Members Can Post Anonymously On This Site
-
Similar Topics
-
By NASA
Explore This Section Exoplanets Home Exoplanets Overview Exoplanets Facts Types of Exoplanets Stars What is the Universe Search for Life The Big Questions Are We Alone? Can We Find Life? The Habitable Zone Why We Search Target Star Catalog Discoveries Discoveries Dashboard How We Find and Characterize Missions People Exoplanet Catalog Immersive The Exoplaneteers Exoplanet Travel Bureau 5 Ways to Find a Planet Strange New Worlds Universe of Monsters Galaxy of Horrors News Stories Blog Resources Get Involved Glossary Eyes on Exoplanets Exoplanet Watch More Multimedia ExEP This artist’s concept pictures the planets orbiting Barnard’s Star, as seen from close to the surface of one of them. Image credit: International Gemini Observatory/NOIRLab/NSF/AURA/P. Marenfeld The Discovery
Four rocky planets much smaller than Earth orbit Barnard’s Star, the next closest to ours after the three-star Alpha Centauri system. Barnard’s is the nearest single star.
Key Facts
Barnard’s Star, six light-years away, is notorious among astronomers for a history of false planet detections. But with the help of high-precision technology, the latest discovery — a family of four — appears to be solidly confirmed. The tiny size of the planets is also remarkable: Capturing evidence of small worlds at great distance is a tall order, even using state-of-the-art instruments and observational techniques.
Details
Watching for wobbles in the light from a star is one of the leading methods for detecting exoplanets — planets orbiting other stars. This “radial velocity” technique tracks subtle shifts in the spectrum of starlight caused by the gravity of a planet pulling its star back and forth as the planet orbits. But tiny planets pose a major challenge: the smaller the planet, the smaller the pull. These four are each between about a fifth and a third as massive as Earth. Stars also are known to jitter and quake, creating background “noise” that potentially could swamp the comparatively quiet signals from smaller, orbiting worlds.
Astronomers measure the back-and-forth shifting of starlight in meters per second; in this case the radial velocity signals from all four planets amount to faint whispers — from 0.2 to 0.5 meters per second (a person walks at about 1 meter per second). But the noise from stellar activity is nearly 10 times larger at roughly 2 meters per second.
How to separate planet signals from stellar noise? The astronomers made detailed mathematical models of Barnard’s Star’s quakes and jitters, allowing them to recognize and remove those signals from the data collected from the star.
The new paper confirming the four tiny worlds — labeled b, c, d, and e — relies on data from MAROON-X, an “extreme precision” radial velocity instrument attached to the Gemini Telescope on the Maunakea mountaintop in Hawaii. It confirms the detection of the “b” planet, made with previous data from ESPRESSO, a radial velocity instrument attached to the Very Large Telescope in Chile. And the new work reveals three new sibling planets in the same system.
Fun Facts
These planets orbit their red-dwarf star much too closely to be habitable. The closest planet’s “year” lasts a little more than two days; for the farthest planet, it’s is just shy of seven days. That likely makes them too hot to support life. Yet their detection bodes well in the search for life beyond Earth. Scientists say small, rocky planets like ours are probably the best places to look for evidence of life as we know it. But so far they’ve been the most difficult to detect and characterize. High-precision radial velocity measurements, combined with more sharply focused techniques for extracting data, could open new windows into habitable, potentially life-bearing worlds.
Barnard’s star was discovered in 1916 by Edward Emerson Barnard, a pioneering astrophotographer.
The Discoverers
An international team of scientists led by Ritvik Basant of the University of Chicago published their paper on the discovery, “Four Sub-Earth Planets Orbiting Barnard’s Star from MAROON-X and ESPRESSO,” in the science journal, “The Astrophysical Journal Letters,” in March 2025. The planets were entered into the NASA Exoplanet Archive on March 13, 2025.
Share
Details
Last Updated Apr 01, 2025 Related Terms
Exoplanets Radial Velocity Terrestrial Exoplanets Keep Exploring Discover More Topics From NASA
Universe
Exoplanets
Search for Life
Exoplanet Catalog
This exoplanet encyclopedia — continuously updated, with more than 5,600 entries — combines interactive 3D models and detailed data on…
View the full article
-
By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
A NASA researcher and innovation architect from the Convergent Aeronautics Solutions project Discovery team collaborating at a whiteboard during a visit to Chapel Hill, N.C. on Aug. 13, 2024.NASA / Ariella Knight Convergent Aeronautics Solutions (CAS) Discovery identifies problems worth solving for the benefit of all.
We formulate “convergent” problems—across multiple disciplines and sectors—and build footholds toward potentially transformative opportunities in aeronautics. As aeronautics rapidly advances, it is increasingly intersecting with other sectors like energy, healthcare, emergency response, economic resilience, the space economy, and more.
CAS Discovery builds new innovation tools and methods, a workforce adept at innovation methods, and transdisciplinary teams of researchers within and beyond NASA that conduct regular “Discovery sprints”—expeditions into cross-sector topic areas that could beneficially transform aeronautics and humanity.
WHAT is Discovery?
Participatory
It is difficult to understand and effectively address stakeholders’ needs & capabilities without engaging them. Discovery, in consultation with key NASA offices and other government agencies, has honed mechanisms to lawfully and respectfully engage and invite participation from stakeholders, communities, industry, NGOs and government to collaboratively formulate complex societal challenges tied to aviation.
Convergent
Typical organizational structures limit convergence across knowledge boundaries. CAS Discovery is intentionally cross-sector and transdisciplinary because the most impactful ideas often lie at the intersection of boundaries, the borderlands where multiple disciplines and communities come together. We work to emerge multi-sector, system-of-systems challenges that integrate political, economic, social, technological, environmental, legal and ethical trends, needs, and capabilities.
Future-Focused
Organizations have a tendency of being driven by short-term thinking and relatively short time horizons. CAS Discovery uses strategic foresight methods to examine 20 to 50-year time horizons, systematically ingesting and synthesizing signals and trends from aero and non-aero sources to envision a variety of scenarios to uncover opportunities for the future of aeronautics.
Ecosystemic
We study the ecosystems that are part of aeronautics and aerospace. This helps in broadening consideration of impacts while practicing foresight. It enhances our awareness of the environment and gives stakeholders the ability to see ripple effects across technologies, economies, communities, etc. We seek to benefit the wellness of the entire ecosystem while also benefiting the constituents.
A group of NASA researchers and leaders from the Convergent Aeronautics Solutions project Discovery team at the agency’s Glenn Research Center in Cleveland, on April 30, 2024.NASA / Ricaurte Chock WHO is Discovery?
NASA Researchers
They are the engine that propels CAS Discovery. Our cross-center Discovery sprint and foresight teams are composed of researchers from NASA’s Ames Research Center and Armstrong Flight Research Center in California, Glenn Research Center in Cleveland, and Langley Research Center in Virginia.
Researchers from Outside of NASA
They collaborate with us as subject matter experts or Discovery sprint team members to contribute their backgrounds in fields less common within NASA, such as energy, economics, anthropology, and other areas. This collaboration happens through many mechanisms, such as freelancing, crowdsourcing, interviews, webinars, and podcasts.
Stakeholders
They are engaged in various ways and to different degrees, often co-envisioning potential futures, co-formulating problems, and co-designing solutions.
Innovation Architects
They are the glue that holds CAS Discovery together and the anti-glue that keeps our teams from getting stuck. They come from a wide range of experience, each bringing deep expertise in leading transdisciplinary teams and stakeholders through processes and methods from strategic foresight, complex systems design, human-centered design, and more.
CAS Center Integration Leads (CILs)
They work with NASA line management at each Aeronautics center to bring NASA researchers and potential new PIs into CAS. CILs also host annual Wicked Wild idea pitch events to bring new problem areas and solution ideas into CAS Discovery and early Execution phases.
Ames Research Center CIL: Ty Huang Armstrong Flight Research Center CIL: Matt Kearns Glenn Research Center CIL: Jeffrey Chin Langley Research Center CIL: Devin Pugh-Thomas CAS Discovery Leads
They oversee Discovery sprint and strategic foresight teams, topics, and processes; new tools and continuous improvement experiments; and the overall health of the CAS innovation front-end pipeline and related strategic outputs.
Discovery Lead: Eric Reynolds Brubaker, Langley Research Center Foresight Lead: Vikram Shyam, Glenn Research Center Sample Discovery Publications
COMING SOON: Links to Technical Memorandums and conference papers.
Facebook logo @NASA@NASAaero@NASA_es @NASA@NASAaero@NASA_es Instagram logo @NASA@NASAaero@NASA_es Linkedin logo @NASA Explore More
2 min read NASA Concludes Wind Study
Article 2 years ago 3 min read NASA Armstrong Supports Wind Study
Article 2 years ago 4 min read NASA Interns Help Identify Aviation Solutions to Health Care Challenges
Article 2 years ago Keep Exploring Discover More Topics From NASA
Convergent Aeronautics Solutions
Science Missions
Aeronautics STEM
Explore NASA’s History
Share
Details
Last Updated Mar 21, 2025 EditorJim BankeContactDiana Fitzgeralddiana.r.fitzgerald@nasa.gov Related Terms
Convergent Aeronautics Solutions View the full article
-
By NASA
Artist’s rendering of a potentially habitable super-Earth orbiting a star called HD 20794. Illustration credit: Gabriel Pérez Díaz, SMM (IAC) The Discovery
A possible “super-Earth” orbits a relatively close, Sun-like star, and could be a habitable world – but one of extreme temperature swings, from scorching heat to deep freeze.
Key Facts
The newly confirmed planet is the outermost of three detected so far around a star called HD 20794, just 20 light-years from Earth. Its 647-day orbit is comparable to Mars in our solar system. But this planet’s orbit is highly eccentric, stretched into an oval shape. That brings the planet close enough to the star to experience runaway heating for part of its year, then carries it far enough away to freeze any potential water on its surface. The planet has been bouncing between these extremes roughly every 300 days – perhaps for billions of years.
Details
The planet spends a good chunk of its year in the “habitable zone” around its star, the orbital distance that would allow liquid water to form on the surface under the right atmospheric conditions. But because of its eccentric orbit, it moves to a distance interior to the inner edge of the habitable zone when closest to the star, and outside the outer edge when farthest away. At its closest, the planet’s distance from the star is comparable to Venus’s distance from the Sun; at its farthest point, it is nearly twice the distance from Earth to the Sun. The planet is possibly rocky, like Earth, but could be a heftier version – about six times as massive as our home planet.
Star HD 20794 and its posse of possible planets have been extensively studied, but the international team of astronomers that confirmed the outer planet, led by Nicola Nari of Light Bridges S.L. and the Instituto de Astrofisica de Canarias, examined more than 20 years worth of data to pin down all three planets’ orbits and likely masses.
The scientists relied on data from two ground-based, precision instruments: HARPS, the High Accuracy Radial velocity Planet Searcher in La Silla, Chile, and ESPRESSO, the Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations in Paranal, Chile. Both instruments, connected to powerful telescopes, measure tiny shifts in the light spectrum of stars, caused by the gravity of planets tugging the star back and forth as they orbit.
But such tiny shifts in the star’s spectrum also can be caused by imposters – spots, flares, or other activity on the star’s surface, carried along as the star rotates and masquerading as orbiting planets. The science team spent years painstakingly analyzing the spectrum shifts, or “radial velocity” data, for any sign of background noise or even jitters from the instruments themselves. They confirmed the reputation of HD 20794 as a fairly quiet star, not prone to outbursts that might be confused for signs of orbiting planets.
Fun Facts
The elliptically orbiting super-Earth appears to be an ideal target for future space-based telescopes designed to search for habitable worlds, seeking possible signs of life. High on the list is NASA’s Habitable Worlds Observatory, which will someday examine the atmospheres of Earth-sized planets around Sun-like stars. When launched in the decades ahead, the observatory would spread the light from such planets into a spectrum to determine which gases are present – including those that might reveal some form of life. The relative closeness of HD 20974, only 20 light-years away, its brightness, and its low level of surface activity – not to mention the third planet’s wild temperature swings – could make this system a prime candidate for scrutiny by HWO.
The Discoverers
The international science team that confirmed the eccentric super-Earth was led by researcher Nicola Nari of the Light Bridges S.L. and the Instituto de Astrofisica de Canarias, and included Dr. Michael Cretignier of the University of Oxford, who first picked up the potential planet’s signal in 2022. Their paper, “Revisiting the multi-planet system of the nearby star HD 20794,” was published online by the journal, Astronomy and Astrophysics, in January 2025.
View the full article
-
By NASA
5 min read
Ultra-low-noise Infrared Detectors for Exoplanet Imaging
A linear-mode avalanche photodiode array in the test dewar. The detector is the dark square in the center. Michael Bottom, University of Hawai’i One of the ultimate goals in astrophysics is the discovery of Earth-like planets that are capable of hosting life. While thousands of planets have been discovered around other stars, the vast majority of these detections have been made via indirect methods, that is, by detecting the effect of the planet on the star’s light, rather than detecting the planet’s light directly. For example, when a planet passes in front of its host star, the brightness of the star decreases slightly.
However, indirect methods do not allow for characterization of the planet itself, including its temperature, pressure, gravity, and atmospheric composition. Planetary atmospheres may include “biosignature” gases like oxygen, water vapor, carbon dioxide, etc., which are known to be key ingredients needed to support life as we know it. As such, direct imaging of a planet and characterization of its atmosphere are key to understanding its potential habitability.
But the technical challenges involved in imaging Earth-like extrasolar planets are extreme. First such planets are detected only by observing light they reflect from their parent star, and so they typically appear fainter than the stars they orbit by factors of about 10 billion. Furthermore, at the cosmic distances involved, the planets appear right next to the stars. A popular expression is that exoplanet imaging is like trying to detect a firefly three feet from a searchlight from a distance of 300 miles.
Tremendous effort has gone into developing starlight suppression technologies to block the bright glare of the star, but detecting the light of the planet is challenging in its own right, as planets are incredibly faint. One way to quantify the faintness of planetary light is to understand the photon flux rate. A photon is an indivisible particle of light, that is, the minimum detectable amount of light. On a sunny day, approximately 10 thousand trillion photons enter your eye every second. The rate of photons entering your eye from an Earth-like exoplanet around a nearby star would be around 10 to 100 per year. Telescopes with large mirrors can help collect as much of this light as possible, but ultra-sensitive detectors are also needed, particularly for infrared light, where the biosignature gases have their strongest effects. Unfortunately, state-of-the-art infrared detectors are far too noisy to detect the low level of light emitted from exoplanets.
With support from NASA’s Astrophysics Division and industrial partners, researchers at the University of Hawai’i are developing a promising detector technology to meet these stringent sensitivity requirements. These detectors, known as avalanche photodiode arrays, are constructed out of the same semiconductor material as conventional infrared sensors. However, these new sensors employ an extra “avalanche” layer that takes the signal from a single photon and multiplies it, much like an avalanche can start with a single snowball and quickly grow it to the size of a boulder. This signal amplification occurs before any noise from the detector is introduced, so the effective noise is proportionally reduced. However, at high avalanche levels, photodiodes start to behave badly, with noise exponentially increasing, which negates any benefits of the signal amplification. Late University of Hawai’i faculty member Donald Hall, who was a key figure in driving technology for infrared astronomy, realized the potential use of avalanche photodiodes for ultra-low-noise infrared astronomy with some modifications to the material properties.
University of Hawai’i team members with cryogenic dewar used to test the sensors. From left to right, Angelu Ramos, Michael Bottom, Shane Jacobson, Charles-Antoine Claveau. Michael Bottom, University of Hawai’i The most recent sensors benefit from a new design including a graded semiconductor bandgap that allows for excellent noise performance at moderate amplification, a mesa pixel geometry to reduce electronic crosstalk, and a read-out integrated circuit to allow for short readout times. “It was actually challenging figuring out just how sensitive these detectors are,” said Michael Bottom, associate professor at the University of Hawai’i and lead of development effort. “Our ‘light-tight’ test chamber, which was designed to evaluate the infrared sensors on the James Webb Space Telescope, was supposed to be completely dark. But when we put these avalanche photodiodes in the chamber, we started seeing light leaks at the level of a photon an hour, which you would never be able to detect using the previous generation of sensors.”
The new designs have a format of one megapixel, more than ten times larger than the previous iteration of sensors, and circuitry that allows for tracking and subtracting any electronic drifts. Additionally, the pixel size and control electronics are such that these new sensors could be drop-in replacements for the most common infrared sensors used on the ground, which would give new capabilities to existing instruments.
Image of the Palomar-2 globular cluster located in the constellation of Auriga, taken with the linear-mode avalanche photodiode arrays, taken from the first on-sky testing of the sensors using the University of Hawai’i’s 2.2 meter telescope. Michael Bottom, University of Hawai’i Last year, the team took the first on-sky images from the detectors, using the University of Hawai’i’s 2.2-meter telescope. “It was impressive to see the avalanche process on sky. When we turned up the gain, we could see more stars appear,” said Guillaume Huber, a graduate student working on the project. “The on-sky demonstration was important to prove the detectors could perform well in an operational environment,” added Michael Bottom.
According to the research team, while the current sensors are a major step forward, the megapixel format is still too small for many science applications, particularly those involving spectroscopy. Further tasks include improving detector uniformity and decreasing persistence. The next generation of sensors will be four times larger, meeting the size requirements for the Habitable Worlds Observatory, NASA’s next envisioned flagship mission, with the goals of imaging and characterizing Earth-like exoplanets.
Project Lead: Dr. Michael Bottom, University of Hawai’i
Sponsoring Organization: NASA Strategic Astrophysics Technology (SAT) Program
Share
Details
Last Updated Feb 18, 2025 Related Terms
Technology Highlights Astrophysics Astrophysics Division Science-enabling Technology Explore More
6 min read Webb Reveals Rapid-Fire Light Show From Milky Way’s Central Black Hole
Article
5 mins ago
2 min read Hubble Captures a Cosmic Cloudscape
Article
4 days ago
5 min read Webb Maps Full Picture of How Phoenix Galaxy Cluster Forms Stars
Article
5 days ago
View the full article
-
By NASA
Hubble Space TelescopeHubble Home OverviewAbout Hubble The History of Hubble Hubble Timeline Why Have a Telescope in Space? Hubble by the Numbers At the Museum FAQs Impact & BenefitsHubble’s Impact & Benefits Science Impacts Cultural Impact Technology Benefits Impact on Human Spaceflight Astro Community Impacts ScienceHubble Science Science Themes Science Highlights Science Behind Discoveries Hubble’s Partners in Science Universe Uncovered Explore the Night Sky ObservatoryHubble Observatory Hubble Design Mission Operations Missions to Hubble Hubble vs Webb TeamHubble Team Career Aspirations Hubble Astronauts NewsHubble News Hubble News Archive Social Media Media Resources MultimediaMultimedia Images Videos Sonifications Podcasts e-Books Online Activities Lithographs Fact Sheets Glossary Posters Hubble on the NASA App More35th Anniversary 7 Min Read NASA Celebrates Edwin Hubble’s Discovery of a New Universe
The Cepheid variable star, called V1, in the neighboring Andromeda galaxy. Credits: NASA, ESA, Hubble Heritage Team (STScI/AURA); Acknowledgement: R. Gendler For humans, the most important star in the universe is our Sun. The second-most important star is nestled inside the Andromeda galaxy. Don’t go looking for it — the flickering star is 2.2 million light-years away, and is 1/100,000th the brightness of the faintest star visible to the human eye.
Yet, a century ago, its discovery by Edwin Hubble, then an astronomer at Carnegie Observatories, opened humanity’s eyes as to how large the universe really is, and revealed that our Milky Way galaxy is just one of hundreds of billions of galaxies in the universe ushered in the coming-of-age for humans as a curious species that could scientifically ponder our own creation through the message of starlight. Carnegie Science and NASA are celebrating this centennial at the 245th meeting of the American Astronomical Society in Washington, D.C.
The seemingly inauspicious star, simply named V1, flung open a Pandora’s box full of mysteries about time and space that are still challenging astronomers today. Using the largest telescope in the world at that time, the Carnegie-funded 100-inch Hooker Telescope at Mount Wilson Observatory in California, Hubble discovered the demure star in 1923. This rare type of pulsating star, called a Cepheid variable, is used as milepost markers for distant celestial objects. There are no tape-measures in space, but by the early 20th century Henrietta Swan Leavitt had discovered that the pulsation period of Cepheid variables is directly tied to their luminosity.
Many astronomers long believed that the edge of the Milky Way marked the edge of the entire universe. But Hubble determined that V1, located inside the Andromeda “nebula,” was at a distance that far exceeded anything in our own Milky Way galaxy. This led Hubble to the jaw-dropping realization that the universe extends far beyond our own galaxy.
In fact Hubble had suspected there was a larger universe out there, but here was the proof in the pudding. He was so amazed he scribbled an exclamation mark on the photographic plate of Andromeda that pinpointed the variable star.
In commemoration of Edwin Hubble’s discovery of a Cepheid variable class star, called V1, in the neighboring Andromeda galaxy 100 years ago, astronomers partnered with the American Association of Variable Star Observers (AAVSO) to study the star. AAVSO observers followed V1 for six months, producing a plot, or light curve, of the rhythmic rise and fall of the star’s light. Based on this data, the Hubble Space Telescope was scheduled to capture the star at its dimmest and brightest light. Edwin Hubble’s observations of V1 became the critical first step in uncovering a larger, grander universe than some astronomers imagined at the time. Once dismissed as a nearby “spiral nebula” measurements of Andromeda with its embedded Cepheid star served as a stellar milepost marker. It definitively showed that Andromeda was far outside of our Milky Way. Edwin Hubble went on to measure the distances to many galaxies beyond the Milky Way by finding Cepheid variables within those levels. The velocities of those galaxies, in turn, allowed him to determine that the universe is expanding.NASA, ESA, Hubble Heritage Team (STScI/AURA); Acknowledgment: R. Gendler As a result, the science of cosmology exploded almost overnight. Hubble’s contemporary, the distinguished Harvard astronomer Harlow Shapley, upon Hubble notifying him of the discovery, was devastated. “Here is the letter that destroyed my universe,” he lamented to fellow astronomer Cecilia Payne-Gaposchkin, who was in his office when he opened Hubble’s message.
Just three years earlier, Shapley had presented his observational interpretation of a much smaller universe in a debate one evening at the Smithsonian Museum of Natural History in Washington. He maintained that the Milky Way galaxy was so huge, it must encompass the entirety of the universe. Shapley insisted that the mysteriously fuzzy “spiral nebulae,” such as Andromeda, were simply stars forming on the periphery of our Milky Way, and inconsequential.
Little could Hubble have imagined that 70 years later, an extraordinary telescope named after him, lofted hundreds of miles above the Earth, would continue his legacy. The marvelous telescope made “Hubble” a household word, synonymous with wonderous astronomy.
Today, NASA’s Hubble Space Telescope pushes the frontiers of knowledge over 10 times farther than Edwin Hubble could ever see. The space telescope has lifted the curtain on a compulsive universe full of active stars, colliding galaxies, and runaway black holes, among the celestial fireworks of the interplay between matter and energy.
Edwin Hubble was the first astronomer to take the initial steps that would ultimately lead to the Hubble Space Telescope, revealing a seemingly infinite ocean of galaxies. He thought that, despite their abundance, galaxies came in just a few specific shapes: pinwheel spirals, football-shaped ellipticals, and oddball irregular galaxies. He thought these might be clues to galaxy evolution – but the answer had to wait for the Hubble Space Telescope’s legendary Hubble Deep Field in 1994.
The most impactful finding that Edwin Hubble’s analysis showed was that the farther the galaxy is, the faster it appears to be receding from Earth. The universe looked like it was expanding like a balloon. This was based on Hubble tying galaxy distances to the reddening of light — the redshift – that proportionally increased the father away the galaxies are.
The redshift data were first collected by Lowell Observatory astronomer Vesto Slipher, who spectroscopically studied the “spiral nebulae” a decade before Hubble. Slipher did not know they were extragalactic, but Hubble made the connection. Slipher first interpreted his redshift data an example of the Doppler effect. This phenomenon is caused by light being stretched to longer, redder wavelengths if a source is moving away from us. To Slipher, it was curious that all the spiral nebulae appeared to be moving away from Earth.
Two years prior to Hubble publishing his findings, the Belgian physicist and Jesuit priest Georges Lemaître analyzed the Hubble and Slifer observations and first came to the conclusion of an expanding universe. This proportionality between galaxies’ distances and redshifts is today termed Hubble–Lemaître’s law.
Because the universe appeared to be uniformly expanding, Lemaître further realized that the expansion rate could be run back into time – like rewinding a movie – until the universe was unimaginably small, hot, and dense. It wasn’t until 1949 that the term “big bang” came into fashion.
This was a relief to Edwin Hubble’s contemporary, Albert Einstein, who deduced the universe could not remain stationary without imploding under gravity’s pull. The rate of cosmic expansion is now known as the Hubble Constant.
Ironically, Hubble himself never fully accepted the runaway universe as an interpretation of the redshift data. He suspected that some unknown physics phenomenon was giving the illusion that the galaxies were flying away from each other. He was partly right in that Einstein’s theory of special relativity explained redshift as an effect of time-dilation that is proportional to the stretching of expanding space. The galaxies only appear to be zooming through the universe. Space is expanding instead.
Compass and scale image titled “Cepheid Variable Star V1 in M31 HST WFC3/UVIS.” Four boxes each showing a bright white star in the center surrounded by other stars. Each box has a correlating date at the bottom: Dec. 17, 2020, Dec. 21, 2010, Dec. 30, 2019, and Jan. 26, 2011. The center star in the boxes appears brighter with each passing date.NASA, ESA, Hubble Heritage Project (STScI, AURA) After decades of precise measurements, the Hubble telescope came along to nail down the expansion rate precisely, giving the universe an age of 13.8 billion years. This required establishing the first rung of what astronomers call the “cosmic distance ladder” needed to build a yardstick to far-flung galaxies. They are cousins to V1, Cepheid variable stars that the Hubble telescope can detect out to over 100 times farther from Earth than the star Edwin Hubble first found.
Astrophysics was turned on its head again in 1998 when the Hubble telescope and other observatories discovered that the universe was expanding at an ever-faster rate, through a phenomenon dubbed “dark energy.” Einstein first toyed with this idea of a repulsive form of gravity in space, calling it the cosmological constant.
Even more mysteriously, the current expansion rate appears to be different than what modern cosmological models of the developing universe would predict, further confounding theoreticians. Today astronomers are wrestling with the idea that whatever is accelerating the universe may be changing over time. NASA’s Roman Space Telescope, with the ability to do large cosmic surveys, should lead to new insights into the behavior of dark matter and dark energy. Roman will likely measure the Hubble constant via lensed supernovae.
This grand century-long adventure, plumbing depths of the unknown, began with Hubble photographing a large smudge of light, the Andromeda galaxy, at the Mount Wilson Observatory high above Los Angeles.
In short, Edwin Hubble is the man who wiped away the ancient universe and discovered a new universe that would shrink humanity’s self-perception into being an insignificant speck in the cosmos.
The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space, based in Denver, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.
Explore More
Edwin Hubble Hubble Views the Star That Changed the Universe The History of Hubble Facebook logo @NASAHubble @NASAHubble Instagram logo @NASAHubble Media Contact:
Claire Andreoli (claire.andreoli@nasa.gov)
NASA’s Goddard Space Flight Center, Greenbelt, MD
Ray Villard
Space Telescope Science Institute, Baltimore, MD
Share
Details
Last Updated Jan 15, 2025 EditorAndrea GianopoulosLocationNASA Goddard Space Flight Center Related Terms
Andromeda Galaxy Astrophysics Astrophysics Division Goddard Space Flight Center Hubble Space Telescope Stars The Universe Keep Exploring Discover More Topics From Hubble
Hubble Space Telescope
Since its 1990 launch, the Hubble Space Telescope has changed our fundamental understanding of the universe.
Discovering a Runaway Universe
Our cosmos is growing, and that expansion rate is accelerating.
The History of Hubble
Hubble’s Night Sky Challenge
View the full article
-
-
Check out these Videos
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.