Sirius A is an A1V main-sequence star, 25× more luminous than the Sun. Its blue-white light makes it appear the brightest star in the sky (apparent magnitude −1.46) despite being only 2.64 pc away.
Sirius B is a DA2 white dwarf — the collapsed remnant of a star that was once ~5 M☉. At 25,200 K it glows hot blue-white, but with only 0.0084 R☉ radius it appears tiny. It was discovered in 1862 by Alvan Clark.
Gravity: Surface gravity of Sirius B is ~330,000× Earth's. A teaspoon of white dwarf material would weigh ~15 tonnes.
Eccentric orbit: The two stars orbit a common barycentre with eccentricity 0.591 — separation varies from ~8.2 AU (periapsis) to ~31.5 AU (apoapsis).