Southern Maine Astronomers
4 November 2021, 1830 hrs
Attending were members Russell Pinizzotto, Ara Jerahian, Greg Thorup, Dwight Lanpher, Bob
Dodge, Forrest Sumner, George Bokinsky, Kerry Kertes, Al DiSabatino, Howie Marshall, David
Manchester, James Shields, Abby Gardner, Scott Lovejoy, Jon Wallace, Rowan Gobele-Bane, Mike
Simmons, Ron Thompson, David Gay, Bert Vanderburg, Chris Parent, Nicholas Wall and Rob
Burgess, and guests Anita DeVito, Doug Lund-Yates, Paul Sasso, Carl Gurtman, Maame Andon
and our speaker, Greg Shanos.
1900: Rob Burgess opened the formal portion of the meeting welcoming new member Christopher
Rob reported that James Shields coordinated an International Observe the Moon star party on Oct
17 at Fort Allen Park on the Eastern Prom that about 30 people attended. The Lady Adventurers
star party at Neptune Dr on Oct 29 was cancelled due to weather. Upcoming events include a virtual
star party using EAA equipment on Tuesday, Nov 9 at 6:30 pm sponsored by the Cape Elizabeth
Public Library. The event will be run by Ara Jerahian and Russ Pinizzotto To join, one must first
register with the library, online. The rain date is Nov 16. The Windham Public Library has asked us
for a talk on how telescopes have affected the development of astronomy, with discussion about the
James Webb Space Telescope on Wednesday Nov 10 from 6-7 pm, followed by a star party two
days later on Nov 12, from 6-8 pm. James Shields is coordinating both events and could use
assistance. The next club event is scheduled for Saturday, Dec 11 at Neptune Drive where we hope
the Lady Adventurers Club will reschedule. The next club meeting will feature club member Jon
Wallace discussing micrometeorites, what they tell us and how he finds them. Our January meeting
will be a reprise of last January’s meeting, offering short topic presentations by club members about
basic observing and telescope use to help our newest members. This was a well-received program
Invited Speaker: Greg Shanos, D Pharm, on Travel to a Comet. Rob introduced Greg who is a
member of the Rhode Island Astronomy Club “Skyscrapers,” a NASA Solar System Ambassador, a
working Pharmacist, and a very keen amateur astronomer. With his background in pharmacology
and chemistry Greg’s interest in comets includes having written more than 35 articles on the
chemical compositions of comets. Greg has also traveled the world to witness twelve total solar
eclipses, three annular solar eclipses and both Transits of Venus in 2004 and 2012. Of late, Greg
has taken up astrophotography and some of his work is archived in the Association of Lunar and
Greg’s interest started with the last appearance of Halley’s Comet in 1986. Greg explained that in
the 4 th century BC Aristotle thought comets were meteorological because they ran contrary to the
perfect universe and the celestial spheres. Their appearance had a negative connotation that
remained until a few hundred years ago of something ominous or foreboding associated with
portentous world events such as wars. Halley didn’t actually discover the comet that bears his name
– it was Kepler who figured out its elliptical orbit – but Halley did predict the comet’s return in 1758.
Unfortunately he did not live to see it. In more recent years comets were described as “flying
sandbags;” it was astronomer Fred Whipple who characterized them as “dirty snowballs,” a term that
has stuck as we have learned more about comets.
Meteor showers occur when Earth passes through the trail of debris left behind by passing comets.
The remnants strike the Earth’s atmosphere and create the meteors that delight us. Cometary
particles that actually make it to the ground are called meteorites. Comet Halley is responsible for
the Orionid Meteor Shower we see every October. There are “short period” comets that reappear
every decade or so, and “long period” comets that might never be seen again for thousands of
We now understand that comets are part of the left over components of the building of our solar
system lying extremely far from the Sun in the Keiper Belt and Oort Cloud regions. It is estimated
that the Oort Cloud contains trillions of such objects, most of which stay locked in this haze of debris
that surround our solar system like a giant swarm of bees. Greg explained that comets contain a
nucleus, a coma, a hydrogen envelope (not visible), a dust tail and a plasma tail. The nucleus is
made of rock, dust and frozen gases, mostly water. The comet gains it familiar appearance as it
approaches the sun and the ices sublimate, going from solid to gas as they warm and producing the
tail that we see. The comet’s tails always points away from the Sun, being driven by the Solar wind
and ionized particles emanating from the Sun. Most comets are under 15 km in size, their density is
low such that would float in water, they are dark in appearance with an albedo of fresh asphalt, and
they are quite fragile, often with stress cracks caused by pressure differentials. On incoming
comets, dust tails start to become visible about at the orbit of Mars. The tails are thought to be
releasing particles the size of smoke grains, pushed away by the pressure of sunlight. The plasma
tails result from the loss of electrons from the gases in the comet. As ionized particles they follow
the course of magnetic fields in interplanetary space. The blue plasma tail seen with many comets
is ionized carbon monoxide. Greg reminded everyone that plasma, or ionized gas, is the most
common form of matter in the universe as we understand things today.
One of the more dramatic events with a comet occurred when comet Shumaker-Levy 9 broke into
about 20 fragments and collided with Jupiter between July 16 and 22, 1994, leaving huge dark
marks in the Jovian atmosphere that were visible for weeks. It was the first time astronomers were
able to actually observe the consequences of a cometary collision with a planet in real time.
Greg then reviewed several recent spacecraft missions to comets conducted by both NASA and the
European Space Agency (ESA). The Giotto Mission, launched by the ESA in 1985, encountered
Comet Halley in March 1986. It flew within 373 miles of the nucleus and determined that that
comets were indeed “dirty snowballs” with estimates that the nucleus was losing approximately three
tons of material every second, 80% of which was water. When Comet Halley appeared in 1910 it
spurred the sale of gas masks because fearful Earthlings by that time knew that the plasma tail
released carbon monoxide!
It had long been speculated that comets seeded the Earth with water. Delving into organic
chemistry, a recurring theme in Greg’s talk, it is now understood that the level of Deuterium in
cometary water (Deuterium having one proton, one electron and one neutron compared to Hydrogen
with one proton and one electron) is twice the amount in ordinary sea water, and hence could not be
the source. Comets undoubtedly contributed to water on Earth but it is now thought that water-rich
asteroids may have been major contributors.
The next mission discussed was Deep Space 1 to Comet 19P Borrelly, launched by NASA in 1998.
The mission was modified after it passed its initial target of Asteroid Braille, similar to Vesta. It then
went on to fly by Comet Borrelly, where it entered the coma in 2001. Its ion-propulsion engines
ceased operation shortly thereafter in December 2001. It found the bowling pin-shaped comet
largely devoid of water ice and quite warm, and got within 1,350 miles of the nucleus.
The Deep Impact mission, launched in January 2005, was put on a collision course with Comet 9P
Tempel 1. On July 4, 2005 the 824 pound copper impactor, dropped off by the mother ship, was
slammed into by the comet, traveling at about 10 miles per second. The resulting blast blew a
stadium sized crater in the comet’s surface and the resulting ejecta was analyzed spectroscopically,
by ground-based and space-based observatories around the world. It found, clay, silicates,
carbonates and sodium and a density more like a snow bank than a solid object. More dust was
ejected than expected, being more like talcum powder than sand. The mother ship was re-routed to
a new target, Comet 103 P Hartley, and the mission renamed Epoxi. The spacecraft arrived at the
comet in November 2010 and found a surprising blend of at least two, possibly three, different ices,
leading to questions about the comet’s formation, as possibly an amalgam of different materials.
In 1999 the Stardust mission was launched by NASA to visit Comet Wild 2. Stardust flew behind
the comet and captured actual particles released by the comet in a silicon material known as
aerogel, that allowed the particles to be absorbed and not transformed by impact. The collection
device was returned to Earth in 2006 where the captured particles have been subject to intense
examination. Among the findings were refractory materials (made in high temperatures), rich in
organic hydrocarbons and polycylic aromatic hydrocarbons, such as amino acids and glycine,
building blocks of proteins.
The final mission discussed was the ESA Rosetta Mission to Comet 67 P Churyumov Gerasimenko.
The mission commenced on March 2, 2004. It took ten years to reach its target comet, getting a
gravity assist from Mars and two asteroids, Steins and Lutetia, arriving on August 6, 2014. Its small
lander, Philae, actually landed on the surface of the comet on Nov 12, 2014. Unfortunately, its
harpoon hooks did not attach to the surface as planned and the lander bounced, ending up in a dark
crevice, which doomed it to a short life of 57 hours since its solar-powered batteries could not
recharge. Rosetta orbited the comet for 17 months. It determined the comet actually had seasons,
based on its rotational characteristics. Rosetta detected the noble gases of krypton, xenon and
argon and also deuterium at almost 3x the level in Earth’s oceans, making comets such as 67P not a
source of water on Earth.
Greg dedicated several slides to the organic chemistry that exists on each of the comets reviewed,
demonstrating that the chemical building blocks necessary for life appear widespread in our Solar
System, and presumably in others in our galaxy.
Russ Pinizzotto provided a fascinating tour of Pegasus, another of the original 48 constellations
established by Ptolemy. Pegasus is the seventh largest constellations and is easily found by
following the pointer stars of the Big Dipper, directly through Polaris, and then about as far again to
the “great square.” The great square is one of easiest of the naked eye asterisms to find, with others
nearby including the circlet in Pisces, the water jar in Aquarius and “Job’s Coffin” in Delphinus.
Russ noted that 51 Pegasi is the first Sun-like star with an exoplanet, Helvetios, discovered in 1995
and resulting in a Nobel Prize for the discoverers in 2019.
The only Messier object in Pegasus is M 15, a stunning globular cluster with an unusually large
number of Cepheid variables used in calculating distance. M 15 is estimated at 33,000 LY.
Pegasus contains three Caldwell objects – 30 (NGC 7331), a spiral galaxy part of the amazing Deer
Lick Group; 43 (NGC 7814), the Little Sombrero Galaxy that had a new supernova discovered in it
this year; and 44 (NGC 7476), the Propeller Galaxy, a Seyfert galaxy showing lots of star formation.
Other interesting objects include NGC 7217, a spiral galaxy, with a blue outside ring and several
concentric inside bluish rings, NGC 7448, an irregular galaxy with active star formation; NGC 7742,
also showing a bright exterior ring but with no bar – the aptly named “Fried Egg Galaxy;” and NGC
7673, a “disturbed” spiral galaxy with lots of star formation. Stephan’s Quintet, NGC 7317, shown in
an amazing Hubble image of five galaxies, near the Deer Lick group.
Finally, Russ showed a Hubble image of Einstein’s Cross, four symmetrical images of a quasar,
some 8 billion night years distant, projected surrounding a foreground galaxy due to gravitational
lensing. There are actually twelve such images of distant objects gravitationally lensed around
foreground objects that have been found by the Gaia spacecraft’s survey of the skies. Each of these
has been instructive in the case for dark matter.
Next month’s constellation: Camelopardalis.
The meeting concluded about 21:50.