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.

4.3.6 Protoplanetary disc example

An image of the protoplanetary disc of the planet Beta Pictoris.
Figure 28 The protoplanetary disc of the planet Beta Pictoris

A complementary method to searching for planets around stars is to search for protoplanetary discs, the dusty discs you learned about earlier, that exist prior to aggregation into discrete planets.

The advantage of this technique over planet observation is that discs can readily be imaged by detection of emission of infrared radiation over and above that expected from a star. The excess radiation results from the presence of dust grains in the disc.

The Infrared Astronomical Satellite (IRAS) made the first observation of an infrared excess around the star Beta Pictoris. Subsequent optical imaging detected a flat disc of dust extending away from the central star – as you can see in the image above.

The disc is ~900 AU across (for comparison, the distance from the Sun to Pluto is ~39.5 AU) but the dust does not extend all the way inwards to the star itself. Images obtained by the Hubble Space Telescope have shown that the central inner zone (a region ~50 AU across) is relatively free from dust, implying that the dust has perhaps been swept up into a planetary system.

In the next section, you’ll be invited to consider whether you think there could be life on an exoplanet.

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