Local Interstellar Cloud

Structure

The Solar System is located within a structure called the Local Bubble, a low-density region of the galactic interstellar medium. Within this region is the Local Interstellar Cloud (LIC), an area of slightly higher hydrogen density. It is estimated that the Solar System entered the LIC within the past 10,000 years. It is uncertain whether the Sun is still inside of the LIC or has already entered a transition zone between the LIC and the G cloud. A recent analysis estimates the Sun will completely exit the LIC in no more than 1,900 years.

The cloud has a temperature of about 7,000 K (7,000 °C; 12,000 °F), about the same temperature as the surface of the Sun. However, its specific heat capacity is very low because it is not very dense, with 0.3 atoms per cubic centimetre (5/cu in). This is less dense than the average for the interstellar medium in the Milky Way (0.5/cm³ or 8/cu in), though six times denser than the gas in the hot, low-density Local Bubble (0.05/cm³ or 0.8/cu in) which surrounds the local cloud. In comparison, Earth's atmosphere at the edge of space (i.e. 100 km above sea level) has around 1.2×10¹³ molecules per cubic centimeter, dropping to around 50 million (5.0×10⁷) at 450 km (280 mi).

The cloud is flowing outwards from the Scorpius–Centaurus association, a stellar association that is a star-forming region, roughly perpendicular to the Sun's own direction.

In 2019, researchers found interstellar iron-60 (⁶⁰Fe) in Antarctica, which they relate to the Local Interstellar Cloud.