Transcript Is M82 “Exploding?” - Astronomy and Astrophysics

Is M82
Cause is not so unusual:
thousands of young stars
and their supernova
explosions (leave it for
Alex), spread over this
dwarf galaxy
Credit: Subaru Telescope
Many outflowing (1000 km/sec),
escaping warm gas filaments ,
Shown in red
Total energy produced is less
than the starlight from the rest
of the galaxy, and it emerges
gradually, along directions of
easiest escape (a slow boil)
An utterly more bizarre jet from M87
(HST image of this Giant Elliptical
Galaxy in the nearby Virgo Cluster
Nucleus of
the galaxy
A highly collimated jet
More Surprises:
1) the M87 jet
produces the most
powerful radio
waves in Virgo
2) its energetic radio
lobes are enormous
• Each zoom step is roughly
factor of 10X magnification
• Maps from the Very Large
Array and a global
interferrometer give lightyear resolution
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2
4
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5
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M87’s jet is not the only one:
More Blasts from the past
• 1960-70’s Radio-astronomers discovered a few
hundred such galaxies —completely unexpected
• The huge double lobes contain a prodigious
amount of high-energy particles (e.g. electrons),
which could only have been accelerated by a
remarkably powerful, long-lived (Myrs) process
• By now many of them have escaped the galaxy, but
they are still radiating energy by the synchrotron
mechanism (when electrons spiral in a magnetic
field at nearly the speed of light)
Most Powerful Radio
Sources in Fornax and
Cygnus
Visible stars;
Radio lobes
Center of galaxy
A pattern in these crimes.
“What kind of monster…?”
(Even Billions of) supernovae couldn’t
possibly have done this!
Where did these blasts originate?
• The maps are strongly suggestive: The giant lobes
are the “smoke” of colossal explosions. Since the
lobes always point back to well-collimated jets
which start out in the galactic nucleus, that must be
where all the power originated
…get a search warrant
Another nearby jet, in Centaurus
Close-up of 1-sided jet
emerging from the center;
blue is X-rays, red is radio
White=nearby peculiar elliptical galaxy, NGC 5128
Blue/green=double radio lobes
Supercomputer Simulations
Re-enact the crime
In this
model
calculation,
High-speed
electron Jet
starts
horizontally
from the
left, and
runs for 5.4
million
years—
Looks very
realistic
Proof: High-energy blasts are
originating from some of these
galactic centers currently
• The jets have many lumps, suggestive of an
erratic energy input.
• Repeated VLBI high-resolution mapping shows
repeated (unpredictable) ejection of new radio
blobs of high-energy particles start out at speeds
of 0.98—0.99c
Several years of observations of M87’s jet—movie from J. Biretta
New ejections usually come from
galactic nuclei which are currently
“active” (Blasts from Quasars)
The famous radio jets are often just
the tip of the iceberg: Far more
power emerges from the Active
Galactic Nucleus at high energies,
including visible light, X-rays and
extreme Gamma-rays; total can
exceed output of all the stars—
trillions of solar luminosities!
Jet from powerful
Quasar 3C273
The Quasar Connection: to understand jets,
we must understand Active Galactic Nuclei
The crime boss behind the whole operation
• AGN produces its power Gamma-ray flare erupts in 8
in a very compact region, hours,
1000X more powerful than the
since:
R < c DT ie
entire Milky Way galaxy
only a few light-hours
across, smaller than our
Solar System!
• The massive central
engine of AGN is the (bipolar) high-energy
particle accelerator, even
Compton Gamma Ray Observatory—
if it’s often turned off
Mattox, Malkan et al
HST Zoom of another jet from a
nearby AGN
• Jet
appears to
emerge
perpendicular to a
gas disk
around the
galactic
center
What is the AGN Central Engine?
The Black Hole Theory
We still can only theorize what makes the Central Engine tick?
• Best jet model is (chaotic) energy release from
magnetized matter in close (disk) orbits
around a giant black hole (highly fuel efficient)
• Spinning disk of gas defines north and south
polar directions—quasar is a long-lived
gyroscope
• The high-speed blasts in our direction have
their brightness amplified by special
relativity—is this why they appear to start out
one-sided?
Just when you thought it was safe to go back to your home on Earth…
Breaking News: Blasts from the heart of
the Milky Way
• The 2.5 Million-solar mass black hole in the
center of our galaxy is usually starved for
fuel, but…
• It bursts in X-rays about 3 times per week
It spreads to our neighborhood…
Will we be next??
Chandra (NASA’s third Great Observatory)
discovered the first flare
serendipitously; then an intensive
followup campaign
• Only the third of five orbits showed
comparably powerful bursts: they are so
unpredictable that patience and luck are
strongly required to study them
2000 October 26-27
(Baganoff et al. 2001)
X-ray
power
from the
center of
our galaxy
Oct 27 05:42 UT
45x, 4 hr
Time
2002 May 22-23 – Orbit 1, Part 1
2002 May 24 – Orbit 1, Part 2
May 24 19:42 UT
5x, 1.7 hr
2002 May 25-27 – Orbit 2
May 26 04:24 UT
6x, 0.75 hr
May 24 19:42 UT
5x, 1 hr
May 26 13:47 UT
5x, 0.5 hr
May 28 15:36 UT
25x, 1 hr
2002 May 28-30 – Orbit 3
May 29 06:03 UT
12x, 1.5 hr
May 29 18:33 UT
13x, 0.5 hr
2002 June 3-4 – Orbit 5
Chandra imaging may even show a weak X-ray jet
left over from earlier activity
Axis of outbursts?
Plane of Milk
Credit: NASA/MIT/F.K. Baganoff et al.
Conclusions
• We “need” strong enough gravity in the Universe to
make many giant black holes in galactic centers (as
a by-product)
• Unique gravitational strength of a black hole is a
tremendous accelerator, and a lot of the accelerated
matter escapes the black hole vicinity at nearly c
• The most bizarre objects in the Universe may
merely be ultra-extreme versions of what lurks in
the centers of most galaxies
• Total energy (in many forms) produced by black
holes in the history of the Universe may not be that
much less than everything generated by fusion in
stars
Faster-than-light jets?
• An illusion, produced when matter travels
near the speed of light, close to our
direction