Spitzer sees ices
in magellanic baby star

IRAS05328-6827 in LMC What astronomers first thought might be a dying star, unexpectedly turned out to be a star that has only just been born. Twenty times as heavy as the Sun, it is less than a million years old - which compared to the 5 billion years age of the Sun is like a baby of a week old compared to an adult human being.

The baby star is called IRAS05328-6827, named after the InfraRed Astronomical Satellite (a predecessor of the Spitzer Space Telescope) and its location on the sky. It was found in a rather unremarkable location in the Large Magellanic Cloud (see the picture on the left), which is a very nearby galaxy of stars and gas: the light from its stars only takes about 165 thousand years to reach us!

IRAS05328-6827 closeup

The picture above shows closeup images of the baby star, taken in different colours of light. The left panel shows a picture in very red "optical" light that the human eye can just about see. The baby star is invisible, because it is surrounded by a dust cloud that does not let the starlight out. The middle panel shows a picture in "infrared" light, which the human eye cannot see but a special detector can. The baby star shows up well, because the dust is not so effective in blocking this type of light. The right panel shows a picture taken with Spitzer - the baby star is extremely bright. The light that we see here is "warmth" radiating from the dust.

We unravelled the light into its different colours, like rain drops make a rainbow out of the sunlight. We call this a "spectrum". The colour becomes redder as it increases in number ("wavelength", measured in micro-metres). Stuff absorbs light of specific colours. The other way 'round, if light of a particular colour is being absorbed, we can figure out what stuff did that. The spectrum shown in the top panel we took with the European Southern Observatory's Very Large Telescope in the Chilean Atacama desert, whilst the bottom panel shows the spectrum we took using Spitzer.

Our baby star is sitting inside a thick dust cloud. Much of the dust is composed of silicates, quite similar to the sand on the beach. Because the dust blocks the light it gets quite cold in the cloud - it is like sitting in the shade on a sunny Winter's day. In fact, it gets much colder in the cloud than it ever gets in an Antartic Winter. It is not surprising then that we find lots of ice out there! Water ice, but even ice made up of methanol, and of carbon dioxide - which on Earth is the gas we breath out!

ices in IRAS05328-6827

This research has now been published as a Letter in the Monthly Notices of the Royal Astronomical Society.