Эрдэмтэд оддын хөгжлийн явцад залгигдах ёстой байсан ч эсэн мэнд үлдсэн гурван том гаригийн тогтолцоог судалж байна.
Хятадын Юньнаний их сургуулийн профессор Цянь Шэнбаны удирдсан судалгааны баг Boötes одны ордод байрлах 24 Boötis болон бусад хоёр одны эргэн тойронд ер бусын гаригууд байгааг тогтоожээ. Эдгээр гаригууд нь тухайн оддын улаан аварга одны үе шат буюу хэмжээгээрээ эрс тэлж, ойр орчмын гаригуудаа залгих үйл явцын бүсэд байрладаг байна. “Proceedings of the National Academy of Sciences” сэтгүүлд нийтэлснээр, эдгээр гаригууд нь оддынхоо одоогийн тойрог замд биш, харин од тэлж байх үедээ эзэлж байсан аюултай бүсэд оршдог ажээ.
Судлаачид астеросейсмологи буюу оддын чичирхийллийг судлах аргыг ашиглан 24 Boötis, HD 12648, TYC 4282-605-1 оддын төлөв байдлыг тодорхойлсон байна. Оддын гэрэлтэлтийн бага зэргийн хэлбэлзэл нь тэдгээрийг улаан аварга үе шатаа дуусгаж, цөмдөө гели шатааж буй “улаан бөөгнөрөл” (red clump) од болохыг илтгэжээ. Компьютерийн загварчлалаар эдгээр од нь өмнө нь одоогийнхоос хамаагүй том хэмжээтэй байсныг тогтоосон бөгөөд энэ нь гаригууд залгигдах ёстой байсан гэсэн дүгнэлтийг бататгаж байна.
Ихэнх тохиолдолд улаан аварга оддын таталцал болон түрлэгийн хүч нь ойр орчмын гаригуудыг татаж, тойрог замыг нь багасган залгидаг болохыг өмнөх судалгаанууд харуулсан. Гэсэн хэдий ч гурван гариг зэрэг эсэн мэнд үлдсэн нь тохиолдлын шинжтэй биш, тодорхой физик үйл явцтай холбоотой байж болзошгүй гэж эрдэмтэд таамаглаж байна. Тухайлбал, од нь өмнө нь өөр нэг одтой нэгдсэн эсвэл дотоод тойргийн гаригаа залгисны улмаас үлдсэн гаригийн тойрог зам өөрчлөгдсөн байх магадлалтай.
Энэхүү ололт нь оддын мөхлийн үе шатанд гаригуудын хувь заяа хэрхэн шийдэгддэг талаарх уламжлалт загварыг дахин авч үзэх шаардлагатайг харуулж байна. Одоогоос таван тэрбум жилийн дараа Нар мөн улаан аварга од болон тэлж, Буд, Сугар гаригийг, магадгүй Дэлхийг ч залгиж болзошгүй юм. Хэдийгээр Дэлхий ийм үйл явцыг даван туулж магадгүй ч, энэ нь амьдралын хувьд сүйрэл авчрах эрсдэлтэй болохыг мэргэжилтнүүд онцолж байна.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
Around a star in the constellation Boötes, faintly visible to the naked eye on a dark night, a planet nearly as heavy as Jupiter completes an orbit every 30 days. It circles at less than a fifth of the distance between Earth and the Sun. By the usual rules of how stars age, it should not be there.
Its star, 24 Boötis, has already lived through its red giant phase, when an aging star swells to many times its original size. At its largest, the star stretched past the planet’s current orbit. Yet the planet is still there, and astronomers have now found two more like it.
The three survivors are described in a study in the Proceedings of the National Academy of Sciences led by Professor Qian Shengbang of Yunnan University, in China. All three planets orbit inside the zone that their stars once filled, the region where any planet should have been engulfed.
Listening to the Stars to Learn Their Age
The three stars are 24 Boötis, HD 12648 and TYC 4282-605-1. Their planets were found between 2015 and 2018, spotted from the slight wobble each one causes in its star. What remained unclear was how far along in life their stars were.
That matters because a red giant and the stage that follows it look almost identical from Earth. Both are large, cool and orange, with similar brightness. The difference lies deep inside: after the red giant phase, a star shrinks back somewhat and starts burning helium in its core, becoming what astronomers call a red clump star.
The way to tell them apart is asteroseismology, the study of starquakes. Stars vibrate, and those vibrations make their brightness flicker very slightly, a little like a heartbeat that reveals the state of the body inside. The flickers of all three stars show that they are burning helium in their cores, so all three have already been through the red giant phase.
The Planets Sit Inside the Danger Zone
Computer models of how stars evolve can show how big each star was at its peak. For each system, the answer is the same: the star once grew larger than the planet’s current orbit.
The closest case is 24 Boötis, about 308 light-years away. Its planet, at least 0.79 times the mass of Jupiter, orbits at 0.19 times the Earth-Sun distance, closer than any other known planet around a red clump star. The star itself is about 1.5 times the mass of the Sun and now about 10 times wider.
The other two planets are bigger and farther out, but still inside the danger zone. HD 12648 b, about 594 light-years away, weighs at least twice as much as Jupiter and takes 134 days to orbit its star. TYC 4282-605-1 b, about 1,500 light-years away, is a giant of nearly 11 Jupiter masses on a 102-day orbit.
Most Planets This Close Do Not Make It
As a red giant swells, it can swallow nearby planets outright. Its gravity also raises tides that slowly shrink the orbits of close planets until they spiral in. A 2025 survey with NASA’s TESS space telescope found that close-in giant planets become rarer as stars begin to grow.
“We expected to see this effect, but we were still surprised by just how efficient these stars seem to be at engulfing their close planets,” said Edward Bryant of the University of Warwick, who led that survey.
For Qian, one survivor could be put down to luck, but three at once point to a shared physical process. His team sees two possible escape routes. The star may once have had a companion star that it interacted or merged with, changing how it grew. Or it may have swallowed an inner planet first, an event that reshaped the orbit of the planet that survived.
The Sun Will Go Through the Same Phase
In about 5 billion years, the Sun will become a red giant too. It will grow large enough to swallow Mercury and Venus, and possibly Earth. The three survivors suggest the fate of planets around dying stars, including our own, may follow paths that classical models do not capture.
“Earth itself might survive the sun’s red giant phase. But life on Earth probably would not,” said Vincent Van Eylen of University College London, a member of the 2025 TESS team.
Enjoyed this article? Subscribe to our free newsletter for engaging stories, exclusive content, and the latest news.
