Chile – Where the stars shine the brightest !

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The majestic band of the Milky Way as seen from Chile’s Atacama !

“Towards Atacama, near the deserted coast, you see a land without men, where there is not a bird, not a beast, nor a tree, nor any vegetation.”
La Araucana by Alonso de Ercilla, 1569

Those words by 16th century Spanish conquerors summed up the stark impression left on their minds by Chile’s most famous landmark – the great Atacama Desert.

Searching for some warm moist air ? Then Atacama is definitely not the place for you to visit. The 1000 kilometre long land, lying to the west of the Andes mountains, is the driest hot desert in the world. In an average year, much of this desert gets less than 1 millimeter (0.04 inch) of rain ! That makes it 50 times drier than Death Valley in California.

Very few life forms can survive in such harsh conditions. But the very attributes that make Atacama inhospitable to life also make it ideal for the oldest of all sciences – Astronomy.

Astronomy is an observational science. Our theories will only be as good as the accuracy of our observations and equipments. Ask an astronomer to describe the perfect place to put a telescope, and here’s what he’ll tell you: Make it cold, make it dark, make it dry, and make it remote. In short, the exact description of the Atacama. Atacama’s exceptionally clear skies and dry air are ideal conditions for getting perhaps the best night sky views we can from this planet.

Being in South America, Chile also holds another ace in the pack considering that Astronomers can observe a different part of the sky than all the northern hemisphere observatories notably in Europe and North America.

The astronomy capital of the world

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Artist’s impression of the upcoming ALMA radio observatory

If asked about where the best telescopes in the world are, then one would probably hazard a guess at North America or Europe. But its Chile that rules the roost.

Chile currently supports 42% of world’s telescope infrastructure and is expected to rise to 70% of the world’s telescope by 2018 . Soon enough, Atacama will be the site of the largest international astronomical project in the world – the Atacama Large Millimeter Array (ALMA) which is a 10 mile diameter giant Radio telescope made up of several smaller telescopes. This amazing telescope could get images of quality 5 times finer than even the Hubble Space Telescope.

To promote future growth, Chilean Universities are offering research based graduate and post-graduate courses in astronomy to attract the top astronomy talent from around the world .

Chile has surplus of telescope time and is looking for talented astronomers to conduct their research thereby benefiting both the country and the astronomer. These astronomers face less competition for telescope time in Chile than in their home countries.This is one of the biggest reasons Chile is and will continue to be the Astronomy capital of the world.

Atacama – the great gift of nature

The Atacama’s geography makes it a place unlike any other on our planet. This vast expanse of barren land has given us the key to unlock the secrets of the universe. We go back as a culture to the study of objects in heaven, like our constellation seeking ancestors did.

What drives us on this journey? Nothing but the feeling of enthusiasm and curiosity that all humans crave for! Lets cherish this beautiful gift that nature has given us in Chile.

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Everyone’s a Scientist !

Science is a beautiful thing. More than the labs and the instruments, it is human curiosity and endeavor which fuels it’s growth. It is more than just an abstract analysis of things. It is a sincere effort to unravel the mysteries of the universe.

For ages, Science has typically been a solo activity. The Newtons and the Einsteins may have collaborated and worked together with other scientists for some duration; but most of their groundbreaking work has been a result of their own perseverance and genius.

But now, the very nature of scientific research has changed. The groundbreaking theories of today are not born out of generating theories based on intuition and logic; the driving force in scientific research today is the element which is perhaps driving the whole world – data. Lots and lots of data. Rather make that an astounding amount of data.

One of the most talked about example of this is the recent 2013 “validation” of the ‘God particle’ – Higgs boson by the clever guys at CERN. The amazing $10 billion Large Hadron Collider machine, which was used used to generate the particle collisions for this experiment, generated so much data that it took months for scientists to analyze it and come to any conclusion. And note that this endeavor was undertaken by thousands of scientists from all over the world.

There is just so much data floating around that researchers can’t simply process all of that. But this data is vital and has the potential to answer some of the biggest questions of our universe. Well then, how do we analyze this data ? Rather who will ?

The answer is YOU ! Yes, it is you and every other person who harbors curiosity about nature and the enthusiasm to contribute. The data revolution has taken science from the labs to desktop computers and made it more accessible to the common public than ever before.

Lets take a look at some of the more interesting citizen science initiatives around.

Are we alone ?

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Search for Extraterrestrial Intelligence(SETI) is one of the earliest programs designed to find an answer to one of the most haunting questions posed to humankind – Are we alone in this universe ? This University of Berkeley initiative listens to radio signals in hope of searching for extraterrestrial intelligent life. Radio signals contain a lot of noise and need to be analyzed digitally. Due to the large amount  of data, it would require a supercomputer to perform such a task constantly.

SETI@home is a virtual supercomputer created by connecting several computers through the internet. You can lend some idle computing power from your laptop for radio signal analysis that SETI does just by downloading their free software.

Decode the mysteries of the stars !

The SCOPE project for example allows users to choose from thousands of unknown star spectra available online and use various analytical tools to classify a star by comparing its spectra to a known star’s spectra. This classification gives an idea about how the temperature, luminosity and mass of the star are related.

This information is useful in understanding the life cycle of any star. The sky offers a laboratory to explore and anyone can do it using their laptop or desktop computer and a basic understanding of physics.

Zooniverse !

Zooniverse is one of the best places around to take part in some real cool projects. It covers a vast variety of projects right from trying to understand Whale communication to cyclone data analysis to galaxy formation. All these projects require only some basic training which is provided on the website itself.

Citizen science – The way forward..

These are just some of the many public science initiatives around. Science for citizens is a great way of promoting science to the general public and help create awareness of all the research being done currently.

Ever dreamed about doing some science, but never got the opportunity ? Now is the time. It is only by standing together that we can hope to unravel nature’s infinite mysteries !

Links to the above initiatives:
http://setiathome.berkeley.edu/
http://scope.pari.edu/
https://www.zooniverse.org/

Black holes !

Black holes are perhaps the most mysterious objects in the universe. In layman’s language, it can be said that a black hole is a body with gravitational pull so intense that not even light can escape from it thus making it ‘black’

So if the black hole is indeed ‘black’, how do you see it ? Well, it turns out that you can’t. In fact we have never actually observed a black hole in the same manner as we can view distant stars and galaxies. We can’t see them; but we can definitely predict their presence and detect their strange effects.

To get an understanding of these effects, we first need to visit one of the theories which changed the way we view our universe – Albert Einstein’s general relativity.

Einstein’s Tower Experiment

You throw a ball high up into the air vertically using only your physical strength. What would you expect will happen to the ball? A reasonable person would say the ball will go up for a certain amount of time before it comes to a halt and then eventually it will drop on the ground.

This happens so the kinetic energy(KE) of the ball (KE is highest at the point of release from the arm) is converted to gravitational potential energy(PE) when the ball is thrown up. The ball stops when all KE is converted to PE .Then while falling down, it converts all its PE to KE in the reverse process. All this is basic High school physics !

Here’s where things can get complicated though; what if you are shooting a beam of light from the surface of the earth vertically up? Would you expect light particles (photons) to lose some of their kinetic energy the same way that a ball would?

Turns out that if we assume that light will not be affected by gravity and lose its kinetic energy as it moves up, then using Einstein’s Energy- mass relationship we come to  strange consequences where extra energy is created! This violates the conservation of energy law – energy can neither be created nor destroyed. Therefore, our assumption that gravity does not affect photons must be wrong and calls for a correction. So we correct our mistake by showing that the photon loses energy when moving vertically up. This phenomenon is called Gravitational Redshift.

Now imagine an observer standing at the top of a tower – stationary w.r.t. ground (not free falling). Put a source of light at the surface of the earth and shoot a beam of light vertically up. The photons lose energy due to earth’s gravity. This means that the frequency of the light wave decreases due to the fact that Energy of photons = Planck’s constant*Frequency. As a consequence, wavelength increases (inversely proportional to freq.) and hence it is called redshift as increasing wavelength shifts towards the red part of the spectrum. The speed of light is a fundamental constant of the Universe, it does not vary.Therefore as the photon loses energy while climbing vertically up from the surface of the earth, the observer will see the wave of light redshifted depending on how high he is standing and the strength of the earth’s gravitation1

Check your clocks !

Imagine a clock built out of frequency of light wave and placed at the surface of the earth. As the beam of light shoots up it will be redshifted by gravity, meaning the frequency will decrease and the clock will seem to slow down from the observer’s point of view. The understanding of this phenomenon revolutionized the world of physics.

Black Holes and General Relativity equations

Einstein derived a set of complex equations popularly known as Einstein field equations to describe the geometry of the Universe and how it “curves” due to mass and energy. So, the way of representing this curved space is, a massive object will put a dent in the space-time fabric and light travelling from near the object will have to cover a longer path causing it to “bend” due to the mass of the object (gravitation).

The most extreme prediction of this theory is a black hole. Well, how do these strange objects come into existence ? They are formed mostly from the death of a star. A star goes through a long evolutionary process starting from just a gas cloud. When stars having masses much higher than our sun are in the last stages of their evolution, the star explodes( the phenomenon is called a supernova) and the remaining mass goes on contracting in size. Correspondingly its gravitational pull keeps on increasing until the stage arrives where not even light can escape from it. So this stage of a star is called a ‘black hole’ due to the fact that no light ever can escape it.

Now look at above figure representing a black hole and let us analyze it from the General relativity point of view. The black hole does not merely dent the space time, but it puts a hole in it called singularity. This singularity could be interpreted as a point (no dimension) where all the BH mass is squeezed into and has theoretically infinite gravity2

 

As a result of light having a finite speed, there may exist a gravitational field so strong that light coming from the mass creating the field will lose all its energy before reaching a stationary observer outside the gravitational field. Such a gravitational field is created by a Black Hole and the corresponding area (no escape zone for light) known as the event horizon is proportional to the Schwarzchild radius3(SR). Information from inside the event horizon cannot reach outside. This is because the speed of light is a fundamental limit that we know on how fast anything can be transmitted from one point to other.

Does that mean BH is a vacuum cleaner that sucks everything inside? If suddenly the Sun turns into a BH would the Earth be sucked inside? No! Things will orbit around the black hole just like they orbit around a star if they are moving fast enough outside the event horizon. If they are moving too slow near the BH gravitational well they will fall towards the center. If they are moving too fast they will get deflected but continue moving in the same direction until acted upon by some other force. Inside the event horizon all world lines lead to singularity!

Astronaut freezes in time !

Go back to tower experiment in the earlier section. This time imagine an observer standing outside the gravitational potential of the Black hole, beyond gravitational potential of BH – stationary w.r.t. the BH. An astronaut is free falling into the black hole. As the astronaut is getting closer and closer to the event horizon the light emitted by his suit is getting more and more redshifted when it reaches the external observer. Hence the astronaut’s clock appears to be moving slower and slower w.r.t. external observer’s clock. But this is only relative, the astronaut perceives his own time moving normally. Now this clock slows down until the astronaut reaches the event horizon at which point the slowing-down-factor approaches infinity, in other words the external observer sees the astronaut frozen in time at the event horizon!

From the astronaut’s (assuming he manages to survive the immense tidal forces created by BH) perspective, all light from outside reaching his eyes will be blueshifted (opposite of redshift, photon gains energy) increasing frequency of wave more and more as he approaches the event horizon. Hence he sees the external observer’s clock moving faster and faster (frequency increases). At the event horizon he sees the observer’s clock moving infinitely faster!

The world’s biggest lenses

Of course we cannot send a person inside a black hole to test these theoretical predictions. Strong tidal forces of the BH are more likely to just rip a person apart before even reaching the event horizon. Instead lets look at what we can observe with telescopes and light sensitive detectors as a result of black holes.

A fascinating phenomenon Black holes (or any massive object creating spacetime curvature for that matter) can produce is called “gravitational lensing”. Imagine a black hole obstructing our view of a further object in some direction in space. The light from this object will bend due to the black hole’s gravitational well – as we saw earlier, light takes longer path to travel due to the curvature in spacetime. This bending may lead to distorted image of the object in the background.  The nature of the distortion and how the image will appear depends upon the angle the lensing object makes with the distant object and an observer on earth. See image below4

Ever since the discovery of gravitational lenses, astronomers have been interested in studying them. These lenses apart from being fascinating may be helpful in making more accurate measurements of distant objects.

Goodbye, Newton?

So there it is, the expansion of physics from Newtonian or classical mechanics with its notion of absolute time to theory of Relativity which integrates 3D space and time into a 4-Dimensional fabric of space-time. Space time has changed the way we look at the universe and it’s workings.

So do we just discard Newton’s classical laws of physics? Absolutely not! Relativistic calculations are not always practical or fruitful in improving our level of accuracy in cases of small influence of gravity (or small velocities we are dealing with). Classical mechanics is still very useful in making several deductions in the field of astronomy.

Footnotes:
1. This has been experimentally verified by putting extremely sensitive atomic clocks at various heights from the surface of the earth and measuring the differences in time due to earth’s gravitational well.
2. Humans have a hard time imagining infinity. It can be said our physics is insufficient at this point to understand this gravitational singularity
3. The Schwarzschild radius is the radius of the event horizon surrounding a non-rotating black hole. If any object is compressed to a physical radius smaller than its Schwarzschild radius, then it will become a black hole. Formula for the Schwarzschild radius is Rs = 2 GM/c^2. M is the mass of the body, G is the universal constant of gravitation, and c is the speed of light.
4.In the formation known as Einstein’s Cross, four images of the same distant quasar appear around a foreground galaxy due to strong gravitational lensing
References
http://www.universetoday.com/33454/how-do-black-holes-form/

Twinkle twinkle little star – How I wonder what you are !

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Astronomy – a simple science?

“Simplicity is the ultimate sophistication.” – Leonardo da Vinci.

Astronomy may not sound like a very simple science. But in reality, many things in astronomy require only basic fundamentals that we all learn in high school. The sky is a natural laboratory for astronomers and fundamentals of physics are used to study the properties of objects in space. To give a demonstration of this, we will take a look at how simple it is to get a rough estimate of the properties of a star which is probably billions of light years away from us.

How do we know about the stars

Even an astronomer having access to state-of-the art technology can obtain values of only two variables – apparent brightness of the star and it’s distance from us.

Apparent brightness and spectrum[1] can be measured and recorded by a variety of light sensitive devices. The distance can be obtained from simple methods like parallax. To demonstrate parallax, hold your index finger at eye level. Shut your left eyelid first (right eyelid open) and look at your finger, then shut your right eyelid and look at the finger. Your finger will appear to move against the backdrop of a more distant object such as the wall of your study room. This apparent motion is called parallax. Astronomers use a similar technique to find distance to the star. Astronomers make one observation each two times a year, when the Earth is on the opposite sides of the sun.

Now let’s go from what we can measure to what we can infer and calculate. We will have a look at how a star’s three most important properties – Luminosity, Surface temperature and the radius – are calculated. Brightness, spectra and distance can be used to obtain these properties.

Let’s first learn a little bit about these quantities and why we are interested in them. Luminosity is an important measure of brightness, which is the power of a star — the amount of energy (light) that a star emits from its surface. It is usually measured in terms of how much more/less bright a star is as compared to the sun. Surface temperature of a star is used for classifying the star into different types. The radius of a star is very important from the point of view of assessing the star’s evolutionary phases[2]. The equations for these quantities are what we learnt in high school or early college years. Let’s get a recap of those:

Equation for Luminosity:
L= 4πD2b
L= Luminosity of the Star
D = Distance of the star from Earth
b = Apparent Brightness
Equation for Surface temperature:
T =  0.0029  ⁄ λmax   
T = Surface Temperature
λmax = Maximum wavelength from spectra
Equation for Radius of Star:
L = σT44πR2
R= Radius of the Star

We already have the values of the inputs (D, b, λmax ). So calculating the outputs (L, T, R) is an easy task.

Astronomers: We work hard too!

Well, now you might say if stellar astronomy is just about three simple equations, then why are astronomers spending hours on research and taking thousands of measurements using precious telescope time? Well, it turns out that getting the initial measurements is not so simple.

When we look at the sky, the stars appear like they are distributed on a huge 2D black canvas. But in reality, there is space between us and the stars. Therefore it’s not uncommon that our view of the stars may be obstructed by some interstellar gas or dust cloud. When starlight passes through this interstellar cloud before reaching earth its spectra will get distorted. Now it’s a challenge to separate which part of the spectrum comes from the stars and which one from the interstellar cloud. This is a real problem and requires several observations. There are various techniques that astronomers use to separate the two. But all of them rely upon using what we know about the stars to infer which parts of spectrum belong to the interstellar cloud. After that astronomers can subtract that part of the spectrum to give them the spectrum of the stars. Once astronomers have learnt about the interstellar spectrum they can use this to correct spectra of other stars in that direction.

Overall, we can see that although the fundamentals are simple to grasp, the practical challenges in astronomy are immense and require a lot of ingenuity and also dedication to the goal of advancing our knowledge about the universe. And in our opinion, that’s what makes it so challenging.


Footnotes:
[1] When astronomers split the light beam coming from a star using a spectrograph (prism like device), the resulting collection of wavelengths of light is called a spectrum.
[2] A star goes through various evolutionary phases starting from a big gas cloud to a huge supernova explosion.  Right now, our Sun is in a phase called the ‘Main Sequence’ which is roughly in the middle of the two aforementioned limits.