Friday, May 18, 2007
Two Strange New Exoplanets to Consider
I have found some interesting stories about new newly discovered exoplanets that are among the strangest worlds we have discovered. The first is about a hot-water, Neptune-sized planet that orbits close to a Red Dwarf. Space.com excerpt:
A Neptune-sized world in a distant solar system orbits very close to its star and might be covered with exotic forms of water not naturally found on Earth, scientists say. The bizarre world is being called a "hot ice planet."
The finding, to be detailed in an upcoming issue of the journal Astronomy and Astrophysics, marks the first time relatively small planets similar to the ice giants Uranus and Neptune in our solar system have been found orbiting very close to their stars.
Prior to this discovery, only gaseous giants known as "hot Jupiters" were known to inhabit such close stellar quarters.
First discovered in 2004, the planet, called GJ 436 b, is about 22 times more massive than Earth. It orbits a diminutive red dwarf star 30 light-years away from us. New observations of the planet as it transited, or passed in front of, its parent star allowed scientists to measure its size and mass. GJ 436 b is the closest, and smallest, transiting planet to be measured in this way.
The measurements, made using a telescope at the Observatoire Francois-Xavier Bagnoud (OFXB) in Saint-Luc, Switzerland, revealed GJ 436 b has a diameter of about 30,000 miles (50,000 kilometers)-four times that of Earth.
Based on its size and mass, scientists think the planet is composed mostly of water. If the planet were a gas giant like Jupiter or Saturn and contained mostly hydrogen and helium, it would be much larger, and if it was made up of rock and iron like Earth and Mars, it would be much smaller, the scientists say.
The water world could be enveloped by a thin atmosphere of hydrogen and helium, like Neptune and Uranus, or could be surrounded entirely by water, like Saturn's moon Enceladus.
GJ 436 b orbits its star from a distance of only about 2.5 million miles (4 million km)-about 14 times closer than Mercury's average distance from the Sun. At such close quarters, scientists think its surface temperature is at least 600 degrees Fahrenheit (300 C) and any water on its atmosphere would be in the form of steam.
Okay, so now we have a liquid planet roughly the size of Neptune orbiting close to a Red Dwarf. The universe is getting stranger every single day with the announcements of these findings. Of course, we have just scratched the surface here since the number of exoplanets we have found is miniscule when compared to the size of the entire galaxy.
Full Hot Liquid Exoplanet Story
But wait, there's more! A more distant star in the constellation Hercules hosts the hottest planet yet discovered. Yahoo News Space.com excerpt:
The hottest planet ever discovered is charcoal black and makes even some stars seem cool. Scientists think the exoplanet absorbs nearly all the starlight that reaches its surface and then reradiates it back out into space as heat.
Called HD149026b, the feverish world emits so much infrared heat that it glows slightly. "It would look like an ember in space, absorbing all incoming light but glowing a dull red," said study leader Joseph Harrington of the University of Central Florida.
Located 279 light-years away in the constellation Hercules, HD 149026b is a so-called hot Jupiter, a giant gas planet that orbits very close to its star. It is a scorching 3,700 degrees Fahrenheit (2,040 degrees Celsius), three times hotter than Mercury and hotter than the coolest stars.
Until very recently, HD 149026b was also the densest planet known. It contains higher levels of heavy elements --those other than hydrogen and helium-than all of the planets in our solar system combined, and its core might have up to 90 times the mass of the Earth.
"HD 149026b is simply the most exotic, bizarre planet," Harrington said. "It's pretty small, really dense, and now we find that it's extremely hot."
How HD 149026b got to be so hot is a mystery. "We've actually done a lot of work to try and answer that question, but the more we think about it, the worse it gets," Harrington said.
One idea, proposed by Jonathan Fortney at NASA's Ames Research Center in California, is that the planet is so hot that metals such as titanium and vanadium can exist in their gaseous forms in the planet's atmosphere. Such metals are "very, very, very strong visible [light] absorbers," said Fortney, who was not involved in the new study.
Fortney also pointed out HD 149026b orbits a very metal-rich star, which could explain why the planet is so abundant in heavy elements. The planet's "atmosphere is probably enhanced in metals compared to most other planets, so it's probably more efficient at absorbing stellar light than other hot Jupiter planets," Fortney said.
Fortney thinks HD 149026b could be the first of a new subgroup of hot Jupiters. "I think what we'll eventually find is that hot Jupiters may end up falling into two classes," he said. One class, Fortney said, would consist of relatively "cool" hot planets, in the range of about 1,300 to 2,000 degrees Fahrenheit (700 to 1,000 degrees C), and the other would have planets with temperatures of 3,000 degrees Fahrenheit (1,700 degrees C) or higher.
So just when you think the universe can't get any more bizarre, along comes a story to top the previous one. It reminds me of the Larry Niven short story Flatlander, in which his character Beowulf Shaeffer got dragged along by a rich friend named Elephant who wanted to find the most unusual planet inside Niven's setting of the Known Space series of stories he wrote in the 1960s and 70s. The pair find an antimatter planet, but don't realize it until it is almost too late. These worlds aren't antimatter planets, but they certainly rank as two of the most unusual objects that have yet been found.
And you've got to love the way Mr. Fortney and his colleagues are ready to begin reclassifying the objects they detect as the differences between one planet and another emerge. I wish them luck, because, as I previously stated, we've just scratched the surface here. I have a feeling that the really interesting stories are yet to come.
Full Hot Gas Giant Story