2019-12-01_Astronomy

23

Nov. 10

25

Dec. 10

25

Jan. 9

24

Feb. 8

23

March 9^24 April 8

23

May 8

0°

5°

10°

15°

20°

A

lt

it

ud

e

Southwest Azimuth West

25°

30°

AS

TR

ON

OM

Y:^

RO

EN

KE

LL

Y

12 ASTRONOMY • DECEMBER 2019

QUANTUM GRAVITY

EVENING STAR. How dazzling is

Venus? Even on a bad day, it

shines nine times brighter than

the night sky’s brightest star,

Sirius. But Venus stands out

even more when it appears far

above the horizon. Conditions

late this winter and early spring

will be ideal for Northern Hemisphere observers. This chart plots the planet’s positions for an observer

at 40° north latitude an hour after sunset. Although Venus reaches its peak altitude — 32.4° — at greatest

elongation March 24, it remains above 30° for nearly two months. — RICHARD TALCOTT

VENUS AT

ITS BEST

Although Venus stands highest

in the west at greatest

elongation, it shines brightest

(magnitude –4.7) in late April.

There’s a triplet of Earth-sized

exoplanetary candidates orbiting

a star just 12 light-years away, according

to a new study by a team from the Red

Dots campaign, which looks for rocky,

Earth-like planets around nearby stars.

All three planets are about 1.4 to 1.

times the mass of Earth and orbit their

star every three to 13 days.

The research was published August 13

on the preprint site arXiv.org, and has

been submitted to the Monthly Notices

of the Royal Astronomical Society. The

planets orbit GJ 1061, a low-mass,

M-dwarf star that’s one of the 25 closest

stars to the Sun. The star is similar to the

Sun’s nearest neighbor, Proxima Centauri,

whose own planet was discovered in 2016.

The new planets were spotted with the

radial-velocity method, which measures

tiny wobbles in a star’s orbit to reveal the

presence of exoplanets tugging on their

sun. This technique typically uncovers

giant exoplanets close to their host star,

but increasingly is used in long-term

campaigns to reveal smaller planets as

well. Data were collected using the High

Accuracy Radial velocity Planet Searcher

instrument on the La Silla Observatory’s

3.6-meter telescope in Chile. Observations

showed the signatures of three planetary

candidates, with a possible fourth.

However, the scientists suspect the fourth

candidate is actually stellar activity, such

as a starspot.

The longest-period planet, dubbed d,

is most interesting to scientists, as it falls

within the star’s habitable zone, where

liquid water could exist on the surface.

But M-dwarf stars, which live longer

than stars like the Sun, typically are more

active in their early years. This means that

a close-in planet like planet d may have

spent millions of years being blasted by

intense radiation, so it may not retain a

life-sustaining atmosphere. Nonetheless,

GJ 1061 shows less violent activity than

Proxima Centauri, suggesting it might

provide a safer environment for life.

“It doesn’t surprise me,” says Michael

Endl at the University of Texas at Austin,

who was not involved with the new

research. “Since NASA’s Kepler mission,

we basically know that small planets are

abundant around those very cool and

small stars.” — MARA JOHNSON-GROH, J.P.

Three Earth-sized exoplanets

discovered nearby

FAST FACT

NEW NEIGHBORS. Three newly discovered

planets make their home around a nearby star

called GJ 1061, a cool red dwarf similar to the

stars TRAPPIST-1 and Proxima Centauri. This

artist’s concept imagines a view from the

surface of one of TRAPPIST-1’s multiple

planets. M. KORNMESSER/ESO