WEBVTT

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<v Speaker 1>Welcome to Bedtime Astronomy. Explore the wonders of the cosmos

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<v Speaker 1>with our soothing Bedtime Astronomy podcast. Each episode offers a

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<v Speaker 1>gentle journey through the stars, planets, and beyond, perfect for

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<v Speaker 1>unwinding after a long day. Let's travel through the mysteries

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<v Speaker 1>of the universe as you drift off into a peaceful

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<v Speaker 1>slumber under the night sky. This week in Astronomy, black

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<v Speaker 1>hole jets, giant molecular cloud and protoplanetary discs. Unveiling black

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<v Speaker 1>hole jets. The study of relativistic jets originating from supermassive

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<v Speaker 1>black holes is a crucial aspect of astrophysics, as these

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<v Speaker 1>jets play a significant role in shaping their surrounding environments.

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<v Speaker 1>An international team of researchers took a major step in

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<v Speaker 1>this direction by utilizing multi wave length observations of active

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<v Speaker 1>galactic nuclei to explore how black holes launched these powerful jets.

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<v Speaker 1>Sixteen sources were observed with the event Horizon telescope during

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<v Speaker 1>its first observational campaign in twenty seventeen, providing an unprecedented

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<v Speaker 1>opportunity to study jets closer to the black holes than

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<v Speaker 1>ever before. The Event Horizon telescope, an array of globally

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<v Speaker 1>distributed radio telescopes achieves extreme angular resolution by combining signals

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<v Speaker 1>from different locations, effectively forming a telescope the size of Earth.

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<v Speaker 1>This level of detail allows scientists to investigate the mechanisms

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<v Speaker 1>that accelerate and magnetize jets as they emerge from the

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<v Speaker 1>immediate vicinity of supermassive black holes. The research team, led

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<v Speaker 1>by scientists from the Max Planck Institute for Radio Astronomy

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<v Speaker 1>in Bond, Germany in the Institute of Astrophism Physics of

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<v Speaker 1>Andalusia in Grenada, Spain, recently published their findings in the

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<v Speaker 1>journal Astronomy and Astrophysics. To test how well the current

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<v Speaker 1>theoretical models described the evolution of jets in active galaxies,

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<v Speaker 1>the researchers compared observations from the event Horizon telescope with

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<v Speaker 1>past studies conducted using the Very Long Baseline Array in

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<v Speaker 1>the Global Millimeter VLBIRA. These latter facilities operate on larger

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<v Speaker 1>spatial scales, providing a more extensive view of the jets

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<v Speaker 1>development over time. This comparative approach allowed scientists to trace

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<v Speaker 1>how the jets evolved from their origins near the black

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<v Speaker 1>hole to vast distances spanning multiple light years into interstellar space.

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<v Speaker 1>The results revealed an intriguing trend. The brightness temperature of

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<v Speaker 1>the jets, which measures the intensity of radiation emitted from

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<v Speaker 1>a given region, generally increases as the jet plasma moves

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<v Speaker 1>farther away from the black hole. This finding challenge has

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<v Speaker 1>long held assumptions about how these jets behave. Traditionally, it

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<v Speaker 1>was believed that jets follow a conical structure, with plasma

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<v Speaker 1>moving at a constant velocity, while the strength of the

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<v Speaker 1>magnetic field and the density of the jet plasma gradually

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<v Speaker 1>decrease with distance from the black hole. However, the new

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<v Speaker 1>observations suggest a more complex picture. Jets are often assumed

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<v Speaker 1>to be smooth and conical, but the research indicates that

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<v Speaker 1>this model may not accurately describe all cases. The internal

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<v Speaker 1>structure of jets appears to be intricate, with some showing

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<v Speaker 1>signs of acceleration. This could mean that either the plasma

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<v Speaker 1>itself is gaining velocity, or that an observational effect caused

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<v Speaker 1>by a bending jet makes it appear as if it

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<v Speaker 1>is moving faster than it actually is. In some cases,

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<v Speaker 1>when a jet shifts direction and aligns more closely with

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<v Speaker 1>Earth's line of sight, it can create the illusion of

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<v Speaker 1>an increase in speed. By examining a sample of sixteen

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<v Speaker 1>active galactic nuclei instead of just individual sources, the researchers

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<v Speaker 1>were able to minimize the influence of unique characteristics specific

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<v Speaker 1>to any single jet. This broader approach provided a clearer

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<v Speaker 1>picture of jet behavior, revealing that brightness tends to increase

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<v Speaker 1>with distance from the black hole, a strong indication that

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<v Speaker 1>acceleration is taking place. These findings suggest that the mechanisms

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<v Speaker 1>behind jet evolution are more dynamic than previously thought. The

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<v Speaker 1>importance of intermediate scale observations in this study was highlighted

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<v Speaker 1>by Eduardo Ross from the Max Plank Institute for Radio Astronomy,

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<v Speaker 1>who also serves as the European scheduler of the Global

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<v Speaker 1>Millimeter vl. The Global Millimeter VLBIRA, which operates at a

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<v Speaker 1>wavelength of three point five millimeters, provides critical information that

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<v Speaker 1>bridges the gap between the highest resolutions of the event

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<v Speaker 1>horizon telescope and the larger scale views of the very

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<v Speaker 1>long baseline array. This was particularly evident in observations of

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<v Speaker 1>the eight seven galaxy, which played a central role in

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<v Speaker 1>the event Horizon Telescope's first major discoveries active galactic nuclei.

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<v Speaker 1>The luminous centers of certain galaxies are powered by supermassive

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<v Speaker 1>black holes, and some of these objects generate relativistic plasma

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<v Speaker 1>jets that extend thousands of light years into intergalactic space.

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<v Speaker 1>Understanding the physics behind these jets requires observations with extreme

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<v Speaker 1>angular resolution, enabling astronomers to examine their origins in detail. Telescope,

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<v Speaker 1>operated by a global network of scientists, provides this capability.

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<v Speaker 1>In twenty seventeen, alongside its groundbreaking observations of the Milky Way,

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<v Speaker 1>Sagittarius A and eight seven S black hole, the telescope

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<v Speaker 1>also observed several active galactic nuclei to further investigate the

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<v Speaker 1>behavior of jets. To assess the reliability of existing models

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<v Speaker 1>describing jet evolution, the researchers compared the Event Horizon Telescope's

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<v Speaker 1>data with previous studies that had mapped the same sources

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<v Speaker 1>on larger spatial scales. This approach enabled them to trace

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<v Speaker 1>jet development from their launch points near the black hole

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<v Speaker 1>to the vast distances they reach an interstellar space. The

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<v Speaker 1>results indicated that as the jet plasma moves farther from

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<v Speaker 1>the black hole, its radiation power per solid angle, known

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<v Speaker 1>as brightness temperature, tends to increase. This discovery contradicts the

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<v Speaker 1>standard model of jets, which assumes a conical geometry and

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<v Speaker 1>a constant velocity for the plasma. Instead, the new observations

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<v Speaker 1>suggest that some jets exhibit acceleration, a phenomenon that may

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<v Speaker 1>be linked to the role of magnetic fields, changes in

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<v Speaker 1>jet structure, or interactions with the surrounding environment. The exact

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<v Speaker 1>nature of this acceleration remains an open question, requiring further

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<v Speaker 1>studies to fully understand the underlying mechanisms. Future research will

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<v Speaker 1>focus on refining models of jet acceleration, the flow of

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<v Speaker 1>energy within jets, and the role of magnetic fields and

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<v Speaker 1>shaping their dynamics. The ongoing expansion of the Event Horizon

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<v Speaker 1>telescope array will play a crucial role in these efforts,

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<v Speaker 1>providing even more detailed observations of these fascinating cosmic structures.

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<v Speaker 1>Jan Rotor, who led the study, emphasized that additional investigations

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<v Speaker 1>are needed to fully grasp the physics of jet formation

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<v Speaker 1>and evolution. J Antonsensis, director of the Max Planck Institute

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<v Speaker 1>for radio astronomy, and a founding chair of the Event

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<v Speaker 1>Horizon Telescope collaboration, highlighted the significance of these findings. The

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<v Speaker 1>study demonstrates the importance of international partnerships, advanced observational techniques,

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<v Speaker 1>and persistent scientific inquiry in advancing our understanding of the universe.

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<v Speaker 1>With upcoming improvements in telescope technology and the next generation

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<v Speaker 1>of observational networks, scientists will continue to explore the complexities

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<v Speaker 1>of black holed jets, uncovering new insights into one of

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<v Speaker 1>the most energetic and mysterious processes in astrophysics. Giant molecular

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<v Speaker 1>cloud found in Milky Way. Astronomers using the Green Bank

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<v Speaker 1>Telescope GBT have identified a massive new giant molecular cloud

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<v Speaker 1>GMC within the Milky Way Galaxy, expanding our understanding of

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<v Speaker 1>the interstellar medium and star formation. This newly discovered cloud

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<v Speaker 1>MAINEM four section seven to zero point eight, extends nearly

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<v Speaker 1>two hundred light years and holds an estimated mass of

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<v Speaker 1>approximately one hundred and sixty thousand times that of the Sun.

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<v Speaker 1>This finding provides valuable insight into the complex processes governing

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<v Speaker 1>the flow of matter in our galaxy. In the birth

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<v Speaker 1>of stars. Giant molecular clouds are vast reservoirs of interstellar

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<v Speaker 1>gas and dust composed primarily of molecular hydrogen. These clouds

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<v Speaker 1>are essential to the galactic ecosystem, serving as the primary

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<v Speaker 1>sites for star formation. GMCs very widely in size, typically

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<v Speaker 1>spanning between fifteen and six hundred light years, and represent

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<v Speaker 1>the densest and coldest regions of the interstellar medium. Because

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<v Speaker 1>they contain the raw material for star formation, studying their structure, movement,

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<v Speaker 1>and composition is fundamental to understanding how galaxies evolve over time.

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<v Speaker 1>The discovery of M four seven to zero point eight

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<v Speaker 1>is particularly significant because of its location within the Milky Way.

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<v Speaker 1>It resides at the midpoint of a dust lane in

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<v Speaker 1>the Galactic Bar, approximately twenty three thousand light years from Earth.

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<v Speaker 1>The dust lanes of the galactic bar play a crucial

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<v Speaker 1>role in transporting material from the outer disk of the

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<v Speaker 1>galaxy toward its center as gas flows inward, simulates in

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<v Speaker 1>dense ring like structures where star formation activity is intensified.

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<v Speaker 1>The presence of a previously unknown GMC in this region

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<v Speaker 1>suggests that the process of material accretion toward the galactic

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<v Speaker 1>center is more complex than previously thought. Observations of M

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<v Speaker 1>four seven to zero point eight have revealed important structural

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<v Speaker 1>characteristics that provide insight into its composition and activity. The

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<v Speaker 1>cloud stretches roughly one hundred and ninety five light years

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<v Speaker 1>in galactic longitude and extends about sixty five light years

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<v Speaker 1>in galactic latitude. It maintains a cold dust temperature of

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<v Speaker 1>around twenty kelvin, highlighting its relatively undisturbed state. This low

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<v Speaker 1>temperature aligns with the typical properties of GMCs, as these

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<v Speaker 1>clouds must remain cold to allow gravity to overcome thermal pressure,

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<v Speaker 1>facilitating the collapse of gas into dense star forming regions.

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<v Speaker 1>One of the most striking aspects of M four seven

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<v Speaker 1>to zero point eight is its internal structure, which exhibits

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<v Speaker 1>two primary components. The first, dubbed the nexus, corresponds to

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<v Speaker 1>the region with the brightest carbon monoxide emissions. This suggests

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<v Speaker 1>it may be the densest and most active part of

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<v Speaker 1>the cloud where gas and dust are accumulating in large quantities.

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<v Speaker 1>The second feature, melon as the filament, is an elongated,

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<v Speaker 1>narrow structure extending from the nexus. Bisfilamentary shape is a

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<v Speaker 1>common trait among star forming regions, as elongated gas streams

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<v Speaker 1>can funnel material towards sites of future star birth. Further

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<v Speaker 1>investigation of M four seven to zero point eight uncovered

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<v Speaker 1>evidence of ongoing or potential star formation. Two specific regions,

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<v Speaker 1>may not be not E were identified as possible sites

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<v Speaker 1>of early stellar development. Not E in particular, exhibits a

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<v Speaker 1>cometary like shape and dense structure, leading astronomers to hypothesize

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<v Speaker 1>that it could be a free floating, evaporating gas globule.

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<v Speaker 1>These types of structures form when intense radiation from nearby

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<v Speaker 1>young stars erode surrounding gas, sculpting the cloud into intricate forms. However,

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<v Speaker 1>additional observations are necessary to confirm this possibility and to

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<v Speaker 1>determine whether these knots will eventually give rise to new stars.

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<v Speaker 1>The observations also revealed an intriguing shell like structure within

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<v Speaker 1>M four seven to zero point eight. This feature appears

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<v Speaker 1>to have a brighter rim in ammonia emissions, with a

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<v Speaker 1>central cavity, suggesting an area where gas has been displaced.

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<v Speaker 1>Such shell like formations can arise from various astrophysical processes,

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<v Speaker 1>including the expansion of shock waves from stellar winds or

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<v Speaker 1>supernova explosions. If this structure is indeed a remnant of

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<v Speaker 1>past energetic activity, it could provide clues about the history

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<v Speaker 1>of the cloud and its role in the dynamic environment

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<v Speaker 1>of the Milky Way's central regions. The detection of M

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<v Speaker 1>four seven to zero point eight not only enriches the

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<v Speaker 1>current catalog of known GMCs, but also enhances the broader

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<v Speaker 1>understanding of how molecular clouds evolve and contribute to galactic structure.

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<v Speaker 1>By analyzing the properties of this cloud, astronomers can refine

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<v Speaker 1>existing models of interstellar matter flow and star formation within

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<v Speaker 1>bart spiral galaxies like the Milky Way. Future studies will

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<v Speaker 1>focus on further characterizing the physical and chemical condition within

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<v Speaker 1>M four section seven to zero point eight, as well

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<v Speaker 1>as searching for additional signs of active star forming regions.

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<v Speaker 1>The discovery underscores the importance of advanced radio telescopes like

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<v Speaker 1>the GBT in probing the unseen structures of our galaxy.

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<v Speaker 1>These powerful instruments enable astronomers to detect and analyze cold

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<v Speaker 1>molecular gas that would otherwise be invisible at optical wavelengths.

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<v Speaker 1>As observational techniques continue to improve, new insights into the

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<v Speaker 1>interstellar medium and the mechanisms that drive star formation will emerge,

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<v Speaker 1>deepening our knowledge of the cosmic processes that shape galaxies

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<v Speaker 1>across the universe. Small protoplanetary disks challenge previous theories. Many

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<v Speaker 1>of the protoplanetary disks where new planets form are significantly

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<v Speaker 1>smaller than previously believed. Using the Atacama Large millimeter slash

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<v Speaker 1>submillimeter Array ALMA, scientists from the Liden Observatory in the

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<v Speaker 1>Netherlands examine seventy three protoplanetary discs located in the Lupus

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<v Speaker 1>star forming region. Their observations revealed that a substantial number

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<v Speaker 1>of young stars are surrounded by relatively modest disks of

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<v Speaker 1>gas and dust, with some measuring as little as one

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<v Speaker 1>point two astronomical units in size. This research, which has

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<v Speaker 1>been accepted for publication in Astronomy and Astrophysics, provides an

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<v Speaker 1>important connection between observed protoplanetary discs and the characteristics of exoplanets.

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<v Speaker 1>Over the past decade, astronomers have used powerful radio telescopes

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<v Speaker 1>like ALMA to capture images of hundreds of protoplanetary discs

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<v Speaker 1>surrounding young stars. Many of these discs extend well beyond

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<v Speaker 1>the uns The orbit of Neptune when compared to the

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<v Speaker 1>size of our Solar system. Additionally, many of them display

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<v Speaker 1>gaps where giant planets are thought to be forming. However,

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<v Speaker 1>new research conducted by pH dot d Candidate Osmar M.

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<v Speaker 1>Geral Varado, postdoctoral researcher Marianna B. Sanchez an assistant professor

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<v Speaker 1>Nancer Vander Merrill from the Leiden Observatory suggests that these

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<v Speaker 1>large discs may not actually be representative of the typical

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<v Speaker 1>protoplanetary disc. By utilizing Alma, the researchers conducted observations of

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<v Speaker 1>all the known protoplanetary discs surrounding young stars in the

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<v Speaker 1>Lupus Region, a star forming area situated approximately four hundred

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<v Speaker 1>light years from Earth in the southern constellation of Lupus.

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<v Speaker 1>Their findings indicate that two thirds of the seventy three

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<v Speaker 1>discs studied are relatively small, with an average radius of

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<v Speaker 1>just six astronomical units, roughly equivalent to the orbit of Jupiter.

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<v Speaker 1>The smallest disk identified in the study measured only zero

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<v Speaker 1>point six astronomical units in radius, making it even smaller

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<v Speaker 1>than Earth's orbit around the Sun. These discoveries fundamentally change

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<v Speaker 1>the existing understanding of what constitutes a typical protoplanetary disc.

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<v Speaker 1>The brightest discs, which are the easiest to observe, tend

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<v Speaker 1>to exhibit large scale gaps, while compact discs without such

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<v Speaker 1>substructures are far more common. Most of the small discs

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<v Speaker 1>were found around low mass stars with masses ranging between

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<v Speaker 1>ten percent and fifty percent of the Sun's mass. This

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<v Speaker 1>type of star is the most common in the universe.

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<v Speaker 1>The observations also suggest that these compact discs may provide

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<v Speaker 1>ideal conditions for the formation of super earths, since most

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<v Speaker 1>of the dust in these systems is located close to

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<v Speaker 1>the star, precisely where super earths are frequently found. Super

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<v Speaker 1>Earths are rocky planets similar to Earth, but with masses

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<v Speaker 1>that can reach up to ten times that of our planet.

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<v Speaker 1>This could help explain why super earths are more commonly

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<v Speaker 1>detected around low mass stars. The findings also suggest that

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<v Speaker 1>the Solar System originated from a large protoplanetary disc that

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<v Speaker 1>gave rise to massive gas planets like Jupiter and Saturn,

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<v Speaker 1>but did not produce any super earths. Given that super

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<v Speaker 1>earths are thought to be the most prevalent type of

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<v Speaker 1>planet in the universe, this makes the solar system somewhat

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<v Speaker 1>unusual compared to the broader population of planetary systems. The

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<v Speaker 1>study provides a crucial missing link between the observed characteristics

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<v Speaker 1>of protoplanetary disks and the properties of known exoplanets. The

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<v Speaker 1>fact that the majority of small discs do not exhibit

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<v Speaker 1>large gaps suggests that most stars do not host giant planets.

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<v Speaker 1>This aligns with exoplanet observations of mature stars, reinforcing the

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<v Speaker 1>connection between disc populations and planetary systems. Prior high resolution

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<v Speaker 1>ALMA studies primarily focused on bright discs, which are often

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<v Speaker 1>significantly larger. In contrast, smaller discs had generally been studied

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<v Speaker 1>only in terms of their brightness, with their sizes remaining uncertain.

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<v Speaker 1>Capturing high resolution images of these fainter discs posed a challenge,

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<v Speaker 1>and it was previously unclear whether ALMA would be capable

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<v Speaker 1>of resolving them. For this research, scientists utilized ALMA observations

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<v Speaker 1>taken in twenty twenty three and twenty twenty four with

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<v Speaker 1>the highest possible resolution of zero point zero three sis

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<v Speaker 1>zero arcseconds. In addition, they incorporated archival data to compile

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<v Speaker 1>the first ever complete high resolution survey of an entire

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<v Speaker 1>star forming region. The results demonstrate that previous assumptions about

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<v Speaker 1>the typical size and structure of protoplanetary discs were incorrect.

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<v Speaker 1>Until now, studies have been heavily biased towards the brightest

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<v Speaker 1>and largest discs. By expanding the scope to include discs

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<v Speaker 1>of all sizes, a more comprehensive and accurate understanding of

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<v Speaker 1>the early stages of planet formation has finally emerged. The

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<v Speaker 1>FAM