18 Aquarii

Last updated
18 Aquarii
Observation data
Epoch J2000       Equinox J2000
Constellation Aquarius
Right ascension 21h 24m 11.49206s [1]
Declination −12° 52′ 41.1928″ [1]
Apparent magnitude  (V) 5.49 [2]
Characteristics
Spectral type F0 V [3]
B−V color index +0.29 [2]
Astrometry
Radial velocity (Rv)−3.0±6.9 [4] km/s
Proper motion (μ)RA: +89.60 [1]   mas/yr
Dec.: +8.62 [1]   mas/yr
Parallax (π)21.23 ± 0.29 mas
Distance 154 ± 2 ly
(47.1 ± 0.6 pc)
Absolute magnitude  (MV)2.12 [4]
Details
Mass 1.54 [5]   M☉
Luminosity 11.8 [4]   L☉
Surface gravity (log g)3.98 [6]   cgs
Temperature 7,194 [6]   K
Metallicity [Fe/H]–0.16 [6]   dex
Rotational velocity (v sin i)138 [7]  km/s
Age 480 [5]   Myr
Other designations
18 Aqr, BD−13° 5923, FK5  1562, HD  203705, HIP  105668, HR  8187, SAO  164364 [8]
Database references
SIMBAD data

18 Aquarii is a single, [9] yellow-white hued star in the equatorial constellation of Aquarius. The designation is from the catalogue of English astronomer John Flamsteed, first published in 1712. The star is faintly visible to the naked eye with an apparent visual magnitude of 5.49 [2] and is located about 154 light-year s (47 parsec s) from Earth. [1]

Star sphere of plasma held together by gravity, undergoing fusion; type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity

A star is type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye from Earth during the night, appearing as a multitude of fixed luminous points in the sky due to their immense distance from Earth. Historically, the most prominent stars were grouped into constellations and asterisms, the brightest of which gained proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. However, most of the estimated 300 sextillion (3×1023) stars in the Universe are invisible to the naked eye from Earth, including all stars outside our galaxy, the Milky Way.

Celestial equator projection of the Earths equator out into space

The celestial equator is the great circle of the imaginary celestial sphere on the same plane as the equator of Earth. This plane of reference bases the equatorial coordinate system. In other words, the celestial equator is an abstract projection of the terrestrial equator into outer space. Due to Earth's axial tilt, the celestial equator is currently inclined by about 23.44° with respect to the ecliptic. The inclination has varied from about 22.0° to 24.5° over the past 5 million years.

Constellation one of the 88 divisions of the celestial sphere, defined by the IAU, many of which derive from traditional asterisms

A constellation is a group of stars that forms an imaginary outline or pattern on the celestial sphere, typically representing an animal, mythological person or creature, a god, or an inanimate object.

This is an F-type main sequence star with a stellar classification of F0 V. [3] It is an estimated 480 [5]  million years old and has a high rate of spin with a projected rotational velocity of 138 km/s. [7] The star has 1.54 [5] times the mass of the Sun and is radiating 11.8 [4] times the Sun's luminosity from its photosphere at an effective temperature of 7,194 K. [6]

Stellar classification Classification of stars based on their spectral characteristics

In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the rainbow of colors interspersed with spectral lines. Each line indicates a particular chemical element or molecule, with the line strength indicating the abundance of that element. The strengths of the different spectral lines vary mainly due to the temperature of the photosphere, although in some cases there are true abundance differences. The spectral class of a star is a short code primarily summarizing the ionization state, giving an objective measure of the photosphere's temperature.

Photosphere A stars outer shell from which light is radiated

The photosphere is a star's outer shell from which light is radiated. The term itself is derived from Ancient Greek roots, φῶς, φωτός/phos, photos meaning "light" and σφαῖρα/sphaira meaning "sphere", in reference to it being a spherical surface that is perceived to emit light. It extends into a star's surface until the plasma becomes opaque, equivalent to an optical depth of approximately 2/3, or equivalently, a depth from which 50% of light will escape without being scattered. In other words, a photosphere is the deepest region of a luminous object, usually a star, that is transparent to photons of certain wavelengths.

The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature when the body's emissivity curve is not known.

Related Research Articles

Delta Aquarii star in the constellation Aquarius

Delta Aquarii, also named Skat, is the third-brightest star in the constellation of Aquarius. The apparent visual magnitude is 3.3, which can be seen with the naked eye. The distance to this star is about 113 light-years based upon parallax measurements, and it has a close companion.

Pi Serpentis, Latinized from π Serpentis, is a solitary white-hued star in the constellation Serpens, located in its head, Serpens Caput. Based upon an annual parallax shift of 18.22 mas as seen from Earth, it is located around 179 light years from the Sun. It is visible to the naked eye with an apparent visual magnitude of 4.82.

Upsilon Tauri star

Upsilon Tauri is a solitary, white-hued star in the zodiac constellation of Taurus, and is a member of the Hyades star cluster. It is faintly visible to the naked eye with an apparent visual magnitude of +4.28. Based upon an annual parallax shift of 21.21 mas as seen from Earth, it is located around 154 light years from the Sun.

Sigma Tauri star system in the constellation Taurus

Sigma Tauri is the Bayer designation for a pair of white-hued stars in the zodiac constellation of Taurus. The system is a visual double star, whose components are designated σ1 Tauri and σ2 Tauri, with the latter being the more northerly star. The two are separated by 7.2 arcminutes on the sky and can be readily split with a pair of binoculars. They have apparent visual magnitudes of +5.07 and +4.70, respectively, which indicated they are both visible to the naked eye. Based upon parallax measurements, σ1 Tauri is about 147 light years from the Sun, while σ2 Tauri is 156 light years distant.

Tau Virginis star in the constellation Virgo

Tau Virginis is a single star in the zodiac constellation Virgo. With an apparent visual magnitude of 4.28, it is faintly visible to the naked eye. The distance to Tau Virginis, based upon parallax measurements, is approximately 225 light years with a margin of error of ±3 light years.

Psi<sup>3</sup> Aquarii Star in the constellation Aquarius

Psi3 Aquarii, Latinized from ψ3 Aquarii, is the Bayer designation for a visual binary star system in the constellation of Aquarius. It has an apparent visual magnitude of 4.98, which is bright enough to be seen with the naked eye. Parallax measurements give a distance estimate of roughly 262 light-years.

Sigma Aquarii Star in the constellation Aquarius

Sigma Aquarii is the Bayer designation for a double star in the equatorial constellation of Aquarius. It is visible to the naked eye with an apparent visual magnitude of 4.81. Based upon parallax measurements, the distance to this star is roughly 290 light-years.

101 Aquarii star

101 Aquarii is a star in the equatorial constellation of Aquarius. 101 Aquarii is the Flamsteed designation, although it also bears the Bayer designation b3 Aquarii. The combined apparent visual magnitude of the pair is 4.71, which is bright enough to be seen with the naked eye from the suburbs. The distance of this star from Earth is estimated as 290 light-years based upon parallax measurements.

107 Aquarii is a double star in the equatorial constellation of Aquarius. 107 Aquarii is the Flamsteed designation, although it also bears the Bayer designation i2 Aquarii. The pair have an angular separation of 6.787 arcseconds. They have a combined apparent visual magnitude of +5.305, with individual magnitudes of 5.72 and 6.72. The annual parallax shift is 13.66 milliarcseconds with an 8% margin of error. This indicates the system is at a distance of around 240 light-years from Earth.

39 Aquarii is a star in the constellation of Aquarius. 39 Aquarii is its Flamsteed designation. It is a faint naked eye star with an apparent visual magnitude of 6.03. Based upon an annual parallax shift of 23.78 measured with a 3% margin of error, this star is at a distance of around 137 light-years from Earth.

Omega<sup>1</sup> Aquarii star in the constellation Aquarius

Omega1 Aquarii, Latinized from ω1 Aquarii, is the Bayer designation for a star in the equatorial constellation of Aquarius. With an apparent visual magnitude of 4.96, this star is visible to the naked eye from the suburbs. The distance to this star can be estimated from the parallax as roughly 142 light-years, with a 5% margin of error.

δ Doradus is a star in the southern constellation of Dorado. Based upon an annual parallax shift of 21.80 mas as seen from Earth, it is located around 150 light years from the Sun. The star is visible to the naked eye with an apparent visual magnitude of +4.34.

HD 211575 star

HD 211575 is a star in the constellation Aquarius in between "Gamma Aquarii", "Pi Aquarii" and "Sadalmelik". It is a member of the corona of the Ursa Major moving group.

Gamma Crateris Star in the constellation Crater

Gamma Crateris is a binary star system, divisible with a small amateur telescope, and located at the center of the southern constellation of Crater. It is visible to the naked eye with an apparent visual magnitude of 4.06. With an annual parallax shift of 39.62 mas as seen from Earth, this star is located 82.3 light years from the Sun. Based upon the motion of this system through space, it is a potential member of the Castor Moving Group.

2 Ceti is a single star in the equatorial constellation of Cetus, near the border with Aquarius. It is visible to the naked eye with an apparent visual magnitude of 4.483. The distance to 2 Ceti can be estimated from its annual parallax shift of 12.0 mas, which yields a value of around 272 light years. It appears to be moving further from the Earth with a heliocentric radial velocity of about +8 km/s.

64 Eridani is a single, yellow-white hued star in the constellation Eridanus with the variable star designation S Eridani. It is a faint star but visible to the naked eye with an apparent visual magnitude of 4.77. The annual parallax shift is measured at 11.24 mas, which provides a distance estimate of about 290 light years. It is moving closer to the Sun with a radial velocity of around −9 km/s.

Phi Geminorum, Latinized from φ Geminorum, is a binary star in the constellation Gemini, to the southwest of Pollux. It is visible to the naked eye with an apparent visual magnitude of 4.95. Based upon an annual parallax shift of 14.66 mas, this system is located around 220 light years from the Sun.

57 Persei, or m Persei, is a triple star system in the northern constellation of Perseus. It is at the lower limit of visibility to the naked eye, having a combined apparent visual magnitude of 6.08. The annual parallax shift of 16.90 mas provides a distance estimate of about 193 light years. 57 Persei is moving closer to the Sun with a radial velocity of about −23 km/s and will make perihelion in around 2.6 million years at a distance of roughly 22 ly (6.6 pc).

Nu2 Lyrae, Latinized from ν2 Lyrae, or sometimes simply Nu Lyrae, is a solitary star in the northern constellation of Lyra. Based upon an annual parallax shift of 14.09 mas as seen from Earth, it is located around 231 light years from the Sun. With an apparent visual magnitude of 5.23, it is bright enough to be faintly visible to the naked eye.

Zeta2 Lyrae is a single, white-hued star in the northern constellation of Lyra. It is a dim star that is just visible to the naked eye with an apparent visual magnitude of 5.74 An annual parallax shift of 20.97 mas as seen from Earth provides a distance estimate of about 156 light years from the Sun. It is moving closer to the Sun with a radial velocity of −25 km/s.

References

  1. 1 2 3 4 5 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv: 0708.1752  Lock-green.svg, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
  2. 1 2 3 Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J.
  3. 1 2 Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988MSS...C04....0H.
  4. 1 2 3 4 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv: 1108.4971  Lock-green.svg, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  5. 1 2 3 4 David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv: 1501.03154  Lock-green.svg, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146.
  6. 1 2 3 4 Soubiran, C.; et al. (June 2010), "The PASTEL catalogue of stellar parameters", Astronomy and Astrophysics, 515: A111, arXiv: 1004.1069  Lock-green.svg, Bibcode:2010A&A...515A.111S, doi:10.1051/0004-6361/201014247.
  7. 1 2 Royer, F.; Zorec, J.; Gómez, A. E. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv: astro-ph/0610785  Lock-green.svg, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224.
  8. ↑ "18 Aqr". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2018-02-02.
  9. ↑ De Rosa, R. J.; Patience, J.; Wilson, P. A.; Schneider, A.; Wiktorowicz, S. J.; Vigan, A.; Marois, C.; Song, I.; MacIntosh, B.; Graham, J. R.; Doyon, R.; Bessell, M. S.; Thomas, S.; Lai, O. (2014), "The VAST Survey - III. The multiplicity of A-type stars within 75 pc", Monthly Notices of the Royal Astronomical Society, 437 (2): 1216, arXiv: 1311.7141  Lock-green.svg, Bibcode:2014MNRAS.437.1216D, doi:10.1093/mnras/stt1932.
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.