The Supernova and Cepheids of Spiral Galaxy UGC 9391
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
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.
