The Nebula of Orion – Then & Now


The View from Galileo’s Telescope

Galileo turned his telescope to the constellation of Orion in early 1610.  Galileo had been observing the Milky Way, and found that regions of the sky that had looked nebulous, or cloudy, were in fact innumerable faint stars packed together that only a telescope could resolve. 



Looking at the nebula of Orion he discovered the same thing.  Instead of the one or two stars visible by eye, he saw dozens of fainter stars, and concluded, as he had with the Milky Way, that the nebulous region of the Sword of Orion would, with more powerful telescopes, be resolved into “groups of small stars wonderfully arranged.” 



Above: Galileo’s original sketch of the three stars in Orion’s belt and the Orion Nebula. (Image credit: Octavo Corp./Warnock Library)



What did YOU See using MicroObservatory?

The Great Nebula of Orion can be seen as a star-like twinkle with the unaided eye. if the skies are dark.  How does the Nebula appear in your image taken by MicroObservatory? Does it look like a “nebula” or cloud, or does microObservatory resolve the nebula into a multitude of stars?  Or is there a mixture of both?


To see your image of Orion more clearly, you may want to open it in our MicroObservatory image processing software.



Above: Archive MicroObservatory image of the Orion Nebula.




The Nebula of Orion - 400 years later

Galileo’s inference that the milky nebula of Orion would be resolved into stars given a good enough telescope was a reasonable one, yet it turned out not to be the case.  The nebula is indeed a massive cloud of gas and dust that is the raw material for producing the next generation of stars in our galaxy.


The Orion nebula is not the only star forming region in the galaxy, but it is the closest one to us.  Gravity causes clumps of the cloud to collapse and as those clumps squeeze smaller, they heat up.  Eventually, the centers of the clumps get so that hot nuclear reactions ignite to form a newborn star.


Thousands of stars are being born in the Orion nebula, and as their intense starlight and winds sweep away the cocoon of gas and dust we can peer into the heart of the star forming factory.  Our Sun was produced by a cloud similar to the Orion Nebula five billion years ago.








Left: A view of the Orion nebula in infrared light using the Spitzer Space Telescope.  (Image credit: NASA/JPL-Caltech/T. Megeath)



Infrared light cuts through the dense clouds of dust and gas much better than visible light, allowing us to see into the very heart of the star forming region.  In this image, the dark regions are not empty space, but dust clouds so think that they block out the light of the stars behind them. The red glow is hydrogen gas that is being heated by the intense ultraviolet light of the newborn stars.



But it’s not just stars that are forming in the Orion Nebula. Many of the new stars are surrounded by dusty discs that, over the next billion years, will condense into the planets and moons that may, in time, be suitable hosts for life.






Above Proplyds – future solar systems – forming within the Orion Nebula. (image credit: NASA/STScI)


Once the newborn stars in Orion sweep clear the remaining nebular gas they will begin to look like the Pleiades and the Beehive, two star clusters studied by Galileo. To take images of them using MicroObservatory, go back to the Galileo menu:







Find Out More


2009 is International Year of Astronomy, chosen to commemorate the 400th anniversary of Galileo’s discoveries with the telescope.  Find out what else is happening by visiting these web sites:


The World site for International Year of Astronomy.


The United States national site for International Year of Astronomy.


NASA’s International Year of Astronomy website.


To see Hubble’s view of the Orion Nebula, go to:


Take a look at the full list of objects in MicroObservatory’s Galileo activity, and see how our understanding has evolved over the last four centuries.