Astronomers discover first direct evidence of white dwarf stars solidifying into crystals

January 9, 2019, University of Warwick
White dwarf star in the process of solidifying. Credit: University of Warwick/Mark Garlick

The first direct evidence of white dwarf stars solidifying into crystals has been discovered by astronomers at the University of Warwick, and our skies are filled with them.

Observations have revealed that dead remnants of stars like our Sun, called white dwarfs, have a core of solid oxygen and carbon due to a phase transition during their lifecycle similar to water turning into ice but at much higher temperatures. This could make them potentially billions of years older than previously thought.

The discovery, led by Dr. Pier-Emmanuel Tremblay from the University of Warwick's Department of Physics, has been published in Nature and is largely based on observations taken with the European Space Agency's Gaia satellite.

White dwarf stars are some of the oldest stellar objects in the universe. They are incredibly useful to astronomers as their predictable lifecycle allows them to be used as cosmic clocks to estimate the age of groups of neighboring stars to a high degree of accuracy. They are the remaining cores of red giants after these huge stars have died and shed their outer layers and are constantly cooling as they release their stored up heat over the course of billions of years.

The astronomers selected 15,000 white dwarf candidates within around 300 light years of Earth from observations made by the Gaia satellite and analysed data on the stars' luminosities and colours.

They identified a pile-up, an excess in the number of stars at specific colours and luminosities that do not correspond to any single mass or age. When compared to evolutionary models of stars, the pile-up strongly coincides to the phase in their development in which latent heat is predicted to be released in large amounts, resulting in a slowing down of their cooling process. It is estimated that in some cases these stars have slowed down their aging by as much as 2 billion years, or 15 percent of the age of our galaxy.

Dr. Tremblay said: "This is the first direct evidence that white dwarfs crystallise, or transition from liquid to solid. It was predicted fifty years ago that we should observe a pile-up in the number of white dwarfs at certain luminosities and colours due to crystallisation and only now this has been observed.

"All white dwarfs will crystallise at some point in their evolution, although more massive white dwarfs go through the process sooner. This means that billions of white dwarfs in our galaxy have already completed the process and are essentially crystal spheres in the sky. The Sun itself will become a crystal white dwarf in about 10 billion years."

Crystallisation is the process of a material becoming a solid state, in which its atoms form an ordered structure. Under the extreme pressures in white dwarf cores, atoms are packed so densely that their electrons become unbound, leaving a conducting electron gas governed by quantum physics, and positively charged nuclei in a fluid form. When the core cools down to about 10 million degrees, enough energy has been released that the fluid begins to solidify, forming a metallic core at its heart with a mantle enhanced in carbon.

Dr. Tremblay adds: "Not only do we have evidence of heat release upon solidification, but considerably more energy release is needed to explain the observations. We believe this is due to the oxygen crystallising first and then sinking to the core, a process similar to sedimentation on a river bed on Earth. This will push the carbon upwards, and that separation will release gravitational energy.

"We've made a large step forward in getting accurate ages for these cooler white dwarfs and therefore old of the Milky Way. Much of the credit for this discovery is down to the Gaia observations. Thanks to the that it is capable of, we have understood the interior of white dwarfs in a way that we never expected. Before Gaia we had 100-200 with precise distances and luminosities—and now we have 200,000. This experiment on ultra-dense matter is something that simply cannot be performed in any laboratory on Earth."

Explore further: Ultra-hot gas around remnants of sun-like stars

More information: Pier-Emmanuel Tremblay et al, Core crystallization and pile-up in the cooling sequence of evolving white dwarfs, Nature (2019). DOI: 10.1038/s41586-018-0791-x

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19 comments

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rrwillsj
2.8 / 5 (5) Jan 09, 2019
Now that? That is ***BLING***!!
Surveillance_Egg_Unit
4.4 / 5 (5) Jan 09, 2019
Interesting. So these old white dwarves eventually solidify/crystallise. But then what happens to them afterwards?
Da Schneib
1.6 / 5 (9) Jan 09, 2019
So jebus dint doit?
Surveillance_Egg_Unit
2.5 / 5 (8) Jan 09, 2019
So jebus dint doit?
says Da Pussyman

Dint do what?
Ojorf
2.5 / 5 (8) Jan 10, 2019
Din't do nuttin.
Da Schneib
3 / 5 (10) Jan 10, 2019
https://www.ncbi....28392301

The origins of religious fundamentalism appear to be brain lesions.
granville583762
2.3 / 5 (9) Jan 10, 2019
Crystal Dwarfs

Crystalline carbon
crystalline oxygen
forms as a star
when in 15Billion years
unburdens its mortal coil
is
Interesting, not because it will give global warmists a fit
with all that potential carbon and oxygen transmuting to CO2
Its interest
is
that it is at the end of life
of 15billion years
because
we have observed
theorised
or
just mused on the speculation of carbon and oxygen crystal dwarfs
the
latest estimate of existence of this vacuum
is 13.8Billion years
so if we ever observe this highly speculative crystal dwarf
Georges Lemaitre
will rise from eternity
will give a sermon non will forget
as
no one is amenable to their theories
confined to history
because
all their life's work is no more
because
potentially
These crystal dwarfs are older than the Cosmic Egg it's self
granville583762
2.3 / 5 (9) Jan 10, 2019
As the doubters

Reach for their scribe
according to phys.org
The Sun itself will become a crystal white dwarf in about 10 billion years
as the earth is 4.5Billion years
that the sun being fractionally older by seniority
maketh this sun
in
our heaveans
when it crystallizes to its dwarf
in
15Billion years
so this theory is interesting
this crystal dwarf is illuminating
this theory is stimulating
in that
it questions existence itself
as all stars in this vacuum are interlinked
as the vacuum consists almost solely of stars
the age of of existence
is entwined with starry existence
that
we cannot observe any star
in theory 15Billion years old
as
the vacuum being 13.8Billion years
that
as we observe these crystal stars
Bang goes our Bigbang
Runesmith
3.8 / 5 (4) Jan 10, 2019
"... although more massive white dwarfs go through the process sooner. This means that billions of white dwarfs in our galaxy have already completed the process and are essentially crystal spheres in the sky. The Sun itself will become a crystal white dwarf in about 10 billion years."

There are more massive stars than the Sun
Have been always; with nowhere to run

Massive white dwarfs have crystallized already
But those little 'uns are still holding steady

Rhyming's good, when you have time to kill
But reading comprehension is an essential skill
Da Schneib
3 / 5 (6) Jan 10, 2019
In about 4 billion years, the Sun will be a red giant.

After that, it will blow off its outer layers and become a white dwarf.

In about another 6 billion years, it will cool off enough to crystallize like this.

Does that get it across?

Sorry I don't care enough to make rhymes. I'll stick with prose.
granville583762
3 / 5 (4) Jan 10, 2019
The age is when our sun becomes a crystal dwarf
Da Schneib> In about 4 billion years, the Sun will be a red giant.
After that, it will blow off its outer layers and become a white dwarf.
In about another 6 billion years, it will cool off enough to crystallize like this.
Does that get it across?
Sorry I don't care enough to make rhymes. I'll stick with prose.

4.5+4.0+6.0 = 14.5
close enough to 15billion years
it's the age when this sun forms
this crystal dwarf
because
that is how we identify our sun
As it will be a crystal dwarf
granville583762
3.4 / 5 (5) Jan 10, 2019
Runesmith

The flaw in this end of life
is when a typical star, our sun
alone in this vacuum with the majority of galactic stars
dead in this vacuum
as
each galaxy is only a sum of its collection of stars
as these stars become cold dead lumps of immensely dense rock
this galactic universe
only exists
because
these stars are regenerating
cold dead lumps of immensely dense rock
will survive billions of trillions of years
without ever encountering another cold dead lump of immensely dense rock
without collisions these lumps off rock
are
10s, 100s or even 1000s of light years apart
Frozen solid alone in this vacuum for eternity
SkyLight
5 / 5 (5) Jan 10, 2019
Marvellous to see the datasets from Gaia being used as the basis of so much new work in astronomy and astrophysics. And there's so much more to come!
SkyLight
5 / 5 (4) Jan 10, 2019
I was wondering at first what rôle electron degeneracy might play in the crystallization process. And then I realized it would be none at all: the crystallization would occur between the ions in the WD's body, and the electron degeneracy would remain untouched by the process.

Also, the pressures and pressures in the WD are far too low for the ions/protons to become degenerate themselves. Wish I could say the same for the neurons in the PO trolls' brains...
granville583762
4 / 5 (4) Jan 10, 2019
Regeneration in crystal form
Skylight> the crystallization would occur between the ions in the WD's body,
the pressures and pressures in the WD are far too low for the ions/protons to become degenerate

Maybe that is the clue, this crystal dwarf regenerates into its constituents nucleons in time
torbjorn_b_g_larsson
5 / 5 (4) Jan 10, 2019
Wish I could say the same for the neurons in the PO trolls' brains...


Yeah, you know that when they go for poetry they are really desperate for attention (but gets less since it is even more incomprehensible chatter). Dense dunces, indeed; but it acts like the gravel on a road, you step on it and you don't even notice after a while. It is when others comment on it that I see it nowadays.
rrwillsj
not rated yet Jan 11, 2019
uhh, granny, perhaps I am misunderstanding? That the galaxies only exist while the stars are shining?

Cause my understanding is there will eventually be a whole lot of cold, dead "Dark Galaxies" consisting of these dead cold dead crystallizing stars. All held together by their mutual gravity.

Temporarily over a span of a trillion years or so. Locally maybe within a few hundred billion parsecs radius.

Long after the expanding Universe separates the gravitational-bound clusters of Galaxies beyond the light-speed boundary.
johnqsmith
not rated yet Jan 14, 2019
"This will push the carbon upwards, and that separation will release gravitational energy." Okay, I can see that energy will be released when the heavier solid oxygen sinks, pushing up carbon, and the friction opposed to these motions will heat the surroundings. I presume this energy release is in addition to the latent heat energy release from only the conversion of liquid oxygen to solid.
JaxPavan
1 / 5 (1) Jan 18, 2019
How long do they have to cool before they are no longer detectable?

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