Eta Carinae's great eruption in the 1840s created the billowing Homunculus Nebula, imaged here by Hubble, and transformed the binary into a unique object in our galaxy. Astronomers cannot yet explain what caused this eruption. The discovery of likely Eta Carinae twins in other galaxies will help scientists better understand this brief phase in the life of a massive star.
Credits: NASA, ESA, and the Hubble SM4 ERO Team.
In a follow-on survey in 2015, the team found two candidate Eta twins in
the galaxy M83, located 15 million light-years away, and one each in NGC
6946, M101 and M51, located between 18 and 26 million light-years away.
These five objects mimic the optical and infrared properties of Eta
Carinae, indicating that each very likely contains a high mass star
buried in five to 10 solar masses of gas and dust. Further study will
let astronomers more precisely determine their physical properties. The
findings were published in the Dec. 20 edition of The Astrophysical Journal Letters.
Researchers found likely Eta twins in four galaxies by comparing the infrared and optical brightness of each candidate source. Infrared images from NASA's Spitzer Space Telescope revealed the presence of warm dust surrounding the stars. Comparing this information with the brightness of each source at optical and near-infrared wavelengths as measured by instruments on Hubble, the team was able to identify candidate Eta Carinae-like objects. Top: 3.6-micron images of candidate Eta twins from Spitzer's IRAC instrument. Bottom: 800-nanometer images of the same sources from various Hubble instruments.
Credits: NASA, ESA, and R. Khan (GSFC and ORAU)
NASA's James Webb Space Telescope,
set to launch in late 2018, carries an instrument ideally suited for
further study of these stars. The Mid-Infrared Instrument (MIRI) has 10
times the angular resolution of instruments aboard Spitzer and is most
sensitive at the wavelengths where Eta twins shine brightest.
"Combined
with Webb's larger primary mirror, MIRI will enable astronomers to
better study these rare stellar laboratories and to find additional
sources in this fascinating phase of stellar evolution," said Sonneborn,
NASA's project scientist for Webb telescope operations. It will take
Webb observations to confirm the Eta twins as true relatives of Eta
Carinae.
The Spitzer Space Telescope is managed by NASA's Jet Propulsion
Laboratory in Pasadena, California. The Spitzer Science Center at the
California Institute of Technology in Pasadena conducts science
operations.
The Hubble Space Telescope is a project of international cooperation
between NASA and the European Space Agency. NASA's Goddard Space Flight
Center manages the telescope. The Space Telescope Science Institute
(STScI) in Baltimore, Maryland, conducts Hubble science operations.
STScI is operated for NASA by the Association of Universities for
Research in Astronomy in Washington, D.C.
For more information about Spitzer, visit: http://www.nasa.gov/spitzer
For more information about Hubble, visit: http://www.nasa.gov/hubble
Francis Reddy
NASA's Goddard Space Flight Center, Greenbelt, Maryland
