EAS BUSINESS…
April Meeting Recap
Dr. Paul Hodge of the UW Astronomy dept.
will be discussing “Exploring Barnard's Galaxy with the HST".
Next Meeting – Saturday May 20th At Providence
Pacific Clinic Hospital – Monte Cristo Room – 7:00 PM
The
Everett Astronomical Society's next meeting will be Saturday May 20th,
at 7:00 PM, in the PROVIDENCE Monte Cristo Room at Providence Hospital
PACIFIC Clinic at 916 Pacific Avenue in Everett.
Dates for
this season’s club star parties:
April 1 May 6 June 3 July 8
Aug 5 Sept 2 Sept 30 Oct 7
Scheduled Meeting Topics:
May 20 –
Brad Snowder WWU- starlore from American Indians
Jun 24 -
Julianne Dalcanton UW
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 –
(speaker not confirmed)
Dec 16 –
Holiday party
Upcoming UW Thursday Afternoon Colloquia
|
DATE
|
SPEAKER
|
INSTITUTION
|
SUBJECT
|
|
May 4
|
Linda Sparke
|
University of Wisconsin
|
Multiply Barred and Lopsided Galaxies
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May 11
|
David Trilling
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University of California, Santa Cruz
|
Extrasolar Planetary Systems: Observations,
Theories and Speculations
|
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May 18
|
Ian Dell'Antonio
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National Optical Astronomy Observatory
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Prospecting for Mass with Wide-field Imaging
Surveys
|
|
May 25
|
Andy McWilliam
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Carnegie Observatory
|
Chemical Composition of the Local Group: the
Galactic Bulge and the Sagittarius Dwarf Galaxy
|
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June 1
|
Fabio Governato
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Osservatorio di Brera-Merate, Milano
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The Morphological Evolution of the Local Group
Satellites
|
Member News
We are still seeking contributors for the KSER radio
show.
Financial Health
The club maintains a safe $1450+ balance. We try to
keep approximately a $500 balance to allow for contingencies.
Club Star Party Info
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
May 2000
May 01 - Asteroid 187
Lamberta At Opposition (10.3 Mag.)
May 04 - Space Day
May 05 - Eta Aquarids
Meteor Shower Peak
May 08 - Mercury
Passes 0.8 Degrees From Jupiter
May 09 - Mercury
Passes 2.1 Degrees From Saturn
May 12 - Asteroid 349
Dembowska At Opposition (10.2 Mag.)
May 13 - Mercury At
Perihelion
May 15 - Asteroid 10
Hygiea At Opposition (9.1 Mag.)
May 15 - Asteroid 5
Astraea At Opposition (10.1 Mag.)
May 16 - Asteroid 19
Fortuna At Opposition (10.7 Mag.)
May 17 - Venus Passes
0.1 Degrees From Jupiter
May 18 - Venus Passes
1.2 Degrees From Saturn
May 19 - Mercury
Passes 1.1 Degrees From Mars
May 19 - Asteroid 89
Julia At Opposition (10.5 Mag.)
May 20 - EAS Meeting 7:00 PM
– Providence Pacific Clinic
May 27-29 Memorial
Day Weekend
May
30 - Asteroid 419 Aurelia At Opposition (10.0 Mag.)
June 2000
Jun 01 - Asteroid 17
Thetis At Opposition (10.1 Magnitude)
Jun 01 - Pluto At
Opposition
Jun 03 - Compton
Gamma Ray Obs. Reenters Atmosphere
Jun 08 - Mercury
Occults 78855 (6.9 Magnitude Star)
Jun 09 - Mercury
Greatest Eastern Elongation (24 Degrees)
Jun 12 - Asteroid 39
Laetitia At Opposition (10.1 Magnitude)
Jun 14 - Asteroid 11
Parthenope At Opposition (9.2 Magnitude)
Jun 15 - Asteroid 4
Vesta Occults TYC 6323 01853 (10.5 Mag Star)
Jun 17 - Asteroid 40
Harmonia Occults TYC 6874 00570 (10.9 Mag Star)
Jun 20 - Asteroid
1605 Milankovitch Occults TYC 5173 01472 (9.4 Mag Star)
Jun 21 - Summer
Solstice, 01:36 UT
Jun 21 - Venus Passes
0.3 Degrees From Mars
Jun 24 - Asteroid 704
Interamnia At Opposition (10.2 Magnitude)
Jun 24 - EAS Meeting 7:00 PM
– Providence Pacific Clinic
Jun 26 - Asteroid 344
Desiderata At Opposition (9.8 Magnitude)
Jun 26 - Charles
Messier's 270th Birthday (1730)
Over The Airwaves
E.A.S.
members, Jim Ehrmin and Pat Lewis 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
May 04 New
Moon
May
11 First Quarter Moon
May
18 Full Moon
May 26 Last
Quarter Moon
Apr 04 New
Moon
Apr
11 First Quarter Moon
Apr
18 Full Moon
Apr 25 Last
Quarter Moon
Up In The Sky -- The Planets
MERCURY, and VENUS are in the dawn twilight and not visible.
MARS is in the evening twilight, at solar conjunction on July 1.
JUPITER and SATURN have disappeared into the sunset.
URANUS and NEPTUNE
are
low in the southeast before dawn at magnitude 6 and 8 respectively.
PLUTO is in
Ophiuchus in the southeast before dawn, but at mag. 14, requires an 8 to
10-inch scope a dark sky, and a good map.
Constellation(s) of the Month
CORONA BOREALIS: (The Northern Crown).
With a midnight culmination date of May 19th, Corona Borealis is perfectly placed for spring viewing. It contains no asterisms, but the stars of
the constellation do trace out an “upside-down letter ‘C’” (the closed portion
of the ‘C’ faces south), situated between the Northern constellations of Bootes
and Hercules. The only other bordering
constellation is that of Serpens, located to its south.
Corona Borealis ranks 11th in overall brightness among the
constellations, but 73rd in size; it takes up almost 179 square degrees of the
entire sky (0.433%). It contains no
known meteor showers, and no Messier objects.
Corona Borealis is completely visible from latitudes North of –50
degrees, and completely invisible from latitudes South of –64 degrees. It has 22 stars greater than magnitude 5.5,
and its central point is at RA=15h48m, Dec.= +33 degrees. The solar conjunction date of Corona
Borealis is November 18th.
Even though Corona Borealis has no Messier objects or known
meteor showers, besides being a visually beautiful constellation, it does
contain two very interesting objects in their own right. Near epsilon Corona Borealis, a nova
suddenly flared up in May, 1866. It
reached 2nd magnitude and remained easily visible for over a week. It is now known as the “Blaze Star” (also
known as T Corona Borealis), and is the most famous example of a recurring
nova. (It last brightened, to 3rd
magnitude, in 1946). There is also another interesting variable star within
Corona Borealis (CrB), known as R CrB.
It is normally a 6th magnitude star, but it dims (at irregular
intervals) to as low as 15th magnitude.
It is suspected that clouds of carbon (e.g., soot and graphite) are
emitted form the star and therefore dim its light; when these materials are
reabsorbed, the star brightens.
There are two well-known legends associated with the
constellation of Corona Borealis. The
Native (North) American Indians considered it to be a semicircle of chiefs, at
council to discuss the future of their peoples. In ancient Greek mythology, Ariadne (daughter of King Minos) was
asked by Bacchus (the god of vegetation and wine) to marry him. But Ariadne did not believe that Bacchus was
a god. To prove that he was, Bacchus asked
Venus (goddess of love) to design a crown of jewels as his wedding present to
Ariadne. When Ariadne saw the crown, she believed that Bacchus was a god, and
consented to marry him. Bacchus was so
overwhelmed with joy, that he threw the crown into the heavens, where it has
resided and shone ever since.
Corona Borealis is a visually beautiful Northern
constellation, and is well placed to be easily enjoyed by any spring
sky-watcher.
Young
Astronomer’s Corner
The Young Astronomer’s Corner is in the middle of a
continuing series all about the planets.
Last time (March, 2000), the subject of this column was the planet
Uranus. This month it will be Neptune
(the eighth planet out from the Sun…most of the time!), as we continue our
journey out to Pluto. We are listing
the astronomical facts about each planet. Again, for the month of May 2000, our
guest planet is Neptune, and these are the facts:
Rotation around the Sun: every 164.79 years
Orbit:
from 29.76 (closest or ‘perihelion’)
to 30.36 (furthest or ‘aphelion’) Astronomical Units (AU)*; this is an orbit that varies between
approximately 2.77 billion and 2.82 billion miles from the sun. (*Note: One AU
equals approximately 93 million miles).
Inclination of Orbit to Ecliptic: 1.8
degrees.
Mean Orbital Velocity: 5.43
km/sec.
Diameter at Equator: 50,538 kilometers (or
31,586 miles).
Mass: 17.2 (approximately 17.2 times
more massive than earth); (5.9742 x (10 e24 (10 to the 24th power)) kilograms =
1 Earth Mass).
Density: approximately 1.80 times that of
water (global density).
Surface Gravity (Earth = 1): 1.19
Period of Rotation on its own axis:
approximately 18 hours, 25 minutes.
Axis tilt: 29.56 degrees.
Satellites (moons): 8, as well as planetary
rings.
Special Notes About Neptune: Neptune is the fourth largest planet in the
solar system (one of the gas giants) in terms of equatorial diameter, but is
more massive than Uranus, the third largest planet in diameter.
Neptune is the most distant of the giant planets, and was
discovered in 1846 by J.G. Galle at the Berlin Observatory, based on French
(Urbain Leverrier) predictions resulting from disturbances in the orbit of
Uranus (there were similar estimates made by Englishman John C. Adams).
Neptune returns to opposition two days later every year, and
appears as an indistinct magnitude 7.7 bluish-green object in binoculars; in
fact, no markings can be seen on its bluish-green disk from earth-bound
telescopes. Neptune’s color arises
primarily from methane within its atmosphere, which is principally helium and
hydrogen and a blend of methane, water, and ammonia.
In 1989, Voyager 2 sent back remarkable images of Neptune
during its fly-by. The Great Dark Spot
was noted in its atmosphere. Like
Jupiter’s Great Red Spot, it occupies a equivalent proportion of the surface
area of Neptune (as the GRS does of Jupiter’s surface area), and is a
high-pressure system around which near-supersonic winds flow in an
anti-clockwise circuit. The Great Dark Spot measures approximately 12,000 by
8,000 kilometers. At about 50-70 kilometers above the main cloud plane, there
are whitish cirrus-like clouds composed of methane ice crystals. Neptune also has belts and zones similar to
Jupiter's, only much fainter.
The core of Neptune is believed to be rocky, composed
primarily of silicon and iron. The
atmosphere of Neptune revolves more slowly than its core, and this is opposite
to the atmospheres of the other gas giants; the implication is that circulation
of Neptune’s atmosphere may take place in a retrograde (backward or opposite)
manner. Neptune also gives off more
energy than it receives from the Sun, suggesting that it has its own internal
source of heat; the planet also has a magnetic field, which is somewhat weaker
than that of the other gas giant planets.
Four dark planetary rings were discovered during the Voyager 2 fly-by in
1989.
Neptune has 8 known moons; six of them were discovered
during the 1989 Voyager 2 fly-by, and the remaining two (Triton and Nereid)
were discovered from Earth. Triton is
the largest moon of Neptune, and was discovered the same year (1846) as the
planet itself; it is about ¾ the size of our own Earth’s Moon. Interestingly, Triton has an orbit in the
opposite direction to that of Neptune (retrograde), and is slowly coiling its
way down towards Neptune. Triton is a
very cold moon, and has a thin atmosphere of mostly nitrogen, with some methane
and carbon monoxide. Its South Pole cap
is pinkish in color (probably nitrogen snow and ice). Triton’s face has been shown to have both craters and long
cracks, but no mountains; its surface resembles that of a cantaloupe. It has also been noted to have geysers of
nitrogen, some reaching 8 km in height!
Nereid was discovered from Earth in 1949, and has a very eccentric orbit
(going from 2 to 10 million kilometers from the planet at various times during
its orbit).
When we talk about Pluto next month in our last column of
this present series, we will tell you why Neptune, and not Pluto, is sometimes
the farthest planet from the Sun. Can
you guess why? Stay tuned; see you next
month!
Astronomy and Telescope “Lingo”
ASTRONOMY
LINGO: BENNETT’S COMET (1970 II): A long-period comet discovered in 1969 by J.C. Bennett from South
Africa. It passed perihelion on March
20, 1971, and by this time the comet was a zero-magnitude object with a tail 11
degrees long and an inclination of 90 degrees.
The Orbiting Geophysical Observatory revealed the comet to be surrounded
by a huge hydrogen envelope..
TELESCOPE LINGO:
PAUL-BAKER TELESCOPE: A wide
field-of-view, compact three mirror telescope, modeled by Maurice Paul in 1935
and modified by James Baker in approximately 1945. This telescope is able to produce a high quality image on a flat
focal plane, with very low image extension: a paraboloidal primary, a convex
ellipsoidal secondary, and a concave spherical tertiary mirror are used..
Astronomy Fun Facts
May Fun Facts:
**! The Milky Way Galaxy is
so large, that a powerful flash of light generated at one edge of the Milky Way
(and traveling at 186,000 miles/second), would take 100,000 years to reach the
other side!! (Another way of saying the same thing: our Milky Way Galaxy is
approximately 100,000 light years across!)
**! Can you go on a
multi-trillion mile, and multi-million year, voyage, without ever turning back,
and still only wind up at your place or origin? Well, technically, yes!!
If a star-ship left Earth at about 190,000 miles per hour, in about 115
million years (are there any espresso shops along the way?), it would meet up
with the Earth and Sun again because of the rotation of the Milky Way
Galaxy. Had it never left Earth, it
would have “arrived” at about the same time!
Of course, it would have been without all the great adventures of the
journey, many of which would have become lore, legend, and conversations of
countless new generations, eons before the actual arrival!!!
**! The great comet of 1843
had a tail that stretched halfway across the sky; it was estimated to be about
500 million miles long (about Jupiter’s distance from the Sun). This comet’s tail, if wrapped around the
Earth’s equator, would circle it about 20,000 times!
“MIRROR”
IMAGES
“MIRROR” IMAGES” is a relatively new column,
appearing for the seventh time in The Stargazer. 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 new
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: OPTICAL DOUBLE STARS: A pair of
stars that appear close together in the sky (as opposed to actually being close
together in the sky: this would be a physical double star system). Optical double stars appear close together
because they lie in roughly the same direction – the same line of sight – as
seen from Earth. However, unlike
physical doubles, they share no gravitational attraction, as they are too far
apart to be members of the same stellar system.
REPRESENTATIVE NORTHERN HEMISPHERE OBJECT: Albireo
(Beta Cygni): This very famous, and very beautiful, double star is a favorite
of all astronomers, and a favorite new object of all budding night-sky
enthusiasts. It is the second brightest
“star” (i.e., it is actually two stars) in Cygnus. The primary star is an orange giant with an apparent visual magnitude of 3.1 and is of spectral type
K5-II; the secondary, 35 arc seconds away, is deep blue, has an apparent visual
magnitude of 5.1, and is of spectral type B8-V. Albireo is 120 parsecs distant from Earth, and its individual
components are separated by about 400 billion miles.
REPRESENTATIVE SOUTHERN HEMISPHERE OBJECT: AL GIEDI
(Alpha Capricorni): The brighter of
the two stars in this system has an apparent visual magnitude of 3.6, and is a
light yellow spectral type G3 supergiant.
The dimmer of the pair has an apparent visual magnitude of 4.2, is also
light yellow in color, and is classified as a G9 giant. Interestingly, each
member of this optical double star system has dimmer, closer companions as
well. The G3 supergiant in the
line-of-sight Alpha Capricorni star system lies 110 light-years away from
Earth, but the G9 giant lies much further away…..1,600 light-years away to be
exact!!
Astronomical Notes --
On & Off the Net...
NASA
astronomers have collected the first-ever radar images of a "main belt" asteroid, a
metallic, dog bone-shaped rock the size
of New Jersey, an apparent leftover from an ancient, violent cosmic collision.
The
asteroid, named 216 Kleopatra, is a large object in the main asteroid belt between Mars and Jupiter;
it measures about 135 miles (217
kilometers) long and about 58 miles (94 kilometers) wide. Kleopatra was
discovered in 1880, but until now, its shape
was unknown.
"With
its dog bone shape, Kleopatra is one of the most unusual asteroids we've seen in the Solar System," said Dr.
Steven Ostro of NASA's Jet Propulsion
Laboratory, Pasadena, CA, who led a team of astronomers observing Kleopatra with the 1,000-foot (305-
meter) telescope of the Arecibo Observatory in Puerto Rico. "Kleopatra could be the remnant of an
incredibly violent collision between
two asteroids that did not completely shatter and disperse all the fragments."
The
astronomers used the telescope to bounce radar signals off Kleopatra. With sophisticated computer-analysis techniques, they decoded the echoes, transformed them
into images, and assembled a computer
model of the asteroid's shape. The
Arecibo telescope underwent major
upgrades in the 1990s, which
dramatically improved its sensitivity and made it feasible to image more distant objects.
These
new radar images were obtained when Kleopatra was about 106 million miles (171 million kilometers)
from Earth. Traveling at the speed of light, the transmitted
signal took about 19 minutes to make
the round trip to Kleopatra and back.
"Getting
images of Kleopatra from Arecibo was like using a Los Angeles telescope the size of the human eye's lens to image
a car in New York," Ostro
said.
Kleopatra
is one of several dozen asteroids whose coloring suggests they contain metal.
Kleopatra's strong reflection of
radar signals indicates it is mostly metal, possibly a nickel-iron alloy.
These objects were once heated, melted and differentiated into structures containing a core, mantle
and crust, much as the Earth was
formed. Unlike Earth, those asteroids
cooled and solidified throughout, and
many underwent massive collisions that
exposed their metallic cores. In
some cases, those collisions launched
fragments that eventually collided with Earth, becoming iron meteorites like the one that created
Meteor Crater in Arizona.
"But
we don't need to worry about Kleopatra -- it will never hit Earth," Ostro said.
"The radar-based reconstruction of
Kleopatra's shape shows the object's
two lobes connected by a handle, forming a shape that resembles a distorted dumbbell, or dog bone," said Dr. R.
Scott Hudson of Washington State
University, Pullman, WA. "The
shape may have been produced by the
collision of two objects that had
previously been thoroughly fractured and ground into piles of loosely consolidated rubble. Or, Kleopatra may once have been two separate lobes in orbit around each other
with empty space between them, with
subsequent impacts filling in the area between the lobes with debris."
"The
radar observations indicated the surface of Kleopatra is porous and loosely consolidated, much like
surface of the Moon, although the
composition is different," said Dr. Michael Nolan of the Arecibo Observatory. "Kleopatra's interior arrangement
of solid metal fragments and loose
metallic rubble, and the geometry of
fractures within any solid components, are unknown. What is clear is that this object's collision
history is extremely unusual."
"It
is amazing that nature has produced a giant metallic object with such a peculiar shape," said Ostro. "We can think of some possible scenarios, but at this point
none is very satisfying. The object's existence is a perplexing
mystery that tells us how far we have
to go to understand more about asteroid
shapes and collisions."
The
Kleopatra images are available at:
http://www.jpl.nasa.gov/pictures/kleopatra
Mass-spectrometer
CIDA of the Garching based Max-Planck-Institut on the NASA spacecraft STARDUST
produces puzzling results
The
first in-situ chemical analysis of interstellar dust particles produces a
puzzling result: These cosmic particles consist mostly of 3-dimensionally
cross-linked organic macro-molecules, so-called polymeric-heterocyclic-
aromates. "They rather resemble tar-like substances than minerals"
say Dr. Franz R. Krueger (contractor) and Dr.Jochen Kissel, Max-Planck-Institut
für extraterrestrische Physik (for extraterrestrial Physics), Garching near
Munich, Germany, in the latest issue of 'Sterne und Weltraum' a monthly, German
language Astronomy magazine in Heidelberg, Germany.
So
far, 5 interstellar dust particles (= dust between the stars) have hit the
Garching built dust impact mass spectrometer CIDA (= Cometary and Interstellar
Dust Analyzer) onboard the NASA spacecraft STARDUST. Launched on Feb 7th 1999
STARDUST will visit comet Wild-2 (pronounce Vild-2) in 2004.
To
reach the comet, STARDUST has to perform three orbits about the sun. At the
close fly-by (miss-distance 500 km/300 miles) another instrument will collect
cometary dust and return it, well packed, to earth in January of 2006. During
its 7 year mission, STARDUST will face the stream of interstellar dust several
times. This dust is part of the local environment in the Milky Way which the
solar system currently passes through at high speed. It has recently be seen by
dust instruments of the Heidelberg-based Max-Planck-Institut für Kernphysik (=
for Nuclear Physics) on both NASA's Galileo and ESA's Ulysses spacecrafts. The
first measuring campaign for CIDA from February through December 1999 has
produced the new results.
During
this time STARDUST was at a distance of about 240 million kilometers (150
million miles) from the earth when the first impact occurred. Just before the
campaign the spacecraft pointed the instrument into the direction of the
interstellar dust, so that it would not measure the more frequent
interplanetary dust particles, which are parts of our solar system.
At
an impact speed of about 30 kilometers/second (18 miles/second) these
interstellar dust particles are vaporized immediately and broken up into
molecular fragments. A fraction of those carries a positive or negative
electronic charge. By its electric field in front of the target CIDA pulls the
positive ions into the instrument to the detector. Depending on their mass it
takes the ions different times to travel the 1.5 meters (5 feet) distance
(heavier ions travel longer). This way they are detected mass after mass with
in some 200 millionth of a second, and a mass spectrum is generated.
"It
is the size of these molecular fragments with nuclear masses of up to 2000
(water e.g. has 18 such units) which surprised us as much as the seemingly
absence of any mineral constituents", explains Dr. Kissel of the
Garching-based Max-Planck-Institut für extraterrestrische Physik. "Only
organic molecules can reach those sizes". The largest molecules found in
space so far are the polycyclic aromatic hydrocarbons (PAH) which reach masses
of a few hundred mass units.
The
details of the mass spectra measured with CIDA show that the molecules of the
interstellar dust must have about 10% of nitrogen and/or oxygen in addition to
hydrogen and carbon. This means that these cannot be pure PAHs, which are
planar, but are especially due to the nitrogen extend into all three spatial
directions.
Such
three dimensional molecules can form links to their neighbors and reach a
thermal stability necessary to survive the trip into the inner solar system
with 300 to 350 Kelvin (70 to 180 degrees Fahrenheit). "The organic
material analyzed with CIDA in the interstellar dust particles is another type
of reactive molecules which we found in the dust of comet Halley 14 years
ago" says Dr. Kissel. "When they got in contact with liquid water on
the young earth, they could have triggered the type of chemical reactions which
are a prerequisite for the origin of life."
*
STARDUST http://stardust.jpl.nasa.gov/
*
CIDA http://www.geo.fmi.fi/PLANETS/
Fiery volcanoes on Jupiter's moon Io are the
main source of dust streams that flow
from the Jupiter system into the rest of
the solar system, according to new findings from NASA's Galileo spacecraft analyzed by an international team
of scientists.
The
scientists, led by Amara Graps of the Max Planck Institute of Nuclear Physics in Heidelberg, Germany, analyzed
the frequency of dust impacts on
Galileo's dust detector subsystem.
They found peaks that coincided with the periods of Io's orbit (approximately 42 hours) and of Jupiter's
rotation (approximately 10 hours).
Although
dust scientists had suspected Io as the source of the dust streams, it was difficult to prove. They ruled out several possible sources, including Jupiter's main ring and
Comet Shoemaker-Levy 9, but Jupiter's
gossamer ring and Io remained as
candidates. The dust scientists
studied several years of Galileo data
to show that the motion of the dust stream particles is strongly influenced by Jupiter's magnetic
field, with a unique signature that
could exist only if Io were the main contributor to the dust streams.
"Now,
for the first time we have direct evidence that Io is the dominant source of the Jovian dust streams," said Graps,
lead author of a paper on the findings
that appears in the May 4 issue of the
journal Nature.
The
Jovian dust streams are intense bursts of submicron- sized particles (as small
as particles of smoke) that originate
in Jupiter's system and flow out about 290 million kilometers (180 million miles), or twice the distance
between Earth and the Sun. They were first discovered in 1992 by the
dust detector onboard the Ulysses
spacecraft during its Jupiter flyby.
"The
escape of dust from the Jovian system in 1992 was a total surprise," said Dr. Mihaly Horanyi, a dust plasma
physicist at the Laboratory for
Atmospheric and Space Physics, Boulder, CO,
and co-author of the paper.
Since 1995, the Galileo dust
detector, a twin to the Ulysses instrument, has observed the streams, both while the spacecraft was en
route to Jupiter and within the Jupiter
system.
Very,
very early in the history of our solar system, before and during the formation of the planets, small dust grains
were much more abundant. These charged grains were influenced by magnetic fields from the early Sun, much as
the dust on Io is affected by Jupiter's
magnetic field today. Thus, studies of
the behavior of these dust grains may
provide insight into processes that led
to the formation of the moons and planets in our solar system.
"The
dust from the Jovian dust streams is clearly
magnetically-controlled dust," said Dr. Eberhard Gruen of the
Max Planck Institute. "Dust particles carry information
about charging processes in regions of
the Jovian magnetosphere, where
information is otherwise sparse or unknown." Gruen built the
dust detectors for several spacecraft,
including Galileo, Ulysses and Cassini.
These
new results provide a useful window on Io.
In-situ dust measurements can
monitor Io's volcanic plume activity,
complementing observations made by Galileo and from Earth-based telescopes.
The
Jovian dust streams, with their Io source, are minor when compared to the huge amounts of dust created in the solar system by comet activity and asteroid
collisions. Nonetheless, they add to the variety of dust sources in
the solar system. In fact, the Jovian dust streams travel so fast
that some particles can actually leave
the solar system to join the local
interstellar medium -- the gas and dust that fill the space between stars.
In
December 2000, during a joint observation of Jupiter by Galileo and Cassini, scientists will have a
unique opportunity to study the Jovian
dust streams using dust instruments on both
spacecraft.
More
information on the Galileo mission is available at
http://galileo.jpl.nasa.gov
An
international team of cosmologists, including scientists at the University of
California, Santa Barbara, has released images that are helping to answer
fundamental questions about the cosmos. These images, the most precise ever
collected of the remnant radiation from the Big Bang, are published in the
April 27 issue of the international scientific journal Nature.
The
first detailed images of structures in the universe when it as only 300,000
years old were obtained by flying a sensitive balloon-borne telescope over
Antarctica. They shed light on some of the most basic questions in cosmology,
including the nature of matter and energy in the universe. They also show that
its geometry is nearly flat, rather than curved.
BOOMERANG
(Balloon Observations of Millimetric Extragalactic Radiation and Geophysics)
obtained the images using an extremely sensitive microwave telescope flown
under a stratospheric balloon that circumnavigated Antarctica over eleven days
in late 1998 and early 1999.
For
16 months, the BOOMERANG team has worked to interpret the vast quantities of
data collected during this flight, resulting in a picture of the universe long
before the first stars or galaxies formed.
"These
maps are incredibly rich; they are telling us about the seeds of galaxies, the
contents of our universe, and even hinting at its ultimate fate," said Tom
Montroy, a UCSB graduate student who works on the project.
Shortly
after the Big Bang, the universe consisted of a primordial soup of subatomic
particles and radiation, hotter than the surface of the sun. The universe
eventually expanded and cooled enough that neutral atoms could form, leaving
the photons free to travel. These photons are still traveling through the
universe today, and are known as the cosmic microwave background (CMB),
radiation that comes from all directions.
Ever
since this cosmic microwave background radiation was discovered in 1965,
scientists have eagerly sought high-resolution images of its faint variations.
NASA's COBE (Cosmic Background Explorer) satellite discovered the first evidence
for these variations in 1991, but its data lacked sufficient detail to show all
the structure. The BOOMERANG images are the first to bring the CMB into sharp
focus, with 40 times the resolution of those reported by COBE. The team's
analysis of the apparent size of CMB structures has produced the most precise
measurements ever made of the geometry of space.
"The
universe acts like a big lens," explained UCSB team leader John Ruhl,
professor of physics at UC Santa Barbara. "According to general relativity,
the power of that lens to bend light is related to the density of mass and
energy in the universe. The cosmic background photons have spent a long time in
that lens, and give us a very sensitive probe of whether light travels in
straight lines or curves in space. The images indicate that light travels in
fairly straight lines, so space must be nearly flat."
The
measured CMB structures also provide cosmologists with a new accounting of the
different forms of mass and energy that exist in the universe. "It looks
like there simply isn't enough normal matter out there, the type of which you
and I are made, to account for the total budget, said Ruhl. "There must be
something else to balance the account." Other ingredients that could make up
the deficit include dark matter and the cosmological constant.
Two
BOOMERANG websites are:
www.physics.ucsb.edu/~boomerang
and
http://oberon.roma1.infn.it/boomerang
Computer
simulations produce spectacular images of Milky Way colliding and merging with
neighbor
The
gigantic clouds of gas and matter that pelted the Milky Way in its infancy are
mere fender benders compared to the catastrophic collision set to occur with
the Andromeda galaxy in several billion years -- and one U of T astrophysicist
has mapped the fallout.
"We're
on a collision course right now," says John Dubinski, professor of
astronomy at U of T and the Canadian Institute for Theoretical Astrophysics,
who led the project with co-author Lars Hernquist of the Harvard-Smithsonian
Center for Astrophysics. "Within three billion years, the Milky Way will
be swallowed up and merged with the Andromeda galaxy."
The
2.2-million-light-year gap between the Milky Way and Andromeda is closing at
about 500,000 kilometers an hour, he explains. That pace will quicken as the
two galaxies near each other.
According
to Dubinski, merging galaxies are not uncommon. In fact, this type of
interaction plays a key role in helping build larger galaxies and structures in
the universe. While mergers of galaxies are less frequent now than in the early
days of the universe, it is still an ongoing process, and one in which our own
Milky Way and its big sister, the Andromeda galaxy, are active participants, he
notes.
Dubinski
simulated this Milky Way-Andromeda interaction by following the motion of more
than 100 million stars and dark matter particles as the gravitational forces of
the two galaxies force them to collide. The simulation was a feat of parallel
computing that took four days to complete on the San Diego Supercomputing
Center's 1152-processor IBM SP3 "Blue Horizon" -- one of a new class
of supercomputers that can perform more than one trillion arithmetic operations
per second. In the end, the simulation required the equivalent of three years
of continuous operation on a single workstation. The result is a
high-resolution computer animation of the collision and merger of the two
galaxies from start to finish and some very detailed snapshots of the structure
and dynamics of a galaxy merger.
"We
just used the Milky Way and Andromeda galaxies as a test case," says
Dubinski. "It's the first time we've been able to develop a full picture
of tens of millions of stars in two separate galaxies merging and interacting.
The power of these new machines will allow us to improve the dynamic range and
reliability of our simulations of galaxies and large-scale structures in the
universe."
Perhaps
even more intriguing is the fact that life on Earth -- whatever it may be --
will probably live through and witness the entire merger over the billion-year
dance of the two galaxies, he says. The reason is that the expected lifetime of
our sun is projected to last another five billion years. Plus, the likelihood
of stars and planets slamming into each other is very low because the distance
between them is so vast. The interaction will be "collision-less,"
with the most significant effect involving huge gravitational distortions of
the systems as they coalesce.
At
some point three billion years hence, the night sky will be completely filled
by the approaching Andromeda galaxy and when the two galaxies intersect there
will be two bands of light arching overhead -- looking like two Milky Ways,
says Dubinski. With the merger, two possible fates await the sun and Earth --
we could be flung into the depths of intergalactic space and escape the galaxy
forever or hurled into the center of the merging pair where new stars will be
formed.
And
for those on Earth, it will be a spectacular display of galactic fireworks, he
says. Massive stars near the sun will be exploding as supernovae at such a rate
that the night sky will be bright enough to read a newspaper.
For
MPEG movie of the Andromeda-Milky Way encounter: ftp://holstein.cita.utoronto.ca/pub/tflops/tflops.mpg [6.3 MB]
A
team of astronomers from the Joint Astronomy Center (JAC) in Hawaii today
announced the first image of a magnetic field in star-formation regions of
another galaxy. M82 is one of the closest 'starburst' galaxies, with dozens of
very active sites around the nucleus where stars are being born. The new
discovery shows a giant magnetic 'bubble' 3000 light years across, apparently
blown outwards by the superwind from the galaxy's stars and supernovae.
"This
is the first time we've been able to see right into the heart of the
star-forming activity and image the magnetic structure", said JAC
astronomer Jane Greaves, who led the research team. By observing at short radio
wavelengths of about a millimeter, they can probe through obscuring
interstellar dust clouds that block out the nucleus in traditional optical
images.
The
team was surprised to see the huge 'bubble' outlined in the image. The most
likely explanation is that enormously energetic winds -- outflows of
interstellar gas powered by stars and supernovae -- are forcing the magnetic
field out into the halo of the galaxy. "One of the most exciting
things", said team member Wayne Holland, "is that we see some field
lines pointing right into the nucleus". "Magnetic fields can help gas
clouds fall inwards, so we may have a clue to why this galaxy has such a
condensation of star-forming activity near the center."
The
astronomers used a new technique that detects tiny differences in emission from
interstellar dust, by looking at different angles on the sky. The dust grains
are lined up by local magnetic fields, just like iron filings around an
ordinary magnet. The differencing technique, wavelength-wavelength polarimetry,
has never before been used to look at another galaxy.
M82
is one of our closer galaxy neighbors, at a distance of about 11 million light
years. It is object number 82 in the famous catalogue of 'fuzzy objects'
compiled by Messier in 18th century. The starburst activity was most likely
triggered by a close flyby of the neighbor galaxy M81, which can be seen in the
Image Gallery at the website of the Chandra X-ray Observatory http://xrtpub.harvard.edu/photo/0094/what.html
How
was the new image obtained?
The
new image was obtained using the 15-meter James Clerk Maxwell Telescope at the
Mauna Kea Observatory in Hawaii. The JCMT is the world's largest telescope
dedicated to the study of light at 'submillimeter' wavelengths. The team of
astronomers used a revolutionary new camera called SCUBA (Submillimeter Common
User Bolometer Array), which was built by the Royal Observatory in Edinburgh
(now the UK Astronomical Technology Center). The Polarimeter was built by Queen
Mary and Westfield College in London, and funded by a joint science initiative
of the UK and Japan.
SCUBA
uses detectors cooled to a tenth of a degree above absolute zero (-273 degrees
Celsius) to measure the tiny amounts of heat emission from small dust particles
at a wavelength close to one millimeter. SCUBA by itself detects both of the
two perpendicular waves ('planes of polarization') of which light of any
wavelength is made up. The Polarimeter uses a very fine (6 micron spacing) grid
that passes only one plane, and a bi-refringent quartz plate that rotates the
source polarization. Together these produce slightly different images every 30
seconds, that are analyzed to measure the magnetic field directions.
Information
and images are available on the World Wide Web at
http://www.jach.hawaii.edu/~jsg/m82_press.html
For
the past decade astronomers have looked for vast quantities of hydrogen that were cooked-up in the Big Bang
but somehow managed to disappear into
the empty blackness of space.
Now,
NASA's Hubble Space Telescope has uncovered this long- sought missing hydrogen.
It accounts for nearly half of the
"normal" matter in the universe -- the rest is locked up in
myriad galaxies.
Astronomers
believe at least 90 percent of the matter in the universe is hidden in exotic "dark" form that has not
yet been seen directly. But more
embarrassing is that, until now, they have
not been able to see most of the universe's ordinary, or baryonic, matter (normal protons, electrons and
neutrons).
The
confirmation of this missing hydrogen will shed new light on the large-scale structure of the
universe. The detection also confirms
fundamental models of how much hydrogen was manufactured in the first few minutes of the universe's
birth in the Big Bang.
"This
is a successful, fundamental test of cosmological models," said Todd Tripp of Princeton University, Princeton,
NJ. "This provides strong evidence
that the models are on the right
track." The results of Tripp and his collaborators, Edward
Jenkins from Princeton and Blair Savage
from the University of Wisconsin- Madison, are being published in the May 1
issue of the Astrophysical Journal
Letters.
Previous
observations show that billions of years ago this missing matter formed vast complexes of hydrogen clouds --
but since then has vanished. Even
Hubble's keen eye didn't see the
hydrogen directly because it is too hot and rarified. Instead,
Hubble found a telltale elemental tracer -- highly ionized (energized) oxygen -- between galaxies,
which the hydrogen heats to the
temperatures observed in intergalactic space. The presence of highly ionized oxygen between the
galaxies implies there are huge
quantities of hydrogen in the universe, which is so hot it escapes detection by normal observational
techniques.
In
recent years, supercomputer models of the expanding, evolving universe have predicted an intricate web of gas
filaments where hydrogen is
concentrated along vast chain-like structures.
Clusters of galaxies form where the filaments intersect. The models predict that vast hydrogen clouds
flowing along the chains should collide
and heat up. This would squelch the
formation of more galaxies in the
hottest regions, so star birth was more
abundant in the early universe when the hydrogen was cool enough to coalesce.
The
oxygen "tracer" was probably created when exploding stars in galaxies spewed the oxygen (created in
their cores through nuclear fusion)
back into intergalactic space where it mixed with the hydrogen and then was shocked and heated to temperatures
over 360,000 degrees Fahrenheit
(100,000 degrees Kelvin).
Astronomers
detected the highly ionized oxygen by using the light of a distant quasar to probe the invisible space between
the galaxies, like shining a flashlight
beam through a fog. Hubble's Space
Telescope Imaging Spectrograph found the spectral "fingerprints" of intervening oxygen superimposed on
the quasar's light. Slicing across
billions of light-years of space, the
quasar's brilliant beam penetrated at least four separate filaments of the invisible hydrogen laced
with the telltale oxygen.
Hubble's
ultraviolet sensitivity and high-resolution
spectroscopic capability allowed it to probe the nearby universe, where spectral features of hot gas can be
seen at ultraviolet wavelengths and the
problems faced by X-ray astronomers are
avoided. "This result
beautifully illustrates the power of
spectroscopy for revealing fundamental information about the presence and nature of the gaseous matter in
the universe," according to Hubble
spectroscopist Blair Savage.
Still,
the hot hydrogen could not be seen directly because it is fully ionized and so the hydrogen atoms
are stripped of their electrons. Without electrons, no spectral features were
etched into the quasar's earth-bound
light. The oxygen is highly ionized
too, but still retains a few electrons which absorb specific colors from the quasar's light. A
ground-based image and illustration associated
with this release are available on the Internet at: http://hubble.stsci.edu/go/news
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.
