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
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
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
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 
.
Image of the Week 30/07/10: Star birth gone wild
At Galaxy Zoo, several of us have been lucky enough to get this soft-looking beauty to classify:
The Sloan Digital Sky Survey's view of ARP 220
From the SDSS telescope in New Mexico, which supplied the images for Galaxy Zoo’s first two projects. You can look up more details from the SDSS pages here.
From the funny shape, especially the loops towards the right, we can see that it’s a past merger – a collision of two galaxies many millions of years ago. While it’s unlikely that any stars or planets crashed into each other (they are just too far apart), the immense gravity drags both structures around like an adventurous octopus playing with ribbons.
We can also see that it’s got a huge dust lane in the middle. Dust is usually larger particles than the hydrogen and helium gas which is abundant in the Universe, and from which stars form – it’s much rarer, but if it lies over a large enough area it blocks light (this is why we can’t see the centre of our own Galaxy).
The name ARP 220 comes from the Atlas of Peculiar Galaxies, compiled by Halton Arp. ARP 220 is in the constellation Serpens, and 250 million light years away.
It’s been an object of interest before. Back in 1997, it was Astronomy Picture of the Day.
And it’s continued to be interesting. Yesterday, Chris Lintott sent a tweet about a conference he’s attending – an entire talk was given to this object. I did not know until that moment that ARP 220 is the most luminous object in the local Universe.
Here is Hubble’s view:
Hubble has just had a bit of a field day imaging this monster with its Advanced Camera for Surveys, which revealed a cosmic sort of “baby boom”. This often happens with mergers: gas clouds, formerly minding their own business and cheerfully orbiting the centre of their Galaxy with everything else, suddenly get slammed into other gas clouds from the intruding galaxy, collapse, and set off a firework display of new star birth.
In ARP 220, it’s happening as never before. Over a 5,000 light year area – which is pretty titchy for space, only 5% of the Milky Way – there is as much gas as the Milky Way contains.
The clusters of star birth are so close together that they look like individual stars. There are two main groups which have been surveyed: one is only 10 million years old, the other about 70 million. The younger group contains larger stars. It is not yet known whether there were two “baby booms” or whether ARP 220 is undergoing a continuous starforming phase.
The dust blocks the view, but glows brilliantly in infra-red light. Its X-ray output has also captured the attention of astronomers – the intense activity has created a “superwind” that Chandra has picked up, and its effects can be seen 75,000 light years away.
The further out lobes are probably remnants of the merger. These filaments of gas are still hot – glowing, but unlikely to form new stars for a long time.
Astronomers say the conditions in ARP 220 may mimic an earlier, smaller Universe in which galaxy collisions and outrageous star formation were a lot more common.
One final version of this picture comes not from the past but from the Futurity science blog – the Saburu telescope obtained a false-colour image of the merger’s far-flung tidal debris.
If that’s not enough pretty pictures for you, Google Images yields a healthy crop. French speakers should particularly enjoy this one!
Image of the Week 23/07/10 – Catching a Cluster of Stars
This week’s image is another Cassini image. This time of the globular cluster Omega Centauri or NGC 5139.
Catching a Cluster of Stars Credit: NASA/JPL/SSI
The image was captured by the spacecraft’s narrow-angle camera on March 29 2009 when the space craft was orbiting 1.2 million kilometres from Saturn itself.
The craft was photographing the planet’s F ring when the cluster happened to pass through the camera’s field of view. NASA has compiled the 13 images containing the cluster into a short video sequence visible here.
Omega Centauri is thought to be the remnant of a former satellite galaxy that merged with the Milky Way early in our galaxy’s life. The majority of the galaxy is believed to have been torn apart with only the dense gravitationally bound core remaining intact orbiting the Milky Way itself. This core is believed to contain several million stars with the core being so dense that a star may only be 1/10 of a light year from its nearest neighbour. In comparison in Sol whose nearest neighbour is Proxima Centauri located 4.2 light years away.
Omega Centauri is located around 15800 light years from Earth and is the only globular cluster visible with the naked eye and can be observed in the constellation Centaurus.
Image of the Week – The Record Breaking Gamma Ray Burst – 16/07/10
This image was captured by NASA’s Swift telescope on June 21st 2010.
The Record breaking GRB Credit: NASA/Swift/Stefan Immler
The image shows the after glow of the most powerful gamma ray burst (GRB) in the X-ray spectrum yet detected.
The reds and oranges in the image so the X-ray’s detected whilst the blue and greens show the visible and ultra violet radiation picked up by the telescope.
The burst was so powerful the X-ray detection software on the telescope had to shut down as it was being overloaded with as much as 143,000 X-rays every second.
The GRB named GRB 100621A was nearly 170 times more powerful in the X-ray emission age than the standard GRB and 5 times as powerful as the next largest burst detected by swift.
Oddly the burst appeared very ordinary in the visible and ultra violent range showing that there is much about GRBs that we don’t yet understand.
For further reading you may like here
Please Note: – The Image of the Week section has been moved from Saturdays to Fridays
Image of the week – Daphnis by Cassini – 10/07/10
This week’s image of the week was taken by the Cassini Saturn Obiter on the 5th of July this year.
Daphnis as viewed by Cassini Credit; NASAESAISA
This image is the closest view humanity has yet been able to achieve of Saturn’s small moon Daphnis.
The moon was discovered on the 6th of May 2005 by the Cassini Orbiter and is one of Saturn’s shepherd moons. With the exception of the moon Pan it is the only shepherd moon within the main ring system.
Daphnis is found within the Keeler Gap within the A ring, this image also shows the distortions in the ring caused by the moon’s gravity as it orbits the planet.
More information about Saturn and its rings can be found here
Information about Saturn’s largest moon – Titan – can be found here
For a larger version of the image click here
Astro-image of the week – R Coronae Australis – 03/07/10
This is a new section of the site and one we hope you will enjoy. Every week one of the editors on the site will select their favourite astronomy based image of the week, show it to you and give a little background about it.
These images will be all grouped in the IOTW (Image of the Week) section and can be viewed in sequence starting from the most recent and working back by clicking the ‘IOTW’ tab at the top of the page.
This week I have chosen this image as featured by the ESO (European Southern Observatory)
R Coronae Australis Credit ESO Source http://www.eso.org/public/archives/images/screen/eso1027a.jpg
The image shows the star forming region of nebulae surrounding the star R Coronae Australis.
The image, which shows an area of sky roughly the same size as a full moon, was taken by the La Silla Observatory located in Chile. This image is actually a combination of 12 images taken through the telescope’s red, green and blue filters. It is this combination of images that allows the final shot to have such an impressive level of quality.
R Coronae Australis itself is a suspected variable star. A variable star is a star whose luminosity changes in cycles over time – the northern Pole star Polaris is also a variable star.
It has the luminosity of 2.7 Sols (our sun) – This means if it was situated in our solar system rather than Sol the Earth’s sun would be nearly three times as bright.
It is a hot spectral class A5IIev - This in simpler terms means it is a blue-white ‘bright giant’ that shows changes in its spectra – hence its designation as a variable star.
The nebula in the surrounding area is known as the Coronae Australis Complex and unlike many other star forming nebulae does not glow as the stars it is creating are like our sun in mass and so don’t produce enough ultraviolet light to make the nebula fluoresce.
More information on nebulae can be found here
To read more about stellar spectral classes try here and here
