Looks like the Sagittarius Teapot’s got a new whistle. On March 15, John Seach of Chatsworth Island, NSW, Australia
discovered a probable nova in the heart of the constellation using a DSLR camera and fast 50mm lens.
This
view shows the sky facing south-southeast just before the start of dawn
in mid-March from the central U.S. The nova’s located squarely in the
Teapot constellation. Source: Stellarium
Checks revealed no bright asteroid or variable star at the location.
At the time, the new object glowed at the naked eye limit of magnitude
+6, but a more recent observation by Japanese amateur Koichi Itagaki
puts the star at magnitude +5.3, indicating it’s still on the rise.
A 5th magnitude nova’s not too difficult to spot with the naked eye
from a dark sky, and binoculars will show it with ease. Make a morning
of it by setting up your telescope for a look at Saturn and the nearby
double star Graffias (Beta Scorpii), one of the prettiest, low-power
doubles in the summer sky.
Close-in
map of Sagittarius showing the nova’s location (R.A. 18h36m57s Decl.
-28°55’42”) and neighboring stars with their magnitudes. For clarity,
the decimal points are omitted from the magnitudes, which are from the
Tycho catalog. Source: Stellarium
Nova means “new”, but novae aren’t fresh stars coming to life but an
explosion occurring on the surface of an otherwise faint star no one’s
taken notice of – until the blast causes it to brighten 50,000 to
100,000 times. A nova occurs in a close binary star system, where a
small but extremely dense and massive (for its size)
white dwarf siphons hydrogen
gas from its closely orbiting companion. After swirling about in a disk
around the dwarf, it’s funneled down to the star’s 150,000 F° surface
where gravity compacts and heats the gas until detonates in a
titanic thermonuclear explosion. Suddenly, a faint star that wasn’t on
anyone’s radar vaults a dozen magnitudes to become a standout “new
star”.
Novae
occur in close binary systems where one star is a tiny but extremely
compact white dwarf star. The dwarf pulls material into a disk around
itself, some of which is funneled to the surface and ignites in a nova
explosion. Credit: NASA
Regular nova observers may wonder why so many novae are discovered in
the Sagittarius-Scorpius Milky Way region. There are so many more stars
in the dense star clouds of the Milky Way, compared to say the Big
Dipper or Canis Minor, that the odds go up of seeing a relatively rare
event like a stellar explosion is likely to happen there than where the
stars are scattered thinly.
A now-you-see-it-now-you-don’t animation showing the nova field before and after discovery. Credit: Ernesto Guido and Nick Howes
Given this galactic facts of life, that means most of will have to
set our alarms to spot this nova. Sagittarius doesn’t rise high enough
for a good view until the start of morning twilight. For the central
U.S., that’s around 5:45-6 a.m.
Find a location with a clear view to the southeast and get oriented
at the start of morning twilight or about 100 minutes before
sunrise.
Using the maps, locate Sagittarius below and to the east (left) of
Scorpius. Once you’ve arrived, point your binoculars into the Teapot and
star-hop to the nova’s location. I’ve included visual magnitudes of
neighboring stars to help you estimate the nova’s brightness and track
its changes in the coming days and weeks.
Whether it continues to brighten or soon begins to fade is anyone’s
guess at this point. That only makes going out and seeing it yourself
that much more enticing.
New photo of Nova Sagittarii. Note the “warm” color from hydrogen alpha emission. Credit: Erneso Guido and Nick Howes
UPDATE: A
spectrum of the object was obtained with the
Liverpool Telescope
March 16 confirming that the “new star” is indeed a nova. Gas has been
clocked moving away from the system at more than 6.2 million mph (10
million kph)!
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