Name: Donnie
Status: Student
Grade: 9-12
Location: MI
Country: United States
Date: March 2006
Question:
How is it known that the sun will eventually destroy the Earth?
Replies:
Donnie,
There are two possibilities:
1) The the Sun will simply cool off and thus the Earth
will also.
2) The Sun will explode, possibly in a supernova. In that
case the explosion will impact most of the planets in
the solar system. The Earth may be destroyed, or just
partially destroyed and the remains thrown out of the
solar system.
However, neither of these will happen for many millions
to billions of years; certainly not within our lifetimes.
David R. Cook
Climate Research Section
Environmental Science Division
Without going into the details (which can be found in many books and/or
websites) stars of different masses undergo various stages of their life
cycles. That this is the case has been demonstrated by astronomical
observations of many star systems. For stars in the mass range of the Sun
the primary source of its energy is the conversion of hydrogen into helium.
As the Sun "burns" its hydrogen it loses mass (in the form of radiation and
high energy particles). The gravitational energy is balanced by the
radiation pressure. However, as the supply of hydrogen is depleted, the
reduced mass causes the star to increase in size, and to "cool" becoming a
red giant star with a diameter that exceeds the distance from the Sun to the
Earth. Of course, life would not be able to be sustained long before this
actually occurred. That part of the cycle is many millions of years away, so
it is of no particular practical interest. The human race has many more
potentially catastrophic events and ways to self-destruct long before that
becomes an issue.
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