Our Solar System is old. Our best estimates from radiometric dating of meteorites suggest the Sun and its planets (including Earth) were forming some 4.6 billion years ago. The Universe itself appears to be some 13.8 billion years old based on its observed rate of expansion and the properties of the Cosmic Microwave Background. That means, perhaps surprisingly, that the Earth has been here for a third of the lifetime the Universe has existed.  That is an impressive fraction to be sure, but let us look at a star which is much, much older. A star so old, it seemed to have been born before the Universe itself!

This is a Digitized Sky Survey image of HD 140283, the oldest star with a well-determined age in our galaxy. HD 140283 is starting to show its age, it is approaching the red giant phase of its existence. The Anglo-Australian Observatory (AAO) UK Schmidt telescope photographed the star in blue light. (Image credit: Digitized Sky Survey (DSS), STScI/AURA, Palomar/Caltech, and UKSTU/AAO)

This is a Digitized Sky Survey image of HD 140283, the oldest star with a well-determined age in our galaxy. HD 140283 is starting to show its age, it is approaching the red giant phase of its existence. The Anglo-Australian Observatory (AAO) UK Schmidt telescope photographed the star in blue light. (Image credit: Digitized Sky Survey (DSS), STScI/AURA, Palomar/Caltech, and UKSTU/AAO)

 

A seventh magnitude star in the constellation Libra, HD 140283 has always been seen as unusual.  For more than a century astronomers have been ware of its fast motion across the sky. It is speeding through our galactic neighbourhood at a staggering 800 000 miles per hour (1 280 000 km/h). This rapid motion shows us that the star is just passing through our region of space. Currently about 190 light years from the Sun, it is endlessly circling the Galactic Core in an orbit, vast in size and duration, which carries it down through the plane of our galaxy to the halo of ancient stars that encircle the Milky Way. Halo stars are old, dating back to the formation of the Milky Way some 12.6 billion years ago. This suggests HD 140283 is an elderly star but when astronomers used their tested techniques to calculate its age they got a shocking result. HD 140283 appeared to be 16 billion years old, more than two billion years older than the rest of the cosmos (measured to be 13.78 ± 0.037 billion years old)!

A star older than the Universe is an absurdity, enough to give cosmologists a few grey hairs, how could this be true? The star’s age was assessed by two independent techniques. Knowing a star’s intrinsic brightness is essential for estimating its age, to know its intrinsic brightness you must know its distance from Earth. Unfortunately the distance to HD 140283 was not known as precisely as astronomers would have liked.  Alternatively the chemical composition of stars should change at a known rate enabling their ages to be calculated by observing the relative proportions of the their constituent elements. However astronomers are refining their models of exactly how stars work all the time.  The estimated age of 16 billion years had an uncertainty of two billion years from the inaccuracy of its measured distance alone, if any of the predicted details of the star’s interior processes were off this uncertainty could be larger still. Astronomers revisited the matter of HD 140283’s age.

The most recent estimates using both improved theories of stellar structure and more accurate distance data from the Hubble Space Telescope give a more reasonable estimate of 14.5 billion years (with an uncertainty of plus or minus 800 million years). This makes HD 140283 the oldest known star with a well-determined age. It has been called the “Methuselah Star”, and although it looks quite normal at first, looking closely we see what a strange star it is. Its diameter is almost half as a large again as our own Sun, but its surface temperature is roughly the same as the Sun’s. This combination of size and temperature means HD 140283 is almost four times as bright as our Sun. None of these statistics are unusual, but the star’s composition has been known to be anomalous since the 1950s. Compared to other relatively nearby stars HD 140283 is “metal-poor”, in astronomical jargon this means it is lacking in elements heavier than hydrogen and helium. This may not seem particularly odd but is a vital clue in determining the star’s age.

As far as we know only hydrogen and helium formed in the seething chaos of the Big Bang. Every other naturally occurring element came later, formed by nuclear fusion in the giant atom crushing machines that are the cores of stars or even in the titanic stellar detonations called supernovae. The process in which stars turn light elements like hydrogen into heavier elements is called nucleosynthesis. For billions of years, new stars have formed from hydrogen and helium salted with traces of heavier elements forged inside previous generations of stars. A star rich in hydrogen and helium but deficient in all the heavier elements must be a very old star, dating back to an early phase of the Universe’s life before heavy elements were common. HD 140283 fits this description perfectly having only 1/250th  of the heavier element content of our Sun and other stars in our part of the Galaxy.

Metal-poor stars like our subject are said to belong to Population II, today’s stars with a richer mix of elements are Population I, while Population III are theoretical stars composed of hydrogen and helium only. Population III represents the very first generation of gigantic stars dating from only a few hundred million years after the Big Bang. No Population III stars are believed to exist in the present era, as such large stars would live short fiery lives a few million years long before exploding as supernovae. Any later generation of stars had to be built from the hot gases of these ancient detonations but could not form until the debris had cooled down enough. Theorists expected there to have been a distinct gap between these two generations of stars. HD 140283 ‘s great age suggests that the gap between Population III and II stars was shorter than anyone had though. HD 140283 and its stellar generation may have arose only millions of years after the explosive deaths of their predecessors.

HD 140283 is a visitor from the milky way's halo. Population II stars are there, as they are in globular clusters and the central bulge of galaxies. (Image credit: NASA / ESA / A. Feild (STScI))

HD 140283 is a visitor from the Milky Way’s halo. Population II stars are common there, as they are in globular clusters and the central bulge of galaxies. They are rare in the galaxy’s disc which is dominated by Population I stars. (Image credit: NASA / ESA / A. Feild (STScI))

 

It is tempting to speculate if HD 140283 could have a family of planets, even one bearing life. Imagine beings that have evolved over most of the age of the Universe , what heights of achievement could they have attained! (If this kind of speculation fascinates you, you really need to read Stephen Baxter’s Xeelee books!) Sadly life is extremely  implausible around HD 140283, any planets it may have will be gas giants,  great globes of hydrogen and helium like Jupiter and Saturn but lacking the organic compounds which colour their atmospheres. An ancient planet of this sort has been discovered, in the form of a 13 billion year old gas giant in an odd binary system in the globular cluster M4.  Gas giant planets around HD 140283 are perfectly plausible but worlds like Earth or Mars are made of heavy stuff, iron, oxygen, silicon and so on. When HD 140283 was born heavy elements were so scarce it is hard to imagine it could accumulated enough from the primordial nebula where it was born to possess any rocky planets.

As the Universe has grown old around it HD 140283 has seen many changes. Born in a primeval dwarf galaxy, the star blazed bright in a Universe smaller and denser by far than it is now. After a billion years or more the developing Milky Way’s gravitational grip seized the dwarf galaxy. Eventually, over 12 billion years ago, the dwarf galaxy was absorbed into the growing Milky Way. The star’s current elongated orbit is evidence of this long ago cannibalism. This remarkable “living fossil” star is a direct link to a lost and mysterious epoch in the history of the Universe.

(Article – 300th since Astronotes changed to blog format – by Colin Johnston, Science Communicator)


27 Comments

kunal · February 17, 2017 at 02:55

Is that possible another galaxy is present ….?

Sam Halls · November 1, 2015 at 19:53

According to this website here, WASP-29b is 15 billion years old. I’m not sure if that’s correct.

Gene Preston · August 18, 2015 at 21:19

There is one thing to consider in measuring time and that is the rate of flow of time itself which is a function of gravity potential. As a clock is raised to a higher gravity potential the clock speeds up compared to a clock that is not raised to a higher potential – i.e. the Pound-Rebka experiment in agreement with GR. As the universe expands what happens? Mass moves farther apart which causes a higher gravity potential with time. So if the universe was more compact in the past the clocks must have ran more slowly than today. Measuring the age of the universe with today’s clocks projects backwards to 13.8 billion years at today’s rate of time flow. However if you were to make that measurement a billion years ago the age of the universe might have been 13.3 billion years. So the universe being 13.8 billion years old using today’s clocks means the actual age is likely to be much longer since clocks ran more slowly in the past. This concept has one other feature. Our ever faster rate of time flow now would make objects appear to red shift even more than a linear projection, i.e. the acceleration that we now observe. So you see that taking a variagle rate of time flow into account in accordance with GR will predict the acceleration we now observe. Why has no scientist done this analysis and written a paper on what seems obvious to me.

    James · October 20, 2017 at 20:31

    Have you found any literature on this yet?

    James · October 21, 2017 at 11:27

    I haven’t sussed the equations for Gravitational TIme Dilations, but it strikes me that as we go back closer to the Big Bang, those clocks will really start whizzing. What looks to us as a millionth of a second after the Big Bang may have been a trillion years local time. Similarly in a trillion years time, observers will see our epoch as being within moments of the Big Bang, maybe by a millionth of a second or so…is it possible that this might produce a result that is not only orders of magnitude greater than 13.8 billion years,but one which is immeasurably larger?

      James · October 21, 2017 at 20:20

      I feel like an idiot. It’s the reverse of course. Seen by an observer, the clock runs slower the closer it gets to the source of gravity so the closer we get to the Big Bang the slower the clock if there were an observer to see this phenomenon, which produces a paradox as the observer has to be part of this universe. Never mind…

Rumo · December 18, 2014 at 00:05

I got quite tired of hearing people suggest that because man created the concept of time, that we also affected it when we did so. All we did was create a way to understand it; not actually create it. Also, can we leave religeon out of this, please? I was under the impression that this was a rational debate

    Hector · November 4, 2016 at 19:00

    Time is just measured movement. Nothing else.

Omar Jamal · December 6, 2014 at 13:11

I personally think that this discovery could be evidence of their actually being evidence for the multiverse. But i could be dead wrong.

Cameron Reed · November 4, 2014 at 18:21

Well how do you know that the big bang theory is correct you can say you have proof but you do not have a reliable source if so. I believe that God has created the universe. And you could say who created god he was already here and will never go away. I believe that god has made other life forms on distant planets. and until we can get them here or we go there we will not be able to meet with them. and admin can you absolutely tell Alex that the universe is 13.7 billion years old so he is not wrong and you are not wrong those are opinions. And i would like to say that Im not trying to persuade you towards me Im just stating my opinion Genisus:1.1 In the beging God created the heavens and earth.

alex · October 27, 2014 at 01:17

Couldnt you argue that maybe there was empty space before the big bang and time and matter only existed after the big bang.

    admin · October 27, 2014 at 09:55

    Dear Alex, sorry but that’s not the way it works. Based on the measurable rate of expansion of space the Universe itself must have been very tiny 13.7 billion years ago.

Keith · October 21, 2013 at 23:16

Space was a product of the Big Bang. The problem with thinking of the Big Bang as an explosion is you try to visualize it happening in some finite location. The Big Bang happened EVERYWHERE. As the universe expanded out, matter could only travel less than the speed of light. The only thing that can travel faster than light is nothingness. Empty space is a very real thing. It’s speedier expansion created the distances now present between matter. Space’s properties are seen in the permativity of free space which limits the speed of light to 300,000,000 m/s.

    Hysen berisha · September 29, 2014 at 03:45

    Where did you get the notion that there is such thing as empty space? Are you and academic of astrophysics and have you done any research in that matter? As of right now all scientist and astrophysicists know that here is no such thing of empty space any where in the universe; or anywhere else for that matter. Your comment is purely rubbish.

      Talavar · December 5, 2014 at 16:08

      Easy, there Hysen.. lol.. Not everyone has a total grip on our current scientific theories. He’s on the right track.. Do less insulting and more educating. humanity progresses slowly through small collective bits of conversation. Insulting simply perpetuates ignorance. You should attempt to be more helpful, and apply constructive criticism.. Trust me, it goes a lot farther than insults!

Brian Stephenson · September 18, 2013 at 16:20

Surely, space must have always existed…as a place in which the big bang was eventually to happen. Space did not `happen` at any point in time…unless you know differently?

It could be argued that time and distance did not exist until man found a way of measuring it, that is to say man `invented` time, and that in itself is an accepted construct that may well exist differently elsewhere in the vastness of space.

    Talavar · December 5, 2014 at 16:03

    Space is actually not an absence. Space is “something”. It bends and twists. it can be influenced by gravity. This very nature shows an actual existence, rather than non-existence. This is actually strange, as it leaves one to ponder on “then what is a total absence?” The fact that we can actually measure time and distance also point to an existence. And as strange as it sounds, space actually weighs something. It weighs roughly the amount of 3 hydrogen atoms per 3 square meters. You can look up “cosmological constant” It will explain all sorts of tidbits about it. Good stuff! 🙂

    Talavar · December 5, 2014 at 16:45

    ((Continued)) On top of this Distance would not have existed before the big bang, as distance by definition is the measurement of space between two objects. Before the big bang, there was nothing to measure! Not even space itself existed! (according to current theory)

Philip Smeeton · August 19, 2013 at 21:22

Time is eternal,infinite. If the big bang theory is correct there are countless other bigbangs,universes in the same dimension as us spread throughout the infinity of space. Time and space are independent of bigbangs, which need time and space in order to exist and evolve.

    Gibbygoo · September 4, 2013 at 02:33

    Where did you hear that, Philip? Couldn’t you argue the opposite–that time and space can only exist as a result of the bang? To the best of my knowledge, neither standard nor m-theory models propose time and/or space existing outside of the universe.

    Cameron Reed · November 4, 2014 at 18:15

    Well how do you know that the big bang theory is correct you can say you have proof but you do not have a reliable source if so. I believe that God has created the universe. And you could say who created god he was already here and will never go away. I believe that god has made other life forms on distant planets

      Augustus Iliano · February 6, 2016 at 19:56

      You do not have a reliable source. Those are just fairy tails. All scriptures from the past civilizations about religion are just made up stories, to try to explain the world, and it’s phenomenons.

    Talavar · December 5, 2014 at 15:56

    Philip, this is actually incorrect. Physics has shown us that time is in-fact not infinite. Time and our physical laws began at the moment of the big bang. I know it’s hard to grasp, but not even space existed before the big-bang. This is the universally accepted theory at this current time, as all evidence points to it. You can prove that time is actually finite simply by imagining you are going backwards in time. If time is infinite, then there was also an infinite amount of time before now, therefore, you could never reach this point in time. This in itself rules out the possibility of infinite time.

      Samuel Vasilevskiy · September 5, 2015 at 18:31

      The only “universally accepted theory” about the big bang is that physics breaks down well before we reach that point of matter density. What time and space were before, and if they even existed, are currently left to speculation. It could have been that nothing existed, and then, suddenly everything existed. As far as we know, it is just as likely that time and space ran backwards until the point where matter condensed enough to attain big bang conditions, then rebounded. Also, time being infinite does NOT mean there is infinite time between two points in time. There are infinite real numbers between 1 and 3, but the distance between them can easily be measured as 2.

L’espace, c’est n’importe-quoi | Et si on disait du mal ? · June 4, 2014 at 21:40

[…] Une étoile plus ancienne que l’univers […]

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