We Finally Know How These Exoplanets Get So Freakishly Big


Post 8249

We Finally Know How These Exoplanets Get So Freakishly Big

Tuesday 2:00pm

Artist’s rendition of a Hot Jupiter. Image: Hubble

“Hot Jupiters” aren’t particularly sexy exoplanets—just clingy ones. These gas giants orbit tightly around their host stars, and despite their name, they’re typically more massive than Jupiter. And, as you’d expect, much hotter.

According to the University of Arecibo, 74o of the 3,442 confirmed exoplanetsare Hot Jupiters. These distant giants—full of gas and mystery—have certainly piqued our interest in recent years as exoplanet research has evolved. As Space.com notes, some hot Jupiters defy theoretical models of planetary formation because they’re so damn large. But new research suggests we might have the answer to that enigma, at least: Hot Jupiters aren’t born abnormally big—they just “puff” up over time.

Using the Hungarian-made Automated Telescope Network (HATNet) in Mount Hopkins, Arizona and Mauna Kea, Hawaii, a team of scientists identified two particularly large Hot Jupiters, dubbed HAT-P-65b and HAT-P-66b. These exoplanets—2,745 and 3,025 lightyears from Earth, respectively—orbit their star 10 times closer than Mercury orbits our sun.

After comparing these two Hot Jupiters to 200 other exoplanets, the scientists found that HAT-P-65b and HAT-P-66b are unusually large for their respective ages (5.46 billion and 4.66 billion years-old). The team hypothesized that since these two Hot Jupiters orbit so closely to their host stars, they receive enormous amounts of radiation, over time expanding like cosmic pufferfish. The group’s findings have been published in the December issue of The Astronomical Journal.

Joel Hartman, a lead author on the study, suggests the research offers new insights about these elusive giants.

“[We found] many [Hot Jupiters] are a lot larger than predicted by theoretical models of planetary structure (some planets are up twice the size of Jupiter, but the largest they could be, according to the models, is about 1.5 times the size of Jupiter),” he told Gizmodo. “Some of them are on wildly inclined orbits with respect to the spins of their hosts—some even orbit backwards around their stars.”

It’s no coincidence that HAT-P-65b and HAT-P-66b have ballooned to become 1.9 and 1.6 times Jupiter’s diameter. Hartman and his team found that both of the planets’ respective stars have completed 80 percent of their life cycles, meaning they’re nearing the end of the main sequence. Before they die, stars burn brighter and emit more radiation, which could cause their Hot Jupiters to expand.

“As stars get older they also get brighter, and deposit more energy into the upper atmospheres of any close-in planets they might harbor,” Hartman said. “If this energy can make its way down to the core of a gas giant planet it would cause the planet to expand. This idea has been floating around for quite a while as a possible explanation for why some hot Jupiters can be extremely large. But, no one has been able to convincingly demonstrate a mechanism for transporting the energy deep into the interior of the planet.”

This study is much more than unlocking the secrets of a cool space mystery, though it totally does that, too. The research helps us better understand how a star’s radiation can impact the way planets evolve.

“Furthermore, if we want to apply these theoretical models to infer the properties of smaller and more distantly orbiting planets which are harder to observe in detail (e.g., habitable Earth-like planets), we need to test the theories, and make sure they work for the planets that we can study in the most detail,” Hartman said.

[The Astronomical Journal]

Space Writer, Gizmodo

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Why Spaceflight Ruins Your Eyesight


Post 8248

Why Spaceflight Ruins Your Eyesight

11/28/16 10:30am

NASA astronaut Scott Kelly inside a Soyuz simulator at the Gagarin Cosmonaut Training Center in 2015. (Image: NASA/Bill Ingalls)

Astronauts who return to Earth after long-duration space missions suffer from untreatable nearsightedness. Scientists have now isolated the cause, but finding a solution to the problem will prove easier said than done.

The problem, say researchers from the University of Miami Miller School of Medicine, has to do with volume changes in the cerebrospinal fluid (CSF) found around the brain and spinal cord. Prolonged exposure to microgravity triggers a build-up of this fluid, causing the astronauts’ eyeballs to flatten, which can lead to myopia. A build-up of CSF also causes astronauts’ optic nerves to stick out, which is also not good, as the optic nerve sends signals to the brain from the retina. This is causing nearsightedness among long-duration astronauts, and it’s problem with no clear solution in sight (so to speak).

It’s well documented that astronauts who fly long-duration space missions suffer from blurry vision upon returning. “People initially didn’t know what to make of it, and by 2010 there was growing concern as it became apparent that some of the astronauts had severe structural changes that were not fully reversible upon return to earth,” noted lead study author Noam Alperin in a statement. The syndrome, dubbed visual impairment intracranial pressure (VIIP), was reported in nearly two-thirds of astronauts following long-duration missions aboard the International Space Station (ISS).

 Prior to the new study, scientists thought the problem had to do with a shift of vascular fluid towards the upper body during exposure to microgravity. The new research (which will be presented today at the annual meeting of the Radiological Society of North America), points to the normally protective cerebrospinal fluid as the likely culprit.
Too much pressure: A build-up of cerebrospinal fluid is cited as the cause of nearsightedness in long-duration astronauts. (Image: Alperin et al.)

On Earth, the CSF system can accommodate sudden changes in pressure, such as when a person rises from a lying position to sitting or standing position. But in space, this system is confused by the lack of the posture-related pressure changes. Brain scans taken of astronauts both before and after long-duration space missions revealed the flattening of the eyeballs and increased optic nerve protrusion. Importantly, the astronauts also exhibited significantly greater post-flight increases in CSF volume in the area around the optic nerves and the cavity where CSF is produced.

Armed with this new information, scientists will now have to find a way to prevent this from happening (artificial gravity, anyone?), and to treat the condition when the astronauts arrive back on Earth (laser eye surgery is one possibility, but this procedure may not address the full scope of the damage done). In the meantime, space will continue to be a discouragingly inhospitable place for humans.

[The annual meeting of the Radiological Society of North America (RSNA)]

George is a contributing editor at Gizmodo and io9.

How Astronauts’ Brains Are Changed By Spaceflight


Post 8247

How Astronauts’ Brains Are Changed By Spaceflight

Yesterday 1:15pm

Image: NASA

Spaceflight is not for the faint of heart—literally. The first results of NASA’stwin study, released just this week, revealed that space physically impacts astronauts on multiple levels, right down to shifts in gene expression. Now, a group of scientists at the University of Michigan have released research that suggests spaceflight alters astronauts’ brains.

The team studied 26 astronauts who spent various amounts of time in space, between 2008 to 2012. Twelve of the astronauts spent two weeks as shuttle crew members, while the other 14 spent six months aboard the International Space Station (ISS). After examining structural MRIs from all the astronauts taken before and after spaceflight, the researchers found that all subjects experienced both increases and decreases in the volume of gray matter in different regions of the brain. Gray matter is responsible for many key functions, including muscle control, emotions, memory and sensory perception.

Naturally, those who spent more time in space were impacted more dramatically. The team’s findings were published on December 19, 2016 inNature Microgravity.

“Some of the areas show decreases in gray matter volume, and I don’t want anyone to think that means you go to space and lose brain cells,” University of Michigan professor Rachel Seidler, a co-author on the study, told Gizmodo. “The losses are coming from shifts in fluid in the brain that happen with flight.”

Blue regions show areas where gray matter volume decreased; Orange represents areas where gray matter increased. (Image: University of Michigan)

Specifically, the shifts in gray matter volume appear due microgravity, which describes the very slight presence of gravity aboard the ISS.

“Imagine gravity pulling all the fluids toward your feet, and in space you don’t have that happening.” Seidler said. “There’s more fluid toward the head—you may have seen photos of astronauts where they have puffy faces in space—but there’s a shift in fluid in the brain as well.”

The group found that during spaceflight, gray matter volume increased in small regions of the brain that control leg movement, which could reflect how the brain retrains the body to move in microgravity. In other areas of the brain, gray matter volume decreased, possibly due to a redistribution of thecerebrospinal fluid that coats the central nervous system.

John Phillips aboard the ISS. (Image: NASA)

Astonishingly enough, we know almost nothing about how space impacts the brain. This study is the first to ever analyze how brain structure could change due to microgravity. While it’s still unclear how—or if—gray matter volume returned to pre-flight levels in the astronauts studied, Steidler is conducting a separate ongoing study that analyzes astronauts’ brains in the six months after their returns from space.

“Because of the amount of exercise they’re doing now, astronauts are coming back with their [muscles and bones] pretty well protected,” Steidler said. “But the brain is really still an open question…we don’t yet have available follow-up data to see how long it takes the brain to recover.”

With certain Earthlings’ grand ambitions to go to Mars, it’s important to understand how long stints in space can affect the human body. But this research could also be key to understanding health conditions here on Earth. Steidler said studies like this could help medical professionals better understand brain disorders like normal pressure hydrocephalus, which is caused by a build up of fluid in the brain.

“It’s very interesting to use this as a model to study the maximum capacity for neuroplasticity in the healthy brain,” she explained. “It’s an important model for understanding how much the brain can change when faced with an environment you’ve never been in before.”

[University of Michigan]

Space Writer, Gizmodo

WHAT IS THE WEATHER LIKE ON MARS?


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Mars is often referred to as “Earth’s Twin”, due to the similarities it has with our planet. They are both terrestrial planets, both have polar ice caps, and (at one time) both had viable atmospheres and liquid water on their surfaces. But beyond that, the two are quite different. And when it comes to their atmospheres and climates, Mars stands apart from Earth in some rather profound ways.

For instance, when it comes to the weather on Mars, the forecast is usually quite dramatic. Not only does Martian weather vary from day to day, it sometimes varies from hour to hour. That seems a bit unusual for a planet that has an atmosphere that is only 1% as dense as the Earth’s. And yet, Mars manages to really up the ante when it comes to extreme weather and meteorological phenomena.

Mars’ Atmosphere:

Mars has a very thin atmosphere which is composed of 96% carbon dioxide, 1.93% argon and 1.89% nitrogen, along with traces of oxygen and water. The atmosphere is quite dusty, containing particulates that measure 1.5 micrometers in diameter, which is what gives the Martian sky its tawny color when seen from the surface. Mars’ atmospheric pressure ranges from 0.4 to 0.87 kPa, which is the equivalent of about 1% of Earth’s at sea level.

This image illustrates possible ways methane might get into Mars’ atmosphere and also be removed from it. Credit: NASA/JPL-Caltech/SAM-GSFC/Univ. of Michigan

Because of this thin atmosphere, and its greater distance from the Sun, the surface temperature of Mars is much colder than what we experience here on Earth. The planet’s average temperature is -46 °C (-51 °F), with a low of -143 °C (-225.4 °F) during the winter at the poles, and a high of 35 °C (95 °F) during summer and midday at the equator.

Due to the extreme lows in temperature at the poles, 25-30% of the carbon dioxide in the atmosphere freezes and becomes dry ice that is deposited on the surface. While the polar ice caps are predominantly water, the Martian North Pole has a layer of dry ice measuring one meter thick in winter, while the South Pole is covered by a permanent layer that is eight meters deep.

Trace amounts of methane and ammonia have also been detected in the Martian atmosphere. In the case of the former, it has an estimated concentration of about 30 parts per billion (ppb), though the Curiosity rover detected a “tenfold spike” on December 16th, 2014. This detection was likely localized, and the source remains a mystery. Similarly, the source of ammonia is unclear, though volcanic activity has been suggested as a possibility.

Meteorological Phenomena:

Mars is also famous for its intense dust storms, which can range from small tornadoes to planet-wide phenomena. Instances of the latter coincide with dust being blown into the atmosphere, causing it to be heated up from the Sun. The warmer dust-filled air rises and the winds get stronger, creating storms that can measure up to thousands of kilometers in width and last for months at a time. When they get this large, they can actually block most of the surface from view.

Image capturing an active dust storm on Mars. Image credits: NASA/JPL-Caltech/MSSS

Due to its thin atmosphere, low temperatures and lack of a magnetosphere, liquid precipitation (i.e. rain) does not take place on Mars. Basically, solar radiation would cause any liquid water in the atmosphere to disassociate into hydrogen and oxygen. And because of the cold and thin atmosphere, there is simply not enough liquid water on the surface to maintain a water cycle.

Occasionally, however, thin clouds do form in the atmosphere and precipitation falls in the form of snow. This consists primarily ofcarbon dioxide snow, which has been observed in the polar regions. However, small traces of frozen clouds carrying water have also been observed in Mars’ upper atmosphere in the past, producing snow that is restricted to high altitudes.

One such instance was observed on September 29th, 2008, when the Phoenix lander took pictures of snow falling from clouds that were 4 km (2.5 mi) above its landing site near the Heimdal Crater. However, data collected from the lander indicated that the precipitation vaporized before it could reach the ground.

Aurorae on Mars:

Auroras have also been detected on Mars, which are also the result of interaction between magnetic fields and solar radiation. While Mars has little magnetosphere to speak of, scientists determined that aurorae observed in the past corresponded to an area where the strongest magnetic field is localized on the planet. This was concluded by analyzing a map of crustal magnetic anomalies compiled with data from Mars Global Surveyor.

Mars has magnetized rocks in its crust that create localized, patchy magnetic fields (left). In the illustration at right, we see how those fields extend into space above the rocks. At their tops, auroras can form. Credit: NASA

A notable example is the one that took place on August 14th, 2004, and which was spotted by the SPICAM instrument aboard the Mars Express. This aurora was located in the skies above Terra Cimmeria – at geographic coordinates 177° East, 52° South – and was estimated to be quite sizable, measuring 30 km across and 8 km high (18.5 miles across and 5 miles high).

More recently, an aurora was observed on Mars by the MAVENmission, which captured images of the event on March 17th, 2015, just a day after an aurora was observed here on Earth. Nicknamed Mars’ “Christmas lights”, they were observed across the planet’s mid-northern latitudes and (owing to the lack of oxygen and nitrogen in Mars’ atmosphere) were likely a faint glow compared to Earth’s more vibrant display.

To date, Mars’ atmosphere, climate and weather patterns have been studied by dozens of orbiters, landers, and rovers, consisting of missions by NASA, Roscomos, as well as the European Space Agency and Indian federal space program. These include the Mariner 4probe, which conducted the first flyby of Mars – a two-day operation that took place between July 14th and 15th, 1965.

The crude data it obtained was expanded on by the later laterMariner 6 and 7 missions (which conducted flybys in 1969). This was followed by the Viking 1 and 2 missions, which reached Mars in 1976 and became the first spacecraft to land on the planet and send back images of the surfaces.

 

Since the turn of the century, six orbiters have been placed in orbit around Mars to gather information on its atmosphere – 2001 Mars Odyssey, Mars Express, Mars Reconnaissance Orbiter, MAVEN, Mars Orbiter Mission and ExoMars Trace Gas Orbiter. These have been complimented by rover and lander missions like Pheonix, Spirit and Opportunity, and Curiosity.

In the future, several additional missions are scheduled to reach the Red Planet, which are expected to teach us even more about its atmosphere, climate and weather patterns. What we find will reveal much about the planet’s deep past, its present condition, and perhaps even help us to build a future there.

We have written many interesting articles about Martian weather here at Universe Today. Here’s Mars Compared to Earth, It Only Happens on Mars: Carbon Dioxide Snow is Falling on the Red Planet,Snow is Falling from Martian Clouds, Surprise! Mars has Auroras Too! and NASA’s MAVEN Orbiter Discovers Solar Wind Stripped Away Mars Atmosphere Causing Radical Transformation.

For more information, check out this NASA article about how space weather affects Mars.

Finally, if you’d like to learn more about Mars in general, we have done several podcast episodes about the Red Planet at Astronomy Cast. Episode 52: Mars, and Episode 91: The Search for Water on Mars.

Sources: