On April 2, 2018, NASA announced that astronomers using the Hubble Space Telescope have uncovered the farthest individual star ever seen. The massive blue star dubbed ‘Icarus’ lies 9 billion light years from Earth, appearing to us at a time when the universe was a third of its current age.

Though nearly impossible to view with some of the world’s largest telescopes, astronomers pinpointed it by using gravitational lensing that amplified the star’s faint glow. This method of observation has created a new method for researchers to analyze single stars in distant galaxies allowing a rare and detailed look at how luminous stars form.

Gravitational Lensing

Using gravity from the foreground, such as from a massive cluster of galaxies, serves as a natural lens in space to bend and amplify light. To discover Icarus, the galaxy cluster MACS J1149+2223, located 5 billion light-years away from Earth, became its natural magnifying glass. Combining this method with Hubble’s sophisticated specs allows astronomers to observe and study Icarus. It is anticipated that with the launch of NASA’s James Webb Space Telescope, many more stars like Icarus shall be revealed. The JWST will allow highly detailed measurements of such distant objects, even being able to determine whether or not they rotate. Impressive humanity, there may be some hope yet.

Scientists found that the Hubble data from MACS J1149+2223 Lensed Star 1 (Icarus) matches the model for a blue supergiant. The agreement shows a remarkably good fit, and indicates that Icarus is approximately twice as hot as the Sun. The solid blue line shows the model spectrum of the blue supergiant, adjusted for the distance to the host galaxy of the highly magnified star. The red diamonds are the actual data measured for Icarus. The observed wavelength of the Balmer discontinuity relative to its intrinsic wavelength (at about 365 nm) is an indicator of the distance to the star. The strength of the Balmer discontinuity depends on the strength of the star’s gravity at its surface and its temperature.
Credits: NASA, ESA, and A. Feild (STScI)

 

The star is named after the hero in Greek mythology who flew too close to the Sun. Like its literary counterpart, the star Icarus brightened about 2000 times when magnified for just a few moments with gravitational lensing.

Icarus serves as an important discovery that will be used to test a dark matter theory and for additional study of a foreground galaxy cluster.