|-
! style="background-color: #FFFFC0;" colspan="2" | Characteristics
|-
| Spectral type

Stellar classification

In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...

 

| ? (primary)/M (b)
|- style="vertical-align: top;"
| 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...

 
(infrared, I band)
| 15.61 (system)
|- style="vertical-align: top;"
| Variable type

Variable star

A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth...

| Eclipsing binary
|-
! style="background-color: #FFFFC0;" colspan="2" | Binary orbit

Binary star

A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...

|- style="vertical-align: top;"
| Period

Orbital period

The orbital period is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.There are several kinds of...

 (P)
| 7.269 day

Day

A day is a unit of time, commonly defined as an interval equal to 24 hours. It also can mean that portion of the full day during which a location is illuminated by the light of the sun...

s
|- style="vertical-align: top;"
| Eccentricity (e)
| 0.205
|- style="vertical-align: top;"
| Inclination

Inclination

Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit...

 (i)
| 88–90°
OGLE-TR-122 is a binary

Binary star

A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...

 stellar system containing one of the smallest main-sequence star

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...

s whose radius

Radius

In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...

 has been measured. It was discovered when the Optical Gravitational Lensing Experiment

Optical Gravitational Lensing Experiment

The Optical Gravitational Lensing Experiment or OGLE is a Polish astronomical project based at the University of Warsaw that is chiefly concerned with discovering dark matter using the microlensing technique. Since the project began in 1992, it has discovered several extrasolar planets as a side...

 (OGLE) survey observed the smaller star eclipsing the larger primary. The orbital period is approximately 7.3 days. The system's primary is thought to resemble 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...

.

The smaller star, OGLE-TR-122b, is estimated to have a radius

Radius

In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...

 around 0.12 solar radii, or around 20% larger than Jupiter

Jupiter

Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...

's, and a 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:...

 of around 0.1 solar mass

Solar mass

The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...

es, or approximately 100 times Jupiter's. This makes its average density

Density

The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...

 approximately 50 times the Sun's. OGLE-TR-122b's mass is close to the lowest possible mass, estimated to be around 0.07 or 0.08 solar masses, for a hydrogen

Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

-fusing star. The observed transit provides the first direct evidence for a star with a radius comparable to Jupiter's.