We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What is Absolute Magnitude?

By Ray Hawk
Updated May 21, 2024
Our promise to you
All The Science is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At All The Science, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject-matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

Absolute magnitude is an astronomical term that refers to an object's true level of brightness in space, not what may be perceived as its brightness, which can be altered by the distance of the object, gravitational effects, and stellar material the light must pass through to reach the observer. Despite this clear definition, the term is relative. as an object's absolute magnitude brightness must be further broken down by defining the spectrum of electromagnetic radiation being measured. If making an observation based on the total energy output of a stellar object, the term bolometric magnitude is used, named after Samuel Langley who invented the bolometer in 1878 for measuring electromagnetic radiation.

Calculating absolute magnitude for any one object in space can be complicated, as its apparent magnitude must first be quantified or the brightness perceived by an Earth bound observer. Then, luminosity distance must be determined in parsecs, which is the actual distance of the object if it's located within the Milky Way galaxy. Redshift, or the effect of gravity on light for distant objects, must also be accounted for, with light shifting towards the red end of the spectrum as an object moves away from Earth. Finally, with objects beyond our local galaxy, general relativity calculations must be employed to determine absolute magnitude.

Another process used in absolute magnitude determinations is to calculate an object's absolute magnitude temperature, with the colors of light being produced by the object broken down into the chemical signature that they indicate for photons emitted from various elements. The classification system for stars has an absolute magnitude temperature that ranges from “O” for the hottest with a blue color, to “M” as the coolest with a red color. O class stars are considered to be the rarest in space, only comprising around 0.00003% of the total, with red M-class stars accounting for the bulk at 76.45% of the total. The hottest burning O-class blue stars are also the most massive, and have the shortest lifespan, degrading eventually to red giants, with stars one-quarter the size of the sun degrading to the stage of a white dwarf.

The process of determining and classifying the brightness of objects in space can be traced back to the Greek astronomer Hipparchus, who devised the first magnitude system in 150 B.C.E. At the time, there were only six classifications for brightness based on what one could see with the naked eye. Today, absolute magnitude is a much more refined process, with adaptations to the original process giving negative magnitude values such as for our sun, with -26.74 being its apparent magnitude. Larger negative numbers on the scale indicate bright, nearby objects, with the star Sirius receiving a -1.4 apparent magnitude rating as one of the closest stars to Earth, the planet Venus a -4.4, and the Earth's Moon at a -12.6.

All The Science is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
All The Science, in your inbox

Our latest articles, guides, and more, delivered daily.

All The Science, in your inbox

Our latest articles, guides, and more, delivered daily.