Note: after running each link above in CELESTIA, Right Drag its window with your mouse to get a sense of the 3-D aspects of the stars and their orbits.
Are you unfamiliar with our 1.6.x and 1.4.1 links? For an explanation click here.
Many stars exist not singly, but rather as components of multi-star systems. Here are a few examples of how they and their companions may orbit mutually around each other. Note that each pair of stars can be substituted for any single star in another system to form triple-stars, quadruple stars and so on!
The following will help you enjoy this page's 1.6.x and 1.4.1 links that run events directly in CELESTIA. If you're new to the program, these tips will also help you learn to use it.
You'll find more information about many of CELESTIA's controls on our Learning Center page.
"Black Holes are the most mysterious
of all stellar remnants."
Animation © SkyMarvels.com
derived from NASA/GSFC SVS animation.
PROTOSTARS, STARS & STELLAR REMNANTS
Stars are the mighty lampposts that light the Universe. In addition, they are the miraculous nuclear foundries that have fabricated the heavier elements that make all life as we know it possible.
Our own Sun is a star—in fact, a rather ordinary one. Like all stars, it produces its prodigious energy through self-sustaining nuclear reactions. These proceed stably, depending on a star's type, from millions to billions of years.
From NASA's CHANDRA X-Ray Observatory site, here's a nice Flash animation that begins to acquaint you with Stellar Objects. Entitled Stellar Evolution, it introduces stars themselves, the protostars from which they form, and stellar remnants. Also from the Chandra site, here's an awesome Stellar Evolution poster.
From NASA's HubbleSite, here's an excellent Flash animation that highlights A Star's Life.
© SkyMarvels, enhancement of NASA/JPL-Caltech image
Protostars, the precursors of stars, are massive objects born from the gravitational collapse of immense clouds of interstellar gas and dust. Protostars represent the "toddler" phase of star development, which lasts only a tiny fraction of a star's overall age. For example, for a star with a mass similar to our Sun's, its phase as a protostar may last only 100,000 years.
INTERESTING PROTOSTARS LINKS
From LASP at the University of Colorado at Boulder site, here is a page with lots of excellent info, graphics and Flash demos showing protostar formation. Fittingly it's called A Star is Born.
Stars are incredibly massive objects that, for at least a portion of their lives, radiate prodigious quantities of energy produced through nuclear fusion. This colossal outflow is balanced by the relentless pull of each star's own gravity, which holds it in equilibrium for millions to billions of years. This imposes a predictable order on stars, which are most commonly classified according to their spectra and brightness, as shown in the venerable H-R diagram below.
From UNL, here are some excellent HTML5 interactives highlighting stars:
Excellent Interactive H-R Diagram. Click anywhere to create a star. Then drag your star or the triangles on the graph axes. Awesome!
From the King's Centre for Visualization in Science (KCVS), here are some excellent Flash interactives highlighting stars:
Relationship Between a Star's Color and Surface Temperature. For example, the Sun's surface temperature is about 5,800° Kelvin.
Birth of a Sun-like Star and how long it takes to arrive on the Main Sequence.
Stellar Models: how a star's temperature and density are related to its radius.
From the excellent Las Cumbres Observatory site, here is a fantastic interactive feature that shows how a star's properties (mass, age, brightness, etc.) and its location on the HR-diagram are related. Highly reommended! Star in a Box: Interactive H-R Diagram.
Though it's a little hard to read, here is an interesting Flash demo that maps 32 Nearby Stars in 3-D. There are stars of spectral type A through M in the demo.
List of Brightest Stars (apparent magnitude)
List of Most Luminous Stars (absolute magnitude)
image credit: NASA
After seeing star-types like "supergiants", "giants" and "dwarfs" in the H-R diagram above, it should come as little surprise that stars come in a wide variety of sizes. You can get a good idea of the relative sizes of various well-known stars and the diverse classes to which they may belong with these two extraordinary Flash demos: Magnifying the Universe and Scale of the Universe 2.
NUCLEAR FUSION IN STARS
For stars of roughly 1¼ solar masses and lower, the Proton-Proton (P-P) cycle is the primary way in which hydrogen ions (protons) are fused to yield helium and energy. The process involves several interactions of 6 overall protons, which ultimately yield one Helium-4 nucleus, two positrons, two gamma rays (energy), two neutrinos and two protons.
For stars of greater than roughly 1¼ solar masses, the Carbon-Nitrogen-Oxygen (C-N-O) cycle dominates in producing helium and energy from hydrogen ions (protons). This process involves several interactions of 4 overall protons along with a carbon-12 nucleus, the latter acting as a catalyst as it is converted to isotopes of nitrogen, oxygen and finally carbon-12 again.
In massive stars, heavier elements are progressively built-up in great shells around the core, resulting in a structure likened to the layers of an onion!.
From the King's Centre for Visualization in Science (KCVS), here's a nice Flash interactive that shows the Evolving Onion Structure of a 25-Solar-Mass Star.
MORE INTERESTING STAR LINKS
WHITE & BLACK DWARFS, NOVAE & SUPERNOVAE, NEUTRON STARS,
QUARK STARS AND BLACK HOLES
All stars eventually succumb to natural processes and "die". They go through a process of expansions and contractions, shed a percentage of their outer layers, and undergo a final collapse. But this does not occur in the same way for all stars.
By far, most stars (perhaps 95% or more) approach their final stages as white dwarfs! These are fantastically dense objects. Roughly Earth-sized, a typical white dwarf may still be half as massive as the Sun! This means that one is so dense that a white dwarf's gravity can noticeably bend the light of stars passing behind it! Nonetheless, at this stage it can no longer radiate any energy through fusion, but only by virtue of its final contraction. Eventially it will cool to become a black dwarf, though not for an incredibly long time. In fact, astronomers now estimate that the Universe is not yet old enough to have produced any black dwarfs! Here are Wikipedia's White Dwarf and Black Dwarf pages.
Some stars approach their final stages with a series of explosions (novae) or a single devastating explosion (supernovae). These return great amounts of matter back to the interstellar medium, matter that eventually contributes to the immense clouds that may one day spawn other stars. From the University of Arizona's astronomy site, here's a nice page highlighting Novae and Supernovae. From NASA/Conceptual Image Lab/Goddard Space Flight Center, here are nice animations depicting V407 Cygni "Going Nova" and a Type Ia Supernova". And here are Wikipedia's Nova and Supernova pages. And, from the Chandra site, here is a pair of enlightening Flash demos: Blasts from the Past: Historic Supernovas and Locating Historic Supernovas in the Milky Way.
When a star's final collapse yields an object of between 1.4 and 3.2 solar masses, its gravity becomes sufficient to literally squeeze its electrons into its atomic nuclei! This yields a neutron star, an object with a diameter of roughly 12 miles (20 km) but a mass that's greater than that of our Solar System! Ranking among the most exotic objects in the universe, neutron stars can take several forms, as these next images and animations from NASA show. One may simply be a single pulsar, or may be a pulsar drawing matter from a much larger companion, which can generate strong gravitational waves! Or it may also be a magnetar, a neutron star with an incredibly strong magnetic field. It has even been theorized that in some cases there are Binary Neutron Stars That Merge! Here's the link to NASA's Imagine the Universe: Neutron Stars and Pulsars page. And here are Wikipedia's Neutron Star, Pulsar, and Magnetar pages.
It has been theorized that there may be objects that are too massive to remain neutron stars, yet not massive enough to become black holes. These objects are quark stars, whose gravity is sufficient to disassociate its neutrons' "bound quarks" into "free quarks!" Quark stars would not be much smaller than neutron stars, as this intriguing comparison from Chandra's site shows: A Neutron Star and Quark Star in the Grand Canyon! But it must be stressed that this comparison is only illustrative of relative sizes. If a neutron star and quark star were ever so near to us, Earth would have already been destroyed by their gravity! Here is Wikipedia's Quark Star page.
As this excellent demo from HubbleSite shows, with black holes we reach the "end of the line" of our stellar remnants! When stars of a sufficient mass eventually collapse, their gravity is so powerful that nothing, not even light, can escape from them! They may even become Star Eaters! Here is Wikipedia's Black Holes page. From Chandra's site here's another intriguing Flash demo: The Truth and Lies about Black Holes. And here is a link to a nice animation on the University of Chicago's COSMUS site that shows Stars Orbiting the Milky Way's Supermassive Black Hole!
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SCALE OF THE COSMOS
SKY-FUN / SKY-GAMES
FUN FACTS ABOUT
Virtually all elements heavier than hydrogen and helium were produced in stars!
Well over ⅔ of all stars are dim red dwarfs! In addition, most of these are single stars, (that is, they have no companion stars!)
Most "bright" stars exist as components of binary or multiple star systems!
According to some experts, the Universe is not yet old enough to have produced any black dwarfs!
Because gravity so greatly "bends" the light radiated from a neutron star, more than ⅔ of its surface can be simultaneously visible to an observer! If the same were true on Earth, an observer in geosynchronous orbit could see ALL of the Antarctic and the Arctic at the same time!
Scientists now theorize that "quark" stars exist! A quark star is more dense than a neutron star but not dense enough to become a black hole!
The more massive a star, the shorter its lifespan!
Some "type-O" high-mass stars remain on the main sequence for only 500,000 years, while some "type-M" low-mass stars remain on it for over 75 BILLION years!
STELLAR OBJECTS INTERACTIVES
QUICK ACCESS LIST
Note: some links are echoed elsewhere on this page and may include descriptive text. Note too that there are a few links to interactives in the center column immediately next to this list, so they are not duplicated here.
NASA's CHANDRA Site's Stellar Evolution
NASA's Spitzer Mission's An Infrared Search for Origins
Here's KCVS's cool Proton-Proton Cycle
Here's KCVS's cool Carbon-Nitrogen-Oxygen Cycle
Here's KCVS's cool Astronometric Wobble
Here's KCVS's cool Two Line Spectroscopic Binary
HUBBLE-Site's Black Holes
CHANDRA's The Truth and Lies about Black Holes