Free Astronomy Magazine May-June 2016

SPACE CHRONICLES Hubble breaks cosmic distance record by NASA U sing the NASA/ESA Hubble Space Telescope an interna- tional team of astronomers has measured the distance to this new galaxy, named GN-z11. Although ex- tremely faint, the galaxy is unusually bright considering its distance from Earth. The distance measurement of GN-z11 provides additional strong evidence that other unusually bright galaxies found in earlier Hubble im- “Our spectroscopic observations re- veal the galaxy to be even further away than we had originally thought, right at the distance limit of what Hubble can observe,” explains Ga- briel Brammer of the Space Tele- scope Science Institute and second author of the study. This puts GN-z11 at a distance that was once thought only to be reachable with the up- coming NASA/ESA/CSA James Webb Space Telescope. The JWST is a col- laboration between NASA, the Euro- pean Space Agency (ESA) and the Ca- ages are really at extraordinary dis- tances, showing that we are closing in on the first galaxies that formed in the Universe. Previously, astronomers had estimated GN-z11’s distance by analysing its colour in images taken with both Hubble and the NASA Spit- zer Space Telescope. Now, for the first time for a galaxy at such an extreme distance, the team has used Hubble’s Wide Field Camera 3 (WFC3) to pre- cisely measure the distance to GN-z11 spectroscopically by splitting the light into its component colours. T his image shows the position of the most distant gal-axy discovered so far within a deep sky Hubble Space Telescope sur- vey called GOODS North (Great Observatories Origins Deep Sur- vey North). The survey field con- tains tens of thousands of galaxies stretching far back into time. The remote gal-axy GN-z11, shown in the inset, existed only 400 million years after the Big Bang, when the Universe was only 3 percent of its current age. It belongs to the first generation of galaxies in the Universe and its discovery provides new in- sights into the very early Uni- verse. This is the first time that the distance of an object so far away has been measured from its spectrum, which makes the mea- surement extremely reliable. GN- z11 is actually ablaze with bright, young, blue stars but these look red in this image because its light was stretched to longer, redder, wavelengths by the expansion of the Universe. [NASA, ESA, and P. Oesch (Yale University)]