Asteron

Asteron, known as Telstar (テルスター) in Japan, is a hovering starfish-type Badnik created by Dr. Robotnik. Making their first appearance in Sonic the Hedgehog 2, Asteron Badniks are simply designed and are located usually on walls. They are able to self-destruct and fire its five sharp parts in many directions.

Sonic the Hedgehog 2
Asteron makes its debut in Sonic the Hedgehog 2, where it is one of the three deadly Badnik types featured at Metropolis Zone. These Badniks hide at walls, floors and ceilings, where they cannot be harmed. When approached, however, it will move closer to the player, and then fire its star points, which are like spears, in five different directions. Its red eye helps it to detect the player when they are close enough.

In a certain part of Metropolis Zone, there is a giant tower which can be scaled by running up a screw on a nut, and there are about four to six Asterons along the way. Their threat is increased as their spear attack can cause the player to fall off the nut, often requiring the player to move away to scroll the screw off-screen to reset the nut at the bottom.

In the 2013 re-release of the game, a couple of Asterons are present at the beginning of the Metropolis Zone segment in Boss Attack Zone.

Sonic the Hedgehog Pocket Adventure
Asteron Badniks make their next appearance in Sonic the Hedgehog Pocket Adventure, where they are featured at Gigantic Angel Zone. As Gigantic Angel has many identical gimmicks and elements from Metropolis Zone, it has also the same Badnik models with similar attack patterns. However Asterons are seen hovering in the air and the player is able to destroy these Badniks before its self-destruction, thus freeing the animal inside of it. Asteron Badniks also are seen flashing red before its exploding.

Sonic the Hedgehog 4
Asteron make a reappearance in Sonic the Hedgehog 4: Episode I, with a slightly different design. They are featured at Mad Gear Zone, which again has the same Badniks. Despite that, these Badniks retain identical patterns from previous appearances, but the player is once again not able to destroy these Badniks. Before its self-destruction, these Badniks spin around.

Physical Appearance
Asteron has a simple, flat starfish-shaped appearance. Its core body is colored light-yellow and in the middle of the body is grey hole with red eye on the hole. All five sharp points have grey spears, that are pointing towards five directions. Asteron's appearance in Sonic the Hedgehog 4 is more detailed, even though involving only slight changes.

Abilities
Asteron Badniks can found hiding in walls, floors and ceilings, waiting for Sonic to come close to it. When Sonic approaches, Asteron then moves closer to the hedgehog and suddenly self-destructs, firing all five spears in five directions.

Sonic the Comic
Asteron has made few appearances in Fleetway's Sonic the Comic, as being typically part of Robotnik's Badnik army. The only appearance in the comic's original run has been in issue 79's story "Revolution", where Asteron was as one of the Badniks unleashed on the civilians to remind them that Doctor Robotnik was in charge Brutus' troops are seen to feature one Asteron as well. All of these Badniks have got destroyed by Sonic, Amy and Johnny Lightfoot. Before that, Asteron has also featured on one pin-up of issue 67.

Archie Comics
Several Asteron Badniks made small appearance on one panel of Archie's Sonic the Hedgehog comic issue 229. They are guarding Metropolis Zone like other Badniks during the Genesis story arc, as Sonic tries to get past of them during his mission to get to the core of Eggman's base. Sonic uses meter-wide screw to make progress on his journey and also uses it to squash Asterons to the ceiling.

Asterons reappear in one panel of Sonic the Hedgehog #255. In this issue, these Badniks are part of the forces dispatched to prevent Sonic, Tails, and Bunnie's escape from Metropolis Zone.

Trivia

 * In the Sonic the Hedgehog 2 Debug Mode, it is possible to destroy Asteron Badniks simply by Spin Jumping on them and freeing animals inside them if these Badniks aren't set on to walls. Because the original game doesn't let the player to have the chance to destroy these Badniks, animals inside them are apparently killed after the Badnik's activation and self-destruction. However, it is likely that the animals inside Asteron Badniks are non-canon.
 * Asteron and Crawl are the only Badniks in Sonic the Hedgehog 4 that are not featured in the game's website.
 * Asteron seems to be a better fit for Oil Ocean Zone, as it would fit in with the zone's motif of having sea creature-based enemies.