New Planet "Bonanza" Discovered at Center of Milky Way

Blake de Pastino in Washington, D.C.
National Geographic News
October 4, 2006
A "bonanza" of new planets has been found at the heart of our galaxy, NASA astronomers announced today.

Sixteen potential planets have been detected in the region known as the Galactic Bulge, the mass of stars and hot gas at the center of the Milky Way some 26,000 light-years away.

This makes the newfound planets the most distant worlds ever discovered.

Of the 16 newly detected bodies, 7 have been deemed likely planets, with the remaining 9 awaiting confirmation.

If all 16 are confirmed, the find would constitute the largest number of new planets detected in a single observation.

A team of astronomers discovered the planets during a seven-day survey of the constellation Sagittarius using the Hubble Space Telescope in February 2004.

The faraway find has dramatic implications for the ongoing search for other, possibly habitable planets, scientists said. Most notably, the survey reveals that planets are as plentiful around distant stars as they are around stars closer to our solar system.

"We had [already] found all of these planets relatively near the sun. We wanted to know, Are they there all across the galaxy?" said Mario Livio, an astronomer with the Hubble project, at a press conference today at NASA headquarters in Washington, D.C.

"The answer was yes, they are there, even at the center of the galaxy. … This allows us to say now with a very high degree of confidence that there are literally billions of planets in our galaxy."

Fastest-Orbiting Planets

The findings include an additional surprise: Five of the new planets orbit their respective stars in just one Earth day or less.

The newfound bodies are the fastest-orbiting planets ever detected and constitute a whole new class of "ultrashort period" planets, the scientists said.

One of the planets completes its orbit in only ten hours, meaning that one solar year passes on the far-flung world in about the same time you spend between breakfast and dinner.

The planets, which are gas giants about the size of Jupiter, also orbit closer to their stars than any other known worlds.

They are only able to survive such close proximities because the stars they orbit are relatively light and dim, the scientists explained.

"These planets [are] extremely close to their stars—so close that they get heated by the stars' radiation to almost 3000 degrees Fahrenheit [1650 degrees Celsius]," said Kailash Sahu, principal investigator of the project.

If denser, brighter stars like our sun had similar planets orbiting so closely, "they would simply evaporate," he added.

Clues to New Planets

The astronomers were able to spot the planets using a pair of crucial clues.

One is a telltale "wobble" that a star often adopts in its path through space when a planet is orbiting it.

The other is a slight dimming that occurs when a planet passes in front of a star.

(See National Geographic magazine's "Search for Other Earths.")

But the would-be worlds' record-setting distance from Earth adds an element of uncertainty to the findings, the scientists said.

To confirm that an observed body is a planet, astronomers must be able to gauge its mass. The team was only able to do this with two of the planet candidates so far.

"These 16 candidates have passed every conceivable test that we could think of, in terms of [us] not being fooled by something else mimicking a planet," Livio said.

"However, without being able to tell the mass of [all of] these objects precisely … we came up with this very conservative estimate that at least seven surely should be planets. Two we know are planets. [But] it could be all 16 are planets."

While the remoteness of these objects poses certain challenges, Livio added, it also reinforces the significance of the discovery.

The more planets that are identified farther from our solar system, he explained, the greater the odds that a planet like Earth may one day be discovered.

"Ultimately, all of us are dreamers, and eventually we would like to find life elsewhere and perhaps even intelligent life," he said.

"What this study has shown is that there are many, many planets—that the galaxy is full of these planets—so chances are that somewhere out there you may find these other things."

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