HR 3497 Velorum

(The Planet Project)

Vel HR 3497 hosts another of the "hot Jupiters," which, with a low measured mass, may be more of a "hot Saturn."


The circle shows the location of the class G dwarf star HR 3497 (the faint star at dead center), found in the rich star fields of the constellation Vela. The planet orbits its parent star with a very short period of 3.51 days (among the shortest known), at an average distance of 0.046 Astronomical Units (6.9 million kilometers, 4.3 million miles), 12 percent Mercury's distance from the Sun and just 8 times the radius of the parent star. Only a handful of the known planets are closer. The measured mass, which is a lower limit to the true mass, is also very low, only 0.42 times that of Jupiter, or 1.4 times that of Saturn. Though very close to its star, the planet still has a small orbital eccentricity of about 5 percent. From the planet, the star would appear to be nearly 14 degrees across, nearly three times the separation between the front bowl stars of the Big Dipper.


HR 3497, also called HD 75289, is a sixth magnitude (6.36) class G0 dwarf star in Vela. Too faint to have a proper or Greek letter name, or even Flamsteed number, it is known best by its numbers in the Bright Star(HR) and the Henry Draper (HD) Catalogues. From a distance of 94 light years, it shines with a luminosity 1.94 times that of the Sun with a surface temperature of 6140 Kelvin, 360 degrees warmer than the Sun, from which we derive a mass 1.23 solar, a radius 1.23 times that of the Sun, and find that the star is rather young. Like most stars with planets, HR 3497 is notably metal-rich, its iron content (relative to hydrogen) 1.9 times solar. HR 3497 is oddly listed in the catalogues as a supergiant, clearly an error, as the luminosity and temperature put it squarely among the dwarfs. In addition to its planet, HR 3497 has a distant red dwarf companion that lies at least 620 AU away. With a low mass of but 14 percent that of the Sun, it must take at least 13,000 years to orbit. While there is no visual magnitude measurement, such stars hover around absolute magnitude 13 (0.0005 times that of the Sun). From the orbiting planet (at the stated distance), the companion would therefore shine only about as bright as Venus does from Earth.
Written by Jim Kaler. Return to The Planet Project or go to STARS.