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A Dragon and a former pole star

Tonight, if you have a dark sky, you’ll be able to pick out the constellation Draco the Dragon winding around the North Star, Polaris. The image at the top of this post shows Draco as depicted in an old star atlas by Johannes Hevelius in 1690. See the circle? That circle indicates the changing position of the north celestial pole over a cycle of 26,000 years.

Circle around north, with locations marked for 0 BC, 9000 BC, 2000 AD, and 8000 AD.

The 26,000-year precession cycle causes the north celestial pole to move counter-clockwise relative to the backdrop stars. Whichever star is closest to the north celestial pole is the Pole Star. Thuban reigned as the North Star some 5,000 years ago.

How can you see the Dragon? The Big Dipper can help guide you. Just remember … the entire Dragon requires a dark sky to be seen. You’ll find the Big Dipper high in the north on June evenings. The two outer stars in the Dipper’s bowl point to Polaris, the North Star, which marks the end of the Little Dipper’s handle.

The Dragon winds between the Big and Little Dippers, as shown on the chart below:

Diagram with Big and Little Dippers and constellation Draco winding between them.

If you can find the Big and Little Dippers, you can find the constellation Draco the Dragon.

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The Little Dipper is relatively faint. If you can find both Dippers, then your sky is probably pretty dark. And you’ll need that dark sky to see Draco. You’ll have to let your eyes and imagination drift a bit to see the entire winding shape of the Dragon in the northern heavens.

Also – if you can find both Dippers, and if your sky is relatively dark – you can easily pick out another noteworthy star in Draco. This star is Thuban, easy to find by looking between the Dippers. Thuban is famous for having served as a pole star around 3000 B.C. This date coincides with the beginning of the building of the pyramids in Egypt. It’s said that the descending passage of the Great Pyramid of Khufu at Gizeh was built to point directly at Thuban. So our ancestors knew and celebrated this star.

There are two more prominent stars to look for in the Dragon. These stars are Eltanin and Rastaban, and they lie in the head of Draco. They represent the Dragon’s Eyes.

For years, I’ve glanced randomly up in the north at this time of year and noticed these two stars, Eltanin and Rastaban, in Draco. They’re noticeable because they’re relatively bright and near each other. There’s always that split-second when I ask myself with some excitement what two stars are those? It’s then that my eyes drift to blue-white Vega nearby … and I know, by Vega’s nearness, that they are the Dragon’s Eyes. Notice the relationship between Vega and the Dragon’s Eyes on the chart below:

Diagram with stars Rastaban and Eltanin in upper left and Vega lower right.

Stars Eltanin and Rastaban, near bright star Vega

Eltanin and Rastaban are fun to pick out, and, what’s more, they nearly mark the radiant point for the annual October Draconid meteor shower. Double bonus!

From tropical and subtropical latitudes in the Southern Hemisphere, the stars Rastaban and Eltanin shine quite low in the northern sky (below Vega). In either hemisphere, at all time zones, the Dragon’s eyes climb highest up in the sky around midnight (1 a.m. daylight saving time) in mid-June, 11 p.m. (midnight daylight saving time) in early July, and 9 p.m. (10 p.m. daylight saving time) in early August.

From temperate latitudes in the Southern Hemisphere (southern Australia and New Zealand), the Dragon’s eyes never climb above your horizon (but you can catch the star Vega way low in your northern sky).

Meanwhile, people at mid-northern latitudes get to view the Dragon’s eyes all night long! Circumpolar … remember?

Cleaning tips from a chemist who researches disinfectants

“I doubt that many people read the directions carefully on the cleaning products they use, but it’s important to do so,” says Emory chemist Bill Wuest, an expert in disinfectants.

By Carol Clark

Many household cleaners, once ubiquitous and taken for granted, are flying off store shelves faster than they are restocked, as people strive to keep surfaces free of the coronavirus that causes COVID-19. The Centers for Disease Control and Prevention recently released a survey on consumer knowledge and practices for disinfecting coronavirus and found that 39 percent of the respondents had misused cleaning products.

“This pandemic has caused me to think more about the knowledge of cleaning protocols of the everyday person,” says Bill Wuest, an associate professor of chemistry at Emory University who studies disinfectants. “It’s important to communicate our research to the general public to generate clear messages.”

An active ingredient commonly seen in household cleaners, including some disinfectant sprays and liquids, and anti-bacterial sanitizing wipes and soaps, are quaternary ammonium compounds, or QACs.

One of the first QACs to enter the marketplace as a cleaning agent was benzalkonium chloride. Known as BAC for short, it was introduced in Lysol around the beginning of the 20th century, became widely adopted by the manufacturers of a range of cleaning products, and has remained a staple ever since.

In fact, if you read the labels of the cleaning supplies in your household, you will likely see benzalkonium chloride listed among the active ingredients on at least one of them, if not more. “There are basically four or five QACs, including BAC, that have been the workhouse disinfectants for around 100 years, on the frontline of most homes and hospitals,” Wuest says. “Very little has been done to change them around, because they work so well against many common bacteria, viruses, molds and fungi and they’re so simple and cheap to make.”

QACs are surfactants, or surface-acting agents, he explains. Their molecules have an ammonia atom at the center of two methyl stubs and two long carbon chains. In the simplest terms, the positively charged heads of the carbon chains are drawn to the negatively charged fatty membranes encasing many bacteria and viruses, including coronaviruses. The heads of the carbon chains act like spearpoints, breaking apart the fatty membranes and causing the pathogens to disintegrate.

The Wuest lab is a leader in studies of QACs. One issue Wuest and his colleagues have identified is the fact that a few bacteria strains are slowly developing some resistance to BAC. If that trend continues, it could cause serious problems years down the road for sanitation in hospitals. In the U.S. alone, at least 2.8 million people get antibiotic-resistant infections, according to the Center for Disease Control and Prevention, leading to more than 35,000 deaths.

Research has frequently confirmed that QACs work against influenza viruses as well as bacterial strains and coronaviruses that have similar outer membranes as SARS-CoV-2.

Wuest offers the following tips for consumers.

Avoid “antibacterial” sanitizers and soaps

BAC is the active ingredient in most “antibacterial” wipes, hand sanitizers and soaps. Wuest recommends choosing plain soap or plain alcohol-based sanitizers whenever possible, to avoid potentially contributing to the growing problem of antibiotic resistance. While products containing BAC are convenient and practical, especially for cleaning large surfaces, plain soap and water also work well against coronaviruses and other common pathogens.

Follow instructions closely

“I doubt that many people read the directions carefully on the cleaning products they use, but it’s important to do so,” Wuest says. He notes that some products state that, after application, the cleaning agent needs to stay on the surface being sanitized for several minutes before being wiped off.

Never mix cleaning agents

Consumers should never try to mix cleaning agents to try to “improve” them, Wuest stresses. Bleach combined with ammonia, for example, generates toxic chloramine vapor, which will cause chemical burns to the eyes and lungs and can permanently damage the respiratory system. Even mixing bleach with the seemingly innocuous ingredient of household vinegar is dangerous, as that combination creates deadly chlorine gas.

“Never mix any cleaning product with another cleaning product,” he says. “It’s an extremely dangerous thing to do, as many of the ingredients are hazardous if not used as directed.”

Check latest CDC recommendations

For more guidance on cleaning in the era of COVID-19, Wuest points to a web page, Cleaning and Disinfection for Households, outlining current recommendations from the Centers for Disease Control and Prevention.

Related:
Getting back to chemistry basics: How simple soap saves lives
Chemists teach old drug new tricks to target deadly staph bacteria

from eScienceCommons https://ift.tt/2zEJEsE

Avoid “antibacterial” sanitizers and soaps

Follow instructions closely

Never mix cleaning agents

Check latest CDC recommendations

ESA’s Solar Orbiter made its 1st close approach to the sun today

The European Space Agency (ESA) announced on June 15, 2020, that its Solar Orbiter spacecraft – which sped into space this past February in a dramatic night launch – has made its first close approach to our star. It swept as close to the sun’s surface as about 50 million miles (77 million km), or about half the average distance between the sun and Earth. No images yet! The first ones are expected to be released in July. Meanwhile, the scientists say they will:

… test the spacecraft’s 10 science instruments, including the six telescopes on-board, which will acquire close-up images of the sun in unison for the first time.

Today is THE DAY! The day of Solar Orbiter's first perihelion. We are about 77 million km from the Sun's surface, half the distance between Earth and the Sun. No one has ever been closer with a camera to the beast. Read more: https://t.co/3MG3VUovZ7 pic.twitter.com/jG8uSAw2w2

— ESA's Solar Orbiter (@ESASolarOrbiter) June 15, 2020

Solar Orbiter Project Scientist Daniel Müller commented in a statement from ESA:

We have never taken pictures of the sun from a closer distance than this. There have been higher resolution close-ups, e.g. taken by the 4-meter Daniel K. Inouye Solar Telescope in Hawaii earlier this year. But from Earth, with the atmosphere between the telescope and the sun, you can only see a small part of the solar spectrum that you can see from space.

The sun's surface, looking like caramel corn.

The 1st published image from the Daniel K. Inouye Solar Telescope in Hawaii. This telescope takes higher-resolution images than Solar Orbiter will, but it can see only a small part of the range of energy emitted by our sun. Image via NSO/ NSF/ AURA.

NASA’s Parker Solar Probe, launched in 2018, makes closer approaches, ESA pointed out. But that spacecraft doesn’t carry telescopes capable of looking directly at the sun. Daniel commented:

Our ultraviolet imaging telescopes have the same spatial resolution as those of NASA’s Solar Dynamic Observatory (SDO), which takes high-resolution images of the sun from an orbit close to Earth. Because we are currently at half the distance to the sun, our images have twice SDO’s resolution during this perihelion.

A large, mottled, bluish ball, obviously shining, with a flare on the lower right.

The sun today (June 15, 2020), via NASA SDO’s Atmospheric Imaging Assembly (AIA). This instrument provides full-disk observations of the sun’s chromosphere and corona in the ultraviolet. In contrast, at ultraviolet wavelengths, Solar Orbiter is expected to see the sun’s surface about twice as clearly as SDO when Solar Orbiter is at perihelion, or closest to the sun.

Solar Orbiter was launched on February 10 of this year. As of today (June 15), its commissioning phase is complete. Now the craft will commence its cruise phase, which will last until November 2021. The spacecraft will continue getting closer and closer to the sun. During the main science phase ahead, it’ll get as close as 26 million miles (42 million km) to the sun’s surface, which is closer than the innermost planet Mercury. ESA said:

The spacecraft will reach its next perihelion in early 2021. During the first close approach of the main science phase, in early 2022, it will get as close as 48 million km [about 30 million miles].

Solar Orbiter operators will then use the gravity of Venus to gradually shift the spacecraft’s orbit out of the ecliptic plane, in which the planets of the solar system orbit. These fly-by maneuvers will enable Solar Orbiter to look at the sun from higher latitudes and get the first ever proper view of its poles. Studying the activity in the polar regions will help the scientists to better understand the behavior of the sun’s magnetic field, which drives the creation of the solar wind that in turn affects the environment of the entire solar system.

Since the spacecraft is currently 134 million km [about 80 million miles] from Earth, it will take about a week for all perihelion images to be downloaded via ESA’s 35-meter deep-space antenna in Malargüe, Argentina. The science teams will then process the images before releasing them to the public in mid-July. The data from the in-situ instruments will become public later this year after a careful calibration of all individual sensors.

Daniel commented:

We have a 9-hour download window every day but we are already very far from Earth so the data rate is much lower than it was in the early weeks of the mission when we were still very close to Earth. In the later phases of the mission, it will occasionally take up to several months to download all the data because Solar Orbiter really is a deep space mission.

A square spacecraft, with solar panel wings and what looks like a large camera 'eye,' with the sun in the background.

Artist’s concept of the European Space Agency’s sun-exploring Solar Orbiter. Launched this past February 9, 2020, the craft made its first close approach to the star on June 15, sweeping as close as about 50 million miles (77 million km), or about half Earth’s distance from the sun. Image via ESA.

Bottom line: Solar Orbiter swept as close as 50 million miles (77 million km) to our sun’s surface on June 15, 2020. New images are being downloaded now and are expected to be released in July. Over the next several years, Solar Orbiter will sweep even closer to our star – closer than the innermost planet Mercury – and obtain very clear images of its surface.

Via ESA

from EarthSky https://ift.tt/3cYbCNy

… test the spacecraft’s 10 science instruments, including the six telescopes on-board, which will acquire close-up images of the sun in unison for the first time.

Today is THE DAY! The day of Solar Orbiter's first perihelion. We are about 77 million km from the Sun's surface, half the distance between Earth and the Sun. No one has ever been closer with a camera to the beast. Read more: https://t.co/3MG3VUovZ7 pic.twitter.com/jG8uSAw2w2

— ESA's Solar Orbiter (@ESASolarOrbiter) June 15, 2020

Solar Orbiter Project Scientist Daniel Müller commented in a statement from ESA:

We have never taken pictures of the sun from a closer distance than this. There have been higher resolution close-ups, e.g. taken by the 4-meter Daniel K. Inouye Solar Telescope in Hawaii earlier this year. But from Earth, with the atmosphere between the telescope and the sun, you can only see a small part of the solar spectrum that you can see from space.

NASA’s Parker Solar Probe, launched in 2018, makes closer approaches, ESA pointed out. But that spacecraft doesn’t carry telescopes capable of looking directly at the sun. Daniel commented:

Our ultraviolet imaging telescopes have the same spatial resolution as those of NASA’s Solar Dynamic Observatory (SDO), which takes high-resolution images of the sun from an orbit close to Earth. Because we are currently at half the distance to the sun, our images have twice SDO’s resolution during this perihelion.

The spacecraft will reach its next perihelion in early 2021. During the first close approach of the main science phase, in early 2022, it will get as close as 48 million km [about 30 million miles].

Solar Orbiter operators will then use the gravity of Venus to gradually shift the spacecraft’s orbit out of the ecliptic plane, in which the planets of the solar system orbit. These fly-by maneuvers will enable Solar Orbiter to look at the sun from higher latitudes and get the first ever proper view of its poles. Studying the activity in the polar regions will help the scientists to better understand the behavior of the sun’s magnetic field, which drives the creation of the solar wind that in turn affects the environment of the entire solar system.

Since the spacecraft is currently 134 million km [about 80 million miles] from Earth, it will take about a week for all perihelion images to be downloaded via ESA’s 35-meter deep-space antenna in Malargüe, Argentina. The science teams will then process the images before releasing them to the public in mid-July. The data from the in-situ instruments will become public later this year after a careful calibration of all individual sensors.

Daniel commented:

We have a 9-hour download window every day but we are already very far from Earth so the data rate is much lower than it was in the early weeks of the mission when we were still very close to Earth. In the later phases of the mission, it will occasionally take up to several months to download all the data because Solar Orbiter really is a deep space mission.

Via ESA

from EarthSky https://ift.tt/3cYbCNy

Coronavirus reports – Part 5: “I have tried to be positive all the way through”

We caught up with people living with cancer across the country, to find out how the coronavirus pandemic has been affecting them and their families.

Katherine: “I had to undo the gown myself and that was the worst part – I felt so lonely”

Katherine was diagnosed with breast cancer in October 2019, after discovering lumps below her collarbone. “I was diagnosed on Halloween. The lumps were quite big – the two high up and then two more further in on the chest wall.”

Katherine began chemotherapy at the beginning of December. Her last round of chemotherapy was scheduled the day after the lockdown was announced so, like many, Katherine had to attend alone.

“My surgery was planned for 28 April – it was to be a mastectomy and reconstruction.  I went for the pre-op 10 days before – that was the first time I had come face to face with staff in masks.” The following day, Katherine got a call from her surgeon to say the date for the surgery would have to be changed and the reconstruction wouldn’t be able to go ahead.

Katherine was diagnosed with breast cancer in 2019.

“The surgeon said that she knew how upset I  was and said she could do the operation a week earlier than planned, on 21 April which was just in a couple of days’ time.” For Katherine, it was a good thing that it was rescheduled sooner, “I didn’t have eight days of anxiety and thinking about the fact that it wasn’t the reconstruction too – I just had to focus on getting ready for that.”  

Katherine had the mastectomy but, like the chemotherapy, had to go alone, “I had to walk into the theatre myself and saw everyone in the PPE equipment.  I had to undo the gown myself and that was the worst part – I felt so lonely. It was very strange and such a difficult  experience,  but I am so grateful that it was possible.”

After the operation, Katherine was back in her garden at home that afternoon.

Katherine received the good news that they had successfully removed the tumour and there was no need for radiotherapy at the end of April. Afterwards, her sister did a head shave to raise money for Cancer Research UK, “then my younger sister arranged a special socially distanced celebration for me with people waving and driving their cars past with balloons! My partner was in on it too, and I cried and cried. It was pouring with rain and it did not deter them.”

Katherine is shielding until the end of June and is taking that time to consider her next steps. “With regard to the reconstruction, I am due to see my specialist in September to discuss options. It is good to have a few months to think about what I want to do.”

Until then, Katherine is focusing on a time when she will be able to celebrate with her family and friends. “I have tried to be positive all the way through.”

Anisha: “There are definitely highs and lows of lockdown, but I’ve tried to stay so positive”

Anisha was diagnosed with bowel cancer in September 2018. She had surgery followed by three months of chemotherapy.

Anisha, who works as a GP, was concerned that coronavirus was preventing people from visiting the doctor, particularly delays to referrals and diagnoses, changes which have been reflected at her own practice.

“I would usually be seeing a lot of people with moles being checked out at this time of

Anisha, a GP, was diagnosed with bowel cancer in 2018.

year and I am not seeing as many people with “bowel problems” – that means a lot to me personally after my own diagnosis.”

Throughout the pandemic, Anisha has been trying to juggle her passion and commitment to her job with home life but her previous experiences have helped her throughout this difficult time.

“I feel cancer robbed us of invaluable family time, and now we are all facing COVID-19 now – there are definitely highs and lows of lockdown, but I’ve tried to stay so positive through COVID-19, telling myself that there are those enduring far worse and that we have been through far tougher times than this as a family.”

Anisha is using her weekends to unwind and relax as a family. “I am enjoying endless experimenting and baking, not rushing about from place to place, slowly getting some jobs done in the house, allowing myself to do nothing sometimes, getting all the games and toys out of the cupboards.”

Sophie: “I feel so tired and sick, and stuck in the four walls”

After nearly a year of persistent headaches, Sophie had a seizure while driving, and was eventually referred to a neurologist. She was diagnosed with a type of brain cancer known as a diffuse astrocytoma in 2016, when she was 21 years old.

“My surgeon took a big bulk of this tumour and I was so grateful that he had removed around 50%, but  I  still underwent radiotherapy and chemotherapy to stop any growth.”

In January 2020 Sophie was told that the benign tumour in her brain had started to grow again. She returned to her neurosurgeon, who recommended a further operation as the biopsy showed that the tumour had become cancerous.

Sophie had a recent MRI scan, which was stable, and is currently on her fourth cycle

Sophie was diagnosed with a diffuse astrocytoma in 2016.

of chemo. “I feel so tired and sick, and stuck in the four walls. I can’t do the things I want to. It is incredibly difficult. After the first surgery, I could do more things but there are no distractions now – I would love to be able to go out for a coffee – there is only so much you can do in the house.”

And even though she is living with her boyfriend and his family, she is in touch with her family – and her mum is regularly dropping off cakes and biscuits on her doorstep.

Despite changes to the shielding made by the Government, Sophie’s oncologist has advised her not to go out yet. “I think I am more anxious than ever now, especially now more people are out and about. I live about 200m from the beach and I can see visitors coming to our street to go to the beach.”

Charlotte: “I’m on a mission to help young cancer patients during the coronavirus pandemic”

Charlotte is dedicated to helping young cancer patients during the coronavirus pandemic, after her own childhood experience.

She said: “I had cancer when I was a teenager so I know how isolating it can be, let alone now in these times. I was diagnosed with ALL when I was 12 years old and finished treatment when I was 15.”

“Crafts really helped me when I was having treatment so I have been making creative care packages to supply to hospitals – each pack contains fun and creative things to do, including colouring books, puzzles, sewing kits and notebooks.”

Charlotte started with making packs for 10 young cancer patients at The Royal Marsden in Sutton, “and they loved them!”

She was then contacted by the hospital and asked to create more packs to help more patients through these extremely difficult times.

In order to make a real impact, Charlotte started a crowdfunding page in order to raise money for the packs. With the support of the public, Charlotte was able to raise over £1,000. “I have since put together over 100 creative care packages for patients at both the Royal Marsden Hospital in Sutton and St George’s Hospital in Tooting.”

Lilly

Read more coronavirus reports:

“I know I’m in a queue, but things feel uncertain“

“I should have known when they came back in PPE“

“We’re ahead when it comes to isolation”

“I’m taking things week by week”

Thanks to Katherine, Anisha, Sophie and Charlotte for sharing their experiences with our Media Volunteer Liaison team.

If you would like to share your story with us, please visit our website. And if you have questions about cancer, you can talk to our nurses Monday to Friday, 9-5pm, on freephone 0808 800 4040.

from Cancer Research UK – Science blog https://ift.tt/2Cac3rn

We caught up with people living with cancer across the country, to find out how the coronavirus pandemic has been affecting them and their families.

Katherine: “I had to undo the gown myself and that was the worst part – I felt so lonely”

Katherine began chemotherapy at the beginning of December. Her last round of chemotherapy was scheduled the day after the lockdown was announced so, like many, Katherine had to attend alone.

Katherine was diagnosed with breast cancer in 2019.

After the operation, Katherine was back in her garden at home that afternoon.

Until then, Katherine is focusing on a time when she will be able to celebrate with her family and friends. “I have tried to be positive all the way through.”

Anisha: “There are definitely highs and lows of lockdown, but I’ve tried to stay so positive”

Anisha was diagnosed with bowel cancer in September 2018. She had surgery followed by three months of chemotherapy.

“I would usually be seeing a lot of people with moles being checked out at this time of

Anisha, a GP, was diagnosed with bowel cancer in 2018.

year and I am not seeing as many people with “bowel problems” – that means a lot to me personally after my own diagnosis.”

Throughout the pandemic, Anisha has been trying to juggle her passion and commitment to her job with home life but her previous experiences have helped her throughout this difficult time.

Sophie: “I feel so tired and sick, and stuck in the four walls”

“My surgeon took a big bulk of this tumour and I was so grateful that he had removed around 50%, but  I  still underwent radiotherapy and chemotherapy to stop any growth.”

Sophie had a recent MRI scan, which was stable, and is currently on her fourth cycle

Sophie was diagnosed with a diffuse astrocytoma in 2016.

And even though she is living with her boyfriend and his family, she is in touch with her family – and her mum is regularly dropping off cakes and biscuits on her doorstep.

Charlotte: “I’m on a mission to help young cancer patients during the coronavirus pandemic”

Charlotte is dedicated to helping young cancer patients during the coronavirus pandemic, after her own childhood experience.

Charlotte started with making packs for 10 young cancer patients at The Royal Marsden in Sutton, “and they loved them!”

She was then contacted by the hospital and asked to create more packs to help more patients through these extremely difficult times.

Lilly

Read more coronavirus reports:

“I know I’m in a queue, but things feel uncertain“

“I should have known when they came back in PPE“

“We’re ahead when it comes to isolation”

“I’m taking things week by week”

Thanks to Katherine, Anisha, Sophie and Charlotte for sharing their experiences with our Media Volunteer Liaison team.

If you would like to share your story with us, please visit our website. And if you have questions about cancer, you can talk to our nurses Monday to Friday, 9-5pm, on freephone 0808 800 4040.

from Cancer Research UK – Science blog https://ift.tt/2Cac3rn

Wowzer! Pluto spacecraft sees parallax for Proxima

A star field, with one star shifting position.

View larger. | The New Horizons spacecraft, which visited Pluto in 2015, is really out there! This 2-frame animation shows Proxima Centauri, the nearest star to Earth. On the left, Proxima against the star background seen by the spacecraft. On the right, Proxima and its background as we see them from Earth. The difference is due to parallax, the same effect you see if you hold up a finger and close one eye, then the other. It’s a shift in perspective, caused by New Horizons’ great distance from Earth.

Reprinted from a June 10, 2020, article at NASA.gov.

For the first time, a spacecraft has sent back pictures of the sky from so far away that some stars appear to be in different positions than we’d see from Earth.

More than four billion miles (6 billion km) from home and speeding toward interstellar space, NASA’s New Horizons has traveled so far that it now has a unique view of the nearest stars. Alan Stern, New Horizons principal investigator from Southwest Research Institute (SwRI) in Boulder, Colorado, said:

It’s fair to say that New Horizons is looking at an alien sky, unlike what we see from Earth.

And that has allowed us to do something that had never been accomplished before – to see the nearest stars visibly displaced on the sky from the positions we see them on Earth.

On April 22-23, the spacecraft turned its long-range telescopic camera to a pair of the “closest” stars, Proxima Centauri and Wolf 359, showing just how they appear in different places than we see from Earth. Scientists have long used this “parallax effect” – how a star appears to shift against its background when seen from different locations — to measure distances to stars.

An easy way to see parallax is to place one finger at arm’s length and watch it jump back and forth when you view it successively with each eye. Similarly, as Earth makes it way around the sun, the stars shift their positions. But because even the nearest stars are hundreds of thousands of times farther away than the diameter of Earth’s orbit, the parallax shifts are tiny, and can only be measured with precise instrumentation. Stern commented:

No human eye can detect these shifts.

But when New Horizons images are paired with pictures of the same stars taken on the same dates by telescopes on Earth, the parallax shift is instantly visible. The combination yields a 3D view of the stars “floating” in front of their background star fields. Tod Lauer, New Horizons science team member from the National Science Foundation’s National Optical-Infrared Astronomy Research Laboratory, who coordinated the parallax demonstration, said:

The New Horizons experiment provides the largest parallax baseline ever made – over 4 billion miles – and is the first demonstration of an easily observable stellar parallax.

Lauer, New Horizons Deputy Project Scientist John Spencer of SwRI, and science team collaborator, astrophysicist, Queen guitarist and stereo imaging enthusiast Brian May created the images that clearly show the effect of the vast distance between Earth and the two nearby stars. May said:

It could be argued that in astro-stereoscopy – 3D images of astronomical objects – NASA’s New Horizons team already leads the field, having delivered astounding stereoscopic images of both Pluto and the remote Kuiper Belt object Arrokoth.

But the latest New Horizons stereoscopic experiment breaks all records. These photographs of Proxima Centauri and Wolf 359 – stars that are well-known to amateur astronomers and science fiction aficionados alike – employ the largest distance between viewpoints ever achieved in 180 years of stereoscopy!

The companion images of Proxima Centauri and Wolf 359 were provided by the Las Cumbres Observatory, operating a remote telescope at Siding Spring Observatory in Australia, and astronomers John Kielkopf, University of Louisville, and Karen Collins, Harvard and Smithsonian Center for Astrophysics, operating a remote telescope at Mt. Lemmon Observatory in Arizona. Lauer said:

The professional and amateur astronomy communities had been waiting to try this, and were very excited to make a little space exploration history. The images collected on Earth when New Horizons was observing Proxima Centauri and Wolf 359 really exceeded my expectations.

Download the images (and learn more about creating and posting your own parallax perspectives) here.

An interstellar navigation first

Throughout history, navigators have used measurements of the stars to establish their position on Earth. Interstellar navigators can do the same to establish their position in the galaxy, using a technique that New Horizons has demonstrated for the first time. While radio tracking by NASA’s Deep Space Network is far more accurate, its first use is a significant milestone in what may someday become human exploration of the galaxy.

At the time of the observations, New Horizons was more than 4.3 billion miles (about 7 billion kilometers) from Earth, where a radio signal, traveling at the speed of light, needed just under 6 hours and 30 minutes to reach home.

Launched in 2006, New Horizons is the first mission to Pluto and the Kuiper Belt. It explored Pluto and its moons in July 2015 – completing the space-age reconnaissance of the planets that started 50 years earlier – and continued on its unparalleled voyage of exploration with the close flyby of Kuiper Belt object Arrokoth in January 2019. New Horizons will eventually leave the solar system, joining the Voyagers and Pioneers on their paths to the stars.

Click here for more information about New Horizons.

Bottom line: The New Horizons spacecraft – which visited Pluto in 2015 – has now accomplished another first. It has seen the nearest stars visibly displaced on the sky from the positions we see them on Earth. The effect is one of parallax, and is caused by New Horizons’ great distance from Earth.

from EarthSky https://ift.tt/2N1Kjr7

Reprinted from a June 10, 2020, article at NASA.gov.

For the first time, a spacecraft has sent back pictures of the sky from so far away that some stars appear to be in different positions than we’d see from Earth.

It’s fair to say that New Horizons is looking at an alien sky, unlike what we see from Earth.

And that has allowed us to do something that had never been accomplished before – to see the nearest stars visibly displaced on the sky from the positions we see them on Earth.

No human eye can detect these shifts.

The New Horizons experiment provides the largest parallax baseline ever made – over 4 billion miles – and is the first demonstration of an easily observable stellar parallax.

It could be argued that in astro-stereoscopy – 3D images of astronomical objects – NASA’s New Horizons team already leads the field, having delivered astounding stereoscopic images of both Pluto and the remote Kuiper Belt object Arrokoth.

But the latest New Horizons stereoscopic experiment breaks all records. These photographs of Proxima Centauri and Wolf 359 – stars that are well-known to amateur astronomers and science fiction aficionados alike – employ the largest distance between viewpoints ever achieved in 180 years of stereoscopy!

The professional and amateur astronomy communities had been waiting to try this, and were very excited to make a little space exploration history. The images collected on Earth when New Horizons was observing Proxima Centauri and Wolf 359 really exceeded my expectations.

Download the images (and learn more about creating and posting your own parallax perspectives) here.

An interstellar navigation first

Click here for more information about New Horizons.

from EarthSky https://ift.tt/2N1Kjr7

Where is the largest waterfall on Earth?

Side view of water flowing over a natural dam beneath the ocean.

View larger. | This infographic illustrates how a large underwater cataract (waterfall) naturally forms underneath the waves within the Denmark Strait. (A map in the upper right of the graphic shows the location of Denmark Strait, between Greenland and Iceland.) Warmer surface waters flow northward. These warmer waters gradually lose heat to the atmosphere and sink. Denser, cold water flows southward in a deep current along the sea floor over an undersea ridge in the Strait. The height of the Denmark Strait cataract is approximately 11,500 feet (3,500 meters). By comparison, the largest waterfall on land is 3,212 feet (980 meters). Image via NOAA.

Rivers flowing into Earth’s gorges create waterfalls that are natural wonders, drawing millions of visitors. But Earth’s largest and most powerful waterfall doesn’t attract many tourists. That’s because it lies beneath the ocean, under the Denmark Strait, which separates Iceland and Greenland.

The waterfall – known as the Denmark Strait cataract – under the Denmark Strait near the southern tip of Greenland – begins 2,000 feet (600 meters) under the ocean surface and plunges to a depth of 10,000 feet (3,000 meters), nearly a 2-mile (3.2 km) drop.

Map showing Greenland to upper left and Iceland southeast of it, with parts of Europe and North America visible.

The Denmark Strait. Image via Wikipedia.

The Denmark Strait cataract is more than 3 times the height of Angel Falls in Venezuela, which is considered Earth’s tallest waterfall (on land). And the Denmark Strait cataract carries an estimated 123 million cubic feet (3.5 million cubic meters) of water per second. That’s equivalent to almost 2,000 Niagara Falls at peak flow.

Very high rugged cliff with narrow waterfall pouring over it into treetops at base.

Angel Falls in Venezuela, the tallest waterfall on land, is 3 times shorter than the Denmark Strait cataract, and Niagara Falls carries 2,000 times less water, even during peak flows. Image via beautifulworld.com.

But how can there be waterfalls in the ocean? It’s because cold water is denser than warm water, and in the Denmark Strait, southward-flowing frigid water from the Nordic Seas meets warmer water from the Irminger Sea. The cold, dense water quickly sinks below the warmer water and flows over the huge drop in the ocean floor, creating a downward flow estimated at well over 123 million cubic feet (3.5 million cubic meters) per second. Because it flows beneath the ocean surface, however, the massive turbulence of the Denmark Strait goes completely undetected without the aid of scientific instruments.

When the water from the Denmark Strait cataract reaches the ocean floor, it forms a massive current traveling south, replacing warmer surface water that’s flowing north. The amount of water in this gigantic flow equals between 20 and 40 times the sum of all river water that flows into the Atlantic.

Bottom line: Earth’s largest waterfall – known as the Denmark Strait cataract – is under the ocean.

Via National Ocean Service/ NOAA

from EarthSky https://ift.tt/2C9jP4M

The Denmark Strait. Image via Wikipedia.

Bottom line: Earth’s largest waterfall – known as the Denmark Strait cataract – is under the ocean.

Via National Ocean Service/ NOAA

from EarthSky https://ift.tt/2C9jP4M

Where is Proxima Centauri?

Stars within 12 light-years of the sun, via Guy Ottewell's Astronomical Companion. Click to view larger, Guy says:

View larger. | Stars within 12 light-years of our sun. The lines on the grid are 4 light-years apart. Proxima is part of the triple star system we see as the single star Alpha Centauri. Diagram published originally in Guy Ottewell’s beloved Astronomical Companion. Do click in to view larger; Guy commented, “It’s quite vivid when it fills the screen.”

Editor’s Note: Proxima Centauri is the nearest star to Earth. It’s part of the triple Alpha Centauri star system, visible as a single star from very southerly latitudes in the Northern Hemisphere and best seen from the Southern Hemisphere. Generally speaking, the three stars in the Alpha Centauri system are 4.4 light-years away. Proxima is the closest of the three at 4.2 light-years.

The diagram above shows you where Alpha Centauri is, with respect to other nearby stars. Included are stars within 12 light-years from the sun. The glows of light representing the stars are millions of times larger than the stars themselves, which would be microscopically small on this scale.

The grid serves to show the equatorial plane, and also the scale, the lines being 4 light-years apart. The slightly thicker line is the vernal equinox direction (the Earth-sun direction around every March 20).

Imaginary stalks from the plane to the stars show how far north or south they are. I’ve cropped the picture so that some of the stars are off the top or bottom, but they are obscure stars you may not have heard of, with designations such as Lalande 21185, Luyten 726-8, DX Cancri. Most stars, including most of those near to us, are smaller than our sun: red dwarfs.

The exceptions near to us are Sirius, Procyon, and Alpha Centauri.

Alpha Centauri is the third-brightest star (that is, as seen from our place in space, and not counting the sun). Like the first- and second-brightest – Sirius and Canopus – it is a southern star. Indeed it’s much farther south than either of those, which is why it has no traditional name in our culture (except a rather faux-traditional one, Rigil Kentaurus).

The space diagram shows it at a steep southward angle from the sun. This angle (its declination -61°) means it doesn’t peep above the horizon until you go down to the latitude of northern Florida; to see it properly you might go south of Earth’s equator.

Then you would see in your telescope that it is a double star – one of the widest and easiest to “split.” Here is part of my diagram of the pair with which I used to fill a space in Astronomical Calendar 2016:

The double star of Alpha Centauri, via Astronomical Calendar 2016 by Guy Ottewell.

The double star of Alpha Centauri. Astronomers call them Alpha Centauri A and B. Image via Astronomical Calendar 2016 by Guy Ottewell.

Again, the symbols for the stars are vastly larger than the bodies of the stars would be. It isn’t really that the B star revolves around the A one: they both revolve around their common center of gravity. You can see that this year, 2016, is the year when B appears closest to A, though in the true (untilted) orbit it will reach periastron in 2035. The blue lines are one second of arc apart – that’s the apparent size of a tennis ball 10 miles away.

Alpha Centauri A is a star much like the sun, slightly larger and of about the same 4.6-billion-year age or slightly older; B is slightly smaller and cooler. In their elliptical orbits around their common center of gravity, they range from about 11 Astronomical Units (sun-Earth distances) apart when closest, to 36 when farthest apart – in other words, from something like the sun-Saturn to something like the sun-Pluto distance.

And the distance of this star system from us is only 4.4 light-years: nearer than all other stars … except for one, Proxima, discovered in 1915 (by Robert Jones in South Africa).

Proxima is one of those numerous dwarfs whose surfaces are reddish, meaning cooler and dimmer. Only about 1/7 as wide as the sun, and at a magnitude (brightness) of 11, it is about 100 times too dim to be seen with the unaided eye. Proxima is more than 2 degrees away from the Alpha Centauri pair; on observatory photographs, there are thousands of background stars in between. Yet studies of it found that it is only 4.24 light-years away from us, closer than the other two stars in the Alpha Centauri system.

Hence it is dubbed Proxima Centauri, with the word Proxima having the same root as the word proximity, meaning near.

The nearest stars not only have the largest parallax (apparent angular shift as we go around the sun) but are liable to have large proper motion (travel across the starry background from year to year). Proxima is found to be still coming gradually toward us; it will be nearest, at only about 3 light-years, about 27,000 years into the future. And it is probably, though not quite certainly, gravitationally bound to the Alpha Centauri pair 0.2 light-year away from it, in an enormous, slow orbit of something like 500,000 years. So it can be called Alpha Centauri C.

Yes, these are humiliating numbers, and I hesitate to crush you further with the reminder that a light-year is nearly 6,000,000,000,000 miles, and the distance across the Milky Way galaxy is something like 30,000 times greater than the distance to these our nearest neighbors in it.

Thus – even if there is a Proximan with a telephone, and one day you receive a call from her asking, “What is your name, how many legs do you have, and how many sexes are there in your world?” – it will be more than four years before she receives your reply and more than eight before you know what she thinks of it.

Bottom line: Diagram and explanation from astronomer Guy Ottewell, showing the location in space of the Alpha Centauri system and, in particular, the star Proxima Centauri, the nearest star to Earth.

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