Galileo
By looking into space with the telescope.
Galileo Galilei . He only helped support the theory through his observations , he didn't invent the model, Copernicus did.
Galileo
Copernicus proposed the theory of a heliocentric model while Galileo improved the telescope, studied Jupiter's moons, and supported the heliocentric model
I believe you are confusing two things here; there is no such thing as a "heliocentric model of telescope". There is a heliocentric model of our Solar System, and there are telescopes. The two are unrelated.
By looking into space with the telescope.
heliocentric theory
the Earth revolves around the Sun, which challenged the geocentric model of the universe. His discoveries also supported the heliocentric model proposed by Copernicus. Galileo's observations with the telescope provided evidence for this idea.
They started seeing Venus through the telescope
Galileo's discoveries showed faults with the old Ptolemaic theory, which had the Sun at the centre. So he was right to publicise these but not to proclaim that the heliocentric theory of Copernicus was correct. Tycho produced a geocentric theory that explained the phenomena discovered by Galileo, which were (mainly) the full range of phases dislplayed by Venus. Eventually Johannes Kepler brought out a new heliocentric theory with novel elliptical orbits for the planets. It was later backed up by Newton's theoretical discoveries and by later measurements, and it is the model used and accepted today.
Galileo Galilei discovered phases in Venus -- pretty much proof of a heliocentric solar system -- in 1610 September.
None of it but Galileo's discoveries with the telescope were very important in raising questions about the old Ptolemaic theory, which was geocentric. However Galileo's discovery of Venus's phases was not a proof of the heliocentric principle because Tycho produced a geocentric model that explained Venus's phases.