ALMA Detects Seismic Ripples in Disk of Oldest Known Spiral Galaxy; BRI 1335–0417 Offers Insights Into Milky Way’s Origins

In the history of star clusters, bar structure plays a vital role in driving galaxies' evolution and shaping disc structure. The galactic bars can also drive the radial migration of stars and gas, which explains the observed kinematics of galaxies resembling the Milky Way. In a new snapshot of an ancient galaxy, astronomers capture the motion of the gas around it and reveal the formation of a seismic wave.

A Look at an Ancient Spiral Galaxy

At over 12 billion years old, BRI 1335-0417 is the oldest and furthest known spiral galaxy in the cosmos. It is so far away that the light reaching us today offers a glimpse into its younger days when the universe was only 10% of its current age.

Despite having a mass that resembles that of the Milky Way, this ancient galaxy forms stars at a rate several hundred times faster. Recent observations have also revealed interesting characteristics, such as a spiral structure and a bar-like formation.

This galactic bar can affect the movement of gas in a galaxy and create features like a bulge or a nuclear disc. Aside from this, its presence may also be connected to the activity of black holes in the star cluster.

Although direct observation cannot capture a galaxy's evolution over time, the use of computer simulations plays an important role in reconstructing its story based on the available snapshots.

Evolution of Early Spiral Galaxies

To investigate BRI 1335-0417 in much greater detail, a team of scientists used the state-of-the-art Atacama Large Millimeter/Submillimeter Array (ALMA) telescope. As a revolutionary astronomical observatory, ALMA is considered one of the largest and most complex ground-based astronomical projects.

Led by Dr. Takafumi Tsukui, the researchers aim to understand how gas is supplied to sustain rapid star formation in this ancient galaxy. The team was specifically interested in how gas moves into and throughout the galaxy. Since gas is a key component of stellar formation, it can also provide important insights into how a galaxy fuels a forming star.

The unprecedented observation made by the team revealed the dynamic growth patterns of BRI 1335-0417. Aside from this, the observation also showcased the galaxy's disk as a flat, rotating collection of dust, gas, and stars. The motion of these galactic components creates vertically oscillating disk movement, similar to ripples on a pond when a stone is thrown in. This is the first time such phenomena have been observed in an early galaxy.

Dr. Tsukui believes this motion may be due to an external source, either from new gas that streams into the galaxy or by coming into contact with other smaller galaxies. Both theories would bombard the star cluster with new fuel for stellar formation.

Spiral galaxies are rare in the early stages of the universe's formation. Up to now, the exact mechanism of their formation is still unknown. The insights provided by this study give the experts crucial information on the most likely scenario.