Archive for February, 2011

Kepler’s first results

Posted February 21, 2011 By grigoris

Kepler is a space based telescope to study a small area between Cygnus and Lyra for exoplanet transits of all possible targets but mainly to find Earth sized candidates in the habitable zone. A fist publication reveals these numbers:

“On 1 February 2011 the Kepler Mission released data for 156,453 stars observed from the beginning of the science observations on 2 May through 16 September 2009. There are 1235 planetary candidates with transit like signatures detected in this period. These are associated with 997 host stars. Distributions of the characteristics of the planetary candidates are separated into five class-sizes; 68 candidates of approximately Earth-size (radius < 1.25 Earth radii), 288 super-Earth size (1.25 Earth radii < radius < 2 Earth radii), 662 Neptune-size (2 Earth radii < radius < 6 Earth radii), 165 Jupiter-size (6 Earth radii < radius < 15 Earth radii), and 19 up to twice the size of Jupiter (15 Earth radii < radius < 22 Earth radii). In the temperature range appropriate for the habitable zone, 54 candidates are found with sizes ranging from Earth-size to larger than that of Jupiter. Five are less than twice the size of the Earth. Over 74% of the planetary candidates are smaller than Neptune. The observed number versus size distribution of planetary candidates increases to a peak at two to three times Earth-size and then declines inversely proportional to area of the candidate. Our current best estimates of the intrinsic frequencies of planetary candidates, after correcting for geometric and sensitivity biases, are 6% for Earth-size candidates, 7% for super-Earth size candidates, 17% for Neptune-size candidates, and 4% for Jupiter-size candidates. Multi-candidate, transiting systems are frequent; 17% of the host stars have multi-candidate systems, and 33.9% of all the candidates are part of multi-candidate systems.” [ Borucki WJ et al 2011, arXiv1102.0541v1 ]

And all these in 105 square degrees field of view which is (well, rather large for an astronomical instrument) only a small part of the whole sky, only 1/400 ! The numbers are more exciting if we include the fact that all of these systems are transits which means that a specific geometry is needed in order to see the dimming of the stars’ brightness due to the pass of the planet(s) in front of them. But more time is needed to validate these results as the transits must been seen again and again in order to be sure that what is seen is real and not something else, that’s why they are candidates and not confirmed planets yet. But still the numbers are huge and … promising!

More exciting results include the fact that before Kepler none Earth-sized candidates or candidates inside the habitable zone were known and now there are 68 and 54 candidates respectively. In addition, complex systems are discovered like the Kepler-11 which has 6 planets [ Lissauer JL et al 2011, NaturearXiv1102.0291 ] and a rocky planet [Batalha NM et 2011 – arXiv1102.0605 ].

As stated by the NASA Administrator Charles Bolden: ” In one generation we have gone from extraterrestrial planets being a mainstay of science fiction, to the present, where Kepler has helped turn science fiction into today’s reality “.

External variable inside awk

Posted February 16, 2011 By grigoris

Sometimes, a variable may be needed to get inside awk (for or while loop for example). In order to pass the variable inside awk, include it like:
awk -v i=$i '{ .. }' test

Checking header field in IRAF

Posted February 10, 2011 By grigoris

In order to get a specific field from the header of a file you can use the command:

cl> imhead l+ | grep name_of_field

In case you want to do it for many files you just use the wildcard:

cl> imhead inage*.fit l+ | grep name_of_field

Not very sophisticated … but worked fine in my case, that I just wanted a quick eye inspection!

IRAF: add packages with precompiled binaries

Posted February 9, 2011 By grigoris

IRAF has a variety of tools but more packages can be added really easy (when there are precompiled binaries at least!).

Download the package you want (let it be … testpackage-1.4.0) and extract it inside the directory /pathto/iraf/extern/ ,where all external packages are placed [if scisoft is installed then the path is /scisoft/share/iraf/extern/ ]. Download also the precompiled binaries according to the architecture used (linux, windows, solaris, etc) and put them inside the /pathto/iraf/extern/testpackage-1.4.0/bin.redhat (if the architecture is redhat linux, accordingly for the rest).

Continue and create a link to this folder: $ ln -s  testpackage-1.4.0  testpackage
where the version of the package is kept (so as to know what is used) and testpackage is the selected name for the link.

After placing all the necessary files the last step is to define where the package to iraf. Go to /pathto/iraf/iraf/unix/hlib/ and edit the extern.pkg. Follow the same syntax of the previously installed packages and add the new one, in our case (‘/’ at the end is mandatory for unix pathnames!):

reset testpackage  =  /pathto/iraf/extern/testpackage-1.4.0/
task testpackage.pkg  =  testpackage$

Also update the helpdb by putting the line:  ,testpackage$lib/helpdb.mip\
under the long list of similar lines close to the end of the file (but before the closing quote!).

Moreover, edit the in the dame directory to add the description for the new package (following the same simple syntax):  testpackage  –  Fancy tools for exotic stuff

…and that’s it ! If you run cl then you will be able to access the new package! Enjoy!