JPL: Astronomers Upgrade Their Cosmic Light Bulbs

[bystander]

Astronomers Upgrade Their Cosmic Light Bulbs
NASA | JPL-Caltech | UC Berkeley | 2015 Mar 26

[i]A new study analyzes several sites where dead stars once exploded. [b](Credit: SDSS)[/b][/i]

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The brilliant explosions of dead stars have been used for years to illuminate the far-flung reaches of our cosmos. The explosions, called Type Ia supernovae, allow astronomers to measure the distances to galaxies and measure the ever-increasing rate at which our universe is stretching apart.

But these tools aren't perfect. In the cosmic hardware store of our universe, improvements are ongoing. In a new report, appearing March 27 in the journal Science, astronomers identify the best, top-of-the-line Type Ia supernovae for measuring cosmic distances, pushing other, more clunky tools to the back of the shelf.

Using archived data from NASA's Galaxy Evolution Explorer (GALEX), scientists show that a particular class of Type Ia supernovae that occur near youthful stars can improve these measurements with a precision of more than two times that achieved before. ...

The findings will help light the way to understanding dark energy, one of the greatest mysteries in the field of cosmology, the study of the origin and development of the universe. Dark energy is the leading culprit behind the baffling acceleration of our cosmos, a phenomenon discovered in 1998. The acceleration was uncovered when astronomers observed that galaxies are pulling away from each other at increasing speeds. ...

Better ‘Cosmic Candles’ to Illuminate Dark Energy
Symmetry Magazine | 2015 Mar 26

Distances with <4% Precision from Type Ia Supernovae in Young Star-Forming Environments - Patrick L. Kelly et al

• Science 347(6229) 1459 (27 Mar 2015) DOI: 10.1126/science.1261475
  arXiv.org > astro-ph > arXiv:1410.0961 > 03 Oct 2014 (v1), 26 Mar 2015 (v2)

[Ann]

I would have loved to post this in the "Breaking News" forum, but I can't do it since the news is about 30 months old!

Astronomynow wrote:

Click to view full size image

Type Ia supernovae, which occur when burnt-out stars called white dwarfs detonate,
have been used for years to help measure the distances to galaxies and the acceleration
of our universe. Using data from NASA’s Galaxy Evolution Explorer, or GALEX,
astronomers were able to show that a fraction of the Type Ia explosion sites they
looked at are associated with hot young stars. The astronomers then went on to show
that these particular explosions occurred in more consistent ways, and thus are better
standard tools for cosmology. From left to right and top to bottom, the galaxies (and
supernovae) are: NGC 6038 (SN 1999cc), UGC 5234 (SN 2003W), A112539+2249 (SN
2004as), A225942-0000 (SN 2005ku), M+05-54-41 (SN 2006en), UGC 14 (SN 2006sr), UGC 8162
(SN 2007F) and IC 807 (SN 2007cp). Image credit: SDSS

The brilliant explosions of dead stars have been used for years to illuminate the far-flung reaches of our cosmos. The explosions, called Type Ia supernovae, allow astronomers to measure the distances to galaxies and measure the ever-increasing rate at which our universe is stretching apart.

But these tools aren’t perfect. In the cosmic hardware store of our universe, improvements are ongoing. In a new report, appearing March 27th in the journal Science, astronomers identify the best, top-of-the-line Type Ia supernovae for measuring cosmic distances, pushing other, more clunky tools to the back of the shelf.

Using archived data from NASA’s Galaxy Evolution Explorer (GALEX), scientists show that a particular class of Type Ia supernovae that occur near youthful stars can improve these measurements with a precision of more than two times that achieved before.

“We have discovered a population of Type Ia supernovae whose light output depends very precisely on how quickly they fade, making it possible to measure very exact distances to them,” said Patrick Kelly of the University of California, Berkeley, lead author of the new study. “These supernovae are found close to
populations of bright, hot young stars.”
...
The results showed that the Type Ia supernovae affiliated with the
hot, young stars were significantly more reliable at indicating
distances than their counterparts.

“These explosions are likely the result of youthful white dwarfs,” said Kelly...

To me, these result are particularly interesting, since I believe that most white dwarfs in the universe are the end products of stars that are (considerably) more massive than the Sun. The reason for my belief is that most stars with the mass of the Sun aren't old enough to have turned into white dwarfs yet, and to me, white dwarfs from solar-mass stars are a bit of a mystery.

I find it somehow "satisfying" that young white dwarfs near star forming regions are more reliable standard candles than old white dwarfs. It seems obvious to me that young white dwarfs near star forming regions are most likely the end products of stars considerably more massive than the Sun.

Star formation is winding down in the universe. In the future, several billion years from now, there will be fewer youthful massive white dwarfs that can explode as supernovas type Ia and shine as reliable standard candles across billions of light years. Doing cosmology will be harder in the far future, when the universe has moved farther along its path of winding down.

Ann