Starship Asterisk*

heehaw wrote: ↑Mon Apr 09, 2018 9:49 am
Escape velocity from the surface of the sun is 274 m/s2 (here on earth, we only need 9.8 m/s2 to escape): and yet despite that, the sun successfully launches millions of tons of matter each day from its surface, sending that matter out of the solar system at 400 km/s and sometimes causing electrical problems here on Earth.

neufer wrote: ↑Mon Apr 09, 2018 1:43 pm

heehaw wrote: ↑Mon Apr 09, 2018 9:49 am
These two characteristics in combination result in escape velocities of 617.7 km/s and 11.186 km/s respectively.

Wow! Thanks a million for the elucidation, neufer! Of course it really brings out how incredible it is that the sun can manage this, just using magnetic fields (and considering that both earth and sun have average magnetic fields, as I recall, about 1 gauss or so. Sunspots, much larger.)

heehaw wrote: ↑Mon Apr 09, 2018 2:52 pm Wow! Thanks a million for the elucidation, neufer! Of course it really brings out how incredible it is that the sun can manage this, just using magnetic fields (and considering that both earth and sun have average magnetic fields, as I recall, about 1 gauss or so. Sunspots, much larger.)

neufer wrote: ↑Mon Apr 09, 2018 1:43 pm

heehaw wrote: ↑Mon Apr 09, 2018 9:49 am
Escape velocity from the surface of the sun is 274 m/s2 (here on earth, we only need 9.8 m/s2 to escape): and yet despite that, the sun successfully launches millions of tons of matter each day from its surface, sending that matter out of the solar system at 400 km/s and sometimes causing electrical problems here on Earth.

274 m/s² and 9.8 m/s², of course, just represent the surface gravity.

Surface gravity drops off in proportion to the body's radius ... hence, much more slowly for the Sun than the Earth.

These two characteristics in combination result in escape velocities of 617.7 km/s and 11.186 km/s respectively.

De58te wrote: ↑Mon Apr 09, 2018 3:00 pm
Just think. We living in the past 4 or 5 decades are the first humans in all of the past million years to have seen that (in addition to seeing a man walk on the Moon). Not even Albert Einstein could have seen that! (Unless he had eyes with 200/20 Eagle vision.)

https://en.wikipedia.org/wiki/Solar_eclipse_of_July_28,_1851 wrote:

First solar eclipse Daguerreotype: July 28, 1851

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<<The corona is normally invisible due to the brightness of the solar disc, but becomes visible from earth during a total eclipse. Until the twentieth century, solar eclipses provided the only opportunity for scientists to observe and study the sun's corona. With the development of photography during the first half of the nineteenth century, it became theoretically possible to record a still image of the sun during a total eclipse. A variety of processes were used for early photographs, of which the most successful was the Daguerreotype.

Photographing a rare event such as a total eclipse posed unique challenges for early photography, including the extreme contrast between the corona and the dark shadow of the moon, as well as the unusual angle to which photographic equipment had to be oriented. Prior to the eclipse of July 28, 1851, no properly exposed photograph of the solar corona had yet been produced. For this occasion, the Royal Prussian Observatory at Königsberg (now Kaliningrad, Russia) commissioned one of the city's most skilled daguerreotypists, Johann Julius Friedrich Berkowski, to record a still image of the event. The observers attached a small six-centimeter refracting telescope to a 15.8 centimeter Fraunhofer heliometer, and Berkowski made an eighty-four second exposure shortly after the beginning of totality.

Among the other observers were British astronomers Robert Grant and William Swan, and Austrian astronomer Karl Ludwig von Littrow. They deduced that prominences were part of the sun, because the moon was seen to cover and uncover them as it moved in front of the sun.>>

https://en.wikipedia.org/wiki/Coronagraph wrote:

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<<The coronagraph was introduced in 1931 by the French astronomer Bernard Lyot; since then, coronagraphs have been used at many solar observatories. Coronagraphs operating within Earth's atmosphere suffer from scattered light in the sky itself, due primarily to Rayleigh scattering of sunlight in the upper atmosphere. At view angles close to the Sun, the sky is much brighter than the background corona even at high altitude sites on clear, dry days. During a total solar eclipse, the Moon acts as an occluding disk and any camera in the eclipse path may be operated as a coronagraph until the eclipse is over. More common is an arrangement where the sky is imaged onto an intermediate focal plane containing an opaque spot; this focal plane is reimaged onto a detector. Another arrangement is to image the sky onto a mirror with a small hole: the desired light is reflected and eventually reimaged, but the unwanted light from the star goes through the hole and does not reach the detector. Either way, the instrument design must take into account scattering and diffraction to make sure that as little unwanted light as possible reaches the final detector. Lyot's key invention was an arrangement of lenses with stops, known as Lyot stops, and baffles such that light scattered by diffraction was focused on the stops and baffles, where it could be absorbed, while light needed for a useful image missed them.

The High Altitude Observatory's Mark IV Coronagraph on top of Mauna Loa, use polarization to distinguish sky brightness from the image of the corona: both coronal light and sky brightness are scattered sunlight and have similar spectral properties, but the coronal light is Thomson-scattered at nearly a right angle and therefore undergoes scattering polarization, while the superimposed light from the sky near the Sun is scattered at only a glancing angle and hence remains nearly unpolarized.>>

BDanielMayfield wrote: ↑Mon Apr 09, 2018 4:11 pm

neufer wrote: ↑Mon Apr 09, 2018 1:43 pm

heehaw wrote: ↑Mon Apr 09, 2018 9:49 am
Escape velocity from the surface of the sun is 274 m/s2 (here on earth, we only need 9.8 m/s2 to escape): and yet despite that, the sun successfully launches millions of tons of matter each day from its surface, sending that matter out of the solar system at 400 km/s and sometimes causing electrical problems here on Earth.

274 m/s² and 9.8 m/s², of course, just represent the surface gravity.

Surface gravity drops off in proportion to the body's radius ... hence, much more slowly for the Sun than the Earth.

These two characteristics in combination result in escape velocities of 617.7 km/s and 11.186 km/s respectively.

So, the mass of the sun is not exactly constant. Mass is lost due to the solar wind, solar storms producing Coronal Mass Ejections, and even fusion in the core converting mass into energy. (Mass also is gained occasionally whenever a comet or an asteroid hits the sun.)

I realize that such changes are very very small when conpared to the enormous mass of the sun, but even small effects can add up over great spans of time. What is the average rate of change in the sun's mass over time? How much mass is expected to be lost in the next billion years?

Bruce

Chris Peterson wrote: ↑Mon Apr 09, 2018 4:25 pm
The Sun loses about 1.5 million tons of material per second in the form of solar wind, and about 4 million tons per second to fusion. At that rate, it would take about 15 billion years to lose 1% of its mass.

As small as this mass loss is, it results in a measurable increase in the size of Earth's orbit, about 15 mm per year. But this increase doesn't produce any significant effects, even over billions of years.