Our Universe is an amazing place, Frank takes you on an intriguing and sometimes surprising journey of facts and information. Frank Bifulco RAC Advisory Committee
Cosmic Cornucopia Recent advances in astro imaging were made with the updated optics of the Hubble Space Telescope (HST) and the Spizter Space Telescope (SST). These state-of-the-art telescopes have shed new light (no pun intended) on evelopments with globular and open clusters. For starters, there is now some debate as to whether or not the largest globular cluster in the Milky Way, Omega Centauri, is the remnant of a dwarf galaxy which was disrupted and absorbed by the core of the Milky Way Galaxy.
The evidence for this assertion is not conclusive, but it would mesh with the powerful gravitational effects of the supermassive black holes at the center of the Milky Way and other galaxies. We know that galaxies of similar size do collide, so we can deduce that large galaxies and dwarf galaxies do also. Observations of globular M12 with the SST also indicate that this cluster is losing stars as it rotates around the galactic core of the Milky Way Galaxy. With 200,000 stars still remaining (down from over 1 million), M12 in Ophiuchus should have another 4.5 billion years left before it is totally stripped of all her stars. So don’t worry if you wait a few months to observe M12— it’ll still be there ! We also have new information on the density and brightness of globular clusters. Originally, it was thought that the density of globular clusters was lower than we now know and the brightness higher. In fact, density is higher but brightness is lower. This is because most of the stars in a globular cluster are older stars whose absolute magnitude would be less to an observer located in such a cluster. More stars have been found, but these older stars are less luminous. These new developments were made possible because of the ability to image clusters in different wavelengths of light, screening out the effects of gas and other variables.
Conversely, the Arches Cluster near the Milky Way core has a solar density 60,000 times that of our region of space mmediately adjacent to Earth. There are 100 superluminious young giant stars located within 1 light-year of one another— by comparison, we have 4 stars within about 4 light-years (the Sun and the Alpha Centauri system of 3 stars). This cluster is only a few million years old and is composed of very young stars that burn out quickly. Nighttime on planet in the Arches Cluster would have starlight equal to the illumination inside of an office building. Most globular custers, comprised of more but older stars, would give off the light equivalent of a few candles in a dark room. Thanks to in-depth examination of the Arches Cluster, it also appears that the upper limit for a star’s solar mass is about 150 suns. Studying globular clusters provides insightful information about the universe for the same reason that black holes do— they combine the internal thermonuclear dynamism of stellar activity with the gravitational effects of large solar objects. Just as black holes offer insight into the birth and death of stars and the universe, globular clusters are giving us new information on stars and galaxies, and gravitational interactions involving both.
In effect, globular clusters are the middle ground between individual stars and galaxies. In coming months and years, expect more details on the number of globular clusters in some of the galaxies within the Virgo Supercluster as well as more distant superlarge galaxies.
Spacey Thoughts, Weighty Matters
So how much does the universe weight? Hey, you can’t possibly expect me to answer that question here is this short little article... or can you? You’ll don't have to go and check out The Journal of Astrophysics if you want to know how much the universe weighs.
Scientists are able to determine the approximate weights of large celestial objects using solar mass as a reference scale. For instance, the
Sun is 1 solar mass and the black hole at the center of the Milky Way is estimated to weight about 4 million solar masses. The entire Milky Way weighs about 60 billion solar masses.
The Local Group of Galaxies, which extends out to about 3 million light-years and includes both M31 Andromeda and M33 Triangulum, the Small and Large Magellanic Clouds, and another 30 or so galaxies, weighs in on the order of 150 billion solar masses.
Going out further, the Virgo Supercluster goes out to 75 million light-years and encompasses thousands of galaxies. The weight of this gravitationally-bound grouping of galaxies is on the order of 1,000 trillion solar masses, even though 95% of the volume of the entire distance is empty space.
The universe is estimated to contain 125 billion galaxies, so if you want to estimate the weight of the universe, use the weight of the Virgo Supercluster and extrapolate. Just hope your calculator has a lot of zeroes in it.... A LOT of zeroes.