* Astronomy

A seam of stars at the centre of the Milky Way has shown astronomers that an entirely new class of planets closely orbiting distant suns is waiting to be explored, according to a paper published on Thursday.
The finding opens up a new area of investigation for space scientists probing extrasolar planets —planets that orbit stars other than our own, it says.
Astronomers have spotted 202 extrasolar planets since the first was spotted in October 1995.
Their technique is based on the so-called “wobble” method. Under this, the astronomer measures the frequencies of light from the star. There is a telltale oscillation, or wobble, in this light if the star is tugged by a planet.
So far, planets with the shortest orbits, of 1.2-2.5 days, have mainly been found encircling stars that are hot and bright, with a mass at least three-quarters that of our Sun.
An international team of astronomers, using a camera aboard NASA’s Hubble telescope, delved into a zone of the Milky Way known as the “galactic bulge”, thus called because it is rich in stars and in the gas and dust which go to make up stars and planets.
They uncovered the existence of 16 planets in the category of close orbiters, taking between 0.4 and 3.2 days to go around their respective stars. Many of the planets are the size of Jupiter, the largest planet in our Solar System.
Two of the 16 have orbits of less than a day, creating a new category of “ultra-short” orbits.
In addition, the planets generally orbit stars that are somewhat lighter than the typical stars seen in earlier extrasolar discoveries.
The team, led by Kailash Sahu of the Space Telescope Science Institute in Baltimore, Maryland, report their work in Nature, the British weekly science journal.
They believe that any planets which orbited at such a close distance to brighter, hotter stars would be destroyed by solar radiation.
And large Jupiter-sized planets are being spotted at these remarkably close orbits because the star, being of low mass, exerts a relatively low gravitational pull.

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Hubble survey may reveal scores of new planets
The Hubble Space Telescope may have discovered as many as 100 new planets out beyond our solar system orbiting stars in the Milky Way galaxy, astronomers say.

If confirmed, that would double the known population of alien planets since the first one was detected nine years ago, according to Steven Beckwith, the director of the Space Science Telescope Institute in Baltimore, which operates the Hubble.
Astronomers are coming to believe that almost every sunlike star in the galaxy, and probably in the universe, is accompanied by one or more planets like our solar system, vastly increasing the chance that some form of extraterrestrial life could exist.
Hubble's expected harvest of previously unknown planets stems from a sweep of thousands of stars in the dome-like bulge protruding above the flat disk of the Milky Way.
For seven straight days in late February, Kailash Sahu, an astronomer at the Baltimore institute, used the 14-year-old telescope to monitor the amount of light streaming from the brightest stars.
A tiny decrease -- less than a tenth of 1 percent -- in the light was a sign that something, perhaps a planet, was passing in front of the star. A similar phenomenon entranced millions of earthlings when Venus transited the sun June 8, 2004.
Sahu is now employing an older planetary-detection method to confirm that the transiting objects are really planets and not something else, such as dwarf stars or clouds of interstellar gas. Using a large ground-based telescope in Chile, he's looking for small irregularities, or wobbles, in a star's motion that would prove that it's accompanied by one or more planets.
This is the method that's been used since 1995 to spot about 100 extrasolar planets. Three more have been discovered by the new "transit'' technique in the past year.

"If this is confirmed, in seven days we will have doubled the number of planets known in nine years,'' Beckwith earlier this week told a committee of the National Academy of Sciences, which is exploring the future of the Hubble telescope.

He said Sahu already had determined the existence of several new planets from data gathered during the February sweep. At this rate, Beckwith said, the total haul should be about 100.
The Hubble team expects to find 10 to 20 transiting planets among the 100 that are bright enough that their atmospheres can be observed, Beckwith said. All of them are likely to be gas giants like Jupiter or Saturn, much larger than Earth and inhospitable to life as we know it.
NASA is planning telescopes that will be able to detect Earth-size planets and study their atmospheres.
Astronomers believe that other solar systems probably formed much like our own, when a huge cloud of gas and dust collapsed into a swirling "proto-planetary'' disk similar to Saturn's rings. Gravity concentrated the matter at the centre of the disk to form a star. The outlying material clumped into planets, asteroids and comets.
Several such systems containing two or three planets, as well as other proto-planetary disks, have been found around other stars.

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