HD 139139
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Libra |
| Right ascension | 15h 37m 06.215s |
| Declination | −19° 08′ 33.09″ |
| Apparent magnitude (V) | 9.84 |
| Characteristics | |
| Spectral type | G3/G5V |
| Astrometry | |
| Radial velocity (Rv) | 16.36 km/s |
| Proper motion (μ) | RA: −67.594 mas/yr Dec.: −92.516 mas/yr |
| Parallax (π) | 9.2966±0.0472 mas |
| Distance | 351 ± 2 ly (107.6 ± 0.5 pc) |
| Details | |
| Radius | 1.14 R☉ |
| Luminosity (bolometric) | 1.29 L☉ |
| Temperature | 5,766 K |
| Rotation | 14.5 d |
| Age | 1.5±0.4 Gyr |
| Other designations | |
| BD−18°4107, Gaia DR1 6254212216862625024, Gaia DR2 6254212221163830016, Gaia DR3 6254212221163830016, PPM 717808, EPIC 249706694, TIC 70652803, TYC 6193-969-1, GSC 06193-00969, 2MASS J15370623−1908329, DENIS J153706.2−190832, RAVE J153706.2−190833, USNO‑B1.0 0708-00306171 | |
| Database references | |
| SIMBAD | data |
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. Both stars have a similar proper motion, meaning they may form a gravitationally-bound binary pair.
HD 139139 exhibits dips in brightness similar to those caused by transiting Earth-like planets. The Kepler space telescope observed 28 dips in their brightness over an 87-day period (23 August – 20 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 asteroids, and short lived sunspots. 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 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.