Whether Hubble, Chandra, the James Webb Telescope or Euclid: space telescopes are the most important “eyes” of astronomy. Far beyond the Earth’s disturbing atmosphere, they can see further and more clearly into space than terrestrial observatories. They also reveal phenomena in the infrared, X-ray light or radio spectrum that are invisible to us – and have thus decisively shaped and advanced our knowledge of the cosmos.
A new space telescope for NASA
Now a new space telescope is being added: On Sunday afternoon, August 30th, the “Nancy Grace Roman Space Telescope” was launched from Cape Canaveral. A Falcon Heavy rocket from SpaceX launched the almost 13 meter long and 4.40 meter wide telescope into space.
The aim of the new NASA observatory is Lagrange point 2, around 1.5 million kilometers away. This is an extension of the Sun-Earth line and therefore offers a largely light-protected, unobstructed view of the cosmos. An orbit around this point in space is also gravitationally stable, allowing space probes and telescopes to orbit it without consuming fuel. The Roman Space Telescope will join several other observatories at the Lagrange point, including the James Webb Telescope and Euclid.
Where does the name come from?
The new space telescope got its name from NASA astronomer Nancy Grace Roman. It has significantly advanced the development of space-based observatories and is considered the intellectual “mother” of the Hubble Space Telescope. Nancy Roman also designed and co-developed other NASA space telescopes such as the Spitzer infrared telescope, the Compton gamma telescope and the still active Chandra X-ray telescope.
Mirror, camera and coronagraph: The components of the novel space telescope
The main mirror of the new Roman space telescope has a diameter of 2.40 meters. It is the same size as the primary mirror of the Hubble Space Telescope, but only a quarter as heavy. Despite the same mirror size, the new telescope’s field of view is larger: The Wide Field Instrument consists of 18 detectors that can record a total of 300 million pixels at once – 100 times more than the Hubble Telescope’s camera.
The Wide Field Instrument is the main camera of the Roman Space Telescope. Its infrared detectors are arranged in arcs and together cover 300 million pixels. — © NASA/Goddard Space Flight Center
“Together, these extremely sensitive detectors can capture vast areas of the sky in a single image while still revealing incredibly fine detail,” NASA explains. “This allows the Roman telescope to map the cosmos faster and more precisely than ever before.” Another special feature is that the camera does not see the sharpest in the center, as is typical for telescopes, but in a ring-shaped zone. Its detectors are arranged in an arc. “This makes it possible to image a larger area with the same sharpness,” says NASA.
The second instrument of the Roman telescope is the Coronagraph Instrument (CGI). It consists of a system of masks, mirrors, sensors and adaptive optics that are specifically designed to image faint objects around bright stars in visible light. To do this, the instrument specifically covers the bright light of the star. This allows the Roman telescope to photograph exoplanets or protoplanetary disks without their nearby star outshining them.
The Max Planck Institute for Astronomy in Heidelberg was also involved in the development and construction of this coronagraph. “The CGI on board the Roman space telescope is the most sophisticated optical observation instrument that has been used for research in space to date,” says Oliver Krause from the MPI.
The Roman telescope’s Coronagraph Instrument (CGI) will make it possible to image exoplanets and protoplanetary disks around bright stars. To do this, the star’s outshining light must be covered and filtered out. — © NASA/Goddard Space Flight Center
The tasks of the Roman space telescope: “Dark” mapping…
The new space telescope has three main tasks: to detect Earth-like exoplanets, to map the distribution of dark matter more accurately and comprehensively than ever before, and to find out more about dark energy. “With its large field of view and high survey speed, Roman will usher in a new era of discovery and make the invisible visible,” says Nicky Fox from NASA’s Science Directorate.
For the “dark aspects” of its mission, the Roman telescope will record millions of galaxies’ distances, their light spectrum and the subtle gravitational distortions of that light. From this we can conclude how dark matter is distributed and how strongly its counterpart, dark energy, is driving the universe apart. “Astronomers will use this data to create a 3D map of all galaxies measured in the study area out to a distance of approximately 11.5 billion light-years,” explains NASA.
…and Earth-like worlds
The search for exoplanets is primarily about finding small, cooler worlds – including possible Earth twins. These are particularly difficult to find because they leave only a very weak signal in the light of their stars and are at the same time outshone by them. The Roman telescope will search for such exoplanets using three methods – transit, microlensing and direct imaging.
Transits are short-term shadows of stars caused by the planets passing in front of them. With microlensing, distant stars brighten briefly because another star is in front of them and its gravity acts like a magnifying lens. The features of this lensing effect can reveal whether there are planets orbiting the foreground star. NASA expects that the Roman space telescope could detect around 100,000 new exoplanets – a huge leap compared to the almost 6,200 exoplanets known to date.
Does the new space telescope compete with the others?
Like the James Webb Telescope, the Roman Space Telescope operates primarily in the infrared range and has almost the same mirror as the Hubble Space Telescope. However, it cannot replace any of its predecessors – it is intended to complement them. The Roman telescope achieves the same high resolution as the Hubble telescope, but only in the infrared range. Its larger field of view can therefore show objects that Hubble can then image in additional wave ranges such as visible and ultraviolet light.
Although the Roman telescope shares infrared vision with the James Webb telescope, it is more of a wide-angle lens compared to Webb’s zoom capabilities: “Roman’s images provide a comprehensive overview and can detect rare objects,” explains NASA. “Webb can then use its narrower field of view but higher power to target these objects for more detailed observations.”
With the Euclid Space Telescope, the new addition shares its view of the dark side of the universe. Both telescopes are intended to map dark matter and help clarify the mystery surrounding dark energy and the expansion of the cosmos through more precise distance measurements. Euclid does this in a larger section of the sky, but with lower resolution – his view extends around ten billion light years. The Roman telescope will only survey half of the sky, but its resolution is higher and it can see up to 11.6 billion light-years away.
“Never before have we looked at the universe with eyes like Roman’s,” says Julie McEnery, Roman lead project scientist at NASA Goddard Space Flight Center. “It is impossible to predict what we will already know and have seen by this time next year.”
What are the next steps after launch?
In the first few days after launch, the space telescope will deploy its antenna and the extendable cover of its mirror. When it has completed about half of its 90-day flight to Lagrange point 2, a course correction is made and then the testing phase of the optics and instruments begins: The coronagraph is first switched on, tested and calibrated, followed a few weeks later by the space telescope’s main camera, the Wide Field Instrument.
The Roman telescope is expected to deliver the first scientific images in early 2027. The total duration of the mission is five years, with the option of extending it to a further five years. But the space telescope could remain active even longer, as NASA reports: The fuel limits the lifespan of the mission and so far there is no technical solution to maintain or refuel observatories at Lagrange point 2. “However, Roman is designed to be refuelable,” NASA said.
Source: NASA