Science Olympiad - Astronomy

Optical double

not actually binaries

simply two stars lying along same line of sight (similar RA & dec)

Not gravitationally bound

Not usefull in determining stellar masses

Visual binary

both stars resolved independently

if orbital pd not too long, can monitor motion

provides angular separation from center of mass

If dist known, linear separations can be calculated

Astrometric binary

If one significantly brighter, not possible to see both directly

Exitence deduced by observing oscillatory motion of visible member

Spectrum binary

two superimposed independent discernible spectra

Doppler effect causes shifting of spectral lines

Spectroscopic binary

if period not too long

Orbital motion has component along line of sight

Periodic shift in spectral lines observable

Only 1 set of periodically varying spectral lines seen

Systems able to provide us with mass determination

Visual binaries combined with parallax info

Visual binaries with radial velocities available over complete orbit

Eclipsing double-line spectroscopic binaries

O stars

Hottest blue-white stars with few lines

Strong He II absorption (sometimes emission) lines

He I absorption lines becoming stronger

B stars

Hot blue-white

He I absorption lines strongest at B2

H I (Balmer) absorption lines getting stronger

A stars

White

Balmer absorption lines strongest at A), becoming weaker later

Ca II absorption lines becoming stronger

F stars

Yellow-white

Ca II lines continue to increase, Balmer lines decrease

Neutral metal absorption lines (Fe I, Cr I)

G stars

Yellow

Solar-type spectra

Ca II increase

Fe I, other neutral metal increase

K stars

Cool orange

Ca II H & K strongest K0, then decrease

dominated by metal absorption

M stars

Cool red

Molecular absorption bands (TiO, VO)

Neutral metal absorption lines remain strong

L stars

Very cool, dark red

Stronger in infrared

Strong molecular absorption bands of metal hydrides, water, CO, Na, K, Rb, Cs, Alkalis

TiO, VO decrease

T stars

Coolest, Infrared

Strong methane, CO decrease

Wolf-Rayet stars

discovered by C.J.E. Wolf and G. Rayet Paris Observatory in 1867

more than 220 WR identified, most likely more

25,000 to 100,000 K

losing mass at over 10^-5 Solar masses per year

Wind speeds of 800 to 3000+ kilometers per second

Rapidly rotating

Can have starting masses of under 20 solar masses

No dramatic variability

P Cygni profile

Absorption trough at short-wavelength edge superimposed on rather broad emission peak

FU Orionis

contain instabilities in circumstellar accretion disk

Results in 0.01 solar masses being dumped

T-Tauri may go through several stages

Herbig Ae/Be

named for George Herbig

spectral type A or B

strong emission lines

2 to 10 solar masses

tend to be enveloped

much shorter lifetimes

Herbig-Haro objects

contain jets of gas

first discovered in vicinity of Orion nebula by george Herbig & Guillermo Haro in early 1950s

Proplyds

circumstellar disks around stars in Orion Nebula

appear to protoplanetary disks around less than 1million year old stars

Masses more than 2 * 10^25 kg

Wien's law

(Peak wavelength)(Temperature) = 0.002897755 mK

Stefan Boltzmann Law

Luminosity = 4(pi)(radius)^2(stefan-boltzmann constant)(effective temperature)^4

Stefan-Boltzmann constant - 5.670400*10^-8 W m^-2 K^4

Stellar parallax

d = 1/p" pc

Distance modulus

m-M = 5 log d - 5 = 5 log (d/10pc)

Diffuse molecular clouds

Also known as translucent molecular clouds

15 to 50 K

n around 5 10^8 to 510^9 m^-3

M around 3 to 100 solar masses

Several parsecs across

Birth

The life cycle differs between stars depending on their mass. Normal-mass stars begin in stellar nurseries, and some matter condenses to create a protostar. This gains more mass until fusion (H -> He) begins, when it becomes a main-sequence star.

Stellar Nursery

Also called a molecular cloud, is the cloud of matter from which stars originate. They are clouds primarily consisting of hydrogen which are dense and big enough that molecules are formed from atoms. They are not extremely common in the interstellar medium (ISM), but they are the densest objects in it. The molecular gas found in the Milky Way corresponds with its spiral system.

Protostar

When a star is in free-fall collapse.

T Tauri Star

Pre-main-sequence variable stars with spectral classes from F to M. They have many emission lines in their spectra, indicating their strong stellar winds. They are easy to identify and can be used as traces of solar-mass star formation regions. Appear within dark dust clouds.

Main Sequence

Stars spend the majority of their lives (about 80 percent) at this stage. How long a star remains here depends on its mass.

H-R Diagram

Important with regards to stellar evolution because it can be used to identify the life cycle of a star, as well as characteristics of the stars in a star cluster. Most stars will follow certain paths, so by plotting a star, we can estimate its position within the stellar evolutionary cycle.

Hayashi Track

Explains the lives of low-mass stars with solar masses less than 0.5, and it was developed by Japanese scientist Chushiro Hayashi. All stars in this track become fully convective, and so it mostly applies to red dwarves. As the stars become denser, they become less luminous, until fusion begins, when they get warmer. This leads them to the main sequence.

Turnoff Point

The point at which the stars deviate from the main sequence after using up most of their fuel.

Andromeda

M31 galaxy

Cancer

M44 Beehive Cluster

Canes Venatica

M51 Whirlpool Galaxy

Deep Sky Object: NGC 7293

Constellation: Aquarius AKA Helix nebula, large planetary nebula, closest nebula to earth in the constellation Aquarius.

Star: NGC 281

Constellation: Cassiopeia

Deep Sky Object: 30 Doradus

Constellation:Dorado

Stars: Castor & Pollux

Constellation: Gemini

Deep Sky Object: M13 Globular Cluster

Constellation: Hercules

Star: Vega

Constellation: Lyra

Stars: Betelgeuse & Rigel

Constellation: Orion

Star: Algol

Constellation: Perseus

Deep Sky Objects: Sgr A, M17,

G359.23-0.82

Constellation: Sagittarius

Star: Antares

Constellation: Scorpius

Stars: Aldebaran & HL Tau

Constellation: Taurus

Star: Polaris

Constellation: Ursa Minor

Stars: Mizar & Alcor

Constellation: Ursa Major

Star: Velorum

Constellation: Vela

Star: Spica

Constellation: Virgo

Astronomical Unit

A.U.

1.496x10(11) meters

Atomic Mass Constant

Mu

1.6605386x10(-27) kg

Boltzmann Constant

k

1.3806505x10(-23) J K(-1)

Electron Volt

eV

1.60217653x10(-19) J

Gravitational Constant

G

6.6742x10(-11)m(3)kg(-1)s(2)

Gravity Constant over h-bar

G/h C

6.7087x10(-39) ((GeV/c(2))(-2)

Light Year

ly

9.4605x10(15)m

Mass of Proton

Mp

1.67262171x10(-27)kg

Mass of Neutron

Mn

1.67492728x10(-27)kg

Mass of Electron

Me

9.1093826x10(-31)kg

Mass of Hydrogen Atom

Mh

1.6735x10(-27)kg

Parsec

pc

3.0857x10(16) m

Planck Constant

h

6.6260693x10(-34) s

Planck Constant over 2(pi)

h(+)

1.05457168x10(-34) J s

Rydberg Constant

R(infinity)

6.6x10(-12)

Solar Mass

Mo

1.989x10(30)kg

Solar Radius

Ro

6.9599x10(8) m

Solar Luminosity

Lo

3.90x10(26) W

Speed of Light

c

299,792,458 m s(-1)

Standard Atmosphere

101,325 Pa

Stefan-Boltzmann Constant

o

5.670400x10(-8) W m(-2) K(-4)

Wien Displacement Law

b

2.8977685x10(-3) n K

Year - Earth

365.2564 days

3.156x10(7) sec

Cas A

A supernova remnant in the constellation Cassiopeia. It is about 11,000 light years away.

Cygnus X-1

A deep sky object in Cygnus constellation. It is an intense x-ray source neat Eta Cygni and is thought to be a black hole in orbit around the 9th-magnitude blue supergiant about 8,000 light-years away in our own galaxy.

SXP 1062

PSR J0108-1431

NGC 6888

WR 136

M1

a supernova remnant in the constellation Taurus, the supernova was caused by a supergiant collapsing inward and exploding, in the center of the crab pulsar there is a rapidly rotating neutron star, crab pulsar is the strongest persistent source of x-rays and gamma rays

V838 Mon

IC 1396

Aquarius

Found in region often called the sea, Brightest star: Beta Aquarii

Auriga

Brightest Star: Capella; Charioteer constellation is north of celestial equator, a hexagon with a very short side on top. Contains Capella.

Carina

Part of old constellation Argo Navis, Brightest star: Canopus

Centaurus

Brightest star: Alpha Centauri, Nearest star: Proxima Centauri

Cassiopeia

Brightest star: Alpha Cassiopeia; opposite of the Big Dipper on star map

Dorado

Brightest Star: Alpha Dorado

Cygnus

Known as the Northern Cross; Brightest star: Deneb

Gemini

Brightest Star: Pollux; Second Brightest Star: Castor

Libra

Brightest Star: Gliese 570; also contains Gliese 581, which has a planetary system of 6 planets

Hercules

Fifth largest modern constellation, Brightest Star: Beta Herculis

Lyra

Brightest Star: Vega, second brightest star in the northern hemisphere

Orion

Sometimes subtitled The Hunter; Brightest Stars: Rigel and Betelguese

Perseus

Brightest Star: Alpha Persei; most well-known star is Algol, the head of Medusa in Perseus's hand.

Sagittarius

Brightest Star: Epsilon Sagittarii

Scorpius

Brightest Star: Antares; constellation is largest one in southern hemisphere

Taurus

Brightest Star: Aldebaran; Taurus also includes two of the nearest open clusters to Earth, the Hyades and the Pleiades