Space news topic and space related news

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NASA's Juno to Get a Close Look at Jupiter's Moon Ganymede
https://www.nasa.gov/feature/jpl/nasa-s-juno-to-get-a-close-look-at-jupiter-s-moon-ganymede

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Front-row view reveals exceptional cosmic explosion
https://www.desy.de/news/news_search/index_eng.html?openDirectAnchor=2080

Observation challenges established theory of gamma-ray bursts in the universe

Scientists have gained the best view yet of the brightest explosions in the universe: A specialised observatory in Namibia has recorded the most energetic radiation and longest gamma-ray afterglow of a so-called gamma-ray burst (GRB) to date. The observations with the High Energy Stereoscopic System (H.E.S.S.) challenge the established idea of how gamma-rays are produced in these colossal stellar explosions which are the birth cries of black holes, as the international team reports in the journal Science.

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CIBER-2 Takes Its First Flight
https://www.caltech.edu/about/news/ciber-2-takes-its-first-flight

The Cosmic Infrared Background Experiment-2 (CIBER-2) took its first flight late on June 6 Pacific Time, soaring into space for a short time aboard a NASA rocket. The experiment is measuring a mysterious glow of infrared light that fills our skies called the cosmic infrared background.

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CHIME telescope detects more than 500 mysterious fast radio bursts in its first year of operation
https://news.mit.edu/2021/chime-telescope-fast-radio-bursts-0609

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Then There Were 3: NASA to Collaborate on ESA's New Venus Mission
https://www.nasa.gov/feature/then-there-were-3-nasa-to-collaborate-on-esa-s-new-venus-mission

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NASA Approves Asteroid Hunting Space Telescope to Continue Development
https://www.jpl.nasa.gov/news/nasa-approves-asteroid-hunting-space-telescope-to-continue-development

The infrared space telescope is designed to help advance NASA's planetary defense efforts.

NASA has approved the Near-Earth Object Surveyor space telescope (NEO Surveyor) to move to the next phase of mission development after a successful mission review, authorizing the mission to move forward into Preliminary Design (known as Key Decision Point-B). The infrared space telescope is designed to help advance NASA's planetary defense efforts by expediting our ability to discover and characterize most of the potentially hazardous asteroids and comets that come within 30 million miles of Earth's orbit, collectively known as near-earth objects, or NEOs.

"NEO Surveyor will have the capability to rapidly accelerate the rate at which NASA is able to discover asteroids and comets that could pose a hazard to the Earth, and it is being designed to discover 90 percent of asteroids 140 meters in size or larger within a decade of being launched," said Mike Kelley, NEO Surveyor program scientist at NASA Headquarters.

Following completion of the goal to discover 90 percent of all NEOs larger than 1,000 meters (3,280 feet) in size in 2010, the National Aeronautics and Space Administration Act of 2005 (Public Law 109-155) directed NASA to discover 90% of NEOs larger than 140 meters (459 feet) in size. The agency is diligently working to achieve this directive and has currently found approximately 40% of near-Earth asteroids within this size range.

"Each night, astronomers across the globe diligently use ground-based optical telescopes to discover new NEOs, characterize their shape and size, and confirm they do not pose a threat to us," said Kelly Fast, program manager for NASA's NEO Observations Program. "Those telescopes are only able to look for NEOs in the night sky. NEO Surveyor would allow observations to continue day and night, specifically targeting regions where NEOs that could pose a hazard might be found and accelerating the progress toward the Congressional goal."

Discovering, characterizing, and tracking potentially hazardous NEOs as early as possible is crucial in ensuring that deflection or other preparations for impact mitigation can be carried out in time. NASA will test one deflection technology – the kinetic impactor – with its Double Asteroid Redirection Test (DART) mission, to be launched later this year. While there are no known impact threats to Earth for the next century, unpredicted impacts by unknown NEOs – such as the 2013 Chelyabinsk event in Russia – still pose a hazard to Earth. Using sensors that operate in the infrared, NEO Surveyor would help planetary scientists discover NEOs more quickly, including ones that could approach Earth during the day from closer to the direction of the Sun – something that is not currently possible using ground-based optical observatories.

"By searching for NEOs closer to the direction of the Sun, NEO Surveyor would help astronomers discover impact hazards that could approach Earth from the daytime sky," said Amy Mainzer, principal investigator for NEO Surveyor at the University of Arizona. "NEO Surveyor would also significantly enhance NASA's ability to determine the specific sizes and characteristics of newly discovered NEOs by using infrared light, complementing ongoing observations being conducted by ground-based observatories and radar."

NEO Surveyor's approval to move to this next mission milestone brings the telescope one step closer to launch, which is currently scheduled for the first half of 2026. The mission is being developed by NASA's Jet Propulsion Laboratory in Southern California and managed by NASA's Planetary Missions Program Office at Marshall Space Flight Center, with program oversight by the Planetary Defense Coordination Office (PDCO). NASA established the PDCO in 2016 to manage the agency's ongoing efforts in Planetary Defense.

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Astronomers measure heaviest known neutron star with telescope on ISS
https://www.uva.nl/en/shared-content/faculteiten/en/faculteit-der-natuurwetenschappen-wiskunde-en-informatica/news/2021/06/astronomers-measure-heaviest-known-neutron-star-with-telescope-on-iss.html?origin=cnUSYqO%2BT4OvERocBmGxmw&cb

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Mystery of Betelgeuse's dip in brightness solved
https://www.eso.org/public/news/eso2109/

When Betelgeuse, a bright orange star in the constellation of Orion, became visibly darker in late 2019 and early 2020, the astronomy community was puzzled. A team of astronomers have now published new images of the star's surface, taken using the European Southern Observatory's Very Large Telescope (ESO's VLT), that clearly show how its brightness changed. The new research reveals that the star was partially concealed by a cloud of dust, a discovery that solves the mystery of the "Great Dimming" of Betelgeuse.

Betelgeuse's dip in brightness — a change noticeable even to the naked eye — led Miguel Montargès and his team to point ESO's VLT towards the star in late 2019. An image from December 2019, when compared to an earlier image taken in January of the same year, showed that the stellar surface was significantly darker, especially in the southern region. But the astronomers weren't sure why.

The team continued observing the star during its Great Dimming, capturing two other never-before-seen images in January 2020 and March 2020. By April 2020, the star had returned to its normal brightness.

"For once, we were seeing the appearance of a star changing in real time on a scale of weeks," says Montargès, from the Observatoire de Paris, France, and KU Leuven, Belgium. The images now published are the only ones we have that show Betelgeuse's surface changing in brightness over time.

In their new study, published today in Nature, the team revealed that the mysterious dimming was caused by a dusty veil shading the star, which in turn was the result of a drop in temperature on Betelgeuse's stellar surface.

Betelgeuse's surface regularly changes as giant bubbles of gas move, shrink and swell within the star. The team concludes that some time before the Great Dimming, the star ejected a large gas bubble that moved away from it. When a patch of the surface cooled down shortly after, that temperature decrease was enough for the gas to condense into solid dust.

"We have directly witnessed the formation of so-called stardust," says Montargès, whose study provides evidence that dust formation can occur very quickly and close to a star's surface. "The dust expelled from cool evolved stars, such as the ejection we've just witnessed, could go on to become the building blocks of terrestrial planets and life," adds Emily Cannon, from KU Leuven, who was also involved in the study.

Rather than just the result of a dusty outburst, there was some speculation online that Betelgeuse's drop in brightness could signal its imminent death in a spectacular supernova explosion. A supernova hasn't been observed in our galaxy since the 17th century, so present-day astronomers aren't entirely sure what to expect from a star in the lead-up to such an event. However, this new research confirms that Betelgeuse's Great Dimming was not an early sign that the star was heading towards its dramatic fate.

Witnessing the dimming of such a recognisable star was exciting for professional and amateur astronomers alike, as summed up by Cannon: "Looking up at the stars at night, these tiny, twinkling dots of light seem perpetual. The dimming of Betelgeuse breaks this illusion."

The team used the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument on ESO's VLT to directly image the surface of Betelgeuse, alongside data from the GRAVITY instrument on ESO's Very Large Telescope Interferometer (VLTI), to monitor the star throughout the dimming. The telescopes, located at ESO's Paranal Observatory in Chile's Atacama Desert, were a "vital diagnostic tool in uncovering the cause of this dimming event," says Cannon. "We were able to observe the star not just as a point but could resolve the details of its surface and monitor it throughout the event," Montargès adds.

Montargès and Cannon are looking forward to what the future of astronomy, in particular what ESO's Extremely Large Telescope (ELT), will bring to their study of Betelgeuse, a red supergiant star. "With the ability to reach unparalleled spatial resolutions, the ELT will enable us to directly image Betelgeuse in remarkable detail," says Cannon. "It will also significantly expand the sample of red supergiants for which we can resolve the surface through direct imaging, further helping us to unravel the mysteries behind the winds of these massive stars."

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NASA Balloon Detects California Earthquake – Next Stop, Venus?
https://www.jpl.nasa.gov/news/nasa-balloon-detects-california-earthquake-next-stop-venus

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National Science Foundation renews funding to support detection of gravitational waves, led locally by Stephen Taylor
https://news.vanderbilt.edu/2021/06/21/national-science-foundation-renews-funding-to-support-detection-of-gravitational-waves-led-locally-by-stephen-taylor/

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NASA's Webb Will Use Quasars to Unlock the Secrets of the Early Universe
https://www.nasa.gov/feature/goddard/2021/nasa-s-webb-will-use-quasars-to-unlock-the-secrets-of-the-early-universe

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Physicists observationally confirm Hawking's black hole theorem for the first time
https://news.mit.edu/2021/hawkings-black-hole-theorem-confirm-0701

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Gang of black holes spotted at centre of star cluster
https://www.cardiff.ac.uk/news/view/2531857-gang-of-black-holes-spotted-at-centre-of-star-cluster

Scientists have been left stunned by a gang of more than 100 black holes sitting at the centre of a large collection of stars over 80,000 light years from Earth.

The finding has been made inside Palomar 5, a 10-billion-year-old collection of stars that orbits around the Milky Way.

Reporting their findings today in Nature Astronomy, the scientists say Palomar 5 contains about three times as many black holes as they would expect to find in a star cluster of this size, with each black hole having a mass of about 20 times that of the Sun.

They believe that this troupe of ginormous clumps of matter, through which nothing can escape, could be responsible for the mass evacuation of stars from Palomar 5 in what is known as a 'tidal stream'.

A tidal stream is a thin band of stars that are believed to have once been a globular cluster or dwarf galaxy, and that have now been pulled away along the cluster orbit by the Galactic tides.

Palomar 5 has streams of stars extending outward toward the front and rear of the orbital path of itself, stretching to distances of 13,000 light years.

"We do not know how these streams form, but one idea is that they are disrupted star clusters," said lead author of the paper Prof Mark Gieles, from the Institute of Cosmos Sciences of the University of Barcelona.

"However, none of the recently discovered streams have a star cluster associated with them, hence we cannot be sure. So, to understand how these streams formed, we need to study one with a stellar system associated with it. Palomar 5 is the only case, making it a Rosetta Stone for understanding stream formation and that is why we studied it in detail."

To arrive at their findings, the team simulated the orbits and the evolution of each star within Palomar 5 until it finally died, varying the initial properties of the cluster until a good match with the observations of the stream and the cluster was found.

They were able to show that Palomar 5 formed with a lower population of black holes, but then stars escaped more efficiently leaving the black holes behind.

They believe the black holes dynamically puffed up the cluster in gravitational slingshot interactions with stars, which led to even more escaping stars and the formation of the tidal stream.

Co-author of the study Dr Fabio Antonini, from Cardiff University's School of Physics and Astronomy, said: "What we have shown is that an unusually large collection of black holes may not be uncommon, and that the same number, or perhaps even more, could be sitting at the centre of other star clusters that have formed tidal streams".

The new findings could have significant implications for the study of black holes themselves and the ripples of gravitational waves that are produced when two of them collide and merge together.

"It is believed that a large fraction of binary black hole mergers form in star clusters," Dr Antonini continued.

"A big unknown in this scenario is how many black holes there are in clusters, which is difficult to work out because we cannot see black holes. Our new method gives us a way to learn how many black holes there are in a star cluster by simply looking at the stars they eject.''

Palomar 5 is a globular cluster discovered in 1950 by Walter Baade. It is in the Serpens constellation about 80,000 light-years from Earth and is one of the roughly 150 globular clusters that orbit around the Milky Way.

It is one of the "fluffiest" clusters in the halo of our Galaxy, with the average distance between the stars being a few light-years, comparable to the distance from the Sun to its nearest star.

The team say roughly a billion years from now Palomar 5 will consist entirely of black holes.

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Galactic fireworks: new ESO images reveal stunning features of nearby galaxies
https://www.eso.org/public/news/eso2110/

A team of astronomers has released new observations of nearby galaxies that resemble colourful cosmic fireworks. The images, obtained with the European Southern Observatory's Very Large Telescope (ESO's VLT), show different components of the galaxies in distinct colours, allowing astronomers to pinpoint the locations of young stars and the gas they warm up around them. By combining these new observations with data from the Atacama Large Millimeter/submillimeter Array (ALMA), in which ESO is a partner, the team is helping shed new light on what triggers gas to form stars.

Astronomers know that stars are born in clouds of gas, but what sets off star formation, and how galaxies as a whole play into it, remains a mystery. To understand this process, a team of researchers has observed various nearby galaxies with powerful telescopes on the ground and in space, scanning the different galactic regions involved in stellar births.

"For the first time we are resolving individual units of star formation over a wide range of locations and environments in a sample that well represents the different types of galaxies," says Eric Emsellem, an astronomer at ESO in Germany and lead of the VLT-based observations conducted as part of the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) project. "We can directly observe the gas that gives birth to stars, we see the young stars themselves, and we witness their evolution through various phases."

Emsellem, who is also affiliated with the University of Lyon, France, and his team have now released their latest set of galactic scans, taken with the Multi-Unit Spectroscopic Explorer (MUSE) instrument on ESO's VLT in the Atacama Desert in Chile. They used MUSE to trace newborn stars and the warm gas around them, which is illuminated and heated up by the stars and acts as a smoking gun of ongoing star formation.

The new MUSE images are now being combined with observations of the same galaxies taken with ALMA and released earlier this year. ALMA, which is also located in Chile, is especially well suited to mapping cold gas clouds — the parts of galaxies that provide the raw material out of which stars form.

By combining MUSE and ALMA images astronomers can examine the galactic regions where star formation is happening, compared to where it is expected to happen, so as to better understand what triggers, boosts or holds back the birth of new stars. The resulting images are stunning, offering a spectacularly colourful insight into stellar nurseries in our neighbouring galaxies.

"There are many mysteries we want to unravel," says Kathryn Kreckel from the University of Heidelberg in Germany and PHANGS team member. "Are stars more often born in specific regions of their host galaxies — and, if so, why? And after stars are born how does their evolution influence the formation of new generations of stars?"

Astronomers will now be able to answer these questions thanks to the wealth of MUSE and ALMA data the PHANGS team have obtained. MUSE collects spectra — the "bar codes" astronomers scan to unveil the properties and nature of cosmic objects — at every single location within its field of view, thus providing much richer information than traditional instruments. For the PHANGS project, MUSE observed 30 000 nebulae of warm gas and collected about 15 million spectra of different galactic regions. The ALMA observations, on the other hand, allowed astronomers to map around 100 000 cold-gas regions across 90 nearby galaxies, producing an unprecedentedly sharp atlas of stellar nurseries in the close Universe.

In addition to ALMA and MUSE, the PHANGS project also features observations from the NASA/ESA Hubble Space Telescope. The various observatories were selected to allow the team to scan our galactic neighbours at different wavelengths (visible, near-infrared and radio), with each wavelength range unveiling distinct parts of the observed galaxies. "Their combination allows us to probe the various stages of stellar birth — from the formation of the stellar nurseries to the onset of star formation itself and the final destruction of the nurseries by the newly born stars — in more detail than is possible with individual observations," says PHANGS team member Francesco Belfiore from INAF-Arcetri in Florence, Italy. "PHANGS is the first time we have been able to assemble such a complete view, taking images sharp enough to see the individual clouds, stars, and nebulae that signify forming stars."

The work carried out by the PHANGS project will be further honed by upcoming telescopes and instruments, such as NASA's James Webb Space Telescope. The data obtained in this way will lay further groundwork for observations with ESO's future Extremely Large Telescope (ELT), which will start operating later this decade and will enable an even more detailed look at the structures of stellar nurseries.

"As amazing as PHANGS is, the resolution of the maps that we produce is just sufficient to identify and separate individual star-forming clouds, but not good enough to see what's happening inside them in detail," pointed out Eva Schinnerer, a research group leader at the Max Planck Institute for Astronomy in Germany and principal investigator of the PHANGS project, under which the new observations were conducted. "New observational efforts by our team and others are pushing the boundary in this direction, so we have decades of exciting discoveries ahead of us."

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Astronomers Uncover Briefest Supernova-Powered Gamma-Ray Burst
https://www.gemini.edu/pr/astronomers-uncover-briefest-supernova-powered-gamma-ray-burst

Astronomers have discovered the shortest-ever gamma-ray burst (GRB) caused by the implosion of a massive star. Using the international Gemini Observatory, a Program of NSF's NOIRLab, astronomers identified the cause of this 0.6-second flurry of gamma rays as a supernova explosion in a distant galaxy. GRBs caused by supernovae are usually more than twice as long, which suggests that some short GRBs might actually be imposters — supernova-produced GRBs in disguise.

Gamma-ray bursts (GRBs) are among the brightest and most energetic events in the Universe, but scientists are still figuring out exactly what causes these fleeting events [1]. Astronomers divide GRBs into two broad categories based on their duration. Short GRBs blaze into life in less than two seconds and are thought to be caused by the merging of binary neutron stars [2]. Those that last longer are classified as long GRBs, and have been associated with supernova explosions caused by the implosions of massive stars [3]. However, the recent discovery of the shortest-ever GRB produced during a supernova shows that GRBs don't fit neatly into the boxes astronomers have created for them.

"This discovery represents the shortest gamma-ray emission caused by a supernova during the collapse of a massive star," commented Tomás Ahumada, who led this research and is a PhD candidate at the University of Maryland and astronomer at NASA's Goddard Space Flight Center. "It lasted for only 0.6 second, and it sits on the brink between a successful and a failed gamma-ray burst."

The team believes that this and some other supernova-related GRBs are appearing short because the jets of gamma rays that emerge from the collapsing star's poles aren't strong enough to completely escape the star — almost failing to produce a GRB — and that other collapsing stars have such weak jets that they don't produce GRBs at all.

This discovery could also help explain an astronomical mystery. Long GRBs are associated with a specific type of supernova (called Type Ic-BL). However, astronomers observe many more of these supernovae than long GRBs. This discovery of the shortest GRB associated with a supernova suggests that some of these supernova-caused GRBs are masquerading as short GRBs thought to be created by neutron-star mergers, and are therefore not getting counted as the supernova kind.

"Our discovery suggests that, since we observe many more of these supernovae than long gamma-ray bursts, most collapsing stars fail to produce a GRB jet that breaks through the outer envelope of the collapsing star," explained Ahumada. "We think this event was effectively a fizzle, one that was close to not happening at all."

The team was able to determine that this GRB — identified as GRB 200826A — originated from a supernova explosion thanks to the imaging capabilities of the Gemini Multi-Object Spectrograph on Gemini North in Hawai'i. The researchers used Gemini North to obtain images of the GRB's host galaxy 28, 45, and 80 days after the GRB was first detected on 26 August 2020 by a network of observatories that included NASA's Fermi Gamma-ray Space Telescope. Gemini's observations allowed the team to spot the tell-tale rise in energy that signifies a supernova, despite the blast's location in a galaxy 6.6 billion light-years away.

"This was a complicated endeavor as we needed to separate the light of an already faint galaxy from the light of a supernova," said Ahumada. "Gemini is the only ground-based telescope that can do follow-up observations like this with a flexible-enough schedule to let us squeeze in our observations."

This result shows that classifying GRBs based solely on their duration may not be the best approach, and that additional observations are needed to determine a GRB's cause.

"We were originally hunting for merging neutron stars, which are thought to produce short gamma-ray bursts," added Ahumada. "Once we discovered GRB 200826A, however, we realized that this burst was more likely to be caused by a collapsing star's supernova, which was a surprise!"

"The Gemini observatories continue to shed new light on the nature of these incredible explosions occurring across the distant Universe," said Martin Still, Gemini Program Officer at NSF. "Dedicated instrumentation arriving for use over the next decade will maintain Gemini's leadership in the follow-up of these awe-inspiring cosmic events."

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Stanford astrophysicists report first detection of light from behind a black hole
https://news.stanford.edu/2021/07/28/first-detection-light-behind-black-hole/

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New Spin on Planet Formation Mysteries
https://www.caltech.edu/about/news/new-spin-on-unraveling-planet-formation-mysteries

Astronomers have captured the first-ever spin measurements of planets making up the HR 8799 star system.

Discovered in 2008 by the W. M. Keck Observatory and Gemini Observatory, which are both located in Hawaii, the HR 8799 star system is located 129 light-years away and has four so-called super-Jupiter planets, each more massive than Jupiter. HR 8799 is one of the first planetary systems to have its picture directly taken by a telescope.

However, none of the HR 8799 planets' rotation periods, or spin rates, had been measured—and, in fact, the spin rate (which translates into the length of a day on the planet) has been measured for only a handful of the thousands of exoplanets so far discovered.

The breakthrough was made possible by a Caltech and Keck Observatory-led science and engineering team that developed an instrument called the Keck Planet Imager and Characterizer (KPIC). Commissioned between 2018 and 2020, the instrument can observe, with extremely high spectral resolution, exoplanets that were previously imaged. KPIC provides a resolution that is high enough to decipher how fast the planets are spinning.

A study about the findings has been accepted for publication in The Astronomical Journal; the work represents the first science results from KPIC.

The study showed that the minimum rotation speeds of two of the HR 8799 planets, known as HR 8799 d and HR 8799 e, are 10.1 kilometers per second (km/s) and 15 km/s, respectively. This translates to a length of day that could be as short as three hours or could be as long as 24 hours, as on Earth, depending on the tilts of the planets, which are currently undetermined. For context, Jupiter has a rotation speed of about 12.7 km/s, and one day on Jupiter lasts nearly 10 hours.

The team was also able to constrain the spin of a third planet, HR 8799 c, to an upper limit of less than 14 km/s. The rotation rate of the fourth planet, HR 8799 b, could not be conclusively determined.

Knowing the spin rates of planets provides important clues as to how they formed.

"With KPIC, we were able to obtain the highest spectral resolution observations ever conducted of the HR 8799 exoplanets," says Jason Wang, the 51 Pegasi b Postdoctoral Scholar Research Associate in Astronomy at Caltech and lead author of the study. "This allows us to study them with finer granularity than ever before and unlocks the key to gaining a deeper understanding of not just how these four planets formed but how gas giants in general develop throughout the universe."

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Huge Waves in the Sun Discovered with NASA Mission
https://www.nasa.gov/image-feature/goddard/2021/huge-waves-in-the-sun-discovered-nasa-mission-sdo

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New ESO observations show rocky exoplanet has just half the mass of Venus
https://www.eso.org/public/news/eso2112/

A team of astronomers have used the European Southern Observatory's Very Large Telescope (ESO's VLT) in Chile to shed new light on planets around a nearby star, L 98-59, that resemble those in the inner Solar System. Amongst the findings are a planet with half the mass of Venus — the lightest exoplanet ever to be measured using the radial velocity technique — an ocean world, and a possible planet in the habitable zone.

"The planet in the habitable zone may have an atmosphere that could protect and support life," says María Rosa Zapatero Osorio, an astronomer at the Centre for Astrobiology in Madrid, Spain, and one of the authors of the study published today in Astronomy & Astrophysics.

The results are an important step in the quest to find life on Earth-sized planets outside the Solar System. The detection of biosignatures on an exoplanet depends on the ability to study its atmosphere, but current telescopes are not large enough to achieve the resolution needed to do this for small, rocky planets. The newly studied planetary system, called L 98-59 after its star, is an attractive target for future observations of exoplanet atmospheres. Its orbits a star only 35 light-years away and has now been found to host rocky planets, like Earth or Venus, which are close enough to the star to be warm.

With the contribution of ESO's VLT, the team was able to infer that three of the planets may contain water in their interiors or atmospheres. The two planets closest to the star in the L 98-59 system are probably dry, but might have small amounts of water, while up to 30% of the third planet's mass could be water, making it an ocean world.

Furthermore, the team found "hidden" exoplanets that had not previously been spotted in this planetary system. They discovered a fourth planet and suspect there is a fifth, in a zone at the right distance from the star for liquid water to exist on its surface. "We have hints of the presence of a terrestrial planet in the habitable zone of this system," explains Olivier Demangeon, a researcher at the Instituto de Astrofísica e Ciências do Espaço, University of Porto in Portugal and lead author of the new study.

The study represents a technical breakthrough, as astronomers were able to determine, using the radial velocity method, that the innermost planet in the system has just half the mass of Venus. This makes it the lightest exoplanet ever measured using this technique, which calculates the wobble of the star caused by the tiny gravitational tug of its orbiting planets.

The team used the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) instrument on ESO's VLT to study L 98-59. "Without the precision and stability provided by ESPRESSO this measurement would have not been possible," says Zapatero Osorio. "This is a step forward in our ability to measure the masses of the smallest planets beyond the Solar System."

The astronomers first spotted three of L 98-59's planets in 2019, using NASA's Transiting Exoplanet Survey Satellite (TESS). This satellite relies on a technique called the transit method — where the dip in the light coming from the star caused by a planet passing in front of it is used to infer the properties of the planet — to find the planets and measure their sizes. However, it was only with the addition of radial velocity measurements made with ESPRESSO and its predecessor, the High Accuracy Radial velocity Planet Searcher (HARPS) at the ESO La Silla 3.6-metre telescope, that Demangeon and his team were able to find extra planets and measure the masses and radii of the first three. "If we want to know what a planet is made of, the minimum that we need is its mass and its radius," Demangeon explains.

The team hopes to continue to study the system with the forthcoming NASA/ESA/CSA James Webb Space Telescope (JWST), while ESO's Extremely Large Telescope (ELT), under construction in the Chilean Atacama Desert and set to start observations in 2027, will also be ideal for studying these planets. "The HIRES instrument on the ELT may have the power to study the atmospheres of some of the planets in the L 98-59 system, thus complementing the JWST from the ground," says Zapatero Osorio.

"This system announces what is to come," adds Demangeon. "We, as a society, have been chasing terrestrial planets since the birth of astronomy and now we are finally getting closer and closer to the detection of a terrestrial planet in the habitable zone of its star, of which we could study the atmosphere."

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NASA's Ingenuity Mars Helicopter Spots Perseverance From Above
https://www.nasa.gov/feature/jpl/nasa-s-ingenuity-mars-helicopter-spots-perseverance-from-above

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