T Pyxidis (''T Pyx'') is a

recurrent nova A nova (plural novae or novas) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star (hence the name "nova", which is Latin for "new") that slowly fades over weeks or months. Causes of the dramat ...

and

nova remnant A nova remnant is made up of the material either left behind by a sudden explosive fusion eruption by classical novae, or from multiple ejections by recurrent novae. Over their short lifetimes, nova shells show expansion velocities of around 1000& ...

in the constellation

Pyxis Pyxis is a small and faint constellation in the southern sky. Abbreviated from Pyxis Nautica, its name is Latin for a mariner's compass (contrasting with Circinus, which represents a draftsman's compasses). Pyxis was introduced by Nicolas-Lo ...

. It is a binary star system and its distance is estimated at about from

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

. It contains a Sun-like star and a

white dwarf A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes ...

. 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 usual

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's ...

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. Evidence seems to indicate that T Pyxidis may have increased in mass despite the nova eruptions, and is now close to the

Chandrasekhar limit The Chandrasekhar limit () is the maximum mass of a stable white dwarf star. The currently accepted value of the Chandrasekhar limit is about (). White dwarfs resist gravitational collapse primarily through electron degeneracy pressure, compa ...

when it might explode as a supernova. When a white dwarf reaches this limit it will collapse under its own weight and cause a

type Ia supernova A Type Ia supernova (read: "type one-A") is a type of supernova that occurs in binary systems (two stars orbiting one another) in which one of the stars is a white dwarf. The other star can be anything from a giant star to an even smaller white ...

Effect on Earth

Because of its relative proximity, some—in particular, Edward Sion, astronomer & astrophysicist at

Villanova University Villanova University is a private Roman Catholic research university in Villanova, Pennsylvania. It was founded by the Augustinians in 1842 and named after Saint Thomas of Villanova. The university is the oldest Catholic university in Penns ...

, and his team therefrom—contend that a type 1a supernova could have a significant impact on Earth. The received gamma radiation would equal the total (all spectra) radiation of approximately 1,000 solar flares, but the type Ia supernova would have to be closer than to cause significant damage to the ozone layer, and perhaps closer than 500 parsecs. The X-radiation that reaches Earth in such an event, however, would be less than the X-radiation of a single average solar flare. However, Sion's calculations were challenged by Alex Filippenko of the

University of California at Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant uni ...

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 deadly

gamma-ray burst In gamma-ray astronomy, gamma-ray bursts (GRBs) are immensely energetic explosions that have been observed in distant galaxies. They are the most energetic and luminous electromagnetic events since the Big Bang. Bursts can last from ten millise ...

(GRB) occurring 1 kilo

parsec The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (au), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, an ...

from Earth, not a supernova, and T Pyxidis certainly is not expected to produce a GRB. According to another expert, " supernova would have to be 10 times closer o Earthto do the damage described."

Mankind Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...

survived when the radiation from the Crab 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 brightest Iridium (satellite) flares. Recent data indicates his distance estimate is five times too close. Astronomers used NASA's

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most vers ...

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). It has been reported that T Pyx would "soon" become a supernova. However, when

Scientific American ''Scientific American'', informally abbreviated ''SciAm'' or sometimes ''SA'', is an American popular science magazine. Many famous scientists, including Albert Einstein and Nikola Tesla, have contributed articles to it. In print since 1845, it ...

contacted Sion, it became apparent that "soon" was meant in astronomical terms: Sion said that "soon" in the press announcement meant " the accretion rate we derived, the white dwarf in T Pyxidis will reach the Chandrasekhar Limit in ten million years." By that time it will have moved far enough away from the Solar System to have little effect. T-Pyx-Lightcurve-AAVSO

2011 outburst

Mike Linnolt detected T Pyx's first outburst in nearly 45 years on April 14, 2011 at magnitude 13.http://www.aavso.org/aavso-alert-notice-436 T Pyxidis has been discovered in outburst], 2011, AAVSO According to AAVSO observers, it reached magnitude 7.5 in the visual and V bands by April 27, and reached magnitude 6.8 by May 3. T-Pyx-Lightcurve-2011-Eruption-AAVSO

X-ray source

T Pyxidis is a

super soft X-ray source A luminous supersoft X-ray source (SSXS, or SSS) is an astronomical source that emits only low energy (i.e., soft) X-rays. Soft X-rays have energies in the 0.09 to 2.5 keV range, whereas hard X-rays are in the 1–20 keV range. SSSs emit few or no ...

References

External links

* AAVSO Variable Star Of The Month April, 2002: T Pyxidi
PDF

HTML (17 July 2010)
* AAVSO
Quick Look View of AAVSO Observations
(get recent magnitude estimates for T Pyx)
Interview with Brad Schaefer about recurrent novae, and T Pyx
(@19:40 into recording : 30 March 2009)

(Space.com 22 December 2006) * Sion, Edward
A Supernova Could Nuke Us.
''Big Think.'' *

{{DEFAULTSORT:T Pyxidis Pyxis (constellation) Recurrent novae Novae Nova remnants Binary stars Pyxidis, T