Super flare

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Coronal mass ejection from the Sun on August 31, 2012
Time-lapse video of the sun on the same day
(real duration approx. 26 hours)

A superflare (English flare : flickering, torch) is an eruption on a sun-like star , in which an energy of 10 33 to 10 38 ergs is released in one hour . Superflares are up to a million times as energetic as the largest solar flares observed to date.

Superflares also differ from normal flares, such as those that occur in UV Ceti stars , BY Draconis stars , FK Comae Berenices stars , RS Canum Venaticorum stars and interacting Algol stars , only in the amount of energy released .

Emergence

Solar flares and the normal flares in UV Ceti stars (also called flare stars) are a result of magnetic short circuits of the stellar field lines in the corona . The energy released in the process accelerates particles into the chromosphere below the corona, where they collide with the denser matter. The plasma in the chromosphere is heated and accelerated back into the corona at high speed. Flares can be detected in the range of X-ray , ultraviolet and radio radiation as well as in visible light.

Stars with superflares do not necessarily rotate faster than the sun, although in stellar physics this is usually a requirement for high chromospheric activity.

Stars with superflares, however, show a greater coverage of star spots than the sun. There is a relationship between the area covered by star spots and the energy released during the superflare; an equivalent relationship has also been observed on the sun between the area of ​​the sunspot and the bolometric luminosity of flares. This suggests that the magnetic energy emitted during superflares was stored in or around the star spots.

Stars with observed superflares seem to have a much stronger global magnetic field than the sun.

Rejected hypotheses

The assumption that superflares are caused by a short circuit of magnetic fields between a hot Jupiter and an active star has not been confirmed; Sun-like stars with superflares are not orbited by Hot Jupiters.

Observations of superflare stars with the Kepler Space Telescope have also disproved hypotheses that the strong magnetic activity on these stars is the result of a bound rotation between the star and a planet in which the magnetic fields of the two bodies interact.

Occurrence, effects and frequency

The following parameters of G stars with superflares do not differ significantly from those of the sun:

Therefore, superflares may also occur on the sun.

Superflares with energies of over 10 37  erg damage the ozone layer on earth-like planets in the habitable zone and can be the cause of mass extinction of land-based life. Superflares at the lower end of the energy scale with energies of 10 34  ergs occur every 800 years in sun-like stars with rotation periods of 10 days and eruptions of 10 35  ergs occur on average every 5000 years. These events can probably also occur on the sun and would seriously damage the on-board electronics of all satellites as well as the high-voltage electrical network .

Individual evidence

  1. ↑ Hiroyuki Maehara et al .: Superflares on solar-type stars . In: Nature . 2012, p. 478-481 , doi : 10.1038 / nature11063 .
  2. ^ Bradley E. Schaefer et al .: SUPERFLARES ON ORDINARY SOLAR-TYPE STARS . In: Astrophysics. Solar and Stellar Astrophysics . 1999, arxiv : astro-ph / 9909188 .
  3. ↑ Yuta Notsu et al .: Superflares on Solar-Type Stars Observed with Kepler II. Photometric Variability of Superflare-Generating Stars: A Signature of Stellar Rotation and Starspots . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1304.7361v1 .
  4. ↑ Eric P. Rubenstein, Bradley E. Schaefer: Are superflares on solar analogues caused by extra-solar planets? In: Astrophysics. Solar and Stellar Astrophysics . 1999, arxiv : astro-ph / 9909187 .
  5. ↑ Takuya Shibayama et al .: Superflares on Solar Type Stars Observed with Kepler I. Statistical Properties of Superflares . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1308.1480v1 .
  6. ↑ Daisaku Nogami, Yuta Notsu, Satoshi Honda, Hiroyuki Maehara, Shota Notsu, Takuya Shibayama, Kazunari Shibata: Two Sun-like Stars Superflare Rotating as slow as the Sun . In: Astrophysics. Solar and Stellar Astrophysics . 2014, arxiv : 1402.3772v1 .
  7. ↑ Maggie McKee: 'Superflares' erupts on some Sun-like stars . In: Nature . 2012, p. 468 , doi : 10.1038 / nature.2012.10653 .
  8. ↑ Kazunari Shibata et al .: Can Superflares Occur on Our Sun? In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1212.1361 .