Other stars show tails that trail behind them like a comet’s tail.
Scientists used NASA’s Interstellar Boundary Explorer to confirm that
our solar system has one too. From top left and going counter clockwise,
the stars shown are: LLOrionis; BZ Cam; and Mira. Image Credit:
NASA/HST/R.Casalegno/GALEX
Like a comet, the solar system has a tail. NASA's Interstellar
Boundary Explorer (IBEX) has for the first time mapped out the structure
of this tail, which is shaped like a four-leaf clover.
Scientists describe the tail, called the heliotail, based on the
first three years of IBEX imagery in a paper published in the July 10
edition of the Astrophysical Journal.
A new video from NASA explores the solar system's comet-like tail.
While telescopes have spotted such tails around other stars, it
has been difficult to see whether our star produced one. The particles
found in the tail -- and throughout the entire heliosphere, the region
of space influenced by our sun -- do not shine, so they cannot be seen
with conventional instruments.
"By examining the neutral atoms, IBEX has made the first
observations of the heliotail," said David McComas, IBEX principal
investigator at Southwest Research Institute in San Antonio, Texas, and
the paper's lead author. "Many models have suggested the heliotail might
look like this or like that, but we have had no observations. We always
drew pictures where the tail of the solar system just trailed off the
page, since we couldn't even speculate about what it really looked
like."
IBEX measures the neutral particles created by collisions at the solar
system's boundaries. This technique, called energetic neutral atom
imaging, relies on the fact that the paths of neutral particles are not
affected by the solar magnetic field. Instead, the particles travel in a
straight line from collision to IBEX. Consequently, observing where the
neutral particles came from describes what is going on in these distant
regions.
"Since first light in 2008, the IBEX mission team has amazed us
with its discoveries at the interstellar boundary, including a
previously unknown ribbon of energetic neutral particles stretching
across it," said Arik Posner, NASA's IBEX program scientist in
Washington. "The new IBEX image of the heliotail fills in a previously
blank area on the map. We are first-hand witnesses of rapid progress in
heliophysics science."
By combining observations from the first three years of IBEX
imagery, the team showed a tail with a combination of fast and slow
moving particles. There are two lobes of slower particles on the sides
and faster particles above and below. This four-leaf clover shape can be
attributed to the fact that the sun has been sending out fast solar
wind near its poles and slower wind near its equator for the last few
years. This is a common pattern in the most recent phase of the sun's
11-year activity cycle.
The clover shape does not align perfectly with the solar system,
however. The entire shape is rotated slightly, indicating that as it
moves further away from the sun and its magnetic influence, the charged
particles begin to be nudged into a new orientation, aligning with the
magnetic fields from the local galaxy.
Scientists do not know how long the tail is, but think that it
eventually fades away and becomes indistinguishable from the rest of
interstellar space. Scientists are testing their current computer
simulations of the solar system against the new observations to improve
our understanding of the comet-like tail streaming out behind us.
Credits: Production editor: Dr. Tony Phillips | Credit: Science@NASA
More information:
IBEX is a NASA Heliophysics Small Explorer mission. The Southwest
Research Institute leads IBEX with a team of national and international
partners. NASA's Goddard Space Flight Center in Greenbelt, Md., manages
the Explorers Program for NASA's Science Mission Directorate in
Washington.
