北京大学科维理天文与天体物理研究所

Featured Science

When the Stars Align — the First Resolved Microlensed Images

Using VLTI GRAVITY, an international team led by Professor Subo Dong (KIAA) have resolved the two images of a microlensed source star for the first time, more than a century after Einstein first predicted that such image splitting could be caused by the gravity of another (lens) star along the line of sight to the source. This detection fills in the key missing ingredient that yields the mass and distance of the lens star. This technique could be applied in the future to measure the mass of isolated (single) stellar-mass black holes, which have so far remained elusive.

A New Look at an Old Problem: How to Measure Star Formation Rates in Galaxies

Using a large sample of galaxies from the Sloan Digital Sky Survey (SDSS), Ming-Yang Zhuang and Luis C. Ho from the Kavli Institute for Astronomy and Astrophysics at Peking University proposed an updated star formation rate (SFR) calibration using the [O II]λ3727 emission line for star-forming galaxies. Based on photoionization models, they extended the [O II]-based SFR estimator to active galaxies. This work has been published in The Astrophysical Journal (Zhuang & Ho 2019, ApJ, 882, 89).

Discovery of a new Luminous Blue Variable in the outskirt of the Andromeda Galaxy

A study by the research group led by Prof. Huawei Zhang from Department of Astronomy, Peking University and collaborators from Yunnan University report the discovery of a new Luminous Blue Variable (LBV) in the outskirt of the Andromeda Galaxy (M31), using data from the LAMOST spectroscopic surveys, from the Xinglong NAOC 2.16m, Lijiang YNAO 2.4 m optical telescopes and Hale 5m telescope, as well as archival data. The finding has been published in The Astrophysical Journal Letters.

Pulsar emission map thanks to Einstein

Kejia Lee from Kavli Institute for Astronomy and Astrophysics at Peking University joined the international collaboration and has used radio observations of the source PSR J1906+0746 to reconstruct the polarised emission over the pulsar’s magnetic pole and to predict the disappearance of the detectable emission by 2028. Observations of this system confirm the validity of a 50-year old model that relates the pulsar’s radiation to its geometry. The researchers are also able to precisely measure the rate of change in spin direction and find an excellent agreement with the predictions of Einstein’s theory of general relativity.

ALMA Dives into Black Hole’s ‘Sphere of Influence’

New observations with the Atacama Large Millimeter/submillimeter Array (ALMA) provide an unprecedented close-up view of a swirling disk of cold interstellar gas rotating around a supermassive black hole. This disk lies at the center of NGC 3258, a massive elliptical galaxy about 100 million light-years from Earth. Based on these observations, an international team that includes Luis Ho, Director of the Kavli Institute for Astronomy and Astrophysics at Peking University, has determined that this black hole weighs a staggering 2.25 billion solar masses, the most massive black hole measured with ALMA to date.

An X-ray transient as New Signal of Neutron Star Mergers

A bright X-ray burst within a galaxy 6.6 billion light years from Earth has been detected by NASA’s Chandra X-ray Observatory. This event is likely to be the emission from a neutron-star-merger-produced magnetar – a new, heavier, highly magnetized neutron star. It is a totally new signal from neutron star binary mergers, which suggests that the merger of two neutron stars could result in a long lived neutron star rather than a black hole.