Astronomy for Schools

Physics-related topics

Most of the topic suggestions here relate to various aspects of physics. There are a couple of other suggestions for other subjects towards the end.

This first suggestion on spectroscopy is specifically for VCE Physics Unit 2. Other suggestions are more suited to pre-VCE levels.

Asteroids

What is an asteroid? Where do they exist? Are they all in the same area? How do we think they came about? What do their orbits look like? What is a NEO (near Earth object) and TNOs (trans Neptunian object)? Are there other types of asteroids? 

 

The astronomical facility includes a camera that can take very long exposures of star fields. The process of stacking subsequent images can effectively allow the telescope and camera to expose for the entire night. Such a long exposure can be used to identify objects that move against the background of the stars. 

 

  • What does NEO mean in the context of asteroids? What subtypes of NEOs are there? Are NEOs dangerous? Who tracks NEOs? How are NEOs discovered?

  • Take an all-night image (made from a stack of autoguided subexposures). Are all the stars static? Are there any objects moving across the background?

  • What objects could these be (apart from asteroids, there are other objects that can cause this effect)? How can you tell between these things?

  • What are the five brightest asteroids? Can you photograph them?

  • Can you find other known asteroids? Have a look at the IAU Observing Target List to see which bright asteroids you can photograph.

  • What is 3753 Cruithne? What is weird about its orbit?

  • What is 99942 Apophis? Where will its orbit take it in April 2029? How will the media report this? How should the media report this?

 

Can you discover a new asteroid? If you find one and accurately observe it twice, the IAU Minor Planet Centre may register the observatory and school from where it was discovered as an observation site. Your school might get a bit of news coverage!

 

Note that it may not be possible to take exposures of longer than a couple of minutes in a light-polluted area, but photographic techniques can solve this problem. Process a stack of short (say, 30 second images) to maximise trailing.

Spectroscopy

 

Spectroscopy is relevant to the 2023 VCE Physics Study Design Option 2.13. It is a method to investigate light from stars, and to understand a range of aspects about the star. The Hertzsprung-Russell diagram is a tool to classify stars and their stage of evolution.

 

The colours we see from stars determine a lot about that star, including:

  • the mass of the star

  • the age of the star

  • the speed and direction of travel of the star

 

Equipment in the astronomical facility can include a spectroscope (or diffraction grating “star analyser”), which splits the light received from a star into frequencies, showing emission and absorption areas. Students use and understand the spectroscope, formulate a hypothesis, design an experiment and collect and analyse data by using a colour camera attached to the spectroscope. 

 

Additional questions the student may consider are:

  • What is the difference between emission and absorption spectroscopy?

  • How does a spectroscope work? How does a diffraction grating work?

  • Can you make a basic spectroscope using a prism, DVD or CD? Can this show absorption lines?

  • Can you use a telescope to gather spectra of different stars? How are different classes of spectra classified? What does this show about the stars?

  • What is the Hertzsprung-Russell Diagram? What does it suggest is the future for the stars the student has gathered spectra for?

 

Many specific projects are possible. As an example, a poster that uses spectroscopy could be as follows:

  • Title: What’s happening inside Betelgeuse?

  • Introduction: Betelgeuse is a star in the constellation of Orion. Is it a supergiant?

    • Aim: to measure the spectrum of Betelgeuse to confirm where it should go on the Hertzsprung-Russell Diagram.

    • Hypothesis: As Betelgeuse is a supergiant star, it will have moved off the main sequence.

  • Method: use a spectroscope to measure the spectrum of Betelgeuse. This will need a telescope and tracking mount as well as a camera. Spectra of other stars will be used as a comparison. Spectra of all imaged stars will be used to identify the location of the stars on the Hertzsprung-Russell Diagram.

  • Discussion may include observations about the makeup of elements inside the star, how these elements affect the spectrum, and the various nuclear reactions that are occurring inside Betelgeuse.

 

Photometry

Photometry is the study of light intensity received from stars, as well as other objects such as nebulas, planets or galaxies). Photometry requires accurate and consistent photographic observations of the sky.

 

The astronomical facility includes a camera which can take consistent images of stars and other targets through the telescope. Analysis of the images produced will show the intensity of light from each pixel (or small group of pixels), and so the light from stars can be measured scientifically.

 

Take a photograph of a star field – preferably one in a well-known area like the Southern Cross. Get as deep an image as you can – use autoguiding and image stacking. Looking at the photograph, use a planetarium program to identify roughly 10-20 of the brightest stars you can see in the image. For each of these stars, find the brightness of each, which is given in terms of a number called magnitude.

 

  • What is magnitude, and how is it measured?

  • Rank the stars you have identified by their magnitude, and compare this order with your image. Are your stars in the same order?

  • Can stars vary in their brightness? Why?

  • Have a look at a single image and then compare the light intensity with the stars from the stack. Are they the same intensity or the same order? If not, what could be causing the difference?

Our Moon

 

  • Take photos of the Moon several times in a month. This will show the phases of the Moon. Explain what is happening in each phase.

  • See if you can take a photo of the structures called the Lunar X and Lunar V. What are they? Why do they look like this? Why do they only appear occasionally?

  • Take a colour image of the Moon, and enhance the colours by increasing the saturation. What does this show? Why are the colours different?

  • Take photos of the full Moon several times during the year. Are they all exactly the same? Why (or why not)?

  • Take a photo of a lunar eclipse. What do you see? What colour is the Moon? Why?