Post by Dave Dangerously on Jun 16, 2008 14:30:21 GMT -6
WASHINGTON (Reuters) - European researchers said on Monday they discovered a batch of three "super-Earths" orbiting a nearby star, and two other solar systems with small planets as well.
They said their findings, presented at a conference in France, suggest that Earth-like planets may be very common.
"Does every single star harbor planets and, if yes, how many?" asked Michel Mayor of Switzerland's Geneva Observatory. "We may not yet know the answer but we are making huge progress towards it," Mayor said in a statement.
The trio of planets orbit a star slightly less massive than our Sun, 42 light-years away towards the southern Doradus and Pictor constellations. A light-year is the distance light can travel in one year at a speed of 186,000 miles a second, or about 6 trillion miles.
The planets are bigger than Earth -- one is 4.2 times the mass, one is 6.7 times and the third is 9.4 times.
They orbit their star at extremely rapid speeds -- one whizzing around in just four days, compared with Earth's 365 days, one taking 10 days and the slowest taking 20 days.
Mayor and colleagues used the High Accuracy Radial velocity Planet Searcher or HARPS, a telescope at La Silla observatory in Chile, to find the planets.
More than 270 so-called exoplanets have been found. Most are giants, resembling Jupiter or Saturn. Smaller planets closer to the size of Earth are far more difficult to spot.
None can be imaged directly at such distances but can be spotted indirectly using radio waves or, in the case of HARPS, spectrographic measurements. As a planet orbits, it makes the star wobble very slightly and this can be measured.
"With the advent of much more precise instruments such as the HARPS spectrograph ... we can now discover smaller planets, with masses between 2 and 10 times the Earth's mass," said Stephane Udry, who also worked on the study.
The team also said they found a planet 7.5 times the mass of Earth orbiting the star HD 181433 in 9.5 days. This star also has a Jupiter-like planet that orbits every three years.
Another solar system has a planet 22 times the mass of Earth, orbiting every four days, and a Saturn-like planet with a 3-year period.
"Clearly these planets are only the tip of the iceberg," said Mayor.
"The analysis of all the stars studied with HARPS shows that about one third of all solar-like stars have either super-Earth or Neptune-like planets with orbital periods shorter than 50 days."
(Reporting by Maggie Fox; Editing by John O'Callaghan)
Like a cosmic Grim Reaper, a blast of ultraviolet light signals the violent death of the universe's most massive stars. Now astronomers have viewed this heavenly harbinger for the first time.
"Astronomers have been dreaming about seeing the first light from the violent death of a star for over 30 years," said lead researcher Kevin Schawinksi of the University of Oxford. "Our observations open up an entirely new avenue for studying the final stages in the lives of massive stars and the physics of supernovae."
Schawinksi and his colleagues detected the ultraviolet signal of a hefty star on the verge of explosion, which they detail in the June 13 issue of the journal Science.
Usually, when astronomers see a supernova, the star has already been destroyed. "It's very hard to tell much about precisely the kind of star that actually died there," Schawinski told SPACE.com. "The really cool thing about our observations is this light traveling ahead of the shock wave traveled through the star before it was destroyed."
He added, "It's telling us about the properties, the conditions, of the star at the moment it died, but before the shock wave actually disrupted it."
Doomed star
When a massive star, weighing at least 10 suns, runs out of nuclear fuel, it can collapse under its own weight, triggering an explosion called a supernova. The explosion sends the stellar guts spewing away at 20 million mph (10,000 km/sec) in a fireball that's a billion times brighter than the sun, the researchers say.
It's this fireball that scientists observe. What they haven't seen until now are the final moments of the doomed star just before the visible explosion. For the past 30 years or so, theorists have predicted a surge of ultraviolet light should come before the actual visible explosion.
There are several problems for actually seeing this phenomenon. "By the time you see the supernova, it's already days or weeks in the past," Schawinski said. "If you see a supernova you'd have to go back in time. You'd have to be already looking at the position."
The other issue is the fact that Earth's atmosphere absorbs ultraviolet light, and so you'd need a space telescope to actually be able to view the death beacon. The space telescope GALEX, which orbits Earth about every 98.6 minutes and views the universe in ultraviolet, was the answer.
With GALEX, researchers recently got front-row seats to the pre-show of what they suspect was a red supergiant star measuring somewhere between 500 and 1,000 solar radii on the verge of explosion. A red supergiant is a hefty star nearing the end of its life that can swell to 100 times its original size before exploding.
Schawinski and his colleagues looked at GALEX images taken at the positions of supernovae previously identified with optical telescopes in Hawaii.
"We found a new source at the location of one supernova, suddenly outshining its galaxy host in the UV," said Mark Sullivan of the University of Oxford. "It appeared a couple of weeks before the optical discovery of the supernova and marked the first stage in the death of the star."
The final hours
The UV peak represented a unique phase in the formation of the supernova SNLS-04D2dc, just before the shock wave from its collapsed core reached the star's surface to violently eject its shell of hot gas.
During a red supergiant's final hours, a shock wave whizzes outward with the related radiation moving even faster and heating up the star's surface. The temperature at the surface ramps up from a few thousand degrees Celsius to several hundred thousand degrees. Just before the shock wave catches up and reaches the surface (triggering a supernova), the star is producing the same total luminosity as a thousand billion suns, the researchers say.
Once the shock wave catches up, it plows through the outer parts of the star, accelerating several suns' worth of material outward. The surface of the star explodes. A few days later, supernova hunters will spot the bright visible light of the explosion.
Schawinski describes the observations as looking inside of a semi-transparent star as it's dying.
"We saw the whole thing. We saw the radiative precursor, this UV light, moving ahead [of the shock wave]," Schawinski said. "We saw that arrive and then the point at which the shock wave comes to the surface and destroys the star. In a sense we could see the shock move inside the star because the light from the shock was moving ahead of it."
The new UV peak findings, the astrophysicists say, will shed light on deathly details once hidden beneath a star's outer cloak.
"This is a whole new avenue into studying the late stages of massive stars," said Oxford researcher Christian Wolf. "Most of what we know today is based on computer simulations. But as always when you test theory against observations for the first few times, we may be in for surprises."
You gotta be aware of what's going outside Earth, people. It's gonna be more important than anything we know, eventually.
They said their findings, presented at a conference in France, suggest that Earth-like planets may be very common.
"Does every single star harbor planets and, if yes, how many?" asked Michel Mayor of Switzerland's Geneva Observatory. "We may not yet know the answer but we are making huge progress towards it," Mayor said in a statement.
The trio of planets orbit a star slightly less massive than our Sun, 42 light-years away towards the southern Doradus and Pictor constellations. A light-year is the distance light can travel in one year at a speed of 186,000 miles a second, or about 6 trillion miles.
The planets are bigger than Earth -- one is 4.2 times the mass, one is 6.7 times and the third is 9.4 times.
They orbit their star at extremely rapid speeds -- one whizzing around in just four days, compared with Earth's 365 days, one taking 10 days and the slowest taking 20 days.
Mayor and colleagues used the High Accuracy Radial velocity Planet Searcher or HARPS, a telescope at La Silla observatory in Chile, to find the planets.
More than 270 so-called exoplanets have been found. Most are giants, resembling Jupiter or Saturn. Smaller planets closer to the size of Earth are far more difficult to spot.
None can be imaged directly at such distances but can be spotted indirectly using radio waves or, in the case of HARPS, spectrographic measurements. As a planet orbits, it makes the star wobble very slightly and this can be measured.
"With the advent of much more precise instruments such as the HARPS spectrograph ... we can now discover smaller planets, with masses between 2 and 10 times the Earth's mass," said Stephane Udry, who also worked on the study.
The team also said they found a planet 7.5 times the mass of Earth orbiting the star HD 181433 in 9.5 days. This star also has a Jupiter-like planet that orbits every three years.
Another solar system has a planet 22 times the mass of Earth, orbiting every four days, and a Saturn-like planet with a 3-year period.
"Clearly these planets are only the tip of the iceberg," said Mayor.
"The analysis of all the stars studied with HARPS shows that about one third of all solar-like stars have either super-Earth or Neptune-like planets with orbital periods shorter than 50 days."
(Reporting by Maggie Fox; Editing by John O'Callaghan)
Like a cosmic Grim Reaper, a blast of ultraviolet light signals the violent death of the universe's most massive stars. Now astronomers have viewed this heavenly harbinger for the first time.
"Astronomers have been dreaming about seeing the first light from the violent death of a star for over 30 years," said lead researcher Kevin Schawinksi of the University of Oxford. "Our observations open up an entirely new avenue for studying the final stages in the lives of massive stars and the physics of supernovae."
Schawinksi and his colleagues detected the ultraviolet signal of a hefty star on the verge of explosion, which they detail in the June 13 issue of the journal Science.
Usually, when astronomers see a supernova, the star has already been destroyed. "It's very hard to tell much about precisely the kind of star that actually died there," Schawinski told SPACE.com. "The really cool thing about our observations is this light traveling ahead of the shock wave traveled through the star before it was destroyed."
He added, "It's telling us about the properties, the conditions, of the star at the moment it died, but before the shock wave actually disrupted it."
Doomed star
When a massive star, weighing at least 10 suns, runs out of nuclear fuel, it can collapse under its own weight, triggering an explosion called a supernova. The explosion sends the stellar guts spewing away at 20 million mph (10,000 km/sec) in a fireball that's a billion times brighter than the sun, the researchers say.
It's this fireball that scientists observe. What they haven't seen until now are the final moments of the doomed star just before the visible explosion. For the past 30 years or so, theorists have predicted a surge of ultraviolet light should come before the actual visible explosion.
There are several problems for actually seeing this phenomenon. "By the time you see the supernova, it's already days or weeks in the past," Schawinski said. "If you see a supernova you'd have to go back in time. You'd have to be already looking at the position."
The other issue is the fact that Earth's atmosphere absorbs ultraviolet light, and so you'd need a space telescope to actually be able to view the death beacon. The space telescope GALEX, which orbits Earth about every 98.6 minutes and views the universe in ultraviolet, was the answer.
With GALEX, researchers recently got front-row seats to the pre-show of what they suspect was a red supergiant star measuring somewhere between 500 and 1,000 solar radii on the verge of explosion. A red supergiant is a hefty star nearing the end of its life that can swell to 100 times its original size before exploding.
Schawinski and his colleagues looked at GALEX images taken at the positions of supernovae previously identified with optical telescopes in Hawaii.
"We found a new source at the location of one supernova, suddenly outshining its galaxy host in the UV," said Mark Sullivan of the University of Oxford. "It appeared a couple of weeks before the optical discovery of the supernova and marked the first stage in the death of the star."
The final hours
The UV peak represented a unique phase in the formation of the supernova SNLS-04D2dc, just before the shock wave from its collapsed core reached the star's surface to violently eject its shell of hot gas.
During a red supergiant's final hours, a shock wave whizzes outward with the related radiation moving even faster and heating up the star's surface. The temperature at the surface ramps up from a few thousand degrees Celsius to several hundred thousand degrees. Just before the shock wave catches up and reaches the surface (triggering a supernova), the star is producing the same total luminosity as a thousand billion suns, the researchers say.
Once the shock wave catches up, it plows through the outer parts of the star, accelerating several suns' worth of material outward. The surface of the star explodes. A few days later, supernova hunters will spot the bright visible light of the explosion.
Schawinski describes the observations as looking inside of a semi-transparent star as it's dying.
"We saw the whole thing. We saw the radiative precursor, this UV light, moving ahead [of the shock wave]," Schawinski said. "We saw that arrive and then the point at which the shock wave comes to the surface and destroys the star. In a sense we could see the shock move inside the star because the light from the shock was moving ahead of it."
The new UV peak findings, the astrophysicists say, will shed light on deathly details once hidden beneath a star's outer cloak.
"This is a whole new avenue into studying the late stages of massive stars," said Oxford researcher Christian Wolf. "Most of what we know today is based on computer simulations. But as always when you test theory against observations for the first few times, we may be in for surprises."
You gotta be aware of what's going outside Earth, people. It's gonna be more important than anything we know, eventually.