Astronomy - USA (2022-02)

FOURTH TIME’S

THE CHARM

IN 2016, scientists spotted not one, not two,

but three views of the same supernova, referred

to as Supernova Requiem. And they expect

it to appear again in 2037. This is possible

thanks to a galaxy cluster, MACS J0138, that

sits about 6 billion light-years closer to us than

the supernova itself. The mass of this cluster

— about a billion times that of the Sun — is so

great that it bends the light streaming from the

distant explosion around it, an effect known as

gravitational lensing. However, because mass

isn’t evenly distributed within the cluster, light

from Supernova Requiem takes slightly different

paths, resulting in different arrival times at

Earth. The three views of the explosion in this

Hubble image also vary slightly in brightness

and color, indicating they’re showing three

different phases of the supernova. — C.B.

RAIN ACROSS THE SOLAR SYSTEM

Drip, drop. Have you ever thought about the physics of raindrops? Two

researchers at Harvard University did, publishing a paper March 15, 2021, in

the Journal of Geophysical Research: Planets that details how large water

raindrops could get on other planets. They found that on rocky worlds, only

raindrops of a certain size successfully complete the journey between a

cloud and the ground. Drops that are too small evaporate before reaching

the surface, while those that are too large break up on the way. That size is

determined largely by the planet’s mass — and therefore its gravitational pull.

Higher gravity results in smaller raindrops, and vice versa. Note that not all

worlds shown have the right temperature or pressure for liquid water rain,

or a solid surface for drops to fall on. — A.K.

A COMPARISON OF ALIEN RAINDROPS

How big can water raindrops get on other solar system worlds?

continue to exist after their star’s death,” said

lead author Joshua Blackman, an astronomy

postdoctoral researcher at the University of

Tasmania in Australia, in a press release.

Mercury and Venus will be swallowed by the

ballooning Sun, and most signs point to Earth

suffering that same fate. Mars may be the only

inner planet lucky enough to escape.

The future is much rosier for Jupiter and

Saturn. “If humankind wanted to move to a

moon of Jupiter or Saturn before the Sun fried

the Earth during its red supergiant phase,

we’d still remain in orbit around the Sun,”

said co-author David Bennett of the University

of Maryland and NASA’s Goddard Space

Flight Center. But avoiding a scorching death

would leave the door open for a frozen future.

Eventually the Sun will collapse into a white

dwarf, meaning that heat from our star would

be extremely limited at that distance. — C.B.

LEAD AUTHOR: STEVE A. RODNEY (UNIVERSITY OF SOUTH CAROLINA), GABRIEL BRAMMER

(COSMIC DAWN CENTER/NIELS BOHR INSTITUTE/UNIVERSITY OF COPENHAGEN); IMAGE

PROCESSING: JOSEPH DEPASQUALE (STSCI)

WORLD

GRAVITATIONAL

PULL

(relative to Earth)

MAXIMUM

WATER

RAINDROP SIZE

E A R T H J U P I T E R S A T U R N T I T A N

0.

2.

0.

1

0.

0.7 inch/18 mm

0.43 inch/11 mm

0.28 inch/7 mm

0.43 inch/11 mm

1.2 inches/30 mm

0.75 inch

19 mm

0.24 inch

6 mm

GRAIN

OF RICE

U.S.

PENNY

M

A

R

S

ASTRONOMY:

ROEN KELLY