Hubble captures a stunning new image of a sparkling globular cluster
Nearly half a century ago, Turkish-Armenian astronomer Agup Terzan discovered 11 globular clusters. Today, the Hubble Space Telescope views the Terzan clusters in details that could only be dreamed of at the time.
A globular cluster is a spherical cluster of stars with a higher concentration toward the center. The beautiful clusters can contain millions of stars and provide a stunning subject for telescopes, including the Hubble Space Telescope. A new image by Hubble shows one of the Terzan clusters found nearly 50 years ago, Terzan 12. Located in the Milky Way, this cluster of stars is one of about 150 ancient globular clusters on the outskirts of the galaxy.
“These clusters orbit around the galactic center, but well above and below the flat plane of our Galaxy, like bees buzzing around a beehive,” NASA explains. Terzan 12 is located in the constellation Sagittarius, deep within the Milky Way. It is about 15,000 light-years away from Earth, and is covered in gas and dust.
To take a slight digression, it is worth noting that Terzan has discovered 11 globular clusters, yet Hubble’s most recent object is Terzan 12. The story behind this strange naming is that Terzan actually “discovered” the same cluster twice by chance, and named the repeating cluster Terzan. 11 years 1971.
Although the astronomer quickly realized his mistake and tried to correct it, allowing Terzan 12 to become Terzan 11, Terzan never fully made it clear that Terzan 5 and Terzan 11 were the same, so the name Terzan 12 stuck. Although most astronomers accept the strange fact that Terzan 11 does not actually exist, there have been “cases of confusion in the scientific literature over the past few decades,” according to NASA. (https://esahubble.org/images/potw2241a/)
Returning to the new Hubble image of Terzan 12, the dust and gas make some stars appear very red. Furthermore, given the distance between Earth and Terzan 12, there is not only a lot of gas and dust surrounding the cluster itself, but also significant interstellar dust through which the cluster’s light passes on its way to Hubble.
When starlight travels through interstellar dust, blue light is scattered more easily, which means more of the redder wavelengths reach Earth. This causes some distant stars to appear redder than they are, a process called “reddening.”
In a press release of an image of a different globular star cluster, Pismis 26, NASA wrote: “Pismis 26 is located in the constellation Scorpio near the galactic bulge, a region near the center of our galaxy that contains a dense globular cluster. A cluster of stars surrounding the black hole. Due to its location within Dust-laden bulge A process called “reddening” occurs, where the dust scatters shorter-wavelength blue light while longer-wavelength red light passes through. Reddening distorts the apparent color of cosmic objects. Globular clusters are groups of stars held together by mutual gravity. It contains thousands of tightly packed stars and appears roughly spherical. Astronomers used NASA’s Hubble Space Telescope to study visible and infrared light from Pismis 26 to determine the cluster’s redness, age, and metallicity.
“The brightest red stars in the image are bulging, elderly giants, several times larger than our Sun. They lie between Earth and the cluster. Only a few may actually be members of the cluster. The brighter, hot blue stars are also found along the line of sight rather than inside the cluster,” NASA wrote. Which contains only old stars.
Since its launch in 1990, Hubble has imaged numerous globular clusters and has been a pioneer in the study of cosmic clusters. “Hubble’s observations have shed light on the relationship between age and composition in the Milky Way’s inner globular clusters,” NASA explains.
Image credits: NASA, ESA, ESA/Hubble, Roger Cohen (RU)