1st quarter moon is May 29-30

View at EarthSky Community Photos. | Composite image of a moon nearly at 1st quarter with some of the features you can see on the moon at this phase – captured April 30, 2020 – by our friend Dr Ski in the Philippines. He wrote: “… 10 hours before 1st quarter and the Lunar V and Lunar X are well defined …” More about Lunar V and X below. Thank you, Dr Ski!

A first quarter moon rises around noon and sets around midnight. You’ll likely spot it in late afternoon or early evening, when it’s at its highest in the sky. At this moon phase, the moon is showing us precisely half of its lighted half. Or you might say that – at first quarter moon – we’re seeing half the moon’s day side.

We call this moon a quarter and not a half because it is one quarter of the way around in its orbit of Earth, as measured from one new moon to the next. Also, although a first quarter moon appears half-lit to us, the illuminated portion we see of a first quarter moon truly is just a quarter. We’re now seeing half the moon’s day side, that is. Another lighted quarter of the moon shines just as brightly in the direction opposite Earth!

And what about the term half moon? That’s a beloved term, but not an official one.

Lunar X and Lunar V appear when the moon is near its 1st quarter phase. They aren’t really Xs and Vs on the moon. They’re just high areas, catching sunlight, creating an example of pareidolia on the moon. Aqilla Othman in Port Dickson, Negeri Sembilan, Malaysia, caught them both in May of 2017. Notice that he caught Lunar X and Lunar V.

Here’s a closer look at Lunar X and Lunar V. Photo by Izaty Liyana in Port Dickson, Negeri Sembilan, Malaysia. What is Lunar X?

Tom Wildoner wrote: “One of my favorite areas to photograph on the moon near the 1st quarter! I captured this view of the sun lighting up the mountain range called Montes Apenninus. The moon was casting a nice shadow on the back side of the mountains. This mountain range is about 370 miles (600 km) long with some of the peaks rising as high as 3.1 miles (5 km).”

Bottom line: The next 1st quarter moon will come on May 30, 2020, at 03:31 UTC. That’s May 29, 10:31 p.m. CDT.

Read more: Top 4 keys to understanding moon phases

Check out EarthSky’s guide to the bright planets.

Help EarthSky keep going! Please donate.

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

View at EarthSky Community Photos. | Composite image of a moon nearly at 1st quarter with some of the features you can see on the moon at this phase – captured April 30, 2020 – by our friend Dr Ski in the Philippines. He wrote: “… 10 hours before 1st quarter and the Lunar V and Lunar X are well defined …” More about Lunar V and X below. Thank you, Dr Ski!

A first quarter moon rises around noon and sets around midnight. You’ll likely spot it in late afternoon or early evening, when it’s at its highest in the sky. At this moon phase, the moon is showing us precisely half of its lighted half. Or you might say that – at first quarter moon – we’re seeing half the moon’s day side.

We call this moon a quarter and not a half because it is one quarter of the way around in its orbit of Earth, as measured from one new moon to the next. Also, although a first quarter moon appears half-lit to us, the illuminated portion we see of a first quarter moon truly is just a quarter. We’re now seeing half the moon’s day side, that is. Another lighted quarter of the moon shines just as brightly in the direction opposite Earth!

And what about the term half moon? That’s a beloved term, but not an official one.

Lunar X and Lunar V appear when the moon is near its 1st quarter phase. They aren’t really Xs and Vs on the moon. They’re just high areas, catching sunlight, creating an example of pareidolia on the moon. Aqilla Othman in Port Dickson, Negeri Sembilan, Malaysia, caught them both in May of 2017. Notice that he caught Lunar X and Lunar V.

Here’s a closer look at Lunar X and Lunar V. Photo by Izaty Liyana in Port Dickson, Negeri Sembilan, Malaysia. What is Lunar X?

Tom Wildoner wrote: “One of my favorite areas to photograph on the moon near the 1st quarter! I captured this view of the sun lighting up the mountain range called Montes Apenninus. The moon was casting a nice shadow on the back side of the mountains. This mountain range is about 370 miles (600 km) long with some of the peaks rising as high as 3.1 miles (5 km).”

Bottom line: The next 1st quarter moon will come on May 30, 2020, at 03:31 UTC. That’s May 29, 10:31 p.m. CDT.

Read more: Top 4 keys to understanding moon phases

Check out EarthSky’s guide to the bright planets.

Help EarthSky keep going! Please donate.

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

Behavioral studies in era of COVID-19 raise new concerns about diversity

"The digital divide is undoubtedly going to get worse during this pandemic," says Emory psychologist Stella Lourenco. "The is a huge problem for ensuring equal access to education and to work, not just for ensuring diversity in scientific research."

By Carol Clark

The COVID-19 pandemic is accelerating an ongoing trend in cognitive psychology to conduct human behavioral experiments online.

“The world has been growing increasingly digital for a while,” says Stella Lourenco, a developmental psychologist at Emory University. “The global pandemic has turbo charged the move towards virtual connection in most areas of life, including psychology research.”

While the Internet offers a powerful tool for collecting data during a time of social distancing, it also raises new concerns regarding the diversity of study participants. Trends in Cognitive Sciences published an opinion piece outlining these concerns, authored by Lourenco and Arber Tasimi, a developmental psychologist at Stanford University who will be joining the Emory faculty in August.

The authors warn that as more research moves online, a growing lack of Internet access among low-income and minority communities may reduce the diversity of study samples, which would limit the ability to generalize scientific findings. As unemployment soars, more people may be forced to choose between paying their rent and buying food or paying for Internet service.

“The digital divide is undoubtedly going to get worse during this pandemic,” Lourenco says. “This is a huge problem for ensuring equal access to education and to work, not just for ensuring diversity in scientific research.”

In their opinion piece, Lourenco and Tasimi urge scientists and grant-funding agencies to join lobbying efforts for government subsidies for Internet service, and “perhaps even advocate for universal availability of Internet access, which is essential for living and operating in contemporary times.”

In some ways, the challenges to diversity presented by the pandemic are a new twist on an old problem, Lourenco says. In recent years, concerns were raised that participants in some in-person psychology studies were mainly college students who are younger than the general population and also tend to be better educated and from higher-income backgrounds and industrialized countries.

A move towards online experiments of human subjects, using crowdsourcing tools such as Amazon Mechanical Turk, was helping alleviate this problem. Online experiments can allow researchers to tap large numbers of participants in an efficient and cost-effective way. “With crowdsourcing tools, you can potentially reach adults from all over the United States, and in other countries, as long as they have Internet access,” Lourenco says.

Children present unique research challenges, Lourenco says, so studies involving them have remained largely in-person. For instance, children tend to grow restless more quickly than adults when they are asked to sit in front of a computer to perform tasks for experiments.

The pandemic, however, is driving more child development laboratories to go online for the first time, Lourenco notes. Platforms such as the Parent and Researcher Collaborative, an online crowdsourcing tool where labs can post studies for families to participate in, are providing infrastructure to support this trend.

As more studies go online, the pandemic is likely impacting Internet access among some groups. In the pre-pandemic era, even low-income people without home Internet might be able to visit a library, a coffee shop or even the parking lot of a restaurant with free wireless service to connect to high-speed Internet. The current situation makes those scenarios less likely to occur.

And the current situation may represent the start of “a new normal,” Lourenco and Tasimi write, “in which threats of disease may require long-term social distancing practices and may differentially impact those in low-income and minority communities.”

They recommend that researchers strive to provide temporary Internet connection to low-income participants, by purchasing mobile hotspots that could be mailed to them or dropped off at their homes. They also recommend that more scientific journals require authors to report detailed demographic information of study participants, whether the studies are conducted online or in person.

They further recommend considering the development of more mobile laboratories, equipped with personal protective equipment and disinfection protocols. Portable labs would allow off-site testing to reach participants in low-income and minority communities.

“I hope that the pressure that the pandemic puts on behavioral research will ultimately create positive changes in the field,” Lourenco says. “Ultimately, it highlights the need to become more sensitive about the demographics of participants involved in psychological studies and about any claims that are made about the generalization of data.”

Related:
Skeletal shapes key to rapid recognition of objects
Babies' spatial reasoning predicts later math skills



from eScienceCommons https://ift.tt/2Xpa3lO

"The digital divide is undoubtedly going to get worse during this pandemic," says Emory psychologist Stella Lourenco. "The is a huge problem for ensuring equal access to education and to work, not just for ensuring diversity in scientific research."

By Carol Clark

The COVID-19 pandemic is accelerating an ongoing trend in cognitive psychology to conduct human behavioral experiments online.

“The world has been growing increasingly digital for a while,” says Stella Lourenco, a developmental psychologist at Emory University. “The global pandemic has turbo charged the move towards virtual connection in most areas of life, including psychology research.”

While the Internet offers a powerful tool for collecting data during a time of social distancing, it also raises new concerns regarding the diversity of study participants. Trends in Cognitive Sciences published an opinion piece outlining these concerns, authored by Lourenco and Arber Tasimi, a developmental psychologist at Stanford University who will be joining the Emory faculty in August.

The authors warn that as more research moves online, a growing lack of Internet access among low-income and minority communities may reduce the diversity of study samples, which would limit the ability to generalize scientific findings. As unemployment soars, more people may be forced to choose between paying their rent and buying food or paying for Internet service.

“The digital divide is undoubtedly going to get worse during this pandemic,” Lourenco says. “This is a huge problem for ensuring equal access to education and to work, not just for ensuring diversity in scientific research.”

In their opinion piece, Lourenco and Tasimi urge scientists and grant-funding agencies to join lobbying efforts for government subsidies for Internet service, and “perhaps even advocate for universal availability of Internet access, which is essential for living and operating in contemporary times.”

In some ways, the challenges to diversity presented by the pandemic are a new twist on an old problem, Lourenco says. In recent years, concerns were raised that participants in some in-person psychology studies were mainly college students who are younger than the general population and also tend to be better educated and from higher-income backgrounds and industrialized countries.

A move towards online experiments of human subjects, using crowdsourcing tools such as Amazon Mechanical Turk, was helping alleviate this problem. Online experiments can allow researchers to tap large numbers of participants in an efficient and cost-effective way. “With crowdsourcing tools, you can potentially reach adults from all over the United States, and in other countries, as long as they have Internet access,” Lourenco says.

Children present unique research challenges, Lourenco says, so studies involving them have remained largely in-person. For instance, children tend to grow restless more quickly than adults when they are asked to sit in front of a computer to perform tasks for experiments.

The pandemic, however, is driving more child development laboratories to go online for the first time, Lourenco notes. Platforms such as the Parent and Researcher Collaborative, an online crowdsourcing tool where labs can post studies for families to participate in, are providing infrastructure to support this trend.

As more studies go online, the pandemic is likely impacting Internet access among some groups. In the pre-pandemic era, even low-income people without home Internet might be able to visit a library, a coffee shop or even the parking lot of a restaurant with free wireless service to connect to high-speed Internet. The current situation makes those scenarios less likely to occur.

And the current situation may represent the start of “a new normal,” Lourenco and Tasimi write, “in which threats of disease may require long-term social distancing practices and may differentially impact those in low-income and minority communities.”

They recommend that researchers strive to provide temporary Internet connection to low-income participants, by purchasing mobile hotspots that could be mailed to them or dropped off at their homes. They also recommend that more scientific journals require authors to report detailed demographic information of study participants, whether the studies are conducted online or in person.

They further recommend considering the development of more mobile laboratories, equipped with personal protective equipment and disinfection protocols. Portable labs would allow off-site testing to reach participants in low-income and minority communities.

“I hope that the pressure that the pandemic puts on behavioral research will ultimately create positive changes in the field,” Lourenco says. “Ultimately, it highlights the need to become more sensitive about the demographics of participants involved in psychological studies and about any claims that are made about the generalization of data.”

Related:
Skeletal shapes key to rapid recognition of objects
Babies' spatial reasoning predicts later math skills



from eScienceCommons https://ift.tt/2Xpa3lO

Watch NASA coverage of SpaceX astronaut test flight

On May 27, 2020, for the first time since 2011, NASA’s SpaceX Demo-2 mission will return U.S. human spaceflight to the International Space Station from U.S. soil – on an American rocket and spacecraft – with astronauts Robert Behnken and Douglas Hurley. Image via NASA.

Originally published by NASA

NASA will provide coverage of today’s prelaunch and launch activities for the agency’s SpaceX Demo-2 test flight with NASA astronauts Robert Behnken and Douglas Hurley to the International Space Station. These activities are a part of NASA’s Commercial Crew Program, which is working with the U.S. aerospace industry to launch astronauts on American rockets and spacecraft from American soil for the first time since 2011. NASA and SpaceX are targeting 4:33 p.m. EDT Wednesday, May 27, for the launch of the Demo-2 flight. It’ll also be the first time a commercially built and operated American rocket and spacecraft will carry humans to the space station. The launch, as well as other activities leading up to the launch, will air live on NASA Television and the agency’s website.

The SpaceX Crew Dragon spacecraft will launch on a Falcon 9 rocket from historic Launch Complex 39A at NASA’s Kennedy Space Center in Florida. The Crew Dragon is scheduled to dock to the space station at 11:29 a.m. Thursday, May 28.

This will be SpaceX’s final test flight of NASA’s Commercial Crew Program and will provide data on the performance of the Falcon 9 rocket, Crew Dragon spacecraft and ground systems, as well as in-orbit, docking and landing operations.

The test flight also will provide valuable data toward NASA certifying SpaceX’s crew transportation system for regular flights carrying astronauts to and from the space station. SpaceX currently is readying the hardware for the first rotational mission, which would happen after data from this mission is reviewed for NASA’s certification.

NASA’s SpaceX Demo-2 coverage is as follows. All times are EDT [UTC -4; how to translate UTC to your time] and will be updated online:

Wednesday, May 27

12:15 p.m. – NASA TV launch coverage begins for the 4:32 p.m. liftoff

6 p.m. – Administrator postlaunch news conference at Kennedy, with the following representatives:

NASA Administrator Jim Bridenstine
Kathy Lueders, manager, NASA’s Commercial Crew Program
A SpaceX representative
Kirk Shireman, manager, International Space Station Program
An Astronaut Office representative

A media phone bridge will be available for this event.

Thursday, May 28

11:29 a.m. – Docking (NASA Television will have continuous coverage from launch to docking)

The goal of NASA’s Commercial Crew Program is safe, reliable and cost-effective transportation to and from the International Space Station. This could allow for additional research time and increase the opportunity for discovery aboard humanity’s testbed for exploration, including helping us prepare for human exploration of the moon and Mars.

For launch countdown coverage, NASA’s launch blog, and more information about the mission, visit:

https://www.nasa.gov/commercialcrew

Bottom line: Watch the Demo-2 mission launch on May 27, 2020. It’ll carry astronauts to the International Space station, the first launch of astronauts on American rockets and spacecraft, from American soil, since 2011. The launch, as well as other activities leading up to the launch, will air live on NASA Television and the agency’s website.

Robert Behnken’s Twitter feed

Douglas Hurley’s Twitter feed

Via NASA

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

On May 27, 2020, for the first time since 2011, NASA’s SpaceX Demo-2 mission will return U.S. human spaceflight to the International Space Station from U.S. soil – on an American rocket and spacecraft – with astronauts Robert Behnken and Douglas Hurley. Image via NASA.

Originally published by NASA

NASA will provide coverage of today’s prelaunch and launch activities for the agency’s SpaceX Demo-2 test flight with NASA astronauts Robert Behnken and Douglas Hurley to the International Space Station. These activities are a part of NASA’s Commercial Crew Program, which is working with the U.S. aerospace industry to launch astronauts on American rockets and spacecraft from American soil for the first time since 2011. NASA and SpaceX are targeting 4:33 p.m. EDT Wednesday, May 27, for the launch of the Demo-2 flight. It’ll also be the first time a commercially built and operated American rocket and spacecraft will carry humans to the space station. The launch, as well as other activities leading up to the launch, will air live on NASA Television and the agency’s website.

The SpaceX Crew Dragon spacecraft will launch on a Falcon 9 rocket from historic Launch Complex 39A at NASA’s Kennedy Space Center in Florida. The Crew Dragon is scheduled to dock to the space station at 11:29 a.m. Thursday, May 28.

This will be SpaceX’s final test flight of NASA’s Commercial Crew Program and will provide data on the performance of the Falcon 9 rocket, Crew Dragon spacecraft and ground systems, as well as in-orbit, docking and landing operations.

The test flight also will provide valuable data toward NASA certifying SpaceX’s crew transportation system for regular flights carrying astronauts to and from the space station. SpaceX currently is readying the hardware for the first rotational mission, which would happen after data from this mission is reviewed for NASA’s certification.

NASA’s SpaceX Demo-2 coverage is as follows. All times are EDT [UTC -4; how to translate UTC to your time] and will be updated online:

Wednesday, May 27

12:15 p.m. – NASA TV launch coverage begins for the 4:32 p.m. liftoff

6 p.m. – Administrator postlaunch news conference at Kennedy, with the following representatives:

NASA Administrator Jim Bridenstine
Kathy Lueders, manager, NASA’s Commercial Crew Program
A SpaceX representative
Kirk Shireman, manager, International Space Station Program
An Astronaut Office representative

A media phone bridge will be available for this event.

Thursday, May 28

11:29 a.m. – Docking (NASA Television will have continuous coverage from launch to docking)

The goal of NASA’s Commercial Crew Program is safe, reliable and cost-effective transportation to and from the International Space Station. This could allow for additional research time and increase the opportunity for discovery aboard humanity’s testbed for exploration, including helping us prepare for human exploration of the moon and Mars.

For launch countdown coverage, NASA’s launch blog, and more information about the mission, visit:

https://www.nasa.gov/commercialcrew

Bottom line: Watch the Demo-2 mission launch on May 27, 2020. It’ll carry astronauts to the International Space station, the first launch of astronauts on American rockets and spacecraft, from American soil, since 2011. The launch, as well as other activities leading up to the launch, will air live on NASA Television and the agency’s website.

Robert Behnken’s Twitter feed

Douglas Hurley’s Twitter feed

Via NASA

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

ALMA spots the twinkling heart of our Milky Way

This image shows the flickering or twinkling heart of our Milky Way galaxy. These dots represent measurements of changes in the intensity of emission, at millimeter wavelengths, from the galaxy’s center. The changes were detected by the ALMA telescope in Chile. The colossal black hole at the galaxy’s center is called Sagittarius A* (pronounced Sagittarius A-Star). For a more detailed version of this graph, see below. Image via Y. Iwata et al./ Keio University/ ALMA.

Astronomers using the ALMA telescope in Chile’s Atacama Desert have now tracked quasi-periodic (irregular) flickers in millimeter-waves emanating from the center of our Milky Way galaxy.

They’ve interpreted the flickering as coming from spots of radio emission in a disk encircling the 4-million-solar-mass black hole at our Milky Way’s heart. The black hole is known as Sagittarius (Sgr) A* (pronounced Sagittarius A-Star). The radio spots appear to orbit the black hole closer than Mercury orbits our sun. Keio University graduate student Yuhei Iwata is lead author of the paper, published April 2, 2020, in the peer-reviewed Astrophysical Journal Letters. Iwata said in a May 22 statement from ALMA:

It has been known that Sgr A* sometimes flares up in millimeter wavelength. This time, using ALMA, we obtained high-quality data of radio-wave intensity variation of Sgr A* for 10 days, 70 minutes per day. Then we found two trends: quasi-periodic variations with a typical time scale of 30 minutes and hour-long slow variations.

The result is interesting not only because it’s a direct measurement of the flickering, or twinkling, radiation at the heart of the Milky Way, but also because, the astronomers believe, the observations are linked to the way space-time behaves in the extreme gravity environment surrounding a black hole.

Here’s the more detailed verson of the chart at the top of this post. It shows the variation of millimeter emission from Sgr A* detected with the ALMA telescope. The different color dots show the flux at different frequencies (blue: 234.0 GHz, green: 219.5 GHz, red: 217.5 GHz). Variations with about a 30-minute period are seen in the diagram. Image via Y. Iwata et al./ Keio University/ ALMA.

Astronomers have believed for some time that a supermassive black hole – with a mass of 4 million of our suns – is located at the center of Sgr A*. Their statement said:

Flares of Sgr A* have been observed not only in millimeter wavelength, but also in infrared light and X-ray. However, the variations detected with ALMA are much smaller than the ones previously detected, and it is possible that these levels of small variations always occur in Sgr A*.

Most people know that black holes themselves can’t “shine” in any way. By definition, a black hole’s gravity is so immense that nothing, not even light, can escape it. Instead, these astronomers said:

… the source of the emission is the scorching gaseous disk around the black hole. The gas around the black hole does not go straight to the gravitational well, but it rotates around the black hole to form an accretion disk.

In the inner part of this disk, they said, where the emissions are thought to arise, the effect of the black hole’s powerful gravity would be extreme. There, any emissions that arise would be subject not only to the processes of ordinary physics, but also to strange effects described by Einsein’s theory of special relativity. The theory of special relativity explains how space and time are linked for objects that are moving at a consistent speed – and a high speed – in a straight line. It would explain, for example, how space and time may be linked for milllimeter waves emanating from a disk in the vicinity of a supermassive black hole. Tomoharu Oka, a professor at Keio University, said:

This emission could be related with some exotic phenomena occurring at the very vicinity of the supermassive black hole.

The astronomers’ scenario is as follows:

Hot spots are sporadically formed in the disk and circle around the black hole, emitting strong millimeter waves. According to Einstein’s special relativity theory, the emission is largely amplified when the source is moving toward the observer with a speed comparable to that of light. The rotation speed of the inner edge of the accretion disk is quite large, so this extraordinary effect arises. The astronomers believe that this is the origin of the short-term variation of the millimeter emission from Sgr A*.

The team supposes that the variation might affect the (failed) effort to make an image of the Milky Way’s supermassive black hole with the Event Horizon Telescope. A group of astronomers worked hard to try to produce this image; they kept saying they believed they were just months away from capturing it. But they never did capture this image. Instead – to much fanfare in April 2019 – they acquired the first-ever image of a supermassive black hole in the distant galaxy M87. Oka said:

In general, the faster the movement is, the more difficult it is to take a photo of the object. Instead, the variation of the emission itself provides compelling insight for the gas motion.

The astronomers said they hope to implement a long-term monitoring campaign of the Milky Way’s supermassive black hole, with the ALMA telescope, in order to witness the moment when gas from the accretion disk is absorbed by the black hole.

Artist’s concept of the gaseous disk around the supermassive black hole. Hot spots circling around the black hole could produce the quasi-periodic millimeter emission detected with ALMA. Image via Keio University/ ALMA.

Bottom line: Astronomers used the ALMA telescope in Chile to observe irregular flickers in millimeter-waves from the center of our Milky Way galaxy: the twinkling heart of the galaxy.

Source: Time Variations in the Flux Density of Sgr A* at 230 GHz Detected with ALMA

Via ALMA

from EarthSky https://ift.tt/3gkli85

This image shows the flickering or twinkling heart of our Milky Way galaxy. These dots represent measurements of changes in the intensity of emission, at millimeter wavelengths, from the galaxy’s center. The changes were detected by the ALMA telescope in Chile. The colossal black hole at the galaxy’s center is called Sagittarius A* (pronounced Sagittarius A-Star). For a more detailed version of this graph, see below. Image via Y. Iwata et al./ Keio University/ ALMA.

Astronomers using the ALMA telescope in Chile’s Atacama Desert have now tracked quasi-periodic (irregular) flickers in millimeter-waves emanating from the center of our Milky Way galaxy.

They’ve interpreted the flickering as coming from spots of radio emission in a disk encircling the 4-million-solar-mass black hole at our Milky Way’s heart. The black hole is known as Sagittarius (Sgr) A* (pronounced Sagittarius A-Star). The radio spots appear to orbit the black hole closer than Mercury orbits our sun. Keio University graduate student Yuhei Iwata is lead author of the paper, published April 2, 2020, in the peer-reviewed Astrophysical Journal Letters. Iwata said in a May 22 statement from ALMA:

It has been known that Sgr A* sometimes flares up in millimeter wavelength. This time, using ALMA, we obtained high-quality data of radio-wave intensity variation of Sgr A* for 10 days, 70 minutes per day. Then we found two trends: quasi-periodic variations with a typical time scale of 30 minutes and hour-long slow variations.

The result is interesting not only because it’s a direct measurement of the flickering, or twinkling, radiation at the heart of the Milky Way, but also because, the astronomers believe, the observations are linked to the way space-time behaves in the extreme gravity environment surrounding a black hole.

Here’s the more detailed verson of the chart at the top of this post. It shows the variation of millimeter emission from Sgr A* detected with the ALMA telescope. The different color dots show the flux at different frequencies (blue: 234.0 GHz, green: 219.5 GHz, red: 217.5 GHz). Variations with about a 30-minute period are seen in the diagram. Image via Y. Iwata et al./ Keio University/ ALMA.

Astronomers have believed for some time that a supermassive black hole – with a mass of 4 million of our suns – is located at the center of Sgr A*. Their statement said:

Flares of Sgr A* have been observed not only in millimeter wavelength, but also in infrared light and X-ray. However, the variations detected with ALMA are much smaller than the ones previously detected, and it is possible that these levels of small variations always occur in Sgr A*.

Most people know that black holes themselves can’t “shine” in any way. By definition, a black hole’s gravity is so immense that nothing, not even light, can escape it. Instead, these astronomers said:

… the source of the emission is the scorching gaseous disk around the black hole. The gas around the black hole does not go straight to the gravitational well, but it rotates around the black hole to form an accretion disk.

In the inner part of this disk, they said, where the emissions are thought to arise, the effect of the black hole’s powerful gravity would be extreme. There, any emissions that arise would be subject not only to the processes of ordinary physics, but also to strange effects described by Einsein’s theory of special relativity. The theory of special relativity explains how space and time are linked for objects that are moving at a consistent speed – and a high speed – in a straight line. It would explain, for example, how space and time may be linked for milllimeter waves emanating from a disk in the vicinity of a supermassive black hole. Tomoharu Oka, a professor at Keio University, said:

This emission could be related with some exotic phenomena occurring at the very vicinity of the supermassive black hole.

The astronomers’ scenario is as follows:

Hot spots are sporadically formed in the disk and circle around the black hole, emitting strong millimeter waves. According to Einstein’s special relativity theory, the emission is largely amplified when the source is moving toward the observer with a speed comparable to that of light. The rotation speed of the inner edge of the accretion disk is quite large, so this extraordinary effect arises. The astronomers believe that this is the origin of the short-term variation of the millimeter emission from Sgr A*.

The team supposes that the variation might affect the (failed) effort to make an image of the Milky Way’s supermassive black hole with the Event Horizon Telescope. A group of astronomers worked hard to try to produce this image; they kept saying they believed they were just months away from capturing it. But they never did capture this image. Instead – to much fanfare in April 2019 – they acquired the first-ever image of a supermassive black hole in the distant galaxy M87. Oka said:

In general, the faster the movement is, the more difficult it is to take a photo of the object. Instead, the variation of the emission itself provides compelling insight for the gas motion.

The astronomers said they hope to implement a long-term monitoring campaign of the Milky Way’s supermassive black hole, with the ALMA telescope, in order to witness the moment when gas from the accretion disk is absorbed by the black hole.

Artist’s concept of the gaseous disk around the supermassive black hole. Hot spots circling around the black hole could produce the quasi-periodic millimeter emission detected with ALMA. Image via Keio University/ ALMA.

Bottom line: Astronomers used the ALMA telescope in Chile to observe irregular flickers in millimeter-waves from the center of our Milky Way galaxy: the twinkling heart of the galaxy.

Source: Time Variations in the Flux Density of Sgr A* at 230 GHz Detected with ALMA

Via ALMA

from EarthSky https://ift.tt/3gkli85

The young moon, Venus, Mercury and a celebration

View at EarthSky Community Photos. | Yusha Alfa in Malang, East Java, Indonesia, captured these fireworks on May 24, 2020 against the backdrop of the young moon, with 2 bright planets – Mercury and Venus – visible as well. Eid al-Fitr is the Islamic holiday that marks the end of the Ramadan fast. Yusha wrote: “Hi EarthSky, last evening I captured brilliant conjunction young moon (2% illuminated), Mercury and Venus. It was an amazing view. Bonus fireworks passed the crescent that people celebrate Eid Mubarak.” Thank you, Yusha!

View larger at EarthSky Community Photos. | João Pedro Bessa caught the young moon, Mercury, Venus, and a star in the twilight sky above Praia de Barra, Aveiro, Portugal. João wrote: “Taken at the Praia da Barra’s beach, not far away of the seaport entrance, tonight there was a Venus (bottom), Mercury (middle) and the moon with Elnath/Beta Tauri (the one in the same line of Venus and altitude of the moon) also being invited.”

View larger at EarthSky Community Photos. | Marcella Giulia Pace caught the very young moon from near Modica, Sicily, on May 23, 2020. Marcella wrote: “These photos of the thin crescent moon were taken without the use of computerized chasers or automatic finders. I took a very young moon with extreme difficulties. I didn’t see the moon with the unaided eye, not even on the camera screen. I knew however that, at that moment, he was passing in front of my goal. I realized that I had shot it by opening the raw file on the PC and increasing the contrast. The scythe at sunset, however, I saw it with the eye.” Marcella also put together a video of the scene. Thank you, Marcella!

Bottom line: Photos of the May 2020 young moon near the bright planets Venus and Mercury.

from EarthSky https://ift.tt/3gpJt4H

View at EarthSky Community Photos. | Yusha Alfa in Malang, East Java, Indonesia, captured these fireworks on May 24, 2020 against the backdrop of the young moon, with 2 bright planets – Mercury and Venus – visible as well. Eid al-Fitr is the Islamic holiday that marks the end of the Ramadan fast. Yusha wrote: “Hi EarthSky, last evening I captured brilliant conjunction young moon (2% illuminated), Mercury and Venus. It was an amazing view. Bonus fireworks passed the crescent that people celebrate Eid Mubarak.” Thank you, Yusha!

View larger at EarthSky Community Photos. | João Pedro Bessa caught the young moon, Mercury, Venus, and a star in the twilight sky above Praia de Barra, Aveiro, Portugal. João wrote: “Taken at the Praia da Barra’s beach, not far away of the seaport entrance, tonight there was a Venus (bottom), Mercury (middle) and the moon with Elnath/Beta Tauri (the one in the same line of Venus and altitude of the moon) also being invited.”

View larger at EarthSky Community Photos. | Marcella Giulia Pace caught the very young moon from near Modica, Sicily, on May 23, 2020. Marcella wrote: “These photos of the thin crescent moon were taken without the use of computerized chasers or automatic finders. I took a very young moon with extreme difficulties. I didn’t see the moon with the unaided eye, not even on the camera screen. I knew however that, at that moment, he was passing in front of my goal. I realized that I had shot it by opening the raw file on the PC and increasing the contrast. The scythe at sunset, however, I saw it with the eye.” Marcella also put together a video of the scene. Thank you, Marcella!

Bottom line: Photos of the May 2020 young moon near the bright planets Venus and Mercury.

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Moon, in Gemini, points to Mercury and Venus

As darkness falls on May 26, 2020, the moon lies in front of the constellation Gemini the Twins. The lit side of the waxing crescent moon points right at the planets Mercury and Venus. Will you see both planets as shown on our chart above? Maybe. On the other hand, by the time that Mercury pierces the evening twilight, Venus might have already followed the sun beneath the western horizon. Day by day now, Venus is setting closer to the time of sundown. It’ll soon fade from view in the evening sky, as it prepares to pass between us and the sun on June 3.

You can likely see both planets (although maybe not at the same time) with your eye alone. Binoculars always come in handy when searching for objects near the rising or setting sun. Find out when Mercury and Venus set in your sky via TimeandDate or Old Farmer’s Almanac.

As for Gemini’s two brightest stars – Castor and Pollux, representing the starry eyes of the Gemini Twins – they should be fairly easy to see tonight, as both stars stay out past nightfall.

Spotting Mercury will be more of a challenge, especially from southerly latitudes in the Southern Hemisphere. Mercury does not stay out till after dark, but may be glimpsed near the sunset point on the horizon as dusk is giving way to darkness. Mercury follows the sun beneath the horizon about 1 /3/4 hours after sunset at mid-northern latitudes, 1 1/2 hours after sunset at the Earth’s equator, and 1 1/4 hours after sunset at temperate latitudes in the Southern Hemisphere.

Live in the Untied States or Canada? Find out Mercury’s setting time for your sky at Old Farmer’s Almanac.

For virtually anyplace worldwide, you can find out Mercury’s setting time at TimeandDate.

Mercury is as bright as a 1st-magnitude star, but its luster may be tarnished by the glow of evening twilight. If the eye alone doesn’t do the trick, Binoculars help out immensely in any Mercury quest. Remember to use the moon as your arrow in the sky, its lit side pointing directly at Mercury. Gaze in the vicinity of the horizon, starting, perhaps, 3/4 hour after sunset.

By the way, Mercury and the sun are both in front of the constellation Taurus the Bull right now. Mercury passes out of the constellation Taurus and into the constellation Gemini on May 28, 2020. The sun won’t meet up with the constellation Gemini until June 21, 2020.

Want to know which constellation of the zodiac now backdrops the sun? Click on Heavens-Above Sun

On or near May 26, 2020, the moon shines to the south of the Gemini stars, Castor and Pollux. The bright star on the other side of the moon is Procyon, the brightest star in the constellation Canis Minor the Little Dog.

However, you might not catch Procyon from northerly latitudes. From mid-northern latitudes, like those in the Untied States, Procyon hovers over the western horizon at dusk/nightfall, and sinks below the horizon shortly thereafter.

By May 27, 2020, the moon will have passed out of the constellation Gemini and into the constellation Cancer the Crab, one of the faintest constellations of the zodiac.

To know which constellation of the zodiac lies behind the moon, click on Heavens-Above Moon.

Every month, as the moon makes its monthly rounds in front of the constellations of the zodiac, it always passes to the north of Procyon and to the south of the Gemini stars, Castor and Pollux.

Bottom line: On May 26, 2020, the lit side of the waxing crescent moon serves as your arrow in the sky, pointing right at the planets Mercury and Venus. Venus is much brighter, but also lower in the sunset sky. Mercury is fainter, but higher up in the sky after sunset. Will you see them at the same time? Look and see.

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

As darkness falls on May 26, 2020, the moon lies in front of the constellation Gemini the Twins. The lit side of the waxing crescent moon points right at the planets Mercury and Venus. Will you see both planets as shown on our chart above? Maybe. On the other hand, by the time that Mercury pierces the evening twilight, Venus might have already followed the sun beneath the western horizon. Day by day now, Venus is setting closer to the time of sundown. It’ll soon fade from view in the evening sky, as it prepares to pass between us and the sun on June 3.

You can likely see both planets (although maybe not at the same time) with your eye alone. Binoculars always come in handy when searching for objects near the rising or setting sun. Find out when Mercury and Venus set in your sky via TimeandDate or Old Farmer’s Almanac.

As for Gemini’s two brightest stars – Castor and Pollux, representing the starry eyes of the Gemini Twins – they should be fairly easy to see tonight, as both stars stay out past nightfall.

Spotting Mercury will be more of a challenge, especially from southerly latitudes in the Southern Hemisphere. Mercury does not stay out till after dark, but may be glimpsed near the sunset point on the horizon as dusk is giving way to darkness. Mercury follows the sun beneath the horizon about 1 /3/4 hours after sunset at mid-northern latitudes, 1 1/2 hours after sunset at the Earth’s equator, and 1 1/4 hours after sunset at temperate latitudes in the Southern Hemisphere.

Live in the Untied States or Canada? Find out Mercury’s setting time for your sky at Old Farmer’s Almanac.

For virtually anyplace worldwide, you can find out Mercury’s setting time at TimeandDate.

Mercury is as bright as a 1st-magnitude star, but its luster may be tarnished by the glow of evening twilight. If the eye alone doesn’t do the trick, Binoculars help out immensely in any Mercury quest. Remember to use the moon as your arrow in the sky, its lit side pointing directly at Mercury. Gaze in the vicinity of the horizon, starting, perhaps, 3/4 hour after sunset.

By the way, Mercury and the sun are both in front of the constellation Taurus the Bull right now. Mercury passes out of the constellation Taurus and into the constellation Gemini on May 28, 2020. The sun won’t meet up with the constellation Gemini until June 21, 2020.

Want to know which constellation of the zodiac now backdrops the sun? Click on Heavens-Above Sun

On or near May 26, 2020, the moon shines to the south of the Gemini stars, Castor and Pollux. The bright star on the other side of the moon is Procyon, the brightest star in the constellation Canis Minor the Little Dog.

However, you might not catch Procyon from northerly latitudes. From mid-northern latitudes, like those in the Untied States, Procyon hovers over the western horizon at dusk/nightfall, and sinks below the horizon shortly thereafter.

By May 27, 2020, the moon will have passed out of the constellation Gemini and into the constellation Cancer the Crab, one of the faintest constellations of the zodiac.

To know which constellation of the zodiac lies behind the moon, click on Heavens-Above Moon.

Every month, as the moon makes its monthly rounds in front of the constellations of the zodiac, it always passes to the north of Procyon and to the south of the Gemini stars, Castor and Pollux.

Bottom line: On May 26, 2020, the lit side of the waxing crescent moon serves as your arrow in the sky, pointing right at the planets Mercury and Venus. Venus is much brighter, but also lower in the sunset sky. Mercury is fainter, but higher up in the sky after sunset. Will you see them at the same time? Look and see.

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

What is an eclipse season?

View larger. | EarthSky community member Beverley Sinclair captured this beautiful view of a total solar eclipse outside Charleston, South Carolina, on August 21, 2017, and wrote: “The skies were very cloudy leading up to totality but, miraculously, slowly cleared as totality approached. This photo shows the diamond ring and Bailey’s beads.” Thank you, Beverley!

An eclipse season is a 35-day period during which it’s possible for an eclipse to take place. There are four to seven eclipses every calendar year. Typically, there are two eclipse seasons. They recur in cycles of 173.3 days (somewhat shy of six calendar months). Each eclipse season has two or three eclipses. In some years, it’s possible to have a third eclipse season straddling into the previous or following year; that’s how we get to seven eclipses in some years.

We started 2020 in the midst of an eclipse season. There’d been a solar eclipse on December 26, 2019, and there was a lunar eclipse on January 10, 2020.

The next eclipse season starts June 5, 2020. The eclipse season of June and July 2020 will feature three eclipses: a lunar eclipse on June 5-6, a solar eclipse on June 21, and the third eclipse of that eclipse season, a lunar eclipse, on July 4-5. That eclipse season – June and July 2020 – will be the last eclipse season with three eclipses until the year 2029.

We’ll also end 2020 with an eclipse season: a lunar eclipse on November 29-30 and a solar eclipse on December 14.

Here are some words you need to know to understand eclipse seasons: lunar nodes and ecliptic. The ecliptic is the plane of the Earth’s orbit around the sun. A lunar node is the point where, in its monthly orbit of Earth, the moon’s orbit intersects that plane. An eclipse season is when – from Earth’s perspective – the sun is close enough to a lunar node to allow an eclipse to take place. If the sun is close to a lunar node at full moon, we see a lunar eclipse. If the sun is close to a lunar node at new moon, we see a solar eclipse.

To put it another way, if the moon turns new or full in close concert with the moon’s crossing of one of its nodes, then an eclipse is not only possible – but inevitable.

Lunar nodes are where the moon’s orbit cuts through the ecliptic, or Earth-sun plane. When these nodes point directly at the sun, it marks the midpoint of an approximate 35-day eclipse season. The middle of an eclipse season occurred on December 30, 2019. The middle of an eclipse season will occur on June 20, 2020. Image via Go Science Go.

Given that the lunar month (period of time between successive new moons or successive full moons) is about 29.5 days long, a minimum of two eclipses (one solar and one lunar, in either order) happens in one eclipse season. A maximum of three eclipses is possible (either lunar/solar/lunar, or solar/lunar/solar), though the first eclipse of the eclipse season has to come quite early to allow for a third eclipse near the end.

If there are seven eclipses in one calendar year, there are a few possibilities. The first one belongs to an eclipse season that started in the previous year – and/or the seventh eclipse belongs to an eclipse season that ends in the following year. It’s rare for seven eclipses to occur in one calendar year, however. It last happened in the year 1982, and will next occur in the year 2038.

View at EarthSky Community Photos. | Progression into and out of the annular eclipse on December 26, 2019, from Tumon Bay, Guam. Eliot Herman reported: “It was a beautiful day in Guam to observe the eclipse mostly clear blue skies with a little marine haze on the coast. These images were captured with a Questar telescope and a Nikon D850 camera using a Baader solar filter.” Thank you, Eliot!

Any lunar eclipse that comes early, or late, in an eclipse season finds the full moon missing the Earth’s umbra (inner dark shadow), and passing through the penumbra (outer faint shadow) instead.

A solar eclipse can happen only at new moon. A lunar eclipse can happen only at full moon. Additionally – for an eclipse to occur – the new moon or full moon has to take place within an eclipse season. Otherwise, the new moon passes too far north, or south, of the sun for a solar eclipse to take place, and the full moon sweeps too far north, or south, of the Earth’s shadow for a lunar eclipse to take place.

Eclipses are all about alignments. In a solar eclipse, the sun, moon and Earth line up, with the moon in the middle. Image via NASA.

In a lunar eclipse, the sun, Earth and moon line up, with the Earth in the middle. Image via NASA.

Why do we have eclipse seasons?

There are many cycles in the heavens. An eclipse season is just one of these many celestial cycles.

Consider that if the moon orbited Earth on the same plane that the Earth orbits the sun, then we’d have a solar eclipse at every new moon, and a lunar eclipse at every full moon.

But – in reality – the moon’s orbit is inclined by 5 degrees to the ecliptic (Earth’s orbital plane), so most of the time the new moon or full moon swings too far north, or south, of the ecliptic for an eclipse to take place. For instance, in the year 2020, we will have 12 new moons and 13 full moons, but only 2 solar eclipses and 4 lunar eclipses (all of the lunar eclipses in 2020, unfortunately, will be faint and hard-to-see penumbral lunar eclipses).

In the year 2020, there are 12 new moons and 13 full moons. A = annular solar eclipse, T = total solar eclipse, and n = penumbral lunar elcipse. Moon phases via Astropixels.

Twice every month, as the moon circles Earth in its orbit, the moon crosses the ecliptic (Earth’s orbital plane) at points called nodes. If the moon is going from south to north, it’s called the moon’s ascending node, and if the moon is moving from north to south, it’s called the moon’s descending node. The moon was last at its descending node on December 26, 2019, and will reach its ascending node on January 9, 2020.

Read more: Node passages of the Moon: 2001 to 2100

Whenever the lunar nodes point directly at the sun, that momentous event marks the middle of the eclipse season. The alignment of the moon, sun and Earth is most exact when an eclipse happens at the middle of an eclipse season, and the least so when an eclipse occurs at the start, or the end, of an eclipse season. Any lunar eclipse happening early or late in the eclipse season presents a penumbral lunar eclipse, whereas any solar eclipse happening early or late in the eclipse season features a skimpy partial eclipse of the sun.

This year, 2020, the middles of the eclipse seasons fall on June 20, 2020, and December 11, 2020.

Middle of eclipse season: June 20, 2020
First eclipse (lunar): June 5, 2020
Second eclipse (solar): June 21, 2020
Third eclipse (lunar): July 5, 2020

Middle of eclipse season: December 11, 2020
First eclipse (lunar): November 30, 2020
Second eclipse (solar): December 14, 2020

The plane of the moon’s orbit is inclined at 5 degrees to the plane of Earth’s orbit around the sun (the ecliptic). In this diagram, however, the ecliptic is portrayed as the sun’s apparent annual path in front of the constellations of the zodiac. The moon’s orbit intersects the ecliptic at two points called nodes (labeled here as N1 and N2). It’s the middle of the eclipse season whenever this line of nodes points directly at the sun. In the above diagram, the line of nodes does not point at the sun.

Bottom line: An eclipse season is when – from Earth’s perspective – the sun is close enough to a lunar node to allow an eclipse to take place. If the sun is close to a node at full moon, we see a lunar eclipse. If the sun is close to a node at new moon, we see a solar eclipse. A minimum of two eclipses (one solar and one lunar, in either order) happens in one eclipse season. A maximum of three eclipses is possible (either lunar/solar/lunar, or solar/lunar/solar).

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View larger. | EarthSky community member Beverley Sinclair captured this beautiful view of a total solar eclipse outside Charleston, South Carolina, on August 21, 2017, and wrote: “The skies were very cloudy leading up to totality but, miraculously, slowly cleared as totality approached. This photo shows the diamond ring and Bailey’s beads.” Thank you, Beverley!

An eclipse season is a 35-day period during which it’s possible for an eclipse to take place. There are four to seven eclipses every calendar year. Typically, there are two eclipse seasons. They recur in cycles of 173.3 days (somewhat shy of six calendar months). Each eclipse season has two or three eclipses. In some years, it’s possible to have a third eclipse season straddling into the previous or following year; that’s how we get to seven eclipses in some years.

We started 2020 in the midst of an eclipse season. There’d been a solar eclipse on December 26, 2019, and there was a lunar eclipse on January 10, 2020.

The next eclipse season starts June 5, 2020. The eclipse season of June and July 2020 will feature three eclipses: a lunar eclipse on June 5-6, a solar eclipse on June 21, and the third eclipse of that eclipse season, a lunar eclipse, on July 4-5. That eclipse season – June and July 2020 – will be the last eclipse season with three eclipses until the year 2029.

We’ll also end 2020 with an eclipse season: a lunar eclipse on November 29-30 and a solar eclipse on December 14.

Here are some words you need to know to understand eclipse seasons: lunar nodes and ecliptic. The ecliptic is the plane of the Earth’s orbit around the sun. A lunar node is the point where, in its monthly orbit of Earth, the moon’s orbit intersects that plane. An eclipse season is when – from Earth’s perspective – the sun is close enough to a lunar node to allow an eclipse to take place. If the sun is close to a lunar node at full moon, we see a lunar eclipse. If the sun is close to a lunar node at new moon, we see a solar eclipse.

To put it another way, if the moon turns new or full in close concert with the moon’s crossing of one of its nodes, then an eclipse is not only possible – but inevitable.

Lunar nodes are where the moon’s orbit cuts through the ecliptic, or Earth-sun plane. When these nodes point directly at the sun, it marks the midpoint of an approximate 35-day eclipse season. The middle of an eclipse season occurred on December 30, 2019. The middle of an eclipse season will occur on June 20, 2020. Image via Go Science Go.

Given that the lunar month (period of time between successive new moons or successive full moons) is about 29.5 days long, a minimum of two eclipses (one solar and one lunar, in either order) happens in one eclipse season. A maximum of three eclipses is possible (either lunar/solar/lunar, or solar/lunar/solar), though the first eclipse of the eclipse season has to come quite early to allow for a third eclipse near the end.

If there are seven eclipses in one calendar year, there are a few possibilities. The first one belongs to an eclipse season that started in the previous year – and/or the seventh eclipse belongs to an eclipse season that ends in the following year. It’s rare for seven eclipses to occur in one calendar year, however. It last happened in the year 1982, and will next occur in the year 2038.

View at EarthSky Community Photos. | Progression into and out of the annular eclipse on December 26, 2019, from Tumon Bay, Guam. Eliot Herman reported: “It was a beautiful day in Guam to observe the eclipse mostly clear blue skies with a little marine haze on the coast. These images were captured with a Questar telescope and a Nikon D850 camera using a Baader solar filter.” Thank you, Eliot!

Any lunar eclipse that comes early, or late, in an eclipse season finds the full moon missing the Earth’s umbra (inner dark shadow), and passing through the penumbra (outer faint shadow) instead.

A solar eclipse can happen only at new moon. A lunar eclipse can happen only at full moon. Additionally – for an eclipse to occur – the new moon or full moon has to take place within an eclipse season. Otherwise, the new moon passes too far north, or south, of the sun for a solar eclipse to take place, and the full moon sweeps too far north, or south, of the Earth’s shadow for a lunar eclipse to take place.

Eclipses are all about alignments. In a solar eclipse, the sun, moon and Earth line up, with the moon in the middle. Image via NASA.

In a lunar eclipse, the sun, Earth and moon line up, with the Earth in the middle. Image via NASA.

Why do we have eclipse seasons?

There are many cycles in the heavens. An eclipse season is just one of these many celestial cycles.

Consider that if the moon orbited Earth on the same plane that the Earth orbits the sun, then we’d have a solar eclipse at every new moon, and a lunar eclipse at every full moon.

But – in reality – the moon’s orbit is inclined by 5 degrees to the ecliptic (Earth’s orbital plane), so most of the time the new moon or full moon swings too far north, or south, of the ecliptic for an eclipse to take place. For instance, in the year 2020, we will have 12 new moons and 13 full moons, but only 2 solar eclipses and 4 lunar eclipses (all of the lunar eclipses in 2020, unfortunately, will be faint and hard-to-see penumbral lunar eclipses).

In the year 2020, there are 12 new moons and 13 full moons. A = annular solar eclipse, T = total solar eclipse, and n = penumbral lunar elcipse. Moon phases via Astropixels.

Twice every month, as the moon circles Earth in its orbit, the moon crosses the ecliptic (Earth’s orbital plane) at points called nodes. If the moon is going from south to north, it’s called the moon’s ascending node, and if the moon is moving from north to south, it’s called the moon’s descending node. The moon was last at its descending node on December 26, 2019, and will reach its ascending node on January 9, 2020.

Read more: Node passages of the Moon: 2001 to 2100

Whenever the lunar nodes point directly at the sun, that momentous event marks the middle of the eclipse season. The alignment of the moon, sun and Earth is most exact when an eclipse happens at the middle of an eclipse season, and the least so when an eclipse occurs at the start, or the end, of an eclipse season. Any lunar eclipse happening early or late in the eclipse season presents a penumbral lunar eclipse, whereas any solar eclipse happening early or late in the eclipse season features a skimpy partial eclipse of the sun.

This year, 2020, the middles of the eclipse seasons fall on June 20, 2020, and December 11, 2020.

Middle of eclipse season: June 20, 2020
First eclipse (lunar): June 5, 2020
Second eclipse (solar): June 21, 2020
Third eclipse (lunar): July 5, 2020

Middle of eclipse season: December 11, 2020
First eclipse (lunar): November 30, 2020
Second eclipse (solar): December 14, 2020

The plane of the moon’s orbit is inclined at 5 degrees to the plane of Earth’s orbit around the sun (the ecliptic). In this diagram, however, the ecliptic is portrayed as the sun’s apparent annual path in front of the constellations of the zodiac. The moon’s orbit intersects the ecliptic at two points called nodes (labeled here as N1 and N2). It’s the middle of the eclipse season whenever this line of nodes points directly at the sun. In the above diagram, the line of nodes does not point at the sun.

Bottom line: An eclipse season is when – from Earth’s perspective – the sun is close enough to a lunar node to allow an eclipse to take place. If the sun is close to a node at full moon, we see a lunar eclipse. If the sun is close to a node at new moon, we see a solar eclipse. A minimum of two eclipses (one solar and one lunar, in either order) happens in one eclipse season. A maximum of three eclipses is possible (either lunar/solar/lunar, or solar/lunar/solar).

from EarthSky https://ift.tt/39U0YH9