Picture Of The Day - November 11, 2018

What are white dwarfs?

Some curiosities about white dwarfs, a stellar corpse and the future of the sun.

Where a star ends up at the end of its life depends on the mass it was born with. Stars that have a lot of mass may end their lives as black holes or neutron stars.

A white dwarf is what stars like the Sun become after they have exhausted their nuclear fuel. Near the end of its nuclear burning stage, this type of star expels most of its outer material, creating a planetary nebula.

In 5.4 billion years from now, the Sun will enter what is known as the Red Giant phase of its evolution. This will begin once all hydrogen is exhausted in the core and the inert helium ash that has built up there becomes unstable and collapses under its own weight. This will cause the core to heat up and get denser, causing the Sun to grow in size.

It is calculated that the expanding Sun will grow large enough to encompass the orbit’s of Mercury, Venus, and maybe even Earth.

A typical white dwarf is about as massive as the Sun, yet only slightly bigger than the Earth. This makes white dwarfs one of the densest forms of matter, surpassed only by neutron stars and black holes.

The gravity on the surface of a white dwarf is 350,000 times that of gravity on Earth. 

White dwarfs reach this incredible density because they are so collapsed that their electrons are smashed together, forming what is called “degenerate matter.” This means that a more massive white dwarf has a smaller radius than its less massive counterpart. Burning stars balance the inward push of gravity with the outward push from fusion, but in a white dwarf, electrons must squeeze tightly together to create that outward-pressing force. As such, having shed much of its mass during the red giant phase, no white dwarf can exceed 1.4 times the mass of the sun.

While many white dwarfs fade away into relative obscurity, eventually radiating away all of their energy and becoming a black dwarf, those that have companions may suffer a different fate.

If the white dwarf is part of a binary system, it may be able to pull material from its companion onto its surface. Increasing the mass can have some interesting results.

One possibility is that adding more mass to the white dwarf could cause it to collapse into a much denser neutron star.

A far more explosive result is the Type 1a supernova. As the white dwarf pulls material from a companion star, the temperature increases, eventually triggering a runaway reaction that detonates in a violent supernova that destroys the white dwarf. This process is known as a single-degenerate model of a Type 1a supernova. 

If the companion is another white dwarf instead of an active star, the two stellar corpses merge together to kick off the fireworks. This process is known as a double-degenerate model of a Type 1a supernova.

At other times, the white dwarf may pull just enough material from its companion to briefly ignite in a nova, a far smaller explosion. Because the white dwarf remains intact, it can repeat the process several times when it reaches the critical point, briefly breathing life back into the dying star over and over again. 

Image credit: www.aoi.com.au, NASA, Wikimedia Commons, Fsgregs, quora.com, quora.com, NASA’s Goddard Space Flight Center, S. Wiessinger, ESO, ESO, Chandra X-ray Observatory

Source: NASA, NASA, space.com

Picture of the Day - November 9, 2018

Crescent gas giant over an asteroid moon.

Picture of the Day - February 2, 2019 - (Very Late Post)

The core of a galaxy.

Picture of the Day - February 5, 2019 - (Very late post)

I've decided to travel back home in Space Engine.

Earth and the Moon.

New Blog is Up (Rabbits and Sharks)

My second blog, rabbits and shark’s is up and running. Pictures of my two buns are on there. The blog is all about just rabbits and sharks.

I’ll be continuing to update this blog regularly.

https://sharkrabbitandshark.tumblr.com/

🌙

For more beautiful space aesthetics visit calypsoskelper.tumblr.com

Edited screenshot I took of a gas giant from the simulator “Space Engine” [3089x2980]

Ten interesting facts about Saturn

Saturn is sometimes called “The Jewel of the Solar System.” It is a planet that is nothing like our own. Humans have been gazing up at Saturn for a long time. They have been wondering about it for thousands of years.

Here are some fun facts about the Ringed Planet.

Saturn is huge. It is the second largest planet in our Solar System. Jupiter is the only planet that is bigger.

The rings are huge but thin. The main rings could almost go from Earth to the moon. Yet, they are less than a kilometer thick.

Four spacecraft have visited Saturn: Pioneer 11, Voyager 1 and 2, and the Cassini-Huygens mission have all studied the planet. 

Saturn has oval-shaped storms similar to Jupiter’s: The region around its north pole has a hexagonal-shaped pattern of clouds. Scientists think this may be a wave pattern in the upper clouds. The planet also has a vortex over its south pole that resembles a hurricane-like storm.

Saturn is made mostly of hydrogen and helium: It exists in layers that get denser farther into the planet. Eventually, deep inside, the hydrogen becomes metallic. At the core lies a hot interior. (click the image for a better resolution).

Saturn has 62 moons: Some of these are large, like Titan, the second largest moon in the Solar System. But most are tiny – just a few km across, and they have no official names. In fact, the last few were discovered by NASA’s Cassini orbiter just a few years ago. More will probably be discovered in the coming years.

Saturn orbits the Sun once every 29.4 Earth years: Its slow movement against the backdrop of stars earned it the nickname of “Lubadsagush” from the ancient Assyrians. The name means “oldest of the old”.

In Saturn there is aurora: Photographic composition made by the Hubble Space Telescope showing the occurrence of aurora in the southern hemisphere of Saturn at intervals of two days.The aurora is visible only in the ultraviolet.

Saturn spins on its axis very fast. A day on Saturn is 10 hours and 14 minutes.

You can see Saturn with your own eyes: Saturn appears as one of the 5 planets visible with the unaided eye. If Saturn is in the sky at night, you can head outside and see it. To see the rings and the ball of the planet itself, you’ll want to peer through a telescope. But you can amaze your friends and family by pointing out that bright star in the sky, and let them know they’re looking at Saturn.

sources: nasa.gov, universetoday.com and solarsystem.nasa.gov

Picture of the Day - January 28, 2019

Gas giant with purple cloud bands hangs in the sky of a large rocky moon.