TMTS J0526+5934
Smallest known Hydrogen-Burning (Main Sequence) Star
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TMTS J0526+5934 (abbreviated from TMTS J052610.43+593445.1 or ZTF J0526+5934) is an ultracompact binary star system located approximately 2,760 light-years away in the constellation Camelopardalis. It was initially identified in 2019 by the Zwicky Transient Facility (ZTF) as an extremely low-mass (ELM) white dwarf candidate, with further observations refining its classification.[6]
Location of TMTS J0526+5934 | |
| Observation data Epoch J2000.0 Equinox ICRS | |
|---|---|
| Constellation | Camelopardalis[1] |
| Right ascension | 05h 26m 10.42s[2] |
| Declination | +59° 34′ 45.3″[2] |
| Apparent magnitude (V) | 17.76[3] |
| Characteristics | |
| White dwarf | |
| Evolutionary stage | White dwarf[4] |
| Subdwarf | |
| Evolutionary stage | subdwarf[4] |
| Spectral type | sdB[4] |
| Astrometry | |
| Proper motion (μ) | RA: +1.418[2] mas/yr Dec.: +0.781[2] mas/yr |
| Parallax (π) | 1.1826±0.0217 mas[2] |
| Distance | 2,760 ± 50 ly (850 ± 20 pc) |
| Orbit[4] | |
| Period (P) | 20.5062426(53) min |
| Semi-major axis (a) | 0.255 R☉ |
| Eccentricity (e) | 0 (assumed) |
| Inclination (i) | 68.2+3.7 −5.2° |
| Details[4] | |
| A | |
| Radius | 0.011 R☉ |
| B | |
| Mass | ~0.33 M☉ |
| Radius | 0.0661±0.0054 R☉ |
| Luminosity | 1.70+0.31 −0.24 L☉ |
| Surface gravity (log g) | 6.36 cgs |
| Temperature | 25,480 K |
| Other designations | |
| TMTS J052610.43+593445.1, ZTF J0526+5934[5] | |
| Database references | |
| SIMBAD | data |
Discovery
Discovered by ZTF, it was further studied by the Tsinghua University–Ma Huateng Telescopes for Survey (TMTS), leading to its TMTS designation.[7][8][9]
Characteristics
It consists of a hot subdwarf B (sdB) star (J0526B) and a carbon-oxygen white dwarf (CO WD) companion (J0526A), forming a detached double white dwarf (DWD) binary, the fifth object with ultra-short period.[6] It holds the record for the shortest known orbital period of a detached single-degenerate binary at 20.5062426±0.0000053 min.[4][10][7] The subdwarf B star has an estimated radius of 0.0661±0.0054 R☉, representing possibly the smallest non-degenerate star known.[4]
Evolution and Future
TMTS J0526+5934 is expected to merge due to gravitational wave emission in about 1.8–3 million years. The merger could result in a massive white dwarf of roughly solar mass, a helium-rich star, or potentially a Type Ia supernova. Its strong gravitational wave signal makes it a promising verification binary for the ESA's Laser Interferometer Space Antenna (LISA) mission.[11][7][6]