StarDate

A quiet monster lurks in the heart of M31, the Andromeda Galaxy. Known as M31-star, it’s a black hole a hundred million times the mass of the Sun, and 25 times heavier than the black hole at the heart of the Milky Way.

Every large galaxy probably has a supermassive black hole. And many of them are quite bright.

The black hole itself is completely black – it swal...

Two-and-a-half million years ago, Earth was going through some big changes. It was the start of the Pleistocene epoch – a period of major ice ages. And the ancestors of modern humans were just appearing.

That timescale puts a little perspective on the distance to M31, the Andromeda Galaxy – the closest major galaxy to the Milky Way. It’s two-and-a-half million light-ye...

The Moon has had a busy social calendar this week. It’s had meet-and-greets with the twins of Gemini and the planets Mars and Jupiter. And it has one more engagement tomorrow. Regulus, the heart of the lion, will stand above the Moon at dawn. In centuries past, people took a more literal view of lunar social activities. Many thought the Moon was inhabited – including some ast...

For skywatchers across the eastern United States, the planet Jupiter will vanish early tomorrow – hidden behind the crescent Moon. The rest of the country will see an impressively close encounter between the two bodies.

The vanishing act is an occultation – from a Latin word that means “to hide.” Over the centuries, astronomers used these events to learn more about the...

To borrow from “Alice in Wonderland,” the case for life on Mars keeps getting curiouser and curiouser. Two rovers have discovered organic compounds there – the chemical building blocks of life – in locations that are thousands of miles apart. And some recent looks at results from the Viking landers of the 1970s suggests they, too, might have found organics. So it’s possible t...