. Stezelberger
11 M. Boschat
11 K. Schenk*
10 D. Lewis*
9 T. Lovejoy
9 B. McCarty*
7 M. Meyer
Note:
An asterisk denotes a professional member of the SOHO team. Others are amateur
astronomers. "The amateur
discoveries are important because they can help us understand the fragmentation
history of Kreutz sungrazers by monitoring the numbers and brightness of the
smallest ones that we can see with the SOHO coronagraphs. The amateurs are also
finding a few unrelated 'near-Sun' comets [this is not an official name] that
pass within 10 to 20 solar radii of the Sun. This is an under-sampled
population of comets."
If
you're interested in joining the hunt for sungrazing comets, a good place to start
is the Solar and Heliospheric Observatory's real-time images web page where
coronagraph data are posted every 30 minutes, and sometimes even more
frequently. Data from the satellite are available to the general public at the
same time as to the scientific community. If you think you've found something,
first review the basic criteria for a discovery before forwarding the details
to scientists at the Goddard Space Flight Center. Confirmed finds are posted
daily on the "What's New" area of http://sungrazer.gsfc.nasa.gov
"It
was as if we were searching for a dim bulb and instead found a bright flash of
light." -- Lars Bildsten, professor, University of California, Santa
Barbara. Surprised scientists made
provocative observations of an X-ray flare from a celestial object called a
brown dwarf -- the first ever seen from such an object -- giving them strong
hints of the tangled magnetic fields that may exist inside, according to an
article to be published in the July 20 issue of the Astrophysical Journal
Letters.
"We
were most surprised by the fact that it was a flare," said Lars
Bildsten, co-author and professor of physics at the Institute for Theoretical
Physics at the University of California, Santa Barbara. "At best we expected a few photons
every hour," said Bildsten. "Instead, we saw nothing for nine hours
and then a bright flare that lasted nearly two hours. If the observation had
been shorter, we would have nothing to report." "We were shocked," said
Robert Rutledge, of the California Institute of Technology in Pasadena, and
lead author of the paper. "We didn't expect to see flaring from such a
lightweight object. This is really the 'mouse that roared.'"
This
first X-ray flare ever seen from a brown dwarf, or failed star, was detected by
NASA's Chandra X-ray Observatory, the telescope that was launched nearly a year
ago. The bright X-ray flare has implications for understanding the explosive
activity and origin of magnetic fields of extremely low mass stars, according
to the team of four who made the discovery.
"It
was as if we were searching for a dim bulb and instead found a bright flash of
light," said Bildsten. "Less
massive than stars but more massive than planets, brown dwarfs were long
assumed to be rare," explained principal investigator Gibor Basri in
the April issue of Scientific American. "New sky surveys, however, show
that the objects may be as common as stars." Chandra detected no X-rays at all from the brown dwarf known as
"LP 944-20" for the first nine hours of a twelve hour observation,
then the source flared dramatically before it faded away over the next two
hours. The energy emitted in the brown dwarf flare was comparable to a small
solar flare and is believed to come from a twisted magnetic field. "This is the strongest evidence yet
that brown dwarfs and possibly young giant planets have magnetic fields, and
that a large amount of energy can be released in a flare," said
Eduardo Martin, of Caltech, also a member of the team.
Professor
Gibor Basri of the University of California, Berkeley, the principal
investigator for this observation, speculated that "the flare could
have its origin in the turbulent magnetized hot material beneath the surface of
the brown dwarf. A sub-surface flare could heat the atmosphere, allowing
currents to flow and give rise to the X-ray flare -- like a stroke of lightning."
Basri,
an expert in brown dwarfs wrote an article describing them in the April issue
of Scientific American. In that article he explains: "A brown dwarf is
a failed star. A star shines because of the thermonuclear reactions in its
core, which release enormous amounts of energy by fusing hydrogen into helium.
For the fusion reactions to occur, though, the temperature in the star's core
must reach at least three million Kelvins. And because core temperature rises
with gravitational pressure, the star must have a minimum mass: about 75 times
the mass of the planet Jupiter, or about 7 percent of the mass of our sun. A
brown dwarf just misses that mark -- it is heavier than a gas-giant planet but
not quite massive enough to be a star."
The
brown dwarf, named LP 944-20, is about 500 million years old and has a mass
that is about 60 times that of Jupiter, or 6 percent of the sun's mass. Its
diameter is one-tenth that of the sun and has a rotation period of less than
five hours. Located in the constellation Fornax in the southern skies, LP
944-20 is one of the best studied brown dwarfs because it is only 16 light
years from Earth.
The
researchers explained that the absence of X-rays from LP 944-20 during the
non-flaring period is in itself a significant result. It sets the lowest limit
on steady X-ray power produced by a brown dwarf, and shows that million degree
Celsius upper atmospheres, or coronas, cease to exist as the surface
temperature of a brown dwarf cools below about 2500 degrees Celsius. "This is an important confirmation
of the trend that hot gas in the atmospheres of lower mass stars is produced
only in flares," said Bildsten.
Since
brown dwarfs have too little mass to sustain significant nuclear reactions in
their cores, their primary source of energy is the release of gravitational
energy as they slowly contract -- at a rate of a few inches per year. They are
very dim -- one hundredth of 1 percent as luminous as the sun -- and of great
interest to astronomers because they are poorly understood and probably a very
common class of objects that are intermediate between normal stars and giant planets. The 12-hour observation of brown dwarf LP
944-20 was made on December 15, 1999.
FROM THE EDITOR'S TERMINAL
The Stargazer is your newsletter
and therefore it should be a cooperative project. Ads, announcements, suggestions, and literary works should be
received by the editor before the 1st of the month of publication, for example,
material for May's newsletter should be received May 1st. If you wish to contribute an article or
suggestions to The Stargazer please contact Mark Folkerts by telephone (425)
486-9733 or by mail (18925 - 67th Ave SE, Snohomish, WA 98296), or
co-editor Bill O’Neil, at (425) 337-6873.
