? ? ? ? X flares! AR3590 is busy today. First, it released an X1.9 at 22:52 UTC on February 21. Then came an X1.7 at 6:17 UTC on February 22. So far it appears no CMEs. We are waiting to see if the region has more in store.

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— Dr. C. Alex Young (@TheSunToday) February 22, 2024

Sun news another UPDATE for February 21, 2020: Double BAM! The sun releases 2nd X flare

Another X flare! Region AR3590, which released an X1.9 flare at the end of February 21, has let out another one. This time it’s an X1.7 at 6:17 UTC on February 22. As with the previous X flare, the event does not appear to have a CME associated with it. What’s next? Stay tuned.

Sun news UPDATE for February 21, 2020: BAM! The sun blasts an X flare

X1.9 flare! The giant active region on the northeast, AR3590, exploded an X1.9 flare at 23:07 UTC on February 21. We saw growth on this recent sunspot region, transforming from an alpha to beta-gamma magnetic complexity. At the moment of the blast, this active region was showing a beta-gamma-delta configuration, the largest there is. And it’s the largest active region on the solar disk at present. Shortly after the explosion, an R3 (strong) radio blackout affected an area over Fiji Island in the South Pacific Ocean. A brief analysis by specialists reveals the event did not produce a coronal mass ejection (CMEs). But modeling and analysis will continue. This active region is headed toward the center of the sun’s disk, which will put it in an Earth-effective position in the days to come. Maybe more activity awaits us. Stay tuned.

Sun news for February 21, 2024: Solar southeast wakes up with a huge blast

Today’s top news: During the past few days we’ve observed solar activity in the northeast, northwest and southwest, with the southeast remaining dormant. But not anymore! The southeast woke up earlier today with a huge blast, which hurled a gorgeous prominence of solar material into space at around 1:53 UTC this morning. The explosion came from the very edge of the southeast horizon, and was associated with an active region that is soon to rotate into view. And that’s not the only reason the southeast has grabbed our attention; the region has also been graced with a new coronal hole that emerged over the past day. Soon it will move into a geoffective position, meaning that the fast solar wind it produces will be headed our way at Earth. And that brings the possibility for beautiful auroral displays – stay tuned.
Last 24 hours: Sun activity remains low, with only 7 C flares produced between 11 UTC yesterday and 11 UTC today. The largest of these flares was a C4.4 flare, blasted in the southeast by an incoming as-yet-unnumbered active region at 2:17 UTC this morning. It was followed by another bright spark just below the equator on the east limb (edge). The lead flare producer title for the past day is shared by the unnumbered incoming region, AR3590 and AR3583, all blasting two C flares each. AR3590 remains the largest active region on the solar disk, and some growth was observed; it’s now showing a beta-gamma magnetic complexity. Although this classification suggests a strong flaring potential, it remained rather quiet, producing only faint C flares. The other two of the three labeled active regions on the sun show an alpha magnetic configuration – the most simple.
Next 24 hours: The forecast is a 99% chance for C flares, a 30% chance for M flares, and a 5% chance for X flares.
Next expected CME: No coronal mass ejections (CMEs) were observed in available coronagraph imagery during the past day.
Current geomagnetic activity: Earth’s geomagnetic field is quiet at the time of this writing (11 UTC on February 21) but a disturbance was registered late yesterday. This was likely a passing influence from the CME the sun produced on February 16. More unsettled conditions are anticipated today, reducing to quiet by the end of the day as the CME effects wane. After that, quiet conditions are anticipated for tomorrow.

Sun news for February 20, 2024: Think of our sun as a star

The EarthSky sun news team created this video for you. We hope you enjoy it!

Overnight according to clocks in the Americas, a huge blast occurred on a part of the sun we can’t quite see from Earth. We know this because it produced a massive rope of plasma and magnetic fields that appeared over the solar southwest horizon. This rope is known as a prominence. It likely came from sunspot group AR3576, which recently got carried off the solar disk by the sun’s rotation. If this sunspot group stays intact, it’ll arrive back into view on the other horizon in around a couple of weeks. That’s because our sun completes a full rotation in about 25 days at the equator, and a little longer at the poles. So, yes, although we tend to visualize our star as a flat disk in the sky, it’s really a colossal sphere, occupying the same 3D space as 1.3 million Earths. And, while the sun is certainly massive in contrast to our little Earth, it’s only an average-sized star. The biggest star we know of, UY Scuti, is 1,700 times wider than the sun! So even our gigantic sun is still a drop in the ocean of the universe.
Last 24 hours: Sun activity is low, with only 7 C flares produced over the past day. The largest was a C5.7 flare produced by sunspot region AR3590 at 12:47 UTC on February 19. This region was the lead flare producer of the past day with four flares, shortly followed by AR3583 with three. AR3590 is the largest sunspot region on the solar disk, and can be seen without any magnification if you wear the proper eye protection, such as eclipse glasses. Currently the sun bears five labeled active regions, all of which are stable or in decay. In the northwest, the long-lasting prominence we have been observing since yesterday ended with ejecta dancing above the solar horizon. Most of the plasma was returned to the solar surface by the sun’s gravity. Yesterday’s huge prominence in the northeast was registered by the SOHO spacecraft’s LASCO C2 and C3 instruments, showing the characteristic lightbulb shape of a coronal mass ejection (CME). Take a look at our LASCO imagery below.

Sun news for February 19, 2024: Hi, Mercury!

The EarthSky sun news team created this video for you. Thanks for watching!

Today, we welcome Mercury as it enters the field of view of the SOHO spacecraft’s LASCO C3 imagery. It looks beautiful, and it’ll be fun to watch in the coming days as it crosses the sun’s field of view. Mercury is our sun’s innermost planet. It’ll appear near the sun in our sky six times in 2024, crossing either generally behind or generally in front of it as seen from Earth. Mercury’s current crossing is a passage behind the sun. It’ll appear most behind the sun as seen from Earth at around 9 UTC on February 28. Astronomers call this a superior conjunction of Mercury. Meanwhile, a newcomer sunspot region – now labeled AR3590 – has rotated fully into view, making a grand entrance. That is, as it was coming, we saw a fiery northeast limb (edge) on the sun, with a big far side explosion. The explosion came from a long-lasting prominence beyond the northeast horizon. BOOM! The prominence ended in an explosion, and the huge blast hurled large amounts of ejecta into space. At the same time, hello newcomer AR3590! We might expect great things from AR3590, as it is also quite active. Even when it wasn’t quite visible and still unnumbered, we saw it blasting C flares. Now that we can take a look at this guy, it looks big. It’ll surely be the next interesting sunspot region to follow, now that last week’s hero, AR3576, has been carried out of view by the sun’s rotation. Stay with us.
Last 24 hours: Sun activity is low. The sun produced 11 C flares during the past day (11 UTC yesterday and 11 UTC today). The largest was a C6.8 flare blasted by active region AR3590 at 9:40 UTC on February 19. Today we have shared honors for lead flare producer, AR3583 and AR3590, which each produced four C flares. But AR3590 produced the largest of the period. We saw a rather calm solar disk with faint C flares, but there is fiery activity – enormous long-lasting prominences – on three corners of our sun: northeast, northwest and southwest. The sun bears six labeled active regions today. All of them are showing an alpha or beta magnetic configuration, indicating a low potential for flaring. But, for now, it’s still too early to discern a full analysis on AR3590, due to its location too close to the sun’s limb (making us a foreshortened view).

Sun news for February 18, 2024: Huge prominence from solar south pole

The EarthSky sun news team created this video for you. Thanks for watching!

On our side of the sun, activity is low. We’ve had C flares only. But, during the past day, it seems the far side has been active! We saw a fast and huge prominence coming out from the sun’s south polar region. The SDO spacecraft captured its image at 13 UTC on February 17. The large prominence dwarfed the size of Earth, which would be minuscule in contrast. The LASCO C2 coronagraph aboard the SOHO spacecraft registered the explosion at 13:36 UTC. And its brother instrument – LASCO C3 – registered it at 13:54 UTC. LASCO C3 also shows it produced a partial halo event. If we see a partial halo from an event on our side of the sun, we know a coronal mass ejection (CME) is likely headed our way. But, since this prominence blasted off from the sun’s far side, the CME is not Earth-bound.
Last 24 hours: Sun activity is low, with the production of only C flares during the past day (11 UTC yesterday and 11 UTC today). The sun produced 13 C flares and the largest of them  was a C7.9 flare blasted by active region AR3584 at 18:34 UTC on February 17. Lead flare producer of the period was an incoming active region on the northeast, unnumbered yet, who produced six C flares followed by AR3583 producer of four flares. Our just-departed hero AR3576 still is making noise from the far side via gorgeous prominences and jets on the visible sun’s southwest limb. The sun currently has six labeled active regions on its Earth-facing side, all of them showing an alpha or beta magnetic configuration, indicating a low potential for large flares.

The sun in recent days

Sun news images from our community

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Bottom line: Sun news February 21, 2024 UPDATE: BAM! X Flare! The huge active region AR3590 blasted an X1.8 flare at 23:07 UTC on February 21. An R3 (strong) radio blackout over Fiji Island followed.

The post Sun news UPDATE: Double Bam! The sun releases a 2nd X flare first appeared on EarthSky.

Like a pair of twins, two stars shine prominently in the evening skies in February each year. They are Pollux and Castor in the constellation Gemini the Twins. Pollux, also known as Beta Geminorum, is slightly brighter than Castor. It shines with a golden glow while Castor appears whiter. Pollux is the 18th brightest star in Earth’s night sky.

Pollux and Castor are noticeable for being bright and close together. That’s likely how the early stargazers came to identify them as twins. And it’ll be helpful to you, too, when you’re trying to spot these two stars in our night sky.

Pollux is relatively close to us at 34 light-years away.

You can use the easy-to-see constellation Orion to find Castor and Pollux, as shown on the chart above.

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Another way to find them

There are two good ways to find Pollux and Castor. From a Northern Hemisphere location face generally northward to find the Big Dipper asterism in the constellation Ursa Major. Draw an imaginary line diagonally through the bowl of the Big Dipper, from the star Megrez through the star Merak. You are going in the direction opposite to the Big Dipper’s handle.

This line will point to Castor and Pollux.

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Science of Pollux

Pollux is classified as a K0 IIIb star. The K0 means that it is somewhat cooler than the sun, with a surface color that is a light yellowish orange. Keep in mind that when you look at a star, its color depends significantly on the sensitivity of your eyes, and that color is difficult to discern for most point sources.

Pollux is just under two times the mass of our sun. It’s almost nine times the diameter of our sun. And it’s about 30 times the sun’s brightness in visible light.

Pollux also pumps out a good bit of energy in non-visible infrared radiation. With all forms of radiation counted, Pollux is about 43 times more energetic than our sun.

A large planet, at least two times the mass of Jupiter, was confirmed for Pollux in 2006. The International Astronomical Union announced a proper name for this planet in 2015: Thestias. At 34 light-years away, Thestias is one of the nearest of the more than 5,500 known exoplanets discovered so far.

Thestias moves around Pollux with a period of about 590 Earth days, which is reminiscent of Mars’ orbital period of 687 days. Thestias moves in a nearly circular orbit around its star.

Why Pollux is Beta

As mentioned above, Pollux is also known as Beta Geminorum. The Greek letter Beta is normally reserved for the 2nd-brightest star in a constellation. But Pollux is brighter than its brother star Castor, which is Gemini’s Alpha star. Being so close together in the sky, Castor and Pollux are easy to compare. If you look, you’ll agree. Pollux is brighter.

It’s possible that one or both stars have altered in brightness since German astronomer Johann Bayer assigned the designation about 300 years ago. Or maybe Bayer sometimes labeled stars in their order of rising times? Castor rises earlier than Pollux as seen from Bayer’s location in Germany. But there’s a geographical dependency here. From some locations south of the equator, Pollux rises first.

Mythology of Pollux and Castor

There is much mythology associated with these two stars, typically only in conjunction with each other. Generally in mythology they are twins. In Greek mythology, Pollux is immortal, the son of Zeus, and Castor is mortal, the son of King Tyndareus of Sparta.

So they were really half-brothers rather than true twins, with a common mother in Queen Leda. Their conception and birth was a complicated and unlikely affair, though, with their mother succumbing to both Zeus (disguised as a swan) and King Tyndareus on the same night. The resulting birth gave us not only Castor and Pollux, but also their sister, Helen of Troy.

Castor and Pollux are later said to have sailed among the Argonauts with Jason in search of the Golden Fleece. By most accounts, Castor was killed in battle and Pollux could not bear to live without him. Pollux begged Zeus to let him die too. Zeus could not grant the gift quite as asked, since Pollux was a god’s son and therefore immortal. But Zeus decreed that Pollux would spend every other day in Olympus with the gods, and the rest of the time in the underworld with his brother.

To honor the brothers’ devotion, Zeus placed their constellation in the sky as a remembrance.

The twin stars in other cultures

While in many cultures they were the Twins, in India they were the Horsemen, and in Phoenicia they were the two gazelles or two kid-goats. Early Christians sometimes called them David and Jonathan, while the early Arabian stargazers knew them as two peacocks.

Perhaps the most unexpected interpretation for the twins (along with the rest of Gemini) was as a “pile of bricks” as reported by Richard Hinckley Allen. Apparently the pile of bricks stood for the foundation of Rome, and in that context Castor and Pollux were associated with Romulus and Remus, the city’s legendary twin founders.

It’s said that in China they were associated with Yin and Yang, the contrasts and complements of life. In all of these cases, they represent two of something.

You’ll see why if you find these two stars in the night sky.

Pollux’s position is RA: 7h 45m 20s, dec: +28° 01′ 35″.

Bottom line: Pollux, aka Beta Geminorum, is the slightly brighter “twin” of Castor in the constellation Gemini the Twins.

The post Meet Pollux: The brighter twin star of Gemini first appeared on EarthSky.

Castor, the less-bright Twin

Castor, in the constellation Gemini the Twins, shines with a bright white light. That’s in contrast to the golden glow of its brother star in Gemini, Pollux. Despite being labeled as twins, Castor and Pollux are not gravitationally bound. Yet Castor is gravitationally bound into a multiple system of its own. It’s six stars in one!

Castor’s other designation is Alpha Geminorum. And usually an alpha star is the brightest in its constellation. But Castor is 2nd-brightest in Gemini, after Pollux (or Beta Geminorum).

Castor is about 51 light-years away. Pollux is only 34 light-years away. So Pollux is closer to us. And their distances also show Pollux and Castor aren’t gravitationally bound, but only near each other along our line of sight.

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Castor’s complex star system

Castor is three pairs of binary stars – six stars in all – in a complex dance around a common center of mass.

Even a fairly small telescope will show Castor as two stars. You might glimpse a much-fainter star nearby, too; it’s also part of the Castor system. Each of these three stars – called Castor A, B and C – is also double. Telescopes don’t show them as double directly. But a spectroscope – which splits starlight into its component colors – reveals each of the three stars as double.

The two larger visible components in the Castor system are hot A-type stars. The smaller components are cool, M-type red dwarf stars.

The mass of all six stars together is, very roughly, about six times that of our sun.

Visualizing the separation of the stars

Another way to find the Twins

Northern Hemisphere skywatchers can find Castor and Pollux using the Big Dipper as a guide, as shown on the chart at the top of this post. And, from anywhere on the globe, you can use the constellation Orion the Hunter (see chart below) to find the the twins.

Star-hop from Orion to the “twin” stars Castor and Pollux by drawing an imaginary line from Orion’s bright star Rigel through its bright star Betelgeuse. Extend this line about three times the distance between these two stars.

This line will point to Castor and Pollux.

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Greek mythology of Castor and Pollux

The reason for the name Castor is unclear. There appears to be no specific connection with a beaver, which is what the word means in Latin.

However, there is much mythology associated with these two stars, typically in conjunction with each other. Generally in mythology they are twins. In Greek mythology, Pollux is immortal, the son of Zeus, and Castor is mortal, the son of King Tyndareus of Sparta.

So, they were really half-brothers rather than true twins, with a common mother in Queen Leda. Their conception and birth was a complicated and unlikely affair, though, with their mother succumbing to both Zeus (disguised as a swan) and King Tyndareus on the same night. The resulting birth gave us not only Castor and Pollux but also their sister, Helen of Troy.

According to legend, Castor and Pollux sailed among the Argonauts with Jason in search of the Golden Fleece. By most accounts, Castor was killed in battle and Pollux could not bear to live without him. Zeus allowed Pollux to spend every other day in Olympus with the gods, and the rest of the time in the underworld with his brother.

To honor the brothers’ devotion, Zeus placed their constellation in the sky as a remembrance.

Other stories surrounding the stars

While in many cultures they were the Twins, in India they were the Horsemen, and in Phoenicia they were the two gazelles or two kid-goats. Early Christians sometimes called them David and Jonathan, while the early Arabian stargazers knew them as two peacocks.

Perhaps the most unexpected interpretation for the Twins (along with the rest of Gemini) was as a “pile of bricks” as reported by Richard Hinckley Allen. Apparently the pile of bricks stood for the foundation of Rome, and in that context Castor and Pollux were associated with Romulus and Remus, the city’s legendary twin founders.

The twin stars represent Yin and Yang, the contrasts and complements of life, in Chinese culture. In all of these cases, they represent two of something.

You’ll see why if you find these two stars in the night sky.

Castor’s position is RA: 07h 34m 36s, Dec: +31° 53′ 19″

Bottom line: The star Castor, which appears as one of two bright stars in the constellation Gemini the Twins, is actually a six-star system.

The post Castor is 6 stars in one first appeared on EarthSky.

Can you see Canopus?

If you stay at latitudes like those in the northern U.S., you’ll never see Canopus. That’s why this star has become a holy grail of sorts for some Northern Hemisphere skywatchers, who take winter vacations at southerly latitudes (like those in the southern U.S.), just to catch a glimpse of it. From latitudes like those in the southern U.S., Canopus – the sky’s 2nd-brightest star – appears as a bright light closer to the horizon than Sirius (the sky’s brightest star). For those southerly observers, Canopus and Sirius arc across the south together on February evenings.

Will you see Canopus? It depends, basically, on how far south you are, and what time of year you’re looking. Canopus never rises above the horizon for locations north of about 37 degrees north latitude. In the United States, that line runs from roughly Richmond, Virginia; westward to Bowling Green, Kentucky; through Trinidad, Colorado and onward to San Jose, California. Here’s a list of global locations at the 37th parallel north. You must be south of that line to see Canopus.

February evenings are ideal

Right now, February evenings are a perfect time to look for Canopus. Then, this star is at its highest in the sky around 9 p.m. your local time (the time on your clock no matter where you are on the globe). From the Northern Hemisphere, Canopus appears in the southern sky almost directly south of Sirius. When Sirius is at its highest point to the south, Canopus is about 36 degrees below it.

For observers in the Southern Hemisphere, it’s an entirely different story. From latitudes south of the equator, both Canopus and Sirius appear higher in the sky. Indeed, they are like twin beacons crossing overhead together.

For sure, the sight of them is enough to make a northern observer envy the southern skies!

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Canopus in science fiction

In Frank Herbert‘s 1965 novel Dune and other novels in his Dune universe, the fictional planet Arrakis is a vast desert world. It is home to sandworms and Bedouin-like humans called the Fremen. It is the third planet from a real star in our night sky. That star is Canopus.

In Herbert’s novel, the desert planet Arrakis is the only source of “spice,” the most important and valuable substance in the Dune universe. This “spice” is what makes star travel possible, in this fictional universe.

It’s possible, according to Wikipedia (which references the famous book Star Names: Their Lore and Meaning by Richard Hinckley Allen), that Herbert was influenced in his choice of this star as the primary for Arrakis by a common etymological derivation of the name Canopus:

… as a Latinization (through Greek Kanobos) from the Coptic Kahi Nub (“Golden Earth”), which refers to how Canopus would have appeared over the southern desert horizon in ancient Egypt, reddened by atmospheric absorption.

And it’s true … from much of the classical world in ancient times, Canopus would have appeared low in the sky, when it was visible at all. And so, yes, its bright light would be reddened due to looking at it through a greater thickness of atmosphere in the direction toward the horizon. Just as, for example, our sun or moon seen low in the sky looks redder than usual. Golden Earth indeed.

By the way, although Arrakis is fictional, Canopus is not only very real but also much hotter and larger than our sun. See the Science section below.

Science of Canopus

According to data obtained by the Hipparcos Space Astrometry Mission, Canopus is about 310 light-years away.

Spectroscopically, it is an F0 type star, making it significantly hotter than our sun (roughly 13,600 degrees Fahrenheit or 7,500 degrees Celsius) at its surface. This is compared to about 10,000 degrees F or 5,500 degrees C for the sun.

Canopus also has a luminosity class rating of II, which makes it a “bright giant” star much larger than the sun. (Some classifications make it a type Ia “supergiant.”)

If the sun and Canopus were side by side, it would take about 71 suns, altogether, to fit across Canopus. Canopus appears significantly less bright than Sirius, but it is much brighter, blazing with the brilliance of 10,000 suns!

Although its exact age is unknown, Canopus’ great mass dictates that this star must be near the end of its lifetime. It is likely a few million to a few tens of millions of years old. Compared to our sedate middle-aged 5-billion-year-old sun, Canopus has lived in the stellar fast lane and is destined to die young.

History and mythology

Canopus is also called Alpha Carinae, the brightest star in the constellation Carina the Keel. This constellation used to be considered part of Argo Navis, the ship of Jason and his famed Argonauts, as seen in our sky. Canopus originally marked a keel or rudder of this ancient celestial ship. Alas, the great Argo Navis constellation no longer exists. Modern imaginations see it as broken into three parts: the Keel (Carina, of which Canopus is part), sails (Vela) and the poop deck (Puppis).

For those far enough south to see it, Canopus was a star of great importance from ancient times to modern times as a primary navigational star. This is, surely, due to its brightness.

The origin of the name Canopus is subject to question. By some accounts it is the name of a ship’s captain from the Trojan War. Another theory is that it is from ancient Egyptian meaning Golden Earth, a possible reference to the star’s appearance as seen through atmospheric haze near the horizon from Egyptian latitudes.

The position of Canopus is RA: 6h 23m 57s, Dec: -52° 41′ 45″

Bottom line: Canopus is the 2nd-brightest star as seen from Earth. To see Canopus, you must either be in the Southern Hemisphere or below the Northern Hemisphere’s 37th parallel north.

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The post Can you see Canopus, the 2nd-brightest star? first appeared on EarthSky.

Mizar and Alcor

Mizar and its fainter companion star Alcor make up one of the most famous double stars in the sky. These two stars are bound to one another by gravity. And they’re located in the famous Big Dipper, an asterism which is ascending in the northeast on February and March evenings. You can spot this pair easily, and it’s lots of fun to see them! Look at the middle star in the Dipper’s handle. You’ll spot Mizar first, because it’s brighter. Look closely, and you’ll see fainter Alcor right next to Mizar.

Historically, Mizar and Alcor are a test of eyesight. But even people with less-than-perfect eyesight can see the two stars, especially if they’re looking in a dark, clear sky. This pair of stars in the Big Dipper’s handle has the nickname of horse and rider. If you can’t see fainter Alcor with the unaided eye, use binoculars to see Mizar’s nearby companion.

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Mizar alone is a quadruple star

Mizar is perhaps the Big Dipper’s most famous star, glorified in the annals of astronomy many times over. Apart from Alcor, Mizar by itself is a double star. In fact, it was the first double star known. An Italian astronomer brought it to the attention of Galileo in 1617. A third Italian astronomer, Giovanni Battista Riccioli, wrote about Mizar as a double star.

Few, if any, astronomers back then even dreamed that double stars were anything other than chance alignments of physically unrelated stars. Yet, in 1889, a spectroscope revealed that the brighter component of Mizar’s two stars consisted of two stars itself. This made Mizar the first binary star ever discovered by spectroscopic means.

Later, Mizar’s dimmer telescopic component also showed itself to be a spectroscopic binary, meaning that Mizar consists of two sets of binaries, making it a quadruple star.

And Alcor is double

As for Alcor, scientists long believed that Mizar and Alcor were not gravitationally bound and did not form a true binary star system. Not until 2009 did our knowledge expand. Two groups of astronomers independently reported that Alcor is itself a binary, consisting of Alcor A and Alcor B. Astronomers now believe that the Alcor binary system is gravitationally bound to the Mizar quadruple system. That makes this “double” star six stars in all, but we can only see two with the unaided eye.

Mizar and Alcor have proven to not only be a test of human eyesight, but a test of the limits of our technological vision as well.

Bottom line: Famous star pair Mizar and Alcor is easy to find in the handle of the Big Dipper. Mizar is really four stars, and Alcor is two stars. So what we see as two stars are really six in one!

The post Mizar and Alcor in the bend of the Big Dipper first appeared on EarthSky.

February is perfect for both Northern Hemisphere and Southern Hemisphere observers to view the brightest star in the sky: Sirius. As part of the constellation Canis Major the Greater Dog, Sirius also earns the nickname of the Dog Star. From the Northern Hemisphere, Sirius arcs across in the southern sky. From the Southern Hemisphere, it swings high overhead. It’s always easy to spot as the brightest point of light in its region of sky (unless a planet happens to be near it, which none are in early 2024).

It’s a flashy rainbow star

Although white to blue-white in color, Sirius might be called a rainbow star, as it often flickers with many colors. The flickering colors are especially easy to notice when you spot Sirius low in the sky.

The brightness, twinkling and color changes sometimes prompt people to report Sirius as a UFO!

In fact, these changes are simply what happens when such a bright star as Sirius shines through the blanket of Earth’s atmosphere. The varying density and temperature of Earth’s air affect starlight, especially when we’re seeing the star low in the sky.

The shimmering and color changes happen for other stars, too, but these effects are more noticeable for Sirius because Sirius is so bright.

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Finding Sirius

From the mid-northern latitudes such as most of the U.S., Sirius rises in the southeast, arcs across the southern sky, and sets in the southwest. From the Southern Hemisphere, Sirius arcs high overhead.

As seen from around the world, Sirius rises in mid-evening in December. By mid-April, Sirius is setting in the southwest in mid-evening.

Sirius is always easy to find. It’s the sky’s brightest star! Plus, anyone familiar with the constellation Orion can simply draw a line through Orion’s Belt to find this star. Sirius is roughly eight times as far from the Belt as the Belt is wide.

The mythology of Sirius

Sirius is well known as the Dog Star, because it’s the chief star in the constellation Canis Major the Greater Dog. Have you ever heard anyone speak of the dog days of summer? Sirius is behind the sun as seen from Earth in Northern Hemisphere summer. In late summer, it appears in the east before sunrise, near the sun in our sky. The early stargazers might have imagined the double-whammy of Sirius and the sun caused the hot weather, or dog days.

In ancient Egypt, the name Sirius signified its nature as scorching or sparkling. The star was associated with the Egyptian gods Osiris, Sopdet and other gods. Ancient Egyptians noted that Sirius rose just before the sun each year immediately prior to the annual flooding of the Nile River. Although the floods could bring destruction, they also brought new soil and new life. Osiris was an Egyptian god of life, death, fertility and rebirth of plant life along the Nile. Sopdet – who might have an even closer association with the star Sirius – began as an agricultural deity in Egypt, also closely associated with the Nile. The Egyptian new year celebration was a festival known as the Coming of Sopdet.

More mythology of the Dog Star

In India, Sirius is sometimes known as Svana, the dog of Prince Yudhisthira. The prince and his four brothers, along with Svana, set out on a long and arduous journey to find the kingdom of heaven. However, one by one the brothers all abandoned the search until only Yudhisthira and his dog, Svana, remained. At long last they came to the gates of heaven. The gatekeeper, Indra, welcomed the prince but denied Svana entrance.

Yudhisthira was aghast and told Indra that he could not forsake his good and faithful servant and friend. His brothers, Yudhisthira said, had abandoned the journey to heaven to follow their hearts’ desires. But Svana, who had given his heart freely, chose to follow none but Yudhisthira. The prince said that, without his dog, he would forsake even heaven. This is what Indra had wanted to hear, and then he welcomed both the prince and the dog through the gates of heaven.

The brightest star

Astronomers express the brightness of stars in terms of stellar magnitude. The smaller the number, the brighter the star.

The visual magnitude of Sirius is -1.44, lower – brighter – than any other star. There are brighter stars than Sirius in terms of actual energy and light output, but they are farther away and hence appear dimmer.

Normally, the only objects that outshine Sirius in our heavens are the sun, moon, Venus, Jupiter, Mars and Mercury (and usually Sirius outshines Mercury, too).

Not counting the sun, the second-brightest star in all of Earth’s sky – next-brightest after Sirius – is Canopus. It is visible from latitudes like those of the southern U.S.

The third-brightest and, as it happens, the closest major star to our sun is Alpha Centauri. However, it’s too far south in the sky to see easily from mid-northern latitudes.

The science of Sirius

At 8.6 light-years distance, Sirius is one of the nearest stars to us after the sun. By the way, a light year is nearly 6 trillion miles (9.6 trillion km)!

Sirius is classified by astronomers as an A type star. That means it’s a much hotter star than our sun; its surface temperature is about 17,000 degrees Fahrenheit (9,400 Celsius) in contrast to our sun’s 10,000 degrees F (5,500 C). With slightly more than twice the mass of the sun and just less than twice its diameter, Sirius still puts out 26 times as much energy. It’s a main-sequence star, meaning it produces most of its energy by converting hydrogen into helium through nuclear fusion.

Sirius has a small, faint companion star appropriately called Sirius B or the Pup. That name signifies youth, but in fact the companion to Sirius is a white dwarf, a dead star. Once a mighty star, the Pup today is an Earth-sized ember, too faint to be seen without a telescope.

The position of Sirius is RA: 06h 45m 08.9s, dec: -16° 42′ 58″.

Bottom line: Sirius is the brightest star in the night sky as seen from Earth and is visible from both hemispheres. And it lies just 8.6 light-years away in the constellation Canis Major the Greater Dog.

The post See Sirius, the brightest star in the night sky first appeared on EarthSky.

On August evenings, we look toward the center of our Milky Way galaxy. And in January and February, we do the opposite. We look opposite the galaxy’s center, toward the galactic anticenter and the galaxy’s nearest outer edge. The star Elnath (aka Beta Tauri, and sometimes called Alnath) in the constellation Taurus the Bull is the closest bright star on our sky’s dome to the galactic anticenter.

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How to find Taurus’ 2nd brightest star

Elnath is easy to find if you learn to recognize the Face of the Bull in the constellation Taurus. The Face of the Bull in Taurus is shaped like the letter V. The V-shape is fairly easy to pick out from the background stars. These stars are members of the Hyades Cluster. By mid-January, you can find the V-shape nearly overhead about three hours after sunset. This V-shape includes the brightest star in Taurus, red Aldebaran.

If you extend the right side of the letter V (the side that’s opposite Aldebaran), you come to the star Elnath. Elnath represents the Northern Horn of Taurus the Bull. It’s the 2nd-brightest star in Taurus after Aldebaran, which represents the Bull’s bloodshot eye.

So, Elnath isn’t quite as bright as Aldebaran. But it’s also part of a noticeable pattern, and it’s blue-white in color.

Use Orion to find Taurus and Elnath

Can’t find the Face of the Bull? Try finding Orion the Hunter first, an extremely prominent constellation. You can recognize Orion for its Belt, a short, straight row of three medium-bright stars.

Draw a line upward through Orion’s Belt to find Aldebaran and the V-shape group of stars outlining the Bull’s Face. Extend the lines off the top of the V to locate the two stars marking the tips of the Bull’s horns. The northern and brighter horn star is Elnath.

When and where to look for Elnath

In the Northern Hemisphere, we see Taurus and its stars on winter evenings. Elnath stands opposite the sun around mid-December and thus rises around sunset and sets around sunrise. In January and February, Elnath is already up in the southeast at sunset. By June, Elnath will be lost to the sun’s glare and won’t be seen at all. Excepting June, however, you can see Elnath for at least part of the night throughout the year.

Elnath stands a bit north of the ecliptic, the annual pathway of the sun in front of the background stars. Because the moon’s path is always near the ecliptic, the moon swings close to Elnath every month. Generally, the moon swings to the south of Elnath. On occasion, the moon swings far enough north that it occults – passes directly in front of – Elnath. We are currently in the midst of a series of occultations that will last until April 11, 2027.

How to locate the Milky Way’s anticenter

The galactic anticenter lies about 3 degrees to the east of the star Elnath. Three degrees is about the amount of sky that your thumb covers when held at arm’s length. The galactic anticenter isn’t a place, it’s just a direction in the sky from our perspective on Earth. Elnath is about 130 light-years away, whereas the outskirts of our galaxy’s disk are many thousands of light-years away. So Elnath is much closer and just shows the direction.

While the closest bright star to the galactic anticenter is Elnath in Taurus, the anticenter isn’t in Taurus. Instead, it lies in a neighboring constellation, Auriga the Charioteer.

Science of the star Elnath

Elnath sparkles white and is tinged in blue. This star’s color indicates that it has a hot surface temperature of about 13,600 Kelvin (13,300 Celsius or 24,000 Fahrenheit). Contrast this to the surface temperature of our yellow-colored sun, which is 5,800 Kelvin (5,500 C or 10,000 F).

According to the star expert Jim Kaler, Elnath has 4.5 times the sun’s mass and shines with the firepower of 700 suns.

Elnath’s position is RA: 5h 26m 17.5s, dec: +28° 36′ 27″

Bottom line: The galactic anticenter is the position opposite the Milky Way’s center from our viewpoint on Earth. If you want to look toward the anticenter, gaze toward Elnath. This star is the 2nd-brightest star in the constellation Taurus the Bull and is just 3 degrees from the galactic anticenter, which lies nearby in the constellation Auriga.

The post Elnath is a bright star close to the galactic anticenter first appeared on EarthSky.

It’s hard to think of Procyon – the Little Dog Star – without also thinking of the other Dog Star, Sirius. If you’re looking at the right time of the year (or right time of the night), you can always find Sirius because it’s the sky’s brightest star. Procyon is always near its more brilliant brother on the sky’s dome. Procyon isn’t nearly as bright as Sirius. But it’s still the 8th-brightest star in the sky, and the 6th-brightest of stars that are easily visible from the most populated regions of the Northern Hemisphere.

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Procyon, a Northern Hemisphere spring star

Look for Procyon in the evening in the winter and spring months. By March of every year, Procyon is at or near the meridian (highest point in the sky) at early evening. By June, Procyon sets not long after dark.

Procyon is the brightest star in Canis Minor the Lesser Dog. This constellation is small, with only one other noteworthy star, named Gomeisa. Sometimes, Canis Minor is called the “Hot Dog”, maybe because of the high temperature of Gomeisa. Procyon goes by the Lesser Dog Star or Little Dog Star. Our chart shows Procyon as a member of the Winter Triangle asterism. In other words, these stars are not an official constellation, but a group of noticeable stars that happen to form a triangle pattern on the sky’s dome.

Fainter than blue-white Sirius to its south, white Procyon is marginally brighter than orange-red Betelgeuse to the west. The best time to view Procyon is at evening in late winter through spring, when the Winter Triangle (Sirius, Procyon, Betelgeuse) is highest in the sky. At magnitude 0.4, Procyon is almost the same brightness as nearby Betelgeuse in Orion the Hunter, with an average magnitude of 0.45. (Remember, in the magnitude system, larger numbers are fainter, so near-zero is quite bright.)

The science of the Lesser Dog Star

The star Procyon is nearing the end stages of its lifetime, evolving from a normal mature star to the inflated giant stages of old age.

Normal stars spend the large majority of their lifetimes converting hydrogen into helium. As the available hydrogen runs out, a star grows larger and its surface becomes cooler. Eventually, Procyon will become a red giant star, much larger and brighter than our sun, but that is still some millions of years in the future.

Procyon is designated as a F5IV-V star, where the F5 essentially gives the color or temperature of the star’s surface, and the IV-V means that it is in a transitional phase between the main sequence (V) and subdwarf (IV) periods.

Only 11.4 light-years away, Procyon is one of our nearest stellar neighbors. It is about 1.4 times as massive as our sun and has roughly twice its diameter. Slightly more than seven times brighter than the sun, Procyon’s hotter surface (about 11,300 degrees F or 6,260 C, compared to about 10,000 degrees F or 5,540 C for the sun) radiates more of the higher energy but shorter wavelengths of light. As such, it is nearly eight times more energetic (luminous) than the sun.

Procyon is a double star with a faint white dwarf companion that you can only see in telescopes. The white dwarf, Procyon B, is farther along in its evolution than Procyon, and in fact has reached the end of the line. It no longer produces stable hydrogen fusion and is considered a “dead” star. The reasonable assumption is that these two stars formed at the same time, so the fact that Procyon B has already become a stellar corpse indicates that it originally must have been slightly more massive than Procyon. More massive stars tend to burn their fuel hotter and faster, causing them to burn out sooner.

Procyon in history and mythology

Procyon is the alpha star of the constellation Canis Minor the Lesser Dog. In mythology, Canis Minor is the smaller of two of Orion the Hunter’s companion hunting dogs. The constellation Canis Major depicts the Great Dog, highlighted by Sirius, the sky’s brightest star (after the sun).

The name Procyon is from Greek and means “before the dog,” a reference to the rising of this star shortly before Sirius, the larger Dog Star in the constellation Canis Major. Procyon’s rising time was particularly important in ancient Egypt, because the helical rising – or rising just before the sun – of Sirius heralded the annual flooding of the Nile River. Thus, the rising of Procyon just before Sirius gave even more advanced warning.

Procyon still does rise before Sirius as seen from mid-northern latitudes, like those in the northern United States.

But from the southern U.S. and similar latitudes – for example, Cairo in Egypt – Sirius now rises before Procyon! Thus, an observer in Cairo today would find that Sirius rising a couple of minutes before Procyon and the reason for the name “before the dog” no longer applies. This change is due to a kind of long-term wobble in Earth’s motion, called precession.

An aside: “Procyon” is also the genus designation of raccoons. Apparently the “before the dog” appellation indicated that biologists once considered raccoons as the precursors of dogs in the evolutionary sequence, an idea no longer in favor.

The position of Procyon is RA 07h 39m 18.1/17.7s, dec +05° 13′ 29/20″.

Bottom line: The star Procyon is the Little Dog Star. Learn about Procyon and how to find it in your sky.

The post Bright Procyon: The Little Dog Star in Canis Minor first appeared on EarthSky.

Rigel is one of several brilliant stars that grace our night sky in January. It’s also the brightest star in one of the most beloved of constellations, Orion the Hunter. Rigel appears blue-white to the eye. It’s a stunning contrast to red Betelgeuse, Orion’s second-brightest star. Classified as a blue supergiant, Rigel is in the latter stages of its stellar lifetime and will someday become a supernova. Hidden in Rigel’s brilliance are at least three other fainter companion stars that can only be detected using large telescopes.

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How to find Rigel

At magnitude 0.13, Rigel is the 7th-brightest star in the heavens, and the 5th-brightest as viewed from North America. It appears at a lower corner of Orion the Hunter, one of the sky’s best-known constellations. It’s easy to spot because of its brightness and also because of its distinctive blue-white color.

You can catch Orion in the east before dawn during the late Northern Hemisphere summer. On January evenings, Orion shines prominently in the mid-evening sky. Look for Orion high in the south on northern winter (southern summer) evenings. By early March, as soon as the sun sets, Orion is at its highest in the sky. By early May, as seen from around the globe, Orion sets before the sky has a chance to get really dark.

Look for Orion

To find Rigel, first look for its constellation, Orion. You’ll notice three stars in a short, straight line. These stars mark Orion’s Belt. An imaginary line in the sky, heading generally southward – that’s at a right or 90-degree angle from Orion’s Belt – takes you to Rigel. (If you instead draw in the other direction, you’d come to Betelgeuse, with its distinctive reddish tinge.)

Do not confuse Rigel with Sirius, which is farther to the east and farther south. Sirius is similar in appearance, but significantly brighter than Rigel.

The science of Rigel

We couldn’t live as close to Rigel as we do to our sun. That’s because its surface temperature is much hotter, about 21,000 degrees Fahrenheit (11,600 degrees Celsius) in contrast to about 10,000 F (5,500 C) for the sun.

Counting all its radiation (not just visible light, but infrared, ultraviolet and so on), Rigel emits about 120,000 times more energy than the sun. Astronomers calculate this luminosity based on a distance of 860 light-years, a distance derived from data collected by the Hipparcos space telescope. With such enormous energy, you might be surprised to find that Rigel has only 21 times more mass, and is more than 70 times the diameter of our sun.

Rigel is a blue supergiant star, designated as type B8 Ia. According to stellar evolution theory, it is a massive star entering the latter part of its life, having exhausted most of the hydrogen fuel in its core. It’s also a variable star that shows slight irregular fluctuations in brightness. Someday, it will explode as a supernova.

Yet Rigel is not one of the galaxy’s largest stars, as the video below – from the European Southern Observatory – shows.

A little-known fact about Rigel: it is the largest star in a multiple star system. There is a close companion about 400 times fainter than Rigel. That “companion” is actually two stars that can only be resolved by large telescopes. And one of those two companion stars is what’s known as a spectroscopic binary: two stars so close they can be distinguished as two distinct entities only via spectroscopic observations.

In other words, the Rigel system has four known stars!

History and mythology

Historically, the brightest star in a constellation receives the designation Alpha, the second-brightest is Beta, and so on. This system isn’t used for Orion’s stars, however. Instead, the red star Betelgeuse is Alpha Orionis, and Rigel is Beta. But Rigel is the brightest star in Orion.

This deviation from standard stellar designations might be because Betelgeuse is a variable star and has been known to at least approach Rigel in brilliance. The German astronomer Johann Bayer applied the designation Beta Orionis to Rigel in the early 1600s. He sought to systematize stellar naming conventions. It’s possible Betelgeuse was brighter around this time. Nowadays, Rigel outshines Betelgeuse.

The name Rigel comes from an Arabic phrase frequently translated as “The Left Foot of the Central One.” Although Orion was depicted as a giant or warrior in many cultures, in the original Arabic it might have been a reference to a black sheep with a white spot or spots. Thus in the original form, Rigel might have designated the left foot of a sheep! Now, however, many people know it as the left foot of Orion the Hunter.

Aurvandill’s big toe

The mythology related to Rigel is sparse and unclear. Perhaps the most interesting connection is in Norse mythology, which sometimes identified Orion with Aurvandill (also Orwandil, Earendel and others). According to some, Aurvandill was traveling with his companion, the god Thor, when his big toe froze in an unfortunate river-crossing incident. Thor broke off the frozen digit and threw it into the sky, where it became the star we see as Rigel. In some variations, Aurvandill’s other big toe became faint Alcor in Ursa Major.

Rigel’s position is RA: 05h 14m 32.3s, Dec: -08° 12′ 05.9”.

Bottom line: Rigel, the brightest star in the constellation Orion the Hunter, shines a brilliant bluish-white color. It’s much hotter and more massive than our sun, and someday, Rigel will explode as a supernova.

The post Blue-white Rigel is Orion’s brightest star first appeared on EarthSky.

The brightest star in our sky, Sirius, and its white dwarf companion, Sirius B, are currently farthest apart from our perspective. The two stars orbit each other with a period of about 50 years, and they’re having their maximum separation of 11 arcseconds now. While it’s always a challenge to see dim Sirius B next to brilliant Sirius, presently you have a bit of an advantage. Learn how to see Sirius B, below.

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How to see Sirius’ companion

By Florin Andrei. Reprinted with permission.

Sirius the Dog Star is the brightest star in the night sky, visible anywhere on Earth except the far north. If you live in the Northern Hemisphere at a temperate latitude, Sirius is the very bright white star due south every winter in the evening. But did you know that Sirius is also a double star? The companion, Sirius B, also known as the Pup, is a very small star orbiting the primary. You can see it using even small amateur telescopes. It’s not easy to spot but can be done if you follow certain guidelines. Here’s how to do it.

Sirius A and B

While Sirius A, the main component, is a large white star twice as massive as the sun, Sirius B, the companion, is a white dwarf. Sirius B is about as massive as the sun, but very small at about the same volume as Earth. Around 120 million years ago, Sirius B was a large white star five times as massive as the sun, but it has since passed through the red giant phase. Now, it’s the dead remnant of a formerly active star.

Currently, Sirius B is not generating any new heat, as the fusion reactions in its core have stopped. It is steadily cooling down, a process that will take a very long time, because it’s still pretty hot as of now: 25,200 Kelvin (44,900 degrees F or 24,900 C). Basically, Sirius B is the white-hot dead body of a formerly large and very active star. While B is twice as hot as the primary (Sirius A), its very small size makes it much less bright. Sirius B’s luminosity is about 10,000 times less than that of Sirius A.

Tracking the orbit of Sirius B

The two stars, the main component and the companion, orbit each other at a distance of approximately 20 astronomical units (AU). That is about the same as the distance between the sun and Uranus. As a result, when we observe them from Earth, Sirius B appears to describe an ellipse around Sirius A with a period of 50 years.

Seen from Earth, the separation between Sirius A and B varies between 3 and 11 arcseconds on a 50 year cycle. And now they’re at 11 arcseconds apart, so it’s a great time to look for Sirius B. But you have to follow certain rules, since this is not an easy target.

Why this is a difficult observation

Sirius is a double star, with pretty good separation, but with a very large difference in brightness between its stars. Based on separation alone (3 to 11 arcseconds), it should be an easy double to split. But the brightness imbalance is staggering. Sirius B is often lost in Sirius A’s tremendous glare, so you have to take special measures to make B visible.

If you’re an experienced astronomer, you can probably skip some of the following recommendations, as they are probably a matter of your daily routine. But if you’re a beginner, keep reading.

In any case, don’t worry. Sirius B is definitely visible even in a small amateur telescope throughout the 2020s and 2030s. A good 100mm (4-inch) scope or larger should split it in the upcoming years. You can do it. Just play by the rules and be persistent. You will likely not succeed on your first or second attempt. But keep trying, and eventually you’ll see it.

Best time to see Sirius B, and corresponding location on the sky

If you live in the Northern Hemisphere, in the temperate zone, the best time to attempt observing Sirius B is in winter, January and February for the most part. This is when Sirius is at its highest in the sky at a convenient early hour. December is also fine if you don’t mind staying up late, or November if you’re basically an owl. In March, you want to be ready as soon as the sky is dark enough. It is important that the star is not too low in the sky, as seeing (turbulence) becomes much worse close to the horizon, and seeing is absolutely crucial for this observation.

At the 1st of February, you should be outside and already observing around 10 p.m. New Year’s Day, the best time (when Sirius is at the highest point) is around midnight. The 1st of March, the best time is 8 p.m. Come April 1st, Sirius already begins to descend after sunset, so the best observational season is coming to an end.

After you know what time to observe, go outside and look south. That very bright white star not too high in the sky is Sirius. To its right (west), you can see the great constellation of Orion, with bright red Betelgeuse near the top, then the Belt of three stars, then white Rigel at the base.

The importance of seeing

What we in astronomy call seeing is what others call turbulence. Seeing (or air turbulence) blurs the image whenever you’re attempting a high-resolution observation from Earth. It depends on the weather, location and a number of other factors. It is predictable to some extent.

First, go to the Clear Sky Chart site to find the outlook near you. Then, choose a location nearest your place. Next, look at the fourth row in the chart, the one called “Seeing.” When the chart is dark blue, that means good seeing. When the chart is white or light blue, the prediction for seeing is bad.

Excellent seeing is crucial to this observation. It is the most important factor. To see Sirius B, nothing short of excellent seeing will work. Yet, even if the seeing forecast is merely “good,” you should still attempt an observation. Here’s why: There can be brief moments when the air becomes very still even during more vigorous turbulence, and that’s enough to get a short glimpse of Sirius B. But if the forecast is bad, there’s probably no point in trying.

Telescope considerations for seeing Sirius B

Is the primary mirror clean enough?

If your telescope is an open reflector (such as a Dobsonian), dust accumulating on the primary mirror will increase light scattering. If you have cleaned the mirror in the last few months, then feel free to ignore this part. But if it’s been a year or more since the last mirror clean-up, it’s time to give it a bath.

Be very gentle. Use your sense of touch to detect when you hit a dust mote lodged on the surface and avoid dragging it across. Or use cotton balls if your fingers are less sensitive and you’re afraid you’ll scratch the mirror. But apply almost no pressure with the cotton.

At the end, rinse it with plenty of distilled water, then leave it alone and don’t touch it with anything afterward.

Since it’s recommended you do this procedure once a year, perhaps it’s a good idea to schedule it in early January, before you start hunting for Sirius B.

Are the eyepieces clean enough?

The eye-facing lens of any eyepiece is contaminated by grease from eyelashes within seconds of starting an observation. This creates a haze that reduces contrast. It is recommended to clean the lens before any difficult observation. This is the best method.

Use high-concentration alcohol (90% or better) and Q-tips. Make sure the Q-tips are not soaked; if the Q-tip is just a bit wet, that’s when cleaning is most successful. If the Q-tip makes a puddle of alcohol on the lens that persists for a long time, you’re using too much liquid.

Is the telescope collimated?

Collimation is crucial for any high-resolution observation. If previously you’ve only done superficial collimation, now it’s time to get down to business and do it right. There are many techniques and tools for collimation. Here’s a good primer for Newtonian reflectors (such as Dobsonians) using simple tools:

Collimation is a vast topic: you could literally write a whole book discussing nothing but collimation, so keep learning and apply what you learn.

When seeing is good, you could plug a high-power eyepiece into your scope and do a star test to verify collimation. The star test is the ultimate authority for telescope performance, so at least learn the basics.

Is the telescope cooled down?

To deliver peak performance, a telescope must be at thermal equilibrium with the environment. Read about thermal issues at here and here.

Even if you don’t have a mirror fan, at least take the scope outside one hour before you start the observation, and let it cool down to ambient temperature. This should be enough to reap most benefits of thermal equilibrium.

Okay, now go ahead and look for Sirius B

Seeing is great, Sirius is high in the sky, the telescope is in perfect shape … now it’s time to look at Sirius, right?

Not so fast. Before that, take a look to the west (to the right) of Sirius, and observe the large constellation of Orion.

On the above map, Betelgeuse is on top, bright and red. In the middle, there’s the “Belt” made of 3 stars. Then at the bottom there’s Rigel, a bright white star.

Rigel itself is a double star. The separation between Rigel A and B is similar to the separation between Sirius A and B. Except the brightness difference between Rigel A and B is much less than the difference between Sirius A and B, which makes Rigel a much easier double to split.

So grab a high-power eyepiece, plug it into the scope, and point the instrument at Rigel. You’ll see a bright white star, and nearby a much smaller star, which is supposed to be white but looks quite yellow to me. Try to memorize the distance between Rigel A and B, because it’s similar to the current distance between Sirius A and B.

If you can’t see Rigel B, either seeing is so bad or your scope is out of whack, and there’s no point to even try to see Sirius B.

Time to actually describe the observation of Sirius B

You should use very high magnification. Forget what you’ve heard on forums or from word-of-mouth about “magnification limits;” just plug in a strong eyepiece. For a 150mm (6-inch) scope, 300x is not too much; for a 200mm (8-inch) scope, up to 400x; for a 300mm (12-inch) scope, up to 600x. Try the highest magnification available, then back off a little if things are too fuzzy. You should not use less than half the magnifications indicated above: In other words, for a 200mm (8-inch) scope, stay between 200x and 400x.

Point the scope at Sirius, turn off tracking (if your scope has it), and let the star drift across the field. Sirius B is currently close to due east from A (east-northeast), so it should be trailing the primary star, following the primary a little bit off to the side of A’s trajectory.

A comfortable chair helps you relax and breathe slowly. Keep looking at the primary star and be mindful of the surrounding area trailing the star as it drifts across the field. There will be a lot of light scattered from the primary, making it hard to see anything in the vicinity. Just relax and keep watching.

Sometimes the eye is covered in excess fluid (tears, basically) which blurs the image. Back off from the eyepiece a few millimeters and blink slowly and firmly a couple times (but don’t squeeze it shut too hard), then resume.

How Sirius B appears

In theory, Sirius B should be just outside the bundle of shimmering brightness centered on Sirius A, but – being pretty weak – it’s hidden by the tremendous glare from the primary. Once in a while, something will coalesce out of nothing, and you’ll see the unmistakable round pattern of a star.

Even in good seeing, it’ll wink in and out of existence. Or you’ll see it for a few moments, then it’ll vanish again for a long time. Don’t confuse it with a diffraction artifact from the primary. Stars are round, whereas artifacts are typically more linear or oddly shaped.

Only when seeing is very good will you be able to see Sirius B for extended periods of time. Usually it’s more elusive than that.

When your eyes are tired, take a break, go observe the Great Orion Nebula or Rigel A/B again. Then get back to hunting Sirius B.

If you fail at your first attempt, well, that’s normal. Try again tomorrow. It’s hard to catch the perfect seeing required, so persistence is important. Perfect seeing, a telescope in perfect shape, high magnification, and persistence: That’s how it’s done.

Good luck, and clear skies.

Bottom line: Now is a great time to see Sirius’ dim companion, the white dwarf Sirius B. The two are currently at their maximum separation of 11 arcseconds, as viewed from Earth.

The post Sirius B: Now is the best time to see Sirius’ companion first appeared on EarthSky.