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.
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.
In physics, the value of a theory is measured by how well it agrees with experimental data. But how should the physics community gauge the value of an emerging theory that cannot yet be tested experimentally? With no reality check, a less than rigorous hypothesis such as string theory may linger on, even though physicists have been unable to work out its actual value in describing nature.
A vibrant online astronomy community created by PhD students highlights new research and advice for professional growth.
Among the founders and contributors of Astrobites are, from left, Aaron Bray (G2), Elisabeth Newton (G2), Nathan Sanders (G2), Joshua Suresh (G2), Christopher Faesi (G1), and Courtney Dressing (G2), here pictured on their home turf, the observatory at 60 Garden Street.
Cambridge, MA - Seven years ago, astronomers boggled when they found the first runaway star flying out of our Galaxy at a speed of 1.5 million miles per hour. The discovery intrigued theorists, who wondered: If a star can get tossed outward at such an extreme velocity, could the same thing happen to planets?
New research shows that the answer is yes. Not only do runaway planets exist, but some of them zoom through space at a few percent of the speed of light - up to 30 million miles per hour.
How did the first stars and galaxies bring the young universe out of its dark ages and into the light? Three prominent researchers, including Harvard Astronomy Professor Avi Loeb, discuss how new instruments and observational techniques may find the answer.
The cores of most galaxies are thought to harbor black holes with masses of a million or more suns. But many remain unseen until an unlucky star passes too close and is pulled apart by tidal forces. The stellar debris gathers into a disk and spirals towards the black hole in the center. As it does, it may form a jet of material that beams high-energy light like a flashlight. Last spring, the Swift satellite measured a flare of x rays and gamma rays from a distant galaxy that has the hallmarks of such a jet that happens to point right at us.... Read more about Synopsis: Tidal Disruption of a Star (N. Stone and A. Loeb)
Before Ed Turner and Avi Loeb tell you about their research, they want to make one thing perfectly clear: they do not claim there's a city on Pluto. But if there were, they say, we could see it. And, as they suggest in a paper they've submitted to the journal Astrobiology, it's worth taking a look, just in case.
By Karen Weintraub Cambridge, Massachusetts November 8, 2011
Hollywood is wrong about aliens. They don't have oddly shaped heads, bulging eyes or even an eery green hue. Dimitar Sasselov is pretty convinced of that.
He's not even sure we'll know them when we see them. Prof Sasselov, an astrophysicist, thinks that if life exists elsewhere - and he believes it does - it will likely be based on different building blocks than ours, and so may not even be recognizable as life.
A project he's heading at Harvard University, called the Origins of...