Pi Mensae (π Men), also known as HD 39091, is a

yellow dwarf star A G-type main-sequence star (Spectral type: G-V), also often, and imprecisely called a yellow dwarf, or G star, is a main sequence, main-sequence star (luminosity class V) of stellar classification, spectral type G. Such a star has about 0.9 to 1 ...

in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

of Mensa. This star has a high

proper motion Proper motion is the astrometric measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more dista ...

. The

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 li ...

is 5.67, which can be visible to the

naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying, light-collecting optical instrument, such as a telescope or microscope, or eye protection. Vision corrected to normal ...

in exceptionally dark, clear skies. It is nearly 60

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s away. The star is slightly larger than the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

in terms of

mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementar ...

, size,

luminosity Luminosity is an absolute measure of radiated electromagnetic power (light), the radiant power emitted by a light-emitting object over time. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a st ...

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

and

metallicity In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...

, and is about 730 million years younger. It hosts three known planets.

Planetary system

On October 15, 2001, an

extrasolar planet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

was found orbiting the star. Pi Mensae b is one of the most massive planets ever discovered, and has a very

eccentric Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-center, in geometry * Eccentricity (graph theory) of a v ...

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a p ...

that takes approximately to complete. Because of its eccentricity, and being a massive

brown dwarf Brown dwarfs (also called failed stars) are substellar objects that are not massive enough to sustain nuclear fusion of ordinary hydrogen ( 1H) into helium in their cores, unlike a main-sequence star. Instead, they have a mass between the most ...

that passes through the

habitable zone In astronomy and astrobiology, the circumstellar habitable zone (CHZ), or simply the habitable zone, is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure.J. F. Kas ...

, it would have disrupted the orbits of any Earth-like planets, and possibly thrown them into the star, or out into the

interstellar medium In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstella ...

. Incorporating more accurate ''

Hipparcos ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial obj ...

'' data yields a mass range for the companion to be anywhere from 10.27 to 29.9 times that of Jupiter, confirming its substellar nature with the upper limit of mass putting it in the

range. In 2020, the true mass of Pi Mensae b was measured to be via

astrometry Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, the Milky Way. His ...

. Since this is greater than 13 Jupiter masses, the object could be considered a brown dwarf, although more recent astrometric results suggest a slightly lower mass. Pi Mensae was ranked 100th on the list of top 100 target stars for the planned (but now-canceled)

Terrestrial Planet Finder The Terrestrial Planet Finder (TPF) was a proposed project by NASA to construct a system of space telescopes for detecting extrasolar terrestrial planets. TPF was postponed several times and finally cancelled in 2011. There were two telescope ...

mission to search for Earth-like planets. On September 16, 2018, a

preprint In academic publishing, a preprint is a version of a scholarly or scientific paper that precedes formal peer review and publication in a peer-reviewed scholarly or scientific journal. The preprint may be available, often as a non-typeset versio ...

was posted to

arXiv arXiv (pronounced "archive"—the X represents the Greek letter chi ⟨χ⟩) is an open-access repository of electronic preprints and postprints (known as e-prints) approved for posting after moderation, but not peer review. It consists of ...

detailing the discovery of a

super-Earth A super-Earth is an extrasolar planet with a mass higher than Earth's, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17 times Earth's, respectively. The term "super-Earth" refers only to ...

on a 6.27-day orbit around the star, the first exoplanet detection by the

Transiting Exoplanet Survey Satellite Transiting Exoplanet Survey Satellite (TESS, Explorer 95 or MIDEX-7) is a space telescope for NASA's Explorer program, designed to search for exoplanets using the transit method in an area 400 times larger than that covered by the ''Kepler' ...

(TESS) submitted for publication. This was confirmed two days later, where the attention was called that the system is amenable for future planet atmospheric studies. In 2020, an analysis with

Gaia DR2 The ''Gaia'' catalogues are star catalogues created using the results obtained by ''Gaia'' space telescope. The catalogues are released in stages that will contain increasing amounts of information; the early releases also miss some stars, especia ...

and ''Hipparcos''

showed that planets b and c are located on orbits mutually inclined by 49°−131° (1 sigma), which causes planet c to not transit most of the time, and acquire large misalignments with its host star's spin axis. Planet c likely formed on a wide orbit, and then migrated inward under the gravitational influence of the planet or

b. It is likely to retain a portion of primordial, highly volatile atmosphere. In 2022, the discovery by the

radial velocity method Doppler spectroscopy (also known as the radial-velocity method, or colloquially, the wobble method) is an indirect method for finding extrasolar planets and brown dwarfs from radial-velocity measurements via observation of Doppler shifts in t ...

of a third planet,

Pi Mensae d The number (; spelled out as "pi") is a mathematical constant that is the ratio of a circle's circumference to its diameter, approximately equal to 3.14159. The number appears in many formulas across mathematics and physics. It is an irratio ...

, on a 125-day orbit was announced. Another 2022 study did not confirm this planet, but a 2023 study did detect it.

References

External links

The Extrasolar Planet Encyclopedia: HD 39091

SIMBAD: Pi Mensae

{{DEFAULTSORT:Pi Mensae G-type main-sequence stars Planetary systems with two confirmed planets Mensa (constellation) Mensae, Pi CD-80 00195 9189 039091 026394

2022 File:2022 collage V1.png, Clockwise, from top left: Road junction at Yamato-Saidaiji Station several hours after the assassination of Shinzo Abe; 2022 Sri Lankan protests, Anti-government protest in Sri Lanka in front of the Presidential Secretari ...

144 144 may refer to: * 144 (number), the natural number following 143 and preceding 145 * AD 144, a year of the Julian calendar, in the second century AD * 144 BC, a year of the pre-Julian Roman calendar * 144 (film), ''144'' (film), a 2015 Indian com ...

Planetary system

See also

References

External links