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BD+05 4868

Visualization of the simulated dust tail transiting in front of the primary Credit: Hon et al.
Observation data Epoch J2000      Equinox J2000
Constellation	Pegasus
BD+05 4868A
Right ascension	21 47 26.52
Declination	+06° 36′ 17.50″
Apparent magnitude (V)	10.16
BD+05 4868B
Right ascension	21 47 26.71
Declination	+06° 36′ 18.38″
Characteristics
Evolutionary stage	main-sequence star
Spectral type	mid-K+M
Astrometry
BD+05 4868A
Radial velocity (Rv)	–25.56 ±0.15 km/s
Proper motion (μ)	RA: 205.593 ±0.017 mas/yr Dec.: 106.359 ±0.012 mas/yr
Parallax (π)	22.9322 ± 0.0163 mas
Distance	142.2 ± 0.1 ly (43.61 ± 0.03 pc)
BD+05 4868B
Radial velocity (Rv)	–24.62 ±1.60 km/s
Proper motion (μ)	RA: 212.158 ±0.064 mas/yr Dec.: 112.173 ±0.049 mas/yr
Parallax (π)	23.1585 ± 0.0629 mas
Distance	140.8 ± 0.4 ly (43.2 ± 0.1 pc)
Details
BD+05 4868A
Mass	0.70 ±0.02 M☉
Radius	0.69 ±0.02 R☉
Luminosity	0.192 ±0.005 L☉
Surface gravity (log g)	4.60+0.03 −0.02 cgs
Temperature	4540 ±110 K
Metallicity	−0.07 ±0.09 dex
Age	11.1+1.7 −3.0 Gyr
BD+05 4868B
Mass	0.43 ±0.03 M☉
Radius	0.42 ±0.02 R☉
Luminosity	0.023 ±0.001 L☉
Surface gravity (log g)	4.83 ±0.03 cgs
Temperature	3480 ±70 K
Position (relative to BD+05 4868A)
Component	BD+05 4868B
Epoch of observation	October 2024
Angular distance	3″
Projected separation	132.037 ±0.002 AU
Other designations
BD+05 4868A: HIP 107587, G 93-37, LSPM J2147+0636, LTT 18540, 2MASS J21472654+0636178, TIC 466376085, TYC 556-856-1, UCAC2 34205672, WISE J214726.69+063618.9, Gaia DR3 2700378125204437760
BD+05 4868B: Gaia DR3 2700378125203895808
Database references
BD+05 4868A
SIMBAD	data
BD+05 4868B
SIMBAD	data

BD+05 4868 is a binary star consisting of a K-dwarf and an M-dwarf. Around the primary one rocky planet is detected. This planet, called BD+05 4868Ab orbits the star so close that it disintegrates, creating a large comet-like tail, seen in transits.

BD+05 4868 was first cataloged in the Bonner Durchmusterung and in 1961 the star was identified as a proper motion star by Giclas et al. In 1984 its spectrum was observed for the first time, identifying it as a K5: type star. The star was first identified as a binary from Gaia data. The common proper motion and parallax indicate that the pair is physically bound. The binary was also detected with the Las Cumbres Observatory Global Telescope (LCOGT) 2 m Faulkes Telescope North and with Keck NIRC2.

Planetary system

The planet BD+05 4868Ab was discovered with TESS in transits. The transits are unusually deep with variable depth of 0.8-2.0%. The transits are also asymmetric with a short ingress followed by a long egress. The researchers were also are able to detect the transits in ground-bases ASAS-SN and LCOGT 2m telescope data. Seven spectra of the primary were obtained with the WIYN 3.5m Telescope, detecting no radial velocity signal larger than a few m/s. The researchers interpret the transits as a disintegrating rocky planet, similar to Kepler-1520b, KOI-2700b and K2-22b. The difference is that BD+05 4868Ab is around a relative bright (V=10.16 mag) host star, making follow-up observations and characterization of the rocky interior of a planet easier. The planet also has a relative low equilibrium temperature of 1820±45 Kelvin, which could lead to differences in dust properties, when compared to other disintegrating planets. Comparisons to models suggest that the planet began with a mass larger than Mercury, but lost mass over several billion years. The mass of the planet is not known, but the researchers assume a mass of about 0.02 M_E (about lunar-mass) in their modelling. Currently the mass-loss rate is at 10 M_E per billion years, meaning it will evaporate in several million years.

References

1. ^ Hon, Marc; Rappaport, Saul; Shporer, Avi; Vanderburg, Andrew; Collins, Karen A.; Watkins, Cristilyn N.; Schwarz, Richard P.; Barkaoui, Khalid; Yee, Samuel W. (2025-01-09). "A Disintegrating Rocky Planet with Prominent Comet-like Tails Around a Bright Star". arXiv:2501.05431 .
2. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
3. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
4. Argelander, Friedrich Wilhelm August (1903-01-01). "Bonner Durchmusterung des nordlichen Himmels". Eds Marcus and Weber's Verlag: 0. Bibcode:1903BD....C......0A.
5. Giclas, Henry L.; Burnham, Robert; Thomas, Norman Gene (1961-01-01). "Lowell proper motions III : proper motion survey of the Northern Hemisphere with the 13-inch photographic telescope of the Lowell Observatory". Lowell Observatory Bulletin. 6: 61–132. Bibcode:1961LowOB...5...61G.
6. Lee, S. -G. (1984-05-01). "Spectral classification of high-proper-motion stars". The Astronomical Journal. 89: 702–719. Bibcode:1984AJ.....89..702L. doi:10.1086/113569. ISSN 0004-6256.

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• Durchmusterung objects
• Exoplanets discovered in 2024
• Pegasus (constellation)
• Transiting exoplanets
• Exoplanets discovered by TESS
• Sub-Earth exoplanets