Are you a dog person? 🐶 On 26 August we celebrate International Dog Day with the cosmos’ most famous celestial canine, Sirius A, also known as the Dog Star! Sirius A shines as the brightest star in our night sky, just 8.6 light-years away. Look closely and you’ll spot its faint companion, Sirius B, a white dwarf star only 12 000 km in diameter—about the size of Earth! These two stars dance around each other every 50 years, with Sirius B’s light being 10 000 times fainter than its dazzling partner. Thanks to Hubble’s advanced imaging, astronomers have been able to study Sirius B’s spectrum, revealing its surface temperature of 25 000°C and a mass nearly equal to our Sun’s. White dwarfs like Sirius B are the remnants of stars like our Sun and play a key role in understanding stellar evolution and cosmology, including the mysterious dark energy stretching our Universe. So, as we honor our furry friends on Earth, let’s also look up and marvel at this stellar “dog” in the sky, remindi...