See moon and stars of Taurus before sunrise

The moon is soon to swing by the Pleiades star cluster and star Aldebaran, which rank as the two most prominent signposts in the constellation Taurus the Bull. The moon swings to the south of the Pleiades cluster on June 29, 2019, and then to the north of Aldebaran on June 30, 2019. Finally, the moon will meet up with the planet Venus in the glow of morning dawn on or near July 1, 2019.

Here’s the tricky part of this observation. You probably won’t see all of the aforementioned objects at the same time. By the time that Venus rises into your sky, chances are the Pleiades star cluster and Aldebaran will have faded from sight in the glare of morning twilight. Venus, like the moon, also shines in front of the constellation Taurus in late June and early July 2019.

However, the moon will move out of the constellation Taurus and into the constellation Gemini on or near July 2. Then, Venus too will move out of of Taurus and into Gemini, on or near July 4.

The chart below shows the moon’s movement in late June and early July with respect to Venus. Will you see the star Aldebaran in the morning twilight, at the same time as Venus? Maybe. Venus is much, much brighter. Both Aldebaran and Venus will be near the sunrise, so you’ll need an unobstructed horizon to see them. Binoculars might help, too!

It’ll be a big challenge to catch the star Aldebaran and the planet Venus before sunrise in late June and early July 2019.

The Pleiades star cluster – a tiny, misty dipper in a dark-enough sky – is fainter still. You’ll probably need to be up before dawn’s first light, to see the Pleiades with the eye alone. Astronomers have a special name for dawn’s first light; it’s the same name they use for the last traces of evening twilight. They call it astronomical twilight. Want to know when astronomical twilight arrives in your sky? Click here and check the astronomical twilight box.

Want to know when the moon rises into your sky? Click here and check the moonrise and moonset box.

To find out the rising time of Aldebaran, click here and choose Aldebaran as your celestial object of interest.

We in the Northern Hemisphere tend to associate the constellation Taurus with the winter season because that’s when this constellation comes at nightfall and beautifies our winter nights. If you live in the Southern Hemisphere, then the constellation Taurus lights up your summer evenings.

The sun passes in front of the constellation Taurus each year from about May 14 to June 21, at which time this constellation is lost in the sun’s glare. Taurus is just beginning to make its return to the morning sky in late June and early July.

Despite the hot weather in the Northern Hemisphere at present, the first inklings of winter season – the constellation Taurus – can now be seen before sunrise. (Or if you live in the Southern Hemisphere, Taurus’ initial morning appearance signals the inevitable coming of summer.) Because the stars rise some four minutes earlier daily, or 1/2 hour earlier weekly or two hours earlier monthly, the constellation Taurus the Bull’s presence in the morning sky will become more prominent with each passing month.

By the middle of November, the Pleiades cluster will be out all night long; and by around December 1, the star Aldebaran will put on its all-night appearance. The all-night appearances of the Pleiades cluster and then the star Aldebaran some two weeks later signal that late autumn is soon to give way to winter in the Northern Hemisphere.

Bottom line: On these late June and early July mornings, let the waning crescent moon serve as your guide to the constellation Taurus’ two major signposts: the Pleiades star cluster and the red giant star, Aldebaran. Wait just before sunrise, and you’ll see Venus rise over your eastern horizon, too.

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

The moon is soon to swing by the Pleiades star cluster and star Aldebaran, which rank as the two most prominent signposts in the constellation Taurus the Bull. The moon swings to the south of the Pleiades cluster on June 29, 2019, and then to the north of Aldebaran on June 30, 2019. Finally, the moon will meet up with the planet Venus in the glow of morning dawn on or near July 1, 2019.

Here’s the tricky part of this observation. You probably won’t see all of the aforementioned objects at the same time. By the time that Venus rises into your sky, chances are the Pleiades star cluster and Aldebaran will have faded from sight in the glare of morning twilight. Venus, like the moon, also shines in front of the constellation Taurus in late June and early July 2019.

However, the moon will move out of the constellation Taurus and into the constellation Gemini on or near July 2. Then, Venus too will move out of of Taurus and into Gemini, on or near July 4.

The chart below shows the moon’s movement in late June and early July with respect to Venus. Will you see the star Aldebaran in the morning twilight, at the same time as Venus? Maybe. Venus is much, much brighter. Both Aldebaran and Venus will be near the sunrise, so you’ll need an unobstructed horizon to see them. Binoculars might help, too!

It’ll be a big challenge to catch the star Aldebaran and the planet Venus before sunrise in late June and early July 2019.

The Pleiades star cluster – a tiny, misty dipper in a dark-enough sky – is fainter still. You’ll probably need to be up before dawn’s first light, to see the Pleiades with the eye alone. Astronomers have a special name for dawn’s first light; it’s the same name they use for the last traces of evening twilight. They call it astronomical twilight. Want to know when astronomical twilight arrives in your sky? Click here and check the astronomical twilight box.

Want to know when the moon rises into your sky? Click here and check the moonrise and moonset box.

To find out the rising time of Aldebaran, click here and choose Aldebaran as your celestial object of interest.

We in the Northern Hemisphere tend to associate the constellation Taurus with the winter season because that’s when this constellation comes at nightfall and beautifies our winter nights. If you live in the Southern Hemisphere, then the constellation Taurus lights up your summer evenings.

The sun passes in front of the constellation Taurus each year from about May 14 to June 21, at which time this constellation is lost in the sun’s glare. Taurus is just beginning to make its return to the morning sky in late June and early July.

Despite the hot weather in the Northern Hemisphere at present, the first inklings of winter season – the constellation Taurus – can now be seen before sunrise. (Or if you live in the Southern Hemisphere, Taurus’ initial morning appearance signals the inevitable coming of summer.) Because the stars rise some four minutes earlier daily, or 1/2 hour earlier weekly or two hours earlier monthly, the constellation Taurus the Bull’s presence in the morning sky will become more prominent with each passing month.

By the middle of November, the Pleiades cluster will be out all night long; and by around December 1, the star Aldebaran will put on its all-night appearance. The all-night appearances of the Pleiades cluster and then the star Aldebaran some two weeks later signal that late autumn is soon to give way to winter in the Northern Hemisphere.

Bottom line: On these late June and early July mornings, let the waning crescent moon serve as your guide to the constellation Taurus’ two major signposts: the Pleiades star cluster and the red giant star, Aldebaran. Wait just before sunrise, and you’ll see Venus rise over your eastern horizon, too.

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

US revamps volcano early warning system

Aerial view of the Halema’uma’u crater within Hawaii’s Kilauea volcano taken from a helicopter on June 18, 2018. Image via U.S. Geological Survey.

There are 161 active volcanoes in the United States, distributed within 12 states and two territories, and more than 1/3 of these have been classified as posing a very high or high threat to nearby communities. To ensure that communities are given adequate warnings in the event of an impending eruption, a new law was enacted on March 12, 2019. This new law Public Law No. 116-9 – aims to improve volcano monitoring at potentially dangerous volcanoes.

Historically, the United States has experienced several damaging volcanic eruptions. In 1980, for example, the eruption at Mount St. Helens in Washington caused 57 deaths and 1.1 billion dollars in damage. More recently, in 2018, a slow eruption at K?lauea in Hawaii destroyed hundreds of homes that were in the path of the lava flow.

Volcanoes are somewhat unique among destructive natural hazards such as earthquakes and tornadoes in that scientists can often make accurate predictions of an eruption well in advance of the event. Thus, evacuations and other protective measures can be taken to minimize the damage. However, such predictions are only possible if monitoring technology is installed at a volcano.

David Applegate, associate director for natural hazards at the U.S. Geological Survey, commented on the new law as it was being proposed to lawmakers during a hearing in 2017. He said:

Unlike many other natural disasters…volcanic eruptions can be predicted well in advance of their occurrence if adequate in-ground instrumentation is in place that allows earliest detection of unrest, providing the time needed to mitigate the worst of their effects.

Clearly, volcano monitoring technology can save lives and is a worthwhile investment.

The new legislation that was finally passed and signed into law on March 12, 2019, will boost the nation’s capacity to respond to volcano-related hazards. Specifically, the new law will create (1) a unified National Volcano Early Warning System (NVEWS), (2) a watch office that will be staffed continuously around the clock, and (3) a grant system for funding volcano monitoring research.

The new legislation can be expected to improve the monitoring systems that are already in place at five critical areas, namely, the Alaska Volcano Observatory, Hawaiian Volcano Observatory, Cascades Volcano Observatory, Yellowstone Volcano Observatory, and California Volcano Observatory, through equipment upgrades and other types of activities. The new legislation will also help to expand coverage to potentially dangerous volcanoes where there are no monitoring systems in place.

Seismic monitoring stations used by the Yellowstone Volcano Observatory. Image via University of Utah.

You can access more details about the new initiative in the EOS article published April 23, 2019.

Bottom line: The United State’s volcano monitoring system will be improved following passage of a new law on March 12, 2019. The improvements will include equipment upgrades, an expansion of monitoring sites, and enhanced coordination of volcano monitoring activities.

Donate: Your support means the world to us

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

Aerial view of the Halema’uma’u crater within Hawaii’s Kilauea volcano taken from a helicopter on June 18, 2018. Image via U.S. Geological Survey.

There are 161 active volcanoes in the United States, distributed within 12 states and two territories, and more than 1/3 of these have been classified as posing a very high or high threat to nearby communities. To ensure that communities are given adequate warnings in the event of an impending eruption, a new law was enacted on March 12, 2019. This new law Public Law No. 116-9 – aims to improve volcano monitoring at potentially dangerous volcanoes.

Historically, the United States has experienced several damaging volcanic eruptions. In 1980, for example, the eruption at Mount St. Helens in Washington caused 57 deaths and 1.1 billion dollars in damage. More recently, in 2018, a slow eruption at K?lauea in Hawaii destroyed hundreds of homes that were in the path of the lava flow.

Volcanoes are somewhat unique among destructive natural hazards such as earthquakes and tornadoes in that scientists can often make accurate predictions of an eruption well in advance of the event. Thus, evacuations and other protective measures can be taken to minimize the damage. However, such predictions are only possible if monitoring technology is installed at a volcano.

David Applegate, associate director for natural hazards at the U.S. Geological Survey, commented on the new law as it was being proposed to lawmakers during a hearing in 2017. He said:

Unlike many other natural disasters…volcanic eruptions can be predicted well in advance of their occurrence if adequate in-ground instrumentation is in place that allows earliest detection of unrest, providing the time needed to mitigate the worst of their effects.

Clearly, volcano monitoring technology can save lives and is a worthwhile investment.

The new legislation that was finally passed and signed into law on March 12, 2019, will boost the nation’s capacity to respond to volcano-related hazards. Specifically, the new law will create (1) a unified National Volcano Early Warning System (NVEWS), (2) a watch office that will be staffed continuously around the clock, and (3) a grant system for funding volcano monitoring research.

The new legislation can be expected to improve the monitoring systems that are already in place at five critical areas, namely, the Alaska Volcano Observatory, Hawaiian Volcano Observatory, Cascades Volcano Observatory, Yellowstone Volcano Observatory, and California Volcano Observatory, through equipment upgrades and other types of activities. The new legislation will also help to expand coverage to potentially dangerous volcanoes where there are no monitoring systems in place.

Seismic monitoring stations used by the Yellowstone Volcano Observatory. Image via University of Utah.

You can access more details about the new initiative in the EOS article published April 23, 2019.

Bottom line: The United State’s volcano monitoring system will be improved following passage of a new law on March 12, 2019. The improvements will include equipment upgrades, an expansion of monitoring sites, and enhanced coordination of volcano monitoring activities.

Donate: Your support means the world to us

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

Asteroid Day 2019 is June 30

Image via Debbie Lewis.

The fifth annual International Asteroid Day happens this Sunday, June 30, 2019. Recognized by the United Nations, Asteroid Day marks a global opportunity to raise awareness of the threat and opportunity posed by the numerous rocky bodies zooming through space.

This year, Asteroid Day events will focus on the role of asteroids in the formation of our solar system and advances in technology to better detect, track and analyze asteroids and review our ability to deflect a rogue asteroid headed towards Earth.

Asteroid Day events range from asteroid quizzes in a Dublin bar, to high-level discussions of policy and programs at the National Air and Space Museum in Washington, D.C. There’s a list of events all around the world here. To find an Asteroid Day event near you, scroll down to the middle of the page and enter your location.

A new program of Asteroid Day 2019 is Asteroid Day TV. The five-day broadcast – on asteroids and space topics – begins June 27 at 10:00 UTC (translate UTC to your time). There’s a program schedule, plus how to watch, wherever you are, here.

Find out more and keep up with the action by visiting the Asteroid Day website, Youtube channel or Twitter.

Image via Asteroid Day.

The @UN officially designated #AsteroidDay in a global movement to protect our planet. Join us and learn more.
Follow @AsteroidDay and sign the 100X Declaration https://t.co/vu6pmKG6Nm pic.twitter.com/2f7JFR5esC

— Asteroid Day ? (@AsteroidDay) June 22, 2019

Central to Asteroid Day this year is what’s called the 100x Declaration, calling for a 100-fold increase in the detection and monitoring of asteroids. Signed to date by more than 50,000 people around the world, the Declaration resolves to “solve humanity’s greatest challenges to safeguard our families and quality of life on Earth in the future.” If you want to sign, the Declaration is available online here.

Early in the morning on February 15, 2013, a small, previously unknown asteroid entered Earth’s atmosphere at 37,280 miles per hour (66,000 km/h) and exploded high above Chelyabinsk, Russia, with 20–30 times the energy of the Hiroshima atomic bomb. Photo via Alex Alishevskikh/Flickr.

Asteroid Day is held on the anniversary of the most devastating asteroid impact in Earth’s recent history – an event that took place on June 30, 1908, known as the Tunguska explosion, when a small asteroid struck the Earth over Tunguska, Siberia. Here’s the premise of Asteroid Day, in the words of co-founder Brian May, astrophysicist, guitarist and songwriter for the band Queen:

Our goal is to dedicate one day each year to learn about asteroids, the origins of our universe, and to support the resources necessary to see, track and deflect dangerous asteroids from Earth’s orbital path. Asteroids are a natural disaster we know how to prevent.

The story of Asteroid Day.

For asteroid news and updates, follow AsteroidWatch on Twitter.

Bottom line: International Asteroid Day 2019 happens on Sunday, June 30.

from EarthSky https://ift.tt/2KDhe65

Image via Debbie Lewis.

The fifth annual International Asteroid Day happens this Sunday, June 30, 2019. Recognized by the United Nations, Asteroid Day marks a global opportunity to raise awareness of the threat and opportunity posed by the numerous rocky bodies zooming through space.

This year, Asteroid Day events will focus on the role of asteroids in the formation of our solar system and advances in technology to better detect, track and analyze asteroids and review our ability to deflect a rogue asteroid headed towards Earth.

Asteroid Day events range from asteroid quizzes in a Dublin bar, to high-level discussions of policy and programs at the National Air and Space Museum in Washington, D.C. There’s a list of events all around the world here. To find an Asteroid Day event near you, scroll down to the middle of the page and enter your location.

A new program of Asteroid Day 2019 is Asteroid Day TV. The five-day broadcast – on asteroids and space topics – begins June 27 at 10:00 UTC (translate UTC to your time). There’s a program schedule, plus how to watch, wherever you are, here.

Find out more and keep up with the action by visiting the Asteroid Day website, Youtube channel or Twitter.

Image via Asteroid Day.

The @UN officially designated #AsteroidDay in a global movement to protect our planet. Join us and learn more.
Follow @AsteroidDay and sign the 100X Declaration https://t.co/vu6pmKG6Nm pic.twitter.com/2f7JFR5esC

— Asteroid Day ? (@AsteroidDay) June 22, 2019

Central to Asteroid Day this year is what’s called the 100x Declaration, calling for a 100-fold increase in the detection and monitoring of asteroids. Signed to date by more than 50,000 people around the world, the Declaration resolves to “solve humanity’s greatest challenges to safeguard our families and quality of life on Earth in the future.” If you want to sign, the Declaration is available online here.

Early in the morning on February 15, 2013, a small, previously unknown asteroid entered Earth’s atmosphere at 37,280 miles per hour (66,000 km/h) and exploded high above Chelyabinsk, Russia, with 20–30 times the energy of the Hiroshima atomic bomb. Photo via Alex Alishevskikh/Flickr.

Asteroid Day is held on the anniversary of the most devastating asteroid impact in Earth’s recent history – an event that took place on June 30, 1908, known as the Tunguska explosion, when a small asteroid struck the Earth over Tunguska, Siberia. Here’s the premise of Asteroid Day, in the words of co-founder Brian May, astrophysicist, guitarist and songwriter for the band Queen:

Our goal is to dedicate one day each year to learn about asteroids, the origins of our universe, and to support the resources necessary to see, track and deflect dangerous asteroids from Earth’s orbital path. Asteroids are a natural disaster we know how to prevent.

The story of Asteroid Day.

For asteroid news and updates, follow AsteroidWatch on Twitter.

Bottom line: International Asteroid Day 2019 happens on Sunday, June 30.

from EarthSky https://ift.tt/2KDhe65

Moonlit night in Yosemite

View at EarthSky Community Photos. | Image via Fred Walder.

Fred Walder captured this image on June 17, 2019 in California’s Yosemite National Park. Fred wrote:

In the spring around the nights of the full moon when the snow is melting in the mountains, it is possible to see rainbows at night in the mist of waterfalls in Yosemite National Park. These lunar rainbows, to the camera, look like the ones produced by sunlight during the days that are visible to our eyes.

This image was taken during the June full moon at lower Yosemite Falls. It is a combination of 25x 30-second images to provide the equivalent of 12 and half minutes of exposure to show the stars circling the north pole. The camera lens needed to be wiped dry between shots due to the large amount of mist at the base of the waterfall, so the star trails wiggle a little as this moved the camera a bit … I find it really cool that the light of the full moon can produce this rich color at night.

You can see the euqipment Fred used for the photo, and post-processing details here.

Thank you Fred!

from EarthSky https://ift.tt/2FA5Jbu

View at EarthSky Community Photos. | Image via Fred Walder.

Fred Walder captured this image on June 17, 2019 in California’s Yosemite National Park. Fred wrote:

In the spring around the nights of the full moon when the snow is melting in the mountains, it is possible to see rainbows at night in the mist of waterfalls in Yosemite National Park. These lunar rainbows, to the camera, look like the ones produced by sunlight during the days that are visible to our eyes.

This image was taken during the June full moon at lower Yosemite Falls. It is a combination of 25x 30-second images to provide the equivalent of 12 and half minutes of exposure to show the stars circling the north pole. The camera lens needed to be wiped dry between shots due to the large amount of mist at the base of the waterfall, so the star trails wiggle a little as this moved the camera a bit … I find it really cool that the light of the full moon can produce this rich color at night.

You can see the euqipment Fred used for the photo, and post-processing details here.

Thank you Fred!

from EarthSky https://ift.tt/2FA5Jbu

Latest sunsets follow summer solstice

Image at top: Peter Gipson in Stowmarket, Suffolk, England, June 2018. Submit your image to EarthSky here.

For people living around 40 degrees north latitude, the latest sunset of the year happens on or near June 27. And in the Southern Hemisphere, at 40 degrees south latitude, it’s the year’s latest sunrise that happens around now. That’s in spite of the fact that the Northern Hemisphere’s longest (or Southern Hemisphere’s shortest) day of the year fell on the June 21st solstice.

The year’s latest sunset always comes after the summer solstice, even though the exact date of the latest sunset depends on your latitude. Farther north – at Seattle – the latest sunset happened around June 25. Farther south – at Mexico City or Hawaii – the latest sunset won’t happen until early July.

Want to know your date of latest sunset? Try this custom sunrise/sunset calendar.

June sunset – Pere Marquette Beach in Muskegon, Michigan – via Jerry James Photography. Thank you, Jerry!

The latest sunset comes after the summer solstice because the day is more than 24 hours long at this time of the year.

For several weeks, around the June solstice, the day (as measured by successive returns of the midday sun) is nearly 1/4 minute longer than 24 hours. Hence, the midday sun (solar noon) comes later by the clock in late June than it does on the June solstice. Therefore, the sunrise and sunset times also come later by the clock, as the table below helps to explain.

For Denver, Colorado

Date	Sunrise	Midday (Solar Noon)	Sunset	Daylight Hours
June 21	5:32 a.m.	1:01 p.m.	8:31 p.m.	14h 59m 14s
June 27	5:33 a.m.	1:03 p.m.	8:32 p.m.	14h 58m 07s

Source: timeanddate.com

Juan Argudin in Pembroke Pines, Florida, wrote on June 21, 2018: “We’ve taken dozens of sunset pictures but cannot remember such beautiful sunset colors. This was the first sunset after summer solstice, taken between 2 live oak trees in front of our house. Thank you for your excellent newsletter. We have learned a lot.” Photo by Olga Argudin. Thank you, Juan and Olga!

If the Earth’s axis stood upright as our world circled the sun, and if, in addition, the Earth stayed the same distance from the sun all year long, then clock time and sun time would always agree. However, the Earth’s axis is titled 23.44 degrees out of vertical, and our distance from the sun varies by about 3 million miles (5 million km) throughout the year. At and around the equinoxes, solar days are shorter than 24 hours, yet at the solstices, solar days are longer than 24 hours.

The latest sunset always comes on or near June 27 at mid-northern latitudes every year.

Bottom line: Why don’t the latest sunsets come on the longest day (the solstice)? In a nutshell, it’s a discrepancy between the sun and the clock. Thus, for mid-northern latitudes, the latest sunsets always come in late June.

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Donate: Your support means the world to us

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

Image at top: Peter Gipson in Stowmarket, Suffolk, England, June 2018. Submit your image to EarthSky here.

For people living around 40 degrees north latitude, the latest sunset of the year happens on or near June 27. And in the Southern Hemisphere, at 40 degrees south latitude, it’s the year’s latest sunrise that happens around now. That’s in spite of the fact that the Northern Hemisphere’s longest (or Southern Hemisphere’s shortest) day of the year fell on the June 21st solstice.

The year’s latest sunset always comes after the summer solstice, even though the exact date of the latest sunset depends on your latitude. Farther north – at Seattle – the latest sunset happened around June 25. Farther south – at Mexico City or Hawaii – the latest sunset won’t happen until early July.

Want to know your date of latest sunset? Try this custom sunrise/sunset calendar.

June sunset – Pere Marquette Beach in Muskegon, Michigan – via Jerry James Photography. Thank you, Jerry!

The latest sunset comes after the summer solstice because the day is more than 24 hours long at this time of the year.

For several weeks, around the June solstice, the day (as measured by successive returns of the midday sun) is nearly 1/4 minute longer than 24 hours. Hence, the midday sun (solar noon) comes later by the clock in late June than it does on the June solstice. Therefore, the sunrise and sunset times also come later by the clock, as the table below helps to explain.

For Denver, Colorado

Date	Sunrise	Midday (Solar Noon)	Sunset	Daylight Hours
June 21	5:32 a.m.	1:01 p.m.	8:31 p.m.	14h 59m 14s
June 27	5:33 a.m.	1:03 p.m.	8:32 p.m.	14h 58m 07s

Source: timeanddate.com

Juan Argudin in Pembroke Pines, Florida, wrote on June 21, 2018: “We’ve taken dozens of sunset pictures but cannot remember such beautiful sunset colors. This was the first sunset after summer solstice, taken between 2 live oak trees in front of our house. Thank you for your excellent newsletter. We have learned a lot.” Photo by Olga Argudin. Thank you, Juan and Olga!

If the Earth’s axis stood upright as our world circled the sun, and if, in addition, the Earth stayed the same distance from the sun all year long, then clock time and sun time would always agree. However, the Earth’s axis is titled 23.44 degrees out of vertical, and our distance from the sun varies by about 3 million miles (5 million km) throughout the year. At and around the equinoxes, solar days are shorter than 24 hours, yet at the solstices, solar days are longer than 24 hours.

The latest sunset always comes on or near June 27 at mid-northern latitudes every year.

Bottom line: Why don’t the latest sunsets come on the longest day (the solstice)? In a nutshell, it’s a discrepancy between the sun and the clock. Thus, for mid-northern latitudes, the latest sunsets always come in late June.

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

Donate: Your support means the world to us

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

dJ-DP4 and iJ-DP4: including coupling constants

I have written quite a number of posts on using quantum mechanics computations to predict NMR spectra that can aid in identifying chemical structure. Perhaps the most robust technique is Goodman’s DP4 method (post), which has seen some recent revisions (updated DP4, DP4+). I have also posted on the use of computed coupling constants (posts).

Grimblat, Gavín, Daranas and Sarotti have now combined these two approaches, using computed ¹H and ¹³C chemical shifts and ³J_HH coupling constants with the DP4 framework to predict chemical structure.¹

They describe two different approaches to incorporate coupling constants:

• dJ-DP4 (direct method) incorporates the coupling constants into a new probability function, using the coupling constants in an analogous way as chemical shifts. This requires explicit computation of all chemical shifts and ³J_HH coupling constants for all low-energy conformations.
• iJ-DP4 (indirect method) uses the experimental coupling constants to set conformational constraints thereby reducing the number of total conformations that need be sampled. Thus, large values of the coupling constant (³J_HH > 8 Hz) selects conformations with coplanar hydrogens, while small values (³J_HH < 4 Hz) selects conformations with perpendicular hydrogens. Other values are ignored. Typically, only one or two coupling constants are used to select the viable conformations.

The authors test these two variants on 69 molecules. The original DP4 method predicted the correct stereoisomer for 75% of the examples, while dJ-DP4 correct identifies 96% of the cases. As a test of the indirect method, they examined marilzabicycloallenes A and B (1 and 2). DP4 predicts the correct stereoisomer with only 3.1% (1) or <0.1% (2) probability. dJ-DP4 predicts the correct isomer for 1 with 99.9% probability and 97.6% probability for 2. The advantage of iJ-DP4 is that using one coupling constant reduces the number of conformations that must be computed by 84%, yet maintains a probability of getting the correct assignment at 99.2% or better. Using two coupling constants to constrain conformations means that only 7% of all of the conformations need to be samples, and the predictive power is maintained.

1

2

Both of these new methods clearly deserve further application.

References

1. Grimblat, N.; Gavín, J. A.; Hernández Daranas, A.; Sarotti, A. M., “Combining the Power of J Coupling and DP4 Analysis on Stereochemical Assignments: The J-DP4 Methods.” Org. Letters 2019, 21, 4003-4007, DOI: 10.1021/acs.orglett.9b01193.

InChIs

1: InChI=1S/C15H21Br2ClO4/c1-8-15(20)14-6-10(17)12(19)7-11(18)13(22-14)5-9(21-8)3-2-4-16/h3-4,8-15,19-20H,5-7H2,1H3/t2-,8-,9+,10-,11+,12+,13+,14+,15-/m0/s1
InChIKey=APNVVMOUATXTFG-NTSAAJDMSA-N

2: InChI=1S/C15H21Br2ClO4/c1-8-15(20)14-6-10(17)12(19)7-11(18)13(22-14)5-9(21-8)3-2-4-16/h3-4,8-15,19-20H,5-7H2,1H3/t2-,8-,9-,10-,11+,12+,13+,14+,15-/m0/s1
InChIKey=APNVVMOUATXTFG-SSBNIETDSA-N

from Computational Organic Chemistry https://ift.tt/2YbmMYC

I have written quite a number of posts on using quantum mechanics computations to predict NMR spectra that can aid in identifying chemical structure. Perhaps the most robust technique is Goodman’s DP4 method (post), which has seen some recent revisions (updated DP4, DP4+). I have also posted on the use of computed coupling constants (posts).

Grimblat, Gavín, Daranas and Sarotti have now combined these two approaches, using computed ¹H and ¹³C chemical shifts and ³J_HH coupling constants with the DP4 framework to predict chemical structure.¹

They describe two different approaches to incorporate coupling constants:

• dJ-DP4 (direct method) incorporates the coupling constants into a new probability function, using the coupling constants in an analogous way as chemical shifts. This requires explicit computation of all chemical shifts and ³J_HH coupling constants for all low-energy conformations.
• iJ-DP4 (indirect method) uses the experimental coupling constants to set conformational constraints thereby reducing the number of total conformations that need be sampled. Thus, large values of the coupling constant (³J_HH > 8 Hz) selects conformations with coplanar hydrogens, while small values (³J_HH < 4 Hz) selects conformations with perpendicular hydrogens. Other values are ignored. Typically, only one or two coupling constants are used to select the viable conformations.

The authors test these two variants on 69 molecules. The original DP4 method predicted the correct stereoisomer for 75% of the examples, while dJ-DP4 correct identifies 96% of the cases. As a test of the indirect method, they examined marilzabicycloallenes A and B (1 and 2). DP4 predicts the correct stereoisomer with only 3.1% (1) or <0.1% (2) probability. dJ-DP4 predicts the correct isomer for 1 with 99.9% probability and 97.6% probability for 2. The advantage of iJ-DP4 is that using one coupling constant reduces the number of conformations that must be computed by 84%, yet maintains a probability of getting the correct assignment at 99.2% or better. Using two coupling constants to constrain conformations means that only 7% of all of the conformations need to be samples, and the predictive power is maintained.

1

2

Both of these new methods clearly deserve further application.

References

1. Grimblat, N.; Gavín, J. A.; Hernández Daranas, A.; Sarotti, A. M., “Combining the Power of J Coupling and DP4 Analysis on Stereochemical Assignments: The J-DP4 Methods.” Org. Letters 2019, 21, 4003-4007, DOI: 10.1021/acs.orglett.9b01193.

InChIs

1: InChI=1S/C15H21Br2ClO4/c1-8-15(20)14-6-10(17)12(19)7-11(18)13(22-14)5-9(21-8)3-2-4-16/h3-4,8-15,19-20H,5-7H2,1H3/t2-,8-,9+,10-,11+,12+,13+,14+,15-/m0/s1
InChIKey=APNVVMOUATXTFG-NTSAAJDMSA-N

2: InChI=1S/C15H21Br2ClO4/c1-8-15(20)14-6-10(17)12(19)7-11(18)13(22-14)5-9(21-8)3-2-4-16/h3-4,8-15,19-20H,5-7H2,1H3/t2-,8-,9-,10-,11+,12+,13+,14+,15-/m0/s1
InChIKey=APNVVMOUATXTFG-SSBNIETDSA-N

from Computational Organic Chemistry https://ift.tt/2YbmMYC

A small asteroid hit us last weekend

The small, harmless, 4-meter near-Earth asteroid – now designated 2019 MO – created this bright flash when it struck Earth’s atmosphere on June 22, 2019, over the Caribbean. Images via RAMMB/CIRA/Colorado State University.

Scientists have confirmed a meteor impact with Earth’s atmosphere over the Caribbean last weekend. The bright flash was detected by by NOAA’s GOES-16 satellite and other meteorological satellites, showing the event occurred on Saturday, June 22, 2019, at around 5:25 p.m. EDT (21:25 UTC) some 170 miles (274 km) south of Puerto Rico. Astronomer Peter Brown, a meteor expert from Western University in Ontario, Canada, said that an infrasound station located in Bermuda did detect airwaves produced by the space rock’s impact in the atmosphere. The object is believed to have been a small asteroid, and it was unusual in that it was detected prior to its impact – in the hours before – by the Atlas (Asteroid Terrestrial-impact Last Alert System) in Hawaii. Brown said the impact was:

… consistent with 3 to 5 kilotons (of energy).

By contrast, the atomic bomb dropped on Hiroshima on August 6, 1945, exploded with an energy of about 15 kilotons of TNT. Both the energy released, as well as the observations made from the Atlas Observatory, suggest the June 22 space rock was about 13 feet (4 meters) in diameter. Originally designated A10eoM1, the rock has now been designated as asteroid 2019 MO.

Just released MPEC with official designation (2019 MO) for A10eoM1 (that impacted earth's atmosphere around
June 22 21:30 UTC) https://t.co/B9wcLpHaZT & https://t.co/LqrbGzpfJc #asteroids #astronomy cc @pgbrown @Yeqzids @fallingstarIfA @frankie57pr

— Ernesto Guido (@comets77) June 25, 2019

Although small space rocks and fragments rain down on Earth’s atmosphere continuously, experts at NASA’s Center for Near Earth Object Studies say that large events such as the one on June 22 occur about once or twice a year. Earth’s atmosphere does its job in protecting us in these cases, causing drag or friction that disintegrates most of these small objects before they strike the ground (although a few do strike, and more fall into the ocean). Read more: Whoa! 26 atom-bomb-scale asteroid impacts since 2000

Earth got hit a few days ago by newly-discovered asteroid 2019 MO.@pgbrown has more graphics.

Here is a simulation of this event.https://t.co/UySMtOL8B4
An article by Brian Skiffhttps://t.co/fcK1ksvedD pic.twitter.com/WXsxZytpUs

— Tony Dunn (@tony873004) June 25, 2019

After analyzing the satellite images, expert meteor photographer Frankie Lucena commented:

Looks to be a mighty impressive event, for sure.

Some satellite images show the bright flash produced by the meteor, and seconds later, a line of its dissipating smoke trail.

Asteroid 2019 MO is believed to have had an orbit outside that of Earth and extending almost to Jupiter’s orbit. Image via NASA/JPL-Caltech.

According to Italian amateur astronomer Ernesto Guido, this is only the fourth time in history that an impacting object was observed prior to atmospheric entry.

Bottom line: Asteroid 2019 MO exploded in Earth’s atmosphere on June 22, 2019, with an energy equivalent to about 3 to 5 kilotons of TNT. Such events happen unexpectedly, once or twice yearly, astronomers say. This one was unusual in that the asteroid was detected in the hours before it struck.

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

The small, harmless, 4-meter near-Earth asteroid – now designated 2019 MO – created this bright flash when it struck Earth’s atmosphere on June 22, 2019, over the Caribbean. Images via RAMMB/CIRA/Colorado State University.

Scientists have confirmed a meteor impact with Earth’s atmosphere over the Caribbean last weekend. The bright flash was detected by by NOAA’s GOES-16 satellite and other meteorological satellites, showing the event occurred on Saturday, June 22, 2019, at around 5:25 p.m. EDT (21:25 UTC) some 170 miles (274 km) south of Puerto Rico. Astronomer Peter Brown, a meteor expert from Western University in Ontario, Canada, said that an infrasound station located in Bermuda did detect airwaves produced by the space rock’s impact in the atmosphere. The object is believed to have been a small asteroid, and it was unusual in that it was detected prior to its impact – in the hours before – by the Atlas (Asteroid Terrestrial-impact Last Alert System) in Hawaii. Brown said the impact was:

… consistent with 3 to 5 kilotons (of energy).

By contrast, the atomic bomb dropped on Hiroshima on August 6, 1945, exploded with an energy of about 15 kilotons of TNT. Both the energy released, as well as the observations made from the Atlas Observatory, suggest the June 22 space rock was about 13 feet (4 meters) in diameter. Originally designated A10eoM1, the rock has now been designated as asteroid 2019 MO.

Just released MPEC with official designation (2019 MO) for A10eoM1 (that impacted earth's atmosphere around
June 22 21:30 UTC) https://t.co/B9wcLpHaZT & https://t.co/LqrbGzpfJc #asteroids #astronomy cc @pgbrown @Yeqzids @fallingstarIfA @frankie57pr

— Ernesto Guido (@comets77) June 25, 2019

Although small space rocks and fragments rain down on Earth’s atmosphere continuously, experts at NASA’s Center for Near Earth Object Studies say that large events such as the one on June 22 occur about once or twice a year. Earth’s atmosphere does its job in protecting us in these cases, causing drag or friction that disintegrates most of these small objects before they strike the ground (although a few do strike, and more fall into the ocean). Read more: Whoa! 26 atom-bomb-scale asteroid impacts since 2000

Earth got hit a few days ago by newly-discovered asteroid 2019 MO.@pgbrown has more graphics.

Here is a simulation of this event.https://t.co/UySMtOL8B4
An article by Brian Skiffhttps://t.co/fcK1ksvedD pic.twitter.com/WXsxZytpUs

— Tony Dunn (@tony873004) June 25, 2019

After analyzing the satellite images, expert meteor photographer Frankie Lucena commented:

Looks to be a mighty impressive event, for sure.

Some satellite images show the bright flash produced by the meteor, and seconds later, a line of its dissipating smoke trail.

Asteroid 2019 MO is believed to have had an orbit outside that of Earth and extending almost to Jupiter’s orbit. Image via NASA/JPL-Caltech.

According to Italian amateur astronomer Ernesto Guido, this is only the fourth time in history that an impacting object was observed prior to atmospheric entry.

Bottom line: Asteroid 2019 MO exploded in Earth’s atmosphere on June 22, 2019, with an energy equivalent to about 3 to 5 kilotons of TNT. Such events happen unexpectedly, once or twice yearly, astronomers say. This one was unusual in that the asteroid was detected in the hours before it struck.

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