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

Editor's Notes

April showers have now passed, & the mild month of May is upon us. I'm looking forward to my planetarium show, "South Sea Skies", which will be shown to the public on the 18th & repeated for our meeting on the 31st.

You may remember that in the 12/10 issue of this newsletter, I ran an article, "Suppose it wasn't there", about the possibility that there was no dark matter in our solar system's neighborhood in the Milky Way. This was a summary of a letter, "No Evidence for a Dark Matter Disk Within 4 kpc From The Galactic Plane", in vol. DCCXXIV, no. 1 of Astrophysical Journal Letters. Items in Astrophysical Journal Letters are often followed up by a full article in the Astrophysical Journal, if further investigation warrants. Last month, I learned that not only did the team of astronomers who produced the letter continue their research, but that the European Southern Observatory, where they conducted their research, released an announcement to the press about their findings, which reinforce their 2010 letter. I am running the full text of the announcement in this issue. This further research casts doubt on a pillar of current cosmology, the "CDM" of ΛCDM, where Λ (lambda) stands for dark energy, & CDM stands for cold dark matter, for without dark matter, something else must be operating to cause the stars to orbit the center of the Milky Way in the way they do. Next month's issue will include a bulletin about research on the satellite galaxies of the Milky Way!

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 May 2012


Family Science Night
at the Owens
6 PM
Star Party at Northway Field
9 PM
Planetarium show at the Owens
7:30 PM
Star Party at Northway Field
9 PM
General Meeting at the Owens
7:30 PM
(June 1)
Planetarium show at the Owens
7:30 PM

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

Star Party & Business Meeting Reports

April 2: Business Meeting:

Summer programing ideas:

 * Movies-Several possibilities from Elizabeth. Also: The Dish?

Outreach to Busboys & Poets as a City Dark (CD) venue that has better 'legs' than the New Deal? Also Mark's Kitchen as a site for CD advertisement. We don't have posters yet, but once we do, we hit both places & others with them.

Further discussion of CD @ New Deal-one showing is all we are allowed. Do we want to go in with the Owens on getting a showing for them?

We will need handouts for this occasion. Also our projector. Remember the date-5/21 [since postponed-CL].

 * Elizabeth's suggestion for hands-on activities: One or two at a time-flour craters, Play-Dough, fun with shading or color enhancing. Clean-up: Use disposable tableclothes. Elizabeth showed off the nifty NASA material she got the other week.

Observatory issues: Power, other-Doug wants to put the generator in the cellar over the summer. Approved.

Upcoming issues & programs-Sue this month, myself in May. Martha will be gone during the summer. E. will do hands-on science in July; activity packets for the kids, info sheet of ideas for parents.

Venus transit-6/5-us, GAC, & Owens. E. & I have the solar screen for the Astroscan™, other folks have Coronados or solar filters.

Labor Day-we'll have a special program with an information table & food booth.

Special programs: Cooperating with GAC, publicity-posting material in venues outside of Greenbelt?

April 14: Star Party: Clouded Out.

April 26: General Meeting: Sue delivered a speech on the upcoming transit of Venus & on the history of observing transits:

Times for the next transit in June: External contact-that is, when the disk of Venus is tangent to the Sun-at 1804 local time,  internal contact-that is, when the disk of Venus is fully visible against the Sun-at 1821, & sundown at 2030. Places further west will see the whole event. Venus will be a substantial dot.

Transits of Venus occur in a cycle of 8 years. separated by 122.5 years, then another 8, & then another 105.5. There have been only 11 transits since 1396, so a transit of Venus is about the rarest thing you'll see. Venus should transit across lower half of the Sun in June.

17th century-Copernican/Keplerian theory give you a proportional size of the solar system & the paths of the planets. Kepler predicted that Mercury would transit, & that Venus would transit. Gassendi observed the Mercury transit, showing that the paths were right.

Horrocks & Crabtree - Cambridge pals & mathematicians; H is a clerk, C is a clothier; H uses transit tochecks two different tables-Kepler's & Landsberg's-H manages to see some of the 1639 transit, C sees some of it too. H died of an illness, & C was killed in the English Civil War.

Halley produces mathematical proof that you can send teams across the world to use triangulation to get a true distance of the solar system. His work was implemented in the 18th century, during which numerous expeditions were sent all over the world. These faced several problems. On top of the troubles with getting to many of these remote locations & getting killed by local diseases (or locals, in the case of Capt. Cook), the researchers had to deal with the problems of the observations themselves, including distortion from Earth's atmosphere, Venus' atmosphere, & the "black drop" illusion. These factor messed with exact timing of the transits, so size of the AU was miscalculated to 95.4 million miles.

19th century-America got into the game, & there was popular attention in the press. Some scientists claimed that there was no need to run more transit expeditions, but expeditions were despatched; some expeditions were not funded to reduce their observations.

20th century-no transits took place, but direct radar ranging of the planets made finding their distances by transits irrelevant anyway.

21st-2004, which [Craig] missed, & June! However, there is still a lot of interest about transits from another side of astronomy: NASA's Kepler probe hunts for exoplanets by looking for transits of planets across stars in the Summer Triangle.

June  presentation: We'll see The Dish, set at Australia's Parkes Observatory in the summer of '69!

April 28/29 : Star Party & Sidewalk Astronomy: No report.

Last Chance to See...

On June 5, 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: 1874, 1882, 2004, & this one. The next one 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:

The SN 2012aw, Mars, and Space Shuttle Discovery
by G.W. Gliba

I was able to observe SN 2012aw in M95 from Mountain Meadows, West Virginia at the observatory of Jim Crowley, of the National Capital Astronomers, on Saturday night, March 31st. The 13th magnitude SN was seen with a 20-inch Starmaster Dobsonian at 100x and 132x. The bar of this barred spiral galaxy was also visible, despite the close proximity of the Moon at 132x. Jim and I also observed Mars nearby. We could both make out good detail in the several mara that were visible. We could also see a polar cap and a white cloud on the terminator in the southern hemisphere near the other pole. We also observed M66 and the beautiful double stars Algieba, before clouds rolled in and ended our viewing.

Earlier, from our cabin a little ways down Southbranch Mountain, I was able to get a good look at the Moon with the 3-inch F/12.5 Zhumell refractor. The crater Copernicus was just on the terminator, and was still in complete darkness, including the central peak, but the rim was in sunlight. It was very dramatic. Sort of what Galileo first saw. Also, I took a look at Mars, which showed Syrtis Major near the meredian, but much less detail than I was to see in Jim's 20-inch a bit later. I also saw a couple nice meteors casually, including a nice 2nd magnitude short trailed blue-white sporadic, and later a fine 1st magnitude yellow-white long trailed sporadic, between broken clouds. I heard the Spring Peepers in the background, and on two occasions, a Barred Owl in the distance; then close-by. The clouds later prevented me from doing any formal meteor observing, but I got a good look at Corona Borealis, and Bootes, as well as the rising Milky Way in Cygnus before it got completely overcast again.

On Tuesday, April 17, the Space Shuttle Discovery made a low pass over the NASA/GSFC at about 10:18 am EDT. I saw her at Goddard that day, along with thousands of NASA civil servants and contractors on the Mall at GSFC. People were cheering, yelling, and clapping their hands as the most veteran of Space Shuttles, with 148 million miles traveled in Space, displayed herself in all her glory. It was an emotional moment for me, as 31 years earlier I saw the maiden launch of the Space Shuttle Columbia from Cape Canaveral, Florida.
Unfortunately, she was one of two Space Shuttles who later had catastrophic accidents, killing their entire crews of brave astronauts. But this was a happy ending for Discovery, the ship that took the mighty Hubble Space Telescope into orbit.  Seeing her was also bittersweet, as it was the celebrated end of the Shuttle Era. There were great achievements, discoveries, and accomplishments made by NASA, because of this fine fleet of great spaceships and brave astronauts.

News From the European Southern Observatory:

Serious Blow to Dark Matter Theories?

New study finds mysterious lack of dark matter in Sun’s neighbourhood

18 April 2012

The most accurate study so far of the motions of stars in the Milky Way has found no evidence for dark matter in a large volume around the Sun. According to widely accepted theories, the solar neighbourhood was expected to be filled with dark matter, a mysterious invisible substance that can only be detected indirectly by the gravitational force it exerts. But a new study by a team of astronomers in Chile has found that these theories just do not fit the observational facts. This may mean that attempts to directly detect dark matter particles on Earth are unlikely to be successful.

A team using the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory, along with other telescopes, has mapped the motions of more than 400 stars up to 13 000 light-years from the Sun. From this new data they have calculated the mass of material in the vicinity of the Sun, in a volume four times larger than ever considered before.

The amount of mass that we derive matches very well with what we see — stars, dust and gas — in the region around the Sun,” says team leader Christian Moni Bidin (Departamento de Astronomía, Universidad de Concepción, Chile). “But this leaves no room for the extra material — dark matter — that we were expecting. Our calculations show that it should have shown up very clearly in our measurements. But it was just not there!

Dark matter is a mysterious substance that cannot be seen, but shows itself by its gravitational attraction for the material around it. This extra ingredient in the cosmos was originally suggested to explain why the outer parts of galaxies, including our own Milky Way, rotated so quickly, but dark matter now also forms an essential component of theories of how galaxies formed and evolved.

Today it is widely accepted that this dark component constitutes about the 80% of the mass in the Universe [1], despite the fact that it has resisted all attempts to clarify its nature, which remains obscure. All attempts so far to detect dark matter in laboratories on Earth have failed.

By very carefully measuring the motions of many stars, particularly those away from the plane of the Milky Way, the team could work backwards to deduce how much matter is present [2]. The motions are a result of the mutual gravitational attraction of all the material, whether normal matter such as stars, or dark matter. Astronomers’ existing models of how galaxies form and rotate suggest that the Milky Way is surrounded by a halo of dark matter. They are not able to precisely predict what shape this halo takes, but they do expect to find significant amounts in the region around the Sun. But only very unlikely shapes for the dark matter halo — such as a highly elongated form — can explain the lack of dark matter uncovered in the new study [3].

The new results also mean that attempts to detect dark matter on Earth by trying to spot the rare interactions between dark matter particles and “normal” matter are unlikely to be successful.

Despite the new results, the Milky Way certainly rotates much faster than the visible matter alone can account for. So, if dark matter is not present where we expected it, a new solution for the missing mass problem must be found. Our results contradict the currently accepted models. The mystery of dark matter has just become even more mysterious. Future surveys, such as the ESA Gaia mission, will be crucial to move beyond this point.” concludes Christian Moni Bidin.


[1] According to current theories dark matter is estimated to constitute 83% of the matter in the Universe with the remaining 17% in the form of normal matter. A much larger amount of dark energy also seems present in the Universe, but is not expected to affect the motions of the stars within the Milky Way.

[2] The observations were made using the FEROS spectrograph on the MPG/ESO 2.2-metre telescope, the Coralie instrument on the Swiss 1.2-metre Leonhard Euler Telescope, the MIKE instrument on the Magellan II Telescope and the Echelle Spectrograph on the Irene du Pont Telescope. The first two telescopes are located at ESO’s La Silla Observatory and the latter two telescopes are located at the Las Campanas Observatory, both in Chile. A total of more than 400 red giant stars at widely differing heights above the plane of the galaxy in the direction towards the south galactic pole were included in this work.

[3] Theories predict that the average amount of dark matter in the Sun’s part of the galaxy should be in the range 0.4-1.0 kilograms of dark matter in a volume the size of the Earth. The new measurements find 0.00±0.07 kilograms of dark matter in a volume the size of the Earth.

More information

This research was presented in a paper, “Kinematical and chemical vertical structure of the Galactic thick disk II. A lack of dark matter in the solar neighborhood”, by Moni-Bidin et al. to appear in The Astrophysical Journal.

The team is composed of C. Moni Bidin (Departamento de Astronomía, Universidad de Concepción, Chile), G. Carraro (European Southern Observatory, Santiago, Chile), R. A. Méndez (Departamento de Astronomía, Universidad de Chile, Santiago, Chile) and R. Smith (Departamento de Astronomía, Universidad de Concepción, Chile).

The year 2012 marks the 50th anniversary of the founding of the European Southern Observatory (ESO). ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 40-metre-class European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.