In this artist’s view, two gas planets orbit the bright star HD 152843. These planets were discovered by the citizen science project TESS Planet Hunters, in collaboration with professional scientists. Credit: NASA/Scott Weisinger
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At night, seven-year-old Miguel likes to talk to his father, Cesar Rubio, about planets and stars. “I try to take care of it,” says Rubio, a mechanic in Pomona, California, who makes parts for mining equipment and power plants.
Now, the boy can claim that his father also helped find the planets. Cesar Rubio is one of thousands of volunteers participating in Tess’s planet hunter, a NASA-funded citizen science project looking for evidence of planets outside our solar system or exoplanets. Citizen science is a way for community members to collaborate with scientists. More than 29,000 people worldwide have joined Planet Hunters TESS to help scientists find exoplanets.
Cesar Rubio and his son Miguel love to talk about space together. Credit: Cesar Rubio
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Planet Hunters TESS announced the discovery of two exoplanets in a study published online at Monthly Notices of the Royal Astronomical Society, and the inclusion of Rubio and more than a dozen other citizen scientists as coauthors.
This alien world orbits a star called HD 152843, which is located about 352 light-years away. This star has roughly the same mass as the Sun, but is about 1.5 times bigger and slightly brighter.
Planet B, the size of Neptune, is about 3.4 times larger than Earth, and completes an orbit around its star in about 12 days. Planet C, an exoplanet, is about 5.8 times larger than Earth, making it “semi-Saturn”, and its orbital period is between 19 and 35 days. In our solar system, the two planets will orbit Mercury in about 88 days.
said Nora Eisner, a PhD student in astrophysics at the University of Oxford in the UK and lead author of the study.
TESS stands for Transiting Exoplanet Survey Satellite, a NASA spacecraft launched in April 2018. The TESS team used data from the observatory to identify more than 100 exoplanets and more than 2,600 candidates awaiting confirmation.
Planet Hunters TESS, which operates through the Zooniverse website, began in December 2018, shortly after the first TESS data was published. Volunteers looked at graphs showing the different brightnesses of stars over time. Notice which plot shows a brief drop in star brightness and then an upward swing back to its original level. This can happen when a planet crosses the face of its star, blocking out a small amount of light — an event called a “transit.”
Planet Hunters share each brightness scheme called the “Light Curve” with 15 volunteers. In the background of the site, the algorithm collects all the volunteer submissions and selects a light curve that several volunteers have selected. Then Eisner and his colleagues looked at the high-level light curves and determined which ones were good for scientific follow-up.
Alexander Hubert studied to be a teacher of mathematics and Latin but enjoyed a citizen science project in astronomy. Credit: Alexander Hubert
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Even in an era of complex computing technologies like machine learning, having a large group of volunteers look at telescope data is a great help to researchers. Since researchers can’t perfectly train computers to identify potential planetary fingerprints, the human eye is still valuable. “This is why there aren’t many candidates for exoplanets, and why citizen science is such a great thing,” Eisner said.
In the case of HD 152843, the citizen scientist saw a plot of land showing its brightness within a month of TESS observations. The light curves show three distinct tilts, implying that at least one planet could orbit the star. All 15 citizen scientists who have seen this curve have referred to at least two transits, and several have marked the light curve on the Planet Hunters TESS online discussion forum.
Then the scientists took a closer look. By comparing the data with their model, they estimated that two transits came from the inner planet and the other from the second outer planet.
To ensure that the transit signal is coming from the planet and not from another source, such as eclipsing stars, passing asteroids, or the motion of TESS itself, scientists need to look at the star in a different way. They used an instrument called HARPS-N (High Resolution Radial Velocity Planet Finder for the Northern Hemisphere) at the Telescopio Nazionale Galileo in La Palma, Spain, as well as EXPRES (Extreme Resolution Spectrometer), an instrument at the Lowell Observatory in Flagstaff, Arizona. HARPS and EXPRES look for planets by checking if the star’s light is “wobbly” as the planet orbits its star. This technique, called the radial velocity method, allows scientists to estimate the mass of distant planets as well.
While the scientists couldn’t get a clear enough signal to determine the planet’s mass, they did get enough radial velocity data to make mass estimates – about 12 times the mass of Earth for Planet B and about 28 times the mass of Earth for Planet C. Their measurements confirmed the correctness of the signals indicating the existence of the planet; More data is needed to confirm its mass. Scientists continue to monitor planetary systems with HARPS-N and hope to get more information about the planets soon.
Elizabeth Payten has been part of more than a dozen scientific studies published through Zooniverse Projects. Credit: Elizabeth Payten
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Researchers may soon have high-tech tools to find out if these planets have atmospheres and what gases are in them. NASA’s James Webb Space Telescope, due to launch later this year, will be able to see the types of particles that make up the atmospheres of planets like those in this system, particularly the larger exoplanets. Planet HD 152843 is too hot and gassy to support life as we know it, but they are worth studying as scientists study potential planetary arrangements in our galaxy.
“We’re taking small steps toward finding Earth-like planets and studying their atmospheres, and we’re continuing to push the limits of what we can see,” Eisner said.
The resident scientist who assessed the light curve of HD 152843 as a possible source of transiting planets, as well as three moderators of the Planet Hunter discussion forum, were invited to be included as co-authors of the study announcing the discoveries of these planets.
One such resident scholar is Alexander Hubert, an undergraduate student focusing on mathematics and Latin in Würzburg, Germany, who plans to become a high school teacher. To date, more than 10,000 light curves have been classified by Planet Hunters TESS.
“I sometimes regret that in our time we have to limit ourselves to one, maybe two, subjects, like mine for me, Latin and mathematics,” says Hubert. “I am so grateful that at Zooniverse I have the opportunity to be involved in something different.”
Another co-author, Elisabeth Payten of Leuven, Belgium, who works in the reinsurance department, said assessing the light curve at Planet Hunters TESS was “relaxing.” He has been interested in astronomy since childhood, and was one of the original volunteers for Galaxy Zoo, a citizen science project in astronomy that started in 2007. Galaxy Zoo invites participants to classify the shapes of distant galaxies.
While Baeten has been part of more than a dozen studies published through the Zooniverse Project, this new study is Rubio’s first scientific publication. Astronomy has always been a lifelong interest, and he is now able to share it with his son. The two sometimes see Planet Hunters TESS together.
“I feel like I’m contributing, even if it’s only a small part,” said Rubio. “Scientific research in particular, it’s satisfying to me.”
NASA has a wide variety of citizen science collaborations on topics ranging from Earth to Sun science to the wider universe. Anyone in the world can participate. Check out the latest opportunities in science.nasa.gov/citizenscience.
Referensi: “Pemburu Planet TESS III: Dua Planet Transit Di Sekitar Glossy G dwarf HD 152843” Oleh NL Eisner, B. A. Nicholson, O Barragán, S Aigrain, C Lintott, L Kaye, B Klein, G Miller, J Taylor, dan N Zicher, LA Buchhave, DA Caldwell, J Horner, J Llama, A Mortier, VM Rajpaul, K Stassun, A Sporer, A Tkachenko, JM Jenkins, D Latham, G Ricker, S Seager, J Winn, S Alhassan, EML Baeten, SJ Bean DM Bundy, V Efremov, R Ferstenou, BL Goodwin, M Hof, T Hoffman, A Hubert, L Lau, S Lee, D Maetschke, K Peltsch, C Rubio-Alfaro, GM Wilson, 12 Mei 2021, Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093 / mnras / stab1253
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