SalsaJ Astronomical Image Analysis App

SalsaJ was developed to let middle and high school students analyze real astronomical data in the classroom, but it also works as an accessible app for amateurs of all ages.

SalsaJ is a free Java-based application that works in Windows, OS-X, and Linux. It’s a modified version of the ImageJ image analysis software developed by the National Institute of Health. Developers at the European Hands On Universe added astronomy-specific modules and removed or simplified functions to make it more appropriate for classroom astronomy lessons. SalsaJ isn’t just for archived data - a module lets you control a telescope-mounted webcam and use lucky imaging to create sharp images of the Moon, Sun, and planets. 

The regional Hands On Universe organizations provide a wide range of classroom activities that use SalsaJ and real astronomical data. As the home of SalsaJ development, the European Hands On Universe site has many SalsaJ activities such as:

  • Measure the brightness variation of Cepheid stars to calculate the distance between the Solar System and the Small Magellanic Cloud, one of the Milky Way’s satellite galaxies.
  • Use the radial-velocity and transit methods to detect planets orbiting other stars.
  • Find the mass of Sagittarius A, the supermassive black hole at the Milky Way’s core, by measuring the motion of stars.
  • Find the mass of a galaxy by measuring the doppler-shift in its spiral arms.

Researchers with the Las Cumbres Observatory Global Telescope Network wrote several SalsaJ activities that use data from its telescopes. The activities include building lightcurves to detect exoplanet transits and analyzing star clusters using photometry.  

Researchers with the University of Chicago’s Yerkes Observatory created SalsaJ activities that lets students find the mass of Jupiter or the velocity of an asteroid.

Activities posted to the Faulkes Telescope Project’s education resources site walks you through creating a supernova lightcurve or creating a color composite images. Several of the project’s astronomical imaging tutorials use SalsaJ.

Academic papers that describe using SalsaJ:

“Astrophysics datamining in the classroom: Exploring real data with new software tools and robotic telescopes” ( by Doran et al. The SalsaJ team prepared this paper for the American Journal of Physics special issue on using astronomy to teach physics. It explains the motivation behind the SalsaJ project and provides three examples of classroom exercises SalsaJ makes possible. Crater analysis: using images from various Nasa missions of craters on other planets and moons as well as USGS images of craters on Earth students use SalsaJ to analyze the size and shape of the craters and then draw conclusions about the original impactors. Sagittarius A: students animate images captured by the European Southern Observatory’s Very Large Telescope over sixteen years to show how stars at the Milky Way’s core orbit SgrA*, the supermassive black hole at the center of our galaxy. They use SalsaJ to estimate the stars’ orbits and the mass of SgrA*. Exoplanets: students use SalsaJ to detect exoplanets using both radial velocity and transit techniques.