A Dearth of Dark Matter
April 23, 2012
One of the astronomical mysteries of the last century was the missing mass of the Universe. In the 1930s, through measurements of the orbital velocities of stars about the galactic center, it was discovered that our Milky Way Galaxy contained more mass than the sum of its stars. Further evidence came from the orbital velocities of galaxies in clusters, the rotation rate of galaxies; and, more directly, by the gravitational lensing of background objects by galactic clusters.
This nagging problem of missing mass went on for decades, and it occupied the research programs of quite a few astronomers. Many years ago, the American Physical Society had a Physics Limerick Contest, and I submitted this entry summarizing the missing mass problem.
The accountant was ranting and hissing!
Our missing mass now has a name, dark matter, but we still have no idea what it is. Dark matter can't be observed with telescopes, since it neither emits nor absorbs electromagnetic radiation, so its presence is still inferred indirectly. Results from the Wilkinson Microwave Anisotropy Probe show that 83% of the matter in our present universe is dark matter, and this proportion hasn't changed from 13.7 billion years ago (see figure).
So, dark matter is pervasive, right? Pervasive, perhaps, but maybe not uniformly distributed. A recent study by astronomers at the European Southern Observatory shows that dark matter is remarkably absent from the region of space around our solar system.[3-4]
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) made this discovery by a precise measurement of the motion of stars distant from the plane of the galaxy.
These observations, which covered a large volume around the Sun, as shown in the figure, show no evidence for dark matter. The team used several different telescopes to record the motions of more than 400 red giant stars in a volume out to 13,000 light years. This work extended such measurements to four times a larger volume than previously observed. One important aspect of this discovery is that attempts by particle physicists to detect dark matter here, on Earth, would be fruitless.
Said team leader, Christian Moni Bidin,
Such an audit was not of our wishing!
But such was our state,
An astronomer's fate,
Since some of our mass was found missing!
"The amount of mass that we derive matches very well with what we see — stars, dust and gas — in the region around the Sun... 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! ...The mystery of dark matter has just become even more mysterious."
The bottom line of the study is this - Theory predicts that there should be 400-1000 grams of dark matter in the Sun's vicinity in a volume the size of the Earth, whereas the observations indicate no dark matter within an error of 70 grams.
A paper on this work, "Kinematical and chemical vertical structure of the Galactic thick disk II. A lack of dark matter in the solar neighborhood," will appear in The Astrophysical Journal. A preprint of the paper appears on the arXiv web site.
- Physics Limericks-Devlin Gualtieri, American Physical Society Web Site. A local copy can be found here.
- WMAP- Content of the Universe, NASA Web Site.
- Serious Blow to Dark Matter Theories? New study finds mysterious lack of dark matter in Sun's neighbourhood, European Southern Observatory Press Release eso1217, April 18, 2012.
- C. Moni Bidin, G. Carraro, R. A. Mendez, R. Smith, "Kinematical and chemical vertical structure of the Galactic thick disk II. A lack of dark matter in the solar neighborhood," arXiv Preprint Server, April 17, 2012.
Permanent Link to this article
Linked Keywords: Astronomy; missing mass; Universe; orbital velocity; star; galactic center; Milky Way Galaxy; mass; cluster; rotation rate; galaxy; gravitational lensing; research; astronomer; American Physical Society; Physics Limerick Contest; dark matter; telescope; emission spectrum; absorption spectroscop; electromagnetic radiation; Wilkinson Microwave Anisotropy Probe; WMAP; dark energy; universal expansion; deceleration parameter; NASA; European Southern Observatory; solar system; Universidad de Concepción; Chile; Santiago; Universidad de Chile; galactic plane; volume; Sun; red giant; light year; particle physics; Earth; ESO; L. Calçada; Christian Moni Bidin; theory; gram; standard error; The Astrophysical Journal; arXiv.
Latest Books by Dev Gualtieri
Thanks to Cory Doctorow of BoingBoing for his favorable review of Secret Codes!
Blog Article Directory on a Single Page
- J. Robert Oppenheimer and Black Holes - April 24, 2017
- Modeling Leaf Mass - April 20, 2017
- Easter, Chicks and Eggs - April 13, 2017
- You, Robot - April 10, 2017
- Collisions - April 6, 2017
- Eugene Garfield (1925-2017) - April 3, 2017
- Old Fossils - March 30, 2017
- Levitation - March 27, 2017
- Soybean Graphene - March 23, 2017
- Income Inequality and Geometrical Frustration - March 20, 2017
- Wireless Power - March 16, 2017
- Trilobite Sex - March 13, 2017
- Freezing, Outside-In - March 9, 2017
- Ammonia Synthesis - March 6, 2017
- High Altitude Radiation - March 2, 2017
- C.N. Yang - February 27, 2017
- VOC Detection with Nanocrystals - February 23, 2017
- Molecular Fountains - February 20, 2017
- Jet Lag - February 16, 2017
- Highly Flexible Conductors - February 13, 2017
- Graphene Friction - February 9, 2017
- Dynamic Range - February 6, 2017
- Robert Boyle's To-Do List for Science - February 2, 2017
- Nanowire Ink - January 30, 2017
- Random Triangles - January 26, 2017
- Torricelli's law - January 23, 2017
- Magnetic Memory - January 19, 2017
- Graphene Putty - January 16, 2017
- Seahorse Genome - January 12, 2017
- Infinite c - January 9, 2017
- 150 Years of Transatlantic Telegraphy - January 5, 2017
- Cold Work on the Nanoscale - January 2, 2017
- Holidays 2016 - December 22, 2016
- Ballistics - December 19, 2016
- Salted Frogs - December 15, 2016
- Negative Thermal Expansion - December 12, 2016
- Verbal Cues and Stereotypes - December 8, 2016
- Capacitance Sensing - December 5, 2016
- Gallium Nitride Tribology - December 1, 2016
- Lunar Origin - November 27, 2016
- Pumpkin Propagation - November 24, 2016
- Math Anxiety - November 21, 2016
- Borophene - November 17, 2016
- Forced Innovation - November 14, 2016
- Combating Glare - November 10, 2016
- Solar Tilt and Planet Nine - November 7, 2016
- The Proton Size Problem - November 3, 2016
- Coffee Acoustics and Espresso Foam - October 31, 2016
- SnIP - An Inorganic Double Helix - October 27, 2016
- Seymour Papert (1928-2016) - October 24, 2016
- Mapping the Milky Way - October 20, 2016
- Electromagnetic Shielding - October 17, 2016
- The Lunacy of the Cows - October 13, 2016
- Random Coprimes and Pi - October 10, 2016
- James Cronin (1931-2016) - October 6, 2016
- The Ubiquitous Helix - October 3, 2016
- The Five-Second Rule - September 29, 2016
- Resistor Networks - September 26, 2016
- Brown Dwarfs - September 22, 2016
- Intrusion Rheology - September 19, 2016
- Falsifiability - September 15, 2016
- Fifth Force - September 12, 2016
- Renal Crystal Growth - September 8, 2016
- The Normality of Pi - September 5, 2016
- Metering Electrical Power - September 1, 2016
Deep Archive 2006-2008