Planetary system

Last updated

An artist's concept of a planetary system Artist Concept Planetary System.jpg
An artist's concept of a planetary system

A planetary system is a set of gravitationally bound non-stellar bodies in or out of orbit around a star or star system. Generally speaking, systems with one or more planets constitute a planetary system, although such systems may also consist of bodies such as dwarf planets, asteroids, natural satellites, meteoroids, comets, planetesimals [1] [2] and circumstellar disks. For example, the Sun together with the planetary system revolving around it, including Earth, form the Solar System. [3] [4] The term exoplanetary system is sometimes used in reference to other planetary systems.

Contents

As of 24 July 2024, there are 7,026 confirmed exoplanets in 4,949 planetary systems, with 1007 systems having more than one planet . [5] Debris disks are known to be common while other objects are more difficult to observe.

Of particular interest to astrobiology is the habitable zone of planetary systems where planets could have surface liquid water, and thus, the capacity to support Earth-like life.

History

Heliocentrism

Heliocentrism is the doctrine that the Sun is at the centre of the universe, as opposed to geocentrism (placing Earth at the centre of the universe).

The notion of a heliocentric Solar System with the Sun at its centre is possibly first suggested in the Vedic literature of ancient India, which often refers to the Sun as the "centre of spheres". Some interpret Aryabhatta's writings in Āryabhaṭīya as implicitly heliocentric.

The idea was first proposed in Western philosophy and Greek astronomy as early as the 3rd century BC by Aristarchus of Samos, [6] but received no support from most other ancient astronomers.

Discovery of the Solar System

Heliocentric model of the Solar System in Copernicus' manuscript De Revolutionibus manuscript p9b.jpg
Heliocentric model of the Solar System in Copernicus' manuscript

De revolutionibus orbium coelestium by Nicolaus Copernicus, published in 1543, presented the first mathematically predictive heliocentric model of a planetary system. 17th-century successors Galileo Galilei, Johannes Kepler, and Sir Isaac Newton developed an understanding of physics which led to the gradual acceptance of the idea that the Earth moves around the Sun and that the planets are governed by the same physical laws that governed Earth.

Speculation on extrasolar planetary systems

In the 16th century the Italian philosopher Giordano Bruno, an early supporter of the Copernican theory that Earth and other planets orbit the Sun, put forward the view that the fixed stars are similar to the Sun and are likewise accompanied by planets. He was burned at the stake for his ideas by the Roman Inquisition. [7]

In the 18th century, the same possibility was mentioned by Sir Isaac Newton in the "General Scholium" that concludes his Principia . Making a comparison to the Sun's planets, he wrote "And if the fixed stars are the centres of similar systems, they will all be constructed according to a similar design and subject to the dominion of One." [8]

His theories gained popularity through the 19th and 20th centuries despite a lack of supporting evidence. Long before their confirmation by astronomers, conjecture on the nature of planetary systems had been a focus of the search for extraterrestrial intelligence and has been a prevalent theme in fiction, particularly science fiction.

Detection of exoplanets

The first confirmed detection of an exoplanet was in 1992, with the discovery of several terrestrial-mass planets orbiting the pulsar PSR B1257+12. The first confirmed detection of exoplanets of a main-sequence star was made in 1995, when a giant planet, 51 Pegasi b, was found in a four-day orbit around the nearby G-type star 51 Pegasi. The frequency of detections has increased since then, particularly through advancements in methods of detecting extrasolar planets and dedicated planet-finding programs such as the Kepler mission.

Origin and evolution

Illustration of the dynamics of a proplyd Opo0113i.jpg
Illustration of the dynamics of a proplyd

Planetary systems come from protoplanetary disks that form around stars as part of the process of star formation.

During formation of a system, much material is gravitationally-scattered into distant orbits, and some planets are ejected completely from the system, becoming rogue planets.

Evolved systems

High-mass stars

Planets orbiting pulsars have been discovered. Pulsars are the remnants of the supernova explosions of high-mass stars, but a planetary system that existed before the supernova would likely be mostly destroyed. Planets would either evaporate, be pushed off of their orbits by the masses of gas from the exploding star, or the sudden loss of most of the mass of the central star would see them escape the gravitational hold of the star, or in some cases the supernova would kick the pulsar itself out of the system at high velocity so any planets that had survived the explosion would be left behind as free-floating objects. Planets found around pulsars may have formed as a result of pre-existing stellar companions that were almost entirely evaporated by the supernova blast, leaving behind planet-sized bodies. Alternatively, planets may form in an accretion disk of fallback matter surrounding a pulsar. [9] Fallback disks of matter that failed to escape orbit during a supernova may also form planets around black holes. [10]

Lower-mass stars

Protoplanetary discs observed with the Very Large Telescope. Protoplanetary discs observed with SPHERE.jpg
Protoplanetary discs observed with the Very Large Telescope.

As stars evolve and turn into red giants, asymptotic giant branch stars, and planetary nebulae they engulf the inner planets, evaporating or partially evaporating them depending on how massive they are. [12] [13] As the star loses mass, planets that are not engulfed move further out from the star.

If an evolved star is in a binary or multiple system, then the mass it loses can transfer to another star, forming new protoplanetary disks and second- and third-generation planets which may differ in composition from the original planets, which may also be affected by the mass transfer.

System architectures

The Solar System consists of an inner region of small rocky planets and outer region of large giant planets. However, other planetary systems can have quite different architectures. Studies suggest that architectures of planetary systems are dependent on the conditions of their initial formation. [14] Many systems with a hot Jupiter gas giant very close to the star have been found. Theories, such as planetary migration or scattering, have been proposed for the formation of large planets close to their parent stars. [15] At present,[ when? ] few systems have been found to be analogous to the Solar System with terrestrial planets close to the parent star. More commonly, systems consisting of multiple Super-Earths have been detected. [16]

Classification

Planetary system architectures may be partitioned into four classes based on how the mass of the planets is distributed around the host star: [17] [18]

Peas in a pod

Multiplanetary systems tend to be in a "peas in a pod" configuration meaning they tend to have the following factors: [19]

Components

Planets and stars

The Morgan-Keenan spectral classification Morgan-Keenan spectral classification.svg
The Morgan-Keenan spectral classification

Most known exoplanets orbit stars roughly similar to the Sun: that is, main-sequence stars of spectral categories F, G, or K. One reason is that planet-search programs have tended to concentrate on such stars. In addition, statistical analyses indicate that lower-mass stars (red dwarfs, of spectral category M) are less likely to have planets massive enough to be detected by the radial-velocity method. [20] [21] Nevertheless, several tens of planets around red dwarfs have been discovered by the Kepler space telescope by the transit method, which can detect smaller planets.

Circumstellar disks and dust structures

Debris disks detected in HST archival images of young stars, HD 141943 and HD 191089, using improved imaging processes (April 24, 2014). NASA-14114-HubbleSpaceTelescope-DebrisDisks-20140424.jpg
Debris disks detected in HST archival images of young stars, HD 141943 and HD 191089, using improved imaging processes (April 24, 2014).

After planets, circumstellar disks are one of the most commonly-observed properties of planetary systems, particularly of young stars. The Solar System possesses at least four major circumstellar disks (the asteroid belt, Kuiper belt, scattered disc, and Oort cloud) and clearly-observable disks have been detected around nearby solar analogs including Epsilon Eridani and Tau Ceti. Based on observations of numerous similar disks, they are assumed to be quite common attributes of stars on the main sequence.

Interplanetary dust clouds have been studied in the Solar System and analogs are believed to be present in other planetary systems. Exozodiacal dust, an exoplanetary analog of zodiacal dust, the 1–100 micrometre-sized grains of amorphous carbon and silicate dust that fill the plane of the Solar System [22] has been detected around the 51 Ophiuchi, Fomalhaut, [23] [24] Tau Ceti, [24] [25] and Vega systems.

Comets

As of November 2014 there are 5,253 known Solar System comets [26] and they are thought to be common components of planetary systems. The first exocomets were detected in 1987 [27] [28] around Beta Pictoris, a very young A-type main-sequence star. There are now a total of 11 stars around which the presence of exocomets have been observed or suspected. [29] [30] [31] [32] All discovered exocometary systems (Beta Pictoris, HR 10, [29] 51 Ophiuchi, HR 2174, [30] 49 Ceti, 5 Vulpeculae, 2 Andromedae, HD 21620, HD 42111, HD 110411, [31] [33] and more recently HD 172555 [32] ) are around very young A-type stars.

Other components

Computer modelling of an impact in 2013 detected around the star NGC 2547-ID8 by the Spitzer Space Telescope, and confirmed by ground observations, suggests the involvement of large asteroids or protoplanets similar to the events believed to have led to the formation of terrestrial planets like the Earth. [34]

Based on observations of the Solar System's large collection of natural satellites, they are believed common components of planetary systems; however, the existence of exomoons has not yet been confirmed. The star 1SWASP J140747.93-394542.6, in the constellation Centaurus, is a strong candidate for a natural satellite. [35] Indications suggest that the confirmed extrasolar planet WASP-12b also has at least one satellite. [36]

Orbital configurations

Unlike the Solar System, which has orbits that are nearly circular, many of the known planetary systems display much higher orbital eccentricity. [37] An example of such a system is 16 Cygni.

Mutual inclination

The mutual inclination between two planets is the angle between their orbital planes. Many compact systems with multiple close-in planets interior to the equivalent orbit of Venus are expected to have very low mutual inclinations, so the system (at least the close-in part) would be even flatter than the Solar System. Captured planets could be captured into any arbitrary angle to the rest of the system. As of 2016 there are only a few systems where mutual inclinations have actually been measured [38] One example is the Upsilon Andromedae system: the planets c and d have a mutual inclination of about 30 degrees. [39] [40]

Orbital dynamics

Planetary systems can be categorized according to their orbital dynamics as resonant, non-resonant-interacting, hierarchical, or some combination of these. In resonant systems the orbital periods of the planets are in integer ratios. The Kepler-223 system contains four planets in an 8:6:4:3 orbital resonance. [41] Giant planets are found in mean-motion resonances more often than smaller planets. [42] In interacting systems the planets' orbits are close enough together that they perturb the orbital parameters. The Solar System could be described as weakly interacting. In strongly interacting systems Kepler's laws do not hold. [43] In hierarchical systems the planets are arranged so that the system can be gravitationally considered as a nested system of two-bodies, e.g. in a star with a close-in hot Jupiter with another gas giant much further out, the star and hot Jupiter form a pair that appears as a single object to another planet that is far enough out.

Other, as yet unobserved, orbital possibilities include: double planets; various co-orbital planets such as quasi-satellites, trojans and exchange orbits; and interlocking orbits maintained by precessing orbital planes. [44]

Number of planets, relative parameters and spacings

The spacings between orbits vary widely amongst the different systems discovered by the Kepler space telescope. Orbits of some Kepler Planetary Systems.jpg
The spacings between orbits vary widely amongst the different systems discovered by the Kepler space telescope.

Planet capture

Free-floating planets in open clusters have similar velocities to the stars and so can be recaptured. They are typically captured into wide orbits between 100 and 105 AU. The capture efficiency decreases with increasing cluster size, and for a given cluster size it increases with the host/primary[ clarification needed ] mass. It is almost independent of the planetary mass. Single and multiple planets could be captured into arbitrary unaligned orbits, non-coplanar with each other or with the stellar host spin, or pre-existing planetary system. Some planet–host metallicity correlation may still exist due to the common origin of the stars from the same cluster. Planets would be unlikely to be captured around neutron stars because these are likely to be ejected from the cluster by a pulsar kick when they form. Planets could even be captured around other planets to form free-floating planet binaries. After the cluster has dispersed some of the captured planets with orbits larger than 106 AU would be slowly disrupted by the galactic tide and likely become free-floating again through encounters with other field stars or giant molecular clouds. [45]

Zones

Habitable zone

Location of habitable zone around different types of stars Habitable zone - HZ.png
Location of habitable zone around different types of stars

The habitable zone around a star is the region where the temperature range allows for liquid water to exist on a planet; that is, not too close to the star for the water to evaporate and not too far away from the star for the water to freeze. The heat produced by stars varies depending on the size and age of the star; this means the habitable zone will also vary accordingly. Also, the atmospheric conditions on the planet influence the planet's ability to retain heat so that the location of the habitable zone is also specific to each type of planet.

Habitable zones have usually been defined in terms of surface temperature; however, over half of Earth's biomass is from subsurface microbes, [46] and temperature increases as depth underground increases, so the subsurface can be conducive for life when the surface is frozen; if this is considered, the habitable zone extends much further from the star. [47]

Studies in 2013 indicate that an estimated 22±8% of Sun-like [a] stars have an Earth-sized [b] planet in the habitable [c] zone. [48] [49]

Venus zone

The Venus zone is the region around a star where a terrestrial planet would have runaway greenhouse conditions like Venus, but not so near the star that the atmosphere completely escapes. As with the habitable zone, the location of the Venus zone depends on several factors, including the type of star and properties of the planets such as mass, rotation rate, and atmospheric clouds. Studies of the Kepler spacecraft data indicate that 32% of red dwarfs have potentially Venus-like planets based on planet size and distance from star, increasing to 45% for K-type and G-type stars. [d] Several candidates have been identified, but spectroscopic follow-up studies of their atmospheres are required to determine whether they are like Venus. [50] [51]

Galactic distribution of planets

90% of planets with known distances are within about 2000 light years of Earth, as of July 2014. Planet Discovery Neighbourhood in Milky Way Galaxy.jpeg
90% of planets with known distances are within about 2000 light years of Earth, as of July 2014.

The Milky Way is 100,000 light-years across, but 90% of planets with known distances are within about 2000 light years of Earth, as of July 2014. One method that can detect planets much further away is microlensing. The upcoming Nancy Grace Roman Space Telescope could use microlensing to measure the relative frequency of planets in the galactic bulge versus the galactic disk. [52] So far, the indications are that planets are more common in the disk than the bulge. [53] Estimates of the distance of microlensing events is difficult: the first planet considered with high probability of being in the bulge is MOA-2011-BLG-293Lb at a distance of 7.7 kiloparsecs (about 25,000 light years). [54]

Population I, or metal-rich stars, are those young stars whose metallicity is highest. The high metallicity of population I stars makes them more likely to possess planetary systems than older populations, because planets form by the accretion of metals.[ citation needed ] The Sun is an example of a metal-rich star. These are common in the spiral arms of the Milky Way.[ citation needed ] Generally, the youngest stars, the extreme population I, are found farther in and intermediate population I stars are farther out, etc. The Sun is considered an intermediate population I star. Population I stars have regular elliptical orbits around the Galactic Center, with a low relative velocity. [55]

Population II, or metal-poor stars, are those with relatively low metallicity which can have hundreds (e.g. BD +17° 3248) or thousands (e.g. Sneden's Star) times less metallicity than the Sun. These objects formed during an earlier time of the universe.[ citation needed ] Intermediate population II stars are common in the bulge near the center of the Milky Way,[ citation needed ] whereas Population II stars found in the galactic halo are older and thus more metal-poor.[ citation needed ] Globular clusters also contain high numbers of population II stars. [56] In 2014, the first planets around a halo star were announced around Kapteyn's star, the nearest halo star to Earth, around 13 light years away. However, later research suggests that Kapteyn b is just an artefact of stellar activity and that Kapteyn c needs more study to be confirmed. [57] The metallicity of Kapteyn's star is estimated to be about 8 [e] times less than the Sun. [58]

Different types of galaxies have different histories of star formation and hence planet formation. Planet formation is affected by the ages, metallicities, and orbits of stellar populations within a galaxy. Distribution of stellar populations within a galaxy varies between the different types of galaxies. [59] Stars in elliptical galaxies are much older than stars in spiral galaxies. Most elliptical galaxies contain mainly low-mass stars, with minimal star-formation activity. [60] The distribution of the different types of galaxies in the universe depends on their location within galaxy clusters, with elliptical galaxies found mostly close to their centers. [61]

See also

Notes

  1. ↑ For the purpose of this 1 in 5 statistic, "Sun-like" means G-type star. Data for Sun-like stars were not available so this statistic is an extrapolation from data about K-type stars
  2. ↑ For the purpose of this 1 in 5 statistic, Earth-sized means 1–2 Earth radii
  3. ↑ For the purpose of this 1 in 5 statistic, "habitable zone" means the region with 0.25 to 4 times Earth's stellar flux (corresponding to 0.5–2 AU for the Sun).
  4. ↑ For the purpose of this, terrestrial-sized means 0.5–1.4 Earth radii, the "Venus zone" means the region with approximately 1 to 25 times Earth's stellar flux for M and K-type stars and approximately 1.1 to 25 times Earth's stellar flux for G-type stars.
  5. ↑ Metallicity of Kapteyn's star estimated at [Fe/H]= −0.89. 10−0.89 ≈ 1/8

Related Research Articles

<span class="mw-page-title-main">Exoplanet</span> Planet outside the Solar System

An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not then recognized as such. The first confirmation of the detection occurred in 1992. A different planet, first detected in 1988, was confirmed in 2003. As of 7 November 2024, there are 5,787 confirmed exoplanets in 4,320 planetary systems, with 969 systems having more than one planet. The James Webb Space Telescope (JWST) is expected to discover more exoplanets, and to give more insight into their traits, such as their composition, environmental conditions, and potential for life.

GJ 1061 is a red dwarf star located 12 light-years from Earth in the southern constellation of Horologium. Even though it is a relatively nearby star, it has an apparent visual magnitude of about 13, so it can only be seen with at least a moderately-sized telescope.

<span class="mw-page-title-main">Upsilon Andromedae</span> Star in the constellation Andromeda

Upsilon Andromedae is a binary star located 44 light-years from Earth in the constellation of Andromeda. The system consists of an F-type main-sequence star and a smaller red dwarf.

<span class="mw-page-title-main">Habitable zone</span> Orbits where planets may have liquid surface water

In astronomy and astrobiology, the habitable zone (HZ), or more precisely the circumstellar habitable zone (CHZ), is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure. The bounds of the HZ are based on Earth's position in the Solar System and the amount of radiant energy it receives from the Sun. Due to the importance of liquid water to Earth's biosphere, the nature of the HZ and the objects within it may be instrumental in determining the scope and distribution of planets capable of supporting Earth-like extraterrestrial life and intelligence.

HD 210277 is a single star in the equatorial constellation of Aquarius. It has an apparent visual magnitude of 6.54, which makes it a challenge to view with the naked eye, but it is easily visible in binoculars. The star is located at a distance of 69.6 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −20.9 km/s.

<span class="mw-page-title-main">Exomoon</span> Moon beyond the Solar System

An exomoon or extrasolar moon is a natural satellite that orbits an exoplanet or other non-stellar extrasolar body.

<span class="mw-page-title-main">HD 10180</span> Star in the constellation Hydrus

HD 10180, also designated 2MASS J01375356-6030414, is a Sun-like star in the southern constellation Hydrus that is notable for its large planetary system. Since its discovery, at least six exoplanets have been observed orbiting it, and some studies have proposed up to nine potential planets, which would make it potentially the largest of all known planetary systems, including the Solar System.

<span class="mw-page-title-main">Discoveries of exoplanets</span> Detecting planets located outside the Solar System

An exoplanet is a planet located outside the Solar System. The first evidence of an exoplanet was noted as early as 1917, but was not recognized as such until 2016; no planet discovery has yet come from that evidence. What turned out to be the first detection of an exoplanet was published among a list of possible candidates in 1988, though not confirmed until 2003. The first confirmed detection came in 1992, with the discovery of terrestrial-mass planets orbiting the pulsar PSR B1257+12. The first confirmation of an exoplanet orbiting a main-sequence star was made in 1995, when a giant planet was found in a four-day orbit around the nearby star 51 Pegasi. Some exoplanets have been imaged directly by telescopes, but the vast majority have been detected through indirect methods, such as the transit method and the radial-velocity method. As of 24 July 2024, there are 7,026 confirmed exoplanets in 4,949 planetary systems, with 1007 systems having more than one planet. This is a list of the most notable discoveries.

<span class="mw-page-title-main">Habitability of K-type main-sequence star systems</span> Overview of the habitability of K-type main-sequence star systems

K-type main-sequence stars, also known as orange dwarfs, may be candidates for supporting extraterrestrial life. These stars are known as "Goldilocks stars" as they emit enough radiation in the non-UV ray spectrum to provide a temperature that allows liquid water to exist on the surface of a planet; they also remain stable in the main sequence longer than the Sun by burning their hydrogen slower, allowing more time for life to form on a planet around a K-type main-sequence star. The planet's habitable zone, ranging from 0.1–0.4 to 0.3–1.3 astronomical units (AU), depending on the size of the star, is often far enough from the star so as not to be tidally locked to the star, and to have a sufficiently low solar flare activity not to be lethal to life. In comparison, red dwarf stars have too much solar activity and quickly tidally lock the planets in their habitable zones, making them less suitable for life. The odds of complex life arising may be better on planets around K-type main-sequence stars than around Sun-like stars, given the suitable temperature and extra time available for it to evolve. Some planets around K-type main-sequence stars are potential candidates for extraterrestrial life.

HD 38858 is a G-type star, much like The Sun, with one detected planet. The planet, designated HD 38858 b, is about twice the mass of Uranus and orbits in the star's habitable zone.

<span class="mw-page-title-main">Exocomet</span> Comet outside the Solar System

An exocomet, or extrasolar comet, is a comet outside the Solar System, which includes rogue comets and comets that orbit stars other than the Sun. The first exocomets were detected in 1987 around Beta Pictoris, a very young A-type main-sequence star. There are now a total of 27 stars around which exocomets have been observed or suspected.

<span class="mw-page-title-main">Habitability of binary star systems</span> Potential conditions for extraterrestrial life in binary star systems

Planets in binary star systems may be candidates for supporting extraterrestrial life. Habitability of binary star systems is determined by many factors from a variety of sources. Typical estimates often suggest that 50% or more of all star systems are binary systems. This may be partly due to sample bias, as massive and bright stars tend to be in binaries and these are most easily observed and catalogued; a more precise analysis has suggested that the more common fainter stars are usually singular, and that up to two thirds of all stellar systems are therefore solitary.

Kepler-1229 is a red dwarf star located about 875 light-years (268 pc) away from the Earth in the constellation of Cygnus. It is known to host a super-Earth exoplanet within its habitable zone, Kepler-1229b, which was discovered in 2016.

<span class="mw-page-title-main">Teegarden's Star b</span> Goldilocks terrestrial exoplanet orbiting Teegardens Star

Teegarden's Star b is an exoplanet found orbiting within the habitable zone of Teegarden's Star, an M-type red dwarf 12.5 light years away from the Solar System. It had the highest Earth Similarity Index (ESI) of any exoplanet, but in February 2024 a new study updated the parameters of the planet, thus reducing its ESI to 0.90, making it no longer the planet with the hightest ESI. Along with Teegarden's Star c, it is among the closest known potentially habitable exoplanets.

Planet-hosting stars are stars which host planets, therefore forming planetary systems.

Tau Ceti f is a potential super-Earth or mini-Neptune orbiting Tau Ceti that was discovered in 2012 by statistical analyses of the star's variations in radial velocity, based on data obtained using HIRES, AAPS, and HARPS. It is of interest because its orbit places it in Tau Ceti's extended habitable zone, but a 2015 study implies that there may not be a detectable biosignature because it has only been in the temperate zone for less than one billion years. In 2017, it was again recovered from radial-velocity data, along with Tau Ceti e. Despite this, it remains an unconfirmed candidate.

References

  1. ↑ p. 394, The Universal Book of Astronomy, from the Andromeda Galaxy to the Zone of Avoidance, David J. Dsrling, Hoboken, New Jersey: Wiley, 2004. ISBN   0-471-26569-1.
  2. ↑ p. 314, Collins Dictionary of Astronomy, Valerie Illingworth, London: Collins, 2000. ISBN   0-00-710297-6.
  3. ↑ p. 382, Collins Dictionary of Astronomy.
  4. ↑ p. 420, A Dictionary of Astronomy, Ian Ridpath, Oxford, New York: Oxford University Press, 2003. ISBN   0-19-860513-7.
  5. ↑ Schneider, J. "Interactive Extra-solar Planets Catalog". The Extrasolar Planets Encyclopedia . Retrieved July 24, 2024.
  6. ↑ Dreyer (1953), pp.135–48; Linton (2004), pp.38–9). The work of Aristarchus's in which he proposed his heliocentric system has not survived. We only know of it now from a brief passage in Archimedes's The Sand Reckoner .
  7. ↑ "Cosmos" in The New Encyclopædia Britannica (15th edition, Chicago, 1991) 16:787:2a. "For his advocacy of an infinity of suns and earths, he was burned at the stake in 1600."
  8. ↑ Newton, Isaac; Cohen, I. Bernard; Whitman, Anne (1999) [First published 1713]. The Principia: A New Translation and Guide . University of California Press. p. 940. ISBN   0-520-20217-1.
  9. ↑ Podsiadlowski, Philipp (1993). "Planet formation scenarios". In: Planets Around Pulsars; Proceedings of the Conference. 36: 149. Bibcode:1993ASPC...36..149P.
  10. ↑ The fate of fallback matter around newly born compact objects, Rosalba Perna, Paul Duffell, Matteo Cantiello, Andrew MacFadyen, (Submitted on December 17, 2013)
  11. ↑ "Sculpting Solar Systems - ESO's SPHERE instrument reveals protoplanetary discs being shaped by newborn planets". www.eso.org. Retrieved December 7, 2016.
  12. ↑ Ferreira, Becky (May 3, 2023). "It's the End of a World as We Know It - Astronomers spotted a dying star swallowing a large planet, a discovery that fills in a "missing link" in understanding the fates of Earth and many other planets". The New York Times . Archived from the original on May 3, 2023. Retrieved May 3, 2023.
  13. ↑ Ferreira, Becky (August 19, 2022). "The Juicy Secrets of Stars That Eat Their Planets - As scientists study thousands of planets around the galaxy, they are learning more about worlds that get swallowed up by their stars". The New York Times . Retrieved August 19, 2022.
  14. ↑ Hasegawa, Yasuhiro; Pudritz, Ralph E. (2011). "The origin of planetary system architectures - I. Multiple planet traps in gaseous discs". Monthly Notices of the Royal Astronomical Society. 417 (2): 1236–1259. arXiv: 1105.4015 . Bibcode:2011MNRAS.417.1236H. doi: 10.1111/j.1365-2966.2011.19338.x . ISSN   0035-8711. S2CID   118843952.
  15. ↑ Stuart J. Weidenschilling & Francesco Marzari (1996). "Gravitational scattering as a possible origin for giant planets at small stellar distances". Nature. 384 (6610): 619–621. Bibcode:1996Natur.384..619W. doi:10.1038/384619a0. PMID   8967949. S2CID   4304777.
  16. ↑ Types and Attributes at Astro Washington.com.
  17. ↑ Mishra, Lokesh; Alibert, Yann; Udry, Stéphane; Mordasini, Christoph (February 1, 2023). "Framework for the architecture of exoplanetary systems - I. Four classes of planetary system architecture". Astronomy & Astrophysics. 670: A68. arXiv: 2301.02374 . Bibcode:2023A&A...670A..68M. doi: 10.1051/0004-6361/202243751 . ISSN   0004-6361.
  18. ↑ Mishra, Lokesh; Alibert, Yann; Udry, Stéphane; Mordasini, Christoph (February 1, 2023). "Framework for the architecture of exoplanetary systems - II. Nature versus nurture: Emergent formation pathways of architecture classes". Astronomy & Astrophysics. 670: A69. arXiv: 2301.02373 . Bibcode:2023A&A...670A..69M. doi: 10.1051/0004-6361/202244705 . ISSN   0004-6361.
  19. 1 2 Mishra, Lokesh; Alibert, Yann; Leleu, Adrien; Emsenhuber, Alexandre; Mordasini, Christoph; Burn, Remo; Udry, Stéphane; Benz, Willy (December 1, 2021). "The New Generation Planetary Population Synthesis (NGPPS) VI. Introducing KOBE: Kepler Observes Bern Exoplanets - Theoretical perspectives on the architecture of planetary systems: Peas in a pod". Astronomy & Astrophysics. 656: A74. arXiv: 2105.12745 . Bibcode:2021A&A...656A..74M. doi: 10.1051/0004-6361/202140761 . ISSN   0004-6361.
  20. ↑ Andrew Cumming; R. Paul Butler; Geoffrey W. Marcy; et al. (2008). "The Keck Planet Search: Detectability and the Minimum Mass and Orbital Period Distribution of Extrasolar Planets". Publications of the Astronomical Society of the Pacific. 120 (867): 531–554. arXiv: 0803.3357 . Bibcode:2008PASP..120..531C. doi:10.1086/588487. S2CID   10979195.
  21. ↑ Bonfils, Xavier; Forveille, Thierry; Delfosse, Xavier; Udry, Stéphane; Mayor, Michel; Perrier, Christian; Bouchy, François; Pepe, Francesco; Queloz, Didier; Bertaux, Jean-Loup (2005). "The HARPS search for southern extra-solar planets VI: A Neptune-mass planet around the nearby M dwarf Gl 581". Astronomy and Astrophysics. 443 (3): L15–L18. arXiv: astro-ph/0509211 . Bibcode:2005A&A...443L..15B. doi:10.1051/0004-6361:200500193. S2CID   59569803.
  22. ↑ Stark, C.; Kuchner, M. (2008). "The Detectability of Exo-Earths and Super-Earths Via Resonant Signatures in Exozodiacal Clouds". The Astrophysical Journal. 686 (1): 637–648. arXiv: 0810.2702 . Bibcode:2008ApJ...686..637S. doi:10.1086/591442. S2CID   52233547.
  23. ↑ Lebreton, J.; van Lieshout, R.; Augereau, J.-C.; Absil, O.; Mennesson, B.; Kama, M.; Dominik, C.; Bonsor, A.; Vandeportal, J.; Beust, H.; Defrère, D.; Ertel, S.; Faramaz, V.; Hinz, P.; Kral, Q.; Lagrange, A.-M.; Liu, W.; Thébault, P. (2013). "An interferometric study of the Fomalhaut inner debris disk. III. Detailed models of the exozodiacal disk and its origin". Astronomy and Astrophysics. 555: A146. arXiv: 1306.0956 . Bibcode:2013A&A...555A.146L. doi:10.1051/0004-6361/201321415. S2CID   12112032.
  24. 1 2 Absil, O.; Le Bouquin, J.-B.; Berger, J.-P.; Lagrange, A.-M.; Chauvin, G.; Lazareff, B.; Zins, G.; Haguenauer, P.; Jocou, L.; Kern, P.; Millan-Gabet, R.; Rochat, S.; Traub, W. (2011). "Searching for faint companions with VLTI/PIONIER. I. Method and first results". Astronomy and Astrophysics. 535: A68. arXiv: 1110.1178 . Bibcode:2011A&A...535A..68A. doi:10.1051/0004-6361/201117719. S2CID   13144157.
  25. ↑ di Folco, E.; Absil, O.; Augereau, J.-C.; Mérand, A.; Coudé du Foresto, V.; Thévenin, F.; Defrère, D.; Kervella, P.; ten Brummelaar, T. A.; McAlister, H. A.; Ridgway, S. T.; Sturmann, J.; Sturmann, L.; Turner, N. H. (2007). "A near-infrared interferometric survey of debris disk stars". Astronomy and Astrophysics. 475 (1): 243–250. arXiv: 0710.1731 . Bibcode:2007A&A...475..243D. doi:10.1051/0004-6361:20077625. S2CID   18317389.
  26. ↑ Johnston, Robert (August 2, 2014). "Known populations of solar system objects". Archived from the original on June 9, 2019. Retrieved January 19, 2015.
  27. ↑ Ferlet, R.; Vidal-Madjar, A.; Hobbs, L. M. (1987). "The Beta Pictoris circumstellar disk. V - Time variations of the CA II-K line". Astronomy and Astrophysics . 185: 267–270. Bibcode:1987A&A...185..267F.
  28. ↑ Beust, H.; Lagrange-Henri, A.M.; Vidal-Madjar, A.; Ferlet, R. (1990). "The Beta Pictoris circumstellar disk. X - Numerical simulations of infalling evaporating bodies". Astronomy and Astrophysics . 236: 202–216. Bibcode:1990A&A...236..202B.
  29. 1 2 Lagrange-Henri, A. M.; Beust, H.; Ferlet, R.; Vidal-Madjar, A.; Hobbs, L. M. (1990). "HR 10 - A new Beta Pictoris-like star?". Astronomy and Astrophysics . 227: L13–L16. Bibcode:1990A&A...227L..13L.
  30. 1 2 Lecavelier Des Etangs, A.; et al. (1997). "HST-GHRS observations of candidate β Pictoris-like circumstellar gaseous disks". Astronomy and Astrophysics . 325: 228–236. Bibcode:1997A&A...325..228L.
  31. 1 2 Welsh, B. Y. & Montgomery, S. (2013). "Circumstellar Gas-Disk Variability Around A-Type Stars: The Detection of Exocomets?". Publications of the Astronomical Society of the Pacific . 125 (929): 759–774. Bibcode:2013PASP..125..759W. doi: 10.1086/671757 .
  32. 1 2 Kiefer, F.; Lecavelier Des Etangs, A.; et al. (2014). "Exocomets in the circumstellar gas disk of HD 172555". Astronomy and Astrophysics . 561: L10. arXiv: 1401.1365 . Bibcode:2014A&A...561L..10K. doi:10.1051/0004-6361/201323128. S2CID   118533377.
  33. ↑ "'Exocomets' Common Across Milky Way Galaxy". Space.com. January 7, 2013. Retrieved January 8, 2013.
  34. ↑ NASA's Spitzer Telescope Witnesses Asteroid Smashup
  35. ↑ – "Mamajek thinks his team could be either observing the late stages of planet formation if the transiting object is a star or brown dwarf, or possibly moon formation if the transiting object is a giant planet"
  36. ↑ Российские астрономы впервые открыли луну возле экзопланеты (in Russian) – "Studying of a curve of change of shine of WASP-12b has brought to the Russian astronomers unusual result: regular splashes were found out.<...> Though stains on a star surface also can cause similar changes of shine, observable splashes are very similar on duration, a profile and amplitude that testifies for benefit of exomoon existence."
  37. ↑ Dvorak, R.; Pilat-Lohinger, E.; Bois, E.; Schwarz, R.; Funk, B.; Beichman, C.; Danchi, W.; Eiroa, C.; Fridlund, M.; Henning, T.; Herbst, T.; Kaltenegger, L.; Lammer, H.; Léger, A.; Liseau, R.; Lunine, Jonathan I.; Paresce F, Penny, A.; Quirrenbach, A.; Röttgering, H.; Selsis, F.; Schneider, J.; Stam, D.; Tinetti, G.; White, G.; "Dynamical habitability of planetary systems", Institute for Astronomy, University of Vienna, Vienna, Austria, January 2010
  38. ↑ Mills, Sean M.; Fabrycky, Daniel C. (2017). "Kepler-108: A Mutually Inclined Giant Planet System". The Astronomical Journal. 153 (1): 45. arXiv: 1606.04485 . Bibcode:2017AJ....153...45M. doi: 10.3847/1538-3881/153/1/45 . S2CID   119295498.
  39. ↑ Deitrick, Russell; Barnes, Rory; McArthur, Barbara; Quinn, Thomas R.; Luger, Rodrigo; Antonsen, Adrienne; Fritz Benedict, G. (2014). "The 3-dimensional architecture of the Upsilon Andromedae planetary system". The Astrophysical Journal. 798: 46. arXiv: 1411.1059 . doi:10.1088/0004-637X/798/1/46. S2CID   118409453.
  40. ↑ "NASA – Out of Whack Planetary System Offers Clues to a Disturbed Past". Nasa.gov. May 25, 2010. Retrieved August 17, 2012.
  41. ↑ Emspak, Jesse (March 2, 2011). "Kepler Finds Bizarre Systems". International Business Times. International Business Times Inc. Retrieved March 2, 2011.
  42. ↑ Winn, Joshua N.; Fabrycky, Daniel C. (2015). "The Occurrence and Architecture of Exoplanetary Systems". Annual Review of Astronomy and Astrophysics. 53: 409–447. arXiv: 1410.4199 . Bibcode:2015ARA&A..53..409W. doi:10.1146/annurev-astro-082214-122246. S2CID   6867394.
  43. ↑ Fabrycky, Daniel C. (2010). "Non-Keplerian Dynamics". arXiv: 1006.3834 [astro-ph.EP].
  44. ↑ Migaszewski, Cezary; Goździewski, Krzysztof (2009). "Equilibria in the secular, non-co-planar two-planet problem". Monthly Notices of the Royal Astronomical Society. 395 (4): 1777–1794. arXiv: 0812.2949 . Bibcode:2009MNRAS.395.1777M. doi: 10.1111/j.1365-2966.2009.14552.x . S2CID   14922361.
  45. ↑ On the origin of planets at very wide orbits from the recapture of free-floating planets, Hagai B. Perets, M. B. N. Kouwenhoven, 2012
  46. ↑ Amend, J. P.; Teske, A. (2005). "Expanding frontiers in deep subsurface microbiology". Palaeogeography, Palaeoclimatology, Palaeoecology. 219 (1–2): 131–155. Bibcode:2005PPP...219..131A. doi:10.1016/j.palaeo.2004.10.018.
  47. ↑ Further away planets 'can support life' say researchers, BBC, January 7, 2014 Last updated at 12:40
  48. ↑ Sanders, R. (November 4, 2013). "Astronomers answer key question: How common are habitable planets?". newscenter.berkeley.edu. Archived from the original on November 7, 2014. Retrieved November 6, 2014.
  49. ↑ Petigura, E. A.; Howard, A. W.; Marcy, G. W. (2013). "Prevalence of Earth-size planets orbiting Sun-like stars". Proceedings of the National Academy of Sciences . 110 (48): 19273–19278. arXiv: 1311.6806 . Bibcode:2013PNAS..11019273P. doi: 10.1073/pnas.1319909110 . PMC   3845182 . PMID   24191033.
  50. ↑ Habitable Zone Gallery - Venus
  51. ↑ Kane, Stephen R.; Kopparapu, Ravi Kumar; Domagal-Goldman, Shawn D. (2014). "On the Frequency of Potential Venus Analogs from Kepler Data". The Astrophysical Journal. 794 (1): L5. arXiv: 1409.2886 . Bibcode:2014ApJ...794L...5K. doi:10.1088/2041-8205/794/1/L5. S2CID   119178082.
  52. ↑ SAG 11: Preparing for the WFIRST Microlensing Survey Archived February 22, 2014, at the Wayback Machine , Jennifer Yee
  53. ↑ Toward a New Era in Planetary Microlensing Archived November 3, 2014, at the Wayback Machine , Andy Gould, September 21, 2010
  54. ↑ MOA-2011-BLG-293Lb: First Microlensing Planet possibly in the Habitable Zone, V. Batista, J.-P. Beaulieu, A. Gould, D.P. Bennett, J.C Yee, A. Fukui, B.S. Gaudi, T. Sumi, A. Udalski, (Submitted on October 14, 2013 (v1), last revised October 30, 2013 (this version, v3))
  55. ↑ Charles H. Lineweaver (2000). "An Estimate of the Age Distribution of Terrestrial Planets in the Universe: Quantifying Metallicity as a Selection Effect". Icarus. 151 (2): 307–313. arXiv: astro-ph/0012399 . Bibcode:2001Icar..151..307L. doi:10.1006/icar.2001.6607. S2CID   14077895.
  56. ↑ T. S. van Albada; Norman Baker (1973). "On the Two Oosterhoff Groups of Globular Clusters". Astrophysical Journal. 185: 477–498. Bibcode:1973ApJ...185..477V. doi: 10.1086/152434 .
  57. ↑ Stellar activity mimics a habitable-zone planet around Kapteyn's star, Paul Robertson (1 and 2), Arpita Roy (1 and 2 and 3), Suvrath Mahadevan (1 and 2 and 3) ((1) Dept. of Astronomy and Astrophysics, Penn State University, (2) Center for Exoplanets & Habitable Worlds, Penn State University, (3) The Penn State Astrobiology Research Center), (Submitted on May 11, 2015 (v1), last revised June 1, 2015 (this version, v2))
  58. ↑ Two planets around Kapteyn's star : a cold and a temperate super-Earth orbiting the nearest halo red-dwarf, Guillem Anglada-Escudé, Pamela Arriagada, Mikko Tuomi, Mathias Zechmeister, James S. Jenkins, Aviv Ofir, Stefan Dreizler, Enrico Gerlach, Chris J. Marvin, Ansgar Reiners, Sandra V. Jeffers, R. Paul Butler, Steven S. Vogt, Pedro J. Amado, Cristina Rodríguez-López, Zaira M. Berdiñas, Julian Morin, Jeff D. Crane, Stephen A. Shectman, Ian B. Thompson, Mateo Díaz, Eugenio Rivera, Luis F. Sarmiento, Hugh R.A. Jones, (Submitted on June 3, 2014)
  59. ↑ Habitable Zones in the Universe, G. Gonzalez, (Submitted on March 14, 2005 (v1), last revised March 21, 2005 (this version, v2))
  60. ↑ John, D, (2006), Astronomy, ISBN   1-4054-6314-7, p. 224-225
  61. ↑ Dressler, A. (March 1980). "Galaxy morphology in rich clusters - Implications for the formation and evolution of galaxies". The Astrophysical Journal. 236: 351–365. Bibcode:1980ApJ...236..351D. doi: 10.1086/157753 .

Further reading

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.