Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Pisces |
Right ascension | 23h 46m 23.51645s [1] |
Declination | +03° 29′ 12.5190″ [1] |
Apparent magnitude (V) | 4.79 - 5.20 [2] |
Characteristics | |
Spectral type | C7,2 [3] |
U−B color index | +3.33 [4] |
B−V color index | +2.60 [4] |
Variable type | Lb [2] |
Astrometry | |
Radial velocity (Rv) | +11.5±1.5 [5] km/s |
Proper motion (μ) | RA: −32.086 [1] mas/yr Dec.: −24.545 [1] mas/yr |
Parallax (π) | 4.0894 ± 0.2124 mas [1] |
Distance | 800 ± 40 ly (240 ± 10 pc) |
Absolute magnitude (MV) | −2.22 [5] |
Details | |
Mass | 1 –3 [6] M☉ |
Radius | 295 [6] R☉ |
Luminosity | 7,019 –7,876 [6] L☉ |
Surface gravity (log g) | −0.2 –−0.5 [6] cgs |
Temperature | 3,080 –3,170 [6] K |
Metallicity [Fe/H] | −0.39 [7] dex |
Other designations | |
Database references | |
SIMBAD | data |
TX Piscium (19 Piscium) is a variable red giant star in the constellation Pisces. It is amongst the reddest naked eye stars, with a significant reddish hue when seen in binoculars. It is approximately 800 light years from Earth.
TX Piscium is a very red star, 2.6 magnitudes fainter at blue wavelengths than in the middle of the visual range, and another 3.3 magnitudes fainter in the ultraviolet. [4]
It has been given a spectral class C7,2, indicating a relatively cool carbon star with only modest C2 band strength. [3] It has alternately been classified as C-N5 C24, suggesting a warmer star with stronger C2 bands. [8] Spectral features have been observed to vary. [9]
The apparent magnitude of TX Piscium varies between +4.9 and +5.5 and it is classified as a slow irregular variable. [2] Photometry has shown some periodicity in the brightness of 224 days, and some spectral variation over 450 days, suggesting the star is not entirely irregular. [9]
The star apparently lies on the period-luminosity relation corresponding to fundamental mode pulsations, unusual for a low-amplitude semi-regular or irregular variable which usually pulsate in an overtone. [11] The angular diameter has been measured at around 10 mas, although this varies depending on the observed wavelength and the atmosphere appears to be highly asymmetric. There may be one or more "blobs" of ejected material near the star. [11] [9] Some observations show the angular diameter to change in synchrony with the visual brightness. [11]
TX Piscium is a thermally-pulsing asymptotic giant branch (TP-AGB) red giant star, which means that it is alternately fusing helium in a shell around its core and fusing hydrogen in a shell closer to its surface. Stars on the TP-AGB are generally unstable, with high mass loss and pulsations.
The periodic flashes of the helium shell in a red giant star are known as thermal pulses and cause the hydrogen shell to be extinguished. This creates strong convection and the third dredge-up (TDU) which brings helium fusion products such as carbon to the surface. After several TDUs, the abundance of carbon in the atmosphere begins to exceed that of oxygen and then the star is known as a carbon star. In TX Piscium, the carbon/oxygen ratio is calculated to be 1.03, which is at the low end of the scale of carbon stars. [7] It is thought to be a relatively new carbon-rich red giant star. [9]
TX Piscium has a mass of approximately 2 M☉. Modelling of its observed properties suggest a mass between 1 and 2 M☉, while evolutionary models suggest a mass between 2 and 3 M☉. In particular, stars with a mass below 2 M☉ are not expected to become carbon stars. [6]
The temperature of TX Piscium is thought to vary between 3,080 K at minimum visual brightness and 3,170 K at visual maximum. Similarly, its luminosity varies between 7,019 and 7,876 L☉. Many of its physical properties are uncertain due to uncertainty in its distance. The Hipparcos parallax corresponds to a distance of 275 parsecs, but other estimates give distances as high as 315 parsecs. [6]
Chi Cygni is a Mira variable star in the constellation Cygnus, and also an S-type star. It is around 500 light years away.
Lambda Aquarii, informally known as Hydor, is a variable star in the equatorial constellation of Aquarius. The name is Latinized from the Bayer designation λ Aquarii. The apparent visual magnitude of this star ranges from 3.57 down to 3.80, which is bright enough to be visible with the naked eye. It lies just 0.39 degrees south of the ecliptic and so is subject to lunar occultations. The star is eclipsed by the sun from about 1-4 March; thus the star can be viewed the whole night, crossing the sky, in early September, in the current epoch. Lambda Aquarii is located at a distance of approximately 310 light-years (95 pc) from the Sun based on parallax, but is drifting closer with a radial velocity of −10.5 km/s.
UU Aurigae is a carbon star in the constellation Auriga. It is approximately 341 parsecs from Earth.
12 Canis Majoris is a variable star located about 707 light years away from the Sun in the southern constellation of Canis Major. It has the variable star designation HK Canis Majoris; 12 Canis Majoris is the Flamsteed designation. This body is just barely visible to the naked eye as a dim, blue-white hued star with a baseline apparent visual magnitude of +6.07. It is moving away from the Earth with a heliocentric radial velocity of +16 km/s. This is the brightest star in the vicinity of the open cluster NGC 2287, although it is probably not a member based on its proper motion.
La Superba is a strikingly red giant star in the constellation Canes Venatici. It is a carbon star and semiregular variable.
R Andromedae is a Mira-type variable star in the constellation Andromeda. Its spectral class is type S because it shows absorption bands of zirconium monoxide (ZrO) in its spectrum. It was among the stars found by Paul Merrill to show absorption lines of the unstable element technetium, establishing that nucleosynthesis must be occurring in stars. The SH molecule was found for the first time outside earth in the atmosphere of this star. The star is losing mass due to stellar winds at a rate of 1.09×10−6M☉/yr.
V Aquilae is a carbon star and semiregular variable star in the constellation Aquila. It has an apparent magnitude which varies between 6.6 and 8.4 and is located around 400 parsecs (1,300 ly) away.
T Cephei is a Mira variable star in the constellation Cepheus. Located approximately 600 light-years distant, it varies between magnitudes 5.2 and 11.3 over a period of around 388 days.
NO Aurigae is a pulsating variable star in the constellation Auriga. It is an unusually-luminous asymptotic giant branch star about 3,500 light years away.
U Camelopardalis is a semiregular variable star in the constellation Camelopardalis. Based on parallax measurements made by the Hipparcos spacecraft, it is located about 3,000 light-years away from the Earth. Its apparent visual magnitude is about 8, which is dim enough that it cannot be seen with the unaided eye.
Omicron1 Orionis is a binary star in the northeastern corner of the constellation Orion. It is visible to the naked eye with an apparent visual magnitude of 4.7. Based upon an annual parallax shift of 5.01±0.71 mas, it is located approximately 650 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an interstellar absorption factor of 0.27 due to intervening dust.
X Cancri is a variable star in the northern constellation of Cancer. It has a red hue and is visible to the naked eye at its brightest. The distance to this object is approximately 1,860 light years based on parallax measurements, but is drifting closer with a radial velocity of −5 km/s. It lies very close to the ecliptic and so is subject to lunar occultations.
Y Lyncis is a semiregular variable star in the constellation Lynx. It is an asymptotic giant branch star of spectral type M6S, with a luminosity class of Ib, indicating a supergiant luminosity. It is around 1,160 light years away.
TW Horologii is a carbon star and semiregular variable in the southern constellation of Horologium, near the eastern constellation border with Reticulum. It has a ruddy hue and, with an apparent visual magnitude that ranges from 5.52 down to 5.95, is visible to the naked eye and one of the brightest carbon stars. Based on parallax measurements, it is located at a distance of approximately 1,370 light years from the Sun. It is drifting further away with a radial velocity of +14 km/s. In the past this star has been considered a member of the open cluster NGC 1252, but this now seems unlikely.
S Cassiopeiae is a Mira variable and S-type star in the constellation Cassiopeia. It is an unusually cool star, rapidly losing mass and surrounded by dense gas and dust producing masers.
IK Tauri or NML Tauri is a Mira variable star located about 280 parsecs (910 ly) from the Sun in the zodiac constellation of Taurus.
W Orionis is a carbon star in the constellation Orion, approximately 400 parsecs (1,300 ly) away. It varies regularly in brightness between extremes of magnitude 4.4 and 6.9 roughly every 7 months.
II Lupi is a Mira variable and carbon star located in the constellation Lupus. It is the brightest carbon star in the southern hemisphere at 12 μm.
V957 Scorpii is a variable star in the constellation of Scorpius. It is a blue straggler in the open cluster Messier 7, a star that is unexpectedly hot compared to other members of the cluster.
R Fornacis is a Mira variable and carbon star located in the constellation Fornax. It is around 1,800 light years away based on parallax measurements.