Explore the Night with Bob King

9,096 Stars in the Sky—Is That All?

Ten thousand stars bedazzle the eye on a dark night. Wait, how many?

Science-based Q&A

How Far is the Closest Star?

Barring the Sun, the closest star to Earth is a triple system called Alpha Centauri, which is over four light years away.

Science-based Q&A

What are constellations?

In 1930, the International Astronomical Union (IAU) divided the sky into 88 constellations. Each constellation is defined by an imaginary boundary on the sky and named after a classical star pattern within those boundaries. So when we say a star is “in” a particular constellation, we mean it lies within the IAU-defined boundaries of that constellation.

Science-based Q&A

How Many Stars are There in the Universe?

By measuring the number and luminosity of observable galaxies, astronomers put current estimates of the total stellar population of the observable universe at roughly 70 billion trillion.

Astronomy Questions & Answers

What is the brightest star in the sky?

The brightest star in the sky is Sirius, also known as the “Dog Star” or, more officially, Alpha Canis Majoris, for its position in the constellation Canis Major.

Astronomy Questions & Answers

How Do Stars Die and How Long Do Stars Live?

Both the life and death of a star depend on its mass. Generally speaking, the more massive a star, the faster it burns its fuel and the shorter its life. The most massive stars meet their end in a supernova explosion after only a few million years of fusion, while the tiniest stars continue to feebly burn for upwards of a trillion years.

Astronomy Questions & Answers

What Is a Star?

A star is a luminous ball of gas held together by its own gravity. Nuclear fusion in its core supports the star against gravity and produces photons and heat. The Sun is the closest star to Earth.

Astronomy Questions & Answers

Why Do Stars Twinkle?

Though it wouldn’t work so well in the nursery rhyme, a star’s twinkling actually has a technical term, astronomical scintillation: the effect of our planet’s atmosphere on starlight.

Stargazing Basics

The Stellar Magnitude System

Why do larger numbers mean less light? Here's the story of astronomy's odd but beloved scheme for describing star brightnesses.

Ursa Major from Urania's Mirror

Stargazing Basics

Star Names: Where Do They Come From and What Do They Mean?

Confused by the bizarre names that astronomers have given the stars? Here's where they come from and what they mean.