I hope you are all safe and doing well.
As the COVID climate of the country continually changes, it is essential to maintain safety. Especially during an especially virulent outbreak, our safety is in our hands, in the precautions that we take and the measures we use to constrain the spread of the virus.
In such uncertain times—where certainty is forged by our actions!—it is often a fitting escape to look to the incredible science occurring in the heavens. Not just in the powerful phenomena that the universe undergoes, but in the incredible instrumentation that we are creating on Earth to explore these phenomena.
Last time, we began our discussion of the James Webb Space Telescope (JWST) by exploring the ways that it improved upon its predecessor—the Hubble Space Telescope. Today, we’re going to go into the granularity of how, exactly, this improvement is done. For the JWST has much more than simply a larger mirror; the engineering used to create it is lightyears beyond the engineering of the Hubble, and, therefore, has the potential to return lightyears more information to science. *Note that my usage of lightyears in this context is purely literary (unit of distance, not quantity!)*
But anyway, let’s begin our discussion of the facets of the JWST. So sit back, relax, and enjoy the ride!
Before we start our conversation about why the JWST’s incredible instrumentation is so impactful, we need to revisit a concept that we explored in our post about Doppler Effect: cosmological redshift.
The universe is so vast that we never see anything in real-time. If a star is 1 million lightyears away, it has taken 1 million years for that starlight to reach us. So, we’re actually seeing what that star looked like 1 million years ago.
Now, this principle is extended the farther away something is. The observable universe is almost 96 billion lightyears across, meaning that we can look as far as about 48 billion lightyears away in any direction. This means that we’re looking extremely far into the past the farther that we look into the universe. But what does any of this have to do with redshift?
Because the universe is expanding, the farther away something is, the faster it is moving from Earth. The light that it emits is, therefore, stretched more. The farther something is, the more stretched its light is. The more stretched light gets, the redder it appears. All of this builds to the conclusion that in order to look far back in time, we need the capacity to observe extremely redshifted objects.
The JWST’s primary distinction from the Hubble Space Telescope is its ability to detect extremely redshifted objects. The sensitive instrumentation on the JWST can observe faint red objects and infrared radiation with far more precision than Hubble, detecting 100x fainter objects than Hubble. In other words, the JWST has the ability to peer into the origin of the universe.
The JWST contains three specialized instruments for infrared study: the Near InfraRed Camera (NIRCam), the Near InfraRed Spectrograph (NIR Spectrograph), and the Mid InfraRed Instrument.
The Near InfraRed Camera specializes in infrared imagery. It contains ten mercury-cadmium-telluride (HgCdTe) detector arrays. That may seem like technobabble, but the detector arrays serve the same role for the instrument that grids of pixels do in cameras, sensitive technology that can accurately image photons with near-infrared wavelengths.
The Near InfraRed Spectrograph accomplishes advanced infrared spectroscopy. Its specialized design allows for specific areas of the sky to be observed at specific times, using microshutter arrays—detectors about the size of human hair—to make its observations more precise. Using magnetic fields, the spectrograph has the capability to capture infrared photons like never before.
Lastly, the Mid InfraRed Instrument combines these two specific detectors into a cohesive instrument that allows for the probing of infrared photons throughout the universe. It has the ability to access a wide band of infrared emissions, pushing the envelope of infrared exploration forwards.
The combination of imagery and spectroscopy that these instruments will provide is unparalleled, and will be instrumental to pushing the horizon of infrared astronomy—and cosmology—as a whole.
The JWST excited astrophysicists as it is not only a successor to Hubble, but it can detect objects much farther and much fainter than Hubble ever could. In searching for our origins in the universe, it is essential to know what the early universe was like. And the JWST would allow us to do just that. In the JWST, we have a lens onto the very fundamentals of our existence and our origin, a mechanism for the systematic, detailed study of our evolution from life into who we are today. And as it begins returning images in a few months, we know that it has the potential to change the way we look at the universe—and at ourselves—forever.