Credit: Axel Aitoff - people.physics.tamu.edu · perigalacticon distance of 1.8 x 1013 m = 120 AU...
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Credit: Axel Aitoff
Transcript of Credit: Axel Aitoff - people.physics.tamu.edu · perigalacticon distance of 1.8 x 1013 m = 120 AU...
Credit: Axel Aitoff
Milky Way Galaxy
Our Galaxy is a collection of stars and interstellar matter - stars, gas, dust, neutron stars, black holes -
held together by gravity
Composite near-IR (2 micron) Image from the Two Micron All Sky Survey (IPAC/Caltech/UMass)
The Morphology of the Galaxy
The solar Galactocentric distance, R0, is still debated. In 1985 the International Astronomical Union (IAU) adopted R0 = 8.5 kpc. Recent studies
find R0 = 8 kpc (Eisenhauer 2003). Your book uses this latter value.
The Galaxy is composed of a bulge, a thin and thick disk, and a halo.
Most stars are in disk components. Disk contains lots of gas and dust.
Halo has low density and it contains many globular clusters.
Milky Way Galaxy
The Galactic Bulge
COBE Satellite image of Milky Way at 1.2-3.5 micron.
from Digital Sky LLC
Spiral Structure
Galaxy M 51
Morphology of the Milky Way
from Digital Sky LLC
Sun
R0 = 8 kpc
from Digital Sky LLC
http://www.youtube.com/watch?v=Suugn-p5C1M
The Galactic Center
Challenging to observe because of all the dust/gas !
But, in 15 million years, the Sun will be 85 pc above the Galactic midplane, we would presumably have a much better view then !
The Galactic Center
Astronomers use high angular resolution images in the near-IR (~2 micron) to help see through the dust. This is helpful because
there are large number of K and M giant stars (T ~ 4000 K) in the central part of the galaxy, and
these are brightest in at 2-micron.
Note that the nearest star to the Sun is ~1 pc away. The density of
stars is much higher in the Galactic Center !
From Schödel et al. 2002
The Galactic Center
Astronomers use high angular resolution images in the near-IR (~2 micron) to help see through the dust. This is helpful because there are large
number of K and M giant stars (T ~ 4000 K) in the central part of the galaxy, and these are brightest in at 2-micron.
Astronomer group led by Rainer Schödel and Reinhard Genzel followed the orbits of K-giants near the Galactic center.
One star, S2, has a period of 15.2 yr with eccentricity e=0.87 and perigalacticon distance of 1.8 x 1013 m = 120 AU (a few times bigger than
Pluto’s orbit).
You can work out from Kepler’s laws that the mass interior to S2’s orbit is ~3.5 x 106 solar masses.
The Galactic Center
The Galactic Center
The Galactic CenterProf. Andrea Ghez’s UCLA group.
The Galactic Center
Nature, Vol. 419, p. 694 (2002)
The Galactic Center
Nature, Vol. 419, p. 694 (2002)
The Galactic Center
Degeneracy between distance to center of Galaxy and Mass
of supermassive blackhole
What would happen to a star that ventures too close to the Galactic Supermassive Blackhole?
http://arxiv.org/pdf/1205.0252v1.pdf
What would happen to a star that ventures too close to the Galactic Supermassive Blackhole?
What would happen to a star that ventures too close to the Galactic Supermassive Blackhole?
Gezari et al. (2012, Nature): http://arxiv.org/pdf/1205.0252v1.pdf
What would happen to a star that ventures too close to the Galactic Supermassive Blackhole?
http://arxiv.org/pdf/1205.0252v1.pdf
