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Gorgeous triple sunset on
newfound planet?
July 13, 2005
Courtesy the California Institute of Technology
and World Science staff
A newfound planet has three suns, a scientist
says—a discovery that highlights the unimagined beauties the cosmos still has in store for
us, suggests planets are even more common than previously believed, and could rewrite theories of planet formation.
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An artist's concept of how a triple sunset might look like near the
newfound planet. Since the planet is thought to be a gaseous giant, it
would probably be impossible in practical terms to view the sunset from
there. Therefore, the artist envisioned the sunset as viewed from a
hypothetical moon of that planet. The large yellow sun is already
halfway over the horizon. The planet also appears in the upper left.
(Caltech)
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The California Institute of Technology
researcher reported finding the planet in the
direction of the constellation Cygnus (The Swan), in a paper published in the July 14 issue of the research journal
Nature.
| Viewing the animation Researchers
released an artist’s animation of a sunset in the triple-star system
where they say a new planet was found.
Click here
for the
movie, which is in Quicktime format. The animation shows the scene
not as it would appear not
from the newfound planet itself, but from a hypothetical rocky moon of
that planet.
If you cannot view the movie (such
as if you get a “broken Quicktime icon”) you may be able to fix the
problem by downloading the latest free version of Quicktime here.
Although it says Windows XP users need the version with
"Itunes," this may cause problems, and you can use the other
version instead. |
The planet is slightly larger than Jupiter,
the author said, and the fact that it’s being pulled in three different directions by the
gravity of nearby stars makes it hard to see how it survives.
The finding promises to “seriously challenge our current understanding of how planets are formed,” according to an emailed statement from the
institute.
The finding could shed light on the possibility that planets can exist in
multiple star systems—groups of two, three or more stars that orbit each other
due to their mutual gravity.
In the paper, Maciej Konacki, a senior postdoctoral scholar at the institute, said the
newfound world orbits one star of a triple-star system known as HD 188753.
It doesn’t orbit the other two, so these aren’t its “suns” in the traditional sense of being stars around which it orbits. But they do
circle around the same, main star that the planet orbits.
The three stars are about 149 light-years from Earth, Konacki said. A light-year is the distance light travels in a year. The stars are about as close to one another as the distance between
our sun and Saturn, he added.
A viewer on the planet would see three bright “suns,” according to Konacki. One of these three suns, the one that the planet orbits, would look huge, he added. This is because the planet is extremely close to that star, and
therefore orbits it quickly: its year is only 3½ days long. That star would also be yellow, being similar to our own sun.
The larger of the other two suns would be orange, and the smaller red, Konacki said.
Konacki calls the new type of planet a “Tatooine planet,” because of a similarity to Luke Skywalker’s view of his home planet’s sky in
Star Wars. That planet, however, had a mere two suns.
“The environment in which this planet exists is quite spectacular,” said Konacki. “With three suns, the sky view must be out of this
world—literally and figuratively.”
The fact that a planet can even exist in a multiple-star system is amazing, he added. Double-, triple- and multiple stars are quite common in our
corner of the galaxy, and in fact these systems outnumber single stars by some 20 percent.
Researchers have found most of the planets discovered so far outside our solar
system by carefully measuring the speed of the stars, a technique that is
simpler with single stars.
Experts generally avoided
planet-hunting in multiple-star systems where the stars are close to each other,
as in this case, Konacki explained. This is because existing planet detection techniques fail for such complicated
systems, and most solar-system formation theories suggest planets are unlikely to form in such environments.
Konacki said he made his discovery by developing a new method that lets him precisely measure velocities of all
stars in such systems. He used the technique to hunt for planets in such systems with the Keck I telescope in Hawaii. The planet in the HD 188753 system is the first one from this
survey, he said.
“Planets from complicated stellar systems will put our theories of planet formation to a strict
test,” Konacki remarked. “If we believe that the same basic processes lead to the formation of planets around single stars and components of multiple stellar systems, then such processes should be equally feasible, regardless of the presence of stellar
companions.”
Scientists in 1995 discovered the first “hot Jupiter,” a planet outside our Solar System that is a giant, like Jupiter, and that orbits very close to its parent star. Today, more than 20 such planets are known to orbit other stars.
Such planets are believed to form in a disk of gas and dust that extends beyond three astronomical units, or three times the 93-million-mile distance between the sun and Earth. After formation,
the planets are thought to migrate inward to their present close orbits.
But this doesn’t explain how a planet forms in a system such as the one Konacki
identified, he said. This is because if another star closely orbits the star with the disk, the other star would pull away material from the disk, leaving too little for a planet to form.
“How that planet formed in such a complicated setting is very puzzling. I believe there is yet much to be learned about how giant planets are formed,”
he said.
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