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How to make a solar system

Scientists have a pretty clear picture of how the solar system was formed 4.6 billion years ago. But how do astronomers know what was going on way back then – without hopping into a time machine?

Luckily, there are many star systems out there (beyond our solar system), and some are very young and in the process of being formed. By studying these newborn stars and planets, we can learn a lot about our own past. And a very unique mode of Near-Infrared Imager and Slitless Spectrograph (NIRISS), the Canadian instrument aboard the James Webb Space Telescope, will allow astronomers to do just that!

Studying planets in formation

Our solar system was created about 4.6 billion years ago, when a giant cloud of gas and dust collapsed on itself because of physical forces, forming a protoplanetary disc – a massive area primed for the formation of planets.

Our star, the Sun, was formed at the centre of this disc. Clumps of material stuck together and grew throughout the rest of the disc, eventually forming the planets, including Earth.

An image of a planet being formed inside the star PDS 70's protoplanetary disc taken by the SPHERE instrument on the Very Large Telescope in Chile. (Credit: ESO/A. Müller et al.)

We know that our galaxy, the Milky Way, contains hundreds of billions of other stars, and they are all at different stages in their lives. Some, like the Sun, are right in the middle of their lives. Others are at the very start of their lives and can be studied while they are still surrounded by their protoplanetary disc. These discs can be quite hard to spot because this stage of a star system's life lasts no more than 10 or 20 million years – a fraction of a star's life, which can ultimately last billions of years.

Not only can we see stars and their dusty, planet-producing discs in these systems, but we can also sometimes even see planets beyond our solar system as they are being born. Studying these very young exoplanets can tell us a lot about how different types of planets are formed.

Imaging protoplanetary discs

This real image of the protoplanetary disc around the star HL Tauri was taken by the Atacama Large Millimeter Array (ALMA) using the technique of interferometry. (Credit: ALMA)

Telescopes have captured some truly beautiful images of galaxies and nebulas. Unfortunately, it is much more difficult to take a picture of a planet or a solar system because they are much smaller and harder to observe. The great majority of exoplanet images seen online are artistic representations rather than real images.

It is possible to take a real image of an exoplanetary system or a protoplanetary disc, and one of the methods to do this is called interferometry. This technique uses the fact that light waves coming from a distant object like a star can interact together and cause patterns that scientists can analyze.

Using these patterns, researchers can take images of objects that are very close together that would otherwise be impossible to see properly using a normal camera. This same technique was used by the Event Horizon Telescope Collaboration to take the first-ever image of a black hole in .

Webb's Canadian instrument

The James Webb Space Telescope promises to revolutionize our understanding of the universe, with the help of a Canadian-made instrument and fine guidance sensor. (Credits: Canadian Space Agency, NASA, Northrop Grumman, ESA)

One of Canada's contributions to the James Webb Space Telescope is the scientific instrument NIRISS, the Near-Infrared Imager and Slitless Spectrograph. One of its special modes is called Aperture Masking Interferometry (AMI), designed to allow NIRISS to take pictures of hard-to-observe objects like protoplanetary discs.

Through its participation in Webb, Canada has guaranteed access to up to 450 hours of telescope time during the first few years of the mission through the Guaranteed Time Observations (GTO) program. One of Canada's GTO programs will use NIRISS's AMI mode to study and image planets being formed around young stars in protoplanetary discs. University of Victoria graduate student Doron Blakely will use these observations as part of his thesis research. Led by Dr. Doug Johnstone, senior research officer at National Research Council of Canada's Herzberg Astronomy and Astrophysics Research Centre, the program will allow astronomers to test theories of planet formation using the telescope's careful observations.

An international collaboration between NASA, the European Space Agency and the Canadian Space Agency, the James Webb Space Telescope is the most complex and powerful space telescope ever built. Canada contributed two key elements to Webb: the Fine Guidance Sensor (FGS) and the NIRISS.

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