Southern Cross: A southern sky signpost

Tonight, we’re paying tribute to the Southern Cross, also known as the constellation Crux, for our friends in the Southern Hemisphere. No matter where you live in the Southern Hemisphere, look in your southern sky for the Southern Cross as soon as darkness falls.

At temperate latitudes in the Southern Hemisphere, where it’s now the winter season, we astronomers say the Southern Cross swings to upper meridian transit – its high point in the sky – around nightfall, or approximately 6 p.m. local time.

Image top of post is the Southern Cross as seen from Manila – latitude 14 degrees N. of the equator – in 2012. The photo is from EarthSky Facebook friend Jv Noriega. View it larger.

The meridian is the imaginary semi-circle that divides your sky into its eastern and western hemispheres. A star reaches it highest point when it crosses the meridian at upper transit, and its lowest point when it crosses the meridian at lower transit.

Because the Southern Cross is circumpolar – always above the horizon – at all places south of 35^o south latitude, people at mid-southern latitudes can count on seeing the Southern Cross all night long, every night of the year. Watch for the Southern Cross to move like a great big hour hand, circling around the south celestial pole in a clockwise direction throughout the night. The Southern Cross will sweep to lower meridian transit – its low point in the sky – around 6 a.m. local time tomorrow.

Star-hopping to south celestial pole via the Southern Cross and the bright stars Alpha Centauri and Hadar.

If the Southern Cross is circumpolar in your sky, then the Big Dipper never climbs above your horizon.

Conversely, if the Big Dipper is circumpolar in your sky, then the Southern Cross never climbs above your horizon. Additionally, the W or M-shaped constellation Cassiopeia is also circumpolar at northerly latitudes. See the animation below.

However, if you live in the tropics, there are times when you can actually see the Big Dipper and the Southern Cross in the same sky together. In late June, for instance, the Southern Cross and Big Dipper reach upper transit – their high point – at virtually the same time, or around 6 p.m. local time.

You have a better chance of seeing the Southern Cross and the Big Dipper in the same sky right now from the southern tropics. That’s because the winter season in the Southern Hemisphere ushers in an earlier sunset time than at comparable latitudes in the northern tropics, where it is now summer.

The Big Dipper and the W-shaped constellation Cassiopeia circle around Polaris, the North Star, in a period of 23 hours and 56 minutes. The Big Dipper is circumpolar at 41^o N. latitude, and all latitudes farther north.

Bottom line: A tribute to the Southern Cross, also known as the constellation Crux.

from EarthSky http://ift.tt/28PkOW0

Tonight, we’re paying tribute to the Southern Cross, also known as the constellation Crux, for our friends in the Southern Hemisphere. No matter where you live in the Southern Hemisphere, look in your southern sky for the Southern Cross as soon as darkness falls.

At temperate latitudes in the Southern Hemisphere, where it’s now the winter season, we astronomers say the Southern Cross swings to upper meridian transit – its high point in the sky – around nightfall, or approximately 6 p.m. local time.

Image top of post is the Southern Cross as seen from Manila – latitude 14 degrees N. of the equator – in 2012. The photo is from EarthSky Facebook friend Jv Noriega. View it larger.

The meridian is the imaginary semi-circle that divides your sky into its eastern and western hemispheres. A star reaches it highest point when it crosses the meridian at upper transit, and its lowest point when it crosses the meridian at lower transit.

Because the Southern Cross is circumpolar – always above the horizon – at all places south of 35^o south latitude, people at mid-southern latitudes can count on seeing the Southern Cross all night long, every night of the year. Watch for the Southern Cross to move like a great big hour hand, circling around the south celestial pole in a clockwise direction throughout the night. The Southern Cross will sweep to lower meridian transit – its low point in the sky – around 6 a.m. local time tomorrow.

Star-hopping to south celestial pole via the Southern Cross and the bright stars Alpha Centauri and Hadar.

If the Southern Cross is circumpolar in your sky, then the Big Dipper never climbs above your horizon.

Conversely, if the Big Dipper is circumpolar in your sky, then the Southern Cross never climbs above your horizon. Additionally, the W or M-shaped constellation Cassiopeia is also circumpolar at northerly latitudes. See the animation below.

However, if you live in the tropics, there are times when you can actually see the Big Dipper and the Southern Cross in the same sky together. In late June, for instance, the Southern Cross and Big Dipper reach upper transit – their high point – at virtually the same time, or around 6 p.m. local time.

You have a better chance of seeing the Southern Cross and the Big Dipper in the same sky right now from the southern tropics. That’s because the winter season in the Southern Hemisphere ushers in an earlier sunset time than at comparable latitudes in the northern tropics, where it is now summer.

The Big Dipper and the W-shaped constellation Cassiopeia circle around Polaris, the North Star, in a period of 23 hours and 56 minutes. The Big Dipper is circumpolar at 41^o N. latitude, and all latitudes farther north.

Bottom line: A tribute to the Southern Cross, also known as the constellation Crux.

from EarthSky http://ift.tt/28PkOW0

We are heading for the warmest climate in half a billion years

Gavin Foster, Professor of Isotope Geochemistry, University of Southampton; Dana Royer, Professor of Earth and Environmental Sciences, Wesleyan University, and Dan Lunt, Professor of Climate Science, University of Bristol

This article was originally published on The Conversation. Read the original article.

Carbon dioxide concentrations are heading towards values not seen in the past 200m years. The sun has also been gradually getting stronger over time. Put together, these facts mean the climate may be heading towards warmth not seen in the past half a billion years.

A lot has happened on Earth since 500,000,000BC – continents, oceans and mountain ranges have come and gone, and complex life has evolved and moved from the oceans onto the land and into the air. Most of these changes occur on very long timescales of millions of years or more. However, over the past 150 years global temperatures have increased by about 1℃, ice caps and glaciers have retreated, polar sea-ice has melted, and sea levels have risen.

Some will point out that Earth’s climate has undergone similar changes before. So what’s the big deal?

Scientists can seek to understand past climates by looking at the evidence locked away in rocks, sediments and fossils. What this tells us is that yes, the climate has changed in the past, but the current speed of change is highly unusual. For instance, carbon dioxide hasn’t been added to the atmosphere as rapidly as today for at least the past 66m years.

In fact, if we continue on our current path and exploit all convention fossil fuels, then as well as the rate of CO₂ emissions, the absolute climate warming is also likely to be unprecedented in at least the past 420m years. That’s according to a new study we have published in Nature Communications.

Life in the planet’s last greenhouse period, the Eocene. Jay Matternes / Smithsonian Museum, CC BY

In terms of geological time, 1℃ of global warming isn’t particularly unusual. For much of its history the planet was significantly warmer than today, and in fact more often than not Earth was in what is termed a “greenhouse” climate state. During the last greenhouse state 50m years ago, global average temperatures were 10-15℃ warmer than today, the polar regions were ice-free, palm trees grew on the coast of Antarctica, and alligators and turtles wallowed in swamp-forests in what is now the frozen Canadian Arctic.

In contrast, despite our current warming, we are still technically in an “icehouse” climate state, which simply means there is ice on both poles. The Earth has naturally cycled between these two climate states every 300m years or so.

Just prior to the industrial revolution, for every million molecules in the atmosphere, about 280 of them were CO₂ molecules (280 parts-per-million, or ppm). Today, due primarily to the burning of fossil fuels, concentrations are about 400 ppm. In the absence of any efforts to curtail our emissions, burning of conventional fossil fuels will cause CO₂ concentrations to be around 2,000ppm by the year 2250.

This is of course a lot of CO₂, but the geological record tells us that the Earth has experienced similar concentrations several times in the past. For instance, our new compilation of data shows that during the Triassic, around 200m years ago, when dinosaurs first evolved, Earth had a greenhouse climate state with atmospheric CO₂ around 2,000-3,000ppm.

So high concentrations of carbon dioxide don’t necessarily make the world totally uninhabitable. The dinosaurs thrived, after all.

That doesn’t mean this is no big deal, however. For a start, there is no doubt that humanity will face major socio-economic challenges dealing with the dramatic and rapid climate change that will result from the rapid rise to 2,000 or more ppm.

If we burnt all fossil fuel reserves the vast Antarctic ice sheet may disappear. vladsilver / shutterstock

But our new study also shows that the same carbon concentrations will cause more warming in future than in previous periods of high carbon dioxide. This is because the Earth’s temperature does not just depend on the level of CO₂ (or other greenhouse gases) in the atmosphere. All our energy ultimately comes from the sun, and due to the way the sun generates energy through nuclear fusion of hydrogen into helium, its brightness has increased over time. Four and a half billion years ago when the Earth was young the sun was around 30% less bright.

So what really matters is the combined effect of the sun’s changing strength and the varying greenhouse effect. Looking through geological history we generally found that as the sun became stronger through time, atmospheric CO₂ gradually decreased, so both changes cancelled each other out on average.

But what about in the future? We found no past time period when the drivers of climate, or climate forcing, was as high as it will be in the future if we burn all the readily available fossil fuel. Nothing like it has been recorded in the rock record for at least 420m years.

A central pillar of geological science is the uniformitarian principle: that “the present is the key to the past”. If we carry on burning fossil fuels as we are at present, by 2250 this old adage is sadly no longer likely to be true. It is doubtful that this high-CO₂ future will have a counterpart, even in the vastness of the geological record.

 

from Skeptical Science http://ift.tt/2tgaphs

Gavin Foster, Professor of Isotope Geochemistry, University of Southampton; Dana Royer, Professor of Earth and Environmental Sciences, Wesleyan University, and Dan Lunt, Professor of Climate Science, University of Bristol

This article was originally published on The Conversation. Read the original article.

Carbon dioxide concentrations are heading towards values not seen in the past 200m years. The sun has also been gradually getting stronger over time. Put together, these facts mean the climate may be heading towards warmth not seen in the past half a billion years.

A lot has happened on Earth since 500,000,000BC – continents, oceans and mountain ranges have come and gone, and complex life has evolved and moved from the oceans onto the land and into the air. Most of these changes occur on very long timescales of millions of years or more. However, over the past 150 years global temperatures have increased by about 1℃, ice caps and glaciers have retreated, polar sea-ice has melted, and sea levels have risen.

Some will point out that Earth’s climate has undergone similar changes before. So what’s the big deal?

Scientists can seek to understand past climates by looking at the evidence locked away in rocks, sediments and fossils. What this tells us is that yes, the climate has changed in the past, but the current speed of change is highly unusual. For instance, carbon dioxide hasn’t been added to the atmosphere as rapidly as today for at least the past 66m years.

In fact, if we continue on our current path and exploit all convention fossil fuels, then as well as the rate of CO₂ emissions, the absolute climate warming is also likely to be unprecedented in at least the past 420m years. That’s according to a new study we have published in Nature Communications.

Life in the planet’s last greenhouse period, the Eocene. Jay Matternes / Smithsonian Museum, CC BY

In terms of geological time, 1℃ of global warming isn’t particularly unusual. For much of its history the planet was significantly warmer than today, and in fact more often than not Earth was in what is termed a “greenhouse” climate state. During the last greenhouse state 50m years ago, global average temperatures were 10-15℃ warmer than today, the polar regions were ice-free, palm trees grew on the coast of Antarctica, and alligators and turtles wallowed in swamp-forests in what is now the frozen Canadian Arctic.

In contrast, despite our current warming, we are still technically in an “icehouse” climate state, which simply means there is ice on both poles. The Earth has naturally cycled between these two climate states every 300m years or so.

Just prior to the industrial revolution, for every million molecules in the atmosphere, about 280 of them were CO₂ molecules (280 parts-per-million, or ppm). Today, due primarily to the burning of fossil fuels, concentrations are about 400 ppm. In the absence of any efforts to curtail our emissions, burning of conventional fossil fuels will cause CO₂ concentrations to be around 2,000ppm by the year 2250.

This is of course a lot of CO₂, but the geological record tells us that the Earth has experienced similar concentrations several times in the past. For instance, our new compilation of data shows that during the Triassic, around 200m years ago, when dinosaurs first evolved, Earth had a greenhouse climate state with atmospheric CO₂ around 2,000-3,000ppm.

So high concentrations of carbon dioxide don’t necessarily make the world totally uninhabitable. The dinosaurs thrived, after all.

That doesn’t mean this is no big deal, however. For a start, there is no doubt that humanity will face major socio-economic challenges dealing with the dramatic and rapid climate change that will result from the rapid rise to 2,000 or more ppm.

If we burnt all fossil fuel reserves the vast Antarctic ice sheet may disappear. vladsilver / shutterstock

But our new study also shows that the same carbon concentrations will cause more warming in future than in previous periods of high carbon dioxide. This is because the Earth’s temperature does not just depend on the level of CO₂ (or other greenhouse gases) in the atmosphere. All our energy ultimately comes from the sun, and due to the way the sun generates energy through nuclear fusion of hydrogen into helium, its brightness has increased over time. Four and a half billion years ago when the Earth was young the sun was around 30% less bright.

So what really matters is the combined effect of the sun’s changing strength and the varying greenhouse effect. Looking through geological history we generally found that as the sun became stronger through time, atmospheric CO₂ gradually decreased, so both changes cancelled each other out on average.

But what about in the future? We found no past time period when the drivers of climate, or climate forcing, was as high as it will be in the future if we burn all the readily available fossil fuel. Nothing like it has been recorded in the rock record for at least 420m years.

A central pillar of geological science is the uniformitarian principle: that “the present is the key to the past”. If we carry on burning fossil fuels as we are at present, by 2250 this old adage is sadly no longer likely to be true. It is doubtful that this high-CO₂ future will have a counterpart, even in the vastness of the geological record.

 

from Skeptical Science http://ift.tt/2tgaphs

New study confirms the oceans are warming rapidly

As humans put ever more heat-trapping gases into the atmosphere, the Earth heats up. These are the basics of global warming. But where does the heat go? How much extra heat is there? And how accurate are our measurements? These are questions that climate scientists ask. If we can answer these questions, it will better help us prepare for a future with a very different climate. It will also better help us predict what that future climate will be.

The most important measurement of global warming is in the oceans. In fact, “global warming” is really “ocean warming.” If you are going to measure the changing climate of the oceans, you need to have many sensors spread out across the globe that take measurements from the ocean surface to the very depths of the waters. Importantly, you need to have measurements that span decades so a long-term trend can be established. 

These difficulties are tackled by oceanographers, and a significant advancement was presented in a paper just published in the journal Climate Dynamics. That paper, which I was fortunate to be involved with, looked at three different ocean temperature measurements made by three different groups. We found that regardless of whose data was used or where the data was gathered, the oceans are warming.

Ocean heat content increase globally (top frame) and in four ocean basins (bottom frames). Illustration: Wang et al. (2017), Climate Dynamics

In the paper, we describe perhaps the three most important factors that affect ocean-temperature accuracy. First, sensors can have biases (they can be “hot” or “cold”), and these biases can change over time. An example of biases was identified in the 1940s. Then, many ocean temperature measurements were made using buckets that gathered water from ships. Sensors put into the buckets would give the water temperature. Then, a new temperature sensing approach started to come online where temperatures were measured using ship hull-based sensors at engine intake ports. It turns out that bucket measurements are slightly cooler than measurements made using hull sensors, which are closer to the engine of the ship.

During World War II, the British Navy cut back on its measurements (using buckets) and the US Navy expanded its measurements (using hull sensors); consequently, a sharp warming in oceans was seen in the data. But this warming was an artifact of the change from buckets to hull sensors. After the war, when the British fleet re-expanded its bucket measurements, the ocean temperatures seemed to fall a bit. Again, this was an artifact from the data collection. Other such biases and artifacts arose throughout the years as oceanographers have updated measurement equipment. If you want the true rate of ocean temperature change, you have to remove these biases.

Another source of uncertainty is related to the fact that we just don’t have sensors at all ocean locations and at all times. Some sensors, which are dropped from cargo ships, are densely located along major shipping routes. Other sensors, dropped from research vessels, are also confined to specific locations across the globe. 

Currently, we are heavily using the ARGO fleet, which contains approximately 3800 autonomous devices spread out more or less uniformly across the ocean, but these only entered service in 2005. Prior to that, temperatures measurements were not uniform in the oceans. As a consequence, scientists have to use what is called a “mapping” procedure to interpolate temperatures between temperature measurements. Sort of like filling in the gaps where no data exist. The mapping strategy used by scientists can affect the ocean temperature measurements.

Finally, temperatures are usually referenced to a baseline “climatology.” So, when we say temperatures have increased by 1 degree, it is important to say what the baseline climatology is. Have temperatures increased by 1 degree since the year 1990? Since the year 1970? Since 1900? The choice of baseline climatology really matters.

In the study, we looked at the different ways that three groups make decisions about mapping, bias, and climatology. We not only asked how much the oceans are warming, but how the warming differs for various areas (ocean basins) and various depths. We found that each ocean basin has warmed significantly. Despite this fact, there are some differences amongst the three groups. For instance, in the 300-700 meter oceans depths in the Pacific and Southern oceans, significant differences are exhibited amongst the tree groups. That said, the central fact is that regardless of how you measure, who does the measurements, when or where the measurements are taken, we are warming.

The lead author, Dr. Gonjgie Wang described the importance of the study this way:

Click here to read the rest

from Skeptical Science http://ift.tt/2tgAwVj

As humans put ever more heat-trapping gases into the atmosphere, the Earth heats up. These are the basics of global warming. But where does the heat go? How much extra heat is there? And how accurate are our measurements? These are questions that climate scientists ask. If we can answer these questions, it will better help us prepare for a future with a very different climate. It will also better help us predict what that future climate will be.

The most important measurement of global warming is in the oceans. In fact, “global warming” is really “ocean warming.” If you are going to measure the changing climate of the oceans, you need to have many sensors spread out across the globe that take measurements from the ocean surface to the very depths of the waters. Importantly, you need to have measurements that span decades so a long-term trend can be established. 

These difficulties are tackled by oceanographers, and a significant advancement was presented in a paper just published in the journal Climate Dynamics. That paper, which I was fortunate to be involved with, looked at three different ocean temperature measurements made by three different groups. We found that regardless of whose data was used or where the data was gathered, the oceans are warming.

Ocean heat content increase globally (top frame) and in four ocean basins (bottom frames). Illustration: Wang et al. (2017), Climate Dynamics

In the paper, we describe perhaps the three most important factors that affect ocean-temperature accuracy. First, sensors can have biases (they can be “hot” or “cold”), and these biases can change over time. An example of biases was identified in the 1940s. Then, many ocean temperature measurements were made using buckets that gathered water from ships. Sensors put into the buckets would give the water temperature. Then, a new temperature sensing approach started to come online where temperatures were measured using ship hull-based sensors at engine intake ports. It turns out that bucket measurements are slightly cooler than measurements made using hull sensors, which are closer to the engine of the ship.

During World War II, the British Navy cut back on its measurements (using buckets) and the US Navy expanded its measurements (using hull sensors); consequently, a sharp warming in oceans was seen in the data. But this warming was an artifact of the change from buckets to hull sensors. After the war, when the British fleet re-expanded its bucket measurements, the ocean temperatures seemed to fall a bit. Again, this was an artifact from the data collection. Other such biases and artifacts arose throughout the years as oceanographers have updated measurement equipment. If you want the true rate of ocean temperature change, you have to remove these biases.

Another source of uncertainty is related to the fact that we just don’t have sensors at all ocean locations and at all times. Some sensors, which are dropped from cargo ships, are densely located along major shipping routes. Other sensors, dropped from research vessels, are also confined to specific locations across the globe. 

Currently, we are heavily using the ARGO fleet, which contains approximately 3800 autonomous devices spread out more or less uniformly across the ocean, but these only entered service in 2005. Prior to that, temperatures measurements were not uniform in the oceans. As a consequence, scientists have to use what is called a “mapping” procedure to interpolate temperatures between temperature measurements. Sort of like filling in the gaps where no data exist. The mapping strategy used by scientists can affect the ocean temperature measurements.

Finally, temperatures are usually referenced to a baseline “climatology.” So, when we say temperatures have increased by 1 degree, it is important to say what the baseline climatology is. Have temperatures increased by 1 degree since the year 1990? Since the year 1970? Since 1900? The choice of baseline climatology really matters.

In the study, we looked at the different ways that three groups make decisions about mapping, bias, and climatology. We not only asked how much the oceans are warming, but how the warming differs for various areas (ocean basins) and various depths. We found that each ocean basin has warmed significantly. Despite this fact, there are some differences amongst the three groups. For instance, in the 300-700 meter oceans depths in the Pacific and Southern oceans, significant differences are exhibited amongst the tree groups. That said, the central fact is that regardless of how you measure, who does the measurements, when or where the measurements are taken, we are warming.

The lead author, Dr. Gonjgie Wang described the importance of the study this way:

Click here to read the rest

from Skeptical Science http://ift.tt/2tgAwVj

Launch and Catapult Science

Test your skills with launching and catapulting science projects and activities.

from Science Buddies Blog http://ift.tt/2tiVcgd

Test your skills with launching and catapulting science projects and activities.

from Science Buddies Blog http://ift.tt/2tiVcgd

Expect colorful clouds from rocket launch

This map shows the projected visibility of the vapor tracers during the rocket launch, now scheduled for the predawn hours on June 29. The vapor tracers may be visible from New York to North Carolina and westward to Charlottesville, Virginia. Image via NASA.

NASA said on June 26, 2017 that the launch of its Terrier-Improved Malemute sounding rocket is scheduled for between 4:15 and 4:45 a.m. this Thursday, June 29. It said the launch window is determined by sun angles and also by whether the moon is up or down. The rocket is to test a new multi-canister ejection system for deploying vapors in rocket missions for studying Earth’s upper atmosphere and ionosphere, aka aurora soundings. Upon launch of the rocket, the vapors will form luminescent, blue-green and red, artificial clouds expected to be seen from New York to North Carolina.

Grab a cup of coffee and join us early for the vapor rocket launch from @NASA_Wallops now set for 4:15-4:45 a.m., Thursday. June 29.

— NASA Wallops (@NASA_Wallops) June 26, 2017

Backup launch day is June 30.

The Visitor Center at the Wallops Flight Facility on the eastern shore of Virginia will open at 3:30 a.m. on launch day, for those wishing to view the launch live. Live coverage online begins on the Wallops Ustream site at 3:45 a.m. on launch day and Wallops Facebook Live coverage begins at 4 a.m. on launch day. You might also check Twitter (@NASA_Wallops).

Illustration showing the trajectory of a sounding rocket. It’s a standard sounding rocket technique to create visible trails and “clouds” through the release of vapors that either glow on their own (i.e., luminescence) or scatter sunlight. Scientists monitor and take pictures of the subsequent trails and clouds to learn how the upper atmosphere and/or the ionosphere moves and evolves. Image via NASA.

The launch was originally scheduled for early June and has been postponed several times. NASA explained:

These clouds, or vapor tracers, allow scientists on the ground to visually track particle motions in space.

The development of the multi-canister ampoule ejection system will allow scientists to gather information over a much larger area than previously allowed when deploying the tracers just from the main payload …

The vapor tracers are formed through the interaction of barium, strontium and cupric-oxide. The tracers will be released at altitudes 96 to 124 miles high and pose no hazard to residents along the mid-Atlantic coast.

Read more from NASA

Read more about how sounding rockets work

This NASA sounding rocket will launch soon, creating colorful clouds in space. Image via @NASA_Wallops.

Bottom line: A launch of NASA’s Terrier-Improved Malemute sounding rocket expected to form colorful clouds in space, visible from New York to North Carolina. Launch currently scheduled for between 4:15 and 4:45 a.m., Thursday, June 29. Backup launch day June 30.

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

This map shows the projected visibility of the vapor tracers during the rocket launch, now scheduled for the predawn hours on June 29. The vapor tracers may be visible from New York to North Carolina and westward to Charlottesville, Virginia. Image via NASA.

NASA said on June 26, 2017 that the launch of its Terrier-Improved Malemute sounding rocket is scheduled for between 4:15 and 4:45 a.m. this Thursday, June 29. It said the launch window is determined by sun angles and also by whether the moon is up or down. The rocket is to test a new multi-canister ejection system for deploying vapors in rocket missions for studying Earth’s upper atmosphere and ionosphere, aka aurora soundings. Upon launch of the rocket, the vapors will form luminescent, blue-green and red, artificial clouds expected to be seen from New York to North Carolina.

Grab a cup of coffee and join us early for the vapor rocket launch from @NASA_Wallops now set for 4:15-4:45 a.m., Thursday. June 29.

— NASA Wallops (@NASA_Wallops) June 26, 2017

Backup launch day is June 30.

The Visitor Center at the Wallops Flight Facility on the eastern shore of Virginia will open at 3:30 a.m. on launch day, for those wishing to view the launch live. Live coverage online begins on the Wallops Ustream site at 3:45 a.m. on launch day and Wallops Facebook Live coverage begins at 4 a.m. on launch day. You might also check Twitter (@NASA_Wallops).

Illustration showing the trajectory of a sounding rocket. It’s a standard sounding rocket technique to create visible trails and “clouds” through the release of vapors that either glow on their own (i.e., luminescence) or scatter sunlight. Scientists monitor and take pictures of the subsequent trails and clouds to learn how the upper atmosphere and/or the ionosphere moves and evolves. Image via NASA.

The launch was originally scheduled for early June and has been postponed several times. NASA explained:

These clouds, or vapor tracers, allow scientists on the ground to visually track particle motions in space.

The development of the multi-canister ampoule ejection system will allow scientists to gather information over a much larger area than previously allowed when deploying the tracers just from the main payload …

The vapor tracers are formed through the interaction of barium, strontium and cupric-oxide. The tracers will be released at altitudes 96 to 124 miles high and pose no hazard to residents along the mid-Atlantic coast.

Read more from NASA

Read more about how sounding rockets work

This NASA sounding rocket will launch soon, creating colorful clouds in space. Image via @NASA_Wallops.

Bottom line: A launch of NASA’s Terrier-Improved Malemute sounding rocket expected to form colorful clouds in space, visible from New York to North Carolina. Launch currently scheduled for between 4:15 and 4:45 a.m., Thursday, June 29. Backup launch day June 30.

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

The enduring mystique of Barnard’s Star

Our sun’s closest neighbors among the stars, including Barnard’s Star. Image via NASA PhotoJournal.

Perhaps you know that, over the scale of our human lifespans, the stars appear fixed relative to one another. But Barnard’s Star – sometimes called Barnard’s Runaway Star – holds a speed record of sorts as the fastest-moving star in Earth’s skies. It moves fast with respect to other stars because it’s relatively close, only about 6 light-years away. What does its fast motion mean? It means Barnard’s Star is nearby! It’s only about six light-years away. Relative to other stars, Barnard’s Star moves 10.3 arcseconds per year, or about the width of a full moon in 174 years. This might not seem like much. But – to astronomers – Barnard’s Star is virtually zipping across the sky. Follow the links below to learn more about Barnard’s Star, which has high interest for astronomers and the public alike.

Barnard’s Star in history and popular culture

How to see Barnard’s Star

The science of Barnard’s Star

Barnard’s star, 1985 to 2005. Most stars are fixed with respect to each other, but – being close to us – Barnard’s Star appears to move. Image via Steve Quirk/ Wikimedia Commons.

Barnard’s Star in history and popular culture  Yerkes Observatory astronomer E. E. Barnard discovered the large proper motion of Barnard’s Star – that is, motion across our line of sight – in 1916.

He noticed it while comparing photographs of the same part of the sky taken in 1894 and again in 1916. The star appeared in significantly different positions, betraying its rapid motion.

Later, Harvard astronomer Edward Pickering found the star on photographic plates taken in 1888.

Barnard’s Star is named for this astronomer, E.E. Barnard, seen here posing with the 36? refractor at Lick Observatory. Image via OneMinuteAstronomer.

Barnard’s star came to our attention barely 100 years ago and cannot even be seen with the human eye, so the ancients did not know about it. It doesn’t figure into the lore of any constellation or cultural tradition. But that doesn’t mean that it doesn’t a have certain mystique about it that extends beyond the known facts.

For example, even as long ago as the 1960s and ’70s – long before successful planet-hunters like the Kepler spacecraft – there were suggestions that Barnard’s Star might have a family of planets. At that time, reported discrepancies in the motion of the star led to a claim that at least one Jupiter-size planet orbits it. Although the evidence was disputed and the claim now largely discredited, there is still a chance of planetary discoveries.

It’s likely due to this rumor of planets that Barnard’s Star has found a place in science fiction. It’s featured in, for example, The Hitchhiker’s Guide to the Galaxy by Douglas Adams; The Garden of Rama by Arthur C. Clarke and Gentry Lee; and several novels of physicist Robert L. Forward. In these works, the hypothetical planets are locations for early colonization or way-stations for exploration further into the cosmos.

Barnard’s Star also was the hypothetical target of Project Daedalus, a design study by members of the British Interplanetary Society, in which they envisioned an interstellar craft that could reach its destination within a human lifetime.

And Barnard’s Star has been featured in online games.

Clearly, Barnard’s Star captures peoples’ imaginations!

Image via BBC/ Sky at Night/ Paul Wootton. Read more.

How to see Barnard’s Star. Barnard’s Star is faint; its visual magnitude of about 9.5. Thus this star can’t be seen with the eye alone.

Whats more, its motion – though large in astronomical terms – is still too slow to be noticed in a single night or even easily across a human lifetime.

Since Barnard’s Star can’t be seen without powerful binoculars or a telescope, finding it requires both experience and perseverance. It is currently located in the constellation Ophiuchus, which is well placed on June, July and August evenings.

Because Barnard’s Star is a telescopic object, details on how to observe it are beyond the scope of this article, but Britain’s Sky at Night magazine has a good procedure online here: http://bit.ly/2rZNDe1

Artist’s concept of a red dwarf star – similar to Barnard’s Star – with a planet of about 12 Jupiter-masses. There has been speculation about planets orbiting Barnard’s Star, but none have been confirmed. Also, Barnard’s Star is thought to be considerably older than our sun, which could affect the potential for finding life there. Image via NASA/ ESA/ G. Bacon (STScI)/ Wikimedia Commons.

The science of Barnard’s Star. The fame of Barnard’s Star is in its novelty, the fact that it moves fastest through Earth’s skies. But its real importance to astronomy lies in the fact that being so close, it is one of the best sources for studying red dwarfs, the most abundant stars in the universe.

With only about 14% of the solar mass and less than 20% of the radius, it would take roughly seven Barnard’s Stars to match the mass of our sun, and 133 to match our sun’s volume.

Like all stars, Barnard’s Star shines via thermonuclear fusion, changing light elements (hydrogen) into more massive elements (helium), while releasing enormous amounts of energy. Even so, the lower mass of Barnard’s Star makes it about 2,500 times less powerful than our sun.

In other words, Barnard’s Star is much dimmer and cooler than our sun. If it replaced the sun in our solar system, it would shine only about four ten-thousandths as brightly as our sun. At the same time, it would be about 100 times brighter than a full moon. No life on Earth would be possible if we orbited Barnard’s Star instead of our sun, however. The much-decreased stellar heat would plunge Earth’s global temperatures to hundreds of degrees below zero.

Although very common, red dwarfs like Barnard’s Star are typically dim. Thus they are notoriously faint and hard to study. In fact, not a single red dwarf can be seen with the unaided human eye. But because Barnard’s Star is relatively close and bright, it has become a go-to model for all things red dwarf.

At nearly six light-years’ distance, Barnard’s Star is often cited as the second-closest star to our sun (and Earth). This is true only if you consider the triple star system Alpha Centauri as one star.

Proxima Centauri, the smallest and faintest of Alpha Centauri’s three components, is the closest known star to the sun at just 4.24 light years away. It, too, is a red dwarf. So Barnard’s Star is only the second-closest red dwarf star. It is perhaps more important for astronomical purposes, though, because Proxima is four times fainter and thus harder to study.

Special thanks to David J. Darling and Jack Schmidling for their help with this article.

Of course, all stars are moving through the space of our Milky Way galaxy. So even the “fixed” stars move over time. This illustration shows the distances to the nearest stars – including Barnard’s Star – in a time range between 20,000 years in the past and 80,000 years in the future. Image via FrancescoA/ Wikimedia Commons.

Bottom line: Barnard’s Star is the fastest-moving star in Earth’s skies, in terms of its proper motion. It moves fast because it’s relatively close, only about 6 light-years away.

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

Our sun’s closest neighbors among the stars, including Barnard’s Star. Image via NASA PhotoJournal.

Perhaps you know that, over the scale of our human lifespans, the stars appear fixed relative to one another. But Barnard’s Star – sometimes called Barnard’s Runaway Star – holds a speed record of sorts as the fastest-moving star in Earth’s skies. It moves fast with respect to other stars because it’s relatively close, only about 6 light-years away. What does its fast motion mean? It means Barnard’s Star is nearby! It’s only about six light-years away. Relative to other stars, Barnard’s Star moves 10.3 arcseconds per year, or about the width of a full moon in 174 years. This might not seem like much. But – to astronomers – Barnard’s Star is virtually zipping across the sky. Follow the links below to learn more about Barnard’s Star, which has high interest for astronomers and the public alike.

Barnard’s Star in history and popular culture

How to see Barnard’s Star

The science of Barnard’s Star

Barnard’s star, 1985 to 2005. Most stars are fixed with respect to each other, but – being close to us – Barnard’s Star appears to move. Image via Steve Quirk/ Wikimedia Commons.

Barnard’s Star in history and popular culture  Yerkes Observatory astronomer E. E. Barnard discovered the large proper motion of Barnard’s Star – that is, motion across our line of sight – in 1916.

He noticed it while comparing photographs of the same part of the sky taken in 1894 and again in 1916. The star appeared in significantly different positions, betraying its rapid motion.

Later, Harvard astronomer Edward Pickering found the star on photographic plates taken in 1888.

Barnard’s Star is named for this astronomer, E.E. Barnard, seen here posing with the 36? refractor at Lick Observatory. Image via OneMinuteAstronomer.

Barnard’s star came to our attention barely 100 years ago and cannot even be seen with the human eye, so the ancients did not know about it. It doesn’t figure into the lore of any constellation or cultural tradition. But that doesn’t mean that it doesn’t a have certain mystique about it that extends beyond the known facts.

For example, even as long ago as the 1960s and ’70s – long before successful planet-hunters like the Kepler spacecraft – there were suggestions that Barnard’s Star might have a family of planets. At that time, reported discrepancies in the motion of the star led to a claim that at least one Jupiter-size planet orbits it. Although the evidence was disputed and the claim now largely discredited, there is still a chance of planetary discoveries.

It’s likely due to this rumor of planets that Barnard’s Star has found a place in science fiction. It’s featured in, for example, The Hitchhiker’s Guide to the Galaxy by Douglas Adams; The Garden of Rama by Arthur C. Clarke and Gentry Lee; and several novels of physicist Robert L. Forward. In these works, the hypothetical planets are locations for early colonization or way-stations for exploration further into the cosmos.

Barnard’s Star also was the hypothetical target of Project Daedalus, a design study by members of the British Interplanetary Society, in which they envisioned an interstellar craft that could reach its destination within a human lifetime.

And Barnard’s Star has been featured in online games.

Clearly, Barnard’s Star captures peoples’ imaginations!

Image via BBC/ Sky at Night/ Paul Wootton. Read more.

How to see Barnard’s Star. Barnard’s Star is faint; its visual magnitude of about 9.5. Thus this star can’t be seen with the eye alone.

Whats more, its motion – though large in astronomical terms – is still too slow to be noticed in a single night or even easily across a human lifetime.

Since Barnard’s Star can’t be seen without powerful binoculars or a telescope, finding it requires both experience and perseverance. It is currently located in the constellation Ophiuchus, which is well placed on June, July and August evenings.

Because Barnard’s Star is a telescopic object, details on how to observe it are beyond the scope of this article, but Britain’s Sky at Night magazine has a good procedure online here: http://bit.ly/2rZNDe1

Artist’s concept of a red dwarf star – similar to Barnard’s Star – with a planet of about 12 Jupiter-masses. There has been speculation about planets orbiting Barnard’s Star, but none have been confirmed. Also, Barnard’s Star is thought to be considerably older than our sun, which could affect the potential for finding life there. Image via NASA/ ESA/ G. Bacon (STScI)/ Wikimedia Commons.

The science of Barnard’s Star. The fame of Barnard’s Star is in its novelty, the fact that it moves fastest through Earth’s skies. But its real importance to astronomy lies in the fact that being so close, it is one of the best sources for studying red dwarfs, the most abundant stars in the universe.

With only about 14% of the solar mass and less than 20% of the radius, it would take roughly seven Barnard’s Stars to match the mass of our sun, and 133 to match our sun’s volume.

Like all stars, Barnard’s Star shines via thermonuclear fusion, changing light elements (hydrogen) into more massive elements (helium), while releasing enormous amounts of energy. Even so, the lower mass of Barnard’s Star makes it about 2,500 times less powerful than our sun.

In other words, Barnard’s Star is much dimmer and cooler than our sun. If it replaced the sun in our solar system, it would shine only about four ten-thousandths as brightly as our sun. At the same time, it would be about 100 times brighter than a full moon. No life on Earth would be possible if we orbited Barnard’s Star instead of our sun, however. The much-decreased stellar heat would plunge Earth’s global temperatures to hundreds of degrees below zero.

Although very common, red dwarfs like Barnard’s Star are typically dim. Thus they are notoriously faint and hard to study. In fact, not a single red dwarf can be seen with the unaided human eye. But because Barnard’s Star is relatively close and bright, it has become a go-to model for all things red dwarf.

At nearly six light-years’ distance, Barnard’s Star is often cited as the second-closest star to our sun (and Earth). This is true only if you consider the triple star system Alpha Centauri as one star.

Proxima Centauri, the smallest and faintest of Alpha Centauri’s three components, is the closest known star to the sun at just 4.24 light years away. It, too, is a red dwarf. So Barnard’s Star is only the second-closest red dwarf star. It is perhaps more important for astronomical purposes, though, because Proxima is four times fainter and thus harder to study.

Special thanks to David J. Darling and Jack Schmidling for their help with this article.

Of course, all stars are moving through the space of our Milky Way galaxy. So even the “fixed” stars move over time. This illustration shows the distances to the nearest stars – including Barnard’s Star – in a time range between 20,000 years in the past and 80,000 years in the future. Image via FrancescoA/ Wikimedia Commons.

Bottom line: Barnard’s Star is the fastest-moving star in Earth’s skies, in terms of its proper motion. It moves fast because it’s relatively close, only about 6 light-years away.

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

Where’s the moon? Waxing crescent

Waxing crescent moon about 30-45 minutes after sunset on Sunday evening – June 25, 2017 – from Ouachita National Forest near Hot Springs, Arkansas by Kenny Cagle.

A waxing crescent moon – sometimes called a young moon – is always seen in the west after sunset.

In general, a waxing moon is seen one day to several days after new moon. It’s always seen in the evening, and it’s always seen in the west. On these days, the moon rises one hour to several hours behind the sun and follows the sun across the sky during the day. When the sun sets, and the sky darkens, the moon pops into view in the western sky.

The moon is now waxing toward first quarter. Next first quarter moon will be July 1, 2017 at 00:51 UTC. Next full moon is July 9 at 04:07 UTC; translate UTC to your time zone.

Much of the world will see the star Regulus near the waxing crescent moon, after sunset on Tuesday, June 27. From northwest South America, the moon will occult Regulus – pass in front of this star – at nightfall on June 27. Read more.

Some people think a moon visible in the west after sunset is a rising moon. But it’s not; it’s a setting moon. All objects in our sky rise in the east and set in the west, due to Earth’s spin under the sky. When you see a waxing crescent, you know the Earth, moon and sun are located nearly on a line in space. If they were more precisely on a line, as they are at new moon, we wouldn’t see the moon. The moon would travel across the sky during the day, lost in the sun’s glare.

But a waxing crescent moon is far enough away from that Earth-sun line to be visible near the sun’s glare – that is, in the west after sunset.

Note also that a crescent moon has nothing to do with Earth’s shadow on the moon. The only time Earth’s shadow can fall on the moon is at full moon, during a lunar eclipse. There is a shadow on a crescent moon, but it’s the moon’s own shadow. Night on the moon happens on the part of the moon submerged in the moon’s own shadow. Likewise, night on Earth happens on the part of Earth submerged in Earth’s own shadow.

2017 started out with a beautiful waxing crescent moon. This day-lapse composite image combines the earthshine moon from New Year’s Day with the crescent moon from the following day. A wide-field image with Venus at sunset and more information on how to make day-lapse images is available from Robert Pettengill of Austin, Texas.

Because the waxing crescent moon is nearly on a line with the Earth and sun, its illuminated hemisphere – or day side – is facing mostly away from us. We see only a slender fraction of the day side: a crescent moon. Each evening, because the moon is moving eastward in orbit around Earth, the moon appears farther from the sunset glare. It is moving farther from the Earth-sun line in space. Each evening, as the moon’s orbital motion carries it away from the Earth-sun line, we see more of the moon’s day side. Thus the crescent in the west after sunset appears to wax, or grow fatter each evening.

Very young moon with a pale earthshine glow, by Edmund Buras.

The pale glow on the darkened portion (night side) of a crescent moon is called earthshine. Is caused by light reflected from Earth’s day side onto the moon. After all, when you see a crescent moon in Earth’s sky, any moon people looking back at our world would see a nearly full Earth. Read more: What is earthshine?

As the moon orbits Earth, it changes phase in an orderly way. Follow these links to understand the various phases of the moon.

Four keys to understanding moon phases

Where’s the moon? Waxing crescent
Where’s the moon? First quarter
Where’s the moon? Waxing gibbous
What’s special about a full moon?
Where’s the moon? Waning gibbous
Where’s the moon? Last quarter
Where’s the moon? Waning crescent
Where’s the moon? New phase

Check out EarthSky’s guide to the bright planets.

from EarthSky http://ift.tt/1trITpz

Waxing crescent moon about 30-45 minutes after sunset on Sunday evening – June 25, 2017 – from Ouachita National Forest near Hot Springs, Arkansas by Kenny Cagle.

A waxing crescent moon – sometimes called a young moon – is always seen in the west after sunset.

In general, a waxing moon is seen one day to several days after new moon. It’s always seen in the evening, and it’s always seen in the west. On these days, the moon rises one hour to several hours behind the sun and follows the sun across the sky during the day. When the sun sets, and the sky darkens, the moon pops into view in the western sky.

The moon is now waxing toward first quarter. Next first quarter moon will be July 1, 2017 at 00:51 UTC. Next full moon is July 9 at 04:07 UTC; translate UTC to your time zone.

Much of the world will see the star Regulus near the waxing crescent moon, after sunset on Tuesday, June 27. From northwest South America, the moon will occult Regulus – pass in front of this star – at nightfall on June 27. Read more.

Some people think a moon visible in the west after sunset is a rising moon. But it’s not; it’s a setting moon. All objects in our sky rise in the east and set in the west, due to Earth’s spin under the sky. When you see a waxing crescent, you know the Earth, moon and sun are located nearly on a line in space. If they were more precisely on a line, as they are at new moon, we wouldn’t see the moon. The moon would travel across the sky during the day, lost in the sun’s glare.

But a waxing crescent moon is far enough away from that Earth-sun line to be visible near the sun’s glare – that is, in the west after sunset.

Note also that a crescent moon has nothing to do with Earth’s shadow on the moon. The only time Earth’s shadow can fall on the moon is at full moon, during a lunar eclipse. There is a shadow on a crescent moon, but it’s the moon’s own shadow. Night on the moon happens on the part of the moon submerged in the moon’s own shadow. Likewise, night on Earth happens on the part of Earth submerged in Earth’s own shadow.

2017 started out with a beautiful waxing crescent moon. This day-lapse composite image combines the earthshine moon from New Year’s Day with the crescent moon from the following day. A wide-field image with Venus at sunset and more information on how to make day-lapse images is available from Robert Pettengill of Austin, Texas.

Because the waxing crescent moon is nearly on a line with the Earth and sun, its illuminated hemisphere – or day side – is facing mostly away from us. We see only a slender fraction of the day side: a crescent moon. Each evening, because the moon is moving eastward in orbit around Earth, the moon appears farther from the sunset glare. It is moving farther from the Earth-sun line in space. Each evening, as the moon’s orbital motion carries it away from the Earth-sun line, we see more of the moon’s day side. Thus the crescent in the west after sunset appears to wax, or grow fatter each evening.

Very young moon with a pale earthshine glow, by Edmund Buras.

The pale glow on the darkened portion (night side) of a crescent moon is called earthshine. Is caused by light reflected from Earth’s day side onto the moon. After all, when you see a crescent moon in Earth’s sky, any moon people looking back at our world would see a nearly full Earth. Read more: What is earthshine?

As the moon orbits Earth, it changes phase in an orderly way. Follow these links to understand the various phases of the moon.

Four keys to understanding moon phases

Where’s the moon? Waxing crescent
Where’s the moon? First quarter
Where’s the moon? Waxing gibbous
What’s special about a full moon?
Where’s the moon? Waning gibbous
Where’s the moon? Last quarter
Where’s the moon? Waning crescent
Where’s the moon? New phase

Check out EarthSky’s guide to the bright planets.

from EarthSky http://ift.tt/1trITpz