Recent studies have increased the estimates for stars in the Milky Way galaxy and total numbers of galaxies in the visible universe and another study suggests that up to half of all the stars lie in between galaxies.
Combined they would suggest
at least 2 trillion galaxies
perhaps 500 billion stars in the Milky Way
And another 500 billion stars in between each galaxy
This would mean an estimate of at least 2 trillion trillion stars in the visible universe.
This is 2 Septillion stars (2 x 10 ^ 24)
1. The European Space Agency (ESA) released the first data from its €750 million Gaia star-mapping mission. The new catalog contains sky positions for 1.1 billion stars, 400 million of which have never been seen before. For many stars, the positional accuracy is 300 microarcseconds—the width of a human hair. Thus there are 400 million more stars in an area previously believed to have about 700 million stars.
2. An international team of astronomers, led by Christopher Conselice, Professor of Astrophysics at the University of Nottingham, have found that the universe contains at least two trillion galaxies, ten times more than previously thought.
Astronomers have long sought to determine how many galaxies there are in the observable universe, the part of the cosmos where light from distant objects has had time to reach us. Over the last 20 years scientists have used images from the Hubble Space Telescope to estimate that the universe we can see contains around 100 - 200 billion galaxies. Current astronomical technology allows us to study just 10% of these galaxies, and the remaining 90% will be only seen once bigger and better telescopes are developed.
3. As many as half of all stars in the universe lie in the vast gulfs of space between galaxies, an unexpected discovery made in a new study using NASA rockets. These stars could help solve mysteries regarding missing light and particles that theory had suggested should exist, scientists say. The stars were ejected from their birthplaces by galaxy collisions or mergers.
Some estimations suggest up to 100,000 times more rogue planets than stars in the Milky Way.