Eric Bell, an associate professor in astronomy, and Colin Slater, an astronomy Ph.D. student, found Andromeda XXVIII and XXIX---that's 28 and 29. They did it by using a tested star-counting technique on the newest data from the Sloan Digital Sky Survey, which has mapped more than a third of the night sky. They also used follow-up data from the Gemini North Telescope in Hawaii.
At 1.1 million and 600,000 light years from Andromeda, these are two of the furthest satellite galaxies ever detected. Invisible to the naked eye, the galaxies are 100,000 times fainter than Andromeda, and can barely be seen even with large telescopes.
The findings are published in the current Nov. 20 edition of Astrophysical Journal.
These astronomers set out looking for dwarf galaxies around Andromeda to help them understand how matter relates to dark matter, an invisible substance that doesn't emit or reflect light, but is believed to make up most of the universe's mass. Astronomers believe it exists because they can detect its gravitational effects on visible matter. With its gravity, dark matter is believed to be responsible for organizing visible matter into galaxies.
"These faint, dwarf, relatively nearby galaxies are a real battleground in trying to understand how dark matter acts at small scales," Bell said. "The stakes are high."
The prevailing hypothesis is that visible galaxies are all nestled in beds of dark matter, and each bed of dark matter has a galaxy in it. For a given volume of universe, the predictions match observations of large galaxies.
"But it seems to break down when we get to smaller galaxies," Slater said. "The models predict far more dark matter halos than we observe galaxies. We don't know if it's because we're not seeing all of the galaxies or because our predictions are wrong."
"The exciting answer," Bell said, "would be that there just aren't that many dark matter halos." Bell said. "This is part of the grand effort to test that paradigm."
The papers are titled, "Andromeda XXIX: A New Dwarf Spheroidal Galaxy 200 kpc from Andromeda," and Andromeda XXVIII: A Dwarf Galaxy more than 350 kpc from Andromeda."
The research is funded in part by the National Science Foundation.
For more information:Eric Bell: http://www.astro.lsa.umich.edu/~ericbell/
Abstract of Andromeda XXIX: A New Dwarf Spheroidal Galaxy 200 kpc from Andromeda: http://iopscience.iop.org/2041-8205/742/1/L15
Nicole Casal Moore | Newswise Science News
Computer model predicts how fracturing metallic glass releases energy at the atomic level
20.07.2018 | American Institute of Physics
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences