2017 Hunter’s Moon on night of November 3

Moon rising behind the Metéora monastery in Greece. It’s one of the largest and most important complexes of Greek Orthodox monasteries in Greece, second only to Mount Athos. Photo via Aimilianos Gkekas

In skylore, every full moon has many names, and most are tied to the months of the year. But some moons are tied to seasons, such as the Harvest and Hunter’s Moons. The Harvest Moon is the full moon closest to the autumnal equinox. The Hunter’s Moon is the full moon after the Harvest Moon. For us in the Northern Hemisphere, the 2017 autumnal equinox came on September 22, and the October 5 full moon was the Northern Hemisphere’s Harvest Moon. Depending on whom you ask, this Hunter’s Moon may – or may not – be a supermoon. Follow the links below to learn more about the 2017 Hunter’s Moon.

What makes a Hunter’s Moon special?

2017 Hunter’s Moon also a supermoon?

When should I look for the Hunter’s Moon?

Is a Hunter’s Moon always bigger, or brighter or more colorful?

How did the Hunter’s Moon get its name?

What if I’m in the Southern Hemisphere?

Minor lunar standstill makes a subtle Hunter’s Moon in 2016

EarthSky lunar calendars are cool! They make great gifts. Order now. Supplies limited.

Rising Hunter’s Moon. Photo by Abhinav Singhai, 2014.

What makes a Hunter’s Moon special? Nature is particularly cooperative around the time of the autumn equinox to make the fall full moonrises unique.

Here’s what happens. On average, the moon rises about 50 minutes later each day. But when a full moon happens close to the autumnal equinox – either a Harvest or a Hunter’s Moon – the moon (at mid-temperate latitudes) rises only about 30 to 35 minutes later daily for several days before and after the full moon. The reason is that the ecliptic – or the moon’s orbital path – makes a narrow angle with the evening horizon around the time of the autumn equinox.

The result is that there’s a shorter-than-usual lag time between successive moonrises around the full Hunter’s Moon.

These early evening moonrises are what make every Hunter’s Moon special. Every full moon rises around sunset. After the full Hunter’s Moon, you’ll see the moon ascending in the east relatively soon after sunset for a few days in a row at northerly latitudes.

The moon’s orbit around Earth is very nearly circular, but not a perfect circle. Sometimes the moon is closer to Earth than at other times. That’s the case with the Hunter’s Moon of 2016. Diagram by Brian Koberlein.

2017 Hunter’s Moon also a supermoon? In some months, the full moon is closer to us in orbit than others. The 2017 Hunter’s Moon happens fairly close to perigee, the moon’s closest point to Earth in its monthly orbit. Perigee comes on November 6 at 00:09 UTC (translate to your time zone), about one day and 19 hours after the crest of the moon’s full phase on November 4 at 5:23 UTC.

Nowadays, people call these close full moons supermoons. But commentators disagree on whether this full moon comes close enough to be dubbed a supermoon.

November 2017 full moon an supermoon?

Some don’t like the word supermoon … but we like it. Full moons at their closest to Earth do look brighter. They have a larger-than-usual effect on earthly tides. Although most of us can’t detect that a supermoon appears larger to the eye, very careful and experienced observers say it’s possible.

So you won’t likely see a bigger-than-usual moon (unless you see it near the horizon, an effect known as the moon illusion). But you can notice how brightly the moon is shining, especially on the nights of November 3 and 4!

Next month – in December 2017 – the full moon and perigee (closest point) come even closer together to stage the largest full moon of the year on December 3. Full moon comes on December 3 at 15:47 UTC and perigee arrives less than one day later on December 4 at 8:42 UTC.

That November 2016 full moon will feature the closest supermoon since 1948!

In autumn, the angle of the ecliptic – or sun and moon’s path – makes a narrow angle with the horizon. Image via classicalastronomy.com.

The narrow angle of the ecliptic means the moon rises noticeably farther north on the horizon, from one night to the next. So there is no long period of darkness between sunset and moonrise, and, around the time of full moon, many people see the moon in a twilight sky. Image via classicalastronomy.com.

When should I look for the Hunter’s Moon? If you’re in the Northern Hemisphere, look for the moon to be bright and full-looking for several nights beginning around November 3. Around all of these nights, you’ll see a bright round moon in your sky, rising around the time of sunset, highest in the middle of the night.

The precise time of the November full moon is November 4, 2017 at 5:23 UTC. At North American time zones, that places the time of the full moon at 1:23 a.m. EDT, 12:23 a.m. CDT – and on November 3 at 11:23 p.m. MDT and 10:23: p.m. PDT. Translate to your time zone here.

Want to know the time of moonrise in your location? My favorite source of that information is this Custom Sunrise Sunset Calendar. Once you get to that page, be sure to click the box for ‘moon phases’ and ‘moonrise and moonset times.’

Is a Hunter’s Moon always bigger, or brighter or more colorful? Hunter’s Moon is just an ordinary full moon with a special path across our sky. Most Hunter’s Moons aren’t really bigger or brighter. They’re definitely no more colorful than any other full moon. Still, many of us do think the Hunter’s Moon always looks bigger … or brighter … and more orange than usual. Why?

It’s because the Hunter’s Moon has a powerful mystique. Many people look for it shortly after sunset around the time of full moon. After sunset around any full moon, the moon will always be near the horizon … because full moons rise at sunset. It’s the location of the moon near the horizon that causes the Hunter’s Moon – or any full moon – to look big and orange in color.

Orange moon near the horizon. The orange color of a moon near the horizon is a true physical effect. It stems from the fact that – when you look toward the horizon – you are looking through a greater thickness of Earth’s atmosphere than when you gaze up and overhead. The atmosphere scatters blue light – that’s why the sky looks blue. The greater thickness of atmosphere in the direction of a horizon scatters blue light most effectively, but it lets red light pass through to your eyes. So a full moon near the horizon – any full moon near the horizon – takes on a yellow or orange or reddish hue.

Big moon near the horizon. The bigger-than-usual size of a moon seen near the horizon is something else entirely. It’s a trick that your eyes are playing – an illusion – called the Moon Illusion. You can find lengthy explanations of the Moon Illusion by googling those words yourself.

How did the Hunter’s Moon get its name? We hear many, many different explanations for the name Hunter’s Moon.

In the autumn months, there’s no long period of darkness between sunset and moonrise for several days in a row, around the time of full moon. In the days before tractor lights, the lamp of the Harvest Moon helped farmers to gather their crops, despite the diminishing daylight hours. As the sun’s light faded in the west, the moon would soon rise in the east to illuminate the fields throughout the night. A month later, after the harvest was done, the full Hunter’s Moon was said to illuminate the prey of hunters, scooting along in the stubble left behind in the fields.

Who named the Harvest and Hunter’s Moon? Those names probably sprang to the lips of farmers and hunters throughout the world, on autumn evenings, at times of the full moon.

What if I’m in the Southern Hemisphere? If you’re in the Southern Hemisphere, your Harvest and Hunter’s moons center on the March equinox, your autumn equinox. Much of what we say in his post – the general information about Harvest and Hunter’s Moons – applies to you, too … next March and April. Right now, your full moon will be doing the opposite of a Hunter’s Moon. That is, for the Southern Hemisphere around the time of the October and November full moons, there’s a longer-than-usual time between moonrises on successive nights.

Bottom line: The Hunter’s Moon for the Northern Hemisphere in 2017 comes on the nights of November 3 and 4. The Harvest Moon is the full moon closest to the autumnal equinox, which in 2017 came on October 5. The Hunter’s Moon is the next full moon after the Harvest Moon. Learn the lore of the Hunter’s Moon – and what to look for – here.

See great photos of 2015’s Hunter’s Moon

from EarthSky http://ift.tt/1aMDEac

Moon rising behind the Metéora monastery in Greece. It’s one of the largest and most important complexes of Greek Orthodox monasteries in Greece, second only to Mount Athos. Photo via Aimilianos Gkekas

In skylore, every full moon has many names, and most are tied to the months of the year. But some moons are tied to seasons, such as the Harvest and Hunter’s Moons. The Harvest Moon is the full moon closest to the autumnal equinox. The Hunter’s Moon is the full moon after the Harvest Moon. For us in the Northern Hemisphere, the 2017 autumnal equinox came on September 22, and the October 5 full moon was the Northern Hemisphere’s Harvest Moon. Depending on whom you ask, this Hunter’s Moon may – or may not – be a supermoon. Follow the links below to learn more about the 2017 Hunter’s Moon.

What makes a Hunter’s Moon special?

2017 Hunter’s Moon also a supermoon?

When should I look for the Hunter’s Moon?

Is a Hunter’s Moon always bigger, or brighter or more colorful?

How did the Hunter’s Moon get its name?

What if I’m in the Southern Hemisphere?

Minor lunar standstill makes a subtle Hunter’s Moon in 2016

EarthSky lunar calendars are cool! They make great gifts. Order now. Supplies limited.

Rising Hunter’s Moon. Photo by Abhinav Singhai, 2014.

What makes a Hunter’s Moon special? Nature is particularly cooperative around the time of the autumn equinox to make the fall full moonrises unique.

Here’s what happens. On average, the moon rises about 50 minutes later each day. But when a full moon happens close to the autumnal equinox – either a Harvest or a Hunter’s Moon – the moon (at mid-temperate latitudes) rises only about 30 to 35 minutes later daily for several days before and after the full moon. The reason is that the ecliptic – or the moon’s orbital path – makes a narrow angle with the evening horizon around the time of the autumn equinox.

The result is that there’s a shorter-than-usual lag time between successive moonrises around the full Hunter’s Moon.

These early evening moonrises are what make every Hunter’s Moon special. Every full moon rises around sunset. After the full Hunter’s Moon, you’ll see the moon ascending in the east relatively soon after sunset for a few days in a row at northerly latitudes.

The moon’s orbit around Earth is very nearly circular, but not a perfect circle. Sometimes the moon is closer to Earth than at other times. That’s the case with the Hunter’s Moon of 2016. Diagram by Brian Koberlein.

2017 Hunter’s Moon also a supermoon? In some months, the full moon is closer to us in orbit than others. The 2017 Hunter’s Moon happens fairly close to perigee, the moon’s closest point to Earth in its monthly orbit. Perigee comes on November 6 at 00:09 UTC (translate to your time zone), about one day and 19 hours after the crest of the moon’s full phase on November 4 at 5:23 UTC.

Nowadays, people call these close full moons supermoons. But commentators disagree on whether this full moon comes close enough to be dubbed a supermoon.

November 2017 full moon an supermoon?

Some don’t like the word supermoon … but we like it. Full moons at their closest to Earth do look brighter. They have a larger-than-usual effect on earthly tides. Although most of us can’t detect that a supermoon appears larger to the eye, very careful and experienced observers say it’s possible.

So you won’t likely see a bigger-than-usual moon (unless you see it near the horizon, an effect known as the moon illusion). But you can notice how brightly the moon is shining, especially on the nights of November 3 and 4!

Next month – in December 2017 – the full moon and perigee (closest point) come even closer together to stage the largest full moon of the year on December 3. Full moon comes on December 3 at 15:47 UTC and perigee arrives less than one day later on December 4 at 8:42 UTC.

That November 2016 full moon will feature the closest supermoon since 1948!

In autumn, the angle of the ecliptic – or sun and moon’s path – makes a narrow angle with the horizon. Image via classicalastronomy.com.

The narrow angle of the ecliptic means the moon rises noticeably farther north on the horizon, from one night to the next. So there is no long period of darkness between sunset and moonrise, and, around the time of full moon, many people see the moon in a twilight sky. Image via classicalastronomy.com.

When should I look for the Hunter’s Moon? If you’re in the Northern Hemisphere, look for the moon to be bright and full-looking for several nights beginning around November 3. Around all of these nights, you’ll see a bright round moon in your sky, rising around the time of sunset, highest in the middle of the night.

The precise time of the November full moon is November 4, 2017 at 5:23 UTC. At North American time zones, that places the time of the full moon at 1:23 a.m. EDT, 12:23 a.m. CDT – and on November 3 at 11:23 p.m. MDT and 10:23: p.m. PDT. Translate to your time zone here.

Want to know the time of moonrise in your location? My favorite source of that information is this Custom Sunrise Sunset Calendar. Once you get to that page, be sure to click the box for ‘moon phases’ and ‘moonrise and moonset times.’

Is a Hunter’s Moon always bigger, or brighter or more colorful? Hunter’s Moon is just an ordinary full moon with a special path across our sky. Most Hunter’s Moons aren’t really bigger or brighter. They’re definitely no more colorful than any other full moon. Still, many of us do think the Hunter’s Moon always looks bigger … or brighter … and more orange than usual. Why?

It’s because the Hunter’s Moon has a powerful mystique. Many people look for it shortly after sunset around the time of full moon. After sunset around any full moon, the moon will always be near the horizon … because full moons rise at sunset. It’s the location of the moon near the horizon that causes the Hunter’s Moon – or any full moon – to look big and orange in color.

Orange moon near the horizon. The orange color of a moon near the horizon is a true physical effect. It stems from the fact that – when you look toward the horizon – you are looking through a greater thickness of Earth’s atmosphere than when you gaze up and overhead. The atmosphere scatters blue light – that’s why the sky looks blue. The greater thickness of atmosphere in the direction of a horizon scatters blue light most effectively, but it lets red light pass through to your eyes. So a full moon near the horizon – any full moon near the horizon – takes on a yellow or orange or reddish hue.

Big moon near the horizon. The bigger-than-usual size of a moon seen near the horizon is something else entirely. It’s a trick that your eyes are playing – an illusion – called the Moon Illusion. You can find lengthy explanations of the Moon Illusion by googling those words yourself.

How did the Hunter’s Moon get its name? We hear many, many different explanations for the name Hunter’s Moon.

In the autumn months, there’s no long period of darkness between sunset and moonrise for several days in a row, around the time of full moon. In the days before tractor lights, the lamp of the Harvest Moon helped farmers to gather their crops, despite the diminishing daylight hours. As the sun’s light faded in the west, the moon would soon rise in the east to illuminate the fields throughout the night. A month later, after the harvest was done, the full Hunter’s Moon was said to illuminate the prey of hunters, scooting along in the stubble left behind in the fields.

Who named the Harvest and Hunter’s Moon? Those names probably sprang to the lips of farmers and hunters throughout the world, on autumn evenings, at times of the full moon.

What if I’m in the Southern Hemisphere? If you’re in the Southern Hemisphere, your Harvest and Hunter’s moons center on the March equinox, your autumn equinox. Much of what we say in his post – the general information about Harvest and Hunter’s Moons – applies to you, too … next March and April. Right now, your full moon will be doing the opposite of a Hunter’s Moon. That is, for the Southern Hemisphere around the time of the October and November full moons, there’s a longer-than-usual time between moonrises on successive nights.

Bottom line: The Hunter’s Moon for the Northern Hemisphere in 2017 comes on the nights of November 3 and 4. The Harvest Moon is the full moon closest to the autumnal equinox, which in 2017 came on October 5. The Hunter’s Moon is the next full moon after the Harvest Moon. Learn the lore of the Hunter’s Moon – and what to look for – here.

See great photos of 2015’s Hunter’s Moon

from EarthSky http://ift.tt/1aMDEac

Pisces? Here’s your constellation

Pisces the Fishes illustration courtesy of Old Book Art Image gallery

Pisces the Fishes is sometimes called the first constellation of the zodiac because the sun appears in front of this constellation at the time of the March equinox. One tropical year is usually defined as the period of time between successive March equinoxes. So – in this sense – the March equinox marks the beginning of a new year. And that is why Pisces – backdrop to the sun on the March equinox – often appears as marking the starting point of the zodiac. Follow the links below to learn more about the constellation Pisces the Fishes.

When can I see the constellation Pisces?

Pisces’ lone Messier object

Pisces in mythology and star lore

How long is the Age of Pisces?

As seen from mid-northern latitudes, the constellation Pisces appears in the southeast as darkness falls in November. Image via Wikimedia Commons

When can I see the constellation Pisces? In our time, the sun’s annual passage in front of the constellation Pisces is from about March 12 to April 19. Then the sun passes in front of the constellation Aries from about April 19 to May 14.

Of course, March and April are not good for seeing Pisces because this constellation is lost in the sun’s glare at that time of year. Instead, a Northern Hemisphere autumn (or Southern Hemisphere spring) – say, November – presents an opportune time for viewing Pisces in the evening sky.

As seen from across the globe, Pisces reaches its high point for the night at about 10 p.m. local standard time in early November and at about 8 p.m. in early December.

You need a dark country sky to see this fairly dim constellation swimming in what the early stargazers considered to be a watery region of the lore-laden heavens. Pisces is found to the northeast of the constellation Aquarius the Water Bearer and to the northwest of the constellation Cetus the Sea-monster.

Fortunately, Pisces can be found rather handily by referring to the signpost known as the Great Square of Pegasus, as shown on the sky chart below. Look first for the Circlet of Pisces – otherwise known as the head of the Western Fish – to the south of the Square of Pegasus. Once you’ve found the Western Fish, go on from there to catch the Eastern Fish that’s jumping upward to the east of the Square of Pegasus. The entire constellation looks like the letter V, and a very graceful and lovely V at that. The Alpha star of the constellation (though not the brightest star) is Al Risha. By the way, as seen from the northern tropics or the Southern Hemisphere, the Eastern Fish appears to be plunging downward.

First find the signpost known as the Great Square of Pegasus. That’s your jumping off spot for finding Pisces’ place in the great celestial sea. Click here for a larger chart.

Part of Pisces, the Circlet in Pisces, and the Great Square of Pegasus by Susan Jensen in Odessa, Washington. Thank you, Susan.

Pisces’ lone Messier object. Pisces can only claim one Messier object – that is, a fuzzy object resembling a comet but really a star cluster, nebula or galaxy – within its borders. It’s Messier 74, a face-on spiral galaxy looming at an estimated 35 million light-years distant. In the month of March, when it’s technically possible – yet difficult – to see all the Messier objects in the span of one night, this Messier object in the constellation Pisces is one that is commonly missed.

Messier 74 as seen by the Hubble Space Telescope. Image via NASA,ESA and the Hubble Heritage

There are two reasons why Messier 74 is so hard to catch during the annual Messier Marathons in March and/or April. At that time of year, Messier 74 lurks rather low in the western sky at nightfall and quickly sinks out of view shortly thereafter. Plus, this distant galaxy has an extremely low surface brightness, so excellent seeing conditions are absolutely critical for catching Messier 74. You don’t need a large telescope as much as you need a dark, transparent sky.

But if you want to nab this faint galaxy that is Messier 74, the months around November are a grand time of year to do so. Try, possibly with averted vision, on a dark, clear moonless night.

Ruins of Palmyra, ancient Syrian city to the northeast of Damascus. Image via Wikimedia Commons

Pisces in mythology and star lore. Greek and Roman versions of Pisces’ sky lore seemed to have come from Syria, where fish were regarded as divine. There seems to be some confusion as to whether the ancient Syrians abstained from fish altogether or only fish from the Chalos River (presently called the Queiq or Aleppo River).

The Syrian goddess of love and fertility, Atagartis, is often portrayed as half woman and half fish. She is thought to be the origin of the Greek goddess Aphrodite and the Roman goddess Venus.

According to Greek mythology, the fire-breathing monster Typhon was about to devour Aphrodite (the Roman Venus) and her son Eros (the Roman Cupid), except that they turned into fish and jumped into the Euphrates River to make a great escape. Mother and son tied themselves together with a cord to make sure they would not lose one another in the tumbling waters.

1948 night sky star map showing the constellations of the ancient Sea imagined by the ancients in this part of the sky. Look for the Western Fish swimming along the celestial equator, to the northeast of Aquarius and the northwest of Cetus. Image via etsy.com

How long is the Age of Pisces? By some definitions, we’ll continue to live within the Age of Pisces as long the sun shines in front of this constellation on the March equinox. By the way, although the sun hasn’t appeared in front of the constellation Aries on the equinox for over 2,000 years, we still refer to the March equinox point as the First Point in Aries.

If we accept the constellation boundaries as defined by the International Astronomical Union, the Age of Pisces started in 68 B.C. and the Age of Aquarius will begin in 2597.

But there are many varied views on this, some of which you can read about in this post: When does the Age of Aquarius begin?

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

Bottom line: How to see the constellation Pisces. Plus sky lore and science.

Taurus? Here’s your constellation
Gemini? Here’s your constellation
Cancer? Here’s your constellation
Leo? Here’s your constellation
Virgo? Here’s your constellation
Libra? Here’s your constellation
Scorpius? Here’s your contellation
Sagittarius? Here’s your constellation
Capricornus? Here’s your constellation
Aquarius? Here’s your constellation
Pisces? Here’s your constellation
Aries? Here’s your constellation
Birthday late November to early December? Here’s your constellation

from EarthSky http://ift.tt/2zaYulT

Pisces the Fishes illustration courtesy of Old Book Art Image gallery

Pisces the Fishes is sometimes called the first constellation of the zodiac because the sun appears in front of this constellation at the time of the March equinox. One tropical year is usually defined as the period of time between successive March equinoxes. So – in this sense – the March equinox marks the beginning of a new year. And that is why Pisces – backdrop to the sun on the March equinox – often appears as marking the starting point of the zodiac. Follow the links below to learn more about the constellation Pisces the Fishes.

When can I see the constellation Pisces?

Pisces’ lone Messier object

Pisces in mythology and star lore

How long is the Age of Pisces?

As seen from mid-northern latitudes, the constellation Pisces appears in the southeast as darkness falls in November. Image via Wikimedia Commons

When can I see the constellation Pisces? In our time, the sun’s annual passage in front of the constellation Pisces is from about March 12 to April 19. Then the sun passes in front of the constellation Aries from about April 19 to May 14.

Of course, March and April are not good for seeing Pisces because this constellation is lost in the sun’s glare at that time of year. Instead, a Northern Hemisphere autumn (or Southern Hemisphere spring) – say, November – presents an opportune time for viewing Pisces in the evening sky.

As seen from across the globe, Pisces reaches its high point for the night at about 10 p.m. local standard time in early November and at about 8 p.m. in early December.

You need a dark country sky to see this fairly dim constellation swimming in what the early stargazers considered to be a watery region of the lore-laden heavens. Pisces is found to the northeast of the constellation Aquarius the Water Bearer and to the northwest of the constellation Cetus the Sea-monster.

Fortunately, Pisces can be found rather handily by referring to the signpost known as the Great Square of Pegasus, as shown on the sky chart below. Look first for the Circlet of Pisces – otherwise known as the head of the Western Fish – to the south of the Square of Pegasus. Once you’ve found the Western Fish, go on from there to catch the Eastern Fish that’s jumping upward to the east of the Square of Pegasus. The entire constellation looks like the letter V, and a very graceful and lovely V at that. The Alpha star of the constellation (though not the brightest star) is Al Risha. By the way, as seen from the northern tropics or the Southern Hemisphere, the Eastern Fish appears to be plunging downward.

First find the signpost known as the Great Square of Pegasus. That’s your jumping off spot for finding Pisces’ place in the great celestial sea. Click here for a larger chart.

Part of Pisces, the Circlet in Pisces, and the Great Square of Pegasus by Susan Jensen in Odessa, Washington. Thank you, Susan.

Pisces’ lone Messier object. Pisces can only claim one Messier object – that is, a fuzzy object resembling a comet but really a star cluster, nebula or galaxy – within its borders. It’s Messier 74, a face-on spiral galaxy looming at an estimated 35 million light-years distant. In the month of March, when it’s technically possible – yet difficult – to see all the Messier objects in the span of one night, this Messier object in the constellation Pisces is one that is commonly missed.

Messier 74 as seen by the Hubble Space Telescope. Image via NASA,ESA and the Hubble Heritage

There are two reasons why Messier 74 is so hard to catch during the annual Messier Marathons in March and/or April. At that time of year, Messier 74 lurks rather low in the western sky at nightfall and quickly sinks out of view shortly thereafter. Plus, this distant galaxy has an extremely low surface brightness, so excellent seeing conditions are absolutely critical for catching Messier 74. You don’t need a large telescope as much as you need a dark, transparent sky.

But if you want to nab this faint galaxy that is Messier 74, the months around November are a grand time of year to do so. Try, possibly with averted vision, on a dark, clear moonless night.

Ruins of Palmyra, ancient Syrian city to the northeast of Damascus. Image via Wikimedia Commons

Pisces in mythology and star lore. Greek and Roman versions of Pisces’ sky lore seemed to have come from Syria, where fish were regarded as divine. There seems to be some confusion as to whether the ancient Syrians abstained from fish altogether or only fish from the Chalos River (presently called the Queiq or Aleppo River).

The Syrian goddess of love and fertility, Atagartis, is often portrayed as half woman and half fish. She is thought to be the origin of the Greek goddess Aphrodite and the Roman goddess Venus.

According to Greek mythology, the fire-breathing monster Typhon was about to devour Aphrodite (the Roman Venus) and her son Eros (the Roman Cupid), except that they turned into fish and jumped into the Euphrates River to make a great escape. Mother and son tied themselves together with a cord to make sure they would not lose one another in the tumbling waters.

1948 night sky star map showing the constellations of the ancient Sea imagined by the ancients in this part of the sky. Look for the Western Fish swimming along the celestial equator, to the northeast of Aquarius and the northwest of Cetus. Image via etsy.com

How long is the Age of Pisces? By some definitions, we’ll continue to live within the Age of Pisces as long the sun shines in front of this constellation on the March equinox. By the way, although the sun hasn’t appeared in front of the constellation Aries on the equinox for over 2,000 years, we still refer to the March equinox point as the First Point in Aries.

If we accept the constellation boundaries as defined by the International Astronomical Union, the Age of Pisces started in 68 B.C. and the Age of Aquarius will begin in 2597.

But there are many varied views on this, some of which you can read about in this post: When does the Age of Aquarius begin?

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

Bottom line: How to see the constellation Pisces. Plus sky lore and science.

Taurus? Here’s your constellation
Gemini? Here’s your constellation
Cancer? Here’s your constellation
Leo? Here’s your constellation
Virgo? Here’s your constellation
Libra? Here’s your constellation
Scorpius? Here’s your contellation
Sagittarius? Here’s your constellation
Capricornus? Here’s your constellation
Aquarius? Here’s your constellation
Pisces? Here’s your constellation
Aries? Here’s your constellation
Birthday late November to early December? Here’s your constellation

from EarthSky http://ift.tt/2zaYulT

Star of the week: Al Risha

Al Risha, the Alpha star of Pisces the Fishes, via the Space Telescope Science Institute.

2018 EarthSky lunar calendars are here!

Alpha Piscium, or Al Risha, is not one of the sky’s brightest stars. In fact, it’s only about 4th magnitude, which is getting down to a level of faintness that will require a dark sky to see. But Al Risha is a fascinating star in a prominent place in the zodiacal constellation Pisces the Fishes, which is one of the sky’s most graceful and beautiful constellations. Follow the links below to learn more about Alpha Piscium, aka Al Risha.

The constellation Pisces appears in the shape of the letter V. Al Risha lies at the tip of the V, where the two lines come together. You might also notice The Circlet in Pisces.

How to see Al Risha

Al Risha in star history and mythology

Al Risha in science

How to see Al Risha. The star Al Risha is very easy to pick out in Pisces if you have a dark sky.

Pisces the Fishes is always shown as a pair of fish, swimming in opposite directions. The Western Fish lies in the graceful line of stars south of the Great Square of Pegasus, and the Northern Fish is another line of stars to the east of the Square. Al Risha represents the knot or cord that ties the two Fish together by ribbons at their tails. In fact, Al Risha means “the cord” in Arabic.

Northern Hemisphere autumn (or Southern Hemisphere spring) is a good time to see the constellation Pisces, with the star Al Risha at its heart, in the evening sky. As seen from across the globe, Pisces reaches its high point for the night at about 10 p.m. local standard time in early November and at about 8 p.m. in early December.

If you can find the Great Square of Pegasus – which really is very noticeable as a large square pattern on the sky’s dome, with four medium-bright stars marking its corners – you can find Pisces. You can, that is, if your sky is dark enough.

You’ll probably pick out the Western Fish first, because it contains an asterism – or noticeable pattern of stars – known as The Circlet. The little circle of faint stars forming the Circlet in Pisces can be seen easily in a dark sky on the southern edge of the Great Square.

The rest of the constellation Pisces forms a beautiful V shape – like the letter V – on two sides of the Square.

Pisces the Fishes illustration courtesy of Old Book Art Image gallery

Title page copperplate engraving for Johann Bayer’s Uranometria, courtesy of the United States Naval Observatory Library via Wikimedia Commons

Al Risha in star history and mythology Although the star Al Risha is not very bright, its location within its constellation – at the tip of the V in Pisces – makes it very noticeable.

That’s surely why the German astronomer Johann Bayer, in 1603, gave this star the designation Alpha in his star atlas Uranometria (named after Urania, the Greek Muse of Astronomy), even though Al Risha is only the third-brightest star in its constellation. Bayer’s system was to assign a lower-case Greek letter (alpha, beta, gamma and so on) to each star he catalogued, combined with the Latin name of the star’s parent constellation in genitive (possessive) form. So, for example, the star Al Risha is also Alpha Piscium, the Alpha star of Pisces.

Most of the time, the Alpha star is the brightest star in a constellation, but not always. There are two brighter stars in Pisces (although not much brighter). They are Eta and Gamma Piscium. Al Risha, by the way, is also one of the only stars in Pisces with a proper name. The early Arabian stargazers, who named it, noticed it, too.

In Roman mythology, the constellation Pisces is associated with the legend of Venus and Cupid (or, in the Greek myths, Aphrodite and her son Eros). These two escaped the monster Typhon (or Typhoon) by transforming themselves into fishes and jumping into a river. Venus and Cupid are said to have bound themselves together so that, in escaping the monster, they would not be separated. The gods were pleased and placed the Fishes in the sky to commemorate the event.

A drawing of the two stars that make up what we see a one Al Risha. This drawing is by Jeremy Perez of the interesting website The Belt of Venus.

Al Risha in science. Al Risha appears single, but it is a close double star, that is, two stars orbiting a common center of gravity. It consists of pair of class A stars that lie some 120 A.U. (Astronomical Units) apart, with one A.U. equally one Earth-sun distance. So the two stars that we see as Al Risha are in fact 120 times the distance between our Earth and sun, or about the distance between our sun and Pluto.

The two stars in the Al Risha system take 720 years to orbit each other. Yet these stars appear so close together from our earthly vantage point that amateur astronomers using backyard telescopes must look carefully to see both of them. Plus, from our perspective, the two stars are appearing to get closer together as they pursue their vast mutual orbit. It’s estimated they will appear closest, as seen from Earth, in the year 2060. Both stars are white, though some observers have reported subtle colors.

Al Risha’s position is: RA 02h 02m 03s, Dec +02° 45′ 50″

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Pisces? Here’s your constellation

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Al Risha, the Alpha star of Pisces the Fishes, via the Space Telescope Science Institute.

2018 EarthSky lunar calendars are here!

Alpha Piscium, or Al Risha, is not one of the sky’s brightest stars. In fact, it’s only about 4th magnitude, which is getting down to a level of faintness that will require a dark sky to see. But Al Risha is a fascinating star in a prominent place in the zodiacal constellation Pisces the Fishes, which is one of the sky’s most graceful and beautiful constellations. Follow the links below to learn more about Alpha Piscium, aka Al Risha.

The constellation Pisces appears in the shape of the letter V. Al Risha lies at the tip of the V, where the two lines come together. You might also notice The Circlet in Pisces.

How to see Al Risha

Al Risha in star history and mythology

Al Risha in science

How to see Al Risha. The star Al Risha is very easy to pick out in Pisces if you have a dark sky.

Pisces the Fishes is always shown as a pair of fish, swimming in opposite directions. The Western Fish lies in the graceful line of stars south of the Great Square of Pegasus, and the Northern Fish is another line of stars to the east of the Square. Al Risha represents the knot or cord that ties the two Fish together by ribbons at their tails. In fact, Al Risha means “the cord” in Arabic.

Northern Hemisphere autumn (or Southern Hemisphere spring) is a good time to see the constellation Pisces, with the star Al Risha at its heart, in the evening sky. As seen from across the globe, Pisces reaches its high point for the night at about 10 p.m. local standard time in early November and at about 8 p.m. in early December.

If you can find the Great Square of Pegasus – which really is very noticeable as a large square pattern on the sky’s dome, with four medium-bright stars marking its corners – you can find Pisces. You can, that is, if your sky is dark enough.

You’ll probably pick out the Western Fish first, because it contains an asterism – or noticeable pattern of stars – known as The Circlet. The little circle of faint stars forming the Circlet in Pisces can be seen easily in a dark sky on the southern edge of the Great Square.

The rest of the constellation Pisces forms a beautiful V shape – like the letter V – on two sides of the Square.

Pisces the Fishes illustration courtesy of Old Book Art Image gallery

Title page copperplate engraving for Johann Bayer’s Uranometria, courtesy of the United States Naval Observatory Library via Wikimedia Commons

Al Risha in star history and mythology Although the star Al Risha is not very bright, its location within its constellation – at the tip of the V in Pisces – makes it very noticeable.

That’s surely why the German astronomer Johann Bayer, in 1603, gave this star the designation Alpha in his star atlas Uranometria (named after Urania, the Greek Muse of Astronomy), even though Al Risha is only the third-brightest star in its constellation. Bayer’s system was to assign a lower-case Greek letter (alpha, beta, gamma and so on) to each star he catalogued, combined with the Latin name of the star’s parent constellation in genitive (possessive) form. So, for example, the star Al Risha is also Alpha Piscium, the Alpha star of Pisces.

Most of the time, the Alpha star is the brightest star in a constellation, but not always. There are two brighter stars in Pisces (although not much brighter). They are Eta and Gamma Piscium. Al Risha, by the way, is also one of the only stars in Pisces with a proper name. The early Arabian stargazers, who named it, noticed it, too.

In Roman mythology, the constellation Pisces is associated with the legend of Venus and Cupid (or, in the Greek myths, Aphrodite and her son Eros). These two escaped the monster Typhon (or Typhoon) by transforming themselves into fishes and jumping into a river. Venus and Cupid are said to have bound themselves together so that, in escaping the monster, they would not be separated. The gods were pleased and placed the Fishes in the sky to commemorate the event.

A drawing of the two stars that make up what we see a one Al Risha. This drawing is by Jeremy Perez of the interesting website The Belt of Venus.

Al Risha in science. Al Risha appears single, but it is a close double star, that is, two stars orbiting a common center of gravity. It consists of pair of class A stars that lie some 120 A.U. (Astronomical Units) apart, with one A.U. equally one Earth-sun distance. So the two stars that we see as Al Risha are in fact 120 times the distance between our Earth and sun, or about the distance between our sun and Pluto.

The two stars in the Al Risha system take 720 years to orbit each other. Yet these stars appear so close together from our earthly vantage point that amateur astronomers using backyard telescopes must look carefully to see both of them. Plus, from our perspective, the two stars are appearing to get closer together as they pursue their vast mutual orbit. It’s estimated they will appear closest, as seen from Earth, in the year 2060. Both stars are white, though some observers have reported subtle colors.

Al Risha’s position is: RA 02h 02m 03s, Dec +02° 45′ 50″

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Pisces? Here’s your constellation

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What is the moon illusion?

We’ve all seen a full moon looming large shortly after it rises, when it’s still hugging the horizon. Scientists say that large moon is an illusion, a trick your brain is playing. It’s called the moon illusion. Its causes aren’t precisely known, but the video above, from AsapSCIENCE, offers some explanation.

By the way, a large moon seen low in the sky might also appear red or orange in color. And that reddish color is not an illusion. It’s a true physical effect, caused by the fact that – when the moon is low in the sky – you’re seeing it through a greater thickness of Earth’s atmosphere than when it’s overhead. The atmosphere filters out the bluer wavelengths of white moonlight (which is really reflected sunlight). Meanwhile, it allows the red component of moonlight to travel straight through to your eyes. So a low moon is likely to look red or orange to you.

How do people get those photos of extra big moons seen near a horizon? They’re the result of photographic tricks and techniques, which you can read about here.

More photography tips: Super moon photography

Bottom line: A full moon, in particular, might look big seen near a horizon. But all full moons seen near a horizon look big, due to a psychological effect called the moon illusion.

Can you tell me the full moon names?

from EarthSky http://ift.tt/1BsRjQA

We’ve all seen a full moon looming large shortly after it rises, when it’s still hugging the horizon. Scientists say that large moon is an illusion, a trick your brain is playing. It’s called the moon illusion. Its causes aren’t precisely known, but the video above, from AsapSCIENCE, offers some explanation.

By the way, a large moon seen low in the sky might also appear red or orange in color. And that reddish color is not an illusion. It’s a true physical effect, caused by the fact that – when the moon is low in the sky – you’re seeing it through a greater thickness of Earth’s atmosphere than when it’s overhead. The atmosphere filters out the bluer wavelengths of white moonlight (which is really reflected sunlight). Meanwhile, it allows the red component of moonlight to travel straight through to your eyes. So a low moon is likely to look red or orange to you.

How do people get those photos of extra big moons seen near a horizon? They’re the result of photographic tricks and techniques, which you can read about here.

More photography tips: Super moon photography

Bottom line: A full moon, in particular, might look big seen near a horizon. But all full moons seen near a horizon look big, due to a psychological effect called the moon illusion.

Can you tell me the full moon names?

from EarthSky http://ift.tt/1BsRjQA

Unexpected view from Gaia, the galactic surveyor

Gaia Measurements of Extreme Space Weather in September 2017

Editor’s note: Today’s post was contributed by Edmund Serpell, from the Gaia team at ESOC.

Gaia Credit: ESA/ATG medialab; background image: ESO/S. Brunier

ESA’s Gaia mission, in orbit since December 2013, is surveying more than a thousand million stars in our Galaxy, monitoring each target star about 70 times over a five-year period and precisely charting their positions, distances, movements and brightness. 

Although Gaia is not equipped with a dedicated radiation monitor, it can provide information about space weather – and the solar particles and radiation – that it encounters at its unique orbital position, L2, 1.5 million km from Earth in the direction away from the Sun.

This information is useful for studies of the Sun and the interplanetary radiation environment that will be encountered by future missions beyond Earth’s protective magnetosphere.

Solar cycle 24 and recent activity

Solar cycle 24 is the current 11-year period of varying activity which peaked in 2014; it  has been notable because the Sun has been much quieter in this cycle than in the preceding ones. In September 2017, however, the Sun burst into life, erupting with the largest flare of the current cycle followed a few days later by another large flare. These flares were associated with a sunspot region with a complex magnetic structure (see image below) and were combined with a release of high-energy particles and coronal mass ejections.

Sunspots imaged in H-alpha light prior to flare activity in September 2017 with a blue dot showing the size of Earth for comparison. Region 2673 is visible at top right. This region can be seen to be magnetically complex (twisty) and dense/energetic. Credit: ESA/E.Serpell

According to spaceweatherlive.com these flares, which are observed and characterised in optical and x-ray wavelengths, had peak magnitudes¹ of X9.3 and X8.2 and were the 8th and 11th largest observed since June 1996 respectively (see also @esaspaceweather here and here). It is interesting to note that with two entries in the top 11, the responsible region was perhaps the second most active of the last 21 years. This is rather surprising considering the previously observed nature of cycle 24 and the timing within this cycle.

Gaia as a particle detector

Gaia is continuously exposed to a stream of charged particles mostly emitted by the Sun, with the addition of some cosmic rays from much further away.

When charged particles pass through the CCD pixels of the spacecraft’s camera, they leave trails of charge that are read out from the detector. Depending on the angle between the direction of flight of the particle and the focal plane, there can be particle trails created with lengths from single pixels up to several hundred pixels.

The onboard computers of the camera are programmed with an algorithm that identifies these signals as prompt particle events (PPE), so called because the particles are high energy and therefore fast (prompt). The computers accumulate counters of these events, which are regularly sent to the ground allowing a measurement of the PPE rate to be calculated.

A WFS snapshot captured during normal space weather conditions showing multiple images of a bright star in a grid pattern and a small number of particle tracks (light dots). Credit: ESA

To assess the alignment of the on-board telescopes, Gaia is equipped with a pair of wavefront sensors (WFS; essentially, small cameras) that take snapshot pictures of specially imaged bright stars. Sometimes the WFS can be tricked by the bright signal due to a prompt particle track and a snapshot of this track is captured and transmitted to the ground (see figure above). These WFS snapshots contain a wealth of data about the particles that left the tracks, including incident direction and kinetic energy.

Gaia observations of a large flare in September 2017

The largest particle flux measured by Gaia since launch was detected after the magnitude X8.2 flare that peaked in x-rays at 16:06 (all times UTC), 10 September 2017. The first particles are apparent in the Gaia PPE counters at about 16:20 and the first WFS images start to appear from about 16:40. The signal peak occurred in both Gaia data sets at about 00:00 on 11 September and continued until at least 12:00 on 12 September (see charts below).

PPE counts (top) and WFS energy measurements (bottom) showing the high-energy particle environment around Gaia due to a solar flare in September 2017. Credit: ESA

Particle energies are measured in units of electron-volts, eV, and high-energy protons have a velocities that are significant fractions of the speed of light, c, as listed below (with the time of travel from the Sun to Gaia);

• 1MeV : 0.05c (180 minutes)
• 10MeV : 0.14c (57 minutes)
• 100MeV : 0.43c (19 minutes)
• 1000MeV : 0.87c (9 minutes)

Although it is not known at what point during the flare the first particles were released toward Gaia, the time of arrival after the peak (< 1 hour) is consistent with the energies (>10MeV) reported by the US GOES spacecraft, which is equipped with specific particle instrumentation that monitored this event from Earth orbit.

The WFS algorithm can be tricked to take an image of high energy particles instead of bright stars. Multiple particle tracks of varying lengths were captured in this example WFS snapshot near the peak of measured activity following a solar flare in September 2017. Credit: ESA/E. Serpell

The intensity of the flare can be appreciated by inspecting WFS snapshots taken near to the observed peak (see figure above) in comparison to images from quieter periods.

There is a relationship between the energy loss as a particle passes through the detector and the kinetic energy of the particle. From sufficiently long tracks it is possible to measure the energy of individual particles and it is hoped that in future an energy spectral analysis of the event will be computed.

The spectacular track in the example WFS snapshot above, if it was a proton, would have had a kinetic energy of 375MeV.

Note:

(1) Solar flares are classed according to the energy they release at X-ray wavelengths. There are five major categories: A, B, C, M and X, further divided into 10 subclasses. M1 flares are 10 times more powerful than C1, and X1 flares are 10 times more powerful than M1 flares, or 100 times more powerful than C1.

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v

Gaia Measurements of Extreme Space Weather in September 2017

Editor’s note: Today’s post was contributed by Edmund Serpell, from the Gaia team at ESOC.

Gaia Credit: ESA/ATG medialab; background image: ESO/S. Brunier

ESA’s Gaia mission, in orbit since December 2013, is surveying more than a thousand million stars in our Galaxy, monitoring each target star about 70 times over a five-year period and precisely charting their positions, distances, movements and brightness. 

Although Gaia is not equipped with a dedicated radiation monitor, it can provide information about space weather – and the solar particles and radiation – that it encounters at its unique orbital position, L2, 1.5 million km from Earth in the direction away from the Sun.

This information is useful for studies of the Sun and the interplanetary radiation environment that will be encountered by future missions beyond Earth’s protective magnetosphere.

Solar cycle 24 and recent activity

Solar cycle 24 is the current 11-year period of varying activity which peaked in 2014; it  has been notable because the Sun has been much quieter in this cycle than in the preceding ones. In September 2017, however, the Sun burst into life, erupting with the largest flare of the current cycle followed a few days later by another large flare. These flares were associated with a sunspot region with a complex magnetic structure (see image below) and were combined with a release of high-energy particles and coronal mass ejections.

Sunspots imaged in H-alpha light prior to flare activity in September 2017 with a blue dot showing the size of Earth for comparison. Region 2673 is visible at top right. This region can be seen to be magnetically complex (twisty) and dense/energetic. Credit: ESA/E.Serpell

According to spaceweatherlive.com these flares, which are observed and characterised in optical and x-ray wavelengths, had peak magnitudes¹ of X9.3 and X8.2 and were the 8th and 11th largest observed since June 1996 respectively (see also @esaspaceweather here and here). It is interesting to note that with two entries in the top 11, the responsible region was perhaps the second most active of the last 21 years. This is rather surprising considering the previously observed nature of cycle 24 and the timing within this cycle.

Gaia as a particle detector

Gaia is continuously exposed to a stream of charged particles mostly emitted by the Sun, with the addition of some cosmic rays from much further away.

When charged particles pass through the CCD pixels of the spacecraft’s camera, they leave trails of charge that are read out from the detector. Depending on the angle between the direction of flight of the particle and the focal plane, there can be particle trails created with lengths from single pixels up to several hundred pixels.

The onboard computers of the camera are programmed with an algorithm that identifies these signals as prompt particle events (PPE), so called because the particles are high energy and therefore fast (prompt). The computers accumulate counters of these events, which are regularly sent to the ground allowing a measurement of the PPE rate to be calculated.

A WFS snapshot captured during normal space weather conditions showing multiple images of a bright star in a grid pattern and a small number of particle tracks (light dots). Credit: ESA

To assess the alignment of the on-board telescopes, Gaia is equipped with a pair of wavefront sensors (WFS; essentially, small cameras) that take snapshot pictures of specially imaged bright stars. Sometimes the WFS can be tricked by the bright signal due to a prompt particle track and a snapshot of this track is captured and transmitted to the ground (see figure above). These WFS snapshots contain a wealth of data about the particles that left the tracks, including incident direction and kinetic energy.

Gaia observations of a large flare in September 2017

The largest particle flux measured by Gaia since launch was detected after the magnitude X8.2 flare that peaked in x-rays at 16:06 (all times UTC), 10 September 2017. The first particles are apparent in the Gaia PPE counters at about 16:20 and the first WFS images start to appear from about 16:40. The signal peak occurred in both Gaia data sets at about 00:00 on 11 September and continued until at least 12:00 on 12 September (see charts below).

PPE counts (top) and WFS energy measurements (bottom) showing the high-energy particle environment around Gaia due to a solar flare in September 2017. Credit: ESA

Particle energies are measured in units of electron-volts, eV, and high-energy protons have a velocities that are significant fractions of the speed of light, c, as listed below (with the time of travel from the Sun to Gaia);

• 1MeV : 0.05c (180 minutes)
• 10MeV : 0.14c (57 minutes)
• 100MeV : 0.43c (19 minutes)
• 1000MeV : 0.87c (9 minutes)

Although it is not known at what point during the flare the first particles were released toward Gaia, the time of arrival after the peak (< 1 hour) is consistent with the energies (>10MeV) reported by the US GOES spacecraft, which is equipped with specific particle instrumentation that monitored this event from Earth orbit.

The WFS algorithm can be tricked to take an image of high energy particles instead of bright stars. Multiple particle tracks of varying lengths were captured in this example WFS snapshot near the peak of measured activity following a solar flare in September 2017. Credit: ESA/E. Serpell

The intensity of the flare can be appreciated by inspecting WFS snapshots taken near to the observed peak (see figure above) in comparison to images from quieter periods.

There is a relationship between the energy loss as a particle passes through the detector and the kinetic energy of the particle. From sufficiently long tracks it is possible to measure the energy of individual particles and it is hoped that in future an energy spectral analysis of the event will be computed.

The spectacular track in the example WFS snapshot above, if it was a proton, would have had a kinetic energy of 375MeV.

Note:

(1) Solar flares are classed according to the energy they release at X-ray wavelengths. There are five major categories: A, B, C, M and X, further divided into 10 subclasses. M1 flares are 10 times more powerful than C1, and X1 flares are 10 times more powerful than M1 flares, or 100 times more powerful than C1.

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Full Hunter’s Moon on November 3-4

Image at top is 2016’s Hunter’s Moon from Kurt Zeppetello in Monroe, Connecticut. He said it looked like this to the eye, but, to get the photo to come out as he wanted, he combined a short exposure with a longer exposure.

Tonight – November 3, 2017 – the full Hunter’s Moon will grace North American skies once more. Hunter’s Moon is the name for the full moon that immediately follows the Harvest Moon, which is the full moon closest to the autumnal equinox. In 2017, the Northern Hemisphere’s Harvest Moon fell on October 5, nearly 13 days after the September 22 equinox. So it’s a late Hunter’s Moon this year for the Northern Hemisphere. In fact, November 4 is about the latest possible date for a full Hunter’s Moon.

Coincidently, it’s also the 2nd-largest full moon of 2017. As seen from around the world, this full moon will parade across the sky from dusk until dawn. Full moon is November 3 or 4, depending on the location of your clock and calendar. The moon will reach the crest of its full phase on November 4, 2017 at precisely 5:23 UTC. At North American time zones, that translates to November 4 at 2:23 a.m. ADT, 1:23 a.m. EDT, 12:23 a.m. CDT – and on Friday, November 3 at 11:23 p.m. MST, 10:23 p.m. PST and 9:23 p.m. AKDT. Click here to translate to your time zone.

A Hunter’s Moon has special characteristics; the time between sunset and each night’s successive moonrise is noticeably short). Those characteristics can be seen by Northern Hemisphere full moon-watchers this weekend, although the effect is mitigated this year, due to the late date of this year’s full Hunter’s Moon.

Meanwhile, the Southern Hemisphere has a full moon with these same characteristics every April or May. The Southern Hemisphere will see its next full Harvest Moon on March 31, 2018, and its next full Hunter’s Moon on April 30, 2018. And, right now, in the Southern Hemisphere, the time between sunset and each night’s successive moonrise is noticeably long.

Thus, for Northern Hemisphere dwellers this month (and Southern Hemisphere dwellers in April and May), the lamp of the Harvest and Hunter’s Moons helps to compensate for the waning autumn daylight.

Image via EarthView. Day and night sides of Earth at the instant of the full moon (2017 November 4 at 5:23 UTC. World map courtesy of Earth and Moon Viewer

Bottom line: As the full moon after the Harvest Moon, the November 3-4, 2017 full moon bears the Hunter’s Moon name for us in the Northern Hemisphere.

What’s special about the Harvest Moon?

Is the November 2017 full moon a supermoon?

November 2017 guide to the five visible planets

from EarthSky http://ift.tt/2xShPqG

Image at top is 2016’s Hunter’s Moon from Kurt Zeppetello in Monroe, Connecticut. He said it looked like this to the eye, but, to get the photo to come out as he wanted, he combined a short exposure with a longer exposure.

Tonight – November 3, 2017 – the full Hunter’s Moon will grace North American skies once more. Hunter’s Moon is the name for the full moon that immediately follows the Harvest Moon, which is the full moon closest to the autumnal equinox. In 2017, the Northern Hemisphere’s Harvest Moon fell on October 5, nearly 13 days after the September 22 equinox. So it’s a late Hunter’s Moon this year for the Northern Hemisphere. In fact, November 4 is about the latest possible date for a full Hunter’s Moon.

Coincidently, it’s also the 2nd-largest full moon of 2017. As seen from around the world, this full moon will parade across the sky from dusk until dawn. Full moon is November 3 or 4, depending on the location of your clock and calendar. The moon will reach the crest of its full phase on November 4, 2017 at precisely 5:23 UTC. At North American time zones, that translates to November 4 at 2:23 a.m. ADT, 1:23 a.m. EDT, 12:23 a.m. CDT – and on Friday, November 3 at 11:23 p.m. MST, 10:23 p.m. PST and 9:23 p.m. AKDT. Click here to translate to your time zone.

A Hunter’s Moon has special characteristics; the time between sunset and each night’s successive moonrise is noticeably short). Those characteristics can be seen by Northern Hemisphere full moon-watchers this weekend, although the effect is mitigated this year, due to the late date of this year’s full Hunter’s Moon.

Meanwhile, the Southern Hemisphere has a full moon with these same characteristics every April or May. The Southern Hemisphere will see its next full Harvest Moon on March 31, 2018, and its next full Hunter’s Moon on April 30, 2018. And, right now, in the Southern Hemisphere, the time between sunset and each night’s successive moonrise is noticeably long.

Thus, for Northern Hemisphere dwellers this month (and Southern Hemisphere dwellers in April and May), the lamp of the Harvest and Hunter’s Moons helps to compensate for the waning autumn daylight.

Image via EarthView. Day and night sides of Earth at the instant of the full moon (2017 November 4 at 5:23 UTC. World map courtesy of Earth and Moon Viewer

Bottom line: As the full moon after the Harvest Moon, the November 3-4, 2017 full moon bears the Hunter’s Moon name for us in the Northern Hemisphere.

What’s special about the Harvest Moon?

Is the November 2017 full moon a supermoon?

November 2017 guide to the five visible planets

from EarthSky http://ift.tt/2xShPqG

Heavy atom tunneling in semibullvalene

Another prediction made by quantum chemistry has now been confirmed. In 2010, Zhang, Hrovat, and Borden predicted that the degenerate rearrangement of semibullvalene 1 occurs with heavy atom tunneling.¹ For example, the computed rate of the rearrangement including tunneling correction is 1.43 x 10^-3 s^-1 at 40 K, and this rate does not change with decreasing temperature. The predicted half-life of 485 s is 10¹⁰ shorter than that predicted by transition state theory.

Now a group led by Sander has examined the rearrangement of deuterated 2.² The room temperature equilibrium mixture of d⁴–2 and d²–2 was deposited at 3 K. IR observation showed a decrease in signal intensities associated with d⁴–2 and concomitant growth of signals associated with d²–2. The barrier for this interconversion is about 5 kcal mol^-1, too large to be crossed at this temperature. Instead, the interconversion is happening by tunneling through the barrier (with a rate about 10^-4 s^-1), forming the more stable isomer d²–2 preferentially. This is exactly as predicted by theory!

References

1. Zhang, X.; Hrovat, D. A.; Borden, W. T., "Calculations Predict That Carbon Tunneling Allows the Degenerate Cope Rearrangement of Semibullvalene to Occur Rapidly at Cryogenic Temperatures." Org. Letters 2010, 12, 2798-2801, DOI: 10.1021/ol100879t.

2. Schleif, T.; Mieres-Perez, J.; Henkel, S.; Ertelt, M.; Borden, W. T.; Sander, W., "The Cope Rearrangement of 1,5-Dimethylsemibullvalene-2(4)-d1: Experimental Evidence for Heavy-Atom Tunneling." Angew. Chem. Int. Ed. 2017, 56, 10746-10749, DOI: 10.1002/anie.201704787.

InChIs

1: InChI=1S/C8H8/c1-3-6-7-4-2-5(1)8(6)7/h1-8H
InChIKey=VEAPRCKNPMGWCP-UHFFFAOYSA-N

d⁴–2: InChI=1S/C10H12/c1-9-5-3-7-8(4-6-9)10(7,9)2/h3-8H,1-2H3/i5D
InChIKey=WUJOLJNLXLACNA-UICOGKGYSA-N

d²–2: InChI=1S/C10H12/c1-9-5-3-7-8(4-6-9)10(7,9)2/h3-8H,1-2H3/i7D
InChIKey=WUJOLJNLXLACNA-WHRKIXHSSA-N

from Computational Organic Chemistry http://ift.tt/2A9m2I5

Another prediction made by quantum chemistry has now been confirmed. In 2010, Zhang, Hrovat, and Borden predicted that the degenerate rearrangement of semibullvalene 1 occurs with heavy atom tunneling.¹ For example, the computed rate of the rearrangement including tunneling correction is 1.43 x 10^-3 s^-1 at 40 K, and this rate does not change with decreasing temperature. The predicted half-life of 485 s is 10¹⁰ shorter than that predicted by transition state theory.

Now a group led by Sander has examined the rearrangement of deuterated 2.² The room temperature equilibrium mixture of d⁴–2 and d²–2 was deposited at 3 K. IR observation showed a decrease in signal intensities associated with d⁴–2 and concomitant growth of signals associated with d²–2. The barrier for this interconversion is about 5 kcal mol^-1, too large to be crossed at this temperature. Instead, the interconversion is happening by tunneling through the barrier (with a rate about 10^-4 s^-1), forming the more stable isomer d²–2 preferentially. This is exactly as predicted by theory!

References

1. Zhang, X.; Hrovat, D. A.; Borden, W. T., "Calculations Predict That Carbon Tunneling Allows the Degenerate Cope Rearrangement of Semibullvalene to Occur Rapidly at Cryogenic Temperatures." Org. Letters 2010, 12, 2798-2801, DOI: 10.1021/ol100879t.

2. Schleif, T.; Mieres-Perez, J.; Henkel, S.; Ertelt, M.; Borden, W. T.; Sander, W., "The Cope Rearrangement of 1,5-Dimethylsemibullvalene-2(4)-d1: Experimental Evidence for Heavy-Atom Tunneling." Angew. Chem. Int. Ed. 2017, 56, 10746-10749, DOI: 10.1002/anie.201704787.

InChIs

1: InChI=1S/C8H8/c1-3-6-7-4-2-5(1)8(6)7/h1-8H
InChIKey=VEAPRCKNPMGWCP-UHFFFAOYSA-N

d⁴–2: InChI=1S/C10H12/c1-9-5-3-7-8(4-6-9)10(7,9)2/h3-8H,1-2H3/i5D
InChIKey=WUJOLJNLXLACNA-UICOGKGYSA-N

d²–2: InChI=1S/C10H12/c1-9-5-3-7-8(4-6-9)10(7,9)2/h3-8H,1-2H3/i7D
InChIKey=WUJOLJNLXLACNA-WHRKIXHSSA-N

from Computational Organic Chemistry http://ift.tt/2A9m2I5