Giant impacts caused by interplanetary collisions

February 5, 2019, University of Bristol
**Giant impacts caused by interplanetary collisions
One frame from the middle of a hydrodynamical simulation of a high-speed head-on collision between two 10 Earth-mass planets. The temperature range of the material is represented by four colours grey, orange, yellow and red, where grey is the coolest and red is the hottest. Such collisions eject a large amount of the silicate mantle material leaving a high-iron content, high-density remnant planet similar to the observed characteristics of Kepler-107c. Credit: Zoe Leinhardt and Thomas Denman, University of Bristol

Astronomers have found fresh evidence for significant planetary diversity within a single exoplanet system, suggesting that giant high-speed collisions are partly responsible for planetary evolution.

An international team of scientists led by Italy's National Institute for Astrophysics (INAF) and involving physicists from the University of Bristol spent three years observing the exoplanetary system Kepler-107 via the Telescopio Nazionale Galileo in La Palma.

They gathered more than a hundred spectroscopic measurements of all four sub-Neptune mass in Kepler-107 – named after the NASA Kepler space telescope that discovered the exoplanetary system five years ago. Unlike Earth's relation to the sun, the planets in the Kelper-107 system are much closer to each other and their host star (their equivalent of our sun). All of the planets have an orbital period of days as opposed to years.

It is not uncommon for the planet that is closest to the host star to be the densest due to heating and interaction with the which can cause atmosphere loss. However, as reported in Nature Astronomy, in the case of Kepler-107, the second planet, 107c, is denser than the first, 107b. So much so that 107c contains in its core an iron mass fraction at least twice as large as that of 107b, indicating that at some point, 107c had a head-on high-speed giant collision with a protoplanet of the same mass or more collisions with multiple planets of a lower mass. These impacts would have ripped off part of the rock and silicate mantle of Kepler-107c, suggesting that it is denser now than it was originally.

Credit: University of Bristol

Bristol's Dr. Zoe Leinhardt, computational astrophysicist and co-author of the paper, from the University of Bristol's School of Physics, explains: "Giant impacts are thought to have had a fundamental role in shaping our current solar system. The moon is most likely the result of such an , Mercury's high density may be also, and Pluto's large satellite Charon was likely captured after a giant impact but until now, we hadn't found any evidence of giant impacts occurring in planetary systems outside of our own.

"If our hypothesis is correct, it would connect the general model we have for the formation of our solar system with a planetary system that is very different from our own."

Aldo Bonomo, researcher at INAF and lead author, said: "With this discovery we have added another piece in the understanding of the origin of the extraordinary diversity in composition of small exoplanets. We already had evidence that the strong irradiation of the star contributes to such diversity leading to partial or total erosion of the atmospheres of the hottest planets. However, stochastic collisions between protoplanets also play a role, and may produce drastic variations in the internal composition of an , as we think it happened for Kepler-107c."

Co-author Li Zeng, from the Harvard Origins of Life Initiative in the Department of Earth and Planetary Sciences and the Harvard-Smithsonian Center for Astrophysics, added: "This is one out of many interesting exoplanet systems that the Kepler space telescope has discovered and characterized. This discovery has confirmed earlier theoretical work suggesting that giant impact between planets has played a role during planet formation."

Giant impacts are thought to have occurred in our own solar system. If catastrophic disruptions occur frequently in planetary systems, then astronomers predict finding many other examples like Kepler-107 as an increasing number of exoplanet densities are determined.

Explore further: Boy meets world: Life-long space buff and Western graduate student discovers exoplanet

More information: Aldo S. Bonomo et al. A giant impact as the likely origin of different twins in the Kepler-107 exoplanet system, Nature Astronomy (2019). DOI: 10.1038/s41550-018-0684-9

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wduckss
1.6 / 5 (7) Feb 05, 2019
Classical disrespect of physics.

Earth at 1 AU has a molten core (Sun 5.772 ° K).
Kepler 107c circulates to 0.0564 AU (Kepler 107, 5.851 ° K), mass 9.39 ± 1.77 M Earth.
The mass of the Earth and tidal forces sufficient to melt the interior of the country at 1 AU.

Authors 107c compare with Mercury!

Kepler 107 has a larger mass than Sun (1.18 M Sun, 1,41 R Sun), the planet 107c has 9 times the mass of Earth and the distance from the star of 0.0564 AU and the huge effects of tidal forces…

Maybe it's just about total ignorance.
dirk_bruere
not rated yet Feb 06, 2019
That simulation looks like the planets collided at a good fraction of the speed of light
wduckss
1 / 5 (1) Feb 06, 2019
https://en.wikipe.../WASP-12
Details WASP-12
Mass 1.35 ± 0.14 M☉
Radius 1.57 ± 0.07 R☉
Temperature 6300 −100+200 K
Metallicity 0.3 −0.15+0.05

WASP-12b
Physical characteristics
Semi-major axis, 0.0229 ± 0.0008 AU
Mean radius, 1.900+0.057−0.055, 1.736±0.056 RJ
Mass 1.39 ± 0.04 MJ
Mean density, 326 kg/m3 (549 lb/cu yd)
Surface gravity, 1.16 g
Temperature, 2525 K

https://en.wikipe...pler-10b ; http://exoplanet....i_125_b/ ; http://exoplanet....k2-52_b/ ; http://exoplanet....p-137_b/ ; http://exoplanet....ts-55_b/ etc..
torbjorn_b_g_larsson
not rated yet Feb 06, 2019
The obvious problem is that, besides the measurement uncertainties, planetary compositions are known from modeling to have a degeneracy vs mass. That is, they really cannot tell the inner composition uniquely and well, so it is a guessing game at this point. That scientists cannot agree on how nearby Mercury formed [ https://en.wikipe...tructure ] - despite the claim of a paper author here - illustrates that problem!

@wduckss_ You troll; it is inefficient. Since this is unreadable: "The mass of the Earth and tidal forces sufficient to melt the interior of the country at 1 AU." But of interpreted as the claim that the core is heated by tidal forces means *your* ignorance is total [ https://en.wikipe...ner_core ].
torbjorn_b_g_larsson
not rated yet Feb 06, 2019
- ctd- In fact, the sentence looks like it has been pushed through Google Translate. That makes yourself out like a member of a troll factory tired of trolling political confusion and instead trying trolling science sites.
rrwillsj
1 / 5 (1) Feb 06, 2019
It is a sign of internal anxiety issues when people get so upset at an unpredictable series of random events, such as described ib this article.

Fulminating against new data resulting in new POVs.

Discumboobelating the most cherished opinion that a single, neat little explanation, fitting into a neat little box. That can we can neatly put on a neat shelf until the next time someone needs a simplistic solution for typecasting complex phenomena.

I can see why they reject continuous "Wild & Crazy". There are damn few reliable answers to any of our questions.

& as soon as we delude ourselves that we are in control of understanding the Cosmos? Some lousy-son-of-a-bitch comes up hitting us over our heads with a brickbat of "unique". Followed with a hefty boot of unwanted data vigorously applied to our fundamental "I didn't know that?!"
wduckss
not rated yet Feb 07, 2019
If trol = contemporary science on real evidence, OK.
You look in the wrong direction.
In the article https://www.svemi...correct, 26 planets are displayed with temperatures above 1500 ° K.
Pay particular attention to the discussion (table): Mass up to 15 MJ / (vs) Mass above 15 MJ and at https://en.wikipe...class_Y.
In the discussion with me. do not help quotes (Reassessment of the old but still employed theories of Universe through database checking).
wduckss
not rated yet Feb 07, 2019

Mass up to 15 MJ/(vs) Mass above 15 MJ
Brown dwarf (& planets)..Mass of Jupiter..Temperature °K…Planets orbit AU
ROXs 42Bb………………9……………… 1.950 ± 100……..157
54 Piscium B…………….50……………….810±50

DH Tauri b………………12……………….2.750……………330
ULAS J133553.45……….15 _31………….500 -550

OTS 44………………….11,5……………..1.700 - 2.300
Epsilon Indi Ba and Bb….40 – 60 (28±7)…1.300-1400 (880-940)…1.500 (between 2,1)

2MASS J2126-8140…….13,3 (± 1,7)……..1.800………………….6.900
Gliese 570………………~50 ……………..750 – 800……………..1.500
Etc.
wduckss
not rated yet Feb 07, 2019
Mass vs Mass
2M 044144………………9.8±1.8…………1.800…………………15 ± 0.6
DT Virginis……………...8.5 ± 2.5………..695±60………………1.168

Teide 1………………….57± 15…………2.600±150
Epsilon Indi Ba and Bb..40 – 60 (28±7)….1.300-1400 (880-940)…1.500 (between 2,1)

B Tauri FU…………………15……………..2.375……………………700
DENIS J081730.0-615520…15……………….950

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