ACAMAR collaboration success stories

A slightly exaggerated impression of the real shape of our warped and twisted Milky Way. Credit: Xiaodian Chen, National Astronomical Observatories, Chinese Academy of Sciences.

An ongoing international collaboration focused on stellar astrophysics has discovered a warped and twisted disc of young, massive stars at the edge of our Milky Way.

The discovery was made by compiling a new catalogue of bright, young variable stars – known as Cepheids – and using this to develop the first accurate three-dimensional (3D) picture of the Milky Way’s stellar disc out to its far outer regions.

The catalogue was originally created from observations made by NASA’s Wide-field Infrared Survey Explorer (WISE), a space telescope fitted with long-wavelength infrared glasses. Ideal to look through any dust in the Milky Way’s disc, the resulting 3D map has allowed astronomers to update their understanding of our galaxy’s stellar motions and the origins of the Milky Way’s disc.

The collaboration behind this discovery consists of the Stars and Stellar Systems group at the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) – led by Prof. Licai Deng, and the Stellar Astrophysics group at the Research Centre for Astronomy, Astrophysics and Astrophotonics based at Macquarie University – led by Prof. Richard de Grijs.

The success of this collaboration was immediately evident after the joint paper related to this discovery was published in Nature Astronomy. The story of our Milky Way’s warped and twisted stellar disc inspired the public’s imagination and gathered a significant amount of global press coverage upon its release. Selected as Radio Canada’s 2019 science highlight, the story reached number 60 in the 2019 Altmetric Top 100 (an annual list of the public’s favourite research stories) from over 2.7 million articles tracked.

3D distribution of the classical Cepheid variable stars in the Milky Way’s warped disc (red and blue points) centred on the location of the Sun (shown as a large orange symbol). The units kpc are kiloparsecs (1 kpc = about 3,262 light years) along the image’s three axes are used by astronomers to indicate distances on galaxy-wide scales. Credit: Taken from – An intuitive 3D map of the Galactic warp's precession traced by classical Cepheids, Chen X., Wang S., Deng L., de Grijs R., Liu C., Tian H., 2019, Nat. Astron., 3, 320; doi: 10.1038/s41550-018-0686-7

Moving on from this discovery, the collaboration has recently been focused on the Zwicky Transient Facility (ZTF) data releases. Using a camera with an extremely wide field-of-view, ZTF scans the entire Northern sky every two days. The resulting survey allows a broad range of time-domain science to be undertaken, from the study of near-Earth asteroids to that of distant superluminous supernovae.

While having a determined focus on this new line of research, the NAOC/Macquarie collaboration is also concerned with promoting the interest of students within its own partnership. One of the initiatives currently receiving Australian Government funding (under their New Colombo Plan) sees two Macquarie undergraduates per year sent to the NAOC group for a significant fraction of a semester as part of Macquarie’s Public and Community Engagement program.

Joint PhD studentships have also been enabled by the collaboration. Former joint PhD student, Chengyuan Li from Peking University, moved to Macquarie University as a Research Fellow and subsequently obtained a full professorship at Sun Yat-sen University in Guangdong, China. In addition, joint vacation studentships have been funded by Macquarie, combined with joint master’s student supervision of Women in STEM students from the Birla Institute of Technology and Science in Pilani, India.

For more information on the collaboration, please contact the Australian Lead, Prof. Richard de Grijs from the Research Centre for Astronomy, Astrophysics and Astrophotonics, Macquarie University.