The goal of this blog is to create a list of super facts. Important facts that are true with very high certainty and yet surprising, misunderstood, or disputed by many. This blog aims to be challenging, educational, and fun, without it being clickbait. I determine veracity using evidence, data from reputable sources and longstanding scientific consensus. Prepare to be challenged (I am). Intentionally seek the truth not confirmation of your belief.
Super fact 102: Stars twinkle but planets do not. Planets reflect sunlight, like the moon, whereas stars emit intense light like the sun. However, stars are thousands of times further away.
The light from stars is intense allowing stars to have much smaller discs in the sky for the same amount of light as a planet. Shutter Stock Illustration ID: 566774353 by Nostalgia for Infinity.
The Sun and the Moon appear to have roughly the same sized disk in the sky, about 0.5 degrees of arc, because the Sun is roughly 400 times wider than the Moon but also about 400 times farther away. However, the moon, which reflects sunlight but does that emit any, is much fainter than the sun in our sky. The Sun provides approximately 400,000 times more light to Earth than the full Moon. If you were to move the sun farther away until it provided the same amount of light as the moon you would have to move the sun 632 times farther away until it became a tiny point in comparison to the moon.
The planets in our solar system, Venus, Jupiter, Mars, Mercury, Saturn, etc., appear in the sky as small discs reflecting light whereas the stars appear as intense points of light with a disc diameter that is thousands of times smaller than that of the planets. However, we can’t see the difference with the naked eye. Both planets and stars appear like points of lights to us, but the difference in disc size in the sky is very big.
Planets reflect light whereas the stars appear as intense points. Shutterstock asset id: 2709145593 by buradaki
Because stars are tiny intense points of light Earth’s atmosphere can easily refract (bend) their light. This is known as scintillation. I can add that the light from stars that are low in sky go through more atmosphere and therefore twinkle more. Since planets appear as tiny discs rather than tiny points, planets create a steadier beam of light, which averages out atmospheric turbulence. In addition, dust particles in space and in the atmosphere can more easily block the light from stars compared to that of planets, because the planets have much larger discs in the sky (thousands of times larger).
To the naked eye a planet and a star point look light points of light. In a telescope the planet will turn into a disc, but the star will remain a bright point of light. For example, a piece of space dust can easily make the star twinkle by moving in front of it but won’t do that to the planet. Note: planets are much smaller than stars, but they are much closer and can look bigger.
Since this fact is not scientifically under question, a lot of people don’t know it, and it is kind of important to anyone interested in the night sky, I consider it a super fact. I should say that I borrowed this super fact from Jacqui Murray’s blog worddreams.
Planets Reflect Light like the Moon
Planets reflect light. They don’t shine and emit light like the sun or the stars.
Jupiter in true color, taken by the Hubble Space Telescope in January 2024Saturn and its prominent rings, as captured by the Cassini orbiter. This natural color view of the planet Saturn was created from images collected shortly after Cassini began its extended Equinox Mission in July 2008.Pluto from NASA/JHUAPL/SwRI. NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute, Public domain, via Wikimedia Commons. NASA’s New Horizons spacecraft captured this high-resolution enhanced color view of Pluto in 2015.
If you place a light bulb (white light includes a spectrum of colors) in front of a container filled with hydrogen and then you let the light pass through a prism, it will split into the different colors (red, yellow, blue, etc.) forming a rainbow, as prisms do. You see this every time you see a rainbow in nature. However, if you measure carefully, as in the experimental setup below, you will notice that some frequencies are missing. That’s because the hydrogen gas will absorb certain frequencies.
This is true, not just for hydrogen, but for all elements/atoms and molecules. Atoms and molecules have light absorption patterns that are unique to the atom/element in question. The dark lines in the spectra are referred to as Frauenhofer lines. In a sense, all elements have a thumb print resulting from their so called absorption spectra. This makes it possible to identify the elements in a star and their proportions.
Absorption spectrum / Frauenhofer lines of the hydrogen atom. Shutterstock asset id: 1305568666 by Emir Kaan
Before the discovery of absorption spectra, it was sometimes believed that humanity would never know the chemical elements of stars. Even today many people are surprised to hear that we can indeed know what stars are composed of just by looking at their light. In addition to identifying elements in the upper layers / atmosphere of stars you can use the same absorption spectra to determine the relative velocity of stars compared to us and sometimes the distance to the stars. This is an old discovery that is surprising and important to our understanding of the world and therefore a super fact in my opinion.
Examples of Absorption Spectra
An interesting, related fact is that Helium was discovered in the Sun before it was found on Earth, with the help of emission spectra (August 18, 1868). Emission spectra are the opposite of absorption spectra. It should be noted that while emission spectra are commonly used for identifying the composition of interstellar gas, absorption spectra are commonly used for identifying the composition of stars.
Absorption and Emission Spectrum of Helium Shutterstock asset id: 1724296909 by MoFaroukAbsorption and Emission Spectrum of Carbon Shutterstock asset id: 1725934867 by MoFaroukSolar spectrum with Fraunhofer lines as it appears visually. The solar spectrum is a combination of spectra from multiple elements: nl:Gebruiker:MaureenVSpectrum-sRGB.svg: Phrood~commonswikiFraunhofer_lines_DE.svg: *Fraunhofer_lines.jpg: Saperaud 19:26, 5. Jul. 2005derivative work: Cepheiden (talk)derivative work: Cepheiden, Public domain, via Wikimedia Commons.
Using Redshift to Determine how fast Stars are Moving Compared to us
A star or galaxy that is moving towards us will have a blue shifted spectrum. A star or galaxy that is moving away from us will have a red shifted spectrum. Red shifted means that the absorption lines have moved towards red because the frequency of the light has been shifted due to the motion.
This is called the doppler effect. You can notice this phenomenon for the case of sound when an ambulance is coming towards you and then speeding by you. The sound changes. The astronomer Hubble was using redshift to the determine that the further away a galaxy was from us the faster it was moving away from us. Measuring the redshift of a faraway galaxy or star, not only tells us its speed compared to us but can indirectly help us determine the distance to the galaxy or star.
Visualization of redshifted absorption lines are redshifted due to velocity away from observer. Top lines are for an object at rest and in the bottom picture the object is moving away. Maxmath12, CC0, via Wikimedia Commons. This file is made available under the Creative Commons CC0 1.0 Universal Public Domain Dedication.
There are other things you can tell from the light from stars and from their electromagnetic spectrum such as the type of star, the size of the star, and the age of the star, but that is for another post. This post is long enough.
Super fact 79 : Distant galaxies appear redder (redshifted) because of the universe’s expansion. The farther away the galaxy, the redder it is. This cosmological redshift is also increasing because the Universe’s expansion is accelerating. Our Universe is getting more and more red every day.
Many people are aware that the Universe is expanding but may not know that this results in a measurable redshift. The faster a galaxy is moving away from us the redder it appears. This is called the cosmological redshift. Measuring these redshifts was how we discovered that our Universe is expanding.
As the Universe expands and galaxies are moving away from each other the light will be stretched. Stretched light with longer wavelengths are more red. The phenomenon is called redshift. Shutterstock Asset id: 1180828402 by VectorMine.
At the end of the 1990’s it was also discovered that the Universe’s expansion was accelerating. This discovery came from measuring the redshifts (and apparent dimness) of distant Type Ia supernovae. I should add that measuring the increase in the cosmological redshift directly is difficult. However, it is expected to be possible when the Extremely Large Telescope (ELT) starts gathering data in 2027. I can add that there are also other types of evidence showing that the Universe’s expansion is accelerating.
Another surprising aspect is, if the Big Bang was like an explosion, gravity would pull back the galaxies making the expansion slow down and perhaps eventually even reverse. However, the opposite is happening. A common explanation is that a repulsive force, a sort of anti-gravity, referred to as dark energy, is responsible for this acceleration.
I call this a super fact because this is an observed phenomenon, it is important knowledge for how we view the world, and it is surprising. Many people have heard bits and pieces of this but do not have the fuller picture.
The Doppler Effect
The cosmological redshift is an example of the so called doppler effect. The doppler effect is the change in the frequency or wavelength of a wave in relation to an observer if the origin of the wave and the observer are moving compared to each other. If an object is moving towards you, let say an ambulance, the frequency of its sound will be higher (wavelength shorter).
After it passes you and moves away from the frequency will be lower (wavelength longer). In other words, the sound changes when the ambulance passes you. The same is true for other kinds of waves, including waves on the water, and light. If a light is travelling towards you at a high speed, it will look bluer. If a light is travelling away from you at a high speed it will look redder. The latter is what is called a redshift, cosmological redshift in our case.
Change of wavelength caused by motion of the source. When an object moves toward you the wavelengths get shorter and the frequency higher. When an object moves away from you the wavelengths get longer and the frequency lower. Original: Tkarcher Vector: Tatoute, CC BY-SA 3.0 <http://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia CommonsThe Doppler effect causes a car engine or siren to sound higher in pitch when it is approaching than when it is receding. The red circles represent sound waves. Charly Whisky 18:20, 27 January 2007, CC BY-SA 3.0 <http://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons
Below is a three minute video explaining the doppler effect and redshift.
I can add that the constancy of the speed of light in vacuum changes the exact size of the doppler effect. The doppler effect remains as is for the most part but the formulas for the classical doppler effect, which you would use for sound, and the relativistic doppler effect, which you would use for light in space, are different. It is just to pick the right formula.
The classical formula for the doppler effect. There is a medium (air) but you don’t need to consider the constancy of the speed of light in vacuum. You use it for sound and water waves. Shutterstock Asset id: 2365938267 by Sasha701.The relativistic formula for the doppler effect considers the constancy of the speed of light in vacuum but there is no medium to worry about. You use this formula for the doppler effect of light in space. Shutterstock Asset id: 2416786951 by Sasha701.
Measuring redshift
A common misconception is that astronomers take pictures of distant galaxies and somehow measure the “redness” of them, but that is not the case. When you take a spectrum of a heated element (such as hydrogen or helium in stars) it creates characteristic dark lines in the spectrum — like a fingerprint. Everything on the periodic table has its own characteristic fingerprint of lines at characteristic frequencies. In addition to measuring the cosmological redshift it makes it possible to identify the elements in a star and their proportions. See the picture below.
Visualization of redshifted absorption lines are redshifted due to velocity away from observer. Top lines are for an object at rest and in the bottom picture the object is moving away. Maxmath12, CC0, via Wikimedia Commons. This file is made available under the Creative Commons CC0 1.0 Universal Public Domain Dedication.
Expanding Universe Hazy IPA
Expanding Universe is a Hazy IPA, or a so called New England style IPA from First State Brewing, ABV 6.5%, IBU 25 (IBU = International Bitter Units). The fact that it is an IPA (India Pale Ale) means that it is Ale and therefore not a Lager. The fact that it is an IPA means that it is hop-forward and has an intense flavor and aroma. The fact that it is a Hazy / New England style IPA means that it is more fruity than bitter and looks cloudy, hazy, like juice. The flavor of Expanding Universe is mango, pineapple, and grapefruit. It has a low bitterness, it is fruity, juicy, and it is great if you like New England IPAs.
Super fact 78 : A neutron star is vastly denser than the Sun, typically hundreds of trillions of times denser. In addition, the gravity on a neutron star is a few billion times stronger than on the Sun’s surface. Therefore, a cubic meter of neutron star material weighs roughly septillion times (1,000,000,000,000,000,000,000,000 times) more than a cubic meter of Sun’s average density material placed on the sun’s surface.
A neutron star is the core of a collapsed supergiant star. It is the remnant of a supernova explosion of a massive star. The original star typically has a mass of 10 to 25 solar masses and the core remnant a mass between 1.4 to 2 times the mass of the sun but confined into a sphere with a diameter of on average 12 miles. That is quite small for so much mass and will result in a material so compressed that it is hundreds of trillions of times denser than our sun. A tablespoonful of a neutron star would have the same mass as Mount Everest.
The neutron star is so compressed that it has the density of an atomic nucleus. The extreme pressure causes the electrons and protons in normal matter to combine into neutrons. If the core remnant would be a bit more than 2.2 times the mass of the sun it would turn into a black hole. In that sense a neutron star is the last stop before a collapsing giant star becomes a black hole.
Let’s do the calculation. Let’s say the density of a neutron star is 200 trillion times that of the Sun, and the gravity is 5 billion times stronger (100 billion to 200 billion times stronger than Earth’s gravity). That results in the matter on a neutron star weighing a septillion time (1,000,000,000,000,000,000,000,000 times) more than the same volume of matter of the average density of the sun on the sun’s surface. I should say I asked ChatGPT to make this calculation using its own numbers, and it got roughly the same answer.
I can add that the average density of the sun is 1.4 grams per cubic centimeter which is less than that the average density of the earth, which is 5.5 grams per cubic centimeter. On the other hand, the gravity on the Sun’s surface is about 28 times stronger than on Earth, so if you make these comparisons with Earth instead of the sun the numbers get seven times worse, or seven septillion (7,000,000,000,000,000,000,000,000). I can add that even though neutron stars are extreme they are not rare. NASA estimates that there are a billion of them in our Milky Way Galaxy.
I consider this a super fact because it is true, and it is somewhat important to be aware of the extremes of the Universe. It tells us about who we are and our place in the Universe. A septillion times more weight, for the same volume and densities hundreds of trillions of times larger than the Sun or the Earth are surprising and shocking numbers.
Neutron star on a black background. Superdense remnant of a star in space. A small star with a huge mass. ShutterstockAsset id: 2369752833 by Nazarii_Neshcherenskyi
To watch a seven minute video about Neutron stars, see below.
Different Types of Neutron Stars
Neutron stars are extreme stars. They are small super dense stars with extreme gravitational fields. They are in a sense like a gigantic atomic nucleus. Perhaps it is not surprising that they are extreme in other ways as well. There are pulsars, neutron stars which emit twin beams of radiation from their magnetic poles. Those poles may not be precisely aligned with the neutron star’s rotation axis, so as the neutron star spins, the beams sweep across the sky, like beams from a lighthouse. To observers on Earth, this can make it look as though the pulsar’s light is pulsing on and off.
There are magnetars, neutron stars with extremely powerful magnetic fields trillions and quadrillion times stronger than Earth’s magnetic field at the surface. If one were to get close to Earth, at the distance about the same as the moon, you would see a small new star in the sky, as cars and other metallic objects lift from the ground and the magnetic strips of credit cards and computer hard drives are erased.
There are additional classes of neutron stars such as black widow pulsars, blasting a nearby star with radiation thus killing the star, soft gamma repeaters, magnetars emitting short burst of X-rays and gamma rays in irregular repeating patterns. There are binary neutron stars (two neutron stars orbiting each other) and they sometimes merge, collide, emitting detectable gravity waves. Click on the link to see a video visualization.
Magnetar – neutron star in deep space. For use with projects on science, research, and education. 3D illustration. Shutterstock Asset id: 1138434620 by Jurik PeterCourtesy NASA/JPL-Caltech, Attribution, via Wikimedia Commons
Super fact 75 : Magnetars are a type of neutron star with extremely powerful magnetic fields ranging from 10,000,000,000,000 Gauss to 1,000,000,000,000,000 Gauss. In comparison, Earth’s magnetic field varied from about 0.25 to 0.65 Gauss at the surface. In other words, the magnetar magnetic fields are from 20 or 40 Trillion times to 2 or 4 Quadrillion times stronger than Earth’s magnetic field at the surface.
Magnetar – neutron star in deep space. For use with projects on science, research, and education. 3D illustration. Shutterstock Asset id: 1138434620 by Jurik Peter
The magnetic fields of magnetars are trillions of times stronger than the sun’s magnetic field, which is 1 Gauss on a quiet sun surface and 2,000 to 4,000 Gauss in sunspots. The magnetic field of an MRI’s machine is also incredibly strong (2,000 Gauss to 100,000 Gauss). It is thousands to over a hundred thousand times stronger than Earth’s magnetic field. That’s why you should not have metals around an MRI machine. However, the magnetic field of a magnetar is still hundreds of millions to tens of billions of times stronger than the magnetic field of an MRI machine, and the magnetic field is not confined to a small machine but surrounds a neutron star and stretches far out into space.
If you placed a magnetar halfway to the moon from Earth (a magnetar is around 12 miles in diameter), it would erase all the credit cards on Earth (see video below). If you get close to a Magnetar (1000 kilometers) cars and other metal would float up in the air and the atoms in yourbody would stretch into rods making organic chemistry impossible and kill you. If you placed a steel beam on the surface of a magnetar the magnetic field would pulverize it and destroy the atoms.
In 2004 a magnetar named SGR 1806-20 located 50,000 light years from our solar system (700 million times farther than the planet Jupiter) had a starquake disturbing the magnetic field and sending out a gamma burst that disrupted radio communication on Earth. I consider the existence of magnetars a super fact because the existence of these super magnetic monsters is shocking and not well known amongst the public, and yet their existence has been confirmed.
On 27 December 2004, a burst of gamma rays from SGR 1806−20 passed through the Solar System (artist’s conception shown). The burst was so powerful that it had effects on Earth’s atmosphere, at a range of about 50,000 light-years. U Harvard, Public domain, via Wikimedia Commons.
What Are Neutron Stars and Magnetars?
A neutron star is the gravitationally collapsed core of a massive supergiant star. The collapse causes it to become super compact and relatively small by volume. As the name implies the atoms are crushed, and protons and electrons merge into neutrons, making the neutron star mostly neutrons. The typical diameter of a neutron star ranges from 10 to 25 km (6 to 15 miles) depending on its mass. Neutron star material is extremely dense.
A normal-sized matchbox containing neutron-star material would have a weight of approximately 3 billion tons, the same weight as a 0.5-cubic-kilometer chunk of the Earth (a cube with edges of about 800 meters) from Earth’s surface, or a very large mountain. In addition, the gravity on a neutron star is immense, about 100 billion to 200 billion times stronger than Earth’s gravity.
Magnetars are neutron stars with extremely powerful magnetic fields. They have the universe’s most powerful magnetic fields (trillions of times stronger than Earth’s) that power intense X-ray/gamma-ray bursts as its field decays, often seen as highly variable pulsars. They were first theorized in 1992 to explain Soft Gamma Repeaters (SGRs) and Anomalous X-ray Pulsars (AXPs). As of July 2021, 24 magnetars have been confirmed. According to the video below 30 magnetars have been confirmed in the Milky Way. There might be 3,000 in our Galaxy.
Courtesy NASA/JPL-Caltech, Attribution, via Wikimedia Commons
