Transcript Stars and Their Life Cycles

Stars
Counting Stars
Nebulae
• A nebula is a cloud of dust, hydrogen gas
and plasma.
• The material clumps together to form
larger masses that eventually are big
enough to form a protostar.
• This is the first stage in the star life cycle.
• Nebulae often create star-forming regions,
such as the Eagle Nebula.
The Eagle
Nebula is
also called
the Pillars of
Creation
Cat’s Eye Nebula
Ant Nebula
Crab Nebula
Protostar – a newborn star
Oldest Star (2/11/14)
13 billion years old
6,000 light years from Earth
In Milky Way Galaxy
Called SMSS J031300.362670839.3
formed from the remains of a primordial star
unexpected composition of mostly carbon and no iron
heavy elements went into a black hole that formed when
the star exploded
because of its low mass, it has a long lifetime
Brown Dwarf
• bigger than a big planet like Jupiter but smaller
that a small star
• any object 15 to 75 times the mass of Jupiter
• the object would not have been able to sustain
fusion like a regular star - called "failed stars"
• all are parts of a binary system (two stars orbit
around one another)
• possible that brown dwarfs represent a lot of the
mass in the universe
Main Sequence Star (our Sun)
Main Sequence Stars
• all stars fuse hydrogen into helium
• 90% of all stars, including our Sun, are
main sequence stars (average stars)
• range from high luminosity (brightness)
and high surface temperature to low
luminosity and low surface temperature
Red Giant
• When a middle
aged star begins to
die, the temperature
near the core rises.
• The star expands.
• This will happen to
our Sun in about 5
billion years.
• Once the red giant runs
out of energy, it collapses
and becomes a white
dwarf, a small and dense
star.
• A white dwarf is the core of
the original star. It is very
hot and cools down over
the next billion years.
• The part that is blown off
may become a planetary
nebula.
White Dwarf
- star near the
end of its life
- was a red
giant star
that lost its
outer
atmosphere
- just the core
is left
White Dwarves photo taken by the Hubble Space Telescope
BPM 37093 is a huge white dwarf star
nicknamed Lucy after The Beatles’ hit
Lucy in the Sky with Diamonds.
BPM 37093 – aka Lucy
• is 50 light years from Earth
in the constellation Centaurus
• is 2500 miles across
• weighs 2.27 thousand trillion
trillion tonnes
BPM 37093 – aka Lucy
• has a core 50% to 90% of its
mass (size of our moon!)
• The core is Diamond!!!!!
• equal to 10 billion trillion trillion
carats, which is a 1 with 34
zeroes (1 carat = 200 mg)
• will happen to our sun in 7
billion years
Black Dwarf - a white dwarf that cooled, lost its energy and
no longer gives off light. It is a black object in space.
Our Sun’s Life Cycle
Our Sun is an average star.
Protostar
Main Sequence Star
Red Giant
White Dwarf
Black Dwarf
Giant Stars are 10 to 100 times larger in diameter
than our Sun are therefore more luminous (brighter).
Supergiant Stars are more than 100 times the diameter of
our Sun. They are more luminous than giant stars.
They are relatively cool stars but they are bright because
they are so large. Betelgeuse is a supergiant star.
A Mystery
Young, massive stars shine
brightly in UV, heating the
gas around them. Why
doesn’t the hot gas explode?
Why do these stars flicker
like candles?
American Museum of Natural History, New York City
January 24, 2014
Massive stars begin to shine while they are still forming instead of
afterward. Their UV light heats the nebula to 10,000 degrees Celsius. As
the star forms, dense filamentary structures that absorb the UV radiation
are created. As a result, the nebula flickers like a candle and the star does
not explode.
Karl G. Jansky Very Large Array (VLA) in New Mexico
ALL stars
become red
giants but
ONLY the
largest stars
explode in a
supernova.
Supernova – collapse of the core of a red giant that produces
a shock wave that blasts the star’s outer layers into space
Remains from a supernova
Neutron Star – the
core left behind after
a supernova may be
only a few dozen
miles across but a
sugar-cubed-size
piece would weigh 1
billion tons on Earth.
They have so much gravity that if you
dropped a marshmallow on a neutron star,
the impact would generate as much energy
as an atom bomb!
Pulsar – a neutron star
that spins very fast and
emits burst of radio waves.
A supernova results in
either a Neutron Star OR a
pulsar.
The just discovered blue
pulsar here is a “dead” star
beaming out more energy
than 10 million suns!
• Einstein’s mathematical formulas
predicted the existence of very
dense invisible stars but he did not
believe they actually existed.
• As a giant star collapses, its core
plunges inward and temperatures
reach 100 billion degrees.
• Hunks of iron bigger than Mount
Everest are compacted to the size of
grains of sand.
• Atoms are shattered into electrons,
protons, neutrons and these are
pulped into quarks, leptons, and
gluons.
• Tinier and tinier, denser and
denser…………………………
• Most massive stars become
black holes when they die.
• The dividing line between
inside and outside a black
hole is called the event
horizon.
• Quasars are galaxies with
black holes at their center.
The Milky Way Galaxy has
a black hole at its center
named Sagittarius A*.
Black Hole
Here is a picture of a black hole.
Black Hole
• Up until the 1960s, we could only see visible
light from the universe. Then x-ray and radio
wave telescopes began to be used.
• The term, black hole, was first used by
American physicist John Wheeler during a talk at
Columbia University in NYC in 1967.
• Both general relativity and quantum mechanics
theories cannot explain black holes.
Black Hole
• To escape Earth’s gravity
you need to accelerate at
7 miles per second (12
times faster than a bullet).
We have been able to do
this with rockets since
1959.
• The gravity of a black hole
is so strong that even light
can’t escape. The speed
of light (186,282 miles per
second) is too low!
Sgr A*
• 4.3 million times as heavy as the
Sun. This is a small black hole!
• Gas cloud G2 is moving toward it at
1,800 miles per second. Within one
year, G2 will “fall into” Sgr A*.
• Because black holes spin like
whirlpools, 90% of matter may be
flung off into space and form new
stars.
Sgr A* in 2011, 2012, 2013,
2014 and 2016 as it “eats” G2.
The action began on March 31, 2014. The light that just
misses being dragged in should be bent by the black hole’s
gravity into a halo that frames it. If this doesn’t happen,
Einstein’s theory of gravity will need to be revised.
NASA X-ray Telescopes Find Black Hole May Be a Neutrino
Factory.
The giant black hole at the center of the Milky Way may be
producing mysterious particles called neutrinos.
NuStar – Nuclear Spectroscopic Telescope Array
Launched in 2012 to
study black holes
and collapsed stars
The 2015 Rossi Astrophysics
Prize has been awarded to
Fiona Harrison, the principal
investigator of NASA's
NuSTAR project.
Life Cycle of a
Giant Star
Supergiant Star
•
•
•
•
•
Protostar
Giant Star
Red Giant
Supernova
Neutron Star
or Pulsar
▪ Protostar
▪ Supergiant
▪ Super Red
Giant
▪ Supernova
▪ Black Hole
HertzsprungRussell
Diagram
Classifies stars based on
their absolute magnitude
and surface temperature.
Absolute magnitude is
how bright a star would
be if all of the stars were
the same distance from
Earth.
Surface temperature is
related to a star’s color.
Time is affected by gravity.
• Extremely accurate clocks
placed on the lowest and
highest levels of the
Empire State Building tick
at different rates.
• Clocks on GPS satellites
have to be set to tick
slightly slower than those
on Earth’s surface to
make GPS accurate.
• One minute on the Sgr A*
event horizon is 1000
years on Earth.
• Therefore, black holes are
time machines.
Mrs. Donahue’s brain now explodes…
What happens if you cross the
event horizon into a black hole?
a) You burn up in the fire wall.
b) Nothing. You pass through. You’re fine.
c) Then you get “spaghettified.”
a) As you fall, gravity gets stronger so the pull
on your feet is greater than the tug on your
head and you get stretched until you are
ripped apart.
b) The pieces that reach the bottom encounter
a singularity. ???????????????????????
2.11.16
Scientists detected gravitational waves! Gravity is a wave!
These are ripples in the fabric of space time.
Einstein predicted this 100 years ago.
An international team of astrophysicists used a $1.1 billion
instrument to detect waves from the distant crash of two black
holes.
New Thoughts
• We are in a multiverse – a collection of
universes, each of which is a separate
bubble of reality.
• The Big Bang that created our universe
was the result of a singularity “opening.”