Moon, Antares, Saturn on August 29

Tonight – August 29, 2017 – use the moon to find the star Antares and the planet Saturn, the 6th planet outward from the sun. Saturn now shines in front of the constellation Ophiuchus, sometimes called the forgotten zodiac constellation. Find out more about Ophiuchus here.

Find out more about the star Antares here.

Saturn’s rings and the moon Prometheus, as seen by the Cassini spacecraft. The wonderful Cassini mission is drawing to a close. In 2017, the spacecraft has been diving between Saturn and its innermost rings, exploring uncharted territory. It’s currently on its final set of 5 dives, dipping the spacecraft into the top of Saturn’s atmosphere, giving Cassini’s instruments the chance to make the first direct sampling of the planet, studying its chemical composition and analyzing its temperature at different altitudes. The dives will also provide close-up images of the planet’s atmospheric features, including its polar vortex and aurora. Image via NASA/JPL-Caltech/Space Science Institute. Read more about Cassini’s Grand Finale.

Saturn is the most distant world you can easily see with your unaided eye. Plus, you can view Saturn’s majestic rings with nothing more than a modest backyard telescope. All of the four outer planets (planets orbiting the sun outside the asteroid belt) – including Jupiter, Saturn, Uranus and Neptune – have a ring system of sorts. But Saturn’s rings are the most spectacular by leaps and bounds.

This year, in 2017, the north side of Saturn’s rings are maximally tilted toward Earth. So right now is a great time to dust off that telescope and gaze at Saturn, the crown jewel of the solar system.

Jupiter, Saturn, Uranus and Neptune are all gas giants (though Uranus and Neptune are sometimes referred to as ice giants). Overall, gas giant and ice giant planets have no solid surfaces. The smaller four inner planets with solid surfaces – Mercury, Venus, Earth and Mars – are called terrestrial or rocky planets.

Image of outer planets via NASA/JPL. From bottom to top, and in their outward order from the sun, these planets are Jupiter, Saturn, Uranus and Neptune.

There are no rings around any terrestrial solar system planet at present. Is there some reason why gas and ice giants have rings whereas terrestrial planets don’t? Cathy Jordon says at Cornell University’s Ask an Astronomer site:

It turns out that all of the planets, Earth included, did have rings at one time. The thing is, these rings were unstable and the material was either lost to space or collected into the satellites of these planets. The difference between the terrestrial and giant planets is the giant planets have the gravity to capture and hold onto a large satellite system, and these satellite systems are the source of the ring material.

It’s thought that Mars’ inner moon Phobos might break up and form a ring around Mars, some 50 million years from now. That’s because this moon is below the synchronous orbit radius – the distance at which the moon orbits Mars in the same time period that Mars rotates upon its axis. Because Phobos’ orbit is unstable, this moon is slowly but surely plunging toward its day of reckoning.

Bottom line: Let the moon on August 29, 2017 guide you to the planet Saturn, and if you have a telescope, use it to get an eyeful of Saturn’s marvelous rings.

from EarthSky http://ift.tt/2tSpRO5

Tonight – August 29, 2017 – use the moon to find the star Antares and the planet Saturn, the 6th planet outward from the sun. Saturn now shines in front of the constellation Ophiuchus, sometimes called the forgotten zodiac constellation. Find out more about Ophiuchus here.

Find out more about the star Antares here.

Saturn’s rings and the moon Prometheus, as seen by the Cassini spacecraft. The wonderful Cassini mission is drawing to a close. In 2017, the spacecraft has been diving between Saturn and its innermost rings, exploring uncharted territory. It’s currently on its final set of 5 dives, dipping the spacecraft into the top of Saturn’s atmosphere, giving Cassini’s instruments the chance to make the first direct sampling of the planet, studying its chemical composition and analyzing its temperature at different altitudes. The dives will also provide close-up images of the planet’s atmospheric features, including its polar vortex and aurora. Image via NASA/JPL-Caltech/Space Science Institute. Read more about Cassini’s Grand Finale.

Saturn is the most distant world you can easily see with your unaided eye. Plus, you can view Saturn’s majestic rings with nothing more than a modest backyard telescope. All of the four outer planets (planets orbiting the sun outside the asteroid belt) – including Jupiter, Saturn, Uranus and Neptune – have a ring system of sorts. But Saturn’s rings are the most spectacular by leaps and bounds.

This year, in 2017, the north side of Saturn’s rings are maximally tilted toward Earth. So right now is a great time to dust off that telescope and gaze at Saturn, the crown jewel of the solar system.

Jupiter, Saturn, Uranus and Neptune are all gas giants (though Uranus and Neptune are sometimes referred to as ice giants). Overall, gas giant and ice giant planets have no solid surfaces. The smaller four inner planets with solid surfaces – Mercury, Venus, Earth and Mars – are called terrestrial or rocky planets.

Image of outer planets via NASA/JPL. From bottom to top, and in their outward order from the sun, these planets are Jupiter, Saturn, Uranus and Neptune.

There are no rings around any terrestrial solar system planet at present. Is there some reason why gas and ice giants have rings whereas terrestrial planets don’t? Cathy Jordon says at Cornell University’s Ask an Astronomer site:

It turns out that all of the planets, Earth included, did have rings at one time. The thing is, these rings were unstable and the material was either lost to space or collected into the satellites of these planets. The difference between the terrestrial and giant planets is the giant planets have the gravity to capture and hold onto a large satellite system, and these satellite systems are the source of the ring material.

It’s thought that Mars’ inner moon Phobos might break up and form a ring around Mars, some 50 million years from now. That’s because this moon is below the synchronous orbit radius – the distance at which the moon orbits Mars in the same time period that Mars rotates upon its axis. Because Phobos’ orbit is unstable, this moon is slowly but surely plunging toward its day of reckoning.

Bottom line: Let the moon on August 29, 2017 guide you to the planet Saturn, and if you have a telescope, use it to get an eyeful of Saturn’s marvelous rings.

from EarthSky http://ift.tt/2tSpRO5

Evolutionary ecology could benefit beekeepers battling diseases

An electron mictrograph shows a Verroa destructor mite (right) on an adult honeybee host. The parasitic Varroa mite and the numerous viruses it carries are considered the primary causes of honeybee colony losses worldwide. (USDA photo) 

By Carol Clark

Some commercial beekeeping practices may harm honeybees more than help them, scientists warn in a paper published in the journal Nature Ecology and Evolution.

“Western honeybees — the most important pollinators for U.S. food crops — are facing unprecedented declines, and diseases are a key driver,” says Berry Brosi, an evolutionary biologist at Emory University and a lead author of the review paper. “The way commercial operations are managing honeybees might actually generate more damaging parasites and pathogens by creating selection pressure for higher virulence.”

The paper draws on scientific studies to recommend ways to reduce disease impacts, such as limiting the mixing of bees between colonies and supporting natural bee behaviors that provide disease resistance. The paper also highlights honeybee management practices in need of more research. 

During the past 15 years, ecological and evolutionary approaches have changed how scientists tackle problems of infectious diseases among humans, wildlife and livestock. “This change in thinking hasn’t sunk in with the beekeeping field yet,” says Emory evolutionary biologist Jaap de Roode, co-lead author of the paper. “We wanted to outline scientific approaches to help understand some of the current problems facing beekeepers, along with potential control measures.”

Co-authors of the paper include Keith Delaplane, an entomologist at the University of Georgia, and Michael Boots, an evolutionary biologist at the University of California, Berkeley.

Managed honeybees are important to the production of 39 of the 57 leading crops used for human consumption, including fruits, nuts, seeds and vegetables. In recent years, however, managed honeybee colonies have declined at the rate of more than one million per year, representing annual losses between 30 and 40 percent.

Two drone pupae of the Western honeybee infected with Varroa mites. (Photo by Waugsberg via Wikipedia Commons.)

While pesticides and land-use changes are factors involved in these losses, parasites are a primary driver — especially the aptly named Varroa destructor. The parasitic Varroa mite and the numerous viruses it carries are considered the primary causes of honeybee colony losses worldwide.

Varroa mites are native to Asia, where the Eastern honeybee species co-evolved with them before humans began managing bee colonies on commercial scales. As a result of this co-evolution, the Eastern honeybee developed behaviors — such as intensive mutual grooming — that reduce the mites’ negative impacts.

The Western honeybee species of the United States and Europe, however, has remained relatively defenseless against the mites, which spread to the United States during the late 1970s and 1980s. The mites suck the blood of the bees and reduce their immunity. Even more potentially destructive, however, are the multiple viruses the mites transmit through their saliva. Deformed-wing virus, for instance, can cripple a honeybee’s flying ability and is associated with high bee larval mortality.

Following are some of the potential solutions, in need of further study, outlined in the Nature Ecology & Evolution paper.

Reduce mixing of colonies: A common practice at beekeeping apiaries is to move combs containing brood — eggs and developing worker bees — between colonies. While the practice is meant to equalize colony strength, it can also spread parasites and pathogens.

Colonies are also mixed at regional and national scales. For instance, more than half of all honeybees in the country are involved in almond pollination in California. “For a lot of beekeeping operations, trucking their bees to California for almond pollination is how they make ends meet,” Brosi says. “It’s like the Christmas season for retailers.”

Pollination brokers set up contracts for individual beekeepers on particular almond farms. “If the brokers separated individual beekeeping operations beyond the distance that the average honeybee forages, that could potentially help reduce the mixing of bees and the rate of pathogen transmission between the operations,” Brosi says.

Varroa destructor (USDA)

Improve parasite clearance: Most means of dealing with Varroa mites focus on reducing their numbers in a colony rather than wiping them out, as the mites are developing increased resistance to some of the chemicals used to kill them. Such incomplete treatments increase natural selection for stronger, more virulent parasites. Further compounding the problem is that large commercial beekeeping operations may have tens of thousands of colonies, kept in close quarters.

“In a natural setting of an isolated bee colony living in a tree, a parasite that kills off the colony has nowhere to go,” de Roode explains. “But in an apiary with many other colonies nearby, the cost of parasite virulence goes way down.”

Allow sickened colonies to die out: Keeping bees infected with parasites and viruses alive through multiple interventions dilutes natural selection for disease resistance among the bees. In contrast, letting infections take their course in a colony and using the surviving bees for stock could lead to more resistant bees with fewer disease problems.

Support behavioral resistance: Beekeepers tend to select for bees that are more convenient to manage, but may have behavioral deficiencies that make them less fit. Some honeybees mix their saliva and beeswax with tree resin to form what is known as propolis, or bee glue, to seal holes and cracks in their hives. Studies have also shown that propolis helps keep diseases and parasites from entering the hive and inhibits the growth of fungi, bacteria and mites.

“Propolis is sticky. That annoys beekeepers trying to open hives and separate the components so they try to breed out this behavior,” de Roode says.

The paper concedes that commercial beekeeping operations face major challenges to shift to health management practices rooted in fundamental principles of evolution and ecology.

“Beekeeping is a tough way to make a living, because it operates on really thin margins,” Brosi says. “Even if there are no simple solutions, it’s important to make beekeepers aware of how their practices may affect bees in the long term. And we want researchers to contribute scientific understanding that translates into profitable and sustainable practices for beekeeping.”

Related:
Monarch butterflies use drugs to protect their offspring from parasites
Bees betray their flowers when pollinator species decline
The top 10 policies needed now to protect pollinators

from eScienceCommons http://ift.tt/2xrFT3E

An electron mictrograph shows a Verroa destructor mite (right) on an adult honeybee host. The parasitic Varroa mite and the numerous viruses it carries are considered the primary causes of honeybee colony losses worldwide. (USDA photo) 

By Carol Clark

Some commercial beekeeping practices may harm honeybees more than help them, scientists warn in a paper published in the journal Nature Ecology and Evolution.

“Western honeybees — the most important pollinators for U.S. food crops — are facing unprecedented declines, and diseases are a key driver,” says Berry Brosi, an evolutionary biologist at Emory University and a lead author of the review paper. “The way commercial operations are managing honeybees might actually generate more damaging parasites and pathogens by creating selection pressure for higher virulence.”

The paper draws on scientific studies to recommend ways to reduce disease impacts, such as limiting the mixing of bees between colonies and supporting natural bee behaviors that provide disease resistance. The paper also highlights honeybee management practices in need of more research. 

During the past 15 years, ecological and evolutionary approaches have changed how scientists tackle problems of infectious diseases among humans, wildlife and livestock. “This change in thinking hasn’t sunk in with the beekeeping field yet,” says Emory evolutionary biologist Jaap de Roode, co-lead author of the paper. “We wanted to outline scientific approaches to help understand some of the current problems facing beekeepers, along with potential control measures.”

Co-authors of the paper include Keith Delaplane, an entomologist at the University of Georgia, and Michael Boots, an evolutionary biologist at the University of California, Berkeley.

Managed honeybees are important to the production of 39 of the 57 leading crops used for human consumption, including fruits, nuts, seeds and vegetables. In recent years, however, managed honeybee colonies have declined at the rate of more than one million per year, representing annual losses between 30 and 40 percent.

Two drone pupae of the Western honeybee infected with Varroa mites. (Photo by Waugsberg via Wikipedia Commons.)

While pesticides and land-use changes are factors involved in these losses, parasites are a primary driver — especially the aptly named Varroa destructor. The parasitic Varroa mite and the numerous viruses it carries are considered the primary causes of honeybee colony losses worldwide.

Varroa mites are native to Asia, where the Eastern honeybee species co-evolved with them before humans began managing bee colonies on commercial scales. As a result of this co-evolution, the Eastern honeybee developed behaviors — such as intensive mutual grooming — that reduce the mites’ negative impacts.

The Western honeybee species of the United States and Europe, however, has remained relatively defenseless against the mites, which spread to the United States during the late 1970s and 1980s. The mites suck the blood of the bees and reduce their immunity. Even more potentially destructive, however, are the multiple viruses the mites transmit through their saliva. Deformed-wing virus, for instance, can cripple a honeybee’s flying ability and is associated with high bee larval mortality.

Following are some of the potential solutions, in need of further study, outlined in the Nature Ecology & Evolution paper.

Reduce mixing of colonies: A common practice at beekeeping apiaries is to move combs containing brood — eggs and developing worker bees — between colonies. While the practice is meant to equalize colony strength, it can also spread parasites and pathogens.

Colonies are also mixed at regional and national scales. For instance, more than half of all honeybees in the country are involved in almond pollination in California. “For a lot of beekeeping operations, trucking their bees to California for almond pollination is how they make ends meet,” Brosi says. “It’s like the Christmas season for retailers.”

Pollination brokers set up contracts for individual beekeepers on particular almond farms. “If the brokers separated individual beekeeping operations beyond the distance that the average honeybee forages, that could potentially help reduce the mixing of bees and the rate of pathogen transmission between the operations,” Brosi says.

Varroa destructor (USDA)

Improve parasite clearance: Most means of dealing with Varroa mites focus on reducing their numbers in a colony rather than wiping them out, as the mites are developing increased resistance to some of the chemicals used to kill them. Such incomplete treatments increase natural selection for stronger, more virulent parasites. Further compounding the problem is that large commercial beekeeping operations may have tens of thousands of colonies, kept in close quarters.

“In a natural setting of an isolated bee colony living in a tree, a parasite that kills off the colony has nowhere to go,” de Roode explains. “But in an apiary with many other colonies nearby, the cost of parasite virulence goes way down.”

Allow sickened colonies to die out: Keeping bees infected with parasites and viruses alive through multiple interventions dilutes natural selection for disease resistance among the bees. In contrast, letting infections take their course in a colony and using the surviving bees for stock could lead to more resistant bees with fewer disease problems.

Support behavioral resistance: Beekeepers tend to select for bees that are more convenient to manage, but may have behavioral deficiencies that make them less fit. Some honeybees mix their saliva and beeswax with tree resin to form what is known as propolis, or bee glue, to seal holes and cracks in their hives. Studies have also shown that propolis helps keep diseases and parasites from entering the hive and inhibits the growth of fungi, bacteria and mites.

“Propolis is sticky. That annoys beekeepers trying to open hives and separate the components so they try to breed out this behavior,” de Roode says.

The paper concedes that commercial beekeeping operations face major challenges to shift to health management practices rooted in fundamental principles of evolution and ecology.

“Beekeeping is a tough way to make a living, because it operates on really thin margins,” Brosi says. “Even if there are no simple solutions, it’s important to make beekeepers aware of how their practices may affect bees in the long term. And we want researchers to contribute scientific understanding that translates into profitable and sustainable practices for beekeeping.”

Related:
Monarch butterflies use drugs to protect their offspring from parasites
Bees betray their flowers when pollinator species decline
The top 10 policies needed now to protect pollinators

from eScienceCommons http://ift.tt/2xrFT3E

Biblical signs in the sky?

Just a few of the results of a Google image search for the words September 23, 2017 and Revelation 12.

Originally printed at The Catholic Astronomer. Re-printed here with permission.

One day last fall I was working in my office when my desk phone rang. It was a reader of The Catholic Astronomer, calling me with a question. He asked why the Vatican Observatory blog was full of discussion on black holes or whatnot, when there was something much more momentous to talk about.

It turns out that the momentous thing to which my caller was referring was an arrangement of celestial bodies that will occur this year (2017) on September 23. On that date, according to various Internet sources, the heavens themselves will be a tableau of Revelation 12 in the Bible:

A great sign appeared in the sky, a woman clothed with the sun, with the moon under her feet, and on her head a crown of 12 stars. She was with child and wailed aloud in pain as she labored to give birth … She gave birth to a son, a male child, destined to rule all the nations with an iron rod.

On September 23, 2017 the sun will be in the zodiac constellation Virgo — “a woman clothed with the sun”. The moon will be at the feet of Virgo — “with the moon under her feet”. The ‘nine’ stars of the zodiac constellation Leo, plus three planets (Mercury, Venus, and Mars), will be at the head of Virgo — “on her head a crown of 12 stars”. The planet Jupiter will be in the center of Virgo, and, as the weeks pass after September 23, Jupiter will exit Virgo to the east, past her feet, so to speak — “She was with child and wailed aloud in pain as she labored to give birth”. Jupiter is the largest of the planets, the “king” of the planets, so to speak — “She gave birth to a son, a male child, destined to rule all the nations with an iron rod”.

Must this not be a sign of something momentous, like the Internet sources say?

Now, I know that the readers of this blog are diverse. People with interest in astronomy are a diverse group! And you all will have diverse reactions to this question. Some of you are probably saying right now, “what a bunch of nonsense!” Others of you may be thinking that my caller had a good point, and you would like to learn more. Fortunately, I am a community college professor! Community college people are the ‘A-Team’ of the academic world (as in B.A., Hannibal, and the crew from the TV show and the movie — who are tougher than anyone else and able to save the day using duct tape, PVC pipe, and a butane lighter). We thrive on diversity! No question phases us!

We know that there are a lot of smart people out there who have not had much formal education in a topic like astronomy, and that interest in questions like this reflects a basic interest in astronomy combined with interest in religion and scripture.

My caller was familiar with the Stellarium sky software. He could call up the skies of September 23, 2017 on Stellarium and see for himself that this celestial arrangement was a real thing. His was a reasonable question. Scientists need to be able to answer questions people have like this one, without treating the questions as nonsense, because the questions will not go away just because they are dismissed. And thus before long I was having a nice conversation with the caller, and I ended up telling him I would look into his question, and write a post on this topic.

But I said it was unlikely to be the post he was looking for. He was OK with that.

And so, Mr. Caller:

The constellation Virgo on September 23, 2017, according to the Stellarium sky software. The moon’s size is exaggerated for visibility. See the annotated image below. Image via Christopher M. Graney.

Green arrows show the “9” stars of Leo. Blue arrows show the planets Mercury, Venus, and Mars. Red arrow is Jupiter. Violet arrow is the moon (shown enlarged). The sun is at Virgo’s shoulder. Image via Christopher M. Graney.

First, in one year, thanks to the Earth’s annual orbit, the sun travels the entirety of the ecliptic, and thus passes through every one of the 12 constellations of the zodiac. The sun is in Virgo every September.

Second, in one month the moon goes through its cycle of phases, and travels the entirety of the ecliptic, and thus passes through every constellation of the zodiac—all owed to the period of the moon’s orbit being one month. Therefore there is always a day or two every year when the sun is in Virgo and the moon is just to the east of Virgo (just past the “feet”).

So, the celestial “woman clothed with the sun with the moon at her feet” is as common in September as is the U.S. holiday of Labor Day.

But what of the crown of 12 “stars,” comprised of three planets and the nine stars of Leo? The response to this question is another question — why nine stars in Leo? There are many more than nine stars in Leo. Those nine are just brighter ones that are often depicted as comprising the general outline or shape of the constellation. But in fact there are scads of stars in Leo and surrounding the “head” of Virgo.

There are many more than 9 stars in the constellation Leo. Image via Christopher M. Graney.

And not all depictions of Leo show those nine as its outline. Some show the outline of Leo as consisting of 10 stars, for example. That would give Virgo a crown of 13 stars here!

Two depictions of Leo outlined with 10 or 11 stars rather than 9. The depiction on the left is from an astronomy book for children; the depiction on the right is from an old National Geographic atlas. Image via Christopher M. Graney.

And yes, multiple planets being at Virgo’s head while Jupiter is in Virgo’s center and the moon is at Virgo’s feet is somewhat unusual. But it is not that unusual. The period of Jupiter’s orbit is a little less than 12 years, and therefore Jupiter will be in Virgo (with the sun there, too, and the moon at the feet) once every 11 or 12 years.

So the sun in Virgo, the moon at Virgo’s “feet”, and Jupiter in the constellation are regular occurrences. This leaves the planets at the “head” (the number depending on the number of stars granted to Leo) as the determining factor in making a “momentous” celestial arrangement. Indeed – while various Internet sources speak of the specific celestial arrangement here as being “unique in human history” or “once in 7,000 years” – in fact, it is not unique to September 23, 2017.

This basic arrangement happened before — in September 1827, in September 1483, in September 1293, and in September 1056. These are all shown at the end of this post. I only searched back one thousand years, from 2017 to 1017 — there are undoubtedly other examples outside of that time period, and probably a couple examples that I missed within that time period.

No doubt someone could go diving into the history books to scrounge up some events from 1827, 1483, 1293, and 1056 that the September skies of those years supposedly foretold. That’s the way it is with astrology. A person reads his or her daily horoscope and finds that it says “obstacles will be placed in your path today.” Then, that person picks those instances of getting stuck in traffic, or in a long line at the grocery store, or wherever, and says “hey, that horoscope was right,” when, of course, we all encounter such things every day.

It is true that astrology — reading the heavens for signs — is something astronomers used to believe was valid (or, my guess is that many of them pretended to believe it was valid, because it paid the bills). But astrology has been found to have no more scientific basis than Harry Potter’s wand. It doesn’t work (something that does not seem to hinder its popularity). If astrology had anything going for it, astronomers would not need to go begging for money to fund astronomical research. We could just use our astronomical knowledge to divine which way the stock market was going, invest accordingly, become “astronomically” wealthy, and fund astronomical research from our surplus.

As it is, watching the heavens for signs of what is to come is a waste of time. And it is doubly a waste of time because “signs in the sky” appeal, for some reason, to all sorts of people out there — all of whom can use Stellarium to find this or that momentous “sign” signifying whatever they want to signify.

And that is why astronomers ignore the seemingly momentous celestial arrangement of September 23, 2017, and talk instead about black holes or whatnot.

The constellation Virgo on September 24, 1827, according to Stellarium. In this and the images below, the moon’s size is exaggerated for visibility. Image via Christopher M. Graney.

The constellation Virgo on September 6, 1483. Image via Christopher M. Graney.

The constellation Virgo on September 5, 1293. Image via Christopher M. Graney.

The constellation Virgo on September 14, 1056. Venus and the star Regulus in Leo are very close to one another. Image via Christopher M. Graney.

Bottom line: From the standpoint of astronomy, there’s nothing unique or unusual about the sun, moon and planets – or the constellation Virgo – on September 23, 2017, despite claims on the Internet of a unique and significant celestial event, supposedly “mirroring” the Bible’s Book of Revelation. In the past 1,000 years, this same event has happened at least four times already, in 1827, 1483, 1293, and 1056.

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

Just a few of the results of a Google image search for the words September 23, 2017 and Revelation 12.

Originally printed at The Catholic Astronomer. Re-printed here with permission.

One day last fall I was working in my office when my desk phone rang. It was a reader of The Catholic Astronomer, calling me with a question. He asked why the Vatican Observatory blog was full of discussion on black holes or whatnot, when there was something much more momentous to talk about.

It turns out that the momentous thing to which my caller was referring was an arrangement of celestial bodies that will occur this year (2017) on September 23. On that date, according to various Internet sources, the heavens themselves will be a tableau of Revelation 12 in the Bible:

A great sign appeared in the sky, a woman clothed with the sun, with the moon under her feet, and on her head a crown of 12 stars. She was with child and wailed aloud in pain as she labored to give birth … She gave birth to a son, a male child, destined to rule all the nations with an iron rod.

On September 23, 2017 the sun will be in the zodiac constellation Virgo — “a woman clothed with the sun”. The moon will be at the feet of Virgo — “with the moon under her feet”. The ‘nine’ stars of the zodiac constellation Leo, plus three planets (Mercury, Venus, and Mars), will be at the head of Virgo — “on her head a crown of 12 stars”. The planet Jupiter will be in the center of Virgo, and, as the weeks pass after September 23, Jupiter will exit Virgo to the east, past her feet, so to speak — “She was with child and wailed aloud in pain as she labored to give birth”. Jupiter is the largest of the planets, the “king” of the planets, so to speak — “She gave birth to a son, a male child, destined to rule all the nations with an iron rod”.

Must this not be a sign of something momentous, like the Internet sources say?

Now, I know that the readers of this blog are diverse. People with interest in astronomy are a diverse group! And you all will have diverse reactions to this question. Some of you are probably saying right now, “what a bunch of nonsense!” Others of you may be thinking that my caller had a good point, and you would like to learn more. Fortunately, I am a community college professor! Community college people are the ‘A-Team’ of the academic world (as in B.A., Hannibal, and the crew from the TV show and the movie — who are tougher than anyone else and able to save the day using duct tape, PVC pipe, and a butane lighter). We thrive on diversity! No question phases us!

We know that there are a lot of smart people out there who have not had much formal education in a topic like astronomy, and that interest in questions like this reflects a basic interest in astronomy combined with interest in religion and scripture.

My caller was familiar with the Stellarium sky software. He could call up the skies of September 23, 2017 on Stellarium and see for himself that this celestial arrangement was a real thing. His was a reasonable question. Scientists need to be able to answer questions people have like this one, without treating the questions as nonsense, because the questions will not go away just because they are dismissed. And thus before long I was having a nice conversation with the caller, and I ended up telling him I would look into his question, and write a post on this topic.

But I said it was unlikely to be the post he was looking for. He was OK with that.

And so, Mr. Caller:

The constellation Virgo on September 23, 2017, according to the Stellarium sky software. The moon’s size is exaggerated for visibility. See the annotated image below. Image via Christopher M. Graney.

Green arrows show the “9” stars of Leo. Blue arrows show the planets Mercury, Venus, and Mars. Red arrow is Jupiter. Violet arrow is the moon (shown enlarged). The sun is at Virgo’s shoulder. Image via Christopher M. Graney.

First, in one year, thanks to the Earth’s annual orbit, the sun travels the entirety of the ecliptic, and thus passes through every one of the 12 constellations of the zodiac. The sun is in Virgo every September.

Second, in one month the moon goes through its cycle of phases, and travels the entirety of the ecliptic, and thus passes through every constellation of the zodiac—all owed to the period of the moon’s orbit being one month. Therefore there is always a day or two every year when the sun is in Virgo and the moon is just to the east of Virgo (just past the “feet”).

So, the celestial “woman clothed with the sun with the moon at her feet” is as common in September as is the U.S. holiday of Labor Day.

But what of the crown of 12 “stars,” comprised of three planets and the nine stars of Leo? The response to this question is another question — why nine stars in Leo? There are many more than nine stars in Leo. Those nine are just brighter ones that are often depicted as comprising the general outline or shape of the constellation. But in fact there are scads of stars in Leo and surrounding the “head” of Virgo.

There are many more than 9 stars in the constellation Leo. Image via Christopher M. Graney.

And not all depictions of Leo show those nine as its outline. Some show the outline of Leo as consisting of 10 stars, for example. That would give Virgo a crown of 13 stars here!

Two depictions of Leo outlined with 10 or 11 stars rather than 9. The depiction on the left is from an astronomy book for children; the depiction on the right is from an old National Geographic atlas. Image via Christopher M. Graney.

And yes, multiple planets being at Virgo’s head while Jupiter is in Virgo’s center and the moon is at Virgo’s feet is somewhat unusual. But it is not that unusual. The period of Jupiter’s orbit is a little less than 12 years, and therefore Jupiter will be in Virgo (with the sun there, too, and the moon at the feet) once every 11 or 12 years.

So the sun in Virgo, the moon at Virgo’s “feet”, and Jupiter in the constellation are regular occurrences. This leaves the planets at the “head” (the number depending on the number of stars granted to Leo) as the determining factor in making a “momentous” celestial arrangement. Indeed – while various Internet sources speak of the specific celestial arrangement here as being “unique in human history” or “once in 7,000 years” – in fact, it is not unique to September 23, 2017.

This basic arrangement happened before — in September 1827, in September 1483, in September 1293, and in September 1056. These are all shown at the end of this post. I only searched back one thousand years, from 2017 to 1017 — there are undoubtedly other examples outside of that time period, and probably a couple examples that I missed within that time period.

No doubt someone could go diving into the history books to scrounge up some events from 1827, 1483, 1293, and 1056 that the September skies of those years supposedly foretold. That’s the way it is with astrology. A person reads his or her daily horoscope and finds that it says “obstacles will be placed in your path today.” Then, that person picks those instances of getting stuck in traffic, or in a long line at the grocery store, or wherever, and says “hey, that horoscope was right,” when, of course, we all encounter such things every day.

It is true that astrology — reading the heavens for signs — is something astronomers used to believe was valid (or, my guess is that many of them pretended to believe it was valid, because it paid the bills). But astrology has been found to have no more scientific basis than Harry Potter’s wand. It doesn’t work (something that does not seem to hinder its popularity). If astrology had anything going for it, astronomers would not need to go begging for money to fund astronomical research. We could just use our astronomical knowledge to divine which way the stock market was going, invest accordingly, become “astronomically” wealthy, and fund astronomical research from our surplus.

As it is, watching the heavens for signs of what is to come is a waste of time. And it is doubly a waste of time because “signs in the sky” appeal, for some reason, to all sorts of people out there — all of whom can use Stellarium to find this or that momentous “sign” signifying whatever they want to signify.

And that is why astronomers ignore the seemingly momentous celestial arrangement of September 23, 2017, and talk instead about black holes or whatnot.

The constellation Virgo on September 24, 1827, according to Stellarium. In this and the images below, the moon’s size is exaggerated for visibility. Image via Christopher M. Graney.

The constellation Virgo on September 6, 1483. Image via Christopher M. Graney.

The constellation Virgo on September 5, 1293. Image via Christopher M. Graney.

The constellation Virgo on September 14, 1056. Venus and the star Regulus in Leo are very close to one another. Image via Christopher M. Graney.

Bottom line: From the standpoint of astronomy, there’s nothing unique or unusual about the sun, moon and planets – or the constellation Virgo – on September 23, 2017, despite claims on the Internet of a unique and significant celestial event, supposedly “mirroring” the Bible’s Book of Revelation. In the past 1,000 years, this same event has happened at least four times already, in 1827, 1483, 1293, and 1056.

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

Powering Through: Navy Scientists Develop Underwater Wireless Charger

Navy scientists are developing a way to recharge unmanned undersea vehicles (UUV)s using wireless technology

from http://ift.tt/2wLPlSg

Navy scientists are developing a way to recharge unmanned undersea vehicles (UUV)s using wireless technology

from http://ift.tt/2wLPlSg

Dark for 2 years after dino-killing asteroid?

Artist’s concept of an asteroid impacting Earth. Image via NASA and NCAR/UCAR.

Researchers say they’ve used a world-class computer model to learn that Earth was plunged into darkness for nearly two years, following an asteroid impact 66 million years ago, at the end of Earth’s Cretaceous Period. The National Center for Atmospheric Research (NCAR) led the study, with support from NASA and the University of Colorado Boulder. An August 21, 2017 statement from NCAR/UCAR, written by Laura Snider (@lauracsnider), said:

This would have shut down photosynthesis, drastically cooled the planet, and contributed to the mass extinction that marked the end of the age of dinosaurs.

Details of the study were published August 21 in the peer-reviewed journal Proceedings of the National Academy of Sciences.

It’s thought that more than three-quarters of all species on Earth, including all non-avian dinosaurs, disappeared at the boundary of the Cretaceous-Paleogene periods, an event known as the K-Pg extinction.

Evidence suggests that the extinction occurred at the same time that a large asteroid hit Earth in what is now the Yucatán Peninsula. The collision would have triggered earthquakes, tsunamis, and even volcanic eruptions.

Badlands near Drumheller, Alberta, where erosion has exposed the K–Pg boundary. Image via Wikimedia Commons.

Scientists also calculate that the force of the impact would have launched vaporized rock high above Earth’s surface, where it would have condensed into small particles known as spherules. As the spherules fell back to Earth, they would have been heated by friction to temperatures high enough to spark global fires and broil Earth’s surface. A thin layer of spherules can be found worldwide in the geologic record.

NCAR scientist Charles Bardeen, who led the study, said:

The extinction of many of the large animals on land could have been caused by the immediate aftermath of the impact, but animals that lived in the oceans or those that could burrow underground or slip underwater temporarily could have survived.

Our study picks up the story after the initial effects — after the earthquakes and the tsunamis and the broiling. We wanted to look at the long-term consequences of the amount of soot we think was created and what those consequences might have meant for the animals that were left.

In past studies, researchers have estimated the amount of soot that might have been produced by global wildfires by measuring soot deposits still preserved in the geologic record. For the new study, Bardeen and his colleagues used the NCAR-based Community Earth System Model (CESM) to simulate the effect of the soot on global climate going forward. They used the most recent estimates of the amount of fine soot found in the layer of rock left after the impact (15,000 million tons), as well as larger and smaller amounts, to quantify the climate’s sensitivity to more or less extensive fires.

In the simulations, soot heated by the sun was lofted higher and higher into the atmosphere, eventually forming a global barrier that blocked the vast majority of sunlight from reaching Earth’s surface. Brian Toon of the University of Colorado at Boulder, who co-authored the study, said:

At first it would have been about as dark as a moonlit night.

While the skies would have gradually brightened, photosynthesis would have been impossible for more than a year and a half, according to the simulations. Because many of the plants on land would have already been incinerated in the fires, the darkness would likely have had its greatest impact on phytoplankton, which underpin the ocean food chain. The loss of these tiny organisms would have had a ripple effect through the ocean, eventually devastating many species of marine life.

The research team also found that photosynthesis would have been temporarily blocked even at much lower levels of soot. For example, in a simulation using only 5,000 million tons of soot — about a third of the best estimate from measurements — photosynthesis would still have been impossible for an entire year.

In the simulations, the loss of sunlight caused a steep decline in average temperatures at Earth’s surface, with a drop of 50 degrees Fahrenheit (28 degrees Celsius) over land and 20 degrees Fahrenheit (11 degrees Celsius) over the oceans.

While Earth’s surface cooled in the study scenarios, the atmosphere higher up in the stratosphere actually became much warmer as the soot absorbed light from the Sun. The warmer temperatures caused ozone destruction and allowed for large quantities of water vapor to be stored in the upper atmosphere. The water vapor then chemically reacted in the stratosphere to produce hydrogen compounds that led to further ozone destruction. The resulting ozone loss would have allowed damaging doses of ultraviolet light to reach Earth’s surface after the soot cleared.

The large reservoir of water in the upper atmosphere formed in the simulations also caused the layer of sunlight-blocking soot to be removed abruptly after lingering for years, a finding that surprised the research team. As the soot began to settle out of the stratosphere, the air began to cool. This cooling, in turn, caused water vapor to condense into ice particles, which washed even more soot out of the atmosphere. As a result of this feedback loop — cooling causing precipitation that caused more cooling — the thinning soot layer disappeared in just a few months.

While the scientists think the new study gives a robust picture of how large injections of soot into the atmosphere can affect the climate, they also caution that the study has limitations.

For example, the simulations were run in a model of modern-day Earth, not a model representing what Earth looked like during the Cretaceous Period, when the continents were in slightly different locations. The atmosphere 66 million years ago also contained somewhat different concentrations of gases, including higher levels of carbon dioxide.

Additionally, the simulations did not try to account for volcanic eruptions or sulfur released from the Earth’s crust at the site of the asteroid impact, which would have resulted in an increase in light-reflecting sulfate aerosols in the atmosphere.

Read more about this study from NCAR/ UCAR

Bottom line: A team led by researchers at the National Center for Atmospheric Research used computer modeling to learn that Earth was plunged into darkness for nearly two years, following the massive asteroid strike that ended the age of the dinosaurs, 66 million years ago.

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

Artist’s concept of an asteroid impacting Earth. Image via NASA and NCAR/UCAR.

Researchers say they’ve used a world-class computer model to learn that Earth was plunged into darkness for nearly two years, following an asteroid impact 66 million years ago, at the end of Earth’s Cretaceous Period. The National Center for Atmospheric Research (NCAR) led the study, with support from NASA and the University of Colorado Boulder. An August 21, 2017 statement from NCAR/UCAR, written by Laura Snider (@lauracsnider), said:

This would have shut down photosynthesis, drastically cooled the planet, and contributed to the mass extinction that marked the end of the age of dinosaurs.

Details of the study were published August 21 in the peer-reviewed journal Proceedings of the National Academy of Sciences.

It’s thought that more than three-quarters of all species on Earth, including all non-avian dinosaurs, disappeared at the boundary of the Cretaceous-Paleogene periods, an event known as the K-Pg extinction.

Evidence suggests that the extinction occurred at the same time that a large asteroid hit Earth in what is now the Yucatán Peninsula. The collision would have triggered earthquakes, tsunamis, and even volcanic eruptions.

Badlands near Drumheller, Alberta, where erosion has exposed the K–Pg boundary. Image via Wikimedia Commons.

Scientists also calculate that the force of the impact would have launched vaporized rock high above Earth’s surface, where it would have condensed into small particles known as spherules. As the spherules fell back to Earth, they would have been heated by friction to temperatures high enough to spark global fires and broil Earth’s surface. A thin layer of spherules can be found worldwide in the geologic record.

NCAR scientist Charles Bardeen, who led the study, said:

The extinction of many of the large animals on land could have been caused by the immediate aftermath of the impact, but animals that lived in the oceans or those that could burrow underground or slip underwater temporarily could have survived.

Our study picks up the story after the initial effects — after the earthquakes and the tsunamis and the broiling. We wanted to look at the long-term consequences of the amount of soot we think was created and what those consequences might have meant for the animals that were left.

In past studies, researchers have estimated the amount of soot that might have been produced by global wildfires by measuring soot deposits still preserved in the geologic record. For the new study, Bardeen and his colleagues used the NCAR-based Community Earth System Model (CESM) to simulate the effect of the soot on global climate going forward. They used the most recent estimates of the amount of fine soot found in the layer of rock left after the impact (15,000 million tons), as well as larger and smaller amounts, to quantify the climate’s sensitivity to more or less extensive fires.

In the simulations, soot heated by the sun was lofted higher and higher into the atmosphere, eventually forming a global barrier that blocked the vast majority of sunlight from reaching Earth’s surface. Brian Toon of the University of Colorado at Boulder, who co-authored the study, said:

At first it would have been about as dark as a moonlit night.

While the skies would have gradually brightened, photosynthesis would have been impossible for more than a year and a half, according to the simulations. Because many of the plants on land would have already been incinerated in the fires, the darkness would likely have had its greatest impact on phytoplankton, which underpin the ocean food chain. The loss of these tiny organisms would have had a ripple effect through the ocean, eventually devastating many species of marine life.

The research team also found that photosynthesis would have been temporarily blocked even at much lower levels of soot. For example, in a simulation using only 5,000 million tons of soot — about a third of the best estimate from measurements — photosynthesis would still have been impossible for an entire year.

In the simulations, the loss of sunlight caused a steep decline in average temperatures at Earth’s surface, with a drop of 50 degrees Fahrenheit (28 degrees Celsius) over land and 20 degrees Fahrenheit (11 degrees Celsius) over the oceans.

While Earth’s surface cooled in the study scenarios, the atmosphere higher up in the stratosphere actually became much warmer as the soot absorbed light from the Sun. The warmer temperatures caused ozone destruction and allowed for large quantities of water vapor to be stored in the upper atmosphere. The water vapor then chemically reacted in the stratosphere to produce hydrogen compounds that led to further ozone destruction. The resulting ozone loss would have allowed damaging doses of ultraviolet light to reach Earth’s surface after the soot cleared.

The large reservoir of water in the upper atmosphere formed in the simulations also caused the layer of sunlight-blocking soot to be removed abruptly after lingering for years, a finding that surprised the research team. As the soot began to settle out of the stratosphere, the air began to cool. This cooling, in turn, caused water vapor to condense into ice particles, which washed even more soot out of the atmosphere. As a result of this feedback loop — cooling causing precipitation that caused more cooling — the thinning soot layer disappeared in just a few months.

While the scientists think the new study gives a robust picture of how large injections of soot into the atmosphere can affect the climate, they also caution that the study has limitations.

For example, the simulations were run in a model of modern-day Earth, not a model representing what Earth looked like during the Cretaceous Period, when the continents were in slightly different locations. The atmosphere 66 million years ago also contained somewhat different concentrations of gases, including higher levels of carbon dioxide.

Additionally, the simulations did not try to account for volcanic eruptions or sulfur released from the Earth’s crust at the site of the asteroid impact, which would have resulted in an increase in light-reflecting sulfate aerosols in the atmosphere.

Read more about this study from NCAR/ UCAR

Bottom line: A team led by researchers at the National Center for Atmospheric Research used computer modeling to learn that Earth was plunged into darkness for nearly two years, following the massive asteroid strike that ended the age of the dinosaurs, 66 million years ago.

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

Mystery of high-energy cosmic rays

Here’s a cool new video from NASA about high-energy cosmic rays. This daily shower of particles, which never stops, is a sign of violent events in deep space.

Scientists believe that the majority of cosmic rays come from supernova explosions. According to NASA:

When massive stars explode they blast most of their material into space. The expanding shock waves can break apart interstellar atoms and accelerate the debris to unimaginably high energies. Other, unknown cataclysmic phenomena may be at work, too, especially for the most energetic cosmic rays.

Help EarthSky keep going! Donate

Bottom line: NASA video about the study of high-energy cosmic rays from deep space.

Read more from NASA

from EarthSky http://ift.tt/2vk9Oxq

Here’s a cool new video from NASA about high-energy cosmic rays. This daily shower of particles, which never stops, is a sign of violent events in deep space.

Scientists believe that the majority of cosmic rays come from supernova explosions. According to NASA:

When massive stars explode they blast most of their material into space. The expanding shock waves can break apart interstellar atoms and accelerate the debris to unimaginably high energies. Other, unknown cataclysmic phenomena may be at work, too, especially for the most energetic cosmic rays.

Help EarthSky keep going! Donate

Bottom line: NASA video about the study of high-energy cosmic rays from deep space.

Read more from NASA

from EarthSky http://ift.tt/2vk9Oxq

How far is a light-year?

The large yellow shell depicts a light-year; the smaller yellow shell depicts a light-month. Read more about this image at Wikimedia Commons.

Stars other than our sun are so far distant that astronomers speak of their distances not in terms of kilometers or miles – but in light-years. Light is the fastest-moving stuff in the universe. If we simply express light-years as miles and kilometers, we end up with impossibly huge numbers. But the 20th century astronomer Robert Burnham Jr. – author of Burnham’s Celestial Handbook – devised an ingenious way to portray the distance of one light-year and ultimately of expressing the distance scale of the universe, in understandable terms.

He did this by relating the light-year to the Astronomical Unit – the Earth-sun distance.

One Astronomical Unit, or AU, equals about 93 million miles (150 million km).

Another way of looking at it: the Astronomical Unit is a bit more than 8 light-minutes in distance.

A light beam takes 8 minutes to travel the 93 million miles (150 million km) from the sun to the Earth. Image via Brews OHare on Wikimedia Commons.

Robert Burnham noticed that, quite by coincidence, the number of astronomical units in one light-year and the number of inches in one mile are virtually the same.

For general reference, there are 63,000 astronomical units in one light-year, and 63,000 inches (160,000 cm) in one mile (1.6 km).

This wonderful coincidence enables us to bring the light-year down to Earth. If we scale the astronomical unit – the Earth-sun distance – at one inch, then the light-year on this scale represents one mile (1.6 km).

The closest star to Earth, other than the sun, is Alpha Centauri at some 4.4 light-years away. Scaling the Earth-sun distance at one inch places this star at 4.4 miles (7 km) distant.

The red star in the center of this picture is Proxima Centauri, our sun's nearest neighbor among the stars. A beam of light from this star takes about 4 years to travel to Earth. Image via hyperphysics.phy-astr.gsu.edu

Scaling the Astronomical Unit at one inch (2.5 cm), here are distances to various bright stars, star clusters and galaxies:

Alpha Centauri: 4 miles (6.4 km)

Sirius: 9 miles (14.5 km)

Vega: 25 miles (40 km)

Fomalhaut: 25 miles (40 km)

Arcturus: 37 miles (60 km)

Antares: 600 miles (966 km)

Pleiades open star cluster: 440 miles (708 km)

Hercules globular star cluster (M13): 24,000 miles (38,600 km)

Center of Milky Way galaxy: 27,000 miles (43,500 km)

Great Andromeda galaxy (M31): 2,300,000 miles (3,700,000 km)

Whirlpool galaxy (M51): 37,000,000 miles (60,000,000 km)

Sombrero galaxy (M104): 65,000,000 miles (105,000,000 km)

There are 33 stars within 12.5 light years of our sun. Image via Atlas of the Universe.

Light is the fastest-moving stuff in the universe. It travels at an incredible 186,000 miles (300,000 km) per second.

That’s very fast. If you could travel at the speed of light, you would be able to circle the Earth’s equator about 7.5 times in just one second!

A light-second is the distance light travels in one second, or 7.5 times the distance around Earth’s equator. A light-year is the distance light travels in one year.

How far is that? Multiply the number of seconds in one year by the number of miles or kilometers that light travels in one second, and there you have it: one light-year. It’s about 5.88 trillion miles (9.5 trillion km).

This scale starts close to home but takes us all the way out to the Andromeda Galaxy, the most distant object most people can see with the unaided eye. Image via Bob King / Skyandtelescope.com.

Bottom line: The scale of light-years expressed as miles and kilometers.

What is a light-year?

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

from EarthSky http://ift.tt/13RT78F

The large yellow shell depicts a light-year; the smaller yellow shell depicts a light-month. Read more about this image at Wikimedia Commons.

Stars other than our sun are so far distant that astronomers speak of their distances not in terms of kilometers or miles – but in light-years. Light is the fastest-moving stuff in the universe. If we simply express light-years as miles and kilometers, we end up with impossibly huge numbers. But the 20th century astronomer Robert Burnham Jr. – author of Burnham’s Celestial Handbook – devised an ingenious way to portray the distance of one light-year and ultimately of expressing the distance scale of the universe, in understandable terms.

He did this by relating the light-year to the Astronomical Unit – the Earth-sun distance.

One Astronomical Unit, or AU, equals about 93 million miles (150 million km).

Another way of looking at it: the Astronomical Unit is a bit more than 8 light-minutes in distance.

A light beam takes 8 minutes to travel the 93 million miles (150 million km) from the sun to the Earth. Image via Brews OHare on Wikimedia Commons.

Robert Burnham noticed that, quite by coincidence, the number of astronomical units in one light-year and the number of inches in one mile are virtually the same.

For general reference, there are 63,000 astronomical units in one light-year, and 63,000 inches (160,000 cm) in one mile (1.6 km).

This wonderful coincidence enables us to bring the light-year down to Earth. If we scale the astronomical unit – the Earth-sun distance – at one inch, then the light-year on this scale represents one mile (1.6 km).

The closest star to Earth, other than the sun, is Alpha Centauri at some 4.4 light-years away. Scaling the Earth-sun distance at one inch places this star at 4.4 miles (7 km) distant.

The red star in the center of this picture is Proxima Centauri, our sun's nearest neighbor among the stars. A beam of light from this star takes about 4 years to travel to Earth. Image via hyperphysics.phy-astr.gsu.edu

Scaling the Astronomical Unit at one inch (2.5 cm), here are distances to various bright stars, star clusters and galaxies:

Alpha Centauri: 4 miles (6.4 km)

Sirius: 9 miles (14.5 km)

Vega: 25 miles (40 km)

Fomalhaut: 25 miles (40 km)

Arcturus: 37 miles (60 km)

Antares: 600 miles (966 km)

Pleiades open star cluster: 440 miles (708 km)

Hercules globular star cluster (M13): 24,000 miles (38,600 km)

Center of Milky Way galaxy: 27,000 miles (43,500 km)

Great Andromeda galaxy (M31): 2,300,000 miles (3,700,000 km)

Whirlpool galaxy (M51): 37,000,000 miles (60,000,000 km)

Sombrero galaxy (M104): 65,000,000 miles (105,000,000 km)

There are 33 stars within 12.5 light years of our sun. Image via Atlas of the Universe.

Light is the fastest-moving stuff in the universe. It travels at an incredible 186,000 miles (300,000 km) per second.

That’s very fast. If you could travel at the speed of light, you would be able to circle the Earth’s equator about 7.5 times in just one second!

A light-second is the distance light travels in one second, or 7.5 times the distance around Earth’s equator. A light-year is the distance light travels in one year.

How far is that? Multiply the number of seconds in one year by the number of miles or kilometers that light travels in one second, and there you have it: one light-year. It’s about 5.88 trillion miles (9.5 trillion km).

This scale starts close to home but takes us all the way out to the Andromeda Galaxy, the most distant object most people can see with the unaided eye. Image via Bob King / Skyandtelescope.com.

Bottom line: The scale of light-years expressed as miles and kilometers.

What is a light-year?

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

from EarthSky http://ift.tt/13RT78F