Free Astronomy Magazine September-October 2016

SPACE CHRONICLES T his spectacular image of the Orion Nebula star-formation region was obtained from multi- ple exposures using the HAWK-I infrared camera on ESO’s Very Large Telescope in Chile. This is the deepest view ever of this re- gion and reveals more very faint planetary-mass objects than ex- pected. [ESO/H. Drass et al.] paraíso, Valparaíso, Chile; Max-Planck In- stitut für Astrono- mie, Königstuhl, Ger- many), a co-author of the new study and member of the research team, ex- plains why this is important: “Under- standing how many low-mass objects are found in the Orion Nebula is very impor- tant to constrain cur- rent theories of star formation. We now realise that the way these very low-mass objects form de- pends on their envi- ronment.” This new image has caused ex- citement because it reveals a unexpected wealth of very-low-mass objects, which in turn suggests that the Orion Nebula may be forming pro- portionally far more low-mass ob- jects than closer and less active star formation regions. Astronomers count up how many objects of different masses form in regions like the Orion Nebula to try to understand the star-formation process. (This information is used to create something called the Initial Mass Function (IMF) — a way of de- scribing how many stars of different masses make up a stellar population at its birth. This provides an insight into the stellar population’s origins. In other words, determining an ac- curate IMF, and having a solid theory to explain the origin of the IMF is of fundamental importance in the study of star formation.) Before this research the greatest number of objects were found with masses of about one quarter that of our Sun. The discovery of a plethora of new objects with masses far low- er than this in the Orion Nebula has now created a second maximum at a much lower mass in the distribu- tion of star counts. These observa- tions also hint tantalisingly that the number of planet-sized objects might be far greater than previous- ly thought. Whilst the technology to readily observe these objects does not e- xist yet, ESO’s future European Ex- tremely Large Telescope (E-ELT), scheduled to begin operations in 2024, is designed to pursue this as one of its goals. Lead scientist Hol- ger Drass (Astronomisches Institut, Ruhr-Universität Bochum, Bochum, Germany; Pontificia Universidad Ca- tólica de Chile, Santiago, Chile) en- thuses: “Our result feels to me like a glimpse into a new era of planet and star formation science. The huge number of free-floating planets at our current observational limit is giving me hope that we will discover a wealth of smaller Earth- sized planets with the E-ELT.” T his sequence compares an infrared image of the Ori- on Nebula star-formation region that was obtained from multiple exposures using the HAWK-I infrared cam- era on ESO’s Very Large Telescope with a picture of the same part of the sky imaged in visible light with the WFI camera on the MPG/ESO 2.2-metre telescope. The longer wavelength light detected by HAWK-I can pene- trate the dusty regions of the nebula and expose many young stars that are normally invisible and also reveal many curious features created by very young stars and the jets that they expel. [ESO/H. Drass/Igor Chekalin] n The relative proximity of the Orion Nebula (it’s estimated to lie about 1350 light-years from Earth) makes it an ideal testbed to better under- stand the process and history of star formation, and to determine how many stars of different masses form. Amelia Bayo (Universidad de Val-