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

Visit the Star Sailor Podcast website at: http://thewittyastronomers.wordpress.com/

Debris around the Earth. (credit: ESA)

In 2008 – when ESA (European Space Agency) published the image above, showing how much trash there was in orbit – this subject became a concern to many countries around the world. Seven years ago, two American researchers, Donald Kessler and Philip Anz-Meador, said that by 2020 it  might be not possible to perform space operations near the Earth.

Today, our planet is surrounded by around 50 thousand objects, but less than 7 thousand of these are more than 20 centimetres in size. It means, these objects are, in fact, debris of our spacecraft rather than natural moons\captured asteroids. Although most of the debris in Earth Orbit is small, it’s travelling extremely fast. Below altitudes of 2,000 km, the average relative impact speed is 36,000kmph (or 21,600 mph). A crash involving even one piece can be a major disaster.

In an attempt to solve this problem, the United States president Barack Obama added a section in the new National Space Policy (USA) dedicated to the protection of the space environment and draws attention to the dangers of space debris.

“The policy seeks to minimize the creation of new debris and also to research operations for removing debris with other countries, and so you can see how international cooperation would be a very important foundation for this aspect of the policy,” Barry Pavel, senior director for defense policy and strategy at the White House National Security Council, said during a June 28 conference call with reporters.

Despite the concern expressed by the U.S. government, no one knows exactly how and when the cleaning of the Earth’s neighbourhood will be done.

The new Lego Shuttle Adventure kit released in mid-2010. Credit: Lego

As I type this blog post, I am currently working on building the new Lego space shuttle. Why is it becoming a big seller? Not just because it’s considered a rare item, or has 1204 pieces, but because the shuttle program is ending, and everybody wants their last bit of memorabilia. Do you think Lego hasn’t done this before? While doing research, I discovered that there have been at least 3 or 4, probably even more, attempts at the Lego space shuttle. How successful were they? Well, how many of them have you seen or even heard of? Prior to this new set, I had never heard of one of them.

On top of the $100 per kit Lego corporation is making off of the shuttle retirement, the shuttle has done such good for us here on Earth. No, not just Velcro and tang! How are your tires? I can tell you they’re improved after working on the shuttle’s landing gear. You know how certain things don’t catch fire in your house suddenly? How about Kevlar and other similar materials. You’re outside and it’s freezing cold out. What would most people do? Put on a warm jacket. Thank you for using the materials in the spacesuits used on the shuttle during EVAs in our jackets here on Earth.

The list just goes on and on and on! Not only have we had the numerous spin-offs, but we’ve learned a lot from the shuttle. What do I mean by that? The Hubble Space Telescope wasn’t launched in any ordinary rocket. The space shuttle Discovery launched it in 1990, and all 5 servicing missions were performed using the beautiful birds. What about long duration space flight? True the shuttle can’t fly to the moon, but it can bring up nodes and astronauts to the International Space Station, helping perform scientific activities, bringing up useful supplies, and returning some back to our home planet.

The Earth's atmosphere with a full moon as taken by the crew of STS-35 aboard the shuttle Columbia in 1990. Credit: NASA

Plus, some of the most amazing photography of our very own planet, our blue marble Earth, have been taken from the space shuttle. When you see a picture from out the window and see how small of an atmosphere protects us here on Earth, it makes you think twice about what we’re doing to our planet.

Originally, and to this day, thought of as a huge waste of money that’s dangerous, the space shuttle is now getting the credit it finally deserves…30 years too late. With the best manned safety record, the space shuttle was America’s low earth orbit dream realized. It was a beautiful machine, and it’s going to be tough to say goodbye. However, the space shuttle will always remain in history, and in the hearts of those who were alive to witness its beauty.

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

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

Project Galaxy will detail the various categories and subcategories that exist in galactic morphology (shape and structure). This post is a simple list of some of the main types and gives an example for the main categories. The main project will go into each group and subgroup in much greater detail.

Spirals

AHZ10003aj Credit; Galaxy Zoo

The example I chose for the spirals section is this lovely two-armed number.

I chose it as it has well formed arms and a very bright (potentially active) nucleus (centre).

The galaxy’s spectrum as viewed on AEGIS has a reasonably high peak in H beta. This is hydrogen that has been energized previously but is now losing energy and this process emits radiation at a very specific wavelength. Whilst a galaxy having a large amount of H beta relative to another variety of hydrogen - H alpha – is very unusual, the spectrum available on AEGIS isn’t complete and lacks the H alpha frequency range, so this galaxy may be remarkable or it may not be. No matter it is still a beautiful example of the spirals.

Those wishing to learn more about H beta information can be found here and for the various states of hydrogen in general here

Edge-on Spirals

AHZ400070z Credit; Galaxy Zoo

It, in my opinion, is a fine example of its group.

Thin and long as we are looking at the galaxy through its narrow edge. The Milky Way could look much like this galaxy if viewed from particular angles outside the galaxy.

Information on edge- on spirals can be found here.

It is important to note that edge-on spirals are essentially the same as normal spirals as it is our viewing angle that provides the difference not the galaxies themselves, as they are viewed looking at them from the ‘side’ so the spiral features are hidden.

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Ellipticals

AHZ100048j Credit; Galaxy Zoo

Ellipticals are large oval galaxies which in general thought to be ‘red and dead’. New evidence has emerged that not all are as lifeless as once thought, see here.

This elliptical caught my eye with its very prominent nucleus which may indicate anAGN.

I delved into AEGIS for the spectrum (which can be viewed here). The galaxy has a huge peak (but ‘narrow’)  in doubly ionized oxygen or OIII.

This should not be confused with O₃ which is the molecule ozone. This spectral feature identifies the galaxy as a Seyfert 1 class AGN. This is a specific kind of galaxy that contain very active nuclei and are thought to have supermassive black holes at their cores. The black hole ionizes surrounding gas producing very prominent spectral lines.

Unfortunately the spectrum was once again incomplete but the galaxy is still superb

Irregulars

AHZ100007z Credit; Galaxy Zoo

As for this one your guess is as good as mine.

I selected it for its utter irregularity. The galaxy itself may not have taken on its final shape yet, or may have been ripped apart by a close encounter with another.

Regardless about what happened to this poor thing it is still a nice one to look at scratch your head over. Whatever may have caused its shape it is an excellent example of just how irregular, irregular galaxies can be.

Whilst Irregular galaxies are quite common in the the Hubble database for me this one is extra special and worth putting on display here.

Clumpy

AHZ40005th Credit; Galaxy Zoo

I chose this galaxy for the clumpy section as I think its shape is very interesting.

The two clumps sit one on top of the the other rather like an hour glass. The clumps also appear to be quite bright in relation to the galaxy which may indicate that it is active and star forming.

The galaxy also, unlike many of the other galaxies found within the HST’s, database appears almost symmetrical without any major irregularities.

Clumpy galaxies may form from several clumps of intense star formation that have ‘stuck’ together, though this is still up for debate.

Other Types of Galaxy

AHZ10005dh Credit; Galaxy Zoo

This galaxy is unusual in that it has a large dust lane visible over the main galaxy itself.

The galaxy itself could be a spiral or a lenticular galaxy – a spiral galaxy that has lost its arms. Whilst this is difficult to determine based on this image alone the galaxy does have an interesting shape and with the dust lane looks like a small ghost in my opinion.

It too has a very bright nucleus showing a potentially active nucleus.

The dust lane may lie within the galaxy or more likely, going from the image,  the dust lane lies somewhat outside the main galaxy itself.

I think you will agree that this galaxy really is spectacular.

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Project Galaxy will also have a a section for things that can be confused with galaxies but are in fact something else entirely.

Stars

AHZ6000fun Credit; Galaxy Zoo

This lovely star is actually obscuring a faint galaxy that was the actual target of this image.

I was unable to gain any information about the star itself. I hope you will agree that such information is unnecessary to admire its beauty.

The beautiful displays of light surrounding the star are due to the over exposure of the image as the survey had been calibrated to view very faint distant galaxies and not close bright stars.

This image was captured by the SDSS and has the classical red surrounding hues – Hubble stars tend to be blue and orange rather than red.

Other Artefacts

AHZ6000ccn Credit; Galaxy Zoo

The vivid green trail in this image is actually the trail of a satellite as it passed overhead as the image was being taken (the image was captured  by the SDSS – Sloan Digital Sky Survey a ground based telescope).

I think this image is particularity nice as it also contains a star in the top left hand corner.

Whilst satellite trails are very vivid in the images this is only because of the long exposure time and sensitive equipment. In the night sky the satellites appear as a fast  moving pinprick of light however they are difficult to see and are easily obscured by light pollution. A satellite may be whizzing over your head right now!

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And because it is so spectacular and deserves its own section …

AHZ5000fbb Credit; Galaxy Zoo

This is  one of the nicest galaxies I have classified within the Galaxy Zoo.

It is a beautiful blue two-armed spiral.

It has the rather bland name NGC 0768

The galaxy itself is located 317 million light years away from Earth and is moving away from us at 7021 km per second.

It my opinion the galaxy is perfectly formed with beautiful arms and a lovely nucleus.

Its pristine condition is a sign of  a peaceful existence. Such well formed features are easily destroyed by mergers and close encounters with other galaxies.

More information about this galaxy can be found here and here

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Now you have had a taster of Project Galaxy (a very small one at that), we hope it has whet your appetite for the main event which should begin sometime soon

We hope you will enjoy the main event as much as we will producing it.

Till next time

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

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

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