Featured Research

from universities, journals, and other organizations

Four white dwarf stars caught in the act of consuming 'Earth-like' exoplanets

Date:
May 3, 2012
Source:
University of Warwick
Summary:
Astrophysicists have pinpointed four white dwarfs surrounded by dust from shattered planetary bodies which once bore striking similarities to the composition of Earth.

Artist's impression of the three steps leading up to the destruction of the exoplanets. The second image shows the inner region of an exo-planetary system where four terrestrial planets orbit a solar-like star. The third image shows the host star is running out of hydrogen in the core, swells up, and its surface becomes cooler. It is also losing mass, which causes the planets to move further out. The perturbation of the orbits may lead to collisions that will generate large amounts of rocky debris. The bottom image depicts what the researchers are now observing. A white dwarf sits in the center of the remnant of a planetary system. Asteroid sized debris is scattered inwards by interaction with the remaining planets and is tidally disrupted as it approaches the white dwarf forming a disc of dust some of which is raining down onto the star. The researchers have found that the composition of the debris that has just fallen onto the four white dwarfs matches the composition of Earth-like rocky worlds.
Credit: All images © Mark A. Garlick / space-art.co.uk / University of Warwick

University of Warwick astrophysicists have pinpointed four white dwarfs surrounded by dust from shattered planetary bodies which once bore striking similarities to the composition of Earth.

Using the Hubble Space Telescope for the biggest survey to date of the chemical composition of the atmospheres of white dwarf stars, the researchers found that the most frequently occurring elements in the dust around these four white dwarfs were oxygen, magnesium, iron and silicon -- the four elements that make up roughly 93 per cent of Earth.

However an even more significant observation was that this material also contained an extremely low proportion of carbon, which matched very closely that of Earth and the other rocky planets orbiting closest to our own Sun.

This is the first time that such low proportions of carbon have been measured in the atmospheres of white dwarf stars polluted by debris. Not only is this clear evidence that these stars once had at least one rocky exoplanet which they have now destroyed, the observations must also pinpoint the last phase of the death of these worlds.

The atmosphere of a white dwarf is made up of hydrogen and/or helium, so any heavy elements that come into their atmosphere are dragged downwards to their core and out of sight within a matter of days by the dwarf's high gravity. Given this, the astronomers must literally be observing the final phase of the death of these worlds as the material rains down on the stars at rates of up to 1 million kilograms every second.

Not only is this clear evidence that these stars once had rocky exoplanetary bodies which have now been destroyed, the observations of one particular white dwarf, PG0843+516, may also tell the story of the destruction of these worlds.

This star stood out from the rest owing to the relative overabundance of the elements iron, nickel and sulphur in the dust found in its atmosphere.

Iron and nickel are found in the cores of terrestrial planets, as they sink to the centre owing to the pull of gravity during planetary formation, and so does sulphur thanks to its chemical affinity to iron.

Therefore, researchers believe they are observing White Dwarf PG0843+516 in the very act of swallowing up material from the core of a rocky planet that was large enough to undergo differentiation, similar to the process that separated the core and the mantle of Earth.

The study by B. T. Gδnsicke, D. Koester, J. Farihi, J. Girven, S.G.Parsons, and E. Breedt is accepted for publication in the Monthly Notices of the Royal Astronomical Society.

Professor Boris Gδnsicke of the Department of Physics at the University of Warwick, who led the study, said the destructive process which caused the discs of dust around these distant white dwarfs is likely to one day play out in our own solar system.

"What we are seeing today in these white dwarfs several hundred light years away could well be a snapshot of the very distant future of Earth.

"As stars like our Sun reach the end of their life, they expand to become red giants when the nuclear fuel in their cores is depleted.

"When this happens in our own solar system, billions of years from now, the Sun will engulf the inner planets Mercury and Venus.

"It's unclear whether Earth will also be swallowed up by the Sun in its red giant phase -- but even if it survives, its surface will be roasted.

"During the transformation of the Sun into a white dwarf, it will lose a large amount of mass, and all the planets will move further out.

"This may destabilise the orbits and lead to collisions between planetary bodies as happened in the unstable early days of our solar system. This may even shatter entire terrestrial planets, forming large amounts of asteroids, some of which will have chemical compositions similar to those of the planetary core.

"In our solar system, Jupiter will survive the late evolution of the Sun unscathed, and scatter asteroids, new or old, towards the white dwarf.

"It is entirely feasible that in PG0843+516 we see the accretion of such fragments made from the core material of what was once a terrestrial exoplanet."

The University of Warwick led team surveyed more than 80 white dwarfs within a few hundred light years, using the Cosmic Origin Spectrograph onboard the Hubble Space Telescope.


Story Source:

The above story is based on materials provided by University of Warwick. Note: Materials may be edited for content and length.


Journal Reference:

  1. B.T. Gaensicke, D. Koester, J. Farihi, J. Girven, S.G. Parsons, E. Breedt. The chemical diversity of exo-terrestrial planetary debris around white dwarfs. Monthly Notices of the Royal Astronomical Society, (accepted) 2012 [link]

Cite This Page:

University of Warwick. "Four white dwarf stars caught in the act of consuming 'Earth-like' exoplanets." ScienceDaily. ScienceDaily, 3 May 2012. <www.sciencedaily.com/releases/2012/05/120503104117.htm>.
University of Warwick. (2012, May 3). Four white dwarf stars caught in the act of consuming 'Earth-like' exoplanets. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/2012/05/120503104117.htm
University of Warwick. "Four white dwarf stars caught in the act of consuming 'Earth-like' exoplanets." ScienceDaily. www.sciencedaily.com/releases/2012/05/120503104117.htm (accessed July 25, 2014).

Share This




More Space & Time News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: ISS Cargo Ship Launches in Kazakhstan

Raw: ISS Cargo Ship Launches in Kazakhstan

AP (July 23, 2014) — The Progress 56 cargo ship launched from the Baikonur Cosmodrome in Kazakhstan Wednesday. NASA says it will deliver cargo and crew supplies to the International Space Station. (July 23) Video provided by AP
Powered by NewsLook.com
Raw: Cargo Craft Undocks from Space Station

Raw: Cargo Craft Undocks from Space Station

AP (July 22, 2014) — A Russian Soyuz cargo-carrying spacecraft undocked from the International Space Station on Monday. The craft is due to undergo about ten days of engineering tests before it burns up in the Earth's atmosphere. (July 22) Video provided by AP
Powered by NewsLook.com
NASA Ceremony Honors Moon Walker Neil Armstrong

NASA Ceremony Honors Moon Walker Neil Armstrong

AP (July 21, 2014) — NASA honored one of its most famous astronauts Monday by renaming a historic building at the Kennedy Space Center in Florida. It now bears the name of Neil Armstrong, the first man to walk on the moon. (July 21) Video provided by AP
Powered by NewsLook.com
Neil Armstrong's Post-Apollo 11 Life

Neil Armstrong's Post-Apollo 11 Life

Newsy (July 19, 2014) — Neil Armstrong gained international fame after becoming the first man to walk on the moon in 1969. But what was his life like after the historic trip? Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

    Health News

      Environment News

        Technology News



          Save/Print:
          Share:  

          Free Subscriptions


          Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

          Get Social & Mobile


          Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

          Have Feedback?


          Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
          Mobile iPhone Android Web
          Follow Facebook Twitter Google+
          Subscribe RSS Feeds Email Newsletters
          Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins