Students in New Jersey will hear from NASA astronauts Chris Williams and Jessica Meir as they answer prerecorded STEM questions while aboard the International Space Station.

The Earth-to-space call will begin at 12:05 p.m. EDT, Thursday, June 18, and will stream live on the agency’s Learn With NASA YouTube channel.

This event is hosted by Newton Public Schools in Newton, New Jersey, for students in grades K-12 and members of the community. This unique opportunity aims to deepen understanding of space exploration and enhance awareness of STEM careers.

Media interested in covering the event must RSVP no later than 5 p.m. EDT, Wednesday, June 17, to Dr. Joseph Piccirillo at: 973-383-7392, x4229 or jpiccirillo@newtonnj.org.

For more than 25 years, astronauts have continuously lived and worked aboard the space station, testing technologies, performing science, and developing skills needed to explore farther from Earth. Astronauts communicate with NASA’s Mission Control Center in Houston 24 hours a day through SCaN’s (Space Communications and Navigation) Near Space Network.

Research and technology investigations taking place aboard the space station benefit people on Earth and lay the groundwork for other agency deep space missions. As part of NASA’s Artemis program, the agency will send astronauts to the Moon to prepare for future human exploration of Mars, inspiring the world through discovery in a new Golden Age of innovation and exploration.

For more information on NASA in-flight calls, visit:

https://www.nasa.gov/stemonstation

Students in New Jersey will hear from NASA astronauts Chris Williams and Jessica Meir as they answer prerecorded STEM questions while aboard the International Space Station.

The Earth-to-space call will begin at 12:05 p.m. EDT, Thursday, June 18, and will stream live on the agency’s Learn With NASA YouTube channel.

This event is hosted by Newton Public Schools in Newton, New Jersey, for students in grades K-12 and members of the community. This unique opportunity aims to deepen understanding of space exploration and enhance awareness of STEM careers.

Media interested in covering the event must RSVP no later than 5 p.m. EDT, Wednesday, June 17, to Dr. Joseph Piccirillo at: 973-383-7392, x4229 or jpiccirillo@newtonnj.org.

For more than 25 years, astronauts have continuously lived and worked aboard the space station, testing technologies, performing science, and developing skills needed to explore farther from Earth. Astronauts communicate with NASA’s Mission Control Center in Houston 24 hours a day through SCaN’s (Space Communications and Navigation) Near Space Network.

Research and technology investigations taking place aboard the space station benefit people on Earth and lay the groundwork for other agency deep space missions. As part of NASA’s Artemis program, the agency will send astronauts to the Moon to prepare for future human exploration of Mars, inspiring the world through discovery in a new Golden Age of innovation and exploration.

For more information on NASA in-flight calls, visit:

https://www.nasa.gov/stemonstation

Scientists await a big splash in the Pacific Ocean as one of the most research-packed Dragon spacecraft to date returns, completing the 34th SpaceX commercial resupply mission to the International Space Station for NASA. Biological and materials samples, along with tested hardware, are heading back to research teams on Earth for further analysis, advancing NASA’s work to prepare humans for exploration beyond low Earth orbit and to deliver benefits back home.

Tiny cells, huge health insights

Some samples returning are for NASA’s Hematopoietic Stem Cell Expansion in Space: Pathfinder Investigation (InSPA-StemCellEX-H2), which seeks to use the microgravity environment to scale up the production of stems cells. On Earth, lab-produced blood stem cells lose their ability to form different cell types, like red and white blood cells that are critical to treating patients with certain blood diseases and cancers. In microgravity, researchers believe this ability will be better preserved while also growing these stem cells in greater numbers. The returning samples will undergo further analysis to determine if space-based efforts produce larger quantities of enhanced stem cells suitable for clinical use.

The team behind NASA’s Streptococcus pneumoniae (Spn) Infection of Cardiac Tissue (MVP Cell-09) experiment is awaiting the return of stem cell-derived heart tissues that were intentionally infected with a pneumonia-causing bacterium as part of ongoing microgravity research. Pneumonia increases the risk of heart disease, which is not fully understood. Because bacteria tend to become more active and virulent in microgravity, this experiment could amplify their effects, making it possible to detect cellular responses that cannot be observed on Earth.

NASA’s Megakaryocyte Flying-One (MeF1) samples are returning to Earth to help understand how large cells found in bone marrow, known as megakaryocytes, and the platelets they produce adapt to spaceflight. Megakaryocytes and platelets play important roles in the formation of blood clots and immune responses. The returning samples, including those taken from astronauts, could show us how the human immune system reacts aboard the space station and help prepare for future exploration missions.

Driving design enhancements

Many spacecraft use cryogenic fuels for propulsion, but temperature swings in space can cause these extremely cold fuels to slowly evaporate and escape their tank, reducing fuel efficiency and complicating mission planning. NASA’s Zero Boil-Off Tank Noncondensables (ZBOT-NC) investigation aboard station studies how gases that do not condense into liquids at cold temperatures affect pressure control and fluid behaviors in propellant tanks. Hardware returning aboard Dragon, including drives containing fluid-physics data, could help validate models and contribute to the design of more efficient cryogenic fuel storage systems for long-duration missions.

Semiconductor research samples as part of NASA’s In-Space Production of Semimetal-Semiconductor Composite Bulk Crystals in Microgravity (SUBSA-InSPA-SSCug) investigation are returning to Earth for further analysis. This study manufactured semimetal-semiconductor composite alloy crystals in space, which have applications in many electronics, including sensors and lasers. Researchers believe microgravity could enable the production of significantly greater and higher-quality crystals, supporting the development of next-generation semiconductor technologies.

Innovative medical research mix

NASA’s DNA Nano Therapeutics-3 research team will receive tiny, space-assembled DNA-inspired materials that are combined with medicines to create active cancer treatments. Producing these treatments in microgravity can improve how well they perform in the body. This research could improve patient outcomes by helping therapies reach tumors more effectively, stay in the body longer, and improve medicine release.

Tissue models of the brain, heart, liver, and kidney that were tested with novel RNA-based medicines as part of NASA’s InSPA-Sachi Nanoligomer investigation are also returning. Microgravity can accelerate aging and disease processes, giving researchers a unique environment to better observe how well these new drugs work on different organs ahead of clinical trials.

Samples from ESA’s (European Space Agency) Green Bone investigation are returning to Earth to help understand how bone cells grow and develop on a new scaffold made from wood. Designed to mimic real bone, this scaffold was tested in microgravity to understand its ability to heal defects and fractures. Because living in microgravity simulates conditions like osteoporosis, a skeletal disorder which affects millions of people worldwide, the results could help treat patients with these fragile bone conditions. 

NASA’s 3D Bone Marrow Analog research team will analyze the returning 3D-printed tissues that mimic parts of the bone marrow. Spaceflight can cause aging-like changes, including bone and muscle loss. To investigate potential countermeasures, these tissue models were exposed to small vibrations aboard the space station to simulate exercise. After the samples return to Earth, researchers will measure bone-like mineral formations and observe cellular and genetic changes. Findings from this investigation could help develop new strategies to maintain astronaut bone and muscle health during future long-duration missions.

In the United States, more than 900,000 knee cartilage injuries occur annually, with many requiring surgery. NASA’s InSPA-Auxilium Bioprinter-Cell Printing is investigating how to treat these injuries and is returning 3D-printed cartilage tissue samples from space station. This investigation uses the orbiting laboratory’s unique microgravity environment to bioprint cartilage tissues with more evenly distributed cells compared to those printed on Earth. The results could help produce higher-quality cartilage prints to treat joint injuries.

Scientists await a big splash in the Pacific Ocean as one of the most research-packed Dragon spacecraft to date returns, completing the 34th SpaceX commercial resupply mission to the International Space Station for NASA. Biological and materials samples, along with tested hardware, are heading back to research teams on Earth for further analysis, advancing NASA’s work to prepare humans for exploration beyond low Earth orbit and to deliver benefits back home.

Tiny cells, huge health insights

Some samples returning are for NASA’s Hematopoietic Stem Cell Expansion in Space: Pathfinder Investigation (InSPA-StemCellEX-H2), which seeks to use the microgravity environment to scale up the production of stems cells. On Earth, lab-produced blood stem cells lose their ability to form different cell types, like red and white blood cells that are critical to treating patients with certain blood diseases and cancers. In microgravity, researchers believe this ability will be better preserved while also growing these stem cells in greater numbers. The returning samples will undergo further analysis to determine if space-based efforts produce larger quantities of enhanced stem cells suitable for clinical use.

The team behind NASA’s Streptococcus pneumoniae (Spn) Infection of Cardiac Tissue (MVP Cell-09) experiment is awaiting the return of stem cell-derived heart tissues that were intentionally infected with a pneumonia-causing bacterium as part of ongoing microgravity research. Pneumonia increases the risk of heart disease, which is not fully understood. Because bacteria tend to become more active and virulent in microgravity, this experiment could amplify their effects, making it possible to detect cellular responses that cannot be observed on Earth.

NASA’s Megakaryocyte Flying-One (MeF1) samples are returning to Earth to help understand how large cells found in bone marrow, known as megakaryocytes, and the platelets they produce adapt to spaceflight. Megakaryocytes and platelets play important roles in the formation of blood clots and immune responses. The returning samples, including those taken from astronauts, could show us how the human immune system reacts aboard the space station and help prepare for future exploration missions.

Driving design enhancements

Many spacecraft use cryogenic fuels for propulsion, but temperature swings in space can cause these extremely cold fuels to slowly evaporate and escape their tank, reducing fuel efficiency and complicating mission planning. NASA’s Zero Boil-Off Tank Noncondensables (ZBOT-NC) investigation aboard station studies how gases that do not condense into liquids at cold temperatures affect pressure control and fluid behaviors in propellant tanks. Hardware returning aboard Dragon, including drives containing fluid-physics data, could help validate models and contribute to the design of more efficient cryogenic fuel storage systems for long-duration missions.

Semiconductor research samples as part of NASA’s In-Space Production of Semimetal-Semiconductor Composite Bulk Crystals in Microgravity (SUBSA-InSPA-SSCug) investigation are returning to Earth for further analysis. This study manufactured semimetal-semiconductor composite alloy crystals in space, which have applications in many electronics, including sensors and lasers. Researchers believe microgravity could enable the production of significantly greater and higher-quality crystals, supporting the development of next-generation semiconductor technologies.

Innovative medical research mix

NASA’s DNA Nano Therapeutics-3 research team will receive tiny, space-assembled DNA-inspired materials that are combined with medicines to create active cancer treatments. Producing these treatments in microgravity can improve how well they perform in the body. This research could improve patient outcomes by helping therapies reach tumors more effectively, stay in the body longer, and improve medicine release.

Tissue models of the brain, heart, liver, and kidney that were tested with novel RNA-based medicines as part of NASA’s InSPA-Sachi Nanoligomer investigation are also returning. Microgravity can accelerate aging and disease processes, giving researchers a unique environment to better observe how well these new drugs work on different organs ahead of clinical trials.

Samples from ESA’s (European Space Agency) Green Bone investigation are returning to Earth to help understand how bone cells grow and develop on a new scaffold made from wood. Designed to mimic real bone, this scaffold was tested in microgravity to understand its ability to heal defects and fractures. Because living in microgravity simulates conditions like osteoporosis, a skeletal disorder which affects millions of people worldwide, the results could help treat patients with these fragile bone conditions. 

NASA’s 3D Bone Marrow Analog research team will analyze the returning 3D-printed tissues that mimic parts of the bone marrow. Spaceflight can cause aging-like changes, including bone and muscle loss. To investigate potential countermeasures, these tissue models were exposed to small vibrations aboard the space station to simulate exercise. After the samples return to Earth, researchers will measure bone-like mineral formations and observe cellular and genetic changes. Findings from this investigation could help develop new strategies to maintain astronaut bone and muscle health during future long-duration missions.

In the United States, more than 900,000 knee cartilage injuries occur annually, with many requiring surgery. NASA’s InSPA-Auxilium Bioprinter-Cell Printing is investigating how to treat these injuries and is returning 3D-printed cartilage tissue samples from space station. This investigation uses the orbiting laboratory’s unique microgravity environment to bioprint cartilage tissues with more evenly distributed cells compared to those printed on Earth. The results could help produce higher-quality cartilage prints to treat joint injuries.

Si ritiene che la materia oscura costituisca la maggior parte della materia presente nell’universo, e che l’unico modo in cui interagisce con l’ambiente circostante sia attraverso la gravità. Ciò significa che se due buchi neri in collisione finissero per fondersi all’interno di una regione densa di materia oscura, le onde gravitazionali prodotte dall’evento potrebbero trasportare un’impronta di quella materia oscura. È l’ipotesi sulla quale si è esercitato un team di ricercatori di alcune università europee (guidate dall’Université Catholique de Louvain, in Belgio) e del Massachusetts Institute of Technology (Mit). Ipotesi illustrata in un articolo, pubblicato il mese scorso su Physical Review Letter, nel quale viene presentato un nuovo metodo che permette di prevedere le caratteristiche che dovrebbe avere un’onda gravitazionale se fosse generata da buchi neri che si muovono, appunto, attraverso la materia oscura anziché nello spazio vuoto. Il metodo è stato poi messo alla prova sui dati registrati dagli interferometri della Collaborazione Ligo-Virgo-Kagra (Lvk).

Gli autori dello studio hanno rappresentato la materia oscura tramite un campo scalare leggero, ipotizzando dunque che sia composta da particelle molto leggere (con una massa di circa 10⁻¹² eV) che si accumulano attorno ai buchi neri formando delle nubi. Attraverso un nuovo modello matematico semi-analitico, hanno poi calcolato come la presenza di questo campo scalare – che si comporta fluidodinamicamente – modifichi l’orbita dei buchi neri.

Considerando la particella come un’onda quantistica, quando questa si avvicina a un buco nero rotante la sua energia viene amplificata riuscendo a “rubare” momento angolare al buco nero stesso. Poiché però questo bosone ha una massa, seppur piccolissima, non riesce a sfuggire e viene tirato indietro dall’attrazione gravitazionale, creando un ciclo che si ripete. Questo evento ciclico, chiamato “instabilità superradiante”, fa sì che il campo scalare si gonfi, creando una densa zona di materia oscura che frena l’orbita dei buchi neri prima della fusione.

Applicando questo modello ai dati degli interferometri, i ricercatori hanno analizzato le onde gravitazionali relative a 28 eventi di merging – quelli con i segnali più nitidi – registrati durante le prime tre campagne di osservazione. Mentre la quasi totalità degli eventi è risultata associata a segnali compatibili con fusioni avvenute nel vuoto, l’evento catalogato come Gw 190728 ha mostrato un’anomalia sorprendente: le analisi indicano infatti che – con una probabilità superiore al 95 per cento – questa collisione non è avvenuta in uno spazio vuoto, mostrando indizi della presenza di materia oscura.

«La significatività statistica di questo risultato non è sufficientemente elevata per affermare di aver rilevato la materia oscura, occorre che gruppi indipendenti effettuino ulteriori verifiche», mette le mani avanti Josu Aurrekoetxea, ricercatore postdoc al Mit e coautore dello studio. «Ciò che riteniamo importante sottolineare è che, senza modelli di forma d’onda come il nostro, potremmo rilevare fusioni di buchi neri in ambienti di materia oscura classificandole però sistematicamente come avvenute nel vuoto».

«Ora abbiamo la possibilità di scoprire la materia oscura intorno ai buchi neri, dato che i rilevatori Lvk continueranno a raccogliere dati nei prossimi anni», aggiunge il primo autore Soumen Roy, della Uc Louvain, che ha guidato la parte di analisi dei dati del lavoro. «È un momento entusiasmante per la ricerca di nuova fisica utilizzando le onde gravitazionali».

«Sarebbe fantastico utilizzare i buchi neri per cercare la materia oscura», cocnlude il coautore Rodrigo Vicente, dell’Università di Amsterdam, che ha sviluppato il modello analitico del segnale. «Ci consentirebbe di sondare la materia oscura su scale molto più piccole rispetto a quanto fatto finora».

Per saperne di più:

• Leggi su Physical Review Letter l’articolo “Scalar fields around black hole binaries in LIGO-Virgo-KAGRA” di Soumen Roy, Rodrigo Vicente, Josu C. Aurrekoetxea, Katy Clough e Pedro G. Ferreira

 

NASA astronaut Anil Menon will be available for limited media interviews beginning at 9 a.m. EDT Monday, June 22, to discuss his upcoming mission to the International Space Station as part of Expeditions 74/75.

The virtual interviews will take place from the Gagarin Cosmonaut Training Center in Star City, Russia, and will stream live on the agency’s YouTube channel.

Media interested in participating must submit a request to the newsroom at NASA’s Johnson Space Center in Houston no later than 5 p.m. Wednesday, June 17, by emailing jsccommu@mail.nasa.gov. A copy of NASA’s media accreditation policy is online.

Menon is scheduled to launch to the space station Tuesday, July 14, from the Baikonur Cosmodrome in Kazakhstan aboard the Roscosmos Soyuz MS-29 spacecraft with Roscosmos cosmonauts Pyotr Dubrov and Anna Kikina. The trio will spend about eight months aboard the orbiting laboratory before returning to Earth in spring 2027.

During his expedition, Menon will conduct scientific investigations and technology demonstrations to help humans prepare for future exploration missions to the Moon and Mars, and to provide benefits on Earth. Among the hundreds of experiments planned during his mission, he will participate in studies to better understand astronaut vein structure, blood flow, and blood composition in microgravity. He also will test producing intravenous fluids using the space station’s potable water.

The Soyuz MS-29 mission will be his first spaceflight after he was selected as part of NASA’s 2021 astronaut class. A native of Minneapolis, Menon is an emergency medicine physician, mechanical engineer, and colonel in the United States Space Force. He also has served as an expedition flight surgeon supporting the agency’s crew members aboard the space station.

For more than 25 years, people have lived and worked continuously aboard the International Space Station, advancing scientific knowledge and making research breakthroughs not possible on Earth. The space station helps NASA understand and overcome the challenges of human spaceflight, expand commercial opportunities in low Earth orbit, and build on the foundation for long-duration missions to the Moon, as part of the Artemis program, and to Mars.

To learn more about International Space Station research, operations, and its crews, visit: 

https://www.nasa.gov/station

-end- 

Jimi Russell  
Headquarters, Washington 
202-358-1100 
james.j.russell@nasa.gov

Anna Schneider / Mary Pfister
Johnson Space Center, Houston
281-483-5111
anna.c.schneider@nasa.gov / mary.m.pfister@nasa.gov

NASA astronaut Anil Menon will be available for limited media interviews beginning at 9 a.m. EDT Monday, June 22, to discuss his upcoming mission to the International Space Station as part of Expeditions 74/75.

The virtual interviews will take place from the Gagarin Cosmonaut Training Center in Star City, Russia, and will stream live on the agency’s YouTube channel.

Media interested in participating must submit a request to the newsroom at NASA’s Johnson Space Center in Houston no later than 5 p.m. Wednesday, June 17, by emailing jsccommu@mail.nasa.gov. A copy of NASA’s media accreditation policy is online.

Menon is scheduled to launch to the space station Tuesday, July 14, from the Baikonur Cosmodrome in Kazakhstan aboard the Roscosmos Soyuz MS-29 spacecraft with Roscosmos cosmonauts Pyotr Dubrov and Anna Kikina. The trio will spend about eight months aboard the orbiting laboratory before returning to Earth in spring 2027.

During his expedition, Menon will conduct scientific investigations and technology demonstrations to help humans prepare for future exploration missions to the Moon and Mars, and to provide benefits on Earth. Among the hundreds of experiments planned during his mission, he will participate in studies to better understand astronaut vein structure, blood flow, and blood composition in microgravity. He also will test producing intravenous fluids using the space station’s potable water.

The Soyuz MS-29 mission will be his first spaceflight after he was selected as part of NASA’s 2021 astronaut class. A native of Minneapolis, Menon is an emergency medicine physician, mechanical engineer, and colonel in the United States Space Force. He also has served as an expedition flight surgeon supporting the agency’s crew members aboard the space station.

For more than 25 years, people have lived and worked continuously aboard the International Space Station, advancing scientific knowledge and making research breakthroughs not possible on Earth. The space station helps NASA understand and overcome the challenges of human spaceflight, expand commercial opportunities in low Earth orbit, and build on the foundation for long-duration missions to the Moon, as part of the Artemis program, and to Mars.

To learn more about International Space Station research, operations, and its crews, visit: 

https://www.nasa.gov/station

-end- 

Jimi Russell  
Headquarters, Washington 
202-358-1100 
james.j.russell@nasa.gov

Anna Schneider / Mary Pfister
Johnson Space Center, Houston
281-483-5111
anna.c.schneider@nasa.gov / mary.m.pfister@nasa.gov

A period of unsettled weather brought scattered showers and thunderstorms to California’s Bay Area on May 27, 2026. That afternoon, a break in the clouds left downtown San Francisco and nearby communities beneath mostly cloud-free skies, allowing an astronaut aboard the International Space Station to take this photograph.

Services Catalog

Click here to view the FY26 Services Catalog

The catalogs provide service description, chargeback rate, unit of measure, and service level indicators for each NSSC service.

Service Level Agreement (SLA)

Click here to view the Service Level Agreement

The SLA provides information about roles, responsibilities, rates, and service level indicators for all NASA Centers. The SLA is negotiated on an annual basis in line with the fiscal year. A single SLA is shared by all NASA Centers and signed by the Associate Administrator, Chief Financial Officer, Chief Information Officer, and the Office of Inspector General. The SLA provides for the delivery of specific services from the NSSC to NASA Centers and Headquarters Operations in the areas of:

• Financial Management
• Procurement
• Human Resources
• Information Technology
• Agency Business Services

NSSC Bill (Formerly know as Performance and Utilization Report (PUR))

*** On-Line Course Management and Training Purchases have been realigned to the OLC &Training Purchases section of the bill in accordance with the realignment of training funds. Center Special Projects have been consolidated into one Special Projects bill with the funding Center identified for each project.***

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Sembra che in un angolino vicino al centro della nostra galassia potrebbe esserci un resto di supernova mai visto prima che, se confermato, sarebbe uno dei più vicini al buco nero supermassiccio al centro della Via Lattea, una regione estremamente affollata di stelle, lunghi filamenti radio e dense nubi di gas che orbitano rapidamente intorno al centro galattico.

Le prove dell’esistenza di questo resto di supernova, a circa 26mila anni luce dalla Terra, provengono dai dati X di Chandra e di Xmm-Newton dell’Esa, che rivelano una “chiazza” di emissione X che potrebbe essere riconducibile ai resti di una stella massiccia esplosa come supernova, sepolta all’interno di una più grande nube di gas in espansione.

La nuova immagine composita include raggi X da Chandra e Xmm-Newton (in blu) e dati radio dal telescopio MeerKat (in rosso) in Sudafrica, combinati con un’immagine ottica dai telescopi Pan-Starrs alle Hawaii (rosso, verde e blu). Il piano della galassia scorre orizzontalmente da sinistra a destra, e il buco nero centrale si trova a sinistra dell’immagine. Il candidato resto di supernova si trova in una bolla di gas in cui gli elettroni sono stati strappati dall’idrogeno – una cosiddetta regione H II – che circonda una stella giovane e massiccia. Questa bolla è una brillante sorgente radio, chiamata Sagittarius C (Sgr C). Se si trattasse davvero di un resto di supernova, si espanderebbe a circa 3 milioni di chilometri all’ora e avrebbe almeno 1.700 anni.

In precedenza, osservazioni con Sofia della Nasa, ora dismessa, avevano mostrato evidenze di un guscio di gas in espansione attorno a Sgr C, suggerendo che nello stesso punto fosse avvenuta un’esplosione stellare. I lunghi filamenti visibili nell’immagine radio sono causati da particelle energetiche che viaggiano lungo campi magnetici orientati prevalentemente perpendicolarmente al piano della galassia.

I nuclei delle stelle, dove avvengono le fusioni nucleari, creano elementi più pesanti, a partire dall’idrogeno e dall’elio che erano abbondanti agli albori dell’universo. Quando, al termine della loro vita, le stelle massicce esplodono come supernove , diffondono nello spazio interstellare gli elementi sintetizzati, fornendo il materiale per la generazione successiva di stelle e pianeti.

Il gruppo di astronomi – di cui fa parte anche Gabriele Ponti dell’Inaf di Brera – ha cercato nei dati X segnali di un aumento di specifici elementi chiave nel resto, che potrebbero essere stati prodotti dall’esplosione stellare. Non averli rilevati potrebbe indicare che i detriti stellari si sono già mescolati al gas circostante. Oppure, un’ipotesi alternativa potrebbe essere che la “chiazza” di raggi X provenga da un insieme di stelle massicce nella regione. Gli autori dello studio, però, non sono propensi a favorire questa interpretazione, poiché l’emissione X è oltre dieci volte più luminosa di quella di grandi ammassi stellari noti, inclusi quelli con stelle brillanti e massive.

Un’ulteriore immagine pubblicata la scorsa settimana dalla Nasa mostra i dati del Telescopio Spaziale James Webb aggiunti ai dati X e radio. Il colore azzurro rappresenta la luce infrarossa proveniente dal gas nella regione H II, mentre il blu più scuro indica i raggi X del candidato resto di supernova, visibile nella parte destra dell’immagine. I raggi X vicino al centro dell’immagine sono invece associati alla regione H II, probabilmente causati da materiale soffiato via da stelle massicce che ha riscaldato il gas a milioni di gradi, producendo emissione X.

«Quando si pensa al centro della Via Lattea, l’attenzione si concentra spesso sul buco nero supermassiccio Sagittarius A*», conclude Ponti. «Questo risultato ci ricorda però che anche le stelle massicce, attraverso le loro esplosioni finali, possono avere un impatto profondo sull’ambiente circostante, contribuendo a modellare il gas e, potenzialmente, ad alimentare i flussi di materia ed energia che emergono dal centro galattico».

Per saperne di più:

• Leggi su The Astrophysical Journal l’articolo “Diffuse X-Ray Emission in the Sagittarius C Complex” di Zhenlin Zhu, Mark R. Morris, Gabriele Ponti e Ping Zhou

 

Immaginate di concentrare una quantità immensa di energia in un singolo punto. I destini possibili sembrano essere solo due: o l’energia si disperde nuovamente nello spazio vuoto, oppure la gravità ha la meglio, facendola collassare in un buco nero. Ma cosa succede esattamente sulla linea di confine tra questi due scenari? A dare una risposta matematica a questo interrogativo è ora uno studio puramente teorico, condotto da ricercatori delle università di Vienna e Francoforte, pubblicato su Physical Review Letters il mese scorso.

Fino a oggi, il comportamento della materia su questo confine precario era un mistero quasi impenetrabile. Negli anni ’90, il fisico Matthew Choptuik scoprì che su questa soglia critica è come se lo spaziotempo impazzisse, creando uno stato intermedio altamente instabile. «A volte basta una causa minuscola, apparentemente insignificante, per innescare un cambiamento enorme e drammatico. Prendiamo ad esempio l’acqua liquida a zero gradi Celsius», dice Daniel Grumiller, tra gli autori del nuovo studio. «È sufficiente un cambiamento minimo perché l’acqua si congeli. A quel punto, le molecole d’acqua si dispongono spontaneamente in una struttura regolare e formano un cristallo di ghiaccio».

Il problema è che le equazioni di Einstein in quattro dimensioni sono così complesse che questo “collasso critico” poteva essere studiato solo tramite pesanti simulazioni al computer. Per aggirare l’ostacolo e trovare finalmente una soluzione analitica esatta, con carta e penna, gli autori della nuova ricerca hanno utilizzato una scorciatoia matematica tanto elegante quanto insolita: hanno imposto la condizione di energia alla soglia critica utilizzando un campo scalare privo di massa, calato in uno spaziotempo a infinite dimensioni. La necessità di usare un campo non massivo deriva dal fatto che solo così si evita di introdurre una lunghezza fissa (lunghezza d’onda Compton), preservando l’esattezza matematica della soluzione. Ma perché aggiungere dimensioni?

«Il nostro universo ha quattro dimensioni: tre spaziali e una temporale», spiega Christian Ecker, primo autore dello studio. «Ma in linea di principio, nulla ci impedisce di scrivere equazioni fisiche per un numero maggiore di dimensioni: cinque, quarantadue o persino un numero infinito». L’aver portato le dimensioni a infinito è servito per “arginare” matematicamente le onde gravitazionali. In uno spaziotempo a quattro dimensioni, infatti, le continue oscillazioni del campo tra implosione ed esplosione genererebbero turbolenze che modificherebbero il campo stesso, rendendo il calcolo impossibile.

Il risultato di questo stato critico isolato è una soluzione analitica chiamata autosimilarità discreta: un frattale concentrico che mantiene lo stesso pattern via via che si fa zoom verso il centro del collasso. Questo schema geometrico che si ripete su scale di grandezza sempre più piccole è il motivo per cui ci si riferisce a esso come a un cristallo spaziotemporale.

 

«Questo cristallo è un oggetto davvero singolare e affascinante», riprende Grumiller. «Si tratta di una sorta di stato intermedio, un punto instabile che può evolversi in due direzioni diverse. Potrebbe dissolversi di nuovo, lasciando uno spaziotempo ordinario. Ma se viene aggiunta una minuscola quantità di energia, l’evoluzione prende una piega completamente diversa: l’insignificante cristallo spaziotemporale si trasforma in un buco nero».

Siccome il pattern si ripete a scale via via più microscopiche prima che l’equilibrio si rompa, queste soluzioni dimostrano la possibilità teorica di generare buchi neri di dimensioni infinitesime.

Ovviamente le ipotesi di partenza sono delle astrazioni matematiche, ma il risultato fornisce uno strumento formidabile per sondare i limiti della relatività generale e capire come la gravità si comporti in condizioni estreme. Inoltre, questa dinamica teorica potrebbe offrire nuovi indizi sulla formazione dei buchi neri primordiali, nati dal caos dell’universo neonato.

«La nostra tecnica si è rivelata straordinariamente stabile. A seconda della precisione desiderata, possiamo migliorare sistematicamente le nostre formule ricorrendo a ulteriori metodi di approssimazione», conclude Florian Ecker. «Questo ci offre un nuovo metodo per studiare fenomeni legati ai buchi neri che in precedenza non potevano essere analizzati analiticamente».

Per saperne di più:

• Leggi su Physical Review Letter l’articolo “Analytic Discrete Self-Similar Solutions of Einstein-Klein-Gordon at Large D ” Christian Ecker, Florian Ecker e Daniel Grumiller