Could dark matter be powering the EMdrive? (Synopsis) [Starts With A Bang]

“…axions are potentially detectable through their weak coupling to electromagnetism…” -Aaron Chou

We know, from hundreds of years of experience with the laws of physics, that momentum is strictly conserved, and therefore a reactionless drive is impossible. What’s not impossible is an engine that has a reaction that’s simply invisible, or otherwise undetectable to us. This has been seen in experiments involving neutrinos, but NASA’s impossible space engine, the EMdrive, offers another possibility: a dark matter reaction.

Image credit: ESO/L. Calçada, of the illustration of the dark matter halo surrounding the luminous disk of our galaxy.

You see, one of the leading candidates for dark matter is the axion, an ultra-light, massive, abundant particle that would couple to microwave photons under the right conditions. While ADMX, the axion dark matter experiment, looks for this coupling in a microwave cavity, it’s come up empty so far. Could the tinkerer who invented the EMdrive have accidentally stumbled upon dark matter instead?

The surface magnetic field of an active EMdrive, during the NASA test. Image credit: NASA Spaceflight forums, via Chris Bergin.

It’s a highly speculative possibility, and it’s far more likely that the EMdrive simply doesn’t work. But this is why we do the experiments in the first place, with more to follow!

from ScienceBlogs http://ift.tt/2fLyhiD

“…axions are potentially detectable through their weak coupling to electromagnetism…” -Aaron Chou

We know, from hundreds of years of experience with the laws of physics, that momentum is strictly conserved, and therefore a reactionless drive is impossible. What’s not impossible is an engine that has a reaction that’s simply invisible, or otherwise undetectable to us. This has been seen in experiments involving neutrinos, but NASA’s impossible space engine, the EMdrive, offers another possibility: a dark matter reaction.

Image credit: ESO/L. Calçada, of the illustration of the dark matter halo surrounding the luminous disk of our galaxy.

You see, one of the leading candidates for dark matter is the axion, an ultra-light, massive, abundant particle that would couple to microwave photons under the right conditions. While ADMX, the axion dark matter experiment, looks for this coupling in a microwave cavity, it’s come up empty so far. Could the tinkerer who invented the EMdrive have accidentally stumbled upon dark matter instead?

The surface magnetic field of an active EMdrive, during the NASA test. Image credit: NASA Spaceflight forums, via Chris Bergin.

It’s a highly speculative possibility, and it’s far more likely that the EMdrive simply doesn’t work. But this is why we do the experiments in the first place, with more to follow!

from ScienceBlogs http://ift.tt/2fLyhiD

What would Earth be like with no moon?

Most moons in our solar system are tiny relative to the planets they orbit. These planets wouldn’t miss a moon or two if one got knocked out of orbit. But Earth’s moon is relatively large. So Earth without its large nearby moon would be a very different world indeed.

Imagine … no solar or lunar eclipses.

No calendars based on a system of months. The word month, after all, stems from a word that means moon. That’s because many calendars are based on the changing phases of the moon.

With no moon, there’d be no nearby world for astronauts to visit. We might never have begun to venture out into the solar system.

The moon and sun together cause the tides. If we’d never had a moon, we’d still have tides, but they wouldn’t be as strong.

What’s more, the moon has a place in human culture. Imagine no romantic moonlight walks – no concept of moon madness, or lunacy.

But the biggest change – for us humans and for other earthly life – would be in the length of Earth’s day. Without a moon, Earth would spin faster. Our day would be shorter. Why?

It’s because, billions of years ago when Earth was young, our planet spun around on its axis much faster. Our world’s cycle of day and night was less than 10 hours long. The ebb and flow of the tides are what put the brakes on Earth’s spin. So – if you’re imagining Earth with no moon – you have to imagine our day on Earth much shorter than our present-day 24 hours.

Selected moons of the solar system, with the Earth for scale. Notice that the moon is pretty big relative to Earth. But Pluto and its moon are even closer in size. Image via NASA.

Bottom line: Some differences on Earth today, if Earth didn’t have a moon.

from EarthSky http://ift.tt/2gx5zDr

Most moons in our solar system are tiny relative to the planets they orbit. These planets wouldn’t miss a moon or two if one got knocked out of orbit. But Earth’s moon is relatively large. So Earth without its large nearby moon would be a very different world indeed.

Imagine … no solar or lunar eclipses.

No calendars based on a system of months. The word month, after all, stems from a word that means moon. That’s because many calendars are based on the changing phases of the moon.

With no moon, there’d be no nearby world for astronauts to visit. We might never have begun to venture out into the solar system.

The moon and sun together cause the tides. If we’d never had a moon, we’d still have tides, but they wouldn’t be as strong.

What’s more, the moon has a place in human culture. Imagine no romantic moonlight walks – no concept of moon madness, or lunacy.

But the biggest change – for us humans and for other earthly life – would be in the length of Earth’s day. Without a moon, Earth would spin faster. Our day would be shorter. Why?

It’s because, billions of years ago when Earth was young, our planet spun around on its axis much faster. Our world’s cycle of day and night was less than 10 hours long. The ebb and flow of the tides are what put the brakes on Earth’s spin. So – if you’re imagining Earth with no moon – you have to imagine our day on Earth much shorter than our present-day 24 hours.

Selected moons of the solar system, with the Earth for scale. Notice that the moon is pretty big relative to Earth. But Pluto and its moon are even closer in size. Image via NASA.

Bottom line: Some differences on Earth today, if Earth didn’t have a moon.

from EarthSky http://ift.tt/2gx5zDr

2016-17 winter outlook for US

NOAA’s Climate Prediction Center issued this U.S. 2016-17 winter weather outlook for the United States in late October.

NOAA forecasters said La Niña is expected to influence winter conditions this year, predicting the climate phenomenon is likely to develop in late fall or early winter. According to a NOAA statement:

La Niña favors drier, warmer winters in the southern U.S and wetter, cooler conditions in the northern U.S. If La Niña conditions do materialize, forecasters say it should be weak and potentially short-lived.

What is La Niña?

Will your winter look like this? Photo via Rebecca Walker

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

Bottom line: Winter weather outlook for 2016-2017 from NOAA’s Climate Prediction Center.

Read more from NOAA

from EarthSky http://ift.tt/2fQtob3

NOAA’s Climate Prediction Center issued this U.S. 2016-17 winter weather outlook for the United States in late October.

NOAA forecasters said La Niña is expected to influence winter conditions this year, predicting the climate phenomenon is likely to develop in late fall or early winter. According to a NOAA statement:

La Niña favors drier, warmer winters in the southern U.S and wetter, cooler conditions in the northern U.S. If La Niña conditions do materialize, forecasters say it should be weak and potentially short-lived.

What is La Niña?

Will your winter look like this? Photo via Rebecca Walker

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

Bottom line: Winter weather outlook for 2016-2017 from NOAA’s Climate Prediction Center.

Read more from NOAA

from EarthSky http://ift.tt/2fQtob3

Milky Way over Eagle Lake, Maine

Photo by Manish Mamtani.

Manish Mamtani captured this image over Eagle Lake in Acadia National Park, Maine.

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

Photo by Manish Mamtani.

Manish Mamtani captured this image over Eagle Lake in Acadia National Park, Maine.

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

Aced: TGO data relay capability

On 22 November 2016, the NASA radio system on ESA's Trace Gas Orbiter (TGO), which arrived at Mars in October, succeeded in its first test of receiving data transmitted from NASA Mars rovers, both Opportunity and Curiosity. Below we've posted an extract from the JPL web news article with some additional tech details from the TGO mission team at ESOC.

Strengthening the Mars Telecommunications Network credit: NASA/JPL-Caltech/ESA

Here's an extract from the NASA/JPL news article:

NASA Radio on Europe's New Mars Orbiter Aces Relay Test

The transmissions from NASA rovers Opportunity and Curiosity, received by one of the twin Electra radios on the orbiter on Nov. 22, mark a strengthening of the international telecommunications network supporting Mars exploration. The orbiter's main radio for communications with Earth subsequently relayed onward to Earth the data received by Electra.

ESA's ExoMars Trace Gas Orbiter (TGO) carries two Electra radios provided by NASA. This image shows a step in installation and testing of the first of the two radios, inside a clean room at Thales Alenia Space, in Cannes, France, in June 2014. Credit: NASA/JPL-Caltech/ESA/TAS

The European Space Agency's (ESA's) ExoMars/Trace Gas Orbiter reached Mars on Oct. 19, 2016. As planned, its initial orbit shape is highly elliptical, ranging from as far as 60,000 miles (98,000 kilometres) above the surface to less than 200 miles (less than 310 kilometres). Each loop takes 4.2 days to complete.

Frequent use of TGO's relay capability to support Mars rover operations is planned to begin more than a year from now. That's after the orbiter finishes adjusting its orbit to a near-circular path about 250 miles (400 kilometres) above Mars' surface.

"The arrival of ESA's Trace Gas Orbiter at Mars, with its NASA-provided Electra relay payload on board, represents a significant step forward in our Mars relay capabilities," said Chad Edwards, manager of the Mars Relay Network Office within the Mars Exploration Program at NASA's Jet Propulsion Laboratory, Pasadena, California. "In concert with our three existing NASA orbiters and ESA's earlier Mars Express orbiter, we now have a truly international Mars relay network that will greatly increase the amount of data that future Mars landers and rovers can return from the surface of the Red Planet."

The JPL-designed Electra radios include special features for relaying data from a rover or stationary lander to an orbiter passing overhead. Relay of information from Mars-surface craft to Mars orbiters, then from the Mars orbiters to Earth, enables receiving much more data from the surface missions than would be possible with a direct-to-Earth radio link from the rovers or landers.

TGO Flight Director Michel Denis Credit: ESA/J. Mai

"We already have almost 13 years' experience using ESA's Mars Express as an on-call backup for data relay from active Mars rovers, and TGO will greatly expand this to routine science-data relay," said Michel Denis, TGO flight director at ESA's European Space Operations Centre, Darmstadt, Germany. "In 2020, TGO will extend this relay support to ESA's ExoMars rover and the Russian Surface Platform, an important capability together with its science mission that enhances the international data network at Mars."

As an example of Electra capabilities, during a relay session between an Electra on the surface and one on an orbiter, the radios can maximize data volume by actively adjusting the data rate to be slower when the orbiter is near the horizon from the surface robot's perspective, faster when it is overhead.

Access full text here

Here are some tech details on the successful test, contributed by the TGO mission team at ESOC.

Scenes at ESA/ESOC, Darmstadt, Germany, on 19 October 2016 during the arrival of ExoMars. Credit: ESA/J. Mai

TGO's Electra radio system was already put through some initial testing while the spacecraft was enroute to Mars, and was successfully used in the so-called 'Open Loop' recording mode to record signals from Schiaparelli during the test module's separation from TGO and during Schiaparelli's Entry, Descent and Landing on Mars on 19 October.

The purpose of the two tests performed on 22 November was to receive, for the first time, data transmitted from the NASA rovers on the surface of Mars.

• A 'Raw data mode relay session' with the Curiosity vehicle in a 20-minute window between 15:17 - 15:37 UTC at Mars allowed TGO and its Electra system to fetch and relay to Earth 9.9 Mbits of rover data.
• Shortly later, during a 10-minute slot between 16:40-16:50 UTC, a 'Return link session' with MER-B Opportunity succeeded in relaying more than 3.3 Mbits of rover data.

Both tests enabled maintaining a continuous and uninterrupted rover-to-orbiter radio data link that can be used for future relay activities. The two overflights happened outside of real-time visibility from ground stations, and used TGO's prime Electra unit (there is also a back-up unit on board).

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v

On 22 November 2016, the NASA radio system on ESA's Trace Gas Orbiter (TGO), which arrived at Mars in October, succeeded in its first test of receiving data transmitted from NASA Mars rovers, both Opportunity and Curiosity. Below we've posted an extract from the JPL web news article with some additional tech details from the TGO mission team at ESOC.

Strengthening the Mars Telecommunications Network credit: NASA/JPL-Caltech/ESA

Here's an extract from the NASA/JPL news article:

NASA Radio on Europe's New Mars Orbiter Aces Relay Test

The transmissions from NASA rovers Opportunity and Curiosity, received by one of the twin Electra radios on the orbiter on Nov. 22, mark a strengthening of the international telecommunications network supporting Mars exploration. The orbiter's main radio for communications with Earth subsequently relayed onward to Earth the data received by Electra.

ESA's ExoMars Trace Gas Orbiter (TGO) carries two Electra radios provided by NASA. This image shows a step in installation and testing of the first of the two radios, inside a clean room at Thales Alenia Space, in Cannes, France, in June 2014. Credit: NASA/JPL-Caltech/ESA/TAS

The European Space Agency's (ESA's) ExoMars/Trace Gas Orbiter reached Mars on Oct. 19, 2016. As planned, its initial orbit shape is highly elliptical, ranging from as far as 60,000 miles (98,000 kilometres) above the surface to less than 200 miles (less than 310 kilometres). Each loop takes 4.2 days to complete.

Frequent use of TGO's relay capability to support Mars rover operations is planned to begin more than a year from now. That's after the orbiter finishes adjusting its orbit to a near-circular path about 250 miles (400 kilometres) above Mars' surface.

"The arrival of ESA's Trace Gas Orbiter at Mars, with its NASA-provided Electra relay payload on board, represents a significant step forward in our Mars relay capabilities," said Chad Edwards, manager of the Mars Relay Network Office within the Mars Exploration Program at NASA's Jet Propulsion Laboratory, Pasadena, California. "In concert with our three existing NASA orbiters and ESA's earlier Mars Express orbiter, we now have a truly international Mars relay network that will greatly increase the amount of data that future Mars landers and rovers can return from the surface of the Red Planet."

The JPL-designed Electra radios include special features for relaying data from a rover or stationary lander to an orbiter passing overhead. Relay of information from Mars-surface craft to Mars orbiters, then from the Mars orbiters to Earth, enables receiving much more data from the surface missions than would be possible with a direct-to-Earth radio link from the rovers or landers.

TGO Flight Director Michel Denis Credit: ESA/J. Mai

"We already have almost 13 years' experience using ESA's Mars Express as an on-call backup for data relay from active Mars rovers, and TGO will greatly expand this to routine science-data relay," said Michel Denis, TGO flight director at ESA's European Space Operations Centre, Darmstadt, Germany. "In 2020, TGO will extend this relay support to ESA's ExoMars rover and the Russian Surface Platform, an important capability together with its science mission that enhances the international data network at Mars."

As an example of Electra capabilities, during a relay session between an Electra on the surface and one on an orbiter, the radios can maximize data volume by actively adjusting the data rate to be slower when the orbiter is near the horizon from the surface robot's perspective, faster when it is overhead.

Access full text here

Here are some tech details on the successful test, contributed by the TGO mission team at ESOC.

Scenes at ESA/ESOC, Darmstadt, Germany, on 19 October 2016 during the arrival of ExoMars. Credit: ESA/J. Mai

TGO's Electra radio system was already put through some initial testing while the spacecraft was enroute to Mars, and was successfully used in the so-called 'Open Loop' recording mode to record signals from Schiaparelli during the test module's separation from TGO and during Schiaparelli's Entry, Descent and Landing on Mars on 19 October.

The purpose of the two tests performed on 22 November was to receive, for the first time, data transmitted from the NASA rovers on the surface of Mars.

• A 'Raw data mode relay session' with the Curiosity vehicle in a 20-minute window between 15:17 - 15:37 UTC at Mars allowed TGO and its Electra system to fetch and relay to Earth 9.9 Mbits of rover data.
• Shortly later, during a 10-minute slot between 16:40-16:50 UTC, a 'Return link session' with MER-B Opportunity succeeded in relaying more than 3.3 Mbits of rover data.

Both tests enabled maintaining a continuous and uninterrupted rover-to-orbiter radio data link that can be used for future relay activities. The two overflights happened outside of real-time visibility from ground stations, and used TGO's prime Electra unit (there is also a back-up unit on board).

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v

Rumba decides to spontaneously reboot

Today's post contributed by Cluster spacecraft operations manager Bruno Sousa.

Another day in the life of an operations team

On 23 November, at around 19:00 CET, the Spacecraft Controller (Spacon) on shift for the four satellites of the Cluster II mission, had just initiated a ground contact from ESA’s ground station at Villafranca, Spain. He noted the weak signal that was arriving at the spacecraft, but – given that the spacecraft was able to lock onto it anyway – he proceeded to initiate the contact and prepare the download of the scientific data stored onboard. As the first commands were uplinked (including a change in the telemetry bit rate), quite suddenly, the spacecraft went mute. No more telemetry was received.

Cluster team in the DCR. Credit: ESA

After troubleshooting for potential problems with the ground segment, including a possible misconfiguration of the station as a result of the change in telemetry mode, the Spacon contacted the on-call operations engineer, who quickly came into the control room. Together they initiated the contingency procedure that covers “loss of telemetry”. The procedure included switching on the on-board radio transponder, and this immediately restored the flow of telemetry.

After a preliminary analysis of the data the spacecraft was generating, we determined that its status was consistent with a ‘reboot’ (the status of a software ‘flag’ that disables further reboots was enabled, indicating that one had just taken place). The spacecraft stores in a protected area of memory a list of events that are generated by the software around the reboot. Once we downloaded these, we could immediately tell that the software had entered an exception clause while decoding a command.

The last time we had seen something like this was back in 2010 when a very similar occurrence took place. Luckily, we record very thoroughly all such occurrences including all the investigation efforts done to get to the source of the problem.

It had been determined in those earlier investigations that, upon reception of a command (and only of a  very specific type), the software validates it, and if it finds that the command is reported as having ‘size 0’ (indicating that the command has become corrupted), it then immediately triggers a reboot of the on-board processor – and this happens even before that function has a chance to do a validation of the command’s checksum, which would have identified the corruption and cause it to simply be rejected.

The corruption of the command was most likely due to the poor signal strength received onboard. The reason the signal was so weak was not possible to determine. We did note that, once we changed the station from Villafranca to Maspalomas station, the signal improved quite significantly, but we couldn’t determine any problem with the first station.  

Maspalomas station. Credit: ESA/F. Macia

Following the reboot, the spacecraft remained in the so-called ‘Nominal Survival Mode’, which includes leaving the transponder off, and hence, we saw no more telemetry from the spacecraft. Another consequence of the reboot is that the onboard solid state memory, where the science data is recorded, is also switched off. Because the technology for this hardware dates from the mid-90’s, a switch off means that all data stored there at that time is lost; in this case that represented more than 40 hours of recorded data, which unfortunately cannot be recovered.

The Cluster flight control team communicates avidly via mobile text messaging, and soon the on-call engineer was being assisted by two other colleagues who came in to provide assistance. When running long and complicated procedures, it’s always handy to have another pair of eyes looking over your shoulder so that you don’t forget anything.

Together, they swiftly proceeded to recover the nominal configuration for the spacecraft, including reactivating most of the payloads. As the visibility from the ground station was coming to an end, the team had to select the payloads that could still be re-activated within the available time, with the remaining activations carried on the following station pass. At around 01:00 AM, the team concluded its intervention and the engineers went home to a well-deserved rest.

And that was another day in the life of an operations team!

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Today's post contributed by Cluster spacecraft operations manager Bruno Sousa.

Another day in the life of an operations team

On 23 November, at around 19:00 CET, the Spacecraft Controller (Spacon) on shift for the four satellites of the Cluster II mission, had just initiated a ground contact from ESA’s ground station at Villafranca, Spain. He noted the weak signal that was arriving at the spacecraft, but – given that the spacecraft was able to lock onto it anyway – he proceeded to initiate the contact and prepare the download of the scientific data stored onboard. As the first commands were uplinked (including a change in the telemetry bit rate), quite suddenly, the spacecraft went mute. No more telemetry was received.

Cluster team in the DCR. Credit: ESA

After troubleshooting for potential problems with the ground segment, including a possible misconfiguration of the station as a result of the change in telemetry mode, the Spacon contacted the on-call operations engineer, who quickly came into the control room. Together they initiated the contingency procedure that covers “loss of telemetry”. The procedure included switching on the on-board radio transponder, and this immediately restored the flow of telemetry.

After a preliminary analysis of the data the spacecraft was generating, we determined that its status was consistent with a ‘reboot’ (the status of a software ‘flag’ that disables further reboots was enabled, indicating that one had just taken place). The spacecraft stores in a protected area of memory a list of events that are generated by the software around the reboot. Once we downloaded these, we could immediately tell that the software had entered an exception clause while decoding a command.

The last time we had seen something like this was back in 2010 when a very similar occurrence took place. Luckily, we record very thoroughly all such occurrences including all the investigation efforts done to get to the source of the problem.

It had been determined in those earlier investigations that, upon reception of a command (and only of a  very specific type), the software validates it, and if it finds that the command is reported as having ‘size 0’ (indicating that the command has become corrupted), it then immediately triggers a reboot of the on-board processor – and this happens even before that function has a chance to do a validation of the command’s checksum, which would have identified the corruption and cause it to simply be rejected.

The corruption of the command was most likely due to the poor signal strength received onboard. The reason the signal was so weak was not possible to determine. We did note that, once we changed the station from Villafranca to Maspalomas station, the signal improved quite significantly, but we couldn’t determine any problem with the first station.  

Maspalomas station. Credit: ESA/F. Macia

Following the reboot, the spacecraft remained in the so-called ‘Nominal Survival Mode’, which includes leaving the transponder off, and hence, we saw no more telemetry from the spacecraft. Another consequence of the reboot is that the onboard solid state memory, where the science data is recorded, is also switched off. Because the technology for this hardware dates from the mid-90’s, a switch off means that all data stored there at that time is lost; in this case that represented more than 40 hours of recorded data, which unfortunately cannot be recovered.

The Cluster flight control team communicates avidly via mobile text messaging, and soon the on-call engineer was being assisted by two other colleagues who came in to provide assistance. When running long and complicated procedures, it’s always handy to have another pair of eyes looking over your shoulder so that you don’t forget anything.

Together, they swiftly proceeded to recover the nominal configuration for the spacecraft, including reactivating most of the payloads. As the visibility from the ground station was coming to an end, the team had to select the payloads that could still be re-activated within the available time, with the remaining activations carried on the following station pass. At around 01:00 AM, the team concluded its intervention and the engineers went home to a well-deserved rest.

And that was another day in the life of an operations team!

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v

Moon and Mercury on November 30

Tonight – November 30, 2016 – if your western horizon is clear and unobstructed, you’ll find the moon and Mercury below dazzling Venus in the sunset direction, for a brief time after the sun goes down.

Everyone in the world has a chance to see it, but we’ll all see it oriented slightly differently with respect to the horizon … and we’ll all see the moon closer to or farther from Mercury than others in other parts of the world. The chart at the top of this post, for example, shows the view from mid-northern latitudes in the Americas. At mid-northern latitudes in Europe, the planets are similarly positioned, although the moon sits closer to the horizon.

That means, after sunset November 30, we expect the tiny sliver of the very young waxing crescent moon to be easier to see from North America (and Hawaii) than at corresponding latitudes in Europe.

But don’t worry about these tiny differences! Just know that – no matter where you are – you’ll want to look for the moon and Mercury on November 30 shortly after the sun goes down, very near the spot the sun set.

At nightfall, look for the red planet Mars above Venus. It’ll be easier to catch than Mercury!

From northerly latitudes, the planet Mercury is not that easy to catch. You’ll want to bring along your binoculars, in case you want them to scan for the moon and Mercury in the glow of evening twilight.

On the other hand, Venus – the sky’s brightest planet – is in the west after sunset now, too. It’s very bright and easy to spot, and should pop out some 20 minutes (or sooner) after sunset. Once you spot Venus, try hopping from Venus to Mercury – drawing an imaginary line between Venus and the spot on the horizon where the sun went down.

Click here for almanac recommendations; an almanac can help you find setting times for the moon and Mercury in your sky.

In North America, on November 30, the moon sets after Mercury; south of the equator – in South America – Mercury sets after the moon. From mid-northern North American latitudes, you might see the moon – but not Mercury; in southern South America, you might see Mercury – but not the moon. At and near the equator, the moon and Mercury set at nearly the same time, so this could be the good spot to see the both the moon and Mercury after sunset on November 30.

Western evening dusk on November 30, 2016, from the vantage point of Santiago, Chile

Far and away – of all the places in the world – the Southern Hemisphere has the advantage for seeing Mercury in the evening sky. At temperate latitudes in the Southern Hemisphere, Mercury sets approximately one and one-half hours after the sun. At mid-northern latitudes, on the other hand, Mercury sets about one hour after sunset. From the Southern Hemisphere, especially from New Zealand and Australia, look for the close pairing of the waxing crescent moon and Mercury in your western sky after sunset December 1.

Mercury is climbing away from the glare of sunset day by day, to reach its greatest angular distance from the setting sun on December 11, 2016. If you miss the moon and (or) Mercury after sunset November 30, try again on December 1.

Keep watching! The waxing crescent crescent will be higher up after sunset and staying out later after dark in early December 2016.

Bottom line: We’ll be eager to find out how many EarthSky readers will catch the moon and Mercury at evening dusk on November 30, 2016! Let us know – and post your photos – in the comments below.

from EarthSky http://ift.tt/2eQXP0N

Tonight – November 30, 2016 – if your western horizon is clear and unobstructed, you’ll find the moon and Mercury below dazzling Venus in the sunset direction, for a brief time after the sun goes down.

Everyone in the world has a chance to see it, but we’ll all see it oriented slightly differently with respect to the horizon … and we’ll all see the moon closer to or farther from Mercury than others in other parts of the world. The chart at the top of this post, for example, shows the view from mid-northern latitudes in the Americas. At mid-northern latitudes in Europe, the planets are similarly positioned, although the moon sits closer to the horizon.

That means, after sunset November 30, we expect the tiny sliver of the very young waxing crescent moon to be easier to see from North America (and Hawaii) than at corresponding latitudes in Europe.

But don’t worry about these tiny differences! Just know that – no matter where you are – you’ll want to look for the moon and Mercury on November 30 shortly after the sun goes down, very near the spot the sun set.

At nightfall, look for the red planet Mars above Venus. It’ll be easier to catch than Mercury!

From northerly latitudes, the planet Mercury is not that easy to catch. You’ll want to bring along your binoculars, in case you want them to scan for the moon and Mercury in the glow of evening twilight.

On the other hand, Venus – the sky’s brightest planet – is in the west after sunset now, too. It’s very bright and easy to spot, and should pop out some 20 minutes (or sooner) after sunset. Once you spot Venus, try hopping from Venus to Mercury – drawing an imaginary line between Venus and the spot on the horizon where the sun went down.

Click here for almanac recommendations; an almanac can help you find setting times for the moon and Mercury in your sky.

In North America, on November 30, the moon sets after Mercury; south of the equator – in South America – Mercury sets after the moon. From mid-northern North American latitudes, you might see the moon – but not Mercury; in southern South America, you might see Mercury – but not the moon. At and near the equator, the moon and Mercury set at nearly the same time, so this could be the good spot to see the both the moon and Mercury after sunset on November 30.

Western evening dusk on November 30, 2016, from the vantage point of Santiago, Chile

Far and away – of all the places in the world – the Southern Hemisphere has the advantage for seeing Mercury in the evening sky. At temperate latitudes in the Southern Hemisphere, Mercury sets approximately one and one-half hours after the sun. At mid-northern latitudes, on the other hand, Mercury sets about one hour after sunset. From the Southern Hemisphere, especially from New Zealand and Australia, look for the close pairing of the waxing crescent moon and Mercury in your western sky after sunset December 1.

Mercury is climbing away from the glare of sunset day by day, to reach its greatest angular distance from the setting sun on December 11, 2016. If you miss the moon and (or) Mercury after sunset November 30, try again on December 1.

Keep watching! The waxing crescent crescent will be higher up after sunset and staying out later after dark in early December 2016.

Bottom line: We’ll be eager to find out how many EarthSky readers will catch the moon and Mercury at evening dusk on November 30, 2016! Let us know – and post your photos – in the comments below.

from EarthSky http://ift.tt/2eQXP0N