Cosmic Teacup

Category: Astronomy & the Universe

Stars, galaxies, constellations, black holes and telescopes

  • Why build bigger and bigger telescopes, such as European Southern Observatory’s Extremely Large Telescope (ELT

    Why build bigger and bigger telescopes, such as European Southern Observatory’s Extremely Large Telescope (ELT

    by Kate Green

    October 19, 2024

    The drive to build bigger and bigger telescopes, like the ESO’s Extremely Large Telescope (ELT), stems from the desire to push the boundaries of our understanding of the universe. Larger telescopes have greater light-gathering power and higher resolution, enabling astronomers to see fainter and more distant objects in unprecedented detail.

    Here’s why bigger telescopes are essential, and how they benefit not only science but also society as a whole:

    Why Aim for Bigger Telescopes?

    1. Better Light-Gathering Power:

      • The size of a telescope’s primary mirror determines how much light it can collect. Larger telescopes, like the ELT with its 39-meter mirror, can capture light from extremely distant and faint objects that smaller telescopes cannot detect. This allows us to look further back in time, revealing the early stages of the universe, star formation, and galaxy evolution.

    2. Higher Resolution:

      • Bigger telescopes also provide higher angular resolution, which means they can discern finer details. The ELT’s adaptive optics system will correct for atmospheric distortion, enabling it to deliver images that are much sharper than those of smaller telescopes or even those taken by space-based telescopes. This clarity is vital for studying the surfaces of distant exoplanets or resolving the structure of far-off galaxies.

    3. Addressing Fundamental Questions:

      • Larger telescopes like the ELT are essential for tackling some of the most pressing questions in astronomy, such as:

        • What are the conditions for life beyond Earth?

        • How did galaxies and black holes form in the early universe?

        • What is the nature of dark matter and dark energy?

    How Does This Effort Pay Back Society?

    While the primary goal of building large telescopes is to advance our understanding of the cosmos, the societal impact of such projects goes far beyond astronomy.

    Here are some key ways this investment benefits society as a whole:

    1. Technological Innovation:

      • The engineering challenges involved in constructing and operating massive telescopes like the ELT drive the development of cutting-edge technologies. These innovations often find applications in other fields. For example:

        • Adaptive optics technology, developed for telescopes, is now used in medical imaging, such as ophthalmology, to improve the quality of retinal scans.

        • Precision engineering techniques, developed to build the telescope’s components, benefit industries such as manufacturing and aerospace.

    2. Inspiring Education and STEM Careers:

      • Large-scale scientific projects like the ELT inspire future generations of scientists, engineers, and innovators. These projects are often used as tools to promote STEM education (Science, Technology, Engineering, Mathematics), encouraging students to pursue careers in these fields. This helps develop a highly skilled workforce that drives technological advancement and economic growth.

    3. Global Collaboration and Diplomacy:

      • Telescopes like the ELT are often international projects, bringing together expertise and funding from countries around the world. This promotes global collaboration in science and fosters peaceful cooperation between nations.

    4. Economic Development in Host Regions:

      • The construction and operation of large observatories contribute to local and regional economic development. In the case of the ELT, Chile’s Atacama Desert has become a hub for astronomical research, attracting scientists, engineers, and tourists. Local economies benefit from the creation of jobs, infrastructure development, and international investment.

    5. Spinoff Technologies:

      • Many technologies developed for astronomy later find widespread applications in everyday life. For example:

        • Data analysis algorithms developed for processing astronomical data are now used in finance, healthcare, and artificial intelligence.

        • Cryogenic technologies, which are used to cool sensitive astronomical instruments, have applications in fields like superconductors and quantum computing.

    6. Cultural and Philosophical Impact:

      • Astronomy has a profound impact on how humans see their place in the universe. Discovering exoplanets, studying black holes, or learning about the early universe encourages a sense of wonder and curiosity. These discoveries also fuel philosophical discussions about life, the cosmos, and humanity’s future, enriching culture and society.

    Conclusion:

    The drive to build larger telescopes, like the ELT, is not only about making groundbreaking astronomical discoveries. It’s about pushing the limits of human knowledge, fostering innovation, and inspiring future generations. The benefits extend beyond the scientific community, impacting technology, education, global collaboration, and even the way we perceive our place in the universe. The investment in large-scale observatories ultimately pays back to society in numerous ways, both tangible and intangible.

    Image: Artist’s impression of completed Extremely Large Telescope (ELT). Credit: European Southern Observatory (ESO)

  • Protecting the ELT from Earthquakes

    by Kate Green

    October 19, 2024

    The Extremely Large Telescope (ELT) in the Atacama Desert is equipped with sophisticated anti-seismic technology to ensure that it remains stable and operational even in the event of an earthquake. Since the region is seismically active, incorporating earthquake-resistant features is critical to protecting the telescope’s delicate instruments and optics. Here’s how this clever technology works:

    1. Base Isolation System:

    One of the key technologies used is base isolation, a system designed to decouple the telescope’s structure from ground motion during an earthquake. Here’s how it works:

    • Elastomeric Bearings: Large rubber and steel bearings are placed between the foundation and the telescope structure. These bearings can deform elastically during seismic activity, absorbing the earthquake’s energy and reducing the amount of shaking transmitted to the telescope.

    • Sliding Bearings: In some systems, sliding bearings are also used, allowing the structure to move slightly relative to the ground, which further reduces the impact of ground movement on the telescope.

    2. Dampers:

    In addition to base isolation, seismic dampers are installed to absorb the energy generated during an earthquake. These are specialized devices that:

    • Dissipate Vibrational Energy: Dampers convert the vibrational energy from the earthquake into heat, reducing the amount of movement the telescope experiences.

    • Shock Absorption: These devices provide a buffering effect, protecting both the mechanical and optical components from shocks.

    3. Structural Flexibility:

    The steel structure of the telescope dome is designed with flexibility in mind, meaning it can absorb and distribute seismic forces without cracking or deforming. The use of flexible joints and materials ensures that the structure bends rather than breaks, which helps protect the telescope’s sensitive optics.

    4. Automated Safety Systems:

    To further safeguard the telescope during seismic events, automated systems are in place to detect the onset of an earthquake. These systems may:

    • Shut Down Operations: Automatically stop observations and move the telescope into a “safe” position to prevent damage to the delicate instruments.

    • Secure Instruments: Lock down movable parts to minimize internal damage.

    Why It’s Crucial:

    Seismic protection is especially important because the ELT’s optics and adaptive systems require an incredibly high degree of precision. Even slight movements or distortions caused by seismic activity could affect the alignment of mirrors or damage equipment, impacting the telescope’s ability to capture high-resolution images.

    By combining these technologies, the ELT is built to withstand the region’s seismic challenges and continue its groundbreaking observations with minimal interruption.

    Video Credit: European Southern Observatory (ESO)

  • Re-analysis of Milky Way’s central supermassive black hole shows elongated structure

    Re-analysis of Milky Way’s central supermassive black hole shows elongated structure

    by National Astronomical Observatory of Japan

    October 25, 2024

    A research team led by Assistant Professor Makoto Miyoshi of the National Astronomical Observatory of Japan (NAOJ) has independently re-analysed observation data of the supermassive black hole at the centre of the Milky Way galaxy obtained and published by the international joint observation project Event Horizon Telescope (EHT). They found that the structure is slightly elongated in the east-west direction.

    This research, published in the Monthly Notices of the Royal Astronomical Society, takes a new look at the publicly available EHT data and demonstrates the scientific process in which the certainty of the answer increases as different researchers continue to examine and discuss a theory.

    The Milky Way galaxy, in which we live, contains more than 100 billion sun-like stars. There are countless such large galaxies in the universe, most of which are thought to have supermassive black holes at their centres with masses millions to billions of times that of the sun. The Milky Way galaxy also has a supermassive black hole at its centre, called Sagittarius A* (A star).

    The black hole swallows everything, including light, making it impossible to see the supermassive black hole itself, but analysis of stars circling the black hole at high speed indicates that Sagittarius A* has a mass approximately 4 million times that of the sun. By closely observing its surroundings, we can obtain clues to the nature of the invisible black hole.

    The EHT observed Sagittarius A* in 2017 with a network of eight ground-based radio telescopes using a technique known as radio interferometry to combine the results from the various telescopes. The results of these observations were published in 2022, including an image of a bright ring structure surrounding a central dark region, indicating the presence of a black hole.

    In contrast to typical photography, data from observations linking several widely separated radio telescopes contain many gaps in the completeness, so special algorithms are used to construct an image from the data. In this research, the team applied widely used traditional methods to EHT data, as opposed to the EHT’s own original analysis method.

    Miyoshi explains, “Our image is slightly elongated in the east-west direction, and the eastern half is brighter than the western half. We think this appearance means the accretion disk surrounding the black hole is rotating.”

    The EHT’s observational data and analysis methods are freely available, and many researchers have validated the results of EHT analysis. This research is also part of these regular verification activities.

    Radio interferometry connecting telescopes across the globe is a developing technology, and research on data analysis and image processing is ongoing, incorporating knowledge from statistics and other related disciplines.

    The structures presented in this research differ from the results of the EHT team, but both are plausible structures derived from the data using the respective methods. The EHT plays an important role in black hole research by soliciting independent verification and providing open data for verification.

    It is hoped that a more reliable picture of Sagittarius A* will emerge from active discussion by researchers based on improved analysis methods and data from follow-up observations conducted since 2018.

    Journal:

    Makoto Miyoshi et al, An independent hybrid imaging of Sgr A* from the data in EHT 2017 observations, Monthly Notices of the Royal Astronomical Society (2024).

    DOI: 10.1093/mnras/stae1158

    Image:

    Final image of Sgr A* obtained from our imaging process. Credit: Monthly Notices of the Royal Astronomical Society (2024). DOI: 10.1093/mnras/stae1158

  • Scientists delving into the Origin of ‘Rogue Stars’

    Scientists delving into the Origin of ‘Rogue Stars’

    by Kate Green

    November 12, 2024

    Scientists are delving into the origin of “rogue stars”—those that wander through space, unbound by gravity to galaxies or star clusters. Although stars usually group together due to gravitational forces, these loners, known as intracluster light, were first observed in 1951 by Fritz Zwicky. However, recent research led by the Hubble Space Telescope has offered new insights into their age and origin.

    The Hubble survey studied ten galactic clusters up to 10 billion light-years away, revealing that the proportion of intracluster light remains consistent across time. This constancy suggests that these stars are ancient—likely billions of years old—rather than recently separated from galaxies by gravitational forces, or “stripping.” If stripping were the cause, scientists would expect an increase in intracluster light over time.

    The researchers theorize that these rogue stars may have formed in small, early galaxies with weaker gravitational pulls, making them susceptible to “bleeding” stars into the vastness of space. Co-author James Jee of Yonsei University notes that current theories can’t fully explain the results, but the team suspects that conditions in the early universe may have led to the widespread dispersal of these stars.

    “We don’t exactly know what made them homeless. Current theories cannot explain our results, but somehow they were produced in large quantities in the early universe,” James Jee, an astronomer at Yonsei University in South Korea and co-author on the new research, said in a statement. “In their early formative years, galaxies might have been pretty small and they bled stars pretty easily because of a weaker gravitational grasp.”

    “If we figure out the origin of intracluster stars, it will help us understand the assembly history of an entire galaxy cluster, and they can serve as visible tracers of dark matter enveloping the cluster,” co-author Hyungjin Joo, also of Yonsei University, said in the same statement.

    The Hubble and James Webb Space Telescopes will continue to investigate these stars, potentially uncovering clues about dark matter—the mysterious force believed to bind galaxies together. By understanding how these wandering stars were created, scientists might reveal the formation history of entire galaxy clusters and gain insight into the dark matter that surrounds them.

    The team’s findings were published on January 04, 2023 in Nature.

    Journal:

    Joo, H., & Jee, M. J. (2023). Intracluster light is already abundant at redshift beyond unity. Nature, 613(7942), 37-41. https://arxiv.org/pdf/2301.01523 

    Image:

    Two panels show blueish glow around stars (Image credit: NASA, ESA, STScI, James Jee (Yonsei University)/IMAGE PROCESSING: Joseph DePasquale (STScI))

  • Shielding the Extremely Large Telescope from the Atacama Desert

    by Kate Green

    October 19, 2024

    The Extremely Large Telescope (ELT), currently under construction in the Atacama Desert, is set to become the world’s largest optical/near-infrared telescope. Once completed, it will have a segmented primary mirror 39 meters in diameter, allowing it to capture unprecedented levels of detail in the universe. The Atacama Desert, with its high altitude, clear skies, and extremely dry conditions, is an ideal location for such an advanced astronomical instrument.

    The harsh environment of the desert poses challenges, such as temperature extremes, wind, and dust. To address this, the ELT’s steel dome is being covered with specialized cladding, which includes insulating layers and sheets of aluminum. This protective covering will help regulate internal temperatures, minimize expansion and contraction of materials, and protect the delicate optics from external elements, such as wind, dust, and thermal variations.

    Balancing structural durability with maintaining a stable internal environment for the telescope’s optics is critical, especially in extreme conditions like those in the Atacama Desert.

    1. Thermal Regulation: The insulating layers in the cladding prevent rapid temperature fluctuations, which can affect both the steel structure and the telescope’s optics. The aluminum sheets reflect sunlight and minimize heat absorption during the day, while insulation prevents heat from escaping too quickly at night. This ensures that the internal environment stays stable despite drastic temperature changes outside.

    2. Vibration Damping: The cladding also helps dampen vibrations caused by wind, reducing their impact on the telescope’s sensitive instruments. Additionally, the steel dome is designed with materials and shapes that absorb or deflect these forces to minimize interference.

    3. Environmental Sealing: The cladding, combined with precise engineering of joints and seals, protects against dust, sand, and moisture. Even in a dry environment, dust particles can be damaging to delicate optics over time. The sealing and layers will prevent these contaminants from infiltrating the dome.

    4. Active Climate Control: In addition to the cladding, the team is using active climate control systems to manage temperature and humidity levels inside the dome. This ensures the telescope’s environment stays within strict operational limits.

    5. Material Selection: The steel used for the dome is designed to withstand the environmental conditions while minimizing thermal expansion. This, combined with the cladding, ensures that structural integrity is maintained without causing stress to the telescope’s components.

    The ELT will play a critical role in advancing our understanding of the universe, contributing to research on exoplanets, black holes, and the formation of galaxies. Its capabilities will surpass those of any existing telescope, making it a key asset for astronomers worldwide.

    Video Credit: European Southern Observatory (ESO)

  • What Are Black Holes?

    What Are Black Holes?

    by Francis Reddy, NASA

    September 08, 2020

    A black hole is an astronomical object with a gravitational pull so strong that nothing, not even light, can escape it. A black hole’s “surface,” called its event horizon, defines the boundary where the velocity needed to escape exceeds the speed of light, which is the speed limit of the cosmos. Matter and radiation fall in, but they can’t get out.

    Two main classes of black holes have been extensively observed. Stellar-mass black holes with three to dozens of times the Sun’s mass are spread throughout our Milky Way galaxy, while supermassive monsters weighing 100,000 to billions of solar masses are found in the centres of most big galaxies, ours included.

    Astronomers had long suspected an in-between class called intermediate-mass black holes, weighing 100 to more than 10,000 solar masses. While a handful of candidates have been identified with indirect evidence, the most convincing example to date came on May 21, 2019, when the National Science Foundation’s Laser Interferometer Gravitational-wave Observatory (LIGO), located in Livingston, Louisiana, and Hanford, Washington, detected gravitational waves from a merger of two stellar-mass black holes. This event, dubbed GW190521, resulted in a black hole weighing 142 Suns.

    A stellar-mass black hole forms when a star with more than 20 solar masses exhausts the nuclear fuel in its core and collapses under its own weight. The collapse triggers a supernova explosion that blows off the star’s outer layers. But if the crushed core contains more than about three times the Sun’s mass, no known force can stop its collapse to a black hole. The origin of supermassive black holes is poorly understood, but we know they exist from the very earliest days of a galaxy’s lifetime.

    Once born, black holes can grow by accreting matter that falls into them, including gas stripped from neighbouring stars and even other black holes.

    In 2019, astronomers using the Event Horizon Telescope (EHT) — an international collaboration that networked eight ground-based radio telescopes into a single Earth-size dish — captured an image of a black hole for the first time. It appears as a dark circle silhouetted by an orbiting disk of hot, glowing matter. The supermassive black hole is located at the heart of a galaxy called M87, located about 55 million light-years away, and weighs more than 6 billion solar masses. Its event horizon extends so far it could encompass much of our solar system out to well beyond the planets.

    Another important discovery related to black holes came in 2015 when scientists first detected gravitational waves, ripples in the fabric of space-time predicted a century earlier by Albert Einstein’s general theory of relativity. LIGO detected the waves from an event called GW150914, where two orbiting black holes spiraled into each other and merged 1.3 billion years ago. Since then, LIGO and other facilities have observed numerous black hole mergers via the gravitational waves they produce. 

     

    These are exciting new methods, but astronomers have been studying black holes through the various forms of light they emit for decades. Although light can’t escape a black hole’s event horizon, the enormous tidal forces in its vicinity cause nearby matter to heat up to millions of degrees and emit radio waves and X-rays. Some of the material orbiting even closer to the event horizon may be hurled out, forming jets of particles moving near the speed of light that emit radio, X-rays and gamma rays. Jets from supermassive black holes can extend hundreds of thousands of light-years into space.

    NASA’s Hubble, Chandra, Swift, NuSTAR, and NICER space telescopes, as well as other missions, continue to take the measure of black holes and their environments so we can learn more about these enigmatic objects and their role in the evolution of galaxies and the universe at large.

    Image:

    The first picture of a black hole was made using observations of the center of galaxy M87 taken by the Event Horizon Telescope. The image shows a bright ring formed as light bends in the intense gravity around a black hole 6.5 billion times the Sun’s mass.

    Credit: Event Horizon Telescope Collaboration

    Image:

    Radio data from the National Science Foundation’s Very Large Array facility was used to construct this image of Cygnus A, the brightest radio source in the sky located outside our galaxy. Long, thin particle jets produced by a supermassive black hole in the galaxy’s center link to vast lobes where speeding electrons trapped by magnetic fields emit radio waves. From tip to tip, the structure spans half a million light-years.

    Credit: NRAO/AUI

  • What is a ‘Rogue Star’?

    What is a ‘Rogue Star’?

    A rogue star, also known as an intergalactic or orphan star, is a star that drifts through space without being gravitationally bound to a galaxy or star cluster. Unlike most stars, which exist within the structured environment of galaxies (like our Sun in the Milky Way), rogue stars are solitary travelers in the vast emptiness of space, moving independently without a nearby galaxy to call home.

    Rogue stars can originate from several potential processes:

    1. Galactic Interactions: In galaxy collisions or interactions, intense gravitational forces can pull stars out of galaxies and propel them into intergalactic space.

    2. Stripping: During interactions with massive galactic clusters, gravitational forces (known as tidal forces) can strip stars from galaxies, leaving them to wander alone.

    3. Early Universe Phenomena: Some rogue stars may have formed independently in the early universe, perhaps in small, loosely bound galaxies that later disintegrated or “bled” stars into space due to weaker gravitational pulls.

    Rogue stars are intriguing to scientists because they offer a unique perspective on the history and structure of the universe, as well as a potential way to understand dark matter.

    Here is a list of notable rogue stars and their past or future encounters with our solar system:

    1. Gliese 710 (Constellation Serpens)

    • Type: Rogue star, not a hypervelocity star.

    • Speed: About 51,499 km/h.

    • Visibility: Magnitude 9.66 (requires a telescope to observe).

    • Approach Timeline: In approximately 1.29 million years, it will come within 4,303 AU of the Sun, closer than Pluto.

    • Outcome: Will not collide with our solar system but will become the closest star to the Sun, surpassing Proxima Centauri’s current distance of 4 light-years (268,142 AU).

    2. V2689 Orionis (Gliese 208)

    • Past Encounter: Passed Earth at a distance of 5 light-years around 50,000 years ago, farther out than Proxima Centauri.

    • Current Status: This close encounter is over, and the star continues to travel away from us.

    3. Scholz’s Star (Constellation Monoceros)

    • Past Encounter: Estimated to have crossed through the Oort Cloud approximately 70,000 years ago.

    • Effect on Solar System: No significant impact on Earth, but it may have nudged objects in the Oort Cloud.

    4. HIP 85605

    • Current Trajectory: Moving toward our solar system, expected to pass through the Oort Cloud.

    • Approach Timeline: Estimated to arrive within 240,000 to 470,000 years.

    • Potential Impact: May disturb the Oort Cloud, possibly redirecting comets toward the Sun. There will be time to address any threats posed by comet collisions.

    5. Gamma Microscopii

    • Past Close Encounter: Passed within 0.35 to 1.34 parsecs (1.1 to 4.3 light-years) of the Sun approximately 3.9 million years ago.

    • Type: A large G-type giant star (G6 or G8III) with about 2.5 times the mass of the Sun.

    • Impact on Solar System: Likely influenced the Oort Cloud, potentially sending comets toward Earth. Some impact craters on Earth may be linked to this encounter.

    These stars demonstrate how close stellar encounters can potentially influence the solar system, particularly by disturbing the Oort Cloud and potentially sending comets inward. The timeframes for such encounters are vast, giving Earth plenty of time to prepare for any indirect effects.

    Image:

    Illustration of a ‘runaway’ white dwarf. Credit Robert Lea

  • Rogue Stars

    Rogue Stars

    by Kate Green

    Intergalactic stars, or rogue stars, are unique stars that are not bound to any particular galaxy, traveling alone through the vast stretches of intergalactic space. Unlike typical stars bound to galaxies by gravitational forces, rogue stars have likely been ejected from their original galaxies due to intense gravitational interactions.

    Origins and Formation

    The exact formation of intergalactic stars is still under study, but scientists propose several main hypotheses:

    1. Galactic Collisions: When galaxies collide, gravitational forces can eject stars into intergalactic space, especially in smaller galaxies where the gravitational pull is weaker.

    2. Encounters with Supermassive Black Holes: Stars in multi-star systems that venture too close to a supermassive black hole (common in the centers of galaxies) can be ejected at high speeds. Some of these ejected stars may even reach hypervelocity, escaping the galaxy entirely.

    Discovery

    The existence of intergalactic stars was first confirmed in 1997 when the Hubble Space Telescope identified them in the Virgo Cluster, where up to a trillion intergalactic stars are now estimated to exist.

    Later discoveries include:

    • Fornax Cluster: Intergalactic stars were also found in this cluster following the Virgo findings.

    • Milky Way Edge: Astronomers have identified around 675 rogue stars at the Milky Way’s edge near the Andromeda Galaxy, believed to have been ejected from the Milky Way’s center by its supermassive black hole.

    Observation and Properties

    Intergalactic stars, particularly hypervelocity stars, are observed using the Doppler technique to measure their high speeds. Some of these stars are moving over a million miles per hour, demonstrating the immense forces that expelled them.

    These stars often have distinct characteristics:

    • High Velocity: Some rogue stars, especially hypervelocity stars, can reach speeds exceeding a million miles per hour.

    • Metallicity: Rogue stars often have high metallicity, suggesting they originated in the inner regions of galaxies, where younger, metal-rich stars are more common.

    • Diffuse Radiation: Observations in the 2000s revealed a faint, diffuse glow from the intergalactic medium, likely due to these stars and contributing to the extragalactic background radiation.

    Significance

    • Mass Contribution: It’s estimated that intergalactic stars make up about 10% of the Virgo Cluster’s mass, suggesting their significant presence throughout the universe.

    • Dark Matter and Mass Mystery: Rogue stars may contribute to the dark matter debate by explaining part of the “missing” mass, particularly through the observed diffuse extragalactic radiation.

    Known Locations

    • Virgo Cluster: The first intergalactic stars were observed here, approximately 300,000 light-years from the nearest galaxy.

    • Milky Way’s Edge: Around 675 hypervelocity stars have been identified near the Andromeda Galaxy, suggesting they were likely ejected from the Milky Way.

    The study of rogue stars continues to provide insight into galactic evolution, dark matter, and cosmic dynamics, as these stars challenge our understanding of how galaxies and star systems interact and evolve.

    Image:

    The Virgo cluster of galaxies, where the phenomenon known as intergalactic stars was discovered. Photo of the Centre of the Virgo Cluster of Galaxies with names and magnitudes. Credit: Taken by Bernd Gährken at 14. March 1999 from 1:25 to 1:40 CET on Kodak Pro Gold 400. telescope: 900/150mm 1:5 Newton.

    Image:

    Collisions between galaxies are commonly thought to be a source of intergalactic stars. The Advanced Camera for Surveys (ACS), the newest camera on NASA/ESA Hubble Space Telescope, has captured a spectacular pair of galaxies engaged in a celestial dance of cat and mouse or, in this case, mouse and mouse. Located 300 million light-years away in the constellation Coma Berenices, the colliding galaxies have been nicknamed “The Mice” because of the long tails of stars and gas emanating from each galaxy. Otherwise known as NGC 4676, the pair will eventually merge into a single giant galaxy. Credit: NASA, H. Ford (JHU), G. Illingworth (UCSC/LO), M.Clampin (STScI), G. Hartig (STScI), the ACS Science Team, and ESA – APOD 2004-06-12.

    Image:

    Proposed mechanisms for the ejection of intergalactic stars by supermassive black holes. This illustration shows one possible mechanism for how the star HE 0437-5439 acquired enough energy to be ejected from our Milky Way galaxy. Credit: NASA, ESA, O. Gnedin (University of Michigan, Ann Arbor), and W. Brown (Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass.) – http://hubblesite.org/newscenter/archive/releases/2010/19/image/c/

    References:

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    2. “NewsCenter – Hubble Finds Intergalactic Stars (01/14/1997)”. HubbleSite. 14 January 1997.

    3. Witze, Alexandra (2014). “Half of Stars Lurk Outside Galaxies”. Nature. Nature Publishing Group.

    4. Tillman, Nola Taylor (27 August 2015). “Lonely Supernova Likely Exiled by Merging Black Holes”. Space.com.

    5. Roy Britt, Robert (26 January 2006). “Exiled Stars: Milky Way Boots Members”. Space.com.

    6. “Hyperfast Star Was Booted From Milky Way”. NASA Science. 21 July 2010.

    7. Cooray, Asantha; Smidt, Joseph; De Bernardis, Francesco; et al. (2012). “A measurement of the intrahalo light fraction with near-infrared background anisotropies”. Nature. 490 (7421): 514–516.

    8. Zemcov, Michael; Smidt, Joseph; Arai, Toshiaki; et al. (7 November 2014). “On the origin of near-infrared extragalactic background light anisotropy”. Science. 346 (6210): 732–735.

    9. Salisbury, David (30 April 2012). “Rogue stars ejected from the galaxy found in intergalactic space”. Research News. Vanderbilt University.

    10. Stallard, Brian (7 June 2015). “Between Galaxies: Lonely Supernovae Identified”. Nature World News.

    11. Bromley, Benjamin C.; Kenyon, Scott J.; Brown, Warren R.; Geller, Margaret J. (1 November 2018). “Nearby High-speed Stars in Gaia DR2”. The Astrophysical Journal. 868 (1): 25 (15 pp.).

    12. de la Fuente Marcos, R.; de la Fuente Marcos, C. (8 July 2019). “Flying far and fast: the distribution of distant hypervelocity star candidates from Gaia DR2 data”. Astronomy and Astrophysics. 627: A104 (17 pp.).

    13. “Giant Gas Cloud Surrounds Our Milky Way Galaxy”. Space.com. 24 September 2012.

    14. Choi, Charles Q. (6 November 2014). “Lost in Space: Half of All Stars Drifting Free of Galaxies”. Space. Purch.