STARS WITH HIGH GALACTIC-AMPLITUDES
HOST FEWER SMALL PLANETS
By combining astrometry from the Gaia mission with the Kepler and K2 planet population, I discovered a trend: stars oscillating with large amplitudes about the plane of the Milky Way tend to have fewer super-Earths (planets slightly larger than Earth) and sub-Neptunes (planets slightly smaller than Neptune) around them. This population of short-period planets orbits their host star within the orbital span of Mercury. It is well known that stars with larger galactic amplitudes have a reduced metal inventory (a key building block for planet formation), but the identified trend exceeds these expectations, indicating that the overall location within the Milky Way also has an impact either planet formation or their inherent system dynamics. The underlying mechanism responsible for this planet deficit in the thick disk remains unclear. The displayed figure shows the downward trend in short-period sub-Neptune occurrence as a function of how high the host stars bob above the galactic midplane. The depicted [Fe/H] trend represents the expected occurrence reduction as a function of the reduced disk metal content associated with high-amplitude stars.
NASA Discovery Alert
Manuscript - Zink et al. (2023)
HOST FEWER SMALL PLANETS
By combining astrometry from the Gaia mission with the Kepler and K2 planet population, I discovered a trend: stars oscillating with large amplitudes about the plane of the Milky Way tend to have fewer super-Earths (planets slightly larger than Earth) and sub-Neptunes (planets slightly smaller than Neptune) around them. This population of short-period planets orbits their host star within the orbital span of Mercury. It is well known that stars with larger galactic amplitudes have a reduced metal inventory (a key building block for planet formation), but the identified trend exceeds these expectations, indicating that the overall location within the Milky Way also has an impact either planet formation or their inherent system dynamics. The underlying mechanism responsible for this planet deficit in the thick disk remains unclear. The displayed figure shows the downward trend in short-period sub-Neptune occurrence as a function of how high the host stars bob above the galactic midplane. The depicted [Fe/H] trend represents the expected occurrence reduction as a function of the reduced disk metal content associated with high-amplitude stars.
NASA Discovery Alert
Manuscript - Zink et al. (2023)
HOT JUPITERS ARCHITECTURES
Hot Jupiters (short-period gas-giants) are an enigmatic class of planets that seem to violate in-situ planet formation models. I examined the intriguing characteristics of planetary systems containing giant planets, drawing insights from an extensive analysis of the California Legacy Survey planet catalog. In this investigation, we pinpointed three noteworthy traits that are commonly associated with hot Jupiters. Firstly, systems hosting giant planets, even those without a hot Jupiter, often include at least one outer giant planet companion. Secondly, we observed that the mass distributions of hot Jupiters and other giant planets are remarkably similar. However, within a planetary system featuring a hot Jupiter, the outer giant planet companions tend to be at least three times more massive than their inner hot Jupiter counterparts. Lastly, we noted that the eccentricity distribution of the outer companions is enhanced in hot Jupiter systems when compared to outer planets in systems lacking hot Jupiters. These findings lead us to conclude that the presence of two gas giants, with the outermost planet exhibiting high eccentricity and being significantly more massive, plays a pivotal role in the formation of hot Jupiters. This research favors coplanar high-eccentricity migration as the primary mechanism behind hot Jupiter formation and evolution. The provided figure highlights the three times increase in mass for outer giant companions. astrobites review Manuscript - Zink & Howard (2023)
Hot Jupiters (short-period gas-giants) are an enigmatic class of planets that seem to violate in-situ planet formation models. I examined the intriguing characteristics of planetary systems containing giant planets, drawing insights from an extensive analysis of the California Legacy Survey planet catalog. In this investigation, we pinpointed three noteworthy traits that are commonly associated with hot Jupiters. Firstly, systems hosting giant planets, even those without a hot Jupiter, often include at least one outer giant planet companion. Secondly, we observed that the mass distributions of hot Jupiters and other giant planets are remarkably similar. However, within a planetary system featuring a hot Jupiter, the outer giant planet companions tend to be at least three times more massive than their inner hot Jupiter counterparts. Lastly, we noted that the eccentricity distribution of the outer companions is enhanced in hot Jupiter systems when compared to outer planets in systems lacking hot Jupiters. These findings lead us to conclude that the presence of two gas giants, with the outermost planet exhibiting high eccentricity and being significantly more massive, plays a pivotal role in the formation of hot Jupiters. This research favors coplanar high-eccentricity migration as the primary mechanism behind hot Jupiter formation and evolution. The provided figure highlights the three times increase in mass for outer giant companions. astrobites review Manuscript - Zink & Howard (2023)
K2 OCCURRENCE RATES
When two of its reaction wheels failed, the Kepler spacecraft was no longer able to keep its gaze on the same area for a long time, thus ending its original mission. Nevertheless, it was able to collect data in 80-day intervals from various parts of the galactic plane. I developed an automated system for detecting exoplanets that transit in this data, which enabled us to conduct studies on the occurrence rate in different parts of the galaxy. This work led to the discovery of over 300 new planets and has given rise to numerous results. Forbes Article Manuscript - Zink et al. (2021) Manuscript - Zink et al. (2020)
Small planets: Given the inherent homogeneity of the Kepler and K2 missions, examining populations planets orbiting around FGK dwarf stars shed light on the origin and ubiquity of our own solar system. These two samples span different regions of the night sky and provide a baseline for galactic population extrapolation. By comparing these different regions, we can assess the overall homogeneity of the Milky Way. Overall, we find that both Kepler and K2 provide comparable occurrence measurements, suggesting that planets are generally forming consistently across our local Milky Way galaxy. The figure provided shows the occurrence of super-Earths (planets slightly larger than Earth) and sub-Neptunes (planets slightly smaller than Neptune) as a function of orbital period. These short period planets are abundant, and provide a natural test-bed for planet formation mechanisms.
Manuscript - Zink et al. (2023)
Manuscript - Zink et al. (2020)
Sub-Saturns: The origin of sub-Saturns (planets slightly smaller than Saturn) is puzzling. The mass range associated with this type of planet should give rise to runaway accretion, forming a much larger planet. Thus, sub-Saturns should be more rare than their more massive Jovian-sized counterparts. However, their short-period Jupiter-like planets occur with similar frequency as sub-Saturns, challenging this standard planet formation mechanism. Our occurrence measurements shed light on this unique population of planets, showing that their underlying population closely resembles the sub-Neptunes planet population, a smaller class of planets. This suggests some interwoven formation history between sub-Neptunes and sub-Saturns. One possible theory is that sub-Saturns merely represent a population of inflated sub-Neptunes, rather than partially formed gas giants. The figure shows a similarity in total occurrence for sub-Saturns and short-period Jupiters, but the uptick in occurrence beyond 10 day periods is more closely aligned with the sub-Neptune population.
Manuscript - Zink et al. (2023)
Jupiters: There exists an unexpected inverse relationship between the number of short-period planets and the mass of the star they orbit. This is surprising because one would expect that stars with more mass would have disks with more material available to form planets and thus more planets. However, our study of planets discovered by Kepler and K2 suggests that the number of Jovian planets is not strongly dependent on the mass of the star (or its surface temperature). This lack of correlation for Jovian sized planets may provide insight into the unusual trends observed for smaller planets. It is possible that massive planets are more successful in preventing material from being used to form smaller planets around more massive stars, thus reducing the efficiency of small planet formation. The figure depicts the reduced occurrence trend for hotter (and more massive) stars across all planet classes ---with the expectation of Jupiters, which appears independent of the stellar type.
Manuscript - Zink et al. (2023)
When two of its reaction wheels failed, the Kepler spacecraft was no longer able to keep its gaze on the same area for a long time, thus ending its original mission. Nevertheless, it was able to collect data in 80-day intervals from various parts of the galactic plane. I developed an automated system for detecting exoplanets that transit in this data, which enabled us to conduct studies on the occurrence rate in different parts of the galaxy. This work led to the discovery of over 300 new planets and has given rise to numerous results. Forbes Article Manuscript - Zink et al. (2021) Manuscript - Zink et al. (2020)
Small planets: Given the inherent homogeneity of the Kepler and K2 missions, examining populations planets orbiting around FGK dwarf stars shed light on the origin and ubiquity of our own solar system. These two samples span different regions of the night sky and provide a baseline for galactic population extrapolation. By comparing these different regions, we can assess the overall homogeneity of the Milky Way. Overall, we find that both Kepler and K2 provide comparable occurrence measurements, suggesting that planets are generally forming consistently across our local Milky Way galaxy. The figure provided shows the occurrence of super-Earths (planets slightly larger than Earth) and sub-Neptunes (planets slightly smaller than Neptune) as a function of orbital period. These short period planets are abundant, and provide a natural test-bed for planet formation mechanisms.
Manuscript - Zink et al. (2023)
Manuscript - Zink et al. (2020)
Sub-Saturns: The origin of sub-Saturns (planets slightly smaller than Saturn) is puzzling. The mass range associated with this type of planet should give rise to runaway accretion, forming a much larger planet. Thus, sub-Saturns should be more rare than their more massive Jovian-sized counterparts. However, their short-period Jupiter-like planets occur with similar frequency as sub-Saturns, challenging this standard planet formation mechanism. Our occurrence measurements shed light on this unique population of planets, showing that their underlying population closely resembles the sub-Neptunes planet population, a smaller class of planets. This suggests some interwoven formation history between sub-Neptunes and sub-Saturns. One possible theory is that sub-Saturns merely represent a population of inflated sub-Neptunes, rather than partially formed gas giants. The figure shows a similarity in total occurrence for sub-Saturns and short-period Jupiters, but the uptick in occurrence beyond 10 day periods is more closely aligned with the sub-Neptune population.
Manuscript - Zink et al. (2023)
Jupiters: There exists an unexpected inverse relationship between the number of short-period planets and the mass of the star they orbit. This is surprising because one would expect that stars with more mass would have disks with more material available to form planets and thus more planets. However, our study of planets discovered by Kepler and K2 suggests that the number of Jovian planets is not strongly dependent on the mass of the star (or its surface temperature). This lack of correlation for Jovian sized planets may provide insight into the unusual trends observed for smaller planets. It is possible that massive planets are more successful in preventing material from being used to form smaller planets around more massive stars, thus reducing the efficiency of small planet formation. The figure depicts the reduced occurrence trend for hotter (and more massive) stars across all planet classes ---with the expectation of Jupiters, which appears independent of the stellar type.
Manuscript - Zink et al. (2023)
THE END OF THE SOLAR SYSTEM
In about 7 billion years, long after Mercury, Venus, and Earth have all been engulfed by the red giant solar phase, the Sun will finish fusing elements and begin shedding its outer envelope. During this period, the Sun is expected to lose roughly half of its current mass, and the orbits of the outer gas giants (Jupiter, Saturn, Neptune, and Uranus) will expand by a factor of two in concert. We showed that this orbital expansion leads to Jupiter and Saturn being locked into a 5:2 mean-motion resonance. Furthermore, over the course of the next few billion years, neighboring stars will pass by gravitationally perturbing orbits of the gas giants. Eventually, a large enough stellar flyby will pull Jupiter and Saturn out of this mean-motion resonance configuration, and orbital chaos ensues, leading to the eventual ejection of all remaining Solar System planets. Our simulation shows that the final planet will be ejected from the Solar System in roughly 100 billion years. The provided figure shows three of our simulations and the corresponding growth in eccentricity of the outer Solar System planets and their eventual ejection.
AAS Research Highlight
Manuscript - Zink et al. (2020)
In about 7 billion years, long after Mercury, Venus, and Earth have all been engulfed by the red giant solar phase, the Sun will finish fusing elements and begin shedding its outer envelope. During this period, the Sun is expected to lose roughly half of its current mass, and the orbits of the outer gas giants (Jupiter, Saturn, Neptune, and Uranus) will expand by a factor of two in concert. We showed that this orbital expansion leads to Jupiter and Saturn being locked into a 5:2 mean-motion resonance. Furthermore, over the course of the next few billion years, neighboring stars will pass by gravitationally perturbing orbits of the gas giants. Eventually, a large enough stellar flyby will pull Jupiter and Saturn out of this mean-motion resonance configuration, and orbital chaos ensues, leading to the eventual ejection of all remaining Solar System planets. Our simulation shows that the final planet will be ejected from the Solar System in roughly 100 billion years. The provided figure shows three of our simulations and the corresponding growth in eccentricity of the outer Solar System planets and their eventual ejection.
AAS Research Highlight
Manuscript - Zink et al. (2020)
SOLVING THE KEPLER DICHOTOMY
The Kepler mission has completely changed our understanding of the frequencies and characteristics of planets orbiting stars similar to the Sun. Initially, it seemed that there was an abundance of single-transit systems in the data. I demonstrated that the surplus of single-transiting planet systems around stars like the Sun can be largely explained by a more intricate completeness mapping. Taking into account the order in which the candidates were identified (within the system's light curve), our technique is able to reproduce this apparent surplus of single-planet systems using a simple Poissonian multiplicity distribution.
Manuscript - Zink et al. (2019)
The Kepler mission has completely changed our understanding of the frequencies and characteristics of planets orbiting stars similar to the Sun. Initially, it seemed that there was an abundance of single-transit systems in the data. I demonstrated that the surplus of single-transiting planet systems around stars like the Sun can be largely explained by a more intricate completeness mapping. Taking into account the order in which the candidates were identified (within the system's light curve), our technique is able to reproduce this apparent surplus of single-planet systems using a simple Poissonian multiplicity distribution.
Manuscript - Zink et al. (2019)
: @jonKzink