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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.
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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
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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
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By NASA
Astronomers have released a set of more than a million simulated images showcasing the cosmos as NASA’s upcoming Nancy Grace Roman Space Telescope will see it. This preview will help scientists explore a myriad of Roman’s science goals.
“We used a supercomputer to create a synthetic universe and simulated billions of years of evolution, tracing every photon’s path all the way from each cosmic object to Roman’s detectors,” said Michael Troxel, an associate professor of physics at Duke University in Durham, North Carolina, who led the simulation campaign. “This is the largest, deepest, most realistic synthetic survey of a mock universe available today.”
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This video begins with a tiny one-square-degree portion of the full OpenUniverse simulation area (about 70 square degrees, equivalent to an area of sky covered by more than 300 full moons). It spirals in toward a particularly galaxy-dense region, zooming by a factor of 75. This simulation showcases the cosmos as NASA’s Nancy Grace Roman Space Telescope could see it, allowing scientists to preview the next generation of cosmic discovery now. Roman’s real future surveys will enable a deep dive into the universe with highly resolved imaging, as demonstrated in this video. NASA’s Goddard Space Flight Center and M. Troxel The project, called OpenUniverse, relied on the now-retired Theta supercomputer at the DOE’s (Department of Energy’s) Argonne National Laboratory in Illinois. The supercomputer accomplished a process that would take over 6,000 years on a typical computer in just nine days.
In addition to Roman, the 400-terabyte dataset will also preview observations from the Vera C. Rubin Observatory, which is jointly funded by the National Science Foundation and the U.S. Department of Energy, and approximate simulations from ESA’s (the European Space Agency’s) Euclid mission, which has NASA contributions. The Roman data is available now here, and the Rubin and Euclid data will soon follow.
The team used the most sophisticated modeling of the universe’s underlying physics available and fed in information from existing galaxy catalogs and the performance of the telescopes’ instruments. The resulting simulated images span 70 square degrees, equivalent to an area of sky covered by more than 300 full moons. In addition to covering a broad area, it also covers a large span of time — more than 12 billion years.
Each tiny dot in the image at left is a galaxy simulated by the OpenUniverse campaign. The one-square-degree image offers a small window into the full simulation area, which is about 70 square degrees (equivalent to an area of sky covered by more than 300 full moons), while the inset at right is a close-up of an area 75 times smaller (1/600th the size of the full area). This simulation showcases the cosmos as NASA’s Nancy Grace Roman Space Telescope could see it. Roman will expand on the largest space-based galaxy survey like it – the Hubble Space Telescope’s COSMOS survey – which imaged two square degrees of sky over the course of 42 days. In only 250 days, Roman will view more than a thousand times more of the sky with the same resolution. The project’s immense space-time coverage shows scientists how the telescopes will help them explore some of the biggest cosmic mysteries. They will be able to study how dark energy (the mysterious force thought to be accelerating the universe’s expansion) and dark matter (invisible matter, seen only through its gravitational influence on regular matter) shape the cosmos and affect its fate. Scientists will get closer to understanding dark matter by studying its gravitational effects on visible matter. And by studying the simulation’s 100 million synthetic galaxies, they will see how galaxies and galaxy clusters evolved over eons.
Repeated mock observations of a particular slice of the universe enabled the team to stitch together movies that unveil exploding stars crackling across the synthetic cosmos like fireworks. These starbursts allow scientists to map the expansion of the simulated universe.
This simulation showcases the dynamic universe as NASA’s Nancy Grace Roman Space Telescope could see it over the course of its five-year primary mission. The video sparkles with synthetic supernovae from observations of the OpenUniverse simulated universe taken every five days (similar to the expected cadence of Roman’s High-Latitude Time-Domain Survey, which OpenUniverse simulates in its entirety). On top of the static sky of stars in the Milky Way and other galaxies, more than a million exploding stars flare into visibility and then slowly fade away. To highlight the dynamic physics happening and for visibility at this scale, the true brightness of each transient event has been magnified by a factor of 10,000 and no background light has been added to the simulated images. The video begins with Roman’s full field of view, which represents a single pointing of Roman’s camera, and then zooms into one square.NASA’s Goddard Space Flight Center and M. Troxel Scientists are now using OpenUniverse data as a testbed for creating an alert system to notify astronomers when Roman sees such phenomena. The system will flag these events and track the light they generate so astronomers can study them.
That’s critical because Roman will send back far too much data for scientists to comb through themselves. Teams are developing machine-learning algorithms to determine how best to filter through all the data to find and differentiate cosmic phenomena, like various types of exploding stars.
“Most of the difficulty is in figuring out whether what you saw was a special type of supernova that we can use to map how the universe is expanding, or something that is almost identical but useless for that goal,” said Alina Kiessling, a research scientist at NASA’s Jet Propulsion Laboratory (JPL) in Southern California and the principal investigator of OpenUniverse.
While Euclid is already actively scanning the cosmos, Rubin is set to begin operations late this year and Roman will launch by May 2027. Scientists can use the synthetic images to plan the upcoming telescopes’ observations and prepare to handle their data. This prep time is crucial because of the flood of data these telescopes will provide.
In terms of data volume, “Roman is going to blow away everything that’s been done from space in infrared and optical wavelengths before,” Troxel said. “For one of Roman’s surveys, it will take less than a year to do observations that would take the Hubble or James Webb space telescopes around a thousand years. The sheer number of objects Roman will sharply image will be transformative.”
This synthetic OpenUniverse animation shows the type of science that astronomers will be able to do with future Roman deep-field observations. The gravity of intervening galaxy clusters and dark matter can lens the light from farther objects, warping their appearance as shown in the animation. By studying the distorted light, astronomers can study elusive dark matter, which can only be measured indirectly through its gravitational effects on visible matter. As a bonus, this lensing also makes it easier to see the most distant galaxies whose light the dark matter magnifies. Caltech-IPAC/R. Hurt “We can expect an incredible array of exciting, potentially Nobel Prize-winning science to stem from Roman’s observations,” Kiessling said. “The mission will do things like unveil how the universe expanded over time, make 3D maps of galaxies and galaxy clusters, reveal new details about star formation and evolution — all things we simulated. So now we get to practice on the synthetic data so we can get right to the science when real observations begin.”
Astronomers will continue using the simulations after Roman launches for a cosmic game of spot the differences. Comparing real observations with synthetic ones will help scientists see how accurately their simulation predicts reality. Any discrepancies could hint at different physics at play in the universe than expected.
“If we see something that doesn’t quite agree with the standard model of cosmology, it will be extremely important to confirm that we’re really seeing new physics and not just misunderstanding something in the data,” said Katrin Heitmann, a cosmologist and deputy director of Argonne’s High Energy Physics division who managed the project’s supercomputer time. “Simulations are super useful for figuring that out.”
OpenUniverse, along with other simulation tools being developed by Roman’s Science Operations and Science Support centers, will prepare astronomers for the large datasets expected from Roman. The project brings together dozens of experts from NASA’s JPL, DOE’s Argonne, IPAC, and several U.S. universities to coordinate with the Roman Project Infrastructure Teams, SLAC, and the Rubin LSST DESC (Legacy Survey of Space and Time Dark Energy Science Collaboration). The Theta supercomputer was operated by the Argonne Leadership Computing Facility, a DOE Office of Science user facility.
The Nancy Grace Roman Space Telescope is managed at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with participation by NASA’s Jet Propulsion Laboratory and Caltech/IPAC in Southern California, the Space Telescope Science Institute in Baltimore, and a science team comprising scientists from various research institutions. The primary industrial partners are BAE Systems, Inc in Boulder, Colorado; L3Harris Technologies in Rochester, New York; and Teledyne Scientific & Imaging in Thousand Oaks, California.
Download high-resolution video and images from NASA’s Scientific Visualization Studio
By Ashley Balzer
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Media Contact:
Claire Andreoli
NASA’s Goddard Space Flight Center, Greenbelt, Md.
301-286-1940
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Last Updated Jan 14, 2025 EditorAshley BalzerContactAshley Balzerashley.m.balzer@nasa.govLocationGoddard Space Flight Center Related Terms
Nancy Grace Roman Space Telescope Astrophysics Dark Energy Dark Matter Galaxies Galaxies, Stars, & Black Holes Galaxies, Stars, & Black Holes Research Galaxy clusters Goddard Space Flight Center High-Tech Computing Science & Research Stars Supernovae Technology The Universe Explore More
6 min read How NASA’s Roman Space Telescope Will Illuminate Cosmic Dawn
Article 6 months ago 6 min read Why NASA’s Roman Mission Will Study Milky Way’s Flickering Lights
Article 1 year ago 7 min read Simulated Image Shows How NASA’s Roman Could Expand on Hubble’s Deepest View
Article 3 years ago View the full article
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By NASA
Credit: NASA NASA Administrator Bill Nelson and Nicky Fox, associate administrator, Science Mission Directorate, will host a media teleconference at 1 p.m. EST, Tuesday, Jan. 7, to provide an update on the status of the agency’s Mars Sample Return Program.
The briefing will include NASA’s efforts to complete its goals of returning scientifically selected samples from Mars to Earth while lowering cost, risk, and mission complexity.
Audio of the media call will stream live on the agency’s website.
Media interested in participating by phone must RSVP no later than two hours prior to the start of the call to: dewayne.a.washington@nasa.gov. A copy of NASA’s media accreditation policy is online.
The agency’s Mars Sample Return Program has been a major long-term goal of international planetary exploration for more than two decades. NASA’s Perseverance rover is collecting compelling science samples that will help scientists understand the geological history of Mars, the evolution of its climate, and prepare for future human explorers. The return of the samples also will help NASA’s search for signs of ancient life.
For more information about NASA’s Mars exploration, visit:
https://nasa.gov/mars
-end-
Meira Bernstein / Dewayne Washington
Headquarters, Washington
202-358-1100
meira.b.bernstein@nasa.gov / dewayne.a.washington@nasa.gov
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Last Updated Jan 03, 2025 EditorJessica TaveauLocationNASA Headquarters Related Terms
Mars Sample Return (MSR) Science Mission Directorate View the full article
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By NASA
3 min read
January’s Night Sky Notes: The Red Planet
by Kat Troche of the Astronomical Society of the Pacific
Have you looked up at the night sky this season and noticed a bright object sporting a reddish hue to the left of Orion? This is none other than the planet Mars! January will be an excellent opportunity to spot this planet and some of its details with a medium-sized telescope. Be sure to catch these three events this month.
Martian Retrograde
Mars entered retrograde (or backward movement relative to its usual direction) on December 7, 2024, and will continue throughout January into February 23, 2025. You can track the planet’s progress by sketching or photographing Mars’ position relative to nearby stars. Be consistent with your observations, taking them every few nights or so as the weather permits. You can use free software like Stellarium or Stellarium Web (the browser version) to help you navigate the night as Mars treks around the sky. You can find Mars above the eastern horizon after 8:00 PM local time.
This mid-January chart shows the path of Mars from September 2024 to June 2025 as it enters and then exits in retrograde motion. Mars appears to change its direction of motion in the sky because Earth is passing the slower-moving Mars in its orbit. Stellarium Hide and Seek
On the night of January 13th, you can watch Mars ‘disappear’ behind the Moon during an occultation. An occultation is when one celestial object passes directly in front of another, hiding the background object from view. This can happen with planets and stars in our night sky, depending on the orbit of an object and where you are on Earth, similar to eclipses.
A simulated view of the Moon as Mars begins its occultation on January 13, 2025. Stellarium Depending on where you are within the contiguous United States, you can watch this event with the naked eye, binoculars, or a small telescope. The occultation will happen for over an hour in some parts of the US. You can use websites like Stellarium Web or the Astronomical League’s ‘Moon Occults Mars’ chart to calculate the best time to see this event.
Closer and Closer
As you observe Mars this month to track its retrograde movement, you will notice that it will increase in brightness. This is because Mars will reach opposition by the evening of January 16th. Opposition happens when a planet is directly opposite the Sun, as seen from Earth. You don’t need to be in any specific city to observe this event; you only need clear skies to observe that it gets brighter. It’s also when Mars is closest to Earth, so you’ll see more details in a telescope.
Want a quick and easy way to illustrate what opposition is for Jupiter, Saturn, Mars, or other outer worlds? Follow the instructions on our Toolkit Hack: Illustrating Opposition with Exploring the Solar System page using our Exploring Our Solar System activity!
A mosaic of the Valles Marineris hemisphere of Mars projected into point perspective, a view similar to that which one would see from a spacecraft. The mosaic is composed of 102 Viking Orbiter images of Mars. NASA/JPL-Caltech Mars has fascinated humanity for centuries, with its earliest recorded observations dating back to the Bronze Age. By the 17th century, astronomers were able to identify features of the Martian surface, such as its ice caps and darker regions. Since the 1960s, exploration of the Red Planet has intensified with robotic missions from various space organizations. Currently, NASA has five active missions, including rovers and orbiters, with the future focused on human exploration and habitation. Mars will always fill us with a sense of wonder and adventure as we reach for its soil through initiatives such as the Moon to Mars Architecture and the Mars Sample Return campaign.
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