A number of such dwarf galaxies orbit larger galaxies, such as the Milky Way or the Andromeda Galaxy. They are believed to have been created by gravitational forces in the early phases of the creation of these larger galaxies, or as a result of crashes in between galaxies, forming from streams of material and dark matter ejected from the parent galaxies. The Milky Way galaxy features at least 14 satellite dwarf galaxies orbiting it. They are believed to be modern versions of some of the remote galaxies observed in deep field galaxy studies, and can hence assist us to comprehend the early phases of galaxy and star development in the young Universe.
Hubble Space Telescope image of NGC 5477, a stereotypical dwarf galaxy in the Messier 101 group. Without apparent structure, but with noticeable indications of ongoing starbirth, NGC 5477 looks similar to an archetypal dwarf irregular galaxy. The brilliant nebulae that extend throughout much of the galaxy are clouds of glowing hydrogen gas in which brand-new stars are forming. These radiance pinkish red in real life, although the choice of infrared and green filters through which this image was taken makes them appear practically white. Credit: ESA/Hubble & & NASA
Dwarf galaxies are small galaxies made up of a couple of billion stars.
Compared to their bigger cousins, which can include hundreds of billions of stars, dwarf galaxies are usually home to a simply few billion stars. A number of such dwarf galaxies orbit bigger galaxies, such as the Milky Way or the Andromeda Galaxy. They are thought to have actually been created by gravitational forces in the early phases of the creation of these larger galaxies, or as an outcome of crashes in between galaxies, forming from streams of product and dark matter ejected from the moms and dad galaxies. The Milky Way galaxy includes a minimum of 14 satellite dwarf galaxies orbiting it. They are believed to be contemporary versions of a few of the remote galaxies observed in deep field galaxy surveys, and can thus help us to understand the early phases of galaxy and star development in the young Universe.
Dwarf galaxies are small galaxies composed of a couple of billion stars. Credit: NASA & & ESA
The importance of dwarf galaxies in regards to cosmology is in plain contrast to their unimpressive shapes, as they are believed to be essential in our understanding of the overall evolution of galaxies. Dwarf irregulars tend to have low metallicity and fairly large amounts of gas, and are believed to be comparable to the earliest galaxies that populated deep space.
A global group of astronomers used data from both the Hubble Space Telescope and ESAs Gaia satellite to straight measure the 3D motions of private stars in the neighboring Sculptor Dwarf Galaxy, which lives 300,000 light-years away. The achieved accuracy was much better than for any previous measurement of a galaxy beyond the Milky Way. The motions provided a field test of the currently-accepted cosmological model and likewise measured the trajectory of the galaxy through space.
Dwarf Galaxy. Credit: ESA/Hubble & & NASA
Hubble has also made in-depth observations of the dwarf galaxy NGC 2366, which is house to a bright, star-forming nebula and is close enough for astronomers to discern its specific stars. While we see the stars because they shine brightly, galaxies are overwhelmingly made up of the empty space between them. Hubbles high-resolution images can catch this completely. The telescopes field of view for its observations of the galaxy were equivalent to a little over a fifth of the diameter of the moon. Although this is relatively big by the standard of Hubbles images, NGC 2366 is much too faint to observe with the naked eye.
This Hubblecast episode looks at starburst dwarf galaxies at a time when most of the stars in deep space were formed, and how Hubble observations show that dwarf galaxies played a larger role than anticipated in the early history of the Universe.