New confirmation of Einstein's General Theory of Relativity

June 7, 2017, Embry-Riddle Aeronautical University
This illustration reveals how the gravity of a white dwarf star warps space and bends the light of a distant star behind it. Credit: NASA, ESA, and A. Feild (STScI)

Albert Einstein predicted that whenever light from a distant star passes by a closer object, gravity acts as a kind of magnifying lens, brightening and bending the distant starlight. Yet, in a 1936 article in the journal Science, he added that because stars are so far apart "there is no hope of observing this phenomenon directly."

Now, an international research team directed by Kailash C. Sahu has done just that, as described in their June 9, 2017 article in Science. The study is believed to be the first report of a particular type of Einstein's "gravitational microlensing" by a star other than the sun.

In a related perspective piece in Science, entitled "A centennial gift from Einstein," Terry Oswalt of Embry-Riddle Aeronautical University says the discovery opens a new window to understanding "the history and evolution of galaxies such as our own."

More specifically, Oswalt adds, "The research by Sahu and colleagues provides a new tool for determining the masses of objects we can't easily measure by other means. The team determined the mass of a collapsed stellar remnant called a white dwarf star. Such objects have completed their hydrogen-burning life cycle, and thus are the fossils of all prior generations of stars in our Galaxy, the Milky Way."

Oswalt, an astronomer and chair of the Department of Physical Sciences at Embry-Riddle's Daytona Beach, Florida campus, says further, "Einstein would be proud. One of his key predictions has passed a very rigorous observational test."

This time-lapse movie, made from eight Hubble Space Telescope images, shows the apparent motion of the white dwarf star Stein 2051 B as it passes in front of a distant star. The observations were taken between Oct. 1, 2013, and Oct. 14, 2015. The path of Stein 2051 B, due to its proper motion combined with its parallax due to the motion the Earth around the Sun, is shown by the wavy cyan line. Its proper motion in one year is shown by an arrow. Its parallax, enlarged by a factor of 5, is shown by an ellipse. Credit: NASA, ESA, and K. Sahu (STScI)
Understanding 'Einstein Rings'

The gravitational microlensing of stars, predicted by Einstein, has previously been observed. Famously, in 1919, measurements of starlight curving around a total eclipse of the Sun provided one of the first convincing proofs of Einstein's general theory of relativity - a guiding law of physics that describes gravity as a geometric function of both space and time, or spacetime.

"When a star in the foreground passes exactly between us and a background star," Oswalt explains, " results in a perfectly circular ring of light - a so-called 'Einstein ring.'"

Astronomers made the Hubble observations of the white dwarf, the burned-out core of a normal star, and the faint background star over a two-year period. Hubble observed the dead star passing in front of the background star, deflecting its light. During the close alignment, the distant starlight appeared offset by about 2 milliarcseconds from its actual position. This deviation is so small that it is equivalent to observing an ant crawl across the surface of a quarter from 1,500 miles away. From this measurement, astronomers calculated that the white dwarf’s mass is roughly 68 percent of the sun’s mass. Credit: NASA, ESA, and K. Sahu (STScI)

Sahu's group observed a much more likely scenario: Two objects were slightly out of alignment, and therefore an asymmetrical version of an Einstein ring formed. "The ring and its brightening were too small to be measured, but its asymmetry caused the distant star to appear off-center from its true position," Oswalt says. "This part of Einstein's prediction is called 'astrometric lensing' and Sahu's team was the first to observe it in a star other than the Sun."

Sahu, an astronomer at the Space Telescope Science Institute in Baltimore, Maryland, took advantage of the superior angular resolution of the Hubble Space Telescope (HST). Sahu's team measured shifts in the apparent position of a as its light was deflected around a nearby white dwarf star called Stein 2051 B on eight dates between October 2013 and October 2015. They determined that Stein 2051 B - the sixth-closest to the Sun - has a mass that is about two-thirds that of the sun.

"The basic idea is that the apparent deflection of the background star's position is directly related to the mass and gravity of the white dwarf - and how close the two came to exactly lining up," explains Oswalt.

This animation shows the motion of a white dwarf star passing in front of a distant background star. During the passage, the faraway star appears to change its position slightly, because its light path has been altered by the white dwarf’s gravity. When the white dwarf Stein 2051 B passed in front of a background star, the distant star’s light was offset by only about 2 milliarcseconds from its actual position. This deviation is so small that it is equivalent to observing an ant crawl across the surface of a quarter from 1,500 miles away. From this measurement, astronomers calculated that the white dwarf’s mass is roughly 68 percent of the sun’s mass. Credit: NASA, ESA, and G. Bacon (STScI)

Among astronomers, the findings are significant for at least three reasons, according to Oswalt:

  • First, the research "solves a long-standing mystery about the mass and composition of Stein 2051 B," he says.
  • Second, he notes, "Sahu's team nicely confirms astrophysicist Subrahmanyan Chandrasekhar's 1930 Nobel Prize-winning theory about the relationship between the mass and radius of white dwarf stars. We now know that Stein 2051 B is perfectly normal; it's not a massive white dwarf with an exotic composition, as has been believed for nearly a century."
  • Third, Oswalt concludes, "This new tool for determining masses will be very valuable as huge new surveys uncover many other chance alignments over the next few years."
Looks can be deceiving. In this Hubble Space Telescope image, the white dwarf star Stein 2051B and the smaller star below it appear to be close neighbors. The stars, however, reside far away from each other. Stein 2051B is 17 light-years from Earth; the other star is about 5,000 light-years away. Stein 2051B is named for its discoverer, Dutch Roman Catholic priest and astronomer Johan Stein. Credit: NASA, ESA, and K. Sahu (STScI)

For the average star-gazer, he says, the findings are meaningful because "at least 97 percent of all the that have ever formed in the Galaxy, including the Sun, will become or already are white dwarfs - they tell us about our future, as well as our history."

Dr. Terry Oswalt discusses results from a new study by Sahu et al., reporting the first successful measurement of a star’s weight using Einstein’s theory of general relativity. Dr. Oswalt gives a physical demonstration using props to show how a star’s gravity deflects light. Scientists can then use this deflection of light to calculate the weight of star. Credit: Embry-Riddle Aeronautical University / Robert H. Score

Explore further: A rare opportunity for planet hunting in Alpha Centauri A predicted for 2028

More information: K.C. Sahu el al., "Relativistic deflection of background starlight measures the mass of a nearby white dwarf star," Science (2017). … 1126/science.aal2879

"A centennial gift from Einstein," Science (2017). … 1126/science.aan2996

Related Stories

What is gravitational lensing? (w/ Video)

February 6, 2015

Everyone here is familiar with the practical applications of gravity. If not just from exposure to Loony Tunes, with an abundance of scenes with an anthropomorphized coyote being hurled at the ground from gravitational acceleration, ...

Space telescopes pinpoint elusive brown dwarf

November 10, 2016

In a first-of-its-kind collaboration, NASA's Spitzer and Swift space telescopes joined forces to observe a microlensing event, when a distant star brightens due to the gravitational field of at least one foreground cosmic ...

Hubble's bright shining lizard star

April 28, 2017

In space, being outshone is an occupational hazard. This NASA/ESA Hubble Space Telescope image captures a galaxy named NGC 7250. Despite being remarkable in its own right—it has bright bursts of star formation and recorded ...

Recommended for you

An exoplanet with an 11-hour orbit

February 22, 2019

The Transiting Exoplanet Survey Satellite (TESS) was launched on April 18 of last year with the primary objective of discovering transiting planets smaller than Neptune around stars bright enough for spectroscopic investigations ...


Adjust slider to filter visible comments by rank

Display comments: newest first

5 / 5 (1) Jun 07, 2017
Once again Einstein is correct - a veritable God among the cranks
1 / 5 (9) Jun 07, 2017
TGR has been proven better in 1919 using the Sun. Asking why? because there could be no enough "dark matter" between Earth and the Sun to be taken into consideration.

This experiment was not as convincing since such a gravitational lensing was also observed where there were no passing stars or stars at all and in such a case observed gravitational lensing was attributed to invisible dark matter" clustering.

So light bending was observed without any normal matter around so the original Einstein experiment offers better proof.
Jun 07, 2017
This comment has been removed by a moderator.
4.3 / 5 (11) Jun 07, 2017
There can be a variety of causes at play....
Name one.
Jun 07, 2017
This comment has been removed by a moderator.
4.3 / 5 (14) Jun 07, 2017
And in other news, "Pseudo-science Armchair Nobodies Continue to Dispute Einstein!"

4.5 / 5 (15) Jun 07, 2017
> What they have observed is a deflection of light, which can of course just as easily be the result of electromagnetic fields as well.

No, it really can't. Electromagnetic fields do not deflect light. In some situations they can modify a medium to deflect light in different ways, but not on their own. Electromagnetic fields only act on electrically charged particles, and light has no electric charge, therefore cannot be moved by EM fields.
not rated yet Jun 07, 2017
Da Schneib
4 / 5 (8) Jun 08, 2017
Electromagnetic fields can't act on uncharged photons.

This is another of the EUdiot lies.
2 / 5 (4) Jun 08, 2017
1.8 / 5 (10) Jun 08, 2017
it not gravity but due to the Laws of Refraction in different Mediums... it not gravity but Laws of Refraction in different Mediums acts as a kind of magnifying lens, brightening and bending the distant starlight....

Jun 08, 2017
This comment has been removed by a moderator.
Jun 08, 2017
This comment has been removed by a moderator.
5 / 5 (6) Jun 08, 2017
While "...Historians and sociologists have had a lot to say about this ..." [1919 expedition], scientists and astronomers have since shown that the deflection of light is correct. So whether or not it was measured correctly in 1919 is a point only of interest to historians.
4 / 5 (2) Jun 08, 2017
Can someone you has gone through the research help me understand if they have accounted for refraction of light through the stars atmosphere?
4.6 / 5 (11) Jun 08, 2017
Stars are so small, in terms of cosmology, that they're still mostly just 'point' sources of light. When you see them spread out over an area in a picture, that's mostly distortions from the telescope and sensor. So if Einstein thought two stars broadly aligning was practically impossible, it's way less likely to imagine that the light has grazed through the not-glowing 'atmosphere' of a star.

But even if it had passed through such an atmosphere, then we would see spectral lines from the atoms/ions in the gas of the atmosphere as it did so.

I point this out to also follow up on the above mentions of whether EM fields can deflect light. EM fields *can* modify media (like an atmosphere, say) to change how it deflects light, but if such an effect occurred here, we would see evidence of that medium as well.
4.6 / 5 (10) Jun 08, 2017
What... do you think polarization, edge diffraction, frequency separation in a prism, photon capture and the impact boundary that results in radiation pressure are?... heat "mirage"
With the exception of polarization, these are all instances of photons interacting with a medium, i.e. matter consisting of charged particles. I think the other commenters are assuming electromagnetic fields in free space.
Jun 08, 2017
This comment has been removed by a moderator.
4.3 / 5 (12) Jun 08, 2017
I'm not sure what the discussion here is about. Gravitational microlensing has been used for some years as a method of detecting exoplanets. That this microlensing occurs is not in doubt. It has been confirmed by follow up observations. It is a done deal.

The fourth microlensing planet revisited
4.6 / 5 (11) Jun 08, 2017
So, pray tell, when the observation of the lensing predicts what should happen based purely on gravity, and those predictions are confirmed, what else are we supposed to think? That God did it? Where is the alternative explanation within the scientific literature? More to the point, what does it predict, and where can I read it? If you can't answer those questions you have nothing more than hot air, based on the fact that you don't like a particular, well observed phenomenon that doesn't fit into your worldview.
Links to the above, please.
4 / 5 (12) Jun 08, 2017
Crap. You have shown nothing. As I requested show me where this has been spelled out in a scientific paper. Not your vague rantings with nothing to back it up. Please point me to the scientific geniuses who are questioning this. WHERE IS THE WORK? Not your vague drivel.
And what sort of experiment would you like? How are you getting two stars in a fecking laboratory.? Jesus. Einstein predicted it before we ever saw it. Nobody has ever claimed it was some wishy washy EM bollocks. Except you, as far as I can see. So back it up.
Like I said, this is a done deal. Nobody is questioning it. If they are, then show me their work.
1.5 / 5 (8) Jun 08, 2017
The yearning to find confirmation of a theory results in bias... it's called researcher's bias.

Scientists should be attempting to falsify the theory to prove its validity. Strangely enough, there is absolutely no way to falsify this theory because every time that occurs, an ad hoc explanation is postulated.

Falsify > Confirm .... that's how science attempts to avoid incorrect paradigms.

So tell me...we see a lensing effect... OK. If you were a scientist and wanted to actually prove the validity of GR in just this example, how could you conceivably ever falsify the idea that gravity (and more so the curvature of space itself) must be the source of that lensing? What observation could you make that would show gravity must not be the answer?

The answer... you can't. And that's the consequence of a poor theory.
3.9 / 5 (11) Jun 08, 2017
"Appeals to authority do not constitute scientific debate. What you believe and why you do is your worldview and that you accept what you are being told is your choice. I am dealing in actual physical interactions and you are plugging a theory with more holes and question marks than should exist given how definitive you state things that are far from definitive."

There is no scientific debate. There is no alternative, scientifically valid hypothesis. You cannot point to one, despite repeated requests. Until you can, there is nothing to debate.

P.S. note to all cranks; posting sh*te on a science news website does not constitute an alternative scientific hypothesis! Cranks everywhere are doing that all the time. Write it up. Scientifically. Then get back to us. Pointless debating non-existent bobbins with unqualified laymen.

4.1 / 5 (13) Jun 08, 2017
What observation could you make that would show gravity must not be the answer?

The answer... you can't. And that's the consequence of a poor theory.

Crap. Tell it to Einstein, woo boy. What you do is say...."Mr. Einstein, if your theory is correct, what would happen if a large mass is directly in front of another one? Of course, we've never seen this, but what is your prediction?"

And then Mr. Einstein tells you. And many years later is shown to be correct. Then the cranks come along with their uneducated bollocks saying that he's got it all wrong. And when you ask them for a scientific paper outlining how he's got it wrong, they can't come up with one. Because it doesn't exist. And they think that posting their crap on a site such as this means that they have thrown doubt onto a well accepted theory, matched by observation, as predicted before it was ever seen. Guess what? No, they haven't, and nobody is taking a blind bit of notice of their woo.
3.9 / 5 (11) Jun 08, 2017
^^^And still cannot provide any scientific literature to back up these imbecilic claims. And on it goes. Do you ever wonder why nobody ever takes cranks seriously? Show us the alternate hypothesis. There isn't one, so I'm not holding my breath.
Let me make this easy for the hard of thinking; if there were an alternative, somebody, far smarter than you, would have thought of it, and written it up in the scientific literature. Use Google scholar. Find that (non-existent) paper, and post a link to it here. It ain't rocket science. Otherwise there is no debate. You need two competing hypotheses for that. Only one exists. Except in your mind. Which is no use to anyone, until you write it up. That is how science works. Not by posting vague rubbish on a science news website. In case you hadn't noticed.
4.1 / 5 (14) Jun 08, 2017
This is like that debate in which you refused to admit that an increase in photons meant that something was brightening

Wrong. Not me.

For the cognitively challenged, the alternate hypothesis has been iterated here by myself three times and Chris Reeve twice. Only an idiot would assume that a hypothesis has to originate from a specific individual or group

Unqualified cranks posting on a science news website comments section IS NOT an alternative hypothesis! Scientific debate takes place within the scientific literature. Show me where that debate is. That is, where is the peer reviewed paper? Any idiot can post rubbish on the internet. Happens all the time. Without a scientifically valid hypothesis, there is nothing to debate. Reeve believes in Velikovskian bollocks, who on Earth would take him seriously?

5 / 5 (13) Jun 08, 2017
This is the core of bschott's hypothesis:
"Matter is nothing more than an increase in density, interaction and structure of a given number quantum fields and the energy intrinsic to said fields . These fields are magnetic"

This of course bears 0 resemblance to anything meant by matter, density, interaction, structure, quantum fields or magnetic fields within the realm of science.

Matter doesn't, strictly speaking, have a definition in fundamental physics. There are just particles that arise within fields, those fields having some coupling to each other described by some group symmetry. We can say that certain varieties of these particles, when bound together in large configurations form something that classically we'd call matter.

And precisely zero of those fields are 'magnetic.' There is an electromagnetic field, but it only exists as both electric and magnetic together, never as separate fields.
4 / 5 (12) Jun 08, 2017
And on websites, at coffee machines, over breakfast on television...yup scientific debate has no restrictions on where you can or cannot do it.

And have zero impact on scientific thinking. Nobody gives a rat's arse what you, Reeve or I think and post on an irrelevant website. The only way to challenge a theory is to posit it within the scientific literature. Without that there is no debate.

5 / 5 (4) Jun 09, 2017
EM fields have nothing to do with lensing. All our observations show lensing to be proportional to the mass of an object, not the EM field associated with it.

The only thing that could be debatable is the exact mechanism by which gravity does it. There are multiple possibilities that could result in the same obersvations. Considering light has no mass it can't directly alter it's course. Relativity is based on distortions to spacetime, curved space/time etc. So that light is still traveling in a straight line, it is the path that is curved.
3 / 5 (2) Jun 09, 2017
But, couldn't gravity have an affect on space such as making nearby space "thicker" and the bending we observable is actually from refraction rather curved space time?
3 / 5 (2) Jun 09, 2017
Could always induce a big magnetic field near one of those LIGO lasers and see if it shines on New Zealand
5 / 5 (5) Jun 09, 2017
>couldn't gravity have an affect on space such as making nearby space "thicker"

There are ways of interpreting your supposition that correlate to things in science. Rulers are indeed shorter closer to massive bodies than they are far away from them (clocks also run more quickly, because you can't separate the two ). So if you want to call this "thicker space", maybe.

But locally, the speed of light is still c, so it's not like classical refraction where a medium creates a lower speed of transmission for EM fields through it.
1 / 5 (2) Jun 13, 2017
Once again Einstein is correct - a veritable God among the cranks

negative sir this observation is wrongly interpreted to suit einstein's GR
Jun 13, 2017
This comment has been removed by a moderator.
not rated yet Jun 13, 2017
We have discovered a wealth of information about light and fundememtal particles through experiments such as the double slit showing the wave like nature of light. But, we don't know why light behaves the way it does, we just know varies properties of light. We have calculated universal constants such as C, but again we don't know why these values are what they are. The closest theory we have for explaining things such as this is string theory. I am not sure what happened to string theory, haven't heard anything about it in a long time.

Anyways, I would imagine there are physical reasons as to why light moves the way it does through the universe and it is likely due to the fabric of space/time itself. If we could determine this, then I think many mysterious, such as dark matter and energy would be discovered.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.