Meta & Fysikken: Afsnit 82: Astronomiske nyheder!
Vi tager en tur med forskellige ASTRO nyheder… Og vi snakker om hvor vanvittigt det egentlig er, at så fintfølende apparater og mekanik, kan fungere i rummet, hvor partikler flyver rundt med ekstremt høj hastighed. Hvorfor går det så sjældent galt?
Og hvad observerer vi egentlig med alle disse nymodens teleskoper? Vi taler om nogle af de ting vi er blevet klogere på, siden de nyeste teleskoper er taget i brug!
Her er Karina’s shownotes til dagens episode:
1 : JWST: Meget gammel galakse:
https://videnskab.dk/rummet/lillebitte-galakse-kan-give-svaret-paa-stor-gaade
Forskere fra Kbh ledte efter en SN i en gravitationel linse og fandt ved et tilfælde en lille galakse der ligger 13 milliarder lysår væk. Pga. linsen er den forstørret 20 gange.
Det er den mindste galakse der er fundet så langt væk, den er kun en milliontedel af Mælkevejen i volumen. Til gengæld danner den lige så mange nye stjerner som Mælkevejen.
Denne overproduktion og så endda af så lille en galakse, så tidligt i universet (500 millioner år efter Big Bang) kan forklare hvorfra fotonerne til Re-ioniseringen af universet kom.
Universet:
I begyndelsen var det ioniseret. Efter Big Bang var temperaturen enormt høj, og atomer kunne ikke dannes. Elektronerne, der normalt hvirvler rundt om et atoms kerne, kunne ikke blive i deres baner og flød derfor frit rundt.
Cirka 400.000 år efter Big Bang har universet udvidet sig så meget og er kølet tilpas meget ned til, at elektronerne kan binde sig til atomkernerne. Universet stopper med at være ioniseret og bliver neutralt.
Omkring 500 millioner år efter Big Bang begynder universet at blive ioniseret igen. Det er denne periode, astronomer har ledt efter en forklaring på. Hvordan og hvor hurtigt blev universet reioniseret – og hvilke eventuelle objekter var ansvarlige for processen?
2: Coupling Constant ikke konstant, teori:
https://www.sciencealert.com/the-entire-universe-could-be-twice-as-old-as-we-thought?
Vi forstår ikke hvorfor de Galakser vi ser langt tilbage i tiden er så modne i deres stjerne produktion. (selvom at de 'kun' er 500 millioner år gamle)
Her er en teori som kan forklare det. (kun en teori)
As light takes time to travel, redder light is older light, having been pulled over a greater distance. Working backward on this estimated growth rate, it's possible to use expansion to
determine when the Universe was a compact volume seething with concentrated energy.
Gupta's hybrid hypothesis presumes the Universe really is as big as we believe, having expanded to its size from a Big Bang event in the past. He starts with two expanding Universe models: one based on standard assumptions about the evenness and flatness of the cosmos and a second one that introduces some tweaks involving what's known as a coupling constant.
Coupling constants describe interactions of forces between particles, such as the way the electromagnetic fields of two protons held in close proximity will affect each other's behavior in specific ways.
All forces have a coupling constant, which isn't necessarily constant at all, changing with energy. This leaves room for coupling constants to vary enough to affect how light behaves. If this constant has changed over time, our calculations on the age of the Universe could be out by a significant amount.
"Our newly-devised model stretches the galaxy formation time by several billion years, making the universe 26.7 billion years old, and not 13.7 as previously estimated," says Gupta.
One of the problems with tired light theory is that a loss of energy in a light wave would correspond with a loss of momentum, affecting the appearance of far distant objects. With ancient galaxies looking unusually petite, this conflict might actually be a reason to reconsider the hypothesis.
3: Gammaglimt
Det mest energirige gammaglimt nogensinde er observeret af forskere.
GRB 221009A – Gamma Ray Burst 9 oktober 2022. BOAT – en forkortelse for ’Brightest of All Time’.
Astronomer fra blandt andet Københavns Universitet har opfanget det kraftigste gammaglimt fra rummet, vi kender til. I løbet af de 290 sekunder (4.8 min), som GRB 221009A varede, udløste det omtrent 1.000 gange så meget energi, som vores sol har udsendt i hele dens 4,5 milliarder år lange levetid
»Teoretisk set forventer vi, at et så kraftigt glimt kun burde hænde én gang i 10.000 år,« forklarer Malesani.
»Det får os til at overveje, om vores opdagelse er rent og skær held, eller om der er noget, vi har misforstået omkring gammaglimtenes natur.«
Der er to slags gammaglimt, de korte og de lange. De korte varer kun brøkdele af sekunder og de lange op til flere minutter, og de dannes på forskellig måde. (These objects can radiate other wavelengths for weeks. It is only in Gamma that they are short and bright.)
I dag mener man, at de korte gammaglimt med en varighed på brøkdele op til 1-2 sekunder skabes ved sammenstød mellem to neutronstjerner. Ved at sådant sammenstød skabes et sort hul, men samtidig udsendes også en meget kraftig gammastråling.
De lange gammaglimt skabes formodentlig af såkaldte hypernovaer, udbrud, der er langt kraftigere end almindelige supernovaer. De opstår, når stjerner mellem fem og 10 gange vores sols masse afslutter deres liv ved at implodere og ender som sorte huller. Hypernovaer producerer 100 gange mere energi end typiske supernovaudbrud, og man mener, at de skabes af stjerner, der roterer usædvanligt hurtigt eller har et særligt stærkt magnetfelt.
https://videnskab.dk/rummet/det-mest-energirige-gammaglimt-nogensinde-er-observeret-af-forskere/
70 times brighter and far more energetic than the previous record holder.
Observationer i andre bølgelængder viser at jet formen er anderledes.
https://www.nasa.gov/feature/jpl/brightest-cosmic-explosion-ever-detected-had-other-unique-features
4: Kilonova
JWST telescope traced an incredibly bright gamma-ray burst to a kilonova, a dramatic event believed to forge heavy elements like gold.
Men denne her var meget lang GRB i forhold til at kilden er hvad normalt er kilde til short gamma ray bursts.
The GRB lasted around 34 seconds and was spotted by multiple other telescopes, which is what allowed it to be triangulated back to its kilonova source by astronomers.
Designated GRB 230307A, it was initially detected by NASA's Fermi Gamma-ray Space Telescope on March 7, 2023, and is the second-brightest GRB ever seen.
This is the first time JWST has been used to detect emissions from such an event, and the powerful space telescope was also able to detect the signature of heavy elements being forged in the explosive event. In particular, the team saw evidence of the heavy element tellurium and the creation of lanthanides — a group of 15 metals heavier than lead.
"These observations demonstrate that nucleosynthesis in GRBs can create r-process elements across a broad atomic mass range and play a central role in heavy element nucleosynthesis across the universe.
Måske så 'langt' et GRB fordi vi er tæt nok på eller har den rigtige synsvinkel til at se lys fra grunstof dannelsen.
8.3 million light-years away from Earth
https://www.space.com/james-webb-space-telescope-kilonova-neutron-stars?
5: Betelgeuse er måske alligevel snart færdig?
https://www.sciencealert.com/a-stunning-revelation-could-mean-betelgeuse-is-set-to-blow
A little more than 650 light-years from Earth, an old, red star lies dying. A fresh prognosis on Betelgeuse's condition based on its pulsations gives the celebrated supergiant just a few decades before it collapses in a final flash of glory.
Fordi dens størrelse varier/pulserer er det svært at slå fast hvor gammel den kan blive.
Mindre stjerner brænder langsommer og bliver ældre, hvor store stjerner brænder hurtigt op. Live strong die Young.
6: Backgrounds gravitational wave hum.
"We've been on a mission for the last 15 years to find a low-pitch hum of gravitational waves resounding throughout the Universe and washing through our galaxy to warp space-time in a measurable way," astrophysicist Stephen Taylor of Vanderbilt University and chair of NANOGrav, the team in the US, said in a press briefing.
"We're very happy to announce that our hard work has paid off, and … we have exciting evidence of this background of gravitational waves."
Gravitational wave astronomy is a relatively new field, following the detection of space-time ripples caused by two colliding black holes in 2015. Since then, our Earth-based gravitational wave detectors have picked up nearly 100 confirmed gravitational wave events at the time of this writing, all created by mergers of compact stellar-mass objects – black holes and neutron stars.
Now imagine how many black holes must be colliding across the Universe. And how many other massive events must be generating these ripples. Space-time should be absolutely humming with gravitational waves, but there's a problem. Earth is simply too small to detect them at the longer wavelengths on the nanohertz scale that can extend for lightyears, those expected of more massive events, like the mergers of the supermassive black holes at the centers of galaxies.
Luckily, however, we live in a galaxy that is much bigger than Earth. And there's something in our galaxy that emits very precisely timed signals that can be affected by nanohertz gravitational waves: radio pulsars. These are neutron stars that rotate extremely fast, with jets of radio light erupting from their magnetic poles. As they rotate, these beams sweep past Earth like a cosmic lighthouse, and because the timing of these pulses is so precise, we can use them to detect the way space stretches and squeezes as gravitational waves roll through.
One minor glitch in the timing is not enough. But if you have enough pulsars with correlated glitches over a long enough time frame, you can compile evidence of a large gravitational wave. This is what the different teams around the world did, studying a total of 115 pulsars between them, for up to 18 years for the Parkes Pulsar Timing Array in Australia.