Gravity-Bent Starlight Reveals a New Planet

dfab writes "The first experimental proof of Einstein's general theory has been revamped to discover planets around distant stars. Yesterday astronomers announced that a new technique called gravitational microlensing has found a star that hosts a roughly Jupiter-sized planet in a roughly Jupiter-sized orbit by observing its effect on the light from a bright star beyond that planetary system. See the NASA report or the gory details."

"The first experimental proof"

[DynaSoar]

...failed. Eddington's measurements were flawed, and the good ones weren't good enough. He was lucky. His unsupportable "result" was correct.

Interesting

[hords]

This image from the "gory details" [princeton.edu] gives you a quick understanding of what they mean. Pretty cool that they use one star to see the planet around another star.

More Info

[mizidymizark]

Space.com [space.com] also had an article [space.com] about this yesterday. It gives a little better timeline to when it will be available to check low mass stars in the future, as well as doing a comparision on other extrasolar planetary detection techniques.

I can draw this stroy. Neat, huh?

[Anonymous Coward]

actual apparent position
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earth

Re:I can draw this stroy. Neat, huh?

[FuzzyDaddy]

Not really... microlensing causes an increase in the brightness of the star, not a change in the apperent position. Although you've drawn a nice picture of gravitational lensing. (see, for example, einsteins cross)

Re:I can draw this stroy. Neat, huh?

[RobertB-DC]

Not really... microlensing causes an increase in the brightness of the star, not a change in the apperent position.

I'm no expert, but the gory details page [princeton.edu] notes that the microlensing event does cause a change in the apparent position (see this pic [princeton.edu]). In fact, you're seeing two distorted copies of the star.

It's just that in this case, there's not enough distance between the distorted images, so they show up as a single, brighter dot where there used to be a single, duller dot.

The AC's exaggerated angula

How it works

[GlobalEcho]

For those who want a quick excerpt of the science:

Gravitational microlensing uses a distant star (or other massive object) to bend light the same way as a lens would. If that star is perfectly aligned with an even more distant star (from our perspective) then the lens will call the more distant star to brighten, at least for as long as the alignment lasts.

The brightening comes with a spike (from "caustics" which are like irregularities in the lens), as the alignment gets good and them bad again. If you see a second, smaller spike, or an unusual extra image, that's evidence of a planet.

I'm not sure how you distinguish planets from weird caustics.

Note: this technique is good for detecting planets with long-period orbits, whereas the doppler-shift techniques are lousy for that, because they only work if the planet's revolution period is small (like in days).

Re:What happened to the original experiment?

[IMSoP]

Um, I think you're getting a bit confused - that's a completely different experiment, entirely unrelated. This is just a load of clever deductions based on some cool telescopic images, revealing a distant planet. The only connection is they both make use of the gory details of Einsteinian physics.

As far as I know, the satellite you're thinking of has to sit up there for a few months yet, so that we can see if it's moved by a few gazillionths of a millimetre or something - I can hardly wait! ;-)

Re:What happened to the original experiment?

[Tango42]

Not that experiment. The one they are refering to is the one about watching stars during solar eclipses, and they are in the wrong place due to the sun's gravity bending the light. The one you are thinking of it completely different, and is about frame-dragging.

Re:What happened to the original experiment?

[Mercenary_56]

Ummm, I'm guessing you are referring to Gravity Probe B?

Not only is it going to take 1-2 years to test the theory, it hasn't been launched yet. It's new\rescheduled launch date isn't till April 19, 2004.

So to answer your question of what happened to the results??

It's hard to give results on a project that hasn't been launched yet.

Read more about this project here. [stanford.edu]

Lucky

[Tango42]

This doesn't seem like a reliable method, because it requires a star to be right behind the one you want to find a planet around, which must be quite unlikely, unless I'm missing something.

In fact, having just scanned through the article, they do mention that problem:

"Because the effect works only in rare instances, when two stars are perfectly aligned, millions of stars must be monitored."

There's a reason

[barakn]

.... they're looking towards the center of our galaxy [nasa.gov], although a globular cluster [nasa.gov] might also be a good candidate.

Re:Lucky

[catkarma]

True, it may seem inefficient in terms of old school stare-at-one-point astronomy, but this is one example of a new field in astronomical research: data mining of large sky surveys.

Projects like the OGLE surveys sample many millions of objects many times: just to produce this sort of variability data. Its not a question of reliably finding the objects during an observation, but more being able to identify them when they do occur, throughout a long sequence of observations.

Re:Lucky

[Lars T.]

"Because the effect works only in rare instances, when two stars are perfectly aligned, millions of stars must be monitored."

Well, since the guys who found this [astrouw.edu.pl] say that: "In the 2004 Galactic bulge season about 120 million stars are regularly monitored and analyzed by the EWS system.", I don't think that should be a problem.

Burnt?

[Tablizer]

What keeps something from focusing the light of a bright star/nova on the Earth like sun thru a magnifying glass on an ant, and cooking the whole planet? I suppose the perfect "burn" alignment would not last long enough to do large damage.

Re:Burnt?

[Ayaress]

The lensing bends a very tiny amount of the supernova's output - It doesn't work exactly like a lens, per-se. It only focuses a ring of light around it on the focal point (us). The light passing closer to the sun that that ring is deflected to far, and focuses before it reaches us, and the light passing farther out doesn't get bent enough and focuses "behind" us. The extreme distances add up, and the lensed supernova will be much brighter than it normally would, but it still wouldn't be dangerously bright.

Re:Burnt?

[Tablizer]

The lensing bends a very tiny amount of the supernova's output - It doesn't work exactly like a lens, per-se. It only focuses a ring of light around it on the focal point (us). The light passing closer to the sun that that ring is deflected to far, and focuses before it reaches us, and the light passing farther out doesn't get bent enough and focuses "behind" us.

In other words, it is far from a perfect "lens". Sort of like astigmatism or a non-geometricly perfect lens?

Re:Burnt?

[Ayaress]

I'm not sure how those lenses work, but if you look up pictures of ideal setups for stellar or galactic lensing, it produces a + -shapped arrangement. The central image is the lensing object, and it has four images of the lensed object around it. More often, the lensed object isn't aligned perfectly, and we don't even see that much - one image or two. Also, after reading up on the subject, I made a mistake in my first post: The lensed supernova would be no brighter than a normal one. It would just appear t

The planet is the lens, not the focus

[jfengel]

Interesting. I had the idea that some star was being used to help focus light from the planet, acting as a gravitational lens and giving us a better view of the planet.

Instead, the planet is lensing some star beyond it, and then (later) so is the star that planet is around, as the planet+star moves past the object being focused.

This shows up as two sharp spikes in the brightness of the star over time (I guess one on each side of the planet, imperfectly aligned?) and one broader curve as it passes the star. The shape of the curves tell you how massive the planet and star are.

It looks like it's about Jupiter's size and a bit nearer in than Jupiter. That's comforting; thus far the only planets we ever seem to detect are bigger than Jupiter and closer than Mercury, which really boggles my mind. This system looks a lot more like ours.

Neat. What will those clever astrophysicists think of next.

I thought this experiment was done a long time ago

[edunbar93]

The first experimental proof of Einstein's general theory

I seem to recall that Einstein's General Theory of Relativity was used to explain the irregularities in observations of Mercury's orbit as it passed behind the sun, shortly after his theory was published. And using this theory explained those irregularities with a very high degree of accuracy.