EAS BUSINESS…
March Meeting Recap
The March meeting included a presentation
by Project Astro coordinator Karen Peterson.
Next Meeting – Saturday April 29th At
Providence Pacific Clinic Hospital – Monte Cristo Room – 7:00 PM
The
Everett Astronomical Society's next meeting will be Saturday April 29th,
at 7:00 PM, in the PROVIDENCE Monte Cristo Room at Providence Hospital
PACIFIC Clinic at 916 Pacific Avenue in Everett. Dr. Paul Hodge of the UW Astronomy dept. will be discussing
“Exploring Barnard's Galaxy with the HST"
Future Activities
All students, partners, families, and friends are invited to
the UW Astronomy Department Open House
When/Where:
Saturday
May 13, 2000, 2 PM to 6 PM
UW Physics-Astronomy Building, A Wing
This year's theme:
Astrobiology
http://www.astro.washington.edu/openhouse/openhouse.html
Activities
include:
·
Keynote speakers Dr. Don Brownlee and Dr. Peter Ward,
Co-authors, RARE EARTH
·
Astronomers at the Movies: Live astronomer panel on science
fiction flicks
·
"Drop-in" Slide Shows
·
The Sky at Night: continuous planetarium shows, on each half
hour.
·
Hands-on Astronomy for kids and adults
·
Real Magic: Live physics demonstrations
·
Sundial & Pendulum tours
·
Astronomy songs
·
Undergraduate Astronomy Institute will present their
progress on their radio telescope and other projects.
·
Undergraduate and Graduate Student research posters
·
Project ASTRO classroom projects
·
Seattle Astronomical Society will have telescopes set up in
the courtyard
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:
Apr 29 – Dr
Paul Hodge - Exploring Barnard’s Galaxy with HST
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
Attention NorthWest Astronomers:
TeleVue's
Steve White will be in our shop Saturday, April 29, from 10:00 AM – 5:00 PM, to
answer any questions related to TeleVue's products. It is our intention to have
EVERY TeleVue product on display. TeleVue will be donating a 10mm Radian and
ATWB will be donating a 35mm Panoptic as door prizes. The drawing will be at
2:00 PM and if you win one you can either take it or apply the retail value to
any other TeleVue product in the shop. We will have one day only in store
discounts on TeleVue products.
This is the warm up for Al
and Judie’s visit next year, so let's show them how many loyal TeleVue
customers we have out here in the sticks.
:-)
- Herb and
Paula York and the ATWB Team.
http://www.buytelescopes.com
Anacortes Telescope and Wild Bird
(360)588-9000
Member News
Project ASTRO Seeks
Astronomers
Project ASTRO, a
unique program that partners teachers with amateur and professional
astronomers, is recruiting amateur and professional astronomers in the Puget
Sound region. We presently have 59
partnerships in schools throughout the Puget Sound region and will recruit 25
more this year. Over two-thirds of our
astronomer partners are amateurs. ASTRO
partners from the EvAS include Mark Folkerts Lani Schonberg, and Ron Tam.
As a Project ASTRO astronomer, you will visit your teacher's
classroom at least five times during the school year to lead hands-on astronomy
activities, host star parties, and/or help the students with a long-term
project such as building a telescope.
Additional Project ASTRO-sponsored activities include star parties,
lectures, camp-outs, workshops, and events at the Museum of Flight and the
Pacific Science Center.
A mandatory training workshop will be held July 7-8 on the
UW campus in Seattle. At this workshop
you will receive a teaching guide containing over 85 hands-on astronomy
activities and receive training in several hands-on activities and tips on how
create a successful partnership with your teacher. You will also work with your teacher to create a plan for your
school visits.
We make every effort to match astronomers with a school
located close to their work or home and to match any grade preferences. We welcome applications from astronomers who
have already identified a teacher they wish to work with (though we need to
receive an application from the teacher too).
The application deadline is May 1.
For more information or to request an application, contact the Project
ASTRO coordinator, Dr. Karen Peterson, at (206) 543-9541, or
kpeterso@astro.washington.edu. You can
also visit the Project ASTRO Web site at
http://www.astro.washington.edu/projastro/
Karen Peterson, Ph.D.
Program Coordinator
- Project ASTRO
Box 351580
Department of Astronomy, University of Washington
Seattle, WA
98195-1580
Ph: (206) 543-9541
Fax: (206) 685-0403
We are also still seeking contributors for the KSER
radio show.
Financial Health
The club maintains a safe $1050+ 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
April 2000
Apr 02 - Daylight
Saving - Set Clock Ahead 1 Hour (N. America)
Apr 02 - Asteroid 26
Proserpina At Opposition (10.5 Magnitude)
Apr 03-09 - Astronomy
Week
Apr 06 - Mars Passes
1.0 Degrees From Jupiter
Apr 07 - Asteroid 44
Nysa At Opposition (9.7 Magnitude)
Apr 08 - Astronomy Day – Everett Library 10-5, Legion Park
Apr 11 - Asteroid 385
Ilmatar At Opposition (10.9 Magnitude)
Apr 14 - Asteroid 20
Massalia At Opposition (9.2 Magnitude)
Apr 15 - Mars Passes
2.3 Degrees From Saturn
Apr 17 - Asteroid 129
Antigone At Opposition (10.1 Magnitude)
Apr 22 - Earth Day
Apr 22 - Lyrids
Meteor Shower Peak
Apr 22 - Jupiter
Passes 0.1 Degr From 93108 (7.7 Mag. Star)
Apr 23 - Easter
Sunday
Apr 25 - 10th
Anniversary (1990), Hubble (HST) Deployment
Apr 26 - Moon Occults
Neptune
Apr 28 - Mercury
Passes 0.3 Degrees From Venus
Apr 29 - EAS Meeting 7:00 PM – Providence Pacific Clinic
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.)
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
Apr 04 New
Moon
Apr
11 First Quarter Moon
Apr
18 Full Moon
Apr 25 Last
Quarter Moon
May 04 New
Moon
May
11 First Quarter Moon
May
18 Full Moon
May 26 Last
Quarter Moon
Up In The Sky -- The Planets
MERCURY, and VENUS are in the dawn twilight and not visible.
MARS is red-orange magnitude +1.5 in Pisces, very low in the WNW during twilight, slowly sliding toward solar conjunction on July 1.
JUPITER and SATURN are about to disappear from the early evening sky, as they disappears 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
AQUILA (THE EAGLE): A beautiful constellation, and an integral part of the Summer
Triangle, Aquila borders on the constellations of Aquarius, Capricornus,
Delphinus, Hercules, Ophiuchus, Sagitta, Sagittarius, Scutum, and Serpens. Its overall brightness is listed at 7.2
(41st brightest), and it is the 22nd largest constellation in size. Its central point is located at RA=19h37m,
and DEC.= +3.5 degrees, and it is completely visible from latitudes +78 degrees
to –71 degrees; portions are visible worldwide. It has 47 stars brighter than magnitude 5.5, the most famous of
which is Altair (alpha), which, with Vega and Deneb, forms the famous Summer
Triangle. Its midnight culmination date
is July 16th, making it perfectly placed for summer observing. It has no associated Messier objects or
Meteor showers, but is interesting in several other ways. Nova Aquilae (one of the most famous of
recent times) shined brightly on the night of June 8th, 1918; it was the
brightest nova to appear since Kepler’s in 1604. Altair itself is known for its extremely rapid rotation, spinning
once every 6.5 hours. Such rapid
rotation distorts a star: it has been estimated that the equatorial diameter of
Altair is twice its polar diameter. The
star with the lowest measured luminosity is also found within Aquila. “Van Biesbroeck’s Star” has an absolute
magnitude of +19.3. If it were placed
side by side with our own sun, it would only be 1/758,000th as bright as the
sun. Aquila is a very notable and
interesting constellation indeed; try to enjoy it during your summer observing
this year.
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. Next month, it will be
Neptune. We are taking a bit of a
breather in our series about the planets, and re-running a couple of less
technical (and a bit more fun) columns, from past issues. These columns first ran almost two years
ago, and might be enjoyed again, as well as by our newer young
astronomers. The first is on the
“special clouds” of interest to astronomers, and the second column is about all
the constellations with animal names.
So, for a change of pace, enjoy!
Neptune will be our guest next month when our planet series returns (it
will finish the following month when we talk about Pluto). See you then!
TOPIC: SPECIAL (!) CLOUDS: When one
thinks of clouds, we usually associate a weather phenomenon with them, and many
of us are familiar with their names.
Such clouds as cirrus (high ice clouds), cumulonimbus (thunderstorm
clouds), and cumulus (fair weather clouds), and many others such as stratus and
nimbostratus, are familiar to many.
However, did you know that there are some clouds which are often more
associated with astronomical observations than weather observations, or at
least equally so? There are two in
particular which bear mentioning: nacreous, and noctilucent, the two highest
clouds of all. Nacreous clouds are
iridescent clouds (those that may present with many colors), and are the second
highest of all clouds, being located 12 to 20 miles up; as a result of this,
they are extremely cold clouds.
Nacreous clouds, or “mother-of-pearl” clouds, are caused by cloud water
droplets or ice needles (small enough that they approach the wavelength of
light, causing interference patterns), and show the finest of all iridescence
(thus the nickname), and are only visible when the sun is low or actually below
the horizon. Noctilucent clouds, the
highest of all clouds, are located 70-90 kilometers up, where generally there
is little evidence of particles in the sky.
They can only be seen during twilight, and are best seen when the sun is
between 5 and approximately 15 degrees below the horizon, and are best observed
at high latitudes, where there are long twilight periods, (especially around
the time of the summer solstice). They
are located in the coldest and highest portion of the earth’s atmosphere, and
although their name means “night-shining”, they can shine no later than late
twilight. However, under the above
conditions, twilight can last a very long time. The shining of these clouds, like the nacreous, is due to the
light of the setting sun and its afterglow.
These clouds have been determined to be made up of cosmic dust such as
micrometeoroids and particulate remains of burned up meteors; some of this
material may be ice-coated. Noctilucent clouds are all silver-blue in color,
but may also be golden at the bottom, and can show structure such as waves, billows,
and whirls, and are very, very fast moving clouds (moving at speeds of up to
500 miles per hour!!), although this may not be very perceptible to
observers. So, next time you get the
opportunity to observe, try to look
closely for these beautiful clouds (especially this summer) if you can. You might just get lucky and see some!
TOPIC: THE
FARMER IN THE SKY: When we
look at the night sky, we may be able to see many beautiful things, such as the
day-old moon, noctilucent clouds (see last month’s edition), some of the
planets, and the stars of many colors.
But did you know that there is a veritable “farm” up there as well. The ancient Greeks and Arabics, who named many of the stars and
constellations, had economies which were agricultural, and many of their myths
and legends relied heavily on animal images; this is also reflected in the
names of many of the constellations that have been handed down for
centuries. Let’s go through them all
(constellation name is first; name of animal in parentheses): Apus (Bird of
Paradise); Aquila (The Eagle); Aries (the Ram); Camelopardalis (the Giraffe);
Cancer (the Crab); Canes Venatici (The Hunting Dogs); Canis Major and Minor
(the Greater and Lesser Dogs); Capricornus (the Sea Goat); Cetus (the Whale);
Chamaeleon (the Chameleon); Columba (Noah’s Dove); Corvus (the Crow); Cygnus
(the Swan); Delphinus (the Dolphin); Dorado (the Swordfish); Draco (the
Dragon); Equuleus (the Foal); Grus (the Crane); Hydra (the Water Snake); Hydrus
(the Southern Water Snake); Lacerta (the Lizard); Leo and Leo Minor (the Lion
and Cub); Lepus (the Hare); Lupus (the
Wolf); Lynx (the Lynx); Monoceros (the Unicorn: fictional or not!!); Musca (the
Fly); Pavo (the Peacock); Pegasus (the Winged Horse: see Monoceros!!); Phoenix
(the Phoenix); Pisces (the Fishes); Piscis Austrinus (the Southern Fish);
Scorpius (the Scorpion); Serpens (the Serpent); Taurus (the Bull); Tucana (the
Toucan); Ursa Major and Minor (the Bear and Cub); Volans (the Flying Fish); and
Vulpecula (the Fox). If we’ve missed any heavenly animals, please let us
know!! So, the next time you come home
from the zoo, tell your friends that you have more animal observing to do that
night!!!! See you next time for our
continuation of our planet series, with Neptune as our “guest” for the month.
Astronomy and Telescope “Lingo”
ASTRONOMY
LINGO: Rho Ophiuchi Cloud:
A very complex area of molecular and dark clouds, and emission and
reflection nebulae, close to the star known as rho Ophiuchi in (obviously)
Ophiuchus. Observations in the X-ray
and infrared wavelengths show that star formation is occurring in the region of
the dark cloud.
TELESCOPE LINGO:
Dwingeloo Radio Observatory:
The administrative headquarters of what used to be the Netherlands
Foundation for Research in Astronomy (NFRA); it is currently known as ASTRON
(Stichting Astronomisch Onderzoek in Nederland). It came into operation in 1955, and has a 25-meter dish capable
of observing at 1.42, 1.66, and 5 GHz.
Astronomy Fun Facts
April Fun Facts:
** The star S Doradus is a
very bright, variable supergiant star, which also happens to be located in the
Large Magellanic Cloud. Its average
luminosity is 500,000 times brighter than the Sun (because of its variability,
its luminosity can exceed that of the Sun’s by over 1,000,000 times). If S Doradus were our “Sun”, and were
located over 700 times farther away from Earth than the present Sun, it would
still generate the same amount of energy as the Earth currently receives from
the “real” Sun!
** One of the largest stars known
in the entire Universe is the red giant VV Cephei (in Cepheus). It is located almost 4,000 light years from
Earth, and its diameter is 1,900 times greater than that of the Sun. If the Sun were no bigger than a chick-pea,
VV Cephei would be a large, hot-air balloon almost 12 meters in diameter!! If VV Cephei were centered on our Solar
System, it would extend out to the orbit of Saturn!
** Not counting the Sun, the
light from all stars is equal to about one-fifteenth the light of the full
Moon, or one six-millionth the light of the Sun itself. If the total of all such starlight could be
focused in one object, it would be equal to about a 100-watt bulb seen from a
distance of almost 190 meters – approximately the length of two football
fields!
“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. )
“MIRROR” IMAGES”, as of this year, is a bimonthly
column. Last month’s entry concerned
reflection nebulae. See you in May for
our next column; topic: “double stars”.
Astronomical Notes --
On & Off the Net...
NEAR
Shoemaker has successfully completed the first phase of its exploration of Eros,
focusing on global mapping from an approximately circular 200 km orbit. The
spacecraft is now in a transfer orbit that will take it to its next stage of
exploration, mapping from 100 km orbit, that will start on April 12. Tucked in
amidst the many thousands of images and infrared, x-ray and gamma ray spectra,
not to mention the hundred thousands of laser returns, there is another data
set garnered in the 200 km orbit that deals with an entirely different aspect
of the nature and history of Eros; the magnetic field.
NEAR
Shoemaker's magnetometer is searching for a magnetic field generated by Eros.
So far, no asteroid has been shown conclusively to produce a magnetic field,
although there were hints of such fields from the asteroids Gaspra and Ida that
were the targets of Galileo flybys in 1992 and 1993 respectively. Many
meteorites, which are pieces of asteroids that fall to Earth, are magnetized,
having picked up and retained magnetization from their parent bodies. If Eros
turns out to have a magnetic field as strong as that of many meteorites, NEAR
Shoemaker should detect this field once close enough to the asteroid.
Most
magnetized objects, when studied from far enough outside their surfaces, have a
magnetic field like that of an ordinary bar magnet, forming what is called a
"magnetic dipole". A compass needle has such a field, and it has a
"north-seeking" pole that points to (magnetic) north on Earth. An
arrow that points from the south-seeking pole (S) to the north-seeking pole (N)
of a compass needle is aligned with the "magnetic dipole moment" of
the needle. This is a quantity with a direction (S to N) and a magnitude
defining the strength of the magnetic field (i.e., it is a "vector").
The magnetic fields of the Sun and the Earth have prominent magnetic dipole
moments, as well as most of the planets (all but Mars and Venus which have
unmeasurably small dipole moments, and Pluto whose dipole moment is unknown).
Earth's own magnetic dipole moment is "upside down" -- it points
roughly in the direction from geographic north to geographic south.
Close
to the surface of a magnetized body, it is commonly found that the field is
more complex than that of a magnetic dipole, as if there were additional pairs
of north-seeking and south-seeking poles on the surface of the body besides the
main pair. Ordinary refrigerator magnets, for example, have more complex fields
than do simple bar magnets -- often the north-seeking poles and south-seeking
poles of a refrigerator magnet are arranged in alternating stripes. This has
the effect of concentrating the magnetic field close to the surface where it's
needed to cause the magnet to stick to the refrigerator. The magnetic field of
Mars turns out to have some similarities -- the main dipole moment of Mars is
almost or completely absent, but there are numerous north-seeking and
south-seeking poles located in "magnetic stripes" in the southern
highlands.
The
magnetic field strength of a magnetic dipole has the property of decreasing as
the inverse cube of the distance from the body (aside from an angular
dependence). That is, at twice the distance, the field strength is reduced by
2x2x2 = 8. The field strength at Earth's surface near the equator is about
30000 nanotesla (nT). At one Earth radius above the surface, the field strength
has decreased by a factor of 8, and by two radii above the surface (which is
three times the distance from the center) the field has decreased by a factor
of 27. The magnetic dipole has the property of being the arrangement of
magnetic poles that causes magnetic fields to stretch farthest from the body --
any more complex arrangement of poles would cause field strength to decrease
even more rapidly away from the planet.
This
is why NEAR Shoemaker has to orbit close to Eros -- to be able to detect any
magnetic field that may be produced. NEAR's magnetometer can detect an external
magnetic field of only 1 nT, but Eros would have to be almost as strongly
magnetized as the Earth in order to generate a 1 nT field as far away as the
200 km orbit. An Eros surface field of hundreds to thousands of nT, like that
of many meteorites, would be detectable only in lower orbits. There are
complications of course - the spacecraft itself generates a magnetic field, and
the solar wind carries a magnetic field -- but so far, no Eros magnetic field
has been detected. Will Eros turn out to be magnetic? We shall see.
http://near.jhuapl.edu/news/sci_updates/000407.html
Melting
glaciers rather than flowing surface water could have carved out the Red
Planet's distinctive valleys.
Branching
networks of small valleys have led many scientists to conclude that rivers of
running water once flowed freely across the surface of Mars. But this would
mean that the Red Planet once had a much warmer climate than it does today and,
apart from its valleys, there is no evidence to suggest that Mars was ever warm
(New Scientist, 17 April 1999, p 48).
But
Pascal Lee, a planetary scientist at NASA's Ames Research Center in Mountain
View, California, says the answer may be found on Devon Island in the Canadian
Arctic, where he is studying valleys carved by glacial meltwater. "What
we've been finding on Devon Island," says Lee, "is a wide
variety of valley types, from canyons to little networks of small valleys, that
bear an uncanny resemblance to specific counterparts on Mars."
In
particular, he says, the Martian valleys "cut through a desert that
otherwise has very little sign of water flowing nearby". The constant
width and depth of Martian valleys over long distances, their flat floors and
steep walls are all distinctive features also found on Devon Island, but
uncommon on river networks.
Lee
believes that other Martian landforms, notably some large canyons on the west
end of Vallis Marineris, could actually have been carved by flowing glacial
ice. Devon Island also has canyons like these.
If Lee is correct, Mars may have had a cold climate, in which snowfall
piled up to form glaciers that later melted in the heat generated inside the
planet. Mars expert Jim Head of Brown University, Rhode Island, welcomes Lee's
work, saying the analogy to Devon Island is helping him visualize how melting
snow might have produced valleys on Mars.
-
New Scientist issue: 25th March 2000
http://www.newscientist.com
As
often happens in science, an experiment looking for something else entirely has
stumbled upon a dramatic new finding: The ionized vapor trails left behind by
comets as they zing past our sun may be billions of miles longer than anyone
previously recognized. That means that comets have probably been spreading more
"star stuff" around the solar system than had been thought, and it
opens up the possibility of new ways to capture and measure the contents of
comets, which are believed to be frozen records of our solar system's
birth. The finding, announced in the
April 6 edition of the British journal Nature, came from some strange readings
radioed to Earth in 1996 by the spacecraft Ulysses, which is supposed to be
studying solar winds. On May 1, 1996, the data from Ulysses suddenly went
haywire for a few hours, explained Nathan Schwadron.
The
solar wind, which usually blows past the spacecraft at about 700 kilometers per
second, became strangely hot and calm, and the number of charged particles
encountered by the spacecraft soared at precisely the same instant. This
disturbance lasted for only a few hours and was missed until very recently. "We said, 'All right, we've got
something. Now, what is it?'" said Prof. George Gloeckler of the U-M
Department of Atmospheric, Oceanic and Space Sciences. "It turns out,
after you do all the numbers, that we sailed right through the wake of Comet
Hyakutake." The comet, named for a Japanese amateur astronomer who
discovered it, blazed across our night skies in spectacular fashion in 1996 and
made an unusually close pass by the sun.
"This tail extends more than a half a billion kilometers,"
Schwadron said. "That's more than three times the distance from the
Earth to the sun. It's just unbelievable."
"Comets
are the most primordial things in our solar system," Geiss said.
"If we can better understand their chemical makeup, we can get a handle
on what was going on in the past, and where we've been." Some
theorists even propose that comets "seeded" Earth and other planets
with the building blocks of life.
Not
only did Ulysses show that comet tails are longer than anyone realized, this
data is significant just because it's only the fourth time anyone has directly
sampled the contents of a comet like this. Ulysses is equipped with
spectrometers, instruments that can identify chemicals. Hyakutake's tail was
found to be mostly carbon and oxygen with some nitrogen, and water. Coincidentally, in the same edition of
Nature, another team operating a magnetometer aboard Ulysses reports that
magnetic field lines were altered for precisely the same period that the Michigan
team detected the change in solar wind and a dramatic, 1,000-fold rise in
particles. "If you were not looking at these data closely, you would
have missed it," Schwadron said.
"It brings up a whole new way to study comets, and I think opens
up a whole new area of science," Schwadron said. With better data from
instruments designed to intercept these long tails of ionized comet dust,
"we would know exactly how stars have processed material over time,"
he said. And that, in turn, leads astrophysicists and cosmologists to pondering
some really cosmic questions: "Where did we come from? How old
is the universe? What were the initial conditions for creating our solar
system?"
Ulysses
studies the sun from a "high latitude" orbit, one which is mostly at
right-angles to the plane of the planetary orbits in our solar system. It was
launched on Oct. 6, 1990, by the shuttle Discovery and then went on a
sling-shot maneuver around Jupiter to attain the high speed needed for its
elliptical orbit. Its mission is to explore what the sun's magnetic field, solar
winds and cosmic rays are like closer to the sun's North and South Poles,
rather than around its equator, where our planet orbits.
Animations: http://www-personal.engin.umich.edu/~nathanas/Distrib/index.html
Solar-Heliospheric
Lab http://www.sprl.umich.edu/
Ulysses http://ulysses.jpl.nasa.gov/
Scientists
have discovered a new source for some of the large scale eruptions on the Sun
known as coronal mass ejections, or CMEs. These eruptions are a key ingredient
of strong geomagnetic storms that can cause bright auroras, damage sensitive
satellite instruments in space, and even disrupt power generation and
transmission by inducing strong electric currents below the surface of the
Earth.
Dr.
Josef I. Khan and Dr. Hugh S. Hudson report that shock waves launched from
solar flares can cause CMEs elsewhere in the solar corona. They found that such
mass ejections do not emanate from structures directly above the eruptive
flare, a more common pattern, but rather from off to one side. Khan and Hudson
are both currently based at Japan's Institute of Space and Astronautical
Science (ISAS) in Kanagawa, where they conducted their investigations using the
Yohkoh ("sunbeam") satellite. Studying X-ray images of the Sun, they
examined very large hot loops of solar material that sometimes connect sunspot
regions in the Sun's northern and southern hemispheres. They found that such
loops, known as interconnecting X-ray loops, can simply disappear suddenly,
ejecting huge amounts of material. In particular, Khan and Hudson found three
similar disappearances on May 6, 8, and 9, 1998. All of the observed
interconnecting X-ray loops disappeared and were followed by looplike CMEs.
Each CME event could be tracked far out into the corona via images obtained from
another instrument, the Large Angle Spectroscopic Coronagraph (LASCO) on the
Solar and Heliospheric Observatory (SOHO) satellite.
The
researchers say the association between these disappearing loops and solar
flares is novel and interesting. Scientists debate the relationship between
CMEs and other phenomena, including solar flares and prominence eruptions.
Solar flares release large amounts of energy across the electromagnetic
spectrum, while prominence eruptions are the ejection of large suspensions of cool
material in the Sun's hot outer atmosphere, or corona. Some, but not all,
prominence eruptions and CMEs are associated with flares.
There
is, however, a clear relationship between prominence eruptions and CMEs on the
one hand and X-ray brightenings seen in the corona below these ejections. The
question before scientists is what causes what, and which therefore is the more
important phenomenon physically. Khan and Hudson found that for the events they
studied, and contrary to the normal pattern, the flare is not located directly
below the CME. It is, rather, located off to one side, in a sunspot region
outside the structures that erupt to become part of the CME. Put another way,
the mass ejected in the CME does not come from the structures directly above
the flare.
Khan
and Hudson, studying Yohkoh X-ray images, were able to determine fairly
accurately the timing of the disappearance of the interconnecting loops. They
found that the solar flare occurs before the loops disappear and, therefore,
before the start of the coronal mass ejection. Further, by studying these X-ray
data and simultaneous data from radio telescopes, they found evidence for shock
waves. In every instance they examined, they found that the interconnecting
loops disappear when the shocks cross their vicinity. These observations led to a new scenario Khan and Hudson have put
forward to explain some CMEs. A shock wave generated by the flare crosses a
large interconnecting loop, causing it to become unstable and erupt. This
ejects hot X-ray material, which becomes a significant fraction of the coronal
mass ejection. The researchers acknowledge that this hypothesis requires
further exploration, and they recognize that it does not apply to all CMEs,
only the type they reported.
Planet-hunting
astronomers have crossed an important
threshold in planet detection, with the discovery of two planets that may be smaller in mass than Saturn. Of the 30 extrasolar planets around Sun-like
stars detected previously, all have
been the size of Jupiter or larger.
The existence of these
Saturn-sized candidates suggests that many
stars harbor smaller planets, in addition to the Jupiter-sized ones.
Finding Saturn-sized planets reinforces the theory that planets form by a snowball effect of growth
from small ones to large, in a
star-encircling dust disk. The 20-year-old theory predicts there should be more smaller planets than large
planets, and this is a trend the
researchers are beginning to see in their
data. "It's like looking
at a beach from a distance," explained Geoff Marcy of the University of California at Berkeley. "Previously we only saw the large
boulders, which were Jupiter- sized planets or larger. Now we are seeing the
'rocks,' Saturn- sized planets or smaller.
We still don't have the capability of
detecting Earth-like planets, which would be equivalent to seeing pebbles on the beach."
Jupiter
alone is three times the mass of Saturn. This has left the nagging possibility open that some of the
extrasolar planets might really be
stillborn stars, called brown dwarfs,
which would form like stars through the collapse of a gas cloud. But now researchers are better assured these
"Jupiters" are only the tip
of the iceberg, and there are many more planets to be found that are the mass of Saturn or smaller. "Now we are confident we are seeing
a distinctly different population of
bodies that formed out of dust disks like the disks Hubble Space Telescope has imaged around stars," said
Marcy.
The
discovery was made by planet-sleuths Marcy, Paul Butler of the Carnegie Institution, and Steve Vogt
of UC Santa Cruz, using the mighty Keck
telescope in Mauna Kea, Hawaii. They discovered a planet at least 80 percent the mass of Saturn orbiting 3.8
million miles from the star HD46375,
109 light-years away in the constellation Monoceros, and a planet 70 percent the mass of Saturn orbiting 32.5 million miles around the star 79 Ceti (also known as
HD16141), located 117 light-years away
in the constellation Cetus. These
planets are very close to their stars and so have short orbits. They whirl around their parent stars
with periods of 3.02 days and 75 days
respectively. This allowed for their relatively rapid discovery.
The
astronomers detected the small wobble of a star caused by the gravitational tug of the unseen planets.
For the past five years Marcy and
Butler have used this technique successfully to catalog 21 extrasolar planets. Boosted by the
light-gathering power of Keck, they
have steadily increased the precision of their
measurements so they can look for the gravitational effects of ever-smaller bodies. In this latest
detection, the change in a star's
velocity -- rhythmically moving toward and then away from Earth -- is only 36 feet per second, a
little faster than a human sprints.
The
Saturn-mass planets are presumably gas giants, made mostly of primordial hydrogen and helium, rather than the
rocky material Earth is made of. They
are so close to their parent stars they
are extremely hot, and are not abodes for life as we know it. The planet orbiting 79 Ceti has an average
temperature of 1530 degrees Fahrenheit
(830 degrees Celsius). The planet orbiting
HD46375 has an average temperature of 2070 degrees Fahrenheit (1130 degrees Celsius). They probably formed at a farther distance
from the star, where they could
accumulate cool gas, and then migrated into their present orbits. Along the way they would have disrupted the
orbits of any smaller terrestrial
planets like Earth. These "marauding" gas giants seem more the rule than the exception among the
planets surveyed so far, because Marcy
and Butler's detection technique favors
finding massive planets in short-period orbits. This seems to be the case for approximately six percent
of the stars surveyed so far.
Their
research is part of a multi-year project to look for wobbles among 1,100 stars within 300 light-years of Earth.
UP
TO 25,000 black holes are hiding in the heart of our Galaxy, claim two
astronomers in the US. "The black holes are buzzing like flies around
the center," says Jordi Miralda Escudé of Ohio State University.
Although only half a dozen black hole candidates are known to exist in the
Milky Way, some astronomers think the Galaxy is swarming with black holes
created by exploding stars. Miralda and his Ohio State colleague Andrew Gould
say that these holes will cluster in the center of the Galaxy because they tend
to transfer some of their orbital energy to smaller objects every time they
have a stellar encounter. "The black holes therefore lose energy and
fall to the center," says Miralda.
The
migration is very slow, however. Miralda and Gould calculate that in the
10-billion-year lifetime of our Galaxy, only those holes born within 15 light
years of the center would have had enough time to make it to the middle. To
gauge how many have made it, the astronomers estimated how many black
hole-spawning supernovae have gone off within this 15-light-year radius over
the past 10 billion years. "We assumed about a fifth of the stars
bigger than eight times the Sun's mass left black holes at the end of their
lives," says Miralda. "That gave us the figure of 25 000."
According
to the astronomers, the black hole cluster will be depleted as holes are
occasionally gobbled up by the giant black hole thought to dominate the middle
of the Milky Way. But it will be replenished as others slowly migrate in. Other
galaxies should also have similar black hole clusters in their hearts, they
believe. Experts in the field agree
that such gatherings are plausible. "I certainly think the black hole
cluster story is interesting," says Martin Rees of Cambridge.
Detecting
the black holes may be difficult, however. One possibility is picking up a
burst of gravitational waves -- the death cry of a black hole as it swoops
close to the central giant hole before being swallowed. However, this will
require a space-based gravitational wave detector such as the European Space
Agency's LISA, which isn't due to be launched for another 10 years. But there could be other ways to observe the
cluster. The stellar encounters that sap the holes' energy can also boost the
orbital energy of stars, throwing them out into the farther reaches of the
Galaxy. Therefore Miralda and Gould predict that astronomers should find very
few old, low-mass stars in the central region, as most would have been ejected
over time. What's more, they predict that any remaining stars should have been
kicked into highly elliptical orbits by black hole encounters. "There is a good chance of seeing
both these effects," says Miralda.
- New Scientist issue: 8th April 2000 http://www.newscientist.com
Researchers
at the University of Chicago have seen the surface of an exploding neutron
star, and it isn't pretty. Waves of gaseous metals, the billion-degree
