Astronomy Picture of the Day
    


The Supernova and Cepheids of Spiral Galaxy UGC 9391
<< Yesterday 6.06.2016 Tomorrow >>
The Supernova and Cepheids of Spiral Galaxy UGC 9391
Credit & Copyright: NASA, ESA, and A. Riess (STScI/JHU) et al.
Explanation: What can this galaxy tell us about the expansion rate of the universe? Perhaps a lot because UGC 9391, featured, not only contains Cepheid variable stars (red circles) but also a recent Type Ia supernova (blue X). Both types of objects have standard brightnesses, with Cepheids typically being seen relatively nearby, while supernovas are seen much further away. Therefore, this spiral is important because it allows a calibration between the near and distant parts of our universe. Unexpectedly, a recent analysis of new Hubble data from UGC 9391 and several similar galaxies has bolstered previous indications that Cepheids and supernovas are expanding with the universe slightly faster than expected from expansion measurements of the early universe. Given the multiple successes of early universe concordance cosmology, astrophysicists are now vigorously speculating about possible reasons for this discrepancy. Candidate explanations range from the sensational, such as the inclusion of unusual cosmological components types such as phantom energy and dark radiation, to the mundane, including statistical flukes and underestimated sources of systematic errors. Numerous future observations are being planned to help resolve the conundrum.

Astrophysicists: Browse 1,250+ codes in the Astrophysics Source Code Library

January
February
March
April
May
June
July
August
September
October
November
December
 < June 2016  >
Mo Tu We Th Fr Sa Su


12345
6789101112
13141516171819
20212223242526
27282930


Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Web Site Statements, Warnings, and Disclaimers
NASA Official: Jay Norris. Specific rights apply.
A service of: LHEA at NASA / GSFC
& Michigan Tech. U.

Based on Astronomy Picture Of the Day

Publications with keywords: supernova - cepheid - spiral galaxy
Publications with words: supernova - cepheid - spiral galaxy
See also:
All publications on this topic >>