Located at a distance of somewhere around 390 million light years (120 Mpc) , Markarian 266 is a pair of spiral galaxies that are in the process of merging together, and it looks like a complete mess. The bulges that were at the centers of the two original galaxies are still visible, but the disks have been completely scrambled, and what's left consists of some sort of asymmetric, lumpy cloud of stars enveloping the centers of the two progenitor galaxies as well as weird arcs of gas and stars created by the tidal forces involved in the merging process.
This object was first discovered in the late 1700s , and it was also included in the New General Catalogue and given the designation NGC 5256 . However, the object was largely ignored until it appeared in one of Benjamin Markarian's catalogs of galaxies in the 1960s, which is when the object was given the designation Markarian 266. I have now featured a few episodes about objects named after Benjamin Markarian, but I have never provided a complete biography of the man and his work. So, I will now present the life of the Armenian astronomer Benjamin Markarian.
Benjamin Markarian was both in 1913 in what is now the small town of Shahumian in Georgia near the border with Armenia . This was a turbulent time in the history of the region, as it was initially part of czarist Russia and then briefly became independent from 1918 to 1920 before being reconquered as part of the Soviet Union. Nonetheless, Benjamin Markarian apparently excelled in his schooling and took an interest in astronomy at a young age . Markarian first studied at Yerevan State University, graduating in 1938, and then continued his education at Leningrad University, but then World War II interrupted his studies . After serving in the Soviet army in Iran, Markarian began working in positions at both Yerevan Astronomical Observatory and Yerevan State University while earning his PhD in 1944 . He would then switch positions from Yerevan Astronomical Observatory to Byurakan Observatory when that second observatory was constructed in 1946 .
Benjamin Markarian initially started his career performing surveys of star clusters, especially young clusters with bright blue stars, and he won awards for his work . However, he would eventually shift his attention towards galaxies. After the installation of a new telescope at Byurakan Observatory in 1960, Benjamin Markarian discovered multiple galaxies were unusually bright at ultraviolet wavelengths, and he would go on to perform multiple surveys of the sky to identify these galaxies . The surveys extended from 1965 to 1980, and the ultraviolet-bright galaxies identified in these surveys were given new designations beginning with the name Markarian or the letter M. Benjamin Markarian lived until 1985, recognized as one of the greatest Armenian astronomers of all time as well as one of the leading international researchers in extragalactic astronomy in the mid-twentieth century . All astronomers, including me, will always remember his contributions to science because so many galaxies are named after him.
So let's return to Markarian 266, which appeared in the second of the many catalogs of ultraviolet-bright galaxies that Benjamin Markarian published . People understood in the 1960s that Markarian 266 and other galaxies from Markarian's surveys were unusual because they were so bright at ultraviolet wavelengths, but they did not understand why they were so bright at ultraviolet wavelengths. Astronomers in the 1960s also did not understand why Markarian 266 seemed to have two separate bulges.
Since Markarian's surveys, however, we have now learned that many galaxies, including Markarian 266, look bright at ultraviolet wavelengths because they are forming lots of stars, including lots of very big, very bright, very hot blue stars that produce lots of ultraviolet emission but that have very short lifespans before they explode as supernovae. When astronomers see ultraviolet light from any galaxy, they know that that galaxy must have formed stars relatively recently, and since Markarian 266 is exceptionally bright at ultraviolet wavelengths, astronomers know that it must be forming many more stars than the typical galaxy .
Additionally, when Benjamin Markarian started publishing his catalogs in the 1960s, people did not really understand how galaxies could merge to form new galaxies, but people now understand this process and also understand that Markarian 266 is an example of a pair of galaxies in the process of merging. Astronomers have also learned that, when two galaxies merge together, a combination of gravitational tidal forces and collisions cause the interstellar gas clouds in those two galaxies to collapse and form lots of stars. This explains specifically why Markarian 266 is forming many more stars than the typical galaxy.
However, while astronomers could study many other merging galaxies, Markarian 266 has a special gimmick. Each of the nuclei of the two merging galaxies in Markarian 266 contains what is called an active galactic nucleus (AGN) [7, 8]. An AGN contains a supermassive black hole millions or millions of times larger than the Sun; in Markarian 266 specifically, each supermassive black hole in each of its AGN is 250 million times the mass of the Sun . Each of the two AGN in Markarian 266 also contains a disk of gas and dust falling into the central black hole and jets of gas that have appeared above the poles of the black hole. These jets originate from infalling gas that got really hot and then got deflected from the surface of the black hole by magnetic fields. While the black holes in Markarian 266 do not produce light, the disks of gas and the jets can produce lots of electromagnetic radiation. While it isn't clear to me whether the AGN in Markarian 266 produce extra-strong ultraviolet emission, they definitely do produce extra-strong X-ray emission [8, 9].
I have the sense that Markarian 266 is a particularly popular astronomical object to study because it has two AGN. More specifically, I think it works as kind of a gimmick, sort of like how some musicians wear masks to hide their faces or how some professional wrestlers portray characters with goth or undead themes. In the case of Markarian 266, I think professional astronomers can write proposals to study the object that say, "Hey, look, this galaxy has two AGN, and that makes it twice as exciting as those other galaxies with only one AGN," and the people who read these proposals then think that this makes Markarian 266 sound really special, when in actuality, the two AGN in Markarian 266 are not really all that different from any other AGN. Nonetheless, you can expect to see more hype about the object with two AGN in future.