Early in the morning of April 21, 1910, astronomers at Harvard University sighted Halley’s comet making its return to Earth’s skies after nearly 75 years. Across New England in Redding, Conn., at his estate, Stormfield, Mark Twain faced the last day of his life.

He died later that day around sunset, seven months before his 75th birthday. The writer was born Samuel Langhorne Clemens, on Nov. 30, 1835, the same month the comet was seen above his Missouri home.

“It will be the greatest disappointment of my life if I don’t go out with Halley’s comet,” Twain said. “The Almighty has said, no doubt: ‘Now here are these two unaccountable freaks; they came in together, they must go out together.’ “

The comet did not disappoint the writer, but in his final years, his family and associates did. Suffering from painful angina and high blood pressure, the widower was buffeted by family scandal, slipshod financial dealings and the drowning of his daughter Jean, who had epilepsy, in a bathtub on Christmas Eve 1909.

Hailed for his humor and generous spirit in those classics “Tom Sawyer,” “Huckleberry Finn” and “The Prince and the Pauper” and his short stories, Twain’s writing had become bitter, sacrilegious and despairing in his old age.

Such works as “The Mysterious Stranger” branded life “a swindle” and “Letters From the Earth,” not published until 1962 because of its sexual nature, was full of anger and bitterness.

With his cottony white mop of hair, drooping mustache and white suit and shoes, Twain was the most well-known figure in the nation when he died, a man beloved for his infectious humor and puckish personality.

He adopted the pseudonym Mark Twain as a reporter early in his career. His image was widely recognized from his many product endorsements, his opinion was sought eagerly around the world and his books were read by millions.

Now, 100 hundred years later, biographers are divided on how the writer’s little-remembered troubles affected his work or perhaps hastened his death.

“Mark Twain was the highest-paid writer in the United States when he died,” said Laura Skandera Trombley, author of “Mark Twain’s Other Woman: The Hidden Story of His Final Years” ($27.95), “but his quality had dropped. The most interesting stuff wouldn’t see the light of day until after he was dead.”

Twain plunged into a frantic round of appearances and travels following the death of his wife, Olivia, in 1904. “He lost his anchor in Olivia,” said Trombley, president of Pitzer College in Claremont, Calif.

Twain was really having a good time, believes Michael Shelden, author of “Mark Twain: Man in White. The Grand Adventures of his Final Years” ($30).

“After his wife died, he became a boy again,” said Shelden, who teaches English at Indiana State University. “I got the feeling he was trying to be Tom or Huck, going where he wanted, doing what he wanted, and the press never stopped following him around.”

Twain’s longtime assistant, Isabel Lyons, and his business partner, Ralph Ashcroft, managed to acquire complete control of his finances in 1907. A vindictive Clara convinced her father to fire Lyons and Ashcroft and take control of his bank accounts.

The legal haggling was widely reported in New York newspapers, humiliating Twain, who was already facing another scandal: disclosure that Clara was involved with a married man.

There’s another aspect to Twain’s later years that raises eyebrows today — his fondness for little girls. He collected a group of them, ages 12 to early teens, calling them his “Angelfish.” Twain entertained them on his frequent trips to Bermuda and invited them with a parent to his Connecticut estate.

“There was never a hint of bad behavior,” said Shelden, who called the Angelfish “surrogate granddaughters.”