Sixty years ago today, on November 3, 1957, the U.S.S.R. launched the second artificial satellite of Earth, commonly known today as Sputnik 2. Coming barely a month after Sputnik 1, the new Soviet space coup was almost as sensational as the first, because this time the satellite had a live animal on board.

In the decades since, the story of Laika the dog has been retold countless times in books, articles and popular documentaries, and has become imprinted in our collective memory. But due to a combination of Soviet secrecy, the complexity of spaceflight, and the proliferation of stories both true and untrue on the Internet, there are still a number of myths surrounding this pioneering space shot.

Perhaps the most debated and misunderstood aspect of the story is Laika’s fate after her launch into orbit. Initial reports in the Western press, based on Soviet announcements, suggested that Laika remained alive in space as late as November 7, or four days after launch. Some early stories even claimed that she would parachute back to Earth. On November 8, however, the daily Soviet communiqués about the mission stopped mentioning the dog, and it quickly became clear that Laika had embarked on a one-way trip.

For many years after, vague reports in the official Soviet press left the world under the impression that Laika had survived in orbit for as long as a week, during which time the ship’s batteries kept her life-support system running. There were suggestions that the dog had been put to sleep or poisoned with her last meal at the end of the mission. Even today, some veterans of the launch still claim that Laika was expected to live in orbit from eight to 10 days—obviously an impossibility, since Sputnik’s batteries were only built to last between five and seven days.

It wasn’t until 2002, or 45 years after the flight, that a report from the Institute of Biological Problems of Spaceflight revealed that problems with the thermal control system on Sputnik 2 led to a severe overheating of Laika’s cabin that ended her life after just a few hours in orbit.

In 2011, the Russian government added more detail to the story when it published a previously top-secret letter signed by top industry officials, including the de-facto founder of the Soviet space program, Sergei Korolev. Dated November 10, 1957, or just a week after the launch, document number SK-3/2468 was delivered to the Central Committee of the Communist Party, which essentially meant the top brass of the Soviet leadership, including Nikita Khrushchev.

According to the letter, preliminary processing of the telemetry from Sputnik 2 revealed that:

The condition of the animal (dog) at the beginning of the flight was satisfactory. During the first three orbits [approximately four and a half hours], the breath and heartbeat were normal. During the third orbit, the movements of the animal were registered. During that orbit, a considerable increase in temperature inside the cabin was registered (up to 43 degrees celsius). On the second day, (15th, 16th and the 17th orbit) sensors (measuring) blood pressure, heartbeat and breathing were showing no data. The electro-cardio sensor had been functioning, and based on its data it was established that the dog was alive. As of 5 a.m. (Moscow Time) on November 6, based on received information, no heartbeat, pressure or movement of the animal had been registered…

This document can probably be considered a final verdict on the fate of Laika, unless more detailed information surfaces in the future. Unfortunately, new details might not be forthcoming, because the project’s veterans long ago admitted that they themselves received very limited data from the satellite. As it turns out, the rocket carrying Sputnik 2 experienced a later-than-expected engine cutoff, resulting in a higher-than-planned orbit. That threw off the timing of data transmissions to Soviet tracking stations on the ground, so that Soviet scientists received only fragmentary information about Laika’s condition.

To make things worse, the satellite’s initial orbit was mostly, if not entirely, in sunlight, which likely overwhelmed the rudimentary climate control system inside the dog’s cabin.

Taken together, and in the absence of other vital signs from Laika, these facts put in doubt the claim in the November 10 official letter to the government about electro-cardio activity on the second day of the flight.

The batteries on Sputnik 2 ultimately gave out after six days in orbit, and the satellite stopped transmitting data on November 10. With all its systems dead, the spacecraft continued circling the Earth until April 14, 1958, when it reentered the atmosphere and burned up.