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Ocean Sunfish (Mola mola) with school of wimplefish
My biggest blogging regret last year was not writing more about fish. Ferrebeekeeper has traditionally addressed fish more-or-less exclusively by describing catfish (the order Siluriformes). Only occasionally have I mentioned other sorts of fish–like the bizarre oarfish or the gigantic extinct Leedsichthys, but all of that is about to change! In order to enliven 2015 (and celebrate the extraordinary beauty, diversity, and complexity of the natural world), we are going to write about all sorts of fish from now on! Ichthyophiles rejoice! And, if, for some perverse reason, you do not love fishes—ancient, ancestral, beautiful, and sacred—then Ferrebeekeeper is out to convert you!
To start out on this enormous topic we are starting with an enormous fish—Mola mola, the common ocean sunfish. Some of my American readers may know sunfish as the endearing little freshwater fish which live in ponds and small rivers everywhere. However the ocean sunfish is nothing like bluegills, bass, and crappies (er, except for the fact that it is indeed also a fish). The Mola mola is the largest bony fish in the world in terms of mass. It lives in tropical and temperate waters around the planet ranging from Norway in the north to Patagonia in the south (and continuously east and west). The first time I saw a mola fish I had an unreasoning moment of horror that a huge shark had bitten the poor fish in half! The molidae lack caudal fins—which gives them the appearance of giant truncated heads. To swim, the fish relies on large powerful dorsal and anal fins (although the clavus of the sunfish is a sort of pseudofin). Because of this unique anatomy, the great fish is as taller than it is long. And it can be quite tall indeed: the largest specimens measure 4.2 m (14 feet) from fin tip to fin tip, although they are a more modest 3.3 m (11 feet) in length. The sunfish is very heavily built and weighs up to 2,300 kg (5,100 lb) in mass. Among fish, only the largest cartilaginous fish are bigger.
Ocean Sunfish (Mola mola) with human diver
To reach this prodigious weight, the sunfish is an omnivore. It eats ocean grass, small fish, crustaceans, and mollusks, however, most of all, the great fish feeds on jellyfish and salps (free-swimming tunicates). Adults lose the ability to open and close their mouth–which forms into a beak-like structure (with four teeth fusing into a sort of funnel). Sunfish do not have swim bladders. Additionally, they have only 16 vertebrae, the smallest number among all fish (though not among vertebrates: some amphibians have only a single vertebra).
Adult sunfish are too large for most animals to prey on, however they are sometimes eaten by sharks and killer whales. Sea lions will occasionally tear off sunfish fins for fun and then leave the poor finless fish to die! Sunfish fry are smaller and thus vulnerable to a much greater number of predators. To protect themselves, Mola mola fry take the shape of stars covered with spikes! Just try swallowing a dodecahedron, and you will learn how these creatures survive long enough to become the largest teleosts!
Although Mola mola fry (pictured, greatly enlarged) hardly start out very big!
Naturally, the practice of swallowing sunfish has been readily adopted by our own voracious species. Sunfish are eaten by humans in East Asia (although there is an unresolved debate about whether they contain toxins like their close relatives the pufferfish). Additionally they are also threatened by plastic bags, which they eat in the mistaken belief that they are jellyfish, and by fishers who catch them accidentally and then throw them away dead as by-catch. Because they are primarily pelagic (living in the deep ocean) their numbers have never been accurately calculated, so we don’t know if they are endangered (!) but there are certainly far fewer these days than there used to be.
Here’s an awesome iron-on patch from Etsy, in case you want your own sunfish
A strangely horrifying illustration of the supermassive black hole located in the middle of the very dense miniature galaxy M60-UCD1
Fifty million light years away from Earth is the dwarf galaxy M60-UCD1. This tiny globular galaxy is 300 light years across–whereas our own beloved spiral galaxy, the Milky Way, is 120,000 light years in diameter! Yet within that 300 million light year sphere, M60-UCD1 is a crazy place. Despite its (comparatively) tiny area, the dwarf galaxy is teaming with stars: astronomers estimate it contains 140 million star systems. If Earth were located in M60-UCDI, the night sky would positively glow with millions of visible tars (as opposed to the measly 4000 which are visible to the naked eye in our present location). This is all quite odd, yet only recently did astronomers discover the strangest thing about M60-UCDI. At the center of the tiny galaxy is a supermassive black hole which weighs more than twenty million suns. To quote the European Space Agency’s website, “The supermassive black hole at the centre of M60-UCD1 makes up a huge 15 percent of the galaxy’s total mass, and weighs five times that of the black hole at the center of the Milky Way.”
Messier 60 with M60-UCDI (Composite image from NASA’s Hubble & Chandra space telescopes)
Astronomers speculate that something went terribly wrong to form this oddball of a galaxy. A prime culprit is Messier 60, a large scary galaxy which lurks near the little dwarf galaxy. The black hole at the center of Messier 60 is 4.5 billion times the size of our Sun! Perhaps once upon a time M60-UCDI was a normal galaxy with billions of stars…till it wandered too close to Messier 60. The larger galaxy tore off the majority of the stars which made up M60-UCDI and added them to itself (while Messier 60’s black hole swallowed up its fair share of star systems). It is a horrifying image of galactic bullying! Why can’t we all get along?
A Composite Image of M104–The Sombrero Galaxy–taken from the Hubble Space Teelscope in Summer of 2003 (click on the image for a full-sized version)
Today I am posting some pictures of what I think is the most beautiful deep space object. The Sombrero Galaxy (M104) is a nearby galaxy which is visible edge-on in the constellation of Virgo. Actually, calling it an object might be a bit misleading since M104 consists of more than 400 billion stars–not to mention numerous associated globular clusters, innumerable planets, immense clouds of gas & gas, and a supermassive black hole which lies in the center. The black hole in the center of M104 isn’t a mild mannered & quiescent black hole like the one in the center of the Milky Way either. Based on the speed of revolution of the stars near the middle of M104, astronomers calculate that the central black hole has a billion times the mass of the sun.
An Infrared false-color image of the Sombrero Galaxy
In cosmic terms, the Sombrero galaxy is nearby—which is to say it is merely 28-odd million light years away. The galaxy was discovered in the late eighteenth century by Pierre Méchain . Other prominent 18th century astronomers subsequently observed and studied M104, including Charles Messier (which is the reason the galaxy is included in the “Messier” catalog and has a M-designation) and the redoubtable William Herschel who noted a “dark-stratum” bounding the luminous central bulge. We now know that this ring around M104 is a toroid dust lane of vast proportions which halos the galaxy. Astronomers initially thought that the Sombrero Galaxy was an unbarred spiral galaxy, but thanks to observations from NASA’s Spitzer space telescope (an infrared scope orbiting Earth), the scientific community has revised their estimation of its size upward. It lies somewhere between a spiral galaxy and an elliptical galaxy. In other words, when you look at the Sombrero Galaxy, you are looking at something vast beyond human comprehension—a galaxy bigger than our own filled with who knows what things we will never know. And yet if you expand the Hubble photo at the top of this post, you will see that all of the little stars shining around M104 are other galaxies farther away.
Olé!
The constellation Sagittarius (from “Urania’s Mirror” a set of constellation cards published in England circa 1825)
My apologies for the blogging break last week. Usually I try to write a new post every weekday, but last week was a blogging holiday. To reinvigorate things after the lost week, let’s turn to a big subject—in fact a super-massive subject! Long ago, Ferrebeekeeper featured a post about Eta Carinae, a blue hypergiant with a hundred times the mass of the sun (which is itself a million times more massive than Earth). Stars like Eta Carinae are rarely formed and short lived—there are probably less than a dozen in our galaxy. However compared to the most massive object in the galaxy, Eta Carinae is puny and common. Twenty six thousand light years away from the solar system there exists a truly monstrous space object!
In 1974, Astronomers discovered an astronomical feature which was emitting exotic radio waves in the Sagittarius constellation. The scientists named the feature “Sagittarius A” and set out to determine what it was. Part of the feature seems to be the remnants of a star which had gone supernova. A second part of the feature is a cloud of ionized gas surrounded by an even larger torus of molecular gas. In the middle of Sagittarius A is something which is emitting most of the high energy electromagnetic radiation visible to radio telescopes. The cloud of ionized gas seems to be emptying into it and nearby stars orbit it with greater velocity than stars move anywhere else in the galaxy (in fact the object affects the proper motion of thousands of nearby stars). And yet the space object at the center of Sagittarius A has a diameter of only 44 million kilometers–a bit less than the distance between the middle of the sun and Mercury at its perihelion (when the rocky planet is closest to the sun). By calculating the proper motion of thousands of nearby stars, scientists determined that the mysterious object at the center of Sagittarius A (which they took to calling Sagitarrius A*) has mass of 4.31 million suns (i.e. solar masses). Whatever lies at the center of Sagittarius A–which I probably should have mentioned, is also the center of the Milky Way Galaxy–is smaller in volume than a large star, but has a mass which exceeds by many orders of magnitude even exotic hypergiants like Eta Carina.
Of course the only kinds of discrete objects which we know (or even hypothesize) to be capable of attaining such mass are black holes. It is believed that most (indeed probably all) galaxies have super-massive black hole at their centers. Smaller galaxies have small super massive black holes (forgive the oxymoron) but large galaxies have immense central black holes which can equal billions of solar masses. Radio astronomers have observed plumes of exotic electromagnetic radiation coming from the center of other galaxies, and they wondered where the Milky Way’s galactic center was located. It seems that a supernova near the galactic center blew away a great deal of the dust and gas on which the black hole would otherwise “feed” thereby making the galactic center of the Milky Way less energetic than the active center of farther (e.g. older) galaxies.
Artist’s Conception of Galactic Center
The super massive black holes which lie at the center of galaxies may be a result of the accretion of matter around stellar-sized black holes (which could grow quickly in matter-rich galactic cores) but most astrophysicists believe they are instead a primordial feature of the Big Bang around which galaxies themselves coalesced. The ultimate nature of super massive black holes remains unknown and seems to be tied to the nature and shape of our universe.
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