Astronomy and Planetary Science Thread

Rhinocrates

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Although these radiolytic reactions yield energy far more slowly than the sun and underground thermal processes, the researchers have shown that they are fast enough to be key drivers of microbial activity in a broad range of settings—and that they are responsible for a diverse pool of organic molecules and other chemicals important to life. According to Jack Mustard, a planetary geologist at Brown University who was not involved in the new work, the radiolysis explanation has “opened up whole new vistas” into what life could look like, how it might have emerged on an early Earth, and where else in the universe it might one day be found.

 

Flyaway

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Flyaway

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Identification of an [α/Fe]—Enhanced Thick Disk Component in an Edge-on Milky Way Analog

Abstract
The Milky Way disk consists of two prominent components—a thick, alpha-rich, low-metallicity component and a thin, metal-rich, low-alpha component. External galaxies have been shown to contain thin- and thick-disk components, but whether distinct components in the [α/Fe]–[Z/H] plane exist in other Milky Way-like galaxies is not yet known. We present Very Large Telescope (VLT)—Multi Unit Spectroscopic Explorer (MUSE) observations of UGC 10738, a nearby, edge-on Milky Way-like galaxy. We demonstrate through stellar population synthesis model fitting that UGC 10738 contains alpha-rich and alpha-poor stellar populations with similar spatial distributions to the same components in the Milky Way. We discuss how the finding that external galaxies also contain chemically distinct disk components may act as a significant constraint on the formation of the Milky Way's own thin and thick disk.

 
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Flyaway

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Oort cloud Ecology II: The chronology of the formation of the Oort cloud

We present a chronology on the formation and early evolution of the Oort cloud, and test the sequence of events of its formation by simulating the formation process in subsequent amalgamated steps. These simulations start with the Solar system being born with planets and asteroids in a stellar cluster orbiting the Galactic center. Upon ejection from its birth environment, we continue to follow the Solar system's evolution while it sojourns the Galaxy as an isolated planetary system. We conclude that the range in semi-major axis between ∼100\,au and several ∼103\,au still bears the signatures of the Sun being born in a $\apgt 1000$\,\Msun/pc3 star cluster, and that most of the outer Oort cloud formed after the Solar system escaped. The escape, we argue, happened between ∼20\,Myr and 50\,Myr after birth of the Solar system. Today, the bulk of the material in the Oort cloud (∼70\%) originates from the region in the circumstellar disk that was located between ∼15\,au and ∼35\,au, near the current location of the ice-giants and the Centaur family of asteroids. This population is eradicated if the ice-giant planets were born in orbital resonance. Planet migration or chaotic orbital reorganization, occurring while the Solar system is still a cluster member is, according to our model, inconsistent with the presence of the Oort cloud. About half the inner Oort cloud, between 100 and 104\,au, and a quarter of the material in the outer Oort cloud $\apgt 10^4$\,au could be non-native to the Solar system but was captured from free-floating derbis in the cluster or from the circumstellar disk of other stars in the birth cluster. Characterizing this population will help us to reconstruct the Solar system's history.

 

Flyaway

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How Sublimation Delays the Onset of Dusty Debris Disk Formation Around White Dwarf Stars

Although numerous white dwarf stars host dusty debris disks, the temperature distribution of these stars differs significantly from the white dwarf population as a whole. Dusty debris disks exist exclusively around white dwarfs cooler than 27,000 K. This is all the more enigmatic given that the formation processes of dusty debris disks should favor younger, hotter white dwarfs, which likely host more dynamically unstable planetary systems. Here we apply a sophisticated material sublimation model to white dwarf systems to show that these statistics are actually a natural result of the interplay of thermal and tidal forces, and show how they define the circumstellar regions where dusty debris disks can form. We demonstrate that these processes tend to prevent stability against both sublimative destruction and reaccretion into planetesimals for rocky materials until white dwarfs cool to below ~25,000-32,000 K, in agreement with the observed limit of ~27,000 K. For pure water ice, this critical temperature is less than 2,700 K (requiring a cooling age older the universe); this precludes pure water ice-rich debris disks forming through the accepted two-step mechanism. The critical temperature is size-dependent; more massive white dwarfs could potentially host dusty debris disks at warmer temperatures. Our model suggests that the location of the disks within the PG 0010+280, GD 56, GD 362, and PG 1541+651 systems are consistent with a forsterite-dominated olivine composition. We also find that very cool white dwarfs may simultaneously host multiple, independently formed dusty debris disks, consistent with observations of the LSPM J0207+3331 system.

 

Flyaway

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CHIME has detected 535 new FRBs including 18 repeaters between 2018 and 2019. The repeaters also look different to the one off events. They occur evenly across the sky and at estimated rate of 9000 per day.

 
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Flyaway

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Astronomers have spotted a giant 'blinking' star towards the centre of the Milky Way, more than 25,000 light years away.

An international team of astronomers observed the star, VVV-WIT-08, decreasing in brightness by a factor of 30, so that it nearly disappeared from the sky. While many stars change in brightness because they pulsate or are eclipsed by another star in a binary system, it's exceptionally rare for a star to become fainter over a period of several months and then brighten again.

 

Flyaway

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Related paper:

VVV-WIT-08: the giant star that blinked

We report the serendipitous discovery of a late-type giant star that exhibited a smooth, eclipse-like drop in flux to a depth of 97 per cent. Minimum flux occurred in April 2012 and the total event duration was a few hundred days. Light curves in V, I and Ks from the Optical Gravitational Lensing Experiment and VISTA Variables in the Via Lactea surveys show a remarkably achromatic event. During 17 years of observational coverage of this source only one such event was detected. The physical properties of the giant star itself appear somewhat unusual, which may ultimately provide a clue towards the nature of the system. By modelling the event as an occultation by an object that is elliptical in projection with uniform transparency, we place limits on its physical size and velocity. We find that the occultation is unlikely to be due to a chance alignment with a foreground object. We consider a number of possible candidates for the occulter, which must be optically thick and possess a radius or thickness in excess of 0.25 au. None are completely satisfactory matches to all the data. The duration, depth and relative achromaticity of the dip mark this out as an exceptionally unusual event, whose secret has still not been fully revealed. We find two further candidates in the VVV survey and we suggest that these systems, and two previously known examples, may point to a broad class of long period eclipsing binaries wherein a giant star is occulted by a circumsecondary disc.

 

Flyaway

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The moons of planets that have no parent star can possess an atmosphere and retain liquid water. Astrophysicists at LMU have calculated that such systems could harbor sufficient water to make life possible – and sustain it.


Researchers from Penn’s Department of Physics and Astronomy have developed a new method for better understanding the relationship between a star’s chemical composition and planet formation.

 

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The moons of planets that have no parent star can possess an atmosphere and retain liquid water. Astrophysicists at LMU have calculated that such systems could harbor sufficient water to make life possible – and sustain it.


Interesting that they have found liquid water on exomoons that have no parent planet, I wonder what type of life would these exomoons have?
 

Flyaway

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By managing to automate the search through the K2 mission data produced by the Kepler space telescope astronomers have managed to discover 372 new exoplanet candidates including 18 multi-planetary systems.

 

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By managing to automate the search through the K2 mission data produced by the Kepler space telescope astronomers have managed to discover 372 new exoplanet candidates including 18 multi-planetary systems.


Amazing to think that the scientists that used Kepler are still finding exoplanets using data from the now dead satellite, I would like to think how many exoplanets are still to be found in the last data that got sent from Kepler before it died.
 

Flyaway

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By managing to automate the search through the K2 mission data produced by the Kepler space telescope astronomers have managed to discover 372 new exoplanet candidates including 18 multi-planetary systems.


Amazing to think that the scientists that used Kepler are still finding exoplanets using data from the now dead satellite, I would like to think how many exoplanets are still to be found in the last data that got sent from Kepler before it died.
I am sure I read something about other gyros from the same company failing on other satellites. But I really cannot remember any of the details.
 

dan_inbox

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Planets that have no parent star should likely be extremely cold. Like, a few °K cold.
There might be water, but at those temperatures it would be ice.

More generally, in my book it is doubtful whether a planet without a parent star would be a thermodynamic system with enough ongoing energy input to fuel the chemical reactions that lead to life, during the billion+ years they take.
 

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Planets that have no parent star should likely be extremely cold. Like, a few °K cold.
There might be water, but at those temperatures it would be ice.

More generally, in my book it is doubtful whether a planet without a parent star would be a thermodynamic system with enough ongoing energy input to fuel the chemical reactions that lead to life, during the billion+ years they take.
This is true for planets, but the surprising result in the recent paper is that a large enough gas giant with large enough moons that have thick enough atmospheres can keep the moons hot enough for liquid water on the surface for billions of years, through tidal forces alone.

The energy gradients available for life to exploit would be much less steep than those on earth, so this probably limits the complexity of possible life on those world.
 

Rhinocrates

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Paper:

 

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Paper:


At least we finally know what caused the dimming of Betelgeuse, at one point I was thinking that it was getting ready to explode as a Supernova.
 

FighterJock

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At least we finally know what caused the dimming of Betelgeuse, at one point I was thinking that it was getting ready to explode as a Supernova.
Many astronomers were fearing the same thing, I believe.

At least we can all breath a sigh of relief that Betelgeuse is not going to explode as a Supernova in the current time period. Though when it does explode it will be as bright as the Moon and be visible during the day.
 

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Paper:

Related paper:

 

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Highly interesting news Grey Havoc. I always wondered if there was any signs of possible geological activity on Venus, while it is not plate tectonics as on Earth it means that Venus is not as dead as was previously thought.
 

Flyaway

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Here’s the related paper. It could be an analogue for early pre plate tectonic Earth.

A globally fragmented and mobile lithosphere on Venus

Abstract

Venus has been thought to possess a globally continuous lithosphere, in contrast to the mosaic of mobile tectonic plates that characterizes Earth. However, the Venus surface has been extensively deformed, and convection of the underlying mantle, possibly acting in concert with a low-strength lower crust, has been suggested as a source of some surface horizontal strains. The extent of surface mobility on Venus driven by mantle convection, however, and the style and scale of its tectonic expression have been unclear. We report a globally distributed set of crustal blocks in the Venus lowlands that show evidence for having rotated and/or moved laterally relative to one another, akin to jostling pack ice. At least some of this deformation on Venus postdates the emplacement of the locally youngest plains materials. Lithospheric stresses calculated from interior viscous flow models consistent with long-wavelength gravity and topography are sufficient to drive brittle failure in the upper Venus crust in all areas where these blocks are present, confirming that interior convective motion can provide a mechanism for driving deformation at the surface. The limited but widespread lithospheric mobility of Venus, in marked contrast to the tectonic styles indicative of a static lithosphere on Mercury, the Moon, and Mars, may offer parallels to interior–surface coupling on the early Earth, when global heat flux was substantially higher, and the lithosphere generally thinner, than today.

 

Flyaway

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Here’s a good target for JWST.

Extremely eccentric minor planet to visit inner solar system this decade

The outskirts of our solar system is teeming with mysterious objects – and now one of them is heading our way. Astronomers have discovered a minor planet that’s about to make its closest pass to the Sun on its 600,000-year orbit.

The object in question is designated 2014 UN271, and it was only recently identified in data from the Dark Energy Survey captured between 2014 and 2018. Size estimates place it anywhere between 100 and 370 km (62 and 230 miles) wide. If it’s a comet, it’s quite a big one, especially for one coming from the outer solar system.

 

Flyaway

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Schwamb toned down the size estimate, saying 2014 UN271 is probably between 60 and 93 miles (100-150 km) in length, not even close to a dwarf planet in terms of size—nor is it likely to be spherical, she noted. Astronomers calculated its size by measuring the object’s reflectivity; as it gets nearer, they’ll be able to refine the size estimate even further.

That said, should the object develop a coma and tail during its perihelion in 2031, it will rank as among the largest comets ever recorded. Other examples of big comets include Comet Sarabat (observed in 1729), with an estimated nucleus around 62 miles (100 km) in diameter, and Comet Hale-Bopp, which had a nucleus from 25 to 50 miles (40 to 80 km). The newly detected object could very well be a record breaker, but we’ll have to wait for more precise size estimates to be sure.

Lawler agreed that the Vera Rubin Observatory, set to begin operations in the next year or two, will be “perfect” for monitoring the object as it nears, but she expressed some concerns about our ongoing ability to make these sorts of astronomical observations.

 

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Schwamb toned down the size estimate, saying 2014 UN271 is probably between 60 and 93 miles (100-150 km) in length, not even close to a dwarf planet in terms of size—nor is it likely to be spherical, she noted. Astronomers calculated its size by measuring the object’s reflectivity; as it gets nearer, they’ll be able to refine the size estimate even further.

That said, should the object develop a coma and tail during its perihelion in 2031, it will rank as among the largest comets ever recorded. Other examples of big comets include Comet Sarabat (observed in 1729), with an estimated nucleus around 62 miles (100 km) in diameter, and Comet Hale-Bopp, which had a nucleus from 25 to 50 miles (40 to 80 km). The newly detected object could very well be a record breaker, but we’ll have to wait for more precise size estimates to be sure.

Lawler agreed that the Vera Rubin Observatory, set to begin operations in the next year or two, will be “perfect” for monitoring the object as it nears, but she expressed some concerns about our ongoing ability to make these sorts of astronomical observations.


If this new comet is as big as the astronomers say it is then we might be getting a potential daylight comet, this comet will be a lot brighter than Hale-Bopp in 1997 when it approaches Earth.
 

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If this new comet is as big as the astronomers say it is then we might be getting a potential daylight comet, this comet will be a lot brighter than Hale-Bopp in 1997 when it approaches Earth.

It doesn't come close enough to the Sun for that. Will be visible with binoculars at best.

Thanks Tuna, a shame that it won’t be a daylight comet, looks like I will have to get my binoculars out to see it.
 

Flyaway

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I wonder if there’s any way this mission could be re-configured to visit this monster comet.

 

FighterJock

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I wonder if there’s any way this mission could be re-configured to visit this monster comet.


I would really like this up coming mission to be re-targeted to the new comet now because there is only one chance to observe such a big comet such as this one, by the looks of things from what I have read online, it is this comets first time into the solar system.
 

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