University Level Astronomy Projects

 

Most of the following 11 tutorials have been prepared in the framework of the D-Space and COSMOS projects. You are welcome to use them for non-profitable purposes. However, we would greatly appreciate if you acknowledged Skinakas Observatory as their source, and also let us know about their usefulness.


- CCD image analysis, p1
- CCD Photometry, p2
- Colour in Astronomy, p3
- The HR diagram. Open Clusters, p4
- Globular Cluster, p5
- Planetary Nebulae, p6
- Galaxies, p7
- Stellar Spectra: Classification, p8
- Stellar Spectra: Temperature, p9
- SuperNova Remnants, p10
- Near Infrared Observations, p11


Some video tutorials associated with those projects can be found here.

 

 

 

 

 

 

Project 1. CCD image analysis

 

Summary:

 

Objective

Prior to the derivation of astronomical magnitudes the CCD images have to be corrected for unwanted effects. The students will learn how to assess the quality of a CCD image, calculate the appropriate aperture and become familiar with the calibration techniques of astronomical images.


Observations

-frames before and after the observations

-flat fields for each filter

-CCD images of a low-populated field at various exposures


Theoretical background

The characteristics of a CCD, seeing, signal-to-noise, point spread function, calibration techniques. The meaning of these concepts is explained in simple terms. Especially emphasis is put on the understanding of the calibration process.


Analysis

Image processing (Bias & flat field correction), seeing estimation, background determination, uncertainty if the measurements (signal to noise ratio)

 

Download: Full Project, Sample Data

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Project 2. CCD Photometry

 

Summary:

 

Objective

 The objective of this project is the determination of astronomical magnitudes of point sources through the use of CCDs and aperture photometry. The process of transformation to a standard system is also described in detailed.


Observations

-a set of bias frames at the beginning and at the end of the night.

-a set of flat-field images for each filter, B and V

-a set of CCD images of a couple of standard fields measured at various (at least 4) different values of the airmass.

-a CCD image of a target star (it can be one of the standard stars) taken through the B and V filters


Theoretical Background

 Absolute and instrumental magnitudes, colour of a star, atmospheric extinction, transformation equations, standard system.

Analysis

 Calibration of CCD images, obtain instrumental magnitudes, calculate atmospheric extinction, obtain magnitudes outside atmosphere, transform to the standard system

 

Download: Full project, Sample Data

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Project 3. Colour in Astronomy

 

Summary:

 

Objective

Explain what colour means in an astronomical context and its relationship with the temperature of a star. Learn how to create colour-colour diagrams and how to use these diagrams to distinguish between different types of objects. Introduce Wein's Displacement Law.


Observations

- BVR observations of a blue star and a red star.

- BVR observations of a Messier object to create three-colour images

- FLAT-FIELD and BIAS frames


Theoretical Background

colour of a star, colour index, colour and temperature, blackbody radiation, Planck's and Wien's laws.


Analysis

Obtain magnitudes and colours of different type of stars, create a program to derive temperature versus peak wavelength, derive Wien's constant, make three-colour images.


Download: Full Project, Sample Data

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Project 4: The HR diagram. Open clusters

 

Summary:

 

Objective

The aim is to measure accurately the B and V magnitudes of several stars in the cluster, and plot them on a Color Magnitude Diagram. The students will be asked to identify the   Main Sequence of the stars in the cluster, and measure their temperature and mass.


Observations

This exercise requires the acquisition of two images, in B and V filters, of an open cluster.


Theoretical Background

Open clusters, HR diagram, colour-colour diagram, stellar evolution, spectral type and luminosity class of stars.


Analysis

Create an HR diagram (colour-colour plot) of an open cluster. Determine the position of different type of stars in the diagram and their physical properties.


Download: Full Project, Sample Data

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Project 5: Globular cluster

Objective

 The objective of this exercise is the calculation of the core and tidal radius of a globular cluster in the Milky Way.


Observations

V- or R-band images of a globular cluster. More than one field may be necessary to ensure that the background is reached.


Theoretical Background

Globular clusters, radial profile


Analysis

After standard bias subtraction and flat fielding of the observed fields, the student needs to find all stars visible on the frames. The student needs to find the star number density and plot it as a function of radius. Comparison against models leads to the derivation of the tidal radius and concentration parameter of the cluster.


Download: Full Object, Sample Data

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nii_ngc6781.jpg (43948 bytes)

Project 6. Planetary Nebulae

 

Summary:

 

Objective

The purpose of this exercise is twofold. The first one is to become familiar with the analysis of narrow band images and the second is to examine the spatial distribution of the extinction related to an extended object. The absorption is mainly influenced by the Earth's atmosphere as well as by processes related to the nebulae itself. Interstellar absorption is also present and can be significant depending on the actual distance of the object and its position in the galaxy.


Observations

The students will make use of a robotic telescope to acquire images in the hydrogen emission lines (Hα and Hβ) of a planetary nebula. Τhe same procedure can be followed in the case of an emission line nebulae, e.g. a supernova remnant. Clearly, the physics between the two classes of objects differ but the reduction process will still remain the same. Images of standard stars in order for calibration purposes are also needed.

- Flat field frames, 4 in each filter (Hα, Hβ, and continuum filter)

- Bias frames, a total of 10 spanning over the night

- Object frames, 1 at each filter (minimum). E.g. for NGC 6720

- Standard star frames, 10, at least, at 3 different airmasses.


Theoretical Background

Planetary nebula, narrow filters, interstellar and atmospheric extinction


Analysis

The first task is to determine the atmospheric absorption and correct the planetary nebulae images for this effect. Subsequently, they will perform the necessary operations in order to map the effects of the intrinsic and interstellar absorption in a two dimensional space.


Download: Full Project, Sample Data

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Project 7: Galaxies

 

Summary:

 

Objective

Be aware of the grandiosity of the Universe. The topics covered in the previous lesson plans restrict themselves to our “neighbourhood”. However, the Universe extends much beyond the Milky Way. In this project the student can learn the different type of galaxies, its morphology and stellar contents.


Observations

This exercise requires the acquisition of two images, in B and V filters, of a number of spiral and elliptical galaxies that belong to different classes.


Theoretical Background

Types of galaxies, stellar content of a galaxy, radial light distribution in elliptical galaxies


Analysis

The students will be able to measure the size of the galaxy along its two major axis. Using these measurements they will be able to classify them and hence get accustomed to the Galactic classification system. Furthermore, the students will perform photometry on the galaxies as a whole, and will determine their integrated B-V colours. In this way, they will be able to infer the appropriate information regarding the age of their stellar population, and its relation to the respective Galactic types.


Download: Full Project, Sample Data

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Project 8 : Stellar Spectra: Classification

 

Summary:

 

Objective

The main objective of this project is to teach how to find out the spectral type of stars from the stellar spectra. At the completion of the project the students should i) understand the process of classifying different spectra by the relative strengths of lines, ii) to be familiar with the sequence of spectral types, iii) to be able to recognise the distinguishing characteristics of different spectral types. This project also introduce the concepts of equivalent width and Full Width at Half Maximum of a spectral line and explain how to obtain them.


Theoretical Background

Spectral types Luminosity classes - Characterization of a line profile - Equivalent width - FWHM - Peak intensity - Spectral classification - spectral lines - cross correlation with standards


Download: Full Project, Sample Data.

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Project 9: Stellar Spectra:  Temperature

 

Summary:

 

Objective

The main objective of this project is to show the students how to estimate the temperature of a star. Two different methods are shown. First, an estimate of the effective temperature of a star can be done by applying Wien's law. This method simply takes into account the wavelength at which the spectrum exhibits maximum flux. The second method consists of measuring the equivalent width of some spectral lines that are sensitive to changes in temperature. The lines used in this project are the hydrogen Hα line at 6563 Å and the doublet Na I lines at 5890 Å and 5896 Å. In this project the student can also learn how to extract information from the shape of a spectral line. The Equivalent Width and Full Width at Half Maximum are defined and their relationship with some physical properties of the stars and the instrumental set-up used to obtain the spectrum is explained.


Theoretical Background

The electromagnetic spectrum

Stellar spectra

Stellar temperature


Download: Full Project, Sample Data

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Project 10: SuperNova Remnants

 

Summary:

 

Objective

The aim of this exercise focuses on the analysis of narrow band images (as in the case of planetary nebulae) and on the nature of the emission from extended objects.  Emission observed in Hα at 6563 Å and the forbidden lines of singly ionized sulphur at 6716 and 6731 Å may originate from photoionization or from shock heated gas. Their relation can be a useful diagnostic tool.


Observations

The students will make use of one of the telescopes available at Skinakas Observatory to acquire images in the hydrogen emission line Hα and sulphur [SII]. Images of standard stars for the calibration of the narrow band images are also required.

- Flat field frames, 4 in each filter (Hα, [SII]6716, 6731 Å and continuum filter)

- Bias frames, a total of 10 spanning over the night

- Object frames, 1 at each filter (minimum). e.g. for G65.3+5.7

- Standard star frames, 10, at least, at 3 different airmasses.

Theory topics

Supernova remnants, narrow band filters, forbidden line emission, Balmer line emission


Analysis

As in all cases, the bias level and flat field frames need to be derived. Data frames will be corrected and the calibrations constants should be determined. Subsequently, the student will calibrate the Hα and [SII] images. Once this is done, the student will be able to determine the [SII]/ Hα ratio and consequently, the nature of the observed emission.

 

Download: Full Project, Sample Data

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Project 11: Near Infrared Imaging

 

Summary:

 

Objective

Among the most important physical properties we often need to measure in extragalactic astrophysics is the stellar mass of distant galaxies. In principle this is not a trivial question as due to the distance of these objects we can not resolve, let along count, the billions and billions of individual stars they contain. As a result we have to rely on the integrated light emitted by the galaxies and find a way to estimate from this the mass and type of stars they contain.

In this exercise we will present how one can use observations in infrared wavelengths in order to estimate the stellar mass in a galaxy.

We will analyze ground based observations with the 1kx1k near-infrared camera of the 1.3m Skinakas Observatory to measure the stellar mass of a galaxy in Hickson Compact Group (HCG) 54. This is a group of four galaxies located at a distance of 19.6 Mpc.