The Hubble Space Telescope has just offered a better view of our Milky Way Galaxy's most massive stars. The image shows a pair of colossal stars, WR 25 and Tr16-244, located within the open cluster Trumpler 16. This cluster is embedded within the Carina Nebula, an immense cauldron of gas and dust that lies 7,500 light years from Earth.

The nebula contains several ultra-hot stars, including these two star systems and the widely studied, explosive star Eta Carinae, which has the highest luminosity yet confirmed. The stars are hot and bright, emitting most of their radiation in ultraviolet and therefore appearing blue. They are so powerful that they burn through their hydrogen fuel source faster than other types of stars.

WR 25 attracts maximum attention due to its massive size. Its true nature was revealed two years ago when an international group of astronomers, led by Roberto Gamen, then at the Universidad de La Serena in Chile, discovered that it is composed of at least two stars. The more massive is the Wolf-Rayet star and it may weigh more than 50 times the mass of our sun, while its more mundane binary companion is probably about half its size.

Another view by astronomers, led by Jesus Maiz Apellaniz at the Instituto de Astrofisico De Andalucia in Spain, believe that the radiation from the two star clusters may be causing a giant gas globule in the Carina Nebula to evaporate, inducing new stars to form and giving the globule its strange shape.

These Hubble observations have revealed that the Tr16-244 system is actually a triple star. Often the individual stars are so physically close to each other that it is very difficult to resolve them in telescopes as separate objects. The brightness and proximity of the components of such massive double and triple stars makes it particularly challenging to discover the properties of massive stars.