In 2025, the Roman space telescope Nancy Grace will launch into 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 used. With a camera as sensitive as its predecessor and next-generation surveying capabilities, Roman will have the power of “One Hundred Hubbles”.
In order to achieve his scientific goals and to uncover some of the greatest mysteries of the cosmos, Roman is fitted with a series of infrared filters. With the decision to add a new near infrared filter, Roman will surpass its original design and be able to explore 20% of the infrared universe. This opens the door to exciting new research and discovery, from the edge of the solar system to the most distant areas of space.
New function
With this new filter, Roman can now achieve the near-infrared K-band (2.0 to 2.4 microns), giving an effective range of 0.5 to 2.3 microns in the infrared wavelength. While Roman is optimized for exploring exoplanets and expanding the cosmos (to explore dark energy), his vast field of view will capture all kinds of cosmological phenomena.
This composite image shows the ability to observe the Roman “Ultra-Deep Field” space telescope. Photo credit: NASA / ESA / A. Koekemoer (STScI) / DSS
Thanks to this new filter, the mission can look further into space, dig deeper into the dusty regions of the universe, and see more of the weaker, cooler types of objects. George Helou, one of the proponents of the change, is the director of IPAC at Caltech in Pasadena. As he stated in NASA’s press release:
“A seemingly small change in the wavelength range has enormous effects. Roman will see things 100 times weaker than the best ground-based K-band surveys due to the advantages of space for infrared astronomy. It is impossible to predict all the puzzles that Roman will solve using this filter. “
In addition, this enhancement of his capabilities will allow for more collaborations between Roman and NASA’s other “major observatories” that will still be in operation. These include the venerable Hubble (which has been continuously exploring the cosmos for 30 years) and the James Webb Space Telescope (scheduled to launch on October 31, 2021). Each of these observatories has its own viewing area.
While Hubble can see light with a wavelength of 0.2 to 1.7 micrometers, which allows observation of ultraviolet to near infrared light, James Webb can measure 0.6 to 28 micrometers – from near infrared to mid infrared plus a small amount in visible light. Thanks to Roman’s improved range and much larger field of view, additional targets can be identified for follow-up observations from these other observatories.
Central region of the Milky Way in infrared light, captured by NASA’s Spitzer Space Telescope. Photo credit: NASA / JPL-Caltech / S. Stolovy (Spitzer Science Center / Caltech)
Objects closer to home …
For starters, these upgrades will allow the study of small dark bodies, such as the many icy objects that make up the large ring of debris at the edge of the solar system (the Kuiper Belt). This enables him to study cosmological bodies that would otherwise be impossible to study, such as dust rings, cooler stars, and planets. It will also allow scientists to observe smaller, darker objects in the solar system and compile a census of them.
This is especially useful when examining objects outside of Neptune’s orbit, 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 debris from the protoplanetary disk that orbited our sun about 4.5 billion years ago (and from which the planets of the solar system were formed).
They are important research opportunities because they have remained largely unchanged since the beginning of the solar system. This region is also the source of long-term comets that are believed to have played an important role in the distribution of water throughout the solar system. Studying Kuiper Belt Objects (KBOs) therefore gives astronomers an insight into the early solar system and how much of the earth’s water came from comets.
In the heart of our galaxy …
One of the most frustrating aspects of studying the cosmos is the way dust and gas make it harder to see things clearly. Along the plane of the Milky Way, many objects are surrounded by clouds of material that float between stars – known as the interstellar medium (ISM). These cause visible light to be scattered and absorbed, making it particularly difficult to see the center of our galaxy and what lies behind it.
Because infrared light travels in longer waves, it can pass through these clouds more freely, allowing astronomers to penetrate cloudy spots and examine objects that would otherwise be invisible. With Roman’s new filter, the observatory can see through clouds of dust up to three times closer than before, which helps us learn more about the structure and population of the Milky Way.
Roman’s expanded perspective will also allow astronomers to study the class of “failed stars” known as brown dwarfs. This refers to objects that are not massive enough to experience nuclear fusion in their cores. In particular, astronomers look forward to studying brown dwarfs near the heart of our galaxy, where supernovae are known to be more common.
It is already known that supernovae colonize their surroundings with new elements when they explode. Astronomers believe this could have had an impact on the formation of stars and planets in this environment. By measuring the composition of brown dwarfs, they can learn more about the differences between objects near the heart of our galaxy and objects in the spiral arms.
As Julie McEnery, senior project scientist for the Roman Space Telescope at NASA’s Goddard Space Flight Center, recently stated in a NASA press release:
“It is incredible that we can change the mission so effectively after all major components have passed their critical design reviews. With the new filter, we can see all of the infrared that the telescope can see, maximizing the science that Roman can do. “
The electromagnetic spectrum is visualized. Photo credit: NASA
And beyond!
The new upgrades to the Roman will also offer new ways to explore the widest reaches of space. As light moves through the expanding universe, its wavelength is lengthened so far 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 only visible at the microwave end of the spectrum (10-3 m).
Thanks to the latest upgrade, Roman can watch the universe as it was just 300,000 years after the Big Bang. This time coincides with the cosmic “dark age” when the first stars and galaxies only began to form. The only photons that existed at this point were those created by recombination (visible as CMB) and those released by neutral hydrogen atoms – visible as 21 cm radiation.
In short, Roman could study the first galaxies in the universe while they were still in the process of being formed. The new filter could be another means of measuring the rate of expansion of the universe, also known as Hubble’s constant. This will be possible by examining variable stars such as Cepheids and RR Lyrae variables, which are known to periodically lighten and dim.
By comparing the intrinsic brightness of these stars with their apparent brightness from Earth, astronomers can determine how far away they are. It is for this reason that astronomers look for these stars in distant clusters and galaxies to measure their distance and the speed at which they are moving further away from us.
By comparing the motion of galaxies closer to our own and galaxies billions of light years away, astrophysicists can limit the overall rate of expansion. Thanks to the introduction of observatories such as the Hubble Space Telescope, astronomers have been able to see further into the cosmos (and thus into the past). This has shown that the rate of expansion has accelerated for 3 billion years.
By observing Cepheid and RR Lyrae stars in infrared light, scientists can measure cosmic distances more accurately. This, in turn, will remove inconsistencies found in previous measurements of the Hubble constant. As McEnery summarized:
“By further improving Roman’s view of the infrared, astronomers will have a powerful new tool for exploring our universe. With the new filter, we will make discoveries over a wide area, from distant galaxies to our local neighborhood. “
Further reading: NASA
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