How to Take Part

To get started, Login or Register for an account. Once logged in, Choose a Plate , select a star from the plate and classify the star! Your previous star classifications are recorded and can be viewed through your account under My Stars.

You can log in or register in the top right corner of any page or click on the Classify menu item. If you do not have an account or are not logged in, you will be prompted to authenticate yourself. The adventure begins!

Choose a Plate

Choose a plate (or a collection of stars) from the list by clicking on the plate name that you see on the Classify page after you have logged in. You will also be able to see the Right Ascension (abbreviated RA) and Declination (abbreviated DEC) of each plate. This is a system of coordinates used by astronomers to keep track of where stars and galaxies are in the sky. To learn more about this system, click on The Science. After choosing a plate, it will be displayed in a separate window. If it does not appear, check that your browser is not blocking the pop-up.

Pick a Star

After choosing a plate, an image of the plate will be displayed. You can use the scroll bars to move the image around and see different parts of the plate and the stars that are on it. Stars that are available for selection are outlined with blue borders on the plate image. Select a star by clicking or tapping on it. This will bring up a dialog box with the name and location of the star. Click 'OK' to choose that star or 'Cancel' to select another.

The classifier window will now load and you are ready to start the classification process!

Classify Your Star

You are now ready to classify your star. The top spectral line is the star you chose. Below it is a placeholder that will be loaded with the standard star type you think matches best. At the bottom are selections of the 7 major spectral types. Double click (computer) or tap (mobile device) on the spectral class that best matches your star (ie.B0V).

Once you find a standard star type from the 7 major classes that you think is a close match to your unknown star, you have the option of using the Zoom and Shift tools to verify your suspicions (see Using the Tools below).

If you are happy with your selection, click on "View Next Level" (circled button, top image). You now see all of the subclasses for the major class you selected.

When you are happy with you classification, click on "Save the Classification" at the top of the page (circled button, bottom image). You will be shown your classification and given the opportunity to make a comment. Your comment may be about features that didn't match, trouble you had deciding between two different subclasses, or any suggestions for SCOPE's improvement, for example. Click on "Record" and your classification will be saved in the database.

Using the Tools

The Expand Tool allows you to shift and zoom the two spectra in order to ensure that all of their spectral lines match. You can use the two large green arrows to shift the top spectrum left and right, respectively. The magnifying glasses allow you to zoom in, reset the ratio, and zoom out the two spectra, respectively. A comparison image also shows below the two spectra at all times to show how well your classification matches the unknown.

You may notice that the comparison tool from SCOPE 2.1 is no longer being used. It was removed because, unfortunately,

View Your Stars

Once you have classified a few stars, feel free to view your classified stars by clicking on the My Stars menu item shown under the My SCOPE tab at the top of this page. Here you can see all of the stars that you have classified, how many times those stars have been classified by others, and the official star type (if it has been determined). Your comments may be viewed here as well. To print your previously classified stars, use the 'Print' options on this page.

Get Some Classification Experience

For fun, try your hand at classifying a star!

This can provide you some experience classifying stars or serve as a refresher course for those who may have forgotten the process.

Shown below are the 7 major star classes. Notice the differences in the images, specifically the number and placement of the spectral lines.

In the B and A stars, the dark lines are due mostly to hydrogen. In the later stars, the hydrogen lines don't dominate quite as much. Instead, we see other sets of more complicated patterns of lines. When you classify a star, your objective is to match as closely as possible the unknown star spectrum (patterns of lines) to one of the known stars like those shown below.

O
B
A
F
G
K
M

Below is a spectrum of a star. Look at the pattern of lines. Match the pattern to the one above that fits the best. Then, put your mouse cursor over the spectrum below to see if you guessed the correct star spectral classification.

Another star is shown below. Look at the pattern of lines again. Notice how the pattern is somewhat similar to the star you just looked at, but there are not quite as many lines. Go ahead and classify the star by comparing it to one of the comparison stars above. Run your mouse cursor over the image to see how you did.

Here's another star. Look at the pattern of lines again. Notice how the pattern is different than the previous two stars you just looked at. The pattern is more compicated. Go ahead and classify the star - which one does it match best? Run your mouse cursor over the image to see how you did.

Here are several more to practice on:

Great! Now let's go one step further. Each of the star types you just classified is subdivided to match finer details in a star's spectrum. For example, the B type stars have subclasses B1, B2, B3, B4, B5, B6, B7, and B8

B0V
B2V
B3V
B4V
B6V
B8V

Below is a B type star.

Which one of the B subclasses does it look closest to? Put your cursor over the image to check your classification.

Here's another example. This time, you are shown the subclasses of M type stars.

M0V
M1V
M1I
M2I
M3III
M4III
M5V
M5III

Here's an M type star.

Which one of the M subclasses does it look closest to? Put your cursor over the image to check your classification.

Have you noticed the letter "III" in the classification you just did for the M3III star? You will often see other designations like "I" or "III" or "V" in the list of comparison star spectra. The "I" means the star is a Supergiant, "III" means the star is a Giant star, and "V" means the star is a Main Sequence Star. See The Science section of this website for more details about these designations.

Because the spectral classifications include the Main Sequence, Supergiant, and Giant types, the list of comparison star spectra will be longer than shown for the B type stars above. This will make classification a bit more challenging. But, this is why we are asking you to contribute. Classifying hundreds of thousands of stars by one person is a daunting task, but with your help, we can more deeply explore our neighborhood of the Milky Way Galaxy!

You are now ready to classify stars.