by Michael Zemcov, Rochester Institute of Technology
Dozens of space-based telescopes operate near Earth, providing incredible images of the universe. But imagine a telescope far away in the outer solar system, 10 or even 100 times farther from the Sun than the Earth. The ability to look back at our solar system or look into the darkness of the distant cosmos would make this a uniquely powerful scientific tool.
I am an astrophysicist studying the formation of structure in the universe. Since the 1960s, scientists like me have been pondering the important scientific questions we might be able to answer with a telescope placed in the outer solar system.
So what would such a mission look like? And what science could one do?
A small telescope far from home
The scientific power of a telescope far from Earth would come primarily from its location, not its size. Plans for a telescope in the outer solar system would place it somewhere outside Saturn’s orbit, about a billion or more miles from Earth.
We only needed to send a very small telescope – with a lens the size of a small plate – to obtain some completely unique astrophysical insights. Such a telescope could be built to weigh less than 20 pounds (9 kg) and could be carried on almost any mission to Saturn or beyond.
Although small and simple compared to telescopes like Hubble or James Webb, such an instrument operating away from the bright light of the Sun can make measurements that are difficult or downright impossible from a vantage point near Earth.
Outside looking in
Unfortunately for astronomers, getting a selfie of the solar system is a challenge. But being able to see the solar system from an outside vantage point would reveal a lot of information, especially about the shape, distribution, and composition of the dust cloud that surrounds the Sun.
Imagine a street lamp on a foggy night – by standing far away from the lamp, the swirling mists are visible in a way that anyone standing under the street light could never see.
For years, astrophysicists have been able to take pictures of and study the dust disks in the solar systems around other stars in the Milky Way. But these stars are very far away, and there are limits to what astronomers can learn about them. Using observations looking back at the Sun, astronomers were able to compare the shape, functions, and composition of these distant clouds of dust with detailed data about the Earth’s own solar system. These data would fill gaps in knowledge about solar dust clouds and make it possible to understand the history of production, migration and destruction of dust in other solar systems that there is no hope of traveling to in person.
The deep darkness of the room
Another advantage of placing a telescope far from the Sun is the lack of reflected light. The dust disk in the plane of the planets reflects the sun’s light back to Earth. This creates a haze that is between 100 and 1,000 times brighter than light from other galaxies and hides the view of the cosmos from near Earth. Sending a telescope outside this cloud of dust would place it in a much darker area of space, making it easier to measure the light coming from outside the solar system.
Once there, the telescope could measure the brightness of the universe’s ambient light over a wide range of wavelengths. This could provide insight into how matter condensed to the first stars and galaxies. It would also allow scientists to test models of the universe by comparing the predicted sum of light from all galaxies with an accurate measurement. Discrepancies could point to problems with models of structure formation in the universe or perhaps to exotic new physics.
Into the unknown
Finally, increasing a telescope’s distance from the Sun would also allow astronomers to perform unique science that utilizes an effect called gravitational lenses, in which a massive object distorts the path that light takes as it moves past an object.
One use of gravitational lenses is to search for and weigh rogue planets – planets that roam interstellar space after being flung out of their home solar systems. Since rogue planets do not emit light on their own, astrophysicists can look for their effect on the light from background stars. To distinguish between the distance of the lens object and its mass, it requires observations from another place far from Earth.
Gravitational lenses caused by a planet passing in front of a distant star will bend light from that star, and it can also be used to detect dark planets that have been ejected from solar systems. NASA Ames / JPL-Caltech / T. Pyle via WikimediaCommons
In 2011, scientists used a camera on the EPOXI mission to the asteroid belt to detect and weigh an object the size of Neptune that hovered freely among stars in the Milky Way. Only a few rogue planets have been found, but astronomers suspect that they are very common and may contain traces of the formation of solar systems and the spread of planets around stars.
But perhaps the most interesting need for a telescope in the outer solar system would be the potential to use the very gravitational field of the Sun as a giant lens. This type of measurement can allow astrophysicists to actually map planets in other star systems. Maybe one day we will be able to name continents on an Earth-like planet around a distant star.
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Since Pioneer 10 became the first man-made object to cross Jupiter’s orbit in 1973, only a handful of astrophysical studies have been performed outside Earth’s orbit. Missions to the outer solar system are rare, but many teams of scientists are conducting studies to show how an extra-solar telescope project would work and what one could learn from one.
Every 10 years or so, leaders in astrophysics and astronomy gather to set goals for the following decade. That plan for the 2020s is scheduled to be released on November 4, 2021. In it, I expect to see discussions about the next telescope that could revolutionize astronomy. Taking a telescope to the outer solar system, though ambitious, is within the technological capabilities of NASA or other space agencies. I hope that one day soon a small telescope out on a solitary mission in dark areas of the solar system will give us an incredible insight into the universe.
Michael Zemcov, Associate Professor of Physics, Rochester Institute of Technology
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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