Download What`s Brewing in the Teapot - Indiana University Astronomy

What’s Brewing in the Teapot?
M22
M8
M6
Caty Pilachowski
IU Astronomy
M7
Introducing the
Milky Way
Our
very
own
spiral
galaxy
Four
Galaxies
similar
to the
MW
Barred
spirals
(seen
face-on)
The Milky Way
What’s in the
Milky Way?
• Stars and Star Clusters
• Clouds – giant molecular clouds, H I clouds, H II
regions, dust
• Nebulae – reflection nebulae, emission nebulae,
nova/supernova remnants, planetary nebulae
Solar Neighborhood
Our Local
Neighborhood
• The nearest
stars are
cool and
dim, and
small
• Mostly too
faint to see
with the
naked eye
Solar Neighborhood
• Most nakedeye stars are
intrinsically
brighter and
more distant,
within a few
hundred light
years
Our Local
Neighborhood
Finding the Center of
the Milky Way
The discovery of certain types of
variable stars allowed Harlow
Shapley to determine the distances
to globular star clusters
The globular clusters concentrate
near the center of the Milky Way
The distance
to the
Galactic
Center is
about 26,000
light years
Milky Way Specs
A spiral galaxy shaped like a disk
Diameter ~100,000 light years
Thickness ~300 light years
The Sun is ~2/3 of the way out from the center
to the edge
 Mass about 200 billion Suns (from the orbits of
stars)
 The Sun orbits the center of the Galaxy
moving toward Cygnus
speed of ~220 kilometers/second
one Galactic orbit takes ~240 MILLION years




The Galactic Center!
At visual wavelengths,
this region is totally hidden
from us by gas and dust
that dim the light by a factor of
10 billion!
The Galactic Center in the Near
Infrared
In infrared light, we
can see through the
gas and dust to
observe many of the
stars near the
Galactic center.
But the Galactic
center itself remains
undetected in
infrared light –
hidden behind thick
clouds of dust and
gas.
The Galactic Center in the Infrared
Behind the
gas and dust
are
countless
stars – and
we can see
them in
infrared
light
40”
4’
5”
>220 stars in 5”x5”
UH-88”, Courtesy W.Brandner, 0.65” seeing
Gemini N/Hokupa’a-QUIRC (U of H/NSF)
The Galactic Center further in
the Infrared
Now we can see
not only stars, but
warm gas that
glows in the
infrared
Sgr A* is the
center of the MW
SgrA*
Galactic Center at Radio
Wavelengths – It’s a MESS!
• Sgr A* is bright in
radio light!
• Supernova remnants
• Arcs and threads
The Galactic Center in X-rays
This false-color image of the
central region of our Milky
Way Galaxy was made with
the Chandra X-ray telescope.
The bright, point-like source
at the center of the image
was produced by a huge X-ray
flare at the center of the
Galaxy.
Galactic Center Finally Detected
in Infrared Light!
• Seen with ESO
Very Large
Telescope (8-m)
and Keck 10-m
Telescope
• Bright flare in
infrared light
• SgrA* is faint
but stars nearby
are bright
SgrA* is a supermassive black hole!
“A supermassive black hole at the
center of our galaxy is adequate
to explain the observations that
have been seen.”
Orbit of star S2 (followed for
ten years) around the central
mass is consistent with a 2.63.3 million solar mass object
within 10 light days of Sgr A*
Galactic Center Research at MPE
What is a
Black Hole?
•Black holes are objects with such strong gravity that
not even light can escape
•Since nothing can travel faster than light, nothing can
escape from inside a black hole
•Objects of any mass can (in principle) become black
holes if sufficiently compressed
•How compressed? – depends on mass
radius = 3 km x mass (in solar masses)
•The Sun would become a black hole if compressed to a
radius of 3 kilometers
What is a Black Hole?
•Since nothing can travel faster than
light, nothing can escape from inside a
black hole
•Even in Isaac Newton’s time, scientists
speculated that such objects could
exist
•Space and time near a black hole
become so warped that time practically
stops (from Theory of Relativity)
Defining Terms
• Singularity – The place at the center of a black hole
where, in principle, gravity crushes all matter to an
infinitely tiny and dense point.
• Event Horizon – The boundary that marks the “point
of no return” between a black hole and the outside
universe. Events that occur within the event horizon
can have no influence on our observable universe.
• Schwarzschild Radius – A measure of the size of the
event horizon of a black hole.
Exploring the Schwarzschild Radius
•The size of a black hole depends on mass
•A black hole can have any mass, from billions of times
Any object with mass
can become a black hole
if it can be crushed to a
small enough radius!
The graph shows the
radius at which a
given mass (in solar
masses) will become a
black hole if all of the
mass is compressed
into a sphere that
size or smaller.
Schwarzschild Radius (km)
the mass of the Sun to very small (even your mass!)
10000000
1000000
100000
10000
1000
100
10
1
0.1
0.01
0.001
0.0001
0.00001
1.0E-06
1.0E-04
1.0E-02
1.0E+00
1.0E+02
Solar Masses
1.0E+04
1.0E+06
1.0E+08
What evidence do astronomers use to infer the
presence of a black hole?
Matter flowing into a black
hole emits X-rays before it
crosses the event horizon
Astronomers look for
massive objects orbiting unseen centers
The unseen objects must
be black holes
And what do you see if
you fall into a black
hole’s event horizon?
…the black void is suddenly replaced by an
unimaginable array of views.
We don’t know what you may see inside the black hole
and, unfortunately, you can never tell us about your
discoveries. Any signal you send to us is sucked into
the black hole with you.
You are lost to our universe forever.
And within a few seconds, you are swept into the
massive singularity at the center of the black hole!
What would you see if you went
right up to a Black Hole?
Two computer generated
images:
left: normal star field
(find Orion’s belt)
right: a black hole has
been added at the
center of the field
•The black hole has such strong gravity that light is noticeably bent towards it
- causing some very unusual visual distortions.
• In the distorted frame, every star in the normal frame has at least two bright
images - one on each side of the black hole.
•Near the blackhole, you can see the whole sky - light from every direction is
bent around and comes back to you.
Approaching a Black Hole
Key Ideas –
The Galactic
Center
• Powerful radio source
• Stars very densely packed
• Surrounded by ring of gas of hydrogen
molecules (H2) that is empty in the center
• Central object is small – less than 4 AU
• Stars near the center are moving rapidly
• Black Hole! – 2-3 million times the mass of the
Sun
Black Holes
in the
Centers of
MOST (all?)
Galaxies
Left: Image of galaxy NGC4261, 45 million light
years from Earth. The orange part is radio
signals represented in false color.
Right: Hubble's space telescope image of the
center of the same galaxy. It is suspected that
there is a black hole at the center of this image.
Supermassive
Black Holes
A key
discovery
of Hubble
Enjoy the
Teapot’s
brew
tonight!
Caty Pilachowski
IU Astronomy
Visiting
Kirkwood
Observatory
@ IUB
• Open Wednesday evenings after dark
• See http://www.astro.indiana.edu/kirk_sch.shtml
• Call the hotline for open hours at (812) 855-7736
• Receive the monthly Kirkwood Observatory
Bulletin by email – request at
[email protected]