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
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 – 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
The Tarantula Nebula – like you have never seen it before
Astronomers working with the ESO’s VISTA (Visible and Infrared Survey Telescope for Astronomy) telescope have produced this stunning image of the Tarantula Nebula in the Large Magellanic Cloud.
Tarantula Nebula as seen by VISTA Credit: ESO
For a larger image click here
The Large Magellanic Cloud is one of the Milky Way’s satellite galaxies. It orbits the Milky Way and is very close to Earth, in universal terms at only 160,000 light years away. It like its cousin the Small Magellanic Cloud, is an irregular dwarf galaxy that has been caught in the gravitational influence of the Milky Way in the same way a moon orbits a planet only on a much larger scale.
The LMC is host to the most active region of star formation in the Local group – Doradus 30 or the Tarantula Nebula.
The nebula itself is around 650 light years across and contains a dense star cluster at its centre R136. This cluster is only around 35 light years in diameter but contains 450 000 times the mass of the sun! At its core there are a tight group of 13 gigantic stars including R136a1 – the largest and most luminous star yet discovered by astronomers at around 265 solar masses and at 10,000,000 times more luminous than Sol (look out for another post on this monster that will be coming out soon 
). This star cluster is the bright area near the centre of the main nebula in the above the image.
It is this cluster that provides most of the energy to make the nebula visible. In fact the nebula is so luminous that if it was placed at the same distance from Earth as the Orion Nebula (the closest star forming region to us) it would cast shadows!
The Tarantula nebula is not the only interesting feature captured in this VISTA image. Some of these features are captured in this composite image of the most interesting areas of the main image.
Extracts from the VISTA Magellanic Cloud Survey view of the Tarantula Nebula Credit ESO
Top right is the amazing supernova remnant SN 1987A which looks rather insignificant in this wide field shot however I assure you it is not. If you would like to read more about SN 1987A try reading this post.
Bottom left is the globular cluster NGC 2100 which is still young for a globular cluster. It lies east of the Tarantula nebula, and may soon have a new neighbour globular cluster in R136 which given its high density and mass is expected to from into a globular cluster as it develops.
Finally in the bottom right are NGC 2080 or The Ghost Head Nebula and NGC 2083. The Ghost Head Nebula is a star forming region and has been captured close up in this Hubble Space Telescope image.
NGC 2080 Credit: NASA; ESA; HST
NGC 2083 is an emission nebula\star cluster and thus is emitting its own light making it visible to the survey.
These features can be seen in relation to the main image here on the annotated version.
The image have been collected as part of the VISTA Magellanic Cloud Survey (VMC), which intends to cover an area of the sky roughly the area of 1000 full moons in an effort to fully map the complete Magellanic system (both the LMC and SMC). With the hopes of obtaining a complete knowledge of the structure of the system and the areas star formation history. The survey is expected to take the first five years of VISTA’s observational life.
The survey captures images in the near-infra red bad of the electromagnetic spectrum which allows it to cut through the majority of the dust that normally obscures young stars and other interesting objects from view in the visible spectrum.
VISTA is an ESO telescope housed at the Paranal Observatory in northern Chile, and is the World’s largest survay telescope.
Read more about the images here
and read more about VISTA here
That isn’t an explosion … THIS is an explosion!
Astronomers working with the ESO’s Very Large telescope (VLT) have made detailed observations on a supernova.
Supernovae, the final explosions for dying high mass stars, are relativity common in the universe with at least one occurring somewhere in the universe every second, this figure may be an underestiate on the true number of supernovae as the figure could be closer to 3 suaernovae per second!
Despite their apparent frequency supernovae generally occur rarely in any one particular galaxy with long gaps in between bursts. This is not always the case though particularly in starburst galaxies in which large numbers of high mass stars are created and die in a short period of time.
These new observations are for SN 1987A and allow us to see the debris in a way never before achieved – in 3D.
The video below shows the structure of the debris in wonderful detail. This is an ESO video and more information on it can be found here.
The video shows everything from the outer most layers of the explosion moving in closer and closer towards the centre becoming a more and more hostile place as it does.
In fact it is the innermost area of this supernova that is particularly interesting. As can be seen near the end of the video, the central debris is deformed and unsymmetrical - it bulges out more in one direction than the others.
This kind of detail is only possible to obtain as the VLT has such high resolution and the supernova’s relative proximity to the Earth. At ‘only’ 168,000 light years at the edge of the Tarantula nebula in the Large Magellanic Cloud, it is the closest observed supernova since the invention of the telescope and was first observed as its name suggests in 1987.
The new observations allow astronomers to conclude that the supernova was more powerful in one direction - hence the outward bulge. This agrees with the more recent computer models on the development of supernovae explosions. However the direction of the bulge disagrees with the what the models expect in relation to the other debris so it seems the models aren’t perfect just yet.
Another interesting fact about this supernova is that it was the first to have been preceded by a detectable neutrino radiation pulse. Neutrinos are a type of subatomic particle and are produced in HUGE numbers at the very start of a supernova. Models predict that as much as 99% of a supernova’s energy can be released in a neutrino surge. The first detection of such an event bodes well for this theory.
A final interesting anomaly with this supernova is that its missing its neutron star. As star that created the supernova is believed to have been a B3 supergiant, the result of the supernova should have been a a neutron star but as of yet no such object has been detected. A number of ideas have been put forward, one is that the neutron star is there but is shrouded too deeply in gas and dust for us to detect it. The second idea is that enough matter fell back onto the neutron star after the supernova that it further collapsed into a black hole hence its absence. The third idea is that the star collapsed into a more exotic for of star – a quark star.
For the moment it is impossible to know which one of these ideas is correct or even if any of them are! Hopefully one day we will reveal all this explosion’s secrets.
The Antennae Galaxies
NASA has just released this beautiful image of the Antennae Galaxies.
The Antennae galaxies - Credit: NASA, ESA, HST, Chandra, Spitzer
This image is actually a combination of several images taken by several space observatories over several years. The image shows data from the Chandra X-ray Observatory (shown in blue), the Hubble Space Telescope (shown in gold and brown), and the Spitzer Infra-red Space Telescope (visible in red).
The Antennae Galaxies are in the process of merging to form one large galaxy. They are located around 62 million light years away from the Earth and take their name from feathery arm like structures visible in wide shots of the area. These were caused by gravitational interactions between the two galaxies throwing material into space as the two merge.
The two began merging around 100 million years ago and the process is still ongoing. The merging of two galaxies is a long process that causes many changes with the galaxies themselves and completely changes their structure. Gravitational influences compress huge volumes of interstellar dust and gas creating a wave of star formation which can spread all over the galaxy. Some of the gold and white areas of this image are areas of intense star formation. Such a wave of star formation bears a heavy price for the galaxies involved. Most if not all of the star forming material is used up in the ‘Starburst’, this in turn means that the galaxies star formation can come to a quick end, never to be rekindled.
As in all galaxies high mass stars are formed and die very quickly in merging galaxies, they explodes as supernovae and distribute a huge amount of mineral wealth enriching the surrounding area and providing the dust that can form planets. In the Antennae galaxies a large portion of this debris is still hot enough to produce large amounts of X-ray radiation and so can be picked up by Chandra and shown in blue on the image.
The areas of red are the warm star forming regions of the galaxies. Unsurprisingly the most active areas are in the overlap between the two galaxies, showing the beginnings of a potential starburst that is yet to spread to the main galaxies, yet millions or stars have already been formed.
The bright points of light are actually produced by black holes and neutron stars accreting and absorbing matter, the matter becomes extremely hot and emits large amount of radiation before finally becoming absorbed. Some of the black holes may have as much as 100 times the mass of the sun.
Our galaxy may seem dull in comparison but it may one day be just as chaotic. In around 4.5 billion years the Andromeda galaxy may collide with the Milky Way (our galaxy) with the results being just as spectacular. However the two galaxies may miss each other, or brush close past it is currently impossible to tell. The effects on the Solar System are not something to be concerned about as any chance of direct effect of the system itself is very remote, though it may be flung out of the galaxy completely. It is probable by this time that the Earth will have been uninhabitable for billions of years due to the increasing warmth of the sun. In any case it is not something to be concerned over .
Read more about the Antennae Galaxies here
Image of the Week 06/08/10 – WR 22
This week’s image comes from the ESO, and is of the star WR 22 and its surroundings.
WR 22 Credit ESO
The image was captured by the ESO’s La Silla Observatory in Chile.
The main focus of the image is the star WR 22 which is in the heart of the image. For those of you with some knowledge of how stars of named may have deduced that this is a Wolf-Rayet star. If you have you are correct. For those readers who are unfamiliar Wolf-Rayet stars, they are bright blue giant stars that are sheding vast quantities of their atmosphere into space in a vain attempt to remain stable. Soon enough Wolf-Rayet stars detonate as supernovae. They are spectral class W stars and can be designated by WR followed by a number.
This particular star is located in the Carina Nebula (NGC 3372), the same nebula that houses the monster star Eta Carinae. It is around 5000 light years from Earth and can sometimes be seen with the naked eye if conditions are good. As the nebula’s name suggests it can be found in the Southern Constellation Carina.
WR 22 is around 70 times the size of our sun and is located within a binary system.
As well as the star itself this image contains some of the surrounding nebula, containing mostly hydrogen that has been ionised by the harsh ultraviolet light of nearby high mass stars including WR 22 (this is shown as pink in the image). The nebula also has darker, denser, dustier regions that may be forming new stars within, some of which can be seen in this image.
Finally – Thanks to Alice who stepped in to do last week’s IOTW whilst I was on holiday and did a marvellous job 
.
Magnetic Magic – Introduction
The sun, Sol, the most influential of the forces that affect our planet. The sun’s influence is far deeper than just the visible light it provides us to see. Deeper even than the role it plays in providing the light plants need to photosynthesize and in doing so producing the essential oxygen and sugars for the rest of the planet’s life.
The Sun and Clouds Credit Thai Jasmine
This is a series of posts focusing on our nearest star and all its wonders.
The sun like all stars releases a constant stream of charged particles along with a vast quantity of photons (the ‘particle’ of light). Combined this equates to the sun releasing four million tons of material per second – the mass of the average Supertanker here on Earth. Despite this vast amount of mass loss it equates to just 0.1% of the sun’s total mass since its birth around 4.5 billion years ago.
This series of posts concentrates on the charged particles being thrown out of the sun rather than the photons.
What follows is a list of the areas covered by the series.
What exactly is the solar wind, and how is it formed?
How far does it travel into space?
What happens where it stops and why does it stop?
Can it change over time and is it always the same?
Can it affect the Earth, and the other planets?
The project is a collaboration by PeterC and HannahH
Please Note – The project is on hold until the completion of Project Nebula and Project Galaxy.
The Exiled Star
As described in binary stars blitzed many of the stars in the universe are found in binary (2 stars) or multiple (more than 2 stars) systems.
One hundred million years ago one such ternary system (three stars) had a mishap that seriously affected the systems’ evolution.
HE 0437-5439 Image: NASA/ESA/G Bacon (STScI)
The three wandered a little too close to the Milky Way’s monstrous centre and the supermassive black hole Sagittarius A*. The most likely situation is that the black hole overcame the gravitational attraction between the outer most star in the system and absorbed it. The remaining two stars which were believed to be a close orbiting pair, received the momentum to break free of the gravitational influence of both the black hole and the Milky Way itself. The stars were fired out from the galaxy at 1.6 million miles per hour – twice the velocity needed to escape the Milky Way’s gravitational clutches. Stars like these that are traveling at incredible speeds are known as Hyper Velocity Stars or HVSs. The stars moved outwards from the galaxy towards their current location and here astronomers encountered a significant problem – there is only one star and it should not be there. The actual HVS described in this post is known as HE 0437-5439 a spectral class B main sequence star located 200,000 light years from the galactic centre. You may be wondering why a pair of stars has now become a single star in my writing, I assure you that I have not lost the plot or made a massive typo all we be explained shortly. The single star detected in 2005 is the result of a stellar merger and is thus a blue straggler. Astronomers now believe that as the more massive of the binary pair neared the end of its life and began to expand into the helium burning phase as a red giant it completely engulfed its less massive partner. The less massive star spun in closer to the core of the more massive star and eventually the two fused – becoming one single blue main sequence star being around 8.5 solar masses. The story requires this odd twist as a hot B class star burns out in around twenty million years meaning that at the stars current velocity that the star should be only one fifth as far from the galactic core. This created two possibilities…
The star was a blue straggler remnant of a binary pair or it was a ‘standard’ B class main sequence star thrown from the much closer (in relative terms) dwarf galaxy the Large Magellanic Cloud (LMC) a mere sixty five thousand light years from the star.
Without evidence to point to one idea over the other no one could say with any confidence which was the correct solution. In 2008 astronomers believed that they had identified a similar chemical identity of the star with a group of stars within the LMC. The final conclusions were made using data from the Hubble Space Telescope. The position of the star was mapped by Hubble 3 1/2 years apart. The measurements plotted the stars position against the location of several other stars and galaxies, when the two images were compared the star had moved relative to the background. Despite this movement being tiny only 4% the width of one pixel it provided the astronomers with two points and thus the ability to trace the stars trajectory – the path of its movement. This trajectory traced back to the Milky Way’s core confirming the blue straggler solution.
The system's theorised evolution Credit: NASA, ESA, and A. Feild (STScI)Science Credit: NASA, ESA, O. Gnedin (University of Michigan, Ann Arbor), and W. Brown (Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass.)
Whilst such an event occurs very rarely this is not the only HVS known to astronomers. There are 19 confirmed HVS though there are no doubt more that remain undetected. The current ideas about the detection of new HVSs involve looking in the outer regions of the Milky Way’s core or bulge. As star density – number of stars per unit volume of space – is much lower than in the more central areas it makes it much easier to pick out candidates. These are O or B class stars that tend to be very rare in the outskirts of the galaxy so there is a higher chance that these kinds of stars have been thrown from the central core’ close to which they are far more common.
It has been estimated that for every one hundred thousand standard stars in the galaxy there is one HVS, meaning that such events that produce such stars are exceedingly rare but not unique.
As many of the stars are as yet undetected the true number remains uncertain.
Thankfully there is a way you can help search for more. Galaxy Zoo has a sub project – the Hyper Velocity Star project dedicated to the hunt for new HVS. The project’s forum page can be found here, its catalogue of known HVSs here and the project’s blog here. The project would very much appreciate any help you could provide. All the information to help get you started can be found here.
Let’s hope this is the start of a flurry of new information on HVSs but in the mean time I salute you HE0437-5439 as you boldly go … yeah I shall stop there before I get charged with copyright infringement…
Star Birth in Centaurus
Illustration of IRAS 13481-6124; credit: ESO/M Kornmesser/L Calçada
This fantastic artist’s illustration shows the star IRAS 13481-6124. At 60,000 years old this star is not long from being formed; hence the dusty circumstellar disk surrounding it, the left-over’s from the stars formation. The star lies 10,000 light years away in the constellation Centaurus, and is the first star to have its disk directly observed! So what’s so special about this young star?
Disk of IRAS 13481-6124; credit: ESO/S Kraus
In star formation the formation of stars under ten solar masses is pretty straight forward: you take one huge molecular cloud, cool it and let gravity do all the rest. The gas cloud then collapses in on itself to form a ball of plasma and a star is born! What is confusing for astronomers are stars with a mass over ten solar masses, they are unsure as to how they form. One theory states that stars could not form and weigh in at over ten solar masses as its final mass, it had to be ten or below because radiation pressure would stop material collecting onto a stars surface after the star has gone past that limit, so how do we get stars much bigger? One theory suggests that it’s due to stars merging with others. So to put a spanner in the works: IRAS 13481-6124 weighs in at over 20 solar masses!
Evidence from the Spitzer space telescope and the APEX telescope shows bow shocks around the star, which in turn shows that the star has a jet which has thrown out material along the poles of the star. This jet is powered by the accretion disk still around the star; you find these stellar jets around similar newly born stars of below ten solar masses.
So now the astronomers had indirect evidence of a disk left over from the stars formation they had to get direct evidence. For this they used the ESO’s Very Large Telescope Interferometer (the VLTI), and with this they directly observed the disk .The disk is over 1,000 solar masses and its 130 AU wide; which is much less than a light year. The inner part of the disk has a temperature of around 2000 K, whereas the parts of the disk farther out are cooler. The stars disk will not last for much longer; it will soon be dispersed by the light being emitted by the star, which is 30,000 times brighter than our own star.
You can read more about it here, and the research paper (in PDF format) here!
