Constellations

Constellations are groups of stars that appear to form a pattern. Ancient societies labelled these based on what they looked like, for example Orion the Hunter. These objects form a pattern 2D on our sky but are not actually close together in a 3D map. The patterns on the sky would change if we were to look at them from another angle.

Image credit to the Astronomical Image Data Archive

Introduction

To the left is an image of the constellation of Orion and below a table which shows the magnitudes and distances of the seven major stars of the constellation (two stars representing his shoulders, three in the middle for his belt and two at the bottom for his feet).

Star Name	Part of Orion	Magnitude	Distance (Light-years)
Betelgeuse	Left shoulder	0.45	427
Saiph	Left foot	2.07	720
Bellatrix	Right shoulder	1.64	243
Rigel	Right foot	0.18	773
Alnitak	Left belt	1.82	815
Alnilam	Center belt	1.69	1,350
Mintaka	Right belt	2.41	916

Magnitude is a measurement of brightness. The brighter the star the lower its magnitude. A difference of 5 in magnitude corresponds to a factor of 100 difference in brightness. A magnitude 5 star is 100 times brighter than a magnitude 10 star.

Light-years are a measurement of distance. Light travels 9,458,000,000,000 km in one year.

From the table above we can also see how magnitude does not decrease with distance and so not necessarily the dimmest stars are the ones furthest away.

In the following activity students will find the 20 brightest objects in your plate. These objects can be stars, galaxies or quasars. And each will be at different distances from us even though they have similar brightness. On your plate they may form a two-dimensional image!

This activity helps students learn about constellations by:

Exploring the SDSS plate and identifying specific objects

Discovering their own constellation on the plate

Step 1: Finding the brightest objects on your plate

By accessing the SDSS database through an SQL query you can obtain a table with information about the 20 brightest objects on your plate

Go onto the SDSS SQL search tool by clicking here.
Delete all the text in the box and copy and paste the text below, replacing XXXX with your 4-digit number plate.

select top 20 spa.ra, spa.dec, spa.dered_r as magnitude, spa.class, spa.z, soa.xfocal as x, soa.yfocal as y 
from specphotoAll as spa
join specObjAll as soa on soa.specObjID = spa.specObjID
where spa.plate = XXXX and spa.dered_r > 0
order by spa.dered_r asc

Tick the “CSV” option for Output Format.
Click Submit.
Your browser should automatically download a file with all 20 brightest objects.

Step 2: Plot the location of the Objects

Create a new Sheet, and import the .csv file that you downloaded in step 5 above using File -> Import. You should see your data neatly arranged in a table.
Select the last two columns (x and y) and create a “Scatter Plot” by doing Insert->Chart and choosing “Scatter Chart”. x and y are the coordinates in mm of the positions of each object on the plate, with the origin being located at the centre of the plate.
You can remove the grid lines and axes ticks by double clicking on the graph to open the Graph Editor, and unticking the box “Major gridlines” for both the x- and y-axis. You should get a plot like the one shown below.
Resize the chart to make the plot area square
You can save the chart as a picture to use in other activities, e.g. asking pupils to design a constellation.

Next, we will use a spreadsheet to plot the positions of the 20 brightest objects of your plate. The example used here is done in Google Sheets, which requires a free Goggle Account, but you can use MS Excel, or any other spreadsheet software available to you.

Step 3: Locating the Objects on your Plate

Use the Finding Objects on your Plate page to find and mark each object on the table.

The x and y positions given on the table are in millimetres and the centre hole on your plate represents the point (0,0).

After doing this activity you will be able to:

Find data about the objects on your plate through an SQL query
Find the hole that corresponds to a specific object on your plate

Teacher’s Pack

Below you can find slides to introduce this activity with some background information. Also linked below is a teacher sheet with learning intentions, list of materials needed, links to curriculum and common mistakes.