HIP 11915 is a

G-type main-sequence 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 star (luminosity class V) of spectral type G. Such a star has about 0.9 to 1.1 solar masses and an effective temper ...

located about 190

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 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 surface ...

in the constellation

Cetus Cetus () is a constellation, sometimes called 'the whale' in English. The Cetus was a sea monster in Greek mythology which both Perseus and Heracles needed to slay. Cetus is in the region of the sky that contains other water-related constell ...

. It is best known for its characteristics, which are very similar to those of 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 ...

, including the mass, radius, temperature, metallicity and age, which means that it is almost a solar twin, being just 500 million years younger than the Sun and with a lower

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 ...

. It is also known for its planetary companion, HIP 11915 b, which has a mass and orbital distance very similar to that of

Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandth th ...

, but probably with a slightly higher

orbital eccentricity In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values bet ...

. This star is entry number 11915 in the

Hipparcos Catalogue ''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 ...

. The star is located at 02:33:49.02495

right ascension Right ascension (abbreviated RA; symbol ) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the (hour circle of the) point in question above the earth. When paired w ...

, −19° 36' 42.5032" dec. Too faint to be seen with the unaided eye, the star can be spotted with good

binoculars Binoculars or field glasses are two refracting telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes ( binocular vision) when viewing distant objects. Most binoculars are sized to be held ...

Stellar characteristics

HIP 11915 is a G-type main sequence star that is just about the same mass of and likely 101% the radius of the

. It has a temperature of 5760 K and is 4.16 billion years old, nearly 500 million years younger than the Sun, which is about 4.6 billion years old and has a temperature of 5778 K. The star is slightly poor in metals, with a

( e/H of about −0.059, or about 87% of the amount of iron and other heavier metals found in the Sun. Given the similar properties of the Sun, HIP 11915's luminosity is likely close to the same as the Sun (give or take about 10% in uncertainty).

Planetary system

The system contains a gas giant, HIP 11915 b, with a mass and orbit very similar to that of

, located at approximately the same distance from its star. The discovery of HIP 11915 b is significant, because it is the first, and to date only, distant planetary system found that may be somewhat like the

Solar System The Solar System Capitalization 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 "Solar ...

. The radial velocity data also indicates that there is no large gas giant in this system with an orbital period of less than 1000 days. This means that there could be one or more terrestrial planets in the inner parts of the system, and the possibility of a habitable Earth-like planet. This new discovery was made at the

La Silla Observatory La Silla Observatory is an astronomical observatory in Chile with three telescopes built and operated by the European Southern Observatory (ESO). Several other telescopes are located at the site and are partly maintained by ESO. The observatory i ...

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

, using the

High Accuracy Radial Velocity Planet Searcher The High Accuracy Radial Velocity Planet Searcher (HARPS) is a high-precision echelle planet-finding spectrograph installed in 2002 on the ESO's 3.6m telescope at La Silla Observatory in Chile. The first light was achieved in February 2003. ...

instrument mounted on the

European Southern Observatory The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an intergovernmental research organisation made up of 16 member states for ground-based ast ...

's 3.6-meter telescope. According to Jorge Meléndez, who led the

University of São Paulo The University of São Paulo ( pt, Universidade de São Paulo, USP) is a public university in the Brazilian state of São Paulo. It is the largest Brazilian public university and the country's most prestigious educational institution, the best ...

, Brazil team that discovered HIP 11915 b, "the quest for an Earth 2.0, and for a complete Solar System 2.0, is one of the most exciting endeavors in astronomy".

Comparison to the Sun

This chart compares the properties of the Sun to HIP 11915.

Footnotes

References

{{DEFAULTSORT:HIP 11915 Cetus (constellation) Planetary systems with one confirmed planet Solar twins G-type main-sequence stars 016008 011915 BD-20 0481