با استفاده از مطالعه‌ی جمعیت ستاره‌ای^۱ کهکشان‌ها می‌توان آن‌ها را به دو دسته‌ی کلی ستاره‌زا^۲ و غیرستاره‌زا یا خاموش^۳ طبقه‌بندی کرد. دسته‌ی اول شامل کهکشان‌هایی است که جوان و در حال ستاره‌زایی هستند و دسته‌ی دوم کهکشان‌هایی را شامل می‌شود که ستاره‌زایی در آن‌ها متوقف شده است و جمعیت ستاره‌ای پیرتری دارند. یکی از اهداف اصلی تلسکوپ فضایی جیمز وب^۴، پاسخ به یکی از چالش‌برانگیزترین سوالات در مطالعه‌ی ساختار و تحول کهکشان‌ها است: چگونگی شکل‌گیری سریع جرم کهکشان‌ها در یک بازه‌ی زمانی بسیار کوتاه، پایان یافتن ستاره‌زایی آن‌ها و قرار گرفتن آن‌ها در دسته‌ی خاموش یا غیرستاره‌زا.

بر اساس تئوری‌های موجود در زمینه‌ی تحول کهکشان‌ها پیش‌بینی می‌شود که برای مصرف تمام گاز مورد نیاز برای ستاره‌زایی به زمانی از مرتبه‌ی میلیارد سال نیاز است (هر چند عواملی مانند بادهای‌ ستاره‌ای^۵، بازخورد هسته‌ی فعال کهکشانی^۶، ادغام‌^۷ و برهم‌کنش با دیگر کهکشان‌ها می‌توانند این فرآیند را تسریع کنند). در نتیجه انتظار می‌رود با نگاه کردن به فواصل دورتر (نگاه به گذشته در زمان) شاهد تعداد کم‌تری از کهکشان‌های خاموش باشیم.

نویسندگان این مقاله با استفاده از داده‌های به دست آمده از طیف‌سنج فروسرخ نزدیک تلسکوپ فضایی جیمز وب (NIRSpec) حضور یک کهکشان خاموش به نام GS-9209 با جرم ستاره‌ای نزدیک به ۳۸ میلیون برابر جرم خورشید در انتقال به سرخ‌ ۴/۶۵۸، تنها ۱/۲۵ میلیارد سال بعد از انفجار بزرگ^۸ را گزارش می‌کنند. بر اساس مطالعات انجام شده توسط این گروه به نظر می‌رسد تمام جرم ستاره‌ای این کهکشان تنها در یک بازه‌ی زمانی ۲۰۰ میلیون ساله، قبل از به پایان رسیدن فعالیت ستاره‌زایی در انتقال به سرخ ۶/۵ معادل با زمانی که عمر کیهان تنها ۸۰۰ میلیون سال بوده‌است، تشکیل شده باشد.

در این مقاله، نویسندگان خطوط جذبی طیف کهکشان GS-9209 را مطالعه کرده‌اند. بررسی خطوط جذبی طیف‌ کهکشان‌ها، یکی از روش‌های مطالعه‌ی تاریخچه‌ی خاموشی کهکشان‌های ستاره‌زا است. تصویر۱ طیف کهکشان GS-9209 را که توسط تلسکوپ فضایی جیمز وب رصد شده‌است، نشان می‌دهد. این طیف در بازه‌ی طول موجی۵/۱ -۱/۷میکرومتر قرار دارد که شامل تعداد زیادی خطوط جذبی بالمر^۹ (خط جذبی حاصل از گذار الکترون از تراز۲ به ترازهای بالاتر) است. طیف به دست آمده از این کهکشان خاموش با حضور این خطوط جذبی بالمر شباهت بسیار زیادی به طیف ستارگان نوع A داشته که با استفاده از آن‌ها می‌توان تحولات ستاره‌زایی را در طول زمانی از مرتبه‌ی حدود ۱۰۰ میلیون سال بررسی کرد. به بیان ساده‌تر، این ستارگان اطلاعات مربوط به تغییرات ستاره‌زایی در طی ۱۰۰ میلیون سال اخیر را در بر دارند. حضور این جمعیت ستاره‌ای یادآور کهکشان‌های پساستاره‌زا^۱۰ در انتقال به سرخ‌های پایین‌تر و نشان‌دهنده‌ی پایان ستاره‌زایی در یک بازه‌ی کوتاه، در حدود طول عمر ستارگان نوع A بر روی رشته‌ی اصلی است. نویسندگان این مقاله برای تعیین عمق هر کدام از این خطوط جذبی پهنای-هم‌عرض^۱۱ این خطوط را گزارش می‌کنند (پهنای-هم‌عرض معیاری است که شدت یک خط جذبی را توصیف می‌کند). مطالعه‌ی پهنای-هم‌عرض خطوط مشاهده شده‌ی جذبی سری بالمر و پهن‌شدگی نسبی خط نشری نیتروژن-۲ نسبت به خط نشری پهن شده‌‌ی هیدروژن-آلفا (حاصل از گذار الکترون برانگیخته از تراز ۳ به ۲) به ترتیب نمایان‌گر غالب بودن جمعیت‌ ستاره‌ای در پیوستار و حضور هسته‌ی فعال کهکشانی است.

شکل ۱. طیف گرفته‌شده از GS-9209 با استفاده از طیف‌سنج تلسکوپ فضایی جیمز وب در ناحیه‌ی فروسرخ نزدیک. خط سیاه مدل‌ به دست آمده از کد Bagpipes برای برازش بر روی خطوط جذبی و نشری موجود در طیف را نمایش می‌دهد. این کد با بهره‌گیری از آمار بیز و همچنین در برداشتن فرضیات گسترده در مورد تاریخچه‌ی ستاره‌زایی برای مدل سازی طیف کهکشان‌ها استفاده می‌شود.

شکل ۲. نرخ ستاره‌زایی کهکشان GS-9209 بر اساس تابعی از زمان. طبق این نمودار، کهکشان GS-9209، عمده‌ی جمعیت ستاره‌ای خود را طی یک بازه‌ی زمانی ۲۰۰ میلیون ساله، از حدود ۶۰۰ تا ۸۰۰ میلیون سال پس از انفجار بزرگ شکل داده‌است.

مطالعات خط نشری پهن شده‌ی هیدروژن-آلفا و نیتروژن-۲ بر روی طیف کهکشان GS-9209 نشان می‌دهد که این کهکشان دربردارنده‌ی یک ابرسیاه‌چاله‌^۱۲ با جرمی ۴-۵ برابر جرم قابل انتظار برای کهکشان‌هایی با جرم ستاره‌ای مشابه GS-9209 است. بر اساس نتایج به دست آمده از بررسی تاریخچه‌ی ستاره‌زایی در این کهکشان، میانگین نرخ ستاره‌زایی این کهکشان در ۱۰۰ میلیون سال گذشته تقریبا برابر با صفر است و این کهکشان را در دسته‌بندی غیرستاره‌زا قرار می‌دهد. بررسی بیش‌تر بر روی پیشینه‌ی فعالیت این ابرسیاه‌چاله‌، بازخورد فعالیت‌های ناشی از هسته‌ی فعال کهکشانی را یکی از دلایل احتمالی برای توقف ستاره‌زایی در این کهکشان می‌داند. هسته‌ی فعال کهکشانی باعث گرمایش گاز سرد (سوخت اصلی ستاره‌زایی) شده و کهکشان‌ها را از حالت فعال ستاره‌زایی به حالت غیرفعال تبدیل می‌کند. GS-9209 یک نمونه‌ی جالب توجه است که نشان می‌دهد تشکیل ساختارهای عظیمی مانند کهکشان‌ها، در همان یک میلیارد سال اولیه‌ی عالم و خاموشی ستاره‌زایی حداکثر تا ۸۰۰ میلیون سال بعد از انفجار بزرگ به خوبی صورت گرفته‌است.

While it did not recreate the historic Super Heavy booster catch it pulled off last time, SpaceX continued to push the envelope during the sixth test flight of its Starship spacecraft. The largest and most powerful rocket ever built lifted off from SpaceX’s Starbase launchpad in Texas on Tuesday evening, Super Heavy’s 33 Raptor engines creating aContinue reading "SpaceX Starship Flight 6: No booster catch, but still pushing the envelope"

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Not so far from Earth, an infant planet is just getting its start at life. And by peeking beneath the thick cocoon of material surrounding it, astronomers could be getting a rare chance to watch a world for which our solar system has no equivalent settle into its early life. The planet closely orbits theContinue reading "This young, shrouded super-Neptune could help teach us how such planets form"

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Author(s): Carlos Mejuto-Zaera

A new framework that embeds electrons in a surrounding bath captures nonlocal correlation effects that are relevant to metals, semiconductors, and correlated insulators.

[Physics 17, 164] Published Wed Nov 20, 2024

Author(s): Ryan Wilkinson

Contrary to conventional wisdom, a lattice of engineered nanoparticles called meta-atoms can have a chiral optical response even when each meta-atom is not chiral.

[Physics 17, s135] Published Wed Nov 20, 2024

In October, The Wall Street Journal reported that Boeing may shed its space business to focus on commercial aircraft and defense systems. This could be due in part to this summer’s test flight of its Starliner crew transport to the International Space Station (ISS), which adversely reshaped public opinion of the beleaguered aerospace titan. ButContinue reading "The past, present, and future of Boeing in space"

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Jeff Schilling from Houston, Texas The dark nebulae LDN 935/6 contrast with billowing clouds of bright emission from the North America Nebula (NGC 7000). For this close-up study of light and dark in motion, the imager took 13¼ hours of exposure in Hubble-palette filters.

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The game is afoot! Astronomers may have found some of the universe’s missing matter, thanks to one team’s cosmic detective work. The case has been open for more than 20 years. In the 1990s and early 2000s, scientists sleuthed out the universe’s contents using observations from the cosmic microwave background radiation and Big Bang models.Continue reading "Scientists discover significant ‘missing matter’ in the gas between galaxy clusters"

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On Saturday, Nov. 16, in Flagstaff, Arizona, the astronomy world changed a bit.  Lowell Observatory has long been a beacon of history in the cosmic universe. Here, Boston Brahmin Percival Lowell founded an institution to study the heavens from the far west in 1894. Here he famously studied Mars, an early obsession, believing it toContinue reading "Lowell Observatory celebrates a monumental renewal"

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Author(s): Charles Day

Low-frequency radio observations could allow researchers to distinguish among several dark matter models, thanks to dark matter’s influence on the early Universe.

[Physics 17, s132] Published Tue Nov 19, 2024

Author(s): Michael Schirber

The experimental confirmation of supersolid vortices opens the prospect of making and studying laboratory analogues of rotating neutron stars.

[Physics 17, 166] Published Mon Nov 18, 2024

Author(s): Benjamin Rotenberg

The identification of a new type of symmetry in statistical mechanics could help scientists derive and interpret fundamental relationships in this branch of physics.

[Physics 17, 163] Published Mon Nov 18, 2024

How big is the ellipse that our planet travels in a year around the Sun? J.J. MüdespacherMexico City, Mexico Earth’s orbit around the Sun is not circular, but an ellipse that is slightly elongated with an eccentricity of 0.017. (An eccentricity of 0 is a circle, while the dwarf planet Pluto has a relatively highContinue reading "How big is Earth’s orbit around the Sun?"

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SpaceX is targeting the sixth test flight of its Starship spacecraft and Super Heavy booster — which comprise the largest and most powerful rocket system ever built — as early as Monday. Both the rocket and booster were moved to the launch mount this week for stacking. The mission, which like previous Starship flights willContinue reading "SpaceX Starship Flight 6: What to watch for"

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Astronomer Francesco D’Eugenio wasn’t looking for a murdered galaxy.  His team set out to measure the motions of stars in a distant galaxy and to understand why they appeared so old. Similar massive galaxies in the early universe were typically bustling with new star formation, and D’Eugenio, a scientist at the Kavli Institute for CosmologyContinue reading "JWST just found a black hole starving its host galaxy to death"

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Kfir Simon, taken from Tivoli Farm, Namibia At a distance of 3,900 light-years in Norma the Square lies NGC 6164/5, also known as the Dragon’s Egg. Astronomers think the binary star at its center, HD 148937, was originally a triple system. The billowing outer shell was caused by stellar winds early in the system’s life;Continue reading "Draconic fratricide"

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Friday, November 15We’re starting out the week strong with the Moon on center stage. November’s Full Moon, also called the Beaver Moon, occurs at 4:29 P.M. EST. But there’s more to this Full Moon — it’s a Super Moon, which occurs when the Moon reaches Full near its closest point to Earth, called perigee. ItContinue reading "The Sky This Week from November 15 to 22: 2024’s last Super Moon occults the Pleiades"

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The European Space Agency’s Gaia emission has revealed two unexpected black holes orbiting stars like our own Sun. One minor problem: we’re not exactly sure how black holes like this should form. But a team of researchers might have an answer.  Astronomers can’t directly observe black holes. That’s because by definition they do not emitContinue reading "How some black holes maintain long-distance relationships"

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Author(s): Ryan Wilkinson

The observation of a previously unseen photon delay in the production of quantum light has implications for the development of quantum technologies.

[Physics 17, s130] Published Thu Nov 14, 2024

Researchers using the Low Frequency Array (LOFAR) radio telescope in Europe have discovered the second generation of Starlink satellites emit higher levels of radio waves that could pose a serious risk to radio astronomy. This issue of radio-wave emission is in addition to the sunlight that Starlink and other satellites reflect, which can be visibleContinue reading "New Starlink satellites could be 32 times brighter in radio waves than before"

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Author(s): Agnese Curatolo

A new frequency-based analysis of recordings from neurons in the brain may give insight into brain pathologies such as Parkinson’s disease.

[Physics 17, s145] Published Wed Nov 13, 2024

Black holes are the universe’s shadowy figures, with many millions of them roaming unseen in our galaxy alone. These cosmic heavyweights famously destroy anything that wanders too close, tearing stars and other objects to shreds with their immense gravitational pull.  But that may not be the end of the story for those doomed objects. AContinue reading "Could black holes create dark energy? "

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Marco Meniero taken from Poggio Pinzuti, Italy The stars pirouette around Polaris above the hills of Tuscany near Pisa in this two-panel panorama taken with a Nikon Z9 mirrorless camera and a 70mm zoom lens. The imager captured 170 exposures of 15 seconds at f/4.5 and ISO 250.

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In a 1998 research breakthrough, Saul Perlmutter of the University of California, Berkeley, and his colleagues in the Supernova Cosmology Project found the expansion rate of the universe is accelerating. Perlmutter and his team made the discovery by observing distant type Ia supernovae, whose brightnesses are well known, at different distances. His team made observationsContinue reading "What is dark energy?"

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Inside the bright but unassumingly named nebula Gum 55 lies a dark nebula — a rift of dust grains that absorb visible light — creating a swatch of darkness against the glow of bright gas. Fittingly named for its shape, the Dark Wolf Nebula is no mere puppy — it spans an area some fourContinue reading "ESO captures Dark Wolf Nebula stalking across the Milky Way "

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Author(s): Marric Stephens

Researchers have characterized the naturally occurring background radiation hitting a typical quantum circuit—a result that might help with the engineering of devices that are less vulnerable to radiation-induced decoherence.

[Physics 17, s140] Published Tue Nov 12, 2024

Star struck Wisconsin Historical Society PressMadison, WI In Chasing the Stars, authors Kelly Tyrell and James Lattis discuss the astronomical achievements of Washburn Observatory at the University of Wisconsin. The book’s 256 pages feature many images and details the early days of stargazing in the region, as well as Washburn’s many modern discoveries in theContinue reading "New astronomy products to be thankful for"

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Lynn Hilborn from Grafton, Ontario The origin of the reflection nebula van den Bergh 9 in Cassiopeia is the Cepheid variable star SU Cas; its blue light is reflected by surrounding dust, which are themselves partially shrouded by thicker dust clouds. This image represents 5 hours of exposure on an 8-inch scope in RGB filters.

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In this episode, Dave Eicher invites you to observe the what happens when our planet, during its journey around the Sun, runs into a stream of particles in its orbit. Such an event is called a meteor shower, and because the streaks of light from these meteors seem to all come from a point in theContinue reading "The Leonid meteor shower: This Week in Astronomy with Dave Eicher"

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What is the universe expanding into? Euan TobinEdinburgh, Scotland This excellent question forces us to confront a region beyond the bounds of our intuition, so please bear with me. When you inflate a balloon, the balloon’s membrane moves outward, closer to the boundaries of whatever room encloses it. You can easily visualize this expansion becauseContinue reading "What is the universe expanding into?"

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Mars is tantalizingly similar to Earth in many ways, but especially in its surface features, which often resemble Earth deserts to an eerie degree. Both Earth and Mars share features such as valleys; canyons; fanlike washes of sand and rock; and long, winding gravel ridges called eskers. All are formed by flowing water, marking theContinue reading "How carbon dioxide glaciers gave Mars liquid water"

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Author(s): Michael Schirber

A theoretical model shows that exchange of information plays a key role in the molecular machines found in biological cells.

[Physics 17, 162] Published Fri Nov 08, 2024

Roughly every 15 years, Earth passes through the plane of Saturn’s rings, causing them to nearly disappear from view — not to mention generating a variety of other interesting phenomena. The next such edge-on appearance will be in March 2025, though Saturn will unfortunately be too close to the Sun (only 9.5° away) for usContinue reading "How to see a Saturn ring mirage"

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The sixth test flight of Starship — the largest and most powerful rocket to ever fly — will launch no earlier than 5 p.m. EST on Monday, November 18, SpaceX said Wednesday. The previous test flight of Starship, which SpaceX also refers to simply as “Ship,” and the Super Heavy booster resulted in the unprecedented catchContinue reading "SpaceX: Starship Flight 6 coming later this month"

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Friday, November 8Although the constellation Perseus is perhaps best known for housing the famous Double Cluster, it’s also home to another open star cluster: M34, one of the Hero’s two Messier objects.  M34 is some 180 million years old and sits 1,400 light-years from Earth. The cluster contains about 100 stars and takes up roughlyContinue reading "The Sky This Week from November 8 to 15: Catch the Leonids early"

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Author(s): Matteo Rini

Two dark matter searches report that their detectors have likely recorded neutrinos coming from the Sun—spotting the “neutrino fog” that could imperil future dark matter searches.

[Physics 17, 161] Published Thu Nov 07, 2024

Author(s): Charles Day

Crystals that have both a particular structure and a particular combination of electronic orbitals can be simultaneously ferromagnetic and ferroelectric.

[Physics 17, s131] Published Thu Nov 07, 2024

Many constellations are well-known for having one very special deep-sky object within their borders, something so famous that when you read or hear that constellation’s name, you instantly think of it, like an astronomical word association game. Orion? The Orion Nebula! Andromeda? The Andromeda Galaxy, of course! Lyra? Easy — the Ring Nebula. And Perseus?Continue reading "Five ‘shy,’ lesser-known deep-sky gems to observe"

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