M51 Supernova brightening. Supernova 2011dh, which was discovered
in the Whirlpool Galaxy, M51, on May 31st, has been brightening ever
since — though the brightening is now leveling off. As of June 16th the
supernova was about V magnitude 12.6 and visible in a lot more amateur
telescopes.
The
M51 supernova is marked with the yellow tick. Lynn Hilborn of Grafton,
Ontario, writes that she took this deep image of the galaxy on March
24th and added the supernova data from a second image taken June 7th.
North is up. Wider view. Lynn Hilborn
On the evening of the 16th S&T's Dennis di Cicco
imaged the galaxy and supernova again with his 16-inch scope and was
able to glimpse it visually with a 6-inch despite the moonlight. He
writes, "With the Moon leaving the early-evening sky [as of about June
19th] and M51 seen best as soon as it gets dark, now is the time for
people to have a look. With higher magnification and a moderately good
sky, anyone with an 8-inch or larger scope should be able to spot the
supernova. I can’t remember the last time we had one that was this
easily visible."
Here's an up-to-date light curve from the American Association of Variable Star Observers. See our article. Plot an AAVSO comparison-star chart (enter the name SN 2011dh).
Friday, June 17
The Moon rises in the
east-southeast in late evening, depending on where you are. Far to its
upper left shines Altair. Farther on in the same direction are the other
two stars of the Summer Triangle: Vega and lesser Deneb.
Saturday, June 18
The two brightest stars
of summer are Vega, high in the east these evenings, and Arcturus, even
higher in the southwest. They're moderately near neighbors of ours as
stars go: 25 and 37 light-years away, respectively. But that's only part
of why they appear so bright. Vega is hotter, larger, and 50 times more
luminous than the Sun, and Arcturus puts out 150 times the light of the
Sun.
The
little constellation Lyra dangles to Vega's lower right these evenings.
For most of the time, Beta Lyrae is almost exactly as bright as Gamma.
Akira Fujii
Sunday, June 19
The eclipsing binary star Beta
Lyrae (near Vega) should be at minimum light all evening (centered on
0:00 June 20th UT) — magnitude 4.3 instead of its maximum of 3.3 or 3.4.
That will make Beta obviously fainter than Gamma Lyrae next to it,
which is magnitude 3.2. See the article in the June Sky & Telescope, page 60.
Monday, June 20
Look low in the
west-northwest for Pollux and Castor as twilight fades away. They're
lined up not quite horizontally. These two "winter" stars have far
outstayed their season. How much longer can you follow them down? Past
the first day of summer tomorrow?
Tuesday, June 21
The June solstice occurs
at 1:16 p.m. EDT. This is the moment when the Sun is farthest north for
the year and begins its six-month return southward. Summer begins in the
Northern Hemisphere, where this is the year's longest day. In the
Southern Hemisphere, winter begins.
If you have a good view of the west-northwest horizon (from mid-northern
latitudes), mark precisely where the Sun sets. In a few days you should
be able to detect that it's again starting to set a little south of
this point. Build your own Stonehenge?
Wednesday, June 22
Now that the Moon is
gone from the evening sky, try hunting out galaxies hear the head of
Serpens using Sue French's "Deep-Sky Wonders" chart, photos, and article
in the June Sky & Telescope,
page 62. Find the Sombrero galaxy above Corvus right after dark using
page 45. And check out "Galaxies near Bright Stars" on page 68.
Thursday, June 23
Last-quarter Moon (exact
at 7:48 a.m. EDT). The Moon rises very late tonight, around 1 a.m. EDT
on the 24th depending on your location. Look above it for the Great
Square of Pegasus.
Friday, June 24
With summer here, look
south-southeast after dark for the bright constellation Scorpius, "the
Orion of summer," now reasonably high and standing upright. Like Orion,
Scorpius is marked by several 2nd-magnitude blue-white stars and one of
the two brightest red supergiants in the sky (Antares in Scorpius,
Betelgeuse in Orion). However, Scorpius is some 30° farther south.
Saturday, June 25
These evenings, look high
in the east to spot bright Vega. The brightest star to its lower left,
by two or three fist-widths at arm's length, is Deneb (the head of the
Northern Cross). Farther to Vega's lower right is bright Altair. These
three stars form the Summer Triangle. The summer Milky Way runs right
through it, along the length of the Northern Cross, if you have a dark
enough sky.
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