Betelgeuse has found a companion — and now it is unclear when it will explode

Astronomers have for the first time obtained a direct image of a companion star that was considered a legend for almost two hundred years. The discovery changes predictions for the explosion of one of the most famous red supergiants in the night sky.

A star that has been followed for thousands of years class=»notranslate»>__GTAG8__

Betelgeuse is perhaps the most recognizable star of Orion: a massive red supergiant that flares up and dims, and in addition is a candidate for an imminent (by cosmic standards) supernova explosion. People have been watching it for centuries — images are even found in prehistoric drawings. But one detail could only be clarified now.

A team of astronomers led by Miguel Montarges from the Paris-based Laboratory of Instruments and Research in Astrophysics used the European Southern Observatory's Very Large Telescope in Chile to directly photograph a companion star orbiting with Betelgeuse for the first time. The results were published in the journal Astronomy & Astrophysics.

A giant with a giant

Betelgeuse itself is about 16.5–19 times more massive than the Sun, and its radius is 750–850 times greater than the solar radius — if we put it in the place of our star, the surface of the star would reach the orbit of Jupiter. It shines 100,000 times brighter than the Sun.

The discovered satellite is also not a dwarf: its mass is 2.6–3.1 times that of the Sun, its diameter is almost twice as large, and its luminosity is 92 times that of the Sun. The pair are 500 to 600 light-years from Earth and orbit each other at a distance comparable to Saturn's orbit around the Sun—about 8.8 times farther than Earth is from the Sun.

Suspected for a long time, only now proven

The hypothesis of a companion star has been discussed for about a century, and in recent years indirect evidence has appeared. But it was the new work that became the first unambiguous evidence: Betelgeuse really has a neighbor, and it was possible to “see” him directly, and not calculate him by indirect signs.

According to Montarges, this logically fits into the overall picture: massive stars are almost never born alone, but form in pairs or more complex systems.

By the way, Betelgeuse’s variable brightness was previously associated not with a companion, but with a cloud of matter that the star ejects into space from time to time — it cools, turns into dust and obscures part of the light.

The main question: when the explosion

Betelgeuse is a literal supergiant sprinter: it is only about 10 million years old, while the Sun is 4.5 billion with an expected life of 10 billion. The star is believed to be in its final stages before exploding into a supernova.

Previously, while Betelgeuse was thought to be single, estimates pointed to an explosion somewhere between 10 thousand and 100 thousand years. Now these calculations have to be revised. Montarges directly admits that the presence of a companion capable of interacting with the star makes the forecast much less certain — the interaction of two bodies can either accelerate or delay the end. It is now impossible to unambiguously predict the moment of the outbreak.

For terrestrial observers, however, there is no reason for alarm: even with an explosion in the coming millennia, a distance of hundreds of light years excludes any danger — the event will remain an exclusively spectacular astronomical phenomenon.

Sources:

1. Reuters — original news about the discovery
2. Astronomy & Astrophysics — scientific publication of the study
3. European Southern Observatory (eso.org) — data on the Very Large Telescope and observations of Betelgeuse

Xrust Betelgeuse found a companion — and now it’s unclear when it will explode