[deleted] t1_j2ibmuo wrote on January 1, 2023 at 3:26 PM

Reply to comment by [deleted] in Black holes, exoplanets and distant galaxies: James Webb Space Telescope’s best discoveries after one year in space by Soupjoe5

But perhaps most excitingly, there are one or two instances where bright stars can be seen at the ends of the gaseous fingers. These are the young stars themselves, and each one could be attended by a solar system of planets.

And even though the team behind MIRI had always had this observation in mind, the end result still took them by surprise. “We’ve planned to do it for all these years, we knew it would be exciting. But it’s different when you actually see it, and you have the data. I think it’s just really exciting,” says Gillian Wright, the European principal investigator for MIRI.

By revealing more details than ever before, the JWST’s new views of the Pillars of Creation will help researchers test their knowledge of star formation, and improve their computer models of the process. Understanding more about the precise number of young stars in these regions, and the spread of masses, along with the actual quantities of gas and dust that make up the nebula, is vital for understanding the way galaxies replenish their supply of stars.

At the other end of the stellar life cycle, the JWST has also been revealing the way stars die. Stars like the Sun swell to become red giant stars and then collapse into compact stellar corpses known as white dwarfs. In this collapse, they eject their outer layers to form a so-called (but woefully misnamed) planetary nebula. The JWST’s image of the Southern Ring Nebula shows how beautiful this process can be.

For thousands of years before it became a white dwarf, the star would periodically eject shells of matter from its outer layers. What was left of the star would then contract and heat up, sparking a new round of energy generation that would set off a new round of pulsation, leading to the ejection of another shell of material. On and on this went until there was simply not enough remaining matter to squeeze the star’s core sufficiently to spark nuclear fusion any more. At this point, it became a white dwarf. This is the fate that awaits our own Sun in around 4.5 billion years.

Exoplanets

When it comes to planets beyond our Solar System, not even the JWST can deliver a detailed image. An exoplanet, especially one the size of Earth, is so small and dim compared to its central star that it will take a dedicated space mission using numerous space telescopes working together in clever ways to produce anything with any level of detail at all. Nevertheless, the JWST has managed to take one exoplanet image.

The planet is called HIP 65426 b. It is somewhere between six to 12 times the mass of Jupiter and orbits its star about 100 times further than Earth is from the Sun. To see the alien world, the JWST used devices called coronagraphs on its NIRCam and MIRI instruments.

A coronagraph blocks out the light from the central star, making the fainter surroundings easier to see. Its name comes from the fact that astronomers developed such an instrument to study the faint, outer atmosphere of our own Sun, which is called its corona. Now it can be used to see fainter objects such as exoplanets near distant stars.

Prof Sasha Hinkley, an astrophysicist at the University of Exeter, led these observations. “It was really impressive how well the Webb coronagraphs worked to suppress the light of the host star,” he said when NASA released the image on 1 September 2022.

[deleted] t1_j2ibpth wrote on January 1, 2023 at 3:26 PM

This is not the first direct image of an exoplanet ever taken from space, the Hubble Space Telescope had previously captured a direct image of a planet in orbit around the star Fomalhaut, but it is a proof of concept that the JWST can do this at infrared wavelengths.

But when it comes to exoplanet research, the JWST’s biggest contribution is undoubtedly its ability to break down the light it receives into spectra. Spectra are a measure of how much light at each wavelength is being received.

A lot of science can be extracted from spectra, because atoms and molecules each like to interact with different wavelengths. This creates a pattern of dark lines in the spectra that are effectively like fingerprints, each one unique to a specific atom or molecule. The JWST is so important in this regard because molecules really like to interact with infrared wavelengths. Hence, an infrared spectrum of a celestial object can reveal its chemical composition.

This is exactly what astronomers did with the JWST’s NIRISS instrument on the exoplanet WASP-96 b. The resulting graph showed the distribution of infrared light from 0.6 to 2.8 micrometres. WASP-96 b is notable because it often passes in front of its parent star.

A small proportion of the star’s light therefore passes through the exoplanet’s atmosphere, where the constituent atoms and molecules absorb their preferred wavelengths. This shows up as a drop in the intensity at those wavelengths. In this particular case, the JWST showed that WASP-96 b contained water vapour in its atmosphere.

The planet is a ‘hot Jupiter’, so-called because it has a mass of around half that of Jupiter in our own Solar System, yet orbits so close to its star that a year lasts just 3.4 days. The results themselves are still preliminary because a computer model of the planet’s atmosphere must be constructed. The model includes things like the abundance of various gases in the planet’s atmosphere, and the height and thickness of any clouds in the exoplanet’s atmosphere.

The next phase of this research is to extend this work to smaller and smaller exoplanets, eventually analysing Earth-sized worlds. This is more difficult, because smaller worlds have less dense atmospheres, but astronomers are optimistic.

“The JWST opens the door to smaller planets and cooler planets, more similar to our own Earth. And it will allow us to study giant planets in much more detail than we’ve ever had access to before,” says Laura Kreidberg, an exoplanet expert from the Max Planck Institute for Astronomy, Germany. “I feel like we’re at the very, very beginning of a really exciting journey.”

Planetary systems

It is not just planets around other stars that the JWST has been looking at. It has also been targeting some of the planets in our own Solar System. In its first released image of Jupiter, different wavelengths from the NIRCam instrument were combined to create an image where brightness represented altitude in the Jovian atmosphere. The higher a feature is, the more infrared light it reflects, so the brighter it appears.

Jupiter’s Great Red Spot, for example, a storm system so large that it could engulf the entire planet Earth, is so high in the planet’s atmosphere that it appears extremely bright at infrared wavelengths. The deeper cloud layers and hazes appear much darker by contrast. The auroras show up at the northern and southern poles of the planet in this image too. They are created when particles trapped in Jupiter’s magnetic field are funnelled into the giant world’s atmosphere, where they strike atoms and molecules and cause them to fluoresce.

[deleted] t1_j2ibt7s wrote on January 1, 2023 at 3:27 PM

The JWST also focused NIRCam on distant Neptune. Six times further from the Sun than Jupiter, Neptune is not seen in so much detail but the results are similar. A series of bright patches in the planet’s southern hemisphere represent high-altitude methane-ice clouds, while a more subtle ring of brightness circling the planet’s equator could portray a kind of ‘jet-stream’, a circulating band of atmosphere that powers Neptune’s winds and storms.

One recent observational campaign that the JWST was well placed to assist with was the asteroid deflection test of Dimorphos. On 26 September, NASA’s DART spacecraft intentionally crashed headfirst into the small asteroid in order to test our ability to deflect an asteroid should one be found to be on a collision course with Earth.

This image was taken around four hours after the impact and shows the enormous dust cloud that was ejected from the collision. Analysing the amount of material that was blown into space by DART will allow theoreticians to understand more about the interior composition and structure of Dimorphos, and asteroids in general. This knowledge will be crucial when designing a mission to deflect an asteroid for real. In the months after the collision, the JWST has continued to observe Dimorphos in order to gain as much insight as possible.

And it is still early days. The images that have been released so far are more like proofs of concept rather than full scientific results. They represent a promise from the astronomers involved that the telescope is working, and that the analyses, results and breakthroughs will follow.

“It’s really fun and exciting at the moment. There’s something new in everything the JWST touches,” says Wright. “There’s something you look at and you go ‘wow!’”