A Tour of the Triangulum Galaxy [4K]

[Music] the milky way is surrounded by more than 50 near neighbor galaxies that make up the local group [Music] most of these are small immature and relatively insignificant dwarf galaxies with the two largest being us and andromeda but we also have an often overlooked third large galaxy in our neighborhood the triangulum galaxy a small spiral galaxy which is essentially its own mini milky way while this galaxy shares many parallels with our own it also has some stark and significant differences which make it one of the clearest and most fascinating places to study in the entire local group today we will be traveling through the triangulum galaxy as we peel back its layers to reveal the secrets of its past present and future [Music] the triangulum galaxy gets its most common name from the northern hemisphere constellation in which it can be found when viewing the three stars that make up the triangle this faint galaxy can be seen somewhat to the right but only in the very darkest of skies around sixty thousand light years in diameter the triangulum galaxy is around half the size of the milky way but only contains around one-tenth of the stars rendering it much dimmer and more diffused than its next door neighbor the andromeda galaxy and highly sensitive to lights pollution on earth thus it managed to evade the unaided eyes of the ancients and isn't known to have been discovered until after the invention of the telescope the earliest known mention of the galaxy came in the year 1654 when italian astronomer giovanni batista hodania made mention of a cloud-like nebulosity near the triangle hink indy in his catalogue of admirable night sky objects but the galaxy wasn't officially classified until the following century when it was added as the 33rd entry in french astronomer charles messier's 1771 catalogue of deep sky objects that were not comets thus giving it the official designation we know it as today messier 33 in this same catalogue the andromeda galaxy is the 31st object and is also known by its messier classification m31 charles messier like most astronomers at the time believed these objects to be nebulae lying within the bounds of the milky way galaxy they were among the first so-called spiral nebulae identified by william parsons in 1850 with these objects thought to be some sort of prerequisite to a star-forming cloud [Music] in all fairness 19th century astronomers weren't entirely off the money in associating m33 with starburst in fact the triangulum galaxy contains some of the most prominent star-forming regions in the entire local group some so large and distinctive that they warranted their own entries in 19th century sky catalogues mentioning m33 we've come a long way since then and in recent decades we've enjoyed great success in studying our galactic neighbours by the 1920s we'd realized that the spiral nebulae were actually other galaxies like the milky way lying incomparably further away than any star or nebula and ever since we've continually pointed our best and most powerful observatories towards m33 thanks to its inclination of 54 degrees it lies pretty much face on to the earth allowing us to gauge an uncompromised snapshot of its overarching structure without significant obstruction from its dust and gas almost a century after edwin hubble proved that m33 was a separate galaxy his namesake telescope regularly snaps beautiful optical and ultraviolet images of its structure and in addition nasa's spitzer telescope has stared right through this galaxy in the infrared wavelengths infrared radiation can pass through thick opaque galactic mediums where visible light is absorbed making it the wavelength of choice for creating a complete cross-section of the galaxy at wavelengths of 3.6 microns we can clearly see m33 stars whereas between 8 and 24 microns we see the galaxy's dust and gas at various temperatures the recently launched james webb telescope is an infrared observatory with a comprehensive range of wavelength coverage so who knows what else about the triangulum galaxy nasa's pioneering new mission will uncover similarly justice infrared emissions can be used to shed new light on the inner workings of a galaxy so too can x-rays and gamma rays both nasa's chandra x-ray observatory and its swift gamma-ray burst explorer continue to gather high energy signatures from m33 to this day searching for signs of dead stars and supernova remnants which can be used as tracers in establishing the galaxy's chemical past we'll cover all of this in more detail shortly but in summary all of this has contributed to a gloriously broad and deep understanding of our galactic neighbor our measurements are rapidly becoming precise enough to resolve individual stars in the galaxy along with clouds clusters supernovae and satellites these are the checkpoints in the triangulum galaxy that make up our tour today [Music] according to gerrard's de valculia's revised hubble sandage system of galaxy morphology classification messier 33 is of the type s-a-s-c-d the first s denotes that it is a spiral galaxy like the milky way while the a indicates that it is non-barred many spiral galaxies including the milky way and andromeda exhibit a long bar shaped concentration of more tightly packed stars within their cores m33 lacks such a structure and its spiral arms emerge directly from the heart of the galaxy as indicated by the small s finally the cd component of its classification indicates that the spiral arms are relatively loosely wound with two branching from the inner core that feed into a series of more outlying spirals given the galaxy's neat wheel-like appearance it is often incorrectly referred to as the pinwheel galaxy however the actual pinwheel galaxy is known to be messier 101 another face-on spiral galaxy lying 21 million light years from the milky way the triangulum galaxy is estimated to lie around 2.7 to 2.8 million light years from earth around 750 000 light years from the andromeda galaxy and as such it is not clear whether this galaxy is a satellite of m31 on the one hand it would be an unusually large settled and structured satellite galaxy most satellites constitute only small gaseous dwarf irregular types like the small and large magellanic clouds their faces tarnished and deformed by asymmetric tidal influences from the primary body however with the exception of a past encounter with andromeda the triangulum galaxy structure does not appear to show much evidence of past interactions with its neighbours it does not appear to have an extended disk of stars scattered by collisions beyond its gaseous component the likes of which make andromeda the largest galaxy in the local group and it lacks the tidal trails and spheroidal satellites that trace the torrid path of the milky way's past encounters we've only ever managed to identify two tentative satellites around m33 the first lgs3 also known as the pisces dwarf galaxy is a small faint transitioning spheroidal type it may have been formed by a past interaction but it lies suspended pretty much equidistantly between m31 and m33 a million light years from each and so it could be a satellite of either the other candidate discovered more recently is known as tri-3 it is classed as an isolated ultra-faint dwarf lying around 230 000 light years from m-33 but it also cannot be ruled out as a satellite of andromedas there may be other ultra-faint satellites lurking around m33 that we've not yet managed to spot but broadly speaking the galaxy lacks significant satellites and external gravitational influences to distort its neat structure and so one would expect a relatively smooth and isotropic distribution in the galaxy's stars and gas and yet interestingly that's not what seems to be the case in fact there is an apparent disparity in the galaxy's structure between the northern and southern halves when viewed from earth the southern region shows a steeper spectrum with high concentrations of hot blue stars many of which die in explosive supernovae whereas the northern half of the galaxy shows a distinctly higher level of thermal emission home to a much higher concentration of ionized emission nebulae these nebulae represent one of the triangulum galaxy's standout features it's uncharacteristically enormous and massive clouds of ionized hydrogen gas where new star formation is taking place these are known as h2 regions they occur when neutral interstellar nebulous gas becomes superheated and electrically charged by the radiation of young stars forming inside this is in contrast to an h1 region which constitutes a cold cloud of non-reacting neutral hydrogen gas both types of cloud are prone to internal fragmentation and gravitational collapse which ignites the formation of clusters of massive scorching short-lived stars producing large quantities of stellar wind the strong ultraviolet emissions from these stars stream through the atomic hydrogen within the nebula stripping off their electrons and ionizing the gas turning it into a charged plasma which emits a much broader range of detectable emissions we've observed a great many of these h2 regions dotted around our galaxy and in the rest of the universe the orion nebula being one such example but m33s h2 regions are unlike anything found in the milky way and are some of the largest and most starbursting clouds in the entire local group the spitzer telescope identified more than 500 discrete sources of infrared emission with an m33 during its operational years with the majority attributed to clouds like these the largest of which was so prominent that they warranted their own designations in john louis emile dreyer's 1888 new general catalog they are ngc 588 ngc 592 ngc 595 and finally ngc 604 ngc 588 and ngc 595 constitute large but diffuse star-forming nebulae on the outskirts of the triangulum galaxy [Music] ngc 592 also takes the form of a diffuse emission nebula and houses a 15 000 solar mass star cluster containing several volatile high metal wolf rayon stars with estimated ages of about 5 million years but none of these nebulae come close to rivalling the largest of all of m33s h2 regions ngc 604 in fact there is little in the local group that does at more than 1 500 light years by largest extension this cloud is more than 40 times the size of the orion nebula and is a staggering 6 300 times more luminous if it were to lie the same distance from earth as the orion nebula it would be the brightest object in the night sky by the moon observations of this region using the chandra telescope found it to be populated with bubbles of multi-million kelvin ionized plasma which are potent sources of x-ray emissions which help to highlight the nebula's composition the region shows a peculiar fragmented internal structure with a large bridge of gas separating its less active and massive eastern side from its much more massive and volatile western side where we find ngc 604's principal cluster it weighs more than a hundred thousand solar masses and contains over 200 blue variable and wolf rayet stars with scorching surface temperatures of more than 30 000 kelvin strong enough to ionize the entire nebula and drive it to the extreme scale that made its standouts to its discoverer william herschel all the way back in 1784 [Music] h2 regions aren't the only place where we find clusters in the triangulum galaxy either in fact we've identified at least 54 globular clusters within its bounds and about 70 more tentative candidates these clusters all appear to be many billions of years younger than the globular clusters of the milky way most of which formed rapidly little under 13 billion years ago whereas m33s clusters display almost the opposite trait its rate of cluster formation actually seems to have risen to its highest level in the last 100 million years possibly due to a recent inflowing of gas to its core the source of which remains unknown elsewhere in the galaxy we've actually been able to resolve some individual instances of its largest and most extreme stars m33 is home to many asymptotic giant branch stars the final phase in a low mass star's nuclear activity after the red giant phase researchers have used dozens of these stars to pinpoint m33s chemical past identifying their levels of enrichment to determine how the galaxy's metallicity has changed over time and thus we now believe that m33 has followed an inside to outpath of chemical evolution much like the milky way and andromeda in addition we've also catalogued slightly earlier phased large stars in the form of its red giants as the largest type of star in the triangulum galaxy these are the stars we have the best chance of resolving and as such they have been used to constrain estimates for the galaxy's distance by comparing the light from these stars to the red giants that surround earth whose intrinsic properties we know we can estimate a red giant's luminosity and then compare that to its apparent brightness from earth to give a rough estimate of its distance the results of which are in broad agreement that m33 lies between 2.7 to 3 million light years from earth we've identified other types of stars in the triangulum galaxy as well scientists have recently discovered many instances of blue variable stars an exceedingly rare type of late stage star which pulsates and varies drastically as it burns at ungodly temperatures the most significant of these stars is vhk83 also known as var 83 it is another luminous blue variable which lies on the outskirts of the galaxy and stands out despite its vast distance as being one of the most luminous stars we know of with a diameter of about 150 times that of the sun and a mass of 60 suns this star doesn't stand out in terms of its dimensions but with an estimated luminosity between two and a half and four and a half million times that of the sun it outshines every other star we've seen in the triangulum galaxy with surface temperatures believed to be as high as 37 000 kelvin one can only imagine the kind of catastrophic supernova that this star will cause when it reaches the end of its energy-generating cycle speaking of supernovae we found more than 130 signatures for the deaths of stars dotted around m33 it is estimated that a supernova occurs within the galaxy once every 150 years or so and thus we haven't been able to catch one in the act of exploding but we have been able to identify the nebulous remnants they leave behind thanks to their potent x-ray emissions both supernova nebulae and planetary nebulae which are left behind by asymptotic giant branch stars that don't explode can also be used as traces in the galaxy's chemical evolution and also as makeshift standard candles for constraining its distance supernovae often leave behind other sources of x-rays too namely neutron stars and black holes and while we haven't found any tangible evidence of the former within m33 astronomers were able to identify a black hole inside his bounds m33x7 is an x-ray signature that can be detected every three and a half days from earth indicative of a transiting black hole in a binary star system where the other component is a blue giant of 70 solar masses the black hole is the collapsed core of the star's binary twin and it's just under 16 solar masses it was the heaviest black hole of the type created by a dying star the tweet discovered at the time of course it doesn't come close to rivalling the colossal intermediate and supermassive black holes which lie at the hearts of clusters and galaxies but those didn't form via the collapse of a single star and for those that do m33x7 is exceptionally massive and must have been accreting mata for hundreds of millions of years on the subject of supermassive black holes what about the nucleus of the triangulum galaxy we know that most galaxies including the milky way and andromeda contain a central supermassive black hole more than a million times the mass of the sun so what kind of black hole is m33 hiding within its core well actually it doesn't seem like there is one not a supermassive black hole anyway unlike most spiral galaxies m33 lacks a stellar bulge in its core it doesn't feature a bar-like structure or any such region where the density of stars significantly increases instead lying at the core of the triangulum galaxy is yet another h2 region an ionized emission nebula containing an ultraluminous x-ray source ultraluminous x-ray sources are a class of extremely radiative intergalactic signal theorized to be the result of moderate mass black holes accreting material from their surrounding stars but crucially these kinds of signals are not associated with supermassive black holes and therefore it is unlikely that there is one within the core of m33 moreover astronomers have measured the random velocities of stars within a parsec of the center of the galaxy to search for signs of strong gravitational influences acting on their surroundings the higher the random velocities the stronger the force acting on these stars must be which would imply a larger black hole but instead scientists found that random velocities actually seem to decrease when approaching the innermost part of the galaxy's nuclear region this implies that if there is a black hole at the center of m33 it must be very small indeed the research paper in question proposed an upper bound limit of just 3 000 solar masses but some research takes this figure to be just half that for context we would expect to find more massive black holes within globular clusters around the milky way the majority of which contain only a few hundred thousand stars over a few hundred light years compared with this 60 000 light year galaxy containing 40 billion and so m33 is tangible evidence that galaxies don't need supermassive black holes to exist and that the size of a galaxy does not always correlate with the size of its nucleus however the size of a galaxy's central bulge of stars might well be linked to the size of the black hole nucleus which would explain why we don't see a substantial increase in stellar densities near the triangulum galaxy's core perhaps the lack of a substantial heart for the triangulum galaxy weighs in favor of it being a satellite of andromedas as we briefly touched on earlier the relationship between m33 and m31 is unclear and though m33 is an awesome little galaxy in its own right it may indeed be a child of andromeda in 2012 scientists confirmed evidence for a faint bridge of hydrogen which appears to connect the two galaxies this strongly suggests that they have interacted within the past two to eight billion years although this would have been a relatively minor pass by as opposed to a close encounter which would have left significant imprints on m33 structure however we now know that these two galaxies are destined for another more significant encounter in the next few billion years measurements of m33's radial velocity have shown that it is a blue shifted galaxy which is approaching the milky way at a speed of around 24 kilometers per second scientists believe that this is because m33 is either at the tail end of a very long orbit around andromeda or the more likely hypothesis is that it is beginning an infall into our galactic neighborhood this shouldn't come as a big surprise after all the andromeda galaxy is also known to be headed right for us our neighboring galaxies are so massive and close that they are able to reach out and attract each other despite the vastness of space slowly drawing the major bodies of the local group together into a final compound galaxy merger the head-on collision of the milky way and andromeda galaxies will make up the most significant part of this merger event ultimately combining to form a golden giant elliptical galaxy but where does m33 fit into all of this will it be sucked into the collision and absorbed as well will it survive the initial impact and continue to orbit as a satellite or will it escape the bounds of the local group entirely and float into intergalactic space the short answer is that we don't know but the long answer is that any one of these scenarios is possible what we do know for sure is that in around 4 billion years the milky way and andromeda will have begun their merger event fundamentally deforming their spiral structures and sending enormous gravitational reverberations cascading across the local group by this time there is an outside possibility that m33 may have already met its demise should its current in-falling trajectory bring it too close to m31 being smaller and less dense than both of its galactic neighbors any close encounter with either andromeda or the new galaxy it forms will shred m33 right down to its individual stars which would quickly be absorbed into andromeda and then the new galaxy however simulations of the local group's future lean more towards the triangulum galaxy getting involved towards the end of this merger event in the more likely scenario that m33's current in-falling trajectory guides it around the collision epicenter then it will most likely survive being absorbed in the interim at least in this case it may settle into an uneasy satellite orbit around the new elliptical galaxy such an orbit would probably result in m33 being consumed in the long run but this might not happen for tens of billions of years all the while whatever lies in the triangulum galaxy will be able to enjoy a spectacular bystander view of the milky way's collision or perhaps m33 may be able to escape being consumed altogether one final possibility is that as the triangulum galaxy comes back around in its orbit around the merger tidal reverberations from the epicenter may slingshot m33 on a trajectory out of the local group into intergalactic space by this time the universe's rate of expansion is expected to be much higher than it is today and so this ejection would likely prove irreversible m33 would be cast over the cosmic tide and may never encounter another galaxy again this may sound like a more favorable outcome for the triangulum galaxy but in the absence of tidal invigoration and gas supplementation catalyzed by galaxy mergers m33 would soon begin to exhaust its star-forming potential as it burns through the last of its gas and with no new stars being produced to replace old ones its body would begin to recede and shrink with its stars and planets becoming unbound and so ironically in this scenario the triangulum galaxy would simply die of old age probably well before the elliptical galaxy which now constitutes the entirety of the local group over the very longest cosmic timescales there are few happy endings but rest assured that in the event of any of these scenarios it's unlikely that m33 stars would actually meet their doom even if they are absorbed straight into andromeda or the preceding elliptical galaxy the chances of any one star actually colliding with another is remote at best and so whatever the outcome for m33 anything lying within the triangulum galaxy right now would almost certainly have more than enough time for its stories to play out with some spectacular nightly views lined up in the meantime you

Channel: SEA

Views: 739,981

Keywords: Sea, Space, astronomy, science, m-33, m 33, messier 33, Triangulum galaxy, journey, journey to the Triangulum galaxy, tour, galaxy, local group, milky way, andromeda, m 31, messier 31, ngc 604, h2 regions, h ii regions, emission nebula, nebula, red giant, asymptotic giant, agb, luminous blue variable star, wolf rayet star, smbh, black hole, m 33 x 7, stellar black hole, Milky Way and Andromeda collision, collision, galaxy merger, milkdromeda, milkomeda, spiral galaxy, pinwheel galaxy

Id: 6nCsGkbT8Es

Length: 32min 56sec (1976 seconds)

Published: Tue May 31 2022