Google's search results will cut off all titles that are too long. Based on some articles I've found (such as this one), Google allocates a little over 500 pixels for each title, which translates into approximately 57 characters (it may be a little more or less than that since Google uses a non-fixed-width font).
I found this Search Engine Optimization Starter Guide written by Google. It includes tips for web developers on how to improve their web sites so that Google can more easily crawl, index, and understand their content. On page 5, it describes how Google will only show a portion of long titles in the search results:
Use brief, but descriptive titles
Titles can be both short and informative. If the title is too long, Google will show only a portion of it in the search result.
- using extremely lengthy titles that are unhelpful to users
- stuffing unneeded keywords in your title tags
As you can see, Google wants to discourage web developers from using really long titles that may be unhelpful or difficult for users to read. Google also wants to prevent web developers from spamming their titles with a bunch of keywords. Truncating long titles helps Google achieve these goals.