A careful look at this colorful cosmic snapshot reveals a surprising number of galaxies both near and far toward the constellation Ursa Major.
The most striking is NGC 3718, the warped spiral galaxy near picture center. NGC 3718’s spiral arms look twisted and extended, mottled with young blue star clusters. Drawn out dust lanes obscure its yellowish central regions. A mere 150 thousand light-years to the right is another large spiral galaxy, NGC 3729.
The two are likely interacting gravitationally, accounting for the peculiar appearance of NGC 3718. While this galaxy pair lies about 52 million light-years away, the remarkable Hickson Group 56 can also be seen clustered above NGC 3718, near the top of the frame. Hickson Group 56 consists of five interacting galaxies and lies over 400 million light-years away.
There are over 5000 galaxies in this image down to 24th magnitude.
Let me introduce… The names of galaxies
The names of astronomical objects, and therefore of galaxies, are generally composed of letters and numbers, only the most renowned of them have a proper noun. The letters refer to the catalogues in which they are listed, while the numbers indicate the object’s entry in the catalogue. This is why a galaxy can have multiple names, for example, the Andromeda Galaxy is also known as M31 or NGC 224.
Some of the most common catalogues are:
- M (Messier): A catalogue compiled by Charles Messier and several colleagues in the eighteenth century. In this catalogue there are many of the brightest and most remarkable objects, including nebulae and star clusters.
- NGC/IC (New General Catalogue) / (Index Catalogue): The catalogue, compiled by JLE Dreyer from the 1860s-1880s, includes —in addition to star clusters and nebulae— about 10,000 of the most important galaxies and the first collection of astronomical photographs. Until recently, almost all the known galaxies belonged to this catalogue.
- Arp: In 1966, Halton Arp published the Atlas of Peculiar Galaxies, which contains 338 galaxies in total. The main purpose of the catalogue was to present photographically examples of different types of unusual galaxies’ structures. It was therefore a tool to facilitate the work of understanding what determines the form of elliptical or spiral galaxies.
- UGC (Uppsala General Catalogue): It contains data for 12,921 galaxies north of declination = -2° 30’. The catalogue was published in 1973 by Peter Nilsson, classifying objects by location, size, orientation, and magnitude from Palomar Sky Survey photographs.
Other names, instead, refer to a survey name and the object’s coordinates. The digits, therefore, indicate the right ascension and declination (RA+/-DEC) or (α+/-δ) —either for epoch 1950 or 2000.
In this case some of the most common catalogues are:
- PKS: Radio sources from the Parkes radio telescope (i.e. PKS 0521-36).
- IRAS: Infrared Astronomical Satellite (i.e. IRAS 09104+4109).
All the other data (whether they are numbers, letters, initials or abbreviation) are explained in the introductory part of each catalogue.
You can find the catalogue listing the beautiful Galactic Rose here.
Hosted by physicist Brian Greene, ‘The Fabric of the Cosmos’ is a journey to the frontiers of known physics in an effort to explore the deepest and most puzzling cosmological queries.
Hard as it is to swallow, cutting-edge theories are suggesting that our universe may not be the only universe. Instead, it may be just one of an infinite number of universes that make up the “multiverse.” In this show, Brian Greene takes us on a tour of this brave new theory at the frontier of physics, showing what some of these alternate realities might be like. Some universes may be almost indistinguishable from our own; others may contain variations of all of us, where we exist but with different families, careers, and life stories. In still others, reality may be so radically different from ours as to be unrecognizable. Brian Greene reveals why this radical new picture of the cosmos is getting serious attention from scientists. It won’t be easy to prove, but if it’s right, our understanding of space, time, and our place in the universe will never be the same.
You can watch the program HERE.