How to start observations of variable stars with a webcamera. A short review of the characteristic constellations and methods which allow us to find stars suitable for amateur observations in the sky.
How to start observations of variable stars with a webcamera. A short review of the characteristic constellations and methods which allow us to find stars suitable for amateur observations in the sky.
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This is an introduction to stars, including the basics of observing and classifying stars as well as their evolution and life cycle. This is a modification of a presentation I found online.
The Sky
Astronomy is about us. As we learn about astronomy, we learn about ourselves. We search for an answer to the question “What are we?” The quick answer is that we are thinking creatures living on a planet that circles a star we call the sun. In this chapter, we begin trying to understand that answer. What does it mean to live on a planet?
The preceding chapter gave us a quick overview of the universe, and chapters later in the book will discuss the details. This chapter and the next help us understand what the universe looks like seen from the surface of our spinning planet.
But appearances are deceiving. We will see in Chapter 4 how difficult it has been for humanity to understand what we see in the #sky every day. In fact, we will discover that modern science was born when people tried to understand the appearance of the sky.
1
KYA 306
Distance Scales
2
• Stellar, galactic, and extragalactic astrophysics, and cosmology all
require accurate distances.
• Search for standard candles (or in rare instances, standard
rulers). For the nearby Universe observed angular quantities scale
very simply to physical properties.
• The ideal standard candle would be something so close to the Sun
that it can be measured using trigonometric parallax, and bright
enough to be observed in the most distant known galaxies, with zero
intrinsic dispersion.
• Bootstrap approach, linking geometrically measured distances to
physical scaling relations that are more (or less) well understood
theoretically.
The Distance Ladder
€
3
Methods used at larger distances require calibration based on methods
used closer in. Red stars show the most widely used (and mostly, least
model-dependent) methods.
€
maser galaxies
4
The first reasonably
accurate
measurements of
distances to nearby
galaxies showed that
all but the closest are
receding away from
us at a rate that
increases linearly
with distance.
This observation is
the basis of modern
cosmology - defines
the expansion of the
universe.
The Hubble Constant
€
accurate distances and velocities allow the size and
age of the Universe to be measured, through the
value of the Hubble constant H0
5
1. Use a satellite (e.g., the ESA GAIA mission) to get the trigonometric
parallax of a large number of nearby Cepheid variable stars to
calibrate the zero point of the period-luminosity relation (Leavitt Law).
2. Use a space telescope to get Cepheid distances and tip of the red
giant branch distances to nearby galaxies (<25 Mpc), to calibrate
other methods based on the virial theorem and the dynamics of
individual galaxies (Tully-Fisher, Fundamental Plane).
3. Use TF, FP, and other methods to get distances beyond the point
where individual galaxy velocities contribute significantly to the
observed redshift.
4. Among the other: Type Ia supernovae, which are “standardisable
candles” (2011 Nobel Prize in physics for the acceleration of the
Universe).
Steps to the Hubble Constant
€
6
• Ground-based optical
parallaxes ~few milliarcseconds
➙ few 102 pc
• VLBI maser parallaxes ~10s of
microarcsec ➙ few 10s of kpc
• Satellite: Hipparcos
(1989-1993) ~ 1 mas for 105
stars (➙ ~1 kpc)
• Gaia (launched 2013, catalog
~2020) ~ 20 microarcsec for 108
stars ➙ 10% accuracy at
Galactic centre
Trigonometric Parallaxes
€
7
Intermediate mass stars,
evolved off the main
sequence to the helium-
burning stage, so they are
luminous.
Can be seen out to Virgo
cluster galaxies by the
Hubble Space Telescope.
Age few x108 yr, so only
observable in large numbers
in spiral galaxies, and the
larger irregular galaxies.
Cepheid Period-Luminosity
€
8
Radial pulsation in
supergiant stars
where the helium
ionisation zone is
at the proper depth
to excite global
oscillations.
Ce ...
introduction to galaxies in space.
chapter 9 earth and space class.
about the scientist edwin hubble.
and his theories. The study of asstronomy. space study of planets and galaxies.
Similar to Ast Observing Project Tr03, 2010 Spring (20)
1. Astronomy: Final Exam Study Guide
• Using the H-R Diagram, what part of the diagram
corresponds to the main sequence?
• Using the H-R Diagram, what part of the diagram
corresponds to the sun’s location?
• In which area of the Hertzsprung-Russell diagram do stars
spend the majority of their lives? B A
• Use the Stellar Motions diagram to answer the next two
questions:
• The star’s proper motion equals
• The star’s radial velocity equals
• Using Table 1 as a resource, which of the following stars is E
Star B in the HR Diagram below? (second, or colored
diagram)
C
• Using Table 1 as a resource, which of the following stars is
coolest? F
• What is the magnification produced in a 6-inch (150mm)
reflector by a 16mm eyepiece? The telescope’s focal length is D
1200mm.
• What is the f/number of the above telescope?
• __________ first classified galaxies into elliptical, spiral, and
irregular categories.
• __________ galaxies are divided into normal and barred
• __________ galaxies are spherical or egg shaped
• “c” is equal to
• A 6-inch Newtonian telescope could suffer from
• A star of magnitude -1 is __________ than a star of magnitude
+6.
• A well-known black hole candidate is
• According to Hubble’s law, the __________ a galaxy is, the
__________ it is receding.
• At what distance would a star’s absolute and apparent
magnitude be equal?
• Elements heavier than iron were created by
• For the northern hemisphere, the celestial sphere appears to
rotate about an axis directed towards the star
• How many of the modern 88 constellations came from ancient
Greece?
• If the critical density is great enough,
• In a pair of 10x50 binoculars, the “50” refers to the
• Johann Bayer selected the letters of which alphabet to name
the skies brightest stars?
• Johann Dreyer compiled the
• M13 is a/an
• Our galaxy appears to have formed
• Our Milky Way belongs to a typical small galaxy cluster
named
• Population I stars reside within the __________ of a galaxy, population II stars reside within the __________ and __________ of a galaxy.
• Stellar evolution is a function of a star’s (select best answer)
• The __________ lies at the center of the celestial sphere
• The average length of the solar cycle, or the length between one solar maximum and the next, is about
• The Crab Nebula was created by
• The distance from one part of a wave to the next corresponding part is
• The extension of earth’s equator onto the celestial sphere is called the __________
• The following people named many of our bright stars (select the best answer).
• The height of Polaris above the north horizon is equal to an observer’s
• The matter between stars is termed the
• The method of safe solar observing that involves observing the sun’s image on a flat surface such as paper or cardboard is termed
• The most distant and powerful objects in the universe are
• The oldest of a galaxy’s stars are termed
• The part of the celestial sphere corresponding to the Prime Meridian is the
• The pattern of dark lines in a star’s spectrum tells what about the star (select best answer)?
• The possessive form of the star name Sirius would be
• The rival of the Big Bang theory, the Steady State, claims that
• The Schmidt-Cassegrain is a popular type of
2. • The star Aldebaran lies in which constellation?
• The study of the origin, structure, evolution, and destiny of the universe is
• The sun travels about ____ along the ecliptic each day. This apparent motion of
the sun is caused by earth’s __________.
• The theory of rapid acceleration just after the Big Bang occurred is termed
• This astronomer compiled 110 of the skies brightest deep sky objects in a list.
• This astronomer created the magnitude scale.
• Vega is a bright star in which constellation?
• What constellation is termed the Great Bear?
• What constellation is termed the Hunter?
• What does the Doppler Effect indicate about our universe?
• What form of electromagnetic radiation has the longest wavelengths?
• What is albireo?
• What is the general term for the creation of elements within a star?
• What is the major element that formed the stars and sun?
• What is the name of the point directly overhead?
• What is the name of the sun’s direction of motion in space?
• What is the significance of the zodiac?
• What magnitude is the approximate limit of human vision?
• What phenomenon accounts for a 26,000-year shift in the position of the north celestial pole?
• What star will be the North Star in 14,000 AD?
• What use do Cepheid variable stars have for astronomers?
• Where is our sun in the following list of stellar evolution milestones?
• Which celestial coordinate is analogous to longitude on a terrestrial globe?
• Which celestial coordinate ranges 90º above or below the celestial equator?
• Which celestial coordinate ranges from 0-24 hours along the celestial equator?
• Which constellation is considered the 13th member of the zodiac
• Which of the following are apparent outbursts or arches of gases visible along the edge of the sun?
• Which of the following are north circumpolar constellations?
• Which of the following describes an absorption spectrum?
• Which of the following describes the oscillating Big Bang model of the universe? (best answer)
• Which of the following is a famous planetary nebula?
• Which of the following is used to measure the distances to nearby stars?
• Which of the following stars is brightest?
• Which star has the greatest proper motion?
• Which type of telescope uses only lenses to collect light?
• Which types of stars were originally thought to emit signals from an alien civilization?
• Why are astronomers searching for missing mass?
• Your fist measures an angle of about _____ on the sky?
Table 01
Star Apparent Magnitude Spectral Class Distance (light years) Absolute Magnitude
Barnard’s Star 9.56 M3 6 13.4
Betelgeuse 0.50 M2 1400 -7.2
Procyon 0.38 F5 11.4 2.6
Rigel 0.12 B8 1400 -8.1
Sirius -1.46 A1 8.6 1.4
Sirius b 8.11 White Dwarf 8.6 11.3
Spica 0.98 B1 220 -3.2
Vega 0.03 A0 25 0.6
HR Diagram for
underlined questions
(right)