HD 139139

HD 139139

Star field around HD 139139
(north is up, field is approximately 20′ wide)
Observation data
Epoch J2000      Equinox J2000
Constellation Libra[1]
Right ascension 15h 37m 06.215s[2][3]
Declination −19° 08′ 33.09″[2][3]
Apparent magnitude (V) 9.84[4]
Characteristics
Spectral type G3/G5V[5]
Astrometry
Radial velocity (Rv)16.36[6] km/s
Proper motion (μ) RA: −67.594[6] mas/yr
Dec.: −92.516[6] mas/yr
Parallax (π)9.2966 ± 0.0472 mas[6]
Distance351 ± 2 ly
(107.6 ± 0.5 pc)
Details
Radius1.14[6] R☉
Luminosity (bolometric)1.29[6] L☉
Temperature5,766[6] K
Rotation14.5 d[7]
Age1.5±0.4[7] Gyr
Other designations
2MASS J15370623−1908329, BD-18°4107, GSC 06193-00969, TYC 6193-969-1, Gaia DR2 6254212221163830016
Database references
SIMBADdata

HD 139139 (also known as EPIC 249706694) is likely part of a bound pair system of main sequence stars about 350 light-years (110 parsecs) away from Earth in the constellation Libra. HD 139139 is a G-type main-sequence star, a little larger and more luminous than the Sun, and at an almost identical temperature. It has an apparent magnitude of 9.8. The companion star is thought to be a K5-K7 red dwarf 3.3″ away from HD 139139. It is about three magnitudes fainter and has a temperature of between 4,100 and 4,300 K.[7] Both stars have a similar proper motion, meaning they may form a gravitationally-bound binary pair.

A light curve for HD 139139 showing the irregularly spaced dimmings, adapted from Rappaport et al. (2019)[7]

HD 139139 exhibits dips in brightness similar to those caused by transiting Earth-like planets.[7] The Kepler space telescope observed 28 dips in their brightness over an 87-day period (23 August – 20 November 2017).[8][9] The dips do not appear to be periodic as would be expected if they were due to transiting planets.[10][11][12]

It is unknown which of the two stars produces the dimming events.[7] 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 asteroids, and short lived sunspots.[7][13][14] 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.[12][15]
  1. ^ Cite error: The named reference DJM-2008 was invoked but never defined (see the help page).
  2. ^ a b Cite error: The named reference SIMBAD-HD139139 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference STScI-2019 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference tycho2 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Houk-Smith-1988 was invoked but never defined (see the help page).
  6. ^ a b c d e f g Cite error: The named reference dr2 was invoked but never defined (see the help page).
  7. ^ a b c d e f g Cite error: The named reference Rappaport-2019 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference SciA-20190702 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference PHY-20190703 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference SA-20190703 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference GZM-20190703 was invoked but never defined (see the help page).
  12. ^ a b Cite error: The named reference NS-20190702 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference HO-20190629 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference RD-20190630 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference TDG-20190703 was invoked but never defined (see the help page).