Author Topic: Astronomy Thread  (Read 92077 times)

Offline ExoExplorer

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Re: Astronomy Thread
« Reply #500 on: 07/14/2018 08:15 AM »
An asteroseismic view of the radius valley: stripped cores, not born rocky (arXiv accepted paper)

[Snipped abstract]

It seems that things have rapidly moved on from the question as to whether there is a 'Fulton gap' to questions about the characterisation of that gap! I also note that the gap itself is being used to clearly delineate super-Earths from sub-Neptunes. Previously it seemed that people used these as synonyms for exoplanets with sizes between Earth and Neptune.

Of course the use of Earth and Neptune in a classification scheme is, if not entirely arbitrary, somewhat anthropocentric. After all, there's no clear distinction between a super-Earth, Earth and, say, Venus, or between a sub-Neptune, Neptune and, say, Uranus. I suspect that sooner or later these terms will give way to classifications that span these objects and have the gap as their upper and lower bounds.

There is something different between Earth and super-Earths, and Neptune and sub-Neptunes. The ambiguity of these dictions lead people to think super-Earths are just the scaled up Earth and sub-Neptunes are just simply the scaled down Neptune with no clear compositional or formational distinctions, defining the boundary is just the matter of time.

In fact, they actually represent totally distinct planet populations which do not present in our solar system. Solar system planets can be compositionally categorized into three groups: rocky planets with little ice (<1%) and no gases (Mercury, Venus, Earth and Mars), gaseous (>80%) planets with little rocks and ice (Jupiter, Saturn), and icy (>50%) planets with little gases (<20%) and rocks (Neptune, Uranus).

Based on the location of the gap and atmospheric escape models, now we have a good reason to suspect that the majority of planets with radius under 1.6 (the so-called super-Earths) is actually rocky planets with >1% gases and no ice, but the atmospheres were blown away during later evolution. This population implies a formation process of rocky planets that is complete different from that of solar system rocky planets. Most planets with radius between 1.6 and 3 might share similar formation process (mainly rock with higher mass fraction of gases) with super-Earths but are enveloped by higher mass fraction of gases which could not be blown away. That is exactly why we need ARIEL to show us how alien these planets are.

Ah, the vagaries of astronomical terminology! :) It seemed to me (I could, of course, be under a misapprehension; but, that's how it seemed to me) that initially the term 'super-Earth' simply meant any planet with a mass bigger than Earth but less than Neptune and the term 'sub-Neptune' meant any planet with a mass less than Neptune but bigger than Earth. The overlap was obvious, but different astronomers preferred one or the other and as there was no scientific justification at the time to prefer one or the other both terms persisted. There was a tendency over time for some people to prefer 'super-Earth' for objects at the lower end of that mass range and 'sub-Neptune' for those at the upper, but nothing definitive until the demonstration of the Fulton or radius gap gave a clear(ish) boundary to hang such a distinction on. And that's where it seems to me the position is at present!

(One wrinkle is that people initially defined these terms with reference to the planet's mass (as given by radial velocity detections) but this is giving way to defining them with reference to the radius (as given by transit detections). There is some correlation of course, but both definitions seem to be persisting and should ideally be sorted out! Perhaps the use of r and m subscripts? :) )

I take your point about the different formation histories of the rocky planets of the solar system and those in the gap itself. Perhaps these should indeed be put into separate classes with (presumably!) the term super-Earth being reserved for the class which has the Earth as a member. And something similar for the term sub-Neptune? If so, this makes the mass or radius of the Earth and Neptune seem even more arbitrary as boundaries for these classes! What would be the real distinction between Venus, Earth and a super-Earth, etc?

My one caveat in having different classification classes for such objects based on their formation history is that although the distinction is clear conceptually, in practice how easy is it to determine the formation history of a particular object?
Complete understandable, some scientists have already begin to change the astronomical language and terms, like this one https://doi.org/10.1038/s41550-017-0042

Online eeergo

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Re: Astronomy Thread
« Reply #501 on: 07/14/2018 10:21 AM »
MeerKAT radio telescope inaugurated in South Africa – reveals clearest view yet of centre of the Milky Way


http://www.ska.ac.za/media-releases/meerkat-radio-telescope-inaugurated-in-south-africa-reveals-clearest-view-yet-of-center-of-the-milky-way/
-DaviD-

Offline Star One

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Astronomy Thread
« Reply #502 on: 07/14/2018 10:38 AM »
Could those filaments be “cosmic strings” caught in the gravity well of the SMB?
« Last Edit: 07/14/2018 11:01 AM by Star One »

Online eeergo

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Re: Astronomy Thread
« Reply #503 on: 07/14/2018 01:26 PM »
These filaments have been known since the 90s, and there's still debate about what causes them, but the current consensus seems to point toward magnetically-stabilized (rather than gravitationally) dust:

http://www.astronomy.com/news/2018/02/milky-way-core-revealed-in-clearest-infrared-image-yet (February)
https://gizmodo.com/new-south-african-telescope-releases-epic-image-of-the-1827572028 (July)
https://www.nrao.edu/pr/2004/filaments/ (2004)
https://link.springer.com/chapter/10.1007/978-94-009-1687-6_31 (1996)
« Last Edit: 07/14/2018 01:28 PM by eeergo »
-DaviD-

Offline Star One

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Re: Astronomy Thread
« Reply #504 on: 07/16/2018 06:56 AM »
The Hunt for Earth’s Deep Hidden Oceans

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According to the standard tale, Earth’s water was imported. The region around the sun where the planet formed was too hot for volatile compounds like water to condense. So the nascent Earth started out dry, getting wet only after water-rich bodies from the distant solar system crashed into the planet, delivering water to the surface. Most of these were likely not comets but rather asteroids called carbonaceous chondrites, which can be up to 20 percent water by weight, storing it in a form of hydrogen like ringwoodite.

But if there’s a huge stockpile of water in the transition zone, this story of water’s origin would have to change. If the transition zone could store 1 percent of its weight in water — a moderate estimate, Jacobsen said — it would contain twice the world’s oceans. The lower mantle is much drier but also voluminous. It could amount to all the world’s oceans (again). There’s water in the crust, too. For subduction to incorporate that much water from the surface at the current rate, it would take much longer than the age of the planet, Jacobsen said.

https://www.quantamagazine.org/the-hunt-for-earths-deep-hidden-oceans-20180711/

Offline Star One

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Re: Astronomy Thread
« Reply #505 on: 07/17/2018 03:46 PM »
12 New Moons of Jupiter Discovered

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It may come as a surprise, then, that astronomers still find new moons orbiting the largest planet in the solar system. But 12 more moons were just discovered, bringing the total to 79, the most of any planet that orbits the sun. These small moons were not discovered by a spacecraft, but rather by powerful telescopes on Earth—and by a team, led by Carnegie Institution for Science astronomer Scott Sheppard, that didn't even set out to look for them.

"These moons are the last remnants of the objects that the planets were built from," Sheppard tells Popular Mechanics via email. "Most of the small objects that helped build the planets we see today were incorporated into the planets themselves, and these moons are all that remains."

https://www.popularmechanics.com/space/a22185640/dozen-new-moons-discovered-jupiter/


Offline Star One

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Re: Astronomy Thread
« Reply #506 on: 07/17/2018 08:26 PM »
The Hawaii Infrared Parallax Program. III. 2MASS J0249-0557 c: A Wide Planetary-mass Companion to a Low-mass Binary in the beta Pic Moving Group

We have discovered a wide planetary-mass companion to the β Pic moving group member 2MASSJ02495639-0557352 (M6 VL-G) using CFHT/WIRCam astrometry from the Hawaii Infrared Parallax Program. In addition, Keck laser guide star adaptive optics aperture-masking interferometry shows that the host is itself a tight binary. Altogether, 2MASSJ0249-0557ABc is a bound triple system with an 11.6+1.0−1.3 MJup object separated by 1950±200 AU (40") from a relatively close (2.17±0.22 AU, 0.04") pair of 48+12−13 MJup and 44+11−14 MJup objects. 2MASSJ0249-0557AB is one of the few ultracool binaries to be discovered in a young moving group and the first confirmed in the β Pic moving group (22±6 Myr). The mass, absolute magnitudes, and spectral type of 2MASSJ0249-0557 c (L2 VL-G) are remarkably similar to those of the planet β Pic b (L2, 13.0+0.4−0.3 MJup). We also find that the free-floating object 2MASSJ2208+2921 (L3 VL-G) is another possible β Pic moving group member with colors and absolute magnitudes similar to β Pic b and 2MASSJ0249-0557 c. β Pic b is the first directly imaged planet to have a "twin," namely an object of comparable properties in the same stellar association. Such directly imaged objects provide a unique opportunity to measure atmospheric composition, variability, and rotation across different pathways of assembling planetary-mass objects from the same natal material.

https://arxiv.org/abs/1807.05235

Offline ExoExplorer

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Re: Astronomy Thread
« Reply #507 on: 07/19/2018 04:41 AM »
A new planet transiting LHS 1140 is discovered with an orbital period 3.8 day. The real properties like radius are yet to be published. I will do some calculation to show a possible radius and compositional range of this planet.
A 3.8 day planet signal with less than 3 Earth-mass is also discovered in radial velocity date after reanalyzing the Dittmann et al's work.
Transmission spectroscopy study revises the LHS 1140 b radius to 1.63 Earth-radius.
« Last Edit: 07/19/2018 06:50 AM by ExoExplorer »

Offline ExoExplorer

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Re: Astronomy Thread
« Reply #508 on: 07/19/2018 06:47 AM »
Just did a little calculation with the transit depth of LHS-1140c in the graph.

There are three sources of LHS-1140 radius available: 0.186±0.013 Rs (original study), ~0.2 Rs (new transmission spectroscopy), and 0.223±0.013 Rs (Gaia DR2).

planet radius (in Earth unit) = Transit depth^0.5 * stellar radius / Earth radius

According to the graph, I am pretty confident that the relative flux of LHS-1140 drops to ~0.997 when planet c transits, so the transit depth is 0.003.

Take 0.19 Rs (new transmission spectroscopy) and 0.23 Rs (Gaia DR2) as stellar radius lower limit and upper limit, I get 1.25±0.12 Rp for the radius of planet c.

The additional radial velocity of c is presented in arxiv.org/abs/1807.02483, showing that the mass likely falls somewhere in between 1.5 and 2 Earth-mass.
Therefore, the bulk density of c would be 5.4±2.2g/cm3.

Its composition lies between oceanworld and rocky planet (including Earth-like composition). Unless we can further constrain the planetary mass and radius, there is no a sure conclusion to its volatile inventory.

The short orbital distance makes this planet extremely hot and uninhabitable, contrasting to its neighbor b.
« Last Edit: 07/19/2018 06:53 AM by ExoExplorer »

Offline Star One

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Re: Astronomy Thread
« Reply #509 on: 07/19/2018 01:32 PM »
Wandering Star May Have Disrupted Outer Solar System's Order

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There's something strange about the outer solar system — and that could be the signature of a long-ago visit to our neighborhood, according to a new study that looked to simulate how the outer solar system might have ended up so oddly arranged.

https://www.space.com/41212-wandering-star-disturbed-outer-solar-system.html

Offline Star One

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Re: Astronomy Thread
« Reply #510 on: 07/19/2018 02:04 PM »
Supersharp Images from New VLT Adaptive Optics

ESO’s Very Large Telescope (VLT) has achieved first light with a new adaptive optics mode called laser tomography — and has captured remarkably sharp test images of the planet Neptune, star clusters and other objects. The pioneering MUSE instrument in Narrow-Field Mode, working with the GALACSI adaptive optics module, can now use this new technique to correct for turbulence at different altitudes in the atmosphere. It is now possible to capture images from the ground at visible wavelengths that are sharper than those from the NASA/ESA Hubble Space Telescope. The combination of exquisite image sharpness and the spectroscopic capabilities of MUSE will enable astronomers to study the properties of astronomical objects in much greater detail than was possible before.

The MUSE (Multi Unit Spectroscopic Explorer) instrument on ESO’s Very Large Telescope (VLT) works with an adaptive optics unit called GALACSI. This makes use of the Laser Guide Star Facility, 4LGSF, a subsystem of the Adaptive Optics Facility (AOF). The AOF provides adaptive optics for instruments on the VLTs Unit Telescope 4 (UT4). MUSE was the first instrument to benefit from this new facility and it now has two adaptive optics modes — the Wide Field Mode and the Narrow Field Mode [1].

The MUSE Wide Field Mode coupled to GALACSI in ground-layer mode corrects for the effects of atmospheric turbulence up to one kilometre above the telescope over a comparatively wide field of view. But the new Narrow Field Mode using laser tomography corrects for almost all of the atmospheric turbulence above the telescope to create much sharper images, but over a smaller region of the sky [2].

With this new capability, the 8-metre UT4 reaches the theoretical limit of image sharpness and is no longer limited by atmospheric blur. This is extremely difficult to attain in the visible and gives images comparable in sharpness to those from the NASA/ESA Hubble Space Telescope. It will enable astronomers to study in unprecedented detail fascinating objects such as supermassive black holes at the centres of distant galaxies, jets from young stars, globular clusters, supernovae, planets and their satellites in the Solar System and much more.

Adaptive optics is a technique to compensate for the blurring effect of the Earth’s atmosphere, also known as astronomical seeing, which is a big problem faced by all ground-based telescopes. The same turbulence in the atmosphere that causes stars to twinkle to the naked eye results in blurred images of the Universe for large telescopes. Light from stars and galaxies becomes distorted as it passes through our atmosphere, and astronomers must use clever technology to improve image quality artificially.

To achieve this four brilliant lasers are fixed to UT4 that project columns of intense orange light 30 centimetres in diameter into the sky, stimulating sodium atoms high in the atmosphere and creating artificial Laser Guide Stars. Adaptive optics systems use the light from these “stars” to determine the turbulence in the atmosphere and calculate corrections one thousand times per second, commanding the thin, deformable secondary mirror of UT4 to constantly alter its shape, correcting for the distorted light.

MUSE is not the only instrument to benefit from the Adaptive Optics Facility. Another adaptive optics system, GRAAL, is already in use with the infrared camera HAWK-I. This will be followed in a few years by the powerful new instrument ERIS. Together these major developments in adaptive optics are enhancing the already powerful fleet of ESO telescopes, bringing the Universe into focus.

This new mode also constitutes a major step forward for the ESO’s Extremely Large Telescope, which will need Laser Tomography to reach its science goals. These results on UT4 with the AOF will help to bring ELT’s engineers and scientists closer to implementing similar adaptive optics technology on the 39-metre giant.

https://www.eso.org/public/news/eso1824/

Here’s a video as well.




Offline Star One

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Re: Astronomy Thread
« Reply #511 on: 07/20/2018 07:55 PM »
How Disc Galaxies Work

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Disc galaxies like our own Milky Way, characterized by a flattened disc of stars and gas (often with a central bulge of material as well) have a wide range of masses, spatial extents, and stellar content. Nonetheless all disc galaxies, both locally and in the distant Universe, share some strikingly similar properties. Most notable is that the star formation rate correlates tightly with the galaxy’s gas content, the gas motions (the "velocity dispersion"), and the dynamical lifetime (roughly, the time it takes for the galaxy to rotate once). Moreover, this curiously universal rate is remarkably small: only about one per cent of the gas in disc galaxies turns into stars over that timescale, with much of the activity concentrated in the galaxies’ central regions. Most simple models of star formation predict that gravity should be much more effective in forming stars as it compresses the gas in molecular clouds. Observations indicate that both the correlations and the inefficiency extend down to the scale of individual molecular clouds.

https://www.cfa.harvard.edu/news/su201829

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Re: Astronomy Thread
« Reply #512 on: 07/22/2018 02:07 AM »
The first super-Earth Detection from the High Cadence and High Radial Velocity Precision Dharma Planet Survey (arXiv pdf)

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(Abstract)
The Dharma Planet Survey (DPS) aims to monitor about 150 nearby very bright FGKM dwarfs (within 50 pc) during 2016−2020 for low-mass planet detection and characterization using the TOU very high resolution optical spectrograph (R≈100,000, 380-900nm). TOU was initially mounted to the 2-m Automatic Spectroscopic Telescope at Fairborn Observatory in 2013-2015 to conduct a pilot survey, then moved to the dedicated 50-inch automatic telescope on Mt. Lemmon in 2016 to launch the survey. Here we report the first planet detection from DPS, a super-Earth candidate orbiting a bright K dwarf star, HD 26965. It is the second brightest star (V = 4.4 mag) on the sky with a super-Earth candidate. The planet candidate has a mass of 8.47±0.47MEarth, period of 42.38 ± 0.01 d, and eccentricity of 0.04+0.05−0.03. This RV signal was independently detected by Diaz et al. (2018), but they could not confirm if the signal is from a planet or from stellar activity. The orbital period of the planet is close to the rotation period of the star (39−44.5 d) measured from stellar activity indicators. Our high precision photometric campaign and line bisector analysis of this star do not find any significant variations at the orbital period. Stellar RV jitters modeled from star spots and convection inhibition are also not strong enough to explain the RV signal detected. After further comparing RV data from the star’s active magnetic phase and quiet magnetic phase, we conclude that the RV signal is due to planetary-reflex motion and not stellar activity.

HD 26965 is the star named Keid, the primary or A component of the 40 Eridani triple star system (and the host star of the planet Vulcan in Star Trek). I know that (for good reasons) astronomers prefer to use modern catalogue designations to identify stars rather than proper names or old designations such as the Flamsteed designation 40 Eridani. However, if they're concerned to leverage popular interest in astronomy they should give some thought to including such alternate designations or names to attract the attention of said populace, or at least of journalists - it only takes a sentence!

It's interesting how automatic telescopes are enabling more frequent radial-velocity observations improving detection of exoplanets:

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Every target will be initially observed ∼30 consecutive observable nights to target close-in low-mass planets detection. After that, each target will be observed an additional ∼70 times randomly spread over 420 days. The automatic nature of the 50-inch telescope and its flexible queue observation schedule are key to realizing this nearly homogenous high cadence.

I also note they used R-V observations from Keck/HIRES, HARPS, PFS and CHIRON, a good example of how science is cumulative.

As a bit of an astronomical terminology buff, I note they called this a super-Earth. This is despite noting that it "likely possesses a gaseous atmosphere". At a minimum mass of 8.47 times Earth, it will have a radius of over twice that of Earth if of the same average density and an even bigger radius with a gaseous atmosphere (which I take to mean a large gaseous envelope as all atmospheres are gaseous!) as that would reduce the average density. That puts it on the upper edge if not over the so-called Fulton or radius gap. Given that the mass is likely above the minimum, I think this planet is better described as a sub-Neptune!

Offline Star One

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Astronomy Thread
« Reply #513 on: 07/23/2018 07:45 PM »
Preservation of potential biosignatures in the shallow subsurface of Europa

Jupiter’s moon Europa, which is thought to possess a large liquid water ocean beneath its icy crust, is one of the most compelling targets in the search for life beyond Earth. Its geologically young surface, along with a number of surface features, indicate that material from Europa’s interior may be emplaced on the surface. However, the surface is affected by the harsh radiation environment of Jupiter’s magnetosphere, which over time may lead to chemical alteration and destruction of potential biosignatures. We show that radiation dose rates are highly dependent on surface location. Radiation processing and destruction of potential biosignatures is found to be significant down to depths of ~1 cm in mid- to high-latitude regions, and to depths of 10–20 cm within ‘radiation lenses’ centred on the leading and trailing hemispheres. These results indicate that future missions to Europa’s surface do not need to excavate material to great depths to investigate the composition of endogenic material and search for potential biosignatures.

https://www.nature.com/articles/s41550-018-0499-8

NASA Press Release

Radiation Maps of Jupiter's Moon Europa: Key to Future Missions

https://www.jpl.nasa.gov/news/news.php?release=2018-170&rn=news.xml&rst=7191
« Last Edit: 07/23/2018 07:59 PM by Star One »

Offline Star One

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Re: Astronomy Thread
« Reply #514 on: 07/23/2018 08:17 PM »
Storm Chasers' on Mars Searching for Dusty Secrets

Storm chasing takes luck and patience on Earth -- and even more so on Mars.

For scientists watching the Red Planet from data gathered by NASA's orbiters, the past month has been a windfall. "Global" dust storms, where a runaway series of storms creates a dust cloud so large it envelops the planet, only appear every six to eight years (that's three to four Mars years). Scientists still don't understand why or how exactly these storms form and evolve.



In June, one of these dust events rapidly engulfed the planet. Scientists first observed a smaller-scale dust storm on May 30. By June 20, it had gone global.

For the Opportunity rover, that meant a sudden drop in visibility from a clear, sunny day to that of an overcast one. Because Opportunity runs on solar energy, scientists had to suspend science activities to preserve the rover's batteries. As of July 18th, no response has been received from the rover.

Luckily, all that dust acts as an atmospheric insulator, keeping nighttime temperatures from dropping down to lower than what Opportunity can handle. But the nearly 15-year-old rover isn't out of the woods yet: it could take weeks, or even months, for the dust to start settling. Based on the longevity of a 2001 global storm, NASA scientists estimate it may be early September before the haze has cleared enough for Opportunity to power up and call home.

When the skies begin to clear, Opportunity's solar panels may be covered by a fine film of dust. That could delay a recovery of the rover as it gathers energy to recharge its batteries. A gust of wind would help, but isn't a requirement for a full recovery..

While the Opportunity team waits in earnest to hear from the rover, scientists on other Mars missions have gotten a rare chance to study this head-scratching phenomenon.

The Mars Reconnaissance Orbiter, Mars Odyssey, and Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiters are all tailoring their observations of the Red Planet to study this global storm and learn more about Mars' weather patterns. Meanwhile, the Curiosity rover is studying the dust storm from the Martian surface.

Here's Here's how each mission is currently studying the dust storm, and what we might learn from it:


Mars Odyssey

With the THEMIS instrument (Thermal Emission Imaging System), scientists can track Mars' surface temperature, atmospheric temperature, and the amount of dust in the atmosphere. This allows them to watch the dust storm grow, evolve, and dissipate over time.

"This is one of the largest weather events that we've seen on Mars," since spacecraft observations began in the 1960s, said Michael Smith, a scientist at NASA's Goddard Spaceflight Center in Greenbelt, Maryland who works on the THEMIS instrument. "Having another example of a dust storm really helps us to understand what's going on."

Since the dust storm began, the THEMIS team has increased the frequency of global atmospheric observations from every 10 days to twice per week, Smith said. One mystery they're still trying to solve: How these dust storms go global. "Every Mars year, during the dusty season, there are a lot of local- or regional-scale storms that cover one area of the planet," Smith said. But scientists aren't yet sure how these smaller storms sometimes grow to end up encircling the entire planet.

Mars Reconnaissance Orbiter (MRO)

Mars Reconnaissance Orbiter has two instruments studying the dust storm. Each day, the Mars Color Imager (MARCI) maps the entire planet in mid-afternoon to track the evolution of the storm. Meanwhile, MRO's Mars Climate Sounder (MCS) instrument measures how the atmosphere's temperature changes with altitude. Since the end of May, the instruments have observed the onset and rapid expansion of a dust storm on Mars.

With these data, scientists are studying how the dust storm changes the planet's atmospheric temperatures. Just as in Earth's atmosphere, changing temperature on Mars can affect wind patterns and even the circulation of the entire atmosphere. This provides a powerful feedback: Solar heating of the dust lofted into the atmosphere changes temperatures, which changes winds, which may amplify the storm by lifting more dust from the surface.

Scientists want to know the details of the storm -- where is the air rising or falling? How do the atmospheric temperatures now compare to a storm-less year? And as with Mars Odyssey, the MRO team wants to know how these dust storms go global.

"The very fact that you can start with something that's a local storm, no bigger than a small [U.S.] state, and then trigger something that raises more dust and produces a haze that covers almost the entire planet is remarkable," said Rich Zurek of NASA's Jet Propulsion Laboratory, Pasadena, California, the project scientist for MRO.

Scientists want to find out why these storms arise every few years, which is hard to do without a long record of such events. It'd be as if aliens were observing Earth and seeing the climate effects of El Niño over many years of observations -- they'd wonder why some regions get extra rainy and some areas get extra dry in a seemingly regular pattern.

MAVEN

Ever since the MAVEN orbiter entered Mars' orbit, "one of the things we've been waiting for is a global dust storm," said Bruce Jakosky, the MAVEN orbiter's principle investigator.

But MAVEN isn't studying the dust storm itself. Rather, the MAVEN team wants to study how the dust storm affects Mars' upper atmosphere, about 62 miles (more than 100 kilometers) above the surface -- where the dust doesn't even reach. MAVEN's mission is to figure out what happened to Mars' early atmosphere. We know that at some point billions of years ago, liquid water pooled and ran along Mars' surface, which means that its atmosphere must have been thicker and more insulating, similar to Earth's. Since MAVEN arrived at Mars in 2014, its investigations have found that this atmosphere may have been stripped away by a torrent of solar wind over several hundred million years, between 3.5 and 4.0 billion years ago.

But there are still nuances to figure out, such as how dust storms like the current one affect how atmospheric molecules escape into space, Jakosky said. For instance, the dust storm acts as an atmospheric insulator, trapping heat from the Sun. Does this heating change the way molecules escape the atmosphere? It is also likely that, as the atmosphere warms, more water vapor rises high enough to be broken down by sunlight, with the solar wind sweeping the hydrogen atoms into space, Jakosky said.

The team won't have answers for a while yet, but each of MAVEN's five orbits per day will continue to provide invaluable data.

Curiosity

Most of NASA's spacecraft are studying the dust storm from above. The Mars Science Laboratory mission's Curiosity rover has a unique perspective: the nuclear-powered science machine is largely immune to the darkened skies, allowing it to collect science from within the beige veil enveloping the planet.

"We're working double-duty right now," said JPL's Ashwin Vasavada, Curiosity's project scientist. "Our newly recommissioned drill is acquiring a fresh rock sample. But we are also using instruments to study how the dust storm evolves."

Curiosity has a number of "eyes" that can determine the abundance and size of dust particles based on how they scatter and absorb light. That includes its Mastcam, ChemCam, and an ultraviolet sensor on REMS, its suite of weather instruments. REMS can also help study atmospheric tides -- shifts in pressure that move as waves across the entire planet's thin air. These tides change drastically based on where the dust is globally, not just inside Gale crater.

The global storm may also reveal secrets about Martian dust devils and winds. Dust devils can occur when the planet's surface is hotter than the air above it. Heating generates whirls of air, some of which pick up dust and become dust devils. During a dust storm, there's less direct sunlight and lower daytime temperatures; this might mean fewer devils swirling across the surface.

Even new drilling can advance dust storm science: watching the small piles of loose material created by Curiosity's drill is the best way of monitoring winds.

Scientists think the dust storm will last at least a couple of months. Every time you spot Mars in the sky in the weeks ahead, remember how much data scientists are gathering to better understand the mysterious weather of the Red Planet.



Offline Star One

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Astronomy Thread
« Reply #515 on: 07/23/2018 08:29 PM »
NASA Launches X-ray Telescope on Sounding Rocket to Study Star Wreckage

Editor's note, July 23, 2018: The Micro-X team reports that while the detector functioned as expected during the flight, demonstrating the technology in space flight for the first time, the observatory’s pointing system was unable to lock onto its target, Cassiopeia A. The team will be looking forward to its next opportunity for a reflight.

NASA launched a prototype telescope and instrument to observe the X-rays emitted by Cassiopeia A, the expanding debris of an exploded star. The High-Resolution Microcalorimeter X-ray Imaging Rocket (Micro-X) launched July 22 aboard a sub-orbital launch vehicle called a sounding rocket and successfully tested its detector technology. 

“The flight time of a sounding rocket is short compared to orbiting satellites, so you have to get as much light as you can to do the science you want,” said Principal Investigator Enectali Figueroa-Feliciano, an associate professor of physics at Northwestern University in Evanston, Illinois. “There are only a couple of X-ray sources in the sky that are bright enough for the few minutes of observation time such flights give us, and Cassiopeia A is one of the brightest. Our study will build on the current knowledge of supernova remnants, how they exploded and evolve, and we will get new insights into the history of Cassiopeia A.”

Launched from the U.S. Army’s White Sands Missile Range in New Mexico, Micro-X soared to an altitude of 100 miles (160 kilometers) — required to detect X-rays that are absorbed by Earth’s atmosphere — and observed the remnant for the next five minutes. At its pinnacle Micro-X reached an altitude of 167 miles (270 kilometers).

The mission incorporates the first array of transition-edge sensor X-ray microcalorimeters to fly into space. These sensors act as highly sensitive thermometers and make ideal detectors for an X-ray telescope.

The microcalorimeter is comprised of three main parts: an absorber which takes in light and converts it to heat, a thermistor that alters its own resistance due to changing temperature and a heat sink that cools the microcalorimeter back down.

For Micro-X, a refrigerator cools the detector to about 459 degrees below zero Fahrenheit (0.075 degree Celsius above absolute zero), or nearly the minimum temperature possible. When the instrument detects X-rays, the light’s energy is converted into heat. This causes a slight rise in temperature, prompting the refrigerator to cool the detector back to its original temperature. The energy of each X-ray can be determined from the change in temperature.

One of the many questions that scientists are interested in using the data to answer is whether or not the temperatures of the gases ejected from the star’s explosion are the same for iron and silicon, two elements which were previously measured by NASA’s Chandra X-ray Observatory. Such an analysis was not possible with Chandra’s spectrometers.

“With Chandra, different regions of the supernova remnant overlap in the spectrometer,” said F. Scott Porter, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who is participating in the mission. “Micro-X is different because it can take every single photon in its field of view, tell the exact energy and make a spectrum.”

The information collected by Micro-X will also be used to help answer the question of how much oxygen resides in Cassiopeia A, create a survey of the various other elements in the remnant and measure the speed of the ring-like ejecta from the exploded star.

One aspect of research that was not possible before Micro-X was the measurement of weak spectral lines. These observations will now tell scientists which gases are present as well as their speed and direction. This is possible because light from sources moving toward or away from us causes a shift in wavelength depending on their speed, a phenomenon known as the Doppler shift.

Both the mission of Micro-X and the utilization of transition-edge sensors will continue in the future. The Micro-X team plans to direct their attention to other cosmic objects. “In future flights we can look at other sources like other supernova remnants or clusters of galaxies,” said Figueroa-Feliciano. “We have even thought about using this type of rocket to look for dark matter.”

Transition-edge sensors will also be incorporated in upcoming orbital missions. ESA’s (European Space Agency) Advanced Telescope for High Energy Astrophysics (ATHENA), planned for launch in the early 2030s, will wield an array of about 5,000 pixels, nearly 40 times the size of Micro-X’s 128-pixel detector. ATHENA will study hot gas structures — such as groups of galaxies — and conduct a census of black holes.

In addition to NASA and Northwestern University, Micro-X is supported by the National Institute of Standards and Technology in Boulder, Colorado, the Massachusetts Institute of Technology in Cambridge, Massachusetts, and the University of Wisconsin-Madison.

NASA's Sounding Rocket Program is conducted at the agency's Wallops Flight Facility at Wallops Island, Virginia, which is managed by Goddard. NASA's Heliophysics Division manages the sounding rocket program for the agency. The development of the Micro-X payload was supported by NASA’s Astrophysics Division.

https://www.nasa.gov/feature/goddard/2018/nasa-launches-x-ray-telescope-on-sounding-rocket-to-study-star-wreckage
« Last Edit: 07/23/2018 08:31 PM by Star One »

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Astronomy Thread
« Reply #516 on: 07/26/2018 04:10 PM »
First successful test of Einstein’s General Relativity near a Super Massive Black Hole

« Last Edit: 07/26/2018 04:12 PM by Star One »

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Re: Astronomy Thread
« Reply #517 on: 07/27/2018 08:44 PM »
Black holes really just ever-growing balls of string, researchers say

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Black holes aren’t surrounded by a burning ring of fire after all, suggests new research.

Some physicists have believed in a “firewall” around the perimeter of a black hole that would incinerate anything sucked into its powerful gravitational pull.

But a team from The Ohio State University has calculated an explanation of what would happen if an electron fell into a typical black hole, with a mass as big as the sun.

https://news.osu.edu/black-holes-really-just-ever-growing-balls-of-string-researchers-say/

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Re: Astronomy Thread
« Reply #518 on: 07/30/2018 08:43 PM »
Blueberry Earth

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This paper explores the physics of the what-if question "what if the entire Earth was instantaneously replaced with an equal volume of closely packed, but uncompressed blueberries?" While the assumption may be absurd, the consequences can be explored rigorously using elementary physics. The result is not entirely dissimilar to a small ocean-world exoplanet.

https://arxiv.org/abs/1807.10553

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Astronomy Thread
« Reply #519 on: 08/01/2018 06:47 AM »
Ancient space crystals may prove the sun threw heated tantrums as a tot

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It’s natural to assume even our 4.6 billion-year-old sun had a messy heyday in its youth, but without any hard evidence to prove this was case, the only thing many scientists had going for them were strong suspicions. New data, focused around a peculiar set of ancient blue crystals from space, seems to suggest the sun emitted a much higher flux of cosmic rays in its early history than we once thought.
Those blue crystals are called hibonite, and they’ve arrived here on Earth by way of meteorite impacts. Hibonite are effectively some of the first minerals formed in the solar system, created by the cooling gas derived from the sun. The new study, published in Nature Astronomy, focuses on the Murchison meteorite, which fell in Australia in 1969, likely originating from an asteroid in the asteroid belt—and which possesses pieces of micron barely larger than the width of human hair.

https://www.popsci.com/space-crystal-meteorite-early-sun

Plate tectonics not needed to sustain life

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There may be more habitable planets in the universe than we previously thought, according to Penn State geoscientists, who suggest that plate tectonics—long assumed to be a requirement for suitable conditions for life—are in fact not necessary.

https://phys.org/news/2018-07-plate-tectonics-sustain-life.amp?
« Last Edit: 08/01/2018 06:51 AM by Star One »