Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Orion [1] |
Right ascension | 05h 50m 30.03s [2] |
Declination | +02° 01′ 28.9″ [2] |
Apparent magnitude (V) | 5.976 [2] |
Characteristics | |
Cool primary | |
Evolutionary stage | Horizontal branch [3] |
Spectral type | K0II [4] |
Apparent magnitude (B) | 6.83±0.015 [2] |
Apparent magnitude (G) | 5.64 [2] |
Apparent magnitude (J) | 4.193±0.238 [2] |
Apparent magnitude (H) | 3.502±0.194 [2] |
Apparent magnitude (K) | 3.337±0.19 [2] |
B−V color index | 1.12 [4] |
Hot secondary | |
Evolutionary stage | B-type main-sequence star + A-type main-sequence star |
Spectral type | B7V/B8V + A0V [4] |
B−V color index | -0.09 [4] |
Astrometry | |
Radial velocity (Rv) | 4.24 [4] km/s |
Proper motion (μ) | RA: 1.097 mas/yr [2] Dec.: -5.161 mas/yr [2] |
Parallax (π) | 1.47±0.23 mas [5] |
Distance | 2300+350 −270 ly (707.6+107 −83.3 pc) [5] |
Absolute magnitude (MV) | –2.53 (–2.3 (primary) + –0.75 (secondary)) [4] |
Orbit | |
Primary | Cool primary |
Companion | Hot secondary |
Period (P) | 2570±13 d 7.04±0.04 year [6] |
Semi-major axis (a) | 4.7×108 km 3.14 AU [6] |
Eccentricity (e) | 0.3±0.007 [6] |
Details | |
K-type giant | |
Mass | 3.3+0.3 −0.27 [3] M☉ |
Radius | 23.5+3.7 −1.9 [3] R☉ |
Luminosity | 535 [7] L☉ |
Surface gravity (log g) | 1.52 [8] cgs |
Temperature | 4,550 [8] K |
Metallicity [Fe/H] | -0.34 [8] dex |
Rotational velocity (v sin i) | 4.19 [9] km/s |
Age | 257 [3] Myr |
B-type star | |
Temperature | 11,300 [10] K |
Other designations | |
BD+01 1148, Gaia DR2 3316078695157768448, Gaia DR3 3316078695157768448, HD 39118/39119, HIP 27588, HR 2024, SAO 113198, PPM 149543, TIC 158867386, TYC 120-877-1, GSC 00120-00877, IRAS 05478+0200, 2MASS J05503003+0201290 | |
Database references | |
SIMBAD | data |
HD 39118 (HD 39119, HR 2024) is a spectroscopic binary star in the constellation Orion, close to the celestial equator. It is made up from three stars: a cool primary (a K-type giant star) and a hot secondary, which is a binary star formed from a B-type main-sequence star and an A-type main-sequence star. A 2021 estimate derive a distance of 708 parsecs (2,310 ly) to HD 39118, and it is moving away from Earth at a speed of 4.24 km/s. The apparent magnitude is 5.976, making it visible to the naked eye only from dark skies.
HR 2024 is a spectroscopic binary (more precisely a single-lined spectroscopic binary) [11] made up of a cool primary and a hot secondary, which is also a binary star. [4] The designations “cold” and “hot” refer to the effective temperature of the components. They are separated by 4.7×108 kilometres (3.1 AU ), and complete an orbit around each other every 2,570 days (7 years). [6] The orbital eccentricity is equivalent to 0.3. [6]
HD 39118 can be seen in the northern celestial hemisphere, close to the celestial equator, at a distance of 708 parsecs (2,310 light-years) in the constellation Orion. [2] [5] [1] It has an apparent magnitude of 5.976. [2] At this magnitude, it is visible to the naked eye only in dark skies, being close to the limiting magnitude to naked-eye vision of 6.5. [12] The absolute magnitude, i.e. its brightness if it was seen at a distance or 10 parsecs (32.6 ly), is –2.53. [4] It is moving away from Earth at a velocity of 4.24 km/s. [2]
It was double cataloged in the Henry Draper Catalogue, receiving the designations HD 39118 and HD 39119. [2]
The primary has an spectral classification of K0II, [4] meaning that it is a K-type star that has left the main sequence, being now a bright giant star. Currently, it is in the horizontal branch of evolution. [3] It is 3.28 times more massive has expanded to 25 times the Sun's size. [3] It emitts a luminosity 535 [7] times the solar luminosity from its photosphere at an effective temperature of 4,550 K, which is around 1,200 K cooler than the Sun. [8] [a] It has a subsolar metallicity, having an abundance of iron on its surface equivalent to 46% that of the Sun. [8] [b] The age of the primary is estimated at 263 million years, [3] much younger than the Sun (4.6 billion years) despite its advanced evolutionary stage. It rotates under its own axis at a velocity of 4.19 km/s. [9] The B-V index is of 1.12, [4] giving it the typical orange hue of a K-type star. [c]
The hot companion is made up of two other stars, one is a late B-type main-sequence star (spectral type B7V/B8V) and the other is an early A-type main-sequence star (spectral type A0V). [4] It has an absolute magnitude about 1.55 magnitudes fainter than the primary companion. [4] The B-type star has an effective temperature of 11,300 K. [10] The B-V index of the hot companion is of –0.09, [4] meaning that it has a typical hue of a B-type star. [c]