StarDate

Pollux, the brighter of the “twin” stars of Gemini, is a giant. It’s expanded to about nine times the diameter of the Sun — a beach ball to the Sun’s golf ball. That’s made Pollux much cooler than the Sun, so it looks orange. And it’s more than 30 times brighter than the Sun. Careful measurements of its diameter, combined with measurements of subtle “ripples” across its surface, have yielded the mass of Pollux as well: 1.9 times the Sun’s mass. Astronomers have combined that with measurements of its

The planets that flank Earth huddle close together in the dawn sky over the next few days. Venus and Mars are quite low in the east-southeast during the waxing twilight, so you need a clear horizon to spot them. And binoculars wouldn’t hurt. Venus is the second planet out from the Sun, Earth is third, and Mars is fourth. Their orbits are separated by tens of millions of miles. Yet all three worlds are inside the Sun’s “habitable zone.” That’s the distance from the Sun where the temperature is just