Featured Science

Multiple generations of stars in star clusters may resemble adopted rather than natural children

Astronomers had long thought that the old, dense swarms of stars known as globular clusters formed their millions of stars in bulk at around the same time, with each cluster's stars having very similar ages. Using the Hubble Space Telescope, a team led by KIAA researchers Chengyuan Li and his supervisor Richard de Grijs has for the first time found young populations of stars within globular clusters that have apparently developed courtesy of star-forming gas flowing in from outside of the clusters themselves. The theory of newborn stars arising in clusters as they "adopt" interstellar gas dates back to a 1952 paper. More than a half-century later, this once speculative idea suddenly has key evidence to support it. The new discovery is published as a Letter to Nature on 28 January 2016.

Record-Shattering Cosmic Blast Could Help Crack the Case of Extreme Supernova Explosions

Stunned astronomers have witnessed a cosmic explosion about 200 times more powerful than a typical supernova—events which already rank amongst the mightiest outbursts in the universe—and more than twice as luminous as the previous record-holding supernova. At its peak intensity, the explosion—called ASASSN-15lh—shone with 570 billion times the luminosity of the Sun. If that statistic does not impress, consider that this luminosity level is approximately 20 times the entire output of the 100 billion stars comprising our Milky Way galaxy. The record-breaking blast is thought to be an outstanding example of a "superluminous supernova," a recently discovered, supremely rare variety of explosion unleashed by certain stars when they die. Scientists are frankly at a loss, though, regarding what sorts of stars and stellar scenarios might be responsible for these extreme supernovae.

KIAA Scientists Discover the Most Luminous Quasar with an Ultramassive Black Hole in the Distant Universe

An international team led by Xue-Bing Wu, the associate director of Kavli Institute for Astronomy and Astrophysics (KIAA) and a professor at Department of Astronomy of Peking University, discovered a new quasar with a central black hole mass of 12 billion solar masses and a luminosity of 430 trillion solar luminosity, at a distance of 12.8 billions light years from the Earth. This is the most luminous quasar ever discovered in the early Universe, powered by the most massive black hole yet known at that time. The discovery of this quasar, named SDSS J0100+2802, marks an important step in understanding how quasars, the most powerful objects in the Universe, have evolved from the earliest epoch, only nine hundred million years after the Big Bang. This discovery was published in the top scientific journal Nature on February 26, 2015.

Star cluster evolution not as simple as thought

Using Hubble Space Telescope observations of a 2 billion-year-old Large Magellanic Cloud star cluster, KIAA PhD student Chengyuan Li and his supervisor, Richard de Grijs, showed that the recent paradigm shift from star clusters as single-age stellar populations to complex populations may need a major reverse correction. Morphological features in the cluster's diagnostic Hertzsprung-Russell diagram that are commonly interpreted as evidence of cluster-internal age spreads may instead be owing to the presence of a population of rapidly rotating stars. These latest results resolve nearly a decade of debate among scientists; the resulting paper is published in the 17 December 2014 issue of the journal Nature.

Longstanding Quasar Puzzle Solved

New KIAA faculty member Yue Shen and KIAA Director Luis Ho have solved a two-decade long mystery in quasar research. Namely, what drives the diverse properties of quasars into a well-defined main sequence, known as "Eigenvector 1" (EV1). Shen and Ho showed conclusively that Eddington ratio (the efficiency of BH accretion) is the main driver of EV1. Their work is published in the September 11 issue of the journal Nature.