What exactly do we wish upon when we wish upon a star? That's the subject of "Journey to the Stars," the latest show at New York's Hayden Planetarium.

The dramatic original music in the "Journey to the Stars" show complements the exploding supernovas, star clusters and other stellar images projected on the planetarium's dome, all of which are based on precise mathematical models and actual astronomical observations.

A star is born

Almost five billion years ago, the sun (circled) and its siblings were born in a cloud of gas and dust, forming a cluster of stars much like this one. Click photo to enlarge

Stars begin their life cycles as gas clouds in a galaxy. When those clouds go unstable, they collapse.

"… and where they collapse, they get hot," says astrophysicist and Hayden Planetarium Director Neil de Grasse Tyson. "And there is a point where they collapse with enough material, and the temperature gets hot enough that it spontaneously begins nuclear fusion."

Fusion occurs when two atoms come together to make a bigger atom, and energy is released.

"And therein is the birth of a star!" Tyson adds, with an almost familial affection.    

Stars contain elements of life

In the early universe, only 300 million years after the Big Bang, the first stars form from clouds of gas drawn together by the gravity of the mysterious substance called dark matter. Click photo to enlarge

The temperature in the core of an average star is about 15 million degrees Celsius. Radiation and convection carry that energy outward to the star's surface and to its atmosphere beyond. When the atmosphere gets hot enough to become transparent, the energy escapes into space in the form of light.

Stars also release matter, such as oxygen, nitrogen, carbon, silicon and potassium.

"These are the elements the planets and living things are made of," Tyson says. "So the life cycle of stars is inextricably bound to life itself."

Indeed, scientists estimate that every human body contains about a teaspoonful of stellar material from the early universe.  

Magnetic fields encircle stars

In the stellar nursery within the Orion Nebula, young stars are forming before our eyes from a giant cloud of interstellar gas and dust much as the sun did almost five billion years ago. Click photo to enlarge

Here in our solar system, the constant churning of the sun's gases creates a giant, pulsing magnetic field, which NASA solar scientist and "Journey to the Stars" consultant Madhulika Guhathakurta likens to a heartbeat. 

"And this magnetic field can get really stressed from all of these churnings and rotations," she says "and eventually it will just snap!"
     
 And when it snaps, it creates huge solar eruptions in the form of electrons and protons, which travel through space at speeds up to 3.6 million kilometers per hour. Indeed, such "space weather" can interfere with Earth's own magnetic field, knocking out communications satellites and damaging the power transformers that humans depend on for electricity.   

All stars share essential properties

Life on Earth depends on energy released by the fusion of hydrogen atoms to form helium in the blazing heart of the star known as our sun. Click photo to enlarge

The planetarium show vividly illustrates how stars vary widely in mass, temperature, age, color, luminosity and size. But the underlying physics for each of the estimated 100 billion stars in our Milky Way galaxy - and in the 100 billion other galaxies - is the same.

"Every star is essentially a ball of gas trying to collapse under its own gravity," says astrophysicist and show co-curator Mordecai-Mark Mac Low. "What prevents that from happening is the immense pressure outward produced from hot gas that is heated by nuclear fusion in its center."

Stars maintain this equilibrium through middle age, which can last a few million years for the hottest, bluest stars, to trillions of years for the smallest, coolest, red stars.

What will happen to the sun?

Traveling some five billion years into the future, viewers witness a startling sight: Our own familiar yellow sun has ballooned into a red giant nearly engulfing Earth. Click photo to enlarge

Our sun's middle age will last 5 to 10 billion years, when it will become unstable, cool off, turn from yellow to red, and expand.

"It becomes so large," says Neil de Grasse Tyson, "that the surface of the sun will come near enough to Earth that it will bring the oceans to a rolling boil, and life as we know it on Earth will cease." 

Ever the optimist, Tyson confidently predicts that humans will either be extinct from other causes by then "or we will have moved to a more distant planet by then - just to get a safe distance from the sun that's about to kill us." 

Soon after that, the sun will contract from a red giant into what astrophysicists call a "white dwarf." It will then stop generating fuel and slowly go cold like a piece of spent charcoal. But not to worry: As the "Journey to the Stars" show points out, there will be trillions of new stars, with perhaps quadrillions of planets, to take its place.