I tried googling it and just found this https://ubuntuforums.org/showthread.php?t=2234886 and this https://bugs.launchpad.net/ubuntu/+source/gnome-disk-utility/+bug/1165437.
But it is not so clear.
So I thought the star icon represent a boot drive. And check my first drive the partition is 1.1GB ext4 bootable and the second partition is on LVM2 PV. Then, but when I put my secondary internal drive, backup the data and convert it from ntfs to ext4, all the 3 partition on the second drive has the star icon.
The star icon will just show if the partition is mounted at startup. but when I remove them in the /etc/fstab the star button is gone.
So what is really the star icon? If it is for the boot drive, my secondary drive is just for data, I will not boot from it. And so how I can remove the start icon without removing it from the /etc/fstab?