10 CVN (10 Canum Venaticorum). Solar type stars are for obvious reasons inherently fascinating. Those with known planets are even more so. In between are stars with circumstellar dusty debris disks like the one around our own Sun (caused by colliding small bodies, disintegrating comets, etc.) in which planets might be buried but are so far hidden. Flamsteed 10, in Canes Venatici (the Hunting Dogs, south of the Big Dipper), a class G (G0) dwarf a hair up the spectral scale from our G2 Sun, is a fine example, though there is a notable departure from a true sunlike character (see below). While faint to the naked eye, just sixth magnitude (5.95), 10 Canum Venaticorum is remarkably easy to find just barely south of a line between Cor Caroli and Chara (respectively Alpha and Beta CVn), which together make most of the constellation. Oddly, Chara and 10 CVn share the same spectral class. Two dozen measures of 10 CVn's temperature give an accurate average reading of 5855 Kelvin, just 75 Kelvin warmer than the Sun and consistent with the star's spectral class. From a super-accurate distance of 567 light years, give or take only 0.3, and a small correction for radiation outside the visual band, 10 CVn is seen to shine with a luminosity just seven percent greater than that of the Sun, luminosity and temperature combining for a radius of 1.01 times solar. The most recent projected equatorial rotation velocity of 3.0 kilometers per second together with a published rotation period of 13.0 days gives an axial tilt of 50 degrees to the line of sight. All these properties point to a "solar clone." But 10 CVn does not quite make it as the star is fairly metal-poor, with an iron abundance relative to hydrogen that is only a third the solar value. Consistent with 10 CVn's chemical properties, it's also pounding along with a speed relative to the Sun of 86 kilometers per second, around five times average. The star is thus a visitor from a different part of the Galaxy, probably from the inner halo, published analysis suggesting a mass of 0.86 Suns. Most intriguing, however, is the dusty disk that surrounds the star, which is big enough to have been directly imaged in the infrared part of the spectrum. Modelling of the observations suggest a disk with a radius of 70 to 80 Astronomical Units in the form of an annulus perhaps 10 AU wide, which is rather reminiscent of our Sun's Kuiper Belt beyond the orbit of Neptune. We might wonder if there is not some kind of yet-undetected earthlike planet orbiting inside the disk closer to the star. If anybody's there they might be looking back at our 6.0 magnitude Sun, which for them would lie on the border between Sculptor and Pheonix. Perhaps too they might note several planets, maybe even the third one out. (Disk and some stellar data from J. P. Marshall et al., Astronomy and Astrophysics, 570A, 114, 2014.)

Written byJim Kaler 8/14/15. Return to STARS.