Sun news for December 19, 2023: More beautiful auroras as storming comes to an end

Today’s top news: After another night of mesmerising auroral displays during a G1 (minor) geomagnetic storm, action at Earth has finally calmed. This fantastic show came after a period of crazy activity on the sun. As the effects of several coronal mass ejections (CMEs) and fast solar wind fade, more action seems to be on the way; let’s see what our star next has in store for us.
Last 24 hours: Sun activity is back to low, but action seems to be picking up. With prominences adorning the limbs (edges) of our star, fresh sunspot groups seem to be just out of view. In fact, incoming sunspots have been observed with helioseismology over the horizon on the eastern limb, soon to rotate into view. Between 11 UTC yesterday and 11 UTC today, 12 C flares were fired. The largest was a C7.4 flare, fired at 3:04 UTC on December 19 by sunspot group AR3528. This active region was the lead flare producer of the period with five Cs. AR3520 was close behind with four C flares. The sun currently has nine labeled active regions on its Earth-facing side, including three newcomers: AR3527 in the west, AR3528 close to the central meridian in the northeast, and AR3529 in the southeast.
Next 24 hours forecast: The forecast is a 99% chance for C flares, a 25% chance for M flares, and a 5% chance for X flares.
Next expected CME:  No Earth-directed coronal mass ejections (CMEs) were observed in the available imagery.
Current geomagnetic activity: Earth’s geomagnetic field is quiet at the time of this writing (11 UTC on December 19), but a G1 (minor) geomagnetic storm was registered at 23:59 UTC, December 18. Unsettled conditions are expected during the rest of the day through tomorrow as the CMEs from December 14 to 15 start to wane, while we continue to experience the effects of fast solar wind from a coronal hole.

Sun news for December 18, 2023: Night #2 for great auroras!

Sun news for December 18, 2023. More auroras! Join EarthSky’s Deborah Byrd in the video above, for more.
It’s been two fabulous night of auroras! At the time of this writing (11 UTC on Monday, December 18), Earth is experiencing yet more geomagnetic storming, due to coronal mass ejections (CMEs) and high speed solar wind from a coronal hole. The storming is at G2 (moderate) levels at this time. Aurora reports were arguably fewer Sunday night (December 17-18) than Saturday night (December 16-17). But both nights were grand! And we might see auroral activity later today. Stay tuned!
Last 24 hours: Sun activity due to flares is moderate with one M1.1 flares and 12 C flares observed. The largest event was an M1.1 flare from sunspot region AR3520 at 20:08 UTC December 17. AR3520 produced five flares including the M1.1. There is significant activity beyond the west limb (edge), most likely due to AR3514 acting up. Several eruptions are visible from this area in 304-angstrom light from SDO and GOES-16. The Earth-facing side of the sun currently has six active regions.

This is insane tonight
Aurora pulsating overhead ??? pic.twitter.com/iv9i7Ou0rh

— ?Angel Brise’ Alaska Adventurer? (@AngelBrise1) December 18, 2023

Another successful #aurorahunting tour last night here in #Yellowknife! Level 4.5 -23C windchill -31C! More Aurora dreams come true! Book now make your Aurora #dreamcometrue! #auroraborealis #northernlights #bestplacetoseeaurora #bucketlist #indigenousbusiness #livelife #lovelife pic.twitter.com/J0X5tRG3DV

— NorthStarAdventures (@NStarAdventures) December 18, 2023

Despite the weak, glancing blow of the CME, there was enough energy in its wake that pushed a relatively brief, but highly visible ?#Aurora substorm into mid-lat, on the horizon- Even as far south as Hartford in S Wisconsin and further! ? Of course the car headlight too! ? pic.twitter.com/3kIH8zsV1X

— Jake Stehli (@eljakeo30) December 18, 2023

Sun news for December 17, 2023: Auroras! And more coming …

Good morning! Here’s a little green to start your Sunday :) pic.twitter.com/bVsb0wYcnU

— Vincent Ledvina (@Vincent_Ledvina) December 17, 2023

We’ve got auroras! One or more of the anticipated coronal mass ejections (CMEs) from December 14 and 15 may have reached Earth. At the time of this writing (11 UTC on Sunday, December 17), we are experiencing a G1 (minor) geomagnetic storm and we are starting to see some aurora reports. The reports are mostly from Canada and Alaska. Over the next day we will wait to see if there are any signs of additional CME impacts and resulting geomagnetic storming and auroras. Stay tuned!
Last 24 hours: Sun activity due to flares is low with 16 C-class flares observed. The largest event was a back-to-back set of flares from sunspot region AR3514, a C8.4 and C8.1 at 13:19 and 14:12 UTC respectively. AR3514 produced most of the flares at 14 of 16. It has almost completely rotated out of view over the west limb. It has decayed, losing its delta region, but this sunspot group still has the potential for some significant flaring. The Earth-facing side of the sun currently has nine active regions.

Another photo from late this morning. 7:45am in Kodiak, Alaska pic.twitter.com/ucqKPOCyMD

— Kris Luckenbach (@KrisLuckPhoto) December 18, 2023

More amazing #AuroraBorealis imagery from space overnight during yet another geomagnetic storm. This sun cycle rocks! https://t.co/N94utqlp7f pic.twitter.com/otomroBJa6

— UW-Madison CIMSS (@UWCIMSS) December 17, 2023

We’re on!
202312170657
Northeast of Strathmore Alberta #Aurora #Auroraborealis #northernlights pic.twitter.com/yWaGfITCld

— Harlan Thomas (@theauroraguy) December 17, 2023

Woohoo! She’s dancing in Central Alberta now. #TeamTanner #Aurora @TamithaSkov @chunder10 @scottrockphoto @PeakToSailPhoto @hillsblockview pic.twitter.com/6ad856jUaC

— Dar Tanner (@dartanner) December 17, 2023

The aurora in Alaska went nuts tonight, wow! pic.twitter.com/1L5GSLvEqB

— Vincent Ledvina (@Vincent_Ledvina) December 17, 2023

Decent aurora potential now if you’re in Alaska or Siberia… Europe get ready for a potential mid-latitude aurora breakout, although we need to monitor activity over the next several hours. Nice substorm in GOES Mag, AE is healthy… pic.twitter.com/lPrBrtqrVR

— Vincent Ledvina (@Vincent_Ledvina) December 17, 2023

The sun in recent days

Sun images from our community

Are you a fan of sun news? We invite you all to send us your beautiful recent photos of sunspots and auroras. Naturally, we love receiving your photos! And to those of you who’ve already posted a photo to our community page, thank you.

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Bottom line: Sun news December 19, 2023. Beautiful auroras were enjoyed for another night, as the recent flurry of geomagnetic activity finally came to a close.

The post Sun news: More beautiful auroras as storming comes to an end first appeared on EarthSky.

Menkar in Cetus the Whale

Menkar isn’t the brightest star in Cetus the Whale. Instead, Diphda – aka Deneb Kaitos, the Whale’s Tail – is brightest. And Menkar isn’t even the Whale’s most famous star. That honor goes to Mira, sometimes called Mira the Wonderful, a renowned variable star.

Still, Menkar is an interesting star, with its own claims to fame. It’s the 2nd-brightest star in Cetus at a +2.6 magnitude. And it’s designated the alpha star in Cetus. Why? It could be because Menkar sits closer to the ecliptic, which marks the sun’s yearly circuit in front of the background stars.

What’s more, Star Trek fans might recognize the name Menkar. Keep reading to learn more about this star.

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The Whale’s alpha star in TV and film

Hello, Star Trek fans! Remember the star that played a key role in an original Star Trek episode called Space Seed (1967)? And the second Star Trek film Star Trek II: The Wrath of Khan (1982) also featured it.

Khan and his crew are exiled to the planet Ceti Alpha V in Space Seed, and they escape from there in Wrath of Khan after the planet becomes uninhabitable. Ceti Alpha. Alpha Ceti. It’s named after Menkar, despite its flipped Bayer designation.

By the way, as of December 5, 2023, there are 5,552 confirmed exoplanets in 4,091 planetary systems, with 887 systems having more than one planet. However, there are no known planets around Menkar (Alpha Ceti).

Star Trek II: The Wrath Of Khan (1982) was the first film to have a scene created entirely by CG graphics and the first time a movie had been released that was a sequel to a TV show episode, following on as it does from the Star Trek episode Space Seed (1967). pic.twitter.com/FWwhhEZZOK

— FilmFrame (@FilmFrameATRM) August 9, 2019

When is the best time to see Menkar?

As seen from northern temperate and polar latitudes, Menkar shines due south around 9 p.m. your local time around the December winter solstice (on or near December 21). Because all the stars, except the sun, return to the same place in the sky about 2 hours earlier with each passing month, that places Menkar highest up and due south around 7 p.m. on January 21.

The V-shaped Hyades star cluster – Face of the Bull in the constellation Taurus – serves as a directional arrow, pointing the way to the star Menkar. Hold your fist at arm’s length. Then hop two fist-widths from the point of the “V” to locate Menkar’s approximate position in the star-studded heavens.

It’s pretty easy to see Menkar and the circle of stars outlining the Head of Cetus the Whale in a dark sky. In the lore of the sky, this fearsome creature almost gobbled up the Princess Andromeda, the daughter of King Cepheus and Queen Cassiopeia. But Perseus the hero rescued the Ethiopian princess in the nick of time.

Alpha Ceti is a pulsating red giant star ? 249 light years away in Cetus

Notes: About 48 times the radius and 380 times brighter than our Sun ?

(Click link to explore the Milky Way ? and beyond)https://t.co/rOzvZewby5 pic.twitter.com/um1xbmbvLr

— MR Humble ????? (@Todd_Scheve) February 14, 2019

Science of Menkar

A small telescope shows Menkar to be a colorful double star. The orange giant star, Menkar, contrasts with its fainter blue-white companion, the star 93 Ceti. These two stars are not physically related. They just happen to lie along our line of sight, as seen from Earth. Menkar resides some 250 light-years away, while 93 Ceti lies at about twice that distance away.

Menkar’s ruddy complexion reveals that it’s a cool star in the autumn of its years, and 93 Ceti’s blue-white radiance indicates a hot star in the heyday of youth.

Menkar has about twice the sun’s mass. However, Menkar is in a different stage of its evolution than our sun. In fact, it has exhausted the hydrogen and helium fuel at its core and has expanded to become a giant star with about 89 times the radius of our sun. The large area of Menkar’s photosphere – or visible outer layer – means that it is emitting about 1,455 times as much energy as the sun, even though the effective temperature is only 3,795 K (compared to 5,778 K on the sun). The low temperature is the reason Menkar shines with a reddish hue.

Red stars are cooler than white stars, just as red hot on Earth indicates something cooler than white hot.

As Menkar continues to evolve – and to burn carbon at its core – it’s thought this star will become unstable and ultimately become a variable star. So, perhaps it’ll be similar to Mira, Cetus the Whale’s famous variable star.

Bottom line: The star Menkar is the alpha star in the constellation Cetus the Whale. History, lore, claims to fame, and science information here.

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The post Menkar – a visual double – is the Whale’s alpha star first appeared on EarthSky.

The orange star Aldebaran – the fiery eye of the Bull in the constellation Taurus – is easy to find. It’s part of a V-shaped group of stars – the Hyades – that forms the Bull’s face. You can locate Aldebaran using the famous constellation Orion as a guide. Notice the three stars of Orion’s Belt. Then draw an imaginary line through the Belt to the right. The first bright star you come to will be Aldebaran with its distinctive reddish-orange glow.

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When to spot Aldebaran

Aldebaran is the 14th brightest star, but five of those that outshine it are only barely visible or not visible at all from much of the Northern Hemisphere. Aldebaran is primarily a winter and spring star for us on the northern part of Earth. That’s when this orange star is most easily visible in the evening sky. By early December, it rises shortly after sunset and is visible all night. Three months later it is high to the south at sunset, and sets at around midnight. By early May, it hangs low about the western sunset glow – and before the end of the month, it’s lost altogether. It returns to the predawn sky around late June.

By the way, although it appears among them, Aldebaran is not actually a member of the V-shaped Hyades cluster. It is actually much closer to us in space than the other Hyades stars.

History and mythology of Aldebaran

Artists often depict Aldebaran as the fiery eye of Taurus the Bull. Because it is bright and prominent, ancient Persians honored Aldebaran one of the Four Royal Stars, the other three being Regulus, Antares and Fomalhaut.

The name Aldebaran is from the Arabic for the follower, presumably as a hunter following prey, which was likely the star cluster we call the Pleiades. Some viewed the latter as a flock of birds, perhaps doves. According to Richard Hinckley Allen in his classic book Star Names: Their Lore and Meaning, people once applied the name Aldebaran to the entire Hyades star cluster, a large loose collection of faint stars.

More star lore

In Hindu myth, Aldebaran was a beautiful young woman named Rohini, disguised as an antelope and pursued by her lecherous father, disguised as a deer, Mriga. Several other ancient peoples associated the star with rain. In a Dakota Sioux myth, Aldebaran was a star which had fallen to the Earth and whose killing of a serpent led to the formation of the Mississippi River. Allen notes a number of other alternate names, but precious little mythology is known for Aldebaran separately.

Also, Aldebaran is the name of one of the chariot horses in the movie and book “Ben Hur.”

On a different note, astronomer Jack Eddy has suggested a connection with the Big Horn Medicine Wheel, an ancient circle of stones atop a mountain in Wyoming. Eddy wrote that the ancient Americans may have used this site as a sort of observatory to view the rising of Aldebaran just before the sun in June to predict the June solstice.

Interestingly, in about two million years, the NASA space probe Pioneer 10, now heading out into deep space, will pass Aldebaran.

Science of Aldebaran

Aldebaran is a huge aging star. The diameter is about 44 times the size of our sun. If Aldebaran replaced our sun, its surface would extend past the orbit of Mercury.

Aldebaran glows with the orangish color of a K5 giant star. In visible light, it is about 153 times brighter than the sun, although its surface temperature is lower, roughly 4,000 K (about 3,700 degrees C or 6,700 degrees F) compared to 5,800 K (about 5,500 C or 10,000 F) for the sun.

Although Aldebaran is associated with the stars of the Hyades, it’s much closer at 65 light-years distant. The Hyades are about 150 light-years away.

Aldebaran is an erratic variable with minor variations too small to see with the eye. Also, five faint stars are visible near Aldebaran, but so far none have been confirmed to be gravitationally bound to Aldebaran.

Aldebaran’s position is RA: 4h 35m 55s, dec: 16°30’35”

Bottom line: Aldebaran is an enormous, orange-colored star that marks one of the eyes of Taurus the Bull. It also marks one point of the V-shape of the Bull’s face.

The post Aldebaran is Taurus the Bull’s bloodshot eye first appeared on EarthSky.

Mirfak is the brightest star in the constellation Perseus the Hero. This star and its constellation lie high in the east-northeast on December evenings, as seen from the Northern Hemisphere. It makes a great companion to the sky’s most celebrated eclipsing binary star, which is called Algol, sometimes called the Ghoul Star or Demon Star. Mirfak and Algol are about 10 degrees, or a fist-width, apart in Perseus. As you watch the variable star Algol dip and then regain brightness, compare it to the more constant Mirfak. You’ll soon see why Algol perplexed the early stargazers, and why Mirfak seemed steadfast in comparison.

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How to find Mirfak

The name Mirfak comes from Arabic and means the Elbow of the Pleiades. Mirfak is also another name for Alpha Persei. In fact, the constellation Perseus lies due north of the Pleiades star cluster, also called the Seven Sisters. You can find Mirfak and Perseus between the Pleiades cluster and Polaris, the North Star.

Or you can also take a more direct route to Mirfak, if you’re familiar with the M or W-shaped constellation Cassiopeia the Queen. Draw an imaginary line through the Cassiopeia stars Navi (Gamma Cassiopeiae) and Ruchbah to jump over to Mirfak.

Mirfak is the lone star of Perseus that stands out in moderately light-polluted skies, as its brilliance matches that of the stars of the famous Big Dipper.

Science of Alpha Persei

At a distance of about 510 light-years, Mirfak lies much farther than the Big Dipper stars, so this star has to be intrinsically very luminous to shine so brightly in our sky. If Mirfak stood at the sun’s distance from Earth, its disk would cover several thousand times more sky. Moreover, Mirfak would shine thousands of times more brightly than our sun. In fact, it’s about 5,000 times more luminous than our sun.

On a dark night, you might discern a faint array of stars clustering around Mirfak, a bejeweled realm of the heavens that glitters all the more in binoculars. This assemblage of stars is known as the Alpha Persei Moving Group (Melotte 20), of which Mirfak is the most prominent member. Although some feel that this stellar grouping is too dispersed to be called a star cluster, these stars nonetheless move in the same general direction through space and were born from the same cloud of gas and dust some 30 to 50 million years ago.

Bottom line: Mirfak is the brightest star in the constellation Perseus and is visible even from light-polluted locations. This star is a member of the Alpha Persei Moving Cluster of stars.

The post Mirfak is the brightest star in Perseus the Hero first appeared on EarthSky.

Look for Achernar from southerly latitudes

The 9th-brightest star in all the heavens, Achernar, is well known to observers in the Southern Hemisphere. But many northern stargazers know this star by its name only. That’s because – although it shines at magnitude +0.45, making it one of our sky’s brightest stars – it’s extremely far south on the dome of stars surrounding Earth. If you’re north of about 33 degrees north latitude, Achernar never rises above your horizon at all. And yet this star remains one of the sky’s most famous stars as the star at the end of the River.

The River is – of course – the constellation Eridanus, which is large and easy to see in a dark-enough sky, even if you’re fairly far north on Earth’s globe. The northern part of this constellation is located near the extremely prominent constellation Orion the Hunter. Eridanus appears to swell up in a great loop near Orion, then meander southward. Finally – for most in the Northern Hemisphere – it drops out of sight below the southern horizon before it reaches its end.

But if you are far enough south – below 33 degrees north latitude – you’ll easily spot the River’s end as the bright star Achernar.

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How to see Achernar

For all practical purposes, you must be even further south – around 25 degrees north latitude – to see Achernar well. That is a line drawn around the entire globe passing through Miami in the U.S. and Taipei in Taiwan.

Nowhere in North America has it easy, seeing this star. For example, from Key West, Florida, Achernar rises only about 8 degrees above the southern horizon. Even farther south, from the southern tip of Hawaii’s Big Island, Achernar never quite makes it to 14 degrees.

And yet, if you are far-enough south, you can see Achernar easily. After all, this star is very bright!

Just as Achernar marks the end of the River, the River also has a beginning. The star Beta Eridani or Cursa, which itself is easily visible from the Northern Hemisphere, shines near Orion’s brightest star, Rigel.

It is visible from North America?

On most nights of the year, Achernar is not visible from anywhere in North America. However, around October 20 it skirts the southern horizon around midnight, never getting very high. Then as the months pass, it is visible earlier at night, around 10 p.m. in November, 8 p.m. in December and just after sunset in January. Being far to the south with no bright stars around it, Achernar stands out in its isolation. If you have a dark sky, and are far enough south, you’ll easily see Achernar’s constellation Eridanus making its loop under the constellation Orion.

@GEO101SUNY Here is a beautiful image of the meandering Owens River out in California!https://t.co/NbKG4o7GYt pic.twitter.com/XHawVHkoKr

— hayden (@haydenmhoyt) November 18, 2023

Earthly rivers are sometimes known for meandering. In the sky, the stars representing Eridanus the River – Achernar’s constellation – have a similar quality.

Achernar’s history and mythology

In fact, the name Achernar derives from an Arabic phrase meaning End of the River.

Interestingly, in early classical times the name Achernar was given to the star we now know as Theta Eridani, or Acamar. At that time Acamar was the brightest star of the constellation visible from Greece, and thus was considered the River’s end.

When voyagers discovered the brighter star farther to the south, it became Achernar, and the former Achernar became Acamar.

Apparently both names derive from the same phrase, “Al Ahir al Nahr,” according to Richard Hinckley Allen, whose 1899 book Star Names: Their Lore and Meaning is still the best around.

Science of Achernar

Data from the Hipparcos mission placed Achernar at about 144 light-years away. It is a B3V star, meaning that it belongs to the main sequence of stars. And, the B means the star is blue and it’s the bluest star among the top 10 brightest stars.

Achernar is much hotter and brighter than our sun. In fact, it’s estimated to be over 3,100 times the luminosity, of our sun. It’s about six times the mass of the sun.

Brighter, hotter (and bluer) than the sun, Achernar produces more energy in the non-visible ultraviolet (UV) wavelengths. When you take this into consideration, it pumps out some 3,000 to 5,000 times the solar energy level. The discrepancy is due to an uncertainty in the amount of UV radiation it produces.

Achernar is also a binary star system. The companion star – called Alpha Eridani B – is a white main sequence star with about two solar masses. It orbits the primary star at a distance of 12 astronomical units every 14 to 15 years.

Its rapid rotation results in a flattened star

As mentioned above, Achernar’s mass is about six times that of our sun, and its average diameter is nearly eight to 10 times that of the sun. But, while our sun spins on its axis once about every 25 days, Achernar completes one rotation in slightly more than two days, or nearly 15 times faster than our sun. This fast rotation produces an odd, flattened shape, first discovered by the European Southern Observatory’s Very Large Telescope (VLT) in 2003. Up close, Achernar would look more like a blue M&M, while our sun would look more like an orange. Read more about Achernar’s flattened shape from ESO.

This flattening of Achernar makes an exact surface temperature for this star hard to determine. The flattening causes the star’s poles to be hotter than the equator. Estimates range from about 14,500 to 19,300 kelvin (about 14,200 to 19,026 C or around 26,000 to 34,200 F).

In today's episode of fun space objects:

Archernar. The currently "least spherical" known star in the Milky Way, owning its shape to its rapid rotation.

Here it is compared in shape (and size) with our Sun. pic.twitter.com/CTXPckWsSs

— George Ioannidis (@Qupeplex) February 6, 2023

Achernar’s position is RA: 01h 37m 42.8s, dec: -57° 14′ 12″.

Bottom line: Achernar is the 9th brightest star and flattest star known. It marks the end of Eridanus the River. Here’s why much of Earth never sees it … and how you can.

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The post Achernar is the End of the River of Eridanus constellation first appeared on EarthSky.

Al Risha binds the Fishes together

Alpha Piscium, or Al Risha (also spelled Alrisha), isn’t one of the sky’s brightest stars. In fact, it’s only about 4th magnitude. That means you need a dark sky to see it.

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But Al Risha is a fascinating star in a prominent place in the zodiacal constellation Pisces the Fish. Pisces is one of the sky’s most graceful and beautiful constellations. Al Risha is very easy to pick out in Pisces if you have a dark sky.

Pisces the Fish is always shown as a pair of fish, swimming in opposite directions. The Western Fish lies in the graceful line of stars south of the Great Square of Pegasus. And the Northern Fish is another line of stars to the east of the Square. Al Risha represents the knot or cord that ties the two Fish together by ribbons at their tails. In fact, Al Risha means “the cord” in Arabic.

How to see Al Risha

Northern Hemisphere autumn (or Southern Hemisphere spring) is a good time to see the constellation Pisces, with the star Al Risha at its heart, in the evening sky. As seen from across the globe, Pisces reaches its high point for the night at about 10 p.m. your local standard time in early November and at about 8 p.m. in early December.

If you can find the Great Square of Pegasus – which is very noticeable as a large square pattern on the sky’s dome, with four medium-bright stars marking its corners – you can find Pisces. You can, that is, if your sky is dark enough. To find a dark location near you, visit EarthSky’s Best Places to Stargaze.

You’ll probably pick out the Western Fish first, because it contains an asterism – or noticeable pattern of stars – known as the Circlet. The little circle of faint stars forming the Circlet in Pisces is visible in a dark sky on the southern edge of the Great Square.

The rest of the constellation Pisces forms a beautiful V shape – like the letter V – on two sides of the Square.

Al Risha in star history and mythology

Although the star Al Risha is not very bright, its location within its constellation – at the tip of the V in Pisces – makes it very noticeable.

That’s surely why the German astronomer Johann Bayer, in 1603, gave this star the designation alpha in his star atlas Uranometria (named after Urania, the Greek Muse of Astronomy), even though Al Risha is only the 3rd brightest star in its constellation. Bayer’s system was to assign a Greek letter (alpha, beta, gamma and so on) to each star he catalogued, combined with the Latin name of the star’s parent constellation in genitive (possessive) form. So, for example, the star Al Risha is also Alpha Piscium, the alpha star of Pisces.

Most of the time, the alpha star is the brightest star in a constellation, but not always. There are two brighter stars in Pisces (although not much brighter). They are Eta and Gamma Piscium. Al Risha, by the way, is also one of the only stars in Pisces with a proper name. The early Arabian stargazers, who named it, noticed it, too.

In Roman mythology, the constellation Pisces is associated with the legend of Venus and Cupid (or, in the Greek myths, Aphrodite and her son Eros). These two escaped the monster Typhon (or Typhoon) by transforming themselves into fish and jumping into a river. Venus and Cupid are said to have bound themselves together so that, in escaping the monster, they would not be separated. The gods were pleased and placed the Fishes in the sky to commemorate the event.

Star of the week: Al Risha knots Fishes of Pisces https://t.co/PDv4XrvbEE pic.twitter.com/JakZxqyBEP

— Luca de Ioanna (@io_luca) November 6, 2015

Al Risha in science

Al Risha appears single, but it is a close double star, that is, two stars orbiting a common center of gravity. It consists of pair of class A stars that lie some 120 astronomical units (AU) apart, with one AU equaling one Earth-sun distance. So the two stars that we see as Al Risha are in fact separated by 120 times the distance between our Earth and sun, or about the distance between our sun and Pluto.

The two stars in the Al Risha system take 720 years to orbit each other. Yet these stars appear so close together from our earthly vantage point that amateur astronomers using backyard telescopes must look carefully to see both of them. Plus, from our perspective, the two stars are appearing to get closer together as they pursue their vast mutual orbit. It’s estimated they will appear closest, as seen from Earth, in the year 2060. Both stars are white, though some observers have reported subtle colors.

Al Risha is approximately 139 light-years away.

Al Risha’s position is: RA 02h 02m 03s, Dec +02° 45′ 50″

Bottom line: The star Al Risha, or Alrisha, shines at the point of the V-shaped constellation Pisces the Fish.

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Meet Pisces the Fish, 1st constellation of the zodiac

The post Al Risha binds the Fishes of Pisces together first appeared on EarthSky.

Start watching for Hamal in November

Hamal – also known as Alpha Arietis – shines as the brightest star in the constellation Aries the Ram. This star and two others – Sheratan and Mesarthim – make up the Head of the Ram. Aries is small. But the compact pattern of these three stars makes Aries relatively easy to find.

As seen from mid-northern latitudes, Hamal lights up the eastern sky on November evenings, will shine high in the southern sky by January evenings, and will sit low in the west by March evenings. This star is easily visible from Earth’s Southern Hemisphere, too. Try Stellarium to find Hamal’s height in your sky from your exact location on the globe.

As seen from the whole Earth, Hamal disappears from the night sky around April. It returns to the eastern sky before sunrise by about June, to begin another cycle of visibility.

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Aries finder charts

Hamal was an equinox star

It’s fun to spot Hamal and its brother stars in the night sky. As an ancient equinox star, Hamal also has a profound significance in the history of astronomy.

In our modern era, if you could see the stars in daytime, you’d see the sun and Hamal in conjunction – lined up with one another, due north and south in right ascension – on or near April 24.

But, long ago, they were in conjunction exactly at the March equinox.

Nowadays, April 24 – the date of Hamal’s conjunction with the sun – is a little more than a month after the March equinox, which always takes place around March 20. This is the Northern Hemisphere’s spring equinox, and it’s a time of renewal throughout the northern half of Earth. So of course this time of year had significance to our ancestors, who were very much aware of their connection to the land and sky.

Precession of the equinoxes

If you could backtrack some 2,500 years, you’d find the annual conjunction of the sun and Hamal happening on the March equinox. In fact, if you could backtrack 2,200 years, we’d also find the March equinox sun in conjunction with another star in Aries, Sheratan.

So you see that the location of the sun at the March equinox sun drifts in front of the stars. It moves westward in front of the backdrop constellations by about one degree (two sun diameters) every 72 years. This drifting is due to a well-known motion of Earth called precession, or sometimes the precession of the equinoxes.

The March equinox sun shone in front of the constellation Aries from about 2,000 to 100 BCE. At present, the sun shines in front of the constellation Pisces on the March equinox.

First point of Aries

Even though the sun is no longer in front of Aries at the time of the March equinox, many people pay homage to the Ram and still refer to the March equinox point as the First Point of Aries.

This point on the celestial sphere – now in Pisces, due to precession – is one of the two points on the celestial sphere at which the celestial equator crosses the ecliptic. The other point – not as well known – is called the First Point of Libra (although it is now in Virgo), located exactly 180 degrees from it.

The First Point of Aries is considered to be the celestial “prime meridian” from which right ascension (like longitude in earthly coordinate systems) is calculated.

Bottom line: The star Hamal is the brightest star in Aries the Ram. Thousands of years ago, the sun was in conjunction – or aligned north and south – with this star at the time of the March equinox.

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The post Meet Hamal, an ancient equinox star first appeared on EarthSky.

Almach is 4 stars

The constellation Andromeda the Princess is renowned for the Andromeda galaxy. But even a modest telescope will show another excellent target in Andromeda: the multiple star system Almach (Gamma Andromedae). It appears through a small telescope as one of the finest double stars in all the heavens. One component of this telescopic double appears golden, and the other component appears indigo blue. Further research has shown that Almach is really four stars.

Some double star aficionados believe Almach’s vibrancy of color even surpasses that of the star Albireo in the constellation Cygnus, generally regarded as the sky’s finest double star. In autumn, both Almach and Albireo are there for the viewing, so check them out and decide for yourself.

Try different eyepieces at your small telescope, to see which one gives you the most vivid view of this colorful double.

Today, it’s known that the smaller blue star is a triple star system, making Almach four stars in all. This quadruple star system is located an estimated 350 light-years away.

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Almach star-system science

German astronomer Johann Tobias Mayer was the first to report Almach or Gamma Andromedae as double in 1778. The main components of the star system are named Gamma¹ Andromedae and Gamma² Andromedae or Gamma Andromedae A and Gamma Andromedae BC. The apparent pair of contrasting stars appears to be around 10 arcseconds apart in the sky. The single star and the triple star system orbit each other with a period of around 4700 years.

The brighter component, Gamma¹ Andromedae, shines at a magnitude of +2.26. It’s a K-type giant star. Compared to our sun, this star is 80 times bigger in radius, big enough to reach the orbit of Venus. It has a surface temperature of 4500 K (about 4200 C or 7600 F) and is 2,000 times more luminous than our sun with a rotational velocity of 17 km/s (about 10 mps).

Gamma² Andromedae itself is a multiple star system with spectroscopic binaries Gamma Andromedae B and Gamma Andromedae C. These 5th and 6th magnitude dwarf binaries orbit each other in 63.7 years and are separated by barely 0.3 arcseconds. That translates to approximately 33 astronomical units (AU, or Earth-sun distances), comparable to the distance between our sun and the planet Neptune. The brighter star of the two, Gamma Andromedae B, is another binary system. Its companion is detectable only with a spectrograph. The two stars are very close and orbit each other in 2.7 days. The estimated mass for this triple star system is 8.7 solar masses. Gamma² is thus a triple-star system, making Almach a quadruple-star system.

How to find the star Almach

In skylore, Almach marks the Princess Andromeda’s left foot. Star-hop to Almach from the Great Square of Pegasus, the signature star formation of Northern Hemisphere autumn.

Two streamers of stars fly outward from the Great Square, starting at the star Alpheratz. These streamers of stars are the constellation Andromeda.

Jump three stars over on the lower streamer to locate Almach. At 2nd-magnitude brightness, Almach shines pretty much on a par with the stars of the Big Dipper.

Almach shines relatively close to the famous variable star Algol in the constellation Perseus. When Algol shines at maximum brilliance, it matches Almach in brightness.

Bottom line: Almach looks single to the eye. But a small telescope transforms Almach into two colorful suns, one golden and the other blue. And astronomical research has revealed that one component is a triple star system, making the Almach system four stars in all.

Mirfak: Perseus’ brightest star

Capella: Golden Goat Star

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The post Almach, a quadruple star system in Andromeda first appeared on EarthSky.

Why is Algol the Demon Star?

What’s the scariest star in the sky? If you were one of the early stargazers, you might have chosen Algol in the constellation Perseus. That is probably why early astronomers nicknamed Algol the Demon Star. Shivers!

When you look at Algol, it doesn’t appear any scarier than any other star. But in skylore it’s associated with a mythical scary monster – the Gorgon Medusa – who had snakes for hair. Legend said that her appearance was so terrifying that if anyone even looked at her, they would turn to stone.

The star Algol takes its name from an Arabic word meaning the Demon’s Head or, literally the Ghoul. It represents the terrifying snaky head of the Medusa monster.

Perseus was a great hero often depicted mounted on Pegasus the Flying Horse. In the mythology of the skies, Perseus slew Medusa. Then, he used Medusa’s head to his advantage, showing it to Cetus the Sea-monster to turn him into stone. So, perhaps the ancients associated this star’s variable brightness with the evil, winking eye of the Medusa.

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Algol is a variable star

Winking? Yes. In fact, Algol is a known variable star, which waxes and wanes in brightness.

The early stargazers surely knew about its changing brightness. This probably led them to name the strangely behaving star in the sky for a mythological demon.

There are many variable stars known throughout the heavens, but Algol might well be the most famous of them all. The Demon Star brightens and dims with clockwork regularity. It completes one cycle in 2 days, 20 hours and 49 minutes. Plus, you can view its entire cycle with your eye alone.

Algol’s variation is easy to observe. At its brightest, Algol shines about three times more brightly than at its faintest. When it reaches maximum brilliance, Algol matches the brightness of the nearby second-magnitude star Almach. At minimum, Algol’s light output fades to that of the star Epsilon Persei.

Modern-day astronomy has unlocked the secret of Algol’s mood swings. It’s an eclipsing binary star. This kind of binary star is composed of two stars, with each star revolving around the other. From Earth, we see the orbital plane of this binary star almost exactly edge-on. Therefore, when the dimmer of the two stars swings in front of the brighter star, we see Algol at minimum brightness.

How to find Algol the Demon Star

The Demon Star is easy to find. Our sky chart shows the northeastern sky for autumn evenings, especially around Halloween.

The conspicuous W or M-shaped constellation Cassiopeia enables you to star-hop to Perseus. Look below Cassiopeia toward the horizon to spot the dangling icicle shape of Perseus. Off to the right of the icicle is Algol. At mid-northern latitudes, the Demon Star appears for at least part of the night all year round. But it’s best seen in the evening sky from autumn to spring. It’s visible in the northeast sky in autumn, shines high overhead in winter, then swings to the northwest sky by spring.

Bottom line: Algol has the nickname the Demon Star because it represents the head of Medusa. This variable star probably intrigued the ancients with its fluctuating behavior.

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Deneb Kaitos: Whale’s tail

Deneb Kaitos is the brightest star in the constellation Cetus the Whale (or Sea-Monster). In star names, the word deneb usually means tail. And so it is with this star. It marks the tail of Cetus. Deneb Kaitos is also known by two alternate names, Beta Ceti and Diphda. It shines at magnitude 2, making it about as bright as Polaris, the North Star. Neither Polaris nor Deneb Kaitos shines brightly enough to be super noticeable. But both are well within the limit of visibility to the unaided eye. Based on parallax measurements, Deneb Kaitos lies at an estimated distance of 96 light-years from Earth.

Deneb Kaitos reaches its highest in the sky on October and November evenings every year. For those of us in the Northern Hemisphere, it appears in the southern sky. It’s closer to overhead as seen from Earth’s Southern Hemisphere.

The stars return to the same place in the sky about two hours earlier with each passing month (or four minutes earlier with each passing day). In middle January, look for Deneb Kaitos to reach its high point around 7 p.m. local time. On February evenings, this star drifts into the southwest sky, and disappears from the evening sky by March.

Deneb Kaitos has almost three times the sun’s mass. Its diameter is some 17 times greater than our sun’s. Check out this star with binoculars, and note its orange complexion. The orange color indicates a rather low surface temperature, and also lets us know that this star is entering into the autumn of its years.

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The Whale doesn’t look very whale-like

Finder charts for locating Deneb Kaitos

Mira is another famous star in Cetus

By the way, don’t confuse Deneb Kaitos with a famous variable star also in Cetus. The variable star is called Mira the Wonderful. Mira typically remains much too faint to see with the unaided eye. But periodically Mira brightens enough to be visible. Its typical magnitude when brightest is about magnitude 3.5 (fainter than Deneb Kaitos). Mira’s most recent maximum brightness was mid-June 2023. And during its next expected maximum brightness in mid-May 2024, it’ll be too close to the sun to see.

Bottom line: Deneb Kaitos, aka Beta Ceti, is the brightest star in Cetus the Whale, a constellation of otherwise faint stars.

The post Deneb Kaitos marks the tail of Cetus the Whale first appeared on EarthSky.