James webb

Early Galaxies

/ Stephen Mackintosh / Leave a comment

The above montage shows six recent images of ‘potentially’ massive galaxies photographed by the James Webb space telescope, going back to epochs around 600 million years after the universe began.

If the six red dots are confirmed to indeed be large galactic structures, these examples contradict almost all known models of galaxy formation from the early history of the universe and would suggest stellar masses over 100 times greater than previously predicted in this early period. Existing models of galaxy formation predict large galaxies would require several billion years to form, so if true these findings will require extensive revisions to our understanding of the large structure evolution of the universe.

Truth told we still know very little about the formation of galaxies. Their evolution is still shrouded in deep mystery, for example what forms the large bars we see in the centre of most mature spiral galaxies, including our own Milky Way?

And of course their rotational dynamics have lead to the conclusion that clouds of invisible matter must surround them in giant halos (dark matter).

Hubble vs Webb

/ Stephen Mackintosh / Leave a comment
Hubble composite SMACS 0723
Webb composite SMACS 0723

The above images of galaxy cluster SMACS 0723 (located 4.6 billion light years away) highlights the huge resolution jump from Hubble to Webb.

Webb’s first full colour image took just 12.5 hours of integration time to capture and already reveals detail surpassing Hubble’s deepest field images, some of which took weeks of accumulated processing time.

The area of space imaged in this composite is equivalent to holding a grain of sand to the night sky at arms length. Almost all the individual points of light here are separate and independent galaxies, each containing 100s of billions of stars, and captured in various stages of historical morphology going back as far as 13 billion years (due to the help of gravitational lensing).

While greater mirror diameter and enhanced sensor resolution accounts for much of the extra clarity Webb has over Hubble, it should be remembered that James Webb is an Infrared telescope, so less detail in its deep field images gets obscured by opaque interstellar dust, which can block some of the visible wavelengths of light Hubble sees. Also, visible light that has experienced extreme red shifts (due to the expansion of the universe) can end up stretched into the Infrared, so Webb can look much further back in time than Hubble, revealing some of the oldest first generation galaxies yet seen.

James Webb – First Fully Aligned Image

/ Stephen Mackintosh / Leave a comment

Fine phasing of James Webb’s honeycomb mirror segments is now complete, revealing this first fully aligned image of star 2MASS J17554042+6551277 via the telescope’s NIRCam sensor.

This test image has exceeded NASAs expectations in terms of resolving power and clarity. You can even see well defined distant spiral galaxies in the background.

Unlike the Hubble space telescope the wavelengths of light gathered here is around 2 microns, within the infrared band of the electromagnetic spectrum (the region Webb has been designed to observe). These are wavelengths longer than the human eye can detect but ideal for revealing the evolutionary structure and morphology of stars and distant galaxies.

The Webb team will now continue with calibration of the on-board spectrographs, completing the full scientific instrument setup.

This process is expected to take several more months, but so far so good.

James Webb First Light

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Here is the first ever image processed from the James Webb space telescope’s primary mirror. It shows copies of a distant star HD 84406, individually imaged through Webb’s 18 honey-comb like mirror segments.

This is part of the primary mirror alignment phase. A bit like the process backyard observers go through when we collimate our telescopes.

Over the next several weeks these individual points will converge to form a single image of the star, completing the alignment process and ensuring all components of the 6.5 meter primary mirror are working as one.

You can see the gold plated hexagonal components of the primary mirror in this second picture, which is a selfie the telescope took of its main mirror from outer space.

The astrophysical community awaits Webb’s first active mission pictures which I understand will be images of three of the largest low-albedo asteroids, as well as Jupiter’s red spot and Neptune’s southern polar vortex.