The Meteor
The Newsletter of the Astronomical Society of Greenbelt
  June 2012

Editor's Notes

On June 5, please come to the Goddard Visitors' Center, as an event we are never to see again will be visible as the Sun sets: The transit of Venus. "But", you say, "wasn't there one just a while back?" Indeed there was! Transits of Venus repeat, but in such a way that shows that the dance of the planets is a complicated one. They appear in pairs. Each transit in a pair is separated by eight years, but the pairs of transits are either one hundred and five or one hundred and twenty-two years apart. The next transit of Venus will take place in 2117, so we had best make the most of this great opportunity. NASA has an excellent webpage with more details at: Incidentally, Mercury will transit the Sun in four years.

Also, as promised in the May issue, this month's issue has a new angle on the Dark Matter mystery: Looking for Dark Matter's effect on the motions of the satellite galaxies & globular clusters of the Milky Way.

We will be moving our meetings to the Greenbelt Community Center for the summer, as the staff of the Owens will take a well-earned vacation from educating tomorrow's astronomers.

Elected officers for 2011-2012

Email Address
Martha Gay AT
Ray Stevens
stvns.jacht AT
Cleton Henry
Cleton.Henry AT
Sue Bassett
wb3enm AT

Astronomical Events Around Greenbelt in June 2012


Planetarium show at the Owens
7:30 PM
Transit of Venus-see it at Goddard
5 PM
Star Party at Northway Field
9:30 PM
Star Party at Northway Field
9:30 PM
General Meeting at the GCC, rm. 114
7:30 PM

For other astronomical events in the DC area, see: Astronomy in DC

Star Party & Business Meeting Reports

May 7: Officers' Meeting (from Cleton):
May 12: Star Party
(from Doug): It wasn't clear, but Scott Huber and wife(?) and later 2 friends showed up to peer at Venus, Mars and Saturn through the sucker holes.  We stayed until 10:30 taking pictures with cellphones and other cameras, and singing old songs. 


There was TP in back of the dome, someone had left the adapter and cap off of the eyepiece holder, and the City had mowed my iris down.  The new control paddle stopped working for a moment as I was clicking switches to try and slow the motors down.  I think I turned the drive off with one of them.

May 26: Star Party (from Martha): We opened and looked at the Moon. Had two customers plus Mike
Chesnes and friends. The mount needs work. The declination clutch is slipping. Couldn't use the dew shield because of that. We only had a little bit more than an hour before the clouds moved in.

May 31: Business Meeting: Ray, Martha, Cleton, Doug, Richard, & I came to the Owens for what must be one of our more unusual business meetings. Instead of the usual routine, we held an info table for a group called SMART, a pro-science literacy organization that's also based in our county.

Owens Family Science Night & Minor Meteor Showers

by G.W. Gliba

On Friday evening, May 4th, the Family Science Night at the H.B. Owens Science Center was held, and it was a big success. Myself and GAC/NCA member Jeff Guerber attended, bringing our traveling meteorite displays, which were a big hit. Several hundred people, both kids and adults, from many families from all over P.G. County attended to learn more about the wonders of nature, and scientific discovery. Several free planetarium shows were presented by Planetarium Director Patty Seaton, and free NASA Imagine DVDs, and Teacher Workbooks about Meteorites were passed out to students and teachers respectively. ASG member and Owens employee Russ Waugh ran the Challenger Center.  ASG president, and longtime officer, Martha Gay, was also present to answer questions about ASG and the City of Greenbelt Observatory. We tried to encourage students to try to learn more about nature, and science in general. Although it didn't clear up to allow telescope viewing until this event had ended, many people who attended were able to spot the nearly full Super Moon, which is the rare Full Moon at Perigee, when they left for home as the sky became partly clear later. It was a great ending to a good night.

The giant Sunspot #1476 was seen with only the naked-eye and proper filters by several GAC members when it was near the solar meridian. Several ASG & GAC members also viewed the sunspot complex with telescopes.  Lynne and I saw the big spot with the naked-eye and a Thousand Oaks solar filter then. A few days later, we were able to see it with our 3.15-inch F/12.5 Zhumell refractor from our cabin at Mountain Meadows, West Virginia on May 12th. It is the largest sunspot we have seen in a few years. It somewhat resembled the state of Hawaii, but of course was very much larger.  Lynne also noticed a halo around the sun, which I was also able to observe through the thin clouds. Unfortunately, the sky remained mostly to partly cloudy the rest of that day and night. However, I was able to do some meteor watching later that night when it became mostly clear, but hazy. At one time I could see down to about 6.2, but the average limiting magnitude was about 5.5 magnitude. Not great, but fairly good. It seemed that when the lightning bugs were more pronounced there were less stars visible, which may have been the temperature difference, or was just a coincidence.

Early after dark, I observed a nice 3rd magnitude satellite in the NE going due north. A little while later I saw my first meteor of the night, which was a nice blue-white 2nd magnitude sporadic. After midnight it finally cleared up enough to do some formal meteor watching. From 12:47 until 2:47 am EDT I was able to see 18 meteors under partly cloudy skies.  The Eta Lyrids and Alpha Scorpids were active, and the Sporadic count was good. The second hour had better, but only fair conditions. The best meteors was a lovely 0 magnitude blue-green colored Sporadic seen at 2:33 am EDT, and a nice 1st magnitiude yellow-orange Alpha Scorpid (ANT) meteor seen at 1:10 am EDT. After meteor observing, I got a good view of the Moon with the 3.15-inch refractor.  The southern highlands showed Clavius very well, and the large crater Copernicus looked great. I was also impressed by the view of the Appenine Mountain Range.  Earlier that night Lynne and I both heard Spring Peepers, and field crickets. Later, I also heard a whippoorwill, mockingbird, and another bird that I can't identify. It was a pretty nice warm night for observing.

From the Royal Astronomical Society:

Do the Milky Way’s companions spell trouble for dark matter?

Last Updated on Wednesday, 25 April 2012 08:58

Astronomers from the University of Bonn in Germany have discovered a vast structure of satellite galaxies and clusters of stars surrounding our Galaxy, stretching out across a million light years. The work challenges the existence of dark matter, part of the standard model for the evolution of the universe. PhD student and lead author Marcel Pawlowski reports the team’s findings in a paper in the journal Monthly Notices of the Royal Astronomical Society [MNRAS]*.

VV340 - smallThe galaxy pair UGC 9618 / VV 340, two spiral galaxies at the beginning of a collision. Credit: NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)The Milky Way, the galaxy we live in, consists of around three hundred thousand million stars as well as large amounts of gas and dust arranged with arms in a flat disk that wind out from a central bar. The diameter of the main part of the Milky Way is about 100,000 light years, meaning that a beam of light takes 100,000 years to travel across it. A number of smaller satellite galaxies and spherical clusters of stars (so-called globular clusters) orbit at various distances from the main Galaxy.

Conventional models for the origin and evolution of the universe (cosmology) are based on the presence of ‘dark matter’, invisible material thought to make up about 23% of the content of the cosmos that has never been detected directly. In this model, the Milky Way is predicted to have far more satellite galaxies than are actually seen.

In their effort to understand exactly what surrounds our Galaxy, the scientists used a range of sources from twentieth century photographic plates to images from the robotic telescope of the Sloan Deep Sky Survey. Using all these data they assembled a picture that includes bright ‘classical’ satellite galaxies, more recently detected fainter satellites and the younger globular clusters.

“Once we had completed our analysis, a new picture of our cosmic neighbourhood emerged”, says Pawlowski. The astronomers found that all the different objects are distributed in a plane at right angles to the galactic disk. The newly-discovered structure is huge, extending from as close as 33,000 light years to as far away as one million light years from the centre of the Galaxy.

Team member Pavel Kroupa, professor for astronomy at the University of Bonn, adds “We were baffled by how well the distributions of the different types of objects agreed with each other”. As the different companions move around the Milky Way, they lose material, stars and sometimes gas, which forms long streams along their paths. The new results show that this lost material is aligned with the plane of galaxies and clusters too. “This illustrates that the objects are not only situated within this plane right now, but that they move within it”, says Pawlowski. “The structure is stable.”

The various dark matter models struggle to explain this arrangement. “In the standard theories, the satellite galaxies would have formed as individual objects before being captured by the Milky Way”, explains Kroupa. “As they would have come from many directions, it is next to impossible for them to end up distributed in such a thin plane structure.”

Postdoctoral researcher and team member Jan Pflamm-Altenburg suggests an alternative explanation. “The satellite galaxies and clusters must have formed together in one major event, a collision of two galaxies.” Such collisions are relatively common and lead to large chunks of galaxies being torn out due to gravitational and tidal forces acting on the stars, gas and dust they contain, forming tails that are the birthplaces of new objects like star clusters and dwarf galaxies.

Pawlowski adds, “We think that the Milky Way collided with another galaxy in the distant past. The other galaxy lost part of its material, material that then formed our Galaxy’s satellite galaxies and the younger globular clusters and the bulge at the galactic centre. The companions we see today are the debris of this 11 billion year old collision.”

Kroupa concludes by highlighting the wider significance of the new work. “Our model appears to rule out the presence of dark matter in the universe, threatening a central pillar of current cosmological theory. We see this as the beginning of a paradigm shift, one that will ultimately lead us to a new understanding of the universe we inhabit.”

*A preprint of the article in MNRAS can be read through this link. An animation of our galaxy's neighborhood can be seen here.