Earth-sized planet Archives

TTVs from the ground-based follow-up campaign of P23 (black circles) including the high-precision Spitzer observations (gray squares), and our new Palomar/WIRC follow-up observations (orange stars), with 100 random posterior draws from our damped eccentricity TTV model (red) and free eccentricity TTV model (blue) for LP 791-18 c (top panel) and d (bottom panel). Our Palomar/WIRC timing measurements for LP 791-18 c are the most precise TTV observations of this system so far, a factor of 1.5-3x more precise than Spitzer, and drive the TTV model constraints for LP 791-18 d. -- astro-ph.EP

Updated Mass, Eccentricity, and Tidal Heating Constraints for the Earth-sized Planet LP 791-18 d

by Keith CowingFebruary 5, 2025September 18, 2025

LP 791-18 d is a temperate Earth-sized planet orbiting a late M dwarf, surrounded by an interior super-Earth (LP 791-18 b, RP = 1.2 R⊕, P=0.95 days) and an exterior […]

Instellation flux as a function of planet escape velocity, in log-log scale. Based on data from the NASA Exoplanet Archive (2024) downloaded on June 30, 2024. The empirical “cosmic shoreline” and the water vapor greenhouse runaway threshold (Zahnle & Catling 2017) are shown as cyan and yellow shaded regions, respectively. Planets are categorized into terrestrial planets (magenta), sub-Neptunes (blue), Neptune-like planets (green), and gas giants (yellow) based on radius, see legend. The red rectangles represent escape velocities calculated based on HD 101581 planets’ mean estimated masses assuming Hypatia Catalog metallicity. Because only radius, but not mass, is known, we further plot light red regions covering all possible interior compositions, ranging from pure iron to pure silicates. Height of the rectangles represent uncertainties in insolation. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

Two Earth-size Planets and an Earth-size Candidate Transiting the Nearby Star HD 101581

by Keith CowingDecember 13, 2024December 13, 2024

We report the validation of multiple planets transiting the nearby (d=12.8 pc) K5V dwarf HD 101581 (GJ 435, TOI-6276, TIC 397362481).

Schematic view of the seven planetary systems studied in this work. In the upper panel, the location on the x-axis shows the orbital semi-major axis of the planets in question, on a linear scale, with the horizontal lines reaching out from the planet showing the range of its orbit from pericentre to apocentre. The size of the marker for each planet gives the observed radius, as presented in the discovery work, whilst the colour of the marker gives the measured mass for the planet. In the case of the planets orbiting HD 63433, no measured mass has been obtained to date, and we therefore plot an estimated mass for the two planets in that system, based on Figure 3 of Chen & Kipping (2017). In the case of TOI 1670 b, the mass given is an upper limit. The lower panel presents most of the same information (mass, radius, etc.), but shows the separation of the planetary systems in terms of their orbital periods, with the period of the inner planet in each system set to unity. The parent stars are shown sized relative to one another, but not to scale with their planets, and their colour in the plot denotes their effective temperatures, Teff. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

The Search For The Inbetweeners: How Packed Are TESS Planetary Systems?

by Keith CowingNovember 7, 2024November 7, 2024

In this work, we examine seven systems discovered by TESS, to see whether there is any room in those systems for an additional planet (or several) to lurk unseen between […]

LP 791-18 d, shown here in an artist’s concept, is an Earth-size world about 90 light-years away. The gravitational tug from a more massive planet in the system, shown as a blue disk in the background, may result in internal heating and volcanic eruptions – as much as Jupiter’s moon Io, the most geologically active body in the solar system. Astronomers discovered and studied the planet using data from NASA’s Spitzer Space Telescope and TESS (Transiting Exoplanet Survey Satellite) along with many other observatories. Credit: NASA’s Goddard Space Flight Center/Chris Smith (KRBwyle)

Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Gaia - Planetary Perspectives, Habitable Zones, Lava / magma ocean / Volcanic Worlds, Status Report

Thermal and Magnetic Evolution Of An Earth-like Planet With A Basal Magma Ocean

by Keith CowingSeptember 11, 2024

Earth’s geodynamo has operated for over 3.5 billion years. The magnetic field is currently powered by thermocompositional convection in the outer core, which involves the release of light elements and […]

Radial velocity (RV) variations of TOI-6255 b (orange dashed line) measured by KPF (circles) and CARMENES (stars). A Gaussian Process Model (blue dotted line) has been included to remove any stellar activity and instrumental variation on timescales longer than the orbital period of TOI-6255 b. On Nov 24, 2023, we took a set of 21 continuous exposures of TOI6255 with KPF (inset). The resultant RVs followed clearly reveal the 5.7-hour orbit of TOI-6255 b. -- astro-ph.EP

Astrogeology, Astronomy & Telescopes, Exoplanets, -moons, -comets, Gaia - Planetary Perspectives, Habitable Zones, Status Report

An Earth-sized Planet On The Verge Of Tidal Disruption

by Keith CowingAugust 1, 2024August 1, 2024

TOI-6255~b (GJ 4256) is an Earth-sized planet (1.079±0.065 R⊕) with an orbital period of only 5.7 hours. With the newly commissioned Keck Planet Finder (KPF) and CARMENES spectrographs, we determined […]

The observed deviation ∆ for the resonant-chain systems with well-measured ages vs. the cumulative eccentricity damping, i.e. all terms in Eqn. 2 except the reduced tidal quality factor. The solid lines shows the theoretically predicted ∆ at various reduced tidal quality factors. We have labelled each resonant-chain system with the radius of the planet that is expected to experience the strongest tides. TOI-1136 (700-Myr-old; Dai et al. 2023a) and AU Mic (20-Myr-old; Plavchan et al. 2020) are still deep in resonances (∆ ∼ 0.1%), and the inferred reduced tidal quality factor is roughly 104 − 105 , which is consistent with Uranus (e.g. Gomes & Correia 2024). However, HD 109833 (10 to 16-Myr-old; Wood et al. 2023), TOI-2076 (Hedges et al. 2021, 200-Myr-old;) are substantially far away from resonance (∆ ∼ 1%) that the required reduced tidal quality factor Q ′ p < 10 seems unphysical. Other processes such as disk e-damping (Choksi & Chiang 2020), disk turbulence (Goldberg & Batygin 2023), obliquity tides (Millholland & Laughlin 2019), planetesimal scattering (Chatterjee & Ford 2015) should be included to explain the observed ∆ distribution. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Status Report, Stellar Cartography

The Prevalence of Resonance Among Young, Close-in Planets

by Keith CowingJune 12, 2024June 12, 2024

Multiple planets undergoing disk migration may be captured into a chain of mean-motion resonances with the innermost planet parked near the disk’s inner edge. Subsequent dynamical evolution may disrupt these […]

Comparison of SPECULOOS-3 b with other rocky exoplanets. a) Sizes of host stars and incident stellar flux of known sub-Neptune-sized exoplanets. The size of the symbols scales linearly with the radius of the planet. The background is colour-coded according to stellar size (in units of the Sun’s size), with the ultra-cool dwarf regime shown in orange. The positions of the Solar System terrestrial planets are shown for reference. One can see on this Figure that SPECULOOS-3 b extends the unique planet sample of TRAPPIST-1 to a larger stellar flux. b) SPECULOOS-3 b in the context of other known transiting terrestrial exoplanets (Rp < 1.6R⊕) that are cool enough (Teq < 880 K [80]) to have a dayside made of solid rock (in contrast to hotter magma worlds with molten surfaces). The planets are shown as a function of their radius and their Emission Spectroscopy Metric [62]. They are color-coded as a function of their equilibrium temperature. The shaded green area highlights planetary radii most similar to Earth’s (0.9–1.1 R⊕). The dashed horizontal line represents the threshold of ESM=7.5 recommended by ref. [62] to identify the top targets for emission spectroscopy with JWST. SPECULOOS-3 b is one of the smallest planets amenable to emission spectroscopy with MIRI/LRS. Data from https://exoplanetarchive.ipac.caltech.edu (16th of October 2023). -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

Detection Of An Earth-sized Exoplanet Orbiting The Nearby Ultracool Dwarf Star SPECULOOS-3

by Keith CowingJune 4, 2024June 4, 2024

Located at the bottom of the main sequence, ultracool dwarf stars are widespread in the solar neighbourhood. Nevertheless, their extremely low luminosity has left their planetary population largely unexplored, and […]

An artist’s concept of the exoplanet SPECULOOS-3 b orbiting its red dwarf star. The planet is as big around as Earth, while its star is slightly bigger than Jupiter – but much more massive. Credit: NASA/JPL-Caltech

Astronomy & Telescopes, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Press Release

Astronomers Discover Earth-sized Exoplanet Orbiting Ultra-cool Star

by Keith CowingMay 15, 2024May 15, 2024

An international scientific team, with the participation of researchers from the Instituto de Astrofísica de Canarias (IAC), confirms the existence of an Earth-sized planet orbiting an ultra-cold red dwarf located […]

HD 63433d is the third planet found in orbit around a star called HD 63433.

Astronomy & Telescopes, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Press Release

Earth-sized Planet HD 63433d Discovered In Our Solar Backyard

by Keith CowingJanuary 13, 2024January 13, 2024

A team of astronomers have discovered a planet closer and younger than any other Earth-sized world yet identified. It’s a remarkably hot world whose proximity to our own planet and […]

Like Kepler-10 b, illustrated above, the exoplanet HD 63433 d is a small, rocky planet in a tight orbit of its star. HD 63433 d is the smallest confirmed exoplanet younger than 500 million years old. It's also the closest discovered Earth-sized planet this young, at about 400 million years old. NASA/Ames/JPL-Caltech/T. Pyle

Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Press Release

Earth-sized Planet HD 63433 d Has A Lava Hemisphere

by Keith CowingJanuary 12, 2024January 12, 2024

The discovery: In a system with two known planets, astronomers spotted something new: a small object transiting across the Sun-sized star. This turned out to be another planet: extra hot […]