FLA: A Star is Born, literally

Like many stars, the source of the Sun’s light is the nuclear fusion reaction that occurs in its core. Hydrogen nuclei react with other Hydrogen nuclei to generate Helium—in process, releasing enormous radiation in form of heat and light. The temperature in the core of the Sun is, therefore, near 15 million Kelvin (27 million F). It takes about a hundred thousand years for this radiation to reach the surface of the sun, from where it reaches the Earth in 8 minutes, providing heat and light to the planet.

Hydrogen nuclei fuse to form Helium and liberate energy. Source: WJEC.co.uk

The process of nuclear fusion is what forces otherwise inactive elements to react with each other to form heavier elements. Nuclear collision and high pressure makes these reactions possible, thus creating heavier elements like Iron, Gold, etc. Iron is the most stable element. Past Iron, energy is now required to create further higher elements. This is possible only through supernova explosions. Given this, we can consider stars as chemical factories, liberating energy and light as a by-product of the chemical reactions. The process of fusion of atomic nuclei is known as nucleosynthesis.

Higher, heavier elements are formed. Source: LA Radioactive.com
Stars are chemical factories

The process of star formation is a quite inefficient process of combining gas clouds that could be the remnants of a dead star (e.g.: induced star formation). These gases collide and combine to trigger nuclear fusion thus forming stars. In the process, about 99.9% of the gas clouds are consumed, leaving the remainder for rocky or gaseous planets to form.

Depending on the mass of a star, its glorious life can end in two different stages. If the mass of a star is less than 1.4 times that of the Sun, which is also known as the Chandrasekhar limit, it collapses into a dense carbon-rich white dwarf. However, if the mass of a star is more than 1.4 times the Sun, it could either end up as a neutron star or a black hole depending on how massive it is. Further, for stars with high mass between 1.5 to 3 times the mass of the Sun, the main sequence stage is followed by a supergiant, leading to a supernova, and thus ending up as a dense neutron star. This neutron star is made up of dense neutron material, which is like a large atomic nucleus with an atomic number close to 1054. This star is the size of a small city, of about 10-20 km in diameter, with the density of trillions of grams per cubic meter.

Life and Death of a Star

If the mass of a star is more than three to five times that of the Sun, it is more likely to collapse into itself due to gravity and end up as a black hole. This end result is so dense that it compresses to a stage even smaller than an atom, known as singularity – the center of a black hole. The gravity of singularity is so strong that even light cannot escape from its field. This entrapment of light gives a sense of utter darkness surrounding it, the edge of which is known as the event horizon.

FLA: Discovering New Planets

The discovery of new exoplanets has rapidly grown in past two decades. While there are three major ways of detecting these exoplanets in distant galaxies, two of these methods are indirect in approach. These two methods are Doppler and Transit. In the Doppler method, a giant planet’s gravity pulls the star it revolves around, which causes it to wobble. This wobble can be subtle, but can still be detected from Earth. This method reveals the mass of the exoplanets. However, it requires the orbits of these exoplanets to be in the plane of the Earth’s sky.

Doppler Method. Source: University of Wisconsin-Madison

The second indirect method, Transit, detects exoplanets each time they pass in front of their stars. Passing in front of the stars blocks a portion of the light coming from these stars. This eclipse reveals the size and chemical composition of the exoplanets.

Transit method. Notice the drop in brightness when the exoplanet passes in front of its star. Source: NASA.

The third method, the direct method of imaging, is the most obvious but extremely difficult. The weak reflected light from the exoplanets is too low to be detected from Earth. On one hand, given the stronger direct light coming from the star makes it even harder to locate the exoplanet. On the other hand, if the exoplanet is further away from its star for it to be easily discernible, the reflected light goes down by twice the factor of the distance. Both these methods are examples of how difficult it is to directly image exoplanets, and requires complicated and precise models to subtract stars from the process of imaging.

Imaging method. Source: Wikimedia.

Thousands of exoplanets have been found this far. Kepler telescope has a dedicated mission to stare at a portion of deep space, searching for these planets. The more planets we find, the more similarities and differences we find between our solar system and these distant planet systems. First, both the planet systems have two types of planets: terrestrial and Jovian. Terrestrial planets are rocky planets, found closer to the sun, with a possible water world, for example: Earth. Jovian planets are gaseous, usually further away from the sun, for example: Jupiter. Each solar system has a habitable zone, which consists of an area at a distance from the Sun, where the temperature makes it habitable by providing affordances for several biomarkers, for example: water.

While there are some similarities between the two planet systems, there are also differences in the placing of these exoplanets and possibility of life. Some planet systems were found with massive planets very close to their suns. Jupiter’s presence in the solar system adds stability to our solar system. Jupiter is five times further away from Sun than Earth. When a massive planet is closer to its sun than Jupiter is to our Sun, it could make their planet system inhabitable.

Also, whatever chemical compositions is available on these planets, it is not necessary that these planets also support a carbon-based life form or oxygen generating microbes. We should be open to possibilities of alternate life forms on these planets.

For the Love of Astronomy: Telescopes in Space

Telescopes are tools to extend the human vision. The requirement of telescopes stems from two major limitations of the human eye. First, the aperture of the human eye is too small to register enough light to resolve between distant celestial objects. Second, the human eye is capable of detecting only the visible portion of the electromagnetic spectrum—which constitutes only a tiny factor of the entire spectrum. This significantly truncates the information that most of the electromagnetic radiation from the universe has to offer.

As a solution to the first problem, designing telescopes with larger diameter allows it to capture more photons of light per unit area, thus producing brighter images. In addition, the larger is the telescope, the smaller is the angle that can be resolved. This means that distant objects can be distinguished and seen in better quality.

40-meter-class European Extremely Large Telescope (E-ELT) Source: ESO

As a solution to the second problem, even though we have telescopes that can register electromagnetic spectrum beyond the visible light, Earth-based telescopes can still not detect other electromagnetic waves such as infrared, gamma rays, X-rays, etc. This is because the Earth’s atmosphere acts as a natural filter to these and does not allow most of these electromagnetic waves to pass. What penetrates the Earth’s atmosphere are visible light, radio waves, portions of infrared band, etc. In addition, light pollution in most parts of the world limits the detail of the view from Earth, making astronomy extremely difficult. Finally, Earth’s atmosphere also creates turbulence for light, thus creating an effect of blurring, which affects the image created by the telescopes on ground.

Portions of the Electromagnetic Spectrum blocked by the atmosphere. Source: JCCC.edu

Given the limit cast due to the atmosphere, Earth-based telescopes are restricted to a tiny portion of information that light carries from distant galaxies. To solve this problem, astronomers launched and planted large telescopes above the Earth’s atmosphere in low orbits in space. These telescopes, liberated from the shortcomings of the Earth’s atmosphere, can now detect X-rays (Chandra space telescope), Infrared (Spitzer space telescope), and deep space (Hubble space telescope), etc. These telescopes can now register bright lights from distant galaxies, revealing information unbeknownst to the humankind before. This generates a tremendous amount of data for astronomers and physicists, and therefore opens a magnificent range of possibilities to answer some of the most pivotal questions about the existence of the universe and its properties. There is also a new telescope, James Webb, ready to replace Hubble, which will be able to detect the very first light in the universe. Thinking of the results of this telescope is just too exciting to comprehend.

Some of these large space-based telescopes work with specific band of spectrum. For example, the Chandra Space Telescope captures the X-rays and generates images with information that was earlier invisible to the naked eye. The Spitzer Infrared telescope, on the other hand, reveals the temperature across the universe. This is possible because infrared reveals the heat of each object that emits it, thus providing information that was not possible with the visible spectrum.

North America Nebula – by Spitzer Infrared Telescope. Source: CalTech

Launching and maintaining these telescopes in space comes at a great cost (in billions of dollars). But this cost proves its worth by producing a flood of data that could hold the key to most gripping questions of the humankind. If one could evaluate the cost and return of large space-based telescopes, the returns would out-weigh the cost each time.

This post included additional information, like the images, that were not included in the writing assignment

For the Love of Astronomy

My childhood love and passion for astronomy had its share of ebb and flow. While it peaked in 9th grade, when my friend and I ogled at images of deep space in our library encyclopedia, the zeal to pursue this passion was lost somewhere in the race for a “practical” education.

Fortunately, as my colleagues in the EPET program inspire me in different ways, my myriad disjointed conversations with them led to rekindling the remnants of some forgotten passions. One of the examples is how, with time, I got in tandem with pursuing an old interest in learning about astronomy.

From almost a year now, I have spent a handsome share of my leisure time reading about physics and astronomy. Recently, when I found a Cousera MOOC (Massive Open Online Course) on ‘Astronomy: Exploring Space and Time’ by Dr. Chris Impey, I jumped to the chance and enrolled myself for the nerdy fun I had waited for over 10 years.

pillars of creation - source es-static.us
Pillars of Creation

In this class, we look at the essential concepts in astronomy, physics, and chemistry that help understand the science behind some of most wonderful phenomena. The course requires some prior knowledge of the field–which reminds me to thank the turn-of-events that led to me choosing science and electrical engineering in school and college, respectively.

In the first two weeks, not only I have learned some of the most amazing facts and concepts that I had never understood before, I have also realized the profound importance of scientific literacy among general public.

Now, this course requires us to complete a bunch of tiny quizzes and three brief writing exercises. I think it would be a great idea for me to share these writing assignments on my blog here.

The next post is on Telescopes in Space. I will follow this introduction with this first writing exercise to share the fun that I am having in this course. I hope you enjoy reading this as much as I enjoyed the previous two weeks learning about