Thursday, February 11, 2010

Close encounters with a black hole

New black hole simulator uses real star data
New Scientist: A new interactive program reveals the spectacular light show you'd see if you dared to wander close to a black hole... A black hole forms when a massive star explodes at the end of its life, the core collapsing to a point with huge density and an enormous gravitational pull. Even at a safe distance from the black hole, its gravity can distort the apparent positions of background stars, an effect called gravitational lensing.

Last year, scientists at the University of Colorado demonstrated a video of what you'd see if you fell into a black hole. Now [Thomas] Mueller and [University of] Stuttgart colleague Daniel Weiskopf have gone a step further, creating a program that lets you alter various inputs to tour a black hole's environs.

The program incorporates the real positions of around 118,000 stars mapped by the European Space Agency's Hipparcos satellite. Users can choose their distance from a black hole, then go into orbit or plunge straight in. At the start of each tour, you see a black circle that marks the hole's event horizon -- the boundary from which nothing, not even light, can escape...

This example simulation shows the view while orbiting a black hole at a radius five times larger than the even horizon... As well as accounting for gravitational lensing, the simulator shows how star colours would change near a black hole. The intense gravity makes background stars appear redder because it saps the energy of photons passing near the event horizon; the photons stretch to longer, redder wavelengths as they 'climb out' of the gravitational trap.

But this effect is counteracted by your speed when you're falling freely towards a black hole -- traveling at nearly the speed of light, stars in the black hole's backdrop turn bluer due to the Doppler effect. In a simulation mimicking such unhindered freefall, the light of the entire universe appears concentrated into a bright ring once you reach the middle of the black hole.

Video: Black Hole Light Show (or on standalone player here)
Other flight simulations: Welcome to the Black Hole
Image source here.