SKY_July2014.pdf

SkyandTelescope.com July 2014 11

Letters

Cheering Underground Successes

The creation of the remarkable feats in

mirror engineering Robert Zimmerman

describes in “How to Build a Giant Tele-

scope” (S&T: Mar. 2014, p. 24) take place

in the massive laboratory directly under

the grounds of the University of Arizona’s

football stadium. To a point, one could

say that during a televised game some

Arizona Wildcat fans may be cheering the

football team while others cheer the engi-

neering machinations occurring under

the fi eld of play.

Jerry Fontes, class of 1982

Chatham, New Jersey

Amateur Spectra of SN 2014J

We obtained spectra of the recent super-

nova SN 2014J in M82 (S&T: Apr. 2014,

p. 14) on six dates during the month follow-

ing its discovery. Each had a total exposure

time of 1 hour and was made with an Orion

ED 102-mm f/7 refractor, a 200 line/mm

diff raction grating, and an SBIG ST

CCD, yielding a spectral dispersion of 1.

nanometers/pixel. We then processed the

spectra with RSpec software, adjusted the

spectral fl ux data for instrument response,

and normalized them.

Several of our fellow members in the

Cepheids Astronomy Facebook group, as

well as the RSpec Yahoo! Group, helped

us interpret the data. Our spectra show

the prominent, singly ionized silicon

(Si II) absorption feature that is used to

identify Type Ia supernovae. One day after

the supernova, the feature was blueshifted

from its normal wavelength of 635.5 nm

by 36.0 nm. The shift decreased during

the 30 days of observation, allowing us

to estimate changes in the expanding

shell’s velocity over time. Day 1’s expan-

sion velocity was 16,995 kilometers/second

(38,017,000 mph). By day 31, the Si II line

had shifted to 611.5 nm, indicating that

over 4 weeks, the expansion velocity had

slowed by 5,700 km/sec to 11,300 km/sec.

Mark D. Bunnell

Price, Utah

Vikrant K. Agnihotri

Kota, Rajasthan, India

Editor’s Note: These velocities are consistent

with those reported by Ariel Goobar (Stock-

holm University, Sweden) and colleagues

in the March 20th Astrophysical Journal

Letters. That team used several diff erent

professional instruments, including a spectro-

graph on the 3.5-meter scope at Apache Point

Observatory in New Mexico.

Cat Chuckles

The Focal Point article about Edwin

Hubble and his cat was great! (S&T: Feb.

2014, p. 86.) As cat lovers, my brother and I

found it wonderful that such an outstand-

ing astronomer had such a love for his cat.

It was funny to read that Copernicus the

cat didn’t like Aldous Huxley very much.

We’ve read this article many times over.

Liede-Marie Haitsma

Walnut Creek, California

Inspiring the Next Generation

You never know what a view through a

telescope might do for a person. In the late

1970s, I was on the faculty of the biological

sciences department at Loyola University

in New Orleans. My wife and I often had

students come over to the house to eat

supper with us. One night I pulled out my

5-inch refl ector and showed them what I

could. New Orleans is not the ideal place

to observe: light pollution is a real problem

and the skies are usually hazy. This particu-

lar night was clearer than most, and I man-

aged to show them the thin crescent Moon,

Jupiter, Saturn, and one or two deep-sky

objects. I explained to them what they were

seeing and told them about Sky & Telescope

and showed them some of my copies.

One young man, Frank, was espe-

cially interested. He later graduated and

became a dentist in New Orleans, and I

moved to North Carolina to take a faculty

position. Several years later I returned to

New Orleans for a conference and called

Frank. He told me that the one evening

at my telescope had engendered in him a

love for astronomy. He had bought a very

nice telescope, was an avid observer, and

400 420 440 460 480 500 520 540 560 580 600 620 640 660 680 700

Relative flux

Nanometers ( 1 nm = 10 angstroms)

SN 2014J Spectra

+14 days

+4 days

+3 days

+1 day

+26 days

611.

Blueshifted

wavelengths

Rest wavelength

of Si II

610.

610.

602.

600.

599.

+31 days

From January 22nd to February 21st, an amateur team obtained low-resolution spectra of the M

supernova and calculated the changing velocity of the expanding shell based on the changing blue-

shift of an absorption line of ionized silicon. Days are measured from the supernova’s appearance

on January 21st, and each spectral profi le is a stack of sixty 1-minute exposures.

S&T: LEAH TISCIONE

S&T:

LEAH TISCIONE; SOURCE: M. D. BUNNELL / V. K. AGNIHOTRI / CEPHEIDS ASTRONOMY