The brightness of any stellar object or any object in space is measured by the apparent magnitude of that body. Well, that’s just one way to do it. Apparent magnitude is the level of brightness witnessed by an observer on the Earth. Brightness and the magnitude value have an inverse relationship, i.e. more the brightness less will be its apparent magnitude value. Right now, our Sun has an apparent magnitude of –26.74.
An another criteria for measuring stellar brightness is the absolute magnitude. In this case, the brightness of any star is measured from a constant distance of 32.6 light years or 10 parsecs. We’ve made a list of the brightest stars in the universe based on their apparent magnitude. So let’s find out which star shines the most.
Antares between σ and τ Scorpii
Distance: 550 light years
Apparent Magnitude: +0.6 – 1.6
Antares also known as Alpha Scorpii is the brightest star in the Scorpius Constellation. On a comparative scale, the brightness of Antares is almost 10,000 times (visual wavelength) that of the Sun, but due to the fact that it radiates almost all of its energy in the infrared wavelength, the true bolometric value of Antares is more than 100,000 times that of the Sun.
Occultation of Aldebaran by the Moon/ Image Courtesy: Christina Irakleous
Distance: 65.3 light years
Apparent Magnitude: +0.86
Aldebaran is a red giant of spectral class K, which has evolved from its main sequence phase after depleting its hydrogen core. The current Stellar model predicts that while Aldebaran has only about 50% more mass than the Sun, it has 425 times its luminosity largely due to inflated radius. One of NASA’s oldest and farthest probe Pioneer 10 is currently heading in its direction and should make its nearest approach in approximately two million years.
13. Alpha Crucis
Distance: 320 light years
Apparent Magnitude: +0.76
Alpha Crucis is a multiple star system located nearly 320 light-years away from the Sun in the constellation of Crux and is a part of the Southern Cross asterism. With a combined visual magnitude of 0.76, it is the brightest star in Crux and the 13th brightest star in the night sky. It is the southernmost first-magnitude star, just a little more southerly than Alpha Centauri.
Distance: 16.73 light years
Apparent Magnitude: +0.76
If you are into stars, then you probably have heard about the age old love story of Altair and Vega. According to the Chinese mythology, these two were deeply in love, but forever separated due to the celestial river of the Milky Way galaxy.
Once a year, in the 7th day of the 7th month of the Chinese calendar Vega cried so hard that every single Magpies in the fly’s up and form a bridge with their wings so that these two lovers can be together for the one night.
Back to some facts, Altair is an A-type main sequence star with a visual magnitude of 0.77 and has almost twice the mass of the Sun and 11 times its luminosity.
11. Beta Centuari
Distance: 390 light years
Apparent Magnitude: +0.61
Popularly known as Agena and Hadar, Beta Centuari is a multiple star system located in the constellation of Centaurus. The system has three stellar components: Beta Centauri A1, A2 and B. All the detected spectral lines from this system points that all three stars are B-type main sequence star with just a few variations. It’s combined visual magnitude of +0.61 makes Beta Centuari the brightest star in the constellation of Centaurus only after our neighbor Alpha Centauri.
HST images of Betelgeuse showing asymmetrical pulsations
Distance: 727 light years
Apparent Magnitude: +0.50
Betelgeuse is one of the most famous and well studied stars out there. Also known as the Alpha Orionis, it’s the second brightest star in the constellation Orion. It distinctly reddish appearance has been described in various ancient astronomical sources, most notably by Ptolemy.
Betelgeuse is a semiregular variable star whose magnitude fluctuates from 0.0 to +1.3, the largest known of any first magnitude star. In 1836, a significant variation in its brightness was detected by Sir John Hershel, it was the first record of such case in its observational history. Under normal circumstances, Rigel always remains brighter of the two, but from 1836 to 1840 Betelgeuse became so bright in the night sky that it actually outshone Rigel.
Image Courtesy: University of Illinois
Distance: 139 light years
Apparent Magnitude: +0.46
Archernar is among the brightest binary star system in the sky located in the constellation Eridanus. The binary system is composed of two stars namely Archenar A and Archenar B. The much brighter of the two, Archenar A is classified as a B-type main sequence star, which are one of the most luminous of all the stars according to the modern stellar classification.
It has a mass 7 times that of the Sun and about 3,150 times more luminous. Achernar has an extremely high rotational velocity, causing it to become oblate in shape. In the northern hemisphere, the star becomes invisible after 32 degrees north latitude, while it’s best observed from 33 degree southern hemisphere.
Image Courtesy: Yunji Kitahara
Distance: 11.46 light years
Apparent Magnitude: +0.34
Procyon is the brightest star in the northern constellation of Canis Minoris. It’s a binary star comprised of a brighter main sequence star (Procyon A) which is accompanied by a faint white dwarf known as Procyon B. Its estimated stellar temperature is around 6,530 K and have twice the solar radius with 7 times its luminosity.
Along with bright star Sirius and Betelgeuse, it creates the winter Triangle asterism joining three different constellations of Canis Major, Orion, and Canis Minor. The star can be clearly observed during the late winter evening.
7. Rigel A
Distance: 860 light years
Apparent Magnitude: +0.03
Rigel’s visual double star status has been established since at least 1820s, when it was thoroughly studied by German -Russian astronomer Friedrich von Struve. The system appears to be composed of three to five stars, with the most prominent being Rigel A. It’s a blue supergiant, which is at least 120,000 times more luminous than the Sun.
Located in the constellation of Orion, it always outshone Betelgeuse (Alpha Orion). Its companion, Rigel B is much fainter about 500 times than its much brighter stellar partner. Rigel A is most prominent in the night sky during the winters in the northern hemisphere and during the summers in the southern hemisphere.
6. Capella Aa/Ab
Distance: 42.9 light years
Apparent Magnitude: +0.08
After Arcturus and Vega, its the third brightest star in the northern celestial hemisphere and the brightest in the constellation of Auriga. Although, Capella appears to be a single star when observed from the Earth, it’s actually a quadruple star system revolving in two binary pairs.
The first and most prominent pair consist of two yellow giants, both more than twice as massive as the Sun. Designated as Capella Aa and Ab, both have used up most of their hydrogen reserve and moving away from the main sequence. Out of those two, Capella Aa is more luminous with 78 times Sun’s luminosity.
A mid-infrared (24 μm) image of the debris disk around Vega
Distance: 25.4 light years
Apparent Magnitude: +0.03
Over the years, Vega has been intensely studied by astronomers. According to some scientists, it is the second most important star after the Sun. At around 12,000 BC, Vega was a pole star in the northern hemisphere and will again circle back its position at around 13,700.
Vega can be observed in the constellation of Lyra, near the zenith (above your head) in the mid latitudes during the summers in the northern hemisphere, while in the southern hemisphere it can be seen above the northern horizon during the winters in the Southern Hemisphere.
Distance: 36.7 light years
Apparent Magnitude: -0.05
Arcturus is one of the brightest stars in the night sky outshone only by three stars, Sirius, Canopus and Alpha Centauri. It’s a red giant star with an estimated age of more than 7 billion years. According to the estimation, it is 110 times more brighter than the Sun, while its bolometric power output is nearly 180 times greater than the Sun’s.
3. Alpha Centauri A
Image Courtesy: ESO/DSS 2
Distance: 4.37 light years
Apparent Magnitude: -0.27
At the distance of 4.37 light years, the Alpha Centauri is the closest triple-star system to our Sun, consisting of Alpha Centauri A, B and Alpha Centauri C. Without a telescope, the two most prominent stars in this system, including Alpha Centauri A appear as a single bright star in the constellation of Centaurus. The star is about 1.1 times more massive and 1.5 times more luminous than the Sun.
Image of Canopus taken from the International Space Station
Distance: 310 light years
Apparent Magnitude: -0.74
Also known as Alpha Carinae, Canopus is the brightest star in the constellation of Carina. Under normal conditions, this A-type main sequence star is clearly visible throughout the year in the southern hemisphere, especially during the summer. It was once estimated that the distance of this star is about 100 to 1200 light years from the Earth, but was later corrected to its current value.
If the earlier estimation were correct, then it certainly would have been the most luminous of all stars in the Milky Way galaxy. Not only that the Canopus is currently the brightest of all stars at that distance from the Earth, it remained so for the past few million years. Do you know that the Mount Canopus located in Antarctica is named after this star?
Image Courtesy: NASA, ESA, H. Bond (STScI)
Distance: 8.6 light years
Apparent magnitude: -1.47
After the Sun, Sirius is the second brightest star in the night sky, when observed from the Earth. Since the historic times, Sirius was believed to be a single star, but it’s now proven to be a binary star system, consisting of Sirius A, a white main sequence star and Sirius B, a white dwarf.
Sirius A is about 25 times more luminous than the Sun and twice as massive. It’s been estimated that over the period of the next 60,000 years, Sirius will slowly move closer to the earth (solar system), which will slightly increase its brightness furthermore.
This star also has a strong historic relevance as the ancient Greeks feared Sirius and believed that it brings hot summer times as a punishment for humanity. While Egyptians worshiped Sirius as the goddess of fertility.