Hubble Spies Dark Energy
The Hubble Space Telescope has been able to shed some light on the evolution and the eventual fate of the universe.
Though detailed observations of the galaxy cluster Abell 1689 the nature of dark energy has been more accurately studied.
Abell 1689 Dark Matter Map Credit; NASA; ESA; HST ;E. Jullo (Jet Propulsion Laboratory), P. Natarajan (Yale University), and J.-P. Kneib (Laboratoire d'Astrophysique de Marseille, CNRS, France)
This image shows part of the cluster with the overlay in blue showing the calculated distribution of dark matter.
Hang on you may be saying, when did dark energy become dark matter?
The answer is it hasn’t, but to fully understand dark energy you need to fully understand gravity and how it is affecting the space around the cluster, which requires an understanding of both dark matter and normal matter. Boy that was was sentence and and a half!
To get right back to basics, our universe so far as we can tell contains three kinds of ‘stuff’. ‘Normal’ or Baryonic (so called because it is made up mostly of Baryons by mass that is) matter, that by the way is the stuff you, me and all the stars in the universe are made of.
Then we have Dark matter, this can exert (create) gravitational ‘forces’ on normal matter like you and me. Though unlike you and me it can’t be detected by its effects of electromagnetic radiation, i.e. it neither emits any and doesn’t scatter\ reflect\refract any.
Though dark matter is not entirely undetectable, it still has a mass and so can exert gravitational effects on the normal matter stuff, like stars and galaxies. It was the rapid movement of stars around the edges of galaxies that lead to the proposition of dark matter. The galaxies didn’t have enough normal matter to ‘produce’ enough gravity to hold the stars in place and so the galaxies should be flinging itself to bits, as this clearly wasn’t the case a new idea had to be created to explain the observed movements. Enter dark matter. Dark matter can be used to explain why the stars weren’t escaping into space – with a higher total mass the galaxies had a stronger than predicted gravitational ‘pull’ (technically they have deeper gravity wells rather than stronger ‘pulls’, though the reason why is for another day) and so could hold on to the stars at the high speeds being recorded.
While this works wonderfully in theory (as all the laws of physics are preserved) there is a rather more complex issue. By accepting the idea of dark energy you have accepted the idea that only around 20% of the ‘matter’ in the universe (in fact it is a bit less) is observable and is made up of the same stuff you and I are. The remaining 80% of matter in the universe is dark energy which for some has just been ‘invented’ to make the job of astrophysicists a bit easier and who are understandably sceptical of the idea that ‘normal’ matter is the minority.
This huge difference in proportions is due to the galaxies being a lot lighter than they ‘should’ be and it takes this rather large amount of dark energy to balance the scales if you will. The dark matter sceptics point out that perhaps it is our understanding of gravity that is to blame for the rather bizarre results rather than the effect of a illusive ’material’. You can look at this point of view in a mathematical sense – If we know the answer i.e. the observational result about the rotational speed of the stars, but cannot get that result through our calculations, after they have been checked for numerical errors a logical conclusion would be that some of our input values are wrong – i.e. we have accounted for all the visible matter but not the dark matter so our input for total mass should be increased accordingly. Once the mass of dark matter has been calculated and used in the equation if we obtain the observational result it is logical to assume we were correct in our addition of dark matter. This is the though process adopted by the dark matter supporters.
Whilst the above reasoning is perfectly sound it is only sound from that point of view and there is an equally reasonable way of looking at the problem.
Lets go back to our problem starting in the same place. We know the answer but can’t obtain it through calculation. We know our measurements are reliable and accurate to an appropriate degree. So you can view that it is not the inputs that are to blame but the operation - or what we are doing to the inputs that is to blame. For example we have the inputs 2 and 3 and we know the answer is five. We must deduce how to get to the number five from the numbers 2 and 3. I can multiply 2 and 3 together and get 6, no matter how many times I try the answer will always be 6. Now in this problem the solution is simple I should add the two and the three to give five, and in real terms the solution is much more complicated of course but the basic principle is the same. It is not my observational values on the amount of mass in the universe that is wrong but what I’m trying to do to those observations to match the observations on the rotational speed of the stars around galaxies. Meaning that it is my understanding of gravity that is to blame (by my I mean the current scientific understanding of gravity not my own which is sadly quite limited).
Without evidence to disprove one of the thought processes above both are equally valid.
Still with me? Good.
Now for value three – dark energy. The common ground between dark matter and Baryonic matter is that both exert gravity and are affected by it. This means that individual particles like (on a big scale) to be pulled together into large structures (spheres if you are curious). Dark energy doesn’t – it is the hypothised mysterious entity that is overriding gravity’s hold and is causing the universe to expand.
Of all the stuff in the universe Normal matter forms around 5%, dark matter around 23% and the rest is dark energy.
With these new observations – and assuming dark matter exists and that our notions about gravity aren’t wrong - suggest that the universe will continue to expand ‘forever’. This is obtained by careful studing of the light that has been ‘lensed’ around the galaxy cluster (bent isn’t technically the correct way to describe it as, as far as the ‘light rays’ (photons) are concerned they have travelled in a straight line, again that is for another day 
). This light is from galaxies many millions of light years behind Abell 1689 but is still detectable.
Abell 1689 Credit SDSS
As these results suggest that the universe will expand indefinitely it allows us to create a provisional end chapter to the life of the universe. As there is a fixed amount of matter in the universe (again not strictly accurate – there is a fixed amount of energy in the universe the ‘amount’ of matter changes constantly – yes that is for another day too) eventually there will come a time where the hydrogen gas is too spread out to allow new stars to form. The universe will continue to cool as it has been doing since it was formed, it will also start to dim as the amount of stars being produced drops below the rate of stars dying giving a net decrease in the numbers of stars present. Eventually the last star will ‘wink out’ and the universe will be a cold dark place. Actually even that is not the end of the real story but all you get to read about today
Before some people leave this post thinking ‘we are all doomed!’ that is not something you have to worry about just yet. Our star, the Sun has got another good 5 billion(ish) years left in it and stars will continue to be form long after our star fades from view. Like nearly all things at huge scales this process will be slow and very gradual but the universe will eventually, many billions of years in the future a very big barren space.
Read more here
Image of the Week – A shocking Image – 3/09/10
The latest Hubble image of SNR 1987A Credit NASA, ESA, K. France (University of Colordo, Boulder), and P. Challis and R. Kirshner (Harvard-Smithsonian Center for Astrophysics)
I recently produced a post detailing the results of the latest ESO observations of the SNR 1987A (you can view my post here and the ESO article here) .
A team working with the Hubble Space Telescope have imaged a debris ring surrounding the more concentrated debris from the supernova event itself.
This debris is thought to have come from a precursor outburst around 20,000 years before the star finally blew itself to bits. The debris has expanded colliding with the interstellar medium and heating it up in the process. Currently this has created a ring of between 30 and 40 ‘hotspots’ – areas of the medium that are particullary hotter than average. These hotspots glow brightly and are clearly visable in the image.
Current ideas about the evolution of supernova remnants suggest that the hotspots will expand as the age and merge together to form a complete ring around the detonation site, though only time will tell – as this type of long term interactions are difficult to predict for example the medium may be slightly denser causing the expansion to slow on one side and giving an oval, again only time will tell.
To learn more about supernovae remnants try here
Read more about this latest image here
The Dusty Mysteries of NGC 4696
NGC 4696 credit: ESA/Hubble and NASA
This is NGC 4696, an ancient ball of old and dying stars 150 million light years away. This elliptical galaxy lurks in the Centaurus Galaxy Cluster.
It has a wonderful ‘S’ shaped lane of dust winding its way for 30,000 light years around the nucleus of the galaxy. This dust lane is also home to wispy clouds of hydrogen that has been ionized, which is electrons being knocked off of an atom by, say, ultraviolet radiation for instance, making the atoms Ions.
Right in the centre of the galaxy lies its supermassive black hole; unlike a high percentage of galaxies in the universe it is active and drawing in material from around it, surrounding itself with an ‘accretion’ disk of material such as stars, gas and dust. This material while on its one-way trip down into oblivion creates friction as it rubs up against other material in the disk; this releases massive amounts of radiation in the shorter – and very energetic – wavelengths of the electromagnetic spectrum, such as gamma rays, ultraviolet and x-rays. The magnetic field being generated at the nucleus forces radiation out as jets of plasma travelling relativistically – meaning near to the speed of light – along the poles of the black hole, these jets can stretch out for thousands of light years!
Now I can’t resist a bit of speculation, so far I haven’t read anywhere about the ionized hydrogen in the galaxy being linked to the active supermassive black hole, is this indeed the case? Could the radiation being emitted from the black hole have ionized the hydrogen? If anyone could shed any light on this please comment!
That scenario reminds me of a lovely collection of galaxies we have at Galaxy Zoo called the Voorwerpjes. The clouds of gas in these galaxies – which are also host to active super massive black holes – are ionized and lit up by the radiation these galaxies are being bathed in by their active nucleus, showing us amazing views of filaments of hydrogen gas stretching for in some cases 90,000 light years across!
Voorwerpjes; Credit: SDSS
Back to NGC 4696, whilst reading up on if this is the case I came across an interesting paper published in 1982 by H.E Jorgensen and H.U Norgaard-Neilsen in the ESO’s journal. It mentions some interesting things going on inside the galaxy in the areas where the dust lane lies. . .
Between the galaxies in the central part of any galaxy cluster is the intracluster medium, this is comprised of plenty of ionized gas, mostly helium and hydrogen, which emits plenty of x-rays in the process. This medium has a temperature of 10-100 megakelvins, which is 10 million and a hundred million degrees celsius respectively; so it’s pretty hot stuff!
According to this paper, as NGC 4696 speeds through this medium the gas in the galaxy, specifically around where the dust lanes are, have been squashed together. Also, the medium itself as it is cooling is falling onto the galaxies at the centre of the cluster.
You can read more here!
Hannah
Mergers at Massive Scales
Collisions are powerful events; from the small scale the devastating results of car crashes, moving to the slow yet unstoppable collisions of tectonic plate creating or destroying pieces of the Earth’s crust. Even more powerful are the collisions of a forming planet (or planetesimal to be fancy) and another within a forming solar system. We don’t even have to look very far to see the effects of such collisions – our Moon is believed to be the result of a collision between the Earth and a Mars size body early in its formation. The Moon is not the only example of such a collision in our Solar System, Uranus odd orbital tilt is believed to be a result of a collision between it’s forming self and a rocky ball estimated to be similar is size to the Earth!
You can read an interesting article on the nature of dust in close orbiting binary stars here. How is this related I here you say? To give the short version, new observational evidence suggests that at least some of it comes from obliterated planets that were thrown about by the twin star’s gravity.
Whilst planetary (well if I’m pedantic my examples above would have involved proto planets) collisions are important and significant in the ‘local’ scale of a solar system there are other collisions out there that have much more far reaching effects.
In galactic mergers (that is when two or three galaxies get gravitationally entwined with each other), entire galaxies can be dragged through one another, spat out again or completely torn apart. An example of a galactic merger would be SDSS 587726033843585149 (better known on the Galaxy Zoo forum as Alice’s Penguin )
SDSS ID 587726033843585149 - Alice's Penguin
What is important to understand with these styles of mergers is that it is not actual stars and planets that colliding but it is the mergers and disruption of the large scale structures through gravitational interactions that contain the individual stars themselves.These affect the galaxies involved but there is an even larger kind of merger that affect whole groups of galaxies; to be more specific galactic cluster mergers.
The galaxy cluster Abell 1758 (which is located around 3.2 billion years away from us) has been shown in a new way with the use of combined data from NASAs X-ray Chandra telescope, the Giant Metrewave Radio Telescope (GMRT) and the Digitized Sky Survey (DSS) which sees the sky much the same way we do i.e. in visible light (The DSS should not be confused with the SDSS – Sloan Digital Sky Survey).
The combined data produces this image: -
The Chandra data which shows high energy photons showing lots of activity within the galaxy cluster. The Optical data is shown in yellow\orange\gold and plots the base position of the galaxies and visually close stars. The Red radio data in the most interesting however as it shows that the cluster has ‘radio halos’.
Abell 1758 is actually the result of the merger of two smaller galaxy clusters, is still in the process of merging and throwing matter around within itself like a tantruming toddler, this tantrum gives itself away as the ‘cloud’ of x-ray emission surrounding the cluster.
This image was created as part of a survey of 31 galaxy clusters, the results of which allow us to gain a better understanding of the processes behind the construction of galaxy clusters. Of the galaxy clusters surveyed some had the ‘radio halos’ (those that there were still forming vis the absorption of gas) while those that have finished forming lack these features. As the large galaxy clusters form through the mergers of smaller ones understanding the merger processes that drive their creation will help us better unsterdand how individual galactic mergers progress an visa versa.
Galactic clusters are the largest gravitationally bound objects in the universe and understanding them would be a big step forward in achieving a greater understanding of the universe.
Read more here
Now THIS is a Solar System
Astronomers using the ESO’s Very Large Telescope (VLT), specifically its HARPS (or the High Accuracy Radial velocity Planet Searcher if you prefer) have made a very interesting analysis of a star system not to far removed from out own.
An artist's impression of the planets surrounding HD 10180 Credit: ESO/L. Calçada
You can see a range of larger image sizes here
The star that has been the centre of the investigations is a star similar in size and mass to our own sun that goes by the ‘name’ HD 10180 (it is in fact a G1V star which makes it slightly less massive than Sol).
The star is quite close in universal terms lying just 127 light years from Earth in the constellation Hydrus (not to be confused with Hydra).
Close up of HD 10180 Credit ESO and Digitized Sky Survey 2. Acknowledgment: Davide De Martin
HD10180 is the bright star in the centre of the image. As this was collected from several exposures and then layered together image processing ‘artefacts’ have unfortunately been introduced – they have manifested themselves in this image as the bright white line coming from the star and the blue and orange halos.
The data collected by no less than 190 separate HARPS observations the tiniest motions of the star were plotted. This process relies on the gravity of the planets surrounding the star to make it ‘wobble’. This process finds detecting high mass planets orbiting close to their parent star easiest as they have the the largest gravitational influence and so cause the biggest wobbles.
When the data set was complete and the analysis began it was clear that the star’s backwards and forward motions in space were caused by at least five planets tugging this way and that way as they orbited the star. I say at least five as seven gravitational signals were detected as a two further less obvious weaker signals were also detected, these may very well be planets, however as there is a slight margin for false detection (less than 2%) they have not yet been confirmed though for the rest of this post I assume the detections to be correct.
Even with five planets in its system it is already has the joint largest exoplanetary system, a title it ‘shares’ with the star 55 Cancri.
The two other signals are weaker for two different reasons. One of the signals corresponds to a Saturn like planet with a mass of at least 65 times that of the Earth. That may should like enough to create a strong pull on the star one that should be easy to detect. If the planet was closer to the star it would certainly give a large tug. Unfortunately it sits further out from the star than the Neptune like worlds (its orbit take around 2200 days which makes its average distance from its star as around 3.3 AU – as calculated by Wolfram Alpha)
The second signal is even weaker, not because it is further away quite the opposite in fact, but because of its low mass. A mass that has been calculated at around 1.4 Earth masses. This potentially puts it in the bracket of the types of planets that could support life as we know it. At omitting one detail it looks pretty perfect. Its about the right size – large enough to hold an atmosphere but not large enough to squash everything into pancakes with a ridiculously strong gravitational field. It is in orbit of a nice sun like star: – not one prone to undergo random bursts of radiation spikes like some red dwarfs (these are a sub ‘class’ of red dwarfs called flare stars) and not belching out ultraviolet radiation to turn the planet into a global sunbed, nor is it likely to go supernova blowing up with enough force to vaporise everything nearby.
Before you go and pack for your extrasolar holiday you may want to know about that one little detail. With its parent star being slightly less massive and thus slight cooler a habitable planet should be slightly closer in relative to Earth’s orbit around the sun …
Unfortunately this world sits rather closer than required … ok a LOT closer – it orbits at just 2% the distance the Earth does or (0.02 AU)
Its safe to assume that temperatures on the surface would not be pleasant, hotter than Mercury without question. Best unpack then. Being so close to a star gives more than an oven like temperature, sitting so close to the star means that the planet has a phenomenally short year in this case only 1.18 Earth days!!!
Despite being the least massive exoplanet yet discovered and the most ‘Earth like’ in that respect, it is still along way off from a ‘Garden World’ that would be pleasant, or even safe for us to venture outside our space ship. it does however mark a giant leap forward in exoplanet detection and with a few years it is expected that the first Earth mass planets will be detected with the more moderate temperature band around a star somewhere near by, that who knows could be our first extrasolar life bearing world only time will tell…
A beautiful video showing an artist’s impression of moving wards through the system starting with the third planet.
Credit: ESO/L. Calçada
You can read more about the system here
ESO/A. Fujii/Digitized Sky Survey Music: John Dyson (from the album “Darklight”).
Image of the Week – The Cosmic Rose -27/08/10
NASA’s WISE observatory has captured this beautiful image of the Rosette Nebula.
The Rosette Nebula Image credit: NASA/JPL-Caltech/UCLA
The Rosette Nebula is located within the Milky Way at a distance of between 4,500 and 5000 light years from the Earth and is also known as NGC 2237.
It surrounds the young star cluster NGC 2244 which can be seen as the bright smudge in the centre of the image.
The nebula is a large cloud of hydrogen gas and dust that is forming new stars, the largest of which produce enough radiation in the form of ultraviolet light to blow the gas away from the centre of the nebula creating the central void. This radiation ionises the surrounding nebula and causes it to emit its own light and in doing so become visible.
The Rosette Nebula is located with the constellation Monoceros- the Unicorn.
It is visible using a set of good binoculars or a small amateur telescope.
Its central star cluster has been known to astronomers since its discovery by John Flamsteed in around 1690, the nebula itself was not identified for another 150 years (due to its fainter nature). It was finally discovered by John Hershel the son of the more famous William Hershel. himself famed for the discovery of infra-red light – fitting as this image has been captured using infra-red light.
The green streak in the bottom left of the image is a satellite trail – the path a satellite trail took as it moved across the field of view as the image was being taken.
Read more here
In the search for E.T should we be looking for artifical intelligence instead?
SETI, the search for extraterrestrial intelligence has so far been searching for radio signals coming from worlds like earth, but recently some astronomers at SETI one of which who is called Dr Seth Shostak has said that the time for aliens to develop radio technology and AI (artificial intelligence) would be short and that the odds on SETI finding alien life are in favour of finding AI rather than biological life.
Many scientists involved in SETI have been saying for a long time that nature will have most probably solved the problem of life using different chemicals or designs and that not only would alien life not look like us but also that it might not at a biological level even work like us. However most of the SETI scientists agree that alien life would be ‘alive’ in sense that we know it, e.g they would be sentient, be able to reproduce and also have to consume solids and liquids to survive.
But other scientists believe that if our civilisation and the way in which we are advancing technologically is anything to go by then it is highly likely that any alien civilization that have been able to broadcast radio messages into space would very soon after be able of creating thinking machines or AI. Although Dr Shostak does admit that decoding any messages we may receive from alien AI would most likely be more difficult than decoding messages from biological aliens.
This idea of alien AI does provide scientists with new places to look in the search for alien life as Dr Shostak says that AI would mostly want to live in places where both energy and matter are in abundant supply as he believes that these two things would be the only things of interest to machines. this means that SETI may need to focus some of its attention near hot young stars or towards the centre of the galaxy and in globular clusters where the conditions for bilogical life are very hostile but where artificially intelligent aliens may be hanging out.
The large Allen Telescope Array is one of the many radio telescope Arrays scanning the heavens for alien signals Credit: SETI
We know how black holes form. Don’t we …?
Recently it seems the more we look into the stars and galaxies that populate this universe, objects we used to thing we had figured out quite well, it has become clear that we are not as educated in the workings of the cosmos as we once thought.
The Mystery Magnetar Credit: ESO
The basic results of star death have been thought to be rather simple. A low mass star, that is one with less than about 10 solar masses forms a white dwarf a medium mass star between 10 and 25 solar masses go supernova and leave behind a neutron star\pulsar. The high mass stars (those above 25 solar masses) also go supernova and create a black hole from their cores’. (The most massive stars are actually theorised to explode and leave nothing – the explosion is so forceful it vaporises the entire star – such an explosion is known as a pair instability supernova but that is for another day).
Astronomers using the ESO’s Very Large Telescope (VLT) have made a very interesting discovery while surveying the super star cluster Westerlund 1, that once again shows that perhaps we don’t know as much as we thought we did. Westerlund 1 is the closest super star cluster to Earth yet discovered, it lies between 3.5 and 5 kiloparsecs (or somewhere between around 11,500 and 16,500 light years if you prefer) away in the southern hemisphere constellation Ara – The Altar.
You may be wondering while the distance figure is less than accurate, unfortunately it is down to the distance being measure itself. It is so far for the more accurate parallax measuring system to be used and so other methods must be employed. These methods can give different results based on different conditions hence the rather large estimate range. Despite this the rough estimate puts the cluster at the outer edge of the Milky Way’s galactic Bar which may go someway in explaining how the cluster grew to such proportions – it contains many high mass stars including a large number of highly evolved supergiants.
The cluster can be seen in its full glory in this annotated image from the ESO’s VLT.
Westerlund 1 Credit: ESO
A larger version can be viewed here.
The labelled magnetar is the star of particular interest in this marvellous cluster. A magnetar is a type of supernova remnant; specifically a neutron star with an incredibly strong magnetic field many thousands of times more powerful than the Earth’s own magnetic field, they are very rare as only a handful have been identified in the Milky Way.
The cluster contains stars that formed in a single formation event over a short period of cosmological time between 3.5-5 million years ago. Using this age figure calculated from the rate of stellar evolution in stars of different masses – the more massive a star is the faster it dies, thus the age of the cluster can be determined by measuring the highest mass star in the cluster (this has been achieved by carefully studying binary systems which allows for the mass of the stars to be accurately measured by detecting stight changes in their orbits). This puts an upper limit on the age of the cluster because had it been any older this star to would have gone supernova.
Neutron stars as I stated above are thought to form from ‘progenitor’ stars of between around 10-25 solar masses. Based on age estimates on the cluster (as detailed above) the magnetar’s parent star weighed in at least 40 solar masses! This means it was well above the mass of a star that was thought to collapse into a stellar mass black hole. Whilst the limit is be no means exact, a star that is almost double the rough limit is very unusual and very interesting.
Whilst no one is quite sure how a magnetar forms as apposed to a ‘normal’ neutron star, it does still have the same basic structure and they are still subject to the gravitational forces that formed them and are constantly trying to crush them further into a black hole. As this has clearly not happened in this case, this single star presents a rather large problem. Some may be quick to say that the accepted mass limit for neutron stars in obviously wrong.
However, as this star seems to be the exception to the rule rather than a common occurrence, perhaps it is circumstances that are to blame, rather than a flaw in our understanding. If the parent star had been contained in a binary system its partner may have removed sufficient mass via mass transfer and accretion and in doing so lowered the mass sufficiently to avoid the total gravitational collapse of the star into a black hole.
Though this idea creates a number of questions too, where is the companion star? As far as we can currently tell the magnetar is alone with out a binary partner though it is quite possible that the force of the supernova detonation blew the pair apart, this helps to explain why the magnetar is on the outer edge of the cluster. Though a massive amount of material would have had to be removed, which makes it a difficult idea for some to accept. Perhaps one day we will know for certain, finding the star’s partner would certainly help.
Who knows the next big discovery could be just around the corner.
I leave you with this artist’s impression video of travelling through the cluster to the magnetar.
Video credit to ESO
Read more about the discovery here and more about black holes here
Image of the Week – 20/08/10 – The Galactic Volcano
Due to the website maintenance this post is a day late. I apologise for the delay.
This image is a combination of data from the Chandra X-ray ( shown in blue) observatory image and one captured in the radio section of the electromagnetic spectrum by NSF’s Very Large Array (VLA) (Shown in red and orange).
The Galactic Volcano Credit X-ray (NASA/CXC/KIPAC/N. Werner, E. Million et al); Radio (NRAO/AUI/NSF/F. Owen)
They show the galaxy M87 an Elliptical galaxy located 55 million light years away in the Northern Virgo Cluster. It contains a well studied AGN (Active Galactic Nucleus) and is one of the most ‘radio loud’ objects visible from Earth.
The below image shows only the Chandra data
Chandra Image of the Galactic Volcano Credit: X-ray (NASA/CXC/KIPAC/N. Werner, E. Million et al)
The cluster containing M37 contains lots of hot gas and dust (this can be seen in the outskirts of the Chandra only image.) Under normal circumstances this material would ‘fall’ under the influence of gravity into the galaxy, cool and form new stars.
The combined data shows that this is not the case with M37 however; its central supermassive black hole has other ideas for the in-falling matter. The black hole has powerful jets blasting into space these pass on some kinetic energy to the cooling gas and dust near the centre of the galaxy and through it into space at supersonic speeds as the plumes of gas visible in the combined image.
This has been compared to the recent eruption of the Icelandic volcano Eyjafjallajokull, which caused significant air travel disruption across Europe. The similarities are not the two effect on humans as M37 is far to distant to have any tangible effect on the Earth or any part of the Milky Way for that matter. In the eruption hot volcanic gasses created at the local site of the eruption threw ash particles high into the atmosphere and allowed them to travel for several thousand miles. This is not unlike the hot x-rays produced by the central black hole ‘uplifting’ the cooler material and carrying it far into space.
To conclude here is an annotated version of the image showing the location of the plumes and black hole in relation to the rest of the image.
Labelled Image of the Galactic Volcano Credit: X-ray (NASA/CXC/KIPAC/N. Werner, E. Million et al); Radio (NRAO/AUI/NSF/F. Owen)
To read more about black holes click here
To read more about this particular galaxy and black hole click here
Image of the Week – The Undead Galaxies – 13/08/10
Astronomers using NASA’s Galaxy Evolution Explorer and the Hubble Space Telescope have made a remarkable discovery, galaxies that have returned from the star formation grave.
Ultraviolet rings surrounding aged galaxies. Image credit: NASA/ESA /JPL-Caltech/STScI/UCLA
The story began with the Galaxy Evolution Explorer’s ultraviolet scan of the night sky, in which it discovered 30 elliptical and lenticular galaxies – generally devoid of hot young stars that produce large amounts of ultra violet light and are also known as early- type galaxies - that were particularly luminous in UV. The Galaxy Evolution Explorer lacked the resolution to identify any detail on the identified galaxies, in essence it could tell that the galaxies where ultraviolet luminous but not why or if there was any features within the galaxies themselves. To pick out the finer details astronomers turned to the Galaxy Evolution Explorer big brother Hubble.
Hubble produced images (a few of which are shown above) of the galaxies and revealed huge ring like structures within around 75% of the galaxies in question, whilst showing that the galaxies themselves contained mostly old ageing stars as you could expect from a more standard early- type galaxy.
This means that the galaxy had aged as usual ending their star formation and becoming ‘red and dead’. Later they must have received a new supply of gas and dust that allowed star formation to begin a new. This second ‘starburst’ is what created the ring as new high mass ultraviolet producing stars were born.
In a few of these galaxies’ it is likely that an ultraviolet echo is visible left over from the galaxies first star producing phase but this cannot explain the bulk of the phenomena. Some of the rings are large enough to encircle a galaxy several times larger that the Milky Way, others even show hints of other structures.
The question now facing astronomers is how this material was delivered into the ageing galaxies; currently there are two main ideas – either a galactic merger or the galaxy simply sucks up enough gas from the interstellar medium to ignite a new burst of star formation.
Proponents of the merger scenario point out that a merger could produce the ring structures observed. Others are just as quick to point out that such a merger needs a precise alignment and so would be exceedingly rare.
All astronomers agree that more detailed observations are required to end the debate. These new observations will look for finer structures within the rings and attempt to detect clouds of hydrogen alpha (a particular type of ionised hydrogen) than marks star formation.
Read more here
