Pi Mensae
Encyclopedia
Pi Mensae is a yellow subgiant star
in the constellation
of Mensa
. This star has a high proper motion
. The apparent magnitude
is 5.67, which can be visible to the naked eye
in exceptionally dark, clear skies. It is nearly 60 ly away. The star dwarfs the Sun
in terms of mass
, size, luminosity
, temperature
, and metallicity
and is about 730 million years younger. It ranks 100th on the list of top 100 target stars for the planned Terrestrial Planet Finder
mission to search for Earth-like planets.
was found orbiting the star. It is one of the most massive planets ever discovered. It has a very eccentric
orbit
that takes approximately 2151 days (5.89 years). Because of its eccentricity, and being a massive superjovian that passes through the habitable zone
, it would have disrupted the orbits of any Earth-like planets, and possibly thrown them into the star, or out into the interstellar medium
.
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
of Mensa
Mensa (constellation)
Mensa is a constellation in the southern sky, created in the 18th century. Its name is Latin for table. It covers a keystone-shaped wedge of sky stretching from approximately 4h to 7.5h of right ascension, and −71 to −85.5 degrees of declination. Other than the south polar constellation...
. This star has a high proper motion
Proper motion
The proper motion of a star is its angular change in position over time as seen from the center of mass of the solar system. It is measured in seconds of arc per year, arcsec/yr, where 3600 arcseconds equal one degree. This contrasts with radial velocity, which is the time rate of change in...
. The apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
is 5.67, which can be visible to the naked eye
Naked eye
The naked eye is a figure of speech referring to human visual perception unaided by a magnifying or light-collecting optical device, such as a telescope or microscope. Vision corrected to normal acuity using corrective lenses is considered "naked"...
in exceptionally dark, clear skies. It is nearly 60 ly away. The star dwarfs the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
in terms of mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
, size, luminosity
Luminosity
Luminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...
, temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
, and metallicity
Metallicity
In astronomy and physical cosmology, the metallicity of an object is the proportion of its matter made up of chemical elements other than hydrogen and helium...
and is about 730 million years younger. It ranks 100th on the list of top 100 target stars for the planned Terrestrial Planet Finder
Terrestrial Planet Finder
The Terrestrial Planet Finder was a proposed project by NASA to construct a system of telescopes for detecting extrasolar terrestrial planets. TPF was postponed several times and finally cancelled...
mission to search for Earth-like planets.
Planetary system
On October 15, 2001, an extrasolar planetExtrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...
was found orbiting the star. It is one of the most massive planets ever discovered. It has a very eccentric
Orbital eccentricity
The orbital eccentricity of an astronomical body is the amount by which its orbit deviates from a perfect circle, where 0 is perfectly circular, and 1.0 is a parabola, and no longer a closed orbit...
orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
that takes approximately 2151 days (5.89 years). Because of its eccentricity, and being a massive superjovian that passes through the habitable zone
Habitable zone
In astronomy and astrobiology, a habitable zone is an umbrella term for regions that are considered favourable to life. The concept is inferred from the empirical study of conditions favourable for Life on Earth...
, it would have disrupted the orbits of any Earth-like planets, and possibly thrown them into the star, or out into the interstellar medium
Interstellar medium
In astronomy, the interstellar medium is the matter that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, dust, and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space...
.