The Cobbler [The Think Tank of : Orian/25,000 BC/Part Four]

Large galaxies, like our own starlit spiral Milky Way, are usually accompanied by a sparkling entourage of smaller galactic satellites that travel on bound orbits around their massive, luminous host. This is similar to the way that planets within our own Solar System are gravitationally bound to our Sun. These smaller satellites lead tumultuous lives because of their messy interactions both with other satellites and their larger host galaxy, known as the primary galaxy. However, astronomers have learned to expect the unexpected when it comes to objects that dance their weird way throughout the observable Universe, and the distant, ancient galaxy dubbed Messier 94 (M94) has proven to be full of surprises. In January 2019 a team of astronomers announced their new findings that, even though M94 is about the same size as our Milky Way–that is richly endowed with a family of circling satellites–they have detected only two galaxies orbiting M94. Also, the distant dancing duo have very few stars each.

In astronomy long ago is the same as far away. The more distant an object is in Space, the more ancient it is in Time (Spacetime). The discovery of the relatively isolated M94 suggests that fewer galaxies were born in the early Universe than astronomers expected. This possibility could potentially create new questions for galaxy physics, according to the study conducted by University of Michigan (Ann Arbor) astronomers.

It has been known for a long time that our Milky Way is accompanied by about 10 smaller satellite galaxies that circle it, each hosting at least a million fiery stars. Indeed, our Milky Way’s largest satellite, the Large Magellanic Cloud (LMC) contains up to more than a billion stars.

Using the powerful Subaru Telescope, astronomers can now study galaxies five to 10 times the distance from our Milky Way, such as M94. They can use the physics explaining how satellite galaxies are born surrounding our Millky Way in order to predict the number of satellite galaxies a similar-sized galaxy may have.

So, for this reason, when the University of Michigan astronomers peered at M94, they expected to see a similar number of satellite galaxies in orbit around it. Alas, they only found the lonely, almost completely starless, dancing duo. Their results, led by Dr. Adam Smercina, are published in the journal Astrophysical Letters. Dr. Smercina is a National Science Foundation (NSF) space  in the University of Michigan’s Department of Astronomy.

“More than just an observational oddity, we show that the current crop of galaxy formation models cannot produce such a satellite system. Our results indicate that Milky Way-like galaxies most likely host a much wider diversity of satellite populations than is predicted by any current model,” Dr. Smercina explained in a January 9, 2019 University of Michigan Press Release.

Galaxy Wonderland

Galaxies are gravitationally bound systems of stars, dust, gas, stellar relics, and mysterious non-atomic dark matter. Galaxies come in different sizes, and can range from small dwarfs hosting only a few hundred million stars to giants that contain one hundred trillion stellar constituents, each in orbit around its galaxy’s center of mass.

In astronomical literature, the capitalized word “Galaxy” usually refers to our own Milky Way, thus distinguishing it from other galaxies. The English term Milky Way has been traced back to a story written by the English poet Geoffrey Chaucer (1340?-1400) in 1380: