The galactic habitable zone in elliptical galaxies

AbstractThe concept of a Galactic Habitable Zone (GHZ) was introduced for the Milky Way galaxy a decade ago as an extension of the earlier concept of the Circumstellar Habitable Zone. In this work, we consider the extension of the concept of a GHZ to other types of galaxies by considering two elliptical galaxies as examples, M87 and M32. We argue that the defining feature of the GHZ is the probability of planet formation which has been assumed to depend on the metallicity. We have compared the metallicity distribution of nearby stars with the metallicity of stars with planets to document the correlation between metallicity and planet formation and to provide a comparison to other galaxies. Metallicity distribution, based on the [Fe/H] ratio to solar, of nearby stars peaks at [Fe/H]≈−0.2 dex, whereas the metallicity distribution of extrasolar planet host stars peaks at [Fe/H]≈+0.4 dex. We compare the metallicity distribution of extrasolar planet host stars with the metallicity distribution of the outer star clusters of M87 and M32. The metallicity distribution of stars in the outer regions of M87 peaks at [Fe/H]≈−0.2 dex and extends to [Fe/H]≈+0.4 dex, which seems favourable for planet formation. The metallicity distribution of stars in the outer regions of M32 peaks at [Fe/H]≈−0.2 dex and extends to a much lower [Fe/H]. Both elliptical galaxies met the criteria of a GHZ. In general, many galaxies should support habitable zones.

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Extrasolar Planets and Prospects for Terrestrial Planets

Symposium - International Astronomical Union ◽

10.1017/s0074180900192903 ◽

2004 ◽

Vol 213 ◽

pp. 11-24 ◽

Cited By ~ 1

Author(s):

Geoffrey W. Marcy ◽

R. Paul Butler ◽

Steven S. Vogt ◽

Debra A. Fischer

Keyword(s):

Solar System ◽

Milky Way ◽

Extrasolar Planets ◽

Terrestrial Planets ◽

Habitable Zone ◽

Milky Way Galaxy ◽

System Architectures ◽

Rocky Planets ◽

Host Stars ◽

Eccentricity Orbit

Examination of ∼2000 sun–like stars has revealed 97 planets (as of 2002 Nov), all residing within our Milky Way Galaxy and within ∼200 light years of our Solar System. They have masses between 0.1 and 10 times that of Jupiter, and orbital sizes of 0.05–5 AU. Thus planets occupy the entire detectable domain of mass and orbits. News & summaries about extrasolar planets are provided at: http://exoplanets.org. These planets were all discovered by the wobble of the host stars, induced gravitationally by the planets, causing a periodicity in the measured Doppler effect of the starlight. Earth–mass planets remain undetectable, but space–based missions such as Kepler, COROT and SIM may provide detections of terrestrial planets within the next decade.The number of planets increases with decreasing planet mass, indicating that nature makes more small planets than jupiter–mass planets. Extrapolation, though speculative, bodes well for an even larger number of earth–mass planets. These observations and the theory of planet formation suggests that single sun–like stars commonly harbor earth–sized rocky planets, as yet undetectable. The number of planets increases with increasing orbital distance from the host star, and most known planets reside in non–circular orbits. Many known planets reside in the habitable zone (albeit being gas giants) and most newly discovered planets orbit beyond 1 AU from their star. A population of Jupiter–like planets may reside at 5–10 AU from stars, not easily detectable at present. The sunlike star 55 Cancri harbors a planet of 4–10 Jupiter masses orbiting at 5.5 AU in a low eccentricity orbit, the first analog of our Jupiter, albeit with two large planets orbiting inward.To date, 10 multiple–planet systems have been discovered, with four revealing gravitational interactions between the planets in the form of resonances. GJ 876 has two planets with periods of 1 and 2 months. Other planetary systems are “hierarchical”, consisting of widely separated orbits. These two system architectures probably result from gravitational interactions among the planets and between the planets and the proto-planetary disk out of which they formed.

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Earth-size planet formation in the habitable zone of circumbinary stars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa757 ◽

2020 ◽

Vol 494 (1) ◽

pp. 1045-1057 ◽

Cited By ~ 1

Author(s):

G O Barbosa ◽

O C Winter ◽

A Amarante ◽

A Izidoro ◽

R C Domingos ◽

...

Keyword(s):

Numerical Simulations ◽

Planet Formation ◽

Terrestrial Planet ◽

Close Binary ◽

Habitable Zone ◽

Density Profiles ◽

Habitable Planets ◽

Habitable Zones ◽

Test Particles ◽

The Stability

ABSTRACT This work investigates the possibility of close binary (CB) star systems having Earth-size planets within their habitable zones (HZs). First, we selected all known CB systems with confirmed planets (totaling 22 systems) to calculate the boundaries of their respective HZs. However, only eight systems had all the data necessary for the computation of HZ. Then, we numerically explored the stability within HZs for each one of the eight systems using test particles. From the results, we selected five systems that have stable regions inside HZs, namely Kepler-34,35,38,413, and 453. For these five cases of systems with stable regions in HZ, we perform a series of numerical simulations for planet formation considering discs composed of planetary embryos and planetesimals, with two distinct density profiles, in addition to the stars and host planets of each system. We found that in the case of the Kepler-34 and 453 systems, no Earth-size planet is formed within HZs. Although planets with Earth-like masses were formed in Kepler-453, they were outside HZ. In contrast, for the Kepler-35 and 38 systems, the results showed that potentially habitable planets are formed in all simulations. In the case of the Kepler-413system, in just one simulation, a terrestrial planet was formed within HZ.

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The Potential for Archaeology Within and Beyond the Habitable Zones (HZ) of the Milky Way

Symposium - International Astronomical Union ◽

10.1017/s0074180900193799 ◽

2004 ◽

Vol 213 ◽

pp. 505-510

Author(s):

John B. Campbell

Keyword(s):

Remote Sensing ◽

Solar System ◽

Milky Way ◽

Extrasolar Planets ◽

Habitable Zone ◽

The Moon ◽

Habitable Zones ◽

Remote Sensing Techniques ◽

Main Region

As archaeology is established on Earth and we are actively exploring the Solar System and beyond, there is the potential to develop a number of forms of exo-archaeology. The archaeology of the things intelligent species do in theory could be practised anywhere, provided one can detect the evidence. Sites are being created by us elsewhere within our star's habitable zone (HZ), namely on the Moon and Mars, and at least molecular traces of human-created probes are being left beyond the HZ (Venus, Jupiter etc.). The successful detection of extrasolar planets and the possible identification of HZs round other stars raise the possibility for the development of extrasolar archaeology, at least initially by remote sensing techniques. Within the Milky Way the main region to investigate is the galactic habitable zone (GHZ), though there could be archaeological traces of technological behaviours beyond it.

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How many suns are in the sky? Multiplicity surveys of exoplanet host stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319001595 ◽

2018 ◽

Vol 14 (S345) ◽

pp. 316-317 ◽

Cited By ~ 1

Author(s):

M. Mugrauer ◽

C. Ginski ◽

N. Vogt ◽

R. Neuhäuser ◽

C. Adam

Keyword(s):

Milky Way ◽

Planet Formation ◽

High Contrast ◽

Contrast Imaging ◽

Direct Imaging ◽

High Contrast Imaging ◽

Multiple Stars ◽

First Results ◽

Formation And Evolution ◽

Host Stars

AbstractIn order to determine the true impact of stellar multiplicity on the formation and evolution of planets, we initiated direct imaging surveys to search for (sub)stellar companions of exoplanet host stars on close orbits, as their gravitational impact on the planet bearing disk at first and on formed planets afterwards is expected to be maximal. According to theory these are the most challenging environments for planet formation and evolution but might occur quite frequently in the milky way, due to the large number of multiple stars within our galaxy. On this poster we showed results, obtained so far in the course of our AO and Lucky-imaging campaigns of exoplanet host stars, conducted with NACO/ESO-VLT for southern and with AstraLux/CAHA2.2m for northern targets, respectively. In addition, we introduced our new high contrast imaging survey with SPHERE/ESO-VLT to search for close companions of southern exoplanet host stars, and presented some first results.

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Laboratory astrophysics for the interpretation of stellar spectra

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320000824 ◽

2019 ◽

Vol 15 (S350) ◽

pp. 345-349

Author(s):

Ulrike Heiter

Keyword(s):

Milky Way ◽

Chemical Elements ◽

Spectral Lines ◽

Laboratory Astrophysics ◽

Atomic Data ◽

Milky Way Galaxy ◽

Infrared Wavelength ◽

Stellar Spectra ◽

Continuous Activities ◽

Host Stars

AbstractHigh-resolution stellar spectra are important tools for studying the chemical evolution of the Milky Way Galaxy, tracing the origin of chemical elements, and characterizing planetary host stars. Large amounts of data have been accumulating, in particular in the optical and infrared wavelength regions. The observed spectral lines are interpreted using model spectra that are calculated based on transition data for numerous species, in particular neutral and singly ionized atoms. We rely heavily on the continuous activities of laboratory astrophysics groups that produce high-quality experimental and theoretical atomic data for the relevant transitions. We give examples for the precision with which the chemical composition of stars observed by different surveys can be determined, and discuss future needs from laboratory astrophysics.

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ARGOS – II. The Galactic bulge survey

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/sts305 ◽

2012 ◽

Vol 428 (4) ◽

pp. 3660-3670 ◽

Cited By ~ 90

Author(s):

K. Freeman ◽

M. Ness ◽

E. Wylie-de-Boer ◽

E. Athanassoula ◽

J. Bland-Hawthorn ◽

...

Keyword(s):

Radial Velocity ◽

Milky Way ◽

Radial Velocities ◽

Galactic Centre ◽

Red Giants ◽

Formation Processes ◽

Galactic Bulge ◽

Milky Way Galaxy ◽

Selection For ◽

Metallicity Distribution

Abstract We describe the motivation, field locations and stellar selection for the Abundances and Radial velocity Galactic Origins Survey (ARGOS) spectroscopic survey of 28 000 stars in the bulge and inner disc of the Milky Way galaxy across latitudes of b = −5° to −10°. The primary goal of this survey is to constrain the formation processes of the bulge and establish whether it is predominantly a merger or instability remnant. From the spectra (R = 11 000), we have measured radial velocities and determined stellar parameters, including metallicities and [α/Fe] ratios. Distances were estimated from the derived stellar parameters and about 14 000 stars are red giants within 3.5 kpc of the Galactic Centre. In this paper, we present the observations and analysis methods. Subsequent papers (III and IV) will discuss the stellar metallicity distribution and kinematics of the Galactic bulge and inner disc, and the implications for the formation of the bulge.

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Formation, Frequency and Spacing of Habitable Planets

International Astronomical Union Colloquium ◽

10.1017/s0252921100014809 ◽

1997 ◽

Vol 161 ◽

pp. 289-297

Author(s):

Jack J. Lissauer

Keyword(s):

Planet Formation ◽

Orbital Stability ◽

Young Stars ◽

Giant Planets ◽

Terrestrial Planets ◽

Habitable Zone ◽

Habitable Planets ◽

Habitable Zones ◽

Planetary Orbits ◽

Rocky Planets

AbstractModels of planet formation and of the orbital stability of planetary systems are described and used to discuss estimates of the abundance of habitable planets which may orbit stars within our galaxy. Modern theories of star and planet formation, which are based upon observations of the Solar System and of young stars and their environments, predict that most single stars should have rocky planets in orbit about them. Terrestrial planets are believed to grow via pairwise accretion until the spacing of planetary orbits becomes large enough that the configuration is stable for the age of the system. Giant planets orbiting within or near the habitable zone could either prevent terrestrial planets from forming, destroy such planets or remove them from habitable zones. The implications of the giant planets found in recent radial velocity searches for the abundances of habitable planets are discussed.

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Detection of Exomoons Inside the Habitable Zone

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313012751 ◽

2012 ◽

Vol 8 (S293) ◽

pp. 168-170

Author(s):

Luis Ricardo M. Tusnski ◽

Adriana Valio

Keyword(s):

The Other ◽

Planetary Orbit ◽

Habitable Zone ◽

The Moon ◽

Stellar Activity ◽

Orbital Parameters ◽

Hot Jupiters ◽

Habitable Zones ◽

Observational Bias ◽

Host Stars

AbstractSince the discovery of the first exoplanets, those most adequate for life to begin and evolve have been sought. Due to observational bias, however, most of the discovered planets so far are gas giants, precluding their habitability. However, if these hot Jupiters are located in the habitable zones of their host stars, and if rocky moons orbit them, then these moons may be habitable. In this work, we present a model for planetary transit simulation considering the presence of moons around a planet. The moon orbit is considered to be circular and coplanar with the planetary orbit. The other physical and orbital parameters of the star, planet, and moon, can be adjusted in each simulation. It is possible to simulate as many successive transits as desired. Since the presence of spots on the surface of the star may produce a signal similar to that of the presence of a moon, our model also allows for the inclusion of starspots. The goal is to determine the criteria for detectability of moons using photometry with the CoRoT and Kepler telescopes taking into account the stellar activity.

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Terrestrial planet accretion constrained by isotopes: Implications for Earth-like habitats

10.5194/epsc2021-721 ◽

2021 ◽

Author(s):

Helmut Lammer ◽

Manuel Scherf ◽

Nikolai V. Erkaev

Keyword(s):

Sea Water ◽

Terrestrial Planet ◽

Building Blocks ◽

Habitable Zone ◽

Isotopic Data ◽

Habitable Zones ◽

Siderophile Elements ◽

The Right ◽

Host Stars ◽

Planet Accretion

Here we discuss terrestrial planet formation by using Earth and our knowledge from various isotope data such as 182Hf-182W, U-Pb, lithophile-siderophile elements, atmospheric 36Ar/38Ar, 20Ne/22Ne, 36Ar/22Ne isotope ratios, the expected solar 3He abundance in Earth&#8217;s deep mantle and Earth&#8217;s D/H sea water ratios as an example. By analyzing the available isotopic data one finds that, the bulk of Earth&#8217;s mass most likely accreted within 10 to 30 million years after the formation of the solar system. Proto-Earth most likely accreted a mass of 0.5 to 0.6 MEarth during the disk lifetime of 3 to 4.5 million years and the rest after the disk evaporated (see also Lammer et al. 2021; DOI: 10.1007/s11214-020-00778-4). We also show that particular accretion scenarios of involved planetary building blocks, large planetesimals and planetary embryos that lose also volatiles and moderate volatile rock-forming elements such as the radioactive decaying isotope 40K determine if a terrestrial planet in a habitable zone of a Sun-like star later evolves to an Earth-like habitat or not. Our findings indicate that one can expect a large diversity of exoplanets with the size and mass of Earth inside habitable zones of their host stars but only a tiny number may have formed to the right conditions that they could potentially evolve to an Earth-like habitat. Finally, we also discuss how future ground- and space-based telescopes that can characterize atmospheres of terrestrial exoplanets can be used to validate this hypothesis. &#160;&#160;

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Bernoulli, Darwin, and Sagan: the probability of life on other planets

International Journal of Astrobiology ◽

10.1017/s1473550416000148 ◽

2016 ◽

Vol 16 (2) ◽

pp. 185-189 ◽

Cited By ~ 4

Author(s):

D. Kim Rossmo

Keyword(s):

Binomial Distribution ◽

Milky Way ◽

Large Error ◽

Probabilistic Framework ◽

Extraterrestrial Life ◽

Milky Way Galaxy ◽

Bernoulli Trial ◽

Habitable Zones

AbstractThe recent discovery that billions of planets in the Milky Way Galaxy may be in circumstellar habitable zones has renewed speculation over the possibility of extraterrestrial life. The Drake equation is a probabilistic framework for estimating the number of technological advanced civilizations in our Galaxy; however, many of the equation's component probabilities are either unknown or have large error intervals. In this paper, a different method of examining this question is explored, one that replaces the various Drake factors with the single estimate for the probability of life existing on Earth. This relationship can be described by the binomial distribution if the presence of life on a given number of planets is equated to successes in a Bernoulli trial. The question of exoplanet life may then be reformulated as follows – given the probability of one or more independent successes for a given number of trials, what is the probability of two or more successes? Some of the implications of this approach for finding life on exoplanets are discussed.

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