Substellar Objects in the Orion Nebula found by Hubble

Substellar Objects in the Orion Nebula found by Hubble

NASA’s Hubble Space Telescope have uncovered the largest known population of brown dwarfs sprinkled among newborn stars

In an unprecedented deep survey for small, faint objects in the Orion Nebula, researchers not only found several very-low-mass brown dwarf companions, but also three giant planets. They even found an example of binary planets where two planets orbit each other in the absence of a parent star.

Located 1,350 light-years away, the Orion Nebula is a relatively nearby laboratory for studying the star formation process across a wide range, from opulent giant stars to diminutive red dwarf stars and elusive, faint brown dwarfs.

Brown dwarfs are a strange class of celestial object that have masses so low that their cores never become hot enough to sustain nuclear fusion, which powers stars. Instead, brown dwarfs cool and fade as they age. Despite their low mass, brown dwarfs provide important clues to understanding how stars and planets form, and may be among the most common objects in our Milky Way galaxy.

This image is part of a Hubble Space Telescope survey for low-mass stars, brown dwarfs, and planets in the Orion Nebula. Each symbol identifies a pair of objects, which can be seen in the symbol’s center as a single dot of light. Special image processing techniques were used to separate the starlight into a pair of objects. The thicker inner circle represents the primary body, and the thinner outer circle indicates the companion. The circles are color-coded: red for a planet; orange for a brown dwarf; and yellow for a star. Located in the upper left corner is a planet-planet pair in the absence of a parent star. In the middle of the right side is a pair of brown dwarfs. The portion of the Orion Nebula measures roughly four by three light-years.        Credits: NASA , ESA, and G. Strampelli (STScI)

It is known that brown dwarfs are colder than stars and they have water in their atmospheres.  The team leader of the Space Telescope Institute in Baltimore, Maryland, Massimo Robberto explained:

“These are so cold that water vapor forms, and water is a signature of substellar objects.  It’s an amazing and very clear mark. As the masses get smaller, the stars become redder and fainter, and you need to view them in the infrared. And in infrared light, the most prominent feature is water.”

From the Earth’s surface we can’t see the hot water vapor in the atmosphere of brown dwarfs, due to the absorbing effects of water in our atmosphere. Fortuanetely, Hubble Space Telescope is above the atmosphere and also has a near-infrared vision that can spot water on distant worlds.

1,200 candidate reddish stars were identified by the Hubble team in the Orion Nebula. Thanks to this, scientists created two categories: those with water, and those without. The bright reddish stars with water were confirmed to be faint red dwarfs. Many other stars without water were also detected, but these are backgroud stars in the Milky Way, passing through interstellar dust. This type is not relevant to the team’s study.

Red Dwarf Star in comparison with our Sun

In all, the team found 17 candidate brown dwarf companions to red dwarf stars, one brown dwarf pair, and one brown dwarf with a planetary companion.  The study also identified three potential planetary mass companions: one associated to a red dwarf, one to a brown dwarf, and one to another planet.

“We experimented with a method, high-contrast imaging post processing, that astronomers have been relying on for years. We usually use it to look for very faint planets in the close vicinity of nearby stars, by painstakingly observing them one by one. This time around, we decided to combine our algorithms with the ultra-stability of Hubble to inspect the vicinity of hundreds of very young stars in every single exposure obtained by the Orion survey. It turns out that even if we do not reach the deepest sensitivity for a single star, the sheer volume of our sample allowed us to obtain an unprecedented statistical snapshot of young exoplanets and brown dwarf companions in Orion,” said Laurent Pueyo at the Space Telescope Science Institute.

Combining the two unique techniques, imaging in the water filters and high-contrast image processing, the survey provided an unbiased sample of newly formed low-mass sources, both dispersed in the field and companions of other low-mass objects.

“We could reprocess the entire Hubble archive and try to find jewels there,” Robberto said.

More images of Orion Nebula taken by Hubble can be found here.




Article originally posted here.



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