Changing Constellations

Abstract

Do you like to look up into the night sky? There are so many stars, it can be mind boggling! Some ancient people marked time by the changes in star patterns. We still use changes in constellation patterns to mark astronomical time. Do constellations change more in one hour, one day, one month, or one year?

Summary

Areas of Science

Astronomy

Difficulty

Method

Scientific Method

Time Required

Very Short (≤ 1 day)

Prerequisites

None

Material Availability

Readily available

Cost

Very Low (under $20)

Safety

No hazards

Credits

Sara Agee, Ph.D., Science Buddies

Science Buddies is committed to creating content authored by scientists and educators. Learn more about our process and how we use AI.

Objective

In this experiment you will investigate how the constellations change in the night sky over different periods of time.

Introduction

The telling of time is an ancient art, and different ways of marking time have been used by people of different cultures over the ages. Before the introduction of modern standard time, people had to use astronomical features to mark time, mainly the sun, moon and stars. Different calendars were created by different cultures who marked time by using different methods. Here are just a few:

• Gregorian Calendar: This calendar marks time by the rising and setting of the sun, called solar time. It was introduced in 1582 as a reform to the Julian calendar of 45 B.C. that had been initiated by the Romans. Before Gregorian and Julian time, people had been marking solar time with sundials and waterclocks set to the sun for thousands of years. This calendar was made obsolete by the introduction of Standard Time. However, the passage of the sun over the Greenwich meridian is still the standard scientific reference of world-time (UTC) for modern timekeeping.
• Lunar Calendar: In China, India and other eastern cultures people mark time by the cycles of the moon, called lunar time. Because the moon cycles are not exactly a month long, a leap month is added to the calendar now and then so that the lunar calendar changes with the seasons. The Romans saw this as too arbitrary, and so replaced the lunar calendar with the Julian calendar. In Islam, a purely lunar calendar is kept which does not add a leap month and strictly coun as twelve lunar months, and so is about 11 days shorter than the solar year.
• Zodiac Calendar: Instead of tracking time by the sun or moon, the Zodiac Calendar tracks time by the stars, called sidereal time. Sidereal time is mainly used for astronomical observation. The siderical calendar year, or Zodiac Calendar, has days that are shorter by four minutes. Each year is one day longer because a sidereal day is defined as the time it takes to see the stars in the same position in the sky: 23 hr. and 56 minutes.

How do the positions of the stars change over time? In this experiment you will investigate how the constellations change in the night sky over different periods of time. Will the patterns of constellations and stars in the sky change more in one hour, one day, one month or one year?

Terms and Concepts

To do this type of experiment you should know what the following terms mean. Have an adult help you search the internet, or take you to your local library to find out more!

• star
• constellation
• time
• moon
• sun

Questions

• Which constellations are in your night sky?
• How do they change over time?
• Do some stars change more than others?

Materials and Equipment

• Internet access
• Optiona: printer

This project follows the Scientific Method. Review the steps before you begin.

1. First, you will need to decide on a date and time to start your experiment. Choose today's date and write it down along with a time in the evening that you can go outside and look at stars, like 8PM.
2. Find a "start chart" or "sky map" app or website online. Many such sites and apps are available. They show you a map or chart of what stars you will see in the sky at a specific date and time (Figure 1). 
   
   Figure 1. Example star chart.
3. Print out the first image (for example, for today's date at 8PM) or save the image to your computer. Write the date and time on the printed image or include the date and time in the filename.
4. Now, change the time to test one of your variables. To test the one hour variable, change the time one hour ahead of the last star chart by clicking on time and choosing the next hour (change 8PM to 9PM). Print or save the new star chart and write the full date and time on the page.
5. To test the date variable, change the date to one day ahead by clicking on the date and choosing the next date (for example, change 20th to the 21st). Print or save the new star chart and write the full date and time on the page.
6. To test the month variable, change the month to one month ahead by clicking on the month and choosing the next one (for example, change May to June). Print or save the new star chart and write the full date and time on the page.
7. To test the year variable, change the year to one year ahead by clicking on the year and choosing the next one (for example, change 2025 to 2026). Print or save the new star chart and write the full date and time on the page.
8. Arrange all of your star charts on the table and look for either of the main navigational constellations, Ursa Minor or Crixa. On each page, circle these constellations with a marker.
9. Try to find your favorite constellation near the center of the chart in the first star chart. Compare that chart to the other charts. Which chart is the most similar? Which chart is the most different? Do the stars change in position more in an hour, a day, a month or a year? Are the same constellations present on each page?

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Variations

Careers

If you like this project, you might enjoy exploring these related careers:

Astronomer

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Astronomers think big! They want to understand the entire universe—the nature of the Sun, Moon, planets, stars, galaxies, and everything in between. An astronomer's work can be pure science—gathering and analyzing data from instruments and creating theories about the nature of cosmic objects—or the work can be applied to practical problems in space flight and navigation, or satellite communications. Read more

Cartographer or Photogrammetrist

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Career Profile

Maps can give us much more information than ways to get from A to B. Maps can give us topographic, climate, and even political information. Cartographers and photogrammetrists collect a vast amount of data, such as aerial data and survey data to produce accurate maps and models. For example, by collecting rainfall data, a cartographer can make an accurate model of how rainfall can affect an area's watershed. The maps and models can then be used by policy makers to make informed decisions. Read more

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