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Why Scientists Say the Universe is 13.8 Billion Years Old

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Why Scientists Say the Universe is 13.8 Billion Years Old

Why Scientists Say the Universe is 13.8 Billion Years Old

Key Takeaways

  • The Universe is estimated to be 13.8 billion years old, based on measurements of the cosmic microwave background, the expansion rate of the Universe, and the age of the oldest known stars.
  • Two primary methods for determining the Universe’s age involve dating the oldest objects and applying general relativity to the expanding Universe.
  • The Hubble tension, a discrepancy between different measurements of the Universe’s expansion rate, poses a challenge to the current age estimate but does not significantly alter it.
  • Cosmic inflation, a rapid expansion before the hot Big Bang, suggests that the Universe could be older than 13.8 billion years, but this remains speculative.
  • The age of the Universe is a crucial aspect of modern cosmology, providing insights into the origins and ultimate fate of the cosmos.
Why Scientists Say the Universe is 13.8 Billion Years Old
The globular cluster Messier 69 is very old. It formed when the Universe was just 5% of its current age, making it about 13 billion years old. Despite its age, it has a high metal content, with metals at 22% of what we find in our Sun. In Messier 69, the brighter stars are in the red giant phase. This means they are running out of fuel in their cores. There are also a few blue stars. These blue stars are called blue stragglers. They form from the merging of other stars. (Credit: Hubble Legacy Archive (NASA/ESA/STScI))

The Hot Big Bang Theory: The Universe’s Beginning?

The theory of the hot Big Bang suggests that the Universe had a definitive beginning, often described as “a day without a yesterday.” This idea, once controversial and mind-boggling, is now a cornerstone of modern cosmology. The concept of a beginning to the Universe aligns with some religious texts, causing skepticism among certain circles. However, from a scientific perspective, the hot Big Bang is not the absolute start of the Universe but rather the aftermath of a preceding epoch, possibly cosmic inflation.

Despite this nuance, when asked about the age of the Universe, cosmologists and astrophysicists consistently respond with “13.8 billion years.” This figure has been reached through various methods, including the analysis of the CMB and the study of distant galaxies and star clusters. But where do we start counting the Universe’s age, and what are the implications of this starting point?

Why Scientists Say the Universe is 13.8 Billion Years Old
The life cycles of stars can be understood using the color/magnitude diagram shown here. As stars get older, they leave the diagram. This helps us figure out the age of a star cluster. The oldest globular star clusters, like the very old cluster shown on the right, are over 13 billion years old. But many globular clusters also have a second, younger group of stars. This shows that these clusters had more than one period of star formation. (Credit: Richard Powell (L), R.J. Hall (R))

Measuring the Universe’s Age: Two Main Methods

There are two primary approaches to determining the age of the Universe:

  1. Dating the Oldest Objects: By measuring the age of the oldest stars or star clusters, we can establish a lower bound for the Universe’s age.
  2. Cosmic Expansion and General Relativity: By applying our understanding of general relativity and the known components of the Universe, we can calculate the time elapsed since the hot Big Bang.
Why Scientists Say the Universe is 13.8 Billion Years Old (8)
In the top panel, our modern Universe has the same properties everywhere. This includes temperature. These properties originated from a region with the same characteristics.
In the middle panel, space could have had any curvature. Inflation made the space expand so much that we can’t see any curvature today. This solves the flatness problem.
In the bottom panel, high-energy relics existed before. Inflation pushed these relics away. This solves the high-energy relic problem.
These examples show how inflation solves three major puzzles. The Big Bang alone cannot explain these puzzles. (Credit: E. Siegel/Beyond the Galaxy)

Method 1: Dating the Oldest Objects

As cosmology evolved from astronomy and physics, one of the first reliable methods for estimating the age of the Universe involved studying the oldest stars and star clusters. Globular clusters, in particular, are dense groups of stars that formed early in the Universe’s history. These clusters are invaluable for estimating the age of the Universe.

Globular clusters contain stars of varying masses, colors, and lifespans. The most massive and brightest stars exhaust their nuclear fuel quickly, leaving behind only cooler, dimmer stars. By studying these remaining stars and the absence of their massive counterparts, scientists can estimate the age of the cluster, which often exceeds 12 billion years. This method provides a lower bound for the Universe’s age, confirming that it must be at least as old as the oldest stars, around 12.5 to 13 billion years.

Method 2: Cosmic Expansion and General Relativity

The second method involves applying general relativity to the expanding Universe. The Friedmann equations, derived from Einstein’s general relativity, describe how the Universe expands over time. By inputting data such as the current expansion rate (known as the Hubble constant) and the composition of the Universe, scientists can calculate how long it has been expanding since the hot Big Bang.

Why Scientists Say the Universe is 13.8 Billion Years Old (8)
Blue and red lines show a “traditional” Big Bang scenario. In this view, everything starts at time t=0. This includes spacetime itself.
In an inflationary scenario, shown in yellow, we never reach a singularity. A singularity is a point where space is infinitely small. Instead, space just becomes very small in the past while time keeps going backward forever.
The last tiny fraction of a second, from the end of inflation, leaves its mark on our observable Universe today.
At the start of the hot Big Bang, the size of the now-observable Universe could not have been smaller than about 1 cubic meter in volume.
(Credit: E. Siegel)

The most accurate data for this calculation comes from the CMB, the remnant radiation from the Big Bang, and large-scale galaxy clustering. The Universe’s composition is primarily:

  • 68% dark energy
  • 27% dark matter
  • 4.9% normal matter
  • 0.1% neutrinos
  • 0.01% photons

Given these proportions and an expansion rate of 67 km/s/Mpc, the calculations yield an age of approximately 13.8 billion years. However, this conclusion is not without contention.

Why Scientists Say the Universe is 13.8 Billion Years Old
By looking back in time and distance from today, we can learn about how the Universe will change in the future. We do this by finding a connection between how fast the Universe is expanding and the amount of matter and energy it has. When we measure the expansion rate, we can guess how long it’s been since the hot Big Bang started.
In the late 1990s, data from exploding stars called supernovae showed something surprising. The data suggested that the Universe has a lot of dark energy, not just matter and radiation. This was a new discovery. (Credit: Saul Perlmutter/UC Berkeley)

The Hubble Tension: A Challenge to the Age of the Universe?

One of the most significant challenges to the current estimate of the Universe’s age is the so-called Hubble tension. This discrepancy arises because different methods of measuring the Hubble constant (the Universe’s expansion rate) yield slightly different values. Early Universe measurements, like those from the CMB, suggest a rate of 67 km/s/Mpc, while late-time methods, such as the cosmic distance ladder, indicate a higher rate of around 73-74 km/s/Mpc.

If the higher rate is correct, it could imply a younger Universe, possibly around 13.6 billion years. However, the relationship between the expansion rate, dark energy, and dark matter introduces complexities. A faster expansion rate would require adjusting the proportions of dark energy and dark matter, slightly lowering the Universe’s age but not drastically altering it. Even with this adjustment, the difference is marginal, reinforcing the robustness of the 13.8 billion-year estimate.

Why Scientists Say the Universe is 13.8 Billion Years Old
This graph shows the values of the Hubble constant on the left, which is the y-axis. These values best fit the data from the cosmic microwave background. The cosmic microwave background is the leftover radiation from the Big Bang. Data comes from three sources: ACT, ACT + WMAP, and Planck. A higher Hubble constant is allowed. However, this means the Universe would have more dark energy and less dark matter. (Credit: ACT Collaboration DR4)

Cosmic Milestones: When Should We Start Counting?

Another intriguing question is when to start counting the Universe’s age. The CMB, which we observe today, was emitted 380,000 years after the Big Bang when the Universe cooled enough for neutral atoms to form. But should we start counting from this point, or should we go back further to earlier milestones?

Several significant events occurred before the CMB was emitted, such as Big Bang nucleosynthesis (which took place just minutes after the Big Bang) and the formation of the cosmic neutrino background, which imprinted itself when the Universe was just one second old. These events suggest that counting should start even earlier than the CMB, although the difference is negligible in the context of 13.8 billion years.

Why Scientists Say the Universe is 13.8 Billion Years Old
A visual history of the expanding Universe shows the hot, dense state known as the Big Bang. After the Big Bang, the Universe grew and formed structures. The whole set of data, including the observations of light elements and the cosmic microwave background, points only to the Big Bang as a valid explanation for everything we see. When the Universe expands, it also cools. This cooling allows ions, neutral atoms, and eventually molecules to form. Gas clouds, stars, and finally galaxies form as a result. (Credit: NASA/CXC/M. Weiss)

The Role of Cosmic Inflation: What Came Before the Big Bang?

One of the most fascinating aspects of modern cosmology is the realization that the hot Big Bang may not have been the true beginning. Before the Big Bang, the Universe likely underwent a period of cosmic inflation, a rapid expansion driven by a high-energy state. This inflation smoothed out any irregularities and set the stage for the Big Bang.

Why Scientists Say the Universe is 13.8 Billion Years Old (8)
Inflation started from a pre-existing state. It predicts that many independent universes will form as inflation continues. Each universe will be completely separate, with more inflating space in between. One of these “bubbles,” where inflation ended, created our Universe about 13.8 billion years ago. Today, dark energy dominates our Universe. It causes space to expand very quickly. These scenarios might be related. However, we do not know how long inflation lasted before the hot Big Bang. We can only say “at least 10^-32 seconds.” (Credit: Nicolle Rager Fuller)

If cosmic inflation preceded the Big Bang, then the Universe’s true age could be even greater than 13.8 billion years. However, the duration of inflation is uncertain, and it could have lasted for an extraordinarily brief time. Thus, the age of the Universe is conventionally measured from the start of the hot Big Bang, as this is the earliest Era we can confidently describe using known physics.

The Universe’s age of 13.8 billion years is a well-supported estimate based on multiple lines of evidence. From the oldest stars to the cosmic microwave background and the expansion of space itself, all indicators converge on this figure. While there are challenges and differences, such as the Hubble tension and the role of cosmic inflation, the fundamental conclusion remains robust.

Why Scientists Say the Universe is 13.8 Billion Years Old (8)
If these three different regions of space couldn’t thermalize, share information, or transmit signals to one another, then why are they all the same temperature? Thermalize means to reach the same temperature. This is a problem with the initial conditions of the Big Bang. How could these regions all have the same temperature unless they started that way somehow? (Credit: E. Siegel/Beyond the Galaxy)

Whether the Universe’s true beginning was the hot Big Bang or an earlier inflationary phase, the age of 13.8 billion years remains a cornerstone of modern cosmology. This understanding not only informs us about the past but also provides a foundation for exploring the Universe’s future and the ultimate fate of all that exists.

#UniverseAge, #Cosmology, #BigBang, #CosmicInflation, #HubbleTension, #DarkMatter, #DarkEnergy, #GeneralRelativity, #Astrophysics, #ScienceExplained

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Space Debris Management

Black Holes and Space: Can Black Hole Mergers Reveal Hawking Radiation?

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Journey into the black hole. Space shuttle flies straight into black holes singularity with lens flare. 3D render illustration. Elements of this image were furnished by NASA. Black Holes and Space: Can Black Hole Mergers Reveal Hawking Radiation?

Black Holes and Space: Can Black Hole Mergers Reveal Hawking Radiation?

Key Takeaway

A new theory suggests that tiny black holes, called “morsel” black holes, created during the merger of larger black holes might be the key to finally detecting Hawking Radiation.

Summary

  • Hawking Radiation is a theory that black holes emit radiation over long periods of time, but it has never been observed.
  • Researchers believe that black hole mergers may create small black holes called “morsel” black holes.
  • The Hawking Radiation from these morsel black holes is predicted to be much stronger and easier to detect due to their small size.
  • This radiation would produce a specific kind of gamma ray burst with high-energy photons.
  • Existing telescopes like HAWC Gamma-ray observatory might be able to detect these gamma rays.
  • Some challenges remain, such as the morsel black holes’ environment during emission potentially affecting the radiation and limitations in our understanding of physics at high energies.
  • If detected, this Hawking Radiation could reveal new physics beyond our current knowledge.
  • The existence of these morsel black holes themselves could also be a sign of dark matter, leftover from the early universe.
This is a simulation of merging supermassive black holes. The credit goes to NASA's Goddard Space Flight Center and Scott Noble. Black Holes and Space
This is a simulation of merging supermassive black holes. The credit goes to NASA’s Goddard Space Flight Center and Scott Noble.

Black Hole Burps: Could Tiny Holes Finally Reveal Hawking Radiation?

Black holes are enigmatic giants, warping spacetime with their immense gravity and shrouding themselves in an event horizon, a point of no return for even light. One of the biggest mysteries surrounding them is Hawking Radiation, a theory proposed by Stephen Hawking in the 1970s. This theory suggests that black holes, despite their immense gravity, slowly leak energy and particles over vast stretches of time, eventually evaporating entirely.

The problem? Hawking Radiation is incredibly weak, especially for stellar-mass black holes, making it nearly impossible to detect directly. Here’s where things get interesting. A recent study published in a paper titled “Measuring Hawking Radiation from Black Hole Morsels in Astrophysical Black Hole Mergers” proposes a fascinating new way to observe this elusive phenomenon.

The study hinges on the idea of “morsel” black holes, theorized tiny black holes created during the violent mergers of larger black holes. These mergers, first predicted and then confirmed through gravitational wave detections, are incredibly energetic events. Researchers believe that these mergers might also eject a number of these morsel black holes, some as small as asteroids.

The key here is size. Because Hawking Radiation is inversely proportional to mass, these tiny black holes would emit Hawking Radiation at a much stronger rate compared to their larger counterparts. This stronger radiation is predicted to manifest as a specific kind of gamma-ray burst with high-energy photons.

The good news? Existing gamma-ray telescopes like the HAWC Gamma-ray Observatory might be powerful enough to detect these unique gamma-ray signatures. This opens up a new window for finally observing Hawking Radiation and validating a cornerstone of theoretical physics.

However, there are still challenges to overcome. The intense gravitational environment during a black hole merger could affect the Hawking Radiation emitted by the morsel black holes. Additionally, our current understanding of physics at extremely high energies might have limitations, making it difficult to precisely predict the radiation’s characteristics.

Even with these challenges, the prospect of detecting Hawking Radiation is a scientific game-changer. Not only would it confirm a major prediction by Stephen Hawking, but it could also shed light on new physics beyond our current knowledge. The study mentions that the properties of the gamma-ray bursts could reveal new forces or particles not yet accounted for in the Standard Model.

The existence of the morsel black holes themselves is also intriguing. Some researchers speculate that these tiny black holes, leftovers from the early universe with different physical conditions, could be a form of dark matter, the mysterious substance that makes up a significant portion of the universe’s mass.

The ongoing quest to understand black holes might soon yield groundbreaking discoveries, with these tiny morsel black holes playing a crucial role in unveiling the secrets of Hawking Radiation and the fundamental nature of the universe.

Sources: 

  1. CERN (European Organization for Nuclear Research): “Supersymmetry.” Available at: https://www.home.cern/science/physics/supersymmetry
  2. Department of Energy: “The Standard Model of Particle Physics.” Available at: https://www.energy.gov/science/doe-explainsthe-standard-model-particle-physics
  3. HAWC Observatory: Available at: https://www.hawc-observatory.org/
  4. Wikipedia: “Hawking radiation.” Available at: https://en.wikipedia.org/wiki/Hawking_radiation
  5. ArXiv: “Title of the paper.” Available at: https://arxiv.org/abs/2405.12880

Hastags:

#HawkingRadiation, #BlackHoles, #BlackHoleMergers, #DarkMatter, #GammaRays, #Astrophysics, #Cosmology, #UniverseToday, #MorselBlackHoles, #NewPhysics
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James Webb Space Telescope Newest Images

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James Webb Space Telescope Newest Images

James Webb Space Telescope Newest Images

Key Takeaways

  • The James Webb Space Telescope (JWST) has captured breathtaking images in 2024, showcasing the universe’s wonders.
  • These images provide insights into the early universe, stellar nurseries, and potential habitable exoplanets.
  • Webb’s advanced technology allows for unprecedented clarity and detail, enhancing our understanding of space.

View Slideshow as Thumbnail Gallery. (opens in new tab) 

Summary

  • Early Universe Observations:
    • Captured light from galaxies formed shortly after the Big Bang.
    • Provided new data on galaxy formation and evolution.
  • Stellar Nurseries:
    • Revealed intricate details of star-forming regions.
    • Showcased the life cycle of stars from birth to death.
  • Exoplanet Studies:
    • Identified atmospheres and potential biosignatures on distant planets.
    • Offered insights into the habitability of exoplanets.
  • Technological Advancements:
    • Utilized infrared capabilities for clearer and deeper space views.
    • Enhanced by adaptive optics and high-resolution spectrometry.

View Slideshow as Thumbnail Gallery. (opens in new tab) 

James Webb Space Telescope Newest Images
“Hot Gas-giant Exoplanet WASP-43 b: Temperature Maps; MIRI Low-Resolution Spectroscopy.” It shows purple to yellow temperature maps of the planet’s telescope-facing hemisphere at 4 orbital positions. A gray line with arrows pointing counterclockwise forms the orbital path around the star. The temperature scale at the lower left, labeled in °F and K, grades from purple at the left to yellow at the right. 1,000°F is purple, 1,500°F is pink, 2,000°F is orange, and 2,500°F is yellow. At 1,000 K, the color is dark pink. At 1,500 K, the color is orange-yellow.
When the planet is behind the star, labeled “Permanent Dayside,” its hemisphere is yellow in the center, grading to orange at the edges. When the planet is to the left of the star, the color grades from yellow at the right edge facing the star to purple at the left edge facing away. When the planet is in front of the star, labeled “Permanent Nightside,” it is purple slightly to the right of the center, grading to dark pink at the edges. When the planet is to the right of the star, the color grades from yellow at the left edge facing the star to purple at the right edge facing away.
Credits:
Illustration: NASA, ESA, CSA, Ralf Crawford (STScI)
Science: Taylor Bell (BAERI), Joanna Barstow (The Open University), Michael Roman (University of Leicester)

James Webb Space Telescope Newest Images: Latest Images of 2024

The James Webb Space Telescope (JWST) has provided unprecedented views of the early universe. In 2024, Webb’s latest images revealed galaxies formed a few hundred million years after the Big Bang. This has opened new avenues for understanding galaxy formation and evolution. By analyzing these ancient galaxies, scientists can infer the processes that led to the creation of the cosmos as we know it.

Table 1: Notable Early Universe Discoveries by JWST

Discovery Description
Earliest Galaxies Detection of galaxies formed within 500 million years post-Big Bang.
Galaxy Clusters Observations of galaxy clusters shedding light on dark matter distribution.
Star Formation Insights into star formation rates in the early universe.

Stellar Nurseries

Webb’s 2024 images also provided a glimpse into stellar nurseries, where stars are born. These regions, filled with gas and dust, are illuminated by the intense radiation of young stars. The telescope’s infrared capabilities allowed it to penetrate these dense clouds, unveiling the intricate processes of star formation.

Exoplanet Studies

One of the most exciting aspects of Webb’s 2024 observations is the study of exoplanets. The telescope has identified atmospheres on several distant planets, analyzing their chemical compositions. This information is crucial for assessing the habitability of these worlds.

Webb’s spectrometers have detected water vapor, methane, and other potential biosignatures. These findings are significant steps toward answering the age-old question: Are we alone in the universe?

Table 2: Key Exoplanet Discoveries by JWST

Exoplanet Atmosphere Composition Potential Habitability
Kepler-1649c Water vapor, methane High
TRAPPIST-1e Oxygen, carbon dioxide Moderate
Proxima Centauri b Nitrogen, ozone Low

Technological Advancements

The success of these observations is largely due to Webb’s advanced technology. Its infrared capabilities allow it to capture images that are beyond the reach of visible light telescopes. Additionally, adaptive optics help correct for distortions caused by Earth’s atmosphere, ensuring crystal-clear images.

Webb’s high-resolution spectrometry provides detailed chemical analyses of celestial objects. This capability is particularly useful in studying the atmospheres of exoplanets and the composition of distant galaxies.

Specific Discoveries

The Birth of Stars in the Orion Nebula

One of the most stunning images from Webb in 2024 is of the Orion Nebula, a stellar nursery located about 1,344 light-years away. This image revealed thousands of young stars in various stages of formation. The detailed view provided by Webb allowed astronomers to study the dynamics of star birth in great detail, observing how stars interact with their surroundings.

The Andromeda Galaxy

Another remarkable image captured by Webb is of the Andromeda Galaxy, our closest galactic neighbor. The clarity of the image has provided new insights into the structure and composition of this galaxy. Webb’s instruments detected star clusters, nebulae, and even hints of black holes, contributing to our understanding of galactic evolution.

Exploring Exoplanetary Atmospheres

Webb’s analysis of the exoplanet Kepler-1649c revealed an atmosphere rich in water vapor and methane, two essential ingredients for life as we know it. This discovery has fueled speculations about the potential for life on this distant world. The detailed spectral data provided by Webb allows scientists to model the planet’s climate and assess its habitability.

The Future of Space Exploration

The James Webb Space Telescope’s 2024 images are not just beautiful pictures; they are a treasure trove of data that will drive scientific research for decades. As Webb continues to observe the cosmos, it will undoubtedly make more groundbreaking discoveries. Future missions will build on Webb’s findings, using its data to plan new explorations and develop new technologies.

Webb’s discoveries not only answer existing questions but also raise new ones, driving the quest for knowledge forward. As we continue to explore the universe, the James Webb Space Telescope stands as a testament to human ingenuity and our enduring curiosity about the cosmos.

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References

  1. NASA. (2024). James Webb Space Telescope: Latest Discoveries. Retrieved from NASA.
  2. European Space Agency. (2024). Webb’s New Images. Retrieved from ESA.
  3. MIT. (2024). Exoplanet Research with Webb. Retrieved from MIT.
  4. View Slideshow as Thumbnail Gallery. (opens in new tab) 

Hashtags

#JamesWebbSpaceTelescope, #NASA, #SpaceExploration, #Astronomy, #Exoplanets, #Galaxies, #Cosmology, #Science, #SpaceTech, #OrionNebula, #AndromedaGalaxy
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Update on Solar System’s Ghost: Planet Nine

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Update on Solar System's Ghost Planet Nine

Update on Solar System’s Ghost: Planet Nine

Key Takeaway:

Scientists continue to gather evidence suggesting the existence of a mysterious ninth planet in our Solar System, dubbed Planet Nine. Recent research by astronomers Mike Brown and Konstantin Batygin, along with their colleagues, presents compelling data supporting the presence of this elusive celestial body.

Through careful simulations and analysis of Trans-Neptunian Objects (TNOs), they offer tantalizing clues about Planet Nine’s potential influence on the outer reaches of our Solar System. While the hunt for Planet Nine remains ongoing, the findings underscore the dynamic nature of scientific inquiry and the quest to unravel the mysteries of our cosmic neighborhood.

Summary:

  • Planet Nine, a hypothetical planet in the outskirts of our Solar System, was first proposed in 2016 by astronomers Mike Brown and Konstantin Batygin.
  • Evidence supporting Planet Nine’s existence stems from the clustering of orbits of Extreme Trans-Neptunian Objects (ETNOs).
  • Recent research led by Brown, Batygin, Morbidelli, and Nesvorny presents further evidence through N-body simulations of Trans-Neptunian Objects (TNOs).
  • These simulations suggest that the gravitational influence of Planet Nine could explain the unique orbits of certain TNOs.
  • While the evidence is compelling, it falls short of definitive proof, leaving room for alternative explanations such as the Galactic Tide or cluster dynamics.
  • The upcoming Vera Rubin Observatory could provide crucial data to test the existence of Planet Nine.
  • If confirmed, the nature of Planet Nine—whether it’s a remnant of the Solar System’s early days, a rogue planet, or a captured object—remains an intriguing question in astronomy.
Update on Solar System's Ghost Planet Nine
The Rubin Observatory is being constructed and was viewed by a drone in 2023. It features an 8.4-meter telescope. The construction is nearing completion, aiming for its first light in 2025. This observatory might help solve several major questions, such as whether Planet Nine exists. Image Credit: Rubin Observatory/NSF/AURA/A. Pizarro D

Update on Solar System’s Ghost: Planet Nine

Does another undetected planet languish in our Solar System’s distant reaches? Does it follow a distant orbit around the Sun in the murky world of comets and other icy objects? For some researchers, the answer is “almost certainly.”

The case for Planet Nine (P9) goes back at least as far as 2016. In that year, astronomers Mike Brown and Konstantin Batygin published evidence pointing to its existence. Along with colleagues, they’ve published other work supporting P9 since then.

“The solar system’s distant reaches exhibit a wealth of anomalous dynamical structure, hinting at the presence of a yet-undetected, massive trans-Neptunian body—Planet Nine (P9).” – Brown et al.

Update on Solar System's Ghost Planet Nine
The image from the study displays the closest approach to the Sun (perihelion distance) for particles in two scenarios: one with Planet Nine (P9) included (left) and one without P9 (right). The simulation without P9 reveals a quick drop in the number of particles as their distance to the Sun decreases. This is because Neptune’s orbit creates a significant dynamic barrier, the researchers note. Image Credit: Batygin et al. 2024.

There’s lots of evidence for the existence of P9, but none of it has reached the threshold of definitive proof. The main evidence concerns the orbits of Extreme Trans-Neptunian Objects (ETNOs). They exhibit a peculiar clustering that indicates a massive object. P9 might be shepherding these objects along on their orbits.

The names Brown and Batygin, both Caltech astronomers, come up often in regard to P9. Now, they’ve published another paper along with colleagues Alessandro Morbidelli and David Nesvorny, presenting more evidence supporting P9.

Their paper, titled “Generation of Low-Inclination, Neptune-Crossing TNOs by Planet Nine,” is published in The Astrophysical Journal Letters.

Update on Solar System's Ghost Planet Nine
The panels show the evolution of selected particles. These particles achieve nearly flat (i < 40°) orbits that cross Neptune’s path in the last 500 million years of the study. The researchers state, “Collectively, these examples indicate that P9-facilitated dynamics can naturally produce objects similar to those depicted in Figure 1.” The panels are organized as follows: the top panel shows the semimajor axis over time, the middle panel shows the perihelion distance, and the bottom panel shows the inclination. The rate at which the particles’ paths change unpredictably increases when they start crossing Neptune’s orbit. Image Credit: Batygin et al. 2024.

To dig deeper into the issue, Batygin, Brown, Morbidelli, and Nesvorny examined Trans-Neptunian Objects (TNOs) with more conventional orbits. They carried out N-body simulations of these objects that included everything from the tug of giant planets and the Galactic Tide to passing stars.

The researchers’ goal was to analyze these objects’ origins and determine if they could be used as a probe for P9. To accomplish this, they conducted two separate sets of simulations: one with P9 in the Solar System and one without.

Update on Solar System's Ghost Planet Nine
This image from Batygin et al. 2024 displays 17 planets. It illustrates their orbits, perihelions, and semi-major axes. It also shows the inclination of each planet. Image Credit: Batygin et al. 2024.

These simulations yielded interesting results. They showed that the presence of P9 could indeed explain the observed orbital dynamics of certain TNOs. The simulations began at t=300 million years, meaning 300 million years into the Solar System’s existence. At that time, “intrinsic dynamical evolution in the outer solar system is still in its infancy,” the authors explain, while enough time has passed for the Solar System’s birth cluster of stars to disperse and for the giant planets to have largely concluded their migrations.

An important result of this work is that it results in falsifiable predictions. And we may not have to wait long for the results to be tested.

“Excitingly, the dynamics described here, along with all other lines of evidence for P9, will soon face a rigorous test with the operational commencement of the VRO (Vera Rubin Observatory).” – Brown et al.

Update on Solar System's Ghost Planet Nine
This orbital diagram features Planet Nine, shown in lime green and labeled “P9.” It also includes several extreme trans-Neptunian objects. The background is divided into squares, each measuring 100 AU across. Image credit: Tomruen – Own work, CC BY-SA 4.0, available at https://commons.wikimedia.org/w/index.php?curid=68955415

If P9 is real, what is it? It could be the core of a giant planet ejected during the Solar System’s early days. It could be a rogue planet that drifted through interstellar space until being caught up in our Solar System’s gravitational milieu. Or it could be a planet that formed on a distant orbit, and a passing star shepherded it into its eccentric orbit.

But the big question dominates for now and likely will for a while longer: Is there a Planet Nine?

Hashtags:

#PlanetNine, #Astronomy, #Cosmology, #SpaceExploration, #ScientificInquiry

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How Many Stars Exist in the Universe?

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How Many Stars Exist in the Universe?

How Many Stars Exist in the Universe?

Key Takeaway

The Universe contains an astonishingly large number of stars, estimated to be between 10^22 to 10^24 stars, gathered into billions of galaxies, with our Milky Way galaxy alone containing about 100 billion stars. Attempting to count the stars in the universe has been likened to trying to count the grains of sand on a beach on Earth. Just as we might estimate the number of sand grains by measuring the surface area and depth of the beach, astronomers employ ingenious methods to approximate the number of stars.

Summary

  • The number of stars in the Universe has been a subject of fascination for scientists, philosophers, and dreamers throughout history.
  • With the naked eye, a few thousand stars are visible on a clear night, but even modest telescopes reveal millions more.
  • Stars are not scattered randomly but are grouped into vast galaxies, with our Milky Way galaxy alone estimated to contain about 100 billion stars.
  • There are millions upon millions of other galaxies in the Universe, each containing billions of stars.
  • A rough estimate suggests there could be between 10^22 to 10^24 stars in the entire Universe, although this is an approximation as galaxies vary in size and number of stars.
  • Counting individual stars is impractical; instead, scientists measure integrated quantities like the number and luminosity of galaxies.
  • ESA’s Herschel space observatory contributed by ‘counting’ galaxies in the infrared and measuring their luminosity in this range, providing insight into star formation rates.
  • Herschel revealed that early star formation was hidden by thick dust clouds, which block visible light but emit infrared radiation, indicating more stars than previously thought.
  • The Hubble Space Telescope suggested a peak in star formation around 7 billion years ago, but infrared observations from Herschel revealed more stars forming in the early Universe.
  • The Gaia mission is studying one billion stars in the Milky Way, charting their positions, distances, movements, and brightness changes, building an unprecedented picture of our Galaxy’s structure and evolution.
  • Missions like Herschel, Hubble, Hipparcos, and Gaia are helping astronomers refine their estimates of the total number of stars in the Universe.

How Many Stars Exist in the Universe

Uncovering the Mind-Boggling Number of Stars in the Universe

When we gaze up at the night sky, the twinkling stars seem countless, yet they represent merely a fraction of what the cosmos truly harbors. For centuries, the enigma of quantifying the stars has captured the imagination of scientists, philosophers, and dreamers alike.

Imagine standing under a dark, pristine sky, away from the artificial glow of city lights. With the naked eye, you can discern a few thousand shimmering stars, each a celestial beacon in the vast expanse. However, this is merely the tip of the iceberg. Even modest amateur telescopes reveal millions more, hinting at the unimaginable vastness that awaits beyond our limited perceptions.

Stars are not scattered randomly throughout the universe; instead, they congregate into vast, gravitationally bound structures called galaxies. Our cosmic home, the Milky Way, is one such galaxy, and it alone is estimated to harbor a staggering 100 billion stars. But the Milky Way is merely a speck in the grand fabric of the universe, for it is accompanied by millions upon millions of other galaxies, each a colossal metropolis of stars in its own right.

Attempting to count the stars in the universe has been likened to trying to count the grains of sand on a beach on Earth. Just as we might estimate the number of sand grains by measuring the surface area and depth of the beach, astronomers employ ingenious methods to approximate the number of stars.

By studying a representative sample of galaxies and extrapolating their star counts, scientists have arrived at a mind-boggling estimate: the universe could contain anywhere between 10^22 to 10^24 stars. This range, covering from a trillion trillion to a quadrillion trillion stars, is a testament to the sheer immensity of the cosmos and the limitations of our comprehension.

One of the challenges in accurately estimating the number of stars lies in the obscuring effects of cosmic dust. These opaque clouds, composed of gas and microscopic particles, can block the visible light emitted by stars, rendering them invisible to telescopes operating in the optical wavelengths.

Enter the Herschel Space Observatory, a pioneering infrared telescope launched by the European Space Agency (ESA). By observing in the infrared spectrum, Herschel could peer through the veil of cosmic dust, unveiling a hidden universe of stars that had remained elusive to previous telescopes.

Herschel’s groundbreaking observations revealed that early star formation was more prolific than previously thought, with thick dust clouds obscuring much of the stellar activity in the universe’s younger epochs. This newfound insight challenged the notion that star formation peaked around 7 billion years ago, as suggested by the iconic Hubble Deep Field image.

While space telescopes like Herschel and Hubble have expanded our understanding of the universe’s stellar populations, the Gaia mission focuses its gaze closer to home, studying one billion stars within our galactic neighborhood, the Milky Way.

Launched in 2013, Gaia is meticulously charting the positions, distances, movements, and brightness changes of these stars, building an unprecedented map of our galaxy’s structure and evolution. By precisely tracking each of its one billion target stars multiple times during its mission, Gaia is providing astronomers with invaluable data to unravel the mysteries of our cosmic home and refine our estimates of its stellar inhabitants.

As we stand on the shoulders of these groundbreaking space missions, we inch closer to answering the age-old question: “How many stars are there in the universe?” Yet, with each new discovery, the cosmos reveals itself to be more vast, more complex, and more awe-inspiring than we ever imagined.

The astonishing estimates of stars in the universe not only challenge our comprehension but also ignite a sense of wonder and humility within us. We are but tiny specks in a cosmos teeming with uncountable celestial beacons, each a potential harbinger of life, and each a testament to the greatness and majesty of the universe we call home.

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#astronomy, #universe, #stars, #galaxies, #cosmology, #space, #science, #exploration, #wonders, #vastness, #MilkyWay, #Herschel, #Hubble, #Gaia, #HubbleDeepField #How Many Stars Exist in the Universe?

Source: ESA – European Space Agency Link: Read more

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Why We Should Consider a Gravitational Wave Observatory on the Moon

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Why We Should Consider a Gravitational Wave Observatory on the Moon

Why We Should Consider a Gravitational Wave Observatory on the Moon

Key Takeaway

The Lunar Gravitational Wave Antenna (LGWA), a proposed gravitational wave observatory on the Moon, could revolutionize our understanding of the universe by detecting gravitational waves in a frequency range that is currently inaccessible, owing to the Moon’s unique environment of seismic silence and extreme temperatures.

Summary

  • The LGWA aims to detect gravitational waves in the frequency range of 1 mHz to 1 Hz, bridging the gap between space-borne detectors like LISA and future terrestrial detectors like Einstein Telescope or Cosmic Explorer.
  • The Moon’s extremely low seismic activity and permanently shadowed regions (PSRs) with extreme cold temperatures make it an ideal location for the LGWA, enabling highly sensitive detections free from Earth’s seismic noise.
  • The LGWA would consist of four detectors placed in a PSR crater at one of the lunar poles, taking advantage of the Moon’s unique conditions.
  • The LGWA could advance our understanding of various cosmic events, including white dwarf tidal disruption events, Type Ia supernovae, intermediate-mass black hole binaries in the early universe, and double white dwarf mergers outside our galaxy.
  • It would provide early warnings of solar mass compact binary mergers, including neutron stars, weeks or months in advance.
  • The LGWA could help measure the Hubble Constant more accurately by observing double white dwarf mergers outside our galaxy.
  • Its seismic observations would reveal the Moon’s internal structure and geological processes in unprecedented detail, shedding light on its formation, history, and evolution.
  • The Soundcheck mission, selected by ESA in 2023, will conduct preliminary investigations and technology demonstrations for the LGWA, including seismic measurements, magnetic fluctuations, and temperature monitoring.
  • While gravitational wave science is still in its infancy, the LGWA holds immense potential for unexpected and fundamental discoveries in astrophysics and cosmology, ushering in a new era of multi-messenger astronomy.
Why We Should Consider a Gravitational Wave Observatory on the Moon
This diagram represents a detector from LGWA. It’s located on the surface within a lunar PSR (Permanently Shadowed Region).

Why We Should Consider a Gravitational Wave Observatory on the Moon

Gravitational waves, the ripples in the fabric of spacetime predicted by Einstein’s theory of general relativity, have opened up a new window into the cosmos. Since their first detection in 2015, scientists have been eager to develop more advanced detectors to unlock the secrets of the universe. However, Earth-based observatories face limitations due to seismic noise and atmospheric disturbances. Enter the Lunar Gravitational Wave Antenna (LGWA), a bold proposal to establish a gravitational wave observatory on the Moon, where the unique environment could provide unparalleled sensitivity and a new frontier for cosmic exploration.

One of the key advantages of the Moon as a host for the LGWA is its extremely low seismic activity. Unlike Earth, which experiences constant tectonic movements and seismic vibrations, the Moon’s seismic activity is primarily driven by tidal forces and occasional meteorite impacts. This seismic silence translates into an exceptionally quiet environment, free from the noise that plagues terrestrial observatories, enabling the LGWA to detect fainter gravitational wave signals with unprecedented precision.

In addition to its seismic tranquility, the Moon’s permanently shadowed regions (PSRs) offer another unique advantage for the LGWA. These craters, located near the lunar poles, experience temperatures as low as -233°C (-388°F), providing ideal conditions for the super-cooled detectors required to sense the minute distortions caused by gravitational waves. By combining the seismic silence and extreme cold, the LGWA could achieve unparalleled sensitivity, unlocking a new frequency range of gravitational waves that has been inaccessible to current observatories.

The scientific possibilities offered by the LGWA (Low-Frequency Gravitational Wave Antenna) are extensive and diverse. Operating within a frequency range of 1 millihertz to 1 hertz, this observatory would fill the gap between space-based detectors like LISA and upcoming ground-based detectors such as the Einstein Telescope or Cosmic Explorer. From this distinct perspective, researchers could explore fresh avenues for investigating various cosmic phenomena, including:

  1. White Dwarf Tidal Disruption Events and Type Ia Supernovae: The LGWA could provide invaluable insights into these cataclysmic events, which play a crucial role in our understanding of stellar evolution and the expansion of the universe.
  2. Intermediate-Mass Black Hole Binaries in the Early Universe: By detecting the mergers of these elusive objects, the LGWA could shed light on the formation and evolution of the supermassive black holes that reside at the heart of most galaxies.
  3. Double White Dwarf Mergers Outside Our Galaxy: Observing these events could help refine our measurements of the Hubble Constant, a fundamental parameter in cosmology that has been the subject of ongoing debate and discrepancies.
  4. Early Warnings of Compact Binary Mergers: The LGWA’s unique capabilities could provide advance notice of weeks or even months before the merger of solar-mass compact binaries, including neutron stars, enabling coordinated multi-messenger observations with other telescopes across the electromagnetic spectrum.

Beyond its astronomical revelations, the LGWA’s seismic observations could also unveil unprecedented insights into the Moon itself. By monitoring the lunar seismic activity with unparalleled sensitivity, the observatory could shed light on the Moon’s internal structure, geological processes, and formation history, filling gaps in our understanding of our celestial neighbor.

Before the LGWA can become a reality, however, crucial preparatory work is underway. In 2023, the European Space Agency (ESA) selected the Soundcheck mission as part of its Reserve Pool of Science Activities for the Moon. Soundcheck will not only measure seismic surface displacement, magnetic fluctuations, and temperature but also serve as a technology demonstration mission, validating the deployment, mechanics, thermal management, and leveling systems essential for the LGWA’s success.

As gravitational wave science continues to evolve, the LGWA represents a significant step towards a new era of multi-messenger astronomy. By combining the observations from gravitational wave detectors, electromagnetic telescopes, neutrino detectors, and cosmic ray observatories, scientists could gain unprecedented insights into the most extreme and enigmatic events in the universe.

While the exploration of the cosmos through gravitational waves is still in its infancy, the LGWA holds immense potential for unexpected and fundamental discoveries in astrophysics and cosmology. By harnessing the unique advantages of the lunar environment, this ambitious observatory could open new frontiers in our quest to unravel the mysteries of the universe and our place within it.

HASHTAGS:

#GravitationalWaves, #LunarObservatory, #Astronomy, #Astrophysics, #Cosmology, #ScienceExploration, #MultimessengerAstronomy, #BlackHoles, #SupernovaeEvents, #HubbleConstant, #ESAMissions

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