Science

Gravity's light-bending effect seen in the dance of distant stars

Gravity's light-bending effect...
Astronomers have observed gravitational microlensing in action, as the gravity of a close star bends the light of a more distant one, to make the latter appear to change position in the sky
Astronomers have observed gravitational microlensing in action, as the gravity of a close star bends the light of a more distant one, to make the latter appear to change position in the sky
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Astronomers have observed gravitational microlensing in action, as the gravity of a close star bends the light of a more distant one, to make the latter appear to change position in the sky
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Astronomers have observed gravitational microlensing in action, as the gravity of a close star bends the light of a more distant one, to make the latter appear to change position in the sky

According to Einstein's general theory of relativity, the gravity from huge objects like stars and galaxies can curve the fabric of spacetime, to the point that passing light will bend from its usual straight path. This can alter how we see distant stars through a phenomenon called gravitational lensing, and now astronomers have seen a rare form of the process in action, directly observing a star bend the light of another, more distant star.

Gravitational lensing has been used in the past to help us find objects hiding behind closer and brighter objects, but for the light-bending effects to make an observable impact, the "lens" object is usually gigantic, like a galaxy or even a cluster of galaxies.

Gravitational microlensing uses a much smaller object as a lens, like a single star or galaxy. From our perspective here on Earth, when a "nearby" star passes in front of a more distant one, the background star will appear to change its position in the sky, as the closer object's gravity causes the light to bend. Albert Einstein called this effect astrometric lensing, and it's been seen in action in the past using our own Sun as a lens.

But there's a glaring problem: the Sun is so bright that it washes out the light from the stars, so the effect can only be seen during a solar eclipse. In a new study, a team of astronomers has used the Hubble Space Telescope to measure how this interaction takes place between two other stars, using a relatively-nearby white dwarf, Stein 2051 B, as a lens to magnify a background star.

The researchers took measurements of the background star's light on eight different days over a two-year period, and noticed that the further star seems to wobble around as Stein 2051 B passes by in front of it (as seen in the video above). This not only marks the first time this kind of gravitational microlensing has been observed in stars other than the Sun, but using the data collected the astronomers managed to work backwards to solve some mysteries about the closer star itself.

Stein 2051 B is the sixth-closest white dwarf star to us, but its composition and mass were still largely unknown. By measuring the extent of the lensing effect, the team was able to determine that the star has a mass about two-thirds that of the Sun. In future, this method could help scientists determine the mass and makeup of other stars, and shed light on white dwarves in general.

"(The) team nicely confirms astrophysicist Subrahmanyan Chandrasekhar's 1930 Nobel Prize-winning theory about the relationship between the mass and radius of white dwarf stars," says Terry Oswalt, a professor at Embry-Riddle Aeronautical University who wrote a perspective piece on the study. "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."

The study, as well as Oswalt's related article, were both published in the journal Science. Oswalt demonstrates the effects in the video below.

Source: Embry-Riddle Aeronautical University

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8 comments
Reid Barnes
Einstein claimed that the bending of light passing near the Sun, famously measured by Author Eddington during a solar eclipse, were due to space-time deformation as characterized by his general theory of relativity. Of course, if space-time deformation is not the explanation, it remains for us to look for the explanation or explanations. In any event, whether "space" physically interacts in a gravitational field or not does not address the problem that the non-Euclidean geometry of the general theory of relativity is self-contradicting. Even if Einstein were correct that "space" does interact in a gravitational field or near massive bodies, his statement that "in the presence of a gravitational field the geometry is not Euclidean" cannot be correct if that non-Euclidean geometry is self-contradicting.
Bob
As I have always said "Nothing we see is anywhere near where it was billions of years ago and may no longer exist."
Bob Flint
Right on Bob, nothing is as it seems, we are staring into the past twinkling light rays and hypothesizing of the past which likely is already gone. But surely we can plot out the past much as we are examining our history on our own planet, & possibly working backwards equate the present, and maybe even the future.
Don Duncan
"...will bend from its usual straight line..."?? All lines are curved, so-called straight lines are a small part on a curve that are referred to as straight and can be so considered over short distances. Your example does not apply, e.g., the distances are immense compared to earth measurements. Can space/time get bent? The photons traveling through space/time are attracted to any mass, having their path bent, but that is all.
Bob
Mr. Flint, the biggest problem with your logic is that any tiny error in extrapolating billions of years backward or forward makes such an exercise futile. A ray of light could be bent by gravity an unknown number of times over time and pass through different mediums in space. When I worked with WDXRF ( Wavelength Dispersive X-ray Fluorescence) spectra I used several mathematical models for x-rays that changed for different conditions. Which model was right? The one that looks right. Was it correct? It fit our preconceived assumptions. Is it proof? Not till we have far more repeatable data. I get really upset when theorists extrapolate beyond reasonable limits with unprovable, non-reproducible data and claim their assumptions are fact. These scientists should be called hypothesists and not theorists.
ChrisWalker
still not sure about this obsession with gravity. Kinetic energy is fundamentally the exact same force. consider the moons lack of gravity, why? it does not spin, ergo no kinetic energy. Why does Jupiter have so much gravity? it spins really fast, it has an abundance of kinetic energy. And the Sun, such a large mass spinning superfast, ergo it has a lot of kinetic energy, like a giant gyroscope in the vacuum of space.
but take that aside, magnetism has been proven to bend light, just take a magnet to a neon light, now imagine the enormous elecrtomagnetic charge of a star and what it could do to light, and again, look at Jupiter's magnetic field and how small it is in comparison to this small star in tbis solar system.
making gravity the reason for everything is the most stupid short sighted insane thing possible. again, not sure about this obsession with gravity
Imran Sheikh
Are the sure about it, Cant the bending be due to total internal reflection OR refraction OR Diffraction. Probably due to atmosphere or dust clouds..
Tanstar
ChrisWalker: "Kinetic energy is fundamentally the exact same force. consider the moons lack of gravity, why? it does not spin, ergo no kinetic energy."
You realize that the moon has a gravity 1/8th the strength of Earth's, right?