I was very sad to read in the news this week about NASAs decision to bring the Spitzer Space Telescope’s mission to an end early in 2020. This telescope, which has been imaging the universe at infra-red wavelengths since 2003, has enabled amazing new views and increased understanding of many different astronomical topics, including formation of stars and planetary systems, and the development of galaxies.
This striking image by Spitzer shows a nebula known as ‘The Spider and the Fly’ or, more formally, IC417. It is actually a cloud of interstellar hydrogen gas and dust known as a molecular cloud, that is glowing due to the light from baby stars forming within in. Such molecular clouds often form ‘stellar nurseries’ – if they become dense enough, parts of the cloud start to collapse due to gravity, compressing the gas more and more densely until baby stars are created within the cloud. As the stars start to shine, they light up the cloud from within, as in the central area of the image; and as the stars get larger and brighter, the cloud around starts to clear away, as you can see in the centre right.
Molecular clouds are typically star-forming regions – but that doesn’t mean that all the stars forming there are the same. Even if stars form at the same time, they are likely to be of different sizes and their lifetimes can vary hugely, depending on their mass – the more massive a star, the hotter and faster it burns and the shorter its lifetime.
So dying stars can co-exist with youthful ones in the same ‘nursery’, as evidenced in this image of star forming region NGC 3582 from ESOs La Silla Observatory - the huge arcs that you can see are thought to be loops of gas expelled by dying stars.
Outward forces
As the growing stars in a star-forming region get hotter and brighter, their radiation and stellar winds get stronger, pushing outwards against the gravitational pressure of the collapsing cloud.
In this beautiful image by Spitzer of the Westerhout 40 nebula, you can see gaps in the cloud cleared by stars, and two large bubbles of matter expelled by the most energetic central stars.
This disperal of a cloud around newly forming stars can actually prevent new stars forming afterwards in that particular area since there is no longer any material available for them to form from.
1. Spitzer Space Telescope/NASA
2. ESO, Digitized Sky Survey 2 and Joe DePasquale
3. NASA/JPL-Caltech
Find out more:
http://www.spitzer.caltech.edu/mission/38-Science
https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA20357
https://www.eso.org/public/images/eso1113a/
http://www.spitzer.caltech.edu/images/6583-ssc2019-04a-Space-Butterfly