Chapter 1: Understanding Redshift

The term "redshift" plays a crucial role in astronomical discussions, particularly concerning the early Universe and the expansion of space. Redshift describes the phenomenon where the wavelength of light is shifted towards the red end of the electromagnetic spectrum, which encompasses visible light, X-rays, ultraviolet, infrared, and microwaves.

When celestial objects move away from us, their light takes progressively longer to reach our observation point. Since red wavelengths are longer than those of other colors, objects that recede from us appear more red than expected.

The electromagnetic spectrum. Notice the longer wavelengths of red compared to blue. Credit: SERC

A comparable phenomenon known as the Doppler Effect can be observed with sound waves. For instance, when a police siren passes by, the pitch change you perceive is directly due to the Doppler Effect, which causes sound waves to compress as they approach and stretch as they recede, resulting in a higher pitch when coming closer and a lower pitch when moving away.

While redshift is akin to the Doppler Effect, it is significantly less perceptible on smaller scales. Light travels at an astonishing speed—approximately a million times faster than sound—making redshift unnoticeable in everyday experiences. However, this effect becomes significantly more evident when we consider cosmic scales.

It’s essential to clarify that redshift does not occur for the same reasons as the Doppler Effect. Instead of galaxies zipping past us, redshift arises from the Universe's expansion. Two objects in space can be completely stationary yet still exhibit redshift due to the expansion of the space between them. A good analogy is baking a loaf of bread with raisins; as the dough rises, the raisins move away from each other, not because they are moving but because the space around them is expanding.

Illustration of how redshift operates on cosmological scales, emphasizing its significance in studying the early Universe. Credit: NASA, ESA, AND L. Hustak (STSci)

A significant aspect of an astronomer's responsibilities involves the study of redshift. Observations from Earth indicate that nearly every celestial object exhibits some degree of redshift (although some, such as the Andromeda Galaxy, exhibit blueshift because they are moving closer to us).

Objects that are farther away tend to show more pronounced redshift. In fact, from our vantage point, it appears that we are stationary relative to most galaxies, which seem to be receding from us. If we return to the bread analogy, if you were a raisin in the rising dough, you would perceive all other raisins moving away from you while you appear to remain still. However, another raisin would observe you moving away. This scenario mirrors the dynamics of the universe.

Studying redshift is vital for understanding the early Universe, which encompasses the stars and galaxies formed shortly after the Big Bang. The challenge with investigating the early Universe is that its expansion has shifted it so far away that it is no longer visible in the form of light waves we can detect. These early cosmic objects have been redshifted into the infrared spectrum.

The galaxy GN-z11, named for its location in the GOODS-North field, is currently the most distant galaxy discovered, captured by the Hubble Space Telescope. James Webb will uncover even older cosmic objects. Credit: NASA

To observe the early Universe, specialized telescopes are essential. This is where instruments like the James Webb Space Telescope come into play. Designed to detect infrared wavelengths invisible to the human eye, James Webb will enable astronomers to explore early cosmic structures, thereby deepening our understanding of the Universe's formation.

Chapter 2: The Role of Telescopes in Observing Redshift

The first video titled "What is REDSHIFT?" provides a detailed explanation of the concept of redshift and its implications in astronomy.

The second video, "AWS Redshift Service Overview," explores the applications and functionalities of AWS Redshift in data management.