Tabby's Star

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Tabby's Star
KIC 8462852 in IR and UV.png
Tabby's Star in infrared (left) and ultraviolet (right)
Observation data
Epoch J2000.0        Equinox J2000.0 (ICRS)
Constellation Cygnus
Right ascension 20h 06m 15.45265s [1]
Declination +44° 27′ 24.7909″ [1]
Apparent magnitude  (V)+11.705±0.017 [2]
Characteristics
KIC 8462852 A
Evolutionary stage Main sequence [2]
Spectral type F3V [2]
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
KIC 8462852 B
Spectral type M2V [3]
Astrometry
KIC 8462852 A
Radial velocity (Rv)−0.46±3.91 [1]  km/s
Proper motion (μ)RA: −10.375±0.012  mas/yr [1]
Dec.: −10.273±0.011  mas/yr [1]
Parallax (π)2.2545 ± 0.0099  mas [1]
Distance 1,447 ± 6  ly
(444 ± 2  pc)
Absolute magnitude  (MV)3.08 [2] [4]
KIC 8462852 B
Proper motion (μ)RA: −10.097±0.231  mas/yr [5]
Dec.: −10.610±0.254  mas/yr [5]
Parallax (π)2.2470 ± 0.1620  mas [5]
Distance 1,500 ± 100  ly
(450 ± 30  pc)
Position (relative to Tabby's Star) [3]
ComponentKIC 8462852 B
Epoch of observation 2019
Angular distance 1951.88±0.06 mas
Position angle 96.062±0.004°
Projected separation 880±10 AU
Details
KIC 8462852 A
Mass 1.43 [2]   M☉
Radius 1.58 [2]   R☉
Luminosity (bolometric)4.68 [2]   L☉
Surface gravity (log g)4.0±0.2 [6]   cgs
Temperature 6750±120 [2]   K
Metallicity 0.0±0.1 [2]
Rotation 0.8797±0.0001 days [2]
Rotational velocity (v sin i)84±4 [2]  km/s
KIC 8462852 B
Mass 0.44±0.02 [3]   M☉
Radius 0.45±0.02 [3]   R☉
Temperature 3720±70 [3]   K
Other designations
TYC 3162-665-1, Boyajian's Star, WISE J200615.45+442724.7, KIC 8462852, NSVS 5711291, Gaia DR2 2081900940499099136, 2MASS J20061546+4427248, UCAC4 673-083862, TIC 185336364, APASS 52502626
Database references
SIMBAD data
B

Tabby's Star (also known as Boyajian's Star and WTF Star, and designated KIC 8462852 in the Kepler Input Catalog) is an F-type main-sequence star in the constellation Cygnus approximately 1,470 light-years (450 parsecs ) from Earth. A distant red dwarf companion has been reported, making Tabby's Star a binary stellar system.

Contents

Unusual light fluctuations of Tabby's Star, including up to a 22% dimming in brightness, were discovered by citizen scientists as part of the Planet Hunters project. The discovery was made from data collected by the Kepler space telescope, which observed changes in the brightness of distant stars to detect exoplanets. Several hypotheses have been proposed to explain the star's large irregular changes in brightness, but as of 2024, none of them fully explain all aspects of the resulting light curve. It has been suggested that it is an alien megastructure, but evidence tends to discount this suggestion. [7]

In September 2019, astronomers reported that the observed dimmings of Tabby's Star may have been produced by fragments resulting from the disruption of an orphaned exomoon. Tabby's Star is not the only star that has large irregular dimmings, but other such stars include young stellar objects called YSO dippers, which have different dimming patterns.

Nomenclature

The names "Tabby's Star" and "Boyajian's Star" refer to American astronomer Tabetha S. Boyajian, who was the lead author of the scientific paper that announced the discovery of the star's irregular light fluctuations in 2015. [8] [9] The nickname "WTF Star" is a reference to the paper's subtitle "where's the flux?", which highlights the observed dips in the star's radiative flux. [10] [11] [12] [13] The star has also been given the nickname "LGM-2" – a homage to the first pulsar discovered, PSR B1919+21, which was given the nickname "LGM-1" when it was originally theorized to be a transmission from an extraterrestrial civilization. [14] Other designations in various star catalogues have been given to Tabby's Star. In the Kepler Input Catalog, a collection of astronomical objects catalogued by the Kepler space telescope, Tabby's Star is known as KIC 8462852. [2] In the Tycho-2 Catalogue, an enhanced collection of stars catalogued by Hipparcos , the star is known as TYC 3162-665-1. [2] In the infrared Two Micron All-Sky Survey (2MASS), the star is identified as 2MASS J20061546+4427248. [2]

Location

Cygnus constellation map.svg
Red circle.svg
Location of Tabby's Star in the constellation Cygnus (circled in red)
Finder image: KIC 8462852 (blue square) and nearby stars - stable reference stars are in red circles.(FOV=12.5 x 9.6 minutes of arc, NE at upper-left) KIC8462852BlueSquare&NearbyStars-20180603.jpg
Finder image: KIC 8462852 (blue square) and nearby stars – stable reference stars are in red circles.(FOV=12.5 × 9.6 minutes of arc, NE at upper-left)

Tabby's Star in the constellation Cygnus is roughly halfway between the bright stars Deneb and Delta Cygni as part of the Northern Cross. [16] [17] It is situated south of 31 Cygni, and northeast of the star cluster NGC 6866. [17] 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 (130 mm) telescope [18] in a dark sky with little light pollution.

History of observations

Tabby's Star was observed as early as the year 1890. [19] [20] [21] The star was cataloged in the Tycho, 2MASS, UCAC4, and WISE astronomical catalogs [22] (published in 1997, 2003, 2009, and 2012, respectively). [23] [24] [25] [26]

The main source of information about the luminosity fluctuations of Tabby's Star is the Kepler space telescope. During its primary and extended mission from 2009 to 2013 it continuously monitored the light curves of over 100,000 stars in a patch of sky in the constellations Cygnus and Lyra. [27]

2017 light fluctuations

Normalized flux for Tabby's Star
KIC 8462852 Daily Normalized Flux by Bruce Gary, 20170502-20180504.png
2 May 2017 to 4 May 2018: g′
Bruce Gary ( HAO ) [28] [29] [30]
Prominent dimmings [31] − start dates (est.):
  • 14 May 2017 ("Elsie"; 2% dip)
  • 11 June ("Celeste"; 2% dip)
  • 2 August ("Skara Brae"; 1% dip)
  • 5 September ("Angkor"; 2.3%; [32] 3% [33] dip)
  • 20 November (unnamed; 1.25% [29] dip) [34]
  • 16 March 2018 ("Caral-Supe"; 1%; [35] 5% [36] dip)
  • 24 March ("Evangeline"; >5% dip)

On 20 May 2017, Boyajian and her colleagues reported, via The Astronomer's Telegram , on an ongoing dimming event (named "Elsie") [34] [37] which possibly began on 14 May 2017. [38] It was detected by the Las Cumbres Observatory Global Telescope Network, specifically by its telescope in Maui (LCO Maui). This was verified by the Fairborn Observatory (part of the N2K Consortium) in Southern Arizona (and later by LCO Canary Islands). [39] [40] [41] Further optical and infrared spectroscopy and photometry were urgently requested, given the short duration of these events, which may be measured in days or weeks. [38] Observations from multiple observers globally were coordinated, including polarimetry. [42] Furthermore, the independent SETI projects Breakthrough Listen and Near-InfraRed Optical SETI (NIROSETI), both at Lick Observatory, continue to monitor the star. [38] [43] [44] [45] By the end of the three-day dimming event, [46] a dozen observatories had taken spectra, with some astronomers having dropped their own projects to provide telescope time and resources. More generally the astronomical community was described as having gone "mildly bananas" over the opportunity to collect data in real-time on the unique star. [47] The 2% dip event was named "Elsie" (a homophone of "LC", in reference to Las Cumbres and light curve). [48]

Initial spectra with FRODOSpec at the two-meter Liverpool Telescope showed no changes visible between a reference spectrum and this dip. [43] [44] [45] Several observatories, however, including the twin Keck telescopes (HIRES) and numerous citizen science observatories, acquired spectra of the star, [38] [44] [45] showing a dimming that had a complex shape, and initially had a pattern similar to the one at 759.75 days from the Kepler event 2, epoch 2 data. Observations were taken across the electromagnetic spectrum.

Evidence of a second dimming event (named "Celeste") [37] was observed on 13–14 June 2017, which possibly began 11 June, by amateur astronomer Bruce L. Gary. [49] While the light curve on 14–15 June indicated a possible recovery from the dimming event, the dimming continued to increase afterwards, [49] and on 16 June, Boyajian wrote that the event was approaching a 2% dip in brightness. [34] [50]

A third prominent 1% dimming event (named "Skara Brae") [37] was detected beginning 2 August 2017, [51] [52] and which recovered by 17 August. [34] [53]

A fourth prominent dimming event (named "Angkor") [37] began 5 September 2017, [54] and is, as of 16 September 2017, between 2.3% [32] and 3% [33] dimming event, making it the "deepest dip this year". [34] [55]

Another dimming event, amounting to a 0.3% dip, began around 21 September 2017 and completely recovered by 4 October 2017. [28]

On 10 October 2017, an increasing brightening, lasting about two weeks, of the starlight from KIC 8462852 was noted by Bruce L. Gary of the Hereford Arizona Observatory [57] and Boyajian. [58] A possible explanation, involving a transiting brown dwarf in a 1,600-day eccentric orbit near KIC 8462852, a "drop feature" in dimness and predicted intervals of brightening, to account for the unusual fluctuating starlight events of KIC 8462852, has been proposed. [57] [59] [60]

On about 20 November 2017, a fifth prominent dimming event began and had deepened to a depth of 0.44%; as of 16 December 2017, the event recovered, leveled off at dip bottom for 11 days, faded again, to a current total dimming depth of 1.25%, and was recovering again. [57] [29]

Dimming and brightening events of the star continue to be monitored; related light curves are updated and released frequently. [35] [61]

2018 light fluctuations

The star was too close to the Sun's position in the sky from late December 2017 to mid February 2018 to be seen. Observations resumed in late February. [35] [62] A new series of dips began on 16 March 2018. By 18 March 2018 the star was down in brightness by more than 1% in g-band, according to Bruce L. Gary, [35] and about 5% in r-band, making it the deepest dip observed since the Kepler Mission in 2013, according to Tabetha S. Boyajian. [36] [63] [64] A second even deeper dip with a depth of >5% started on 24 March 2018, as confirmed by AAVSO observer John Hall. [65] [66] As of 27 March 2018, that second dip was recovering. [67]

2019 light fluctuations

The 2019 observing season began in mid-March, when the star reappeared after its yearly conjunction with the Sun. [68]

The ground based observation campaign was supplemented by the Transiting Exoplanet Survey Satellite (TESS), which observed the star every 2 minutes between 18 July and 11 September 2019. [69] [70] It observed a 1.4% dip in brightness between 3–4 September 2019. [71]

Between October 2019 and December 2019, at least seven separate dips were observed, the deepest of which had a depth of 2%. By the end of the observing season in early January 2020, the star had once again recovered in brightness. The total combined depth of the dips in 2019 was 11%, comparable to that seen in 2011 and 2013, but spread over a long time interval. [72] This cluster of dips is roughly centered on the 17 October 2019 date predicted by Sacco et al. [73] for a reappearance, given a 1,574-day (4.31-year) period, of orbiting material comprising the original "D800" dip.

Luminosity

Observations of the luminosity of the star by the Kepler space telescope show small, frequent, non-periodic dips in brightness, along with two large recorded dips in brightness two years apart. The amplitude of the changes in the star's brightness, and the aperiodicity of the changes, mean that this star is of particular interest for astronomers. [74] The star's changes in brightness are consistent with many small masses orbiting the star in "tight formation". [75]

The first major dip, on 5 March 2011, reduced the star's brightness by up to 15%, and the next 726 days later (on 28 February 2013) by up to 22%. (A third dimming, around 8%, occurred 48 days later.) 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. [74] Due to the failure of two of Kepler's reaction wheels, the star's predicted 750-day dip around February 2015 was not recorded. [2] [76] The light dips do not exhibit an obvious pattern. [77]

In addition to the day-long dimmings, a study of a century's worth of photographic plates suggests that the star has gradually faded in 100 years (from c. 1890 to c. 1990) by about 20%, which would be unprecedented for any F-type main-sequence star. [19] [20] Teasing accurate magnitudes from long-term photographic archives is a complex procedure, however, requiring adjustment for equipment changes, and is strongly dependent on the choice of comparison stars. Another study, examining the same photographic plates, concluded that the possible century-long dimming was likely a data artifact, and not a real astrophysical event. [21] Another study from plates between 1895 and 1995 found strong evidence that the star has not dimmed, but kept a constant flux within a few percent, except an 8% dip on 24 October 1978, resulting in a period of the putative occulter of 738 days. [78]

A third study, using light measurements by the Kepler observatory over a four-year period, determined that Tabby's Star dimmed at about 0.34% per year before dimming more rapidly by about 2.5% in 200 days. It then returned to its previous slow fade rate. The same technique was used to study 193 stars in its vicinity and 355 stars similar in size and composition to Tabby's Star. None of these stars exhibited such dimming. [79]

In 2018, a possible 1,574-day (4.31-year) periodicity in dimming of the star was reported. [73]

Stellar companion

A red dwarf stellar companion at projected separation 880±10 AU from Tabby's Star was confirmed to be comoving in 2021. [3] [80] For comparison, this is around 180 times the orbit of Jupiter, [81] around 30 times the orbit of Neptune, [82] or around 5.5 times [83] the distance to Voyager 1 as of 2023.

Hypotheses

Originally, and until Kohler's work of 2017, it was thought that, based on the spectrum and stellar type of Tabby's Star, its changes in brightness could not be attributed to intrinsic variability. [2] Consequently, a few hypotheses have been proposed involving material orbiting the star and blocking its light, although none of these fully fit the observed data. [84]

Some of the proposed explanations involve interstellar dust, a series of giant planets with very large ring structures, [85] [86] a recently captured asteroid field, [2] the system undergoing Late Heavy Bombardment, [87] [88] and an artificial megastructure orbiting the star. [89]

By 2018, the leading hypothesis was that the "missing" heat flux involved in the star's dimming could be stored within the star's interior. Such variations in luminosity might arise from a number of mechanisms affecting the efficiency of heat transport inside the star. [90] [91]

However, in September 2019, astronomers reported that the observed dimmings of Tabby's Star may have been produced by fragments resulting from the disruption of an orphaned exomoon. [92] [93]

Circumstellar dust ring

Artist's concept of an "uneven ring of dust" orbiting Tabby's Star PIA22081-KIC8462852-TabbysStar-UnevenDustRing-Illustration-20171004.png
Artist's concept of an "uneven ring of dust" orbiting Tabby's Star

Meng et al. (2017) suggested that, based on observational data of Tabby's Star from the Swift Gamma-Ray Burst Mission, Spitzer Space Telescope, and Belgian AstroLAB IRIS Observatory, only "microscopic fine-dust screens", originating from "circumstellar material", are able to disperse the starlight in the way detected in their measurements. [94] [95] [96] [97] Based on these studies, on 4 October 2017, NASA reported that the unusual dimming events of Tabby's Star are due to an "uneven ring of dust" orbiting the star. [94] Although the explanation of a significant amount of small particles orbiting the star regards "long-term fading" as noted by Meng, [95] the explanation also seems consistent with the week-long fadings found by amateur astronomer Bruce L. Gary and the Tabby Team, coordinated by astronomer Tabetha S. Boyajian, in more recent dimming events. [98] [34] [28] [99] [100] A related, but more sophisticated, explanation of dimming events, involving a transiting "brown dwarf" in a 1600-day eccentric orbit near Tabby's Star, a "drop feature" in dimness, and predicted intervals of "brightening", has been proposed. [57] [59] [60] [101] Dimming and brightening events of Tabby's Star continue to be monitored; related light curves are updated and released frequently. [35] [102]

Nonetheless, data similar to that observed for Tabby's Star, along with supporting data from the Chandra X-ray Observatory, were found with dust debris orbiting WD 1145+017, a white dwarf that also has unusual light curve fluctuations. [103] Further, the highly variable star RZ Piscium, which brightens and dims erratically, has been found to emit excessive infrared radiation, suggesting that the star is surrounded by large amounts of gas and dust, possibly resulting from the destruction of local planets. [104] [105]

A cloud of disintegrating comets

Artist's impression of an orbiting swarm of dusty comet fragments PIA20053-PossibleCometSwarmAroundKIC8462852-ArtistConcept-20151124.jpg
Artist's impression of an orbiting swarm of dusty comet fragments

One proposed explanation for the reduction in light is that it is due to a cloud of disintegrating comets orbiting the star elliptically. [2] [87] [106] [107] This scenario would assume that a planetary system around Tabby's Star has something similar to the Oort cloud and that gravity from a nearby star caused comets from said cloud to fall closer into the system, thereby obstructing the spectra of Tabby's Star. Evidence supporting this hypothesis includes an M-type red dwarf within 132 billion kilometers (885  AU ) of Tabby's Star. [2] The notion that disturbed comets from such a cloud could exist in high enough numbers to obscure 22% of the star's observed luminosity has been doubted. [74]

Submillimetre-wavelength observations searching for farther-out cold dust in an asteroid belt akin to the Sun's Kuiper Belt suggest that a distant "catastrophic" planetary disruption explanation is unlikely; the possibility of a disrupted asteroid belt scattering comets into the inner system is still to be determined. [108]

Younger star with coalescing material around it

Artist's impression of a young star with coalescing material around it Artist's Impression of a Baby Star Still Surrounded by a Protoplanetary Disc.jpg
Artist's impression of a young star with coalescing material around it

Astronomer Jason T. Wright and others who have studied Tabby's Star have suggested that if the star is younger than its position and speed would suggest, then it may still have coalescing material around it. [10] [13] [109]

A 0.8–4.2-micrometer spectroscopic study of the system using the NASA Infrared Telescope Facility (NASA IRTF) found no evidence for coalescing material within a few astronomical units of the mature central star. [87] [88]

Planetary debris field

Artist's impression of a massive collision with a proto-planet PIA18469-AsteroidCollision-NearStarNGC2547-ID8-2013.jpg
Artist's impression of a massive collision with a proto-planet

High-resolution spectroscopy and imaging observations have also been made, as well as spectral energy distribution analyses using the Nordic Optical Telescope in Spain. [2] [85] 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. [74] Other researchers think the planetary debris field explanation is unlikely, given the very low probability that Kepler would ever witness such an event due to the rarity of collisions of such size. [2]

As with the possibility of coalescing material around the star, spectroscopic studies using the NASA IRTF found no evidence for hot close-in dust or circumstellar matter from an evaporating or exploding planet within a few astronomical units of the central star. [87] [88] Similarly, a study of past infrared data from NASA's Spitzer Space Telescope and Wide-field Infrared Survey Explorer found no evidence for an excess of infrared emission from the star, which would have been an indicator of warm dust grains that could have come from catastrophic collisions of meteors or planets in the system. This absence of emission supports the hypothesis that a swarm of cold comets on an unusually eccentric orbit could be responsible for the star's unique light curve, but more studies are needed. [87] [6]

Consumption of a planet

In December 2016, a team of researchers proposed that Tabby's Star swallowed a planet, causing a temporary and unobserved increase in brightness due to the release of gravitational energy. As the planet fell into its star, it could have been ripped apart or had its moons stripped away, leaving clouds of debris orbiting the star in eccentric orbits. Planetary debris still in orbit around the star would then explain its observed drops in intensity. [110] Additionally, the researchers suggest that the consumed planet could have caused the star to increase in brightness up to 10,000 years ago, and its stellar flux is now returning to the normal state. [110] [111]

Large planet with oscillating rings

Sucerquia et al. (2017) suggested that a large planet with oscillating rings may help explain the unusual dimmings associated with Tabby's Star. [112] [113]

Large ringed planet followed by Trojan swarms

Ballesteros et al. (2017) proposed a large, ringed planet trailed by a swarm of Trojan asteroids in its L5 Lagrangian point, and estimated an orbit that predicts another event in early 2021 due to the leading Trojans followed by another transit of the hypothetical planet in 2023. [114] The model suggests a planet with a radius of 4.7 Jupiter radii, large for a planet (unless very young). An early red dwarf of about 0.5 R☉ would be easily seen in infrared. The current radial velocity observations available (four runs at σv ≈ 400 m/s) hardly constrain the model, but new radial velocity measurements would greatly reduce the uncertainty. The model predicts a discrete and short-lived event for the May 2017 dimming episode, corresponding to the secondary eclipse of the planet passing behind KIC 8246852, with about a 3% decrease in the stellar flux with a transit time of about 2 days. If this is the cause of the May 2017 event, the planet's orbital period is more precisely estimated as 12.41 years with a semi-major axis of 5.9 AU. [114]

Intrinsic luminosity variations

The reddening observed during the deep dimming events of Tabby's Star is consistent with cooling of its photosphere. [115] It does not require obscuration by dust. Such cooling could be produced by a decreased efficiency of heat transport caused e.g. by decreased effectiveness of convection due to the star's strong differential rotation, or by changes in its modes of heat transport if it is near the transition between radiative and convective heat transport. The "missing" heat flux is stored as a small increase of internal and potential energy. [90]

The possible location of this early F star near the boundary between radiative and convective transport seems to be supported by the finding that the star's observed brightness variations appear to fit the "avalanche statistics" known to occur in a system close to a phase-transition. [116] [117] "Avalanche statistics" with a self-similar or power-law spectrum are a universal property of complex dynamical systems operating close to a phase transition or bifurcation point between two different types of dynamical behavior. Such close-to-critical systems are often observed to exhibit behavior that is intermediate between "order" and "chaos". Three other stars in the Kepler Input Catalog likewise exhibit similar "avalanche statistics" in their brightness variations, and all three are known to be magnetically active. It has been conjectured that stellar magnetism may be involved in Tabby's Star. [117]

An artificial megastructure

Artist's impression of a Dyson swarm Dyson Swarm - 2.png
Artist's impression of a Dyson swarm

Some astronomers have speculated that the objects eclipsing Tabby's Star could be parts of a megastructure made by an alien civilization, such as a Dyson swarm, [75] [10] [89] [107] a hypothetical structure that an advanced civilization might build around a star to intercept some of its light for their energy needs. [118] [119] [120] According to Steinn Sigurðsson, the megastructure hypothesis is implausible and disfavored by Occam's razor and fails to sufficiently explain the dimming. He says that it remains a valid subject for scientific investigation, however, because it is a falsifiable hypothesis. [116] Due to extensive media coverage on this matter, Tabby's Star has been compared by Kepler's Steve Howell to KIC 4150611 , [121] a star with an odd light curve that was shown, after years of research, to be a part of a five-star system. [122] The likelihood of extraterrestrial intelligence being the cause of the dimming is purely speculative; [100] however, the star remains an outstanding SETI target because natural explanations have yet to fully explain the dimming phenomenon. [10] [89] The latest results have ruled out explanations involving only opaque objects such as stars, planets, swarms of asteroids, or alien megastructures. [123]

Exomoons

Two papers published in summer 2019 offered plausible scientific scenarios involving large moons being stripped from their planets. Numeric simulations were performed of the migration of gas giant planets, and their large gaseous moons, during the first few hundred million years after the formation of the planetary system. In approximately 50% of the cases, the results produce a scenario where the moon is freed from its parent planet and its orbit evolves to produce a light curve similar to that of Tabby's Star. [93] [124] [125] [126]

Follow-up studies

As of 2015, numerous optical telescopes were monitoring Tabby's Star in anticipation of another multi-day dimming event, with planned follow-up observations of a dimming event using large telescopes equipped with spectrographs to determine if the eclipsing mass is a solid object, or composed of dust or gas. [127] Additional follow-up observations may involve the ground-based Green Bank Telescope, the Very Large Array Radio Telescope, [85] [128] and future orbital telescopes dedicated to exoplanetology such as the Nancy Grace Roman Space Telescope, TESS, and PLATO. [89] [120]

In 2016, a Kickstarter fund-raising campaign was led by Tabetha Boyajian, the lead author of the initial study on the star's anomalous light curve. The project proposed to use the Las Cumbres Observatory Global Telescope Network for continuous monitoring of the star. The campaign raised over US$100,000, enough for one year of telescope time. [129] [ needs update ] Furthermore, as of 2016, more than fifty amateur astronomers working under the aegis of the American Association of Variable Star Observers were providing effectively full coverage since AAVSO's alert about the star in October 2015, [130] namely a nearly continuous photometric record. [131] In a study published in January 2018, Boyajian et al. reported that whatever is blocking Tabby's Star filters different wavelengths of light differently, so it cannot be an opaque object. They concluded that it is most likely space dust. [98] [34] [132]

In December 2018, a search for laser light emissions from Tabby's Star was carried out using the Automated Planet Finder (APF), which is sensitive enough to detect a 24 MW laser at this distance. Although a number of candidates were identified, further analysis showed that they are coming from the Earth and not from the star. [133]

SETI results

In October 2015, the SETI Institute used the Allen Telescope Array to look for radio emissions from possible intelligent extraterrestrial life in the vicinity of the star. [134] [135] After an initial two-week survey, the SETI Institute reported that it found no evidence of technology-related radio signals from the star system. [136] [137] [138] No narrowband radio signals were found at a level of 180–300  Jy in a 1  Hz channel, or medium-band signals above 10 Jy in a 100 kHz channel. [137]

In 2016, the VERITAS gamma-ray observatory was used to search for ultra-fast optical transients from astronomical objects, with astronomers developing an efficient method sensitive to nanosecond pulses with fluxes as low as about one photon per square meter. This technique was applied on archival observations of Tabby's Star from 2009 to 2015, but no emissions were detected. [139] [140]

In May 2017, a related search, based on laser light emissions, was reported, with no evidence found for technology-related signals from Tabby's Star. [141] [142]

In September 2017, some SETI@Home workunits were created based on a previous RF survey of the region around this star. [143] This was coupled with a doubling in the size of SETI@Home workunits, so the workunits related to this region will probably be the first workunits to have less issues with quantization noise.

EPIC 204278916

A star called EPIC 204278916, [144] [145] as well as some other young stellar objects, have been observed[ when? ] to exhibit dips with some similarities to those observed in Tabby's Star. They differ in several respects, however. EPIC 204278916 shows much deeper dips than Tabby's Star, and they are grouped over a shorter period, whereas the dips at Tabby's Star are spread out over several years. Furthermore, EPIC 204278916 is surrounded by a proto-stellar disc, whereas Tabby's Star appears to be a normal F-type star displaying no evidence of a disc. [144]

Other stars

An overall study of 21 other similar stars was presented in 2019. [146] [147]

See also

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Theta Cygni is a star in the northern constellation of Cygnus. It has an apparent visual magnitude of 4.5, so it can be seen from the northern hemisphere with the naked eye in sufficiently dark skies. Based upon parallax measurements, it is at a distance of about 59.8 light-years from the Earth. It is suspected of hosting an extrasolar planet.

The Kepler Input Catalog is a publicly searchable database of roughly 13.2 million targets used for the Kepler Spectral Classification Program (SCP) and Kepler.

Kepler-12b is a hot Jupiter that orbits G-type star Kepler-12 some 900 parsecs (2,900 ly) away. The planet has an anomalously large radius that could not be explained by standard models at the time of its discovery, almost 1.7 times Jupiter's size while being 0.4 times Jupiter's mass. The planet was detected by the Kepler spacecraft, a NASA project searching for planets that transit their host stars. The discovery paper was published on September 5, 2011.

Kepler-1520 is a K-type main-sequence star located in the constellation Cygnus. The star is particularly important, as measurements taken by the Kepler spacecraft indicate that the variations in the star's light curve cover a range from about 0.2% to 1.3% of the star's light being blocked. This indicates that there may be a rapidly disintegrating planet, a prediction not yet conclusively confirmed, in orbit around the star, losing mass at a rate of 1 Earth mass every billion years. The planet itself is about 0.1 Earth masses, or just twice the mass of Mercury, and is expected to disintegrate in about 100-200 million years. The planet orbits its star in just 15.7 hours, at a distance only two stellar diameters away from the star's surface, and has an estimated effective temperature of about 2255 K. The orbital period of the planet is one of the shortest ever detected in the history of the extrasolar planet search. In 2016, the planet was confirmed as part of a data release by the Kepler spacecraft.

<span class="mw-page-title-main">Planet Hunters</span> Citizen science project to find exoplanets

Planet Hunters is a citizen science project to find exoplanets using human eyes. It does this by having users analyze data from the NASA Kepler space telescope and the NASA Transiting Exoplanet Survey Satellite. It was launched by a team led by Debra Fischer at Yale University, as part of the Zooniverse project.

<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">Kepler-90</span> Star in the constellation Draco, orbited by eight planets

Kepler-90, also designated 2MASS J18574403+4918185, is a F-type star located about 2,790 light-years (855 pc) from Earth in the constellation of Draco. It is notable for possessing a planetary system that has the same number of observed planets as the Solar System.

<span class="mw-page-title-main">Kepler-90h</span> Exoplanet in the constellation Draco

Kepler-90h is an exoplanet orbiting within the habitable zone of the early G-type main sequence star Kepler-90, the outermost of eight such planets discovered by NASA's Kepler spacecraft. It is located about 2,840 light-years, from Earth in the constellation Draco. The exoplanet was found by using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured.

<span class="mw-page-title-main">Kepler-90g</span> Super-puff exoplanet in the constellation Draco

Kepler-90g is a super-puff exoplanet orbiting the early G-type main sequence star Kepler-90, one of eight planets around this star discovered using NASA's Kepler space telescope. It is located about 2,840 light-years (870 pc) from Earth, in the constellation Draco. The exoplanet was found by using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. It orbits its parent star about every 210.5 days at a distance of 0.71 astronomical units.

<span class="mw-page-title-main">Breakthrough Listen</span> Initiative to search for intelligent extraterrestrial life

Breakthrough Listen is a project to search for intelligent extraterrestrial communications in the Universe. With $100 million in funding and thousands of hours of dedicated telescope time on state-of-the-art facilities, it is the most comprehensive search for alien communications to date. The project began in January 2016, and is expected to continue for 10 years. It is a component of Yuri Milner's Breakthrough Initiatives program. The science program for Breakthrough Listen is based at Berkeley SETI Research Center, located in the Astronomy Department at the University of California, Berkeley.

<span class="mw-page-title-main">Tabetha S. Boyajian</span> American astronomer

Tabetha "Tabby" Suzanne Boyajian is an American astronomer and associate professor at Louisiana State University. She works in of stellar interferometry, stellar spectroscopy, exoplanet research, and high angular resolution astronomy, all particularly at optical and infrared wavelengths. Boyajian was the lead author of the September 2015 paper "Where's the Flux?", which investigated the highly unusual light curve of KIC 8462852; the star is colloquially known as Tabby's Star in her honor.

WD 1145+017 is a white dwarf approximately 476 light-years from Earth in the constellation of Virgo. It is the first white dwarf to be observed with a transiting minor planet orbiting it.

Kepler-1625b is a super-Jupiter exoplanet orbiting the Sun-like star Kepler-1625 about 2,500 parsecs away in the constellation of Cygnus. The large gas giant is approximately the same radius as Jupiter, and orbits its star every 287.4 days. In 2017, hints of a Neptune-sized exomoon in orbit of the planet was found using photometric observations collected by the Kepler Mission. Further evidence for a Neptunian moon was found the following year using the Hubble Space Telescope, where two independent lines of evidence constrained the mass and radius to be Neptune-like. The mass-signature has been independently recovered by two other teams. However, the radius-signature was independently recovered by one of the teams but not the other. The original discovery team later showed that this latter study appears affected by systematic error sources that may influence their findings.

<span class="mw-page-title-main">Hereford Arizona Observatory</span> Observatory

Hereford Arizona Observatory (HAO), IAU-code G95, is an astronomical observatory, owned and operated by amateur astronomer Bruce L. Gary. Observational studies of unusual starlight fluctuations in Tabby's Star and WD 1145+017 are recent interests.

<span class="mw-page-title-main">RZ Piscium</span> Star in the constellation Pisces

RZ Piscium is a UX Orionis type variable star 608 light-years (186 pc) away, in the constellation Pisces. Over the years, the star has been found to brighten and dim erratically, dimming by as much as a tenth of its usual luminosity. RZ Piscium has been found to emit large amounts of infrared radiation, suggesting the presence of a substantial mass of gas and dust orbiting the star, possibly from a "disrupted planet".

<span class="mw-page-title-main">Disrupted planet</span> Planet or related being destroyed by a passing object

In astronomy, a disrupted planet is a planet or exoplanet or, perhaps on a somewhat smaller scale, a planetary-mass object, planetesimal, moon, exomoon or asteroid that has been disrupted or destroyed by a nearby or passing astronomical body or object such as a star. Necroplanetology is the related study of such a process.

<span class="mw-page-title-main">VVV-WIT-07</span> Star noted for unusual dimming events

VVV-WIT-07 is a unique variable star which presents a sequence of recurrent dimmings with a possible deep eclipse in July 2012. The star, located in the Scorpius constellation about 23,000 ly (7,100 pc) away, is not a binary star, which would eliminate such a system from explaining the various observed dimmings.

Kepler-1708b is a Jupiter-sized exoplanet orbiting the Sun-like star Kepler-1708, located in the constellation of Cygnus approximately 5,600 light years away from Earth. It was first detected in 2011 by NASA's Kepler mission using the transit method, but was not identified as a candidate planet until 2019. In 2021, a candidate Neptune-sized exomoon in orbit around Kepler-1708b was found by astronomer David Kipping and colleagues in an analysis using Kepler transit data. However, subsequent research has raised discrepancies about the possible existence of an exomoon, similar to that of Kepler-1625b.

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