James Webb Space Telescope¶
Just What’s a Space Telescope?
A super cool, giant infra-red eye.
From nearby galaxies it shows a view of the dust of the galaxies as it glows in the infra-red.
Further out it sees galaxies red-shifted due to the speed of their Hubble driven recession.
Then there are quasars too.
The light from the glowing of the dust is stretched by the slowing of time by the baby galaxy’s central black hole.
The end result is that it is difficult to judge the distance of a galaxy.
Size, distance, mass of central black hole all affect the actual red shift.
And then there are the beauties of de-Sitter Space to consider.
Geodesics which separate expontentially in both forwards and backwards time.
We see each source blue shifted, but a small finite part, which might in fact be quite large, before it shifts for ever into the Hubble flow.
Space is spinning by, not expanding, but rather bouncing in harmonies.
Red-shift is more complicated than a simple matter of distance.
Will we see baby galaxies that are red shifted due to dust clouds close enough to central black holes that the infra-red energy we see is in fact the light from the stars in the galaxy, red-shifted by the massive black hole driving a quasar?
JWST Data¶
If you can just find the url of the fits file you want then things are quite simple.
The way to find what you are looking for is to query the Mast database.
The simplest query you can make is to call query region and pass it the location in the sky you are interested in.
To get the actual location to query there is another handy database that you can query to get the location if you know it’s name.
Right now, I happen to be interested in M74, also known as NGC 628.
Update 2022/8/20¶
The code here has been on a bit of an adventure, because I wanted to get this running under pyodide in the browser.
There is no access to sockets, so querying databases is more complex.
There is no requests module on pyodide but there is pyodide-requests that implements a minimal requests using javascript apis.
Everything is working except for the download of the file, which the browser blocks due to it being a cross origin request sharing issue.
The code has got a little more complicated, but no longer requires astroquery, which is also unavailable on pyodide.
But what is JWST seeing?¶
There has been a lot of excitement about galaxies of high redshift. The key number is z and is the ratio of the wavelenth we observe to what it was at the origin.
There are many reports of many z>=10 in the first images. There has also been some recalibration of the instrument that has generally reduced the red shifts observed.