Nearest Star To Earth | Proxima Centauri B
Nearest Star To Earth
The star closest to our Earth is our Sun, but after the Sun the nearest star that is visible to us from our Earth is called Proxima Centauri.
Proxima Centauri is the closest star to the Solar System. This is represented by its parallax angle, measured by the Gaia satellite, equal to 0.768 thousandths of an arc second. To clarify, that’s a small angle: about 4.7 mils of that size, or rather smaller, only takes 1 degree to make an angle. However, this is the largest parallax angle described by any star as visible from Earth.
This gives us a distance of “only” 1.301 parsecs, or 4.244 light years, which is over 40,000 billion kilometers. This is about 270,000 times the distance between the Earth and the Sun, but, in astronomical terms, it is much smaller: hence it is called Proxima, a Latin name meaning next, which is visible to all stars (except the Sun). is closest in.
The small red dwarf, which belongs to the spectral class M5.5, is the third and dumbest member of Alpha Centauri’s triple system. It orbits the system’s two main stars, which are similar in characteristics to the Sun, describing a very long ellipsoid that spans approximately 547,000 years. It is currently located approximately at apostor of its orbit, that is, close to the point of maximum distance from the center of gravity of the system, where its distance from the two central stars will reach 13,000 astronomical units.
As a red dwarf, Proxima is much smaller and less luminous than the Sun. The mass and radius are 12% and 15% of their respective solar values, respectively. The effective temperature is about 3,000 K. The bolometric luminosity (that is, the total radiation emitted) is only 0.15% of the solar luminosity, which is equivalent to an energy of 5.8 × 10²³ watts. But the radiation emitted by Proxima is shifted towards the red end of the spectrum relative to the Sun. It follows that, in visible light, the luminosity of the red dwarf is even lower, resulting in only 0.005% of the solar luminosity.
However, in one thing, Proxima outshines our star: in old age. Its age is estimated at 4.8 billion years, which is about 200 million years older than the Sun. But red dwarfs consume their atomic hydrogen reserves at a much lower rate, so its life (i.e. living on the so-called main sequence) has just begun, so to speak, while the Sun is already a middle-aged man.
Proxima Centauri B
Because of its proximity, Proxima Centauri has long been the target of choice for exoplanet discovery. Unfortunately the photometric observations did not give the desired results. No planet appears to be passing in front of the red dwarf disk.
On the other hand, research using the radial velocity method has yielded very interesting results. In 2016 the discovery of Proxima b was announced, a planet of Earth-like mass in close orbit around the star, precisely identified through the oscillations of Proxima’s radial velocity.
The effective mass of Proxima b is unknown, as we do not know the inclination of its orbit with respect to our observation point. However, we know that its minimum mass is equal to 1.27 land masses. Statistical analysis also indicates that there is a 90% chance that the actual mass of the planet is less than 3 Earth masses. The radius of Proxima b is also unknown, as the planet does not pass in front of the stellar disk.
Obviously we don’t know if Proxima b actually has liquid water. Not knowing the planet’s radius, we also currently do not know whether it is a rocky planet with a solid surface like Earth or a Neptunian-type planet covered with a dense atmosphere rich in hydrogen and helium. What we do know is that Proxima b receives radiation of 877 ± 44 W/m² from the red dwarf, which is equivalent to 64% of the radiation energy the Sun puts out on Earth at the top of the atmosphere.
[Nearest Star To Earth | Proxima Centauri B]