Understanding Relativity

In this week’s Hubble Picture of the Week, we are presented with a captivating display of spiral galaxies. The image showcases four distinct galaxies, each with its own unique characteristics. While the scene may initially give the impression that some of these galaxies are in close proximity to one another, upon closer examination, we discover that appearances can be deceiving.

Situated on the right side of the image, the largest and most prominent spiral galaxy is designated NGC 1356. To its left, we find two seemingly smaller spiral galaxies: LEDA 467699 positioned above NGC 1356, and LEDA 95415 located very close to its left. On the left side of the frame, we can observe IC 1947 completing this ensemble of cosmic wonders.

One of the intriguing aspects of this image is the challenge it presents in discerning whether two galaxies are genuinely close or merely appear so from our vantage point on Earth. A cursory glance might lead us to believe that NGC 1356, LEDA 467699, and LEDA 95415 are closely intertwined while IC 1947 stands at a greater distance. However, we must bear in mind that two-dimensional representations, like this image, only provide an indication of angular separation—the distribution of objects across the celestial sphere. These images do not capture the true distance between celestial bodies.

For example, although NGC 1356 and LEDA 95415 seem to be in close quarters, their actual distances from Earth are significantly disparate. NGC 1356 resides approximately 550 million light-years away, while LEDA 95415 is roughly 840 million light-years distant. This astounding revelation unveils an astonishing separation of almost 300 million light-years between them. Consequently, LEDA 95415 is likely not as much smaller than NGC 1356 as it initially appears.

On the other hand, while NGC 1356 and IC 1947 might seem to be separated by a wide expanse, their physical proximity is considerably closer in three-dimensional space. IC 1947, despite their apparent distance, sits a mere 500 million light-years away from Earth. By some estimates, the angular separation portrayed in this image translates to less than four hundred thousand light-years. Therefore, NGC 1356 and IC 1947 are actually much closer neighbors than NGC 1356 and LEDA 95415.

Beyond the captivating interplay between these four galaxies, the image also reveals a celestial backdrop populated by numerous stars and distant galaxies, adding depth and context to the scene. Amongst these distant cosmic neighbors, one bright star stands out, radiating its brilliance amidst the galactic tapestry.

This image serves as a reminder of the awe-inspiring complexity of our universe. It impels us to challenge our initial perceptions and underscores the importance of considering three-dimensional distances rather than relying solely on two-dimensional visual cues. As we continue to explore the vast expanse of space, each photograph captured by the Hubble Space Telescope adds another piece to the cosmic puzzle, enticing us further into the depths of scientific inquiry.