Astronomy

What types of planets have been discovered so far?

400 extra solar planets have been discovered so far. Hot Jupiter planets.

How do accretion disks form?

Accretion is a process in which a massive object grows by gravitationally attracting more matter, typically gaseous matter in an accretion disc. An accretion disk is an astronomical term that refers to the rapidly spiraling matter that is in the process of falling into an astronomical object. In principle, any star could have an accretion disk, but in practice, accretion disks are often associated with highly collapsed stars such as black holes or neutron stars.

How are black holes created? What is the event horizon and Schwarzschild radius?

Black holes are created after a supernova explosion when the core of a star is larger than that mass. Black holes are spherical region at which the escape velocity is exactly equal to the speed of light. The event horizon or Schwarzschild is referred to any object that reaches a distance of approximately 9 km from the singularity can never escape, even if it were moving at the speed of light.

★ Do black holes suck?

Black holes do NOT suck. That assumption is bad astronomy. It is just an object with mass. And as long as you stay at least 1000 km away from the black hole, you could safely orbit the black hole.

Describe how Cepheid variable stars can be used to measure distances

Cepheid variable stars are used to measure distances because if you can measure the period of the variability (the time from one peak brightness to the next peak brightness), that the period is proportional to the luminosity of the star.

What physical process occurred in the Algol system that led to an apparent paradox?

Eclipsing

What happens to matter that gets too close to a black hole?

Matter that gets too close to a black hole would experience strong tides. The difference in the gravitational pull from one side of a person to another near a black hole can be enormous. It is so strong, that a person or a star is likely to be torn apart.

Neutrons stars are created after the core of a star collapses at the beginning of a type II supernova explosion. Neutron star have an upper mass limit of about 3Msun, most neutron stars have a 1.4Msun. These objects are about 10 kilometers in radius and the density of a neutron star is astounding.

Neutrons stars are created after the core of a star collapses at the beginning of a type II supernova explosion. Neutron star have an upper mass limit of about 3Msun, most neutron stars have a 1.4Msun. These objects are about 10 kilometers in radius and the density of a neutron star is astounding.

What is the difference between a nova and a Type Ia supernova?

Nova and Type 1a supernova both originate in binary star systems.In a nova, the nuclear explosion occurs on the surface of the white dwarf, and does not destroy the white dwarf.In a type 1a supernova, the influx of material allows the star to start nuclear reactions and blows the entire star apart. Type Ia = white dwarf explosion, no hydrogen in the spectrum, because no H in the white dwarf.

Compare and contrast an open star cluster to a globular star cluster

Open clusters do not have any shape, with several thousand stars with some gas and dust, most of the stars are blue. Globular star cluster have about a million of stars, mostly red stars, very dense (but mostly empty), stars never touch each other. Nearly spherical. They are concentrating in the core, far away from each other.

What are pulsars? Why are only some pulsars detected by us on Earth?

Pulsars are regularly repeating pulses of radio light with periods of about 1 second. We detect pulse of light from a neutron star and they happen to be the neutron stars oriented such that the Earth lies in the path of their lighthouse beam. Pulsars spin quickly because of conservation of angular momentum.

What are the orbits of most extra solar planets like -- how do they compare to the orbit of Earth around the Sun?

The orbit of most extra solar planets

Compare and contrast the three different methods we discussed in detail for discovering binary stars and extrasolar planets.

The three different methods are: Spectroscopy, eclipsing, and astrometry. Spectroscopy is the spectrum of the two stars that shows that when one of the stars is moving away from us, the other is moving toward us. Eclipsing we can observe the periodic dimming of the system as one star passes in front of the other. Astrometry the motion of the stars in their orbit is in the plane of the sky.

What is a Type II supernova?

Type II are core collapse, but also have H in their spectrum.

How can we detect black holes in binary star systems?

We can detect black holes in binary star if it contains an unseen companion with a mass of more than 3 solar masses. The companion does not appear to emit any of its own light.

How do we know the size and shape of the Milky Way?

We know the size and shape of the Milky Way because we study more distant galaxies and use them to infer properties of the Milky Way. We compared our milky way to the nearest similar galaxy, which is M31 or the Andromeda galaxy.