December 1, 2022


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【▲ 白色矮星「WD J2147-4035」と「WD J1922+0233」、その周囲を公転する惑星の残骸を描いたイメージ図。WD J2147-4035は暗く赤い色、WD J1922+0233は青い色をしているとされる(Credit: University of Warwick/Dr Mark Garlick)】

A planetary system formed more than 10 billion years ago? The results of the search for cold white dwarfs | Sorae Portal site to space


طالبة دكتوراه في جامعة وارويكأبيجيل إلمسفريق البحث بقيادة「WD J2147-4035نشرنا نتائج بحث عن الأقزام البيضاء الباردة ، بما في ذلك

وفقًا لفريق البحث ، اكتشف الغلاف الجوي لـ WD J2147-4035 عناصر يعتقد أنها تأتي من حطام الكواكب الساقطة ، وهو ما يعتبر دليلاً على وجود نظام كوكبي تشكل منذ أكثر من 10 مليارات سنة.

اكتشاف العناصر التي يُعتقد أنها نشأت من كواكب في الأقزام البيضاء ربما تكونت أنظمة الكواكب منذ أكثر من 10 مليارات سنة

القزم الأبيض هو جسم فلكي نشأ من نجم خفيف نسبيًا مثل الشمس (أقل من ثمانية أضعاف كتلة الشمس) عبر مرحلة العملاق الأحمر. يُعتقد أن العمالقة الحمراء تطلق الغاز من طبقاتها الخارجية إلى الفضاء الخارجي ، تاركة وراءها نواة ستصبح قزمًا أبيض. القزم الأبيض النموذجي هو جرم سماوي عالي الكثافة يبلغ قطره تقريبًا نفس قطر الأرض ، لكن كتلته تقارب ثلاثة أرباع كتلة الشمس.

[▲ صورة تقارن بين القزم الأبيض Sirius B (يسار) والأرض (يمين) (Credit: ESA / NASA)]

[▲ صورة تقارن بين القزم الأبيض Sirius B (يسار) والأرض (يمين) (Credit: ESA / NASA)]

This time, the research team teamed up with the aforementioned WD J2147-4035 and a white dwarf star about 129 light-years away in the direction of Aquila.「WD J1922 + 0233When we analyzed the spectrum (the intensity of each wavelength of electromagnetic waves), we detected sodium and potassium from both, lithium from WD J2147-4035, and calcium from WD J1922+0233. Rice field. The carbon was also initially revealed from WD J2147-4035.

These elements are found in the surface atmosphere of white dwarfs, which are generally composed of hydrogen and helium. Elements heavier than helium in the white dwarf’s atmosphere are believed to settle inside the white dwarf, but occasionally heavy elements are detected from the atmosphere like this time. These heavy elements are believed to be contaminated by celestial bodies, such as planetary debris that fell on the white dwarf relatively recently.

When the star that is the main star of the planetary system evolves into a white dwarf, it is believed that this process will cause confusion in the planetary system and in some cases destroy the planet. Destructive planetary debris orbits the white dwarf, some of which eventually falls into the white dwarf. According to the research team, it is possible that what fell on WD J1922 + 0233 was debris with a chemical composition similar to the Earth’s continental crust.


[▲ انطباع فنان عن القزم الأبيض “G238-44” (Credit: NASA، ESA، Joseph Olmsted (STScI))]

Connection:Inferred perturbation of the planetary system scale caused by dying stars from observational data of white dwarfs

According to the research team, the two white dwarfs have lower surface temperatures, WD J2147-4035 at about 3050 K (about 2,777 °C) and WD J1922 + 0233 at about 3340 K (about 3067 °C). WD J2147-4035, which has an atmosphere composed mostly of helium, has a dark red color, while WD J1922+0233, which has a mixed atmosphere of hydrogen and helium, has a blue color despite its lower surface temperature.

When a white dwarf is born, it glows at a high temperature of about 100,000 degrees Celsius, but because it glows due to preheating when it was a star, it cools over a long period of time. The research team that determined the age of the white dwarf based on the observed surface temperature,WD J2147-4035 was born as a star about 10.7 billion years agoand found that it began cooling into a white dwarf about 10.2 billion years ago. The other, WD J1922+0233, is slightly smaller and is believed to have cooled about 9 billion years ago.

Based on the above results, the research team concluded that a planetary system with WD J2147-4035 as its main star formed more than 10 billion years ago, the only one found so far in a white dwarf star in the Milky Way. …concluded that it is the oldest known planetary system.

“We have discovered the oldest stellar remnants in the Milky Way that were contaminated by an Earth-like planet,” said Elms, who led the study. “It’s amazing that the planet died so long before the Earth was formed.”

This finding may lead to new knowledge about planet formation. This is because heavy elements, which are planetary materials, are said to have resulted from nuclear fusion reactions within stars, or by violent phenomena such as supernova explosions and neutron star mergers. Compared to the formation of the Solar System about 4.6 billion years ago, the abundance of heavy elements was low when these two white dwarfs formed as stars, indicating that the planets at that time formed under conditions different from those in the Solar System. It is possible.

It’s so important to understand white dwarfs, Elms says, that 97 percent of all stars arrive, especially from the ultra-cool white dwarfs studied in this study, which are closer to the oldest stars in the Milky Way. He commented that it would provide information on the formation and evolution of planetary systems.


Text / Matsumura Takehiro

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