Introduction to AstronomyIntroduction to Astronomy

to see the levels of structure in our to see the levels of structure in our universeuniverse

to get some sense about the to get some sense about the physical nature of various objectsphysical nature of various objects

to see how we explore the universe.to see how we explore the universe.

Astronomy vs. AstrologyAstronomy vs. Astrology

Astro-nomy means the Astro-nomy means the ““namingnaming”” of of the stars, but today refers to the the stars, but today refers to the study of celestial objects.study of celestial objects.

Astro-logy means the study of stars, Astro-logy means the study of stars, but today refers to how patterns but today refers to how patterns among the stars may related to the among the stars may related to the course of human events.course of human events.

The Scientific MethodThe Scientific Method

Recognize Patterns

Collect Data

Predict New Observations

Form Hypothesis

Scales of the UniverseScales of the Universe

The speed of light: c = 3x10The speed of light: c = 3x1055 km/s. km/s.

Source Distance (km) Light Travel time London 6,000 0.02 s Moon 385,000 1.3 s Sun 1.5 x 108 500 s (8.3 min) Jupiter 7.8 x 108 43 min Nearest Star 4 x 1013 4.3 years Most Distant Galaxy 1.4 x 1023 14 billion years

Whenever you see "light-(time)", that means we are talking about distance, not time.

The finite speed of light lets us “look” into the past!

11,000 l-years

Earth

Supernova

now8993 BC

Consider this:If you had friends throughout the galaxy, how could youcreate a “live” TV show of the past?

Survey QuestionSurvey Question Sound travels at a speed of 300 meters per

second. In analogy to the light-year, what does 1 sound-minute equal?

The time sound takes to travel 300 meters.

The time delay of a sound heard 300 meters away.

The distance traveled by sound in 1 minute.

The speed of sound 1 minute later.

Survey QuestionSurvey Question

If the Universe is infinite in size and 14 billion years old, the most distant object that we could ever hope to see is:

1) 100,000 light-years away

2) 14 billion light-years away

3) 14 billion years away

4) there is no limit – if we look hard enough, we will see all objects.

A Sense of SpaceA Sense of Space

1. The Sun would hold 1.3 million Earths.

2. There are ~100 billion "Suns" in a galaxy like our own Milky Way Galaxy. 3.Astronomers can see billions of galaxies.

Various motions of the Various motions of the Earth, Moon, and SunEarth, Moon, and Sun

The Birth, Life and Death of The Birth, Life and Death of StarsStars

How can we learn about the lives of stars when little changes except on timescales much longer than all of human history?

Suppose you had never seen a tree before, and you were given one minute in a forest to determine the life cycle of trees. Could you piece together the story without ever seeing a tree grow?

This is about the equivalent of a human lifetime to the lifetime of the Sun.

Stellar Stellar ““ForestForest””

Supernova 1987a before/after

The Milky WayThe Milky Way• How do we know

where we are in a galaxy?

• How do we know that we are not at the center of the Galaxy

• What is the shape of the Milky Way galaxy?

• What are in the Galaxy?

A Forest of Stars, Gas, and A Forest of Stars, Gas, and DustDust

The colors in the Milky Way reveal much about what’s going on physically. However there can be several explanations for the same color—so more detailed analysis is required to understand it

Kinds of Kinds of NebulaeNebulae

Emission & Reflection Nebula Globular Cluster Open Cluster

Dark Nebula Planetary Nebula Spiral Nebula

GalaxiesGalaxies What is a What is a ““standard standard

candlecandle””? Why is it ? Why is it useful?useful?

What are the basic What are the basic types of galaxies?types of galaxies?

What holds them What holds them together?together?

How did they form?How did they form? How do they evolve?How do they evolve?

The Andromeda Galaxy The Andromeda Galaxy

About 2 million light years away.

Angular size (about 2 degrees) ---> the size of the Milky Way.

Another island universe!

The Local The Local GroupGroup

D~50 kpcR~2kpc

~3 dozen

D~700 kpcR~20 kpc

D~700 kpcR~5 kpc

Galaxy Galaxy ClustersClusters

Coma cluster

In a typical cluster of galaxies, the galaxies orbit at over 1000 km/sec. From Newton’s laws one can determine how much mass must be present to prevent the cluster from dissolving.

~1000 galaxies in 1 arcmin2

The whole sky is ~ 108

larger!

~100 billion galaxies in whole sky currently detectable!

Virtually everyspeck in this

image is agalaxy!

Hubble Deep FieldHubble Deep Field

CosmologyCosmologyCosmology is the study of the origin and the Cosmology is the study of the origin and the

development of the Universe, addressing the development of the Universe, addressing the grandest issues:grandest issues:

Does it have an "edge"?Does it have an "edge"? Does it have a centerDoes it have a center How does it look like on How does it look like on

large scales (> 300 ly)large scales (> 300 ly)?? How did it start?How did it start? How old is it?How old is it? How long will it live?How long will it live?

The Evolving UniverseThe Evolving UniverseCosmological Simulations

Observational Cosmology

Formation of the Large-Scale Formation of the Large-Scale StructureStructure

Klypin, Kravtsov, GottlöberDark Matter Simulation

A Sense of TimeA Sense of Time

If we were to compress the time since the Big Bang into one year, and make the time of the Big Bang January 1, The Earth was formed in mid-September. The mammals appeared on December 26. All human prehistory (from the first known stone tools) and history have occurred in the last ½ hour of New Year's Eve.

All of human history is but a fleeting instant on the cosmic timescale.

Astronomy Colloquium talk: Quenching of star formation in massive galaxiesPlace: LGRT 1033Time: 4:00PM (this Thursday)

Kate Whitaker

Guest presentation: LMT Science and InstrumentationNext Monday

Prof. Gopal Narayanan

• Please finish the Observatory Visit Assignment (due Oct. 15).

• Please start to read articles for the team project/discussion assignment.

D:\download\symphony.mov

Large Millimeter TelescopeLarge Millimeter Telescope

The Symphony of LightThe Symphony of Light

Radio infrared

X-rayoptical

Optical SkyOptical Sky

Near-infrared sky Near-infrared sky

Boldt et al.

Radio SkyRadio Sky

Soft X-ray SkySoft X-ray Sky

Gamma-ray all-sky mapGamma-ray all-sky map

Fermi Gamma-ray Space Telescope

Observational Astronomy Observational Astronomy at UMassat UMass

How does the Hubble Sequence form?

Stars very old,formed at z>2

(25% of the cosmic time)

Still forming stars

“Early Types”,spheroidal systems,pressure supported(velocity dispersion)

σ≈250 km/s for M≈1012 M

(1 M = 2x1030 kg) “Late Types”, disk systems (spiral galaxies),rotationally supported

vrot≈250 km/s for M≈1012 M

Daniela Calzetti’s ScienceDaniela Calzetti’s ScienceDaniela’s science interests are in the field of star formation, as garnered from galaxies outside our Milky Way. The process of star formation tells us how gas in the Universe is converted into stars, thus transforming darkness into light, and providing a path for the evolution of galaxies across cosmic times.Her science requires data across the electromagnetic spectrum. She is working on projects that have some of the largest time allocations on major facilities, including the newly launched ESA/Herschel Space Telescope and the Hubble Space Telescope.

M82

Question: how do galaxies, with theircomplicated inflows, outflows, etc., evolve?

QSO Absorption Spectroscopy

Galaxies and SMBHGalaxies and SMBH

Mass of a Mass of a galaxygalaxy’’s central s central black hole is black hole is closely related to closely related to mass of its bulgemass of its bulgeDevelopment of Development of central black central black hole must be hole must be somehow somehow related to galaxy related to galaxy evolutionevolution

Magorrian,Ferrarese,

Merritt, etc.

Red: 1-2.5 keV Green: 2.5-4 keV Blue: 4-9 keV

Wang et al. 2002

• MMBHBH=4x10=4x1066MM

• LLxx= 3x10= 3x103333 erg/s, erg/s, or ~ 10or ~ 10-11 -11 LLEE

• LLbolbol= a few x10= a few x103636 erg/s, mostly in erg/s, mostly in radio to submm.radio to submm.

• What is the mode What is the mode of the accretion, of the accretion, and what and what determines the determines the luminosity?luminosity?

• If we have If we have answers to these answers to these questionsquestions,, we we may understand may understand a large class of a large class of ultra-dim galactic ultra-dim galactic nuclei.nuclei.

Sgr A* Sgr A*

Temporal decomposition of Temporal decomposition of the Sgr A* X-ray datathe Sgr A* X-ray data

Detected flares account for ~1/3 of the total X-ray flux Detected flares account for ~1/3 of the total X-ray flux of Sgr A* (of Sgr A* (J. Neilsen et al. 2013).J. Neilsen et al. 2013).

No sign of line emission in detected flare spectrum.No sign of line emission in detected flare spectrum.

Quiescent emission

X-ray emission line X-ray emission line spectroscopyspectroscopy

halo

HD simulations of stellar winds HD simulations of stellar winds around Sgr A* around Sgr A*

Cuadra et al 2006

Shadow and light-bending Shadow and light-bending of black holesof black holes

Feedback Source: Feedback Source: Old StarsOld Stars

0.5-1 keV1-2 keV2-8 keV

IRAC 8 microK-band0.5-2 keV

Li & Wang 2007

Lx~2x1038 erg/s

Such gentle, long-lasting outflows can effectively affect the ecosystem (Tang et al. 2009).

Diffuse hot gas in the bulge of M31Diffuse hot gas in the bulge of M31

Tang, Wang, MacLow, & Joung 2009

Galactic coronae: examplesGalactic coronae: examples

Li & Wang 2012

Determining the role of Determining the role of cosmic-ray/magnetic field in regulating cosmic-ray/magnetic field in regulating

outflowsoutflows

Based on a 2-hr C-array 1.5 GHz JVLA test observation (Irwin et al. 2012).

Feedback Source: Massive StarsFeedback Source: Massive StarsRed - X-ray Green – H Blue – Far-UV/optical

30 Doradus nebula (Wang 1999)

LMC N11

• Is the expansion driven mainly by radiation or mechanical energy?

• What fraction of the energy is consumed locally?

• What fraction can escape into galactic halos?