the presence of giant planets 11 times more massive than Jupiter at 0.5 AU distance from Sirius A, 6–7 times the mass of Jupiter at 1–2 AU distance, and down to around 4 times the mass of Jupiter at 10 AU distance. Similarly, Lucas and colleagues did not detect any companions around Sirius B. Sirius A Sirius A has a mass of . The radius of this star has been measured by an astronomical interferometer, giving an estimated angular diameter of 5.936±0.016 mas. The projected rotational velocity is a relatively low 16 km/s, which does not produce any significant flattening of its disk. This is at marked variance with the similar-sized Vega, which rotates at a much faster 274 km/s and bulges prominently around its equator. A weak magnetic field has been detected on the surface of Sirius A. Stellar models suggest that the star formed during the collapsing of a molecular cloud and that, after 10 million years, its internal energy generation was derived entirely from nuclear reactions. The core became convective and used the CNO cycle for energy generation. It is calculated that Sirius A will have completely exhausted the store of hydrogen at its core within a billion () years of its formation, and will then evolve away from the main sequence. It will pass through a red giant stage and eventually become a white dwarf. Sirius A is classed as a type because the spectrum shows deep metallic absorption lines, indicating an enhancement of its surface layers in elements heavier than helium, such as iron. The spectral type has been reported as which indicates that it would be classified as A1 from hydrogen and helium lines, but A0 from the metallic lines that cause it to be grouped with the Am stars. When compared to the Sun, the proportion of iron in the atmosphere of Sirius A relative to hydrogen is given by meaning iron is 316% as abundant as in the Sun's atmosphere. The high surface content of metallic elements is unlikely to be true of the entire star; rather the iron-peak and heavy metals are radiatively levitated towards the surface. Sirius B Sirius B is one of the most massive white dwarfs known. With a mass of , it is almost double the average. This mass is packed into a volume roughly equal to the Earth's. The current surface temperature is 25,200 K. Because