The supermassive black hole at the center of the Milky Way, seen in this image from NASA's Chandra X-ray Observatory, may be producing mysterious particles called neutrinos, as described in our latest press release.
Neutrinos are tiny particles that have virtually no mass and carry no
electric charge. Unlike light or charged particles, neutrinos can emerge
from deep within their sources and travel across the Universe without
being absorbed by intervening matter or, in the case of charged
particles, deflected by magnetic fields.
While the Sun produces neutrinos that constantly bombard the Earth,
there are also other neutrinos with much higher energies that are only
rarely detected. Scientists have proposed that these higher-energy
neutrinos are created in the most powerful events in the Universe like
galaxy mergers, material falling onto supermassive black holes, and the
winds around dense rotating stars called pulsars.
Using three NASA X-ray
telescopes, Chandra, Swift, and NuSTAR, scientists have found evidence
for one such cosmic source for high-energy neutrinos: the
4-million-solar-mass black hole at the center of our Galaxy
called Sagittarius A* (Sgr A*, for short). After comparing the arrival
of high-energy neutrinos at the underground facility in Antarctica,
called IceCube, with outbursts from Sgr A*, a team of researchers found a
correlation. In particular, a high-energy neutrino was detected by
IceCube less than three hours after astronomers witnessed the largest
flare ever from Sgr A* using Chandra. Several flares from neutrino
detections at IceCube also appeared within a few days of flares from the
supermassive black hole that were observed with Swift and NuSTAR.
This Chandra image shows the region around Sgr A* in low, medium, and high-energy X-rays that have been colored
red, green, and blue respectively. Sgr A* is located within the white
area in the center of the image. The blue and orange plumes around that
area may be the remains of outbursts from Sgr A* that occurred millions
of years ago. The flares that are possibly associated with the IceCube
neutrinos involve just the Sgr A* X-ray source.
This latest result may also contribute to the understanding of another major puzzle in astrophysics: the source of high-energy cosmic rays.
Since the charged particles that make up cosmic rays are deflected by
magnetic fields in our Galaxy, scientists have been unable to pinpoint
their origin. The charged particles accelerated by a shock wave near Sgr
A* may be a significant source of very energetic cosmic rays.
The paper describing these results was published in Physical Review D and is also available online.
The authors of the study are Yang Bai, Amy Barger, Vernon Barger, R.
Lu, Andrea Peterson, J. Salvado, all from the University of Wisconsin,
in Madison, Wisconsin.
NASA's Marshall Space Flight Center in Huntsville, Alabama, manages
the Chandra program for NASA's Science Mission Directorate in
Washington. The Smithsonian Astrophysical Observatory in Cambridge,
Massachusetts, controls Chandra's science and flight operations.
Fast Facts for Sagittarius A*:
Release Date: November 13, 2014
Scale: Image is about 12 arcmin across (about 91 light years)
Category: Black Holes, Milky Way Galaxy
Coordinates (J2000): RA 17h 45m 40s | Dec -29° 00' 28.00"
Constellation: Sagittarius
Observation Date: 43 pointings from September 21, 1999 to May 18, 2009
Observation Time: 278 hours (11 days 14 hours).
Obs. ID: 242, 1561, 2943, 2951-2954, 3392, 3393, 3549, 3663, 3665, 4683, 4684, 5360, 5950-5954, 6113, 6363, 6639, 6640-6646, 7554-7759, 9169-9174, 10556
Instrument: ACIS
Also Known As: Galactic Center
References: Bai, et al, 2014, Physics Review D, 90, 063012; arXiv:1407.2243
Color Code: Energy: Red (2-3.3 keV), Green (3.3-4.7 keV), Blue (4.7-8 keV)
Distance Estimate: About 26,000 light years
Source: NASA’s Chandra X-ray Observatory
