NASA’s Hubble Tracks Down a ‘Blue Lurker’ Among Stars
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NASA, ESA, Leah Hustak (STScI)
The name “blue lurker” might sound like a villainous character from a superhero movie. But it is a rare class of star that NASA’s Hubble Space Telescope explored by looking deeply into the open star cluster M67, roughly 2,800 light-years away.
Forensics with Hubble data show that the star has had a tumultuous life, mixing with two other stars gravitationally bound together in a remarkable triple-star system. The star has a kinship to so-called “blue stragglers,” which are hotter, brighter, and bluer than expected because they are likely the result of mergers between stars.
Evolution of a “Blue Lurker” Star in a Triple System Panel 1: A triple star system containing three Sun-like stars. Two are very tightly orbiting. The third star has a much wider orbit. Panel 2: The close stellar pair spiral together and merge to form one more massive star. Panel 3: The merged star evolves into a giant star. As the huge photosphere expands, some of the material falls onto the outer companion, causing the companion to grow larger and its rotation rate to increase. Panels 4-5: The central merged star eventually burns out and forms a massive white dwarf, and the outer companion spirals in towards the white dwarf, leaving a binary star system with a tighter orbit. Panel 6: The surviving outer companion is much like our Sun but nicknamed a “blue lurker.” Although it is slightly brighter bluer than expected because of the earlier mass-transfer from the central star and is now rotating very rapidly, these features are subtle. The star could easily be mistaken for a normal Sun-like star despite its exotic evolutionary history. NASA, ESA, Leah Hustak (STScI)
The blue lurker is spinning much faster than expected, an unusual behavior that led to its identification. Otherwise it looks like a normal Sun-like star. The term “blue” is a bit of a misnomer because the star’s color blends in with all the other solar-mass stars in the cluster. Hence it is sort of “lurking” among the common stellar population.
The spin rate is evidence that the lurker must have siphoned in material from a companion star, causing its rotation to speed up. The star’s high spin rate was discovered with NASA’s retired Kepler space telescope. While normal Sun-like stars typically take about 30 days to complete one rotation, the lurker takes only four days.
How the blue lurker got that way is a “super complicated evolutionary story,” said Emily Leiner of Illinois Institute of Technology in Chicago. “This star is really exciting because it’s an example of a star that has interacted in a triple-star system.” The blue lurker originally rotated more slowly and orbited a binary system consisting of two Sun-like stars.
Around 500 million years ago, the two stars in that binary merged, creating a single, much more massive star. This behemoth soon swelled into a giant star, dumping some of its own material onto the blue lurker and spinning it up in the process. Today, we observe that the blue lurker is orbiting a white dwarf star — the burned out remains of the massive merger.
“We know these multiple star systems are fairly common and are going to lead to really interesting outcomes,” Leiner explained. “We just don’t yet have a model that can reliably connect through all of those stages of evolution. Triple-star systems are about 10 percent of the Sun-like star population. But being able to put together this evolutionary history is challenging.”
Hubble observed the white dwarf companion star that the lurker orbits. Using ultraviolet spectroscopy, Hubble found the white dwarf is very hot (as high as 23,000 degrees Fahrenheit, or roughly three times the Sun’s surface temperature) and a heavyweight at 0.72 solar masses. According to theory, hot white dwarfs in M67 should be only about 0.5 solar masses. This is evidence that the white dwarf is the byproduct of the merger of two stars that once were part of a triple-star system.
“This is one of the only triple systems where we can tell a story this detailed about how it evolved,” said Leiner. “Triples are emerging as potentially very important to creating interesting, explosive end products. It’s really unusual to be able to put constraints on such a system as we are exploring.”
Leiner’s results are being presented at the 245th meeting of the American Astronomical Society in Washington, D.C.
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.
Facebook logo @NASAHubble @NASAHubble Instagram logo @NASAHubbleMedia Contact:
Claire Andreoli (claire.andreoli@nasa.gov)
NASA’s Goddard Space Flight Center, Greenbelt, MD
Ray Villard
Space Telescope Science Institute, Baltimore, MD
Science Contact:
Emily Leiner
Illinois Institute of Technology, Chicago, IL
- Astrophysics
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Did Pluto ‘kiss and capture’ its largest moon?
Nature, Published online: 13 January 2025; doi:10.1038/d41586-025-00034-1
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415 Years Ago: Astronomer Galileo Discovers Jupiter’s Moons
On Jan. 7, 1610, Italian astronomer Galileo Galilei peered through his newly improved 20-power homemade telescope at the planet Jupiter. He noticed three other points of light near the planet, at first believing them to be distant stars. Observing them over several nights, he noted that they appeared to move in the wrong direction with regard to the background stars and they remained in Jupiter’s proximity but changed their positions relative to one another. Four days later, he observed a fourth point of light near the planet with the same unusual behavior. By Jan. 15, Galileo correctly concluded that he had discovered four moons orbiting around Jupiter, providing strong evidence for the Copernican theory that most celestial objects did not revolve around the Earth.
Two of Galileo’s telescopes.National Geographic. Painting by Giuseppe Bertini (1858) of Galileo demonstrating his telescope to the Doge of Venice.gabrielevanin.it Page from Galileo’s notebook about his observations of Jupiter’s satellites.University of Michigan Special Collections Library.In March 1610, Galileo published his discoveries of Jupiter’s satellites and other celestial observations in a book titled Siderius Nuncius (The Starry Messenger). As their discoverer, Galileo had naming rights to Jupiter’s satellites. He proposed to name them after his patrons the Medicis and astronomers called them the Medicean Stars through much of the seventeenth century, although in his own notes Galileo referred to them by the Roman numerals I, II, III, and IV, in order of their distance from Jupiter. Astronomers still refer to the four moons as the Galilean satellites in honor of their discoverer.
In 1614, the German astronomer Johannes Kepler suggested naming the satellites after mythological figures associated with Jupiter, namely Io, Europa, Ganymede, and Callisto, but his idea didn’t catch on for more than 200 years. Scientists didn’t discover any more satellites around Jupiter until 1892 when American astronomer E.E. Barnard found Jupiter’s fifth moon Amalthea, much smaller than the Galilean moons and orbiting closer to the planet than Io. It was the last satellite in the solar system found by visual observation – all subsequent discoveries occurred via photography or digital imaging. As of today, astronomers have identified 95 moons orbiting Jupiter.
Image of Jupiter and three of its four Galilean satellites through an amateur telescope, similar to what Galileo might have seen. Hubble Space Telescope image of Jupiter and three of its four Galilean satellites during a rare triple transit.Although each of the Galilean satellites has unique features, such as the volcanoes of Io, the heavily cratered surface of Callisto, and the magnetic field of Ganymede, scientists have focused more attention on Europa due to the tantalizing possibility that it might be hospitable to life. In the 1970s, NASA’s Pioneer 10 and 11 and Voyager 1 and 2 spacecraft took ever increasingly detailed images of the large satellites including Europa during their flybys of Jupiter. The photographs revealed Europa to have the smoothest surface of any object in the solar system, indicating a relatively young crust, and also one of the brightest of any satellite indicating a highly reflective surface. These features led scientists to hypothesize that Europa is covered by an icy crust floating on a subsurface salty ocean. They further postulated that tidal heating caused by Jupiter’s gravity reforms the surface ice layer in cycles of melting and freezing.
Image of Europa taken by Pioneer 10 during its flyby of Jupiter in 1973. Image of Europa taken by Voyager 1 during its 1979 flyby of Jupiter. Image of Europa taken by Voyager 2 during its 1979 flyby of Jupiter.More detailed observations from NASA’s Galileo spacecraft that orbited Jupiter between 1995 and 2003 and completed 11 close encounters with Europa revealed that long linear features on its surface may indicate tidal or tectonic activity. Reddish-brown material along the fissures and in splotches elsewhere on the surface may contain salts and sulfur compounds transported from below the crust and modified by radiation. Observations from the Hubble Space Telescope and re-analysis of images from Galileo revealed possible plumes emanating from beneath Europa’s crust, lending credence to that hypothesis. While the exact composition of this material is not known, it likely holds clues to whether Europa may be hospitable to life.
Global view of Europa from the Galileo spacecraft. More detailed views of varied terrain on Europa from Galileo. Cutaway illustration of Europa’s icy crust, subsurface ocean and possible vents that transport material to the surface.Future robotic explorers of Europa may answer some of the outstanding questions about this unique satellite of Jupiter. NASA’s Europa Clipper set off in October 2024 on a 5.5-year journey to Jupiter. After its arrival in 2030, the spacecraft will enter orbit around the giant planet and conduct 49 flybys of Europa during its four-year mission. Managed by the Jet Propulsion Laboratory in Pasadena, California, and the Applied Physics Laboratory at Johns Hopkins University in Baltimore, Maryland, Europa Clipper will carry nine instruments including imaging systems and a radar to better understand the structure of the icy crust. Data from Europa Clipper will complement information returned by the European Space Agency’s JUICE (Jupiter Icy Moon Explorer) spacecraft. Launched in April 2023, JUICE will first enter orbit around Jupiter in 2031 and then enter orbit around Ganymede in 2034. The spacecraft also plans to conduct studies of Europa complementary with Europa Clipper’s. The two spacecraft should greatly increase our understanding of Europa and perhaps uncover new mysteries.
Illustration of the Europa Clipper spacecraft investigating Europa. Illustration of the JUICE spacecraft exploring Europa.European Space Agency.Cosmic carnage: planetary rubble spotted at a dying star
Nature, Published online: 08 January 2025; doi:10.1038/d41586-025-00006-5
Dust cloud is thought to be the first debris disk to be seen around a planetary nebula.Origins of black holes revealed in their spin, study finds
The size and spin of black holes can reveal important information about how and where they formed, according to new research. The study tests the idea that many of the black holes observed by astronomers have merged multiple times within densely populated environments containing millions of stars.
The team, involving researchers from the University of Cambridge, examined the public catalogue of 69 gravitational wave events involving binary black holes detected by The Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo Observatory for clues about these successive mergers, which they believe create black holes with distinctive spin patterns.
They discovered that a black hole’s spin changes when it reaches a certain mass, suggesting it may have been produced through a series of multiple previous mergers.
Their study, published in the journal Physical Review Letters, shows how spin measurements can reveal the formation history of a black hole and offers a step forward in understanding the diverse origins of these astrophysical phenomena.
“As we observe more black hole mergers with gravitational wave detectors like LIGO and Virgo, it becomes ever clearer that black holes exhibit diverse masses and spins, suggesting they may have formed in different ways,” said lead author Dr Fabio Antonini from Cardiff University. “However, identifying which of these formation scenarios is most common has been challenging.”
The team pinpointed a clear mass threshold in the gravitational waves data where black hole spins consistently change.
They say this pattern aligns with existing models which assume black holes are produced through repeat collisions in clusters, rather than other environments where spin distributions are different.
This result supports a robust and relatively model-independent signature for identifying these kinds of black holes, something that has been challenging to confirm until now, according to the team.
“Our study gives us a powerful, data-driven way to identify the origins of a black hole’s formation history, showing that the way it spins is a strong indicator of it belonging to a group of high-mass black holes, which form in densely populated star clusters where small black holes repeatedly collide and merge with one another,” said co-author Dr Isobel Romero-Shaw, from Cambridge’s Department of Applied Mathematics and Theoretical Physics.
Their study will now help astrophysicists further refine computer models which simulate the formation of black holes, helping to shape how future gravitational wave detections are interpreted.
“Collaborating with other researchers and using advanced statistical methods will help to confirm and expand our findings, especially as we move toward next-generation detectors,” said co-author Dr Thomas Callister from the University of Chicago. “The Einstein Telescope, for example, could detect even more massive black holes and provide unprecedented insights into their origins.”
Reference:
Fabio Antonini, Isobel M. Romero-Shaw, and Thomas Callister. 'Star Cluster Population of High Mass Black Hole Mergers in Gravitational Wave Data.' Physical Review Letters (2025). DOI: 10.1103/PhysRevLett.134.011401
Adapted from a Cardiff University media release.
Gravitational waves data held clues for high-mass black holes’ violent beginnings
NASA, ESA, and D. Coe, J. Anderson, and R. van der Marel (STScI)Computer-simulated image of a supermassive black hole at the core of a galaxy.
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<b>Spacecraft makes closest-ever fly-by of Sun: what the trip will tell us</b>
Nature, Published online: 06 January 2025; doi:10.1038/d41586-025-00009-2
NASA’s Parker Solar Probe could solve the mysteries of the solar wind and test Einstein’s theory of relativity.Pluto may have captured its moon Charon with a brief kiss
Quadrantid meteor shower to light up northern hemisphere sky
Annual new year event of bright blue fireballs expected to peak this weekend
While fireworks are a traditional way to welcome the new year, a natural phenomenon will be lighting up the northern sky this weekend as the annual Quadrantid meteor shower reaches its peak.
Taking its name from a now obsolete constellation known as Quadrans Muralis, the event is best viewed in the northern hemisphere, with the meteors appearing to radiate from the constellation Boötes, which is found near the collection of stars often dubbed the Plough or the Big Dipper.
Continue reading...A pulsar-like polarization angle swing from a nearby fast radio burst
Nature, Published online: 01 January 2025; doi:10.1038/s41586-024-08184-4
FRB 20221022A, detected by the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst project, shows a pronounced change in polarization during the burst, providing important clues into the nature of the source.Magnetospheric origin of a fast radio burst constrained using scintillation
Nature, Published online: 01 January 2025; doi:10.1038/s41586-024-08297-w
The detection of scintillation caused by inhomogeneous plasma near a fast radio burst indicates an emission process that occurs within or just beyond the magnetosphere of a compact object.Could 2025 be the year we finally start to understand dark energy?
Red and Green Aurora Move Through Earth’s Atmosphere
Peering through the window of the SpaceX Dragon Endeavour spacecraft, NASA astronaut Matthew Dominick captured this image on Oct. 7, 2024 of the SpaceX Dragon Freedom spacecraft as vivid green and pink aurora swirled through Earth’s atmosphere while the International Space Station soared 273 miles above the Indian Ocean.
Visit Dominick’s photography on station to experience the wonders of space through his eyes, enriched by his remarkable journey of orbiting the Earth 3,760 times.
To see a short-term forecast of the location and intensity of the next aurora check this link: Aurora – 30 Minute Forecast and also NASA’s Guide to Finding and Photographing Auroras.
Image Credit: NASA/Matthew Dominick
Red and Green Aurora Move Through Earth’s AtmosphereWhat’s Up: January 2025 Skywatching Tips from NASA
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Four Planets in One View!
Each evening this month, enjoy a sweeping view of four bright planets at once. Also look for a close approach of Venus and Saturn, Mars occulted by the Moon, and meteors!
Skywatching HighlightsJanuary 3 – Quadrantid meteor shower peaks: This is a moderate shower, usually delivering 20 to 30 meteors per hour under clear, dark skies at its peak. No interference from the Moon makes this year’s peak a better bet for meteor watching.
January 13 – Moon Occults Mars: For skywatchers in the continental U.S. and Eastern Canada, the Moon will appear to pass in front of Mars this evening. Times vary by location, so check your favorite skywatching app for details.
January 17-18 – Venus and Saturn conjunction: Over a couple of weeks, the two planets come within just a couple of finger widths’ distance apart in the sky (about 2 degrees). They’re at their closest on the 17th and 18th.
All month – Four planets Visible: In the first couple of hours after dark, you’ll find Venus and Saturn in the southwest, Jupiter high overhead, and Mars in the east. (Uranus and Neptune are there too, but a telescope is needed to see them.) Planets always appear a long a line on the sky to the “alignment” isn’t special. What’s less common is seeing four or five bright planets at once, which doesn’t happen every year. Is it a “planet parade”? This isn’t a technical term in astronomy, so call it what you wish!
All month – Mars at Opposition: The Red Planet is directly opposite the Sun from Earth and shines brightly all night. It’s in the east as night falls and in the southwest at dawn.
TranscriptWhat’s Up for January?
Cue the planet parade, Saturn and Venus cross paths, Mars expresses its opposition, and the outlook for the Quadrantid meteors.
In January, you’ll have the opportunity to take in four bright planets in a single, sweeping view.
Sky chart showing the planetary lineup visible after dark in January 2025. NASA/JPL-Caltech
All month after dark, you’ll find Venus and Saturn in the southwest for the first couple of hours, while Jupiter shines brightly high overhead, and Mars rises in the east. Uranus and Neptune are there too, technically, but they don’t appear as “bright planets.” These multi-planet viewing opportunities aren’t super rare, but they don’t happen every year, so it’s worth checking it out.
Now, these events are sometimes called “alignments” of the planets, and while it’s true that they will appear more or less along a line across the sky, that’s what planets always do. That line is called the ecliptic, and it represents the plane of the solar system in which the planets orbit around the Sun. This is, incidentally, why we sometimes observe planets appearing to approach closely to each other on the sky, as we view them along a line while they careen around the cosmic racetrack.
Sky chart showing Venus and Saturn appearing quite close together on Jan. 17 and 18, 2025. NASA/JPL-Caltech
This is exactly what we’ll be seeing from Venus and Saturn as they head for a super close approach in mid-January. After the beginning of the month, they quickly get closer and closer each evening, appearing at their most cozy on the 17th and 18th before going their separate ways. Remember, they’re really hundreds of millions of miles apart in space, so when you observe them, you’re staring clear across the solar system!
Mars reaches “opposition” this month, which is when the planet lies directly on the opposite side of Earth from the Sun, forming a straight line. This is around the time when the planet is at its closest to Earth, making it appear at its biggest and brightest. For Mars, oppositions happen about every two years. This one won’t be the most spectacular ever, but it’s still closer than average, and provides a great opportunity to observe the nearby planet where NASA has five missions currently operating.
And on the 13th, the full Moon cozies up to Mars, appearing super close to the Red Planet that evening. Across the U.S. and Eastern Canada, the Moon will appear to pass in front of Mars over a couple of hours, as the pair rise into the eastern sky. Mars also will be the lone planet in the sky on January mornings. You’ll find it hanging out in the west in morning twilight.
The Quadrantid meteors peak in the early morning hours on January 3rd. Interference from moonlight won’t be a problem, as the Moon is a mere crescent and sets early in the night. The way to see the most meteors is to observe after midnight from clear, dark skies away from bright city lights, and let your eyes adapt to the dark. The meteor rate will be highest as dawn approaches, and you’ll see more meteors from rural locations than in the suburbs. Now, this is a shower best seen from the Northern Hemisphere, and observers in the Northwest and Pacific region will likely have the best viewing this year.
Here are the phases of the Moon for January:
The phases of the Moon for January 2025. NASA/JPL-Caltech
Stay up to date on all of NASA’s missions exploring the solar system and beyond at science.nasa.gov. I’m Preston Dyches from NASA’s Jet Propulsion Laboratory, and that’s What’s Up for this month.
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