• We hope all of you have a great holiday season and an incredible New Year. Thanks so much for being part of the Space community!

Never-before-seen rocks found in these exoplanet graveyards

Catastrophe

The devil is in the detail
I don't understand this:

"Researchers worked out the ratio of different elements in the white dwarf atmospheres by analyzing the light given off by the stars; then, they calculated the most likely makeup of the minerals that would have formed the obliterated alien worlds."

Surely any elemental composition can correspond to mixtures of a number of rock compositions? Also, the dwarf atmospheres could have accumulated over time and the elements thus being the result of different acquisitions of minerals / rocks. See also Wiki 'Rocks'.

Looking at Fe rocks will help to understand my point. From Wiki 'Iron ore':

"Iron ores[1] are rocks and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in color from dark grey, bright yellow, or deep purple to rusty red. The iron is usually found in the form of magnetite (Fe3O4, 72.4% Fe), hematite (Fe2O3, 72.9% Fe), goethite (FeO(OH), 62.9% Fe), limonite (FeO(OH)·n(H2O), 55% Fe) or siderite (FeCO3, 48.2% Fe)."

And you have the rocks from which Iron cannot be economically extracted.

By this, I mean that different rocks/minerals might have been accumulated over a long time period, and their 'perceived composition' might be very different from the 'averaged out' composition.


Cat :)
 
Last edited:
  • Like
Reactions: rod

rod

Oct 22, 2019
2,363
944
3,560
Cat post #2 is interesting. I note from the article, "Normally, the atmosphere of a white dwarf contains only hydrogen and helium, because any heavier elements sink into the star's super-dense core. So, when the light the stars give off shows the presence of other heavier elements, researchers assume that those must come from exoplanet accretion. Scientists have estimated that about 25% of all white dwarfs contain the remains of dead exoplanets or are so-called polluted white dwarfs. These exoplanet graveyards have become a hot topic of research among astronomers because scientists can use them to infer properties about the bodies that once circled them."

*polluted white dwarfs* are reported more and more and the conventional stellar evolution model is used to explain. One issue I see, the chemical composition of the MMSN and the composition of rocks found on Earth. Apparently for the *polluted white dwarfs*, their postulated early protoplanetary disks contained some metals very different than our solar system meteorites for example, or what Earth has today. Thus rocky planets could be different too. We do not have meteorites to study from these white dwarfs or other exoplanet systems so we cannot compare radiometric ages obtained from them for example. The recent Chinese lunar rocks dated were 2 billion years old compared to the Apollo samples, all much older ages reported (some 3.2 to 4.5 billion years old).
 
  • Like
Reactions: Catastrophe

rod

Oct 22, 2019
2,363
944
3,560
Rod, what implicationa do you see?

Cat :)
Interesting question Cat. Here is an implication I see. Q: what happens to white dwarf stellar evolution theory *if the metals interpreted as pollution from destroyed exoplanets, is not from destroyed exoplanets in the white dwarf spectrums?

I like the explanation for *polluted white dwarfs* but recognize that direct observations of a rocky exoplanet falling into a white dwarf star - remains unconfirmed presently like my telescope observations of the Galilean moons moving around Jupiter or numerous other exoplanet confirmed observations using radial velocity or transit measurements :)
 
  • Like
Reactions: Catastrophe

ASK THE COMMUNITY

TRENDING THREADS