Temperature
3725 K
3678 to 4089.5
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Stellar HostProfile
K2-257
Unclassified star • 64.01 pc
Records
3
literature rows
Planets
1
system count
References
4
distinct source labels
TIC: TIC 130640162
Approximate color
from effective temperature
Canonical Summary
Adopted host values from one source row
Values come from the row with the most populated summary measurements. Missing values stay missing. Ranges and counts describe all source rows.
Stellar source: Livingston et al. 2018 • System source: TICv8
Mass
0.52 Msun
0.50 to 0.52
Radius
0.50 Rsun
0.50 to 0.50
Distance
64.01 pc
single adopted value
Planets
1
Stable across source rows
Scale Comparison
Radius against the Sun
Current adopted radius: 0.50 R☉ (circles scaled linearly by radius)
Sun
1.0 R☉ baseline
K2-257
0.50 R☉
System Layout
Known planets
1 planets linked to this host
K2-257 b
Transit
◌
Discovery
2018
Period
1.61 days
Radius
0.83 R⊕
Mass
—
Eq. Temp
789 K
K2-257 b: A Sub-Earth
K2-257 is a single-star system 209 light-years from Earth, with one known planet in orbit. The host star has a mass of 0.52 solar masses, a radius of 0.5 solar radii, and a temperature of 3730 K. The star's reported mass estimate is smaller than the Sun's, its reported radius estimate is smaller than the Sun's, and its reported temperature is cooler than the Sun's.
The system's only cataloged planet, K2-257 b, was discovered by transit in 2018. That method detects a planet as it crosses in front of its star, dimming the starlight. K2-257 b completes an orbit every 1.61 days. Its radius is 0.83 Earth radii, making it a Sub-Earth, a size class defined by a radius smaller than Earth's. A Sub-Earth classification reflects size alone, not composition.
Provenance
Underlying measurements and references
Evidence Summary
Rows
3
Stellar refs
3
System refs
1
Distancestable
Parallaxstable
Temperaturedisputed
Massdisputed
Radiusdisputed
Luminositystable
Surface Gravitydisputed
Metallicitystable