If you are an undergraduate and are looking for potential research opportunities to complete during your undergraduate, there are few that may be of interest.
In the School of Physics at the University of Melbourne, they run every year the Laby Research Scholars Program in the summer and winter. There is usually a variety of topics available, but you can find more information here: https://physics.unimelb.edu.au/study/awards-prizes-and-scholarships/laby-research-scholars-program. Y
If have a grade average of >75 in your subjects, another possibility is that should also consider doing the science research project: https://handbook.unimelb.edu.au/subjects/scie30001 in your second semester of your third year (you can also do this earlier, but usually this is when people do it). This will give you a taste of whether you enjoy research or not and would be a good subject for your degree.
However, outside of the University of Melbourne there are a few winter and summer opportunities there are other opportunities available.
Astronomy related:
ANU: https://rsaa.anu.edu.au/study/undergraduate/winter-school or https://rsaa.anu.edu.au/study/undergraduate/aitc-summer-student-program-northrop-grumman-global-externship-program
Swinburne: http://astronomy.swin.edu.au/study/vacstudents.html
CSIRO: https://www.atnf.csiro.au/research/summer_vacation/index.html (this has astro related one, but CSIRO does much more than astro)
ESO Summer Research Programme - https://eso.org/sci/meetings/2025/SummerResearch2025.html (check for most up to date program)
ASTRON/JIVE International Summer Students Programme - https://www.astron.nl/education/summer-research-programme/
Max Planck Institute for Astronomy Summer Internship - https://www.mpia.de/en/careers/internships/summer
Non astro related
https://www.petermac.org/education/research-education/research-placements
https://www.monash.edu/study/fees-scholarships/scholarships/summer-winter
Note that this list is not complete and there are likely many more opportunities available so if you find some that should be included, let me know and I can add it to this list!