Seth Jacobson
@sethajacobson.bsky.social
Planetary Scientist @MSU www.planetarymakerspace.org
Lastly, both Bailey et al. (2016) and Gomes et al. (2017) showed independently that the Sun's obliquity may be explained by the ejection and re-capturing of an outer wide planet.
6/7
6/7
May 27, 2025 at 6:09 PM
Lastly, both Bailey et al. (2016) and Gomes et al. (2017) showed independently that the Sun's obliquity may be explained by the ejection and re-capturing of an outer wide planet.
6/7
6/7
A giant planet instability is the leading explanation for the orbits of the giant planets (aka the Nice model), and the best hypotheses for how that instability does eject planet-sized bodies (some as large Uranus or Neptune). It also explains a number of other features of the solar system.
3/7
3/7
May 27, 2025 at 6:09 PM
A giant planet instability is the leading explanation for the orbits of the giant planets (aka the Nice model), and the best hypotheses for how that instability does eject planet-sized bodies (some as large Uranus or Neptune). It also explains a number of other features of the solar system.
3/7
3/7
From a planet formation perspective, the same history and physics that leads to the creation of the Oort Cloud of comets would also apply to planet-sized bodies. Objects ejected from the planet region can be bound back onto wide elliptical orbits in the presence of the Sun's birth cluster.
2/7
2/7
May 27, 2025 at 6:09 PM
From a planet formation perspective, the same history and physics that leads to the creation of the Oort Cloud of comets would also apply to planet-sized bodies. Objects ejected from the planet region can be bound back onto wide elliptical orbits in the presence of the Sun's birth cluster.
2/7
2/7
"Do you think Planet 9 exists?"
The observational evidence is limited by small number statistics. That's often enough for many to conclude, somewhere between unlikely and no. But, I lean further towards more-likely-than-not, and a new paper out today helps explain why I've thought this way.
1/7
The observational evidence is limited by small number statistics. That's often enough for many to conclude, somewhere between unlikely and no. But, I lean further towards more-likely-than-not, and a new paper out today helps explain why I've thought this way.
1/7
May 27, 2025 at 6:09 PM
"Do you think Planet 9 exists?"
The observational evidence is limited by small number statistics. That's often enough for many to conclude, somewhere between unlikely and no. But, I lean further towards more-likely-than-not, and a new paper out today helps explain why I've thought this way.
1/7
The observational evidence is limited by small number statistics. That's often enough for many to conclude, somewhere between unlikely and no. But, I lean further towards more-likely-than-not, and a new paper out today helps explain why I've thought this way.
1/7
The bulk C/O ratio within a planet may reveal much about the origin of the planet's building blocks. In the plot below, Cavalié et al. point out that even within the solar system, transforming atmospheric abundances into a bulk ratio is fraught. 1/2
arxiv.org/abs/2407.07515
arxiv.org/abs/2407.07515
May 19, 2025 at 2:21 AM
The bulk C/O ratio within a planet may reveal much about the origin of the planet's building blocks. In the plot below, Cavalié et al. point out that even within the solar system, transforming atmospheric abundances into a bulk ratio is fraught. 1/2
arxiv.org/abs/2407.07515
arxiv.org/abs/2407.07515
Illuminating map of where humanity has done deep sea diving expeditions. Most of the ocean floor has been unexplored!
Note that the hotspots over-emphasized explored regions because the actual areas visited are very small. From: www.science.org/doi/10.1126/...
Note that the hotspots over-emphasized explored regions because the actual areas visited are very small. From: www.science.org/doi/10.1126/...
May 12, 2025 at 9:24 PM
Illuminating map of where humanity has done deep sea diving expeditions. Most of the ocean floor has been unexplored!
Note that the hotspots over-emphasized explored regions because the actual areas visited are very small. From: www.science.org/doi/10.1126/...
Note that the hotspots over-emphasized explored regions because the actual areas visited are very small. From: www.science.org/doi/10.1126/...
The verdict is still out on which is the right interpretation, but I'll stop this thread with two relevant facts.
1. Meteorites from Vesta have been interpreted as being sourced from a fully differentiated world. No metal blebs or other signs of incomplete differentiation. 6/7
1. Meteorites from Vesta have been interpreted as being sourced from a fully differentiated world. No metal blebs or other signs of incomplete differentiation. 6/7
April 30, 2025 at 9:19 PM
The verdict is still out on which is the right interpretation, but I'll stop this thread with two relevant facts.
1. Meteorites from Vesta have been interpreted as being sourced from a fully differentiated world. No metal blebs or other signs of incomplete differentiation. 6/7
1. Meteorites from Vesta have been interpreted as being sourced from a fully differentiated world. No metal blebs or other signs of incomplete differentiation. 6/7
The other scenario:
2) Vesta is a piece of planetary ejecta---giant impacts during the era of planet formation may have created lots of Vesta-sized debris (see figure from Asphaug et al., 2006). This debris would have had varying silicate-to-metal contents. 5/7
2) Vesta is a piece of planetary ejecta---giant impacts during the era of planet formation may have created lots of Vesta-sized debris (see figure from Asphaug et al., 2006). This debris would have had varying silicate-to-metal contents. 5/7
April 30, 2025 at 9:19 PM
The other scenario:
2) Vesta is a piece of planetary ejecta---giant impacts during the era of planet formation may have created lots of Vesta-sized debris (see figure from Asphaug et al., 2006). This debris would have had varying silicate-to-metal contents. 5/7
2) Vesta is a piece of planetary ejecta---giant impacts during the era of planet formation may have created lots of Vesta-sized debris (see figure from Asphaug et al., 2006). This debris would have had varying silicate-to-metal contents. 5/7
The moment of inertia of a planetary body reveals how mass is distributed within it. The re-analyzed Dawn data revealed the moment of inertia of Vesta for the first time and established a best-fit model for the interior with a nearly constant density through the interior of the body. 3/7
April 30, 2025 at 9:19 PM
The moment of inertia of a planetary body reveals how mass is distributed within it. The re-analyzed Dawn data revealed the moment of inertia of Vesta for the first time and established a best-fit model for the interior with a nearly constant density through the interior of the body. 3/7
Vesta is the 2nd largest asteroid and the parent body to many asteroid family members and meteorites that made their way to Earth. It was the target of NASA's Dawn mission, which orbited it for 14 months in 2011-2012. It's a leftover from the era of planet formation. But what kind of leftover? 1/7
April 30, 2025 at 9:19 PM
Vesta is the 2nd largest asteroid and the parent body to many asteroid family members and meteorites that made their way to Earth. It was the target of NASA's Dawn mission, which orbited it for 14 months in 2011-2012. It's a leftover from the era of planet formation. But what kind of leftover? 1/7
I didn't know this existed until now, but here is an amazing animated gif of observations of the plume from the volcano Tvashtar on Io taken by NASA's New Horizons when it flew by Jupiter. ALT Text has detailed description.
Credit: NASA / JHUAPL / SwRI.
Credit: NASA / JHUAPL / SwRI.
March 27, 2025 at 1:28 PM
I didn't know this existed until now, but here is an amazing animated gif of observations of the plume from the volcano Tvashtar on Io taken by NASA's New Horizons when it flew by Jupiter. ALT Text has detailed description.
Credit: NASA / JHUAPL / SwRI.
Credit: NASA / JHUAPL / SwRI.
Europlanet is confusing because it’s both a member org and some sort of pan-national thing with member national orgs as part of the EU?
But they do advocacy: www.europlanet.org/europlanet-a...
But they do advocacy: www.europlanet.org/europlanet-a...
March 11, 2025 at 10:27 PM
Europlanet is confusing because it’s both a member org and some sort of pan-national thing with member national orgs as part of the EU?
But they do advocacy: www.europlanet.org/europlanet-a...
But they do advocacy: www.europlanet.org/europlanet-a...
Tonight you will be visited by three spirits …
December 24, 2024 at 11:34 PM
Tonight you will be visited by three spirits …
Saw an advertisement for this book, and immediately thought that Kevin had taken up popular science writing. I was suspicious that there was a second middle initial though, and sure enough, the author included a Kevin J. Walsh disclaimer.
November 20, 2024 at 1:45 PM
Saw an advertisement for this book, and immediately thought that Kevin had taken up popular science writing. I was suspicious that there was a second middle initial though, and sure enough, the author included a Kevin J. Walsh disclaimer.
US college textbook prices stopped rising in 2015. The BLS Producer's Price Index for college textbooks, showing a steady rise in prices until 2000, a faster rise until 2015, and then a turnover to a seemingly flat level from 2015 until today. (data.bls.gov/dataViewer/v...) What happened in 2015?
November 19, 2024 at 8:41 PM
US college textbook prices stopped rising in 2015. The BLS Producer's Price Index for college textbooks, showing a steady rise in prices until 2000, a faster rise until 2015, and then a turnover to a seemingly flat level from 2015 until today. (data.bls.gov/dataViewer/v...) What happened in 2015?
Pretty sure that this means Bialetti thinks water droplets look like macaroni? See Fig A.
September 2, 2023 at 11:49 PM
Pretty sure that this means Bialetti thinks water droplets look like macaroni? See Fig A.
MSU is searching for teaching faculty in one of our fastest growing departments (in terms of student enrollment and hiring). Computational astrophysical, planetary, or Earth scientists with a PhD do have the requisite skills for applying. My lab would be eager to collaborate.
August 18, 2023 at 3:15 PM
MSU is searching for teaching faculty in one of our fastest growing departments (in terms of student enrollment and hiring). Computational astrophysical, planetary, or Earth scientists with a PhD do have the requisite skills for applying. My lab would be eager to collaborate.