Thursday, December 22, 2011

Kepler - Bring on the world

Kepler-22b, 20e and f,
Out shone all the rest by being Earth-like the best.
Showing us transits that give us their size not their mass.
We can only guess that they aren’t all just gas.

Now 22b is in the goldilocks zone, 
meaning liquid water could make it a home.
But 20e and 20f are unlikely the best, 
to plan a voyage and settle down for a rest.
They orbit their star at a maddening pace, 
with three other planets joining in for the chase.
Each system is exciting, 
but we’d all like to know,
when Kepler will find us a place to call Home. 

Seager-MIT Physics department news
This is just a short poem about Kepler's earth-sized worlds I wrote when I could not sleep one night. Happy Holidays! 

Friday, December 16, 2011

The Good, The Bad, and The IDL

Astrophysics (fortunately or unfortunately) involves one form of coding or another. In my case that code is IDL. Now if you talk to certain people about different codes they become… let’s just say, passionate. I however am in the group that codes because they have to and learns the code that the person they work for uses, as they will hopefully know more than you do.

I am sad to say that in the month since I finished my literature review I have spent my days coding away in IDL. It is not all bad though, what I have found is that in writing a code or even looking up routines on the internet you learn a great deal about the process that reveal your results. 

The ‘beauty’ of coding it that when things are going well you feel like nothing can stop you, you have a clear plan and an end goal in mind. When things go bad, however, it feels like it will never work and you want to break down and cry right there at your desk. In this situation I suggest you swiftly put on something to hide the tears, I usually go with Stargate but the end scene from V for vendetta works wonders too! 

And remember Google is your friend!
;Finding the centroid of a star;
                Xcenter = TOTAL(TOTAL(array,2) * (INDGEN(length of  array)) / TOTAL(array)
                Ycenter = TOTAL(TOTAL(array,1) * (INDGEN(length of  array)) / TOTAL(array)
;Multiple line plots;
                Plot1 = PLOT(x, y, TITLE=’plot’, XTITLE=’x’, YTITLE=’y’, NAME=’array1’)
                Plot2 = PLOT(x2,y2, ‘green’, NAME=’array2’,  /OVERPLOT)
                Legend1 = LEGEND(TARGET=[plot1,plot2], POSITION=[0.75,0.75])

                errplot = ERRORPLOT(array, errarray, TITLE=’error plot’, XTITLE=’x’, YTITLE=’y’, ERRORBAR_COLOR=’red’)

Tuesday, December 6, 2011

Goldilocks' Porridge

Image from - Window to the universe
Just because it is in the goldilocks zone does not mean that the porridge won't kill you!

The habitable zone is named due to the fact that for life to exist, if there is a chance a planet will be inhabited, liquid water needs to be present. The habitable zone forms an annulus, donut shaped, region around a star, where water is condensed but not frozen so it is not too hot or cold.  This gives it the more popularized name, the 'goldilocks zone'.

Although the ability to harbour liquid water greatly increases the likelihood of life evolving on a planet it does not automatically mean any planet within this zone is habitable. This can even be seen within our own solar system, Venus is just inside and mars is just outside, the edges of our suns habitable zone. Yet the presence of life on mars seems to be in continuous debate with evidence that liquid water once flowed on the surface although it sits outside the habitable zone. At the other end of the scale it is clear that there is no chance of life on the surface of Venus, where temperatures soar due to the planet’s atmosphere causing the greenhouse effect trapping vast amounts of solar radiation (as well as high volcanic activity).

The recent announcement by the Kepler team of Kepler-22b has been hyped up in the media to be earths twin. Kepler-22b is the first planet in the Kepler list to have an orbit similar to that of earth around a very average sun like star. Its orbit is also keeps it within its stars habitable zone. Currently the published data for Kepler-22b states that the radius is 2.4 Re (2.4 times the radius of the Earth) with a temperature of around 22 degrees celcius. These values are still preliminary estimates and with no information on the massdensity and composition cannot be estimated.
Also as has been shown with other exoplanets, the radius varies with wavelength due to atmospheric absorption. Different chemical species in the atmosphere block out different portions of light at specific wavelengths. The different species will then have an effect on the temperature of the planet due to their interaction with stellar radiation, such as the greenhouse effect seen on earth and to a larger extent on Venus. Follow up observations of this planet have likely been bumped to the top of the list and with more data come more understanding (in most cases). It may be shown to have liquid water in the future but the atmosphere is the key.

So what I ask of the readers is that, although any planet in the habitable zone is likely to be very interesting to study, you should not assume life could ever exist there. Venus ('Earth's sister') is a habitable zone planet but I would hold off on booking a holiday visit.
I look forward to the many fascinating worlds that we will get to explore, albeit from afar, and hope to keep an open mind concerning habitable zone planets but will hold off until greater atmospheric data presents itself. 

Saturday, December 3, 2011

More planets than days

On December 1st 2011 the NASA Kepler planet finding mission celebrated its 1000th day in space and with over 1000 planetary candidates and 27 confirmed planets observed I would say that it was 1000 days’ worth celebrating. 

On March 6th 2009 Kepler was launched as NASA’s 10th Discovery mission. The mission was designed to survey our region of the galaxy to determine what fraction of stars have terrestrial-size planets in or near the habitable zone and for the last 1000 days it has been doing just that and more.

Kepler is a 0.95 meter telescope with a high precision photometer (light counter) which is able to continuously observe over 100,000 stars. Out of these stars the Kepler has discovered, 2165 eclipsing binaries, and 27 confirmed planets. Recently Kepler also released a list of 1235 planetary candidates so called as follow up observations need to be made to verify that they are in fact planets and not a result of other astrophysical phenomena. 

The illustration from the Kepler NASA website shows the expected size of these planetary candidates and their position in the field of view of the telescopes detectors. The aim of the mission is to put our solar system into context something which requires observations of the vast number of stars. Kepler provides a great opportunity for detailed photometric observations and although it is only looking at a very tiny portion of the sky the results thus far gives us great hope for finding an Earth like planet in the future. 

You too can help look for exoplanets  is one of a number of outreach programs that uses the public to analyse scientific data as the collective human brain is a fantastic engine for pattern recognition. Who knows you could help find the next Earth-like exoplanet and the potential for life 
outside our own solar system. 

This week the first Kepler science conference is being held and a great number of new discoveriesrs are sure to be anounced as a result.
Kepler anounced a further 1094 bringing the total up to 2326 associated with 1792 stars in just 16 months!
Follow the progress - Kepler conference. There is also an informative press vidoe up on YouTube - NASA's Kepler Mission Announces Latest Planetary Discovery 

I will leave you with this quote from a very wise man.
“It is known that there is an infinite number of worlds, but that not every one is inhabited. Therefore, there must be a finite number of inhabited worlds. Any finite number divided by infinity is as near to nothing as makes no odds. So, if every planet in the universe has a population of zero, then the entire population of the universe must also be zero, and any people you may actually meet from time to time are merely the products of a deranged imagination” - Douglas Adams

Sunday, November 27, 2011

The Very Beginning

You know the song was right it is a very good place to start!

I knew for a long time that I would end up doing a PhD as it seemed like the natural course for all the careers I could think of. However, it was not until after I got my acceptance letter that I sat down and asked myself the ultimate question. What is a PhD? And to tell you the truth I am still not entirely clear on the answer to that.

As a PhD student, although you get paid, you are still that; a student. Each PhD student has a supervisor who guides you through the learning process, is normally an active researcher in your field of study, and who is in charge of your progress and assessment. So in essence, your boss! You will also have a mentor. A member of academic staff outside your field of study whom you can go to with other problems; like when your supervisor, how can I put this delicately, is being… unreasonable.

During the first few weeks there is unfortunately a number of mandatory administration classes/meetings that you will need to attend though very little useful information is gleamed from them. For this is suggest you talk to the second year PhD students who will have recently gone through the same process but will have found their feet and understood their role (hopefully).

The first task is to talk to your supervisor and decide on a topic area, this is usually something discussed at the application stage however a little clarification at the star is never amiss. Your job over the next term will then be to research already published results/theories in this area and write a literature review on your findings. Although it may sometimes feel like a waste of time it is a great way to get information about your subject area and in many cases will form part of the introduction to your final thesis at the end of your PhD.
In my literature review I discussed the origins of understanding the atmospheres of our solar system of planets and moved onto the methods we use to investigate those extrasolar worlds. During my research I read many conflicting opinions on data interpretation and found out which planets had already been investigated and the findings from those observations. It is very important to understand and know what has already been done and to what extent as the real aim of your PhD will be to contribute new findings/theories/interpretations in your field.

Having completed my literature review I have now moved onto processing observational data in the hopes of furthering my understanding of my chosen field of study and to for a basis for my own unique work in the future.
I hope that gives you a rough idea of the first steps of a PhD hopefully I will be able to give more insight as my journey as a PhD student continues.

Sunday, November 6, 2011

It’s about time!

With the increased volume of exoplanets being discovered we are able to put our own solar system into context with observations that still baffle even the most seasoned astronomers. But what do we really know about these worlds and there always be more to learn?

Since the first exoplanet was discovered orbiting the main sequence star, 51 Pegasi, in 1995 via radial velocity measurements a whole host of stars have been found to have their own orbiting planets.
A number of different methods of discovery have radically expanded the field of exoplanetary science. There are now over 600 known exoplanets and over 1000 more potential planetary host candidates from the KEPLER list. By the end of this decade the number will almost certainly be in the 2000 region.
Thus far exoplanet discoveries have been concentrated around large planets in tight orbits around bright stars. This is because they are the easiest to detect via radial velocity measurements or observed in transits, the two most lucrative techniques so far.

The beauty of the transit method is that when the planet passes in front of its star we are also able to detect the atmosphere of the planet, and most are expected to possess an atmosphere.
This method of observing exoplanetary atmospheres is called transmission spectroscopy and can tell us of different atmospheric species, their extent, and concentration throughout the planet’s atmosphere.
Planets that have been found in transiting systems also produce an effect called the secondary eclipse. The secondary eclipse is when the planet passes behind the star, this will most likely have the same duration as the transit of the planet in front of the star. During the secondary eclipse, when the planet is completely behind the star, the amount of light measured is only coming from the star. When the planet is out of the secondary eclipse, just before and after disappearing behind the star, the amount of light measure is a combination of the star light, reflected light from the planet and thermal emissions from the planet itself. By measuring this change it is possible to calculate the temperature of the planet on the illuminated dayside, to determine transport in the atmosphere, and even cloud structures.

These two methods; transmission spectroscopy and secondary eclipse, allow for further classification of exoplanets. Though these methods have been exploited on only a handful of known exoplanets thus far, future measurements and observations will bring understanding and context to our currently unique solar system.

Image from MSNBC media

Sunday, October 16, 2011

Bright Lights, Big Planets

HD209458 and HD189733 are the most documented transiting extrasolar planet systems. So what lends them so well to our current observation methods?

HD 209458 and HD 189733 are the brightest known exoplanets host stars. This means that there is a good Signal-to-noise ratio making them ideal candidates for transmission spectroscopy studies. Meaning a large amount of information about their size and composition can be gleamed.

Transmission spectroscopy is a method used to determine the extent and composition of exoplanetary atmospheres in a transiting system. When a planet transits its star (passes in front of it) the light from the star is partially blocked this gives information about the expected size of the planetary companion.
Most exoplanets are expected to possess an atmosphere; so as the planet transits the star the amount of starlight that is blocked will not be a sharp change but a gradual one as the atmosphere blocks a small amount of the light first.

HD 209458b was the first exoplanets to have its atmosphere investigated using transmission spectroscopy. Using the Hubble Space Telescope Charbonneau et al. (2002) detected a 0.02% deeper transit in sodium D lines than in the continuum light curve. This was confirmed using the ground based Subaru telescope on the summit of Mauna Kea in Hawaii by Snellen et al. (2008) (follow up observations are an important process in any scientific investigation and are highly anticipated in all exoplanetary discoveries).
HD189733b was the second planet investigated using transmission spectroscopy. Observations measured in transits (from optical to Infra-red) show that the planets radius follows a model for Rayleigh scattering in the atmosphere. Rayleigh scattering is the scattering of radiation by particles that are much smaller than the wavelength of the observed radiation. The detection of HD189733b’s atmosphere was the first ground-based atmospheric detection of an exoplanets carried out by Redfield et al. (2008) using the Hobby-Eberly Telescope near Austin, Texas. They showed that the relative absorption in the sodium D line is roughly 3 times larger than that detected in HD209458b.

If an exoplanet has a large atmosphere it is also easier to detect as it will have lower surface gravity and a higher effective temperature. Both HD209458b and HD189733b have a observed effective temperatures and surface gravities that lend themselves perfectly to having large atmospheres and thus the observation techniques used. A summary of the molecular species observed in the atmospheres of both these planets can be seen in the data boxes below.

Almost everything known about Hot Jupiters to date comes from the investigation of these two planets, and there is still much left to investigate. Watch this space!

HD 209458*
Distance = 47 Pc
Spectral Type = G0 V
Apparent Magnitude V = 7.65
Mass = 1.148 Mo
Radius = 1.146 Ro
Effective Temperature = 6075 K

HD 209458b (1999)
Mass = 0.714 Mj
Radius = 1.38 Rj
Semi-major axis = 0.047 AU
Orbital Period = 3.524 days
Eccentricity = 0.014
Inclination = 86.59 degrees
MOLECULES: Hydrogen, Sodium, Water, Titanium Oxide, Vanadium Oxide.

HD 189733*
Distance = 19.3 Pc
Spectral Type = K1 – K2
Apparent Magnitude V = 7.67
Mass = 0.8 Msun
Radius = 0.788 Rsun
Effective Temperature = 4980 K

HD 189733b (2005)
Mass = 1.138 Mj
Radius = 1.178 Rj
Semi-major axis = 0.03142 AU
Orbital Period = 2.2148 days
Eccentricity = 0.0041
Inclination = 85.51 degrees
MOLECULES: Sodium, Water, Carbon Monoxide, Methane.

Thursday, September 29, 2011

The Earth from Afar

What would our planet look like from afar? Would it look the same if it was closer into the Sun or even if it was orbiting a different type of star?
A team of scientists aim to answer these questions with a model.

A network of scientists brought together by NASA form the Virtual Planetary Laboratory (VPL) and their goal is to use computer simulations to test what a habitable planet looks like over time.
The model integrates a number of factors that cause a planet to be habitable such as; geology, atmospheric parameters and its position relative to other astronomical bodies such as its star.
The task is by no means an easy one as the model will need to reflect the complexity observed of Earths system.

The current count of exoplanets is over 600, most of which are large gaseous worlds. There are, however, a number of Earth like candidates and with missions like NASA's Kepler Telescope which is hunting for exoplanets around solar-like stars or NASA's future planned Terrestrial Planet Finder (TPF) mission; the number of potentially habitable worlds is set to rapidly increase (potentially, being the operative word in that sentence).
This, however, still means that these planets will be viewed as point sources. Where dimensions are inferred and any information about atmospheres concerns the whole planet and not individual regions or clouds.

This is where computer models come in! Observational astronomers will be able to tell you what we can see, be it a signature for water or just an average temperature. Models are then used to determine the possible planetary and atmospheric structure from the data which increasingly requires more complex models with more informational parameters.

The VPL teams model is designed to be a complex model of the Earth as viewed from afar where the atmospheric, and geographical parameters are displayed over the whole planet (in essence it is an extremely pixelated view of the Earth). It also includes a number of changeable astrophysical parameters such as different wavelengths of light, if orbiting a different type of star, and the observation angle, to determine the effect of light off of oceans.
With the collaborative work of a number of teams like this and observations made around the world and from space we may be able to find another Earth.
The image was taken from the paper written by the VPL team .

Friday, September 23, 2011

Book Review - Strange New Worlds

If you wanted to know how to look for Earth-like planets and other solar systems, or just want to explore the galaxy of worlds out there; this is the book to read.

Ray Jayawardhana is a professor and award winning science writer and when reading Strange New Worlds you can see why. The book takes you on a path of discovery from the earliest ideas about exoplanets to the most up to date findings in the rapidly advancing field of discovery and classification. He easily explains the different methods used for exoplanets detection while pointing out the hardships taking the reader through a journey of the scientific process.

It is also a fantastic story of collaboration with credit given to amateurs and academic, graduate students and professors. He also includes some personal insight from his own early discoveries and takes the reader through the excitement of discovery through to the rewards of publication.

This Popular-science book brings you up to date ideas in one of the fastest moving fields of research today. It does not skimp on the scientific details but puts the reader in a position of easy comprehension. The chapters are short with a number of sub-chapters that outline the past, present and future of exoplanetary discovery clearly with compelling descriptions and fantastic storytelling.

It is a refreshing read that presents the most up tp date ideas in a new but increasingly expanding field of research. You will not be able to put it down.

I whole heartedly recommend this book. It is a true journey that fits remarkably well with the iconic words of Captain Jean-Luc Picard in the opening credits of Star Trek: The Next Generation.
“… Its continuing mission: to explore Strange New Worlds, to seek out new life, and new civilizations. To boldly go where no one has gone before!”

You can by Ray Jayawardhana's Strange New Worlds on Amazon
or at waterstones

Thursday, September 15, 2011

Is Kepler 16b George Lucus’ Tatooine?

NASA’s Kepler Mission team announced today that they have detected the signature of a planet orbiting a binary star system. Was George Lucas’ alien image of a double sunset on Tatooine in Star Wars IV genuine scientific foresight or just a matter of cinematic depiction?

The binary system is 200 lightyears away in the direction of Cygnus (the region where the Kepler planetary search is focused). Binary stars are common in our galaxy, as well as many others, and the term merely describes two stars that orbit each other. In this case the two stars are orbiting each other in a period of 41 days and at a distance within that of Mercury’s orbit around the Sun.

Unlike the stars depicted from Tatooine the two stars in the binary system are very different to each other and both are smaller and dimmer than the sun. The larger star is 69% the mass of the Sun; glowing a deep orange and is 100 times brighter than its dim red companion star which has a mass just 20% of the Suns.

The Kepler lightcurve also shows that the stars are active; this means that we can observe large starspots on their ‘surface’ (starspots are cooler regions of the stellar atmosphere and appear as black dots on our own sun).

The planet is in a wide orbit around both of these stars with a period of 229 days and a nearly circular orbit. This orbit means that it feels the gravitational pull of the two stars as one single point. The planet is a cold, gaseous world similar to Saturn and is not thought to harbour life.

The dynamics of the system, or any binary system, means that the area (like the one we live in) around a star known as the goldilocks zone or the habitable zone is a dynamic one. The temperature change due to the two stars orbiting each other would have an effect on the planetary temperature as well as the change in light due to an eclipsing binary system and the differences in the stars themselves would mean that the light from the two ‘Suns’ would have different effects on the planet and the seasons as we know them would not exist.

This would most clearly be seen in the sunset as Laurance Doyle said at the Kepler press conference earlier today the whole process is dynamic. At some point they both might set together, or one may set as the other rises, or there may be only a short difference as seen in the shot of Luke staring out across Tatooine. He concluded the thought by saying that, “If you wanted to tell time on Tatooine with a sundial you'd need to use calculus”

So, unfortunately there is not much chance of standing on the surface of the planet gazing like Luke Skywalker out at the double sunset while being serenaded by John Williams.

This system may not be the Tatooine that George Lucus dreamed up but it is a huge step forward in the hunt for habitable exoplanets as most of the stars we look at up in the sky are in fact binary systems. And if we can find one planet orbiting two stars that is dynamically stable you can bet that we are going to go out and look for some more.

If you want to go looking for Kepler 16b you can find the star system with a magnitude of 11.5 in the right wing of the Cygnus constallation.

Wednesday, September 14, 2011

Sci-Fi's Final Flight

Where once we had the space fairing imagination depicting solar systems and space ships, we now have homebound technology and parallel universes.

The imagination in Sci-Fi seems, like all things, to move forward. This itself would never be considered a bad thing; but is it moving away to fast have we finished telling the stories of space adventures too soon?
It is all well and good that new shows from extraordinary imaginations are depicting a more quantum universe with time jumps and parallel worlds but are we ready to entirely move on from space travel and the adventure of whole new worlds to discover.
The last in over well over two decades worth of space fairing Sci-Fi series ended this year, also marking the end of the nearly 15 year run of the Stargate franchise. Stargate Universe followed a group of scientists, military and civilian personnel stranded on an Ancient ship called Destiny. Destiny takes them on a course through solar systems across galaxies following a path back to the birth of the universe.
Though the Stargate franchise is the only space fairing franchise among many (star trek, star wars, Battlestar Galactic, ...) to depict/suggest real-time travel between galaxies many other shows such as BSG, Farscape and the short lived series Firefly have been 'seeded' from Earth and inhabit systems within the milky way. Others like Star Trek look at the whole galaxy and the endless number of world within it forming regions of political and/or technological differences that present the mired of story lines depicted over its 5 series' and a total of 11 movie run.

I feel, or rather i have noticed that with increased knowledge of real life exoplanets, we are now in some cases able to take spectra and determine atmospheric properties, there is a decrease in the number of shows creating stories around their discovery and origin. Have we reached a point in our knowledge of exosystems that we feel any story would be farfetched or not able to be rooted in reality as we had once hoped? With the discontinuation of the Space Shuttle should we be turning away from telling stories of space ships? In my opinion, NO, now is the time where space exploration in Sci-Fi should be taking off we want new ship designs we want to know what types of world we can imagine and as we have seen most of the world found outside our solar system are far beyond our imagination we have to do a double take and question what we know. Those gifted with the extraordinary imaginations that brought us Stargate and Star Trek and all the other amazing show i do not have the time to list here have all these real world stories to follow and take those of us without such gifts on a journey with them and the characters they create to these other worlds.
I do not think that we should throw space exploration entirely over to factual discovery, not yet at least.