Merger of two سیاه چاله ها has three stages: inspiral, merger and ringdown phases. Characteristic امواج گرانشی are emitted in each phase. The last ringdown phase is very brief and encode information about properties of final سیاه چاله. Reanalysis of data from binary سیاه چاله merger event GW190521 has provided, for the first time, evidence of signature aftershocks of the merger in the form of two separate faint ringdown frequencies produced by the resulting single سیاه چاله as it settled down to a stable symmetrical form. This is the first detection of multiple gravitational-wave frequencies in the ringdown stage. Just like a bell ‘rings’ for some time after being stuck, the resulting single distorted سیاه چاله formed after the merger ‘rings’ for some time emitting faint امواج گرانشی before achieving symmetrical stable form. And, just the way shape of the bell determines the specific frequencies with which the bell rings, similarly, as per no-hair theorem, mass and spin of the سیاه چاله determine ringdown frequencies. Hence, this development paves the way for use of ringdown frequencies to study properties of final سیاه چاله.
سیاه چاله ها are massive objects with extremely strong gravitational fields. When two در حال چرخش سیاه چاله ها spiral around each other and eventually coalesce, the fabric of فضا-times around them are disturbed that creates ripples of امواج گرانشی radiating outwards. Since September 2015 when gravitational-wave astronomy began with LIGO’s first detection of امواج گرانشی generated by merger of two سیاه چاله ها 1.3 billion light years away, merging سیاه چاله ها are now routinely detected almost once every week.
ادغام سیاه چاله ها has three phases. When the two سیاه چاله ها are widely separated, they slowly مدار each other emitting weak gravitational waves. The binary gradually moves to smaller and smaller مدار as the energy of the system is lost in the form of امواج گرانشی. این هست فاز الهام بخش از ادغام بعدی این است مرحله ادغام وقتی آن دو سیاه چاله ها get close enough to coalesce to form a single سیاه چاله with distorted shape. Strongest gravitational waves (GWs) are emitted at this stage which are now routinely detected and recorded by gravitational-wave observatories.
مرحله ادغام یک مرحله بسیار کوتاه به نام مرحله ringdown wherein the resulting single distorted سیاه چاله quickly achieves more stable spherical or spheroidal form. امواج گرانشی emitted in the ringdown phase are damped and much fainter than the GWs released in the merger phase. Just as a bell ‘rings’ for some time after being stuck, the resulting single سیاه چاله ‘rings’ for some time emitting much fainter امواج گرانشی before achieving symmetrical stable form.
The faint multiple ringdown frequencies of امواج گرانشی released during the ringdown phase of merger of two سیاه چاله ها were undetected so far.
A research team has recently been successful in detecting multiple gravitational-wave frequencies in the ringdown stage of binary سیاه چاله merger event GW190521. They searched for individual fading tones in the ringdown frequencies without considering any relation with frequencies and damping times and were successful in identifying two modes implying the resulting deformed سیاه چاله emitted at least two frequencies after the merger. This was predicted by Einstein’s general relativity hence the result confirms the theory. Further, researchers compared the frequencies and damping times of the two ringdown modes found in the merger event to test the “no-hair theorem” (that سیاه چاله ها are completely characterised by mass and spin and no other “hair” is needed to describe its features) and found nothing beyond general relativity.
این یک نقطه عطف است زیرا به طور گسترده تصور می شد که مشاهده فرکانس های چرخشی متعدد قبل از در دسترس قرار گرفتن آشکارسازهای موج گرانشی نسل بعدی در آینده امکان پذیر نخواهد بود.
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منابع:
- کاپانو، سی دی و همکاران. 2023. طیف شبه طبیعی چند حالته از سیاهچاله آشفته. نامه های بررسی فیزیکی جلد 131، شماره 22. 1 دسامبر 2023. DOI: https://doi.org/10.1103/PhysRevLett.131.221402
- Max-Planck-Institut fürGravitationsphysik(Albert-Einstein-Institut)، 2023. اخبار - سیاهچاله برای چه کسی حلقه می زند. موجود در https://www.aei.mpg.de/749477/for-whom-the-black-hole-rings?c=26160
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