HR 8734 Piscium

(The Planet Project)

Aqr HR 8734 Piscium hosts a hot Jupiter in a small orbit.


The circle at upper left shows the location of the class G "subgiant" (but probably dwarf) HR 8734 Piscium relative to stars of Aquarius. The star is near the border between the two constellations, though just over to the Pisces side. HR 8734's planet has a mass at least 1.28 times that of Jupiter. It orbits its star with a period of only 7.11 days at an average distance of but 0.07 Astronomical Units (10.5 million kilometers, 6.5 million miles, 18 percent Mercury's distance from the Sun, 13 stellar radii), the closeness making it one of the many "hot Jupiters." An orbital eccentricity of about 12 percent takes the planet between 0.08 and 0.06 AU from its star.


HR 8734 Piscium is a mid-sixth magnitude (6.18) class G8 star in Pisces that lies just over the constellation's border with Aquarius. Too faint to have a proper or Greek letter name, it is known best by its numbers in the Bright Star(HR) and the Henry Draper (HD) Catalogues. From a distance of 64 light years, it shines with a luminosity of 1.16 times that of the Sun from a surface at 5649 Kelvin (130 degrees cooler than the Sun), which tells of a star with a radius 1.13 solar and a mass very close to that of the Sun. Though classed as a subgiant, the star is really on ordinary, though ageing, dwarf. To have a higher luminosity and lower temperature, the star must be older and more evolved than the Sun by perhaps a couple billion years. Like most stars with planets, 54 Psc is rich in metals, its iron abundance (relative to hydrogen) quite high, 2.3 times solar. From the planet the star would appear some 15 times larger in angle than the Sun does from Earth.

The circle toward lower right shows HD 210277 Aquarii, which also supports a planet.
Written by Jim Kaler. Return to The Planet Project or go to STARS.