Upsilon Andromedae d (υ Andromedae d, abbreviated Upsilon And d, υ And d), formally named Majriti , is a
super-Jupiter
A super-Jupiter is a gas giant exoplanet that is more massive than the planet Jupiter. For example, substellar companion, companions at the planet–brown dwarf borderline have been called super-Jupiters, such as around the star Kappa Andromedae. ...
exoplanet
An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...
orbiting within the
habitable zone
In astronomy and astrobiology, the habitable zone (HZ), or more precisely the circumstellar habitable zone (CHZ), is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressu ...
of the
Sun-like star
Solar-type stars, solar analogs (also analogues), and solar twins are stars that are particularly similar to the Sun. The stellar classification is a hierarchy with solar twin being most like the Sun followed by solar analog and then solar-type. ...
Upsilon Andromedae A, approximately 44
light-year
A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astr ...
s (13.5
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, and ...
s, or nearly 416.3 trillion
km) away from
Earth
Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
in the constellation of
Andromeda. Its discovery made it the first
multiplanetary system to be discovered around a
main-sequence
In astronomy, the main sequence is a classification of stars which appear on plots of stellar color versus brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or dwarf stars, and positions of star ...
star, and the first such system known in a
multiple star
A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. It may sometimes be used to refer to a single star. A large group of stars bound by gravitation is generally called a ''st ...
system. The exoplanet was found by using the
radial velocity method, where periodic
Doppler shift
The Doppler effect (also Doppler shift) is the change in the frequency of a wave in relation to an observer who is moving relative to the source of the wave. The ''Doppler effect'' is named after the physicist Christian Doppler, who described t ...
s of
spectral line
A spectral line is a weaker or stronger region in an otherwise uniform and continuous spectrum. It may result from emission (electromagnetic radiation), emission or absorption (electromagnetic radiation), absorption of light in a narrow frequency ...
s of the host star suggest an orbiting object.
Name
In July 2014 the
International Astronomical Union
The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...
launched
NameExoWorlds
NameExoWorlds (also known as IAU NameExoWorlds) were various projects managed by the International Astronomical Union (I.A.U.) to encourage names to be submitted for astronomical objects, notably exoplanets. The accepted names would later be cons ...
, a process for giving proper names to certain exoplanets and their host stars. The process involved public nomination and voting for the new names. In December 2015, the IAU announced the planet would be named "Majriti". The winning name was submitted by the Vega Astronomy Club of
Morocco
Morocco, officially the Kingdom of Morocco, is a country in the Maghreb region of North Africa. It has coastlines on the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to Algeria–Morocc ...
, honoring the 10th-century scientist
Maslama al-Majriti.
Characteristics
Mass, radius and temperature
Upsilon Andromedae d is a
super-Jupiter
A super-Jupiter is a gas giant exoplanet that is more massive than the planet Jupiter. For example, substellar companion, companions at the planet–brown dwarf borderline have been called super-Jupiters, such as around the star Kappa Andromedae. ...
, an exoplanet that has a
mass
Mass is an Intrinsic and extrinsic properties, intrinsic property of a physical body, body. It was traditionally believed to be related to the physical quantity, quantity of matter in a body, until the discovery of the atom and particle physi ...
larger than that of the planet
Jupiter
Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
. It has a temperature of .
It has a mass of 10.25 .
Host star
The planet orbits a (
F-type)
star
A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...
named Upsilon Andromedae A. The star has a mass of 1.27 and a radius of around 1.48 . It has a temperature of 6,074
K and is 3.12 billion years old. In comparison, the Sun is about 4.6 billion years old and has a temperature of 5,778 K. The star is slightly metal-rich, with a
metallicity
In astronomy, metallicity is the Abundance of the chemical elements, abundance of Chemical element, elements present in an object that are heavier than hydrogen and helium. Most of the normal currently detectable (i.e. non-Dark matter, dark) matt ...
(
e/H of 0.09, or about 123% of the solar amount. Its luminosity () is 3.57 times that of the Sun.
The star's
apparent magnitude
Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...
, or how bright it appears from Earth's perspective, is 4.09. Therefore, Upsilon Andromedae can be seen with the naked eye.
Orbit
Upsilon Andromedae d orbits its star nearly every 3.5 years (about 1,276 days) in an
eccentric orbit, more eccentric than that of any of the known planets in the
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...
. To explain the planet's orbital eccentricity, some have proposed a close encounter with a now-lost outer planet of Upsilon Andromedae A. The encounter would have moved planet "d" into an eccentric orbit closer to the star and ejected the outer planet.
Habitability

While Upsilon Andromedae d is likely a gas giant and therefore uninhabitable, it may have a moon or moons that are habitable.
The planet lies in the habitable zone of Upsilon Andromedae A as defined both by the ability for an Earthlike world to retain
liquid
Liquid is a state of matter with a definite volume but no fixed shape. Liquids adapt to the shape of their container and are nearly incompressible, maintaining their volume even under pressure. The density of a liquid is usually close to th ...
water at its surface and based on the amount of
ultraviolet radiation
Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of t ...
received from the star.
For a stable orbit, the ratio between a moon's
orbital period
The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...
''P''
s around its primary and that of the primary (planet) around its star ''P''
p must be < 1/9, e.g. if a planet takes 90 days to orbit its star, the maximum stable orbit for a moon of that planet is less than 10 days.
Simulations suggest that a moon with an orbital period less than about 45 to 60 days will remain safely bound to a massive giant planet or
brown dwarf
Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main sequence, main-sequence stars. Their mass is approximately 13 to 80 Jupiter mass, times that of Jupiter ()not big en ...
that orbits 1
AU from a Sun-like star.
In the case of Upsilon Andromedae d, the orbital period would have to be no greater than 120 days (around 4 months) in order to have a stable orbit.
Discovery and further studies
Upsilon Andromedae d was detected by measuring variations in its star's
radial velocity
The radial velocity or line-of-sight velocity of a target with respect to an observer is the rate of change of the vector displacement between the two points. It is formulated as the vector projection of the target-observer relative velocity ...
as a result of the planet's
gravity
In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force b ...
. This was done by making precise measurements of the
Doppler shift
The Doppler effect (also Doppler shift) is the change in the frequency of a wave in relation to an observer who is moving relative to the source of the wave. The ''Doppler effect'' is named after the physicist Christian Doppler, who described t ...
of the
spectrum
A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...
of Upsilon Andromedae A. At the time of discovery, Upsilon Andromedae A was already known to host one extrasolar planet, the
hot Jupiter
Hot Jupiters (sometimes called hot Saturns) are a class of gas giant exoplanets that are inferred to be physically similar to Jupiter (i.e. Jupiter analogue, Jupiter analogues) but that have very short orbital periods (). The close proximity to t ...
Upsilon Andromedae b; however, by 1999, it was clear that the inner planet could not explain the velocity curve.
In 1999, astronomers at both
San Francisco State University
San Francisco State University (San Francisco State, SF State and SFSU) is a Public university, public research university in San Francisco, California, United States. It was established in 1899 as the San Francisco State Normal School and is ...
and the
Harvard-Smithsonian Center for Astrophysics independently concluded that a three-planet model best fit the data. The two new planets were designated
Upsilon Andromedae c and Upsilon Andromedae d.
Preliminary
astrometric
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.
History ...
measurements suggest the orbit of Upsilon Andromedae d may be inclined at 155.5° to the plane of the sky. However, these measurements were later proved useful only for upper limits,
and contradict even the inner planet υ And b's inclination of >30°. The mutual inclination between c and d meanwhile is 29.9 degrees.
The true inclination of Upsilon Andromedae d was determined as 23.8° after combined results were measured from the
Hubble Space Telescope
The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the Orbiting Solar Observatory, first space telescope, but it is one of the largest and most ...
and radial velocity measurements.
When it was discovered, a limitation of the radial velocity method used to detect Upsilon Andromedae d is that the orbital inclination is unknown, and only a lower limit on the planet's
mass
Mass is an Intrinsic and extrinsic properties, intrinsic property of a physical body, body. It was traditionally believed to be related to the physical quantity, quantity of matter in a body, until the discovery of the atom and particle physi ...
can be obtained, which was estimated to be about 4.1 times as massive as Jupiter. However, by combining radial velocity measurements from ground-based telescopes with astrometric data from the
Hubble Space Telescope
The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the Orbiting Solar Observatory, first space telescope, but it is one of the largest and most ...
, astronomers have determined the orbital inclination as well as the actual
mass
Mass is an Intrinsic and extrinsic properties, intrinsic property of a physical body, body. It was traditionally believed to be related to the physical quantity, quantity of matter in a body, until the discovery of the atom and particle physi ...
of the planet, which is about 10.25 times the mass of
Jupiter
Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
.
See also
*
Eccentric Jupiter
*
Planetary habitability
Planetary habitability is the measure of a planet's or a natural satellite's potential to Abiogenesis, develop and sustain an environment hospitable to life. Life may be abiogenesis, generated directly on a planet or satellite endogenously. Res ...
*
List of exoplanets discovered before 2000
References
{{DEFAULTSORT:Upsilon Andromedae d
Upsilon Andromedae
Exoplanets discovered in 1999
Exoplanets detected by radial velocity
Exoplanets detected by astrometry
Giant planets in the habitable zone
Exoplanets with proper names