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Tabby's Star

Coordinates: Sky map 20h 06m 15.457s, +44° 27′ 24.61″
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This is an old revision of this page, as edited by BatteryIncluded (talk | contribs) at 00:00, 23 October 2015 (A weak hypothesis that it has a "companion star" that disturbs its Oort cloud to that degree.). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

KIC 8462852[1]

Map showing location of NGC 6866. KIC 8462852 is northeast between NGC 6866 and ο¹ Cygni.
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Cygnus
Right ascension 20h 06m 15.457s
Declination +44° 27′ 24.61″
Apparent magnitude (V) +11.705±0.017
Characteristics
Evolutionary stage Main sequence[1]
Spectral type F3 V/IV
B−V color index 0.557
V−R color index 0.349
R−I color index 0.305
J−H color index 0.212
J−K color index 0.264
Astrometry
Distance1480 ly
(454 pc)
Absolute magnitude (MV)3.08[1][2]
Details
A
Mass1.43 M☉
Radius1.58 R☉
Luminosity (bolometric)4.7 L☉
Luminosity (visual, LV)5 L☉
Surface gravity (log g)4.0±0.2 cgs
Temperature6750±120 K
Metallicity0.0±0.1
Rotation0.8797±0.0001 days[1]
Rotational velocity (v sin i)84±4 km/s
B
Spectral type M
Other designations
TYC 3162-665-1, 2MASS J20061546+4427248
Database references
SIMBADdata
KICdata

KIC 8462852[1] – eponymously Tabby's star (after Tabetha S. Boyajian) or WTF star (for "Where's The Flux?")[3][4][5][6] – is an F-type main-sequence star located in the constellation Cygnus approximately 454 parsecs (1,480 ly) from Earth. In September 2015, several astronomers published a paper, as part of the Planet Hunters project,[1] analyzing the unusual light fluctuations of the star as measured by the Kepler space telescope,[1][7] which observes changes in the brightness of distant orbiting stars in order to detect exoplanets.[8]

The star's large irregular changes in brightness are consistent with many small masses together orbiting the star in "tight formation".[7] Several hypotheses have been proposed to explain the star's unusual light profile, most notably that its unusual light curve could be signs of activity associated with intelligent extraterrestrial life.[7][9][10][11]

Apparent location

KIC 8462852 in Cygnus[12] is located in the sky roughly halfway between the major visually apparent bright stars Deneb (α Cyg, α Cygni, Alpha Cygni) and Rukh (δ Cyg, δ Cygni, Delta Cygni) to the eye as part of the Northern Cross.[13] KIC 8462852 is situated south of Omicron¹ Cygni (ο¹ Cygni, 31 Cygni), and northeast of the star cluster NGC 6866.[13] While only a few arcminutes away from the cluster, it is unrelated and closer to the Sun than it is to the star cluster. With an apparent magnitude of 11.7, the star cannot be seen by the naked eye, but is visible with a 5-inch telescope[14] in a dark sky with little light pollution.

Observed Kepler data

Luminosity data about the star from the Kepler space telescope shows small non-periodic dips in brightness of inconsistent intensity occurring frequently, along with two massive recorded dips in brightness appearing to occur roughly every ~750 days. The sheer intensity and aperiodic variance of the observed dips in star brightness has puzzled scientists.[11] The star's changes in brightness are consistent with many small masses orbiting the star in "tight formation".[7]

The first major dip[when?] obscured the star's brightness by up to 15%, and the other by up to 22%. In comparison, a planet the size of Jupiter would only obscure a star of this size by 1%, indicating that whatever is blocking light during the star's major dips is not a planet, but rather something covering up to half the width of the star.[11] Due to the failure of two of Kepler's reaction wheels, the star's predicted 750-day dip around April 2015 was not recorded;[1][10] further observations are planned for May 2017.[15]

Hypotheses

Based on the star's spectral and star type, the star's changes in brightness could not be attributed to intrinsic variability,[1] so a few hypotheses have been proposed involving material orbiting the star and blocking its light, but none of these fully explain the observed data.

One explanation for the star's odd reduction in light is that it is due to a cloud of disintegrating comets orbiting the star elliptically.[1][16] Under this scenario, gravity from a nearby star may have caused comets from the star's Oort cloud to fall in towards the star. Evidence to support this hypothesis includes the fact that a red dwarf star exists 132 billion kilometers (885 AU) away to this star. However, the notion that disturbed Oort cloud comets orbiting elliptically close to the star could exist in high enough numbers to obscure 22% of the star's observed luminosity has been doubted.[11]

Another hypothesis for the star's irregular dips in luminosity proposes that the star recently captured an asteroid field.[1]

Other proposed explanations that might block the light from the star involve instrument/data artifacts, variable B(e) star, interstellar dust, a companion, young star with a protoplanetary disk or a series of giant planets with very large ring structures.[17][18]

High resolution spectroscopy and imaging observations have also been made, as well as spectral energy distribution analyses using the Nordic Optical Telescope in Spain.[1][17] A massive collision scenario would create warm dust that glows in infrared wavelengths, but there is no observed excess infrared energy, ruling out massive planetary collision debris.[11] Other researchers think the planetary debris field explanation is unlikely, given there is a very low probability that Kepler could ever witness such an event.[1]

Astronomer Jason Wright and others who have studied the star wrote a paper stating that if the star is younger than its position and speed would suggest, then it may still have coalescing material around it.[3][19] In addition they hypothesized that the objects eclipsing the star could be parts of a megastructure made by an alien civilization, such as a Dyson swarm,[3][7][16][19][20][21] a hypothetical structure that an advanced civilization might build around a star to intercept some of its light for their energy needs.[22][23][24]

Followup studies

On 19 October 2015, the SETI Institute announced that it had begun using the Allen Telescope Array to look for radio emissions from possible intelligent extraterrestrial life in the vicinity of the star.[25] Additional follow-up observations are being proposed separately by other astronomers, potentially using the ground-based Green Bank Telescope, the Very Large Array Radio Telescope,[17][26] and future orbital telescopes dedicated to exoplanetology such as WFIRST, TESS, and PLATO.[19][24]

See also

  • CTA-102 (quasar) - initially postulated by Nikolai Kardashev to be a potential signal from an extraterrestrial civilization
  • Drake equation

References

  1. ^ a b c d e f g h i j k l m Boyajian, T. S.; LaCourse, D. M.; Rappaport, S. A.; Fabrycky, D.; Fischer, D. A.; et al. (11 September 2015). "Planet Hunters X. KIC 8462852 - Where's the Flux?". arXiv:1509.03622 [astro-ph.SR]. Submitted to Monthly Notices of the Royal Astronomical Society.
  2. ^ Pecaut, Mark J.; Mamajek, Eric E. (10 July 2013). "Intrinsic Colors, Temperatures, and Bolometric Corrections of Pre-main-sequence Stars". The Astrophysical Journal. 208 (1). IOP Publishing (published 4 September 2013): 9. arXiv:1307.2657. Bibcode:2013ApJS..208....9P. doi:10.1088/0067-0049/208/1/9.
  3. ^ a b c Wright, Jason (15 October 2015). "KIC 8462852: Where's the Flux?". AstroWright. Pennsylvania State University. Retrieved 16 October 2015.
  4. ^ Newsome, John (16 October 2015). "Space anomaly gets extraterrestrial intelligence experts' attention". CNN News. Retrieved 16 October 2015.
  5. ^ Staff (15 October 2015). "Discovery of a strange star could mean alien life". Fox News. Retrieved 16 October 2015.
  6. ^ King, Bob (16 October 2015). "What's Orbiting KIC 8462852 – Shattered Comet or Alien Megastructure?". Universe Today. Retrieved 16 October 2015.
  7. ^ a b c d e Andersen, Ross (13 October 2015). "The Most Mysterious Star in Our Galaxy". The Atlantic. Retrieved 13 October 2015.
  8. ^ Grush, Loren (16 October 2015). "Why it's so hard for astronomers to discuss the possibility of alien life". The Verge. Retrieved 17 October 2015.
  9. ^ Kaplan, Sarah (15 October 2015). "The strange star that has serious scientists talking about an alien megastructure". The Washington Post. Retrieved 15 October 2015.
  10. ^ a b Aron, Jacob (18 September 2015). "Citizen scientists catch cloud of comets orbiting distant star". New Scientist. Retrieved 15 October 2015.
  11. ^ a b c d e Plait, Phil (14 October 2015). "Did Astronomers Find Evidence of an Alien Civilization? (Probably Not. But Still Cool.)". Slate. Retrieved 15 October 2015.
  12. ^ "KIC10 Search Results". Space Telescope Science Institute. Retrieved 16 October 2015.
  13. ^ a b Sinnott, Roger W. (2010), Sky & Telescope's Pocket Sky Atlas, Sky Publishing Corporation, Cambridge, Massachusetts, U.S.A., ISBN 978-1-931559-31-7 (flexi-softcover, spiral bound). 3rd version 2010 (1st & 2nd printings 2006).
  14. ^ "The Virtual Telescope Project 2.0: KIC 8462852: A star and its secrets". 16 October 2015. Retrieved 22 October 2015.
  15. ^ "Massive cloud of comets causing unexplained dip in a distant star's glow". The Watchers. 19 September 2015. Retrieved 22 October 2015.
  16. ^ a b Fecht, Sarah (13 October 2015). "Have We Detected Megastructures Built By Aliens Around A Distant Star? Or Just A Cloud Of Comets? Scientists Want To Investigate Further". Popular Science. Retrieved 14 October 2015.
  17. ^ a b c Rzetelny, Xaq (16 October 2015). "Something—we're not sure what—is radically dimming a star's light No satisfying explanations, but guesses range from comets to colliding planets". Ars Technica. Retrieved 17 October 2015.
  18. ^ Siegel, Ethan (16 October 2015). "No, Astronomers Probably Haven't Found 'Alien Megastructures'". Forbes. Retrieved 17 October 2015.
  19. ^ a b c Wright, Jason T.; Cartier, Kimberly M. S.; Zhao, Ming; Jontof-Hutter, Daniel; Ford, Eric B. (15 October 2015). "The G Search For Extraterrestrial Civilizations With Large Energy Supplies. IV. The Signatures And Information Content Of Transiting Megastructures". arXiv. Retrieved 16 October 2015. Submitted to The Astrophysical Journal.
  20. ^ "Good night, sleep tight: Advanced alien civilisations rare or absent in the local Universe" (Press release). ASTRON. 15 September 2015. Retrieved 15 October 2015.
  21. ^ Williams, Lee (15 October 2015). "Astronomers may have found giant alien 'megastructures' orbiting star near the Milky Way". The Independent. Retrieved 15 October 2015.
  22. ^ Jones, Morris (November–December 2015). "Reconsidering macro-artefacts in SETI searches". Acta Astronautica. 116: 161–165. doi:10.1016/j.actaastro.2015.07.011.
  23. ^ O'Neill, Ian (14 October 2015). "Has Kepler Discovered an Alien Megastructure?". Discovery Communications. Retrieved 17 October 2015.
  24. ^ a b Siemion, Andrew (29 September 2015). "Prepared Statement by Andrew Siemion - Hearing on Astrobiology Status Report - House Committee on Science, Space, and Technology". SpaceRef.com. Retrieved 19 October 2015. {{cite web}}: line feed character in |title= at position 63 (help)
  25. ^ Wall, Mike (19 October 2015). "Search For Intelligent Aliens Near Bizarre Dimming Star Has Begun". Space.com. Retrieved 20 October 2015.
  26. ^ Mack, Eric (17 October 2015). "The story behind 'alien megastructures' scientists may have found (but probably didn't)". CNET. Retrieved 19 October 2015.
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