Chapter 1: The Dance of Galaxies

Welcome back to the Monday Astronomy Picture Ponderings (MAPPs) series! Each week, I spotlight an entry from NASA's Astronomy Picture of the Day (APOD). Today, we delve into the mesmerizing phenomena of supermassive black holes co-orbiting within the galaxy 3C 75.

In earlier installments of MAPPs, we've examined merging galaxies engaging in a cosmic waltz, where they influence and reshape one another over millennia.

The image above features the interacting galaxies known as Arp 273, highlighted by NASA, ESA, and the Hubble Heritage Team. The larger upper galaxy resembles our Milky Way, while the smaller lower galaxy is elliptical. Their mutual gravitational interactions are evident in the distortions observed.

Recently, we’ve also explored the groundbreaking images of black holes, including the historic capture of M87* in 2019 and our very own SgrA*, revealed just last month (May 12, 2022).

Black holes are undeniably intriguing. We have learned that they are the end state for sufficiently massive stars, typically those exceeding three solar masses. Initially theorized as "dark stars" in the 1780s, the concept was revitalized after Einstein's formulation of general relativity, which linked gravity to massive celestial objects. It wasn't until 1971 that scientists identified a black hole, Cygnus X-1, through the orbital dynamics of nearby objects. Today, we recognize that supermassive black holes, ranging from 0.1 to 1 million times the mass of our Sun, reside at the heart of galaxies.

While often portrayed as ominous entities in science fiction, black holes are quite prevalent and largely harmless, provided you maintain a safe distance. They exert a strong gravitational pull, but they won’t pursue you like a predator.

However, some black holes exhibit motion beyond the typical orbits of stars within their host galaxies. In the case of galaxy 3C 75, we witness two supermassive black holes engaged in a captivating orbital dance, reminiscent of merging galaxies. The accompanying image captures this event in x-ray (blue) and radio (pink) wavelengths.

Notably, each of these supermassive black holes once powered its own separate galaxy, which eventually merged. Now, we observe them orbiting one another within a single galactic entity. According to the NASA APOD page:

“Astronomers conclude that these two supermassive black holes are bound together by gravity in a binary system in part because the jets’ consistent swept-back appearance is most likely due to their common motion as they speed through the hot cluster gas at about 1200 kilometers per second.”

These black holes are situated approximately 25,000 light-years apart and 300 million light-years from Earth. Such interactions appear to be common occurrences in galaxy clusters throughout the distant universe.

It’s remarkable to witness similar interactions between various astronomical entities, serving as a reminder that analogous phenomena can transpire across vastly different scales. This beautiful dance exemplifies the intricate cause-and-effect relationships woven into the cosmic tapestry of our universe.

Chapter 2: The Endless Wonders of Astronomy

Every Monday, I select an entry from NASA’s APOD to explore in depth. The field of astronomy is boundless, with endless possibilities awaiting discovery.

Many images featured in NASA's APOD are copyrighted, captured by skilled astrophotographers deserving of recognition and protection. When this occurs, I use a copyright-free representation of the subject and provide a link to the original APOD article.

I highly encourage you to explore the other six images from the week and to either revisit past selections or follow along with new entries moving forward. It’s an incredible resource accessible to everyone!