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Transcript
August First Light Newsletter
1 message
August, 2014
Issue 122
AlachuaAstronomyClub.org
North Central Florida's
Amateur Astronomy Club
Serving Alachua County since 1987
BREAKING NEWS -- ROSETTA HAS JUST
ARRIVED AT COMET 67/P
Initiated in late 1993 by Europe and the
USA, and launched in 2004, the
International Rosetta Mission is an historic
first: Send a spacecraft to chase and orbit
a comet, ride along as the comet plunges
sun ward to learn how a frozen comet
transforms by the Sun's warmth, and
dispatch a controlled lander to make in
situ measurements and make first images
from a comet's surface.
Ten years later Rosetta has now
Member Member
Astronomical League
Member
NASA Night Sky Network
arrived at Comet 67P/ChuryumovGerasimenko and just successfully made
orbit today, 2014 August 6!
Unfortunately, global events have
foreshadowed this memorable event and
news media have largely ignored this
impressive space mission.
AAC Member photo:
The Rosetta comet mission may be the
beginning of a story that will tell more
about us -- both about our origins and
evolution. (Hence, its name "rosetta" for
the black basalt stone with inscriptions
giving the first clues to deciphering
Egyptian hieroglyphics.) Pictures received
over past weeks are remarkable with the
latest in the past 24 hours showing
awesome and incredible detail including
views that show the comet is a connected
binary object rotating as a unit in 12
hours.
Anyone see the glorious pairing of Venus
and Jupiter this morning (2016 Aug. 18)?
For images see http://www.esa.int/
spaceinimages/Missions/
Except when Mars is occasionally brighter
Rosetta
than Jupiter, these two planets are the
brightest nighttime sky objects (discounting
Example Image (Aug. 6 above).
the Moon).
Shows a smooth region at base of comet
from 130 km
My quick photo does not do the scene
(80 mi) with 2.4 meter per pixel
justice (below). Photo taken at 6:25 a.m.
resolution and a
EDT when they were 10 degrees above the
range of features, including boulders,
brightening ENE horizon. Separation was
craters and steep cliffs. Note: Comet 67/P 0.3 degrees or slightly more than a half
moves in an eccentric
moon diameter. This was a bit wider than
orbit (eccentricity 0.64) with a 6.45 year their closest approach (0.2 degrees), but
period that takes it from just outside
that happened several hours earlier (before
Jupiter's orbit (5.7 AU) to just outside
they rose). My pinkie easily hid both.
Earth's orbit (1.2 AU).
Neither planet was at greatest brilliancy but
Events are being streamed by ESA at:
still spectacular: Venus was at magnitude
http://sci.esa.int/rosetta/54457-rosetta- -3.85, Jupiter -1.80. (This made Venus 6.6
arrives
times brighter looking than Jupiter.)
-at-comet-67pc-g---follow-the-event-live
For more on this mission see:
http://www.esa.int/Our_
Activities/Space_Science/
Rosetta
http://rosetta.jpl.nasa.gov/
Howard L. Cohen
Emeritus Assoc. Professor of Astronomy
Department of Astronomy
University of Florida
If you didn’t get up to see this, you missed
a beautiful sight. Tomorrow morning their
separation will have increased to 1-1/4
degrees. This should still make a neat
scene.
Howard L Cohen
Droughts, Floods and the Earth's Gravity,
by the GRACE of NASA
Space Place article by Dr. Ethan Siegel
When you think about gravitation here on Earth, you very likely think about how constant it is, at 9.8 m/s2 (32 ft/s2).
Only, that's not quite right. Depending on how thick the Earth's crust is, whether you're slightly closer to or farther
from the Earth's center, or what the density of the material beneath you is, you'll experience slight variations in
Earth's gravity as large as 0.2%, something you'd need to account for if you were a pendulum-clock-maker.
But surprisingly, the amount of water content stored on land in the Earth actually changes the gravity field of where
you are by a significant, measurable amount. Over land, water is stored in lakes, rivers, aquifers, soil moisture, snow
and glaciers. Even a change of just a few centimeters in the water table of an area can be clearly discerned by our
best space-borne mission: NASA's twin Gravity Recovery and Climate Experiment (GRACE) satellites.
Since its 2002 launch, GRACE has seen the water-table-equivalent of the United States (and the rest of the world)
change significantly over that time. Groundwater supplies are vital for agriculture and provide half of the world's
drinking water. Yet GRACE has seen California's central valley and the southern high plains rapidly deplete their
groundwater reserves, endangering a significant portion of the nation's food supply. Meanwhile, the upper Missouri
River Basin undefined recently home to severe flooding undefined continues to see its water table rise.
NASA's GRACE satellites are the only pieces of equipment currently capable of making these global, precision
measurements, providing our best knowledge for mitigating these terrestrial changes. Thanks to GRACE, we've been
able to quantify the water loss of the Colorado River Basin (65 cubic kilometers), add months to the lead-time water
managers have for flood prediction, and better predict the impacts of droughts worldwide. As NASA scientist
Matthew Rodell says, "Without GRACE we would have no routine, global measurements of changes in groundwater
availability. Other satellites can’t do it, and ground-based monitoring is inadequate." Even though the GRACE
satellites are nearing the end of their lives, the GRACE Follow-On satellites will be launched in 2017, providing us
with this valuable data far into the future. Although the climate is surely changing, it's water availability, not sea
level rise, that's the largest near-term danger, and the most important aspect we can work to understand!
Learn more about NASA’s GRACE mission here: http://www.nasa.gov/mission_pages/Grace/
Kids can learn all about launching objects into Earth’s orbit by shooting a (digital) cannonball on NASA’s Space
Place website. Check it out at: http://spaceplace.nasa.gov/how-orbits-work/
Image credit: NASA Earth Observatory image by Jesse Allen, using GRACE data provide courtesy of Jay
Famigleitti, University of California Irvine and Matthew Rodell, NASA Goddard Space Flight Center. Caption by
Holli Riebeek.
Kids can test their knowledge about the Sun at NASA’s Space Place:
http://spaceplace.nasa.gov/solar-tricktionary/
Schools
Mike Toomey
Outreach & Star Parties
Ivo Rabell
In September we have one
youth event scheduled. The
O2BKids Parent Night
Out on Friday, September 26,
2014. Guests arrive at 7:30
p.m. Telescope set up begins
at 6:30 p.m. at 6680 W.
Newberry Road, Gainesville,
FL 32605. Please note that AAC volunteers
can access the observing field through a
First I want to thank the
Kelly’s for doing a terrific job
feeding and hosting 12
members and 6 guests at their
home. They supplied
sandwiches, cokes, beer, wine,
etc. We all appreciated them
for their hospitality.
Even though I was right when predicting the
gate located off N.W. 9th Blvd. (a block
north of RedLobster). Additional details and
information can be found on the club's
website under Events Calendar.
Thanks, Mike
Upcoming Events
For full details of events, please visit our
website's events calendar.
September Public Meeting
Tuesday, Sept. 9, 2014, 7-9 p.m.
Florida Museum of Natural History
University of Florida Cultural Plaza
3215 Hull Road
Gainesville, FL 32611-2710
Join us for an interesting evening when our
speaker, Dr. Haywood Smith a member of
the Astronomy Department at the
University of Florida will present The
Discovery of Neptune.
International Observe the Moon Night
Saturday, Sept. 6, 2014, 7 p.m.
Behind Easton Newberry Sports Complex
24880 N.W 16th Avenue
Newberry, FL 32660
Please join the AAC in observing our nearest
celestial neighbor. Open to the public and
telescopes provided.
New Members
Welcome to new AAC members!
John Snyder (Joined June 26)
Mark Kelly (Joined Jule 27)
Patrick Norby (Joined July 9)
Pater Karahalios (Joined July 26)
President's Report
Andy Howell
sky would clear at around 9:15 pm, it did
not last. Within 30 minutes, except for a
small portion of the southern sky, the clouds
took over. We had no rain but a lot of sheet
lightning to the east of us. Only four
members set up their telescopes or
cameras.
Howard Cohen took beautiful images of
Milky Way including Scorpius and
Sagittarius. Images are forthcoming. Terry
Smiljanich set up his Tom Dobbins telescope
and we all got to look at a few open
clusters, globular clusters in both Scorpius
and Sagittarius. He also showed Albireo in
Cygnus. Lisa Eager showed Saturn with its
moon Titan and what I though was a terrific
Ring Nebula. After spending a long time
setting up his terrific telescope, the eastern
and western sky clouded up and Paul Coia
was not able to star align his telescope to be
able to track. I can’t wait until we have a
clear sky, star party and be able to look
through his telescope.
We all got to see a few satellites sweeping
across the sky and a meteor going from
East to West, which Terry said, had a blue
tail before it disintegrated. Even though the
weather hampered viewing after a short
time I believe everyone had a great time
and some of us didn’t leave until close to
11:00 pm.
I want to personally thank all members at
last night’s Kelly’s Star Party.
Mark Kelly
Ron Spink
Marie Lucas
Terry Smiljanich
Howard and Marian Cohen
Amir and Mary Abdullah
Paul Coia and Laura Wright
Lisa Eager
Margarita Quinteros
I also want to thank two guest students that
I invited, Matt Given and Morgan Gates.
Cheers,
Ivo Rabell
Star Party Coordinator
First Light Newsletter Editor
Laura Wright
VOLUNTEER FOR 2015
THE CLUB NEEDS YOU
during 2015. We urgently need
volunteers to fill the following
positions during 2015:
Vice President
Secretary
Treasurer
To express your interest, email and tell us which
position:
[email protected]
alachuaastronomyclub.org
We were very sorry to lose
one of our long time
members, Dr. Neil White in
August. He presented to the
Club on August 14, 2012 a
talk on "Orit Determination:
How I Found Your Ellipse". He also
donated a telescope to the Club that he
had used when he was a youngster
growing up in Michigan. He will be
missed. Part of his obituary is below
from Gainesville.com.
Gainesville - Dr. Neil Lawrence White,
69, resident of Gainesville, Florida, died
Monday, August 11, 2014, in the North
Florida Regional Medical Center,
following an ongoing illness.
Dr. White was born on January 25, 1945
in Midland, Michigan, to the late Halbert
and Vivian Spear White. He received his
Bachelors Degree from Michigan State
University, and then his PhD in
Mathematics from Harvard University.
In 1973, Dr. White began his career in
the Math Department at the University
of Florida, where he spent the next 35
years, until his retirement in 2008. His
interests were many, and varied, a
member of the Gainesville Stamp Club,
the Gainesville Bridge Club, the Alachua
Astronomy Club and the Gator Volleyball
Attack Club; he was a volunteer for
Guardian Ad Litem and the Florida
Museum of Natural History.
Other opportunities include
Telescopes Coordinator
Programs Coordinator
Public Outreach Coordinator
To express your interest, email
and tell us which position:
[email protected]
alachuaastronomyclub.org
A Memorial Service will be held on
Sunday, September 7, 2014 at 3:00
P.M., in the Florida Museum of Natural
History, 3215 Hull Road, Gainesville. In
lieu of flowers, contributions toward the
Neil White Excellence in Teaching award
may be sent to the Department of
Mathematics, PO Box 118105, Univ of
FL, Gainesville 32611-8105. Checks
should be made out to the Dept. of
Mathematics. Please visit his memorial
page at
www.williamsthomasfuneralhome.com.
Enjoy exploring the night sky.
Regards,
Laura
Night-Sky Observing during August / September
Meteor Showers: August’s Perseids
by Andy Howell
The annual meteor shower known as the Perseids came to their peak during August 10-14, peaking in the pre-dawn
hours of August 12. Unfortunately, the moon was near full and weather did not cooperate with visual observers.
However, an automated video camera in my Gainesville backyard was able to capture 46 meteors on the evening of
August 11/12. Approximately half of these were Perseids. At one point during the night, a trio of meteors were
captured within a single 8.5 second interval (below).
A meteor trio, evening of Aug 11/12
Alpha Tau (Aldebaran) is the star in the upper right.
NIRCam Education & Outreach Newsletter
July-August, 2014
by Larry Lebofsky and Don McCarthy (University of Arizona)
Used with permission.
The Nighttime Sky
Below is a fisheye view of the sky at 10 pm on August 1. The annual path of the Sun, the ecliptic (shown as the
yellow line toward the bottom of the image), is low in the sky. It is winter when the Sun passes through these
constellations! Below we highlight four prominent constellations that are higher in the sky during our summer
evenings: Hercules, the Roman mythological hero; Lyra, the lyre (similar to a small harp); Cygnus, the swan; and
Aquila, the eagle. Three of these constellations (Lyra, Cygnus, and Aquila) form the familiar asterism, the Summer
Triangle.
Fisheye view of sky on September 1, 2014 at 10pm DST
(click to enlarge)
As we mentioned in the last Newsletter, concepts that are important to our background knowledge include size and
distance (scale). It is important to put our Sun in the context of the other stars we see in the sky, so we will
emphasize how big (mass and diameter) and bright (luminous) these stars are relative to our Sun. Also, because of
the continuing discoveries of extrasolar planets, we will emphasize these concepts when we highlight the
constellations.
Hercules
The constellation of Hercules is somewhat faint although quite famous. It possesses 15 stars with a total of 17 known
exoplanets. yet only two stars brighter than third magnitude. The brightest star (Kornephoros or Beta Herculis) is a
G-type (yellow, 4,900K) giant star that has used up the hydrogen in its core and is dying. With a mass is ~3 times
that of the Sun and a diameter ~17 times that of the Sun, it is ~150 times more luminous than the Sun. The secondbrightest star (Zeta Herculis) is a multiple star system with an F-type primary component (yellow-white, 5,800K;
slightly hotter than the Sun) that is just starting to evolve off of the main sequence. The secondary star is a G-type
(yellow, 5,300K) main sequence star very similar to our Sun. This star orbits the primary at about 15 AU (1.3 arc
seconds as seen from the Earth) with an orbital period ~34.5 years. The star system is estimated to be about 6.2
billion years old. The distances from Earth to Beta and Zeta Her are about 150 and 35 light-years, respectively.
Lyra
Lyra has only one star, Vega (Alpha Lyrae), brighter than third magnitude. However, Vega (Jody Foster’s star from
the movie “Contact”) is perhaps the most influential star to astronomers because it not only defines the universal
standard for brightness but also was one of the first stars discovered with an orbiting ring of debris from which
planets may be forming.
Vega is the fifth-brightest star in the night sky, an A-type (white, 9,600K) main sequence star about 455 million
year-old. With a mass is about twice that of the Sun and a diameter ~2.6x that of the Sun, it is ~40 times more
luminous. However, there is a catch. From Earth we see Vega nearly pole-on. While the Sun rotates once in 25 to 34
days (it rotates faster at the equator than at the poles), Vega rotates in just 12.5 hours (over 270 km/s at the equator)!
If it rotated only 10% faster, its gravity would not be strong enough to keep it from flying apart. Because of this,
Vega is “polar flattened” by 19%. Also, Vega is hotter at the poles (about 10,000K) than it is at the equator (about
8,000K). You can read more about this phenomenon at:
http://www.space.com/1930-rapid-rotation-distorts-bright-star-vega.html
Aquila
Aquila has three stars brighter than third magnitude: Altair (Alpha Aquilae), Tarazed (Gamma Aquilae), and Deneb
el Okab (tail of the falcon; Zeta Aquilae). Altair is an A-type (white, average temperature 7,700K) main sequence
star. Its mass is 1.8 times that of the Sun and its diameter is 1.8 times larger. It is 11 times as luminous as the Sun.
However, similar to Vega, it is rotating very rapidly, rotating once in 8.9 hours (a rotation velocity of 240 km/s at the
equator). Because of this, the temperature ranges from 6,900K at the equator to 8,500K at the pole. Altair’s
equatorial diameter is twice that of the Sun and its pole-to-pole diameter is only 1.6 times that of the Sun. Altair is a
multiple-star system with three companions with magnitudes between 10 and 11.
Tarazed at magnitude 2.7 is a K-type (orange, 4,200K) giant star that has evolved off the main sequence even though
it is estimated to be only 10 million years old. Its mass is ~6 times that of the Sun and its diameter is ~95 times that
of the Sun. It is about 2,500 times more luminous than the Sun. The distances to Altair and Tarazed are about 17 and
460 light-years, respectively. Aquila has 10 stars with 12 known exoplanets.
Cygnus
The constellation Cygnus is the focus of NASA’s Kepler Mission which has detected many exoplanets in a
continuous search of 150,000 stars. Cygnus’ brightest star is Deneb (Alpha Cygni) with a magnitude of 1.25. Deneb
is an A-type (white, 8,500K) supergiant star that has already evolved off of the main sequence. It is thought that it
will go supernova within a few million years. Its mass is about 20 times that of the Sun and its diameter is about 200
times that of the Sun. Its luminosity is estimated to be 200,000 times that of the Sun, making it one of the most
luminous stars known. The distance to Deneb has been estimated by several methods to be about 2,600 light-years,
but one method places it at “only" 1,600 light-years away which would reduce its diameter to about 100 times that of
the Sun and its luminosity to 60,000 times that of the Sun. There is a discussion of this at the Wikipedia site for
Deneb. At the minimum estimated distance Deneb is the most distant of the 35 brightest stars that we can see. At its
maximum estimated distance, it would be the most distant of the 100 brightest stars that we can see.
The fifth brightest star in Cygnus, Albireo (Beta Cygni). is a very famous binary star system, easily resolved in small
telescopes as a colorful pair of stars. Alberio A is a K-type (orange, 4100 K) giant star with ~5x the mass of our Sun
and 1000x the Sun’s luminosity. About 35 arcsec away is Albireo B, a B- type (blue-white, 12,000K) main sequence
star with a mass 3.7x that of the Sun and a luminosity about 200 times more. Based on the estimated distances, 400
to 430 light-years from the Earth, it is thought that Albireo B is in a 100,000-year orbit around Albireo A. Albireo B
is a fast rotator, with a 15-hour period of rotation. However, in this case, this is fast enough for it to be losing
material to space so that it is surrounded by a disk of gas. Alberio A is itself a binary star that is only detectable from
its spectrum with two stars separated by the width of our Solar System (~40 AU).
Earth’s Pole stars
The Earth is like a top that wobbles (“precesses”) over a period of about 25,800 years. Because of this, over time
different stars are aligned in the direction of Earth’s rotation axis. At the present time, Polaris in Ursa Minor is our
pole star. At the moment, Polaris is 0.7 degrees (1.4 times the diameter of the Moon) away from Earth’s axis of
rotation and will be closest around 2100 AD. Around 2800 BC Thuban, the heart of Draco the Dragon, was the pole
star. If we wait around, Deneb will be within 5 degrees of the pole around 10000 AD and Vega will be the pole star
(within about 4 degrees) around 14000 AD.
Clear Skies and Good Observing!
Copyright © 2014 Alachua Astronomy Club, Inc. All rights reserved.
Contact email: [email protected]
Alachua Astronomy Club, Inc.
P.O. Box 141591
Gainesville, FL 32614-1591
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