Yad Al Jausa — and other bad-ass stars

Actually this one is called Betelgeuse, and it’s going to blow up soon. So at least learn how to pronounce its name.

This star is located in the constellation of Orion, and is one of the brighter stars in the heavens. I have known it since early childhood, when my father pronounced it Bet-ai-goi-tse, as all Germans do. Actually the name is a typo. Originally it was derived from the Arabic يد الجوزاء, which is normally transcribed Yad al-Jauzā’ and means “the shoulder of Orion”. Medieval translators, however, misread the Arabic letter for Y as B, and the English pronunciation migrated to some variation of Bettle-juice or Beetle-juice. In other languages you will find some more adventurous pronunciations. Perhaps it would be best we call it Yettle-juice. But I think maybe not.

Anyhow, my father use to tell me, on dark nights, the story of Betelgeuse and Rigel. They are on the opposite sides of Orion’s belt. Orion is one of the most recognizable constellations in the night sky, located on the celestial equator and visible throughout the world. The Arabs saw in it a warrior with sword and shield. The images on the left are from this very informative Wikipedia page.

Betelgeuse is the ninth-brightest star in the night sky. Actually it varies in magnitude from +0.0 to +1.3. The Bayer catalogue name α Orionis is not justified — the blue giant Rigel (which my father pronounce Ree-gel) is generally brighter and only occasionally outshone by Betelgeuse, which is a clear orange-red, while Rigel is crisp blue-white. Look up into the sky on a clear winter night and admire this most beautiful (and very interesting) constellation.

An aside: I feel a need to mention an incident during a visit to Argentina. We had a campfire dinner, and at some stage our guide looked up and said: “Hey, Orion’s rising.” — “You are wrong,” I said, “that’s not Orion.” When the constellation was fully visible I had to admit he was right. But the constellation was upside down! Southern hemisphere!

Back to today’s scare story: Betelgeuse is a very young star, hardly more than ten million years old. But it is big. If it were in the place of our Sun it would encompass the orbits of the planets Mercury, Venus, Earth and Mars, reaching close to Jupiter. If you want to visualise how big that is you can read my article “True dimensions of Space” and scroll through Josh Worth’s tediously accurate map of the solar system”.

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This video, by a VFX Artist on the largest stars in our galaxy, gives you a vivid impression of how big Betelgeuse is. On this scale (1:190,000,000) our own sun is a 24-foot-wide ball on the helicopter landing deck (bottom right), and the earth is the size of a tennis ball. It’s all truly mind boggling.

In my childhood my father built me a fairly powerful refractor telescope, which I used all the time. The Moon and planets were very interesting, the stars however somewhat disappointing, since they were always just points of light — never disks. The only challenge was to look for the faintest of them. Or resolve double or multiple star systems. Which I duly did.

With more powerful (and expensive) telescope equipment Betelgeuse is the only star, I believe, that can be resolved from the earth as more than a point.* This image was captured using the NACO adaptive optics instrument on ESO’s Very Large Telescope.

* After reading this article my astronomer friend Dr. Christian Sasse of iTelescope reminded me that our Sun is also a star. Oops. Also telescopes, he says, have improved and today over 20 stars can be resolved beyond a point source. Okay, but Betelgeuse was the first of the bunch.

Betelgeuse takes up roughly 37 milli-arcseconds of the sky, which would be the width of a tennis ball in orbit at the height of the International Space Station. In the image you see the stellar disk, an extended atmosphere and a plume of surrounding gas.

Betelgeuse is very big, but it is also over 600 light-years away. That is enough to make it fairly harmless to us when it blows up. Which is what it is expected to do. As mentioned above, this is a very young star, just ten million years old. It has spent around 40,000 years as a red supergiant, which means it has been burning helium instead of hydrogen, and creating oxygen, carbon and other elements up to iron, number 26 on the periodic table, in its core. Such stars are expected to end their lives when their core collapses, in a supernova explosion. And that is likely to happen in the very near future — astronomically speaking that translates to the next 100,000 years. It could be later than that, but it could also be tonight that it explodes. Theoretically it could even have already gone supernova, sometime in the last 600 years —and the light and radiation would still not have reached us.

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This is what the Betelgeuse Supernova will look like over London and Sydney (video by V101 Science)

But let’s not panic: the 600+ light-year distance fortunately means that the effects of Betelgeuse going supernova will most likely not bother us too much. It will appear like a very bright star in the night sky, as bright as the moon, and will also be visible during the day. But the material ejected will have cooled to harmlessness long before it reaches the Earth. And the radiation will only have a minor impact — the source is too far away to significantly ionize Earth’s atmosphere.

How do we know that, how can we be so sure? Well, apart from meticulous astrophysical calculations, you should remember that we have been through this before, in historical times: in 1572 Tycho’s Supernova, SN 1572, went off in the constellation Cassiopeia — the inset is an infrared image of the remnants today. This explosion was seen by many astronomers (and interpreted by some as an evil omen). It was –4.0 in magnitude — as bright as Venus — and remained visible for over a year, gradually dimming until it faded from view. The supernova explosion took place between 8000 and 10,000 light years from Earth.

Half a generation later, SN 1604, also know as Kepler’s Supernova, exploded. It happened in 1604 —just five years before Galileo had constructed his first primitive telescope and transformed astrophysics. The supernova was 23,000 light-years away from us and reached a maximum brightness of –2.5. That was the last time, I believe, that humans saw a supernova with naked eyes — perhaps with the exception of SN 1987A, which occurred in our dwarf galaxy neighbour, the Large Magellanic Cloud, three decades ago, and reached a maximum luminosity of 3 (outshining its entire host galaxy). You could see it if you knew exactly where to look. I did.

The first time human beings saw and recorded a supernova was just under a thousand years ago. This became clear, in the 19th century, when astronomers found a strange object they called the “Crab Nebula.” It was first thought to be a comet, but since it didn’t move across the sky the idea was soon discarded. More powerful telescope equipment in the 20th century made it out to be a nebula that was expanding. Tracing back the expansion of the gas clouds revealed this must be the result of a stellar explosion 900 year earlier. And indeed, historical records showed that Chinese astronomers had recorded a “new star,” bright enough to be seen in the daytime, in the year 1054.

Clearly that was a supernova. It had a maximum brightness of –4.5- to –7, and remained visible for two years. The Crab Nebula is expanding matter from the supernova the Chinese had seen. In the mid-1900s a neutron star was identified in the middle of the nebula. It is under 30 km in diameter, highly magnetized and rotating at a rate of (I kid you not) 30.2 times per second! While doing this it emits pulses of gamma, X-rays and radio waves, at greater strength than any other source in our night sky. In fact astronomers have used these rays and waves to analyse matter in our Solar System through which they pass. Distance of the pulsar and nebula: around 6000 light years.

Recently (November 2019) there has been speculation that the disappearance of megafauna at the end of the Pliocene period, 2.6 million years ago, may not have been the result of climate change but in fact have been caused by a supernova explosion — or a series of them. The idea, described here, was brought on by the discovery of the radioactive isotope iron-60, which is associated with supernovae, in the sea floor from that period of time.

Now Betelgeuse, at around 600 light years, is much closer than any of the above supernovae. But still its explosion will not be devastating for Earth. That would only be the case if a supernova were to go off closer than 25 light-years away. Gamma rays would convert molecular nitrogen and oxygen in our atmosphere into nitrogen oxides, the ozone layer would be depleted, phytoplankton would be destroyed, the base of the marine food chain eliminated. Recent studies have found indirect chemical evidence of supernova explosions around 300 light years distant that happened a few million years ago. They bombarded Earth with four times the amount of radiation Betelgeuse could produce, but there is no clear sign that this had any effect on life. No Chicxulub-type mass extinction or anything like that.

So it’s pretty much all-clear for Betelgeuse, and astronomers have yet to find a close-by star that has supernova potential. Of course, if you are addicted to worrying you can look up “white dwarf binary system” in which one very faint dwarf star accretes mass from its companion and can go supernova. These systems are hard to spot and to identify, so there may be some lurking close by. Astronomers think such a near-Earth supernova event might occur every 15 million years, others estimate they should happen every 240 million years. So you see we really don’t know.

But why waste your time not worrying? Here’s something that can give you more sleepless nights. I was reminded to include it by Christian Sasse, mentioned above.

Betelgeuse is bad-ass, but far enough away. However we can thank our lucky stars (pun intended) that Eta Carinae is even further: seven and a half thousand light years. Because the “bomb star” is something really special. While Betelgeuse is around ten to twenty times as massive as the sun, Eta Carinae (picture on the left by NASA, ESA, Hubble) is a double star system that has a total mass of over a hundred times that of our Sun — and a combined luminosity five million times greater. Yes, that’s right, it is currently five million, 5 x 1⁰⁶, times brighter than Sol. I say “currently” because it has been even brighter in the past. In the 19th century it suffered a “Great Eruption” — this 4th-magnitude star suddenly outshone Rigel. That was in 1837, and in March 1856 it became the second-brightest star in our skies (before fading back to naked eye invisibility). In 1892 there was another similar eruption, once again with supernova intensity. But somehow Eta C survived — this fascinating animation shows how it most likely to have happened. Today the system has brightened to a 4.5 magnitude star you can easily pick out with binoculars.

Clearly Eta Carinae is at the end of its life. The accretion of matter from one of the binary stars from the other is going to speed things up. Fortunately due to its distance it will not be mortally dangerous to Earth. But we’ll experience is the most spectacular light show ever. And crab or octopus astronomers in other galaxies will look up and say “Blamm!!, they had a really big one!” Eta C will outshine the entire Milky Way — all two hundred billion stars of it.

In closing I would like to remind you, dear reader, that the human body consists of 10% hydrogen, generated from primordial protons and neutrons in the first minutes after the Big Bang, 13.8 billion years ago. But the elements that make up the other 90% — oxygen, carbon, nitrogen, calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium, and many others, did not exist at the time. So where did they come from?

Well, apart from hydrogen, every atom in your body was forged billions of years after the Big Bang, in the centre of stars. The matter there, elements heavier than hydrogen and helium, normally remain virtually forever within the star. But occasionally they are released in the supernova explosions and become available for the formation of new stars — but also planets, and the creatures living on them. So supernovae are directly responsible for providing the building blocks of life to the rest of the galaxy. 10% of you may be from the Big Bang, the origin of the Universe, but the remaining 90% is “stardust”, matter that formed at the centre of stars and released into the galactic space by cataclysmic supernova explosions.

Addendum: Today (Christmas Eve 2019) many astronomy sites are reporting that Betelgeuse has become noticeably dimmer since late October and is at a “modern all-time low” magnitude. “One of two things could be happening here,” C|net speculates. “Betelgeuse is a variable star that has been dimming and re-brightening for millennia at this point. We could just be seeing its most significant dip in the past half-century or so, which is less than the blink of an eye in this star’s lifespan. The other possibility is that Betelgeuse is finally out of fuel and it has begun to collapse in on itself — a process that is expected to end in a spectacular supernova explosion.” So keep watching — the dimming can be noticed with naked eyes.

Like this article? Interested in astonomy and Space? Then read:

Written by

Frederic Alois Friedel, born in 1945, science journalist, co-founder of ChessBase, studied Philosophy and Linguistics at the University of Hamburg and Oxford.

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