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Two Villanova University astrophysics professors led a research team that has discovered the long hidden physical properties of Polaris, popularly known as "The North Star." Until now, scientists' wide-ranging estimates of the star's distance from the Earth (322-520 light years), made determining its physical makeup difficult. But, equipped with precise distance measurements recently made by the European Space Agency's (ESA) Gaia Mission (447+/- 1.6 light years), the Villanova team has been able to determine Polaris's radius, intrinsic brightness, age and mass.
#ESA #Polaris #NorthStar
#ESA #Polaris #NorthStar
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Space | Hitting the Moon
What if you hit the Moon with a stone which a kid could comfortably hold in a fist? Well, it depends on how hard you hit it. If the stone aka piece of space debris is flying around at cometary speeds, it would hit hard enough to melt rock and make it shine brightly. Brightly enough to be seen all the way on Earth.
Yup, those flashes in the animation are rocks the size of walnuts. That small.
I'm feeling so happy about the 200 km of thin air and 10 km of thick air that prevent these things from hitting us on our heads hard enough to bury us instantly. After all, the Moon is in the same orbit as the Earth. Thank you, air, for burning up these things and saving us.
Thanks also to +Elizabeth Therese Niwel for sharing this wonderful find.
#space #moon #earth #meteoroid #ImpactCrater
What if you hit the Moon with a stone which a kid could comfortably hold in a fist? Well, it depends on how hard you hit it. If the stone aka piece of space debris is flying around at cometary speeds, it would hit hard enough to melt rock and make it shine brightly. Brightly enough to be seen all the way on Earth.
Yup, those flashes in the animation are rocks the size of walnuts. That small.
I'm feeling so happy about the 200 km of thin air and 10 km of thick air that prevent these things from hitting us on our heads hard enough to bury us instantly. After all, the Moon is in the same orbit as the Earth. Thank you, air, for burning up these things and saving us.
Thanks also to +Elizabeth Therese Niwel for sharing this wonderful find.
#space #moon #earth #meteoroid #ImpactCrater
Two lunar flashes light up darkened Moon
On 17 July 2018, an ancient lump from space thwacked into the Moon with enough energy to produce a brilliant flash of light. With another space rock seemingly in pursuit, a second flash lit up a different region of the Moon almost exactly 24 hours later (see GIF).
http://www.esa.int/spaceinimages/Images/2018/07/Two_lunar_flashes_GIF
Current estimates suggest these two impacting ‘meteoroids’ — fragments of asteroids and comets — were both about the size of a walnut. They likely originated from the Alpha Capricornids meteor shower — itself the result of Earth and the Moon passing through the dusty tail of comet 169P/NEAT.
For at least a thousand years people have claimed to witness short-lived phenomena occurring on the face of the Moon. By definition these transient flashes are hard to study, and determining their cause remains a challenge.
For this reason scientists are studying these ‘transient lunar phenomena’ with great interest, not only for what they can tell us about the Moon and its history, but also about Earth and its future.
The first systematic attempt to identify impact flashes began with CCD cameras dating back to 1997, and is continued today by the Moon Impacts Detection and Analysis System (MIDAS). With a series of telescopes endowed with high-sensitivity CCD video cameras, the MIDAS project is currently made up of three astronomical observatories across Spain.
Working together in coordination, these instruments identify rocks hitting the dark faces of the lunar surface.
Jose Maria Madiedo from MIDAS explains: “By studying meteoroids on the Moon we can determine how many rocks impact it and how often, and from this we can infer the chance of impacts on Earth.
In principle the upcoming July 2018 lunar eclipse should make it easier to observe any potential meteoroid impacts, but this will depend on how dark the Moon becomes. At MIDAS we observe impacts on the ‘dark side’ of the Moon, meaning impact flashes stand out against the dark lunar ground”.
Unlike the ‘far side’ of the Moon which always faces away from Earth, the dark side refers to any part of the Moon that is not currently illuminated by the Sun, although — such as during a crescent Moon — it may still be facing Earth.
Credit: ESA
Copyright: Moon Impacts Detection and Analysis System (MIDAS)/Jose Maria Madiedo
For mor, click on.
#TheMoon #ESA #MIDAS #Earth #ESO #SolarSystem #TheSun #AlphaCapricornidsMeteorShower #Meteorids #Meteors #Earth #NEAT #MeteoridsStudy #EarthScience #Space #Spacescience #SpaceObservations #MoonScience
On 17 July 2018, an ancient lump from space thwacked into the Moon with enough energy to produce a brilliant flash of light. With another space rock seemingly in pursuit, a second flash lit up a different region of the Moon almost exactly 24 hours later (see GIF).
http://www.esa.int/spaceinimages/Images/2018/07/Two_lunar_flashes_GIF
Current estimates suggest these two impacting ‘meteoroids’ — fragments of asteroids and comets — were both about the size of a walnut. They likely originated from the Alpha Capricornids meteor shower — itself the result of Earth and the Moon passing through the dusty tail of comet 169P/NEAT.
For at least a thousand years people have claimed to witness short-lived phenomena occurring on the face of the Moon. By definition these transient flashes are hard to study, and determining their cause remains a challenge.
For this reason scientists are studying these ‘transient lunar phenomena’ with great interest, not only for what they can tell us about the Moon and its history, but also about Earth and its future.
The first systematic attempt to identify impact flashes began with CCD cameras dating back to 1997, and is continued today by the Moon Impacts Detection and Analysis System (MIDAS). With a series of telescopes endowed with high-sensitivity CCD video cameras, the MIDAS project is currently made up of three astronomical observatories across Spain.
Working together in coordination, these instruments identify rocks hitting the dark faces of the lunar surface.
Jose Maria Madiedo from MIDAS explains: “By studying meteoroids on the Moon we can determine how many rocks impact it and how often, and from this we can infer the chance of impacts on Earth.
In principle the upcoming July 2018 lunar eclipse should make it easier to observe any potential meteoroid impacts, but this will depend on how dark the Moon becomes. At MIDAS we observe impacts on the ‘dark side’ of the Moon, meaning impact flashes stand out against the dark lunar ground”.
Unlike the ‘far side’ of the Moon which always faces away from Earth, the dark side refers to any part of the Moon that is not currently illuminated by the Sun, although — such as during a crescent Moon — it may still be facing Earth.
Credit: ESA
Copyright: Moon Impacts Detection and Analysis System (MIDAS)/Jose Maria Madiedo
For mor, click on.
#TheMoon #ESA #MIDAS #Earth #ESO #SolarSystem #TheSun #AlphaCapricornidsMeteorShower #Meteorids #Meteors #Earth #NEAT #MeteoridsStudy #EarthScience #Space #Spacescience #SpaceObservations #MoonScience
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Saturn's Shadow Magic | NASA Cassini
Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius about nine times that of Earth. It has only one-eighth the average density of Earth, but with its larger volume, Saturn is over 95 times more massive. Saturn is a gas giant because it is predominantly composed of hydrogen and helium. It lacks a definite surface, though it may have a solid core.
(Source: Wikipedia)
The Cassini spacecraft ended its mission on Sept. 15, 2017.
For more information about the Cassini-Huygens mission visit: https://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini
The Cassini-Huygens mission was a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, California, managed the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center was based at the Space Science Institute in Boulder, Colorado.
Credit: NASA/JPL-Caltech/SSI/Jason Major
Image Date: July 30, 2006
Release Date: June 31, 2018
+NASA Jet Propulsion Laboratory
+NASA Solar System Exploration
+European Space Agency, ESA
+Carolyn Porco
+Carolyn Porco Fan Page
#NASA #Astronomy #Science #Space #Saturn #Planet #Rings #SolarSystem #Exploration #Cassini #Spacecraft #JPL #California #UnitedStates #ESA #ASI #History #STEM #Education
Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius about nine times that of Earth. It has only one-eighth the average density of Earth, but with its larger volume, Saturn is over 95 times more massive. Saturn is a gas giant because it is predominantly composed of hydrogen and helium. It lacks a definite surface, though it may have a solid core.
(Source: Wikipedia)
The Cassini spacecraft ended its mission on Sept. 15, 2017.
For more information about the Cassini-Huygens mission visit: https://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini
The Cassini-Huygens mission was a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, California, managed the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center was based at the Space Science Institute in Boulder, Colorado.
Credit: NASA/JPL-Caltech/SSI/Jason Major
Image Date: July 30, 2006
Release Date: June 31, 2018
+NASA Jet Propulsion Laboratory
+NASA Solar System Exploration
+European Space Agency, ESA
+Carolyn Porco
+Carolyn Porco Fan Page
#NASA #Astronomy #Science #Space #Saturn #Planet #Rings #SolarSystem #Exploration #Cassini #Spacecraft #JPL #California #UnitedStates #ESA #ASI #History #STEM #Education
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Fast Stars and Rogue Planets in the Orion Nebula
Start with the constellation of Orion. Below Orion's belt is a fuzzy area known as the Great Nebula of Orion. In this nebula is a bright star cluster known as the Trapezium, marked by four bright stars near the image center. The newly born stars in the Trapezium and surrounding regions show the Orion Nebula to be one of the most active areas of star formation to be found in our area of the Galaxy.
In Orion, supernova explosions and close interactions between stars have created rogue planets and stars that rapidly move through space. Some of these fast stars have been found by comparing different images of this region taken by the Hubble Space Telescope many years apart. Many of the stars in the featured image, taken in visible and near-infrared light, appear unusually red because they are seen through dust that scatters away much of their blue light.
Image & info via APOD
https://apod.nasa.gov/apod/ap170321.html
Image Credit: NASA, ESA, Hubble
#NASA #ESA #Hubble #space #universe #science
Start with the constellation of Orion. Below Orion's belt is a fuzzy area known as the Great Nebula of Orion. In this nebula is a bright star cluster known as the Trapezium, marked by four bright stars near the image center. The newly born stars in the Trapezium and surrounding regions show the Orion Nebula to be one of the most active areas of star formation to be found in our area of the Galaxy.
In Orion, supernova explosions and close interactions between stars have created rogue planets and stars that rapidly move through space. Some of these fast stars have been found by comparing different images of this region taken by the Hubble Space Telescope many years apart. Many of the stars in the featured image, taken in visible and near-infrared light, appear unusually red because they are seen through dust that scatters away much of their blue light.
Image & info via APOD
https://apod.nasa.gov/apod/ap170321.html
Image Credit: NASA, ESA, Hubble
#NASA #ESA #Hubble #space #universe #science
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Symphony of stars: The science of stellar sound waves
We can’t hear it with our ears, but the stars in the sky are performing a concert, one that never stops. The biggest stars make the lowest, deepest sounds, like tubas and double basses. Small stars have high-pitched voices, like celestial flutes. These virtuosos don’t just play one "note" at a time, either — our own Sun has thousands of different sound waves bouncing around inside it at any given moment.
Understanding these stellar harmonies represents a revolution in astronomy. By "listening" for stellar sound waves with telescopes, scientists can figure out what stars are made of, how old they are, how big they are and how they contribute to the evolution of our Milky Way galaxy as a whole. The technique is called asteroseismology. Just as earthquakes (or Earth’s seismic waves) tell us about the inside of Earth, stellar waves — resulting in vibrations or "star quakes" — reveal the secret inner workings of stars.
NASA’s Kepler space telescope, now approaching the end of its mission, has been a key player in that revolution, delivering observations of waves in tens of thousands of stars since its 2009 launch. NASA’s Transiting Exoplanet Survey Satellite (TESS), which launched in April 2018, may observe sound waves in up to one million red giants — the massive, evolved stars that represent what our Sun will look like in about 5 billion years. While both Kepler and TESS are most famous for hunting for planets beyond our solar system (exoplanets), they are also powerful, sensitive tools for detecting stellar vibrations. And, the more we know about stars, the more we know about planets that orbit them.
"We are using seismology to provide an exquisite characterization of the host stars — and hence the planets — we’ve discovered," said William Chaplin, professor of astrophysics at the University of Birmingham, United Kingdom, who leads the Kepler’s asteroseismology effort for Sun-like stars.
What are these waves?
Like bubbles rising in a pot of boiling water, sound waves move through a star’s interior because of temperature changes. They begin in the star’s convection zone, which is the upper 30 percent of a star’s volume if it is similar to the Sun. Hot gas moves upward to the star’s surface, where it cools off and falls back down — though far more violently and turbulently than in your kitchen. Convection, this movement of heat rising and falling, creates waves that bounce around in the star in different ways.
A similar process happens on Earth: seismic waves, caused by convection, make plates on the planet’s surface move and bump up against one another, eventually leading to earthquakes. The Moon also has quakes, measured by instruments that NASA’s Apollo astronauts delivered. And NASA’s InSight lander, on its way to Mars, will be delving into the interior of Mars by measuring seismic waves there. But unlike on these planetary bodies, stellar sound waves are generated continuously by turbulence in the near-surface layers of stars.
Convection-driven waves cause the whole star to expand and contract, in effect ringing the star like a bell. So many waves propagate at once that the overall stellar surface jostles around like Jell-O, but so subtly that the motion would not be visible to the eye. In close-up images of our own Sun, we see the effects of waves as localized areas of brightening and dimming. These are distinct from the dark spots we know as sunspots on our Sun. Sunspots form in areas where the Sun’s magnetic field lines weaken the amount of energy brought to the surface, and represent temporarily cooler regions on the surface of the star.
Some waves ripple around the entire circumference of the star, while others dart right through the star’s core. The bigger the star, the longer it takes sound waves to travel in its interior. In the Sun, a typical wave completes one cycle in five minutes. Any given wave lasts a few days in Sun-like stars, but because new waves crop up all the time, stars are always vibrating. Red giants, which are dozens of times as big as the Sun, have lower-frequency waves that can propagate for weeks to months. By studying stars of various ages, scientists learn about what will happen to our own Sun as it gets older.
What are we measuring?
Because the Sun is the closest star to us, it’s not surprising that scientists first discovered stellar vibrations there. In 1962, a group of scientists led by Caltech physicist Robert Leighton noted "cells" of moving material at the Sun’s surface, associated with variations in surface brightness, while using the 60-foot solar tower at Mount Wilson Observatory near Los Angeles. Follow-up studies in the 1970s revealed that waves of different frequencies accounted for this behavior. By tracking the Sun’s waves, scientists realized in 1977 that our star’s convection zone ran much deeper than predicted. Since then, the field of helioseismology has gained a much better understanding of the Sun’s rotation and interior structure.
Most other stars are so far away that telescopes can only view them as single points of light, and directly seeing detailed surface features is impossible. The actual changes in a star’s overall brightness caused by sound waves are unimaginably small: about four parts in a million. Those subtle variations are the equivalent of turning your cell phone flashlight on and off in a room full of very bright spotlights, such as the ones that form the famous light beam at the Luxor Hotel and Casino in Las Vegas, said Jennifer van Saders, astronomer at the University of Hawaii. From afar, the building would still appear to emit one unchanging light, because the effect of the flickering flashlight is so subtle.
One way of picking out stellar vibrations uses a principle called the Doppler effect – that light coming toward the observer shifts more blue, and light moving away shifts more red. As the surface of the star moves, an instrument called a spectrograph picks up these shifts. A second method is to measure the overall brightness of light coming from the star over time, which is how Kepler and TESS work.
Subtle changes in brightness are hard to discern with ground-based telescopes because Earth’s atmosphere and weather activity get in the way, and because daylight interrupts observations. For continuous listening to the stellar orchestra, astronomers needed space telescopes. The Convection, Rotation and Planetary Transits (CoRoT) satellite, launched in 2006 and led by the French space agency (CNES), and Kepler, launched in 2009, were the pioneers in exploring helioseismology in an expanse of stars in greater detail than ever before.
"Kepler stares at these points of light and it watches them twinkle — not twinkle as they do here on Earth, because that’s the atmosphere causing them to twinkle — but twinkle because they’re actually changing brightness," van Saders said.
Stellar Mysteries
In its first four years, Kepler stared at one patch of sky and measured starlight every minute — the longest continuous observations ever of any stars. (In its current K2 mission, the spacecraft changes its field of view about every three months). This unique dataset, together with nearly six years of data from CoRoT, demonstrated that many stars in the galaxy do not have interiors like the Sun — even those only 20 to 30 percent more massive. The low voices of giant stars confirmed predictions about the interior structures of red giants for the first time.
"That’s what Kepler gave us — the ability to really test what’s going on in the interiors for stars that aren’t just the Sun," van Saders said.
Asteroseismology is also useful for measuring how the surface of a star rotates compared to its interior. While studying stellar sound waves, scientists also were surprised to learn that in one type of red giant, the core rotates rapidly while the surface rotates slowly. A 2012 study using Kepler data found three giant stars whose interiors spin 10 times faster than their surfaces. There’s much more work to be done in terms of creating models of the inner and outer portions of stars.
"Kepler really started to tell that story — TESS will do the census," said Tom Barclay, research scientist with the TESS mission at NASA’s Goddard Space Flight Center, Greenbelt, Maryland.
Scientists are still exploring how the Sun’s vibrations compare to stars with different masses and ages, and how that "ringing" will change as the Sun ages into a red giant. "This is one of the things we are trying to figure out, and that Kepler and TESS and other missions can help us understand," said Dan Huber, astronomer at the University of Hawaii, Honolulu.
Know thy star, know thy planet
Many important aspects of a planet — including size, age and whether or not it could support life – can only be determined from what scientists know about its host star.
When a planet passes in front of its star, Kepler detects this "transit" by measuring a sharp dip in the brightness of the star as the planet blocks some of its light (very different from the ripple-like quake signatures). The amount of dimming of the star’s light during a transit is related to the size of the planet relative to the size of the star. So, in order to calculate the planet’s diameter, scientists need the diameter of the star — something that they can determine using asteroseismology. Similarly, while a technique called radial velocity allows scientists to calculate a planet’s mass relative to its star’s mass, scientists must calculate the star’s mass to "weigh" the planet. Asteroseismology is a way to determine the mass.
"Knowing the size of the star is very important for actually knowing what the size of the planet is," Huber said.
Stellar vibrations also help scientists determine how old a star is, which will affect the environment of its planets. A young star is more likely to have violent outbursts, and its planets may still be shuffling around in their orbits. An older star has less frequent flare-ups, and its planets may be more stable.
"Getting precise estimates of ages is incredibly difficult, but this is something that asteroseismology is really well suited to," Chaplin said. "The ticking heartbeat of the star allows us to get precise measurements."
Galactic archaeology
The more stars astronomers can examine through seismology, the better they can map where the young and old stars are, and understand which regions of the Milky Way formed first. This is the science of galactic archaeology. By following the trails of vibrations in stars, like an interstellar Indiana Jones would, astronomers can reconstruct how our Milky Way formed.
"Much like digging through the archaeological site of an old city, you can look at what happened in each of those 'rooms' in our galaxy," said Steve Howell, head of the space and astrobiology division at NASA's Ames Research Center in California’s Silicon Valley.
TESS will record the vibrations of up to one million red giants. As it will do a survey of stars across the entire sky, it will in effect be listening in "surround sound." The European Space Agency’s Gaia mission, which recently released positions and distance indicators for more than one billion stars, offers a powerful addition to Kepler and TESS in charting the history of the galaxy. By calculating the ages of stars and determining how long they have been in the red giant phase, and knowing their distances, scientists will get a fuller picture of how the stars of the galaxy came together and how it is evolving.
While Kepler is running low on fuel and its mission will soon end, scientists will be using its data to make discoveries about the Milky Way’s stars for years to come. TESS will complement its predecessor’s detailed observations of the celestial orchestra, and continue unlocking mysteries as it listens to more of the grand ensemble of the galaxy.
By Elizabeth Landau,
NASA's Exoplanet Exploration Program
Read more, and listen to sounds at:
https://exoplanets.nasa.gov/news/1516/symphony-of-stars-the-science-of-stellar-sound-waves/
Image:
This artist’s concept shows how a few individual waves travel through a hypothetical star that has an orbiting planet.
Credit: Gabriel Perez Diaz /Instituto de Astrofisica de Canarias
#NASA #ESA #Science #Stars #StellarSoundWaves #TheSun #Sun #Space #TESS #MilkyWay #Galaxy #Kepler #SpaceTelescope #EarthsSeismicWaves #Planets #SpaceScience #RedGiants #GaiaMission #SpaceMissions
We can’t hear it with our ears, but the stars in the sky are performing a concert, one that never stops. The biggest stars make the lowest, deepest sounds, like tubas and double basses. Small stars have high-pitched voices, like celestial flutes. These virtuosos don’t just play one "note" at a time, either — our own Sun has thousands of different sound waves bouncing around inside it at any given moment.
Understanding these stellar harmonies represents a revolution in astronomy. By "listening" for stellar sound waves with telescopes, scientists can figure out what stars are made of, how old they are, how big they are and how they contribute to the evolution of our Milky Way galaxy as a whole. The technique is called asteroseismology. Just as earthquakes (or Earth’s seismic waves) tell us about the inside of Earth, stellar waves — resulting in vibrations or "star quakes" — reveal the secret inner workings of stars.
NASA’s Kepler space telescope, now approaching the end of its mission, has been a key player in that revolution, delivering observations of waves in tens of thousands of stars since its 2009 launch. NASA’s Transiting Exoplanet Survey Satellite (TESS), which launched in April 2018, may observe sound waves in up to one million red giants — the massive, evolved stars that represent what our Sun will look like in about 5 billion years. While both Kepler and TESS are most famous for hunting for planets beyond our solar system (exoplanets), they are also powerful, sensitive tools for detecting stellar vibrations. And, the more we know about stars, the more we know about planets that orbit them.
"We are using seismology to provide an exquisite characterization of the host stars — and hence the planets — we’ve discovered," said William Chaplin, professor of astrophysics at the University of Birmingham, United Kingdom, who leads the Kepler’s asteroseismology effort for Sun-like stars.
What are these waves?
Like bubbles rising in a pot of boiling water, sound waves move through a star’s interior because of temperature changes. They begin in the star’s convection zone, which is the upper 30 percent of a star’s volume if it is similar to the Sun. Hot gas moves upward to the star’s surface, where it cools off and falls back down — though far more violently and turbulently than in your kitchen. Convection, this movement of heat rising and falling, creates waves that bounce around in the star in different ways.
A similar process happens on Earth: seismic waves, caused by convection, make plates on the planet’s surface move and bump up against one another, eventually leading to earthquakes. The Moon also has quakes, measured by instruments that NASA’s Apollo astronauts delivered. And NASA’s InSight lander, on its way to Mars, will be delving into the interior of Mars by measuring seismic waves there. But unlike on these planetary bodies, stellar sound waves are generated continuously by turbulence in the near-surface layers of stars.
Convection-driven waves cause the whole star to expand and contract, in effect ringing the star like a bell. So many waves propagate at once that the overall stellar surface jostles around like Jell-O, but so subtly that the motion would not be visible to the eye. In close-up images of our own Sun, we see the effects of waves as localized areas of brightening and dimming. These are distinct from the dark spots we know as sunspots on our Sun. Sunspots form in areas where the Sun’s magnetic field lines weaken the amount of energy brought to the surface, and represent temporarily cooler regions on the surface of the star.
Some waves ripple around the entire circumference of the star, while others dart right through the star’s core. The bigger the star, the longer it takes sound waves to travel in its interior. In the Sun, a typical wave completes one cycle in five minutes. Any given wave lasts a few days in Sun-like stars, but because new waves crop up all the time, stars are always vibrating. Red giants, which are dozens of times as big as the Sun, have lower-frequency waves that can propagate for weeks to months. By studying stars of various ages, scientists learn about what will happen to our own Sun as it gets older.
What are we measuring?
Because the Sun is the closest star to us, it’s not surprising that scientists first discovered stellar vibrations there. In 1962, a group of scientists led by Caltech physicist Robert Leighton noted "cells" of moving material at the Sun’s surface, associated with variations in surface brightness, while using the 60-foot solar tower at Mount Wilson Observatory near Los Angeles. Follow-up studies in the 1970s revealed that waves of different frequencies accounted for this behavior. By tracking the Sun’s waves, scientists realized in 1977 that our star’s convection zone ran much deeper than predicted. Since then, the field of helioseismology has gained a much better understanding of the Sun’s rotation and interior structure.
Most other stars are so far away that telescopes can only view them as single points of light, and directly seeing detailed surface features is impossible. The actual changes in a star’s overall brightness caused by sound waves are unimaginably small: about four parts in a million. Those subtle variations are the equivalent of turning your cell phone flashlight on and off in a room full of very bright spotlights, such as the ones that form the famous light beam at the Luxor Hotel and Casino in Las Vegas, said Jennifer van Saders, astronomer at the University of Hawaii. From afar, the building would still appear to emit one unchanging light, because the effect of the flickering flashlight is so subtle.
One way of picking out stellar vibrations uses a principle called the Doppler effect – that light coming toward the observer shifts more blue, and light moving away shifts more red. As the surface of the star moves, an instrument called a spectrograph picks up these shifts. A second method is to measure the overall brightness of light coming from the star over time, which is how Kepler and TESS work.
Subtle changes in brightness are hard to discern with ground-based telescopes because Earth’s atmosphere and weather activity get in the way, and because daylight interrupts observations. For continuous listening to the stellar orchestra, astronomers needed space telescopes. The Convection, Rotation and Planetary Transits (CoRoT) satellite, launched in 2006 and led by the French space agency (CNES), and Kepler, launched in 2009, were the pioneers in exploring helioseismology in an expanse of stars in greater detail than ever before.
"Kepler stares at these points of light and it watches them twinkle — not twinkle as they do here on Earth, because that’s the atmosphere causing them to twinkle — but twinkle because they’re actually changing brightness," van Saders said.
Stellar Mysteries
In its first four years, Kepler stared at one patch of sky and measured starlight every minute — the longest continuous observations ever of any stars. (In its current K2 mission, the spacecraft changes its field of view about every three months). This unique dataset, together with nearly six years of data from CoRoT, demonstrated that many stars in the galaxy do not have interiors like the Sun — even those only 20 to 30 percent more massive. The low voices of giant stars confirmed predictions about the interior structures of red giants for the first time.
"That’s what Kepler gave us — the ability to really test what’s going on in the interiors for stars that aren’t just the Sun," van Saders said.
Asteroseismology is also useful for measuring how the surface of a star rotates compared to its interior. While studying stellar sound waves, scientists also were surprised to learn that in one type of red giant, the core rotates rapidly while the surface rotates slowly. A 2012 study using Kepler data found three giant stars whose interiors spin 10 times faster than their surfaces. There’s much more work to be done in terms of creating models of the inner and outer portions of stars.
"Kepler really started to tell that story — TESS will do the census," said Tom Barclay, research scientist with the TESS mission at NASA’s Goddard Space Flight Center, Greenbelt, Maryland.
Scientists are still exploring how the Sun’s vibrations compare to stars with different masses and ages, and how that "ringing" will change as the Sun ages into a red giant. "This is one of the things we are trying to figure out, and that Kepler and TESS and other missions can help us understand," said Dan Huber, astronomer at the University of Hawaii, Honolulu.
Know thy star, know thy planet
Many important aspects of a planet — including size, age and whether or not it could support life – can only be determined from what scientists know about its host star.
When a planet passes in front of its star, Kepler detects this "transit" by measuring a sharp dip in the brightness of the star as the planet blocks some of its light (very different from the ripple-like quake signatures). The amount of dimming of the star’s light during a transit is related to the size of the planet relative to the size of the star. So, in order to calculate the planet’s diameter, scientists need the diameter of the star — something that they can determine using asteroseismology. Similarly, while a technique called radial velocity allows scientists to calculate a planet’s mass relative to its star’s mass, scientists must calculate the star’s mass to "weigh" the planet. Asteroseismology is a way to determine the mass.
"Knowing the size of the star is very important for actually knowing what the size of the planet is," Huber said.
Stellar vibrations also help scientists determine how old a star is, which will affect the environment of its planets. A young star is more likely to have violent outbursts, and its planets may still be shuffling around in their orbits. An older star has less frequent flare-ups, and its planets may be more stable.
"Getting precise estimates of ages is incredibly difficult, but this is something that asteroseismology is really well suited to," Chaplin said. "The ticking heartbeat of the star allows us to get precise measurements."
Galactic archaeology
The more stars astronomers can examine through seismology, the better they can map where the young and old stars are, and understand which regions of the Milky Way formed first. This is the science of galactic archaeology. By following the trails of vibrations in stars, like an interstellar Indiana Jones would, astronomers can reconstruct how our Milky Way formed.
"Much like digging through the archaeological site of an old city, you can look at what happened in each of those 'rooms' in our galaxy," said Steve Howell, head of the space and astrobiology division at NASA's Ames Research Center in California’s Silicon Valley.
TESS will record the vibrations of up to one million red giants. As it will do a survey of stars across the entire sky, it will in effect be listening in "surround sound." The European Space Agency’s Gaia mission, which recently released positions and distance indicators for more than one billion stars, offers a powerful addition to Kepler and TESS in charting the history of the galaxy. By calculating the ages of stars and determining how long they have been in the red giant phase, and knowing their distances, scientists will get a fuller picture of how the stars of the galaxy came together and how it is evolving.
While Kepler is running low on fuel and its mission will soon end, scientists will be using its data to make discoveries about the Milky Way’s stars for years to come. TESS will complement its predecessor’s detailed observations of the celestial orchestra, and continue unlocking mysteries as it listens to more of the grand ensemble of the galaxy.
By Elizabeth Landau,
NASA's Exoplanet Exploration Program
Read more, and listen to sounds at:
https://exoplanets.nasa.gov/news/1516/symphony-of-stars-the-science-of-stellar-sound-waves/
Image:
This artist’s concept shows how a few individual waves travel through a hypothetical star that has an orbiting planet.
Credit: Gabriel Perez Diaz /Instituto de Astrofisica de Canarias
#NASA #ESA #Science #Stars #StellarSoundWaves #TheSun #Sun #Space #TESS #MilkyWay #Galaxy #Kepler #SpaceTelescope #EarthsSeismicWaves #Planets #SpaceScience #RedGiants #GaiaMission #SpaceMissions
Symphony of stars: The science of stellar sound waves
exoplanets.nasa.gov
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Dust and Cosmic Rays on Comet 67P
Previously unreleased imagery from the European Space Agency's Rosetta spacecraft reveal ice and dust on the surface of Comet 67P/Churyumov-Gerasimenko. The images were captured on June 1, 2016, over the course of 25 minutes at an altitude of roughly 13 km above the surface of the comet. Comet 67P is a Jupiter-family comet originally from the Kuiper belt and has an orbital period of 6.45 years.
The majority of the "snow" is actually caused by cosmic rays hitting the camera sensor and saturating pixels. These high energy particles pervade the Universe and originate from extrasolar phenomena such as supernovae, galactic nuclei, quasars, and gamma-ray bursts. The Earth's atmosphere protects us from the deleterious effects of cosmic rays.
Source: https://twitter.com/landru79/status/988490703075463168
#ScienceGIF #Science #GIF #Comet #67P #Comet67P #Rosetta #OSIRIS #Probe #Cosmic #Ray #CosmicRay #Stars #Snow #Dust #Churyumov #Gerasimenko #ESA #Space #Exploration #Discovery #Lander
Previously unreleased imagery from the European Space Agency's Rosetta spacecraft reveal ice and dust on the surface of Comet 67P/Churyumov-Gerasimenko. The images were captured on June 1, 2016, over the course of 25 minutes at an altitude of roughly 13 km above the surface of the comet. Comet 67P is a Jupiter-family comet originally from the Kuiper belt and has an orbital period of 6.45 years.
The majority of the "snow" is actually caused by cosmic rays hitting the camera sensor and saturating pixels. These high energy particles pervade the Universe and originate from extrasolar phenomena such as supernovae, galactic nuclei, quasars, and gamma-ray bursts. The Earth's atmosphere protects us from the deleterious effects of cosmic rays.
Source: https://twitter.com/landru79/status/988490703075463168
#ScienceGIF #Science #GIF #Comet #67P #Comet67P #Rosetta #OSIRIS #Probe #Cosmic #Ray #CosmicRay #Stars #Snow #Dust #Churyumov #Gerasimenko #ESA #Space #Exploration #Discovery #Lander
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Dr. Brownstone will be discussing how Diabetes can affect your eyes on Thursday August 9! To reserve your seat, call the Center for Healthy Lifestyles at (309) 661-5151. #Diabetes #Eyes #DiabeticRetinopathy #ESA #SeetheDifference
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