In the night sky: Orion
In the night sky: Orion

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

2.1.8 Protostar

An image shows the protostar V1647 Orionis.
Figure 8 The protostar V1647 Orionis

The cloud clumps heat up as they collapse and also begin to spin more rapidly.

As they spin more rapidly, they change their shape, becoming flatter and more disc-like. Material falling onto the central protostar now passes through a flattened region surrounding it called an accretion disc.

Figure 8 shows a small region of Orion, where a hot young protostar is picked out by the light it is radiating at infrared wavelengths.

At the same time, as material falls onto the equatorial regions of the protostar, powerful jets of material are ejected from its poles. Astronomers are currently unsure of the detailed processes that cause these jets, but their effect is to remove both material and energy from the protostar.

Eventually, the core of the protostar will become so hot that nuclear fusion reactions can begin and a new star is born.

This whole process is surprisingly rapid and is thought to be complete within about 100 million years for the lowest mass stars. More massive protostars have a greater gravitational attraction, so material is pulled onto them at a much higher rate, so more massive stars form more quickly. Stars with masses more than 15 times that of the Sun form in only about 100,000 years.

In the next section, you will be taking a photograph of Orion.

Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to University-level study, we offer two introductory routes to our qualifications. You could either choose to start with an Access module, or a module which allows you to count your previous learning towards an Open University qualification. Read our guide on Where to take your learning next for more information.

Not ready for formal University study? Then browse over 1000 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus371