This article was updated on August 3, 2020, at 11:55 am.
Astronomers have a saying about how difficult it is to see a distant planet outside of our own solar system: It’s like spotting a firefly next to a lighthouse.
Stars are so luminous that they block our view of planets that might be orbiting nearby, so astronomers have to work around them. They use special instruments on telescopes to block the light coming from these celestial beacons. With the glare gone, they can detect something else: heat radiating off of planets. In the resulting observations, the worlds are easier to spot—glowing orbs in the darkness, like fireflies hovering in the heat of a summer night.
This is how astronomers captured two planets around a star that resides about 300 light-years away from Earth. The portrait, released yesterday, is rare. Astronomers have directly taken images of individual exoplanets before. And they have previously captured cosmic family portraits: planets together with stars brighter and heavier than our sun. But this is the first time anyone has captured two exoplanets around a sunlike star.
In the photo at the top of this story, the star is at left. The planets are not rocky like Earth, but gaseous like Jupiter, and more massive than Jupiter too. They are also extremely hot, still cooling down from their fiery formation out of a stew of dust and gas. At 17 million years old, their star is a baby version of our sun. Matthew Kenworthy, an astronomy professor at Leiden University, in the Netherlands, who was involved with the research, told me that if our sun was his age, 46, this star would be just nine weeks old.*
This other solar system looks almost cozy, but these planets are a few hundred times farther from their star than Saturn and Jupiter are from our own. There might be rocky planets like Earth somewhere in this system, Kenworthy said, but they would be too small for even our most powerful telescopes to spot. As far as we can tell, this system is not like our home in the cosmos, and yet its landscape seems somehow familiar, like seeing a photograph of a famous skyline with a few skyscrapers missing. My first thought when I saw this image was, Huh, I wonder how things are going there. Maybe they’re having a better time of it than we are.
This is, I realize, an absurd thought—a knee-jerk projection of pandemic stress at a time when the fight against the coronavirus in the United States feels more frustrating and helpless each day. Our world seems particularly exhausting right now, and these kinds of astronomical observations provide a strange sense of comfort. They present a different version of something recognizable, and an opportunity to imagine a calmer existence, in which the pandemic isn’t always on our minds.
Maddalena Reggiani, a postdoctoral researcher at KU Leuven, in Belgium, and one of the researchers in this study, gets a similar feeling—not my desperate wishful thinking about an alternate reality, but the sense that she is looking at a cosmic doppelgänger. This image, after all, resembles how our own solar system appears in textbooks and on classroom posters: as a ball of fire suspended in the darkness, with a few glassy marbles circling it.
To produce the image, Kenworthy and his colleagues compared multiple observations of the solar system. In the first set, the star is surrounded by several blobs of glowing gas, any one of which could be a planet. In the second set, taken some time later, some of the orbs have moved, while others have stayed put, as unmoving as the star itself. The objects that shifted turned out to be other stars, somewhere in the background, moving along on their own journey through space. The objects that stuck around, the researchers concluded, were planets.
Astronomers seek out such cosmic doppelgängers to learn about our own history. By studying a baby version of the sun somewhere else, they can better understand how our own adult sun—all the planets around it—came to be. Studying images of similar solar systems is like looking at a childhood photo album. “We can’t, during our lifetime, look at how a planetary system is born and how it evolves,” Reggiani told me. “All we can do is look at stars at different ages so we can guess a little bit at the history of our solar system.”
Cosmic analogues can also help scientists understand the kinds of circumstances that can lead to a planet sprouting life, even if all they see is gas planets capable of producing only swirling cloud tops instead of squirming organisms. Spotting a couple of gas planets in another solar system is not the triumphant discovery that detecting an Earthlike atmosphere on a rocky exoplanet would be, but it is an important bread crumb in the search for life in the universe.
That’s because outer, Jupiter-like planets help protect inner, rocky planets. Research has shown that Jupiter might have spared Earth from collisions with small objects in the early solar system, when stuff was flying around all over the place. Without these big planets, rocky objects could have coalesced into a cloud in the inner solar system and showered Earth with enough collisions to strip away its atmosphere. With Saturn and Jupiter standing by, conditions near Earth remained stable enough for life to start stirring in the water. Even today, Jupiter often deflects comets and asteroids.
Emily Deibert, a doctoral student in astronomy and astrophysics at the University of Toronto who studies exoplanets, told me that this new research makes her think about of Earth’s place in the universe. “Especially seeing something like this, an actual image of another planetary system, which is really rare, it makes me think about how unique our Earth is and how difficult it would be to find somewhere else suitable for us to live,” said Deibert, who was not involved in the research.
Pictures like this can provide a dose of awe amid the doom-scrolling, a tiny break from a reality that itself feels like an alternate timeline for 2020, much in the same way that the sight of a fuzzy comet called NEOWISE has dazzled stargazers around the world in recent weeks. These are temporary delights. The comet will eventually fade from view, not to return for thousands of years, and the solar system in the new photograph is too far away to ever visit. But turning our attention to something otherworldly, even for a few moments, can distract us from pandemic despair.
Deibert wonders whether a planet like Earth is hidden in that other solar system hundreds of light-years away, and whether someone there is gazing back at us, trying to see past the glare of our sun. “Perhaps some other intelligent civilization out there might be looking at our system right now and only seeing our two biggest gas giants,” she said. What might those inhabitants be thinking, as they look upon a home that is almost like theirs?
*This article previously misstated the age of the distant star in relation to our own sun.
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