The Magellanic Clouds are two irregular dwarf galaxies visible in the Southern Celestial Hemisphere; they are members of the Local Group and are orbiting the Milky Way galaxy. Because they both show signs of a bar structure, they are often reclassified as Magellanic spiral galaxies. The two galaxies are:
Image credit: Primoz Cigler, Joseph Brimacombe,
Ed Dunens and EkantTakePhotos
Stars orbiting the Supermassive Black Hole at our Galactic Center.
This demo shows the observed and predicted orbits of thirteen stars that were used by astronomers at the Keck/UCLA Galactic Center Group to predict the position of a huge black hole at the center of the Milky Way. This data was provided by Andrea Ghez and Jessica Lu.
On the shore of Lake Dumbleyung
This vibrant image from NASA’s Spitzer Space Telescope shows the Large Magellanic Cloud, a satellite galaxy to our own Milky Way galaxy.
Image credit: NASA/JPL-Caltech/STScI
On this day in 1889 was born the astronomer Edwin Hubble!
Edwin Hubble played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology and is regarded as one of the most important astronomers of all time.
Hubble discovered that many objects previously thought to be clouds of dust and gas and classified as “nebulae” were actually galaxies beyond the Milky Way. He used the strong direct relationship between a classical Cepheid variable’s luminosity and pulsation period (discovered in 1908 by Henrietta Swan Leavitt) for scaling galactic and extragalactic distances.
Hubble provided evidence that the recessional velocity of a galaxy increases with its distance from the earth, a property known as “Hubble’s law”, a preliminary version of which was proposed earlier by Georges Lemaître. Hubble’s Law implies that the universe is expanding. A decade before, the American astronomer Vesto Slipher had provided the first evidence that the light from many of these nebulae was strongly red-shifted, indicative of high recession velocities.
Hubble’s name is most widely recognized for the Hubble Space Telescope which was named in his honor, with a model prominently displayed in his hometown of Marshfield, Missouri.
Hubble also devised the most commonly used system for classifying galaxies, grouping them according to their appearance in photographic images. He arranged the different groups of galaxies in what became known as the Hubble sequence .
In 1929 he demonstrated that the galaxies move away at great speed and that this speed increases with the distance. The relationship between velocity and distance from Earth is known as the Hubble Law and the ratio between the two values is known as Hubble’s Constant. If a galaxy is approaching, the light shifts to the blue color and if it is moving away from the light to the red color (Doppler effect). In each case, the relative variation of length is proportional to the speed at which the source moves.
Hubble’s law is the name for the observation in physical cosmology that:
When you hear the name “Hubble”, you probably think of the NASA/ESA Hubble Space Telescope. But, decades before the Hubble Space Telescope, Dr Edwin Powell Hubble revolutionised the field of astronomy. In the newest Hubblecast, we take a look at the life and work of this brilliant American astronomer for whom the Hubble Space Telescope is named.
Probably yes, astronomers believe that practically every galaxy has a black hole in its center, in…
Supermassive Black Hole Sagittarius A*. Animation of the Stellar Orbits around the Galactic Center.