Earliest sunsets for 40 degrees N. around now

Image at top: New York City sunset by Flickr user Jerry Ferguson.

For the southernmost U.S. and similar latitudes – around 30 degrees north latitude – the earliest sunsets of the year happen in late November and early December. For latitudes further north – around 40 degrees N. latitude – the year’s earliest sunsets happen around December 7. That would be the latitude of New York City; Philadelphia, Pennsylvania; Kansas City, Missouri; Denver, Colorado; Reno, Nevada; Beijing, China; Madrid, Spain; and Naples, Italy.

Southern Hemisphere? For 40 degrees south latitude, the year’s earliest sunrises happen around December 7, as you progress toward your year’s longest day at the December solstice.

Closer to the Arctic and Antarctic Circles, the earliest sunset and earliest sunrise happen nearer the solstice.

The exact date of the Northern Hemisphere’s earliest sunset and the Southern Hemisphere’s earliest sunrise varies by latitude. But, at temperate latitudes, both of these annual hallmarks in our sky come a few to several weeks before the December solstice, not on the solstice as you might expect.

The 2020 lunar calendars are here! Order yours before they’re gone. Makes a great gift.

The next solstice in 2019 comes on December 21 or 22 (depending on time zone) and marks an unofficial beginning for winter in the Northern Hemisphere. For this hemisphere, this upcoming solstice brings the shortest day and longest night of the year.

Why isn’t the earliest sunset on the year’s shortest day?

It’s because of the discrepancy between the clock and the sun. A clock ticks off exactly 24 hours from one noon to the next. But an actual day – as measured by the spin of the Earth, from what is called one “solar noon” to the next – rarely equals 24 hours exactly.

Solar noon is also called simply midday. It refers to that instant when the sun reaches its highest point for the day. In the month of December, the time period from one solar noon to the next is actually half a minute longer than 24 hours. On December 7, the sun reaches its noontime position at 11:52 a.m. local standard time. Two weeks later – on the winter solstice – the sun will reach its noontime position around 11:59 a.m. That’s 7 minutes later than on December 7.

Click here to know the clock time for sunrise, solar noon and sunset plus day length in your part of the world, remembering to check the solar noon and day length boxes.

The later clock time for solar noon also means a later clock time for sunrise and sunset. The table below helps to explain.

For Philadelphia, Pennsylvania

Date	Sunrise	Solar Noon (Midday)	Sunset	Daylight Hours
December 7	7:08 a.m.	11:52 a.m.	4:35 p.m.	9 hours 27 minutes
December 21	7:18 a.m.	11:58 a.m.	4:38 p.m.	9 hours 20 minutes

As you might have guessed, the latest sunrises and sunsets aren’t on the day of the solstice either. For middle latitudes in the Northern Hemisphere, the latest sunrises come in early January.

So there’s variation in the exact dates, but the sequence is always the same for both hemispheres. First: earliest sunset before the winter solstice, the winter solstice itself, latest sunrise after the winter solstice. Half a year later: earliest sunrise before the summer solstice, the summer solstice itself, latest sunset.

The earliest and latest sunsets and sunrises are lovely phenomena that happen around every solstice. People around the world notice them and often ask about them.

Click here for more details on why the earliest sunset doesn’t fall on the shortest day.

EarthSky Facebook friend Dutch McClintock in Livingston, Montana, took this photo. Livingston’s latitude is about 45 degrees N., so – for Dutch and all those living at that latitude – the earliest sunset will happen closer to the December solstice.

December sunset in Pike County, Illinois, via Russ Adams. The earliest sunsets for this location happen in early December.

Hong Kong sunset, at the Hong Kong Science Park, from Kins Cheung. Hong Kong is at 22 degrees N. latitude, so the earliest sunset there has already happened.

Sunset in Manila by EarthSky Facebook friend Jv Noriega. Manila is at 14 degrees N. latitude, so the earliest sunset there happens even earlier than in Hong Kong.

Bottom line: The 2019 solstice comes on December 22 by Universal Time, but the earliest sunsets at mid-northern latitudes – say, 40 degrees north latitude – happen on or near December 7. Latitudes closer to the equator had their earliest sunsets in late November, or earlier in December. Latitudes closer to the Arctic Circle have their earliest sunsets closer to the December solstice.

Solstice tale of two cities: New York, NY, and St. Augustine, FL

from EarthSky https://ift.tt/2G0Y8VR

Image at top: New York City sunset by Flickr user Jerry Ferguson.

For the southernmost U.S. and similar latitudes – around 30 degrees north latitude – the earliest sunsets of the year happen in late November and early December. For latitudes further north – around 40 degrees N. latitude – the year’s earliest sunsets happen around December 7. That would be the latitude of New York City; Philadelphia, Pennsylvania; Kansas City, Missouri; Denver, Colorado; Reno, Nevada; Beijing, China; Madrid, Spain; and Naples, Italy.

Southern Hemisphere? For 40 degrees south latitude, the year’s earliest sunrises happen around December 7, as you progress toward your year’s longest day at the December solstice.

Closer to the Arctic and Antarctic Circles, the earliest sunset and earliest sunrise happen nearer the solstice.

The exact date of the Northern Hemisphere’s earliest sunset and the Southern Hemisphere’s earliest sunrise varies by latitude. But, at temperate latitudes, both of these annual hallmarks in our sky come a few to several weeks before the December solstice, not on the solstice as you might expect.

The 2020 lunar calendars are here! Order yours before they’re gone. Makes a great gift.

The next solstice in 2019 comes on December 21 or 22 (depending on time zone) and marks an unofficial beginning for winter in the Northern Hemisphere. For this hemisphere, this upcoming solstice brings the shortest day and longest night of the year.

Why isn’t the earliest sunset on the year’s shortest day?

It’s because of the discrepancy between the clock and the sun. A clock ticks off exactly 24 hours from one noon to the next. But an actual day – as measured by the spin of the Earth, from what is called one “solar noon” to the next – rarely equals 24 hours exactly.

Solar noon is also called simply midday. It refers to that instant when the sun reaches its highest point for the day. In the month of December, the time period from one solar noon to the next is actually half a minute longer than 24 hours. On December 7, the sun reaches its noontime position at 11:52 a.m. local standard time. Two weeks later – on the winter solstice – the sun will reach its noontime position around 11:59 a.m. That’s 7 minutes later than on December 7.

Click here to know the clock time for sunrise, solar noon and sunset plus day length in your part of the world, remembering to check the solar noon and day length boxes.

The later clock time for solar noon also means a later clock time for sunrise and sunset. The table below helps to explain.

For Philadelphia, Pennsylvania

Date	Sunrise	Solar Noon (Midday)	Sunset	Daylight Hours
December 7	7:08 a.m.	11:52 a.m.	4:35 p.m.	9 hours 27 minutes
December 21	7:18 a.m.	11:58 a.m.	4:38 p.m.	9 hours 20 minutes

As you might have guessed, the latest sunrises and sunsets aren’t on the day of the solstice either. For middle latitudes in the Northern Hemisphere, the latest sunrises come in early January.

So there’s variation in the exact dates, but the sequence is always the same for both hemispheres. First: earliest sunset before the winter solstice, the winter solstice itself, latest sunrise after the winter solstice. Half a year later: earliest sunrise before the summer solstice, the summer solstice itself, latest sunset.

The earliest and latest sunsets and sunrises are lovely phenomena that happen around every solstice. People around the world notice them and often ask about them.

Click here for more details on why the earliest sunset doesn’t fall on the shortest day.

EarthSky Facebook friend Dutch McClintock in Livingston, Montana, took this photo. Livingston’s latitude is about 45 degrees N., so – for Dutch and all those living at that latitude – the earliest sunset will happen closer to the December solstice.

December sunset in Pike County, Illinois, via Russ Adams. The earliest sunsets for this location happen in early December.

Hong Kong sunset, at the Hong Kong Science Park, from Kins Cheung. Hong Kong is at 22 degrees N. latitude, so the earliest sunset there has already happened.

Sunset in Manila by EarthSky Facebook friend Jv Noriega. Manila is at 14 degrees N. latitude, so the earliest sunset there happens even earlier than in Hong Kong.

Bottom line: The 2019 solstice comes on December 22 by Universal Time, but the earliest sunsets at mid-northern latitudes – say, 40 degrees north latitude – happen on or near December 7. Latitudes closer to the equator had their earliest sunsets in late November, or earlier in December. Latitudes closer to the Arctic Circle have their earliest sunsets closer to the December solstice.

Solstice tale of two cities: New York, NY, and St. Augustine, FL

from EarthSky https://ift.tt/2G0Y8VR

Astronomers catch a comet outburst

This animation shows an explosive outburst of dust, ice and gases from comet 46P/Wirtanen that began on September 26, 2018, and dissipated over the next 20 days. NASA’s TESS spacecraft acquired an image of the comet every 3 hours during the first 3 days of the outburst. Image via Farnham et al./NASA/University of Maryland.

What makes a comet flare up suddenly? No one knows exactly, but astronomers do know that outbursts are sometimes seen when comets are near their parent stars. Now University of Maryland astronomers say they’ve made the most complete and detailed observations to date of the formation and dissipation of a comet outburst. The comet is none other than 46P/Wirtanen, which last swept closest to the Earth and sun in its 5.4-year orbit in late 2018. You might remember this comet. We published many beautiful images of it, captured in November and December 2018 by members of the EarthSky community.

Shortly before earthly astrophotographers began to ogle it, the comet entered the field of view of NASA’s Transiting Exoplanet Survey Satellite (TESS), whose job is to seek exoplanets. As it happened, while TESS was aimed its way, 46P/Wirtanen underwent an outburst. Researchers were able to gain a clear start-to-finish image sequence of the explosive emission of dust, ice and gases. Team members reported their results in the November 22, 2019 issue of The Astrophysical Journal Letters.

University of Maryland astronomer Tony Farnham is the lead author of the study. He said in a statement:

TESS spends nearly a month at a time imaging one portion of the sky. With no day or night breaks and no atmospheric interference, we have a very uniform, long-duration set of observations. As comets orbit the sun, they can pass through TESS’ field of view. Wirtanen was a high priority for us because of its close approach in late 2018, so we decided to use its appearance in the TESS images as a test case to see what we could get out of it.

We did so and were very surprised!

Farnham said that, although Wirtanen came closest to Earth on December 16, 2018, the outburst began in September. The astronomers’ statement explained:

The initial brightening of the outburst occurred in two distinct phases, with an hour-long flash followed by a more gradual second stage that continued to grow brighter for another 8 hours. This second stage was likely caused by the gradual spreading of comet dust from the outburst, which causes the dust cloud to reflect more sunlight overall.

After reaching peak brightness, the comet faded gradually over a period of more than two weeks.

EarthSky lunar calendars make great gifts for astronomy-minded friends and family. Order now. Going fast!

Comet 46P/Wirtanen on November 26, 2018, by Gerald Rhemann in Namibia. View more photos of the comet.

In its search for exoplanets, it’s TESS’ job to acquire detailed composite images every 30 minutes. And so the team studying the comet was able to view each phase of the outburst in what they called “exquisite detail.” Farnham said:

With 20 days’ worth of very frequent images, we were able to assess changes in brightness very easily. That’s what TESS was designed for, to perform its primary job as an exoplanet surveyor. We can’t predict when comet outbursts will happen. But even if we somehow had the opportunity to schedule these observations, we couldn’t have done any better in terms of timing. The outburst happened mere days after the observations started.

Farnham and his colleagues said they’re also the first to observe Wirtanen’s dust trail. Unlike a comet’s tail — the spray of gas and fine dust that follows behind a comet, growing as it approaches the sun — a comet’s trail is a field of larger debris that traces the comet’s orbital path as it travels around the sun. Unlike a tail, which changes direction as it is blown by the solar wind, the orientation of the trail stays more or less constant over time, they said. Astronomer Michael Kelley – a co-author on the new paper – explained:

The trail more closely follows the orbit of the comet, while the tail is more offset from it, as it gets pushed around by the sun’s radiation pressure. What’s significant about the trail is that it contains the largest material. Tail dust is very fine, a lot like smoke. But trail dust is much larger—more like sand and pebbles.

We think comets lose most of their mass through their dust trails. When the Earth runs into a comet’s dust trail, we get meteor showers.

Their statement said:

The team has generated a rough estimate of how much material may have been ejected in the outburst (about 2.2 million pounds [1 million kg], which could have left a crater close to 65 feet [20 meters] across), but further analysis of the estimated particle sizes in the dust tail may help improve this estimate. Observing more comets will also help to determine whether multi-stage brightening is rare or commonplace in comet outbursts.

Farnham said:

We also don’t know what causes natural outbursts and that’s ultimately what we want to find. There are at least four other comets in the same area of the sky where TESS made these observations, with a total of about 50 comets expected in the first two years’ worth of TESS data. There’s a lot that can come of these data. We’re still finding out the capabilities of TESS, so hopefully we’ll have more to report on this comet and others very soon.

According to Farnham, the TESS observations of comet Wirtanen were the first to capture all phases of a natural comet outburst, from beginning to end. The astronomers’ statement explained:

… three other previous observations came close to recording the beginning of an outburst event. Observations of a 2007 outburst from comet 17P/Holmes began late, missing several hours of the initial brightening phase of the event. In 2017, observations of an outburst from comet 29P/Schwassmann-Wachmann 1 (SW1) concluded early, due to limitations on pre-scheduled observation time. And, while observations from the Deep Impact mission captured an outburst from comet Tempel 1 in unprecedented detail in 2005, the outburst was not natural
created instead by the mission’s impactor module. However, the current observations are the first to capture the dissipation phase in its entirety.

While the current study describes initial results, Farnham, Kelley and their colleagues said they look forward to further analyses of Wirtanen, as well as other comets in TESS’ field of view.

Jack Fusco Photography in California wrote in December 2018: “Hi EarthSky! I’m so excited to share my 1st photo of comet 46P/Wirtanen! We took our boxer, Kona, out to the Anza Borrego Desert with us and came home with a new family photo. : ) I shared some behind-the-scenes and outtakes over on my blog as well.” Awesome photo, and thanks for the how-to-photograph info on your blog, Jack! View more photos of the comet.

Bottom line: Comet 46P/Wirtanen passed about 7 million miles from Earth at its closest, on December 16, 2018. That’s expected to be the brightest close approach for this comet for the next 20 years. Shortly before its closest approach to the Earth and sun, NASA’s TESS planet-hunter happened to catch a start-to-finish sequence showing an outburst of this comet. Astronomers are delighted.

Source: First Results from TESS Observations of Comet 46P/Wirtanen

Via University of Maryland

from EarthSky https://ift.tt/33OZUQM

This animation shows an explosive outburst of dust, ice and gases from comet 46P/Wirtanen that began on September 26, 2018, and dissipated over the next 20 days. NASA’s TESS spacecraft acquired an image of the comet every 3 hours during the first 3 days of the outburst. Image via Farnham et al./NASA/University of Maryland.

What makes a comet flare up suddenly? No one knows exactly, but astronomers do know that outbursts are sometimes seen when comets are near their parent stars. Now University of Maryland astronomers say they’ve made the most complete and detailed observations to date of the formation and dissipation of a comet outburst. The comet is none other than 46P/Wirtanen, which last swept closest to the Earth and sun in its 5.4-year orbit in late 2018. You might remember this comet. We published many beautiful images of it, captured in November and December 2018 by members of the EarthSky community.

Shortly before earthly astrophotographers began to ogle it, the comet entered the field of view of NASA’s Transiting Exoplanet Survey Satellite (TESS), whose job is to seek exoplanets. As it happened, while TESS was aimed its way, 46P/Wirtanen underwent an outburst. Researchers were able to gain a clear start-to-finish image sequence of the explosive emission of dust, ice and gases. Team members reported their results in the November 22, 2019 issue of The Astrophysical Journal Letters.

University of Maryland astronomer Tony Farnham is the lead author of the study. He said in a statement:

TESS spends nearly a month at a time imaging one portion of the sky. With no day or night breaks and no atmospheric interference, we have a very uniform, long-duration set of observations. As comets orbit the sun, they can pass through TESS’ field of view. Wirtanen was a high priority for us because of its close approach in late 2018, so we decided to use its appearance in the TESS images as a test case to see what we could get out of it.

We did so and were very surprised!

Farnham said that, although Wirtanen came closest to Earth on December 16, 2018, the outburst began in September. The astronomers’ statement explained:

The initial brightening of the outburst occurred in two distinct phases, with an hour-long flash followed by a more gradual second stage that continued to grow brighter for another 8 hours. This second stage was likely caused by the gradual spreading of comet dust from the outburst, which causes the dust cloud to reflect more sunlight overall.

After reaching peak brightness, the comet faded gradually over a period of more than two weeks.

EarthSky lunar calendars make great gifts for astronomy-minded friends and family. Order now. Going fast!

Comet 46P/Wirtanen on November 26, 2018, by Gerald Rhemann in Namibia. View more photos of the comet.

In its search for exoplanets, it’s TESS’ job to acquire detailed composite images every 30 minutes. And so the team studying the comet was able to view each phase of the outburst in what they called “exquisite detail.” Farnham said:

With 20 days’ worth of very frequent images, we were able to assess changes in brightness very easily. That’s what TESS was designed for, to perform its primary job as an exoplanet surveyor. We can’t predict when comet outbursts will happen. But even if we somehow had the opportunity to schedule these observations, we couldn’t have done any better in terms of timing. The outburst happened mere days after the observations started.

Farnham and his colleagues said they’re also the first to observe Wirtanen’s dust trail. Unlike a comet’s tail — the spray of gas and fine dust that follows behind a comet, growing as it approaches the sun — a comet’s trail is a field of larger debris that traces the comet’s orbital path as it travels around the sun. Unlike a tail, which changes direction as it is blown by the solar wind, the orientation of the trail stays more or less constant over time, they said. Astronomer Michael Kelley – a co-author on the new paper – explained:

The trail more closely follows the orbit of the comet, while the tail is more offset from it, as it gets pushed around by the sun’s radiation pressure. What’s significant about the trail is that it contains the largest material. Tail dust is very fine, a lot like smoke. But trail dust is much larger—more like sand and pebbles.

We think comets lose most of their mass through their dust trails. When the Earth runs into a comet’s dust trail, we get meteor showers.

Their statement said:

The team has generated a rough estimate of how much material may have been ejected in the outburst (about 2.2 million pounds [1 million kg], which could have left a crater close to 65 feet [20 meters] across), but further analysis of the estimated particle sizes in the dust tail may help improve this estimate. Observing more comets will also help to determine whether multi-stage brightening is rare or commonplace in comet outbursts.

Farnham said:

We also don’t know what causes natural outbursts and that’s ultimately what we want to find. There are at least four other comets in the same area of the sky where TESS made these observations, with a total of about 50 comets expected in the first two years’ worth of TESS data. There’s a lot that can come of these data. We’re still finding out the capabilities of TESS, so hopefully we’ll have more to report on this comet and others very soon.

According to Farnham, the TESS observations of comet Wirtanen were the first to capture all phases of a natural comet outburst, from beginning to end. The astronomers’ statement explained:

… three other previous observations came close to recording the beginning of an outburst event. Observations of a 2007 outburst from comet 17P/Holmes began late, missing several hours of the initial brightening phase of the event. In 2017, observations of an outburst from comet 29P/Schwassmann-Wachmann 1 (SW1) concluded early, due to limitations on pre-scheduled observation time. And, while observations from the Deep Impact mission captured an outburst from comet Tempel 1 in unprecedented detail in 2005, the outburst was not natural
created instead by the mission’s impactor module. However, the current observations are the first to capture the dissipation phase in its entirety.

While the current study describes initial results, Farnham, Kelley and their colleagues said they look forward to further analyses of Wirtanen, as well as other comets in TESS’ field of view.

Jack Fusco Photography in California wrote in December 2018: “Hi EarthSky! I’m so excited to share my 1st photo of comet 46P/Wirtanen! We took our boxer, Kona, out to the Anza Borrego Desert with us and came home with a new family photo. : ) I shared some behind-the-scenes and outtakes over on my blog as well.” Awesome photo, and thanks for the how-to-photograph info on your blog, Jack! View more photos of the comet.

Bottom line: Comet 46P/Wirtanen passed about 7 million miles from Earth at its closest, on December 16, 2018. That’s expected to be the brightest close approach for this comet for the next 20 years. Shortly before its closest approach to the Earth and sun, NASA’s TESS planet-hunter happened to catch a start-to-finish sequence showing an outburst of this comet. Astronomers are delighted.

Source: First Results from TESS Observations of Comet 46P/Wirtanen

Via University of Maryland

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Orion’s Belt and the Celestial Bridge

In early December, the constellation Orion is rising in your eastern sky around 8 to 9 p.m. Orion climbs highest up for the night around 1 a.m. local time (the time on your clock no matter where you are on the globe), and sits low in your western sky around 5 to 6 a.m. Notice the three stars at the mid-section of Orion. We know these stars as Orion’s Belt, but the Aymara people of Bolivia, Peru and Chile call them the Celestial Bridge.

To the Aymara, the Celestial Bridge links the sky’s Northern and Southern Hemispheres. And there’s good reason for that.

We know the westernmost star of the Belt – or Bridge – as Mintaka. This star is special because it sits almost directly astride the celestial equator – the projection of Earth’s equator onto the stellar sphere.

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The celestial equator is an imaginary great circle on the dome of Earth’s sky, drawn directly above the equator of the Earth. Image via Physics.csbsju.edu.

How you see the celestial equator in your sky depends on your latitude. But, because it’s above Earth’s equator, no matter where you are on the globe, the celestial equator intersects your horizon at points due east and due west. Image via Physics.csbsju.edu.

Its location on the celestial equator makes Mintaka a good guidepost for finding directions here on Earth. That is, Mintaka and the other stars of the Celestial Bridge are visible worldwide. From all over the world, Mintaka rises due east and sets due west, and remains in the sky for 12 hours.

Mintaka climbs to its highest point in the sky midway between rising and setting. If, at this time, this star shines at your zenith (your straight-overhead point), then you must be at the equator. If this star shines in the southern half of your sky, then you must be north of the equator. From most of South America, the star Mintaka appears in the northern sky, telling the Aymara and other skywatchers who know this star that they’re south of the equator.

From the Arctic north to the Antarctic south, the heavenly Celestial Bridge marks the Earthly wayfarer’s way to the equator – the meeting place of the northern and southern skies.

The constellation Orion straddles the celestial equator, which is indicated by a green line on this chart. Since the celestial equator intersects horizons all over the world at points due east and due west (as shown on the chart above this one), the star Mintaka – the one directly on the green line – can be used to find those cardinal directions in your sky. Image via Aloha.net.

Bottom line: To the Aymara – indigenous people in the Andes and Altiplano regions of South America – the famous sky feature we know as Orion’s Belt is seen as a Celestial Bridge between the sky’s Northern and Southern Hemispheres. The westernmost star in the Belt, or Celestial Bridge – a star called Mintaka – lies directly on the celestial equator.

from EarthSky https://ift.tt/2EvXZIL

In early December, the constellation Orion is rising in your eastern sky around 8 to 9 p.m. Orion climbs highest up for the night around 1 a.m. local time (the time on your clock no matter where you are on the globe), and sits low in your western sky around 5 to 6 a.m. Notice the three stars at the mid-section of Orion. We know these stars as Orion’s Belt, but the Aymara people of Bolivia, Peru and Chile call them the Celestial Bridge.

To the Aymara, the Celestial Bridge links the sky’s Northern and Southern Hemispheres. And there’s good reason for that.

We know the westernmost star of the Belt – or Bridge – as Mintaka. This star is special because it sits almost directly astride the celestial equator – the projection of Earth’s equator onto the stellar sphere.

EarthSky lunar calendars are cool! They make great gifts. Order now. Going fast!

The celestial equator is an imaginary great circle on the dome of Earth’s sky, drawn directly above the equator of the Earth. Image via Physics.csbsju.edu.

How you see the celestial equator in your sky depends on your latitude. But, because it’s above Earth’s equator, no matter where you are on the globe, the celestial equator intersects your horizon at points due east and due west. Image via Physics.csbsju.edu.

Its location on the celestial equator makes Mintaka a good guidepost for finding directions here on Earth. That is, Mintaka and the other stars of the Celestial Bridge are visible worldwide. From all over the world, Mintaka rises due east and sets due west, and remains in the sky for 12 hours.

Mintaka climbs to its highest point in the sky midway between rising and setting. If, at this time, this star shines at your zenith (your straight-overhead point), then you must be at the equator. If this star shines in the southern half of your sky, then you must be north of the equator. From most of South America, the star Mintaka appears in the northern sky, telling the Aymara and other skywatchers who know this star that they’re south of the equator.

From the Arctic north to the Antarctic south, the heavenly Celestial Bridge marks the Earthly wayfarer’s way to the equator – the meeting place of the northern and southern skies.

The constellation Orion straddles the celestial equator, which is indicated by a green line on this chart. Since the celestial equator intersects horizons all over the world at points due east and due west (as shown on the chart above this one), the star Mintaka – the one directly on the green line – can be used to find those cardinal directions in your sky. Image via Aloha.net.

Bottom line: To the Aymara – indigenous people in the Andes and Altiplano regions of South America – the famous sky feature we know as Orion’s Belt is seen as a Celestial Bridge between the sky’s Northern and Southern Hemispheres. The westernmost star in the Belt, or Celestial Bridge – a star called Mintaka – lies directly on the celestial equator.

from EarthSky https://ift.tt/2EvXZIL

This white dwarf star has a giant, evaporating planet

Artist’s concept of the white dwarf star WDJ0914+1914 and its Neptune-like exoplanet. Since the planet orbits very close to the hot white dwarf, the star’s extreme ultraviolet radiation strips away the planet’s atmosphere. Most of this stripped gas escapes into space, but some of it swirls into a disk, accreting onto the white dwarf itself. Image via ESO/M. Kornmesser.

Giant planets – like Jupiter, Saturn, Uranus or Neptune in our own solar system – have been found orbiting many distant stars, including sunlike stars and red dwarfs. But no giant exoplanet had been detected around a white dwarf star, until now. Astronomers say they discovered this giant exoplanet, which orbits the white dwarf WDJ0914+1914, using the European Southern Observatory’s Very Large Telescope in Chile. What’s more, they say, this giant planet is evaporating.

The new peer-reviewed results were published on December 4, 2019, in the journal Nature.

Astronomers have found smaller rocky worlds orbiting white dwarfs before, but this is the first-ever discovery of a giant exoplanet orbiting a white dwarf star. White dwarfs are, as the name implies, small, typically only slightly bigger than Earth. This planet is thought to be at least twice as big as its star! It orbits its star in only about 10 Earth-days. Astronomers knew something strange was happening with the star when they noticed it dimming a bit, as though something were passing in front of it. Boris Gänsicke of the University of Warwick led the study. He said:

It was one of those chance discoveries. We knew that there had to be something exceptional going on in this system, and speculated that it may be related to some type of planetary remnant.

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This chart shows the location of WDJ0914+1914 in the constellation Cancer (in red circle). Image via ESO/IAU/Sky & Telescope.

He was thinking in terms of a remnant, because white dwarfs are evolved stars. They’ve passed through their time on the main sequence (where our sun is now), ballooned up into red giants, then sloughed off their outer layers, leaving the white dwarf, essentially a compact stellar core, behind.

These researchers used the Sloan Digital Sky Survey to peer at 7,000 white dwarf stars before finding one – WDJ0914+1914 – that showed evidence of harboring a giant planet. This white dwarf is 1,500 light-years away in the direction of the constellation Cancer the Crab.

The team not only found evidence that the planet exists, but also that it’s evaporating. This conclusion came after the discovery of hydrogen, oxygen and sulfur in the vicinity of the white dwarf. These elements weren’t in the star itself, these astronomers explained, but rather in a disk of gas surrounding the star. Material in the disk appears to be swirling into the star. According to study co-author Matthias Schreiber of the University of Valparaiso in Chile:

It took a few weeks of very hard thinking to figure out that the only way to make such a disk is the evaporation of a giant planet.

Why would the planet be evaporating? Because, although the white dwarf is very small, it is still extremely hot, about 50,432 degrees Fahrenheit (28,000 degrees Celsius).

Artist’s concept of a planet – in this case the 1st planet – discovered orbiting a white dwarf star. That was in 2015. The planet orbits the white dwarf WD1145+017. Both this planet – and the giant planet found this year – are thought to be disintegrating. Image via The Verge/Mark Garlick.

According to these researchers, the planet probably started out similar to Uranus or Neptune, ice giant worlds in our own solar system. The planet orbiting white dwarf WDJ0914+1914 appears to have quantities of hydrogen, oxygen and sulfur similar to what’s found in the deep atmospheres of Uranus and Neptune. If it were orbiting close to a white dwarf, an ice giant like Uranus or Neptune would have the outer layers of its atmosphere stripped away by ultraviolet radiation. The gases would form a disk around the star and start to swirl into the star itself. As one of the researchers – Odette Toloza from the University of Warwick – noted:

This is the first time we can measure the amounts of gases like oxygen and sulphur in the disk, which provides clues to the composition of exoplanet atmospheres.

What’s more, according to these researchers’ study, there may be other planets orbiting WDJ0914+1914:

The orbit of the planet is most likely the result of gravitational interactions, indicating the presence of additional planets in the system.

In 2015, the Kepler Space Telescope discovered the first planet orbiting another white dwarf star, called WD1145+017. Similar to the newly discovered giant planet, this smaller, rocky world is disintegrating. That white dwarf is 570 light-years away in the direction of the constellation Virgo. This article by Loren Grush in The Verge gives a good overview of that discovery.

About 5 billion years from now, our own sun will burn up all the hydrogen in its core and expand into a red giant, swallowing up the inner planets, including Earth. Then, after the red giant loses its outer layers, all that will remain is the burnt-out core, a white dwarf. Image via Encyclopedia Britannica.

Clearly, this new finding – a giant planet orbiting a white dwarf – parallels the future fate of our own solar system. In fact, Gänsicke added:

The discovery … opens up a new window into the final fate of planetary systems.

That is, our sun will itself one day become a white dwarf, after it burns up all the hydrogen in its core. About 5 billion years from now, the sun will expand into a red giant, swallowing up the inner planets, including Earth. After the red giant sun loses its outer layers, all that remains will be the burnt-out core: a white dwarf where our sun used to be. Do the outer gas and ice giants in our solar system await a similar fate as the giant planet around WDJ0914+1914? As Gänsicke concluded:

Until recently, very few astronomers paused to ponder the fate of planets orbiting dying stars. This discovery of a planet orbiting closely around a burnt-out stellar core forcefully demonstrates that the universe is time and again challenging our minds to step beyond our established ideas.

Boris Gänsicke at the University of Warwick led the study that identified the giant, evaporating planet orbiting a white dwarf star. Image via University of Warwick.

Bottom line: For the first time, astronomers have discovered a giant planet orbiting a white dwarf star, and it seems to be evaporating.

Source: Accretion of a giant planet onto a white dwarf

Via ESO

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Artist’s concept of the white dwarf star WDJ0914+1914 and its Neptune-like exoplanet. Since the planet orbits very close to the hot white dwarf, the star’s extreme ultraviolet radiation strips away the planet’s atmosphere. Most of this stripped gas escapes into space, but some of it swirls into a disk, accreting onto the white dwarf itself. Image via ESO/M. Kornmesser.

Giant planets – like Jupiter, Saturn, Uranus or Neptune in our own solar system – have been found orbiting many distant stars, including sunlike stars and red dwarfs. But no giant exoplanet had been detected around a white dwarf star, until now. Astronomers say they discovered this giant exoplanet, which orbits the white dwarf WDJ0914+1914, using the European Southern Observatory’s Very Large Telescope in Chile. What’s more, they say, this giant planet is evaporating.

The new peer-reviewed results were published on December 4, 2019, in the journal Nature.

Astronomers have found smaller rocky worlds orbiting white dwarfs before, but this is the first-ever discovery of a giant exoplanet orbiting a white dwarf star. White dwarfs are, as the name implies, small, typically only slightly bigger than Earth. This planet is thought to be at least twice as big as its star! It orbits its star in only about 10 Earth-days. Astronomers knew something strange was happening with the star when they noticed it dimming a bit, as though something were passing in front of it. Boris Gänsicke of the University of Warwick led the study. He said:

It was one of those chance discoveries. We knew that there had to be something exceptional going on in this system, and speculated that it may be related to some type of planetary remnant.

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This chart shows the location of WDJ0914+1914 in the constellation Cancer (in red circle). Image via ESO/IAU/Sky & Telescope.

He was thinking in terms of a remnant, because white dwarfs are evolved stars. They’ve passed through their time on the main sequence (where our sun is now), ballooned up into red giants, then sloughed off their outer layers, leaving the white dwarf, essentially a compact stellar core, behind.

These researchers used the Sloan Digital Sky Survey to peer at 7,000 white dwarf stars before finding one – WDJ0914+1914 – that showed evidence of harboring a giant planet. This white dwarf is 1,500 light-years away in the direction of the constellation Cancer the Crab.

The team not only found evidence that the planet exists, but also that it’s evaporating. This conclusion came after the discovery of hydrogen, oxygen and sulfur in the vicinity of the white dwarf. These elements weren’t in the star itself, these astronomers explained, but rather in a disk of gas surrounding the star. Material in the disk appears to be swirling into the star. According to study co-author Matthias Schreiber of the University of Valparaiso in Chile:

It took a few weeks of very hard thinking to figure out that the only way to make such a disk is the evaporation of a giant planet.

Why would the planet be evaporating? Because, although the white dwarf is very small, it is still extremely hot, about 50,432 degrees Fahrenheit (28,000 degrees Celsius).

Artist’s concept of a planet – in this case the 1st planet – discovered orbiting a white dwarf star. That was in 2015. The planet orbits the white dwarf WD1145+017. Both this planet – and the giant planet found this year – are thought to be disintegrating. Image via The Verge/Mark Garlick.

According to these researchers, the planet probably started out similar to Uranus or Neptune, ice giant worlds in our own solar system. The planet orbiting white dwarf WDJ0914+1914 appears to have quantities of hydrogen, oxygen and sulfur similar to what’s found in the deep atmospheres of Uranus and Neptune. If it were orbiting close to a white dwarf, an ice giant like Uranus or Neptune would have the outer layers of its atmosphere stripped away by ultraviolet radiation. The gases would form a disk around the star and start to swirl into the star itself. As one of the researchers – Odette Toloza from the University of Warwick – noted:

This is the first time we can measure the amounts of gases like oxygen and sulphur in the disk, which provides clues to the composition of exoplanet atmospheres.

What’s more, according to these researchers’ study, there may be other planets orbiting WDJ0914+1914:

The orbit of the planet is most likely the result of gravitational interactions, indicating the presence of additional planets in the system.

In 2015, the Kepler Space Telescope discovered the first planet orbiting another white dwarf star, called WD1145+017. Similar to the newly discovered giant planet, this smaller, rocky world is disintegrating. That white dwarf is 570 light-years away in the direction of the constellation Virgo. This article by Loren Grush in The Verge gives a good overview of that discovery.

About 5 billion years from now, our own sun will burn up all the hydrogen in its core and expand into a red giant, swallowing up the inner planets, including Earth. Then, after the red giant loses its outer layers, all that will remain is the burnt-out core, a white dwarf. Image via Encyclopedia Britannica.

Clearly, this new finding – a giant planet orbiting a white dwarf – parallels the future fate of our own solar system. In fact, Gänsicke added:

The discovery … opens up a new window into the final fate of planetary systems.

That is, our sun will itself one day become a white dwarf, after it burns up all the hydrogen in its core. About 5 billion years from now, the sun will expand into a red giant, swallowing up the inner planets, including Earth. After the red giant sun loses its outer layers, all that remains will be the burnt-out core: a white dwarf where our sun used to be. Do the outer gas and ice giants in our solar system await a similar fate as the giant planet around WDJ0914+1914? As Gänsicke concluded:

Until recently, very few astronomers paused to ponder the fate of planets orbiting dying stars. This discovery of a planet orbiting closely around a burnt-out stellar core forcefully demonstrates that the universe is time and again challenging our minds to step beyond our established ideas.

Boris Gänsicke at the University of Warwick led the study that identified the giant, evaporating planet orbiting a white dwarf star. Image via University of Warwick.

Bottom line: For the first time, astronomers have discovered a giant planet orbiting a white dwarf star, and it seems to be evaporating.

Source: Accretion of a giant planet onto a white dwarf

Via ESO

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How does the solar wind affect Earth?

Here’s a new NASA video, released November 24, 2019, on the solar wind, the stream of particles that begins in the sun’s inner atmosphere and continues out beyond our solar system.

How strong is the solar wind? Well, the wind speed of a Category 5 hurricane can top at well over 150 miles (240 km) per hour The average speed of the solar wind is almost a million miles (1.4 km) per hour. It’s the solar wind hitting Earth’s magnetosphere that’s responsible for the gorgeous auroras typically seen at high latitudes. The solar wind can also set off space weather storms that disrupt satellites in space, ship communications on our oceans, and power grids on land. Watch the video to learn more.

Bottom line: NASA video on the solar wind and how it affects Earth.

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Here’s a new NASA video, released November 24, 2019, on the solar wind, the stream of particles that begins in the sun’s inner atmosphere and continues out beyond our solar system.

How strong is the solar wind? Well, the wind speed of a Category 5 hurricane can top at well over 150 miles (240 km) per hour The average speed of the solar wind is almost a million miles (1.4 km) per hour. It’s the solar wind hitting Earth’s magnetosphere that’s responsible for the gorgeous auroras typically seen at high latitudes. The solar wind can also set off space weather storms that disrupt satellites in space, ship communications on our oceans, and power grids on land. Watch the video to learn more.

Bottom line: NASA video on the solar wind and how it affects Earth.

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Aldebaran is the Bull’s fiery eye

If you can find the prominent constellation Orion, you can find the bright red star Aldebaran. Orion’s Belt always points to Aldebaran. Extending that line takes you generally toward the Pleiades, or Seven Sisters. Look east in mid-evening in December. Check Stellarium for the view at your location.

The reddish star Aldebaran – fiery eye of the Bull in the constellation Taurus – is easy to find. It’s part of a V-shaped star grouping that forms the Bull’s face. This pattern is called the Hyades. You can locate Aldebaran using the famous constellation Orion as a guide. Notice the three stars of Orion’s Belt. Then draw an imaginary line through the belt to the right. The first bright star you come to will be Aldebaran with its distinctive reddish-orange glow.

Aldebaran is the 14th brightest star, but five of those that outshine it are only barely visible or not visible at all from much of the Northern Hemisphere. Aldebaran is primarily a winter and spring star for us on the northern part of Earth. That is when this red star is most easily visible in the evening sky. By early December, it rises shortly after sunset and is visible all night. Three months later it is high to the south at sunset, and sets at around midnight. By early May, it hangs low about the western sunset glow – and before the end of the month, it’s lost altogether. It returns to the predawn sky around late June.

By the way, although it appears among them, Aldebaran is not actually a member of the V-shaped Hyades cluster. It is actually much closer to us in space than the other Hyades stars.

Read more about the Hyades: Face of Taurus

Constellation Taurus. See Aldebaran marked as the Bull’s Eye? View larger.

History and mythology of Aldebaran. Aldebaran is often depicted as the fiery eye of Taurus the Bull. Because it is bright and prominent, Aldebaran was honored as one of the Four Royal Stars in ancient Persia, the other three Royal Stars being Regulus, Antares and Fomalhaut.

The name Aldebaran is from the Arabic for “the follower,” presumably as a hunter following prey, which here likely was the star cluster we call the Pleiades. The latter was often viewed as a flock of birds, perhaps doves. According to Richard Hinckley Allen in his classic book Star Names, the name Aldebaran once was applied to the entire Hyades star cluster, a large loose collection of faint stars.

In Hindu myth, Aldebaran was sometimes identified with a beautiful young woman named Rohini, disguised as an antelope and pursued by her lecherous father, disguised as a deer, Mriga. Apparently several ancient peoples associated the star with rain. The Wikipedia entry notes a Dakota Sioux story in which Aldebaran was a star which had fallen to the Earth and whose killing of a serpent led to the formation of the Mississippi River. Allen notes a number of other alternate names, but precious little mythology is known for Aldebaran separately.

Aldebaran is the name of one of the chariot horses in the movie Ben Hur.

On a different note, astronomer Jack Eddy has suggested a connection with the Big Horn Medicine Wheel, an ancient circle of stones atop a mountain in Wyoming. Eddy wrote that the ancient Americans may have used this site as a sort of observatory to view the rising of Aldebaran just before the sun in June to predict the June solstice.

Interestingly, in about two million years, the NASA space probe Pioneer 10, now heading out into deep space, will pass Aldebaran.

Compare the size of Aldebaran with our sun. Image via Wikipedia

Aldebaran is an aging star and a huge star! The computed diameter is between 35 and 40 solar diameters. If Aldebaran were placed where the sun is now, its surface would extend almost to the orbit of Mercury.

Science of Aldebaran. This star glows with the orangish color of a K5 giant star. In visible light, it is about 153 times brighter than the sun, although its surface temperature is lower (roughly 4000 kelvins compared to 5800 kelvins for the sun).

Aldebaran is about 65 light-years away, much closer than the stars of the Hyades with which it misleadingly seems associated. The Hyades are about 150 light-years away.

Aldebaran is an erratic variable with minor variations too small to be noticed by the eye. It also has a small, faint companion star, an M-type red dwarf, some 3.5 light-days away. In other words, light from Aldebaran would need to travel for 3.5 days to reach the companion, in contrast to light from our sun, which requires 8 minutes to travel to Earth.

Aldebaran’s position is RA: 4h 35m 55s, dec: 16°30’35”

Bottom line: The star Aldebaran is so huge that, if it were in our sun’s place, its surface would extend almost to the orbit of Mercury.

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If you can find the prominent constellation Orion, you can find the bright red star Aldebaran. Orion’s Belt always points to Aldebaran. Extending that line takes you generally toward the Pleiades, or Seven Sisters. Look east in mid-evening in December. Check Stellarium for the view at your location.

The reddish star Aldebaran – fiery eye of the Bull in the constellation Taurus – is easy to find. It’s part of a V-shaped star grouping that forms the Bull’s face. This pattern is called the Hyades. You can locate Aldebaran using the famous constellation Orion as a guide. Notice the three stars of Orion’s Belt. Then draw an imaginary line through the belt to the right. The first bright star you come to will be Aldebaran with its distinctive reddish-orange glow.

Aldebaran is the 14th brightest star, but five of those that outshine it are only barely visible or not visible at all from much of the Northern Hemisphere. Aldebaran is primarily a winter and spring star for us on the northern part of Earth. That is when this red star is most easily visible in the evening sky. By early December, it rises shortly after sunset and is visible all night. Three months later it is high to the south at sunset, and sets at around midnight. By early May, it hangs low about the western sunset glow – and before the end of the month, it’s lost altogether. It returns to the predawn sky around late June.

By the way, although it appears among them, Aldebaran is not actually a member of the V-shaped Hyades cluster. It is actually much closer to us in space than the other Hyades stars.

Read more about the Hyades: Face of Taurus

Constellation Taurus. See Aldebaran marked as the Bull’s Eye? View larger.

History and mythology of Aldebaran. Aldebaran is often depicted as the fiery eye of Taurus the Bull. Because it is bright and prominent, Aldebaran was honored as one of the Four Royal Stars in ancient Persia, the other three Royal Stars being Regulus, Antares and Fomalhaut.

The name Aldebaran is from the Arabic for “the follower,” presumably as a hunter following prey, which here likely was the star cluster we call the Pleiades. The latter was often viewed as a flock of birds, perhaps doves. According to Richard Hinckley Allen in his classic book Star Names, the name Aldebaran once was applied to the entire Hyades star cluster, a large loose collection of faint stars.

In Hindu myth, Aldebaran was sometimes identified with a beautiful young woman named Rohini, disguised as an antelope and pursued by her lecherous father, disguised as a deer, Mriga. Apparently several ancient peoples associated the star with rain. The Wikipedia entry notes a Dakota Sioux story in which Aldebaran was a star which had fallen to the Earth and whose killing of a serpent led to the formation of the Mississippi River. Allen notes a number of other alternate names, but precious little mythology is known for Aldebaran separately.

Aldebaran is the name of one of the chariot horses in the movie Ben Hur.

On a different note, astronomer Jack Eddy has suggested a connection with the Big Horn Medicine Wheel, an ancient circle of stones atop a mountain in Wyoming. Eddy wrote that the ancient Americans may have used this site as a sort of observatory to view the rising of Aldebaran just before the sun in June to predict the June solstice.

Interestingly, in about two million years, the NASA space probe Pioneer 10, now heading out into deep space, will pass Aldebaran.

Compare the size of Aldebaran with our sun. Image via Wikipedia

Aldebaran is an aging star and a huge star! The computed diameter is between 35 and 40 solar diameters. If Aldebaran were placed where the sun is now, its surface would extend almost to the orbit of Mercury.

Science of Aldebaran. This star glows with the orangish color of a K5 giant star. In visible light, it is about 153 times brighter than the sun, although its surface temperature is lower (roughly 4000 kelvins compared to 5800 kelvins for the sun).

Aldebaran is about 65 light-years away, much closer than the stars of the Hyades with which it misleadingly seems associated. The Hyades are about 150 light-years away.

Aldebaran is an erratic variable with minor variations too small to be noticed by the eye. It also has a small, faint companion star, an M-type red dwarf, some 3.5 light-days away. In other words, light from Aldebaran would need to travel for 3.5 days to reach the companion, in contrast to light from our sun, which requires 8 minutes to travel to Earth.

Aldebaran’s position is RA: 4h 35m 55s, dec: 16°30’35”

Bottom line: The star Aldebaran is so huge that, if it were in our sun’s place, its surface would extend almost to the orbit of Mercury.

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What is a scream? The acoustics of a primal human call

Getty Images

Screams are prompted by a variety of emotions — from joyful surprise to abject terror. No matter what sparks them, however, human screams share distinctive acoustic parameters that listeners are attuned to, suggests a new study published by the Journal of Nonverbal Behavior.

 “Screams require a lot of vocal force and cause the vocal folds to vibrate in a chaotic, inconsistent way,” says senior author Harold Gouzoules, a professor of psychology at Emory University. “Despite the inherent variation in the way that screams are produced, our findings show that listeners can readily distinquish a scream from other human calls. And we are honing in on how they make that distinction.”

Jay Schwartz is first author of the paper and Jonathan Engleberg is a co-author. They are both Emory PhD candidates in Gouzoules’ Bioacoustics Lab. Gouzoules began researching monkey screams in 1980, before becoming one of the few scientists studying human screams about 10 years ago. He is interested in the origins of screams and the role they played in human development.

“Animal screams occur almost always in the context of a fight or in response to a predator,” Gouzoules says. “Human screams happen in a much broader array of contexts, which makes them much more interesting.”

Gouzoules' Bioacoustics Lab has amassed an impressive library of high-intensity, visceral sounds — from TV and movie performances to the screams of non-actors reacting to actual events posted to online sites such as YouTube.

For the current study, the researchers presented 182 participants with a range of human calls. Some of the calls were screams of aggression, exclamation, excitement, fear or pain. Others calls included cries, laughter and yells.

The participants showed strong agreement for what classified as a scream. An acoustical analysis for the calls the participants classified as screams, compared to those they did not, included a higher pitch and roughness, or harshness, to the sound; a wider variability in frequency; and a higher peak frequency.

The current paper is part of an extensive program of research into screams by Gouzoules. In another recently published article, his lab has found that listeners cannot distinguish acted screams from naturally occurring screams. Listeners can, however, correctly identify whether pairs of screams were produced by the same person or two different people.

from eScienceCommons https://ift.tt/2rTkNwQ

Getty Images

Screams are prompted by a variety of emotions — from joyful surprise to abject terror. No matter what sparks them, however, human screams share distinctive acoustic parameters that listeners are attuned to, suggests a new study published by the Journal of Nonverbal Behavior.

 “Screams require a lot of vocal force and cause the vocal folds to vibrate in a chaotic, inconsistent way,” says senior author Harold Gouzoules, a professor of psychology at Emory University. “Despite the inherent variation in the way that screams are produced, our findings show that listeners can readily distinquish a scream from other human calls. And we are honing in on how they make that distinction.”

Jay Schwartz is first author of the paper and Jonathan Engleberg is a co-author. They are both Emory PhD candidates in Gouzoules’ Bioacoustics Lab. Gouzoules began researching monkey screams in 1980, before becoming one of the few scientists studying human screams about 10 years ago. He is interested in the origins of screams and the role they played in human development.

“Animal screams occur almost always in the context of a fight or in response to a predator,” Gouzoules says. “Human screams happen in a much broader array of contexts, which makes them much more interesting.”

Gouzoules' Bioacoustics Lab has amassed an impressive library of high-intensity, visceral sounds — from TV and movie performances to the screams of non-actors reacting to actual events posted to online sites such as YouTube.

For the current study, the researchers presented 182 participants with a range of human calls. Some of the calls were screams of aggression, exclamation, excitement, fear or pain. Others calls included cries, laughter and yells.

The participants showed strong agreement for what classified as a scream. An acoustical analysis for the calls the participants classified as screams, compared to those they did not, included a higher pitch and roughness, or harshness, to the sound; a wider variability in frequency; and a higher peak frequency.

The current paper is part of an extensive program of research into screams by Gouzoules. In another recently published article, his lab has found that listeners cannot distinguish acted screams from naturally occurring screams. Listeners can, however, correctly identify whether pairs of screams were produced by the same person or two different people.

from eScienceCommons https://ift.tt/2rTkNwQ