Astro News
Science & Discovery
Unintended Radiation from Starlink May Endanger Radio Astronomy
September 18, 2024 — The electronics on SpaceX’s newest version of its Starlink satellites are leaking even more bright interfering radiation, say researchers in a new study published today in Astronomy & Astrophysics. The scientists focused on “unintended electromagnetic radiation,” or UEMR, which is different from the radio signals such satellites use for communication. UEMR is the radiation leaking from the electrical devices and systems that sit onboard satellites.
The astronomers used the LOFAR radio telescope array to observe communication satellites in two radio bands: 10 to 88 MHz and also 110 to 188 MHz. In a paper published last year, the same researchers focused on the latter higher-frequency band. At the time of that paper, co-author Cees Bassa from ASTRON, the Netherlands Institute for Radio Astronomy, said, “This frequency range includes a protected band between 150.05 and 153 MHz specifically allocated to radio astronomy by the International Telecommunications Union (ITU).”
Astronomers surveyed the sky again in July using LOFAR. During their two hour-long observations, 141 Starlink satellites were predicted to pass through the field in the lower-frequency band, while 97 satellites were expected to pass through the 110 to 188 MHz band. Those Starlink satellites are a combination of the company’s first generation and second generation. (The astronomers have observed SpaceX satellites because the company has the most in orbit.) After comparing the locations of these satellites on the sky to detected signals, the astronomers could analyze the leakage from the satellites themselves. They found the newest iteration of Starlink leaks 32 times more radiation than the previous version, and is leaking radiation in both frequency bands.
According to the new study, the Radiocommunication Sector of the International Telecommunications Union, known as ITU-R, does not have strict regulatory limits on the leaking UEMR. Such interference limits “protect certain parts of the spectrum for radio astronomical applications.” The astronomers urge industry to follow stricter standards, to minimize such leaking radiation, like how radio observatories mitigate such unintended signals. “We have the solutions for this symbiosis in space as well — we just need the regulators to support us, and the industry to meet us half-way,” said Jessica Dempsey, the ASTRON director in a press statement. “Without mitigations, very soon the only constellations we will see will be human-made.” — L. K. ✰
[T. Hansen/IAU OAE/Creative Commons Attribution]
NASA
Education & Inspiration
Seeking CubeSats for Education
August 15, 2024 — NASA has put out a call for education-related proposals for its CubeSat Launch Initiative. Selected CubeSats would likely launch between 2026 and 2029 into low-Earth orbit or for deployment from the International Space Station. According to a recent press statement, NASA “selects projects with an educational component that also can benefit the agency in better understanding education, science, exploration, and technology,” said Jeanie Hall, CSLI program executive at NASA Headquarters in Washington.
CubeSats are small space satellites, comprised of at least one standardizable unit (“U”), where each unit is 10 centimeters x 10 cm x 11 cm in size (3.9 inches x 3.9 in x 4.5 in). Most CubeSats use off-the-shelf electronics and parts, making than less expensive than many other types of spacecrafts.
Proposals are due November 15, and NASA expects to make selections by March 14, 2025. For more about the application process and the types of CubeSat projects that have flown in the past, see NASA’s CubeSat Launch Initiative website. — L. K. ✰
Education & Inspiration
Translating Data into Sound Aids Learning
July 18, 2024 — Astronomy has long been a visual science, but in the past decade scientists have been translating electromagnetic observations into sound. These so-called "sonification" projects aid those who are blind and low-vision (BLV), and in doing so, they also communicate the science to broader audiences and help researchers uncover aspects of the visible astronomical objects.
In a paper published earlier this year in Frontiers in Communication, researchers studied the responses of 3,184 people from sighted or BLV communities to three sonifications. The three astronomical objects they listened to were the galactic center (presented here), the Cassiopeia A supernova remnant, and the Chandra Deep Field South X-ray view. According to the study, the listeners reported that sound enhanced the learning experience and they were inspired to learn more about the universe.
While this study focused on soundscapes at NASA’s A Universe of Sound, there are other global projects to further incorporate audio into science communication and education. Several researchers, including those involved with Audio Universe, discussed these projects at this week’s Royal Astronomical Society meeting. In a press statement focusing on these sonification projects, Christine Malec, a member of the BLV community who also supports the NASA project, said “When I first heard a sonification, it struck me in a visceral, emotional way that I imagine sighted people experience when they look up at the night sky.” — L. K. ✰
X-ray: NASA/CXC/SAO; Optical: NASA/STScI; IR: Spitzer NASA/JPL-Caltech; Sonification: NASA/CXC/SAO/K. Arcand, SYSTEM Sounds (M. Russo, A. Santaguida)
ESA/Hubble & NASA, M. Häberle
Science & Discovery
Omega Centauri’s Black Hole
July 10, 2024 — A favorite observing target in the southern sky hosts an elusive medium-size black hole, say astronomers in a Nature paper published July 10. The researchers scoured 20 years of data comprising more than 500 observations from the Hubble Space Telescope (HST) of Omega (ω) Centauri, a rich globular star cluster about 17,700 light years away from Earth and in our galaxy’s halo. (Research over the past 15 years has suggested Omega Centauri is not actually a globular cluster but instead the remnants of a dwarf galaxy that had its outer stars stripped away by the Milky Way’s gravity.)
Using those HST data, astronomers measured the velocities of 1.4 million stars. Seven stars are speeding so fast around Omega Centauri’s center that they should escape the cluster’s gravitational pull — unless something massive is holding them there by its gravity. The most likely explanation is an invisible compact object, a black hole, near Omega Centauri's core.
The researchers used the stars' orbits and speeds to calculate a mass of no less than 8,200 times the mass of our Sun. This value falls well above the so-called stellar mass black holes, which form by the energetic implosion of a massive star. And the value falls well below supermassive black holes, which are found at the centers of all massive galaxies and are usually millions to billions of solar masses. The unseen compact object near the core of Omega Centauri would be of the intermediate variety. Astronomers don’t know how supermassive black holes form, but they think intermediate ones may provide a missing link to the growth of the more massive variety.
This new Nature paper isn’t the first study to suggest such a black hole lives in this globular cluster, but “previous studies had prompted critical questions of ‘So where are the high-speed stars?’” said lead author Nadine Neumayer of Max Planck Institute for Astronomy in a press statement. “We now have an answer to that, and the confirmation that Omega Centauri contains an intermediate-mass black hole.” — L. K. ✰
Science & Discovery
How Hubble Observes is Changing
June 5, 2024 — The Hubble Space Telescope (HST) has been in safe mode since May 24, due to one of its remaining gyroscopes not operating as it should. Over the past six months, the telescope has been unable to collect science data multiple times due to a faulty gyroscope. While HST has six gyroscopes on board, spinning instruments that precisely point the observatory toward its observing targets, three have stopped working since the last servicing mission in 2009. With one of the remaining three gyroscopes operating irregularly, NASA announced June 4 it would change the telescope to single-gyro mode and conserve the other good gyroscope for future single-gyro use. The space agency anticipates the telescope will be back to science operation in mid-June, using this new mode.
By using just one gyroscope, HST will use its magnetic-field instrument, star trackers, and sun sensors to help point the telescope before the fine guidance sensors take over. These additional instruments take more time to adequately align the telescope, and so HST will lose some 12 percent efficiency in this new mode, says NASA. In addition, researchers will not be able to track moving objects closer to the telescope than Mars. Even with these changes and restrictions, however, “we do not see Hubble as being on glass legs,” said Patrick Crouse, the HST project manager during a press conference on June 4.
The HST team expects the telescope to continue its science observations into the 2030s. In fact, they said during the press conference a 70 percent probability it will observe until 2035. — L. K. ✰
ESA/Euclid/Euclid Consortium/NASA; image processing by J.-C. Cuillandre (CEA Paris-Saclay), G. Anselmi
Science & Discovery
Euclid Team Releases Early Science Results
May 29, 2024 — The Euclid observatory has been in space for nearly a year and has been surveying the sky since February 2014. The European Space Agency, who operates the mission, released several new images and early science papers on May 23. Shown here is one of those images, which captures the massive galaxy cluster Abell 2390.
This image of the galaxy cluster reveals some 50,000 member galaxies. Zooming in toward the center shows a quirk of gravity: curves and arcs of light. These are the result of light from background galaxies bending as that light passes through the massive gravity of Abell 2390. Euclid captures both visible-light and infrared images, and this particular view took about three hours of total observation in both types of light.
Euclid’s main science objective is to study the dark universe by mapping three-dimensionally the visible cosmos. The goal is to capture galaxies and other visible structure whose light has traveled for at least 10 billion years. Those visible structures of galaxies and their larger conglomerates balance upon a scaffolding of invisible dark matter. Dark energy, a mysterious pervasive something, works against the growth of structure; it expands our universe at a faster and faster rate. — L. K. ✰
Science & Discovery
Found: Three Ancient Stars
May 14, 2024 — Astronomers search for the earliest stars, which inform them of what the early universe was like, but these stars have proven difficult to find. While most of the earliest stars have burned out, some are still around. Stars fuse in their cores low-mass elements like hydrogen and helium into heavier ones. Later stellar generations, including our Sun, contain heavier elements that formed in those former stars. So, to search for the earliest stars, astronomers look for stars with fewer heavy elements.
A new study published online May 14 in the Monthly Notices of the Royal Astronomical Society identifies several newly found stars in our Milky Way Galaxy. The scientists say these suns likely formed some 12 to 13 billion years ago — making them some of the oldest stars yet found.
While many early stars are found in ultra-faint dwarf galaxies, the researchers in this new paper discuss how such galaxies and their member stars are difficult to pin down and study. In the new work, the astronomers focus on a different population of stellar systems: leftover old stars living currently in the Milky Way’s diffuse outer “halo.” The researchers think these stars are the remnants of previously captured satellite dwarf galaxies.
This new study builds off a student classroom project led by MIT professor Anna Frebel to learn how to discover and analyze ancient stars using archival data captured with the Magellan Clay Telescope at Las Campanas Observatory. “This class immediately put us at the frontier of research in astrophysics,” said Hillary Andales, former student and lead author of the study, in a press release. — L. K. ✰
Photograph by Yuri Beletsky, courtesy of the Carnegie Institution for Science
NASA/JPL-Caltech/ASU/MSSS
Science & Discovery
NASA Revising Its Mars Sample Return Plan
April 15, 2024 — In 2022, The U.S. National Academies published its Planetary Science and Astrobiology Decadal Survey 2023-2032. In it, the committee listed the Mars Sample Return mission as the top priority. The survey also included a recommended budget estimate of $5.3 billion (and no more than 20 percent above that number) for a mission to travel to the Red Planet, obtain samples NASA’s Perseverance Rover has been collecting, launch off Mars, and return those samples to Earth.
A NASA independent review board in September 2023, however, published a report that such a mission would cost between $8 billion and $11 billion. In addition, the NASA budget released last month constrains the timeline, estimating the samples wouldn’t land at Earth until 2040. “The bottom line is that $11 billion dollars is too expensive and not returning samples until 2040 is unacceptably too long,” said NASA’s Administrator Bill Nelson today during a press conference with reporters. Such a mission cost, he said, “would cause NASA to have to cannibalize other programs — other science programs — and there are so many that are absolutely important.”
In response to these constraints, the space agency announced today it has reached out to industry partners and individual NASA centers to investigate innovative technologies that could be used in the Mars sample return mission. The aim is to stay within the recommended budget estimates and a sooner timeline. The partners will report back in the fall, said Nelson during the teleconference. “We are committed to retrieving the samples that are there,” he added. — L. K. ✰
Mercury & ASP
Solar Eclipse Content Archived
April 9, 2024 — To prepare readers for the total solar eclipse that crossed over North America, we compiled all of Mercury's eclipse content here. And while the April 8, 2024, total solar eclipse has passed, all the educational solar eclipse content will remain freely available on this website. Please use this content to help prepare for the next total solar eclipses: August 12, 2026; August 2, 2027; July 22, 2028; and November 25, 2030. — L. K. ✰
ESO/P. Aniol, M. Druckmüller, P. Horálek
NASA/CXC
Science & Discovery
Chandra X-ray Observatory on Cutting Block
March 25, 2024 — Earlier this month, NASA released its 2025FY budget and one of the surprising elements is the dramatic reduction in funding for the Chandra X-ray Observatory. Chandra’s funding was $68.3 million spent in 2023, however, only $41.1 million is proposed for 2025. NASA projects annual spending on Chandra to fall to just $5.2 million by 2029. The funding levels provided in the new budget plan and the years that follow are consistent with levels for end of operations of the Chandra science mission.
The Chandra X-ray Observatory, one of NASA's "Great Observatories," the premiere high-energy astrophysics facility, has revolutionized high-energy astrophysics by providing unparalleled imaging of the X-ray universe. Its imaging of the “Bullet Cluster,” for example, has provided direct evidence for dark matter, and the observatory has also made transformative advances in our understanding of active galaxies and supernova remnants. Its imaging capabilities and observing efficiency still exceed pre-launch requirements after 25 years of operations, and Chandra science team members say it is capable of many more years of operation and scientific discovery. Launched in 1999, NASA’s flagship X-ray telescope is still oversubscribed, highly efficient, and there is nothing planned to replace its unique imaging capabilities for at least the next decade.
NASA’s budget decisions are a consequence of a debt-ceiling agreement with Republicans two years ago that caps overall spending in order to get agreement on a new spending bill. As a result, NASA ended up with a 2 percent cut in 2024 versus 2023. “In a little agency that is doing an awful lot,” said NASA Administrator Bill Nelson during a press call, “it makes a big difference.”
Since the announcement, the response from the astronomy community has been to mount a letter and online campaign to reverse the decision. This is not the first time that a public engagement campaign has been used in astronomy to save a mission. It was the public outcry that saved the Hubble Space Telescope from a canceled final servicing mission that would have meant the telescope ceased operations in 2007, and even the famed JWST from being canceled just over a decade ago. By sharing the argument against cancellation and inviting the public to contact their Congress representative, the hope is that they can make a difference and #SaveChandra. — S. V. ✰
Science & Discovery
New Horizons Mission Has Led to Discovery of 89 Kuiper Belt Objects
March 14, 2024 — Scientists now know of dozens more objects in the Kuiper Belt, the diffuse disk region beyond Neptune’s orbit. And it’s all thanks to the New Horizons mission and its related searches to better understand the Kuiper Belt.
New Horizons, which visited Pluto and Charon in July 2015, has been flying through the Kuiper Belt for a decade. To find additional flyby targets and learn how dense the region is, mission scientists used the ground-based 6.5-meter Magellan Telescopes at Las Campanas Observatory, Chile, and the Subaru Telescope at Mauna Kea, Hawaii. According to a preprint paper posted to the physics arXiv March 7, the researchers discovered 80 Kuiper Belt Objects (KBOs) via those ground searches. Other observations with the Hubble Space Telescope found another five, including 2014 MU₆₉, also known as Arrokoth, the lobed object New Horizons flew by and observed in 2019. In total, onboard observations combined with these other searches discovered 89 previously unknown KBOs.
The New Horizons spacecraft (illustrated here) is still trekking through the Kuiper Belt, and scientists estimate it will exit the region in 2028 or 2029. With no additional known KBOs on its path, the spacecraft’s instruments are instead capturing heliophysics data to study the Sun’s effects at this outer solar system region. The team is also searching for another possible KBO to study during New Horizon’s trajectory through the Kuiper Belt. — L. K. ✰
NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Science & Discovery
A Commercial Craft Sticks its Landing
February 23, 2024 — The Moon has one more visitor. The Odysseus spacecraft, built and operated by Texas-based company Intuitive Machines, successfully touched down at the lunar south polar region on February 22, at 6:23 p.m. Eastern Standard Time. It marks the first time a private corporation has landed on the Moon, and the first time in more than five decades America has put machinery on the lunar surface. (Several other countries have soft-landed spacecraft on the Moon: the Soviet Union decades ago; and Japan, India, and China in the past decade.)
The Intuitive Machines mission is part of NASA’s Commercial Lunar Payload Services (CLPS) initiative, which works with aerospace companies to bring private and NASA-led experiments to the lunar surface. This mission is the first successful one in the program.
After launching off Earth’s surface February 15 atop a SpaceX Falcon 9 rocket, Intuitive Machines’s Odysseus craft made its way to the Moon. It entered lunar orbit on February 21, and successfully touched down a week later. Odysseus, or “Odie” as the mission team affectionally calls it, brought along several NASA experiments and payloads from other paying customers. Its solar panels are functioning well, capturing sunlight to power its instruments. However, within nine days, due to solar system geometry, the Sun will no longer be in view. Intuitive Machines does not expect the spacecraft’s electronics to make it through the long and cold lunar night. — L. K. ✰
Science & Discovery
Solar Gamma Ray Oddities
February 7, 2024 — The Sun spews radiation from low-energy microwaves through visible light and up to high-energy gamma rays. Astronomers first spied gamma-ray solar light in 1972, during two energetic solar flares. Some two decades later, with longer-term gamma-ray telescopes in space, they began to study the high-energy light that comes from our star. And for the past 15 years, the Fermi space-based gamma-ray observatory has mapped high-energy rays across the full sky.
Scientists recently sorted through Fermi observations of the Sun spanning August 2008 to January 2022. In their February 7 paper in The Astrophysical Journal, Bruno Arsioli and Elena Orlando describe a surprising asymmetry: The solar polar regions emitted more gamma rays at times that seemed to coincide with the Sun’s 11-year magnetic cycle.
Other solar activity like flares and sunspots, tend to increase and then decrease, following an 11-year pattern. The previous "solar maximum" was in 2014, and the next one is expected to peak later this year or next year. Scientists know solar activity is due to the Sun’s intense magnetic fields’s motions through the hot gaseous sphere. The field lines become more tangled as solar maximum approaches and they travel to higher latitudes. Then, the magnetic poles flip, and the process repeats. Arsioli and Orlando found the gamma rays were concentrated at the Sun’s polar regions (higher latitudes) during June 2014, which is when the magnetic poles flipped. "Our findings suggest that the Sun's magnetic configuration plays a significant role in shaping the resulting gamma-ray signature,” say the researchers in their paper. The image at right shows the density (color-coded) of gamma rays superimposed on an ultraviolet-light image of the Sun captured by the Solar Dynamics Observatory. — L. K. ✰
Arsioli and Orlando 2024 & NASA/SDO/Duberstein
Science & Discovery
Reprocessing Voyager 2's Titania Map
January 18, 2024 — The seventh planet from the Sun, Uranus, has had only one spacecraft investigate it and its moons. Voyager 2 first targeted the ice giant in its instruments’ crosshairs in November 1985. Over the next few months, the spacecraft captured images of Uranus and its five largest satellites (the only ones known at that time), and it also discovered 10 other moons. Although those data were collected nearly four decades ago, they are still leading to new discoveries.
In a paper published online January 17 in The Planetary Science Journal, Erica Nathan and her Brown University colleagues used modern techniques to reprocess images of the largest Uranian moon, Titania. Uranus and its system are about 19 astronomical units away from the Sun (where 1 AU is the average Earth-Sun distance), and thus they receive much less sunlight than our planet and its satellite. In addition, Voyager 2 flew by Uranus at thousands of miles per hour. Those two factors meant the spacecraft captured blurred images of Titania (60 percent of its surface).
The planetary scientists applied a complex computational algorithm to the archived images to improve the views of the moon (shown at bottom left) and also map Titania and its geologic surface features. The satellite’s surface, say the scientists in their paper, has more fracturing than previously seen, additional craters, and what may be multiple concentric rings arising from a former impact. This new map, the researchers add, can help with planning the next proposed flagship planetary science mission, aimed at Uranus and its moons. — L. K. ✰
Science & Discovery
Our Galaxy's Crowded Core
December 1, 2023 — For four hours in September, the near-infrared camera on JWST stared at a molecular cloud in the center of our galaxy. NASA released the resulting image, a compilation of data through four filters, in November. Within the released image that spans 50 light-years, a smaller region of which is shown at right, there are about 500,000 stars.
The researchers who proposed the JWST observation of Sagittarius C were especially interested in star formation in the region and a massive forming star known as G359.44-0.102. That star is at the center of image at right, and emits outflowing material, shown as the pink lobed-blob.
The lead scientist on the observations, University of Virginia student Sam Crowe, and his colleagues are analyzing the JWST observations. They have also studied the same region with data from several other infrared telescopes, including SOFIA and Spitzer. — L. K. ✰
NASA, ESA, CSA, STScI, Samuel Crowe (UVA)
ESA/Webb, NASA, CSA, M. Barlow (UCL), N. Cox (ACRI-ST), R. Wesson (Cardiff University)
Science & Discovery
Planetary Nebula Captured
August 28, 2023 — The gas wisps and streams making up the Ring Nebula (known as M57 and NGC 6720) were once layers of a star, which has evolved into a planetary nebula. The leftover stellar core, now a dense remnant known as a white dwarf, sits at the center of this nebula and heats the gas, making it glow. Our Sun may exhibit a similar fate in several billion years. (In the Ring Nebula, however, astronomers suspect a companion star at the center. Our Sun, on the other hand, is a lone star.)
This near-infrared image combines data from four filters using NASA's JWST observatory. In it, astronomers see outer concentric rings, incredibly hot gas at the center, and some 20,000 clumps of dense hydrogen. — L. K. ✰
Science & Discovery
Euclid's First View
August 1, 2023 — The European Space Agency's Euclid space telescope launched July 1, 2023, with the mission goal to create a three-dimensional map of galaxies out to about one-third of the way through cosmic history. With this data, scientists will track how structure grew and changed through time. The plan is to use that information to learn about the universe's invisible dark matter and the even more mysterious dark energy. These dark bits constitute some 95 percent of the universe.
On July 31, the Euclid team released the telescope's first test images. Shown at right is the view from one of its 36 visible-light sensors. — L. K. ✰
ESA/Euclid/Euclid Consortium/NASA
Hermann Göll - Aus fernen Welten by Bruno H. Brugel/wikimedia
History & Culture
Hipparchus’ Star Catalog Found
March 31, 2023 — Several passages of the long-lost and oldest-rumored star catalog has been found. The discovery not only confirms the catalog, created by ancient Greek astronomer Hipparchus, existed, but also shows those stars’ positions were more accurate than a catalog created many centuries later. The new study is detailed in the November 2022 issue of The Journal for the History of Astronomy.
While studying a document known as Codex Climaci Rescriptus, researcher Peter Williams with the Tyndale House, a biblical research library in Cambridge, England, noted astronomical markings and measurements. Using a database of images collected in 2017 to 2018 by the Early Manuscripts Electronic Library and the Lazarus Project at the University of Rochester and the Rochester Institute of Technology, Williams and his collaborators researchers could decipher some of the faint text. It turned out some of the original text had been rubbed out and then used for another document in the early medieval period.
The historians could read some once-erased passages about several constellations, and, given the time the text was written and removed in addition to the subject material, they determined the passages are from Hipparchus. Those passages, the researchers say in their paper, confirms the Hipparchus star catalog was compiled in equatorial coordinates. — L. K. ✰
Science & Discovery
Venus Hosts Active Volcanism
March 31, 2023 — Inspired by a forthcoming mission to Earth’s brutally toasty sibling planet, Venus, researcher Robert Herrick looked back at 30-year-old images from a previous mission. And the University of Alaska scientist found an exciting surprise. In images captured eight months apart in 1991 via NASA’s Magellan spacecraft, Herrick noted a volcanic vent changed shape and nearby plains gained a different texture. In a new study published in the March 13 issue of Science, he and his coauthor Scott Hensley of the Jet Propulsion Laboratory say that sometime between the two images, magma oozed at the Venusian surface. This would be the first time active volcanism has been directly observed at the toasty planet next door.
The volcanic vent, known as Maat Mons, in the first image from February 1991 appeared round and covered 1 square mile (2.2 square kilometers). In the image captured in October 1991, the same vent was no longer circular, and it then covered double the area. The researchers used computer simulations to compare different physical mechanisms that could have altered the vent shape, including landslides, but volcanism seems the most likely, they say. “While this is just one data point for an entire planet, it confirms there is modern geological activity,” said Hensley in a press statement. — L. K. ✰
NASA/JPL-Caltech
NASA/ESA/S. Kruk, et al.
Science & Discovery
Satellites Streak Hubble Images
March 31, 2023 — The fleet of communications satellites in low-Earth orbit, and specifically the SpaceX Starlink crafts, have been a contentious topic among professional astronomers. Thanks to a new study published March 2 in Nature Astronomy, astronomers know specifically how much of an effect those satellites have on images captured by the Hubble Space Telescope (HST).
Astronomer and data scientist Sandor Kruk of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, leads a Zooniverse project titled Hubble Asteroid Hunter. In the project, the 11,000 citizen scientist volunteers scoured images in the European HST archive and marked possible asteroids and other anomalies. Kruk and colleagues later analyzed those images via two machine learning algorithms and found 2.7 percent of HST exposures captured between 2002 and 2021 have satellites streaking across the field.
Kruk and colleagues also calculated the probability of a satellite streak in the HST field of view by the time there are 60,000 to 100,000 satellites in orbit, which incorporates proposed future communication constellations like Astra and Guowang. With that many satellites in low-Earth orbit, the researchers say, there would be between 20 and 50 percent chance one would cross the HST field of view during an observation. — L. K. ✰
Science & Discovery
Light Pollution at Observatories
March 31, 2023 — Some two-thirds of the largest professional astronomy observatories across the world have already surpassed “acceptable” light pollution levels — meaning, scattering light greater than 10 percent over natural levels. This comes from a recent study published in the Monthly Notices of the Royal Astronomical Society, surveying the locations of 28 observatories that host telescopes larger than 10 feet (3 meters) and several additional sites.
The astronomers compared five indicators measuring the scattering of light off atmospheric particles, or “radiance,” at several locations, including, at zenith and averaged in the first 30 degrees above the horizon. Most professional observatories cannot observe closer to the horizon than 30 degrees. The paper includes 28 professional observatories, in addition to several historic sites (like Lowell Observatory in Flagstaff, Arizona) and also amateur astronomy observing sites (like Astrofarm at La Palma in the Canary Islands, and New Mexico Skies near Mayhill, New Mexico).
All major observatories in the continental United States have already surpassed the acceptable limit; this includes Lick Observatory, Mount Wilson Observatory, Palomar Observatory, the Fred Lawrence Whipple Observatory, and Kitt Peak National Observatory. Maunakea Observatory in Hawaii is at the limit. The least-light-polluted sites in the study are all in Chile: Paranal Observatory at Cerro Paranal, Cerro Armazones Observatory, and University of Tokyo Atacama Observatory. — L. K. ✰
KPNO/NOIRLab/NSF/AURA/B. Tafreshi
Mercury is distributed by the Astronomical Society of the Pacific, a nonprofit organization dedicated to astronomy literacy, education, and outreach.
Mercury is an advertisement-free publication. If you are interested in supporting Mercury, please email us.
