HD 154857 c is an unconfirmed extrasolar planet

Extrasolar 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...

 located approximately 224 light-year

Light-year

A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...

s away 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 Ara

Ara (constellation)

Ara is a southern constellation situated between Scorpius and Triangulum Australe. Its name is Latin for "altar". Ara was one of the 48 Greek constellations described by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations defined by the International Astronomical...

, orbiting the 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...

 HD 154857

HD 154857

|- bgcolor="#FFFAFA"| Equatorial [ g ] || 54,7 m/s2HD 154857 is a yellow main-sequence star approximately 224 light years away in the constellation of Ara.-Planetary system:...

. This planet takes at least 1900 days (5.2 years) to orbit the star. It was discovered on 9 February 2007 by O’Toole in Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

 using the method Doppler spectroscopy

Doppler spectroscopy

Doppler spectroscopy, also known as radial velocity measurement, is a spectroscopic method for finding extrasolar planets. It involves the observation of Doppler shifts in the spectrum of the star around which the planet orbits....

, along with HD 23127 b

HD 23127 b

HD 23127 b is a jovian extrasolar planet orbiting the star HD 23127 at the distance of 2.29 AU, taking 3.32 years to orbit. The orbit is very eccentric, a so-called "eccentric Jupiter". At periastron, the distance is 1.28 AU, putting in its outer edge of the habitable zone, and at apastron, the...

 and HD 159868 b

HD 159868 b

HD 159868 b is a extrasolar planet that orbits HD 159868. It is a jovian planet. The orbit is extremely eccentric at the average distance of 2 AU. The orbital distance ranges from as close as 0.62 AU to as far as 3.38 AU....

. The orbit has not yet been completely observed, so the values quoted are lower limits. The best fit solution gives a period of 7.94 years and a minimum mass

Minimum mass

In astronomy, minimum mass is the lower-bound calculated mass of observed objects such as planets, stars and binary systems, nebulae, and black holes. Minimum mass is a widely cited statistic for extrasolar planets...

 of 18.4 Jupiter mass

Jupiter mass

Jupiter mass , is the unit of mass equal to the total mass of the planet Jupiter . Jupiter mass is used to describe masses of the gas giants, such as the outer planets and extrasolar planets. It is also used in describing brown dwarfs....

es, which would imply that it is in fact a brown dwarf

Brown dwarf

Brown dwarfs are sub-stellar objects which are too low in mass to sustain hydrogen-1 fusion reactions in their cores, which is characteristic of stars on the main sequence. Brown dwarfs have fully convective surfaces and interiors, with no chemical differentiation by depth...

.