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2019 SkS Weekly Climate Change & Global Warming News Roundup #18

A chronological listing of news articles posted on the Skeptical Science Facebook Page during the past week, i.e., Sun, Apr 28 through Sat, May 4, 2019

Editor's Pick 

Remembering Wallace Broecker, the Prophet of Climate Change

Wallace Broecker 

Dr. Wallace Broecker—lovingly called “Wally” by his coworkers, friends, and family—never wanted to be known as the prophet of climate change. He was the prank-playing, puzzle-loving, New Balance-wearing, colorblind, dented-Toyota-owning, dyslexic, opinionated rock of Columbia University’s Lamont-Doherty Earth Observatory. Broecker saw the big picture.

Broecker was a nationally renowned climate scientist who won the most prestigious awards in his field. He passed away on February 18 at 87 years old. The Washington Post, the New York Times, and other major news sources covered Broecker’s academic achievements, including the fact that he popularized the term “global warming,” but they missed a crucial part of him: the immense influence he had on the lives of others.

Every so often, he would put climate puzzles out in Lamont cafeteria, posing questions like, “Where did all that carbon dioxide go during the ice ages?” He often offered cash rewards to those who could answer them. In his most personalized puzzle, he offered money to whoever could dig up an earlier citation of the term global warming. One of his students succeeded. 

Remembering Wallace Broecker, the Prophet of Climate Change by Katie Santamaria, Columbia Daily Spectator, May 2, 2019 

Links posted on Facebook

Sun Apr 28, 2019

Mon Apr 29, 2019

Tue Apr 30, 2019

Wed May 1, 2019

Thu May 2, 2019

Fri May 3, 2019

Sat May 4, 2019



from Skeptical Science http://bit.ly/2Jo1RgD
A chronological listing of news articles posted on the Skeptical Science Facebook Page during the past week, i.e., Sun, Apr 28 through Sat, May 4, 2019

Editor's Pick 

Remembering Wallace Broecker, the Prophet of Climate Change

Wallace Broecker 

Dr. Wallace Broecker—lovingly called “Wally” by his coworkers, friends, and family—never wanted to be known as the prophet of climate change. He was the prank-playing, puzzle-loving, New Balance-wearing, colorblind, dented-Toyota-owning, dyslexic, opinionated rock of Columbia University’s Lamont-Doherty Earth Observatory. Broecker saw the big picture.

Broecker was a nationally renowned climate scientist who won the most prestigious awards in his field. He passed away on February 18 at 87 years old. The Washington Post, the New York Times, and other major news sources covered Broecker’s academic achievements, including the fact that he popularized the term “global warming,” but they missed a crucial part of him: the immense influence he had on the lives of others.

Every so often, he would put climate puzzles out in Lamont cafeteria, posing questions like, “Where did all that carbon dioxide go during the ice ages?” He often offered cash rewards to those who could answer them. In his most personalized puzzle, he offered money to whoever could dig up an earlier citation of the term global warming. One of his students succeeded. 

Remembering Wallace Broecker, the Prophet of Climate Change by Katie Santamaria, Columbia Daily Spectator, May 2, 2019 

Links posted on Facebook

Sun Apr 28, 2019

Mon Apr 29, 2019

Tue Apr 30, 2019

Wed May 1, 2019

Thu May 2, 2019

Fri May 3, 2019

Sat May 4, 2019



from Skeptical Science http://bit.ly/2Jo1RgD
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Find the radiant point for the Eta Aquariid meteor shower

Eta Aquariid meteors appear to radiate from near a famous asterism – or noticeable star pattern – called the Water Jar in Aquarius.

The annual Eta Aquariid meteor shower peaks this weekend, and people will inevitably ask about its radiant point. That’s point in the sky from which meteors in annual showers appear to radiate.

You don’t have to locate the radiant to watch the Eta Aquariid meteors. Instead, the meteors will appear unexpectedly in all parts of the sky. Yet if you traced their paths backwards, all of these meteors would appear to radiate from a single point in our sky, from a Y-shaped group of stars – an asterism – called the Water Jar in the constellation Aquarius.

The Y-shaped Water Jar marks the radiant of the Eta Aquariid meteor shower. Notice the bright star Fomalhaut. It can guide your eye to much-fainter Aquarius.

Aquarius is faint. You’ll need a dark sky to spot it. The bright star Fomalhaut in the constellation Pisces Austrinus, the Southern Fish, is near it and can guide your eye. On old star charts, the Aquarius the Water Carrier is often pictured pouring water into the open mouth of the Southern Fish, from the Water Jar. In a very dark sky, you can see a zigzag line of star leading downward from the Water Jar to the star Fomalhaut.

Or try star-hopping to the Water Jar from the Great Square of Pegasus (see star chart below). Four medium-bright stars mark the corners of the Square. Looking eastward in the hour or two before sunup in May, the Great Square of Pegasus glitters like a celestial baseball diamond. Imagine the bottom star as home base. Draw a line from the third base star through the first base star, then go twice that distance to locate the star Sadal Melik in Aquarius.

To the lower left of Sadal Melik is the small Y-shaped Water Jar, marking the approximate radiant of the Eta Aquariid meteor shower.

Use the Great Square of Pegasus to star-hop to the radiant of the Eta Aquariid meteor shower.

Bottom line: Eta Aquariid meteors radiate from the Water Jar in the constellation Aquarius. Just remember, you don’t need to know the shower’s radiant point to watch the meteors!



from EarthSky http://bit.ly/2V0hqNl

Eta Aquariid meteors appear to radiate from near a famous asterism – or noticeable star pattern – called the Water Jar in Aquarius.

The annual Eta Aquariid meteor shower peaks this weekend, and people will inevitably ask about its radiant point. That’s point in the sky from which meteors in annual showers appear to radiate.

You don’t have to locate the radiant to watch the Eta Aquariid meteors. Instead, the meteors will appear unexpectedly in all parts of the sky. Yet if you traced their paths backwards, all of these meteors would appear to radiate from a single point in our sky, from a Y-shaped group of stars – an asterism – called the Water Jar in the constellation Aquarius.

The Y-shaped Water Jar marks the radiant of the Eta Aquariid meteor shower. Notice the bright star Fomalhaut. It can guide your eye to much-fainter Aquarius.

Aquarius is faint. You’ll need a dark sky to spot it. The bright star Fomalhaut in the constellation Pisces Austrinus, the Southern Fish, is near it and can guide your eye. On old star charts, the Aquarius the Water Carrier is often pictured pouring water into the open mouth of the Southern Fish, from the Water Jar. In a very dark sky, you can see a zigzag line of star leading downward from the Water Jar to the star Fomalhaut.

Or try star-hopping to the Water Jar from the Great Square of Pegasus (see star chart below). Four medium-bright stars mark the corners of the Square. Looking eastward in the hour or two before sunup in May, the Great Square of Pegasus glitters like a celestial baseball diamond. Imagine the bottom star as home base. Draw a line from the third base star through the first base star, then go twice that distance to locate the star Sadal Melik in Aquarius.

To the lower left of Sadal Melik is the small Y-shaped Water Jar, marking the approximate radiant of the Eta Aquariid meteor shower.

Use the Great Square of Pegasus to star-hop to the radiant of the Eta Aquariid meteor shower.

Bottom line: Eta Aquariid meteors radiate from the Water Jar in the constellation Aquarius. Just remember, you don’t need to know the shower’s radiant point to watch the meteors!



from EarthSky http://bit.ly/2V0hqNl
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Storm cell over Australia

Huge white cloud boiling up. Foreground: brown field and distant horizon.

Image via Lynton Brown.



from EarthSky http://bit.ly/2H11pDh
Huge white cloud boiling up. Foreground: brown field and distant horizon.

Image via Lynton Brown.



from EarthSky http://bit.ly/2H11pDh
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News digest – obesity research, HPV detection in urine, breast cancer treatment test and diet

Cancer radiotherapy

Major study highlights impact of obesity on health

Results from an unpublished study of 2.8 million people, presented at a conference, has shown the scale of obesity challenge in the UK. The BBC reports on the major study, linking a significant increase in death and disease to weight gain. They also cover the measures authorities in Leeds have taken to tackle obesity in local nursey school children.

Gel-filled capsules could aid weight loss

Swallowing gel-filled capsules before a meal may help people feel fuller and avoid overeating, reports the Guardian. According to a small, unpublished study, the capsules taken before a meal canswell up, helping to fill the stomach. Some researchers say they could help some people trying to lose weight through eating a balanced diet and exercising, to stay on track with their healthy lifestyle changes.

Study suggests single dose of radiotherapy could treat some prostate cancers

ITV News covered unpublished results presented at a radiotherapy conference suggesting, in some cases, one session of radiotherapy treatment may be enough to treat certain prostate cancer patients. A high dose of radiation in a single session, using a technique that gets rights into the centre of the tumour, could save patients multiple hospital visits.

Urine test can detect HPV

iNews covered a small trial suggesting a urine test could be as good at detecting the virus that causes virtually all cases of cervical cancer, as current methods. But this study only looked at people who had already had abnormal cell changes detected, so much bigger trials are needed to make sure the urine test works for the general population.

Genetic test could spare some breast cancer patients chemo

A test that analyses the genetic makeup of breast cancers could help predict which patients would benefit from chemo. Our news report and ITV News have the details on the study that suggests the genetic test could spare some women from unnecessary treatment.

Can CRISPR boost cancer treatment?

According to STAT News, US scientists are seeking approval to test the gene-editing tool CRISPR in a trial of people with lung cancer. They want to use these ‘molecular scissors’ to snip out a gene in lung cancer that makes some patients’ tumours resistant to chemo. The theory behind the proposed trial is that disabling this gene could allow standard chemotherapy to work better and longer and give patients more time.

A ‘Google Earth’ for cancer

One of our Grand Challenge scientists, Professor Josephine Bunch, talks to PharmaTimes about what the early stages of their ‘Google Earth’ for cancer has discovered so far. We’ve covered this cancer map before too.

And finally

Sky News reports that women have a lower risk of breast cancer after the menopause if they consume more foods high in phenolic acids, like fruit, veg and wholegrains. But eating lots of these foods usually means people have a healthier lifestyle overall, and so it’s hard to untangle the link between these specific foods and cancer. The take home message? You guessed it: aim for a healthy, balanced diet rather than getting hung up on fad foods.

Gabi



from Cancer Research UK – Science blog http://bit.ly/2LoNhYD
Cancer radiotherapy

Major study highlights impact of obesity on health

Results from an unpublished study of 2.8 million people, presented at a conference, has shown the scale of obesity challenge in the UK. The BBC reports on the major study, linking a significant increase in death and disease to weight gain. They also cover the measures authorities in Leeds have taken to tackle obesity in local nursey school children.

Gel-filled capsules could aid weight loss

Swallowing gel-filled capsules before a meal may help people feel fuller and avoid overeating, reports the Guardian. According to a small, unpublished study, the capsules taken before a meal canswell up, helping to fill the stomach. Some researchers say they could help some people trying to lose weight through eating a balanced diet and exercising, to stay on track with their healthy lifestyle changes.

Study suggests single dose of radiotherapy could treat some prostate cancers

ITV News covered unpublished results presented at a radiotherapy conference suggesting, in some cases, one session of radiotherapy treatment may be enough to treat certain prostate cancer patients. A high dose of radiation in a single session, using a technique that gets rights into the centre of the tumour, could save patients multiple hospital visits.

Urine test can detect HPV

iNews covered a small trial suggesting a urine test could be as good at detecting the virus that causes virtually all cases of cervical cancer, as current methods. But this study only looked at people who had already had abnormal cell changes detected, so much bigger trials are needed to make sure the urine test works for the general population.

Genetic test could spare some breast cancer patients chemo

A test that analyses the genetic makeup of breast cancers could help predict which patients would benefit from chemo. Our news report and ITV News have the details on the study that suggests the genetic test could spare some women from unnecessary treatment.

Can CRISPR boost cancer treatment?

According to STAT News, US scientists are seeking approval to test the gene-editing tool CRISPR in a trial of people with lung cancer. They want to use these ‘molecular scissors’ to snip out a gene in lung cancer that makes some patients’ tumours resistant to chemo. The theory behind the proposed trial is that disabling this gene could allow standard chemotherapy to work better and longer and give patients more time.

A ‘Google Earth’ for cancer

One of our Grand Challenge scientists, Professor Josephine Bunch, talks to PharmaTimes about what the early stages of their ‘Google Earth’ for cancer has discovered so far. We’ve covered this cancer map before too.

And finally

Sky News reports that women have a lower risk of breast cancer after the menopause if they consume more foods high in phenolic acids, like fruit, veg and wholegrains. But eating lots of these foods usually means people have a healthier lifestyle overall, and so it’s hard to untangle the link between these specific foods and cancer. The take home message? You guessed it: aim for a healthy, balanced diet rather than getting hung up on fad foods.

Gabi



from Cancer Research UK – Science blog http://bit.ly/2LoNhYD
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Why more Eta Aquariid meteors in Southern Hemisphere?

Eta Aquarid meteor shower in 2015 from Atacama Desert thanks to our friend Yuri Beletsky! Visit Yuri on Facebook.

Eta Aquarid meteor shower in 2015 from Chile’s Atacama Desert. Composite image by Yuri Beletsky.

The famous Eta Aquariid meteor shower – one of the year’s major meteor showers – peaks every year in early May. In 2019, the peak centers around May 5. This shower is known to be richer as seen from Earth’s Southern Hemisphere than from the Northern Hemisphere. Why?

If you traced the paths of Eta Aquarid meteors backward on the sky’s dome, you’d find that these meteors appear to stream from an asterism, or recognizable pattern of stars, known as the Water Jar in the constellation Aquarius.

This spot in the sky is the radiant point of the Eta Aquarid meteor shower. The meteors seem to emanate from the vicinity of the Water Jar, before spreading out and appearing in all parts of the sky.

The radiant point of the Eta Aquarid meteor shower is near the famous Water Jar asterism of the constellation Aquarius.

The radiant point of the Eta Aquarid meteor shower is near the famous Water Jar asterism of the constellation Aquarius.

Because the Water Jar is on the celestial equator – an imaginary great circle directly above the Earth’s equator – the radiant of the Eta Aquarid shower rises due east as seen from all over the world. Moreover, the radiant rises at about the same time worldwide, around 1:40 a.m. local time (2:40 a.m. Daylight Saving Time) in early May, around the shower’s typical peak date.

So you’d think the shower would be about the same as seen from around the globe.

But it’s not. The reason it’s not is that sunrise comes later to the Southern Hemisphere (where it’s autumn in May) and earlier to the Northern Hemisphere (where it’s spring in May).

Later sunrise means more dark time to watch meteors. And it also means the radiant point of the Eta Aquarid shower has a chance to climb higher into the predawn sky as seen from more southerly latitudes. That’s why the tropics and southern temperate latitudes tend to see more Eta Aquarid meteors than we do at mid-northern latitudes.

Cruise to a southerly latitude, anyone?

Everything you need to know: Eta Aquarid meteor shower

Eta Aquarius in 2013 by Colin Legg

Eta Aquarids in 2013 by Colin Legg in Australia.

Bottom line: Everyone around the globe can enjoy the Eta Aquariid meteor shower in early May. Best for the Southern Hemisphere! Peak in 2019 is on or near the morning of May 5.

Read more: EarthSky’s annual meteor shower guide



from EarthSky http://bit.ly/2ZWmJkD
Eta Aquarid meteor shower in 2015 from Atacama Desert thanks to our friend Yuri Beletsky! Visit Yuri on Facebook.

Eta Aquarid meteor shower in 2015 from Chile’s Atacama Desert. Composite image by Yuri Beletsky.

The famous Eta Aquariid meteor shower – one of the year’s major meteor showers – peaks every year in early May. In 2019, the peak centers around May 5. This shower is known to be richer as seen from Earth’s Southern Hemisphere than from the Northern Hemisphere. Why?

If you traced the paths of Eta Aquarid meteors backward on the sky’s dome, you’d find that these meteors appear to stream from an asterism, or recognizable pattern of stars, known as the Water Jar in the constellation Aquarius.

This spot in the sky is the radiant point of the Eta Aquarid meteor shower. The meteors seem to emanate from the vicinity of the Water Jar, before spreading out and appearing in all parts of the sky.

The radiant point of the Eta Aquarid meteor shower is near the famous Water Jar asterism of the constellation Aquarius.

The radiant point of the Eta Aquarid meteor shower is near the famous Water Jar asterism of the constellation Aquarius.

Because the Water Jar is on the celestial equator – an imaginary great circle directly above the Earth’s equator – the radiant of the Eta Aquarid shower rises due east as seen from all over the world. Moreover, the radiant rises at about the same time worldwide, around 1:40 a.m. local time (2:40 a.m. Daylight Saving Time) in early May, around the shower’s typical peak date.

So you’d think the shower would be about the same as seen from around the globe.

But it’s not. The reason it’s not is that sunrise comes later to the Southern Hemisphere (where it’s autumn in May) and earlier to the Northern Hemisphere (where it’s spring in May).

Later sunrise means more dark time to watch meteors. And it also means the radiant point of the Eta Aquarid shower has a chance to climb higher into the predawn sky as seen from more southerly latitudes. That’s why the tropics and southern temperate latitudes tend to see more Eta Aquarid meteors than we do at mid-northern latitudes.

Cruise to a southerly latitude, anyone?

Everything you need to know: Eta Aquarid meteor shower

Eta Aquarius in 2013 by Colin Legg

Eta Aquarids in 2013 by Colin Legg in Australia.

Bottom line: Everyone around the globe can enjoy the Eta Aquariid meteor shower in early May. Best for the Southern Hemisphere! Peak in 2019 is on or near the morning of May 5.

Read more: EarthSky’s annual meteor shower guide



from EarthSky http://bit.ly/2ZWmJkD
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Comet Halley’s 2 meteor showers

Map showing Comet Halley's place in solar system for May 5, 2019

Comet Halley’s position in May 2019. The view is from the north side of the solar system. Although the planets orbit our sun in a counterclockwise direction, Comet Halley orbits clockwise. Click here for Comet Halley’s present position, or change the date to view its position in any chosen year

Halley’s Comet, proud parent of two meteor showers, swings into the inner solar system about every 76 years. At such times, the sun’s heat causes the comet to loosen its icy grip over its mountain-sized conglomeration of ice, dust and gas. At each pass near the sun, the crumbly comet sheds a fresh trail of debris into its orbital stream. It lost about 1/1,000th of its mass during its last flyby in 1986. It’s because comets like Halley are so crumbly that we see annual meteor showers, like the Eta Aquariid meteor shower that’s going on now.

Keep reading to learn more about Comet Halley, the meteor showers it spawns, and about how astronomers calculate the velocities of meteors streaking across our sky.

Comet Halley on May 29, 1910 from Wikimedia Commons

Comet Halley on May 29, 1910 via Wikimedia Commons.

Kuiper Airborne Observatory acquired this image of Comet Halley in April 1986, as the comet crossed in front of the Milky Way. Image via NASA.

Comet Halley’s 2 meteor showers. Because Comet Halley has circled the sun innumerable times over countless millennia, cometary fragments litter its orbit. That’s why the comet doesn’t need to be anywhere near the Earth or the sun in order to produce a meteor shower. Instead, whenever our Earth in its orbit intersects Comet Halley’s orbit, cometary bits and pieces – oftentimes no larger than grains of sand or granules of gravel – smash into Earth’s upper atmosphere, to vaporize as fiery streaks across our sky: meteors.

It so happens we intersect Comet Halley’s orbit not once, but twice each year. In early May, we see bits of this comet as the annual Eta Aquariid meteor shower.

Then some six months later, in October, Earth in its orbit again intersects the orbital path of Comet Halley. This time around, these broken-up chunks from Halley’s Comet burn up in Earth’s atmosphere as the annual Orionid meteor shower.

By the way, these small fragments are called meteoroids when in outer space, and meteors when they vaporize in the Earth’s atmosphere.

Meteors in annual showers – made from the icy debris of comets – don’t hit the ground. They vaporize high in Earth’s atmosphere. The more rocky or metallic asteroids are what sometimes hit the ground, and then they are called meteorites.

Eta Aquariid meteors appear to radiate from near a famous asterism - or noticeable star pattern - called the Water Jar in Aquarius.

Eta Aquariid meteors appear to radiate from near a famous asterism – or noticeable star pattern – called the Water Jar in Aquarius. The shower is coming up on the mornings of May 5 and 6, 2018.

Where is Comet Halley now? Often, astronomers like to give distances of solar system objects in terms of astronomical units (AU), which is the sun-Earth distance. Comet Halley lodges 0.587 AU from the sun at its closest point to the sun (perihelion) and 35.3 AU at its farthest point (aphelion).

In other words, Halley’s Comet resides about 60 times farther from the sun at its closest than it does at its farthest.

It was last at perihelion in 1986, and will again return to perihelion in 2061.

At present, Comet Halley lies outside the orbit of Neptune, and not far from its aphelion point. See the image at the top of this post – for May, 2017 – via Fourmilab.

Even so, meteroids swim throughout Comet Halley’s orbital stream, so each time Earth crosses the orbit of Halley’s Comet, in May and October, these meteoroids turn into incandescent meteors once they plunge into the Earth’s upper atmosphere.

Sideways view shows that the orbit of Halley's Comet is highly inclined to the plane of the ecliptic. Green color depicts the part of orbit to the south of the ecliptic while the blue highlights the part of the orbit to the north of the ecliptic.

Sideways view shows that the orbit of Halley’s Comet is highly inclined to the plane of the ecliptic. Green color depicts the part of orbit to the south of the ecliptic (Earth-sun orbital plane) while the blue highlights the part of the orbit to the north of the ecliptic.

Of course, Comet Halley isn’t the only comet that produces a major meteor shower …

Parent bodies of other major meteor showers

Meteor Shower Parent Body Semi-major axis Orbital Period Perihelion Aphelion
Quadrantids 2003 EH1 (asteroid) 3.12 AU 5.52 years 1.19 AU 5.06 AU
Lyrids Comet Thatcher 55.68 AU 415 years 0.92 AU 110 AU
Eta Aquariids Comet 1/P Halley 17.8 AU 75.3 years 0.59 AU 35.3 AU
Delta Aquariids Comet 96P/Machholz 3.03 AU 5.28 years 0.12 AU 5.94 AU
Perseids Comet 109P/Swift-Tuttle 26.09 AU 133 years 0.96 AU 51.23 AU
Draconids Comet 21P/Giacobini–Zinner 3.52 AU 6.62 years 1.04 AU 6.01 AU
Orionids Comet 1/P Halley 17.8 AU 75.3 years 0.59 AU 35.3 AU
Taurids Comet 2P/Encke 2.22 AU 3.30 years 0.33 AU 4.11 AU
Leonids Comet 55P/Tempel-Tuttle 10.33 AU 33.22 years 0.98 AU 19.69 AU
Geminids 3200 Phaethon (asteroid) 1.27 AU 1.43 years 0.14 AU 2.40 AU

How fast do meteors from Comet Halley travel? If we can figure how fast Comet Halley travels at the Earth’s distance from the sun, we should also be able to figure out how fast these meteors fly in our sky.

Some of you may know that a solar system body, such as a planet or comet, goes faster in its orbit as it nears the sun and more slowly in its orbit as it gets farther away. Halley’s Comet swings inside the orbit of Venus at perihelion – the comet’s nearest point to the sun. At aphelion – its most distant point – Halley’s Comet goes all the way beyond the orbit of Neptune, the solar system’s outermost (known) planet.

Diagram via SurveyMonkey. We're looking down upon the north side of the solar system plane, whereby the planets revolve around the sun counterclockwise and Halley's Comet revolves around the sun clockwise.

Diagram via SurveyMonkey. We’re looking down upon the north side of the solar system plane. The planets revolve around the sun counterclockwise, and Halley’s Comet revolves around the sun clockwise.

When the meteoroids from the orbital stream of Halley’s Comet streak across the sky as Eta Aquariid or Orionid meteors, we know these meteoroids/meteors have to be one astronomical unit (Earth’s distance) from the sun. It might be tempting to assume that these meteoroids at one astronomical unit from the sun travel through space at the same speed Earth does: 67,000 miles per hour (108,000 km/h).

However, the velocity of these meteoroids through space does not equal that of Earth at the Earth’s distance from the sun. For that to happen, Earth and Halley’s Comet would have to orbit the sun in the same period of time. But the orbital periods of Earth and Comet Halley are vastly different. Earth takes one year to orbit the sun whereas Halley’s Comet takes about 76 years.

However, thanks to the great genius, Isaac Newton, we can compute the velocity of these meteoroids/meteors at the Earth’s distance from the sun by using Newton’s Vis-viva equation, his poetic rendition of instantaneous motion.

The answer, giving the velocity of these meteoroids through space at the Earth’s distance from the sun, is virtually at our fingertips. All we need to know is Comet Halley’s semi-major axis (mean distance from the sun) in astronomical units. Here you have it:

Comet Halley’s semi-major axis = 17.8 astronomical units.

Once we know is a comet's semi-major axis in astronomical units, we can compute its velocity at any distance from the sun with the easy-to-use Vis-viva equation. The sun resides at one of the two foci of the comet's elliptical orbit.

Once we know is a comet’s semi-major axis in astronomical units, we can compute its velocity at any distance from the sun with the easy-to-use Vis-viva equation. The sun resides at one of the two foci of the comet’s elliptical orbit.

In the easy-to-use Vis-viva equation below, r = distance from sun in astronomical units, and a = semi-major axis of Comet Halley’s orbit in astronomical units. In other words, r = 1 AU and a = 17.8 AU.

Vis-viva equation (r = distance from sun = 1 AU; and a = semi-major axis = 17.8 AU):

Velocity = 67,000 x the square root of (2/r – 1/a)
Velocity = 67,000 x the square root of (2/1 – 1/17.8)
Velocity = 67,000 x the square root of (2 – 0.056)
Velocity = 67,000 x the square root of 1.944
Velocity = 67,000 x 1.39
Velocity = 93,130 miles per hour or 25.87 miles per second

The above answer gives the velocity of these meteoroids through space at the Earth’s distance from the sun. However, if these meteoroids were to hit Earth’s atmosphere head-on, that would push the velocity up to an incredible 160,130 miles per hour (257,704 km/h) because 93,130 + 67,000 = 160,130. NASA gives the velocity for the Eta Aquariid meteors and Orionid meteors at 148,000 miles per hour (238,000 km/h), which suggests the collision of these meteoroids/meteors with Earth is not all that far from head-on.

We can also use the Vis-viva equation to find out the velocity of Halley’s Comet (or its meteoroids) at the perihelion distance of 0.59 AU and aphelion distance of 35.3 AU.

Perihelion velocity = 122,331 miles per hour (200,000 km/h)

Aphelion velocity = 1,464 miles per hour (2,400 km/h)

Comets develop gas and dust tails as they approach the sun. Depending on the comet, the comet can orbit the sun counter-clockwise (as above) or clockwise (as Comet Halley does). Read more: Why do comets develop tails?

Comets develop gas and dust tails as they approach the sun. Depending on the comet, the comet can orbit the sun counter-clockwise (as above) or clockwise (as Comet Halley does). Read more: Why do comets develop tails?

Bottom line: The famous Comet Halley spawns the Eta Aquariids – going on now – and the Orionids in October. Plus where the comet is now, parent bodies of other meteor showers … and Isaac Newton’s Vis-viva equation, his poetic rendition of instantaneous motion.



from EarthSky http://bit.ly/2GV5VSr
Map showing Comet Halley's place in solar system for May 5, 2019

Comet Halley’s position in May 2019. The view is from the north side of the solar system. Although the planets orbit our sun in a counterclockwise direction, Comet Halley orbits clockwise. Click here for Comet Halley’s present position, or change the date to view its position in any chosen year

Halley’s Comet, proud parent of two meteor showers, swings into the inner solar system about every 76 years. At such times, the sun’s heat causes the comet to loosen its icy grip over its mountain-sized conglomeration of ice, dust and gas. At each pass near the sun, the crumbly comet sheds a fresh trail of debris into its orbital stream. It lost about 1/1,000th of its mass during its last flyby in 1986. It’s because comets like Halley are so crumbly that we see annual meteor showers, like the Eta Aquariid meteor shower that’s going on now.

Keep reading to learn more about Comet Halley, the meteor showers it spawns, and about how astronomers calculate the velocities of meteors streaking across our sky.

Comet Halley on May 29, 1910 from Wikimedia Commons

Comet Halley on May 29, 1910 via Wikimedia Commons.

Kuiper Airborne Observatory acquired this image of Comet Halley in April 1986, as the comet crossed in front of the Milky Way. Image via NASA.

Comet Halley’s 2 meteor showers. Because Comet Halley has circled the sun innumerable times over countless millennia, cometary fragments litter its orbit. That’s why the comet doesn’t need to be anywhere near the Earth or the sun in order to produce a meteor shower. Instead, whenever our Earth in its orbit intersects Comet Halley’s orbit, cometary bits and pieces – oftentimes no larger than grains of sand or granules of gravel – smash into Earth’s upper atmosphere, to vaporize as fiery streaks across our sky: meteors.

It so happens we intersect Comet Halley’s orbit not once, but twice each year. In early May, we see bits of this comet as the annual Eta Aquariid meteor shower.

Then some six months later, in October, Earth in its orbit again intersects the orbital path of Comet Halley. This time around, these broken-up chunks from Halley’s Comet burn up in Earth’s atmosphere as the annual Orionid meteor shower.

By the way, these small fragments are called meteoroids when in outer space, and meteors when they vaporize in the Earth’s atmosphere.

Meteors in annual showers – made from the icy debris of comets – don’t hit the ground. They vaporize high in Earth’s atmosphere. The more rocky or metallic asteroids are what sometimes hit the ground, and then they are called meteorites.

Eta Aquariid meteors appear to radiate from near a famous asterism - or noticeable star pattern - called the Water Jar in Aquarius.

Eta Aquariid meteors appear to radiate from near a famous asterism – or noticeable star pattern – called the Water Jar in Aquarius. The shower is coming up on the mornings of May 5 and 6, 2018.

Where is Comet Halley now? Often, astronomers like to give distances of solar system objects in terms of astronomical units (AU), which is the sun-Earth distance. Comet Halley lodges 0.587 AU from the sun at its closest point to the sun (perihelion) and 35.3 AU at its farthest point (aphelion).

In other words, Halley’s Comet resides about 60 times farther from the sun at its closest than it does at its farthest.

It was last at perihelion in 1986, and will again return to perihelion in 2061.

At present, Comet Halley lies outside the orbit of Neptune, and not far from its aphelion point. See the image at the top of this post – for May, 2017 – via Fourmilab.

Even so, meteroids swim throughout Comet Halley’s orbital stream, so each time Earth crosses the orbit of Halley’s Comet, in May and October, these meteoroids turn into incandescent meteors once they plunge into the Earth’s upper atmosphere.

Sideways view shows that the orbit of Halley's Comet is highly inclined to the plane of the ecliptic. Green color depicts the part of orbit to the south of the ecliptic while the blue highlights the part of the orbit to the north of the ecliptic.

Sideways view shows that the orbit of Halley’s Comet is highly inclined to the plane of the ecliptic. Green color depicts the part of orbit to the south of the ecliptic (Earth-sun orbital plane) while the blue highlights the part of the orbit to the north of the ecliptic.

Of course, Comet Halley isn’t the only comet that produces a major meteor shower …

Parent bodies of other major meteor showers

Meteor Shower Parent Body Semi-major axis Orbital Period Perihelion Aphelion
Quadrantids 2003 EH1 (asteroid) 3.12 AU 5.52 years 1.19 AU 5.06 AU
Lyrids Comet Thatcher 55.68 AU 415 years 0.92 AU 110 AU
Eta Aquariids Comet 1/P Halley 17.8 AU 75.3 years 0.59 AU 35.3 AU
Delta Aquariids Comet 96P/Machholz 3.03 AU 5.28 years 0.12 AU 5.94 AU
Perseids Comet 109P/Swift-Tuttle 26.09 AU 133 years 0.96 AU 51.23 AU
Draconids Comet 21P/Giacobini–Zinner 3.52 AU 6.62 years 1.04 AU 6.01 AU
Orionids Comet 1/P Halley 17.8 AU 75.3 years 0.59 AU 35.3 AU
Taurids Comet 2P/Encke 2.22 AU 3.30 years 0.33 AU 4.11 AU
Leonids Comet 55P/Tempel-Tuttle 10.33 AU 33.22 years 0.98 AU 19.69 AU
Geminids 3200 Phaethon (asteroid) 1.27 AU 1.43 years 0.14 AU 2.40 AU

How fast do meteors from Comet Halley travel? If we can figure how fast Comet Halley travels at the Earth’s distance from the sun, we should also be able to figure out how fast these meteors fly in our sky.

Some of you may know that a solar system body, such as a planet or comet, goes faster in its orbit as it nears the sun and more slowly in its orbit as it gets farther away. Halley’s Comet swings inside the orbit of Venus at perihelion – the comet’s nearest point to the sun. At aphelion – its most distant point – Halley’s Comet goes all the way beyond the orbit of Neptune, the solar system’s outermost (known) planet.

Diagram via SurveyMonkey. We're looking down upon the north side of the solar system plane, whereby the planets revolve around the sun counterclockwise and Halley's Comet revolves around the sun clockwise.

Diagram via SurveyMonkey. We’re looking down upon the north side of the solar system plane. The planets revolve around the sun counterclockwise, and Halley’s Comet revolves around the sun clockwise.

When the meteoroids from the orbital stream of Halley’s Comet streak across the sky as Eta Aquariid or Orionid meteors, we know these meteoroids/meteors have to be one astronomical unit (Earth’s distance) from the sun. It might be tempting to assume that these meteoroids at one astronomical unit from the sun travel through space at the same speed Earth does: 67,000 miles per hour (108,000 km/h).

However, the velocity of these meteoroids through space does not equal that of Earth at the Earth’s distance from the sun. For that to happen, Earth and Halley’s Comet would have to orbit the sun in the same period of time. But the orbital periods of Earth and Comet Halley are vastly different. Earth takes one year to orbit the sun whereas Halley’s Comet takes about 76 years.

However, thanks to the great genius, Isaac Newton, we can compute the velocity of these meteoroids/meteors at the Earth’s distance from the sun by using Newton’s Vis-viva equation, his poetic rendition of instantaneous motion.

The answer, giving the velocity of these meteoroids through space at the Earth’s distance from the sun, is virtually at our fingertips. All we need to know is Comet Halley’s semi-major axis (mean distance from the sun) in astronomical units. Here you have it:

Comet Halley’s semi-major axis = 17.8 astronomical units.

Once we know is a comet's semi-major axis in astronomical units, we can compute its velocity at any distance from the sun with the easy-to-use Vis-viva equation. The sun resides at one of the two foci of the comet's elliptical orbit.

Once we know is a comet’s semi-major axis in astronomical units, we can compute its velocity at any distance from the sun with the easy-to-use Vis-viva equation. The sun resides at one of the two foci of the comet’s elliptical orbit.

In the easy-to-use Vis-viva equation below, r = distance from sun in astronomical units, and a = semi-major axis of Comet Halley’s orbit in astronomical units. In other words, r = 1 AU and a = 17.8 AU.

Vis-viva equation (r = distance from sun = 1 AU; and a = semi-major axis = 17.8 AU):

Velocity = 67,000 x the square root of (2/r – 1/a)
Velocity = 67,000 x the square root of (2/1 – 1/17.8)
Velocity = 67,000 x the square root of (2 – 0.056)
Velocity = 67,000 x the square root of 1.944
Velocity = 67,000 x 1.39
Velocity = 93,130 miles per hour or 25.87 miles per second

The above answer gives the velocity of these meteoroids through space at the Earth’s distance from the sun. However, if these meteoroids were to hit Earth’s atmosphere head-on, that would push the velocity up to an incredible 160,130 miles per hour (257,704 km/h) because 93,130 + 67,000 = 160,130. NASA gives the velocity for the Eta Aquariid meteors and Orionid meteors at 148,000 miles per hour (238,000 km/h), which suggests the collision of these meteoroids/meteors with Earth is not all that far from head-on.

We can also use the Vis-viva equation to find out the velocity of Halley’s Comet (or its meteoroids) at the perihelion distance of 0.59 AU and aphelion distance of 35.3 AU.

Perihelion velocity = 122,331 miles per hour (200,000 km/h)

Aphelion velocity = 1,464 miles per hour (2,400 km/h)

Comets develop gas and dust tails as they approach the sun. Depending on the comet, the comet can orbit the sun counter-clockwise (as above) or clockwise (as Comet Halley does). Read more: Why do comets develop tails?

Comets develop gas and dust tails as they approach the sun. Depending on the comet, the comet can orbit the sun counter-clockwise (as above) or clockwise (as Comet Halley does). Read more: Why do comets develop tails?

Bottom line: The famous Comet Halley spawns the Eta Aquariids – going on now – and the Orionids in October. Plus where the comet is now, parent bodies of other meteor showers … and Isaac Newton’s Vis-viva equation, his poetic rendition of instantaneous motion.



from EarthSky http://bit.ly/2GV5VSr
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When does Ramadan begin in 2019?

Crescent moon viewed beside minaret tower of a mosque against deep twilight sky.

Traditionally, the first sighting of a young moon marks the beginning of Ramadan. Image via Emirates 24/7.

The Islamic holy month of Ramadan falls at a different time each year because the Islamic calendar is a lunar calendar, based on the moon’s natural cycles. That’s why there isn’t a fixed date for Ramadan, which is the ninth month in this calendar, traditionally determined by an actual sighting of a crescent moon by the UAE’s moon-sighting committee. May 4, 2019, is the date of new moon, that is, a moon most directly between the Earth and sun for this month. New moon comes at 22:45 UTC on May 4; translate UTC to your time. That exact time of new moon makes the coming young moon sighting for the Middle East relatively clear; a young moon will be visible through telescopes and binoculars on May 5. Therefore, 2019’s Ramadan will most likely begin on May 6.

Will anyone on Earth be able to see the moon on May 5 with the eye alone? Yes. Possibly. But not from Europe or the Middle East, and likely not from the eastern half of North America. The chances are best for those for those living at longitudes farther and farther west in North or Central America, or on islands in the Pacific. The farther west you are on May 5, the more time will have passed on your clock since the instant of new moon. Thus, because the moon orbits Earth continuously, the moon will have had more time to move away from our line of sight to the sun, on the sky’s dome.

In other words, the farther west you are, the longer after sunset the moon will set and the darker your sky will be. For those reasons, the farther west you are on May 5, the more likely it is you’ll be able to see a young crescent in the western twilight sky after sunset with the eye alone.

Very thin crescent moon in orange twilight over sea and hill.

Jv Noriega caught a very young moon in March 2014, over the West Philippine Sea. Notice it’s set against a background of bright twilight.

Let’s consider the youngest moon that can be seen with the eye alone. By youngest I mean closest to new moon.

A longstanding, though somewhat doubtful, record for youngest moon seen with the eye was held by two British housemaids, said to have seen the moon 14 3/4 hours after new moon, in the year 1916. That story has been around for over 100 years. Is it true? Who knows?

A more reliable record was achieved by well-known writer, photographer, and naturalist Stephen James O’Meara in May 1990. He saw a young crescent with the unaided eye 15 hours and 32 minutes after new moon. Stephen had amazing eyesight when he was younger; he saw a number of noteworthy astronomical sights. Click here to read more about the youngest moons it’s possible to see.

I haven’t heard of anyone besting Stephen’s record, so let’s assume 15 hours and 32 minutes is the record for the youngest moon.

Will it be possible to see a young moon after sunset on May 5 from the Middle East? With the eye alone, probably not, but with optical aid, maybe. Let’s use Dubai in the United Arab Emirates (UAE) as an example. Dubai is four hours ahead of UTC. New moon is 22:45 UTC on May 4; so the new moon comes at 02:45 a.m. on May 5 in Dubai. At sunset that evening (6:51 p.m.), as seen from Dubai, the moon will be about 18 hours old. I’ve seen an 18-hour-old moon with the eye alone – once, in all my 40-plus years of stargazing – under extremely pristine conditions, from the catwalk of a major astronomical observatory. It was very ghostly and hard to see! But I did see it without optical aid. It can be done, and springtime is the best time of year to do it (because, in spring, young moons are more directly above the sunset, instead of to one side of it).

The best place to attempt to catch sight of the young moon on May 5 with the unaided eye will be an island in the Pacific Ocean. Honolulu, Hawaii, for example, is 10 hours behind UTC. So new moon happens on May 4 at 12:45 p.m. for Honolulu. The next day, May 5, the sun sets at 6:58 p.m. On that evening, after sunset, the moon will be about 30 hours old and fairly easily visible.

As you go west from Hawaii to the International Date Line, the potential for a young moon sighting on May 5 continues to get better. It gets better still when you cross the International Date Line, into, say, Asia. From much of Asia on May 6, the young moon will be possible to see.

And – as Earth spins under the sky, and the moon moves in orbit, putting distance between itself and our line of sight to the sun – the moon will get easier and easier to see. It should be possible to see the moon from India or the Middle East on May 6, assuming you have excellent sky conditions.

Very thin crescent moon against black sky.

This young moon – June 2016 – marked a beginning of Ramadan. Abdulmajeed Alshatti took this photo from Kuwait.

Ramadan, for observant Muslims, is a time of fasting, prayer and charitable giving. Here is a beautiful poem about Ramadan, by Rumi, a 13th-century Persian poet and mystic:

O moon-faced Beloved,
the month of Ramadan has arrived
Cover the table
and open the path of praise.
O fickle busybody,
it’s time to change your ways.
Can you see the one who’s selling the halvah
how long will it be the halvah you desire?
Just a glimpse of the halvah-maker
has made you so sweet even honey says,
“I’ll put myself beneath your feet, like soil;
I’ll worship at your shrine.”
Your chick frets within the egg
with all your eating and choking.
Break out of your shell that your wings may grow.
Let yourself fly.
The lips of the Master are parched
from calling the Beloved.
The sound of your call resounds
through the horn of your empty belly.
Let nothing be inside of you.
Be empty: give your lips to the lips of the reed.
When like a reed you fill with His breath,
then you’ll taste sweetness.
Sweetness is hidden in the Breath
that fills the reed.
– Rumi

Perspective view with multi-domed mosque in background and long lines of men kneeling.

Men praying during Ramadan – a time of fasting, prayer and charitable giving – at the Blue Mosque in Mazar-i-Sharif, Afghanistan.

Bottom line: The Islamic holy month begins with the sighting of a young crescent moon. New moon is May 4, 2019. The young crescent moon in the west after sunset should be possible to see with binoculars and telescopes on May 5, although those in far-western North America and islands in the Pacific might see the May 5 moon with the eye alone. The young crescent moon in the west after sunset should become visible to the eye alone for all of us on Earth (assuming clear skies) on May 6.



from EarthSky http://bit.ly/2IXfDr6
Crescent moon viewed beside minaret tower of a mosque against deep twilight sky.

Traditionally, the first sighting of a young moon marks the beginning of Ramadan. Image via Emirates 24/7.

The Islamic holy month of Ramadan falls at a different time each year because the Islamic calendar is a lunar calendar, based on the moon’s natural cycles. That’s why there isn’t a fixed date for Ramadan, which is the ninth month in this calendar, traditionally determined by an actual sighting of a crescent moon by the UAE’s moon-sighting committee. May 4, 2019, is the date of new moon, that is, a moon most directly between the Earth and sun for this month. New moon comes at 22:45 UTC on May 4; translate UTC to your time. That exact time of new moon makes the coming young moon sighting for the Middle East relatively clear; a young moon will be visible through telescopes and binoculars on May 5. Therefore, 2019’s Ramadan will most likely begin on May 6.

Will anyone on Earth be able to see the moon on May 5 with the eye alone? Yes. Possibly. But not from Europe or the Middle East, and likely not from the eastern half of North America. The chances are best for those for those living at longitudes farther and farther west in North or Central America, or on islands in the Pacific. The farther west you are on May 5, the more time will have passed on your clock since the instant of new moon. Thus, because the moon orbits Earth continuously, the moon will have had more time to move away from our line of sight to the sun, on the sky’s dome.

In other words, the farther west you are, the longer after sunset the moon will set and the darker your sky will be. For those reasons, the farther west you are on May 5, the more likely it is you’ll be able to see a young crescent in the western twilight sky after sunset with the eye alone.

Very thin crescent moon in orange twilight over sea and hill.

Jv Noriega caught a very young moon in March 2014, over the West Philippine Sea. Notice it’s set against a background of bright twilight.

Let’s consider the youngest moon that can be seen with the eye alone. By youngest I mean closest to new moon.

A longstanding, though somewhat doubtful, record for youngest moon seen with the eye was held by two British housemaids, said to have seen the moon 14 3/4 hours after new moon, in the year 1916. That story has been around for over 100 years. Is it true? Who knows?

A more reliable record was achieved by well-known writer, photographer, and naturalist Stephen James O’Meara in May 1990. He saw a young crescent with the unaided eye 15 hours and 32 minutes after new moon. Stephen had amazing eyesight when he was younger; he saw a number of noteworthy astronomical sights. Click here to read more about the youngest moons it’s possible to see.

I haven’t heard of anyone besting Stephen’s record, so let’s assume 15 hours and 32 minutes is the record for the youngest moon.

Will it be possible to see a young moon after sunset on May 5 from the Middle East? With the eye alone, probably not, but with optical aid, maybe. Let’s use Dubai in the United Arab Emirates (UAE) as an example. Dubai is four hours ahead of UTC. New moon is 22:45 UTC on May 4; so the new moon comes at 02:45 a.m. on May 5 in Dubai. At sunset that evening (6:51 p.m.), as seen from Dubai, the moon will be about 18 hours old. I’ve seen an 18-hour-old moon with the eye alone – once, in all my 40-plus years of stargazing – under extremely pristine conditions, from the catwalk of a major astronomical observatory. It was very ghostly and hard to see! But I did see it without optical aid. It can be done, and springtime is the best time of year to do it (because, in spring, young moons are more directly above the sunset, instead of to one side of it).

The best place to attempt to catch sight of the young moon on May 5 with the unaided eye will be an island in the Pacific Ocean. Honolulu, Hawaii, for example, is 10 hours behind UTC. So new moon happens on May 4 at 12:45 p.m. for Honolulu. The next day, May 5, the sun sets at 6:58 p.m. On that evening, after sunset, the moon will be about 30 hours old and fairly easily visible.

As you go west from Hawaii to the International Date Line, the potential for a young moon sighting on May 5 continues to get better. It gets better still when you cross the International Date Line, into, say, Asia. From much of Asia on May 6, the young moon will be possible to see.

And – as Earth spins under the sky, and the moon moves in orbit, putting distance between itself and our line of sight to the sun – the moon will get easier and easier to see. It should be possible to see the moon from India or the Middle East on May 6, assuming you have excellent sky conditions.

Very thin crescent moon against black sky.

This young moon – June 2016 – marked a beginning of Ramadan. Abdulmajeed Alshatti took this photo from Kuwait.

Ramadan, for observant Muslims, is a time of fasting, prayer and charitable giving. Here is a beautiful poem about Ramadan, by Rumi, a 13th-century Persian poet and mystic:

O moon-faced Beloved,
the month of Ramadan has arrived
Cover the table
and open the path of praise.
O fickle busybody,
it’s time to change your ways.
Can you see the one who’s selling the halvah
how long will it be the halvah you desire?
Just a glimpse of the halvah-maker
has made you so sweet even honey says,
“I’ll put myself beneath your feet, like soil;
I’ll worship at your shrine.”
Your chick frets within the egg
with all your eating and choking.
Break out of your shell that your wings may grow.
Let yourself fly.
The lips of the Master are parched
from calling the Beloved.
The sound of your call resounds
through the horn of your empty belly.
Let nothing be inside of you.
Be empty: give your lips to the lips of the reed.
When like a reed you fill with His breath,
then you’ll taste sweetness.
Sweetness is hidden in the Breath
that fills the reed.
– Rumi

Perspective view with multi-domed mosque in background and long lines of men kneeling.

Men praying during Ramadan – a time of fasting, prayer and charitable giving – at the Blue Mosque in Mazar-i-Sharif, Afghanistan.

Bottom line: The Islamic holy month begins with the sighting of a young crescent moon. New moon is May 4, 2019. The young crescent moon in the west after sunset should be possible to see with binoculars and telescopes on May 5, although those in far-western North America and islands in the Pacific might see the May 5 moon with the eye alone. The young crescent moon in the west after sunset should become visible to the eye alone for all of us on Earth (assuming clear skies) on May 6.



from EarthSky http://bit.ly/2IXfDr6
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