How Far Away Is It - 04 - Comets and the Heliosphere (4K)

the Sun is moving through the Galactic medium like a ship in the ocean and we're just tagging along as we discussed earlier the Sun is a thermonuclear fireball that continuously ejects large quantities of high energetic particles into space this is the solar wind and it goes out in all directions the extent of the solar wind defines the final frontier of the influence of the Sun it's called the heliosphere the solar winds strength dies down as it spreads over ever-increasing volumes of space as it approaches the strength of the interstellar wind coming from the rest of the Milky Way its motion slows down abruptly this is called the termination shock beyond this is a transitional region called a heliosheath that terminates at the outermost edge of the heliosphere called the heliopause and like ocean water being pushed aside by the bow of a great ship the Sun with its solar wind does the same in the Galactic medium that's why they call the final boundary the bow shock this marks the final extent to the solar wind and defines the outer limits of the heliosphere [Music] unlike the other objects in the solar system that can be seen and triangulated to determine how far away they are the only way to find out how far away the termination and bow shocks are and therefore calculate the full size of the solar system is to go there measure which way the wind is blowing and report back how far you've gone this is exactly what Voyager 1 and Voyager 2 have done launched in 1977 both spacecraft have passed through the termination shock Voyager 1 crossed at 94 astronomical units in December 2004 Voyager 2 crossed at 84 astronomical units in August 2007 so we see that the boundary is not exactly a sphere as of October 2017 both voyagers are deep into the heliosheath after 40 years their instruments still report on cosmic rays charged particles magnetic fields and plasma waves when they detect a change in the direction of the wind we'll know that they have entered interstellar space they are expected to have enough energy to continue reporting through 2020 so there is still a chance we'll see it happen recent magnetic field data from the Voyager probes Cassini and ibex the interstellar boundary Explorer mission indicate that the heliosphere may be more rounded than previously thought if correct tail we see here will be replaced by the interstellar medium research is ongoing in this area NASA's Godard Space Flight Center in cooperation with international partners manages a fleet of spacecraft monitoring all aspects of the heliosphere this fleet is called sentinels of the heliosphere the grey mesh around the earth that you see is called the magnetosphere it's the Earth's magnetic field pushed back by the solar wind it's critical for life on Earth because it routes charged particles in the wind around the earth instead of lending it bombard us head-on that makes it very important for us to understand here's the near-earth fleet is monitoring solar activity and orbiting Earth every 92 minutes [Music] [Music] now we are taking a look at the geospatial eat that orbits deep into and around magnetosphere cluster is a group of four satellites to fly in formation to measure the three-dimensional boundaries of the magnetosphere as it intersects with the solar wind gol conducts measurements of electrons and ions in the Earth's magnetotail that magnetosphere pushed back by the solar wind stereo a and B observed the Sun with images and particle detectors and they fly off the Earth's Sun line providing a three-dimensional view of solar activity watch they use the moon to set themselves apart at the best possible distance to view the heliosphere here we see the l1 Fleet orbiting the Lagrange point number one between the Earth and the Sun l1 is the point between the Earth and the Sun where the gravitational pull is approximately equal in both directions spacecraft can orbit this location for continuous coverage of the Sun out here there is no magnetosphere so a good look at the solar wind as possible ace measures the composition and characteristics of the solar wind wind measures particle flows and fields in the solar wind Soho it's a famous satellite that studies the Sun from its deep core to the outer corona and the solar wind here we see the theme asleep of five satellites that study how magnetospheric instabilities produced the aurora borealis [Music] helio pause fleet is Voyager 1 and Voyager 2 Voyager 1 has traveled the farthest at a hundred and forty astronomical units that's a hundred and forty times further away from the Sun than we are it takes light almost 19 and a half hours to reach Voyager one here's a solar storm that erupted on August 21st 2012 it's like the one on October 14th 2014 that's Soho and other spacecraft tracked across the solar system this kind of storm is called a coronal mass ejection or CME for short CME's are billion ton clouds of solar plasma launched by a single explosion a typical velocity is around 300 kilometers per second that's 186 miles per second this 2014 CME washed over spacecraft throughout the inner solar system including curiosity on Mars an DSA's rosetta orbiting comet 67p measuring these storms enables scientists to predict a CME's path and strength this is important because CMI's can disrupt communications and power systems on earth if we are not prepared these solar storms with their coronal mass ejections are responsible for the aurora borealis or northern lights and the Aurora Australis or Southern Lights here's a look at the aurora borealis and Aurora Australis taken from the space station the aurora lights were a mystery for most of man's existence it wasn't until our modern understanding of the magnetosphere by a satellite observations in the second half of the 20th century was combined with quantum mechanics developed in the first half of the 20th century that a real understanding was reached [Music] what happens is that the magnetosphere routes the solar wind charged particles along the Earth's magnetic field lines to the north and south polar regions there they collide with oxygen and nitrogen atoms in the thermosphere quantum mechanics explains how these collisions create light I'll take a minute to explain this because it's relevant for understanding how a star's light can tell us how far away the star is thanks to the work of Niels Bohr a Danish physicist we discovered that electrons attached to atoms occupy quantized discrete energy levels called shells the further the shell is from the nucleus the greater the energy level and the larger the quantum number and thanks to Albert Einstein we discovered that light was also quantized as photons and that they were created when electrons dropped from higher to lower energy levels sometimes referred to as taking a quantum leap and absorbed when a photon collides with an atom and drives an electron to a higher energy level in the case of the aurora the high velocity particles from the solar wind collide with the oxygen and nitrogen atoms in the thermosphere driving electrons in those atoms to higher energy levels when they drop back down photons are created for oxygen emissions we get mostly green light the most common Aurora's from nitrogen emissions we get mostly blue or red we'll go deeper into quantum mechanics and light at the beginning of our segment on distant stars the comet is a small solar system object made of a mixture of frozen water ammonia and various hydrocarbons such as methane when passing close to the Sun it heats up and begins to out gas and displays a visible atmosphere or coma and sometimes a tail the coma pushed back by the solar wind you can see the Jets in this close-up photo of comet Hartley 2 comet nuclei range from a few hundred metres to tens of kilometers across the coma and tail are much larger and if sufficiently bright may be seen from Earth without a telescope like this image of comet is o-n from ancient Greece to the middle of the 16th century comets were thought to be luminous vapours in the Earth's atmosphere here's a tapestry that illustrates the 1066 comet here's the great comet of 1577 as seen over Prague Tycho Brahe studied this very bright comet that shone in the night sky for 74 days he found that he could not see any parallax from his data he concluded that the comet must be at least six times further away from the earth than the moon this took it out of the Earth's atmosphere and started people thinking differently about comets and planets remember that the Ptolemais model had rotating spheres holding each planet in place Tycho's findings would have comets crashing through these crystals as you can imagine this tipped the scales in favor of the Copernican Sun centric model and left open the question about just what holes the Comets up using the great comet of 1680 Edmund Halley worked with Isaac Newton to find out if comets were subject to the same forces as Newton had proposed for the planets the data showed that the long elliptical paths of the Comets fit Newton's theory of gravity perfectly in 1705 Halle studied the recorded paths for the Comets of 1531 1607 and 1682 he proposed that they were all reappearances of the same comet and that it would be back again in 1758 it was this was a spectacular vindication of his bold conjecture and of Newton's gravitational theory for his success the comet was named after him Halley's Comet I saw it in 1986 his orbit goes out past Pluto and it won't be back again until 2060 one comets come at us from all directions and we have seen that they have two kinds of orbits long and short long period comets can take thousands of years and have unpredictable orbits here are a few of them sighting spring visited us in 2013 and 2014 and came very close to Mars Mars orbiters at the time detected hundreds of kilograms per hour of the Comets dust sighting spring won't be back for millions of years [Music] hell bob was one of the brightest comets in decades it was visible to the naked eye for 18 months that was twice as long as the previous record held by the great comet of 1811 El Bob is expected to be back in the year 43 85 Lovejoy 2014 approached earth 2 with it half the distance from the Sun it had traveled inbound for 11,000 years and it won't return for almost 20,000 more years [Music] short period comets also known as periodic comets take as few as 3 and as long as 200 years they are also much more predictable 67p has an orbital period of just under six and a half years at the end of this segment we'll be covering the Rosetta mission that landed a probe on this comet in 2014 Anke orbits the Sun in just three point three years it is thought to be the originator of several meteor showers here on earth and we have already discussed Halley's Comet my grandchildren will see it in 2061 the fact that there are two kinds of orbits long and short led to the idea that comets originate from two different places with the short period comets coming from the Kuiper belt and the longer period comets coming from a proposed area called the Oort cloud short period comets visit the Sun so often that they quickly evaporate vanishing in only a few hundred thousand years here's one that evaporated in the Sun's corona in July 2011 it was traveling at 644 kilometers per second that's 400 miles per second here we see it in time-lapse from the Solar Dynamics Observatory the comet enters on the right in this video in this second pass I've marked it along the way it starts out with the mass of an aircraft carrier and it's completely evaporated in 20 minutes by the searing heat of the Sun's corona they evaporate so quickly compared to the age of the solar system that we shouldn't see any left at all yet we routinely track dozens of them every year in 1951 Gerard Kuiper proposed that there must be a belt of icy bodies orbiting beyond Neptune that is the source for new comets it is much further away much larger and far less dense than the asteroid belt it starts at 30 astronomical units from the Sun and is 20 astronomical units wide 1992 qb1 was the first Kuiper belt object in 2002 a large KBO hundreds of kilometers in diameter named koala was found in 2004 KBO Sedna was discovered and we have seen the Pluto and Makemake our dwarf planet KBO's it is estimated that the Kuiper belt contains a hundred million comets in 1950 in order to explain long period orbits the Dutch astronomer Yan Oort proposed the existence of a cloud of comets between 5,000 and 55,000 units from the Sun other estimates haven't going out much further all estimates put the Oort cloud well outside the heliosphere Oort estimated that this reservoir contains a hundred billion comets maybe a trillion citing spring L Bob and Lovejoy 2014 are three of them no space probe has yet been sent to the area of the Oort cloud Voyager 1 in the heliosheath is traveling at 1.6 million kilometers per day that's a million miles per day it will take over 1,200 years just to reach the Oort cloud and over 12,000 years to pass through it so its existence will remain a theory for some time to come we'll end our segment on comets with a look at two of them that changed our thinking and our capabilities when it comes to these objects in 1994 the comet shoemaker-levy collided with Jupiter the first impact occurred at 2013 on July 16 when fragment a of the nucleus entered Jupiter's southern hemisphere at a speed of about 60 kilometers per second that's 37 miles per second instruments on the nearby Galileo spacecraft detected a fireball pluton that reached a height of almost 3,200 kilometers that's 2,000 miles remember that our atmosphere extends only a few hundred kilometers above us observers soon saw a huge dark spot after the first impact six thousand kilometers wide over the next six days 21 distinct impacts were observed with the largest occurring on July 18 this impact created a giant dark spot larger than the earth Jupiter absorbed them all the changes to the planet were dramatic but disappeared after a few months but if shoemaker-levy had hit the earth instead of Jupiter it would have wiped us out this highlighted for everyone the importance of understanding comets and asteroids and how to change their trajectory should we ever find one this size heading our way progress in this area has been made here's a close-up look at comet 67p its overall length is 5 kilometers and the larger of its two lobes is 4.1 kilometers wide that might not sound like much but here's what an object this size would look like if we placed it over a city like Toronto Canada European Space Agency launched the spacecraft Rosetta in 2004 its mission was to rendezvous with comet 67p deploy a lander called fillet to its surface and is fourth the comet as it orbits the Sun 10 years later on August 6th 2014 after getting several gravity assist velocity boosts and traveling 6.4 billion kilometers Rosetta rendezvous with 67p delay landed on the surface on November 12th becoming the first spacecraft to land on a comet here we see the Landers big bounce off the comet with these pictures captured by its orbiting mothership this is where it first landed you can see the before and after pictures where filler' made its mark but the harpoons that were meant to anchor it to the comet did not deploy it ended in the shade and lost its power but Rosetta continued to transmit for another two years before its power ran out as well at that point in September 2016 the Rosetta mission ended with a controlled impact into the comet here's the collision course into the comet from an altitude of around nineteen kilometers Rosetta targeted a region on the small lobe of the comet close to a region of active pits pits are of particular interest because they play an important role in a comet's activity transmissions continued up to the moment of impact the comet is now beyond the orbit of Jupiter and heading for the Kuiper belt it will return with Rosetta's wreckage on board in 2021 now that we have a feel for the size of the heliosphere the Kuiper belt and the Oort cloud let's review how far the main objects in our solar system are the Sun is 150 million kilometers away and a million earths could fit inside it Mars's orbit is half again as far away as that at 78 million kilometers from ours Jupiter the largest planet in the Solar System is 5.2 times further away from the Sun than the earth is that puts its orbit at 772 million kilometers away from ours the asteroid belt fits between the orbits of Mars and Jupiter Pluto's orbit in the Kuiper belt is 5.6 billion kilometres away we have seen that the Kuiper belt goes from four and a half billion kilometers out to seven and a half billion kilometers and the termination shock is 18 billion kilometres away and our estimate for the bow shock is that it's 19 billion kilometers away we have just seen that the Oort cloud starts much further away than that at 748 billion kilometers and extends out to eight point two trillion kilometers or more we have used direct measurement by going there triangulation and planetary parallax to calculate these solar system distances in our next segment on nearby stars will advance our cosmic distance ladder to cover how we know how far away it is to Proxima Centauri our nearest stellar neighbor

Channel: David Butler

Views: 510,074

Rating: 4.8574424 out of 5

Keywords: STEM, Heliosphere, Sentinels, solar wind, Borealis, Aurora Borealis, Comets, Kuiper Belt, Oort Cloud, Termination Shock, Heliopause, Heliosheath, SOHO, Magnetosphere, Australis, Halley’s Come, 67P, Solar System

Id: 1oDUN74yzuo

Length: 26min 56sec (1616 seconds)

Published: Tue Nov 21 2017