Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Cygnus |
Right ascension | 19h 40m 57.01599s[2] |
Declination | +32° 37′ 05.7555″[2] |
Apparent magnitude (V) | 7.26 - 8.0[3] |
Characteristics | |
Evolutionary stage | AGB |
Spectral type | C5,4e(N3e)[3] |
B−V color index | +2.917±0.073[4] |
Variable type | SRb[5] |
Astrometry | |
Radial velocity (Rv) | −49.0±3.1[4] km/s |
Proper motion (μ) | RA: −5.178[2] mas/yr Dec.: −1.832[2] mas/yr |
Parallax (π) | 1.4908 ± 0.0368 mas[2] |
Distance | 2,190 ± 50 ly (670 ± 20 pc) |
Absolute magnitude (MV) | −1.297 (var.)[6] |
Details | |
Radius | 166[7] R☉ |
Luminosity | 2,735[8] L☉ |
Surface gravity (log g) | −0.4[8] cgs |
Temperature | 3,200[8] K |
Other designations | |
Database references | |
SIMBAD | data |
TT Cygni is a carbon star located 561 parsecs (1,830 ly) away in the northern constellation of Cygnus. It is classified as a semiregular variable of subtype SRb that ranges in brightness from magnitude 7.26 down to 8.0 with a period of 118 days.[3] This object is called a carbon star because it has a high ratio of carbon to oxygen in its surface layers. The carbon was produced by helium fusion, dredged up from inside the star by deep convection triggered by a flash from the helium shell.
A thin spherical shell around the star, about half a light year across, was emitted 7,000 years ago.[10] It was first detected from its carbon monoxide emission and has a mass around four thousandths M☉, of which about a tenth is dust. The dust is thought to be mostly amorphous carbon.[8]
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