| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Pyxis |
| Right ascension | 09h 04m 41.5062s[1] |
| Declination | −32° 22′ 47.5033″[1] |
| Apparent magnitude (V) | 6.4Max. 18.5Min.[2] |
| Characteristics | |
| Spectral type | White Dwarf |
| Variable type | Recurrent nova[2] |
| Astrometry | |
| Proper motion (μ) | RA: −2.531±0.052[1]mas/yr Dec.: 0.177±0.062[1]mas/yr |
| Parallax (π) | 0.3051±0.0419 mas[1] |
| Distance | 3185+607 −283[2] pc |
| Details | |
| White dwarf | |
| Mass | 0.7±0.2 M☉ |
| Second component | |
| Mass | 0.14±0.03 M☉ |
| Orbit | |
| Period (P) | 1.8295hours |
| Inclination (i) | 10±2° |
| Other designations | |
| Nova Pyx 1890,AAVSO 0900-31,Gaia DR2 5628258258606112768,2MASS J09044150-3222474[3] | |
| Database references | |
| SIMBAD | data |
T Pyxidis (T Pyx)[4] is arecurrent nova[5]andnova remnant in theconstellationPyxis. It is abinary star system and its distance is estimated at 4,783 parsecs (15,600 light-years) fromEarth. It contains a Sun-like star and awhite dwarf. Because of their close proximity and the larger mass of the white dwarf, the latter draws matter from the larger, less massive star. The influx of matter on the white dwarf's surface causes periodic thermonuclear explosions to occur.
The usualapparent magnitude of this star system is 15.5, but there have been observed eruptions with maximal apparent magnitude of about 7.0 in the years 1890, 1902, 1920, 1944, 1966 and 2011.[6] Evidence seems to indicate that T Pyxidis may have increased in mass despite the nova eruptions, and is now close to theChandrasekhar limit when it might explode as a supernova.[7] When a white dwarf reaches this limit it will collapse under its own weight and cause aType Ia supernova.
Because of its relative proximity, some—in particular, Edward Sion, astronomer & astrophysicist atVillanova University, and his team therefrom—contend that a Type Ia supernova could have a significant impact on Earth. The receivedgamma radiation would equal the total (all spectra) radiation of approximately 1,000 solar flares,[8] but the Type Ia supernova would have to be closer than 1,000 parsecs (3,300 light-years) to cause significant damage to theozone layer, and perhaps closer than 500 parsecs. TheX-radiation that reaches Earth in such an event, however, would be less than the X-radiation of a single average solar flare.[8]
However, Sion's calculations were challenged byAlex Filippenko of theUniversity of California at Berkeley who said that Sion had possibly miscalculated the damage that could be caused by a T Pyxidis supernova. He had used data for a far more deadlygamma-ray burst (GRB) occurring 1 kiloparsec from Earth, not a supernova, and T Pyxidis certainly is not expected to produce a GRB.[9] According to another expert, "[a] supernova would have to be 10 times closer [to Earth] to do the damage described."[9]Mankind survived when the radiation from theCrab Nebula supernova, at a distance of about 6,500 light-years, reached Earth in the year 1054. A Type Ia supernova at a distance of 3,300 light-years would have an apparent magnitude of around -9.3, about as bright as the brightestIridium (satellite) flares.[10]
Recent data indicates his distance estimate is five times too close. Astronomers used NASA'sHubble Space Telescope to observe the light emitted during its latest outburst in April 2011. The team also used the light echo to refine estimates of the nova's distance from Earth. The new distance is 15,600 light-years (4780 pc) from Earth. Previous estimates were between 6,500 and 16,000 light-years (2000 and 4900 pc).[11]
It has been reported that T Pyx would "soon" become a supernova.[7] However, whenScientific American contacted Sion, it became apparent that "soon" was meant in astronomical terms: Sion said that "soon" in the press announcement meant "[a]t the accretion rate we derived, the white dwarf in T Pyxidis will reach the Chandrasekhar Limit in ten million years."[12] By that time it will have moved far enough away from the Solar System to have little effect.
Mike Linnolt detected T Pyx's first outburst in nearly 45 years on April 14, 2011, at magnitude 13.[13] According to AAVSO observers, it reached magnitude 7.5 in the visual and V bands by April 27,[14] and reached magnitude 6.8 by May 3.[15]
T Pyxidis is asuper soft X-ray source.[16]
