Tag: solar wind

Touching the Sun

An illustration of NASA’s Parker Solar Probe flying past the sun. The spacecraft has a carbon-carbon heat shield (carbon fibers in a carbon matrix) that can protect it from temperatures of up to 2500 F, about the melting point of steel.  (NASA’s Goddard Space Flight Center)

The Parker Solar Probe is the stuff of superlatives and marvels.

Later this week, it will pass but 5.3 million miles from the sun — much closer than Mercury or any other spacecraft  have ever come — and it will be traveling at a top speed of 101 miles per second, the fastest human-made object ever created.

It’s designed to withstand temperatures of 2,500 degrees Fahrenheit and solar radiation 475 times the intensity at Earth orbit.

And as it reaches its perihelion, or closest pass of this orbit, it will be on only its 10th of 24 planned progressively closer solar passes.  In the years ahead, it will ultimately skim into the upper corona, the atmosphere of charged and unimaginably hot plasma that surrounds the sun and other stars.  The Parker Probe will, quite literally, touch the sun.

Something rather awe-inspiring to think about this coming Sunday, when the next pass takes place.

The mission, however, surely does not have record-setting as its goal.  Rather, those records are necessary to achieve the scientific goals — to fly close enough to the sun to understand how and where the gravity-defying force of the “solar wind” originates; to determine the structure and dynamics of the magnetic fields and switchbacks that are hotly debated as a possible source of that solar wind; and to resolve the mystery of why the sun’s corona is unexpectedly hotter than the solar “surface” below it.

“Parker Solar Probe is already telling us many important things about the sun that we didn’t know,” said Nour Raouafi, Parker Solar Probe project scientist at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland.  “We are definitely getting closer to understanding some of the big questions we had before, such as the source of the solar wind.  But we have to be mindful that in whatever we find, the Sun is always changing.”

And incidently, he said, more than 99.9 percent of all the matter in our solar system is in and around the sun.

 

Solar wind activity at different scales as imaged by the Parker Probe’s Wide-field Imager (WISPR) instrument earlier this year during.
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The Stellar Side of The Exoplanet Story

K2-33b, shown in this illustration, is one of the youngest exoplanets detected to date. It makes a complete orbit around its star in about five days. Credits: NASA/JPL-Caltech

K2-33b, shown in this illustration, is one of the youngest exoplanets detected to date. It makes a complete orbit around its star in about five days, and as a result its characteristics are very much determined by its host. (NASA/JPL-Caltech)

 

When it comes to the study of exoplanets, it’s common knowledge that the host stars don’t get much respect.

Yes, everyone knows that there wouldn’t be exoplanets without stars, and that they serve as the essential background for exoplanet transit observations and as the wobbling object that allows for radial velocity measurements that lead to new exoplanets discoveries.

But stars in general have been seen and studied for ever, while the first exoplanet was identified only 20-plus years ago.  So it’s inevitable that host stars have generally take a back seat to the compelling newly-found exoplanets that orbit them.

As the field of exoplanet studies moves forward, however, and tries to answer questions about the characteristics of the planets and their odds of being habitable, the perceived importance of the host stars is on the rise.

The logic:  Stars control space weather, and those conditions produce a space climate that is conducive or not so conducive to habitability and life.

Space weather consists of a variety of enormously energetic events ranging from solar wind to solar flares and coronal mass ejections, and their characteristics are defined by the size, variety and age of the star.  It is often said that an exoplanet lies in a “habitable zone” if it can support some liquid water on its surface, but absent some protection from space weather it will surely be habitable in name only.

A recognition of this missing (or at least less well explored) side of the exoplanet story led to the convening of a workshop this week in New Orleans on “The Impact of Exoplanetary Space Weather On Climate and Habitability.”

“We’re really just starting to detect and understand the secret lives of stars,”  said Vladimir Airapetian, a senior scientist at the Goddard Space Flight Center.  He organized the highly interdisciplinary workshop for the Nexus for Exoplanet Space Studies (NExSS,) a NASA initiative.

“What has become clear is that a star affects and actually defines the character of a planet orbiting around it,” he said.  “And now we want to look at that from the point of view of astrophysicists, heliophysicists, planetary scientists and astrobiologists.”

William Moore, principal investigator for a NASA-funded team also studying how host stars affect their exoplanets, said the field was changing fast and that “trying to understand those (space weather) impacts has become an essential task in the search for habitable planets.”… Read more

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