
A detail showing how Sirius, which rises on Jun 25, i.e. is seen above the horizon, marks the start of the Nile River flood, and was in ancient times believed to "kindle the vapor of the sun" (Pliny, 77AD), a theory which therein connects Sirius to the rebirth of the sun.

A detail showing how Sirius, which rises on Jun 25, i.e. is seen above the horizon, marks the start of the Nile River flood, and was in ancient times believed to "kindle the vapor of the sun" (Pliny, 77AD), a theory which therein connects Sirius to the rebirth of the sun.

In astronomy, Sirius, aka “dog star” or “Stella Maris”, called Sothis (Ѻ), by the Egyptians, personified by the goddess Septet and or Isis, depending, in astro-theology, is the []

Cycle
The star Sirius disappears annually for a period of 70-days, which is the number of days the Egyptians used to do the mummification process. [2]

The helical rising of Sirius, after its disappearance for 70-days, marks the start of the annual 150-day Nile River flood.

Sirius, which has a magnitude of -1.5 and is 8.6 light years from earth, rises about one hour after Orion. [3]

Sirius B
In 1844, it was predicted, on dynamical grounds, that Sirius A has a twin star named Sirius B (which is invisible to the naked eye); it was first observed via telescope 1862 by Alvin Clark. (Ѻ)

In 1950, French Africanist scholars Marcel Griaule and Germaine Dieterlen, in their “A Sudanese System of Sirius”, outlined the finding or assertion that the Dogan tribe, of Mali, West Africa, have ceremony called the “Sigui” enacted every sixty years, wherein priests put on masks and perform a complex dance, which they state is based on the apparent motion of the Sirius. The Dogan, according to the interpretations of these scholars, asserted that Sirius was a binary or even a tertiary (Ѻ) star. [4]

In 1976, Robert Temple, in his the Sirius Mystery, based on the findings of Griaule and Dieterlen, asserted the that the Dogon people, of Mali, West Africa, knew that Sirius was a binary star (Sirius A and Sirius B). Here, if Temple's hypothesis were true, we would note that Osiris has to be raised in the presence of not only Sirius (or Sirius A), aka Isis (or Stella Maris), but also by its twin star Sirius B, aka Nephthys (Maris’ sister): [5]

The so-called Temple hypothesis, namely that Egyptians knew about Sirius B, accordingly, while curious, seems doubtful. (Ѻ) All of the conjectural extrapolations that the Dogon knew about the big bang, the spiral nature of the Milky-way, the binary star Sirius, etc. (Ѻ) , is but modern scholars non-objectively “reading into” old texts so to cater to their own preconceived beliefs and ideas, similar to the way modern Islam apologeticists read modern science into obscure passages of the Quran, or the way, to mock the former, Richard Carrier made a list of 22 scientific principles or “predictions” found in Lucretius poem.

In 1979, Robert Bauval, after reading Temple's The Sirius Mystery, began working on the connection between the pyramids, Sirius, and Osiris.

Quotes
The following are related quotes:

“Who is there that does not know that the vapor of the sun is kindled by the rising of the dog-star [Sirius]? The most powerful effects are felt on the earth from this star. "When it rises, the seas are troubled, the wines in our cellars ferment, and stagnant waters are set in motion. There is a wild beast, named by the Egyptians Oryx, which, when the star rises, is said to stand opposite to it, to look steadfastly at it, and then to sneeze, as if it were worshiping it. There is no doubt that dogs, during the whole of this period, are peculiarly disposed to become rabid.”
— Pliny the elder (77AD), “On the Rising of the Dog Star” [1]

References
1. Pliny (the Elder). (77AD). Natural History, Volume 1 (translators: John Bostock and H.T. Riley) (pg. 67). Henry G. Bohn, 1855.
2. Anon. (2016). “The Story of Osiris – Ancient Egyptian God Documentary” (Ѻ), YouTube, Ancient World History, Dec 23.
3. Bauval, Robert. (1994). The Orion Mystery: Unlocking the Secrets of the Pyramids (rises one hour after Osiris, pg. 282). Three Rivers Press.
4. (a) Griaule, Marcel. and Dieterlen, Germaine. (1950). “A Sudanese System of Sirius” (“Un System Soudanais de Sirius”), Journal de la Societe des Africanists, 20:273-94.
(b) Bauval, Robert. (1994). The Orion Mystery: Unlocking the Secrets of the Pyramids (pg. 8). Three Rivers Press.
5. Scranton, Laird. (2006). The Science of the Dogon: Decoding the African Mystery Tradition (pg. 128). Inner Traditions.

External links
● Sirius – Wikipedia.