Images by Date
Images by Category
Solar System
White Dwarfs
Neutron Stars
Black Holes
Milky Way Galaxy
Normal Galaxies
Galaxy Clusters
Cosmology/Deep Field
Images by Interest
Space Scoop for Kids
Sky Map
Photo Blog
Top Rated Images
Image Handouts
Fits Files
Image Tutorials
Photo Album Tutorial
False Color
Cosmic Distance
Look-Back Time
Scale & Distance
Angular Measurement
Images & Processing
Image Use Policy
Web Shortcuts
Chandra Blog
RSS Feed
Email Newsletter
News & Noteworthy
Image Use Policy
Questions & Answers
Glossary of Terms
Download Guide
Get Adobe Reader
Comets ISON & PanSTARRS Animations
Click for low-resolution animation
Tour of Comets ISON & PanSTARRS
Quicktime MPEG With closed-captions (at YouTube)

People on Earth have been watching comets in the sky for many thousands of years. Although many ancient cultures saw comets as signs of impending danger, today scientists know that comets are really frozen balls of dust, gas, and rock. They may have been responsible for delivering water to planets like Earth billions of years ago.

It may surprise people to hear that comets can provide information about other aspects of our Solar System. In particular, comets can be used as laboratories to study the behavior of the stream of particles flowing away from the Sun, known as the solar wind.

Recently, astronomers have performed such a study using observations with Chandra of two comets, named ISON and PanSTARRS. Chandra observed these two comets in 2013 when both were relatively close to Earth.

Scientists know that comets produce X-ray emission when particles in the solar wind strike the atmosphere of the comet. The Chandra data allowed scientists to estimate the amount of elements like carbon and nitrogen in the solar wind. They found values that agree with those from other missions, showing the value of X-ray observations for deriving the composition of the solar wind.
[Runtime: 02:21]

(Credit: NASA/CXC/A. Hobart)

Return to Comets ISON & PanSTARRS (April 18, 2016)