The illusion of being faster than light: how a star problem was solved

A jet of particles released by two colliding stars appears to be moving seven timesthe speed of light but astronomers blame it to be a cosmic illusion.

• Astronomers have detected a blast of energy from space that appears to betravelling seven times faster than the speed of light.
• The jet of particles (ultra-relativistic material) in question has resulted from the collision of two neutron stars located roughly 140 million light-years from Earth.
• The collision was so powerful it created ripples in the fabric of space-time; such disturbances are known as gravitational waves.
• According to a study publishedin the journal Nature, the jet of energy blasted out of a collision site at a staggering 99.97% of the speed of light, certainly not more than the speed of light.

Neutron stars:

• They are stellar corpses, left behind after a star has experienced a supernova explosion and reached the end of its lifetime.
• They are extremely dense, containing more mass than the sun in a sphere that is a few tens of kilometers wide.

How did astronomers make this observation?

• Both gravitational waves and visible waves were produced after the Collison. Large Interferometer Gravitational-Wave Observatory (LIGO) first detected the Gravitation waves.
• Astronomers at NASA's Hubble Space Telescope, and the European Space Agency's GAIA space observatory saw visible evidence of a high-speed jet of particles, blazing out of the collision site.
• With these observations, the team calculated both the actual speed of the jet and the perceived physics-defying speed.

Beyond light-speed illusion:

• The beyond-light-speed illusion arises from the difference in speed between the particles in the jet, and the light particles (or photons) that they emit.
• Because the jet's particles move nearly as fast as the light they emit, it can appear as though particles in the early part of the jet are arriving at Earth at nearly the same time as photons in the later stages of the jet, making it appear as though the jet is actually moving faster than the speed of light. Hence, exhibiting superluminal motion.
• Superluminal motion occurs as a special case of a more general phenomenon arising from the difference between the apparent speed of distant objects moving across the sky and their actual speed as measured at the source.