dc, 22 17 bytes

[**********]ddddff

Invoked in bash as

echo [**********]ddddff | dc

Explanation:

[**********] # This is dc's way of making a string, which is then pushed onto the stack
dddd         # d is for duplicate, so we duplicate it 4 times on the stack
ff           # print the whole stack twice, which contains 5 repetitions of 10 *'s (x2)

Thanks to LeakyNun for saving 5 bytes

dc, 22 18 bytes

[**********]ddddff

Invoked in bash as

echo [**********]ddddff | dc

Explanation:

[**********] # This is dc's way of making a string, which is then pushed onto the stack
dddd         # d is for duplicate, so we duplicate it 4 times on the stack
ff           # print the whole stack twice, which contains 5 repetitions of 10 *'s (x2)

Thanks to LeakyNun for saving 5 4 bytes; Edited from 5 since I can't count.

dc, 22 bytes

[**********]dddddddddf

Invoked in bash as

echo [**********]dddddddddf | dc

Explanation:

[**********] # This is dc's way of making a string, which is then pushed onto the stack
ddddddddd    # d is for duplicate, so we duplicate it 9 times on the stack
f            # print the whole stack, which contains 10 repetitions of 10 *'s

dc, 22 17 bytes

[**********]ddddff

Invoked in bash as

echo [**********]ddddff | dc

Explanation:

[**********] # This is dc's way of making a string, which is then pushed onto the stack
dddd         # d is for duplicate, so we duplicate it 4 times on the stack
ff           # print the whole stack twice, which contains 5 repetitions of 10 *'s (x2)

Thanks to LeakyNun for saving 5 bytes