New 'earth-sized' planet confirmed

A new "earth-sized" planet in the Kepler star field has been discovered by space- and ground-based observations.

 

The US' National Optical Astronomy Observatory said the planet, dubbed Kepler 21b, is about 1.6 times the radius of the Earth but has a year only 2.8 days long.

 

But the researchers said the planet will likely be very hot due to its closeness to the star it is orbiting.

 

"With a period of only 2.8 days, this planet, designated Kepler-21b, is only about 6 million km away from its parent star. By comparison Mercury, the closest planet to the Sun, has a period of 88 days and a distance from the Sun almost 10 times greater, or 57 million km. So Kepler-21b is far hotter than any place humans could venture," the NOAO said.

 

On the other hand, the research team calculated the temperature at the surface of the planet is about 1900 Kelvin, or 2,960 degrees Fahrenheit.

 

"While this temperature is nowhere near the habitable zone in which liquid water might be found, the planet's size is approaching that of the Earth," the NOAO said.

 

The Kepler mission had been designed to survey a portion of our region of the Milky Way Galaxy to discover Earth-size planets in or near the "habitable zone."

 

A "habitable zone" is defined as an area where liquid water can exist. Discovery in the Kepler star field

 

Researchers led by Steve Howell of the NASA Ames Research Center found Kepler 21b circling one of the brightest stars in the Kepler star field.

 

"(The planet has) a radius only 1.6 that of the Earth's radius and a mass no greater that 10 Earth masses, circling its parent star with a 2.8-day period," NOAO said.

 

With such a short period, and such a bright star, the team of over 65 astronomers that included David Silva, Ken Mighell, and Mark Everett of NOAO needed multiple telescopes on the ground to support and confirm their Kepler observations.

 

These included the 4-meter Mayall telescope and the WIYN telescope at Kitt Peak National Observatory.

 

NOAO said the Kepler mission observed this field for over 15 months, and the team combined the observations to enable them to detect this tiny, periodic signal.

 

They also relied on spectroscopic and imaging data from a number of ground-based telescopes.

 

The results of this work have been accepted for publication in the Astrophysical Journal.

 

Parent star similar to our sun

 

NOAO said Kepler 21b's parent star, HD 179070, is "quite similar to our Sun," with a mass of 1.3 solar masses.

 

"Its radius is 1.9 solar radii, and its age, based on stellar models, is 2.84 billion years (or a bit younger than the Sun's 4.6 billion years). HD 179070 is spectral type F6 IV, a little hotter and brighter than the Sun. By astronomical standards, HD 179070 is fairly close, at a distance from the Sun of 352 light-years," it said.

 

"While it cannot be seen by the unaided eye, a small telescope can easily pick it out," it added.

 

NOAO said part of the difficulty in detecting this planet is the realization from the Kepler mission, that many stars show short-period brightness oscillations.

 

The effect of these must be removed from the stellar light to uncover the regular, but very small, dimming caused by the planet passing in front of the star. — TJD, GMA News