We’ll reveal seven of the brightest stars with a visual magnitude below 0.1 and their constellations in today’s article. If you want to learn more dazzling stars, look at our new infographic.
How to measure the brightness of a star?
Astronomers measure the brightness of stars, planets, and other space objects using a magnitude scale. There are two types of magnitude — apparent and absolute. Apparent (or visual) magnitude is the brightness of an object as it appears in the night sky from the Earth. Apparent magnitude depends on an object’s intrinsic luminosity, distance, and other factors reducing its brightness. The lower its apparent magnitude, the brighter an object appears to observers. Space bodies with negative magnitude numbers are exceptionally bright.
Absolute magnitude is an apparent magnitude an object would have if it were located at a distance of 10 parsecs. For example, the apparent magnitude of the Sun is -26.7 — it’s the brightest celestial object we can see from the Earth. However, if the Sun were 10 parsecs away, its apparent magnitude would be only 4.7. By considering stars at a fixed distance, astronomers can compare the real — intrinsic — brightnesses of different stars.
What are the brightest stars seen from Earth?
Based on the apparent magnitude, the Sun is the brightest star as viewed from the Earth. However, we should note that not all lists of the brightest stars include the Sun, since many of them consider only the stars observable in the night sky. Thus, they designate Sirius as the brightest star.
The second brightest star, Sirius, has an apparent magnitude of -1.46 and is visible worldwide. This dazzling star is located in the constellation Canis Major; it is the Alpha star of this constellation. Sirius is about 8.6 light-years away from us, which is much closer than the next member of our list.
The brilliant Canopus or Alpha Carinae is the third brightest star in the night sky. This star shines at a visual magnitude of -0.74 in the constellation Carina which is best visible in the Southern Hemisphere. Canopus is placed further than any other star in this list — around 310 light-years away from the Sun!
Alpha Centauri is a closer yet a bit fainter star that got fourth place in the list. This star is actually a system consisting of three stars, the brightest of which is also known as Rigil Kentaurus. Alpha Centauri is placed in the constellation Centaurus shining with a visual magnitude of -0.1. Lying at a distance of just 4.4 light-years from us, this star system is the closest neighbor to the Sun. The system is in the Southern sky and isn’t visible to observers above the latitude of 29° north.
The fifth brightest star is Arcturus, the main member of the Bootes constellation. Having the apparent magnitude of -0.05, Arcturus is best visible in the winter sky from the Northern Hemisphere. This orange giant is placed about 37 light-years away.
Vega that takes sixth place, is the brightest star in the northern constellation of Lyra, and also a part of the Summer Triangle asterism. This star lies 25 light-years away from our Solar System. Vega was taken as “zero value” to reference the other star magnitudes, but this isn’t the case anymore — further studies measured its magnitude as 0.03. For the visual observations, Vega still can be used as the zero point, but for more advanced observations, an elaborate calibration system is used.
The last member of our list is Capella — the seventh brightest star of the entire sky. It’s visible in the Northern Hemisphere most of the year. Capella is the brightest star of the constellation Auriga and designated Alpha Aurigae. Located about 43 light-years from us, Capella, in fact, is a multiple star system consisting of two yellow binaries.
You can observe all the stars mentioned above (and more!) with Star Walk 2. Just point your device up and tap the brightest dots you see on the screen. If you want to find a particular star or a space object, use the magnifier icon in the screen’s lower-left corner.
The measurement obstacles
The exact order of the brightest stars can’t be perfectly defined since there are some obstacles:
- First of all, traditionally, stellar brightness is based on the apparent visual magnitude perceived by the human eye. After the invention of telescopes, astronomers proved the existence of double stars and multiple star systems. Nowadays, stellar brightness could be expressed as either individual or combined magnitude. For example, the double star Alpha Centauri AB has a combined visual magnitude of -0.27, while its two components have magnitudes of 0.01 and 1.33.
- New technologies can measure stellar magnitudes slightly differently — this may change the brightest stars’ order. Also, scientists developed different kinds of magnitude systems based on different wavelengths, so apparent magnitude values can vary dramatically.
- There are variable stars, like Betelgeuse or Antares — they’re changing their magnitude over days, months, or years. Usually, to exactly define an apparent magnitude, you should take either the repeated maximum brightness or a simple average magnitude.
We hope that you learned something new from today’s article. Share it on social media and let us know your opinion. Happy stargazing!