Tabby's Star
An F-type main-sequence star with unusual light fluctuations, including up to a 22% dimming in brightness.
via Wikipedia: Disrupted planet · see source
Tabby's Star, also known as Boyajian's Star and cataloged as KIC 8462852, is a binary system in the constellation Cygnus. It consists of an F-type main-sequence star and a red dwarf companion. The star's unusual brightness dips—sometimes as deep as 22%—were first spotted by citizen scientists working with data from the Kepler space telescope as part of the Planet Hunters project. Many ideas have been put forward to explain these erratic changes, but none fully account for the observed light curve. One popular suggestion, an extraterrestrial megastructure, has been largely ruled out by evidence. In September 2019, astronomers proposed that the dimming might be caused by debris from a shattered orphaned exomoon.
The star has no official name from the International Astronomical Union. The informal names "Tabby's Star" and "Boyajian's Star" honor Tabetha S. Boyajian, who led the 2015 paper announcing the discovery. Some astronomers and science communicators, including Jason Wright, Douglas Vakoch, and Phil Plait, prefer "Boyajian's Star," arguing that "Tabby's Star" is sexist because it uses a diminutive of her first name, breaking the tradition of naming stars after surnames. Plait noted that Boyajian herself uses "Boyajian's Star," though she understands the appeal of "Tabby's Star" due to her surname's pronunciation. Another nickname, "Where's the Flux? Star," comes from the subtitle of the discovery paper, which highlighted the star's dips in radiative flux. It has also been called "LGM-2," a nod to the first pulsar discovered, PSR B1919+21, originally nicknamed "LGM-1" when it was thought to be an alien signal. The star appears in several catalogs: as KIC 8462852 in the Kepler Input Catalog, as TYC 3162-665-1 in the Tycho-2 Catalogue, and as 2MASS J20061546+4427248 in the Two Micron All-Sky Survey.
In the sky, Tabby's Star lies in Cygnus, roughly halfway between the bright stars Deneb and Delta Cygni, part of the Northern Cross. It sits south of 31 Cygni and northeast of the star cluster NGC 6866. Though only a few arcminutes from the cluster, it is unrelated and closer to the Sun. With an apparent magnitude of 11.7, it is invisible to the naked eye but can be seen with a telescope in a dark sky with little light pollution.
Observations of the star date back to 1890. It was cataloged in the Tycho, 2MASS, UCAC4, and WISE surveys, published in 1997, 2003, 2009, and 2012 respectively. The main source of data on its brightness fluctuations came from the Kepler space telescope, which monitored over 100,000 stars in Cygnus and Lyra continuously from 2009 to 2013.
On May 20, 2017, Boyajian and colleagues reported an ongoing dimming event, named "Elsie," which may have started on May 14. It was first detected by the Las Cumbres Observatory telescope in Maui and later confirmed by the Fairborn Observatory in Arizona and LCO Canary Islands. Urgent requests went out for optical and infrared spectroscopy and photometry, as these events last only days or weeks. Observations were coordinated globally, including polarimetry, while the SETI projects Breakthrough Listen and NIROSETI at Lick Observatory continued monitoring. By the end of the three-day event, a dozen observatories had taken spectra, with some astronomers dropping their own projects to help. The astronomical community was described as going "mildly bananas" over the chance to collect real-time data. The 2% dip was named "Elsie" (a homophone of "LC," for Las Cumbres and light curve). Initial spectra from the Liverpool Telescope showed no changes between a reference spectrum and the dip, but other observatories, including the Keck telescopes and citizen science setups, captured spectra showing a complex dimming pattern similar to one seen in Kepler data. Observations spanned the electromagnetic spectrum. A second dimming event, named "Celeste," was observed on June 13–14, 2017, possibly starting June 11, by amateur astronomer Bruce L.
- Stellar type
- F-type main-sequence star
- Known for
- Unusual light fluctuations, including up to a 22% dimming in brightness
Lore & Background
Tabby's Star, also known as KIC 8462852, is a binary star system located in the constellation Cygnus, approximately 1470 light-years from Earth. The primary component is an F-type main-sequence star, accompanied by a red dwarf companion. The system is too faint to be seen with the naked eye, with an apparent magnitude of 11.7, but is observable with a 5-inch telescope under dark skies. Its position in the sky lies roughly halfway between the bright stars Deneb and Delta Cygni, part of the Northern Cross, and is situated south of 31 Cygni and northeast of the star cluster NGC 6866, though it is unrelated to that cluster and lies closer to the Sun. The star’s defining characteristic is its highly unusual and irregular light fluctuations, first identified by citizen scientists in data from the Kepler space telescope. These dips in brightness can reach up to 22%, a depth far exceeding what is typical for exoplanet transits. Numerous hypotheses have been proposed to explain these dimmings, including the disruption of an orphaned exomoon, but no single explanation accounts for all features of the observed light curve. The star has no official IAU name, but is informally called Tabby's Star or Boyajian's Star after astronomer Tabetha S. Boyajian, who led the 2015 discovery paper. Other nicknames include "Where's the Flux?" Star and LGM-2, a reference to the first pulsar.
Reader's Guide
Tabby's Star (KIC 8462852) is an F-type main-sequence star exhibiting unusual light fluctuations, including up to a 22% dimming in brightness. Several hypotheses have been proposed to explain these irregular changes, but none to date fully explain all aspects of the curve. One explanation is that an "uneven ring of dust" orbits Tabby's Star. 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. The star is also listed as an example of a parent star considered to have disrupted a planet.
Did You Know?
- Tabby's Star is also designated KIC 8462852.
- The star exhibits dimming of up to 22% in brightness.
- In September 2019, astronomers reported that the dimmings may be caused by fragments from a disrupted orphaned exomoon.
- Tabby's Star is an F-type main-sequence star.
- One hypothesis for the dimming is an "uneven ring of dust" orbiting the star.
The Anomalous Light Curve
Tabby's Star (KIC 8462852) is an F-type main-sequence star exhibiting unusual light fluctuations, including up to a 22% dimming in brightness. Several hypotheses have been proposed to explain these irregular changes, but none to date fully explain all aspects of the curve. One explanation is that an "uneven ring of dust" orbits Tabby's Star.
The Disrupted Exomoon Hypothesis
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. This relates to the broader field of necroplanetology, the study of planets and planetary-mass objects that have been disrupted or destroyed by a nearby or passing astronomical body. The result of such a disruption may be the production of excessive amounts of related gas, dust and debris, which may eventually surround the parent star in the form of a circumstellar disk or debris disk.
A Family of Flickering Stars
Tabby's Star is one of several parent stars considered to have disrupted a planet. Other examples include EPIC 204278916, PDS 110, RZ Piscium, WD 1145+017 and 47 Ursae Majoris. The common thread is that the orbiting debris field may be an "uneven ring of dust", causing erratic light fluctuations in the apparent luminosity of the parent star. Excessive amounts of infrared radiation may be detected from such stars, suggestive evidence in itself that dust and debris may be orbiting the stars.
The Ongoing Mystery and Scientific Discourse
Several hypotheses have been proposed to explain the irregular changes of Tabby's Star, but none to date fully explain all aspects of the curve. One explanation is that an "uneven ring of dust" orbits Tabby's Star. In September 2019, astronomers reported that the observed dimmings may have been produced by fragments resulting from the disruption of an orphaned exomoon. The star continues to be studied, with video presentations available from researchers including Tabetha S. Boyajian and Issac Arthur.
Frequently Asked Questions
What makes Tabby's Star so mysterious?
The star exhibits irregular, unexplained dimming events that can reduce its brightness by as much as 22%, far exceeding what typical transiting planets or dust clouds produce. No single conventional explanation has fully accounted for both the depth and the irregular pattern of these fluctuations.
Who first noticed the strange dimming of Tabby's Star?
Citizen scientists analyzing publicly released data from NASA's Kepler space telescope first flagged the anomalous light curve. Their discovery prompted professional astronomers to investigate the system more closely.
Is Tabby's Star an alien megastructure?
That was one of the more sensational early hypotheses proposed to explain the irregular dimming, but no evidence has confirmed the presence of any extraterrestrial structure. Leading explanations under investigation involve dust clouds, disintegrating planetesimals, or other natural phenomena, though the exact cause remains unresolved.
Why is Tabby's Star important to the search for life?
The star became a cultural touchstone in the search-for-life conversation because it demonstrated that even powerful instruments like Kepler can present puzzles no existing model neatly solves. It also highlighted the value of open data and citizen science in driving new astronomical research.
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