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Showing posts from September, 2015

Ultra-Compact Dwarfs and stellar streams : astrophysics @arXiv

Title : NGC 3628-UCD1 : A possible omega centauri analog embedded in a stellar stream.

Let me give you a bit of an introduction in the first place. Stellar streams are streams of stars around a central galaxy, streams assumed to be filled with left over stars from a galaxy merger between a minor galaxy and said central galaxy. In this case, NGC 3628 is the central galaxy and the newly discovered UCD1 is proposed to be a remnant of such a merger-interaction. Also, FYI UCDs stands for Ultra-Compact Dwarfs.

Moving on, as the authors mention in the second section, they were observing the galaxy NGC 3628 and it's associated stellar stream in 2009 when they discovered a bigger object/clump seemingly embedded in the stellar stream. They finally got around to observing the clump in 2014 (what i'm going to take away from this is the fact that there aren't enough grad students to reduce/analyze all the data being acquired so yeah, maybe I'll find a grad position somewhere! :D).

#FaveAstroPlot : Binary pulsars and general relativity

Another interesting astronomical plot is one that ended up providing an indirect evidence of a prediction of general relativity, gravitational waves. General relativity, proposed by Albert Einstein, predicts that gravitational masses can radiate energy in the form of gravitational waves but in reality, these waves are so weak (because gravity itself is weakly interacting) that it is hard to detect them directly. There are experiments to detect them directly (eg : LIGO and LISA) and indirectly (Pulsar Timing Array) but it was indirectly proved by Hulse & Taylor in 1974 when they discovered a double pulsar PSR 1913+16. This peculiar double pulsar had the interesting property that it's period was decaying, instead of remaining constant. As you can see from this plot on twitter, the horizontal line is what is expected if we assume that there is zero orbital decay and the data points are observed time periods over the course of a couple of decades. What's happening behind the …

Pocket reading list : Week 2, Sep

The Homeless Scientist Who Tried to Prove Selflessness Doesn't Exist - Dr. Price came up with an equation that quantified altruism, or it seemed like it for the most part. He developed a mathematical framework to understand the selfless behavior of various animals. This is the tale of what happened after.

The End of Gangs - A beautiful article about the gangs in Los Angeles, how they came to rule the streets there and how law enforcement finally figured out how to clean the streets and make neighborhoods safe again. I kept getting reminded of the TV show 'The Wire' as I was reading this, how empty lots becomes a cesspool for addicts, how streets are rules by gangs and the violence between gangs. It's also a story of how policing isn't just about beating the perpetrator with the other end of the stick but about community relations and foot work.

The Sign Language Interpreter of the Rappers - I was surprised to hear that deaf people went to concerts in the first place!…

#FaveAstroPlot : Pulsars

Here's a tweet showing the radio pulses observed from a pulsar, in fact the first radio pulsar discovered by Jocelyn Bell Burnell, for which her thesis adviser got a Nobel prize (which he didn't share with her but that's a whole different story). There's also a fairly interesting story behind the image itself that can be found here.

Firstly, put yourself in a time and age when radio astronomy was still nascent and people were just scratching the surface of various radio sources. Also, this wasn't the era of milli-arcsecond resolution radio astronomy but it was the era of single dish-arcminute resolution astronomy. Radio astronomers used to perform lunar occultations to reduce the uncertainty of an astronomical object's position. Secondly, this was before digital devices were ubiquitous for recording and displaying the radio signals. There were analog chart recorders which used to plot the total strength of the radio signal that the telescope receives on ginormo…

#FaveAstroPlot : Exoplanet transits

I won't be as verbose this time but it's still something that I find just as interesting. The in thing about astronomy at the moment is exoplanets. Everyone talks about them, everyone wants to know if there's another planet out there like earth and EVERYONE wants to know if there is alien life somewhere else in this universe. What I find more interesting is the science behind how exoplanets are found and characterized.

This is a tweet by Phil Plait of Bad Astronomy fame (if you don't already follow him on twitter, you definitely should!). It is a plot of intensity or brightness of a central star as a function of time. As mentioned on the x-axis, over the course of ~4 hours, the brightness of a star fell to 0.985 times it's prior brightness and then went back to normal. This dip in brightness is because this star is being eclipsed by a planet that is revolving around it (and luckily, in the plane of sight!). Astronomers were able to distinguish this drop of intensit…

#FaveAstroPlot : The HR diagram of brown dwarfs

An awesome thing happened over the weekend. To give you a bit of a backstory, I went a crazy over the last week and started following a bunch of Professors and grad students who pursue astronomy, all around the world. And over the weekend, someone started the hashtag #FaveAstroPlot and tweets started pouring in! There are probably a lot of curated lists of tweets and this is one such is by Emily Lakdawalla.

Now, I thought that it'll be interesting to take up a couple of those plots and write follow up articles detailing what exactly what the plots are about and why they are important/relevant. I also want to get back on the horse and start adding more things to my astro_data_projects repository on Github.

For this week, let's look at the HR diagram of brown dwarfs here. One can find the relevant data here which Trent Dupuy has kindly made available publicly (This is one thing I love about astronomy, most of the data is in the public domain!).

For the uninitiated, let me tell …

This week's reading list

Best Practices for Scientific Computing : Everyone needs to get their hansd dirty and write programs in this digital age of ours. It'd probably be for the best too, literacy could soon come to include the ability to program, in any language of choice. And the same way spoken languages are standardised such that no matter where you go, you can speak and understand the other person (for example in English.). Similarly, a lot of us will have to read other people's programs from time to time and from what i've experienced, it's one of the hardest things to do. A must read for any student or scientist to who are learning programming such that they can cultivate these rules into their workflow to produce not only working programs but readable and extendable programs.

Learning to Speak Lingerie : At some point or the other, we've all come across that shop run by an immigrant, one who might not even speak the same language as ours or maybe he can barely speak enough to keep…