Hubble Studies the Hourglass Nebula in M8

This NASA Hubble Space Telescope (HST) image reveals a pair of one-half

light-year long interstellar “twisters” — eerie funnels and twisted-rope

structures (upper left) — in the heart of the Lagoon Nebula (Messier 8).

The central hot star, O Herschel 36 (upper left), is the primary source of the

ionizing radiation for the brightest region in the nebula, called the

Hourglass. Other hot stars, also present in the nebula, are ionizing the

extended optical nebulosity. The ionizing radiation induces photo-evaporation

of the surfaces of the clouds (seen as a blue “mist” at the right of the

image), and drives away violent stellar winds tearing into the cool clouds.

Analogous to the spectacular phenomena of Earth tornadoes, the large

difference in temperature between the hot surface and cold interior of the

clouds, combined with the pressure of starlight, may produce strong

horizontal shear to twist the clouds into their tornado-like appearance.

Though the spiral shapes suggest the clouds are “twisting”, future

observations will be needed, perhaps with Hubble’s next generation

instruments, with the spectroscopic capabilities of the Space Telescope

Imaging Spectrograph (STIS) or the Near Infrared Camera and Multi-Object

Spectrometer (NICMOS), to actually measure velocities.

This Hubble picture reveals a variety of small scale structures in the

interstellar medium, small dark clouds called Bok globules, bow shocks around

stars, ionized wisps, rings, knots and jets.

In this image, even finer details of the gaseous flows and turbulences show

up. Herschel 36 shows up brightly.

The Lagoon Nebula and nebulae in other galaxies are sites where new stars are

being born from dusty molecular clouds. These regions are the “space

laboratories” for the astronomers to study how stars form and the interactions

between the winds from stars and the gas nearby. By studying the wealth of

data revealed by HST, astronomers will understand better how stars form in the

nebulae.

These color-coded images are the combination of individual exposures taken in

July and September, 1995 with Hubble’s Wide Field and Planetary Camera 2

(WFPC2) through three narrow-band filters (red light — ionized sulphur atoms,

blue light — double ionized oxygen atoms, green light — ionized hydrogen).

This work is based on public data retrieved from the HST Archive, cosmic-ray

cleaned, calibrated and combined by Adeline Caulet (Space Telescope European

Coordinating Facility, European Space Agency). The data were collected

as part of a scientific HST program by the WFPC2 Science Team.

Credit: A. Caulet (ST-ECF, ESA) and NASA