Credit X-ray: NASA/CXC/University of Colorado/T.Ayres; Optical: Zdeněk Bardon/ESO
A new study involving long-term monitoring of Alpha Centauri by NASA's Chandra X-ray Observatory
indicates that any planets orbiting the two brightest stars are likely
not being pummeled by large amounts of X-ray radiation from their host
stars, as described in our press release.
This is important for the viability of life in the nearest star system
outside the Solar System. Chandra data from May 2nd, 2017 are seen in
the pull-out, which is shown in context of a visible-light image taken from the ground of the Alpha Centauri system and its surroundings.
Alpha Centauri is a triple star system located just over four light years,
or about 25 trillion miles, from Earth. While this is a large distance
in terrestrial terms, it is three times closer than the next nearest
Sun-like star.
The stars in the Alpha Centauri system include a pair called "A" and
"B," (AB for short) which orbit relativelydow close to each other. Alpha
Cen A is a near twin of our Sun in almost every way, including age,
while Alpha Cen B is somewhat smaller and dimmer but still quite similar
to the Sun. The third member, Alpha Cen C (also known as Proxima), is a
much smaller red dwarf star that travels around the AB pair in a much
larger orbit that takes it more than 10 thousand times farther from the
AB pair than the Earth-Sun distance. Proxima currently holds the title
of the nearest star to Earth, although AB is a very close second.
The Chandra data reveal that the prospects for life in terms of
current X-ray bombardment are actually better around Alpha Cen A than
for the Sun, and Alpha Cen B fares only slightly worse. Proxima, on the
other hand, is a type of active red dwarf star known to frequently send
out dangerous flares of X-ray radiation, and is likely hostile to life.
Planets in the habitable zone around Proxima receive an average dose of
X-rays about 500 times larger than the Earth, and 50,000 times larger
during a big flare.
Credit: Thomas Ayres
Download this video (MP4)
This movie shows Chandra observations of Alpha Centauri A and B taken
about every 6 months between 2005 and 2018. Alpha Cen A is the star to
the upper left. The motion of the pair from left to right is their
"proper motion", showing the movement of the pair in our galaxy with
respect to the solar system. The change in relative positions of the
pair shows the motion in their 80 year long orbit and the wobbles show
the small apparent motion (called parallax) caused by the year long
orbit of the Earth around the Sun. The Chandra images are shown in black
and white. To place these semi-annual images in context, the two
colored circles show the expected motion of Alpha Cen A (yellow) and
Alpha Cen B (orange) when taking account of proper motion, orbital
motion and parallax. The size of the circles is proportional to the
X-ray brightness of the source.
Tom Ayres of the University of Colorado at Boulder presented these
results at the 232rd meeting of the American Astronomical Society
meeting in Denver, Colorado, and some of these results were published in
January 2018 in the Research Notes of the American Astronomical Society.
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 Alpha Centauri:
Scale: About 2 arcmin across (2.4x10-4 light years) (2.3 billion km)
Category: Neutron Stars/X-ray Binaries
Coordinates (J2000): RA 14h 39m 37s | Dec -60° 50´ 2"
Constellation: Centaurus
Observation Date: May 2, 2017
Observation Time: 2 hours 45 minutes
Obs. ID: 16681
Instrument: HRC
References: T. Ayres, 2018, Res. Notes AAS, 2, 17
Color Code: X-ray: Blue
Distance Estimate: About 1.3 pc (4.2 light years)
Source: NASA’s Chandra X-ray Observatory
