September 30, 2022

Galactic Lyman-Alpha Brightness of Our Galaxy Measured by New Horizons Space Probe

In many of our planetary system, the background is dominated by Lyman-alpha photons released by the sun and spread by interstellar hydrogen atoms that are going through. In the outer solar system, however, where the New Horizons spacecraft travels, the scattered sunshine element of the Lyman-alpha signal is far less intense and the fainter elements from the close-by regions of the Milky Way become simpler to differentiate.
” The stellar Lyman-alpha background comes from hot regions around huge stars which ionize all the matter near them, which is mostly hydrogen, as that is the most abundant aspect in the universe,” stated Dr. Randy Gladstone, the studys lead author. “When the protons and electrons ultimately return together, or recombine, they nearly always emit Lyman-alpha photons.”
Hydrogen atoms between the stars scatter these photons into an approximately uniform radiance throughout space. They are noticeable, Gladstone said, but just at the Lyman-alpha wavelength, which is at a wavelength about four times much shorter than can be seen by human eyes.
” The Lyman-alpha background has actually been studied a lot near the Earths orbit, and is bright enough that if we could see it, the night sky would never ever get darker than golden,” Gladstone described. “Its so intense from solar Lyman-alpha that we werent specific how much the Milky Way galaxy contributed to its overall brightness.
With the SwRI-led Alice UV imaging spectrograph aboard New Horizons, Gladstone was able to properly measure the brightness of the galactic element of the Lyman-alpha background for the first time.
” New Horizons has been flying away from the Sun for more than 15 years now,” Gladstone explained. “The farther we moved far from the Sun, the less we were blinded by the solar part of the Lyman-alpha background.”
With New Horizons now far beyond Pluto, Gladstone had the ability to determine the brightness of the Lyman-alpha background from the Milky Way for the first time: about 20 times less bright than the Lyman-alpha background is near Earth.
” This has been something thats been rated by astronomers for decades,” Gladstone said. “Now we have a lot more precise number.”
Gladstone hopes that this discovery will assist astronomers better comprehend the nearby areas of the Milky Way galaxy.
” The special position of New Horizons in the far away Kuiper Belt permits it to make discoveries like this that no other spacecraft can,” stated New Horizons primary detective and SwRI area division associate vice president Dr. Alan Stern. “What an excellent resource New Horizons is, not simply for the exploration of the Kuiper Belt, however likewise to comprehend more about our galaxy and even deep space beyond our galaxy through this and other observations by our clinical instrument payload.”
The Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, developed, built, and operates the New Horizons spacecraft, and manages the mission for NASAs Science Mission Directorate. The MSFC Planetary Management Office provides the NASA oversight for the New Horizons. Southwest Research Institute, based in San Antonio, directs the mission through Principal Investigator Stern, and leads the science group, payload operations and encounter science planning. New Horizons is part of the New Frontiers Program managed by NASAs Marshall Space Flight Center in Huntsville, Alabama.

This false-color map reveals numerous scans of the Lyman-alpha background over the sky, acquired by the Alice ultraviolet spectrograph on the New Horizons spacecraft when it was 45 AU from the Sun. The information concurs well with an underlying model of the solar element of the Lyman-alpha background to which a constant brightness from the Milky Way has been included. The space Lyman-alpha ultraviolet background was very first spotted in the 1960s, and its presence was later confirmed in 1971.” The Lyman-alpha background has been studied a lot near the Earths orbit, and is intense enough that if we might see it, the night sky would never get darker than twilight,” Gladstone discussed. “Its so intense from solar Lyman-alpha that we werent certain how much the Milky Way galaxy contributed to its overall brightness.

This false-color map reveals several scans of the Lyman-alpha background over the sky, obtained by the Alice ultraviolet spectrograph on the New Horizons spacecraft when it was 45 AU from the Sun. The information agrees well with an underlying model of the solar part of the Lyman-alpha background to which a consistent brightness from the Milky Way has been included. The background is brighter at both directions near our Sun, which is marked here by an orange dot. Credit: SwRI
Researcher made use of SwRI-developed instrument on New Horizons to determine just how much Lyman-alpha light the Milky Way galaxy is shining on our solar system.
A new study led by Southwest Research Institute identified the brightness of the galactic Lyman-alpha background using a SwRI-developed instrument aboard NASAs Kuiper Belt area probe, New Horizons.
The space Lyman-alpha ultraviolet background was very first identified in the 1960s, and its existence was later on validated in 1971. This ultraviolet radiance penetrates area and can be used to characterize the rare wind of hydrogen atoms which blows through our solar system. It has also been utilized by SwRI instruments on NASA spacecraft to image completely dark craters near the north and south poles of the Moon.

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