Why Do Periodic Extinctions on Earth Occur Every 25 Million Years?

Why Do Periodic Extinctions on Earth Occur Every 25 Million Years?

Possible Source Of Periodic Extinctions Over The Past 250 Million Years


  1. Fossil records show that periodic mass extinctions occurred on Earth every 26M(million) years, which could be caused by a large orbiting celestial body.
  2. This body could be located in a region where the influence of other stars would be insignificant allowing the body’s orbit to be stable, with a periodicity of 26M Years.
  3. The celestial body could enter our Solar System and perturb the orbits of small and large asteroids from the Asteroid Belt and other regions, allowing some of these displaced asteroids to enter the Earth’s orbit, causing impacts and mass extinctions.


It is well known that many periodic extinctions have occurred on Earth over the past 250M years. The extinction rates at these events have been extracted from the fossil records and reported in many journals.

An example of these events is shown below in Figure A. Notice that the timing of these extinctions is highly periodic, they occurred roughly every 26M years. Also the time span shown in Figure A is 250 million years, which is about one galactic year, the time taken by the Milky Way Galaxy to orbit once around its center.

Screen Shot 2017-05-18 at 5.09.21 PM

As Fig A shows, one well known extinction occurred about 64M years ago when the dinosaurs and other large animals, which had survived for millions of years, died off.

The location of that catastrophic event has been traced to a large asteroid that hit the Earth near Chicxzulub in Yucatan, Mexico.

From the intense amount of iridium found in the soil in the region, it was determined that the event was from an extraterrestrial source.

There has also been two more large die-offs since then, at 38M and 12M years ago.

There were two earlier mass extinctions earlier than the chart period, that occurred with the same periodicity.

-The End Ordovician, which occurred about 440M years ago.

-Then the Late Devonian which occurred around 350M years ago, when up to 90           percent of all species were eradicated in a slow moving extinction.

Possible Reason for Periodic Extinctions

These highly periodic events could be caused by a large celestial body with an extended orbit around our Sun that enters our Solar System every 26M years. It could cause displacements of asteriods and other space debris from the Asteroid Belt, Kuyper Belt and Oort Cloud, in our Solar System.

Some of these displaced objects, large or small, pulled out of their normal orbits by the passing celestial body then struck the Earth, as it orbited around the Sun at 64,000miles/hour.

The size and numbers of displaced asteroids from such an event could vary. This variation could have produced a different intensity of impacts on Earth at different cycles.

For example, during older extinction periods at 195M, 169M and 116M shown in Fig A, the larger asteroids displaced out of their normal Solar orbit during these times, simply missed the Earth’s orbit, so no significant impact and resulting die-off occurred.

And during the large extinctions that occurred at 247M, 64M and 38M, there were possibly a large number of displaced asteroids that impacted Earth.

Extending this possibility into the future, we could expect the next possible extinction event to occur in 14M years.

Analytical Review of Orbit
There is an equation that relates the time of an orbit, which can be used to compute the semi-major axis for an interstellar object orbiting our Solar System every 26M years.

T = 2πSqrt(A3/G*M)

Where: T is the orbit time in years.

A is the semi-major axis of the periodic orbit.

G is the universal gravitational constant.

M is the mass of the Our Solar system.
However, if the distance of the proposed celestial orbit extends out too many light-years from Earth, then other stars could perturb its orbit and it would not be so periodic.  But if it’s a few light-years, then the orbit periodicity could persist and support this theory.

Screen Shot 2017-05-18 at 5.09.48 PM

Results of Analysis

The equation above applied to our Solar System calculates a semi-axis distance of the proposed celestial object’s orbit of 1.3 light years. Thus the proposed celestial object would travel a maximum distance of 2.6 light years from our Solar System.

Since the complete orbit length is 4 times the semi-axis distance, the object’s complete orbit distance would be 5.2 light years. And since this orbit would take 26M years to complete, the object’s velocity would be about 2 miles/second.

In the Milky Way Galaxy this is about 10% of the average relative velocity of stars in the region of our Sun, which is about 15-25miles/second.

Further Investigation

Now with the orbit distance calculated, the next point to review is how much interstellar space is available in our Galaxy, for the orbit to be stable and uninfluenced by other nearby Star Systems.

That will depend on their location and mass. For example, the closest Suns to our Solar System are Alpha Centauri A and B, which are 4.4 light years distance with a combined stellar mass of 2.1Sols (Our Sun’s mass). Sirius A and B are about the same distance, with a combined mass of 3Sols.

Obviously if the orbit of our notional celestial object was directly aligned with either of these star systems, their gravitational attraction would exceed that of our Solar system and the celestial object’s orbit would be destroyed.

But what if there is enough space available at other angles in the Galactic plane? To address that question, a chart of the locations of nearby stars and their locations in the galactic plane is shown in Figure C.

Screen Shot 2017-05-18 at 5.10.01 PM

The data is based on a chart from NASA Inst. for Advanced Concepts. Nearby stars and their locations are plotted on the chart, including their Equivalent Solar Mass in Sols. Now we can more clearly observe the strongest gravitational sources, Sirius A&B with a combined solar mass of 3 Sols and Alpha Centauri A&B with combined mass of 2.1 Sols.

Review of the vertical region of the chart above reveals that there is a clear space of almost 8 light years where no stars are present. There is a range of possible stable orbits of the notional object in this region, as shown in red above.

This 45 degree band could allow a large celestial object to orbit our Sun without any significant influence from other stars in the surrounding 8 light-year area.


-Fossil records show that periodic extinctions occurred on Earth every 26M years or so.

-This could be caused by a large orbiting celestial body with a semi-axis of 1.3 light years.

-This body would have an orbital distance of 2.6 light years and could located be in a region where the influence of other stars would be insignificant.

-The body’s orbit could be stable with a periodicity of 26M Years.

-The large body could enter our Solar System and perturb the orbits of small and large asteroids from the Asteroid Belt, Kuyper Belt, Oort Cloud and other regions.

-Some of these displaced asteroids could enter the Earth’s orbit and be struck at speeds in excess of 64,000mph.

-Depending on the size and number of the asteroids displaced and then entering Earth orbit, the extinction rate and its time span could vary greatly.

-The magnitude of the impacts could be massive, as occurred 12M, 38M, 64M and 247M years ago.

-The impacts could be smaller and extended over more time when the displaced asteroids were more widespread across the Solar System, as occurred 90M, 142M and 221M years ago.

-There may have been little or no impacts that occurred 116M, 169M and 195M years ago.

Alex Nicolson

Nearest stars to our Sun: http://www.johnstonsarchive.net/astro/nearstar.html



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