Black Holes and Gaseous Giants:

[beecee]

https://phys.org/news/2018-02-black-hole-blasts-mini-neptunes-rocky.html

Black hole blasts may transform 'mini-Neptunes' into rocky worlds:

A team of astrophysicists and planetary scientists has predicted that Neptune-like planets located near the center of the Milky Way were transformed into rocky planets by outbursts generated by the nearby supermassive black hole.
 

These findings combine computer simulations with data from recent exoplanet findings, as well as X-ray and ultraviolet observations of stars and black holes.

"It's pretty wild to think of black holes shaping the evolutionary destiny of a planet, but that very well may be the case in the center of our galaxy," said Howard Chen of Northwestern University in Illinois, who led the study.

Chen and collaborators from the Harvard-Smithsonian Center for Astrophysics (CfA) examined the environment around the closest supermassive black hole to Earth: the 4 million solar mass black hole known as Sagittarius A*.

Read more at: https://phys.org/news/2018-02-black-hole-blasts-mini-neptunes-rocky.html#jCp

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the paper:

http://iopscience.iop.org/article/10.3847/2041-8213/aaab46/meta

Habitable Evaporated Cores and the Occurrence of Panspermia Near the Galactic Center:

Abstract

Black holes growing via the accretion of gas emit radiation that can photoevaporate the atmospheres of nearby planets. Here, we couple planetary structural evolution models of sub-Neptune-mass planets to the growth of the Milky Way's central supermassive black hole, Sgr A*, and investigate how planetary evolution is influenced by quasar activity. We find that, out to ~20  pc from Sgr A*, the XUV flux emitted during its quasar phase can remove several percent of a planet's H/He envelope by mass; in many cases, this removal results in bare rocky cores, many of which are situated in the habitable zones of G-type stars. Near the Galactic Center, the erosion of sub-Neptune-sized planets may be one of the most prevalent channels by which terrestrial super-Earths are created. As such, the planet population demographics may be quite different close to Sgr A* than in the galactic outskirts. The high stellar densities in this region (about seven orders of magnitude greater than the solar neighborhood) imply that the distance between neighboring rocky worlds is short (500–5000 au). The proximity between potentially habitable terrestrial planets may enable the onset of widespread interstellar panspermia near the nuclei of our galaxy. More generally, we predict these phenomena to be ubiquitous for planets in nuclear star clusters and ultra-compact dwarfs. Globular clusters, on the other hand, are less affected by the central black holes.

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OK, another interesting article and hypothesis re planetary systems. Which prompts me to ask the question re our own system in  5 billion years time, when the Sun swells to a red giant. Could stellar winds  and other probable violent activity in that period of our system, have a similar effect on Jupiter and Saturn? How about on Neptune and Uranus further out? Temperatures from the red giant would certainly be cooler, but violent stellar winds etc, could possibly have the same effects, on our gassy and icy giants, exposing their rocky cores.

Nice to see one of my own pet hypotheticals getting a mention also...Panspermia.

Continuing in the same vane, when our red giant Sun blows off the outer layer in a planetary nebula, leaving a White Dwarf, how many of the rocky cores that have been exposed could support any life if Panspermia was also an effect. White Dwarfs are incredibly hot when first formed and can maintain their heat for an incredible period before becoming a Black cinder.