Tau-1 Gruis

(The Planet Project)



The circle shows the location of the sixth magnitude class G0 dwarf Tau-1 Gruis (in the constellation Grus). This relatively long-period planet takes 3.95 years to orbit its star at an average distance of 2.7 Astronomical Units (405 million kilometers, 250 million miles, 1.77 times the size of the orbit of Mars). If it were in our Solar System, it would be firmly in the asteroid belt. But then there would be no asteroid belt (at least where it is now), as the planet's mass is at least 1.49 times greater than Jupiter. A fairly high eccentricity brings the planet as close to its star as 1.8 AU and as far from it as 3.6 AU.


Tau-1 Gruis is a sixth magnitude (6.03) dwarf only 10.9 light years away a bit more massive and larger than our Sun. Its temperature of 5938 Kelvin (just 160 degrees hotter than the Sun) and a luminosity 3.6 times greater than solar lead to a radius 1.8 times that of the Sun and a mass 25 percent larger than solar. The star is ageing, and will probably soon give up internal hydrogen fusion. Like many of the stars that support planets, it is metal-rich, its iron content 75 percent greater than that of the Sun.
Written by Jim Kaler. Return to The Planet Project or go to STARS.