6 mins read 22 Jul 2021

Galactic fireworks light up new stars

An international team of astronomers, including two Australian astronomers, have captured spectacular images of nearby galaxies showing their different components in distinct colours. The images may shed new light on the mystery of star formation and the role galaxies play in this. 

Galaxy NGC 4254 (55.7 million light years away) as seen with MUSE on ESO’s VLT at several wavelengths of light. Credit: ESO/ALMA (ESO/NAOJ/NRAO)/PHANGS

Stars are born within clouds of dust and gas known as stellar nurseries. Each stellar nursery in the Universe can form thousands or even tens of thousands of new stars during its lifetime.  

Australians Dr. Rebecca McElroy, from the University of Sydney and Dr. Brent Groves, from the University of Western Australia, are two members of an international team of scientists exploring the mystery of how stars are born or more specifically, what sets off their formation and what role galaxies play in this.  

Over 90 scientists from across the world are involved in the project called PHANGS (Physics at High Angular Resolution in Nearby GalaxieS) using telescopes operated by the European Southern Observatory (ESO) in Chile’s Atacama Desert. 

The team has captured stunning images showing the different components of the galaxies in distinct colours, allowing astronomers to pinpoint the locations of young stars and the gas they warm up around them. 

The resulting images are not only spectacular, resembling galactic fireworks, but also shed light on the makeup of stellar nurseries in the galaxies closest to us.

(l-r) NGC 4303 is a spiral galaxy, with a bar of stars and gas at its centre, located 55 million light-years from Earth in the constellation Virgo, and NGC 1300, a spiral galaxy, with a bar of stars and gas at its centre, located 61 million light-years from Earth in the constellation Eridanus. Both as seen with MUSE on ESO’s VLT at several wavelengths of light. Credit: ESO/ALMA (ESO/NAOJ/NRAO)/PHANGS

“By combining observations from some of the world’s most powerful telescopes, we can examine the galactic regions where star formation is happening, compared to where it is expected to happen,” said Dr. Rebecca McElroy PHANGS team member from the Sydney Institute for Astronomy, University of Sydney. 

“This will give us a chance to better understand what triggers, boosts or holds back the birth of new stars,” she said.

Included in these powerful telescopes are ESO’s Very Large Telescope (VLT) and the Atacama Large Millimeter/submillimeter Array (ALMA) as well as NASA’s Hubble telescope.

ALMA combines radio wavelength signals from 66 dish-shaped antennas while the VLT consists of four large 8-metre telescopes and four smaller telescopes that can be used separately or combined into a single larger instrument. Attached to the VLT is an instrument called the Multi-Unit Spectroscopic Explorer, or MUSE. 

MUSE collects spectra – the “bar codes” of light that astronomers scan to unveil the properties and nature of cosmic objects – at every single location within its field of view, providing much richer information than traditional instruments. For the PHANGS project, MUSE observed 30,000 clouds of warm gas and collected about 15 million spectra of different galactic regions.

“MUSE has given us an unprecedented view of what’s going on inside galaxies,” said Dr. Brent Groves, a PHANGS team member from the University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR).

The ALMA observations allowed astronomers to map about 100,000 cold-gas regions across 90 nearby galaxies, producing an unprecedented accurate atlas of stellar nurseries in the close Universe. They include nearby galaxies such as Messier 100, located about 55 million light-years from Earth. 

The resulting images are a combination of observations conducted at different wavelengths of light to map stellar populations and gas. 

  • ALMA’s observations are represented in brownish-orange tones and highlight the clouds of cold molecular gas that provide the raw material from which stars form. 
  • The MUSE data shows up mainly in gold and blue. 
  • The bright golden glows map the warm clouds of mainly ionised hydrogen, oxygen and sulphur gas, marking the presence of newly born stars,
  • The bluish regions reveal the distribution of slightly older stars.

“By combining these observations with those from ALMA, we’re able to see newborn stars while they’re still surrounded by the blanket of gas they’ve formed from,” Dr. Groves said.

“The resulting images are absolutely stunning – they allow us a spectacularly colourful insight into the stellar nurseries of our neighbouring galaxies.”

NGC 3627 is a spiral galaxy located approximately 31 million light-years from Earth in the constellation Leo as seen with MUSE on ESO’s VLT at several wavelengths of light. Credit: ESO/ALMA (ESO/NAOJ/NRAO)/PHANGS

The PHANGS project also uses observations from NASA’s Hubble Telescope with the various observatories allowing different wavelengths (visible, near-infrared and sub-millimetre), with each wavelength range unveiling the processes occurring within an observed galaxy.    

The work carried out by the PHANGS project will be further developed by upcoming telescopes and instruments, such as NASA’s James Webb Space Telescope.

ESO and Australia

The Milky Way’s stars, gas and dust, arc over the ESO-operated VLT site, with the four 8.2 metre telescopes known as Antu, Kueyen, Melipal and Yepun. Credit: Miguel Claro/ESO.

The European Southern Observatory is an astronomy organisation with 16 member states. It plays a leading role in promoting and organising international research cooperation while providing state-of-the-art research facilities to astronomers. 

In July 2017 Australia entered a ten-year strategic partnership with the European Southern Observatory (ESO). The partnership aimed to strengthen ESO’s program, both scientifically and technically, and give Australian astronomers and industry access to the La Silla Paranal Observatory. Australia will financially contribute to ESO for ten years, with the potential of then obtaining full membership.  Find out more about Australian-ESO projects and history as well as the facilities hosted by the ESO in Chile.

Last month (June 2021) ESO signed an agreement with an international consortium to build and operate MAVIS, a unique instrument to be installed on ESO’s Very Large Telescope (VLT) that will provide images up to three times sharper than the Hubble Space Telescope. MAVIS will tackle a range of research questions, from how the first stars formed 13 billion years ago to how weather changes on the planets and moons of the Solar System. 

MAVIS (Multi-conjugate-adaptive-optics-Assisted Visible Imager and Spectrograph) will produce images sharper than space telescopes operating today by removing the blur caused by turbulence in the Earth’s atmosphere.

The MAVIS consortium is led by the Australian Astronomical Optics (AAO), with the National Institute for Astrophysics (INAF) in Italy being a major partner; the Laboratoire d’Astrophysique (LAM) in France and ESO is also part of the consortium. MAVIS is being designed by two Australian institutes in the AAO consortium — the Australian National University and Macquarie University — representing a significant milestone for ESO’s growing relationship with Australia.

MAVIS will be installed on the VLT Unit Telescope 4 (Yepun) at ESO’s Paranal Observatory in northern Chile and is expected to start operating in 2027.

Read more about MAVIS from Dr Tayyaba Zafar (Australian Astronomical Optics (AAO) at Macquarie University).