The universe is a marvelously complex place, filled with galaxies and larger-scale structures that have evolved over its 13.7-billion-year history. Those began as small perturbations of matter that grew over time, like ripples in a pond, as the universe expanded. By observing the large-scale cosmic wrinkles now, we can learn about the initial conditions of the universe. But is now really the best time to look, or would we get better information billions of years into the future - or the past?
New calculations by Harvard theorist Avi Loeb show that the ideal time to study the cosmos was more than 13 billion years ago, just about 500 million years after the Big Bang. The farther into the future you go from that time, the more information you lose about the early universe.
An artistic rendition of a nomad object wandering the interstellar medium. The object is intentionally blurry to represent uncertainty about whether or not it has an atmosphere. A nomadic object may be an icy body akin to an object found in the outer Solar System, a more rocky material akin to asteroid, or even a gas giant similar in composition to the most massive Solar System planets and exoplanets. (Image by Greg Stewart/SLAC)
Planets simply adrift in space may not only be common in the cosmos; in the Milky Way Galaxy alone, their number may be in the quadrillions. Three experts discussed what this might mean, whether a nomad planet could drift close to our solar system, and how it is possible for a nomad planet to sustain life.
See this roundtable discussion at the Kavli Foundation that features Harvard Professor Dimitar D. Sasselov and others.
Scientists were able to observe the demise of a star and its digestion by a previously dormant supermassive black hole in real time. f a star passes too close to a black hole, tidal forces can rip it apart, and its constituent gases then swirl in toward the black hole. Friction heats the gases and causes them to glow. By searching for newly glowing supermassive black holes, astronomers can spot them in the midst of a feast. Harvard Professor Edo Berger is a co-author on this study.
The Tycho supernova remnant is the result of a Type Ia supernova explosion. The explosion was observed by Danish astronomer Tycho Brahe in 1572. More than 400 years later, the ejecta from that explosion has expanded to fill a bubble 55 light-years across. In this image, low-energy X-rays (red) show expanding debris from the supernova explosion and high energy X-rays (blue) show the blast wave - a shell of extremely energetic electrons. Credit: X-ray: NASA/CXC/Rutgers/K.Eriksen et al.; Optical: DSS
CFA Clay Fellow R. Foley and Harvard Astronomy Professor R. Kirshner publish new findings. The exploding stars known as Type Ia supernovae serve an important role in measuring the universe, and were used to discover the existence of dark energy. They're bright enough to see across large distances, and similar enough to act as a "standard candle" - an object of known luminosity. The 2011 Nobel Prize in Physics was awarded for the discovery of the accelerating universe using Type Ia supernovae. However, an embarrassing fact is that astronomers still don't know what star systems make Type Ia supernovae.