Somewhere in this Hubble image, two galaxies collide. And no, not the two large spiral galaxies that slide past each other.
The large galaxy in this week’s satellite image is NGC 105. This spiral galaxy is located in the constellation Pisces, 215 million light-years from Earth. The object was discovered in 1884 by French astronomer Edouard Stephan. NGC 105 cannot be seen even with good binoculars. You need a big telescope, which also explains why the galaxy was discovered relatively late.
To the left of NGC 105 we see another galaxy. It appears that this galaxy – PGC 212515 (or LEDA 212515) – collides with NGC 105. In fact, there is nothing wrong. The distance between PGC 212515 and Earth is 350 million light years. This means that there are more than a hundred million light-years of “space” between the so-called colliding galaxies and this is more than enough. To put it in perspective, the Andromeda galaxy is only 2.5 million light-years away from our Milky Way.
However, there are colliding galaxies that can be seen in this beautiful image. Then we first have to zoom in properly. In the background there are many irregular galaxies of different shapes and sizes. Certainly two colliding galaxies are visible. Take a look at the chapter below. Colliding galaxies can be seen just below the center of the image.
But there is more to see in the photo. You see this bright star in the upper right of NGC 105? This star is in our Milky Way. So this object is hundreds of thousands of times closer to Earth than NGC 105. You also see countless red dots. All of these galaxies are billions of light years away from Earth. Fascinating!
The changing star steals the show
The reason NGC 105 is imaged by the Hubble Space Telescope is that this galaxy is home to the so-called Cepheid variable. This is a variable star that is regularly expanding and shrinking. As the star swells, the temperature increases and the cadaverium glows. After this peak, the gaseous field shrinks again and the star cools by about a thousand degrees. Cepheids are also very large stars, called supergants. The average Cepheid variant has a diameter of fifty million kilometers. In comparison, the diameter of the Sun is more than a million kilometers.
Various supernovae
NGC 105 also contains three Type Ia supernovae, SN 1997w, SN 2006tg, and SN 2007A. This type of supernova occurs in narrow binary star systems, where one star is a white dwarf and the other a red giant (or second white dwarf). Type Ia supernovae play an important role in our understanding of the universe. A Type Ia supernova is the brightest type of supernova: radiating more than a billion times the energy of our Sun. This allows them to see them at great distances. In addition, in their violent explosions, they eject many elements from which new stars and galaxies appear.
Astronomers can use Type Ia supernovae and Cepheids to more accurately determine the distance to distant galaxies. In this regard, NGC 105 is the perfect “guinea pig” for astronomers, since both objects are present here.
