Chapter 1: The Expanding Universe

In our continuously expanding universe, light from far-off galaxies takes considerable time to reach us, and it might eventually become invisible. When we observe celestial bodies millions of light-years away, we're essentially looking back in time. The light we see today may have traveled beyond our current observational capacity or may no longer exist. This makes it particularly fascinating when astronomers identify regions of our distant universe that seem to be moving closer. A recent study focusing on the Messier 90 spiral galaxy has highlighted this phenomenon.

According to a statement from Hubble representatives reported by LiveScience, astronomers can gauge the movement of this galaxy, located roughly 60 million light-years away, by analyzing the light it emits. As Messier 90 approaches us, the wavelengths of its light compress, akin to a slinky being squished. This phenomenon, known as ‘blueshift,’ signifies that the galaxy is moving closer, with shorter wavelengths appearing blue to our eyes.

Section 1.1: Understanding Light Measurement

Astrophysicists often determine the universe's expansion through an opposing phenomenon known as redshift, indicating movement away from us. Despite their names, these terms don’t represent actual colors but rather describe our perception of the visible light spectrum, where longer wavelengths appear red. Interestingly, blueshift is the term used for the compression of light frequencies indicating proximity, even though violet corresponds to the shorter end of the spectrum.

Image credit: NASA

These terms help us approximate color over vast distances. However, light frequencies can alter when interacting with various matter across the universe. For instance, Earth's atmosphere acts as a barrier to most electromagnetic wavelengths while remaining largely transparent to the visible light spectrum. The absorbed part of the visible spectrum gives us the blue sky we see rather than a white one.

Image credit: ESA

When observing distant galaxies, they often appear flat, similar to objects viewed from a great distance. Yet, the colors captured in images like that of Messier 90 provide more than just visual interest. Advanced telescopes like Hubble utilize filters to obtain monochromatic images of specific electromagnetic wavelength ranges. This method not only aids in measuring light distance but also utilizes color to represent that distance in published images. While not all space images use color for the same purpose, it can convey critical information in context.

Chapter 2: The Enigma of Messier 90

Despite our ability to measure the movements of distant galaxies, the reason why Messier 90 appears to be moving closer while most galaxies seem to recede remains a mystery. Scientists suggest that this could be attributed to the Virgo Cluster, which contains over 1,200 galaxies, including Messier 90. The massive gravitational pull of Virgo seems to create unusual orbits for its galaxies, leading them to oscillate between distances from our vantage point on Earth.

With approximately 60 million light-years separating the Milky Way from Messier 90, our understanding is based solely on the visual data collected by telescopes like Hubble. More data is needed to fully comprehend the dynamics occurring at such extreme distances. Although we can capture stunning images of remote galaxies and analyze their light, we are limited to observing only the light that reaches us, which has altered throughout its journey.

The future of telescope technology promises even more accurate measurements, potentially revealing that our current understanding of these cosmic landscapes is far from complete. Nonetheless, it is remarkable to inhabit a time when we can routinely glimpse into regions of our universe that exist millions of light-years away.

Top image credit: ESA/Hubble & NASA, W. Sargent et al.

Now read: Astronomers Assemble the Most Detailed Picture of the Universe Ever Hubble Will Use ‘Natural Telescopes’ To Find the Oldest Galaxies in the Universe NASA May Have Fixed Hubble By Shaking It and Turning It Off and On

The second video explores the surprising fact that many galaxies are moving faster than the speed of light, challenging our understanding of cosmic expansion.