> Their results favour a scenario in which the young Sun engulfed a super-Earth around 5–10 times the mass of Earth
Given the state of the early solar system, it would be surprising if the Sun didn't swallow a lot of metallic and carbonaceous rocks and pebbles. But it seems unclear to me how the researchers would distinguish between one super-Earth and >10^10 smaller rocks? Chemically I feel the two would be largely the same.
This, but how do they rule out the extra stuff landing in the sun much earlier - when the solar system was still a pre-solar nebula, and which bits would end up where (sun vs. planets vs. whatever) was far from settled?
>But it seems unclear to me how the researchers would distinguish between one super-Earth and >10^10 smaller rocks?
I have a similar feeling when life on earth is suggested to be "alien", arriving via debris in the solar system as the earth formed. Isn't everything in the solar system coalesced from the same debris?
The life-bearing debris would have to arrive quite some time after formation of Earth, as it was molten. Surviving atmospheric entry is hard, surviving after landing in lava is impossible.
That always felt like a deus ex machina answer to me too. We don't know exactly how abiogenesis happened on earth so some people just like to cut off the chain of causation with the idea of, "it was seeded"... but then how did abiogenesis happen elsewhere?
I don't think that's a very popular theory among anyone who knows what they're talking though.
A hypothesis I'd seen (from the "aliens" guy, Abraham "Avi" Loeb, at Harvard) is that early in the evolution of the Universe everything was roughly in the Goldilocks zone (warm enough for liquid water, not so hot as to generate steam, not so cold as to result in ice), and ... more dense. If life more-or-less inevitably arises under such circumstances, then there's some credence to the argument that life might have arisen in many parts of the Universe, potentially hybernating in some sort of spore / inactive form, until rocky planets arose later. But we have no specific proof of this, and it seems strongly plausible that life could instead have arisen independently on individual planets and/or moons.
Same thing with people who naively believe that amino acids can only be formed in space and can only be brought to Earth in asteroids, as opposed to forming *ON* Earth.
Well if we found current or fossil life with a common ancestor on other bodies it would certainly demonstrate that it arrived via debris; whereas if we find life with no common ancestor or find no evidence of life at all that would reject the hypothesis. It wouldn't necessarily answer which body was the original birthplace, but for the purposes of modelling, whether life happened to start here is a much less impactful question than whether life had to start here. If all life here started here, then life had to develop quickly; if we could potentially descend from stuff in the pre-solar system debris field that could add billions of years to the clock, and makes interstellar panspermia highly plausible.
I don't fully follow (not being an astrophysicist), but it seems like the depth of the metallic material within the star matters a lot for their model. A planet can "bury" it (their word) a lot deeper than small rocks by physically sinking in before it gets destroyed. Sections 4.2 and 4.5 (among others I assume) in the actual paper linked above talk about this stuff.
MESA, a piece of software referenced in this article, is a pretty incredible system. (Even referring to it as software underplays the extent of its community and impact.)
Many people are involved in MESA and Bill Paxton was always quick to point out the many new folks that worked on it, but this article does a great job of celebrating his impact:
It's amazing to me that he went from being the voice on the other end of the Mother Of All Demos to having such a major impact on stellar astrophysics during his "retirement." He passed away in 2025.
You have to get nearly halfway from the surface of the sun (photospere) to its core before the density of the sun’s material is equivalent to that of the earth.
Has someone got a quick explainer for why adding a planet would result in less lithium? Is it just that a super-earth would be big enough and have so little lithium that it would measurably water down the other elements?
Not an astrophysicist, but since they mentioned the lithium is depleted, I wonder if that implies the collision of a planetary body with a sun would consume or react with the solar lithium.
Neither an astrophysics. I skimmed the paper. IIUC the collision with the planet mixed internal layers of the Sun and a lot of the Lithium went to the core and got fussed with Hydrogen.
The book Seveneves is about civilization confronting impending doom from the moon exploding. I never finished the book because I felt it was depressingly realistic.
This might just be me, but I find metaphors like ''Fingerprints' inside the Sun' harder to read than the title of the original paper, which is probably what should be linked here per HN submission guidelines:
For the press release, something like The Real Sun and Its Simulations Disagree. A Planet That Fell In Early Might Explain It. might be easier to follow.
Clearly wasn’t a “planet” — failed catastrophically at clearing its neighborhood. The Royal Astronomical Society should be ashamed for publishing something so un-scientific. /s
There are obviously many things KSP's patched conics approximation can't account for, like lagrange points or how orbits often get twisted around over time, or how the small effects from all the other solar bodies add up to be significant over time.
The simplest thing that comes to mind here is that KSP simulates a mature solar system, where space is mostly empty. This event happens in an early solar system, where there's lots of stuff everywhere. Running into stuff can steal some of the planet's momentum, causing it to fall deeper, causing it to run into more stuff
But planetary migration can be a lot more complicated than that. [1] has an overview. You might also enjoy the Grand Tack hypothesis [2] which involves early Jupiter spiraling into the inner solar system until around the orbit of current-day Mars, before eventually reversing course and getting to its current orbit further out
33 comments
[ 3.0 ms ] story [ 29.3 ms ] threadGiven the state of the early solar system, it would be surprising if the Sun didn't swallow a lot of metallic and carbonaceous rocks and pebbles. But it seems unclear to me how the researchers would distinguish between one super-Earth and >10^10 smaller rocks? Chemically I feel the two would be largely the same.
I have a similar feeling when life on earth is suggested to be "alien", arriving via debris in the solar system as the earth formed. Isn't everything in the solar system coalesced from the same debris?
I don't think that's a very popular theory among anyone who knows what they're talking though.
See this thread: <https://news.ycombinator.com/item?id=37850997>.
From which:
Kurzgesagt did a video on the concept: <https://www.youtube.com/watch?v=JOiGEI9pQBs>.
Avi Loeb, "The habitable epoch of the early Universe". International Journal of Astrobiology, vol. 13, 4."
<https://www.cambridge.org/core/journals/international-journa...>
Many people are involved in MESA and Bill Paxton was always quick to point out the many new folks that worked on it, but this article does a great job of celebrating his impact:
https://www.kitp.ucsb.edu/news/an-accidental-astrophysicist
It's amazing to me that he went from being the voice on the other end of the Mother Of All Demos to having such a major impact on stellar astrophysics during his "retirement." He passed away in 2025.
PS: The paper says that that actual A(Li)=1.1 instead of the expected A(Li)=3.3. I needed a lot of search to understand it until Gemini kindly liked this page. https://astronomy.stackexchange.com/questions/61814/what-do-...
A(Li)=1.1 means the Li/H ratio is 10^(-10.9) = 10^(-8.9)%
A(Li)=3.3 means the Li/H ratio is 10^(-9.7) = 10^(-7.7)%
Imagine being a civilization on a planet that knows it's going to be swallowed by their sun.. (during the lifetime of the living members)
> Planetary engulfment as a solution to solar-model discrepancies and its implications for planetary systems https://doi.org/10.1093/mnras/stag1527
For the press release, something like The Real Sun and Its Simulations Disagree. A Planet That Fell In Early Might Explain It. might be easier to follow.
- approach and hit directly, without spiraling
- approach, make a close fly-by and fly off into deep space again
- be in a steady, eliptical orbit
My knowledge is basically that of a Kerbal.
The simplest thing that comes to mind here is that KSP simulates a mature solar system, where space is mostly empty. This event happens in an early solar system, where there's lots of stuff everywhere. Running into stuff can steal some of the planet's momentum, causing it to fall deeper, causing it to run into more stuff
But planetary migration can be a lot more complicated than that. [1] has an overview. You might also enjoy the Grand Tack hypothesis [2] which involves early Jupiter spiraling into the inner solar system until around the orbit of current-day Mars, before eventually reversing course and getting to its current orbit further out
1: https://en.wikipedia.org/wiki/Planetary_migration
2: https://en.wikipedia.org/wiki/Grand_tack_hypothesis
Discussions on X, Reddit and HN titled "Is this it" or "Heat death is medically comfortable".
Crazy stuff.