When does the sun cross your meridian at noon?

An analemma on a globe at the Globe Museum in Vienna, Austria. The analemma shows difference between sun noon and clock noon for every day of the year. Image via Wikimedia Commons.

In the jargon of astronomers and celestial navigators, your local meridian is an imaginary line that crosses your sky from due north to due south. The point where the sun crosses that line – when the sun is highest for that day – is variously called solar noon, or midday, or high noon, or local noon or just plain noon.

An astronomer might say that the sun is making an upper meridian transit at such a time.

When does it happen for you each day? It might or might not surprise you to learn it doesn’t usually happen at noon on your clock.

The sun crosses your local meridian – the imaginary semicircle that crosses the sky from due north to due south – at local noon.

At solar noon, the sun can be at one of three places: at zenith (straight overhead), north of zenith or south of zenith. At temperate latitudes in the Northern Hemisphere, the noonday sun is never at zenith but is always found in the southern sky.

At temperate latitudes in the Southern Hemisphere, the noonday sun is never at zenith but is always found in the northern sky.

The noonday sun can only be at zenith in the tropics.

Worldwide map via Wikipedia. The temperate latitudes in the Northern Hemisphere lie in between the Tropic of Cancer and the Arctic Circle, and the temperate latitudes in the Southern Hemisphere extend from the Tropic of Capricorn to the Antarctic Circle.

The shortest shadow of the day comes at solar noon, or when the sun transits your local meridian. North of the Tropic of Cancer, the noonday shadow always points due north.

South of the tropic of Capricorn, the noonday shadow always points due south.

Generally speaking, noon by the sun and noon by the clock seldom – very seldom – agree. Noon by sun is a natural phenomenon, based on the sun’s highest point for the day. Noon as defined by the sun long preceded the invention of clocks and the introduction of time zones. Needless to say, noon by the sun also preceded so-called daylight saving time or summer time, whereby you pretend that it’s one hour later than it is.

Consider that – within a single time zone – noon by the sun comes earlier by the clock at the eastern edge of the time zone, yet later by the clock at the western edge of the time zone. You might notice if you routinely travel east or west within your time zone.

Although the noon by the clock happens at the same instant throughout any single time zone, noon by the sun comes earlier by the clock in the eastern (right) part of the time zone, yet later by the clock in the western (left) part of the time zone.

You don’t need a clock to find out when the sun reaches its noontime position. At solar noon, the shortest shadow of the day points due north at northern temperate latitudes (or due south at southern temperate latitudes).

With the eye alone, it’s difficult to know exactly when the shadow shrinks to its shortest length. But, given a full day of sunshine, we can use the method of equal altitudes to find due north (or due south) and our local meridian.

Here’s how you do it. Place a plumb or vertical stick into the ground. Note the length of any morning shadow. Then wait until the shadow reaches this same length in the afternoon. Bisect this angle to find due north (or due south). For a fuller explanation, click into MySundial online and scroll down to 4. The “Method of Equal Altitudes”.

Don’t want to try this at home?

Here’s an easy way to find your local noon. Click here to find out the clock time for solar noon (sun on your meridian) in your sky, remembering to check the solar noon box.

Of course, the sun is not the only celestial object to climb highest up for the day when it crosses the meridian at upper transit. The same goes for the moon, planets and stars. But it’s easier to determine your meridian by using the sun.

Bottom line: In the jargon of astronomers, the sun is said to make an upper meridian transit when it reaches its highest point for the day at solar noon (midday).

from EarthSky https://ift.tt/3kdGz5g

An analemma on a globe at the Globe Museum in Vienna, Austria. The analemma shows difference between sun noon and clock noon for every day of the year. Image via Wikimedia Commons.

In the jargon of astronomers and celestial navigators, your local meridian is an imaginary line that crosses your sky from due north to due south. The point where the sun crosses that line – when the sun is highest for that day – is variously called solar noon, or midday, or high noon, or local noon or just plain noon.

An astronomer might say that the sun is making an upper meridian transit at such a time.

When does it happen for you each day? It might or might not surprise you to learn it doesn’t usually happen at noon on your clock.

The sun crosses your local meridian – the imaginary semicircle that crosses the sky from due north to due south – at local noon.

At solar noon, the sun can be at one of three places: at zenith (straight overhead), north of zenith or south of zenith. At temperate latitudes in the Northern Hemisphere, the noonday sun is never at zenith but is always found in the southern sky.

At temperate latitudes in the Southern Hemisphere, the noonday sun is never at zenith but is always found in the northern sky.

The noonday sun can only be at zenith in the tropics.

Worldwide map via Wikipedia. The temperate latitudes in the Northern Hemisphere lie in between the Tropic of Cancer and the Arctic Circle, and the temperate latitudes in the Southern Hemisphere extend from the Tropic of Capricorn to the Antarctic Circle.

The shortest shadow of the day comes at solar noon, or when the sun transits your local meridian. North of the Tropic of Cancer, the noonday shadow always points due north.

South of the tropic of Capricorn, the noonday shadow always points due south.

Generally speaking, noon by the sun and noon by the clock seldom – very seldom – agree. Noon by sun is a natural phenomenon, based on the sun’s highest point for the day. Noon as defined by the sun long preceded the invention of clocks and the introduction of time zones. Needless to say, noon by the sun also preceded so-called daylight saving time or summer time, whereby you pretend that it’s one hour later than it is.

Consider that – within a single time zone – noon by the sun comes earlier by the clock at the eastern edge of the time zone, yet later by the clock at the western edge of the time zone. You might notice if you routinely travel east or west within your time zone.

Although the noon by the clock happens at the same instant throughout any single time zone, noon by the sun comes earlier by the clock in the eastern (right) part of the time zone, yet later by the clock in the western (left) part of the time zone.

You don’t need a clock to find out when the sun reaches its noontime position. At solar noon, the shortest shadow of the day points due north at northern temperate latitudes (or due south at southern temperate latitudes).

With the eye alone, it’s difficult to know exactly when the shadow shrinks to its shortest length. But, given a full day of sunshine, we can use the method of equal altitudes to find due north (or due south) and our local meridian.

Here’s how you do it. Place a plumb or vertical stick into the ground. Note the length of any morning shadow. Then wait until the shadow reaches this same length in the afternoon. Bisect this angle to find due north (or due south). For a fuller explanation, click into MySundial online and scroll down to 4. The “Method of Equal Altitudes”.

Don’t want to try this at home?

Here’s an easy way to find your local noon. Click here to find out the clock time for solar noon (sun on your meridian) in your sky, remembering to check the solar noon box.

Of course, the sun is not the only celestial object to climb highest up for the day when it crosses the meridian at upper transit. The same goes for the moon, planets and stars. But it’s easier to determine your meridian by using the sun.

Bottom line: In the jargon of astronomers, the sun is said to make an upper meridian transit when it reaches its highest point for the day at solar noon (midday).

from EarthSky https://ift.tt/3kdGz5g

August 2020 guide to the bright planets

Click the name of a planet to learn more about its visibility in August 2020: Jupiter, Saturn, Mars, Venus, Mercury

Try Stellarium for a precise view of the planets from your location.

Want precise planet rise and set times? Click here for recommended almanacs

Look for the bright moon to appear in the vicinity of Jupiter and Saturn for several days, centered on or near August 1, 2020. Read more.

Th waning gibbous moon swings close to Mars on the sky’s dome for several days, centered on or near August 8, 2020. Read more.

If you’re more of an early bird than a night owl, look for the moon and Mars much higher up in the predawn/dawn sky. Note: the moon appears larger on the sky chart than it does in the real sky. Read more.

Two major celestial events happen almost concurrently in the predawn sky on August 12 or 13, 2020 (the exact date depends on your time zone). The planet Venus swings to its greatest elongation in the morning sky, while the Perseid meteor shower showcases the peak number of meteors. Read more.

It’ll be worth getting up for, as the waning crescent moon meets up with the queen planet Venus on the sky’s dome for several days, centered on August 15, 2020. Read more.

The moon swings by the planets Jupiter and Saturn for several days in late August 2020, centered around August 28 or 29, 2020. Read more.

Jupiter and Saturn are the planets to watch as darkness falls in August 2020. They are near one another on the sky’s dome, with Saturn following Jupiter westward across the sky from dusk/nightfall until the wee hours of the morning. Last month, July 2020, was a banner month for these gas giant worlds, as Jupiter and Saturn both came to opposition in July.

Earth – in its yearly orbit – swung between these outer worlds and the sun in July 2020. Thus we were closest to Jupiter and Saturn for the year in July. Jupiter and Saturn, in turn, shone at their brightest best and were out all night long.

Read more: Jupiter at opposition on July 13-14

Read more: Saturn at opposition on July 20

Jupiter and Saturn climb highest up for the night at mid-to-late evening in early August, and by early-to-mid evening by the month’s end. Read more.

In some respects, though, August gives us a better month than July for viewing Jupiter and Saturn in the evening sky. That’s because these two worlds remain bright and beautiful throughout August, yet appear higher up in the sky at nightfall. That’s good news for those whose eastern horizon is obstructed, such as by trees and/or mountains.

That’s also good news for people with telescopes who don’t want to stay up until late night. Typically, the view of Jupiter’s 4 major moons and Saturn’s glorious rings through the telescope is sharper when these worlds are higher up in the sky. The thickness of the Earth’s atmosphere near the horizon tends to blur the spectacle.

Positions of Jupiter’s moons via Sky & Telescope

Look first for brilliant Jupiter; Saturn is the bright object immediately to Jupiter’s east. Although Saturn is easily as bright as a 1st-magnitude star – as bright as the brightest stars in our sky – the ringed planet can’t compete with the the king planet Jupiter, which outshines Saturn by some 15 times. After all, Jupiter ranks as the fourth brightest celestial object, after the sun, moon, and the planet Venus, respectively.

Around the world, Jupiter and nearby Saturn still lurk rather low in the southeast sky in early August, and transit (reach their highest point for the night) at late evening. By the month’s end, these two worlds will transit at early-to-mid evening.

For the first time since the year 2000, look for Jupiter and Saturn to showcase their great conjunction in 2020, the closest Jupiter-Saturn conjunction since the year 1623. Astronomers use the word conjunction to describe meetings of planets and other objects on our sky’s dome. They use the term great conjunction to describe a meeting of the king planet Jupiter and golden Saturn. The last great Jupiter-Saturn conjunction was May 28, 2000. The next one will be December 21, 2020. But August 2020 presents a fine time to start watching these worlds.

Read more: Before 2020 ends, a great conjunction for Jupiter and Saturn

Watch for the moon in the vicinity of Jupiter and Saturn for several days, centered on or near August 1, and then again near the month’s end, centered on or near August 28.

Mars is the only bright evening planet (Mars, Jupiter and Saturn) not to pop out first thing at dusk/nightfall. In early August, look for Mars to be up by mid-to-late evening; and by the month’s end, Mars rises by early-to-mid evening. Thus Mars is coming up earlier daily, heading for its own opposition on October 13, 2020. At that wondrous time, Mars will actually supplant Jupiter as the sky’s fourth-brightest celestial body, after the sun, moon, and the planet Venus. That will be something to see!

In August 2020, you’ll find Mars heading toward that dramatic brightening. This month, Mars is respectably bright, more brilliant even than a 1st-magnitude star, or one of the sky’s brightest stars. Earth is now rushing along in its smaller, faster orbit, gaining on Mars, the fourth planet outward from the sun. Throughout the next three months, watch for Mars to brighten dramatically as Earth closes in on Mars, passing between it and the sun in October 2020.

At mid-northern latitudes, Mars rises roughly 10 p.m. (11 p.m. daylight saving time) in early August. By the month’s end, Mars will be up around 9 p.m. (10 p.m. daylight saving time).

At temperate latitudes in the Southern Hemisphere, Mars comes up at or near the 11 p.m in early August, and about an hour earlier by the month’s end.

Let the waning moon help guide your eye to Mars on the mornings of August 7, 8 and 9, 2020.

View at EarthSky Community Photos. | From Paul Armstrong, who took this photo of Mars, Saturn and Jupiter on the morning of April 15, 2020, from Exmoor, U.K. Jupiter is at the upper right, Mars at center left, with Saturn between them. In May 2020, Jupiter and Saturn were closer together, whereas Mars was farther away from Jupiter and Saturn. Thanks, Paul!

Venus – the brightest planet – flew between the Earth and sun (at inferior conjunction) on June 3, 2020. Some 10 weeks later, Venus will reach its greatest elongation from the sun in the morning sky on August 12 or 13 (depending upon your time zone).

At mid-northern latitudes, Venus rises about 3 1/2 hours before the sun all month long.

At and near the equator, Venus rises over 3 hours before the sun in early August, decreasing slightly to 3 hours near the month’s end.

At temperate latitudes in the Southern Hemisphere, Venus rises over 3 hours before the sun in early August, decreasing to over 2 1/2 hours by the month’s end.

Inferior conjunction – when Venus sweeps between the sun and Earth – happened on June 3, 2020. Just before inferior conjunction, we saw Venus as a thin waning crescent in the evening sky; and just after inferior conjunction, we saw Venus as a thin waxing crescent in the morning sky. In August 2020, Venus will start the month about 43% illuminated and end the month about 59% illuminated. Image via UCLA.

Throughout August, Venus in its faster orbit around the sun will be going farther and farther away from Earth. As viewed through the telescope, Venus’ waxing crescent phase will widen, yet its overall disk size will shrink. Venus’ disk is 43% illuminated in early August, and about 59% illuminated by the month’s end; Venus’ angular diameter, on the other hand, will shrink to 70% of its initial size by the month’s end.

Watch for the waning crescent moon to shine in the vicinity of Venus for several days, centered on or near August 15.

Mercury transitions out the morning sky and into the evening sky this month, so the innermost planet of the solar system is pretty much lost in the sun’s glare throughout August 2020. From northerly latitudes, you might catch Mercury before sunrise in early August; or from southerly latitudes, you might catch Mercury shortly after sunset in late August. September 2020 will feature a particularly fine evening apparition of Mercury in the Southern Hemisphere.

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.

Skywatcher, by Predrag Agatonovic.

Bottom line: August 2020 presents 4 of the 5 bright solar system planets. Catch Jupiter and Saturn at nightfall and throughout most of the night, Mars between late evening and dawn, Venus in the predawn/dawn sky. Mercury shifts over from the morning to evening sky, and is pretty much lost in the solar glare.

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

Visit EarthSky’s Best Places to Stargaze, and recommend a place we can all enjoy.

Help EarthSky keep going! Donate now.

Post your planet photos at EarthSky Community Photos

from EarthSky https://ift.tt/1YD00CF

Click the name of a planet to learn more about its visibility in August 2020: Jupiter, Saturn, Mars, Venus, Mercury

Try Stellarium for a precise view of the planets from your location.

Want precise planet rise and set times? Click here for recommended almanacs

Look for the bright moon to appear in the vicinity of Jupiter and Saturn for several days, centered on or near August 1, 2020. Read more.

Th waning gibbous moon swings close to Mars on the sky’s dome for several days, centered on or near August 8, 2020. Read more.

If you’re more of an early bird than a night owl, look for the moon and Mars much higher up in the predawn/dawn sky. Note: the moon appears larger on the sky chart than it does in the real sky. Read more.

Two major celestial events happen almost concurrently in the predawn sky on August 12 or 13, 2020 (the exact date depends on your time zone). The planet Venus swings to its greatest elongation in the morning sky, while the Perseid meteor shower showcases the peak number of meteors. Read more.

It’ll be worth getting up for, as the waning crescent moon meets up with the queen planet Venus on the sky’s dome for several days, centered on August 15, 2020. Read more.

The moon swings by the planets Jupiter and Saturn for several days in late August 2020, centered around August 28 or 29, 2020. Read more.

Jupiter and Saturn are the planets to watch as darkness falls in August 2020. They are near one another on the sky’s dome, with Saturn following Jupiter westward across the sky from dusk/nightfall until the wee hours of the morning. Last month, July 2020, was a banner month for these gas giant worlds, as Jupiter and Saturn both came to opposition in July.

Earth – in its yearly orbit – swung between these outer worlds and the sun in July 2020. Thus we were closest to Jupiter and Saturn for the year in July. Jupiter and Saturn, in turn, shone at their brightest best and were out all night long.

Read more: Jupiter at opposition on July 13-14

Read more: Saturn at opposition on July 20

Jupiter and Saturn climb highest up for the night at mid-to-late evening in early August, and by early-to-mid evening by the month’s end. Read more.

In some respects, though, August gives us a better month than July for viewing Jupiter and Saturn in the evening sky. That’s because these two worlds remain bright and beautiful throughout August, yet appear higher up in the sky at nightfall. That’s good news for those whose eastern horizon is obstructed, such as by trees and/or mountains.

That’s also good news for people with telescopes who don’t want to stay up until late night. Typically, the view of Jupiter’s 4 major moons and Saturn’s glorious rings through the telescope is sharper when these worlds are higher up in the sky. The thickness of the Earth’s atmosphere near the horizon tends to blur the spectacle.

Positions of Jupiter’s moons via Sky & Telescope

Look first for brilliant Jupiter; Saturn is the bright object immediately to Jupiter’s east. Although Saturn is easily as bright as a 1st-magnitude star – as bright as the brightest stars in our sky – the ringed planet can’t compete with the the king planet Jupiter, which outshines Saturn by some 15 times. After all, Jupiter ranks as the fourth brightest celestial object, after the sun, moon, and the planet Venus, respectively.

Around the world, Jupiter and nearby Saturn still lurk rather low in the southeast sky in early August, and transit (reach their highest point for the night) at late evening. By the month’s end, these two worlds will transit at early-to-mid evening.

For the first time since the year 2000, look for Jupiter and Saturn to showcase their great conjunction in 2020, the closest Jupiter-Saturn conjunction since the year 1623. Astronomers use the word conjunction to describe meetings of planets and other objects on our sky’s dome. They use the term great conjunction to describe a meeting of the king planet Jupiter and golden Saturn. The last great Jupiter-Saturn conjunction was May 28, 2000. The next one will be December 21, 2020. But August 2020 presents a fine time to start watching these worlds.

Read more: Before 2020 ends, a great conjunction for Jupiter and Saturn

Watch for the moon in the vicinity of Jupiter and Saturn for several days, centered on or near August 1, and then again near the month’s end, centered on or near August 28.

Mars is the only bright evening planet (Mars, Jupiter and Saturn) not to pop out first thing at dusk/nightfall. In early August, look for Mars to be up by mid-to-late evening; and by the month’s end, Mars rises by early-to-mid evening. Thus Mars is coming up earlier daily, heading for its own opposition on October 13, 2020. At that wondrous time, Mars will actually supplant Jupiter as the sky’s fourth-brightest celestial body, after the sun, moon, and the planet Venus. That will be something to see!

In August 2020, you’ll find Mars heading toward that dramatic brightening. This month, Mars is respectably bright, more brilliant even than a 1st-magnitude star, or one of the sky’s brightest stars. Earth is now rushing along in its smaller, faster orbit, gaining on Mars, the fourth planet outward from the sun. Throughout the next three months, watch for Mars to brighten dramatically as Earth closes in on Mars, passing between it and the sun in October 2020.

At mid-northern latitudes, Mars rises roughly 10 p.m. (11 p.m. daylight saving time) in early August. By the month’s end, Mars will be up around 9 p.m. (10 p.m. daylight saving time).

At temperate latitudes in the Southern Hemisphere, Mars comes up at or near the 11 p.m in early August, and about an hour earlier by the month’s end.

Let the waning moon help guide your eye to Mars on the mornings of August 7, 8 and 9, 2020.

View at EarthSky Community Photos. | From Paul Armstrong, who took this photo of Mars, Saturn and Jupiter on the morning of April 15, 2020, from Exmoor, U.K. Jupiter is at the upper right, Mars at center left, with Saturn between them. In May 2020, Jupiter and Saturn were closer together, whereas Mars was farther away from Jupiter and Saturn. Thanks, Paul!

Venus – the brightest planet – flew between the Earth and sun (at inferior conjunction) on June 3, 2020. Some 10 weeks later, Venus will reach its greatest elongation from the sun in the morning sky on August 12 or 13 (depending upon your time zone).

At mid-northern latitudes, Venus rises about 3 1/2 hours before the sun all month long.

At and near the equator, Venus rises over 3 hours before the sun in early August, decreasing slightly to 3 hours near the month’s end.

At temperate latitudes in the Southern Hemisphere, Venus rises over 3 hours before the sun in early August, decreasing to over 2 1/2 hours by the month’s end.

Inferior conjunction – when Venus sweeps between the sun and Earth – happened on June 3, 2020. Just before inferior conjunction, we saw Venus as a thin waning crescent in the evening sky; and just after inferior conjunction, we saw Venus as a thin waxing crescent in the morning sky. In August 2020, Venus will start the month about 43% illuminated and end the month about 59% illuminated. Image via UCLA.

Throughout August, Venus in its faster orbit around the sun will be going farther and farther away from Earth. As viewed through the telescope, Venus’ waxing crescent phase will widen, yet its overall disk size will shrink. Venus’ disk is 43% illuminated in early August, and about 59% illuminated by the month’s end; Venus’ angular diameter, on the other hand, will shrink to 70% of its initial size by the month’s end.

Watch for the waning crescent moon to shine in the vicinity of Venus for several days, centered on or near August 15.

Mercury transitions out the morning sky and into the evening sky this month, so the innermost planet of the solar system is pretty much lost in the sun’s glare throughout August 2020. From northerly latitudes, you might catch Mercury before sunrise in early August; or from southerly latitudes, you might catch Mercury shortly after sunset in late August. September 2020 will feature a particularly fine evening apparition of Mercury in the Southern Hemisphere.

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.

Skywatcher, by Predrag Agatonovic.

Bottom line: August 2020 presents 4 of the 5 bright solar system planets. Catch Jupiter and Saturn at nightfall and throughout most of the night, Mars between late evening and dawn, Venus in the predawn/dawn sky. Mercury shifts over from the morning to evening sky, and is pretty much lost in the solar glare.

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

Visit EarthSky’s Best Places to Stargaze, and recommend a place we can all enjoy.

Help EarthSky keep going! Donate now.

Post your planet photos at EarthSky Community Photos

from EarthSky https://ift.tt/1YD00CF

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.

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January birthstone
February birthstone
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April birthstone
May birthstone
July birthstone
August birthstone
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October birthstone
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News digest – sponge on a string, junk food watershed, prostate cancer AI and mobile phones?

With news about the coronavirus pandemic developing daily, we’re pulling together the latest government and NHS health updates from across the UK in a separate blog post, which we’re updating regularly.

Sponge on a string could transform oesophageal cancer diagnosis

A new ‘sponge on a string’ test could identify 10 times more people with Barrett’s oesophagus – a precursor to oesophageal cancer – than current testing methods, according to our scientists. Find out more in our blog post and the Express & Star.

Find out more about the latest results from the ‘sponge on a string' test that can detect oesophageal cancer earlier: https://t.co/mKCq6Zz1cf pic.twitter.com/vT840o8BpN

— Cancer Research UK (@CR_UK) July 31, 2020

New obesity strategy launched in ‘landmark day for nation’s health’

The UK Government has launched a new strategy to tackle obesity in the UK. New measures include restrictions on junk food marketing on TV and online, along with bans on multi-buy offers and certain instore promotions on high fat food products. There are also new rules for displaying calories on restaurant menus. The new strategy arrives amid growing evidence of a link between obesity and an increased risk from COVID-19. Head over to our blog or BBC News for the story.

AI could help detect prostate cancer

Using artificial intelligence (AI) software to scan biopsy samples could help flag prostate cancers that may otherwise have gone undetected. Medical experts have said that while the algorithm could be useful in overcoming pathologists’ own biases, the findings don’t necessarily prove that the AI’s diagnosis can be considered superior to humans, and that more research with larger samples sizes is needed. More on this at iNews.

Scientists identify new drug target for aggressive breast cancer

iNews reports scientists have uncovered a way to slow breast cancer stem cell growth in the lab. The team were particularly interested in stem cells that are resistant to hormone therapy, which can often be present when breast cancers come back after treatment, and believe the target they’ve identified could open the door to new treatments. Dr Bruno Simões from the University of Manchester said: “There’s a very long way to go before we can say if this approach will help these women, but we are excited by our findings.”

‘Higher end of normal’ blood platelet count could indicate cancer

Blood platelet counts at the high end of normal could be linked to an increased risk of cancer in men aged 60 or over, according to new research by the University of Exeter. High platelet count (otherwise known as thrombocytosis) has previously been linked to cancer, but this study looked at the records of 300,000 patients with platelet counts that were at the high end of the normal range. But despite the size of the study, more research is needed to confirm the link and talk of a diagnostic tool may be premature. Read more at MedicalXpress.

Scientists develop new method to selectively kill off cancer cells

New Atlas reports on a new development where scientist use “synthetic lethality” – when a build-up of DNA errors that normally wouldn’t harm a cell suddenly become deadly – to selectively kill off cancer without harming healthy cells in the lab. It’s still early days, but researchers hope the study could open the door to new drug targets.

And finally…

Mobile phones and cancer have hit the headlines again, as new research claims to have found a link between levels of blue light – used in billboard ads as well as many tablet and mobile devices – and an increased risk of bowel cancer.

But despite some bold headlines, the study only compared levels of blue light in different neighbourhoods using satellite images, rather than looking at individual people’s exposure. The study found that residents in areas with the highest exposure to outdoor blue light – the same light used in many tablet and mobile devices – had a higher risk compared to those with the lowest exposure.

Experts have said that while the findings are ‘interesting’, the research wasn’t able to take in consideration several factors linked to bowel cancer, and it’s impossible to tell from this study whether artificial light causes the disease. More on this at Daily Mail and Sky News.

Scarlett Sangster is a writer for PA Media Group

from Cancer Research UK – Science blog https://ift.tt/2PgsN3i

With news about the coronavirus pandemic developing daily, we’re pulling together the latest government and NHS health updates from across the UK in a separate blog post, which we’re updating regularly.

Sponge on a string could transform oesophageal cancer diagnosis

A new ‘sponge on a string’ test could identify 10 times more people with Barrett’s oesophagus – a precursor to oesophageal cancer – than current testing methods, according to our scientists. Find out more in our blog post and the Express & Star.

Find out more about the latest results from the ‘sponge on a string' test that can detect oesophageal cancer earlier: https://t.co/mKCq6Zz1cf pic.twitter.com/vT840o8BpN

— Cancer Research UK (@CR_UK) July 31, 2020

New obesity strategy launched in ‘landmark day for nation’s health’

The UK Government has launched a new strategy to tackle obesity in the UK. New measures include restrictions on junk food marketing on TV and online, along with bans on multi-buy offers and certain instore promotions on high fat food products. There are also new rules for displaying calories on restaurant menus. The new strategy arrives amid growing evidence of a link between obesity and an increased risk from COVID-19. Head over to our blog or BBC News for the story.

AI could help detect prostate cancer

Using artificial intelligence (AI) software to scan biopsy samples could help flag prostate cancers that may otherwise have gone undetected. Medical experts have said that while the algorithm could be useful in overcoming pathologists’ own biases, the findings don’t necessarily prove that the AI’s diagnosis can be considered superior to humans, and that more research with larger samples sizes is needed. More on this at iNews.

Scientists identify new drug target for aggressive breast cancer

iNews reports scientists have uncovered a way to slow breast cancer stem cell growth in the lab. The team were particularly interested in stem cells that are resistant to hormone therapy, which can often be present when breast cancers come back after treatment, and believe the target they’ve identified could open the door to new treatments. Dr Bruno Simões from the University of Manchester said: “There’s a very long way to go before we can say if this approach will help these women, but we are excited by our findings.”

‘Higher end of normal’ blood platelet count could indicate cancer

Blood platelet counts at the high end of normal could be linked to an increased risk of cancer in men aged 60 or over, according to new research by the University of Exeter. High platelet count (otherwise known as thrombocytosis) has previously been linked to cancer, but this study looked at the records of 300,000 patients with platelet counts that were at the high end of the normal range. But despite the size of the study, more research is needed to confirm the link and talk of a diagnostic tool may be premature. Read more at MedicalXpress.

Scientists develop new method to selectively kill off cancer cells

New Atlas reports on a new development where scientist use “synthetic lethality” – when a build-up of DNA errors that normally wouldn’t harm a cell suddenly become deadly – to selectively kill off cancer without harming healthy cells in the lab. It’s still early days, but researchers hope the study could open the door to new drug targets.

And finally…

Mobile phones and cancer have hit the headlines again, as new research claims to have found a link between levels of blue light – used in billboard ads as well as many tablet and mobile devices – and an increased risk of bowel cancer.

But despite some bold headlines, the study only compared levels of blue light in different neighbourhoods using satellite images, rather than looking at individual people’s exposure. The study found that residents in areas with the highest exposure to outdoor blue light – the same light used in many tablet and mobile devices – had a higher risk compared to those with the lowest exposure.

Experts have said that while the findings are ‘interesting’, the research wasn’t able to take in consideration several factors linked to bowel cancer, and it’s impossible to tell from this study whether artificial light causes the disease. More on this at Daily Mail and Sky News.

Scarlett Sangster is a writer for PA Media Group

from Cancer Research UK – Science blog https://ift.tt/2PgsN3i

Moon, Jupiter, Saturn July 31 to August 3

EarthSky’s yearly crowd-funding campaign is in progress. In 2020, we are donating 8.5% to No Kids Hungry. Please donate to help us keep going, and help feed a kid!

As darkness falls in late July and early August 2020, let the bright moon introduce you to the king planet Jupiter and the ringed planet Saturn. As shown on the chart above, you’ll see them easily as the brightest objects near the moon. Both Jupiter and Saturn reached opposition – when Earth flew between these worlds and the sun – in July. So both are nearly at their brightest for the year right now. Thus, although the glare of the almost-full waxing gibbous moon will wash many stars from the blackboard of night, Jupiter and Saturn are easily bright enough to withstand the moon’s glare.

Jupiter and Saturn have been close on our sky’s dome throughout 2020. They’re headed for a great conjunction – their first in 20 years – before 2020 ends. That’ll be interesting, but Jupiter and Saturn will be only 30 degrees east of the sunset at the time of their conjunction. They’ll be better when this weekend, when they’re up all night, or in the several months ahead. Come to know them this weekend near the moon, and you’ll enjoy watching them!

Far and away, Jupiter is the brighter of these two worlds, beaming some 14 times more brilliantly than Saturn. Even so, Saturn is respectably bright, shining on par with the sky’s brightest stars.

Read more: Jupiter at opposition July 13-14

Read more: Saturn at opposition July 20

Read more: Jupiter gives us Pluto in 2020

Read more: Before 2020 ends, a great conjunction of Jupiter and Saturn

View at EarthSky Community Photos. | Binoculars will let you capture a glimpse of a moon or 2 of Jupiter’s, and a small telescope reveals all 4 of the largest Jovian moons, the Galilean satellites, spread out in a line across Jupiter’s midsection. This photo comes from Mohamed Mohamed in Tripoli, Libya. He captured it on July 29, 2020.

Because the Earth spins from west to east on its axis of rotation, you can expect the moon, Jupiter and Saturn to travel across the night sky from east to west, just as the sun does during the day and for the same reason. Around now, these three worlds – the moon, Jupiter and Saturn – are climbing up highest for the night around midnight and setting in the west before the onset of morning dawn.

Relative to the backdrop stars and planets of the zodiac, the moon moves eastward at the rate of about 1/2 degree (the moon’s own angular diameter) per hour. In other words, the moon moves eastward on our sky’s dome around 13 degrees eastward per day.

Thus, in late July, you’ll see the moon to the west of Jupiter and Saturn. But, by early August, the moon will be sweeping past these planets.

More precisely, the moon will swing 1.5 degrees south of Jupiter on August 1, 2020, at 23:30 Universal Time (UTC) and then 2.3 degrees south of Saturn on August 2, 2020, at 13:17 UTC. Depending on where you live worldwide, the moon may or may not have its exact conjunction with either planet during the nighttime hours.

No matter where you live, look for the moon to pass by Jupiter and Saturn over the next several days. If you wish to check out the moon’s present position in front of the constellations of the zodiac, visit Heavens-Above.

Of course, although we see the moon sweep close to Jupiter and Saturn on the sky’s dome, the moon and these planets don’t come close together in space. The moon, our nearest celestial neighbor, resides about 238,000 miles (483,000 km) away from Earth. Jupiter lies way beyond the moon, somewhere around 16,000 times the moon’s distance from Earth. Saturn, the farthest world that’s easily visible to the unaided eye, is well over twice Jupiter’s distance from Earth.

Find out the moon’s present distance from Earth (in miles, kilometers or astronomical units) via The Moon Tonight.

Find out the present distance of Jupiter and Saturn from the sun and Earth (in astronomical units) via Heavens-Above.

Because the moon always appears full for two to three nights in a row, around the exact time of full moon, it’s hard to tell when the moon turns full just by looking at it. The early August 2020 full moon turns precisely full after its encounter with Jupiter and Saturn:

August 1, 2020 at 23:30 UTC: Moon 1.5 degrees south of Jupiter
August 2, 2020 at 13:17 UTC: Moon 2.3 degrees south of Saturn
August 3, 2020 at 15:59 UTC: Full moon

Remember when we said the oppositions of Jupiter and Saturn happened on July 14 and July 20, respectively? Opposition of an outer planet has much in common with full moon. That is, like a full moon, a planet at opposition is opposite the sun in Earth’s sky.

Enjoy these bright worlds: the moon, Jupiter and Saturn!

Bottom line: As darkness falls on these late July and early August evenings, let the bright moon introduce you to bright Jupiter and golden Saturn.

Read more: When Jupiter and Saturn meet

from EarthSky https://ift.tt/2Xe9A6J

EarthSky’s yearly crowd-funding campaign is in progress. In 2020, we are donating 8.5% to No Kids Hungry. Please donate to help us keep going, and help feed a kid!

As darkness falls in late July and early August 2020, let the bright moon introduce you to the king planet Jupiter and the ringed planet Saturn. As shown on the chart above, you’ll see them easily as the brightest objects near the moon. Both Jupiter and Saturn reached opposition – when Earth flew between these worlds and the sun – in July. So both are nearly at their brightest for the year right now. Thus, although the glare of the almost-full waxing gibbous moon will wash many stars from the blackboard of night, Jupiter and Saturn are easily bright enough to withstand the moon’s glare.

Jupiter and Saturn have been close on our sky’s dome throughout 2020. They’re headed for a great conjunction – their first in 20 years – before 2020 ends. That’ll be interesting, but Jupiter and Saturn will be only 30 degrees east of the sunset at the time of their conjunction. They’ll be better when this weekend, when they’re up all night, or in the several months ahead. Come to know them this weekend near the moon, and you’ll enjoy watching them!

Far and away, Jupiter is the brighter of these two worlds, beaming some 14 times more brilliantly than Saturn. Even so, Saturn is respectably bright, shining on par with the sky’s brightest stars.

Read more: Jupiter at opposition July 13-14

Read more: Saturn at opposition July 20

Read more: Jupiter gives us Pluto in 2020

Read more: Before 2020 ends, a great conjunction of Jupiter and Saturn

View at EarthSky Community Photos. | Binoculars will let you capture a glimpse of a moon or 2 of Jupiter’s, and a small telescope reveals all 4 of the largest Jovian moons, the Galilean satellites, spread out in a line across Jupiter’s midsection. This photo comes from Mohamed Mohamed in Tripoli, Libya. He captured it on July 29, 2020.

Because the Earth spins from west to east on its axis of rotation, you can expect the moon, Jupiter and Saturn to travel across the night sky from east to west, just as the sun does during the day and for the same reason. Around now, these three worlds – the moon, Jupiter and Saturn – are climbing up highest for the night around midnight and setting in the west before the onset of morning dawn.

Relative to the backdrop stars and planets of the zodiac, the moon moves eastward at the rate of about 1/2 degree (the moon’s own angular diameter) per hour. In other words, the moon moves eastward on our sky’s dome around 13 degrees eastward per day.

Thus, in late July, you’ll see the moon to the west of Jupiter and Saturn. But, by early August, the moon will be sweeping past these planets.

More precisely, the moon will swing 1.5 degrees south of Jupiter on August 1, 2020, at 23:30 Universal Time (UTC) and then 2.3 degrees south of Saturn on August 2, 2020, at 13:17 UTC. Depending on where you live worldwide, the moon may or may not have its exact conjunction with either planet during the nighttime hours.

No matter where you live, look for the moon to pass by Jupiter and Saturn over the next several days. If you wish to check out the moon’s present position in front of the constellations of the zodiac, visit Heavens-Above.

Of course, although we see the moon sweep close to Jupiter and Saturn on the sky’s dome, the moon and these planets don’t come close together in space. The moon, our nearest celestial neighbor, resides about 238,000 miles (483,000 km) away from Earth. Jupiter lies way beyond the moon, somewhere around 16,000 times the moon’s distance from Earth. Saturn, the farthest world that’s easily visible to the unaided eye, is well over twice Jupiter’s distance from Earth.

Find out the moon’s present distance from Earth (in miles, kilometers or astronomical units) via The Moon Tonight.

Find out the present distance of Jupiter and Saturn from the sun and Earth (in astronomical units) via Heavens-Above.

Because the moon always appears full for two to three nights in a row, around the exact time of full moon, it’s hard to tell when the moon turns full just by looking at it. The early August 2020 full moon turns precisely full after its encounter with Jupiter and Saturn:

August 1, 2020 at 23:30 UTC: Moon 1.5 degrees south of Jupiter
August 2, 2020 at 13:17 UTC: Moon 2.3 degrees south of Saturn
August 3, 2020 at 15:59 UTC: Full moon

Remember when we said the oppositions of Jupiter and Saturn happened on July 14 and July 20, respectively? Opposition of an outer planet has much in common with full moon. That is, like a full moon, a planet at opposition is opposite the sun in Earth’s sky.

Enjoy these bright worlds: the moon, Jupiter and Saturn!

Bottom line: As darkness falls on these late July and early August evenings, let the bright moon introduce you to bright Jupiter and golden Saturn.

Read more: When Jupiter and Saturn meet

from EarthSky https://ift.tt/2Xe9A6J

Juno’s new images reveal Ganymede’s north pole

The north pole of Ganymede, as seen in the infrared by Juno on December 26, 2019. Image via NASA/ JPL-Caltech/ SwRI/ ASI/ INAF/ JIRAM.

EarthSky’s yearly crowd-funding campaign is in progress. In 2020, we are donating 8.5% of all incoming revenues to No Kids Hungry. Click to learn more and donate.

Ganymede is Jupiter’s largest moon, and the ninth-largest object in our solar system. This moon is even bigger than the planet Mercury. The last time we had good close-up images of it was from the Galileo mission to Jupiter in the late 1990s. Those images provided a detailed look at much of Ganymede’s surface, but Galileo never managed to capture Jupiter’s north pole. Now, thanks to NASA’s Juno spacecraft currently orbiting Jupiter, we have the first images of the north pole of this large Jovian moon.

Unlike the Galileo mission, Juno isn’t designed specifically to study Jupiter’s moons. Juno’s images aren’t as high-resolution as those of Galileo in the 1990s, in part because they were taken from farther away. And the Juno images show the view in infrared – showing the amount of heat radiated by Ganymede at various points near its pole – rather than being visible light images revealing what our eyes would see.

Still, the images provide a glimpse of this part of Ganymede that was unseen until now. The JIRAM instrument on the Juno spacecraft – aka the Jovian Infrared Auroral Mapper – acquired the images as part of the spacecraft’s mapping of the northern regions of the moon. JIRAM used high-contrast imaging and spectroscopy to study Jupiter’s polar regions during the December 26, 2019, flyby of Jupiter. At that time, Ganymede happened to be within view of Juno. The spacecraft was programmed to turn its instruments toward Ganymede during this time.

At closest approach to Ganymede – about 62,000 miles (100,000 km) – JIRAM collected 300 infrared images of the moon’s surface, with a spatial resolution of 14 miles (23 km) per pixel.

Now … what do the new images show?

Various infrared views of Ganymede’s north polar, captured by the Juno spacecraft on December 26, 2019. Image via NASA/ JPL-Caltech/ SwRI/ ASI/ INAF/ JIRAM.

We knew already that, like many moons in the outer solar system, Ganymede is composed largely of water ice. It’s thought to have a water ocean beneath an outer ice crust.

A significant finding from these new Juno images is that the ice at Ganymede’s north pole isn’t pristine. It’s been acted upon by plasma from Jupiter’s colossal magnetosphere, which is some 20,000 times stronger than Earth’s magnetosphere. Ganymede has only an extremely thin atmosphere, so plasma from Jupiter can reach the surface unimpeded, greatly affecting the surface ice. Alessandro Mura, a Juno co-investigator at the National Institute for Astrophysics in Rome, commented:

The JIRAM data show the ice at and surrounding Ganymede’s north pole has been modified by the precipitation of plasma. It is a phenomenon that we have been able to learn about for the first time with Juno because we are able to see the north pole in its entirety.

The researchers can also see that the ice near Ganymede’s north and south poles has a different infrared signature than ice at Ganymede’s equator. This polar ice is amorphous, that is, lacking a definite shape or form. The amorphousness is due to Ganymede’s being the only moon in the solar system with its own magnetic field. Charged particles follow the moon’s magnetic field lines to the poles, where they impact and wreak havoc on the ice, preventing it from having an ordered (or crystalline) structure.

Scientists have found that even frozen water molecules in these regions have no order in their arrangement.

The new data from Juno show how it can contribute to the study of Jupiter’s moons, even though its primary mission is the study of Jupiter itself. According to Giuseppe Sindoni, program manager of the JIRAM instrument for the Italian Space Agency:

These data are another example of the great science Juno is capable of when observing the moons of Jupiter.

Ganymede, as seen in enhanced color by the Galileo spacecraft in the late 1990s. Image via NASA/ Phys.org.

Another, natural color view of Ganymede from Galileo in the late 1990s. Image via NASA.

Artist’s concept of auroras on Ganymede. This is made possible by the fact that Ganymede is the only moon known to have a magnetic field. Image via NASA/ ESA.

Cross-section of Ganymede’s interior showing a subsurface ocean of water. Image via NASA/ ESA/ A. Feild (STScI)/ Space.com.

JIRAM’s primary task is to look at infrared light coming from within the deep atmosphere of Jupiter itself. It can probe down to 30 to 45 miles (50 to 70 km) below Jupiter’s cloud tops. But, along with Ganymede, the instrument can also be used to study the moons Io, Europa and Callisto. Those four moons are known as the Galilean moons, named after the astronomer Galileo who discovered them in 1610. They are the four largest moons of Jupiter.

Thanks to its magnetic field, Ganymede also has auroras, like Earth, even though its atmosphere is extremely tenuous and almost non-existent. Ganymede’s ocean is estimated to be 60 miles (100 km) thick – 10 times deeper than Earth’s oceans – and is buried under a 95-mile (150-km) crust of mostly ice.

With a diameter of 3,273 miles (5,268 km), it is 26% larger than the planet Mercury by volume, although it is only 45% as massive. Ganymede has an iron core, a rocky mantle surrounded by an ice mantle, a water ocean ocean surrounding the mantles and an ice crust on top.

Giuseppe Sindoni, program manager of the JIRAM instrument for the Italian Space Agency. Image via ResearchGate.

Juno can see Ganymede only from a distance, but the European Space Agency’s (ESA’s) JUpiter ICy moons Explorer (JUICE), scheduled for launch in 2022, will study Ganymede, Callisto and Europa in detail after it arrives at Jupiter in 2029. This will be the first such mission to do so since Galileo.

For now, Juno has provided at least a glimpse of Ganymede’s north pole for scientists to study. In the not-too-distant future, missions like JUICE will reveal much more about this tantalizing world.

Read more about NASA’s Juno mission.

Bottom line: NASA’s Juno spacecraft has taken the first-ever images of Ganymede’s north pole.

Via Jet Propulsion Laboratory

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

The north pole of Ganymede, as seen in the infrared by Juno on December 26, 2019. Image via NASA/ JPL-Caltech/ SwRI/ ASI/ INAF/ JIRAM.

EarthSky’s yearly crowd-funding campaign is in progress. In 2020, we are donating 8.5% of all incoming revenues to No Kids Hungry. Click to learn more and donate.

Ganymede is Jupiter’s largest moon, and the ninth-largest object in our solar system. This moon is even bigger than the planet Mercury. The last time we had good close-up images of it was from the Galileo mission to Jupiter in the late 1990s. Those images provided a detailed look at much of Ganymede’s surface, but Galileo never managed to capture Jupiter’s north pole. Now, thanks to NASA’s Juno spacecraft currently orbiting Jupiter, we have the first images of the north pole of this large Jovian moon.

Unlike the Galileo mission, Juno isn’t designed specifically to study Jupiter’s moons. Juno’s images aren’t as high-resolution as those of Galileo in the 1990s, in part because they were taken from farther away. And the Juno images show the view in infrared – showing the amount of heat radiated by Ganymede at various points near its pole – rather than being visible light images revealing what our eyes would see.

Still, the images provide a glimpse of this part of Ganymede that was unseen until now. The JIRAM instrument on the Juno spacecraft – aka the Jovian Infrared Auroral Mapper – acquired the images as part of the spacecraft’s mapping of the northern regions of the moon. JIRAM used high-contrast imaging and spectroscopy to study Jupiter’s polar regions during the December 26, 2019, flyby of Jupiter. At that time, Ganymede happened to be within view of Juno. The spacecraft was programmed to turn its instruments toward Ganymede during this time.

At closest approach to Ganymede – about 62,000 miles (100,000 km) – JIRAM collected 300 infrared images of the moon’s surface, with a spatial resolution of 14 miles (23 km) per pixel.

Now … what do the new images show?

Various infrared views of Ganymede’s north polar, captured by the Juno spacecraft on December 26, 2019. Image via NASA/ JPL-Caltech/ SwRI/ ASI/ INAF/ JIRAM.

We knew already that, like many moons in the outer solar system, Ganymede is composed largely of water ice. It’s thought to have a water ocean beneath an outer ice crust.

A significant finding from these new Juno images is that the ice at Ganymede’s north pole isn’t pristine. It’s been acted upon by plasma from Jupiter’s colossal magnetosphere, which is some 20,000 times stronger than Earth’s magnetosphere. Ganymede has only an extremely thin atmosphere, so plasma from Jupiter can reach the surface unimpeded, greatly affecting the surface ice. Alessandro Mura, a Juno co-investigator at the National Institute for Astrophysics in Rome, commented:

The JIRAM data show the ice at and surrounding Ganymede’s north pole has been modified by the precipitation of plasma. It is a phenomenon that we have been able to learn about for the first time with Juno because we are able to see the north pole in its entirety.

The researchers can also see that the ice near Ganymede’s north and south poles has a different infrared signature than ice at Ganymede’s equator. This polar ice is amorphous, that is, lacking a definite shape or form. The amorphousness is due to Ganymede’s being the only moon in the solar system with its own magnetic field. Charged particles follow the moon’s magnetic field lines to the poles, where they impact and wreak havoc on the ice, preventing it from having an ordered (or crystalline) structure.

Scientists have found that even frozen water molecules in these regions have no order in their arrangement.

The new data from Juno show how it can contribute to the study of Jupiter’s moons, even though its primary mission is the study of Jupiter itself. According to Giuseppe Sindoni, program manager of the JIRAM instrument for the Italian Space Agency:

These data are another example of the great science Juno is capable of when observing the moons of Jupiter.

Ganymede, as seen in enhanced color by the Galileo spacecraft in the late 1990s. Image via NASA/ Phys.org.

Another, natural color view of Ganymede from Galileo in the late 1990s. Image via NASA.

Artist’s concept of auroras on Ganymede. This is made possible by the fact that Ganymede is the only moon known to have a magnetic field. Image via NASA/ ESA.

Cross-section of Ganymede’s interior showing a subsurface ocean of water. Image via NASA/ ESA/ A. Feild (STScI)/ Space.com.

JIRAM’s primary task is to look at infrared light coming from within the deep atmosphere of Jupiter itself. It can probe down to 30 to 45 miles (50 to 70 km) below Jupiter’s cloud tops. But, along with Ganymede, the instrument can also be used to study the moons Io, Europa and Callisto. Those four moons are known as the Galilean moons, named after the astronomer Galileo who discovered them in 1610. They are the four largest moons of Jupiter.

Thanks to its magnetic field, Ganymede also has auroras, like Earth, even though its atmosphere is extremely tenuous and almost non-existent. Ganymede’s ocean is estimated to be 60 miles (100 km) thick – 10 times deeper than Earth’s oceans – and is buried under a 95-mile (150-km) crust of mostly ice.

With a diameter of 3,273 miles (5,268 km), it is 26% larger than the planet Mercury by volume, although it is only 45% as massive. Ganymede has an iron core, a rocky mantle surrounded by an ice mantle, a water ocean ocean surrounding the mantles and an ice crust on top.

Giuseppe Sindoni, program manager of the JIRAM instrument for the Italian Space Agency. Image via ResearchGate.

Juno can see Ganymede only from a distance, but the European Space Agency’s (ESA’s) JUpiter ICy moons Explorer (JUICE), scheduled for launch in 2022, will study Ganymede, Callisto and Europa in detail after it arrives at Jupiter in 2029. This will be the first such mission to do so since Galileo.

For now, Juno has provided at least a glimpse of Ganymede’s north pole for scientists to study. In the not-too-distant future, missions like JUICE will reveal much more about this tantalizing world.

Read more about NASA’s Juno mission.

Bottom line: NASA’s Juno spacecraft has taken the first-ever images of Ganymede’s north pole.

Via Jet Propulsion Laboratory

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Jupiter gives us Pluto in 2020

The year’s 3rd and final conjunction of Jupiter and Pluto will take place on November 12, 2020. The first conjunction happened on April 5, 2020, and the second one on June 30, 2020.

See the moon, Jupiter and Saturn on July 31 to August 3, 2020

The year 2020 is exceptional for Jupiter and Pluto. These two worlds are having a triple conjunction this year, coming together, moving apart and coming together again three times in 2020. The first conjunction took place on April 5. The second one came on June 30, and the final one will come on November 12. Because all of these Jupiter-Pluto conjunctions happen when these two planets are in our night sky (as opposed to being lost in the sun’s glare), this year’s Jupiter-Pluto alignment might be the best for centuries to come.

This year, very bright Jupiter and very faint Pluto will remain near each other throughout the year, closely aligned in front of the constellation Sagittarius. Pluto requires a telescope to be seen. No telescope? Try NASA’s Night Sky Network to find star parties and/or astronomy clubs near you.

And you don’t need a telescope to use your imagination. Throughout 2020, dazzling Jupiter will enable us to envision Pluto with the mind’s eye on the sky’s dome. First find Jupiter and – presto – you’ve nearly stumbled upon Pluto. Just remember, Jupiter outshines Pluto by several million times.

Where are these worlds now? In late July and August 2020, Jupiter and Pluto are in the east at nightfall. They climb upward during the evening hours, to reach the meridian around or just after midnight. Then, in the hours before dawn, they are descending in the western half of the sky.

Look for the almost-full waxing gibbous moon to stroll by Jupiter and Saturn on or near August 1, 2020. Although not shown, the dwarf planet Pluto is quite close to Jupiter on the sky’s dome. Read more.

Of course, although Jupiter and Pluto nearly align along the same line of sight throughout 2020, these two worlds aren’t close together in space. Jupiter is a bit more than 5 astronomical units (AU) from the sun, while Pluto lodges way beyond Jupiter, in the Kuiper Belt, at about 34 AU from the sun. One astronomical unit (AU) = one sun/Earth distance.

Jupiter’s and Pluto’s present distance in AU via Heavens-Above

Here’s some observational data about Pluto for 2020, from In-the-Sky.org

Steven Bellavia in Mattituck, New York, captured Pluto on 2 separate nights, June 24 and June 27, 2019. In this animated gif, you can see that Pluto moved in front of the stars between those 2 nights. Steven wrote: “Most of the motion you see is actually from the Earth, not Pluto, since our motion changes our perspective of the much-closer Pluto against the backdrop of the much-farther stars.” Thanks, Steven!

Mosaic image of Pluto and its largest moon Charon, captured around the time the New Horizons spacecraft swept closest to them on July 14, 2015. Image via NASA/ JHUAPL/ SwRI.

Two planets are said to be in conjunction whenever they reside north and south of one another on the sky’s dome. Conjunctions of Jupiter and Pluto recur in periods of 12 to 13 years. The previous Jupiter-Pluto conjunction happened on December 11, 2007, and the one before that on December 2, 1994. After 2020, the next Jupiter-Pluto conjunction will occur on February 4, 2033, and the one following that on April 12, 2045. But the gap between Jupiter and Pluto at each one of these conjunctions is quite far apart, and the conjunctions of 1994, 2007, and 2033 happen so close to the sun that even Jupiter is lost in the sun’s glare.

Far and away, 2020 presents the best alignment of Jupiter and Pluto in the 21st century (2001 to 2100). What’s more, Jupiter and Pluto stage three conjunctions this year, as Jupiter passes less than one degree north of Pluto at each conjunction on April 5, June 30 and November 12, 2020. (For reference, the moon’s angular diameter spans about 1/2 degree of sky.) All of these conjunctions in 2020 take place in front of the constellation Sagittarius, with Jupiter first passing Pluto on April 5 in prograde (going eastward in front of the backdrop stars), then sweeping past Pluto on June 30 in retrograde (going westward relative to the background stars), and then for the final Jupiter-Pluto conjunction on November 12 in prograde (eastward).

All three Jupiter-Saturn conjunctions on April 5, June 30 and November 12, 2020, take place in front of the constellation Sagittarius, not far from the 5th-magnitude star 56 Sagittarii. Constellation chart via International Astronomical Union (IAU).

Most of the time, a Jupiter-Pluto conjunction in any year is a solitary event, as Jupiter laps Pluto going eastward, and never looks back. Triple conjunctions of Jupiter and Pluto – which occur over a period of about 7.4 months – are rare because Jupiter has to first catch Pluto going prograde (eastward), then in retrograde (westward) and then in prograde (eastward) again. The three-peat performance last happened in 1955-56 (November 2, 1955; February 8 and June 16, 1956), and will next occur in 2106-07 (July 13 and November 2, 2106; February 19, 2107). Yet, all three conjunctions in 1955-56 were widely spaced, and all three conjunctions in 2106-07 will be widely spaced, too.

Illustration showing why a superior planet appears to go in retrograde (westward in front of the backdrop stars of the zodiac). As seen from the north side of the solar system, all the planets orbit counterclockwise. When the faster-moving Earth goes by a slower-moving superior planet, that planet appears to go backward (in retrograde). In 2020, Mars is in retrograde from September 9 to November 15, Jupiter from May 14 to September 13, and Saturn from May 11 to September 29. Image via Wikimedia Commons.

In other words, as we said above, 2020 may well showcase the best Jupiter-Pluto alignment for centuries to come. Most excitingly, both Jupiter and Pluto reached opposition in mid-July 2020. At opposition, a superior planet – any planet revolving around the sun outside of Earth’s orbit – resides opposite the sun in Earth’s sky.

Opposition happens when Earth flies between a superior planet, like Mars, and the sun. This happens yearly for most of the outer planets (and every other year for Mars). Illustration via Heavens-Above.

At opposition, a superior planet (or superior dwarf planet) rises at sunset and sets at sunrise, and is out all night long. It’s at opposition that a planet shines at its brightest best in Earth’s sky, and it’s at or near opposition that a planet comes closest to Earth for the year.

Jupiter reached opposition on July 14, 2020, at about 08:00 UTC, and was closest to Earth on July 15, 2020, at about 10:00 UTC.

Pluto reached opposition on July 15, 2020, at about 19:00 UTC, and was closest to Earth on July 13, 2020, at about 09:00 UTC.

In an uncanny bit of timing, the oppositions of Jupiter and Pluto happened almost concurrently in mid-July 2020. A planet reaches opposition midway through a retrograde. However, since Pluto resides so much farther from the sun than Jupiter does, Pluto’s retrograde lasts nearly 1 1/2 months (six weeks) longer than Jupiter’s four-month retrograde. So for near-unison oppositions, Pluto’s retrograde has to start – and end – approximately three weeks before – and after – Jupiter’s retrograde.

Jupiter and Pluto retrograde/opposition in 2020

Jupiter began retrograde: May 14, 2020, in front of the constellation Sagittarius
Jupiter at opposition: July 14, 2020, in front of the constellation Sagittarius
Jupiter ends retrograde: September 13, 2020, in front of the constellation Sagittarius

Pluto began retrograde: April 25, 2020, in front of the constellation Sagittarius
Pluto at opposition: July 15, 2020, in front of the constellation Sagittarius
Pluto ends retrograde: October 4, 2020, in front of the constellation Sagittarius

Jupiter-Pluto conjunction tables via Richard Nolle

Call it serendipity or synergy – or whatever – but the spectacular alignment of the king planet Jupiter with the dwarf planet Pluto doesn’t get much better than in 2020. A similarly good Jupiter-Pluto rendezvous might not happen again for a number of centuries to come.

Pluto as seen with a 12″ S/C telescope (14.3 mag.) on July 10, 2015. Photo by Efrain Morales of Sociedad de Astronomia del Caribe. More information about Pluto’s current location.

Bottom line: Jupiter is as easy to find as the dwarf planet Pluto is difficult. Jupiter is bright! It ranks as the fourth-brightest celestial object to light up the heavens, after the sun, moon and Venus. Pluto, on the other hand, is 1,600 times dimmer than the faintest star visible to the unaided eye. But Jupiter can help you find – or at least envision – Pluto this year. That’s because these two worlds are having a triple conjunction this year; they’re near each other on the sky’s dome all year and will come exceptionally close three times in 2020.

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

The year’s 3rd and final conjunction of Jupiter and Pluto will take place on November 12, 2020. The first conjunction happened on April 5, 2020, and the second one on June 30, 2020.

See the moon, Jupiter and Saturn on July 31 to August 3, 2020

The year 2020 is exceptional for Jupiter and Pluto. These two worlds are having a triple conjunction this year, coming together, moving apart and coming together again three times in 2020. The first conjunction took place on April 5. The second one came on June 30, and the final one will come on November 12. Because all of these Jupiter-Pluto conjunctions happen when these two planets are in our night sky (as opposed to being lost in the sun’s glare), this year’s Jupiter-Pluto alignment might be the best for centuries to come.

This year, very bright Jupiter and very faint Pluto will remain near each other throughout the year, closely aligned in front of the constellation Sagittarius. Pluto requires a telescope to be seen. No telescope? Try NASA’s Night Sky Network to find star parties and/or astronomy clubs near you.

And you don’t need a telescope to use your imagination. Throughout 2020, dazzling Jupiter will enable us to envision Pluto with the mind’s eye on the sky’s dome. First find Jupiter and – presto – you’ve nearly stumbled upon Pluto. Just remember, Jupiter outshines Pluto by several million times.

Where are these worlds now? In late July and August 2020, Jupiter and Pluto are in the east at nightfall. They climb upward during the evening hours, to reach the meridian around or just after midnight. Then, in the hours before dawn, they are descending in the western half of the sky.

Look for the almost-full waxing gibbous moon to stroll by Jupiter and Saturn on or near August 1, 2020. Although not shown, the dwarf planet Pluto is quite close to Jupiter on the sky’s dome. Read more.

Of course, although Jupiter and Pluto nearly align along the same line of sight throughout 2020, these two worlds aren’t close together in space. Jupiter is a bit more than 5 astronomical units (AU) from the sun, while Pluto lodges way beyond Jupiter, in the Kuiper Belt, at about 34 AU from the sun. One astronomical unit (AU) = one sun/Earth distance.

Jupiter’s and Pluto’s present distance in AU via Heavens-Above

Here’s some observational data about Pluto for 2020, from In-the-Sky.org

Steven Bellavia in Mattituck, New York, captured Pluto on 2 separate nights, June 24 and June 27, 2019. In this animated gif, you can see that Pluto moved in front of the stars between those 2 nights. Steven wrote: “Most of the motion you see is actually from the Earth, not Pluto, since our motion changes our perspective of the much-closer Pluto against the backdrop of the much-farther stars.” Thanks, Steven!

Mosaic image of Pluto and its largest moon Charon, captured around the time the New Horizons spacecraft swept closest to them on July 14, 2015. Image via NASA/ JHUAPL/ SwRI.

Two planets are said to be in conjunction whenever they reside north and south of one another on the sky’s dome. Conjunctions of Jupiter and Pluto recur in periods of 12 to 13 years. The previous Jupiter-Pluto conjunction happened on December 11, 2007, and the one before that on December 2, 1994. After 2020, the next Jupiter-Pluto conjunction will occur on February 4, 2033, and the one following that on April 12, 2045. But the gap between Jupiter and Pluto at each one of these conjunctions is quite far apart, and the conjunctions of 1994, 2007, and 2033 happen so close to the sun that even Jupiter is lost in the sun’s glare.

Far and away, 2020 presents the best alignment of Jupiter and Pluto in the 21st century (2001 to 2100). What’s more, Jupiter and Pluto stage three conjunctions this year, as Jupiter passes less than one degree north of Pluto at each conjunction on April 5, June 30 and November 12, 2020. (For reference, the moon’s angular diameter spans about 1/2 degree of sky.) All of these conjunctions in 2020 take place in front of the constellation Sagittarius, with Jupiter first passing Pluto on April 5 in prograde (going eastward in front of the backdrop stars), then sweeping past Pluto on June 30 in retrograde (going westward relative to the background stars), and then for the final Jupiter-Pluto conjunction on November 12 in prograde (eastward).

All three Jupiter-Saturn conjunctions on April 5, June 30 and November 12, 2020, take place in front of the constellation Sagittarius, not far from the 5th-magnitude star 56 Sagittarii. Constellation chart via International Astronomical Union (IAU).

Most of the time, a Jupiter-Pluto conjunction in any year is a solitary event, as Jupiter laps Pluto going eastward, and never looks back. Triple conjunctions of Jupiter and Pluto – which occur over a period of about 7.4 months – are rare because Jupiter has to first catch Pluto going prograde (eastward), then in retrograde (westward) and then in prograde (eastward) again. The three-peat performance last happened in 1955-56 (November 2, 1955; February 8 and June 16, 1956), and will next occur in 2106-07 (July 13 and November 2, 2106; February 19, 2107). Yet, all three conjunctions in 1955-56 were widely spaced, and all three conjunctions in 2106-07 will be widely spaced, too.

Illustration showing why a superior planet appears to go in retrograde (westward in front of the backdrop stars of the zodiac). As seen from the north side of the solar system, all the planets orbit counterclockwise. When the faster-moving Earth goes by a slower-moving superior planet, that planet appears to go backward (in retrograde). In 2020, Mars is in retrograde from September 9 to November 15, Jupiter from May 14 to September 13, and Saturn from May 11 to September 29. Image via Wikimedia Commons.

In other words, as we said above, 2020 may well showcase the best Jupiter-Pluto alignment for centuries to come. Most excitingly, both Jupiter and Pluto reached opposition in mid-July 2020. At opposition, a superior planet – any planet revolving around the sun outside of Earth’s orbit – resides opposite the sun in Earth’s sky.

Opposition happens when Earth flies between a superior planet, like Mars, and the sun. This happens yearly for most of the outer planets (and every other year for Mars). Illustration via Heavens-Above.

At opposition, a superior planet (or superior dwarf planet) rises at sunset and sets at sunrise, and is out all night long. It’s at opposition that a planet shines at its brightest best in Earth’s sky, and it’s at or near opposition that a planet comes closest to Earth for the year.

Jupiter reached opposition on July 14, 2020, at about 08:00 UTC, and was closest to Earth on July 15, 2020, at about 10:00 UTC.

Pluto reached opposition on July 15, 2020, at about 19:00 UTC, and was closest to Earth on July 13, 2020, at about 09:00 UTC.

In an uncanny bit of timing, the oppositions of Jupiter and Pluto happened almost concurrently in mid-July 2020. A planet reaches opposition midway through a retrograde. However, since Pluto resides so much farther from the sun than Jupiter does, Pluto’s retrograde lasts nearly 1 1/2 months (six weeks) longer than Jupiter’s four-month retrograde. So for near-unison oppositions, Pluto’s retrograde has to start – and end – approximately three weeks before – and after – Jupiter’s retrograde.

Jupiter and Pluto retrograde/opposition in 2020

Jupiter began retrograde: May 14, 2020, in front of the constellation Sagittarius
Jupiter at opposition: July 14, 2020, in front of the constellation Sagittarius
Jupiter ends retrograde: September 13, 2020, in front of the constellation Sagittarius

Pluto began retrograde: April 25, 2020, in front of the constellation Sagittarius
Pluto at opposition: July 15, 2020, in front of the constellation Sagittarius
Pluto ends retrograde: October 4, 2020, in front of the constellation Sagittarius

Jupiter-Pluto conjunction tables via Richard Nolle

Call it serendipity or synergy – or whatever – but the spectacular alignment of the king planet Jupiter with the dwarf planet Pluto doesn’t get much better than in 2020. A similarly good Jupiter-Pluto rendezvous might not happen again for a number of centuries to come.

Pluto as seen with a 12″ S/C telescope (14.3 mag.) on July 10, 2015. Photo by Efrain Morales of Sociedad de Astronomia del Caribe. More information about Pluto’s current location.

Bottom line: Jupiter is as easy to find as the dwarf planet Pluto is difficult. Jupiter is bright! It ranks as the fourth-brightest celestial object to light up the heavens, after the sun, moon and Venus. Pluto, on the other hand, is 1,600 times dimmer than the faintest star visible to the unaided eye. But Jupiter can help you find – or at least envision – Pluto this year. That’s because these two worlds are having a triple conjunction this year; they’re near each other on the sky’s dome all year and will come exceptionally close three times in 2020.

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