# Are any of the zodiac stars about to go supernova anytime soon?

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I have read that Betelgeuse, known as Ardra in Hindu astrology, could go supernova. Are any of the zodiac stars or the stars of lunar mansions about to become a black hole or supernova?

I don't really know what you mean by "Zodiac stars". I suppose you mean the stars of the 12 traditional Zodiac constellations.

Alpha Scorpii, known as Antares, or Jyeshtha in Hindu astrology, is a red supergiant. It is in a similar stage of its lifecycle to Betelgeuse. It is expected to explode in a supernova in the next 10000-100000 years (the timing is not very well understood)

Other potential supernova progenitors are more distant and fainter, such as HD 168625 in Saggitarius, which is not visible with the naked eye. There is also the recurrant nova U Scorpii, a candidate for a type Ia supernova (which occurs when a white dwarf accretes a critical amount of matter) Again it is far to faint, even during an outburst, to be a naked eye star (but it would certainly be visible if it exploded in a supernova).

I assume that by "zodiac stars or the stars of lunar mansions" you're referring to visible stars that are within 8° or so of the ecliptic, since that's the ecliptic latitude range where the Sun, Moon, and planets appear.

Wikipedia has an article listing the known Milky Way supernova candidates. Some of those are currently visible stars in zodiac constellations, including Spica and Antares. Spica is not expected to go supernova for at least a million years or two. Antares could explode in the next ten thousand years or so.

There are two main causes of supernova: thermal runaway and core collapse. Thermal runaway can occur when a white dwarf (an old star that has stopped nuclear fusion) accretes a large amount of matter from a companion star, or collides with that companion.

A white dwarf star may accumulate sufficient material from a stellar companion to raise its core temperature enough to ignite carbon fusion, at which point it undergoes runaway nuclear fusion, completely disrupting it.

If we can estimate the accretion rate, or determine from their orbits how long it will take for the stars to collide with each other, we can make a rough estimate of how long it will be before the supernova occurs.

The other kind of supernova happens when a large star runs out of nuclear fuel and its core collapses.

Very massive stars can undergo core collapse when nuclear fusion becomes unable to sustain the core against its own gravity; passing this threshold is the cause of all types of supernova except type Ia. The collapse may cause violent expulsion of the outer layers of the star resulting in a supernova, or the release of gravitational potential energy may be insufficient and the star may collapse into a black hole or neutron star with little radiated energy.

Core collapse supernovae occur in stars with a mass in the range of 8 to 40 or 50 $$M_odot$$ (solar masses), depending on composition.

It's much harder to estimate when a core collapse supernova will occur because we can't see the star's core. As a large star ages, it performs a series of nuclear reactions in its core. The rates of these reactions are highly dependent on temperature and pressure, and the more massive stars have higher core pressures and temperatures.

Each reaction in the series operates at a much higher temperature than the previous reaction, but it takes a long time for energy produced in the core of a star to propagate to the outer parts of the star and cause visible effects. For example, for energy produced in the solar core

the photon diffusion time scale (or "photon travel time") from the core to the outer edge of the radiative zone [is] about 170,000 years. From there they cross into the convective zone (the remaining 25% of distance from the Sun's center), where the dominant transfer process changes to convection, and the speed at which heat moves outward becomes considerably faster.

The photon diffusion time is even longer in more massive stars.

Perhaps in the future we'll be able to get more timely information about stellar core fusion processes, using neutrino telescopes, but our current neutrino detectors are far too crude for that.

For most of a star's life, it "burns" hydrogen into helium. The later fusion reactions operate on shorter and shorter time scales. For example,

a star of 25 solar masses burns hydrogen in the core for $$10^7$$ years, helium for $$10^6$$ years and carbon for only $$10^3$$ years. [… ] the process will use up most of the carbon in the core in only 600 years. The duration of this process varies significantly depending on the mass of the star.

The following stages are even faster: neon burning and oxygen burning in a 25 $$M_odot$$ star last for only a few years at most, and the final set of reactions, silicon burning, can only occur for a few days before the core collapses.

So if we knew that a star was doing carbon fusion in its core we'd be able to make a good estimate of when it's likely to go supernova. But the heat of carbon fusion simply doesn't have enough time to reach the surface of the star before the supernova happens.

## NASA Hubble observations exposes truth about potential Betelgeuse supernova

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### NASA provides 3D recreation of supernova remnant Crab Nebula

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Between December and January, a distant star known as Betelgeuse began dimming rapidly, leaving astronomers questioning whether the star, which is 725 lightyears from Earth, was ready to explode. In December, Betelgeuse went from one of the top 10 brightest stars visible to the naked eye to the 21st in January &ndash of roughly 5,000 which can be seen.

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The dimming suggested it was expected to supernova. Stars supernova when they are at the end of their lives having run out of fuel after millions of years.

However, the star has now regained some of its brightness, prompting an investigation from NASA's Hubble Telescope.

The space agency revealed the star ejected hot material from its core, which formed around Betelgeuse.

This in turn led to the perceived dimming of the star, at least from Earth's perspective.

NASA Hubble observations reveal truth about potential Betelgeuse supernova (Image: GETTY)

Betelgeuse ejection (Image: NASA)

Andrea Dupree, associate director of the Center for Astrophysics at Harvard & Smithsonian (CfA), Cambridge, Massachusetts, said: &ldquoWith Hubble, we see the material as it left the star&rsquos visible surface and moved out through the atmosphere, before the dust formed that caused the star to appear to dim.

&ldquoWe could see the effect of a dense, hot region in the southeast part of the star moving outward.

"This material was two to four times more luminous than the star's normal brightness.

"And then, about a month later, the south part of Betelgeuse dimmed conspicuously as the star grew fainter.

&ldquoWith Hubble, we see the material as it left the star&rsquos visible surface and moved out through the atmosphere" (Image: GETTY)

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"We think it is possible that a dark cloud resulted from the outflow that Hubble detected. Only Hubble gives us this evidence that led up to the dimming."

However, this is possibly not the end of the story and the mass ejection may be a sign that Betelgeuse is set to supernova after all.

Stars supernova when they are at the end of their lives having run out of fuel after millions of years.

When they do, they implode, collapsing in on themselves under their gravitational force before a huge explosion occurs.

With Betelgeuse being an ageing star, it could explode yet (Image: GETTY)

And with Betelgeuse being an ageing star, it could explode yet, claimed Dr Dupree, although she conceded this is difficult to judge.

She said: "No one knows what a star does right before it goes supernova, because it's never been observed.

"Astronomers have sampled stars maybe a year ahead of them going supernova, but not within days or weeks before it happened.

"But the chance of the star going supernova anytime soon is pretty small."

If, hypothetically, Betelgeuse were to supernova, it will be brighter than any star implosion ever observed from Earth, dwarfing that of the Kepler&rsquos Star supernova.

Hubble in numbers (Image: EXPRESS)

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Kepler&rsquos Star produced a visible supernova in 1604, producing a bright enough light which was visible during the day time for three weeks.

However, Betelgeuse would outshine Kepler&rsquos Star, according to Daniel Brown, a lecturer in astronomy at Nottingham Trent University.

Mr Brown has said: &ldquoIf [Betelgeuse supernova] did occur, it would become the brightest supernova ever observed.

&ldquoIn a matter of days, it would become as bright as the full moon, be visible during day time and be bright enough at night to cast shadows on Earth.

&ldquoBetelgeuse would then start a phase of final, rapid dimming and again reach its current brightness level after possibly three years.&rdquo

## Betelgeuse about to go supernova?

Bottom left, that little green guy, not sure what he is up to!

### #53 kmparsons

The two greatest things I have seen in the sky were Hale-Bopp in '97 and the '17 total solar eclipse. Betelgeuse going supernova would be the tops. The dream would be to be looking right at it when it occurred. I know that Tycho Brahe was walking home from his lab (he was an alchemist before he was an astronomer) on the evening of November 11, 1572 when he noticed a "new star" in Cassiopeia. That had to be a thrill, but seeing it as it occurs would be even better. Truly a once-in-many-lifetimes event. The only sad part would be that after it dims, we would never again see the Orion that humans have always seen.

### #54 earlyriser

The two greatest things I have seen in the sky were Hale-Bopp in '97 and the '17 total solar eclipse. Betelgeuse going supernova would be the tops. The dream would be to be looking right at it when it occurred. I know that Tycho Brahe was walking home from his lab (he was an alchemist before he was an astronomer) on the evening of November 11, 1572 when he noticed a "new star" in Cassiopeia. That had to be a thrill, but seeing it as it occurs would be even better. Truly a once-in-many-lifetimes event. The only sad part would be that after it dims, we would never again see the Orion that humans have always seen.

Does anyone know how fast a supernova increases in brightness? The curves I've seen on line indicate that peak brightness occurs a few days or weeks after core collapse, but they don't really tell me how abrupt the initial brightening is.

### #55 Uranotopia

After a few days and nights with many clouds and snowfall from time to time, I had last night unexpectedly the opportunity to observe Betelgeuse for fifteen minutes or more here from Kasakhstan (where I stay for holidays).

It was about 1.00 Kasakh time (on 10th January),. that means 19.00 Universal Time on 9th of January). Seeing was rather turbulent, although there was little haze above the horizon. The observation was disturbed by bright moonlight and light pollution caused by the city Kostanay.
For the observation I used my eyes and a 15x70 binocular.

So I took the tme to compare Betelgeuse with Belatrix, Aldebaran, Castor (not recommended by the AAVSO) and Pollux. I saw Betelgeuse little brighter than Belatrix and Castor, but little fainter than Pollux. But Aldebaran seemed to be not only little than Betelgeuse.

So my estimation for Betelgeuse's brightness was 1.4 mag. For me the colour seemed not significant different to my memory of former observations. But I'm not sure, as I am not used to comparing colours of the stars so accurate.

Edited by Uranotopia, 10 January 2020 - 06:25 AM.

### #56 Grimnir

Uranotopia your estimate of 1.4 mag is good and Betelgeuse continues to dim.

### #57 MikiSJ

Much better a supernova than a super volcano like in Yellowstone

Especially if you live to the SE of Yellowstone.

### #58 earlyriser

I found this on Wikipedia:

"The visual light curves of the different supernova types all depend at late times on radioactive heating, but they vary in shape and amplitude because of the underlying mechanisms, the way that visible radiation is produced, the epoch of its observation, and the transparency of the ejected material. The light curves can be significantly different at other wavelengths. For example, at ultraviolet wavelengths there is an early extremely luminous peak lasting only a few hours corresponding to the breakout of the shock launched by the initial event, but that breakout is hardly detectable optically."

I wonder it this luminous peak in UV could pose any hazards to eyesight for those watching Betelgeuse through a large reflector, for example.

Edited by earlyriser, 11 January 2020 - 10:28 AM.

### #59 Uranotopia

earlyriser, on 11 Jan 2020 - 9:27 PM, said:

I found this on Wikipedia:

"The visual light curves of the different supernova types all depend at late times on radioactive heating, but they vary in shape and amplitude because of the underlying mechanisms, the way that visible radiation is produced, the epoch of its observation, and the transparency of the ejected material. The light curves can be significantly different at other wavelengths. For example, at ultraviolet wavelengths there is an early extremely luminous peak lasting only a few hours corresponding to the breakout of the shock launched by the initial event, but that breakout is hardly detectable optically."

I wonder it this luminous peak in UV could pose any hazards to eyesight for those watching Betelgeuse through a large reflector, for example.

### #60 DLuders

As noted in Post 56 above, Spaceweather.com has a good story about it, but since it will go off of the main page soon, here is the hyperlink that will stay around regarding "The Fainting of Betelgeuse - Update": https://spaceweather. geuse-update/

### #61 Grimnir

An update and interesting article on Betelgeuse here:

Betelgeuse is now about 1.0 mag dimmer than in September, minimum brightness is expected on Feb 21st +/- 7 days.

### #62 Littlegreenman

Based on what I have read on various other places on the internet, and then filtered through my memory, I think I remember the following. But, please correct me if I'm wrong!

If Betelgeuse goes Supernova, it could be as bright as a full moon.

But, it would be a point source.

which means it could damage eyes if looked at directly or through a telescope.

Note to self: find out what filter(s) would be good to provide safe viewing and market them as the Betelgeuse Supernova Filter.

It may take anywhere between hours to years to fade. Meaning, that our night sky for hours or several years will have another light source as bright as the full moon. And some of the time both will be shining down on us at the same time! You could probably read by the combined light. Nothing the Dark Sky Association can do about it.

A nebula would form and over time evolve and likely expand.

Even so, I'd still like to see it.

One of my favorite astronomical views, circa 2003?, was the moon eclipsing Saturn. This occurred about 12:00 noon, within a few degrees of the sun.

Edited by Littlegreenman, 10 February 2020 - 09:42 PM.

### #63 MartinPond

Would we detect gravity waves?

Not really. most supernovas are roughly symmetrical

and centered around what used to be, gravitationally..

And it would be a "tapered off pulse" instead of a wave.

We need something really obvious and repeatedly wobbling, like

two black holes in a death spiral..

I wonder if there would be a nicely textured plasma show, like1987A.

Edited by MartinPond, 12 February 2020 - 12:52 AM.

### #64 25585

Betelgeuse is one of the most beautiful stars in the sky. I hope it outlives me!

### #65 hallelujah

One of the more interesting astronomy stories that came out at the tail end of 2019 was the bizarre behavior of the nearby star known as Betelgeuse. It sits somewhere between 520 and 650 light-years from Earth, and that’s extremely close in the grand scheme of things, making its behavior of particular interest to us here on Earth.

Months ago, scientists alerted us to the fact that Betelgeuse is getting dimmer. This massive star is currently a red supergiant, and the fact that it appeared to be dimming hinted at a number of possible outcomes, including a possible collapse and supernova explosion. Now, with several more weeks of observations under their belt, researchers have discovered that Betelgeuse isn’t just dimming, it’s dimming in a very bizarre way.

As Phil Plait of SYFY Wire reports, high-resolution images captured by the Very Large Telescope reveal that Betelgeuse is indeed dimming… but only part of it is actually changing in brightness. Check it out:

a close up of a ball: Capture© Provided by BGR Capture “The red supergiant star Betelgeuse, in the constellation of Orion, has been undergoing unprecedented dimming,” the European Southern Observatory writes. “This stunning image of the star’s surface, taken with the SPHERE instrument on ESO’s Very Large Telescope late last year, is among the first observations to come out of an observing campaign aimed at understanding why the star is becoming fainter. When compared with the image taken in January 2019, it shows how much the star has faded and how its apparent shape has changed.”

Because only part of the star is changing in brightness, its shape appears to be altered, giving it an oblong appearance as opposed to a more uniform circular shape. So, what’s the deal?

As Plait points out, nobody can say for certain, at least not yet, but one possibility is that the supergiant star’s surface has been stained with a particularly large sunspot. Our own star gets sunspots from time to time, but they’re usually quite small. On a star like Betelgeuse, things are a lot different, and the turbulent magnetic forces at work may have produced a particularly massive sunspot that is actually making the entire star appear less bright.

The odds that Betelgeuse is preparing to blow its stop still appear very slim, and it’s highly unlikely we’re about to witness the supergiant go full supernova anytime soon. Still, until anyone can conclusively explain what’s going on with the star, scientists will be keeping a particularly close eye on it.

## Evidence of Past Supernova Close to Earth

Some interesting recent-ish findings detecting past supernova within 300LY of Earth.

Supporting research papers linked in the older article --

Edited by BillP, 13 May 2021 - 09:47 PM.

### #2 Sleep Deprived

I don't know why this should surprise us. It is estimated that a supernova happens in a galaxy like the Milky Way once every 100 years or so, so to have some happen close by over a period of millions of years makes sense. Someone else can do the volumetric math, but I think it makes sense on the surface of it all. Especially if we happen to be near a star birth area at the time.

I think the surprise is that we can detect it - that we have gone to the right place, looked for these isotopes with the right equipment, and found what we were looking for. This certainly intrigues me. 100 years from now, after technology has advanced another 100 years, I wonder what types of things we will discover. Also, with our current technology, I wonder what we have NOT discovered simply because no one has thought to look in the right way/place for evidence.

I don't think there is anything nearly as close as is claimed in these studies that could threaten us with a supernova - anytime soon, anyway. Even so, IF it were to happen really close, I can only imagine the havoc it would wreak on our technology. We could easily see a spike in cancers, but not before all our satellites are space junk and most of our earthbound electronics are fried, too. I would bet the danger would be over some period of time, too. It may be too 'hot' in orbit to place replacements for a few years, but I don't know. If there is a 'steady' stream of high-energy particles from a supernova (highest energy arrives soonest, but slower ones arrive over time) things could be 'hot' for quite a long time, at least in human terms.

## A Giant Star Is Dimming, Which Could Be a Sign It Is About to Explode

A long time ago in a constellation not that far away, a bright star rapidly dimmed—and 600 years later, astronomers detected the change on Earth.

The star Betelgeuse comprises the shoulder of the constellation Orion, and its abrupt change in brightness hints that it may be on the brink of death. If this star is indeed at the end of its life, it will not go gently into that good night. Before Betelgeuse blips out for good, it will explode in a supernova—a violent stellar cataclysm that could outshine the moon and make it visible even in daylight, reports Deborah Byrd for EarthSky .

The chances of this stellar explosion happening anytime soon are pretty low, says Jackie Faherty, an astrophysicist at the American Museum of Natural History, on Twitter. But the star’s recent spate of symptoms has prompted some speculation. Once among the ten brightest stars in the sky, Betelgeuse has grown progressively dimmer since October, dropping out of even the top 20, reports Nadia Drake for National Geographic. A supernova, some say, could be nigh.

The star’s brightness has flickered before. Betelgeuse is a red supergiant about 700 times as wide as the sun, positioned about about 600 light-years from Earth. The giant is a variable star, meaning it regularly experiences dips in brightness. It's recent bout of faintness could be part of this regular cycle, but the star has dimmed more than at any other point in the last century.

When massive stars like Betelgeuse start to sound their death knells, their brightness is thought to ebb and flow more erratically as they eject enormous amounts of mass that can obscure their light, Sarafina Nance, who studies stellar explosions at the University of California, Berkeley, tells Drake. But humankind has never had the opportunity to closely observe a star in its final stages before—and whether this is what’s currently happening to Betelgeuse is far from guaranteed.

Astronomers are unsure what will happen next. Perhaps Betelgeuse will perk back up in a matter of weeks. But “if it keeps getting fainter, then all bets are off,” Edward Guinan, an astronomer at Villanova University, tells Drake.

Don’t hold your breath, though. Astronomers have known for decades that Betelgeuse is eventually going to go supernova—and, because of its distance from us, perhaps it already has. At 600 light-years away, Betelgeuse’s light takes 600 years to reach us. Perhaps the star blew its top in medieval times, and we have yet to see witness the aftermath.

The far likelier case, though, is that Betelgeuse’s end is still a long way off. Most astronomical predictions put its demise within a million years of present day, Elizabeth Howell reported for Space.com in 2017.

Still, that doesn’t mean you should shelve your telescope. Dying or not, Betelgeuse is worth a glimpse. And who knows? If it does boom out soon, this may be one of our last shots to glimpse the glowing red behemoth.

## Betelguese, one of the sky's brightest stars, is now the faintest it's been in a century. But despite rampant speculation that it's about to go supernova, astronomers say that probably won't happen anytime soon.

Betelgeuse is about 500 light-years away, not near enough to cause serious damage. We might see a little bit of damage to the ozone layer, or some small increase of radiation on the ground on Earth, but these would be too small to matter.

There was supposed to be an Earth-shattering kaboom! Where's the Earth-shattering kaboom?!

I am now more worried than when I went in to the article. I had no idea about solar proton emission form the sun.

But what if one of its magnetic poles is pointing at us?

Nothing would be cooler than to see a supernova that was big enough to be visible during daylight hours. I hope we get to witness that.

careful with what you wish for. please take that back.

when you cant see it anymore just call its name 3 times.

If there are infinite realities then there is one where that star went supernova at the exact moment they say its name 3 times during the movie.

Hopefully Ford will be okay

I understand this reference.

Shit, probably have to watch an episode or two this afternoon.

It's funny, in the news this morning the headline is :"Astronomers think star may explode AT ANY MOMENT".

Reading the article: "they say it could take 100,000 years or so".

Funnily enough, in astronomical terms that IS any moment. 100000 years in terms of the Sun’s age (4.6 billion years old) is only .002% of how long it’s been alive for.

For some useless perspective. If the average human lives 77 years, that percentage of time would be 81 minutes.

## Meet Betelgeuse

Betelgeuse, which is located approximately 640 light-years from Earth in the constellation Orion — is one of the biggest and brightest stars in our galactic neighborhood. It could swallow the Sun 20 times over. Ultimately, this beast emits 100,000 times more light than our own star.

If that doesn’t convey its sheer enormity, let me put it this way: If you were to replace Betelgeuse with our Sun, it would extend all the way to Jupiter, engulfing Earth and all of the planets in the inner solar system.

## The illumination of Betelgeuse

Many astronomers secretly hoped the star would explode, even though an approaching supernova was the least likely explanation for its behaviour.

“I would love to see it blow up. It would be just fantastic,” Ed Guinan, an astronomer at Villanova University who studies variable stars and has tracked Betelgeuse for decades, told National Geographic just before the star started brightening.

But when Guinan plotted the recurring fluctuations in Betelgeuse’s brightness, he began to suspect that the star wasn’t on a one-way trip into the cosmic afterlife. At least two of the star’s periodic cycles were overlapping near their low points, a coincidence that could explain why Betelgeuse dimmed so dramatically, he says.

Guinan took a look at the timing of the stellar cycles, and he realised that if the star’s behavior matched a particularly pronounced, roughly 425-day fluctuation, Betelgeuse should start brightening again around late February—which, after hovering near its minimum recorded brightness for a week or so, it did.

“We had the minimum on February 20, plus or minus some days,” Guinan says. ”I am of course very happy that I was right, who wouldn't be, but I was hoping in my heart that the star would fade, and fade, and go supernova. I would love to see it.”

## NASA star signs: Space agency's bombshell about YOUR zodiac - 'Didn't change any zodiacs'

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### Astrology: Expert reveals new zodiac dates as stars realign

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The horoscope and its star signs remain intact, at least as far as NASA is concerned. Earlier this month, astrology enthusiasts took to social media to spread of awareness of the star sign Ophiuchus, supposedly discovered by the US space agency. According to claims made on platforms like Twitter and Facebook, NASA had accidentally changed everyone's birth signs by introducing a new constellation into the mix.

### Trending

One person on Twitter said: "What's the symbol for Ophiuchus? That's what my zodiac sign is now apparently."

Another person said: "Instead of getting back to sleep, why am I reading articles about the 13th zodiac Ophiuchus?

"Now I'm confused if this was officially introduced as the 13th zodiac sign since I've been reading articles that NASA did not create it."

A third person said: "So it turns out NASA figures out that the Astrologists and planetary scientist of ancient times got the #zodiac signs wrong and forgot a sign #Ophiuchus so of your into astrology your sign changed! I&rsquom no longer a #Gemini"

NASA star signs: Did the US space agency intriduce a new zodiac sign? (Image: NASA)

NASA star signs: The news caused a storm on social media (Image: TWITTER)

### READ MORE

However, the US space agency has denied meddling with people's horoscope.

In a blog post published this weekend on Tumblr, NASA said it does not concern itself with astrology as it is not a science.

Instead, the agency argued why astronomically there are 13 star signs and not just 12.

NASA said: "Did you recently hear that NASA changed the zodiac signs? Nope, we definitely didn&rsquot&hellip

"Here at NASA, we study astronomy, not astrology. We didn't change any zodiac signs, we just did the math."

### Related articles

We didn't change any zodiac signs

NASA

Unlike astrology, which studies the supposed influence of celestial bodies on our lives, astronomy is the scientific study of everything that is in space.

NASA said: "Astronomers and other scientists know that stars many light-years away have no effect on the ordinary activities of humans on Earth."

The star signs people base their astrological zodiacs on are represented by constellations in the night sky - imaginary lines drawn between bright stars.

Think of the Earth racing around the Sun and imagine a very long arrow pointing from our planet and through the Sun to the other side.

### READ MORE

The 12 zodiacs happen to be whatever constellation the arrow is pointing at as the planet orbits the Sun.

Nearly 3,000 years ago, the signs of the zodiac were divided into 12 equal parts with 12 corresponding constellations - much like cutting into a pizza.

According to NASA, this was done by the ancient Babylonians who kept time through a 12-month calendar.

But there is a small caveat - the Babylonians knew of 13 constellations in the zodiac.

NASA said: "So they picked one, Ophiuchus, to leave out.

### Related articles

"Even then, some of the chosen 12 didn't fit neatly into their assigned slice of the pie and crossed over into the next one."

So, when the Babylonians decided someone born between July 23 and August 22 would be born under Leo 3,000 years ago, today anyone born between dates would be born under a different sign.

The night sky is different now than it was then because the planet's axis along the North Pole does not point in the same direction anymore.

The constellations also all vary in size, meaning the Sun and Earth are lined up with the signs for different amounts of time.

NASA star signs: The 13 zodiacs including Ophiucus (Image: NASA)

NASA star signs: Astrology is not a science unlike astronomy (Image: EXPRESS)

NASA said: "The line from Earth through the sun points to Virgo for 45 days, but it points to Scorpius for only seven days.

"To make a tidy match with their 12-month calendar, the Babylonians ignored the fact that the sun actually moves through 13 constellations, not 12.

"Then they assigned each of those 12 constellations equal amounts of time.

"So, we didn&rsquot change any zodiac signs&hellipwe just did the math."

## Are any of the zodiac stars about to go supernova anytime soon? - Astronomy

Over the history of life on Earth there have been many extinction events, but the top 5 mass extinctions are the big ones. Fortunately, such events don’t happen often. Understanding what caused these massive die-offs is inherently interesting, just so that we better understand the world, but might also provide some insight into potential future threats. A recent study suggests an interesting potential cause for one of these mass extinctions – nearby supernova.

These 5 mass extinction events are:

Ordovician-Silurian extinction – 444 million years ago – this is thought to have been caused by global cooling, resulting in increased polar ice, dropping of the ocean which reduced shallow habitats and changed its chemistry, allowing for more toxic minerals and less oxygen. This extinction saw the loss of 85% of species.

Late Devonian extinctions – 383-359 million years ago – this extinction correlates with a dramatic decrease in ocean oxygenation. The cause of this drop is not well understood, but candidates include asteroid impact, volcanic eruptions, and increased soil weathering due to the evolution of land plants. The species loss in this extinction was 70-80%.

Permian-Triassic extinction – 252 million years ago – this is the biggest mass extinction on Earth ever. Over 96% of sea species, and 75% of land species went extinct over about 60,000 years. Ecosystems did not recover for millions of years. These numbers actually underestimate the devastation, as these are the loss of species. But if you look at individual creatures, almost everything on Earth died, which just the slightest residue of life left. This was probably triggered by massive volcanic activity, releasing CO2, warming the planet, and causing acid rain.

Triassic-Jurassic extinction – 201 million years ago – this was caused also by global warming from an increase in atmospheric CO2 by a factor of four. This was in turn also caused by volcanic activity – this time from the Central Atlantic Magmatic Province. In this extinction about 80% of species were lost.

Cretaceous-Paleogene extinction – 66 million years ago – this is the one everyone knows about, because it saw the end of the non-avian dinosaurs. This was almost certainly caused by a large impact, but there persists a minority opinion regarding the contribution of volcanic activity from the Deccan Traps in what is now India. Along with the non-avian dinosaurs, 76% of species on Earth went extinct.

Some themes emerge from these mass extinctions. First, there often appears to be multiple potential causes. This might be because for such a mass extinction to occur, multiple factors have to conspire to stress life beyond its limits. Four of the five events also resulted at least in part from extreme climate change, two with cooling and two with warming. These in turn involved changes in atmospheric CO2 and ocean oxygenation and chemistry. One mass extinction, the K-Pg, resulted primarily from a massive impact. But impacts may occasionally play a role in other extinctions.

The new study involves the Late Devonian extinction, the one whose cause is the least well understood. Actually, this is a series of extinction events over 24 million years. Again, we know these events correlates with a significant drop in ocean oxygenation. There are many theories as to what caused this drop. For example, increased flow of nutrients from the land to the sea could cause algae blooms which in turn cause dead zones of decreased oxygenation. This may also correlate with a period of climate change, probably global cooling, but also warming at other times.

One other factor that seems to be playing a role is the decrease in the ozone layer. The ozone layer blocks out certain kinds of radiation (including harmful UV light) and a dramatic decrease would certainly be a stressor on life. The evidence for this comes from pollen from the time period which shows an increase in malformations, known to be due to ionizing radiation. This then leads to the question of what caused the depletion of the ozone layer. This is where the new paper comes in – the authors hypothesize that ozone depletion could have been triggered by nearby supernova. This would make the Late Devonian extinction events the only ones known to be cause by such astronomical phenomena.

“Here we study an alternative possible cause for the postulated ozone drop: a nearby supernova explosion that could inflict damage by accelerating cosmic rays that can deliver ionizing radiation for up to 100 ky. We therefore propose that the end-Devonian extinctions were triggered by supernova explosions at ∼20 pc , somewhat beyond the “kill distance” that would have precipitated a full mass extinction.” (100 ky = 100,000 years 20 pc = 20 parsecs or about 67 light years).

It makes sense that sometime in the last few billion years our sun would have been relatively close to a supernova. Right now there are no stars within our “kill distance” that will go supernova anytime soon. Perhaps the closest such star is Betelgeuse, which is 600 light years away – a safe distance. The radiation from one or more supernova, they argue, could have depleted the ozone, resulting in a series of extinctions until the ozone could be repleted.

If you want to delve into the details of how the ionizing radiation from a nearby supernova would deplete the ozone, read the original paper. It is surprisingly accessible. Basically they propose that increased surface temperatures increased water vapor in the stratosphere, which lead to an increase in free radical formation, which chemically degraded ozone.

At this point this should be considered a hypothesis, but a plausible one with some evidence. But the Late Devonian extinctions remain perhaps the most complex and least understood of the extinction events.

This idea also raises the broader question of – what are the implications of this for the possibility of life throughout the universe? The more densely packed a stellar system’s local area is packed with other stars, the more likely it is that they will be hit by a nearby supernova. Or looked at another way – the more frequently this will happen. If the supernova is close enough, within the “kill distance”, then any life on planets in that system could be 100% wiped out – entirely sterilized. The same would happen if a relatively nearby gamma ray burst was aimed in your direction. So it is certainly safer, from this perspective, to live in a system that is relatively far away from other stars.

However, the conditions for life formation might not be best in the outer reaches of galaxies. The “matallicity” of stars varies based on their location in the galaxy. High metallicity (containing lots of heavier elements from previous stars) is good for the formation of life. Higher metallicity stars tend to exist in denser parts of the galaxy, because metallicity correlates with supernova seeding gas clouds that form later star systems. So life both needs and is threatened by supernova. But there is a sweet spot where there is enough metallicity to form life, but enough distance not to get sterilized on a regular basis. And of course, our system is in this goldilocks galactic zone. But we don’t really know for sure what the prospects are for life in other zones of the galaxy.

One interesting thing to consider is that about 50% of all stars in the universe are not even in galaxies. They are drifting between galaxies. Yet, it is likely that they formed in galaxies but where then flung out of their galaxies by gravitational interactions. This could be the best-case scenario for life – a star that forms in a high metallicity zone, then gets flung out to the vast emptiness of intergalactic space, safe from any nearby supernova or gamma ray bursts. Most life in the universe, therefore, may exist in intergalactic rather than galactic systems. We may be a rare exception.

In fact, there is a lot to be said for being far away from the dense galactic rings. There are fewer interstellar objects that could impact your planet, or disturb the Oort cloud and send comets into the inner stellar system causing more impacts. A rogue planet may wander by and change the orbits of planets in your system. There is also less of a chance of a close encounter with another star, also causing gravitational havoc. In the right location, you might even be gifted with a beautiful face-on view of a spiral galaxy.

The downside is that your neighbors would be far away, so interstellar travel would be even more difficult. But given the laws of physics, this may not ultimately matter.

It makes sense, living as we are at the edge of the safe zone of our galaxy, that we would have had some close calls in the past. I do wonder how lucky we have been. What are the odds that life on Earth has survived for almost 4 billion years? We came super close to complete extinction 252 million years ago. Do most systems in our situation not survive as long as we have?