The next great space telescope is expected to launch in the year 2027. The Nancy Grace Roman Space Telescope will create panoramic fields of view 100 times greater than Hubble. One of the objectives of the Roman Telescope is to complete a census of exoplanets to answer questions about habitability.

The Roman Space Telescope can measure the dust in distant solar systems to help find planets.

Our Solar System has a type of dust called zodiacal dust. The dust comes from cometary activity and asteroids. It isn't primordial dust from the early days of the Solar System. The early dust is gone.

The zodiacal dust in our Solar System can be found in a region from near the Sun to the asteroid belt. The second-brightest thing in the sky next to the Sun is the dust. There is a problem when studying exoplanets. The haze from a remote solar system can obscure the planets in that system.

Dust can be a problem, but it can also be a valuable signal.

The Roman Telescope can be used to look for dust in distant solar systems. The presence of rocky bodies is indicated by the presence of exozodiacal dust around a star. That increases the chance of planets that are not in the water. The solar system is a good target for future observations with optical telescopes because there is no dust in the way.

The lead author of the new paper is an astronomer at the University of Tucson. The paper was published in the journal of the Astronomical Society of the Pacific.

“No one knows much about exozodiacal dust because it’s so close to its host star that it’s usually lost in the glare, making it notoriously difficult to observe.”

Study co-author Bertrand Mennesson, JPL.

Future missions will be able to see potential planets if we don't find a lot of this dust around a particular star. It's a win-win for science.

The amount of dust in a solar system shows how much activity is going on. A lot of zodiacal dust comes from comets that pass through the inner Solar System. A high level of cometary activity is suggested by the amount of exozodiacal dust found in a system.

Zodiacal light can be seen in the sky before sunrise or after sunset. Credit: Yuri Beletsky/ESO Paranal
This image shows zodiacal light in the sky. It’s visible before sunrise or after sunset. Credit: Yuri Beletsky/ESO Paranal

The distribution of the dust is a clue. The distribution pattern could indicate that planets are sculpting the debris.

We don't know much about the dust in other systems. It is hard to see.

No one knows much about exozodiacal dust because it is so close to the star that it is hard to see.

The telescope's coronagraph is crucial to this. A coronagraph is similar to sunglasses. Astronomers can see fainter objects in distant solar systems because it blocks out the blinding glare of stars. Without a coronograph, it would be difficult to see the dust in other systems. The most powerful coronagraph will be used by Roman.

The Hubble has coronographs. The Roman Telescope is more complex than the Hubble. The Roman Telescope uses filters and mirrors to remove the starlight from the images.

The Roman Coronagraph has special sensors and mirrors that will measure and subtract starlight in real-time. The Space Telescope Science Institute in Baltimore has an astronomer named Debes.

There is a new horizon in astronomy with exozodiacal dust. Astronomers have imaged cold dust at great distances from their host stars, dust that's further from the star than Neptune is from the Sun. Nobody has seen the warmer dust close to the stars.

The Large Binocular Telescope Interferometer gave us a glimpse of the warm dust. The HOSTS survey was the first step towards a better understanding of exozodiacal dust. It was a stepping stone towards understanding exozodiacal dust thatHOSTS determined the brightness and density of warm dust floating in nearby stars. It helped determine how powerful future telescopes need to be to see distant exoplanets.

The Roman Space Telescope has more to offer than the coronagraph. It won't suffer from the limitations that Hubble has. The Hubble has to contend with the Earth as it studies distant objects. The Roman will be located at the LaGrange Point 2, 1.6 million kilometres from Earth.

Astronomers want to study the warmer exozodiacal dust closer to distant stars because there are critical differences between it and the more visible, colder dust further from the star. The dust near the star is dominated by rocky grains. One type isn't an analogue for the other.

By prospecting for this dust, we could learn about the processes that shape planetary systems while providing important information for future missions that aim to image habitable-zone planets, according to co-author Debes. The Roman Coronagraph could offer a crucial steppingstone in the search for Earth analogs.

Other aspects of exoplanet science are affected by the exozodiacal dust. Studying exoplanet atmospheres can be used to determine habitability or detect biosignatures. Dust is the primary source of background light that will limit detailed characterization of reflected starlight.

The Habitable Exoplanet Observatory is a mission that the Roman Space Telescope could pave the way for. HabEx is still in the concept and design phase, and if it comes to fruition, its current proposed launch date isn't until 2035. The mission of HabEx is to image planetary systems around Sun-like stars. It will sense all types of planets, but the focus is on Earth-like worlds. HabEx will be able to image some of the planets. They will analyze their atmospheres for habitability signatures or biosignatures.

The approach of the HabEx mission is unique. Rather than an onboard coronagraph, it will use a separate starshade. The starshade is 77,000 km away from the telescope and would block the light from distant stars and allow light from planets to reach the telescope's instruments.

The authors used simulations to figure out how many of the pre-selected target stars would be seen by the Roman Telescope. The advanced coronagraph of the Roman Telescope gives it more power to see planets in the stars. HabEx will face scattered background light from exozodiacal dust when it begins its observations.

This graph from the study shows some of the predicted results from the Roman Telescope. It's based on a sample of 149 target stars that are considered optimal targets for the HabEx mission. The graph shows that 74 of HabEx's 149 target stars have at least a part of their HZ accessible to the Roman's observations. 16 of them are observable down to their EEID, which means Earth-equivalent insolation distance, the distance from a star at which an exoplanet would receive the same amount of solar energy as the Earth does. IWA means Inner Working Angle and is a geometrical limit in coronagraphs. The Roman's IWA is a strength of its design. Image Credit: Douglas et al. 2022.
This graph from the study shows some of the predicted results from the Roman Telescope. It’s based on a sample of 149 target stars that are considered optimal targets for the HabEx mission. The graph shows that 74 of HabEx’s 149 target stars have at least a part of their HZ accessible to the Roman’s observations. Sixteen of them are observable down to their EEID, which means Earth-equivalent insolation distance, the distance from a star at which an exoplanet receives the same amount of solar energy as Earth. IWA means Inner Working Angle and is a geometrical limit in coronagraphs. The Roman’s IWA is a strength of its design. Image Credit: Douglas et al. 2022.

The paper says the Roman Coronagraph will place new limits on scattered light brightness from exozodiacal dust.

The HabEx mission will be helped by the knowledge that the Roman Telescope will give.

The authors write that this has the potential to maximize the exoplanet observing strategy of future missions by allowingselective targeting of less dusty systems.

The Roman Telescope will make contributions to astronomy. The link between the Roman and HabEx is only one inter-mission linkup. Dark energy and the expansion of the Universe will be studied by the Roman.

We are living in an excellent age for astronomy. The Hubble Space Telescope is almost impervious, the Nancy Grace Roman will launch in a few years, and the long-awaited James Webb Space Telescope will begin observations soon. The Vera Rubin Observatory will be a ground-based observatory with telescopes like the E-ELT and the Magellan Telescope joining it.

If there are Earth-like planets out there that host life, we may be on the verge of finding them.

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