Imagine two nearby exoplanets orbiting the same sun, each with its own indigenous civilisation. They're going through history either as companionable neighbours or deadly rivals. This is a familiar situation in science fiction, but could it ever happen?
Stochastic acceleration and shock acceleration are well recognized as key mechanisms for cosmic ray generation since first proposed by Fermi. So far, these two mechanisms have been investigated widely by analytical models and numerical simulations, but often modeled separately. Researchers have found that the two mechanisms can occur naturally in sequential two stages when a lepton flow propagates in a background interstellar plasma.
A planet discovered last year sitting at an unusually large distance from its star - 16 times farther than Pluto is from the sun - may have been kicked out of its birthplace close to the star in a process similar to what may have happened early in our own solar system's history.
VY Canis Majoris is a stellar goliath, a red hypergiant, one of the largest known stars in the Milky Way. It is 30-40 times the mass of the Sun and 300 000 times more luminous. In its current state, the star would encompass the orbit of Jupiter, having expanded tremendously as it enters the final stages of its life.
Astronomers have identified the hottest white dwarf ever discovered in our Galaxy. With a temperature of 250,000 degrees Celsius, this dying star at the outskirts of the Milky Way has already even entered its cooling phase.
With nearly 2000 exoplanets found to date, it is no wonder so many of them will resemble our planet in some way. But which exoplanets are similar enough to the Earth that they could actually be habitable?
Astronomers have found a galaxy with a heartbeat - and they've taken its pulse. It is the first time scientists have measured the effect that pulsating, older red stars have on the light of their surrounding galaxy.
'Interplanetary dust' is hugely important. It is thought to have played a crucial role in the formation and evolution of our solar system. What?s more, it may even have provided our planet with water - and kick-started life.
The dilemma of whether to accept the cost of acting or risk disaster by waiting is the kind of strategic problem studied by game theory. A situation like the space debris problem, where players act just for their own benefit instead of taking group interests into account, is referred to in game theory as the 'tragedy of the commons'.