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.
Thank you, that definitely was an interesting read. Sad to learn of Bill Paxton's passing. Clearly his legacy and impact however live on, like this research demonstrates.
It seems he preferred the term "software instrument" to refer to MESA:
> Bildsten and Paxton have taken to calling programs like MESA "software instruments,” according to the latter. “Just like you can’t do observational astrophysics without an instrument like a telescope," he said, "you can’t do computational astrophysics without an instrument such as MESA."
It's amazing what impact one good piece of software, freely available to anyone anywhere to use, can have on a field. I think this quote illustrated the problem he was able to solve very well:
> Ideally, you want to be able to run an experiment, but you can’t go grab a star, run an experiment for a billion years, and come back later to see how it turned out.
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.
This isn't a "changed"title. The title matches the linked "newspaper" article. But the op was saying that the research paper the article talks about has a better, easier to read, title.
> 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.
>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?
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 about 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.
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.
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.
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.
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.
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?
> Researchers also found that such a world could survive its passage through the Sun's outer layers while losing very little mass, which suggests that planets may leave detectable fingerprints inside their host stars long after they have disappeared.
So I guess the large size would have permitted it to smuggle stuff into the core that would have just vaporised in the corona if carried by many smaller objects?
It's not plain to me where you're going. But the answer about the core of a planet engulfed by the sun is that it vaporizes eventually, just not right away.
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?
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.
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.
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
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.
On a similar note, the Large low-shear-velocity provinces (LLSVPs) are structures in Earth's lower mantle that are hyothized to be remnants of Theia (the planetary-scale body that collied with, resulting in the formation of the Moon):
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.
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
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.
It seems he preferred the term "software instrument" to refer to MESA:
> Bildsten and Paxton have taken to calling programs like MESA "software instruments,” according to the latter. “Just like you can’t do observational astrophysics without an instrument like a telescope," he said, "you can’t do computational astrophysics without an instrument such as MESA."
It's amazing what impact one good piece of software, freely available to anyone anywhere to use, can have on a field. I think this quote illustrated the problem he was able to solve very well:
> Ideally, you want to be able to run an experiment, but you can’t go grab a star, run an experiment for a billion years, and come back later to see how it turned out.
> 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.
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.
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 about 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...>
Our current best guess is a geothermal vent in a high phosphorus 'soda lake' like the one in Canada. https://www.science.org/content/article/unusual-soda-lakes-m...
So I guess the large size would have permitted it to smuggle stuff into the core that would have just vaporised in the corona if carried by many smaller objects?
But also what the fuck happens to the core of such a planet when that happens?
We aren't actually sure what gave our core the spin it has, right? I'm not fully awake yet but I think it's plain where I'm going with this.
We are, it’s from the conservation of angular momentum. The material that made our planet also had a non-zero angular momentum.
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)%
- 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
https://www.nature.com/articles/s41586-023-06589-1
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)
Discussions on X, Reddit and HN titled "Is this it" or "Heat death is medically comfortable".
Crazy stuff.