Ahli Astronom Temui Sistem Berbilang Planet Berdekatan Dengan Dua Planet Bersaiz Bumi

Ahli astronomi MIT telah menemui sistem multiplanet baharu yang terletak hanya 10 parsec, atau kira-kira 33 tahun cahaya, dari Bumi, menjadikannya salah satu sistem berbilang planet yang paling dekat dengan kita. Bintang di tengah-tengah sistem berkemungkinan menempatkan sekurang-kurangnya dua planet terestrial, sebesar Bumi. Kredit: MIT News, dengan angka TESS Satellite ihsan NASA

Terletak hanya 33 tahun cahaya dari Bumi, sistem itu kelihatan menjadi tuan rumah dua planet berbatu, sebesar Bumi.

Sistem multiplanet baharu dalam kejiranan galaksi kita telah ditemui oleh ahli astronomi di[{” attribute=””>MIT and elsewhere. It lies just 10 parsecs, or about 33 light-years, from Earth, making it one of the closest known multiplanet systems to our own.

At the heart of the system lies a small and cool M-dwarf star, named HD 260655, and astronomers have found that it hosts at least two terrestrial, Earth-sized planets. The rocky worlds have relatively tight orbits, exposing the planets to temperatures that are too high to sustain liquid surface water. Therefore, they are unlikely to be habitable.

Nevertheless, scientists are excited about this system because the proximity and brightness of its star will give them a closer look at the properties of the planets and signs of any atmosphere they might hold.

“Both planets in this system are each considered among the best targets for atmospheric study because of the brightness of their star,” says Michelle Kunimoto, a postdoc in MIT’s Kavli Institute for Astrophysics and Space Research and one of the discovery’s lead scientists. “Is there a volatile-rich atmosphere around these planets? And are there signs of water or carbon-based species? These planets are fantastic test beds for those explorations.”

The team will present its discovery on June 15, 2022, at the meeting of the American Astronomical Society in Pasadena, California. Team members at MIT include Katharine Hesse, George Ricker, Sara Seager, Avi Shporer, Roland Vanderspek, and Joel Villaseñor, along with collaborators from institutions around the world.

NASA TESS in Space

Illustration of NASA’s Transiting Exoplanet Survey Satellite (TESS) at work. Credit: NASA’s Goddard Space Flight Center

Data power

The new planetary system was initially identified by NASA’s Transiting Exoplanet Survey Satellite (TESS), an MIT-led mission that is designed to observe the nearest and brightest stars, and detect periodic dips in light that could signal a passing planet.

In October 2021, Kunimoto, a member of MIT’s TESS science team, was monitoring the satellite’s incoming data when she noticed a pair of periodic dips in starlight, or transits, from the star HD 260655.

She ran the detections through the mission’s science inspection pipeline, and the signals were soon classified as two TESS Objects of Interest, or TOIs — objects that are flagged as potential planets. The same signals were also found independently by the Science Processing Operations Center (SPOC), the official TESS planet search pipeline based at NASA Ames. Scientists typically plan to follow up with other telescopes to confirm that the objects are indeed planets.

The process of classifying and subsequently confirming new planets can often take several years. For HD 260655, that process was shortened significantly with the help of archival data.

Keck Observatory Domes

The Keck observatory domes atop Mauna Kea. Credit: T. Wynne / JPL

Soon after Kunimoto identified the two potential planets around HD 260655, Shporer looked to see whether the star was observed previously by other telescopes. As luck would have it, HD 260655 was listed in a survey of stars taken by the High Resolution Echelle Spectrometer (HIRES), an instrument that operates as part of the Keck Observatory in Hawaii. HIRES had been monitoring the star, along with a host of other stars, since 1998, and the researchers were able to access the survey’s publicly available data.

HD 260655 was also listed as part of another independent survey by CARMENES, an instrument that operates as part of the Calar Alto Observatory in Spain. As these data were private, the team reached out to members of both HIRES and CARMENES with the goal of combining their data power.

“These negotiations are sometimes quite delicate,” Shporer notes. “Luckily, the teams agreed to work together. This human interaction is almost as important in getting the data [as the actual observations].”

Tarikan planet

Akhirnya, usaha kerjasama ini dengan cepat mengesahkan kehadiran dua planet di sekitar HD 260655 dalam masa kira-kira enam bulan.

Untuk mengesahkan bahawa isyarat daripada TESS memang dari dua planet yang mengorbit, para penyelidik meneliti data HIRES dan CARMENES bintang itu. Kedua-dua tinjauan mengukur goyangan graviti bintang, juga dikenali sebagai halaju jejarinya.

“Setiap planet yang mengorbit bintang akan mempunyai sedikit tarikan graviti pada bintangnya,” jelas Kunimoto. “Apa yang kami cari ialah sebarang pergerakan kecil bintang itu yang boleh menunjukkan objek berjisim planet sedang menariknya.”

Daripada kedua-dua set data arkib, para penyelidik menemui tanda-tanda signifikan secara statistik bahawa isyarat yang dikesan oleh TESS sememangnya dua planet yang mengorbit.

“Kemudian kami tahu kami mempunyai sesuatu yang sangat menarik,” kata Shporer.

Pasukan itu kemudian melihat dengan lebih teliti pada data TESS untuk menentukan sifat kedua-dua planet, termasuk tempoh dan saiz orbitnya. Mereka menentukan bahawa planet dalam, yang digelar HD 260655b, mengorbit bintang setiap 2.8 hari dan kira-kira 1.2 kali lebih besar daripada Bumi. Planet luar kedua, HD 260655c, mengorbit setiap 5.7 hari dan 1.5 kali lebih besar daripada Bumi.

Daripada data halaju jejari dari HIRES dan CARMENES, para penyelidik dapat mengira jisim planet, yang berkaitan secara langsung dengan amplitud di mana setiap planet menarik bintangnya. Mereka mendapati planet dalam adalah kira-kira dua kali lebih besar daripada Bumi, manakala planet luar adalah kira-kira tiga jisim Bumi. Daripada saiz dan jisim mereka, pasukan menganggarkan ketumpatan setiap planet. Planet dalam yang lebih kecil sedikit lebih tumpat daripada Bumi, manakala planet luar yang lebih besar agak kurang tumpat. Kedua-dua planet, berdasarkan kepadatannya, berkemungkinan terrestrial, atau berbatu dalam komposisi.

Para penyelidik juga menganggarkan, berdasarkan orbit pendek mereka, bahawa permukaan planet dalam adalah 710 kelvin yang dipanggang (818 darjah). Fahrenheit), manakala planet luar adalah sekitar 560 °K (548 °F).

“Kami menganggap julat itu di luar zon boleh didiami, terlalu panas untuk air cecair wujud di permukaan,” kata Kunimoto.

“Tetapi mungkin terdapat lebih banyak planet dalam sistem,” tambah Shporer. “Terdapat banyak sistem multiplanet yang menganjurkan lima atau enam planet, terutamanya di sekitar bintang kecil seperti ini. Mudah-mudahan, kita akan menemui lebih banyak lagi, dan seseorang mungkin berada di zon boleh didiami. Itu pemikiran optimis.”

Penyelidikan ini disokong sebahagiannya oleh NASA, Max-Planck-Gesellschaft, Consejo Superior de Investigaciones Científicas, Ministerio de Economía y Cometitividad, dan Dana Pembangunan Wilayah Eropah.

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Ahli Astronom Temui Sistem Berbilang Planet Berdekatan Dengan Dua Planet Bersaiz Bumi


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