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R. N. Mohapatra
experience mass loss, implying that its gravitational force on the planets will
become weaker and that will push the planets like the Earth, Venus, and
Mercury farther from the sun. That way, we on Earth may be spared from
the heat death due to the red giant expansion of the Sun. However, we do not
know for sure how much mass loss the sun will have, if any.
After the stars become red giants, they burn helium to carbon, followed
by carbon to oxygen, then neon, silicon, magnesium, and sulfur, until finally
they reach a stage where the stellar core is filled with iron. Further compression
after that will not generate any radiation energy from nuclear reactions. As a
result, the star, if it is massive enough, will explode as a supernova. The star
will thus melt and die. Some will become neutron stars and some will end up
as black holes floating in the sky, which would move around like an endless
parade of zombies. They would whistle occasionally when they fall into each
other, giving out gravity waves and possibly some flashes of light, and maybe
even neutrinos. Such gravity waves from black hole pairs and neutron star pairs
have indeed been seen at the LIGO and VIRGO observatories, and no doubt
more will be seen in the future, confirming the general outline (not details) of
this picture.
If the star has a smaller mass, after the red giant phase it will become a white
dwarf and then cool down to become a black dwarf. Stars which have masses
of about a few percents of the solar mass cannot sustain nuclear reactions and
remain as what is known as brown dwarfs.
The galaxies are part of clusters which have many galaxies. As a result, they
can collide with each other as they move through the sky. So would the stars
in a galaxy, which we discuss next. For example, our galaxy is known to be on
a collision course with the closest galaxy to us, the Andromeda Galaxy, and
the encounter is likely to occur in some four to six billion years from now.
This was first suspected by Vesto Slipher in 1913. When that happens, the
two galaxies may merge and the solar system will have different “zip code.”
Some astronomers have called the new galaxy resulting from this merger as
“Milkomeda,” which will most likely be an elliptical galaxy, unlike the Milky
Way, which is a spiral galaxy. In fact, it is now established that our own
galaxy has merged with several dwarf galaxies over the course of time. So a
galaxy merger is not an uncommon feature. The Hubble Telescope has found
evidence for many other galaxy mergers, which have been analyzed by NASA
teams and provided a clearer picture of merger rates, say one to a few in ten
billion years.
Of course contrary to what we may expect, in galactic collision, there is
hardly any collision between the stars in the galaxy since the density of stars
in a galaxy is very low. However, the interstellar gases will collide and that can
R. N. Mohapatra
experience mass loss, implying that its gravitational force on the planets will
become weaker and that will push the planets like the Earth, Venus, and
Mercury farther from the sun. That way, we on Earth may be spared from
the heat death due to the red giant expansion of the Sun. However, we do not
know for sure how much mass loss the sun will have, if any.
After the stars become red giants, they burn helium to carbon, followed
by carbon to oxygen, then neon, silicon, magnesium, and sulfur, until finally
they reach a stage where the stellar core is filled with iron. Further compression
after that will not generate any radiation energy from nuclear reactions. As a
result, the star, if it is massive enough, will explode as a supernova. The star
will thus melt and die. Some will become neutron stars and some will end up
as black holes floating in the sky, which would move around like an endless
parade of zombies. They would whistle occasionally when they fall into each
other, giving out gravity waves and possibly some flashes of light, and maybe
even neutrinos. Such gravity waves from black hole pairs and neutron star pairs
have indeed been seen at the LIGO and VIRGO observatories, and no doubt
more will be seen in the future, confirming the general outline (not details) of
this picture.
If the star has a smaller mass, after the red giant phase it will become a white
dwarf and then cool down to become a black dwarf. Stars which have masses
of about a few percents of the solar mass cannot sustain nuclear reactions and
remain as what is known as brown dwarfs.
The galaxies are part of clusters which have many galaxies. As a result, they
can collide with each other as they move through the sky. So would the stars
in a galaxy, which we discuss next. For example, our galaxy is known to be on
a collision course with the closest galaxy to us, the Andromeda Galaxy, and
the encounter is likely to occur in some four to six billion years from now.
This was first suspected by Vesto Slipher in 1913. When that happens, the
two galaxies may merge and the solar system will have different “zip code.”
Some astronomers have called the new galaxy resulting from this merger as
“Milkomeda,” which will most likely be an elliptical galaxy, unlike the Milky
Way, which is a spiral galaxy. In fact, it is now established that our own
galaxy has merged with several dwarf galaxies over the course of time. So a
galaxy merger is not an uncommon feature. The Hubble Telescope has found
evidence for many other galaxy mergers, which have been analyzed by NASA
teams and provided a clearer picture of merger rates, say one to a few in ten
billion years.
Of course contrary to what we may expect, in galactic collision, there is
hardly any collision between the stars in the galaxy since the density of stars
in a galaxy is very low. However, the interstellar gases will collide and that can