| Observation data EpochJ2000.0 EquinoxJ2000.0 (ICRS) | |
|---|---|
| Constellation | Microscopium |
| Right ascension | 21h 00m 06.3576s[2] |
| Declination | −42° 38′ 44.9350″[2] |
| Apparent magnitude (V) | 11.0 - 11.7[3] |
| Characteristics | |
| Spectral type | K2 III[4] or K5/M0 IIIe[5] |
| U−Bcolor index | +0.37[6] |
| B−Vcolor index | +1.57[6] |
| Variable type | Z And[3] |
| Astrometry | |
| Proper motion (μ) | RA: −10.080mas/yr[2] Dec.: −2.035mas/yr[2] |
| Parallax (π) | 0.1072±0.0205 mas[2] |
| Distance | 1-2,000[4] pc |
| Orbit[7] | |
| Primary | yellow giant |
| Companion | White dwarf |
| Period (P) | 1,442 d |
| Eccentricity (e) | 0.22 |
| Periastronepoch (T) | 2,445,560 |
| Argument of periastron (ω) (primary) | 261° |
| Semi-amplitude (K1) (primary) | 4.6 km/s |
| Details | |
| yellow giant | |
| Mass | 1.45[8] M☉ |
| Radius | 103[9] R☉ |
| Surface gravity (log g) | 0.25[8] cgs |
| Temperature | 3,941[8] K |
| Metallicity [Fe/H] | −0.93±0.06[10] dex |
| Rotational velocity (v sin i) | <3[7] km/s |
| Other designations | |
| DD Mic,CD−43°14304,GSC 07973-00869[11] | |
| Database references | |
| SIMBAD | data |
DD Microscopii, also known asCD−43°14304, is abinary star system in theconstellationMicroscopium. The system has a combined averageapparent magnitude around 11,[12] making it readily visible intelescopes but not to thenaked eye. It is thought to be at a distance of one or two thousand parsecs,[4] althoughparallax measurements place the system at a distance of around 30,000light years.[2]
It is asymbiotic star system composed of an orangegiant with a class of either K2 III[4] or K5/M0 IIIe.[5] Bothstellar classifications of the primary indicate ared giant, but one has a regular spectrum while the other shows an evolved star with the characteristics of a K5 and M0 giant star plusemission lines in itsspectrum. The secondary is awhite dwarf in close orbit, ionizing the stellar wind of the larger star.[citation needed] The giant star and white dwarf both take about 4years to orbit each other.[7]
The primary has an enlargedradius of103 R☉[9] and aneffective temperature of3,941 K,[8] giving a red hue when viewed through a telescope. DD Microscopii is extremely metal deficient, with aniron abundance only 12% of theSun,[10] and spins leisurely with aprojected rotational velocity lower than3 km/s.[7] The star system has its origin in thegalactic halo of theMilky Way as indicated by the highgalactic latitude.[4] DD Microscopii is cataloged as aZ Andromedae variable, a type ofsymbiotic binary with occasional outbursts. It fluctuates betweenmagnitudes 11.0 and 11.7 over a span of almost 400days.[13]
