Thursday, October 17, 2024

NASA's Hubble Sees a Stellar Volcano

Credits/Image: NASA, ESA, Matthias Stute , Margarita Karovska , Davide De Martin (ESA/Hubble), Mahdi Zamani (ESA/Hubble)

Credits/Visualization: NASA, ESA, Matthias Stute , Margarita Karovska , Davide De Martin , Mahdi Zamani , N. Bartmann (ESA/Hubble)

Credits/Visualization: NASA, ESA, Matthias Stute , Margarita Karovska , Davide De Martin , Mahdi Zamani , N. Bartmann (ESA/Hubble)


A bright binary star surrounded by a colorful nebula on the black background of space. The star in the center is a large white spot surrounded by a circular glow. It has a large, X-shaped set of diffraction spikes around it. The nebula extends far above, below, left and right of the star in long, arcing shapes made of thin, multicolored filaments — mostly red and greenish colors, but lit in a bright cyan near the star where its light illuminates the gas.

NASA's Hubble Space Telescope has provided a dramatic and colorful close-up look at one of the most rambunctious stars in our galaxy, weaving a huge spiral pattern among the stars.

Located approximately 700 light-years away, a binary star system called R Aquarii undergoes violent eruptions that blast out huge filaments of glowing gas. The twisted stellar outflows make the region look like a lawn sprinkler gone berserk. This dramatically demonstrates how the universe redistributes the products of nuclear energy that form deep inside stars and jet back into space.

R Aquarii belongs to a class of double stars called symbiotic stars. The primary star is an aging red giant and its companion is a compact burned-out star known as a white dwarf. The red giant primary star is classified as a Mira variable that is over 400 times larger than our Sun. The bloated monster star pulsates, changes temperature, and varies in brightness by a factor of 750 times over a roughly 390-day period. At its peak the star is blinding at nearly 5,000 times our Sun's brightness.

When the white dwarf star swings closest to the red giant along its 44-year orbital period, it gravitationally siphons off hydrogen gas. This material accumulates on the dwarf star's surface until it undergoes spontaneous nuclear fusion, making that surface explode like a gigantic hydrogen bomb. After the outburst, the fueling cycle begins again.

This outburst ejects geyser-like filaments shooting out from the core, forming weird loops and trails as the plasma emerges in streamers. The plasma is twisted by the force of the explosion and channeled upwards and outwards by strong magnetic fields. The outflow appears to bend back on itself into a spiral pattern. The plasma is shooting into space over 1 million miles per hour – fast enough to travel from Earth to the Moon in 15 minutes! The filaments are glowing in visible light because they are energized by blistering radiation from the stellar duo.

Hubble first observed the star in 1990. R Aquarii was resolved into two very bright stars separated by about 1.6 billion miles. The ESA/Hubble team now has made a unique timelapse of R Aquarii's dynamic behavior, from observations spanning from 2014 to 2023. Across the five images, the rapid and dramatic evolution of the binary star and its surrounding nebula can be seen. The binary star dims and brightens due to strong pulsations in the red giant star.

The scale of the event is extraordinary even in astronomical terms. Space-blasted material can be traced out to at least 248 billion miles from the stars, or 24 times our solar system's diameter. Images like these and more from Hubble are expected to revolutionize our ideas about such unique stellar "volcanoes" as R Aquarii.

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, Colorado, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, Maryland, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.



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Ray Villard
Space Telescope Science Institute, Baltimore, Maryland

Bethany Downer
ESA/Hubble

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Wednesday, October 16, 2024

A yet better view

Messier 90(M90)
A spiral galaxy. It has a bright core with light spilling out, and its disc is filled with thick clumps of dark reddish dust, which swirls around the galaxy following its rotation. Parts of the disc are speckled with blue, showing brighter and hotter stars. A halo of faintly-lit gas wraps around the galaxy, extending beyond the edges of the image. Credit: ESA/Hubble & NASA, D. Thilker, J. Lee and the PHANGS-HST Team

The striking spiral galaxy featured in this week’s Hubble Picture of the Week is Messier 90 (M90, also NGC 4569), located in the constellation Virgo. In 2019, an image of M90 was released using data from the older Wide Field and Planetary Camera 2 — data taken in 1994 soon after the camera’s installation. That image has a distinctive stair-step pattern due to the layout of WFPC2’s sensors. WFPC2 was replaced in 2010 by the Wide Field Camera 3, and Hubble used WFC3 when it turned its aperture to Messier 90 again in 2019 and 2023. The resulting data was processed to create this stunning new image, providing a much fuller view of the galaxy’s dusty disc, its gaseous halo and its bright core.

The inner regions of M90’s disc are sites of star formation, which is highlighted here by red H-alpha light from nebulae, but this is absent in the rest of the galaxy. M90 sits among the galaxies of the relatively nearby Virgo Cluster, and the course of its orbit took it on a path near the cluster’s centre about three hundred million years ago. The density of gas in the inner cluster weighed on M90 like a strong headwind, stripping enormous quantities of gas from the galaxy and creating the diffuse halo that can be seen around it here. This gas is no longer available for M90 to form new stars with, and it will eventually fade as a spiral galaxy as a result.

M90 is located 55 million light-years from Earth, but it’s one of the very few galaxies getting closer to us. Its orbit through the Virgo cluster has accelerated it so much that it’s in the process of escaping the cluster entirely, and by happenstance it’s moving in our direction — other galaxies in the Virgo cluster have been measured at similar speeds, but in the opposite direction. Over the coming billions of years, we will be treated to a yet better view of M90 while it evolves into a lenticular galaxy.



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Tuesday, October 15, 2024

Black Hole Destroys Star, Goes After Another, NASA Missions Find

AT2019qiz
Credit X-ray: NASA/CXC/Queen's Univ. Belfast/M. Nicholl et al.; Optical/IR: PanSTARRS, NSF/Legacy Survey/SDSS;
Illustration: Soheb Mandhai / The Astro Phoenix; Image Processing: NASA/CXC/SAO/N. Wolk




NASA’s Chandra X-ray Observatory and other telescopes have identified a supermassive black hole that has torn apart one star and is now using that stellar wreckage to pummel another star or smaller black hole, as described in our latest press release. This research helps connect two cosmic mysteries and provides information about the environment around some of the bigger types of black holes.

This artist’s illustration shows a disk of material (red, orange, and yellow) that was created after a supermassive black hole (depicted on the right) tore apart a star through intense tidal forces. Over the course of a few years, this disk expanded outward until it intersected with another object — either a star or a small black hole — that is also in orbit around the giant black hole. Each time this object crashes into the disk, it sends out a burst of X-rays detected by Chandra. The inset shows Chandra data (purple) and an optical image of the source from Pan-STARRS (red, green, and blue).

In 2019, an optical telescope in California noticed a burst of light that astronomers later categorized as a “tidal disruption event”, or TDE. These are cases where black holes tear stars apart if they get too close through their powerful tidal forces. Astronomers gave this TDE the name of AT2019qiz.

Meanwhile, scientists were also tracking instances of another type of cosmic phenomena occasionally observed across the Universe. These were brief and regular bursts of X-rays that were near supermassive black holes. Astronomers named these events “quasi-periodic eruptions,” or QPEs.

This latest study gives scientists evidence that TDEs and QPEs are likely connected. The researchers think that QPEs arise when an object smashes into the disk left behind after the TDE. While there may be other explanations, the authors of the study propose this is the source of at least some QPEs.

In 2023, astronomers used both Chandra and Hubble to simultaneously study the debris left behind after the tidal disruption had ended. The Chandra data were obtained during three different observations, each separated by about 4 to 5 hours. The total exposure of about 14 hours of Chandra time revealed only a weak signal in the first and last chunk, but a very strong signal in the middle observation.

Timelapse: X-ray Inset on Optical Background, 30 seconds
This series of images shows Chandra X-ray data of the area around AT2019qiz changing over time from December 9, 2023 at 10:44:59 UTC to December 9, 2023 at 20:09:07 UTC and then to December 10, 2023 at 14:49:06 UTC. Also included is a wide field optical image from Pan-STARRS. Chandra and other telescopes have identified this supermassive black hole that has torn apart one star and is now using that stellar wreckage to pummel another star or smaller black hole. Credit: NASA/CXC/A. Hobart

From there, the researchers used NASA’s Neutron Star Interior Composition Explorer (NICER) to look frequently at AT2019qiz for repeated X-ray bursts. The NICER data showed that AT2019qiz erupts roughly every 48 hours. Observations from NASA’s Neil Gehrels Swift Observatory and India’s AstroSat telescope cemented the finding.

The ultraviolet data from Hubble, obtained at the same time as the Chandra observations, allowed the scientists to determine the size of the disk around the supermassive black hole. They found that the disk had become large enough that if any object was orbiting the black hole and took about a week or less to complete an orbit, it would collide with the disk and cause eruptions.

This result has implications for searching for more quasi-periodic eruptions associated with tidal disruptions. Finding more of these would allow astronomers to measure the prevalence and distances of objects in close orbits around supermassive black holes. Some of these may be excellent targets for the planned future gravitational wave observatories.

The paper describing these results appears in the October 9, 2024 issue of the journal Nature. The first author of the paper is Matt Nicholl (Queen’s University Belfast in Ireland) and the full list of authors can be found in the paper, which is available online at: https://arxiv.org/abs/2409.02181

NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.




Visual Description:

This release features an artist's rendering that illustrates the destructive power of a supermassive black hole. The digital image depicts a disk of stellar material surrounding one such black hole. At its outer edge a neighboring star is colliding with and flying through the disk.

The black hole sits halfway down our right edge of the vertical image. It resembles a jet black semicircle with a domed cap of pale blue light. The bottom half of the circular black hole is hidden behind the disk of stellar material. In this illustration, the disk is viewed edge on. It resembles a band of swirling yellow, orange, and red gas, cutting diagonally from our middle right toward our lower left.

Near our lower left, the outer edge of the stellar debris disk overlaps with a bright blue sphere surrounded by luminous white swirls. This sphere represents a neighboring star crashing through the disk. The stellar disk is the wreckage of a destroyed star. An electric blue and white wave shows the hottest gas in the disk.

As the neighboring star crashes through the disk it leaves behind a trail of gas depicted as streaks of fine mist. Bursts of X-rays are released and are detected by Chandra.

Superimposed in the upper left corner of the illustration is an inset box showing a close up image of the source in X-ray and optical light. X-ray light is shown as purple and optical light is white and beige.



Fast Facts for AT2019qiz:

Scale: Image is about 5 arcmin (305,000 light-years) across. X-ray movie is about 1 arcminute (61,000 light-years) across.
 Category: Black Holes, Quasars & Active Galaxies
Coordinates (J2000): RA 4h 46m 37.9s | Dec -10° 13´ 34.9"
 Constellation: Eridanus
Observation Dates: 3 observations between Dec 09, 2023 and Dec 10, 2023
 Observation Time: 13 hours 58 minutes
 Obs. ID: 26788, 29099, 29100
 Instrument: ACIS
References: Nicholl, M, et al., 2024, Nature; arXiv:2409.02181
Color Code: X-ray: purple; Optical/IR: red, green, and blue.
 Distance Estimate: About 210 million light-years (z=0.0151)

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Monday, October 14, 2024

NASA's Hubble, New Horizons Team Up for a Simultaneous Look at Uranus

In this image, two three-dimensional shapes (top) of Uranus are compared to the actual views of the planet from NASA's Hubble Space Telescope (bottom left) and NASA's New Horizon's spacecraft (bottom right). These two missions recently simultaneously observed the gas giant, comparing high-resolution images from Hubble to the smaller view from New Horizons. This combined perspective will help researchers learn more about what to expect while imaging planets around other stars with future observatories.
The gas giant planets in our solar system have dynamic and variable atmospheres with changing cloud cover. By knowing the details of what the clouds on Uranus looked like from Hubble, researchers are able to verify what is interpreted from the New Horizons data.

While it was clear the cloud features were not changing with the planet's rotation, Uranus appeared dimmer in the New Horizons data than expected.

Researchers found this has to do with how the planet reflects light at a different phase than what Hubble can see. This showed that exoplanets may be dimmer than predicted at partial and high phase angles, and that the atmosphere reflects light differently at partial phase. Credits Science: NASA, ESA, STScI, Samantha Hasler (MIT), Amy Simon (NASA-GSFC), New Horizons Planetary Science Theme Team/Image Processing: Joseph DePasquale (STScI), Joseph Olmsted (STScI)

This illustration shows NASA's New Horizons spacecraft's view of our solar system from deep in the Kuiper Belt. New Horizons is currently at an estimated distance of more than 5 billion miles from Earth. The probe was 6.5 billion miles away from Uranus when it recently observed the planet. In this study, researchers used the gas giant as an exoplanet proxy, comparing high-resolution images from NASA's Hubble Space Telescope to the smaller view from New Horizons to learn more about what to expect while imaging planets around other stars. Credits Artwork? NASA, ESA, Christian Nieves (STScI), Ralf Crawford (STScI), Greg Bacon (STScI)


NASA's Hubble Space Telescope and New Horizons spacecraft simultaneously set their sights on Uranus recently, allowing scientists to make a direct comparison of the planet from two very different viewpoints. The results inform future plans to study like types of planets around other stars.

Astronomers used Uranus as a proxy for similar planets beyond our solar system, known as exoplanets, comparing high-resolution images from Hubble to the more-distant view from New Horizons. This combined perspective will help scientists learn more about what to expect while imaging planets around other stars with future telescopes.

"While we expected Uranus to appear differently in each filter of the observations, we found that Uranus was actually dimmer than predicted in the New Horizons data taken from a different viewpoint," said lead author Samantha Hasler of the Massachusetts Institute of Technology in Cambridge and New Horizons science team collaborator.

Direct imaging of exoplanets is a key technique for learning about their potential habitability, and offers new clues to the origin and formation of our own solar system. Astronomers use both direct imaging and spectroscopy to collect light from the observed planet and compare its brightness at different wavelengths. However, imaging exoplanets is a notoriously difficult process because they're so far away. Their images are mere pinpoints and so are not as detailed as the close-up views that we have of worlds orbiting our Sun. Researchers can also only directly image exoplanets at "partial phases," when only a portion of the planet is illuminated by their star as seen from Earth.

Uranus was an ideal target as a test for understanding future distant observations of exoplanets by other telescopes for a few reasons. First, many known exoplanets are also gas giants similar in nature. Also, at the time of the observations, New Horizons was on the far side of Uranus, 6.5 billion miles away, allowing its twilight crescent to be studied—something that cannot be done from Earth. At that distance, the New Horizons view of the planet was just several pixels in its color camera, called the Multispectral Visible Imaging Camera.

On the other hand, Hubble, with its high resolution, and in its low-Earth orbit 1.7 billion miles away from Uranus, was able to see atmospheric features such as clouds and storms on the day side of the gaseous world.

"Uranus appears as just a small dot on the New Horizons observations, similar to the dots seen of directly-imaged exoplanets from observatories like Webb or ground-based observatories," added Hasler. "Hubble provides context for what the atmosphere is doing when it was observed with New Horizons."

The gas giant planets in our solar system have dynamic and variable atmospheres with changing cloud cover. How common is this among exoplanets? By knowing the details of what the clouds on Uranus looked like from Hubble, researchers are able to verify what is interpreted from the New Horizons data. In the case of Uranus, both Hubble and New Horizons saw that the brightness did not vary as the planet rotated, which indicates that the cloud features were not changing with the planet’s rotation.

However, the importance of the detection by New Horizons has to do with how the planet reflects light at a different phase than what Hubble, or other observatories on or near Earth, can see. New Horizons showed that exoplanets may be dimmer than predicted at partial and high phase angles, and that the atmosphere reflects light differently at partial phase.

NASA has two major upcoming observatories in the works to advance studies of exoplanet atmospheres and potential habitability.

"These landmark New Horizons studies of Uranus from a vantage point unobservable by any other means add to the mission's treasure trove of new scientific knowledge, and have, like many other datasets obtained in the mission, yielded surprising new insights into the worlds of our solar system," added New Horizons principal investigator Alan Stern of the Southwest Research Institute.

NASA's upcoming Nancy Grace Roman Space Telescope, set to launch by 2027, will use a coronagraph to block out a star's light to directly see gas giant exoplanets. NASA's Habitable Worlds Observatory , in an early planning phase, will be the first telescope designed specifically to search for atmospheric biosignatures on Earth-sized, rocky planets orbiting other stars.

"Studying how known benchmarks like Uranus appear in distant imaging can help us have more robust expectations when preparing for these future missions," concluded Hasler. "And that will be critical to our success." Launched in January 2006, New Horizons made the historic flyby of Pluto and its moons in July 2015, before giving humankind its first close-up look at one of these planetary building block and Kuiper Belt object, Arrokoth, in January 2019. New Horizons is now in its second extended mission, studying distant Kuiper Belt objects, characterizing the outer heliosphere of the Sun, and making important astrophysical observations from its unmatched vantage point in distant regions of the solar system.

The Uranus results are being presented this week at the 56th annual meeting of the American Astronomical Society Division for Planetary Sciences, in Boise, Idaho. 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, Colorado, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, Maryland, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.

The Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, built and operates the New Horizons spacecraft and manages the mission for NASA's Science Mission Directorate. Southwest Research Institute, based in San Antonio and Boulder, Colorado, directs the mission via Principal Investigator Alan Stern and leads the science team, payload operations and encounter science planning. New Horizons is part of NASA's New Frontiers program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama.



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Hannah Braun
Space Telescope Science Institute, Baltimore, Maryland
Ray Villard
Space Telescope Science Institute, Baltimore, Maryland

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Samantha Hasler
Massachusetts Institute of Technology, Cambridge, Massachusetts

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NASA's Hubble Watches Jupiter's Great Red Spot Behave Like a Stress Ball

Close-up of Jupiter's Great Red Spot (8-Panel)Using Hubble Space Telescope data spanning approximately 90 days (between December 2023 and March 2024) when the giant planet Jupiter ranged from 391 million to 512 million miles from the Sun, astronomers measured the Great Red Spot's size, shape, brightness, color, and vorticity over one full oscillation cycle. The data reveal that the Great Red Spot is not as stable as it might look. It was observed going through an oscillation in its elliptical shape, jiggling like a bowl of gelatin. The cause of the 90-day oscillation is unknown. Credits: Science: NASA, ESA, Amy Simon (NASA-GSFC)/ Image Processing: Joseph DePasquale (STScI)

Using Hubble Space Telescope data spanning approximately 90 days (between December 2023 and March 2024) when the giant planet Jupiter ranged from 391 million to 512 million miles from the Sun, astronomers measured the Great Red Spot's size, shape, brightness, color, and vorticity over a full oscillation cycle. The data reveal that the Great Red Spot is not as stable as it might look. It was observed going through an oscillation in its elliptical shape, jiggling like a bowl of gelatin. The cause of the 90-day oscillation is unknown. The observation is part of the observing programs led by Amy Simon of NASA's Goddard Space Flight Center in Greenbelt, Maryland. Credits: Science: NASA, ESA, Amy Simon (NASA-GSFC)/ Image Processing: Joseph DePasquale (STScI)


This time-lapse movie is assembled from Hubble Space Telescope observations spanning approximately 90 days (between December 2023 and March 2024) when the giant planet Jupiter ranged from 391 million to 512 million miles from the Sun. Astronomers measured the Great Red Spot's size, shape, brightness, color, and vorticity over a full oscillation cycle. The data reveal that the Great Red Spot is not as stable as it might look. It was observed going through an oscillation in its elliptical shape, jiggling like a bowl of gelatin. The cause of the 90-day oscillation is unknown.Credits: Science: NASA, ESA, Amy Simon (NASA-GSFC)/ Image Processing: Joseph DePasquale (STScI)

This animated diagram shows the position of Earth relative to Jupiter during a period spanning approximately 90 days (between December 2023 and March 2024) when the giant planet Jupiter ranged from 391 million to 512 million miles from the Sun. During this period the Hubble Space telescope monitored changes in Jupiter's atmosphere as part of the observing programs led by Amy Simon of NASA Goddard Space Flight Center in Greenbelt, Maryland. Jupiter's orbital period is approximately 12 years. The angular size of the planet shrinks in Hubble's view, as faster-moving Earth pulls ahead of the giant planet. Credits Video: NASA, ESA, Joseph DePasquale (STScI)


Astronomers have observed Jupiter's legendary Great Red Spot (GRS), an anticyclone large enough to swallow Earth, for at least 150 years. But there are always new surprises – especially when NASA's Hubble Space Telescope takes a close-up look at it.

Hubble's new observations of the famous red storm, collected 90 days between December 2023 to March 2024, reveal that the GRS is not as stable as it might look. The recent data show the GRS jiggling like a bowl of gelatin. The combined Hubble images allowed astronomers to assemble a time-lapse movie of the squiggly behavior of the GRS.

"While we knew its motion varies slightly in its longitude, we didn't expect to see the size oscillate as well. As far as we know, it's not been identified before," said Amy Simon of NASA's Goddard Space Flight Center in Greenbelt, Maryland, lead author of the science paper published in The Planetary Science Journal. "This is really the first time we've had the proper imaging cadence of the GRS. With Hubble's high resolution we can say that the GRS is definitively squeezing in and out at the same time as it moves faster and slower. That was very unexpected, and at present there are no hydrodynamic explanations."

Hubble monitors Jupiter and the other outer solar system planets every year through the Outer Planet Atmospheres Legacy program (OPAL) led by Simon, but these observations were from a program dedicated to the GRS. Understanding the mechanisms of the largest storms in the solar system puts the theory of hurricanes on Earth into a broader cosmic context, which might be applied to better understanding the meteorology on planets around other stars.

Simon's team used Hubble to zoom in on the GRS for a detailed look at its size, shape, and any subtle color changes. "When we look closely, we see a lot of things are changing from day to day," said Simon. This includes ultraviolet-light observations showing that the distinct core of the storm gets brightest when the GRS is at its largest size in its oscillation cycle. This indicates less haze absorption in the upper atmosphere.

"As it accelerates and decelerates, the GRS is pushing against the windy jet streams to the north and south of it," said co-investigator Mike Wong of the University of California at Berkeley. "It's similar to a sandwich where the slices of bread are forced to bulge out when there's too much filling in the middle." Wong contrasted this to Neptune, where dark spots can drift wildly in latitude without strong jet streams to hold them in place. Jupiter's Great Red Spot has been held at a southern latitude, trapped between the jet streams, for the extent of Earth-bound telescopic observations.

The team has continued watching the GRS shrink since the OPAL program began 10 years ago. They predict it will keep shrinking before taking on a stable, less-elongated, shape. "Right now it's over-filling its latitude band relative to the wind field. Once it shrinks inside that band the winds will really be holding it in place," said Simon. The team predicts that the GRS will probably stabilize in size, but for now Hubble only observed it for one oscillation cycle.

The researchers hope that in the future other high-resolution images from Hubble might identify other Jovian parameters that indicate the underlying cause of the oscillation.

The results are being presented at the 56th annual meeting of the American Astronomical Society Division for Planetary Sciences, in Boise, Idaho.

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, Colorado, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, Maryland, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.



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Ray Villard:
Space Telescope Science Institute, Baltimore, Maryland

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Amy Simon
NASA Goddard Space Flight Center, Greenbelt, Maryland

Michael H. Wong
University of California, Berkeley, Berkeley, California

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Sunday, October 13, 2024

Interacting Galaxies NGC 5366 & PGC 49574

Interacting Galaxies NGC 5366 & PGC 49574
Images: Low Res.（68.4 KB) / Mid Res（1.17 MB) / High Res.(9.94 MB)

Detail：A wide variety of galaxy interactions exist in the Universe. NGC 5366, the face-on galaxy at the top of the image, and PGC 49574, the edge-on galaxy at the bottom, are a rare pair of interacting galaxies located in the constellation Virgo. In addition to the difference in galactic disk inclination, the two galaxies show contrasting colors. In NGC 5366, star-forming regions appear blue, while in PGC 49574, the dark dust lane of the galactic disk looks reddish. The gravitational interaction between these galaxies has created the widely extended tail-like structures.

Distance from Earth: About 420 million light-years
 Instrument: Hyper Suprime-Cam (HSC)


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NASA's Webb Reveals Unusual Jets of Volatile Gas from Icy Centaur 29P

Centaur 29P Outgassing (Artist's Concept)
Credits: Artwork: NASA, ESA, CSA, Leah Hustak (STScI)

Centaur 29P Outgassing (NIRSpec)
Credits: Illustration: NASA, ESA, CSA, Leah Hustak (STScI), Sara Faggi (NASA-GSFC, American University)

Inspired by the half-human, half-horse creatures that are part of Ancient Greek mythology, the field of astronomy has its own kind of centaurs: distant objects orbiting the Sun between Jupiter and Neptune. NASA’s James Webb Space Telescope has mapped the gases spewing from one of these objects, suggesting a varied composition and providing new insights into the formation and evolution of the solar system.

Centaurs are former trans-Neptunian objects that have been moved inside Neptune’s orbit by subtle gravitational influences of the planets in the last few million years, and may eventually become short-period comets. They are “hybrid” in the sense that they are in a transitional stage of their orbital evolution: Many share characteristics with both trans-Neptunian objects (from the cold Kuiper Belt reservoir), and short-period comets, which are objects highly altered by repeated close passages around the Sun.

Since these small icy bodies are in an orbital transitional phase, they have been the subject of various studies as scientists seek to understand their composition, the reasons behind their outgassing activity — the loss of their ices that lie underneath the surface — and how they serve as a link between primordial icy bodies in the outer solar system and evolved comets.

A team of scientists recently used Webb’s NIRSpec (Near-Infrared Spectrograph) instrument to obtain data on Centaur 29P/Schwassmann-Wachmann 1 (29P for short), an object that is known for its highly active and quasi-periodic outbursts. It varies in intensity every six to eight weeks, making it one of the most active objects in the outer solar system. They discovered a new jet of carbon monoxide (CO) and previously unseen jets of carbon dioxide (CO2) gas, which give new clues to the nature of the centaur’s nucleus. “Centaurs can be considered as some of the leftovers of our planetary system’s formation. Because they are stored at very cold temperatures, they preserve information about volatiles in the early stages of the solar system,” said Sara Faggi of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and American University in Washington, DC, lead author of the study. “Webb really opened the door to a resolution and sensitivity that was impressive to us — when we saw the data for the first time, we were excited. We had never seen anything like this.”

Webb and the Jets

Centaurs’ distant orbits and consequent faintness have inhibited detailed observations in the past. Data from prior radio wavelength observations of Centaur 29P showed a jet pointed generally toward the Sun (and Earth) composed of CO. Webb detected this face-on jet and, thanks to its large mirror and infrared capabilities, also sensitively searched for many other chemicals, including water (H2O) and CO2. The latter is one of the main forms in which carbon is stored across the solar system. No clear indication of water vapor was detected in the atmosphere of 29P, which could be related to the extremely cold temperatures present in this body.

The telescope’s unique imaging and spectral data revealed never-before-seen features: two jets of CO2 emanating in the north and south directions, and another jet of CO pointing toward the north. This was the first definitive detection of CO2 in Centaur 29P.

Based on the data gathered by Webb, the team created a 3D model of the jets to understand their orientation and origin. They found through their modeling efforts that the jets were emitted from different regions on the centaur’s nucleus, even though the nucleus itself cannot be resolved by Webb. The jets’ angles suggest the possibility that the nucleus may be an aggregate of distinct objects with different compositions; however, other scenarios can’t yet be excluded.

“The fact that Centaur 29P has such dramatic differences in the abundance of CO and CO2 across its surface suggests that 29P may be made of several pieces,” said Geronimo Villanueva, co-author of the study at NASA Goddard. “Maybe two pieces coalesced together and made this centaur, which is a mixture between very different bodies that underwent separate formation pathways. It challenges our ideas about how primordial objects are created and stored in the Kuiper Belt.”

Persisting Unanswered Questions (For Now)

The reasons for Centaur 29P’s bursts in brightness, and the mechanisms behind its outgassing activity through the CO and CO2 jets, continue to be two major areas of interest that require further investigation. In the case of comets, scientists know that their jets are often driven by the outgassing of water. However, because of the centaurs’ location, they are too cold for water ice to sublimate, meaning that the nature of their outgassing activity differs from comets. “We only had time to look at this object once, like a snapshot in time,” said Adam McKay, a co-author of the study at Appalachian State University in Boone, North Carolina. “I’d like to go back and look at Centaur 29P over a much longer period of time. Do the jets always have that orientation? Is there perhaps another carbon monoxide jet that turns on at a different point in the rotation period? Looking at these jets over time would give us much better insights into what is driving these outbursts.” The team is hopeful that as they increase their understanding of Centaur 29P, they can apply the same techniques to other centaurs. By improving the astronomical community’s collective knowledge of centaurs, we can simultaneously better our understanding on the formation and evolution of our solar system.

These findings have been published in Nature.

The observations were taken as part of General Observer program 2416.

The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).



About This Release

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Abigail Major
Space Telescope Science Institute, Baltimore, Maryland

Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland

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Saturday, October 12, 2024

The exotic stellar population of Westerlund 1

A dense cluster of bright stars, each with six large and two small diffraction spikes, due to the telescope’s optics. They have a variety of sizes depending on their brightness and distance from us in the cluster, and different colours reflecting different types of star. Patches of billowing red gas can be seen in and around the cluster, lit up by the stars. Small stars in the cluster blend into a background of distant stars and galaxies on black. Credit: ESA/Webb, NASA & CSA, M. Zamani (ESA/Webb), M. G. Guarcello (INAF-OAPA) and the EWOCS team

The open cluster Westerlund 1, showcased in this new Webb Picture of the Month, is located roughly 12 000 light-years away in the southern constellation Ara (the Altar) where it resides behind a huge interstellar cloud of gas and dust. It was discovered in 1961 from Australia by Swedish astronomer Bengt Westerlund. Westerlund 1 is an incomparable natural laboratory for the study of extreme stellar physics, helping astronomers to find out how the most massive stars in our Galaxy live and die.

The unique draw of Westerlund 1 is its large, dense, and diverse population of massive stars, which has no counterpart in other known Milky Way galaxy clusters in terms of the number of stars and the richness of spectral types and evolutionary phases. All stars identified in this cluster are evolved and very massive, spanning the full range of stellar classifications including Wolf-Rayet stars, OB supergiants, yellow hypergiants (nearly as bright as a million Suns) and luminous blue variables. Because such stars have a rather short life, Westerlund 1 is very young, astronomically speaking. Astronomers estimate the cluster’s age to be somewhere between 3.5 and 5 million years (its exact age is still a matter of debate), making it a newborn cluster in our galaxy. In the future, it is believed that it will likely evolve from an open cluster into a globular cluster. These are roughly spherical, tightly packed collections of old stars bound together by gravity.

Currently, only a handful of stars form in our galaxy each year, but in the past the situation was different. The Milky Way galaxy used to produce many more stars, likely hitting its peak of churning out dozens or hundreds of stars per year about 10 billion years ago and then gradually declining ever since. Astronomers think that most of this star formation took place in massive clusters of stars, known as “super star clusters”. These are young clusters of stars that contain more than 10,000 times the mass of the Sun, packed into an unbelievably small volume. They represent the most extreme environments in which stars and planets can form. Only a few super star clusters still exist in our galaxy — of which Westerlund 1 is one — but they offer important clues about this earlier era when most of our galaxy’s stars formed.

Westerlund 1 is an impressive example of a super star cluster: it contains hundreds of very massive stars, some shining with a brilliance of almost one million Suns and others two thousand times larger than the Sun (as large as the orbit of Saturn). Indeed, if the Solar System was located at the heart of this remarkable cluster, our sky would be full of hundreds of stars as bright as the full Moon. It appears to be the most massive compact young cluster yet identified in the Milky Way galaxy: astronomers believe that this extreme cluster contains between 50 000 and 100 000 times the mass of the Sun, yet all of its stars are located within a region less than six light-years across. Even so, it is the biggest of these remaining super star clusters in the Milky Way galaxy, and the closest super star cluster to Earth. These qualities make Westerlund 1 an excellent target for studying the impact of a super star cluster’s environment on the formation process of stars and planets, as well as the evolution of stars over a broad range of masses.

The huge population of massive stars in Westerlund 1 suggests that it will have a very significant impact on its surroundings. The cluster contains so many massive stars that in a time span of less than 40 million years, it will be the site of more than 1 500 supernovae. This super star cluster now provides astronomers with a unique perspective towards one of the most extreme environments in the Universe. Westerlund 1 will certainly provide new opportunities in the long-standing quest for more and finer details about how stars, and especially massive stars, form.

This image was captured as part of the The Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) with Webb’s Near-InfraRed Camera (NIRCam). This survey is a dedicated Webb program (GO 1905, PI: M. G. Guarcello) that aims to study star and planet formation and stellar evolution in starburst regions in Westerlund 1 and Westerlund 2, two of the closest super star clusters to the Sun.

With its unparalleled performance in the infrared, Webb offers astronomers the opportunity to unveil the population of low-mass stars in local super star clusters for the first time, and to study the environments around these clusters’ most massive stars. Webb observations of the massive stars in super star clusters can shed light on how feedback (stellar winds, supernovae and other ejected material) from these stars impacts their surrounding environments and the overall star formation process within their parental clouds.

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Friday, October 11, 2024

Space oddity: Most distant rotating disc galaxy found

PR Image eso2415a
The REBELS-25 galaxy

PR Image eso2415b
ALMA image and motion of the cold gas in REBELS-25 (side-by-side)

PR Image eso2415c
ALMA image of the cold gas in REBELS-25

PR Image eso2415d
Motion of the cold gas in REBELS-25 as seen by ALMA

PR Image eso2415e
Infrared image of stars and galaxies near the REBELS-25 galaxy



Videos

Most distant rotating galaxy yet is a space oddity | ESO News
PR Video eso2415a
Most distant rotating galaxy yet is a space oddity | ESO News

Zooming in on REBELS-25
PR Video eso2415b
Zooming in on REBELS-25


Researchers have discovered the most distant Milky-Way-like galaxy yet observed. Dubbed REBELS-25, this disc galaxy seems as orderly as present-day galaxies, but we see it as it was when the Universe was only 700 million years old. This is surprising since, according to our current understanding of galaxy formation, such early galaxies are expected to appear more chaotic. The rotation and structure of REBELS-25 were revealed using the Atacama Large Millimeter/submillimeter Array (ALMA), in which the European Southern Observatory (ESO) is a partner.

The galaxies we see today have come a long way from their chaotic, clumpy counterparts that astronomers typically observe in the early Universe. “According to our understanding of galaxy formation, we expect most early galaxies to be small and messy looking,” says Jacqueline Hodge, an astronomer at Leiden University, the Netherlands, and co-author of the study.

These messy, early galaxies merge with each other and then evolve into smoother shapes at an incredibly slow pace. Current theories suggest that, for a galaxy to be as orderly as our own Milky Way — a rotating disc with tidy structures like spiral arms — billions of years of evolution must have elapsed. The detection of REBELS-25, however, challenges that timescale.

In the study, accepted for publication in Monthly Notices of the Royal Astronomical Society, astronomers found REBELS-25 to be the most distant strongly rotating disc galaxy ever discovered. The light reaching us from this galaxy was emitted when the Universe was only 700 million years old — a mere five percent of its current age (13.8 billion) — making REBELS-25’s orderly rotation unexpected. “Seeing a galaxy with such similarities to our own Milky Way, that is strongly rotation-dominated, challenges our understanding of how quickly galaxies in the early Universe evolve into the orderly galaxies of today's cosmos,” says Lucie Rowland, a doctoral student at Leiden University and first author of the study.

REBELS-25 was initially detected in previous observations by the same team, also conducted with ALMA, which is located in Chile’s Atacama Desert. At the time, it was an exciting discovery, showing hints of rotation, but the resolution of the data was not fine enough to be sure. To properly discern the structure and motion of the galaxy, the team performed follow-up observations with ALMA at a higher resolution, which confirmed its record-breaking nature. “ALMA is the only telescope in existence with the sensitivity and resolution to achieve this,” says Renske Smit, a researcher at Liverpool John Moores University in the UK and also a co-author of the study.

Surprisingly, the data also hinted at more developed features similar to those of the Milky Way, like a central elongated bar, and even spiral arms, although more observations will be needed to confirm this. “Finding further evidence of more evolved structures would be an exciting discovery, as it would be the most distant galaxy with such structures observed to date,” says Rowland.

These future observations of REBELS-25, alongside other discoveries of early rotating galaxies, will potentially transform our understanding of early galaxy formation, and the evolution of the Universe as a whole.

Source: ESO/News


More information
This research is presented in a paper entitled “REBELS-25: Discovery of a dynamically cold disc galaxy at z=7.31” to appear in Monthly Notices of the Royal Astronomical Society.

The observations were conducted as part of the ALMA Large Program REBELS: Reionization Era Bright Emission Lines Survey.

The team is composed of L. E. Rowland (Leiden Observatory, Leiden University, the Netherlands [Leiden]), J. Hodge (Leiden), R. Bouwens (Leiden), P. M. Piña (Leiden), A. Hygate (Leiden), H. Algera (Astrophysical Science Center, Hiroshima University, Japan [HASC]; National Astronomical Observatory of Japan, Japan), M. Aravena (Núcleo de Astronomía, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Chile), R. Bowler (Jodrell Bank Centre for Astrophysics, University of Manchester, UK), E. da Cunha (International Centre for Radio Astronomy Research, University of Western Australia, Australia; ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions), P. Dayal (Kapteyn Astronomical Institute, University of Groningen, the Netherlands), A. Ferrara (Scuola Normale Superiore, Italy [SNS]), T. Herard-Demanche (Leiden), H. Inami (HASC), I. van Leeuwen (Leiden), I. de Looze (Sterrenkundig Observatorium, Ghent University, Belgium), P. Oesch (Department of Astronomy, University of Geneva, Switzerland; Cosmic Dawn Center, Denmark), A. Pallottini (SNS), S. Phillips (Astrophysics Research Institute, Liverpool John Moores University, UK [LJMU]), M. Rybak (Faculty of Electrical Engineering, Delft University of Technology, the Netherlands; Leiden; Netherlands Institute for Space Research, the Netherlands), S. Schouws (Leiden), R. Smit (LJMU), L. Sommovigo (Center for Computational Astrophysics, Flatiron Institute, USA), M. Stefanon (Departament d’Astronomia i Astrofísica, Universitat de València, Spain; Grupo de Astrofísica Extragaláctica y Cosmología, Universitat de València, Spain), P. van der Werf (Leiden).

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science and Technology Council (NSTC) in Taiwan and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI). ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

The European Southern Observatory (ESO) enables scientists worldwide to discover the secrets of the Universe for the benefit of all. We design, build and operate world-class observatories on the ground — which astronomers use to tackle exciting questions and spread the fascination of astronomy — and promote international collaboration for astronomy. Established as an intergovernmental organisation in 1962, today ESO is supported by 16 Member States (Austria, Belgium, Czechia, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom), along with the host state of Chile and with Australia as a Strategic Partner. ESO’s headquarters and its visitor centre and planetarium, the ESO Supernova, are located close to Munich in Germany, while the Chilean Atacama Desert, a marvellous place with unique conditions to observe the sky, hosts our telescopes. ESO operates three observing sites: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its Very Large Telescope Interferometer, as well as survey telescopes such as VISTA. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. Together with international partners, ESO operates ALMA on Chajnantor, a facility that observes the skies in the millimetre and submillimetre range. At Cerro Armazones, near Paranal, we are building “the world’s biggest eye on the sky” — ESO’s Extremely Large Telescope. From our offices in Santiago, Chile we support our operations in the country and engage with Chilean partners and society.



Links


Contacts

Lucie Rowland
Leiden Observatory, University of Leiden
Leiden, The Netherlands
Tel: +31 71 527 2727
Email: lrowland@strw.leidenuniv.nl

Jacqueline Hodge
Leiden Observatory, University of Leiden
Leiden, The Netherlands
Tel: +31 71 527 8450
Email: hodge@strw.leidenuniv.nl

Renske Smit
Astrophysics Research Institute, Liverpool John Moores University
Liverpool, UK
Tel: +44-151-231-2922
Email: R.Smit@ljmu.ac.uk

Bárbara Ferreira
ESO Media Manager
Garching bei München, Germany
Tel: +49 89 3200 6670
Cell: +49 151 241 664 00
Email: press@eso.org

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Thursday, October 10, 2024

Starbursts on grand scale

A close-in, face-on view of a spiral galaxy. It has two large arms which curve outwards from the round, bright central region to nearly the corners of the image. They are lined by bright pink, glowing points where stars are forming, and channels of dark reddish dust that blocks light. These also spread across the galaxy’s oval disc, which is cloudy in form and speckled with stars. A black background is visible behind it. Credit: ESA/Hubble & NASA, F. Belfiore, J. Lee and the PHANGS-HST Team

The sparkling scene depicted in this week’s Hubble Picture of the Week is of the spiral galaxy NGC 5248, located 42 million light-years from Earth in the constellation Boötes. It is also known as Caldwell 45, having been included in a catalogue of visually interesting celestial objects that were known, but weren’t as commonly observed by amateur astronomers as the more famous Messier objects.

NGC 5248 is one of the so-called ‘grand design’ spirals, with prominent spiral arms that reach from near the core out through the disc. It also has a faint bar structure in the centre, between the inner ends of the spiral arms, which is not quite so obvious in this visible-light portrait from Hubble. Features like these which break the rotational symmetry of a galaxy have a huge influence on how matter moves through it, and eventually its evolution through time. They feed gas from a galaxy’s outer reaches to inner star-forming regions, and even to a galaxy’s central black hole where it can kick-start an active galactic nucleus.

These flows of gas have shaped NGC 5248 in a big way; it has many bright ‘starburst regions’ of intense star formation spread across its disc, and it is dominated by a population of young stars. The galaxy even has two very active, ring-shaped starburst regions around its nucleus, filled with young clusters of stars. These ‘nuclear rings’ are remarkable enough, but normally a nuclear ring tends to block gas from getting further into the core of a galaxy. NGC 5248 having a second ring inside the first is a marker of just how forceful its flows of matter and energy are! Its relatively nearby, highly visible starburst regions make the galaxy a target for professional and amateur astronomers alike.

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Wednesday, October 09, 2024

Rocky Planet Around a White Dwarf Resembles Earth — 8 Billion Years From Now

Artist’s illustration of a distant white dwarf with an Earth-like planet in an orbit just beyond where Mars is in our solar system. Earth could end up in such an orbit circling a white dwarf in about 8 billion years, if, like this exoplanet, it can survive the Sun’s red giant phase on its way to becoming a white dwarf. Credit: W. M. Keck Observatory/Adam Makarenko

A video depicting one possible fate for Earth when the Sun expands into a red giant. If the red giant sheds its mass quickly enough to allow Earth to migrate to a wider orbit, it will escape being engulfed by the expanding surface of the red giant, eventually settling into an orbit about twice its current size. In the process, however, it will be heated to a lava planet, becoming uninhabitable long before the red giant becomes a white dwarf. Scientists have found one example of an Earth-like planet that escaped destruction and now orbits a white dwarf, showing that it is possible. Animation credit: W. M. Keck Observatory/Adam Makarenko


Existence Of Earth-like Planet Around Dead Sun Offers Hope For Our Planet’s Ultimate Survival

Maunakea, Hawaiʻi – The discovery of an Earth-like planet 4,000 light years away in the Milky Way galaxy provides a preview of one possible fate for our planet billions of years in the future, when the Sun has turned into a white dwarf, and a blasted and frozen Earth has migrated beyond the orbit of Mars.

This distant planetary system, identified by a University of California (UC) Berkeley-led team of astronomers after observations with the W. M. Keck Observatory on Maunakea, Hawaiʻi Island, looks very similar to expectations for the Sun-Earth system: it consists of a white dwarf about half the mass of the Sun and an Earth-size companion in an orbit twice as large as Earth’s today.

That is likely to be Earth’s fate. The Sun will eventually inflate like a balloon larger than Earth’s orbit today, engulfing Mercury and Venus in the process. As the star expands to become a red giant, its decreasing mass will force planets to migrate to more distant orbits, offering Earth a slim opportunity to survive farther from the Sun. Eventually, the outer layers of the red giant will be blown away to leave behind a dense white dwarf no larger than a planet, but with the mass of a star. If Earth has survived by then, it will probably end up in an orbit twice its current size.

The discovery, published online today in the journal Nature Astronomy, tells scientists about the evolution of main sequence stars like the Sun, through the red giant phase to a white dwarf, and how it affects the planets around them. Some studies suggest that for the Sun, this process could begin in about 1 billion years, eventually vaporizing Earth’s oceans and doubling Earth’s orbital radius — if the expanding star doesn’t engulf our planet first.

Eventually, about 8 billion years from now, the Sun’s outer layers will have dispersed to leave behind a dense, glowing ball — a white dwarf — that is about half the mass of the Sun, but smaller in size than Earth.

“We do not currently have a consensus whether Earth could avoid being engulfed by the red giant Sun in 6 billion years,” said study lead author Keming Zhang, a former doctoral student at the UC Berkeley, who is now an Eric and Wendy Schmidt AI in Science Postdoctoral fellow at UC San Diego. “In any case, planet Earth will only be habitable for around another billion years, at which point Earth’s oceans would be vaporized by runaway greenhouse effect — long before the risk of getting swallowed by the red giant.”

The planetary system provides one example of a planet that did survive, though it is far outside the habitable zone of the dim white dwarf and unlikely to harbor life. It may have had habitable conditions at some point, when its host was still a Sun-like star.

“Whether life can survive on Earth through that (red giant) period is unknown. But certainly the most important thing is that Earth isn’t swallowed by the Sun when it becomes a red giant,” said Jessica Lu, associate professor and chair of astronomy at UC Berkeley. “This system that Keming found is an example of a planet — probably an Earth-like planet originally on a similar orbit to Earth — that survived its host star’s red giant phase.”

Microlensing makes star brighten a thousandfold

The far-away planetary system, located near the bulge at the center of our galaxy, came to astronomers’ attention in 2020 when it passed in front of a more distant star and magnified that star’s light by a factor of 1,000. The gravity of the system acted like a lens to focus and amplify the light from the background star.

The team that discovered this “microlensing event” dubbed it KMT-2020-BLG-0414 because it was detected by the Korea Microlensing Telescope Network in the Southern Hemisphere.

The system included a star about half the mass of the Sun, a planet about the mass of Earth and a very large planet about 17 times the mass of Jupiter — likely a brown dwarf. Brown dwarfs are failed stars, with a mass just shy of that required to ignite fusion in the core.

The analysis also concluded that the Earth-like planet was between 1 and 2 astronomical units from the star — that is, about twice the distance between the Earth and Sun.

To identify the type of the host star, Zhang, Lu, and fellow UC Berkeley astronomer Joshua Bloom looked more closely at the lensing system in 2023 using Keck Observatory’s second generation Near-Infrared Camera (NIRC2) paired with the Observatory’s adaptive optics system to eliminate the blur caused by Earth’s atmosphere.

But Zhang detected nothing in two separate Keck Observatory images.

“Our conclusions are based on ruling out the alternative scenarios, since a normal star would have been easily seen,” Zhang said. “Because the lens is both dark and low mass, we concluded that it can only be a white dwarf.”

“This is a case of where seeing nothing is actually more interesting than seeing something,” said Lu, who looks for microlensing events caused by free-floating stellar-mass black holes in the Milky Way.

Images of the area of the microlensing event, indicated by perpendicular white lines, years before the event (a), shortly after peak magnification of the background star in 2020 (b) and in 2023 after its disappearance (c). The planetary system with a white dwarf, an Earth-like planet and a brown dwarf cannot be seen; the point of light in (c) is from the background source star that is no longer magnified. Credit: OGLE, CFHT, W. M. Keck Observatory

“Microlensing has turned into a very interesting way of studying other star systems that can’t be observed and detected by the conventional means, i.e. the transit method or the radial velocity method,” Bloom said. “There is a whole set of worlds that are now opening up to us through the microlensing channel, and what’s exciting is that we’re on the precipice of finding exotic configurations like this.”

One purpose of NASA’s Nancy Grace Roman Telescope, scheduled for launch in 2027, is to measure light curves from microlensing events to find exoplanets, many of which will need follow up using other telescopes to identify the types of stars hosting the exoplanets.

“What is required is careful follow up with the world’s best facilities, i.e. adaptive optics and the Keck Observatory, not just a day or a month later, but many, many years into the future, after the lens has moved away from the background star so you can start disambiguating what you’re seeing,” Bloom said.

Zhang noted that even if Earth gets engulfed during the Sun’s red giant phase in a billion or so years, humanity may find a refuge in the outer solar system. Several moons of Jupiter, such as Europa, Callisto and Ganymede, and Enceladus around Saturn, appear to have frozen water oceans that will likely thaw as the outer layers of the red giant expand.

“As the Sun becomes a red giant, the habitable zone will move to around Jupiter and Saturn’s orbit, and many of these moons will become ocean planets,” Zhang said. “I think, in that case, humanity could migrate out there.”

Learn more:

“This rocky planet around a white dwarf resembles Earth — 8 billion years from now” – UC Berkeley Press Release, September 26



About NIRC2
The Near-Infrared Camera, second generation (NIRC2) works in combination with the Keck II adaptive optics system to obtain very sharp images at near-infrared wavelengths, achieving spatial resolutions comparable to or better than those achieved by the Hubble Space Telescope at optical wavelengths. NIRC2 is probably best known for helping to provide definitive proof of a central massive black hole at the center of our galaxy. Astronomers also use NIRC2 to map surface features of solar system bodies, detect planets orbiting other stars, and study detailed morphology of distant galaxies.

About ADAPTIVE OPTICS
W. M. Keck Observatory is a distinguished leader in the field of adaptive optics (AO), a breakthrough technology that removes the distortions caused by the turbulence in the Earth’s atmosphere. Keck Observatory pioneered the astronomical use of both natural guide star (NGS) and laser guide star adaptive optics (LGS AO) and current systems now deliver images three to four times sharper than the Hubble Space Telescope at near-infrared wavelengths. AO has imaged the four massive planets orbiting the star HR8799, measured the mass of the giant black hole at the center of our Milky Way Galaxy, discovered new supernovae in distant galaxies, and identified the specific stars that were their progenitors. Support for this technology was generously provided by the Gordon and Betty Moore Foundation, Mt. Cuba Astronomical Foundation, NASA, NSF, and W. M. Keck Foundation.

About W. M. Keck Observatory
The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

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