Space news topic and space related news

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Puzzling six-exoplanet system with rhythmic movement challenges theories of how planets form
https://www.eso.org/public/news/eso2102/

Using a combination of telescopes, including the Very Large Telescope of the European Southern Observatory (ESO's VLT), astronomers have revealed a system consisting of six exoplanets, five of which are locked in a rare rhythm around their central star. The researchers believe the system could provide important clues about how planets, including those in the Solar System, form and evolve.

The first time the team observed TOI-178, a star some 200 light-years away in the constellation of Sculptor, they thought they had spotted two planets going around it in the same orbit. However, a closer look revealed something entirely different. "Through further observations we realised that there were not two planets orbiting the star at roughly the same distance from it, but rather multiple planets in a very special configuration," says Adrien Leleu from the Université de Genève and the University of Bern, Switzerland, who led a new study of the system published today in Astronomy & Astrophysics.

The new research has revealed that the system boasts six exoplanets and that all but the one closest to the star are locked in a rhythmic dance as they move in their orbits. In other words, they are in resonance. This means that there are patterns that repeat themselves as the planets go around the star, with some planets aligning every few orbits. A similar resonance is observed in the orbits of three of Jupiter's moons: Io, Europa and Ganymede. Io, the closest of the three to Jupiter, completes four full orbits around Jupiter for every orbit that Ganymede, the furthest away, makes, and two full orbits for every orbit Europa makes.

The five outer exoplanets of the TOI-178 system follow a much more complex chain of resonance, one of the longest yet discovered in a system of planets. While the three Jupiter moons are in a 4:2:1 resonance, the five outer planets in the TOI-178 system follow a 18:9:6:4:3 chain: while the second planet from the star (the first in the resonance chain) completes 18 orbits, the third planet from the star (second in the chain) completes 9 orbits, and so on. In fact, the scientists initially only found five planets in the system, but by following this resonant rhythm they calculated where in its orbit an additional planet would be when they next had a window to observe the system.

More than just an orbital curiosity, this dance of resonant planets provides clues about the system's past. "The orbits in this system are very well ordered, which tells us that this system has evolved quite gently since its birth," explains co-author Yann Alibert from the University of Bern. If the system had been significantly disturbed earlier in its life, for example by a giant impact, this fragile configuration of orbits would not have survived.

Disorder in the rhythmic system
But even if the arrangement of the orbits is neat and well-ordered, the densities of the planets "are much more disorderly," says Nathan Hara from the Université de Genève, Switzerland, who was also involved in the study. "It appears there is a planet as dense as the Earth right next to a very fluffy planet with half the density of Neptune, followed by a planet with the density of Neptune. It is not what we are used to." In our Solar System, for example, the planets are neatly arranged, with the rocky, denser planets closer to the central star and the fluffy, low-density gas planets farther out.

"This contrast between the rhythmic harmony of the orbital motion and the disorderly densities certainly challenges our understanding of the formation and evolution of planetary systems," says Leleu.

Combining techniques
To investigate the system's unusual architecture, the team used data from the European Space Agency's CHEOPS satellite, alongside the ground-based ESPRESSO instrument on ESO's VLT and the NGTS and SPECULOOS, both sited at ESO's Paranal Observatory in Chile. Since exoplanets are extremely tricky to spot directly with telescopes, astronomers must instead rely on other techniques to detect them. The main methods used are imaging transits — observing the light emitted by the central star, which dims as an exoplanet passes in front of it when observed from the Earth — and radial velocities — observing the star's light spectrum for small signs of wobbles which happen as the exoplanets move in their orbits. The team used both methods to observe the system: CHEOPS, NGTS and SPECULOOS for transits and ESPRESSO for radial velocities.

By combining the two techniques, astronomers were able to gather key information about the system and its planets, which orbit their central star much closer and much faster than the Earth orbits the Sun. The fastest (the innermost planet) completes an orbit in just a couple of days, while the slowest takes about ten times longer. The six planets have sizes ranging from about one to about three times the size of Earth, while their masses are 1.5 to 30 times the mass of Earth. Some of the planets are rocky, but larger than Earth — these planets are known as Super-Earths. Others are gas planets, like the outer planets in our Solar System, but they are much smaller — these are nicknamed Mini-Neptunes.

Although none of the six exoplanets found lies in the star's habitable zone, the researchers suggest that, by continuing the resonance chain, they might find additional planets that could exist in or very close to this zone. ESO's Extremely Large Telescope (ELT), which is set to begin operating this decade, will be able to directly image rocky exoplanets in a star's habitable zone and even characterise their atmospheres, presenting an opportunity to get to know systems like TOI-178 in even greater detail.

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The 7 rocky planets orbiting TRAPPIST-1 may be made of similar stuff
https://www.technology.org/2021/01/26/the-7-rocky-planets-orbiting-trappist-1-may-be-made-of-similar-stuff/

The TRAPPIST-1 star system is home to the largest batch of roughly Earth-size planets ever found outside our solar system. Discovered in 2016 some 40 light-years away, these seven rocky siblings offer a glimpse at the tremendous variety of planetary systems that likely fill the universe.

A study accepted by the Planetary Science Journal shows that the planets share similar densities. That could mean they all contain roughly the same ratio of materials thought to be common to rocky planets, such as iron, oxygen, magnesium and silicon. If so, then while the TRAPPIST-1 planets might be similar to each other, they appear to differ notably from Earth: They're about 8% less dense than they would be if they had the same chemical composition as our planet.

These findings give astronomers new data that they're using to try to pin down the precise composition of these planets, and compare them not just to Earth, but to all the rocky planets in our solar system, according to lead author Eric Agol, a University of Washington professor of astronomy.

"This is one of the most precise characterizations of a set of rocky exoplanets, which gave us high-confidence measurements of their diameters, densities and masses," said Agol. "This is the information we needed to make hypotheses about their composition and understand how these planets differ from the rocky planets in our solar system."

Since the initial detection in 2016 of the TRAPPIST-1 worlds, scientists have studied this planetary family with multiple space- and ground-based telescopes, including NASA's now-retired Kepler Space Telescope and Spitzer Space Telescope. Spitzer alone provided over 1,000 hours of targeted observations of the system before being decommissioned in January 2020. Since they're too small and faint to view directly, all seven exoplanets were found via the so-called transit method: looking for dips in the star's brightness created when the planets cross in front of it.

Previous calculations had shown that the planets are roughly the size and mass of Earth and thus must also be rocky, or terrestrial — as opposed to gas-dominated worlds like Jupiter and Saturn. This new study offers the most precise density measurements to date for any group of exoplanets.

"The night sky is full of planets, and it's only been within the last 30 years that we've been able to start unraveling their mysteries," said co-author Caroline Dorn of the University of Zurich. "The TRAPPIST-1 system is fascinating because around this one star we can learn about the diversity of rocky planets within a single system. And we can actually learn more about a planet by studying its neighbors as well, so this system is perfect for that."

The team — which includes scientists based in the United States, Switzerland, France, the United Kingdom and Morocco — used observations of the starlight dips and precise measurements of the timing of the planets' orbits to make detailed measurements of each planet's mass and diameter, and from there to determine its density. Agol and UW co-authors Zachary Langford and Victoria Meadows, a professor of astronomy, analyzed data and performed computer simulations that constrained the orbits of the TRAPPIST-1 planets and calculated their densities.

With more precise measurements of an object's density, we can know more about its composition. A baseball and a paperweight may be the same size, but the baseball is much lighter. Width and weight together reveal each object's density, and from there it is possible to infer that the baseball is made of lighter materials, like string and leather, while the paperweight has a heavier composition, like glass or metal.

In our own solar system, the densities of the eight planets vary widely. The gas giants — Jupiter, Saturn, Uranus and Neptune — are larger, but much less dense than the four rocky planets. Earth, Venus and Mars have similar densities, but Mercury contains a much higher percentage of iron, so although it is the solar system's smallest planet in diameter, Mercury has the second-highest density of all eight planets.

The seven TRAPPIST-1 planets, on the other hand, all share a similar density, which makes the system quite different from our own. The difference in density between the TRAPPIST-1 planets and Earth, Venus and Mars, may seem small — about 8% — but it is significant on a planetary scale. For example, one way to explain the lower density is that the TRAPPIST-1 planets have a similar composition to Earth, but with a lower percentage of iron — about 21% compared to Earth's 32%, according to the study.

Alternatively, the iron in the TRAPPIST-1 planets might be infused with high levels of oxygen, forming iron oxide, or rust. The additional oxygen would decrease the planets' densities. The surface of Mars gets its red tint from iron oxide, but like its three terrestrial siblings, it has a core composed of non-oxidized iron. By contrast, if the lower density of the TRAPPIST-1 planets were caused entirely by oxidized iron, then the planets would have to be rusty throughout and could not have iron cores.

Agol said the answer might be a combination of the two scenarios — less iron overall and some oxidized iron.

The team also looked into whether the surface of each planet could be covered with water, which is even lighter than rust and which would change the planet's overall density. If that were the case, water would have to account for about 5% of the total mass of the outer four planets. By comparison, water makes up less than 0.1% of Earth's total mass. The three inner TRAPPIST-1 planets, positioned too close to their star for water to remain a liquid under most circumstances, would require hot, dense atmospheres like on Venus, where water could remain bound to the planet as steam. But this explanation seems less likely because it would be a coincidence for all seven planets to have just enough water present to have such similar densities, according to Agol.

When it launches, NASA's James Webb Space Telescope should have the capabilities to probe this system further, including gathering more detailed information about the atmospheres of the seven TRAPPIST-1 worlds.

"There are many more questions to answer about TRAPPIST-1 and its worlds," said Agol. "And in a way, answering them helps us understand our own solar system, too."

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Astronomers find possible hints of gravitational waves
https://news.cornell.edu/stories/2021/01/astronomers-find-possible-hints-gravitational-waves

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New research on carbon cracks open secrets deep inside exoplanets
https://www.technology.org/2021/01/29/new-research-on-carbon-cracks-open-secrets-deep-inside-exoplanets/

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Hubble Spots an Interstellar Interaction
https://www.nasa.gov/image-feature/goddard/2021/hubble-spots-an-interstellar-interaction

The life of a planetary nebula is often chaotic, from the death of its parent star to the scattering of its contents far out into space. Captured here by the NASA/ESA Hubble Space Telescope, ESO 455-10 is one such planetary nebula, located in the constellation of Scorpius (The Scorpion).

The oblate shells of ESO 455-10, previously held tightly together as layers of its central star, not only give this planetary nebula its unique appearance, but also offer information about the nebula. Seen in a field of stars, the distinct asymmetrical arc of material over the north side of the nebula is a clear sign of interactions between ESO 455-10 and the interstellar medium.

The interstellar medium is the material such as diffuse gas between star systems and galaxies.  The star at the center of ESO 455-10 allows Hubble to see the interaction with the gas and dust of the nebula, the surrounding interstellar medium, and the light from the star itself. Planetary nebulae are thought to be crucial in galactic enrichment as they distribute their elements, particularly the heavier metal elements produced inside a star, into the interstellar medium which will in time form the next generation of stars.

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TESS discovers four exoplanets orbiting a nearby sun-like star
https://news.mit.edu/2021/tess-discovers-four-exoplanets-orbiting-nearby-sun-like-star-0128

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Astronomers detect extended dark matter halo around ancient dwarf galaxy
https://news.mit.edu/2021/astronomers-detect-extended-dark-matter-halo-ancient-dwarf-galaxy-0201

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True identity of mysterious gamma-ray source revealed
https://www.technology.org/2021/02/04/true-identity-of-mysterious-gamma-ray-source-revealed/

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How Mars 2020 Will Help Bring Part of the Red Planet Back to Earth
https://www.caltech.edu/about/news/how-mars-2020-will-help-bring-part-of-the-red-planet-back-to-earth

Out in the cold, empty void beyond Earth, NASA's latest Mars mission is hurtling at 43,000 miles per hour toward the Red Planet. The mission, Mars 2020, passed the halfway point of its journey in October 2020 and is expected to touch down on solid ground on February 18.

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NASA Selects Firefly Aerospace for Artemis Commercial Moon Delivery in 2023
https://www.nasa.gov/press-release/nasa-selects-firefly-aerospace-for-artemis-commercial-moon-delivery-in-2023/

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A new Class of Exoplanets can Shrink, From Subneptunes Into Superearths
https://www.universetoday.com/149924/a-new-class-of-exoplanets-can-shrink-from-subneptunes-into-superearths/

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50 Years Ago: Apollo 14 Lands at Fra Mauro
https://www.nasa.gov/feature/50-years-ago-apollo-14-lands-at-fra-mauro/

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Researchers Explore Laser-Beaming Energy for Lunar and Terrestrial Needs
https://www.technology.org/2021/02/08/researchers-explore-laser-beaming-energy-for-lunar-and-terrestrial-needs/

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Nearby Ancient Dwarf Galaxies Have a Surprising Amount of Dark Matter
https://www.technology.org/2021/02/09/nearby-ancient-dwarf-galaxies-have-a-surprising-amount-of-dark-matter/

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A New Technique to Find Cold Gas Streams That Might Make up the Missing (Normal) Matter in the Universe
https://www.universetoday.com/150068/a-new-technique-to-find-cold-gas-streams-that-might-make-up-the-missing-normal-matter-in-the-universe/

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Astronomers Confirm Solar System's Most Distant Known Object Is Indeed Farfarout
https://www.gemini.edu/pr/astronomers-confirm-solar-system-s-most-distant-known-object-indeed-farfarout

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There's a tantalizing sign of a habitable-zone planet in Alpha Centauri
https://www.technologyreview.com/2021/02/10/1017908/tantalizing-sign-habitable-zone-planet-alpha-centauri/

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Hubble Uncovers Concentration of Small Black Holes
https://www.nasa.gov/feature/goddard/2021/hubble-uncovers-concentration-of-small-black-holes

https://www.youtube.com/watch?v=ifwJ9ueDgBs&feature=emb_logo

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NASA's TESS Discovers New Worlds in a River of Young Stars
https://www.nasa.gov/feature/goddard/2021/nasa-s-tess-discovers-new-worlds-in-a-river-of-young-stars

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NASA's Next Mars Rover Is Ready for the Most Precise Landing Yet
https://www.nasa.gov/feature/jpl/nasa-s-next-mars-rover-is-ready-for-the-most-precise-landing-yet

What to expect when the Mars 2020 Perseverance rover arrives at the Red Planet on Feb. 18, 2021.

With about 2.4 million miles (3.9 million kilometers) left to travel in space, NASA's Mars 2020 Perseverance mission is days away from attempting to land the agency's fifth rover on the Red Planet. Engineers at NASA's Jet Propulsion Laboratory in Southern California, where the mission is managed, have confirmed that the spacecraft is healthy and on target to touch down in Jezero Crater at around 3:55 p.m. EST (12:55 p.m. PST) on Feb. 18, 2021.

"Perseverance is NASA's most ambitious Mars rover mission yet, focused scientifically on finding out whether there was ever any life on Mars in the past," said Thomas Zurbuchen, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington. "To answer this question, the landing team will have its hands full getting us to Jezero Crater – the most challenging Martian terrain ever targeted for a landing."

Jezero is a basin where scientists believe an ancient river flowed into a lake and deposited sediments in a fan shape known as a delta. Scientists think the environment here was likely to have preserved signs of any life that gained a foothold billions of years ago – but Jezero also has steep cliffs, sand dunes, and boulder fields. Landing on Mars is difficult – only about 50% of all previous Mars landing attempts have succeeded – and these geological features make it even more so. The Perseverance team is building on lessons from previous touchdowns and employing new technologies that enable the spacecraft to target its landing site more accurately and avoid hazards autonomously.

"The Perseverance team is putting the final touches on the complex choreography required to land in Jezero Crater," said Jennifer Trosper, deputy project manager for the mission at JPL. "No Mars landing is guaranteed, but we have been preparing a decade to put this rover's wheels down on the surface of Mars and get to work."