This summer, countless eyes will be focused on the constellation Corona Borealis for a rare nova that is expected to appear there before September and will be visible to the naked eye in the northern hemisphere night sky.

Once in a lifetime

CNN reported on the 11th, citing NASA, that this nova, which has attracted much attention from astronomers and astronomy enthusiasts, will appear in the binary star system T Coronae Borealis, about 3,000 light-years from Earth in the constellation Corona Borealis. A nova refers to an astronomical phenomenon in which a white dwarf suddenly brightens when it explodes and is thus regarded as a newly formed star.

The Corona Borealis binary system consists of a white dwarf and a red giant. The white dwarf is the size of the Earth and has a mass similar to that of the Sun. Its gravity continuously attracts hydrogen from the red giant, accumulating it on its surface, accumulating pressure and heat, and eventually causing a thermonuclear explosion, bursting out with dazzling light. White dwarfs are stars at the end of their evolution, usually very dim and difficult to detect, but their brightness surges during an explosion.

Scientists have discovered that T. Borealis is a recurrent nova that explodes multiple times, once every 80 years on average. Rebecca Hounsell, a nova research expert at NASA's Goddard Space Flight Center, said that the explosion of T. Borealis will be an astronomical event that can only be seen "once in a lifetime."

Haunsel said that although some recurrent nova explosions have very short cycles, it is rare for a person to see the same nova explosion twice in his lifetime, especially this kind of nova explosion that is relatively close to the Earth. This is equivalent to watching a nova explosion "in the front row," which is "incredibly exciting."

Visible to the naked eye

The earliest recorded observation of T nova in Coronae Borealis was in the autumn of 1217, when a European man recorded "a dim star that became very bright for a period of time."

The last time humans saw this nova from Earth was in 1946. NASA said the nova's behavior over the past 10 years has been strikingly similar to that of the same period before the 1946 outburst.

William J. Cook, head of NASA's Meteoroid Environment Office, said that most nova explosions occur suddenly without warning, but T. Borealis is one of the 10 known recurring novae in the Milky Way. "From the 1946 explosion, we know that the white dwarf in T. Borealis will become dim for more than a year and then brighten rapidly." The star began to dim in March last year, so some researchers have inferred that it may explode again between now and September this year.

Once the nova Coronae Borealis explodes, it will be visible to the naked eye from the Earth's northern hemisphere, but it will not be visible for more than a week, after which it will gradually dim and disappear.

Is it possible that T. Borealis will fail to explode? Goddard Spaceflight Center astrophysicist Atsuji Mukai said that the time of the next explosion of a re-nova cannot be 100% certain. "When you think they can't follow a certain pattern, they run (according to the pattern); and when you start to expect them to repeat the same pattern, they completely deviate. What will the situation of T. Borealis be like? Let's wait and see."