NASA’s James Webb Space Telescope is set to radically change our understanding of the universe.
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It's expected to supercharge the hunt for exoplanets, the study of the birth and death of stars, the study of the early universe, and even the exploration of Mars.
The successor to the Hubble Space Telescope, Webb will allow us to not only see much further into the cosmos but to see it in different wavelengths of the electromagnetic (EM) spectrum, giving us access to an untapped wealth of information.
Goodbye, Hubble
Since its launch in 1990, the Hubble Space Telescope has wowed the world with its breath-taking photography, as well as being the source of data for some 13,000 academic papers, making it one of the most successful scientific endeavors in history.
Its greatest achievements include finding evidence of both dark energy and dark matter, refining the expansion rate of the universe, helping to confirm the existence of supermassive black holes at the center of galaxies, snapping the first photo of a planet orbiting another star, finding new moons in our own solar system, shedding light on the mystery of gamma ray bursts, documenting the collisions of Shoemaker-Levy 9 into Jupiter, among many, many others.
Despite all of the success, Hubble is not expected to last more than a few more years, mainly due to the wear and tear of its sensitive equipment. In fact, during its last servicing mission in 2009, NASA installed mechanisms to deorbit it, either through capture or a controlled reentry, although there are no specific plans yet to use them.
What Makes Webb Different?
Webb’s main eye is the The Optical Telescope Element (OTE), which is a mirror composed of 18 hexagonal pieces with a total diameter of 6.5 meters. Compared to Hubble’s 2.4 meter mirror, this will allow it see orders of magnitude farther.
However, the heart of the telescope are the four instruments in the Integrated Science Instrument Module (ISIM), all of which work with wavelengths lower than Hubble.
The Near-Infrared Camera (NIRCam) detects EM wavelengths that are 0.6 to 5 microns. This also contains a coronagraph, which blocks out brighter objects such as stars, allowing fainter objects to be detected.
The Near-Infrared Spectrograph (NIRSpec) also detects 0.6 to 5 micron wavelengths, but this uses a spectrograph to spread out the light into a spectrum. This reveals gaps in the spectrum based on the elements and molecules present in the object being observed, which can be used to calculate its temperature, mass, etc. This instrument can observe 100 objects at once.
The Mid-Infrared Instrument (MIRI) will also have a spectrograph and a coronagraph, but it works in the 5 to 28 microns range, allowing it see a different class of objects, such as nascent stars, red-shifted galaxies, and faint comets. This will be responsible for high resolution astrophotography, similar to what Hubble produces but much better.
The Fine Guidance Sensor/Near InfraRed Imager and Slitless Spectrograph (FGS/NIRISS) works in the 0.8 to 5.0 micron range and also has a spectrograph. It is also responsible for keeping Webb and its instruments pin-pointed on an object to reduce motion blur.
These instruments will offer a different and more detailed view of the universe, as Hubble could only see in the visual, near-infrared, and near-ultraviolet parts of the EM spectrum.
The Hunt for Exoplanets
Finding other planets is difficult mainly because the host star is millions of times brighter. Exoplanets discovered so far have been found by seeing the star periodically dim as the planet transits in front or by measuring the tiny wobbles the planet gives to the star as it orbits. A few planets have been found by using basic coronagraphs, which can block the stars light, much like the moon during a solar eclipse, but these are not sensitive enough for most exoplanets.
Webb, however, has coronagraphs that can see exoplanets “10 million, or optimistically, 100 million times fainter” than their host stars, according to Sasha Hinkley, the lead of Webb’s exoplanet team.
Exoplanets also radiate in the infrared, meaning Webb can detect them if they have large separations from their host star.
As of now, there are just over 4,000 confirmed exoplanets, with the first one only being found in 1992. This number is expected to grow rapidly once Webb is operational, perhaps eventually finding an nearby Earth-like world suitable for colonization.
The Birth and Death of Stars
A nearby dwarf galaxy known as the Small Magellanic Cloud contains a stellar nursery known as NGC 346, where giant young stars are born rapidly.
This nebula is unique because it contains only the two simplest elements: hydrogen and helium, meaning it mimics the conditions of the universe a few billions years after the Big Bang. That is, hydrogen and helium were created in the Big Bang, and anything heavier was created by the fusion of these elements in the furnaces at the center of stars.
Therefore, studying this area offers a window into how the earliest stars formed and evolved, as they are devoid of the heavier elements found in later generation stars.
Margaret Meixner from the Space Telescope Science Institute believes “The Small Magellanic Cloud could be a local astrophysical laboratory to study processes that happened at the peak star-formation epoch.”
The problem, though, is that large amounts of dust obscures the view in higher frequency wavelengths of NGC 346 from Earth. Webb’s ability to see in the infrared is necessary because these longer wavelengths are not blocked by the dust.
Moreover, Webb’s ramped-up resolution will be used to study the little understood phenomenon of light-year long jets being shot out of young stars.
As a ball of gas collapses to form a star, large amounts are spit out in opposite directions by the magnetic poles, forming jets of gas that move hundreds of miles per second and can extend light-years into space. How and why this happens is not fully known, partly because new stars are shrouded by dust, again obscuring the view from Earth.
Webb can pick up the infrared light coming through the dust, such as in the case of Herbig-Haro (HH) 212, which is a star still forming about 1,400 light-years away in the constellation Orion.
Mark McCaughrean from the European Space Agency says that “By studying HH 212, and objects like it, we want to learn how jets and outflows help the star escape from its cocoon.”
Furthermore, Webb will be collecting unique data on the remnants of supernovas, when large stars collapse in on themselves and explode at the end of their lives. For example, researchers plan on studying SN 1987A because of the several mysteries that still haven’t been solved since it was discovered over 3 decades ago, when light from the supernova reached Earth after traveling 160,000 light-years.
The Early Universe
The universe is roughly 13.7 billion years old, and questions abound about how it developed. In particular, scientists are curious about how the first galaxies formed.
Collecting data on this topic requires looking farther into the universe, as the farther one looks, the further back in time the objects are, in that the light from these objects has taken longer to reach Earth.
However, there are two main obstacles to this.
The first obstacle is the fact that the more distant an object is, the more cosmic dust is likely to be in the way. Second, because of the expansion of the universe, the farther away an object is, the more red-shifted its light becomes. Therefore, objects far enough away to reveal information about the early universe are so red-shifted that they are only detectable in the infrared spectrum.
Webb can solve both these problems with its infrared equipment, which should reveal some of the earliest galaxies for the first time. It will also utilize gravitational lensing to observe objects blocked from view by massive objects like galaxies. As explained by General Relativity, mass bends space-time, thus influencing the direction of objects and light as they pass nearby.
Because of this, large objects like galaxies can bend space-time enough to alter the path of light coming from objects behind, making it appear as if the objects are in a different position. This allows researchers to essentially see through close galaxies, giving them a view of farther and therefore older galaxies.
Abell 2744, which is a cluster of four small galaxies, is one of a handful of candidates to be used for gravitational lensing.
Exploring Mars
Webb will also be an integral part of exploring Mars, as researchers are confident it can help determine why water dried up, if life ever existed on the planet, etc.
First of all, Webb will be used to detect deuterium in Mars’ atmosphere. Deuterium is an isotope of hydrogen and it too can be used to make water molecules, although these have more mass, giving them the name heavy water.
Heavy water is naturally occurring and exists along side normal water in a specific ratio (about 1:3,200). Because of this, scientists plan to use Webb to analyze the ratio of water to heavy water in Mars’ atmosphere, thus revealing how much regular water has been lost into space.
Likewise, Webb can measure the amount of methane in the atmosphere with more precision than ever before. Methane is a byproduct of bacteria and its presence is a good indicator of life, although it is produced in geological processes as well.
In June 2018, NASA announced the Curiosity rover found evidence for seasonal variations of methane in the atmosphere, suggesting it was produced by life. Webb is expected to add substantial amounts of data in this area, adding to the evidence of life on Mars.
Godspeed, Webb
Webb is now positioned roughly a million miles from Earth in the L2 Lagrange point, meaning servicing it is near impossible. If something goes wrong, it could turn into a $10 billion dollar piece of space junk, but, with a bit of luck, it will complete its 10 year mission and surpass Hubble as the most productive scientific endeavor in history.
Originally published at http://thehappyneuron.com on July 27, 2019.
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