Alpha Canum Venaticorum is a system of a big and a small white star. Generally only the brighter of the two, Alpha-2, is called Cor Caroli.

This star has a magnetic field several hundred times stronger than that of the Sun. Therefore is has got large spots which vary its luminosity for 0.1 magnitudes.

Constellation: Canes Venatici

Distance: 110 light-years

Space between Alpha-1 and Alpha-2 Canum Venaticorum: 675 AU

II (not the roman number 2) Pegasi is a very narrow double star of two orange-red stars. On star A in December 2005 a flare occured, 100 million times stronger than a regular solar flare. It was the most powerful flare seen so far with an intensity of an ordinary nova.

Due to the mutual tidal forces both stars spin very rapidly, about four times faster than the Sun. This probably benefited the enormous flare.

Constellation: Pegasus

Distance: 138 light-years

Spectral class: K0

Visual magnitude: 7.37

Luminosity A + B: 1.59 * Sun

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11/07/2006

The orange-red subgiant Hyadum I or Gamma Tauri is the brightest and most heavy star in the open star cluster of the Hyades. The approximately 350 stars of the cluster emerged all at the same time and move to the same direction.

Constellation: Taurus

Age: 650 million years

Distance: 150 light-years

Spectral class: K0

Visual magnitude: 3.65

Luminosity: 80 * Sun

Mass: 3 * Sun

Diameter: 12 * Sun

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HR 8210 or IK Pegasi is probably the most dangerous star in our stellar neighborhood. It is a narrow double made of a Delta Scuti star (A) and a very big white dwarf (B).

Their separation from each other is too big for an interchange of matter. But this will change as soon as the A-star starts to expand to become a red giant. Then it will nearly reach the orbit of the white dwarf and this will suck off the hull of the red one. Thereby the white dwarf will soon exceed the Chandrasekhar limit of 1.44 solar masses.

It is quite certain that HR 8210 will explode as a type Ia supernova some time in the future. Maybe in 10 000 years, but more likely in several million years. Hopefully it won't be too soon and hopefully then the star will be much further away. Because an Ia supernova in a distance of 150 light-years could cause some serious problems for life on Earth.

Constellation: Pegasus

Distance: 150 light-years

Radial velocity: -11.4 km/sec

Space between HR 8210 A and B: 0.41 AU

Orbit period of HR 8210 A and B: 21.7 days

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14/12/2006

This relatively young sunlike star rotates very fast, which gave it the nickname 'Speedy Mic'. On it for the first time the source of a flare was localized. The location of the flare, which was 100 times stronger than a large solar flare, surprisingly does not correspond to the star's spots.

Constellation: Microscopium

Distance: 150 light-years

Spectral class: K0V

Visual magnitude: 9.44

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12/21/2007

The white star as one of very few stars is perceived by some people as green. Others see it white. Zubeneschamali indeed glows strongest in green light, but the other spectral colors are also very strong. This results in the combination color white.

The star rotates about 100 times faster as our Sun.

Constellation: Libra

Distance: 160 light-years

Spectral class: B8

Visual magnitude: 2.7

Luminosity: 130 * Sun

Mass: 4 * Sun

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07/19/2006

Even in the best telescopes this object only appears as a dot. It is a very narrow system of four orange stars, with about half solar mass each. Stars can't form in such a small distance from each other. Probably they all evolved out of one gaseous disk, which forced the four stars in those narrow orbits.

Constellation: Aquarius

Age: 500 million years

Distance: 166 light-years

Space between BD 22°5866 A and B: 5.8 AU

Orbit period of BD 22°5866 A and B: 9 years

Space between BD 22°5866 A1 and A2: 0.06 AU

Orbit period of BD 22°5866 A1 and A2: 5 days

Space between 22°5866 B1 and B2: 0.26 AU

Orbit period of BD 22°5866 B1 and B2: 55 days

Spectral class: K5

Visual magnitude: 10.1

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01/17/2008

This double is either a pair of young (about 30 million years old) brown dwarfs or of older red dwarfs, with a mass of less than one tenth solar each. It has the nickname 'Hang-loose Binary', the catalogue numbers for the two objects are 2MASS J012655.49-502238.8 and 2MASS J012702.83-502321.1. It has the longest known orbit period of a double star. If two brown dwarfs, the very week binding probably will be disconnected some time in the future by the passing of another star.

Constellation: Phoenix

Distance: 200 light-years

Space between 2MASS J012655.49-502238.8 and 2MASS J012702.83-502321.1: 5100 AU

Orbit period of 2MASS J012655.49-502238.8 and 2MASS J012702.83-502321.1: 500 000 years

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04/19/2007

The red giant Gamma Com is the brightest star of the open cluster Melotte 111. This cluster, which is visible to the naked eye, probably gave the constellation its name, Berenice's Hair. The small stellar cluster contains only 37 stars, which are all bigger than the Sun and which all move to the same direction. Apparently the cluster has lost its smaller stars.

Constellation: Coma Berenices

Age: 450 million years

Distance: 288 light-years

Spectral class: K1

Visual magnitude: 4.3

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05/09/2008

The brighter, smaller star A of this very close double system is a white dwarf with a magnetic field 14 million times stronger than that of the Sun.

Its partner was 500 million years ago a red dwarf. Since then the white dwarf ceaselessly pulls matter from it and transformed it into a very strange object. It is neither star nor brown dwarf, but a new kind of cosmic objekt. Its surface temperature is merely 1700 kelvin.

Constellation: Eridanus

Distance: 300 light-years

Visual magnitude: 13.7

Orbit period of EF Eridanus A and B: 81 minutes

The blue star Alpha Arae, an emission star, is also known in Chinese as Tchou or Choo. It is one of the fastest rotating stars known, 50 times faster as our Sun. Its rotation speed is up to 470 km/s. Only a bit faster and it would be torn apart.

So the star is flattened at its poles. Around its equator is a large gas hull. From the poles a stellar wind with even up to 2000 km/s is ejected.

Constellation: Ara

Distance: 300 light-years

Spectral class: B2e

Visual magnitude: 2.84

Luminosity: 6000 * Sun

Mass: 10 * Sun

Diameter: 5 * Sun

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09/21/2006

This is a double of an orange star and a white dwarf. The white dwarfs rotates every 33 seconds and, like apulsar, emits X-rays at its magnetic poles. These are caused by incoming gas from the partner star. It is the first white dwarf, where such a behaviour was discovered.

Constellation: Aquarius

Distance: 332 light-years

Orbit period of AE Aquarii A and B: 0.412 days

Spectral class: K5

Visual magnitude: 11.5

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01/03/2008

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08/03/2006

The blue star HD 101065 was named after its discoverer, Antoni Przybylski. This star shows in its spectrum a very peculiar chemical composition. Commonly frequent metals like iron and nickel are scarce here, but a lot of rare metals like strontium, niobium, caesium, many lanthanoids and even uranium are highly overabundant. The reason for this is unknown. This star could either be a main sequence star or a subgiant.

Constellation: Centaurus

Distance: 410 light-years

Spectral class: B5p

Visual magnitude: 8.01

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04/11/2009

On this blue star Promethium can be found, a very rare and radioactive chemical element. This is known from no other star. This is astonishing, because even the most stable Promethium isotope has a half-life of only 17.7 years.

Therefore the Promethium must be continuously created anew by the star. How it does this is not known.

From its state of development GY Andromedae reminds of Alpha-2 Canum Venaticorum. The star is orbited by an invisible companion every 273 days.

Constellation: Andromeda

Distance: 455 light-years

Spectral class: B9pe

Visual magnitude: 6.27 - 6.41

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07/06/2006