Credit: NASA, ESA, P. Kalas, J. Graham,
E. Chiang, and E. Kite
(University of California, Berkeley),
M. Clampin (NASA Goddard
Space Flight Center, Greenbelt, Md.),
M. Fitzgerald (Lawrence Livermore
National Laboratory, Livermore, Calif.),
and K. Stapelfeldt and J. Krist
(NASA Jet Propulsion
Laboratory, Pasadena, Calif.)
E. Chiang, and E. Kite
(University of California, Berkeley),
M. Clampin (NASA Goddard
Space Flight Center, Greenbelt, Md.),
M. Fitzgerald (Lawrence Livermore
National Laboratory, Livermore, Calif.),
and K. Stapelfeldt and J. Krist
(NASA Jet Propulsion
Laboratory, Pasadena, Calif.)
Space is big. The Hubble Space Telescope is small. How did the folks at NASA know where to point the camera?
It all goes back to the process of science. About 300 extrasolar planets have been discovered, but we haven't ever 'seen' one of them. The existence of such a planet can be postulated when there's something off-kilter about the interactions between a star and the objects around it.
In the case of Formalhaut, the planet's existence was predicted by the particular shape of the dust ring surrounding the star:
Hubble astronomer Paul Kalas, of the University of California at Berkeley, and team members proposed in 2005 that the ring was being gravitationally modified by a planet lying between the star and the ring's inner edge.
Circumstantial evidence came from Hubble's confirmation that the ring is offset from the center of the star. The sharp inner edge of the ring is also consistent with the presence of a planet that gravitationally "shepherds" ring particles. Independent researchers have subsequently reached similar conclusions.
Now, Hubble has actually photographed a point source of light lying 1.8 billion miles inside the ring's inner edge. The results are being reported in the November 14 issue of Science magazine.
"Our Hubble observations were incredibly demanding. Fomalhaut b is 1 billion times fainter than the star. We began this program in 2001, and our persistence finally paid off," Kalas says.
"Fomalhaut is the gift that keeps on giving. Following the unexpected discovery of its dust ring, we have now found an exoplanet at a location suggested by analysis of the dust ring's shape. The lesson for exoplanet hunters is 'follow the dust,'" said team member Mark Clampin of NASA's Goddard Space Flight Center in Greenbelt, Md.
Circumstantial evidence came from Hubble's confirmation that the ring is offset from the center of the star. The sharp inner edge of the ring is also consistent with the presence of a planet that gravitationally "shepherds" ring particles. Independent researchers have subsequently reached similar conclusions.
Now, Hubble has actually photographed a point source of light lying 1.8 billion miles inside the ring's inner edge. The results are being reported in the November 14 issue of Science magazine.
"Our Hubble observations were incredibly demanding. Fomalhaut b is 1 billion times fainter than the star. We began this program in 2001, and our persistence finally paid off," Kalas says.
"Fomalhaut is the gift that keeps on giving. Following the unexpected discovery of its dust ring, we have now found an exoplanet at a location suggested by analysis of the dust ring's shape. The lesson for exoplanet hunters is 'follow the dust,'" said team member Mark Clampin of NASA's Goddard Space Flight Center in Greenbelt, Md.
(Warning: 7th-grade physics ahead)
Isaac Newton figured out that objects will be attracted to each other by the force of gravity. When two objects are close together and large, there's a stronger attraction than when they're far apart and small. Mathematically, Newton expressed it as
where m1 and m2 are the masses of the objects and r is the distance between the objects.
A slight wobble in the spin of a star often gives us a big clue that there's something large lurking nearby, but we'd had no actual pictures of any extrasolar planets.
Does this mean that we don't know that something exists until we see a picture of it? Of course not! (How many of us have seen an individual atom?) Rather, this shows that inferences based on known physical laws have strong predictive powers. We didn't have to have a visible light picture to know that these planets exist.
Still, there are some folks who will ask "Were you theeeere?" They're ones who'd refuse to acknowledge the evidence from studying the wobbly stars.
Let's say that you're on the jury for a trial in which the defendant had the means, motive, and opportunity to murder the victim, with reams of incriminating circumstantial evidence presented, but no eyewitnesses or confession . . . would you be able to find the defendant guilty?
On the other hand, if eyewitness testimony is the only incriminating evidence that exists in the murder case, could you convict the person? Most attorneys agree that eyewitness testimony is notoriously unreliable.
Such is the power of the scientific method: direct observation isn't necessary as long as there are other means of getting consistent information. Scientists are rightly obsessed with finding these other means of figuring out how our world works.
posted by Cheryl Shepherd-Adams
