Does the sun have an evil twin?
Nemesis is a hypothetical astronomical object, more precisely a red dwarf or brown dwarf star,
orbiting the Sun at a distance of (approximately) 50,000 to 100,000 astronomical units,
just beyond the Oort Cloud. The existence of this star was originally postulated as a
possible explanation of mass extinction cycles in Earth's history. In 1984 paleontologists
David Raup and Jack Sepkoski published an article claiming to have identified
a statistical periodicity in mass extinctions that have occurred over the past 250 million years,
using different forms of time series analysis. The two authors focused the extinction on the
intensity of fossil families of marine vertebrates, invertebrates and protozoa,
identifying 12 extinction events in the time period considered. The average time interval
between extinction events was estimated at 26 million years. To date, two of the extinction
events identified (Cretaceous-Tertiary and Late Eocene) could be related to
events of great impact. Although Raup and Sepkoski could not identify the causes of their
alleged periodicities, they assumed that these events may have a non-terrestrial connection.
The challenge of identifying a non-terrestrial mechanism has been faced by several astronomers.
Two teams of astronomers (Whitmire & Jackson and the Davis, Hut and Muller team) independently
published similar hypotheses in 1984 to explain the mass extinctions advanced by Raup and Sepkoski
in the journal Nature. One of these hypotheses proposes that the sun could have an undefined
companion star, in a very wide elliptical orbit, which would periodically disturb the Oort Cloud,
causing an increase in the number of comets traveling towards the center
of ours. Solar system with a consequent increase in any impacts on the Earth.
This hypothetical star takes the name of Nemesis or, as it was promptly renamed by the media,
Death Star ("Star of Death", the name of the Star Wars Death Star).
Granted the existence of such a star, the exact nature of Nemesis is still uncertain. Richard A.
Muller suggests that the object is most likely a red dwarf with a magnitude between 7 and 12;
while Daniel P. Whitmire and Albert A. Jackson argue that it is a brown dwarf. Previous studies
on solar-type stars showed that 84% of them are part of a binary system. Muller, who at the time
worked at the Leuschner Observatory telescope at the Lawrence Berkeley National Laboratory,
commissioned astrophysicist Saul Perlmutter to locate Nemesis, who in 1986 finished his
thesis "Astronomical research of a stellar companion of the Sun" without being able
to confirm its existence. The last major extinction event was (about) 5 million years ago,
so Muller estimates the distance of Nemesis from us at about 1-1 al, identifying the
position of the star in the portion of the sky occupied by the constellation Hydra:
idea based on a supposed orbit, derived from the observation of long atypical periods of comets
describing an orbital arc meeting the specifics of Muller's hypothesis. If Nemesis existed it could
be detected by next-generation astronomical telescopes and if it were a brown dwarf,
as proposed by Dr. Dan Whitmire and Albert A. Jackson IV, then the WISE mission (which
began on December 14, 2009) could easily find it. Matese and Whitman have suggested that the
hypothetical periodic extinction could be caused by the oscillation of the Solar System across the
plane of the Milky Way. These oscillations can lead to gravitational disturbances in
the Oort cloud with the same consequences proposed by the possible orbit of Nemesis.
However, the period of oscillation is not well observable and could differ from the 26 million
years (necessary for the theory) up to 40% more. From 2000 onwards, planetoids have been observed
(beyond Neptune's orbit), such as (148209) 2000 CR105, having a very pronounced elliptical orbit
and a high perihelion value such as to exclude the influence of Neptune on these planetoids. In
these cases, generally, the remote possibility of the passage of gas giants or stars in the extreme
periphery of the Solar System is invoked (in our case it could coincide with Nemesis). Nemesis has
also begun to influence literature: Isaac Aimov, a science fiction writer, has dedicated a book to
this star. There are some scientific inaccuracies (the catastrophes caused by the brown dwarf - or
red dwarf, we do not yet know - are exaggerated and the star is not described as a companion of
the sun) but, when we talk about Nemesis it is still an interesting topic. The name Nemesis
derives from that of the Greek goddess Nemesis. Nemesis (in ancient Greek: Nέμεσις, Némesis) is
a goddess of Greek mythology, according to some, daughter of Zeus, according to others daughter
of Ocean and Night and then possessed by Zeus himself in the temple of Ramnunte: she generates
an egg that is collected and delivered to Leda and from which Elena and the Dioscuri will come out.
Her name comes from the Greek νέμεσις (némesis), νέμω (némō, "to distribute"), from
the Indo-European root nem- in Greek mythology, and was the name of the goddess "Distribution
of Justice"; justice understood as a juridical code was instead attributed to the goddess Diche.
Nemesis was especially concerned with bringing justice to unresolved or
unpunished crimes, distributing and infusing joy or pain according to what was right, especially
persecuting the wicked and the ungrateful to fate. There is no corresponding goddess in the
Roman Religion who instead inherited the Diche hour as the goddess of jurisdiction, the current
Iustitia with the blindfold and the scales in her hand, however the Romans dedicated an altar
on the Capitol where the soldiers were to Nemesis. used to lay down a sword before leaving for war.
In Isaac Asimov’s science fiction novel “Nemesis”, Nemesis is a red dwarf discovered by chance by
Eugenia Insigna, an astronomer who lives on Rotor, one of the colonies founded by the Earth:
it is almost invisible and very close to the Sun (2.5 light years) on a collision course
with the solar system. The scientist immediately turns to a high exponent among the Rotorians,
Janus Pitt, who, however, orders her to remain silent on this incredible discovery: this is
because Pitt dreams of building a new civilization detached from his native planet destined to
conquer even the entire galaxy. Eugenia, albeit reluctant for her pride as an astronomer,
is therefore forced to silence her discovery from all of her, including her husband, Crile
Fisher. This does not prevent the astronomer from receiving the possibility of baptizing the newly
discovered star, which will be called Nemesis, a reference to the Greek goddess of justice.
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Researchers from the University of California (Berkeley) and Harvard University have shown
with a mathematical model that all stars would be born in binary or multiple systems, consequently
our Sun should also have had its twin. The scholars, coordinated by theoretical physicist
Steven Stahler and radio astronomer Sarah Sadavoy, who follows Hubble on behalf of NASA
at the prestigious Smithsonian Astrophysical Observatory, have practically dusted off the
theory of Nemesis, the 'bad' twin of the Sun which cyclically - every 27 millions of years - would
reappear at the edge of the solar system. The star is called in this unflattering way because,
according to some studies, many of which conducted in the late 1980s, due to the gravitational force
it would bring with it dangerous comets capable of targeting the planets of the Solar System,
including our Earth. Although there is no direct evidence, Nemesis would be responsible for the
mass extinctions observed on our planet, which occur with a disturbing periodic cycle. Non-avian
dinosaurs and other groups of animals, 64 million years ago, in the late Cretaceous, would be
extinct precisely because of an asteroid "carried" by Nemesis. But let's go back to the study that
gave new life to this suggestive theory. Scholars have determined the non-solitary birth of stars
thanks to the study of the molecular cloud of Perseus, considered a real cradle for stars in
formation. Through the VANDAM mission, several young class 0 stars (less than 500,000 years
old) and class 1 stars (less than a million years old) have been surveyed inside the cloud, which is
600 light years from us. Combining this data with other observations, the researchers identified 45
lone stars, 19 binary systems and 5 multiple systems. From the analysis of the distances,
positions and distribution of the stars, through a mathematical model, Sadavoy and colleagues came to
the conclusion that they all arose from binary or multiple systems. "Solar-type stars are not
primordial - underlined Professor Stahler - but they are the result of the rupture of binary
systems". According to estimates, the Sun's twin should currently be at a distance of three light
days, or about 500UA (astronomical units, the distance between the Earth and the Sun),
hidden somewhere in the heart of the Milky Way. Although it is defined twin, Nemesis could be
a weak brown dwarf, reduced in this situation by the Sun which, during the accretion phases,
would have stripped most of the dust and gas from it. Evidence of its existence, as specified,
has never been found, however some think it can be read in the curious orbit of the dwarf planet
Senda, influenced by the gravitational force of a mysterious celestial object.
Steven Stahler, an astronomer from the University of Berkeley, and Sarah Sadavoy, a colleague from
Harvard University, following a research carried out on a molecular cloud (a type of interstellar
cloud in which the density and temperature allow the formation of molecules of hydrogen starting
from single hydrogen atoms) in the constellation of Perseus have brought to light new elements
that would confirm the possible existence of Nemesis, the hypothesized twin star of our Sun.
The research was published in the scientific journal of the Royal Astronomical Society.
The research of the two astronomers was based on the study of data relating to the Perseus Cloud,
a huge cloud of gas and dust about 600 light years from Earth, collected between 2013 and 2015
through the Very Large Array, the grouping of radio telescopes located in New Mexico,
which made it possible to photograph the star formations within the cloud.
Stahler and Sadavoy, combining these data with those that emerged from another study referred to
the Gould’s Belt (a partial ring of stars that extends for about 3000 light years), through
mathematical models they carried out a real census of the single and double stars of Perseus,
ascertaining that there were fifty-five young stars of which forty-five are lone stars, nineteen
are binary systems and five are multiple ones. Research has focused on low-mass stars - such as
the Sun or smaller - to understand whether it is normal for two or more stars to be born together,
thus forming binary or multiple systems. Over the decades, in fact, astronomical observations have
shown that systems formed by two or more stars are very common, especially among stars of large mass.
For a long time, therefore, scholars have wondered if they were generated in this way or if they were
stars born separately and joined by gravitational attraction only later. Thanks to this research,
the two astronomers came to the conclusion that all stars of low mass, therefore similar to the
Sun, were born in binary or multiple systems from which they separated in 60 percent of
cases. It follows that it is highly probable, therefore, that our Sun was also born with at
least one twin star, the Nemesis star which has been hypothesized to exist for about thirty years
and which should be, according to some estimates, at about 500 AU. (Astronomical Units,
ie the Earth-Sun distance) from the Sun. Obviously this is only "circumstantial evidence" and further
studies on other clouds will be necessary to verify the real effectiveness of the mathematical
model, but in the meantime the suggestions on the twin of the Sun are come back to the fore.
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