https://www.jasonhsteffen.com/home daily 1.0 2022-01-01 https://www.jasonhsteffen.com/media daily 0.75 2023-12-12 https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/1fb7c4a5-a09d-45ee-a54f-f262ac2b7235/50821753961_224b3c8d18_c.jpg Media - More Airplane Boarding Reported in the Wall Street Journal (among other places). https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/a109fe20-d9af-4277-a299-40d65601df0d/webbimage.jpeg Media - JWST First Images Reported in The Las Vegas Sun Times. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/b378548b-55bb-461d-b2ef-4a664b4cbb2b/steffen.jpeg Media - Thoughts on JWST Launch Reported in the Las Vegas Sun. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/0fc77597-b965-4e37-9a06-b9ac6b91c9ce/kepler.jpeg Media - Kepler planets set to music Reported in Eos. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/7f2e01cc-2b02-4980-bd81-15c45baac695/kepler10.jpeg Media - Piece on NASA’s TESS mission Published in The Conversation. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/c09108c9-077c-44ea-8157-41aec4f7bd35/airplane.jpeg Media - Airplane Boarding One of many. This from CGP Grey youtube. https://www.jasonhsteffen.com/art daily 0.75 2022-01-03 https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/71c00883-7175-46e4-b202-0eaa1a659c86/mandelbrot.png Art Different portions of the Mandelbrot set https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/08667999-d2b2-4572-aaab-5c5c3a8c2f82/spiral_dark.png Art The prime spiral on a grid https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/a26babe3-797d-4197-9484-985c2e40fd79/sequencefull.png Art A graphical representation of the Recaman Sequence https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/bd5dfd68-1034-4d03-a80c-4c56825d8959/keplerpairsBG.png Art Pairs of Kepler planets near mean-motion resonance https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/1f44aea6-b180-46ac-aa85-d80f19d4bde3/primepyramid.png Art Frequency of differences between pairs of adjacent prime numbers https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/d44fc9ad-f19c-496b-be22-f5ba00a1fe30/KeplerFOV.png Art Kepler first light https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/604493f0-c58a-41b7-b1c0-fd9eec6481a3/axions.png Art Axion misalignment angles https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/2fa4d62b-794b-4863-b24d-9c065df72caa/PlanetWakes.jpeg Art Planetary wakes https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/be93a016-842b-45a5-8872-9685087e610e/planetcollage.png Art Kepler's multiplanet systems https://www.jasonhsteffen.com/research daily 0.75 2026-06-08 https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/6de7e723-ade3-4cd1-a670-e811da38bd4b/GCEfig.jpg Research The stellar age and CMF (%) of planets from A. Weeks et al. (2025) with 1σ uncertainties. The CMF is found with MAGRATHEA, given the masses and radii in A. Weeks et al. (2025). The planet’s equilibrium temperature is represented by the color and the planet’s mass by the size of the circle. The three gold lines of the CMF with age from our results are shown measured at 1 au around a solar mass star (note that this distance is exterior to most detected exoplanets, thus there is an implicit assumption that the observed planets migrated inward after formation). “Norm.” is when elemental abundances are normalized to the solar system, while “+HM” is enriched in high-mass material, and “+LM” has increased low-mass material. Earth and Mercury are also shown for reference. Note that the x-axis in this case is the age of the star and thus the inverse of the previous plots. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/93a82107-84cd-464a-86be-1ba12d7e47b0/arches.png Research Scatter plot showing the period ratio as a function of the inner planet period, in days, for Kepler (blue), TESS (green), and K2 (red). The solid blue line in the lower left corner indicates a lower limit to observed period ratios (1). https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/9d04bcdf-1728-47dd-b88b-e4e1e025bad1/trappist.jpg Research The median and 1σ wmfs of all five outer T1 planets across r-cmf are shown by the various colored lines and hatched regions. T1-b and T1-c’s median and 1σ cmfs are also shown with zero wmf. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/f1847adb-eee0-4337-8451-9ddacb63770a/COfigure.png Research The total carbon (green) and oxygen (red) fractions summed over all radii for simulations with a given initial C/O. The vertical solid line indicates the solar C/O simulation. Purely dotted lines correspond to C/O=0.01 and 100. Dashed and dotted lines correspond to C/O=0.1 and 10. The purely dashed line corresponds to C/O=1. (Left) In order from left to right: C/O=0.01, C/O=0.1, C/O=1, C/O=10, C/O=100 are located at C/O values of 0.762, 0.828, 1.005, 2.457, and 37.633, respectively. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/1011e211-9034-493f-a992-c9e07236f7f8/1-s2.0-S1384107624001295-gr11.jpg Research Final Masses and Core Mass Fractions for the remaining objects in 50 REBOUND simulations with different distributions of core material in the initial disc. (a) shows the step-function distribution, (b) shows the linear distribution, and (c) shows the exponential distribution. The top row shows results from our Differentiated Body Composition Tracker (DBCT) and the bottom row shows results from the composition tracking code (CT) created by Childs and Steffen (2022). The blue, dotted line shows the initial mass given to embryos in each simulation, the orange, dash-dotted line shows the initial mass given to all planetesimals in each simulation, and the red, dashed line shows the average CMF of the initial disc for each distribution. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/4526cfc6-6e57-42a6-9be7-a96a69bfa040/apjlad73dbf4_lr.jpg Research The median frequency of planet radius from 500 Gaussian KDEs where each planet's radius is drawn from a normal distribution centered at the planet's reported radius and standard deviation set the average of the plus and minus uncertainties. This is then repeated for each set of planets limited by minimum gap complexity given by the color. The 1σ uncertainty is given at three points for the entire set of planets and planets with C > 0.4. While the uncertainty increases from the smaller sample size, there is a systematic increase in super-Earth and a decrease in sub-Neptune frequency. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/03c9fbfd-fe9b-4ef8-bfbb-9e63c465f7ce/watermass.png Research The average (with one-sigma error bars) wt% of water and the 12 elements we consider for each of our average simulated TRAPPIST-1 planets. Earth's values are shown in black. The bodies that begin with a water mass fraction (WMF) of 50% are shown in the top panel and the bodies that begin with a WMF of 20% are shown in the bottom panel. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/0bd47ea7-916c-4233-afe9-fc4c6ac00df8/regimeHistFIT40funcMain.png Research Histogram of the combined regime occurrences over regime length for all simulations which exhibit Tidally Locked with Sporadic Rotation (TLSR) spin states. These include Tidally Locked with the initial substellar point at zero degrees and 180 degrees, as well as periods where the initial substellar point rotates and where it exhibits Prolonged Transient Behavior (PTB) as the planet transitions between states. The bin boundaries of the log-log histogram also use a log scale and are shown with dotted blue lines. The blue shaded area defines the 'well-behaved' sample data used to find the best-fit power laws for the probability density functions of the three regime types. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/65c2babe-604b-4632-879b-81fb3e19b583/binallearth.png Research Stability time for suites of simulations with non-equal-mass planets. The mass of each planet in the system is chosen from a normal distribution with a mean of one Earth mass and with the standard deviation indicated. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/5cfe072f-f820-47e3-8a19-f83518cbd5ce/yarkovsky.png Research Change in the semimajor axes of asteroids with different obliquities, thermal inertias, and radii after a 0.01 Myr long simulation on a log-log plot. Obliquities are denoted by opacity and radii are shown using color. A dashed line indicates an obliquity of 90° where the body’s semimajor axis is only affected by the seasonal component of the Yarkovsky effect, and a dotted line indicates an obliquity of 0° or 180° where the diurnal component’s effect on the object’s semimajor axis is at a maximum. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/60b42109-178e-42cc-914a-93aecfb8dda2/group2.png Research Conference photo for Exoplanets IV https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/07c672f8-56ff-4874-9bda-1327ab23284a/zachimage.png Research X-ray diffraction images without (left) and with (right) a new laser heating method to reduce systematic uncertainties in high pressure measurements. “D” marks diffraction spots from diamonds. The goal is to measure the radii of circles that pass through the remaining points. Note that the method used on the right shows high-quality circles, making them easier to measure. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/3791329f-d074-4fbb-9d99-28d1bb43c3d7/WMF_f_100.png Research Water mass fraction of planets formed from the same initial conditions (top) with fragmentation (middle) and with perfect merging (bottom). https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/b91e863f-0a36-4346-b3af-cb7535302a84/ternaryfinal.png Research Results of planetary interior models with differing compositions and the time required to execute the model. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/32b98973-e018-4695-8560-734d94213579/fig5.png Research Orbital evolution of different planets as the Sun evolves. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/04832247-ef35-47d8-b5f3-01bd85718143/lines.jpeg Research Time evolution of the snow and rock lines due to stellar outbursts. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/47f0a49b-3157-4d8c-ae4e-3fa22952835f/density_map.png Research Internal structure of water-rich planets using a new equation of state. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/8df53cca-4a72-47b1-8cb8-8cb8447ae174/childs.png Research Loss of planet forming material in the presence of outer giant planets. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/c8abd7b5-e97c-48c9-a16b-026062c85fb9/rice.png Research Ratio of collision time to encounter time for unstable planetary systems compared to the relative orbital inclination of those planets. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/678241dc-be88-4804-b0e1-533d08a07b68/prt.png Research Fraction of constant alpha disk models that reach a specified peak temperature. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/809ba96e-ca26-473a-a12d-2edbb28cb1c9/sigmaevo.png Research Evolving surface density of Calcium and Silicon in a protoplanetary disk. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/b7594ad5-a61b-425a-a88f-f32972560283/MoonCollage_Color.png Research Orbits of moons that survive planetary ejections. https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/cdb94130-4815-4b87-8202-bd3828d46aa4/comp_e.png Research Period ratio distribution arising from dynamical instability with different initial eccentricity and inclination distributions and compared with Kepler observations (black). https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/948e1c15-fe90-44c9-8c38-e1e170b3c4b4/boisvert.png Research Possible planet pairs mischaracterized as single planets with eccentric orbits. https://www.jasonhsteffen.com/jason-steffen daily 0.75 2024-02-02 https://images.squarespace-cdn.com/content/v1/61cd4c8814fb9202a7c1ed3a/60473c7e-49ee-4c35-8ea9-de45bd29a1a9/Fall+Minis_0984.jpg About 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