In a typical year, it is not uncommon for a dozen or so comets to come within range of amateur telescopes. During the month of October, 2010, a small comet will pass unusually close to Earth. On Oct. 20, Comet Hartley 2 will pass just over 11 million miles (18 million km) from Earth. That is close enough for the comet to be seen through binoculars or even, in the darkest skies, with the naked eye.
Amateur stargazers aren’t the only ones looking out for Hartley 2 this month. In September 2007, NASA woke up its hibernating DI spacecraft and, in November, sent it the maneuvering instructions to intercept Hartley 2. The spacecraft is precisely on schedule to rendezvous with the comet on November 4 as it approaches the sun.
This week’s online current events activity is a study of comets, the Hartley 2 Comet, and NASA’s attempt to study it.
Begin your investigation into comets by visiting Worldbook@NASA, which features excellent overviews on many topics related to space and astronomy, including Comets. As you read this page, look for answers to the following questions:
- What are some of the ingredients that make up a comet?
- How big are most comets?
- How does a comet tail form, and which direction does it always point?
- What is the relationship between comets and meteor showers?
- What have scientists learned about the nucleus of a comet?
More information about comets can be found at the Nine Planets site. As you read, look for answers to these questions:
- Name two examples of comet appearances in antiquity (ancient human history)
- How many comets have been cataloged?
- What are the five parts of a comet?
- How do comets “die”?
Comet Hartley 2
Now that you have some solid background information about comets in general, let’s see what we can learn about Comet Hartley 2. Start by going to the web site of Sky and Telescope magazine, and read Comet Hartley 2 At Its Best, written by Greg Bryant. This first half of the page is an ongoing blog with dated status updates, followed by the original article. As you read, just understand that you are reading backwards in time.
When you get to the October 8 update, watch the wide-field animation created by Ernesto Guido and Giovanni Sostero. Can you see the slight movement of the comet against the stationary star field?
As you read the original article, look for answers to the following questions:
- In what year was Hartley 2 discovered?
- Why does the moon play a factor in viewing comets?
- What does the EPOXI spacecraft’s name stand for?
- How close will the spacecraft get to the comet?
- What does the number 2 mean in “Hartley 2”?
- Why was this comet beyond visual discovery until after 1982?
Learn more about the EXOXI mission by visiting the official mission web site. From the home page, click Mission on the left and read the 10 phases of the mission. What is the purpose of the Earth fly-bys? What happens during the Comet Approach Phase? What will scientists be looking for during the Encounter Phase? What data will be gathered?
Finish your online study of comets this week by Comparing Comets. This is a student activity developed by NASA in which students can make their own observations based on photos of two different comet nuclei. Print this worksheet or follow along online and record your answers separately. Follow the directions on each page. On page 2, as you are looking at the two photos of comet surfaces, listen to this audio recording of students making their own observations about the comets in a teacher-led discussion.
Comets are not easy to study. Because of their speed and orbit, it is (currently) impossible for humans to travel to comets to make firsthand observations. Instead, scientists send up remotely controllable probes to intercept comets, take photographs, and make a variety of different measurements. This practice is not limited to astronomers. For centuries humans have been creating tools used to measure, weigh, count, or in many other ways analyze things that are beyond our physical senses. In a current or recent issue of the e-edition, look for news stories that cite examples of people using tools to measure or analyze. A good example might be DNA testing for criminal evidence, but you will find many others. Based on your findings, how important have these tools become in our daily lives? Why is it becoming increasingly important to measure, collect, and analyze information?