Origins of the Moon Challenged

The commonly accepted theory among scientists concerning Moon formation could be altered by a new study of lunar isotopes. (Variations of elements containing differing amounts of neutrons).

Luna Credit: NASA

Nearly half of the Moon was postulated to be from Theia, a planetary body, thought to have collided with Earth four point five billion years ago. The recent study by Junjun Zhang, an isotope geo-chemist at the Chicago Center for Cosmo-chemistry and his team challenged this premise. Initially, an analysis of twenty-four rocks from the lunar surface revealed a paucity of indications concerning similarities between the Moon and Earth. However, the group failed to consider the effect of cosmic rays, streams of charged particles racing through space. After amending their research on the Moon’s isotopes of titanium, they found its ratio to be in the ballpark of our planet’s chemistry.

The unlikelihood of Theia’s chemistry being nearly identical to the Earth prompted scientists to reconsider their model. They theorized, perhaps the planetary body collided and caused more joining of debris than previously suggested. This could infer, the majority of Theia’s constitution is hidden deep within the Moon, while Earth’s composition lays conspicuously on the surface.

Suggestions of a collision between a dual moon systems arose as well, inferring that one of our past satellites had a chemistry similar to the Earth. Scientists cannot know for sure, whether their ideas are correct or not, they are still theories. However, the research team plans on conducting more experiments on the isotopes of different elements found on the Moon.

You can read more about these findings at http://news.yahoo.com/moon-formation-theory-challenged-study-160608598.html

Astronomy Tech – Cassini-Huygens – Recovered

Since the beginning of the Space Age, man has sent many manned and unmanned missions into space. Very powerful telescopes, built around the world, broaden our vision and understanding of the universe. Spacecraft, whether visiting other worlds or orbiting the Earth send us images and data collected from our outer atmosphere to the outer planets and beyond.

However, all this was only possible thanks to the incredibly rapid development of technology in recent years. Only then, could the essential resources for the construction of the current generation of spaceships be developed.

So, let us talk a little about some of the most important of space exploration’s tools and its greatest discoveries in this series, called Astronomy Tech.

In this first post, let’s get to know Cassini-Huygens a bit better. It is a joint mission between NASA, the European Space Agency (ESA) and the Italian Space Agency (ISA), which has uncovering the secrets of Saturn, including its rings and moons, as its primary objective.

An artist's impression of Cassini-Huygens Credit: NASA

On October 15th, 1997, the Cassini-Huygens spacecraft – composed of NASA’s Cassini orbiter and the ESA’s Huygens probe – was launched, beginning a long and complex seven-year journey, including gravitational slingshot manoeuvres around Venus, Earth and Jupiter. After arriving at its destination, the mother ship; Cassini, began its main objective exploring Saturn, whilst the Huygens probe was lunched and landed on Titan –Saturn’s largest moon and the second largest in the Solar System, after Jupiter’s moon Ganymede.

The spacecraft’s name was a tribute to the Italian Jean-Dominique Cassini (1625-1712) – discover of the Saturnine satellites Iapetus, Rhea, Tethys and Dione. In 1675 he discovered what is known today as the ‘Cassini Division’, the narrow gap separating Saturn’s A and B rings. Christiaan Huygens (1629-1695) was a Dutch scientist who first described Saturn’s rings and, in 1655 he discovered the moon Titan.

Cassini’s “senses”

The Cassini spacecraft has a set of 12 instruments on-board. Some of them work in similar ways to our own. However, the instruments on the Cassini spacecraft are much more advanced than our own.

Cassini can “see” in wavelengths of light that the human eye cannot. The instruments on the spacecraft can “feel” things about magnetic fields and tiny dust particles that no human hand could detect. This means that Cassini can, for example ‘see the temperature’ of the objects it observes.

The magnetic field and particle detectors take direct sensing measurements of the environment around the spacecraft. These instruments measure magnetic fields, mass, electrical charges and densities of atomic particles. They also measure the quantity and composition of dust particles, the saturation of plasma (electrically charged gases), and radio waves.

Exploring the Ringed Planet

The expected return to Saturn – which hadn’t been visited by any spacecraft since Voyager 2 left Saturn’s orbit in 1981, – happened in July 2004. Since then, Cassini has made great discoveries about the Saturnine System and taken some terrific pictures, like the one below.

An Eclipse of Saturn, with the Rings Visible Credit: Cassini/NASA

A few days after reaching Saturn, Cassini released the Huygens probe to land on Titan. On January 14, 2005, during its fall, six instruments analysed Titan’s atmosphere. According to the returned data, Titan has a nitrogen rich atmosphere. It also confirmed that Titan’s orange colour is due to the presence of hydrocarbons, formed when sunlight breaks down the abundant methane molecules within the atmosphere.

These results have given scientists a glimpse of what Earth might have been like before life evolved. They now believe Titan possesses many similarities to the Earth, including lakes, rivers, channels, dunes, rain, snow, clouds, mountains and possibly volcanoes.

Cassini’s mission

Isn’t over yet; every day, it sends us vast amounts of data, back to astronomers allowing them to resolve and answer questions about Saturn and our own planet.

You can see more about Cassini on its official website. If you want to hear the news first hand, you can follow Cassini on Twitter.

Image of the Week – Martian Dust Devil Goes for a Spin – 09/04/12

NASA’s Mars Reconnaissance Orbiter has produced a truly stunning image of a Martian dust devil using its High Resolution Imaging Science Experiment (HiRISE) instrument.

The Martian Dust Devil Credit: NASA/JPL-Caltech/UA

The Devil is about 12 miles high (though only 70 meters across) and was produced as the Sun warmed the ground in such a way that a vortex was created. This sort of weather feature is most common when the sun’s heating effect is felt most strongly and fittingly this particular event occurred just two weeks before the northern hemisphere’s summer solstice.

NASA scientists have put together this video showing the dust devil in action

You can read more about this weather phenomenon here

Potential Research at the Poles

Note from the Young Astronomers Admin Team:

This is the first by our new editor YusefK and we would all like to welcome him to the team!

When you picture the world’s best site for astronomy, places like the Gemini Observatory in Chile or the W.M. Keck in Hawaii probably come to mind. Well think again, because the new epicenter of observing could be the coldest place on earth, Antarctica. After performing a careful analysis of the continent, scientists from America and Australia have pinpointed a prime location for ground based research. Several countries have already laid claim to the icy real estate, such as China, France, Russia and South Africa. The success of these countries’ scientific bases led to the development of more stations. We could owe our future understanding of the universe to those who work and live in this region.

Antarctica Credit: NASA, Davepape

Radio astronomers have already conducted research in the polar area. It was Martin Pomerantz who postulated that Antarctica was the best place for ground based astronomy. He was correct, but only under certain wavelengths. Until now, those who wanted to see the universe were out of luck. Nevertheless, the new site found by American and Australian scientists is expected to yield images three times sharper than today’s best observatories. Those of us who spend clear nights under the stars understand the importance of certain atmospheric factors. Things like water vapor in the air, temperature changes and darkness greatly affect our observing.

The location of this new site is a frozen plateau called Ridge A. Ridge A’s atmosphere is steady enough for average instruments to perform better than today’s common observatories. Imagine the potential of an eight inch Cassegrain in perfect weather conditions and the images would be stunning, when the larger facilities are established. The night sky above the summit is perfect for astronomical observing because it is calmer, dryer and darker than any ever known. Those who study and live in Antarctica will benefit from this treasure trove of unexplored skies. However, they will have to contend with several inhospitable factors foreign to the common scientist.

Living in Antarctica seems to be a challenge taken by the very eccentric or very passionate. Generally, scientists take a plane to the Falkland Islands and then a ship to Antarctica. There, they work with several professionals in the coldest and driest place on earth. Nevertheless, I have read the quarters are comfortable and the canned food isn’t half bad, either. Scientists work with a diverse group of people for months at a time and under strange and adverse conditions. So, for all budding astronomers and researchers, consider the South Pole for future endeavors in understanding the universe.

Sources:

http://www.antarctica.ac.uk/employment/locations/antarctica/living_in_antarctica.php

http://www.nsf.gov/pubs/1997/antpanel/4past.htm

http://www.physorg.com/news170932769.html

http://www.universetoday.com/38749/astronomers-find-worlds-best-observing-site/

The International Space Station

240 miles above your head a 420 tonne satellite orbits the Earth at 17000mph. It has been there, albeit in various states of construction, for 14 years, and for the last 11 of those it has been continuously occupied.

The fantastic photo taken by Italian ESA astronaut Paolo Nespoli from a Soyuz capsule that is currently my desktop background. Source: ESA/NASA

The International Space Station is a feat of engineering like no other. Not only does it demonstrate our technical ability to construct, launch, and maintain a permanent presence in space, but also our ability to coordinate the work of five different space agencies and their operations all over the planet.

But the journey from its conception has not been an easy one, the ISS was born out of three separate national programmes: NASA’s Freedom station, proposed in the early ‘80s as a response to the Soviet space stations Mir and Salyut, the Russian (formerly Soviet) Mir-2 project designed as a replacement for the aging Mir station, and the European Columbus space station project.

Budgetary constraints brought on by post-Cold War political changes made it increasingly clear that no single national programme was going to create a fully functioning scientific outpost. Instead the suggestion to combine the three programmes into a single international one was put forward and agreed in 1993 by US Vice-President Al Gore and Russian Prime Minister Viktor Chernomyrdin.

The first component, the Russian Zarya cargo block originally intended for the Mir-2 station was launched in 1998, and since then the station has expanded, first with the addition of connecting and services modules such as NASA’s Unity and RKA’s Zvezda, and later with more specialist modules such as ESA’s Columbus laboratory and the Cupola observation module, the largest window in space. In total the ISS consists of fifteen pressurised modules, with one more, Russian research laboratory Nauka still to be added. They comprise laboratories, docks and airlocks, and living areas, and their combined volume is just less than 1,000 cubic metres.

That all of these modules fitted together perfectly is a success story in itself. Many had not been built when the first pieces were launched, and for most their mating in orbit was the first time they were put together. Though there have been a few minor problems, they have always been resolved quickly, and at no point has the station ever had to be evacuated.

The station’s unique conditions have allowed a large variety of experiments to be performed, many of which would be impossible on Earth. Research is being done into how structures such as crystals and organic cells form and develop outside the influence of the Earth’s gravity. NASA is also taking the opportunity to do closer studies on the effects of prolonged exposure to microgravity on astronauts and the possible implications on future manned missions to the Moon, asteroids, or Mars.

Until the end of the shuttle program in August of last year, crew and supplies were transported by a variety of means including the space shuttles, and the Soyuz and Progress spacecraft. The 6-man Soyuz craft operated by Roscosmos, the Russian Federal Space Agency, is now the only method of sending new crews to the station.

Each contributory nation retains ownership of and responsibility for the components that it added. This responsibility extends to the disposal of the station when it reaches the end of its operational life, which the current time frame places somewhere in the 2020s, depending on whether and for how long its decommissioning is postponed after the initial 2020 date. Given the huge amount of money that has been invested in the station as well as the later than expected completion date, it is very likely that the ISS’s operational life will be extended some way beyond that deadline. By that point it is also expected that commercial space ventures will play a much larger role in the life and upkeep of the station, so they too may play some role in its end-of-life decisions.

Stellar Newborns Kick Up a Fuss

The Orion nebula is the closest region of large scale star formation to Earth sitting just 1340 light years from where you are reading this post.

The nebula is in the process of birthing the next generation of stars, with many still cocooned within the clouds from which they are forming, from peering eyes. Well that’s in the visible spectrum at least. Using infra red observations we can looks through the obsuring dust as if it isn’t there at all.

This is exactly what astronomers using the Sptizer and Hershel Space telescopes have done to produce this gorgeous image:

The Orion Nebula in I-R Credit: NASA/ESA/JPL-Caltech/IRAM

The rainbow effect is due to the combination of different sets of observations through different filters. by combining the individual images the compound image can reveal the nebula in stunning detail with each colour displaying a different wavelength of I-R radiation. Using two telescopes also has advantages, as Sptizer is designed to observe at shorter wavelengths than Hershel and so by combining the two sets of data astronomers can get a more complete view of what is going on.

In this case the data revealed something very unusual indeed. Several of the young protostars have been flickering wildly, with their brightness fluctuating by as much as 20% in just a few weeks. Based on the cool temperatures of the material involved, the fluctuations had to occur far from the hot regions near the growing star, but such material should be far enough away from the star to spend years or even centuries in a slow decaying orbit before accreating onto the star’s surface.

Currently the explanation for how such a process could be so drastically accelerated is still up for debate though there are several suggestions. The other material may not be evenly distributed around the star, with some regions being more densely occupied than others. That may allow some of the denser clumps or filaments to collide with an inner, warmer shell of material causing the flare ups. It could also be caused by material piling up at the edge of the inner disk and so casting a shadow on the outer disk.

You can read more about this image here and here

Image of the Week – Hubble Spies A Glittering Jewel

The NASAESA Hubble Space Telescope has obtained the highest quality image of the globular cluster Messier 9 (M9) ever produced.

Messier 9 as seen by Hubble Credit: NASAESA

This glorious sphere of stars is far too faint to be detected by the human eye, yet Hubble can resolve it as upwards of a 1/4 of a million individual glistening stars.

M9 sits towards the centre of our own galaxy, and yet whilst relaivly close by in the grand scale of the universe it is still 25,000 light years from Earth.

The stars within M9 are twice the age of our own sun and are metal poor as a result – as they formed at a time when the cosmos was still largely deprived of the heavier elements like iron, oxygen and nickel.

The cluster was first discovered in 1764 by the French astronomer Charles Messier and was included as object 9 on his list of astronomical objects (hence its name!).

The image above covers and area of sky roughly equal to a pin head held at arms reach,a true testiment to the power of Hubble.

You can read more here

ATV 3 – Edoardo Amaldi – Successfully Docks with the ISS

Yesterday the third in the European Space Agency’s (ESA) line of Automated Transfer Vehicles (ATV) – The Edoardo Amaldi docked successfully with the International Space Station (ISS).

The craft brings 7 tons of food, water and other cargo to the station. It will remain docked for six months before being loaded with the station’s refuse prior to being de orbited and destroyed by atmospheric re-entry heat.

The next two ATVs planned are ATV-4 Albert Einstein, which is to be launched in 2013 followed by ATV-5 Georges Lemaître in 2014.

Schematic of an ATV Credit: ESA

Cosmic Candles – Updated

The universe is truly huge. It stretches for at least 13.5 billion light years (1.277×10²³ km) in every direction (considerably further in fact), and its massive size poses an equally large problem how can you accurately measure how far away objects are?

Over such large distances conventitional methods of measuring distances (like using the time taken for light to hit and object and reflect back) become impractical and very, very slow.

Thankfully astronomers can use other methods developed over the years to deal with these monumental universal distances. The three main methods they can achieve this are:

• Parallax
• Cepheid variables
• and Redshift

Parallax uses changes in the relative positions of celestial objects throughout the year to estimate how far away they are using trigonometry. A star that is closer to the Earth will appear to move more than a star that is further away. The same principle applies when you look out of the window in a moving car, objects close to you wizz past while those in the distance move lazily across your field of vision for some time (provided you don’t move your head of course).

Parallax is only useful for distances that are relatively small as after a certain point (16,000 light years distant – which may seem like a huge distance but it is actually less than 1% of our Galaxy’s diameter, tiny in comparison with the rest of the universe) the relative position of a distant object changes so little it is impossible to measure with any accuracy.

The standard unit of parallax is the Parsec or Parallax Arcsecond. Without going into too much detail of how it is calculated, a star that is one parsec away will have apparently changed in position by a fixed amount in the sky. A star that is two parsecs away will have appeared to have moved 1/2 as much and so on and so forth.

One parsec is approximately equal to 3.26 light years, which puts Earth’s nearest star (after the sun) Alpha Proxima Centauri at 1.29 parsecs away (4.2 light years).

Parallax forms the ‘bottom rung’ on the universal distance ladder (covering the shortest distances), skipping over the middle rung for now and moving to top – redshift.

Not only is the universe really, really big it is expanding – quickly. This is a direct result of the initial explosion that sparked our universe’s formation – the Big Bang. This was not an explosion in any conventional sense, it did not expand from a single point, instead it happened everywhere in the universe at once. This means that even today every single object in the universe is moving away from everything else (yes it is mind-blowing). This expansion is constant no matter where you are in the universe (as far as we can tell though this is the subject of some debate) and has been measured at 70.4 kms/Mpc (within a small range of uncertainty). Or in plain English, if two objects are a million parsecs away from each other they will be moving away from each other at 70.4 kilometres per second.

The Expanding Universe Credit: NASA / WMAP Science Team

Now at first glance this may not seem all that useful in determining distances, but over large distances it is a very powerful method indeed.

As this rate of expansion is fixed and is occurring throughout the universe, and most importantly everything is moving away from everything else (thanks to the space around it literally stretching), an object that is 2 million parsecs away will be moving at 140.8 kms, an object that is 3 million parsecs away will be whizzing away from us at 211.2 kms and so on.

That means we can infer the distance of an object by measuring its relative velocity. The only question is how do we measure the velocity of something that is literally half way across the universe? The answer comes from a somewhat unusual source.

Light as most people know travels at a fixed speed (3×10⁸ ms) in a vacuum. Regardless of what you try to do it, its speed is constant. As the universe expands you would expect light to appear to slow down as it has to travel further, in actual fact it stretches with the universe.

This manifests as in increase in the light’s wavelength (the distance between two adjacent, identical points on a wave). An increase in wavelength means the light has ‘lost’ energy and appearers redder hence the term redshift. Redshift is calculated by measuring the difference between observed spectral features in cellestial objects and comparing them to measurements taken here on Earth i.e. where redshift = 0. Redshift can be shortened to z and is the only practical method of determining distances to objects far into the universe.

So far we have dealt with Parallax which is used for very short distances (in universal standards), and Redshift which deals with very large distances. Whilst these are each very useful to have there is a reasonable gap between the two meaning that some objects within our own galaxy could not be distanced with any accuracy, and we would have no way of checking the reliability of either as there is practically no overlap in the measurement range of the two. This means that the results obtained for both methods could not be compared and checked to see if they agreed with each other.

Thankfully there is a middle rung on the cosmological distance lader – the Cepheid variables.

Cepheid variables (more accurately Population I Cepheids or Classical Cepheids) take their name from the second to be discovered - Delta Cephei.

Classical Cepheids are all yellow supergiant stars that fall in the spectral class bracket F6 – K2 (For information spectral classes of stars see here and here).

They were once main sequence B class stars like many of those found within the Pleiades open star cluster (right).

The PleiadesM45 Credit: Tad Denton/Adam Block/NOAO/AURA/NSF

These stars are all somewhere between 4 and 20 times the mass of the sun and spent just a few million years as a main sequence star fusing hydrogen into helium, before departing the main sequence and evolving into the supergiants we see today.

Such yellow supergiants are inherently unstable, having regular pulsations as the interior of the star changes in cycles which alter how much radiation the star retains causing it to swell and then contract as radiation is released into space at a faster rate causing it to return to its original size.

This cycle repeats again and again, in a relationship that is directly linked to the luminosity of the star. The more luminous the star the longer its pulsation period (the time taken for one expansion phase followed by one contraction phase). As this is fixed for all Cepheid variables regardless of their distance from Earth, two stars that have the same pulsation period with differing luminosities are at different distances.

That means that relative distances can be calculated by comparing Cepheids. Whilst that would be useful in itself there is more to the Cepheids, some of them are close enough to have their distance calculated by Parallax and other methods. So with a starting point for comparison the actual distances of all Cepheids regardless of their distance can be calculated accurately.

Cepheids have also been used to refine our results and estimates of important cosmological constants including values for the Hubble constant – a measure of how the universe is expanding.

So far around 700 classical Cepheids have been identified within the Milky Way, with an overall total of several thousand known as far out as NGC 4603 – 100 million light years away. Cepheids have been detected, and have had their properties measured, at distances at which redshift has become detectable bridging the gap between the two measurements and providing a way of comparing and confirming calculated distances for the very close and very distant universe.

For our mathematically minded readers (anyone else is welcome to have a look but if the site of an equation makes you cringe you are more than welcome to skip on ahead) I will now detail how to first calculate the luminosity of a classical Cepheid and then how to use the luminosity to calculate how far away the star is from Earth.

For the first stage all that is required is the pulsation period of the star. This is obtained by monitoring the star’s brightness over a long period of time and identifying the time for the star to dim from its peak brightness to its dimmest and to brighten back to its peak again. This is recorded for several cycles and averaged to reduce uncertainties in the measurements and to minimise the effect of any mild random fluctuations in the star itself.

The value for the period – P – is then substituted into the equation:

It looks rather complicated but the equation really isn’t, if you are careful it can even be done in one step using a calculator!

In this case M is the mean absolute magnitude of the star – a measure of distance adjusted brightness.

The second stage in the calculation is essentially a comparison between the mean absoultude magnitude and the mean apparent (average observed magnitude over the full pulsation cycle). Is this case the larger the difference the greater the distance involved – as of course, the further away an object is the dimmer it appears.

The equation we use in this case is:

Where:

• M is the calculated mean absolute magnitude
• m is the observed mean apparent magnitude
• and D is the distance in parsecs

This formula can in turn be rearranged to give an equation where D is in the subject:

And all you need do is plug in the numbers.

For example lets imagine we measure Cepheid to have a period of 51 days and a mean apparent magnitude of 18.5.

Its mean absolute magnitude would be:

-2.78(log51)-1.35 = M = -6.10 (Try it yourself if you don’t believe me!)

So now if we substitute M and m into the distance equation we get:

D = 10^4.92Parsecs

Which can also be written as: 83200 Parsecs or roughly 1.6 times the distance to the Large Magellanic Cloud.

There you go, not so scary after all!

An example of a Cepheid Variable (left) with its spectrum (below).

SDSS ID: 1237646647833788777 Credit: SDSS, DR8

Recently the distances calculated using Cepheids have been called into some doubt with concerns over the stars themselves.

It has long been though that their may be some change in the period of the star’s pulsations. This was predicted as stars slowly use mass over time as they blow out a fraction of their mass as their solar wind and in the emission of thermal and electromagnetic radiation (heat and light).

Spectrum of SDSS ID: 1237646647833788777 Credit: SDSS, DR8

This mass would then form a shell of material surrounding the star. This dust would absorb visible light from its parent star and re-emit it in the infra-red frequency range. Thus a star would appear dimmer than it truly is in visible light and brighter in infra-red light. Despite the differences being quite small it would introduce large uncertainties in the calculated distance of the star which in turn would cause serious inaccuracies in the values calculated from such measurements, thus proof of this mass loss and a way to compensate for it is vital in maintaining the integrity of the cosmic distance ladder and cosmology as a whole.

Recently, astrophysicists using NASA’s Sptizer Space Telescope have confirmed this mass loss by taking detailed images of the class’ namesake Delta Cephei. They show an intense bow shock surrounding the star, caused by the high speed interactions between the star’s stellar wind and the surrounding interstellar gas and dust.

The Bow Shock Surrounding Dela Cephei Credit: In image

Other observations also show similar bow shocks surrounding at least 25% of currently known Cepheids.

With these new measurements of mass loss a correction program can now be used to compensate for the reduction in luminosity of the variables and so allow for better measures of distances and more accurate calculation of the variables that define our universe.

You can read more on Cepheid Variables here

 

The Potentially Earth Like Exoworld – Updated

Back in late September 2010, Astronomers made an important discovery that may eventually change the way we view our place in the cosmos.

The story begins with the all together average star Gliese 581 The star is a spectral class M3 main sequence dwarf, not dissimilar to the image on the left.

An artist's impression of an M class dwarf Credit: NASA/Walt Feimer

At roughly 31% the mass of the sun but only 1.3% its luminosity (that is taking all wavelengths into account not  just visual i.e. its Bolometric luminosity).

The star is classified as a variable star due to fluctuations in its brightness over time.

To be more specific it is a BY Draconis variable star as the variability (if confirmed as it currently falls close to the accepted margin for false detection) is expected to be caused by the presence of starspots (the general name for a sunspot that occurs on a star other than the sun) combined with the star’s rotation.

Whilst the star is itself an interesting object, it is what is orbiting it that has caused the media interest beginning in spring 2007.The star has been a target in the search for Exoplanets for some time, the excitement spread when its second planet – Gliese 581c – was revealed to sit just at the inner edge of the systems ‘habitable’ zone.

The term ‘habitable zone’ for a start deeply aggravates me as it means only that the area is neither too hot or too cold, I would prefer it to be known as the ‘temperate’ zone but perhaps that is just me (18 going on a grumpy 60 year old).

Gliese 581 Credit: Digital Sky Survey / ESO

The word habitable implies that the world is suitable for life in every way not just one. Professional astronomers refer to this zone as the ‘Goldilocks zone’ instead as this only refers to the distance from a star that liquid water could theoretically exist on the surface of a terrestrial (rocky) world. Without leading to the assumption that as planet x is y km from its star then it must have life. All this position means is that planet x is in the most likely area of its system for a planet to have liquid water.

The attention soon waned as it became clear that the planet is likely to have a runaway greenhouse effect creating a Venusian world far too hot for life.

The media hype began again with the discovery of the Gliese 581d which sits at the very edge or just outside the Goldilocks  zone and so can be expected to be similar to Mars. Then interest peaked again with the discovery of Gliese 581 e which despite sitting very close to the star was the exoplanet with the closest mass to that of the Earth yet discovered with a minimum mass of 1.94 Earth masses.

The current media extravaganza is centred on Gliese 581 g a planet that sits well within the Goldilocks zone, and within the acceptable mass limits for a stable terrestrial planet meaning that it COULD Potentially be suitable for life. However as I have mentioned the issue is far more complex than just having a planet at roughly the right distance from a star.

The Gliese 581 System. Showing each planet's orbital distance in relation to the projected location of the habitable zone and relative to our own Solar System. Credit: ESO derivative work: Henrykus

Yes could be a life bearing world but there is no proof either way quite yet.

Well as the planet is sitting just 20.3 light years away from us, if it indeed harbours life it would go some way to showing just how common life is likely to be within the universe.

However a spanner may have been thrown into the works.

All exoplanet detections must be confirmed, i.e. by the detection of the planet in more than one dataset. So far Gliese 581 g (and Gliese 581 f, announced at the same time though more mundane as it falls well outside the habitable zone and is expected to be similar to Neptune or a super terrestrial planet) has only been detected in one set of measurements; a set of combined data from HIRES spectrometer on the Keck telescope in Hawaii and the HARPS instrument on the ESO’s La Silla Observatory in Chile.Later measurements taken by HARPS failed to detect the planet, so it may not exist at all.

Though as Martin Rees once said, “Lack of evidence is not evidence for absence.” Who knows the planet may yet be confirmed in later measurements though that’s not quite the end of our story.

During the buzz of attention surrounding the discovery of Gliese 581 c, a radio transmission was sent to the system containing messages selected by users of the social networking site Bebo.The transmission was sent in 2008 and will reach the planet in early 2029 with the potential for a reply from any intelligent life on the planet by 2050.

A member of the Galaxy Zoo Forum (Djj) wrote this limerick for my Object of the Day on the same subject,

“Send a message in radio mime
That we’re here and we’re still in our prime;
Gliese five-eighty-one
Might be sombody’s sun —
We could hear back in forty years’ time!”

I will end this post with one of the more indulgent artist’s impressions of Gliese 581 g:

Gliese 581 g Credit: NASA

For our more technically minded readers, you can obtain the original announcement paper for Gliese 581 g here