In 2025, the Nancy Grace Roman space telescope will launch to space. Named in honor of NASA’s first chief astronomer (and the “Mother of Hubble“), the Roman telescope will be the most advanced and powerful observatory ever deployed. With a camera as sensitive as its predecessors, and next-generation surveying capabilities, Roman will have the power of “One-Hundred Hubbles.”
In order to meet its scientific objectives and explore some of the greatest mysteries of the cosmos, Roman will be fitted with a number of infrared filters. But with the decision to add a new near-infrared filter, Roman will exceed its original design and be able to explore 20% of the infrared Universe. This opens the door for exciting new research and discoveries, from the edge of the Solar System to the farthest reaches of space.
With this new filter, Roman will now have the capacity to near-infrared K band (2.0 to 2.4 microns), which will give it an effective range of 0.5 to 2.3 microns in the infrared wavelength. While Roman is optimized for the study of exoplanets and the expansion of the cosmos (for the sake of researching Dark Energy), its enormous field of view will capture all kinds of cosmological phenomena.
Thanks to this new filter, the mission will able to see farther out into space, probe deeper into the dusty regions of the Universe, and view more of the fainter, cooler types of objects. George Helou, one of the advocates for the modification, is the director of IPAC at Caltech in Pasadena. As he explained in the NASA press release:
“A seemingly small change in wavelength range has an enormous effect. Roman will see things that are 100 times fainter than the best ground-based K-band surveys can see because of the advantages of space for infrared astronomy. It’s impossible to foretell all of the mysteries Roman will help solve using this filter.”
In addition, this improvement in its capabilities will allow for more collaborations between Roman and NASA’s other “big observatories” that will still be operational. These include the venerable Hubble (which has been studying the cosmos steadily for 30 years) and the James Webb Space Telescope (scheduled to launch on Oct. 31st, 2021). Each of these observatories has its own viewing range.
Whereas Hubble can see light 0.2 to 1.7 microns in wavelength, which allows for observation in ultraviolet to near-infrared light, James Webb will be able to survey from 0.6 to 28 microns – from the near-infrared to the mid-infrared, plus a small amount of visible light. Thanks to Roman’s improved range and its much larger field of view, it will be able to reveal additional targets for follow-up observations by these other observatories.
For starters, these upgrades will enable the study of small dark bodies, such as the many icy objects that occupy the large debris ring at the edge of the Solar System (the Kuiper Belt). This will allow it to examine cosmological bodies and that would be otherwise impossible to study, such as dust rings, cooler stars, and planets. It will also allow for scientists to observe smaller, darker objects in the Solar System and create a census of them.
This will be especially helpful when it comes to the study of objects beyond the orbit of Neptune, which is populated by a belt of icy objects known as the Kuiper Belt. Along with the Main Asteroid Belt, objects in this region are essentially leftover material from the protoplanetary disk that orbited our Sun roughly 4.5 billion years ago (and from which the Solar System’s planets formed).
They are vital opportunities for research since they have remained largely unchanged since the early days of the Solar System. This region is also the source of long-term comets, which are believed to have played a vital role in the distribution of water throughout the Solar System. Studying Kuiper Belt Objects (KBOs) will therefore give astronomers insight into the early Solar System and how much of Earth’s water came from comets.
One of the most frustrating aspects of studying the cosmos is the way that dust and gas make it harder to see things clearly. Along the plane of the Milky Way, many objects are shrouded by clouds of material that drifts between stars – known as the Interstellar Medium (ISM). These cause visible light to become scattered and absorbed, making it especially difficult to view the center of our galaxy and what lies beyond.
Since infrared light travels in longer waves, it is able to pass more freely through these clouds, letting astronomers pierce through hazy patches and study objects that would otherwise be invisible. With Roman’s new filter, the observatory will be able to see through dust clouds up to three times denser than before, which will help us to learn more about the structure and population of the Milky Way.
Roman’s expanded view will also allow astronomers to study the class of “failed stars” known as brown dwarfs, which refers to objects that are not massive enough to undergo nuclear fusion in their cores. In particular, astronomers are looking forward to studying brown dwarfs located near the heart of our galaxy, where supernovae are known to happen more often.
It is already well-understood that supernovae seed their surroundings with new elements when they explode. Astronomers believe that this may have had an effect on the formation of stars and planets in this vicinity. By measuring the compositions of brown dwarfs, they will be able to learn more about the differences between objects near the heart of our galaxy and those located in the spiral arms.
As Julie McEnery, the Roman Space Telescope senior project scientist at NASA’s Goddard Space Flight Center, explained in a recent NASA press release:
“It’s incredible that we can make such an impactful change to the mission after all of the primary components have already passed their critical design reviews. Using the new filter, we will be able to see the full infrared range the telescope is capable of viewing, so we’re maximizing the science Roman can do.”
The Roman‘s new upgrades will also present new opportunities to probe the farthest reaches of space. As light travels through the expanding Universe, its wavelength is lengthened to the point that it is only visible in other parts of the spectrum. For example, the “relic radiation” left over from the Big Bang – the Cosmic Microwave Background (CMB) – is visible only in the microwave end of the spectrum (10-3 m).
Thanks to the latest upgrade, Roman will be able to observe the Universe as it was just 300,000 years after the Big Bang. This time coincides with the cosmic “Dark Ages” when the first stars and galaxies were only beginning to form. The only photons that existed at this time were those created as a result of recombination (visible as the CMB) and those released by neutral hydrogen atoms – visible as 21 cm radiation.
In short, Roman would be able to study the first galaxies in the Universe when they were still in the process of formation. The new filter could provide another means to measure the expansion rate of the Universe, otherwise known as the Hubble constant. This will be possible by studying variables stars, such as Cepheids and RR Lyrae variables, which are known to brighten and dim periodically.
By comparing the intrinsic brightness of these stars to their apparent brightness from Earth, astronomers can determine how far away they are. Because of this, astronomers look for these stars in distant clusters and galaxies as a way of gauging their distance and the rate at which they are moving farther away from us.
By comparing the movement of galaxies that are closer to our own and those that are billions of light-years away, astrophysicists are able to place constraints on the overall rate of expansion. Thanks to the introduction of observatories like the Hubble Space Telescope, astronomers have been able to see farther into the cosmos (and hence, back in time). What this showed is that as of 3 billion years ago, the rate of expansion has accelerated.
By observing Cepheid and RR Lyrae stars in infrared light, scientists will be able to measure cosmic distances with greater accuracy. In turn, this will clear up discrepancies that previous measurements of the Hubble Constant have produced. As McEnery summarized:
“Enhancing Roman’s vision further into the infrared provides astronomers with a powerful new tool to explore our universe. Using the new filter we will make discoveries over a vast area, from distant galaxies all the way to our local neighborhood.”
Further Reading: NASA
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