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THE SOLAR INTERSTELLAR NEIGHBOURHOOD

The stars (including the Sun) with their planets located within the vicinity of our Sun, make up the Solar Interstellar Neighbourhood.  It is a collection of around 80 star systems, consisting of about 100 stars.  Some of the more well known stars in this group include, Alpha Centauri (the nearest star system), Sirius (the brightest star in the night sky), and TRAPPIST-1.


It is now known that other stars have planets orbiting them, just as the Sun does.  Planets outside our Solar System, are referred to as exoplanets.  There are in fact over 1,000 known exoplanets in the Milky Way, but there are likely millions or billions existing in our galaxy, with countless others throughout the Universe.

 

Alpha Centauri

The Alpha Centauri star system, actually consists of three stars.  In fact, most stars we see in the night sky are either double, or triple star systems.  It consists of Alpha Centauri A (known also as Rigil Kentaurus, Alpha Centauri B, and Alpha Centauri C (known also as Proxima Centauri).  Proxima Centauri is thought to be gravitationally bound to the Alpha Centauri system and is the nearest individual star to our Sun.

Alpha Centauri A and Alpha Centauri B.  The distance between these two stars varies, being as little as the Sun to Saturn distance, to as great as the Sun to Pluto distance.


Image credit: Hubble Space Telescope, ESA/NASA.

 
Alpha Centauri Facts

Alpha Centauri A (Rigil Kentaurus)


Diameter: 1,700,000 kilometres (1 million, 700 thousand kilometres), or 1,060,000 miles (1 million, and 60 thousand miles)

Surface temperature: 5,500 degrees Celsius or, 9,960 degrees Fahrenheit

Distance from the Sun: 41,343,392,000,000 kilometres (41 trillion, 343 billion, 392 million kilometres), or 25,689,593,000,000 miles (25 trillion, 689 billion, 593 million miles)

Distance from Alpha Centauri B: Varies between about 1,680,000,000 kilometres (1 billion, 680 million kilometres), or 1,044,000,000 miles (1 billion, and 44 million miles), and 5,330,000,000 kilometres (5 billion, 330 million kilometres), or 3,312,000,000 miles (3 billion, 312 million miles)

Orbital period with Alpha Centauri B: 79.91 Earth years

Rotation period: 22 Earth days

Planets: Nil known at present



Alpha Centauri B


Diameter: 1,200,000 kilometres (1 million, 200 thousand kilometres), or 748,000 miles (748 thousand miles)

Surface temperature: 5,000 degrees Celsius, or 9,000 Fahrenheit

Distance from the Sun: 41,343,392,000,000 kilometres (41 trillion, 343 billion, 392 million kilometres), or 25,689,593,000,000 miles (25 trillion, 689 billion, 593 million miles)

Rotation period: 41 days

Planets: None confirmed at present



Alpha Centauri C (Proxima Centauri)


Diameter: 196,000 kilometres (196 thousand kilometres), or 122,000 miles (122 thousand miles)

Surface temperature: 2,770 degrees Celsius, or 5,015 degrees Fahrenheit

Distance from the Sun: 40,170,262,000,000 kilometres (40 trillion, 170 billion, 262 million kilometres), or 24,960,643,000,000 miles (24 trillion, 960 billion, 643 million miles)

Distance from Alpha Centauri AB: 1,986,753,000,000 kilometres (1 trillion, 986 billion, 753 million kilometres), or 1,234,511,000,000 miles (1 trillion, 234 billion, 511 million miles)

Orbital period around Alpha Centauri AB: Possibly 500,000 years (500 thousand years) or more

Rotation period: 82.6 Earth days

Planets: Proxima Centauri b [orbital period (year) = 11.186 Earth days; distance from Proxima Centauri = 7,500,000 kilometres (7 million, 500 thousand kilometres), or 4,660,000 miles (4 million, 660 thousand miles)]

 
Sirius

Sirius is a double-star system, made up of Sirius A and its smaller companion, Sirius B.  The stars are sometimes also referred to as Alpha Canis Majoris A and Alpha Canis Majoris B.

Sirius A is the larger and brighter of the star system, with Sirius B being the smaller companion star.  Sirius B, is about the same diameter as planet Earth, but its mass is about the same as the Sun.


Image credit: Hubble Space Telescope, ESA/NASA.

 
Sirius Facts

Sirius A


Diameter: 2,381,000 kilometres (2 million, 381 thousand kilometres), or 1,479,000 miles (1 million, 479 thousand miles)

Surface temperature: 9,660 degrees Celsius, or 17,400 degrees Fahrenheit

Distance from the Sun: 81,362,000,000,000 kilometres (81 trillion, 362 billion kilometres), or 50,556,000,000,000 miles (50 trillion, 556 billion miles)

Planets: None confirmed


Sirius B


Diameter: 11,690 kilometres, or 7,260 miles

Surface temperature: 24,930 degrees Celsius, or 44,900 Fahrenheit

Distance from the Sun: 81,362,000,000,000 kilometres (81 trillion, 362 billion kilometres), or 50,556,000,000,000 miles (50 trillion, 556 billion miles)

Distance from Sirius A: Varies between 1,226,700,000 kilometres (1 billion, 226 million, 700 thousand kilometres), or 762,240,000 miles (762 million, 240 thousand miles) and 4,712,330,000 kilometres (4 billion, 712 million, 330 thousand kilometres), or 2,928,100,000 miles (2 billion, 928 million, 100 thousand miles)

Orbital period around Sirius A: 50 Earth years

 
TRAPPIST-1
TRAPPIST-1 is an ultra-cool dwarf star, which is only slightly larger than the planet Jupiter.  Surprisingly, despite its small size, it has 7 known terrestrial planets orbiting it.
TRAPPIST-1 Facts

Diameter: 158,600 kilometres (158 thousand, 600 kilometres), or 98,560 miles (98 thousand, 560 miles)

Surface temperature: 2,280 degrees Celsius, or 4,130 degrees Fahrenheit

Distance from the Sun: 373,699,000,000,000 kilometres (373 trillion, 699 billion kilometres), or 232,206,000,000,000 miles (232 trillion, 206 billion miles)

Rotation period: 3.3 Earth days

Planets: 7 in total, namely TRAPPIST-1b, TRAPPIST-1c, TRAPPIST-1d, TRAPPIST-1e, TRAPPIST-1f, TRAPPIST-1g, TRAPPIST-1h

Artists impression of the TRAPPIST-1 system compared with the inner planets of our Solar System.


Image credit: NASA/JPL-Caltech.