Looking around 10 μm at η-Car

Project Members

• G.W.H. van den Akker
• prof. dr. L.B.F.M. Waters (supervisor)

Summary

In the southern hemisphere is a constellation, through which the Milky Way passes. It is called Carina, and in it lies a giant diffuse nebula with one of the largest known HII regions in our galaxy, even larger than the well-known Orion Nebula. In the center of this nebula lies a very peculiar star: η-Car. This star has been catalogued the past few centuries as a star of the fourth magnitude, only to erupt at the beginning of the 19th century as one of the first, only to be outshone by Sirius. The eruption caused by this supermassive star caused an nebula to expand: I studied observations made from this giant cloud of dust.

The main objective of this project was to study if the nebula surrounding η-Car has just olivine grains, or that some other material is present. To do this, I used spectra observed by MIDI (Mid-Infrared Interferometric Instrument) from two slides over the central star in the nebula. The ten spectra that were obtained were normalised at 10 μm, after which I compared them and fitted black bodies to determine the temperature. After finding these, I subtracted the black bodies from the spectra and compared the bump that was left with graphs from olivine grains with a diameter of 0.1 μm and 2 μm.

Computer programs used

In the research and writing process, I used several computer programs:

• LaTeX: LaTeX is a document markup language and document preparation system. In contrast to wysiwyg text editors such as Word, you only see the result after compiling the source. But once you created a template or framework, you can reuse it and thus concentrate on the text and contents of the text, instead of having to trouble yourself with trivialities like the placement of illustrations or footnotes.
• Gimp: Gimp is an image retouching and editing tool.
• IDL: This interface description language, or IDL for short, is the specification language used at the Anton Pannekoek Institute to describe a software component his interface and easily create small programs that allow you to, for example, analyse data from observatories.