N VEL (N Velorum). Bayer could not see most of the stars of Argo. The Greek letters were assigned in the 1700s by that intrepid explorer of the southern skies, Nicolas de Lacaille. Breaking giant Argo into three parts, he distributed Greek letters among them, but then assigned Roman letters, first lower case and then upper case, within each of them. It's a testimony to the plethora of bright stars in Vela (the Sails: the other parts Carina, the Keel, and Puppis, the Stern) that third magnitude (3.13) N Velorum was placed so far down on the list. Anywhere else it would probably be a notable part of the constellation outline. Of course it could always be added in as the outlines are hardly official. Just past the eastern edge of the "False Cross" (made of Delta and Kappa Vel and Iota and Epsilon Carinae), which might fool the unwary into thinking it is the Southern Cross, N Vel is just barely north of the border with Carina. It is thus the southernmost lettered star in Vela. (There are no Flamsteed numbers in the deep southern hemisphere, and of such numbers assigned by others only 30 Doradus, a massive diffuse nebula in the Large Magellanic Cloud, and the globular cluster 47 Tucanae survive.) Aside from standing out as a rather bright star, N Vel is a more or less ordinary orange class K giant 239 light years away (give or take 2), albeit at subclass K5 a bit cooler (4045 Kelvin) than most of them. Commonality, however, hardly takes away from significance. That there appear to be so many class K giants is an example of observational selection. Compared to the general stellar population there are not that many, but they stand out because of their brightness. None of the most common kind of stars, the red class M dwarfs (like Proxima Centauri), is bright enough to be seen with the naked eye. But back to our orange giant. After correction for a fair bit of infrared radiation, we see that N Vel shines brightly, with the luminosity of 642 Suns, not bad for any star, which leads to a radius of 52 times that of the Sun, nearly a quarter of an Astronomical Unit, 62 percent the size of Mercury's orbit. Theory then spots the mass at around 3.5 times solar and the age at maybe 200-plus million years. Correction for an uncertain amount of dimming by interstellar dust increases the luminosity by 16 percent and the radius by 8 percent, but makes little difference in the mass. Possibly an irregular variable (magnitudes 3.10 to 3.16), N Vel is most likely brightening and preparing to fire its helium core or brightening for the second time with a dead carbon core. Only time will tell. However, nobody nearby will witness it, as the star seems decidedly single. N Vel will eventually slough off its outer layers and turn into a white dwarf with a mass of about 55 percent that of the Sun.

Written byJim Kaler 5/09/14. Return to STARS.