White dwarf discovery creates new questions for Earth’s survival
The discovery of a white dwarf with planetary debris has provided scientists with interesting theories around Earth’s distant future when our sun runs out of fuel in about five billion years
READING LEVEL: ORANGE
Billions of years from now, the sun is expected to run out of fuel and greatly expand
into what is called a red giant*, eventually shedding its outer layers and leaving behind its dense core, a white dwarf*. Some of the planets in our solar system would be destroyed, while others might survive.
So what will happen to Earth when the sun burns out? Scientists say the discovery of a white dwarf with planetary debris swirling around it in an unusual configuration may offer a peek into one possible outcome for our solar system in the distant future.
Unlike in similar systems previously observed, the debris disc* surrounding this white dwarf appears to be made up of two distinct rings. The researchers said the disc may have been
shaped by two planetary or smaller rocky bodies that are embedded in the rings after managing to survive the star’s dramatic death.
The white dwarf, named J1328−1450, is located in the Milky Way roughly 1600 light-years from Earth, in the constellation Virgo. A light-year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km).
The observations were made using the European Southern Observatory’s Chile-based Very Large Telescope.
Prior to this discovery, astronomers had identified 21 white dwarfs with debris surrounding them, all of which had a single disc and not a double ring of material like the newly discovered white dwarf.
“It shows that the remnants of a planetary system can have a much more complex structure than we previously thought, and provides further support to the idea that planetary rocky bodies may survive the transformation of a star into a white dwarf,” said astronomer Dr Felipe Lagos-Vilches of Universidad Técnica Federico Santa María in Chile, one of the authors of the study published in the journal Nature Astronomy.
The white dwarf has a mass about 47 per cent that of the sun, jam-packed into a diameter roughly the same as that of Earth.
The surviving planetary bodies may be pieces of larger and heavily disrupted planets. One of them may be around the size of the dwarf planet Pluto, with the other one smaller than that.
Dr Lagos-Vilches said the original star may have hosted a planetary system before it expanded dramatically into a red giant, engulfing some of the innermost planets while ones with more distant orbits survived.
“The planetary system did not completely disappear. Some surviving rocky bodies may have been gravitationally perturbed* onto highly eccentric* orbits that brought them close to the
white dwarf,” Dr Lagos-Vilches said.
“Objects that came sufficiently close were disrupted by the white dwarf’s gravitational force*. Their material was spread into a debris disc containing dust and gas. However, two relatively large rocky bodies may have survived within this debris,” Dr Lagos-Vilches said.
The presence of the two bodies may help explain the different types of material found in the pair of concentric* gaseous rings, Dr Lagos-Vilches said.
“The outer ring is strongly depleted in magnesium compared with the inner ring. This suggests that they may originate from different parent bodies, or possibly from different layers of a rocky body that was disrupted when it went too close to the white dwarf due to its strong gravitational field,” Dr Lagos-Vilches said.
A GLIMPSE INTO THE FUTURE
In about five billion years, the sun will become a red giant, Dr Lagos-Vilches said.
“It will eventually lose its outer layers and become a white dwarf,” he said. “The inner solar system will be dramatically affected. Mercury and Venus are expected to be engulfed by the expanding sun, while there is still no clear consensus on whether Earth will also be engulfed during this phase.
“The fate of the outer planets is different. Jupiter, Saturn and the more distant bodies should have a much better chance of surviving.”
After the sun becomes a white dwarf, surviving planetary remnants, moons and asteroids could potentially be drawn close enough to the white dwarf to be torn apart by gravitational
forces.
“A debris disc like the one around J1328−1450 could therefore represent one possible stage in the very distant future of our own planetary system,” Dr Lagos-Vilches said.
Minor edits have been made to this story for Kids News. Reuters reporting by Will Dunham in Washington; editing by Daniel Wallis
POLL
GLOSSARY
- red giant: a giant, late stage star that has run out of the hydrogen fuel in its core and swelled to many times its original size
- white dwarf: the dense, stellar core left after a red giant sheds its outer layer
- debris disc: a ring or belt of space dust, asteroids, comets and other rocky or icy fragments orbiting a mature star
- gravitationally perturbed: the physical path of an object has been altered by the extra gravitational pull of a neighbouring body or external force
- eccentric: an orbital path that deviates quite a bit from a circle and is stretched out into an oval or ellipse
- gravitational force: the invisible attractive force that exists between any two objects that have mass, pulling objects towards each other. It’s the force that makes heavy, solid things fall down when you drop them
- concentric: two circles or spheres that sit inside one another while having the exact same centre point
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QUICK QUIZ
1. What is expected to eventually happen to the sun?
2. In how many years is this estimated to occur?
3. What is unique about this newly discovered white dwarf?
4. How does this white dwarf compare to the mass of our sun?
5. How do the white dwarf’s two rings compare?
LISTEN TO THIS STORY
CLASSROOM ACTIVITIES
1. Life cycle of a star
Work with a partner to create a labelled diagram or flowchart showing the stages of a star as described in the Kids News article.
In your explanation make sure you include the following as well as a picture;
1. The Sun as it is today.
2. The Sun running out of fuel.
3. Expansion into a red giant.
4. Loss of the Sun’s outer layers.
5. Formation of a white dwarf.
Share your diagram with your classmates.
Time: allow 25 minutes to complete this activity
Curriculum Links: English, Science, Visual Arts, Personal and Social, Critical and Creative Thinking
2. Extension
The article explains that a light-year is the distance light travels in one year, approximately 9.5 trillion kilometres.
Can you explain why astronomers use light-years instead of kilometres when describing distances between stars? Draw a picture if it helps your explanation.
Time: allow 10 minutes to complete this activity
Curriculum Links: English, Science, Personal and Social, Critical and Creative Thinking
VCOP ACTIVITY
BAB it!
Show you have read and understood the article by writing three sentences using the connectives “because’’, “and”, and “but” (BAB). Your sentences can share different facts or opinions, or the same ones but written about in different ways.