Pleione (star)

Coordinates: Sky map 03h 49m 11.2161s, +24° 08′ 12.163″
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Pleione
Image of the Pleiades star cluster
Pleione (circled) is located just above Atlas in the East of the Pleiades cluster.
Observation data
Epoch J2000      Equinox J2000
Constellation Taurus
Right ascension 03h 49m 11.2166s[1]
Declination 24° 08′ 12.157″[1]
Apparent magnitude (V) 4.77 - 5.50[2]
Characteristics
Evolutionary stage Main sequence
Spectral type B8Vne[3]
B−V color index −0.08[4]
Variable type γ Cas[2]
Distance
450 ± 8 ly
(138 ± 2 pc)
Absolute magnitude (MV)−0.347[6]
Details
Myr
HR 1180, SAO
 76229
Database references
SIMBADdata

Pleione

fifth magnitude star
.

The brighter star of the Pleione binary pair, component A, is a hot

type B star 184 times more luminous than the Sun. It is classified as Be star with certain distinguishing traits: periodic phase changes and a complex circumstellar environment composed of two gaseous disks at different angles to each other. The primary star rotates rapidly, close to its breakup velocity, even faster than Achernar
. Although some research on the companion star has been performed, stellar characteristics of the orbiting B component are not well known.

Nomenclature

28 Tauri is the star's

variable star designation. The name Pleione originates with Greek mythology; she is the mother of seven daughters known as the Pleiades. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[11] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[12] included a table of the first two batches of names approved by the WGSN; which included Pleione for this star. It is now so entered in the IAU Catalog of Star Names.[13]

Visibility

Chart of the constellation Taurus
The location of the Pleiades (circled) in the constellation Taurus.

With an

northern hemisphere at latitudes greater than 66° North. Once late April arrives, the cluster can be spotted briefly in the deepening twilight of the western horizon, soon to disappear with the other setting stars.[15]

Pleione is classified as a

circumstellar disks
formed of material being ejected from the star.

There has been significant debate as to the star's actual distance from

mas, indicating a distance around 138 pc. This is relatively imprecise for a Gaia result due to the brightness of the star, but still with a statistical margin of error similar to the Hipparcos results.[1]

Properties

In 1942

bolometric luminosity of 184 L☉ assuming a distance of roughly 130 pc.[7] With a radius of 3.7 R☉ and mass that is 2.9 M☉, Pleione is considerably smaller than the brightest stars in the Pleiades. Alcyone for instance has a radius that is 10 R☉ with a luminosity 2,400 L☉, making it roughly 30 times more voluminous than Pleione and about 13 times brighter.[note 3]

Be star

Artist's impression of the Phi Persei system. Classical Be stars like Pleione and Phi Persei exhibit gaseous equatorial disks, likely caused by rapid rotation.[21]

Pleione is a classical

decretion disks", because they consist of material being thrown off the star (as opposed to accretion disks which comprise material falling toward the star).[26]

Be Stars are fast rotators (>200 km/s), causing them to be highly oblate, with a substantial stellar wind and high mass loss rate.[22] Pleione's rotational velocity of 329 km/s is considerably faster than the 251 km/s of Achernar, a prototypical Be star.[9][27] Pleione revolves on its axis once every 11.8 hours, compared to 48.4 hours for Achernar.[note 4] For comparison, the Sun takes 25.3 days to rotate. Pleione is spinning so fast that it is close to the estimated breakup velocity for a B8V star of about 370–390 km/s, which is why it is losing so much mass.[28]

Artist's impression of Alpha Arae rotating with a velocity close to breakup and losing mass through a stellar wind emerging from the poles.[29]

Pleione is unusual because it alternates between three different phases: 1) normal

B star, 2) Be star and 3) Be shell star. The cause is changes in the decretion disc, which appears, disappears, and reforms. Material in the disc is pulled back towards the star by gravity, but if it has enough energy it can escape into space, contributing to the stellar wind.[25] Sometimes, Be stars form multiple decretion discs simultaneously, producing complex circumstellar dynamics.[30]

Broad-band optical light curve for Pleione[31]

As a result of such dynamics, Pleione exhibits prominent long-term

spectroscopic variations encompassing a period of about 35 years.[30] During the 20th century, Pleione went through several phase changes: it was in a Be phase until 1903, a B phase (1905–1936), a B-shell phase (1938–1954), followed by another Be phase (1955–1972).[28] It then returned to the Be-shell phase in 1972, developing numerous shell absorption lines in its spectrum. At the same time, the star showed a decrease in brightness, beginning at the end of 1971. After reaching a minimum brightness in late 1973, the star gradually re-brightened. In 1989, Pleione entered a Be phase which lasted until the summer of 2005.[30]

These phase changes are ascribed to the evolution of a decretion disc that formed in 1972.[30] Polarimetric observations show the intrinsic polarization angle has changed, indicating a change in orientation of the disc axis.[32] Because Pleione has a stellar companion with a close orbit, the shift in the polarization angle has been attributed to the companion causing a precession (wobble) of the disk, with a precession period of roughly 81 years.[32]

Photometric and spectroscopic observations from 2005 to 2007 indicated that a new disc had formed around the equator – producing a two discs at different inclination angles (60° and 30°).[30][32] Such a misaligned double-disc structure had not been observed around other Be stars.[30][32]

Star system

Pleione is known to be a

AU, assuming a distance of 120 parsecs.[35]

Ethnological influences

Oceanid nymph. Painting from French artist Gustave Doré
.

Mythology

Main article: Pleione (mythology)

Pleione was an

Titan, and mother of the Hyas, Hyades and Pleiades.[39]

Etymology

When names were assigned to the stars in the Pleiades cluster, the bright pair of stars in the East of the cluster were named Atlas and Pleione, while the seven other bright stars were named after the

Valerius Flaccus to apply to the cluster as a whole, and Riccioli called the star Mater Pleione.[40]

There is some diversity of opinion as to the origin of the names Pleione and Pleiades. There are three possible derivations of note. Foremost is that both names come from the Greek word πλεῖν, (pr. ple'-ō), meaning "to sail".[40][41] This is particularly plausible given that ancient Greece was a seafaring culture and because of Pleione's mythical status as an Oceanid nymph. Pleione, as a result, is sometimes referred to as the "sailing queen" while her daughters the "sailing ones". Also, the appearance of these stars coincided with the sailing season in antiquity; sailors were well advised to set sail only when the Pleiades were visible at night, lest they meet with misfortune.[39]

Another derivation of the name is the Greek word Πλειόνη[37] (pr. plêionê), meaning "more", "plenty", or "full"—a lexeme with many English derivatives like pleiotropy, pleomorphism, pleonasm, pleonexia, plethora and Pliocene. This meaning also coincides with the biblical Kīmāh and the Arabic word for the Pleiades — Al Thurayya.[40] In fact, Pleione may have been numbered amongst the Epimelides (nymphs of meadows and pastures) and presided over the multiplication of the animals, as her name means "to increase in number".[42]

Finally, the last comes from

doves'), a reference to the sisters' mythical transformation by Zeus into a flock of doves following their pursuit by Orion, the giant huntsman, across the heavens.[43]

Modern legacy

In the best-selling 1955

Time-Life called The World We Live In, there is an artist's impression of Pleione entitled Purple Pleione.[44] The illustration is from the famed space artist Chesley Bonestell
and carries the caption: "Purple Pleione, a star of the familiar Pleiades cluster, rotates so rapidly that it has flattened into a flying saucer and hurled forth a dark red ring of hydrogen. Where the excited gas crosses Pleione's equator, it obscures her violet light."

Given its mythical connection with

track dedicated to 28 Tauri.[48]

See also

Notes

  1. ^ Pronounced /ˈplaɪəniː/ PLY-anee or /ˈpliːəniː/ PLEE-ənee
  2. ^ The brightness ratio of Atlas versus Pleione is derived from the formula for apparent magnitude and is based on their respective visual magnitudes: Atlas () at 3.62 and Pleione () at 5.05. Therefore:
  3. volumes. It is assumed that the volume of each star is reasonably approximated by the formula for a sphere
    :
    VA ≈ 4⁄3π × 103 ≈ 4,188.79 VSun
    VP ≈ 4⁄3π × 3.23 ≈ 137.26 VSun
    Therefore, the volume of Alcyone compared to Pleione ≈ 4,188.79 ÷ 137.26 ≈ 30.52 Alcyone's luminosity compared to Pleione is:
    2,400L☉ ÷ 190L☉ = 12.63 (or 13 rounded)
  4. ^ The time it takes for Achernar (TA) and Pleione (TP) to rotate on its own axis is determined by taking the star's radius in solar units, multiplying by the Sun's radius in kilometers, then calculating the star's circumference at the equator and dividing by its speed of rotation per hour. Therefore:
    TA = 10 R☉ × 696,000 km × 2 × π ÷ 251 km/s ÷ 3,600 ≈ 48.4 hrs
    TP = 3.2 R☉ × 696,000 km × 2 × π ÷ 329 km/s ÷ 3,600 ≈ 11.8 hrs

References

  1. ^
    doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR
    .
  2. ^
    Bibcode:2009yCat....102025S
    .
  3. Bibcode:2008PZP.....8....6T
    .
  4. ^ Nicolet, B. (1978). "Catalogue of homogeneous data in the UBV photoelectric photometric system".
    Bibcode:1978A&AS...34....1N
    .
  5. S2CID 119231169
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  6. ^
    doi:10.1051/0004-6361/201014840
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  11. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  12. ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
  13. ^ "IAU Catalog of Star Names". Retrieved 28 July 2016.
  14. ^ Getsova, I.; et al. (2002). "All About The Pleiades". Catch a Star 2002. European Southern Observatory. Archived from the original on 2020-10-27. Retrieved 2010-09-15.
  15. ^ Bakich, M. E. (22 April 2009). "See Mercury, the Moon, and the Pleiades together in the night sky". Astronomy. Retrieved 2010-09-14. Don't miss a stunning sight around 9 P.M. local daylight time April 26 when a crescent Moon joins Mercury and the Pleiades in the deepening twilight.
  16. ^ a b For an in-depth discussion of
    S2CID 16420237
    .
  17. ^ Allen, J.; Boyd, P. (15 April 1997). "Finding Stellar Distances". Ask an Astrophysicist. NASA. Retrieved 2010-09-14. A straightforward summary of the different methods used by astronomers to measure stellar distances.
  18. ^ Perryman, M. A. C.; et al. (1997). "The Hipparcos Catalogue".
    mas
    yielding a distance of about 119 ± 1.0pc or 388 ± 3.2ly
  19. ^ a b Weaver, D.; Soderblom, D. (1 June 2004). "Hubble Refines Distance to Pleiades Star Cluster". Hubblesite Newscenter. Retrieved 2010-09-13.
  20. ^ Struve, O. (1943). "The Story of Pleione".
    Bibcode:1943PA.....51..233S
    .
  21. ^ "Classical Be Stars". Research in Astronomy & Astrophysics at Lehigh. Lehigh University. Retrieved 2010-09-16.
  22. ^ a b Stee, P. "What is a Be star?". Hot and Active Stars Research. Retrieved 2010-06-20.
  23. ^ Plait, P. (5 August 2009). "To B[e] or not to B[e]". Bad Astronomy. Archived from the original on 2010-07-11. Retrieved 2010-09-20.
  24. ^ Porter, J. M.; Rivinius, T. (2003). "Classical Be Stars".
    doi:10.1086/378307
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  25. ^ a b "Glasgow astronomers explain hot star disks". SpaceRef. 1 November 2002. Retrieved 2010-06-20.[permanent dead link]
  26. ^ Thizy, O. "Be Stars". Shelyak Instruments. Archived from the original on 2011-09-27. Retrieved 2010-06-20.
  27. ^ "HR 20472". Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991).
    Centre de Données astronomiques de Strasbourg
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  28. ^ a b Hirata, Ryuko (1995). "Interpretation of the Long-Term Variation in Late-Type Active Be Stars".
    Bibcode:1995PASJ...47..195H
    .
  29. ^ Getsova, I.; et al. (20 September 2006). "To Be or Not to Be: Is It All About Spinning?" (Press release). European Southern Observatory. Retrieved 2010-09-16.
  30. ^ a b c d e f g Tanaka, K.; et al. (2007). "Dramatic Spectral and Photometric Changes of Pleione (28 Tau) between 2005 November and 2007 April" (PDF).
    doi:10.1093/pasj/59.4.l35
    . Retrieved 2010-06-13.
  31. doi:10.1093/mnras/stx1050
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  32. ^ a b c d Hirata, R. (2007). "Disk Precession in Pleione".
    Bibcode:2007ASPC..361..267H
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  33. ^ McAlister, H. A.; et al. (1989). "ICCD speckle observations of binary stars. IV – Measurements during 1986–1988 from the Kitt Peak 4 M telescope".
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  34. ^ Katahira, Jun-Ichi; et al. (1996). "Period Analysis of the Radial Velocity in PLEIONE".
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  35. ^ Mason, B. D.; et al. (1996). "Pleione". Alcyone (Star Information Tool). Retrieved 2010-09-21.
  36. ^ Andrews, M. (2004). The Seven Sisters of the Pleiades – Stories from around the world.
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  37. ^ a b Smith, W. (1873). "Plei'one". A dictionary of Greek and Roman biography and mythology. John Murray. Retrieved 2010-06-17.
  38. ^ Athena, A. (8 July 2010). "Nymphs". Women in Greek Myths. Retrieved 2010-10-07.
  39. ^ a b Apollodorus (1921). "Book 3, Chapter 10, Section 1". The Library. Translated by Frazer, J. G. Retrieved 2010-06-17.
  40. ^ a b c Allen, R. H. (1963). "Star Names: Their Lore and Meaning". Dover Publications. p. 408. Retrieved 2010-06-11.
  41. National Astronomy and Ionosphere Center. Archived from the original
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  42. ^ Atsma, A. J. (8 March 2010). "Pleione". Theoi Greek Mythology. Retrieved 2010-06-14.
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  44. ^ Barnett, L. (1955). The World We Live In. Simon & Schuster. p. 284.
  45. ^ "Team Pleione". Marblehead International One Design Class. Retrieved 2010-10-07.[permanent dead link]
  46. ^ Taylor, J. (19 March 2009). "Fast Boats in the 'Spirit of Tradition'". Jim Taylor Yacht Designs. Archived from the original on 17 February 2010. Retrieved 2010-10-07.
  47. ^ Chami, C. (9 January 2008). "Paul Andreu – The Oriental Arts Centre in Shanghai". Archinnovations. Archived from the original on 2012-03-07. Retrieved 2010-10-07.
  48. ^ Hundred Eight Stars at Discogs

External links

Wikimedia Commons has media related to Pleione (star).
  1. Orion, the giant huntsman, in pursuit of the Pleiades
  2. Himalayan Skyscape
  3. Pleiades and the Milky Way
  4. Pleiades and the Interstellar Medium

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