Wearing the Star of David became compulsory for Jews in the Netherlands in September 1941.
They would be fined heavily, or imprisoned, or beaten, or killed. Sources
I believe that some Jews would not mind wearing the 'Star of David' as they was proud of being Jewish. On the other hand many would feel great anger as they would realize by wearing it other non-jewish Germans would look down upon them as not part of true German society.
Generally speaking, you should be fine wearing a Star of David necklace in London, but I would avoid wearing it in Muslim-majority areas (like Edgeware Road or some districts in East London) to prevent attracting unwanted attention.
Nazi guards shot them on sight.
If you were a Jew and you got caught without the Star of David, you would either be killed, or tortured.
David was a renowned King of Israel and the star of David was emblazoned on his sheild. It is a national and historical symbol, not a religious one. Jews use it as an expression of who they are. In modern times it is also widely used organizationally; for example the Israeli equivalent of the red cross is the "Mogen Dovid Adom"--the red star of David. ___ However, under Nazi rule it was used as a badge of discrimination and no, they didn't like wearing what was meant to be a badge of shame! You won't find many individual Jews wearing it voluntarily.
Star of David Jewelry would be purchased by Jewish people. It can be found online at Amazon, Judaica Web Store, Zion Judaica, Israel Catalog, Canaan Online, and Star of David.
they took off the star
It would be better to ask what would happen if Earth hit a star, as stars are much larger than Earth is. The planet would be vaporized by the intense heat.
jewish people had to wear a star of david on all of there cloths so people would know they were jews so it would be "ok" to disrespect them
The David in the Star or Shield of David is King David from the Tanach (Jewish Bible).