Astronomy Picture of the Day -- The Supernova and Cepheids of Spiral Galaxy UGC 9391

NASA ^ | Monday, June 06, 2016 | (see photo credit)

[SunkenCiv]

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.

[SunkenCiv]

[Credit: NASA, ESA, and A. Riess (STScI/JHU) et al.]

[SunkenCiv]

There are three images on their page, small size with, and without, annotation, and the Big One, which is without. They also offer a supplemental download, "Astrophysicists: Browse 1,250+ codes in the Astrophysics Source Code Library."

The Big One

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[Red Badger]

...Cepheids and supernovas are expanding with the universe slightly faster than expected from expansion measurements of the early universe.

Well, yeah, it wasn't as big then................................

[mikrofon]

Candidate explanations range from the sensational, such as the inclusion of unusual cosmological components types such as phantom energy