What do modern scientists think the star followed by the three wise men to Bethlehem could have been?

The 3 brightest stars in the Orion Belt aptly called "The Three Kings" (see link "The Three Kings of Orion" below).

The star Sirius or Dog Star. When Sirius aligns with the Three Kings star of the Orion Belt on the night of the Dec 24th, it will point where the new Sun of the winter solstice (when the day will be longer than night) will rise on the morning of Dec 25th. Depending on where you live, you can observe this alignment with naked eye on the night of Dec 24, mark where it points and observe where the sun rises on Dec 25.

See related link "Sirius" below