Light travels at a finite speed, meaning it takes time to cover vast distances. Astronomers leverage this to investigate ancient epochs in the universe’s history by examining distant celestial objects. Due to inherent geometric and physical constraints, objects become smaller and dimmer the farther away they are. Additionally, when trying to focus a telescope on a small, faint, and distant target, your view might be obstructed by something larger, closer, and more luminous.
In certain scenarios, scientists can circumvent this limitation and even turn it into an advantage. Like matter, light is influenced by gravity; its trajectory curves as it passes through a gravitational field. The larger an object, the stronger its gravitational pull, resulting in more pronounced bending of light.
When confronted by a massive entity like a galaxy cluster, the light from objects positioned behind it is significantly bent, leading to distorted and magnified images, akin to passing through a lens. This effect, where a distant object appears enlarged due to the gravity of a nearby massive object, is known as gravity lensing.
A group of astronomers recently studied an ancient galaxy, A1689-zD1, which is gravitationally lensed by the galaxy cluster Abel 1689. A1689-zD1 is currently about 25 billion light-years away from us, equivalent to 150 sextillion miles or 240 sextillion kilometers. The light we observe from it has traveled for approximately 13 billion years, around the same duration as the universe’s 14 billion-year lifespan.
By analyzing this light, astronomers can explore the characteristics of galaxies as they were 13 billion years ago. They hypothesize that galaxies at this distance are in the initial phases of their formation and evolution, a period they refer to as the dawn of the universe. Investigating galaxies from this era provides astronomers with valuable insights into the formation processes of galaxies.
To conduct their observations, the team gathered data from multiple sources, including a radio telescope situated in the Atacama Desert in Chile. They utilized the Atacama Large Millimeter/Submillimeter Array (ALMA) to analyze light emitted by oxygen and carbon ions in galaxies. They also employed the Green Bank Observatory VEGAS spectrometer, which searches for light emitted by carbon monoxide molecules in galaxies. The radiation from these ions and molecules aids astronomers in determining a galaxy’s structure and examining the motion and interaction of its various components. Finally, the team integrated archival images from A1689-zD1 from the Hubble Space Telescope and the Spitzer Space Telescope to create a composite image in ultraviolet and infrared light, allowing for comparison with their radio data.
While gravitational lenses are beneficial to astronomers by revealing hidden light sources and enhancing them, they often produce distorted representations of objects. To ascertain the galaxy’s true shape, the research team needed to account for these distortions, utilizing Abel 1689’s model of light’s gravitational bending effect. By employing the software Lenstool, the research team accurately characterized the dynamics of A1689-zD1 to within less than 1% of the Milky Way’s width, measuring 200 parsecs, or around 4 quintillion miles and 6 quintillion kilometers.
The team discovered that A1689-zD1 is substantially larger than what a previous study estimated, which suggested a mass between 2 to 4 billion times that of the Sun. The new findings indicate its total mass to be around 20 billion times that of the Sun. They also observed that this mass is divided into five distinct regions, each exhibiting different movements and locations. Moreover, these parts displayed no indications of forming a single rotating disk, unlike the familiar spirals of the Milky Way.
The researchers proposed three potential explanations for this observation. One possibility is that these regions represent components of a single extended galaxy, existing as large molecular clouds or star-forming clusters. Another conjecture is that A1689-zD1 resulted from the merger of at least two smaller galaxies, with the differing regions emerging from the collision and gravitational interactions of the merging galaxies. Lastly, they suggested that the first two hypotheses may not be mutually exclusive, but current data does not allow for determining the extent of either occurrence.
The researchers noted that much of this uncertainty could be clarified through follow-up investigations using the James Webb Space Telescope (JWST). They also highlighted that considerable aspects of A1689-zD1 remain obscured in the studied wavelength range, contributing to the ongoing discrepancy between mass estimates derived from starlight counting and those determined by analyzing stellar motion. Overall, they concluded that their findings suggest galaxies in the universe’s infancy present a diverse and intricate nature.
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Source: sciworthy.com
