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Astronomers Use Alien Signals to “Probe” the Milky Way’s Halo

Scientists have detected three fast radio bursts originating from the early periods of the universe. This image is an artists impression of how a FRB travels through space to reach Earth. Credit: ESO/M. KORNMESSER

A new study led by University of Toronto doctoral candidate Amanda Cook reveals that the Milky Way's halo contains significantly less gas than previously thought, thanks to the analysis of fast radio bursts (FRBs).

Fast Radio Bursts Uncover Secrets of the Milky Way’s Invisible Halo

Utilizing mysterious cosmic signals called fast radio bursts (FRBs), astronomers have made a breakthrough in understanding the Milky Way’s halo. The research, led by Amanda Cook from the University of Toronto, indicates that the gaseous halo enveloping our galaxy contains far less gas than previously estimated.

The Intriguing Phenomenon of Fast Radio Bursts

FRBs, brief flashes of radio waves originating from enigmatic celestial objects, are considered one of astronomy’s most perplexing mysteries. These cosmic phenomena produce high-frequency (blue light equivalent) and low-frequency (red light equivalent) radio waves simultaneously. However, as they pass through gas, the high-frequency waves slow down more than their low-frequency counterparts, causing a delay in their arrival at a telescope.

Dispersion: A Tool for Detecting Invisible Gas

Astronomers like Cook refer to this time smearing as “dispersion” and use it to detect otherwise undetectable gas across the cosmos. As explained in a statement from The University of Toronto, Cook likens the study of dispersion to analyzing your home heating bill to understand the winter weather: it reveals whether the winter was harsh or mild but not the specific temperatures on individual dates. Similarly, the dispersion observed allows astronomers to infer the total amount of material the FRB signal has encountered on its journey from the source to Earth, without determining the distribution of the material along the way.

Measuring the Milky Way’s Halo Gas Content

Cook employed the dispersion method to measure the gas content in the Milky Way’s halo, a vast galactic “atmosphere” extending half a million light-years in all directions. The team utilized FRB signals collected by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) radio telescope, discovering that the Milky Way’s halo contains significantly less gas than previously predicted. The findings were published in the Astrophysical Journal under the title “An FRB Sent Me a DM.” (Pretty genius if you ask me.)

A First-of-its-Kind Study with CHIME Telescope

This study marks the first time the halo’s gas content has been measured using a large, uniform sample of FRBs, made possible by the CHIME telescope. Cook and her team analyzed FRB signals at varying distances from Earth to obtain their results.

Challenging Conventional Astronomical Models

Working with her supervisor, Professor Bryan Gaensler, Cook found the research to be more difficult than anticipated. As a result, the team sought input from experts in an entirely different field – statistics – to apply a new set of methods to their approach.

Gaensler emphasizes that this groundbreaking method of studying the Milky Way can also be applied to other aspects of space. FRB signals can be used to examine the structure of various celestial objects the signal traverses, including intergalactic material, the halos of other galaxies, and the gas within galaxies.

Future Applications: A 3D Map of the Milky Way’s Halo

With the anticipation of many more FRB discoveries, Cook and her team hope to create a 3D map of the Milky Way’s halo by collecting additional FRB data. Each FRB provides a measurement of the halo in one direction, allowing for the construction of a comprehensive picture over time.

Understanding the Early Universe

Ultimately, these findings contribute to our knowledge of the early universe and the formation of our galaxy. Gaining insight into the Milky Way’s halo allows astronomers to learn more about the evolution of the galaxy as a whole, shedding light on how it has come to be the way we observe it today. As researchers continue to explore the mysteries of fast radio bursts and the universe, we can expect even more remarkable discoveries in the years to come.

A thing or two about FRBs

Fast Radio Bursts (FRBs) are enigmatic, transient cosmic signals that have captured the attention of astronomers worldwide. These brief, intense flashes of radio waves originate from unknown celestial objects, and their mysterious nature has sparked a multitude of theories and hypotheses. The intrigue surrounding FRBs lies not only in unraveling their origins but also in their potential to serve as powerful tools for probing the universe. By analyzing these alien signals, astronomers can unlock valuable insights into cosmic structures and phenomena, shedding light on the vast, unexplored depths of the cosmos.

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