What are the measurements that IBEX makes?

The sensors on the IBEX spacecraft are able to detect energetic neutral atoms (ENAs) at a variety of energy levels. By studying the amounts and directions of travel of these ENAs, measurements of atoms of different energy levels can tell the scientists a lot about the processes occurring at the edge of our Solar System.

IBEX–Lo can detect particles with energies ranging from 10 electron–volts to 2,000 electron–volts (0.01 keV to 2 keV) in 8 separate energy bands. IBEX–Hi can detect particles with energies ranging from 300 electron–volts to 6,000 electron–volts (.3 keV to 6 keV) in 6 separate energy bands. 

For comparison:

  • Visible light photons have electron volt energies of 1.5 to 3.5 electron–volts (1.5 eV to 3.5 eV).
  • 13.6 eV is the energy required to remove a hydrogen atom’s single electron.
  • High–energy diagnostic medical X–ray photons have energies of around 200,000 eV (0.2 MeV).
  • 1 trillion electron volts (1 TeV) is the total energy of motion of a flying mosquito.
  • Cosmic rays have energies from 1 million eV to 300 million TeV.

Looking across the entire sky, interactions occurring at the edge of our Solar System produce ENAs at different energy levels and in different amounts, depending on the process. Studying the images created using IBEX data can provide information about the three–dimensional configuration of the termination shock region, where the outflowing solar wind begins to interact with the material between the stars, called the "interstellar medium." Subtle differences in the images also enable scientists to determine the solar wind flow patterns beyond the termination shock.

In addition to studying the edge of our Solar System, IBEX measurements of specific neutral atoms – namely hydrogen, helium, oxygen, and neon – can also provide information about interactions occurring farther out, beyond the farthest Solar System boundary.

Image Credit: NASA/IBEX/Adler Planetarium