Astronomers discover Earth-sized planets forming near start of universe

Kepler-444 hosts five Earth-sized planets in very compact orbits. The planets were detected from the dimming that occurs when they transit the disc of their parent star, as shown in this artist’s conception. Image credit: Tiago Campante/Peter Devine

An international team of astronomers has discovered a sun-like star with five orbiting planets, dating back to the dawn of the galaxy. At 11.2 billion years, old it is the oldest star with Earth-size planets yet found and suggests that such planets have formed throughout the history of the universe.

The discovery, announced today in the Astrophysical Journal, used observations made by NASA’s Kepler spacecraft over a period of four years.

The old, sun-like star, named Kepler-444, hosts five planets smaller than Earth, with sizes varying between those of Mercury and Venus. Kepler-444 formed 11.2 billion years ago, when the universe was less than 20% of its current age. This makes Kepler-444 the oldest known system of terrestrial-sized planets. The Kepler-444 system was already older than our own solar system is today when our sun and planets were born.

Dr. Daniel Huber from the University of Syndey’s School of Physics is author on the paper. Huber said:

We’ve never seen anything like this. It is such an old star and the large number of small planets make it very special.

It is extraordinary that such an ancient system of terrestrial-sized planets formed when the universe was just starting out, at a fifth its current age. Kepler-444 is two and a half times older than our solar system, which is only a youthful 4.5 billion years old.

This tells us that planets this size have formed for most of the history of the universe and we are much better placed to understand exactly when this began happening.

To determine the age of the star and planets, team used asteroseismology — listening to the host star’s oscillations – natural resonances, which are caused by sound trapped within it

These oscillations lead to minuscule changes or pulses in the star’s brightness and allow researchers to measure its diameter, mass, and age. The presence and size of the planets is detected by the dimming that occurs when the planets pass across the face of the star. This fading in the intensity of the light received from the star enables scientists to accurately measure the sizes of the planets relative to the size of the star. Dr. Huber said:

Asteroseismology allows us to precisely measure the radius of Kepler-444 and hence the sizes of its planets. For the smallest planet in the Kepler-444 system, which is slightly larger than Mercury, we measured its size with an uncertainty of only 100 km,” Dr. Huber said.

It was clear early on that we had discovered something very unusual because we had five planets orbiting a very bright star — one of the brightest Kepler has observed. It is fantastic that we can use asteroseismology to date the star and determine just how old it is.

In the case of Kepler-444, the researchers said, the planets orbit their parent star in less than 10 days, at less than one-tenth the Earth’s distance from the sun. Their closeness to their host star means they are uninhabitable because of the lack of liquid water and high levels of radiation.

Dr. Tiago Campante, the research leader from the University of Birmingham said:

We now know that Earth-size planets have formed throughout most of the universe’s 13.8-billion-year history, which could provide scope for the existence of ancient life in the galaxy.

Read more from Yale University

from EarthSky http://ift.tt/1D4uySI

Kepler-444 hosts five Earth-sized planets in very compact orbits. The planets were detected from the dimming that occurs when they transit the disc of their parent star, as shown in this artist’s conception. Image credit: Tiago Campante/Peter Devine

An international team of astronomers has discovered a sun-like star with five orbiting planets, dating back to the dawn of the galaxy. At 11.2 billion years, old it is the oldest star with Earth-size planets yet found and suggests that such planets have formed throughout the history of the universe.

The discovery, announced today in the Astrophysical Journal, used observations made by NASA’s Kepler spacecraft over a period of four years.

The old, sun-like star, named Kepler-444, hosts five planets smaller than Earth, with sizes varying between those of Mercury and Venus. Kepler-444 formed 11.2 billion years ago, when the universe was less than 20% of its current age. This makes Kepler-444 the oldest known system of terrestrial-sized planets. The Kepler-444 system was already older than our own solar system is today when our sun and planets were born.

Dr. Daniel Huber from the University of Syndey’s School of Physics is author on the paper. Huber said:

We’ve never seen anything like this. It is such an old star and the large number of small planets make it very special.

It is extraordinary that such an ancient system of terrestrial-sized planets formed when the universe was just starting out, at a fifth its current age. Kepler-444 is two and a half times older than our solar system, which is only a youthful 4.5 billion years old.

This tells us that planets this size have formed for most of the history of the universe and we are much better placed to understand exactly when this began happening.

To determine the age of the star and planets, team used asteroseismology — listening to the host star’s oscillations – natural resonances, which are caused by sound trapped within it

These oscillations lead to minuscule changes or pulses in the star’s brightness and allow researchers to measure its diameter, mass, and age. The presence and size of the planets is detected by the dimming that occurs when the planets pass across the face of the star. This fading in the intensity of the light received from the star enables scientists to accurately measure the sizes of the planets relative to the size of the star. Dr. Huber said:

Asteroseismology allows us to precisely measure the radius of Kepler-444 and hence the sizes of its planets. For the smallest planet in the Kepler-444 system, which is slightly larger than Mercury, we measured its size with an uncertainty of only 100 km,” Dr. Huber said.

It was clear early on that we had discovered something very unusual because we had five planets orbiting a very bright star — one of the brightest Kepler has observed. It is fantastic that we can use asteroseismology to date the star and determine just how old it is.

In the case of Kepler-444, the researchers said, the planets orbit their parent star in less than 10 days, at less than one-tenth the Earth’s distance from the sun. Their closeness to their host star means they are uninhabitable because of the lack of liquid water and high levels of radiation.

Dr. Tiago Campante, the research leader from the University of Birmingham said:

We now know that Earth-size planets have formed throughout most of the universe’s 13.8-billion-year history, which could provide scope for the existence of ancient life in the galaxy.

Read more from Yale University

from EarthSky http://ift.tt/1D4uySI