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To celebrate its 28th anniversary in space, the NASA/ESA Hubble Space Telescope, which was launched on April 24, 1990, at 08:33:51 a.m. EDT, released this dazzling image of the Lagoon Nebula. The observations were taken recently by Hubble’s Wide Field Camera 3 between Feb. 12 and Feb. 18, 2018.
The image below shows a small part (4 light-years across) of the turbulent star-formation region in the Lagoon Nebula, located within our Milky Way galaxy. At the center of the photo, the giant young star Herschel 36, 200,000 times brighter than our Sun, is blasting powerful ultraviolet radiation and stellar winds of subatomic particles, sculpting the gas and dust surrounding it. The gases get ionized and glow, emitting radiation that can be detected by Hubble. The gas in the nebula is dominated by Hydrogen, with small amounts of Helium, Oxygen and Nitrogen.
This region epitomizes a typical, dynamic stellar nursery full of birth and destruction. Star formation in the neighborhood of the star is suppressed due to its strong emissions. However, at the dark edges of this system, where the radiation is weaker, stars are forming within dense clouds of gas and dust. Within a few million years, most of the gas and dust will be blown away leaving behind a cluster of bright stars.
Here is the image in visible light, which highlights the vast clouds of gas and dust surrounding Herschel 36.
The next image is taken in infrared light, which enables Hubble to peer through the shrouds of gas and dust. The image shows as abundance of stars, most of which are more distant, background stars located behind the nebula itself. However, some of these pinpricks of light are young stars within the Lagoon Nebula. The giant star Herschel 36, near the center of the frame, shines even brighter in this infrared view.
Dark smudges known as Bok globules mark the thickest parts of the nebula, where dust protects still-forming stars and their planets. While Hubble cannot penetrate these dusty cocoons, the Webb space telescope will be able to see through them.
Here are the two images side-by-side -
The Lagoon Nebula, about 4,000-6,000 light-years away, is much larger than the small region highlighted in the previous images; it is about 110 light-years wide and 50 light-years tall. The image below shows a fuller view of the nebula.
Here are a couple of stunning videos, starting with a ground-based view of the night sky, and then zooming into the Lagoon Nebula and the region hosting Herschel 36 -
The Lagoon Nebula
The Lagoon Nebula (aka Messier 8, M8 and NGC 6523) is a giant interstellar cloud of gas and dust. The nebula is located in the Sagittarius constellation, within the Milky Way Galaxy. It lies in the direction of the galaxy’s center.
It is 110 x 50 light-years across and 4,000 - 6,000 light-years from Earth. It subtends an arc of about 1.5 degrees across the sky (3 times the angular width of the moon) and is visible through binoculars and small telescopes.
M8 is classified as an emission nebula and as an H II region. It is composed mainly of ionized Hydrogen, that emits light of various wavelengths. The ionization is caused by strong ultraviolet radiation from two very hot stars – 6th-magnitude 9 Sagitarii (visible to the human eye) and the smaller and fainter 9th-magnitude star Herschel 36.
Herschel 36 is an O-type star (aka a blue star); it is 32 times more massive and 8 times hotter than our Sun. It is nearly 9 times our Sun’s diameter. Herschel 36 is still very active because it is young by a star’s standards, only 1 million years old. Based on its mass, it is estimated to last another 5 million years, before it goes supernova, after have synthesized many of the heavy elements. In comparison, our smaller Sun is 5 billion years old and will live another 5 billion years.
What is an H II Region?
The following information is derived mainly from the wiki page on H II regions.
An H II region (pronounced "H two") is formed inside a giant molecular cloud (GMC), a cold (10–20 K) and dense cloud consisting mostly of molecular hydrogen. GMCs can exist in a stable state for long periods of time — the tiny force of gravity that could compel the cloud to collapse is counterbalanced by the very faint pressure of the gas in the cloud. However, shock waves due to supernovae, collisions between galaxies/clouds, and magnetic interactions can trigger its collapse and lead to star formation.
As stars are born within a GMC, the most massive ones emit strong UV radiation that can ionize the surrounding gas, stripping Hydrogen molecules of electrons. The energetic photons create an ionization front, which sweeps through the surrounding gas at supersonic speeds. Star formation near the star itself is suppressed as gas and dust is pushed away. Farther away from the ionizing star, the ionization front slows to subsonic speeds, and is overtaken by the shock front of particles ejected from the stars. The shock waves also play a role in stellar formation by compacting and causing further gravitational collapse in distant regions of the cloud.
In the cooler regions of the nebula, additional stars are born in the disturbed gas and dust. They too undergo a similar process of emitting UV radiation and stellar winds; after they drive away their 'cocoon' of surrounding gas, the stars becomes visible.
Many young stars in H II regions also show evidence of planetary systems. The Hubble Space Telescope has revealed hundreds of protoplanetary disks (proplyds) in the Orion Nebula.
H II regions, such the Lagoon Nebula, last just a few million years and may give birth to thousands of stars. In the end, supernova explosions and strong stellar winds from the most massive stars in the resulting star cluster will drive most (as much as 90%) of the gas away, leaving behind a cluster of stars; the Pleiades are an example of such a star cluster left over from an ancient H II region.
The Sun
Our own star - the Sun, formed about 4.6 billion years ago in a similar manner — from the collapse of part of a giant molecular cloud. Presence of heavy molecules indicates that shock waves from a nearby supernova probably triggered the formation of the Sun by compressing the matter within the molecular cloud and causing certain regions to collapse under their own gravity. The Sun did not grow large enough to go Supernova.
The Hubble Space Telescope
Hubble was launched 28 years ago on April 24, 1990, at 08:33:51 a.m. EDT. After five servicing missions, between 1993 and 2009, Hubble is still going strong and is expected to last beyond 2030. Even today, it outshines other space and ground based telescopes due to its unique ability to see in visible and near-infrared light from its vantage point high above the Earth’s atmosphere.
Here are some interesting nuggets of info. about Hubble —
- Hubble’s main mirror is 2.4-meters in diameter (JWST has a 6.5-meter-diameter segmented mirror)
- Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared spectra.
- Hubble has so far made more than 1.3 million observations.
- Hubble has circled Earth and traveled more than 4 billion miles along a circular low earth orbit, about 540 km in altitude and 95 minutes in period.
- Hubble generates about 10 terabytes of new data per year. The total archive is currently over 150 TB in size.
- There are proposals on the drawing board for future servicing missions to extend the life and capabilities of Hubble.
The universe became a lot “bigger”, thanks to Hubble.
Epilogue
The Hubble telescope is a symbol of humanity’s ingenuity and its quest to understand the universe. The Webb telescope (JWST), which will be launched in a year (or more) will be able to peer deeper and farther, in space and time, building on Hubble’s success. Hopefully, Hubble, like the Energizer bunny, will keep on going and going ...
Further Reading
- Lagoon Nebula (Visible-light View) — www.nasa.gov/...
- Lagoon Nebula wiki — en.wikipedia.org/…
- Hubble Telescope — hubblesite.org
- Hubble Wiki — en.wikipedia.org/...
- Hubble Twitter — twitter.com/...
- Galaxy and Nebulae photo galleries — hubblesite.org/… hubblesite.org/… eso.org/...
- Galaxies and Nebulae by Hubble (2017) — www.dailykos.com/…
- Galaxies and Nebulae by Hubble (2016) — www.dailykos.com/…