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Gamma rays have the most energy of any wave in the electromagnetic spectrum (which includes more familiar radiation such as x-rays, radio, and visible light). The wavelength of gamma rays (10 picometers and smaller–which is a subatomic scale) is less than that of any other sort of EM radiation. Such radiation is created in the event horizons of massive black holes and during the destruction of gigantically massive stars. Comic book enthusiasts know gamma rays as the mysterious super force which created and empowers the incredible hulk, although actual cell biologists recognize gamma rays as ionizing radiation–supremely hazardous to living entities.
On Saturday, April 27, the Fermi Gamma-Ray Telescope (a NASA satellite which orbits around Earth) detected a sudden brilliant surge of gamma radiation from the collapse of a super massive star in a galaxy 3.6 billion light-years away. Gamma ray burst travel in vastly powerful beams which are very narrow–an effect which is a result of the shape of supernovae, as illustrated in the picture above. Our old friend Eta Carinae has probably exploded and produced such a burst by now. A gamma ray bust from a nearby Wolf–Rayet would probably fry away life on our planet if it were aimed directly at Earth, but such explosions are increasingly rare as the universe ages. Scientists can monitor gamma bursts from the edge of the universe (i.e. the distant past) but such a powerful event has never been monitored by our modern satellites and observatories from a middle range until now.
As the gamma ray burst fades (and the astronomy community begins to assess the initial data) other observatories will be on the lookout for the next wave of phenomena associated with the supernova. Most of the energy of a supernova explosion is believed to be dissipated as neutrinos (esoteric subatomic particles which react very little with physical matter in this universe). Fortunately humankind now possesses a sophisticated neutrino observatory on the South Pole where thousands of sensors are imbedded within a vast amount of Antarctic ice. In the rare cases where neutrinos interact with matter, they produce a cascade of charged particles which can emit Cherenkov radiation (familiar as the spooky blue glow in a nuclear reactor). Understanding the neutrino signature of such an event would potentially further our understanding of the physical parameters of existence.
Also, a luminous flash of less energetic radiation (x-rays, radio waves, light, and so forth) should be following the gamma ray burst. We understand these parts of supernovae better (since they are visible from many angles unlike the linear gamma ray bursts), but it should still be pretty–and round out our understanding of the full astronomical event.
Brian May is an astrophysicist who pursued a career in music. He is the guitarist for the rock band Queen and he is more famous for writing “Fat Bottomed Girls”, “We Will Rock You”, & “Who Wants to Live Forever” than for anything he wrote while obtaining his Astrophysics degrees. Brian was popularizing Galaxy Zoo on his blog (Galaxy Zoo is an online project which seeks public help in classifying vast numbers of galaxies. A Dutch fan, Hanny van Arkel (a schoolteacher by trade), became interested in the project and started working on the site when she spotted a huge weird glowing green thing below spiral galaxy IC 2497. She presented her findings to professional astronomers, who were also perplexed by the ghostly shape. They duly named the object in her honor “Hanny’s Voorwerp” (which is Dutch for “Hanny’s thing”).
So what is Hanny’s Voorwerp? The leading theory is that the supermassive black hole in the center of IC 2497 created huge jets of energy and gas as it (messily) devoured great masses of matter at the center of that galaxy. These esoteric plumes interacted with an unrelated stream of gaseous matter hundreds of thousands of light years long (which is longer than our galaxy). The thin clouds of glass then fluoresced like a krypton sign or a Scooby-Doo ghost.
Thanks Brian May and Hanny! This is one fancy voorwerp.
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.
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.
One of life’s disappointments is the dearth of fine art concerning outer space. Outer space is vast beyond imagining: it contains everything known. Indeed, we live in space (albeit on a little blue planet hurtling around an obscure yellow star)–but cosmic wonders do not seem to have called out to the greatest artists of the past as much as religious or earthly subjects. There are of course many commercial illustrations featuring the elements of science fiction: starships, ringed planets, exploding suns, and tentacled aliens (all of which I like) and there are also didactic scientific illustrations, which attempt to show binary stars, ring galaxies, quasars and other celestial subjects. Yet only rarely does a fine artist turn his eyes towards the heavens, and it is even less frequent that such a work captures the magnificence and enormity of astronomy.
Fortunately the Dutch artist MC Escher was such an artist. His space-themed engravings utilize religious, architectural, and biological elements in order to give a sense of scale and mystery. The familiar architecture and subjects are transcended and eclipsed by the enormity of the cosmic subjects. Here are two of his woodcuts which directly concern outer space.
The first print is a wood engraving entitled The Dream (Mantis Religiosa) shows a fallen bishop stretched on a catafalque as a huge otherworldly praying mantis stands on his chest (the whole work is a sort of pun on the mantis’ taxonomical name Mantis religiosa “the religious mantis”. The buildings arround the bishop and the bug are dissipating to reveal the wonders of the night sky. The bishop’s world of religious mysteries and social control are vanishing in the face of his death. Greater mysteries are coming to life and beckoning the anxious viewer.
The colored woodcut “Other World” shows a simurgh standing above, below and in front of the viewer in a spatially impossible gazebo on an alien world. The simurgh is a mythical animal from ancient Persian literature and art which combines human and avian elements. Sufi mystics sometimes utilize the simurgh as a metaphor for the unknowable nature of divinity. Yet here the simurgh is dwarfed by the craters beneath him and by the planetary rings filling up the sky above. A strange horn hangs above, below, and to the side of the viewer. Perhaps it is a shofar from ancient Judea or a cornucopia from the great goat Amalthea. Whatever the case, the viewer has become unfixed in mathematical space and is simultaneously looking at the world from many different vantage points. A galaxy hangs in the sky above as a reminder of the viewer’s insignificance.
Above all it is Escher’s manipulation of spatial constructs within his art that makes the viewer realize the mathematical mysteries which we are daily enmeshed in. The multidimensional geometric oddities rendered by Escher’s steady hand in two dimensions characterize a universe which contains both order and mystery. Giant bugs and bird/human hybrids are only symbols of our quest to learn the underpinnings of the firmament. Escher’s art is one of the few places where science and art go together hand in hand as partners. This synthesis gives a lasting greatness to his artwork, which are undiminished by popularity and mass reproduction.
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.
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.
During the 1950’s, astronomers using the first radio telescopes started discovering a mysterious class of heavenly objects. Certain discreet points in the sky blazed brightly with low-frequency electromagnetic radiation–yet when the scientists looked at the spots through conventional optic telescopes, it was impossible to discover a source for this energy. Some of these radio flares came from incredibly faint smudges and some issued from what seemed like empty space. Astronomers called the mystery flares “quasi-stellar radio sources” (QUASAR) because they believed such discreetly focused energy must come from stellar-like objects. Further study revealed that the photons issuing from quasars were red-shifted, which meant that the quasars were rushing away from the solar system at high velocities.
Only in the 60’s did optical telescopes become powerful enough to associate certain quasars with the cores of extremely distant galaxies. The reason no luminous objects were initially associated with quasars was because quasars turned out to be profoundly distant—the closest were billions of light years away. They were visible to early radio telescopes only because of their immense energy output and their beam-like focus.
Scientific consensus concerning these massive energy flares did not fully coalesce until the 1980s. Today astronomers believe that quasars are powered by accretion of material into super-massive black holes which lie at the center of dynamic young galaxies. Such phenomena are called “active galactic nuclei” (AGN). As radio telescopes and time-space modeling grew more sophisticated it became obvious that quasars (which produce low-frequency radiation) were not the only energy flares associated with AGN. Giant beams of different spectrums of electromagnetic radiation are possible depending on the galaxy. Quasars and their ilk produce incomprehensible amounts of energy—the most luminous active galactic nuclei radiate exotic energy at a rate that can exceed the output of an average galaxy by a thousand times (equivalent to the energy from two trillion suns). To produce such energy the brightest known quasars consume roughly 1000 solar masses of matter within an earth year (which is equivalent to swallowing/burning 600 Earths per minute).
Galaxies change as they age. Today the Milky Way Galaxy is a mostly responsible middle aged galaxy (which only occasionally cuts lose with something crazy like the luminous blue hypergiant Eta Carinae) however there are reasons to think that in the past the Milky Way was a deeply troubled teen-aged galaxy ablaze with self-destructive fury just like the AGN galaxies we see at the far edges of space. Assuming they exist, alien astronomers in galaxies billions of light years away probably see our galaxy as a blazing quasar–because they are looking at its distant violent past.
Of course galaxies are not always quiescent. Some astrophysicists theorize that in 3 to 5 billion years, when the Andromeda Galaxy collides with the Milky Way, the black holes in the center of one or both galaxies could begin swallowing up matter (or could merge) reigniting a super bright fountain of high energy particles again visible throughout the universe.
Since the moon is the closest celestial body to earth and the most easily observed with a telescope, it was a natural place for Herschel to begin his search for extraterrestrials. In a letter to a friend, Herschel described how he believed the craters of the moon were Lunarian cities and dwellings (laid out like the Roman “circus” meaning a large ring):
As upon the Earth several Alterations have been, and are daily, made of a size sufficient to be seen by the inhabitants of the Moon, such as building Towns, cutting canals for Navigation, making turnpike roads &c: may we not expect something of a similar Nature on the Moon? – There is a reason to be assigned for circular-Buildings on the Moon, which is that, as the Atmosphere there is much rarer than ours and of consequence not so capable of refracting and (by means of clouds shining therein) reflecting the light of the sun, it is natural enough to suppose that a Circus will remedy this deficiency, For in that shape of Building one half will have the directed light and the other half the reflected light of the Sun. Perhaps, then on the Moon every town is one very large Circus?…Should this be true ought we not to watch the erection of any new small Circus as the Lunarians may the Building of a new Town on the Earth….By reflecting a little on the subject I am almost convinced that those numberless small Circuses we see on the Moon are the works of the Lunarians and may be called their Towns….Now if we could discover any new erection it is evident an exact list of those Towns that are already built will be necessary. But this is no easy undertaking to make out, and will require the observation of many a careful Astronomer and the most capital Instruments that can be had. However this is what I will begin.
Of course this spectacular misapprehension becomes more comprehensible considering how long it took humanity to understand the nature of craters (it wasn’t until the 1960’s that work by astrogeologist Gene Shoemaker, brought about widespread scientific consensus that craters were caused by impacts). Yet Herschel was so devoted to his Lunarians that he came perilously close to inventing findings. As he carefully scrutinized the moon for other living things night after night, imperfect optics and his yearning for alien life sometimes got the best of him. Here is a drawing of a shadow which he perceived might be a forest.
Herschel did not believe that the moon was the only other sphere to support life–he believed that life could be found on all heavenly bodies which are spherical from self-gravitation. And Herschel really meant all such bodies: in the Royal Society’s Philosophical Transactions in 1795 he speculated about beings living on the sun,
The sun…appears to be nothing else than a very eminent, large, and lucid planet, evidently the first, or in strictness of speaking, the only primary one of our system….Its similarity to the other globes of the solar system …leads us to suppose that it is most probably inhabited …by beings whose organs are adapted to the peculiar circumstances of that vast globe.
Hershel thought that all of the stars in the universe were like the sun—densely habited and supporting an orbiting network of habited worlds. He wrote “since stars appear to be suns, and suns, according to the common opinion, are bodies that serve to enlighten, warm, and sustain a system of planets, we may have an idea of numberless globes that serve for the habitation of living creatures.” Additionally, Herschel believed that the nebula he observed were other “universes” like our own, each containing innumerable stars—all of which were habited. He was wrong in his interpretation of the particular gaseous nebulae he was looking at, but he was quite right about the existence and nature of other galaxies (although this idea was not proved or accepted until the work of Edwin Hubble).
Poor Herschel’s hunches about extraterrestrial life seem quaint to us now. Couched in boyish exuberance and 18th century idioms, they almost seem risible. Yet Herschel was right about exoplanets and about galaxies beyond our own. He seems to have been the only person of his time to begin to apprehend how vast the universe really is. Thanks to the work of many scientists and explorers we can write off life on the moon and (almost certainly) the sun. However, even with our robot probes and our telescopes, the solar system is shockingly unknown. And beyond the solar system, the large exoplanets we currently know about are strange hot giants we did not expect. The preliminary results of the Kepler mission are beginning to trickle in, and they hint at a profusion of planets (and other things) much more heterogeneous and odd than cosmic uniformitarians might expect. If blogging has taught me one thing, it is not to underestimate Sir Frederick William Herschel (a conclusion I hardly anticipated). So while I chuckle about the perfectly circular cities of the lunarians, I am also keeping an open mind about the immense number of unknown worlds.
Also (as I suspect Sir William felt), I am sad about how many things are simply unknowable.