Astronomy

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Excavation began August 14 on the site of

the Giant Magellan Telescope (GMT) at Las

Campanas Observatory in Chile’s Atacama

Desert. Over the next five months, workers will

remove over 140,000 cubic feet (4,000 cubic

meters) of rock to prepare the site for the con-

crete foundations that will underpin the tele-

scope and its support facilities.

Work at the 8,200-foot (2,500 m) Las

Campanas Peak is challenging, and crews must

excavate 23 feet (7 m) deep before pouring the

cement that will serve as the telescope’s pier.

Care must be taken to prevent compromising

the integrity of the bedrock, which must support

the full weight of the telescope’s 1,000-ton

(907,000 kilograms) steel structure. The telescope

will sit inside a building 22 stories high and

almost 185 feet (56 m) wide.

When the GMT is completed, its seven primary

mirrors will form a telescope with a diameter of

80 feet (24.5 m). Thus far, five of these segments

have been successfully cast. The GMT’s deform-

able secondary mirror will counteract the effects

of Earth’s atmosphere, offering astronomers the

ability to see objects with 10 times the resolution,

or sharpness, of the Hubble Space Telescope.

“With the start of construction of the perma-

nent buildings on the site, the GMT is showing

tangible progress toward completion,” said GMT

Organization Project Manager James Fanson in

a press release. “In total, we expect to remove

5,000 cubic meters or 13,300 tons of rock from

the mountain, and will need 330 dump truck

loads to remove it from the summit.”

First light for the GMT is planned for as early

as 2024. — A.K.

A bizarre rogue planet without a star is

roaming the Milky Way just 20 light-years

from the Sun. New research published

July 31 in The Astrophysical Journal shows

this strange, nomadic world has an

incredibly powerful magnetic field some

4 million times stronger than Earth’s,

generating spectacular aurorae that

would put our northern lights to shame.

The peculiar object — succinctly

named SIMP J01365663+0933473 (we’ll

call it SIMP for simplicity’s sake) — was

first discovered in 2016. At the time,

researchers thought SIMP was a brown

dwarf: an object too big to be a planet but

too small to be a star. However, last year

another study showed that SIMP is just

small enough, at 12.7 times the mass and

1.2 times the radius of Jupiter, to be con-

sidered a planet, albeit a mammoth one.

Gigantic by planetary standards,

SIMP also has a mighty magnetic field

that produces stunning light shows.

However, its aurorae are not generated

in the same way as those on our planet.

On Earth, the charged particles that

cause aurorae primarily come from the

Sun in the form of solar wind. But on

Jupiter, which also experiences aurorae,

the charged particles mainly come from

its moon Io. Because SIMP does not have

a star bombarding it with particles like

Earth does, the researchers believe that

SIMP’s aurorae may be produced more

like Jupiter’s, which means SIMP likely

has a moon.

According to the researchers, the

new study, which detected radio emis-

sion associated with SIMP’s aurorae, is

important because it opens the door for

future insights into exoplanetary mag-

netic fields and aurorae. Furthermore,

the team says this detection method

could be used to find other exoplanets

without stars, which are notoriously

difficult to find. — J.P.

Giant Magellan Telescope excavation begins

Starless planet

has a mighty

magnetic field

SMALL PACKAGES. Astronomers discovered a black hole almost the same size as the Milky Way’s inside an ultra-

compact dwarf galaxy just 300 light-years across. Such a large black hole was not expected within a galaxy of that size.

CONSTRUCTION SITE. The summit of Chile’s Las Campanas Peak, imaged by drone in May 2018, will be the home

of the Giant Magellan Telescope. Excavation has begun for the telescope’s pier and support buildings.

SOLITARY SIMP. Shown here in this artist’s

concept, SIMP J01365663+0933473 is a massive,

starless exoplanet with a powerful aurora-

generating magnetic field.

From Mars, Earth would dazzle at

magnitude –3.9 and appear about twice

as bright as magnitude –3.2 Venus.

ASTRONOMY

: ROEN KELLY

TWIN WONDERS.

As skywatchers continue

to enjoy Mars shining

brightly in the evening sky,

have you ever imagined

the view a Martian might

have? The stars lie so far

away that they wouldn’t

look at all different, but

the planets are another

story. In early December,

Earth would appear 44°

from the Sun — near its

greatest elongation — and

would be a beacon in the

morning sky among the

background stars of Leo.

And Venus, just a bit

fainter than our planet,

would lurk nearby in Virgo.

— Richard Talcott

GIANT MAGELLAN TELESCOPE — GMTO CORPORATION

CHUCK CARTER, CALTECH, NRAO/AUI/NSF

RED PLANET DELIGHT