When astronomers refer to “compact objects,” they are generally referring to objects significantly more dense than a star or a planet. For example, white dwarfs or neutron stars are extremely dense stars that have collapsed, no longer able to produce a sufficient amount of pressure within to prevent their outer layers from falling into their centers. Under extreme conditions, these collapses…Continue reading
Roughly 13.7 billion years ago, the universe started expanding from a dense, hot volume. In the early universe, some 400,000 years after the Big Bang, conditions cooled enough to allow the formation of hydrogen atoms from free protons and electrons. After this early phase, known as "recombination," the universe began to take shape as objects - galaxies, stars, planets – coalesced from the…Continue reading
One of the most important and surprising scientific discoveries of the twentieth century is that the expansion of space is not slowing down, but speeding up – contrary to what we expect the gravitational pull of all the matter in the Universe to do. This discovery was recognized with the 2011 Nobel Prize in Physics.
Mostly Dark Energy
Though the driver of this accelerating…Continue reading
Only about five percent of the total matter + energy content of the Universe is familiar to us. The identity of the remaining 95 percent, roughly 1/3 of it dubbed as "dark matter" and roughly 2/3, dubbed as "dark energy" is unknown. Though scientists have not yet detected it directly in laboratories on Earth, dark matter’s existence has been deduced from its gravitational effects on the stars…Continue reading
Much in the same way archeologists reconstruct past civilizations by looking at remains in the present, cosmologists reconstruct the universe’s past by looking at the constituents of the current universe. By doing so, they can infer how the universe began, how it evolved into its present state, and how it will continue to change over time. The study of the early universe is one of the most…Continue reading
The universe is awash in highly energetic particles with velocities approaching the speed of light. Though these particles exist in many places throughout the universe – and can even be found slamming into our own atmosphere – scientists don’t yet fully understand their origins.
Nature’s High-Performance Accelerator
Celestial objects such as neutron stars or the remnants of…Continue reading
More than 2000 planets have been discovered orbiting other stars. These extrasolar planets, or exoplanets, span a vast range of properties, and most form systems very different than our own, ranging from giant ‘hot Jupiters’ that are closer to their star than Mercury, to tightly-packed systems of multiple “super-earth” planets orbting faint red stars.