(AND LIFTOFF!)
(JAMES WEBB BEGINS A VOYAGE BACK TO THE BIRTH OF THE UNIVERSE)
When the James Webb Space Telescope launched it was the realization of a dream
more than 30 years in the making. But there were still some crucial milestones
to come before the most powerful telescope ever to fly in space could deliver on its promise.
First, the telescope’s protective sunshield and its primary mirror,
made up of 18 gold-coated segments, had to unfold without a hitch.
Then, Webb had to travel about 1.5 million kilometres, to a point in space called L2,
where gravitational forces allow the telescope to remain in a constant position relative to Earth.
Finally, mission operators had to align the telescope’s mirror segments
so they can act as one giant mirror 6.5-metres across.
Now comes the real moment of truth. The release of the first full-colour images that will show
the world what the new telescope can do. Because Webb is bigger and has different capabilities than
its predecessor, the Hubble space telescope, it’s virtually guaranteed to make new discoveries.
The question is will have the same cultural impact that Hubble has had over its 32-year lifespan.
Hubble managed this despite getting off to a very shaky start.
(THERE'S A SIGNIFICANT SPHERICAL ABERRATION.)
Soon after launch, astronomers discovered there was a flaw in its main mirror.
It was a disaster.
But a few years later astronauts installed
new optical components to correct for the flaw, and the results were mind-blowing.
Back then, digital cameras were still in their early days,
so public impressions of space were guided by images that were shot decades earlier
on film or photographic plates.
In this 1959 photo of the Orion Nebula,
the nebula looks purplish-red because the photographic medium is picking up to the
red light emitted by hydrogen gas, plus a bluish tinge from scattered starlight.
Now look at the Orion Nebula as seen by Hubble in 1995.
Here, astronomers assigned the colour green to hydrogen
in order to distinguish it from other gasses in the nebula.
It’s a very different look — one that was echoed in science fiction films and TV shows at the time.
In a sense, you could say that Hubble changed how people expected space to look.
(IT'S BEAUTIFUL.)
So what can we expect from Webb? Unlike Hubble, the new telescope mostly
sees in the infrared part of the spectrum, which the human eye can't see.
That means astronomers will have a lot of latitude in how they assign
colours to the Webb data. It will be interesting to see what kinds choices they make and how they’ll
be guided by artistic convention.
Here’s an example of what I mean. This Hubble picture almost looks three dimensional
because of the way the human eye responds to the red-coloured gas.
We tend to see it in the foreground while the cooler colours like blue and green recede into
the background. That’s an artistic choice on the part of the team that made this image.
Because Webb operates in the infrared it will show us familiar objects in a different way.
For example, here’s the well known Andromeda galaxy at wavelengths the human eye can see.
Now here’s what Andromeda looks like through the Spitzer Space Telescope which is sensitive
to infrared light, just like Webb. Webb’s view will be more like this,
only deeper and sharper.
With its giant mirror, Webb also gathers more light and therefore shows fainter,
more diffuse objects than Hubble is able to. Simulations made before Webb was launched
suggest the universe could look a lot more crowded when seen through the new telescope
because the will be more to see in the background.
There’s one other variable in all this, which is the difference between media audiences today
compared to those who were looking at the first Hubble photos back in the mid-1990s.
We've all seen a lot more CGI since then so the Webb photos will have that to compete with.
(DIE SPACESHIP!)
Even so, I think there’s a good chance Webb will impress us.
After all, it’s not just the image that matters, but what it represents,
and when it comes to the universe, there’s a lot of power in knowing you’re looking at the real thing.