2019-04-01_Astronomy

Deneb

Vega

Altair

LY R A

CYGNUS AQUILA

Radiant

10°

April 23, 1 A.M.

Looking east

Lyrid meteor shower

WWW.ASTRONOMY.COM 37

METEORWATCH

The long wait is over. After the

Quadrantid meteor display lights

up early January’s sky, observers

must hold out until April to view

the year’s second major shower.

The Lyrids peak the night of

April 22/23. In the best of years,

skywatchers can expect to see

nearly 20 meteors per hour shortly

before dawn. Unfortunately, 2019

is not the best year.

The Moon is just three days past

Full at the shower’s peak and will

drown out fainter Lyrids. The mete-

ors appear to radiate from a point

in the constellation Lyra the Lyre,

which rises around 9 P.M. local day-

light time. Although this radiant

climbs 30° high by midnight and

passes nearly overhead as morning

twilight begins, bright moonlight

fills the sky after our satellite rises

The Lyre plays

a sad song

— Continued on page 42

Lyrid meteor s

Active dates: April 14–30

Peak: April 22

Moon at peak: Waning gibbous

Maximum rate at peak:

18 meteors/hour

an hour or two before dawn.
It then lies nearly 30° above
the horizon for observers at
mid-northern latitudes. The
greater altitude means that
Jupiter’s light passes through
less of Earth’s turbulent atmo-
sphere and planetary details
come into sharper focus.
Point any telescope toward
Jupiter and you’ll see a broad
disk featuring two dark equa-
torial belts straddling a
brighter zone that coincides
with the equator. Although
the Equatorial Zone often
appears bland, last year it
sported several ocher-colored
festoons. Any such features
should become easier to see as
the disk’s diameter swells dur-
ing April, from 40" across on
the 1st to 43" on the 30th.
Bigger scopes reveal an
alternating series of more sub-
tle dark belts and lighter zones
that stretch north and south of
their equatorial counterparts.
Fine details along the edges of
these bands pop into view dur-
ing moments of good seeing.

Langrenus and Petavius

RISINGMOON

Observers of the waxing crescent Moon love

spring. Naked-eye and binocular skywatch-

ers have unparalleled views of the Moon

bathed in earthshine, perched in an indigo

sky painted with a horizon of fiery orange

and red. Selenophiles — or “lunatics,” as

friends call them — marvel at the large crater

walls and mountains that cast long shadows

on the lunar crescent. And the enjoyment

lasts for a long time, because the Moon

stands high in the twilight sky from the

Northern Hemisphere, thanks to the steep

angle the ecliptic makes to the western hori-

zon after sunset. In other seasons, the cres-

cent hangs lower and sets more quickly.

Some of the best views will come the

evening of April 9. The terminator — the

dividing line between sunlight and dark-

ness on the lunar surface that marks where

sunrise occurs on a waxing Moon — then

cuts across the western walls of the large

craters Langrenus and Petavius.

Youthful Langrenus measures

about 80 miles across. Although not as

young as Copernicus, this crater’s features

appear sharper than those of most older

impact structures. A couple of prominent

mountain peaks stand out at Langrenus’

center. Check back two or three nights later,

and you’ll clearly see its secondary craters,

debris apron, and ejecta rays.

Petavius to the south is nearly 30 miles

wider, a bit older, and sports extra features.

Its rim appears softer, a telltale sign of its

longer life facing bombardment from solar

system debris. Notice the huge radial frac-

ture that emanates from the crater’s cluster

of central peaks. Look more closely, and you

should pick out a large, curved crack closer

to the rim. Both of these fractures formed

when lava from below heaved up the cra-

ter’s floor and later subsided.

Craters crowd together on the crescent Moon

around 11:30 P.M. Still, you should

keep an eye out for the occasional

meteor flash. Lucky observers

could spot up to five per hour.

Although a waning gibbous Moon

will wash out many Lyrids, stay alert

for the occasional bright streak.

Asteroid 2 Pallas glows at magnitude 7.9 — the brightest it has

been in five years — when it reaches opposition April 9.

OBSERVING

HIGHLIGHT

N

E

Mare

Fecunditatis

Langrenus

Petavius

The waxing crescent Moon features these two

large craters on the shores of Mare Fecunditatis.

CO NSO LI DATED LU NAR ATL A S/UA/LPL; INSET: NASA/GSFC/ASU