SPACE NEWS
CNN
Wed, June 21, 2023
The Geminid meteor shower, which lights up the sky each December, is one of the most active and dependable celestial displays of the year.
But the actual origin of the winter light show is something of a mystery. Now, astronomers using NASA’s Parker Solar Probe have gained more insight into the underlying cause of the Geminids.
The meteor shower was first recorded in 1862 and appears to radiate from the Gemini constellation. During the meteor shower’s peak in mid-December, 120 bright yellow meteors can be seen per hour if skies are clear.
Meteors typically originate from the leftover bits and pieces of comets orbiting around the sun. When comets, which originate in the icy outskirts of the solar system, pass close to the sun, they shed trails of particles. Meteor showers appear in Earth’s skies when our planet passes through the debris trails. As the particles collide with Earth’s atmosphere, they blaze up and disintegrate, leaving fiery streaks behind, according to NASA.
The Geminids, however, are unusual in that they have been traced to the asteroid 3200 Phaethon. Scientists have debated the very nature of what Phaethon is. It’s possible that Phaethon is a “dead comet,” with an icy shell that eventually melted away. The closely tracked near-Earth asteroid has been likened to comets, so it’s been called a “rock comet.”
“What’s really weird is that we know that Phaethon is an asteroid, but as it flies by the Sun, it seems to have some kind of temperature-driven activity. Most asteroids don’t do that,” said Jamey Szalay, a research scientist at Princeton University, in a statement. Szalay is the coauthor of a study about the asteroid published on June 15 in The Planetary Science Journal.
Although the Parker Solar Probe, launched in 2018, is on a mission to “touch” and study the sun, the spacecraft’s increasingly close proximity to our star is useful for scientists wanting to study the dust swirling around the inner solar system. The probe’s instruments have provided scientists with a detailed view of the dust particles shed by comets and asteroids on their treks around the sun — and in doing so shed new light on the Geminids-Phaethon connection.
How an asteroid sparked a meteor shower
While the spacecraft doesn’t actually carry a dust counting instrument to measure the grains, the particles impact the Parker Solar Probe as it orbits the sun. As dust hits the spacecraft, it creates electrical signals that can be picked up by the probe’s instruments, including one that measures electric and magnetic fields near the sun.
The Geminid meteor shower streaks across the night sky over the Lhasa River in Tibet on December 14, 2022. - Jiang Feibo/China News Service/VCG/Getty Images
Data collected by the Parker Solar Probe was used by scientists to model three different scenarios for the Geminid meteor shower, which were then compared with models based on observations from Earth.
The data revealed that the most probable cause of the meteor shower was a sudden, violent event, likely a rapid collision of the asteroid with another space rock or even some kind of gaseous explosion that caused the Geminids to first appear in our skies in 1862.
Phaethon was discovered on October 11, 1983, by astronomers using the Infrared Astronomical Satellite.
After Phaethon’s discovery, astronomer Fred Whipple realized that the asteroid and the Geminid meteor shower stream had nearly identical orbits, and he made a connection between the two.
It’s the first asteroid to be associated with a meteor shower, and it measures about 3.17 miles (5.10 kilometers) across. Astronomers have studied the space rock for years in an attempt to determine why it behaves like a comet.
The space rock was named after the Greek myth about the son of Helios, the sun god, because it closely approaches our sun.
Phaethon orbits the sun closer than any other asteroid and takes 1.4 years to complete its orbit.
Even before studying dust in our solar system with Parker Solar Probe, astronomers determined that the asteroid heats up to about 1,300 degrees Fahrenheit (704 degrees Celsius) on its closest approach to the sun, which causes Phaethon to shed more dusty debris.
These particles cause the meteor shower each year when they plunge into Earth’s atmosphere at 79,000 miles per hour (127,000 kilometers per hour), vaporizing in the streaks we call “shooting stars.”
For more CNN news and newsletters create an account at CNN.com
Watch sunlight dance across Earth from solstice to solstice in this gorgeous video
Tereza Pultarova
Tereza Pultarova
SPACE
Wed, June 21, 2023 a
a shadow moves across the face of the Earth
An amazing new video demonstrates how Earth's tilt changes throughout the year, causing days to lengthen and shorten from north to south as the planet orbits the sun.
The Northern Hemisphere is experiencing the longest day of the year as our planet reached the moment of the summer solstice today, June 21, at 10:57 a.m. EDT (1457 GMT).
The summer solstice is the moment when the Earth's Northern Hemisphere is most tilted toward the sun, therefore receiving the maximum amount of sunlight during the day. That means the day is the longest for the half of the planet north of the equator where the summer season is entering its peak.
Related: Stonehenge's summer solstice orientation is seen in monuments all over the UK in amazing photos
an illustration depicting how the Earth's tilt affects the seasons
But while the Northern Hemisphere is basking in sunshine, the Southern Hemisphere is trudging through its darkest day of culminating winter. From tomorrow on, the Southern Hemisphere's day will begin to lengthen while the Northern Hemisphere will start losing minutes of daylight.
The new video above released by Simon Proud, an Earth-observation scientist at the National Center for Earth Observation in the U.K., shows the terminator line, the boundary between the day and night, as it moves throughout the year.
"This video, using @eumetsat weather satellite data, shows how the sun appears to move during the year: It is made using 365 pictures, all taken at 6 a.m. on each day over the past year," Proud said in a tweet.
As we know, the sun doesn't really move across the sky (even though it does orbit the center of our galaxy the Milky Way). Its apparent motion overhead is caused by the Earth's rotation around its tilted axes, which means the arc the sun draws in the sky changes day by day, growing larger in the Northern Hemisphere from the winter solstice in December to the summer solstice in June and vice versa.
Related stories:
— June Solstice 2023: How twilight zones affect day length
— The summer solstice: When is it and when does it occur? — What is an equinox?
The video is a sequence of images taken by the European weather satellite Meteosat, which observes the planet from its perch in the geostationary orbit, an orbit at an altitude of 22,200 miles (36,000 kilometers), where spacecraft appear suspended above a fixed spot above Earth's equator.
The planet is now beginning its move toward the autumn equinox, which takes place in September and which sees both hemispheres receiving an equal amount of sunshine on that given day.
Wed, June 21, 2023 a
a shadow moves across the face of the Earth
An amazing new video demonstrates how Earth's tilt changes throughout the year, causing days to lengthen and shorten from north to south as the planet orbits the sun.
The Northern Hemisphere is experiencing the longest day of the year as our planet reached the moment of the summer solstice today, June 21, at 10:57 a.m. EDT (1457 GMT).
The summer solstice is the moment when the Earth's Northern Hemisphere is most tilted toward the sun, therefore receiving the maximum amount of sunlight during the day. That means the day is the longest for the half of the planet north of the equator where the summer season is entering its peak.
Related: Stonehenge's summer solstice orientation is seen in monuments all over the UK in amazing photos
an illustration depicting how the Earth's tilt affects the seasons
But while the Northern Hemisphere is basking in sunshine, the Southern Hemisphere is trudging through its darkest day of culminating winter. From tomorrow on, the Southern Hemisphere's day will begin to lengthen while the Northern Hemisphere will start losing minutes of daylight.
The new video above released by Simon Proud, an Earth-observation scientist at the National Center for Earth Observation in the U.K., shows the terminator line, the boundary between the day and night, as it moves throughout the year.
"This video, using @eumetsat weather satellite data, shows how the sun appears to move during the year: It is made using 365 pictures, all taken at 6 a.m. on each day over the past year," Proud said in a tweet.
As we know, the sun doesn't really move across the sky (even though it does orbit the center of our galaxy the Milky Way). Its apparent motion overhead is caused by the Earth's rotation around its tilted axes, which means the arc the sun draws in the sky changes day by day, growing larger in the Northern Hemisphere from the winter solstice in December to the summer solstice in June and vice versa.
Related stories:
— June Solstice 2023: How twilight zones affect day length
— The summer solstice: When is it and when does it occur? — What is an equinox?
The video is a sequence of images taken by the European weather satellite Meteosat, which observes the planet from its perch in the geostationary orbit, an orbit at an altitude of 22,200 miles (36,000 kilometers), where spacecraft appear suspended above a fixed spot above Earth's equator.
The planet is now beginning its move toward the autumn equinox, which takes place in September and which sees both hemispheres receiving an equal amount of sunshine on that given day.
The Milky Way's monster black hole let out a huge blast 200 years ago. We can now listen to its echo (video)
Keith Cooper
an orange ring on a black background
The gravitational tidal forces around a black hole as massive as Sagittarius A* are strong enough to rip apart anything that wanders too close in a frenzied act of violence. This process releases a flare of X-rays as a gas cloud, a star or even an asteroid is torn asunder, and the debris forms a hot disc of material that spirals into the black hole's maw.
NASA's IXPE spacecraft can measure the polarization of X-ray light from such events. Polarization refers to light waves oscillating in a preferred direction, which can reveal information about how the light has been produced and reflected. IXPE found that the X-ray echoes have a polarization angle consistent with an origin in the direction of Sagittarius A*. Furthermore, the strength of the polarization indicates that the X-rays were emitted a little over 200 years ago in an event that lasted less than a year-and-a-half.
clouds of purple gas in space
"Our work presents the missing piece of evidence that X-rays from the giant molecular clouds are due to reflection of an intense, yet short-lived flare produced at or nearby Sgr A*," Marin's team wrote in a paper describing their findings.
The brightness of the X-ray echoes indicates that this outburst increased the black hole's X-ray luminosity a millionfold compared to its dormant state today. The total amount of energy released is estimated to be between 1039 – 1044 ergs. This is comparable with a breed of active galaxy called a Seyfert, which have supermassive black holes that feeding on large amounts of material but over a much longer period of time.
RELATED STORIES:
— Brilliant gamma-ray flare 100 times brighter than our entire galaxy reveals 1 monster black hole is actually 2
— The loneliest monster black holes may also be the hungriest
— Sagittarius A* in pictures: The 1st photo of the Milky Way's monster black hole explained in images
Exactly what unfortunate object fell too close to Sagittarius A* to be ripped apart remains unknown. The existence of stars that orbit very close to the black hole, and clouds of gas that pass dangerously close and are distorted by the black hole's gravity, suggest that there is a ready supply of material that will eventually fall into the black hole.
The findings were published on June 21 in the journal Nature.
Keith Cooper
SPACE
Wed, June 21, 202
purple clouds of gas in space
The supermassive black hole at the center of our Milky Way galaxy woke up and unleashed a fierce outburst of X-rays around the turn of the 19th century, according to new observations of the 'echoes' of the event.
Astronomers have noticed that immense clouds of star-forming molecular gas that inhabit the central region of the Milky Way galaxy shine brighter in X-rays than expected. One possible explanation put forward was that this X-ray light was not intrinsic to the gas clouds, but was being reflected off of them following an outburst from the black hole, which is named Sagittarius A* (Sgr A*) and has a mass 4.1 million times that of our sun.
The theory is that, sometime in the relatively recent past, the Sagittarius A* devoured something in just this fashion, and the flash of X-rays is being reflected by the molecular gas clouds in the vicinity of the black hole. Now, a team led by Frédéric Marin of the University of Strasbourg has used NASA's Imaging X-ray Polarimetry Explorer (IXPE) satellite has not only found strong evidence that this was the case, but has also been able to put an approximate date on when it happened.
Related: Sagittarius A*: The Milky Way's supermassive black hole
Wed, June 21, 202
purple clouds of gas in space
The supermassive black hole at the center of our Milky Way galaxy woke up and unleashed a fierce outburst of X-rays around the turn of the 19th century, according to new observations of the 'echoes' of the event.
Astronomers have noticed that immense clouds of star-forming molecular gas that inhabit the central region of the Milky Way galaxy shine brighter in X-rays than expected. One possible explanation put forward was that this X-ray light was not intrinsic to the gas clouds, but was being reflected off of them following an outburst from the black hole, which is named Sagittarius A* (Sgr A*) and has a mass 4.1 million times that of our sun.
The theory is that, sometime in the relatively recent past, the Sagittarius A* devoured something in just this fashion, and the flash of X-rays is being reflected by the molecular gas clouds in the vicinity of the black hole. Now, a team led by Frédéric Marin of the University of Strasbourg has used NASA's Imaging X-ray Polarimetry Explorer (IXPE) satellite has not only found strong evidence that this was the case, but has also been able to put an approximate date on when it happened.
Related: Sagittarius A*: The Milky Way's supermassive black hole
an orange ring on a black background
The gravitational tidal forces around a black hole as massive as Sagittarius A* are strong enough to rip apart anything that wanders too close in a frenzied act of violence. This process releases a flare of X-rays as a gas cloud, a star or even an asteroid is torn asunder, and the debris forms a hot disc of material that spirals into the black hole's maw.
NASA's IXPE spacecraft can measure the polarization of X-ray light from such events. Polarization refers to light waves oscillating in a preferred direction, which can reveal information about how the light has been produced and reflected. IXPE found that the X-ray echoes have a polarization angle consistent with an origin in the direction of Sagittarius A*. Furthermore, the strength of the polarization indicates that the X-rays were emitted a little over 200 years ago in an event that lasted less than a year-and-a-half.
clouds of purple gas in space
"Our work presents the missing piece of evidence that X-rays from the giant molecular clouds are due to reflection of an intense, yet short-lived flare produced at or nearby Sgr A*," Marin's team wrote in a paper describing their findings.
The brightness of the X-ray echoes indicates that this outburst increased the black hole's X-ray luminosity a millionfold compared to its dormant state today. The total amount of energy released is estimated to be between 1039 – 1044 ergs. This is comparable with a breed of active galaxy called a Seyfert, which have supermassive black holes that feeding on large amounts of material but over a much longer period of time.
RELATED STORIES:
— Brilliant gamma-ray flare 100 times brighter than our entire galaxy reveals 1 monster black hole is actually 2
— The loneliest monster black holes may also be the hungriest
— Sagittarius A* in pictures: The 1st photo of the Milky Way's monster black hole explained in images
Exactly what unfortunate object fell too close to Sagittarius A* to be ripped apart remains unknown. The existence of stars that orbit very close to the black hole, and clouds of gas that pass dangerously close and are distorted by the black hole's gravity, suggest that there is a ready supply of material that will eventually fall into the black hole.
The findings were published on June 21 in the journal Nature.
Sun unleashes giant X-flare in outburst that could spark auroras on Mars (video)
Elizabeth Howell
Wed, June 21, 2023
a close-up of the sun in false color wavelengths, with a burst of flare on the left limb
Behold the power of the sun!
Our star unleashed an X-flare — the strongest type of solar radiation outburst — at 1:09 p.m. EDT (1709 GMT) on Tuesday (June 20).
Footage of the flare was caught by NASA's Solar Dynamics Observatory, which keeps a constant watch on sun activity alongside other agency satellites and observatories from the European Space Agency, among other entities.
Related: Space weather: What is it and how is it predicted?
NASA Solar Dynamics Observatory captured the newly arrived sunspot AR3341 blasting out a powerful X1.1 solar flare on June 20, 2023. (Image credit: NASA/SDO)
"Solar flares are powerful bursts of radiation," NASA's sun account on Twitter stated. "Harmful radiation from a flare cannot pass through Earth's atmosphere to physically affect humans on the ground. However — when intense enough — they can disturb the atmosphere in the layer where GPS and communications signals travel."
The flare was associated with a coronal mass ejection (CME), a huge cloud of superheated plasma that the sun blasted into space. The CME was not aimed at Earth and, as such, it will not ramp up any auroral displays here, according to SpaceWeather.com, citing a NASA model.
But the solar plasma may spark a glowing light show on Mars that will be visible in a few days to orbiters there, such as NASA's Mars Atmosphere and Volatile Evolution (MAVEN).
RELATED STORIES:
— How hot is the sun?
— How was the sun formed?
— See amazing new sun photos from the world's largest solar telescope
The sun is currently nearing the peak of its 11-year activity cycle, with many sunspots clustering on the surface. Sunspots — hotbeds of magnetic activity — serve as launch pads for flares and CMES.
Normally, these eruptions are harmless to humanity, causing only light shows. But NASA and other agencies keep an eye on the sun just in case a warning is required to protect essential infrastructure, like power lines or satellites.
Elizabeth Howell
Wed, June 21, 2023
a close-up of the sun in false color wavelengths, with a burst of flare on the left limb
Behold the power of the sun!
Our star unleashed an X-flare — the strongest type of solar radiation outburst — at 1:09 p.m. EDT (1709 GMT) on Tuesday (June 20).
Footage of the flare was caught by NASA's Solar Dynamics Observatory, which keeps a constant watch on sun activity alongside other agency satellites and observatories from the European Space Agency, among other entities.
Related: Space weather: What is it and how is it predicted?
NASA Solar Dynamics Observatory captured the newly arrived sunspot AR3341 blasting out a powerful X1.1 solar flare on June 20, 2023. (Image credit: NASA/SDO)
"Solar flares are powerful bursts of radiation," NASA's sun account on Twitter stated. "Harmful radiation from a flare cannot pass through Earth's atmosphere to physically affect humans on the ground. However — when intense enough — they can disturb the atmosphere in the layer where GPS and communications signals travel."
The flare was associated with a coronal mass ejection (CME), a huge cloud of superheated plasma that the sun blasted into space. The CME was not aimed at Earth and, as such, it will not ramp up any auroral displays here, according to SpaceWeather.com, citing a NASA model.
But the solar plasma may spark a glowing light show on Mars that will be visible in a few days to orbiters there, such as NASA's Mars Atmosphere and Volatile Evolution (MAVEN).
RELATED STORIES:
— How hot is the sun?
— How was the sun formed?
— See amazing new sun photos from the world's largest solar telescope
The sun is currently nearing the peak of its 11-year activity cycle, with many sunspots clustering on the surface. Sunspots — hotbeds of magnetic activity — serve as launch pads for flares and CMES.
Normally, these eruptions are harmless to humanity, causing only light shows. But NASA and other agencies keep an eye on the sun just in case a warning is required to protect essential infrastructure, like power lines or satellites.
Why didn't the infant universe collapse into a black hole?
Paul Sutter
Wed, June 21, 2023
spindly purple swirls in deep space, representing star formation in the early universe
You may have wondered: Why didn't the universe collapse into a black hole during the earliest moments of the Big Bang? Simply put, because that's not how you make a black hole.
If you want to make a black hole yourself, it's relatively straightforward: You just take any object and squeeze it as hard as possible. If you can resist all of the other forces and squeeze any amount of matter below a certain critical threshold, then gravity will take over and do the rest of the work for you, crunching that matter down into an infinitely small point and creating a black hole.
That threshold, known as the Schwarzschild radius, depends on the amount of matter you want to squeeze. If you were to take a human body and squeeze it down to the size of roughly an atomic nucleus, you would end up with a human-mass black hole the width of an atomic nucleus. If you were to repeat the process with our planet, you would end up with an Earth-mass but bean-sized black hole.
Related: What happens at the center of a black hole?
Nature makes black holes all the time through the deaths of massive stars. When they run out of fuel, their own gravitational attraction pulls as much material as possible into as small a volume as possible, eventually overwhelming any other force of nature and creating black holes a few miles across with the mass of a few suns.
So that's the simple, one-step trick to making black holes: You take a lot of matter and squeeze it to incredibly high densities.
The early universe
But the centers of massive stars are not the only locales in the universe that have reached incredibly high densities. About 13.77 billion years ago, our entire visible universe was crammed into a volume no bigger than a peach with a temperature of over a quadrillion degrees. That's a rather high density.
So why didn't the entire universe collapse into a black hole? There are two reasons.
One, the creation of a black hole relies on not only incredibly high densities but also density differences. To make a black hole, you need a lot of material crammed into a very small volume, with nothing else surrounding it. Gravity works only on differences. If the density is the same from place to place, then there are no gravitational differences and thus no chance to trigger the formation of a black hole.
Yes, the early universe was incredibly dense. But it was dense everywhere, with barely any differences. Without those differences, black holes couldn't form, because there was no difference in gravity that could lead to the sudden collapse of matter.
RELATED STORIES:
— Could the universe collapse into a singularity? New study explains how.
— Are there any black holes left over from the Big Bang?
— Tiny primordial black holes could have created their own Big Bang
A dynamic universe
But even without density differences, what about the entire universe recollapsing into the singularity that birthed the Big Bang itself? Just to be clear, that wouldn't make the universe turn into a black hole. A black hole is an ultradense collection of matter within space. When we're talking about the expansion or contraction of the universe, we're talking about the evolution of space itself.
But even if it wasn't a black hole, what prevented the collapse into a singularity? What prevented it is that the early universe wasn't static — it was dynamic. It was evolving. It was changing. And most importantly, it was expanding.
The rules of black hole formation simply don't apply in an expanding universe. It's no longer like a star sitting in the middle of empty space, imploding on itself. To collapse into a singularity, it's not enough to have a ton of mass sitting around. You need an overwhelming amount of mass to counteract the natural expansion of the universe and force it to collapse.
And there simply wasn't enough mass in the universe to do that — back then and even now. For decades, cosmologists wondered if there might be enough matter in the universe to cause the present-day expansion to slow down, stop and reverse, eventually leading to a "big crunch" and a return to a singularity.
But multiple measurements have confirmed that there isn't enough stuff to get the job done. Our universe will, as far as we can tell, continue expanding well into the future. Which is a good thing for us — life as we know it doesn't tend to do well inside black holes.
Paul Sutter
Wed, June 21, 2023
spindly purple swirls in deep space, representing star formation in the early universe
You may have wondered: Why didn't the universe collapse into a black hole during the earliest moments of the Big Bang? Simply put, because that's not how you make a black hole.
If you want to make a black hole yourself, it's relatively straightforward: You just take any object and squeeze it as hard as possible. If you can resist all of the other forces and squeeze any amount of matter below a certain critical threshold, then gravity will take over and do the rest of the work for you, crunching that matter down into an infinitely small point and creating a black hole.
That threshold, known as the Schwarzschild radius, depends on the amount of matter you want to squeeze. If you were to take a human body and squeeze it down to the size of roughly an atomic nucleus, you would end up with a human-mass black hole the width of an atomic nucleus. If you were to repeat the process with our planet, you would end up with an Earth-mass but bean-sized black hole.
Related: What happens at the center of a black hole?
Nature makes black holes all the time through the deaths of massive stars. When they run out of fuel, their own gravitational attraction pulls as much material as possible into as small a volume as possible, eventually overwhelming any other force of nature and creating black holes a few miles across with the mass of a few suns.
So that's the simple, one-step trick to making black holes: You take a lot of matter and squeeze it to incredibly high densities.
The early universe
But the centers of massive stars are not the only locales in the universe that have reached incredibly high densities. About 13.77 billion years ago, our entire visible universe was crammed into a volume no bigger than a peach with a temperature of over a quadrillion degrees. That's a rather high density.
So why didn't the entire universe collapse into a black hole? There are two reasons.
One, the creation of a black hole relies on not only incredibly high densities but also density differences. To make a black hole, you need a lot of material crammed into a very small volume, with nothing else surrounding it. Gravity works only on differences. If the density is the same from place to place, then there are no gravitational differences and thus no chance to trigger the formation of a black hole.
Yes, the early universe was incredibly dense. But it was dense everywhere, with barely any differences. Without those differences, black holes couldn't form, because there was no difference in gravity that could lead to the sudden collapse of matter.
RELATED STORIES:
— Could the universe collapse into a singularity? New study explains how.
— Are there any black holes left over from the Big Bang?
— Tiny primordial black holes could have created their own Big Bang
A dynamic universe
But even without density differences, what about the entire universe recollapsing into the singularity that birthed the Big Bang itself? Just to be clear, that wouldn't make the universe turn into a black hole. A black hole is an ultradense collection of matter within space. When we're talking about the expansion or contraction of the universe, we're talking about the evolution of space itself.
But even if it wasn't a black hole, what prevented the collapse into a singularity? What prevented it is that the early universe wasn't static — it was dynamic. It was evolving. It was changing. And most importantly, it was expanding.
The rules of black hole formation simply don't apply in an expanding universe. It's no longer like a star sitting in the middle of empty space, imploding on itself. To collapse into a singularity, it's not enough to have a ton of mass sitting around. You need an overwhelming amount of mass to counteract the natural expansion of the universe and force it to collapse.
And there simply wasn't enough mass in the universe to do that — back then and even now. For decades, cosmologists wondered if there might be enough matter in the universe to cause the present-day expansion to slow down, stop and reverse, eventually leading to a "big crunch" and a return to a singularity.
But multiple measurements have confirmed that there isn't enough stuff to get the job done. Our universe will, as far as we can tell, continue expanding well into the future. Which is a good thing for us — life as we know it doesn't tend to do well inside black holes.
No comments:
Post a Comment