scholarly journals Which stars can see Earth as a transiting exoplanet?

2020 ◽  
Vol 499 (1) ◽  
pp. L111-L115
Author(s):  
L Kaltenegger ◽  
J Pepper
Keyword(s):  
Main Sequence ◽  
Line Of Sight ◽  
Main Sequence Stars ◽  
Target List ◽  
Distant Observer ◽  
Spectroscopic Observations ◽  
Transiting Planets ◽  
Vantage Points ◽  
Life On Earth ◽  
Gaia Dr2

ABSTRACT Transit observations have found the majority of exoplanets to date. Also spectroscopic observations of transits and eclipses are the most commonly used tool to characterize exoplanet atmospheres and will be used in the search for life. However, an exoplanet’s orbit must be aligned with our line of sight to observe a transit. Here, we ask, from which stellar vantage points would a distant observer be able to search for life on Earth in the same way? We use the TESS Input Catalog and data from Gaia DR2 to identify the closest stars that could see Earth as a transiting exoplanet: We identify 1004 main-sequence stars within 100 parsecs, of which 508 guarantee a minimum 10-h long observation of Earth’s transit. Our star list consists of about 77 percent M-type, 12 percent K-type, 6 percent G-type, 4 percent F-type stars, and 1 percent A-type stars close to the ecliptic. SETI searches like the Breakthrough Listen Initiative are already focusing on this part of the sky. Our catalogue now provides a target list for this search. As part of the extended mission, NASA’s TESS will also search for transiting planets in the ecliptic to find planets that could already have found life on our transiting Earth .

scholarly journals TESS Giants Transiting Giants. I.: A Noninflated Hot Jupiter Orbiting a Massive Subgiant

2022 ◽  
Vol 163 (2) ◽  
pp. 53
Author(s):  
Nicholas Saunders ◽  
Samuel K. Grunblatt ◽  
Daniel Huber ◽  
Karen A. Collins ◽  
Eric L. N. Jensen ◽  
...  
Keyword(s):  
Main Sequence ◽  
Planetary System ◽  
Scattered Light ◽  
Image Data ◽  
Velocity Measurements ◽  
Main Sequence Stars ◽  
Transiting Planets ◽  
Depth Difference ◽  
Evolved Stars ◽  
Hot Jupiter

Abstract While the population of confirmed exoplanets continues to grow, the sample of confirmed transiting planets around evolved stars is still limited. We present the discovery and confirmation of a hot Jupiter orbiting TOI-2184 (TIC 176956893), a massive evolved subgiant (M ⋆ = 1.53 ± 0.12 M ⊙, R ⋆ = 2.90 ± 0.14 R ⊙) in the Transiting Exoplanet Survey Satellite (TESS) Southern Continuous Viewing Zone. The planet was flagged as a false positive by the TESS Quick-Look Pipeline due to periodic systematics introducing a spurious depth difference between even and odd transits. Using a new pipeline to remove background scattered light in TESS Full Frame Image data, we combine space-based TESS photometry, ground-based photometry, and ground-based radial velocity measurements to report a planet radius of R p = 1.017 ± 0.051 R J and mass of M p = 0.65 ± 0.16 M J . For a planet so close to its star, the mass and radius of TOI-2184b are unusually well matched to those of Jupiter. We find that the radius of TOI-2184b is smaller than theoretically predicted based on its mass and incident flux, providing a valuable new constraint on the timescale of post-main-sequence planet inflation. The discovery of TOI-2184b demonstrates the feasibility of detecting planets around faint (TESS magnitude > 12) post-main-sequence stars and suggests that many more similar systems are waiting to be detected in the TESS FFIs, whose confirmation may elucidate the final stages of planetary system evolution.

scholarly journals HALO7D I. The Line-of-sight Velocities of Distant Main-sequence Stars in the Milky Way Halo

2019 ◽  
Vol 876 (2) ◽  
pp. 124 ◽  
Author(s):  
Emily C. Cunningham ◽  
Alis J. Deason ◽  
Constance M. Rockosi ◽  
Puragra Guhathakurta ◽  
Zachary G. Jennings ◽  
...  
Keyword(s):  
Main Sequence ◽  
Milky Way ◽  
Line Of Sight ◽  
Main Sequence Stars ◽  
Milky Way Halo

scholarly journals From birth associations to field stars: mapping the small-scale orbit distribution in the Galactic disc

2020 ◽  
Vol 495 (4) ◽  
pp. 4098-4112 ◽  
Author(s):  
Johanna Coronado ◽  
Hans-Walter Rix ◽  
Wilma H Trick ◽  
Kareem El-Badry ◽  
Jan Rybizki ◽  
...  
Keyword(s):  
Main Sequence ◽  
Milky Way ◽  
Space Distribution ◽  
Small Scale ◽  
Galactic Disc ◽  
Main Sequence Stars ◽  
Orbital Phase ◽  
Angle Space ◽  
Order Of Magnitude ◽  
Gaia Dr2

ABSTRACT Stars born at the same time in the same place should have formed from gas of the same element composition. But most stars subsequently disperse from their birth siblings, in orbit and orbital phase, becoming ‘field stars’. Here, we explore and provide direct observational evidence for this process in the Milky Way disc, by quantifying the probability that orbit-similarity among stars implies indistinguishable metallicity. We define the orbit similarity among stars through their distance in action-angle space, Δ(J, θ), and their abundance similarity simply by Δ[Fe/H]. Analysing a sample of main-sequence stars from Gaia DR2 and LAMOST, we find an excess of pairs with the same metallicity (Δ[Fe/H] < 0.1) that extends to remarkably large separations in Δ(J, θ) that correspond to nearly 1 kpc distances. We assess the significance of this effect through a mock sample, drawn from a smooth and phase-mixed orbit distribution. Through grouping such star pairs into associations with a friend-of-friends algorithm linked by Δ(J,θ), we find 100s of mono-abundance groups with ≥3 (to ≳20) members; these groups – some clusters, some spread across the sky – are over an order-of-magnitude more abundant than expected for a smooth phase-space distribution, suggesting that we are witnessing the ‘dissolution’ of stellar birth associations into the field.

scholarly journals Can Self-Replicating Species Flourish in the Interior of a Star?

2020 ◽  
Author(s):  
Luis Anchordoqui ◽  
Eugene M. Chudnovsky
Keyword(s):  
Low Temperature ◽  
Nucleic Acids ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Atoms And Molecules ◽  
Form Of Life ◽  
Advanced Form ◽  
Life On Earth

The existing view of biological life is that it evolves under suitable conditions in the low-temperature world of atoms and molecules on the surface of a planet. It is believed that any plausible extraterrestrial form of life must resemble the life on Earth that is ruled by biochemistry of nucleic acids, proteins, and sugars. Going against this dogma, we argue that an advanced form of life based upon short-lived species can exist inside main-sequence stars like our Sun.

scholarly journals LAMOST telescope reveals that Neptunian cousins of hot Jupiters are mostly single offspring of stars that are rich in heavy elements

2017 ◽  
Vol 115 (2) ◽  
pp. 266-271 ◽  
Author(s):  
Subo Dong ◽  
Ji-Wei Xie ◽  
Ji-Lin Zhou ◽  
Zheng Zheng ◽  
Ali Luo
Keyword(s):  
Main Sequence ◽  
The Other ◽  
Heavy Elements ◽  
Main Sequence Stars ◽  
Hot Jupiters ◽  
Transiting Planets ◽  
Short Period ◽  
Data Release ◽  
Order Of Magnitude ◽  
Solar Type

We discover a population of short-period, Neptune-size planets sharing key similarities with hot Jupiters: both populations are preferentially hosted by metal-rich stars, and both are preferentially found in Kepler systems with single-transiting planets. We use accurate Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Data Release 4 (DR4) stellar parameters for main-sequence stars to study the distributions of short-period (1d<P<10d)Kepler planets as a function of host star metallicity. The radius distribution of planets around metal-rich stars is more “puffed up” compared with that around metal-poor hosts. In two period–radius regimes, planets preferentially reside around metal-rich stars, while there are hardly any planets around metal-poor stars. One is the well-known hot Jupiters, and the other one is a population of Neptune-size planets (2R⊕≲Rp≲6R⊕), dubbed “Hoptunes.” Also like hot Jupiters, Hoptunes occur more frequently in systems with single-transiting planets although the fraction of Hoptunes occurring in multiples is larger than that of hot Jupiters. About 1% of solar-type stars host Hoptunes, and the frequencies of Hoptunes and hot Jupiters increase with consistent trends as a function of [Fe/H]. In the planet radius distribution, hot Jupiters and Hoptunes are separated by a “valley” at approximately Saturn size (in the range of 6R⊕≲Rp≲10R⊕), and this “hot-Saturn valley” represents approximately an order-of-magnitude decrease in planet frequency compared with hot Jupiters and Hoptunes. The empirical “kinship” between Hoptunes and hot Jupiters suggests likely common processes (migration and/or formation) responsible for their existence.

scholarly journals Observed versus modelled stellar CME rates

2018 ◽  
Vol 14 (S345) ◽  
pp. 246-247
Author(s):  
Martin Leitzinger ◽  
Petra Odert ◽  
Krisztian Vida ◽  
Levente Kriskovics ◽  
Eike W. Guenther ◽  
...  
Keyword(s):  
Coronal Mass Ejections ◽  
Main Sequence ◽  
Late Type ◽  
Main Sequence Stars ◽  
Planetary Evolution ◽  
Spectroscopic Observations ◽  
Parameter Distributions

AbstractStellar coronal mass ejections (CMEs) may play an important role in stellar and planetary evolution, therefore the knowledge on parameter distributions of this energetic activity phenomenon is highly relevant. During the last years several attempts have been made to detect stellar CMEs of late-type main-sequence and pre main-sequence stars from dedicated optical spectroscopic observations. Up to now only a handful of distinct stellar CME detections are known which contradicts the results from stellar CME modelling, which predict higher CME rates. We report on dedicated ongoing and future observational attempts to detect stellar CMEs and discuss the observational results with respect to the results from stellar CME modelling.

Kinematics of main-sequence stars from the Gaia DR2 and PMA proper motions

2020 ◽  
Vol 494 (1) ◽  
pp. 1430-1447
Author(s):  
Anna B Velichko ◽  
P N Fedorov ◽  
V S Akhmetov
Keyword(s):  
Velocity Field ◽  
Main Sequence ◽  
Vertical Gradient ◽  
Model Parameters ◽  
Separate Analysis ◽  
Proper Motions ◽  
Kinematic Parameters ◽  
Main Sequence Stars ◽  
Stellar Velocity ◽  
Gaia Dr2

ABSTRACT We aim at analysis of kinematics of main-sequence stars from the GaiaDR2 and PMA catalogues as well as comparison of kinematic parameters derived from their proper motions. We decompose the stellar velocity field on to a set of vector spherical harmonics (VSH), and, using the relations between the decomposition coefficients and the Ogorodnikov–Milne (O–M) model parameters, calculate the latter. The method of VSH allowed to detect all systematic constituents present in the GaiaDR2 and PMA stellar velocity fields. We notice incompleteness of the O–M model, discuss the kinematic parameters derived within its framework, as well as significant decomposition coefficients that do not have analogues within this model. For separate analysis of the kinematic parameters in the Northern and Southern Galactic hemispheres, we apply the decomposition on to a set of zonal VSH (ZVSH). Modelling the stellar velocity field allowed to confirm the causes of some significant beyond-the-model harmonics. Based on stellar proper motions from the Gaia DR2 and PMA catalogues, we confirm the previous conclusion that the values of ω1 and $M^+_{23}$ O–M model parameters derived in the Northern and Southern Galactic hemispheres have opposite signs. This fact takes place due to a vertical gradient of the linear rotation velocity about the Galactic centre. We estimate influence of the vertical gradient on the value of solar velocity component Y⊙. We confirm that the beyond-the-model coefficients t211 and s310 are caused by the vertical gradient as well.

Supersolar metallicity in G0–G3 main-sequence stars with V < 15. II. An extension of the sample

2020 ◽  
Vol 493 (4) ◽  
pp. 5807-5815
Author(s):  
M Chávez ◽  
C Tapia-Schiavon ◽  
E Bertone ◽  
R López-Valdivia
Keyword(s):  
Main Sequence ◽  
Wavelength Region ◽  
Interstellar Extinction ◽  
Main Sequence Stars ◽  
Data Set ◽  
Class V ◽  
Full Sample ◽  
Gaia Dr2 ◽  
Temperature Surface ◽  
Good Agreement

ABSTRACT We present the spectroscopic analysis at intermediate resolution of a new sample of 146 Sun-like stars (of spectral types G0–G3 and luminosity class V), which complements the data set of 233 targets previously investigated. Aimed at identifying objects with supersolar metallicity, we conducted observations at the Observatorio Astrofísico Guillermo Haro and derived the basic stellar atmospheric parameters, namely the effective temperature, surface gravity, and global metallicity, based on a set of absorption spectroscopic indices in the wavelength region 3800–4800 Å. The newly derived set of parameters is in good agreement with previous determinations collected from sources in the literature. Considering the full sample of our investigation (379 stars), we also compared the effective temperatures of stars in common (354 objects) with Gaia DR2 for which temperatures are available, and found that, on average, our values are about 100 K higher. We show that most of the largest temperature discrepancies can plausibly be ascribed to interstellar extinction effects on Gaia’s photometry. Finally, within the working sample we found four more stars that present supermetallicity, one of which was previously reported in the literature.

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