Redefining astronomy with technology: the Christmas tree galaxy cluster

A team of international scientists, led by Dr. Haojing Yan of the University of Missouri, used NASA’s James Webb Space Telescope (JWST) to discover 14 new transient objects in the Christmas Tree galaxy cluster , 4.3 billion light years away. These transients, which appear as flickering lights in space, were recognized thanks to a time-lapse study of the galaxy cluster MACS0416. Two of the transients discovered are supernovae, allowing the team to explore their host galaxies. Innovation and technology today spoke with Dr. Haojing Yan about this groundbreaking discovery and how innovative technologies are redefining space exploration.

Innovation and technology today: How is the James Webb Space Telescope (JWST) different from other telescopes? How has technology helped you discover ephemeral objects in the Christmas Tree galaxy cluster?

Dr. Haojing Yan: To explain the technological part, it is better to make a comparison with two other NASA space telescopes, the Hubble Space Telescope (HST), which is still operating, and the Spitzer Space Telescope (Spitzer), which ceased operations in 2020. HST operates in the ultraviolet to near-infrared range and measures only 2.4 meters in diameter. Spitzer worked from near infrared to far infrared, but is only 0.85 meters in diameter. JWST operates primarily in the near-infrared to mid-infrared and measures 6.5 meters in diameter. JWST is much more sensitive and has much better spatial resolution than either of the other space telescopes mentioned because it has a much larger mirror. The unprecedented sensitivity and spatial resolution of JWST in the infrared enabled our discovery.

I&T today: What motivated your team to study the MACS0416 galaxy cluster, and why is it called the Christmas Tree galaxy cluster?

Yan: In previous studies using the Hubble Space Telescope, astronomers found some transients in this cluster. The conclusion was that these transients are individual stars in background galaxies (e.g., much more distant than the cluster itself). They were temporarily amplified enormously due to the gravitational lensing of the cluster, so that they were visible by HST for a short duration (e.g., “transients”). Detecting an individual star in distant galaxies is a real challenge. Without gravitational lensing, we could never achieve such a goal. Our team’s program, called “Prime Extragalactic Areas for Reionization and Lensing Science” (PEARLS), led by Professor Rogier Windhorst of Arizona State University, chose to take on this challenge. We nicknamed MACS0416 that because it is very colorful and the transients look like the twinkling lights you would put on a Christmas tree.

I&T today: How do transient objects such as supernovae help us understand the universe? What can we learn by studying them?

Yan: The 14 transients in our study fall into two different categories: 12 of them are extremely amplified temporary stars in distant galaxies, which are intact stars; the other two are supernovae (also located in distant galaxies), which are dead, exploding stars, increasing their brightness by more than a billion times. Simply put, studying all 12 stars can help us understand how the stellar constituents of distant galaxies might be different from (or the same as) our galaxy and study the dark matter content of the lens cluster (MACS0416 ) in detail. was never possible before. The study of supernovae will help us test our cosmological model and understand the nature of dark energy. What we were able to discover here is just the tip of the iceberg, and JWST has opened a whole new window of study of transients that will have a profound impact on scientific research.

I&T today: What challenges or difficulties did your team encounter during the research?

Yan: The biggest challenge was validating our results and we did this using extremely careful analysis. My graduate student, Bangzheng Sun, contributed greatly to this effort.

I&T today: What impact could current and future technological advances in space telescopes have on future astronomical research and discoveries?

Yan: In my opinion, JWST is revolutionizing astronomy. This has already given us so many surprises.

I&T today: Are there any specific plans or hopes for using JWST in future research projects?

Yan: Many members of our team have recently submitted proposals to study different aspects of the universe using JWST.

I&T today: Given the evolving nature of space technology and astronomy, how do you see future technological advances influencing our understanding of the universe?

Yan: Looking at the development of observational astronomy from a different perspective, we could also benefit enormously from a larger space telescope working in the UV-visible wavelength.