Extragalactic planet

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An extragalactic planet is an exoplanet whose (observed or suspected) location is outside the Milky Way . The name is also related to the place of origin .

Due to the great distance of extragalactic celestial bodies , extragalactic planets are very difficult to discover and verify with today's means .

Discovery Claims (Selection)

So far (as of February 2018) there has been no confirmed and secure discovery of individual planets by experts. Individual microlensing observations refer to one-off and non-repeatable events for which an extragalactic planet is only one possible (but not mandatory) interpretation of the data - even if this possibility has been most clearly highlighted as the most interesting in the popular scientific media. Individual such observations or other data collections, for which an extragalactic planet was a possible explanation, led to reports about the (possibly) first (possibly or allegedly actually) observed extragalactic planet in popular scientific media or in the general press.

Planet in the foreground of quasar Q0957 + 561

The quasar Q0957 + 561 is doubly visible due to a galaxy on the line of sight to it, which acts as a gravitational lens and is therefore also known as the twin quasar . In 1995, the astrophysicist Rudolph Schild , who works at the Harvard-Smithsonian Center for Astrophysics , published the observation of micro- lens events in the images of the quasar. For a certain event in image "A" he gave as a possible explanation the existence of objects (for example MACHOs ) with a total mass of 10 −5 solar masses (about 3 earth masses ) in the foreground galaxy acting as a gravitational lens. This led to speculation in the popular scientific media about the actual discovery of an extragalactic planet of 3 Earth masses, even if this was not claimed in the original publication.

Planets in the Andromeda Galaxy

In 2009, an international group of researchers published a study of how extragalactic planets can be identified using the microlens effect in the Andromeda Galaxy , the closest galactic neighbor of the Milky Way . A possible planet with a mass of 6–7 Jupiter was identified, the existence of which is compatible with data recorded in 2004.

HIP 13044 b

In November 2010, the European Southern Observatory (ESO) announced the discovery of an extragalactic planet with a minimum mass of 1.25 Jupiter's masses orbiting the star HIP 13044 . However, this star is actually located within the Milky Way (about 2000 light years away), it is only regarded as a member of the Helmi Current , a stellar current that is said to originate from a dwarf galaxy that was absorbed by the Milky Way 6 to 9 billion years ago . This means that only the presumed point of origin would lie outside the Milky Way, but not the observed place.

A new analysis of the radial velocity data published in January 2014 rejected the discovery. According to today's (April 2015) knowledge, it can be assumed that a planet with the dates of the discovery publication does not exist.

Planet population in a foreground galaxy of quasar RX J1131−1231

According to a study published in February 2018, observational data of the quasar RX J1131−1231 , which is about 6 billion light years away in the constellation Becher , suggests that a galaxy about 3.8 billion light years away between the solar system and this quasar has a large number of loners - may contain planets . This foreground galaxy creates four images of the quasar through the gravitational lensing effect . In 38 images of the Chandra X-ray telescope examined , characteristic changes in the iron K line of the quasar depicted were found due to the microlens effect . These can be explained by a population of solitary planets in the foreground galaxy. It is assumed that more than 2000 objects with masses between the Earth's moon and Jupiter per main sequence star or more than 200 objects between Mars and Jupiter per such star. Planets bound to stars should not contribute significantly to the observed effect, since their light is masked by their star. However, other scientists do not consider the conclusion to such lonely planets to be mandatory; for example, according to the Heidelberg astronomer Joachim Wambsganß , a population of stars and brown dwarfs could also produce the measurement results.

Individual evidence

  1. ↑ Designation in this sense used e.g. B. for the later unconfirmed exoplanet of HIP 13044 in: Jupiter from another galaxy. Max Planck Society, November 18, 2010, accessed April 26, 2015 . - Quote (italics added): "But thanks to the merging of this dwarf galaxy with our own Milky Way, we now have an extragalactic planet within range of our telescopes."
  2. ↑ Rudolph E. shield: microlensing variability of the lensed quasar Q0957 + 561 gravitionally A, B . In: Astrophysical Journal 464 . September 5, 1995, p. 125-130 , bibcode : 1996ApJ ... 464..125S .
  3. ↑ The Q0957 + 561 planet. Extrasolar Visions, October 23, 2004, archived from the original on March 30, 2012 ; Retrieved April 24, 2015 .
  4. ↑ G. Ingrosso, S. Calchi Novati, F. De Paolis, Ph. Jetzer, AA Nucita, AF Zakharov: Pixel-lensing as a way to detect extrasolar planets in M31 . In: Monthly Notices of the Royal Astronomical Society . tape 399 , no. 1 , October 1, 2009, p. 219-228 , doi : 10.1111 / j.1365-2966.2009.15184.x , arxiv : 0906.1050 .
  5. ↑ First extragalactic exoplanet may have been found. New Scientist, June 10, 2009, accessed April 24, 2015 .
  6. ↑ Calista Fischer: First planet found in the Andromeda galaxy? (PDF) (No longer available online.) University of Zurich - Faculty of Mathematics and Natural Sciences, June 25, 2009, archived from the original on June 11, 2015 ; Retrieved April 24, 2015 .
  7. ↑ A planet from a strange galaxy discovered. ESO Science News Release, November 18, 2010, accessed April 26, 2015 .
  8. ↑ Kerstin Holzheimer: Extragalactic planet discovered. Frankfurter Rundschau, November 19, 2010, accessed on April 26, 2015 .
  9. ^ John Matson: Extragalactic Expat: Newfound Exoplanet Likely Came from Another Galaxy. Scientific American, November 18, 2010, accessed April 24, 2015 .
  10. ↑ MI Jones, JS Jenkins: No evidence of the planet orbiting the extremely metal-poor extragalactic star HIP 13044 . In: Astronomy & Astrophysics . 562, January 2, 2014, p. A129. arxiv : 1401.0517 . bibcode : 2014A & A ... 562A.129J . doi : 10.1051 / 0004-6361 / 201322132 .
  11. ↑ Xinyu Dai, Eduardo Guerras: Probing Planets in Extragalactic Galaxies Using Quasar Microlensing . In: The Astrophysical Journal Letters . tape 853 , no. 2 , February 2, 2018, p. L27 , doi : 10.3847 / 2041-8213 / aaa5fb , arxiv : 1802.00049 .
  12. ↑ Thorsten Dambeck: Researchers find planets outside the Milky Way for the first time. Spiegel Online , February 6, 2018, accessed February 6, 2018 .