Sky and Telescope - January 2017 - 48

JANUARY 2017 OBSERVING
Celestial Calendar by Alan MacRobert

RW Tauri, an Action-Packed Eclipser
RW

RW Tauri hides in plain sight
near the Pleiades & Aldebaran.
It's the deepest eclipsing
binary known.
RW Tauri
Dec. 27, 1976

Visual magnitude

8.5
9.0
9.5
10.0
10.5
11.0
11.5
12.0
2:00

3:00

4:00

5:00

Universal time

W

ell do I remember my first night
with a telescopic eclipsing binary
star. It was deepest December 1976.
Sky & Telescope had published a list
of upcoming eclipses predicted for
RW Tauri, the most extreme eclipsing
binary known. Like amateur astronomers had for generations, I read that
this 8.0-magnitude B8 star fades, then
positively plummets, to about magnitude 11.6. It sits there unchanged for
80 minutes, glimmering with a slight
orange tint, then leaps back up to, eventually, brilliant whiteness - "brilliant"
being relative, after you've been watching it sit there ½5 as bright barely above
the sky background in your eyepiece.
Most of the show runs through its
course in about five hours.

p The central 5 hours of an eclipse. Peering into a 6-inch reflector, I took extreme care in estimating RW's magnitude every 5 to 10 minutes. The effort paid off with this very clean light curve.

48

J A N U A R Y 2 0 1 7 * SK Y & TELESCOPE

I made a night of it. In the list of
predictions, I found an eclipse timed so
I could follow Taurus through openings
in my trees for two hours before and
after the midpoint. I shoveled a space
in the snow for me and my 6-inch f/8
reflector. The appointed night was clear.
Every 5 or 10 minutes I made as careful
an estimate as I possibly could of where
RW Tauri stood with respect to the
brightnesses of the comparison stars
around it. I kept at it for more than
four hours. As I communed so intently
with this tiny point far above the silent
world, its performance proved even
more of an adventure than I'd hoped.
The next morning I plotted my
brightness estimates on graph paper.
The result was the beautiful, symmetric,
flat-bottomed light curve at lower left.
By folding the paper straight down the
middle so the descending and rising
curves aligned when I shone a light
through the paper, I judged that mideclipse had happened at 3:32 UT.
And that was the whole point of this
project. Many eclipsing binaries show
slight changes in their orbital periods,
for various reasons predictable and
unpredictable. A period change as small
as one part per million will add up over
time, until the eclipses come measurably early or late to an amateur eyeballing the star through a modest telescope.
Professionals and amateurs have timed
eclipsing binaries for generations to create long records of what's going on.
I reported my data and timing to
the Eclipsing Binary section of the
American Association of Variable Star
Observers. There it resides: one of about
17,000 eclipsing binary timings made by
AAVSO members since 1965.
Nowadays amateurs do the job much

A K IR A FUJII

A flat-bottomed eclipsing binary star shines high near the Pleiades.



Sky and Telescope - January 2017

Table of Contents for the Digital Edition of Sky and Telescope - January 2017

Contents
Sky and Telescope - January 2017 - Cover1
Sky and Telescope - January 2017 - Cover2
Sky and Telescope - January 2017 - 1
Sky and Telescope - January 2017 - Contents
Sky and Telescope - January 2017 - 3
Sky and Telescope - January 2017 - 4
Sky and Telescope - January 2017 - 5
Sky and Telescope - January 2017 - 6
Sky and Telescope - January 2017 - 7
Sky and Telescope - January 2017 - 8
Sky and Telescope - January 2017 - 9
Sky and Telescope - January 2017 - 10
Sky and Telescope - January 2017 - 11
Sky and Telescope - January 2017 - 12
Sky and Telescope - January 2017 - 13
Sky and Telescope - January 2017 - 14
Sky and Telescope - January 2017 - 15
Sky and Telescope - January 2017 - 16
Sky and Telescope - January 2017 - 17
Sky and Telescope - January 2017 - 18
Sky and Telescope - January 2017 - 19
Sky and Telescope - January 2017 - 20
Sky and Telescope - January 2017 - 21
Sky and Telescope - January 2017 - 22
Sky and Telescope - January 2017 - 23
Sky and Telescope - January 2017 - 24
Sky and Telescope - January 2017 - 25
Sky and Telescope - January 2017 - 26
Sky and Telescope - January 2017 - 27
Sky and Telescope - January 2017 - 28
Sky and Telescope - January 2017 - 29
Sky and Telescope - January 2017 - 30
Sky and Telescope - January 2017 - 31
Sky and Telescope - January 2017 - 32
Sky and Telescope - January 2017 - 33
Sky and Telescope - January 2017 - 34
Sky and Telescope - January 2017 - 35
Sky and Telescope - January 2017 - 36
Sky and Telescope - January 2017 - 37
Sky and Telescope - January 2017 - 38
Sky and Telescope - January 2017 - 39
Sky and Telescope - January 2017 - 40
Sky and Telescope - January 2017 - 41
Sky and Telescope - January 2017 - 42
Sky and Telescope - January 2017 - 43
Sky and Telescope - January 2017 - 44
Sky and Telescope - January 2017 - 45
Sky and Telescope - January 2017 - 46
Sky and Telescope - January 2017 - 47
Sky and Telescope - January 2017 - 48
Sky and Telescope - January 2017 - 49
Sky and Telescope - January 2017 - 50
Sky and Telescope - January 2017 - 51
Sky and Telescope - January 2017 - 52
Sky and Telescope - January 2017 - 53
Sky and Telescope - January 2017 - 54
Sky and Telescope - January 2017 - 55
Sky and Telescope - January 2017 - 56
Sky and Telescope - January 2017 - 57
Sky and Telescope - January 2017 - 58
Sky and Telescope - January 2017 - 59
Sky and Telescope - January 2017 - 60
Sky and Telescope - January 2017 - 61
Sky and Telescope - January 2017 - 62
Sky and Telescope - January 2017 - 63
Sky and Telescope - January 2017 - 64
Sky and Telescope - January 2017 - 65
Sky and Telescope - January 2017 - 66
Sky and Telescope - January 2017 - 67
Sky and Telescope - January 2017 - 68
Sky and Telescope - January 2017 - 69
Sky and Telescope - January 2017 - 70
Sky and Telescope - January 2017 - 71
Sky and Telescope - January 2017 - 72
Sky and Telescope - January 2017 - 73
Sky and Telescope - January 2017 - 74
Sky and Telescope - January 2017 - 75
Sky and Telescope - January 2017 - 76
Sky and Telescope - January 2017 - 77
Sky and Telescope - January 2017 - 78
Sky and Telescope - January 2017 - 79
Sky and Telescope - January 2017 - 80
Sky and Telescope - January 2017 - 81
Sky and Telescope - January 2017 - 82
Sky and Telescope - January 2017 - 83
Sky and Telescope - January 2017 - 84
Sky and Telescope - January 2017 - Cover3
Sky and Telescope - January 2017 - Cover4
Sky and Telescope - January 2017 - SGA17RAL
Sky and Telescope - January 2017 - 90
Sky and Telescope - January 2017 - SGA17R
Sky and Telescope - January 2017 - SGA17RA
Sky and Telescope - January 2017 - SGA17EAL
Sky and Telescope - January 2017 - 94
Sky and Telescope - January 2017 - SGA17E
Sky and Telescope - January 2017 - SGA17EA
Sky and Telescope - January 2017 - SGA17SAL
Sky and Telescope - January 2017 - 98
Sky and Telescope - January 2017 - SGA17S
Sky and Telescope - January 2017 - SGA17SA
https://www.nxtbook.com/nxtbooks/aas/st_202112
https://www.nxtbook.com/nxtbooks/aas/st_202111
https://www.nxtbook.com/nxtbooks/aas/st_202110
https://www.nxtbook.com/nxtbooks/aas/st_202109
https://www.nxtbook.com/nxtbooks/aas/st_202108
https://www.nxtbook.com/nxtbooks/aas/st_202107
https://www.nxtbook.com/nxtbooks/aas/st_202106
https://www.nxtbook.com/nxtbooks/aas/st_202105
https://www.nxtbook.com/nxtbooks/aas/st_202104
https://www.nxtbook.com/nxtbooks/aas/st_202103
https://www.nxtbook.com/nxtbooks/aas/st_202102
https://www.nxtbook.com/nxtbooks/aas/st_202101
https://www.nxtbook.com/nxtbooks/aas/skywatch_2021
https://www.nxtbook.com/nxtbooks/aas/st_202012
https://www.nxtbook.com/nxtbooks/aas/st_202011
https://www.nxtbook.com/nxtbooks/aas/st_202010
https://www.nxtbook.com/nxtbooks/aas/st_202009
https://www.nxtbook.com/nxtbooks/aas/st_202008
https://www.nxtbook.com/nxtbooks/aas/st_202007
https://www.nxtbook.com/nxtbooks/aas/st_202006
https://www.nxtbook.com/nxtbooks/aas/st_202005
https://www.nxtbook.com/nxtbooks/aas/st_202004
https://www.nxtbook.com/nxtbooks/aas/st_202003
https://www.nxtbook.com/nxtbooks/aas/st_202002
https://www.nxtbook.com/nxtbooks/aas/st_202001
https://www.nxtbook.com/nxtbooks/aas/st_201912
https://www.nxtbook.com/nxtbooks/aas/st_201911
https://www.nxtbook.com/nxtbooks/aas/st_201910
https://www.nxtbook.com/nxtbooks/aas/st_201909
https://www.nxtbook.com/nxtbooks/aas/st_201908
https://www.nxtbook.com/nxtbooks/aas/st_201907
https://www.nxtbook.com/nxtbooks/aas/st_201906
https://www.nxtbook.com/nxtbooks/aas/st_201905
https://www.nxtbook.com/nxtbooks/aas/st_201904
https://www.nxtbook.com/nxtbooks/aas/st_201903
https://www.nxtbook.com/nxtbooks/aas/st_201902
https://www.nxtbook.com/nxtbooks/aas/st_201901
https://www.nxtbook.com/nxtbooks/aas/st_201812
https://www.nxtbook.com/nxtbooks/aas/st_201811
https://www.nxtbook.com/nxtbooks/aas/st_201810
https://www.nxtbook.com/nxtbooks/aas/st_201809
https://www.nxtbook.com/nxtbooks/aas/st_201808
https://www.nxtbook.com/nxtbooks/aas/st_201807
https://www.nxtbook.com/nxtbooks/aas/st_201806
https://www.nxtbook.com/nxtbooks/aas/st_201805
https://www.nxtbook.com/nxtbooks/aas/st_201804
https://www.nxtbook.com/nxtbooks/aas/st_201803
https://www.nxtbook.com/nxtbooks/aas/st_201802
https://www.nxtbook.com/nxtbooks/aas/st_201801
https://www.nxtbook.com/nxtbooks/aas/st_201712
https://www.nxtbook.com/nxtbooks/aas/st_201711
https://www.nxtbook.com/nxtbooks/aas/st_201710
https://www.nxtbook.com/nxtbooks/aas/st_201709
https://www.nxtbook.com/nxtbooks/aas/st_201708
https://www.nxtbook.com/nxtbooks/aas/st_201707
https://www.nxtbook.com/nxtbooks/aas/st_201706
https://www.nxtbook.com/nxtbooks/aas/st_201705
https://www.nxtbook.com/nxtbooks/aas/st_201704
https://www.nxtbook.com/nxtbooks/aas/st_201703
https://www.nxtbook.com/nxtbooks/aas/st_201702
https://www.nxtbook.com/nxtbooks/aas/st_201701
https://www.nxtbook.com/nxtbooks/aas/st_201612
https://www.nxtbook.com/nxtbooks/aas/st_201611
https://www.nxtbook.com/nxtbooks/newtrack/st_201612
https://www.nxtbook.com/nxtbooks/aas/st_201610
https://www.nxtbook.com/nxtbooks/aas/st_201609
https://www.nxtbook.com/nxtbooks/aas/st_201608
https://www.nxtbook.com/nxtbooks/aas/st_201607
https://www.nxtbook.com/nxtbooks/aas/st_201606
https://www.nxtbook.com/nxtbooks/aas/st_201605
https://www.nxtbook.com/nxtbooks/aas/st_201604
https://www.nxtbook.com/nxtbooks/aas/st_201603
https://www.nxtbook.com/nxtbooks/aas/st_201602
https://www.nxtbook.com/nxtbooks/aas/st_201601
https://www.nxtbook.com/nxtbooks/aas/st_201512
https://www.nxtbook.com/nxtbooks/aas/st_201511
https://www.nxtbook.com/nxtbooks/aas/st_201510
https://www.nxtbook.com/nxtbooks/aas/st_201509
https://www.nxtbook.com/nxtbooks/aas/st_201508
https://www.nxtbook.com/nxtbooks/aas/st_201507
https://www.nxtbook.com/nxtbooks/aas/st_201506
https://www.nxtbook.com/nxtbooks/aas/st_201505
https://www.nxtbook.com/nxtbooks/aas/st_201504
https://www.nxtbook.com/nxtbooks/aas/st_201503
https://www.nxtbook.com/nxtbooks/aas/st_201502
https://www.nxtbook.com/nxtbooks/aas/st_201501
https://www.nxtbook.com/nxtbooks/aas/st_201412
https://www.nxtbook.com/nxtbooks/aas/st_201411
https://www.nxtbook.com/nxtbooks/aas/st_201410
https://www.nxtbook.com/nxtbooks/aas/st_201409
https://www.nxtbook.com/nxtbooks/aas/st_201408
https://www.nxtbook.com/nxtbooks/aas/st_201407
https://www.nxtbook.com/nxtbooks/aas/st_201406
https://www.nxtbook.com/nxtbooks/aas/st_mars
https://www.nxtbook.com/nxtbooks/aas/st_201405
https://www.nxtbook.com/nxtbooks/aas/st_201404
https://www.nxtbook.com/nxtbooks/aas/st_201403
https://www.nxtbook.com/nxtbooks/aas/st_201402
https://www.nxtbook.com/nxtbooks/aas/st_201401
https://www.nxtbook.com/nxtbooks/aas/st_201312
https://www.nxtbook.com/nxtbooks/aas/st_201311
https://www.nxtbook.com/nxtbooks/aas/st_201310
https://www.nxtbook.com/nxtbooks/aas/st_201309
https://www.nxtbook.com/nxtbooks/aas/st_201308
https://www.nxtbook.com/nxtbooks/aas/st_201307
https://www.nxtbook.com/nxtbooks/aas/st_201306
https://www.nxtbook.com/nxtbooks/aas/st_201305
https://www.nxtbook.com/nxtbooks/aas/st_201304
https://www.nxtbook.com/nxtbooks/aas/st_201303
https://www.nxtbook.com/nxtbooks/aas/st_201302
https://www.nxtbook.com/nxtbooks/aas/st_201301
https://www.nxtbook.com/nxtbooks/aas/st_201212
https://www.nxtbook.com/nxtbooks/aas/st_201211
https://www.nxtbook.com/nxtbooks/aas/st_201210
https://www.nxtbook.com/nxtbooks/aas/st_201209
https://www.nxtbook.com/nxtbooks/aas/st_201208
https://www.nxtbook.com/nxtbooks/aas/st_201207
https://www.nxtbook.com/nxtbooks/aas/st_201206
https://www.nxtbook.com/nxtbooks/aas/st_201205
https://www.nxtbook.com/nxtbooks/aas/st_201204
https://www.nxtbook.com/nxtbooks/aas/st_201203
https://www.nxtbook.com/nxtbooks/aas/st_201202
https://www.nxtbook.com/nxtbooks/aas/st_201201
https://www.nxtbook.com/nxtbooks/aas/st_201112
https://www.nxtbook.com/nxtbooks/aas/st_201111
https://www.nxtbook.com/nxtbooks/aas/st_201110
https://www.nxtbook.com/nxtbooks/aas/st_201109
https://www.nxtbook.com/nxtbooks/aas/st_201108
https://www.nxtbook.com/nxtbooks/aas/st_201107
https://www.nxtbook.com/nxtbooks/aas/st_201106
https://www.nxtbook.com/nxtbooks/aas/st_201105
https://www.nxtbook.com/nxtbooks/aas/st_201104
https://www.nxtbook.com/nxtbooks/aas/st_201103
https://www.nxtbook.com/nxtbooks/aas/st_201102
https://www.nxtbook.com/nxtbooks/aas/st_201101
https://www.nxtbook.com/nxtbooks/aas/st_201012
https://www.nxtbook.com/nxtbooks/aas/st_201011
https://www.nxtbook.com/nxtbooks/aas/st_201010
https://www.nxtbook.com/nxtbooks/aas/st_201009
https://www.nxtbook.com/nxtbooks/aas/st_201008
https://www.nxtbook.com/nxtbooks/aas/st_201007
https://www.nxtbook.com/nxtbooks/aas/st_201006
https://www.nxtbook.com/nxtbooks/aas/st_201005
https://www.nxtbook.com/nxtbooks/aas/st_201004
https://www.nxtbook.com/nxtbooks/aas/st_201003
https://www.nxtbook.com/nxtbooks/aas/st_201002
https://www.nxtbook.com/nxtbooks/aas/st_201001
https://www.nxtbookmedia.com