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What’s the August birthstone?

Peridot. Photo via Boykung/Shutterstock

Peridot

Peridot is a gem-quality transparent variety of olivine, a mineral composed of magnesium-iron silicates. The color of olivine ranges from olive to lime green, sometimes with a brownish tinge. The green color is due to the presence of iron, while the brownish tinge indicates a higher iron content.

Peridot

Some of the finest peridot stones are called “evening emeralds” because they appear greener under artificial light.

An island in the Red Sea – named Zabargad, which means olivine in Arabic-has been mined for peridot since ancient times. It is a small desolate island – nothing grows, there is no fresh water, and it is scorchingly hot all year round except the middle of winter. In some locations on the island, fissures are lined with gem crystals ranging from millimeters to several centimeters. Beaches near the deposits have a greenish hue due to tiny green peridot crystals.

Peridot crystals are also found in the Mogok district of Burma, Norway, Brazil, China, Kenya, Sri Lanka, Australia, and Mexico. In the United States, small stones can be found in the San Carlos Indian Reservation in Arizona. Peridot has also been found in some meteorites.

Peridot is among the oldest known gemstones. The “topaz” on the breastplate of Aaron, High Priest of the Hebrews in the Old Testament, was believed to actually be peridot. Ancient Egyptians, around 1580 B.C. to 1350 B.C., created beads from peridot. For Greeks and Romans, peridot was in popular use as intaglios, rings, inlays, and pendants.

The peridot was regarded since ancient times as the symbol of the sun. The Greeks believed that it brought royal dignity upon its wearer. During the Middle Ages, peridot was pierced, then strung on the hair of an ass and attached to the left arm to ward off evil spirits. The Crusaders thought that peridots were emeralds, and brought them back to Europe where they were featured as ornaments in churches.

Peridots were a prized gem late in the Ottoman empire (1300-1918). Turkish Sultans collected what is believed to be the world’s largest collection. The gold throne in Istanbul’s Topkapi museum is decorated with 955 peridot cabochons (gems or beads cut in convex form and highly polished) up to 1 inch across, and there are also peridots used as turban ornaments and on jeweled boxes. The largest stone is believed to be a 310 carat gem that belongs to the Smithsonian. A 192 carat stone of fine clear olive-green is part of the Russian crown jewels, in the Kremlin.

Sardonyx

Sardonyx is a variety of the silica mineral called chalcedony. This sort of mineral contains layers of tiny quartz fibers, which are stacked on top of each other to give a banded appearance. The layers in these stones range from translucent to opaque. The stones vary in color, too. They may be white or gray, ranging to many colorful varieties.

Sardonyx. Image via Arpingstone.

Sardonyx stones usually contain flat-banded, white and brownish-red bands. The word Sardonyx is derived from the Greek, sard meaning “reddish brown,” and onyx meaning “veined gem.” The best stones are found in India. They are also found in Germany, Czechoslovakia, Brazil, and Uruguay. In the United States, sardonyx can be found in the Lake Superior region and in Oregon.

Cameos and intaglios are often carved from sardonyx. Cameos are figures carved on a stone, where the white layer appears as relief, and the colored layer is the background. Intaglios are the reverse of cameos. They are incised figures on the stone, where the stone is carved through the dark layer to reveal the light layer.

Sardonyx is a relatively common and inexpensive gemstone. It was a favorite gemstone in ancient times, popular not only because it was attractive, but also because it was widely available. Unlike most rare gemstones that could only be bought with the wealth of royalty and nobility, sardonyx could be obtained by many less-wealthy people.

Roman soldiers wore sardonyx talismans (objects bearing a sign of astrological influence to guard from evil and bring good fortune) engraved with heroes such as Hercules or Mars, god of war. They believed that the stone would make the wearer as brave and daring as the figured carved on it. During the Renaissance, sardonyx was believed to bring eloquence upon the wearer and was regarded with great value by public speakers and orators.

Perhaps the most famous sardonyx stone was set in a gold ring, carved with the portrait of Queen Elizabeth I of England. It was given to the Earl of Essex by the Queen as a token of friendship, and she assured him that she would always come to his aid if he ever requested it. The Earl, imprisoned for treason, was condemned to be beheaded. He tried to send the ring to his Queen but it fell into the hands of Lady Nottingham, whose husband was an enemy of the Earl of Essex. Thinking that the Earl was too proud to ask for her mercy, the Queen allowed his execution. It wasn’t until the deathbed confession of Lady Nottingham that the Queen learned the truth, which left her heart-broken.

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Find out about the birthstones for the other months of the year.
January birthstone
February birthstone
March birthstone
April birthstone
May birthstone
July birthstone
August birthstone
September birthstone
October birthstone
November birthstone
December birthstone



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Peridot. Photo via Boykung/Shutterstock

Peridot

Peridot is a gem-quality transparent variety of olivine, a mineral composed of magnesium-iron silicates. The color of olivine ranges from olive to lime green, sometimes with a brownish tinge. The green color is due to the presence of iron, while the brownish tinge indicates a higher iron content.

Peridot

Some of the finest peridot stones are called “evening emeralds” because they appear greener under artificial light.

An island in the Red Sea – named Zabargad, which means olivine in Arabic-has been mined for peridot since ancient times. It is a small desolate island – nothing grows, there is no fresh water, and it is scorchingly hot all year round except the middle of winter. In some locations on the island, fissures are lined with gem crystals ranging from millimeters to several centimeters. Beaches near the deposits have a greenish hue due to tiny green peridot crystals.

Peridot crystals are also found in the Mogok district of Burma, Norway, Brazil, China, Kenya, Sri Lanka, Australia, and Mexico. In the United States, small stones can be found in the San Carlos Indian Reservation in Arizona. Peridot has also been found in some meteorites.

Peridot is among the oldest known gemstones. The “topaz” on the breastplate of Aaron, High Priest of the Hebrews in the Old Testament, was believed to actually be peridot. Ancient Egyptians, around 1580 B.C. to 1350 B.C., created beads from peridot. For Greeks and Romans, peridot was in popular use as intaglios, rings, inlays, and pendants.

The peridot was regarded since ancient times as the symbol of the sun. The Greeks believed that it brought royal dignity upon its wearer. During the Middle Ages, peridot was pierced, then strung on the hair of an ass and attached to the left arm to ward off evil spirits. The Crusaders thought that peridots were emeralds, and brought them back to Europe where they were featured as ornaments in churches.

Peridots were a prized gem late in the Ottoman empire (1300-1918). Turkish Sultans collected what is believed to be the world’s largest collection. The gold throne in Istanbul’s Topkapi museum is decorated with 955 peridot cabochons (gems or beads cut in convex form and highly polished) up to 1 inch across, and there are also peridots used as turban ornaments and on jeweled boxes. The largest stone is believed to be a 310 carat gem that belongs to the Smithsonian. A 192 carat stone of fine clear olive-green is part of the Russian crown jewels, in the Kremlin.

Sardonyx

Sardonyx is a variety of the silica mineral called chalcedony. This sort of mineral contains layers of tiny quartz fibers, which are stacked on top of each other to give a banded appearance. The layers in these stones range from translucent to opaque. The stones vary in color, too. They may be white or gray, ranging to many colorful varieties.

Sardonyx. Image via Arpingstone.

Sardonyx stones usually contain flat-banded, white and brownish-red bands. The word Sardonyx is derived from the Greek, sard meaning “reddish brown,” and onyx meaning “veined gem.” The best stones are found in India. They are also found in Germany, Czechoslovakia, Brazil, and Uruguay. In the United States, sardonyx can be found in the Lake Superior region and in Oregon.

Cameos and intaglios are often carved from sardonyx. Cameos are figures carved on a stone, where the white layer appears as relief, and the colored layer is the background. Intaglios are the reverse of cameos. They are incised figures on the stone, where the stone is carved through the dark layer to reveal the light layer.

Sardonyx is a relatively common and inexpensive gemstone. It was a favorite gemstone in ancient times, popular not only because it was attractive, but also because it was widely available. Unlike most rare gemstones that could only be bought with the wealth of royalty and nobility, sardonyx could be obtained by many less-wealthy people.

Roman soldiers wore sardonyx talismans (objects bearing a sign of astrological influence to guard from evil and bring good fortune) engraved with heroes such as Hercules or Mars, god of war. They believed that the stone would make the wearer as brave and daring as the figured carved on it. During the Renaissance, sardonyx was believed to bring eloquence upon the wearer and was regarded with great value by public speakers and orators.

Perhaps the most famous sardonyx stone was set in a gold ring, carved with the portrait of Queen Elizabeth I of England. It was given to the Earl of Essex by the Queen as a token of friendship, and she assured him that she would always come to his aid if he ever requested it. The Earl, imprisoned for treason, was condemned to be beheaded. He tried to send the ring to his Queen but it fell into the hands of Lady Nottingham, whose husband was an enemy of the Earl of Essex. Thinking that the Earl was too proud to ask for her mercy, the Queen allowed his execution. It wasn’t until the deathbed confession of Lady Nottingham that the Queen learned the truth, which left her heart-broken.

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

Find out about the birthstones for the other months of the year.
January birthstone
February birthstone
March birthstone
April birthstone
May birthstone
July birthstone
August birthstone
September birthstone
October birthstone
November birthstone
December birthstone



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Finding PEACE and remembering my brother Mark – Dave’s story

At just 28 years old Dave Sims lost his twin brother Mark, a doctor from Bristol, to skin cancer. By raising awareness of the disease, Mark wanted to make sure that fewer people have to go through what he did. Though he may not be here today, by joining our PEACE study Mark continues to be part of a research journey that could improve the outlook for people like him in the future.

Dave tells us the inspiring story of his brother, which is just one of those featured in our Annual Review, highlighting the progress we’re making and our aims for the future.

When Mark was 15, his hairdresser noticed a dark patch of skin on his head that was getting bigger between haircuts. His doctor diagnosed it as melanoma, a type of skin cancer. He had the dark patch removed to treat the disease and we hoped it wouldn’t come back, but it had already grown quite large by that point.

He didn’t spend his whole life worrying about what might happen, but the situation definitely made Mark more interested in health and motivated him to help people like himself. That’s part of the reason he chose to become a doctor. When he later learned about melanoma during one of his lectures, Mark realised that the risk of his cancer returning was higher than he’d thought.

He didn’t spend his whole life worrying about what might happen

In 2015, 12 years after Mark’s first diagnosis, his cancer returned. But by the time the cancer was discovered for the second time it had already spread to several parts of his body.

Mark accepted his diagnosis and was resilient, staying optimistic but realistic. He understood that his cancer was serious, so he wanted to be proactive and do the best he could in the time that he had. Immediately after his diagnosis he got involved with Cancer Research UK and became an ambassador.

He knew it was important to raise both money for research and awareness about melanoma. As a doctor and being diagnosed so young, Mark realised his story would resonate with people. He started writing a blog to tell people about his journey and set up a fundraising page. Within hours of posting the fundraising page on Facebook he raised £5,000; over the next few days that went up to £25,000.

‘Mark always thought about others more than himself’

End of life conversations between doctors and patients are difficult, but when doctors approached Mark about the PEACE study there was no question of whether he’d join; we all knew it was something he would want to do. The tissue he donated will let scientists really see how the cancer drugs Mark took interacted with his body.

“We want to know why some patients don’t respond or stop responding to certain cancer drugs, and understand how and why some cancers spread,” says Dr Mariam Jamal-Hanjani from University College London, one of the lead researchers behind the PEACE study, who had the opportunity to meet Dave.

“Because if we can understand how they develop and get worse, then we might be able to come up with new treatments and ways to stop that from happening.

“What makes the study so powerful is that as well as looking at samples from patients that are collected while they’re alive, we’re also collecting tissue from shortly after they die from their disease. Those patients won’t directly benefit from the study, but future patients will benefit from what we’ve learned through gathering information that we’ve never had before.

“It’s incredibly humbling that these selfless people are going through the most difficult time of their lives, yet they want to be part of pioneering research, knowing they won’t benefit from it.”

‘It’s never going to be easy, but he’s making a difference’

By the end of May this year Mark had raised over £183,000, but in some ways his contribution to the PEACE study is more valuable than the money he’s raised. He always thought about others more than himself and wanted to contribute as much as he possibly could so that in 20 years’ time, another Mark Sims doesn’t go through the same thing that he did. The PEACE study gave him another opportunity to do that.

Mark knew that research takes a long time and that we won’t know the benefit of the study for many years, but by raising awareness about it hopefully more people will get involved too – the more, the better.

On top of raising money for research like this, one of my main motivations for sharing Mark’s story is helping to make people more aware about melanoma itself and encouraging them to take care of their skin. It’s a cancer where you can do things to lower your risk, like not going on sunbeds and covering up your skin when you’re out in the sun. And by looking out for signs of the disease on the skin, so hopefully doctors can catch it early.

We are all really proud of Mark. Although it’s never going to be easy without him, the situation has inspired us to know that he’s making a difference. That’s made things a little easier.



from Cancer Research UK – Science blog http://ift.tt/2vhU8td

At just 28 years old Dave Sims lost his twin brother Mark, a doctor from Bristol, to skin cancer. By raising awareness of the disease, Mark wanted to make sure that fewer people have to go through what he did. Though he may not be here today, by joining our PEACE study Mark continues to be part of a research journey that could improve the outlook for people like him in the future.

Dave tells us the inspiring story of his brother, which is just one of those featured in our Annual Review, highlighting the progress we’re making and our aims for the future.

When Mark was 15, his hairdresser noticed a dark patch of skin on his head that was getting bigger between haircuts. His doctor diagnosed it as melanoma, a type of skin cancer. He had the dark patch removed to treat the disease and we hoped it wouldn’t come back, but it had already grown quite large by that point.

He didn’t spend his whole life worrying about what might happen, but the situation definitely made Mark more interested in health and motivated him to help people like himself. That’s part of the reason he chose to become a doctor. When he later learned about melanoma during one of his lectures, Mark realised that the risk of his cancer returning was higher than he’d thought.

He didn’t spend his whole life worrying about what might happen

In 2015, 12 years after Mark’s first diagnosis, his cancer returned. But by the time the cancer was discovered for the second time it had already spread to several parts of his body.

Mark accepted his diagnosis and was resilient, staying optimistic but realistic. He understood that his cancer was serious, so he wanted to be proactive and do the best he could in the time that he had. Immediately after his diagnosis he got involved with Cancer Research UK and became an ambassador.

He knew it was important to raise both money for research and awareness about melanoma. As a doctor and being diagnosed so young, Mark realised his story would resonate with people. He started writing a blog to tell people about his journey and set up a fundraising page. Within hours of posting the fundraising page on Facebook he raised £5,000; over the next few days that went up to £25,000.

‘Mark always thought about others more than himself’

End of life conversations between doctors and patients are difficult, but when doctors approached Mark about the PEACE study there was no question of whether he’d join; we all knew it was something he would want to do. The tissue he donated will let scientists really see how the cancer drugs Mark took interacted with his body.

“We want to know why some patients don’t respond or stop responding to certain cancer drugs, and understand how and why some cancers spread,” says Dr Mariam Jamal-Hanjani from University College London, one of the lead researchers behind the PEACE study, who had the opportunity to meet Dave.

“Because if we can understand how they develop and get worse, then we might be able to come up with new treatments and ways to stop that from happening.

“What makes the study so powerful is that as well as looking at samples from patients that are collected while they’re alive, we’re also collecting tissue from shortly after they die from their disease. Those patients won’t directly benefit from the study, but future patients will benefit from what we’ve learned through gathering information that we’ve never had before.

“It’s incredibly humbling that these selfless people are going through the most difficult time of their lives, yet they want to be part of pioneering research, knowing they won’t benefit from it.”

‘It’s never going to be easy, but he’s making a difference’

By the end of May this year Mark had raised over £183,000, but in some ways his contribution to the PEACE study is more valuable than the money he’s raised. He always thought about others more than himself and wanted to contribute as much as he possibly could so that in 20 years’ time, another Mark Sims doesn’t go through the same thing that he did. The PEACE study gave him another opportunity to do that.

Mark knew that research takes a long time and that we won’t know the benefit of the study for many years, but by raising awareness about it hopefully more people will get involved too – the more, the better.

On top of raising money for research like this, one of my main motivations for sharing Mark’s story is helping to make people more aware about melanoma itself and encouraging them to take care of their skin. It’s a cancer where you can do things to lower your risk, like not going on sunbeds and covering up your skin when you’re out in the sun. And by looking out for signs of the disease on the skin, so hopefully doctors can catch it early.

We are all really proud of Mark. Although it’s never going to be easy without him, the situation has inspired us to know that he’s making a difference. That’s made things a little easier.



from Cancer Research UK – Science blog http://ift.tt/2vhU8td

Moon near star Antares on August 1

Tonight – August 1, 2017 – the bright star near the moon is Antares in the constellation Scorpius the Scorpion. You’ve got about another month or two to see this uniquely summer star for us in the Northern Hemisphere, during the evening hours. Antares is the brightest star near the moon tonight, while the other nearby bright beauty is the planet Saturn.

If you’re in the Northern Hemisphere, Antares and Saturn are visible in the southern to southwest sky as night begins. If you’re in the Southern Hemisphere, they’re more overhead for you.

The moon has now passed the first quarter phase and now exhibits a curvature to its terminator line – the line between dark and light on the moon. This moon phase is called waxing gibbous. The waxing gibbous moon, Antares and Saturn will drift westward throughout the night, to set after midnight at mid-northern latitudes.

Like all stars, Antares sets some 4 minutes earlier with each passing night, or 2 hours earlier with each passing month. By October, this star will be tough to spot in the southwestern twilight after sunset.

In ancient Chinese thought, the summer season was associated with the direction south, with the element fire, and with the color red. No wonder, then, that this reddish star in the south each summer – beautiful Antares – was considered the Fire Star of the ancient Chinese.

Antares appears as a bright reddish star that rides relatively low in the south throughout our northern summer. We know it as a great ball of gases, a thermonuclear cauldron radiating unimaginable amounts of energy into the blackness and vastness of space.

Yet to us – as to the ancient Chinese – Antares appears so near the southern horizon that we must view it through a great thickness of air. The air through which we view Antares causes this star to twinkle rapidly! On any summer evening, if you see a bright red star low in the south that’s twinkling fiercely … it’s probably Antares.

Want to know more about Antares? History, lore, science here.

View larger. | Beautiful shot of the constellations Sagittarius (l) and Scorpius as you'll see them every August, in the south as viewed from Earth's Northern Hemisphere. EarthSky Facebook friend Duke Marsh took this photo in August 2013. Thank you, Duke.

View larger. | Beautiful shot of the constellations Sagittarius (l) and Scorpius as you’ll see them every August, in the south as viewed from Earth’s Northern Hemisphere. Antares is the brightest star in Scorpius. EarthSky Facebook friend Duke Marsh took this photo in August 2013. Thank you, Duke.

Bottom line: The bright star near the moon on August 1, 2017 is Antares, brightest star in the constellation Scorpius. This star can be seen near the moon tonight from around the world.

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Tonight – August 1, 2017 – the bright star near the moon is Antares in the constellation Scorpius the Scorpion. You’ve got about another month or two to see this uniquely summer star for us in the Northern Hemisphere, during the evening hours. Antares is the brightest star near the moon tonight, while the other nearby bright beauty is the planet Saturn.

If you’re in the Northern Hemisphere, Antares and Saturn are visible in the southern to southwest sky as night begins. If you’re in the Southern Hemisphere, they’re more overhead for you.

The moon has now passed the first quarter phase and now exhibits a curvature to its terminator line – the line between dark and light on the moon. This moon phase is called waxing gibbous. The waxing gibbous moon, Antares and Saturn will drift westward throughout the night, to set after midnight at mid-northern latitudes.

Like all stars, Antares sets some 4 minutes earlier with each passing night, or 2 hours earlier with each passing month. By October, this star will be tough to spot in the southwestern twilight after sunset.

In ancient Chinese thought, the summer season was associated with the direction south, with the element fire, and with the color red. No wonder, then, that this reddish star in the south each summer – beautiful Antares – was considered the Fire Star of the ancient Chinese.

Antares appears as a bright reddish star that rides relatively low in the south throughout our northern summer. We know it as a great ball of gases, a thermonuclear cauldron radiating unimaginable amounts of energy into the blackness and vastness of space.

Yet to us – as to the ancient Chinese – Antares appears so near the southern horizon that we must view it through a great thickness of air. The air through which we view Antares causes this star to twinkle rapidly! On any summer evening, if you see a bright red star low in the south that’s twinkling fiercely … it’s probably Antares.

Want to know more about Antares? History, lore, science here.

View larger. | Beautiful shot of the constellations Sagittarius (l) and Scorpius as you'll see them every August, in the south as viewed from Earth's Northern Hemisphere. EarthSky Facebook friend Duke Marsh took this photo in August 2013. Thank you, Duke.

View larger. | Beautiful shot of the constellations Sagittarius (l) and Scorpius as you’ll see them every August, in the south as viewed from Earth’s Northern Hemisphere. Antares is the brightest star in Scorpius. EarthSky Facebook friend Duke Marsh took this photo in August 2013. Thank you, Duke.

Bottom line: The bright star near the moon on August 1, 2017 is Antares, brightest star in the constellation Scorpius. This star can be seen near the moon tonight from around the world.

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

EarthSky astronomy kits are perfect for beginners. Order today from the EarthSky store

Donate: Your support means the world to us



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

August guide to the bright planets

Look for the bright waxing gibbous moon to be near the planet Saturn for several days, centered on or near August 2, 2017. Read more.

Three of the five bright planets – Jupiter, Saturn and Venus – are easy to see in August 2017. Bright Jupiter is the first “star” to pop into view at nightfall and stays out until mid-to-late evening. Golden Saturn is highest up at nightfall and stays out until late night. Brilliant Venus rises before the sun, shining in front of the constellation Gemini the Twins for most of the month. Meanwhile, Mercury will be hard to catch after sunset from northerly latitudes, yet fairly easy to spot from the Southern Hemisphere. And – for all of Earth – Mars sits deep in the glare of sunrise all month long, and probably won’t become visible in the morning sky until September 2017. Follow the links below to learn more about the planets in August 2017.

Jupiter brightest “star” in evening sky

Saturn out from dusk till late night

Venus, brilliant in east at morning dawn

Mars lost in the glare of sunrise

Mercury briefly visible after sunset

See 4 planets during the August 21 total solar eclipse

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Astronomy events, star parties, festivals, workshops

Visit a new EarthSky feature – Best Places to Stargaze – and add your fav.

The waxing crescent moon shines in the vicinity of Jupiter (and the star Spica) for several days, centered on or near August 25, 2017. Read more.

Jupiter brightest “star” in evening sky. Jupiter reached opposition on April 7. That is, it was opposite the sun as seen from Earth then and so was appearing in our sky all night. The giant planet came closest to Earth for 2017 one day later, on April 8. Although Jupiter shone at its brightest and best in April, it’ll still be the brightest starlike object in the evening sky! Overall, Jupiter beams as the fourth-brightest celestial body, after the sun, moon and Venus. In August, Jupiter shines at dusk and evening; meanwhile, Venus appears only in the predawn/dawn sky.

Click here for an almanac telling you Jupiter’s setting time and Venus’ rising time in your sky.

Watch for the moon to join up with Jupiter for several days, on August 23, August 24 and August 25. See the above sky chart. Wonderful sight!

From the Northern Hemisphere, Jupiter appears fairly low in the southwest to west as darkness falls; and from the Southern Hemisphere, Jupiter appears rather high up in the sky at nightfall. From all of Earth, Jupiter sinks in a westerly direction throughout the evening, as Earth spins under the sky. In early August, at mid-northern latitudes, Jupiter sets in the west around mid-evening (roughly 10 p.m. local time or 11 p.m. daylight-saving time); and by the month’s end, Jupiter sets around nightfall (about one and one-half hours after sunset).

Jupiter stays out longer after sunset at more southerly latitudes. At temperate latitudes in the Southern Hemisphere, Jupiter sets in the west at late evening in early August, and around mid-evening by the month’s end.

Jupiter shines in front of the constellation Virgo, near Virgo’s sole 1st-magnitude star, called Spica.

Fernando Roquel Torres in Caguas, Puerto Rico captured Jupiter, the Great Red Spot (GRS) and all 4 of its largest moons – the Galilean satellites – on the date of Jupiter’s 2017 opposition (April 7).

If you have binoculars or a telescope, it’s fairly easy to see Jupiter’s four major moons, which look like pinpricks of light all on or near the same plane. They are often called the Galilean moons to honor Galileo, who discovered these great Jovian moons in 1610. In their order from Jupiter, these moons are Io, Europa, Ganymede and Callisto.

These moons orbit Jupiter around the Jovian equator. In cycles of six years, we view Jupiter’s equator edge-on. So, in 2015, we were able to view a number of mutual events involving Jupiter’s moons, through high-powered telescopes. Starting in late 2016, Jupiter’s axis began tilting enough toward the sun and Earth so that the farthest of these four moons, Callisto, has not been passing in front of Jupiter or behind Jupiter, as seen from our vantage point. This will continue for a period of about three years, during which time Callisto is perpetually visible to those with telescopes, alternately swinging above and below Jupiter as seen from Earth.

Click here for a Jupiter’s moons almanac, courtesy of skyandtelescope.com.

James Martin in Albuquerque, New Mexico caught this wonderful photo of Saturn on its June 15, 2017 opposition.

Let the moon guide your eye to the planet Saturn and the star Antares on August 28, 29 and 30. Read more.

Saturn out from dusk till late night. Saturn reached its yearly opposition on June 15, 2017. At opposition, Saturn came closest to Earth for the year, shone brightest in our sky and stayed out all night. It was highest up at midnight (midway between sunset and sunrise).

In August 2017, Saturn shines higher in the sky at nightfall than it did in June or July. Moreover, Saturn transits – climbs its highest point for the night at dusk or early evening – a few hours earlier than it did in July 2017. So, if you’re not a night owl, August may actually present a better month for viewing Saturn, which is still shining at better than first-magnitude brightness.

Click here to find out Saturn’s transit time, when Saturn soars highest up for the night.

Look for Saturn as soon as darkness falls. It’s in the southern sky at dusk or nightfall as seen from Earth’s Northern Hemisphere, and high overhead at early evening as viewed from the Southern Hemisphere. Your best view of Saturn, from either the Northern or Southern Hemisphere, is around nightfall because that’s when Saturn is highest up for the night.

Be sure to let the moon guide you to Saturn (and the nearby star Antares) on August 2, and then again at the month’s end: August 28, August 29 and August 30.

Saturn, the farthest world that you can easily view with the eye alone, appears golden in color. It shines with a steady light.

Binoculars don’t reveal Saturn’s gorgeous rings, by the way, although binoculars will enhance Saturn’s color. To see the rings, you need a small telescope. A telescope will also reveal one or more of Saturn’s many moons, most notably Titan.

Saturn’s rings are inclined at nearly 27o from edge-on, exhibiting their northern face. In October 2017, the rings will open most widely for this year, displaying a maximum inclination of 27o.

As with so much in space (and on Earth), the appearance of Saturn’s rings from Earth is cyclical. In the year 2025, the rings will appear edge-on as seen from Earth. After that, we’ll begin to see the south side of Saturn’s rings, to increase to a maximum inclination of 27o by May 2032.

Click here for recommended almanacs; they can help you know when the planets rise, transit and set in your sky.

Jenney Disimon in Sabah, Borneo captured Venus before dawn.

The waning crescent moon swings close to the dazzling planet Venus on August 18 and 19. Read more.

Venus, brilliant in east at morning dawn Venus is always brilliant and beautiful, the brightest celestial body to light up our sky besides the sun and moon. If you’re an early bird, you can count on Venus to be your morning companion until nearly the end of 2017.

Venus reached a milestone as the morning “star” when it swung out to its greatest elongation from the sun on June 3, 2017. At this juncture, Venus was farthest from the sun on our sky’s dome, and the telescope showed Venus as half-illuminated in sunshine, like a first quarter moon. For the rest of the year, Venus will wax toward full phase.

Click here to know Venus’s present phase, remembering to select Venus as your object of interest.

Enjoy the picturesque coupling of the waning crescent moon and Venus in the eastern sky before sunrise on August 18 and August 19.

From mid-northern latitudes (U.S. and Europe), Venus rises about three hours before the sun throughout the month.

At temperate latitudes in the Southern Hemisphere (Australia and South Africa), Venus rises about two and one-half hours before sunup in early August. By the month’s end that’ll taper to about one and one-half hours.

Click here for an almanac giving rising times of Venus in your sky.

The chart below helps to illustrate why we sometimes see Venus in the evening, and sometimes before dawn.

Earth's and Venus' orbits

The Earth and Venus orbit the sun counterclockwise as seen from earthly north. When Venus is to the east (left) of the Earth-sun line, we see Venus as an evening “star” in the west after sunset. After Venus reaches its inferior conjunction, Venus then moves to the west (right) of the Earth-sun line, appearing as a morning “star” in the east before sunrise.

Mars, Mercury, Earth’s moon and the dwarf planet Ceres. Mars is smaller than Earth, but bigger than our moon. Image via NASA/JPL-Caltech/UCLA.

Mars lost in the glare of sunrise. Mars transitioned out of the evening sky and into the morning sky on July 27, 2017, at which juncture Mars was on the far side of the sun at what astronomers call superior conjunction.

Look for Mars to emerge in the east before dawn in mid-September or October 2017. The conjunction of Mars and Venus on October 5, 2017, will likely present the first view of Mars in the morning sky for many skywatchers.

Exactly one year after Mars’s superior conjunction on July 27, 2017, Mars will swing to opposition on July 27, 2018. This will be Mars’s best opposition since the historically close opposition on August 28, 2003. In fact, Mars will become the fourth-brightest heavenly body to light up the sky in July 2018, after the sun, moon and the planet Venus. It’s not often that Mars outshines Jupiter, normally the four-brightest celestial object.

Wow! Wonderful shot of Mercury – over the Chilean Andes – January 2017, from Yuri Beletsky Nightscapes.

Before sunrise on September 16, 2017, draw an imaginary line from the waning crescent moon through the dazzling planet Venus to find the planets Mercury and Mars in conjunction near the horizon. Binoculars may come in handy! Read more.

Mercury briefly visible after sunset. When we say Mercury is visible in the evening sky, we’re really talking about the Southern Hemisphere. For the Southern Hemisphere, the year’s best evening apparition of Mercury happened in July 2017, but the tail end of this favorable apparition extends into the first week or two in September.

Mercury is tricky. If you look too soon after sunset, Mercury will be obscured by evening twilight; if you look too late, it will have followed the sun beneath the horizon. Watch for Mercury low in the sky, and near the sunset point on the horizon, being mindful of Mercury’s setting time.

Throughout August, Mercury will move closer to the sunset day by day, and then will pass behind the sun at superior conjunction on August 26, 2017. At superior conjunction, Mercury leaves the evening sky to enter the morning sky. The Northern Hemisphere will enjoy a favorable morning apparition of Mercury in September 2017.

For a fun sky watching challenge, try to glimpse Mercury and Mars in the east just as nightfall is giving way to dawn on or near September 16. You may need binoculars to view Mars next to Mercury!

What do we mean by bright planet? By bright planet, we mean any solar system planet that is easily visible without an optical aid and that has been watched by our ancestors since time immemorial. In their outward order from the sun, the five bright planets are Mercury, Venus, Mars, Jupiter and Saturn. These planets actually do appear bright in our sky. They are typically as bright as – or brighter than – the brightest stars. Plus, these relatively nearby worlds tend to shine with a steadier light than the distant, twinkling stars. You can spot them, and come to know them as faithful friends, if you try.

From late January, and through mid-February, 5 bright planets were visible at once in the predawn sky. This image is from February 8, 2016. It's by Eliot Herman in Tucson, Arizona. View on Flickr.

This image is from February 8, 2016. It shows all 5 bright planets at once. Photo by our friend Eliot Herman in Tucson, Arizona.

Skywatcher, by Predrag Agatonovic.

Skywatcher, by Predrag Agatonovic.

Bottom line: In August 2017, two of the five bright planets are easy to see in the evening sky: Jupiter and Saturn. Venus is found exclusively in the morning sky. Mercury shifts over into morning sky whereas Mars is lost in the glare of sunrise.

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Look for the bright waxing gibbous moon to be near the planet Saturn for several days, centered on or near August 2, 2017. Read more.

Three of the five bright planets – Jupiter, Saturn and Venus – are easy to see in August 2017. Bright Jupiter is the first “star” to pop into view at nightfall and stays out until mid-to-late evening. Golden Saturn is highest up at nightfall and stays out until late night. Brilliant Venus rises before the sun, shining in front of the constellation Gemini the Twins for most of the month. Meanwhile, Mercury will be hard to catch after sunset from northerly latitudes, yet fairly easy to spot from the Southern Hemisphere. And – for all of Earth – Mars sits deep in the glare of sunrise all month long, and probably won’t become visible in the morning sky until September 2017. Follow the links below to learn more about the planets in August 2017.

Jupiter brightest “star” in evening sky

Saturn out from dusk till late night

Venus, brilliant in east at morning dawn

Mars lost in the glare of sunrise

Mercury briefly visible after sunset

See 4 planets during the August 21 total solar eclipse

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Astronomy events, star parties, festivals, workshops

Visit a new EarthSky feature – Best Places to Stargaze – and add your fav.

The waxing crescent moon shines in the vicinity of Jupiter (and the star Spica) for several days, centered on or near August 25, 2017. Read more.

Jupiter brightest “star” in evening sky. Jupiter reached opposition on April 7. That is, it was opposite the sun as seen from Earth then and so was appearing in our sky all night. The giant planet came closest to Earth for 2017 one day later, on April 8. Although Jupiter shone at its brightest and best in April, it’ll still be the brightest starlike object in the evening sky! Overall, Jupiter beams as the fourth-brightest celestial body, after the sun, moon and Venus. In August, Jupiter shines at dusk and evening; meanwhile, Venus appears only in the predawn/dawn sky.

Click here for an almanac telling you Jupiter’s setting time and Venus’ rising time in your sky.

Watch for the moon to join up with Jupiter for several days, on August 23, August 24 and August 25. See the above sky chart. Wonderful sight!

From the Northern Hemisphere, Jupiter appears fairly low in the southwest to west as darkness falls; and from the Southern Hemisphere, Jupiter appears rather high up in the sky at nightfall. From all of Earth, Jupiter sinks in a westerly direction throughout the evening, as Earth spins under the sky. In early August, at mid-northern latitudes, Jupiter sets in the west around mid-evening (roughly 10 p.m. local time or 11 p.m. daylight-saving time); and by the month’s end, Jupiter sets around nightfall (about one and one-half hours after sunset).

Jupiter stays out longer after sunset at more southerly latitudes. At temperate latitudes in the Southern Hemisphere, Jupiter sets in the west at late evening in early August, and around mid-evening by the month’s end.

Jupiter shines in front of the constellation Virgo, near Virgo’s sole 1st-magnitude star, called Spica.

Fernando Roquel Torres in Caguas, Puerto Rico captured Jupiter, the Great Red Spot (GRS) and all 4 of its largest moons – the Galilean satellites – on the date of Jupiter’s 2017 opposition (April 7).

If you have binoculars or a telescope, it’s fairly easy to see Jupiter’s four major moons, which look like pinpricks of light all on or near the same plane. They are often called the Galilean moons to honor Galileo, who discovered these great Jovian moons in 1610. In their order from Jupiter, these moons are Io, Europa, Ganymede and Callisto.

These moons orbit Jupiter around the Jovian equator. In cycles of six years, we view Jupiter’s equator edge-on. So, in 2015, we were able to view a number of mutual events involving Jupiter’s moons, through high-powered telescopes. Starting in late 2016, Jupiter’s axis began tilting enough toward the sun and Earth so that the farthest of these four moons, Callisto, has not been passing in front of Jupiter or behind Jupiter, as seen from our vantage point. This will continue for a period of about three years, during which time Callisto is perpetually visible to those with telescopes, alternately swinging above and below Jupiter as seen from Earth.

Click here for a Jupiter’s moons almanac, courtesy of skyandtelescope.com.

James Martin in Albuquerque, New Mexico caught this wonderful photo of Saturn on its June 15, 2017 opposition.

Let the moon guide your eye to the planet Saturn and the star Antares on August 28, 29 and 30. Read more.

Saturn out from dusk till late night. Saturn reached its yearly opposition on June 15, 2017. At opposition, Saturn came closest to Earth for the year, shone brightest in our sky and stayed out all night. It was highest up at midnight (midway between sunset and sunrise).

In August 2017, Saturn shines higher in the sky at nightfall than it did in June or July. Moreover, Saturn transits – climbs its highest point for the night at dusk or early evening – a few hours earlier than it did in July 2017. So, if you’re not a night owl, August may actually present a better month for viewing Saturn, which is still shining at better than first-magnitude brightness.

Click here to find out Saturn’s transit time, when Saturn soars highest up for the night.

Look for Saturn as soon as darkness falls. It’s in the southern sky at dusk or nightfall as seen from Earth’s Northern Hemisphere, and high overhead at early evening as viewed from the Southern Hemisphere. Your best view of Saturn, from either the Northern or Southern Hemisphere, is around nightfall because that’s when Saturn is highest up for the night.

Be sure to let the moon guide you to Saturn (and the nearby star Antares) on August 2, and then again at the month’s end: August 28, August 29 and August 30.

Saturn, the farthest world that you can easily view with the eye alone, appears golden in color. It shines with a steady light.

Binoculars don’t reveal Saturn’s gorgeous rings, by the way, although binoculars will enhance Saturn’s color. To see the rings, you need a small telescope. A telescope will also reveal one or more of Saturn’s many moons, most notably Titan.

Saturn’s rings are inclined at nearly 27o from edge-on, exhibiting their northern face. In October 2017, the rings will open most widely for this year, displaying a maximum inclination of 27o.

As with so much in space (and on Earth), the appearance of Saturn’s rings from Earth is cyclical. In the year 2025, the rings will appear edge-on as seen from Earth. After that, we’ll begin to see the south side of Saturn’s rings, to increase to a maximum inclination of 27o by May 2032.

Click here for recommended almanacs; they can help you know when the planets rise, transit and set in your sky.

Jenney Disimon in Sabah, Borneo captured Venus before dawn.

The waning crescent moon swings close to the dazzling planet Venus on August 18 and 19. Read more.

Venus, brilliant in east at morning dawn Venus is always brilliant and beautiful, the brightest celestial body to light up our sky besides the sun and moon. If you’re an early bird, you can count on Venus to be your morning companion until nearly the end of 2017.

Venus reached a milestone as the morning “star” when it swung out to its greatest elongation from the sun on June 3, 2017. At this juncture, Venus was farthest from the sun on our sky’s dome, and the telescope showed Venus as half-illuminated in sunshine, like a first quarter moon. For the rest of the year, Venus will wax toward full phase.

Click here to know Venus’s present phase, remembering to select Venus as your object of interest.

Enjoy the picturesque coupling of the waning crescent moon and Venus in the eastern sky before sunrise on August 18 and August 19.

From mid-northern latitudes (U.S. and Europe), Venus rises about three hours before the sun throughout the month.

At temperate latitudes in the Southern Hemisphere (Australia and South Africa), Venus rises about two and one-half hours before sunup in early August. By the month’s end that’ll taper to about one and one-half hours.

Click here for an almanac giving rising times of Venus in your sky.

The chart below helps to illustrate why we sometimes see Venus in the evening, and sometimes before dawn.

Earth's and Venus' orbits

The Earth and Venus orbit the sun counterclockwise as seen from earthly north. When Venus is to the east (left) of the Earth-sun line, we see Venus as an evening “star” in the west after sunset. After Venus reaches its inferior conjunction, Venus then moves to the west (right) of the Earth-sun line, appearing as a morning “star” in the east before sunrise.

Mars, Mercury, Earth’s moon and the dwarf planet Ceres. Mars is smaller than Earth, but bigger than our moon. Image via NASA/JPL-Caltech/UCLA.

Mars lost in the glare of sunrise. Mars transitioned out of the evening sky and into the morning sky on July 27, 2017, at which juncture Mars was on the far side of the sun at what astronomers call superior conjunction.

Look for Mars to emerge in the east before dawn in mid-September or October 2017. The conjunction of Mars and Venus on October 5, 2017, will likely present the first view of Mars in the morning sky for many skywatchers.

Exactly one year after Mars’s superior conjunction on July 27, 2017, Mars will swing to opposition on July 27, 2018. This will be Mars’s best opposition since the historically close opposition on August 28, 2003. In fact, Mars will become the fourth-brightest heavenly body to light up the sky in July 2018, after the sun, moon and the planet Venus. It’s not often that Mars outshines Jupiter, normally the four-brightest celestial object.

Wow! Wonderful shot of Mercury – over the Chilean Andes – January 2017, from Yuri Beletsky Nightscapes.

Before sunrise on September 16, 2017, draw an imaginary line from the waning crescent moon through the dazzling planet Venus to find the planets Mercury and Mars in conjunction near the horizon. Binoculars may come in handy! Read more.

Mercury briefly visible after sunset. When we say Mercury is visible in the evening sky, we’re really talking about the Southern Hemisphere. For the Southern Hemisphere, the year’s best evening apparition of Mercury happened in July 2017, but the tail end of this favorable apparition extends into the first week or two in September.

Mercury is tricky. If you look too soon after sunset, Mercury will be obscured by evening twilight; if you look too late, it will have followed the sun beneath the horizon. Watch for Mercury low in the sky, and near the sunset point on the horizon, being mindful of Mercury’s setting time.

Throughout August, Mercury will move closer to the sunset day by day, and then will pass behind the sun at superior conjunction on August 26, 2017. At superior conjunction, Mercury leaves the evening sky to enter the morning sky. The Northern Hemisphere will enjoy a favorable morning apparition of Mercury in September 2017.

For a fun sky watching challenge, try to glimpse Mercury and Mars in the east just as nightfall is giving way to dawn on or near September 16. You may need binoculars to view Mars next to Mercury!

What do we mean by bright planet? By bright planet, we mean any solar system planet that is easily visible without an optical aid and that has been watched by our ancestors since time immemorial. In their outward order from the sun, the five bright planets are Mercury, Venus, Mars, Jupiter and Saturn. These planets actually do appear bright in our sky. They are typically as bright as – or brighter than – the brightest stars. Plus, these relatively nearby worlds tend to shine with a steadier light than the distant, twinkling stars. You can spot them, and come to know them as faithful friends, if you try.

From late January, and through mid-February, 5 bright planets were visible at once in the predawn sky. This image is from February 8, 2016. It's by Eliot Herman in Tucson, Arizona. View on Flickr.

This image is from February 8, 2016. It shows all 5 bright planets at once. Photo by our friend Eliot Herman in Tucson, Arizona.

Skywatcher, by Predrag Agatonovic.

Skywatcher, by Predrag Agatonovic.

Bottom line: In August 2017, two of the five bright planets are easy to see in the evening sky: Jupiter and Saturn. Venus is found exclusively in the morning sky. Mercury shifts over into morning sky whereas Mars is lost in the glare of sunrise.

Don’t miss anything. Subscribe to EarthSky News by email

Enjoy knowing where to look in the night sky? Please donate to help EarthSky keep going.



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Earth’s eclipses are special

You may have heard that the Earth is the only planet that experiences eclipses. That is not true. Granted, our eclipses are special, but hypothetical observers on other planets also could experience partial and total solar eclipses.

Generally speaking, an eclipse occurs when one astronomical body (such as a moon) passes in front of another (such as the Sun). Mercury and Venus, having no moons at all, never have eclipses of any kind.

venera13
Observers on the searing hot surface of Venus, would never directly experience an eclipse even if the planet had a moon, simply because it is constantly enveloped by thick clouds. The images here are from the Soviet Venera 13 lander, which landed on the surface of Venus on March 3, 1982. The perpetually cloud covered sky can be seen in the triangular wedged at the upper corners of each photo. Images courtesy of NASA/JPL/NSSDCA & Roscosmos.

But Martians, if they existed, would occasionally experience transits by the planet’s moons Deimos and Phobos.  Transits occur when the nearer body appears too small to cover the farther body. This is essentially a partial eclipse and geometrically equivalent to annular eclipses seen on Earth.

Observers, floating at cloud-top level on Jupiter, Saturn, Uranus or Neptune could experience total eclipses, too. Even far-off Plutonians would on quite rare occasion see a moon pass in front of the Sun from their distant dwarf world.

So if solar eclipses are not exclusive to Earth, why are they so special?

Not to stress the obvious, but there are observers on Earth to view eclipses, something no other planet in our Solar System can boast. Aside from that, the main reason is that the Sun and Moon appear roughly the same size in the sky, allowing particularly impressive total solar eclipses. During totality of a solar eclipse, the silhouette of the Moon leaves a gaping “black hole” in the sky, surrounded by the ghostly glow of the Sun’s outer atmosphere, the corona.

This fortuitous circumstance happens because although the Moon’s diameter is about 400 times smaller than the Sun’s, it also is about 400 times closer. That makes the Sun and Moon to appear roughly the same size in the sky, about a half-degree.  If the Moon were 10% closer, as it was about a billion years ago*, it would always appear appreciatively larger than the Sun, and some of the magic of today’s total solar eclipses would be lost.

If the Moon were 10% farther away, as it will be roughly a billion years in the future*, it would appear too small to completely cover the Sun’s disk, and we would never experience a total solar eclipse.

So while our eclipse experience on Earth today is virtually unrivaled anywhere in the Solar System, it is simply a temporary coincidence.

Phobos_Sun_transit

In this image, Martian moon Phobos passes in front of the Sun as viewed by the Curiosity Rover on August 20, 2013. Click here for a short video on Wikimedia: http://ift.tt/2tSeDt6)

Elsewhere in the Solar System, the Moons of Mars, Phobos and Deimos, are too small and too far from the planet for anything but partial eclipses.

From the major moons of Jupiter, Saturn, Uranus and Neptune, the Sun appears so small that total eclipses occur. The major moons of these planets, however, appear considerably larger than the Sun, so the spectacular type of total eclipse visible from Earth is generally not possible. However,  a couple of moons of the outer planets, viewed from the top of the planet’s atmosphere, would appear roughly the same size as the Sun seen from the same location, but the moons  are irregular in shape. Jupiter’s moon Amalthea and Saturn’s moons Pandora and Prometheus are examples.

Sun seen near Charon

The image here is a simulation showing the approximate size of the Sun with Pluto’s large moon Charon, as seen by an observer on the surface of Pluto. To a real observer, however, the Sun would be dazzlingly bright and Charon would show up silhouetted as a black disk.

From Pluto, the Sun is little more than an intensely bright star. In fact, it is only about the same size as the planet Jupiter as viewed from Earth. But Pluto’s large moon Charon appears from Pluto nearly four times as large as Earth’s Moon from Earth. A solar eclipse from Pluto would be more like a lunar occultation of a star from Earth.

The same moons that cause solar eclipses also can experience them as well, so there are literally dozens of places in the Solar System where eclipses occur. As mentioned above, there also is a special eclipse-relative called a transit, in which another planet is seen to pass in front of the Sun. Mercurians could see no eclipses or transits, since it has no moon and there is no planet closer to the Sun. Observers on Venus would have no Moon to cause an eclipse, and while orbital geometry allows for transits of Mercury, none can be seen from the surface because of the thick, obscuring clouds.

Earth observers can view transits of both Mercury and Venus, the last being a transit of Venus on June 5, 2012). Lucky Martian observers can seen transits of Mercury, Venus and Earth. Arthur C. Clarke, famed science/science fiction writer, even wrote a short story, “Transit of Earth,” about the Earth crossing the solar disk as viewed from Mars on May 11, 1984. Although the story is fictional, and there were no human observers on Mars at the time, the transit actually occurred on that date. Mars Curiosity Rover’s robotic eyes observed a transit of Mercury in 2014, the first time ever that an transit has been “observed” from a planet other than Earth.

PIA18389_mercury_transit-640-640x350

The animated image here shows the planet Mercury transiting the Sun as viewed from the NASA/JPL Curiosity Mars Rover on June 3, 2014. The two prominent black dots are sunspots. (http://ift.tt/2vgEtu9)

Similar transit events can be seen from all the outer planets and moons, although increasing distance from the Sun makes them more rare.

While eclipses and transits can occur almost everywhere in the Solar System (Except from poor Mercury), the unique circumstances we have in the Earth-Moon system provides the most spectacular examples.


(*Note: these are simplistic estimations based on the Moon’s current recession rate from Earth. These can be taken only rough approximations because the rate varies over time.)

Jupiter occultation by Moon photo by Easy n – Easy n at Hebrew Wikipedia (Created by Easy n at Hebrew Wikipedia) [CC BY-SA 3.0 (http://ift.tt/HKkdTz)], via Wikimedia Commons



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You may have heard that the Earth is the only planet that experiences eclipses. That is not true. Granted, our eclipses are special, but hypothetical observers on other planets also could experience partial and total solar eclipses.

Generally speaking, an eclipse occurs when one astronomical body (such as a moon) passes in front of another (such as the Sun). Mercury and Venus, having no moons at all, never have eclipses of any kind.

venera13
Observers on the searing hot surface of Venus, would never directly experience an eclipse even if the planet had a moon, simply because it is constantly enveloped by thick clouds. The images here are from the Soviet Venera 13 lander, which landed on the surface of Venus on March 3, 1982. The perpetually cloud covered sky can be seen in the triangular wedged at the upper corners of each photo. Images courtesy of NASA/JPL/NSSDCA & Roscosmos.

But Martians, if they existed, would occasionally experience transits by the planet’s moons Deimos and Phobos.  Transits occur when the nearer body appears too small to cover the farther body. This is essentially a partial eclipse and geometrically equivalent to annular eclipses seen on Earth.

Observers, floating at cloud-top level on Jupiter, Saturn, Uranus or Neptune could experience total eclipses, too. Even far-off Plutonians would on quite rare occasion see a moon pass in front of the Sun from their distant dwarf world.

So if solar eclipses are not exclusive to Earth, why are they so special?

Not to stress the obvious, but there are observers on Earth to view eclipses, something no other planet in our Solar System can boast. Aside from that, the main reason is that the Sun and Moon appear roughly the same size in the sky, allowing particularly impressive total solar eclipses. During totality of a solar eclipse, the silhouette of the Moon leaves a gaping “black hole” in the sky, surrounded by the ghostly glow of the Sun’s outer atmosphere, the corona.

This fortuitous circumstance happens because although the Moon’s diameter is about 400 times smaller than the Sun’s, it also is about 400 times closer. That makes the Sun and Moon to appear roughly the same size in the sky, about a half-degree.  If the Moon were 10% closer, as it was about a billion years ago*, it would always appear appreciatively larger than the Sun, and some of the magic of today’s total solar eclipses would be lost.

If the Moon were 10% farther away, as it will be roughly a billion years in the future*, it would appear too small to completely cover the Sun’s disk, and we would never experience a total solar eclipse.

So while our eclipse experience on Earth today is virtually unrivaled anywhere in the Solar System, it is simply a temporary coincidence.

Phobos_Sun_transit

In this image, Martian moon Phobos passes in front of the Sun as viewed by the Curiosity Rover on August 20, 2013. Click here for a short video on Wikimedia: http://ift.tt/2tSeDt6)

Elsewhere in the Solar System, the Moons of Mars, Phobos and Deimos, are too small and too far from the planet for anything but partial eclipses.

From the major moons of Jupiter, Saturn, Uranus and Neptune, the Sun appears so small that total eclipses occur. The major moons of these planets, however, appear considerably larger than the Sun, so the spectacular type of total eclipse visible from Earth is generally not possible. However,  a couple of moons of the outer planets, viewed from the top of the planet’s atmosphere, would appear roughly the same size as the Sun seen from the same location, but the moons  are irregular in shape. Jupiter’s moon Amalthea and Saturn’s moons Pandora and Prometheus are examples.

Sun seen near Charon

The image here is a simulation showing the approximate size of the Sun with Pluto’s large moon Charon, as seen by an observer on the surface of Pluto. To a real observer, however, the Sun would be dazzlingly bright and Charon would show up silhouetted as a black disk.

From Pluto, the Sun is little more than an intensely bright star. In fact, it is only about the same size as the planet Jupiter as viewed from Earth. But Pluto’s large moon Charon appears from Pluto nearly four times as large as Earth’s Moon from Earth. A solar eclipse from Pluto would be more like a lunar occultation of a star from Earth.

The same moons that cause solar eclipses also can experience them as well, so there are literally dozens of places in the Solar System where eclipses occur. As mentioned above, there also is a special eclipse-relative called a transit, in which another planet is seen to pass in front of the Sun. Mercurians could see no eclipses or transits, since it has no moon and there is no planet closer to the Sun. Observers on Venus would have no Moon to cause an eclipse, and while orbital geometry allows for transits of Mercury, none can be seen from the surface because of the thick, obscuring clouds.

Earth observers can view transits of both Mercury and Venus, the last being a transit of Venus on June 5, 2012). Lucky Martian observers can seen transits of Mercury, Venus and Earth. Arthur C. Clarke, famed science/science fiction writer, even wrote a short story, “Transit of Earth,” about the Earth crossing the solar disk as viewed from Mars on May 11, 1984. Although the story is fictional, and there were no human observers on Mars at the time, the transit actually occurred on that date. Mars Curiosity Rover’s robotic eyes observed a transit of Mercury in 2014, the first time ever that an transit has been “observed” from a planet other than Earth.

PIA18389_mercury_transit-640-640x350

The animated image here shows the planet Mercury transiting the Sun as viewed from the NASA/JPL Curiosity Mars Rover on June 3, 2014. The two prominent black dots are sunspots. (http://ift.tt/2vgEtu9)

Similar transit events can be seen from all the outer planets and moons, although increasing distance from the Sun makes them more rare.

While eclipses and transits can occur almost everywhere in the Solar System (Except from poor Mercury), the unique circumstances we have in the Earth-Moon system provides the most spectacular examples.


(*Note: these are simplistic estimations based on the Moon’s current recession rate from Earth. These can be taken only rough approximations because the rate varies over time.)

Jupiter occultation by Moon photo by Easy n – Easy n at Hebrew Wikipedia (Created by Easy n at Hebrew Wikipedia) [CC BY-SA 3.0 (http://ift.tt/HKkdTz)], via Wikimedia Commons



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Walking your dog is good for your health (and your pet’s) [Life Lines]

A new study shows that walking your dog is good for your health. Here is a YouTube video summarizing the findings of the study:

Let’s not forget that walking your dog is also very good for your dog. According to PetMD, some benefits include weight control, keeping your dog limber, controlling destructive behaviors and hyperactivity, and of course building a bond between you and your pet.

If you have a cat however, it might be best to just let the cat walk you as demonstrated in this YouTube video:



from ScienceBlogs http://ift.tt/2wei9OZ

A new study shows that walking your dog is good for your health. Here is a YouTube video summarizing the findings of the study:

Let’s not forget that walking your dog is also very good for your dog. According to PetMD, some benefits include weight control, keeping your dog limber, controlling destructive behaviors and hyperactivity, and of course building a bond between you and your pet.

If you have a cat however, it might be best to just let the cat walk you as demonstrated in this YouTube video:



from ScienceBlogs http://ift.tt/2wei9OZ

Universe’s Largest Black Hole May Have An Explanation At Last (Synopsis) [Starts With A Bang]

“Ultramassive black holes — that is, black holes with masses exceeding 10 billion solar masses — are probably not rare; several and even dozens of these colossal black holes may exist.” -Julie Hlavacek-Larrondo

The largest black hole in the Universe was a shocker when it was first discovered. At 40 billion solar masses, it certainly is impressively large. Like other quasars and active galaxies, it has a luminous accretion disk that can be seen from a great distance. Like only a few, one of its two incredibly energetic, polar jets is pointed directly at Earth, creating a blazar, the brightest of all active galaxies.

When an active galaxy has one of its jets pointed directly at Earth, we observe an ultra-luminous phenomenon known as a blazar. These are the brightest objects seen in the entire Universe. Image credit: NASA / JPL.

But what makes this object, known as S5 0014+81, so special is that it got so big and massive so quickly. Its light comes to us from a time when the Universe was only 1.6 billion years old: just 12% of its current age. If this brilliant, massive object were located a mere 280 light years away, or ‘only’ 18 million times the Earth-Sun distance, it would shine as brightly as our life-giving star.

If this quasar were 18 million times as far away as our Sun (280 light years from Earth), it would shine as bright in the sky as our life-giving star does. Image credit: Wikimedia Commons user Alan 2988.

Come learn about the largest ultramassive black hole known in the Universe, what explains its existence, and how there might be an even more massive one out there for Mostly Mute Monday!



from ScienceBlogs http://ift.tt/2welm14

“Ultramassive black holes — that is, black holes with masses exceeding 10 billion solar masses — are probably not rare; several and even dozens of these colossal black holes may exist.” -Julie Hlavacek-Larrondo

The largest black hole in the Universe was a shocker when it was first discovered. At 40 billion solar masses, it certainly is impressively large. Like other quasars and active galaxies, it has a luminous accretion disk that can be seen from a great distance. Like only a few, one of its two incredibly energetic, polar jets is pointed directly at Earth, creating a blazar, the brightest of all active galaxies.

When an active galaxy has one of its jets pointed directly at Earth, we observe an ultra-luminous phenomenon known as a blazar. These are the brightest objects seen in the entire Universe. Image credit: NASA / JPL.

But what makes this object, known as S5 0014+81, so special is that it got so big and massive so quickly. Its light comes to us from a time when the Universe was only 1.6 billion years old: just 12% of its current age. If this brilliant, massive object were located a mere 280 light years away, or ‘only’ 18 million times the Earth-Sun distance, it would shine as brightly as our life-giving star.

If this quasar were 18 million times as far away as our Sun (280 light years from Earth), it would shine as bright in the sky as our life-giving star does. Image credit: Wikimedia Commons user Alan 2988.

Come learn about the largest ultramassive black hole known in the Universe, what explains its existence, and how there might be an even more massive one out there for Mostly Mute Monday!



from ScienceBlogs http://ift.tt/2welm14

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