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Skywatching

Space telescope gives a closer look at the birth of stars

The birth of a star

Stars are the universe's Swiss Army knives.

Starting from the primordial hydrogen dating back to the beginning of the universe, they produce all the elements required for making planets and living things. In addition they provide the light and heat needed for that life to form and thrive.

Without stars the universe would be a dark, cold place, without even the ingredients for life.

Because they are so important in the universe, stars attract a lot of scientific interest. We have a lot of observational information on stars during their lives, and on how their lives end, because the mass ejections, explosions and brightness variations are relatively easy to observe, as are the stellar remains, such as white dwarf stars, neutron stars and supernova remnants.

Observing star birth is more difficult, since the big event is discreetly hidden inside clouds of gas and dust.

There is, however, a solution. If you have ever driven in fog and found wearing orange or red glasses makes it easier to see, you were seeing the answer. The problem is mostly due to a process called “scattering,” where the light is radiated off in all directions by tiny dust particles, or water droplets in the case of fog.

Scattering is strongly dependent on the wavelength of the light. Short wavelengths, such as blue and green are strongly scattered, red much less so. Infrared light has a longer wavelength than red light and is scattered even less, ideal for looking inside stellar birth clouds, except that those wavelengths are absorbed by our atmosphere.

We need to observe cosmic infrared light from above the atmosphere, in space. That is where the James Webb Space Telescope (JWST) comes in. It is designed to observe at infrared wavelengths that do not reach the ground. This makes it ideal for studying the birth and extreme youth of stars.

One of the most recent JWST images shows a sun-like star that has been shining for no more than 50,000 years. The object, poetically named HH212, lies in the constellation of Orion. This constellation, named after a mythical hunter, is the most spectacular star grouping in our winter skies.

The most easy-to-spot feature is a line of three stars, representing the hunter's belt. HH212 is close to these stars, and lies at a distance of about 1,300 light years from us. The JWST image shows two pink jets shooting out in opposite directions. That pink colour is produced by hydrogen. Since clouds take around a million years to produce stars, and sun-like stars shine for maybe 10 billion years, that star is very young. It has probably achieved nuclear fusion, but still growing by pulling in material from its birth cloud.

Any random cloud of gas and dust in space is generally travelling in some direction, and is also rotating. Just as in the case of a twirling skater or ballerina pulling in her arms, the rotation accelerates as the cloud shrinks.

Part of the material forms a rapidly rotating protostar (star to be). The rest forms a disc, some of which is rotating too quickly to collapse onto the star. This will form planets, asteroids and other bodies.

There are magnetic fields in the cloud, which also get concentrated in the disc and in the young star. These combine with very hot gas to form a material rather like putty. This resists being compressed by infalling material from the disc and squeezes out from the pole regions of the star as two jets, more or less at right angles to the disc.

This young star has not yet settled down to steady shining and is producing lots of little burps and explosions, which launch shock waves outward. These make the hydrogen in those jets glow with that characteristic pink colour.

If we could see back 4.5 billion years to the birth of our sun, we would probably see something like this.

•••

• Saturn lies in the south after sunset, with Jupiter in the east.

• Venus will rises in the early hours.

• The Moon will reach its first quarter on Nov. 20.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.



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About the Author

Ken Tapping is an astronomer born in the U.K. He has been with the National Research Council since 1975 and moved to the Okanagan in 1990.  

He plays guitar with a couple of local jazz bands and has written weekly astronomy articles since 1992. 

Tapping has a doctorate from the University of Utrecht in The Netherlands.

[email protected]



The views expressed are strictly those of the author and not necessarily those of Castanet. Castanet does not warrant the contents.

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