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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
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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
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7 min read
Newly Selected Citizen Science Proposals: A Peek at What’s Next
Last year, the NASA citizen science community saw a prize from the White House and two prizes from professional societies: one from the Division of Planetary Sciences and one from the American Astronomical Society. Our teams published two papers in the prestigious journal, Nature, one on a planetary crash and one about a distant world that seems to have auroras. 2024 was a year of 5000 comets, two solar eclipses and plenty of broken records.
But we’re not stopping to rest on our laurels. In 2024, NASA selected 25 new citizen science proposals for funding that will lead to new projects and new results to look forward to in 2025 and beyond. Here’s a roundup of those selections and the principal investigators (PIs) of each team—a sneak peek at what’s coming next in NASA citizen science! Note that these investigations are research grants–some of them will result in new opportunities for the public, others will use results from earlier citizen science projects or develop new tools.
Bright green glow observed from Texas on June 1, 2024, by Stephen Hummel. A new grant to the Spritacular project team will support citizen science research on this newly-discovered phenomenon. Stephen Hummel Citizen Science Seed Funding Program (CSSFP)
The CSSFP aims to support scientists and other experts to develop citizen science projects and to expand the pool of scientists who use citizen science techniques in their science investigations. Four divisions of NASA’s Science Mission Directorate are participating in the CSSFP: the Astrophysics Division, the Biological and Physical Sciences Division, the Heliophysics Division, and the Planetary Science Division. Nine new investigations were recently selected through this program:
Astrophysics Division
SuPerPiG Observing Grid, PI Rachel Huchmala, Boise State University. Use a small telescope to monitor exoplanets to improve our knowledge of their orbits. Understanding the Nature of Clumpy Galaxies with Clump-Scout 2: a New Citizen-Science Project to Characterize Star-Forming Clumps in Nearby Galaxies. PI Claudia Scarlata, University of Minnesota. Label clumps of distant galaxies to help us understand Hubble Space Telescope data. ‘Backyard Worlds: Binaries’ — Discovering Benchmark Brown Dwarfs Through Citizen Science. PI Aaron Meisner, NSF’s NOIRLab. Search for planet-like objects called brown dwarfs that orbit nearby stars. Mobile Toolkits to Enable Transient Follow-up Observations by Amateur Astronomers. PI Michael Coughlin, University of Minnesota. Use your own telescope to observe supernovae, kilonovae and other massive explosions. Planetary Science Division
A Citizen Scientist Approach to High Resolution Geologic Mapping of Intracrater Impact Melt Deposits as an input to Numerical Models, PI Kirby Runyon, Planetary Science Institute. Help map lunar craters so we can better understand how meteor impacts sculpt the moon’s surface. Identifying Active Asteroids in Public Datasets, PI Chad Trujillo, Northern Arizona University, Search for icy, comet-like bodies hiding in the asteroid belt using new data from the Canada-France-Hawaii telescope. Heliophysics Division
Enabling Magnetopause Observations With Informal Researchers (EMPOWR). PI Mo Wenil, Johns Hopkins University. Investigate plasma layers high above the Earth using data from NASA’s Magnetospheric Multiscale (MMS) mission and the Zooniverse platform. High-resolution Ionospheric Imaging using Dual-Frequency Smartphones. PI Josh Semeter, Boston University. Study the upper atmosphere using cell phone signals. Large Scale Structures Originating from the Sun (LASSOS) multi-point catalog: A citizen project connecting operations to research. PI Cecelia Mac Cormack, Catholic University of America. Help build a catalog of structures on the Sun. Comet Identification and Image Annotation Modernization for the Sungrazer Citizen Science Project. PI Oliver Gerland. Search for comets in data from ESA and NASA’s Solar and Heliospheric Observatory (SOHO) mission using new web tools. Heliophysics Citizen Science Investigations (HCSI)
The HCSI program supports medium-scale citizen science projects in the Heliophysics Division of NASA’s Science Mission Directorate. Six investigations were recently selected through this program:
Investigation of green afterglow observed above sprite and gigantic jet tops based on Spritacular project database, PI Burcu Kosar. Photograph electric phenomena above storm clouds to help us understand a newly discovered green glow and learn about atmospheric chemistry. Machine Learning competition for Solar Wind prediction in preparation of solar maximum. PI Enrico Camporeale, University of Colorado, Boulder. Take part in a competition to predict the speed of the solar wind using machine learning. A HamSCI investigation of the bottomside ionosphere during the 2023 annular and 2024 total solar eclipses. PI Gareth Perry, New Jersey Institute of Technology. Use Ham Radio data to investigate the effects of solar eclipses on the ionosphere. Dynamic footprint in mid-latitude mesospheric clouds. PI Chihiko Cullens, University of Colorado, Boulder. Collect and analyze data on noctilucent clouds, rare high-altitude clouds that shine at night. Monitoring Solar Activity During Solar Cycle 25 with the GAVRT Solar Patrol Science and Education Program. PI Marin Anderson, Jet Propulsion Laboratory. Track solar activity during the period leading up to and including solar maximum. What is the total energy input to the heliosphere from solar jets? PI Nour Rawafi, The Johns Hopkins University Applied Physics Laboratory. Identify solar jets in images from the Solar Dynamics Observatory Citizen Science for Earth Systems Program (CSESP)
CSESP opportunities focus on developing and implementing projects that harness contributions from members of the general public to advance our understanding of Earth as a system. Proposals for the 2024 request were required to demonstrate a clear link between citizen science and NASA observation systems to advance the agency’s Earth science mission. Nine projects received funding.
Engaging Citizen Scientists for Inclusive Earth Systems Monitoring, PI Duan Biggs, Northern Arizona University. Measure trees in tropical regions south of the equator with the GLOBE Observer App to improve models of vegetation structure and biomass models from NASA’s Global Ecosystem Dynamics Investigation (GEDI) mission. Integrating Remote Sensing and Citizen Science to Support Conservation of Woodland Vernal Pools, PI Laura Bourgeau-Chavez, Michigan Technological University. Map and monitor shallow, seasonal wetlands in Michigan, Wisconsin and New York to better understand these key habitats of amphibians and other invertebrates. Citizen-Enabled Measurement of PM2.5 and Black Carbon: Addressing Local Inequities and Validating PM Composition from MAIA, Albert Presto/Carnegie Mellon University. Deploy sensors to measure sources of fine airborne particle pollution filling gaps in data from NASA’s Multi-Angle Imager for Aerosols (MAIA) mission. Expanding Citizen Science Hail Observations for Validation of NASA Satellite Algorithms and Understanding of Hail Melt, PI Russ Schumacher, Colorado State University. Measure the sizes and shapes of hailstones, starting in the southeastern United States, using photographs and special pads to help us understand microwave satellite data. X-Snow: A Citizen-Science Proposal for Snow in the New York Area, PI, Marco Tedesco, Columbia University. Measure snow in the Catskill and Adirondacks regions of New York to help improve NASA’s models of snow depth and water content. Coupling Citizen Science and Remote Sensing Observations to Assess the Impacts of Icebergs on Coastal Arctic Ecosystems, PI, Maria Vernet, University of California, San Diego. Measure phytoplankton samples in polar regions to understand how icebergs and their meltwater affect phytoplankton concentration and biodiversity. Forecasting Mosquito-Borne Disease Risk in a Changing Climate: Integrating GLOBE Citizen Science and NASA Earth System Modeling, PI Di Yang, University of Florida, Gainesville. Using data on mosquitoes from the GLOBE Observer App to predict future changes in mosquito-borne disease risk. Ozone Measurements from General Aviation: Supporting TEMPO Satellite Validation and Addressing Air Quality Issues in California’s San Joaquin Valley with Citizen Science, PI Emma Yates, NASA Ames Research Center. Deploy air-quality sensors around Bakersfield, California and compare the data to measurements from NASA’s Tropospheric Emissions Monitoring of Pollution instrument (TEMPO). Under the Canopy: Capturing the Role of Understory Phenology on Animal Communities Using Citizen Science, PI Benjamin Zuckerberg, University of Wisconsin, Madison. Measure snow depth, temperature, and sound in forest understories to improve satellite-based models of vegetation and snow cover for better modeling of wildlife communities. For more information on citizen science awards from previous years, see articles from:
September 2023 August 2022 July 2021 For more information on NASA’s citizen science programs, visit https://science.nasa.gov/citizenscience.
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Last Updated Jan 13, 2025 Related Terms
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By NASA
Skywatching Home Skywatching The Next Full Moon is the Wolf… Skywatching Home What’s Up Eclipses Explore the Night Sky Night Sky Network More Tips and Guides FAQ 27 Min Read The Next Full Moon is the Wolf Moon
The Moon sets over Homestead National Historic Park in Nebraska. Credits:
National Park Service/Homestead The next full Moon is the Wolf Moon; the Ice or Old Moon; the Moon after Yule; the start of Prayag Kumbh Mela; Shakambhari Purnima; Paush Purnima; the Thiruvathira, Thiruvathirai, or Arudhra Darisanam festival Moon; and Duruthu Poya.
The phases of the Moon for January 2025. NASA/JPL-Caltech The next full Moon will be Monday evening, Jan. 13, 2025, appearing opposite the Sun (in Earth-based longitude) at 5:27 p.m. EST. This will be Tuesday from the South Africa and Eastern European time zones eastward across the remainder of Africa, Europe, Asia, Australia, etc., to the International Date Line in the mid-Pacific. The Moon will appear full for about three days around this time, from Sunday evening (and possibly the last part of Sunday morning) into Wednesday morning. On the night of the full Moon, for most of the continental USA as well as parts of Africa, Canada, and Mexico, the Moon will pass in front of the planet Mars.
The Maine Farmers’ Almanac began publishing Native American names for full Moons in the 1930s. Over time these names have become widely known and used. According to this almanac, as the full Moon in January this is the Wolf Moon, from the packs of wolves heard howling outside the villages amid the cold and deep snows of winter.
European names for this Moon include the Ice Moon, the Old Moon, and (as the full Moon after the winter solstice) the Moon after Yule. Yule was a three to 12-day festival near the winter solstice in pre-Christian Europe. In the tenth century King Haakon I associated Yule with Christmas as part of the Christianization of Norway, and this association spread throughout Europe. The exact timing of this pre-Christian celebration is unclear. Some sources now associate Yule with the 12 days of Christmas, so that the Moon after Yule is after Twelfth Night on January 6. Other sources suggest that Yule is an old name for the month of January, so the Moon after Yule is in February. In the absence of more reliable historic information, I’m going with the full Moon after the winter solstice as the Moon after Yule.
This full Moon corresponds with the start of the 44-day festival Prayag Kumbh Mela, also known as Maha Kumbh. This Hindu pilgrimage and festival is held every 12 years in the Indian city of Prayagraj at the confluence of three rivers, the Ganges, the Yamuna, and the mythical Sarasvati. It is expected to draw around 400 million visitors. Similar Kumbh celebrations are held approximately every 12 years at the convergence of three rivers in three other Indian cities, Nashik (upcoming in 2027), Ujjain (in 2028), and Haridwar (in 2033).
In the Hindu calendar, this full Moon is Shakambhari Purnima, the last day in the 8-day Shakambari Navratri holiday that celebrates the goddess Shakambhari. In the Purnimanta tradition that ends months on the full Moon day, this full Moon is Paush Purnima, the last day of the Hindu month of Paush. The day after Paush Purnima is the start of the month of Magha, a period of austerity. Bathing in the holy waters of India is an important activity for both Shakambari Navratri and Magha.
This full Moon corresponds with the Thiruvathira, Thiruvathirai, or Arudhra Darisanam festival, celebrated by Hindus in the Indian states of Kerala and Tamil Nadu.
For the Buddhists of Sri Lanka, this is Duruthu Poya, which commemorates Siddhartha Gautama Buddha’s first visit to Sri Lanka.
In many lunar and lunisolar calendars the months change with the new Moon and full Moons fall in the middle of the lunar month. This full Moon is in the middle of the 12th and final month of the Chinese Year of the Rabbit. The new Moon on January 29 will be Chinese New Year, the start of the Year of the Snake. This full Moon is in the middle of Tevet in the Hebrew calendar and Rajab, the seventh month of the Islamic calendar. Rajab is one of the four sacred months in which warfare and fighting are forbidden.
As usual, the wearing of suitably celebratory celestial attire is encouraged in honor of the full Moon. Take care in the cold weather and take advantage of these early sunsets to enjoy and share the wonders of the night sky. And avoid starting any wars.
Here are the other celestial events between now and the full Moon after next, with times and angles based on the location of NASA Headquarters in Washington, D.C.:
As winter continues in the Northern Hemisphere, the daily periods of sunlight continue to lengthen. Our 24-hour clock is based on the average length of a day with the solar days near the solstices longer than those near the equinoxes. For Washington, D.C. and similar latitudes (I’ve not checked for other areas) the latest sunrise of the year (ignoring Daylight Saving Time) occurred on January 4. Monday, January 13 (the day of the full Moon), morning twilight will begin at 6:24 a.m. EST, sunrise will be at 7:26 a.m., solar noon will be at 12:17 p.m. when the Sun will reach its maximum altitude of 29.8 degrees, sunset will be at 5:08 p.m., and evening twilight will end at 6:11 p.m. By Wednesday, February 12 (the day of the full Moon after next), morning twilight will begin at 6:04 a.m., sunrise will be at 7:03 a.m., solar noon will be at 12:23 p.m. when the Sun will reach its maximum altitude of 37.7 degrees, sunset will be at 5:43 p.m., and evening twilight will end at 6:41 p.m.
This should be a good time for planet watching, especially with a backyard telescope. Venus, Jupiter, Mars, Saturn, and Uranus will all be in the evening sky. Brightest will be Venus, appearing in the southwestern sky. With a telescope you should be able to see it shift from half-full to a 29% illuminated crescent during this lunar cycle as it brightens and moves closer to the Earth.
Venus will reach its brightest for the year just after the full Moon after next. Second in brightness will be Jupiter in the eastern sky. With a telescope you should be able to see Jupiter’s four bright moons, Ganymede, Callisto, Europa, and Io, noticeably shifting positions in the course of an evening. Jupiter was at its closest and brightest in early December. Third in brightness will be Mars low in the east-northeastern sky. Mars will be at its closest and brightest for the year a few days after this full Moon. Fourth in brightness will be Saturn, appearing near Venus in the southwestern sky. With a telescope you should be able to see Saturn’s bright moon Titan and maybe its rings. The rings are appearing very thin and will be edge-on to the Earth in March 2025. We won’t get the “classic” view of Saturn showing off its rings until 2026. Saturn was at its closest and brightest in early September and will appear its closest to Venus (2.2 degrees apart) the evening of January 18. Fifth in brightness and technically bright enough to see without a telescope (if you are in a very dark location and your eyesight is better than mine) will be Uranus high in the southeastern sky. Uranus was at its closest and brightest in mid-November.
During this lunar cycle these planets will be rotating westward around the pole star Polaris (with Venus shifting more slowly) making them easier to see earlier in the evening, and friendlier for backyard stargazing, especially if you have young ones with earlier bedtimes.
Comets
As mentioned in my last posting, the sungrazing comet C/2024 G3 (ATLAS) will be passing very near the Sun on January 13. There is a chance that this comet will break up and vanish from view as it approaches the Sun, much as comet C/2024 S1 (ATLAS) did in October. In addition, its visual magnitude might not be bright enough to see in the daytime due to the glow of the nearby Sun. If it does not break up and is bright enough, Northern Hemisphere viewers will have the best viewing near its closest approach. For the Washington, D.C. area, it could be brightest the evening of January 12 before it sets on the southwestern horizon. You will need to find a distant object to block direct sunlight so you can safely look about 5 degrees to the upper right of the Sun. If the horizon is very clear, your best chance might be after sunset at 5:07 p.m. EST, but before the comet sets about 10 minutes later. Southern Hemisphere viewers will have the best viewing after closest approach, immediately after sunset from mid-January on (dimming each evening as it moves away from the Sun and the Earth). You may need binoculars or a telescope to see it, although comets are hard to predict.
Meteor Showers
Two minor meteor showers, the γ-Ursae Minorids (404 GUM) and α-Centaurids (102 ACE), will peak during this lunar cycle. The light of the waning Moon will interfere with the γ-Ursae Minorids peak on January 18. The α-Centaurids, only visible from the Southern Hemisphere, are expected to peak on February 8. In recent years the average peak has been 6 visible meteors per hour (under ideal conditions), although this shower showed bursts of 20 to 30 meteors per hour in 1974 and 1980. The best viewing conditions will likely be after the waxing gibbous Moon sets in the early mornings around the peak.
Evening Sky Highlights
On the evening of Monday, Jan. 13, 2025 (the evening of the full Moon), as twilight ends (at 6:11 p.m. EST), the rising Moon will be 13 degrees above the east-northeastern horizon with the bright planet Mars (the third brightest planet) 2 degrees to the lower left and the bright star Pollux (the brighter of the twin stars in the constellation Gemini, the twins) 3 degrees to the upper left of the Moon. The brightest planet visible will be Venus at 29 degrees above the southwestern horizon, with the planet Saturn (fourth brightest) 6 degrees to the upper left of Venus. The second brightest planet, Jupiter, will be 47 degrees above the eastern horizon. The bright star closest to overhead will be Capella at 50 degrees above the east-northeastern horizon. Capella is the 6th brightest star in our night sky and the brightest star in the constellation Auriga (the charioteer). Although we see Capella as a single star it is actually four stars (two pairs of stars orbiting each other). Capella is about 43 light years from us.
As this lunar cycle progresses, the planets and the background of stars will appear to rotate westward around the pole star Polaris each evening, with Venus initially shifting the other direction. Mars will be at its closest and brightest on January 15. Venus and Saturn will appear closest to each other on January 18. Mars and Pollux will appear nearest each other on January 22 and 23. Venus will appear at its highest above the horizon (as twilight ends) on January 27, after which it will start shifting toward the horizon again. Jupiter and Aldebaran will appear at their closest on January 31. The waxing Moon will pass by Saturn on January 31; Venus on February 1; the Pleiades star cluster on February 5; and Mars and Pollux on February 10.
By the evening of Wednesday, February 12 (the evening of the full Moon after next), as twilight ends (at 6:41 p.m. EST), the rising Moon will be 7 degrees above the east-northeastern horizon with the bright star Regulus 2 degrees to the right. The brightest planet in the sky will be Venus at 28 degrees above the west-southwestern horizon, appearing as a crescent through a telescope. Next in brightness will be Jupiter at 71 degrees above the south-southeastern horizon. Third in brightness will be Mars at 48 degrees above the eastern horizon. Saturn will be 11 degrees above the west-southwestern horizon. Uranus, on the edge of what is visible under extremely clear, dark skies, will be 68 degrees above the south-southwestern horizon. The bright star closest to overhead will still be Capella at 75 degrees above the northeastern horizon.
Also high in the sky will be the constellation Orion, easily identifiable because of the three stars that form Orion’s Belt. This time of year, we see many bright stars in the sky at evening twilight, with bright stars scattered from the south-southeast toward the northwest. We see more stars in this direction because we are looking toward the Local Arm of our home galaxy (also called the Orion Arm, Orion-Cygnus Arm, or Orion Bridge). This arm is about 3,500 light years across and 10,000 light years long. Some of the bright stars we see from this arm are the three stars of Orion’s Belt, as well as Rigel (860 light years from Earth), Betelgeuse (548 light years), Polaris (about 400 light years), and Deneb (about 2,600 light years).
Facing toward the south from the northern hemisphere, to the upper left of Orion’s Belt is the bright star Betelgeuse (be careful not to say this name three times). About the same distance to the lower right is the bright star Rigel. Orion’s belt appears to point down and to the left about seven belt lengths to the bright star Sirius, the brightest star in the night sky. Below Sirius is the bright star Adara. To the upper right of Orion’s Belt (at about the same distance from Orion as Sirius) is the bright star Aldebaran. Nearly overhead is the bright star Capella. To the left (east) of Betelgeuse is the bright star Procyon. The two stars above Procyon are Castor and Pollux, the twin stars of the constellation Gemini (Pollux is the brighter of the two). The bright star Regulus appears farther to the left (east) of Pollux near the eastern horizon. Very few places on the East Coast are dark enough to see the Milky Way (our home galaxy), but if you could see it, it would appear to stretch overhead from the southeast to the northwest. Since we are seeing our galaxy from the inside, the combined light from its 100 billion to 400 billion stars make it appear as a band surrounding the Earth.
Morning Sky Highlights
On the morning of Monday, Jan. 13, 2025 (the morning of the full Moon), as twilight begins (at 6:23 a.m. EST), the setting full Moon will be 11 degrees above the west-northwestern horizon. This will be the last morning the planet Mercury will rise before morning twilight begins, although it will be bright enough to see in the glow of dawn after it rises for another week or so. This will leave Mars at 18 degrees above the west-northwestern horizon as the only planet in the sky. The bright star appearing closest to overhead will be Arcturus at 69 degrees above the south-southeastern horizon. Arcturus is the brightest star in the constellation Boötes (the herdsman or plowman) and the 4th brightest star in our night sky. It is 36.7 light years from us. While it has about the same mass as our Sun, it is about 2.6 billion years older and has used up its core hydrogen, becoming a red giant 25 times the size and 170 times the brightness of our Sun. One way to identify Arcturus in the night sky is to start at the Big Dipper, then follow the arc of the dipper’s handle as it “arcs toward Arcturus.”
As this lunar cycle progresses Mars and the background of stars will appear to rotate westward around the pole star Polaris by about 1 degree each morning. The waning Moon will appear near Mars and Pollux on January 13 and 14, Regulus on January 16, Spica on January 21, Antares on January 24 and 25, and (rising after morning twilight begins) Mercury on January 28. January 22 will be the last morning the planet Mercury will be above the horizon 30 minutes before sunrise. Mars and Pollux will be near their closest to each other the morning of January 23. February 4 will be the last morning the planet Mars will be above the northwestern horizon as morning twilight begins. The waxing Moon will appear near Pollux on February 9 (setting before twilight begins) and 10.
By the morning of Wednesday, February 12 (the morning of the full Moon after next), as twilight begins (at 6:04 a.m. EST), the setting full Moon will be 13 degrees above the western horizon. No planets will appear in the sky. The bright star appearing closest to overhead will still be Arcturus at 65 degrees above the southeastern horizon.
Detailed Daily Guide
Here is a day-by-day listing of celestial events between now and the full Moon on Feb. 12, 2025. The times and angles are based on the location of NASA Headquarters in Washington, D.C., and some of these details may differ for where you are (I use parentheses to indicate times specific to the D.C. area). If your latitude is significantly different than 39 degrees north (and especially for my Southern Hemisphere readers), I recommend using an astronomy app set for your location or a star-watching guide from a local observatory, news outlet, or astronomy club.
Tuesday evening, January 7 At 7:07 p.m. EST, the Moon will be at perigee, its closest to the Earth for this orbit.
Thursday evening, January 9 The waxing gibbous Moon will pass in front of the Pleiades star cluster. This may be viewed best with binoculars, as the brightness of the Moon will make it hard to see the stars in this star cluster. As evening twilight ends at 6:07 p.m. EST, the Pleiades will appear 1 degree to the lower left of the full Moon. Over the next few hours, including as the Moon reaches its highest for the night at 8:37 p.m., the Moon will pass in front of the Pleiades, blocking many of these stars from view. By about midnight the Pleiades will appear about 1 degree below the Moon, and the Moon and the Pleiades will separate as Friday morning progresses.
Also on Thursday night, January 9, the planet Venus will reach its greatest angular separation from the Sun as seen from the Earth for this apparition (called greatest elongation). Because the angle between the line from the Sun to Venus and the line of the horizon changes with the seasons, the date when Venus and the Sun appear farthest apart as seen from Earth is not always the same as when it appears highest above the west-southwestern horizon as evening twilight ends, which occurs on January 27.
Friday evening, January 10 The bright planet Jupiter will appear near the waxing gibbous Moon. As evening twilight ends at 6:08 p.m. EST, Jupiter will be 5 degrees to the lower right. As the Moon reaches its highest for the night at 9:37 p.m., Jupiter will be 6 degrees below the Moon. The pair will continue to separate until Jupiter sets Saturday morning at 4:45 a.m.
Sunday afternoon, January 12 There is a slight chance that the sungrazing comet, C/2024 G3 (ATLAS) might be visible near the setting Sun. Most likely, this comet will not be bright enough to see in the daytime or will break up and vanish from view like comet C/2024 S1 (ATLAS) did in October. The odds are low, but if the sky is clear, find an object to block direct sunlight (the farther away the object the better) so you can safely look about 5 degrees to the upper right of the Sun. If the west-southwestern horizon is clear, your best chance might be after sunset at 5:07 p.m. EST, but before the comet sets about 10 minutes later. This will only be visible from the Northern Hemisphere. Southern Hemisphere viewers may be able to see this comet from mid-January on immediately after sunset (dimming each evening as it moves away from us).
Monday morning, January 13 This is the morning of the full Moon. It will be the last morning Mercury will rise before morning twilight begins, although it will be bright enough to see in the glow of dawn after it rises for another week or so.
The Moon will be full Monday evening at 5:27 p.m. EST. This will be on Tuesday from the South Africa and Eastern European time zones eastward across the rest of Africa, Europe, Asia, Australia, etc., to the International Date Line in the mid-Pacific. The Moon will appear full for about three days around this time, from Sunday evening (and possibly the last part of Sunday morning) into Wednesday morning.
On Monday night the full Moon will appear near and pass in front of the bright planet Mars, with the bright star Pollux above the pair. As evening twilight ends at 6:11 p.m. EST, the three will form a triangle, with Mars 2 degrees to the lower left and Pollux 3 degrees to the upper left of the Moon. For most of the continental USA as well as parts of Africa, Canada, and Mexico, the Moon will pass in front of Mars. Times will vary for other locations, but for NASA Headquarters in Washington, D.C., Mars will vanish behind the bottom of the Moon at about 9:16 p.m. and reappear from behind the upper right of the Moon at about 10:31 p.m. By the time the Moon reaches its highest for the night early on Tuesday morning at 12:37 a.m., Mars will be 1 degree to the right of the Moon and Pollux 5 degrees to the upper right. As morning twilight begins at 6:23 a.m., Mars will be 4 degrees and Pollux 8 degrees to the lower right of the Moon.
Wednesday night January 15 The planet Mars will be at opposition, so called because it will be opposite the Earth from the Sun, effectively a “full” Mars. Near opposition Mars will be at its closest and brightest for the year. On Wednesday night, as evening twilight ends at 6:13 p.m. EST, Mars will be 14 degrees above the east-northeastern horizon. Mars will reach its highest in the sky early Thursday morning at 12:21 a.m., and will be 15 degrees above the west-northwestern horizon as morning twilight begins at 6:23 a.m. Only planets that orbit farther from the Sun than the Earth can be seen at opposition from the Earth.
Wednesday night into Thursday morning, January 15 to 16 The bright star Regulus will appear near the waning gibbous Moon. As Regulus rises on the east-northeastern horizon at 7:52 p.m. EST, it will be more than 8 degrees below the Moon. By the time the Moon reaches its highest for the night on Thursday morning at 2:17 a.m. Regulus will be 5.5 degrees to the lower left of the Moon. As morning twilight begins at 6:23 a.m. Regulus will be 4 degrees to the left of the Moon.
Saturday evening, January 18 Venus and Saturn will appear nearest to each other. As evening twilight ends at 6:15 p.m. EST, Venus will be 30 degrees above the southwestern horizon with Saturn 2.2 degrees to the lower left. Saturn will set first on the western horizon almost 3 hours later at 9:04 p.m.
Monday night, January 20 At 11:53 p.m. EST, the Moon will be at apogee, its farthest from the Earth for this orbit.
Tuesday morning, January 21 The bright star Spica will appear near the waning gibbous Moon. As the Moon rises on the east-southeastern horizon at 12:11 a.m. EST Spica will be 1 degree above the Moon. By the time the Moon reaches its highest for the night at 5:41 a.m., Spica will be 3.5 degrees to the upper right, with morning twilight beginning 40 minutes later at 6:21 a.m. For parts of Western Africa and the Atlantic Ocean the Moon will pass in front of Spica.
Tuesday afternoon, the waning Moon will appear half-full as it reaches its last quarter at 3:31 p.m. EST (when we can’t see it).
Wednesday morning, January 22 This will be the last morning Mercury will be above the horizon 30 minutes before sunrise, an approximation of the last morning it might be visible in the glow of dawn.
Throughout this lunar cycle, Mars and the bright star Pollux will appear near each other, with Wednesday night into Thursday morning and Thursday night into Friday morning (January 22, 23, and 24) the nights when they will be at their closest, 2.5 degrees apart. They will be up all night for both nights, with Mars at its highest on Wednesday night at 11:41 p.m. EST, and Thursday night at 11:36 p.m.
Friday morning, January 24 The bright star Antares will appear to the lower left of the waning crescent Moon. As Antares rises on the southeastern horizon at 3:54 a.m. EST, it will be 8 degrees from the Moon. By the time morning twilight begins less than 2.5 hours later at 6:19 a.m., Antares will be 6.5 degrees from the Moon. For part of the Indian Ocean the Moon will actually pass in front of Pollux.
Saturday morning, January 25 The Moon will have shifted to the other side of Antares. As the Moon rises at 4:20 a.m. EST, Antares will be 6 degrees to the upper right of the Moon. By the time morning twilight begins 2 hours later at 6:19 a.m., Antares will be 7 degrees from the Moon.
Monday evening, January 27 Venus will be at its highest above the west-southwestern horizon (31 degrees) as evening twilight ends at 6:25 p.m. EST, appearing as a 41% illuminated crescent through a telescope.
Wednesday morning, January 29 At 7:36 a.m. EST there will be a new Moon, when the Moon passes between the Earth and the Sun, and the Moon will not be visible from the Earth. The day of, or the day after, the New Moon marks the start of the new month for most lunisolar calendars. The first month of the Chinese calendar starts on Wednesday, January 29, making this Chinese New Year, the start of the Year of the Snake! Chinese New Year and related celebrations throughout much of Asia and in areas with significant Chinese populations celebrate the end of winter and start of spring. Traditional festivities start on the eve of Chinese New Year and continue until the Lantern Festival on the 15th day of the first lunar month.
Sundown on Wednesday, January 29 This marks the start of Shevat in the Hebrew calendar.
Sundown on Thursday, January 30 In the Islamic calendar, the months traditionally start with the first sighting of the waxing crescent Moon. Many Muslim communities now follow the Umm al-Qura Calendar of Saudi Arabia, which uses astronomical calculations to start months in a more predictable way. Using this calendar, sundown on Thursday, January 30, will probably mark the beginning of Shaʿbān, the eighth month of the Islamic year and the month before Ramadan.
Friday evening, January 31 Saturn will appear 4 degrees to the upper left of the waxing crescent Moon. The Moon will be 17 degrees above the west-southwestern horizon as evening twilight ends at 6:29 p.m. EST, and will set on the western horizon 99 minutes later at 8:08 p.m. For part of Asia the Moon will actually pass in front of Saturn.
Throughout this lunar cycle the bright star Aldebaran will appear below the bright planet Jupiter, with Friday, January 31 the evening they appear at their closest, about 5 degrees apart. As evening twilight ends at 6:29 p.m. EST, Jupiter will be 65 degrees above the southeastern horizon with Aldebaran to the lower right. Jupiter will reach its highest for the night, 73 degrees above the southern horizon at 8:01 p.m., with Aldebaran below Jupiter. As Aldebaran sets on the west-northwestern horizon almost 7 hours after that at 2:56 a.m. it will be to the lower left of the Moon.
Saturday evening, February 1 Venus will appear near the waxing crescent Moon. The Moon will be 30 degrees above the west-southwestern horizon as evening twilight ends at 6:30 p.m. EST, with Venus 2.5 degrees to the upper right. Venus will be 2.5 degrees to the lower right as it sets first on the western horizon 2.75 hours later at 9:15 p.m.
Saturday night, at 9:38 p.m. EST, the Moon will be at perigee, its closest to the Earth for this orbit.
Saturday also is Imbolc or Imbolg, and the next day (Sunday, February 2) is Candlemas or Groundhog’s Day. We currently divide the year into four seasons based upon the solstices and equinoxes, with spring starting on the vernal equinox. This approximates winter as the quarter of the year with the coldest temperatures. Much of pre-Christian northern Europe celebrated “cross-quarter days” halfway between the solstices and equinoxes, dividing the seasons on these days. Using this definition, winter was the quarter of the year with the shortest daily periods of daylight, and spring started on Imbolc (the middle of our winter).
The tradition in some European countries was to leave Christmas decorations up until February 1st, the eve of Candlemas, and it was considered bad luck to leave decorations up past this date. Robert Herrick (1591-1674) starts his poem “Ceremonies for Candlemas Eve” with “Down with the rosemary and bays, down with the mistletoe; Instead of holly, now up-raise the greener box (for show).”
We have a tradition in the United States that winter will end on Groundhog Day if the groundhog sees its shadow. If not, winter will last six weeks more (ending around the time of the spring equinox). Groundhog Day appears to tie back to European lore about whether or not badgers, wolves, or bears (instead of groundhogs) see their shadows. Many believe that these Groundhog Day and Candlemas traditions tie back to these earlier celebrations for the start of spring. It seems plausible to me that it was confusing to have two competing dates for the end of winter. Perhaps it was best to let a natural event such as an animal’s shadow decide which definition to use, rather than arguing with your neighbors for the next six weeks.
Tuesday morning, February 4 This will be the last morning Mars will be above the northwestern horizon as morning twilight begins.
Wednesday morning, February 5 The Moon will appear half-full as it reaches its first quarter at 3:02 a.m. EST (when we can’t see it).
Wednesday evening the waxing gibbous Moon will appear near the Pleiades star cluster. As evening twilight ends at 6:34 p.m. EST, this star cluster will be 5 degrees to the upper left of the Moon. The Pleiades will shift closer toward the Moon until the Moon sets on the west-northwestern horizon less than 8 hours later at 2:16 a.m. Some North American locations farther west will actually see the Moon pass in front of some of the stars in the Pleiades.
Sunday morning, February 9 Mars will appear to the upper left of the waxing gibbous Moon. In the early morning at about 2 a.m. EST, Mars will be 8 degrees from the Moon. By the time the Moon sets on the northwestern horizon at 5:58 a.m., Mars will have shifted to 6 degrees from the Moon. For parts of Asia and Northern Europe the Moon will pass in front of Mars.
Also Sunday morning, Mercury will be passing on the far side of the Sun as seen from the Earth, called superior conjunction. Because Mercury orbits inside of the orbit of Earth it will be shifting from the morning sky to the evening sky and will begin emerging from the glow of dusk on the west-southwestern horizon after about February 17 (depending upon viewing conditions).
Sunday evening into Monday morning, February 9 to 10 The waxing gibbous Moon will have shifted to the other side of Mars (having passed in front of Mars in the afternoon when we could not see them). As evening twilight ends at 6:38 p.m. EST, the Moon will be between Mars and the bright star Pollux, with Mars 3 degrees to the upper right and Pollux 3 degrees to the lower left. By the time the Moon reaches its highest for the night at 10:27 p.m., Mars will be 4.5 degrees to the right of the Moon and Pollux 2.5 degrees to the upper left of the Moon. Mars will set first on the northwestern horizon Monday morning at 5:44 a.m. just 22 minutes before morning twilight begins at 6:06 a.m.
Wednesday morning, February 12 The full Moon after next will be at 8:53 a.m. EST, with the bright star Regulus nearby. This will be on Thursday morning from Australian Central Time eastward to the International Date Line in the mid-Pacific. The Moon will appear full for about three days around this time, from Monday night into early Thursday evening.
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By NASA
3 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Next Generation Lunar Retroreflector, or NGLR-1, is one of 10 payloads set to fly aboard the next delivery for NASA’s CLPS (Commercial Lunar Payload Services) initiative in 2025. NGLR-1, outfitted with a retroreflector, will be delivered to the lunar surface to reflect very short laser pulses from Earth-based lunar laser ranging observatories. Photo courtesy Firefly Aerospace Apollo astronauts set up mirror arrays, or “retroreflectors,” on the Moon to accurately reflect laser light beamed at them from Earth with minimal scattering or diffusion. Retroreflectors are mirrors that reflect the incoming light back in the same incoming direction. Calculating the time required for the beams to bounce back allowed scientists to precisely measure the Moon’s shape and distance from Earth, both of which are directly affected by Earth’s gravitational pull. More than 50 years later, on the cusp of NASA’s crewed Artemis missions to the Moon, lunar research still leverages data from those Apollo-era retroreflectors.
As NASA prepares for the science and discoveries of the agency’s Artemis campaign, state-of-the-art retroreflector technology is expected to significantly expand our knowledge about Earth’s sole natural satellite, its geological processes, the properties of the lunar crust and the structure of lunar interior, and how the Earth-Moon system is changing over time. This technology will also allow high-precision tests of Einstein’s theory of gravity, or general relativity.
That’s the anticipated objective of an innovative science instrument called NGLR (Next Generation Lunar Retroreflector), one of 10 NASA payloads set to fly aboard the next lunar delivery for the agency’s CLPS (Commercial Lunar Payload Services) initiative. NGLR-1 will be carried to the surface by Firefly Aerospace’s Blue Ghost 1 lunar lander.
Developed by researchers at the University of Maryland in College Park, NGLR-1 will be delivered to the lunar surface, located on the Blue Ghost lander, to reflect very short laser pulses from Earth-based lunar laser ranging observatories, which could greatly improve on Apollo-era results with sub-millimeter-precision range measurements. If successful, its findings will expand humanity’s understanding of the Moon’s inner structure and support new investigations of astrophysics, cosmology, and lunar physics – including shifts in the Moon’s liquid core as it orbits Earth, which may cause seismic activity on the lunar surface.
“NASA has more than half a century of experience with retroreflectors, but NGLR-1 promises to deliver findings an order of magnitude more accurate than Apollo-era reflectors,” said Dennis Harris, who manages the NGLR payload for the CLPS initiative at NASA’s Marshall Space Flight Center in Huntsville, Alabama.
Deployment of the NGLR payload is just the first step, Harris noted. A second NGLR retroreflector, called the Artemis Lunar Laser Retroreflector (ALLR), is currently a candidate payload for flight on NASA’s Artemis III mission to the Moon and could be set up near the lunar south pole. A third is expected to be manifested on a future CLPS delivery to a non-polar location.
“Once all three retroreflectors are operating, they are expected to deliver unprecedented opportunities to learn more about the Moon and its relationship with Earth,” Harris said.
Under the CLPS model, NASA is investing in commercial delivery services to the Moon to enable industry growth and support long-term lunar exploration. As a primary customer for CLPS deliveries, NASA aims to be one of many customers on future flights. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the development of seven of the 10 CLPS payloads carried on Firefly’s Blue Ghost lunar lander.
Learn more about. CLPS and Artemis at:
https://www.nasa.gov/clps
Alise Fisher
Headquarters, Washington
202-358-2546
Alise.m.fisher@nasa.gov
Headquarters, Washington
202-358-2546
Alise.m.fisher@nasa.gov
Corinne Beckinger
Marshall Space Flight Center, Huntsville, Ala.
256-544-0034
corinne.m.beckinger@nasa.gov
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Last Updated Jan 02, 2025 EditorBeth RidgewayContactCorinne M. Beckingercorinne.m.beckinger@nasa.govLocationMarshall Space Flight Center Related Terms
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By NASA
Artist’s concept depicts new research that has expanded our understanding of exoplanet WASP-69 b’s “tail.” NASA/JPL-Caltech/R. Hurt (IPAC) The Planet
WASP-69 b
The Discovery
The exoplanet WASP-69 b has a “tail,” leaving a trail of gas in its wake.
Key Takeaway
WASP-69 b is slowly losing its atmosphere as light hydrogen and helium particles in the planet’s outer atmosphere escape the planet over time. But those gas particles don’t escape evenly around the planet, instead they are swept into a tail of gas by the stellar wind coming from the planet’s star.
Details
Hot Jupiters like WASP-69 b are super-hot gas giants orbiting their host stars closely. When radiation coming from a star heats up a planet’s outer atmosphere, the planet can experience photoevaporation, a process in which lightweight gases like hydrogen and helium are heated by this radiation and launched outward into space. Essentially, WASP-69 b’s star strips gas from the planet’s outer atmosphere over time.
What’s more, something called the stellar wind can shape this escaping gas into an exoplanetary tail.
The stellar wind is a continuous stream of charged particles that flow outwards into space from a star’s outer atmosphere, or corona. On Earth, the Sun’s stellar wind interacts with our planet’s magnetic field which can create beautiful auroras like the Northern Lights.
On WASP-69 b, the stellar wind coming from its host star actually shapes the gas escaping from the planet’s outer atmosphere. So, instead of gas just escaping evenly around the planet, “strong stellar winds can sculpt that outflow in tails that trail behind the planet,” said lead author Dakotah Tyler, an astrophysicist at the University of California, Los Angeles, likening this gaseous tail to a comet’s tail.
Because this tail is created by the stellar wind, however, that means it’s subject to change.
“If the stellar wind were to taper down, then you could imagine that the planet is still losing some of its atmosphere, but it just isn’t getting shaped into the tail,” Tyler said, adding that, without the stellar wind, that gas escaping on all sides of the planet would be spherical and symmetrical. “But if you crank up the stellar wind, that atmosphere then gets sculpted into a tail.”
Tyler likened the process to a windsock blowing in the breeze, with the sock forming a more structured shape when the wind picks up and it fills with air.
The tail that Tyler and his research team observed on WASP-69 b extended more than 7.5 times the radius of the planet, or over 350,000 miles. But it’s possible that the tail is even longer. The team had to end observations with the telescope before the tail’s signal disappeared, so this measurement is a lower limit on the tail’s true length at the time.
However, keep in mind that because the tail is influenced by the stellar wind, changes in the stellar wind could change the tail’s size and shape over time. Additionally changes in the stellar wind influence the tail’s size and shape, but since the tail is visible when illuminated by starlight, changes in stellar activity can also affect tail observations.
Exoplanet tails are still a bit mysterious, especially because they are subject to change. The study of exoplanet tails could help scientists to better understand how these tails form as well as the ever-changing relationship between the stellar and planetary atmospheres. Additionally, because these exoplanetary tails are shaped by stellar activity, they could serve as indicators of stellar behavior over time. This could be helpful for scientists as they seek to learn more about the stellar winds of stars other than the star we know the most about, our very own Sun.
Fun Facts
WASP-69 b is losing a lot of gas — about 200,000 tons per second. But it’s losing this gaseous atmosphere very slowly — so slowly in fact that there is no danger of the planet being totally stripped or disappearing. In general, every billion years, the planet is losing an amount of material that equals the mass of planet Earth.
The solar system that WASP-69 b inhabits is about 7 billion years old, so even though the rate of atmosphere loss will vary over time, you might estimate that this planet has lost the equivalent of seven Earths (in mass) of gas over that period.
The Discoverers
A team of scientists led by Dakotah Tyler of the University of California, Los Angeles published a paper in January, 2024 on their discovery, “WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 Rp,” in the journal, “The Astrophysical Journal.” The observations described in this paper were made by Keck/NIRSPEC (NIRSPEC is a spectrograph designed for Keck II).
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