How Planets Can Affect The Sun? (Planetary Science)

The Institute of Astrophysics of Andalusia (IAA-CSIC) is involved in developing a theory that supports the hypothesis that planets affect the Sun’s magnetic activity. It shows how the small influence of the planets could set a rhythm in a system like the Sun that, if confirmed, would allow events such as solar storms to be predicted more accurately 

In 2012, a study in which the Institute of Astrophysics of Andalusia (IAA-CSIC) participated published the hypothesis that the planets could influence the Sun: the solar magnetic activity during the last ten thousand years was reconstructed by analyzing the concentration of beryllium -10 and carbon-14 in ice from Antarctica and Greenland and compared with the movement of the planets around the Sun. Coincidences were found that suggested a link, a result opposed to the general conviction that the influence of the planets on the Sun is negligible. A theoretical explanation of how this could happen is published today, a new model that, if confirmed, will allow more accurate predictions of solar phenomena.

NEW EXPLANATION FOR A CONTROVERSIAL HYPOTHESIS

An international scientific team comprising researchers from the IAA-CSIC, the EAWAG of the Swiss Federal Institute of Technology (ETH) and the Zurich University of Applied Sciences (ZHAW) proposes an explanation for how the small tidal effect of the planets could influence the Sun’s magnetic activity: stochastic resonance. Under certain conditions, this phenomenon can amplify weak, mostly periodic signals to the point where they produce significant consequences.

The stochastic resonance mechanism was proposed in 1981 to explain the alternation between terrestrial glacial and interglacial periods as a consequence of the variation of the Earth’s orbital parameters (known as the Milankovitch theory), and is related to the concept of bistability.

The Sun has an eleven-year cycle, during which its magnetic activity (manifested in the form of spots, explosions and ejections of matter into interplanetary space) ranges from a minimum to a maximum. But there are other cycles of longer periods. “We have been able to show that the Sun has two stable states of activity: an active state with great amplitude and high solar activity, and a calmer state with a small amplitude and less solar activity –indicates Carlo Albert, an EAWAG-ETH researcher involved in the study–. It would be a bistable system: we suppose that the Sun jumps between these two states due to the turbulence in its interior”. And, since turbulence occurs randomly, these changes would be expected to occur in a completely irregular and unpredictable way.

Data for measuring solar activity suggest, however, that the jump from one state to another does not occur randomly, but often has a rate of about two hundred years. It would be a cycle superimposed on the eleven-year cycle, which the 2012 work attributed to the influence of the planets but without explaining how such small bodies could affect the Sun, whose mass constitutes 99.86% of the entire Solar System.

In the work published today in the Astrophysical Journal Letters, a way to amplify that influence is proposed. “The ingredients of our model are three: bistability, a periodically modulated signal (coming from the weak tidal force exerted by the planets), and noise in the system, caused by the turbulent convection existing in an area of ​​the Sun that goes from the surface to a depth of about 200,000 kilometers –indicates Antonio Ferriz Mas, IAA-CSIC researcher and professor at the University of Vigo who participates in the work–. There is an optimal noise intensity such that the weak signal from the planets’ tidal forces is amplified enough to influence the generation of the Sun’s magnetic field.

Image of the Sun combining data at various wavelengths and showing the complexity of the solar magnetic field. A large active region can be seen in the center of the solar disk. Credit: ESO/P. Horálek/SOHO (NASA&ESA)/SDO (NASA).

TOWARDS A NEW GRAND SOLAR MINIMUM?

In a next step, the team will study to what extent observations of solar activity over the past centuries can be reproduced with this method. This would confirm the theory and also allow one more step: to predict solar activity for the next decades and centuries.

Such a prediction would be of great interest, since it seems that we are facing a turning point in solar activity. According to the 2012 hypothesis, now supported by this work, the Sun is at the end of an active phase and slowly moving towards a calmer one, and the first signs that the eleven-year cycle is weakening have been observed.

These quiet phases are known as great minima, and the data suggests that the Sun has experienced several over the past millennia. The last occurrence of a great minimum, which took place between approximately 1645 and 1715, coincided with the most intense stage of an especially cold period in much of Europe, known as the Little Ice Age (although it is not clearly demonstrated that there is a cause-effect relationship between both phenomena). It will, however, be a few more years before we know for sure whether the Sun will enter a new grand minimum.

Filament of solar material ejected into space during a coronal mass ejection, one of the phenomena associated with solar magnetic activity. Credit: NASA.

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Reference: 

C. Albert, A. Ferriz-Mas et al. “Can Stochastic Resonance explain Recurrence of Grand Minima?”. Astrophysical Journal Letters, July 2021. https://iopscience.iop.org/article/10.3847/2041-8213/ac0fd6

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Provided by IAA CISC

Astronomers Discovered Super Neptune Around M-dwarf Star (Planetary Science)

Using precision radial velocity (RVs) from the near infrared (NIR) Habitable-zone Planet Finder spectrograph (HPF), a team of international astronomers reported the discovery and confirmation of a super Neptune, TOI-532b, orbiting an M-dwarf star TOI-532 in a ∼ 2.3 day circular orbit. Their findings recently appeared in Arxiv.

TOI-532 is an early type metal-rich M dwarf star located in the constellation of Orion. It was observed by TESS in Sector 6 in Camera 1 from 11 December 2018 to 7th January 2019 at two minute cadence.

Figure 1. Short cadence (2 minute) time series TESS PDCSAP photometry (without detrending) from Sector 6, with the binned data (in 1 hour bins), along with the TOI-532b transits overlaid in blue. © Shubham Kanodia et al.

Now, a team of international astronomers led by Shubham Kanodia reported the discovery of a super neptune orbiting TOI-532. They performed a comprehensive characterization of the stellar and planetary properties using space-based photometric observations from TESS, additional ground-based transit observations, adaptive optics imaging, and high-contrast speckle imaging.

Table 1: Derived Parameters for the TOI-532 System © Shubham Kanodia et al.

They showed that, TOI-532 is a metal-rich M dwarf with an effective temperature of 3957 K and [Fe/H] = 0.38; it hosts a transiting gaseous planet with a period of ∼ 2.3 days. Joint fitting of the radial velocities with the TESS and ground-based transits revealed a planet with radius of 5.82 R, and a mass of 61.5 M (more parameters are shown in Table 1 above).

“TOI-532b is the largest and most massive super Neptune detected around an M dwarf with both mass and radius measurements, and it bridges the gap between the Neptune-sized planets and the heavier Jovian planets known to orbit M dwarfs.”

— they said.

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Additionally, it has been shown that the planet is situated at the edge of the Neptune desert in the Radius–Insolation plane, which will help place constraints on the mechanisms responsible for sculpting this region of planetary parameter space.

Figure 2. They showed TOI-532b (circled) in different planet parameter space along with other M dwarf planets with mass measurements at > 3σ © Shubham Kanodia et al.

Finally, they suggested that, TOI-532 is relatively faint (J = 11.46), but is still accessible from 10-m class telescopes, as a potential target for detecting atmospheric escape using the He 10830 Å triplet.

“The discovery and mass measurement of gas giants such as TOI-532b adds to the small sample of such planets around M dwarf host stars, and can help inform theories of planetary formation and evolution. Therefore, we encourage future observations to place limits on atmospheric escape using the He 10830 Å transition.”

— they concluded.

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Featured image: Neptune Illustration © Getty images

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Reference: Shubham Kanodia, Gudmundur Stefansson, Caleb I. Canas, Marissa Maney, Andrea S. Lin, Joe P. Ninan, Sinclaire Jones, Andrew J. Monson, Brock A. Parker, Henry A. Kobulnicky, Jason Rothenberg, Corey Beard, Jack Lubin, Paul Robertson, Arvind F. Gupta, Suvrath Mahadevan, William D. Cochran, Chad F. Bender, Scott A. Diddams, Connor Fredrick, Samuel P. Halverson, Suzanne L. Hawley, Fred R. Hearty, Leslie Hebb, Ravi K. Kopparapu, Andrew J. Metcalf, Lawrence W. Ramsey, Arpita Roy, Christian Schwab, Maria Schutte, Ryan C. Terrien, John P. Wisniewski, Jason T. Wright, “TOI-532b: The Habitable-zone Planet Finder confirms a Large Super Neptune in the Neptune Desert orbiting a metal-rich M dwarf host”, Arxiv, 2021. https://arxiv.org/abs/2107.13670

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HR 8799 Super-Jupiters’ Days Measured For The First Time, Gives A New Spin On Unraveling Planet Formation Mystery (Planetary Science)

Keck Observatory Planet Imager and Characterizer Instrument Delivers First Science, Capturing Spin Measurements of HR 8799 Exoplanets

Astronomers have captured the first-ever spin measurements of HR 8799, the famed system that made history as the very first exoplanetary system to have its image taken.

Discovered in 2008 by two Maunakea Observatories in Hawaiʻi – W. M. Keck Observatory and the international Gemini Observatory, a Program of NSF’s NOIRLab  – the HR 8799 star system is located 129 light-years away and has four planets more massive than Jupiter, or super-Jupiters: HR 8799 planets b, c, d, and e. None of their rotation periods had ever been measured, until now.

The breakthrough was made possible by a Caltech and Keck Observatory-led science and engineering team that has developed an instrument capable of observing known imaged exoplanets at spectral resolutions that are detailed enough to allow astronomers to decipher how fast the planets are spinning.

Using the state-of-the-art Keck Planet Imager and Characterizer (KPIC) on the Keck II telescope atop Hawaiʻi Island’s Maunakea, astronomers found that the minimum rotation speeds of HR 8799 planets d and e clocked in at 10.1 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 up to 24 hours such as on Earth depending on the axial tilts of the HR 8799 planets, which are currently undetermined. For context, one day on Jupiter lasts nearly 10 hours; its rotation speed is about 12.7 km/s.

As for the other two planets, the team was able to constrain the spin of HR 8799 c to an upper limit of less than 14 km/s; planet b’s rotation measurement was inconclusive.

The findings are KPIC’s first science results, which have been accepted for publication in The Astronomical Journal; the study is available in pre-print format on arXiv.org.

Visualization of the spinning HR 8799 planets as viewed in the infrared. Bright patches correspond to holes in the clouds where we can see into the hotter depths of their atmospheres. Each planet is labeled in the upper left. Because the orientations of their spin axes are unknown, this is just one plausible way for how they would look like from Earth. Credit: W. M. Keck Observatory/Adam Makarenko

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“With KPIC, we were able to obtain the highest spectral resolution observations ever conducted of the HR 8799 exoplanets,” says Jason Wang, an astronomer 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.”

DIZZY DATA UNVEILS PLANETS’ PAST

How fast a planet spins gives insight into its formation history. Created out of gas and dust kicked up by a newborn star, baby planets start spinning faster as they accumulate more material and grow – a process called core accretion. It is believed that planetary magnetic fields then slow and cap their rotation speed. After the fully-formed planet is finished accreting and cools off, it spins back up.

“The spins of HR 8799 planets d and e are consistent with the theory that the planets’ magnetic fields put a brake on their spins in their natal years,” says Wang. “The spin measurements also hint at the notion that lower mass planets spin faster because they are less affected by magnetic braking, which might tell us something important about how they form. I find this tantalizing.”

Wang stresses this possible trend is unconfirmed; to validate it requires more KPIC spin measurements of lower mass companions. The team’s goal is to find a common link between the rotation periods of the HR 8799 planets, the giant planets in our own solar system, Jupiter and Saturn, and other known super-Jupiters and brown dwarfs.

“With enough spin measurements, we’ll be able to identify trends that would reveal how the physical processes driving planet formation work,” says co-author Jean-Baptiste Ruffio, a David and Ellen Lee Postdoctoral Scholar Research Associate in Astronomy at Caltech. “This is something that people have already started doing, but KPIC is allowing us to do this for the smallest, faintest, and closest imaged alien worlds.”

KPIC’S FIRST LIGHT SUCCESS

Commissioned between 2018 to 2020, KPIC’s specialty is detecting exoplanets and brown dwarfs that orbit so close to their host stars that the glare from the starlight makes it difficult to ʻsee’ these celestial bodies from Earth. The instrument filters unwanted starlight by way of an innovative fiber injection unit that routes light from the Keck II telescope adaptive optics (AO) system into the Observatory’s Near-Infrared Spectrograph (NIRSPEC).

KPIC’s first light results are outlined in a technical paper that has been accepted in the Journal of Astronomical Telescopes, Instruments, and Systems (JATIS) and is available in pre-print format on arXiv.org.

“KPIC is a game-changer in the field of exoplanet characterization,” says KPIC Principal Investigator Dimitri Mawet, Professor of Astronomy at Caltech. “It allows us to measure a planet’s length of day, orbit, and molecular makeup of its atmosphere.”

KPIC made strong detections of water and carbon monoxide, but no methane, in three of the four HR 8799 planets – c, d, and e – which is consistent with what is known of the planets’ atmospheres.

Discovered in 2008, HR 8799 is the very first multiple-planet system beyond our solar system to have its picture taken. This timelapse animation of HR 8799, which includes 7 direct images captured by W. M. Keck Observatory over a period of 7 years, shows the orbital motion of the four planets in this system. Credit: J. Wang, Caltech/C. Marois, NRC-HIA

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“It’s exciting to see KPIC’s superpower manifest,” says Keck Observatory AO Scientist/Engineer Jacques Delorme, lead author of the JATIS paper. “Because this is the first technology of its kind, we didn’t know if KPIC was going to work as well as it did. Now that we have successfully demonstrated its capabilities, we can move on to Phase 2 of the project to further improve the instrument’s overall performance.”

“We have yet to unlock KPIC’s full science potential,” says Caltech Lead Instrument Scientist Nemanja Jovanovic, co-author of the technical paper. “Through more instrument upgrades, we hope to observe exoplanets in the near future with such a high degree of detail, that we’ll be able to study weather phenomena and map clouds of gas giant planets.”

Phase 2 of the KPIC upgrades are planned for this Winter. If all goes well, Keck Observatory’s science community may begin using the technology in the second half of 2022.

Support for KPIC is generously provided by the Heising-Simons Foundation, Simons Foundation, Caltech, and NASA Jet Propulsion Laboratory. This project is conducted in collaboration with W. M. Keck Observatory, UC Santa Cruz, UCLA, and the University of Hawaiʻi Institute for Astronomy.

Featured image: ARTIST’S RENDITION OF HR 8799 PLANETS B, C, D, AND E AS VIEWED IN THE INFRARED.Credit: W. M. Keck Observatory/Adam Makarenko

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Provided by W.M. Keck Observatory

Astronomers Show How Planets Form in Binary Systems Without Getting Crushed (Planetary Science)

Astronomers have developed the most realistic model to date of planet formation in binary star systems.

“Planet formation in binary systems is more complicated, because the companion star acts like a giant eggbeater, dynamically exciting the protoplanetary disc”

— Roman Rafikov

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The researchers, from the University of Cambridge and the Max Planck Institute for Extra-terrestrial Physics, have shown how exoplanets in binary star systems – such as the ‘Tatooine’ planets spotted by NASA’s Kepler Space Telescope – came into being without being destroyed in their chaotic birth environment.

They studied a type of binary system where the smaller companion star orbits the larger parent star approximately once every 100 years – our nearest neighbour, Alpha Centauri, is an example of such a system.

“A system like this would be the equivalent of a second Sun where Uranus is, which would have made our own solar system look very different,” said co-author Dr Roman Rafikov from Cambridge’s Department of Applied Mathematics and Theoretical Physics.

Rafikov and his co-author Dr Kedron Silsbee from the Max Planck Institute for Extra-terrestrial Physics found that for planets to form in these systems, the planetesimals – planetary building blocks which orbit around a young star – need to start off at least 10 kilometres in diameter, and the disc of dust and ice and gas surrounding the star within which the planets form needs to be relatively circular.

The research, which is published in Astronomy and Astrophysics, brings the study of planet formation in binaries to a new level of realism and explains how such planets, a number of which have been detected, could have formed.

Planet formation is believed to begin in a protoplanetary disc – made primarily of hydrogen, helium, and tiny particles of ices and dust – orbiting a young star. According to the current leading theory on how planets form, known as core accretion, the dust particles stick to each other, eventually forming larger and larger solid bodies. If the process stops early, the result can be a rocky Earth-like planet. If the planet grows bigger than Earth, then its gravity is sufficient to trap a large quantity of gas from the disc, leading to the formation of a gas giant like Jupiter.

“This theory makes sense for planetary systems formed around a single star, but planet formation in binary systems is more complicated, because the companion star acts like a giant eggbeater, dynamically exciting the protoplanetary disc,” said Rafikov.

“In a system with a single star the particles in the disc are moving at low velocities, so they easily stick together when they collide, allowing them to grow,” said Silsbee. “But because of the gravitational ‘eggbeater’ effect of the companion star in a binary system, the solid particles there collide with each other at much higher velocity. So, when they collide, they destroy each other.”

Many exoplanets have been spotted in binary systems, so the question is how they got there. Some astronomers have even suggested that perhaps these planets were floating in interstellar space and got sucked in by the gravity of a binary, for instance.

Rafikov and Silsbee carried out a series of simulations to help solve this mystery. They developed a detailed mathematical model of planetary growth in a binary that uses realistic physical inputs and accounts for processes that are often overlooked, such as the gravitational effect of the gas disc on the motion of planetesimals within it.

“The disc is known to directly affect planetesimals through gas drag, acting like a kind of wind,” said Silsbee. “A few years ago, we realised that in addition to the gas drag, the gravity of the disc itself dramatically alters dynamics of the planetesimals, in some cases allowing planets to form even despite the gravitational perturbations due to the stellar companion.”

“The model we’ve built pulls together this work, as well as other previous work, to test the planet formation theories,” said Rafikov.

Their model found that planets can form in binary systems such as Alpha Centauri, provided that the planetesimals start out at least 10 kilometres across in size, and that the protoplanetary disc itself is close to circular, without major irregularities. When these conditions are met, the planetesimals in certain parts of the disc end up moving slowly enough relative to each other that they stick together instead of destroying each other.

These findings lend support to a particular mechanism of planetesimal formation, called the streaming instability, being an integral part of the planet formation process. This instability is a collective effect, involving many solid particles in the presence of gas, that is capable of concentrating pebble-to-boulder sized dust grains to produce a few large planetesimals, which would survive most collisions.

The results of this work provide important insights for theories of planet formation around both binary and single stars, as well as for the hydrodynamic simulations of protoplanetary discs in binaries. In future, the model could also be used to explain the origin of the ‘Tatooine’ planets – exoplanets orbiting both components of a binary – about a dozen of which have been identified by NASA’s Kepler Space Telescope.

Featured image: Artist’s impression of the planet around proxima centuari B © University of Cambridge

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Reference:
Kedron Silsbee and Roman R. Rafikov. ‘Planet Formation in Stellar Binaries: Global Simulations of Planetesimal Growth.’ Astronomy and Astrophysics (2021). DOI:10.1051/0004-6361/20214113

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Provided by University of Cambridge

Why More Massive Stars Tend To Host Larger Planets? (Planetary Science)

Focusing on MKG stars, Pascucci and colleagues suggested that most common planet around a lower mass stars is small in mass. They also suggested that the radius of planet depends on the stellar mass. Meaning, it increases with the stellar mass. Now, Lozovsky and colleagues explored why more massive stars tend to host larger planets. Using exoplanetary data of planets with measured masses and radius, they explored 3 possible explanations for the identified correlation between the planetary radius and stellar mass.

• Case-1: Planets are larger due to thermal inflation: since more massive stars are more luminous, larger stellar irradiation could inflate the planetary radius.
• Case-2: Planets around more massive stars are more massive and are in consequence larger for any given composition.
• Case-3: Planets around more massive stars tend to be more volatile-rich and are therefore larger in size.

They first confirmed that planets surrounding larger stars tend to be larger in mass and radius.

Later, they showed that, larger radii of planets surrounding more massive stars (like G and K) cannot be explained by inflation due to higher irradiation of the star, nor by a higher planetary mass (i.e. Case 1 and 2): the effect of both properties on the radius was found to be significantly smaller than the observed difference. In other words, they showed that the difference in planetary mass, which is given by RV/TTV data, is insufficient to explain the observed difference in planetary radii, and the planetary temperature is even found to anticorrelate with the radius.

Histogram of simulated fH-He for their planetary samples. Planets that cannot be modeled with any H-He mass fraction are not presented © authors

Finally, it has been shown that the larger planetary radii can be explained by a larger fraction of volatile material (H-He atmospheres) among planets surrounding more massive stars (i.e. by Case-3). This is because planets forming around more massive stars tend to accrete H-He atmospheres more efficiently. This can be a result of more massive protoplanetary disks that lead to faster core growth; allowing the cores to accrete substantial gaseous envelopes before the gas disk dissipates.

“Thus, we argue that planets around G- and K-stars are different by formation.”, they wrote. “It is desirable to have further constraints available to test our findings. Further information on the planetary composition would come from JWST and Ariel missions with constraints on atmospheric composition, which will greatly shed more light into the diversity of planetary volatile envelopes, their formation efficiencies and evolutions.” they concluded.

Featured image credit: Getty Images

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Reference: Michael Lozovsky, Ravit Helled, Illaria Pascucci, Caroline Dorn, Julia Venturini, Robert Feldmann, “Why do more massive stars host larger planets?”, Arxiv, 2021.
arXiv:2107.09534

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Kepler Telescope Glimpses Population Of Free-floating Planets (Planetary Science)

Tantalising evidence has been uncovered for a mysterious population of “free-floating” planets, planets that may be alone in deep space, unbound to any host star. The results include four new discoveries that are consistent with planets of similar masses to Earth, published today in Monthly Notices of the Royal Astronomical Society.

The study, led by Iain McDonald of the University of Manchester, UK, (now based at the Open University, UK) used data obtained in 2016 during the K2 mission phase of NASA’s Kepler Space Telescope. During this two-month campaign, Kepler monitored a crowded field of millions of stars near the centre of our Galaxy every 30 minutes in order to find rare gravitational microlensing events.

The study team found 27 short-duration candidate microlensing signals that varied over timescales of between an hour and 10 days. Many of these had been previously seen in data obtained simultaneously from the ground. However, the four shortest events are new discoveries that are consistent with planets of similar masses to Earth.

These new events do not show an accompanying longer signal that might be expected from a host star, suggesting that these new events may be free-floating planets. Such planets may perhaps have originally formed around a host star before being ejected by the gravitational tug of other, heavier planets in the system.

Predicted by Albert Einstein 85 years ago as a consequence of his General Theory of Relativity, microlensing describes how the light from a background star can be temporarily magnified by the presence of other stars in the foreground. This produces a short burst in brightness that can last from hours to a few days. Roughly one out of every million stars in our Galaxy is visibly affected by microlensing at any given time, but only a few percent of these are expected to be caused by planets.

Kepler was not designed to find planets using microlensing, nor to study the extremely dense star fields of the inner Galaxy. This meant that new data reduction techniques had to be developed to look for signals within the Kepler dataset.

Iain notes: “These signals are extremely difficult to find. Our observations pointed an elderly, ailing telescope with blurred vision at one the most densely crowded parts of the sky, where there are already thousands of bright stars that vary in brightness, and thousands of asteroids that skim across our field. From that cacophony, we try to extract tiny, characteristic brightenings caused by planets, and we only have one chance to see a signal before it’s gone. It’s about as easy as looking for the single blink of a firefly in the middle of a motorway, using only a handheld phone.”

Co-author Eamonn Kerins of the University of Manchester also comments, “Kepler has achieved what it was never designed to do, in providing further tentative evidence for the existence of a population of Earth-mass, free-floating planets. Now it passes the baton on to other missions that will be designed to find such signals, signals so elusive that Einstein himself thought that they were unlikely ever to be observed. I am very excited that the upcoming ESA Euclid mission could also join this effort as an additional science activity to its main mission.”

Confirming the existence and nature of free-floating planets will be a major focus for upcoming missions such as the NASA Nancy Grace Roman Space Telescope, and possibly the ESA Euclid mission, both of which will be optimised to look for microlensing signals.

Featured image: Artist’s impression of a free-floating planet. Credit: A. Stelter / Wikimedia Commons

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Reference: Kepler K2 Campaign 9: I. Candidate short-duration events from the first space-based survey for planetary microlensing, Monthly Notices of the Royal Astronomical Society (2021), DOI: 10.1093/mnras/stab1377

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Provided by Royal Astronomical Society

From Atoms To Planets, The Longest-running Space Station Experiment (Astronomy)

As Europe celebrates 20 years of ESA astronauts on the International Space Station, a Russian-European experiment has been running quietly in the weightless research centre for just as long: the Plasma Kristall (PK) suite of investigations into fundamental science.

Roscosmos cosmonaut Oleg Novitsky working on the Plasma Kristall-4 experiment in Europe’s Columbus laboratory on the International Space Station, 18 June 2021. Credit: ESA/NASA–T. Pesquet

Plasma Kristall takes a plasma and injects fine dust particles in weightlessness, turning the dust into highly charged particles that interact with each other, bouncing off each other as their charge causes the particles to attract or repel. Under the right conditions, the dust particles can arrange themselves over time to form organised structures, or plasma crystals.

Visualising the laws of physics © ESA

These interactions and forming of three-dimensional structures resemble the workings of our world on the atomic scale, a world so small that we cannot see move even with an electron microscope. Add a laser to the mix and the dust particles can be seen and recorded for observation by scientists on Earth for a sneak peak of the world beyond our eyes.

These surrogate atoms are a way for researchers to simulate how materials form on an atomic scale, and to test and visualise theories. The experiment cannot be run on Earth because gravity only makes sagging, flattened recreations possible; if you want to see how a crystal is constituted you need to remove the force pulling downwards – gravity.

Sergei with original PK-3 experiment on the Space Station in 2001 © ESA

On 3 March 2001, “PK-3 Plus” was turned on in the Zvezda module, the first physical experiment to run on the Space Station. Led by the German aerospace centre DLR and Russian space agency Roscosmos the experiment was a success and later followed up by a fourth version, installed in 2014 in ESA’s Columbus laboratory, this time as an ESA-Roscosmos collaboration.

Roscosmos cosmonaut Elena Serove installing the Plasma Kristall-4 experiment in Europe’s Columbus laboratory on the International Space Station in 2014. Credit: ESA/NASA

Plasma Kristall-4. Credit: Michael Kretschmer

Planet conceptions

By changing the parameters in PK-4, such as adjusting voltage or using larger dust particles, the atom doppelgangers can simulate different interactions. Complex phenomena such as phase transitions, for example from gas to liquid, microscopic motions, the onset of turbulence and shear forces are well known in physics, but not fully understood at the atomic level.

Using PK-4, researchers across the world can follow how an object melts, how waves spread in fluids and how currents change at the atomic level.  

Around 100 papers have been published based on the Plasma Kristall experiments and the knowledge gained is helping understand how planets form too. At its origin our planet Earth was probably two dust particles that met in space and grew and grew into our world. PK-4 can model these origin moments as they are during the conception of planets.

CADMOS during PK-4 operations © ESA

The huge amount of data that PK-4 creates is so vast it cannot be downloaded through the Space Station’s communication network, so hard disks are physically shipped to space and back with terabytes of information. The experiment is run from Toulouse, France, at the CNES space agency operating centre Cadmos.

Astrid Orr, ESA’s physical sciences coordinator notes “PK-4 is a great example of fundamental science done on the Space Station; through international collaboration and long-term investment we are learning more about the world around us, on the minute scale as well as on the cosmic scale.

“The knowledge from the PK experiments can be directly applied to research on fusion physics – where dust needs to be removed – and the processing of electronic chips, for example in plasma processes in the semiconductor and solar cell industry. In addition, the miniaturisation of the technology required when developing Plasma Kristal is already being applied in plasma-based medical equipment for hospitals.

“The PK experiments address a large range of physical phenomena, so ground-breaking discoveries can happen at any moment.”

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This science news has been confirmed by us from ESA

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Provided by ESA

NASA’s Search for Life: Astrobiology in the Solar System and Beyond (Planetary Science)

Are we alone in the universe? So far, the only life we know of is right here on Earth. But here at NASA, we’re looking.    

NASA is exploring the solar system and beyond to help us answer fundamental questions about life beyond our home planet. From studying the habitability of Mars, probing promising “oceans worlds,” such as Titan and Europa, to identifying Earth-size planets around distant stars, our science missions are working together with a goal to find unmistakable signs of life beyond Earth (a field of science called astrobiology).  

Through the study of astrobiology, NASA invests in understanding the origins, evolution, and limits of life on Earth. This work has been important in shaping ideas about where to focus search for life efforts. As NASA explores the solar system, our understanding of life on Earth and the potential for life on other worlds has changed alongside the many discoveries. The study of organisms in extreme environments on Earth, from the polar plateau of Antarctica to the depths of the ocean, have highlighted that life as we know it is highly adaptable, but not always easy to find. The search for life requires great care, and is based in the knowledge we gain by studying life on Earth through the lens of astrobiology. If there’s something out there, we may not yet know how to recognize it. 

Dive into the past, present, and future of NASA’s search for life in the universe.  

Past Missions   

Viking 1 and 2  

Over 45 years ago, the Viking Project found a place in history when it became the first U.S. mission to land a spacecraft safely on the surface of Mars.   

Viking 1 and 2, each consisting of an orbiter and a lander, were NASA’s first attempt to search for life on another planet and thus the first mission dedicated to astrobiology. The mission’s biology experiments revealed unexpected chemical activity in the Martian soil, but provided no clear evidence for the presence of living microorganisms near the landing sites.   

Galileo  

NASA’s Galileo mission orbited Jupiter for almost eight years, and made close passes by all its major moons. Galileo returned data that continues to shape astrobiology science –– particularly the discovery that Jupiter’s icy moon Europa has evidence of a subsurface ocean with more water than the total amount of liquid water found on Earth. These findings also expanded the search for habitable environments outside of the traditional “habitable zone” of a system, the distance from a star at which liquid water can persist on the surface of a planet. 

Cassini  

For more than a decade, the Cassini spacecraft shared the wonders of Saturn and its family of icy moons –– taking us to astonishing worlds and expanding our understanding of the kinds of worlds where life might exist. 

For the first time, astrobiologists were able to see through the thick atmosphere of Titan and study the moon’s surface, where they found lakes and seas filled with liquid hydrocarbons. Astrobiologists are studying what these liquid hydrocarbons could mean for life’s potential on Titan. Cassini also witnessed icy plumes erupting from Saturn’s small moon Enceladus. When flying through the plumes, the spacecraft found evidence of saltwater and organic chemicals. This raised questions about whether habitable environments could exist beneath the surface of Enceladus.   

Spirit and Opportunity Mars Exploration Rovers  

NASA’s twin Mars Exploration Rovers, Spirit and Opportunity, launched towards Mars in 2003 in search of answers about the history of water on Mars. Originally a three-month prime mission, both robotic explorers far outlasted their original missions and spent years collecting data at the surface of Mars.     

Spirit and Opportunity were the first mission to prove liquid water, a key ingredient for life, had once flowed across the surface of Mars. Their findings shaped our understanding of Mars’ geology and past environments, and importantly suggested Mars’ ancient environments may once have been suitable for life.  

Kepler and K2  

NASA’s first planet-hunting mission, the Kepler Space Telescope, paved the way for our search for life in the solar system and beyond. An important part of Kepler’s work was the identification of Earth-size planets around distant stars.  

After nine years in deep space, collecting data that indicate our sky to be filled with billions of hidden planets – more planets even than stars – the space telescope retired in 2018. Kepler left a legacy of more than 2,600 exoplanet discoveries, many of which could be promising places for life.  

Spitzer  

Over its sixteen years in space, the Spitzer Space Telescope evolved into a premier tool for studying exoplanets, using its infrared view of the universe. Spitzer marked a new age in planetary science as one of the first telescopes to directly detect light from the atmospheres of planets outside the solar system, or exoplanets. This enabled scientists to study the composition of those atmospheres and even learn about the weather on these distant worlds.  

Spitzer’s infrared instruments allowed scientists to peer into cosmic regions that are hidden from optical telescopes, including dusty stellar nurseries, the centers of galaxies, and newly forming planetary systems. Spitzer’s infrared eyes also enabled astronomers to see cooler objects in space, like failed stars (brown dwarfs), extrasolar planets, giant molecular clouds, and organic molecules that may hold the secret to life on other planets.  

Current Missions  

Hubble  

Since it launched in 1990, the Hubble Space Telescope has made immense contributions to astrobiology. Astronomers used Hubble to make the first measurements of the atmospheric composition of extrasolar planets, and Hubble is now vigorously characterizing exoplanet atmospheres with constituents such as sodium, hydrogen, and water vapor. Hubble observations are also providing clues about how planets form, through studies of dust and debris disks around young stars.  

Not all of Hubble’s contributions involve distant targets. Hubble has also been used to study bodies within the solar system, including asteroids, comets, planets, and moons, such as the intriguing ocean-bearing icy moons Europa and Ganymede. Hubble has provided invaluable insight into life’s potential in the solar system and beyond.  

MAVEN  

NASA’s atmosphere-sniffing Mars Atmosphere and Volatile Evolution (MAVEN) mission launched in November 2013 and began orbiting Mars roughly a year later. Since that time, the mission has made fundamental contributions to understanding the history of the Martian atmosphere and climate.     

Astrobiologists are working with this atmospheric data to better understand how and when Mars lost its water and identifying periods in Mars’ history when habitable environments were most likely to exist at the planet’s surface.  

Mars Odyssey  

For two decades, NASA’s Mars Odyssey – the longest-lived spacecraft at the Red Planet – has helped locate ice, assess landing sites, and study the planet’s mysterious moons.    

Odyssey has provided global maps of chemical elements and minerals that make up the surface of Mars. These detailed maps are used by astrobiologists to determine the evolution of the Martian environment and its potential for life.  

Mars Reconnaissance Orbiter  

NASA’s Mars Reconnaissance Orbiter (MRO) is on a search for evidence that water persisted on the surface of Mars for a long period of time. While other Mars missions have shown that water flowed across the surface in Mars’ history, it remains a mystery whether water was ever around long enough to provide a habitat for life.  

Data from MRO is essential to astrobiologists studying the potential for habitable environments on past and present Mars. Additionally, these studies are important in building climate models for Mars, and for use in comparative planetology studies for the potential habitability of exoplanets that orbit distant stars.     

Curiosity Mars Rover  

The Curiosity Mars rover is studying whether Mars ever had environments capable of supporting microbial life. In other words, its mission is to determine whether the planet had all of the ingredients life needs – such as water, carbon, and a source of energy – by studying its climate and geology.   

It’s been nearly nine years since Curiosity touched down on Mars in 2012, and the robot geologist keeps making new discoveries. Curiosity provided evidence that freshwater lakes filled Gale Grater billions of years ago. Lakes and groundwater persisted for millions of years and contained all the key elements necessary for life, demonstrating Mars was once habitable. 

TESS Mission  

The Transiting Exoplanet Survey Satellite (TESS) is the next step in the search for planets outside of our solar system, including those that could support life. Launched in 2018, TESS is on a mission to survey the entire sky and is expected to discover and catalogue thousands of exoplanets around nearby bright stars.  

To date, TESS has discovered more than 120 confirmed exoplanets and more than 2,600 planet candidates. The planet-hunter will continue to find exoplanets targets that NASA’s upcoming James Webb Space Telescope will study in further detail.  

Perseverance Mars Rover  

NASA’s newest robot astrobiologist, the Perseverance Mars rover, touched down safely on Mars on February 18, 2021, and is kicking off a new era of exploration on the Red Planet. Perseverance will search for signs of ancient microbial life, which will advance the agency’s quest to explore the past habitability of Mars.    

What really sets this mission apart is that the rover has a drill to collect core samples of Martian rock and soil, and will store them in sealed tubes for pickup by a future Mars Sample Return mission that would ferry them back to Earth for detailed analysis.   

Upcoming Missions  

James Webb Space Telescope  

The James Webb Space Telescope (Webb), slated to launch in 2021, will be the premier space-based observatory of the next decade. Webb is a large infrared telescope with a 6.5-meter primary mirror.   

Webb observations will be used to study every phase in the history of the universe, including planets and moons in our solar system, and the formation of distant solar systems potentially capable of supporting life on Earth-like exoplanets. The Webb telescope will also be capable of making detailed observations of the atmospheres of planets orbiting other stars, to search for the building blocks of life on Earth-like planets beyond our solar system.  

Europa Clipper Mission  

Jupiter’s moon Europa may have the potential to harbor life. The Europa Clipper mission will conduct detailed reconnaissance of Europa and investigate whether the icy moon could harbor conditions suitable for life. Targeting a 2024 launch, the mission will place a spacecraft in orbit around Jupiter in order to perform a detailed investigation of Europa –– a world that shows strong evidence for an ocean of liquid water beneath its icy crust.    

Europa Clipper is not a life-detection mission, though it will investigate whether the icy moon, with its subsurface ocean, has the capability to support life. Understanding Europa’s habitability will help scientists better understand how life developed on Earth and the potential for finding life beyond our planet.  

Dragonfly Mission to Titan  

The Dragonfly mission will deliver a rotorcraft to visit Saturn’s largest and richly organic moon, Titan. Slated for launch in 2027 and arrival in 2034, Dragonfly will sample and examine dozens of promising sites around Saturn’s icy moon and advance our search for the building blocks of life.     

This revolutionary mission will explore diverse locations to look for prebiotic chemical processes common on both Titan and Earth. Titan is an analog to the very early Earth, and can provide clues to how prebiotic chemistry under these conditions may have progressed.  

Nancy Grace Roman Telescope  

Slated to launch in the mid-2020s, the Roman Space Telescope will have a field of view that is 200 times greater than the Hubble infrared instrument, capturing more of the sky with less observing time. In addition to ground-breaking astrophysics and cosmology, the primary instrument on Roman, the Wide Field Instrument, has a rich menu of exoplanet science. It will perform a microlensing survey of the inner Milky Way that will reveal thousands of worlds orbiting within the habitable zone of their star and farther out, while providing an additional bounty of more than 100,000 transiting exoplanets. 

The mission will also be fitted with “starglasses,” a coronagraph instrument that can block out the glare from a star and allow astronomers to directly image giant planets in orbit around it. The coronagraph will provide the first in-space demonstration of technologies needed for future missions to image and characterize smaller, rocky planets in the habitable zones of nearby stars. Roman coronagraph will make observations that could contribute to the discovery of new worlds beyond our solar system and advance the study of extrasolar planets that could be suitable for life.    

Learn more about the NASA Astrobiology Program: 

https://astrobiology.nasa.gov/  

Featured image credit: NASA

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Provided by NASA

Study Of Young Chaotic Star System Reveals Planet Formation Secrets (Planetary Science)

New observations of young stellar object Elias 2-27 confirm gravitational instabilities and planet-forming disk mass as key to formation of giant planets

A team of scientists using the Atacama Large Millimeter/submillimeter Array (ALMA) to study the young star Elias 2-27 have confirmed that gravitational instabilities play a key role in planet formation, and have for the first time directly measured the mass of protoplanetary disks using gas velocity data, potentially unlocking one of the mysteries of planet formation. The results of the research are published today in two papers in The Astrophysical Journal.

Protoplanetary disks–planet-forming disks made of gas and dust that surround newly formed young stars–are known to scientists as the birthplace of planets. The exact process of planet formation, however, has remained a mystery. The new research, led by Teresa Paneque-Carreño–a recent graduate of the Universidad de Chile and PhD student at the University of Leiden and the European Southern Observatory, and the primary author on the first of the two papers–focuses on unlocking the mystery of planet formation.

During observations, scientists confirmed that the Elias 2-27 star system–a young star located less than 400 light-years away from Earth in the constellation Ophiuchus–was exhibiting evidence of gravitational instabilities which occur when planet-forming disks carry a large fraction of the system’s stellar mass. “How exactly planets form is one of the main questions in our field. However, there are some key mechanisms that we believe can accelerate the process of planet formation,” said Paneque-Carreño. “We found direct evidence for gravitational instabilities in Elias 2-27, which is very exciting because this is the first time that we can show kinematic and multi-wavelength proof of a system being gravitationally unstable. Elias 2-27 is the first system that checks all of the boxes.”

Elias 2-27 is a young star located just 378 light-years from Earth. The star is host to a massive protoplanetary disk of gas and dust, one of the key elements to planet formation. In this graphic illustration, dust is distributed along a spiral-shaped morphology first discovered in Elias 2-27 in 2016. The larger dust grains are found along the spiral arms while the smaller dust grains are distributed all around the protoplanetary disk. Asymmetric inflows of gas were also detected during the study, indicating that there may still be material infalling into the disk. Scientists believe that Elias 2-27 may eventually evolve into a planetary system, with gravitational instabilities causing the formation of giant planets. Because this process takes millions of years to occur, scientists can only observe the beginning stages. © B. Saxton NRAO/AUI/NSF

Elias 2-27’s unique characteristics have made it popular with ALMA scientists for more than half a decade. In 2016, a team of scientists using ALMA discovered a pinwheel of dust swirling around the young star. The spirals were believed to be the result of density waves, commonly known to produce the recognizable arms of spiral galaxies–like the Milky Way Galaxy–but at the time, had never before been seen around individual stars.

“We discovered in 2016 that the Elias 2-27 disk had a different structure from other already studied systems, something not observed in a protoplanetary disk before: two large-scale spiral arms. Gravitational instabilities were a strong possibility, but the origin of these structures remained a mystery and we needed further observations,” said Laura Pérez, Assistant Professor at the Universidad de Chile and the principal investigator on the 2016 study. Together with collaborators, she proposed further observations in multiple ALMA bands that were analyzed with Paneque-Carreño as a part of her M.Sc. thesis at Universidad de Chile.

In addition to confirming gravitational instabilities, scientists found perturbations–or disturbances–in the star system above and beyond theoretical expectations. “There may still be new material from the surrounding molecular cloud falling onto the disk, which makes everything more chaotic,” said Paneque-Carreño, adding that this chaos has contributed to interesting phenomena that have never been observed before, and for which scientists have no clear explanation. “The Elias 2-27 star system is highly asymmetric in the gas structure. This was completely unexpected, and it is the first time we’ve observed such vertical asymmetry in a protoplanetary disk.”

Cassandra Hall, Assistant Professor of Computational Astrophysics at the University of Georgia, and a co-author on the research, added that the confirmation of both vertical asymmetry and velocity perturbations–the first large-scale perturbations linked to spiral structure in a protoplanetary disk–could have significant implications for planet formation theory. “This could be a ‘smoking gun’ of gravitational instability, which may accelerate some of the earliest stages of planet formation. We first predicted this signature in 2020, and from a computational astrophysics point of view, it’s exciting to be right.”

Using gas velocity data, scientists observing Elias 2-27 were able to directly measure the mass of the young star’s protoplanetary disk and also trace dynamical perturbations in the star system. Visible in this animation are the dust continuum 0.87mm emission data (blue), along with emissions from gases C18O (yellow) and 13CO (red). © ALMA (ESO/NAOJ/NRAO)/T. Paneque-Carreño (Universidad de Chile), B. Saxton (NRAO)

Paneque-Carreño added that while the new research has confirmed some theories, it has also raised new questions. “While gravitational instabilities can now be confirmed to explain the spiral structures in the dust continuum surrounding the star, there is also an inner gap, or missing material in the disk, for which we do not have a clear explanation.”

One of the barriers to understanding planet formation was the lack of direct measurement of the mass of planet-forming disks, a problem addressed in the new research. The high sensitivity of ALMA Band 6, paired with Bands 3 and 7, allowed the team to more closely study the dynamical processes, density, and even the mass of the disk. “Previous measurements of protoplanetary disk mass were indirect and based only on dust or rare isotopologues. With this new study, we are now sensitive to the entire mass of the disk,” said Benedetta Veronesi–a graduate student at the University of Milan and postdoctoral researcher at École normale supérieure de Lyon, and the lead author on the second paper. “This finding lays the foundation for the development of a method to measure disk mass that will allow us to break down one of the biggest and most pressing barriers in the field of planet formation. Knowing the amount of mass present in planet-forming disks allows us to determine the amount of material available for the formation of planetary systems, and to better understand the process by which they form.”

Although the team has answered a number of key questions about the role of gravitational instability and disk mass in planet formation, the work is not yet done. “Studying how planets form is difficult because it takes millions of years to form planets. This is a very short time-scale for stars, which live thousands of millions of years, but a very long process for us,” said Paneque-Carreño. “What we can do is observe young stars, with disks of gas and dust around them, and try to explain why these disks of material look the way they do. It’s like looking at a crime scene and trying to guess what happened. Our observational analysis paired with future in-depth analysis of Elias 2-27 will allow us to characterize exactly how gravitational instabilities act in planet-forming disks, and gain more insight into how planets are formed.”

Featured image: Using gas velocity data, scientists observing Elias 2-27 were able to directly measure the mass of the young star’s protoplanetary disk and also trace dynamical perturbations in the star system. Visible in this paneled composite are the dust continuum 0.87mm emission data (blue), along with emissions from gases C18O (yellow) and 13CO (red). © ALMA (ESO/NAOJ/NRAO)/T. Paneque-Carreño (Universidad de Chile), B. Saxton (NRAO)

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Resources

(1) Spiral Arms and a Massive Dust Disk with non-Keplerian Kinematics: Possible Evidence for Gravitational Instability in the Disk of Elias 2-27, Paneque-Carreño et al. ApJ, preview [https://arxiv.org/pdf/2103.14048.pdf] (2) A Dynamical Measurement of the Disk Mass in Elias 2-27, Veronesi et al. ApJ, preview [https://arxiv.org/pdf/2104.09530.pdf]

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Provided by NRAO