Nature article turns theory of stellar evolution upside-down

January 12, 2018 by Mathieu-Robert Sauvé, University of Montreal
Credit: University of Montreal

This week, Nature published an article that could challenge the theory of stellar evolution.

"I think that, over the coming months, stellar astrophysicists will have to redo their calculations," said Gilles Fontaine, a physics professor at Université de Montréal and one of the authors of the article, titled "A large oxygen-dominated core from the seismic cartography of a pulsating white dwarf."

Its lead author is Noemi Giammichele, who completed her doctorate in 2016 under the joint supervision of Fontaine and his colleague Pierre Bergeron, both of whom co-authored the article along with six other researchers. The piece reports on a study of data collected by the Kepler Space Telescope.

"We were able to map the interior of a pulsating with precision, as if we'd sliced it into cross-sections to study its composition," said Giammichele, now a post-doctoral fellow at Université de Toulouse, in France. The map showed the star's vibrations sometimes reach all the way to its centre.

White dwarfs "are the core remnants of nearly 97% of the in the Universe," explained Robert Lamontagne, head of media relations at UdeM's Centre for Research in Astrophysics. "As stars slowly die, inexorably cooling down in the form of , they experience periods of instability in which they vibrate. These deep vibrations – or starquakes – are the key to seeing right into the very interior of these stellar remnants."

From a distance of 1,375 light-years from Earth, white dwarf KIC08626021 emits light that is barely visible by telescopes on Earth. The Kepler, however, can focus on it over an extended period, resulting in significantly more detailed images. Because the Montreal researchers were able to access the space telescope, the authors were able to take a close look at this small star – about the size of the Earth – and its vibrations.

Nearly 300 experts worldwide specialize in studying white dwarfs. Giammichele's initial goal was to verify a theory on this final stage of a star's life cycle. The theory proved correct, but the team's observations led to a number of surprising discoveries.

A bigger core

When examining the star, located at the edges of the Cygnus and Lyra constellations, the researchers discovered that its carbon and oxygen core was twice as big as the theory predicted. "This is a major discovery that will force us to re-evaluate our view of how stars die," said Fontaine. "That said, more work must be done to confirm whether this observation holds true for other stars. It may just be an anomaly."

"We must try to reproduce these results with other celestial bodies before we can make any conclusions," Giammichele agreed. Although KIC08626021 was the first pulsating white dwarf identified by the Kepler telescope, approximately 60 more have since been discovered, she added. "I have enough data to spend the next 20 years analyzing them one by one."

Ground-breaking method

The new article is Fontaine's fourth in Nature, one of the world's top scientific magazines, and its publication closes a circle in his career. In 1978, the professor glimpsed the potential for determining the internal structure of a pulsating white dwarf through a solid understanding of the theory of . "But there was still a long way to go," he recalled. "First, we had no access to high-quality images because terrestrial telescopes gave us very imprecise images of these bodies. Then we had to create the analytical tools, the software, etc. And last but not least, we had to find the right person to pursue this lead."

Fontaine praised his former student, who developed an innovative approach to achieve her goals. As a graduate of Polytechnique Montréal with a master's in mechanical engineering, Giammichele applied methods used for calculating the aerodynamics of airplane wings to astrophysics. "I believe this approach is what allowed us to move forward," said Fontaine, adding that five of the other co-authors studied under him as well.

For her part, Giammichele is pleased that one of the five articles comprising her doctoral thesis will now reach a broader audience. "What I want to do now, in terms of my career, is keep doing research," she said. "That's what I like most: figuring out how to solve problems."

Explore further: New discovery finds starving white dwarfs are binge eaters

More information: N. Giammichele et al. A large oxygen-dominated core from the seismic cartography of a pulsating white dwarf, Nature (2018). DOI: 10.1038/nature25136

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15 comments

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BobSage
1.5 / 5 (15) Jan 12, 2018
But the stellar evolution theory was settled science. Are these researchers deniers?
PTTG
2.4 / 5 (5) Jan 12, 2018
It helps to have evidence.

By the way, be sure to ask your boss about оборот.
Gigel
4.3 / 5 (6) Jan 13, 2018
But the stellar evolution theory was settled science. Are these researchers deniers?

Nothing is settled in science. Anything can still be improved. Models are only approximate and better approximations are possible.
blazmotronic
1.6 / 5 (7) Jan 13, 2018
As technology improves scientists are finding out how little they know..
lots of supposition and conjecture.
torbjorn_b_g_larsson
3.7 / 5 (3) Jan 14, 2018
Seems to me mackita is correct, Fontaine is excited about possibly seeing traces of late stages engulfed planets: http://www.exopla...?lang=en .Not exactly touching the early and main stages of fusion controlled star evolution, but how systems transform to white dwarf systems.

As technology improves scientists are finding out how little they know..
lots of supposition and conjecture.


No, it is the opposite: by testing knowledge we find out that the methods work, the extent of what is assumed, how robust the results are and how much we already know. Consider that they found just twice as much oxygen as expected, and that some or all of the difference could have been external to fusion controlled star evolution.

Millions of scientists have worked hard for 5 centuries on laboriously achieving knowledge, for the first time in human history. Do you really think they would have done that without some modicum of success?
katesisco
1.3 / 5 (3) Jan 14, 2018
mackita sounds good. On utube Dr Albers says 'sun cores' are feeding on the sun. Maybe, I have seen theories that our Sol is the result of a planetary nova. I think something like that produced the inner planets.
ellbeeyoo
5 / 5 (2) Jan 14, 2018
Many questions left unasked and unanswered. What are the limits of each fluctuation? Did the core appear twice as large b/c of a fluctuation? What other characteristics did they get data on? I realize this is just a summary and for complete info we have to read the article/paper itself. But we should get a little more here to even decide if we want to see the full record.
Caliban
1 / 5 (1) Jan 14, 2018
These are interesting observations --there's no denying that.

One can accept, reject, or remain neutral with total impunity at this point, since we are only speaking conjecturally about what mechanism produced these reputedly anomalous conditions.

Like it or not, we'll have to wait for this methodology to be examined and for further observational confirmation by other researchers --aka-- replication of results, before a ruling can be made.

Having said that, it should be obvious to anyone that the stellar environment has a role to play in the evolution of a star, throughout its evolution. Still, it is rather surprising that so much of the star's mass is composed of these light elements following a nova, as sweeping up planetary material to augment the remaining carbon and oxygen to such an extent seems a little far-fetched.

Maybe what they've found is actually one of @Tuxford's matter-emmitting core stars.

contd
Caliban
1 / 5 (1) Jan 14, 2018
contd

In case any of you didn't detect it --the part about the "matter-emitting core star" was pure sarcasm.

I am interested in hearing what Giammichelle's peers have to say regarding the validity of her newly devised analytical method, which must be verified before the debate can legitimately go forward.

If it is found to be valid, however, then it will make it possible to verify many things about the nature and composition of white dwarfs. It seems likely that considerable variability would be the rule, but also likely that the variability will fall into pretty narrow deviations, so it still remains to be seen if this particular star would qualify as an actual anomaly.

As for the "anomaly" itself, how far back in time would we have to go to reconstruct all of the relevant environmental factors that may have been present to lead to its present condition?

It certainly would have been helpful if the writer of this article had provided the Numbers in question.
Hyperfuzzy
1 / 5 (1) Jan 14, 2018
No sure this actually addresses the issue of how many possibilities exists for charge within a large mass( large set of charges, and possibilities of states from the center to the outside boundaries). One may surmise the existence of anti-matter and matter, which always settles or explode; however, often with recurring like events. So the cooling of a star is more likely due to such events. The other events, not containing different orbiters, anti-matter, define a very large set of things. Like massive currents, or currents that dance. Note: the charges near the surface and the boundary conditions under the above and without the above. Without any instability, expect impacts of near charges, scattering charges and reflected charges and the reflected fields. With any of the above constraints, these events may or may not be separable. So I really do not think we know anything about the reality of any star!
Hyperfuzzy
1 / 5 (2) Jan 14, 2018
See https://drive.goo...XPRU3FG, if any argument, please state your Logic; especially, any verifiable axiom. Please don't say a constant speed of light. That's not true. In fact the speed of the field update is relative. One could try a 2 point measurement; however, you need the original speed relative the containing object. Note: that light is simply the sinusoidal field update due to charge motion. That charge may move in a circle, an ellipsoid, or any path that will define that field. So the charge's motion then 2*Pi*r/T = c? Nonsense! So we don't actually know how fast this wavelet moves unless we try c*Lambda_Emitted/Lambda_Observed.
Hyperfuzzy
1 / 5 (1) Jan 14, 2018
Finally, at this distance, the origin of the light is questionable, i.e light that might have traveled through our local galaxy cluster is therefore corrupted. I leave the math to the astronomers and astrophysicist to define first what do we see? Don't give me that space is expanding nonsense. Obliviously we are within stream of galaxies, don't fight the local forces hold galaxies together. This isn't even that hard to verify. Expanding, looking for a freaking constant cause your theory is wrong, nonsense. A force cause these galaxies to move. Therefore due the acceleration as a function of distance to the actual direction these objects are moving. You need 3 vectors over time per object and they may be + or -!
antialias_physorg
5 / 5 (9) Jan 15, 2018
But the stellar evolution theory was settled science.

If there was anything like settled science we wouldn't be doing science.

There's still a lot to learn - that's the fun part.
Hyperfuzzy
1 / 5 (2) Jan 15, 2018
But the stellar evolution theory was settled science.

If there was anything like settled science we wouldn't be doing science.

There's still a lot to learn - that's the fun part.

Theoretical physics has been my hobby since I was 11. Since I'm Black, I wish we had the real interpretations of the Ancient Hieroglyphics. I think there was something there we really need to honor. First civilization not in our history because they were Black, wow! Yes we have a lot to learn. oops https://drive.goo...nXPRU3FG
wduckss
1 / 5 (1) Jan 18, 2018
From 200 to 400 billion stars in the Milky Way, many White dwarfs (60 White dwarfs) have been found! A Very Relevant Number To Cast The Author: "White Dwarfs" are the core remnants of nearly 97% of the stars in the Universe,
Where this knowledge is being studied, that I enroll?

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