Saturday, August 27, 2016

The study of Jupiter and Jupiter-like planets

Astronomers say that in our galaxy alone, a billion or more such Jupiter-like worlds could be orbiting stars other than our sun. And we can use them to gain a better understanding of our solar system and our galactic environment, including the prospects for finding life.

It turns out the inverse is also true -- we can turn our instruments and probes to our own backyard, and view Jupiter as if it were an exoplanet to learn more about those far-off worlds. The best-ever chance to do this is now, with Juno, a NASA probe the size of a basketball court, which arrived at Jupiter in July to begin a series of long, looping orbits around our solar system's largest planet. Juno is expected to capture the most detailed images of the gas giant ever seen. And with a suite of science instruments, Juno will plumb the secrets beneath Jupiter's roiling atmosphere.

It will be a very long time, if ever, before scientists who study exoplanets -- planets orbiting other stars -- get the chance to watch an interstellar probe coast into orbit around an exo-Jupiter, dozens or hundreds of light-years away. But if they ever do, it's a safe bet the scene will summon echoes of Juno.

"The only way we're going to ever be able to understand what we see in those extrasolar planets is by actually understanding our system, our Jupiter itself," said David Ciardi, an astronomer with NASA's Exoplanet Science Institute at Caltech.

Juno's detailed examination of Jupiter could provide insights into the history, and future, of our solar system. The tally of confirmed exoplanets so far includes hundreds in Jupiter's size-range, and many more that are larger or smaller.

The so-called hot Jupiters acquired their name for a reason: They are in tight orbits around their stars that make them sizzling-hot, completing a full revolution -- the planet's entire year -- in what would be a few days on Earth. And they're charbroiled along the way.

But why does our solar system lack a "hot Jupiter?" Or is this, perhaps, the fate awaiting our own Jupiter billions of years from now -- could it gradually spiral toward the sun, or might the swollen future sun expand to engulf it?

Not likely, Ciardi says; such planetary migrations probably occur early in the life of a solar system.

"In order for migration to occur, there needs to be dusty material within the system," he said. "Enough to produce drag. That phase of migration is long since over for our solar system."

Jupiter itself might already have migrated from farther out in the solar system, although no one really knows, he said.

If Juno's measurements can help settle the question, they could take us a long way toward understanding Jupiter's influence on the formation of Earth -- and, by extension, the formation of other "Earths" that might be scattered among the stars.

"Juno is measuring water vapor in the Jovian atmosphere," said Elisa Quintana, a research scientist at the NASA Ames Research Center in Moffett Field, Calif. "This allows the mission to measure the abundance of oxygen on Jupiter. Oxygen is thought to be correlated with the initial position from which Jupiter originated."

Measuring the water is a key step in understanding how and where Jupiter formed.

"If Juno detects a high abundance of oxygen, it could suggest that the planet formed farther out," Quintana said.

A probe dropped into Jupiter by NASA's Galileo spacecraft in 1995 found high winds and turbulence, but the expected water seemed to be absent. Scientists think Galileo's one-shot probe just happened to drop into a dry area of the atmosphere, but Juno will survey the entire planet from orbit.

Where Jupiter formed, and when, also could answer questions about the solar system's "giant impact phase," a time of crashes and collisions among early planet-forming bodies that eventually led to the solar system we have today.

"It definitely was a violent time," Quintana said. "There were collisions going on for tens of millions of years. For example, the idea of how the moon formed is that a proto-Earth and another body collided; the disk of debris from this collision formed the moon. And some people think Mercury, because it has such a huge iron core, was hit by something big that stripped off its mantle; it was left with a large core in proportion to its size.

"For a long time, people thought Jupiter was essential to habitability because it might have shielded Earth from the constant influx of impacts [during the solar system's early days] which could have been damaging to habitability," she said. "What we've found in our simulations is that it's almost the opposite. When you add Jupiter, the accretion times are faster and the impacts onto Earth are far more energetic. Planets formed within about 100 million years; the solar system was done growing by that point," Quintana said.

"If you take Jupiter out, you still form Earth, but on timescales of billions of years rather than hundreds of millions. Earth still receives giant impacts, but they're less frequent and have lower impact energies," she said.

Another critical Juno measurement that could shed new light on the dark history of planetary formation is the mission's gravity science experiment. Changes in the frequency of radio transmissions from Juno to NASA's Deep Space Network will help map the giant planet's gravitational field.

Knowing the nature of Jupiter's core could reveal how quickly the planet formed, with implications for how Jupiter might have affected Earth's formation.

And the spacecraft's magnetometers could yield more insight into the deep internal structure of Jupiter by measuring its magnetic field.

"We don't understand a lot about Jupiter's magnetic field," Ciardi said. "We think it's produced by metallic hydrogen in the deep interior. Jupiter has an incredibly strong magnetic field, much stronger than Earth's."

Mapping Jupiter's magnetic field also might help pin down the plausibility of proposed scenarios for alien life beyond our solar system.

Earth's magnetic field is thought to be important to life because it acts like a protective shield, channeling potentially harmful charged particles and cosmic rays away from the surface.

"If a Jupiter-like planet orbits its star at a distance where liquid water could exist, the Jupiter-like planet itself might not have life, but it might have moons which could potentially harbor life," he said.

An exo-Jupiter's intense magnetic field could protect such life forms, he said.

Juno's findings will be important not only to understanding how exo-Jupiters might influence the formation of exo-Earths, or other kinds of habitable planets. They'll also be essential to the next generation of space telescopes that will hunt for alien worlds. The Transiting Exoplanet Survey Satellite will conduct a survey of nearby bright stars for exoplanets beginning in June 2018, or earlier. The James Webb Space Telescope, expected to launch in 2018, and WFIRST (Wide-Field Infrared Survey Telescope), with launch anticipated in the mid-2020s, will attempt to take direct images of giant planets orbiting other stars.

"We're going to be able to image planets and get spectra," or light profiles from exoplanets that will reveal atmospheric gases, Ciardi said. Juno's revelations about Jupiter will help scientists to make sense of these data from distant worlds.

"Studying our solar system is about studying exoplanets," he said. "And studying exoplanets is about studying our solar system. They go together."

Monday, August 22, 2016

Air Canada brings Olympic athletes home

Air Canada will begin flying members of Canada's Olympic team back to Canada on Monday from the Rio 2016 Olympic Games, with flights arriving at Toronto Pearson airport early Tuesday morning.

The athletes will return to Toronto on Tuesday on flight Air Canada AC091 from Sao Paulo due to arrive at 5:40 a.m. and Air Canada AC1099 due to arrive at 5:15 a.m. from Rio de Janeiro. More athletes and team members will arrive on Wednesday with Air Canada flight AC091 due to land at 5:00 a.m. and Air Canada flight AC099 from Rio de Janeiro at 5:15 a.m.

In total, Air Canada transported approximately 690 athletes, coaches and support staff with the Canadian Team to Rio.

US cargo ship departure from International Space Station

After delivering almost 5,000 pounds of supplies, experiments and equipment - including a docking adapter for future American commercial crew spacecraft - a SpaceX Dragon cargo craft is set to leave the International Space Station Friday.

SpaceX's Commercial Resupply Service-9 mission arrived on station July 20. The Dragon spacecraft will be detached from the Earth-facing port of the Harmony module using the station's Canadarm 2 robotic arm. Robotics controllers will send commands to maneuver the spacecraft into place before it's released by Expedition 48 Flight Engineers Kate Rubins of NASA and Takuya Onishi of the Japan Aerospace Exploration Agency at 6:10 a.m. EDT.

The spacecraft will move to a safe distance from the station and fire its engines at 10:56 a.m. EDT to drop out of orbit and descend back to Earth. A parachute-assisted splashdown in the Pacific is expected at 11:47 a.m. EDT about 326 miles west of Baja California.

A recovery team will retrieve the capsule and about 3,000 pounds of cargo and experiments for researchers and investigators.

In the event of adverse weather conditions in the Pacific, the backup departure and splashdown date is Sunday.

US spacewalk will work on space station cooling system

On Sept. 1, two NASA astronauts will spacewalk outside the International Space Station for the second time in less than two weeks.

The six-and-a-half hour spacewalk is scheduled to begin about 8 a.m. EDT.

Working on the port side of the orbiting complex's backbone, or truss, Expedition 48 Commander Jeff Williams and Flight Engineer Kate Rubins of NASA will retract a thermal radiator that is part of the station's cooling system. The radiator is a backup that had been deployed previously as part of an effort to fix an ammonia coolant leak. They'll also tighten struts on a solar array joint, and install the first of several enhanced high-definition television cameras that will be used to monitor activities outside the station, including the comings and goings of visiting cargo and crew vehicles.

This will be the 195th spacewalk in support of space station assembly and maintenance, the fifth of Williams' career and the second for Rubins. As was the case for their first spacewalk together Aug. 19, Williams will be designated as extravehicular crew member 1 (EV1), wearing a spacesuit with a red stripe, while Rubins will be EV2, wearing a suit with no stripes.

Arianespace ready to launch two Intelsat satellites

Arianespace's fourth Ariane 5 flight of 2016 has been given the "green light" for liftoff on Wednesday following Monday's successful launch readiness review, which was conducted in French Guiana, South America.

The approval also clears the Ariane 5 rocket for Tuesday's rollout from the Final Assembly Building to the ELA-3 launch zone, where it is scheduled for liftoff on Wednesday.

Designated Flight VA232, the mission has an estimated payload lift performance of 10,735 kilograms (23,666 pounds). The rocket will carry Intelsat 33e and Intelsat 36 into space.

Intelsat 33e is to be deployed first during the 41-minute flight sequence and will operate from an orbital position of 60 degrees East. Built by Boeing using a 702MP spacecraft platform, it is the second satellite in Intelsat's next-generation high-throughput Intelsat EpicNG series - joining Intelsat 29e, which was launched by Arianespace aboard another Ariane 5 in January.

Intelsat 36 will be the second passenger released by the Ariane 5. It was manufactured by Space Systems Loral based on the company's 1300 platform, and will operate from the 68.5 degrees East orbital position - where Intelsat 36 will be co-located with the Intelsat 20 satellite launched by Arianespace in August 2012.