The Field of Streams is a patch of sky where several stellar streams are visible and crisscross. The analysis of the streams of the zone determined that the dark matter

Dark matter

In astronomy and cosmology, dark matter is matter that neither emits nor scatters light or other electromagnetic radiation, and so cannot be directly detected via optical or radio astronomy...

 configuration of the Milky Way Galaxy in the inner halo is round, at variance with expectations that it would be oblate.

It was discovered by Vasily Belokurov and Daniel Zucker's team in 2006 by analyzing the Sloan Digital Sky Survey

Sloan Digital Sky Survey

The Sloan Digital Sky Survey or SDSS is a major multi-filter imaging and spectroscopic redshift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico, United States. The project was named after the Alfred P...

 II (SDSS-II) data. The team named the area Field of Streams because of so many crisscrossing trails of stars.

The Sagittarius Stream of the Sagittarius Dwarf Elliptical Galaxy

Sagittarius Dwarf Elliptical Galaxy

The Sagittarius Dwarf Elliptical Galaxy is an elliptical loop-shaped satellite galaxy of the Milky Way Galaxy. It consists of four globular clusters, the main cluster being discovered in 1994...

 (SagDEG) dominates the Field. It has a split trail within the area of the Field of Streams, because SagDEG has wrapped around the Milky Way Galaxy multiple times, which has resulted in overlapping trails. The forking of the trail has made inferences of the organization of dark matter in the inner halo of the Milky Way Galaxy possible, resulting in the determination that it is distributed in a round spherical manner, as opposed to the expected flattened spheroid. The shape of the streams also implies that the dark matter is very cold cold dark matter

Cold dark matter

Cold dark matter is the improvement of the big bang theory that contains the additional assumption that most of the matter in the Universe consists of material that cannot be observed by its electromagnetic radiation and whose constituent particles move slowly...

, due to the thin trails, and persisting existence.

Also appearing in the Field is the Monoceros Ring

Monoceros Ring

The Monoceros Ring is a ring of stars around the Milky Way which is proposed to consist of a stellar stream torn from the Canis Major Dwarf Galaxy as it merges with the Milky Way over the course of billions of years...

, which was not discovered by the team which discovered the Field.

Sources

• The Astrophysical Journal, Volume 658, Issue 1, pp. 337–344. "An Orphan in the Field of Streams"; 2007 March; Belokurov, V. et al.; ; ;
• The Astrophysical Journal, Volume 642, Issue 2, pp. L137-L140. "The Field of Streams: Sagittarius and Its Siblings"; 2006 May; Belokurov, V. et al.; ; ;
• Monthly Notices of the Royal Astronomical Society, Volume 375 Issue 4, pp. 1171–1179. "Is Ursa Major II the progenitor of the Orphan Stream?"; M. Fellhauer et al.; ;
• Science News, "Galactic de Gustibus: Milky Way's snacks shed light on dark matter and galaxy growth", Ron Cowen, 2006 July 1
• Christian Science Monitor, "Big galaxies, it seems, eat little ones", Robert C. Cowen, 2006 May 18 (accessed 2009 March 29)
• New Scientist, "Our galaxy's halo is round not squashed", Maggie McKee, 2006 May 9 (accessed 2009 March 29)