The region of Re50 and Re50N observed in 2006 with SuprimeCam at the
Subaru telescope, and in 2014 with the Gemini Multi-Object Spectrograph
(GMOS) at the Gemini South telescope. A [SII] filter was used for both
images. The seeing was in both cases 0.5 arcsec. Each image is about 3
arcmin wide. North is up and east is left.
In the cosmic “blink of an eye,” astronomers have detected rapid
changes in brightness and appearance of a restless stellar nursery in
Orion. The luminous cloud of gas, going by the designation Re50, first
appeared about half a century ago in the constellation of Orion. Now,
astronomers using the Gemini South telescope, and other telescopes
around the world, have discovered that the chaotic caldron has once
again brightened further. According to team member Bo Reipurth, of the
University of Hawaii’s Institute for Astronomy, “This most recent
brightening, happened, I believe in 2014, when unfortunately we weren’t
able to look since Orion was in the Sun’s glare.” Reipurth adds that
areas of stellar birth, in this case called a Class I protostar, are
extremely dynamic places and change on human timescales, “… while we
missed the initial brightening event, we can still study the changes
going on and learn a lot about what’s happening.” Based on the team’s
observations, they conclude that curtains of obscuring material are
likely casting patterns of illumination and shadows onto the molecular
cloud that envelopes the nursery, “…which gives us a spectacular stellar
light show!” says Reipurth.
Learn more in the team’s paper, which is accepted for publication in The Astrophysical Journal, at: http://arxiv.org/abs/1503.04241.
Abstract:
The luminous Class I protostar HBC 494, embedded in the Orion A cloud,
is associated with a pair of reflection nebulae, Re50 and Re50N, which
appeared sometime between 1955 and 1979. We have found that a dramatic
brightening of Re50N has taken place sometime between 2006 and 2014.
This could result if the embedded source is undergoing a FUor eruption.
However, the near-infrared spectrum shows a featureless very red
continuum, in contrast to the strong CO bandhead absorption displayed by
FUors. Such heavy veiling, and the high luminosity of the protostar, is
indicative of strong accretion but seemingly not in the manner of
typical FUors. We favor the alternative explanation that the major
brightening of Re50N and the simultaneous fading of Re50 is caused by
curtains of obscuring material that cast patterns of illumination and
shadows across the surface of the molecular cloud. This is likely
occurring as an outflow cavity surrounding the embedded protostar breaks
through to the surface of the molecular cloud. Several Herbig-Haro
objects are found in the region.
Source: Gemini Observatory
