Sky & Telescope - May 2019 - 56

MAY 2019 OBSERVING
Deep-Sky Wonders

HIP 81111

HIP 40047

HIP 52849

HIP 81145

HIP 81062

HIP 52885

ultraviolet, so they don't look any bluer
to us. Hot subdwarf stars (sdO and sdB)
are marginally bluer, but there aren't
many bright enough to ﬂaunt their
color. Dwarf and subdwarf stars both
produce their heat via hydrogen fusion,
but subdwarfs are 1.5 to 2 magnitudes
dimmer than dwarf stars of the same
spectral type.
Beaming at magnitude 9.6, HIP
40047 in Camelopardalis has a color
index of −0.30 and is one of the bright-

δ
γ
ρ

θ
ι

Leo

est sdO stars we can see. Although it's
a little past its prime when this issue of
the magazine comes out, the star is circumpolar at mid-northern latitudes and
still high enough to proﬁtably observe at
nightfall throughout May. I was rather
enamored with this star when I ﬁrst
saw it. Through my 130-mm scope, this
is about the faintest blue star whose
color I can distinguish. Roughly the
same magnitude as HIP 40047, the two
stars 10′ to its south cinch the effort,
with the eastern star
gleaming pale yellow
and the western one
smoldering orange.
Looking from star to
star is a big help in
assessing the trio's
μ
κ
colors.
Keeping to targets
ε
brighter
than HIP
λ
40047, here are some
other blue stars you
can try. HIP 52849
in Leo Minor is a
7.0-magnitude mainsequence star (O9V)
with a color index of

75
69
ϕ

HIP 55051

M AY 2 0 1 9 * S K Y & T E L E S C O P E

t Follow a southern meander from Sigma Leonis,
passing through 75 and
69 Leonis to find your way
to HIP 55051. This 7thmagnitude star lies less
than 13 arcminutes from
Phi Leonis.

−0.23. In Leo just 12.8′ north-northwest of Phi (φ) Leonis, 7.4-magnitude
HIP 55051 has a color index of −0.21.
It's also a main-sequence star and has
a spectral type of B2/3V. Compare it to
yellowish Phi to see if you can tell the
difference. Virgo's brightest star, Spica,
is a spectroscopic binary whose stars
are too close together to view separately. Their spectral types are B1V and
B4V, and their combined color index is
−0.24. Spica is rather dazzling through
a telescope, and I ﬁnd it easier to see the
color through binoculars. Brighter than
our ﬁrst subdwarf and nearly as blue,
the sdB star HIP 81145 in Ophiuchus
shines at magnitude 8.9 and has a color
index of −0.28.
As Leslie Peltier, author of the
charming book Starlight Nights, once
said, "Were I to write out one prescription designed to help alleviate at least
some of the self-made miseries of mankind, it would read like this: One gentle
dose of starlight to be taken each clear
night just before retiring." Let's take a
bit of our ease from the starlight of the
night's rubies and sapphires.
¢ Contributing Editor SUE FRENCH
welcomes your comments at scfrench@
nycap.rr.com.
FURTHER READING: Find a data table
that includes positions and color indices for
the stars discussed here at https://is.gd/
DSWMay2019.

HIP 40 047, HIP 52849 & HIP 81145: POSS II / CA LTECH / STSCI /
PA LO M A R OBSERVATORY; HIP 550 51: A K IR A FUJII

p Left: The main-sequence subdwarf star HIP 40047 lies in a mostly undistinguished patch of northern sky. However, a pretty pair of stars, the
eastern component yellow, the western orange, sparkles 10 arcminutes due south of HIP 40047. Middle: The blue light of 7th-magnitude HIP 52849
shines 3½º north-northwest of 46 Leonis Minoris. Right: Ophiuchus, the Serpent Bearer, also carries the hot subdwarf HIP 81145. Find the blue star
1¾º south-southwest of 12 Ophiuchi.

https://is.gd/DSWMay2019 https://is.gd/DSWMay2019

Sky & Telescope - May 2019

Table of Contents for the Digital Edition of Sky & Telescope - May 2019