F-type main-sequence star

An F-type main-sequence star (F V) is a main-sequence, hydrogen-fusing compact star of spectral type F and luminosity class V. These stars have from 1.0 to 1.4 times the mass of the Sun and surface temperatures between 6,000 and 7,600 K.[2]Tables VII and VIII. This temperature range gives the F-type stars a yellow-white hue. Because a main-sequence star is referred to as a dwarf star, this class of star may also be termed a yellow-white dwarf. Famous examples include Procyon A, Gamma Virginis A and B,[3] and KIC 8462852.

New Insights into Debris Discs
Disc of debris around an F-type star[1]

Spectral standard stars

The revised Yerkes Atlas system (Johnson & Morgan 1953)[4] listed a dense grid of F-type dwarf spectral standard stars; however, not all of these have survived to this day as standards. The anchor points of the MK spectral classification system among the F-type main-sequence dwarf stars, i.e. those standard stars that have remained unchanged over years and can be used to define the system, are considered to be 78 Ursae Majoris (F2 V) and pi3 Orionis (F6 V).[5] In addition to those two standards, Morgan & Keenan (1973)[6] considered the following stars to be dagger standards: HR 1279 (F3 V), HD 27524 (F5 V), HD 27808 (F8 V), HD 27383 (F9 V), and Beta Virginis (F9 V). Other primary MK standard stars include HD 23585 (F0 V), HD 26015 (F3 V), and HD 27534 (F5 V).[7] Note that two Hyades members with almost identical HD names (HD 27524 and HD 27534) are both considered strong F5 V standard stars, and indeed they share nearly identical colors and magnitudes. Gray & Garrison (1989)[8] provide a modern table of dwarf standards for the hotter F-type stars. F1 and F7 dwarf standards stars are rarely listed, but have changed slightly over the years among expert classifiers. Often-used standard stars include 37 Ursae Majoris (F1 V) and Iota Piscium (F7 V). No F4 V standard stars have been published. Unfortunately F9 V defines the boundary between the hot stars classified by Morgan, and the cooler stars classified by Keenan, and there are discrepancies in the literature on which stars define the F/G dwarf boundary. Morgan & Keenan (1973)[6] listed Beta Virginis and HD 27383 as F9 V standards, but Keenan & McNeil (1989)[9] listed HD 10647 as their F9 V standard. Eta Cassiopeiae A should probably be avoided as a standard star because it was often considered F9 V in Keenan's publications,[9] but G0 V in Morgan's publications.[7]

Planets

Some of the nearest F-type stars known to have planets include Upsilon Andromedae, Tau Boötis, HD 10647, HD 33564, HD 142, HD 60532 and KOI-3010.

Habitability

Some studies show that there is a possibility that life could also develop on planets that orbit a F-type star.[10] It is estimated that the habitable zone of a relatively hot F0 star would extend from about 2.0 AU to 3.7 AU and between 1.1 and 2.2 AU for a relatively cool F8 star.[10] However, relative to a G-type star the main problems for a hypothetical lifeform in this particular scenario would be the more intense light and the shorter stellar lifespan of the home star.[10]

F-type stars are known to emit much higher energy forms of light, such as UV radiation, which in the long term can have a profoundly negative effect on DNA molecules.[10] Studies have shown that, for a hypothetical planet positioned at the same distance from an F-type star as the Earth is from the Sun, and with a similar atmosphere, life on its surface would receive about 2.5 to 7.1 times more damage from UV light compared to that on Earth.[10] Thus, for its native lifeforms to survive, the hypothetical planet would need to have sufficient atmospheric shielding, such as an ozone layer in the upper atmosphere.[10] Without a robust ozone layer, life could theoretically develop on the planet's surface, but it would most likely be confined to underwater or underground regions.[10]

References

  1. ^ "New Insights into Debris Discs". Retrieved 23 May 2016.
  2. ^ Habets, G. M. H. J.; Heintze, J. R. W. (November 1981). "Empirical bolometric corrections for the main-sequence". Astronomy and Astrophysics Supplement. 46: 193–237. Bibcode:1981A&AS...46..193H.
  3. ^ SIMBAD, entries on Gamma Virginis A, Gamma Virginis B, accessed June 19, 2007.
  4. ^ Fundamental stellar photometry for standards of spectral type on the revised system of the Yerkes spectral atlas H.L. Johnson & W.W. Morgan, 1953, Astrophysical Journal, 117, 313
  5. ^ MK Anchor Points, Robert F. Garrison
  6. ^ a b Spectral Classification, W.W. Morgan & P.C. Keenan, 1973, Annual Review of Astronomy and Astrophysics, vol. 11, p.29
  7. ^ a b Revised MK Spectral Atlas for stars earlier than the sun, W.W. Morgan, W. W., H.A. Abt, J.W. Tapscott, 1978, Williams Bay: Yerkes Observatory, and Tucson: Kitt Peak National Observatory
  8. ^ The early F-type stars – Refined classification, confrontation with Stromgren photometry, and the effects of rotation, R. O. Gray & R. F. Garrison, R. F., 1989, Astrophysical Journal Supplement Series, vol. 69, p. 301
  9. ^ a b The Perkins Catalog of Revised MK Types for the Cooler Stars, P.C. Keenan & R.C McNeil, "Astrophysical Journal Supplement Series" 71 (October 1989), pp. 245–266.
  10. ^ a b c d e f g Hadhazy, Adam (1 May 2014). "Could Alien Life Cope with a Hotter, Brighter Star?". space.com. Space.com. Retrieved 31 March 2018.
14 Eridani

14 Eridani is a star in the Eridanus constellation. It has an apparent visual magnitude of 6.143 and is moving closer to the Sun with a radial velocity of around −5 km/s. The measured annual parallax shift is 29.26 mas, which provides an estimated distance of about 111 light years. Proper motion studies indicate that this is an astrometric binary. The visible component has a stellar classification of F5 V Fe−0.7 CH−0.5, which indicates it has the spectrum of an F-type main-sequence star with underabundances of iron and methylidyne. The system has been detected as a source of X-ray emission.

20 Persei

20 Persei is a binary star in the constellation Perseus. Its combined apparent magnitude is 5.343, and it is located around 230 light-years (71 pc) distant, based on its parallax.20 Persei is a visual binary. The orbit of the two stars has been calculated from the secondary changing its position relative to the primary. The two orbit each other every 31.6 years, separated by 0.22 arcseconds. The combined spectrum of 20 Persei matches that of an F-type main-sequence star, and the two stars are thought to have equal masses, 1.5 times that of the Sun. A ninth-magnitude star, designated 20 Persei C, may be associated with the pair.

24 Cancri

24 Cancri (abbreviated to 24 Cnc) is a triple star system in the constellation Cancer. The system is located about 260 light-years (80 parsecs) away, based on its parallax. The system has a combined apparent magnitude of 6.91.The primary component in the star system is designated 24 Cancri A. It is a F-type giant star. The secondary component, designated 24 Cancri B, is a F-type main-sequence star. It itself is a binary, with an orbital period of about 22 years.

25 Arietis

25 Arietis is a star in the equatorial constellation of Cetus, near the modern constellation boundary with Aries for which it is named. 25 Arietis is the Flamsteed designation. It has an apparent visual magnitude of 6.45, placing it near the lower limit of visibility to the naked eye. The distance to this star can be estimated from its annual parallax shift of 27.38 mas, which yields a separation of 119 light years. The star is moving closer to the Earth with a heliocentric radial velocity of −40 km/s, and is predicted to come as close as 102.8 light-years in 259,000 years. It has a relatively high proper motion, traversing the celestial sphere at the rate of 0.359″ per year.This is an ordinary F-type main-sequence star with a stellar classification of F5 V. It is about 1.6 billion years old with an estimated 1.19 times the mass of the Sun and 1.44 times the Sun's radius. The star is radiating 2.9 times the Sun's luminosity from its photosphere at an effective temperature of around 6,274 K.

39 Boötis

39 Boötis is a triple star system located around 224 light years away from the Sun in the northern constellation of Boötes. It is visible to the naked eye as a faint, yellow-white hued star with a combined apparent magnitude of 5.68. The system is moving closer to the Earth with a heliocentric radial velocity of −31 km/s.The magnitude 6.36 primary, component A, is actually a double-lined spectroscopic binary system with an orbital period of 12.822 days, an eccentricity of 0.39, and an angular separation of 2.021 mas. It has a combined stellar classification of F8V, matching an F-type main-sequence star, with individual massed of 1.29 and 1.05 times the mass of the Sun. Component B is of magnitude 6.72 with a class of F7V and 1.25 solar masses. The A–B pair have a separation of 2.9″ and a period of 1,347.653 years. This system is a source of X-ray emission with a luminosity of 41.4×1028 erg s−1.

41 Aquarii

41 Aquarii (abbreviated 41 Aqr) is a double star in the equatorial constellation of Aquarius. 41 Aquarii is its Flamsteed designation. Its apparent magnitude is 5.354 and is located at a distance of around 230 light-years (71 parsecs) from Earth. The brighter component is a red clump giant star with a stellar classification of K0 III and a magnitude of 5.73. At an angular separation of 5.148 arcseconds, the fainter companion is an F-type main sequence star with a magnitude 7.16 and a classification of F8 V.

5 Andromedae

5 Andromedae is a single, yellow-white hued star in the northern constellation of Andromeda. Its designation comes from a catalogue of stars by English astronomer John Flamsteed, published in 1712. The star is faintly visible to the naked eye, having an apparent visual magnitude of 5.68. Based upon an annual parallax shift of 29.12 mas as seen from Earth, it is located 112 light years away. 5 Andromedae is moving closer to the Sun with a radial velocity of −2.6 km/s. It has a relatively high proper motion, advancing across the celestial sphere at the rate of 0.201 arc seconds per year.This is an ordinary F-type main-sequence star with a stellar classification of F5 V. It is estimated to be 2.3 billion years old and is spinning with a projected rotational velocity of 9.7 km/s. The star has 1.39 times the mass of the Sun. It is radiating 5.6 times the Sun's luminosity from its photosphere at an effective temperature of about 6,605 K.

61 Cancri

61 Cancri (61 Cnc) is the Flamsteed designation for a visual binary star system in the northern constellation Cancer. The pair have a combined apparent magnitude of 6.25, which means 61 Cancri is faintly visible to the naked eye. (According to the Bortle scale, it can be seen from rural or even dark suburban skies.) Based upon parallax measurements, the system is approximately 181 light years away from Earth.

The two components appear to be roughly identical with individual masses of about 1.4 times that of the Sun and apparent magnitudes of 7.0. Their combined stellar classification is F4V, matching that of an F-type main sequence star. They have an angular separation of 0.300″ along a position angle of 129.0° (as of 2014). The pair orbit each other with an estimated period of 40.657 years. No significant level of chromospheric activity has been detected coming from either star.

Chi Cancri

Chi Cancri (χ Cnc, χ Cancri) is a star in the constellation Cancer.

χ Cancri is a yellow-white F-type main sequence star with an apparent magnitude of +5.13. It is approximately 59.6 light years from Earth.

HD 128093

HD 128093 is a double star in the constellation Boötes. The brighter component is an F-type main sequence star with a stellar classification of F5V and an apparent magnitude of 6.33. It has a magnitude 11.33 companion at an angular separation of 28.1 along a position angle of 318°.

HD 136118

HD 136118 is a F-type main-sequence star located approximately 171 light-years away in the constellation of Serpens Cauda. It is an F-type dwarf and has apparent magnitude +6.94.

HD 153950

HD 153950 is an F-type main sequence star that is hotter and larger than our Sun. It is located in the southern constellation Scorpius. It is a 7th magnitude star at a distance of about 188 light years from Earth.

HD 30562

HD 30562 is a 6th magnitude F-type main sequence star located approximately 85 light years away in the constellation of Eridanus. In August 2009, it was found that this star has a Jupiter-like planet that orbits in a very eccentric path.

HD 84117

HD 84117 is a F-type main sequence star in the constellation of Hydra. It has an apparent visual magnitude of approximately 4.94.

HD 86264

HD 86264 is a 7th magnitude F-type main sequence star located approximately 224 light years away in the constellation Hydra. In August 2009, it was announced that an exoplanet was found in an eccentric orbit.

HR 3220

HR 3220 (B Car) is a single-lined spectroscopic binary in the constellation Carina, approximately 65 light years from Earth. The primary is a F-type main sequence star with an apparent magnitude of +4.75. The secondary is most likely a helium white dwarf with 0.47 times the mass of the Sun. Mass transfer from the white dwarf progenitor has given the primary the spectral signature of a blue straggler that appears much younger than its actual age of about 10 billion years.

Kepler-39

Kepler-39 (2MASS J19475046+4602034) is an F-type main sequence star located in the constellation Cygnus. It is located about 3,560 light-years (1,090 parsecs) away. One known substellar companion orbits it, Kepler-39b.

Phi2 Ceti

Phi2 Ceti (φ2 Ceti), is a star located in the equatorial constellation of Cetus. φ2 Ceti is also known as 19 Cet, and HD 4813. Based upon parallax measurements, it is located about 51 light years away. It has an apparent visual magnitude of +5.19, making it bright enough to be seen with the naked eye.

This is an F-type main sequence star with a stellar classification of F7V and an effective temperature of 6,352 Kelvin. It has a mass of 1.1 solar masses. It is an irregular variable.

WASP-17

WASP-17 is an F-type main sequence star approximately 1,300 light-years away in the constellation Scorpius. As of 2009, an extrasolar planet has been confirmed to orbit the star. The planet is thought to orbit in a retrograde orbit (in the opposite direction to the star's rotation).

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