Archive for July, 2013

More Potential Hazardous Asteroids than what we thought – the Chelyabinsk event

Posted July 16, 2013 By grigoris

Zuluaga J.I., Ferrína, I, and Geens, S., 2013, arXiv:1303.1796
The orbit of the Chelyabinsk event impactor as reconstructed from amateur and public footage

The Chelyabinsk meteor is the most important impact event after the Tunguska event, almost 100 years before. The object that entered Earth on February 15, 2013, was a small-sized Apollo asteroid (with a diameter of 17-20m), and caused serious damages. This fact proves according to the authors that the number of Potential Hazardous Asteroids (PHA) are almost double that what is thought, although most of them (with diameters smaller than 100m) are not capable of global damage but can cause severe local damages. They state also the fact that the approaching direction was from the Sun side, which is a totally blind spot currently at the existing optical surveys.

Filed in Astronomy | Tagged: , , , , ,

Pro-Am collaborations in Planetary Astronomy – review paper

Posted July 16, 2013 By grigoris

Mousis O., et al., 2013, arXiv:1305.3647
Instrumental Methods for Professional and Amateur Collaborations in Planetary Astronomy

This is a great collective work on various professional-amateur collaborations (written by both professionals and amateurs) regarding aspects of Planetary Astronomy, such as: terrestial planets (Mercury, Venus, Mars), gaseous planets (Jupiter, Saturn, Uranus, Poseidon), interstellar dust (meteoroids, meteors, fireballs, meteorites), Jupiter impacts, Lunar flashes, asteroids, comets, Kuiper belt objects and Centaurs, exoplanets.

I find it a really inspiring paper for both kinds! I hope that we will see more of these collaborations in the future, since the is a continuous advance in amateur contributions to Astronomy during the last decades.

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“Too many unprocessed floats” in LaTeX

Posted July 6, 2013 By grigoris

! LaTeX Error: Too many unprocessed floats.
This error in LaTeX means that it is unable to handle more than a specific number of figures and tables (yes, there is a limit!  no more than roughly 30).

Unless you want to replot and combine figures an easy solution is to add the package ‘morefloats’:

\usepackage{morefloats}

(ref: UK TeX FAQ)

Filed in Astronomy | Tagged: , , ,

Total number of stars

Posted July 6, 2013 By grigoris

3 X 1023
are the possible number of stars in the universe !

( a number equivalent to the total number of human cells, as mentioned by Conroy)

(source, based on Pieter G. van Dokkum & Charlie Conroy, 2010, Nature, 468,940–942)

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Multiple-line comment for shell scripts

Posted July 3, 2013 By grigoris

How to comment a block of text without inserting the ‘#’ character to all lines?
We just use a ‘<<COMMENT_STRING’ (COMMENT_STRING can be obviously whatever we want) before the line of text we want to comment out and ‘COMMENT_STRING’ after the last line.

An example:

<<HEADER_COMMENT
This is a test comment - lol!
HEADER_COMMENT

[source1,source2]

ps. In source 1 the “:” is placed in front of the “<<COMMENT_STRING”, which is not mentioned in source 2 and from what I tested with bash scripts it seems not necessary.

Filed in Astronomy | Tagged: , ,

Fast note on shuffling a list with Perl

Posted July 1, 2013 By grigoris

Used in a Perl script so I noted now because I will totally forget how to use it!

use List::Util qw(shuffle)
my @coef = (-2..2);
my @random_coef = shuffle @coef;

Thanks to Alexandros M. for this tip!

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