New Scientist issue 2627

“IN NOVEMBER 1572, a dazzling new star appeared in the night sky. It became so bright so quickly that it soon outshone everything except the sun and the moon and could even be seen in daylight.

Danish astronomer Tycho Brahe tracked the star for 16 months. As it slowly faded, the star changed colour from white to yellow then orange and finally faint red.

We now know that what Brahe saw was probably a type Ia supernova, a species of exploding star that, over the past 30 years, has become increasingly important in astrophysics. Because they are all thought to explode with the same brightness, type Ia supernovae are used as "standard candles" to gauge distances across the universe.

But type Ia supernovae are beset with problems. It has become clear that they do not all explode with the same brightness. What's more, though astronomers were once sure they knew...”

The complete article is 1415 words long and is available here
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