There are billions of billions of galaxies in the known universe. They are oriented in countless different ways. A small fraction show their full face toward Earth, while some show an edge-on view. This first example is a nearly face-on view of NGC 4414. Imaged by the Hubble Telescope in 1995, it lies about 60 million lt-yr from Earth. Only about half of the galaxy fit into the detector of Hubble due to its large size.
Three red, green, and blue filtered greyscale images were used to make my color version of this galaxy. The center region is densely populated with older yellow and red stars. This is typical of spiral galaxies. The outer regions are less populated and include younger blue stars. The galaxy has a lot of dust mixed into the spiral arms as evidenced by the dark clouds and bands in silhouette against the bright star glow.
This next galaxy is a nearly perfect edge-on view of NGC 4013. The very bright light source at the heart of this galaxy is actually a star in the foreground much closer than the galaxy. It is part of our Milky Way galaxy and just happens to be in alignment. NGC 4013 is about 55 million lt-yr away in the direction of Ursa Major, the Big Dipper. If we could see it face-on, it would have a spiral shape similar to NGC 4414 above. What stands out clearly in this edge-on view is the dark band of dust cutting across the width of the galaxy. A few blue stars show in the upper right. They are in an outer band and less obscured by the dust.
The Carina constellation lies about 20,000 light years away. It is too far south in the sky for me to see. Within Carina is a cluster of bright stars surrounded by clouds of gas and dust. These stars formed about the same time. Their intense light has blown away the nearby gas and dust revealing the group of bright stars in this ESA image from Chile.
The stars differ in size, mass, temperature, and color. The mass of a star determines the pace of its evolution over time. This cluster contain stars in various stages of their lives. Astronomers are able to do detailed analyses of their life cycles with this snapshot in time.
This cluster NGC 3603 has some of the most massive stars known. They burn through their hydrogen fuel quickly demonstrating the phrase to ‘live fast and die young’.
Zoom into Carina to find the location of NGC 3603. Credit: NASA, ESA, and G. Bacon (STScI).
Below is my version of the colorized NGC 3603 using greyscale images from Hubble. The resulting colors depend on several factors such as color filters used to make the original greyscale images and the choices made in hue and saturation in software such as Photoshop. An important point to make is that various colors help us see different features, structures, and processes. They are not typically what the eye would see.
In the far southern skies is the constellation Piscis Volans, the flying fish. Within Volans lies this galaxy NGC 2442. It is distorted from the more common spiral shape into a meathook appearance. The unusual shape is likely the result of a close encounter with another galaxy not in the field of view. The galaxy lies about 50 million light years away. Visible are darkened dust lanes, young blueish star clusters, and reddish star forming regions. More views are from Astronomy Picture of the Dayhere, here, and here.
I tried my hand at producing a color version of the Meathook galaxy using 3 greyscale images from the Hubble Telescope. The process is described in this previous post. The Hubble images provide rich detail.
Spiral galaxies are common in the universe. This example of the Pinwheel Galaxy M101 from the Hubble Telescope is found in Ursa Major, the Big Dipper.
About ⅔ of the spiral galaxies also have a feature in the center called a bar. This next example, also from Hubble, is known as NGC 1300. Some bars are very long and pronounced, as this one. Other galaxies have a bar that is quite short.
Notice in each galaxy the blue cast in the spiral arms. It comes from the glow of relatively young stars. Older stars tend to glow white, yellow, or orange. The vein-like structures are regions darkened by the absorption of dust.
Centaurus-A is located in the southern hemisphere skies. I have never seen it from my location 42˚ north latitude. It rises only 5˚ above my southern horizon in early December. I’m certain it is very familiar to my blogger friend Roger in Australia. It is the 5th brightest galaxy and easily viewed by amateurs. It contains a black hole of 55 million solar masses ejecting jets of x-ray and radio wavelengths. Models suggest the galaxy collided with another smaller galaxy in the past leading to areas of star formation in the resulting complex structure. I enjoyed combining 3 greyscale Hubble images into this composite. In the center are several newly formed bluish stars. The dark areas are dust blocking the passage of light.