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2018 Div. C (High School) Astronomy Help Session Sunday, Feb. 18Th, 2018 Stellar Evolution and Type II Supernovae Scott Jackson Mt

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1 2018 Div. C (High School) Astronomy Help Session Sunday, Feb. 18th, 2018 Stellar Evolution and Type II supernovae Scott Jackson Mt. Cuba Astronomical Observatory • SO competition on March 3rd . • Resources – two computers or two 3 ring binder or one laptop plus one 3 ring binder – Programmable calculator – Connection to the internet is not allowed! – Help session before competition at Mt. Cuba Astronomical Observatory 2 3 Study aid -1 • Google each object, – Know what they look like in different parts of the spectrum. For example, the IR, optical, UV and Xray – Understand what each part of the spectrum means – Have a good qualitative feel for what the object is doing or has done within the astrophysical concepts that the student is being asked to know. 4 Study aid - 2 • Know the algebra behind the physics – Just because you think you have the right “equation” to use does not mean you know how to use it!!! – Hint for math problems: Solve equations symbolically BEFORE you put in numbers. Things tend to cancel out including parameters you do not need to have values for. – Know how to use scientific notation. 5 The test – 2 parts • Part 1 – multiple choice and a couple fill in the blanks • Part 2 – word problems for astrophysics there will be some algebra Solve the equations symbolically first then put in numbers!!!! Hint: most problems will not need a calculator if done this way Topics - 1 Stellar evolution, including - stellar classification, - spectral features and chemical composition, - H-R diagram transitions, - Accretion disks - Main sequence stars - HII regions - red supergiant giants, - Cepheids - Semiregular variales - Luminous blue variables - hypergiants, Wolf-Rayet stars, Neutron stars - Magnetars, pulsars, stellar mass black holes - Eclipsing binaries, X-ray and gamma-ray binary systems - Type II supernovas Kepler's laws as they apply to binary star systems, Distance latter in the universe, calculating distance and distance modulus Know about specific objects 7 8 RCW 103, - supernovae remnant with young magnetar – slow pulsar or binary IC 443 – Jelly fish nebulae from a supernova explosion Alpha Orionis – The brightest star in the constellation Orion, Betelgeuse RSG HR 5171 A V766 Centauri, a hypergiant star in a triple star system aout 12,000 ly away SN W49B a supernova remnant in the constellation Aquila ASASSN-15lh, Supernova SN-15lh – likely hypernova or a nova from a magnatar AG Carinae, – Star in Constellation Carina. Shedding mass at huge rate, LBV S Doradus, - Bright star in the Large Magellenic Cloud LBV SN 1987A, SuperNova that occurred in 1987 in the large Magellenic Cloud Geminga, -Rapidly rotating neutron star – pulsar in Gemini NGC 6357– Diffuse nebula in Scorpius. Many new stars: OB association NGC 7822, Star forming region in Cepheus: OB association M82 X-2, Xray pulsar in the galaxy M82. PSR B0355+54 Pulsar in the constellation Camelopardalis DEM L241, Supernova remnant in the large Magellanic Cloud Circinus X-1 X-ray binary system in Circinus RCW 103, -Supernova remnant, contains a supernova remnant that is a 9 magnetar (Neutron star with powerful magnetic fields and a very slow pulsar (rotating neutron star in this case rotating once every 6.5 hours – pulsars usually take less than a second to rotate) - Other possibility: A binary system with a companion orbiting a normal pulsar every 6.5 hours - Located about 9000 ly (light years) from earth. - Magnetar is only one of 30 known – age estimated to be 2000 years old – too young for pulsar to slow down to a period of 6.5 hours IC 443 Jellyfish Nebula – 5000 ly from earth 10 Contains a pulsar with a jet and a ring Alpha Orionis High mass star, several million years old, at the 11 end of its life. Expected to explode as a Type II supernova “soon” In the red supergiant (RSG) stage now. 12 to 17 solar masses. First star to have its surface imaged. Tsurface ~ 3400 K. Star is 4.5 au in diameter -- Would almost go out to Jupiter It is surrounded (right) by a large (400 au in diaeter) nebula of gas and dust. HR 5171 A in the constellation Centaurus, around 12,000 light 12 years from Earth. It is either a red supergiant or recent post-red supergiant yellow hypergiant, and one of the largest known stars. 12,000 ly away. May be 1,300 times the diameter of the sun 50% larger than Betelgeuse Part of a binary system with the companion believed to be touching the main stars surface UV light showing tail 13 SN W49B Type II Supernova remnant May have left behind a back hole and not a pulsar May be the youngest black hole in the Xray Milky Way. Supernova occurred around 17,000 to 21,000 years ago. Odd nebula caused by material ejected out the poles instead of the equator Composite Infared 14 ASAS-SN-15lh Supernova discovered using the All-Sky Automated Survey for Supernova. Intrinsically the brightest supernova yet observed – 570 billion x sun. Considered a “hypernova” Z (redshift)=0.2326 [1171 megaparsecs away] 15 AG Carinae, Luminous blue variable star (LBV) came from a star around 50x the mass of the sun. Also known as HD94910 20,000 ly away. May become a Wolf-Rayet star. Loosing a huge amount of mass due to its very strong solar wind pushing the material way from the star and making the nebula you see surrounding the star Visible (HST) Radio S Doradus– One of the most luminous stars known. 1 million x 16 the sun’s luminosity In constellation of Dorado. Luminous Blue Variable star. Lies in open cluster called NGC 1910. It is variable (below) and is in an instability strip (Next slide) Light curve S Doradus– LBV are variable due to dense solar wind that 17 creates a falsely large star. That solar wind dissipates and the brightness drops Apparent radius of the star changes from 100x to 380 x our sun. Most will eventually become Type II SN 6.5- 6- Zero Age main sequence 5.5- Log Luminosity 32,000K 10,000K 3,200K | Log Temperature | | 18 SN 1987A, Type II supernova. Shock wave from the exploding star smashes into a ring of material and caused the ring to brighten. Ring of material was made before the supernova happened – during the time when the star had strong solar winds. Ring is about 1 light year in diameter. Ring is 20,000 years old -- in Large Magellanic Cloud 19 Geminga Remnant of a supernova that occurred 300,000 years ago. Pulsar with a period of 0.24 seconds. Originally observed as an unknown gamma ray source. 250 parsecs away (Gemina Gamma-ray source). Very high proper motion (speed) Through our galaxy Once believed that a bubble around Our solar system came from Geminga 20 NGC 6357 New star forming region in Scorpius. HII region– ionized hydrogen region – hydrogen being ionized from strong radiation form the new stars. 5500 light years away. OB association of stars Composite X-ray 21 NGC 7822 Star forming region in Cepheus. 800 to 1000 parsecs away. Includes one of the hottest nearby stars known : a massive type O stars – surface temperature of 45000K, luminosity of ~100,000x our sun. another OB association 22 23 M82 X-2 Very bright X ray source in the M82 galaxy in the constellation of Urasa Major. A neutron star comsuming material from an adjacent star. Brightness limited by Eddington Luminosity Radiation pressure balances Gravitational forces Flow of material to white dwarf PSR B0355+54 Pulsar in the constellation Camelopardalis 24 3460 light years away. Period is 0.715 seconds. 5 million years old. Pusar is moving through interstellar media and generating a high energy tails (see in Xrays) by the Chandra xray satellite. Pulsar wind nebula https://arxiv.org/pdf/1610.06167.pdf 25 DEM L241, A star that survived a supernova explosion. System contains a neutron star or black hole and a massive companion star. Supernova remnant is DEM L241. IN the large Magellanic Cloud The progenitor star was likey 25x to 40x the mass of the sun. Visible X-ray Composite 26 Circinus X-1 X ray (Neutron) star with a second star (binary system) . Shows X-ray jets that are seen in black hole systems. Young X-ray binary system. Less than 4600 years old. In the constellation Circinus ~9400 parces away radio Visible+Xray+ radio X-ray 27 Circinus X-1 X ray (Neutron) Visible star Light “Echos” from outbursts reflected in nebulae Visible+Xray X-ray 28 Brightness of Stars • Brightness measured as luminosity or magnitude – Luminosity is the total energy output of a star • Depends on size and surface temperature • Usually measure relative to our sun, e.g., 4 times our sun. – A star’s magnitude is the logarithm of its luminosity – Apparent magnitude (m) [what we see] – is determined by four factors • Its temperature or color (wattage of a light bulb) • Its size • How far away it is • If it is obscured by dust (extinction) – Absolute magnitude (M) • Magnitude of a star when viewed from a fixed distance • Most abs magnitudes will be a negative number (bright) 29 Brightness of a star: A star’s magnitude • Magnitude is more often used to describe an objects brightness. • The higher the magnitude the dimmer the object. – The apparent magnitude of our sun is -26.7 – The apparent magnitude of a full moon is -12.6 – The apparent magnitude of the Sirius is ~ -1 – Dimmest star you see (in Wilmington) ~+3.5 – Dimmest star you see in a dark sky location ~+5.5 • The absolute magnitude is the magnitude of the star / object if it was place a fixed distance away (10 parsecs -- later).
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