Flamsteed Astronomy Society

“The Science and Beauty of Nebulae” by Dr Carolin Crawford — February 7, 2011

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Report by Chris Sutcliffe

This lecture was presented by Dr Carolin Crawford, an astronomer at the Institute of Astronomy, Cambridge and a Fellow of Emmanuel College Cambridge.  She is a regular contributor to BBC Radio 4’s programme “Home Planet”.

 Her presentation focused on a number of amazing images of nebulae, how to read and understand them; and also to gain an understanding what lies between the stars.

 Nebulae are huge clouds of interstellar dust and gas, predominantly hydrogen.  Some nebulae show where new stars are being born, and some reveal what happens when stars die as thermonuclear reactions stop after millions or billions of years -- stars end their lives with a spectacular detonation, called a supernova, which blows the star apart.

 The space between the stars is not void, but is full of dust, atoms and molecules – the interstellar media.  It is the reservoir from which stars are formed.

 Carolin showed a galaxy with 100,000 million stars with spiral arms and yellow stars at the centre. The young stars in blue are in the spiral arms, and there are pink traces of gas clouds consisting mainly of hydrogen.

Rosette Nebula

This is 100 light years across and the bright blue stars are 4 million years old. By the time they radiate energy, they heat up causing a bubble around the star. This nebula is a good example of how star clouds and gas clouds live together. There are tiny particles of soot and sand 1/1,000 of the size of human hair which can black out light. Similarly, gas clouds black out light.

Milky Way

This is our galaxy of which the solar system forms part. Within it, there are dark structures consisting of molecular clouds and dust which stops the bright light and heat from the stars from penetrating the cloud.

Orion Nebula

Barnard’s Loop discovered in 1895 is an emission nebula in the constellation of Orion which is part of a giant molecular cloud which also contains the Horsehead (this is darker) and Orion nebulae. The Horsehead nebula is in fact a dark nebula; it is so opaque that it blocks any visible light from stars which lie behind it. The nebula has very low temperatures close to minus 270 degrees C which is low enough for hydrogen atoms to form molecules.

 Blue light gets scattered in a dust cloud in contrast to which, red light has a long wavelength and can penetrate cloud more readily.

 Orion itself is a huge area of star formation with large star clusters being formed.


Dr Carolin Crawford [Pics: Grey Lipley]

The Rosette Nebula NGC2237

[Pic: Brian Lula]

Horsehead and Orion Nebulas

[Pic: Maurice Toet, Steve Loughran, Darren Jehan & Tim Jardine ]

Barnard’s Loop in Orion

[Pic: Wikipedia Commons ]

[Pic: Grey Lipley]