EAS BUSINESS…
February Recap
Dr. Stacy
Palen discussed: 'Where do We Come From? Chemical Enrichment of the Galaxy by Dying
Stars'. She talked about how
stars throughout their lives, produce the heavy elements and metals, and how
those elements wind up as part of the galactic dust and gas that forms new
stars and planets (and people!).
Next EAS Meeting - Saturday March 31st At
Providence Pacific Clinic – 916 Pacific Avenue – 7:00 PM
The
March speaker is scheduled to be Keith Allred, from the Seattle Astronomical
Society, who will give a presentation on “Introduction to Astrophotography.”
Scheduled Meeting Topics:
Mar 31 –
Keith Allred, astrophotography
Apr 21 –
Bill O’Neil, touring radio-telescope arrays
Apr 28 –
Astronomy Day (at the Library) - no meeting
Member News
Request
for Astronomy Assistance: Two elementary school teachers in Snohomish County - both of whom are affiliated with the
Project ASTRO program but are also without astronomers -are requesting some
astronomy help before the end of the current school year. Some E.A.S. club members have already
expressed interest in helping Bill O’Neil to assist these teachers. Activities would possibly include a one-day
(1 or 2 hour) classroom general astronomy session (perhaps focusing on lunar
phases or solar system distances, as examples), slide show, telescope
demonstration, and evening star party for students, family, and friends. If you are interested in helping Bill to
assist these teachers in any capacity, please contact Bill O'Neil at
425-337-6873.
Financial Health
The club maintains a safe $1150+ 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:
March 24 –
Ken & Judy Ward’s
April 27th and 28th – Astronomy Day
star parties at Harborview Park.
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.
Contact Dave Mullen for scope borrow
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 Available No wait list
Astro Calendar
March 2001
Mar 11 - Mercury at Greatest Western Elongation (27 Degrees)
Mar 14 - Asteroid 114 Kassandra At Opposition (10.8 Mag.)
Mar 16 - Asteroid 354 Eleonora At Opposition (9.8 Magnitude)
Mar 20 - Vernal Equinox, 13:14 UT
Mar 23 - Mir Space Station Reenters Into Earth's Atmosphere?
Mar 24 - Star Party, Ken & Judy Ward’s place (near
Monroe)
Mar 25 - The Islamic year 1422 begins at sunset
Mar 31 - EAS Meeting 7:00 PM – Providence Hospital
April 2001
Apr 01 - Daylight
Saving - Set Clock Ahead 1 Hour
Apr 01 - Venus
Occults 109102 (6.7 Mag. Star)
Apr 01 - Asteroid 6
Hebe At Opposition (9.9 Mag.)
Apr 02 - Asteroid 13
Egeria At Opposition (10.1 Mag.)
Apr 06 - Asteroid 29
Amphitrite At Opposition (9.3 Mag.)
Apr 15 - Easter
Sunday
Apr 16 - Ast. 2
Pallas Occults TYC 1544-02005-1 (10.7 Mag.)
Apr 16-19 - AIAA
Gossamer Spacecraft Forum, Seattle, WA
Apr 21 - EAS Meeting
7:00 PM – Providence Hospital
Apr 22 - Lyrids
Meteor Shower Peak
Apr 23-29 - Astronomy
Week
Apr 27 - Asteroid 18
Melpomene Opposition (10.4 Mag.)
Apr 27 - Astronomy Day Star Party #1 at Harborview Park
Apr 28 - Astronomy Day – Library and Harborview Park SP#2
Apr 29 - Asteroid 532
Herculina Opposition (9.0 Mag.)
Over The Airwaves
"We
welcome a new writer, Rubie Johnson, to our group of radio script writers. With
EAS and SAS members Jim Ehrmin, Pat Lewis, Greg Donohue and Ted Vosk she is now
regularly writing and helping to produce our astronomy radio show, "It's
Over Your Head" on radio station KSER, FM 90.7. The six-minute segment is broadcast every Wednesday morning at
approximately 7:20 A.M. and gives a weekly look at what's up in the sky over
Snohomish County, with other information.
If you have a good idea for an astronomy broadcast or would like to try
your hand at writing a script, call Pat Lewis at (206) 524-2006 or email to
joagreen@aol.com If you are a
listener to the program, show your support by giving the program director of
KSER a call!" Web page with lots
of archives and other info is available at http://galaxyguy.bizland.com/radio_program.htm
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
Mar 25 New
Moon
Apr
01 First Quarter Moon
Apr
07 Full Moon
Apr 15 Last
Quarter Moon
Apr 23 New
Moon
Apr
30 First Quarter
Digital Lunar
Orbiter Photographic Atlas of the Moon
The Lunar and Planetary Institute has created a digital
version of the Lunar Orbiter Photographic Atlas of the Moon, and Consolidated
Lunar Atlas available on the web at:
http://www.lpi.usra.edu/research/cla/menu.html
http://www.lpi.usra.edu/research/lunar_orbiter
Up In The Sky -- The Planets
MERCURY was at greatest elongation on March 11, 27 degrees west
of the Sun in the dawn sky, above the east-southeast horizon 30 - 40 minutes
before sunrise. It is well placed for morning twilight observation during the
first half of the month, mostly from the southern hemisphere
VENUS is high in the western sky during evening twilight
shining brilliantly at magnitude -4.6 at the beginning of March. It is a thin
crescent with a 44" diameter. It will drops lower in the western sky as
the month progresses, reaching solar conjunction and disappearing at month end.
MARS is high in the eastern sky before dawn (in
Ophiuchus). It shines at magnitude 0.5, but is only a tiny 8" disk in the
telescope.
JUPITER is to the left of Saturn, high in the sky in the
early evening. It subtends 37" x 35" in the telescope and is at -2.2
magnitude. It is between the Hyades and Pleiades in Taurus
SATURN is high in the sky in the evening, shining at
magnitude 2.3. It is in Taurus south of the Pleiades. It measures 17" x
14", and the rings are tilted by 24o
URANUS and NEPTUNE come out of solar conjunction this
month, entering low in the sky just prior to the onset of morning twilight.
PLUTO is now high in the sky prior to morning twilight. It
is only a 13.8 magnitude object, so
good charts and a large telescope are necessary to see it.
Need
to know exactly what time the sun will set on Sept. 26, 2065? Or when it rose
in 565 BC? How about the length of daylight a week from Tuesday in Albuquerque,
N. M.? Just go to NOAA's solar calculator, now available on the Web. http://www.srrb.noaa.gov/highlights/sunrise/gen.html
International
Space Station – Visible Passes over Seattle
ISS Visibility – (note: times
may change due to maneuvers) http://spaceflight.nasa.gov/realdata/sightings/SSapplications/Post/SightingData/Seattle.html or also see link
http://www.heavens-above.com/PassSummary.asp?lat=47.979&lng=-122.201&alt=0&loc=Everett&TZ=PST&satid=25544
(The station and shuttle are
maneuvering at press time, so predictions cannot be accurately forecast. Check the websites.)
Constellation(s)
of the Month
HYDRA: The Water Snake, as this constellation is also known,
borders on the constellations of Antlia, Cancer, Canis Minor, Centaurus,
Corvus, Crater, Leo, Libra, Monoceros, Puppis, Pyxis, Sextans, and Virgo, and
ranks 71st in overall
brightness among the constellations, containing, ironically enough, 71 stars
brighter than magnitude 5.5. Its
central point is located at RA=11h,33m and Dec.= -14 degrees. It is completely visible from latitudes +55
degrees to –83 degrees, with portions visible worldwide. This constellation ranks 1st in
overall size; the largest constellation takes up over three percent of the
entire sky. One of the most famous
stars in the sky is Alphard (alpha Hydra), an orange giant with a K4-III
spectral type. Alphard (also known as
the “Dragon’s Heart” and “Solitary One”) has an apparent magnitude of 1.97
(making it the 46th brightest star in the sky), and an absolute
magnitude of –0.3; it may also be a minimal variable star, with a magnitude
fluctuation of approximately 0.2 noted.
This beautiful star is located about 95 light years from our solar system. Hydra has one associated meteor shower: the
sigma Hydrids (11 Dec.), and three Messier objects (M-48 (open cluster), M-68
(globular cluster), and M-83 (spiral galaxy).
M-83 is a
nearly face-on spiral, and has been called the finest face-on Sc-type spiral in
the sky. It has a combined (total)
magnitude of 8 (making it one of the 25 brightest galaxies in all the sky as
well), and appears photographically to be about 10 X 8 minutes of arc in
angular size, with a bright nucleus.
Its distance to us is approximately 4.5 megaparsecs, making it also one
of the closest spiral galaxies outside our Local Group. M-83 was actually discovered by Lacaille in
1752. This great loose spiral galaxy is
on the border with the constellation of Centaurus, and can also be located at
about 18 degrees south of the star Spica.
The two main arms forming the spiral pattern of M-83 actually form a
reverse letter “S”; a third and fainter arm sweeps from the nucleus towards the
southwest of the galactic structure.
The spiral arms are branded by abundant star clouds, hot giant stars,
and bright nebulous areas. The nucleus
itself measures about 20” across, and demonstrates an intense emission
spectrum. The total luminosity of M-83
is approximately 5 billion times that of our Sun, and the galaxy has a visible
diameter of approximately 30,000 light years.
Interestingly, at least five supernovae have occurred within the
confines of M-83 in the last 70 years or so, making M-83 a very good target for
patient supernovae hunters!!
M48 (NGC-2548;
open (galactic) cluster) is located near the western border of Hydra, and has
often been regarded as one of the “missing” Messier objects, as no such object
exists at the actual coordinates (actually 4 degrees North of the present
location of M-48) which Messier charted.
The total cluster magnitude is listed at 5.5, and its overall angular
size is about 40’. M-48 contains about
50 stars: 10th and 11th magnitude stars in the central
“chain”, and fainter stars down to approximately 13th magnitude. There are three yellow giants in the
cluster, and the remaining stars are A-type main sequence stars. M-48 is located about 1700 light years from
our solar system. M-68 (globular
cluster), is an ample grouping of stars for larger scopes, but is also a good
object in smaller scopes as well. This
globular grouping contains well over 100,000 stars, and has a thicker inner
mass of stars about 2.0’ in diameter; its total diameter is about 9.0’
(approximately 100 light-years). The
cluster distance has been calculated at about 46,000 light years from Earth,
giving a total luminosity of the cluster at about 100,000 times that of the
Sun (with a total absolute magnitude of
–7.7(and an apparent magnitude of around 8.0)). The integrated spectral type of the cluster has been shown to be
A6, and M-68 contains 38 stars known to be variables.
Hydra also
contains the star R-Hydrae, a well-known variable star that was the third of
all the long-period variables to be discovered (after Omicron Ceti (Mira) and
Chi Cygni). R-Hydrae is one of the
easiest of the long-period pulsators for amateurs to observe because of its
variation: it can reach to magnitude 4 brightness at maximum, but is often very
hard to find visually (becoming approximately 250 times fainter) at minimum:
one must then know its exact location.
Ironically, its maximum luminosity is estimated to be about 250 times
that of our own Sun. Similar to Mira,
R-Hydrae is an M-class giant star, and is clearly reddish in color. Another well-known Hydra entity is V-Hydrae,
a variable star which is often considered the reddest star known. V-Hydrae is a semi-regular red variable: it
is actually one of the rare “carbon stars” visible in the skies; carbon stars
are low-temperature giant stars with spectra demonstrating carbon compound
lines; V-Hydrae has been given a spectral type of N6. Its color has variously been described by noted astronomers down
through the years as “brown red” (Copeland, 1876) and “a most magnificent
copper red” (Dreyer, 1879). V-Hydrae
has a period of approximately 533 days, with an apparent magnitude variation of
between 6.5 and fainter than 12 (a difference of about 6 magnitudes (or, again,
a variation in light intensity of about 250 times)). Another Hydra variable, U-Hydrae, is somewhat brighter (4.7-6.2),
and is almost as red as V-Hydrae.
Hydra also contains a well-known planetary nebula – NGC-3242. This planetary is located about 1.8 degrees
south of Mu-Hydrae, and appears in small telescopes as a pale blue
gently-glowing disc, which measures about 40” x 35”, with a bright inner “human
eye”-like disc, and an outer halo of greenish-blue nebulosity. NGC-3242 has a central star with a visual
magnitude of around 11.4, and the planetary has an overall visual magnitude of
approximately 9.0. Much of the
illumination of NGC-3242 can be attributed to fluorescence induced by the
strong UV radiation of the central hot blue dwarf, a 60,000 degree Kelvin
surface temperature star. The
planetary’s blue-green tint is due to the strong emissions of doubly-ionized
oxygen.
Perhaps most
well known of all the other phenomena associated with this constellation is the
fact that in September 1965, one of the most famous comets of the 20th
century was discovered near Alphard.
Comet Ikeya-Seki (a sungrazer) was, one month later in October, visible
in daylight when only two degrees from the sun!! Hydra has a midnight culmination date of March 15th,
so try to get out (in good dark skies and well above any horizon obstructions),
and enjoy some of the beauties of this famous and marvelous constellation this
late winter and spring.
Young
Astronomer’s Corner
The Young
Astronomer’s Corner started a new feature late last year: Questions and
Answers for Young Astronomers. The
purpose of this new, periodic feature is to engage in a question and answer
column format, responding to some common and familiar questions heard
frequently in young astronomy circles and classrooms. We hope to answer some of your questions in this manner. If not, let us know what your questions are
(by calling an Officer or the Newsletter Co-Editor, for example), and we will
do our best to answer them!!!!!
QUESTION: What is an
asteroid?
ANSWER: An asteroid
is a rock made of iron, stone (or both), which, like the planets, travels
around the Sun. Asteroids are sometimes
called “minor planets” because: 1). they are called ‘minor’ because they are
much smaller than regular planets, and 2). they are called ‘planets’ because,
as mentioned, they travel around the Sun.
Frequently, the solar orbits of asteroids are very predictable (for
example, the asteroid ‘Vesta’ travels around the Sun every 1,325 days (the
Earth, remember, does so every 365 days).
Asteroids can range in size from less than a half-mile in diameter to
over 600 miles in diameter.
QUESTION: What is the “asteroid belt”?
ANSWER: The ‘asteroid belt’ is an area located between the orbital
paths of Mars and Jupiter, and in this area thousands of asteroids have been
found. This area between the orbital
paths of Mars and Jupiter is known as the ‘main’ asteroid belt. Some estimates show that there may be as
many as 100,000 asteroids between the paths of both Mars and Jupiter as they
travel around the Sun. Officially, only
3,000 of these heavenly bodies have been named, although nearly twice as many
have been found in photographs. Where
are the other estimated 95,000 asteroids (approximate number remaining in the
‘main’ belt from those already discovered)?
Even though it is believed they are out there, they are too small to
have been photographed thus far. Of all
those discovered photographically, only about 230 of them are greater than 60
miles in diameter. The vast majority of
the “missing” asteroids are LESS than a mile across!!
QUESTION: What is the largest known asteroid?
ANSWER: The largest
asteroid known is named Ceres.
Naturally enough, it was also the first to be discovered, no doubt
because it IS the largest one known. It
is approximately 600 miles in diameter.
Ceres is really in a class by itself: only two other asteroids are
anywhere even close to approaching the size of Ceres (these two are named
Pallas and Juno), and they are each listed at ‘only’ about 180 miles in
diameter!
Stay tuned
for next month’s Young Astronomer’s Corner, when we will continue with more
questions and answers about asteroids…and some surprising questions and answers
at that!!
Astronomy and Telescope “Lingo”
Astronomy
lingo: F-STARS: Stars designated as spectral type F; they are
white stars with surface temperatures of about 6,000 to 7,400 degrees
Kelvin. Spectral hydrogen lines weaken
rapidly, and lines of ionized calcium strengthen from F0 to F9. There are also numerous lines of neutral and
singly ionized other metals, as well as heavy atoms. Procyon, Polaris, and Canopus are prominent examples of F stars.
Telescope
lingo: VIGNETTING: An uneven or
reduced illumination over the image plane in a telescope, camera, or similar
instrument; vignetting may lead, for
example, to images that fade at the edges.
Astronomy Fun Facts
** The
coldest temperature ever documented on Earth is minus 127 degrees Fahrenheit,
recorded at Vostok, Antarctica in August, 1960. This temperature also happened to be the average temperature of
the Universe when it was around 21 million years old: this is thought to be
when hydrogen was beginning to condense into the protogalactic clouds (the precursors to the galaxies that we see
today).
** On the
first birthday of the Universe, its temperature was approximately 2.5 million
degrees Kelvin, one-sixth the temperature of the core of the Sun. The density of the Universe on its first
birthday was far less than that of air: its density was actually somewhere
between that of the record for a vacuum created on Earth, and a TV picture
tube!!
** The cosmic
background radiation, with a temperature of 2.7 degrees Kelvin, is
invisible. This invisible radiation is
also the oldest and most energetic beacon in the Universe, and represents 99%
of all the known radiation in the Universe.
The remaining 1.0% includes all the radiation energy from the billions
of stars and galaxies in the Universe.
This 1.0% radiation energy, however, is the most important radiation to
us: it is that which gives us life.
“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 is first defined below,
and then a representative object from each hemisphere is described. Note: “MIRROR” IMAGES” is strictly the name of this
column, and is not intended to imply that there is optical mirror symmetry
between the two representative objects.
CLASS OF OBJECT: RED GIANT
STARS: After a
main-sequence star uses up the hydrogen in its core (and it begins to leave the
main sequence of its evolution), it begins to contract. Dense core helium then heats up, making remaining
hydrogen outside the core boundary burn faster, increasing the star’s
brightness. The great energy released
by the burning hydrogen ‘shell’ (and continued gravitational contraction of the
star), makes the star expand into a giant: the outer layers of the star expand
rapidly. These giants have surface
temperatures between 2,000 and 4,000 degrees Kelvin, and diameters anywhere
from 10 to as much as 1,000 times that of our Sun. This expansion causes the star to cool with a lowered gas density
and a dropping surface temperature. The
star then turns red, and becomes known as a “red giant”. Gravitational contraction continues, and the temperature
inside the star rises immensely. Such
stars may contract (to a hotter and denser giant), and then re-inflate back to
the cooler red giant phase more than once during its lifetime; further core
fusion reactions also add heavier elements such as oxygen, sodium, and
magnesium. The helium core does not
expand much during helium burning; without expanding, the star can’t lose the
heat generated (from the helium burning), and the star undergoes a runaway
helium combustion known as the “helium flash”.
Since red giants are often so distended, they frequently lose much mass
into space in the form of stellar winds, because the effects of gravity are
weaker on such distended atmospheric surface layers. Many red giant stars are often variable stars simply because
these surface layers slowly expand and contract; such pulsations can take up to
a year to complete (e.g., Mira-type (long-period) variables). Lower mass red giants will eventually become
planetary nebulae (and subsequently white dwarfs); this is the suspected
evolution of our own Sun. Higher mass
red giants may eventually explode as Type II supernovae.
REPRESENTATIVE NORTHERN HEMISPHERE OBJECT: Betelgeuse: Betelgeuse (alpha Orionis) is the second
brightest star in the constellation of Orion, the tenth brightest in all the
sky, and is a very luminous red supergiant.
Betelgeuse is a semi-regular variable (period = approximately 5.8
years), that is also a strong source of infrared radiation. Its variable magnitude range is 0.3 to 0.9;
its magnitude however has reached as high as 0.15 and has been as low as 1.3. IRAS (Infrared Astronomical Satellite) data
has found long-wave infrared radiation emitted from three concentric shells,
the largest of which has been ejected within the last 100,000 years and has a
radius of 1.5 parsecs. Interferometry
indicates that Betelgeuse has an irregular surface brightness. Betelgeuse lies at a distance of
approximately 650 light years from our solar system, and has a diameter about
500 times that of the Sun. Betelgeuse
has an absolute magnitude of –5.7, and is listed as spectral type M2-I-ab.
REPRESENTATIVE SOUTHERN HEMISPHERE
OBJECT: Mira: Mira (omicron
Ceti) is a red giant in the constellation of Cetus (the Whale); it is also the
prototype for all the long-period pulsating variables. Hevelius gave the name “Mira” to this star;
translated, Mira means “the Wonderful”.
Mira has an average period of 331 days.
The radius of Mira varies by over 20% during its cycle; at maximum size
and brightness its radius is over 330 times that of our Sun. The surface temperature at maximum
brightness has been estimated as high as 2,600 degrees Kelvin; at minimum
brightness, its temperature is approximately 1,900 degrees Kelvin. Visible light emitted during Mira’s cycle
spans about 6.0 magnitudes from peak to trough. The average apparent magnitude at maximum is between 3.0 and 4.0;
however, as recently as 1969, its maximum apparent magnitude was measured to be
2.1. At minimum, Mira’s apparent
magnitude hovers between 8.0 and 10.0.
Mira is also a visual binary (it has a faint peculiar and variable
companion); an optical double; and an infrared source (arising from grains of
dust in the expanding gas envelope of the red giant star). Mira lies at a distance of 40 parsecs from
our solar system, has an absolute magnitude of –1.0, and is of spectral types
M6e to M9e III during its cycle.
Astronomical Notes -- On & Off the Net...
NASA
scientists who monitor the Sun say that our star's awesome magnetic field is
flipping -- a sure sign that solar maximum is here. You can't tell by looking, but scientists say the Sun has just
undergone an important change. Our star's magnetic field, which extends through
the distant reaches of interplanetary space, has flipped. The Sun's magnetic north pole, which was in
the northern hemisphere just a few months ago, now points south. It's a
topsy-turvy situation, but not an unexpected one. "This always happens around the time of solar maximum,"
says David Hathaway, a solar physicist. "The magnetic poles exchange
places at the peak of the sunspot cycle. In fact, it's a good indication that
Solar Max is really here."
The Sun's magnetic poles will remain as they are now, with the north
magnetic pole pointing through the Sun's southern hemisphere, until the year
2012 when they will reverse again. This transition happens, as far as we know,
at the peak of every 11-year sunspot cycle -- like clockwork.
Earth's
magnetic field also flips, but with less regularity. Consecutive reversals are
spaced 5 thousand years to 50 million years apart. The last reversal happened
740,000 years ago. Some researchers think our planet is overdue for another
one, but nobody knows exactly when the next reversal might occur. Although solar and terrestrial magnetic
fields behave differently, they do have something in common: their shape.
During solar minimum the Sun's field, like Earth's, resembles that of an iron
bar magnet, with great closed loops near the equator and open field lines near
the poles. Scientists call such a field a "dipole." The Sun's dipolar
field is about as strong as a refrigerator magnet, or 50 gauss (a unit of
magnetic intensity). Earth's magnetic field is 100 times weaker. When solar maximum arrives and sunspots
pepper the face of the Sun, our star's magnetic field begins to change.
Sunspots are places where intense magnetic loops -- hundreds of times stronger
than the ambient dipole field -- poke through the photosphere. "Meridional flows on the Sun's
surface carry magnetic fields from mid-latitude sunspots to the Sun's poles,"
explains Hathaway. "The poles end up flipping because these flows
transport south-pointing magnetic flux to the north magnetic pole, and
north-pointing flux to the south magnetic pole." The dipole field
steadily weakens as oppositely-directed flux accumulates at the Sun's poles
until, at the height of solar maximum, the magnetic poles change polarity and
begin to grow in a new direction.
Hathaway noticed the latest polar reversal in a "magnetic butterfly
diagram." Using data collected by astronomers at Kitt Peak, he plotted the
Sun's average magnetic field, day by day, as a function of solar latitude and
time from 1975 through the present. The result is a sort of strip chart
recording that reveals evolving magnetic patterns on the Sun's surface. "We
call it a butterfly diagram," he says, "because sunspots make
a pattern in this plot that looks like the wings of a butterfly." The ongoing changes are not confined to the
space immediately around our star, Hathaway added. The Sun's magnetic field envelops
the entire solar system in a bubble that scientists call the
"heliosphere." The heliosphere extends 50 to 100 astronomical units
(AU) beyond the orbit of Pluto. Inside it is the solar system -- outside is
interstellar space. "Changes
in the Sun's magnetic field are carried outward through the heliosphere by the
solar wind," explains Steve Suess. "It takes about a year for
disturbances to propagate all the way from the Sun to the outer bounds of the
heliosphere." Because the Sun
rotates (once every 27 days) solar magnetic fields corkscrew outwards in the
shape of an Archimedean spiral. Far above the poles the magnetic fields twist
around like a child's Slinky toy.
Because of all the twists and turns, "the impact of the field
reversal on the heliosphere is complicated," says Hathaway. Sunspots
are sources of intense magnetic knots that spiral outwards even as the dipole
field vanishes. The heliosphere doesn't simply wink out of existence when the
poles flip -- there are plenty of complex magnetic structures to fill the
void. Or so the theory goes. Researchers have never seen the magnetic
flip happen from the best possible point of view -- that is, from the top down. But now, the unique Ulysses spacecraft may
give scientists a reality check. Every
six years the spacecraft flies 2.2 AU over the Sun's poles. No other probe
travels so far above the orbital plane of the planets. "Ulysses just passed under the Sun's
south pole," says Suess, a mission co-Investigator. "Now it
will loop back and fly over the north pole in the fall." "This is the most important part of
our mission," he says. Ulysses last flew over the Sun's poles in 1994
and 1996, during solar minimum, and the craft made several important
discoveries about cosmic rays, the solar wind, and more. "Now we get to
see the Sun's poles during the other extreme: Solar Max. Our data will cover a
complete solar cycle."
http://science.nasa.gov/headlines/y2001/ast15feb_1.htm
Galaxies
and black holes are so intimately connected that it is almost impossible to
find one without the other, according to University of Michigan astronomer
Douglas Richstone. Over the last decade,
Richstone and a team of researchers have detected massive black holes in all
but one of the 30 spiral galaxies they surveyed. To detect new black holes,
scientists look for abrupt changes in star velocity patterns revealed by stars
orbiting near the center of the galaxy. Based on the galaxy's size and the
velocity pattern of stars at the galaxy's core, scientists can detect the
gravitational force of a black hole and also estimate its mass. "The mass of these objects appears
to correlate with the mass of the central part of their host galaxy,"
said Richstone, a U-M professor of astronomy. "Radiation and
high-energy particles released by the formation and growth of black holes are
the dominant sources of heat and kinetic energy for star-forming gas in protogalaxies.
Black holes and stars compete for baryons, or particles of matter, that form
stars during the early life of galaxies." Comparisons of the history of star formation in the universe with
the history of quasars, conducted by other scientists, reveal that quasars
developed well before most star formation in galaxies. Quasars are extremely
powerful bright objects capable of generating the luminosity of one trillion
suns within a region the size of Mars' orbit. "The massive black holes we now see in centers of
galaxies are relics of these quasars," Richstone explained. "So
black holes must have already been present at the height of the quasar epoch
when the universe was about one billion years old." Even though black holes make up only
two-tenths of one percent of a galaxy's mass, their energy efficiency is 10
times greater per unit of mass than all the stars in the galaxy, according to
Richstone. The thermal and mechanical luminosity of these early black holes
dominates the energy output of young stars forming in the proto-galaxy. "The energy output of a massive
black hole is comparable to the energy of the galaxy over its entire lifetime,"
Richstone said. "Black holes and stars compete for mass, and black
holes heavily influence the thermodynamics of the interstellar gas in young
galaxies. So it is impossible to sensibly discuss the galaxy formation process,
or the history of star formation, without including the formation of black
holes." http://www.astro.lsa.umich.edu/users/dor/n4697c.jpg
Astronomers
have long suspected that the bar systems that dominate the appearance of some
spiral galaxies provide an efficient mechanism for fuelling star births at
their centers. New results from the Hubble Space Telescope provide evidence
that this is indeed the case. The
wonderful barred spiral galaxy NGC 2903 in the constellation of Leo is a
well-known spring observing target for amateur astronomers. With a magnitude
brighter than 10, it is easy to find and identify in a small telescope.
However, only large-aperture telescopes or long-exposure photographs can reveal
its intricate spiral structure. NGC
2903's swirling whirlpool of stars spans 80,000 light-years -- slightly less
than our own Milky Way -- and is located at a distance of some 25 million
light-years. NGC 2903 is one of the more conspicuous northern objects that
Charles Messier missed when compiling his catalogue of nebulous objects, so
leaving its discovery to William Herschel.
A
colorful image, obtained by the Wide Field and Planetary Camera 2 (WFPC2)
onboard Hubble, lays bare the fine detail in the central part of the galaxy's
bar. Up to two-thirds of all spirals
contain bars. Astronomers have long suspected that the bars provide an
efficient mechanism for fuelling star births in the centers of barred
galaxies. Astronomers, using Hubble's
superb vision in the visible and infrared to probe deep into the central
star-forming regions in this spiral, have uncovered a surprise. The core of NGC
2903 is known for its complex, speckled appearance, full of 'hot-spots'. As the
telescope resolved the 'hot-spots' in the center into individual stars and star
clusters for the first time, it became clear that most of the star-forming
action does not actually take place in these hot-spots. "The most
striking feature in the Hubble images is that star formation seems to occur in
nearby large regions of ionized hydrogen instead", says Almudena
Alonso-Herrero from the University of Hertfordshire. "These
star-forming regions are distributed in a mighty 2000 light-year wide ring
around the center of the galaxy, in a circumnuclear ring". Circumnuclear rings are also seen in other
galaxies and are often interpreted as being due to interstellar gas falling in
towards their centers. "We believe that the ring of newly-born stars
around the core of NGC 2903 is created because the bar acts as a transport
mechanism, funneling gas inwards", says Almudena
Alonso-Herrero. "Bars seem to be extremely efficient in triggering the
formation of stars and they act as funnels for the flow of material from the
outer parts of galaxy disks towards their centers".
Hubble's close-up view also
shows other interesting details in the galaxy's center: huge dust lanes and
lots of young stars are gathered in hot blue clusters sprinkled all over the
spiral arms. NGC 2903 bears a close resemblance to the Milky Way, which is also
believed to be a barred spiral galaxy. Barred spirals are excellent
laboratories in which to study the processes that trigger star formation, and
bars may be responsible for providing the gaseous fuel being gobbled up by
massive central black holes in so-called active galaxies.
http://www.pacificsites.com/~hakuna/leo.html
http://www.jps.net/jrfcomet/galaxy/n2903.htm
http://www.surmount.com/oac/gallery/djo-ngc2903.html
http://members.aol.com/tonybouch/ngc2903.html
Perched
on the surface of asteroid 433 Eros, NASA's NEAR spacecraft is beaming back
measurements of gamma-rays leaking from the space rock's dusty soil. When NASA's Near Earth Asteroid Rendezvous
spacecraft left for Eros five years ago, scientists weren't certain what they would
find when the probe arrived. Was Eros a 30-km fragment from a planet that broke
apart billions of years ago? Or perhaps a jumble of space boulders barely held
together by gravity? Was Eros young or old, tough or fragile ... no one knew
for sure. But now, after a year in
orbit and a daring landing on the asteroid itself, NEAR Shoemaker is beaming
back data that could confirm what many scientists have lately come to believe:
Asteroid Eros is not a piece of some long-dead planet or a loose collection of
space debris. Instead, it's a relic from the dawn of our solar system, one of
the original building blocks of planets that astronomers call
"planetesimals." From its
perch on the surface of the asteroid, NEAR's gamma-ray spectrometer (GRS) can
detect key chemical signatures of a planetesimal -- data that scientists are
anxious to retrieve. "The
gamma-ray instrument is more sensitive on the ground than it was in orbit,"
says Goddard's Jack Trombka, team leader for the GRS. "And the longer
we can accumulate data the better."
To do its work the GRS relies partly on cosmic rays, high-energy
particles accelerated by distant supernova explosions. When cosmic rays hit
Eros, they make the asteroid glow, although it's not a glow you can see with
your eyes; the asteroid shines with gamma-rays. "Cosmic rays shatter atomic nuclei in the asteroid's soil,"
explains Trombka. Neutrons that fly away from the cosmic ray impact sites hit
other atoms in turn. "These secondary neutrons can excite atomic nuclei
without breaking them apart." Such excited atoms emit gamma-rays that
the GRS can decipher to reveal which elements are present. "We can detect cosmic-ray excited
oxygen, iron and silicon, along with the naturally radioactive elements
potassium, thorium and uranium," says Trombka. Measuring the
abundances of these substances is an important test of the planetesimal
hypothesis.
Planetesimals
came to be when the solar system was just a swirling interstellar cloud, slowly
collapsing to form the Sun and planets. Dust grains condensed within that
primeval gas. The grains were small, but by hitting and sticking together they
formed pebble-sized objects that fell into the plane of the rotating nebula.
The pebbles accumulated into boulders, which in turn became larger bodies, 1 to
100 km wide. These were planetesimals -- the fundamental building blocks of the
planets. For reasons unknown Eros was
never captured by a growing protoplanet. It remained a planetesimal even as
other worlds in the solar system grew and matured. Fully-developed planets like Earth are chemically segregated --
that is, they have heavier elements near their cores and lighter ones at the
surface. Planetary scientists call this "differentiation." If Eros
were a chip from a planet that broke apart, perhaps in the asteroid belt, it would
exhibit chemical signatures corresponding to some layer from a differentiated
world. For example, Eros might be
iron-rich if it came from the core of such a planet or silicon-rich if it came
from the crust. Instead, "orbital
data from the x-ray spectrometer showed
Eros is very much like a type of undifferentiated meteorite we find on Earth
called ordinary chondrites," says Andrew Cheng, project
scientist. Eros seems to harbor a
mixture of elements that you would only find in a solar system body unaltered
by melting (an unavoidable step in the process of forming rocky planets). But,
says Cheng, there is a possible discrepancy.
"The abundance of the element sulfur on Eros is less than we
would expect from an ordinary chondrite. However, the x-ray spectra tell us
only about the uppermost hundred microns of the surface, and we do not know if
the sulfur depletion occurs only in a thin surface layer or throughout the bulk
of the asteroid." The GRS can
go deeper, as much as 10 cm below the surface. Although the instrument can't
detect sulfur, it is sensitive to gamma-ray emissions from other elements such
as radioactive potassium that are indicators of melting. Like sulfur, potassium
is a volatile element -- it easily evaporates when a rock is heated. Finding plenty
of potassium would strengthen the conclusion that Eros is an unmelted and
primitive body. On the other hand, a
widespread dearth of "volatiles" would hint that Eros isn't so
primitive after all. It might sound
like an ivory-tower question, but knowing the makeup of this asteroid -- both
its internal structure and its chemical composition -- has a practical
application. The solar system is littered with space rocks more or less like
Eros, and many come uncomfortably close to Earth. One day we may need to blow
one apart (or deflect one without blowing it apart) to avoid an unpleasant
collision. Near-Earth asteroids are also potential mining resources as humans
expand into space. In either case, knowing more about them is a good idea! "Our first four data sets are here
and they look great," says Trombka. "We're just hoping to get
as much data as we can before the mission ends." NEAR Shoemaker launched on Feb. 17,
1996 and became the first spacecraft
to orbit an asteroid on Feb. 14, 2000. The car-sized spacecraft gathered 10
times more data during its orbit than originally planned, and completed all the
mission's science goals before its controlled descent.
A
new meteorite study is rekindling a scientific debate over the creation of our
solar system. The study is based on
the microscopic analysis of two rare meteorites recently discovered in
Antarctica and Africa. Most meteorites
found on Earth are believed to be fragments of asteroids - ancient rocks and
that formed during the creation of the solar system about 4.56 billion years
ago. Thousands of asteroids still orbit the Sun in the asteroid belt between
Mars and Jupiter, about 140 million miles from Earth. "Asteroids and meteorites are solids that never got
incorporated into the planets. These objects have survived, unchanged, for 4.56
billion years," says physicist Anders Meibom, a postdoc at
Stanford. Using electron microscopy
and other laboratory techniques, Meibom and his colleagues conducted a detailed
chemical analysis of two chondrites - primitive meteorites made up of thousands
of tiny round particles called chondrules.
"Chondrules are among the oldest objects in the solar system,
dating back to the birth of the Sun," says Meibom, "so when we
look at chondrules, we’re actually looking at the very first steps towards the
creation of our solar system."
Meibom points out that most chondrules are made of silicates and metals
that can only be produced at very high temperatures. Exactly how chondrules
formed in the early solar system is a hotly debated topic among
scientists. "The conventional
view," notes Meibom, "is that chondrules started out as dust
balls in the asteroid belt region some 4.56 billion years ago. Today, the asteroid belt is ultra-cold, but
at that time, the temperature was just below 700 degrees Fahrenheit. The dust balls melted after they were zapped
by quick bursts of lightning or shock waves, which briefly raised temperatures
to about 3000 degrees F."
According to this theory, as the melted particles cooled, they turned
into millimeter-size chondrules, which eventually clumped together to form
larger chondrites.
But
in 1996, astronomer Frank Shu proposed a different theory based in part on
dramatic images from the HST, which - for the first time - allowed astronomers
to witness the actual birth of new stars elsewhere in the Milky Way. The Hubble revealed that most young stars
are created from enormous disks of whirling gas and dust. As the disk contracts, it rotates faster
and faster, funneling tons of interstellar dust toward the center, where
temperatures reach 3000 degrees F or more - hot enough to melt metal and
vaporize most solids. The rotating
disk also produces enormous jets of gas capable of launching debris far into
space at speeds of hundreds of miles per second. Using the Hubble images as a guide, Shu proposed that chondrules
in our solar system were created near the hot central disk of the newly emerging
Sun - not in the relatively cool asteroid belt hundreds of millions of miles
away. According to Shu, dust
particles were melted by the Sun, then launched into space by powerful jets of
gas and solar wind. While in flight, the molten particles solidified into
spherical chondrules, some of which landed in the asteroid belt a few days
later. Others ended up as the raw materials that formed the Earth, Mars and the
rest of the planets in our solar system.
According to Meibom, the March 2 chondrite study in Science magazine
gives Shu’s version of chondrule creation a tremendous boost. "Our findings demonstrate that
Frank Shu’s ideas are not just some fantasy," he notes. "We
now have actual rocks that provide hard numbers, which fit very nicely into the
general framework of Shu’s theory."
Meibom and his colleagues based their study on two rare meteorite
specimens - HH 237, a grapefruit-size chondrite recovered from the Hammadah al
Hamra region of north Africa; and QUE 94411, a walnut-size sample collected
from the Queen Alexander mountain range in Antarctica. "Most chondrites are only seven to
ten percent metal by volume, but these two specimens are about 70 percent iron
and nickel," says Meibom.
Microscopic analysis revealed that these iron-nickel compounds formed by
condensation from hot gas when the temperature was around 2500 degrees F. "Because HH 237 and QUE 94411
contain pristine samples of condensed iron and nickel, we were able to
determine that these metal grains formed on a time scale of a few days.
Furthermore, the newly created metal grains must have been transported out of
their hot formation region very quickly.”
"Shu’s model provides those kind of temperatures and time
scales, and the jets certainly provide a way to kick the grains out to much
colder regions of the solar nebula," adds Meibom. "The scenario we are suggesting is
that of a big blobs of hot gas rising up through the disk - almost like bubbles
in boiling spaghetti sauce. As the gas bubbles rose and cooled, silicate and
metal grains began to condense out of the gas. When these grains got close
enough to the surface of the disk, they became trapped in the powerful jet
streams. Days later, the particles arrived in the asteroid belt, where the
relatively cold temperatures preserved them from destruction." These chondrites allow us to look at the
very frontier of the solar system, concludes Meibom. "For the first time, we’re really building a bridge
between what we observe in the meteorites and what astrophysicists like Shu are
telling us." Frank Shu
agrees. "In these two very
special meteorites we finally have direct evidence that certain portions of
rock had to move from some place very hot to some place very cold in a very
short period of time," comments Shu. "This is a very important
study."
http://www.psrd.hawaii.edu/Sept00/primitiveFeNi.html
http://www.cwru.edu/affil/ansmet/
http://hubble.esa.int
Bright,
flat terrain in long swaths on the surface of Jupiter's icy moon Ganymede may
testify that water or slush emerged there about a billion years ago, say
planetary scientists who have combined stereo images from NASA's Galileo and
Voyager missions to examine provocative features on that moon. This bright
terrain, long since frozen over, lies uniformly in troughs about one kilometer
(0.5 mile) lower than Ganymede's older, darker, cratered terrain. Ganymede is the largest moon in the solar
system and larger than the planet Mercury. The roles that volcanism and various
forms of tectonics have played in molding its complex topography have been
hotly debated over the years. But the newly created images, taking advantage of
the large quantity of Voyager images and the higher resolution of Galileo's,
point to volcanism as the main impetus behind the troughs. "What we
think we're seeing is evidence of an eruption of water on the surface of
Ganymede," said Dr. William B. McKinnon. "We see these long,
smooth troughs that step down up to a full kilometer. They're really very much
like rift valleys on the Earth and they're repaved with something pretty
smooth. The material in the troughs is more like terrestrial lava in terms of
its fluidity than relatively stiff glacial ice." He said the material
is banked up against the edges of the walls of the trough and appears to have
been more fluid than solid ice would have been, even if it were relatively warm
ice. These features support the idea that they were created by volcanism. http://www.jpl.nasa.gov/pictures/jovianmoons
The
researchers used stereo imaging -- a method where three-dimensional objects are
reproduced by combining two or more images of the same subject taken from
slightly different angles -- to reconstruct the physical topography of
Ganymede's terrains. Maps were then generated from the stereo images. "This
is a new kind of stereo topographical information over hundreds of kilometers
across Ganymede," McKinnon said. The images provide new clues about
what happened on Ganymede long ago and how that moon reworks its older, darker
material. One trough extends an
estimated 900 kilometers (about 600 miles). "The long trough is
probably a billion years old, but it's actually one of the younger volcanic
features," McKinnon said. "It's the last gasp of the process
that made the bright terrain."
According
to McKinnon, the geological explanation for such long lanes of flatness is that
they occurred by the extending and opening up of Ganymede's crust. And then
that portion of the crust became flooded with some sort of lava. The
high-resolution Galileo images show that material that flooded the lanes is "no
less liquid than a slush," said McKinnon. "But it is not
glacial ice, which would have big moraines and big round edges like a flowing
glacier does." Moreover, the
images reveal depressions that resemble volcanic calderas along the edges of
the bright terrains. On Earth, calderas are large, more-or-less circular
craters usually caused by the collapse of underground lava reservoirs. "The
caldera-like features make a pretty good circumstantial case for volcanism
causing this topography," McKinnon said. "We think these
particularly bright terrains were formed by volcanism, which means that most or
all the other bright terrains started out this way, and became fractured or
grooved over time through tectonic forces."
Only
35% of the Universe's contents is in the form of matter, according to findings
by astronomers using the Anglo-Australian Telescope near Coonabarabran in
eastern Australia. The rest is believed to be in the form of 'dark energy'.
This measurement, the most accurate to date, is based on data from 141,000
galaxies. It confirms other studies indicating that the Universe will expand
forever because there is too little mass to provide gravity to rein it in. The team has also gathered the best existing
evidence that large-scale structures in the Universe -- giant superclusters of
galaxies -- evolve over time by collapsing under the influence of gravity.
"This has allowed us to weigh the universe," said the paper's
lead author, Professor John Peacock of
the Royal Observatory Edinburgh. The
findings are the first major piece of science to arise from the 2dF (two-degree
field) galaxy survey, which leads the world in mapping galaxies. It has now
mapped more than 150,000 and will reach its target of 250,000 by the end of the
year, making it ten times larger than the largest previous survey. "The matter density of the
Universe is extremely low," said Dr Matthew Colless. "On
average there might be one atom per cubic meter of space." "The major constituent of the Universe
is believed to be some kind 'dark energy', which is pushing the Universe apart." The 2dF survey shows clearly that ninety
percent of galaxies are distributed on the surfaces of big 'bubbles' in space,
with the rest falling into dense clusters.
"We use the galaxies as a tracer of mass in the Universe,"
explained survey team member Richard Ellis.
"Of the total matter in the universe, most is in the form of
'dark matter', which gives off no radiation," he said. "But it
does seem that the visible matter is distributed much like the dark matter.
They know about each other."
As the universe expands, the galaxies recede from us. The recession
velocity (speed) of a galaxy is proportional its distance from us, so the
velocities can be used to determine the positions of the galaxies in
space. The 2dF team used their map of
the galaxy distribution to measure the total mass density of the universe --
what proportion of the Universe's content is mass -- in two ways. In the first method, the astronomers compared
the measured clumping of galaxies into superclusters with the size of small
temperature fluctuations in the cosmic microwave background, which measure
density fluctuations at early times. The amount of growth in structure required
to match the clumping today requires the universe to have a 'flat' geometry
(without spatial curvature), with about 35% of its energy in the form of matter
and about 65% in the form of 'vacuum energy', also known as 'dark energy'. The astronomers also measured the mass density
by looking at how galaxies move under the influence of gravity. As well as its recession velocity, any
galaxy has a velocity that it has acquired by falling towards other
concentrations of mass -- visible galaxies and/or dark matter. These extra velocities distort the structure
of the galaxy survey map in the direction looking out from Earth -- that is,
along our line of sight to the galaxies.
A statistical analysis of these galaxy motions shows that on small
scales the galaxies are typically orbiting each other very rapidly in dense
groups and clusters, but that at larger scales the galaxies are all falling in
towards mass concentrations. The size of this infall is related directly to the
amount of matter in the Universe. This method too gives a figure for the mass
density that agrees well with the standard cosmological model.
In
a case of beginner's luck, a group of international students, who won the
chance to image Mars with a NASA spacecraft camera, have stumbled upon a
surprising cluster of dark-colored boulders situated in the middle of
light-colored terrain. The students' discovery has so far baffled veteran Mars
scientists. The mystery boulders, found in images captured by NASA's Mars
Global Surveyor spacecraft, cover one of three Martian sites targeted by the
young scientists. How the boulders got there and what geological history they
represent on Mars are questions scientists still need to answer. "It's
puzzling," said Michael Carr of the USGS. "I looked at a few
pictures around [the area] and couldn't find anything to explain it. Very
puzzling! These are huge boulders. There are no indications of any outcrops
that could shed such boulders."
"The location and nature of these boulders is unusual, but their
shape and distribution -- in respect to the slope upon which they sit -- is
consistent with a boulder shattered by weathering. The fall to their present
location could also have broken the boulders apart. The mystery is why so much
of the rest of the slope is smooth and devoid of blocks," said Dr.
Michael Malin. Images of the two other
sites chosen by the students revealed an equatorial Martian region with layers
of sediment, possibly deposited by flowing water, and layered terrain of a Martian
polar cap. The students, all members
of the Planetary Society's week-long Red Rover Goes to Mars Training Mission,
range in age from 10 to 16. Under the supervision of scientists at Malin Space
Science Systems, they studied imaging data from Global Surveyor and selected
interesting areas that coincided with the spacecraft's current orbital position
around the red planet. They also selected a candidate landing site for a
possible sample return mission, to be imaged sometime in the next five months
when Global Surveyor's orbit takes it past the target area. "This kind of opportunity makes me
wish I were a student again," said Michelle Viotti, lead for the Mars
Public Engagement Program at JPL. "For those who are still in school,
we hope to open up many more opportunities in the near future for students to
participate personally in the exploration of Mars." Images of the students' three sites, a
close-up of the mystery boulders and information on the students and their
training mission are available at http://planetary.org
The fledgling scientists were chosen through an essay contest from more than
10,000 entrants worldwide.
New
findings provide evidence that Earth's most severe mass extinction -- an event 250 million years ago that wiped out 90 percent of the life on Earth -- was
triggered by a collision with a comet
or asteroid. Over 90 percent of all
marine species and 70 percent of land
vertebrates perished as a result, according to the research team, led by
Dr. Luann Becker of the University of
Washington. The collision wasn't directly responsible for the
extinction but rather triggered a
series of events, such as massive
volcanism, and changes in ocean oxygen, sea level and climate. That in turn led to species extinction on a
wholesale level, according to the
team. "If the species cannot
adjust, they perish. It's a survival-of-the-fittest sort of thing,"
said Becker, UW acting assistant
professor of Earth and Space Sciences. "To knock out 90 percent of organisms, you've got to
attack them on more than one front." The scientists do not know the site of the
impact 250 million years ago, when all
Earth's land formed a supercontinent
called Pangea. However, the space body left a calling card -- complex carbon molecules called
buckminsterfullerenes, or Buckyballs,
with the noble gases helium and argon trapped
inside the caged structure. Fullerenes, which contain at least 60 carbon atoms and have a structure
resembling a soccer ball or a geodesic
dome, are named for Buckminster Fuller, inventor of the geodesic dome.
The
researchers know these particular Buckyballs are extraterrestrial because the noble gases trapped inside have an unusual ratio of isotopes, atoms whose
nuclei have the same number of protons
but different numbers of neutrons.
Terrestrial helium is mostly helium-4, while extraterrestrial helium is mostly helium-3. "These things form in carbon stars.
That's what's exciting about finding
fullerenes as a tracer," Becker said. The extreme temperatures and gas pressures in carbon stars are perhaps the only way extraterrestrial noble
gases could be forced inside a
fullerene, she said. These gas-laden
fullerenes were formed outside the Solar
System, and their concentration in the sedimentary layer at the boundary of the Permian and Triassic
periods means they were delivered by
comets or asteroids. The researchers
estimate the comet or asteroid was roughly 3.75 to 7.5 miles (6 to 12 kilometers) across, or about
the same size as the asteroid believed
responsible for the extinction of the
dinosaurs 65 million years ago.
The telltale fullerenes containing helium and argon were extracted from sites where the
Permian-Triassic boundary layer had
been exposed in Japan, China and Hungary. The evidence was not as strong from the Hungary site, but the
China and Japan samples bear strong
evidence, Becker said. The team's
work was made more difficult because there are few 250 million-year-old rocks left on Earth since most rocks of that age have been recycled through the
planet's tectonic processes. "It
took us two years to do this research, to try
to narrow it down enough so that we could see this fullerene signature," Becker said. Scientists have long known of the mass
extinction 250 million years ago, since
many fossils below the boundary -- such as
trilobites, which once numbered more than 15,000 species -- diminish sharply close to the boundary and
are not found above it. There also is
strong evidence suggesting the extinction
happened very rapidly, on the order of 8,000 to 100,000 years, which the latest research supports. Previously, it was thought that any
asteroid or comet collision would leave
strong evidence of the element iridium,
the signal found in the sedimentary layer from the time of the dinosaur extinction. Iridium was found at
the Permian-Triassic boundary, but not
nearly in the concentration as from the
dinosaur extinction. Becker believes that difference is because the two space bodies that slammed
into Earth had different compositions.
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
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