Astrophysics from Space
Lecture 1: Introduction
Prof. Dr. M. Baes (UGent)
Prof. Dr. C. Waelkens (KUL)
Academic year 2014-2015
The electromagnetic spectrum
radio
Ch. 8
infrared
Ch. 4 & 5
optical
Ch. 2 & 3
high-energy
Ch. 6 & 7
The goal of this course
Discuss the history, benefits, possibilities,
limitations and (some) major accomplishments of
astrophysics space missions in the optical, infrared,
high-energy and radio wavelength regimes.
Why different wavelength regimes ?
Theoretically: no fundamental difference between radiation
in the different wavelength regimes
Practically, there is a huge difference:
• difference in atmospheric properties
• difference in telescope/detector properties
• difference in physical processes dominating the
emission
Each wavelength range contains information
that we usually cannot obtain from
observations in other wavelength regimes.
Radiation processes: blackbody radiation
Planck radiation law
Things to remember
• continuum radiation
• Wien’s displacement law
• Stefan-Boltzmann law
Radiation processes: line radiation
Line radiation can be used in many ways
• chemistry: each element has different lines
• temperature, ionization…: from line ratios
• kinematics: from Doppler shift
• magnetic fields: from Zeeman effect
Example: hydrogen atom
NIR
radio (21 cm)
optical
UV
Even hydrogen, the most abundant
and most simple element, has
different lines in the UV, optical, nearinfrared and radio regimes.
Radiation processes: there are more…
Bremsstrahlung
Synchrotron radiation
Multiwavelength view of Cen A
Optical radiation is
dominated by
emission from
normal stars…
Significant
obscuration by
interstellar dust.
Multiwavelength view of Cen A
NIR radiation is
dominated by
emission from
cooler stars…
Bright central
condensation of
stars.
Obscuration by dust
is much less
pronounced
Multiwavelength view of Cen A
UV radiation is
dominated by
emission from hot
and young stars…
Bulge disappears
and young stellar
disc appears.
Obscuration by dust
is dramatic !
Multiwavelength view of Cen A
Mid-infrared
emission is
dominated by
thermal emission
from warm dust
(reprocessed
energy).
FIR image would
trace the cooler
dust (not in starforming regions).
Multiwavelength view of Cen A
X-ray image shows
synchrotron
radiation from the
jet, coming from
the supermassive
black hole in the
centre.
Isolated X-ray
sources are neutron
stars or background
sources.
Multiwavelength view of Cen A
6 cm radio image is
similar to X-ray
image: dominated
by synchrotron
emission from jets
linked to the
supermassive black
hole.
Main driver for astrophysics from space
A solid understanding
of the Universe
requires a multiwavelength view.
The only way to do
this is observations
from space.
Note: this is not the
only reason why we
want to go to space…
Europe in space: ESA
21 member states
annual budget (2015)
~ 4.43 G€
ESA budget
ESA integrated science program
1983-1984: Horizon 2000
1994-1995: Horizon 2000+ (Cosmic Vision 2005-2015)
2004-2005: Cosmic Vision 2015-2025
Integrated long-term plans identifying the major scientific
questions to be addressed by ESA’s future science missions
• astrophysics, exploration and fundamental physics
• intense collaboration between ESA and community
• Cosmic Vision: combination of S, M and L missions
http://sci.esa.int/science-e/www/area/index.cfm?fareaid=100
Cosmic Vision 2015-2025
S-class missions (<50 M€)
• S1: CHEOPS (selected in 2012, launch in 2017)
M-class missions (<470 M€)
• M1: Solar Orbiter (selected in 2011, launch in 2017)
• M2: Euclid (selected in 2011, launch in 2020)
• M3: PLATO (selected in 2014, launch in 2024)
• M4: selection in 2015, launch in 2025
L-class missions (<900 M€)
• L1: JUICE (selected in 2012, launch in 2022)
• L2: ATHENA (selected in 2014, launch in 2028)
• L3: selection in 2016, launch in 2034
Europe in space: national agencies
1.7 G€
1.3 G€
1 G€
Belgium: has not developed a purely national large space
program (deliberately chosen the European route)
http://www.esa.int/esapub/hsr/HSR_29.pdf
NASA
Remarkable: NASA budget ~ 17.8 billion USD
NASA
• US has enormous history in space exploration since 1950s
• Dramatic cuts in 1970s
• Significant disasters have shaken NASA (with
repercussions on the science program)
1986
2003
NASA Science
NASA Science focuses on four broad themes
- better understanding of Earth itself
- Solar System exploration
- heliophysics
- astrophysics
http://science.nasa.gov/
NASA Great Observatories
Series of four large space missions
- each in a different wavelength region
- each of similar size and cost (at program outset)
- synergy to increase the science output
HST (1990-)
CGRO (1991-2000)
Chandra (1999-)
Spitzer (2003-)
NASA Origins theme
Japan: JAXA
Important player in space astrophysics
- launched its first satellite in 1970
- stress on X-ray and infrared astronomy
- pioneer in radio astronomy from space
Collaboration between JAXA and ESA/NASA for several
missions
Akari
Suzaku
USSR and Russia
USSR was the first space power with many firsts
Striking: almost no involvement in astrophysics programs
Russian space program is focused
on launching and space station.
Other countries
Countries with manned space programmes
Other countries
Countries with space launch capabilities
Other countries
Countries with national space agencies
Many countries have
space agencies and
plans for space
programs in the near
future. Modest
involvement in
astrophysics (so far).