More magic from the James Webb Space Telescope (JWST)
The planet Uranus and its rings.
First observed via telescope in 1781 by astronomer William Herschel, Uranus is the seventh planet in the Solar System was the first one we learned about in modern times. The others – Mercury, Venus, Mars, Jupiter, and Saturn – had all been familiar to ancient peoples across the world. Uranus is visible in telescopes as a small, greenish-blue hue and under ideal conditions, might be able to be spotted under a dark sky if you have great eyesight.
Like all the gas giants in the Solar System, Uranus has a ring system surrounding the planet. The rings around Uranus were discovered by accident in 1977 by astronomers who were looking into the planet’s atmosphere. They’ve been imaged from Earth once before using the Keck telescope and from space as Voyager 2 flew past the planet, but never in such detail as this recent JWST image
Apart from the amazing image of the rings themselves, JWST has also captured the polar cap which unlike anywhere in the Solar System is on the side of the planet – not at the poles. This is because Uranus obits the Sun tilted on its side, resulting in the longest and most extreme seasons of anywhere in the Solar System. It’s thought that Uranus is tilted this way due to an impact with a rocky body about one to three time the size of the Earth sometime in the early formation of Solar System. While JWST is delivering groundbreaking data which will help us better understand and, in some cases, rethink the nature of the large scape structure of the Universe, our largest space-based telescope will also help us learn about our Solar System.
Supernova remnant Cassiopeia A (Cas A)
When stars over certain size reach the end of their lives, they explode in a massive event called a Supernova. The evolution of a star leading up to this event are fascinating and the leftover remnants are some of the more spectacular objects in the sky. Our own Sun will explode as Supernova in about 10 billion years, after becoming a Red Giant in some 5 billion years. (Note to self – add both dates to the BINTEL Astro Calendar….)
The striking colours in this JWST image of Cas A are infrared light which has been translated to the visual colours we can see with our eyes. Cas A has been studied with ground-based telescopes as well as Hubble and is the closest Supernova remnant to the Earth resulting from the explosion of a massive star.
Why Supernova remnants are important.
One of the reasons we observe Supernova remnants is to learn about cosmic “dust”. This is made up of heavier elements than hydrogen and helium and tiny particles of it are distributed into interstellar space during a supernova. It then clumps together over vast periods of time under the influence of gravity, where it forms planets and even us! Yes – the hard matter around you was once part of a supernova explosion. One problem we hope to solve is that we can’t reconcile the amount of dust we see in early galaxies. Careful studies of objects like Cas A might help us understand how the world around us came into existence.
New Star Formation and Galactic Evolution
In the weeks leading up to January 2004, the Hubble Space Telescope carefully photographed a small spot in the sky, capturing faint photons for a total of over 11 days taken over 400 orbits. The image produced by combining some 800 exposures is called the Hubble Ultra Deep Field. It shows a vast collection of galaxies of all types, with some of the smaller, red coloured galaxies already formed when the Universe was only about 800 million years old. Like the earlier Hubble Deep Field image produced in the middle 1990’s, the field of view is so narrow, there’s almost no stars from our own Milky Way in the foreground. It’s basically entirely composed of galaxies. What came from these and subsequent deep-field images – including one taken of the southern skies – was a better appreciation of the early structure of the Universe, that it looks similar in all directions, and that we live a typical place.
Now the JWST has imaged the Hubble Ultra Deep Field (UDF) in less than a day instead of the 11 days it took Hubble. By using the JWST NIRCam’s medium-band image filters, it was able to capture more information for better spectroscopic analysis across almost the entire field. The original Hubble deep field images have been intensely studied over the years and these new JWST images will help add to our knowledge. Plus the fact they were captured in only a fraction of time points to even more amazing views in the coming years.