Category Archives: Orion Nebula

astronomy, Orion, Orion Nebula

Orion Exploration

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Orion from the Isaac Newton Group of Telescopes (Simon Tulloch and Nik Szymanek)
Orion from the Isaac Newton Group of Telescopes (Simon Tulloch and Nik Szymanek)

In the last installment, I started a discussion about the Orion Nebula. Since it’s such an interesting place, I think I’ll talk about it a little more — it’s got so much to explore!

Astronomers refer to the Orion Nebula as an HII region because it is largely made up of hydrogen gas (H2), with a dash each of helium, oxygen, nitrogen, and traces of other elements. When the Orion birth clouds are are heated by nearby stars, they glow (emit light) in various colors — transforming it into a glowing emission nebula. The starbirth nursery may look serene in this image, but the nebula is an incredibly active place. Stellar winds scoop out caverns around the newborns, jets of superheated gas streak out from the stars, and lumpy-looking cloud textures are carved out by the combined actions of jets and winds. In the center of the nebula lies a cluster of newborns less than a million years old. None of these stars are likely to have planets — yet, and even if they did, their brightness would make it extremely difficult to find the tiny planetary pinpoints. Yet, there are things forming here that we can spot if we use an infrared-sensitive instrument to do the searching.

Orion as seen by HST
Orion as seen by HST

Hubble Space Telescope gazed at the central cluster of stars in the Orion Nebula with its optical camera and infrared NICMOS instrument, revealing bright stars in visible light — and hidden among them — about 50 of the so-called “substellar objects” that we all know as brown dwarfs glowing in infrared light. They’re the bright star-like objects in the image on the right. These are too cool to be stars, too hot to be planets and difficult to see, unless you happen to have infrared eyes.

Could our own neck of the galaxy have looked like this about 5 billion years ago? If so, when you gaze at the Orion Nebula, you may very well be see what baby pictures of the Sun and its stellar siblings could have resembled, if there’d been anybody around to do the looking!

hubble space telescope, Orion, Orion Nebula

Blushing Orion

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When you go out to find Orion later this year, it’s a safe bet that what you see through your binoculars or small telescope (or even the naked eye) will be limited to optical wavelengths of light — that is, the light your eyes are most sensitive to. That makes sense, since that’s what “optical” means. But, what if you had eyes that were sensitive to infrared light — specifically to the 1.2 to 2.2 micron infrared wavelength range, and you could zoom in on the constellation Orion and the nebula that lies just beneath the three stars that make up the belt of Orion? You might see something that looks like this 2MASS image.

I’ve discussed the Nebula in this blog before — it’s one of my favorite places to study in the winter sky (and is a familiar summer sight for southern hemisphere stargazers). The nebula contains one of the closest star formation regions in our neck of the galaxy. Small wonder that it’s one of the most heavily studied areas of the sky. Every major observatory ranging from the likes of Hubble Space Telescope to the smallest amateur facility has a picture or some data set relating to this nebula.

Orion as seen by the 2-Micron All-sky Survey (2MASS)
Orion as seen by the 2-Micron All-sky Survey (2MASS)

The visible part of this nebula is only a small part of a huge cloud of gas and dust spread out across the region of the galaxy where the nebula and its “trapezium” of newborn stars inhabit. The whole complex is called the Orion A Molecular Cloud and it is a huge storehouse of containing the raw materials for star formation. Newborn stars already formed in this “stellar nest” are lighting up the rest of the cloud, which enables us to see it from across 1,500 light years of space.

This 2MASS infrared view of the Nebula looks quite different from the many colorful optical light images we’re all used to seeing in books, magazines, and spread out across the planetarium dome. The light we see with our eyes and in those optical photos is given off by glowing gases in the nebula, or reflected off of dust grains. Those gas and dust clouds hide other objects in the nebula. In infrared light the obscuring clouds of dust are more transparent, allowing us to see deeper into the Orion Nebula and revealing the otherwise hidden stars and other objects scatted throughout the region. None of the reddest objects in this picture can be seen in visible light!

If you’d like to look at other familiar sky objects with an infrared eye, take a look at the 2MASS web site. What you see will give you a greater appreciation for how the universe looks through infrared eyes!