Thursday, September 17, 2009 First exam, week from today

Astronomy in the news - end of Ramadan with new Moon.

Pic of the Day - Andromeda in the Ultraviolet What happens when two white dwarfs spiral together?

Larger mass WD has smaller radius Smaller mass, Which WD has the smaller Roche lobe? Larger The smaller mass radius Larger mass, Which fills its Roche Lobe first? Smaller radius Must be the smaller mass As small mass WD loses mass, its radius gets larger, but its Roche Lobe gets smaller! Runaway mass transfer.

Small mass WD transfers essentially all its mass to larger mass WD

Could end up with one larger mass WD

If larger mass hits Mch → could get explosion => Supernova First WD < 1.4 solar masses First WD gets to 1.4 solar masses Classical Nova Recurrent Nova Two WD EXPLOSION! Gravitational Radiation, in-spiral WDs coalesce < 1.4 solar masses > 1.4 solar masses One Big WD EXPLOSION! End of Material for Test 1 Reading for First Exam Chapter 1: 1.2.3, 1.2.4, 1.3.2

Chapter 2: 2.3

Chapter 3: 3.1, 3.2, 3.3, 3.4, 3.8, 3.9, 3.10

Chapter 4: 4.1, 4.2, 4.3, 4.4, 4.5

Chapter 5: ALL Sky Watch Extra Credit Due Thursday, in Class Must be typed on regular 8-1/2x11 paper See web site for more details, or ask! See web site for star charts to help guide you where and when to look. Part of the exercise is to learn how to orient yourself and recognize objects and patterns in the sky. Observe each object only once, but it is never too late to add a missed object to later reports. You need to report what time you see an object or constellation and how far it is above the horizon in what direction. Sky Watch Objects mentioned so far: Ring Nebula, planetary nebula in constellation Lyra Sirius - massive blue main sequence star with white dwarf companion Algol - eclipsing binary system in Perseus Other suggestions: Vega, Castor, Rigel - massive blue main sequence stars Capella, Procyon - on their way to becoming red giants Betelgeuse, Aldebaran - red giants Other examples of these sorts of objects… Sky Watch

Dwarf Novae: SS Cygni - brightest dwarf novae in the sky, but a bit too dim for naked eye. In constellation Cygnus. U Geminorum - in the constellation Gemini

Recurrent Novae - U Sco Sky Watch

Classical Novae: CP Pup, toward constellation Puppis in 1942 Pup 91, another toward Puppis in 1991 (not same place in our Galaxy, just accidently off in the same approximate direction) QU Vul, toward constellation Vulpecula, white dwarf composed of Oxygen, Neon, and Magnesium rather than Carbon and Oxygen. GK Per toward constellation Perseus - has had both a classical nova eruption in 1901 and dwarf nova eruptions. SUPERNOVAE

Catastrophic explosions that end the lives of stars, Provide the heavy elements on which planets and life as we know it depends, Energize the interstellar gas to form new stars,

Produce exotic compact objects, neutron stars and black holes, Provide yardsticks to measure the history and fate of the Universe. Reading:

Chapter 6 Supernovae

Also § 2.1, 2.2, 2.4 & 2.5 for background

Issues to look for in background:

Why is it necessary for a thermonuclear fuel to get hot to burn - charge repulsion § 2.1 & 2.2

Core Collapse § 2.4 & 2.5 One type of supernova is powered by the collapse of the core of a massive star to produce

a neutron star, or perhaps a black hole

The mechanism of the explosion is still a mystery. Chandra X-ray Observatory image The other type of Of Tycho’s supernova of 1572 supernovae (Type Ia) is thought to come from a white dwarf that grows to an explosive condition in a binary system.

These explode completely, like a stick of dynamite, and leave no compact object (neutron star or black hole) behind. Chapter 6 Supernovae Historical Supernovae - in our Milky Way Galaxy observed with naked eye over 2000 years especially by Chinese (preserved records), but also Japanese, Koreans, Arabs, Native Americans, finally Europeans.

SN 386 earliest record NS, jet? SN 1006 brightest No NS SN 1054 Crab Nebula NS, jets SN 1181 (Radio Source 3C58) NS, jets SN 1572 Tycho No NS SN 1604 Kepler No NS ~1680 Cas A NS? jets SN 1987A nearby galaxy NS? jets Vela 10,000 years ago NS, jets G11.2-0.3 = SN 386 65 ms pulsar X-ray image axis structure G11.2-0.3 = SN 386 65 ms pulsar X-ray image axis structureChandra Observatory X-ray image SN 1006 No evidence for neutron star SN 1181 = 3C58 66 ms pulsar axis/torus structure? X-ray image Crab Nebula

Remnant of “Chinese” Guest Star of 1054

Optical Image Chandra Observatory X-Ray Image

Left-over jet Crab 33 ms pulsar axis/torus structure

Direction of motion of neutron star Kepler Tycho Chandra Observatory X-ray Image of Tycho’s Supernova of 1572 No evidence for neutron star

SN 1006 Great Observatories composite of Kepler’s supernova 1604 No sign of neutron star “sideways” alignment?

SN 1572 Tycho Cassiopeia A by Chandra X-ray Observatory

Jet

Counter Jet Compact remnant