Tuesday, September 2, 2014

The Analysis of Comet 67P/Churyumov-Gerasimenko

Comet 67P/Churyumov-Gerasimenko by Rosetta’s OSIRIS narrow-angle camera on 3 August from a distance of 285 km. The image resolution is 5.3 metres/pixel.   Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

67P/Churyumov-Gerasimenko is a periodic comet in our solar system and was discovered by Klim Churyumov Ivanovic in 1969 at the Institute of Astrophysics of Alma-Ata, using a photo taken by Svetlana Ivanovna Gerasimenko that was subsequently analyzed. This celestial body has become an object of study for the European Space Agency's (ESA) Rosetta spacecraft, which was launched March 2, 2004 and came to the comet at a distance of only 100 km on August 6, 2014. With the use of the first images published by ESA and with the definition by the entity of the parameters of scale relative into the scene, it is possible to obtain useful information about the size and the brightness variation along the surface.

An analysis was made of brightness in the image above. As you can see, the comet has a shape far from smooth, but this feature makes it suitable for our purposes.

For the analysis of brightness ImageJ software is used, developed at the National Institutes of Health by an employee of the Federal Government in the course of their official duties.

This is a powerful calculation software based on the development of the pixels within the image, which in this case are the images that are sent by the Rosetta probe during the mission. ImageJ includes several complex tasks based on Fourier analysis and linear and polynomial interpolation of the data extracted from the scanned image or a part of them. This analysis is useful to understand and to identify whether the surface of the comet has weaknesses and subject to sublimation during the flyby with the Sun.

The result produced is the following:

Comet 67P/Churyumov-Gerasimenko by Rosetta’s OSIRIS narrow-angle camera on 3 August from a distance of 285 km. The image resolution is 5.3 metres/pixel.   Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Comet 67P/Churyumov-Gerasimenko by Rosetta’s OSIRIS narrow-angle camera on 3 August from a distance of 285 km. The image resolution is 5.3 metres/pixel. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

In the scale of the color blue represents the lowest brightness and red the highest. The numbers are normalized according to the extracted pixels in the image.

What can be seen very clearly that there is a region, more or less central, where the material has a very high reflection coefficient. That region is a weak area of ​​the comet in which, for its instability, there is a crack, and there is a zone where there is greater concentration of material. The areas with the highest rate of brightness and therefore that more accurately reflect the Sun's light, icy regions, and are subject to produce the tail of the comet during its approach to the Sun, while the darker areas are regions of the celestial body in which c' is greater concentration of dust and little reflective.

As well as interesting information about the bright areas and dark areas of the comet, we can know, from ESA images, the size of the comet, what allows to really understand what kind of object we are interfacing.

From the measurement it turned out that the comet 67/P is an object of the total size of 5x3x4 Km. This means that if we want to contain it in a container, it would be a box of length 5 km, 3 km height and width of 4 Km.

To fully understand the comet 67/P, we pause at this point on the calculation of volume and mass using some approximations that are important for understanding the measured values. The volume you choose to draw it as if we are calculating the volume of a sphere where the radius is given by calculating the mean radius of the comet. According to these considerations, then the celestial body has a volume equal to 21 x 109 m ³, having used the average density for comets which is equivalent to 0.6g / cm ³. Consequently the mass of the comet isequal to 1.25 x 1013 kg.

Finally, having calculated the mass of the comet we can calculate the escape velocity, ie the speed that is necessary so that you can get out of the orbit of the celestial body, without the intervention of external forces additional charges. With approach to the law of Universal Gravitation was able to get an escape velocity equal to, ie, 0.46 m/s to exit from the orbit of the comet is required a speed of about 1.7 kilometers per hour.

The analysis carried out in this work are obtained with analytical measurements and progressive ESA applied to the images published between 3 and 7 August 2014, thanks to ImageJ software which, when used with reasoning and with some changes on the measures, applying a bit of traditional physics. From these aspects derived, it is clearly seen that the comet 67P/Churyumov-Gerasimenko is an object that, if on the one hand complies with certain characteristics of perfect geometry, on the other hand shows accentuated irregularities and discrepancies manifest by the measures made.

With the measurements of the volume, mass and the escape velocity it is finally possible to know the severity that the comet imprints on any celestial body that would be out on its surface.

Neglecting the possibility of measuring the gravity at different points of the surface and then to different kinetic energies and potential shows an average severity estimated about 400 times less than the Earth's gravity. With integration of the latter measure as described, currently known as the comet 67P/Churyumov-Gerasimenko is a small object that is traveling from the confines of the Solar System towards the Sun and is detecting features, integrated with future research module Philae, will lead to important results.

To read the full analysis of the formulas and explanation of the results obtained simply log onto http://www.cometa67p.altervista.org/

Written by: Giuseppe Conzo

1 comment:

  1. Given the comet mass M = 1.25 x 10^13 kg and comet mean radius R = 2 km, the escape velocity will be 0.91 m/s (see "Escape velocity" in Wikipedia for the formula).

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