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Northern Sky

East Bay Moon Crescent/Photo by Stephan Hoglund

Deane Morrison is a science writer at the University of Minnesota. She authors the Minnesota Starwatch column, and contributes to WTIP bi-weekly on the Monday North Shore Morning program through "Northern Sky," where she shares what's happening with stars, planets and more.

 


What's On:
Sumitted by Deane Morrison

Northern Sky: February 15-28, 2020

Deane Morrison is a science writer for the University of MN and authors the Minnesota Starwatch column, and in this feature she share what there is to see in the night sky...in our region.

Northern Sky by Deane Morrison for February 15-28, 2020.

In the second half of February, it doesn’t matter if you’re looking at the post-sunset or the predawn sky; you’re going to see upwardly mobile planets.
 
In the evening, Venus is still blazing away as a gorgeous evening star. If you look to the west, you won’t have any trouble finding it. As it climbs farther above the horizon, it sets later. Venus is currently up and bright for more than three hours after sunset.
 
No bright stars are near Venus, but a young crescent moon stops by on the 25th, 26th, and 27th. The moon is way below Venus at first, but on 27th, it’ll have moved to about the same level as Venus. The bright winter stars are in the south after nightfall, so if the night is clear and moonless, don’t miss the chance to see them if you haven’t already. But even Sirius, the brightest of all, can’t match the candlepower of our sister planet. As they say, location is everything.
 
The three bright outer planets are now assembling in the predawn sky. They’re all fairly low in the southeast, with Mars leading the way—that is, it’s the highest and farthest to the west. Next comes brilliant Jupiter, and finally Saturn. Late in the month, when Saturn is high enough to be easily visible, the three planets form a straight line with Mars at the upper right end, Jupiter in the middle, and Saturn at the lower left end. This assembly sets the stage for some of the closest approaches between these three planets that we’ll ever see, as both Jupiter and Saturn pass Mars.
 
What’s happening is, Earth’s orbital motion is carrying us closer to all three planets; this pushes them higher and farther west each day. But they don’t move west at the same speed. As they orbit the sun, all the planets move eastward against the background of stars. Because Mars orbits eastward at great speed, it resists Earth’s westward push. But Jupiter and Saturn orbit sluggishly, and so Earth’s motion is pushing them westward, toward Mars, rather fast. In just a few weeks we’ll see first Jupiter, then Saturn, catch up to Mars and pass it.
 
Also, since Jupiter’s orbital motion eastward is faster than Saturn’s, it’s slowly closing in on the ringed planet. We can watch this slow approach until December, when Jupiter and Saturn pass each other in the evening sky.
 
In the days leading up to the new moon on the 23rd, a waning the moon plunges through the morning sky, toward the rising sun. On the 18th, the moon passes right in front of Mars. The red planet disappears behind the moon’s bright leading edge, which is to say, behind the lighted crescent. Mars reappears behind the moon’s dark edge, but not until after daylight. If you want to see Mars disappear, get out by 6 a.m. and bring binoculars. This won’t be the most spectacular lunar occultation, as these eclipse-like events are called, because Mars is still pretty far away and small, so don’t feel bad if you miss it.
 
The next morning, the 19th, a thinner crescent moon will be staring right at Jupiter, and on the 20th an even thinner moon rises below Saturn. Try to catch those two about an hour before sunrise, before Saturn gets washed out.
 
Also, between the 24th and 25th, Mars glides right above the star that marks the lid of the Teapot of Sagittarius. Meanwhile, Jupiter pretty much stays put below the softly curving Teaspoon of stars. If you’ve never seen these features of Sagittarius, these planets can be your guide.
 

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Starwatch November 19

Northern Sky: November 23 - December 6

Northern Sky by Deane Morrison

November 23 to December 6, 2019

As we move into the final month of the year, the planets are at play in both the morning and evening skies.
 
In the predawn hour, Mars and Mercury are both in the east-southeast until the end of November and into December. So is Spica, the brightest star in Virgo, the maiden. These three objects form a diagonal line above the horizon with Spica highest, Mercury lowest, and Mars, of course, in the middle. You might want to look on Sunday, November 24, when a thin crescent moon hovers to the left of Mars.  On the 25th, the moon will be thinner and just above the horizon, below Mercury.
 
As the days go by, Mars’s two companions abandon it. Spica keeps climbing higher, thanks to Earth’s orbital motion. But Earth's motion has a relatively weak influence on Mercury's comings and goings because it's an inner planet and much speedier than Earth. When it pops into the morning sky, it’s coming out from a trip between Earth and the sun. The transit of Mercury across the face of the sun on November 11 was also a transit, officially, out of the evening sky and into the morning. But it soon drops down again, as it starts its next trip around the far side of the sun. So as Spica climbs away and Mercury drops away, Mars gets doubly deserted. 
 
In the evening sky, Jupiter and much brighter Venus pass each other in the southwest on the weekend before Thanksgiving, November 23 and 24. The two planets come as close as 1.5 degrees, or about three moon widths. Try to catch them about 40 minutes after sunset. On Thanksgiving evening, a thin crescent moon of the next cycle will be right above Venus, and Jupiter will be below it to the right. This threesome will be impressive if you can catch it before Jupiter sets. If not, that’s okay; Venus and the moon always make a nice pair. 
 
On Friday, November 29, the moon hangs below and left of Saturn. Saturn hasn’t been especially bright this year, so if you haven’t found it, this moon will guide you. Like Jupiter, Saturn is falling toward the sunset as Earth leaves it behind in the orbital race. The ringed planet also gets a visit from Venus, in the second week of December. It'll be fun to watch these two planets approaching each other.
 
If you’re out at nightfall, look to the north to see the Big Dipper sitting right above the horizon. When it’s low like this, you can observe the double star at the bend of the dipper’s handle through binoculars without straining your neck too much. Also, find the pointer stars at the far end of the bowl, that is, away from the handle; these point to Polaris, the North Star. Then see if you can spot a lazy triangle of stars to the upper right of the pointer stars; these mark the head, and rather pointed nose, of the Big Dipper’s home constellation: Ursa Major, the great bear.  
 
Bracketing Polaris are two bright stars, both at about the same distance from Polaris. To the left, in the northwest, is Vega, in the Summer Triangle of stars, and to the right, in the northeast, is Capella, in the winter constellation Auriga, the Charioteer. Hanging from Polaris is the Little Dipper. Its midsection is dim, and it’s about all there is to see in the constellation Ursa Minor, the little bear. But since the Latin name Ursa Major is feminine, and Ursa Minor is so close by, Ursa Minor could well be regarded not just as a little bear, but as a bear cub.

 

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Starwatch Map Nov 2019

Northern Sky: November 9 - 22

Northern Sky by Deane Morrison
Nov. 9-22 2019
 
Now that we’re back on Standard Time, nightfall comes early. The switchover sucked an hour of darkness from the morning sky, so now we have to get out really early to watch the morning stars and planets. Sure, the sun has been rising later each morning since the switchover, but we won’t get all that darkness back again until December 17. The sun will keep coming up later for the rest of December and into January, but on January 6 it starts coming up earlier. 
 
If you’re out an hour before sunrise between November 9 and 13, you can watch Spica, the brightest star in Virgo, the maiden, climb in the eastern sky and slide past Mars. Spica and Mars are closest on the 10th. Then on the 11th and especially the 12th, the two are at virtually the same altitude, with Spica on the right. Spica and the other stars go right on moving higher and westward, but Mars’ orbital motion eastward keeps it from pulling away from the rising sun as fast as the stars do. So Mars will be low and dim for a while, but in less than a year it’ll be the star of the evening show.
 
Over in the west, the sky is waiting for the next “evening star” to climb into prominence. That would be Venus. Venus is slowly pulling itself out of the setting sun’s afterglow. Meanwhile, Jupiter and Saturn are sinking toward it as Earth leaves them behind in the orbital race. By the 22nd, Venus and Jupiter will have drawn close together, very low in the southwest, with Venus, the brighter planet, below Jupiter, getting ready to pass it. As they approach each other and pass, the trick is to catch the planets when it’s gotten dark enough to see them but before they drop too close to the horizon. When Venus and Saturn pass next month, it’ll happen a little higher in the sky.
 
At nightfall on November 10th, the waxing moon will be above the eastern horizon. At about the same altitude, off to the left, is the bright star Capella, in the constellation Auriga the charioteer. Later in the evening, when the bright winter constellations are all up in the east, Capella will be at the top of the heap. As for the moon, to see it closest to full, look westward on the morning of the 12th, at least a half hour before it sets at 6:51 a.m. 
 
On Monday the 11th, the sun rises with a tiny round, black dot on its face. That's Mercury, making a rare transit, which occurs when Mercury passes between Earth and the sun and we see Mercury crossing the face of the sun. Mercury passes between us and the sun three or four times a year, but because the plane of its orbit is tilted seven degrees from Earth’s, its orbit usually carries it above or below the sun from our point of view. If our two planets orbited in the same plane, we’d see transits during every passage of Mercury between Earth and the sun. For us to see a transit during a passage, Earth must, at that moment, be at or very near one of the two points where its orbit intersects the plane of Mercury’s orbit. That puts both Mercury and the sun in our line of sight, and so the planet appears to crawl across the sun’s face. From Minnesota, the transit will be under way at sunrise, but it lasts until 12:04 p.m. Don’t watch it without proper eye protection, especially when some websites will stream it live. Just search online for “live webcast Mercury transit 2019.” 
 

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Northern Sky Map.  Courtesy Deane Morrison.

Northern Sky: August 31 - September 13

NORTHERN SKY
by  Deane Morrison
August 31 - September 13, 2019

Over Labor Day weekend, the moon is a young sliver that sets before or shortly after nightfall. Each night it moves farther eastward, on its monthly tour of the sky. It’s waxing brighter now, and won’t begin withdrawing from the evening sky until after the full phase in mid-September. So if you’re an evening star watcher and you go out during the two weeks after Labor Day, you’ll probably be seeing a lot of the moon.  

As for the stars, this month the Summer Triangle is high in the south, in prime position for evening viewing. The brightest of the three stars, Vega, in the constellation Lyra, the lyre, is just a hair less bright than the star you may have noticed slowly sinking in the west. That’s Arcturus, the anchor of Bootes, the herdsman, and the brightest star in the northern hemisphere of the sky. In the east, the Great Square of Pegasus, a fall constellation, is climbing into prominence.

Every year the stars and constellations are the same, but the planets move around. This summer, we’ve been treated to the sight of Jupiter and Saturn in the south after nightfall—and Jupiter is so bright, it comes out in the twilight, well before Saturn. On the 5th, the waxing moon hovers near Jupiter and almost directly above Antares, the brightest star in Scorpius. At 10:10 that night, Thursday, the 5th, the moon reaches first quarter phase. When the moon is at a quarter phase, the features of the lunar surface cast the deepest shadows, and this makes them stand out in sharpest relief. So this is a good night to explore the lighted part of the moon with binoculars. You don’t have to wait till after ten o’clock, of course; the moon is essentially at the first quarter phase all evening.

On the 7th, the moon will be bigger and brighter, this time closing in on Saturn. You may need binoculars to see it, but the star a few degrees below and right of the moon is the lid of the Teapot of Sagittarius. The Teapot will be somewhat washed out by moonlight, but if you haven’t seen it yet and would like to, that’s where to look for the lid, at least. On the 8th, the moon will be east of Saturn. On the 10th, the moon will be in the middle of the constellation Capricornus, the sea goat. Capricornus is chevron-shaped, and it’s one of the autumn water constellations. It has no bright stars, so it’s hard to find. But if you note where the moon is on the 10th and then find a star chart, that’ll vastly improve your chances of finding this dim constellation of the zodiac.

Three days later, on the 13th, we get a full moonrise. In Grand Marais, the moon rises at 7:36 p.m., four hours before it becomes perfectly full. Because it’s the closest full moon to the equinox, it qualifies as the harvest moon. The harvest moon got its name because near the time of the fall equinox, the moon can rise less than 30 minutes later from night to night as it goes from almost full to full to a couple of days past full, as opposed to forty or fifty minutes later from night to night near the solstices and more than an hour later from night to night near the spring equinox. The harvest moon gave extra moonlight to farmers working late to harvest their crops before they either froze or spoiled in the field. The harvest moon effect isn’t always as strong as the numbers I just gave would imply, but even so, this nickname for a full moon has a pretty solid basis. 
 

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Star Map July 2019 by Deane Morrison

Northern Sky: July 20 - Aug 2

NORTHERN SKY - Deane Morrison
July 20 - August 2, 2019

Today, in honor of the 50th anniversary of the moon landing on July 20, I’d like to talk about how it happened and why it was scientifically important.
 
On July 20, 1969 the moon was a waxing crescent in the evening sky. The Apollo 11 astronauts had a landing site all picked out near the border with Earth’s shadow, where it was just past sunrise. As the computer aboard the lunar module, the Eagle, guided them down, Neil Armstrong and Buzz Aldrin watched the moonscape go by below them. At about 33,000 feet, an alarm suddenly went off. Nothing in their training had prepared them to figure out what it was. They spent several minutes trying to identify it before Mission Control finally told them not to worry; it was just the Eagle’s computer reacting to being overloaded.
 
While the astronauts were chasing this wild goose, the lunar module used a lot of propellant fuel, and when the fuel tank dipped to half full, the propellant started sloshing around and knocking the module every which way. The sloshing also set off a “low fuel” alarm prematurely, and so the crew thought they had less time to land than they actually did.
 
These issues also kept Armstrong from checking out the landing site visually. At about 2,000 feet, he finally did, and he saw that the site was a boulder field—not smooth ground at all. At about 540 feet, Armstrong took manual control of the spacecraft. Despite the disruptions, he was able to guide the lunar module past the boulder field and set it down with just 20 seconds left before they would have been forced to land wherever they were or abort the landing.
 
Apollo 11 brought back 46 pounds of moon rocks. In all, 842 pounds of moon rocks came back on Apollo spacecraft. The oldest are 4.5 billion years old, same age as Earth. They indicated that the moon, like Earth, was also once covered by an ocean of magma. But unlike Earth, which has an iron core, the moon has very little iron and came from the same stuff as Earth’s mantle. These findings support what was once a radical idea: that the moon didn’t condense out of the same cloud of solar system material as Earth, nor was it captured later by Earth, but it formed when another planetary body collided with an infant Earth that was still molten. The collision knocked out material from Earth’s mantle, and perhaps from the other body, and this material coalesced to become the moon.
 
Also, moon rocks record impacts from collisions, and the number of impacts apparently spiked around 700 million years after Earth and the moon formed. An explanation for why so many more objects should have been flying around the solar system and hitting the moon—and Earth, of course—at that time is part of a leading theory of how the solar system formed. Simply put, it says that early on, gravitational interactions between Jupiter and Saturn destabilized the entire solar system and pushed the orbits of Saturn, Uranus and Neptune farther out. This changing gravitational landscape disrupted the orbits of numerous small bodies far from the sun, collectively called protoplanetary debris, and scattered them throughout the solar system. The result was an outbreak of collisions that lasted until most of the debris was cleared. And this outbreak, called the late heavy bombardment, left its signature in the spike of impacts imprinted in the moon rocks.

Scientists are still debating exactly how the moon formed and what the moon rocks tell us. But by any measure, these rocks are among the most valuable items of all time.
 
Deane Morrison writes the Minnesota Starwatch column for the University of Minnesota’s Minnesota Institute for Astrophysics.
 


 
Star Map June by Deane Morrison

Northern Sky - Deane Morrison June 8 - 21

NORTHERN SKY
by  Deane Morrison
June 8-21 2019
 
In the second two weeks of June, planets and stars are on the move. But the sun seems to be standing still, as it always does for about two months around each solstice, a word that literally means “sun standing still.” The summer solstice arrives at 10:54 a.m. on Friday, the 21st. At that moment, the sun will be over the Tropic of Cancer, and an observer in space would see the Earth lighted from the Antarctic Circle up to the North Pole, then beyond to the Arctic Circle on the dark side of our planet.
 
In the west, Mercury has popped into the evening sky. Mercury never gets very high, but if you look at nightfall from night to night, with binoculars if necessary, you may be able to see it climb away from the west-northwestern horizon. It heads straight for Mars, which is extremely dim, and on the 18th it passes only about half a moon width above the red planet. Above and to the right of the planets are the Gemini twins Pollux, the brighter one, and Castor. After their close encounter, Mars and Mercury go their separate ways. And all these objects get lost in the sunset by the end of June.
 
On the 10th, we lap Jupiter in the orbital race. At this moment Jupiter is said to be at opposition, because it’s on the opposite side of Earth from the sun and thus opposite the sun in the sky. At opposition, an outer planet rises around sunset and stays up all night. Jupiter is a brilliant beacon, and it rises in the southeast right behind the constellation Scorpius. The scorpion’s heart is Antares, a gigantic red star a little below and west of Jupiter. Saturn follows Jupiter into the sky by about two hours.
 
The evening of the 15th, a bright waxing moon appears between and above Jupiter and Antares. The evening of the 18th, a bright waning moon rises right below Saturn. For the next several days, Jupiter and Saturn get to shine against a darker sky at nightfall because the moon rises later each night while they rise earlier.
 
In the east, look for the Summer Triangle of bright stars. The brightest is Vega, in the constellation Lyra, the lyre of the mythical Greek musician Orpheus. With binoculars you can easily see the parallelogram of stars that outline the body of the lyre. Vega is only about 25 light-years away, and it has a great claim to fame, thanks to Earth’s habit of wobbling on its axis like a top. This wobbling makes the North Pole point to different stars in sequence as it traces out a circle every 26,000 years. The North Pole now points toward Polaris, but once it pointed toward Vega, and in about 12,000 more years, Vega will again be the north star.
 
When the sky gets dark, Vega and Jupiter form a big, bright triangle with the brilliant star Arcturus, in Bootes, the herdsman. Arcturus is west of Vega and marginally brighter. Grab a star map and look between Vega and Arcturus. Next to Vega is the upside-down form of Hercules, and next to Hercules is a semicircle of stars called Corona Borealis, the northern crown.
 
The night of the 16th to 17th, the moon takes a low trajectory across the night sky and reaches fullness at 3:31 a.m. The low trajectory happens because a full moon is always opposite the sun in the sky. Therefore, when we’re this close to the summer solstice and our hemisphere is tilting strongly toward the sun, it must also tilt away from a full moon, leaving it low in the sky. 
 
 
Deane Morrison writes the Minnesota Starwatch column for the University of Minnesota’s Minnesota Institute for Astrophysics.
 

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Sky Map_June 2019 by Deane Morrison

Northern Sky: May 25 - June 7, 2019

NORTHERN SKY  by Deane Morrison
 
During the last week of May, the moon wanes away in the morning sky, starting with the last quarter phase on Sunday, the 26th. Last time, I mentioned that the quarter phases are good for moon watching because that’s when lunar features like craters stand out in sharpest relief. So on the 26th, you may want to grab your binoculars again. One small caveat: In Grand Marais, the moon doesn’t rise that day until 2:09 a.m., which may be somewhat inconvenient. On the other hand, if you’re a night owl, the last quarter phase gives you the best chance to explore the part of the moon that isn’t visible at first quarter phase.
 
If you are up at that hour, you’ll see the Summer Triangle of bright stars above the moon as it rises in the east-southeast, plus Jupiter—the brightest dot—in the south and Saturn to the lower left of Jupiter. But you don’t have to wait till the middle of the night to see those planets. Earth is about to lap them in the race around the sun, and they’re rising earlier every night. We lap Jupiter on June 10, and by the end of the first week in June, Jupiter will up in the southeast by 10 p.m. Saturn follows Jupiter by about two hours. Just west of Jupiter is the red star Antares, the heart of Scorpius.
 
You might want to try watching Jupiter from night to night. Earth is already starting to lap it, and this makes it moves westward against the backdrop of stars. If you grab those binoculars again, you may detect Jupiter inching westward with respect to several rather dim stars that are near the planet.  
 
And back to the moon for a second. As it wanes, it rises later every morning. If you’re up around 4:30 on June 1 and you have a clear view of the eastern horizon, you may see a very old and thin crescent rising to the lower right of Venus. Moonrise on June 1 is at 4:27 a.m., which is scarcely half an hour before sunrise, so both the moon and Venus will be awash in the sun’s foreglow. 
 
In the evening sky, Spica, the brightest star in Virgo, the maiden, is in the south at nightfall, well below the brilliant star Arcturus. Spica’s not all that bright, but then it’s about 260 light-years away. It’s not a single star, but at least two big ones that orbit each other very closely. Only 11 million miles apart, which is about one-fourth the distance of Mercury from the sun. The strong gravity between these two stars has pulled each of them out into an egg shape, and it’s thought that they spin around like two gigantic eggs with their narrow ends pointed at each other. And they spin really fast: It takes them only four days. This would be incredible to watch if we could get close and look down on these stars.
 
In the west, Mars is resisting being swallowed by the sun as Earth leaves it behind. Mars is as dim as it gets, but have a look around 40 minutes after sunset on June 4. Mercury will be very low in the west-northwest, a young crescent moon will be just to the left of it, and Mars will be almost directly above the moon. Above Mars, the Gemini twins Pollux, the brighter, and Castor are dropping as they make their seasonal exit from the evening sky. This year they’ll leave in the company of Mars and Mercury.
 
Deane Morrison writes the Minnesota Starwatch column for the University of Minnesota’s Minnesota Institute for Astrophysics.
 

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May 2019 Star Map.jpg

Northern Sky: May 11 - 24, 2019

NORTHERN SKY  by  Deane Morrison                May11-24, 2019

 
Here in mid-May, we have two planets that are fairly bright and busy moving into prime viewing position. Those planets are Jupiter and Saturn, and they’re rising in the southeast earlier every day, but still pretty late. Jupiter makes it up before midnight, but Saturn doesn’t; it follows Jupiter around two hours later. You can also see them in the predawn sky, say 4 to 4:30 a.m. Jupiter is the brightest thing after the moon, and Saturn the next brightest thing to the east of Jupiter.
 
The planets are about 27 degrees apart, which isn’t very far. Not coincidentally, Earth is getting ready to lap both of them in the race around the sun. Jupiter on June 10, Saturn on July 9. When we lap an outer planet, it’s up all night, which is ideal for viewing. However, summer’s coming, our hemisphere is tilting away from the night sky, and the sun has stolen a big chunk of it. Right now, we can only see Jupiter and/or Saturn very late in the evening or ridiculously early in the morning.
 
On top of that, between May 11 and 24, the period this broadcast covers, the moon will be big and bright enough to wash out a lot of the stars that form a backdrop for the planets.
 
Well, if you can’t beat ‘em, join ‘em. Let’s look at what the moon can do for us. The evening of the 11th, it’ll be at first quarter phase. This is a good time to pull out your binoculars or small telescope and have a look at the moon. During quarter phases, the moon is 90 degrees from the sun, and lunar features, like craters, appear in sharp relief. Just east of the moon, you’ll see Regulus, the brightest star in Leo, the lion. Regulus is the dot in a backward question mark of stars called the Sickle, which outlines the lion’s head.
 
A night or two later, on the 12th or 13th, the moon will have moved farther east in Leo. The lunar features will still stand out, and a famous one will now be lighted. That’s the Tycho crater, which was named after the great Danish astronomer Tycho Brahe, who died in 1601 at age 54. The crater is near the south pole of the moon and is about 53 miles across. It’s remarkable for the long bright lines radiating from it; these are where material was thrown during the collision with whatever space rock came along and gouged out the crater. The crater has been estimated to be about 100 million years old, which is young for a lunar feature.
 
Between the 15th and 16th of May, the moon passes between Spica, the only reasonably bright star in Virgo, and brilliant Arcturus, in Bootes, the herdsman. Spica will be below the moon, and much closer to it than Arcturus.
 
May’s full moon rises over Grand Marais at 8:27 on the evening of the 18th. It crosses the night sky above Antares, the red heart of Scorpius. Over the next several days, the waning moon sweeps past Antares, then Jupiter and Saturn.
 
In the north, the Big Dipper hangs more or less upside down at nightfall. The two stars at the far end of its bowl—that is, farthest from the handle—point down to Polaris, the North Star. Flanking Polaris, but closer to the horizon, are two bright stars. On the left is Capella, in Auriga, the charioteer, and to the right is Vega, the brightest of the Summer Triangle of bright stars. And if you follow the curve of the Big Dipper’s handle, it’ll take you to Arcturus again.
 
Deane Morrison writes the Minnesota Starwatch column for the U of M’s Minnesota Institute for Astrophysics.
 

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May 7 Skymap.jpg

Northern Sky: April 27 - May 10, 2019

NORTHERN SKY  by Deane Morrison
April 27-May 10 2019

Here we are again, moving from April into May, and the winter stars are disappearing in the west. But they’re not all gone yet. Case in point, a little while ago, a friend asked me about a couple of bright stars he had seen in the west around nine thirty the night before. Both were about the same distance above the horizon. So I took a good guess, and went out that night, and sure enough, what had caught his eye was the winter stars Procyon, in Canis Minor, the little dog, and Capella, in Auriga, the charioteer. Right now these two stars are getting ready to set for the season. If you haven’t seen them but you’d like to, go outside as soon as the sky gets dark, and you should see two bright stars not far above the western horizon. Procyon is on the left, Capella on the right. Above and between them are the Gemini twins, Pollux, that’s the brighter twin, and Castor.

This winter I’ve talked about all these stars except Capella. It’s a beautiful star, and when it’s low in the sky, Earth’s atmosphere often acts like a prism and makes it twinkle red and green. From the latitude of Grand Marais, it’s a circumpolar star. That is, it travels in a circle around the Pole Star, Polaris, and never sets, although in summer it gets a little too low to see very well. The stars of the Big and Little Dippers are also circumpolar. If you could follow a circumpolar star all day long, you’d see it complete one circle around Polaris every day. And if you noted its position at the same time every night for a year, you’d see it circle Polaris then, too.

Capella is also a multistar system. It has a close pair of big yellow stars, both a lot brighter than the sun and with about 2.5 times its mass. It also has a pair of little red dwarf stars orbiting the big yellow stars at a distance of about 10,000 times the distance of Earth to the sun.
The name Capella refers to the “little female goat” that the charioteer is carrying. Below Capella you may be able to make out three fainter stars that form a narrow triangle. These are called the Kids.

On May 7, Capella will be part of a string of objects lined up diagonally from lower left to upper right at nightfall, but not much longer afterward. Starting at the lower left end, we have Betelgeuse, in Orion; then a young crescent moon; then Mars, and finally Capella. On the evening of May 9, a heftier crescent moon will be between Procyon and Pollux.

And speaking of evenings, sundown on April 30 marks the beginning of the astronomically based Celtic holiday called Beltane. It was one of four cross-quarter days falling midway between an equinox and a solstice. Beltane marked the end of the dark half of the old Celtic year. The dark half began at Halloween, when all the evil spirits were set loose upon the world to vex humankind for the next six months. And that made sense; winter is the time when hunger, cold and diseases like flu run rampant. But when the end of April rolled around, things changed. At sundown on April 30, the nasty spirits came out for a last fling. Then, at sunrise on May 1, the party was over, and the spirits were again banished until sundown on October 31. The night of April 30 is also called Walpurgis night, but only because May 1 is associated with St. Walpurga, who had nothing whatsoever to do with any of this.
 

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April Star Map - MN Starwatch

Northern Sky: April 13 - 26, 2019

NORTHERN SKY – by DEANE MORRISON    
April 13-26 2019
 
Well, what a difference a day makes. On Wednesday, April 10, a colossal astronomy story broke. Scientists working from radio telescopes all over the world released the first direct image of a black hole. Apologies if you’ve already heard all about this, but here goes.
    
Black holes are typically found at the centers of galaxies. They concentrate matter so densely, and generate such strong gravity, that nothing that gets too close can escape, including light. The boundary beyond which escape is impossible is called the Event Horizon, and that’s the name of the team that produced the image.
    
This black hole shows up as a dark round area inside a fuzzy, lopsided doughnut of light. It lies at the heart of a monster galaxy called Messier 87, which is one of the most massive galaxies in a cluster of galaxies in the constellation Virgo. The Virgo Cluster is in the general neighborhood of our Milky Way galaxy, and both the Milky Way and Messier 87 are powered by supermassive black holes.
    
But there’s no comparison. The mass of the Milky Way’s black hole is equal to 4 million suns, while Messier 87’s black hole has the mass of 6.5 billion suns; that’s 1,600 times more. The researchers calculated the diameter of the black hole to be 40 billion kilometers, or 25 billion miles. That makes it more than four times the diameter of Neptune’s orbit and nearly the size of our entire solar system. The Messier 87 galaxy is about 55 million light-years away. It’s visible through a small telescope, and May is a good month to observe it.
    
If you want to see where in the sky this galaxy is, and maybe point out its location to children or friends, you can use stars to navigate. Start by facing south after nightfall, at 9:30 or so. You’ll see the constellation Leo, the lion, fairly high in the south. Its brightest star,  Regulus, is the point in a backward question mark of stars that outline the lion’s head. Just east of the lion’s head is a triangle of stars marking the tail and hindquarters. The brightest and most eastern of these stars is Denebola. Okay, remember Denebola. Moving eastward again, you’ll see brilliant Arcturus, not quite as high as Denebola. Much lower, between Denebola and Arcturus, is Spica, the brightest star in Virgo.
    
Put another way, we have brilliant Arcturus well up in the east, Spica far to the lower right of Arcturus, and relatively dim Denebola to the upper right of both. These three stars form a nearly equilateral triangle. In fact, they are often called the Spring Triangle.
    
If you look from Arcturus about three quarters of the way to Denebola, and then down a little, that’s where M87 and its black hole, its heart of darkness, are. On April 17 the moon visits; if you point to a spot directly west of Arcturus and above the moon, you won’t be far off.
       
In the morning sky, Jupiter and Saturn, along with the star group known as the Teapot of Sagittarius, are slowly making their way westward, like a convoy. Jupiter is kind of low but brilliant, Saturn is the next bright object to the east, and the Teapot is between them. The moon visits Jupiter on the 23rd; on the 24th it sits right above the lid of the Teapot, and on the 25th it visits Saturn.
     
April’s full moon arrives on Friday, the 19th at 6:12 a.m. That’s shortly after sunrise and before moonset in Grand Marais. With clear views to east and west, you’ll see a rising sun and a very round, setting moon facing each other from opposite horizons.
 

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