uwp close browser programmatically

I'm creating a simple news feed, it i want it can open the browser to show the details of the news, but i don't know how to close the browser , here is the code of how I open the browser,anyone can teach me how to off the browser using uwp? '

  public async void test()
{
      RootObject mynews = await NewsProxy.GetNews();
        string website = mynews.articles[i].url;
        var uriWeb = new Uri(websites);
        var success = await Windows.System.Launcher.LaunchUriAsync(uriWeb);
        if (success)
        {
            //Uri launched
        }
        else
        {
            // uri launch failed
        }



}