Are stellar explosions created equal?

Aug 22, 2011

Cosmic distances are difficult to grasp and no less difficult to measure. When it comes to other galaxies or even remote parts of our own Milky Way, distance measurements are nothing but assessments, derived from indirect clues.

Highly important among such clues are supernovae, extremely luminous . The distance to a supernova of a particular type, called Type Ia, can be calculated from its brightness: the brighter it appears, the closer it is to the viewer. Thanks to such supernovae, for example, astronomers have famously revealed that our universe is expanding at an accelerated pace, which suggests that it's permeated with mysterious . These calculations, however, are based on the assumption that all have the same luminosity. Are all these explosions indeed created equal?

Type Ia supernovae are thought to be born when an exceedingly called a white dwarf receives more mass from a nearby star, until it's so 'overwhelmed' that it explodes. A new study reported in Science and led by Weizmann Institute researchers, has gained major insight into the nature of these mass 'donors.' The study was performed by Dr. Avishay Gal-Yam and postdoctoral fellow Dr. Assaf Sternberg of Weizmann's Particle Physics and Astrophysics Department, in collaboration with scientists from more than a dozen research centers in the United States, Europe and Australia.

The researchers have revealed that in about a quarter of the cases in spiral galaxies, and possibly more, the that 'donates' its mass to the white dwarf is probably a regular, medium-sized star, largely similar to our own Sun. They reached this conclusion by analyzing the outflow of gas, typical of sun-like stars, observed during the 'donation' of the mass. These findings constitute a major step toward determining the nature of all stellar 'donors,' with the ultimate goal of establishing whether supernovae everywhere evolve in the same manner, having the same luminosity at various stages. Understanding their evolution, in turn, can greatly enhance our ability to measure distances throughout the cosmos and map its evolution and geometry.

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User comments : 7

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omatumr
1 / 5 (6) Aug 22, 2011
Lose of faith in world leaders and government science will continue [e.g., 1] if the most powerful nuclear force - neutron repulsion [2] - is ignored.

That force - recorded in nuclear rest mass data of every nucleus with two or more neutrons - caused our Sun to give birth to the Solar System five billion years (5 Gyr) ago [3].

That is the force that powers the Sun, controls Earth's climate and sustains life.

With kind regards,
Oliver K. Manuel
Former NASA PI for Apollo

1. Gillard convoy of no confidence, The International News Magazine (19 Aug 2011):

http://www.intern...ce-rally]http://arxiv.org/...2.1499v1[/url]

2. Neutron Repulsion, The APEIRON Journal, in press, 19 pages (2011):

http://arxiv.org/...2.1499v1

3. "Strange xenon, extinct super-heavy elements, and the solar neutrino puzzle", Science 195, 208 (1977)
frajo
not rated yet Aug 22, 2011
the assumption that all Type Ia supernovae have the same luminosity
This is but one phrasing underlying the logical reasoning in calculating SN Ia distances.
Another phrasing is the hypothesis that all white dwarfs in an SN Ia combination are exploding in exactly the same way.
This is a bit astonishing as this hypothesis effectively dismisses all physical parameters except mass.
Nik_2213
5 / 5 (1) Aug 22, 2011
You must ask if 'Population II & III' stars, ie those with less metallicity, will go supernova in exactly the same way as our familiar 'I' variety. The differences may be subtle, easily masked by fast rotation and other effects but, IMHO, could skew results in a way that roughly correlates with distance hence age...
FWIW: http://en.wikiped...allicity
hard2grep
not rated yet Aug 22, 2011
You can't blame scientists for feeling their hind ends these days. One day you have a discovery, the next day everyone is wrong. If I ever discover something great, I will first denounce it in preparation of hind sight.
hard2grep
not rated yet Aug 22, 2011
I wonder how many planet-sized diamonds we have foating about the universe?
antialias_physorg
5 / 5 (1) Aug 23, 2011
The differences may be subtle, easily masked by fast rotation and other effects but, IMHO, could skew results in a way that roughly correlates with distance hence age...

Why should that correlate with distance? If anything the differences in Type Ia luminosity should fluctuate around a mean due to variations in factors which _might_ affect luminosity (element content of the star, rotation, gravitational environment, ... )

As for chemical composition: Stars which are further away (older) should have a higher hydrogen content than second/third generation stars. Conversely older stars should have a lower metal content.
Still: the content of other elements is so small - even in newer stars (as a percentage of total mass) - and the creation of these elements prior to/during the supernova is what adds most of those for older and newer stars). So element composition shouldn't matter much.
jsdarkdestruction
not rated yet Aug 25, 2011
I wonder how many planet-sized diamonds we have foating about the universe?

according to this article at least 1.
http://www.physor...deo.html