These things—whether comets, asteroids, maaaaaa, or strange artifacts (depending on who you ask)—are born from another star, and carry valuable data preserved in their gas coma and icy cores.
Astronomers tracked two of these objects and gathered as much information as possible from ground-based and space-based telescopes during their short-lived journey through the solar system. But a planned study using a 6.5-meter Web mirror and an advanced array of infrared cameras will paint a much clearer picture of these interstellar bodies, their foreign host stars, and the singularity of our solar system among the billions of stars that make up the Milky Way. road.
What makes an interstellar object?
On October 19, 2017, the Pan-STARRS telescope in Maui, Hawaii, spotted a strange object penetrating the solar system. The object’s velocity coupled with its extreme eccentricity meant that it was not gravitationally bound to our Sun. This object, called “Oumuamua” (meaning “a messenger from afar arrives first”), was the first interstellar object ever recorded – and what a thing it was.
Described as “cigar-shaped” in length, Oumuamua was 10 times as wide, which is very strange among space objects, and astronomers originally classified this interstellar interstellar as a comet. But because there was no coma, the kind of atmosphere around a comet caused by ice sublimation, NASA reclassified it as an asteroid — but that feather’s naming doesn’t end there.
On its way out of the solar system, ‘Oumuamua accelerated unexpectedly after the sun due to a comet feature called ‘outgassing’. To make matters even more confusing, some astronomers believe ‘Oumuamua is neither a comet nor an asteroid, but rather a kind of “cosmic iceberg.”
Since it was only a quarter of a mile long, Oumuamua was no longer visible by any telescope – ground or orbital – by January 2018. It is estimated that Oumuamua now crosses the orbit of Neptune as it continues its journey toward the constellation of Pegasus. Astronomers will never study this once-in-a-lifetime object again.
“Oumuamua, along with the discovery of the mostly natural rogue comet Borisov in 2019, are the only two interstellar bodies ever recorded in our solar system. Since astronomers have no idea when, or what it will look like, the next interstellar body will appear across the sky, Or how long it can be observed, Webb can round up comet and asteroid experts to be prepared for whatever the galaxy throws at us.
And if ‘Oumuamua is any indication, they’re going to need all the help they can get.
A complex network of interstellar science
Earlier this month, NASA released the first images captured by the $10 billion Webb Telescope. One of the astronomers eagerly awaiting these images was Michael Kelly, a cometologist at the University of Maryland and co-investigator of the interstellar telescope’s object proposal. Although his first taste for Webb’s capabilities lived up to the hype (snap from the Carina Nebula is now a desktop wallpaper), Kelly sees Webb as well-suited to his field.
“I like to call it ‘the cometology machine,'” says Kelly. inverse. That’s because Webb’s imaging and spectroscopy ability will give astronomers like Kelly an extraordinary amount of detail, including whether this comet is interstellar or local.
Comets are mainly made up of three major icicles – water, carbon dioxide and carbon monoxide – and the Webb’s Near Infrared Scale (NIRSpec) will analyze the chemical composition of these ices simultaneously as they slowly evaporate by the sun’s heat. This gives astronomers clues about where an interstellar object might be in its host system. Too much water, for example, could mean an object has coalesced near its star because other ices require cooler temperatures, according to Kelly.
Using the Mid-Infrared Instrument (MIRI) instrument, Webb will also provide some clarity about the composition of dust emitted by these objects. The data it provides could support some of the biggest theories about how oceans formed or how life took hold in our solar system.
“Carbon is a great molecule because it’s the thing that enables life,” says Kelly. “The idea is that comets and asteroids have brought carbon to Earth’s surface…One of the things we’re looking for is that carbon dust.”
Comets are like cosmic time capsules. Because they typically form in the most distant regions of a star system, comets are often covered in ice, maintaining the geology of protoplanetary formation for billions of years.
On the other hand, asteroids are often exposed to warmer temperatures which cause them to melt or change in other ways. While scientists believe that comets make up the majority of interstellar objects (because comets are frequently ejected), an interstellar asteroid is out of the question.
Christina Thomas is a planetary scientist at Northern Arizona University, a research associate at Webb’s proposal, and a comprehensive asteroid expert. While Kelly is interested in the chemistry of interstellar comets, Thomas Laser focuses on what Webb can tell us about the solid surface of a potential interstellar asteroid.
“I think a lot of people think asteroids are kind of homogeneous, like Han Solo flying through an asteroid field,” Thomas says. inverse. “They are actually incredibly different from each other in many different ways.”
Webb will be able to peek at these differences using near and mid-infrared wavelengths and provide data about the asteroid’s silicate, mineral signatures, potential surface wetting, and surface composition—whether it’s rocky or porous (like Bennu).
Because of the asteroid-like features of Oumuamua, Thomas and her team used a cigar-shaped puzzle as a test case to determine what Webb would see if another interstellar asteroid came to our neighboring galaxy.
“With Oumuamua we didn’t get a lot of in-depth feedback. [With Webb]we’d get wide coverage of the wavelengths — it would tell us a lot about the object itself, and that would really allow for a full comparison,” says Thomas. “We might assume other systems have similar building blocks, but to see that would be really cool.”
waiting for robin
While Webb is ready to stare at the next interstellar object to cross its path, there’s still one big hitch—scientists have to find one first.
While two have been found in the past seven years, Kelly believes a more reliable frequency of discovery is the discovery of one interstellar object every decade. Fortunately, a new ground-based telescope perched on the Cerro Passion mountain range in north-central Chile will change all that.
As part of the Survey of the Legacy of Space and Time (LSST), the Vera C. Rubin Observatory will map the Solar System more accurately than ever before. The Hawaiian Pan-STARRS’ ‘Oumuamua telescope has a 1.8-meter mirror. By comparison, Robin is equipped with a mirror more than four times that size, which scientists estimate could blow the known number of objects in our solar system by a factor of 10 (or even more). And among their number could be a number of strange objects whose velocity and deflection indicate interstellar origins.
“We need a new discovery for this project to be successful. It all depends on what is discovered,” says Kelly. “Borisov was easily noticed for a long time. “Oumuamua should have been monitored in a month.”
Since astronomers can detect an interstellar object at any moment, this particular study is part of NASA’s Target of Opportunity program. This software allows teams studying time-sensitive phenomena, such as supernovae or interstellar objects, to interrupt regularly scheduled Webb programming with a time limit of up to three days. This particular study falls under the category of “disruptive target of opportunity,” meaning Webb can focus his gaze on an incoming interstellar object within two weeks of discovery.
In the future, data from Webb on interstellar objects could inform other, more ambitious space missions, such as the European Space Agency’s Comet Interceptor. Launching in 2029, this spacecraft will be parked at Lagrange Point 2 waiting for an appetizing long comet or interstellar object to hunt and study. While the telescopes are fascinating, nothing compares to the science gleaned from a spacecraft mission, which high-profile science projects like Rosetta and Osiris-REx have proven beyond doubt.
“Every time we send a spacecraft somewhere, we learn something completely new,” Thomas says. “But even if James Webb didn’t like sending a spacecraft, we’d still see more…it would change the paradigm for how we think about these things.”