Solstice sun at southernmost point

Image above: “First light of winter,” wrote Karl Diefenderfer in Yardley, Pennsylvania.

You might think of the solstice as a day, but it’s really a moment. The December solstice happens at 4:19 UTC on December 22, 2019. That time – the moment of solstice – marks the sun’s southernmost point in our sky for this year.

Here in North America, the solstice happens on December 21 (11:19 p.m. EST, 10:19 p.m. CST, 9:19 p.m. MST, 8:19 p.m. PST, 7:19 p.m. Alaskan Time and 6:19 p.m. Hawaiian Time). When is the moment of solstice for your location? Translate December 22 at 4:19 UTC to your time zone, here.

Looking at the world map below, you can see that the 2019 December solstice happens when it’s sunset (December 21) in the Pacific Ocean, midnight (December 21-22) in South America, sunrise (December 22) in Africa and the Middle East, and noontime (December 22) for East Asia.

By noontime, we mean midday, or midway between sunrise and sunset. By midnight, we mean the middle of the night, or midway between sunset and sunrise.

Day and night sides of Earth at the instant of the December 2019 solstice (December 22, 2019, at 4:19 UTC). Image via EarthView.

On the December solstice, we celebrate the unofficial first day of winter in the Northern Hemisphere and first day of summer in the Southern Hemisphere. Unofficial? Yes. Winter and summer start at the solstices by tradition, not official decree.

Yet these solstices bring very real occurrences to our sky, which you can witness for yourself. In both the Northern and Southern Hemispheres, the December solstice brings the southernmost sunrise and the southernmost sunset of the year. If you stand in one spot day after day, week after week – for example, gazing out a particular window toward the sunrise or sunset on the horizon – you will surely notice the sunset’s northward trek along the horizon over the coming months.

From time to time, try fixing a bit of tape to your window, on which you’ve written the date, to help you mark the sun’s passage. Or notice it with respect to landmarks in your surroundings, as Peter Lowenstein did, below:

Solstice sunsets, showing the sun’s position on the local horizon at December (left) and June (right) solstices from Mutare, Zimbabwe, via Peter Lowenstein.

In the Northern Hemisphere, the southernmost sunrise and sunset usher in the year’s shortest day and the longest night.

In the Southern Hemisphere, it’s the exact opposite, where the year’s southernmost sunrise and sunset give the Southern Hemisphere its longest day and shortest night.

Not every place worldwide has a sunrise and a sunset on the day of the December solstice. North of the Arctic Circle – or north of 66.5 degrees north latitude – there is no sunrise or sunset today, because the sun stays beneath the horizon all day long. South of the Antarctic Circle – at 66.5 degrees south of the equator – you won’t see a sunrise or sunset either, because the sun stays above the horizon all day.

After the sun reaches its southernmost point on the sky’s dome on the December solstice, watch as the sun seems to pause for a number of days before it starts its northward trajectory on the sky’s dome once again.

Earth has seasons because our world is tilted on its axis with respect to our orbit around the sun. Image via NASA.

Bottom line: In 2019, the December solstice comes on December 21 at 10:19 p.m. CST. That’s December 22 at 4:19 UTC. It’s when the sun on our sky’s dome reaches its farthest southward point for the year. Happy solstice, everyone!

Want more? Click here to read more about the December solstice

A solstice tale of two cities

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Image above: “First light of winter,” wrote Karl Diefenderfer in Yardley, Pennsylvania.

You might think of the solstice as a day, but it’s really a moment. The December solstice happens at 4:19 UTC on December 22, 2019. That time – the moment of solstice – marks the sun’s southernmost point in our sky for this year.

Here in North America, the solstice happens on December 21 (11:19 p.m. EST, 10:19 p.m. CST, 9:19 p.m. MST, 8:19 p.m. PST, 7:19 p.m. Alaskan Time and 6:19 p.m. Hawaiian Time). When is the moment of solstice for your location? Translate December 22 at 4:19 UTC to your time zone, here.

Looking at the world map below, you can see that the 2019 December solstice happens when it’s sunset (December 21) in the Pacific Ocean, midnight (December 21-22) in South America, sunrise (December 22) in Africa and the Middle East, and noontime (December 22) for East Asia.

By noontime, we mean midday, or midway between sunrise and sunset. By midnight, we mean the middle of the night, or midway between sunset and sunrise.

Day and night sides of Earth at the instant of the December 2019 solstice (December 22, 2019, at 4:19 UTC). Image via EarthView.

On the December solstice, we celebrate the unofficial first day of winter in the Northern Hemisphere and first day of summer in the Southern Hemisphere. Unofficial? Yes. Winter and summer start at the solstices by tradition, not official decree.

Yet these solstices bring very real occurrences to our sky, which you can witness for yourself. In both the Northern and Southern Hemispheres, the December solstice brings the southernmost sunrise and the southernmost sunset of the year. If you stand in one spot day after day, week after week – for example, gazing out a particular window toward the sunrise or sunset on the horizon – you will surely notice the sunset’s northward trek along the horizon over the coming months.

From time to time, try fixing a bit of tape to your window, on which you’ve written the date, to help you mark the sun’s passage. Or notice it with respect to landmarks in your surroundings, as Peter Lowenstein did, below:

Solstice sunsets, showing the sun’s position on the local horizon at December (left) and June (right) solstices from Mutare, Zimbabwe, via Peter Lowenstein.

In the Northern Hemisphere, the southernmost sunrise and sunset usher in the year’s shortest day and the longest night.

In the Southern Hemisphere, it’s the exact opposite, where the year’s southernmost sunrise and sunset give the Southern Hemisphere its longest day and shortest night.

Not every place worldwide has a sunrise and a sunset on the day of the December solstice. North of the Arctic Circle – or north of 66.5 degrees north latitude – there is no sunrise or sunset today, because the sun stays beneath the horizon all day long. South of the Antarctic Circle – at 66.5 degrees south of the equator – you won’t see a sunrise or sunset either, because the sun stays above the horizon all day.

After the sun reaches its southernmost point on the sky’s dome on the December solstice, watch as the sun seems to pause for a number of days before it starts its northward trajectory on the sky’s dome once again.

Earth has seasons because our world is tilted on its axis with respect to our orbit around the sun. Image via NASA.

Bottom line: In 2019, the December solstice comes on December 21 at 10:19 p.m. CST. That’s December 22 at 4:19 UTC. It’s when the sun on our sky’s dome reaches its farthest southward point for the year. Happy solstice, everyone!

Want more? Click here to read more about the December solstice

A solstice tale of two cities

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News digest – prostate cancer MRI trial, drug delivery, cancer ‘cures’ on Facebook and weight loss

A prostate cancer MRI trial is in progress

BBC News reports on a new large-scale trial that will test if MRI scans could be used to screen men for prostate cancer. The trial will invite 300 randomly selected men aged 50 to 75 years old to have a 10-minute MRI scan and a PSA blood test. Scientists are hoping to find out if using MRI in this way could help to flag men who have signs of prostate cancer without the need for a biopsy. We’ve blogged before about how scientists are working to improve prostate cancer diagnosis.

Treatment that delivers drug straight to tumour given for the first time

A British woman is the first person in the world to receive a new treatment that aims to deliver high doses of chemotherapy directly to cancer cells. The treatment, which uses tiny clusters of bubbles and liquid droplets to enhance the delivery of chemotherapy, is part of a clinical trial being carried out in London that’s looking to reduce the number of doses of chemotherapy and its side effects for cancer patients. Read the full story in The Metro.

WHO approves cheap copy of common breast cancer drug

A cheaper version of the breast cancer drug Herceptin has been approved by the World Health Organisation (WHO). This decision will make it possible for women in low-income countries to benefit from treatment. This type of hormone therapy blocks off certain cancers’ fuel supply. More on this in The Guardian.

Facebook bans ads promoting fake cancer ‘cures’

Several Facebook groups promoting a dangerous skin cancer ‘treatment’ have been banned from the social media channel, following concerns about ‘sensational health claims’. Groups were promoting a black salve paste, which they claimed had the ability to cure skin cancer by ‘eating away’ at only cancerous cells. According to Buzzfeed News, the groups have been found to be in violation of Facebook rules that prohibit ‘violent and criminal behaviour’. Commenting on the story, experts strongly advised anyone considering taking an alternative or complimentary medicine to seek advice from a trained medical professional.

And finally

The Mail Online covers a study that says that post-menopausal women who are overweight could reduce their risk of breast cancer if they lose at least 20lbs. But the results present quite a complicated picture. Women who had sustained weight loss only had a reduced cancer risk if they weren’t taking hormone replacement therapy (HRT). And because hormone replacement therapy can increase the risk of breast cancer too, it’s hard to untangle which risk factor is having an effect. Unfortunately, there’s still not enough evidence to know what effect different patterns of weight loss can have on cancer risk.

Scarlett Sangster is a writer for PA Media Group 

from Cancer Research UK – Science blog https://ift.tt/2s8j6fw

A prostate cancer MRI trial is in progress

BBC News reports on a new large-scale trial that will test if MRI scans could be used to screen men for prostate cancer. The trial will invite 300 randomly selected men aged 50 to 75 years old to have a 10-minute MRI scan and a PSA blood test. Scientists are hoping to find out if using MRI in this way could help to flag men who have signs of prostate cancer without the need for a biopsy. We’ve blogged before about how scientists are working to improve prostate cancer diagnosis.

Treatment that delivers drug straight to tumour given for the first time

A British woman is the first person in the world to receive a new treatment that aims to deliver high doses of chemotherapy directly to cancer cells. The treatment, which uses tiny clusters of bubbles and liquid droplets to enhance the delivery of chemotherapy, is part of a clinical trial being carried out in London that’s looking to reduce the number of doses of chemotherapy and its side effects for cancer patients. Read the full story in The Metro.

WHO approves cheap copy of common breast cancer drug

A cheaper version of the breast cancer drug Herceptin has been approved by the World Health Organisation (WHO). This decision will make it possible for women in low-income countries to benefit from treatment. This type of hormone therapy blocks off certain cancers’ fuel supply. More on this in The Guardian.

Facebook bans ads promoting fake cancer ‘cures’

Several Facebook groups promoting a dangerous skin cancer ‘treatment’ have been banned from the social media channel, following concerns about ‘sensational health claims’. Groups were promoting a black salve paste, which they claimed had the ability to cure skin cancer by ‘eating away’ at only cancerous cells. According to Buzzfeed News, the groups have been found to be in violation of Facebook rules that prohibit ‘violent and criminal behaviour’. Commenting on the story, experts strongly advised anyone considering taking an alternative or complimentary medicine to seek advice from a trained medical professional.

And finally

The Mail Online covers a study that says that post-menopausal women who are overweight could reduce their risk of breast cancer if they lose at least 20lbs. But the results present quite a complicated picture. Women who had sustained weight loss only had a reduced cancer risk if they weren’t taking hormone replacement therapy (HRT). And because hormone replacement therapy can increase the risk of breast cancer too, it’s hard to untangle which risk factor is having an effect. Unfortunately, there’s still not enough evidence to know what effect different patterns of weight loss can have on cancer risk.

Scarlett Sangster is a writer for PA Media Group 

from Cancer Research UK – Science blog https://ift.tt/2s8j6fw

Remains of Earth’s oldest forest found in New York

Scientists have discovered what’s now Earth’s oldest known forest, at a sandstone quarry near Cairo, New York. They found three types of ancient trees, with what they called “surprisingly modern root systems,” dating back to 386 million years ago. Analysis of these trees suggests our world’s transition toward forests as we know them today began several million years earlier than formerly believed. The findings – published in the December 19, 2019, issue of the journal Current Biology – shed new light on the early evolution of the trees that help shape and reshape our planet’s surface, oceans and air.

The team consisted of scientists at Binghamton University, New York State Museum and Cardiff University. These researchers mapped over 3,000 square meters (around 3/4 of an acre) of the forest at an abandoned quarry in the foothills of the Catskill Mountains, at the northeastern end of the Allegheny Plateau. A statement from Binghamton University explained:

While sifting through fossil soils in the Catskill region … researchers uncovered the extensive root system of 385-million-year old trees that existed during the Devonian Period. While seed plants didn’t appear until some 10 million years later, these preserved root systems show evidence of the presence of trees with leaves and wood – both of which are common in modern seed plants.

Lead author William Stein, emeritus professor of biological sciences at Binghamton University, said:

The Devonian Period represents a time in which the first forest appeared on planet Earth. The effects were of first order magnitude in terms of changes in ecosystems, what happens on the Earth’s surface and oceans, CO2 concentration in the atmosphere and global climate.

So many dramatic changes occurred at that time as a result of those original forests that, basically, the world has never been the same since.

EarthSky 2020 lunar calendars are available! They make great gifts. Order now. Going fast!

Some of the fossilized roots uncovered at the quarry near Cairo, New York. Via Cardiff University.

Before this new discovery, in 2012, Stein and his team had conducted research at the fossil forest at Gilboa in New York State, often described as Earth’s oldest known forest. Their statement explained:

The discovery at Cairo, about a 40-minute drive from the original site, now reveals an even older forest with dramatically different composition.

The Cairo forest is around 2 or 3 million years older than that at Gilboa. The research team commented in a statement from Cardiff University that the Cairo forest is older than the one at Gilboa because the fossils were lower down in the sequence of rocks that occur in the Catskill mountains.

The scientists explained:

The Cairo site presents three unique root systems, leading Stein and his team to hypothesize that much like today, the forests of the Devonian Period were heterogeneous with different trees occupying different places depending on local conditions.

First, Stein and his team identified a rooting system that they believe belonged to a palm tree-like tree called Eospermatopteris. This plant, first identified at the Gilboa site, had relatively rudimentary roots. Like a weed, Eospermatopteris likely occupied many environments, explaining its presence at both sites. But its roots had relatively limited range and probably lived only a year or two before dying and being replaced by other roots that would occupy the same space.

The researchers also found evidence of a tree called Archaeopteris, which shares a number of characteristics with modern seed plants. Although this tree behaved more like a fern during reproduction, by releasing spores into the air instead of forming seeds, it had early hints at what would one day become seed plants: Archaeopteris is the first known plant to form leaves, and was a large woody plant formed from secondary tissues. At Cairo, this tree was now found to also have a strikingly modern underground system allowing for continuous expansion of roots accommodating continuous growth of a long-lived larger type of tree, and potentially dominating the local forest ecosystem.

Cleaning the surface at the Cairo fossil forest site. Image via William Stein/ Binghamton University.

Stein commented:

Archaeopteris seems to reveal the beginning of the future of what forests will ultimately become. Based on what we know from the body fossil evidence of Archaeopteris prior to this, and now from the rooting evidence that we’ve added at Cairo, these plants are very modern compared to other Devonian plants. Although still dramatically different than modern trees, Archaeopteris nevertheless seems to point the way toward the future of forests.

Stein and his team were also surprised to find a third root system in the fossilized soil at Cairo, belonging to a tree thought to only exist during the Carboniferous Period and beyond: “scale trees” belonging to the class Lycopsida. Stein explained:

What we have at Cairo is a rooting structure that appears identical to great trees of the Carboniferous coal swamps with fascinating elongated roots. But no one has yet found body fossil evidence of this group this early in the Devonian. Our findings are perhaps suggestive that these plants were already in the forest, but perhaps in a different environment and earlier than generally believed. Yet we only have a footprint, and we await additional fossil evidence for confirmation.

Co-author of the study Chris Berry of Cardiff University commented:

It is surprising to see plants which were previously thought to have had mutually exclusive habitat preferences growing together on the ancient Catskill delta.

These researchers believe the forest was eventually wiped out by a flood, due to the presence of many fish fossils that were also visible on the surface of the quarry.

Archaeopteris root system at the Cairo fossil forest site at first discovery. Image via Charles Ver Straeten/ Binghamton University.

Bottom line: The oldest known forest, dating to 386 million years ago, was uncovered by scientists at a quarry near Cairo, New York. Their discovery provides new insights into the early evolution of trees that helped reshape our planet and was published in the December 19, 2019, issue of the journal Current Biology.

Source: Mid-Devonian Archaeopteris Roots signal Revolutionary Change in Earliest Fossil Forest

Via Binghamton University

Via Cardiff University

from EarthSky https://ift.tt/34InQpn

Scientists have discovered what’s now Earth’s oldest known forest, at a sandstone quarry near Cairo, New York. They found three types of ancient trees, with what they called “surprisingly modern root systems,” dating back to 386 million years ago. Analysis of these trees suggests our world’s transition toward forests as we know them today began several million years earlier than formerly believed. The findings – published in the December 19, 2019, issue of the journal Current Biology – shed new light on the early evolution of the trees that help shape and reshape our planet’s surface, oceans and air.

The team consisted of scientists at Binghamton University, New York State Museum and Cardiff University. These researchers mapped over 3,000 square meters (around 3/4 of an acre) of the forest at an abandoned quarry in the foothills of the Catskill Mountains, at the northeastern end of the Allegheny Plateau. A statement from Binghamton University explained:

While sifting through fossil soils in the Catskill region … researchers uncovered the extensive root system of 385-million-year old trees that existed during the Devonian Period. While seed plants didn’t appear until some 10 million years later, these preserved root systems show evidence of the presence of trees with leaves and wood – both of which are common in modern seed plants.

Lead author William Stein, emeritus professor of biological sciences at Binghamton University, said:

The Devonian Period represents a time in which the first forest appeared on planet Earth. The effects were of first order magnitude in terms of changes in ecosystems, what happens on the Earth’s surface and oceans, CO2 concentration in the atmosphere and global climate.

So many dramatic changes occurred at that time as a result of those original forests that, basically, the world has never been the same since.

EarthSky 2020 lunar calendars are available! They make great gifts. Order now. Going fast!

Some of the fossilized roots uncovered at the quarry near Cairo, New York. Via Cardiff University.

Before this new discovery, in 2012, Stein and his team had conducted research at the fossil forest at Gilboa in New York State, often described as Earth’s oldest known forest. Their statement explained:

The discovery at Cairo, about a 40-minute drive from the original site, now reveals an even older forest with dramatically different composition.

The Cairo forest is around 2 or 3 million years older than that at Gilboa. The research team commented in a statement from Cardiff University that the Cairo forest is older than the one at Gilboa because the fossils were lower down in the sequence of rocks that occur in the Catskill mountains.

The scientists explained:

The Cairo site presents three unique root systems, leading Stein and his team to hypothesize that much like today, the forests of the Devonian Period were heterogeneous with different trees occupying different places depending on local conditions.

First, Stein and his team identified a rooting system that they believe belonged to a palm tree-like tree called Eospermatopteris. This plant, first identified at the Gilboa site, had relatively rudimentary roots. Like a weed, Eospermatopteris likely occupied many environments, explaining its presence at both sites. But its roots had relatively limited range and probably lived only a year or two before dying and being replaced by other roots that would occupy the same space.

The researchers also found evidence of a tree called Archaeopteris, which shares a number of characteristics with modern seed plants. Although this tree behaved more like a fern during reproduction, by releasing spores into the air instead of forming seeds, it had early hints at what would one day become seed plants: Archaeopteris is the first known plant to form leaves, and was a large woody plant formed from secondary tissues. At Cairo, this tree was now found to also have a strikingly modern underground system allowing for continuous expansion of roots accommodating continuous growth of a long-lived larger type of tree, and potentially dominating the local forest ecosystem.

Cleaning the surface at the Cairo fossil forest site. Image via William Stein/ Binghamton University.

Stein commented:

Archaeopteris seems to reveal the beginning of the future of what forests will ultimately become. Based on what we know from the body fossil evidence of Archaeopteris prior to this, and now from the rooting evidence that we’ve added at Cairo, these plants are very modern compared to other Devonian plants. Although still dramatically different than modern trees, Archaeopteris nevertheless seems to point the way toward the future of forests.

Stein and his team were also surprised to find a third root system in the fossilized soil at Cairo, belonging to a tree thought to only exist during the Carboniferous Period and beyond: “scale trees” belonging to the class Lycopsida. Stein explained:

What we have at Cairo is a rooting structure that appears identical to great trees of the Carboniferous coal swamps with fascinating elongated roots. But no one has yet found body fossil evidence of this group this early in the Devonian. Our findings are perhaps suggestive that these plants were already in the forest, but perhaps in a different environment and earlier than generally believed. Yet we only have a footprint, and we await additional fossil evidence for confirmation.

Co-author of the study Chris Berry of Cardiff University commented:

It is surprising to see plants which were previously thought to have had mutually exclusive habitat preferences growing together on the ancient Catskill delta.

These researchers believe the forest was eventually wiped out by a flood, due to the presence of many fish fossils that were also visible on the surface of the quarry.

Archaeopteris root system at the Cairo fossil forest site at first discovery. Image via Charles Ver Straeten/ Binghamton University.

Bottom line: The oldest known forest, dating to 386 million years ago, was uncovered by scientists at a quarry near Cairo, New York. Their discovery provides new insights into the early evolution of trees that helped reshape our planet and was published in the December 19, 2019, issue of the journal Current Biology.

Source: Mid-Devonian Archaeopteris Roots signal Revolutionary Change in Earliest Fossil Forest

Via Binghamton University

Via Cardiff University

from EarthSky https://ift.tt/34InQpn

December solstice starts shortest season

The December solstice will come on December 22, 2019, at 4:19 UTC. That’s 10:19 p.m. (22:19) CST on December 21 for those in the central time zone in North America. It’s when the sun reaches its southernmost point for the year. This solstice marks the beginning of the winter season in the Northern Hemisphere, and the start of the summer season in the Southern Hemisphere. And, no matter where you are on Earth, it marks the beginning of your shortest season.

By season, we mean the time between a solstice and an equinox, or vice versa. The upcoming season – between the December solstice and March equinox – is a touch shy of 89 days.

Contrast the number of days of the upcoming season with that of the longest season, a Northern Hemisphere summer or Southern Hemisphere winter. The longest season as measured from the June solstice to the September equinox lasts 93.65 days.

Why is the upcoming season nearly five days shorter? Keep reading to learn more.

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Are you a morning person.? Then watch for the moon to go by the celestial line-up: Spica, the brightest star in the constellation Virgo, Zubenelgenubi, the constellation Libra’s alpha star, and Mars, the 4th planet from the sun.

Here’s why the seasons are different lengths. Every year in early January, the Earth swings closest to the sun for the year. Because Earth is nearest the sun at this time, Earth moves most swiftly in its orbit. That’s why a Northern Hemisphere winter or Southern Hemisphere summer is the shortest of the four seasons.

On the other hand, in early July, Earth is farthest from the sun and moving most slowly in its orbit.

Lengths of the astronomical seasons:

December solstice to March equinox: 88.99 days
March equinox to June solstice: 92.76 days
June solstice to September equinox: 93.65 days
September equinox to December solstice: 89.84 days

According to the computational wizard Jean Meeus, a Northern Hemisphere winter or Southern Hemisphere summer became the shortest season after the year 1246. The astronomical season between the December solstice and the March equinox will reach a minimum value of 88.71 days around the year 3500, and will continue to reign as the shortest season until about 6430.

Bottom line: By season, we mean the time between a solstice and an equinox, or vice versa. Shortest season begins on December 22, 2019. It’s a touch shy of 89 days in length.

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The December solstice will come on December 22, 2019, at 4:19 UTC. That’s 10:19 p.m. (22:19) CST on December 21 for those in the central time zone in North America. It’s when the sun reaches its southernmost point for the year. This solstice marks the beginning of the winter season in the Northern Hemisphere, and the start of the summer season in the Southern Hemisphere. And, no matter where you are on Earth, it marks the beginning of your shortest season.

By season, we mean the time between a solstice and an equinox, or vice versa. The upcoming season – between the December solstice and March equinox – is a touch shy of 89 days.

Contrast the number of days of the upcoming season with that of the longest season, a Northern Hemisphere summer or Southern Hemisphere winter. The longest season as measured from the June solstice to the September equinox lasts 93.65 days.

Why is the upcoming season nearly five days shorter? Keep reading to learn more.

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

Are you a morning person.? Then watch for the moon to go by the celestial line-up: Spica, the brightest star in the constellation Virgo, Zubenelgenubi, the constellation Libra’s alpha star, and Mars, the 4th planet from the sun.

Here’s why the seasons are different lengths. Every year in early January, the Earth swings closest to the sun for the year. Because Earth is nearest the sun at this time, Earth moves most swiftly in its orbit. That’s why a Northern Hemisphere winter or Southern Hemisphere summer is the shortest of the four seasons.

On the other hand, in early July, Earth is farthest from the sun and moving most slowly in its orbit.

Lengths of the astronomical seasons:

December solstice to March equinox: 88.99 days
March equinox to June solstice: 92.76 days
June solstice to September equinox: 93.65 days
September equinox to December solstice: 89.84 days

According to the computational wizard Jean Meeus, a Northern Hemisphere winter or Southern Hemisphere summer became the shortest season after the year 1246. The astronomical season between the December solstice and the March equinox will reach a minimum value of 88.71 days around the year 3500, and will continue to reign as the shortest season until about 6430.

Bottom line: By season, we mean the time between a solstice and an equinox, or vice versa. Shortest season begins on December 22, 2019. It’s a touch shy of 89 days in length.

Enjoying EarthSky so far? Sign up for our free daily newsletter today!

EarthSky astronomy kits are perfect for beginners. Order today from the EarthSky store

Donate: Your support means the world to us

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

Scientists see a new kind of explosion on the sun

NASA’s Solar Dynamics Observatory (SDO) has observed a kind of magnetic explosion on the sun that scientists have never seen before. The spacecraft spied the explosion in the scorching upper reaches of the sun’s atmosphere, when a prominence — a large loop of material launched by an eruption on the solar surface — started falling back to the sun’s surface. But before it could make it, the prominence ran into a snarl of magnetic field lines, sparking a magnetic explosion.

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A solar prominence (also known as a filament when viewed against the solar disk) is a large, bright feature extending outward from the sun’s surface. Prominences are anchored to the sun’s surface in the photosphere, and extend outwards into the sun’s hot outer atmosphere, called the corona. A prominence forms over timescales of about a day, and stable prominences may persist in the corona for several months, looping hundreds of thousands of miles into space. This image, from March 2010, shows a solar eruptive prominence, with Earth superimposed for a sense of scale. Image via NASA/SDO.

This new kind of magnetic explosion – called forced magnetic reconnection – has been theoretical until now. According to a NASA statement from December 17, 2019:

Scientists have previously seen the explosive snap and realignment of tangled magnetic field lines on the sun — a process known as magnetic reconnection — but never one that had been triggered by a nearby eruption. The observation, which confirms a decade-old theory, may help scientists understand a key mystery about the sun’s atmosphere, better predict space weather, and may also lead to breakthroughs in the controlled fusion and lab plasma experiments.

Although never seen directly, this kind of forced magnetic reconnection explosion was first theorized 15 years ago. The new observations were published December 17, 2019, in the Astrophysical Journal.

This image shows the sun on May 3, 2012, with the inset showing a close-up of the reconnection event imaged by SDO’s Atmospheric Imaging Assembly instrument, where the signature X-shape is visible. Image via NASA/ SDO/ Abhishek Srivastava/ IIT(BHU).

Read more about the new findings from NASA.

Bottom line: A NASA video explains a new kind of explosion observed from the sun.

Source: On the Observations of Rapid Forced Reconnection in the Solar Corona

Via NASA

from EarthSky https://ift.tt/35CHpRp

NASA’s Solar Dynamics Observatory (SDO) has observed a kind of magnetic explosion on the sun that scientists have never seen before. The spacecraft spied the explosion in the scorching upper reaches of the sun’s atmosphere, when a prominence — a large loop of material launched by an eruption on the solar surface — started falling back to the sun’s surface. But before it could make it, the prominence ran into a snarl of magnetic field lines, sparking a magnetic explosion.

EarthSky 2020 lunar calendars are available! They make great gifts. Order now. Going fast!

A solar prominence (also known as a filament when viewed against the solar disk) is a large, bright feature extending outward from the sun’s surface. Prominences are anchored to the sun’s surface in the photosphere, and extend outwards into the sun’s hot outer atmosphere, called the corona. A prominence forms over timescales of about a day, and stable prominences may persist in the corona for several months, looping hundreds of thousands of miles into space. This image, from March 2010, shows a solar eruptive prominence, with Earth superimposed for a sense of scale. Image via NASA/SDO.

This new kind of magnetic explosion – called forced magnetic reconnection – has been theoretical until now. According to a NASA statement from December 17, 2019:

Scientists have previously seen the explosive snap and realignment of tangled magnetic field lines on the sun — a process known as magnetic reconnection — but never one that had been triggered by a nearby eruption. The observation, which confirms a decade-old theory, may help scientists understand a key mystery about the sun’s atmosphere, better predict space weather, and may also lead to breakthroughs in the controlled fusion and lab plasma experiments.

Although never seen directly, this kind of forced magnetic reconnection explosion was first theorized 15 years ago. The new observations were published December 17, 2019, in the Astrophysical Journal.

This image shows the sun on May 3, 2012, with the inset showing a close-up of the reconnection event imaged by SDO’s Atmospheric Imaging Assembly instrument, where the signature X-shape is visible. Image via NASA/ SDO/ Abhishek Srivastava/ IIT(BHU).

Read more about the new findings from NASA.

Bottom line: A NASA video explains a new kind of explosion observed from the sun.

Source: On the Observations of Rapid Forced Reconnection in the Solar Corona

Via NASA

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Mirfak is Perseus’ brightest star

Image via Fred Espenak/astropixels.com.

The constellation Perseus contains the sky’s most celebrated eclipsing binary star, Algol, sometimes called the Demon Star. Algol wins notoriety for its wild swings in brightness, which recur with clock-like precision. However, Mirfak is the easier of the two stars to find, and can serve as your guide star to Algol.

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While you’re looking at Perseus, be sure to scan with your binoculars for the Double Cluster. The constellation Cassiopeia can help you find it. The Double Cluster nearly marks the radiant of the Perseid meteor shower. Image via madmiked/ Flickr.

How to find Mirfak. The name Mirfak is derived from Arabic, meaning the Elbow of the Pleiades. In fact, the constellation Perseus lies due north of the Pleiades star cluster, also called the Seven Sisters. In other words, you can find Mirfak and Perseus in between the Pleiades cluster and Polaris, the North Star.

Look northeast on December evenings for the graceful shape of the constellation Perseus.

You can also take a more direct route to Mirfak, if you’re familiar with the M or W-shaped constellation Cassiopeia the Queen. Draw an imaginary line through the Cassiopeia stars Navi (Gamma Cassiopeiae) and Ruchbah to jump over to Mirfak.

Mirfak is the one Perseus star to stand out in moderately light-polluted skies, as its brilliance matches that of the stars of the famous Big Dipper.

The Alpha Persei Moving Cluster (Melotte 20). Mirfak is the most prominent member of this grouping of stars. Image via Wikimedia Commons.

Science of Mirfak. At a distance of about 600 light-years, Mirfak lies much farther than the Big Dipper stars, so this star has to be intrinsically very luminous to shine so brightly in our sky. If Mirfak stood at the sun’s distance from Earth, its disk would cover several thousand times more sky. Moreover, Mirfak would shine thousands of times more brightly than our sun.

On a dark night, you might discern a faint array of stars clustering around Mirfak, a bejeweled realm of the heavens that glitters all the more in binoculars. This assemblage of stars is known as the Alpha Persei Moving Group (Melotte 20), of which Mirfak is the most prominent member. Although some feel that this stellar grouping is too dispersed to be called a star cluster, these stars nonetheless move in the same general direction through space, and were born from the same cloud of gas and dust some 30 to 50 million years ago.

Bottom line: How to see the star Mirfak.

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Image via Fred Espenak/astropixels.com.

The constellation Perseus contains the sky’s most celebrated eclipsing binary star, Algol, sometimes called the Demon Star. Algol wins notoriety for its wild swings in brightness, which recur with clock-like precision. However, Mirfak is the easier of the two stars to find, and can serve as your guide star to Algol.

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While you’re looking at Perseus, be sure to scan with your binoculars for the Double Cluster. The constellation Cassiopeia can help you find it. The Double Cluster nearly marks the radiant of the Perseid meteor shower. Image via madmiked/ Flickr.

How to find Mirfak. The name Mirfak is derived from Arabic, meaning the Elbow of the Pleiades. In fact, the constellation Perseus lies due north of the Pleiades star cluster, also called the Seven Sisters. In other words, you can find Mirfak and Perseus in between the Pleiades cluster and Polaris, the North Star.

Look northeast on December evenings for the graceful shape of the constellation Perseus.

You can also take a more direct route to Mirfak, if you’re familiar with the M or W-shaped constellation Cassiopeia the Queen. Draw an imaginary line through the Cassiopeia stars Navi (Gamma Cassiopeiae) and Ruchbah to jump over to Mirfak.

Mirfak is the one Perseus star to stand out in moderately light-polluted skies, as its brilliance matches that of the stars of the famous Big Dipper.

The Alpha Persei Moving Cluster (Melotte 20). Mirfak is the most prominent member of this grouping of stars. Image via Wikimedia Commons.

Science of Mirfak. At a distance of about 600 light-years, Mirfak lies much farther than the Big Dipper stars, so this star has to be intrinsically very luminous to shine so brightly in our sky. If Mirfak stood at the sun’s distance from Earth, its disk would cover several thousand times more sky. Moreover, Mirfak would shine thousands of times more brightly than our sun.

On a dark night, you might discern a faint array of stars clustering around Mirfak, a bejeweled realm of the heavens that glitters all the more in binoculars. This assemblage of stars is known as the Alpha Persei Moving Group (Melotte 20), of which Mirfak is the most prominent member. Although some feel that this stellar grouping is too dispersed to be called a star cluster, these stars nonetheless move in the same general direction through space, and were born from the same cloud of gas and dust some 30 to 50 million years ago.

Bottom line: How to see the star Mirfak.

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Solstice tale of two cities

Simulation of the line of sunrise as it strikes the U.S. eastern seaboard around the December solstice, via the U.S. Naval Observatory.

Around the time of the December solstice, the sun rises at the same time for both New York City and St. Augustine, Florida. On December 21, 2019, the sun rises at 7:16 a.m. Eastern Standard Time (EST). Look above at the simulated view of Earth as the sun is rising over the Atlantic Seaboard of the United States around the time of the December winter solstice. Note that the terminator – the sunrise line – pretty much aligns with the U. S. East Coast, providing a similar sunrise time for coastal dwellers.

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And yet, at this solstice, St. Augustine has about an hour more daylight than New York City. Although the sunrise occurs at the same time for both cities, the sunset happens about an hour later in St. Augustine. (See the sunrise/solar noon/sunset table below.)

Sunrise/solar noon/sunset times on December 21, 2019

City	Sunrise	Solar Noon	Sunset
New York	7:16 a.m.	11:54 a.m.	4:29 p.m.
St. Augustine	7:16 a.m.	12:23 p.m.	5:30 p.m.

Source: Custom Sunset Sunrise Calendar

St. Augustine lodges about 7.5 degrees of longitude to the west of New York City. And our planet takes about 30 minutes to rotate this 7.5 degrees. Therefore, on any day of the year, the sun reaches its noontime position some 30 minutes later in St. Augustine than it does in New York City. For instance, on December 21, 2019, the noonday sun reaches its high point for the day at 11:54 a.m. EST in New York City. In St. Augustine, solar noon comes nearly 30 minutes later, at 12:23 p.m. EST.

St. Augustine resides appreciably south of New York City, so St. Augustine’s morning daylight (from sunrise to solar noon) lasts about 30 minutes longer than it does in New York City on the first day of winter. Thus, the longer period of daylight in St. Augustine cancels out the earlier noontime appearance of the sun in New York City, to give both localities the same sunrise time on the day of the December solstice.

Although New York, New York, and St. Augustine, Florida, both reside in the U.S. Eastern time zone, the noonday sun comes 30 minutes later to St. Augustine because it resides 7.5 degrees of longitude to the west of New York City.

Enter the equinoxes

Some three – and nine – months after the December solstice, St. Augustine and New York City receive the same amount of daylight on the days of the March and September equinoxes. On the equinoxes, noontime as well as sunrise and sunset come about 30 minutes later in St. Augustine than they do in New York City. The simulated view of Earth below shows the terminator – the sunrise line – running due north and south on the equinox. Neither the sunrise terminator nor sunset terminator comes anywhere close to aligning with the U.S. East Coast at either equinox.

Sunrise/solar noon/sunset times on March 20, 2020

City	Sunrise	Solar Noon	Sunset
New York	6:58 a.m.	1:03 p.m.	7:09 p.m.
St. Augustine	7:28 a.m.	1:32 p.m.	7:37 p.m.

The terminator – sunrise line – runs due north and south on the equinoxes. The sunset line, though not shown, also runs north and south. Image via Earth and Moon Viewer.

Sunrise/solar noon/sunset times on September 22, 2020

City	Sunrise	Solar Noon	Sunset
New York	6:44 a.m.	12:49 p.m.	6:54 p.m.
St. Augustine	7:14 a.m.	1:18 p.m.	7:22 p.m.

Source: Custom Sunset Sunrise Calendar

Enter the June solstice

Six months after the December solstice, it’s the June summer solstice for the Northern Hemisphere, coming yearly on or near June 21. Now, the situation is reversed from the December solstice, with New York City receiving about an hour more daylight.

Because New York City lies appreciably north of St. Augustine, New York City’s afternoon daylight (from solar noon to sunset) lasts some 30 minutes longer than in St. Augustine on the day of the June summer solstice. Thus, the more daylight in New York City cancels out the later noontime in St. Augustine, to give both localities the same sunset time on the June solstice. (See sunrise/solar noon/sunset table below.)

The terminator – line of sunset – nearly parallels the Atlantic Seaboard on the day of the June solstice.

Look above at the simulated view of Earth as the sun is setting over the Eastern Seaboard of the United States on the day of the summer solstice. Note that the terminator – the sunset line – pretty much coincides with the East Coast, giving a similar sunset time for residents along the Atlantic Seaboard.

From sunrise to sunset on the day of the June solstice, New York City residents enjoy about an hour more daylight than those in St. Augustine. Although the sunset occurs at about the same time for both cities, the sunrise happens an hour earlier in New York City on the day of the summer solstice.

Sunrise/solar noon/sunset times on June 20, 2020

City	Sunrise	Solar Noon	Sunset
New York	5:25 a.m.	12:58 p.m.	8:30 p.m.
St. Augustine	6:25 a.m.	1:27 p.m.	8:29 p.m.

Source: Custom Sunset Sunrise Calendar

Bottom Line: On the day of the December winter solstice, the sun rises at the same time in both St. Augustine, Florida, and New York City, New York, but St. Augustine enjoys an hour more daylight. Six months later, on the day of the June solstice, it’s the sunset that happens at the same time in both places, but with New York City enjoying the extra hour of daylight.

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Simulation of the line of sunrise as it strikes the U.S. eastern seaboard around the December solstice, via the U.S. Naval Observatory.

Around the time of the December solstice, the sun rises at the same time for both New York City and St. Augustine, Florida. On December 21, 2019, the sun rises at 7:16 a.m. Eastern Standard Time (EST). Look above at the simulated view of Earth as the sun is rising over the Atlantic Seaboard of the United States around the time of the December winter solstice. Note that the terminator – the sunrise line – pretty much aligns with the U. S. East Coast, providing a similar sunrise time for coastal dwellers.

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And yet, at this solstice, St. Augustine has about an hour more daylight than New York City. Although the sunrise occurs at the same time for both cities, the sunset happens about an hour later in St. Augustine. (See the sunrise/solar noon/sunset table below.)

Sunrise/solar noon/sunset times on December 21, 2019

City	Sunrise	Solar Noon	Sunset
New York	7:16 a.m.	11:54 a.m.	4:29 p.m.
St. Augustine	7:16 a.m.	12:23 p.m.	5:30 p.m.

Source: Custom Sunset Sunrise Calendar

St. Augustine lodges about 7.5 degrees of longitude to the west of New York City. And our planet takes about 30 minutes to rotate this 7.5 degrees. Therefore, on any day of the year, the sun reaches its noontime position some 30 minutes later in St. Augustine than it does in New York City. For instance, on December 21, 2019, the noonday sun reaches its high point for the day at 11:54 a.m. EST in New York City. In St. Augustine, solar noon comes nearly 30 minutes later, at 12:23 p.m. EST.

St. Augustine resides appreciably south of New York City, so St. Augustine’s morning daylight (from sunrise to solar noon) lasts about 30 minutes longer than it does in New York City on the first day of winter. Thus, the longer period of daylight in St. Augustine cancels out the earlier noontime appearance of the sun in New York City, to give both localities the same sunrise time on the day of the December solstice.

Although New York, New York, and St. Augustine, Florida, both reside in the U.S. Eastern time zone, the noonday sun comes 30 minutes later to St. Augustine because it resides 7.5 degrees of longitude to the west of New York City.

Enter the equinoxes

Some three – and nine – months after the December solstice, St. Augustine and New York City receive the same amount of daylight on the days of the March and September equinoxes. On the equinoxes, noontime as well as sunrise and sunset come about 30 minutes later in St. Augustine than they do in New York City. The simulated view of Earth below shows the terminator – the sunrise line – running due north and south on the equinox. Neither the sunrise terminator nor sunset terminator comes anywhere close to aligning with the U.S. East Coast at either equinox.

Sunrise/solar noon/sunset times on March 20, 2020

City	Sunrise	Solar Noon	Sunset
New York	6:58 a.m.	1:03 p.m.	7:09 p.m.
St. Augustine	7:28 a.m.	1:32 p.m.	7:37 p.m.

The terminator – sunrise line – runs due north and south on the equinoxes. The sunset line, though not shown, also runs north and south. Image via Earth and Moon Viewer.

Sunrise/solar noon/sunset times on September 22, 2020

City	Sunrise	Solar Noon	Sunset
New York	6:44 a.m.	12:49 p.m.	6:54 p.m.
St. Augustine	7:14 a.m.	1:18 p.m.	7:22 p.m.

Source: Custom Sunset Sunrise Calendar

Enter the June solstice

Six months after the December solstice, it’s the June summer solstice for the Northern Hemisphere, coming yearly on or near June 21. Now, the situation is reversed from the December solstice, with New York City receiving about an hour more daylight.

Because New York City lies appreciably north of St. Augustine, New York City’s afternoon daylight (from solar noon to sunset) lasts some 30 minutes longer than in St. Augustine on the day of the June summer solstice. Thus, the more daylight in New York City cancels out the later noontime in St. Augustine, to give both localities the same sunset time on the June solstice. (See sunrise/solar noon/sunset table below.)

The terminator – line of sunset – nearly parallels the Atlantic Seaboard on the day of the June solstice.

Look above at the simulated view of Earth as the sun is setting over the Eastern Seaboard of the United States on the day of the summer solstice. Note that the terminator – the sunset line – pretty much coincides with the East Coast, giving a similar sunset time for residents along the Atlantic Seaboard.

From sunrise to sunset on the day of the June solstice, New York City residents enjoy about an hour more daylight than those in St. Augustine. Although the sunset occurs at about the same time for both cities, the sunrise happens an hour earlier in New York City on the day of the summer solstice.

Sunrise/solar noon/sunset times on June 20, 2020

City	Sunrise	Solar Noon	Sunset
New York	5:25 a.m.	12:58 p.m.	8:30 p.m.
St. Augustine	6:25 a.m.	1:27 p.m.	8:29 p.m.

Source: Custom Sunset Sunrise Calendar

Bottom Line: On the day of the December winter solstice, the sun rises at the same time in both St. Augustine, Florida, and New York City, New York, but St. Augustine enjoys an hour more daylight. Six months later, on the day of the June solstice, it’s the sunset that happens at the same time in both places, but with New York City enjoying the extra hour of daylight.

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