Week 1 - Quasars.
What I haven't told you guys is, I'm in Trivandrum, Kerela right now. I've been here since last friday.
I am currently a Summer Intern at IIST, Trivandrum under Prof. Anand Narayan of the Earth & Space Sciences Dept here at IIST. I'm working on Astrophysics. To be more specific, i'm working on Quasars, understanding their spectra and the processes involved behind their extreme luminosity. I will give a much more detailed account of the work I've been doing for the last week but let me summarize here what I've experienced here at IIST.
If stepping off the train at Trivandrum to the song It's a long way to the top by AC/DC wasn't enough of a signal, it started to rain the minute i stepped out the train onto trivandrum. Well you could say that it's the rainy season and that it rains in trivandrum a lot but let me remind you that the day i got off the train was on the 31st May, coincidentally the 1st day of this year's monsoon in Kerela. I'm sorry but i take that as kerela's way of welcoming me! Label me superstitious or whatever, i don't really care right now. On a different note, it was indeed a long way to the top, to reach the campus which is ~30 Kms outside the city. It was a looong way and it burned a deep hole in my pocket* but let's not get into that. Settling down on the campus, getting a room for the rest of my stay here, paying for the mess and hostel facilities were quickly taken care of. As getting an ID card was the only thing left, i rang up my prof to tell him that i'd arrived and to ask him for a meeting in the afternoon just to know that he won't be reaching campus for another 4 days i.e the tuesday after. I pretty much spent the weekend in my room, doing all sorts of stuff and dreaming about the project and work i'd be getting once i start. Annd boy was I in for a treat.
Starting tuesday, I've been reading up on Quasars. In short, Quasar stands for Quasi-Stellar-Radio Source. These objects were discovered thanks to their extreme luminosity/brightness in the high energy part of the EM spectrum (UV, X-Ray) but they appeared like point objects i.e stars. It was later on speculated that a single star is not capable of emitting such immense energy and this has since been proven. Quasars are in general classified as an AGN - Active Galactic Nuclei. Given big enough telescopes and good viewing conditions, astronomers were able to resolve (some of) these star like objects and they found that these objects were indeed galaxies. It is further estimated that the immense energy these objects radiate originates from an area of size ~1pc near the center of the galaxy (that's roughly larger the size of our solar system) which is how the name came about - Active Galactic Nuclei. Super massive Black Holes (no, seriously!) are assumed to be the driving force behind these emissions, accreting mass thanks to their immense gravitational fields which eventually leads to Synchrotron, Bremsstrahlung, Thermal and Non-Thermal radiation! (Wiki FTW!).
To get you started off, just the way i did, here are a couple of excellent popular articles on Quasars -
Heyy, heyy. That's enough. Stop patting yourselves and get back to reading now...
Moving further, before i understand the energetic processes in quasars that lead to emission (that's gonna take a looong long tie), i'm supposed study the spectra of known quasars and look for characteristics of Quasar Spectra. Understand the major emission lines and the reason for their line strength, understand how red shift effects the energy spectum of a quasar.
Ohh wait, i haven't told you. Quasars aren't found in the local universe i.e in the milky way or anywhere near andromeda for that. We'll have to look further away. Because quasars are so strong, they can be seen to very large distances, distances so huge that it makes no sense to keep measuring the distance in terms of Gpc. It's measured rather in terms of z - red shift.
Coming back to understanding the spectra of quasars, I've been given a sample set of 14 quasars and was asked to retrieve their images and spectra from the SDSS (Sloan Digita Sky Survey) archive. This is one thing I've wanted to do for a while - Data retrieval. There is literally TBs of data lying on data servers all over the world, data pertaining the spectra and images of stars, galaxies, nebulae - you name it and it's most probably been pictured by some telescope, somewhere on the planet! And the awesome thing is that all of this data is free, Free, FREE!!! You can pretty much open the website, look for an object you want to study and download the relevant data - no hassles!
Let me show you!
So, there's this awesome place on the internet called NASA's Extra-Galactic Database or in short NED which is where you start your journey. The first thing you need to do is to know the RA and Dec of the object you want to study (RA and Dec are like the x,y co-ordinates of the object in astronomical terms).
Now, one of my objects of study is - SDSS J101419.40-002834.2 and here's what shows up when you search NED by name. Once you get used to the naming convention, you'll realize that the first part of the object name is the RA of the object and the second part is the Dec - SDSS J(RA)(Dec), you might want to skip NED but look at all of the information NED has on the object! But wait, we're not done yet! Look at what the SDSS data archive has on this object!
And hey, we're just beginning our journey. Now, one needs to download the spectrum, which is by default a FITS file (a common file type in astronomy) and then work on it, tag different emission and absorption lines to a specific atom's transitions!
If you thought this was all, well actually this is all because i'm not going to document all that happened this week. It'll take me a week to document what happened last week. Ohh wait!
Annyway, there were discussions on stellar formation, metallicity of stars, faith & religion and a looot more things! I found that there is a third kind of stars called Pop 3 stars, the answer to a question that'd been nagging me for a while now! So, well, that's all for now folks, tune in again next week to understand a bit more about the elements whose emission lines are commonly observed in quasar spectra, different problems that arise when one tries to acquire the spectra of a quasar and so on...
Comments are appreciated.
Adios...
I am currently a Summer Intern at IIST, Trivandrum under Prof. Anand Narayan of the Earth & Space Sciences Dept here at IIST. I'm working on Astrophysics. To be more specific, i'm working on Quasars, understanding their spectra and the processes involved behind their extreme luminosity. I will give a much more detailed account of the work I've been doing for the last week but let me summarize here what I've experienced here at IIST.
If stepping off the train at Trivandrum to the song It's a long way to the top by AC/DC wasn't enough of a signal, it started to rain the minute i stepped out the train onto trivandrum. Well you could say that it's the rainy season and that it rains in trivandrum a lot but let me remind you that the day i got off the train was on the 31st May, coincidentally the 1st day of this year's monsoon in Kerela. I'm sorry but i take that as kerela's way of welcoming me! Label me superstitious or whatever, i don't really care right now. On a different note, it was indeed a long way to the top, to reach the campus which is ~30 Kms outside the city. It was a looong way and it burned a deep hole in my pocket* but let's not get into that. Settling down on the campus, getting a room for the rest of my stay here, paying for the mess and hostel facilities were quickly taken care of. As getting an ID card was the only thing left, i rang up my prof to tell him that i'd arrived and to ask him for a meeting in the afternoon just to know that he won't be reaching campus for another 4 days i.e the tuesday after. I pretty much spent the weekend in my room, doing all sorts of stuff and dreaming about the project and work i'd be getting once i start. Annd boy was I in for a treat.
Starting tuesday, I've been reading up on Quasars. In short, Quasar stands for Quasi-Stellar-Radio Source. These objects were discovered thanks to their extreme luminosity/brightness in the high energy part of the EM spectrum (UV, X-Ray) but they appeared like point objects i.e stars. It was later on speculated that a single star is not capable of emitting such immense energy and this has since been proven. Quasars are in general classified as an AGN - Active Galactic Nuclei. Given big enough telescopes and good viewing conditions, astronomers were able to resolve (some of) these star like objects and they found that these objects were indeed galaxies. It is further estimated that the immense energy these objects radiate originates from an area of size ~1pc near the center of the galaxy (that's roughly larger the size of our solar system) which is how the name came about - Active Galactic Nuclei. Super massive Black Holes (no, seriously!) are assumed to be the driving force behind these emissions, accreting mass thanks to their immense gravitational fields which eventually leads to Synchrotron, Bremsstrahlung, Thermal and Non-Thermal radiation! (Wiki FTW!).
To get you started off, just the way i did, here are a couple of excellent popular articles on Quasars -
- The Lives of Quasars
- Quasi Stellar Objects : Surveys from the encyclopedia of Astronomy & Astrophysics.
- The Sloan Digital Sky Survey : Technical Summary - be warned, things get a bit technical here. But still, you should start reading papers sometime or the other, Why not now?! Why not with this one?!
- The emission lines of Quasars and similar objects - well that's a review article which broadly covers the topic of quasars, astrophysical processes in quasars and so on. If you are able to go through this and not drool from the end of you mouth, you should pat yourself on the back.
Heyy, heyy. That's enough. Stop patting yourselves and get back to reading now...
Moving further, before i understand the energetic processes in quasars that lead to emission (that's gonna take a looong long tie), i'm supposed study the spectra of known quasars and look for characteristics of Quasar Spectra. Understand the major emission lines and the reason for their line strength, understand how red shift effects the energy spectum of a quasar.
Ohh wait, i haven't told you. Quasars aren't found in the local universe i.e in the milky way or anywhere near andromeda for that. We'll have to look further away. Because quasars are so strong, they can be seen to very large distances, distances so huge that it makes no sense to keep measuring the distance in terms of Gpc. It's measured rather in terms of z - red shift.
Coming back to understanding the spectra of quasars, I've been given a sample set of 14 quasars and was asked to retrieve their images and spectra from the SDSS (Sloan Digita Sky Survey) archive. This is one thing I've wanted to do for a while - Data retrieval. There is literally TBs of data lying on data servers all over the world, data pertaining the spectra and images of stars, galaxies, nebulae - you name it and it's most probably been pictured by some telescope, somewhere on the planet! And the awesome thing is that all of this data is free, Free, FREE!!! You can pretty much open the website, look for an object you want to study and download the relevant data - no hassles!
Let me show you!
So, there's this awesome place on the internet called NASA's Extra-Galactic Database or in short NED which is where you start your journey. The first thing you need to do is to know the RA and Dec of the object you want to study (RA and Dec are like the x,y co-ordinates of the object in astronomical terms).
Now, one of my objects of study is - SDSS J101419.40-002834.2 and here's what shows up when you search NED by name. Once you get used to the naming convention, you'll realize that the first part of the object name is the RA of the object and the second part is the Dec - SDSS J(RA)(Dec), you might want to skip NED but look at all of the information NED has on the object! But wait, we're not done yet! Look at what the SDSS data archive has on this object!
And hey, we're just beginning our journey. Now, one needs to download the spectrum, which is by default a FITS file (a common file type in astronomy) and then work on it, tag different emission and absorption lines to a specific atom's transitions!
If you thought this was all, well actually this is all because i'm not going to document all that happened this week. It'll take me a week to document what happened last week. Ohh wait!
Annyway, there were discussions on stellar formation, metallicity of stars, faith & religion and a looot more things! I found that there is a third kind of stars called Pop 3 stars, the answer to a question that'd been nagging me for a while now! So, well, that's all for now folks, tune in again next week to understand a bit more about the elements whose emission lines are commonly observed in quasar spectra, different problems that arise when one tries to acquire the spectra of a quasar and so on...
Comments are appreciated.
Adios...