The solstice is June 20

Image at top: The path of the sun across our sky – from about noon to sunset – during the days of the equinoxes and the summer and winter solstices. Photographer Marcella Giulia Pace made these observations from Gatto Corvino village, Sicily, Italy. Read more about this photo, which was the Earth Science Picture of the Day for March 18, 2020, via USRA.

Click here for information on the June 21, 2020 annular – or ring of fire – solar eclipse

For us in the Northern Hemisphere, this solstice signals the beginning of summer. For the Southern Hemisphere, winter starts at this solstice. This 2020 June solstice takes place on Saturday, June 20, at 21:44 UTC; translate UTC to your time. In North America and U.S. time zones, that’s June 20 at 6:44 p.m. ADT, 5:44 p.m. EDT, 4:44 p.m. CDT, 3:44 p.m. MDT, 2:44 p.m. PDT, 1:44 p.m. AKDT (Alaskan Daylight Time) and 11:44 a.m. HAST (Hawaiian-Aleutian Standard Time). The solstice happens at the same instant for all of us, everywhere on Earth; only our clocks differ by time zone.

Keep reading for some quick info that’ll help you connect with nature at this June solstice 2020.

View at EarthSky Community Photos. | Sunrise between a June and December solstice. If you are standing facing east, the sun – from day to day, and week to week – moves progressively to the right (south) between these 2 solstices. Rupesh Sangoi captured separate images of the sunrise, showing the sun’s movement along the horizon between a June and December solstice. He wrote: “Did this for over a year, at sunrise.” Glorious composite, Rupesh! Thank you.

Day and night sides of Earth at the instant of the June 2020 solstice (June 20, 2020, at 21:44 UTC). Map via Fourmilab/ Earth View.

Solstice brings extremes of daylight and darkness. Earth’s orbit around the sun – and tilt on its axis – have brought us to a place in space where our world’s Northern Hemisphere has its time of greatest daylight: its longest day and shortest night. Meanwhile, the June solstice brings the shortest day and longest night south of the equator.

The June solstice gives us the year’s northernmost sunrise and northernmost sunset. The northernmost sunrise and sunset deliver the year’s longest period of daylight to the Northern Hemisphere yet the shortest period of daylight in the Southern Hemisphere. North of the Arctic Circle, the sun neither rises nor sets but stays above the horizon for 24 hours around the clock. South of the Antarctic circle, the sun neither rises nor sets but stays beneath the horizon for 24 hours.

Click here for information on the June 21, 2020 annular – or ring of fire – solar eclipse

In the Northern Hemisphere, noontime shadows are shortest at this solstice. On this solstice, the sun takes its most northerly path across the sky for the year. It’s the year’s highest sun, as seen from the Tropic of Cancer and all places north. Thus your noontime shadow is shortest.

In the Southern Hemisphere, the opposite is true. This solstice marks the lowest sun and longest noontime shadow for those on the southern part of Earth’s globe.

View larger. | Nikolaos Pantazis wrote: “Every year, on the days around summer solstice, the setting sun aligns with that rock, near the village of Platanos, Peloponnese, Greece.”

Each solstice marks a “turning” of the year. Even as this northern summer begins with the solstice, throughout the world the solstice also represents a “turning” of the year. To many cultures, the solstice can mean a limit or a culmination of something. From around the world, the sun is now setting and rising as far north as it ever does. The solstice marks when the sun reaches its northernmost point for the year. After the June solstice, the sun will begin its subtle shift southward on the sky’s dome again.

Thus even in summer’s beginning, we find the seeds of summer’s end.

Oliver Nagy made this cool image between the June and December solstices in 2014. The camera was fixed to a single spot for the entire exposure time, and it continuously recorded the sun’s path as glowing trail s across the sky. The breaks and gaps between the lines are caused by clouds. This image shows the shifting path of the sun over the months between a June and December solstice. As seen from the Northern Hemisphere, the sun’s path gets lower each day.

Longest day for Northern Hemisphere, but not the latest sunset. The latest sunset doesn’t come on the day of the summer solstice. Neither does the earliest sunrise. The exact dates vary with latitude, but the sequence is always the same: earliest sunrise before the summer solstice, longest day on the summer solstice, latest sunset after the summer solstice.

Shortest day for Southern Hemisphere, but not the latest sunrise. The latest sunrise doesn’t come on the day of the winter solstice. Neither does the earliest sunset. The exact dates vary with latitude, but the sequence is always the same: earliest sunset before the winter solstice, shortest day on the winter solstice, latest sunrise after the winter solstice.

Read more about the earliest sunrises here, and read more about the latest sunsets here.

At very northerly latitudes now, the sun is up all night. Here is the sun at 3 a.m. as seen near a June solstice by EarthSky Facebook friend Birgit Boden in northern Sweden.

Bottom line: Some quick info that’ll help you connect with nature at the June solstice 2020!

Click here for information on the June 21, 2020 annular – or ring of fire – solar eclipse

Help support EarthSky! Check out the EarthSky store for fun astronomy gifts and tools for all ages!

All you need to know: June solstice 2020

from EarthSky https://ift.tt/2Brr7QN

Image at top: The path of the sun across our sky – from about noon to sunset – during the days of the equinoxes and the summer and winter solstices. Photographer Marcella Giulia Pace made these observations from Gatto Corvino village, Sicily, Italy. Read more about this photo, which was the Earth Science Picture of the Day for March 18, 2020, via USRA.

Click here for information on the June 21, 2020 annular – or ring of fire – solar eclipse

For us in the Northern Hemisphere, this solstice signals the beginning of summer. For the Southern Hemisphere, winter starts at this solstice. This 2020 June solstice takes place on Saturday, June 20, at 21:44 UTC; translate UTC to your time. In North America and U.S. time zones, that’s June 20 at 6:44 p.m. ADT, 5:44 p.m. EDT, 4:44 p.m. CDT, 3:44 p.m. MDT, 2:44 p.m. PDT, 1:44 p.m. AKDT (Alaskan Daylight Time) and 11:44 a.m. HAST (Hawaiian-Aleutian Standard Time). The solstice happens at the same instant for all of us, everywhere on Earth; only our clocks differ by time zone.

Keep reading for some quick info that’ll help you connect with nature at this June solstice 2020.

View at EarthSky Community Photos. | Sunrise between a June and December solstice. If you are standing facing east, the sun – from day to day, and week to week – moves progressively to the right (south) between these 2 solstices. Rupesh Sangoi captured separate images of the sunrise, showing the sun’s movement along the horizon between a June and December solstice. He wrote: “Did this for over a year, at sunrise.” Glorious composite, Rupesh! Thank you.

Day and night sides of Earth at the instant of the June 2020 solstice (June 20, 2020, at 21:44 UTC). Map via Fourmilab/ Earth View.

Solstice brings extremes of daylight and darkness. Earth’s orbit around the sun – and tilt on its axis – have brought us to a place in space where our world’s Northern Hemisphere has its time of greatest daylight: its longest day and shortest night. Meanwhile, the June solstice brings the shortest day and longest night south of the equator.

The June solstice gives us the year’s northernmost sunrise and northernmost sunset. The northernmost sunrise and sunset deliver the year’s longest period of daylight to the Northern Hemisphere yet the shortest period of daylight in the Southern Hemisphere. North of the Arctic Circle, the sun neither rises nor sets but stays above the horizon for 24 hours around the clock. South of the Antarctic circle, the sun neither rises nor sets but stays beneath the horizon for 24 hours.

Click here for information on the June 21, 2020 annular – or ring of fire – solar eclipse

In the Northern Hemisphere, noontime shadows are shortest at this solstice. On this solstice, the sun takes its most northerly path across the sky for the year. It’s the year’s highest sun, as seen from the Tropic of Cancer and all places north. Thus your noontime shadow is shortest.

In the Southern Hemisphere, the opposite is true. This solstice marks the lowest sun and longest noontime shadow for those on the southern part of Earth’s globe.

View larger. | Nikolaos Pantazis wrote: “Every year, on the days around summer solstice, the setting sun aligns with that rock, near the village of Platanos, Peloponnese, Greece.”

Each solstice marks a “turning” of the year. Even as this northern summer begins with the solstice, throughout the world the solstice also represents a “turning” of the year. To many cultures, the solstice can mean a limit or a culmination of something. From around the world, the sun is now setting and rising as far north as it ever does. The solstice marks when the sun reaches its northernmost point for the year. After the June solstice, the sun will begin its subtle shift southward on the sky’s dome again.

Thus even in summer’s beginning, we find the seeds of summer’s end.

Oliver Nagy made this cool image between the June and December solstices in 2014. The camera was fixed to a single spot for the entire exposure time, and it continuously recorded the sun’s path as glowing trail s across the sky. The breaks and gaps between the lines are caused by clouds. This image shows the shifting path of the sun over the months between a June and December solstice. As seen from the Northern Hemisphere, the sun’s path gets lower each day.

Longest day for Northern Hemisphere, but not the latest sunset. The latest sunset doesn’t come on the day of the summer solstice. Neither does the earliest sunrise. The exact dates vary with latitude, but the sequence is always the same: earliest sunrise before the summer solstice, longest day on the summer solstice, latest sunset after the summer solstice.

Shortest day for Southern Hemisphere, but not the latest sunrise. The latest sunrise doesn’t come on the day of the winter solstice. Neither does the earliest sunset. The exact dates vary with latitude, but the sequence is always the same: earliest sunset before the winter solstice, shortest day on the winter solstice, latest sunrise after the winter solstice.

Read more about the earliest sunrises here, and read more about the latest sunsets here.

At very northerly latitudes now, the sun is up all night. Here is the sun at 3 a.m. as seen near a June solstice by EarthSky Facebook friend Birgit Boden in northern Sweden.

Bottom line: Some quick info that’ll help you connect with nature at the June solstice 2020!

Click here for information on the June 21, 2020 annular – or ring of fire – solar eclipse

Help support EarthSky! Check out the EarthSky store for fun astronomy gifts and tools for all ages!

All you need to know: June solstice 2020

from EarthSky https://ift.tt/2Brr7QN

Forecast: Dust and sand from the Sahara

On June 16, 2020, the GOES-East satellite captured this GeoColor imagery of an expansive plume of dust from the Sahara Desert traveling westward across the Atlantic Ocean. Image via NOAA.

The National Oceanic and Atmospheric Administration (NOAA) said on June 18, 2020, that its GOES-East satellite was tracking a large swath of dust and sand from the Sahara desert in northern Africa, making its way across the Atlantic Ocean. NOAA said the dust is expected to reach the Caribbean by this weekend, and may even make it to parts of the United States next week, adding:

According to NOAA’s Hurricane Research Division, every three to five days from late spring through early fall, a mass of dusty air known as the Saharan Air Layer (SAL) forms over the Sahara Desert and moves westward across the tropical North Atlantic. The SAL, which extends about 5,000 to 20,000 feet (1,500 to 6,000 meters) into the atmosphere, can be transported several thousand miles, reaching as far as the Caribbean, Florida, and the U.S. Gulf Coast when winds are particularly strong. Some of this dust also blows farther south into the Amazon River Basin in South America, where the minerals in the dust replenish nutrients in rainforest soils, which are continually depleted by drenching, tropical rains.

The dry, dusty air associated with the SAL has been known to cause hazy skies over the areas where it blows, as well as toxic algal blooms, according to NASA. It also can help suppress hurricane and tropical storm development in the Atlantic Basin due to its dense, dry air and increased wind shear.

Saharan dust plume, seen by the NOAA-20 satellite on June 17, 2020, via NOAA.

Bottom line: Earth-orbiting satellites are tracking an expansive plume of dust from the Sahara Desert traveling westward across the Atlantic Ocean. The dust may reach the U.S. next week.

Via NOAA

from EarthSky https://ift.tt/2zKO4Oy

On June 16, 2020, the GOES-East satellite captured this GeoColor imagery of an expansive plume of dust from the Sahara Desert traveling westward across the Atlantic Ocean. Image via NOAA.

The National Oceanic and Atmospheric Administration (NOAA) said on June 18, 2020, that its GOES-East satellite was tracking a large swath of dust and sand from the Sahara desert in northern Africa, making its way across the Atlantic Ocean. NOAA said the dust is expected to reach the Caribbean by this weekend, and may even make it to parts of the United States next week, adding:

According to NOAA’s Hurricane Research Division, every three to five days from late spring through early fall, a mass of dusty air known as the Saharan Air Layer (SAL) forms over the Sahara Desert and moves westward across the tropical North Atlantic. The SAL, which extends about 5,000 to 20,000 feet (1,500 to 6,000 meters) into the atmosphere, can be transported several thousand miles, reaching as far as the Caribbean, Florida, and the U.S. Gulf Coast when winds are particularly strong. Some of this dust also blows farther south into the Amazon River Basin in South America, where the minerals in the dust replenish nutrients in rainforest soils, which are continually depleted by drenching, tropical rains.

The dry, dusty air associated with the SAL has been known to cause hazy skies over the areas where it blows, as well as toxic algal blooms, according to NASA. It also can help suppress hurricane and tropical storm development in the Atlantic Basin due to its dense, dry air and increased wind shear.

Saharan dust plume, seen by the NOAA-20 satellite on June 17, 2020, via NOAA.

Bottom line: Earth-orbiting satellites are tracking an expansive plume of dust from the Sahara Desert traveling westward across the Atlantic Ocean. The dust may reach the U.S. next week.

Via NOAA

from EarthSky https://ift.tt/2zKO4Oy

Annular solar eclipse on June 21, 2020

View at EarthSky Community Photos. | Progression into and out of the December 26, 2019, annular solar eclipse, caught from Tumon Bay, Guam, by Eliot Herman of Tucson, Arizona. Thank you, Eliot!

In June 2020, the moon turns new fewer than nine hours after the June 20 solstice. This new moon will sweep right in front of the sun on Sunday, June 21, 2020, to stage an annular – ring of fire – solar eclipse for a narrow but long slice of the world’s Eastern Hemisphere. A much larger swath of Earth will see varying degrees of a partial solar eclipse.

We in the Americas won’t be able to view this solar eclipse at all. It’ll happen during nighttime hours for us on the night of June 20 (early morning of June 21). By the time the sun rises over the Americas on June 21, the eclipse will be long over. Yet, we in the Americas have a slight chance of catching a very young moon – an exceedingly slim crescent, visible only shortly after sunset – on the evening of June 21.

Read more: Young moon after sunset June 22, 23 and 24, 2020.

Also, if the weather holds in various parts of Africa and Asia, it’ll be possible to watch the eclipse online via the Virtual Telescope Project. Gianluca Masi of Virtual Telescope is putting together an international team of observers along various parts of the eclipse path. Note that, for observers in the Americas, the eclipse will take place during the night of June 20. See the poster below, and find details of Virtual Telescope’s eclipse livestream here.

The Virtual Telescope Project live feed of the June 21 annular solar eclipse will happen during the night of June 20, 2020, for us in the Americas. The feed will start on June 21 at 05:30 UTC (June 21 at 1:30 a.m. EDT and 12:30 a.m. CDT; June 20 at 11:30 p.m. MDT and 10:30 p.m. PDT; translate UTC to your time).

If you are watching the eclipse in your sky, proper eye protection must be used throughout the entire June 21 solar eclipse. That’s because an annular eclipse is, essentially, a partial eclipse. Like a total eclipse of the sun, the new moon will move directly in front of the sun. Unlike a total solar eclipse, the new moon during an annular eclipse is too far away to cover the solar disk completely. At mid-eclipse, an annulus – or thin ring – of the sun’s surface will surround the new moon silhouette. Important reminder: No matter where you are, use proper eye protection at all times during the June 21 solar eclipse!

Read more: Top 7 tips for safe solar eclipse viewing

A = total solar eclipse, B = annular eclipse C = partial solar eclipse.

We refer you to the worldwide map and animation below. The long, skinny annular eclipse path in red will swing a solid 1/3 the way around the world, but spans only 53 miles (85 km) at its widest point. Although the entire annular eclipse on a worldwide scale lasts for about 3 3/4 hours, the maximum length of the annular eclipse at any one place is only 1 minute and 22 seconds.

The annular eclipse starts at sunrise in Africa, and then – some 3 3/4 hours later – ends at sunset over the Pacific Ocean. Greatest eclipse will take place at the border of India, Nepal and China. There, the path width shrinks to a minimum of 13 miles (21 km) with annularity lasting a scant 38 seconds.

View an interactive map of the annular eclipse path via Hermit Eclipse

The long yet skinny red path of the annular eclipse starts at sunrise in Africa, and then, about 3 3/4 hours later, ends at sunset over the Pacific Ocean. A much greater swath of the world is in a position to watch a partial solar eclipse. The numbers from 0.20 to 0.80 refer to eclipse magnitude (the portion of the solar diameter covered over by the moon). Image via Fred Espenak/ NASA GSFC.

The eclipse starts at sunrise in Africa and ends at sunset over the Pacific Ocean. The tiny black dot depicts the annular eclipse while the much larger gray circle represents the area of the partial solar eclipse.

On a worldwide scale, the partial solar eclipse starts about one hour before the annularity first begins, and ends about one hour after the annular eclipse comes to an end. Here are the eclipse times on a worldwide scale in Universal Time (UTC):

Partial solar eclipse first begins: 03:46 UTC on June 21, 2020
Annular eclipse first begins: 04:48 UTC on June 21, 2020
Greatest or maximum eclipse: 06:40 UTC on June 21, 2020
Annular eclipse finally ends: 08:32 UTC on June 21, 2020
Partial solar eclipse finally ends: 09:34 UTC on June 21, 2020

Local eclipse times for your part of the world

To find out the local eclipse times for your time zone (no conversion is necessary):

Search for a location via TimeandDate.com eclipse map

Eclipse times for hundred of cities via EclipseWise.com

Why is the annular eclipse so short at greatest eclipse?

Along the annular eclipse path, the duration of annularity is greatest at the path’s beginning (just after sunrise) and ending (just before sunset). The duration is the least at the “greatest” eclipse (at and near noon).

The annular eclipse is 1 minute 22 seconds at the beginning of the eclipse path, and 1 minute and 17 seconds at the end. Midway through the path, at the greatest eclipse, the annular eclipse is only 38 seconds long.

Keep in mind that when the moon is nearer the horizon, it is farther away from where you reside on the Earth’s surface than when the moon is high overhead. Because the moon is relatively close to Earth while the sun resides so far away, the apparent size of the moon changes appreciably during the day whereas the sun’s apparent size does not.

Illustration via Phil Plait. Phil goes on to explain, “The guy at the top of the Earth in the diagram sees the moon on his horizon, and the guy on the side of the Earth sees it overhead. But you can tell the distances aren’t the same: the moon is closer to the guy who sees it as overhead (by an amount roughly equal to the Earth’s radius).”

If this annular eclipse takes place near the horizon, at early morning or late afternoon, then the smaller moon takes more time to cross the solar disk, resulting in a longer annular eclipse.

On the other hand, if the annular eclipse takes place at or around noon, the closer and larger moon takes less time to cross the solar disk, resulting in a shorter annular eclipse.

Exactly six lunar months (six new moons) after this annular eclipse, there’ll be a total eclipse of the sun on December 14, 2020. The new moon will be closer (and therefore larger) than during the June 2020 annular eclipse, so it’ll be a total solar eclipse instead. Yet, the moon will still be more distant (and smaller) at the beginning and the end of the worldwide path of the total solar eclipse, and closer (and larger) at the middle of the path. So it’ll be a shorter total solar eclipse at the beginning and ending of the eclipse path, but a longer total solar eclipse near the middle.

The moon phases in the year 2020 via AstroPixels. A = annular solar eclipse, T = total solar eclipse, and n = penumbral lunar eclipse. The year 2020 has 13 full moons, two of which take place in the month of October.

Bottom line: If you live in the world’s Eastern Hemisphere, you might be in a position to watch the annular solar eclipse on June 21, 2020. If so, please remember to use proper eye protection. Eclipse times, links and viewing charts here.

from EarthSky https://ift.tt/2NeaJ9g

View at EarthSky Community Photos. | Progression into and out of the December 26, 2019, annular solar eclipse, caught from Tumon Bay, Guam, by Eliot Herman of Tucson, Arizona. Thank you, Eliot!

In June 2020, the moon turns new fewer than nine hours after the June 20 solstice. This new moon will sweep right in front of the sun on Sunday, June 21, 2020, to stage an annular – ring of fire – solar eclipse for a narrow but long slice of the world’s Eastern Hemisphere. A much larger swath of Earth will see varying degrees of a partial solar eclipse.

We in the Americas won’t be able to view this solar eclipse at all. It’ll happen during nighttime hours for us on the night of June 20 (early morning of June 21). By the time the sun rises over the Americas on June 21, the eclipse will be long over. Yet, we in the Americas have a slight chance of catching a very young moon – an exceedingly slim crescent, visible only shortly after sunset – on the evening of June 21.

Read more: Young moon after sunset June 22, 23 and 24, 2020.

Also, if the weather holds in various parts of Africa and Asia, it’ll be possible to watch the eclipse online via the Virtual Telescope Project. Gianluca Masi of Virtual Telescope is putting together an international team of observers along various parts of the eclipse path. Note that, for observers in the Americas, the eclipse will take place during the night of June 20. See the poster below, and find details of Virtual Telescope’s eclipse livestream here.

The Virtual Telescope Project live feed of the June 21 annular solar eclipse will happen during the night of June 20, 2020, for us in the Americas. The feed will start on June 21 at 05:30 UTC (June 21 at 1:30 a.m. EDT and 12:30 a.m. CDT; June 20 at 11:30 p.m. MDT and 10:30 p.m. PDT; translate UTC to your time).

If you are watching the eclipse in your sky, proper eye protection must be used throughout the entire June 21 solar eclipse. That’s because an annular eclipse is, essentially, a partial eclipse. Like a total eclipse of the sun, the new moon will move directly in front of the sun. Unlike a total solar eclipse, the new moon during an annular eclipse is too far away to cover the solar disk completely. At mid-eclipse, an annulus – or thin ring – of the sun’s surface will surround the new moon silhouette. Important reminder: No matter where you are, use proper eye protection at all times during the June 21 solar eclipse!

Read more: Top 7 tips for safe solar eclipse viewing

A = total solar eclipse, B = annular eclipse C = partial solar eclipse.

We refer you to the worldwide map and animation below. The long, skinny annular eclipse path in red will swing a solid 1/3 the way around the world, but spans only 53 miles (85 km) at its widest point. Although the entire annular eclipse on a worldwide scale lasts for about 3 3/4 hours, the maximum length of the annular eclipse at any one place is only 1 minute and 22 seconds.

The annular eclipse starts at sunrise in Africa, and then – some 3 3/4 hours later – ends at sunset over the Pacific Ocean. Greatest eclipse will take place at the border of India, Nepal and China. There, the path width shrinks to a minimum of 13 miles (21 km) with annularity lasting a scant 38 seconds.

View an interactive map of the annular eclipse path via Hermit Eclipse

The long yet skinny red path of the annular eclipse starts at sunrise in Africa, and then, about 3 3/4 hours later, ends at sunset over the Pacific Ocean. A much greater swath of the world is in a position to watch a partial solar eclipse. The numbers from 0.20 to 0.80 refer to eclipse magnitude (the portion of the solar diameter covered over by the moon). Image via Fred Espenak/ NASA GSFC.

The eclipse starts at sunrise in Africa and ends at sunset over the Pacific Ocean. The tiny black dot depicts the annular eclipse while the much larger gray circle represents the area of the partial solar eclipse.

On a worldwide scale, the partial solar eclipse starts about one hour before the annularity first begins, and ends about one hour after the annular eclipse comes to an end. Here are the eclipse times on a worldwide scale in Universal Time (UTC):

Partial solar eclipse first begins: 03:46 UTC on June 21, 2020
Annular eclipse first begins: 04:48 UTC on June 21, 2020
Greatest or maximum eclipse: 06:40 UTC on June 21, 2020
Annular eclipse finally ends: 08:32 UTC on June 21, 2020
Partial solar eclipse finally ends: 09:34 UTC on June 21, 2020

Local eclipse times for your part of the world

To find out the local eclipse times for your time zone (no conversion is necessary):

Search for a location via TimeandDate.com eclipse map

Eclipse times for hundred of cities via EclipseWise.com

Why is the annular eclipse so short at greatest eclipse?

Along the annular eclipse path, the duration of annularity is greatest at the path’s beginning (just after sunrise) and ending (just before sunset). The duration is the least at the “greatest” eclipse (at and near noon).

The annular eclipse is 1 minute 22 seconds at the beginning of the eclipse path, and 1 minute and 17 seconds at the end. Midway through the path, at the greatest eclipse, the annular eclipse is only 38 seconds long.

Keep in mind that when the moon is nearer the horizon, it is farther away from where you reside on the Earth’s surface than when the moon is high overhead. Because the moon is relatively close to Earth while the sun resides so far away, the apparent size of the moon changes appreciably during the day whereas the sun’s apparent size does not.

Illustration via Phil Plait. Phil goes on to explain, “The guy at the top of the Earth in the diagram sees the moon on his horizon, and the guy on the side of the Earth sees it overhead. But you can tell the distances aren’t the same: the moon is closer to the guy who sees it as overhead (by an amount roughly equal to the Earth’s radius).”

If this annular eclipse takes place near the horizon, at early morning or late afternoon, then the smaller moon takes more time to cross the solar disk, resulting in a longer annular eclipse.

On the other hand, if the annular eclipse takes place at or around noon, the closer and larger moon takes less time to cross the solar disk, resulting in a shorter annular eclipse.

Exactly six lunar months (six new moons) after this annular eclipse, there’ll be a total eclipse of the sun on December 14, 2020. The new moon will be closer (and therefore larger) than during the June 2020 annular eclipse, so it’ll be a total solar eclipse instead. Yet, the moon will still be more distant (and smaller) at the beginning and the end of the worldwide path of the total solar eclipse, and closer (and larger) at the middle of the path. So it’ll be a shorter total solar eclipse at the beginning and ending of the eclipse path, but a longer total solar eclipse near the middle.

The moon phases in the year 2020 via AstroPixels. A = annular solar eclipse, T = total solar eclipse, and n = penumbral lunar eclipse. The year 2020 has 13 full moons, two of which take place in the month of October.

Bottom line: If you live in the world’s Eastern Hemisphere, you might be in a position to watch the annular solar eclipse on June 21, 2020. If so, please remember to use proper eye protection. Eclipse times, links and viewing charts here.

from EarthSky https://ift.tt/2NeaJ9g

What’s the youngest moon you can see?

View at EarthSky Community Photos. | Mohamed Mohamed of Tripoli, Libya, captured a young moon on April 24, 2020. Thank you, Mohamed!

It’s long been a sport among amateur astronomers to spot the youngest possible moons with optical aid, or with the eye alone. A new moon is more or less between the Earth and sun, crossing the sky with the sun during the day. A young moon is a moon some hours or days after the exact instant of new moon. From the Americas, it might be possible to catch the skinniest of young moons – fresh from the June 21, 2020, annular solar eclipse – at dusk on June 21. To see it, you will need a very clear western horizon, immediately after sunset. You’ll want to bring along your binoculars to sweep for the frail crescent that’ll be only about 0.5% illuminated in sunshine.

Typically, you won’t see a moon less than about 24 hours on either side of new moon. But, if you try, you can sometimes see the moon with the eye alone much closer to the new phase. June 2020’s new moon falls at 06:41 UTC on June 21. At sunset in the central U.S. on that day – say, in Wichita, Kansas, which uses Central Daylight Time – the moon will be about 19 hours old at sunset. As you move westward at mid-northern latitudes in North America into Mountain Daylight Time, the moon will be about 20 hours old at sunset. It’ll be about 21 hours old at sunset for those on the North American west coast, and so on – older and older – as you continue moving west toward islands in Pacific.

So you might see that – in terms of your chances of catching the very young moon – the farther west you are in North America (or on a Pacific island), the better.

Young moons are located some distance east of the sun on the sky’s dome (because the moon always moves eastward in orbit). Young moons appear to our eye as exceedingly slim crescents, likely illuminated by earthshine, seen low in the western sky for a brief interval after sunset.

So watch for the June 21, 2020 young moon! You might catch it.

What is the youngest moon you can see? More about that below.

View larger. | We received the photo above from Sarah Nordin. It’s a very unusual photo of an extremely young moon – caught only 15 hours, 19 minutes after the instant of new moon – in daylight, on November 8, 2018. Be sure to click in and view it larger to appreciate it. Sarah caught this moon at Telok Kemang Observatory in Port Dickson, Malaysia. Camera: Nikon D300s. Telescope: Takahashi TOA-150. Camera setting: ISO160_1/640s_RAW file. Congratulations, Sarah!

What’s the youngest moon it’s possible to see?

As we mentioned, it’s rare to see a moon within about 24 hours of the new phase. But if you try you can see a moon much closer to new. And, if you use optical aid, it turns out you can see the moon all the way until the moment of new moon.

On July 8, 2013, a new record was set for the youngest moon ever photographed (see photos on this page). Thierry Legault – shooting from in Elancourt, France (a suburb of Paris) – captured the July 2013 moon at the precise instant it was new, or most nearly between the Earth and sun for this lunar orbit. Legault’s image (below) shows the thinnest of lunar crescents, in full daylight (naturally, since a new moon is always near the sun in the sky), at 07:14 UTC on July 8, 2013. Legault said on his website:

It is the youngest possible crescent, the age of the moon at this instant being exactly zero. Celestial north is up in the image, as well as the sun. The irregularities and discontinuities are caused by the relief at the edge of the lunar disk (mountains, craters).

Youngest lunar crescent, with the moon’s age being exactly zero when this photo was taken — at the precise moment of the new moon – at 07:14 UTC on July 8, 2013. Image by Thierry Legault. Visit his website. Used with permission.

Here is Thierry Legault and his setup for capturing the youngest possible moon. See more photos and read more on his website.

What’s the youngest moon you’re likely to see with your eye alone?

How young a moon you can expect to see with your eye depends on the time of year and on sky conditions. It’s possible to see the youngest moons – the thinnest crescents, nearest the sunset – around the spring equinox. That would be March for the Northern Hemisphere or September for the Southern Hemisphere.

When Legault captured the image above, the sun and moon were separated only 4.4 degrees – about 9 solar diameters – on the sky’s dome. It is extremely difficult, and risky, to try to capture the moon at such a time. Not only is the sight of our companion world drowned in bright sunlight, but there is also a risk of unintentionally glimpsing the sun and thereby damaging your eyesight.

That’s why Legault used a special photographic setup to capture this youngest possible moon. He wrote:

In order to reduce the glare, the images have been taken in close infrared and a pierced screen, placed just in front of the telescope, prevents the sunlight from entering directly in the telescope.

A longstanding, though somewhat doubtful record for youngest moon seen with the eye was held by two British housemaids, said to have seen the moon 14 3/4 hours after new moon in the year 1916.

A more reliable record was achieved by Stephen James O’Meara in May 1990; he saw the young crescent with the unaided eye 15 hours and 32 minutes after new moon. The record for youngest moon spotted with the eye using an optical aid passed to Mohsen Mirsaeed in 2002, who saw the moon 11 hours and 40 minutes after new moon.

Wow!

And, of course, optical aid enhances your young moon possibilities even more.

But Legault’s photograph at the instant of new moon? That record can only be duplicated, not surpassed.

View larger. | Very young moon – similar to one your’re likely to catch using just your eyes – captured by EarthSky Facebook friend Susan Gies Jensen on February 10, 2013, in Odessa, Washington. Note the bright twilight behind the moon. Beautiful job, Susan! Thank you.

Bottom line: What’s the youngest moon it’s possible to see? As astrophotographer Thierry Legault proved in 2013, it’s possible to capture a moon at the instant the moon is new. How about young moon sightings with the eye alone? The youngest observed moons, and a young moon possibility on June 21, 2020, here.

Click here to check out Thierry Legault’s book on astrophotography.

from EarthSky https://ift.tt/2AY74Xu

View at EarthSky Community Photos. | Mohamed Mohamed of Tripoli, Libya, captured a young moon on April 24, 2020. Thank you, Mohamed!

It’s long been a sport among amateur astronomers to spot the youngest possible moons with optical aid, or with the eye alone. A new moon is more or less between the Earth and sun, crossing the sky with the sun during the day. A young moon is a moon some hours or days after the exact instant of new moon. From the Americas, it might be possible to catch the skinniest of young moons – fresh from the June 21, 2020, annular solar eclipse – at dusk on June 21. To see it, you will need a very clear western horizon, immediately after sunset. You’ll want to bring along your binoculars to sweep for the frail crescent that’ll be only about 0.5% illuminated in sunshine.

Typically, you won’t see a moon less than about 24 hours on either side of new moon. But, if you try, you can sometimes see the moon with the eye alone much closer to the new phase. June 2020’s new moon falls at 06:41 UTC on June 21. At sunset in the central U.S. on that day – say, in Wichita, Kansas, which uses Central Daylight Time – the moon will be about 19 hours old at sunset. As you move westward at mid-northern latitudes in North America into Mountain Daylight Time, the moon will be about 20 hours old at sunset. It’ll be about 21 hours old at sunset for those on the North American west coast, and so on – older and older – as you continue moving west toward islands in Pacific.

So you might see that – in terms of your chances of catching the very young moon – the farther west you are in North America (or on a Pacific island), the better.

Young moons are located some distance east of the sun on the sky’s dome (because the moon always moves eastward in orbit). Young moons appear to our eye as exceedingly slim crescents, likely illuminated by earthshine, seen low in the western sky for a brief interval after sunset.

So watch for the June 21, 2020 young moon! You might catch it.

What is the youngest moon you can see? More about that below.

View larger. | We received the photo above from Sarah Nordin. It’s a very unusual photo of an extremely young moon – caught only 15 hours, 19 minutes after the instant of new moon – in daylight, on November 8, 2018. Be sure to click in and view it larger to appreciate it. Sarah caught this moon at Telok Kemang Observatory in Port Dickson, Malaysia. Camera: Nikon D300s. Telescope: Takahashi TOA-150. Camera setting: ISO160_1/640s_RAW file. Congratulations, Sarah!

What’s the youngest moon it’s possible to see?

As we mentioned, it’s rare to see a moon within about 24 hours of the new phase. But if you try you can see a moon much closer to new. And, if you use optical aid, it turns out you can see the moon all the way until the moment of new moon.

On July 8, 2013, a new record was set for the youngest moon ever photographed (see photos on this page). Thierry Legault – shooting from in Elancourt, France (a suburb of Paris) – captured the July 2013 moon at the precise instant it was new, or most nearly between the Earth and sun for this lunar orbit. Legault’s image (below) shows the thinnest of lunar crescents, in full daylight (naturally, since a new moon is always near the sun in the sky), at 07:14 UTC on July 8, 2013. Legault said on his website:

It is the youngest possible crescent, the age of the moon at this instant being exactly zero. Celestial north is up in the image, as well as the sun. The irregularities and discontinuities are caused by the relief at the edge of the lunar disk (mountains, craters).

Youngest lunar crescent, with the moon’s age being exactly zero when this photo was taken — at the precise moment of the new moon – at 07:14 UTC on July 8, 2013. Image by Thierry Legault. Visit his website. Used with permission.

Here is Thierry Legault and his setup for capturing the youngest possible moon. See more photos and read more on his website.

What’s the youngest moon you’re likely to see with your eye alone?

How young a moon you can expect to see with your eye depends on the time of year and on sky conditions. It’s possible to see the youngest moons – the thinnest crescents, nearest the sunset – around the spring equinox. That would be March for the Northern Hemisphere or September for the Southern Hemisphere.

When Legault captured the image above, the sun and moon were separated only 4.4 degrees – about 9 solar diameters – on the sky’s dome. It is extremely difficult, and risky, to try to capture the moon at such a time. Not only is the sight of our companion world drowned in bright sunlight, but there is also a risk of unintentionally glimpsing the sun and thereby damaging your eyesight.

That’s why Legault used a special photographic setup to capture this youngest possible moon. He wrote:

In order to reduce the glare, the images have been taken in close infrared and a pierced screen, placed just in front of the telescope, prevents the sunlight from entering directly in the telescope.

A longstanding, though somewhat doubtful record for youngest moon seen with the eye was held by two British housemaids, said to have seen the moon 14 3/4 hours after new moon in the year 1916.

A more reliable record was achieved by Stephen James O’Meara in May 1990; he saw the young crescent with the unaided eye 15 hours and 32 minutes after new moon. The record for youngest moon spotted with the eye using an optical aid passed to Mohsen Mirsaeed in 2002, who saw the moon 11 hours and 40 minutes after new moon.

Wow!

And, of course, optical aid enhances your young moon possibilities even more.

But Legault’s photograph at the instant of new moon? That record can only be duplicated, not surpassed.

View larger. | Very young moon – similar to one your’re likely to catch using just your eyes – captured by EarthSky Facebook friend Susan Gies Jensen on February 10, 2013, in Odessa, Washington. Note the bright twilight behind the moon. Beautiful job, Susan! Thank you.

Bottom line: What’s the youngest moon it’s possible to see? As astrophotographer Thierry Legault proved in 2013, it’s possible to capture a moon at the instant the moon is new. How about young moon sightings with the eye alone? The youngest observed moons, and a young moon possibility on June 21, 2020, here.

Click here to check out Thierry Legault’s book on astrophotography.

from EarthSky https://ift.tt/2AY74Xu

Searching for novel connections in cancer metabolism

Imagine a line of dominoes. When one is lightly tapped and falls, the rest tumble.  

The same is true of cancer. When a cell becomes cancerous, important cellular pathways are altered. And like a chain reaction, when one point in a pathway is mutated, the effects can be felt downstream – just like dominoes.  

Some of the pathways that are disrupted in cancer regulate how cells acquire and process energy – their cellular metabolism.  

But while a lot is known about the errors that disrupt metabolic pathways in cancer, not much has been done to link these mutations to how the cells behave. Until now.  

Dr George Poulogiannis is one of our scientists investigating the relationship between cellular metabolism, cancer and diet as part of our Rosetta Cancer Grand Challenges team, who are creating a ‘google earth of cancer’.  

Poulogiannis explained that by completing one part of this complex puzzle – finding novel connections in cancer metabolism – scientists can open the door to a better understanding of individual cancers and, in turn, pave the road to more tailored treatments.  

And for a puzzle this complex, they needed a rather unique tool.  

The iKnife

To assess the metabolic changes that occur in cancer cells, the team acquired an ingenious piece of equipment known as the Intelligent Knife (or iKnife).  

The iKnife was invented by Professor Zoltan Takats at Imperial College London, who works with Poulogiannis on the Rosetta team and was a researcher in this latest study.  

This electrosurgical device – designed to sniff out cancer during surgery – has so far been put to the test in breast cancer, and is starting to be trialled in ovarian cancer too.

“A few years ago, a technology was introduced which was based on a very simple idea, to connect the electro surgical device with a mass spectrometer and measure the ionisation profile of the smoke that is being generated,” Poulogiannis explains. 

Using this technique, the iKnife can precisely differentiate cancer from non-cancerous tissue in real-time. This means that surgeons know if they’re cutting through healthy tissue or cancer only a few seconds after their first cut.  

“We wanted to explore if using this technology could gather even more detailed information about the biology of the cancer and the key drivers of the disease.” 

Hunting for clues  

Poulogiannis and his team were entering unchartered waters.  

The team didn’t know exactly what they were looking for, but they began hunting for patterns that could reveals clues about metabolism and cancer, screening a number of breast cancer cell lines, tumour samples and mouse models. 

“When we did that, we observed something which at the beginning was quite strange,” says Poulogiannis. 

Their analysis revealed that the breast cancer samples could be split up into two distinct groups, based on the presence of particular fats sniffed out by the iKnife. And this split did not correlate with any of the features doctors currently use to group the disease – like hormone receptor status.  

The team investigated further and discovered that the differences in fats could be explained by an error (mutation) in a gene that’s part of an important metabolic pathway, the PIK3CA pathway.  

Pieces of the puzzle 

One of the fats found at particularly high levels in the samples was arachidonic acid. It’s a fatty acid predominantly found in animal fats in our diet but can also be produced by cancer cells.  

Significantly, this same fat plays a major role in the inflammatory response in cancer.  

“We then tried to find what was the mechanism behind it [the stratification of the samples] and we found that some signalling pathways downstream of oncogenic PIK3CA regulate this overproduction of lipids. And the biomarker fatty acid that caught our attention was arachidonic acid, because this serves as the major hub of pro-inflammatory response in cancer. And this is a fatty acid we get both from the diet, and also PIK3CA mutant cancer cells have a unique ability to increase its production” 

Using the iKnife, the team had slowly started to gather together the pieces from various studies and line them up like dominoes, making connections that hadn’t been there before.  

The team found that drugs that interfered with the PIK3CA pathway were far more effective at slowing tumour growth in mice with breast tumours when the mice were also fed a diet without fatty acids.  

Poulogiannis explains how scientists had known for a while that the error in the PIK3CA pathway acted as a marker for a lack of response to certain inhibitors, “but no one quite understood why”. Now, with the help of the iKnife, this research has revealed that this lack of response could be because of the overproduction of arachidonic acid.  

The complete picture 

As the dominoes fell one by one, Poulogiannis and his team followed the clues along the PIK3CA pathway to draw connections between diet, metabolism and cancer, “I think this is one of the first few studies, or maybe even the first, that shows a dietary fat restriction plays a major role in therapy response.” 

It’s been a project filled with unexpected twists and turns, but Poulogiannis is happy with where they’ve ended up – uncovering new features of breast cancer biology and a new and exciting use for the iKnife.  

Although it’s early days, Poulogiannis is excited by the potential of these techniques to change the way we look for novel connections in cancer metabolism, and guide how we treat cancer in the future, which was a key part of the Rosetta project. 

The Rosetta Cancer Grand Challenges team, led by Professor Josephine Bunch, are continuing to map different tumours in unprecedented detail, in order to develop new ways to diagnose and treat the disease.  

“In this study we really managed to capture how metabolic phenotyping, using high-throughput technology, can really help us explain the biology and ultimately identify a novel metabolic vulnerability, a new way to target these tumours which was the whole, I think one of the major goals of this Grand Challenge.”  

Lilly

from Cancer Research UK – Science blog https://ift.tt/3egW60J

Imagine a line of dominoes. When one is lightly tapped and falls, the rest tumble.  

The same is true of cancer. When a cell becomes cancerous, important cellular pathways are altered. And like a chain reaction, when one point in a pathway is mutated, the effects can be felt downstream – just like dominoes.  

Some of the pathways that are disrupted in cancer regulate how cells acquire and process energy – their cellular metabolism.  

But while a lot is known about the errors that disrupt metabolic pathways in cancer, not much has been done to link these mutations to how the cells behave. Until now.  

Dr George Poulogiannis is one of our scientists investigating the relationship between cellular metabolism, cancer and diet as part of our Rosetta Cancer Grand Challenges team, who are creating a ‘google earth of cancer’.  

Poulogiannis explained that by completing one part of this complex puzzle – finding novel connections in cancer metabolism – scientists can open the door to a better understanding of individual cancers and, in turn, pave the road to more tailored treatments.  

And for a puzzle this complex, they needed a rather unique tool.  

The iKnife

To assess the metabolic changes that occur in cancer cells, the team acquired an ingenious piece of equipment known as the Intelligent Knife (or iKnife).  

The iKnife was invented by Professor Zoltan Takats at Imperial College London, who works with Poulogiannis on the Rosetta team and was a researcher in this latest study.  

This electrosurgical device – designed to sniff out cancer during surgery – has so far been put to the test in breast cancer, and is starting to be trialled in ovarian cancer too.

“A few years ago, a technology was introduced which was based on a very simple idea, to connect the electro surgical device with a mass spectrometer and measure the ionisation profile of the smoke that is being generated,” Poulogiannis explains. 

Using this technique, the iKnife can precisely differentiate cancer from non-cancerous tissue in real-time. This means that surgeons know if they’re cutting through healthy tissue or cancer only a few seconds after their first cut.  

“We wanted to explore if using this technology could gather even more detailed information about the biology of the cancer and the key drivers of the disease.” 

Hunting for clues  

Poulogiannis and his team were entering unchartered waters.  

The team didn’t know exactly what they were looking for, but they began hunting for patterns that could reveals clues about metabolism and cancer, screening a number of breast cancer cell lines, tumour samples and mouse models. 

“When we did that, we observed something which at the beginning was quite strange,” says Poulogiannis. 

Their analysis revealed that the breast cancer samples could be split up into two distinct groups, based on the presence of particular fats sniffed out by the iKnife. And this split did not correlate with any of the features doctors currently use to group the disease – like hormone receptor status.  

The team investigated further and discovered that the differences in fats could be explained by an error (mutation) in a gene that’s part of an important metabolic pathway, the PIK3CA pathway.  

Pieces of the puzzle 

One of the fats found at particularly high levels in the samples was arachidonic acid. It’s a fatty acid predominantly found in animal fats in our diet but can also be produced by cancer cells.  

Significantly, this same fat plays a major role in the inflammatory response in cancer.  

“We then tried to find what was the mechanism behind it [the stratification of the samples] and we found that some signalling pathways downstream of oncogenic PIK3CA regulate this overproduction of lipids. And the biomarker fatty acid that caught our attention was arachidonic acid, because this serves as the major hub of pro-inflammatory response in cancer. And this is a fatty acid we get both from the diet, and also PIK3CA mutant cancer cells have a unique ability to increase its production” 

Using the iKnife, the team had slowly started to gather together the pieces from various studies and line them up like dominoes, making connections that hadn’t been there before.  

The team found that drugs that interfered with the PIK3CA pathway were far more effective at slowing tumour growth in mice with breast tumours when the mice were also fed a diet without fatty acids.  

Poulogiannis explains how scientists had known for a while that the error in the PIK3CA pathway acted as a marker for a lack of response to certain inhibitors, “but no one quite understood why”. Now, with the help of the iKnife, this research has revealed that this lack of response could be because of the overproduction of arachidonic acid.  

The complete picture 

As the dominoes fell one by one, Poulogiannis and his team followed the clues along the PIK3CA pathway to draw connections between diet, metabolism and cancer, “I think this is one of the first few studies, or maybe even the first, that shows a dietary fat restriction plays a major role in therapy response.” 

It’s been a project filled with unexpected twists and turns, but Poulogiannis is happy with where they’ve ended up – uncovering new features of breast cancer biology and a new and exciting use for the iKnife.  

Although it’s early days, Poulogiannis is excited by the potential of these techniques to change the way we look for novel connections in cancer metabolism, and guide how we treat cancer in the future, which was a key part of the Rosetta project. 

The Rosetta Cancer Grand Challenges team, led by Professor Josephine Bunch, are continuing to map different tumours in unprecedented detail, in order to develop new ways to diagnose and treat the disease.  

“In this study we really managed to capture how metabolic phenotyping, using high-throughput technology, can really help us explain the biology and ultimately identify a novel metabolic vulnerability, a new way to target these tumours which was the whole, I think one of the major goals of this Grand Challenge.”  

Lilly

from Cancer Research UK – Science blog https://ift.tt/3egW60J

Longest sunsets happen around the solstice

Above photo: June solstice sunset in the nation of Oman, on the Arabian Peninsula, from our friend Priya Kumar. Thank you, Priya!

Here’s a natural phenomenon you might never have imagined. That is, the sun actually takes more time to set around the time of a solstice.

It’s true. The longest sunsets (and sunrises) occur at or near the solstices. The shortest sunsets (and sunrises) occur at or near the equinoxes. This is true whether you live in the Northern or Southern Hemisphere.

And, by the way, when we say sunset here, we’re talking about the actual number of minutes it takes for the body of the sun to sink below the western horizon.

Adrian Strand captured this photo on a beach in northwest England.

When is the solstice? In 2020, the Northern Hemisphere’s summer solstice – and Southern Hemisphere’s winter solstice – will fall on June 20 at 21:44 UTC.

In the United States, that translates to June 20 at 5:44 p.m EDT, 4:44 p.m. CDT, 3:44 p.m. MDT, 2:44 p.m. PDT, 1:44 p.m. Alaska Daylight Time and 11:44 a.m. Hawaii-Aleutian Daylight Time. Translate to your time zone.

Equinoxes and solstices, via Geosync. The Earth’s axis points straight up and down, with north at the top. The solstices are on the left (December solstice at top, June solstice at bottom) and the equinoxes are to the right (March equinox at top. September equinox at bottom).

Why is the sunset longer around the solstice? As viewed from both the Northern and Southern Hemispheres, the sun rises and sets farthest north at the June solstice and farthest south at the December solstice.

Now consider that the farther the sun sets from due west along the horizon, the shallower the angle of the setting sun. That means a longer duration for sunset at the solstices.

Meanwhile, at an equinox, the sun rises due east and sets due west. That means – on the day of an equinox – the setting sun hits the horizon at its steepest possible angle.

The sunset duration varies by latitude, but let’s just consider one latitude, 40 degrees north, the latitude of Denver or Philadelphia in the United States, Sardinia in the Mediterranean, or Beijing in China. At that latitude, on the day of a solstice, the sun sets in about 3 1/4 minutes.

On the other hand, at 40 degrees north latitude, the equinox sun sets in roughly 2 3/4 minutes.

At more northerly temperate latitudes, the sunset duration is greater; and at latitudes closer to the equator, the sunset duration is less. Near the Arctic Circle (65 degrees north latitude), the duration of a solstice sunset lasts about 15 minutes. At the equator (0 degrees latitude), the solstice sun takes a little over 2 1/4 minutes to set.

Regardless of latitude, however, the duration of sunset is always longest at or near the solstices.

As it turns out, the sunset and sunrise are a tad longer on a December solstice than they are on a June solstice. That’s because the sun is closer to Earth in December than it is in June. Therefore, the sun’s disk looms a bit larger in our sky in December, and so it takes slightly longer to set.

Additionally, the closer December sun moves eastward upon the ecliptic at a faster clip, helping to slow down the December solstice sunset (and sunrise) even more. For instance, at 50 degrees north latitude, the winter solstice sunset (sunrise) lasts about 4 minutes and 18 seconds, or about 8 seconds longer than the sunset (sunrise) on the summer solstice.

Solstices and equinoxes take place in Earth’s orbit around the sun.

Bottom line: Here’s a natural phenomenon you might never have imagined. That is, the longest sunsets happen around the time of a solstice.

Help support EarthSky! Visit the EarthSky store for to see the great selection of educational tools and team gear we have to offer.

Help EarthSky keep going! Please donate what you can.

from EarthSky https://ift.tt/2YjP4mt

Above photo: June solstice sunset in the nation of Oman, on the Arabian Peninsula, from our friend Priya Kumar. Thank you, Priya!

Here’s a natural phenomenon you might never have imagined. That is, the sun actually takes more time to set around the time of a solstice.

It’s true. The longest sunsets (and sunrises) occur at or near the solstices. The shortest sunsets (and sunrises) occur at or near the equinoxes. This is true whether you live in the Northern or Southern Hemisphere.

And, by the way, when we say sunset here, we’re talking about the actual number of minutes it takes for the body of the sun to sink below the western horizon.

Adrian Strand captured this photo on a beach in northwest England.

When is the solstice? In 2020, the Northern Hemisphere’s summer solstice – and Southern Hemisphere’s winter solstice – will fall on June 20 at 21:44 UTC.

In the United States, that translates to June 20 at 5:44 p.m EDT, 4:44 p.m. CDT, 3:44 p.m. MDT, 2:44 p.m. PDT, 1:44 p.m. Alaska Daylight Time and 11:44 a.m. Hawaii-Aleutian Daylight Time. Translate to your time zone.

Equinoxes and solstices, via Geosync. The Earth’s axis points straight up and down, with north at the top. The solstices are on the left (December solstice at top, June solstice at bottom) and the equinoxes are to the right (March equinox at top. September equinox at bottom).

Why is the sunset longer around the solstice? As viewed from both the Northern and Southern Hemispheres, the sun rises and sets farthest north at the June solstice and farthest south at the December solstice.

Now consider that the farther the sun sets from due west along the horizon, the shallower the angle of the setting sun. That means a longer duration for sunset at the solstices.

Meanwhile, at an equinox, the sun rises due east and sets due west. That means – on the day of an equinox – the setting sun hits the horizon at its steepest possible angle.

The sunset duration varies by latitude, but let’s just consider one latitude, 40 degrees north, the latitude of Denver or Philadelphia in the United States, Sardinia in the Mediterranean, or Beijing in China. At that latitude, on the day of a solstice, the sun sets in about 3 1/4 minutes.

On the other hand, at 40 degrees north latitude, the equinox sun sets in roughly 2 3/4 minutes.

At more northerly temperate latitudes, the sunset duration is greater; and at latitudes closer to the equator, the sunset duration is less. Near the Arctic Circle (65 degrees north latitude), the duration of a solstice sunset lasts about 15 minutes. At the equator (0 degrees latitude), the solstice sun takes a little over 2 1/4 minutes to set.

Regardless of latitude, however, the duration of sunset is always longest at or near the solstices.

As it turns out, the sunset and sunrise are a tad longer on a December solstice than they are on a June solstice. That’s because the sun is closer to Earth in December than it is in June. Therefore, the sun’s disk looms a bit larger in our sky in December, and so it takes slightly longer to set.

Additionally, the closer December sun moves eastward upon the ecliptic at a faster clip, helping to slow down the December solstice sunset (and sunrise) even more. For instance, at 50 degrees north latitude, the winter solstice sunset (sunrise) lasts about 4 minutes and 18 seconds, or about 8 seconds longer than the sunset (sunrise) on the summer solstice.

Solstices and equinoxes take place in Earth’s orbit around the sun.

Bottom line: Here’s a natural phenomenon you might never have imagined. That is, the longest sunsets happen around the time of a solstice.

Help support EarthSky! Visit the EarthSky store for to see the great selection of educational tools and team gear we have to offer.

Help EarthSky keep going! Please donate what you can.

from EarthSky https://ift.tt/2YjP4mt

Covid-19 spreads through the air. That’s a big challenge for reopening

Coughing, sneezing, talking and even just breathing can produce airborne particles that can spread SARS-CoV-2. Image via Stanislaw Pytel/ Digital Vision/ Getty Images.

Douglas Reed, University of Pittsburgh

I am a scientist that studies infectious diseases and I specialize in severe respiratory infections, but I also serve as a member of my church’s safety team.

Over the past few weeks as states began to loosen restrictions, we have been discussing if and how to safely start services again. But the coronavirus is far from gone. As we try and figure out how to hold services while protecting our members, one question is of particular concern: How common is airborne spread of the virus?

How to spread a virus

Respiratory infections are generally spread in three possible ways: from direct contact, from droplets and from airborne particles.

Contact transmission occurs when a person touches an object that has live virus on it – called a fomite – and gets sick.

Droplets are small particles of mucus or saliva that come from a person’s mouth or nose when they cough or talk. They range in size from 5 microns to hundreds of microns in diameter – a red blood cell to a grain of sand. Most droplets, particularly large ones, fall to the ground within seconds and don’t usually travel more than 3 or 6 feet (1 or 2 meters). If a person coughed on you and you got sick, that would be droplet transmission.

Airborne transmission happens because of airborne particles known as droplet nuclei. Droplet nuclei are any bit of mucus or saliva smaller than 5 microns across. People produce droplet nuclei when they talk, but they can also be formed when small droplets evaporate and shrink in size. Many of these droplets shrink so much that they begin to float before they hit the ground, thus becoming aerosols.

People produce thousands of these droplet nuclei per second while talking and the aerosolized particles can contain live viruses and float in the air for hours. They are easy to inhale, and if they contain live virus, can get people sick. The ability of droplet nuclei to transmit the coronavirus has a massive impact on if and how places like my church can reopen.

Droplet nuclei and other aerosols can float around for hours in the air, and if inhaled, spread the coronavirus. Image via Jorg Greuel/ Photodisc/ Getty Images.

Early on in the pandemic, experts at the Centers for Disease Control and Prevention and the World Health Organization were most concerned about the coronavirus being transmitted from surfaces and from large droplets.

But the more research is done on SARS-CoV-2, the more evidence there is that airborne transmission is occurring although it is controversial. Both the CDC and WHO are now recommending that the general population wear masks, but for people going about their lives and wondering how to reopen public areas across the world, the question remains: Just how important is airborne transmission?

Airborne longevity in the lab

To get infected, a person needs to come in contact with live virus. If the virus dies before a person can inhale it, they won’t get sick.

To test how well SARS-CoV-2 can live in the air, researchers use special equipment to create aerosolized virus and keep it airborne for long periods of time. Researchers can then take samples of the virus and see how long it stays alive in an aerosol. An early study from researchers at the National Institute of Health kept the virus airborne for four hours and found live virus the whole time. A subsequent pre-print study that I was part of found that the coronavirus can stay alive for up to 16 hours in the air.

Neither the initial study nor the one that I was involved with measured the impact of temperature, humidity, ultraviolet light or pollution on survival of the virus in aerosols. There is evidence that simulated sunlight can inactivate 90% of SARS-CoV-2 viruses in saliva on surfaces or in aerosols within seven minutes. These studies suggest that the virus would be rapidly inactivated outdoors, but the risk of transmission indoors would remain.

A choir practice in Washington State was the site of a huge outbreak and offers one of the strongest pieces of evidence for airborne transmission. Image via Satoshi-K/E+/ Getty Images.

Evidence from the real world

Laboratory studies can provide valuable insight, but real world scenarios point to the true risk from airborne transmission.

Reports from China, Singapore and Nebraska have found the virus in patient rooms and at very low levels in the ventilation system of hospitals where COVID-19 patients were treated. The report from China also found evidence of the virus at the entrance of a department store. So far, this sampling has been done using polymerase chain reaction tests which look for pieces of viral DNA, not live virus. They can’t tell researchers if what they are finding is infectious.

For direct evidence of the risks of airborne transmission, we can look to a few case studies in the U.S. and abroad.

One study tracked how a single infected person at a call center in South Korea infected 94 other people. There is also the widely reported of case of one infected person at a restaurant in Guangzhou, China, spreading the virus to nine other people because of the airflow created by an air conditioning unit in the room.

Perhaps most striking, especially for myself as we contemplate how to reopen our church, is the example of the church choir in Skagit County, Washington. A single individual singing at a choir practice infected 52 other people. Singing and loud vocalization in general can produce a lot of aerosols, and evidence shows that some people are super-emitters of aerosols even during normal speech. It’s likely that some infections in this incident occurred from droplets or direct contact, but
the fact that one person was able to infect so many people strongly suggests that airborne transmission was the driving factor in this outbreak.

A paper published just last week compared the success of mitigation measures – like social distancing or mask wearing – to try and determine how the virus is spreading. The authors concluded that aerosol transmission was the dominant route. This conclusion is hotly debated in the scientific community, but this study and others do show the effectiveness of masks in slowing the spread of COVID-19.

Masks, in addition to social distancing, are the best tool available to reduce airborne spread and are necessary as churches and other public places open up. Image via AP Photo/ Damian Dovarganes.

What does this mean for reopening and for individuals?

The evidence strongly suggests that airborne transmission happens easily and is likely a significant driver of this pandemic. It must be taken seriously as people begin to venture back out into the world.

Thankfully, there is an easy, if not perfect way you can reduce airborne transmission: masks. Since people can spread the virus when they are pre-symptomatic or asymptomatic, universal mask wearing is a very effective, low-cost way to slow down the pandemic.

Since the primary risk is indoors, increasing ventilation rates and not recirculating air inside buildings would remove the virus from the indoor environment faster.

My church has decided to reopen, but we are only planning to allow limited numbers of people in the church and spreading them throughout the sanctuary to maintain social distancing. And at least for now, everyone is required to wear masks. Especially while singing.

Douglas Reed, Associate Professor of Immunology, University of Pittsburgh

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bottom line: How the Covid-19 spreads, including how people are getting sick from coronavirus spreading through the air, which is a big challenge for reopening.

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

Coughing, sneezing, talking and even just breathing can produce airborne particles that can spread SARS-CoV-2. Image via Stanislaw Pytel/ Digital Vision/ Getty Images.

Douglas Reed, University of Pittsburgh

I am a scientist that studies infectious diseases and I specialize in severe respiratory infections, but I also serve as a member of my church’s safety team.

Over the past few weeks as states began to loosen restrictions, we have been discussing if and how to safely start services again. But the coronavirus is far from gone. As we try and figure out how to hold services while protecting our members, one question is of particular concern: How common is airborne spread of the virus?

How to spread a virus

Respiratory infections are generally spread in three possible ways: from direct contact, from droplets and from airborne particles.

Contact transmission occurs when a person touches an object that has live virus on it – called a fomite – and gets sick.

Droplets are small particles of mucus or saliva that come from a person’s mouth or nose when they cough or talk. They range in size from 5 microns to hundreds of microns in diameter – a red blood cell to a grain of sand. Most droplets, particularly large ones, fall to the ground within seconds and don’t usually travel more than 3 or 6 feet (1 or 2 meters). If a person coughed on you and you got sick, that would be droplet transmission.

Airborne transmission happens because of airborne particles known as droplet nuclei. Droplet nuclei are any bit of mucus or saliva smaller than 5 microns across. People produce droplet nuclei when they talk, but they can also be formed when small droplets evaporate and shrink in size. Many of these droplets shrink so much that they begin to float before they hit the ground, thus becoming aerosols.

People produce thousands of these droplet nuclei per second while talking and the aerosolized particles can contain live viruses and float in the air for hours. They are easy to inhale, and if they contain live virus, can get people sick. The ability of droplet nuclei to transmit the coronavirus has a massive impact on if and how places like my church can reopen.

Droplet nuclei and other aerosols can float around for hours in the air, and if inhaled, spread the coronavirus. Image via Jorg Greuel/ Photodisc/ Getty Images.

Early on in the pandemic, experts at the Centers for Disease Control and Prevention and the World Health Organization were most concerned about the coronavirus being transmitted from surfaces and from large droplets.

But the more research is done on SARS-CoV-2, the more evidence there is that airborne transmission is occurring although it is controversial. Both the CDC and WHO are now recommending that the general population wear masks, but for people going about their lives and wondering how to reopen public areas across the world, the question remains: Just how important is airborne transmission?

Airborne longevity in the lab

To get infected, a person needs to come in contact with live virus. If the virus dies before a person can inhale it, they won’t get sick.

To test how well SARS-CoV-2 can live in the air, researchers use special equipment to create aerosolized virus and keep it airborne for long periods of time. Researchers can then take samples of the virus and see how long it stays alive in an aerosol. An early study from researchers at the National Institute of Health kept the virus airborne for four hours and found live virus the whole time. A subsequent pre-print study that I was part of found that the coronavirus can stay alive for up to 16 hours in the air.

Neither the initial study nor the one that I was involved with measured the impact of temperature, humidity, ultraviolet light or pollution on survival of the virus in aerosols. There is evidence that simulated sunlight can inactivate 90% of SARS-CoV-2 viruses in saliva on surfaces or in aerosols within seven minutes. These studies suggest that the virus would be rapidly inactivated outdoors, but the risk of transmission indoors would remain.

A choir practice in Washington State was the site of a huge outbreak and offers one of the strongest pieces of evidence for airborne transmission. Image via Satoshi-K/E+/ Getty Images.

Evidence from the real world

Laboratory studies can provide valuable insight, but real world scenarios point to the true risk from airborne transmission.

Reports from China, Singapore and Nebraska have found the virus in patient rooms and at very low levels in the ventilation system of hospitals where COVID-19 patients were treated. The report from China also found evidence of the virus at the entrance of a department store. So far, this sampling has been done using polymerase chain reaction tests which look for pieces of viral DNA, not live virus. They can’t tell researchers if what they are finding is infectious.

For direct evidence of the risks of airborne transmission, we can look to a few case studies in the U.S. and abroad.

One study tracked how a single infected person at a call center in South Korea infected 94 other people. There is also the widely reported of case of one infected person at a restaurant in Guangzhou, China, spreading the virus to nine other people because of the airflow created by an air conditioning unit in the room.

Perhaps most striking, especially for myself as we contemplate how to reopen our church, is the example of the church choir in Skagit County, Washington. A single individual singing at a choir practice infected 52 other people. Singing and loud vocalization in general can produce a lot of aerosols, and evidence shows that some people are super-emitters of aerosols even during normal speech. It’s likely that some infections in this incident occurred from droplets or direct contact, but
the fact that one person was able to infect so many people strongly suggests that airborne transmission was the driving factor in this outbreak.

A paper published just last week compared the success of mitigation measures – like social distancing or mask wearing – to try and determine how the virus is spreading. The authors concluded that aerosol transmission was the dominant route. This conclusion is hotly debated in the scientific community, but this study and others do show the effectiveness of masks in slowing the spread of COVID-19.

Masks, in addition to social distancing, are the best tool available to reduce airborne spread and are necessary as churches and other public places open up. Image via AP Photo/ Damian Dovarganes.

What does this mean for reopening and for individuals?

The evidence strongly suggests that airborne transmission happens easily and is likely a significant driver of this pandemic. It must be taken seriously as people begin to venture back out into the world.

Thankfully, there is an easy, if not perfect way you can reduce airborne transmission: masks. Since people can spread the virus when they are pre-symptomatic or asymptomatic, universal mask wearing is a very effective, low-cost way to slow down the pandemic.

Since the primary risk is indoors, increasing ventilation rates and not recirculating air inside buildings would remove the virus from the indoor environment faster.

My church has decided to reopen, but we are only planning to allow limited numbers of people in the church and spreading them throughout the sanctuary to maintain social distancing. And at least for now, everyone is required to wear masks. Especially while singing.

Douglas Reed, Associate Professor of Immunology, University of Pittsburgh

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bottom line: How the Covid-19 spreads, including how people are getting sick from coronavirus spreading through the air, which is a big challenge for reopening.

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