NGC 7635
Key Astrophysical Data
Catalog Designations
NGC 7635, Sharpless 162 (Sh2-162), Caldwell 11
Position in the Sky
Cassiopeia (RA 23h 20m / Dec +61° 12′)
Apparent Size
~15′ × 8′ (Nebula overall), ~3′ (Bubble)
Apparent Magnitude
+10.0 (Faint, requires a telescope)
Discovery Date
1787 (William Herschel)
Object Type
Emission Nebula / Wind-Blown Bubble
Distance from Earth
~7,100 Light Years
Physical Size
Bubble is ~7 Light Years across
Power Source
BD+60°2522 (SAO 20575) - Massive O-type star
Object Overview & Facts
A Cosmic Illusion: To our eyes, the Bubble Nebula appears as an incredibly delicate, perfect sphere, much like a fragile soap bubble floating through the cosmos. However, this structure is actually the result of violent, tremendous forces. It is a shock wave, expanding outward at over 64,000 kilometers per hour (40,000 mph), slamming into the cold, dense molecular gas of the surrounding interstellar medium.
The Monster Within: The engine driving this spectacular expansion is an extraordinarily hot, massive O-type star known as BD+60°2522. This stellar behemoth is roughly 44 times more massive than our Sun and hundreds of thousands of times more luminous. It burns with such intensity that its stellar wind—a fierce torrent of charged particles—pushes the surrounding gas outward, carving out the glowing cavity we see today.
An Off-Center Engine: One of the most fascinating visual anomalies of the Bubble Nebula is that its powerhouse star is not located in the exact center of the bubble. Because the surrounding molecular cloud is uneven—denser on one side than the other—the expanding stellar wind meets more resistance in one direction. As a result, the bubble expands asymmetrically, leaving the central star noticeably off-center.
A Ticking Time Bomb: The immense mass of BD+60°2522 means that it is living life in the fast lane. Stars of this caliber exhaust their nuclear fuel incredibly quickly. In just a few million years—a blink of an eye in cosmic terms—this star will detonate as a brilliant supernova, obliterating the delicate bubble it spent its short life carving and seeding the Perseus Arm with heavy elements.
Astrophotography Guide: For astrophotographers, the Bubble Nebula is a premier narrowband target. While broadband RGB imaging captures the brilliant red glow of the surrounding Hydrogen-alpha gas, using narrowband SHO (Hubble Palette) filters separates the complex chemistry. The oxygen signal (OIII) reveals the intricate, translucent blue walls of the bubble itself, contrasting magnificently against the chaotic, fiery gold and deep crimson of the outer molecular cloud.
Deep Sky Objects Size Comparison Laboratory
Interactive Scaling Explanation: This panel acts as a dynamic comparator of angular sizes in the night sky. All selected objects are rendered exactly over each other from a common center, allowing an immediate, direct comparison. The overall NGC 7635 complex is about 15' across, but the bubble itself is quite small (about 3'), requiring high focal length optics to resolve clearly against the Full Moon's 31' diameter.
Cosmic Time Machine: NGC 7635 vs. Earth's History
The Photon Arrives: Right now, the light captured in this photograph is ending its roughly 7,100-year journey through deep space, hitting your camera's digital sensor. Move the slider back in time to see what humanity was doing while these precise photons were rushing through the void.
Cosmic Scale: Distance Map Laboratory
Dynamic Linear Scaling & Manipulation: This view builds an interactive, deep-space linear cosmic coordinate system. When swapping objects, the line auto-calculates its limit. Turn on remote galaxies to watch the Milky Way bundle together, or zoom in to see how the Bubble Nebula resides in the Perseus Arm alongside neighbors like the Double Cluster and the Lobster Claw.