HD 139139 (also known as EPIC 249706694) is likely part of a bound pair system of

main sequence In astronomy, the main sequence is a classification of stars which appear on plots of stellar color index, color versus absolute magnitude, brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or d ...

stars about away from Earth in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

Libra Libra generally refers to: * Libra (constellation), a constellation * Libra (astrology), an astrological sign based on the star constellation Libra may also refer to: Arts and entertainment * ''Libra'' (novel), a 1988 novel by Don DeLillo Musi ...

. HD 139139 is a

G-type main-sequence star A G-type main-sequence star (spectral type: G-V), also often, and imprecisely, called a yellow dwarf, or G star, is a main sequence, main-sequence star (luminosity class V) of stellar classification, spectral type G. Such a star has about 0.9 to ...

, a little larger and more luminous than the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

, and at an almost identical temperature. It has an

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

of 9.8. The companion star is thought to be a K5-K7

red dwarf A red dwarf is the smallest kind of star on the main sequence. Red dwarfs are by far the most common type of fusing star in the Milky Way, at least in the neighborhood of the Sun. However, due to their low luminosity, individual red dwarfs are ...

away from HD 139139. It is about three magnitudes fainter and has a temperature of between 4,100 and . Both stars have a similar proper motion, meaning they may form a gravitationally-bound binary pair. HD139139LightCurve

HD 139139 exhibits dips in brightness similar to those caused by transiting Earth-like planets. The

Kepler space telescope The Kepler space telescope is a defunct space telescope launched by NASA in 2009 to discover Earth-sized planets orbiting other stars. Named after astronomer Johannes Kepler, the spacecraft was launched into an Earth-trailing heliocentric orb ...

observed 28 dips in their brightness over an 87-day period (23 August20 November 2017). The dips do not appear to be periodic as would be expected if they were due to transiting planets. It is unknown which of the two stars produces the dimming events. Potential explanations that have been investigated include planets transiting a binary star, planets that are perturbing the orbits of each other producing large transit timing variations, a disintegrating planet, large dust producing

asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...

s, and short lived

sunspot Sunspots are temporary spots on the Sun's surface that are darker than the surrounding area. They are one of the most recognizable Solar phenomena and despite the fact that they are mostly visible in the solar photosphere they usually aff ...

s. According to Andrew Vanderburg, one of the researchers of the original studies, :In astronomy we have a long history of not understanding something, thinking it’s aliens, and later finding out it’s something else ... The odds are pretty good that it’s going to be another one of those. Subsequent observations performed with

CHEOPS Khufu or Cheops (died 2566 BC) was an ancient Egyptian monarch who was the second pharaoh of the Fourth Dynasty, in the first half of the Old Kingdom period (26th century BC). Khufu succeeded his father Sneferu as king. He is generally accep ...

in two observing campaigns in the years 2021 and 2022 detected no transit-like events. The team estimated 4.8% probability of having missed all of them by chance, assuming that the frequency of the events remained unchanged from the 2017 measurements by Kepler. While it is possible that the events detected by Kepler were real, but inactive during observations by CHEOPS, the team also noted that it is not possible to discard also the possibility that they were caused by unidentified and infrequent instrumentation error.

Background

HD 139139 was identified as unusual by two independent groups of visual surveyors (citizen scientists) working in collaboration with professional astronomers. : "But some of these patterns are too complex for computers to tease out; volunteer citizen scientists also comb through the Kepler catalogue, using the human brain's power to uncover surprising signals. In spring 2018 some of these citizen astronomers contacted Vanderburg and told him to check out HD 139139, a sunlike star roughly 350 light-years away." HD 139139 is one of the 0.5% of stars in the sky that can see Earth transit, according to Andrew Vanderburg. "The transit impact parameter would be close to 0.9, so they can just barely see us – the transit duration would be only about 40% the duration we'd expect for a perfectly edge-on transit."

References

External links

* * * * {{DEFAULTSORT:HD 139139 Binary stars G-type main-sequence stars 139139 Libra (constellation) J15370623-1908329 BD-18 4107 J153706.2-190832 Unsolved problems in astronomy

Background

See also

References

External links