Galaxies are glittering cities, huge metropolises filled with stars, mud, gasoline, black holes, magnetic fields, cosmic rays, darkish matter and extra. Separated by thousands and thousands of light-years of primarily nothing, galaxies are extremely remoted, each an island.
Astronomers have recognized three sorts of galaxies: spirals, ellipticals and irregulars, and the variations between these sorts of galaxies reveal their sophisticated histories.
When you had been to depart a galaxy largely left alone, topic solely to the occasional minor merger (or extra precisely, consumption) of a dwarf galaxy, it might naturally develop a set of gorgeous spiral arms.
These spiral arms are created by waves of density rippling throughout the disk of the galaxy, spinning and overlapping on themselves. These waves stem from sources like close by passing galaxies, the occasional galactic snack and even chains of supernova explosions.
Regardless of the daring look of spiral arms, these constructions aren’t rather more dense than galactic common, solely by about 10% or so. However that barely larger density causes a stellar visitors jam, igniting the formation of recent batches of stars. Basically, spiral arms are the websites of lively star formation inside spiral galaxies.
In star-forming areas, all kinds of stars can type. Huge, shiny, blue ones. Medium white ones. Small, dim, pink ones. However from thousands and thousands of light-years away, our eyes and our telescopes pick the intense ones most readily, making the arms visually stand out rather more than their density alone would lead to.
The important thing to stunning spiral arms in a galaxy is the occasional gravitational encounter or disturbance — emphasis on the phrase “occasional.” If a galaxy suffers too many collisions or only one large one the turbulence can completely disfigure a galaxy, without end robbing it of the prospect at magnificence.
The issue is the merger occasion itself. When galaxies collide, the celebrities themselves do not truly smack into one another — there’s approach an excessive amount of empty area for that to occur. However all these additional gravitational interactions, plus a wholesome dose of gasoline clouds passing too shut to one another, set off a spherical of high-intensity star formation. In the midst of a merger occasion, which may take tons of of thousands and thousands of years to finish, the star formation charge can skyrocket to tens and even tons of of instances larger than regular.
For some time, all the things is spectacular. Ablaze with freshly-minted stars, the galaxy shines extra brightly than it ever has earlier than. Alas, it will not final. All these new stars include a price ticket: by utilizing up a lot star-making materials so shortly, the post-merger galaxy stops making stars sooner. In just a few brief hundred million years, all the huge stars shaped throughout the merger occasion die and fade away, with no new stars to interchange them.
The outcome is a huge clump of dim, pink stars. The once-beautiful spiral arms are in tatters and the galaxy misshapen. With sufficient time, the now-giant galaxy settles into an elliptical form, however regardless of its grand measurement stays comparatively dim, clinging onto a tragic and damaged existence for billions of years to come back.
Whereas many of the galaxies in our universe are both stunning, grand spirals or large, boring ellipticals, there are many oddballs. Some galaxies look like stretched and distorted like we’re viewing them in a funhouse mirror. Some galaxies seem to have holes blasted proper by way of their facilities. Some are simply tangled, mangled wrecks, barely discernible as any form of construction in any respect.
The wrongdoer behind these oddballs is gravity. The gravitational affect of the galaxies on one another twists and distorts the pair, drawing large tails of gasoline, mud and stars out of every galaxy like unraveling a spiral. For just a few hundred million years, these two galaxies will look extremely irregular.
Smaller collisions could make for some attention-grabbing galaxies too. For instance, some galaxies appear like they’ve gotten cored after a neighboring galaxy plowed by way of its middle, clearing a path by way of the celebrities.
Irregular galaxies do normally host ongoing star formation, exactly as a result of no matter affect distorted the galaxy created dense bulges and knots the place sufficient materials can condense to type stars.
This makes irregulars a few of the most intriguing galaxies on the market — no two are alike, however they’re all disturbingly stunning.
Be taught extra by listening to the episode “AAS! 144: ASTRO101 PART 6 – WHAT ARE GALAXIES?” on the Ask A Spaceman podcast, out there on iTunes and on the Net at http://www.askaspaceman.com. Because of Mitchell L. for the questions that led to this piece! Ask your individual query on Twitter utilizing #AskASpaceman or by following Paul @PaulMattSutter and fb.com/PaulMattSutter. Observe us on Twitter @Spacedotcom and on Fb.